National Primary Drinking Water Regulations; Announcement of the Results of EPA's Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues, 3518-3552 [2016-31262]

Download as PDF 3518 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules [EPA–HQ–OW–2016–0627; FRL–9957–49– OW] 40 CFR Part 141 RIN 2040–ZA26 National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues Environmental Protection Agency (EPA). ACTION: Request for public comments. AGENCY: The Safe Drinking Water Act (SDWA) requires the U.S. Environmental Protection Agency (EPA) to conduct a review every six years of existing national primary drinking water regulations (NPDWRs) and determine which, if any, need to be revised. The purpose of the review, called the SixYear Review, is to evaluate current information for regulated contaminants to determine if there is new information on health effects, treatment technologies, analytical methods, occurrence and exposure, implementation and/or other factors that provides a health or technical basis to support a regulatory revision that will improve or strengthen public health protection. EPA has completed a detailed review of 76 NPDWRs and at this time has determined that eight NPDWRs are candidates for regulatory revision. The eight NPDWRs are included in the Stage 1 and the Stage 2 Disinfectants and Disinfection Byproducts Rules, the Surface Water Treatment Rule, the Interim Enhanced Surface Water Treatment Rule and the Long Term 1 Enhanced Surface Water Treatment Rule. EPA requests comments on the eight NPDWRs identified as candidates for revision and will consider comments and data as it proceeds with determining whether further action is needed. In addition, as part of this Six-Year Review, EPA identified 12 other NPDWRs that were or continue to be addressed in recently completed, ongoing or pending regulatory actions. EPA thus excluded those 12 NPDWRs from detailed review. This document is not a final regulatory decision, but rather the initiation of a process that will involve more detailed analyses of factors relevant to deciding whether a rulemaking to revise an NPDWR should be initiated. DATES: Comments must be received on or before March 13, 2017. sradovich on DSK3GMQ082PROD with PROPOSALS3 SUMMARY: VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Submit your comments, identified by Docket ID No. EPA–HQ– OW–2016–0627, to the Federal eRulemaking Portal: https:// www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or withdrawn. EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission (i.e. on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https:// www2.epa.gov/dockets/commentingepa-dockets. Mail: Water Docket, Environmental Protection Agency, Mail code: 2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460. Hand Delivery: EPA Docket Center Public Reading Room, EPA Headquarters West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. Hand deliveries are only accepted during the Docket’s normal hours of operation, and special arrangements should be made for deliveries of boxed information. FOR FURTHER INFORMATION CONTACT: For technical inquiries contact: Richard Weisman, (202) 564–2822, or Kesha Forrest, (202) 564–3632, Office of Ground Water and Drinking Water, Environmental Protection Agency. For general information about the existing NPDWRs discussed in this action, contact the Safe Drinking Water Hotline. Callers within the United States may reach the Hotline at (800) 426–4791. The Hotline is open Monday through Friday, excluding Federal holidays, from 10 a.m. to 5:30 p.m. Eastern Time. SUPPLEMENTARY INFORMATION: ADDRESSES: ENVIRONMENTAL PROTECTION AGENCY Abbreviations and Acronyms Used in This Action ADWR—Aircraft Drinking Water Rule AGI—Acute Gastrointestinal Illness AOC—Assimilable Organic Carbon ASDWA—Association of State Drinking Water Administrators ATSDR—Agency for Toxic Substances and Disease Registry PO 00000 Frm 00002 Fmt 4701 Sfmt 4702 AWWA—American Water Works Association BAT—Best Available Technology CBI—Confidential Business Information CDC—Centers for Disease Control and Prevention CFR—Code of Federal Regulations CT—Concentration × Contact Time cVOCs—Carcinogenic Volatile Organic Compounds CWS—Community Water System DBCP—1,2-Dibromo-3-Chloropropane DBP—Disinfection Byproducts D/DBP—Disinfectants/Disinfection Byproducts D/DBPR—Disinfectants/Disinfection Byproducts Rule DEHA—Di(2-ethylhexyl)adipate DEHP—Di(2-ethylhexyl)phthalate DOC—Dissolved Organic Carbon DPD—N,N-diethyl-p-phenylenediamine EDB—Ethylene Dibromide EJ—Environmental Justice EO—Executive Order EPA—U.S. Environmental Protection Agency EQL—Estimated Quantitation Level FAC—Federal Advisory Committee FBRR—Filter Backwash Recycling Rule FDA—U.S. Food and Drug Administration FRN—Federal Register Notice GAC—Granulated Activated Carbon GWR—Ground Water Rule GWUDI—Ground Water Under the Direct Influence of Surface Water HAA5—Haloacetic Acids (five) (sum of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid) HAAs—Haloacetic Acids HAV—Hepatitis A Virus HPC—Heterotrophic Plate Count IARC—International Agency for Research on Cancer ICR—Information Collection Request IESWTR—Interim Enhanced Surface Water Treatment Rule IRIS—Integrated Risk Information System LT1—Long-Term 1 Enhanced Surface Water Treatment Rule LT2—Long-Term 2 Enhanced Surface Water Treatment Rule MCL—Maximum Contaminant Level MCLG—Maximum Contaminant Level Goal MDBP—Microbial and Disinfection Byproducts MDL—Method Detection Limit MRDL—Maximum Residual Disinfectant Level MRDLG—Maximum Residual Disinfectant Level Goal MRL—Minimum Reporting Level NAS—National Academy of Sciences NCWS—Non-Community Water System NDMA—N-Nitrosodimethylamine NDWAC—National Drinking Water Advisory Council NIH—National Institutes of Health NPDWR—National Primary Drinking Water Regulation NRC—National Research Council NTNCWS—Non-Transient Non-Community Water System NTP—National Toxicology Program PCBs—Polychlorinated Biphenyls PCE—Tetrachloroethylene PHS—U.S. Public Health Service E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules PT—Proficiency Testing PQL—Practical Quantitation Limit PWS—Public Water System qPCR—Quantitative Polymerase Chain Reaction RfD—Reference Dose RICP—Research and Information Collection Partnership RSC—Relative Source Contribution RTCR—Revised Total Coliform Rule SDWA—Safe Drinking Water Act SMCL—Secondary Maximum Contaminant Level SOC—Synthetic Organic Chemical SWTR—Surface Water Treatment Rule SWTRs—Surface Water Treatment Rules (including SWTR, IESWTR and LT1) SYR—Six-Year Review TCE—Trichloroethylene TC/EC—Total Coliforms/E. coli TCR—Total Coliform Rule THM—Trihalomethanes TTHM—Total Trihalomethanes (sum of four THMs: chloroform, bromodichloromethane, dibromochloromethane and bromoform) TNCWS—Transient Non-Community Water System TOC—Total Organic Carbon TT—Treatment Technique UCFWR—Uncovered Finished Water Reservoirs UCMR—Unregulated Contaminant Monitoring Rule USGS—U.S. Geological Survey UV—Ultraviolet WBDOSS—Waterborne Disease Outbreak Surveillance System WHO—World Health Organization sradovich on DSK3GMQ082PROD with PROPOSALS3 Table of Contents I. General Information A. Does this action apply to me? B. What should I consider as I prepare my comments for EPA? II. Statutory Requirements for the Six-Year Review III. Stakeholder Involvement in the Six-Year Review Process IV. Regulations Included in the Six-Year Review 3 V. EPA’s Protocol for Reviewing the NPDWRs Included in This Action A. What was EPA’s review process? B. How did EPA conduct the review of the NPDWRs? 1. Initial Review 2. Health Effects 3. Analytical Feasibility 4. Occurrence and Exposure Analysis 5. Treatment Feasibility 6. Risk-Balancing 7. Other Regulatory Revisions C. How did EPA factor children’s health concerns into the review? D. How did EPA factor environmental justice concerns into the review? VI. Results of EPA’s Review of NPDWRs A. What are the review result categories? 1. The NPDWR is Not Appropriate for Revision at This Time 2. The NPDWR is a Candidate for Revision B. What are the detailed results of EPA’s third six-year review cycle? 1. Chemical Phase Rules/Radionuclides Rules VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 2. Fluoride 3. Disinfectants/Disinfection Byproducts Rules (D/DBPRs) 4. Microbial Contaminants Regulations VII. EPA’s Request for Comments References I. General Information A. Does this action apply to me? This action itself does not impose any requirements on individual people or entities. Instead, it notifies interested parties of EPA’s review of existing national primary drinking water regulations (NPDWRs) and its conclusions about which of these NPDWRs may warrant new regulatory action at this time. EPA requests public comment on the eight NPDWRs identified as candidates for revision. EPA will consider comments received as the Agency moves forward with determining whether regulatory actions are necessary for the eight NPDWRs. B. What should I consider as I prepare my comments for EPA? Please see Section VII for the topic areas related to this document for which EPA requests comment and/or information. EPA will accept written or electronic comments (please do not send both). Instructions for submitting comments can be found in the ADDRESSES section of this document. EPA prefers electronic comments. No facsimiles (faxes) will be accepted. Commenters who want EPA to acknowledge receipt of their written comments should also send a selfaddressed, stamped envelope. You may find the following suggestions helpful when preparing your comments: • Explain your views as clearly as possible. • Describe any assumptions that you used. • Provide any technical information and/or data you used that support your views. • If you estimate potential burden or costs, explain how you arrived at your estimate. • Provide specific examples to illustrate your concerns. • Offer alternatives. • Make sure to submit your comments by the comment period deadline. To ensure proper receipt by EPA, identify the appropriate docket identification number in the subject line on the first page of your response. It would also be helpful if you provide the name, date, and volume/page numbers of the Federal Register document you are commenting on. PO 00000 Frm 00003 Fmt 4701 Sfmt 4702 3519 II. Six-Year Review—Statutory Requirements and Next Steps Under the Safe Drinking Water Act (SDWA), as amended in 1996, EPA must periodically review existing NPDWRs and, if appropriate, revise them. Section 1412(b)(9) of the SDWA states: ‘‘The Administrator shall, not less often than every six years, review and revise, as appropriate, each national primary drinking water regulation promulgated under this title. Any revision of a national primary drinking water regulation shall be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons.’’ Pursuant to the 1996 SDWA Amendments, EPA completed and published the results of its first Six-Year Review (Six-Year Review 1) on July 18, 2003 (68 FR 42908, USEPA, 2003b) and the second Six-Year Review (Six-Year Review 2) on March 29, 2010 (75 FR 15500, USEPA, 2010h), after developing a systematic approach, or protocol, for the review of NPDWRs. In this document EPA is announcing the results of the third Six-Year Review (Six-Year Review 3). Consistent with the process applied in the Six-Year Review 2, EPA is requesting comments on this document and will consider the public comments and/or any new, relevant data submitted for the eight NPDWRs listed as candidates for revision as the Agency proceeds with determining whether revisions of these regulations are necessary. The announcement whether or not the Agency intends to revise an NPDWR (pursuant to SDWA § 1412(b)(9)) is not a regulatory decision. Instead, it initiates a process that will involve more detailed analyses of health effects, analytical and treatment feasibility, occurrence, benefits, costs and other regulatory matters relevant to deciding whether a rulemaking to revise an NPDWR should be initiated. The Six-Year Review results do not obligate the Agency to revise an NPDWR in the event that EPA determines during the regulatory process that revisions are no longer appropriate and discontinues further efforts to revise the NPDWR. Similarly, the fact that an NPDWR has not been selected for revision means only that EPA believes that regulatory changes to a particular NPDWR are not appropriate at this time for the reasons given in this action; future reviews may identify information that leads to an initiation of the revision process. The reasons that EPA has identified an NPDWR as a ‘‘candidate for revision’’ E:\FR\FM\11JAP3.SGM 11JAP3 3520 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules is that, at a minimum, the revision presents a meaningful opportunity to: • Improve the level of public health protection, and/or • Achieve cost savings while maintaining or improving the level of public health protection. III. Stakeholder Involvement in the SixYear Review Process The Agency has involved interested stakeholders in the Six-Year Review 3 process. Below are examples of such involvement: • In November 2014, EPA briefed the National Drinking Water Advisory Council (NDWAC) on the Six-Year Review protocol and the key elements of that protocol as they relate to the microbial and disinfection byproducts (MDBP) rules. The briefing included information on how EPA is implementing NDWAC’s previous recommendations (NDWAC, 2000) on the Six-Year Review process in review of the MDBP rules; • In January 2015, states provided input (through the Association of State Drinking Water Administrators (ASDWA)) on rule implementation issues related to the NPDWRs being reviewed as part of the SixYear Review 3 (ASDWA, 2016); • EPA initiated a series of public stakeholder meetings about the review of the Long Term 2 Enhanced Surface Water Treatment Rule (LT2). These meetings were held in accordance with the recommendation of the MDBP Federal Advisory Committee (FAC) 1 to have public meetings following the first round of monitoring under the LT2, and as a result of the Executive Order (E.O.) 13563 ‘‘Improving Regulation and Regulatory Review.’’ 2 E.O. 13563 states that regulations shall be based ‘‘on the open exchange of information and perspectives among state, local, and tribal officials, experts in relevant disciplines, affected stakeholders in the private sector, and the public as a whole.’’ Some affected stakeholders recommended that EPA include the LT2 among the Agency’s top priorities for review under E.O. 13563. EPA included the LT2 in its ‘‘Improving our Regulations: Final Plan for Periodic Retrospective Review of Existing Regulations’’ (USEPA, 2011). EPA agreed to ‘‘assess and analyze new data/information regarding occurrence, treatment, analytical methods, health effects, and risk from all relevant waterborne pathogens to evaluate whether there are new or additional ways to manage risk while assuring equivalent or improved protection, including with respect to the covering of finished water reservoirs’’ (USEPA, 2011). EPA hosted three public meetings in Washington, DC, on December 7, 2011, April 24, 2012 and November 15, 2012. EPA presented information about: The LT2 requirements, monitoring data collected under the LT2, analytical methods, forecasts about the second round of monitoring and the treatment technique requirements. In addition to presentations to educate the public, the meetings included public statements, panel discussions, question and answer sessions and requests by EPA to provide data and information about the implementation of the LT2 to inform the regulatory review. IV. Regulations Included in the SixYear Review 3 Table IV–1 lists all 88 NPDWRs established to date. The table also reports the maximum contaminant level goal (MCLG) and the maximum contaminant level (MCL). The MCLG is ‘‘set at the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety’’ (SDWA § 1412(b)(4)). The MCL is the maximum permissible level of a contaminant in water delivered to any user of a public water system (PWS) and generally ‘‘is as close to the maximum contaminant level goal as is feasible’’ (SDWA § 1412(b)(4)(B)).3 Where it is not ‘‘economically or technically feasible’’ to set an MCL, EPA can establish a treatment technique (TT), which must prevent adverse health effects ‘‘to the extent feasible’’ (SDWA § 1412(b)(7)(A)). In the case of disinfectants (e.g., chlorine, chloramines and chlorine dioxide), the values reported in the table are not MCLGs and MCLs, but maximum residual disinfectant level goals (MRDLGs) and maximum residual disinfectant levels (MRDLs). Table IV–1 also includes NPDWRs that EPA identified as candidates for revision in past Six-Year Reviews. During the Six-Year Review 1, EPA identified the Total Coliform Rule (TCR) as a candidate for revision.4 EPA published the Revised Total Coliform Rule (RTCR) in 2013 (78 FR 10270, USEPA, 2013a). Four additional NPDWRs for acrylamide, epichlorohydrin, tetrachloroethylene (PCE) and trichloroethylene (TCE) were identified as candidates for revision during the Six-Year Review 2. Of the 88 NPDWRs, EPA identified 12 as part of recently completed, ongoing or pending regulatory actions; as a result, these 12 are not subject to a detailed review for the Six-Year Review 3. This action involves the remaining 76 NPDWRs. EPA applied the same protocol used for previous Six-Year Reviews, with minor clarifications (USEPA, 2016f), to the Six-Year Review 3 process. Section V of this action describes the revised protocol used for the Six-Year Review 3 and Section VI describes the results of the review of the NPDWRs. In addition to the regulated chemicals, radiological and microbiological contaminants included in the previous reviews, this document also includes the review of the MDBP regulations that were promulgated under the following actions: The Ground Water Rule (GWR); the Surface Water Treatment Rules (SWTRs); the Disinfectants and Disinfection Byproducts (D/DBP) Rules; and the Filter Backwash Recycling Rule (FBRR). EPA reviewed the LT2 in response to EO 13563 (USEPA, 2011) and as part of the Six-Year Review 3 process. TABLE IV–1—NPDWRS INCLUDED IN SIX-YEAR REVIEW 3 MCLG (mg/L) 1 3 MCL or TT (mg/L) 1 2 3 Contaminants/parameters MCLG (mg/L) 1 3 Acrylamide ......................... Alachlor .............................. Alpha/photon emitters ........ Antimony ............................ Arsenic ............................... sradovich on DSK3GMQ082PROD with PROPOSALS3 Contaminants/parameters 0 ................................ 0 ................................ 0 (pCi/L) .................... 0.006 ......................... 0 ................................ TT .............................. 0.002 ......................... 15 (pCi/L) .................. 0.006 ......................... 0.010 ......................... Ethylbenzene ..................... Ethylene dibromide (EDB) Fluoride .............................. Giardia lamblia 4 ................ Glyphosate ......................... 0.7 .................... 0 ....................... 4.0 .................... 0 ....................... 0.7 .................... 1 https://www.epa.gov/sites/production/files/ 2015-11/documents/stage_2_m-dbp_agreement_in_ principle.pdf. 2 E.O. 13563 requires federal agencies to ‘‘consider how best to promote retrospective analysis of rules that may be outmoded, ineffective, insufficient, or excessively burdensome, and to modify, streamline, expand, or repeal them in accordance with what has been learned.’’ The order required each federal agency to develop a plan ‘‘consistent with law and its resources and VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 regulatory priorities.’’ https://www.gpo.gov/fdsys/ pkg/FR-2011-01-21/pdf/2011-1385.pdf. 3 Under limited circumstances, SDWA § 1412(b)(6)(A) also gives the Administrator the discretion to promulgate an MCL that is less stringent than the feasible level and that ‘‘maximizes health risk reduction benefits at a cost that is justified by the benefits.’’ 4 The NPDWRs apply to specific contaminants/ parameters or groups of contaminants. Historically, PO 00000 Frm 00004 Fmt 4701 Sfmt 4702 MCL or TT (mg/L) 2 3 0.7 0.00005 4.0 TT 0.7 when issuing new or revised standards for these contaminants/parameters, EPA has often grouped the standards together in more general regulations, such as the Total Coliform Rule, the Surface Water Treatment Rule or the Phase V rules. In this action, however, for clarity, EPA discusses the drinking water standards as they apply to each specific regulated contaminant/parameter (or group of contaminants), not the more general regulation in which the contaminant/parameter was regulated. E:\FR\FM\11JAP3.SGM 11JAP3 3521 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules TABLE IV–1—NPDWRS INCLUDED IN SIX-YEAR REVIEW 3—Continued MCL or TT (mg/L) 2 3 MCLG (mg/L) 1 3 MCL or TT (mg/L) 1 2 3 Contaminants/parameters MCLG (mg/L) 1 3 Asbestos ............................ Atrazine .............................. Barium ................................ Benzene ............................. Benzo[a]pyrene .................. Beryllium ............................ Beta/photon emitters .......... Bromate ............................. Cadmium ............................ Carbofuran ......................... Carbon tetrachloride .......... Chloramines ....................... 7 (million fibers/L) ...... 0.003 ......................... 2 ................................ 0 ................................ 0 ................................ 0.004 ......................... 0 (millirems/yr) ........... 0 ................................ 0.005 ......................... 0.04 ........................... 0 ................................ 4 ................................ 7 (million fibers/L) ...... 0.003 ......................... 2 ................................ 0.005 ......................... 0.0002 ....................... 0.004 ......................... 4 (millirems/yr) ........... 0.010 ......................... 0.005 ......................... 0.04 ........................... 0.005 ......................... 4.0 ............................. 0.060 0.0004 0.0002 TT 0.001 0.05 TT TT 0.0002 0.002 0.04 0.1 0 ................................ 4 ................................ 0.8 ............................. 0.8 ............................. 0.1 ............................. 1.3 ............................. 0.002 ......................... 4.0 ............................. 0.8 ............................. 1.0 ............................. 0.1 ............................. TT .............................. 10 ..................... 1 ....................... 0.2 .................... 0 ....................... 0.5 .................... 0 ....................... 10 1 0.2 0.001 0.5 0.0005 Cryptosporidium ................. Cyanide .............................. 2,4-Dichlorophenoxyacetic acid (2,4-D). Dalapon .............................. Di(2-ethylhexyl)adipate (DEHA). Di(2-ethylhexyl)phthalate (DEHP). 1,2-Dibromo-3chloropropane (DBCP). 1,2-Dichlorobenzene (oDichlorobenzene). 1,4-Dichlorobenzene (pDichlorobenzene). 1,2-Dichloroethane (Ethylene dichloride). 1,1-Dichloroethylene .......... cis-1,2-Dichloroethylene .... trans-1,2-Dichloroethylene Dichloromethane (Methylene chloride). 1,2-Dichloropropane .......... Dinoseb .............................. Diquat ................................ E. coli ................................. Endothall ............................ Endrin ................................ Epichlorohydrin .................. 0 ................................ 0.2 ............................. 0.07 ........................... TT .............................. 0.2 ............................. 0.07 ........................... Haloacetic acids (HAA5) ... Heptachlor ......................... Heptachlor epoxide ............ Heterotrophic bacteria 6 ..... Hexachlorobenzene ........... Hexachlorocyclopentadiene Lead ................................... Legionella .......................... Lindane .............................. Mercury (inorganic) ............ Methoxychlor ..................... Monochlorobenzene (Chlorobenzene). Nitrate (as N) ..................... Nitrite (as N) ...................... Oxamyl (Vydate) ................ Pentachlorophenol ............. Picloram ............................. Polychlorinated biphenyls (PCBs). Radium .............................. Selenium ............................ Simazine ............................ n/a 5 .................. 0 ....................... 0 ....................... n/a .................... 0 ....................... 0.05 .................. 0 ....................... 0 ....................... 0.0002 .............. 0.002 ................ 0.04 .................. 0.1 .................... Chlordane .......................... Chlorine .............................. Chlorine dioxide ................. Chlorite ............................... Chromium (total) ................ Copper ............................... sradovich on DSK3GMQ082PROD with PROPOSALS3 Contaminants/parameters 0 (pCi/L) ........... 0.05 .................. 0.004 ................ 5 (pCi/L) 0.05 0.004 0.2 ............................. 0.4 ............................. 0.2 ............................. 0.4 ............................. Styrene .............................. 2,3,7,8-TCDD (Dioxin) ....... 0.1 .................... 0 ....................... 0.1 3.00E–08 0 ................................ 0.006 ......................... Tetrachloroethylene ........... 0 ....................... 0.005 0 ................................ 0.0002 ....................... Thallium ............................. 0.0005 .............. 0.002 0.6 ............................. 0.6 ............................. Toluene .............................. 1 ....................... 1 0.075 ......................... 0.075 ......................... n/a .................... TT 0 ................................ 0.005 ......................... n/a 9 .................. 0.080 0.007 ......................... 0.07 ........................... 0.1 ............................. 0 ................................ 0.007 ......................... 0.07 ........................... 0.1 ............................. 0.005 ......................... Total coliforms (under ADWR 7 and RTCR 8). Total Trihalomethanes (TTHM). Toxaphene ......................... 2,4,5-TP (Silvex) ................ 1,2,4-Trichlorobenzene ...... 1,1,1-Trichloroethane ......... 0 ....................... 0.05 .................. 0.07 .................. 0.20 .................. 0.003 0.05 0.07 0.2 0 ................................ 0.007 ......................... 0.02 ........................... 0 ................................ 0.1 ............................. 0.002 ......................... 0 ................................ 0.005 ......................... 0.007 ......................... 0.02 ........................... MCL 10 and TT 8 ........ 0.1 ............................. 0.002 ......................... TT .............................. 1,1,2-Trichloroethane ......... Trichloroethylene ............... Turbidity 6 ........................... Uranium ............................. Vinyl Chloride .................... Viruses ............................... Xylenes (total) .................... 0.003 ................ 0 ....................... n/a .................... 0 ....................... 0 ....................... 0 ....................... 10 ..................... 0.005 0.005 TT 0.030 0.002 TT 10 1. MCLG: The maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, allowing an adequate margin of safety. 2. MCL: The maximum level allowed of a contaminant in water which is delivered to any user of a public water system. TT: An enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant. 3. Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million. For chlorine, chloramines and chlorine dioxide, values presented are MRDLG and MRDL. 4. The current preferred taxonomic name is Giardia duodenalis, with Giardia lamblia and Giardia intestinalis as synonymous names. However, Giardia lamblia was the name used to establish the MCLG in 1989. Elsewhere in this document, this pathogen will be referred to as Giardia spp. or simply Giardia unless discussing information on an individual species. 5. There is no MCLG for all five haloacetic acids. MCLGs for some of the individual contaminants are: Dichloroacetic acid (zero), trichloroacetic acid (0.02 mg/L), and monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated with this group, but have no MCLGs. 6. Includes indicators that are used in lieu of direct measurements (e.g., of heterotrophic bacteria, turbidity). 7. The Aircraft Drinking Water Rule (ADWR) 40 CFR part 141 Subpart X, promulgated October 19, 2009, covers total coliforms. 8. Under the RTCR, a PWS is required to conduct an assessment if it exceeded any of the TT triggers identified in 40 CFR 141.859(a). It is also required to correct any sanitary defects found through the assessment. 9. There is no MCLG for total trihalomethanes (TTHM). MCLGs for some of the individual contaminants are: Bromodichloromethane (zero), bromoform (zero), dibromochloromethane (0.06 mg/L), and chloroform (0.07 mg/L). 10. A PWS is in compliance with the E. coli MCL unless any of the conditions identified under 40 CFR 141.63(c) occur. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 PO 00000 Frm 00005 Fmt 4701 Sfmt 4702 E:\FR\FM\11JAP3.SGM 11JAP3 3522 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules V. EPA’s Protocol for Reviewing the NPDWRs Included in This Action A. What was EPA’s review process? sradovich on DSK3GMQ082PROD with PROPOSALS3 Overview This section provides an overview of the process the Agency used to review the NPDWRs discussed in this action. The protocol document, ‘‘EPA Protocol for the Third Review of Existing National Primary Drinking Water Regulations,’’ contains a detailed description of the process the Agency used to review the NPDWRs (USEPA, 2016f). The foundation of this protocol was developed for the Six-Year Review 1 based on the recommendations of the NDWAC (2000). The Six-Year Review 3 process is very similar to the process implemented during the Six-Year Review 1 and the Six-Year Review 2, with some clarifications to the elements related to the review of NPDWRs included in the MDBP rules. Figure V– 1 presents an overview of the Six-Year review protocol and review outcomes. The primary goal of the Six-Year Review process is to identify and prioritize NPDWRs for possible regulatory revision. The two major outcomes of the detailed review are either: 1. The NPDWR is not appropriate for revision and no action is necessary at this time. 2. The NPDWR is a candidate for revision. The reasons for a Six-Year Review outcome of ‘‘not appropriate for revision at this time’’ can include: • Regulatory action—recently completed, ongoing or pending. The NPDWR was recently completed, is being reviewed in an ongoing action, or is subject to a pending action. • Ongoing or planned health effects assessment. The NPDWR has an ongoing health effects assessment (i.e., especially for those NPDWRs with an MCL set at the MCLG or where the MCL is based on the SDWA cost benefit provision), or EPA is considering whether a new health effects assessment is needed. • No new information. EPA did not identify any new, relevant information that indicates changes to the NPDWR. • Data gaps/emerging information. There are data gaps or emerging information that need to be evaluated. • Low priority and/or no meaningful opportunity. New information indicates a possible change to the MCLG and/or MCL but changes to the NPDWR are not warranted due to one or more of the following reasons: (1) Possible changes VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 present negligible gains in public health protection; (2) possible changes present limited opportunity for cost savings while maintaining the same or greater level of health protection; and (3) possible changes are a low priority because of competing workload priorities, limited return on the administrative costs associated with rulemaking and the burden on states and the regulated community associated with implementing any regulatory change that would result. Alternatively, the reasons for a SixYear Review outcome that an NPDWR is a ‘‘candidate for revision’’ are that, at a minimum, the revision presents a meaningful opportunity to: • Improve the level of public health protection, and/or • Achieve cost savings while maintaining or improving the level of public health protection. Individual regulatory provisions of NPDWRs that are evaluated as part of the Six-Year Review are: MCLG, MCL, MRDLG, MRDL, TT, other treatment technologies such as best available technology (BAT), and regulatory requirements, such as monitoring requirements. For example, the microbial regulations include TT requirements because there is no reliable method that is economically and technically feasible to measure the microbial contaminants covered by those regulations. These TT requirements rely on the use of indicators that can be measured in drinking water, such as the concentration of a disinfectant, to provide public health protection. As part of the Six-Year Review 3, EPA evaluated new information related to the use of those indicators to determine if there is a meaningful opportunity to improve the level of public health protection. Results of EPA’s review of the MDBP regulations are presented in Sections VI.B.3 and VI.B.4. For the purpose of this document (except where noted for clarity), discussions of the review of MCLGs and MCLs should be assumed to also apply to the review of MRDLGs and MRDLs for disinfectants. Basic Principles EPA applied a number of basic principles to the Six-Year Review process: • The Agency sought to avoid redundant review efforts. Because EPA has reviewed information for certain NPDWRs as part of recently completed, ongoing or pending regulatory actions, PO 00000 Frm 00006 Fmt 4701 Sfmt 4702 these NPDWRs are not subject to the detailed review in this document. • The Agency does not believe it is appropriate to consider revisions to NPDWRs for contaminants with an ongoing or planned health effect assessment and for which the MCL is set equal to the MCLG or based on benefitcost analysis. This principle stems from the fact that any new health effects information could affect the MCL via a change in the MCLG or the assessment of the benefits associated with the MCL. Therefore, EPA noted that these NPDWRs are not appropriate for revision and no action is necessary at this time if the health effects assessment would not be completed during the review period for each contaminant that has either an MCL that is equal to its MCLG or an MCL that is based on the 1996 SDWA Amendments’ cost-benefit provision. If the health effects assessment is completed before the next Six-Year Review, EPA will consider these NPDWRs at that time. • In evaluating the potential for new information to affect NPDWRs, EPA assumed no change to existing policies and procedures for developing NPDWRs. For example, in determining whether new information affected the feasibility of analytical methods for a contaminant, the Agency assumed no change to current policies and procedures for calculating practical quantitation levels. • EPA considered new information from health effects assessments that were completed by the information cutoff date. Assessments completed after this cutoff date will be reviewed by EPA during the next review cycle or (if applicable) during the revision of an NPDWR. The information cutoff date for the Six-Year Review 3 was December 2015. • During the review, EPA identified areas where information is inadequate or unavailable (data gaps) or emerging and is needed to determine whether revision to an NPDWR is appropriate. To the extent EPA is able to fill data gaps or fully evaluate the emerging information, the Agency will consider the information as part of the next review cycle. • EPA may consider accelerating review and potential revision for a particular NPDWR before the next review cycle when justified by new public health risk information. • Finally, EPA assured scientific analyses supporting the review were consistent with the Agency’s peer review policy (USEPA, 2015a). E:\FR\FM\11JAP3.SGM 11JAP3 B. How did EPA conduct the review of the NPDWRs? The protocol for the Six-Year Review 3 is broken down into a series of questions that can inform a decision about the appropriateness of revising an NPDWR. These questions are logically ordered into a decision tree. This section provides an overview of each of the review elements that EPA considered for each NPDWR during the Six-Year Review 3, including the following: Initial review, health effects, analytical feasibility, occurrence and exposure, treatment feasibility, risk balancing and other regulatory revisions. The final review combines the findings from all of these review elements to recommend whether an NPDWR is a candidate for revision. Further information about the review elements is described in the protocol document (USEPA, 2016f). Results from the review of these elements are presented in Section VI. 1. Initial Review EPA’s initial review of all the contaminants included in the Six-Year Review 3 involved a simple identification of the NPDWRs that have either been recently completed, or are being reviewed in an ongoing or pending action since the last Six-Year VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 3523 Review (cutoff date was August 2008). In addition, the initial review also identified contaminants with ongoing health effects assessments that have an MCL equal to the MCLG. Excluding such contaminants from the Six-Year Review 3 prevents duplicative agency efforts. toxicity data, that could potentially affect the MCLG, or otherwise change the Agency’s understanding of the health effects of contaminants under consideration. EPA then evaluated the need to plan the initiation of a new health effects assessment. 2. Health Effects When establishing an NPDWR, EPA identifies a practical quantitation limit (PQL), which is ‘‘the lowest achievable level of analytical quantitation during routine laboratory operating conditions within specified limits of precision and accuracy’’, as noted in the November 13, 1985, Federal Register proposed rule (50 FR 46880, USEPA, 1985). EPA has a separate process in place to approve new analytical methods for drinking water contaminants; therefore, review and approval of potential new methods is outside the scope of the Six-Year Review protocol. EPA recognizes, however, that the approval and adoption in recent years of new and/or improved analytical methods may enable laboratories to quantify contaminants at lower levels than was possible when NPDWRs were originally promulgated. This ability of laboratories to measure a contaminant at lower levels could affect its PQL, the value at which an MCL is set when it is limited The principal objectives of the health effects review are to identify: (1) Contaminants for which a new health effects assessment indicates that a change in the MCLG might be appropriate (e.g., because of a change in cancer classification or a change in reference dose (RfD)), and (2) contaminants for which new health effects information indicates a need to initiate a new health effects assessment. To meet the first objective, EPA reviewed the results of health effects assessments completed before December 2015, the information cutoff date for the Six-Year Review 3. To meet the second objective, the Agency conducted an extensive literature review to identify peerreviewed studies published before December 2015. The Agency reviewed the studies to determine whether there was new health effects information, such as reproductive and developmental PO 00000 Frm 00007 Fmt 4701 Sfmt 4702 3. Analytical Feasibility E:\FR\FM\11JAP3.SGM 11JAP3 EP11JA17.006</GPH> sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules 3524 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 by analytical feasibility. Therefore, the Six-Year Review process includes an examination of whether there have been changes in analytical feasibility that could possibly change the PQL for the subset of the NPDWRs that reached this stage of the review. To determine if changes in analytical feasibility could possibly support changes to PQLs, EPA relied primarily on two alternate approaches to develop an estimated quantitation limit (EQL): an approach based on the minimum reporting levels (MRLs) obtained as part of the Six-Year Review 3 Information Collection Request (ICR), and an approach based on method detection limits (MDLs). An MRL is the lowest level or contaminant concentration that a laboratory can reliably achieve within specified limits of precision and accuracy under routine laboratory operating conditions using a given method. The MRL values provide direct evidence from actual monitoring results about whether quantitation below the PQL using current analytical methods is feasible. An MDL is a measure of analytical method sensitivity. MDLs have been used in the past to derive PQLs for regulated contaminants. EPA used the EQL as a threshold for occurrence analysis to help the Agency determine if there may be a meaningful opportunity to improve public health protection. It should be noted, however, that the use of an EQL does not necessarily indicate the Agency’s intention to promulgate a new PQL. Any revision to PQLs will be part of future rulemaking efforts if EPA has determined that an NPDWR is a candidate for revision. USEPA, 2010a). EPA requested that all states and primacy entities (tribes and territories) voluntarily submit their compliance monitoring data for regulated contaminants in public drinking water systems. Specifically, EPA requested the submission of compliance monitoring data and related information collected between January 2006 and December 2011 for regulated contaminants and related parameters (e.g., water quality indicators). Forty-six states plus eight primacy agencies provided data. The assembled data constitute the largest, most comprehensive set of drinking water compliance monitoring data ever compiled and analyzed by EPA to inform decision making, containing almost 47 million records from approximately 167,000 PWSs, serving approximately 290 million people nationally. Through extensive data management efforts, quality assurance evaluations, and communications with state data management staff, EPA established the SYR3 ICR database (USEPA, 2016i). The number of states and PWSs represented in the dataset varies across contaminants because of variability in state data submissions and contaminant monitoring schedules. Except as noted in Section VI, EPA believes that these data are of sufficient quality to inform an understanding of the national occurrence of regulated contaminants and related parameters. Details of the data management and data quality assurance evaluations are available in the supporting document (USEPA, 2016q). The resulting database is available online on the Six-Year Review Web site (https://www.epa.gov/ dwsixyearreview). 4. Occurrence and Exposure Analysis The occurrence and exposure analysis is conducted in conjunction with other review elements to determine if there is a meaningful opportunity to revise an NPDWR by: • Estimating the extent of contaminant occurrence, i.e., the number of PWSs in which contaminants occur at levels of interest (health-effectsbased thresholds or analytical method limits), and • Evaluating the number of people potentially exposed to contaminants at these levels. To evaluate national contaminant occurrence under the Six-Year Review 3, EPA reviewed data from the Six-Year Review 3 ICR database (SYR3 ICR database), the UCMR datasets (USEPA, 2016j) and other relevant sources. For the Six-Year Review 3, EPA collected SDWA compliance monitoring data through use of an ICR (75 FR 6023, 5. Treatment Feasibility An NPDWR either identifies the BAT for meeting an MCL, or establishes enforceable TT requirements. EPA reviews treatment feasibility to ascertain if there are technologies that meet BAT criteria for a hypothetical more stringent MCL, or if there is new information that demonstrates an opportunity to improve public health protection through revision of an NPDWR TT requirement. To be a BAT, the treatment technology must meet several criteria such as having demonstrated consistent removal of the target contaminant under field conditions. Although treatment feasibility and analytical feasibility together address the technical feasibility requirement for an MCL, historically, treatment feasibility has not been a limiting factor for MCLs. The result of this review element is a determination of whether treatment feasibility would pose a limitation to revising an MCL or VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 PO 00000 Frm 00008 Fmt 4701 Sfmt 4702 provide an opportunity to revise the TT requirement. 6. Risk-Balancing EPA reviews risk-balancing to examine how the Six-Year Review can address tradeoffs in risks among different NPDWRs and take into account unregulated contaminants as well. Under this review, EPA considers whether a change to an MCL and/or TT will increase the public health risk posed by one or more contaminants, and, if so, the Agency considers revisions that will balance overall risks. This review element is relevant only to the NPDWRs included in the MDBP rules, which were promulgated to address risk-balancing between microbial and DBP requirements, and among differing types of DBPs. The riskbalancing approach was based on the SDWA requirements that EPA ‘‘minimize the overall risk of adverse health effects by balancing the risk from the contaminant and the risk from other contaminants the concentrations of which may be affected by the use of a TT or process that would be employed to attain the maximum contaminant level or levels’’ (SDWA § 1412(b)(5)(B)(i)). EPA reviewed risk-balancing between microbial and DBP contaminants. For example, EPA considered the potential impact on DBP concentrations should there be a consideration to increase the stringency of microbial NPDWRs. This approach also was used during the development of more recent MDBP rules such as the LT2 rule and the Stage 2 Disinfectants/Disinfection Byproducts Rule (D/DBPR) rule. In addition, EPA reviewed risk-balancing between different types of DBP contaminants. Depending on the stringency of potential DBP regulations, compliance strategies used by the regulated community might have the effect of increasing the concentrations of other types of contaminants, both regulated and unregulated. EPA considered these potential compliance strategies when conducting its Six-Year Review 3 with a goal to balance the overall health risks. 7. Other Regulatory Revisions In addition to possible revisions to MCLGs, MCLs and TTs, EPA evaluated whether other revisions are needed to regulatory provisions, such as monitoring and system reporting requirements. EPA focused this review element on issues that were not already being addressed through alternative mechanisms, such as a recently completed, ongoing or pending regulatory action. EPA also reviewed implementation-related NPDWR E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules concerns that were ‘‘ready’’ for rulemaking—that is, the problem to be resolved had been clearly identified, along with specific options to address the problem that could be shown to either clearly improve the level of public health protection, or represent a meaningful opportunity for achieving cost savings while maintaining the same level of public health protection. The result of this review element is a determination regarding whether EPA should consider revisions to the monitoring and/or reporting requirements of an NPDWR. C. How did EPA factor children’s health concerns into the review? The 1996 amendments to SDWA require special consideration of sensitive life stages and populations (e.g., infants, children, pregnant women, elderly and individuals with a history of serious illness) in the development of drinking water regulations (SDWA § 1412(b)(3)(C)(V)). As a part of the Six- Year Review 3, EPA completed a literature search covering developmental and reproductive endpoints (e.g., fertility, embryo survival, developmental delays, birth defects and endocrine effects) for information published as of December 2015 for regulated chemicals that had not been the subject of a health effects assessment during this review period. EPA reviewed the results of the literature searches to identify any studies that might suggest a need to revise MCLGs. These studies were considered in EPA’s review of NPDWRs, which is discussed in Section VI. D. How did EPA factor environmental justice concerns into the review? Executive Order (E.O.) 12898, ‘‘Federal Actions to Address Environmental Justice in Minority Populations or Low-Income Populations,’’ establishes a federal policy for incorporating environmental justice (EJ) into federal agency missions 3525 by directing agencies to identify and address disproportionately high and adverse human health or environmental effects of its programs, policies and activities on minority and low-income populations. EPA evaluates potential EJ concerns when developing regulations. This Six-Year Review was developed in compliance with E.O. 12898. Should the Six-Year Review lead to a decision to revise an NPDWR, any subsequent rulemakings will include an EJ component and an opportunity for public comment. VI. Results of EPA’s Review of NPDWRs Table VI–1 lists the results of EPA’s review for each of the 76 NPDWRs discussed in this section of this action, along with the principal rationale for the review outcomes. Table VI–1 also includes a list of the 12 NPDWRs that have been recently completed, or have ongoing or pending regulatory actions. TABLE VI–1—SUMMARY OF SIX-YEAR REVIEW 3 RESULTS Not Appropriate for Revision at this Time. Recently completed, ongoing or pending regulatory action. Not Appropriate for Revision at this Time 2. Health effects assessment in process (as of December 2015) or contaminant nominated for health assessment. No new information, NPDWR remains appropriate after review. sradovich on DSK3GMQ082PROD with PROPOSALS3 Low priority and/or no meaningful opportunity. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 1,2-Dichloroethane (Ethylene dichloride) ........... 1,2-Dichloropropane ........................................... Benzene .............................................................. Carbon Tetrachloride .......................................... Copper Dichloromethane (Methylene chloride) ............... Alpha/photon emitters ......................................... Arsenic ................................................................ Atrazine ............................................................... Benzo(a)pyrene (PAHs) ...................................... Beta/photon emitters ........................................... Cadmium 1 .......................................................... Chromium ........................................................... Di(2-ethylhexyl) phthalate (DEHP) 1 ................... Ethylbenzene ...................................................... Glyphosate 1,2-Dibromo-3-chloropropane (DBCP) ............... 2,4,5-TP (Silvex) ................................................. Antimony ............................................................. Asbestos ............................................................. Bromate .............................................................. Chloramines (under D/DBPR) ............................ Chlorine (under D/DBPR) ................................... Chlorine dioxide .................................................. Chlorobenzene (monochlorobenzene) ............... 1,1,1-Trichloroethane .......................................... 1,1,2-Trichloroethane .......................................... 1,1-Dichloroethylene ........................................... 1,2,4-Trichlorobenzene ....................................... 2,3,7,8-TCDD (Dioxin) ........................................ 2,4-D ................................................................... Acrylamide .......................................................... Alachlor ............................................................... Barium Beryllium ............................................................. Carbofuran .......................................................... Chlordane ........................................................... cis-1,2-Dichloroethylene ..................................... Cyanide ............................................................... Diquat .................................................................. Endothall PO 00000 Frm 00009 Fmt 4701 Sfmt 4702 E. coli. Lead. Tetrachloroethylene (PCE). Total coliforms (under ADWR and RTCR). Trichloroethylene (TCE) Vinyl chloride. Mercury 1 Nitrate 1 Nitrite 1 o-Dichlorobenzene 1 p-Dichlorobenzene 1 Polychlorinated biphenyls (PCBs). Radium. Simazine. Uranium 1 Dalapon. Di(2-ethylhexyl)adipate (DEHA). Dinoseb. Endrin. Ethylene dibromide. Pentachlorophenol. Thallium. trans-1,2-Dichloroethylene. Turbidity. Epichlorohydrin. Fluoride. Heptachlor. Heptachlor epoxide. Hexachlorobenzene. Hexachlorocyclopentadiene. Lindane. Methoxychlor. Oxamyl (Vydate). Picloram. Selenium. Styrene. Toluene. Toxaphene. Xylenes. E:\FR\FM\11JAP3.SGM 11JAP3 3526 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules TABLE VI–1—SUMMARY OF SIX-YEAR REVIEW 3 RESULTS—Continued Candidate for Revision New information ......... Chlorite ................................................................ Cryptosporidium (under SWTR, IESWTR, LT1) Giardia lamblia .................................................... Haloacetic Acids (HAA5) .................................... Heterotrophic Bacteria. Legionella. TTHM. Viruses (under SWTR). 1 Contaminants nominated for Integrated Risk Information System (IRIS) assessments per SYR Protocol. FBRR, and GWR also identified as not appropriate for revision at this time. See Section VI.B.4 for additional information on the results of EPA’s review of these regulations. 2 LT2, A. What are the review result categories? For each of the 76 NPDWRs discussed in detail in the following sections of this action, the review outcomes fall in one of the following categories: 1. The NPDWR is Not Appropriate for Revision at This Time The current NPDWR remains appropriate and no action is necessary at this time. In this category, NPDWRs are grouped under the following subcategories: • Health effects assessment in process (as of December 2015) or contaminant nominated for health assessment, • No new information and NPDWR remains appropriate after review, • Data gaps/emerging information, and • No meaningful opportunity. 2. The NPDWR Is a Candidate for Revision The NPDWR is a candidate for revision based on the review of new information. B. What are the detailed results of EPA’s third six-year review cycle? 1. Chemical Phase Rules/Radionuclides Rules Background The NPDWRs for chemical contaminants, collectively called the Phase Rules, were promulgated between 1987 and 1992 (after the 1986 SDWA amendments). In December 2000, EPA promulgated final radionuclide regulations, which were issued as interim rules in July 1976. Information related to the review for fluoride is discussed separately in Section VI.B.2. sradovich on DSK3GMQ082PROD with PROPOSALS3 Summary of Review Results EPA has decided that it is not appropriate at this time to revise any of the NPDWRs covered under the Phase Rules or Radionuclide Rules. These NPDWRs were determined not to be candidates for revision for one or more of the following reasons: There was no VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 new information to suggest possible changes in MCLG/MCL; new information did not present a meaningful opportunity for health risk reduction or cost savings while maintaining/improving public health protection; or there was an ongoing or pending regulatory action. Details related to the review of all Phase Rules and Radionuclide Rules contaminants can be found in the ‘‘Chemical Contaminant Summaries for the Third Six-Year Review of National Primary Drinking Water Regulations’’ (USEPA, 2016b). Initial Review The initial review identified 12 chemical contaminants with NPDWRs under the Chemical Phase Rules that were being considered as part of ongoing or pending regulatory actions, and 61 chemical or radionuclide NPDWRs were identified as appropriate for review. The NPDWRs with ongoing or pending regulatory actions included eight carcinogenic volatile organic compounds (cVOCs), lead, copper, acrylamide and epichlorohydrin. In 2011, EPA announced its plans to address a group of regulated and unregulated cVOCs in a single regulatory effort. The eight regulated VOCs being currently evaluated for a potential cVOCs group regulation include: Benzene; carbon tetrachloride; 1,2-dichloroethane; 1,2dichloropropane; dichloromethane; PCE; TCE; and vinyl chloride. The regulatory revisions to TCE and PCE, initiated as an outcome of the Six-Year Review 2, are also being considered as part of the group regulatory effort. Since a regulatory effort is ongoing for these eight contaminants, they were excluded from a detailed review as part of the third Six-Year Review. The NPDWRs for acrylamide and epichlorohydrin were also previously identified as candidates for regulatory revision and were pending regulatory action. The polyacrylamides and epichlorohydrin-based polymers PO 00000 Frm 00010 Fmt 4701 Sfmt 4702 available today for water treatment have lower residual monomer content than when EPA promulgated residual content as a TT (USEPA, 2016s). For example, the 90th percentile concentration of acrylamide residual monomer levels was approximately one-half the residual level listed in the current TT and no residual epichlorohydrin was detected. The health benefits associated with the lower impurity levels are already being realized by communities throughout the country; therefore, a regulatory revision will minimally affect health risk. Given resource limitations, competing workload priorities, and administrative costs and burden to states to adopt any regulatory changes associated with the rulemaking, as well as limited potential health benefits, these NPDWRs are considered a low priority and no longer candidates for revision at this time. EPA is also currently considering Long-Term Revisions to the Lead and Copper Rule; and therefore, evaluation of that NPDWR under the Six-Year Review process would be redundant. Health Effects The principal objectives of the health effects review are to identify: (1) Contaminants for which a new health effects assessment indicates that a change in MCLG might be appropriate (e.g., because of a change in cancer classification or an RfD), and (2) contaminants for which the Agency has identified new health effects information suggesting a need to initiate a new health effects assessment. Before identifying chemical NPDWR contaminants for which an updated MCLG may be appropriate, EPA first identified chemicals with ongoing or planned EPA health effects assessments. As of December 31, 2015, 19 chemical/ radiological contaminants reviewed had ongoing or planned formal EPA health effects assessments. Table VI–2 below lists the 19 contaminants with ongoing or planned EPA assessments and the status of those reviews. E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules 3527 TABLE VI–2—SIX-YEAR REVIEW CHEMICAL/RADIOLOGICAL CONTAMINANTS WITH ONGOING OR PLANNED EPA HEALTH ASSESSMENTS Chemical/radionuclide Status Alpha/photon emitters ........................................ Arsenic, inorganic ............................................... EPA is conducting a review of alpha and beta photo emitters. Inorganic arsenic is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). Atrazine and simazine are being assessed under EPA’s pesticide registration review process. Benzo(a)pyrene is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). EPA is conducting a review of alpha and beta photo emitters. Cadmium is included in the EPA IRIS Multi-Year Agenda. Chromium VI is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). DEHP is included in the EPA IRIS Multi-Year Agenda. Ethylbenzene is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). GlyphosateGlyphosate is being assessed under EPA’s pesticide registration review process. Mercury is included in the EPA IRIS Multi-Year Agenda. Nitrate is included in the EPA IRIS Multi-Year Agenda. Nitrite is included in the EPA IRIS Multi-Year Agenda. o-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda. p-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda. PCBs are being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). EPA is conducting a review of radium. Atrazine and simazine are being assessed under EPA’s pesticide registration review process. Uranium is included in the EPA IRIS Multi-Year Agenda. Atrazine .............................................................. Benzo(a)pyrene .................................................. Beta/photon emitters .......................................... Cadmium ............................................................ Chromium (VI) as part of total Cr) ..................... DEHP ................................................................. Ethylbenzene ...................................................... Glyphosate ......................................................... Mercury .............................................................. Nitrate ................................................................. Nitrite .................................................................. o-Dichlorobenzene ............................................. p-Dichlorobenzene ............................................. PCBs .................................................................. Radium (226, 228) ............................................. Simazine ............................................................. Uranium .............................................................. For chemicals that were not excluded due to an ongoing or planned health effects assessment by EPA, or by the National Academy of Sciences (NAS), commissioned by EPA, a more detailed review was undertaken. Of the chemicals that underwent a more detailed review, EPA identified 21 for which there have been official Agency changes in the RfD and/or in the cancer risk assessment from oral exposure or new relevant non-EPA assessments that might support a change to the MCLG. These 21 chemicals were further evaluated as part of the Six-Year Review 3 to determine whether they were candidates for regulatory revision. Table VI–3 lists the 21 chemicals with available new health effects information and the sources of the relevant new information. As shown in this table, 11 chemical contaminants have information that could support a lower MCLG and 10 contaminants have new information that could support a higher MCLG. TABLE VI–3—CHEMICALS WITH AVAILABLE NEW HEALTH ASSESSMENT THAT COULD SUPPORT A CHANGE IN MCLG Chemical Relevant new assessment Potential Decrease in MCLG Carbofuran ...................................................................................................................................................................... Cyanide ........................................................................................................................................................................... cis-1,2-Dichloroethyelene ............................................................................................................................................... Endothal .......................................................................................................................................................................... Hexachloropentadiene .................................................................................................................................................... Methoxychlor ................................................................................................................................................................... Oxamyl ............................................................................................................................................................................ Selenium ......................................................................................................................................................................... Styrene ............................................................................................................................................................................ Toluene ........................................................................................................................................................................... Xylenes ........................................................................................................................................................................... USEPA, 2008a (OPP). USEPA, 2010e (IRIS). USEPA, 2010d (IRIS). USEPA, 2005f (OPP). USEPA, 2001a (IRIS). CalEPA 2010a. USEPA, 2010f (OPP). Health Canada 2014. CalEPA 2010b. USEPA, 2005c (IRIS). USEPA, 2003a (IRIS). sradovich on DSK3GMQ082PROD with PROPOSALS3 Potential Increase in MCLG Alachlor ........................................................................................................................................................................... Barium ............................................................................................................................................................................. Beryllium ......................................................................................................................................................................... 1,1-Dichloroethylene ....................................................................................................................................................... 2,4 Dichlorophenoxy-acetic Acid .................................................................................................................................... Diquat .............................................................................................................................................................................. Lindane ........................................................................................................................................................................... Picloram .......................................................................................................................................................................... 1,1,1-Trichloroethane ...................................................................................................................................................... 1,2,4-Trichlorobenzene ................................................................................................................................................... VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 PO 00000 Frm 00011 Fmt 4701 Sfmt 4702 E:\FR\FM\11JAP3.SGM 11JAP3 USEPA, USEPA, USEPA, USEPA, USEPA, USEPA, USEPA, USEPA, USEPA, ATSDR, 2006a (OPP). 2005b (IRIS). 1998a (IRIS). 2002b (IRIS). 2013b (OPP). 2002a (OPP). 2002d (OPP). 1995 (OPP). 2007a (IRIS). 2010. 3528 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules Details of the health effects review of the chemical and radiological contaminants are documented in the ‘‘Six-Year Review 3—Health Effects Assessment for Existing Chemical and Radionuclides National Primary Drinking Water Regulations—Summary Report’’ (USEPA, 2016h). Analytical Feasibility EPA performed analytical feasibility analyses for the contaminants that reached this portion of the review. These contaminants included the 11 chemical contaminants identified under the health effects review as having potential for a lower MCLG and an additional 14 contaminants with MCLs based on analytical feasibility and MCLs higher than the current MCLGs. The document ‘‘Analytical Feasibility Support Document for the Third SixYear Review of National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules’’ (USEPA, 2016a) describes the first step in the process EPA used to evaluate whether changes in PQL are possible in those instances where the MCL is limited, or may be limited, by analytical feasibility. The EQL analysis is documented in the ’’ Development of Estimated Quantitation Levels for the Third Six-Year Review of National Primary Drinking Water Regulations (Chemical Phase Rules)’’ (USEPA, 2016d). Table VI–4 shows the outcomes of EPA’s analytical feasibility review for two general categories of drinking water contaminants: Contaminants where health effects assessments indicate potential for lower MCLGs; and contaminants where existing MCLs are based on analytical feasibility. • A health effects assessment indicates potential for lower MCLG. This category includes the 11 contaminants identified in the health effects review as having information indicating the potential for a lower MCLG. EPA reviewed analytical feasibility to determine if analytical feasibility could limit the potential for MCL revisions. For six contaminants (carbofuran, cyanide, endothall, methoxychlor, oxamyl and styrene), the current PQL is higher than the potential new MCLG identified in the health effects review. For these contaminants, the PQL assessment did not support reduction of the current PQL, or data were inconclusive or insufficient to reach a conclusion. Consequently, analytical feasibility could be a limiting factor for setting the MCL equal to the potential new MCLG. The current PQL is not a limiting factor for the remaining five contaminants identified by the health effects review for possible changes in their MCLG (i.e., cis-1,2dichloroethylene, hexachlorocyclopentadiene, selenium, toluene and xylene). • Contaminants for which existing MCLs are based on analytical feasibility. This category includes 14 contaminants with existing MCLs that are greater than their MCLGs because they are limited by analytical feasibility. Two of the contaminants (thallium and 1,1,2trichloroethanetrichloroethane) are non- carcinogenic and have a non-zero MCLG and the remaining 12 contaminants are carcinogens with MCLGs equal to zero. EPA evaluated whether the PQL could be lowered for each of these contaminants. For one contaminant, 1,1,2-trichloroethane, EPA concluded that new information from Proficiency Testing (PT) studies, along with MRL and MDL data, indicate the potential to revise the PQL. For two contaminants (dioxin and PCBs), data from PT studies were inconclusive, but MRL and MDL data indicated the potential to revise the PQL. For five contaminants (chlordane, heptachlor, heptachlor epoxide, hexachlorobenzene and toxaphene) data from PT and MRL studies were inconclusive, but MDL data indicate the potential to revise the PQL. For the remaining five contaminants, either EPA did not have sufficient new information to evaluate analytical feasibility or EPA concluded that new information does not indicate the potential for a PQL revision. Where these evaluations indicated the potential for a PQL reduction, Table VI– 4 lists the type of data that support this conclusion. The notation ‘‘PT’’ indicates that the PQL reassessment based on PT data (USEPA, 2016a) supports the reduction. The notations ‘‘MRL’’ and ‘‘MDL’’ indicates that these two approaches support PQL reduction. The findings based on PT offer more certainty. When the PQL reassessment outcome is that the current PQL remains appropriate, Table VI–4 shows the result ‘‘Data do not support PQL reduction.’’ TABLE VI–4—NPDWRS INCLUDED IN ANALYTICAL FEASIBILITY REASSESSMENT AND RESULT OF THAT ASSESSMENT Current PQL (μg/L) Contaminant Analytical feasibility reassessment result 11 Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG Carbofuran .................................................................................. Cyanide ....................................................................................... cis-1,2-Dichloroethylene .............................................................. Endothall ..................................................................................... Hexachlorocyclopentadiene ........................................................ Methoxychlor ............................................................................... Oxamyl ........................................................................................ Selenium ..................................................................................... Styrene ........................................................................................ Toluene ....................................................................................... Xylene ......................................................................................... 7 100 5 90 1 10 20 10 5 5 5 Data do not support PQL reduction. Data do not support PQL reduction. PQL not limiting. PQL reduction supported (MRL, MDL). PQL not limiting. PQL reduction supported (PT, MRL). PQL reduction supported (MRL, MDL). PQL not limiting. PQL reduction supported (PT, MRL, MDL). PQL not limiting. PQL not limiting. sradovich on DSK3GMQ082PROD with PROPOSALS3 14 Contaminants With MCLs Based on Analytical Feasibility and Higher Than MCLGs Benzo(a)pyrene ........................................................................... Chlordane .................................................................................... 1,2-Dibromo-3-chloropropane (DBCP) ....................................... Di(2-ethylhexyl)phthalate (DEHP) ............................................... Ethylene dibromide (EDB) .......................................................... Heptachlor ................................................................................... Heptachlor Epoxide ..................................................................... Hexachlorobenzene .................................................................... Pentachlorophenol ...................................................................... VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 PO 00000 Frm 00012 0.2 2 0.2 6 0.05 0.4 0.2 1 1 Fmt 4701 Sfmt 4702 Data do not support PQL reduction. PQL reduction supported (MRL, MDL). Data do not support PQL reduction. Data do not support PQL reduction. Data do not support PQL reduction. PQL reduction supported (MDL). PQL reduction supported (MDL). PQL reduction supported (PT, MDL). Data do not support PQL reduction. E:\FR\FM\11JAP3.SGM 11JAP3 3529 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules TABLE VI–4—NPDWRS INCLUDED IN ANALYTICAL FEASIBILITY REASSESSMENT AND RESULT OF THAT ASSESSMENT— Continued Current PQL (μg/L) Contaminant PCBs ........................................................................................... Dioxin .......................................................................................... Thallium ....................................................................................... Toxaphene .................................................................................. 1,1,2-Trichloroethane .................................................................. Occurrence and Exposure Using the SYR3 ICR database, EPA conducted an assessment to evaluate national occurrence of regulated contaminants and estimate the potential population exposed to these contaminants. The details of the current chemical occurrence analysis are documented in ‘‘The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Third Six-Year Review of Analytical feasibility reassessment result 0.5 3.0 × 10¥5 2 3 5 Data do not support PQL reduction. PQL reduction supported (MRL, MDL). Data do not support PQL reduction. PQL reduction supported (MDL). PQL reduction supported (PT, MRL, MDL). National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules’’ (USEPA, 2016p). Based on benchmarks identified in the health effects and analytical feasibility analyses, EPA conducted the occurrence and exposure analysis for 18 contaminants. This analysis shows that these 18 contaminants occur at levels above the identified benchmark in a very small percentage of systems, which serve a very small percentage of the population, indicating that revisions to NPDWRs are unlikely to provide a meaningful opportunity to improve public health protection across the nation. Therefore, these contaminants were not identified as candidates for regulatory revision. Table VI–5 lists the benchmarks used to conduct the occurrence analysis, the total number of systems with mean concentrations exceeding a benchmark and the estimated population served by those systems. TABLE VI–5—OCCURRENCE AND POTENTIAL EXPOSURE ANALYSIS FOR CHEMICAL NPDWRS Benchmark 1 (ug/L) Contaminant Number (and percentage) of systems with a mean concentration higher than benchmarks Population served by systems with a mean concentration higher than benchmarks (and percentage of total population) Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG Carbofuran ................................................................................................... Cyanide ........................................................................................................ cis-1,2-Dichloroethylene .............................................................................. Endothall ...................................................................................................... Hexachlorocyclopentadiene ......................................................................... Methoxychlor ................................................................................................ Oxamyl ......................................................................................................... Selenium ...................................................................................................... Styrene ......................................................................................................... Toluene ........................................................................................................ Xylene .......................................................................................................... >5 >50 >10 >50 >40 >1 >9 >40 >0.5 >600 >1,000 1 (0.00%) 98 (0.27%) 4 (0.01%) 1 (0.01%) 0 (0.00%) 1 (0.003%) 2 (0.01%) 49 (0.10%) 117 (0.210%) 0 (0.00%) 2 (0.004%) 993 (0.0004%) 574,038 (0.27%) 5,569 (0.00%) 993 (0.001%) 0 (0.00%) 993 (0.000%) 9,742 (0.004%) 135,685 (0.05%) 571,425 (0.217%) 0 (0.00%) 825 (0.0003%) Contaminants With MCLs Based on Analytical Feasibility and Higher Than MCLGs sradovich on DSK3GMQ082PROD with PROPOSALS3 Chlordane .................................................................................................... Heptachlor .................................................................................................... Heptachlor Epoxide ..................................................................................... Hexachlorobenzene ..................................................................................... 2,3,7,8-TCDD (Dioxin) ................................................................................. Toxaphene ................................................................................................... 1,1,2-Trichloroethane ................................................................................... In addition, EPA performed a source water occurrence analysis for the 10 chemical contaminants in which updated health effects assessments indicated the possibility to increase (i.e., render less stringent) the MCLG values. EPA conducted this analysis to determine if there was a meaningful opportunity to achieve cost savings while maintaining or improving the level of public health protection. The VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 >1 >0.1 >0.04 >0.1 >0.000005 >1 >3 data available to characterize contaminant occurrence was limited because there is no comprehensive dataset that characterizes source water quality for drinking water systems. Data from the U.S. Geological Survey (USGS) National Water Quality Assessment program and the U.S. Department of Agriculture Pesticide Data Program water monitoring survey provide useful insights into potential contaminant PO 00000 Frm 00013 Fmt 4701 Sfmt 4702 3 (0.01%) 3 (0.01%) 14 (0.04%) 6 (0.016%) 2 (0.06%) 6 (0.02%) 0 (0.00%) 1,353 (0.001%) 1,643 (0.00%) 11,659 (0.005%) 8,703 (0.004%) 1,450 (0.002%) 715,106 (0.32%) 0 (0.00%) occurrence in source water. The analysis of the available contaminant occurrence data for potential drinking water sources indicated relatively low contaminant occurrence in the concentration ranges of interest. As a consequence, EPA could not conclude that there is a meaningful opportunity for system cost savings by increasing the MCLG and/or MCL for these 10 contaminants. The results of this E:\FR\FM\11JAP3.SGM 11JAP3 3530 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules analysis were documented in ‘‘Occurrence Analysis for Potential Source Waters for the Third Six-Year Review of National Primary Drinking Water Regulations’’ (USEPA, 2016e). Treatment Feasibility Currently, all of the MCLs for chemical and radiological contaminants are set equal to the MCLGs or PQLs or are based on benefit-cost analysis; none are currently limited by treatment feasibility. EPA considers treatment feasibility after identifying contaminants with the potential to lower the MCLG/MCL that constitute a meaningful opportunity to improve public health. No such contaminants were identified in the occurrence and exposure analysis described above. Other Regulatory Revisions In addition to possible revisions to MCLGs, MCLs and TTs, EPA considered whether other regulatory revisions are needed to address implementation issues, such as revisions to monitoring and system reporting requirements, as a part of the Six-Year Review 3. EPA used the protocol to evaluate which implementation issues to consider (USEPA, 2016f). EPA’s protocol focused on items that were not already being addressed, or had not been addressed, through alternative mechanisms (e.g., as a part of a recent or ongoing rulemaking). Implementation Issues Identified for the Six-Year Review 3 EPA compiled information on implementation related issues associated with the Chemical Phase Rules. EPA also identified unresolved implementation issues/concerns from previous Six-Year Reviews. EPA shared the list of identified potential implementation issues with a group of state representatives convened by ASDWA to obtain input from state drinking water agencies concerning the significance and relevance of the issues (ASDWA, 2016). The complete list of implementation issues related to the Phase Rules and Radionuclide Rules is presented in ‘‘Consideration of Other Regulatory Revisions in Support of the Third Six-Year Review of the National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclide Rules’’ (USEPA, 2016c). The Agency determined that the following three issues, identified by state stakeholders, were within the scope of NPDWR review and were the most substantive: a. Nitrogen monitoring in consecutive systems and the distribution system, b. Alternative nitrate-nitrogen MCL of 20 mg/L for non-community water systems (NCWSs), and c. Synthetic organic chemical (SOC) detection limits. Table VI–6 provides a brief description of the three issues and the Agency’s findings to date. TABLE VI–6—CHEMICAL RULE IMPLEMENTATION ISSUES IDENTIFIED THAT FALL WITHIN THE SCOPE OF AN NPDWR REVIEW Implementation issue Description and findings Nitrogen Monitoring in Consecutive Systems and the Distribution System. Current nitrite and nitrate standards are measured at the point of entry to the distribution system. Under some conditions, nitrification of ammonia in water system distribution networks could potentially result in increased total nitrite or nitrate concentrations at the point of use. To address the concern, certain water systems could develop and implement a nitrification monitoring program, which would include changing or adding additional monitoring locations. Research is needed to further evaluate the extent of this potential issue, including development of criteria to identify the specific systems where distribution system monitoring could be targeted. If the outcome of the research suggests that the magnitude of the problem represents a meaningful opportunity to improve public health protection, the regulation could be considered for revision. EPA evaluated the possibility of removing or further restricting the option for some NCWSs to use an alternative nitrate-nitrogen MCL of up to 20 mg/L. The nitrate-nitrogen MCL in PWSs is 10 mg/L. However, § 141.11 of the Code of Federal Regulations (CFR) provides that states have the discretion to allow some NCWSs to use an alternative nitrate-nitrogen MCL of up to 20 mg/L if certain conditions are met, including conditions where water will not be available to children under six months of age. Other provisions related to this issue are included in § 141.23 of the CFR, which pertains to monitoring. This section states: ‘‘Transient, non-community water systems shall conduct monitoring to determine compliance with the nitrate and nitrite MCL in §§ 141.11 and 141.62 (as appropriate) in accordance with this section.’’ The monitoring section does not address non-transient non-community water systems (NTNCWSs) eligibility to use an alternative nitrate MCL. Two potential concerns identified with the current rule provisions are: • Potential health concerns other than methemoglobinemia associated with the ingestion of nitrate-nitrogen, such as possible effects on fetal development. • The fact that the alternative MCL was initially intended to be used by entities such as industrial plants that do not provide drinking water to children under six months of age (44 FR 42254, USEPA, 1979). Industrial plants are generally considered to be NTNCWSs. Therefore, it is possible the alternative MCL was intended to apply specifically to NTNCWSs and not transient non-community water systems (TNCWSs). The Agency has nominated nitrate and nitrite for an IRIS assessment as a result of the Six-Year Review process, and both of these contaminants are listed in the IRIS multi-year plan. An updated assessment is needed that evaluates health effects other than methemoglobinemia. Specifically, an assessment is needed that evaluates potential health effects of nitrate-nitrogen at levels between 10 and 20 mg/L on adult populations. When completed, the IRIS assessment may support initiation of a rule revision if potential adverse health effects were identified at drinking water concentrations below the alternative nitrate MCL of 20 mg/L for populations other than infants less than six-months of age. sradovich on DSK3GMQ082PROD with PROPOSALS3 Alternative Nitrate-Nitrogen MCL of 20 mg/L for NCWS. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 PO 00000 Frm 00014 Fmt 4701 Sfmt 4702 E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules 3531 TABLE VI–6—CHEMICAL RULE IMPLEMENTATION ISSUES IDENTIFIED THAT FALL WITHIN THE SCOPE OF AN NPDWR REVIEW—Continued Implementation issue Description and findings Synthetic Organic Chemical (SOC) Detection Limits. According to states, some laboratories have reported difficulty in achieving the detection limits for some SOCs on a regular basis. Section 40 CFR 141.24(h)18 provides detection limits for the SOCs, including some pesticides. PWSs that do not detect a SOC contaminant above these concentrations may qualify for reduced monitoring frequency for individual contaminants. It was reported that some SOCs may have detection limits that are lower than levels that can be economically and efficiently achieved by laboratories using approved methods. Thus, some water systems may not be able to qualify for reduced monitoring if the laboratories cannot achieve the listed detection limits. This issue was also identified as a concern by the states during the Six-Year Review 2. To address the SOC method detection limits, the Agency investigated the MRL values for SOCs from the SYR 3 ICR and found there was an existing approved analytical method for each SOC that laboratories can use to achieve the appropriate detection limits in order to reduce monitoring requirements. Using the MRL values, the Agency evaluated the percentage of records in the ICR database at or below the detection limit. EPA considered this percentage as an indication of laboratories’ collective ability to detect contaminant concentrations at or below these levels. The Agency found that for most of the SOCs, nearly half of the records were at or below the detection limit listed in the regulation while other SOCs had a sufficient number of records below the detection limit to determine that there was an approved analytical method that could be used. sradovich on DSK3GMQ082PROD with PROPOSALS3 2. Fluoride Background Fluoride can occur naturally in drinking water as a result of the geological composition of soils and bedrock. Some areas of the country have high levels of naturally occurring fluoride. EPA established the current NPDWR to reduce the public health risk associated with exposure to high levels of naturally occurring fluoride in drinking water sources. Low levels of fluoride are frequently added to drinking water systems as a public health protection measure for reducing the incidence of cavities. The decision to fluoridate a community water supply is made by the state or local municipality, and is not mandated by EPA or any other federal entity. The U.S. Public Health Service (PHS) recommendation for community water fluoridation is 0.7 mg/L (U.S. Department of Health and Human Services, 2015). Fluoride is also added to various consumer products (such as toothpaste and mouthwash) because of its beneficial effects at low level exposures. EPA published the current NPDWR on April 2, 1986 (51 FR 11396, USEPA, 1986) to reduce the public health risk associated with exposure to high levels of naturally occurring fluoride in drinking water sources. The current NPDWR established an MCLG and MCL of 4.0 mg/L to protect against the most severe stage of skeletal fluorosis (referred to as the ‘‘crippling’’ stage) (NRC, 2006a). EPA also established a secondary maximum contaminant level (SMCL) for fluoride of 2.0 mg/L to protect against moderate and severe dental fluorosis, which was considered at the time to be a cosmetic effect. As VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 provided under the statute, the SMCL is not enforceable in the same manner as the MCL. Public notification is required when PWSs exceed the MCL or SMCL. EPA has reviewed the NPDWR for fluoride in previous Six-Year Review cycles. As a result of the first Six-Year Review (68 FR 42908, USEPA, 2003b), EPA requested that the National Research Council (NRC) of the National Academies of Sciences (NAS) conduct a review of the health and exposure data on orally ingested fluoride. In 2006, the NRC published the results of its review and concluded that severe dental fluorosis is an adverse health effect when it causes both a thinning and pitting of the enamel, a situation that compromises the function of the enamel in protecting against decay and infection (NRC, 2006a). The NRC recommended that EPA develop a doseresponse assessment for severe dental fluorosis as the critical effect and update an assessment of fluoride exposure from all sources. During the Six-Year Review 2, the Agency was in the process of developing a dose-response assessment of the non-cancer impacts of fluoride on severe dental fluorosis and the skeletal system. In addition, EPA was in the process of updating its evaluation of the relative source contribution (RSC) of drinking water to total fluoride exposure considering the contributions from dental products, foods, pesticide residues, and other sources such as ambient air and medications. These assessments were not completed at the time of the Six-Year Review 2; thus, no action was taken under the Six-Year Review 2 (75 FR 15500, USEPA, 2010h). In 2010, EPA published fluoride health assessments. The ‘‘Dose Response Analysis for Non-Cancer PO 00000 Frm 00015 Fmt 4701 Sfmt 4702 Effects’’ (USEPA, 2010b) identified an oral RfD for fluoride of 0.08 milligrams per kilograms per day (mg/kg/day) based on studies of severe dental fluorosis among children in the six months to 14 year age group (USEPA, 2010b). The ‘‘Exposure and Relative Source Contribution Analysis’’ (USEPA, 2010c) concluded that the RSC values for drinking water range from 40 to 70 percent, with the higher values associated with infants fed with powdered formula or concentrate reconstituted with residential tap water (70%) and with adults (60%). The major contributors to total daily fluoride intakes for these age groups are drinking water, commercial beverages, solid foods and swallowed fluoridecontaining toothpaste (USEPA, 2010c). Summary of Review Results The Agency has determined that a revision to the NPDWR for fluoride is not appropriate at this time. EPA acknowledges information regarding the exposure and health effects of fluoride (as discussed later in the ‘‘Health Effects’’ and ‘‘Occurrence and Exposure’’ sections). However, with EPA’s identification of several other significant NPDWRs as candidates for near-term revision (see Sections VI.B.3 and VI.B.4), potential revision of the fluoride NPDWR is a lower priority that would divert significant resources from the higher priority candidates for revision that the Agency has identified, as well as other high priority work within the drinking water office. These other candidates for revision include the Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules (D/ DBPRs) that apply to approximately 42,000 PWSs, and for which EPA has identified the potential to further reduce E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 3532 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules bladder cancer risks attributed to exposure to DBPs; the Surface Water Treatment Rules, for which the Agency has identified the potential to further reduce risks from a myriad of serious waterborne diseases (e.g., giardiasis, cryptosporidiosis, legionellosis, hepatitis, meningitis and encephalitis) for approximately 12,000 surface water systems; and the pending revisions to the lead and copper NPDWR which apply to approximately 68,000 PWSs. While EPA has evaluated the available health effects and exposure information related to fluoride (as discussed later in the ‘‘Health Effects’’ and ‘‘Occurrence and Exposure’’ sections), the Agency also recognizes that new studies on fluoride are currently being performed. These include new studies that address health endpoints of concern other than dental fluorosis. Based on the NRC recommendations, EPA evaluated dental fluorosis for the purposes of this action. EPA will continue to monitor the evolving science, and, when appropriate, will reconsider the fluoride NPDWR’s relative priority for revision and take any other available and appropriate action to address fluoride risks under SDWA. Finally, most community water systems (CWSs) that provide fluoridation of their drinking water have already lowered their fluoridation level to a single level of 0.7 mg/L from a previous range of 0.7 to 1.2 mg/L to accommodate the updated PHS recommendation (U.S. Department of Health and Human Services, 2015). The U.S. Food and Drug Administration (FDA) also issued a letter to bottled water manufacturers recommending that they not add fluoride to bottled water in excess of the revised PHS recommendations (FDA, 2015). In addition, the FDA stated it intends to revise the quality standard regulation for fluoride added to bottled water to be consistent with the updated PHS recommendation. Therefore, EPA anticipates that a significant portion of the population’s exposure to fluoride in drinking water, as well as some commercial beverages that use fluoridated water from CWSs and certain bottled water, has already been or will be reduced. Notwithstanding this action’s decision, EPA will continue to address risk associated with fluoride in drinking water, with a specific focus on the small systems with naturally occurring fluoride in their source waters. Initial Review EPA did not identify any recent, ongoing or pending action on fluoride VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 that would exclude fluoride from the Six-Year Review 3. Health Effects Assessment Summary Report’’ (USEPA, 2016h). Health Effects The NRC (2006a) evaluated the impact of fluoride on reproduction and development, neurotoxicity and behavior, the endocrine system, genotoxicity, cancer and other effects, in addition to the tooth and bone effects. At fluoride levels below 4.0 mg/L, the NRC found no evidence substantial enough to support adverse effects other than severe dental fluorosis and skeletal fractures. The NRC concluded that the available data were inadequate to determine if a risk of effects on other endpoints exists at an MCLG of 4.0 mg/ L and made recommendations for additional research. EPA assessments (USEPA, 2010b; 2010c) found that the RSC values are lower than the RSC of 100 percent used to derive the original MCLG of 4.0 mg/ L, where EPA assumed that drinking water was the sole source of exposure to fluoride. EPA has concluded that information on the dose-response and exposure assessment may support lowering the MCLG to reflect levels that would protect against risk of severe dental fluorosis and skeletal fractures. As part of this Six-Year Review, EPA reviewed health effects data on the impact of fluoride on reproduction and development, neurotoxicity and behavior, the endocrine system, genotoxicity, cancer and other effects that were identified by the NRC as requiring additional research (NRC, 2006a). EPA noted limitations in some of these studies such as lack of details and confounding factors. Overall, the new data were insufficient to alter the NRC conclusion that severe dental fluorosis is the critical health effects endpoint for the MCLG. Based upon the recommendations of the NRC, EPA has evaluated dental fluorosis as a critical endpoint of concern for this Six-Year Review (USEPA, 2010b; 2010c). However new studies are underway to examine other health endpoints (i.e., developmental neurobehavior effects, endocrine disruption and genotoxicity). One example is an ongoing National Toxicology Program (NTP) systematic review of animal studies that examined the impact of fluoride on learning and memory (NTP, 2016). For more information about fluoride developmental neurotoxicity visit the National Toxicology Program Web site at https://ntp.niehs.nih.gov/pubhealth/ hat/noms/fluoride/neuro-index.html. Additional information related to the review of the fluoride NPDWR is provided in the ‘‘Six-Year Review 3 Analytical Feasibility The current PQL for fluoride is 0.5 mg/L (USEPA, 2009a). EPA has not identified any changes in analytical feasibility that could limit its ability to revise the MCL/MCLG for fluoride. PO 00000 Frm 00016 Fmt 4701 Sfmt 4702 Occurrence and Exposure EPA analyzed fluoride occurrence using the SYR3 ICR database, which contains fluoride analytical results from approximately 47,000 PWSs in 49 states/entities from 2006 to 2011. Sample records for fluoridated water (i.e., in which a system adds fluoride to maintain a concentration in the 0.7 to 1.2 mg/L range) were omitted from the analysis because the fluoridated systems would not be impacted by revisions to the fluoride NPDWR. EPA estimated the number and percent of systems that have mean fluoride concentrations exceeding various benchmarks and the corresponding estimates of population served by those systems. The data indicated that about 130 systems (0.3 percent), serving approximately 60,000 people (0.03 percent), had an estimated system mean concentration exceeding the current MCL of 4.0 mg/L, whereas more than 900 systems (2 percent), serving approximately 1.5 million people (0.8 percent), had an estimated system mean concentration greater than the SMCL of 2.0 mg/L. Among these systems, many are small systems (serving fewer than 10,000 people) and very small systems (serving fewer than 500 people). Evaluations based on mean (or average) fluoride concentrations generally reflect an approximation of chronic (long-term) exposure. It is important to note that these average concentration-based evaluations help to inform Six-Year Review results, but do not assess compliance with regulatory standards nor should be viewed as compliance forecasts for PWSs. Treatment Feasibility A BAT or small system compliance technology for fluoride was not established in the Code of Federal Regulations (40 CFR 141.62). However, EPA (1998d) identified activated alumina and reverse osmosis as BATs for fluoride. Activated alumina is the most commonly used treatment technology for fluoride removal. It is capable of removing fluoride to concentrations well below the MCL of 4.0 mg/L, but with a shortened media life at lower target concentrations. Membrane technologies, such as reverse osmosis, nanofiltration, and electrodialysis, are E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules also capable of removing fluoride to very low levels (<0.3 mg/L). They are often used to remove fluoride along with other contaminants such as total dissolved solids, arsenic, and uranium. In general, these technologies are costly and complex to operate—and thus likewise present potential challenges for small water systems (USEPA, 2014a). 3. Disinfectants/Disinfection Byproducts Rules (D/DBPRs) sradovich on DSK3GMQ082PROD with PROPOSALS3 Background The D/DBPRs were promulgated in two stages—Stage 1 in 1998 (63 FR 69390, USEPA, 1998b) and Stage 2 in 2006 (71 FR 388, USEPA, 2006d). Disinfection byproducts (DBPs) are formed when the disinfectants commonly used in PWSs to kill microorganisms react with organic and inorganic matter in source water. DBPs have been associated with potential adverse health effects, including cancer and developmental and reproductive effects. Monitoring parameters within the D/DBPRs consist of the following: DBPs—TTHM, HAA5, bromate and chlorite; disinfectants—chlorine, chloramines and chlorine dioxide; and water quality indicators—total organic carbon (TOC) and alkalinity. The rules include MCLGs/MRDLGs, as well as MCLs/MRDLs and TT requirements, which were developed for individual parameters considering their health risks. For organic DBPs, the concern is potential increased risk of cancer and short-term adverse reproductive and developmental effects. For bromate, the concern is potential increased risk of cancer. Chlorite (a regulated DBP) and chlorine dioxide (a disinfectant) are associated with methemoglobinemia, and for infants, young children and pregnant women, effects on the thyroid are also of concern. For chlorine and chloramines, health effects include eye/ nose irritation and stomach discomfort (for chloramines, also anemia). The D/DBPRs apply to all sizes of CWSs and non-transient noncommunity water systems (NTNCWSs) that chemically disinfect their water or receive chemically disinfected water (that is, involving any disinfectants other than ultraviolet (UV) light), as well as transient non-community water systems (TNCWSs) that add chlorine dioxide. The rules require that these systems comply with established MCLs, TTs, operational evaluation levels for DBPs and MRDLs for disinfectants. A major challenge for water suppliers is balancing the risks from microbial pathogens and DBPs. The risk-balancing tradeoff approach was intended to lower VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 the overall risks from DBP mixtures while continuing to provide public health protection from microbial risks. Summary of Review Results EPA has identified the following NPDWRs within the D/DBPRs as candidates for revision under this SixYear Review cycle because of the opportunity to further reduce public health risk from exposure to DBPs: Chlorite, HAA5 and TTHM. This result is based on a scientific review of publicly available information. EPA’s review process follows the protocol described in Section V of this document. New information has strengthened the weight of evidence supporting an association between chlorination DBPs and bladder cancer risk compared to the information available during development of the existing D/DBPRs. New information also is available related to the reproductive/ developmental effects discussed in the Stage 2 D/DBPR. In addition, new toxicological data are available to support the development of MCLGs for some individual DBPs currently lacking MCLGs (for example, dibromoacetic acid). This result will also provide for additional opportunity to address concerns with unregulated DBPs: For example, nitrosamines and chlorate. In the Federal Register document for Preliminary Regulatory Determination 3 (79 FR 62715, USEPA, 2014b), the Agency stated that ‘‘because chlorate and nitrosamines are DBPs that can be introduced or formed in PWSs partly because of disinfection practices, the Agency believes it is important to evaluate these unregulated DBPs in the context of the review of the existing DBP regulations. DBPs need to be evaluated collectively, because the potential exists that the strategy used to control a specific DBP could increase the concentrations of other DBPs. Therefore, the Agency is not making a regulatory determination for chlorate and nitrosamines at this time.’’ Chlorate and chlorite are two different oxidation states of chlorine and are chemically inter-convertible. They occur, and can co-occur, when hypochlorite solution and/or chlorine dioxide are applied during the drinking water treatment process. Chlorite is a regulated DBP. New information has shown that the relative source contribution for chlorite could be lower than previously estimated in the existing D/DBPRs, which could lead to a lower MCLG, and that there are common health endpoints associated with exposure to chlorite and chlorate. PO 00000 Frm 00017 Fmt 4701 Sfmt 4702 3533 Compliance monitoring data evaluated for the Six-Year Review 3 show widespread occurrence of DBPs and their organic precursors (as measured as TOC) in drinking water. Research that has been published since the development of the Stage 2 D/DBPR has improved EPA’s understanding of the effectiveness of and limitations associated with various treatment approaches, such as those for removal of precursors, use of disinfectants other than chlorine and localized treatment. Given that this is the first time EPA is conducting a Six-Year Review of the D/DBPRs, extensive information about review findings is provided below, with further information provided in EPA’s ‘‘Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection Byproducts Rules’’ (USEPA, 2016l). Additional information related to the review of D/DBPRs is provided in the ‘‘Six-Year Review 3 Technical Support Document for Chlorate’’ (USEPA, 2016k) and the ‘‘Six-Year Review 3 Technical Support Document for Nitrosamines’’ (USEPA, 2016o). Initial Review There are no recently completed, ongoing or pending regulatory actions on the D/DBPRs that would exclude them from the Six-Year Review 3. Health Effects Under the Stage 1 and 2 D/DBPRs, toxicology studies for specific DBPs and disinfectant residuals were used to inform MCLGs (and cancer potency factors where MCLGs are zero) and MRDLGs. Epidemiology studies were used to estimate potential risks from DBP mixtures (due to cancer and developmental/reproductive effects) and support the benefits analysis. Epidemiology studies supported a potential association between exposures to elevated THM4 levels in chlorinated drinking water and cancer, but the evidence was insufficient to establish a causal relationship. The most consistent evidence was for bladder cancer. For the development of the benefits analysis for both the Stage 1 and the Stage 2 D/ DBPRs, EPA used five bladder cancer case-control epidemiology studies that were conducted in the 1980s and 1990s (Cantor et al., 1985; 1987; McGeehin et al., 1993; King and Marrett, 1996; Freedman et al., 1997; Cantor et al., 1998). In addition, EPA used one metaanalysis (Villanueva et al., 2003) and one pooled analysis (Villanueva et al., 2004). The five case-control studies used similar (though not identical) exposure metrics based on years of exposure to chlorinated drinking water (primarily chlorinated surface water) to E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 3534 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules estimate odds ratios. All five studies showed an increase in the odds ratio for bladder cancer incidence with an increased duration of exposure. Using the published odds ratio results from these five studies, EPA calculated an estimate for the lifetime cancer risk (population attributable risk) that ranged from 2 to 17 percent; between 2 and 17 percent of bladder cancers occurring in the U.S. could be attributed to long-term exposure to chlorinated drinking water at the time of the Stage 1 D/DBPR. Detailed explanations of these calculations can be found in the benefits analysis for the Stage 2 D/DBPR (USEPA, 2005a). The evidence from the studies in 1985 to 1998, the metaanalysis in 2003 and the pooled analysis in 2004 was strong enough to support the benefit analysis with several thousand potential bladder cancer cases per year estimated as being avoided from the combined effects of the Stage 1 and Stage 2 D/DBPRs (USEPA, 2005a). Studies from the 1970s to 2005 also suggested a possible association between adverse developmental/ reproductive health effects and exposure to chlorinated drinking water. Effects were observed in all areas but lacked consistency across studies and did not provide enough of a basis to quantify risks or benefits. The adverse developmental/reproductive effects consisted of effects on fetal growth (small for gestational age, low birth weight and pre-term delivery), effects on viability (spontaneous abortion, stillbirth) and malformations (neural tube, oral cleft, cardiac or urinary defects). Since the development of the Stage 2 D/DBPR, EPA has identified additional sources of information related to health effects of DBPs. New toxicological information could be used to develop MCLGs for the following regulated DBPs (within HAA5): Dibromoacetic acid (NTP, 2007), other brominated haloacetic acids not currently regulated, including bromochloroacetic acid (NTP, 2009) and bromodichloroacetic acid (NTP, 2014), plus additional unregulated DBPs such as nitrosamines and chlorate (USEPA, 2016k; 2016o). EPA has identified new epidemiological, pharmacokinetic and pharmacodynamic studies that, considered together with studies available during the development of the Stage 2 D/DBPR, add to the weight of evidence for bladder cancer being associated with exposure to chlorination DBPs (notably those containing bromine) in drinking water. Pharmacokinetic and pharmacodynamic studies (Ross and Pegram, 2003; 2004; Leavens et al., VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 2007; Stayner et al., 2014; Kenyon et al., 2015), in conjunction with epidemiology studies (Villanueva et al., 2007; Kogevinas et al., 2010; Cantor et al., 2010), indicate that non-ingestion routes of exposure (dermal and inhalation) from some brominated DBPs may play a significant role in influencing increased bladder cancer risk, and that there may be greater concern about sub-populations with certain genetic characteristics (polymorphisms). EPA’s ‘‘Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection Byproducts Rules’’ (USEPA, 2016l) characterizes the research that informs the mode of action by which brominated DBPs may be contributing to bladder cancer. While uncertainties remain regarding the degree to which specific DBPs contributed to the bladder cancer incidence observed in epidemiology studies, the collective data suggest a stronger case for causality than when the Stage 2 D/DBPR was promulgated (Regli et al., 2015; USEPA, 2016l). However, the Agency recognizes there are also different perspectives on this issue, including suggestions about areas for additional research (Hrudey et al., 2015). Further, the Agency has identified new information about health effects from unregulated DBPs. This includes health effects information on chlorate and nitrosamines that, along with occurrence/exposure information, was previously noted in the Preliminary Regulatory Determination 3 (79 FR 62715, USEPA, 2014b). The Agency is considering the health effects of chlorate and nitrosamines within the broader context of the health effects of regulated DBPs (USEPA, 2016k; 2016o). EPA also identified information about the relative cytotoxicity and genotoxicity of many other unregulated DBPs (Richardson et al., 2007; Richardson et al., 2008; Plewa and Wagner 2009; Plewa et al., 2010; ´ Fernandez et al., 2010; Richardson and Postigo, 2011; Yang et al., 2014). Data from in vitro mammalian cell testing, which compared the cytotoxicity and genotoxicity of iodinated, brominated, and chlorinated DBPs, showed that the iodinated DBPs (those containing iodine) were generally more toxic than the brominated DBPs (those containing bromine), which were in turn more toxic than the chlorinated DBPs (those containing chlorine). Nitrogencontaining DBPs, including haloacetonitriles, haloacetamides and halonitromethanes, were more cytotoxic and genotoxic than the haloacids and PO 00000 Frm 00018 Fmt 4701 Sfmt 4702 halomethanes that did not contain nitrogen. Approximately 40 new studies about developmental/reproductive effects have become available since the development of the Stage 2 D/DBPR. These studies address endpoints such as fetal growth (low birth weight, small for gestational age and pre-term delivery), congenital anomalies and male reproductive outcomes. These studies continue to support a potential health concern, though, as discussed above, the relationship of DBP exposure to these types of adverse outcomes may not be well enough understood to permit quantification of risks or benefits. A recent ‘‘four-lab study’’ on the effects of DBP mixtures on animals, conducted by EPA researchers (Narotsky et al., 2011; 2013; 2015), suggests diminished concern for many developmental/ reproductive endpoints. EPA also examined data about health effects for inorganic DBPs, including information showing that the RSC for chlorite could be lower than 80 percent (which could potentially support lowering the MCLG) because there is more dietary exposure than previously assumed due to the increased use of chlorine dioxide and acidified sodium chlorite as disinfectants in the processing of foods (U.S. EPA, 2006e; WHO, 2008). In addition, chlorate, chlorite and chlorine dioxide may share common health endpoints, namely hematological and thyroid effects (Couri and Abdel-Rahman, 1980; Bercz et al., 1982; Moore and Calabrese, 1982; Abdel-Rahman et al., 1984; Khan et al., 2005; Orme et al., 1985; NTP, 2005; USEPA, 2006e; WHO, 2008; Lee et al, 2013; Nguyen et al, 2014). The Agency did not identify any relevant data that suggest an opportunity to revise the MCLG for bromate, or the MRDLG for chlorine or chloramines. Analytical Feasibility The Agency has not identified any improvements to analytical feasibility that could lead to improvements to the NPDWRs included in the D/DBPRs. Development of these rules was not constrained by the availability of analytical methods, and new EPAapproved methods that would revise this finding have not been identified. Should new, EPA-approved methods for one or more D/DBPRs be identified, that information might be able to help inform potential future regulatory development efforts. Occurrence and Exposure In this Six-Year Review evaluation of D/DBP occurrence and exposure, EPA E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 evaluated compliance monitoring information collected under the SYR3 ICR, which was previously discussed in Section V.B.4. EPA also evaluated information from the DBP ICR database (USEPA, 2000a) that had been used to prepare the original D/DBPRs. Additionally, EPA used data from the third monitoring cycle of the Unregulated Contaminant Monitoring Rule (UCMR3) to evaluate chlorate occurrence in 2013–2015, and data from the UCMR2 to evaluate nitrosamine occurrence in 2008–2010. This information is briefly described below, with additional information in EPA’s ‘‘Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection Byproducts Rules’’ (USEPA, 2016l). It is important to note that the information collected through the SYR3 ICR spans the years 2006–2011. As such, it primarily reflects occurrence following the effective date for the Stage 1 D/DBPR, but prior to the effective date for the Stage 2 D/DBPR. These evaluations help to inform Six-Year Review results but do not assess compliance with regulatory standards. New information since the promulgation of the Stage 2 D/DBPR has improved our understanding on DBP formation and occurrence. As part of this Six-Year Review, EPA has identified literature describing more than 600 specific DBPs that have been found in drinking water (e.g., Richardson et al., 2007); these include chlorinated, brominated and iodinated DBPs, as well as nitrogenous compounds. Additionally, EPA identified literature on the sources of precursors (both organic and inorganic), as well as the influence that different precursors have on DBP formation. For example, some of this literature discusses the extent to which brominated or iodinated DBPs might form as a result of source water bromide or iodide concentrations (Nguyen et al., 2005; Duirk et al, 2011; Lui et al., 2012; Zhang et al., 2012; Callinan et al., 2013; Emelko et al., 2013; Mikkelson et al., 2013; Rice et al., 2013; Samson et al., 2013; Rice and Westerhoff, 2014). Overview of DBP Occurrence EPA collected occurrence information for THMs (includes TTHM along with information on four individual species), HAAs (includes HAA5 along with information on five individual species), bromate and chlorite as part of the SYR3 ICR. Data from the SYR3 ICR show that concentrations at or above the MCLs for TTHM and HAA5 were found in many surface water systems and, to a lesser degree, in ground water systems. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Approximately 32 percent of surface water systems and five percent of ground water systems reported at least one instance of TTHM occurrence at a concentration greater than or equal to the MCL of 80 mg/L. For HAA5, approximately 19 percent of surface water systems and two percent of ground water systems reported at least one instance of occurrence at a concentration greater than or equal to the MCL of 60 mg/L. EPA anticipates that many of these peak concentrations will have been significantly lowered based on implementation of the 2006 Stage 2 D/DBPR, which was designed, in part, to lower such occurrences. Approximately nine percent of systems had one or more samples that were greater than or equal to the bromate MCL of 10 mg/L. Approximately four percent of systems had one or more samples that were greater than or equal to the chlorite MCL of 1,000 mg/L. The occurrence of six nitrosamine species was evaluated by EPA using data from the UCMR2. These data showed elevated concentrations of nitrosamines (relative to their health reference levels) in multiple drinking water systems, especially Nnitrosodimethylamine (NDMA) in systems that use chloramines (USEPA, 2016o). The Agency is seeking public comment regarding potential approaches that provide enhanced protection from health risks posed by nitrosamines in drinking water systems. The occurrence of chlorate was evaluated by EPA using data from the UCMR3 (USEPA, 2016j). These data showed that chlorate levels above the health reference level of 210 mg/L occurred frequently in systems that use hypochlorite, chlorine dioxide or chloramines. In addition, EPA evaluated the co-occurrence of chlorite and chlorate and noted that these contaminants often co-occur (USEPA, 2016k). The Agency is seeking public comment regarding potential approaches that provide enhanced protection from health risks posed by chlorite, chlorate and chlorine dioxide. See Section VII for more information. The American Water Works Association (AWWA), through the Water Industry Technical Action Fund #266, conducted its own survey of postStage 2 D/DBPR occurrence for systems that serve more than 100,000 people. Results from the AWWA survey (Samson, 2015) provide an overview of DBP occurrence for 395 systems across 44 states, covering a time period from 1980 to 2015. In December 2015, EPA issued a proposal for the fourth cycle of the UCMR (80 FR 76897, USEPA, 2015b). PO 00000 Frm 00019 Fmt 4701 Sfmt 4702 3535 That proposal includes provisions for collection of data about unregulated haloacetic acids and related precursors. Such data would help EPA to develop a better understanding of patterns of occurrence for those contaminants. Overview of Water Quality Indicator Occurrence The Stage 1 D/DBPR requires that DBP precursors (measured as TOC) be monitored in source and treated drinking water. EPA evaluated compliance monitoring data from surface water systems for TOC in source and treated water, using the SYR3 ICR database. Data from 2011 showed that approximately 70 percent of all plants had average TOC concentrations greater than 2 mg/L in their source water and that approximately 29 percent of plants had average TOC concentrations greater than 2 mg/L in their treated water. Under the Stage 1 D/DBPR, a system is not required to further remove TOC when its treated water TOC level, prior to the point of continuous chlorination, is less than 2 mg/L. The reader is referred to later portions of this document under ‘‘DBP Precursor Removal’’ for information about EPA’s evaluation of TOC data relative to the Stage 1 D/DBPR TOC removal requirement. As discussed in the background portion of this section, the D/DBPRs require systems to maintain disinfectant residual levels (reported as free and/or total chlorine) in accordance with the MRDL requirements. EPA evaluated free and total chlorine measurements (collected during coliform sampling) from the SYR3 ICR database and found that very few records exceeded 4.0 mg/ L (the MRDL for chlorine and chloramine residuals). Additional information is provided in ‘‘Six-Year Review 3 Technical Support Document for Disinfectants/Disinfection Byproducts Rules’’ (USEPA, 2016l). Treatment Feasibility During the development of the Stage 1 and Stage 2 D/DBPRs, a variety of technologies were evaluated for their effectiveness, applicability, unintended consequences and overall feasibility for achieving compliance with the TT requirements and MCLs, as well as providing a basis for the BATs (63 FR 69390; 71 FR 388; USEPA, 1998b; 2005a; 2005g; 2006d; 2007b). Since the Stage 2 D/DBPR, the Agency has identified information that improves our understanding of technologies available for lowering occurrence of and exposure to regulated and unregulated DBPs. The information addresses the full spectrum of drinking water system E:\FR\FM\11JAP3.SGM 11JAP3 3536 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 operations, including removal of organic precursors to DBPs (measured as TOC), disinfection practices, source water management and localized treatment. The information is briefly discussed below, with additional information in EPA’s ‘‘Six-Year Review 3 Technical Support Document for Disinfectants/ Disinfection Byproducts Rules’’ (USEPA, 2016l). Overall, the information collectively indicates that: (1) Greater removals of DBP precursors can and are being achieved compared to the TT requirement under the Stage 1 D/ DBPR; and (2) occurrence of DBPs can be further controlled. DBP Precursor Removal The SYR3 ICR database (USEPA, 2016i) includes paired source and treated water TOC data. This information was used to evaluate the extent to which TOC was removed from source waters (i.e., percent removal) relative to the Stage 1 D/DBPR TOC removal requirement (i.e., requirement per the 3x3 matrix, which was established based on three different ranges of raw water TOC and alkalinity levels, respectively). This TT requirement is applicable to surface water systems that have conventional treatment plants, unless such systems meet the alternative criteria (63 FR 69390, USEPA, 1998b). The analytical results of TOC removal (i.e., comparing TOC levels from source water to treated water) can help to characterize national treatment baselines among these treatment plants. The data show a wide range of percent TOC removal for each combination of raw water TOC and alkalinity levels provided in the Stage 1 D/DBPR TT requirement. The data also indicate that the mean removal for each element of the 3x3 matrix was six to 19 percent greater than the requirement. These observations are consistent with the notion that ‘‘since the Stage 1 D/ DBPR does not require that all coagulable dissolved organic matter be removed, there is a potential for additional removal of organic matter beyond that required by the 3x3 matrix’’ (McGuire et al., 2014). Some of the TOC removal greater than the Stage 1 D/DBPR requirement may reflect operational optimization of conventional treatment, including use of innovative coagulants/coagulant aids and/or use of biofiltration (Yan et al., 2008; Hasan et al., 2010; McKie et al., 2015; Azzeh et al., 2015; Delatolla et al., 2015; Pharand et al., 2015). Studies have shown that biological filtration can also reduce precursors of the DBPs other than TTHM/HAA5 (Sacher et al., 2008; ´ Farre et al., 2011; Liao et al., 2014; VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Krasner et al., 2015). As noted by McGuire et al. (2014), if the removal of precursors for DBPs other than TTHM/ HAA5 becomes part of the treatment goals, then performance parameters in addition to TOC may also be needed (e.g., parameters indicating both vulnerability and nitrosamine formation potential). As was known during development of the Stage 1 and the Stage 2 D/DBPRs, granular activated carbon (GAC) and membranes can be added to existing treatment trains to achieve additional reductions of DBP formation potential. One longstanding issue has been the extent to which organic precursor removal may cause a shift of chlorinated species to more brominated species (as described earlier in this Section under the ‘‘Health Effects’’) when the bromide level is relatively high in source water (Summers et al., 1993; Symons et al., 1993). The ICR Treatment Study database (USEPA, 2000b) provides extensive bench- and pilot-scale data by which to evaluate the effects of GAC and membrane removal of TOC and resulting shifts in brominated THMs. EPA’s recent analysis of these data generally shows increased percent reduction of brominated THMs as TOC removal by GAC increases (e.g., from a target effluent level of two mg/L to one mg/L), especially for source waters with high bromide concentrations (USEPA, 2016l). It also shows that bromoform formation increases as bromide concentrations increase and that bromoform becomes the dominating species when source water bromide concentrations exceed 200 mg/L. Disinfection Practices Various combinations of disinfectants and precursor removal processes have been used to achieve DBP MCLs, while also meeting the requirements of the microbial standards. Data from successive national drinking water datasets (including the DBP ICR, UCMR2 and UCMR3 datasets) show that the percentage of systems using disinfectants other than chlorine has increased during the past two decades, as had been forecasted in the ‘‘Economic Analysis of Stage 2 D/DBPR’’ (USEPA, 2005a). For example, data from the UCMR3 (2013–2015) and the DBP ICR (1998) have shown a relative increase in use of chloramines, which is associated with the formation of nitrosamines, as a disinfection practice. EPA reviewed information related to the extent to which different types of DBPs may form when disinfectants are applied at different points in the treatment train and/or in combination with other disinfectants. EPA PO 00000 Frm 00020 Fmt 4701 Sfmt 4702 recognized that the extent to which occurrence and associated health effects data may be lacking for one group of DBP contaminants versus another, as well as for DBP mixtures, may make treatment decisions challenging when trying to evaluate DBP risk tradeoffs. Source Water Management New information shows that source waters with relatively elevated sewage contributions have been associated with increased nitrosamine formation (Westerhoff et al., 2015; Krasner et al., 2013) and that source waters with elevated bromide levels from industrial discharges have been associated with increased brominated THMs (McTigue et al., 2014; States et al., 2013). Such factors as these impacts can increase the challenge of controlling DBPs during treatment and distribution. Weiss et al. (2013) developed a model for making source water selection decisions based on real-time DBP precursor concentrations. Information shows that bank filtration can reduce dissolved organic carbon (DOC) and nitrogenous DBP precursors (Brown et al., 2015; Krasner et al., 2015), as well as removing pathogens (USEPA, 2016m). Localized Treatment Localized treatment in distribution systems, such as aeration in storage tanks, sometimes with the addition of GAC, has also been shown to reduce elevated levels of THMs (Walfoort et al., 2008; Fiske et al., 2011; Brooke and Collins, 2011; Johnson et al., 2009; Duranceau, 2015). Aeration approaches have been most successful in reducing concentrations of chloroform and the more volatile brominated species but may have little impact on less volatile species (Johnson et al., 2009; Duranceau, 2015). Risk-Balancing The Agency has considered the riskbalancing aspects of the MDBP rules and has determined that potential revisions to the D/DBPRs could provide greater protection of public health while still being protective of microbial risks. The risk-balancing activities considered by the Agency include those between the microbial and disinfection byproduct rules, as well as those between different groups of DBPs. This includes risk-balancing for the THMs and HAAs included in the D/DBPRs, additional brominated HAAs, nitrosamines identified in the Federal Register document for the Preliminary Regulatory Determination 3 (79 FR 62715, USEPA, 2014b) and other DBP groups such as iodinated DBPs. It also E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules includes risk-balancing for inorganic DBPs such as chlorite and chlorate (79 FR 62715, USEPA, 2014b). Potential revisions could offer enhanced protection from both regulated and unregulated DBPs. Potential revisions that consider areas such as further constraints on precursors, and/or more targeted constraints on precursors (e.g., based on watershed vulnerabilities), could minimize the formation of harmful DBPs without compromising protection against microbial risks. These potential revisions were identified based on a preliminary, qualitative assessment; it is important to note that further assessment would be an important component of any further rulemaking activities. For example, a watershed vulnerability characterization that includes information about wastewater (i.e., sewage) contributions, land use (point/non-point sources of pollution), and streamflow variations over time (for example, sewage contributions during low flow conditions), could help to inform considerations about DBP formation potentials and possible control strategies. The Agency is seeking public comment regarding potential revisions to D/DBPR. See Section VII for more information. Further discussion about potential revisions to existing D/DBPRs will occur as part of a separate regulatory development process. sradovich on DSK3GMQ082PROD with PROPOSALS3 Other Regulatory Revisions In addition to evaluating information about health effects, analytical feasibility, occurrence and exposure, treatment feasibility and risk-balancing related to the NPDWRs included in the D/DBPRs, EPA considered whether other regulatory revisions are needed, such as revisions to monitoring and system reporting requirements, as a part of the Six-Year Review 3. EPA used the protocol to evaluate which of these implementation issues to consider (USEPA, 2016f). As with the Chemical Phase Rules/Radionuclides Rules, EPA shared the list of identified potential implementation issues with the ASDWA to obtain input from state drinking water agencies concerning the significance and relevance of the issues (ASDWA, 2016). Implementation issues will be considered as part of the activities associated with potential future rulemaking efforts; some of these might be addressed through regulatory revision or clarification, while others might be handled through guidance. Examples of implementation-related considerations include the following: VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Stage 2 D/DBPR Consecutive System Monitoring Monitoring in some combined distribution systems may be insufficient to adequately characterize DBP exposure. Some large, hydraulically complex combined water distribution systems may be conducting monitoring that is not adequate to characterize exposure throughout the distribution system. Stage 2 D/DBPR Compliance Monitoring—Chlorine Burn Compliance monitoring for DBPs in some systems may not fully capture DBP levels to which customers may be exposed during certain portions of the year. Systems that use chloramines as a residual disinfectant (generally as part of a compliance strategy to meet DBP MCLs) often temporarily switch to free chlorine as the residual disinfectant for a period (from two to eight weeks) in order to control nitrification in the distribution system. This practice is commonly called a ‘‘chlorine burn.’’ During the chlorine burn, higher levels of DBPs are expected to be formed. Systems often conduct their compliance monitoring outside of the chlorine burn period; and therefore, potentially higher TTHM and HAA5 levels may not be included in compliance calculations. 4. Microbial Contaminants Regulations Background Except for the 1989 Total Coliform Rule, which was reviewed under the Six-Year Review 1, this is the first time EPA is conducting a Six-Year Review of the following microbial contaminant regulations: • Surface Water Treatment Rule (SWTR), • Interim Enhanced Surface Water Treatment Rule (IESWTR), • Long Term 1 Enhanced Surface Water Treatment Rule (LT1), • Long Term 2 Enhanced Surface Water Treatment Rule (LT2), • Filter Backwash Recycling Rule (FBRR), and • Ground Water Rule (GWR). As discussed in Section V, the Initial Review branch of the protocol identifies NPDWRs with recent or ongoing actions and excludes them from the review process to prevent duplicative agency efforts. The cutoff date for the NPDWRs reviewed under the Six-Year Review 3 was August 2008. Based on the Initial Review, EPA excluded the Aircraft Drinking Water Rule, which was promulgated in 2009, and the Revised Total Coliform Rule (RTCR) (the revision of the 1989 TCR), which was promulgated in 2013. PO 00000 Frm 00021 Fmt 4701 Sfmt 4702 3537 In this document, the SWTR, the IESWTR and the LT1 are collectively referred to as the SWTRs because of the close association among the three rules (IESWTR and LT1 were amendments to the SWTR—additional information provided in Section VI.B.4.a). The LT2 is discussed separately in this document because EPA reviewed the LT2 in accordance with the Six-Year Review requirements and the Executive Order 13563 ‘‘Improving Regulation and Regulatory Review’’ (also known as Retrospective Review). Background information on each of the microbial contaminants regulations is presented in the subsequent sections. The microbial contaminants regulations establish treatment technique (TT) requirements in lieu of MCLs. The review elements of the microbial contaminants regulations are: initial review, health effects, analytical feasibility, occurrence and exposure, treatment feasibility, risk-balancing and other regulatory revisions. At this time, the SWTRs are being identified as a candidate for regulatory revision, but the LT2, the FBRR and the GWR are not. A summary of review findings of each rule is described in the subsequent sections. Additional information is provided in the ‘‘Six-Year Review 3 Technical Support Document for Microbial Contaminant Regulations’’ (USEPA, 2016n) and the ‘‘Six-Year Review 3 Technical Support Document for Long-Term 2 Enhanced Surface Water Treatment Rule’’ (USEPA, 2016m). a. SWTRs Background EPA promulgated the SWTR in June 1989. It requires all water systems using surface water sources or ground water under the direct influence of surface water (GWUDI) sources (also known as Subpart H systems) to remove (via filtration) and/or inactivate (via disinfection) microbial contaminants (54 FR 27486, USEPA, 1989). Under the SWTR, EPA established NPDWRs for Giardia, viruses, Legionella, turbidity and heterotrophic bacteria and set MCLGs of zero for Giardia lamblia, viruses and Legionella. Under the IESWTR (63 FR 69477, USEPA, 1998c) and the LT1 (67 FR 1812, USEPA, 2002c), EPA established an NPDWR for Cryptosporidium and set an MCLG of zero. The SWTRs established TT requirements in lieu of MCLs in these NPDWRs. The 1989 SWTR established TT requirements for systems to control G. lamblia by achieving at least 99.9 percent (3-log) removal/inactivation by E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 3538 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules filtration and/or disinfection, and to control viruses by achieving at least 99.99 percent (4-log) removal/ inactivation (54 FR 27486, USEPA, 1989). For a few systems able to meet source water criteria and site-specific conditions (e.g., protective watershed control program and other conditions), they were permitted to achieve the TT requirements by using disinfection only. The SWTR also established TT requirements for disinfectant residuals (54 FR 27486, USEPA, 1989). The residual disinfectant concentration at the entry point to the distribution system may not be less than 0.2 mg/L for more than four hours. The residual disinfectant concentration in the distribution system ‘‘cannot be undetectable in more than 5 percent of the samples each month, for any two consecutive months that the system serves water to the public.’’ (40 CFR 141.72). A detectable residual may be established by: (1) an analytical measurement or (2) having a heterotrophic bacteria concentration less than or equal to 500 per mL measured as heterotrophic plate count (HPC). The purpose of these disinfectant residual requirements was to: • Ensure that the distribution system is properly maintained and identify and limit contamination from outside the distribution system when it might occur, • Limit growth of heterotrophic bacteria and Legionella within the distribution system, and • Provide a quantitative limit, which if exceeded would trigger remedial action. The SWTR also established sanitary survey requirements. The purpose of the sanitary survey requirements, which include consideration of distribution system vulnerabilities, is to identify water system deficiencies that could pose a threat to public health and to permit correction of such deficiencies. As part of the development of the SWTR, EPA needed to clarify which systems would be regulated under Subpart H. In particular, EPA needed to clarify when systems that could be considered as ground water systems were more appropriate to regulate as surface water systems (for example, systems where the drinking water intake was in a riverbed, not in the river). Thus, to identify a system as either ground or surface water, the SWTR defined ‘‘ground water under the direct influence of surface water (GWUDI).’’ GWUDI is any water beneath the surface of the ground with: (1) significant occurrence of insects or other macroorganisms, algae or large-diameter pathogens such as Giardia lamblia, or VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 (2) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity or pH that closely correlate to climatological or surface water conditions. The final SWTR defined GWUDI as being regulated as surface waters because Giardia contamination of infiltration galleries, springs and wells have been found (Hoffbuhr et al., 1986; Hibler et al., 1987). Some contamination of springs and wells have resulted in giardiasis outbreaks (Craun and Jakubowski, 1986). Direct influence was to be determined for individual sources in accordance with criteria established by the state (54 FR 27486, USEPA, 1989). The GWUDI designation identifies PWSs using ground water that must be regulated as if they are surface water systems. All other PWSs using ground water are regulated by the GWR. Surface water and GWUDI systems use concentration x time (CT) tables published by EPA to determine loginactivation credits for the use of a disinfectant to meet the disinfection TT requirements. The ‘‘SWTR Guidance Manual’’ provides CT tables for Giardia and virus inactivation by free chlorine, chloramines, ozone and chlorine dioxide (USEPA, 1991). EPA obtained these CT values from bench-scale experiments with hepatitis A virus (HAV). The IESWTR applies to all PWSs using surface water, or GWUDI, which serve 10,000 or more people. The IESWTR established TT requirements for Cryptosporidium by requiring filtered systems to achieve at least a 99 percent (two-log) removal, revising the definition of GWUDI and watershed control program under the SWTR to include Cryptosporidium, requiring sanitary surveys for all surface water and GWUDI systems, and setting disinfection profiling and benchmarking requirements to prevent increases in microbial risk while systems complied with the Stage 1 D/DBPR. The LT1 (67 FR 1812, USEPA, 2002c) extended the requirements from the IESWTR to systems serving fewer than 10,000 people. Summary of Review Results EPA identified the following NPDWRs under the SWTR as candidates for revision under the Six-Year Review 3 because of the opportunity to further reduce residual risk from pathogens (including opportunistic pathogens such as Legionella) beyond the risk addressed by the current SWTR: • Giardia lamblia, • heterotrophic bacteria, • Legionella, • viruses, and PO 00000 Frm 00022 Fmt 4701 Sfmt 4702 • Cryptosporidium (also under IESWTR and LT1). This result is based on a scientific review of available information, following the protocol described in Section V. Based on the availability of new information, the review focused on the following major provisions of the SWTRs: • Requirements to maintain a minimum disinfectant residual in the distribution system, • GWUDI classification, and • CT criteria for virus disinfection. Collectively, the new information suggests an opportunity to revise the TT provisions of the SWTRs to provide greater protection of public health. More detailed information about the review results related to the major provisions of the SWTRs is provided in the following subsections. Requirements To Maintain a Minimum Disinfectant Residual in the Distribution System EPA evaluated information related to the maintenance of a minimum disinfectant level in the distribution system and determined that there is an opportunity to reduce residual risk from pathogens (includes opportunistic pathogens such as Legionella) beyond the risk addressed by the SWTRs. The detectable concentration of disinfectant residual in the distribution system may not be adequately protective of microbial pathogens because of concerns about analytical methods and the potential for false positives (Wahman and Pressman, 2015; Westerhoff et al., 2010). Maintaining a disinfectant residual above a set numerical value in the distribution system may improve public health protection from a variety of pathogens. Such a change could have benefits for controlling occurrence of all types of pathogens in distribution systems, except for those most resistant to disinfection, such as Cryptosporidium. Given our understanding of the distribution system vulnerabilities (e.g., NRC, 2006b), there may be opportunities to enhance the criteria for indicating distribution system integrity, as well as the potential health risk that may be associated with pathogens potentially growing and released from biofilms. These opportunities include revisiting the distribution system disinfectant residual criteria and revisiting the existing alternative HPC criteria. The NRC report (2006b) describes that water quality integrity is an important factor that water professionals must take into account for the protection of public health, and that the sudden loss of disinfectant residuals E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 can indicate a change in water quality or system characteristics. However, the report was inconclusive on the level of disinfectant residual that should be provided in distribution systems. GWUDI Classification EPA reviewed information on disease outbreaks, a randomized controlled intervention study, pathogenic protozoan occurrence data and studies evaluating parasitic protozoan removal surrogates and hydrogeologic studies, all of which were completed since the SWTR was published. The information suggests that there is an opportunity to provide greater public health protection by improved identification of unrecognized GWUDI PWSs. The data suggest that the SWTR regulation and guidance has performed well in identifying GWUDI for the PWS systems most at risk from Giardia and Cryptosporidium presence in ground water. However, the information (e.g., Colford et al., 2009) suggests that a subset of GWUDI systems are also at risk but are potentially misclassified as ground water systems, and therefore, not subject to requirements that provide protection against parasitic protozoans. Improved public health protection may result if there is improved recognition of GWUDI systems, including those that may disinfect but do not provide engineered filtration or have not conducted a demonstration of performance to document the necessary Cryptosporidium alternative treatment and removal required under the LT2. The potential public health improvement is most relevant to those systems that have a large surface water component and poor subsurface removal capabilities but are not yet recognized as GWUDI and warrants further examination in any rulemaking activities. EPA suggests that the number of potentially misclassified GWUDI PWSs may be estimated by: (1) waterborne disease outbreak compilations, (2) the UCMR3 occurrence data (aerobic spore detections and concentrations), and (3) the SYR2 ICR and the SYR3 ICR (total coliform detections). EPA’s preliminary characterization of the number of the potentially misclassified GWUDI PWSs is described in the ‘‘Six-Year Review 3 Technical Support Document for Microbial Contaminant Regulations’’ (USEPA, 2016n). CT Criteria for Virus Disinfection EPA evaluated whether the current CT criteria based on hepatitis A virus (HAV) are sufficiently protective against other types of viruses. EPA reviewed disinfection studies relevant to the CT VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 tables published in the ‘‘1991 SWTR Guidance Manual’’ (USEPA, 1991). Over the years, many studies have indicated that HAV is less chlorine-resistant than some enteroviruses, such as Coxsackie virus B5 (Black et al., 2009; Cromeans et al., 2010; Keegan et al., 2012), and also less chloramine-resistant than adenovirus (Sirikanchana et al., 2008; Hill and Cromeans, 2010). Based on this review, EPA identified a potential need to update CT values for virus inactivation by free chlorine or chloramines, particularly for water with a relatively high pH. This assessment is also relevant to the LT2 and the GWR, which refer to the same CT tables in the original ‘‘1991 SWTR Guidance Manual.’’ Health Effects This section summarizes EPA’s review of the information related to human health risks from exposure to microbial contaminants in drinking water. EPA evaluated whether any new toxicological data, or waterborne endemic infection or infectious disease information, would justify modifying the MCLGs. EPA reviewed information that included data from the Waterborne Disease and Outbreak Surveillance System (WBDOSS) collected by the Centers for Disease Control and Prevention (CDC) (https://www.cdc.gov/ healthywater/surveillance/drinkingsurveillance-reports.html) and other available data that documents drinking water-associated outbreaks. MCLGs The SWTRs set MCLGs of zero for Giardia lamblia, viruses, Cryptosporidium, and Legionella since any exposure to these microbial pathogens presents a potential health risk. In the Six Year Review 3, EPA did not identify new information related to potentially revising these MCLGs. New dose-response data from some waterborne pathogens are available from both human and animal exposure studies (Teunis et al., 2002a; 2002b; Armstrong and Haas, 2007; 2008; Buse et al., 2012). Concurrently, new models seek to use the new data to provide improved infectivity, morbidity and mortality predictions (Messner et al., 2014; USEPA, 2016m). The newer models are specifically designed to address low dose exposure typical of drinking water rather than high dose exposure typical of food ingestion or vaccine studies. Waterborne Disease Outbreaks Associated With Drinking Water EPA reviewed information from the Waterborne Disease and Outbreaks PO 00000 Frm 00023 Fmt 4701 Sfmt 4702 3539 Surveillance System about the occurrences and causes of drinking water-associated outbreaks. This surveillance system is the primary source of data concerning such outbreaks in the U.S. (Beer et al., 2015). The drinking water-associated outbreak data from 1971–2012 illustrate that there is an observable reduction of reported outbreaks over that time frame, which may be, at least in part, due to the implementation of the TCR and the SWTR beginning in 1991. Although the historic number of drinking water-associated outbreaks is declining, CDC notes that the level of surveillance and reporting activity, as well as reporting requirements, varies across states and localities. For these reasons, outbreak surveillance data likely underestimate actual values, and should not be used to estimate the total number of outbreaks or cases of waterborne disease (Beer et al., 2015). Deficiencies at private wells and premise plumbing systems are increasingly responsible for disease outbreaks associated with drinking water (Beer et al., 2015). Premise plumbing is the portion of the distribution system from the water meter to the consumer tap in homes, schools, and other buildings (NRC, 2006b). In 2011–2012, the two most frequent deficiencies related to drinking-water-associated outbreaks were Legionella in premise plumbing systems (66 percent) and untreated ground water (13 percent) (Beer et al., 2015). In addition to epidemic illness, sporadic illness (i.e., isolated cases not associated with an outbreak) accounts for an unknown but probably significant portion of waterborne disease and is more difficult to recognize (71 FR 65573, USEPA, 2006b). Collectively, the data indicate that outbreaks associated with drinking water may have been reduced as a result of drinking water regulations. However, opportunities remain to address disease outbreaks associated with distribution systems and untreated ground water and, at the same time, to potentially address some of the waterborne disease outbreaks associated with little to no disinfectant residual in the distribution system (Geldreich et al., 1992; Bartrand et al., 2014). The precise burden of disease is not well quantified. Five primarily waterborne diseases (giardiasis, cryptosporidiosis, Legionnaires’ disease, otitis externa, and non-tuberculous mycobacterial infection) were responsible for over 40,000 hospitalizations per year at a cost of nearly $1 billion per year (Collier et al., E:\FR\FM\11JAP3.SGM 11JAP3 3540 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules 2012). Given this information, there are opportunities for substantial cost savings if such incidence can be reduced through better risk management. Most of these costs are attributed to Legionella and nontuberculous mycobacteria. These bacteria can proliferate under favorable conditions at locations in the premise plumbing and in some parts of the distribution system that are further from the central parts of the system, where water has aged the longest and where there may be very little to no disinfectant residual. Further, the quality of the water delivered to building systems and households can affect these pathogens’ ability for growth and disease transmission. There are opportunities to enhance the current disinfectant residual requirements to more effectively kill pathogens or contain their growth, and to better indicate, through a stronger signal of the absence of a residual, when targeted improvements to treatment practices or distribution conditions may provide greater public health protection. sradovich on DSK3GMQ082PROD with PROPOSALS3 GWUDI-Related Disease Outbreaks Wallender et al. (2014) summarized CDC outbreak data for the years 1971– 2008 and determined that GWUDI was a ‘‘contributing factor’’ in 11 percent (six percent with Giardia etiology) of all outbreaks using untreated ground water. The total number of untreated ground water outbreaks during this time period was 248. Three quarters of the outbreaks involved PWSs. These findings indicate that some of the ground water systems examined by CDC that are not currently required to disinfect are contaminated with pathogens. Reclassifying these potentially ‘‘unrecognized’’ GWUDI PWSs may provide greater public health protection against microbial contamination because these PWSs would be subject to stricter requirements. As an example, a 2007 outbreak of giardiasis occurred in a New Hampshire community (205 homes) using untreated ground water (Daly et al., 2010). This GWUDI misclassification-related outbreak was the largest giardiasis drinking waterassociated outbreak in the preceding 10 years. Randomized Controlled Intervention Study A randomized, controlled, tripleblinded drinking water intervention study was conducted in Sonoma County, California (Colford et al., 2009). The purpose of the study was to determine the proportion of acute gastrointestinal illnesses (AGI) attributable to drinking water. Sonoma VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 County obtained water from five horizontal collector wells along the Russian River, four regulated as ground water and one regulated as GWUDI (part of the year). Colford et al. (2009) found that highly credible AGI in the population aged 55 and over was attributable to drinking water exposure. Illness occurred even though the water utility met all federal, state and local drinking water regulations. Pathogenic Protozoa Occurrence in Ground Water In a karst aquifer in France, 18 ground water samples were taken from the Norville (Haute-Normandie) public water supply well (5,000 customers, chlorine treatment) and tested for Cryptosporidium oocysts. Thirteen of the 18 samples were found to be Cryptosporidium positive by solidphase cytometry; the maximum concentration was four oocyst per 100 L (Khaldi et al., 2011). These data show that Cryptosporidium in karst ground water includes, for some highly vulnerable systems, Cryptosporidium occurrence resulting from poor Cryptosporidium removal during infiltration from the surface rather than poor removal during induced infiltration from nearby surface water. Because the SWTR definition assumes that all Cryptosporidium in PWS wells is transported from adjacent surface water, it is silent on the issue of Cryptosporidium transport directly from the surface, as apparently was the case in Norville, France. Karst aquifers are a vital ground water resource in the U.S. According to the USGS, about 40 percent of the ground water used for drinking water comes from karst aquifers (USGS, 2004). Analytical Feasibility Analytical Methods for Chlorine Residuals Because of concerns about analytical methods and the potential for false positives, the detectable concentration of disinfectant residuals in the distribution system may not be adequately protective of microbial pathogens. To further inform these concerns, EPA reviewed analytical methods that have been approved for free chlorine, total chlorine and chlorine dioxide under the SWTR and the D/DBPRs. Nearly all utilities use either the DPD (N,N-diethyl-pphenylenediamine) or amperometric titration methods to measure distribution system disinfectant residual, and these measurements are generally performed in the field (Wahman and Pressman, 2015). A PO 00000 Frm 00024 Fmt 4701 Sfmt 4702 number of constituents can interfere with measurements of disinfectant residuals. In general, most strong oxidants will interfere with measurement of chlorine. In addition, color, turbidity and particles will also interfere with colorimetric techniques such as DPD. For some systems using chloramines (a mixture of biocidal inorganic chloramines, of which monochloramine is the most effective), the presence of organic chloramines can be problematic since these related compounds have minimal biocidal properties, they can interfere with residual monitoring, and they can give the false impression that the finished water contains more active disinfectant than is actually present (Wahman and Pressman, 2015; Westerhoff et al., 2010). Organic chloramines will continue to form in the distribution system while inorganic chloramines decay, and thus areas of the distribution system with relatively high water ages may have residuals containing a significant amount of organic chloramines (Wahman and Pressman, 2015). In addition, EPA reviewed research published regarding potential improvements to methods or technologies used in the determination of free or total chlorine (Dong et al., 2012; Tang et al., 2014; Saad et al., 2005). Analytical methods that can measure inorganic chloramines without the organic chloramine interferences are available, but not approved for determining compliance with NPDWRs. Field test kits based on the indophenol method are available that can specifically measure monochloramine without inclusion of mass from dichloramine or organic chloramines (Lee et al., 2007). Use of Aerobic Spores as Pathogenic Protozoa Surrogates EPA’s existing microbial contaminants regulations require monitoring of pathogenic protozoa in source water (e.g., Cryptosporidium) and microorganisms that indicate a possible pathway for contamination (e.g., total coliform, E. coli). In this SixYear Review, EPA evaluated additional microorganisms that could be used to identify PWSs most at risk from Cryptosporidium in ground water. New data suggest that aerobic spores are useful surrogates for Cryptosporidium occurrence and removal. Aerobic spores originate in shallow soil. The spore presence in a sample from a PWS well indicates that there is a pathway for water infiltration into the well, either vertically from the surface or horizontally from nearby surface water. E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules EPA previously used aerobic spores as surrogate measures of Cryptosporidium removal by alternative treatment in a demonstration of field performance (USEPA, 2010f). Field demonstrations showed that the spores performed well in demonstrating two-log removal of Cryptosporidium at Casper, Wyoming, and Kennewick, Washington (USEPA, 2010f). Spores also performed well in demonstrating that a Nebraska PWS was unable to achieve better than two-log removal of Cryptosporidium, and that UV or other engineered treatment would be required (State of Nebraska, 2013). Headd and Bradford (2015) summarized the relevant scientific literature, conducted spore and Cryptosporidium laboratory experiments, and performed porous media transport modeling. They found that spores are suitable Cryptosporidium surrogates in ground water. These new data suggest that aerobic spores are useful as surrogates for Cryptosporidium removal estimates via subsurface passage (USEPA, 2010f) and may be useful as supplemental surrogates to improve recognition of GWUDI systems. Locas et al. (2008) found that aerobic spores were present in six of nine wells sampled in Quebec, Canada, and in 45 of 109 samples taken. The authors conclude that aerobic spore presence is an indicator of a change in water quality and warrants further investigation to determine the source of potential contamination. In EPA’s investigation of virus occurrence in untreated PWS wells under the UCMR3, 252 of 793 wells (317 of 1,047 samples) were positive for aerobic spores (USEPA, 2016j). Measured concentrations spanned three orders of magnitude, with about three percent having over 100 spore-forming units per 100 ml). Because aerobic spores originating in soil are found in GWUDI and ground water PWS wells, the UCMR3 data suggest that aerobic spores could be used as an indicator of the susceptibility of PWS wells to surface water infiltration. Together with other indicators and/or parasitic protozoa data from PWS wells, newer methods including spores (occurrence, concentration, and/or removal estimates) might be useful in identifying unrecognized GWUDI PWS wells. The LT2 Toolbox Guidance Manual identified aerobic spores as the indicator to determine Cryptosporidium removal for systems using bank filtration for LT2 additional treatment requirements (USEPA, 2010f). Occurrence and Exposure Coliform and/or E. coli occurrence can be an indication of conditions VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 supporting bacterial growth or an intrusion event into the distribution system. On the other hand, the absence of coliforms and/or E. coli does not necessarily mean the absence of pathogens that are more resistant to the disinfectant residual. Detection of coliform bacteria is commonly associated with low distribution system disinfectant residuals. According to LeChevallier et al. (1996), disinfectant residuals of 0.2 mg/L or more of free chlorine, or 0.5 mg/L or more of total chlorine, are associated with reduced levels of coliform bacteria. To assess the relationship between disinfectant residual and occurrence of indicators for pathogens in distribution systems, EPA evaluated information about chlorine residuals and total coliforms and E. coli (TC/EC) using compliance monitoring data from the SYR3 ICR database. EPA paired TC/EC results with field chlorine residual data collected at the same time and location. It is important to note that these evaluations help to inform the SYR3 results, but do not assess compliance with regulatory standards. EPA found that there was a lower rate of occurrence of both TC and EC as the free or total chlorine residual increased to higher levels (note: total chlorine is often used as a measure for systems that use chloramines). For example, the TC positive rate was less than one percent when chlorine residuals were equal to or greater than 0.2 mg/L of free chlorine or 0.5 mg/L of total chlorine. This relationship between chlorine residuals and occurrence of TC and EC was similar to that reported by the Colorado Department of Public Health and Environment (Ingels, 2015). A disinfectant residual also serves as an indicator of the effectiveness of distribution system best management practices. Best management practices include flushing, storage tank maintenance, cross-connection control, leak detection and effective pipe replacement and repair practices. The effective implementation of best management practices helps water suppliers to lower chlorine demand and maintain an adequate disinfectant residual throughout the distribution system. These same practices can also help control DBP formation. Treatment Feasibility EPA reviewed new information related to the TT requirements in the SWTR and identified the following treatment-related topics that support potential revisions to the SWTRs to improve public health protection: • Detectable residual for systems using chloramine disinfection, PO 00000 Frm 00025 Fmt 4701 Sfmt 4702 3541 • State implementation of disinfection residual requirements, • Disinfectant residuals for control of Legionella in premise plumbing systems, • HPC alternative to detectable residual measurement, and • CT criteria for viruses. In addition, EPA reviewed key findings by the Research and Information Collection Partnership (RICP) on drinking water distribution system issues and research and information needs. The RICP is a working group formed on the recommendation of the Total Coliform Rule Distribution System Advisory Committee to identify specific highpriority research and information collection activities and to stimulate water distribution system research and information collection (USEPA, 2008b; USEPA and Water Research Foundation, 2016). Detectable Residual for Systems Using Chloramine Disinfection As discussed in the background portion of this section, for surface water systems or GWUDI systems, the SWTR requires that a disinfectant residual cannot be undetectable in more than five percent of samples each month for any two consecutive months. EPA identified two issues that have implications for the protectiveness of allowing a detectable residual as a surrogate for bacteriological quality: Organic chloramines and nitrification. Organic chloramines affect the effectiveness of disinfectant residuals because they: (1) Form during the use of free chlorine or chloramines, (2) interfere with commonly used analytical methods for free and total chlorine measurements, and (3) are poor disinfectants compared to free chlorine and monochloramine (Wahman and Pressman, 2015). Because chloramination involves introduction of ammonia into drinking water, and decomposition of chloramines can further release ammonia in the distribution system, chloramine use comes with the risk of distribution system nitrification (i.e., the biological oxidation of ammonia to nitrite and eventually nitrate). Drinking water distribution system nitrification is undesirable and can result in water quality degradation. Information shows that maintaining a high enough level of total chlorine or monochloramine residuals in the distribution system can help prevent both nitrification and residual depletion (Stanford et al, 2014). E:\FR\FM\11JAP3.SGM 11JAP3 3542 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules State Implementation of Disinfectant Residual Requirements States may adopt federal drinking water regulations or promulgate more stringent drinking water requirements, including those for disinfectant residuals. Preliminary information shows that 26 states require a detectable disinfectant residual in the distribution system. Twenty of these 26 states require a minimum free chlorine residual of 0.2 mg/L or more (Ingels, 2015; Wahman and Pressman, 2015). Five of the 20 states set standards even more stringent than 0.2 mg/L: Louisiana requires at least 0.5 mg/L free chlorine in its emergency rule, while Florida, Illinois, Iowa, and Delaware require 0.3 mg/L. For minimum total chlorine residual, state requirements vary from 0.05 mg/L (New Jersey) to 1.00 mg/L or higher (Kansas, Oklahoma, Iowa, Ohio, and North Carolina). North Carolina has a numeric requirement for total chlorine residual but not for free chlorine residual. Colorado has amended its minimum disinfectant residual requirements in the distribution system to be greater than or equal to 0.2 mg/L, effective April 1, 2016 (Ingels, 2015). Pennsylvania recently proposed to strengthen its disinfectant residual requirements by increasing the minimum disinfectant residual in the distribution system to 0.2 mg/L free or total chlorine (Pennsylvania Bulletin, 2016). Louisiana’s Emergency Distribution Disinfectant Residual Rule was established in 2013 to control Naegleria fowleri, an amoeba found in several PWSs. That rule requires a minimum free or total chlorine disinfectant level of 0.5 mg/L to be maintained at all times in finished water storage tanks and the entire distribution system (Louisiana Department of Health and Hospitals, 2013). The state agency intends to continue to renew the Emergency Rule until a final rule can be promulgated (Louisiana Department of Health and Hospitals, 2014). sradovich on DSK3GMQ082PROD with PROPOSALS3 Disinfectant Residuals for Control of Legionella in Premise Plumbing Systems Since the reporting of disease outbreaks due to Legionella began in 2001, Legionella has been shown to cause more drinking-water-related outbreaks than any other microorganism. Addressing premise plumbing issues is particularly challenging. Premise plumbing may be largely outside of water utilities’ operations and management control. Also, the characteristic features of premise plumbing (e.g., low disinfectants residuals, stagnation, and VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 warm temperature) tend to support growth and persistence of opportunistic pathogens. Studies indicate that distribution systems can play a role in influencing the transmission and contamination of Legionella in premise plumbing systems (Lin et al., 1998; States et al., 2013). Hospitals served by PWSs using chloramines reported fewer outbreaks of legionellosis than those using free chlorine (Kool et al., 1999; Heffelginger et al., 2003). Some building systems supplied by PWSs which have switched to chloramines have seen marked reduction in the colonization of Legionella (Flannery et al., 2006; Moore et al., 2006). One implication of these studies is the importance of being able to reliably measure and sustain chloramine residuals to increase the likelihood of its effectiveness at controlling Legionella in premise plumbing systems. On the other hand, some studies have indicated that the occurrence of another pathogen, nontubercular Mycobacterium, may increase under chloramination conditions (Pryor et al., 2004; Moore et al., 2006; Duda et al., 2014). Legionella species can multiply in warm, stagnant water environments, such as in community water storage tanks with low disinfectant residuals during warm months. Cohn et al. (2014) observed increased incidence of legionellosis among institutions and private homes near a community water storage tank when the disinfectant residual in the storage tank dropped (from greater than 0.2 mg/L to less than 0.2 mg/L) during hot summer months. Based on these findings, the authors recommended that, regardless of total coliform occurrence, remedial actions be taken (e.g., flushing of mains, checking for closed valves that can result in hydraulic dead-ends, and possibly installing re-chlorination stations) when low chlorine residuals are observed during hot summer months. They also noted that this storage tank had been cleaned subsequent to the outbreak (Cohn et al., 2014; Ashbolt, 2015). To help address concerns about Legionella, EPA developed a document entitled ‘‘Technology for Legionella Control in Premise Plumbing Systems: Scientific Literature Review’’ (USEPA, 2016r). The document summarizes information about the effectiveness of different approaches to control Legionella in a building’s premise plumbing system. EPA expects that use of this document will further improve public health by helping primacy agencies, facility maintenance operators, and facility owners make science-based PO 00000 Frm 00026 Fmt 4701 Sfmt 4702 risk management decisions regarding treatment and control of Legionella in buildings. EPA also reviewed the scientific literature on the effectiveness of disinfectant residuals at controlling biofilm growth. Many factors influence the concentration of the disinfectant residual in the distribution system; and therefore, the ability of the residual to control microbial growth and biofilm formation. These factors include the level of assimilable organic carbon (AOC), the type and concentration of disinfectant, water temperature, pipe materials, and system hydraulics. Problems associated with biofilms in distribution systems include enhanced corrosion of pipes and deterioration of water quality. Biofilms can provide ecological niches that are suited to the potential survival of pathogens (Walker and Morales, 1997; Baribeau et al., 2005; Behnke et al., 2011; Wang et al., 2012; Biyela et al., 2012; Revetta et al., 2013; Ashbolt, 2015). The biofilm can protect microorganisms from disinfectants and can enhance nutrient accumulation and transport (Baribeau et al., 2005). HPC Alternative to Detectable Residual Measurement Under the SWTR, a system may demonstrate that its HPC levels are less than 500 per mL, at any sampling locations, in lieu of demonstrating the presence of a detectable disinfectant residual at that location, per primacy agency approval. EPA reviewed new information that suggests development of criteria which may be more protective than the HPC criterion. For example, criteria used in the Netherlands for systems operating without a distribution system disinfectant residual provides an example of an alternative criteria than the HPC criterion. In the Netherlands, chlorine is not used routinely for primary or secondary disinfection. Dutch water systems use the following general approach to control microbial activity in the distribution system without a disinfectant residual (Smeets et al., 2009): Produce a biologically stable drinking water; use distribution system materials that are non-reactive and biologically stable; and optimize distribution system operations and maintenance practices to prevent stagnation and sediment accumulation. For the determination of a biologically stable water they use AOC as an indicator. CT Criteria for Virus Disinfection EPA reviewed new disinfection studies published since the release of the original CT tables. Collectively, the data in the recent literature indicate that E:\FR\FM\11JAP3.SGM 11JAP3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules EPA CT values for free chlorine disinfection are sufficient to inactivate most enteric viruses in drinking water, except for Coxsackie virus B5 at a pH higher than 7.5 (Black et al., 2009; Cromeans et al., 2010; Keegan et al., 2012). EPA’s CT values for chlorine incorporate a safety factor of three to account for differences between dispersed and aggregated hepatitis A virus and between buffered, demandfree water and environmental water. In light of new information about the hepatitis A virus and the effects of source water quality on chlorine disinfection, EPA concludes that the safety factor of three should be reevaluated to ensure its adequacy. A larger safety factor (thus higher EPA CT values) is expected to enhance waterborne pathogen control but could lead to higher DBP formation and warrants further examination in any rulemaking activity. Adenovirus is the virus that is most resistant to chloramines, through it is very susceptible to free chlorine disinfection. Several studies revealed that monochloramine disinfection might not provide adequate control of adenovirus in drinking water, particularly in waters with relatively high pH and at low temperature (Sirikanchana et al., 2008; Hill and Cromeans, 2010). sradovich on DSK3GMQ082PROD with PROPOSALS3 Research and Information Collection Partnership Findings The RICP partners are EPA and Water Research Foundation. EPA examined information from the 10 high priority RICP areas in the context of the Six-Year Review, particularly information related to the effectiveness of sanitary survey and corrective action requirements under the IESWTR. However, EPA found limited information that would shed light on the frequency and magnitude of distribution system vulnerability events (e.g., backflow events, storage tank breeches), associated risk implication, and costs for preventing such events from occurring. The RICP report identifies potential follow-up research areas that could help to address these gaps (USEPA and Water Research Foundation, 2016). Risk-Balancing The Agency has considered the riskbalancing aspects of the MDBP rules and has determined that potential revisions to the SWTRs could provide improved health protection. The riskbalancing activities considered by the Agency include those between the microbial and disinfection by-product VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 rules, as well as those between different groups of DBPs. This includes balancing the reduction in risks from microbial pathogens should there be additional requirements to maintain a disinfectant residual with the increased risk from D/ DBPs resulting from such requirements. EPA also considered the potential impact of further constraints on DBP precursors on the reduction of demand for disinfectant residual. The riskbalancing review was based on a preliminary, qualitative assessment of unintended consequences; it is important to note that further assessment of such consequences would be an important component of any further rulemaking activities. b. LT2 Background EPA promulgated the LT2 on January 5, 2006 (71 FR 654, USEPA, 2006c). The LT2 applies to all PWSs that use surface water or ground water under the direct influence of surface water as drinking water. The LT2 builds upon the IESWTR and the LT1 by improving control of microbial pathogens, specifically the contaminant Cryptosporidium. The purpose of the LT2 is to reduce illness linked with the contaminant Cryptosporidium and other disease-causing microorganisms in drinking water. The LT2 supplements the IESWTR and the LT1 regulations by establishing additional Cryptosporidium treatment requirements for higher-risk systems. The LT2 requires source water occurrence monitoring which is used to determine additional treatment requirements. The LT2 rule provides for additional CT credits for Cryptosporidium inactivation by ozone and chlorine dioxide. The LT2 also provides UV treatment credits for Cryptosporidium, Giardia and virus inactivation. EPA recognized that research in the field of Cryptosporidium inactivation is ongoing and included a provision in the rule that allows unfiltered systems using a disinfectant other than chlorine to demonstrate the log inactivation that can be achieved. The LT2 also contains provisions to reduce risks from uncovered finished water reservoirs (UCFWRs).5 The rule ensures that systems maintain microbial protection when they take steps to decrease the formation of disinfection byproducts in systems that add a chemical disinfectant (i.e., other than UV light) or receive a chemically disinfected water. Storage of treated drinking water in open reservoirs can 5 LT2 uses the term ‘facilities’’ instead of ‘reservoirs’. The term reservoirs is used in this document. PO 00000 Frm 00027 Fmt 4701 Sfmt 4702 3543 lead to significant water quality degradation and health risks to consumers (USEPA, 1999). Examples of such water quality degradation include increases in algal cells, coliform bacteria, heterotrophic bacteria, particulates, disinfection byproducts, metals, taste and odor, insect larvae, Giardia, Cryptosporidium and nitrate (USEPA, 1999). Contamination of reservoirs occurs through surface water runoff, bird and animal wastes, human activity, algal growth, airborne deposition and insects and fish. The LT2 requires PWSs using uncovered finished water storage facilities to either cover the storage facility or treat the storage facility discharge (i.e., prior to entering the distribution system) to achieve inactivation and/or removal of 4-log virus, 3-log G. lamblia, and 2-log Cryptosporidium spp. on a stateapproved schedule. Under the LT2, PWSs were required to notify their state/primacy agency by April 1, 2008, if they used UCFWRs. Additionally, the LT2 required all PWSs to either meet the requirement to cover the UCFWR, or treat the UCFWR discharge to the distribution system or be in compliance with a state-approved schedule for meeting these requirements no later than April 1, 2009. Under this review, EPA evaluated published information to assess whether allowing a state-approved risk management plan would justify revisions to the LT2. Summary of Review Results Information available since promulgation of the LT2 either supports the current regulatory requirements or does not justify a revision. EPA determined that no regulatory revisions to the UCFWR requirements of the LT2 are warranted at this time based on the review of available information. Health Effects EPA reassessed the health risks resulting from exposure to Cryptosporidium spp., Giardia lamblia and viruses, as well as other potential microbiological risks to human health. The Agency also reviewed new information on other pathogens of potential concern to determine whether additional measures are warranted to provide greater public health protection from these pathogens, particularly in the context of the UCFWR provisions of the LT2. The principal objectives of this health effects review were to: (1) Evaluate whether there are new or additional ways to estimate risks from Cryptosporidium and other pathogenic microorganisms in drinking water and E:\FR\FM\11JAP3.SGM 11JAP3 3544 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 (2) evaluate surveillance and outbreak data on Cryptosporidium and other contaminants of potential concern. Based on the review, the new information does not justify a revision to the health basis for the LT2 at this time. For more information regarding EPA’s review of health effects, see the ‘‘Six-Year Review 3 Technical Support Document for Long-Term 2 Enhanced Surface Water Treatment Rule’’ (USEPA, 2016m). Analytical Feasibility The LT2 specifies approved analytical methods to determine the levels of Cryptosporidium in source waters for the identification of additional treatment needs. The LT2 requires systems and/or laboratories to use either ‘‘Method 1622: Cryptosporidium in Water by Filtration/IMS/FA’’ (EPA 815– R–05–001, USEPA, 2005d) or ‘‘Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA’’ (EPA 815– R–05–002, USEPA, 2005e). EPA Methods 1622 or 1623 is used in monitoring programs to characterize Cryptosporidium levels in the source water of PWSs for the purposes of risktargeted treatment requirements under the LT2. Method recoveries of more than 3,000 matrix spiked samples from the first round of monitoring for the LT2 indicated an average recovery of oocysts with Methods 1622 and 1623 to be 40 percent. In addition to evaluating the results from the first round of monitoring, EPA gathered new information on Cryptosporidium analytical methods by investigating improvements to Methods 1622 and 1623. EPA evaluated whether the required use of a revised method (Method 1623.1) would be justified for Round 2 monitoring under the LT2. Though new information is available that indicates the potential for a regulatory revision, the Agency does not believe it is appropriate to revise the rule to require the use of Method 1623.1, since the Agency believes such a change would not provide substantially greater protection of public health at the national level. The use of Method 1623.1 during the LT2 Round 2 monitoring is optional, and not required. Since EPA is not planning changes to the methods required under the LT2, the schedule for the LT2 Round 2 monitoring remains the same as described in the final LT2, which is scheduled to be completed no later than 2021 for all PWSs. Occurrence and Exposure The LT2 requires PWSs using surface water or ground water under the direct influence of surface water to monitor VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 their source waters for Cryptosporidium spp. (and/or E. coli) to identify additional treatment requirements. PWSs must monitor their source water (i.e., the influent water entering the treatment plant) over two different timeframes (Round 1 and Round 2) to determine the Cryptosporidium level. Monitoring results determine the extent of Cryptosporidium treatment requirements under the LT2. Under the LT2, the date for PWSs to begin monitoring is staggered by PWS size, with smaller PWSs starting at a later time than larger systems. According to the LT2 rule requirements, all PWSs were expected to complete Round 1 in 2012. To reduce monitoring costs, small filtered PWSs (serving fewer than 10,000 people) initially monitor for E. coli for one year as a screening analysis and are required to monitor for Cryptosporidium only if their E. coli levels exceed specified trigger values. Small filtered PWSs that exceed the E. coli trigger, as well as small unfiltered PWSs, must monitor for Cryptosporidium for one or two years, depending on the sampling frequency. Based on the source water monitoring results, filtered systems were classified in one of four risk categories to determine additional treatment needed (Bins 1–4). Systems in Bin 1 are required to provide no additional Cryptosporidium treatment. Filtered systems in Bins 2–4 must achieve 1.0– 2.5 log of treatment (i.e., 90 to 99.7 percent reduction) for Cryptosporidium over and above that provided by conventional treatment, depending on the Cryptosporidium concentrations. Filtered PWSs must meet the additional Cryptosporidium treatment requirements in Bins 2, 3, or 4 by selecting one or more technologies from the microbial toolbox of options for ensuring source water protection and management, and/or Cryptosporidium removal or inactivation. All unfiltered water systems must provide at least 99 or 99.9 percent (2 or 3-log) inactivation of Cryptosporidium, depending on the results of their monitoring. Additionally, all filtered systems that provide, or will provide, 5.5 log treatment for Cryptosporidium are exempt from monitoring and subsequent bin classification. Systems providing 5.5 log Cryptosporidium treatment must notify the state no later than the date by which the system must submit a sampling plan. Six years after the initial bin classification, filtered systems must conduct a second round of monitoring. Round 2 monitoring is in place to understand year-to-year occurrence PO 00000 Frm 00028 Fmt 4701 Sfmt 4702 variability. The difference observed between occurrence at the time of the ICR Supplemental Surveys (USEPA, 2000c) and the LT2 Round 1 monitoring indicates year-to-year variability. Round 2 monitoring began in 2015. Under this review, EPA considered whether a third round of monitoring would be justified at this time, in particular, requiring the use of Method 1623.1. EPA also considered whether a modification to the action bin boundaries should be made based on requiring Method 1623.1. Because of the relatively modest gains in public health protection predicted by the Round 2 monitoring EPA does not believe a third round of monitoring is justified at this time, even if the Agency were to require the use of Method 1623.1 for this monitoring. Round 1 Cryptosporidium occurrence was lower than expected (3.3–5.3 percent of Bin 1 systems from Round 1 would be moved to a higher bin). As mentioned earlier, EPA will not require the use of Method 1623.1 for Cryptosporidium monitoring. Therefore, EPA will not make changes to the action bin boundaries at this time. Treatment Feasibility LT2 includes a variety of treatment and control options, collectively termed the ‘‘microbial toolbox,’’ that PWSs can implement to comply with the LT2’s additional Cryptosporidium treatment requirements. Most options in the microbial toolbox carry prescribed credits toward Cryptosporidium treatment and control requirements. The LT2 Toolbox Guidance Manual (USEPA, 2010f) provides guidance on how to apply the toolbox options. The LT2 also requires all unfiltered PWSs to provide at least 2 to 3-log (i.e., 99 to 99.9 percent) inactivation of Cryptosporidium. Further, under the LT2, unfiltered PWSs must achieve their overall inactivation requirements (including Giardia and virus inactivation as established by earlier regulations) using a minimum of two disinfectants. EPA reviewed information available since the promulgation of the LT2 on the use of the microbial toolbox to determine if the information would support a potential change to the prescribed credits or the associated design and operational criteria. In addition, EPA searched for information on new and emerging tools that would support their potential addition to the toolbox. The Agency also received input on the use and effectiveness of the microbial toolbox tools through public meetings, research of publicly available information and by actively communicating with some systems. EPA E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules also considered benefits and/or difficulties observed by the PWSs when using the available tools. EPA also examined information from some PWSs with UCFWRs to evaluate the potential effectiveness of risk management measures taken by those PWSs for protecting the finished water in the UCFWRs from contamination. The New York City Department of Environmental Protection (NYC DEP) has undertaken more activities than any other PWS to protect their Hillview Reservoir from contamination. These activities include wildlife management (e.g., bird harassment and deterrents, mammal relocation), security measures, runoff control, public health surveillance, microbial monitoring (e.g., Cryptosporidium, E. coli) and a Cryptosporidium and Giardia action plan.6 EPA reviewed information pertaining to these activities and concluded that the information is inadequate to support regulatory changes at the national level. The data is also insufficient to demonstrate that risk management activities provide equivalent public health protection compared to covering the reservoir or treating the outflow from the reservoir. The LT2 includes disinfection profile and benchmark requirements to ensure that any significant change in disinfection, whether for disinfection byproducts control under the Stage 2 D/DBPR, improved Cryptosporidium control under the LT2, or both, does not significantly compromise existing Giardia and virus protection. The profiling and benchmarking requirements under the LT2 are similar to those promulgated under the IESWTR and the LT1 (USEPA, 2002c) and are applicable to systems that make a significant change to their disinfection practices. EPA did not identify information that would support a potential change to the methodology and calculations for developing the disinfection profile and benchmark under the LT2. However, EPA identified information that would support a potential change to the CT values required for virus disinfection (as discussed in the Section VI.B.4.a. ‘‘SWTRs’’). EPA is considering this information in the review of the overall filtration and disinfection requirements in the SWTR. Based on the outcome of this review, EPA determined that no regulatory revisions to the microbial toolbox options are warranted at this time. Any new information available to the Agency 6 https://www.nyc.gov/html/dep/pdf/reports/fad_ 4.1_waterfowl_managementprogram_annual_ report.07-12.pdf. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 either supports the current regulatory requirements or does not justify a revision. For more information regarding EPA’s review of treatment feasibility see the ‘‘Six-Year Review 3 Technical Support Document for LongTerm 2 Enhanced Surface Water Treatment Rule’’ (USEPA, 2016m). c. FBRR Background EPA promulgated the FBRR in 2001 (66 FR 31086, USEPA, 2001b). It requires PWSs to review their backwash water recycling practices to ensure microbial control is not compromised, and it requires PWSs to recycle filter backwash water. Summary of Review Results EPA reviewed this rule as part of the Six-Year Review 3, and the result is to take no action on the basis that EPA did not identify any relevant information that indicate changes to the NPDWR. d. GWR Background EPA promulgated the GWR in 2006 (71 FR 65573, USEPA, 2006b) to provide protection against microbial pathogens in PWSs using ground water sources. The rule establishes a risk-based approach to target undisinfected ground water systems that are vulnerable to fecal contamination. If a system has an initial total coliform positive in the distribution system (based on routine coliform monitoring under the RTCR), followed by a fecal indicator positive (E. coli, enterococci or coliphage) in a follow-up source water sample, it is considered to be at risk of fecal contamination. Systems at risk of fecal contamination must take corrective action to reduce potential illness from exposure to microbial pathogens. Disinfecting systems that can demonstrate 4-log virus inactivation are not subject to the monitoring requirements. In addition to the protection provided by the Revised Total Coliform Rule (RTCR) and GWR monitoring requirements, systems that do not disinfect are also protected by the sanitary survey provisions of the GWR and the Level 1 assessment provisions of the RTCR. Summary of Review Results EPA has not identified the GWR as a candidate for revision under the SixYear Review 3 because EPA needs to evaluate emerging information from full implementation of the GWR (71 FR 65573, USEPA, 2006b) and the RTCR (78 FR 10270, USEPA, 2013a) before PO 00000 Frm 00029 Fmt 4701 Sfmt 4702 3545 determining if there is an opportunity to improve public health protection. Implementation of the GWR was not yet completed for the period of time covered by the SYR3 ICR. The RTCR was promulgated in 2013 and became effective on April 1, 2016. EPA expects that implementation on the RTCR may impact the percent of ground water systems that will be triggered into source water monitoring and taking any corrective actions under the GWR. Therefore, the effects of the GWR and the RTCR implementation in addressing vulnerable ground water systems are not yet known. EPA notes that the GWR was also recently reviewed under Section 610 of the Regulatory Flexibility Act, which required federal agencies to review regulations that have significant economic impact on a substantial number of small entities within 10 years after their adoption as final rules. The 610 Review of the GWR was recently completed; three comments were received. A report is available discussing the 610 Review, comments received, and EPA’s response to major comments (USEPA, 2016g). Health Effects Borchardt et al. (2012) studied the health effects associated with enteric virus occurrence in undisinfected PWS wells in 14 communities in Wisconsin. Drinking water samples were assayed for a suite of viral pathogens using quantitative polymerase chain reaction (qPCR). Community members kept daily diaries to self-report AGI. The study found a statistically significant association between enteric virus occurrence in the drinking water and AGI incidences in the communities. Using the 2005 data, EPA estimated a national average TC detection rate of 2.4 percent for routine samples from undisinfected CWSs with populations less than 4,100 people (USEPA, 2012). The 14 communities (with undisinfected PWS wells) studied by Borchardt et al. (2012) had TC detections of 2.3 percent. These data suggest that the 14 communities studied by Borchardt et al. (2012) had TC detection rates no different from an average undisinfected community PWS in the U.S. Analytical Methods Since the promulgation of the GWR in 2006, EPA has approved several new methods for the analysis of TC samples used as a trigger for GWR source water monitoring, or for source water fecal indicators used under the GWR. These methods can be found on the EPA Web site (https://www.epa.gov/ dwanalyticalmethods/approved- E:\FR\FM\11JAP3.SGM 11JAP3 3546 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 drinking-water-analytical-methods). However, PWSs are not required to use these new methods. Additionally, EPA did eliminate the use of fecal coliforms from the RTCR as an indicator of fecal contamination. Occurrence and Exposure New information suggests that total coliform occurrence varies among small undisinfected ground water systems, depending upon whether the system is a community, non-transient noncommunity or transient non-community PWS (USEPA, 2016n). Statistical modeling of 2011 data (about 60,000 systems based on occurrence data collected from undisinfected ground water systems) shows that undisinfected transient non-community ground water systems have the highest occurrence, at approximately four percent median routine TC positive occurrence as compared with three percent for undisinfected non-transient noncommunity ground water systems and two percent for undisinfected community ground water systems (USEPA, 2016n). These occurrence levels are similar to those estimated during the development of the RTCR using 2005 data (USEPA, 2012). Additionally, according to the 2005 and 2011 datasets, the smaller systems had higher median TC occurrence than the larger systems. All positive total coliform samples were assayed for E. coli; about one in 20 were E. coli positive. A small percentage of undisinfected ground water systems have higher TC detection rates. For example, of the 52,000 undisinfected transient, noncommunity ground water systems serving populations less than 101 people (the total count is from USEPA, 2006b), EPA (2012) estimated that about 2,600 (five percent) of those systems (4.6 percent for the 2005 data set) had TC detection rates of 20 percent or more. Under the third monitoring cycle of the Unregulated Contaminant Monitoring Rule (UCMR3), EPA sampled about 800 randomly selected undisinfected ground water systems serving fewer than 100 people for virus and virus indicators. These data show that only a small number of samples were virus positive by qPCR (16 out of 1,044 or two percent) (USEPA, 2016j). This result contrasts significantly with the virus positive sample rate from Borchardt et al. (2012) (287 out of 1,204 or 24 percent). One difference is that Borchardt et al. (2012) sampled prior to any treatment in the undisinfected wells (e.g., softening, iron/manganese removal). In contrast, many wells in the UCMR3 virus study were sampled after VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 softening or other treatment. The UCMR3 monitoring results are available online at: https://www.epa.gov/dwucmr/ data-summary-third-unregulatedcontaminant-monitoring-rule. VII. EPA’s Request for Comments and Next Steps EPA invites commenters to submit any relevant data or information pertaining to the NPDWRs identified in this action as candidates for revision, as well as other relevant comments. EPA will consider the public comments and/ or any new, relevant data submitted for the eight NPDWRs listed as candidates for revision as the Agency moves forward in determining whether regulatory revisions for these NPDWRs are necessary. The announcement whether or not the Agency intends to revise an NPDWR (pursuant to SDWA § 1412(b)(9)) is not a regulatory decision. Relevant data include studies/ analyses pertaining to health effects, analytical feasibility, treatment feasibility and occurrence/exposure. This information will inform EPA’s evaluation as the Agency moves forward determining whether regulatory revisions for these NPDWRs are necessary. The data and information requested by EPA include peerreviewed science and supporting studies conducted in accordance with sound and objective scientific practices, and data collected by accepted methods or best available methods (if the reliability of the method and the nature of the review justifies use of the data). Peer-reviewed data are studies/ analyses that have been reviewed by qualified individuals (or organizations) who are independent of those who performed the work, but who are collectively equivalent in technical expertise (i.e., peers) to those who performed the original work. A peer review is an in-depth assessment of the assumptions, calculations, extrapolations, alternate interpretations, methodology, acceptance criteria and conclusions pertaining to the specific major scientific and/or technical work products and the documentation that supports them (USEPA, 2015a). Specifically, EPA is requesting comment and/or information related to the following aspects of potential revisions to the MDBP NPDWRs: • Potential approaches that could enhance protection from DBPs, including both those that are regulated and those currently unregulated (e.g., nitrosamines). Specifically, commenters are requested to provide information about requiring greater removal of precursors (e.g., TOC), and/or more PO 00000 Frm 00030 Fmt 4701 Sfmt 4702 targeted constraints on precursors (e.g., based on watershed vulnerabilities) that could provide for an improvement in health protection from mixtures of DBPs while considering risk-balancing. For example, commenters are requested to provide information about an approach that provides for an option to either control source water vulnerabilities (e.g., de facto reuse) or to further constrain precursors associated with unregulated DBPs. In addition, commenters are requested to provide information that considers a comprehensive analysis of source waters for the formation of a wide variety of byproducts (e.g., TTHM, HAA5, and unregulated DBPs such as nitrosamines, brominated and iodinated compounds). • Potential approaches that could enhance protection from chlorite, chlorate, and chlorine dioxide. Specifically, commenters are requested to provide information about approaches that could involve, for example: Setting standards for systems using hypochlorite that address combined exposure to chlorite and chlorate; and setting standards for systems using chlorine dioxide (alone or in combination with other disinfectants) that address combined exposure from chlorite, chlorate, and chlorine dioxide. • Potential approaches that could provide increased protection from microbial pathogens and that take into consideration the issues noted about disinfection residual requirements, while considering the risk-balancing aspects of the MDBP rules. In addition, commenters are requested to provide information about approaches that could offer enhanced protection without the use of a chlorine-based disinfectant residual in the distribution system, including technology and management systems associated with those approaches. • Information about how frequently PWS monitor for DBPs during chlorine burn periods, including revised monitoring schedules for DBPs, taking into account occurrence and exposure to DBPs during chlorine burn periods, and related short-term health effects on sensitive populations. References Abdel-Rahman, M.S., D. Couri, and R.J. Bull. 1984. Toxicity of chlorine dioxide in drinking water. International Journal of Toxicology. 3(4): 277–284. Agency for Toxic Substances and Disease Registry (ATSDR). 2010. Toxicological Profile for Trichlorobenzenes. U.S. Department of Health and Human Services: Atlanta, GA. https:// www.atsdr.cdc.gov/toxprofiles/tp199.pdf E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules Armstrong, T.W. and C.N. Haas. 2007. A quantitative microbial risk assessment model for legionnaires’ disease: assessment of human exposures for selected spa outbreaks. Journal of Occupational and Environmental Hygiene. 4: 634–646. Armstrong, T.W. and C.N. Haas. 2008. Legionnaires’ disease: evaluation of a quantitative microbial risk assessment model. Journal of Water and Health. 6(2): 149–166. Association of State Drinking Water Administrators (ASDWA). 2016. SixYear Review 3 Implementation & Other Regulatory Issues for Potential Consideration—ASDWA Regulatory Committee feedback. Ashbolt, N.J. 2015. Environmental (saprozoic) pathogens of engineered water systems: understanding their ecology for risk assessment and management. Pathogens. 4(2): 390–405. Azzeh, J., L. Taylor-Edmonds, and R.C. Andrews. 2015. Engineered biofiltration for ultrafiltration fouling mitigation and disinfection by-product precursor control. Water Science and Technology: Water Supply. 15(1): 124–133. Baribeau, H., SW. Krasner, R. Chinn, and P.C. Singer. 2005. Impact of biomass on the stability of HAAs and THMs in a simulated distribution system. Journal of American Water Works Association. 97(2): 69–81. Bartrand, T.A., J.J. Causey, and J.L. Clancy. 2014. Naegleria fowleri: an emerging drinking water pathogen. Journal of the American Water Works Association. 106(10): 418–432. Beer, K.D., J.W. Gargano, V.A. Roberts, V.R. Hill, L.E. Garrison, P.K. Kutty, E.D. Hilborn, T.J. Wade, K.E. Fullerton, and J.S. Yoder. 2015. Surveillance for waterborne disease outbreaks associated with drinking water—United States, 2011–2012. Morbidity and Mortality Weekly Report. 64: 842–848. Behnke, S., A.E. Parker, D. Woodall, and A.K. Camper. 2011. Comparing the chlorine disinfection of detached biofilm clusters with those of sessile biofilms and planktonic cells in single- and dualspecies cultures. Applied and Environmental Microbiology. 77(20): 7176–7184. Bercz, J.P., L.L. Jones, L. Garner, L. Murray, D. Ludwig, and J. Boston. 1982. Subchronic toxicity of chlorine dioxide and related compounds in drinking water in the nonhuman primate. Environmental Health Perspectives. 46: 47–55. Biyela, P.T., R. Hodon, A. Brown, A. Alum, M. Abbaszadegan, and B.E. Rittmann. 2012. Distribution systems as reservoirs of Naegleria fowleri and other amoebae. Journal of the American Water Works Association. 104(1): E66–E72. Black, S., J.A. Thurston, and C.P. Gerba. 2009. Determination of CT values for chlorination of resistant enteroviruses. Journal of Environmental Science and Health. 44:336–339. Borchardt, M.A., S.K. Spencer, B.A. Kieke Jr., E. Lambertini, and F.J. Loge. 2012. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Viruses in non-disinfected drinking water from municipal wells and community incidence of acute gastrointestinal illness. Environmental Health Perspectives. 120(9): 1272–1279. Available online at: https://dx.doi.org/ 10.1289/ehp.11044499. Brooke, E., and M.R. Collins. 2011. Posttreatment aeration to reduce THMs. Journal of the American Water Works Association. 103(10): 84–96. Brown, J., R.S. Summers, M. LeChevallier, H. Collins, J.A. Roberson, S. Hubbs, and E. Dickenson. 2015. Biological drinking water treatment? Naturally. Journal of the American Water Works Association. 107(12): 20–31. Buse, H.Y., M.E. Schoen, and N.J. Ashbolt. 2012. Legionellae in engineered systems and use of quantitative microbial risk assessment to predict exposure. Water Research. 46(4): 921–933. California Environmental Protection Agency (CalEPA). 2010a. Public Health Goal for Methoxychlor in Drinking Water. Office of Environmental Health Hazard Assessment: Sacramento, CA. Available at: https://oehha.ca.gov/media/ downloads/water/chemicals/phg/ 091610mxc_0.pdf CalEPA. 2010b. Public Health Goal for Styrene in Drinking Water. Office of Environmental Health Hazard Assessment: Sacramento, CA. https:// oehha.ca.gov/media/downloads/water/ chemicals/phg/122810styrene_0.pdf Callinan, C.W., J.P. Hassett, J.P. Hyde, R.A. Entringer, and R.K. Klake. 2013. Proposed nutrient criteria for water supply lakes and reservoirs. Journal of the American Water Works Association. 105(4): 47–48. Cantor, K.P., R. Hoover, and P. Hartge. 1985. Drinking water source and risk of bladder cancer: A case-control study. In: Water Chlorination: Chemistry, Environmental Impact and Health Effects. R.L. Jolley, R.J. Bull, and W.P. Davis (eds.). 5(1): 145–152. Lewis Publishers, Inc. Cantor, K.P., R. Hoover, P. Hartge, T.J. Mason, D.T. Silverman, R. Altman, D.F. Austin, M.A. Child, C.R. Key, and L.D. Marrett. 1987. Bladder cancer, drinking water source, and tap water consumption: a case-control study. Journal of the National Cancer Institute. 79(6): 1269–79. Cantor, K.P., C.F. Lunch, M. Hildesheim, M. Dosemeci, J. Lubin, M. Alavanja, and G.F. Craun. 1998. Drinking water source and chlorination byproducts I. Risk of bladder cancer. Epidemiology. 9(1): 21– 28. Cantor, K.P., C.M. Villanueva, D.T. Silverman, J.D. Figueroa, F.X. Real, M. Garcia-Closas, N. Malats, S. Chanock, M. Yeager, A. Tardon, and R. Garcia-Closas. 2010. Polymorphisms in GSTT1, GSTZ1, and CYP2E1, disinfection by-products, and risk of bladder cancer in Spain. Environmental Health Perspectives. 118(11): 1545–1550. Cohn, P.D., J.A. Gleason, E. Rudowski, S.M. Tsai, C.A. Genese, and J.A. Fagliano. 2014. Community outbreak of PO 00000 Frm 00031 Fmt 4701 Sfmt 4702 3547 legionellosis and an environmental investigation into a community water system. Epidemiology and Infection. 143(6): 1322–1331. Colford Jr., J.M., J.F. Hilton, C.C. Wright, B.F. Arnold, S. Saha, T.J. Wade, J. Scott, and J.N.S. Eisenberg. 2009. The Sonoma water evaluation trial: A randomized drinking water intervention trial to reduce gastrointestinal illness in older adults. American Journal of Public Health. 99(11): 1988–1995. Collier, S.A., L.J. Stockman, L.A. Hicks, L.E. Garrison, F.J. Zhou, and M.J. Beach. 2012. Direct healthcare costs of selected diseases primarily or partially transmitted by water. Epidemiology and Infection. 140(11): 2002–2013. Couri, D. and M.S. Abdel-Rahman. 1980. Effect of chlorine dioxide and metabolites on glutathione dependent system in rat, mouse and chicken blood. Journal of Environmental Pathology and Toxicology. 3(1–2): 451–460. Craun, G.F. and W. Jakubowski. 1986. Status of waterborne giardiasis outbreaks and monitoring methods. Health Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency. Cromeans, T.L., A.M. Kahler, and V.R. Hill. 2010. Inactivation of adenoviruses, enteroviruses, and murine norovirus in water by free chlorine and monochloramine. Applied and Environmental Microbiology. 76(4): 1028–1033. Daly, E.R., S.J. Roy, D.D. Blaney, J.S. Manning, V.R. Hill, L. Xiao, and J.W. Stull. 2010. Outbreak of giardiasis associated with a community drinkingwater source. Epidemiology and infection. 138(04): 491–500. ´ Delatolla, R., C. Seguin, S. Springthorpe, E. Gorman, A. Campbell, and I. Douglas. 2015. Disinfection byproduct formation during biofiltration cycle: Implications for drinking water production. Chemosphere. 136: 190–197. Dong, Y., G. Li, N. Zhou, R. Wang, Y. Chi, and G. Chen. 2012. Graphene quantum dot as a green and facile sensor for free chlorine in drinking water. Analytical Chemistry. 84: 8378–8382. Duda, S., S. Kandiah, J.E. Stout, J.L. Baron, M. Yassin, M. Fabrizio, J. Ferrelli, R. Hariri, M.M. Wagener, J. Goepfert, J. Bond, J. Hannigan, and D. Rogers. 2014. Evaluation of a new monochloramine generation system for controlling Legionella in building hot water systems. Infection Control and Hospital Epidemiology. 35(11): 1356–1363. Duranceau, S.J. 2015. Spray Aeration as a Trihalomethane Control Measure. 2015 Florida Water Resources Conference Proceedings. The Many Faces of Water. Emelko, M.B., U. Silins, K.D. Bladon, M. Stone, C. Williams, M. Wagner, A. Martens, and X. Geng. 2013. ‘‘The Lost Creek Wildfire of Southern Alberta, Canada: 10 Years, 7 Watersheds and Continued Impacts.’’ Water Research Foundation Workshop: Wildfire Readiness and Response Workshop—Is Your Utility Prepared? April 4, 2013. E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 3548 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules ´ Farre, M.J., J. Reungoat, F.X. Argaud, M. Rattier, J. Keller, and W. Gernjak. 2011. Fate of N-nitrosodimethylamine, trihalomethane and haloacetic acid precursors in tertiary treatment including biofiltration. Water Research. 45(17): 5695–5704. ´ Fernandez, M.R., R.V. Carvalho, F.A. Ogliari, F.A. Beira, A. Etges, and M. Bueno. 2010. Cytotoxicity and genotoxicity of sodium percarbonate: a comparison with bleaching agents commonly used in discoloured pulpless teeth. International Endodontic Journal. 43(2): 102–108. Fiske, P.S., J. Oppenheimer, R. Moore, and R. Everett. 2011. In-tank aeration predicts and reduces THMs. Opflow. 37(11): 22– 24. Flannery, B., L.B. Gelling, D.J. Vugia, J.M. Weintraub, J.J. Salerno, M.J. Conroy, V.A. Stevens, C.E. Rose, M.R. Moore, B.S. Fields, and R.E. Besser. 2006. Reducing Legionella colonization of water systems with monochloramine. Emerging Infectious Diseases. 12(4): 588–596. Freedman, M., K.P. Cantor, N.L. Lee, L.S. Chen, H.H. Lei, C.E. Ruhl, and S.S. Wang. 1997. Bladder cancer and drinking water: a population-based casecontrol study in Washington County, Maryland (United States). Cancer Causes and Control. 8(5): 738–744. Geldreich, E.E., K.R. Fox, J.A. Goodrich, E.W. Rice, R.M. Clark, and D.L. Swerdlow. 1992. Searching for a water supply connection in the Cabool, Missouri disease outbreak of Escherichia coli O157: H7. Water Research. 26(8): 1127– 1137. ¨ Hambsch, B., K. Bockle, and H.M. van Lieverloo. 2007. Incidence of faecal contaminations in chlorinated and nonchlorinated distribution systems of neighbouring European countries. Journal of Water and Health. 5(1): 119– 130. Hasan, F.M., F.A. Ahmed, N.A. Nada, and A.M. Manal. 2010. Using aluminum refuse as a coagulant in the coagulation and flocculation processes. Iraqi Journal of Chemical and Petroleum Engineering. 11: 15–22. Headd, B. and S.A. Bradford. 2015 (epub). Use of aerobic spores as a surrogate for cryptosporidium oocysts in drinking water supplies. Water Research. 90: 185– 202. Available online at: https:// www.ncbi.nlm.nih.gov/pubmed/ 26734779. Health Canada. 2014. Guidelines for Canadian Drinking Water Quality: Selenium. Water and Air Quality Bureau, Healthy Environments and Consumer Safety Branch. Health Canada: Ottawa, Ontario. Heffelfinger, J.D., J.L. Kool, S. Fridkin, V.J. Fraser, J. Hageman, J. Carpenter, and C.G. Whitney. 2003. Risk of hospital-acquired Legionnaires’ disease in cities using monochloramine versus other water disinfectants. Infection Control and Hospital Epidemiology. 24(8): 569–574. Hibler, C.P., C.M. Hancock, L.M. Perger, J.G. Wegrzyn, and K.D. Swabby. 1987. Inactivation of Giardia cysts with chlorine at 0.50 °C to 5.00 °C. AWWA Research Foundation. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Hill, V.R. and T.L. Cromeans. 2010. Contaminant Candidate List Viruses: Evaluation of Disinfection Efficacy. Water Research Foundation. Project #3134. Hoffbuhr, J.W., J. Blair, M. Bartleson, and R. Karlin. 1986. Use of particulate analysis for source and water treatment evaluation. Water Quality Technology Conference 1986 Conference Proceedings. Hrudey, S.E, L.C. Backer, A.R. Humpage, S.W. Krasner, D.S. Michaud, L.E. Moore, P.C. Singer, and B.D. Stanford. 2015. Evaluating evidence for association of human bladder cancer with drinkingwater chlorination disinfection byproducts. Journal of Toxicology and Environmental Health, Part B. 18(5): 213–241. Published online Aug 26. doi: 10.1080/10937404.2015.1067661. Ingels, T. 2015. What does undetectable mean anyway? Colorado’s experience with detection of free chlorine residuals in real world distribution systems. Presentation at the American Water Works Association Annual Conference. Johnson, B.A., J.C. Lin, L.B. Jacobsen, and M. Fang. 2009. Localized treatment for disinfection byproducts. Water Research Foundation. Project #3101. Keegan, A., S. Wati, and B. Robinson. 2012. Chlor(am)ine disinfection of human pathogenic viruses in recycled waters (SWF62M–2114). Prepared by Australia Water Quality Centre for the Smart Water Fund, Victoria. Kenyon, E.M., C. Eklund, T. Leavens, and R.A. Pegram. 2015. Development and application of a human PBPK model for bromodichloromethane to investigate the impacts of multi-route exposure. Journal of Applied Toxicology. 36(9): 1095– 1111. Khaldi, S., M. Ratajczak, G. Gargala, M. Fournier, T. Berthe, L. Favennec, and J.P. Dupont. 2011. Intensive exploitation of a karst aquifer leads to Cryptosporidium water supply contamination. Water Research. 45(9): 2906–2914. Khan, M.A, S.E. Fenton, A.E. Swank, S.D. Hester, A. Williams, and D.C. Wolf. 2005. A mixture of ammonium perchlorate and sodium chlorate enhances alterations of the pituitarythyroid axis caused by the individual chemicals in adult male F344 rats. Toxicologic Pathology. 33: 776–783. King, W.D. and L.D. Marrett. 1996. Casecontrol study of bladder cancer and chlorination by-products in treated water (Ontario, Canada). Cancer Causes & Control. 7(6): 596–604. Kogevinas, M., C.M. Villanueva, L. FontRibera, D. Liviac, M. Bustamante, F. Espinoza, M.J. Nieuwenhuijsen, A. Espinosa, P. Fernandez, D.M. DeMarini, J.O. Grimalt, T. Grummt, and R. Marcos. 2010. Genotoxic effects in swimmers exposed to disinfection by-products in indoor swimming pools. Environmental Health Perspectives. 118(11): 1531–1537. Kool, J.L., J.C. Carpenter, and B.S. Fields. 1999. Effect of monochloramine disinfection of municipal drinking water on risk of nosocomial Legionnaires’ disease. The Lancet. 353: 272–277. PO 00000 Frm 00032 Fmt 4701 Sfmt 4702 Krasner, S.W., R. Shirkani, P. Westerhoff, D. Hanigan, W.A. Mitch, D.L. McCurry, C. Chen, J. Skadsen, and U. von Gunten. 2015. Controlling the formation of nitrosamines during water treatment. Water Research Foundation. Web Report #4370. Krasner, S.W., W.A. Mitch, D.L. McCurry, D. Hannigan, and P. Westerhoff. 2013. Formation, precursors, control, and occurrence of nitrosamines in drinking water: A review. Water Research. 47: 4433–4450. Leavens, T.L., B.C. Blount, D.M. DeMarini, M.C. Madden, J.L. Valentine, M.W. Case, L.K. Silva, S.H. Warren, N.M. Hanley, and R.A. Pegram. 2007. Disposition of bromodichloromethane in humans following oral and dermal exposure. Toxicological Sciences. 99(2): 432–445. LeChevallier, M.W., N.J. Welch, and D.B. Smith. 1996. Full-scale studies of factors related to coliform regrowth in drinking water. Applied and Environmental Microbiology. 62(7): 2201–2211. Lee, W., P. Westerhoff, and J–P. Croue. 2007. Dissolved organic nitrogen as a precursor for chloroform, dichloroacetonitrile, Nnitrosodimethylamine, and trichloronitromethane. Environmental Science & Technology. 41(15): 5485– 5490. Lee, E., D. Haur Phua, B. Leong Lim, and H. Kai Goh, 2013. Severe chlorate poisoning successfully treated with methylene blue. The Journal of Emergency Medicine. 44(2): 381–384. Liao, X., C. Wang, J. Wang, X. Zhang, C. Chen, S.W. Krasner, and I.H. Suffet. 2014. Nitrosamine precursor and DOM control in an effluent-affected drinking water. Journal of the American Water Works Association. 106(7): 307–318. Lin, Y.E., R.D. Vidic, J.E. Stout, and V.L. Yu. 1998. Legionella in water distribution systems. Journal of the American Water Works Association. 90(9): 112–122. Locas, A.C. Barthe, A.B. Margolin, and P. Payment. 2008. Groundwater microbiological quality in Canadian drinking water municipal wells. Canadian Journal of Microbiology. 54(6): 472–478. Louisiana Department of Health and Hospitals. 2013. Declaration of Emergency. Minimum Disinfectant Residual Levels in Public Water Systems. Available online at: https:// dhh.louisiana.gov/assets/oph/CenterEH/engineering/Emergency_Rule/ Emergency_Rule_Notification.pdf. Louisiana Department of Health and Hospitals. 2014. Declaration of Emergency. Minimum Disinfectant Residual Levels in Public Water Systems. Available online at: https:// www.dhh.louisiana.gov/assets/oph/ Center-EH/engineering/Emergency_Rule/ ER_3-6-14.pdf. Lui, Y.S., H.C. Hong, G.J.S. Zheng, and Y. Liang. 2012. Fractionated algal organic materials as precursors of disinfection by-products and mutagens upon chlorination. Journal of Hazardous Materials. 209: 278–284. McGeehin, M.A., J.S. Reif, J.C. Becher, and E.J. Mangione. 1993. Case-control study E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules of bladder cancer and water disinfection methods in Colorado. American Journal of Epidemiology. 138(7): 492–501. McGuire, M.J., T. Karanfil, S.W. Krasner, D.A. Reckhow, J.A. Roberson, R.S. Summers, P. Weseteroff, and Y. Xie. 2014. Not your granddad’s disinfection by-product problems and solutions. Journal of the American Water Works Association. 106(8): 54–73. McKie, M.J., L. Taylor-Edmonds, S.A. Andrews, and R.C. Andrews. 2015. Engineered biofiltration for the removal of disinfection by-product precursors and genotoxicity. Water Research. 81: 196–207. McTigue, N.E., D.A. Cornwell, K. Graf, and R. Brown. 2014. Occurrence and consequences of increased bromide in drinking water sources. Journal of the American Water Works Association 106(11): 492–508. Messner. M.J., P. Berger, and S.P. Nappier. 2014. Fractional Poisson—A simple dose-response model for human norovirus. Risk Analysis. 34(10): 1820– 1829. Mikkelson, K.M., E.R.V. Dickenson, R.M. Maxwell, J.E. McCray, and J.O. Sharp. 2013. Water-quality impacts from climate-induced forest die-off. Nature Climate Change. 3(3): 218–222. Moore, G.S. and E.J. Calabrese. 1982. Toxicological effects of chlorite in the mouse. Environmental Health Perspectives. 46: 31–37. Moore, M.R., M. Pryor, B. Fields, C. Lucas, M. Phelan, and R.E. Besser. 2006. Introduction of monochloramine into a municipal water system: Impact on colonization of buildings by Legionella spp. Applied and Environmental Microbiology. 72(1): 378–383. Narotsky, M.G., D.S. Best, A. McDonald, E.A. Godin, E.S. Hunter III, and J.E. Simmons. 2011. Pregnancy loss and eye malformations in offspring of F344 rats following gestational exposure to mixtures of regulated trihalomethanes and haloacetic acids. Reproductive Toxicology. 31(1): 59–65. Narotsky, M.G., G.R. Klinefelter, J.M. Goldman, D.S. Best, A. McDonald, L.F. Strader, J.D. Suarez, A.S. Murr, I. Thillainadarajah, E.S. Hunter III, S.D. Richardson, T.F. Speth, R.J. Miltner, J.G. Pressman, L.K. Teuschler, G.E. Rice, V.C. Moser, R.W. Luebke, and J.E. Simmons. 2013. Comprehensive assessment of a chlorinated drinking water concentrate in a rat multigenerational reproductive toxicity study. Environmental Science & Technology. 47(18): 10653–10659. Narotsky, M.G., G.R. Klinefelter, J.M. Goldman, A.B. DeAngelo, D.S. Best, A. McDonald, L.F. Strader, A.S. Murr, J.D. Suarez, M.H. George, E.S. Hunter III, and J.E. Simmons. 2015. Reproductive toxicity of a mixture of regulated drinking-water disinfection by-products in a multigenerational rat bioassay. Environmental Health Perspective. 123(6): 564–570. Available online at: https://dx.doi.org/10.1289/ehp.1408579. National Drinking Water Advisory Committee (NDWAC). 2000. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Recommended Guidance for Review of Existing National Primary Drinking Water Regulations. November 2000. National Research Council (NRC). 2006a. Fluoride in drinking-water: A Scientific Review of EPA’s Standards. The National Academies Press, Washington, DC. NRC. 2006b. Drinking Water Distribution Systems: Assessing and Reducing Risks. The National Academies Press, Washington, DC. National Toxicology Program (NTP). 2005. NTP Technical Report on the Toxicology and Carcinogenesis Studies of Sodium Chlorate (CAS No. 7775–09–9) in F344/ N Rats and B6C3F1 Mice (Drinking Water Studies). NTP TR 517 NIH Publication No. 06–4457 National Institutes of Health, Public Health Service, U.S. Department of Health and Human Services. December 2005. NTP. 2007. NTP technical report on the toxicology and carcinogenesis studies of dibromoacetic acid (CAS No. 631–64–1) in F344/N rats and B6C3F1 mice (drinking water studies). NTP Technical Report Series No. 537. NTP, National Institutes of Health, Public Health Service, U.S. Department of Health and Human Services. Available online at: https://ntp.niehs.nih.gov/ index.cfm?objectid=8831333E-F1F6975E-71D4F287C2229308. NTP. 2009. Toxicology and carcinogenesis studies of bromochloroacetic acid (CAS No. 5589–96–8) in F344/N rats and B6C3F1 mice (drinking water studies). Technical Report Series No. 549. Research Triangle Park, NC: U.S. Department of Health and Human Services. NTP. 2014. Toxicology studies of bromodichloroacetic acid (CAS No. 71133–14–7) in F344 rats and B6C3F1 mice and toxicology and carcinogenesis studies of bromodichloroacetic acid in F344/NTac rats and B6C3F1/N mice (drinking water studies). Peer Review Draft, scheduled peer review date; May 22, 2014. Technical Report Series No. 583. Research Triangle Park, NC: U.S. Department of Health and Human Services. NTP. 2016. Systematic Review of the Effects of Fluoride on Learning and Memory in Animal Studies. Available online at https://ntp.niehs.nih.gov/ntp/ohat/pubs/ ntp_rr/01fluoride_508.pdf Nguyen, M.L., P. Westerhoff, L. Baker, Q. Hu, M. Esparza-Soto, and M. Sommerfeld. 2005. Characteristics and reactivity of algae-produced dissolved organic carbon. Journal of Environmental Engineering. 131(11): 1574–1582. Nguyen, V., Hoffman, R. and Nelson, L. 2014. Chlorine dioxide from a dietary supplement causing hemolytic anemia. Clinical Toxicology. 52(4): 323–323. Orme, J., D.H. Taylor, R.D. Laurie, and R.J. Bull. 1985. Effects of chlorine dioxide on thyroid function in neonatal rats. Journal of Toxicology and Environmental Health. 15(2): 315–322. Pennsylvania Bulletin. 2016. Proposed Rulemaking. Disinfection Requirements Rule. 46(8): 857–892. Available online at: PO 00000 Frm 00033 Fmt 4701 Sfmt 4702 3549 https://www.pabulletin.com/secure/data/ vol46/46-8/278.html. Pharand, L., M.I. van Dyke, W.B. Anderson, Y. Yohannes, and P.M. Huck. 2015. Fullscale ozone-biofiltration: Seasonally related effects on NOM removal. Journal of the American Water Works Association. 107(12): 425–436. Plewa, M.J. and E.D. Wagner. 2009. Mammalian cell cytotoxicity and genotoxicity of disinfection by-products. Water Research Foundation. Denver, CO. Plewa, M.J., J.E. Simmons, S.D. Richardson, and E.D. Wagner. 2010. Mammalian cell cytotoxicity and genotoxicity of the haloacetic acids, a major class of drinking water disinfection by- products. Environmental and Molecular Mutagenesis. 51(8–9): 871–878. Pryor, M., S. Springthorpe, S. Riffard, T. Brooks, Y. Huo, G. Davis, and S.A. Sattar. 2004. Investigation of opportunistic pathogens in municipal drinking water under different supply and treatment regimes. Water Science and Technology. 50(1): 83–90. Regli, S., J. Chen, M. Messner, M.S. Elovitz, F.J. Letkiewicz, R.A. Pegram, T.J. Pepping, S.D. Richardson, and J.M. Wright. 2015. Estimating potential increased bladder cancer risk due to increased bromide concentrations in sources of disinfected drinking waters. Environmental Science and Technology. 49(22): 13094–13102. Revetta, R.P., V. Gomez-Alvarez, T.L. Gerke, C. Curioso, J.W. Santo Domingo, and N.J. Ashbolt. 2013. Establishment and early succession of bacterial communities in monochloramine-treated drinking water biofilms. FEMS Microbiology Ecology. 86(3): 404–414. Rice, J., A. Wutich, and P. Westerhoff. 2013. Assessment of de facto wastewater reuse across the US: trends between 1980 and 2008. Environmental Science & Technology. 47(19): 11099–11105. Rice, J. and P. Westerhoff. 2014. Spatial and temporal variation in de facto wastewater reuse in drinking water systems across the USA. Environmental Science & Technology. 49(2): 982–989. Richardson, S. and C. Postigo. 2011. Drinking water disinfection by-products. Emerging Organic Contaminants and Human Health. 20: 93–137. Richardson, S.D., F. Fasano, J.J. Ellington, F.G. Crumley, K.M. Buettner, J. J. Evans, B.C. Blount, L.K. Silva, T.J. Waite, G.W. Luther, A.B. McKague, R.J. Miltner, E.D. Wagner, and M.J. Plewa. 2008. Occurrence and mammalian cell toxicity of iodinated disinfection byproducts in drinking water. Environmental Science & Technology. 42(22): 8330–8338. Richardson, S.D., M.J. Plewa, E.D. Wagner, R. Schoeny, and D.M. DeMarini. 2007. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: a review and roadmap for research. Mutation Research. 636(1–3): 178–242. Ross, M.K. and R.A. Pegram. 2003. Glutathione transferase theta 1–1dependent metabolism of the water disinfection byproduct E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 3550 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules bromodichloromethane. Chemical Research in Toxicology. 16(2): 216–226. Ross, M.K. and R.A. Pegram. 2004. In vitro biotransformation and genotoxicity of the drinking water disinfection byproduct bromodichloromethane: DNA binding mediated by glutathione transferase theta 1–1. Toxicology and Applied Pharmacology. 195(2): 166–181. Saad, B, W.T. Wai, M.S. Jab, W.S.W. Ngah, M.I. Saleh, and J.M. Slater. 2005. Development of flow injection spectrophotometric methods for the determination of free available chlorine and total available chlorine: comparative study. Analytica Chimica Acta. (537): 197– 206. Sacher, F., C.K. Schmidt, C. Lee, and U. von Gunten. 2008. Strategies for minimizing nitrosamine formation during disinfection. Water Research Foundation. Project #2979. Samson, C. 2015. Assessing DBP Occurrence: Impacts of the Stage 2 DBPR. Water Quality Technology Conference 2015 Conference Proceedings. Samson, C., B. Rajagopalan, and S. Summers. 2013. Modeling TOC Threshold Exceedances for Meeting Disinfection ByProduct Drinking Water Regulations under the Impact of Climate Change. In Proceedings of International Annual Meeting of American Society of Agronomy/ Crop Science Society of America/Soil Science Society of America. Sirikanchana, K., J.L. Shisler, and B.J. Marinas. 2008. Inactivation kinetics of adenovirus serotype 2 with monochloramine. Water Research. 42(6): 1467–1474. Smeets, P.W., G.J. Medema, and J.C. Van Dijk. 2009. The Dutch secret: how to provide safe drinking water without chlorine in the Netherlands. Drinking Water Engineering and Science. 2: 1–14. State of Nebraska. 2013. Demonstration of Performance to Establish Natural Filtration Credits for the City of Kearney, Nebraska. Platte River Well Field. Project #130–C1– 054. States, S., G. Cyprych, M. Stoner, F. Wydra, J. Kuchta, J. Monnell, and L. Casson. 2013. Marcellus shale drilling and brominated THMs in Pittsburgh, PA., drinking water. Journal of the American Water Works Association. 105(8): 432–448. Stayner, L.T., M. Pedersen, E. Patelarou, I. Decordier, K. Vande Loock, L. Chatzi, A. Espinosa, E. Fthenou, M.J. Niewenhuijsen, E. Gracia-Lavedan, E.G. Stephanou, M. Kirsch-Volders, M. Kogevinas. 2014. Exposure to brominated trihalomethanes in water during pregnancy and micronuclei frequency in maternal and cord blood lymphocytes. Environmental Health Perspectives. 122(1): 100–106. Summers, R.S., M.A. Benz, H.M. Shukairy, and L. Cummings. 1993. Effect of separation processes on the formation of brominated THMs. Journal of the American Water Works Association. 95: 88–95. Symons, J.M., Krasner, S.W., Simms, L.A., and Sclimenti, M. 1993. Measurement of THM and precursor concentrations revisited: the effect of bromide ion. Journal of the American Water Works Association. 85(1): 51–62. VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 Tang, Y., Y. Su, N. Yang, L. Zhang, and Y. Lv. 2014. Carbon nitride quantum dots: a novel chemiluminescence system for selective detection of free chlorine in water. Analytical Chemistry. 86(9): 4528– 4535. Teunis, P.F., C.L. Chappell, and P.C. Okhuysen. 2002a. Cryptosporidium dose response studies: variation between isolates. Risk Analysis. 22(1): 175–185. Teunis, P.F., C.L. Chappell, and P.C. Okhuysen. 2002b. Cryptosporidium dose response studies: variation between hosts. Risk Analysis. 22(3): 475–485. U. S. Department of Health and Human Services. 2015. U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Available online at: https:// www.publichealthreports.org/documents/ PHS_2015_Fluoride_Guidelines.pdf. U.S. Environmental Protection Agency (USEPA). 1979. Interim Primary Drinking Water Regulations; Amendments. 44 FR 42254. July 19, 1979. USEPA. 1985. National Primary Drinking Water Regulations; Volatile Synthetic Organic Chemicals; Final Rule and Proposed Rule. 50 FR 46880. November 13, 1985. USEPA. 1989. National Primary Drinking Water Regulations; Filtration, Disinfection; Turbidity, Giardia lamblia, Viruses, Legionella, and Heterotrophic Bacteria; Final Rule. Part III. 54 FR 27486. June 29, 1989. USEPA. 1991. Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources. March 1991. Available online at: https:// www.epa.gov/sites/production/files/2015– 10/documents/guidance_manual_for_ compliance_with_the_filtration_and_ disinfection_requirements.pdf. USEPA. 1995. Reregistration Eligibility Decision (RED) for Picloram. Office of Prevention, Pesticides and Toxic Substances: Washington, DC. EPA738– R95–019. https://archive.epa.gov/ pesticides/reregistration/web/pdf/0096.pdf USEPA. 1998a. Toxicological Review of Beryllium and Compounds (CAS No. 7440–41–7): in Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development, Washington, DC. EPA 635–R–98–008. https:// cfpub.epa.gov/ncea/iris/iris_documents/ documents/toxreviews/0012tr.pdf USEPA. 1998b. National Primary Drinking Water Regulations; Disinfectants and Disinfection Byproducts; Final Rule. 63 FR 69390. December 16, 1998. USEPA. 1998c. National Primary Drinking Water Regulations. Interim Enhanced Surface Water Treatment Rule. Final Rule. 63 FR 69477. December 16, 1998. USEPA. 1998d. Small System Compliance Technology: List for the Non-Microbial Contaminants Regulated Before 1996. EPA 815–R–98–002. September 1998. USEPA. 1999. Uncovered Finished Water Reservoirs Guidance Manual. EPA 815–R– PO 00000 Frm 00034 Fmt 4701 Sfmt 4702 99–011. April 1999. Available online at: https://webcache.googleusercontent.com/ search?q=cache:SLzRMA1eR7oJ:https:// www.epa.gov/dwreginfo/interim-enhancedsurface-water-treatment-ruledocuments+&cd=1&hl=en&ct=clnk&gl=us. USEPA. 2000a. ICR Auxiliary 1 Database. EPA 815–C–00–002. USEPA. 2000b. ICR Treatment Study Database. EPA 815–C–00–003. USEPA. 2000c. ICR Supplemental Survey Database. Prepared by DynCorp, Inc. USEPA. 2001a. Toxicological Review of Hexachlorocyclopentadiene (CASRN 77– 47–4): In Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development, Washington, DC. EPA 600– R–01–013. https://cfpub.epa.gov/ncea/iris/ iris_documents/documents/toxreviews/ 0039tr.pdf USEPA. 2001b. National Primary Drinking Water Regulations: Filter Backwash Recycling Rule. 66 FR 31086. June 8, 2001. USEPA. 2002a. Diquat Dibromide HED Risk Assessment for Tolerance Reassessment Eligibility Document (TRED). PC Code No: 032201; DP Barcode: D281890; Submission Barcode: S611057. https:// www.regulations.gov/ #!documentDetail;D=EPA-HQ-OPP-20090920-0007 USEPA. 2002b. Toxicological Review of 1,1Dichloroethylene (CAS No. 75–35–4): In Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development: Washington, DC. EPA 635– R–02–002. https://cfpub.epa.gov/ncea/iris/ iris_documents/documents/toxreviews/ 0039tr.pdf USEPA. 2002c. National Primary Drinking Water Regulations: Long Term 1 Enhanced Surface Water Treatment Rule. Final Rule. 67 FR 1812. January 14, 2002. USEPA. 2002d. Reregistration Eligibility Decision (RED) for Lindane. Office of Prevention, Pesticides and Toxic Substances: Washington, DC. https:// www.regulations.gov/ #!documentDetail;D=EPA-HQ-OPP-20020202-0027 USEPA. 2003a. Toxicological Review of Xylenes (CAS No.1330–20–7): In Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development: Washington, DC. EPA 635–R–03–001. https://cfpub.epa.gov/ncea/iris/iris_ documents/documents/toxreviews/ 0270tr.pdf USEPA. 2003b. National Primary Drinking Water Regulations; Announcement of Completion of EPA’s Review of Existing Drinking Water Standards. Notice. 68 FR 42908. July 18, 2003. USEPA. 2005a. Economic Analysis for the Final Stage 2 Disinfectants and Disinfection Byproducts Rule. EPA 815–R– 05–010. December 2005. USEPA. 2005b. Toxicological Review of Barium and Compounds (CAS No.7440– 39–3): In Support of Summary Information E:\FR\FM\11JAP3.SGM 11JAP3 sradovich on DSK3GMQ082PROD with PROPOSALS3 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development: Washington, DC. EPA 635– R–05–001. https://cfpub.epa.gov/ncea/iris/ iris_documents/documents/toxreviews/ 0010tr.pdf USEPA. 2005c. Toxicological Review of Toluene (CAS No. 108–88–3): In Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development: Washington, DC. EPA 635–R–05–004. https://cfpub.epa.gov/ncea/iris/iris_ documents/documents/toxreviews/ 0118tr.pdf USEPA. 2005d. Method 1622: Cryptosporidium in Water by Filtration/ IMS/FA. EPA 815–R–05–001. USEPA. 2005e. Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA. EPA 815–R–05–002. USEPA. 2005f. Reregistration Eligibility Decision for Endothall (Case Number 2245). EPA 738–R–05–008, Office of Prevention, Pesticides, and Toxic Substances: Washington, DC. https:// archive.epa.gov/pesticides/reregistration/ web/pdf/endothall_red.pdf USEPA. 2005g. Technologies and Costs for the Final Long Term 2 Enhanced Surface Water Treatment Rule and Final Stage 2 Disinfectants and Disinfection Byproducts Rule. EPA 815–R–05–012. December 2005. USEPA. 2006a. Acetochlor/Alachlor: Cumulative Risk Assessment for the Chloroacetanilides. Office of Prevention, Pesticides and Toxic Substances: Washington, DC. USEPA. 2006b. National Primary Drinking Water Regulations: Ground Water Rule; Final Rule. 71 FR 65573. November 8, 2006. USEPA. 2006c. National Primary Drinking Water Regulations: Long Term 2 Enhanced Surface Water Treatment Rule; Final Rule. 71 FR 654. January 5, 2006. USEPA. 2006d. National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule; Final Rule. 71 FR 388. January 4, 2006. USEPA. 2006e. Reregistration Eligibility Decision (RED) for Chlorine Dioxide and Sodium Chlorite (Case 4023). EPA 738–R– 06–007. August 2006. USEPA. 2007a. Toxicological Review of 1,1,1-Trichloroethane (CAS No. 71–55–6): In Support of Summary Information on the Integrated Risk Information System (IRIS). National Center for Environmental Assessment, Office of Research and Development: Washington, DC. EPA–635– R–03–013. https://cfpub.epa.gov/ncea/iris/ iris_documents/documents/toxreviews/ 0197tr.pdf USEPA. 2007b. Simultaneous Compliance Guidance Manual for the Long-Term 2 and Stage 2 DBP Rules. EPA 815–R–07–017. March 2007. USEPA. 2008a. Carbofuran. HED Revised Risk Assessment for the Notice of Intent to Cancel (NOIC). PC 090601. DP# 347038. https://www.regulations.gov/ #!documentDetail;D=EPA-HQ-OPP-20071088-0034 VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 USEPA. 2008b. Total Coliform Rule/ Distribution System (TCRDS) Federal Advisory Committee. Agreement in Principle. Available online at: https:// www.epa.gov/sites/production/files/2015– 10/documents/total_coliform_rule_ distribution_system_advisory_committee_ agreement_in_principle_pdf.pdf. USEPA. 2009a. Analytical Feasibility Support Document for the Second Six-Year Review of Existing National Primary Drinking Water Regulations. EPA 815–B– 09–003. October 2009. USEPA. 2010a. Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment Request; Contaminant Occurrence Data in Support of EPA’s Third Six-Year Review of National Primary Drinking Water Regulations (Renewal); EPA ICR No. 2231.02, OMB Control No. 2040–0275. 75 FR 6023. February 5, 2010. USEPA. 2010b. Fluoride: Dose Response Analysis for Non-Cancer Effects. EPA 820– R–10–019. December 2010. USEPA. 2010c. Fluoride: Exposure and Relative Source Contribution Analysis. EPA 820–R–10–015. December 2010. USEPA. 2010d. Integrated Risk Information System (IRIS): Toxicological Review of cis1,2-Dichloroethylene and trans-1,2Dichloroethylene in Support of Summary Information. National Center for Environmental Assessment, Office of Research and Development: Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_ documents/documents/toxreviews/ 0418tr.pdf USEPA. 2010e. Integrated Risk Information System (IRIS): Toxicological Review of Hydrogen Cyanide and Cyanide Salts in Support of Summary Information. National Center for Environmental Assessment, Office of Research and Development: Washington, DC. https://cfpub.epa.gov/ ncea/iris/iris_documents/documents/ toxreviews/0060tr.pdf USEPA. 2010f. Long Term 2 Enhanced Surface Water Treatment Rule Toolbox Guidance Manual. EPA 815–R–09–016. April 2010. USEPA. 2010g. Memorandum: Updated toxicity endpoints for oxamyl. Office of Chemical Safety and Pollution Prevention, Washington, DC. https:// www.regulations.gov/ #!documentDetail;D=EPA-HQ-OPP-20100028-0011 USEPA. 2010h. National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues. 75 FR 15500. March 29, 2010. USEPA, 2011. Improving our Regulations: Final Plan for Periodic Retrospective Review of Existing Regulations. Available online at: https://www.epa.gov/sites/ production/files/2015–09/documents/ eparetroreviewplan-aug2011_0.pdf USEPA. 2012. Economic Analysis for the Final Revised Total Coliform Rule. EPA 815–R–12–004. September 2012. USEPA. 2013a. 40 CFR parts 141 and 142; National Primary Drinking Water PO 00000 Frm 00035 Fmt 4701 Sfmt 4702 3551 Regulations; Revisions to the Total Coliform Rule; Final Rule. 78 FR 10270. February 13, 2013. USEPA. 2013b. Human Health Risk Assessment for a Proposed Use of 2,4–D Choline on Herbicide-Tolerant Corn and Soybean. Office of Chemical Safety and Pollution Prevention. https:// www.regulations.gov/ #!documentDetail;D=EPA-HQ-OPP-20140195-0007 USEPA. 2014a. Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina. EPA/600/R–14/236. March 2014. USEPA. 2014b. Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water Contaminate Candidate List; Proposed Rule. 79 FR 62715. October 20, 2014. USEPA. 2015a. Peer Review Handbook 4th Edition. October 2015. Available online at: https://www.epa.gov/sites/production/ files/2015–10/documents/epa_peer_ review_handbook_4th_edition_october_ 2015.pdf. USEPA. 2015b. Revisions to the Unregulated Contaminant Monitoring Rule (UCMR4) for Public Water Systems and Announcement of a Public Meeting. 70 FR 76897. December 11, 2015. Available online at: https://www.epa.gov/sites/production/ files/2015–11/documents/ucmr4_proposal_ 151130.pdf. USEPA. 2016a. Analytical Feasibility Support Document for the Third Six-Year Review of National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules. EPA–810–R–16– 005. USEPA. 2016b. Chemical Contaminant Summaries for the Third Six-Year Review of Existing National Primary Drinking Water Regulations. EPA–810–R–16–004. USEPA. 2016c. Consideration of Other Regulatory Revisions in Support of the Third Six-Year Review of the National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules. EPA–810–R–16–003. USEPA. 2016d. Development of Estimated Quantitation Levels for the Third Six-Year Review of National Primary Drinking Water Regulations (Chemical Phase Rules). EPA–810–R–16–002. USEPA. 2016e. Occurrence Analysis for Potential Source Waters for the Third SixYear Review of National Primary Drinking Water Regulations. EPA–810–R–16–008. USEPA. 2016f. EPA Protocol for the Third Review of Existing National Primary Drinking Water Regulations. EPA–810–R– 16–007. USEPA. 2016g. Spring 2016 Regulatory Agenda, Semiannual regulatory flexibility agenda and semiannual regulatory agenda. 81 FR 37374. June 9, 2016. USEPA. 2016h. Six-Year Review 3—Health Effects Assessment for Existing Chemical and Radionuclides National Primary Drinking Water Regulations—Summary Report. EPA–822–R–16–008. USEPA. 2016i. Six-Year Review 3 ICR Database. USEPA, 2016j. Occurrence Data for the Unregulated Contaminant Monitoring Rule. July 2016. E:\FR\FM\11JAP3.SGM 11JAP3 3552 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules sradovich on DSK3GMQ082PROD with PROPOSALS3 USEPA. 2016k. Six-Year Review 3 Technical Support Document for Chlorate. EPA–810– R–16–013. USEPA. 2016l. Six-Year Review 3 Technical Support Document for Disinfectants/ Disinfection Byproducts Rules. EPA–810– R–16–012. USEPA. 2016m. Six-Year Review 3 Technical Support Document for Long-Term 2 Enhanced Surface Water Treatment Rule. EPA–810–R–16–011. USEPA. 2016n. Six-Year Review 3 Technical Support Document for Microbial Contaminant Regulations. EPA–810–R–16– 010. USEPA. 2016o. Six-Year Review 3 Technical Support Document for Nitrosamines. EPA– 810–R–16–009. USEPA. 2016p. The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Third SixYear Review of National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules. EPA–810–R–16– 014. USEPA. 2016q. The Data Management and Quality Assurance/Quality Control (QA/ QC) Process for the Third Six-Year Review Information Collection Rule Dataset. EPA– 810–R–16–015. USEPA. 2016r. Technologies for Legionella Control in Premise Plumbing Systems: Scientific Literature Review. EPA–810–R– 16–001. September 2016. USEPA. 2016s. Support Document for Third Six Year Review of Drinking Water Regulations for Acrylamide and Epichlorohydrin. EPA 810–R–16–019. USEPA and Water Research Foundation. 2016. Summary Document: State of Research on High-Priority Distribution System Issues. U.S. Food and Drug Administration (FDA). 2015. Letter to Manufacturers, Distributors, or Importers of Bottled Water with an Update on Fluoride Added to Bottled Water. Available online at: https://www.fda. gov/food/guidanceregulation/guidance documentsregulatoryinformation/bottled watercarbonatedsoftdrinks/ ucm444373.htm U.S. Geological Survey (USGS). 2004. Digital Engineering Aspects of Karst Map: A GIS Version of Davies, W.E., Simpson, J.H., Ohlmacher, G.C., Kirk, W.S., and Newton, E.G., 1984, Engineering Aspects of Karst: U.S. Geological Survey, National Atlas of the United States of America, Scale VerDate Sep<11>2014 19:28 Jan 10, 2017 Jkt 241001 1:7,500,000. Open-File Report 2004–1352, version 1. Available online only at: https:// pubs.usgs.gov/of/2004/1352/. Villanueva, C.M., F. Fernandez, N. Malats, J.O. Grimalt, and M. Kogenvinas. 2003. Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer. Journal of Epidemiology Community Health. 57: 166– 173. Villanueva, C.M., K.P. Cantor, S. Cordier, J.J.K. Jaakkola, W.D. King, C.F. Lynch, S. Porru, and M. Kogevinas. 2004. Disinfection byproducts and bladder cancer a pooled analysis. Epidemiology. 15(3): 357–367. Villanueva, C.M., K.P. Cantor, J.O. Grimalt, N. Malats, D. Silverman, A. Tardon, R. Garcia-Closas, C. Serra, A. Carrato, G. Castano-Vinyals, R. Marcos, N. Rothman, F.X. Real, M. Dosemeci, and M. Kogevinas. 2007. Bladder cancer and exposure to water disinfection by-products through ingestion, bathing, showering, and swimming in pools. American Journal of Epidemiology. 165(2): 148–156. Wahman, D.G. and J.G. Pressman. 2015. Distribution system residuals—is ‘‘detectable’’ still acceptable for chloramines. Journal of the American Water Works Association. 107(8): 53–63. Walfoort, C., M.J. Messina, and D. Miner. 2008. Storage tank aeration eliminates trihalomethanes. Opflow. 34(5): 28–29. Walker, J.T. and M. Morales. 1997. Evaluation of chlorine dioxide (ClO2) for the control of biofilms. Water Science and Technology. 35(11–12): 319–323. Wallender, E.K., E.C. Ailes, J.S. Yoder, V.A. Roberts, and J.M. Brunkard. 2014. Contributing factors to disease outbreaks associated with untreated ground water. Ground Water. 52(6): 886–897. Wang, H., S. Masters, Y. Hong, J. Stallings, J.O. Falkinham, M.A. Edwards, and A. Pruden. 2012. Effect of disinfectant, water age, and pipe material on occurrence and persistence of Legionella, mycobacteria, Pseudomonas aeruginosa, and two amoebas. Environmental Science & Technology. 46(21): 11566–11574. Weiss, W.J., S.C. Schindler, S. Freud, J.A. Herzner, K.F. Hoek, B.A. Wright, D.A. Reckhow, and W.C. Becker. 2013. Minimizing raw water NOM concentration through optimized source water selection. Journal of the American Water Works Association. 105(10): 73–74. PO 00000 Frm 00036 Fmt 4701 Sfmt 9990 Westerhoff, P., H. Jang, M. Abbaszadegan, and A. Absar. 2010. Organic chloramine formation and influence on disinfection efficacy and nitrification. Water Research Foundation. [National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues; page 140 of 140.] Westerhoff, P., S. Lee, Y. Yang, G.W. Gordon, K. Hristovski, R.U. Halden, and P. Herckes. 2015. Characterization, recovery opportunities, and valuation of metals in municipal sludges from US wastewater treatment plants nationwide. Environmental Science & Technology. 49(16): 9479–9488. World Health Organization (WHO). 2008. ‘‘Safety Evaluation of Certain Food Additives and Contaminants.’’ International Programme on Chemical Safety. Prepared for the 68th meeting of the Joint FAO/WHO Expert Committee on Food Additives (JEFCA). Writer, J.H., A. Hohner, J. Oropeza, A. Schmidt, K.M. Cawley, and F.L. RosarioOrtiz. 2014. Water treatment implications after the High Park Wildfire, Colorado. Journal of the American Water Works Association. 106(4): 189–199. Yan, M., D. Wang, J. Ni, J. Qu, C.W. Chow, and H. Liu. 2008. Mechanism of natural organic matter removal by polyaluminum chloride: effect of coagulant particle size and hydrolysis kinetics. Water Research. 42(13): 3361–3370. Yang, Y., Y. Komaki, S. Kimura, H. Hu, E. Wagner, B. Marinas, and M. Plewa. 2014. Toxic impact of bromide and iodide on drinking water disinfected with chlorine or chloramines. Environmental Science & Technology. 48(20): 12362–12369. Zhang, K-J., N-Y. Gao, Y. Deng, T. Zhang, and C. Li. 2012. Aqueous Chlorination of Algal Odorants: Reaction Kinetics and Formation of Disinfection By-products. Separation and Purification Technology. 92: 93–99. Dated: December 20, 2016. Gina McCarthy, Administrator. [FR Doc. 2016–31262 Filed 1–10–17; 8:45 am] BILLING CODE 6560–50–P E:\FR\FM\11JAP3.SGM 11JAP3

Agencies

ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 82, Number 7 (Wednesday, January 11, 2017)]
[Proposed Rules]
[Pages 3518-3552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-31262]

[[Page 3517]]

Vol. 82

Wednesday,

No. 7

January 11, 2017

Part III

Environmental Protection Agency

-----------------------------------------------------------------------

40 CFR Part 141

National Primary Drinking Water Regulations; Announcement of the
Results of EPA's Review of Existing Drinking Water Standards and
Request for Public Comment and/or Information on Related Issues;
Proposed Rule

Federal Register / Vol. 82 , No. 7 / Wednesday, January 11, 2017 /
Proposed Rules

[[Page 3518]]

-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OW-2016-0627; FRL-9957-49-OW]

40 CFR Part 141

RIN 2040-ZA26

National Primary Drinking Water Regulations; Announcement of the
Results of EPA's Review of Existing Drinking Water Standards and
Request for Public Comment and/or Information on Related Issues

AGENCY: Environmental Protection Agency (EPA).

ACTION: Request for public comments.

-----------------------------------------------------------------------

SUMMARY: The Safe Drinking Water Act (SDWA) requires the U.S.
Environmental Protection Agency (EPA) to conduct a review every six
years of existing national primary drinking water regulations (NPDWRs)
and determine which, if any, need to be revised. The purpose of the
review, called the Six-Year Review, is to evaluate current information
for regulated contaminants to determine if there is new information on
health effects, treatment technologies, analytical methods, occurrence
and exposure, implementation and/or other factors that provides a
health or technical basis to support a regulatory revision that will
improve or strengthen public health protection. EPA has completed a
detailed review of 76 NPDWRs and at this time has determined that eight
NPDWRs are candidates for regulatory revision. The eight NPDWRs are
included in the Stage 1 and the Stage 2 Disinfectants and Disinfection
Byproducts Rules, the Surface Water Treatment Rule, the Interim
Enhanced Surface Water Treatment Rule and the Long Term 1 Enhanced
Surface Water Treatment Rule. EPA requests comments on the eight NPDWRs
identified as candidates for revision and will consider comments and
data as it proceeds with determining whether further action is needed.
In addition, as part of this Six-Year Review, EPA identified 12 other
NPDWRs that were or continue to be addressed in recently completed,
ongoing or pending regulatory actions. EPA thus excluded those 12
NPDWRs from detailed review. This document is not a final regulatory
decision, but rather the initiation of a process that will involve more
detailed analyses of factors relevant to deciding whether a rulemaking
to revise an NPDWR should be initiated.

DATES: Comments must be received on or before March 13, 2017.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2016-0627, to the Federal eRulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or withdrawn. EPA
may publish any comment received to its public docket. Do not submit
electronically any information you consider to be Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. EPA will generally not consider comments or comment contents
located outside of the primary submission (i.e. on the web, cloud, or
other file sharing system). For additional submission methods, the full
EPA public comment policy, information about CBI or multimedia
submissions, and general guidance on making effective comments, please
visit https://www2.epa.gov/dockets/commenting-epa-dockets.
Mail: Water Docket, Environmental Protection Agency, Mail code:
2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460.
Hand Delivery: EPA Docket Center Public Reading Room, EPA
Headquarters West, Room 3334, 1301 Constitution Ave. NW., Washington,
DC. Hand deliveries are only accepted during the Docket's normal hours
of operation, and special arrangements should be made for deliveries of
boxed information.

FOR FURTHER INFORMATION CONTACT: For technical inquiries contact:
Richard Weisman, (202) 564-2822, or Kesha Forrest, (202) 564-3632,
Office of Ground Water and Drinking Water, Environmental Protection
Agency. For general information about the existing NPDWRs discussed in
this action, contact the Safe Drinking Water Hotline. Callers within
the United States may reach the Hotline at (800) 426-4791. The Hotline
is open Monday through Friday, excluding Federal holidays, from 10 a.m.
to 5:30 p.m. Eastern Time.

SUPPLEMENTARY INFORMATION:

Abbreviations and Acronyms Used in This Action

ADWR--Aircraft Drinking Water Rule
AGI--Acute Gastrointestinal Illness
AOC--Assimilable Organic Carbon
ASDWA--Association of State Drinking Water Administrators
ATSDR--Agency for Toxic Substances and Disease Registry
AWWA--American Water Works Association
BAT--Best Available Technology
CBI--Confidential Business Information
CDC--Centers for Disease Control and Prevention
CFR--Code of Federal Regulations
CT--Concentration x Contact Time
cVOCs--Carcinogenic Volatile Organic Compounds
CWS--Community Water System
DBCP--1,2-Dibromo-3-Chloropropane
DBP--Disinfection Byproducts
D/DBP--Disinfectants/Disinfection Byproducts
D/DBPR--Disinfectants/Disinfection Byproducts Rule
DEHA--Di(2-ethylhexyl)adipate
DEHP--Di(2-ethylhexyl)phthalate
DOC--Dissolved Organic Carbon
DPD--N,N-diethyl-p-phenylenediamine
EDB--Ethylene Dibromide
EJ--Environmental Justice
EO--Executive Order
EPA--U.S. Environmental Protection Agency
EQL--Estimated Quantitation Level
FAC--Federal Advisory Committee
FBRR--Filter Backwash Recycling Rule
FDA--U.S. Food and Drug Administration
FRN--Federal Register Notice
GAC--Granulated Activated Carbon
GWR--Ground Water Rule
GWUDI--Ground Water Under the Direct Influence of Surface Water
HAA5--Haloacetic Acids (five) (sum of monochloroacetic acid,
dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and
dibromoacetic acid)
HAAs--Haloacetic Acids
HAV--Hepatitis A Virus
HPC--Heterotrophic Plate Count
IARC--International Agency for Research on Cancer
ICR--Information Collection Request
IESWTR--Interim Enhanced Surface Water Treatment Rule
IRIS--Integrated Risk Information System
LT1--Long-Term 1 Enhanced Surface Water Treatment Rule
LT2--Long-Term 2 Enhanced Surface Water Treatment Rule
MCL--Maximum Contaminant Level
MCLG--Maximum Contaminant Level Goal
MDBP--Microbial and Disinfection Byproducts
MDL--Method Detection Limit
MRDL--Maximum Residual Disinfectant Level
MRDLG--Maximum Residual Disinfectant Level Goal
MRL--Minimum Reporting Level
NAS--National Academy of Sciences
NCWS--Non-Community Water System
NDMA--N-Nitrosodimethylamine
NDWAC--National Drinking Water Advisory Council
NIH--National Institutes of Health
NPDWR--National Primary Drinking Water Regulation
NRC--National Research Council
NTNCWS--Non-Transient Non-Community Water System
NTP--National Toxicology Program
PCBs--Polychlorinated Biphenyls
PCE--Tetrachloroethylene
PHS--U.S. Public Health Service

[[Page 3519]]

PT--Proficiency Testing
PQL--Practical Quantitation Limit
PWS--Public Water System
qPCR--Quantitative Polymerase Chain Reaction
RfD--Reference Dose
RICP--Research and Information Collection Partnership
RSC--Relative Source Contribution
RTCR--Revised Total Coliform Rule
SDWA--Safe Drinking Water Act
SMCL--Secondary Maximum Contaminant Level
SOC--Synthetic Organic Chemical
SWTR--Surface Water Treatment Rule
SWTRs--Surface Water Treatment Rules (including SWTR, IESWTR and
LT1)
SYR--Six-Year Review
TCE--Trichloroethylene
TC/EC--Total Coliforms/E. coli
TCR--Total Coliform Rule
THM--Trihalomethanes
TTHM--Total Trihalomethanes (sum of four THMs: chloroform,
bromodichloromethane, dibromochloromethane and bromoform)
TNCWS--Transient Non-Community Water System
TOC--Total Organic Carbon
TT--Treatment Technique
UCFWR--Uncovered Finished Water Reservoirs
UCMR--Unregulated Contaminant Monitoring Rule
USGS--U.S. Geological Survey
UV--Ultraviolet
WBDOSS--Waterborne Disease Outbreak Surveillance System
WHO--World Health Organization

Table of Contents

I. General Information
A. Does this action apply to me?
B. What should I consider as I prepare my comments for EPA?
II. Statutory Requirements for the Six-Year Review
III. Stakeholder Involvement in the Six-Year Review Process
IV. Regulations Included in the Six-Year Review 3
V. EPA's Protocol for Reviewing the NPDWRs Included in This Action
A. What was EPA's review process?
B. How did EPA conduct the review of the NPDWRs?
1. Initial Review
2. Health Effects
3. Analytical Feasibility
4. Occurrence and Exposure Analysis
5. Treatment Feasibility
6. Risk-Balancing
7. Other Regulatory Revisions
C. How did EPA factor children's health concerns into the
review?
D. How did EPA factor environmental justice concerns into the
review?
VI. Results of EPA's Review of NPDWRs
A. What are the review result categories?
1. The NPDWR is Not Appropriate for Revision at This Time
2. The NPDWR is a Candidate for Revision
B. What are the detailed results of EPA's third six-year review
cycle?
1. Chemical Phase Rules/Radionuclides Rules
2. Fluoride
3. Disinfectants/Disinfection Byproducts Rules (D/DBPRs)
4. Microbial Contaminants Regulations
VII. EPA's Request for Comments
References

I. General Information

A. Does this action apply to me?

This action itself does not impose any requirements on individual
people or entities. Instead, it notifies interested parties of EPA's
review of existing national primary drinking water regulations (NPDWRs)
and its conclusions about which of these NPDWRs may warrant new
regulatory action at this time. EPA requests public comment on the
eight NPDWRs identified as candidates for revision. EPA will consider
comments received as the Agency moves forward with determining whether
regulatory actions are necessary for the eight NPDWRs.

B. What should I consider as I prepare my comments for EPA?

Please see Section VII for the topic areas related to this document
for which EPA requests comment and/or information. EPA will accept
written or electronic comments (please do not send both). Instructions
for submitting comments can be found in the ADDRESSES section of this
document. EPA prefers electronic comments. No facsimiles (faxes) will
be accepted. Commenters who want EPA to acknowledge receipt of their
written comments should also send a self-addressed, stamped envelope.
You may find the following suggestions helpful when preparing your
comments:
Explain your views as clearly as possible.
Describe any assumptions that you used.
Provide any technical information and/or data you used
that support your views.
If you estimate potential burden or costs, explain how you
arrived at your estimate.
Provide specific examples to illustrate your concerns.
Offer alternatives.
Make sure to submit your comments by the comment period
deadline.
To ensure proper receipt by EPA, identify the appropriate docket
identification number in the subject line on the first page of your
response. It would also be helpful if you provide the name, date, and
volume/page numbers of the Federal Register document you are commenting
on.

II. Six-Year Review--Statutory Requirements and Next Steps

Under the Safe Drinking Water Act (SDWA), as amended in 1996, EPA
must periodically review existing NPDWRs and, if appropriate, revise
them. Section 1412(b)(9) of the SDWA states: ``The Administrator shall,
not less often than every six years, review and revise, as appropriate,
each national primary drinking water regulation promulgated under this
title. Any revision of a national primary drinking water regulation
shall be promulgated in accordance with this section, except that each
revision shall maintain, or provide for greater, protection of the
health of persons.''
Pursuant to the 1996 SDWA Amendments, EPA completed and published
the results of its first Six-Year Review (Six-Year Review 1) on July
18, 2003 (68 FR 42908, USEPA, 2003b) and the second Six-Year Review
(Six-Year Review 2) on March 29, 2010 (75 FR 15500, USEPA, 2010h),
after developing a systematic approach, or protocol, for the review of
NPDWRs.
In this document EPA is announcing the results of the third Six-
Year Review (Six-Year Review 3). Consistent with the process applied in
the Six-Year Review 2, EPA is requesting comments on this document and
will consider the public comments and/or any new, relevant data
submitted for the eight NPDWRs listed as candidates for revision as the
Agency proceeds with determining whether revisions of these regulations
are necessary. The announcement whether or not the Agency intends to
revise an NPDWR (pursuant to SDWA Sec. 1412(b)(9)) is not a regulatory
decision. Instead, it initiates a process that will involve more
detailed analyses of health effects, analytical and treatment
feasibility, occurrence, benefits, costs and other regulatory matters
relevant to deciding whether a rulemaking to revise an NPDWR should be
initiated. The Six-Year Review results do not obligate the Agency to
revise an NPDWR in the event that EPA determines during the regulatory
process that revisions are no longer appropriate and discontinues
further efforts to revise the NPDWR. Similarly, the fact that an NPDWR
has not been selected for revision means only that EPA believes that
regulatory changes to a particular NPDWR are not appropriate at this
time for the reasons given in this action; future reviews may identify
information that leads to an initiation of the revision process.
The reasons that EPA has identified an NPDWR as a ``candidate for
revision''

[[Page 3520]]

is that, at a minimum, the revision presents a meaningful opportunity
to:
Improve the level of public health protection, and/or
Achieve cost savings while maintaining or improving the
level of public health protection.

III. Stakeholder Involvement in the Six-Year Review Process

The Agency has involved interested stakeholders in the Six-Year
Review 3 process. Below are examples of such involvement:

In November 2014, EPA briefed the National Drinking
Water Advisory Council (NDWAC) on the Six-Year Review protocol and
the key elements of that protocol as they relate to the microbial
and disinfection byproducts (MDBP) rules. The briefing included
information on how EPA is implementing NDWAC's previous
recommendations (NDWAC, 2000) on the Six-Year Review process in
review of the MDBP rules;
In January 2015, states provided input (through the
Association of State Drinking Water Administrators (ASDWA)) on rule
implementation issues related to the NPDWRs being reviewed as part
of the Six-Year Review 3 (ASDWA, 2016);
EPA initiated a series of public stakeholder meetings
about the review of the Long Term 2 Enhanced Surface Water Treatment
Rule (LT2). These meetings were held in accordance with the
recommendation of the MDBP Federal Advisory Committee (FAC) \1\ to
have public meetings following the first round of monitoring under
the LT2, and as a result of the Executive Order (E.O.) 13563
``Improving Regulation and Regulatory Review.'' \2\ E.O. 13563
states that regulations shall be based ``on the open exchange of
information and perspectives among state, local, and tribal
officials, experts in relevant disciplines, affected stakeholders in
the private sector, and the public as a whole.'' Some affected
stakeholders recommended that EPA include the LT2 among the Agency's
top priorities for review under E.O. 13563. EPA included the LT2 in
its ``Improving our Regulations: Final Plan for Periodic
Retrospective Review of Existing Regulations'' (USEPA, 2011). EPA
agreed to ``assess and analyze new data/information regarding
occurrence, treatment, analytical methods, health effects, and risk
from all relevant waterborne pathogens to evaluate whether there are
new or additional ways to manage risk while assuring equivalent or
improved protection, including with respect to the covering of
finished water reservoirs'' (USEPA, 2011). EPA hosted three public
meetings in Washington, DC, on December 7, 2011, April 24, 2012 and
November 15, 2012. EPA presented information about: The LT2
requirements, monitoring data collected under the LT2, analytical
methods, forecasts about the second round of monitoring and the
treatment technique requirements. In addition to presentations to
educate the public, the meetings included public statements, panel
discussions, question and answer sessions and requests by EPA to
provide data and information about the implementation of the LT2 to
inform the regulatory review.
---------------------------------------------------------------------------

\1\ https://www.epa.gov/sites/production/files/2015-11/documents/stage_2_m-dbp_agreement_in_principle.pdf.
\2\ E.O. 13563 requires federal agencies to ``consider how best
to promote retrospective analysis of rules that may be outmoded,
ineffective, insufficient, or excessively burdensome, and to modify,
streamline, expand, or repeal them in accordance with what has been
learned.'' The order required each federal agency to develop a plan
``consistent with law and its resources and regulatory priorities.''
https://www.gpo.gov/fdsys/pkg/FR-2011-01-21/pdf/2011-1385.pdf.
---------------------------------------------------------------------------

IV. Regulations Included in the Six-Year Review 3

Table IV-1 lists all 88 NPDWRs established to date. The table also
reports the maximum contaminant level goal (MCLG) and the maximum
contaminant level (MCL). The MCLG is ``set at the level at which no
known or anticipated adverse effects on the health of persons occur and
which allows an adequate margin of safety'' (SDWA Sec. 1412(b)(4)).
The MCL is the maximum permissible level of a contaminant in water
delivered to any user of a public water system (PWS) and generally ``is
as close to the maximum contaminant level goal as is feasible'' (SDWA
Sec. 1412(b)(4)(B)).\3\ Where it is not ``economically or technically
feasible'' to set an MCL, EPA can establish a treatment technique (TT),
which must prevent adverse health effects ``to the extent feasible''
(SDWA Sec. 1412(b)(7)(A)). In the case of disinfectants (e.g.,
chlorine, chloramines and chlorine dioxide), the values reported in the
table are not MCLGs and MCLs, but maximum residual disinfectant level
goals (MRDLGs) and maximum residual disinfectant levels (MRDLs).
---------------------------------------------------------------------------

\3\ Under limited circumstances, SDWA Sec. 1412(b)(6)(A) also
gives the Administrator the discretion to promulgate an MCL that is
less stringent than the feasible level and that ``maximizes health
risk reduction benefits at a cost that is justified by the
benefits.''
---------------------------------------------------------------------------

Table IV-1 also includes NPDWRs that EPA identified as candidates
for revision in past Six-Year Reviews. During the Six-Year Review 1,
EPA identified the Total Coliform Rule (TCR) as a candidate for
revision.\4\ EPA published the Revised Total Coliform Rule (RTCR) in
2013 (78 FR 10270, USEPA, 2013a). Four additional NPDWRs for
acrylamide, epichlorohydrin, tetrachloroethylene (PCE) and
trichloroethylene (TCE) were identified as candidates for revision
during the Six-Year Review 2. Of the 88 NPDWRs, EPA identified 12 as
part of recently completed, ongoing or pending regulatory actions; as a
result, these 12 are not subject to a detailed review for the Six-Year
Review 3. This action involves the remaining 76 NPDWRs. EPA applied the
same protocol used for previous Six-Year Reviews, with minor
clarifications (USEPA, 2016f), to the Six-Year Review 3 process.
Section V of this action describes the revised protocol used for the
Six-Year Review 3 and Section VI describes the results of the review of
the NPDWRs.
---------------------------------------------------------------------------

\4\ The NPDWRs apply to specific contaminants/parameters or
groups of contaminants. Historically, when issuing new or revised
standards for these contaminants/parameters, EPA has often grouped
the standards together in more general regulations, such as the
Total Coliform Rule, the Surface Water Treatment Rule or the Phase V
rules. In this action, however, for clarity, EPA discusses the
drinking water standards as they apply to each specific regulated
contaminant/parameter (or group of contaminants), not the more
general regulation in which the contaminant/parameter was regulated.
---------------------------------------------------------------------------

In addition to the regulated chemicals, radiological and
microbiological contaminants included in the previous reviews, this
document also includes the review of the MDBP regulations that were
promulgated under the following actions: The Ground Water Rule (GWR);
the Surface Water Treatment Rules (SWTRs); the Disinfectants and
Disinfection Byproducts (D/DBP) Rules; and the Filter Backwash
Recycling Rule (FBRR). EPA reviewed the LT2 in response to EO 13563
(USEPA, 2011) and as part of the Six-Year Review 3 process.

Table IV-1--NPDWRs Included in Six-Year Review 3
--------------------------------------------------------------------------------------------------------------------------------------------------------
MCL or TT (mg/L) \1\ \2\ Contaminants/ MCL or TT (mg/L) \2\
Contaminants/parameters MCLG (mg/L) \1\ \3\ \3\ parameters MCLG (mg/L) \1\ \3\ \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Acrylamide.................... 0.......................... TT......................... Ethylbenzene.... 0.7.................. 0.7
Alachlor...................... 0.......................... 0.002...................... Ethylene 0.................... 0.00005
dibromide (EDB).
Alpha/photon emitters......... 0 (pCi/L).................. 15 (pCi/L)................. Fluoride........ 4.0.................. 4.0
Antimony...................... 0.006...................... 0.006...................... Giardia lamblia 0.................... TT
\4\.
Arsenic....................... 0.......................... 0.010...................... Glyphosate...... 0.7.................. 0.7

[[Page 3521]]

Asbestos...................... 7 (million fibers/L)....... 7 (million fibers/L)....... Haloacetic acids n/a \5\.............. 0.060
(HAA5).
Atrazine...................... 0.003...................... 0.003...................... Heptachlor...... 0.................... 0.0004
Barium........................ 2.......................... 2.......................... Heptachlor 0.................... 0.0002
epoxide.
Benzene....................... 0.......................... 0.005...................... Heterotrophic n/a.................. TT
bacteria \6\.
Benzo[a]pyrene................ 0.......................... 0.0002..................... Hexachlorobenzen 0.................... 0.001
e.
Beryllium..................... 0.004...................... 0.004...................... Hexachlorocyclop 0.05................. 0.05
entadiene.
Beta/photon emitters.......... 0 (millirems/yr)........... 4 (millirems/yr)........... Lead............ 0.................... TT
Bromate....................... 0.......................... 0.010...................... Legionella...... 0.................... TT
Cadmium....................... 0.005...................... 0.005...................... Lindane......... 0.0002............... 0.0002
Carbofuran.................... 0.04....................... 0.04....................... Mercury 0.002................ 0.002
(inorganic).
Carbon tetrachloride.......... 0.......................... 0.005...................... Methoxychlor.... 0.04................. 0.04
Chloramines................... 4.......................... 4.0........................ Monochlorobenzen 0.1.................. 0.1
e
(Chlorobenzene).
Chlordane..................... 0.......................... 0.002...................... Nitrate (as N).. 10................... 10
Chlorine...................... 4.......................... 4.0........................ Nitrite (as N).. 1.................... 1
Chlorine dioxide.............. 0.8........................ 0.8........................ Oxamyl (Vydate). 0.2.................. 0.2
Chlorite...................... 0.8........................ 1.0........................ Pentachloropheno 0.................... 0.001
l.
Chromium (total).............. 0.1........................ 0.1........................ Picloram........ 0.5.................. 0.5
Copper........................ 1.3........................ TT......................... Polychlorinated 0.................... 0.0005
biphenyls
(PCBs).
Cryptosporidium............... 0.......................... TT......................... Radium.......... 0 (pCi/L)............ 5 (pCi/L)
Cyanide....................... 0.2........................ 0.2........................ Selenium........ 0.05................. 0.05
2,4-Dichlorophenoxyacetic acid 0.07....................... 0.07....................... Simazine........ 0.004................ 0.004
(2,4-D).
Dalapon....................... 0.2........................ 0.2........................ Styrene......... 0.1.................. 0.1
Di(2-ethylhexyl)adipate (DEHA) 0.4........................ 0.4........................ 2,3,7,8-TCDD 0.................... 3.00E-08
(Dioxin).
Di(2-ethylhexyl)phthalate 0.......................... 0.006...................... Tetrachloroethyl 0.................... 0.005
(DEHP). ene.
1,2-Dibromo-3-chloropropane 0.......................... 0.0002..................... Thallium........ 0.0005............... 0.002
(DBCP).
1,2-Dichlorobenzene (o- 0.6........................ 0.6........................ Toluene......... 1.................... 1
Dichlorobenzene).
1,4-Dichlorobenzene (p- 0.075...................... 0.075...................... Total coliforms n/a.................. TT
Dichlorobenzene). (under ADWR \7\
and RTCR \8\).
1,2-Dichloroethane (Ethylene 0.......................... 0.005...................... Total n/a \9\.............. 0.080
dichloride). Trihalomethanes
(TTHM).
1,1-Dichloroethylene.......... 0.007...................... 0.007...................... Toxaphene....... 0.................... 0.003
cis-1,2-Dichloroethylene...... 0.07....................... 0.07....................... 2,4,5-TP 0.05................. 0.05
(Silvex).
trans-1,2-Dichloroethylene.... 0.1........................ 0.1........................ 1,2,4- 0.07................. 0.07
Trichlorobenzen
e.
Dichloromethane (Methylene 0.......................... 0.005...................... 1,1,1- 0.20................. 0.2
chloride). Trichloroethane.
1,2-Dichloropropane........... 0.......................... 0.005...................... 1,1,2- 0.003................ 0.005
Trichloroethane.
Dinoseb....................... 0.007...................... 0.007...................... Trichloroethylen 0.................... 0.005
e.
Diquat........................ 0.02....................... 0.02....................... Turbidity \6\... n/a.................. TT
E. coli....................... 0.......................... MCL \10\ and TT \8\........ Uranium......... 0.................... 0.030
Endothall..................... 0.1........................ 0.1........................ Vinyl Chloride.. 0.................... 0.002
Endrin........................ 0.002...................... 0.002...................... Viruses......... 0.................... TT
Epichlorohydrin............... 0.......................... TT......................... Xylenes (total). 10................... 10
--------------------------------------------------------------------------------------------------------------------------------------------------------
1. MCLG: The maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur,
allowing an adequate margin of safety.
2. MCL: The maximum level allowed of a contaminant in water which is delivered to any user of a public water system.
TT: An enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant.
3. Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million. For chlorine, chloramines
and chlorine dioxide, values presented are MRDLG and MRDL.
4. The current preferred taxonomic name is Giardia duodenalis, with Giardia lamblia and Giardia intestinalis as synonymous names. However, Giardia
lamblia was the name used to establish the MCLG in 1989. Elsewhere in this document, this pathogen will be referred to as Giardia spp. or simply
Giardia unless discussing information on an individual species.
5. There is no MCLG for all five haloacetic acids. MCLGs for some of the individual contaminants are: Dichloroacetic acid (zero), trichloroacetic acid
(0.02 mg/L), and monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated with this group, but have no MCLGs.
6. Includes indicators that are used in lieu of direct measurements (e.g., of heterotrophic bacteria, turbidity).
7. The Aircraft Drinking Water Rule (ADWR) 40 CFR part 141 Subpart X, promulgated October 19, 2009, covers total coliforms.
8. Under the RTCR, a PWS is required to conduct an assessment if it exceeded any of the TT triggers identified in 40 CFR 141.859(a). It is also required
to correct any sanitary defects found through the assessment.
9. There is no MCLG for total trihalomethanes (TTHM). MCLGs for some of the individual contaminants are: Bromodichloromethane (zero), bromoform (zero),
dibromochloromethane (0.06 mg/L), and chloroform (0.07 mg/L).
10. A PWS is in compliance with the E. coli MCL unless any of the conditions identified under 40 CFR 141.63(c) occur.

[[Page 3522]]

V. EPA's Protocol for Reviewing the NPDWRs Included in This Action

A. What was EPA's review process?

Overview
This section provides an overview of the process the Agency used to
review the NPDWRs discussed in this action. The protocol document,
``EPA Protocol for the Third Review of Existing National Primary
Drinking Water Regulations,'' contains a detailed description of the
process the Agency used to review the NPDWRs (USEPA, 2016f). The
foundation of this protocol was developed for the Six-Year Review 1
based on the recommendations of the NDWAC (2000). The Six-Year Review 3
process is very similar to the process implemented during the Six-Year
Review 1 and the Six-Year Review 2, with some clarifications to the
elements related to the review of NPDWRs included in the MDBP rules.
Figure V-1 presents an overview of the Six-Year review protocol and
review outcomes.
The primary goal of the Six-Year Review process is to identify and
prioritize NPDWRs for possible regulatory revision. The two major
outcomes of the detailed review are either:
1. The NPDWR is not appropriate for revision and no action is
necessary at this time.
2. The NPDWR is a candidate for revision.
The reasons for a Six-Year Review outcome of ``not appropriate for
revision at this time'' can include:
Regulatory action--recently completed, ongoing or pending.
The NPDWR was recently completed, is being reviewed in an ongoing
action, or is subject to a pending action.
Ongoing or planned health effects assessment. The NPDWR
has an ongoing health effects assessment (i.e., especially for those
NPDWRs with an MCL set at the MCLG or where the MCL is based on the
SDWA cost benefit provision), or EPA is considering whether a new
health effects assessment is needed.
No new information. EPA did not identify any new, relevant
information that indicates changes to the NPDWR.
Data gaps/emerging information. There are data gaps or
emerging information that need to be evaluated.
Low priority and/or no meaningful opportunity. New
information indicates a possible change to the MCLG and/or MCL but
changes to the NPDWR are not warranted due to one or more of the
following reasons: (1) Possible changes present negligible gains in
public health protection; (2) possible changes present limited
opportunity for cost savings while maintaining the same or greater
level of health protection; and (3) possible changes are a low priority
because of competing workload priorities, limited return on the
administrative costs associated with rulemaking and the burden on
states and the regulated community associated with implementing any
regulatory change that would result.
Alternatively, the reasons for a Six-Year Review outcome that an
NPDWR is a ``candidate for revision'' are that, at a minimum, the
revision presents a meaningful opportunity to:
Improve the level of public health protection, and/or
Achieve cost savings while maintaining or improving the
level of public health protection.
Individual regulatory provisions of NPDWRs that are evaluated as
part of the Six-Year Review are: MCLG, MCL, MRDLG, MRDL, TT, other
treatment technologies such as best available technology (BAT), and
regulatory requirements, such as monitoring requirements.
For example, the microbial regulations include TT requirements
because there is no reliable method that is economically and
technically feasible to measure the microbial contaminants covered by
those regulations. These TT requirements rely on the use of indicators
that can be measured in drinking water, such as the concentration of a
disinfectant, to provide public health protection. As part of the Six-
Year Review 3, EPA evaluated new information related to the use of
those indicators to determine if there is a meaningful opportunity to
improve the level of public health protection. Results of EPA's review
of the MDBP regulations are presented in Sections VI.B.3 and VI.B.4.
For the purpose of this document (except where noted for clarity),
discussions of the review of MCLGs and MCLs should be assumed to also
apply to the review of MRDLGs and MRDLs for disinfectants.
Basic Principles
EPA applied a number of basic principles to the Six-Year Review
process:
The Agency sought to avoid redundant review efforts.
Because EPA has reviewed information for certain NPDWRs as part of
recently completed, ongoing or pending regulatory actions, these NPDWRs
are not subject to the detailed review in this document.
The Agency does not believe it is appropriate to consider
revisions to NPDWRs for contaminants with an ongoing or planned health
effect assessment and for which the MCL is set equal to the MCLG or
based on benefit-cost analysis. This principle stems from the fact that
any new health effects information could affect the MCL via a change in
the MCLG or the assessment of the benefits associated with the MCL.
Therefore, EPA noted that these NPDWRs are not appropriate for revision
and no action is necessary at this time if the health effects
assessment would not be completed during the review period for each
contaminant that has either an MCL that is equal to its MCLG or an MCL
that is based on the 1996 SDWA Amendments' cost-benefit provision. If
the health effects assessment is completed before the next Six-Year
Review, EPA will consider these NPDWRs at that time.
In evaluating the potential for new information to affect
NPDWRs, EPA assumed no change to existing policies and procedures for
developing NPDWRs. For example, in determining whether new information
affected the feasibility of analytical methods for a contaminant, the
Agency assumed no change to current policies and procedures for
calculating practical quantitation levels.
EPA considered new information from health effects
assessments that were completed by the information cutoff date.
Assessments completed after this cutoff date will be reviewed by EPA
during the next review cycle or (if applicable) during the revision of
an NPDWR. The information cutoff date for the Six-Year Review 3 was
December 2015.
During the review, EPA identified areas where information
is inadequate or unavailable (data gaps) or emerging and is needed to
determine whether revision to an NPDWR is appropriate. To the extent
EPA is able to fill data gaps or fully evaluate the emerging
information, the Agency will consider the information as part of the
next review cycle.
EPA may consider accelerating review and potential
revision for a particular NPDWR before the next review cycle when
justified by new public health risk information.
Finally, EPA assured scientific analyses supporting the
review were consistent with the Agency's peer review policy (USEPA,
2015a).

[[Page 3523]]

[GRAPHIC] [TIFF OMITTED] TP11JA17.006

B. How did EPA conduct the review of the NPDWRs?

The protocol for the Six-Year Review 3 is broken down into a series
of questions that can inform a decision about the appropriateness of
revising an NPDWR. These questions are logically ordered into a
decision tree. This section provides an overview of each of the review
elements that EPA considered for each NPDWR during the Six-Year Review
3, including the following: Initial review, health effects, analytical
feasibility, occurrence and exposure, treatment feasibility, risk
balancing and other regulatory revisions. The final review combines the
findings from all of these review elements to recommend whether an
NPDWR is a candidate for revision. Further information about the review
elements is described in the protocol document (USEPA, 2016f). Results
from the review of these elements are presented in Section VI.
1. Initial Review
EPA's initial review of all the contaminants included in the Six-
Year Review 3 involved a simple identification of the NPDWRs that have
either been recently completed, or are being reviewed in an ongoing or
pending action since the last Six-Year Review (cutoff date was August
2008). In addition, the initial review also identified contaminants
with ongoing health effects assessments that have an MCL equal to the
MCLG. Excluding such contaminants from the Six-Year Review 3 prevents
duplicative agency efforts.
2. Health Effects
The principal objectives of the health effects review are to
identify: (1) Contaminants for which a new health effects assessment
indicates that a change in the MCLG might be appropriate (e.g., because
of a change in cancer classification or a change in reference dose
(RfD)), and (2) contaminants for which new health effects information
indicates a need to initiate a new health effects assessment.
To meet the first objective, EPA reviewed the results of health
effects assessments completed before December 2015, the information
cutoff date for the Six-Year Review 3.
To meet the second objective, the Agency conducted an extensive
literature review to identify peer-reviewed studies published before
December 2015. The Agency reviewed the studies to determine whether
there was new health effects information, such as reproductive and
developmental toxicity data, that could potentially affect the MCLG, or
otherwise change the Agency's understanding of the health effects of
contaminants under consideration. EPA then evaluated the need to plan
the initiation of a new health effects assessment.
3. Analytical Feasibility
When establishing an NPDWR, EPA identifies a practical quantitation
limit (PQL), which is ``the lowest achievable level of analytical
quantitation during routine laboratory operating conditions within
specified limits of precision and accuracy'', as noted in the November
13, 1985, Federal Register proposed rule (50 FR 46880, USEPA, 1985).
EPA has a separate process in place to approve new analytical methods
for drinking water contaminants; therefore, review and approval of
potential new methods is outside the scope of the Six-Year Review
protocol. EPA recognizes, however, that the approval and adoption in
recent years of new and/or improved analytical methods may enable
laboratories to quantify contaminants at lower levels than was possible
when NPDWRs were originally promulgated. This ability of laboratories
to measure a contaminant at lower levels could affect its PQL, the
value at which an MCL is set when it is limited

[[Page 3524]]

by analytical feasibility. Therefore, the Six-Year Review process
includes an examination of whether there have been changes in
analytical feasibility that could possibly change the PQL for the
subset of the NPDWRs that reached this stage of the review.
To determine if changes in analytical feasibility could possibly
support changes to PQLs, EPA relied primarily on two alternate
approaches to develop an estimated quantitation limit (EQL): an
approach based on the minimum reporting levels (MRLs) obtained as part
of the Six-Year Review 3 Information Collection Request (ICR), and an
approach based on method detection limits (MDLs).
An MRL is the lowest level or contaminant concentration that a
laboratory can reliably achieve within specified limits of precision
and accuracy under routine laboratory operating conditions using a
given method. The MRL values provide direct evidence from actual
monitoring results about whether quantitation below the PQL using
current analytical methods is feasible. An MDL is a measure of
analytical method sensitivity. MDLs have been used in the past to
derive PQLs for regulated contaminants.
EPA used the EQL as a threshold for occurrence analysis to help the
Agency determine if there may be a meaningful opportunity to improve
public health protection. It should be noted, however, that the use of
an EQL does not necessarily indicate the Agency's intention to
promulgate a new PQL. Any revision to PQLs will be part of future
rulemaking efforts if EPA has determined that an NPDWR is a candidate
for revision.
4. Occurrence and Exposure Analysis
The occurrence and exposure analysis is conducted in conjunction
with other review elements to determine if there is a meaningful
opportunity to revise an NPDWR by:
Estimating the extent of contaminant occurrence, i.e., the
number of PWSs in which contaminants occur at levels of interest
(health-effects-based thresholds or analytical method limits), and
Evaluating the number of people potentially exposed to
contaminants at these levels.
To evaluate national contaminant occurrence under the Six-Year
Review 3, EPA reviewed data from the Six-Year Review 3 ICR database
(SYR3 ICR database), the UCMR datasets (USEPA, 2016j) and other
relevant sources.
For the Six-Year Review 3, EPA collected SDWA compliance monitoring
data through use of an ICR (75 FR 6023, USEPA, 2010a). EPA requested
that all states and primacy entities (tribes and territories)
voluntarily submit their compliance monitoring data for regulated
contaminants in public drinking water systems. Specifically, EPA
requested the submission of compliance monitoring data and related
information collected between January 2006 and December 2011 for
regulated contaminants and related parameters (e.g., water quality
indicators). Forty-six states plus eight primacy agencies provided
data. The assembled data constitute the largest, most comprehensive set
of drinking water compliance monitoring data ever compiled and analyzed
by EPA to inform decision making, containing almost 47 million records
from approximately 167,000 PWSs, serving approximately 290 million
people nationally. Through extensive data management efforts, quality
assurance evaluations, and communications with state data management
staff, EPA established the SYR3 ICR database (USEPA, 2016i). The number
of states and PWSs represented in the dataset varies across
contaminants because of variability in state data submissions and
contaminant monitoring schedules. Except as noted in Section VI, EPA
believes that these data are of sufficient quality to inform an
understanding of the national occurrence of regulated contaminants and
related parameters. Details of the data management and data quality
assurance evaluations are available in the supporting document (USEPA,
2016q). The resulting database is available online on the Six-Year
Review Web site (https://www.epa.gov/dwsixyearreview).
5. Treatment Feasibility
An NPDWR either identifies the BAT for meeting an MCL, or
establishes enforceable TT requirements. EPA reviews treatment
feasibility to ascertain if there are technologies that meet BAT
criteria for a hypothetical more stringent MCL, or if there is new
information that demonstrates an opportunity to improve public health
protection through revision of an NPDWR TT requirement.
To be a BAT, the treatment technology must meet several criteria
such as having demonstrated consistent removal of the target
contaminant under field conditions. Although treatment feasibility and
analytical feasibility together address the technical feasibility
requirement for an MCL, historically, treatment feasibility has not
been a limiting factor for MCLs. The result of this review element is a
determination of whether treatment feasibility would pose a limitation
to revising an MCL or provide an opportunity to revise the TT
requirement.
6. Risk-Balancing
EPA reviews risk-balancing to examine how the Six-Year Review can
address tradeoffs in risks among different NPDWRs and take into account
unregulated contaminants as well. Under this review, EPA considers
whether a change to an MCL and/or TT will increase the public health
risk posed by one or more contaminants, and, if so, the Agency
considers revisions that will balance overall risks. This review
element is relevant only to the NPDWRs included in the MDBP rules,
which were promulgated to address risk-balancing between microbial and
DBP requirements, and among differing types of DBPs. The risk-balancing
approach was based on the SDWA requirements that EPA ``minimize the
overall risk of adverse health effects by balancing the risk from the
contaminant and the risk from other contaminants the concentrations of
which may be affected by the use of a TT or process that would be
employed to attain the maximum contaminant level or levels'' (SDWA
Sec. 1412(b)(5)(B)(i)).
EPA reviewed risk-balancing between microbial and DBP contaminants.
For example, EPA considered the potential impact on DBP concentrations
should there be a consideration to increase the stringency of microbial
NPDWRs. This approach also was used during the development of more
recent MDBP rules such as the LT2 rule and the Stage 2 Disinfectants/
Disinfection Byproducts Rule (D/DBPR) rule. In addition, EPA reviewed
risk-balancing between different types of DBP contaminants. Depending
on the stringency of potential DBP regulations, compliance strategies
used by the regulated community might have the effect of increasing the
concentrations of other types of contaminants, both regulated and
unregulated. EPA considered these potential compliance strategies when
conducting its Six-Year Review 3 with a goal to balance the overall
health risks.
7. Other Regulatory Revisions
In addition to possible revisions to MCLGs, MCLs and TTs, EPA
evaluated whether other revisions are needed to regulatory provisions,
such as monitoring and system reporting requirements. EPA focused this
review element on issues that were not already being addressed through
alternative mechanisms, such as a recently completed, ongoing or
pending regulatory action. EPA also reviewed implementation-related
NPDWR

[[Page 3525]]

concerns that were ``ready'' for rulemaking--that is, the problem to be
resolved had been clearly identified, along with specific options to
address the problem that could be shown to either clearly improve the
level of public health protection, or represent a meaningful
opportunity for achieving cost savings while maintaining the same level
of public health protection. The result of this review element is a
determination regarding whether EPA should consider revisions to the
monitoring and/or reporting requirements of an NPDWR.

C. How did EPA factor children's health concerns into the review?

The 1996 amendments to SDWA require special consideration of
sensitive life stages and populations (e.g., infants, children,
pregnant women, elderly and individuals with a history of serious
illness) in the development of drinking water regulations (SDWA Sec.
1412(b)(3)(C)(V)). As a part of the Six-Year Review 3, EPA completed a
literature search covering developmental and reproductive endpoints
(e.g., fertility, embryo survival, developmental delays, birth defects
and endocrine effects) for information published as of December 2015
for regulated chemicals that had not been the subject of a health
effects assessment during this review period. EPA reviewed the results
of the literature searches to identify any studies that might suggest a
need to revise MCLGs. These studies were considered in EPA's review of
NPDWRs, which is discussed in Section VI.

D. How did EPA factor environmental justice concerns into the review?

Executive Order (E.O.) 12898, ``Federal Actions to Address
Environmental Justice in Minority Populations or Low-Income
Populations,'' establishes a federal policy for incorporating
environmental justice (EJ) into federal agency missions by directing
agencies to identify and address disproportionately high and adverse
human health or environmental effects of its programs, policies and
activities on minority and low-income populations. EPA evaluates
potential EJ concerns when developing regulations. This Six-Year Review
was developed in compliance with E.O. 12898. Should the Six-Year Review
lead to a decision to revise an NPDWR, any subsequent rulemakings will
include an EJ component and an opportunity for public comment.

VI. Results of EPA's Review of NPDWRs

Table VI-1 lists the results of EPA's review for each of the 76
NPDWRs discussed in this section of this action, along with the
principal rationale for the review outcomes. Table VI-1 also includes a
list of the 12 NPDWRs that have been recently completed, or have
ongoing or pending regulatory actions.

Table VI-1--Summary of Six-Year Review 3 Results
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Not Appropriate for Revision at Recently completed, 1,2-Dichloroethane E. coli.
this Time. ongoing or pending (Ethylene dichloride). Lead.
regulatory action. 1,2-Dichloropropane........ Tetrachloroethylene
Benzene.................... (PCE).
Carbon Tetrachloride....... Total coliforms (under
ADWR and RTCR).
Copper Trichloroethylene (TCE)
Dichloromethane (Methylene Vinyl chloride.
chloride).
Not Appropriate for Revision at Health effects Alpha/photon emitters...... Mercury \1\
this Time \2\. assessment in Arsenic.................... Nitrate \1\
process (as of Atrazine................... Nitrite \1\
December 2015) or Benzo(a)pyrene (PAHs)...... o-Dichlorobenzene \1\
contaminant Beta/photon emitters....... p-Dichlorobenzene \1\
nominated for health Cadmium \1\................ Polychlorinated
assessment. Chromium................... biphenyls (PCBs).
Di(2-ethylhexyl) phthalate Radium.
(DEHP) \1\. Simazine.
Ethylbenzene............... Uranium \1\
Glyphosate.................
No new information, 1,2-Dibromo-3-chloropropane Dalapon.
NPDWR remains (DBCP). Di(2-ethylhexyl)adipate
appropriate after 2,4,5-TP (Silvex).......... (DEHA).
review. Antimony................... Dinoseb.
Asbestos................... Endrin.
Bromate.................... Ethylene dibromide.
Chloramines (under D/DBPR). Pentachlorophenol.
Chlorine (under D/DBPR).... Thallium.
Chlorine dioxide........... trans-1,2-
Chlorobenzene Dichloroethylene.
(monochlorobenzene). Turbidity.
Low priority and/or 1,1,1-Trichloroethane...... Epichlorohydrin.
no meaningful 1,1,2-Trichloroethane...... Fluoride.
opportunity. 1,1-Dichloroethylene....... Heptachlor.
1,2,4-Trichlorobenzene..... Heptachlor epoxide.
2,3,7,8-TCDD (Dioxin)...... Hexachlorobenzene.
2,4-D...................... Hexachlorocyclopentadien
Acrylamide................. e.
Alachlor................... Lindane.
Methoxychlor.
Barium Oxamyl (Vydate).
Beryllium.................. Picloram.
Carbofuran................. Selenium.
Chlordane.................. Styrene.
cis-1,2-Dichloroethylene... Toluene.
Cyanide.................... Toxaphene.
Diquat..................... Xylenes.
Endothall..................

[[Page 3526]]

Candidate for Revision............ New information...... Chlorite................... Heterotrophic Bacteria.
Cryptosporidium (under Legionella.
SWTR, IESWTR, LT1). TTHM.
Giardia lamblia............ Viruses (under SWTR).
Haloacetic Acids (HAA5)....
----------------------------------------------------------------------------------------------------------------
\1\ Contaminants nominated for Integrated Risk Information System (IRIS) assessments per SYR Protocol.
\2\ LT2, FBRR, and GWR also identified as not appropriate for revision at this time. See Section VI.B.4 for
additional information on the results of EPA's review of these regulations.

A. What are the review result categories?

For each of the 76 NPDWRs discussed in detail in the following
sections of this action, the review outcomes fall in one of the
following categories:
1. The NPDWR is Not Appropriate for Revision at This Time
The current NPDWR remains appropriate and no action is necessary at
this time. In this category, NPDWRs are grouped under the following
subcategories:
Health effects assessment in process (as of December 2015)
or contaminant nominated for health assessment,
No new information and NPDWR remains appropriate after
review,
Data gaps/emerging information, and
No meaningful opportunity.
2. The NPDWR Is a Candidate for Revision
The NPDWR is a candidate for revision based on the review of new
information.

B. What are the detailed results of EPA's third six-year review cycle?

1. Chemical Phase Rules/Radionuclides Rules
Background
The NPDWRs for chemical contaminants, collectively called the Phase
Rules, were promulgated between 1987 and 1992 (after the 1986 SDWA
amendments). In December 2000, EPA promulgated final radionuclide
regulations, which were issued as interim rules in July 1976.
Information related to the review for fluoride is discussed separately
in Section VI.B.2.
Summary of Review Results
EPA has decided that it is not appropriate at this time to revise
any of the NPDWRs covered under the Phase Rules or Radionuclide Rules.
These NPDWRs were determined not to be candidates for revision for one
or more of the following reasons: There was no new information to
suggest possible changes in MCLG/MCL; new information did not present a
meaningful opportunity for health risk reduction or cost savings while
maintaining/improving public health protection; or there was an ongoing
or pending regulatory action. Details related to the review of all
Phase Rules and Radionuclide Rules contaminants can be found in the
``Chemical Contaminant Summaries for the Third Six-Year Review of
National Primary Drinking Water Regulations'' (USEPA, 2016b).
Initial Review
The initial review identified 12 chemical contaminants with NPDWRs
under the Chemical Phase Rules that were being considered as part of
ongoing or pending regulatory actions, and 61 chemical or radionuclide
NPDWRs were identified as appropriate for review. The NPDWRs with
ongoing or pending regulatory actions included eight carcinogenic
volatile organic compounds (cVOCs), lead, copper, acrylamide and
epichlorohydrin.
In 2011, EPA announced its plans to address a group of regulated
and unregulated cVOCs in a single regulatory effort. The eight
regulated VOCs being currently evaluated for a potential cVOCs group
regulation include: Benzene; carbon tetrachloride; 1,2-dichloroethane;
1,2-dichloropropane; dichloromethane; PCE; TCE; and vinyl chloride. The
regulatory revisions to TCE and PCE, initiated as an outcome of the
Six-Year Review 2, are also being considered as part of the group
regulatory effort. Since a regulatory effort is ongoing for these eight
contaminants, they were excluded from a detailed review as part of the
third Six-Year Review.
The NPDWRs for acrylamide and epichlorohydrin were also previously
identified as candidates for regulatory revision and were pending
regulatory action. The polyacrylamides and epichlorohydrin-based
polymers available today for water treatment have lower residual
monomer content than when EPA promulgated residual content as a TT
(USEPA, 2016s). For example, the 90th percentile concentration of
acrylamide residual monomer levels was approximately one-half the
residual level listed in the current TT and no residual epichlorohydrin
was detected. The health benefits associated with the lower impurity
levels are already being realized by communities throughout the
country; therefore, a regulatory revision will minimally affect health
risk. Given resource limitations, competing workload priorities, and
administrative costs and burden to states to adopt any regulatory
changes associated with the rulemaking, as well as limited potential
health benefits, these NPDWRs are considered a low priority and no
longer candidates for revision at this time.
EPA is also currently considering Long-Term Revisions to the Lead
and Copper Rule; and therefore, evaluation of that NPDWR under the Six-
Year Review process would be redundant.
Health Effects
The principal objectives of the health effects review are to
identify: (1) Contaminants for which a new health effects assessment
indicates that a change in MCLG might be appropriate (e.g., because of
a change in cancer classification or an RfD), and (2) contaminants for
which the Agency has identified new health effects information
suggesting a need to initiate a new health effects assessment.
Before identifying chemical NPDWR contaminants for which an updated
MCLG may be appropriate, EPA first identified chemicals with ongoing or
planned EPA health effects assessments. As of December 31, 2015, 19
chemical/radiological contaminants reviewed had ongoing or planned
formal EPA health effects assessments. Table VI-2 below lists the 19
contaminants with ongoing or planned EPA assessments and the status of
those reviews.

[[Page 3527]]

Table VI-2--Six-Year Review Chemical/Radiological Contaminants With Ongoing or Planned EPA Health Assessments
----------------------------------------------------------------------------------------------------------------
Chemical/radionuclide Status
----------------------------------------------------------------------------------------------------------------
Alpha/photon emitters.................... EPA is conducting a review of alpha and beta photo emitters.
Arsenic, inorganic....................... Inorganic arsenic is being assessed by the EPA IRIS Program. The
assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm).
Atrazine................................. Atrazine and simazine are being assessed under EPA's pesticide
registration review process.
Benzo(a)pyrene........................... Benzo(a)pyrene is being assessed by the EPA IRIS Program. The
assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm).
Beta/photon emitters..................... EPA is conducting a review of alpha and beta photo emitters.
Cadmium.................................. Cadmium is included in the EPA IRIS Multi-Year Agenda.
Chromium (VI) as part of total Cr)....... Chromium VI is being assessed by the EPA IRIS Program. The assessment
status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm).
DEHP..................................... DEHP is included in the EPA IRIS Multi-Year Agenda.
Ethylbenzene............................. Ethylbenzene is being assessed by the EPA IRIS Program. The
assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm).
Glyphosate............................... GlyphosateGlyphosate is being assessed under EPA's pesticide
registration review process.
Mercury.................................. Mercury is included in the EPA IRIS Multi-Year Agenda.
Nitrate.................................. Nitrate is included in the EPA IRIS Multi-Year Agenda.
Nitrite.................................. Nitrite is included in the EPA IRIS Multi-Year Agenda.
o-Dichlorobenzene........................ o-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda.
p-Dichlorobenzene........................ p-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda.
PCBs..................................... PCBs are being assessed by the EPA IRIS Program. The assessment
status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm).
Radium (226, 228)........................ EPA is conducting a review of radium.
Simazine................................. Atrazine and simazine are being assessed under EPA's pesticide
registration review process.
Uranium.................................. Uranium is included in the EPA IRIS Multi-Year Agenda.
----------------------------------------------------------------------------------------------------------------

For chemicals that were not excluded due to an ongoing or planned
health effects assessment by EPA, or by the National Academy of
Sciences (NAS), commissioned by EPA, a more detailed review was
undertaken. Of the chemicals that underwent a more detailed review, EPA
identified 21 for which there have been official Agency changes in the
RfD and/or in the cancer risk assessment from oral exposure or new
relevant non-EPA assessments that might support a change to the MCLG.
These 21 chemicals were further evaluated as part of the Six-Year
Review 3 to determine whether they were candidates for regulatory
revision. Table VI-3 lists the 21 chemicals with available new health
effects information and the sources of the relevant new information. As
shown in this table, 11 chemical contaminants have information that
could support a lower MCLG and 10 contaminants have new information
that could support a higher MCLG.

Table VI-3--Chemicals With Available New Health Assessment That Could
Support a Change in MCLG
------------------------------------------------------------------------
Chemical Relevant new assessment
------------------------------------------------------------------------
Potential Decrease in MCLG
------------------------------------------------------------------------
Carbofuran....................... USEPA, 2008a (OPP).
Cyanide.......................... USEPA, 2010e (IRIS).
cis-1,2-Dichloroethyelene........ USEPA, 2010d (IRIS).
Endothal......................... USEPA, 2005f (OPP).
Hexachloropentadiene............. USEPA, 2001a (IRIS).
Methoxychlor..................... CalEPA 2010a.
Oxamyl........................... USEPA, 2010f (OPP).
Selenium......................... Health Canada 2014.
Styrene.......................... CalEPA 2010b.
Toluene.......................... USEPA, 2005c (IRIS).
Xylenes.......................... USEPA, 2003a (IRIS).
------------------------------------------------------------------------
Potential Increase in MCLG
------------------------------------------------------------------------
Alachlor......................... USEPA, 2006a (OPP).
Barium........................... USEPA, 2005b (IRIS).
Beryllium........................ USEPA, 1998a (IRIS).
1,1-Dichloroethylene............. USEPA, 2002b (IRIS).
2,4 Dichlorophenoxy-acetic Acid.. USEPA, 2013b (OPP).
Diquat........................... USEPA, 2002a (OPP).
Lindane.......................... USEPA, 2002d (OPP).
Picloram......................... USEPA, 1995 (OPP).
1,1,1-Trichloroethane............ USEPA, 2007a (IRIS).
1,2,4-Trichlorobenzene........... ATSDR, 2010.
------------------------------------------------------------------------

[[Page 3528]]

Details of the health effects review of the chemical and
radiological contaminants are documented in the ``Six-Year Review 3--
Health Effects Assessment for Existing Chemical and Radionuclides
National Primary Drinking Water Regulations--Summary Report'' (USEPA,
2016h).
Analytical Feasibility
EPA performed analytical feasibility analyses for the contaminants
that reached this portion of the review. These contaminants included
the 11 chemical contaminants identified under the health effects review
as having potential for a lower MCLG and an additional 14 contaminants
with MCLs based on analytical feasibility and MCLs higher than the
current MCLGs. The document ``Analytical Feasibility Support Document
for the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules'' (USEPA,
2016a) describes the first step in the process EPA used to evaluate
whether changes in PQL are possible in those instances where the MCL is
limited, or may be limited, by analytical feasibility. The EQL analysis
is documented in the '' Development of Estimated Quantitation Levels
for the Third Six-Year Review of National Primary Drinking Water
Regulations (Chemical Phase Rules)'' (USEPA, 2016d).
Table VI-4 shows the outcomes of EPA's analytical feasibility
review for two general categories of drinking water contaminants:
Contaminants where health effects assessments indicate potential for
lower MCLGs; and contaminants where existing MCLs are based on
analytical feasibility.
A health effects assessment indicates potential for lower
MCLG. This category includes the 11 contaminants identified in the
health effects review as having information indicating the potential
for a lower MCLG. EPA reviewed analytical feasibility to determine if
analytical feasibility could limit the potential for MCL revisions. For
six contaminants (carbofuran, cyanide, endothall, methoxychlor, oxamyl
and styrene), the current PQL is higher than the potential new MCLG
identified in the health effects review. For these contaminants, the
PQL assessment did not support reduction of the current PQL, or data
were inconclusive or insufficient to reach a conclusion. Consequently,
analytical feasibility could be a limiting factor for setting the MCL
equal to the potential new MCLG. The current PQL is not a limiting
factor for the remaining five contaminants identified by the health
effects review for possible changes in their MCLG (i.e., cis-1,2-
dichloroethylene, hexachlorocyclopentadiene, selenium, toluene and
xylene).
Contaminants for which existing MCLs are based on
analytical feasibility. This category includes 14 contaminants with
existing MCLs that are greater than their MCLGs because they are
limited by analytical feasibility. Two of the contaminants (thallium
and 1,1,2-trichloroethanetrichloroethane) are non-carcinogenic and have
a non-zero MCLG and the remaining 12 contaminants are carcinogens with
MCLGs equal to zero. EPA evaluated whether the PQL could be lowered for
each of these contaminants. For one contaminant, 1,1,2-trichloroethane,
EPA concluded that new information from Proficiency Testing (PT)
studies, along with MRL and MDL data, indicate the potential to revise
the PQL. For two contaminants (dioxin and PCBs), data from PT studies
were inconclusive, but MRL and MDL data indicated the potential to
revise the PQL. For five contaminants (chlordane, heptachlor,
heptachlor epoxide, hexachlorobenzene and toxaphene) data from PT and
MRL studies were inconclusive, but MDL data indicate the potential to
revise the PQL. For the remaining five contaminants, either EPA did not
have sufficient new information to evaluate analytical feasibility or
EPA concluded that new information does not indicate the potential for
a PQL revision.
Where these evaluations indicated the potential for a PQL
reduction, Table VI-4 lists the type of data that support this
conclusion. The notation ``PT'' indicates that the PQL reassessment
based on PT data (USEPA, 2016a) supports the reduction. The notations
``MRL'' and ``MDL'' indicates that these two approaches support PQL
reduction. The findings based on PT offer more certainty. When the PQL
reassessment outcome is that the current PQL remains appropriate, Table
VI-4 shows the result ``Data do not support PQL reduction.''

Table VI-4--NPDWRs Included in Analytical Feasibility Reassessment and
Result of That Assessment
------------------------------------------------------------------------
Current PQL Analytical feasibility
Contaminant ([mu]g/L) reassessment result
------------------------------------------------------------------------
11 Contaminants Identified Under the Health Effects Review as Having
Potential for Lower MCLG
------------------------------------------------------------------------
Carbofuran..................... 7 Data do not support PQL
reduction.
Cyanide........................ 100 Data do not support PQL
reduction.
cis-1,2-Dichloroethylene....... 5 PQL not limiting.
Endothall...................... 90 PQL reduction supported
(MRL, MDL).
Hexachlorocyclopentadiene...... 1 PQL not limiting.
Methoxychlor................... 10 PQL reduction supported
(PT, MRL).
Oxamyl......................... 20 PQL reduction supported
(MRL, MDL).
Selenium....................... 10 PQL not limiting.
Styrene........................ 5 PQL reduction supported
(PT, MRL, MDL).
Toluene........................ 5 PQL not limiting.
Xylene......................... 5 PQL not limiting.
------------------------------------------------------------------------
14 Contaminants With MCLs Based on Analytical Feasibility and Higher
Than MCLGs
------------------------------------------------------------------------
Benzo(a)pyrene................. 0.2 Data do not support PQL
reduction.
Chlordane...................... 2 PQL reduction supported
(MRL, MDL).
1,2-Dibromo-3-chloropropane 0.2 Data do not support PQL
(DBCP). reduction.
Di(2-ethylhexyl)phthalate 6 Data do not support PQL
(DEHP). reduction.
Ethylene dibromide (EDB)....... 0.05 Data do not support PQL
reduction.
Heptachlor..................... 0.4 PQL reduction supported
(MDL).
Heptachlor Epoxide............. 0.2 PQL reduction supported
(MDL).
Hexachlorobenzene.............. 1 PQL reduction supported
(PT, MDL).
Pentachlorophenol.............. 1 Data do not support PQL
reduction.

[[Page 3529]]

PCBs........................... 0.5 Data do not support PQL
reduction.
Dioxin......................... 3.0 x 10-5 PQL reduction supported
(MRL, MDL).
Thallium....................... 2 Data do not support PQL
reduction.
Toxaphene...................... 3 PQL reduction supported
(MDL).
1,1,2-Trichloroethane.......... 5 PQL reduction supported
(PT, MRL, MDL).
------------------------------------------------------------------------

Occurrence and Exposure
Using the SYR3 ICR database, EPA conducted an assessment to
evaluate national occurrence of regulated contaminants and estimate the
potential population exposed to these contaminants. The details of the
current chemical occurrence analysis are documented in ``The Analysis
of Regulated Contaminant Occurrence Data from Public Water Systems in
Support of the Third Six-Year Review of National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules'' (USEPA,
2016p). Based on benchmarks identified in the health effects and
analytical feasibility analyses, EPA conducted the occurrence and
exposure analysis for 18 contaminants.
This analysis shows that these 18 contaminants occur at levels
above the identified benchmark in a very small percentage of systems,
which serve a very small percentage of the population, indicating that
revisions to NPDWRs are unlikely to provide a meaningful opportunity to
improve public health protection across the nation. Therefore, these
contaminants were not identified as candidates for regulatory revision.
Table VI-5 lists the benchmarks used to conduct the occurrence
analysis, the total number of systems with mean concentrations
exceeding a benchmark and the estimated population served by those
systems.

Table VI-5--Occurrence and Potential Exposure Analysis for Chemical NPDWRs
----------------------------------------------------------------------------------------------------------------
Population served by
Number (and percentage) systems with a mean
Benchmark \1\ of systems with a mean concentration higher
Contaminant (ug/L) concentration higher than benchmarks (and
than benchmarks percentage of total
population)
----------------------------------------------------------------------------------------------------------------
Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG
----------------------------------------------------------------------------------------------------------------
Carbofuran.................................... >5 1 (0.00%) 993 (0.0004%)
Cyanide....................................... >50 98 (0.27%) 574,038 (0.27%)
cis-1,2-Dichloroethylene...................... >10 4 (0.01%) 5,569 (0.00%)
Endothall..................................... >50 1 (0.01%) 993 (0.001%)
Hexachlorocyclopentadiene..................... >40 0 (0.00%) 0 (0.00%)
Methoxychlor.................................. >1 1 (0.003%) 993 (0.000%)
Oxamyl........................................ >9 2 (0.01%) 9,742 (0.004%)
Selenium...................................... >40 49 (0.10%) 135,685 (0.05%)
Styrene....................................... >0.5 117 (0.210%) 571,425 (0.217%)
Toluene....................................... >600 0 (0.00%) 0 (0.00%)
Xylene........................................ >1,000 2 (0.004%) 825 (0.0003%)
----------------------------------------------------------------------------------------------------------------
Contaminants With MCLs Based on Analytical Feasibility and Higher Than MCLGs
----------------------------------------------------------------------------------------------------------------
Chlordane..................................... >1 3 (0.01%) 1,353 (0.001%)
Heptachlor.................................... >0.1 3 (0.01%) 1,643 (0.00%)
Heptachlor Epoxide............................ >0.04 14 (0.04%) 11,659 (0.005%)
Hexachlorobenzene............................. >0.1 6 (0.016%) 8,703 (0.004%)
2,3,7,8-TCDD (Dioxin)......................... >0.000005 2 (0.06%) 1,450 (0.002%)
Toxaphene..................................... >1 6 (0.02%) 715,106 (0.32%)
1,1,2-Trichloroethane......................... >3 0 (0.00%) 0 (0.00%)
----------------------------------------------------------------------------------------------------------------

In addition, EPA performed a source water occurrence analysis for
the 10 chemical contaminants in which updated health effects
assessments indicated the possibility to increase (i.e., render less
stringent) the MCLG values. EPA conducted this analysis to determine if
there was a meaningful opportunity to achieve cost savings while
maintaining or improving the level of public health protection. The
data available to characterize contaminant occurrence was limited
because there is no comprehensive dataset that characterizes source
water quality for drinking water systems. Data from the U.S. Geological
Survey (USGS) National Water Quality Assessment program and the U.S.
Department of Agriculture Pesticide Data Program water monitoring
survey provide useful insights into potential contaminant occurrence in
source water. The analysis of the available contaminant occurrence data
for potential drinking water sources indicated relatively low
contaminant occurrence in the concentration ranges of interest. As a
consequence, EPA could not conclude that there is a meaningful
opportunity for system cost savings by increasing the MCLG and/or MCL
for these 10 contaminants. The results of this

[[Page 3530]]

analysis were documented in ``Occurrence Analysis for Potential Source
Waters for the Third Six-Year Review of National Primary Drinking Water
Regulations'' (USEPA, 2016e).
Treatment Feasibility
Currently, all of the MCLs for chemical and radiological
contaminants are set equal to the MCLGs or PQLs or are based on
benefit-cost analysis; none are currently limited by treatment
feasibility. EPA considers treatment feasibility after identifying
contaminants with the potential to lower the MCLG/MCL that constitute a
meaningful opportunity to improve public health. No such contaminants
were identified in the occurrence and exposure analysis described
above.
Other Regulatory Revisions
In addition to possible revisions to MCLGs, MCLs and TTs, EPA
considered whether other regulatory revisions are needed to address
implementation issues, such as revisions to monitoring and system
reporting requirements, as a part of the Six-Year Review 3. EPA used
the protocol to evaluate which implementation issues to consider
(USEPA, 2016f). EPA's protocol focused on items that were not already
being addressed, or had not been addressed, through alternative
mechanisms (e.g., as a part of a recent or ongoing rulemaking).
Implementation Issues Identified for the Six-Year Review 3
EPA compiled information on implementation related issues
associated with the Chemical Phase Rules. EPA also identified
unresolved implementation issues/concerns from previous Six-Year
Reviews. EPA shared the list of identified potential implementation
issues with a group of state representatives convened by ASDWA to
obtain input from state drinking water agencies concerning the
significance and relevance of the issues (ASDWA, 2016). The complete
list of implementation issues related to the Phase Rules and
Radionuclide Rules is presented in ``Consideration of Other Regulatory
Revisions in Support of the Third Six-Year Review of the National
Primary Drinking Water Regulations: Chemical Phase Rules and
Radionuclide Rules'' (USEPA, 2016c).
The Agency determined that the following three issues, identified
by state stakeholders, were within the scope of NPDWR review and were
the most substantive:
a. Nitrogen monitoring in consecutive systems and the distribution
system,
b. Alternative nitrate-nitrogen MCL of 20 mg/L for non-community
water systems (NCWSs), and
c. Synthetic organic chemical (SOC) detection limits.
Table VI-6 provides a brief description of the three issues and the
Agency's findings to date.

Table VI-6--Chemical Rule Implementation Issues Identified That Fall
Within the Scope of an NPDWR Review
------------------------------------------------------------------------
Implementation issue Description and findings
------------------------------------------------------------------------
Nitrogen Monitoring in Consecutive Current nitrite and nitrate
Systems and the Distribution standards are measured at the point
System. of entry to the distribution
system. Under some conditions,
nitrification of ammonia in water
system distribution networks could
potentially result in increased
total nitrite or nitrate
concentrations at the point of use.
To address the concern, certain
water systems could develop and
implement a nitrification
monitoring program, which would
include changing or adding
additional monitoring locations.
Research is needed to further
evaluate the extent of this
potential issue, including
development of criteria to identify
the specific systems where
distribution system monitoring
could be targeted. If the outcome
of the research suggests that the
magnitude of the problem represents
a meaningful opportunity to improve
public health protection, the
regulation could be considered for
revision.
Alternative Nitrate-Nitrogen MCL EPA evaluated the possibility of
of 20 mg/L for NCWS. removing or further restricting the
option for some NCWSs to use an
alternative nitrate-nitrogen MCL of
up to 20 mg/L. The nitrate-nitrogen
MCL in PWSs is 10 mg/L. However,
Sec. 141.11 of the Code of
Federal Regulations (CFR) provides
that states have the discretion to
allow some NCWSs to use an
alternative nitrate-nitrogen MCL of
up to 20 mg/L if certain conditions
are met, including conditions where
water will not be available to
children under six months of age.
Other provisions related to this
issue are included in Sec. 141.23
of the CFR, which pertains to
monitoring. This section states:
``Transient, non-community water
systems shall conduct monitoring to
determine compliance with the
nitrate and nitrite MCL in Sec.
Sec. 141.11 and 141.62 (as
appropriate) in accordance with
this section.'' The monitoring
section does not address non-
transient non-community water
systems (NTNCWSs) eligibility to
use an alternative nitrate MCL.
Two potential concerns identified
with the current rule provisions
are:
Potential health concerns
other than methemoglobinemia
associated with the ingestion of
nitrate-nitrogen, such as
possible effects on fetal
development.
The fact that the
alternative MCL was initially
intended to be used by entities
such as industrial plants that do
not provide drinking water to
children under six months of age
(44 FR 42254, USEPA, 1979).
Industrial plants are generally
considered to be NTNCWSs.
Therefore, it is possible the
alternative MCL was intended to
apply specifically to NTNCWSs and
not transient non-community water
systems (TNCWSs).
The Agency has nominated nitrate and
nitrite for an IRIS assessment as a
result of the Six-Year Review
process, and both of these
contaminants are listed in the IRIS
multi-year plan. An updated
assessment is needed that evaluates
health effects other than
methemoglobinemia. Specifically, an
assessment is needed that evaluates
potential health effects of nitrate-
nitrogen at levels between 10 and
20 mg/L on adult populations. When
completed, the IRIS assessment may
support initiation of a rule
revision if potential adverse
health effects were identified at
drinking water concentrations below
the alternative nitrate MCL of 20
mg/L for populations other than
infants less than six-months of
age.

[[Page 3531]]

Synthetic Organic Chemical (SOC) According to states, some
Detection Limits. laboratories have reported
difficulty in achieving the
detection limits for some SOCs on a
regular basis. Section 40 CFR
141.24(h)18 provides detection
limits for the SOCs, including some
pesticides. PWSs that do not detect
a SOC contaminant above these
concentrations may qualify for
reduced monitoring frequency for
individual contaminants. It was
reported that some SOCs may have
detection limits that are lower
than levels that can be
economically and efficiently
achieved by laboratories using
approved methods. Thus, some water
systems may not be able to qualify
for reduced monitoring if the
laboratories cannot achieve the
listed detection limits. This issue
was also identified as a concern by
the states during the Six-Year
Review 2.
To address the SOC method detection
limits, the Agency investigated the
MRL values for SOCs from the SYR 3
ICR and found there was an existing
approved analytical method for each
SOC that laboratories can use to
achieve the appropriate detection
limits in order to reduce
monitoring requirements.
Using the MRL values, the Agency
evaluated the percentage of records
in the ICR database at or below the
detection limit. EPA considered
this percentage as an indication of
laboratories' collective ability to
detect contaminant concentrations
at or below these levels. The
Agency found that for most of the
SOCs, nearly half of the records
were at or below the detection
limit listed in the regulation
while other SOCs had a sufficient
number of records below the
detection limit to determine that
there was an approved analytical
method that could be used.
------------------------------------------------------------------------

2. Fluoride

Background

Fluoride can occur naturally in drinking water as a result of the
geological composition of soils and bedrock. Some areas of the country
have high levels of naturally occurring fluoride. EPA established the
current NPDWR to reduce the public health risk associated with exposure
to high levels of naturally occurring fluoride in drinking water
sources.
Low levels of fluoride are frequently added to drinking water
systems as a public health protection measure for reducing the
incidence of cavities. The decision to fluoridate a community water
supply is made by the state or local municipality, and is not mandated
by EPA or any other federal entity. The U.S. Public Health Service
(PHS) recommendation for community water fluoridation is 0.7 mg/L (U.S.
Department of Health and Human Services, 2015). Fluoride is also added
to various consumer products (such as toothpaste and mouthwash) because
of its beneficial effects at low level exposures.
EPA published the current NPDWR on April 2, 1986 (51 FR 11396,
USEPA, 1986) to reduce the public health risk associated with exposure
to high levels of naturally occurring fluoride in drinking water
sources. The current NPDWR established an MCLG and MCL of 4.0 mg/L to
protect against the most severe stage of skeletal fluorosis (referred
to as the ``crippling'' stage) (NRC, 2006a). EPA also established a
secondary maximum contaminant level (SMCL) for fluoride of 2.0 mg/L to
protect against moderate and severe dental fluorosis, which was
considered at the time to be a cosmetic effect. As provided under the
statute, the SMCL is not enforceable in the same manner as the MCL.
Public notification is required when PWSs exceed the MCL or SMCL.
EPA has reviewed the NPDWR for fluoride in previous Six-Year Review
cycles. As a result of the first Six-Year Review (68 FR 42908, USEPA,
2003b), EPA requested that the National Research Council (NRC) of the
National Academies of Sciences (NAS) conduct a review of the health and
exposure data on orally ingested fluoride. In 2006, the NRC published
the results of its review and concluded that severe dental fluorosis is
an adverse health effect when it causes both a thinning and pitting of
the enamel, a situation that compromises the function of the enamel in
protecting against decay and infection (NRC, 2006a). The NRC
recommended that EPA develop a dose-response assessment for severe
dental fluorosis as the critical effect and update an assessment of
fluoride exposure from all sources.
During the Six-Year Review 2, the Agency was in the process of
developing a dose-response assessment of the non-cancer impacts of
fluoride on severe dental fluorosis and the skeletal system. In
addition, EPA was in the process of updating its evaluation of the
relative source contribution (RSC) of drinking water to total fluoride
exposure considering the contributions from dental products, foods,
pesticide residues, and other sources such as ambient air and
medications. These assessments were not completed at the time of the
Six-Year Review 2; thus, no action was taken under the Six-Year Review
2 (75 FR 15500, USEPA, 2010h).
In 2010, EPA published fluoride health assessments. The ``Dose
Response Analysis for Non-Cancer Effects'' (USEPA, 2010b) identified an
oral RfD for fluoride of 0.08 milligrams per kilograms per day (mg/kg/
day) based on studies of severe dental fluorosis among children in the
six months to 14 year age group (USEPA, 2010b). The ``Exposure and
Relative Source Contribution Analysis'' (USEPA, 2010c) concluded that
the RSC values for drinking water range from 40 to 70 percent, with the
higher values associated with infants fed with powdered formula or
concentrate reconstituted with residential tap water (70%) and with
adults (60%). The major contributors to total daily fluoride intakes
for these age groups are drinking water, commercial beverages, solid
foods and swallowed fluoride-containing toothpaste (USEPA, 2010c).
Summary of Review Results
The Agency has determined that a revision to the NPDWR for fluoride
is not appropriate at this time. EPA acknowledges information regarding
the exposure and health effects of fluoride (as discussed later in the
``Health Effects'' and ``Occurrence and Exposure'' sections). However,
with EPA's identification of several other significant NPDWRs as
candidates for near-term revision (see Sections VI.B.3 and VI.B.4),
potential revision of the fluoride NPDWR is a lower priority that would
divert significant resources from the higher priority candidates for
revision that the Agency has identified, as well as other high priority
work within the drinking water office. These other candidates for
revision include the Stage 1 and Stage 2 Disinfectants and Disinfection
Byproducts Rules (D/DBPRs) that apply to approximately 42,000 PWSs, and
for which EPA has identified the potential to further reduce

[[Page 3532]]

bladder cancer risks attributed to exposure to DBPs; the Surface Water
Treatment Rules, for which the Agency has identified the potential to
further reduce risks from a myriad of serious waterborne diseases
(e.g., giardiasis, cryptosporidiosis, legionellosis, hepatitis,
meningitis and encephalitis) for approximately 12,000 surface water
systems; and the pending revisions to the lead and copper NPDWR which
apply to approximately 68,000 PWSs.
While EPA has evaluated the available health effects and exposure
information related to fluoride (as discussed later in the ``Health
Effects'' and ``Occurrence and Exposure'' sections), the Agency also
recognizes that new studies on fluoride are currently being performed.
These include new studies that address health endpoints of concern
other than dental fluorosis. Based on the NRC recommendations, EPA
evaluated dental fluorosis for the purposes of this action. EPA will
continue to monitor the evolving science, and, when appropriate, will
reconsider the fluoride NPDWR's relative priority for revision and take
any other available and appropriate action to address fluoride risks
under SDWA.
Finally, most community water systems (CWSs) that provide
fluoridation of their drinking water have already lowered their
fluoridation level to a single level of 0.7 mg/L from a previous range
of 0.7 to 1.2 mg/L to accommodate the updated PHS recommendation (U.S.
Department of Health and Human Services, 2015). The U.S. Food and Drug
Administration (FDA) also issued a letter to bottled water
manufacturers recommending that they not add fluoride to bottled water
in excess of the revised PHS recommendations (FDA, 2015). In addition,
the FDA stated it intends to revise the quality standard regulation for
fluoride added to bottled water to be consistent with the updated PHS
recommendation. Therefore, EPA anticipates that a significant portion
of the population's exposure to fluoride in drinking water, as well as
some commercial beverages that use fluoridated water from CWSs and
certain bottled water, has already been or will be reduced.
Notwithstanding this action's decision, EPA will continue to address
risk associated with fluoride in drinking water, with a specific focus
on the small systems with naturally occurring fluoride in their source
waters.
Initial Review
EPA did not identify any recent, ongoing or pending action on
fluoride that would exclude fluoride from the Six-Year Review 3.
Health Effects
The NRC (2006a) evaluated the impact of fluoride on reproduction
and development, neurotoxicity and behavior, the endocrine system,
genotoxicity, cancer and other effects, in addition to the tooth and
bone effects. At fluoride levels below 4.0 mg/L, the NRC found no
evidence substantial enough to support adverse effects other than
severe dental fluorosis and skeletal fractures. The NRC concluded that
the available data were inadequate to determine if a risk of effects on
other endpoints exists at an MCLG of 4.0 mg/L and made recommendations
for additional research.
EPA assessments (USEPA, 2010b; 2010c) found that the RSC values are
lower than the RSC of 100 percent used to derive the original MCLG of
4.0 mg/L, where EPA assumed that drinking water was the sole source of
exposure to fluoride. EPA has concluded that information on the dose-
response and exposure assessment may support lowering the MCLG to
reflect levels that would protect against risk of severe dental
fluorosis and skeletal fractures.
As part of this Six-Year Review, EPA reviewed health effects data
on the impact of fluoride on reproduction and development,
neurotoxicity and behavior, the endocrine system, genotoxicity, cancer
and other effects that were identified by the NRC as requiring
additional research (NRC, 2006a). EPA noted limitations in some of
these studies such as lack of details and confounding factors. Overall,
the new data were insufficient to alter the NRC conclusion that severe
dental fluorosis is the critical health effects endpoint for the MCLG.
Based upon the recommendations of the NRC, EPA has evaluated dental
fluorosis as a critical endpoint of concern for this Six-Year Review
(USEPA, 2010b; 2010c). However new studies are underway to examine
other health endpoints (i.e., developmental neurobehavior effects,
endocrine disruption and genotoxicity). One example is an ongoing
National Toxicology Program (NTP) systematic review of animal studies
that examined the impact of fluoride on learning and memory (NTP,
2016). For more information about fluoride developmental neurotoxicity
visit the National Toxicology Program Web site at https://ntp.niehs.nih.gov/pubhealth/hat/noms/fluoride/neuro-index.html.
Additional information related to the review of the fluoride NPDWR is
provided in the ``Six-Year Review 3 Health Effects Assessment Summary
Report'' (USEPA, 2016h).
Analytical Feasibility
The current PQL for fluoride is 0.5 mg/L (USEPA, 2009a). EPA has
not identified any changes in analytical feasibility that could limit
its ability to revise the MCL/MCLG for fluoride.
Occurrence and Exposure
EPA analyzed fluoride occurrence using the SYR3 ICR database, which
contains fluoride analytical results from approximately 47,000 PWSs in
49 states/entities from 2006 to 2011. Sample records for fluoridated
water (i.e., in which a system adds fluoride to maintain a
concentration in the 0.7 to 1.2 mg/L range) were omitted from the
analysis because the fluoridated systems would not be impacted by
revisions to the fluoride NPDWR. EPA estimated the number and percent
of systems that have mean fluoride concentrations exceeding various
benchmarks and the corresponding estimates of population served by
those systems. The data indicated that about 130 systems (0.3 percent),
serving approximately 60,000 people (0.03 percent), had an estimated
system mean concentration exceeding the current MCL of 4.0 mg/L,
whereas more than 900 systems (2 percent), serving approximately 1.5
million people (0.8 percent), had an estimated system mean
concentration greater than the SMCL of 2.0 mg/L. Among these systems,
many are small systems (serving fewer than 10,000 people) and very
small systems (serving fewer than 500 people). Evaluations based on
mean (or average) fluoride concentrations generally reflect an
approximation of chronic (long-term) exposure. It is important to note
that these average concentration-based evaluations help to inform Six-
Year Review results, but do not assess compliance with regulatory
standards nor should be viewed as compliance forecasts for PWSs.
Treatment Feasibility
A BAT or small system compliance technology for fluoride was not
established in the Code of Federal Regulations (40 CFR 141.62).
However, EPA (1998d) identified activated alumina and reverse osmosis
as BATs for fluoride.
Activated alumina is the most commonly used treatment technology
for fluoride removal. It is capable of removing fluoride to
concentrations well below the MCL of 4.0 mg/L, but with a shortened
media life at lower target concentrations. Membrane technologies, such
as reverse osmosis, nanofiltration, and electrodialysis, are

[[Page 3533]]

also capable of removing fluoride to very low levels (<0.3 mg/L). They
are often used to remove fluoride along with other contaminants such as
total dissolved solids, arsenic, and uranium. In general, these
technologies are costly and complex to operate--and thus likewise
present potential challenges for small water systems (USEPA, 2014a).
3. Disinfectants/Disinfection Byproducts Rules (D/DBPRs)
Background
The D/DBPRs were promulgated in two stages--Stage 1 in 1998 (63 FR
69390, USEPA, 1998b) and Stage 2 in 2006 (71 FR 388, USEPA, 2006d).
Disinfection byproducts (DBPs) are formed when the disinfectants
commonly used in PWSs to kill microorganisms react with organic and
inorganic matter in source water. DBPs have been associated with
potential adverse health effects, including cancer and developmental
and reproductive effects. Monitoring parameters within the D/DBPRs
consist of the following: DBPs--TTHM, HAA5, bromate and chlorite;
disinfectants--chlorine, chloramines and chlorine dioxide; and water
quality indicators--total organic carbon (TOC) and alkalinity. The
rules include MCLGs/MRDLGs, as well as MCLs/MRDLs and TT requirements,
which were developed for individual parameters considering their health
risks.
For organic DBPs, the concern is potential increased risk of cancer
and short-term adverse reproductive and developmental effects. For
bromate, the concern is potential increased risk of cancer. Chlorite (a
regulated DBP) and chlorine dioxide (a disinfectant) are associated
with methemoglobinemia, and for infants, young children and pregnant
women, effects on the thyroid are also of concern. For chlorine and
chloramines, health effects include eye/nose irritation and stomach
discomfort (for chloramines, also anemia).
The D/DBPRs apply to all sizes of CWSs and non-transient non-
community water systems (NTNCWSs) that chemically disinfect their water
or receive chemically disinfected water (that is, involving any
disinfectants other than ultraviolet (UV) light), as well as transient
non-community water systems (TNCWSs) that add chlorine dioxide. The
rules require that these systems comply with established MCLs, TTs,
operational evaluation levels for DBPs and MRDLs for disinfectants.
A major challenge for water suppliers is balancing the risks from
microbial pathogens and DBPs. The risk-balancing tradeoff approach was
intended to lower the overall risks from DBP mixtures while continuing
to provide public health protection from microbial risks.
Summary of Review Results
EPA has identified the following NPDWRs within the D/DBPRs as
candidates for revision under this Six-Year Review cycle because of the
opportunity to further reduce public health risk from exposure to DBPs:
Chlorite, HAA5 and TTHM. This result is based on a scientific review of
publicly available information. EPA's review process follows the
protocol described in Section V of this document. New information has
strengthened the weight of evidence supporting an association between
chlorination DBPs and bladder cancer risk compared to the information
available during development of the existing D/DBPRs. New information
also is available related to the reproductive/developmental effects
discussed in the Stage 2 D/DBPR. In addition, new toxicological data
are available to support the development of MCLGs for some individual
DBPs currently lacking MCLGs (for example, dibromoacetic acid).
This result will also provide for additional opportunity to address
concerns with unregulated DBPs: For example, nitrosamines and chlorate.
In the Federal Register document for Preliminary Regulatory
Determination 3 (79 FR 62715, USEPA, 2014b), the Agency stated that
``because chlorate and nitrosamines are DBPs that can be introduced or
formed in PWSs partly because of disinfection practices, the Agency
believes it is important to evaluate these unregulated DBPs in the
context of the review of the existing DBP regulations. DBPs need to be
evaluated collectively, because the potential exists that the strategy
used to control a specific DBP could increase the concentrations of
other DBPs. Therefore, the Agency is not making a regulatory
determination for chlorate and nitrosamines at this time.''
Chlorate and chlorite are two different oxidation states of
chlorine and are chemically inter-convertible. They occur, and can co-
occur, when hypochlorite solution and/or chlorine dioxide are applied
during the drinking water treatment process. Chlorite is a regulated
DBP. New information has shown that the relative source contribution
for chlorite could be lower than previously estimated in the existing
D/DBPRs, which could lead to a lower MCLG, and that there are common
health endpoints associated with exposure to chlorite and chlorate.
Compliance monitoring data evaluated for the Six-Year Review 3 show
widespread occurrence of DBPs and their organic precursors (as measured
as TOC) in drinking water. Research that has been published since the
development of the Stage 2 D/DBPR has improved EPA's understanding of
the effectiveness of and limitations associated with various treatment
approaches, such as those for removal of precursors, use of
disinfectants other than chlorine and localized treatment.
Given that this is the first time EPA is conducting a Six-Year
Review of the D/DBPRs, extensive information about review findings is
provided below, with further information provided in EPA's ``Six-Year
Review 3 Technical Support Document for Disinfectants/Disinfection
Byproducts Rules'' (USEPA, 2016l). Additional information related to
the review of D/DBPRs is provided in the ``Six-Year Review 3 Technical
Support Document for Chlorate'' (USEPA, 2016k) and the ``Six-Year
Review 3 Technical Support Document for Nitrosamines'' (USEPA, 2016o).
Initial Review
There are no recently completed, ongoing or pending regulatory
actions on the D/DBPRs that would exclude them from the Six-Year Review
3.
Health Effects
Under the Stage 1 and 2 D/DBPRs, toxicology studies for specific
DBPs and disinfectant residuals were used to inform MCLGs (and cancer
potency factors where MCLGs are zero) and MRDLGs. Epidemiology studies
were used to estimate potential risks from DBP mixtures (due to cancer
and developmental/reproductive effects) and support the benefits
analysis. Epidemiology studies supported a potential association
between exposures to elevated THM4 levels in chlorinated drinking water
and cancer, but the evidence was insufficient to establish a causal
relationship. The most consistent evidence was for bladder cancer. For
the development of the benefits analysis for both the Stage 1 and the
Stage 2 D/DBPRs, EPA used five bladder cancer case-control epidemiology
studies that were conducted in the 1980s and 1990s (Cantor et al.,
1985; 1987; McGeehin et al., 1993; King and Marrett, 1996; Freedman et
al., 1997; Cantor et al., 1998). In addition, EPA used one meta-
analysis (Villanueva et al., 2003) and one pooled analysis (Villanueva
et al., 2004). The five case-control studies used similar (though not
identical) exposure metrics based on years of exposure to chlorinated
drinking water (primarily chlorinated surface water) to

[[Page 3534]]

estimate odds ratios. All five studies showed an increase in the odds
ratio for bladder cancer incidence with an increased duration of
exposure. Using the published odds ratio results from these five
studies, EPA calculated an estimate for the lifetime cancer risk
(population attributable risk) that ranged from 2 to 17 percent;
between 2 and 17 percent of bladder cancers occurring in the U.S. could
be attributed to long-term exposure to chlorinated drinking water at
the time of the Stage 1 D/DBPR. Detailed explanations of these
calculations can be found in the benefits analysis for the Stage 2 D/
DBPR (USEPA, 2005a). The evidence from the studies in 1985 to 1998, the
meta-analysis in 2003 and the pooled analysis in 2004 was strong enough
to support the benefit analysis with several thousand potential bladder
cancer cases per year estimated as being avoided from the combined
effects of the Stage 1 and Stage 2 D/DBPRs (USEPA, 2005a).
Studies from the 1970s to 2005 also suggested a possible
association between adverse developmental/reproductive health effects
and exposure to chlorinated drinking water. Effects were observed in
all areas but lacked consistency across studies and did not provide
enough of a basis to quantify risks or benefits. The adverse
developmental/reproductive effects consisted of effects on fetal growth
(small for gestational age, low birth weight and pre-term delivery),
effects on viability (spontaneous abortion, stillbirth) and
malformations (neural tube, oral cleft, cardiac or urinary defects).
Since the development of the Stage 2 D/DBPR, EPA has identified
additional sources of information related to health effects of DBPs.
New toxicological information could be used to develop MCLGs for the
following regulated DBPs (within HAA5): Dibromoacetic acid (NTP, 2007),
other brominated haloacetic acids not currently regulated, including
bromochloroacetic acid (NTP, 2009) and bromodichloroacetic acid (NTP,
2014), plus additional unregulated DBPs such as nitrosamines and
chlorate (USEPA, 2016k; 2016o).
EPA has identified new epidemiological, pharmacokinetic and
pharmacodynamic studies that, considered together with studies
available during the development of the Stage 2 D/DBPR, add to the
weight of evidence for bladder cancer being associated with exposure to
chlorination DBPs (notably those containing bromine) in drinking water.
Pharmacokinetic and pharmacodynamic studies (Ross and Pegram, 2003;
2004; Leavens et al., 2007; Stayner et al., 2014; Kenyon et al., 2015),
in conjunction with epidemiology studies (Villanueva et al., 2007;
Kogevinas et al., 2010; Cantor et al., 2010), indicate that non-
ingestion routes of exposure (dermal and inhalation) from some
brominated DBPs may play a significant role in influencing increased
bladder cancer risk, and that there may be greater concern about sub-
populations with certain genetic characteristics (polymorphisms). EPA's
``Six-Year Review 3 Technical Support Document for Disinfectants/
Disinfection Byproducts Rules'' (USEPA, 2016l) characterizes the
research that informs the mode of action by which brominated DBPs may
be contributing to bladder cancer.
While uncertainties remain regarding the degree to which specific
DBPs contributed to the bladder cancer incidence observed in
epidemiology studies, the collective data suggest a stronger case for
causality than when the Stage 2 D/DBPR was promulgated (Regli et al.,
2015; USEPA, 2016l). However, the Agency recognizes there are also
different perspectives on this issue, including suggestions about areas
for additional research (Hrudey et al., 2015).
Further, the Agency has identified new information about health
effects from unregulated DBPs. This includes health effects information
on chlorate and nitrosamines that, along with occurrence/exposure
information, was previously noted in the Preliminary Regulatory
Determination 3 (79 FR 62715, USEPA, 2014b). The Agency is considering
the health effects of chlorate and nitrosamines within the broader
context of the health effects of regulated DBPs (USEPA, 2016k; 2016o).
EPA also identified information about the relative cytotoxicity and
genotoxicity of many other unregulated DBPs (Richardson et al., 2007;
Richardson et al., 2008; Plewa and Wagner 2009; Plewa et al., 2010;
Fern[aacute]ndez et al., 2010; Richardson and Postigo, 2011; Yang et
al., 2014). Data from in vitro mammalian cell testing, which compared
the cytotoxicity and genotoxicity of iodinated, brominated, and
chlorinated DBPs, showed that the iodinated DBPs (those containing
iodine) were generally more toxic than the brominated DBPs (those
containing bromine), which were in turn more toxic than the chlorinated
DBPs (those containing chlorine). Nitrogen-containing DBPs, including
haloacetonitriles, haloacetamides and halonitromethanes, were more
cytotoxic and genotoxic than the haloacids and halomethanes that did
not contain nitrogen.
Approximately 40 new studies about developmental/reproductive
effects have become available since the development of the Stage 2 D/
DBPR. These studies address endpoints such as fetal growth (low birth
weight, small for gestational age and pre-term delivery), congenital
anomalies and male reproductive outcomes. These studies continue to
support a potential health concern, though, as discussed above, the
relationship of DBP exposure to these types of adverse outcomes may not
be well enough understood to permit quantification of risks or
benefits. A recent ``four-lab study'' on the effects of DBP mixtures on
animals, conducted by EPA researchers (Narotsky et al., 2011; 2013;
2015), suggests diminished concern for many developmental/reproductive
endpoints.
EPA also examined data about health effects for inorganic DBPs,
including information showing that the RSC for chlorite could be lower
than 80 percent (which could potentially support lowering the MCLG)
because there is more dietary exposure than previously assumed due to
the increased use of chlorine dioxide and acidified sodium chlorite as
disinfectants in the processing of foods (U.S. EPA, 2006e; WHO, 2008).
In addition, chlorate, chlorite and chlorine dioxide may share common
health endpoints, namely hematological and thyroid effects (Couri and
Abdel-Rahman, 1980; Bercz et al., 1982; Moore and Calabrese, 1982;
Abdel-Rahman et al., 1984; Khan et al., 2005; Orme et al., 1985; NTP,
2005; USEPA, 2006e; WHO, 2008; Lee et al, 2013; Nguyen et al, 2014).
The Agency did not identify any relevant data that suggest an
opportunity to revise the MCLG for bromate, or the MRDLG for chlorine
or chloramines.
Analytical Feasibility
The Agency has not identified any improvements to analytical
feasibility that could lead to improvements to the NPDWRs included in
the D/DBPRs. Development of these rules was not constrained by the
availability of analytical methods, and new EPA-approved methods that
would revise this finding have not been identified. Should new, EPA-
approved methods for one or more D/DBPRs be identified, that
information might be able to help inform potential future regulatory
development efforts.
Occurrence and Exposure
In this Six-Year Review evaluation of D/DBP occurrence and
exposure, EPA

[[Page 3535]]

evaluated compliance monitoring information collected under the SYR3
ICR, which was previously discussed in Section V.B.4. EPA also
evaluated information from the DBP ICR database (USEPA, 2000a) that had
been used to prepare the original D/DBPRs. Additionally, EPA used data
from the third monitoring cycle of the Unregulated Contaminant
Monitoring Rule (UCMR3) to evaluate chlorate occurrence in 2013-2015,
and data from the UCMR2 to evaluate nitrosamine occurrence in 2008-
2010. This information is briefly described below, with additional
information in EPA's ``Six-Year Review 3 Technical Support Document for
Disinfectants/Disinfection Byproducts Rules'' (USEPA, 2016l).
It is important to note that the information collected through the
SYR3 ICR spans the years 2006-2011. As such, it primarily reflects
occurrence following the effective date for the Stage 1 D/DBPR, but
prior to the effective date for the Stage 2 D/DBPR. These evaluations
help to inform Six-Year Review results but do not assess compliance
with regulatory standards.
New information since the promulgation of the Stage 2 D/DBPR has
improved our understanding on DBP formation and occurrence. As part of
this Six-Year Review, EPA has identified literature describing more
than 600 specific DBPs that have been found in drinking water (e.g.,
Richardson et al., 2007); these include chlorinated, brominated and
iodinated DBPs, as well as nitrogenous compounds. Additionally, EPA
identified literature on the sources of precursors (both organic and
inorganic), as well as the influence that different precursors have on
DBP formation. For example, some of this literature discusses the
extent to which brominated or iodinated DBPs might form as a result of
source water bromide or iodide concentrations (Nguyen et al., 2005;
Duirk et al, 2011; Lui et al., 2012; Zhang et al., 2012; Callinan et
al., 2013; Emelko et al., 2013; Mikkelson et al., 2013; Rice et al.,
2013; Samson et al., 2013; Rice and Westerhoff, 2014).
Overview of DBP Occurrence
EPA collected occurrence information for THMs (includes TTHM along
with information on four individual species), HAAs (includes HAA5 along
with information on five individual species), bromate and chlorite as
part of the SYR3 ICR.
Data from the SYR3 ICR show that concentrations at or above the
MCLs for TTHM and HAA5 were found in many surface water systems and, to
a lesser degree, in ground water systems. Approximately 32 percent of
surface water systems and five percent of ground water systems reported
at least one instance of TTHM occurrence at a concentration greater
than or equal to the MCL of 80 [micro]g/L. For HAA5, approximately 19
percent of surface water systems and two percent of ground water
systems reported at least one instance of occurrence at a concentration
greater than or equal to the MCL of 60 [micro]g/L. EPA anticipates that
many of these peak concentrations will have been significantly lowered
based on implementation of the 2006 Stage 2 D/DBPR, which was designed,
in part, to lower such occurrences.
Approximately nine percent of systems had one or more samples that
were greater than or equal to the bromate MCL of 10 [micro]g/L.
Approximately four percent of systems had one or more samples that were
greater than or equal to the chlorite MCL of 1,000 [micro]g/L.
The occurrence of six nitrosamine species was evaluated by EPA
using data from the UCMR2. These data showed elevated concentrations of
nitrosamines (relative to their health reference levels) in multiple
drinking water systems, especially N-nitrosodimethylamine (NDMA) in
systems that use chloramines (USEPA, 2016o). The Agency is seeking
public comment regarding potential approaches that provide enhanced
protection from health risks posed by nitrosamines in drinking water
systems.
The occurrence of chlorate was evaluated by EPA using data from the
UCMR3 (USEPA, 2016j). These data showed that chlorate levels above the
health reference level of 210 [micro]g/L occurred frequently in systems
that use hypochlorite, chlorine dioxide or chloramines. In addition,
EPA evaluated the co-occurrence of chlorite and chlorate and noted that
these contaminants often co-occur (USEPA, 2016k). The Agency is seeking
public comment regarding potential approaches that provide enhanced
protection from health risks posed by chlorite, chlorate and chlorine
dioxide. See Section VII for more information.
The American Water Works Association (AWWA), through the Water
Industry Technical Action Fund #266, conducted its own survey of post-
Stage 2 D/DBPR occurrence for systems that serve more than 100,000
people. Results from the AWWA survey (Samson, 2015) provide an overview
of DBP occurrence for 395 systems across 44 states, covering a time
period from 1980 to 2015.
In December 2015, EPA issued a proposal for the fourth cycle of the
UCMR (80 FR 76897, USEPA, 2015b). That proposal includes provisions for
collection of data about unregulated haloacetic acids and related
precursors. Such data would help EPA to develop a better understanding
of patterns of occurrence for those contaminants.
Overview of Water Quality Indicator Occurrence
The Stage 1 D/DBPR requires that DBP precursors (measured as TOC)
be monitored in source and treated drinking water. EPA evaluated
compliance monitoring data from surface water systems for TOC in source
and treated water, using the SYR3 ICR database. Data from 2011 showed
that approximately 70 percent of all plants had average TOC
concentrations greater than 2 mg/L in their source water and that
approximately 29 percent of plants had average TOC concentrations
greater than 2 mg/L in their treated water. Under the Stage 1 D/DBPR, a
system is not required to further remove TOC when its treated water TOC
level, prior to the point of continuous chlorination, is less than 2
mg/L. The reader is referred to later portions of this document under
``DBP Precursor Removal'' for information about EPA's evaluation of TOC
data relative to the Stage 1 D/DBPR TOC removal requirement.
As discussed in the background portion of this section, the D/DBPRs
require systems to maintain disinfectant residual levels (reported as
free and/or total chlorine) in accordance with the MRDL requirements.
EPA evaluated free and total chlorine measurements (collected during
coliform sampling) from the SYR3 ICR database and found that very few
records exceeded 4.0 mg/L (the MRDL for chlorine and chloramine
residuals). Additional information is provided in ``Six-Year Review 3
Technical Support Document for Disinfectants/Disinfection Byproducts
Rules'' (USEPA, 2016l).
Treatment Feasibility
During the development of the Stage 1 and Stage 2 D/DBPRs, a
variety of technologies were evaluated for their effectiveness,
applicability, unintended consequences and overall feasibility for
achieving compliance with the TT requirements and MCLs, as well as
providing a basis for the BATs (63 FR 69390; 71 FR 388; USEPA, 1998b;
2005a; 2005g; 2006d; 2007b).
Since the Stage 2 D/DBPR, the Agency has identified information
that improves our understanding of technologies available for lowering
occurrence of and exposure to regulated and unregulated DBPs. The
information addresses the full spectrum of drinking water system

[[Page 3536]]

operations, including removal of organic precursors to DBPs (measured
as TOC), disinfection practices, source water management and localized
treatment. The information is briefly discussed below, with additional
information in EPA's ``Six-Year Review 3 Technical Support Document for
Disinfectants/Disinfection Byproducts Rules'' (USEPA, 2016l). Overall,
the information collectively indicates that: (1) Greater removals of
DBP precursors can and are being achieved compared to the TT
requirement under the Stage 1 D/DBPR; and (2) occurrence of DBPs can be
further controlled.
DBP Precursor Removal
The SYR3 ICR database (USEPA, 2016i) includes paired source and
treated water TOC data. This information was used to evaluate the
extent to which TOC was removed from source waters (i.e., percent
removal) relative to the Stage 1 D/DBPR TOC removal requirement (i.e.,
requirement per the 3x3 matrix, which was established based on three
different ranges of raw water TOC and alkalinity levels, respectively).
This TT requirement is applicable to surface water systems that have
conventional treatment plants, unless such systems meet the alternative
criteria (63 FR 69390, USEPA, 1998b). The analytical results of TOC
removal (i.e., comparing TOC levels from source water to treated water)
can help to characterize national treatment baselines among these
treatment plants.
The data show a wide range of percent TOC removal for each
combination of raw water TOC and alkalinity levels provided in the
Stage 1 D/DBPR TT requirement. The data also indicate that the mean
removal for each element of the 3x3 matrix was six to 19 percent
greater than the requirement. These observations are consistent with
the notion that ``since the Stage 1 D/DBPR does not require that all
coagulable dissolved organic matter be removed, there is a potential
for additional removal of organic matter beyond that required by the
3x3 matrix'' (McGuire et al., 2014).
Some of the TOC removal greater than the Stage 1 D/DBPR requirement
may reflect operational optimization of conventional treatment,
including use of innovative coagulants/coagulant aids and/or use of
biofiltration (Yan et al., 2008; Hasan et al., 2010; McKie et al.,
2015; Azzeh et al., 2015; Delatolla et al., 2015; Pharand et al.,
2015). Studies have shown that biological filtration can also reduce
precursors of the DBPs other than TTHM/HAA5 (Sacher et al., 2008;
Farr[eacute] et al., 2011; Liao et al., 2014; Krasner et al., 2015). As
noted by McGuire et al. (2014), if the removal of precursors for DBPs
other than TTHM/HAA5 becomes part of the treatment goals, then
performance parameters in addition to TOC may also be needed (e.g.,
parameters indicating both vulnerability and nitrosamine formation
potential).
As was known during development of the Stage 1 and the Stage 2 D/
DBPRs, granular activated carbon (GAC) and membranes can be added to
existing treatment trains to achieve additional reductions of DBP
formation potential. One longstanding issue has been the extent to
which organic precursor removal may cause a shift of chlorinated
species to more brominated species (as described earlier in this
Section under the ``Health Effects'') when the bromide level is
relatively high in source water (Summers et al., 1993; Symons et al.,
1993). The ICR Treatment Study database (USEPA, 2000b) provides
extensive bench- and pilot-scale data by which to evaluate the effects
of GAC and membrane removal of TOC and resulting shifts in brominated
THMs. EPA's recent analysis of these data generally shows increased
percent reduction of brominated THMs as TOC removal by GAC increases
(e.g., from a target effluent level of two mg/L to one mg/L),
especially for source waters with high bromide concentrations (USEPA,
2016l). It also shows that bromoform formation increases as bromide
concentrations increase and that bromoform becomes the dominating
species when source water bromide concentrations exceed 200 [micro]g/L.
Disinfection Practices
Various combinations of disinfectants and precursor removal
processes have been used to achieve DBP MCLs, while also meeting the
requirements of the microbial standards. Data from successive national
drinking water datasets (including the DBP ICR, UCMR2 and UCMR3
datasets) show that the percentage of systems using disinfectants other
than chlorine has increased during the past two decades, as had been
forecasted in the ``Economic Analysis of Stage 2 D/DBPR'' (USEPA,
2005a). For example, data from the UCMR3 (2013-2015) and the DBP ICR
(1998) have shown a relative increase in use of chloramines, which is
associated with the formation of nitrosamines, as a disinfection
practice.
EPA reviewed information related to the extent to which different
types of DBPs may form when disinfectants are applied at different
points in the treatment train and/or in combination with other
disinfectants. EPA recognized that the extent to which occurrence and
associated health effects data may be lacking for one group of DBP
contaminants versus another, as well as for DBP mixtures, may make
treatment decisions challenging when trying to evaluate DBP risk
tradeoffs.
Source Water Management
New information shows that source waters with relatively elevated
sewage contributions have been associated with increased nitrosamine
formation (Westerhoff et al., 2015; Krasner et al., 2013) and that
source waters with elevated bromide levels from industrial discharges
have been associated with increased brominated THMs (McTigue et al.,
2014; States et al., 2013). Such factors as these impacts can increase
the challenge of controlling DBPs during treatment and distribution.
Weiss et al. (2013) developed a model for making source water selection
decisions based on real-time DBP precursor concentrations.
Information shows that bank filtration can reduce dissolved organic
carbon (DOC) and nitrogenous DBP precursors (Brown et al., 2015;
Krasner et al., 2015), as well as removing pathogens (USEPA, 2016m).
Localized Treatment
Localized treatment in distribution systems, such as aeration in
storage tanks, sometimes with the addition of GAC, has also been shown
to reduce elevated levels of THMs (Walfoort et al., 2008; Fiske et al.,
2011; Brooke and Collins, 2011; Johnson et al., 2009; Duranceau, 2015).
Aeration approaches have been most successful in reducing
concentrations of chloroform and the more volatile brominated species
but may have little impact on less volatile species (Johnson et al.,
2009; Duranceau, 2015).
Risk-Balancing
The Agency has considered the risk-balancing aspects of the MDBP
rules and has determined that potential revisions to the D/DBPRs could
provide greater protection of public health while still being
protective of microbial risks. The risk-balancing activities considered
by the Agency include those between the microbial and disinfection
byproduct rules, as well as those between different groups of DBPs.
This includes risk-balancing for the THMs and HAAs included in the D/
DBPRs, additional brominated HAAs, nitrosamines identified in the
Federal Register document for the Preliminary Regulatory Determination
3 (79 FR 62715, USEPA, 2014b) and other DBP groups such as iodinated
DBPs. It also

[[Page 3537]]

includes risk-balancing for inorganic DBPs such as chlorite and
chlorate (79 FR 62715, USEPA, 2014b).
Potential revisions could offer enhanced protection from both
regulated and unregulated DBPs. Potential revisions that consider areas
such as further constraints on precursors, and/or more targeted
constraints on precursors (e.g., based on watershed vulnerabilities),
could minimize the formation of harmful DBPs without compromising
protection against microbial risks. These potential revisions were
identified based on a preliminary, qualitative assessment; it is
important to note that further assessment would be an important
component of any further rulemaking activities. For example, a
watershed vulnerability characterization that includes information
about wastewater (i.e., sewage) contributions, land use (point/non-
point sources of pollution), and streamflow variations over time (for
example, sewage contributions during low flow conditions), could help
to inform considerations about DBP formation potentials and possible
control strategies.
The Agency is seeking public comment regarding potential revisions
to D/DBPR. See Section VII for more information. Further discussion
about potential revisions to existing D/DBPRs will occur as part of a
separate regulatory development process.
Other Regulatory Revisions
In addition to evaluating information about health effects,
analytical feasibility, occurrence and exposure, treatment feasibility
and risk-balancing related to the NPDWRs included in the D/DBPRs, EPA
considered whether other regulatory revisions are needed, such as
revisions to monitoring and system reporting requirements, as a part of
the Six-Year Review 3. EPA used the protocol to evaluate which of these
implementation issues to consider (USEPA, 2016f). As with the Chemical
Phase Rules/Radionuclides Rules, EPA shared the list of identified
potential implementation issues with the ASDWA to obtain input from
state drinking water agencies concerning the significance and relevance
of the issues (ASDWA, 2016). Implementation issues will be considered
as part of the activities associated with potential future rulemaking
efforts; some of these might be addressed through regulatory revision
or clarification, while others might be handled through guidance.
Examples of implementation-related considerations include the
following:
Stage 2 D/DBPR Consecutive System Monitoring
Monitoring in some combined distribution systems may be
insufficient to adequately characterize DBP exposure. Some large,
hydraulically complex combined water distribution systems may be
conducting monitoring that is not adequate to characterize exposure
throughout the distribution system.
Stage 2 D/DBPR Compliance Monitoring--Chlorine Burn
Compliance monitoring for DBPs in some systems may not fully
capture DBP levels to which customers may be exposed during certain
portions of the year. Systems that use chloramines as a residual
disinfectant (generally as part of a compliance strategy to meet DBP
MCLs) often temporarily switch to free chlorine as the residual
disinfectant for a period (from two to eight weeks) in order to control
nitrification in the distribution system. This practice is commonly
called a ``chlorine burn.'' During the chlorine burn, higher levels of
DBPs are expected to be formed. Systems often conduct their compliance
monitoring outside of the chlorine burn period; and therefore,
potentially higher TTHM and HAA5 levels may not be included in
compliance calculations.
4. Microbial Contaminants Regulations
Background
Except for the 1989 Total Coliform Rule, which was reviewed under
the Six-Year Review 1, this is the first time EPA is conducting a Six-
Year Review of the following microbial contaminant regulations:
Surface Water Treatment Rule (SWTR),
Interim Enhanced Surface Water Treatment Rule (IESWTR),
Long Term 1 Enhanced Surface Water Treatment Rule (LT1),
Long Term 2 Enhanced Surface Water Treatment Rule (LT2),
Filter Backwash Recycling Rule (FBRR), and
Ground Water Rule (GWR).
As discussed in Section V, the Initial Review branch of the
protocol identifies NPDWRs with recent or ongoing actions and excludes
them from the review process to prevent duplicative agency efforts. The
cutoff date for the NPDWRs reviewed under the Six-Year Review 3 was
August 2008. Based on the Initial Review, EPA excluded the Aircraft
Drinking Water Rule, which was promulgated in 2009, and the Revised
Total Coliform Rule (RTCR) (the revision of the 1989 TCR), which was
promulgated in 2013.
In this document, the SWTR, the IESWTR and the LT1 are collectively
referred to as the SWTRs because of the close association among the
three rules (IESWTR and LT1 were amendments to the SWTR--additional
information provided in Section VI.B.4.a). The LT2 is discussed
separately in this document because EPA reviewed the LT2 in accordance
with the Six-Year Review requirements and the Executive Order 13563
``Improving Regulation and Regulatory Review'' (also known as
Retrospective Review). Background information on each of the microbial
contaminants regulations is presented in the subsequent sections.
The microbial contaminants regulations establish treatment
technique (TT) requirements in lieu of MCLs. The review elements of the
microbial contaminants regulations are: initial review, health effects,
analytical feasibility, occurrence and exposure, treatment feasibility,
risk-balancing and other regulatory revisions.
At this time, the SWTRs are being identified as a candidate for
regulatory revision, but the LT2, the FBRR and the GWR are not. A
summary of review findings of each rule is described in the subsequent
sections. Additional information is provided in the ``Six-Year Review 3
Technical Support Document for Microbial Contaminant Regulations''
(USEPA, 2016n) and the ``Six-Year Review 3 Technical Support Document
for Long-Term 2 Enhanced Surface Water Treatment Rule'' (USEPA, 2016m).
a. SWTRs
Background
EPA promulgated the SWTR in June 1989. It requires all water
systems using surface water sources or ground water under the direct
influence of surface water (GWUDI) sources (also known as Subpart H
systems) to remove (via filtration) and/or inactivate (via
disinfection) microbial contaminants (54 FR 27486, USEPA, 1989). Under
the SWTR, EPA established NPDWRs for Giardia, viruses, Legionella,
turbidity and heterotrophic bacteria and set MCLGs of zero for Giardia
lamblia, viruses and Legionella. Under the IESWTR (63 FR 69477, USEPA,
1998c) and the LT1 (67 FR 1812, USEPA, 2002c), EPA established an NPDWR
for Cryptosporidium and set an MCLG of zero.
The SWTRs established TT requirements in lieu of MCLs in these
NPDWRs. The 1989 SWTR established TT requirements for systems to
control G. lamblia by achieving at least 99.9 percent (3-log) removal/
inactivation by

[[Page 3538]]

filtration and/or disinfection, and to control viruses by achieving at
least 99.99 percent (4-log) removal/inactivation (54 FR 27486, USEPA,
1989). For a few systems able to meet source water criteria and site-
specific conditions (e.g., protective watershed control program and
other conditions), they were permitted to achieve the TT requirements
by using disinfection only.
The SWTR also established TT requirements for disinfectant
residuals (54 FR 27486, USEPA, 1989). The residual disinfectant
concentration at the entry point to the distribution system may not be
less than 0.2 mg/L for more than four hours. The residual disinfectant
concentration in the distribution system ``cannot be undetectable in
more than 5 percent of the samples each month, for any two consecutive
months that the system serves water to the public.'' (40 CFR 141.72). A
detectable residual may be established by: (1) an analytical
measurement or (2) having a heterotrophic bacteria concentration less
than or equal to 500 per mL measured as heterotrophic plate count
(HPC). The purpose of these disinfectant residual requirements was to:
Ensure that the distribution system is properly maintained
and identify and limit contamination from outside the distribution
system when it might occur,
Limit growth of heterotrophic bacteria and Legionella
within the distribution system, and
Provide a quantitative limit, which if exceeded would
trigger remedial action.
The SWTR also established sanitary survey requirements. The purpose
of the sanitary survey requirements, which include consideration of
distribution system vulnerabilities, is to identify water system
deficiencies that could pose a threat to public health and to permit
correction of such deficiencies.
As part of the development of the SWTR, EPA needed to clarify which
systems would be regulated under Subpart H. In particular, EPA needed
to clarify when systems that could be considered as ground water
systems were more appropriate to regulate as surface water systems (for
example, systems where the drinking water intake was in a riverbed, not
in the river). Thus, to identify a system as either ground or surface
water, the SWTR defined ``ground water under the direct influence of
surface water (GWUDI).'' GWUDI is any water beneath the surface of the
ground with: (1) significant occurrence of insects or other
macroorganisms, algae or large-diameter pathogens such as Giardia
lamblia, or (2) significant and relatively rapid shifts in water
characteristics such as turbidity, temperature, conductivity or pH that
closely correlate to climatological or surface water conditions. The
final SWTR defined GWUDI as being regulated as surface waters because
Giardia contamination of infiltration galleries, springs and wells have
been found (Hoffbuhr et al., 1986; Hibler et al., 1987). Some
contamination of springs and wells have resulted in giardiasis
outbreaks (Craun and Jakubowski, 1986). Direct influence was to be
determined for individual sources in accordance with criteria
established by the state (54 FR 27486, USEPA, 1989). The GWUDI
designation identifies PWSs using ground water that must be regulated
as if they are surface water systems. All other PWSs using ground water
are regulated by the GWR.
Surface water and GWUDI systems use concentration x time (CT)
tables published by EPA to determine log-inactivation credits for the
use of a disinfectant to meet the disinfection TT requirements. The
``SWTR Guidance Manual'' provides CT tables for Giardia and virus
inactivation by free chlorine, chloramines, ozone and chlorine dioxide
(USEPA, 1991). EPA obtained these CT values from bench-scale
experiments with hepatitis A virus (HAV).
The IESWTR applies to all PWSs using surface water, or GWUDI, which
serve 10,000 or more people. The IESWTR established TT requirements for
Cryptosporidium by requiring filtered systems to achieve at least a 99
percent (two-log) removal, revising the definition of GWUDI and
watershed control program under the SWTR to include Cryptosporidium,
requiring sanitary surveys for all surface water and GWUDI systems, and
setting disinfection profiling and benchmarking requirements to prevent
increases in microbial risk while systems complied with the Stage 1 D/
DBPR. The LT1 (67 FR 1812, USEPA, 2002c) extended the requirements from
the IESWTR to systems serving fewer than 10,000 people.
Summary of Review Results
EPA identified the following NPDWRs under the SWTR as candidates
for revision under the Six-Year Review 3 because of the opportunity to
further reduce residual risk from pathogens (including opportunistic
pathogens such as Legionella) beyond the risk addressed by the current
SWTR:
Giardia lamblia,
heterotrophic bacteria,
Legionella,
viruses, and
Cryptosporidium (also under IESWTR and LT1).
This result is based on a scientific review of available
information, following the protocol described in Section V. Based on
the availability of new information, the review focused on the
following major provisions of the SWTRs:
Requirements to maintain a minimum disinfectant residual
in the distribution system,
GWUDI classification, and
CT criteria for virus disinfection.
Collectively, the new information suggests an opportunity to revise
the TT provisions of the SWTRs to provide greater protection of public
health. More detailed information about the review results related to
the major provisions of the SWTRs is provided in the following
subsections.
Requirements To Maintain a Minimum Disinfectant Residual in the
Distribution System
EPA evaluated information related to the maintenance of a minimum
disinfectant level in the distribution system and determined that there
is an opportunity to reduce residual risk from pathogens (includes
opportunistic pathogens such as Legionella) beyond the risk addressed
by the SWTRs. The detectable concentration of disinfectant residual in
the distribution system may not be adequately protective of microbial
pathogens because of concerns about analytical methods and the
potential for false positives (Wahman and Pressman, 2015; Westerhoff et
al., 2010). Maintaining a disinfectant residual above a set numerical
value in the distribution system may improve public health protection
from a variety of pathogens. Such a change could have benefits for
controlling occurrence of all types of pathogens in distribution
systems, except for those most resistant to disinfection, such as
Cryptosporidium.
Given our understanding of the distribution system vulnerabilities
(e.g., NRC, 2006b), there may be opportunities to enhance the criteria
for indicating distribution system integrity, as well as the potential
health risk that may be associated with pathogens potentially growing
and released from biofilms. These opportunities include revisiting the
distribution system disinfectant residual criteria and revisiting the
existing alternative HPC criteria. The NRC report (2006b) describes
that water quality integrity is an important factor that water
professionals must take into account for the protection of public
health, and that the sudden loss of disinfectant residuals

[[Page 3539]]

can indicate a change in water quality or system characteristics.
However, the report was inconclusive on the level of disinfectant
residual that should be provided in distribution systems.
GWUDI Classification
EPA reviewed information on disease outbreaks, a randomized
controlled intervention study, pathogenic protozoan occurrence data and
studies evaluating parasitic protozoan removal surrogates and
hydrogeologic studies, all of which were completed since the SWTR was
published. The information suggests that there is an opportunity to
provide greater public health protection by improved identification of
unrecognized GWUDI PWSs. The data suggest that the SWTR regulation and
guidance has performed well in identifying GWUDI for the PWS systems
most at risk from Giardia and Cryptosporidium presence in ground water.
However, the information (e.g., Colford et al., 2009) suggests that a
subset of GWUDI systems are also at risk but are potentially
misclassified as ground water systems, and therefore, not subject to
requirements that provide protection against parasitic protozoans.
Improved public health protection may result if there is improved
recognition of GWUDI systems, including those that may disinfect but do
not provide engineered filtration or have not conducted a demonstration
of performance to document the necessary Cryptosporidium alternative
treatment and removal required under the LT2. The potential public
health improvement is most relevant to those systems that have a large
surface water component and poor subsurface removal capabilities but
are not yet recognized as GWUDI and warrants further examination in any
rulemaking activities.
EPA suggests that the number of potentially misclassified GWUDI
PWSs may be estimated by: (1) waterborne disease outbreak compilations,
(2) the UCMR3 occurrence data (aerobic spore detections and
concentrations), and (3) the SYR2 ICR and the SYR3 ICR (total coliform
detections). EPA's preliminary characterization of the number of the
potentially misclassified GWUDI PWSs is described in the ``Six-Year
Review 3 Technical Support Document for Microbial Contaminant
Regulations'' (USEPA, 2016n).
CT Criteria for Virus Disinfection
EPA evaluated whether the current CT criteria based on hepatitis A
virus (HAV) are sufficiently protective against other types of viruses.
EPA reviewed disinfection studies relevant to the CT tables published
in the ``1991 SWTR Guidance Manual'' (USEPA, 1991). Over the years,
many studies have indicated that HAV is less chlorine-resistant than
some enteroviruses, such as Coxsackie virus B5 (Black et al., 2009;
Cromeans et al., 2010; Keegan et al., 2012), and also less chloramine-
resistant than adenovirus (Sirikanchana et al., 2008; Hill and
Cromeans, 2010). Based on this review, EPA identified a potential need
to update CT values for virus inactivation by free chlorine or
chloramines, particularly for water with a relatively high pH. This
assessment is also relevant to the LT2 and the GWR, which refer to the
same CT tables in the original ``1991 SWTR Guidance Manual.''
Health Effects
This section summarizes EPA's review of the information related to
human health risks from exposure to microbial contaminants in drinking
water. EPA evaluated whether any new toxicological data, or waterborne
endemic infection or infectious disease information, would justify
modifying the MCLGs. EPA reviewed information that included data from
the Waterborne Disease and Outbreak Surveillance System (WBDOSS)
collected by the Centers for Disease Control and Prevention (CDC)
(https://www.cdc.gov/healthywater/surveillance/drinking-surveillance-reports.html) and other available data that documents drinking water-
associated outbreaks.
MCLGs
The SWTRs set MCLGs of zero for Giardia lamblia, viruses,
Cryptosporidium, and Legionella since any exposure to these microbial
pathogens presents a potential health risk. In the Six Year Review 3,
EPA did not identify new information related to potentially revising
these MCLGs. New dose-response data from some waterborne pathogens are
available from both human and animal exposure studies (Teunis et al.,
2002a; 2002b; Armstrong and Haas, 2007; 2008; Buse et al., 2012).
Concurrently, new models seek to use the new data to provide improved
infectivity, morbidity and mortality predictions (Messner et al., 2014;
USEPA, 2016m). The newer models are specifically designed to address
low dose exposure typical of drinking water rather than high dose
exposure typical of food ingestion or vaccine studies.
Waterborne Disease Outbreaks Associated With Drinking Water
EPA reviewed information from the Waterborne Disease and Outbreaks
Surveillance System about the occurrences and causes of drinking water-
associated outbreaks. This surveillance system is the primary source of
data concerning such outbreaks in the U.S. (Beer et al., 2015). The
drinking water-associated outbreak data from 1971-2012 illustrate that
there is an observable reduction of reported outbreaks over that time
frame, which may be, at least in part, due to the implementation of the
TCR and the SWTR beginning in 1991.
Although the historic number of drinking water-associated outbreaks
is declining, CDC notes that the level of surveillance and reporting
activity, as well as reporting requirements, varies across states and
localities. For these reasons, outbreak surveillance data likely
underestimate actual values, and should not be used to estimate the
total number of outbreaks or cases of waterborne disease (Beer et al.,
2015).
Deficiencies at private wells and premise plumbing systems are
increasingly responsible for disease outbreaks associated with drinking
water (Beer et al., 2015). Premise plumbing is the portion of the
distribution system from the water meter to the consumer tap in homes,
schools, and other buildings (NRC, 2006b). In 2011-2012, the two most
frequent deficiencies related to drinking-water-associated outbreaks
were Legionella in premise plumbing systems (66 percent) and untreated
ground water (13 percent) (Beer et al., 2015).
In addition to epidemic illness, sporadic illness (i.e., isolated
cases not associated with an outbreak) accounts for an unknown but
probably significant portion of waterborne disease and is more
difficult to recognize (71 FR 65573, USEPA, 2006b).
Collectively, the data indicate that outbreaks associated with
drinking water may have been reduced as a result of drinking water
regulations. However, opportunities remain to address disease outbreaks
associated with distribution systems and untreated ground water and, at
the same time, to potentially address some of the waterborne disease
outbreaks associated with little to no disinfectant residual in the
distribution system (Geldreich et al., 1992; Bartrand et al., 2014).
The precise burden of disease is not well quantified. Five
primarily waterborne diseases (giardiasis, cryptosporidiosis,
Legionnaires' disease, otitis externa, and non-tuberculous
mycobacterial infection) were responsible for over 40,000
hospitalizations per year at a cost of nearly $1 billion per year
(Collier et al.,

[[Page 3540]]

2012). Given this information, there are opportunities for substantial
cost savings if such incidence can be reduced through better risk
management. Most of these costs are attributed to Legionella and non-
tuberculous mycobacteria. These bacteria can proliferate under
favorable conditions at locations in the premise plumbing and in some
parts of the distribution system that are further from the central
parts of the system, where water has aged the longest and where there
may be very little to no disinfectant residual. Further, the quality of
the water delivered to building systems and households can affect these
pathogens' ability for growth and disease transmission. There are
opportunities to enhance the current disinfectant residual requirements
to more effectively kill pathogens or contain their growth, and to
better indicate, through a stronger signal of the absence of a
residual, when targeted improvements to treatment practices or
distribution conditions may provide greater public health protection.
GWUDI-Related Disease Outbreaks
Wallender et al. (2014) summarized CDC outbreak data for the years
1971-2008 and determined that GWUDI was a ``contributing factor'' in 11
percent (six percent with Giardia etiology) of all outbreaks using
untreated ground water. The total number of untreated ground water
outbreaks during this time period was 248. Three quarters of the
outbreaks involved PWSs. These findings indicate that some of the
ground water systems examined by CDC that are not currently required to
disinfect are contaminated with pathogens. Reclassifying these
potentially ``unrecognized'' GWUDI PWSs may provide greater public
health protection against microbial contamination because these PWSs
would be subject to stricter requirements. As an example, a 2007
outbreak of giardiasis occurred in a New Hampshire community (205
homes) using untreated ground water (Daly et al., 2010). This GWUDI
misclassification-related outbreak was the largest giardiasis drinking
water-associated outbreak in the preceding 10 years.
Randomized Controlled Intervention Study
A randomized, controlled, triple-blinded drinking water
intervention study was conducted in Sonoma County, California (Colford
et al., 2009). The purpose of the study was to determine the proportion
of acute gastrointestinal illnesses (AGI) attributable to drinking
water. Sonoma County obtained water from five horizontal collector
wells along the Russian River, four regulated as ground water and one
regulated as GWUDI (part of the year). Colford et al. (2009) found that
highly credible AGI in the population aged 55 and over was attributable
to drinking water exposure. Illness occurred even though the water
utility met all federal, state and local drinking water regulations.
Pathogenic Protozoa Occurrence in Ground Water
In a karst aquifer in France, 18 ground water samples were taken
from the Norville (Haute-Normandie) public water supply well (5,000
customers, chlorine treatment) and tested for Cryptosporidium oocysts.
Thirteen of the 18 samples were found to be Cryptosporidium positive by
solid-phase cytometry; the maximum concentration was four oocyst per
100 L (Khaldi et al., 2011). These data show that Cryptosporidium in
karst ground water includes, for some highly vulnerable systems,
Cryptosporidium occurrence resulting from poor Cryptosporidium removal
during infiltration from the surface rather than poor removal during
induced infiltration from nearby surface water. Because the SWTR
definition assumes that all Cryptosporidium in PWS wells is transported
from adjacent surface water, it is silent on the issue of
Cryptosporidium transport directly from the surface, as apparently was
the case in Norville, France. Karst aquifers are a vital ground water
resource in the U.S. According to the USGS, about 40 percent of the
ground water used for drinking water comes from karst aquifers (USGS,
2004).
Analytical Feasibility
Analytical Methods for Chlorine Residuals
Because of concerns about analytical methods and the potential for
false positives, the detectable concentration of disinfectant residuals
in the distribution system may not be adequately protective of
microbial pathogens. To further inform these concerns, EPA reviewed
analytical methods that have been approved for free chlorine, total
chlorine and chlorine dioxide under the SWTR and the D/DBPRs. Nearly
all utilities use either the DPD (N,N-diethyl-p-phenylenediamine) or
amperometric titration methods to measure distribution system
disinfectant residual, and these measurements are generally performed
in the field (Wahman and Pressman, 2015). A number of constituents can
interfere with measurements of disinfectant residuals. In general, most
strong oxidants will interfere with measurement of chlorine. In
addition, color, turbidity and particles will also interfere with
colorimetric techniques such as DPD.
For some systems using chloramines (a mixture of biocidal inorganic
chloramines, of which monochloramine is the most effective), the
presence of organic chloramines can be problematic since these related
compounds have minimal biocidal properties, they can interfere with
residual monitoring, and they can give the false impression that the
finished water contains more active disinfectant than is actually
present (Wahman and Pressman, 2015; Westerhoff et al., 2010). Organic
chloramines will continue to form in the distribution system while
inorganic chloramines decay, and thus areas of the distribution system
with relatively high water ages may have residuals containing a
significant amount of organic chloramines (Wahman and Pressman, 2015).
In addition, EPA reviewed research published regarding potential
improvements to methods or technologies used in the determination of
free or total chlorine (Dong et al., 2012; Tang et al., 2014; Saad et
al., 2005). Analytical methods that can measure inorganic chloramines
without the organic chloramine interferences are available, but not
approved for determining compliance with NPDWRs. Field test kits based
on the indophenol method are available that can specifically measure
monochloramine without inclusion of mass from dichloramine or organic
chloramines (Lee et al., 2007).
Use of Aerobic Spores as Pathogenic Protozoa Surrogates
EPA's existing microbial contaminants regulations require
monitoring of pathogenic protozoa in source water (e.g.,
Cryptosporidium) and microorganisms that indicate a possible pathway
for contamination (e.g., total coliform, E. coli). In this Six-Year
Review, EPA evaluated additional microorganisms that could be used to
identify PWSs most at risk from Cryptosporidium in ground water. New
data suggest that aerobic spores are useful surrogates for
Cryptosporidium occurrence and removal. Aerobic spores originate in
shallow soil. The spore presence in a sample from a PWS well indicates
that there is a pathway for water infiltration into the well, either
vertically from the surface or horizontally from nearby surface water.

[[Page 3541]]

EPA previously used aerobic spores as surrogate measures of
Cryptosporidium removal by alternative treatment in a demonstration of
field performance (USEPA, 2010f). Field demonstrations showed that the
spores performed well in demonstrating two-log removal of
Cryptosporidium at Casper, Wyoming, and Kennewick, Washington (USEPA,
2010f). Spores also performed well in demonstrating that a Nebraska PWS
was unable to achieve better than two-log removal of Cryptosporidium,
and that UV or other engineered treatment would be required (State of
Nebraska, 2013). Headd and Bradford (2015) summarized the relevant
scientific literature, conducted spore and Cryptosporidium laboratory
experiments, and performed porous media transport modeling. They found
that spores are suitable Cryptosporidium surrogates in ground water.
These new data suggest that aerobic spores are useful as surrogates for
Cryptosporidium removal estimates via subsurface passage (USEPA, 2010f)
and may be useful as supplemental surrogates to improve recognition of
GWUDI systems.
Locas et al. (2008) found that aerobic spores were present in six
of nine wells sampled in Quebec, Canada, and in 45 of 109 samples
taken. The authors conclude that aerobic spore presence is an indicator
of a change in water quality and warrants further investigation to
determine the source of potential contamination.
In EPA's investigation of virus occurrence in untreated PWS wells
under the UCMR3, 252 of 793 wells (317 of 1,047 samples) were positive
for aerobic spores (USEPA, 2016j). Measured concentrations spanned
three orders of magnitude, with about three percent having over 100
spore-forming units per 100 ml). Because aerobic spores originating in
soil are found in GWUDI and ground water PWS wells, the UCMR3 data
suggest that aerobic spores could be used as an indicator of the
susceptibility of PWS wells to surface water infiltration. Together
with other indicators and/or parasitic protozoa data from PWS wells,
newer methods including spores (occurrence, concentration, and/or
removal estimates) might be useful in identifying unrecognized GWUDI
PWS wells. The LT2 Toolbox Guidance Manual identified aerobic spores as
the indicator to determine Cryptosporidium removal for systems using
bank filtration for LT2 additional treatment requirements (USEPA,
2010f).
Occurrence and Exposure
Coliform and/or E. coli occurrence can be an indication of
conditions supporting bacterial growth or an intrusion event into the
distribution system. On the other hand, the absence of coliforms and/or
E. coli does not necessarily mean the absence of pathogens that are
more resistant to the disinfectant residual. Detection of coliform
bacteria is commonly associated with low distribution system
disinfectant residuals. According to LeChevallier et al. (1996),
disinfectant residuals of 0.2 mg/L or more of free chlorine, or 0.5 mg/
L or more of total chlorine, are associated with reduced levels of
coliform bacteria.
To assess the relationship between disinfectant residual and
occurrence of indicators for pathogens in distribution systems, EPA
evaluated information about chlorine residuals and total coliforms and
E. coli (TC/EC) using compliance monitoring data from the SYR3 ICR
database. EPA paired TC/EC results with field chlorine residual data
collected at the same time and location. It is important to note that
these evaluations help to inform the SYR3 results, but do not assess
compliance with regulatory standards.
EPA found that there was a lower rate of occurrence of both TC and
EC as the free or total chlorine residual increased to higher levels
(note: total chlorine is often used as a measure for systems that use
chloramines). For example, the TC positive rate was less than one
percent when chlorine residuals were equal to or greater than 0.2 mg/L
of free chlorine or 0.5 mg/L of total chlorine. This relationship
between chlorine residuals and occurrence of TC and EC was similar to
that reported by the Colorado Department of Public Health and
Environment (Ingels, 2015).
A disinfectant residual also serves as an indicator of the
effectiveness of distribution system best management practices. Best
management practices include flushing, storage tank maintenance, cross-
connection control, leak detection and effective pipe replacement and
repair practices. The effective implementation of best management
practices helps water suppliers to lower chlorine demand and maintain
an adequate disinfectant residual throughout the distribution system.
These same practices can also help control DBP formation.
Treatment Feasibility
EPA reviewed new information related to the TT requirements in the
SWTR and identified the following treatment-related topics that support
potential revisions to the SWTRs to improve public health protection:
Detectable residual for systems using chloramine
disinfection,
State implementation of disinfection residual
requirements,
Disinfectant residuals for control of Legionella in
premise plumbing systems,
HPC alternative to detectable residual measurement, and
CT criteria for viruses.
In addition, EPA reviewed key findings by the Research and
Information Collection Partnership (RICP) on drinking water
distribution system issues and research and information needs. The RICP
is a working group formed on the recommendation of the Total Coliform
Rule Distribution System Advisory Committee to identify specific high-
priority research and information collection activities and to
stimulate water distribution system research and information collection
(USEPA, 2008b; USEPA and Water Research Foundation, 2016).
Detectable Residual for Systems Using Chloramine Disinfection
As discussed in the background portion of this section, for surface
water systems or GWUDI systems, the SWTR requires that a disinfectant
residual cannot be undetectable in more than five percent of samples
each month for any two consecutive months.
EPA identified two issues that have implications for the
protectiveness of allowing a detectable residual as a surrogate for
bacteriological quality: Organic chloramines and nitrification. Organic
chloramines affect the effectiveness of disinfectant residuals because
they: (1) Form during the use of free chlorine or chloramines, (2)
interfere with commonly used analytical methods for free and total
chlorine measurements, and (3) are poor disinfectants compared to free
chlorine and monochloramine (Wahman and Pressman, 2015).
Because chloramination involves introduction of ammonia into
drinking water, and decomposition of chloramines can further release
ammonia in the distribution system, chloramine use comes with the risk
of distribution system nitrification (i.e., the biological oxidation of
ammonia to nitrite and eventually nitrate). Drinking water distribution
system nitrification is undesirable and can result in water quality
degradation. Information shows that maintaining a high enough level of
total chlorine or monochloramine residuals in the distribution system
can help prevent both nitrification and residual depletion (Stanford et
al, 2014).

[[Page 3542]]

State Implementation of Disinfectant Residual Requirements
States may adopt federal drinking water regulations or promulgate
more stringent drinking water requirements, including those for
disinfectant residuals. Preliminary information shows that 26 states
require a detectable disinfectant residual in the distribution system.
Twenty of these 26 states require a minimum free chlorine residual of
0.2 mg/L or more (Ingels, 2015; Wahman and Pressman, 2015). Five of the
20 states set standards even more stringent than 0.2 mg/L: Louisiana
requires at least 0.5 mg/L free chlorine in its emergency rule, while
Florida, Illinois, Iowa, and Delaware require 0.3 mg/L. For minimum
total chlorine residual, state requirements vary from 0.05 mg/L (New
Jersey) to 1.00 mg/L or higher (Kansas, Oklahoma, Iowa, Ohio, and North
Carolina). North Carolina has a numeric requirement for total chlorine
residual but not for free chlorine residual.
Colorado has amended its minimum disinfectant residual requirements
in the distribution system to be greater than or equal to 0.2 mg/L,
effective April 1, 2016 (Ingels, 2015). Pennsylvania recently proposed
to strengthen its disinfectant residual requirements by increasing the
minimum disinfectant residual in the distribution system to 0.2 mg/L
free or total chlorine (Pennsylvania Bulletin, 2016). Louisiana's
Emergency Distribution Disinfectant Residual Rule was established in
2013 to control Naegleria fowleri, an amoeba found in several PWSs.
That rule requires a minimum free or total chlorine disinfectant level
of 0.5 mg/L to be maintained at all times in finished water storage
tanks and the entire distribution system (Louisiana Department of
Health and Hospitals, 2013). The state agency intends to continue to
renew the Emergency Rule until a final rule can be promulgated
(Louisiana Department of Health and Hospitals, 2014).
Disinfectant Residuals for Control of Legionella in Premise Plumbing
Systems
Since the reporting of disease outbreaks due to Legionella began in
2001, Legionella has been shown to cause more drinking-water-related
outbreaks than any other microorganism. Addressing premise plumbing
issues is particularly challenging. Premise plumbing may be largely
outside of water utilities' operations and management control. Also,
the characteristic features of premise plumbing (e.g., low
disinfectants residuals, stagnation, and warm temperature) tend to
support growth and persistence of opportunistic pathogens.
Studies indicate that distribution systems can play a role in
influencing the transmission and contamination of Legionella in premise
plumbing systems (Lin et al., 1998; States et al., 2013). Hospitals
served by PWSs using chloramines reported fewer outbreaks of
legionellosis than those using free chlorine (Kool et al., 1999;
Heffelginger et al., 2003). Some building systems supplied by PWSs
which have switched to chloramines have seen marked reduction in the
colonization of Legionella (Flannery et al., 2006; Moore et al., 2006).
One implication of these studies is the importance of being able to
reliably measure and sustain chloramine residuals to increase the
likelihood of its effectiveness at controlling Legionella in premise
plumbing systems. On the other hand, some studies have indicated that
the occurrence of another pathogen, non-tubercular Mycobacterium, may
increase under chloramination conditions (Pryor et al., 2004; Moore et
al., 2006; Duda et al., 2014).
Legionella species can multiply in warm, stagnant water
environments, such as in community water storage tanks with low
disinfectant residuals during warm months. Cohn et al. (2014) observed
increased incidence of legionellosis among institutions and private
homes near a community water storage tank when the disinfectant
residual in the storage tank dropped (from greater than 0.2 mg/L to
less than 0.2 mg/L) during hot summer months. Based on these findings,
the authors recommended that, regardless of total coliform occurrence,
remedial actions be taken (e.g., flushing of mains, checking for closed
valves that can result in hydraulic dead-ends, and possibly installing
re-chlorination stations) when low chlorine residuals are observed
during hot summer months. They also noted that this storage tank had
been cleaned subsequent to the outbreak (Cohn et al., 2014; Ashbolt,
2015).
To help address concerns about Legionella, EPA developed a document
entitled ``Technology for Legionella Control in Premise Plumbing
Systems: Scientific Literature Review'' (USEPA, 2016r). The document
summarizes information about the effectiveness of different approaches
to control Legionella in a building's premise plumbing system. EPA
expects that use of this document will further improve public health by
helping primacy agencies, facility maintenance operators, and facility
owners make science-based risk management decisions regarding treatment
and control of Legionella in buildings.
EPA also reviewed the scientific literature on the effectiveness of
disinfectant residuals at controlling biofilm growth. Many factors
influence the concentration of the disinfectant residual in the
distribution system; and therefore, the ability of the residual to
control microbial growth and biofilm formation. These factors include
the level of assimilable organic carbon (AOC), the type and
concentration of disinfectant, water temperature, pipe materials, and
system hydraulics.
Problems associated with biofilms in distribution systems include
enhanced corrosion of pipes and deterioration of water quality.
Biofilms can provide ecological niches that are suited to the potential
survival of pathogens (Walker and Morales, 1997; Baribeau et al., 2005;
Behnke et al., 2011; Wang et al., 2012; Biyela et al., 2012; Revetta et
al., 2013; Ashbolt, 2015). The biofilm can protect microorganisms from
disinfectants and can enhance nutrient accumulation and transport
(Baribeau et al., 2005).
HPC Alternative to Detectable Residual Measurement
Under the SWTR, a system may demonstrate that its HPC levels are
less than 500 per mL, at any sampling locations, in lieu of
demonstrating the presence of a detectable disinfectant residual at
that location, per primacy agency approval. EPA reviewed new
information that suggests development of criteria which may be more
protective than the HPC criterion. For example, criteria used in the
Netherlands for systems operating without a distribution system
disinfectant residual provides an example of an alternative criteria
than the HPC criterion. In the Netherlands, chlorine is not used
routinely for primary or secondary disinfection. Dutch water systems
use the following general approach to control microbial activity in the
distribution system without a disinfectant residual (Smeets et al.,
2009): Produce a biologically stable drinking water; use distribution
system materials that are non-reactive and biologically stable; and
optimize distribution system operations and maintenance practices to
prevent stagnation and sediment accumulation. For the determination of
a biologically stable water they use AOC as an indicator.
CT Criteria for Virus Disinfection
EPA reviewed new disinfection studies published since the release
of the original CT tables. Collectively, the data in the recent
literature indicate that

[[Page 3543]]

EPA CT values for free chlorine disinfection are sufficient to
inactivate most enteric viruses in drinking water, except for Coxsackie
virus B5 at a pH higher than 7.5 (Black et al., 2009; Cromeans et al.,
2010; Keegan et al., 2012).
EPA's CT values for chlorine incorporate a safety factor of three
to account for differences between dispersed and aggregated hepatitis A
virus and between buffered, demand-free water and environmental water.
In light of new information about the hepatitis A virus and the effects
of source water quality on chlorine disinfection, EPA concludes that
the safety factor of three should be re-evaluated to ensure its
adequacy. A larger safety factor (thus higher EPA CT values) is
expected to enhance waterborne pathogen control but could lead to
higher DBP formation and warrants further examination in any rulemaking
activity.
Adenovirus is the virus that is most resistant to chloramines,
through it is very susceptible to free chlorine disinfection. Several
studies revealed that monochloramine disinfection might not provide
adequate control of adenovirus in drinking water, particularly in
waters with relatively high pH and at low temperature (Sirikanchana et
al., 2008; Hill and Cromeans, 2010).
Research and Information Collection Partnership Findings
The RICP partners are EPA and Water Research Foundation. EPA
examined information from the 10 high priority RICP areas in the
context of the Six-Year Review, particularly information related to the
effectiveness of sanitary survey and corrective action requirements
under the IESWTR. However, EPA found limited information that would
shed light on the frequency and magnitude of distribution system
vulnerability events (e.g., backflow events, storage tank breeches),
associated risk implication, and costs for preventing such events from
occurring. The RICP report identifies potential follow-up research
areas that could help to address these gaps (USEPA and Water Research
Foundation, 2016).
Risk-Balancing
The Agency has considered the risk-balancing aspects of the MDBP
rules and has determined that potential revisions to the SWTRs could
provide improved health protection. The risk-balancing activities
considered by the Agency include those between the microbial and
disinfection by-product rules, as well as those between different
groups of DBPs. This includes balancing the reduction in risks from
microbial pathogens should there be additional requirements to maintain
a disinfectant residual with the increased risk from D/DBPs resulting
from such requirements. EPA also considered the potential impact of
further constraints on DBP precursors on the reduction of demand for
disinfectant residual. The risk-balancing review was based on a
preliminary, qualitative assessment of unintended consequences; it is
important to note that further assessment of such consequences would be
an important component of any further rulemaking activities.
b. LT2
Background
EPA promulgated the LT2 on January 5, 2006 (71 FR 654, USEPA,
2006c). The LT2 applies to all PWSs that use surface water or ground
water under the direct influence of surface water as drinking water.
The LT2 builds upon the IESWTR and the LT1 by improving control of
microbial pathogens, specifically the contaminant Cryptosporidium. The
purpose of the LT2 is to reduce illness linked with the contaminant
Cryptosporidium and other disease-causing microorganisms in drinking
water. The LT2 supplements the IESWTR and the LT1 regulations by
establishing additional Cryptosporidium treatment requirements for
higher-risk systems. The LT2 requires source water occurrence
monitoring which is used to determine additional treatment
requirements. The LT2 rule provides for additional CT credits for
Cryptosporidium inactivation by ozone and chlorine dioxide. The LT2
also provides UV treatment credits for Cryptosporidium, Giardia and
virus inactivation. EPA recognized that research in the field of
Cryptosporidium inactivation is ongoing and included a provision in the
rule that allows unfiltered systems using a disinfectant other than
chlorine to demonstrate the log inactivation that can be achieved.
The LT2 also contains provisions to reduce risks from uncovered
finished water reservoirs (UCFWRs).\5\ The rule ensures that systems
maintain microbial protection when they take steps to decrease the
formation of disinfection byproducts in systems that add a chemical
disinfectant (i.e., other than UV light) or receive a chemically
disinfected water. Storage of treated drinking water in open reservoirs
can lead to significant water quality degradation and health risks to
consumers (USEPA, 1999). Examples of such water quality degradation
include increases in algal cells, coliform bacteria, heterotrophic
bacteria, particulates, disinfection byproducts, metals, taste and
odor, insect larvae, Giardia, Cryptosporidium and nitrate (USEPA,
1999). Contamination of reservoirs occurs through surface water runoff,
bird and animal wastes, human activity, algal growth, airborne
deposition and insects and fish.
---------------------------------------------------------------------------

\5\ LT2 uses the term `facilities'' instead of `reservoirs'. The
term reservoirs is used in this document.
---------------------------------------------------------------------------

The LT2 requires PWSs using uncovered finished water storage
facilities to either cover the storage facility or treat the storage
facility discharge (i.e., prior to entering the distribution system) to
achieve inactivation and/or removal of 4-log virus, 3-log G. lamblia,
and 2-log Cryptosporidium spp. on a state-approved schedule.
Under the LT2, PWSs were required to notify their state/primacy
agency by April 1, 2008, if they used UCFWRs. Additionally, the LT2
required all PWSs to either meet the requirement to cover the UCFWR, or
treat the UCFWR discharge to the distribution system or be in
compliance with a state-approved schedule for meeting these
requirements no later than April 1, 2009. Under this review, EPA
evaluated published information to assess whether allowing a state-
approved risk management plan would justify revisions to the LT2.
Summary of Review Results
Information available since promulgation of the LT2 either supports
the current regulatory requirements or does not justify a revision. EPA
determined that no regulatory revisions to the UCFWR requirements of
the LT2 are warranted at this time based on the review of available
information.
Health Effects
EPA reassessed the health risks resulting from exposure to
Cryptosporidium spp., Giardia lamblia and viruses, as well as other
potential microbiological risks to human health. The Agency also
reviewed new information on other pathogens of potential concern to
determine whether additional measures are warranted to provide greater
public health protection from these pathogens, particularly in the
context of the UCFWR provisions of the LT2.
The principal objectives of this health effects review were to: (1)
Evaluate whether there are new or additional ways to estimate risks
from Cryptosporidium and other pathogenic microorganisms in drinking
water and

[[Page 3544]]

(2) evaluate surveillance and outbreak data on Cryptosporidium and
other contaminants of potential concern. Based on the review, the new
information does not justify a revision to the health basis for the LT2
at this time. For more information regarding EPA's review of health
effects, see the ``Six-Year Review 3 Technical Support Document for
Long-Term 2 Enhanced Surface Water Treatment Rule'' (USEPA, 2016m).
Analytical Feasibility
The LT2 specifies approved analytical methods to determine the
levels of Cryptosporidium in source waters for the identification of
additional treatment needs. The LT2 requires systems and/or
laboratories to use either ``Method 1622: Cryptosporidium in Water by
Filtration/IMS/FA'' (EPA 815-R-05-001, USEPA, 2005d) or ``Method 1623:
Cryptosporidium and Giardia in Water by Filtration/IMS/FA'' (EPA 815-R-
05-002, USEPA, 2005e). EPA Methods 1622 or 1623 is used in monitoring
programs to characterize Cryptosporidium levels in the source water of
PWSs for the purposes of risk-targeted treatment requirements under the
LT2. Method recoveries of more than 3,000 matrix spiked samples from
the first round of monitoring for the LT2 indicated an average recovery
of oocysts with Methods 1622 and 1623 to be 40 percent. In addition to
evaluating the results from the first round of monitoring, EPA gathered
new information on Cryptosporidium analytical methods by investigating
improvements to Methods 1622 and 1623. EPA evaluated whether the
required use of a revised method (Method 1623.1) would be justified for
Round 2 monitoring under the LT2. Though new information is available
that indicates the potential for a regulatory revision, the Agency does
not believe it is appropriate to revise the rule to require the use of
Method 1623.1, since the Agency believes such a change would not
provide substantially greater protection of public health at the
national level. The use of Method 1623.1 during the LT2 Round 2
monitoring is optional, and not required. Since EPA is not planning
changes to the methods required under the LT2, the schedule for the LT2
Round 2 monitoring remains the same as described in the final LT2,
which is scheduled to be completed no later than 2021 for all PWSs.
Occurrence and Exposure
The LT2 requires PWSs using surface water or ground water under the
direct influence of surface water to monitor their source waters for
Cryptosporidium spp. (and/or E. coli) to identify additional treatment
requirements. PWSs must monitor their source water (i.e., the influent
water entering the treatment plant) over two different timeframes
(Round 1 and Round 2) to determine the Cryptosporidium level.
Monitoring results determine the extent of Cryptosporidium treatment
requirements under the LT2.
Under the LT2, the date for PWSs to begin monitoring is staggered
by PWS size, with smaller PWSs starting at a later time than larger
systems. According to the LT2 rule requirements, all PWSs were expected
to complete Round 1 in 2012.
To reduce monitoring costs, small filtered PWSs (serving fewer than
10,000 people) initially monitor for E. coli for one year as a
screening analysis and are required to monitor for Cryptosporidium only
if their E. coli levels exceed specified trigger values. Small filtered
PWSs that exceed the E. coli trigger, as well as small unfiltered PWSs,
must monitor for Cryptosporidium for one or two years, depending on the
sampling frequency.
Based on the source water monitoring results, filtered systems were
classified in one of four risk categories to determine additional
treatment needed (Bins 1-4). Systems in Bin 1 are required to provide
no additional Cryptosporidium treatment. Filtered systems in Bins 2-4
must achieve 1.0-2.5 log of treatment (i.e., 90 to 99.7 percent
reduction) for Cryptosporidium over and above that provided by
conventional treatment, depending on the Cryptosporidium
concentrations. Filtered PWSs must meet the additional Cryptosporidium
treatment requirements in Bins 2, 3, or 4 by selecting one or more
technologies from the microbial toolbox of options for ensuring source
water protection and management, and/or Cryptosporidium removal or
inactivation. All unfiltered water systems must provide at least 99 or
99.9 percent (2 or 3-log) inactivation of Cryptosporidium, depending on
the results of their monitoring. Additionally, all filtered systems
that provide, or will provide, 5.5 log treatment for Cryptosporidium
are exempt from monitoring and subsequent bin classification. Systems
providing 5.5 log Cryptosporidium treatment must notify the state no
later than the date by which the system must submit a sampling plan.
Six years after the initial bin classification, filtered systems
must conduct a second round of monitoring. Round 2 monitoring is in
place to understand year-to-year occurrence variability. The difference
observed between occurrence at the time of the ICR Supplemental Surveys
(USEPA, 2000c) and the LT2 Round 1 monitoring indicates year-to-year
variability. Round 2 monitoring began in 2015. Under this review, EPA
considered whether a third round of monitoring would be justified at
this time, in particular, requiring the use of Method 1623.1. EPA also
considered whether a modification to the action bin boundaries should
be made based on requiring Method 1623.1.
Because of the relatively modest gains in public health protection
predicted by the Round 2 monitoring EPA does not believe a third round
of monitoring is justified at this time, even if the Agency were to
require the use of Method 1623.1 for this monitoring. Round 1
Cryptosporidium occurrence was lower than expected (3.3-5.3 percent of
Bin 1 systems from Round 1 would be moved to a higher bin). As
mentioned earlier, EPA will not require the use of Method 1623.1 for
Cryptosporidium monitoring. Therefore, EPA will not make changes to the
action bin boundaries at this time.
Treatment Feasibility
LT2 includes a variety of treatment and control options,
collectively termed the ``microbial toolbox,'' that PWSs can implement
to comply with the LT2's additional Cryptosporidium treatment
requirements. Most options in the microbial toolbox carry prescribed
credits toward Cryptosporidium treatment and control requirements. The
LT2 Toolbox Guidance Manual (USEPA, 2010f) provides guidance on how to
apply the toolbox options.
The LT2 also requires all unfiltered PWSs to provide at least 2 to
3-log (i.e., 99 to 99.9 percent) inactivation of Cryptosporidium.
Further, under the LT2, unfiltered PWSs must achieve their overall
inactivation requirements (including Giardia and virus inactivation as
established by earlier regulations) using a minimum of two
disinfectants.
EPA reviewed information available since the promulgation of the
LT2 on the use of the microbial toolbox to determine if the information
would support a potential change to the prescribed credits or the
associated design and operational criteria. In addition, EPA searched
for information on new and emerging tools that would support their
potential addition to the toolbox. The Agency also received input on
the use and effectiveness of the microbial toolbox tools through public
meetings, research of publicly available information and by actively
communicating with some systems. EPA

[[Page 3545]]

also considered benefits and/or difficulties observed by the PWSs when
using the available tools.
EPA also examined information from some PWSs with UCFWRs to
evaluate the potential effectiveness of risk management measures taken
by those PWSs for protecting the finished water in the UCFWRs from
contamination. The New York City Department of Environmental Protection
(NYC DEP) has undertaken more activities than any other PWS to protect
their Hillview Reservoir from contamination. These activities include
wildlife management (e.g., bird harassment and deterrents, mammal
relocation), security measures, runoff control, public health
surveillance, microbial monitoring (e.g., Cryptosporidium, E. coli) and
a Cryptosporidium and Giardia action plan.\6\ EPA reviewed information
pertaining to these activities and concluded that the information is
inadequate to support regulatory changes at the national level. The
data is also insufficient to demonstrate that risk management
activities provide equivalent public health protection compared to
covering the reservoir or treating the outflow from the reservoir.
---------------------------------------------------------------------------

\6\ https://www.nyc.gov/html/dep/pdf/reports/fad_4.1_waterfowl_managementprogram_annual_report.07-12.pdf.
---------------------------------------------------------------------------

The LT2 includes disinfection profile and benchmark requirements to
ensure that any significant change in disinfection, whether for
disinfection byproducts control under the Stage 2 D/DBPR, improved
Cryptosporidium control under the LT2, or both, does not significantly
compromise existing Giardia and virus protection. The profiling and
benchmarking requirements under the LT2 are similar to those
promulgated under the IESWTR and the LT1 (USEPA, 2002c) and are
applicable to systems that make a significant change to their
disinfection practices.
EPA did not identify information that would support a potential
change to the methodology and calculations for developing the
disinfection profile and benchmark under the LT2. However, EPA
identified information that would support a potential change to the CT
values required for virus disinfection (as discussed in the Section
VI.B.4.a. ``SWTRs''). EPA is considering this information in the review
of the overall filtration and disinfection requirements in the SWTR.
Based on the outcome of this review, EPA determined that no
regulatory revisions to the microbial toolbox options are warranted at
this time. Any new information available to the Agency either supports
the current regulatory requirements or does not justify a revision. For
more information regarding EPA's review of treatment feasibility see
the ``Six-Year Review 3 Technical Support Document for Long-Term 2
Enhanced Surface Water Treatment Rule'' (USEPA, 2016m).
c. FBRR
Background
EPA promulgated the FBRR in 2001 (66 FR 31086, USEPA, 2001b). It
requires PWSs to review their backwash water recycling practices to
ensure microbial control is not compromised, and it requires PWSs to
recycle filter backwash water.
Summary of Review Results
EPA reviewed this rule as part of the Six-Year Review 3, and the
result is to take no action on the basis that EPA did not identify any
relevant information that indicate changes to the NPDWR.
d. GWR
Background
EPA promulgated the GWR in 2006 (71 FR 65573, USEPA, 2006b) to
provide protection against microbial pathogens in PWSs using ground
water sources. The rule establishes a risk-based approach to target
undisinfected ground water systems that are vulnerable to fecal
contamination. If a system has an initial total coliform positive in
the distribution system (based on routine coliform monitoring under the
RTCR), followed by a fecal indicator positive (E. coli, enterococci or
coliphage) in a follow-up source water sample, it is considered to be
at risk of fecal contamination. Systems at risk of fecal contamination
must take corrective action to reduce potential illness from exposure
to microbial pathogens. Disinfecting systems that can demonstrate 4-log
virus inactivation are not subject to the monitoring requirements.
In addition to the protection provided by the Revised Total
Coliform Rule (RTCR) and GWR monitoring requirements, systems that do
not disinfect are also protected by the sanitary survey provisions of
the GWR and the Level 1 assessment provisions of the RTCR.
Summary of Review Results
EPA has not identified the GWR as a candidate for revision under
the Six-Year Review 3 because EPA needs to evaluate emerging
information from full implementation of the GWR (71 FR 65573, USEPA,
2006b) and the RTCR (78 FR 10270, USEPA, 2013a) before determining if
there is an opportunity to improve public health protection.
Implementation of the GWR was not yet completed for the period of time
covered by the SYR3 ICR. The RTCR was promulgated in 2013 and became
effective on April 1, 2016. EPA expects that implementation on the RTCR
may impact the percent of ground water systems that will be triggered
into source water monitoring and taking any corrective actions under
the GWR. Therefore, the effects of the GWR and the RTCR implementation
in addressing vulnerable ground water systems are not yet known. EPA
notes that the GWR was also recently reviewed under Section 610 of the
Regulatory Flexibility Act, which required federal agencies to review
regulations that have significant economic impact on a substantial
number of small entities within 10 years after their adoption as final
rules. The 610 Review of the GWR was recently completed; three comments
were received. A report is available discussing the 610 Review,
comments received, and EPA's response to major comments (USEPA, 2016g).
Health Effects
Borchardt et al. (2012) studied the health effects associated with
enteric virus occurrence in undisinfected PWS wells in 14 communities
in Wisconsin. Drinking water samples were assayed for a suite of viral
pathogens using quantitative polymerase chain reaction (qPCR).
Community members kept daily diaries to self-report AGI. The study
found a statistically significant association between enteric virus
occurrence in the drinking water and AGI incidences in the communities.
Using the 2005 data, EPA estimated a national average TC detection
rate of 2.4 percent for routine samples from undisinfected CWSs with
populations less than 4,100 people (USEPA, 2012). The 14 communities
(with undisinfected PWS wells) studied by Borchardt et al. (2012) had
TC detections of 2.3 percent. These data suggest that the 14
communities studied by Borchardt et al. (2012) had TC detection rates
no different from an average undisinfected community PWS in the U.S.
Analytical Methods
Since the promulgation of the GWR in 2006, EPA has approved several
new methods for the analysis of TC samples used as a trigger for GWR
source water monitoring, or for source water fecal indicators used
under the GWR. These methods can be found on the EPA Web site (https://
www.epa.gov/dwanalyticalmethods/approved-

[[Page 3546]]

drinking-water-analytical-methods). However, PWSs are not required to
use these new methods. Additionally, EPA did eliminate the use of fecal
coliforms from the RTCR as an indicator of fecal contamination.
Occurrence and Exposure
New information suggests that total coliform occurrence varies
among small undisinfected ground water systems, depending upon whether
the system is a community, non-transient non-community or transient
non-community PWS (USEPA, 2016n). Statistical modeling of 2011 data
(about 60,000 systems based on occurrence data collected from
undisinfected ground water systems) shows that undisinfected transient
non-community ground water systems have the highest occurrence, at
approximately four percent median routine TC positive occurrence as
compared with three percent for undisinfected non-transient non-
community ground water systems and two percent for undisinfected
community ground water systems (USEPA, 2016n). These occurrence levels
are similar to those estimated during the development of the RTCR using
2005 data (USEPA, 2012). Additionally, according to the 2005 and 2011
datasets, the smaller systems had higher median TC occurrence than the
larger systems. All positive total coliform samples were assayed for E.
coli; about one in 20 were E. coli positive.
A small percentage of undisinfected ground water systems have
higher TC detection rates. For example, of the 52,000 undisinfected
transient, non-community ground water systems serving populations less
than 101 people (the total count is from USEPA, 2006b), EPA (2012)
estimated that about 2,600 (five percent) of those systems (4.6 percent
for the 2005 data set) had TC detection rates of 20 percent or more.
Under the third monitoring cycle of the Unregulated Contaminant
Monitoring Rule (UCMR3), EPA sampled about 800 randomly selected
undisinfected ground water systems serving fewer than 100 people for
virus and virus indicators. These data show that only a small number of
samples were virus positive by qPCR (16 out of 1,044 or two percent)
(USEPA, 2016j). This result contrasts significantly with the virus
positive sample rate from Borchardt et al. (2012) (287 out of 1,204 or
24 percent). One difference is that Borchardt et al. (2012) sampled
prior to any treatment in the undisinfected wells (e.g., softening,
iron/manganese removal). In contrast, many wells in the UCMR3 virus
study were sampled after softening or other treatment. The UCMR3
monitoring results are available online at: https://www.epa.gov/dwucmr/data-summary-third-unregulated-contaminant-monitoring-rule.

VII. EPA's Request for Comments and Next Steps

EPA invites commenters to submit any relevant data or information
pertaining to the NPDWRs identified in this action as candidates for
revision, as well as other relevant comments. EPA will consider the
public comments and/or any new, relevant data submitted for the eight
NPDWRs listed as candidates for revision as the Agency moves forward in
determining whether regulatory revisions for these NPDWRs are
necessary. The announcement whether or not the Agency intends to revise
an NPDWR (pursuant to SDWA Sec. 1412(b)(9)) is not a regulatory
decision.
Relevant data include studies/analyses pertaining to health
effects, analytical feasibility, treatment feasibility and occurrence/
exposure. This information will inform EPA's evaluation as the Agency
moves forward determining whether regulatory revisions for these NPDWRs
are necessary. The data and information requested by EPA include peer-
reviewed science and supporting studies conducted in accordance with
sound and objective scientific practices, and data collected by
accepted methods or best available methods (if the reliability of the
method and the nature of the review justifies use of the data).
Peer-reviewed data are studies/analyses that have been reviewed by
qualified individuals (or organizations) who are independent of those
who performed the work, but who are collectively equivalent in
technical expertise (i.e., peers) to those who performed the original
work. A peer review is an in-depth assessment of the assumptions,
calculations, extrapolations, alternate interpretations, methodology,
acceptance criteria and conclusions pertaining to the specific major
scientific and/or technical work products and the documentation that
supports them (USEPA, 2015a).
Specifically, EPA is requesting comment and/or information related
to the following aspects of potential revisions to the MDBP NPDWRs:
Potential approaches that could enhance protection from
DBPs, including both those that are regulated and those currently
unregulated (e.g., nitrosamines). Specifically, commenters are
requested to provide information about requiring greater removal of
precursors (e.g., TOC), and/or more targeted constraints on precursors
(e.g., based on watershed vulnerabilities) that could provide for an
improvement in health protection from mixtures of DBPs while
considering risk-balancing. For example, commenters are requested to
provide information about an approach that provides for an option to
either control source water vulnerabilities (e.g., de facto reuse) or
to further constrain precursors associated with unregulated DBPs. In
addition, commenters are requested to provide information that
considers a comprehensive analysis of source waters for the formation
of a wide variety of byproducts (e.g., TTHM, HAA5, and unregulated DBPs
such as nitrosamines, brominated and iodinated compounds).
Potential approaches that could enhance protection from
chlorite, chlorate, and chlorine dioxide. Specifically, commenters are
requested to provide information about approaches that could involve,
for example: Setting standards for systems using hypochlorite that
address combined exposure to chlorite and chlorate; and setting
standards for systems using chlorine dioxide (alone or in combination
with other disinfectants) that address combined exposure from chlorite,
chlorate, and chlorine dioxide.
Potential approaches that could provide increased
protection from microbial pathogens and that take into consideration
the issues noted about disinfection residual requirements, while
considering the risk-balancing aspects of the MDBP rules. In addition,
commenters are requested to provide information about approaches that
could offer enhanced protection without the use of a chlorine-based
disinfectant residual in the distribution system, including technology
and management systems associated with those approaches.
Information about how frequently PWS monitor for DBPs
during chlorine burn periods, including revised monitoring schedules
for DBPs, taking into account occurrence and exposure to DBPs during
chlorine burn periods, and related short-term health effects on
sensitive populations.

References

Abdel-Rahman, M.S., D. Couri, and R.J. Bull. 1984. Toxicity of
chlorine dioxide in drinking water. International Journal of
Toxicology. 3(4): 277-284.
Agency for Toxic Substances and Disease Registry (ATSDR). 2010.
Toxicological Profile for Trichlorobenzenes. U.S. Department of
Health and Human Services: Atlanta, GA. https://www.atsdr.cdc.gov/toxprofiles/tp199.pdf

[[Page 3547]]

Armstrong, T.W. and C.N. Haas. 2007. A quantitative microbial risk
assessment model for legionnaires' disease: assessment of human
exposures for selected spa outbreaks. Journal of Occupational and
Environmental Hygiene. 4: 634-646.
Armstrong, T.W. and C.N. Haas. 2008. Legionnaires' disease:
evaluation of a quantitative microbial risk assessment model.
Journal of Water and Health. 6(2): 149-166.
Association of State Drinking Water Administrators (ASDWA). 2016.
Six-Year Review 3 Implementation & Other Regulatory Issues for
Potential Consideration--ASDWA Regulatory Committee feedback.
Ashbolt, N.J. 2015. Environmental (saprozoic) pathogens of
engineered water systems: understanding their ecology for risk
assessment and management. Pathogens. 4(2): 390-405.
Azzeh, J., L. Taylor-Edmonds, and R.C. Andrews. 2015. Engineered
biofiltration for ultrafiltration fouling mitigation and
disinfection by-product precursor control. Water Science and
Technology: Water Supply. 15(1): 124-133.
Baribeau, H., SW. Krasner, R. Chinn, and P.C. Singer. 2005. Impact
of biomass on the stability of HAAs and THMs in a simulated
distribution system. Journal of American Water Works Association.
97(2): 69-81.
Bartrand, T.A., J.J. Causey, and J.L. Clancy. 2014. Naegleria
fowleri: an emerging drinking water pathogen. Journal of the
American Water Works Association. 106(10): 418-432.
Beer, K.D., J.W. Gargano, V.A. Roberts, V.R. Hill, L.E. Garrison,
P.K. Kutty, E.D. Hilborn, T.J. Wade, K.E. Fullerton, and J.S. Yoder.
2015. Surveillance for waterborne disease outbreaks associated with
drinking water--United States, 2011-2012. Morbidity and Mortality
Weekly Report. 64: 842-848.
Behnke, S., A.E. Parker, D. Woodall, and A.K. Camper. 2011.
Comparing the chlorine disinfection of detached biofilm clusters
with those of sessile biofilms and planktonic cells in single- and
dual-species cultures. Applied and Environmental Microbiology.
77(20): 7176-7184.
Bercz, J.P., L.L. Jones, L. Garner, L. Murray, D. Ludwig, and J.
Boston. 1982. Subchronic toxicity of chlorine dioxide and related
compounds in drinking water in the nonhuman primate. Environmental
Health Perspectives. 46: 47-55.
Biyela, P.T., R. Hodon, A. Brown, A. Alum, M. Abbaszadegan, and B.E.
Rittmann. 2012. Distribution systems as reservoirs of Naegleria
fowleri and other amoebae. Journal of the American Water Works
Association. 104(1): E66-E72.
Black, S., J.A. Thurston, and C.P. Gerba. 2009. Determination of CT
values for chlorination of resistant enteroviruses. Journal of
Environmental Science and Health. 44:336-339.
Borchardt, M.A., S.K. Spencer, B.A. Kieke Jr., E. Lambertini, and
F.J. Loge. 2012. Viruses in non-disinfected drinking water from
municipal wells and community incidence of acute gastrointestinal
illness. Environmental Health Perspectives. 120(9): 1272-1279.
Available online at: https://dx.doi.org/10.1289/ehp.11044499.
Brooke, E., and M.R. Collins. 2011. Post-treatment aeration to
reduce THMs. Journal of the American Water Works Association.
103(10): 84-96.
Brown, J., R.S. Summers, M. LeChevallier, H. Collins, J.A. Roberson,
S. Hubbs, and E. Dickenson. 2015. Biological drinking water
treatment? Naturally. Journal of the American Water Works
Association. 107(12): 20-31.
Buse, H.Y., M.E. Schoen, and N.J. Ashbolt. 2012. Legionellae in
engineered systems and use of quantitative microbial risk assessment
to predict exposure. Water Research. 46(4): 921-933.
California Environmental Protection Agency (CalEPA). 2010a. Public
Health Goal for Methoxychlor in Drinking Water. Office of
Environmental Health Hazard Assessment: Sacramento, CA. Available
at: https://oehha.ca.gov/media/downloads/water/chemicals/phg/091610mxc_0.pdf
CalEPA. 2010b. Public Health Goal for Styrene in Drinking Water.
Office of Environmental Health Hazard Assessment: Sacramento, CA.
https://oehha.ca.gov/media/downloads/water/chemicals/phg/122810styrene_0.pdf
Callinan, C.W., J.P. Hassett, J.P. Hyde, R.A. Entringer, and R.K.
Klake. 2013. Proposed nutrient criteria for water supply lakes and
reservoirs. Journal of the American Water Works Association. 105(4):
47-48.
Cantor, K.P., R. Hoover, and P. Hartge. 1985. Drinking water source
and risk of bladder cancer: A case-control study. In: Water
Chlorination: Chemistry, Environmental Impact and Health Effects.
R.L. Jolley, R.J. Bull, and W.P. Davis (eds.). 5(1): 145-152. Lewis
Publishers, Inc.
Cantor, K.P., R. Hoover, P. Hartge, T.J. Mason, D.T. Silverman, R.
Altman, D.F. Austin, M.A. Child, C.R. Key, and L.D. Marrett. 1987.
Bladder cancer, drinking water source, and tap water consumption: a
case-control study. Journal of the National Cancer Institute. 79(6):
1269-79.
Cantor, K.P., C.F. Lunch, M. Hildesheim, M. Dosemeci, J. Lubin, M.
Alavanja, and G.F. Craun. 1998. Drinking water source and
chlorination byproducts I. Risk of bladder cancer. Epidemiology.
9(1): 21-28.
Cantor, K.P., C.M. Villanueva, D.T. Silverman, J.D. Figueroa, F.X.
Real, M. Garcia-Closas, N. Malats, S. Chanock, M. Yeager, A. Tardon,
and R. Garcia-Closas. 2010. Polymorphisms in GSTT1, GSTZ1, and
CYP2E1, disinfection by-products, and risk of bladder cancer in
Spain. Environmental Health Perspectives. 118(11): 1545-1550.
Cohn, P.D., J.A. Gleason, E. Rudowski, S.M. Tsai, C.A. Genese, and
J.A. Fagliano. 2014. Community outbreak of legionellosis and an
environmental investigation into a community water system.
Epidemiology and Infection. 143(6): 1322-1331.
Colford Jr., J.M., J.F. Hilton, C.C. Wright, B.F. Arnold, S. Saha,
T.J. Wade, J. Scott, and J.N.S. Eisenberg. 2009. The Sonoma water
evaluation trial: A randomized drinking water intervention trial to
reduce gastrointestinal illness in older adults. American Journal of
Public Health. 99(11): 1988-1995.
Collier, S.A., L.J. Stockman, L.A. Hicks, L.E. Garrison, F.J. Zhou,
and M.J. Beach. 2012. Direct healthcare costs of selected diseases
primarily or partially transmitted by water. Epidemiology and
Infection. 140(11): 2002-2013.
Couri, D. and M.S. Abdel-Rahman. 1980. Effect of chlorine dioxide
and metabolites on glutathione dependent system in rat, mouse and
chicken blood. Journal of Environmental Pathology and Toxicology.
3(1-2): 451-460.
Craun, G.F. and W. Jakubowski. 1986. Status of waterborne giardiasis
outbreaks and monitoring methods. Health Effects Research
Laboratory, Office of Research and Development, US Environmental
Protection Agency.
Cromeans, T.L., A.M. Kahler, and V.R. Hill. 2010. Inactivation of
adenoviruses, enteroviruses, and murine norovirus in water by free
chlorine and monochloramine. Applied and Environmental Microbiology.
76(4): 1028-1033.
Daly, E.R., S.J. Roy, D.D. Blaney, J.S. Manning, V.R. Hill, L. Xiao,
and J.W. Stull. 2010. Outbreak of giardiasis associated with a
community drinking-water source. Epidemiology and infection.
138(04): 491-500.
Delatolla, R., C. S[eacute]guin, S. Springthorpe, E. Gorman, A.
Campbell, and I. Douglas. 2015. Disinfection byproduct formation
during biofiltration cycle: Implications for drinking water
production. Chemosphere. 136: 190-197.
Dong, Y., G. Li, N. Zhou, R. Wang, Y. Chi, and G. Chen. 2012.
Graphene quantum dot as a green and facile sensor for free chlorine
in drinking water. Analytical Chemistry. 84: 8378-8382.
Duda, S., S. Kandiah, J.E. Stout, J.L. Baron, M. Yassin, M.
Fabrizio, J. Ferrelli, R. Hariri, M.M. Wagener, J. Goepfert, J.
Bond, J. Hannigan, and D. Rogers. 2014. Evaluation of a new
monochloramine generation system for controlling Legionella in
building hot water systems. Infection Control and Hospital
Epidemiology. 35(11): 1356-1363.
Duranceau, S.J. 2015. Spray Aeration as a Trihalomethane Control
Measure. 2015 Florida Water Resources Conference Proceedings. The
Many Faces of Water.
Emelko, M.B., U. Silins, K.D. Bladon, M. Stone, C. Williams, M.
Wagner, A. Martens, and X. Geng. 2013. ``The Lost Creek Wildfire of
Southern Alberta, Canada: 10 Years, 7 Watersheds and Continued
Impacts.'' Water Research Foundation Workshop: Wildfire Readiness
and Response Workshop--Is Your Utility Prepared? April 4, 2013.

[[Page 3548]]

Farr[eacute], M.J., J. Reungoat, F.X. Argaud, M. Rattier, J. Keller,
and W. Gernjak. 2011. Fate of N-nitrosodimethylamine, trihalomethane
and haloacetic acid precursors in tertiary treatment including
biofiltration. Water Research. 45(17): 5695-5704.
Fern[aacute]ndez, M.R., R.V. Carvalho, F.A. Ogliari, F.A. Beira, A.
Etges, and M. Bueno. 2010. Cytotoxicity and genotoxicity of sodium
percarbonate: a comparison with bleaching agents commonly used in
discoloured pulpless teeth. International Endodontic Journal. 43(2):
102-108.
Fiske, P.S., J. Oppenheimer, R. Moore, and R. Everett. 2011. In-tank
aeration predicts and reduces THMs. Opflow. 37(11): 22-24.
Flannery, B., L.B. Gelling, D.J. Vugia, J.M. Weintraub, J.J.
Salerno, M.J. Conroy, V.A. Stevens, C.E. Rose, M.R. Moore, B.S.
Fields, and R.E. Besser. 2006. Reducing Legionella colonization of
water systems with monochloramine. Emerging Infectious Diseases.
12(4): 588-596.
Freedman, M., K.P. Cantor, N.L. Lee, L.S. Chen, H.H. Lei, C.E. Ruhl,
and S.S. Wang. 1997. Bladder cancer and drinking water: a
population-based case-control study in Washington County, Maryland
(United States). Cancer Causes and Control. 8(5): 738-744.
Geldreich, E.E., K.R. Fox, J.A. Goodrich, E.W. Rice, R.M. Clark, and
D.L. Swerdlow. 1992. Searching for a water supply connection in the
Cabool, Missouri disease outbreak of Escherichia coli O157: H7.
Water Research. 26(8): 1127-1137.
Hambsch, B., K. B[ouml]ckle, and H.M. van Lieverloo. 2007. Incidence
of faecal contaminations in chlorinated and non-chlorinated
distribution systems of neighbouring European countries. Journal of
Water and Health. 5(1): 119-130.
Hasan, F.M., F.A. Ahmed, N.A. Nada, and A.M. Manal. 2010. Using
aluminum refuse as a coagulant in the coagulation and flocculation
processes. Iraqi Journal of Chemical and Petroleum Engineering. 11:
15-22.
Headd, B. and S.A. Bradford. 2015 (epub). Use of aerobic spores as a
surrogate for cryptosporidium oocysts in drinking water supplies.
Water Research. 90: 185-202. Available online at: https://www.ncbi.nlm.nih.gov/pubmed/26734779.
Health Canada. 2014. Guidelines for Canadian Drinking Water Quality:
Selenium. Water and Air Quality Bureau, Healthy Environments and
Consumer Safety Branch. Health Canada: Ottawa, Ontario.
Heffelfinger, J.D., J.L. Kool, S. Fridkin, V.J. Fraser, J. Hageman,
J. Carpenter, and C.G. Whitney. 2003. Risk of hospital-acquired
Legionnaires' disease in cities using monochloramine versus other
water disinfectants. Infection Control and Hospital Epidemiology.
24(8): 569-574.
Hibler, C.P., C.M. Hancock, L.M. Perger, J.G. Wegrzyn, and K.D.
Swabby. 1987. Inactivation of Giardia cysts with chlorine at 0.50
[deg]C to 5.00 [deg]C. AWWA Research Foundation.
Hill, V.R. and T.L. Cromeans. 2010. Contaminant Candidate List
Viruses: Evaluation of Disinfection Efficacy. Water Research
Foundation. Project #3134.
Hoffbuhr, J.W., J. Blair, M. Bartleson, and R. Karlin. 1986. Use of
particulate analysis for source and water treatment evaluation.
Water Quality Technology Conference 1986 Conference Proceedings.
Hrudey, S.E, L.C. Backer, A.R. Humpage, S.W. Krasner, D.S. Michaud,
L.E. Moore, P.C. Singer, and B.D. Stanford. 2015. Evaluating
evidence for association of human bladder cancer with drinking-water
chlorination disinfection by-products. Journal of Toxicology and
Environmental Health, Part B. 18(5): 213-241. Published online Aug
26. doi: 10.1080/10937404.2015.1067661.
Ingels, T. 2015. What does undetectable mean anyway? Colorado's
experience with detection of free chlorine residuals in real world
distribution systems. Presentation at the American Water Works
Association Annual Conference.
Johnson, B.A., J.C. Lin, L.B. Jacobsen, and M. Fang. 2009. Localized
treatment for disinfection byproducts. Water Research Foundation.
Project #3101.
Keegan, A., S. Wati, and B. Robinson. 2012. Chlor(am)ine
disinfection of human pathogenic viruses in recycled waters (SWF62M-
2114). Prepared by Australia Water Quality Centre for the Smart
Water Fund, Victoria.
Kenyon, E.M., C. Eklund, T. Leavens, and R.A. Pegram. 2015.
Development and application of a human PBPK model for
bromodichloromethane to investigate the impacts of multi-route
exposure. Journal of Applied Toxicology. 36(9): 1095-1111.
Khaldi, S., M. Ratajczak, G. Gargala, M. Fournier, T. Berthe, L.
Favennec, and J.P. Dupont. 2011. Intensive exploitation of a karst
aquifer leads to Cryptosporidium water supply contamination. Water
Research. 45(9): 2906-2914.
Khan, M.A, S.E. Fenton, A.E. Swank, S.D. Hester, A. Williams, and
D.C. Wolf. 2005. A mixture of ammonium perchlorate and sodium
chlorate enhances alterations of the pituitary-thyroid axis caused
by the individual chemicals in adult male F344 rats. Toxicologic
Pathology. 33: 776-783.
King, W.D. and L.D. Marrett. 1996. Case-control study of bladder
cancer and chlorination by-products in treated water (Ontario,
Canada). Cancer Causes & Control. 7(6): 596-604.
Kogevinas, M., C.M. Villanueva, L. Font-Ribera, D. Liviac, M.
Bustamante, F. Espinoza, M.J. Nieuwenhuijsen, A. Espinosa, P.
Fernandez, D.M. DeMarini, J.O. Grimalt, T. Grummt, and R. Marcos.
2010. Genotoxic effects in swimmers exposed to disinfection by-
products in indoor swimming pools. Environmental Health
Perspectives. 118(11): 1531-1537.
Kool, J.L., J.C. Carpenter, and B.S. Fields. 1999. Effect of
monochloramine disinfection of municipal drinking water on risk of
nosocomial Legionnaires' disease. The Lancet. 353: 272-277.
Krasner, S.W., R. Shirkani, P. Westerhoff, D. Hanigan, W.A. Mitch,
D.L. McCurry, C. Chen, J. Skadsen, and U. von Gunten. 2015.
Controlling the formation of nitrosamines during water treatment.
Water Research Foundation. Web Report #4370.
Krasner, S.W., W.A. Mitch, D.L. McCurry, D. Hannigan, and P.
Westerhoff. 2013. Formation, precursors, control, and occurrence of
nitrosamines in drinking water: A review. Water Research. 47: 4433-
4450.
Leavens, T.L., B.C. Blount, D.M. DeMarini, M.C. Madden, J.L.
Valentine, M.W. Case, L.K. Silva, S.H. Warren, N.M. Hanley, and R.A.
Pegram. 2007. Disposition of bromodichloromethane in humans
following oral and dermal exposure. Toxicological Sciences. 99(2):
432-445.
LeChevallier, M.W., N.J. Welch, and D.B. Smith. 1996. Full-scale
studies of factors related to coliform regrowth in drinking water.
Applied and Environmental Microbiology. 62(7): 2201-2211.
Lee, W., P. Westerhoff, and J-P. Croue. 2007. Dissolved organic
nitrogen as a precursor for chloroform, dichloroacetonitrile, N-
nitrosodimethylamine, and trichloronitromethane. Environmental
Science & Technology. 41(15): 5485-5490.
Lee, E., D. Haur Phua, B. Leong Lim, and H. Kai Goh, 2013. Severe
chlorate poisoning successfully treated with methylene blue. The
Journal of Emergency Medicine. 44(2): 381-384.
Liao, X., C. Wang, J. Wang, X. Zhang, C. Chen, S.W. Krasner, and
I.H. Suffet. 2014. Nitrosamine precursor and DOM control in an
effluent-affected drinking water. Journal of the American Water
Works Association. 106(7): 307-318.
Lin, Y.E., R.D. Vidic, J.E. Stout, and V.L. Yu. 1998. Legionella in
water distribution systems. Journal of the American Water Works
Association. 90(9): 112-122.
Locas, A.C. Barthe, A.B. Margolin, and P. Payment. 2008. Groundwater
microbiological quality in Canadian drinking water municipal wells.
Canadian Journal of Microbiology. 54(6): 472-478.
Louisiana Department of Health and Hospitals. 2013. Declaration of
Emergency. Minimum Disinfectant Residual Levels in Public Water
Systems. Available online at: https://dhh.louisiana.gov/assets/oph/Center-EH/engineering/Emergency_Rule/Emergency_Rule_Notification.pdf.
Louisiana Department of Health and Hospitals. 2014. Declaration of
Emergency. Minimum Disinfectant Residual Levels in Public Water
Systems. Available online at: https://www.dhh.louisiana.gov/assets/oph/Center-EH/engineering/Emergency_Rule/ER_3-6-14.pdf.
Lui, Y.S., H.C. Hong, G.J.S. Zheng, and Y. Liang. 2012. Fractionated
algal organic materials as precursors of disinfection by-products
and mutagens upon chlorination. Journal of Hazardous Materials. 209:
278-284.
McGeehin, M.A., J.S. Reif, J.C. Becher, and E.J. Mangione. 1993.
Case-control study

[[Page 3549]]

of bladder cancer and water disinfection methods in Colorado.
American Journal of Epidemiology. 138(7): 492-501.
McGuire, M.J., T. Karanfil, S.W. Krasner, D.A. Reckhow, J.A.
Roberson, R.S. Summers, P. Weseteroff, and Y. Xie. 2014. Not your
granddad's disinfection by-product problems and solutions. Journal
of the American Water Works Association. 106(8): 54-73.
McKie, M.J., L. Taylor-Edmonds, S.A. Andrews, and R.C. Andrews.
2015. Engineered biofiltration for the removal of disinfection by-
product precursors and genotoxicity. Water Research. 81: 196-207.
McTigue, N.E., D.A. Cornwell, K. Graf, and R. Brown. 2014.
Occurrence and consequences of increased bromide in drinking water
sources. Journal of the American Water Works Association 106(11):
492-508.
Messner. M.J., P. Berger, and S.P. Nappier. 2014. Fractional
Poisson--A simple dose-response model for human norovirus. Risk
Analysis. 34(10): 1820-1829.
Mikkelson, K.M., E.R.V. Dickenson, R.M. Maxwell, J.E. McCray, and
J.O. Sharp. 2013. Water-quality impacts from climate-induced forest
die-off. Nature Climate Change. 3(3): 218-222.
Moore, G.S. and E.J. Calabrese. 1982. Toxicological effects of
chlorite in the mouse. Environmental Health Perspectives. 46: 31-37.
Moore, M.R., M. Pryor, B. Fields, C. Lucas, M. Phelan, and R.E.
Besser. 2006. Introduction of monochloramine into a municipal water
system: Impact on colonization of buildings by Legionella spp.
Applied and Environmental Microbiology. 72(1): 378-383.
Narotsky, M.G., D.S. Best, A. McDonald, E.A. Godin, E.S. Hunter III,
and J.E. Simmons. 2011. Pregnancy loss and eye malformations in
offspring of F344 rats following gestational exposure to mixtures of
regulated trihalomethanes and haloacetic acids. Reproductive
Toxicology. 31(1): 59-65.
Narotsky, M.G., G.R. Klinefelter, J.M. Goldman, D.S. Best, A.
McDonald, L.F. Strader, J.D. Suarez, A.S. Murr, I. Thillainadarajah,
E.S. Hunter III, S.D. Richardson, T.F. Speth, R.J. Miltner, J.G.
Pressman, L.K. Teuschler, G.E. Rice, V.C. Moser, R.W. Luebke, and
J.E. Simmons. 2013. Comprehensive assessment of a chlorinated
drinking water concentrate in a rat multigenerational reproductive
toxicity study. Environmental Science & Technology. 47(18): 10653-
10659.
Narotsky, M.G., G.R. Klinefelter, J.M. Goldman, A.B. DeAngelo, D.S.
Best, A. McDonald, L.F. Strader, A.S. Murr, J.D. Suarez, M.H.
George, E.S. Hunter III, and J.E. Simmons. 2015. Reproductive
toxicity of a mixture of regulated drinking-water disinfection by-
products in a multigenerational rat bioassay. Environmental Health
Perspective. 123(6): 564-570. Available online at: https://dx.doi.org/10.1289/ehp.1408579.
National Drinking Water Advisory Committee (NDWAC). 2000.
Recommended Guidance for Review of Existing National Primary
Drinking Water Regulations. November 2000.
National Research Council (NRC). 2006a. Fluoride in drinking-water:
A Scientific Review of EPA's Standards. The National Academies
Press, Washington, DC.
NRC. 2006b. Drinking Water Distribution Systems: Assessing and
Reducing Risks. The National Academies Press, Washington, DC.
National Toxicology Program (NTP). 2005. NTP Technical Report on the
Toxicology and Carcinogenesis Studies of Sodium Chlorate (CAS No.
7775-09-9) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies).
NTP TR 517 NIH Publication No. 06-4457 National Institutes of
Health, Public Health Service, U.S. Department of Health and Human
Services. December 2005.
NTP. 2007. NTP technical report on the toxicology and carcinogenesis
studies of dibromoacetic acid (CAS No. 631-64-1) in F344/N rats and
B6C3F1 mice (drinking water studies). NTP Technical Report Series
No. 537. NTP, National Institutes of Health, Public Health Service,
U.S. Department of Health and Human Services. Available online at:
https://ntp.niehs.nih.gov/index.cfm?objectid=8831333E-F1F6-975E-71D4F287C2229308.
NTP. 2009. Toxicology and carcinogenesis studies of
bromochloroacetic acid (CAS No. 5589-96-8) in F344/N rats and B6C3F1
mice (drinking water studies). Technical Report Series No. 549.
Research Triangle Park, NC: U.S. Department of Health and Human
Services.
NTP. 2014. Toxicology studies of bromodichloroacetic acid (CAS No.
71133-14-7) in F344 rats and B6C3F1 mice and toxicology and
carcinogenesis studies of bromodichloroacetic acid in F344/NTac rats
and B6C3F1/N mice (drinking water studies). Peer Review Draft,
scheduled peer review date; May 22, 2014. Technical Report Series
No. 583. Research Triangle Park, NC: U.S. Department of Health and
Human Services.
NTP. 2016. Systematic Review of the Effects of Fluoride on Learning
and Memory in Animal Studies. Available online at https://ntp.niehs.nih.gov/ntp/ohat/pubs/ntp_rr/01fluoride_508.pdf
Nguyen, M.L., P. Westerhoff, L. Baker, Q. Hu, M. Esparza-Soto, and
M. Sommerfeld. 2005. Characteristics and reactivity of algae-
produced dissolved organic carbon. Journal of Environmental
Engineering. 131(11): 1574-1582.
Nguyen, V., Hoffman, R. and Nelson, L. 2014. Chlorine dioxide from a
dietary supplement causing hemolytic anemia. Clinical Toxicology.
52(4): 323-323.
Orme, J., D.H. Taylor, R.D. Laurie, and R.J. Bull. 1985. Effects of
chlorine dioxide on thyroid function in neonatal rats. Journal of
Toxicology and Environmental Health. 15(2): 315-322.
Pennsylvania Bulletin. 2016. Proposed Rulemaking. Disinfection
Requirements Rule. 46(8): 857-892. Available online at: https://www.pabulletin.com/secure/data/vol46/46-8/278.html.
Pharand, L., M.I. van Dyke, W.B. Anderson, Y. Yohannes, and P.M.
Huck. 2015. Full-scale ozone-biofiltration: Seasonally related
effects on NOM removal. Journal of the American Water Works
Association. 107(12): 425-436.
Plewa, M.J. and E.D. Wagner. 2009. Mammalian cell cytotoxicity and
genotoxicity of disinfection by-products. Water Research Foundation.
Denver, CO.
Plewa, M.J., J.E. Simmons, S.D. Richardson, and E.D. Wagner. 2010.
Mammalian cell cytotoxicity and genotoxicity of the haloacetic
acids, a major class of drinking water disinfection by- products.
Environmental and Molecular Mutagenesis. 51(8-9): 871-878.
Pryor, M., S. Springthorpe, S. Riffard, T. Brooks, Y. Huo, G. Davis,
and S.A. Sattar. 2004. Investigation of opportunistic pathogens in
municipal drinking water under different supply and treatment
regimes. Water Science and Technology. 50(1): 83-90.
Regli, S., J. Chen, M. Messner, M.S. Elovitz, F.J. Letkiewicz, R.A.
Pegram, T.J. Pepping, S.D. Richardson, and J.M. Wright. 2015.
Estimating potential increased bladder cancer risk due to increased
bromide concentrations in sources of disinfected drinking waters.
Environmental Science and Technology. 49(22): 13094-13102.
Revetta, R.P., V. Gomez-Alvarez, T.L. Gerke, C. Curioso, J.W. Santo
Domingo, and N.J. Ashbolt. 2013. Establishment and early succession
of bacterial communities in monochloramine-treated drinking water
biofilms. FEMS Microbiology Ecology. 86(3): 404-414.
Rice, J., A. Wutich, and P. Westerhoff. 2013. Assessment of de facto
wastewater reuse across the US: trends between 1980 and 2008.
Environmental Science & Technology. 47(19): 11099-11105.
Rice, J. and P. Westerhoff. 2014. Spatial and temporal variation in
de facto wastewater reuse in drinking water systems across the USA.
Environmental Science & Technology. 49(2): 982-989.
Richardson, S. and C. Postigo. 2011. Drinking water disinfection by-
products. Emerging Organic Contaminants and Human Health. 20: 93-
137.
Richardson, S.D., F. Fasano, J.J. Ellington, F.G. Crumley, K.M.
Buettner, J. J. Evans, B.C. Blount, L.K. Silva, T.J. Waite, G.W.
Luther, A.B. McKague, R.J. Miltner, E.D. Wagner, and M.J. Plewa.
2008. Occurrence and mammalian cell toxicity of iodinated
disinfection byproducts in drinking water. Environmental Science &
Technology. 42(22): 8330-8338.
Richardson, S.D., M.J. Plewa, E.D. Wagner, R. Schoeny, and D.M.
DeMarini. 2007. Occurrence, genotoxicity, and carcinogenicity of
regulated and emerging disinfection by-products in drinking water: a
review and roadmap for research. Mutation Research. 636(1-3): 178-
242.
Ross, M.K. and R.A. Pegram. 2003. Glutathione transferase theta 1-1-
dependent metabolism of the water disinfection byproduct

[[Page 3550]]

bromodichloromethane. Chemical Research in Toxicology. 16(2): 216-
226.
Ross, M.K. and R.A. Pegram. 2004. In vitro biotransformation and
genotoxicity of the drinking water disinfection byproduct
bromodichloromethane: DNA binding mediated by glutathione
transferase theta 1-1. Toxicology and Applied Pharmacology. 195(2):
166-181.
Saad, B, W.T. Wai, M.S. Jab, W.S.W. Ngah, M.I. Saleh, and J.M.
Slater. 2005. Development of flow injection spectrophotometric
methods for the determination of free available chlorine and total
available chlorine: comparative study. Analytica Chimica Acta.
(537): 197-206.
Sacher, F., C.K. Schmidt, C. Lee, and U. von Gunten. 2008.
Strategies for minimizing nitrosamine formation during disinfection.
Water Research Foundation. Project #2979.
Samson, C. 2015. Assessing DBP Occurrence: Impacts of the Stage 2
DBPR. Water Quality Technology Conference 2015 Conference
Proceedings.
Samson, C., B. Rajagopalan, and S. Summers. 2013. Modeling TOC
Threshold Exceedances for Meeting Disinfection By-Product Drinking
Water Regulations under the Impact of Climate Change. In Proceedings
of International Annual Meeting of American Society of Agronomy/Crop
Science Society of America/Soil Science Society of America.
Sirikanchana, K., J.L. Shisler, and B.J. Marinas. 2008. Inactivation
kinetics of adenovirus serotype 2 with monochloramine. Water
Research. 42(6): 1467-1474.
Smeets, P.W., G.J. Medema, and J.C. Van Dijk. 2009. The Dutch
secret: how to provide safe drinking water without chlorine in the
Netherlands. Drinking Water Engineering and Science. 2: 1-14.
State of Nebraska. 2013. Demonstration of Performance to Establish
Natural Filtration Credits for the City of Kearney, Nebraska. Platte
River Well Field. Project #130-C1-054.
States, S., G. Cyprych, M. Stoner, F. Wydra, J. Kuchta, J. Monnell,
and L. Casson. 2013. Marcellus shale drilling and brominated THMs in
Pittsburgh, PA., drinking water. Journal of the American Water Works
Association. 105(8): 432-448.
Stayner, L.T., M. Pedersen, E. Patelarou, I. Decordier, K. Vande
Loock, L. Chatzi, A. Espinosa, E. Fthenou, M.J. Niewenhuijsen, E.
Gracia-Lavedan, E.G. Stephanou, M. Kirsch-Volders, M. Kogevinas.
2014. Exposure to brominated trihalomethanes in water during
pregnancy and micronuclei frequency in maternal and cord blood
lymphocytes. Environmental Health Perspectives. 122(1): 100-106.
Summers, R.S., M.A. Benz, H.M. Shukairy, and L. Cummings. 1993.
Effect of separation processes on the formation of brominated THMs.
Journal of the American Water Works Association. 95: 88-95.
Symons, J.M., Krasner, S.W., Simms, L.A., and Sclimenti, M. 1993.
Measurement of THM and precursor concentrations revisited: the
effect of bromide ion. Journal of the American Water Works
Association. 85(1): 51-62.
Tang, Y., Y. Su, N. Yang, L. Zhang, and Y. Lv. 2014. Carbon nitride
quantum dots: a novel chemiluminescence system for selective
detection of free chlorine in water. Analytical Chemistry. 86(9):
4528-4535.
Teunis, P.F., C.L. Chappell, and P.C. Okhuysen. 2002a.
Cryptosporidium dose response studies: variation between isolates.
Risk Analysis. 22(1): 175-185.
Teunis, P.F., C.L. Chappell, and P.C. Okhuysen. 2002b.
Cryptosporidium dose response studies: variation between hosts. Risk
Analysis. 22(3): 475-485.
U. S. Department of Health and Human Services. 2015. U.S. Public
Health Service Recommendation for Fluoride Concentration in Drinking
Water for the Prevention of Dental Caries. Available online at:
https://www.publichealthreports.org/documents/PHS_2015_Fluoride_Guidelines.pdf.
U.S. Environmental Protection Agency (USEPA). 1979. Interim Primary
Drinking Water Regulations; Amendments. 44 FR 42254. July 19, 1979.
USEPA. 1985. National Primary Drinking Water Regulations; Volatile
Synthetic Organic Chemicals; Final Rule and Proposed Rule. 50 FR
46880. November 13, 1985.
USEPA. 1989. National Primary Drinking Water Regulations;
Filtration, Disinfection; Turbidity, Giardia lamblia, Viruses,
Legionella, and Heterotrophic Bacteria; Final Rule. Part III. 54 FR
27486. June 29, 1989.
USEPA. 1991. Guidance Manual for Compliance with the Filtration and
Disinfection Requirements for Public Water Systems Using Surface
Water Sources. March 1991. Available online at: https://www.epa.gov/sites/production/files/2015-10/documents/guidance_manual_for_compliance_with_the_filtration_and_disinfection_requirements.pdf.
USEPA. 1995. Reregistration Eligibility Decision (RED) for Picloram.
Office of Prevention, Pesticides and Toxic Substances: Washington,
DC. EPA738-R95-019. https://archive.epa.gov/pesticides/reregistration/web/pdf/0096.pdf
USEPA. 1998a. Toxicological Review of Beryllium and Compounds (CAS
No. 7440-41-7): in Support of Summary Information on the Integrated
Risk Information System (IRIS). National Center for Environmental
Assessment, Office of Research and Development, Washington, DC. EPA
635-R-98-008. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0012tr.pdf
USEPA. 1998b. National Primary Drinking Water Regulations;
Disinfectants and Disinfection Byproducts; Final Rule. 63 FR 69390.
December 16, 1998.
USEPA. 1998c. National Primary Drinking Water Regulations. Interim
Enhanced Surface Water Treatment Rule. Final Rule. 63 FR 69477.
December 16, 1998.
USEPA. 1998d. Small System Compliance Technology: List for the Non-
Microbial Contaminants Regulated Before 1996. EPA 815-R-98-002.
September 1998.
USEPA. 1999. Uncovered Finished Water Reservoirs Guidance Manual.
EPA 815-R-99-011. April 1999. Available online at: https://webcache.googleusercontent.com/search?q=cache:SLzRMA1eR7oJ:https://www.epa.gov/dwreginfo/interim-enhanced-surface-water-treatment-rule-documents+&cd=1&hl=en&ct=clnk&gl=us.
USEPA. 2000a. ICR Auxiliary 1 Database. EPA 815-C-00-002.
USEPA. 2000b. ICR Treatment Study Database. EPA 815-C-00-003.
USEPA. 2000c. ICR Supplemental Survey Database. Prepared by DynCorp,
Inc.
USEPA. 2001a. Toxicological Review of Hexachlorocyclopentadiene
(CASRN 77-47-4): In Support of Summary Information on the Integrated
Risk Information System (IRIS). National Center for Environmental
Assessment, Office of Research and Development, Washington, DC. EPA
600-R-01-013. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0039tr.pdf
USEPA. 2001b. National Primary Drinking Water Regulations: Filter
Backwash Recycling Rule. 66 FR 31086. June 8, 2001.
USEPA. 2002a. Diquat Dibromide HED Risk Assessment for Tolerance
Reassessment Eligibility Document (TRED). PC Code No: 032201; DP
Barcode: D281890; Submission Barcode: S611057. https://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-0920-0007
USEPA. 2002b. Toxicological Review of 1,1-Dichloroethylene (CAS No.
75-35-4): In Support of Summary Information on the Integrated Risk
Information System (IRIS). National Center for Environmental
Assessment, Office of Research and Development: Washington, DC. EPA
635-R-02-002. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0039tr.pdf
USEPA. 2002c. National Primary Drinking Water Regulations: Long Term
1 Enhanced Surface Water Treatment Rule. Final Rule. 67 FR 1812.
January 14, 2002.
USEPA. 2002d. Reregistration Eligibility Decision (RED) for Lindane.
Office of Prevention, Pesticides and Toxic Substances: Washington,
DC. https://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2002-
0202-0027
USEPA. 2003a. Toxicological Review of Xylenes (CAS No.1330-20-7): In
Support of Summary Information on the Integrated Risk Information
System (IRIS). National Center for Environmental Assessment, Office
of Research and Development: Washington, DC. EPA 635-R-03-001.
https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0270tr.pdf
USEPA. 2003b. National Primary Drinking Water Regulations;
Announcement of Completion of EPA's Review of Existing Drinking
Water Standards. Notice. 68 FR 42908. July 18, 2003.
USEPA. 2005a. Economic Analysis for the Final Stage 2 Disinfectants
and Disinfection Byproducts Rule. EPA 815-R-05-010. December 2005.
USEPA. 2005b. Toxicological Review of Barium and Compounds (CAS
No.7440-39-3): In Support of Summary Information

[[Page 3551]]

on the Integrated Risk Information System (IRIS). National Center
for Environmental Assessment, Office of Research and Development:
Washington, DC. EPA 635-R-05-001. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0010tr.pdf
USEPA. 2005c. Toxicological Review of Toluene (CAS No. 108-88-3): In
Support of Summary Information on the Integrated Risk Information
System (IRIS). National Center for Environmental Assessment, Office
of Research and Development: Washington, DC. EPA 635-R-05-004.
https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0118tr.pdf
USEPA. 2005d. Method 1622: Cryptosporidium in Water by Filtration/
IMS/FA. EPA 815-R-05-001.
USEPA. 2005e. Method 1623: Cryptosporidium and Giardia in Water by
Filtration/IMS/FA. EPA 815-R-05-002.
USEPA. 2005f. Reregistration Eligibility Decision for Endothall
(Case Number 2245). EPA 738-R-05-008, Office of Prevention,
Pesticides, and Toxic Substances: Washington, DC. https://archive.epa.gov/pesticides/reregistration/web/pdf/endothall_red.pdf
USEPA. 2005g. Technologies and Costs for the Final Long Term 2
Enhanced Surface Water Treatment Rule and Final Stage 2
Disinfectants and Disinfection Byproducts Rule. EPA 815-R-05-012.
December 2005.
USEPA. 2006a. Acetochlor/Alachlor: Cumulative Risk Assessment for
the Chloroacetanilides. Office of Prevention, Pesticides and Toxic
Substances: Washington, DC.
USEPA. 2006b. National Primary Drinking Water Regulations: Ground
Water Rule; Final Rule. 71 FR 65573. November 8, 2006.
USEPA. 2006c. National Primary Drinking Water Regulations: Long Term
2 Enhanced Surface Water Treatment Rule; Final Rule. 71 FR 654.
January 5, 2006.
USEPA. 2006d. National Primary Drinking Water Regulations: Stage 2
Disinfectants and Disinfection Byproducts Rule; Final Rule. 71 FR
388. January 4, 2006.
USEPA. 2006e. Reregistration Eligibility Decision (RED) for Chlorine
Dioxide and Sodium Chlorite (Case 4023). EPA 738-R-06-007. August
2006.
USEPA. 2007a. Toxicological Review of 1,1,1-Trichloroethane (CAS No.
71-55-6): In Support of Summary Information on the Integrated Risk
Information System (IRIS). National Center for Environmental
Assessment, Office of Research and Development: Washington, DC. EPA-
635-R-03-013. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0197tr.pdf
USEPA. 2007b. Simultaneous Compliance Guidance Manual for the Long-
Term 2 and Stage 2 DBP Rules. EPA 815-R-07-017. March 2007.
USEPA. 2008a. Carbofuran. HED Revised Risk Assessment for the Notice
of Intent to Cancel (NOIC). PC 090601. DP# 347038. https://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2007-1088-0034
USEPA. 2008b. Total Coliform Rule/Distribution System (TCRDS)
Federal Advisory Committee. Agreement in Principle. Available online
at: https://www.epa.gov/sites/production/files/2015-10/documents/total_coliform_rule_distribution_system_advisory_committee_agreement_in_principle_pdf.pdf.
USEPA. 2009a. Analytical Feasibility Support Document for the Second
Six-Year Review of Existing National Primary Drinking Water
Regulations. EPA 815-B-09-003. October 2009.
USEPA. 2010a. Agency Information Collection Activities; Submission
to OMB for Review and Approval; Comment Request; Contaminant
Occurrence Data in Support of EPA's Third Six-Year Review of
National Primary Drinking Water Regulations (Renewal); EPA ICR No.
2231.02, OMB Control No. 2040-0275. 75 FR 6023. February 5, 2010.
USEPA. 2010b. Fluoride: Dose Response Analysis for Non-Cancer
Effects. EPA 820-R-10-019. December 2010.
USEPA. 2010c. Fluoride: Exposure and Relative Source Contribution
Analysis. EPA 820-R-10-015. December 2010.
USEPA. 2010d. Integrated Risk Information System (IRIS):
Toxicological Review of cis-1,2-Dichloroethylene and trans-1,2-
Dichloroethylene in Support of Summary Information. National Center
for Environmental Assessment, Office of Research and Development:
Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0418tr.pdf
USEPA. 2010e. Integrated Risk Information System (IRIS):
Toxicological Review of Hydrogen Cyanide and Cyanide Salts in
Support of Summary Information. National Center for Environmental
Assessment, Office of Research and Development: Washington, DC.
https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0060tr.pdf
USEPA. 2010f. Long Term 2 Enhanced Surface Water Treatment Rule
Toolbox Guidance Manual. EPA 815-R-09-016. April 2010.
USEPA. 2010g. Memorandum: Updated toxicity endpoints for oxamyl.
Office of Chemical Safety and Pollution Prevention, Washington, DC.
https://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0028-
0011
USEPA. 2010h. National Primary Drinking Water Regulations;
Announcement of the Results of EPA's Review of Existing Drinking
Water Standards and Request for Public Comment and/or Information on
Related Issues. 75 FR 15500. March 29, 2010.
USEPA, 2011. Improving our Regulations: Final Plan for Periodic
Retrospective Review of Existing Regulations. Available online at:
https://www.epa.gov/sites/production/files/2015-09/documents/eparetroreviewplan-aug2011_0.pdf
USEPA. 2012. Economic Analysis for the Final Revised Total Coliform
Rule. EPA 815-R-12-004. September 2012.
USEPA. 2013a. 40 CFR parts 141 and 142; National Primary Drinking
Water Regulations; Revisions to the Total Coliform Rule; Final Rule.
78 FR 10270. February 13, 2013.
USEPA. 2013b. Human Health Risk Assessment for a Proposed Use of
2,4-D Choline on Herbicide-Tolerant Corn and Soybean. Office of
Chemical Safety and Pollution Prevention. https://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2014-0195-0007
USEPA. 2014a. Design Manual: Removal of Fluoride from Drinking Water
Supplies by Activated Alumina. EPA/600/R-14/236. March 2014.
USEPA. 2014b. Announcement of Preliminary Regulatory Determinations
for Contaminants on the Third Drinking Water Contaminate Candidate
List; Proposed Rule. 79 FR 62715. October 20, 2014.
USEPA. 2015a. Peer Review Handbook 4th Edition. October 2015.
Available online at: https://www.epa.gov/sites/production/files/2015-10/documents/epa_peer_review_handbook_4th_edition_october_2015.pdf.
USEPA. 2015b. Revisions to the Unregulated Contaminant Monitoring
Rule (UCMR4) for Public Water Systems and Announcement of a Public
Meeting. 70 FR 76897. December 11, 2015. Available online at:
https://www.epa.gov/sites/production/files/2015-11/documents/ucmr4_proposal_151130.pdf.
USEPA. 2016a. Analytical Feasibility Support Document for the Third
Six-Year Review of National Primary Drinking Water Regulations:
Chemical Phase Rules and Radionuclides Rules. EPA-810-R-16-005.
USEPA. 2016b. Chemical Contaminant Summaries for the Third Six-Year
Review of Existing National Primary Drinking Water Regulations. EPA-
810-R-16-004.
USEPA. 2016c. Consideration of Other Regulatory Revisions in Support
of the Third Six-Year Review of the National Primary Drinking Water
Regulations: Chemical Phase Rules and Radionuclides Rules. EPA-810-
R-16-003.
USEPA. 2016d. Development of Estimated Quantitation Levels for the
Third Six-Year Review of National Primary Drinking Water Regulations
(Chemical Phase Rules). EPA-810-R-16-002.
USEPA. 2016e. Occurrence Analysis for Potential Source Waters for
the Third Six-Year Review of National Primary Drinking Water
Regulations. EPA-810-R-16-008.
USEPA. 2016f. EPA Protocol for the Third Review of Existing National
Primary Drinking Water Regulations. EPA-810-R-16-007.
USEPA. 2016g. Spring 2016 Regulatory Agenda, Semiannual regulatory
flexibility agenda and semiannual regulatory agenda. 81 FR 37374.
June 9, 2016.
USEPA. 2016h. Six-Year Review 3--Health Effects Assessment for
Existing Chemical and Radionuclides National Primary Drinking Water
Regulations--Summary Report. EPA-822-R-16-008.
USEPA. 2016i. Six-Year Review 3 ICR Database.
USEPA, 2016j. Occurrence Data for the Unregulated Contaminant
Monitoring Rule. July 2016.

[[Page 3552]]

USEPA. 2016k. Six-Year Review 3 Technical Support Document for
Chlorate. EPA-810-R-16-013.
USEPA. 2016l. Six-Year Review 3 Technical Support Document for
Disinfectants/Disinfection Byproducts Rules. EPA-810-R-16-012.
USEPA. 2016m. Six-Year Review 3 Technical Support Document for Long-
Term 2 Enhanced Surface Water Treatment Rule. EPA-810-R-16-011.
USEPA. 2016n. Six-Year Review 3 Technical Support Document for
Microbial Contaminant Regulations. EPA-810-R-16-010.
USEPA. 2016o. Six-Year Review 3 Technical Support Document for
Nitrosamines. EPA-810-R-16-009.
USEPA. 2016p. The Analysis of Regulated Contaminant Occurrence Data
from Public Water Systems in Support of the Third Six-Year Review of
National Primary Drinking Water Regulations: Chemical Phase Rules
and Radionuclides Rules. EPA-810-R-16-014.
USEPA. 2016q. The Data Management and Quality Assurance/Quality
Control (QA/QC) Process for the Third Six-Year Review Information
Collection Rule Dataset. EPA-810-R-16-015.
USEPA. 2016r. Technologies for Legionella Control in Premise
Plumbing Systems: Scientific Literature Review. EPA-810-R-16-001.
September 2016.
USEPA. 2016s. Support Document for Third Six Year Review of Drinking
Water Regulations for Acrylamide and Epichlorohydrin. EPA 810-R-16-
019.
USEPA and Water Research Foundation. 2016. Summary Document: State
of Research on High-Priority Distribution System Issues.
U.S. Food and Drug Administration (FDA). 2015. Letter to
Manufacturers, Distributors, or Importers of Bottled Water with an
Update on Fluoride Added to Bottled Water. Available online at:
https://www.fda.gov/food/guidanceregulation/guidancedocumentsregulatoryinformation/bottledwatercarbonatedsoftdrinks/ucm444373.htm
U.S. Geological Survey (USGS). 2004. Digital Engineering Aspects of
Karst Map: A GIS Version of Davies, W.E., Simpson, J.H., Ohlmacher,
G.C., Kirk, W.S., and Newton, E.G., 1984, Engineering Aspects of
Karst: U.S. Geological Survey, National Atlas of the United States
of America, Scale 1:7,500,000. Open-File Report 2004-1352, version
1. Available online only at: https://pubs.usgs.gov/of/2004/1352/.
Villanueva, C.M., F. Fernandez, N. Malats, J.O. Grimalt, and M.
Kogenvinas. 2003. Meta-analysis of studies on individual consumption
of chlorinated drinking water and bladder cancer. Journal of
Epidemiology Community Health. 57: 166-173.
Villanueva, C.M., K.P. Cantor, S. Cordier, J.J.K. Jaakkola, W.D.
King, C.F. Lynch, S. Porru, and M. Kogevinas. 2004. Disinfection
byproducts and bladder cancer a pooled analysis. Epidemiology.
15(3): 357-367.
Villanueva, C.M., K.P. Cantor, J.O. Grimalt, N. Malats, D.
Silverman, A. Tardon, R. Garcia-Closas, C. Serra, A. Carrato, G.
Castano-Vinyals, R. Marcos, N. Rothman, F.X. Real, M. Dosemeci, and
M. Kogevinas. 2007. Bladder cancer and exposure to water
disinfection by-products through ingestion, bathing, showering, and
swimming in pools. American Journal of Epidemiology. 165(2): 148-
156.
Wahman, D.G. and J.G. Pressman. 2015. Distribution system
residuals--is ``detectable'' still acceptable for chloramines.
Journal of the American Water Works Association. 107(8): 53-63.
Walfoort, C., M.J. Messina, and D. Miner. 2008. Storage tank
aeration eliminates trihalomethanes. Opflow. 34(5): 28-29.
Walker, J.T. and M. Morales. 1997. Evaluation of chlorine dioxide
(ClO2) for the control of biofilms. Water Science and Technology.
35(11-12): 319-323.
Wallender, E.K., E.C. Ailes, J.S. Yoder, V.A. Roberts, and J.M.
Brunkard. 2014. Contributing factors to disease outbreaks associated
with untreated ground water. Ground Water. 52(6): 886-897.
Wang, H., S. Masters, Y. Hong, J. Stallings, J.O. Falkinham, M.A.
Edwards, and A. Pruden. 2012. Effect of disinfectant, water age, and
pipe material on occurrence and persistence of Legionella,
mycobacteria, Pseudomonas aeruginosa, and two amoebas. Environmental
Science & Technology. 46(21): 11566-11574.
Weiss, W.J., S.C. Schindler, S. Freud, J.A. Herzner, K.F. Hoek, B.A.
Wright, D.A. Reckhow, and W.C. Becker. 2013. Minimizing raw water
NOM concentration through optimized source water selection. Journal
of the American Water Works Association. 105(10): 73-74.
Westerhoff, P., H. Jang, M. Abbaszadegan, and A. Absar. 2010.
Organic chloramine formation and influence on disinfection efficacy
and nitrification. Water Research Foundation.

[National Primary Drinking Water Regulations; Announcement of the
Results of EPA's Review of Existing Drinking Water Standards and
Request for Public Comment and/or Information on Related Issues; page
140 of 140.]

Westerhoff, P., S. Lee, Y. Yang, G.W. Gordon, K. Hristovski, R.U.
Halden, and P. Herckes. 2015. Characterization, recovery
opportunities, and valuation of metals in municipal sludges from US
wastewater treatment plants nationwide. Environmental Science &
Technology. 49(16): 9479-9488.
World Health Organization (WHO). 2008. ``Safety Evaluation of
Certain Food Additives and Contaminants.'' International Programme
on Chemical Safety. Prepared for the 68th meeting of the Joint FAO/
WHO Expert Committee on Food Additives (JEFCA).
Writer, J.H., A. Hohner, J. Oropeza, A. Schmidt, K.M. Cawley, and
F.L. Rosario-Ortiz. 2014. Water treatment implications after the
High Park Wildfire, Colorado. Journal of the American Water Works
Association. 106(4): 189-199.
Yan, M., D. Wang, J. Ni, J. Qu, C.W. Chow, and H. Liu. 2008.
Mechanism of natural organic matter removal by polyaluminum
chloride: effect of coagulant particle size and hydrolysis kinetics.
Water Research. 42(13): 3361-3370.
Yang, Y., Y. Komaki, S. Kimura, H. Hu, E. Wagner, B. Marinas, and M.
Plewa. 2014. Toxic impact of bromide and iodide on drinking water
disinfected with chlorine or chloramines. Environmental Science &
Technology. 48(20): 12362-12369.
Zhang, K-J., N-Y. Gao, Y. Deng, T. Zhang, and C. Li. 2012. Aqueous
Chlorination of Algal Odorants: Reaction Kinetics and Formation of
Disinfection By-products. Separation and Purification Technology.
92: 93-99.

Dated: December 20, 2016.
Gina McCarthy,
Administrator.
[FR Doc. 2016-31262 Filed 1-10-17; 8:45 am]
BILLING CODE 6560-50-P

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.