National Emission Standards for Organic Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry, 76603-76615 [E6-21869]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 71, Number 245 (Thursday, December 21, 2006)]
[Rules and Regulations]
[Pages 76603-76615]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E6-21869]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2005-00475; FRL-8259-6]
RIN 2060-AK14


National Emission Standards for Organic Hazardous Air Pollutants 
From the Synthetic Organic Chemical Manufacturing Industry

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: In 1994, EPA promulgated national emission standards for 
hazardous air pollutants (NESHAP) for the synthetic organic chemical 
manufacturing industry. This rule is commonly known as the hazardous 
organic NESHAP (HON) and established maximum achievable control 
technology standards to regulate the emissions of hazardous air 
pollutants from production processes that are located at major sources.
    The Clean Air Act directs EPA to assess the risk remaining 
(residual risk) after the application of the maximum achievable control 
technology standards and to promulgate additional standards if required 
to provide an ample margin of safety to protect public health or 
prevent an adverse environmental effect. The Clean Air Act also 
requires us to review and revise maximum achievable control technology 
standards, as necessary, every 8 years, taking into account 
developments in practices, processes, and control technologies that 
have occurred during that time.
    On June 14, 2006, EPA proposed two options regarding whether to 
amend the current emission standards for synthetic organic chemical 
manufacturing industry units. This action finalizes one of those 
options, and reflects our decision not to impose further controls and 
not to revise the existing standards based on the residual risk and 
technology review. It also amends the existing regulations in certain 
aspects.

DATES: This final rule is effective on December 21, 2006.

ADDRESSES: Docket: EPA has established a docket for the final rule 
under Docket ID No. EPA-HQ-OAR-2005-0475. All documents in the docket 
are listed on the www.regulations.gov Web site. Although listed in the 
index, some information is not publicly available, e.g., confidential 
business information or other information whose disclosure is 
restricted by statute. Certain other material, such as copyrighted 
material, is not placed on the Internet and will be publicly available 
only in hard copy form. Publicly available docket materials are 
available either electronically at https://www.regulations.gov or in 
hard copy at the Air and Radiation Docket, EPA West, Room B-102, 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 Air and Radiation Docket is 
(202) 566-1742.


    Note: The EPA Docket Center suffered damage due to flooding 
during the last week of June 2006. The Docket Center is continuing 
to operate. However, during the cleanup, there will be temporary 
changes to Docket Center telephone numbers, addresses, and hours of 
operation for people who wish to make hand deliveries or visit the 
Public Reading Room to view documents. Consult EPA's Federal 
Register notice at 71 FR 38147 (July 5, 2006) or the EPA Web site at 
https://www.epa.gov/epahome/dockets.htm for current information on 
docket operations, locations, and telephone numbers. The Docket 
Center's mailing address for U.S. mail and the procedure for 
submitting comments to www.regulations.gov are not affected by the 
flooding and will remain the same.


FOR FURTHER INFORMATION CONTACT: For further information contact Mr. 
Randy McDonald, U.S. EPA, Office of Air Quality Planning and Standards, 
Sector Policies and Programs Division, Coatings and Chemicals Group 
(E143-01), Research Triangle Park, NC 27711, telephone (919)541-5402, 
fax (919) 541-0246, e-mail mcdonald.randy@epa.gov.

SUPPLEMENTARY INFORMATION: Regulated Entities. Categories and entities 
potentially regulated by the final rule are synthetic organic chemical 
manufacturing industry (SOCMI) facilities that are major sources of 
hazardous air pollutant (HAP)

[[Page 76604]]

emissions. The final rule affects the following categories of sources:

------------------------------------------------------------------------
                                 NAICS*      Examples of  potentially
           Category               Code          regulated  entities
------------------------------------------------------------------------
Industry.....................        325  Chemical manufacturing
                                           facilities.
------------------------------------------------------------------------
* North American Industry Classification System.

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by the 
final rule.
    World Wide Web (WWW). In addition to being available in the docket, 
electronic copies of the final rule are available on the WWW through 
the Technology Transfer Network Web site (TTN). Following signature, 
EPA posted a copy of the final rule on the TTN's policy and guidance 
page for newly proposed or promulgated rules at https://www.epa.gov/ttn/
oarpg. The TTN provides information and technology exchange in various 
areas of air pollution control.
    Judicial Review. Under Clean Air Act (CAA) section 307(b)(1), 
judicial review of this final rulemaking is available only by filing a 
petition for review in the United States Court of Appeals for the 
District of Columbia Circuit by February 20, 2007. Under CAA section 
307(d)(7)(B), only an objection to the final rulemaking that was raised 
with reasonable specificity during the period for public comment may be 
raised during judicial review. Moreover, under CAA section 307(b)(2), 
the rule's requirements may not be challenged separately in any civil 
or criminal proceedings brought by EPA to enforce these requirements.
    Section 307(d)(7)(B) of the CAA further provides a mechanism for us 
to convene a proceeding for reconsideration, ``[i]f the person raising 
an objection can demonstrate to the EPA that it was impracticable to 
raise such objection within [the period for public comment] or if the 
grounds for such objection arose after the period for public comment 
(but within the time specified for judicial review) and if such 
objection is of central relevance to the outcome of the rule.'' Any 
person seeking to make such a demonstration to us should submit a 
Petition for Reconsideration to the Office of the Administrator, U.S. 
EPA, Room 3000, Ariel Rios Building, 1200 Pennsylvania Ave., NW, 
Washington, DC 20460, with a copy to both the person(s) listed in the 
preceding FOR FURTHER INFORMATION CONTACT section, and the Associate 
General Counsel for the Air and Radiation Law Office, Office of General 
Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460.
    Organization of this Document. This preamble is organized as 
follows:

I. Background Information
    A. What Is the Statutory Authority for These Actions?
    B. What Did We Propose?
II. Risk and Technology Review
    A. Final Decision
    B. Summary of Changes to the Rule
III. Responses to Significant Comments
    A. Data Collection
    B. Risk Determination
    C. Administrative Requirements
    D. Impacts Estimation
    E. Clarification Changes
IV. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility
    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 and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect 
Energy Supply, Distribution or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act

I. Background Information

A. What is the statutory authority for these actions?

    Section 112 of the CAA establishes a two-stage regulatory process 
to address emissions of HAP from stationary sources. In the first 
stage, after EPA has identified categories of sources emitting one or 
more of the HAP listed in CAA section 112(b), CAA section 112(d) calls 
for us to promulgate national performance or technology-based emission 
standards for those sources. For ``major sources'' that emit or have 
the potential to emit any single HAP at a rate of 10 tons or more per 
year or any combination of HAP at a rate of 25 tons or more per year, 
these technology-based standards must reflect the maximum reductions of 
HAP achievable (after considering cost, energy requirements, and non-
air quality health and environmental impacts) and are commonly referred 
to as maximum achievable control technology (MACT) standards. We first 
published the MACT standard for SOCMI on April 22, 1994, at 59 FR 19402 
(codified at 40 CFR part 63, subparts F, G, H, and I). EPA is then 
required to review these technology-based standards and to revise them 
``as necessary, taking into account developments in practices, 
processes, and control technologies,'' no less frequently than every 8 
years, under CAA section 112(d)(6).
    The second stage in standard-setting is described in CAA section 
112(f). This provision requires, first, that EPA prepare a Report to 
Congress discussing (among other things) methods of calculating risk 
posed (or potentially posed) by sources after implementation of the 
MACT standards, the public health significance of those risks, the 
means and costs of controlling them, actual health effects to persons 
in proximity to emitting sources, and recommendations as to legislation 
regarding such remaining risk. EPA prepared and submitted this report 
(Residual Risk Report to Congress, EPA-453/R-99-001) in March 1999. The 
Congress did not act on any of the recommendations in the report, 
thereby triggering the second stage of the standard-setting process, 
the residual risk phase.
    CAA Section 112(f)(2) requires us to determine, for each CAA 
section 112(d) source category, whether the MACT standards protect 
public health with an ample margin of safety. If the MACT standards for 
HAP ``classified as a known, probable, or possible human carcinogen do 
not reduce lifetime cancer risks to the individual most exposed to 
emissions from a source in the category or subcategory to less than 1-
in-1 million,'' EPA must promulgate residual risk standards for the 
source category (or subcategory) as necessary to provide an ample 
margin of safety to protect public health. EPA may also adopt more 
stringent standards, if necessary, to prevent an adverse environmental 
effect (defined in CAA section 112(a)(7) as ``any significant and 
widespread adverse effect * * * to wildlife, aquatic life, or natural 
resources * * *.''), after considering cost, energy, safety, and other 
relevant factors.

B. What did we propose?

    On June 14, 2006 (71 FR 34422), we proposed two options regarding 
whether to revise the current emission standards for new and existing 
SOCMI process units. The first proposed option would have imposed no 
further controls, based on a proposed finding that the existing 
standards protect public health with an ample margin of safety and 
prevent adverse environmental effects. Moreover, under the first 
option, we proposed that no further tightening of current standards was 
``necessary'' in

[[Page 76605]]

light of developments in practices, processes, and control 
technologies.
    The second proposed option would have required further reductions 
of organic HAP at certain process units, based on a proposed finding 
that additional controls were reasonable in order to protect public 
health with an ample margin of safety. This option was also based on a 
proposed finding that, in order to further reduce risks, tightening of 
current standards was ``necessary'' after taking into account 
developments in practices, processes, and control technologies. The 
second option would have applied additional controls for equipment 
leaks and controlled some storage vessels and process vents that are 
not required to be controlled under the current rule. The proposed 
changes under Option 2 are summarized in the table below:

------------------------------------------------------------------------
            Emission source               Proposed changes to standards
------------------------------------------------------------------------
Storage vessels.......................  A Group 1 storage vessel also
                                         includes storage vessels that
                                         store one or more HAP listed in
                                         table 38 to subpart G of part
                                         63, and has a combined HAP
                                         emission rate greater than 4.54
                                         megagrams per year (5.0 tons
                                         HAP per year) on a rolling 12-
                                         month average.
Process vents.........................  A Group 1 process vent also
                                         includes process vents for
                                         which the vent stream emits one
                                         or more HAP listed in table 38
                                         to subpart G of part 63, and
                                         the total resource
                                         effectiveness index value is
                                         less than or equal to 4.0.
Equipment leaks.......................  For chemical manufacturing
                                         process units (CMPU) containing
                                         at least one HAP listed in
                                         table 38 to subpart G of part
                                         63, monthly monitoring of
                                         equipment components is
                                         required until the process unit
                                         has fewer than 0.5 percent
                                         leaking valves in gas/vapor
                                         service and in light liquid
                                         service.
------------------------------------------------------------------------

II. Risk and Technology Review

A. Final Decision

    We conclude in this rulemaking that there is no need to revise the 
HON rule under the provisions of either section 112(f) or 112(d)(6) of 
the CAA. This conclusion essentially reflects our decision to select 
Option 1 from the proposal, except for certain minor technical 
amendments we are adopting that are discussed later.
    We are adopting no changes to the current HON rule under CAA 
section 112(f) because the current level of control called for by the 
existing MACT both reduces HAP emissions to levels that present an 
acceptable level of risk and protects public health with an ample 
margin of safety. The finding regarding an ``ample margin of safety'' 
is based on a consideration of the additional costs of further control 
(as represented by Option 2) and the relatively small reductions in 
health risks that are achieved by that alternative.
    As explained at proposal, we judge that the level of risk from the 
current HON rule is acceptable for the following reasons. The maximum 
individual lifetime cancer risk is estimated to be 100-in-1 million, 
and this level of risk occurs at only two facilities. There are no 
people with estimated cancer risks greater than 100-in-1 million 
resulting from exposure to HON HAP emissions, which is the 
presumptively acceptable level of maximum individual lifetime cancer 
risk under the 1989 Benzene NESHAP criteria. The HON process units at 
32 facilities are estimated to pose cancer risks greater than 10-in-1 
million, with 9,000 people estimated to be exposed in this risk range. 
The HON process units at the remaining 206 facilities are estimated to 
pose cancer risks of 10-in-1 million or less. For the exposed 
population, total annual cancer incidence is estimated at 0.14 cases 
per year. The Hazard Index (HI) values (representing long-term 
noncancer public health risks) barely exceed 1, with only 20 people 
estimated to be exposed to HI levels greater than 1. We also found 
minimal concern for noncancer effects from short-term inhalation 
exposures from HAP. The lifetime cancer risk and noncancer adverse 
health effects estimated from multipathway exposure are also well below 
levels generally held to be of concern. Finally, after considering 
costs, energy, safety, and other relevant factors, it is not necessary 
to tighten HON requirements in order to prevent adverse environmental 
effects, or to account for developments in practices, processes, and 
control technologies.
    In determining that the current HON rule protects public health 
with an ample margin of safety, we have determined that the estimated 
annual costs of Option 2 ($6 million per year) would be unreasonable 
given the minor associated improvements in health risks. Baseline 
cancer incidence under the current HON rule is estimated at 0.14 cases 
per year. Proposed Option 2 would reduce incidence by about 0.05 cases 
per year. Statistically, this level of risk reduction means that Option 
2 would prevent one cancer case every 20 years. At proposal we 
estimated costs to be $13 million per year for Option 2. Based on 
public comments, we revised one of the Option 2 control requirements 
and the costing procedure for equipment leaks and this resulted in a 
revised cost estimate $6 million per year. Even at the $6 million per 
year cost, we consider the cost of Option 2 to be unreasonable given 
the level of incidence reduction achieved. The changes in the 
distribution of risks do not warrant the additional costs. The maximum 
individual cancer risk under Option 2 would be reduced from 100-in-1 
million to 60-in-1 million. The cancer risks for 450,000 people would 
be shifted to levels below 1-in-1 million. Further, changes in the 
distribution of risk--that is, the aggregate change in risk across the 
population--reduces risk by only 0.05 cancer cases per year. This 
result suggests that Option 2 would yield very small changes in 
individual risk for most of the affected population. For this reason, 
the estimates of the shift in risk distribution do not serve as 
particularly effective measures of the change in health risk. Finally, 
the maximum HI is barely above 1.0 and would be reduced from above 1.0 
to below 1.0 for only 20 people. We conclude that this degree of 
additional public health protection is not warranted in light of the 
costs to industry of compliance with proposed Option 2. Consequently, 
we have determined that it is not reasonable to impose any additional 
controls to provide an ample margin of safety to protect public health.
    In the technology review, we did not identify any significant 
developments in practices, processes, or control technologies since 
promulgation of the original standards in 1994. We concluded that 
imposing additional controls under proposed Option 2 would achieve, at 
best, minimal emission and risk reductions. Option 2 would reduce 
organic HAP emissions by 1,700 tons per year, reduce cancer incidence 
by 0.05 cases per year, and reduce HI below 1 for about 20 individuals. 
We estimate that no one is currently exposed to emissions from HON 
sources causing cancer risks exceeding 100-in-1 million, the 
presumptively acceptable level for individual lifetime cancer risk 
under the Benzene NESHAP. (The relationship

[[Page 76606]]

between residual risk and the CAA section 112(d)(6) review is explained 
in our proposal at 72 FR 34436.) Thus, because of the lack of any 
significant developments in practices, processes, or technologies, and 
the limited effect in reducing public health risk, we find that 
additional controls are not warranted under CAA section 112(d)(6).

B. Summary of Changes to the Rule

    While we are making no changes to the control requirements of the 
existing standards based on the residual risk and technology review, we 
are publishing three technical amendments under CAA section 112(d)(2) 
designed to clarify provisions of the existing rule and provide for 
effective implementation. At proposal, we solicited comments on a list 
of rule clarifications. After considering public comments, we have 
decided not to adopt some of the proposed changes at this time. We may 
consider some of these proposed changes again in the future, in which 
case we intend to provide an additional opportunity to comment on them. 
However, we are finalizing one minor change on which we solicited 
comments. We are also making two minor changes for which we did not 
solicit comments but which were recommended by commenters. We are also 
clarifying in this preamble that liquid streams generated from control 
devices (e.g., scrubber effluent) are wastewater. No rule changes are 
necessary for this clarification.
1. Group Status Changes for Wastewater
    The revised rule clarifies the requirement to redetermine Group 
status for wastewater streams if process or operational changes occur 
that could reasonably be expected to change the wastewater stream from 
a Group 2 to a Group 1 stream. Examples of such process changes 
include, but are not limited to, changes in production capacity, 
production rate, feedstock type, or catalyst type; or whenever there is 
replacement, removal, or addition of recovery equipment. Although 40 
CFR 63.100(m) generally applies to Group 2 wastewater streams becoming 
Group 1, this change clarifies requirements for redetermining group 
status for wastewater by including provisions analogous to those in 40 
CFR 63.115(e), which requires redetermination of total resource 
effectiveness index value (TRE) for process vents due to process or 
operational changes.
2. Removal of Methyl Ethyl Ketone (MEK) from HON Tables
    In the final rule we have removed MEK from Tables 2 and 4 of 40 CFR 
part 63, subpart F and tables 9, 34, and 36 of 40 CFR part 63, subpart 
G. MEK was removed from the HAP list on December 19, 2005 (70 FR 
75047). At that time, MEK was not removed from various applicability 
tables in the HON, 40 CFR part 63, subparts F and G.
3. Vapor Balancing for Storage Tanks
    In the final rule we have decided to waive all notification and 
reporting requirements for owners or operators of facilities where 
railcars, tank trucks, or barges, which are part of the vapor balancing 
control option, are reloaded or cleaned. We are also allowing off-site 
reloading and cleaning operations to comply with monitoring, 
recordkeeping, and reporting provisions of any other applicable 40 CFR 
part 63 standards in lieu of the monitoring, recordkeeping, and 
reporting in the HON. These provisions have been added to other MACT 
standards because the vapor balancing provisions provide owners and 
operators flexibility in meeting the requirements of the MACT standards 
without sacrificing the level of emission reductions being achieved. 
Further, making these changes provide consistency between similar 
emission sources being controlled under similar rules.
    These amendments reflect a logical outgrowth of our proposed rule, 
and are reasonable decisions made in response to public comments we 
received regarding these issues.

III. Responses to Significant Comments

    The proposal provided a 60-day comment period ending August 14, 
2006. We received comments from 34 commenters. Commenters included 
State agencies, industry, industry trade groups, environmental groups, 
and individuals. We have summarized the significant comments below. A 
complete summary of comments and our responses can be found in the 
public docket for the promulgated rule, EPA-HQ-OAR-2005-0475.

A. Data Collection

    Comment: One commenter stated that a major flaw in the risk 
assessment is that EPA failed to use its CAA section 114 authority to 
collect data for the risk assessment and, instead, used ``voluntary, 
fragmentary, 7-year-old industry-submitted data from well under half of 
the affected facilities.'' The commenter stated that the 1999 Residual 
Risk Report to Congress emphasizes the need for site-specific data for 
more refined assessments, and that EPA has not collected such data in 
the risk assessment for the HON. The commenter stated that the purpose 
of the risk assessment was to determine the residual risk from SOCMI 
facilities, and that the data EPA used to perform the assessment was 
not of the type and quality to achieve that objective.
    Response: The CAA does not specify the type of data, or the method 
of acquiring it, that EPA must use for conducting residual risk 
assessments under CAA section 112(f). EPA can use data other than those 
gained through its CAA section 114 authority, if doing so enables the 
agency to determine the remaining risks presented after application of 
MACT standards. At the time EPA was considering options for data 
collection, the industry trade association (American Chemistry Council) 
volunteered and prepared questionnaires to member companies. EPA 
reviewed the questionnaire and determined that the information 
requested by it would greatly facilitate our conducting a residual risk 
assessment. The data received through the questionnaire represented a 
significant fraction of the facilities in the source category 
(approximately 44 percent), and include site-specific data on emissions 
sources, locations, and release parameters. Where emission release 
parameter data were missing, EPA used environmentally protective 
defaults in the modeling. While it is true that the data are now 7 
years old, a significant amount of time was needed to collect and 
analyze the data, run the models, analyze the results, and prepare the 
rulemaking package. Moreover, the mere age of the data does not 
necessarily affect its utility for assessing whether sources that have 
achieved compliance with MACT continue to present risks of concern, 
given that the essential question addressed by our assessment is 
whether the MACT controls themselves are adequately protective of 
public health with an ample margin of safety.
    Comment: One commenter stated that EPA has performed no analysis to 
determine that the industry data used in the risk assessment are 
representative of the source category as a whole. The commenter stated 
that for EPA to adequately satisfy CAA section 112(f), it must be able 
to accurately identify the risk associated with the most exposed 
individual and accurately estimate risk more generally from sources 
within the source category. The commenter stated that, to do this, EPA 
must have sufficient data regarding all of the important factors for 
estimating risk (including size, quantity of emissions, the specific 
characteristics of emission points, proximity, and population density 
of surrounding communities, important meteorological and

[[Page 76607]]

topological data, co-located emission sources, ambient background 
levels, etc.). The commenter stated that the factor of 2.3 that EPA 
used to scale up the population risk from the assessed facilities to 
the entire source category is arbitrary and unreasonable because it 
assumes constant population density.
    Response: The data used in the assessment were obtained from all 
responses to the industry questionnaire, and include site-specific data 
on emissions sources, locations, and release parameters. The data 
represent a significant fraction of the category (approximately 44 
percent), and include sources with high and low emissions, sources that 
are geographically proportional to the entire source category, and 
sources that emit nearly all organic HAP thought to be emitted from the 
category.
    While the emissions data obtained through the industry 
questionnaire cannot be proven to be proportional to the emissions from 
the entire source category, EPA does have whole-facility emissions data 
for 226 facilities (the entire source category is estimated at 238 
facilities) in the National Emissions Inventory (NEI), and we performed 
a screening-level risk assessment using these data to determine if 
there were HON facilities posing greater public health risks than those 
included in the industry data. Although the NEI data were for the whole 
facility (and not just the HON emission points), we used NEI data codes 
(MACT codes, Standard Industrial Classification codes, and Source 
Classification Codes) to judge whether risks estimated using the NEI 
data could be attributed to the HON source category. We found that the 
highest risks from using the NEI data were of the same order of 
magnitude as those estimated using the industry data. Based on this 
general corroboration with the NEI data, we concluded that the industry 
data were the most detailed and comprehensive data available that were 
specific to the source category, and that the data were appropriate for 
use in conducting the residual risk assessment.
    EPA did use a factor of 2.3 to estimate population risk associated 
with facilities not included in the industry data. This factor is 
simply the ratio of the total number of HON facilities to the number of 
facilities in the industry data, and reflects our expectation, based on 
further comparison to the NEI data, that on average, the population 
densities around the facilities not in the industry data are similar to 
the densities around the facilities that were in the industry data. We 
estimate that there are 61.6 million people living within the 50-
kilometer modeling radius of the 105 HON facilities included in the 
industry data. An estimated 82.8 million people live within the 50-
kilometer modeling radius of the 226 HON facilities modeled using the 
NEI data. Accordingly, the sources in the industry-supplied data are 
located near 75 percent of the total exposed population, but represent 
44 percent of the total number of facilities in the industry. This 
comparison indicates that many of the facilities not in the industry 
data are located in less densely populated areas or in the same areas 
as the facilities included in the industry data. Therefore, the 
population densities around the modeled facilities appear to be 
representative.
    In the risk assessment, EPA showed that facilities with overlapping 
modeling domains (facility ``clusters'') did not lead to significantly 
higher estimated risks to the individual most exposed because such 
risks are generally driven by the nearest facility. However, facility 
clusters did increase the numbers of individuals within certain cancer 
risk ranges. Although the total population around all facilities in the 
source category is not a factor of 2.3 greater than the total 
population around the facilities in the industry data, the additional 
facilities would increase the risks to some of the same segments of the 
population, resulting in higher risk to individuals in the population.

B. Risk Determination

    Comment: One commenter believed that EPA has misinterpreted the CAA 
by adopting the 1989 Benzene two-step framework to set residual risk 
standards under the 1990 CAA. The commenter concluded that the proper 
interpretation is that CAA section 112(f)(2)(A) specifies 1-in-1 
million as a bright line and mandates promulgation of standards to 
reach at least this level of health protection. The commenter believed 
that CAA section 112(f)(2)(B) merely leaves standing, those relevant 
rules that were promulgated under section 112 as it existed prior to 
the 1990 CAA. The commenter disagreed with EPA's position that 
Congressional inaction ratifies EPA's interpretation of CAA section 
112(f)(2)(B). The commenter believed that Congressional failure to 
respond to the EPA Report to Congress, which provided notification of 
the intent to utilize the 1989 Benzene two-step approach, does not 
justify overriding the plain statutory language of CAA section 112(f).
    Response: We disagree with the commenter. Our policy on using the 
Benzene NESHAP for implementing CAA section 112(f) has been fully 
explained in the Coke Oven Batteries NESHAP (see 70 FR 19992, April 15, 
2005) and the Residual Risk Report to Congress, and our approach here 
is fully consistent with our prior practice. The commenter's argument 
that the statute requires CAA section 112(f) residual risk standards to 
reduce cancer risk to the most exposed individual to less than 1-in-1 
million lacks a basis in the statutory text or in policy. CAA Section 
112(f)(2)(A), in stating that EPA is to conduct residual risk 
rulemaking if the ``lifetime excess cancer risk to the individual most 
exposed to emissions from a source in a category or subcategory'' is 
greater than 1-in-1 million, does not establish what the level of the 
standard must be other than to require them to ``provide an ample 
margin of safety to protect public health in accordance with this 
section (as in effect before the date of enactment of the CAA 
Amendments of 1990) [* * *].'' Read in light of CAA section 
112(f)(2)(B)'s express preservation of EPA's pre-enactment 
interpretation of CAA section 112, Congress clearly preserved EPA's 
ability to apply the same two-step formulation established by the 
Benzene NESHAP in making future ``ample margin of safety'' 
determinations under CAA section 112(f)(2).
    Under that test, there is no single risk level establishing what 
constitutes an ample margin of safety. Rather, the Benzene NESHAP 
approach codified in CAA sections 112(f)(2)(A) and (B) is deliberately 
flexible, requiring consideration of a range of factors (among them 
estimates of quantitative risk, incidence, and numbers of exposed 
persons within various risk ranges; scientific uncertainties; and 
weight of evidence) when determining acceptability of risk (the first 
step in the ample margin of safety determination (54 FR 38045, 
September 14, 1989). Determination of an ample margin of safety, the 
second step in the process, requires further consideration of these 
factors, plus consideration of technical feasibility, cost, economic 
impact, and other factors (54 FR 38046, September 14, 1989). As we 
stated in our ``Residual Risk Report to Congress'' (EPA-453/R-99-001) 
issued under CAA section 112(f)(1), we do not consider the 1-in-1 
million individual cancer risk level as a ``bright line'' mandated 
level of protection for establishing residual risk standards, but 
rather as a trigger point to evaluate whether additional reductions are 
necessary to provide an ample margin of safety to protect public 
health. This interpretation is supported by the language in the 
preamble to the Benzene NESHAP, which was

[[Page 76608]]

incorporated by Congress in CAA sections 112(f)(2)(A) and (B).
    The Report to Congress was intended, among other things, to explain 
how EPA would implement CAA section 112(f) by investigating the methods 
available for assessing public health risks after the technology-based 
standards were applied and explaining any uncertainties in the methods. 
Congress also asked us to make recommendations for changes to the CAA 
section 112(f) as a result of the investigation. A plain reading of the 
CAA section 112(f)(2)(A) indicates that if, based on the report, 
Congress judged that residual risk standards were unnecessary or that 
the analytical methods for implementing the provisions were inadequate, 
then Congress would enact revisions to CAA section 112(f). The choice 
by Congress not to respond to the report clearly indicates that we 
should proceed with our general approach as explained in our Report to 
Congress.
    We consequently believe that the commenter's bright line approach 
is not supported by the statute, and is incorrect as a matter of law. 
It is true that the Senate version of CAA section 112(f) mandated 
elimination of lifetime risks of carcinogenic effects greater than 1-
in-10 thousand to the individual in the population most exposed to 
emissions of a carcinogen. (See ``A Legislative History of the Clean 
Air Act Amendments of 1990,'' pages 7598 and 8518.) However, this 
version of the legislation was not adopted. We believe that the 
rejected Senate version of CAA section 112(f) shows that Congress 
considered mandating a level of risk reduction and chose not to do so.
    In any event, EPA has concluded that the flexible approach to risk 
acceptability and ample margin of safety set forth in the Benzene 
NESHAP is reasonable and appropriate in light of the complex judgments 
EPA must make under CAA section 112(f).
    Comment: One commenter argued that CAA section 112(f)(2)(A) very 
clearly prohibits using cost as a consideration for standards 
promulgated to provide an ample margin of safety to protect public 
health. CAA Section 112(f)(2)(A) directs EPA to promulgate standards in 
order to provide an ample margin of safety to protect public health or 
to prevent, taking into consideration costs, energy, safety, and other 
relevant factors, an adverse environmental effect. The commenter 
maintained that this construction allows cost as a consideration only 
for standards designed to prevent an adverse environmental effect where 
such standards are more stringent than necessary to protect human 
health with an ample margin of safety. As part of their argument, the 
commenter cited the Supreme Court decision in American Trucking 
Associations v. Whitman (2001), which addressed ambient air quality 
standards established under section 109 of the CAA, as providing 
precedent that cost cannot be considered in developing regulations to 
protect public health with a margin of safety. The commenter claimed 
that this court decision abrogated the District of Columbia Circuit 
decision on Vinyl Chloride, upon which the Benzene two-step policy is 
based. They also pointed out that the 1990 CAA removed the statutory 
language that Vinyl Chloride relied upon heavily. The commenter pointed 
out that unlike the previous CAA, section 112(f) of the 1990 CAA does 
not contain the phrase ``* * * set the standard at the level which in 
[the Administrator's] judgment provides an ample margin of safety to 
protect public health.'' The commenter claimed that exclusion of the 
specific requirement to use judgment invalidates the basis of Vinyl 
Chloride.
    Response: The clear reading of CAA section 112(f) allows us to take 
cost into consideration within the context of the two-step policy of 
the 1989 Benzene NESHAP. The stipulation in CAA section 112(f)(2)(A) 
that costs, energy, safety, and other factors can be taken into 
consideration in setting standards to prevent an adverse environmental 
effect does not mean that costs cannot be taken into consideration in 
determining standards to protect public health. To the contrary, CAA 
section 112(f)(2)(A) states that residual risk standards are to provide 
an ample margin of safety to protect public health ``in accordance with 
this section (as in effect before the date of enactment of the Clean 
Air Act Amendments of 1990).'' This formulation, coupled with CAA 
section 112(f)(2)(B), which states that nothing in CAA section 
112(f)(2)(A) or any other part of CAA section 112 shall be construed as 
affecting the EPA's interpretation of this section as set forth in the 
preamble to the 1989 Benzene NESHAP, reflects Congress' endorsement of 
the Benzene NESHAP approach, including the use of costs in determining 
an ample margin of safety.
    The court decision cited by the commenter, American Trucking 
Association v. Whitman, has no relevance to decisions on ample margin 
of safety made under section 112 of the CAA. That case addressed the 
consideration of cost in the context of setting national ambient air 
quality standards under CAA section 109. The American Trucking 
Association v. Whitman decision does not specifically address, nor does 
it apply (nor could it have, as a matter of jurisdiction, since the 
court was not faced with an issue requiring a ruling on an 
interpretation of CAA section 112), to the different statutory 
requirements for regulating HAP under CAA section 112 or to any prior 
judicial precedent interpreting CAA section 112. Also, we do not read 
the 1990 CAA as overturning or otherwise disapproving of the court's 
decision in Vinyl Chloride. By directing us under CAA sections 
112(f)(2)(A) and (B) to follow the 1989 Benzene NESHAP policy, the 1990 
CAA requires the Administrator to use judgment both in establishing 
risk levels that constitute a safe level of exposure and in balancing 
costs against remaining risks for determining an ample margin of 
safety. Therefore, by eliminating the wording in CAA section 
112(f)(2)(A) to use ``judgment,'' Congress eliminated a redundant 
specification and did not remove the legal basis of the Vinyl Chloride 
decision.
    Comment: Several commenters contended that revising the HON 
pursuant to CAA section 112(d)(6) is not necessary and not justified. 
The commenters stated that EPA's Option 2 would revise the MACT beyond-
the-floor decisions, that emission reductions to be gained from Option 
2 are significantly overstated, and that the emission reduction does 
not justify the cost. Several commenters noted that Option 2 
alternatives do not represent any ``developments in practices, 
processes, and control technologies'' but rather simply reflect an 
apparent decision by EPA that higher cost options that were rejected in 
the original beyond-the-floor analysis are now somehow acceptable.
    Response: We do not agree that in reviewing a standard under CAA 
section 112(d)(6), the CAA mandates that only the question of whether 
newly developed emission control measures have been identified since 
the publication of the MACT standards be addressed. CAA Section 
112(d)(6) requires that EPA review and revise standards ``as 
necessary.'' As we explain later, the instruction to revise ``as 
necessary'' indicates that EPA should use judgment in this regulatory 
decision, and is not precluded from considering additional relevant 
factors, such as risk and the evolution of costs of previously 
considered measures. At the time of a MACT determination, the beyond-
the-floor decision is made without knowledge of the level of risks 
posed by an industry. In the subsequent reviews of the standards, we 
have substantial discretion in weighing all of the relevant factors, 
including all

[[Page 76609]]

available control measures that are more stringent than that required 
by the current NESHAP, emission reductions, public health risk impacts, 
costs, and any other relevant factors to determine what further 
controls, if any, are necessary.
    Comment: Several commenters contended that the application of CAA 
section 112(d)(6) should incorporate the framework of CAA section 
112(f)(2) because this approach would require the Administrator to 
weigh the potential for future risk reduction under CAA section 
112(d)(6) against the cost of that reduction in the same manner as set 
forth in the second step of the 1989 Benzene NESHAP rule. One commenter 
added that technology reviews that focus solely on the cost-per-ton of 
additional emission controls and do not consider the risk reduction 
potential could result in the imposition of technology controls that 
yield very little, if any, benefit. Another commenter stated that when 
a MACT standard achieves protection of public health with an ample 
margin of safety and prevents adverse environmental effects, as is the 
case with the HON, no further revisions are ``necessary'' even if there 
have been developments in control technologies. The commenter believed 
that a determination of ample margin of safety and no adverse 
environmental effects alone is sufficient to determine that revision of 
the standard is not necessary under CAA section 112(d)(6). The 
commenter supported EPA's position that risk benefits are appropriate 
to consider under the CAA section 112(d)(6) decision.
    Another commenter rejected EPA's interpretation that the term 
``revise as necessary'' allows EPA to import into its 8-year evaluation 
the consideration of cost and risk. The commenter maintained that 
emission standards adopted under CAA section 112(d)(2) themselves were 
the product of a technology-driven evaluation that did not incorporate 
cost as a factor in the initial stages, and did not permit 
consideration of risk at all. The commenter continued that EPA has 
illegally substituted a risk/cost analysis for the requirement to 
perform an analysis of the technical feasibility of emission controls 
to establish the level of control of the best performing HON sources.
    Response: We have addressed the relationship between CAA sections 
112(f) and 112(d) in other recent rulemakings, as well as in the 
proposal for today's final rule. See, e.g., our response to comments 
document for the Dry Cleaning Facilities Residual Risk Rule (71 FR 
42727, July 27, 2006) (EPA's Summary of Public Comments and Responses 
to the Proposed Rule is located at docket no. EPA-HQ-OAR-2005-0155). As 
we explained in our proposal (see 71 FR 34436, June 14, 2006), the 
findings that underlie a CAA section 112(f) risk determination will 
often be key factors in making any subsequent CAA section 112(d)(6) 
technology review determinations. While our action today makes no 
changes to control requirements under the HON and it is, therefore, not 
necessary to respond to their individual points, we disagree with the 
commenters who state that a determination under CAA section 112(f) of 
an ample margin of safety and no adverse environmental effects alone 
will, in all cases, necessarily cause us to determine that a revision 
is not necessary under CAA section 112(d)(6). Our decision today should 
not be viewed as a departure from our general view, articulated in the 
proposal, that in some cases, even if risk factors remain the same from 
one round of CAA section 112(d)(6) review to another, changes in costs 
of or in the availability of control technology may be sufficient to 
alter a previous conclusion about whether to impose further controls.
    In response to the commenter who claimed we may not consider risks 
or costs at all under CAA section 112(d)(6), we continue to interpret 
the use of the phrase ``as necessary'' in that section as conferring 
discretion on the agency to exercise its judgment as to what factors 
may drive an evaluation of available practices, processes, and control 
technologies. The ambiguous term ``as necessary'' inherently requires 
an EPA comparison between control measures and some goal or end. As the 
first rounds of both CAA section 112(f) residual risk and CAA section 
112(d) technology review occur 8 years following MACT, it is reasonable 
to interpret these duties as being compatible with and informative of 
each other, and for the ultimate goal of revising standards as needed 
to protect public health with an ample margin of safety as influencing 
what we determine is generally ``necessary,'' in terms of whether to 
impose further technological controls under CAA section 112(d)(6).
    Comment: One commenter contended that, for residual risk 
assessments, EPA may not rely on actual emissions, which represents 
``over-control'' of emissions, with no comparison to allowable 
emissions. The commenter stated that if sources are being over-
controlled as EPA suggests, then EPA's analysis of risk underestimates 
the risk remaining after implementation of the HON. The commenter added 
that the assessment required in CAA section 112(f)(2)(A) is of the 
``standards'' adopted under CAA section 112(d). If the current 
``standards'' are not adequate to protect public health with an ample 
margin of safety, more stringent standards are necessary. The commenter 
claimed that, if sources are over-controlling, but nothing in the CAA 
section 112(d) standards would prevent backsliding, the statute 
requires EPA to adopt more stringent limits to maintain that over-
control. If the over-control occurs because State or local agencies 
have adopted tighter limits, the commenter concluded that more 
stringent limits are feasible, and EPA must either (a) adopt those 
limits nationally to provide uniform protection or (b) explain why such 
standards would be infeasible.
    Several commenters agreed with EPA that, for this source category, 
the use of 1999 actual emissions data rather than allowable emissions 
do not lead to an underestimating of risk. The commenters pointed out 
that the conservatism of the health benchmark values and the exposure 
estimates outweigh any potential underestimation of emission levels 
based on using actual emissions, and added that EPA emission data based 
on actual emissions is conservatively high since the Toxics Release 
Inventory shows a reduction in emissions since 1999.
    Response: EPA's position on the use of both allowable and actual 
emissions is fully discussed in the final Coke Oven Batteries NESHAP 
(70 FR 19998-19999, April 15, 2005). There we explained that modeling 
the allowable levels of emissions is inherently reasonable since they 
reflect the maximum level sources could emit and still comply with 
national emission standards. But we also explained that it is 
reasonable to consider actual emissions, where data on them is 
available, in both steps of the Benzene NESHAP analysis in order to 
avoid overestimating emissions and their risks (including incidence) 
and to account for how sources typically strive to perform better than 
required by standards to allow for process variability and not exceed 
standards due to emissions increases on individual days. Failure to 
consider these data in risk assessments, we said, would unrealistically 
inflate risk levels.
    The preamble to the proposed HON residual risk standards included a 
discussion of actual versus allowable emissions from HON emission 
points (71 FR 34428). We explained that, for this source category, 
using available data on actual emissions enabled us to approximate 
allowable emissions, and that basing the analysis on actual

[[Page 76610]]

emissions here provided an acceptable method for determining the 
remaining risks to public health and the environment after application 
of the MACT standards. In the HON proposal preamble, we acknowledged 
that there is some uncertainty regarding the differences between actual 
and allowable emissions. For some emission points, it was not possible 
to estimate allowable emissions from available information. A 
requirement to determine the applicability of controls for some 
emission points was intentionally not included in the HON because it 
was seen as an unnecessary burden for points that would be controlled 
anyway. For these emission points there is no readily available data 
that can be used to determine the applicability of control 
requirements. Without such data, there is no accurate way to determine 
allowable emissions under the current rule. However, for equipment 
leaks which represent the most significant impact on the cancer risk at 
the HON facilities, the standards are work practice standards and the 
actual emissions and allowable emissions are likely the same for 
equipment in the leak detection and repair program required by the HON. 
More frequent monitoring of equipment components (for example, monthly 
instead of quarterly) could result in actual emissions being lower than 
allowable emissions, but few, if any, sources monitor more frequently 
than required by the HON.
    We concluded that there is no reason to believe that there is 
either a substantial amount of overcontrol of Group 1 sources or 
voluntary control of Group 2 sources such that actual emissions are not 
a reasonable approximation of allowable emissions. Rather, actual 
emissions appear to reflect the results of our prior application of 
MACT (allowing for process variability), and no evidence in the record 
suggests that sources could make changes that significantly increase 
their emissions and risks but still comply with MACT control 
requirements. Consequently, basing the risk analysis on actual 
emissions in this case enabled us to determine the remaining risks to 
public health and the environment after application of the specific 
MACT standards applicable to HON sources.
    Comment: One commenter argued that EPA must address inorganic HAP. 
The Risk Assessment acknowledges that inorganic HAP, such as 
hydrochloric acid and chlorine, may be emitted from HON sources, but 
that these compounds were not considered because data were not 
available to characterize emissions. The commenter argued that EPA 
cannot rely on the circular justification that the original HON 
regulated only organic HAP. The commenter argued that the residual risk 
provisions of CAA section 112(f) direct EPA to estimate the remaining 
risk for the regulated categories, whatever chemicals that risk may 
encompass. The commenter added that EPA's attempt to screen out 
inorganic HAP from further risk assessment by looking at these 
emissions in isolation is invalid. The commenter contended that EPA 
must look at the combined target organ specific HI from all emissions 
allowed under the current standards, including inorganic emissions, to 
determine if the residual risk is acceptable. Moreover, the commenter 
stated that EPA cannot avoid the consideration of emission controls for 
inorganics based only on a screening analysis; such control decisions 
for both the residual risk and the CAA section 112(d)(6) determination 
must consider other factors such as costs and feasibility.
    Response: We acknowledge that inorganic HAP (such as hydrochloric 
acid and chlorine) are emitted from some HON sources and that these 
pollutants require consideration even though they were not regulated 
HAP in the existing NESHAP. We stated in the preamble to the proposed 
rule that inorganic HAP were not considered in the primary assessment 
because data were not available to characterize emissions. However, we 
conducted an additional analysis using information in the NEI to 
estimate the risk from the entire plant site at which the HON processes 
are located. The NEI contains information on both organic and inorganic 
HAP emitted from each facility. EPA estimated hazard indices (total, 
not target organ specific) for each of the 226 HON facilities for which 
NEI data were available. There were many instances where inorganic HAP 
were responsible for hazard indices exceeding 1, but there were no 
instances where the inorganic HAP were associated with HON processes. 
Therefore, EPA concluded that not including inorganic HAP in the 
primary risk assessment did not affect the results of the analysis, and 
that no further assessment of inorganic HAP emissions was necessary in 
order to determine whether remaining risks from HON sources after 
application of MACT are at acceptable levels. Furthermore, as discussed 
earlier in the preamble, it is not reasonable to impose any additional 
controls to provide an ample margin of safety to protect public health.

C. Administrative Requirements

    Comment: One commenter argued that EPA has not appropriately 
addressed impacts on children and other sensitive receptors. The 
commenter stated that even though EPA acknowledged in the risk 
assessment that children face greater exposure and are more susceptible 
to the adverse health effects from airborne contaminants, these factors 
were not addressed. The commenter stated that EPA determined that 
``[t]he proposed rule is not subject to the Executive Order (13045: 
Protection of Children From Environmental Health Risks and Safety 
Risks) * * * because the Agency does not have reason to believe the 
environmental health or safety risks addressed by this action present a 
disproportionate risk to children.'' This commenter contended that this 
conclusion is based on our assessment of the information on the effects 
on human health and exposures associated with SOCMI operations. The 
commenter could not find such an assessment referenced in the Risk 
Assessment. The commenter also stated that EPA ignored the effects on 
other sensitive receptors, e.g., active adults.
    Response: First, since this rulemaking is not economically 
significant under Executive Order 12866, Executive Order 13045 does not 
apply to this matter.
    EPA acknowledges that population subgroups, including children, may 
have the potential for risk greater than the general population due to 
greater relative exposure and/or greater susceptibility to the 
toxicant. With respect to exposure, the risk assessment implicitly 
accounts for this greater potential for exposure by assuming lifetime 
(rather than simply childhood) exposure, which would tend to yield 
higher estimates of risks. The exposure assessment described the 
maximum modeled lifetime exposure of residents near HON facilities. The 
exposed population was conservatively presumed to be exposed to 
airborne concentrations at their residence continuously, 24 hours per 
day for a full lifetime, including childhood.
    With regard to children's potentially greater susceptibility to 
non-cancer toxicants emitted by HON facilities, the assessment relied 
on Agency (or comparable) hazard identification and dose-response 
values which have been developed to be protective for all subgroups of 
the general population, including children. For example, a review \1\ 
of the chronic reference value

[[Page 76611]]

process concluded that the Agency's reference concentration (RfC) 
derivation processes adequately considered potential susceptibility of 
different subgroups with specific consideration of children, such that 
the resultant RfC values pertain to the full human population 
``including sensitive subgroups,'' a phrase which is inclusive of 
childhood.
---------------------------------------------------------------------------

    \1\ A Review of the Reference Dose and Reference Concentration 
Process. U.S. Environmental Protection Agency. Risk Assessment 
Forum. EPA/630/P-02/002F. December 2002.
---------------------------------------------------------------------------

    On the issue of cancer dose-response values, our revised cancer 
guidelines and new supplemental guidance recommend applying default 
adjustment factors to account for exposures occurring during early-life 
exposure to those chemicals thought to cause cancer via a mutagenic 
mode of action. For these chemicals, the supplemental guidance 
indicates that, in lieu of chemical-specific data on which age or life-
stage specific risk estimates or potencies can be determined, default 
``age dependent adjustment factors'' can be applied when assessing 
cancer risk for early-life exposures to chemicals which cause cancer 
through a mutagenic mode.\2\ However, at the present time, we have not 
determined whether any of the HAP emitted by the HON source category 
cause cancer via a mutagenic mode of action. While several of the HON 
pollutants may be carcinogenic by such a mechanism, our policy is not 
to apply these adjustment factors unless we have completed a peer-
reviewed assessment that explicitly makes this determination after 
consideration of the full scientific literature.
---------------------------------------------------------------------------

    \2\ The ``Supplemental Guidance for Assessing Susceptibility 
from Early-Life Exposure to Carcinogens'' recommends applying 
default adjustment factors to early life stage exposures to 
carcinogens acting through a mutagenic mode of action. The 
Supplemental Guidance recommends an integrative approach that can be 
used to assess total lifetime risk resulting from lifetime or less-
than-lifetime exposure during a specific portion of a lifetime. The 
following adjustments represent the approach suggested in the 
Supplemental Guidance: (1) For exposures before 2 years of age 
(i.e., spanning a 2-year time interval from the first day of birth 
up until a child's second birthday), a 10-fold adjustment; (2) for 
exposures between 2 and less than 16 years of age (i.e., spanning a 
14-year time interval from a child's second birthday up until their 
sixteenth birthday), a 3-fold adjustment; and (3) for exposures 
after turning 16 years of age, no adjustment. Assuming a constant 
lifetime exposure, incorporation of these adjustment factors would 
increase the estimate of lifetime cancer risk by roughly 60 percent 
(factor of 1.6). If exposures were from 3 years to 73 years, the 
adjustment factor would be less than 1.6. If exposures were from 16 
years to 86 years, no adjustment would be necessary.
---------------------------------------------------------------------------

    Although we are not yet certain whether or not a childhood potency 
adjustment is needed, the estimated risks must also be considered in 
the context of the full set of assumptions used for this risk 
assessment. For example, we used a health-protective assumption of a 
70-year exposure duration in our risk estimates; however, using the 
national average residency time of 12 years would reduce the estimate 
of risk by roughly a factor of 6. Our unit risk estimates for HAP are 
considered a plausible upper-bound estimate; actual potency is likely 
to be lower and some of which could be as low as zero. After 
considering these and other factors, we continue to consider the risks 
from emissions after application of the current HON rule to be 
acceptable (within the meaning of the Benzene NESHAP decision framework 
discussed at 69 FR 48339-48340, 48347-48348, August 9, 2004). As 
mentioned in the recently published cancer guidelines, we will continue 
to develop and present, to the extent practicable, an appropriate 
central estimate and appropriate lower and upper-bound estimates of 
cancer potency. Development of new methods or estimates is a process 
that will require independent peer review.
    Comment: One commenter argued that EPA failed to adequately address 
environmental effects or to comply with the requirements of the 
Endangered Species Act (ESA). The commenter objected to EPA's 
assumption in the ecological assessment that the aquatic and 
terrestrial communities surrounding HON sources were healthy and 
unaffected by other stressors. Additionally, the commenter claimed that 
EPA is on record acknowledging its obligation to comply with the ESA 
during the residual risk phase of the air toxics program, and yet EPA 
failed to do so.
    Response: The commenter is correct that EPA has publicly agreed 
that the consultation requirements of the ESA potentially apply to CAA 
section 112(f) residual risk rulemakings. See Sierra Club v. EPA. 353 
F.3d 976 (District of Columbia Circuit, 2004). This is because CAA 
section 112(f)(2)(A) provides us with authority to tighten NESHAP, 
after consideration of costs and other relevant factors, to prevent an 
``adverse environmental effect.'' CAA section 112(a)(7) defines this 
term to mean ``any significant and widespread adverse effect, which may 
reasonably be anticipated, to wildlife, aquatic life, or other natural 
resources, including adverse impacts on populations of endangered or 
threatened species or significant degradation of environmental quality 
over broad areas'' (emphasis added). Therefore, CAA section 112(f) 
clearly provides EPA discretion to promulgate a residual risk rule in a 
manner that inures to the benefit of listed species (see 50 CFR 
402.03), at least in cases where adverse environmental effects are of a 
significant magnitude.
    However, under section 7(a)(2) of the ESA and the implementing 
regulations promulgated by the Fish and Wildlife Service and the 
National Marine Fisheries Service (collectively, the Services), an 
action agency such as EPA has a duty to initiate consultation with the 
services only where it determines that its action may have an impact 
(either beneficial or a