approach to malfunctions is consistent with section 112 and is a
reasonable interpretation of the statute.[rparb]
    In the event that a source fails to comply with the applicable CAA
section 112(d) standards as a result of a malfunction event, the EPA
would determine an appropriate response based on, among other things,
the good faith efforts of the source to minimize emissions during
malfunction periods, including preventative and corrective actions, as
well as root cause analyses to ascertain and rectify excess emissions.
The EPA would also consider whether the source's failure to comply with
the CAA section 112(d) standard was, in fact, ``sudden, infrequent, not
reasonably preventable'' and was not instead ``caused in part by poor
maintenance or careless operation.'' 40 CFR 63.2 (definition of
malfunction).
    Finally, the EPA recognizes that even equipment that is properly
designed and maintained can sometimes fail and that such failure can
sometimes cause an exceedance of the relevant emission standard. (See,
e.g., State Implementation Plans: Policy Regarding Excessive Emissions
During Malfunctions, Startup, and Shutdown (Sept. 20, 1999); Policy on
Excess Emissions During Startup, Shutdown, Maintenance, and
Malfunctions (Feb. 15, 1983)). The EPA is, therefore, proposing to
follow its recently established practice (see, e.g., 76 FR 22566,
22573-74 (Apr. 21, 2011)) and add to the rules an affirmative defense
to civil penalties for exceedances of emission limits that are caused
by malfunctions. See proposed 40 CFR 63.1312 (Group IV Polymers and
Resins), 40 CFR 63.1361 (PAI) and 40 CFR 63.1423 (PEPO). The
regulations define ``affirmative defense'' to mean, in the context of
an enforcement proceeding, a response or defense put forward by a
defendant, regarding which the defendant has the burden of proof, and
the merits of which are independently and objectively evaluated in a
judicial or administrative proceeding. We also are proposing other
regulatory provisions to specify the

elements that are necessary to establish this affirmative defense; the
source must prove by a preponderance of the evidence that it has met
all of the elements set forth in proposed 40 CFR 63.1310(k) (Group IV
Polymers and Resins), 40 CFR 63.1360(k) (PAI) and 40 CFR 63.1420(i)
(PEPO). (See 40 CFR 22.24). The criteria ensure that the affirmative
defense is available only where the event that causes an exceedance of
the emission limit meets the narrow definition of malfunction in 40 CFR
63.2 (sudden, infrequent, not reasonable preventable and not caused by
poor maintenance and or careless operation). For example, to
successfully assert the affirmative defense, the source must prove by a
preponderance of the evidence that excess emissions ``[w]ere caused by
a sudden, infrequent, and unavoidable failure of air pollution control
and monitoring equipment, process equipment, or a process to operate in
a normal or usual manner * * *.'' The criteria also are designed to
ensure that steps are taken to correct the malfunction, to minimize
emissions in accordance with proposed 40 CFR 63.1310(j)(4) (Group IV
Polymers and Resins), 40 CFR 63.1362(i) (PAI) and 40 CFR 63.1420(h)(4)
(PEPO) and to prevent future malfunctions. For example, the source must
prove by a preponderance of the evidence that ``[r]epairs were made as
expeditiously as possible when the applicable emission limitations were
being exceeded * * *'' and that ``[a]ll possible steps were taken to
minimize the impact of the excess emissions on ambient air quality, the
environment and human health * * *.'' In any judicial or administrative
proceeding, the Administrator may challenge the assertion of the
affirmative defense and, if the respondent has not met its burden of
proving all of the requirements in the affirmative defense, appropriate
penalties may be assessed in accordance with section 113 of the CAA
(see also 40 CFR 22.27).
    The EPA included an affirmative defense in these proposed rules in
an attempt to balance a tension, inherent in many types of air
regulation, to ensure adequate compliance while simultaneously
recognizing that despite the most diligent of efforts, emission limits
may be exceeded under circumstances beyond the control of the source.
The EPA must establish emission standards that ``limit the quantity,
rate, or concentration of emissions of air pollutants on a continuous
basis.'' 42 U.S.C. 7602(k) (defining ``emission limitation and emission
standard''). See generally, Sierra Club v. EPA, 551 F.3d 1019, 1021
(D.C. Cir. 2008). Thus, the EPA is required to ensure that section 112
emissions limitations are continuous. The affirmative defense for
malfunction events meets this requirement by ensuring that even where
there is a malfunction, the emission limitation is still enforceable
through injunctive relief. While ``continuous'' limitations, on the one
hand, are required, there is also caselaw indicating that in many
situations it is appropriate for the EPA to account for the practical
realities of technology. For example, in Essex Chemical v. Ruckelshaus,
486 F.2d 427, 433 (D.C. Cir. 1973), the District of Columbia Circuit
acknowledged that, in setting standards under CAA section 111,
``variant provisions'' such as provisions allowing for upsets during
startup, shutdown and equipment malfunction ``appear necessary to
preserve the reasonableness of the standards as a whole and that the
record does not support the `never to be exceeded' standard currently
in force.'' See also, Portland Cement Association v. Ruckelshaus, 486
F.2d 375 (D.C. Cir. 1973). Though intervening caselaw such as Sierra
Club v. EPA and the CAA 1977 amendments undermine the relevance of
these cases today, they support the EPA's view that a system that
incorporates some level of flexibility is reasonable. The affirmative
defense simply provides for a defense to civil penalties for excess
emissions that are proven to be beyond the control of the source. By
incorporating an affirmative defense, EPA has formalized its approach
to upset events. In a Clean Water Act setting, the Ninth Circuit
required this type of formalized approach when regulating ``upsets
beyond the control of the permit holder.'' Marathon Oil Co. v. EPA, 564
F.2d 1253, 1272-73 (9th Cir. 1977). See, Weyerhaeuser Co. v. Costle,
590 F.2d 1011, 1057-58 (D.C. Cir. 1978) (holding that an informal
approach is adequate). The affirmative defense provisions give the EPA
the flexibility to both ensure that its emission limitations are
``continuous'' as required by 42 U.S.C. section 7602(k), and account
for unplanned upsets and thus support the reasonableness of the
standard as a whole.
    In addition to these changes in the provisions related to SSM, we
are also proposing that there be no discharge to the atmosphere from
any pressure relief device (PRD) on any equipment in HAP service within
the process units for these seven source categories. To ensure
compliance with this requirement, facility owners or operators would be
required to install electronic indicators on each PRD that would be
able to identify and record the time and duration of each pressure
release and notify operators that a pressure release has occurred.
While pressure release events may be associated with unplanned,
nonroutine discharges that result from operator error, malfunctions or
other unexpected causes that require immediate venting of gas from
process equipment in order to avoid safety hazards or equipment damage,
we are concerned that a large number of these releases that occur may
emit large quantities of HAP, may not be identified and controlled in a
timely manner and may be due to repeat problems that have not been
corrected. These proposed provisions will clarify that such release
events would be violations of the emissions standards of these rules.
If any pressure release events that occur are related to a process or
control device malfunction, the owner or operator could claim the
affirmative defense described above.
2. Electronic Reporting
    We are proposing to add electronic reporting requirements to the
PAI, PEPO and the Group IV Polymers and Resin Production NESHAP. The
EPA must have performance test data to conduct effective reviews of CAA
section 112 standards, as well as for many other purposes including
compliance determinations, emission factor development and annual
emission rate determinations. In conducting these required reviews, the
EPA has found it ineffective and time consuming, not only for us, but
also for regulatory agencies and source owners and operators, to
locate, collect and submit performance test data because of varied
locations for data storage and varied data storage methods. In recent
years, though, stack testing firms have typically collected performance
test data in electronic format, making it possible to move to an
electronic data submittal system that would increase the ease and
efficiency of data submittal and improve data accessibility.
    Through this proposal, the EPA is presenting a step to increase the
ease and efficiency of data submittal and improve data accessibility.
Specifically, the EPA is proposing that owners and operators of PAI,
PEPO and Group IV Polymers and Resins facilities submit electronic
copies of required performance test reports to the EPA's WebFIRE
database. The WebFIRE database was constructed to store performance
test data for use in developing emission factors. A description of the
WebFIRE database is

available at http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main.
    As proposed above, data entry would be through an electronic
emissions test report structure called the Electronic Reporting Tool
(ERT). The ERT would generate electronic report which would be
submitted using the Compliance and Emissions Data Reporting Interface
(CEDRI). The submitted report would be transmitted through the EPA's
Central Data Exchange (CDX) network for storage in the WebFIRE database
making submittal of data very straightforward and easy. A description
of the ERT can be found at http://www.epa.gov/ttn/chief/ert/index.html
and CEDRI can be accessed through the CDX Web site (http://www.epa.gov/cdx).
    The proposal to submit performance test data electronically to the
EPA would apply only to those performance tests conducted using test
methods that will be supported by the ERT. The ERT contains a specific
electronic data entry form for most of the commonly used EPA reference
methods. A listing of the pollutants and test methods supported by the
ERT is available at http://www.epa.gov/ttn/chief/ert/index.html. We
believe that industry would benefit from this proposed approach to
electronic data submittal. Having these data, the EPA would be able to
develop improved emission factors, make fewer information requests and
promulgate better regulations.
    One major advantage of the proposed submittal of performance test
data through the ERT is a standardized method to compile and store much
of the documentation required to be reported by this rule. Another
advantage is that the ERT clearly states what testing information would
be required. Another important proposed benefit of submitting these
data to the EPA at the time the source test is conducted is that it
should substantially reduce the effort involved in data collection
activities in the future. When the EPA has performance test data in
hand, there will likely be fewer or less substantial data collection
requests in conjunction with prospective required residual risk
assessments or technology reviews. This would result in a reduced
burden on both affected facilities (in terms of reduced manpower to
respond to data collection requests) and the EPA (in terms of preparing
and distributing data collection requests and assessing the results).
    State, local and tribal agencies could also benefit from more
streamlined and accurate review of electronic data submitted to them.
The ERT would allow for an electronic review process rather than a
manual data assessment making review and evaluation of the source
provided data and calculations easier and more efficient. Finally,
another benefit of the proposed data submittal to WebFIRE
electronically is that these data would greatly improve the overall
quality of existing and new emissions factors by supplementing the pool
of emissions test data for establishing emissions factors and by
ensuring that the factors are more representative of current industry
operational procedures. A common complaint heard from industry and
regulators is that emission factors are outdated or not representative
of a particular source category. With timely receipt and incorporation
of data from most performance tests, the EPA would be able to ensure
that emission factors, when updated, represent the most current range
of operational practices. In summary, in addition to supporting
regulation development, control strategy development and other air
pollution control activities, having an electronic database populated
with performance test data would save industry, state, local, tribal
agencies and the EPA significant time, money and effort while also
improving the quality of emission inventories and, as a result, air
quality regulations.

IV. Analytical Results and Proposed Decisions for Group IV Polymers and
Resins Source Categories

A. Acrylonitrile Butadiene Styrene Resin (ABS)

1. What are the results of the risk assessments?
a. Inhalation Risk Assessment Results
    Table 3 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                     Table 3--ABS Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                      (in 1 million) \2\                         Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site acute
   Number of  facilities \1\        Actual         Allowable    risk  >= 1-in-    (cases per        Actual         Allowable        noncancer HQ \4\
                                   emissions       emissions       1 million         year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
5.............................              30              30          32,000           0.003             0.2             0.2  HQREL = 2 acetaldehyde.
                                                                                HQERPG-1 = 0.04
                                                                                acetaldehyde.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the ABS source category is the reproductive system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 3, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 30-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.2, and the maximum off-facility site acute HQ value
could be up to 2, based on the actual emissions level and the REL value
for acetaldehyde. The total estimated national cancer incidence from
these facilities, based on actual emission levels, is 0.003 excess
cancer cases per year or one case in every 333 years.
    Based on our analysis, we believe that actual emissions approximate
emissions allowable under the MACT standards. Therefore, the risk
results for MACT-allowable emissions are approximately equal to those
for actual emissions. For

more detail about this estimate of the ratio of actual to MACT-
allowable emissions and the estimation of MACT-allowable emission
levels and associated risks and impacts, see the memorandum, MACT
Allowable Emissions and Risks for the Pesticide Active Ingredient,
Polyether Polyols, and Polymers and Resins IV Production Source
Categories, in the docket for this rulemaking.
    There were no reported emissions of PB-HAP; therefore, we do not
expect potential for human health multipathway risks or adverse
environmental impacts as a result of PB-HAP.
b. Facility-Wide Risk Assessment Results
    Table 4 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

           Table 4--ABS Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................          5
Cancer Risk:*
    Estimated maximum facility-wide individual cancer risk            30
     (in 1 million)..........................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the ABS source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....
    Number of facilities at which the ABS source category              4
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............        < 1
    Number of facilities with facility-wide maximum noncancer          0
     TOSHI greater than 1....................................
    Number of facilities at which the ABS source category              0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the Group IV Polymers and Resins MACT
standards for ABS resins is estimated to be 30-in-1 million, based on
actual emissions. Of the 5 facilities included in this analysis, none
have a facility-wide MIR of 100-in-1 million. There are 4 facilities
with facility-wide MIR of 1-in-1 million or greater (MIR ranging from
10 to 30 in a million). Each of these facilities has ABS production
operations that contribute greater than 50 percent to the facility-wide
risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be less than 1, based on actual emissions. Of the 5
facilities included in this analysis, none have facility-wide maximum
chronic noncancer TOSHI values greater than 1.
c. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the ABS source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 30-in-1 million due to both actual and allowable emissions. This
value is considerably less than 100-in-1 million, which is the
presumptive level of acceptability. The risk analysis also shows low
cancer incidence (1 in every 333 years), no potential for human health
multipathway effects, and that chronic noncancer health impacts are
unlikely.
    We estimate that the worst-case acute HQ value could exceed a value
of 1 for one HAP, acetaldehyde, with a potential maximum HQ up to 2
based on the acute REL dose-response value. Only one of the five
facilities in this source category had an estimated HQ greater than 1
(REL of 2 for acetaldehyde). All other facilities modeled had an HQ
less than 1. The maximum HQ based on an AEGL-1 or ERPG-1 dose-response
value is 0.04 for acetaldehyde based on the ERPG-1. As described
earlier in this preamble, the acute assessment includes some
conservative assumptions and some uncertainties. Moreover, the REL are
protective and designed to protect the most sensitive individuals in
the population by inclusion of margins of safety and exposures above
the REL do not necessarily indicate that adverse effects will occur.
Considering the improbable assumption that worst-case meteorological
conditions are present at the same time that maximum hourly emissions
of acetaldehyde exceed the average hourly emission rate by a factor of
10 at all emission points simultaneously, coincident with individuals
being in the location of maximum impact, and considering the low acute
HQ values based on the AEGL-1 and ERPG-1 dose-response values
collectively with the REL value, we believe it is unlikely that HAP
emissions from this source category would result in acute health
effects.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 30-in-1 million and that the
maximum chronic exposures are expected to be without appreciable risk
of adverse noncancer health effects.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the ABS source category are acceptable.
d. What is our proposed decision regarding ample margin of safety?
    We considered whether the MACT standards provide an ample margin of
safety to protect public health. In this analysis, we investigated
available emissions control options that might reduce the risk
associated with emissions from the source category and considered this
information along with all of the health risks and other health
information considered in the risk acceptability determination.
    For the ABS source category, we identified only one control option
to further address risks from equipment leaks. This control option
would require sources to install leakless valves to prevent leaks from
those components.

While approximately 15 percent of the emissions from this source
category are due to equipment leaks, these emissions do not contribute
to the maximum individual cancer risks estimated for the source
category.
    We estimated HAP reduction resulting from this control option is
approximately 6 tpy from the baseline actual emissions level. We
estimated that achieving these reductions would involve a capital cost
of approximately $11,000,000, a total annualized cost of about
$1,500,000 and a cost effectiveness of $244,000 per ton of HAP
emissions reduced. The additional control requirement would not achieve
a reduction in the maximum individual cancer risks. We estimate that
the MACT allowable emissions from this source category are
approximately equal to the reported, actual emissions. Therefore, the
estimated emission reduction, risk reduction and costs discussed above
would also be applicable to the MACT allowable emissions level. We
believe that the costs of this option are not reasonable, given the
level of emission and risk reduction.
    In accordance with the approach established in the Benzene NESHAP,
the EPA weighed all health risk measures and information considered in
the risk acceptability determination, along with the costs and economic
impacts of emissions controls, technological feasibility, uncertainties
and other relevant factors in making our ample margin of safety
determination. Considering the health risk information and the
unreasonable cost effectiveness of the option identified, we propose
that the existing MACT standards provide an ample margin of safety to
protect public health and prevent an adverse environmental effect.
2. What are the results of the technology review?
    In the decade since the Group IV Polymers and Resins MACT standards
were promulgated, the EPA has developed 19 air toxics regulations for
source categories that emit organic HAP from the same type of emissions
sources that are present in the five Group IV Polymers and Resins
source categories addressed in this proposed action. We reviewed the
regulatory requirements and/or technical analyses for these 19
regulations for new practices, processes and control technologies. We
also conducted a search of the RBLC for controls for VOC-SOCMI
categories with permits dating back to 1997.
    We identified no advancements in practices, processes, and control
technologies applicable to the emission sources in the Group IV
Polymers and Resins source categories in our technology review.
3. What other actions are we proposing?
a. SSM Provisions
    We are proposing to eliminate the SSM exemption in the Group IV
Polymers and Resins MACT standards. Consistent with Sierra Club v. EPA,
the EPA is proposing that standards in this rule would apply at all
times. We are proposing several revisions to 40 CFR part 63, subpart
JJJ. Specifically, we are proposing to revise Table 1 to indicate that
the requirements of 40 CFR 63.6(e) of the General Provisions do not
apply. The 40 CFR 63.6(e) requires the owner or operator to act
according to the general duty to ``operate and maintain any affected
source, including associated air pollution control equipment and
monitoring equipment, in a manner consistent with safety and good air
pollution control practices for minimizing emissions.'' We are
separately proposing to incorporate this general duty to minimize into
40 CFR 63.1310(j)(4). The 40 CFR 63.6(e) also requires the owner or
operator of an affected source to develop a written SSM plan. We are
proposing to remove the SSM plan requirement. We are proposing to
remove the explanation of applicability of emissions standards during
periods SSM in 40 CFR 63.1310(j); remove the malfunction plan from 40
CFR 63.1335(b); clarify that representative conditions do not include
periods of SSM throughout the rule; remove references to periods of SSM
in monitoring; remove the provisions for excused excursions from 40 CFR
63.1334(g); and revise the SSM-associated recordkeeping and reporting
requirements in 40 CFR 63.1335(b) to require reporting and
recordkeeping for periods of malfunction. We are also proposing to
revise Table 1 to indicate that SSM-related provisions in 40 CFR
63.6(e)(1), 63.6(e)(3), 63.6(f)(1); 40 CFR 63.7(e)(1); 40 CFR
63.8(c)(1); and 40 CFR 63.10(d)(5) of the General Provisions do not
apply. We are also proposing to add requirements in 40 CFR
63.1331(a)(9)) to clarify that PRD releases to the atmosphere are
violations of the emissions standards and to require pressure release
alarms and to add requirements in 40 CFR 63.1335(e)(9) to require
reporting of any pressure device releases to the atmosphere with the
periodic report. In addition, we are proposing to promulgate an
affirmative defense against civil penalties for exceedances of emission
standards caused by malfunctions, as well as criteria for establishing
the affirmative defense.
b. Electronic Reporting
    To increase the ease and efficiency of data submittal and improve
data accessibility, we are proposing to require the submission of
electronic copies of required performance tests for test methods that
are supported by the ERT to EPA's WebFIRE database. These provisions
are added in 40 CFR 63.1335(e)(10).

B. Styrene Acrylonitrile Resin (SAN)

1. What are the results of the risk assessments?
a. Inhalation Risk Assessment Results
    Table 5 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                     Table 5--SAN Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                      (in 1 million) \2\                         Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site acute
   Number of  facilities \1\        Actual         Allowable    risk >= 1-in-1    (cases per        Actual         Allowable        noncancer HQ \4\
                                   emissions       emissions        million          year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
2.............................            0.03            0.03               0        0.000006          0.0002          0.0002  HQREL = 0.007 methylene
                                                                                chloride.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the SAN source category is the respiratory system.

\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 5, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 0.03-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.0002, and the maximum off-facility site acute HQ value
could be up to 0.007, based on the actual emissions level and the REL
value for methylene chloride. The total estimated national cancer
incidence from these facilities based on actual emission levels is
0.000006 excess cancer cases per year or one case in every 166,666
years.
    Based on our analysis, we believe that actual emissions approximate
emissions allowable under the MACT standards. Therefore, the risk
results for MACT-allowable emissions are approximately equal to those
for actual emissions. For more detail about this estimate of the ratio
of actual to MACT-allowable emissions and the estimation of MACT-
allowable emission levels and associated risks and impacts, see the
memorandum, MACT Allowable Emissions and Risks for the Pesticide Active
Ingredient, Polyether Polyols, and Polymers and Resins IV Production
Source Categories, in the docket for this rulemaking.
    There were no reported emissions of PB-HAP; therefore, we do not
expect potential for human health multipathway risks or adverse
environmental impacts as a result of PB-HAP.
b. Facility-Wide Risk Assessment Results
    Table 6 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

           Table 6--SAN Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................          2
Cancer Risk:
    Estimated maximum facility-wide individual cancer risk            20
     (in 1 million)..........................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the SAN source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....
    Number of facilities at which the SAN source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............          2
    Number of facilities with facility-wide maximum noncancer          1
     TOSHI greater than 1....................................
    Number of facilities at which the SAN source category              0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the Group IV Polymers and Resins MACT
standards for SAN resins is estimated to be 20-in-1 million, based on
actual emissions. Of the 2 facilities included in this analysis, none
have a facility-wide MIR of 100-in-1 million. There are 2 facilities
with facility-wide MIR of 1-in-1 million or greater (MIR of 20 and 10
in a million). Neither of these facilities have SAN production
operations that contribute greater than 50 percent to the facility-wide
risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be 2, based on actual emissions. Of the 2 facilities
included in this analysis, only one facility has a facility-wide
maximum chronic noncancer TOSHI value greater than 1 (TOSHI of 2).
c. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the SAN source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 0.03-in-1 million due to both actual and allowable emissions.
This value is less than 1-in-1 million. The risk analysis also shows
low cancer incidence (1 in every 166,666 years), no potential for human
health multipathway effects and that chronic noncancer and acute health
effects are unlikely.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 20-in-1 million. The maximum
chronic noncancer TOSHI is estimated to be 2, but the source category
contributes less than 1 percent to the maximum facility-wide TOSHI.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the SAN source category are acceptable.
d. What is our proposed decision regarding ample margin of safety?
    The SAN source category emits HAP which are known, probable or
possible carcinogens. The EPA evaluated the emissions of these HAP and
determined that the cancer risks to the individual most exposed are
less than 1-in-1 million. Our analysis demonstrated that chronic
noncancer risks are expected to be low, based on actual and MACT
allowable emissions. We determined that emissions from the SAN source
category would result in a chronic noncancer TOSHI less than 1 and an
acute HQ less than 1 for the individual most exposed. The EPA undertook
further analysis to assess whether environmental effects might result
from

emissions from this source category. We assume that human toxicity
values for the inhalation pathway are generally protective of
terrestrial mammals and plants, and thus, we do not anticipate that
actual or MACT allowable emissions would result in acute or chronic
noncancer health effects to these mammals. While we believe this to be
generally true, we acknowledge that there is some associated
uncertainty with this assumption. In addition, this source category had
no reported emissions of PB-HAP and, therefore, no potential for an
adverse environment effect via multipathway exposures was identified as
a result of PB-HAP.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the
existing MACT standards for the SAN source category provide an ample
margin of safety to protect public health and prevent an adverse
environmental effect.
2. What are the results of the technology review?
    The results of the technology review for the Group IV Polymers and
Resins MACT standards are discussed above in section IV.A.2. We
identified no advancements in practices, processes, and control
technologies applicable to the emission sources in the Group IV
Polymers and Resins source categories in our technology review.
3. What other actions are we proposing?
a. SSM Provisions
    The proposed changes to the SSM provisions for the Group IV
Polymers and Resins MACT standards, which apply to the SAN source
category, are discussed above in section IV.A.3.a.
b. Electronic Reporting
    The proposed addition of electronic reporting requirements for
performance tests for the Group IV Polymers and Resins MACT standards,
which apply to the SAN source category, is discussed above in section
IV.A.3.b.

C. Methyl Methacrylate Butadiene Styrene Resin (MBS)

1. What are the results of the risk assessments?
a. Inhalation Risk Assessment Results
    Table 7 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                     Table 7--MBS Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                              Maximum individual cancer risk                                      Maximum chronic noncancer TOSHI
                                    (in 1 million) \2\          Population at    Annual cancer                  \3\                   Maximum off-site
 Number of  facilities \1\  ----------------------------------  risk >= 1-in-1     incidence    ----------------------------------   acute noncancer HQ
                                  Actual         Allowable         million         (cases per         Actual         Allowable              \4\
                             emissions level  emissions level                        year)       emissions level  emissions level
--------------------------------------------------------------------------------------------------------------------------------------------------------
2..........................             0.4              0.4                0          0.00003            0.007            0.007   HQERPG-1 = 9 ethyl
                                                                                acrylate.
                                                                                HQAEGL-1 = 0.01 ethyl
                                                                                acrylate.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the MBS source category is the reproductive system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute threshold. For this source category, the maximum acute values were based on the ERPG-1 HQ for ethyl acrylate, and no REL value
  was available for this HAP. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 7, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 0.4-in-1 million, the maximum chronic noncancer TOSHI value
could up to 0.007 and the maximum off-facility site acute HQ value
could be up to 9, based on the actual emissions level and the ERPG-1
value for ethyl acrylate. The total estimated national cancer incidence
from these facilities, based on actual emission levels is 0.00003
excess cancer cases per year or one case in every 33,333 years.
    Based on our analysis, we believe that actual emissions approximate
emissions allowable under the MACT standards. Therefore, the risk
results for MACT-allowable emissions are approximately equal to those
for actual emissions. For more detail about this estimate of the ratio
of actual to MACT-allowable emissions and the estimation of MACT-
allowable emission levels and associated risks and impacts, see the
memorandum, MACT Allowable Emissions and Risks for the Pesticide Active
Ingredient, Polyether Polyols, and Polymers and Resins IV Production
Source Categories, in the docket for this rulemaking.
    There were no reported emissions of PB-HAP; therefore, we do not
expect potential for human health multipathway risks or adverse
environmental impacts as a result of PB-HAP.
b. Facility-Wide Risk Assessment Results
    Table 8 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

           Table 8--MBS Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................          2
Cancer Risk:
  Estimated maximum facility-wide individual cancer risk (in           2
   1 million)................................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the MBS source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....

    Number of facilities at which the MBS source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............        < 1
    Number of facilities with facility-wide maximum noncancer          0
     TOSHI greater than 1....................................
    Number of facilities at which the MBS source category              0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the Group IV Polymers and Resins MACT
standards for MBS resins is estimated to be 2-in-1 million, based on
actual emissions. Of the 2 facilities included in this analysis, none
have a facility-wide MIR of 100-in-1 million. There is 1 facility with
a facility-wide MIR of 1-in-1 million or greater (MIR of 2 in a
million). The facility with an MIR greater than 1-in-1 million does not
have MBS production operations that contribute greater than 50 percent
to the facility-wide risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be less than 1, based on actual emissions. Of the 2
facilities included in this analysis, neither have facility-wide
maximum chronic noncancer TOSHI values greater than 1.
c. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the MBS source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 0.4-in-1 million due to both actual and allowable emissions. This
value is less than 1-in-1 million. The risk analysis also shows low
cancer incidence (1 in every 33,333 years), no potential for human
health multipathway effects and that chronic noncancer health impacts
are unlikely.
    We estimate that the worst-case acute HQ value could exceed a value
of 1 for one HAP, ethyl acrylate, with a potential maximum HQ up to 9
based on the acute ERPG-1 dose-response value. One of the two
facilities in this source category had an estimated HQ greater than 1
(ERPG-1 of 9 for ethyl acrylate). All other facilities modeled had an
HQ less than 1. The maximum HQ based on an AEGL-1 dose-response value
is 0.01 for ethyl acrylate. For ethyl acrylate, the ERPG-1 value is
indicative of the odor recognition threshold, while the AEGL-1 value is
indicative of a level which could result in eye irritation. This
suggests that, at this worst-case exposure level, a person might smell
the pollutant, but not experience any eye irritation. As described
earlier in this preamble, the acute assessment includes some
conservative assumptions and some uncertainties. Considering the
improbable assumption that worst-case meteorological conditions are
present at the same time that maximum hourly emissions of ethyl
acrylate exceed the average hourly emission rate by a factor of 10 at
all emission points simultaneously, coincident with individuals being
in the location of maximum impact and considering the low acute HQ
value based on the AEGL-1 dose-response value collectively with the
ERPG-1 value, we believe it is unlikely that HAP emissions from this
source category would result in acute health effects.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 2-in-1 million and that the
maximum chronic exposures are expected to be without appreciable risk
of adverse noncancer health effects.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the MBS source category are acceptable.
d. What is our proposed decision regarding ample margin of safety?
    The MBS source category emits HAP which are known, probable or
possible carcinogens. The EPA evaluated the emissions of these HAP and
determined that the cancer risks to the individual most exposed are
less than 1-in-1 million. Our analysis demonstrated that chronic
noncancer risks are expected to be low, based on actual and MACT
allowable emissions. We determined that emissions from the MBS source
category would result in a chronic noncancer TOSHI less than 1 for the
individual most exposed. While the assessment for acute impacts
suggests that short-term ethyl acrylate concentrations at one facility
could exceed the ERPG-1 dose-response value, we believe it unlikely
that acute impacts would occur due to the conservative assumptions and
uncertainties associated with the acute analysis. These assumptions
include having worst-case meteorological conditions present at the same
time that maximum hourly emissions of ethyl acrylate exceed the average
hourly emission rate by a factor of 10, coincident with individuals
being in the location of maximum impact. The EPA undertook further
analysis to assess whether environmental effects might result from
emissions from this source category. We assume that human toxicity
values for the inhalation pathway are generally protective of
terrestrial mammals and plants and, thus, we do not anticipate that
actual or MACT allowable emissions would result in acute or chronic
noncancer health effects to these mammals. While we believe this to be
generally true, we acknowledge that there is some associated
uncertainty with this assumption. In addition, this source category had
no reported emissions of PB-HAP and, therefore, no potential for an
adverse environmental effect via multipathway exposures was identified.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the
existing MACT standards for the MBS source category provide an ample
margin of safety to protect public health and prevent an adverse
environmental effect.
2. What are the results of the technology review?
    The results of the technology review for the Group IV Polymers and
Resins MACT standards are discussed above in section IV.A.2. We
identified no advancements in practices, processes

and control technologies applicable to the emission sources in the
Group IV Polymers and Resins source categories in our technology
review.
3. What other actions are we proposing?
a. SSM Provisions
    The proposed changes to the SSM provisions for the Group IV
Polymers and Resins MACT standards, which apply to the MBS source
category, are discussed above in section IV.A.3.a.
b. Electronic Reporting
    The proposed addition of electronic reporting requirements for
performance tests for the Group IV Polymers and Resins MACT standards,
which apply to the MBS source category, are discussed above in section
IV.A.3.b.

D. Polystyrene Resin

1. What are the results of the risk assessments?
a. Inhalation Risk Assessment Results
    Table 9 provides an overall summary of the inhalation risk
assessment results for the source category.

                                             Table 9--Polystyrene Resins Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                       (in 1 million) \2\                        Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site acute
   Number of  facilities \1\        Actual         Allowable    risk >= 1-in-1    (cases per        Actual         Allowable        noncancer HQ \4\
                                   emissions       emissions        million          year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
11............................               2               2             180         0.00003           0.004           0.004  HQREL = 0.3 styrene.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the polystyrene resin source category is the nervous system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 9, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 2-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.004, and the maximum off-facility site acute HQ value
could be up to 0.3, based on the actual emissions level and the REL
value for styrene. The total estimated national cancer incidence from
these facilities, based on actual emission levels, is 0.00003 excess
cancer cases per year, or one case in every 33,333 years.
    Based on our analysis, we believe that actual emissions approximate
emissions allowable under the MACT standards. Therefore, the risk
results for MACT-allowable emissions are approximately equal to those
for actual emissions. For more detail about this estimate of the ratio
of actual to MACT-allowable emissions and the estimation of MACT-
allowable emission levels and associated risks and impacts, see the
memorandum, MACT Allowable Emissions and Risks for the Pesticide Active
Ingredient, Polyether Polyols, and Polymers and Resins IV Production
Source Categories, in the docket for this rulemaking.
    There were no reported emissions of PB-HAP; therefore, we do not
expect potential for human health multipathway risks or adverse
environmental impacts as a result of PB-HAP.
b. Facility-Wide Risk Assessment Results
    Table 10 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

   Table 10--Polystyrene Resins Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................         11
Cancer Risk:
    Estimated maximum facility-wide individual cancer risk            10
     (in 1 million)..........................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the polystyrene resin                0
     source category contributes 50 percent or more to the
     facility-wide individual cancer risks of 100-in-1
     million or more.........................................
    Number of facilities at which the polystyrene resin                1
     source category contributes 50 percent or more to the
     facility-wide individual cancer risk of 1-in-1 million
     or more.................................................
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............         <1
    Number of facilities with facility-wide maximum noncancer          0
     TOSHI greater than 1....................................
    Number of facilities at which the Polystyrene Resin                0
     source category contributes 50 percent or more to the
     facility-wide maximum noncancer TOSHI of 1 or more......
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the Group IV Polymers and Resins MACT
standards for polystyrene resins is estimated to be 10-in-1 million,
based on actual emissions. Of the 11 facilities included in this
analysis, none have a facility-wide MIR of 100-in-1 million. There are
2 facilities with facility-wide MIR of 1-in-1 million or greater (MIR
of 10 and 2 in a million). One of these facilities has polystyrene
resin production operations that contribute greater than 50 percent to
the facility-wide risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be less than 1, based on

actual emissions. Of the 11 facilities included in this analysis, none
have facility-wide maximum chronic noncancer TOSHI values greater than
1.
c. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the Polystyrene Resin source category, the risk analysis we
performed indicates that the cancer risks to the individual most
exposed could be up to 2-in-1 million due to both actual and allowable
emissions. This value is considerably less than 100-in-1 million, which
is the presumptive level of acceptability. The risk analysis also shows
low cancer incidence (1 in every 33,333 years), no potential for human
health multipathway effects and that acute and chronic noncancer health
impacts are unlikely.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 10-in-1 million and that the
maximum chronic exposures are expected to be without appreciable risk
of adverse noncancer health effects.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the Polystyrene Resin source category are acceptable.
d. What is our proposed decision regarding ample margin of safety?
    We considered whether the MACT standards provide an ample margin of
safety to protect public health. In this analysis, we investigated
available emissions control options that might reduce the risk
associated with emissions from the source category and considered this
information along with all of the health risks and other health
information considered in the risk acceptability determination.
    For the Polystyrene Resin source category, we identified only one
control option to further address risks from equipment leaks, which
were shown to contribute 100 percent to the maximum individual cancer
risks for this source category. This control option would require
sources to install leakless valves to prevent leaks from those
components.
    We estimated HAP reduction resulting from this control option is
approximately 5 tpy from the baseline actual emissions level. We
estimated that achieving these reductions would involve a capital cost
of approximately $9,000,000, a total annualized cost of about
$1,300,000 and a cost effectiveness of $244,000 per ton of HAP
emissions reduced. The additional control requirement would achieve
approximately 20-percent reduction in baseline risks at a very high
cost. We estimate that the MACT allowable emissions from this source
category are approximately equal to the reported, actual emissions.
Therefore, the estimated emission reduction, risk reduction and costs
discussed above would also be applicable to the MACT allowable
emissions level. We believe that the costs of this option are not
reasonable, given the level of emission and risk reduction.
    In accordance with the approach established in the Benzene NESHAP,
the EPA weighed all health risk measures and information considered in
the risk acceptability determination, along with the costs and economic
impacts of emissions controls, technological feasibility, uncertainties
and other relevant factors in making our ample margin of safety
determination. Considering the health risk information and the
unreasonable cost effectiveness of the option identified, we propose
that the existing MACT standards provide an ample margin of safety to
protect public health and prevent an adverse environmental effect.
2. What are the results of the technology review?
    The results of the technology review for the Group IV Polymers and
Resins MACT standards are discussed above in section IV.A.2. We
identified no advancements in practices, processes and control
technologies applicable to the emission sources in the Group IV
Polymers and Resins source categories in our technology review.
3. What other actions are we proposing?
a. SSM Provisions
    The proposed changes to the SSM provisions for the Group IV
Polymers and Resins MACT standards, which apply to the polystyrene
resin source category, are discussed above in section IV.A.3.a.
b. Electronic Reporting
    The proposed addition of electronic reporting requirements for
performance tests for the Group IV Polymers and Resins MACT standards,
which apply to the polystyrene resin source category, are discussed
above in section IV.A.3.b.

E. Poly (Ethylene Terephthalate) Resin (PET)

1. What are the results of our analyses and proposed decisions
regarding unregulated HAP and/or emissions sources?
a. Equipment Leaks
    We identified the absence of a limit for a potentially significant
emissions source within the provisions of the Group IV Polymers and
Resins MACT standards that apply to the PET continuous TPA high
viscosity multiple end finisher subcategory. Specifically, there are no
regulations for equipment leaks for this source subcategory.\22\ As
these processes are potentially major sources of emissions for the one
facility in the source category, we are proposing to set a work
practice standard for equipment leaks under CAA section 112(d)(2) and
(d)(3) in this action. CAA section 112(h)(1) states that the
Administrator may prescribe a work practice standard or other
requirements, consistent with the provisions of CAA sections 112(d) or
(f), in those cases where, in the judgment of the Administrator, it is
not feasible to enforce an emission standard. CAA section 112(h)(2)
defines the phrase ``not feasible to prescribe or enforce an emission
standard'' as follows:
---------------------------------------------------------------------------

    \22\ Note that these uncontrolled emissions were included in the
risk assessment for the PET source category.

    [A]ny situation in which the Administrator determines that (A) a
hazardous air pollutant or pollutants cannot be emitted through a
conveyance designed and constructed to emit or capture such
pollutant, or that any requirement for, or use of, such a conveyance
would be inconsistent with any Federal, State, or local law, or (B)
the application of measurement methodology to a particular class of
sources is not practicable due to technological and economic
---------------------------------------------------------------------------
limitations.

    The work practice standards in this proposed rule are consistent
with CAA section 112(h)(2)(B), because applying a measurement
methodology to this class of sources is not technologically and
economically feasible due to the number of openings and possible
emissions points and because the fugitive emissions cannot be routed to
a conveyance designed to capture such emissions.
    As there is only one facility in the source subcategory, the
emissions level currently being achieved by this facility represents
the MACT floor. However, emissions from equipment leaks are

intermittent and fugitive in nature and, therefore, it is not feasible
to fully measure the mass emission rate from numerous potential leaks
at this facility or to route such emissions through a conveyance
designed and constructed to emit or capture such fugitive pollutants.
For this reason, under CAA section 112(h), we are proposing to
establish the MACT floor for this source subcategory, based on the work
practices this facility currently performs to limit emissions from
equipment leaks. The work practices this facility follows are to
perform a 2- to 3-hour leak check upon startup following an outage
where changes have been made to the facility's esterification
equipment, which is the only area of the facility that has equipment in
gas/vapor service. This is conducted by introducing hot ethylene g1yco1
vapors into the system. Any leaks identified are repaired by tightening
flange bolts before introducing new materials into the process. The
other equipment components at the facility are in vacuum or heavy
liquid service, which are not monitored due to the low vapor pressure
of predominant HAP, ethylene glycol and the low potential for equipment
leak emissions from these components.
    As part of our beyond-the-floor analysis, we considered
alternatives more stringent than the MACT floor option. We identified
the HON LDAR program as one such option, which is the required level of
control for other facilities subject to the Group IV Polymers and
Resins MACT standards. The HON requires the use of sensory monitoring
for pumps, valves, agitators and connectors in heavy liquid service;
the use of EPA Method 21 of 40 CFR part 60, Appendix A, for instrument
monitoring of equipment in gas/vapor service; and equipment in vacuum
service is not required to be monitored. Based on previous information
prepared to examine the equipment leak costs for facilities in the PET
source category,\23\ the capital costs of this option are estimated to
be approximately $13,000 and the total annual costs are estimated to be
approximately $13,000. The estimated HAP decrease is 1.27 tpy, with a
cost effectiveness of approximately $11,000/ton. Table 11 summarizes
the cost and emission reduction impacts of the proposed options.
Because the HAP reduced would be ethylene glycol, which does not
contribute to the cancer risk estimate for the PET source category, the
MIR for the source category would remain at 9. Any impact on the
magnitude of the HI resulting from ethylene glycol emission reductions
due to this control option would be negligible as ethylene glycol
contributes minimally to the chronic noncancer TOSHI of 0.5. These risk
values are discussed further in section IV.E.2 below.
---------------------------------------------------------------------------

    \23\ Memorandum to Group IV Resins Docket, A-92-45, from Ken
Meardon, Pacific Environmental Services, Inc. Re-Evaluation of
Equipment Leak Emissions and Costs at PET Facilities.

                   Table 11--PET Continuous TPA High Viscosity Equipment Leaks Options Impacts
----------------------------------------------------------------------------------------------------------------
                                                                                Cost
                                            HAP emissions     Capital cost                        effectiveness
         Regulatory alternatives                (tpy)              ($)        Annual cost  ($)     ($/ton HAP
                                                                                removed)
----------------------------------------------------------------------------------------------------------------
Baseline................................              1.43              ----              ----              ----
1 (MACT floor)..........................              1.43                 0                 0              ----
2 (Beyond-the-floor)....................              0.16            13,000            13,000            11,000
----------------------------------------------------------------------------------------------------------------

    We believe that the costs of this beyond-the-floor option are not
reasonable, given the level of emission reduction. Therefore, we are
proposing an emission standard that reflects the MACT floor option,
which is a work practice standard.
    We are requesting comment on this analysis and these options.
b. Changes to PCCT Provisions in Response to a Petition for
Reconsideration
    We identified a potentially significant emissions source that is
currently effectively unregulated within the provisions of the Group IV
Polymers and Resins MACT standards that apply to the sources producing
PET using the continuous TPA high viscosity multiple end finisher
process. Specifically, sources have not been required to comply with
the previously promulgated provisions addressing emissions from PCCT
within this source subcategory. We originally promulgated standards for
PCCT in this subcategory in the September 12, 1996, Federal Register
publication of NESHAP for Group IV Polymer and Resin source categories.
On August 29, 2000, the EPA took action to indefinitely stay the
compliance date for the PCCT provisions for this subcategory because
the EPA was in the process of responding to a request to reconsider
portions of the Group IV Polymers and Resins MACT standards that could
result in changes to the emission limitation for PCCT in this
subcategory (65 FR 52319-23). As PCCT are potentially major sources of
emissions for the one facility in the PET continuous TPA high viscosity
multiple end finisher subcategory, we have reconsidered the emissions
and cost data available and we are proposing MACT standards for PCCT
under CAA section 112(d)(2) and (d)(3) in this action.
    As there is only one facility in the source subcategory, the
emissions level currently being achieved by this facility represents
the MACT floor. The facility is currently regulated by the Polymers
Manufacturing New Source Performance Standards, which requires the
facility to maintain an ethylene glycol concentration in the PCCT at or
below 6.0 percent by weight, averaged on a daily basis over a rolling
14-day period of operating days. We are proposing to establish the MACT
floor for this source subcategory, based on the 6.0 percent by weight
ethylene glycol concentration limit this facility is required to
achieve.
    As part of our beyond-the-floor analysis, we considered
alternatives more stringent than the MACT floor option. The original
PCCT regulations promulgated in the Group IV Polymer and Resin NESHAP
established an ethylene glycol concentration limit of 4.0 percent by
weight for PCCT in this source subcategory, based on the information
available on controls and costs, but the source has never been required
to achieve this limit, in light of our August 29, 2000, indefinite stay
of the compliance date. We identified this 4.0-percent concentration
limit as a beyond-the-floor option for our revised analysis. To achieve
the beyond-the-floor option, the facility would need to modify its
existing ethylene glycol

recovery system and increase the amount of steam used to strip ethylene
glycol from the contaminated water. Based on information received from
the only facility in the subcategory after promulgation of the Group IV
Polymers and Resins MACT standards, the capital costs of this option
are estimated to be approximately $8.7 million and the total annual
costs are estimated to be approximately $4.2 million. The estimated HAP
decrease is 49.0 tpy, with a cost effectiveness of approximately
$86,000/ton. Table 12 summarizes the cost and emission reduction
impacts of the proposed options. Because the HAP reduced would be
ethylene glycol, which does not contribute to the cancer risk estimate
for the PET source category, the MIR for the source category would
remain at 9. Any impact on the magnitude of the HI resulting from
ethylene glycol emission reductions due to this control option would be
negligible as ethylene glycol contributes minimally to the chronic
noncancer TOSHI of 0.5. These risk values are discussed further in
section IV.E.2 below. Further information regarding this analysis can
be found in the memorandum, Impacts Assessment for Process Contact
Cooling Towers for the PET Continuous TPA High Viscosity Multiple End
Finisher Subcategory, available in the docket for this action.

  Table 12--PET Continuous TPA High Viscosity Multiple End Finisher Subcategory Process Contact Cooling Towers
                                                 Options Impacts
----------------------------------------------------------------------------------------------------------------
                                                                                Cost
                                            HAP emissions     Capital cost                        effectiveness
         Regulatory alternatives                (tpy)              ($)        Annual cost  ($)     ($/ton HAP
                                                                                removed)
----------------------------------------------------------------------------------------------------------------
Baseline................................             147.0              ----              ----              ----
1 (MACT floor)..........................             147.0                 0                 0              ----
2 (Beyond-the-floor)....................              98.0         8,800,000         4,200,000            86,000
----------------------------------------------------------------------------------------------------------------

    We believe that the costs of this beyond-the-floor option are not
reasonable, given the level of emission reduction. Therefore, we are
proposing to re-set the previously stayed MACT standard as an emission
standard that reflects the MACT floor option, which is the ethylene
glycol concentration limit of 6.0 weight percent.
    We are requesting comment on this analysis and these options.
2. What are the results of the risk assessments?
a. Inhalation Risk Assessment Results
    Table 13 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                    Table 13--PET Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                      (in 1 million) \2\                         Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site  acute
   Number of  facilities \1\        Actual         Allowable    risk >=  1-in-    (cases per        Actual         Allowable        noncancer  HQ \4\
                                   emissions       emissions       1 million         year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                HQREL = 8
                                                                                acetaldehyde.
15............................               9               9           4,200           0.002             0.5             0.5  HQERPG-1 = 1
                                                                                acetaldehyde.
                                                                                HQAEGL-1 = 0.2
                                                                                acetaldehyde.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the PET source category is the respiratory system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 13, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 9-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.5, and the maximum off-facility site acute HQ value
could be up to 8, based on the actual emissions level and the REL value
for acetaldehyde. The total estimated national cancer incidence from
these facilities based on actual emission levels is 0.002 excess cancer
cases per year or one case in every 500 years.
    Based on our analysis, we believe that actual emissions approximate
emissions allowable under the MACT standards. Therefore, the risk
results for MACT-allowable emissions are approximately equal to those
for actual emissions. For more detail about this estimate of the ratio
of actual to MACT-allowable emissions and the estimation of MACT-
allowable emission levels and associated risks and impacts, see the
memorandum, MACT Allowable Emissions and Risks for the Pesticide Active
Ingredient, Polyether Polyols, and Polymers and Resins IV Production
Source Categories, in the docket for this rulemaking.
    One facility reported emissions of PB-HAP, including cadmium
compounds, lead compounds and POM. Therefore, we compared the facility-
specific

emission rates of each of these PB-HAP to the TRIM-Screen emission
threshold values to assess the potential for significant human health
risks or environmental risks via non-inhalation pathways. The emission
rates were less than the emission threshold values; therefore, we do
not expect potential for human health multipathway risks or adverse
environmental impacts as a result of PB-HAP.
b. Facility-Wide Risk Assessment Results
    Table 14 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

           Table 14--PET Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................         15
Cancer Risk:
    Estimated maximum facility-wide individual cancer risk             9
     (in 1 million)..........................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the PET source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....
    Number of facilities at which the PET source category              6
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............          1
    Number of facilities with facility-wide maximum noncancer          1
     TOSHI greater than 1....................................
    Number of facilities at which the PET source category              0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the Group IV Polymers and Resins MACT
standards for PET is estimated to be 9-in-1 million, based on actual
emissions. Of the 15 facilities included in this analysis, none have a
facility-wide MIR of 100-in-1 million. There are 8 facilities with
facility-wide MIR of 1-in-1 million or greater (MIR ranging from 2 to 9
in a million). Six of these facilities have PET production operations
that contribute greater than 50 percent to the facility-wide risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be 1, based on actual emissions. Of the 15 facilities
included in this analysis, one has a facility-wide maximum chronic
noncancer TOSHI value of 1.
c. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the PET source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 9-in-1 million due to both actual and allowable emissions. This
value is considerably less than 100-in-1 million, which is the
presumptive level of acceptability. The risk analysis also shows low
cancer incidence (1 in every 500 years), no potential for human health
multipathway effects and that chronic noncancer health impacts are
unlikely.
    We estimate that the worst-case acute HQ value could exceed a value
of 1 for one HAP, acetaldehyde, with a potential maximum HQ up to 8
based on the acute REL dose-response value. Seven of the 15 facilities
in this source category had an estimated acute HQ greater than 1 (REL
for acetaldehyde ranging from 3 to 8). All other facilities modeled had
an acute HQ less than 1. The maximum acute HQs based on ERPG-1 and
AEGL-1 dose-response values for acetaldehyde are 1 and 0.2,
respectively. As described earlier in this preamble, the acute
assessment includes some conservative assumptions and some
uncertainties. Considering the improbable assumption that worst-case
meteorological conditions are present at the same time that maximum
hourly emissions of acetaldehyde exceed the average hourly emission
rate by a factor of 10 at all emission points simultaneously,
coincident with individuals being in the location of maximum impact and
considering the low acute HQ values, based on the ERPG-1 and AEGL-1
dose-response values collectively with the REL value, we believe it is
unlikely that HAP emissions from this source category would result in
acute health effects.
    Our screening level evaluation of the potential health risks
associated with emissions of PB-HAP did not indicate potential for
adverse multipathway impacts due to emissions of the any of the PB-HAP
associated with the source category.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 9-in-1 million. The maximum
chronic noncancer TOSHI is estimated to be 1, but the source category
contributes only 5 percent to the maximum facility-wide TOSHI.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the PET source category are acceptable.
d. What is our proposed decision regarding ample margin of safety?
    We considered whether the MACT standards provide an ample margin of
safety to protect public health. In this analysis, we investigated
available emissions control options that might reduce the risk
associated with emissions from the source category and considered this
information along with all of the health risks and other health
information considered in the risk acceptability determination.
    For the PET source category, we identified only one control option
to further address risks from equipment leaks, which were shown to
contribute 100 percent to the maximum individual cancer risks for this
source category. This control option would require sources to install
leakless valves to prevent leaks from those components.
    We estimated HAP reduction resulting from this control option is

approximately 123 tpy from the baseline actual emissions level. We
estimated that achieving these reductions would involve a capital cost
of approximately $220,000,000, a total annualized cost of about
$30,000,000 and a cost effectiveness of $244,000 per ton of HAP
emissions reduced. The additional control requirement would achieve
approximately 20-percent reduction in baseline risks at a very high
cost. We estimate that the MACT allowable emissions from this source
category are approximately equal to the reported, actual emissions.
Therefore, the estimated emission reduction, risk reduction and costs
discussed above would also be applicable to the MACT allowable
emissions level. We believe that the costs of this option are not
reasonable, given the level of emission and risk reduction.
    In accordance with the approach established in the Benzene NESHAP,
the EPA weighed all health risk measures and information considered in
the risk acceptability determination, along with the costs and economic
impacts of emissions controls, technological feasibility, uncertainties
and other relevant factors in making our ample margin of safety
determination. Considering the health risk information and the
unreasonable cost effectiveness of the option identified, we propose
that the existing MACT standards provide an ample margin of safety to
protect public health and prevent an adverse environmental effect.
3. What are the results of the technology review?
    The results of the technology review for the Group IV Polymers and
Resins MACT standards are discussed above in section IV.A.2. We
identified no advancements in practices, processes and control
technologies applicable to the emission sources in the Group IV
Polymers and Resins source categories in our technology review.
4. What other actions are we proposing?
a. SSM Provisions
    The proposed changes to the SSM provisions for the Group IV
Polymers and Resins MACT standards, which apply to the PET source
category, are discussed above in section IV.A.3.a.
b. Electronic Reporting
    The proposed addition of electronic reporting requirements for
performance tests for the Group IV Polymers and Resins MACT standards,
which apply to the PET source category, are discussed above in section
IV.A.3.b.

V. Analytical Results and Proposed Decisions for Pesticide Active
Ingredient Production

A. What are the results of the risk assessments?

1. Inhalation Risk Assessment Results
    Table 16 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                    Table 16--PAI Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                       (in 1 million) \2\                        Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site acute
   Number of  facilities \1\        Actual         Allowable    risk >= 1-in-1    (cases per        Actual         Allowable        noncancer HQ \4\
                                   emissions       emissions        million          year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
17............................               7               7          11,000           0.001             0.7               3  HQREL = 8 ethylene
                                                                                glycol ethyl ether.
                                                                                HQERPG-1 = 0.3 chlorine.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the PAI source category is the respiratory system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 16, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 7-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.7, and the maximum off-facility site acute HQ value
could be up to 8, based on the actual emissions level and the REL value
for ethylene glycol ethyl ethers. The total estimated national cancer
incidence from these facilities, based on actual emission levels is
0.001 excess cancer cases per year or one case in every 1,000 years.
    Based on our analysis, we estimate that the MACT-allowable
emissions levels from process vents for organic HAP emissions could be
up to five times the actual emissions and the MACT-allowable level for
chlorine and HCl emissions could be up to six times the actual
emissions from this source category. However, the highest cancer risks
are caused by fugitive emissions and the application of the factor of
five to the organic HAP emissions from point sources did not result in
cancer risks in excess of the levels resulting from actual fugitive
source emissions. Therefore, the cancer risk results for MACT-allowable
emissions are approximately equal to those for actual emissions. The
highest TOSHI at the MACT-allowable level is approximately 3. For more
detail about this estimate of the ratio of actual to MACT-allowable
emissions and the estimation of MACT-allowable emission levels and
associated risks and impacts, see the memorandum, MACT Allowable
Emissions and Risks for the Pesticide Active Ingredient, Polyether
Polyols, and Polymers and Resins IV Production Source Categories, in
the docket for this rulemaking.
    Three facilities reported emissions of PB-HAP, including lead
compounds, PCBs and hexachlorobenzene. We typically would compare the
facility-specific emission rates of each of these PB-HAP to the TRIM-
Screen emission threshold values to assess the potential for
significant human health risks or environmental risks via non-
inhalation pathways. However, while lead is a PB-HAP, the National
Ambient Air Quality Standards (NAAQS) value (which was used for the
chronic noncancer risk assessment) takes into account air-related
multipathway exposures, so a

separate multipathway screening value was not developed here. Since we
did not estimate any exceedances of the NAAQS in our chronic noncancer
risk assessment, we do not expect any unacceptable multipathway
exposure and risk of concern due to lead emissions from these
facilities. In addition, there is currently not a screening value for
PCBs or hexachlorobenzene, and they were not evaluated for potential
non-inhalation risks.
2. Facility-Wide Risk Assessment Results
    Table 17 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

           Table 17--PAI Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................         17
Cancer Risk:
    Estimated maximum facility-wide individual cancer risk            20
     (in 1 million)..........................................
    Number of facilities with estimated facility-wide                  0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the PAI source category              0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....
    Number of facilities at which the PAI source category              4
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............          2
    Number of facilities with facility-wide maximum noncancer          1
     TOSHI greater than 1....................................
    Number of facilities at which the PAI source category              0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the PAI MACT standards is estimated to be
20-in-1 million, based on actual emissions. Of the 17 facilities
included in this analysis, none have a facility-wide MIR of 100-in-1
million. There are 12 facilities with facility-wide MIR of 1-in-1
million or greater (2 facilities with an MIR of 20 in a million and 2
facilities with an MIR of 10 in a million; the remaining 8 facilities
have an MIR below 10 in a million). Four of these facilities have PAI
production operations that contribute greater than 50 percent to the
facility-wide risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be 2, based on actual emissions. Of the 17 facilities
included in this analysis, one has a facility-wide maximum chronic
noncancer TOSHI values greater than 1 (TOSHI of 2).
3. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the PAI source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 7-in-1 million due to both actual and allowable emissions. This
value is considerably less than 100-in-1 million, which is the
presumptive level of acceptability. The risk analysis also shows low
cancer incidence (1 in every 1,000 years) and that chronic noncancer
health impacts are unlikely at the actual emissions levels.
    We estimate that the worst-case acute HQ value could exceed a value
of 1 for six HAP: ethylene glycol ethyl ethers (one facility); acrolein
(one facility); chloroform (one facility); nickel compounds (one
facility); chlorine (one facility); and formaldehyde (one facility).
One facility had acute HQ greater than 1 for three HAP (ethyl glycol
ethyl ether, acrolein and nickel). The potential maximum HQ is up to 8,
based on the acute REL dose-response value for ethylene glycol ethyl
ether. Four of the 17 facilities in this source category had an
estimated HQ greater than 1. All other facilities modeled had an HQ
less than 1. The maximum HQ based on an ERPG-1 or AEGL-1 dose-response
value is 0.3, based on the AEGL-1 for chlorine. As described earlier in
this preamble, the acute assessment includes some conservative
assumptions and some uncertainties. Considering the improbable
assumption that worst-case meteorological conditions are present at the
same time that maximum hourly emissions of ethylene glycol ethyl ether
exceed the average hourly emission rate by a factor of 10 at all
emission points simultaneously for three of these four facilities or a
factor of 2 at all emission points simultaneously for the other
facility, coincident with individuals being in the location of maximum
impact and considering the low acute HQ values, based on the AEGL-1 and
ERPG-1 dose-response values collectively with the REL values, we
believe it is unlikely that HAP emissions from this source category
would result in acute health effects.
    Our screening level evaluation of the potential health risks
associated with emissions of PB-HAP did not indicate potential for
adverse multipathway impacts due to emissions of lead. While there are
no screening values for PCB and hexachlorobenzene, these HAP are not
emitted in appreciable quantities and are not expected to cause
multipathway impacts of concern.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 20-in-1 million. The maximum
chronic noncancer TOSHI is estimated to be 2, but the source category
contributes less than 5 percent to the maximum facility-wide TOSHI.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the PAI source category are acceptable.
4. What is our proposed decision regarding ample margin of safety?
    We considered whether the MACT standards provide an ample margin of
safety to protect public health. In this analysis, we investigated
available

emissions control options that might reduce the risk associated with
emissions from the source category and considered this information
along with all of the health risks and other health information
considered in the risk acceptability determination.
    For the PAI source category, we identified only one control option
to further address risks from equipment leaks, which were shown to
contribute 100 percent to the maximum individual cancer risks for this
source category. This control option would require sources to install
leakless valves to prevent leaks from those components.
    We estimated HAP reduction resulting from this control option is
approximately 101 tpy from the baseline actual emissions level. We
estimated that achieving these reductions would involve a capital cost
of approximately $180,000,000, a total annualized cost of about
$25,000,000 and a cost effectiveness of $244,000 per ton of HAP
emissions reduced. The additional control requirement would achieve
approximately 60-percent reduction in baseline risks at a very high
cost. We estimate that the MACT allowable emissions from equipment
leaks at this source category are approximately equal to the reported,
actual emissions. Therefore, the estimated emission reduction, risk
reduction and costs discussed above would also be applicable to the
MACT allowable emissions level. We believe that the costs of this
option are not reasonable, given the level of emission and risk
reduction.
    In accordance with the approach established in the Benzene NESHAP,
the EPA weighed all health risk measures and information considered in
the risk acceptability determination, along with the costs and economic
impacts of emissions controls, technological feasibility, uncertainties
and other relevant factors in making our ample margin of safety
determination. Considering the health risk information and the
unreasonable cost effectiveness of the option identified, we propose
that the existing MACT standards provide an ample margin of safety to
protect public health and prevent an adverse environmental effect.

B. What are the results of the technology review?

    In the decade since the PAI NESHAP was promulgated, the EPA has
developed 19 air toxics regulations for source categories that emit
organic HAP from the same type of emissions sources that are present in
the PAI source category. We reviewed the regulatory requirements and/or
technical analyses for these 19 regulations for new practices,
processes and control technologies. We also conducted a search of the
RBLC for controls for VOC- and HAP-emitting processes in the
Agricultural Chemical Manufacturing and the SOCMI categories with
permits dating back to 1997.
    We identified no advancements in practices, processes and control
technologies applicable to the emission sources in the PAI source
category in our technology review.

C. What other actions are we proposing?

1. SSM Provisions
    As we have done in other recent risk and technology rulemakings, we
are proposing to eliminate the SSM exemption in the PAI MACT standards.
Consistent with Sierra Club v. EPA, the EPA is proposing that standards
in this rule would apply at all times. We are proposing several
revisions to 40 CFR part 63, subpart MMM. Specifically, we are
proposing to revise Table 1 to indicate that the requirements of 40 CFR
63.6(e) of the General Provisions do not apply. The 40 CFR 63.6(e)
requires owner or operators to act according to the general duty to
``operate and maintain any affected source, including associated air
pollution control equipment and monitoring equipment, in a manner
consistent with safety and good air pollution control practices for
minimizing emissions.'' We are separately proposing to incorporate this
general duty to minimize into 40 CFR 63.1360(e). The 40 CFR 63.6(e)
also requires the owner or operator of an affected source to develop a
written SSM plan. We are proposing to remove the SSM plan requirement.
We are proposing to remove the explanation of applicability of
emissions standards during periods SSM in 40 CFR 63.1360(e); remove the
malfunction plan from 40 CFR 63.1367(a); clarify that representative
conditions do not include periods of SSM throughout the rule; remove
references to periods of SSM in monitoring; and revise the SSM-
associated recordkeeping and reporting requirements in 40 CFR
63.1367(a) to require reporting and recordkeeping for periods of
malfunction. We are also proposing to revise Table 1 to indicate that
SSM-related provisions in 40 CFR 63.6(e)(1), 63.6(e)(3), 63.6(f)(1); 40
CFR 63.7(e)(1); 40 CFR 63.8(c)(1)-(3); 40 CFR 63.10(c)(10), (11), and
(15); and 40 CFR 63.10(d)(5) of the General Provisions do not apply. We
are also proposing to add requirements in 40 CFR 63.1363(b)(4) to
clarify that PRD releases to the atmosphere are violations of the
emissions standards and to require pressure release alarms and to add
requirements in 40 CFR 63.1463(h)(4) to require reporting of any
pressure device releases to the atmosphere with the periodic report. In
addition, following our recently established practice in other risk and
technology review rulemakings, we are proposing to promulgate an
affirmative defense against civil penalties for exceedances of emission
standards caused by malfunctions, as well as criteria for establishing
the affirmative defense.
2. Electronic Reporting
    To increase the ease and efficiency of data submittal and improve
data accessibility, we are proposing to require the submission of
electronic copies of required performance tests for test methods that
are supported by the ERT to EPA's WebFIRE database. These provisions
are added in 40 CFR 63.1368(p).

VI. Analytical Results and Proposed Decisions for Polyether Polyols
Production

A. What are the results of the risk assessments?

1. Inhalation Risk Assessment Results
    Table 19 provides an overall summary of the inhalation risk
assessment results for the source category.

                                                    Table 19--PEPO Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Maximum individual cancer risk                                     Maximum chronic noncancer
                                       (in 1 million) \2\                        Annual cancer             TOSHI \3\
                               --------------------------------  Population at     incidence   --------------------------------  Maximum off-site acute
   Number of  facilities \1\        Actual         Allowable    risk >= 1-in-1    (cases per        Actual         Allowable        noncancer HQ \4\
                                   emissions       emissions        million          year)         emissions       emissions
                                     level           level                                           level           level
--------------------------------------------------------------------------------------------------------------------------------------------------------
23............................              30              30         160,000            0.02             0.8             0.8  HQREL = 6 glycol ethers.
                                                                                HQAEGL-1 = 0.1 acrolein.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum TOSHI. The target organ with the highest TOSHI for the PEPO source category is the respiratory system.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which, in most cases, is the REL. When HQ values exceed 1, we also show HQ values using the next
  lowest available acute dose-response value. See section III.B.3 of this preamble for explanation of acute dose-response values.

    The inhalation risk modeling was performed using actual emissions
level data. As shown in Table 19, the results of the inhalation risk
assessment indicated the maximum lifetime individual cancer risk could
be up to 30-in-1 million, the maximum chronic noncancer TOSHI value
could be up to 0.8 and the maximum off-facility site acute HQ value
could be up to 6, based on the actual emissions level and the REL value
for glycol ethers. The total estimated national cancer incidence from
these facilities, based on actual emission levels is 0.02 excess cancer
cases per year or one case in every 50 years.
    Based on our analysis, we estimate that the MACT-allowable
emissions level for organic non-epoxide HAP emissions from certain
process vents could be up to five times the actual emissions from this
source category. However, the highest cancer risks are caused by
epoxide emissions, and the application of the factor of five to the
non-epoxide organic HAP emissions from point sources did not result in
cancer risks in excess of the levels resulting from actual epoxide
emissions. Therefore, the cancer risk results for MACT-allowable
emissions are approximately equal to those for actual emissions. For
more detail about this estimate of the ratio of actual to MACT-
allowable emissions and the estimation of MACT-allowable emission
levels and associated risks and impacts, see the memorandum, MACT
Allowable Emissions and Risks for the Pesticide Active Ingredient,
Polyether Polyols, and Polymers and Resins IV Production Source
Categories, in the docket for this rulemaking.
    Two facilities reported emissions of PB-HAP, including fluoranthene
(a POM HAP) and lead compounds. We typically compare the facility-
specific emission rates of PB-HAP to the TRIM-Screen emission threshold
values to assess the potential for significant human health risks or
environmental risks via non-inhalation pathways. However, while lead is
a PB-HAP, the NAAQS value (which was used for the chronic noncancer
risk assessment) takes into account multipathway exposures, so a
separate multipathway screening value was not developed. Since we did
not estimate any exceedances of the NAAQS in our chronic noncancer risk
assessment, we do not expect any significant multipathway exposure and
risk due to lead emissions from these facilities. For fluoranthene
emissions, one facility emits this PB-HAP and the emissions exceed the
screening-level threshold level for POM by a factor of four. Based on
this screening analysis, we cannot rule out the potential for
multipathway impacts of concern due to emissions of fluoranthene from
the one facility. However, we do not expect fluoranthene emissions from
PEPO processes, and we specifically request data regarding these
emissions.
2. Facility-Wide Risk Assessment Results
    Table 20 displays the results of the facility-wide risk assessment.
This assessment was conducted based on actual emission levels. For
detailed facility-specific results, see Appendix 4 of the Draft
Residual Risk Assessment for 7 Source Categories in the docket for this
rulemaking.

          Table 20--PEPO Facility-Wide Risk Assessment Results
------------------------------------------------------------------------

------------------------------------------------------------------------
Number of facilities analyzed................................         23
Cancer Risk:
    Estimated maximum facility-wide individual cancer risk            30
     (in 1 million)..........................................
    1Number of facilities with estimated facility-wide                 0
     individual cancer risk of 100-in-1 million or more......
    Number of facilities at which the PEPO source category             0
     contributes 50 percent or more to the facility-wide
     individual cancer risks of 100-in-1 million or more.....
    Number of facilities at which the PEPO source category            14
     contributes 50 percent or more to the facility-wide
     individual cancer risk of 1-in-1 million or more........
Chronic Noncancer Risk:
    Maximum facility-wide chronic noncancer TOSHI............          2
    Number of facilities with facility-wide maximum noncancer          1
     TOSHI greater than 1....................................
    Number of facilities at which the PEPO source category             0
     contributes 50 percent or more to the facility-wide
     maximum noncancer TOSHI of 1 or more....................
------------------------------------------------------------------------

    The facility-wide MIR from all HAP emissions at a facility that
contains sources subject to the PEPO MACT standards is estimated to be
30-in-1 million, based on actual emissions. Of the 23 facilities
included in this

analysis, none have a facility-wide MIR of 100-in-1 million. There are
20 facilities with a facility-wide MIR of 1-in-1 million or greater (10
of these facilities have a facility-wide MIR equal to or greater than
10 in a million). Fourteen of these facilities have PEPO production
operations that contribute greater than 50 percent to the facility-wide
risks.
    The facility-wide maximum individual chronic noncancer TOSHI is
estimated to be 2 based on actual emissions. Of the 23 facilities
included in this analysis, one has facility-wide maximum chronic
noncancer TOSHI values greater than 1 (TOSHI of 2).
3. What is our proposed decision regarding risk acceptability?
    As noted in section III.C of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the number of persons in various cancer and noncancer risk ranges;
cancer incidence; the maximum noncancer HI; the maximum acute noncancer
HQ; the extent of noncancer risks; the potential for adverse
environmental effects; distribution of cancer and noncancer risks in
the exposed population; and risk estimation uncertainty (54 FR 38044,
September 14, 1989).
    For the PEPO source category, the risk analysis we performed
indicates that the cancer risks to the individual most exposed could be
up to 30-in-1 million due to both actual and allowable emissions. This
value is considerably less than 100-in-1 million, which is the
presumptive level of acceptability. The risk analysis also shows low
cancer incidence (1 in every 50 years). The chronic noncancer TOSHI is
estimated to be 1 due to emissions of chlorine.
    We estimate that the worst-case acute HQ value could exceed a value
of 1 for two HAP, glycol ethers and acrolein, with a potential maximum
acute HQ up to 6, based on the acute REL dose-response value for glycol
ethers. For glycol ethers, we used the lowest acute REL of any of the
glycol ethers with such health values (i.e., ethylene glycol monomethyl
ether) to assess the other glycol ethers without such values. Two of
the 23 facilities in this source category had an estimated acute HQ
greater than 1. All other facilities modeled had an acute HQ less than
1. The maximum acute HQ (based on the AEGL-1 dose-response value for
acrolein) is 0.1. As described earlier in this preamble, the acute
assessment includes some conservative assumptions and some
uncertainties. Considering the improbable assumption that worst-case
meteorological conditions are present at the same time that maximum
hourly emissions of glycol ethers exceed the average hourly emission
rate by a factor of 2 at all emission points simultaneously for both of
these facilities and coincident with individuals being in the location
of maximum impact, and considering the low acute HQ values, based on
the AEGL-1 and ERPG-1 dose-response values collectively with the REL
values, we believe it is unlikely that HAP emissions from this source
category would result in acute health effects.
    Our screening level evaluation of the potential health risks
associated with emissions of PB-HAP did not indicate potential for
adverse multipathway impacts due to emissions of lead. The screening
level evaluation indicated that the one facility that reported
fluoranthene emissions exceeded the screening-level threshold for POM
by a factor of 4; however, as explained in section III.B.7.e, our
screening methods use worst-case scenarios and the results are biased
high.
    Our additional analysis of facility-wide risks showed that the
maximum facility-wide cancer risk is 30-in-1 million. The maximum
chronic noncancer TOSHI is estimated to be 3, but the source category
contributes less than one-third to the maximum facility-wide TOSHI.
    The EPA has weighed the various health risk measures and health
factors, including risk estimation uncertainty, discussed above and in
section III.B.7 of this preamble, and we are proposing that the risks
from the PEPO source category are acceptable.
4. What is our proposed decision regarding ample margin of safety?
    We considered whether the MACT standards provide an ample margin of
safety to protect public health. In this analysis, we investigated
available emissions control options that might reduce the risk
associated with emissions from the source category and considered this
information along with all of the health risks and other health
information considered in the risk acceptability determination.
    For the PEPO source category, we identified only one control option
to further address risks from equipment leaks, which were shown to
contribute approximately 47 percent to the maximum individual cancer
risks for this source category. This control option would require
sources to install leakless valves to prevent leaks from those
components.
    We estimated HAP reduction resulting from this control option is
approximately 59 tpy from the baseline actual emissions level. We
estimated that achieving these reductions would involve a capital cost
of about $104,000,000, a total annualized cost of about $14,000,000 and
a cost effectiveness of $244,000 per ton of HAP emissions reduced. The
additional control requirement would achieve approximately 30-percent
reduction in baseline risks at a very high cost. We estimate that the
MACT allowable emissions from equipment leaks at this source category
are approximately equal to the reported, actual emissions. Therefore,
the estimated emission reduction, risk reduction and costs discussed
above would also be applicable to the MACT allowable emissions level.
We believe that the costs of this option are not reasonable, given the
level of emission and risk reduction.
    In accordance with the approach established in the Benzene NESHAP,
the EPA weighed all health risk measures and information considered in
the risk acceptability determination, along with the costs and economic
impacts of emissions controls, technological feasibility, uncertainties
and other relevant factors in making our ample margin of safety
determination. Considering the health risk information and the
unreasonable cost effectiveness of the option identified, we propose
that the existing MACT standards provide an ample margin of safety to
protect public health and prevent an adverse environmental effect.

B. What are the results of the technology review?

    In the decade since the PEPO NESHAP was promulgated, EPA has
developed 19 air toxics regulations for source categories that emit
organic HAP from the same type of emissions sources that are present in
the PEPO source category. We reviewed the regulatory requirements and/
or technical analyses for these 19 regulations for new practices,
processes and control technologies. We also conducted a search of the
RBLC for controls for VOC- and HAP-emitting processes in the SOCMI
categories with permits dating back to 1997.
    We identified no advancements in practices, processes and control
technologies applicable to the emission sources in the PEPO source
category in our technology review.

C. What other actions are we proposing?

1. SSM Provisions
    As we have done in other recent risk and technology review
rulemakings, we are proposing to eliminate the SSM

exemption in the PEPO MACT standards. Consistent with Sierra Club v.
EPA, the EPA is proposing that standards in this rule would apply at
all times. We are proposing several revisions to 40 CFR part 63,
subpart PPP. Specifically, we are proposing to revise Table 1 to
indicate that the requirements of 40 CFR 63.6(e) of the General
Provisions do not apply. The 40 CFR 63.6(e) requires owners or
operators to act according to the general duty to ``operate and
maintain any affected source, including associated air pollution
control equipment and monitoring equipment, in a manner consistent with
safety and good air pollution control practices for minimizing
emissions.'' We are separately proposing to incorporate this general
duty to minimize into 40 CFR 63.1420(h). The 40 CFR 63.6(e) also
requires the owner or operator of an affected source to develop a
written SSM plan. We are proposing to remove the SSM plan requirement.
We are proposing to remove the explanation of applicability of
emissions standards during periods SSM in 40 CFR 63.1420(h); remove the
malfunction plan from 40 CFR 63.1439(b); clarify that representative
conditions do not include periods of SSM throughout the rule; remove
references to periods of SSM in monitoring; remove the provisions for
excused excursions in 40 CFR 63.1438(g) and revise the SSM-associated
recordkeeping and reporting requirements in 40 CFR 63.1439(b) to
require reporting and recordkeeping for periods of malfunction. We are
also proposing to revise Table 1 to indicate that SSM-related
provisions in 40 CFR 63.6(e)(1), 63.6(e)(3), 63.6(f)(1); 40 CFR
63.7(e)(1); 40 CFR 63.8(c)(1); 40 CFR 63.10(c)(10), (11) and (15); and
40 CFR 63.10(d)(5) of the General Provisions do not apply. We are also
proposing to add requirements in 40 CFR 63.1434(c) to clarify that PRD
releases to the atmosphere are violations of the emissions standards
and to require pressure release alarms and to add requirements in 40
CFR 63.1439(e)(9) to require reporting of any pressure device releases
to the atmosphere with the periodic report. In addition, following our
practice established in other risk and technology review rulemakings,
we are proposing to promulgate an affirmative defense against civil
penalties for exceedances of emission standards caused by malfunctions,
as well as criteria for establishing the affirmative defense.
2. Electronic Reporting
    To increase the ease and efficiency of data submittal and improve
data accessibility, we are proposing to require the submission of
electronic copies of required performance tests for test methods that
are supported by the ERT to EPA's WebFIRE database. These provisions
are added in 40 CFR 63.1439(e)(10).

VII. Compliance Dates

    For the three MACT standards being addressed in this action, the
proposed compliance date for the revised SSM requirements and
electronic reporting requirements is the effective date of the
promulgated revised standards. We are proposing these compliance dates
because these requirements should be immediately implementable by the
facilities upon the next occurrence of a malfunction or the performance
of a performance test that is required to be submitted to the ERT. We
also believe that the facilities should already be able to comply with
the existing standards during periods of startup and shutdown.
    In accordance with CAA section 112(i)(3), the compliance date for
PRD monitoring is 3 years from the effective date of the promulgated
standards. This time period will allow facilities to purchase, install
and test the equipment.
    For the facility in the PET continuous TPA high viscosity multiple
end finisher subcategory subject to the Group IV Polymers and Resins
MACT standards, the proposed compliance date for the new MACT standards
applicable to equipment leaks and PCCT is the effective date of the
promulgated standards. Since this facility is already performing the
proposed equipment leak requirements and meeting the proposed PCCT
standards, the facility should be able to comply immediately with the
promulgated rule provisions. It should be feasible for the facility to
conduct any additional recordkeeping required upon the promulgation
date and information required in the next periodic report for these
requirements would only reflect the period of time between the
promulgation date and the periodic report due date.
    Beyond the revised SSM and electronic reporting requirements, there
are no changes to the PAI and PEPO MACT standards.

VIII. Summary of Cost, Environmental and Economic Impacts

A. What are the affected sources?

    We anticipate that each facility in these seven source categories
will be affected by these proposed amendments. We estimate there are 17