[Federal Register: October 10, 2008 (Volume 73, Number 198)]
[Proposed Rules]
[Page 60431-60461]
[DOCID:fr10oc08-29]

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Part III

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutant Emissions:
Group I Polymers and Resins; Marine Vessel Loading Operations; Mineral
Wool Production; Pharmaceuticals Production; and Printing and
Publishing Industry; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2008-0008; FRL-8724-5]
RIN 2060-AO91

National Emission Standards for Hazardous Air Pollutant
Emissions: Group I Polymers and Resins (Epichlorohydrin Elastomers
Production, Hypalon\TM\ Production, Nitrile Butadiene Rubber
Production, Polybutadiene Rubber Production, and Styrene Butadiene
Rubber and Latex Production); Marine Vessel Loading Operations; Mineral
Wool Production; Pharmaceuticals Production; and Printing and
Publishing Industry

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: This proposed action requests public comment on the residual
risk and technology reviews for nine industrial source categories
regulated by five national emission standards for hazardous air
pollutants. The five national emission standards and nine source
categories include: National Emissions Standards for Group I Polymers
and Resins (Epichlorohydrin Elastomers Production, HypalonTM
Production, Nitrile Butadiene Rubber Production, Polybutadiene Rubber
Production, and Styrene Butadiene Rubber and Latex Production);
National Emission Standards for Marine Vessel Loading Operations;
National Emission Standards for Hazardous Air Pollutants for Mineral
Wool Production; National Emission Standards for Pharmaceuticals
Production; and National Emission Standards for the Printing and
Publishing Industry. The underlying national emission standards that
are under review in this action limit and control hazardous air
pollutants.
    We are proposing that no revisions to the five national emission
standards regulating these nine source categories are required at this
time under section 112(f)(2) or 112(d)(6) of the Clean Air Act.

DATES: Comments. Comments must be received on or before November 24,
2008.
    Public Hearing.  If anyone contacts EPA requesting to speak at a
public hearing by October 20, 2008, a public hearing will be held on
October 27, 2008.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2008-0008, by one of the following methods:
     http://www.regulations.gov. Follow the on-line
instructions for submitting comments.
     E-mail<EMAIL_ADDRESS>     Fax:<PHONE_NUMBER>.
     Mail: U.S. Postal Service, send comments to: EPA Docket
Center (2822T), Docket ID No. EPA-HQ-OAR-2008-0008, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460. Please include a total of two
copies.
     Hand Delivery: In person or by courier, deliver comments
to: EPA Docket Center (2822T), EPA West Building, Room 3334, 1301
Constitution Ave., NW., Washington, DC 20004. Please include a total of
two copies. Such deliveries are only accepted during the Docket's
normal hours of operation, and special arrangements should be made for
deliveries of boxed information. We request that a separate copy of
each public comment also be sent to the contact person listed below
(see FOR FURTHER INFORMATION CONTACT).
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2008-0008. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
confidential business information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://
www.regulations.gov or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov, your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket, visit the EPA Docket Center homepage at http://www.epa.gov/
epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the EPA Docket Center,
Docket ID No. EPA-HQ-OAR-2008-0008, EPA, West Building, Room 3334, 1301
Constitution Avenue, NW., Washington, DC. The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
(202) 566-1744, and the telephone number for the EPA Docket Center is
(202) 566-1742.

FOR FURTHER INFORMATION CONTACT:  For questions about this proposed
action, contact Ms. Mary Tom Kissell, Office of Air Quality Planning
and Standards, Sector Policies and Programs Division, Coatings and
Chemicals Group (E143-01), U.S. Environmental Protection Agency,
Research Triangle Park, NC 27711; telephone number:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; and e-mail address<EMAIL_ADDRESS>For
specific information regarding the modeling methodology, contact Ms.
Elaine Manning, Office of Air Quality Planning and Standards, Health
and Environmental Impacts Division, Sector Based Assessment Group
(C539-02), U.S. Environmental Protection Agency, Research Triangle
Park, NC 27711; telephone number:<PHONE_NUMBER>; fax number: (919)
541-0840; and e-mail address<EMAIL_ADDRESS>For information
about the applicability of these five national emission standards for
hazardous air pollutants (NESHAP) to a particular entity, contact the
appropriate person listed in Table 1 to this preamble.

       Table 1--List of EPA Contacts for Group I Polymers and Resins, Marine Vessel Loading, Mineral Wool,
                                  Pharmaceuticals, and Printing and Publishing
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                    NESHAP for:                            OECA contact \1\              OAQPS contact \2\
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Polymers and Resins Production, Group I...........  Scott Throwe,<PHONE_NUMBER>,  David Markwordt, (919) 541-
<EMAIL_ADDRESS>         0837,
<EMAIL_ADDRESS>Marine Vessel Loading Operations..................  Maria Malave,<PHONE_NUMBER>,  David Markwordt, (919) 541-
<EMAIL_ADDRESS>         0837,
<EMAIL_ADDRESS>Mineral Wool Production...........................  Scott Throwe,<PHONE_NUMBER>,  Jeff Telander, (919) 541-
<EMAIL_ADDRESS>         5427<EMAIL_ADDRESS>Pharmaceuticals Production........................  Marcia Mia,<PHONE_NUMBER>,    Randy McDonald, (919) 541-
<EMAIL_ADDRESS>           5402,
<EMAIL_ADDRESS>Printing and Publishing Industry..................  Len Lazarus,<PHONE_NUMBER>,   David Salman,<PHONE_NUMBER>,
<EMAIL_ADDRESS><EMAIL_ADDRESS>----------------------------------------------------------------------------------------------------------------
\1\ OECA stands for EPA's Office of Enforcement and Compliance Assurance.
\2\ OAQPS stands for EPA's Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION: Regulated Entities. The nine regulated
industrial source categories that are the subject of this proposal are
listed in Table 2 to this preamble. Table 2 is not intended to be
exhaustive, but rather provides a guide for readers regarding entities
likely to be affected by the proposed action for the source categories
listed. These standards, and any changes considered in this rulemaking,
would be directly applicable to sources as a Federal program. Thus,
Federal, State, local, and tribal government entities are not affected
by this proposed action. The regulated categories affected by this
action include:

          Table 2--NESHAP for Nine Industrial Source Categories
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                                                    NAICS \1\   MACT \2\
                     Category                          code       code
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Epichlorohydrin Elastomers Production.............     325212       1311
Hypalon \TM\ Production...........................     325212       1315
Nitrile Butadiene Rubber Production...............     325212       1321
Polybutadiene Rubber Production...................     325212       1325
Styrene Butadiene Rubber and Latex Production.....     325212       1339
Marine Vessel Loading.............................       4883       0603
Mineral Wool Production...........................     327993       0409
Pharmaceuticals Production........................       3254       1201
Printing and Publishing Industry..................      32311      0714
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\1\ North American Industry Classification System.
\2\ Maximum Achievable Control Technology.

    To determine whether your facility would be affected, you should
examine the applicability criteria in the appropriate NESHAP. If you
have any questions regarding the applicability of any of these NESHAP,
please contact the appropriate person listed in Table 1 of this
preamble in the preceding FOR FURTHER INFORMATION CONTACT section.
    Submitting Comments/CBI. Direct your comments to Docket ID No. EPA-
HQ-OAR-2008-0008. If commenting on changes to the residual risk and
technology reviews (RTR) database, please submit your comments in the
format described in sections III and IV of this preamble. Do not submit
CBI to EPA through http://www.regulations.gov or e-mail. Instead, send
or deliver information identified as CBI only to the following address:
Mr. Roberto Morales, OAQPS Document Control Officer (C404-02), U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC 27711, Attention Docket ID No.
EPA-HQ-OAR-2008-0008. Clearly mark the part or all of the information
that you claim to be CBI. For CBI information on a disk or CD-ROM that
you mail to Mr. Morales, mark the outside of the disk or CD-ROM as CBI
and then identify electronically within the disk or CD-ROM the specific
information that is claimed as CBI.
    In addition to one complete version of the comment that includes
information claimed as CBI, a copy of the comment that does not contain
the information claimed as CBI must be submitted for inclusion in the
public docket. If you submit a CD-ROM or disk that does not contain
CBI, mark the outside of the disk or CD-ROM clearly that it does not
contain CBI. Information not marked as CBI will be included in the
public docket and EPA's electronic public docket without prior notice.
    If you have any questions about CBI or the procedures for claiming
CBI, please consult the person identified in the FOR FURTHER
INFORMATION CONTACT section. Information marked as CBI will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2.
    Worldwide Web (WWW). In addition to being available in the docket,
an electronic copy of this proposed action will also be available on
the WWW through the Technology Transfer Network (TTN). Following
signature, a copy of the proposed action will be posted on the TTN's
policy and guidance page for newly proposed or promulgated rules at the
following address: http://www.epa.gov/ttn/oarpg/. The TTN provides
information and technology exchange in various areas of air pollution
control.
    As discussed in more detail in sections III and IV of this
preamble, additional information is available on the RTR Phase II Web
page at http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. This information
includes source category descriptions and detailed emissions and other
data that were used as inputs to the risk assessments.
    Public Hearing. If a public hearing is held, it will begin at 10
a.m. on November 10, 2008 and will be held at EPA's campus in Research
Triangle Park, North Carolina, or at an alternate facility nearby.
Persons interested in presenting oral testimony or inquiring as to
whether a public hearing is to be held should contact Ms. Mary Tom
Kissell, Office of Air Quality Planning and Standards, Sector Policies
and Programs Division, Coatings and Chemicals Group (E143-01), U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711;
telephone number:<PHONE_NUMBER>.
    Outline. The information presented in this preamble is organized as
follows:

I. Background
    A. What is the statutory authority for this action?
    B. Overview of RTR
    C. Overview of the Five NESHAP
    D. How did we estimate risk posed by the nine source categories?

    E. What are the results of the risk assessment?
    F. What are our proposed decisions on acceptability and ample
margin of safety?
    G. What are the results of the technology review?
II. Proposed Action
    A. What is the rationale for our proposed action under CAA
section 112(f)?
    B. What is the rationale for our proposed action under CAA
section 112(d)(6)?
III. Request for Comments
IV. How do I submit suggested data corrections?
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. Background

A. What is the statutory authority for this action?

    Section 112 of the CAA establishes a two-stage regulatory process
to address emissions of hazardous air pollutants (HAP) from stationary
sources. In the first stage, after EPA has identified categories of
sources emitting one or more of the HAP listed in section 112(b) of the
CAA, section 112(d) of the CAA calls for us to promulgate NESHAP for
those sources. ``Major sources'' are those that emit or have the
potential to emit any single HAP at a rate of 10 tons or more per year
of a single HAP or 25 tons per year of any combination of HAP. For
major sources, these technology-based standards must reflect the
maximum degree of emission reductions of HAP achievable (after
considering cost, energy requirements, and non-air quality health and
environmental impacts) and are commonly referred to as maximum
achievable control technology (MACT) standards.
    The MACT ``floor'' is the minimum control level allowed for MACT
standards promulgated under section 112(d)(3). For new sources, the
MACT floor cannot be less stringent than the emission control that is
achieved in practice by the best-controlled similar source. The MACT
standards for existing sources can be less stringent than standards for
new sources, but they cannot be less stringent than the average
emission limitation achieved by the best-performing 12 percent of
existing sources in the category or subcategory (or the best-performing
five sources for categories or subcategories with fewer than 30
sources). In developing MACT standards, we must also consider control
options that are more stringent than the floor. We may establish
standards more stringent than the floor based on the consideration of
the cost of achieving the emissions reductions, any non-air quality
health and environmental impacts, and energy requirements.
    EPA is then required to review these technology-based standards and
to revise them ``as necessary (taking into account developments in
practices, processes, and control technologies)'' no less frequently
than every 8 years, under CAA section 112(d)(6). In this proposed rule,
we are publishing the results of our 8-year technology review for the
nine industrial source categories listed in Table 3, which we have
collectively termed ``Group 2A.''
    The second stage in standard-setting focuses on reducing any
remaining ``residual'' risk according to CAA section 112(f). This
provision requires, first, that EPA prepare a Report to Congress
discussing (among other things) methods of calculating risk posed (or
potentially posed) by sources after implementation of the MACT
standards, the public health significance of those risks, the means and
costs of controlling them, actual health effects to persons in
proximity of emitting sources, and recommendations as to legislation
regarding such remaining risk. EPA prepared and submitted this report
(Residual Risk Report to Congress, EPA-453/R-99-001) in March 1999.
Congress did not act in response to the report, thereby triggering
EPA's obligation under CAA section 112(f)(2) to analyze and address
residual risk.
    CAA section 112(f)(2) requires us to determine for source
categories subject to certain CAA section 112(d) standards whether the
emissions limitations provide an ample margin of safety to protect
public health. If the MACT standards for HAP ``classified as a known,
probable, or possible human carcinogen do not reduce lifetime excess
cancer risks to the individual most exposed to emissions from a source
in the category or subcategory to less than 1-in-1 million,'' EPA must
promulgate residual risk standards for the source category (or
subcategory) as necessary to provide an ample margin of safety to
protect public health. In doing so, EPA may adopt standards equal to
existing MACT standards (NRDC v. EPA, No. 07-1053, slip op. at 11, D.C.
Cir., decided June 6, 2008). EPA must also adopt more stringent
standards, if necessary, to prevent an adverse environmental effect,\1\
but must consider cost, energy, safety, and other relevant factors in
doing so. Section 112(f)(2) of the CAA expressly preserves our use of a
two-step process for developing standards to address any residual risk
and our interpretation of ``ample margin of safety'' developed in the
National Emission Standards for Hazardous Air Pollutants: Benzene
Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants,
Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product
Recovery Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989).
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    \1\ ``Adverse environmental effect'' is defined in CAA section
112(a)(7) as any significant and widespread adverse effect, which
may be reasonably anticipated to wildlife, aquatic life, or natural
resources, including adverse impacts on populations of endangered or
threatened species or significant degradation of environmental
qualities over broad areas.
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    The first step in this process is the determination of acceptable
risk. The second step provides for an ample margin of safety to protect
public health, which is the level at which the standards are set
(unless a more stringent standard is required to prevent, taking into
consideration costs, energy, safety, and other relevant factors, an
adverse environmental effect).
    The terms ``individual most exposed,'' ``acceptable level,'' and
``ample margin of safety'' are not specifically defined in the CAA.
However, CAA section 112(f)(2)(B) directs us to use the interpretation
set out in the Benzene NESHAP. See also, A Legislative History of the
Clean Air Act Amendments of 1990, volume 1, p. 877 (Senate debate on
Conference Report). We notified Congress in the Residual Risk Report to
Congress that we intended to use the Benzene NESHAP approach in making
CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p.
ES-11).
    In the Benzene NESHAP, we stated as an overall objective:

    * * * in protecting public health with an ample margin of
safety, we strive to provide maximum feasible protection against
risks to health from hazardous air pollutants by (1) protecting the
greatest number of persons possible to an individual lifetime risk
level no higher than approximately 1-in-1 million; and (2) limiting
to no higher than approximately 1-in-10 thousand [i.e., 100-in-1
million] the estimated risk that a person

living near a facility would have if he or she were exposed to the
maximum pollutant concentrations for 70 years.

    The Agency also stated that, ``The EPA also considers incidence
(the number of persons estimated to suffer cancer or other serious
health effects as a result of exposure to a pollutant) to be an
important measure of the health risk to the exposed population.
Incidence measures the extent of health risk to the exposed population
as a whole, by providing an estimate of the occurrence of cancer or
other serious health effects in the exposed population.'' The Agency
went on to conclude that ``estimated incidence would be weighed along
with other health risk information in judging acceptability.'' As
explained more fully in our Residual Risk Report to Congress, EPA does
not define ``rigid line[s] of acceptability,'' but considers rather
broad objectives to be weighed with a series of other health measures
and factors (EPA-453/R-99-001, p. ES-11). The determination of what
represents an ``acceptable'' risk is based on a judgment of ``what
risks are acceptable in the world in which we live'' (Residual Risk
Report to Congress, p. 178, quoting the Vinyl Chloride decision at 824
F.2d 1165) recognizing that our world is not risk-free.
    In the Benzene NESHAP, we stated that ``EPA will generally presume
that if the risk to [the maximum exposed] individual is no higher than
approximately 1 in 10 thousand, that risk level is considered
acceptable.'' 54 FR at 38045. We discussed the maximum individual
lifetime cancer risk as being ``the estimated risk that a person living
near a plant would have if he or she were exposed to the maximum
pollutant concentrations for 70 years.'' Id. We explained that this
measure of risk ``is an estimate of the upperbound of risk based on
conservative assumptions, such as continuous exposure for 24 hours per
day for 70 years.'' Id. We acknowledge that maximum individual lifetime
cancer risk ``does not necessarily reflect the true risk, but displays
a conservative risk level which is an upperbound that is unlikely to be
exceeded.'' Id.
    Understanding that there are both benefits and limitations to using
maximum individual lifetime cancer risk as a metric for determining
acceptability, we acknowledged in the 1989 Benzene NESHAP that
``consideration of maximum individual risk * * * must take into account
the strengths and weaknesses of this measure of risk.'' Id.
Consequently, the presumptive risk level of 100-in-1 million (1-in-10
thousand) provides a benchmark for judging the acceptability of maximum
individual lifetime cancer risk, but does not constitute a rigid line
for making that determination.
    The Agency also explained in the 1989 Benzene NESHAP the following:
``In establishing a presumption for MIR [maximum individual cancer
risk], rather than rigid line for acceptability, the Agency intends to
weigh it with a series of other health measures and factors. These
include the overall incidence of cancer or other serious health effects
within the exposed population, the numbers of persons exposed within
each individual lifetime risk range and associated incidence within,
typically, a 50 kilometer (km) exposure radius around facilities, the
science policy assumptions and estimation uncertainties associated with
the risk measures, weight of the scientific evidence for human health
effects, other quantified or unquantified health effects, effects due
to co-location of facilities, and co-emission of pollutants.'' Id.
    In some cases, these health measures and factors taken together may
provide a more realistic description of the magnitude of risk in the
exposed population than that provided by maximum individual lifetime
cancer risk alone.
    As explained in the Benzene NESHAP, ``[e]ven though the risks
judged ``acceptable'' by EPA in the first step of the Vinyl Chloride
inquiry are already low, the second step of the inquiry, determining an
``ample margin of safety,'' again includes consideration of all of the
health factors, and whether to reduce the risks even further. In the
second step, EPA strives to provide protection to the greatest number
of persons possible to an individual lifetime risk level no higher than
approximately 1 in 1 million. In the ample margin decision, the Agency
again considers all of the health risk and other health information
considered in the first step. Beyond that information, additional
factors relating to the appropriate level of control will also be
considered, including costs and economic impacts of controls,
technological feasibility, uncertainties, and any other relevant
factors. Considering all of these factors, the Agency will establish
the standard at a level that provides an ample margin of safety to
protect the public health, as required by section 112.'' 54 FR at
38046.

B. Overview of RTR

    We have begun to conduct the RTR for 96 MACT standards covering 174
sources categories. In an effort to streamline the RTR process and
focus our resources on source categories with the greatest potential
for risk to human health and the environment, we combined source
categories to create several groups, e.g., RTR Group 2A (which is the
subject of this proposed rule), and decided the order in which we would
propose each source category group. In deciding how to group source
categories, we considered factors such as the promulgation date of the
NESHAP, our preliminary analysis of the level of risk, completeness of
available emissions data, complexity of the risk assessment, and
whether we anticipated promulgating additional regulations pursuant to
the RTR.
    In general, we are addressing source categories with the earliest
NESHAP promulgation dates first because they have the earliest RTR due
dates and because the 2002 National Emission Inventory (NEI) contains
emissions data which reflect implementation of the NESHAP.
Additionally, we are addressing lower risk source categories first
because they typically require less effort to complete the necessary
analysis than higher risk source categories. We expect that the higher
risk source categories will require more time to evaluate because we
will likely need to perform more refined risk assessments, and because
they may have more complex issues to address, such as the emissions of
persistent and bioaccumulative HAP. Moreover, we believe our reviews of
the higher risk source categories will benefit from an understanding of
the public's concerns about our RTR approaches (through the comments we
receive on the earlier proposals).
    For the nine source categories in today's proposal for RTR Group
2A, we have concluded that emissions levels remaining after compliance
with the existing MACT standards: (1) Pose no unacceptable maximum
individual cancer risks (i.e., because the MIR is less than 100-in-1
million the risk is acceptable); (2) pose no significant chronic
noncancer health effects (i.e., maximum individual target organ-
specific hazard index (HI) values are all less than or equal to 1); (3)
are unlikely to result in acute adverse health effects from peak short-
term excursions; and (4) are unlikely to result in any adverse
environmental effect. Thus, we are proposing that the existing
standards provide an ample margin of safety to protect public health
and prevent adverse environmental effects.
    Future RTR actions for other source categories may require changes
to existing MACT standards to achieve the protection of public health
with an ample margin of safety and/or to

prevent adverse environmental effects. Future actions may also require
additional emission reductions pursuant to the technology review. We
plan to conduct RTR assessments for 12 source categories (RTR Groups 2B
and 2C, which were included in an advanced notice of proposed
rulemaking in March 2007) and propose our findings.\2\ In addition, we
plan to publish at least three more advanced notices of proposed
rulemaking. We may also publish some RTR for individual MACT standards
because of special circumstances such as court ordered deadlines. (See,
for example, the proposed RTR for Petroleum Refineries, 72 FR 50716,
09/04/2007.)
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    \2\ RTR Group 2B: Oil and Natural Gas Production; Natural Gas
Transmission; and Aerospace Operations. RTR Group 2C: Primary
Aluminum; Polymers and Resins IV (seven source categories); and Ship
Building.
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C. Overview of the Five NESHAP

    The nine industrial source categories and five NESHAP that are the
subject of this proposal are listed in Table 3 to this preamble. NESHAP
limit and control HAP that are known or suspected to cause cancer or
that may cause other serious human health or environmental effects. The
NESHAP for these nine source categories generally require
implementation of emissions reduction technologies such as combustion
devices, recovery devices, scrubbers, and fabric filters for point
sources and work practice and equipment standards for fugitive sources.

    Table 3--List of National Emission Standards for Hazardous Air Pollutants (NESHAP) and Industrial Source
                                     Categories Affected by Today's Proposal
----------------------------------------------------------------------------------------------------------------
                                     Source categories
         Title of NESHAP             affected by this      Promulgated rule     Compliance   NESHAP as referred
                                         proposal              reference           date      to in this preamble
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NESHAP: Group I Polymers and       Epichlorohydrin       61 FR 46905 (09/05/      07/31/97  Polymers and Resins
 Resins \1\.                        Elastomers            96).                               I.
                                    Production Hypalon
                                    \TM\ Production.
                                   Nitrile Butadiene
                                    Rubber Production.
                                   Polybutadiene Rubber
                                    Production.
                                   Styrene-Butadiene
                                    Rubber and Latex
                                    Production.
National Emission Standards for    Marine Vessel         60 FR 48388 (09/19/      09/19/99  Marine Vessels.
 Marine Vessel Loading Operations.  Loading Operations.   95).
NESHAP for Mineral Wool            Mineral Wool          64 FR 29489 (06/01/      06/01/02  Mineral Wool.
 Production.                        Production.           99).
National Emission Standards for    Pharmaceuticals       63 FR 50280 (09/21/      09/21/01  Pharmaceuticals.
 Pharmaceuticals Production.        Production.           98).
National Emission Standards for    Printing/Publishing   61 FR 27131 (05/30/      05/30/99  Printing and
 the Printing and Publishing        (Surface Coating).    96).                               Publishing.
 Industry.
----------------------------------------------------------------------------------------------------------------
\1\ The Polymers and Resins I NESHAP regulates nine source categories. We are performing the RTR for five of
  these in this proposal. The four other Polymers and Resins I source categories are being addressed in a
  separate RTR rulemaking. (See National Emission Standards for Hazardous Air Pollutant Emissions: Group I
  Polymers and Resins (Polysulfide Rubber Production, Ethylene Propylene Rubber Production, Butyl Rubber
  Production, Neoprene Production); National Emission Standards for Hazardous Air Pollutants for Epoxy Resins
  Production and Non-Nylon Polyamides Production; National Emission Standards for Hazardous Air Pollutants for
  Source Categories: Generic Maximum Achievable Control Technology Standards (Acetal Resins Production and
  Hydrogen Fluoride Production), proposed on December 12, 2007, at 72 FR 70543.)

1. Polymers and Resins I
    The National Emission Standards for Hazardous Air Pollutant
Emissions: Group I Polymers and Resins were promulgated on September 5,
1996 (62 FR 46925). The Polymers and Resins I NESHAP applies to major
sources and regulates HAP emissions from nine source categories. In
this proposal, we address five of the Polymer and Resins I sources
categories--Epichlorohydrin Elastomers Production, Hypalon \TM\
Production, Nitrile Butadiene Rubber Production, Polybutadiene Rubber
Production, and Styrene Butadiene Rubber and Latex Production.
    The Polymers and Resins I NESHAP regulate HAP emissions resulting
from the production of elastomers (i.e., synthetic rubber). An
elastomer is a synthetic polymeric material that can stretch at least
twice its original length and then return rapidly to approximately its
original length when released. Elastomers are produced via a
polymerization/copolymerization process, in which monomers undergo
intermolecular chemical bond formation to form a very large polymer
molecule. Generally, the production of elastomers entails four
processes: (1) Raw material (i.e., solvent) storage and refining; (2)
polymer formation in a reactor (either via the solution process, where
monomers are dissolved in an organic solvent, or the emulsion process,
where monomers are dispersed in water using a soap solution); (3)
stripping and material recovery; and (4) finishing (i.e., blending,
aging, coagulation, washing, and drying).
    Sources of HAP emissions from elastomers production include raw
material storage vessels, front-end process vents, back-end process
operations, wastewater operations, and equipment leaks. The ``front-
end'' processes include pre-polymerization, reaction, stripping, and
material recovery operations; and the process ``back-end'' includes all
operations after stripping (predominately drying and finishing).
Typical control devices used to reduce organic HAP emissions from
front-end process vents include flares, incinerators, absorbers, carbon
adsorbers, and condensers. In addition, hydrochloric acid formed when
chlorinated organic compounds are combusted are controlled using
scrubbers. Emissions from storage vessels are controlled by floating
roofs or by routing them to a control device. While emissions from
back-end process operations can be controlled with

control devices such as incinerators, the most common method of
reducing these emissions is the pollution prevention method of reducing
the amount of residual HAP that is contained in the raw product going
to the back-end operations. Emissions from wastewater are controlled by
a variety of methods, including equipment modifications (e.g., fixed
roofs on storage vessels and oil water separators; covers on surface
impoundments, containers, and drain systems), treatment to remove the
HAP (steam stripping, biological treatment), control devices, and work
practices. Emissions from equipment leaks are typically reduced by leak
detection and repair work practice programs, and in some cases, by
equipment modifications.
    Each of the five Polymers and Resins I source categories addressed
in this proposal are discussed further below.
a. Epichlorohydrin Elastomers Production
    Epichlorohydrin elastomers are prepared from the polymerization or
copolymerization of epichlorohydrin or other monomers. Epichlorohydrin
elastomers are produced by a solution polymerization process, typically
using toluene as the solvent in the reaction. The main epichlorohydrin
elastomers are polyepichlorohydrin, epi-ethylene oxide (EO) copolymer,
epi-allyl glycidyl ether (AGE) copolymer, and epi-EO-AGE terpolymer.
Epichlorohydrin elastomers are widely used in the automotive industry.
    We identified one epichlorohydrin elastomers production facility
currently subject to the Polymers and Resins I NESHAP. This facility
produces epichlorohydrin elastomers primarily, but the plant site also
has equipment regulated by other NESHAP, which have been or will be
addressed in separate RTR rulemaking actions.
    Toluene accounts for the majority of the HAP emissions from the
epichlorohydrin production processes at this facility (approximately
105 tons per year (TPY) and 99 percent of the total HAP emissions by
mass). This facility also reported relatively small emissions of
epichlorohydrin and ethylene oxide. The majority of HAP emissions are
from back-end process vents (approximately 75 percent of the total HAP
by mass). We estimate that the MACT allowable emissions (i.e., the
maximum emission levels allowed if in compliance with the NESHAP) from
this source category are approximately equal to the reported, actual
emissions.\3\
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    \3\ Our analysis of the impacts of the worst case MACT allowable
emissions as compared to reported actual emissions for each of the
nine source categories is discussed in more detail in ``Estimation
of MACT Allowable Emission Levels and Associated Risks and Impacts
for the RTR Group 2A Source Categories.''.
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b. Hypalon \TM\ Production
    Hypalon,\TM\ or chlorosulfonated polyethylene, is a synthetic
rubber produced by reacting polyethylene with chlorine and sulfur
dioxide, transforming the thermoplastic polyethylene into a vulcanized
elastomer. The reaction is conducted in a solvent reaction medium
containing carbon tetrachloride. These elastomers are commonly used in
wire insulation and jacketing, automotive components, adhesives, and
protective coatings.
    We identified one Hypalon \TM\ production facility currently
subject to the Polymers and Resins I NESHAP. The plant site for this
facility also has other HAP-emitting sources which are regulated under
separate NESHAP, including Marine Vessel Loading Operations, 40 CFR
part 63, subpart Y. Marine Vessel Loading Operations are addressed
separately in this proposed rule, but RTR for the other NESHAP have
been or will be addressed in separate rulemaking actions.
    Carbon tetrachloride accounts for the majority of the HAP emissions
from the Hypalon \TM\ production processes at this facility
(approximately 22 TPY and 71 percent of the total HAP emissions by
mass). This facility also reported relatively small emissions of
chlorine, chloroform, and hydrochloric acid. The majority of HAP
emissions are from front-end process vents (approximately 63 percent of
the total HAP by mass) and back-end process operations (approximately
33 percent of the total HAP by mass). We estimate that MACT allowable
emissions from this source category are approximately equal to
reported, actual emissions.
c. Nitrile Butadiene Rubber Production
    Nitrile butadiene rubber (NBR) is a copolymer of 1,3-butadiene and
acrylonitrile, and the NBR production source category includes any
facility that polymerizes 1,3-butadiene and acrylonitrile. While NBR is
the primary product at these facilities, styrene-butadiene rubber can
also be produced as a minor product by substituting styrene for
acrylonitrile as a monomer. Depending on its specific composition, NBR
can be resistant to oil and chemicals, a property that facilitates its
use in disposable gloves, hoses, seals, and a variety of automotive
applications.
    We identified four NBR production facilities currently subject to
the Polymers and Resins I NESHAP. Two of these facilities are at plant
sites that also have operations which produce styrene-butadiene rubber
and latex, another Polymers and Resins I source category. The styrene-
butadiene rubber and latex processes and emissions are addressed
separately in today's proposed action under the Styrene Butadiene
Rubber and Latex source category. Some of these facilities also have
other HAP-emitting sources that are regulated under separate NESHAP,
which have been or will be addressed in separate RTR rulemaking
actions.
    Styrene, 1,3-butadiene, and acrylonitrile account for the majority
of the HAP emissions from this source category (approximately 46 TPY
and over 99 percent of the total HAP emissions by mass). The facilities
in this source category also reported relatively small emissions of
carbon disulfide. The majority of HAP emissions are from back-end
process operations (approximately 43 percent of the total HAP by mass)
and front-end process vents (approximately 34 percent of the total HAP
by mass) for this source category. However, the emissions from one
facility were not included in this estimation of emissions by source
type, as it was not possible to positively discern which types of
emission sources were responsible for emissions from this facility in
all instances. Based on the emissions release characteristics for this
facility, we estimate that of the facility's 48 TPY of HAP emissions,
the majority are from back-end process operations and equipment leaks
(approximately 58 and 23 percent by mass, respectively). We estimate
that MACT allowable emissions from this source category are
approximately equal to reported, actual emissions.
d. Polybutadiene Rubber Production
    Polybutadiene rubber (PBR) is a homopolymer of 1,3-butadiene (i.e.,
1,3-butadiene is the only monomer used in the production of this
polymer). While both the solution and emulsion polymerization processes
can be used to produce PBR, all currently operating facilities in the
United States use a solution process. In the solution process, the
reaction is conducted in an organic solvent (hexane, toluene, or a non-
HAP organic solvent), which helps to dissipate heat generated by the
reaction and control the reaction rate. While PBR is the primary
product at these facilities, styrene-butadiene rubber can also be
produced as a minor product by adding styrene as a monomer. Most of the
PBR manufactured in the United States is used in the production of
tires in the construction of the tread and

sidewalls. PBR is also used as a modifier in the production of other
polymers and resins (e.g., polystyrene).
    We identified five PBR production facilities currently subject to
the Polymers and Resins I NESHAP. Some of these facilities are located
at plant sites that also have other HAP-emitting sources regulated
under separate NESHAP, which have been or will be addressed in separate
RTR actions.
    Three of the PBR production facilities use hexane as the solvent in
their solution process, one facility uses toluene as its solvent, and
the fifth uses a non-HAP organic solvent. Overall, hexane accounts for
the majority of the HAP emissions from this source category
(approximately 1,455 TPY and 72 percent of the total HAP emissions by
mass). The facilities in this source category also reported substantive
emissions of styrene and 1,3-butadiene and relatively minor quantities
of three other HAP. The majority of HAP emissions are from back-end
process operations (approximately 73 percent of the total HAP by mass).
We estimate that MACT allowable emissions from this source category
could be as high as five times the actual emissions.
e. Styrene Butadiene Rubber and Latex Production
    Styrene butadiene rubber and latex are elastomers prepared from
styrene and butadiene monomer units. The source category is divided
into three subcategories due to technical process and HAP emission
differences: (1) The production of styrene butadiene rubber by
emulsion, (2) the production of styrene butadiene rubber by solution,
and (3) the production of styrene butadiene latex. Styrene butadiene
rubber is coagulated and dried to produce a solid product, while latex
is a liquid product. For both styrene butadiene rubber processes, the
monomers used are styrene and butadiene; either process can be
conducted as a batch or a continuous process. These elastomers are
commonly used in tires and tire-related products.
    We identified two styrene butadiene rubber production facilities
using the emulsion process and 12 styrene butadiene rubber latex
production facilities currently subject to the Polymers and Resins I
NESHAP. Other than the polybutadiene plants that produce styrene
butadiene rubber as a minor product, we did not identify any styrene
butadiene rubber produced in a solution process. Two of these
facilities are located at plant sites that also have operations which
produce NBR, another Polymers and Resins I source category. The NBR
processes and emissions are addressed separately in this proposed
action under the Nitrile Butadiene Rubber source category. Some of
these facilities are located at plant sites that also have other HAP-
emitting sources regulated under separate NESHAP, which have been or
will be addressed in separate RTR actions.
    Overall, styrene accounts for the majority of the HAP emissions
from these facilities (approximately 276 TPY and 90 percent of the
total HAP emissions by mass). These facilities also reported relatively
small emissions of 13 other HAP. The majority of HAP emissions are from
back-end process operations (approximately 80 percent of the total HAP
by mass). We estimate that MACT allowable emissions from this source
category could be as high as four times the actual emissions.
2. Marine Vessels
    The National Emission Standards for Marine Vessel Loading
Operations were promulgated on September 19, 1995 (60 FR 48388). The
Marine Vessel Loading Operations NESHAP applies to major sources and
regulates HAP emissions from: Land-based terminals, off-shore
terminals, and the Alyeska Pipeline Service Company's Valdez Marine
Terminal.
    Marine vessel loading operations are facilities that load and
unload liquid commodities in bulk, such as crude oil, gasoline, and
other fuels, and some chemicals and solvent mixtures. The cargo is
pumped from the terminal's large, above-ground storage tanks through a
network of pipes and into a storage compartment (tank) on the vessel.
Emissions occur as vapors are displaced from the tank as it is being
filled. Most marine tank vessel loading operations are associated with
petroleum refineries, synthetic organic chemical manufacturers, or are
independent terminals.
    The primary emission sources of displaced vapors at marine vessel
loading operations include open tank hatches and overhead vent systems.
Other possible emission points are hatch covers or domes, pressure-
vacuum relief valves, seals, and vents. Emissions may also occur during
ballasting (i.e., the process of drawing ballast as water into a cargo
hold). The NESHAP requires control of all displaced vapors that occur
during product loading. Typical control devices used to reduce HAP
emissions include vapor collection systems routed to combustion or
recovery devices, such as flares, incinerators, absorbers, carbon
adsorbers, and condensers.
    Additional data indicate that approximately 800 terminals load HAP-
containing organic liquids. An unknown fraction of these are
containerized liquids that are not subject to the Marine Vessel Loading
Operations NESHAP. Therefore, we estimate up to 800 facilities may be
subject to the Marine Vessel Loading Operations NESHAP. However, data
in the 2002 NEI were available for only 135 facilities and our analyses
are based on these 135 modeled facilities. We believe the 135 modeled
facilities are representative of the source category because we expect
that generally the same HAP, in the same range of quantities, are
emitted from the 135 modeled facilities as are emitted from rest of the
facilities in the source category. We extrapolated the risk results for
the 135 modeled facilities up to the approximately 800 facilities in
the source category and believe the resulting cancer and noncancer
risks either represent or overstate risk from the 800 facilities in
source category. However, we request comment on this approach,
additional data on pollutant-specific emissions from facilities in the
NEI, and identification of emissions from marine vessel loading
facilities not included in the NEI.
    Marine terminals that are part of the petroleum refineries source
category are not regulated by the Marine Vessel Loading Operations
NESHAP. Therefore, marine terminals that are part of the petroleum
refineries source category were not included in this risk assessment.
The petroleum refineries marine terminals are being addressed in a
separate RTR rulemaking action. (See the proposed RTR for Petroleum
Refineries, 72 FR 50716, 09/04/2007.)
    Hexane, methanol, toluene, and mixed xylenes account for the
majority of the HAP emissions from the 135 NEI facilities
(approximately 184 TPY and 73 percent of the total HAP emissions by
mass). These facilities also reported relatively small emissions of 42
other HAP. These emissions are from the loading operations at the
terminals. MACT allowable emission levels from this source category
could be higher than actual emission levels due primarily to states
requiring controls (typically 90 percent reduction) for some marine
terminals that are not controlled by the Marine Vessel Loading
Operations NESHAP. Based on typical state rule emission reduction
requirements we estimate that the MACT allowable emissions from this
source category would be 10 times the actual emissions for terminals
not controlled by the Marine Vessel Loading Operations NESHAP and
approximately

two times the actual emissions for marine terminals that are controlled
by the Marine Vessel Loading Operations NESHAP.
3. Mineral Wool Production
    The National Emission Standards for Mineral Wool Production were
promulgated on June 1, 1999 (64 FR 29489). The Mineral Wool Production
NESHAP applies to major sources of HAP.
    Mineral wool is a fibrous, glassy substance made from natural rock
(such as basalt), blast furnace slag, or other similar materials. In
the mineral wool manufacturing process, rock and/or blast furnace slag
and other raw materials (e.g., gravel) are melted in a furnace (cupola)
using coke as a fuel. The molten material is then formed into fiber.
Mineral wool is manufactured as either a ``bonded'' product that
incorporates a binder to increase structural rigidity or a less rigid
``nonbonded'' product. Products made from mineral wool are used for
insulation, sound control and attenuation, and fire protection. The
industry is declining significantly due to economic and competitive
reasons (e.g., availability of alternative products such as cellulose
insulation).
    Emission sources at mineral wool production facilities include the
cupola furnace where the mineral charge is melted; a blow chamber, in
which air or a binder is drawn over the fibers, forming them into a
screen; a curing oven that bonds the fibers (for bonded products); and
a cooling chamber. The majority of the emissions originate from the
cupolas and curing ovens. The NESHAP requires control of particulate
matter emissions from the cupolas and formaldehyde emissions from the
curing ovens. Typical control devices used to reduce HAP emissions from
the cupola include baghouses/fabric filters, and emissions from the
curing ovens are generally controlled with thermal incinerators.
    We identified eight facilities currently subject to the Mineral
Wool Production NESHAP. Some of these facilities also have other HAP-
emitting sources that are regulated under separate NESHAP, which have
been or will be addressed in separate RTR rulemaking actions.
    Carbonyl sulfide accounts for the majority of the HAP emissions
from these facilities (approximately 416 TPY and 87 percent of the
total HAP emissions by mass). These facilities also reported relatively
small emissions of 16 other HAP. The majority of HAP emissions are from
the cupolas (approximately 80 percent of the total HAP by mass). The
majority of HAP emissions (primarily formaldehyde) that were
significant in evaluating risk are from the cooling chambers. We
estimate that MACT allowable emissions from this source category could
be as high as two times the actual emissions.
4. Pharmaceuticals Production
    The National Emission Standards for Pharmaceuticals Production were
promulgated on September 21, 1998 (63 FR 50280). The Pharmaceuticals
Production NESHAP applies to major sources of HAP.
    The pharmaceutical manufacturing process consists of chemical
production operations that produce drugs and medication. These
operations include chemical synthesis (deriving a drug's active
ingredient) and chemical formulation (producing a drug in its final
form).
    Emission sources at pharmaceutical production facilities include
breathing and withdrawal losses from chemical storage tanks, venting of
process vessels, leaks from piping and equipment used to transfer HAP
compounds (equipment leaks), and volatilization of HAP from wastewater
streams.
    Typical control devices used to reduce HAP emissions from process
vents include flares, incinerators, scrubbers, carbon adsorbers, and
condensers. Emissions from storage vessels are controlled by floating
roofs or by routing them to a control device. Emissions from wastewater
are controlled by a variety of methods, including equipment
modifications (e.g., fixed roofs on storage vessels and oil water
separators; covers on surface impoundments containers, and drain
systems), treatment to remove the HAP (steam stripping, biological
treatment), control devices, and work practices. Emissions from
equipment leaks are typically reduced by leak detection and repair work
practice programs, and in some cases, by equipment modifications.
    We identified 27 facilities currently subject to the
Pharmaceuticals Production NESHAP. Some of these facilities are located
at plant sites that also have other HAP-emitting sources regulated
under separate NESHAP, which have been or will be addressed in separate
rulemaking actions.
    Methylene chloride, methanol, acetonitrile, and toluene account for
the majority of the HAP emissions from these facilities (approximately
891 TPY and 90 percent of the total HAP emissions by mass). These
facilities also reported relatively small emissions of 65 other HAP.
The majority of HAP emissions are from the process vents (approximately
70 percent of the total HAP by mass emitted from process vents, with 20
percent and 10 percent of the total HAP by mass emitted from equipment
leaks and wastewater operations, respectively). We estimate that MACT
allowable emissions from this source category could be up to 25 percent
greater than the actual emissions, primarily from process vents, as it
is possible that the control devices used at some facilities achieve
greater emission reductions from these emission sources than what is
required by the NESHAP.
5. Printing and Publishing Industry
    The National Emission Standards for the Printing and Publishing
Industry were promulgated on May 30, 1996 (61 FR 27132). The Printing
and Publishing NESHAP applies to major sources of HAP.
    Printing and publishing facilities are those facilities that use
rotogravure, flexography, and other methods, such as lithography,
letterpress, and screen printing, to print on a variety of substrates,
including paper, plastic film, metal foil, and vinyl. The Printing and
Publishing NESHAP focuses on two subcategories: (1) Publication
rotogravure printing and (2) product and packaging rotogravure and
wide-web flexographic printing. Emissions at printing and publishing
facilities result from the evaporation of solvents in the inks and from
cleaning solvents. The emission points include printing presses and
associated dryers and ink and solvent storage. Control techniques
include recovery devices, combustion devices, and the use of non-HAP/
low-HAP inks and cleaning solvents.
    We estimate that approximately 200 facilities are subject to the
Printing and Publishing NESHAP based on the information we gathered in
support of the rule development in 1996. As data were available for 179
major source facilities in the 2002 NEI, our analyses are based on
these 179 facilities. We believe the 179 facilities represent the
source category because: (1) We have no reason to believe that
emissions from the other facilities are different from the facilities
we modeled; (2) the difference between the number of facilities counted
in 1996 and 2002 might be accounted for by facility closures and by
some facilities achieving area source status for HAP before the first
compliance date of the Printing and Publishing NESHAP; and, (3) we
believe in most cases data on 90 percent of the facilities in a source
category will be representative of the source category as a whole. Some
of these facilities are located at plant sites that also have other
HAP-emitting sources regulated

under separate NESHAP, which have been or will be addressed in separate
RTR rulemaking actions.
    Toluene accounts for the majority of the HAP emissions from these
facilities (approximately 6,606 TPY or 88 percent of the total HAP
emissions by mass). These facilities also reported relatively small
emissions of 56 other HAP. These emissions are primarily from the
evaporation of HAP present in the inks and other materials applied with
rotogravure and flexographic processes. We estimate that MACT allowable
emissions from this source category could be up to 5 times greater than
the actual emissions, as it is possible that the capture systems and
control devices used at some facilities achieve greater emission
reductions than what is required by the NESHAP.

D. How did we estimate risk posed by the nine source categories?

    To support the proposed decisions presented in today's notice, EPA
conducted a risk assessment that provided estimates of MIR, maximum
individual cancer risk distribution within the exposed populations,
cancer incidence, hazard indices for chronic exposures to HAP with non-
cancer health effects, hazard quotients (HQ) for acute exposures to HAP
with non-cancer health effects, and estimates of the potential for
adverse environmental effects. The risk assessment consisted of seven
primary activities: (1) Establishing the nature and magnitude of
emissions from the source categories, (2) identifying the emissions
release characteristics (e.g., stack parameters), (3) conducting
dispersion modeling to estimate the concentrations of HAP in ambient
air, (4) estimating long-term and short-term inhalation exposures to
individuals residing within 50 km of the modeled sources, (5)
estimating individual and population-level inhalation risks using the
exposure estimates and quantitative dose-response information, (6)
estimating the potential for adverse human health multipathway risks
and for adverse environmental effects, and (7) characterizing risk. In
general, the risk assessment followed a tiered, iterative approach,
beginning with a conservative (worst case) screening-level analysis
and, where the screening analyses indicated the potential for non-
negligible risks, following that with more refined analyses. The
following sections summarize these activities. For more information on
the risk assessment inputs and models, see ``Residual Risk Assessment
for Nine Source Categories,'' available in the docket.
    We engaged in a consultation with a panel from the Science Advisory
Board (SAB) on the ``Risk and Technology Review (RTR) Assessment Plan''
in December of 2006. The results of this consultation were transmitted
to us in June 2007 in a letter from the SAB which also contained a
summary listing of the key messages from the panel. The letter is
available from the docket and from http://yosemite.epa.gov/sab/
sabproduct.nsf/33152C83D29530F08525730D006C3ABF/$File/sab-07-009.pdf.
In developing the risk assessments for the nine source categories
covered by this proposal, we followed the RTR Assessment Plan,
addressing the key messages from the panel, where appropriate and
relevant to these assessments.
1. Emissions and Emissions Release Characteristic Data
    The basic approach taken to obtain the most accurate and reliable
emissions and emissions release characteristic data was to compile
preliminary data sets using readily available information for each
source category and to share these data with the public via an Advanced
Notice of Proposed Rulemaking (ANPRM). The data sets were then updated
based on comments received on the ANPRM and, in some cases, with
additional information gathered by EPA.
    For the five Polymers and Resins I source categories
(Epichlorohydrin Elastomers Production, HypalonTM Production, Nitrile
Butadiene Rubber Production, Polybutadiene Rubber Production, and
Styrene Butadiene Rubber and Latex Production), we collected emissions
data and emissions release characteristic data directly from industry.
These data generally formed the data sets used in our analyses for
these source categories.
    For the remaining four source categories (Marine Vessel Loading,
Mineral Wool, Pharmaceuticals, and Printing and Publishing), we created
the preliminary data sets using the data in the 2002 NEI Final
Inventory, Version 1 (made publicly available on February 26, 2006)
supplemented by data collected directly from industry when available.
The NEI is a database that contains information about sources that emit
criteria air pollutants and their precursors, and HAP. The database
includes estimates of annual air pollutant emissions from point,
nonpoint, and mobile sources in the 50 States, the District of
Columbia, Puerto Rico, and the Virgin Islands. EPA collects this
information and releases an updated version of the NEI database every 3
years.
    On March 29, 2007, we published an ANPRM (72 FR 29287) specifically
to request comments and updates to these preliminary data sets. We
received comments on emissions data and emissions release
characteristics data for facilities in these nine source categories.
These comments were reviewed, considered, and the emissions information
was adjusted where we concluded the comments supported such adjustment.
After incorporation of changes to the data sets from this public data
review process, the final data sets were created. These data sets were
used to conduct the risk assessments and other analyses that form the
bases for these proposed actions.
    In addition to gathering information regarding the actual emissions
from the sources in the nine source categories, we also examined the
underlying NESHAP to determine whether the emissions that a source was
allowed to emit when in compliance with the NESHAP would significantly
vary from the actual emissions data we had gathered. Where such ``MACT
allowable'' emission levels could be higher than the actual emission
levels, we extrapolated the risks associated with the MACT allowable
emission levels from the risks associated with the actual emission
levels.
    The data sets for these nine source categories and documentation of
the emissions data sets used for each source category are available in
the RTR Group 2A docket. The documentation of the emission data sets
provides a description of the changes in the dataset for each source
category since the ANPRM, describes the data changes requested in
public comments, and documents the analysis of MACT allowable emissions
for each source category.
2. Dispersion Modeling, Inhalation Exposures, and Individual and
Population Inhalation Risks
    Both long-term and short-term inhalation exposure concentrations
and health risk from each of the nine source categories addressed in
this proposal were estimated using the Human Exposure Model (Community
and Sector HEM-3 version 1.1.0). The HEM-3 performs three of the
primary risk assessment activities listed above: (1) Conducting
dispersion modeling to estimate the concentrations of HAP in ambient
air, (2) estimating long-term and short-term inhalation exposures to
individuals residing within 50 km of the modeled sources, and (3)
estimating individual and population-level inhalation risks using the
exposure

estimates and quantitative dose-response information.
    The dispersion model used by HEM-3 is AERMOD, which is one of EPA's
preferred models for assessing pollutant concentrations from industrial
facilities.\4\ To perform the dispersion modeling and to develop the
preliminary risk estimates, HEM-3 draws on three data libraries. The
first is a library of meteorological data, which is used for dispersion
calculations. This library includes 1 year of hourly surface and upper
air observations for 130 meteorological stations, selected to provide
thorough coverage of the United States and Puerto Rico. A second
library of United States Census Bureau census block internal point
locations and populations provides the basis of human exposure
calculations (Census, 2000). In addition, the census library includes
the elevation and controlling hill height for each census block, which
are also used in dispersion calculations. A third library of pollutant
unit risk factors and other health benchmarks is used to estimate
health risks. These risk factors and health benchmarks are the latest
values recommended by EPA for HAP and other toxic air pollutants. These
values are available at http://www.epa.gov/ttn/atw/toxsource/
summary.html and are discussed in more detail later in this section.
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    \4\ Environmental Protection Agency. Revision to the Guideline
on Air Quality Models: Adoption o fa Preferred General Purpose (Flat
and Complex Terrain) Dispersion Model and Other Revisions (70 FR
68218). November 9, 2005.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used
the estimated annual average ambient air concentration of each HAP
emitted by each source for which we have emissions data in the source
category at each nearby census block \5\ centroid as a surrogate for
the chronic inhalation exposure concentration for all the people who
reside in that census block. We calculated the MIR for each facility as
the risk associated with a lifetime (70-year) exposure to the maximum
concentration at the centroid of an inhabited census block. Individual
cancer risks were calculated as the lifetime exposure to the ambient
concentration of each HAP multiplied by its Unit Risk Estimate (URE),
which is an upper bound estimate of an individual's probability of
contracting cancer over a lifetime of exposure to a concentration of
one microgram of the pollutant per cubic meter of air. For residual
risk assessments, we generally use URE values from EPA's Integrated
Risk Information System (IRIS). For carcinogenic pollutants without EPA
IRIS values, we look to other reputable sources of cancer dose-response
values, often using California Environmental Protection Agency (CalEPA)
URE values, where available. In cases where new, scientifically
credible dose-response values have been developed in a manner
consistent with EPA guidelines and have undergone a peer review process
similar to that used by EPA, we may use such dose-response values in
place of or in addition to other values. Total cancer risks were the
sum of the risks of each carcinogenic HAP (including known, probable,
and possible carcinogens) emitted by the modeled source. Air
concentrations of HAP from sources other than the modeled source were
not estimated. Total cancer incidence and the distribution of
individual cancer risks across the population within 50 kilometers of
any source were also estimated as part of these assessments by summing
individual risks. We are using 50 kilometers to be consistent with both
the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the
limitations of Gaussian dispersion modeling.
---------------------------------------------------------------------------

    \5\ A typical census block is comprised of approximately 40
people or about 10 households.
---------------------------------------------------------------------------

    To assess risk of noncancer health effects from chronic exposures,
we summed the HQ for each HAP that affects a common target organ system
to obtain the HI for that target organ system (or target organ-specific
HI, TOSHI). The HQ is the estimated exposure divided by the chronic
reference level, which is either the U.S. EPA Reference Concentration
(RfC), defined as ``an estimate (with uncertainty spanning perhaps an
order of magnitude) of a continuous inhalation exposure to the human
population (including sensitive subgroups) that is likely to be without
an appreciable risk of deleterious effects during a lifetime,'' or in
cases where an RfC is not available, we use the CalEPA Chronic
Reference Exposure Level (REL), which is defined as ``the concentration
level at or below which no adverse health effects are anticipated for a
specified exposure duration,'' or the ATSDR Chronic Minimum Risk Level
(MRL), which is defined as ``an estimate of daily human exposure to a
substance that is likely to be without an appreciable risk of adverse
effects (other than cancer) over a specified duration of exposure.'' In
cases where new, scientifically credible dose-response values have been
developed in a manner consistent with EPA guidelines and have undergone
a peer review process similar to that used by EPA, we may use such
dose-response values in place of or in addition to other values.
    Screening estimates of acute exposures and risks were also
evaluated for each HAP at any location off-site of each facility (i.e.,
not just the census block centroids) assuming the combination of a peak
(hourly) emission rate and hourly dispersion conditions for the 1991
calendar year that would tend to maximize exposure. In each case, acute
HQ values were calculated using best available short-term health
threshold values. These acute threshold values include REL, Acute
Exposure Guideline Levels (AEGL), and Emergency Response Planning
Guidelines (ERPG) for 1-hour exposure durations. Also, for those
pollutants where no other threshold values (REL, AGEL, or ERPG) were
available, we used ATSDR MRL values for 24-hour and greater exposure
durations.
    As described in the California Environmental Protection Agency's
``Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The
Determination of Acute Reference Exposure Levels for Airborne
Toxicants,'' an acute REL (http://www.oehha.ca.gov/air/pdf/
acuterel.pdf) is defined as ``the concentration level at or below which
no adverse health effects are anticipated for a specified exposure
duration is termed the reference exposure level (REL). RELs are based
on the most sensitive, relevant, adverse health effect reported in the
medical and toxicological literature. RELs are designed to protect the
most sensitive individuals in the population by the inclusion of
margins of safety. Since margins of safety are incorporated to address
data gaps and uncertainties, exceeding the REL does not automatically
indicate an adverse health impact.''
    Acute Exposure Guideline Levels, or AEGLs, were derived in response
to recommendations from the National Research Council. As described in
``Standing Operating Procedures (SOP) of the National Advisory
Committee on Acute Exposure Guideline Levels for Hazardous Substances''
(http://www.epa.gov/opptintr/aegl/pubs/sop.pdf), \6\ ``the NRC's
previous name for acute exposure levels--community emergency exposure
levels (CEELs)--was replaced by the term AEGLs to reflect the broad
application of these values to planning, response, and prevention in
the community, the workplace, transportation, the military, and the
remediation of Superfund

sites.'' This document also states (page 2) that AEGLs ``represent
threshold exposure limits for the general public and are applicable to
emergency exposures ranging from 10 min to 8 h.'' The document lays out
the purpose and objectives of AEGLs by stating (page 21) that ``the
primary purpose of the AEGL program and the NAC/AEGL Committee is to
develop guideline levels for once-in-a-lifetime, short-term exposures
to airborne concentrations of acutely toxic, high-priority chemicals.''
In detailing the intended application of AEGL values, the document
states (page 31) that ``It is anticipated that the AEGL values will be
used for regulatory and nonregulatory purposes by U.S. Federal and
State agencies, and possibly the international community in conjunction
with chemical emergency response, planning, and prevention programs.
More specifically, the AEGL values will be used for conducting various
risk assessments to aid in the development of emergency preparedness
and prevention plans, as well as real-time emergency response actions,
for accidental chemical releases at fixed facilities and from transport
carriers.''
---------------------------------------------------------------------------

    \6\ National Academies of Science, 2001. Standing Operating
Procedures for Developing Acute Exposure Levels for Hazardous
Chemicals, page 2.
---------------------------------------------------------------------------

    The AEGL-1 value is then specifically defined as ``the airborne
concentration of a substance above which it is predicted that the
general population, including susceptible individuals, could experience
notable discomfort, irritation, or certain asymptomatic nonsensory
effects. However, the effects are not disabling and are transient and
reversible upon cessation of exposure.'' The document also notes (page
3) that, ``Airborne concentrations below AEGL-1 represent exposure
levels that can produce mild and progressively increasing but transient
and nondisabling odor, taste, and sensory irritation or certain
asymptomatic, nonsensory effects.'' Similarly, the document defines
AEGL-2 values as ``the airborne concentration (expressed as ppm or mg/
m3) of a substance above which it is predicted that the general
population, including susceptible individuals, could experience
irreversible or other serious, long-lasting adverse health effects or
an impaired ability to escape.''
    ERPG are derived for use in emergency response, as described in the
American Industrial Hygiene Association's document entitled,
``Emergency Response Planning Guidelines (ERPG) Procedures and
Responsibilities'' (http://www.aiha.org/1documents/committees/ERP-
SOPs2006.pdf), which states that, ``Emergency Response Planning
Guidelines (ERPGs) were developed for emergency planning and are
intended as health based guideline concentrations for single exposures
to chemicals.'' \7\ The ERPG-1 value is defined as ``the maximum
airborne concentration below which it is believed that nearly all
individuals could be exposed for up to 1 hour without experiencing
other than mild transient adverse health effects or without perceiving
a clearly defined, objectionable odor.'' Similarly, the ERPG-2 is
defined as ``the maximum airborne concentration below which it is
believed that nearly all individuals could be exposed for up to one
hour without experiencing or developing irreversible or other serious
health effects or symptoms which could impair an individual's ability
to take protective action,''.
---------------------------------------------------------------------------

    \7\ ERP Committee Procedures and Responsibilities, 1 November
2006. American Industrial Hygiene Association.
---------------------------------------------------------------------------

    As can be seen from the definitions above, the AEGL and ERPG values
include the similarly defined severity levels 1 and 2. For many
chemicals, the available information does not allow development of a
severity level 1 value AEGL or ERPG; in these instances, higher
severity level AEGL-2 or ERPG-2 values are compared to our modeled
exposure levels to screen for potential acute concerns.
    Acute REL values for a 1-hour exposure duration are typically lower
than their corresponding AEGL-1 and ERPG-1 values. Even though their
definitions are slightly different, AEGL-1 values are often the same as
the corresponding ERPG-1 values, and AEGL-2 values are often equal to
ERPG-2 values. Maximum HQ values from our acute screening risk
assessments typically result when basing them on the acute REL for a
particular pollutant. In cases where our maximum acute HQ value exceeds
1, we also report the HQ value based on the next highest acute
threshold (usually the AEGL-1 and/or the ERPG-1).
    In cases where no acute REL, AEGL or ERPG value is available for
the pollutant being assessed, we have calculated HQ values based on the
Agency for Toxic Substances and Disease Registry's Minimal Risk Levels
(MRL) to determine whether we can clearly assert that there is no
potential for acute impact of concern. The MRL (http://
www.atsdr.cdc.gov/mrls/) is defined as ``an estimate of the daily human
exposure to a hazardous substance that is likely to be without
appreciable risk of adverse noncancer health effects over a specified
duration of exposure.'' Since acute exposure is defined by ATSDR in the
context of MRL as ``exposure that occurs for a short time (1 to 14
days),'' and since we are most interested in trying to assess the
potential impact of shorter-duration high-emission events, we only use
these HQ based on MRL values in the context of a screening check,
wherein we adjust our maximum 1-hour exposures to estimate potential
maximum 24-hour exposures using a meteorological adjustment factor of
0.4.\8\ Because these MRL values are based on longer exposure durations
than our peak 1-hour exposure estimates, they are generally more
stringent than 1-hour thresholds, and therefore provided a very
conservative screen. Thus, HQ values based on MRL which do not exceed 1
provide a strong indication that acute impacts are not of potential
concern. HQ values based on the MRL which exceed 1, however, do not
automatically indicate an adverse health impact and may require further
analysis.
---------------------------------------------------------------------------

    \8\ See ``Screening Procedures for Estimating the Air Quality
Impact of Stationary Sources'' (Revised); EPA-454/R-92-019; Chapter
4; page 15.
---------------------------------------------------------------------------

    To develop screening estimates of acute exposures, we developed
estimates of maximum hourly emission rates by multiplying the average
annual hourly emission rates by a factor of 10. The factor of 10 is
intended to cover routinely variable emissions and startup, shutdown,
and malfunction emissions. We chose to use a factor of 10 based on: (1)
Engineering judgment, and (2) an analysis of short-term emissions data
that compared hourly and annual emissions data for volatile organic
compounds (VOC) for all facilities in a heavily-industrialized 4-county
area (Harris, Galveston, Chambers, and Brazoria Counties, TX) over an
11-month time period in 2001.\9\ The analysis is provided in Appendix 4
of the Draft Residual Risk Assessment for 9 Source Categories and is
available in the docket for this rule. In this study, most peak
emission events were less than twice the annual average hourly emission
rate and the highest peak emission event was 8.5 times the annual
average hourly emission rate. We request comment on the interpretation
of these data and the appropriateness of using a factor of 10 times the
average annual hourly emission rate in these acute exposure screening
assessments.
---------------------------------------------------------------------------

    \9\ See http://www.tceq.state.tx.us/compliance/field_ops/eer/
index.html or docket to access the source of these data.
---------------------------------------------------------------------------

    In cases where all acute HQ values from the screening step were
less than or equal to 1, acute impacts were deemed negligible and no
further analysis was performed. In the cases where an acute HQ from the
screening step was greater than 1, additional site-specific data were
considered to develop a more refined estimate of the

potential for acute impacts of concern. The data refinements considered
included using a better representation of the peak-to-mean hourly
emissions ratio (instead of using the default factor of 10) and using
the site-specific facility layout to distinguish facility property from
an area where the public could be exposed. Ideally we would prefer to
have continuous measurements over time to see how the emissions vary by
each hour over an entire year. Having a frequency distribution of
hourly emission rates over a year would allow us to perform a
probabilistic analysis to estimate potential threshold exceedances and
their frequency of occurrence. We recognize that having this level of
data is rare, hence our use of the factor of 10 multiplier approach.
Such an evaluation could include a more complete statistical treatment
of the key parameters and elements adopted in this screening analysis.
    In the final step of the acute impacts screening, HQ values
exceeding 1 based on REL, AEGL, ERPG, or MRL values are interpreted on
a case-by-case basis, considering the implications of the appropriate
definitions and the related supporting documentation for that specific
value, as well as the context of the HQ based on the next highest acute
threshold value, where one is available.
3. Multipathway Human Health Risks and Environmental Effects Assessment
    The potential for significant human health risks due to exposures
via routes other than inhalation (i.e., multipathway exposures) and the
potential for adverse environmental impacts were evaluated in a two-
step screening process. In the first step, each source category was
screened by determining whether any sources emitted any of the 14 HAP
known to be persistent and bioaccumulative in the environment (also
known as PB-HAP)\10\, as identified in EPA's Air Toxics Risk Assessment
Library (available at http://www.epa.gov/ttn/fera/risk_atra_
vol1.html). As a result of this screening, we determined that four of
the RTR Group 2A source categories--Marine Vessel Loading Operations,
Mineral Wool Production, Pharmaceuticals Production, and the Printing
and Publishing Industry--were responsible for air emissions of four PB-
HAP--cadmium compounds, mercury compounds, lead compounds, and
polycyclic organic matter (POM).
---------------------------------------------------------------------------

    \10\ Persistent and bioaccumulative (PB) HAP are HAP that have
the ability to persist in the environment for long periods of time
and may also have the ability to build up in the food chain to
levels that are harmful to human health and the environment.
---------------------------------------------------------------------------

    In the second step of the screening process, we determined if the
facility-specific emission rates of each of the specific PB-HAP were
large enough to create the potential for significant non-inhalation
risks. To facilitate this step, we developed emission rate thresholds
for each PB-HAP using a hypothetical screening exposure scenario
developed for use in conjunction with the TRIM.FaTE model. The
hypothetical screening scenario was subjected to a sensitivity analysis
to ensure that its key design parameters were established such that
environmental media concentrations were not underestimated (i.e., to
minimize the occurrence of false positives, or results that suggest
that risks might be acceptable when, in fact, actual risks are high),
and to also minimize the occurrence of false positives for human health
endpoints. We call this application of the TRIM.FaTE model TRIM-Screen.
The facility-specific emission rates of each PB-HAP in each source
category were compared to the emission threshold values for each of the
four PB-HAP identified in the source category datasets. None of the
emission rates for the facilities source categories addressed in this
action exceeded the emission threshold values; therefore, none of the
facilities show the potential for causing any significant multipathway
exposures and risks. Had this not been the case, the source categories
would have been further evaluated for potential non-inhalation risks
and adverse environmental impacts through site-specific refined
assessments using EPA's TRIM.FaTE model. For further information on the
multipathway screening see the ``Residual Risk Assessment for 9 Source
Categories'' document (see Docket EPA-HQ-OAR-2008-0008).
4. Risk Characterization
    The final product of the risk assessment is the risk
characterization, in which the information from the previous steps is
integrated and an overall conclusion about risk is derived. Estimates
of health risk are considered in the context of uncertainties and
limitations in the data and methodology. In general, we have attempted
to reduce both uncertainty and bias to the greatest degree possible in
these assessments. A brief discussion of the major uncertainties
associated with the derivation of risk estimates is provided below. The
first section discusses the consideration of ``MACT allowable''
emissions in risk characterization, followed by a discussion of
uncertainties in risk assessments. Following these sections, we have
provided summaries of risk metrics for each source category (including
MIR and noncancer hazards, as well as cancer incidence estimates).
    We note here that several of the carcinogens emitted by these
source categories (i.e., benzo[a]pyrene, dibenz[a,h]anthracene, and
vinyl chloride) have a mutagenic mode of action\11\, EPA's
``Supplemental Guidance for Assessing Susceptibility from Early-Life
Exposure to Carcinogens'' \12\ was applied to the risk estimates for
these four compounds. This guidance has the effect of adjusting the URE
by factors of 10 (for children aged 0-1), 3 (for children aged 2-15),
or 1.6 (for 70 years of exposure beginning at birth), as needed in risk
assessments. In this case, this has the effect of increasing the
estimated lifetime risks for these pollutants by a factor of 1.6. In
addition, although only a small fraction of the total POM emissions
were reported as individual compounds, EPA expresses carcinogenic
potency for compounds in this group in terms of benzo[a]pyrene
equivalence, based on evidence that carcinogenic POM have the same
mutagenic mechanism of action as does benzo[a]pyrene. For this reason
EPA implementation policy \13\ recommends applying the Supplemental
Guidance to all carcinogenic PAHs for which risk estimates are based on
relative potency. Accordingly, we have applied the Supplemental
Guidance to all unspeciated POM mixtures.
---------------------------------------------------------------------------

    \11\ U.S. EPA, 2006. Performing risk assessments that include
carcinogens described in the Supplemental Guidance as having a
mutagenic mode of action. Science Policy Council Cancer Guidelines
Implementation Workgroup Communication II: Memo from W.H. Farland
dated 14 June 2006. http://epa.gov/osa/spc/pdfs/CGIWGCommunication_
II.pdf.
    \12\ U.S. EPA, 2005. Supplemental Guidance for Assessing Early-
Life Exposure to Carcinogens. EPA/630/R-03/003F. http://www.epa.gov/
ttn/atw/childrens_supplement_final.pdf.
    \13\ U.S. EPA, 2005. Science Policy Council Cancer Guidelines
Implementation Workgroup Communication I: Memo from W.H. Farland
dated 4 October 2005 to Science Policy Council. http://www.epa.gov/
osa/spc/pdfs/canguid1.pdf.
---------------------------------------------------------------------------

    Finally, we screened chronic ambient concentration levels of all
individual HAP against their chronic noncancer human health thresholds
in an effort to gauge the potential for adverse environmental impacts,
under the assumption that chronic human toxicity values are generally
protective of direct inhalation impacts on animals and direct contact
impacts on plants. We believe that this assumption is reasonable in
most cases, but acknowledge that it is an uncertainty. Although not
verified for many HAP

because of lacking environmental testing data, this assumption has been
shown to be valid for some organic compounds \14\ where such test data
are available.
a. Consideration of Actual and MACT Allowable Emissions
---------------------------------------------------------------------------

    \14\ ``Evaluation of Wildlife Inhalation Exposure Pathway from
Wood Products Plant Emissions.'' Memorandum to Tim Hunt/AF&PA from
David F. Mitchell and Julie A.F. Kabel, February 25, 2002. This
memorandum is in the docket.
---------------------------------------------------------------------------

    We discussed the use of both MACT allowable and actual emissions in
the final Coke Oven Batteries residual risk rule (70 FR 19998-19999,
April 15, 2005) and in the proposed and final Hazardous Organic NESHAP
(HON) residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609,
December 21, 2006, respectively). In those previous actions, we noted
that assessing the MACT allowable levels of emissions (i.e., the
highest emission levels that could be emitted while maintaining the
same activity level and still complying with the NESHAP requirements)
is inherently reasonable since they reflect the maximum level sources
could emit and still comply with national emission standards. But we
also explained that it is reasonable to consider actual emissions,
where such data are available, in both steps of the risk analysis, in
accordance with the Benzene NESHAP. (54 FR 38044, September 14, 1989).
It is reasonable to consider actual emissions because sources typically
seek to perform better then required by emission standards to provide
an operational cushion to accommodate the variability in manufacturing
processes and control device performance. Failure to consider actual
emissions data in developing risk estimates would unrealistically
inflate estimated risk levels.
    We performed our risk assessments based on estimates of actual
emission levels as developed through the process described earlier in
the preamble. For the nine source categories addressed in this action,
we do not have detailed information regarding MACT allowable emission
levels. However, we estimated the potential differences in MACT
allowable and actual emission levels for each source category and where
MACT allowable emission levels were greater than actual emission
levels, we scaled the risk results by the ratio of MACT allowable to
actual emission levels. In many cases, the requirements of the
regulation result in actual emission levels being a reasonable
approximation of or the same as MACT allowable emission levels. In
section I.E. of this preamble, the potential risk based on
consideration of MACT allowable emission levels is discussed for each
source.
b. Uncertainties in Risk Assessments
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for the nine source categories
affected by this proposal. We reduced some of these uncertainties by
soliciting input from industry and the public to develop the best
emissions data sets possible. Although uncertainty exists, we believe
the risk assessments performed for the nine source categories most
likely overestimate the potential for risks due to the health-
protective assessment approach. A brief discussion of the uncertainties
in the emissions data set, dispersion modeling, inhalation exposure
estimates, and dose-response relationships is presented in this section
of the preamble. A more thorough discussion of these uncertainties is
included in both the ``Residual Risk Assessment for 9 Source
Categories'' (April 2008) and the ``Risk and Technology Review (RTR)
Assessment Plan'' (November 2006), both of which are available in the
docket.
    Uncertainties in the Emissions Data Sets. Although the development
of the RTR data sets involved quality assurance/quality control
processes, the accuracy of emissions values will vary depending on the
source of the data present, incomplete or missing data, errors in
estimating emissions values, and other factors. The emission values
considered in this analysis are annual totals that do not reflect
short-term fluctuations during the course of a year or variations from
year to year. These annual emissions estimates generally do not include
operations such as startup/shutdown and malfunctions; \15\ however,
such emissions are not known to contribute significantly to total
annual emissions. In contrast, the estimates of peak hourly emission
rates for the acute effects screening assessment were based on the
generally health-protective default assumption of 10 times the annual
average hourly rate which is intended to account for emission
fluctuations due to normal facility operations as well as emissions
from startup, shutdown and malfunctions events. More refined estimates
were used for source categories where the screening estimates did not
``screen out'' all sources and more specific information was available.
---------------------------------------------------------------------------

    \15\ The mass balance used to determine emissions from the
publication rotogravure subcategory of the Printing and Publishing
source category includes emissions from startup, shutdown, and
malfunction events.
---------------------------------------------------------------------------

    Facilities in seven of the source categories (Epichlorohydrin
Elastomers Production, Hypalon\TM\ Production, Marine Tank Vessel
Loading, Pharmaceuticals Production, Polybutadiene Rubber Production,
Printing and Publishing, and Styrene Butadiene Rubber and Latex
Production) emit chlorinated compounds and use incineration devices,
creating the possibility for the formation of polychlorinated dioxins.
However, we have no test reports or measurements, conducted by
manufacturers or anyone else, indicating the presence of dioxins in the
emissions from any of these source categories, and EPA's dioxin
inventory does not specifically link dioxins emissions to any of these
source categories. Furthermore, in our judgment, it is improbable that
dioxins are emitted in measurable amounts from these seven source
categories given the low quantity of particulate matter present.
Therefore, we did not consider dioxins in our assessment of these
source categories.
    Overall we believe that the emissions data considered in this
assessment are accurate representations of the actual emissions for
facilities in the nine source categories for the stated purpose.
Nevertheless, we request comment on our emissions data set in general
(including information on individual sources), and specifically on our
approach for estimating: short-term emissions used in assessing acute
risk; emissions and associated risk from start-ups, shutdowns, and
malfunctions (SSM); and on the potential for dioxins emissions from the
source categories affected by this proposal. We also request comment on
evaluating potential emissions mitigation (emission limits, work
practice standards, and best management practices) for SSM events and
the associated reduction in emissions and risks and the associated
costs.
    Uncertainties in Dispersion Modeling. While the analysis employed
EPA's suggested regulatory dispersion model, AERMOD, there is
uncertainty in ambient concentration estimates associated with EPA's
choice and application of the model. Where possible, model options
(e.g., rural/urban, plume depletion, chemistry) were selected to
provide an overestimate of ambient air concentrations. However, because
of practicality and data limitation reasons, some factors (e.g.,
meteorology, building downwash) have the potential in some situations
to overestimate or

underestimate ambient impacts. For example, meteorological data were
taken from a single year (1991), and facility locations can be a
significant distance from the site where these data were taken. Despite
these uncertainties, we believe that at off-site locations and census
block centroids, the approach considered in the dispersion modeling
analysis should generally yield overestimates of ambient
concentrations.
    Uncertainties in Inhalation Exposure. The effects of human mobility
on exposures were not included in the assessment. Specifically, short-
term mobility and long-term mobility \16\ between census blocks in the
modeling domain were not considered. As a result, this simplification
will likely bias the assessment toward overestimating the highest
exposures. In addition, the assessment predicted the chronic exposures
at the centroid of each populated census block as surrogates for the
exposure concentrations for all people living in that block. (On
average census blocks are populated by approximately 40 people.) Using
the census block centroid to predict chronic exposures tends to
overpredict exposures for people in the census block who live further
from the facility and underpredict exposures for people in the census
block who live closer to the facility. Thus, using the census block
centroid to predict chronic exposures may lead to a potential
understatement or overstatement of the true maximum impact, but is an
unbiased estimate of average risk and incidence.
---------------------------------------------------------------------------

    \16\ Short-term mobility is movement from one microenvironment
to another over the course of hours or days. Long-term mobility is
movement from one residence to another over the course of a
lifetime.
---------------------------------------------------------------------------

    The assessments evaluate the cancer inhalation risks associated
with pollutant exposures over a 70-year period, the assumed lifetime of
individuals. In reality, both the length of time that modeled emissions
sources at facilities actually operate (i.e., more or less than 70
years), and the domestic growth or decline of the modeled industry
(i.e., the increase or decrease in the number or size of United States
facilities), will influence the risks posed by a given source category.
Depending on the characteristics of the industry, these factors will
likely result in an overestimate (or possibly an underestimate in the
extreme case where a facility maintains or increases its emission
levels beyond 70 years and residents live beyond 70 years at the same
location) both in individual risk levels and in the total estimated
number of cancer cases. Annual cancer incidence estimates from
exposures to emissions from these sources would not be affected by
uncertainty in the length of time emissions sources operate.
    The exposure estimates used in these analyses assume chronic
exposures to ambient levels of pollutants. Because most people spend
the majority of their time indoors, actual exposures may not be the
same, depending on characteristics of the pollutants modeled. For many
HAP, indoor levels are roughly equivalent to ambient levels, but for
very reactive pollutants or larger particles, these levels are
typically lower. This factor has the potential to result in an
overstatement of 25 to 30 percent of exposures.\17\
---------------------------------------------------------------------------

    \17\ National-Scale Air Toxics Assessment for 1996. (EPA 453/R-
01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    In addition to the uncertainties highlighted above, there are
several factors specific to the acute exposure assessment that need to
be highlighted. The accuracy of an acute inhalation exposure assessment
depends on the simultaneous occurrence of independent factors that may
vary greatly, such as hourly emissions rates, meteorology, and human
activity patterns. In this assessment, we assume that individuals
remain for 1 hour at the point of maximum ambient concentration as
determined by the co-occurrence of peak emissions and worst-case
meteorological conditions. These assumptions would tend to overestimate
actual exposures since it is unlikely that a person would be located at
the point of maximum exposure during the time of worst-case impact.
    Uncertainties in Dose-Response Relationships. There are
uncertainties inherent in the development of the reference values used
in our risk assessments for cancer effects from chronic exposures and
noncancer effects from both chronic and acute exposures. Some
uncertainties may be considered quantitatively, and others generally
are expressed in qualitative terms. We note as a preface to this
discussion a point which pertains to this whole discussion on dose-
response uncertainty and which is brought out in EPA's 2005 Cancer
Guidelines; namely, that ``the primary goal of EPA actions is
protection of human health; accordingly, as an Agency policy, risk
assessment procedures, including default options that are used in the
absence of scientific data to the contrary, should be health
protective.'' (EPA 2005 Cancer Guidelines, pages 1-7) This is the
approach followed here as summarized in the next several paragraphs. A
complete detailed discussion of uncertainties and variabilities in dose
response relationships is given in the risk assessment document.
    Cancer URE values used in our risk assessments are those that have
been developed to generally provide an upper bound estimate of risk.
That is, they represent a ``plausible upper limit to the true value of
a quantity'' (although this is usually not a true statistical
confidence limit).\18\ In some circumstances, the true risk could be as
low as zero; however, in other circumstances the risk could also be
greater.\19\ When developing an upper bound estimate of risk and to
provide risk values that do not underestimate risk, health-protective
default approaches are generally used. EPA typically uses the upper
bound estimates rather than lower bound or central tendency estimates
in our risk assessments, an approach that can have limitations for
other uses (e.g., priority-setting or expected benefits analysis).
---------------------------------------------------------------------------

    \18\ IRIS glossary (http://www.epa.gov/NCEA/iris/help_
gloss.htm).
    \19\ An exception to this is the URE for benzene, which is
considered to cover a range of values, each end of which is
considered to be equally plausible, and which is based on maximum
likelihood estimates.
---------------------------------------------------------------------------

    Chronic noncancer reference (RfC and RfD) values represent chronic
exposure levels that are intended to be health-protective levels.
Specifically, these values provide an estimate (with uncertainty
spanning perhaps an order of magnitude) of daily oral exposure (RfD) or
of a continuous inhalation exposure (RfC) to the human population
(including sensitive subgroups) that is likely to be without an
appreciable risk of deleterious effects during a lifetime. To derive
values that are intended to be ``without appreciable risk,'' the
methodology relies upon an uncertainty factor (UF) approach (U.S. EPA,
1993, 1994) which includes consideration of both uncertainty and
variability. When there are gaps in the available information, UF are
applied to derive reference values that are intended to be protective
against appreciable risk of deleterious effects. Uncertainty factors
are commonly default values,\20\ e.g.,

factors of 10 or 3, used in the absence of compound-specific data;
where data are available, uncertainty factors may also be developed
using compound-specific information. When data are limited, more
assumptions are needed and more uncertainty factors are used. Thus
there may be a greater tendency to overestimate risk-in the sense that
further study might support development of reference values that are
higher (i.e., less potent) because fewer default assumptions are
needed. However, for some pollutants it is possible that risks may be
underestimated.
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    \20\ According to the NRC report Science and Judgment in Risk
Assessment (NRC, 1994) ``[Default] options are generic approaches,
based on general scientific knowledge and policy judgment, that are
applied to various elements of the risk-assessment process when the
correct scientific model is unknown or uncertain.'' The 1983 NRC
report Risk Assessment in the Federal Government: Managing the
Process defined default option as ``the option chosen on the basis
of risk assessment policy that appears to be the best choice in the
absence of data to the contrary'' (NRC, 1983a, p. 63). Therefore,
default options are not rules that bind the agency; rather, the
agency may depart from them in evaluating the risks posed by a
specific substance when it believes this to be appropriate. In
keeping with EPA's goal of protecting public health and the
environment, default assumptions are used to ensure that risk to
chemicals is not underestimated (although defaults are not intended
to overtly overestimate risk). See EPA 2004 An examination of EPA
Risk Assessment Principles and Practices, EPA/100/B-04/001 available
at: http://www.epa.gov/osa/pdfs/ratf-final.pdf.
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    While collectively termed ``UF'', these factors account for a
number of different quantitative considerations when utilizing observed
animal (usually rodent) or human toxicity data in the development of
the reference concentration. The UF are intended to account for: (1)
Variation in susceptibility among the members of the human population
(i.e., inter-individual variability); (2) uncertainty in extrapolating
from experimental animal data to humans (i.e., interspecies
differences); (3) uncertainty in extrapolating from data obtained in a
study with less-than-lifetime exposure (i.e., extrapolating from
subchronic to chronic exposure); (4) uncertainty in extrapolating the
observed data to obtain an estimate of the exposure associated with no
adverse effects; and (5) uncertainty when the database is incomplete or
there are problems with the applicability of available studies.
    Many of the UF used to account for variability and uncertainty in
the development of acute reference values are quite similar to those
developed for chronic durations, but more often using individual UF
values that may be less than 10. UF are applied based on chemical-
specific or health effect-specific information (e.g., simple irritation
effects do not vary appreciably between human individuals, hence a
value of 3 is typically used), or based on the purpose for the
reference value (see the following paragraph). The UF applied in acute
reference value derivation include: (1) Heterogeneity among humans; (2)
uncertainty in extrapolating from animals to humans; (3) uncertainty in
LOAEL to NOAEL adjustments; and (4) uncertainty in accounting for an
incomplete database on toxic effects of potential concern. Additional
adjustments are often applied to account for uncertainty in
extrapolation from observations at one exposure duration (e.g., 4
hours) to derive an acute reference value at another exposure duration
(e.g., 1 hour).
    Not all acute reference values are developed for the same purpose
and care must be taken when interpreting the results of an acute
assessment of human health effects relative to the reference value or
values being exceeded. Where relevant to the estimated exposures, the
lack of threshold values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
Further, when we compare our peak 1-hour exposures against MRL values
(which are derived for 1- to 14-day exposure durations), we note that
peak emission events are unlikely to last more than an hour. As such,
these comparisons are a very conservative screen which is only useful
in ruling out potential exposures of concern, limiting our ability to
interpret situations where MRL values are exceeded.
    Although every effort is made to identify peer-reviewed reference
values for cancer and noncancer effects for all pollutants emitted by
the sources included in this assessment, some pollutants have no peer-
reviewed reference values for cancer or chronic non-cancer or acute
effects. Since exposures to these pollutants cannot be included in a
quantitative risk estimate, an understatement of risk for these
pollutants at environmental exposure levels is possible.
    Additionally, chronic reference values for 26 of the compounds
included in this assessment are currently under EPA IRIS review and
revised assessments may determine that these pollutants are more or
less potent than the current value. We will re-evaluate residual risks
if, as a result of these reviews, a dose-response metric changes enough
to indicate that the risk assessment supporting today's notice may
significantly understate human health risk.
    Uncertainties in the Multipathway and Environmental Effects
Assessment. We generally believe that when exposure levels are not
anticipated to adversely affect human health, they also are not
anticipated to adversely affect the environment. While there are
special considerations for certain HAP, we generally rely on the levels
of PB-HAP emissions to determine whether a full assessment of the
multipathway and environmental effects is necessary. Because emissions
of these chemicals may not be well characterized due to lack of testing
requirements specific to these chemicals (e.g., these compounds may be
aggregated into testing requirements for particulate matter), risks may
be understated.

E. What are the results of the risk assessment?

    The human health risks estimated for the nine source categories are
summarized in this section of the preamble. Details of the assessment
are located in the docket (Docket EPA-HQ-OAR-2008-0008), especially see
``Residual Risk Assessment for 9 Source Categories.'' We believe that
our assessment covers all potential health risks associated with HAP
emissions from the nine source categories affected by this proposal.
    For each of the nine source categories, the cancer MIR from one or
more exposure routes was greater than 1-in-1 million and/or the maximum
HQ for acute exposure was greater than 1. Table 4 provides an overall
summary of the inhalation risk assessment results, and the sections
below provide more detailed discussions about the risk assessment
results for each of the nine source categories.

                  Table 4--Summary of Estimated Inhalation Risks for the Nine Source Categories
----------------------------------------------------------------------------------------------------------------
                                               Maximum
                                              individual   Population                 Maximum
                                Number of    cancer risk   at risk >=     Annual      chronic      Maximum off-
       Source category        facilities\1\     (in a       1-in-a-       cancer     noncancer      site acute
                                               million)     million     incidence    TOSHI \3\   noncancer HQ\4\
                                                 \2\       (1,000's)
----------------------------------------------------------------------------------------------------------------
Epichlorohydrin Elastomers               1            30            4       0.0004          0.2  HQREL = 0.1
 Production.                                                                                epichlorohydri
                                                                                n
HypalonTM Production........             1             1          0.4       0.0004          0.1  HQREL = 0.7
                                                                                chlorine

Nitrile Butadiene Rubber                 4            60           47        0.004          0.9  HQREL = 0.3
 Production.                                                                                styrene
Polybutadiene Rubber                     5            10           16        0.002          0.2  HQREL = 0.3
 Production.                                                                                toluene
Styrene Butadiene Rubber and             9             7           26        0.004          0.1  HQREL = 0.3
 Latex Production.                                                                                styrene
Marine Vessel Loading                 <800             1          2.4         0.01        0.006  HQAEGL	2 = 0.9
 Operations.                                                                                chloroform
Mineral Wool Production.....             8            30          110        0.008          0.4  HQREL = 8
                                                                                HQAEGL	1 = 0.7
                                                                                formaldehyde
                                                                                HQREL = 4
                                                                                arsenic
Pharmaceuticals Production..            27            10          4.9        0.001          0.2  HQREL = 2
                                                                                chloroform
                                                                                HQAEGL	1 = 0.5
                                                                                acetonitrile
Printing and Publishing                179          0.05            0     0.000009         0.08  HQREL = 10
 Industry.                                                                                HQAEGL	1 = 0.5
                                                                                toluene
----------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum target organ specific hazard index (TOSHI). Target organ system represented by the TOSHI varies
  across source categories. Maximum TOSHI is respiratory for the printing and publishing industry, mineral wood
  production, epichlorohydrin elastomers production, and Hypalon[supreg] production. Maximum TOSHI for marine
  vessel loading operations is based on immunological effects. Maximum TOSHI for nitrile butadiene rubber
  production, polybutadiene rubber production, and styrene butadiene rubber and latex production is based on
  reproductive effects. Maximum TOSHI for pharmaceutical production is based on neurological effects.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to
  develop an array of hazard quotient (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 the Mineral Wool Production Category, there were potential exceedances of the
  REL for arsenic (maximum HQ = 4, as noted in the table), but there is no corresponding AEGL-1 value to
  facilitate further interpretation of these exceedances. See Section 2 of this preamble for explanation of
  acute threshold values.

    As shown in Table 4, we estimate, based on actual emissions, that
the MIR remaining from HAP emissions from these nine source categories
affected by this proposal range from 0.05-in-1 million to 60-in-1
million. Cancer incidence ranged from 0.000009 excess cancer cases per
year (or nine cases every 1,000,000 years) to 0.01 excess cancer cases
per year (or one excess cancer case every 100 years). No chronic
noncancer inhalation human health thresholds were exceeded at off-site
receptors for any of the nine source categories. The maximum acute HQ
using the REL ranged from 0.1 to 10 and were all less than 1 (ranging
from 0.3 to 0.9) for the AEGL or ERPG where available. We extrapolated
risks based on MACT allowable emissions in ``Estimation of MACT
Allowable Emission Levels and Associated Risks and Impacts for the RTR
Group 2A Source Categories'' in Docket No. EPA-HQ-OAR-2008-0008).
    For several source categories, no PB-HAP emissions were reported,
while very low levels were reported for other source categories. Our
analyses, based on these low levels of emissions, indicate these source
categories do not pose potential for human health multipathway risks or
adverse environmental impacts.
1. Epichlorohydrin Elastomers Production
    Lifetime maximum individual cancer risks associated with emissions
modeled from the only one epichlorohydrin elastomer production facility
are estimated to be less than 100-in-1 million. The highest maximum
lifetime individual cancer risk was estimated at 30-in-1 million. The
total estimated cancer incidence from this facility is 0.0004 excess
cancer cases per year. We estimate that 4,000 people exposed to HAP
from this source category may experience an increased individual
lifetime cancer risk of greater than or equal to 1-in-1 million.
    We found no significant risk of adverse noncancer health effects
associated with the modeled acute or chronic inhalation exposures from
the Epichlorohydrin Elastomers Production source category. The maximum
chronic noncancer TOSHI value associated with emissions from this
epichlorohydrin elastomer production facility is 0.2, and the maximum
acute screening HQ value was 0.1. There were no reported PB-HAP
emissions for this source category. Our analysis, based on the absence
of PB-HAP, indicates this source category does not pose potential for
human health multipathway risks or adverse environmental impacts.
    These risks are based on reported actual emission levels. Our
analysis of potential differences between actual emission levels and
emissions allowable under the NESHAP indicated that actual and MACT
allowable emission levels are approximately equal. Therefore, we expect
no appreciable differences in risks with consideration of MACT
allowable emission levels.
2. HypalonTM Production
    Lifetime maximum individual cancer risks associated with emissions
modeled from the HypalonTM production facility are estimated
to be less than 100-in-1 million. The highest maximum lifetime
individual cancer risk was estimated at 1-in-1 million. The total
estimated cancer incidence from this facility is 0.0004 excess cancer
cases per year. We estimate that 400 people exposed to HAP from this
source category may experience an increased individual lifetime cancer
risk of greater than or equal to 1-in-1 million. We found no
significant risk of adverse noncancer health effects associated with
the modeled acute or chronic inhalation exposures from the
HypalonTM Production source category. The maximum chronic
noncancer TOSHI value associated with emissions from this
HypalonTM production facility is 0.1, and the maximum acute
screening HQ value was 0.7. There were no reported PB HAP emissions for
this source category. Our analysis, based on the absence of PB HAP,
indicates this

source category does not pose potential for human health multipathway
risks or adverse environmental impacts.
    These risks are based on reported actual emission levels. Our
analysis of potential differences between actual emission levels and
emissions allowable under the NESHAP indicated that actual and MACT
allowable emission levels are approximately equal. Therefore, we expect
no appreciable differences in risks with consideration of MACT
allowable emission levels.
3. Nitrile Butadiene Rubber Production
    All lifetime cancer risks associated with emissions modeled from
the four NBR production facilities are estimated to be less than 100-
in-1 million. The highest maximum lifetime individual cancer risk was
estimated at 60-in-1 million. We estimate that 47,000 people exposed to
HAP from this source category may experience an increased individual
lifetime cancer risk of greater than or equal to 1-in-1 million. The
total estimated cancer incidence from these facilities is 0.004 excess
cancer cases per year. We found no significant risk of adverse
noncancer health effects associated with the modeled acute or chronic
inhalation exposures from the Nitrile Butadiene Rubber Production
source category. The maximum chronic noncancer TOSHI value associated
with emissions from these NBR production facilities is 0.9, and the
maximum acute screening HQ value for styrene is 0.3 (relative to the
acute REL). The maximum HQ for acrylonitrile based on the highest acute
threshold, the AEGL-1, was 0.07, so we do not have any concerns
regarding potential acute impacts. There were no reported PB-HAP
emissions for this source category. Our analysis, based on the absence
of PB-HAP, indicates this source category does not pose potential for
human health multipathway risks or adverse environmental impacts.
    These risks are based on reported actual emission levels. Our
analysis of potential differences between actual emission levels and
emissions allowable under the NESHAP indicated that actual and MACT
allowable emission levels are approximately equal. Therefore, we expect
no appreciable differences in risks with consideration of MACT
allowable emission levels.
4. Polybutadiene Rubber Production
    All lifetime cancer risks associated with emissions modeled from
the five PBR production facilities are estimated to be less than 100-
in-1 million. The highest maximum lifetime individual cancer risk was
estimated at 10-in-1 million. The total estimated cancer incidence from
these facilities is 0.002 excess cancer cases per year. We estimate
that 16,000 people exposed to HAP from this source category may
experience an increased individual lifetime cancer risk of greater than
or equal to 1-in-1 million. We found no significant risk of noncancer
health effects associated with the modeled acute or chronic inhalation
exposures from the Polybutadiene Rubber Production source category. The
maximum chronic noncancer TOSHI value associated with emissions from
these PBR production facilities is 0.2, and the maximum acute screening
HQ value was 0.3. There were no reported PB-HAP emissions for this
source category. Our analysis, based on the absence of PB-HAP,
indicates this source category does not pose potential for human health
multipathway risks or adverse environmental impacts.
    These risks are based on reported actual emission levels. While we
estimate that MACT allowable emissions could be as high as five times
the actual emission levels, we expect no appreciable differences in
risks between actual emission levels and emissions allowable under the
NESHAP because over 99 percent of the HAP comprising the additional
emissions attributable to MACT allowable emission levels have no cancer
potency estimates and because the noncancer risk contribution from
these additional emissions is minimal.
5. Styrene Butadiene Rubber and Latex Production
    All lifetime cancer risks associated with emissions modeled from
the nine styrene butadiene rubber and latex production facilities are
estimated to be less than 100-in-1 million. The highest maximum
lifetime individual cancer risk was estimated at 7-in-1 million. The
total estimated cancer incidence from these facilities is 0.004 excess
cancer cases per year. We estimate that 26,000 people exposed to HAP
from this source category may experience an increased individual
lifetime cancer risk of greater than or equal to 1-in-1 million. We
found no significant risk of adverse noncancer health effects
associated with the modeled acute or chronic inhalation exposures from
the Styrene Butadiene Rubber and Latex Production source category. The
maximum chronic noncancer TOSHI value associated with emissions from
these styrene butadiene rubber and latex production facilities is 0.1,
and the maximum acute screening HQ value was 0.3. There were no
reported PB-HAP emissions for this source category. Our analysis, based