Emergency Planning and Notification; Emergency Planning and List of Extremely Hazardous Substances and Threshold Planning Quantities, 21299-21311 [2011-9096]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 76, Number 73 (Friday, April 15, 2011)]
[Proposed Rules]
[Pages 21299-21311]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-9096]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 355

[EPA-HQ-SFUND-2010-0586; FRL-9295-6]
RIN 2050-AF08


Emergency Planning and Notification; Emergency Planning and List 
of Extremely Hazardous Substances and Threshold Planning Quantities

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing to revise the manner by which the regulated 
community would apply the threshold planning quantities (TPQs) for 
those extremely hazardous substances (EHSs) that are non-reactive solid 
chemicals in solution form. Specifically, facilities with a solid EHS 
in solution would be subject to the Emergency Planning requirements if 
the amount of the solid chemical on-site, when multiplied by 0.2, 
equaled or exceeded the lower published TPQ, based on data that shows 
less potential for the solid chemical in solution to remain airborne in 
the event of an accidental release. Previously, EPA assumed that 100% 
of the chemical could become airborne in the event of an accidental 
release.

DATES: Comments must be submitted on or before June 14, 2011.

[[Page 21300]]


ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
SFUND-2010-0586, by one of the following methods:
     https://www.regulations.gov: Follow the online instructions 
for submitting comments.
     E-mail: superfund.docket@epa.gov.
     Fax: (202) 566-9744.
     Mail: Superfund Docket, Environmental Protection Agency, 
Mail code: [2822T], 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: EPA West, Room 3334, 1301 Constitution 
Ave., NW., Washington, DC. Such deliveries are only accepted during the 
Docket's normal hours of operation, and special arrangements should be 
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-SFUND-
2010-0586. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
https://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or e-mail. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through https://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket, visit the EPA Docket Center homepage at https://www.epa.gov/epahome/dockets.htm. For additional instructions on submitting 
comments, go to Section I.B of the SUPPLEMENTARY INFORMATION section of 
this document.
    Docket: All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
https://www.regulations.gov/or in hard copy at the Superfund Docket, 
EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, 
DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Superfund Docket is (202) 566-0276.

FOR FURTHER INFORMATION CONTACT: Kathy Franklin, Office of Emergency 
Management, Mail Code 5104A, U.S. Environmental Protection Agency, 1200 
Pennsylvania Avenue, NW., Washington, DC 20460-0002; telephone number: 
(202) 564-7987; fax number: (202) 564-2625; e-mail address: 
franklin.kathy@epa.gov. You may also contact the Superfund, TRI, EPCRA, 
RMP and Oil Information Center at (800) 424-9346 or (703) 412-9810 (in 
the Washington, DC metropolitan area). The Telecommunications Device 
for the Deaf (TDD) number is (800) 553-7672 or (703) 412-3323 (in the 
Washington, DC metropolitan area). You may wish to visit the Office of 
Emergency Management (OEM) Internet site at www.epa.gov/emergencies/content/epcra.

SUPPLEMENTARY INFORMATION: Here are the contents of today's preamble.

I. General Information
    A. Who is affected by this proposed rule?
    B. What should I consider as I prepare my comments for EPA?
    C. What is the statutory authority for this proposed rule?
    D. What is the background for this proposed rule?
II. Summary of This Action
    A. What is the scope of this proposed rule?
    B. What is EPA's rationale for proposing the TPQ changes?
    C. What alternative approaches were considered?
    D. What are the peer review results?
    E. What are the economic impacts of the TPQ changes?
    III. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Energy Effects
    I. National Technology Transfer and Advancement Act (``NTAA'')
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Who is affected by this proposed rule?

    Entities that would be affected by this proposed rule are those 
organizations and facilities subject to section 302 of the Emergency 
Planning and Community Right-to-Know Act (EPCRA) and its implementing 
regulations found in 40 CFR part 355, subpart B--Emergency Planning. To 
determine whether your facility is affected by this action, you should 
carefully examine the applicability provisions at 40 CFR part 355. If 
you have questions regarding the applicability of this action to a 
particular entity, consult the person listed in the preceding FOR 
FURTHER INFORMATION CONTACT section.

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

    Tips for Preparing Your Comments. When submitting comments remember 
to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register date and 
page number).
     Follow directions--The Agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree, suggest alternatives, 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible.
     Make sure to submit your comments by the comment period 
deadline identified.

[[Page 21301]]

C. What is the statutory authority for this proposed rule?

    This proposed rule is being issued under the Emergency Planning and 
Community Right-to-Know Act of 1986 (EPCRA), which was enacted as Title 
III of the Superfund Amendments and Reauthorization Act of 1986 (Pub. 
L. 99-499), (SARA). The Agency relies on EPCRA section 328 for general 
rulemaking authority.

D. What is the background of this proposed rule?

    Title III of SARA (EPCRA) establishes authorities for emergency 
planning and preparedness, emergency release notification reporting, 
community right-to-know reporting, and toxic chemical release 
reporting. It is intended to encourage state and local planning for, 
and response to releases of, hazardous substances and to provide the 
public, local governments, fire departments, and other emergency 
officials with information concerning potential chemical hazards 
present in their communities. The implementing regulations for 
emergency planning, emergency release notification and the chemicals 
subject to these regulations (extremely hazardous substances (EHSs)) 
are codified in 40 CFR part 355. The implementing regulations for 
community right-to-know reporting (or hazardous chemical reporting) are 
codified in 40 CFR part 370.
    Subtitle A of EPCRA establishes the framework for local emergency 
planning. The statute requires that EPA publish a list of EHSs. The 
EHSs list was established by EPA to identify chemical substances which 
could cause serious irreversible health effects from accidental 
releases (52 FR 13378). The Agency was also directed to establish 
threshold planning quantities (TPQs) for each extremely hazardous 
substance.
    Under EPCRA section 302, a facility which has an EHS in excess of 
its TPQ on-site must notify the State Emergency Response Commission 
(SERC) and Local Emergency Planning Committee (LEPC), as well as 
participate in local emergency planning activities. Under EPCRA section 
304, the facility owner or operator must report accidental releases of 
EHSs and hazardous substances listed under the Comprehensive 
Environmental Response, Compensation, and Liability Act (CERCLA) listed 
in 40 CFR 302.4 in excess of the reportable quantity (RQ) to the LEPC 
and SERC. Under EPCRA section 311 and 312, facilities which have a 
hazardous chemical defined under the Hazard Communication Standards 
(HCS) of the Occupational Safety and Health Act (OSHA) at or above 
10,000 pounds or an EHS at or above its TPQ or 500 pounds, whichever is 
lower, are required to submit an Emergency and Hazardous Chemical 
Inventory form and Material Safety Data Sheet (MSDS) for that chemical 
to their SERC, LEPC and local fire department.
    The purpose of the EHSs list is to focus initial efforts in the 
development of state and local contingency plans. Inclusion of a 
chemical on the EHSs list does not mean state or local communities 
should ban or otherwise restrict use of a listed chemical. Rather, such 
identification indicates a need for the community to undertake a 
program to investigate and evaluate the potential for accidental 
exposure associated with the production, storage or handling of the 
chemical at a particular site and develop a chemical emergency response 
plan around those risks.
1. Regulatory Background
    The list of EHSs and their TPQs are codified in 40 CFR part 355, 
Appendices A & B. EPA first published the EHSs list and TPQs along with 
the methodology for determining TPQs as an interim final rule on 
November 17, 1986 (51 FR 41570). In the final rule of April 22, 1987 
(52 FR 13378), EPA made a number of revisions. Among other things, the 
final rule republished the EHSs list, added four new chemicals and 
revised the methodology for some TPQs. The final rule also defined TPQs 
for EHS solids in solution, based on comments on the interim final 
rule. Details of the methodology used in determining whether to list a 
substance as an EHS and deriving the TPQs are found in the November 
1986 and April 1987 Federal Register notices and in the technical 
support documents in the rulemaking record (``Threshold Planning 
Quantities Technical Support Document''; ``Chemicals That Were Assigned 
Threshold Planning Quantities Different From the Calculated Index 
Value''; ``Reactive Solids Whose Threshold Planning Quantities Should 
Be Less than 10,000 Pounds''; ``Changes Made to Threshold Planning 
Quantities Between Proposed Rule and Final Rule'': all dated April 7, 
1987, and ``Technical Support Document for Determination of Levels of 
Concern,'' November 11, 1986). These documents are found in the docket 
for this rulemaking.
    EPA has since amended the EHSs list and deleted 51 chemicals. Ten 
chemicals were deleted based on the request of petitioners and the 
remaining 41 chemicals were deleted as a result of Agency review. The 
chemicals were deleted because they did not meet the toxicity criteria 
for the list and/or were originally listed in error. Petitions 
requesting deletion of two chemicals, paraquat dichloride (which is 
discussed below) and isophorone diisocyante have been denied. 
Isophorone diisocyanate was not deleted from the EHSs list because its 
inhalation toxicity met the EHSs listing criteria.
    EPA has also changed the TPQs for some of the EHSs. In the April 
22, 1987 final rule, EPA reduced the TPQs for 36 substances, while it 
raised the TPQs for 12 substances based on updated acute toxicity data. 
Since then, EPA has lowered the TPQ for muscimol because of a 
typographical error in a prior rulemaking; EPA has raised the TPQ for 
isophorone diisocyanate because it was mistakenly based on a physical 
state of reactive solid, when it is actually a liquid; and EPA has 
denied a petition to raise the TPQs for azinphos methyl and fenamiphos.
    After a final rule was published on November 3, 2008 (73 FR 65452) 
which revised the footnotes to Appendix A and B, EPA found some 
printing errors in the Appendix A and B tables of the CFR affecting 11 
EHS listings. This November 3, 2008 rule did not add, delete or revise 
any of the EHS names, RQs or TPQs. For the eleven EHSs listings, their 
RQ and TPQ values are correct, but just appear under the wrong column 
heading in the table and one EHS chemical name mistakenly appears in 
CAS No. column. The errors do not appear in the November 3, 2008 FR 
notice, but only in the 2009 and 2010 versions of the CFR. These errors 
to the CFR will be corrected in a future effort.
2. Petition for Paraquat Dichloride
    Paraquat dichloride was originally listed as paraquat with a CAS 
No. 1910-42-5 on the final EHSs list. The lower TPQ was set at 10 
pounds for paraquat dichloride with a particle size less than 100 
microns in diameter, in molten form or as a solid in solution. The 
higher TPQ was set at 10,000 pounds for a particle size equal to or 
greater than 100 microns in diameter. ICI Americas submitted a petition 
in October 1989 that requested the Agency to remove paraquat from the 
EHSs list or alternatively, revise the TPQ. The TPQ for paraquat was 
based on an Immediately Dangerous to Life and Health (IDLH) value of 
1.5 milligrams per cubic meter (mg/m\3\). The petitioner requested that 
EPA base the TPQ on the LD50 or LC50 test results 
rather than the IDLH level. LD50 is the median lethal dose 
via dermal exposure or ingestion, defined as the dose at which 50 
percent of the test animals died during exposure. LC50 is 
the median lethal concentration, defined as the concentration level at 
which 50

[[Page 21302]]

percent of the test animals died when exposed by inhalation within the 
stated study time. ICI Americas also noted that the CAS No. 1910-42-5 
represented the chemical paraquat dichloride, not the paraquat cation, 
which can form many different salts.
    On October 12, 1994 (59 FR 51816), EPA denied the petition to 
delete paraquat or modify the TPQ, but changed the listed chemical name 
from paraquat to paraquat dichloride. The oral toxicity for paraquat 
dichloride met the listing criteria based on the paraquat ion only, but 
did not meet the listing criteria based on total paraquat dichloride 
weight. Therefore, EPA changed the basis of the listing from an oral 
LD50 of 22 milligrams paraquat ion per kg of body weight 
(mg/kg) to an inhalation LC50 of 0.00138 milligrams paraquat 
dichloride per liter of air (mg/L). Because this inhalation toxicity 
met the EHSs listing criteria, paraquat dichloride was not deleted from 
the EHSs list. Further explanation of EPA's rationale for denying the 
petition can be found in the October 12, 1994 final rule (59 FR 51816).
3. Zeneca's Request To Reconsider the Paraquat Dichloride Petition
    In November 1999, Zeneca (formerly ICI Americas) requested that EPA 
reconsider either removing paraquat dichloride from the EHSs list or 
raising its TPQ. Zeneca claimed that the form of the chemical used in 
inhalation toxicity tests (temporarily atomized powder under laboratory 
conditions) is not relevant data to use for listing paraquat 
dichloride. Zeneca believed that it was highly unlikely that inhalable 
particles or vapors of paraquat dichloride could become airborne during 
an accidental release. Zeneca did not agree with the rationale EPA used 
to assign a TPQ of 10 pounds to paraquat dichloride, which is only 
manufactured, processed and used in solution form. Zeneca claimed that 
EPA did not explain why a greater potential for airborne dispersion for 
solids in solution exists as opposed to liquid chemicals.
    On October 11, 2000, Syngenta (formerly Zeneca) filed an action in 
U.S. District Court for the District of Columbia under the 
Administrative Procedures Act seeking judicial review of EPA's 
decisions regarding paraquat dichloride. In this complaint, Syngenta 
requested EPA to either delete paraquat dichloride from the EHSs list 
or raise its TPQ. On January 23, 2003, EPA filed a Motion for Voluntary 
Remand in order to reconsider the petition. The court granted EPA's 
motion and dismissed Syngenta's complaint on January 31, 2003. By order 
of February 24, 2003, the court denied Syngenta's Motion to Amend 
Judgment. EPA again reviewed the request to delete paraquat dichloride 
and/or to raise its TPQ. In a November 21, 2003 letter to the 
petitioner, EPA reaffirmed its denial to delete paraquat dichloride 
from the EHSs list. EPA concluded that the acute toxicity of paraquat 
dichloride meets the criteria for listing it as an EHS chemical. In the 
same letter to the petitioner, however, EPA agreed to consider a 
revision to the TPQ for paraquat dichloride in the context of a 
proposed rule to amend the TPQ for all EHS chemicals handled as solids 
in solution. This letter is in the docket for today's rulemaking.

II. Summary of This Action

A. What is the scope of this proposed rule?

    The scope of this proposed rule is to revise the manner by which 
the regulated community would apply the TPQ for EHS chemicals that are 
handled as solids in solution. There are 157 EHS chemicals that are 
non-reactive solids at ambient temperature, which could potentially be 
affected by this change, if they are handled by facilities in a 
solution form. The affected chemicals are identified in Appendix C in 
the ``Technical Support Document for Revised TPQ Method for Solids in 
Solution,'' which is in the Docket to this rulemaking. These 157 
chemicals appear with two TPQs, (the higher TPQ is 10,000 pounds) in 
Appendix A and B of 40 CFR part 355. However, this change will not 
apply to the 12 solid EHS chemicals that are reactive solids (noted by 
footnote ``a'' in Appendix A and B of 40 CFR part 355). Reactive solids 
are highly reactive with air or water or are explosive. Because of 
this, they are more likely than other solids to be dispersed into the 
air due to the energy or heat created when they react. Other reactive 
solids form toxic gases when they react with air or water. The 
explanation for not assigning a 10,000 pound TPQ to each of the 
reactive solids is discussed in the document, ``Reactive Solids Whose 
Threshold Planning Quantities Should Be Less Than 10,000 Pounds,'' 
April 7, 1987, which can be found in the docket to this rulemaking.
    Additionally, the proposed methodology of applying TPQs for solids 
in solution does not affect the reporting requirements for Sections 311 
and 312 of EPCRA (40 CFR part 370). Specifically, emergency planning 
notification under Section 302 helps LEPCs identify those facilities 
whose accidental releases pose risks to the surrounding community so 
they can develop emergency plans that identify the location and number 
of affected populations, evacuation or shelter-in-place procedures, 
etc. On the other hand, Sections 311 and 312 require submission of 
MSDSs and an on-site inventory of hazardous chemicals to help emergency 
responders assess how to respond to an emergency release or fire. 
Responders need the amounts, manner of storage and locations of the 
chemical on-site, not only the amount released off-site. They need 
information on the chemical and physical properties, hazard ratings, 
toxicity information and incompatibilities of the chemical, as well as 
measures needed to contain the spill or fire at the facility. They need 
to know what type of protective equipment is needed to protect them 
from exposure, not only airborne, but dermal.
    Solid EHSs (except reactive solids) have a 10,000 pound TPQ or a 
specified lower TPQ for certain forms. For purposes of complying with 
the emergency planning notification requirements of Section 302 of 
EPCRA, EPA is proposing that facilities multiply the amount of EHS 
chemical handled as a solid in solution on-site by 0.2 and then 
determine if this amount equals or exceeds the established lower TPQ. 
If the amount of the solid EHS in solution on-site multiplied by 0.2 
does not equal or exceed the lower TPQ for that solid EHS, then the 
facility is not subject to the EPCRA Section 302 emergency planning 
notification requirements for that substance. This amount includes only 
the weight of the chemical and not the solvent or other chemicals in 
solution. The amount of solid in solution may be determined by 
multiplying the weight percent of the solid in solution in a particular 
container by the weight of the solution. Solutions include aqueous or 
organic solutions, slurries, viscous solutions, suspensions, emulsions, 
and pastes. The revised TPQ methodology for solids in solution is 
similar to the use of the TPQ for EHS chemicals that are molten 
solids.\1\
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    \1\ The TPQ for EHSs that are in a molten form on-site is 
calculated by multiplying the weight of the chemical by 0.3 to 
determine if the lower TPQ is met or exceeded.
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    The emergency release notification requirements under EPCRA Section 
304 are not affected by this proposal. Section 304 requires facilities 
to notify the community emergency coordinator for the LEPC of any area 
likely to be affected by the release and the SERC of any area likely to 
be affected by the release (defined in 40 CFR 355.42) at or above the 
reportable quantity (RQ) of

[[Page 21303]]

any EHS or CERCLA hazardous substance. The RQ is not the same as the 
TPQ. TPQs are based on acute mammalian toxicity and potential for 
airborne dispersion. RQs, on the other hand, are developed using 
several criteria, including aquatic toxicity, mammalian toxicity, 
ignitability, reactivity, chronic toxicity, potential carcinogenicity, 
biodegradation, hydrolysis, and photolysis (50 FR 13468, April 4, 
1985).
    As an example, a facility has 4,000 pounds of a solution of 37% by 
weight paraquat dichloride on-site. Therefore, this solution contains 
1,480 pounds of paraquat dichloride (0.37 x 4,000 pounds). The facility 
would multiply 1,480 pounds by 0.2 which equals 296 pounds. This amount 
is then compared to the TPQ for paraquat dichloride, which is 10 
pounds. Because this amount exceeds the 10 pound TPQ, the facility is 
required to comply with the emergency notification requirements of 
Section 302 of EPCRA. As another example, a facility has 10 gallons of 
a solution of 37% by weight paraquat dichloride on-site. The density of 
the solution is 9.33 pounds per gallon. Therefore, this solution 
contains 34.5 pounds of paraquat dichloride (10 gal x 9.33 lb/gal x 
0.37). The facility would multiply 34.5 pounds by 0.2 which equals 6.9 
pounds. This amount is then compared to the TPQ for paraquat 
dichloride, which is 10 pounds. Because this amount is less than the 10 
pound TPQ, the facility is not required to comply with the emergency 
notification requirements of Section 302 of EPCRA.
    Facilities that handle both the powdered and solution forms of a 
particular solid EHS will have to consider the quantities of each form 
and the particle size to determine whether they exceed a TPQ. Below are 
several examples of how to apply the revised TPQ methods in various 
cases.\2\
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    \2\ For these examples, the EHS is not paraquat dichloride, but 
an unspecified solid EHS.
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    Solid in solution exceed lower TPQ, powder below 10,000 pounds. A 
facility has 5,000 pounds of a pure EHS powder form on-site which is 
less than the 10,000 pound TPQ. However, they have 1,000 gallons of a 
35% by weight EHS solid in solution with a density of 9 pounds per 
gallon. The amount of solids in solution on-site is 3,150 pounds (1000 
gallons x 9 pounds per gallon x 0.35). Multiplying the 3,150 pounds of 
solid in solution by 0.2 equates to 630 pounds, which exceeds the lower 
TPQ of 500 pounds. Thus, the facility must report under Section 302 of 
EPCRA based on exceeding the lower TPQ for the solid in solution form.
    Solid in solution below lower TPQ, powder exceeds 10,000 pounds. A 
facility has 11,000 pounds of a pure EHS solid powder on-site which is 
more than the 10,000 pound TPQ. They also have 2,000 gallons of a 10% 
by weight EHS solid in solution with a density of 9 pounds per gallon. 
The amount of solids in solution on-site is 1,800 pounds (2,000 gallons 
x 9 pounds per gallon x 0.10). Multiplying the 1,800 pounds of solid in 
solution by 0.2 equates to 360 pounds, which is less than the lower TPQ 
of 500 pounds. Thus, the facility must report under Section 302 of 
EPCRA based on exceeding the 10,000 pound TPQ for the solid in powder 
form.
    Solid in solution below lower TPQ, powder below 10,000 pounds. A 
facility has 5,000 pounds of a pure EHS solid powder which is less than 
the 10,000 pound TPQ. They also have 1,500 gallons of a 15% by weight 
EHS solid in solution with a density of 9 pounds per gallon. The amount 
of solids in solution on-site is 2,025 pounds (1.500 gallons x 9 pounds 
per gallon x 0.15). Multiplying the 2,025 pounds of solid in solution 
by 0.2 equates to 405 pounds, which is less than the lower TPQ of 500 
pounds. Thus, the facility is not required to report under Section 302 
of EPCRA because it does not exceed the lower 500 pound TPQ for the 
solid in solution form or the 10,000 pound TPQ for the powder with 
particle size greater than 100 microns.
    Powdered product less than 100 microns, processed into solution. If 
the same amounts of solid EHS were involved as the same scenarios 
above, except the powder has a particle size of less than 100 microns, 
then the lower 500 pound TPQ would apply to the powder instead of the 
10,000 pounds. If either the amount of powder or solid in solution 
exceeds the lower TPQ, the facility would be required to report under 
Section 302 of EPCRA.
    EPA is proposing this change based on data in the literature that 
shows the original assumption of 100% potential airborne release for 
solids in solution is inappropriate because it appears to overestimate 
the amount of chemical that would remain airborne after release. Review 
of the literature for accidental releases of liquid aerosols suggests a 
new methodology for applying the TPQs for solids in solution is 
warranted. The data shows that no more than 20% of the release is 
expected to remain airborne. More detailed discussion can be found in 
Section II.B.4.a of this preamble and in the technical support document 
in the docket to this proposed rule.
    EPA's revised TPQ methodology for EHS solids in solution and 
supporting data was peer reviewed and the technical support document 
was revised based on peer review comments. The results of the peer 
review and response to peer review comments are found in a separate 
document, ``Peer Review of Technical Support Document for Revised TPQ 
Method for EHS Solids in Solution,'' which is available in the docket 
to this rulemaking. A summary of the peer reviewer's comments and EPA 
responses to them are presented in Section II.D of this preamble.

B. What is EPA's rationale for the TPQ changes?

1. Development of Existing TPQs
    The TPQs were initially assigned based on a ranking scheme using a 
Level of Concern (LOC) based on acute toxicity and the potential for 
airborne dispersion. The TPQ methodology is described in detail in the 
``Threshold Planning Quantities Technical Support Document'' dated 
April 7, 1987, which can be found in the docket for this rulemaking. 
For each chemical, a ranking index was calculated which equaled the LOC 
divided by an air dispersion factor (V). For gases, V = 1, while for 
liquids, V was based on a volatilization model using the molecular 
weight and boiling point of the chemical.
    Solid EHS chemicals with a particle size less than 100 microns in 
diameter, molten solids, solids in solution, and solids with a National 
Fire Protection Association (NFPA) reactivity rating of 2, 3, or 4 were 
assigned a V equal to 1. If the EHS solid does not have a particle size 
less than 100 microns, is not molten or handled in solution form, and 
does not have an NFPA reactivity rating of 2, 3, or 4, then the EHS 
chemical was assigned a TPQ of 10,000 pounds, which corresponds to the 
highest index value. Solids with an NFPA reactivity rating of 2, 3, or 
4 are noted with footnote ``b'' in the EHSs list.
    Between one and 10,000 pounds, chemicals were assigned to the 
intermediate TPQ categories of 10, 100, 500 or 1,000 pounds based on 
the order of magnitude ranges of the index values. Also, for solids in 
molten form, before applying the TPQ, the amount of chemical on-site at 
any time is multiplied by an adjustment factor of 0.3 to conservatively 
account for the maximum volatilization of the spilled molten substance 
that is likely to take place.

[[Page 21304]]

2. Petitioner's Arguments for Changing Paraquat Dichloride's TPQ
    In their complaint, Syngenta did not agree with EPA's rationale to 
assign a lower TPQ of 10 pounds to paraquat dichloride, which is only 
manufactured, processed and used in solution form. Syngenta claimed 
that EPA did not explain why it assumed a greater potential for 
airborne dispersion for solids in solution as opposed to liquid 
chemicals. In addition, Syngenta argued that Paraquat Dichloride 
solution is basically a non-volatile salt dissolved in water, and that 
the physical and chemical characteristics of many solids like paraquat 
dichloride limit their capacity to become airborne. Pure paraquat 
dichloride has a very low vapor pressure and decomposes at about 
340[deg] Celsius (C) before it reaches a boiling point. Syngenta 
further argued that using a liquid volatilization model to set a TPQ 
for paraquat dichloride is inappropriate.\3\ Moreover, Syngenta stated 
that ``the laws of physics preclude the possibility of a release of 
paraquat dichloride becoming completely airborne. Regardless of the 
emergency release scenario (extreme temperature, explosion, etc.), the 
amount to become airborne would not only be less than 100%, it would be 
virtually zero.'' Syngenta also stated that although paraquat 
dichloride can be temporarily atomized under laboratory conditions for 
testing animals, they do not believe that inhalable particles or vapors 
of paraquat dichloride can become airborne during an accidental 
release.
---------------------------------------------------------------------------

    \3\ EPA agrees with the petitioner that using the liquid 
volatilization model to set a TPQ for paraquat dichloride, whether 
handled as a pure chemical or in solution, is inappropriate. 
However, the TPQ for paraquat dichloride was not set using the 
volatilization method.
---------------------------------------------------------------------------

    In discussions with EPA, Syngenta also raised the issue of aerosol 
size as a factor to be considered in developing the TPQ methodology for 
EHS solids in solution.
3. Basis for Existing Solids in Solution TPQs
    In the April 7, 1987 ``Threshold Planning Quantities Technical 
Support Document'' (page 27), EPA noted that ``solids may also be 
handled in solution and molten form and could potentially follow a 
liquid release scenario. However, even at molten temperatures, 
significant amounts of vapor are not likely to be generated.'' On page 
24 of the same technical support document, when discussing liquid 
releases, EPA assumed that a spill of a liquid could occur as a result 
of an accidental situation that involves heat (e.g. fire, exothermic 
runaway reaction, or reactions with air or water).
    More specifically, when a solid chemical is in solution form, the 
solution can behave like a liquid during an accidental release and be 
dispersed into the air due to overheating, overpressure or anything 
that can cause a loss of containment from a vessel or piece of 
equipment. An accident involving a release of energy could create a 
liquid aerosol type of release into the air. Such liquid aerosol 
droplets, if small enough, can be dispersed into the air and remain 
airborne beyond the facility boundary, resulting in EHS exposure to the 
surrounding community. Environmental conditions and the properties of 
the specific chemical will dictate the behavior and dispersion of the 
chemical after a release or spill has occurred. For example, the 
solvent can evaporate from solution (especially at higher temperature) 
and small particulates of solid remaining after evaporation of the 
solvent can potentially be carried off-site. EPA recognized that the 
solid EHS (dissolved or suspended in a liquid solution) will not be 
dispersed into the air based on volatilization of the solid, but 
because of the energy released from the accident, or by wind.
    At the time of the April 1987 rulemaking, EPA did not have 
sufficient information to determine how much of the solid EHS in 
solution could be dispersed airborne off-site and conservatively used 
V=1 for this release scenario. Furthermore, although paraquat 
dichloride decomposes at a temperature of 340[deg] C (644[deg] 
Fahrenheit, F), EPA believed that accidents involving aerosol releases 
of paraquat dichloride solution could potentially occur at temperatures 
less than 340[deg] C. Boiling solutions containing non-volatile solids 
result in vaporization of the solvent, but not the solid. However, the 
turbulence of boiling the solution can entrain liquid aerosol droplets 
containing the solid into the air.
4. Airborne Dispersion of Solids in Solution.
    Based on more recent information, EPA has re-evaluated the 
assumption of 100% airborne releases when setting the TPQ for solids in 
solution, not just for paraquat dichloride solution, but for all EHS 
solids in solution, except for the 12 solid EHS chemicals that are 
reactive solids.
a. Liquid Aerosol Release Data
    EPA reviewed data in the literature on releases of aerosols to 
evaluate their potential use for revising the application of the TPQs 
for EHS solids in solution. EPA was specifically looking for data on 
how much of a solution containing a dissolved or suspended solid would 
remain airborne after an accidental release. One problem encountered in 
reviewing the literature was some studies only involved chemicals that 
are pure liquids and which have vapor pressures much higher than solid 
chemicals. That data would likely not represent the release and 
dispersion of a solid chemical that normally has a very low vapor 
pressure. However, the U.S. Department of Energy (USDOE) used 
experimental liquid aerosol release data involving metal salt solutions 
to estimate the Airborne Release Fraction (ARF) of metal salt solutions 
for a wide variety of release scenarios. This information was collected 
in a 1994 report, which is available in the docket to this 
rulemaking.\4\ Many of the USDOE scenarios had very low ARFs; EPA 
considered the scenarios with higher release potential to best serve 
the purposes of emergency planning. Also, scenarios which required 
hypothetical input data to compute the ARF were not used. When median 
and bounding (maximum) values of ARFs were provided for a scenario, EPA 
used the maximum ARF in order to be conservative and cover the worst 
case scenario. EPA summarized the data from those DOE aerosol release 
scenarios with the highest (ARFs) in the table below. (The ARF values, 
release scenarios from the USDOE report and other data are discussed in 
greater detail in the technical support document for this rulemaking, 
which is available in the docket to this rulemaking.) From this data, 
EPA determined that a worst case estimate of the ARF for a solution 
containing non-volatile solids would be 0.2. This particular ARF is 
based on the scenarios of an aqueous solution or air dried salts under 
gasoline fire on a metal surface. The airborne fractions from the USDOE 
report generally contained aerosol sizes less than or equal to 100 
microns. Droplets larger than 100 microns in diameter are expected to 
fall out before they reach a community outside a facility.
---------------------------------------------------------------------------

    \4\ USDOE. 1994. DOE Handbook, Airborne Release Fractions/Rates 
and Respirable Fractions for Nonreactor Nuclear Facilities. December 
1994. US Department of Energy, Washington, DC 20585 DOE-HDBK-3010-
94. Volume 1--Analysis of Experimental Data and Volume II--
Appendices.

------------------------------------------------------------------------
                                                                Maximum
                                                                airborne
                   Aerosol release scenario                     release
                                                                fraction
                                                                 (ARF)
------------------------------------------------------------------------
Thermal Stress from Boiling..................................      0.002

[[Page 21305]]

 
High Pressure Venting Below Liquid Level.....................      0.12
Pressure Venting Above the Liquid Level......................      0.002
Superheated Liquid Temp >= 50 [deg]C and <= 100 [deg]C.......      0.1
Superheated Liquid Temp <= 50 [deg]C.........................      0.01
Burning Organic Layer Over Aqueous Solution..................      0.1
Aqueous Solution or Dry Salt Under Gasoline Fire on Metal....      0.2
Aerodynamic Entrainment and Re-Suspension....................      0.1
------------------------------------------------------------------------

    Using the highest airborne release fraction rather than an average 
result of the scenarios is consistent with the intent of the emergency 
planning program to plan for a reasonable worst case scenario. This 
data is a good surrogate to use to predict the maximum potential 
aerosol release fraction of EHS solids in solution in the event of an 
accidental release. Water is probably the most common solvent that 
would be used with most of the EHS solids, whether they are dissolved, 
suspended or emulsified in water. Many of the EHS solids are pesticides 
and pesticides are commonly applied as water solutions or emulsions.
    EPA also looked at experimental data collected by the Center for 
Chemical Process Safety (CCPS) for aerosol releases of water and 
cyclohexane. CCPS, a directorate of the American Institute of Chemical 
Engineers (AICHE), was established in 1985 to develop and disseminate 
technical information for use in the prevention of major chemical 
process incidents. CCPS develops and publishes guidelines, conducts 
seminars, symposia, training programs and meetings on chemical process-
safety matters; CCPS also cooperates with other organizations, both 
internationally and domestically, to promote process safety. CCPS's 
activities are supported by funding and expertise from over 100 
entities including, industry, consulting firms and governmental 
organizations. USEPA is a member of this organization.
    In 1989, the CCPS Vapor Cloud Modeling Subcommittee began an 
``Aerosol Project'' to meet some of the research objectives proposed to 
the U.S. National Vapor Cloud Research Committee, which included 
developing a superheated liquid release model and developing 
experimental data to validate the model. The experimental field data 
was the result of field controlled-release experimentation by CCPS with 
financial assistance by special grants from some of the CCPS sponsors 
and from the USEPA and USDOE. The experimental superheated liquid 
release data was developed, documented, peer reviewed and, where 
necessary, corrected. The Vapor Cloud Modeling Subcommittee contracted 
a review of the fundamental basis for the RELEASE model and to make 
model improvements to reconcile the cyclohexane, chlorine and 
methylamine test data. The results of the model development and the 
experimental field data used was published in 1999 in a CCPS concept 
book ``RELEASE: A Model with Data to Predict Aerosol Rainout in 
Accidental Releases'' by David W. Johnson and John L. Woodward.
    EPA did not use the aerosol release fraction from the CCPS data 
because these liquids did not contain any solid material in solution. 
Specifically, the reported airborne release fraction for water varied 
from 0.03 to 0.54 and for cyclohexane varied from 0.36 to 0.94. 
Cyclohexane with a vapor pressure of 95 millimeters (mm) mercury (Hg) 
is more volatile than water with its vapor pressure of 24 mm Hg. It is 
not a good comparison to use aerosol release fractions of volatile 
liquids to estimate the aerosol release fractions of a solid in 
solution because solids generally are not very volatile. The water 
aerosol data might be a close surrogate for estimating a release of an 
aqueous solution of the solid, but it does not have the important 
constituent of a dissolved solid, which might influence the amount of 
aerosol remaining entrained in the air. However, the CCPS data for 
water supports EPA's belief that assuming a 100% airborne liquid 
aerosol release is inappropriate because the water aerosol fractions 
measured in the experiments were less than one. CCPS also had 
experimental release data for CFC-11 and chlorine (both gases) and 
methylamine (a highly volatile chemical with a vapor pressure of 300 mg 
Hg), but EPA did not consider this data for use as a good analogy 
because of their high volatility and they did not contain any solids.
    USDOE was interested in applying the experimental aerosol release 
data to estimate airborne fractions of liquid aerosol releases that 
were below respirable size, which they defined as particles of 10 
micron Aerodynamic Equivalent Diameter (AED) or less. By USDOE's 
definition, respirable size particles are those that can be transported 
through the air and inhaled into the human respiratory system.
    For purposes of establishing TPQs, EPA chose a distance of 100 
meters (330 feet) to represent the distance from a source inside a 
chemical facility to the point where the community might be exposed. 
This decision was based on data indicating that a particle size greater 
than 100 microns is not likely to be deposited more than 100 meters 
from the source (``Threshold Planning Quantities Technical Support 
Document,'' USEPA April 7, 1987, Public Docket 300PQ, Document No. 
300PQ-2-21). The 100-micron cutoff is also consistent with CERCLA 
regulations (for reportable quantities) which also uses a 100 micron 
particle size for powdered materials.
    Most of the USDOE experimental aerosol release data had median 
aerosol diameters of less than 100 microns. This size is consistent 
with what EPA believes is the size of aerosols to which the community 
could be exposed. On the other hand, the water and cyclohexane aerosol 
release data compiled by CCPS had much larger mean aerosol diameter 
sizes, generally over 100 microns. For the reasons already discussed 
and because it is likely that aerosol releases with diameters larger 
than 100 microns will fall out of the air before they reach a 
community, the water and cylcohexane aerosol release fractions were not 
used in determining the TPQs for solids in solution.
b. Liquid and Solution TPQ Comparison
    Pure EHS liquids could also be released accidentally as aerosols 
via the same catastrophic scenarios (overpressure, superheating). It 
could be argued that perhaps the TPQ method for solids in solution 
could also apply to liquids. However, this goes against the ranking 
used for setting TPQs based on the extent of airborne releases by 
physical state as being high for gases, less for liquids and even less 
for solids in solution. Currently, the release scenario used for 
developing the liquid TPQs considers a spill of the liquid due to a 
loss of containment. The liquid then escapes into the air by 
volatilization. An airborne release of solids in solution will require 
more than a failure of containment to have appreciable airborne 
dispersion. An energy source, such as overpressure or high temperature 
would be required to disperse the solution into the air and create 
aerosol droplets. Not all of the droplets will stay airborne (unlike 
volatilized vapors) and affect the community, whose exposure depends on 
droplet size and distance from the facility fence line.
    If one assumes that there is an equal potential for airborne 
releases for gases, liquids, small particulate solids and solids in 
solution, then the TPQ ranking scheme would change radically and rely

[[Page 21306]]

almost entirely on the toxicity of the chemical. However, EPA believes 
that airborne dispersibility is a critical factor in determining TPQs. 
Limited state and local resources should be focused on those EHS 
chemicals that can potentially cause the greatest harm and less on 
those that might be toxic, but less likely to be released to the air 
and carried beyond the facility boundary.
    As a hypothetical scenario, EPA determined if the current TPQ 
method for liquids gives more conservative (or at least as 
conservative) TPQs (lower thresholds) as compared to the proposed TPQ 
methodology for solids in solution. To do this, EPA estimated the TPQs 
for liquids by assuming that V = 1, and then divided it by 0.2 (based 
on an expected 20% maximum airborne dispersion) to determine the amount 
of EHS on-site that would trigger emergency planning notification. 
These amounts or ``effective TPQs'' were then compared to the current 
listed TPQs for liquids. For 116 of the 163 EHS liquids, the current 
TPQs for liquids based on volatilization were equal to or lower than 
the new effective TPQs based on aerosolization. Most of the other 47 
liquids had current TPQs that were about twice the effective TPQ. This 
comparison with a table of results for the EHS liquids is discussed in 
the technical support document for this rulemaking. Based on this 
analysis, EPA believes that using the volatilization model to establish 
V for liquid TPQs is still appropriate. The spilled liquid using a 
boiling point scenario is probably the most prevalent worst-case 
scenario that is reasonable to use for establishing TPQs for liquids.
    Further examination of the 47 liquid chemicals was undertaken to 
see why these had TPQs greater than the effective TPQs--that is, about 
twice the effective TPQ. Many of these liquids had effective TPQ values 
of 5, 50 and 5,000 pounds. However, there are no TPQs of 5, 50 or 5,000 
pounds. Rather, the use of order of magnitude index ranges assigned to 
various TPQ levels resulted in assigned TPQ values of 1, 10, 100, 500, 
1,000 and 10,000 pounds. Thus, where the effective TPQs are either 5, 
50, or 5,000 pounds, the comparison of a current TPQ versus an 
effective TPQ may not be valid. More discussion on this can be found in 
the technical support document.

C. What alternative approaches were considered?

    Given the data in the literature available on aerosol releases of 
solids in solution, EPA considered various alternative approaches. One 
alternative was using an index ranking method with an assigned V 
similar to the original method of assigning TPQs. Another alternative 
was to apply the ARF to the existing lower TPQ for solids to develop a 
new TPQ for solids in solution for each solid EHS. A third alternative 
was similar to the approach of multiplying the maximum ARF by the 
amount on-site, except that the ARF would only represent aerosol sizes 
less than respirable size. Below we discuss these alternatives, as well 
as the basis for not selecting them.
1. Index Ranking Method With V Less Than 1
    This alternative would establish TPQs using a ranking approach 
based on each chemical's physical state, acute toxicity and, the 
potential for the chemical to become airborne (V). For this 
alternative, V would be set to 0.2 for EHS solids in solution.
    For the original development of the TPQs, the ranking index was 
defined as the LOC divided by V, where V was set equal to 1 for gases 
and solids in powder form with a particle size less than 100 microns, 
molten solids and solids in solution. For liquid EHSs, V (the potential 
to become airborne) depended upon the property of volatility 
(evaporation of liquid into the gas phase). In the development of V for 
use in setting TPQs for liquids, V represented the mass per time 
evolved to the air per mass of the spill. This is explained in further 
detail in the April 1987 ``Threshold Planning Quantities Technical 
Support Document'' available in the docket.
    Most of the values for V for liquids are approximately 0.1 (see 
Appendix B in the ``Technical Support Document for Revising TPQ Method 
for Solids in Solution'' for this rule). Using a higher V equal to 0.2 
for solids in solution implies that in the event of an accidental 
release, more of the solution would become airborne than if it were 
volatilized from a liquid spill. Even if a liquid were accidentally 
released via aerosol form, the volatility of the liquid chemical will 
increase the fraction that remains dispersed in the air. Therefore, it 
would not be a fair representation to have a solid in solution with a V 
higher than that used for a volatile liquid. Also, because there are 
different mechanisms involved in the two types of releases, it may not 
be comparable to use the 0.2 as a substitute for V for solids in 
solution.
2. Existing TPQ and Aerosol Release Fraction
    Another alternative is to apply the ARF to the existing lower TPQ 
for solids to develop a new TPQ. For example, the lower TPQ for 
paraquat dichloride is 10 pounds. Dividing 10 pounds by 0.2, the 
maximum expected aerosol release fraction for a solution would result 
in a new TPQ of 50 pounds for paraquat dichloride in solution form. For 
each of the 157 non-reactive solids on the EHSs list, a new TPQ for the 
solution form of the EHS solid could be determined and listed. However, 
for each solid non-reactive chemical, there are already two TPQs, one 
developed based on the ranking index methodology of (Index = Level of 
Concern/V) and one based on the default TPQ of 10,000 pounds for non-
molten, non-reactive, non-solution solids with a particle size equal to 
or greater than 100 microns. Including a third set of TPQs for EHS 
solids in solution could be confusing to the regulated community. Thus, 
EPA believes that using the existing lower TPQ for solids and comparing 
that to the product of the amount on-site multiplied by 0.2 is a better 
approach, and similar to the approach used for the molten solids form.
3. Using ARF Limited to Smaller Aerosol Sizes
    Another approach considered is similar to the proposed approach of 
multiplying the maximum ARF by the amount on-site, except that the ARF 
would only represent the fraction of aerosols with particles less than 
respirable size. Through discussions with the petitioner and EPA's 
November 2003 response to the petition, EPA has considered whether 
aerosol size should be used as a factor in developing new TPQs for 
solids in solution. A consultant for Syngenta believes that EPA should 
only consider the dispersion of aerosols with particle sizes less than 
or equal to 4 microns because these smaller aerosols are the size that 
can enter the lung and because the inhalation toxicity tests used for 
the basis of the EHSs listing only used very small particles.
    This approach would require sufficient data on the aerosol size 
distribution for each release scenario to develop a new ARF that would 
include only aerosols of 4 microns and lower. The ARFs currently cited 
for the scenarios used for the preferred approach include aerosol sizes 
of 100 microns and lower. For some of the USDOE accident scenarios, it 
is possible to recalculate the airborne aerosol fractions using the raw 
experimental data to include only aerosols less than or equal to 4 
microns in diameter. This results in smaller airborne release 
fractions.
    EPA does not believe this approach should be used for a number of 
reasons, including:

[[Page 21307]]

     Inhalation toxicity tests are designed to use small 
particles to ensure that the lung is exposed. However, EPA is not using 
the inhalation toxicity for risk assessment, but only as a screening 
tool.
     Although the EHSs listing for paraquat dichloride is based 
on inhalation toxicity, EPA also has concerns regarding dermal and 
ingestion exposure via swallowing for the larger aerosols.
     Solvent evaporation from larger aerosols can also create 
smaller aerosols which can enter the lung.

Each of these is discussed below.
a. Aerosol Size in Toxicity Tests
    Aerosols may be defined as a suspension of solid or liquid 
particles in air. Inhalation acute toxicity tests are purposely 
designed with very small diameter particles in order to ensure that 
particles are small enough to enter the rodent's lungs and test the 
toxicity in the lungs. Larger particles may not enter deep areas of the 
lungs and thus, test results may be misinterpreted if little inhalation 
toxicity is shown. EPA is not attempting to use the airborne aerosol 
fraction for purposes of risk assessment, but only as a tool to set 
screening levels for the amount of chemicals on-site which may 
potentially cause harm if accidentally released. Also, the size of the 
aerosols used in an animal laboratory test cannot be assumed to be the 
same as those that people may be exposed to during an accidental 
release.
b. Particle Size and Exposure
    Inhalable size particles enter the respiratory tract, including the 
head airways and are generally equal to or less than 100 microns. 
Thoracic size particles (generally equal to or less than 10 microns) 
travel past the larynx and reach the lung airways and the gas-exchange 
regions of the lung. Respirable size particles (generally less than or 
equal to 4 microns) are a subset of thoracic particles that are more 
likely to reach the gas-exchange region of the lung.\5\
---------------------------------------------------------------------------

    \5\ USEPA. October 2004. Air Quality Criteria for Particulate 
Matter. Vol I, Chapter 2 and Volume II, Chapter 6. U.S. 
Environmental Protection Agency, Office of Research and Development, 
National Center for Environmental Assessment. Research Triangle 
Park, NC. EPA/600/P-00/002aF and EPA/600/P-00/002bF
---------------------------------------------------------------------------

    Most particles that enter the upper airways are trapped in mucous 
that moves to the throat and is swallowed within a few hours. Thus, 
instead of inhalation exposure deep in the lungs, exposure to larger 
particles of chemicals may occur through dermal exposure to mucous 
membranes or ingestion exposure through swallowing. Emergency planning 
for EHS chemicals is not limited to inhalation exposure only, although 
many of the EHS chemical listings are based on studies which meet the 
EHSs listing criteria for inhalation toxicity. Although airborne 
exposure is the most likely route of exposure, it is not the only route 
of exposure. In the event of an accidental release, EPA is concerned 
about all routes of exposure (inhalation, dermal and ingestion) to the 
community. Thus, exposure to larger size aerosols (e.g. those above 4 
or 10 microns) by any route, such as through the skin or mucous 
membranes) should not be ignored when setting TPQs.
c. Solvent Evaporation From Aerosols
    Even after liquid aerosol droplets are released, some of the 
solvent may evaporate in the air. This would result in even smaller 
size aerosols or solid EHS particulates in the air to which a community 
would be exposed. One concern is that droplets of size greater than 100 
microns could settle quickly, dry into a smaller particle size and then 
become airborne again (re-suspension). In the event of an accidental 
release, the responsible party should clean up chemicals deposited on 
the facility grounds before additional exposure to the community would 
take place. The USDOE report did include data on re-suspension of 
particulates from soil after an aerosol release. However, the amount 
re-suspended did not add much to the reasonable worst case aerosol 
release fraction of 0.2. This scenario is explained further in the 
technical support document for this rule.

D. What are the peer review results?

    EPA's revised TPQ methodology for EHS solids in solution and 
supporting data was peer reviewed and the technical support document 
was revised based on the peer review comments. The description of the 
peer review process, the results of the peer review and EPA's response 
to the peer review comments are found in a separate document, ``Peer 
Review of Technical Support Document for Revised TPQ Method for EHS 
Solids in Solution,'' which is available in the docket to this 
rulemaking. Below are the questions posed to the peer reviewers, a 
summary of the peer reviewers' comments and EPA's responses.
1. Based on your reading and analysis of the information provided, do 
you find the revised TPQ method to be logical with a sound scientific 
basis?
    Two of the three reviewers agreed that the revised TPQ method was 
logical with a sound scientific basis using the USDOE experimental 
aerosol release data. However, one reviewer thought the revised TPQ 
method may not be based on the most sound science because the LOC is 
based on Immediately Dangerous to Health and Life values (IDLH) and 
animal lethality data that he believes may not be appropriate. 
Nonetheless, this reviewer did think that a cursory review of the 
effective TPQ list (Appendix B in technical support document) appears 
to have appropriately listed the ranking of chemicals by potential 
hazard to the public.
    EPA recognizes that use of the IDLH was an imperfect measure for 
determining the LOC, but believes the approach provides a consistent 
relative ranking of the EHS. Where animal lethality data were 
substituted, safety factors were applied to the data to estimate the 
LOC. Human data were taken into account for some chemicals, such as 
chemical warfare agents, and adjustments were made to the TPQ initially 
based on index values. EPA realizes that better data are being 
developed that could be used for the LOC (such as AEGLs--Acute Exposure 
Guideline Levels). However, a re-evaluation of the LOC for all EHS 
chemicals would best be undertaken by a separate rulemaking effort, 
given the extent and complexity of this issue.
2. Is the writing clear and concise? Has EPA provided the right level 
of detail? Is the method understandable? Are the results clearly 
presented?
    Two of the three reviewers thought that the revised method was not 
clear and understandable and suggested improvements. For example, it 
was recommended that EPA clarify the definition of a solution, as well 
as include a flowchart of the method or a graph to help describe the 
approach.
    EPA agrees that improvements were needed in order to present the 
information in a better way for the regulated community to understand 
and apply, and the revised technical support document addresses those 
concerns. Thus, additional supporting background information, 
discussion about the development of TPQs, and examples and calculations 
of how to apply the TPQs for EHS solids in solution have been added to 
the technical support document and has been further

[[Page 21308]]

explained in the preamble to the proposed rule. The proposed rule, 
which was not provided to the peer reviewers, is written more clearly 
and is less technical than the materials given to the peer reviewers to 
review.
    One reviewer thought that EPA had provided the right amount of 
detail, and thought the method is understandable, and the text is for 
the most part readable. However, the reviewer had several 
clarifications and corrections he thought EPA should make. These 
clarifications have been made to the technical support document, 
including improving a description of background on TPQ development, 
clarifying some terms used in the document, and adding some references 
and other editorial comments.
    This same reviewer thought the argument against the alternative 
approach of using V=0.2 for developing TPQ for solids in solutions was 
not that convincing. EPA has revised the discussion of this alternative 
approach by stating that EPA believes that this approach would result 
in TPQs that would be too low as compared to TPQs for liquids of 
similar toxicity because most of the liquids have approximately V=0.1. 
EPA believes that liquids have a higher potential for airborne 
dispersion because of their inherently higher volatility. Also, the 
mechanism for airborne dispersion for liquids using the spill model is 
volatilization, whereas solids in solution will be dispersed via 
aerosolization, so using V=0.2 for solutions may be not comparable.
3. Is the revised method consistent with the overall approach used for 
setting TPQs for other EHS chemicals?
    All three reviewers thought that the revised method was fairly 
consistent with the approach used for setting other TPQs. However, one 
reviewer thought that EPA should consider lowering the TPQs for 46 of 
163 EHS liquids based on the comparison of using the revised TPQ method 
versus the current method. EPA believes that using a V of 0.2 to 
recalculate the TPQ indexes would result in conservatively low TPQs for 
solids in solution as compared to liquids of the same toxicity. Given 
that volatilization requires only the loss of containment of a 
chemical, whereas aerosolization requires the loss of containment and 
usually an energy release, EPA believes the higher potential for 
airborne dispersion should be assigned to liquids as compared to a non-
volatile solid in solution. Because there are different mechanisms 
(volatilization versus aerosolization) involved in the two types of 
releases, it may not be comparable to use 0.2 as a substitute for V for 
solids in solution. Based on the comments, EPA has revised the 
discussion in the preamble to the rule and Section VI.A--Use Orig