National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins; Pesticide Active Ingredient Production; and Polyether Polyols Production

Federal RegisterJan 9, 2012

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2011-0435; FRL-9507-8]

RIN 2060-AR02

National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins; Pesticide Active Ingredient Production; and Polyether Polyols Production

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The EPA is proposing amendments to three national emission standards for hazardous air pollutants (NESHAP): National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins; NESHAP for Pesticide Active Ingredient Production; and NESHAP for Polyether Polyols Production. For all three of these NESHAP rules, the EPA is proposing decisions concerning the following: residual risk reviews; technology reviews; emissions during periods of startup, shutdown and malfunction; standards for previously unregulated hazardous air pollutant emissions; and electronic reporting of performance test results.

DATES:

Comments.

Comments must be received on or before March 9, 2012. Under the Paperwork Reduction Act, comments on the information collection provisions are best assured of having full effect if the Office of Management and Budget (OMB) receives a copy of your comments on or before February 8, 2012.

Public Hearing.

If anyone contacts the EPA requesting to speak at a public hearing by January 19, 2012, a public hearing will be held on February 8, 2012.

ADDRESSES:

Comments.

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2011-0435, by one of the following methods:

•

www.regulations.gov:

Follow the on-line instructions for submitting comments.

•

Email: a-and-r-docket@epa.gov.

Attention Docket ID No. EPA-HQ-OAR-2011-0435.

•

Fax:

(202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-2011-0435.

•

Mail:

U.S. Postal Service, send comments to: EPA Docket Center, EPA West (Air Docket), Attention Docket ID No. EPA-HQ-OAR-2011-0435, U.S. Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460. Please include a total of two copies. In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th Street NW., Washington, DC 20503.

•

Hand Delivery:

U.S. Environmental Protection Agency, EPA West (Air Docket), Room 3334, 1301 Constitution Ave. NW., Washington, DC 20004. Attention Docket ID No. EPA-HQ-OAR-2011-0435. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.

Instructions.

Direct your comments to Docket ID No. EPA-HQ-OAR-2011-0435. The 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 email. The

http://www.regulations.gov

Web site is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through

http://www.regulations.gov

, your email 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, the 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 the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the 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 the EPA's public docket, visit the EPA Docket Center homepage at

http://www.epa.gov/epahome/dockets.htm.

Docket.

The EPA has established a docket for this rulemaking under Docket ID No. EPA-HQ-OAR-2011-0435. 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, is not placed on the Internet and 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, EPA West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742.

Public Hearing.

If a public hearing is held, it will begin at 10 a.m. on February 8, 2012 and will be held at the 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, Sector Policies and Programs Division (E143-01), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, telephone number: (919) 541-4516. If a public hearing will be held, a notification will be posted on the following Web site:

http://www.epa.gov/ttn/oarpg/t3main.html.

FOR FURTHER INFORMATION CONTACT:

For questions about this proposed action, contact Mr. Nick Parsons, Sector Policies and Programs Division (E143-01), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711; telephone number: (919) 541-5372; fax number: (919) 541-0246; email address:

parsons.nick@epa.gov.

For specific information regarding the risk modeling methodology, contact Ms. Elaine Manning, Health and Environmental Impacts Division (C159-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711; telephone number: (919) 541-5499; fax number: (919) 541-0840; email address:

manning.elaine@epa.gov.

For information about the applicability of these three 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 the EPA Contacts for the Rules Addressed in This Proposed Action

NESHAP

OECA contact

OAQPS contact

NESHAP for Group IV Polymers and Resins

Tavara Culpepper, (202) 564-0902,

culpepper.tavara@epa.gov

Nick Parsons, (919) 541-5372,

parsons.nick@epa.gov.

NESHAP for Pesticide Active Ingredient Production

Tavara Culpepper, (202) 564-0902,

culpepper.tavara@epa.gov

Andrea Siefers, (919) 541-1185,

siefers.andrea@epa.gov.

NESHAP for Polyether Polyols

Tavara Culpepper, (202) 564-0902,

culpepper.tavara@epa.gov

Andrea Siefers, (919) 541-1185,

siefers.andrea@epa.gov.

OECA stands for the EPA's Office of Enforcement and Compliance Assurance.

OAQPS stands for the EPA's Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION:

Preamble Acronyms and Abbreviations

Several acronyms and terms used to describe industrial processes, data inventories and risk modeling are included in this preamble. While this may not be an exhaustive list, to ease the reading of this preamble and for reference purposes, the following terms and acronyms are defined here:

ABS—Acrylonitrile Butadiene Styrene Resin

ADAF—Age-Dependent Adjustment Factors

AERMOD—Air Dispersion Model used by the HEM-3 Model

AEGL—Acute Exposure Guideline Levels

ASA/AMSAN—Acrylonitrile Styrene Resin/Alpha Methyl Styrene Acrylonitrile Resin

BACT—Best Available Control Technology

CalEPA—California Environmental Protection Agency

CAA—Clean Air Act

CBI—Confidential Business Information

CDX—Central Data Exchange

CEDRI—Compliance and Emissions Data Reporting Interface

CFR—Code of Federal Regulations

EPA—Environmental Protection Agency

ERPG—Emergency Response Planning Guidelines

ERT—Electronic Reporting Tool

HAP—Hazardous Air Pollutants

HCl—Hydrochloric Acid

HI—Hazard Index

HEM-3—Human Exposure Model, Version 3

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

HQ—Hazard Quotient

ICR—Information Collection Request

IRIS—Integrated Risk Information System

km—Kilometer

LAER—Lowest Achievable Emission Rate

LDAR—Leak Detection and Repair

MACT—Maximum Achievable Control Technology

MACT Code—Code within the NEI used to Identify Processes Included in a Source Category

MBS—Methyl Methacrylate Butadiene Styrene

MIR—Maximum Individual Risk

NAAQS—National Ambient Air Quality Standards

NAICS—North American Industry Classification System

NAS—National Academy of Sciences

NATA—National Air Toxics Assessment

NESHAP—National Emissions Standards for Hazardous Air Pollutants

NEI—National Emissions Inventory

NRC—National Research Council

NTTAA—National Technology Transfer and Advancement Act

OECA—Office of Enforcement and Compliance Assurance

OMB—Office of Management and Budget

P&R IV—National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins

PAI—Pesticide Active Ingredient

PB-HAP—Hazardous Air Pollutants known to be Persistent and Bio-Accumulative in the Environment

PCB—Polychlorinated Biphenyls

PCCT—Process Contact Cooling Tower

PEPO—Polyether Polyols

PET—Poly (Ethylene Terephthalate) Resin

PM—Particulate Matter

POM—Polycyclic Organic Matter

PRD—Pressure Relief Device

RACT—Reasonably Available Control Technology

RBLC—RACT/BACT/LAER Clearinghouse

REL—CalEPA Chronic Reference Exposure Level

RFA—Regulatory Flexibility Act

RfC—Reference Concentration

RfD—Reference Dose

RTR—Residual Risk and Technology Review

SAB—Science Advisory Board

SAN—Styrene Acrylonitrile Resin

SCC—Source Classification Codes

SOCMI—Synthetic Organic Chemical Manufacturing Industry

SOP—Standard Operating Procedures

SSM—Startup, Shutdown and Malfunction

THF—Tetrahydrofuran

TOSHI—Target Organ-Specific Hazard Index

TPA—Terephthalic Acid

tpy—Tons Per Year

TRIM—Total Risk Integrated Modeling System

TRIM.FaTE—EPA's Total Risk Integrated Methodology Fate, Transport and Ecological Exposure Model

TTN—Technology Transfer Network

UF—Uncertainty Factor

UMRA—Unfunded Mandates Reform Act

URE—Unit Risk Estimate

VOC—Volatile Organic Compounds

WWW—World Wide Web

Organization of this Document.

The information in this preamble is organized as follows:

I. General Information

A. What is the statutory authority for this action?

B. Does this action apply to me?

C. Where can I get a copy of this document and other related information?

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

II. Background

A. What are the source categories addressed by this action?

B. What data collection activities were conducted to support this proposed action?

III. Analyses Performed

A. How did we address unregulated emissions sources?

B. How did we estimate risks posed by the source categories?

C. How did we consider the risk results in making decisions for this proposal?

D. How did we perform the technology review?

E. What other issues are we addressing in this proposal?

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

A. Acrylonitrile Butadiene Styrene Resin (ABS)

B. Styrene Acrylonitrile Resin (SAN)

C. Methyl Methacrylate Butadiene Styrene Resin (MBS)

D. Polystyrene Resin

E. Poly (ethylene terephthalate) Resin (PET)

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

A. What are the results of the risk assessments?

B. What are the results of the technology review?

C. What other actions are we proposing?

VI. Analytical Results and Proposed Decisions for Polyether Polyols Production

A. What are the results of the risk assessments?

B. What are the results of the technology review?

C. What other actions are we proposing?

VII. Compliance Dates

VIII. Summary of Cost, Environmental and Economic Impacts

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

IX. Request for Comments

X. Submitting Data Corrections

XI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive

Order 13563: Improving Regulation and Regulatory 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

A red-line version of the regulatory language that incorporates the proposed changes in this action is available in the docket.

I. General Information

A. What is the statutory authority for this action?

Section 112 of the Clean Air Act (CAA) establishes a two-stage regulatory process to address emissions of hazardous air pollutants (HAP) from stationary sources. In the first stage, after the EPA has identified categories of sources emitting one or more of the HAP listed in CAA section 112(b), CAA section 112(d) calls for us to promulgate technology-based NESHAP for those sources. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP. For major sources, these technology-based standards must reflect the maximum degree of emissions 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.

MACT standards must require the maximum degree of emissions reduction achievable through the application of measures, processes, methods, systems or techniques, including, but not limited to, measures that: (1) Reduce the volume of or eliminate pollutants through process changes, substitution of materials or other modifications; (2) enclose systems or processes to eliminate emissions; (3) capture or treat pollutants when released from a process, stack, storage or fugitive emissions point; (4) are design, equipment, work practice or operational standards (including requirements for operator training or certification); or (5) are a combination of the above. CAA section 112(d)(2)(A)-(E). The MACT standards may take the form of design, equipment, work practice or operational standards where the EPA first determines either that: (1) A pollutant cannot be emitted through a conveyance designed and constructed to emit or capture the pollutants or that any requirement for, or use of, such a conveyance would be inconsistent with law; or (2) the application of measurement methodology to a particular class of sources is not practicable due to technological and economic limitations. CAA sections 112(h)(1)-(2).

The MACT “floor” is the minimum control level allowed for MACT standards promulgated under CAA section 112(d)(3) and may not be based on cost considerations. For new sources, the MACT floor cannot be less stringent than the emissions control that is achieved in practice by the best-controlled similar source. The MACT floors for existing sources can be less stringent than floors for new sources, but they cannot be less stringent than the average emissions 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 considerations of the cost of achieving the emissions reductions, any non-air quality health and environmental impacts and energy requirements.

The EPA is then required to review these technology-based standards and 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 conducting this review, the EPA is not obliged to completely recalculate the prior MACT determination.

NRDC

EPA,

529 F.3d 1077, 1084 (DC Cir. 2008).

The second stage in standard-setting focuses on reducing any remaining (

i.e.,

“residual”) risk according to CAA section 112(f). This provision requires, first, that the EPA prepare a

Report to Congress

discussing (among other things) methods of calculating the risks posed (or potentially posed) by sources after implementation of the MACT standards, the public health significance of those risks and the EPA's recommendations as to legislation regarding such remaining risk. The 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 the EPA's obligation under CAA section 112(f)(2) to analyze and address residual risk.

CAA section 112(f)(2) requires the EPA to determine, for source categories subject to certain MACT standards, whether those emissions standards 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 one in one million,” the 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, the EPA may adopt standards equal to existing MACT standards if the EPA determines that the existing standards are sufficiently protective.

NRDC

EPA,

529 F.3d at 1083 (“If EPA determines that the existing technology-based standards provide an ‘ample margin of safety,’ then the agency is free to readopt those standards during the residual risk rulemaking.”). The EPA must also adopt more stringent standards, if necessary, to prevent an adverse environmental effect

but must consider cost, energy, safety and other relevant factors in doing so.

“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.

Section 112(f)(2) of the CAA expressly preserves our use of the two-step process for developing standards to address any residual risk and our interpretation of “ample margin of safety” developed in the

National Emissions 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). 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 to be set (unless an even more stringent standard is necessary 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) preserves the EPA's interpretation set out in the Benzene NESHAP, and the United States Court of Appeals for the District of Columbia Circuit in

NRDC

EPA,

529 F.3d 1077, concluded that the EPA's interpretation of subsection 112(f)(2) is a reasonable one. See

NRDC

EPA,

529 F.3d at 1083 (“[S]ubsection 112(f)(2)(B) expressly incorporates EPA's interpretation of the Clean Air Act from the

Benzene

standard, complete with a citation to the

Federal Register

.”). See also,

A Legislative History of the Clean Air Act Amendments of 1990,

volume 1, p. 877 (

Senate debate on Conference Report

). We also 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 risks 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,

the EPA does not define “rigid line[s] of acceptability,” but rather considers 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

NRDC

EPA,

824 F.2d 1146, 1165 (DC Cir. 1987) (Vinyl Chloride Decision)) recognizing that our world is not risk-free.

In the Benzene NESHAP, we stated that the “EPA will generally presume that if the risk to [the maximum exposed] individual is no higher than approximately one in 10 thousand, that risk level is considered acceptable.” 54 FR 38045. We discussed the maximum individual lifetime cancer risk (or maximum individual risk (MIR)) 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 upper bound 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 upper-bound 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 one million (one in 10 thousand) “provides a benchmark for judging the acceptability of maximum individual lifetime cancer risk (MIR), but does not constitute a rigid line for making that determination.”

Id.

Further, in the Benzene NESHAP, we noted that, “Particular attention will also be accorded to the weight of evidence presented in the risk assessment of potential carcinogenicity or other health effects of a pollutant. While the same numerical risk may be estimated for an exposure to a pollutant judged to be a known human carcinogen, and to a pollutant considered a possible human carcinogen based on limited animal test data, the same weight cannot be accorded to both estimates. In considering the potential public health effects of the two pollutants, the Agency's judgment on acceptability, including the MIR, will be influenced by the greater weight of evidence for the known human carcinogen.”

Id.

at 38046.

The agency also explained in the 1989 Benzene NESHAP the following: “In establishing a presumption for MIR, rather than a 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-emissions 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. [* * *] 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 CAA section 112.”

NRDC

EPA,

529 F.3d 1077, 1082 (DC Cir. 2008), the Court of Appeals held that CAA section 112(f)(2) “incorporates EPA's `interpretation' of the Clean Air Act from the Benzene Standard, and the text of this provision draws no distinction between carcinogens and non-carcinogens.” Additionally, the Court held there is nothing on the face of the statute that limits the Agency's section 112(f) assessment of risk to carcinogens.

Id.

at 1081-82. In the NRDC case, the petitioners argued, among other things, that CAA section 112(f)(2)(B) applied only to non-carcinogens. The DC Circuit rejected this position, holding that the text of that provision “draws no distinction between carcinogens and non-carcinogens,”

Id.,

and that Congress' incorporation of the Benzene standard applies equally to carcinogens and non-carcinogens.

In the ample margin of safety decision process, the agency again considers all of the health risks 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 CAA section 112(f). 54 FR 38046.

B. Does this action apply to me?

The NESHAP and associated 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 industrial 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 proposed action include:

Table 2—NESHAP and Industrial Source Categories Affected by This Proposed Action

NESHAP and source category

NAICS Code

MACT Code

Group IV Polymers and Resins

Acrylic-Butadiene-Styrene Production

325211

1302

Methyl Methacrylate-Acrylonitrile-Butadiene-Styrene Production

325211

1317

Methyl Methacrylate-Butadiene-Styrene Production

325211

1318

Nitrile Resins Production

325211

1342

Polyethylene Terephthalate Production

325211

1328

Polystyrene Production

325211

1331

Styrene-Acrylonitrile Production

325211

1338

Pesticide Active Ingredient Production

325199, 325320

0911

Polyether Polyols Production

325199

1625

North American Industry Classification System.

Maximum Achievable Control Technology.

There are no longer any operating facilities in either the Methyl Methacrylate-Acrylonitrile-Butadiene-Styrene Production or Nitrile Resins Production source categories, and none are anticipated to begin operation in the future. Therefore, this proposal does not address these source categories.

C. Where can I get a copy of this document and other related information?

In addition to being available in the docket, an electronic copy of this proposal will also be available on the World Wide Web (WWW) through the Technology Transfer Network (TTN). Following signature by the EPA Administrator, a copy of this 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/atw/rrisk/rtrpg.html.

The TTN provides information and technology exchange in various areas of air pollution control.

Additional information is available on the residual risk and technology review (RTR) 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.

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

Submitting CBI.

Do not submit information containing CBI to the EPA through

http://www.regulations.gov

or email. 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 the EPA, 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 the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. Send or deliver information identified as CBI only to the following address: Nick Parsons, c/o OAQPS Document Control Officer (C404-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, Attn: Docket ID No. EPA-HQ-OAR-2011-0435.

II. Background

A. What are the source categories addressed by this action?

1. Group IV Polymers and Resins Production Source Categories

The National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins were promulgated on September 12, 1996 (61 FR 48208), and codified at 40 CFR part 63, subpart JJJ. The Group IV Polymers and Resins MACT standards apply to major sources and regulate HAP emissions from seven source categories: acrylonitrile butadiene styrene resin (ABS), styrene acrylonitrile resin (SAN), methyl methacrylate acrylonitrile butadiene styrene resin (MABS), methyl methacrylate butadiene styrene resin (MBS), polystyrene resin, poly (ethylene terephthalate) resin (PET) and nitrile resin.

The Group IV Polymers and Resins MACT standards regulate HAP emissions resulting from the production of thermoplastics. A thermoplastic is a resin that softens with heat and rehardens to a rigid material upon cooling, without generally showing any change in the physical properties of the thermoplastic, even with repeated heating and cooling. Thermoplastics are composed of high-molecular-weight polymers which are synthesized from monomers; the thermoplastics covered

in these seven source categories, with one exception, use styrene monomer as the basic feedstock. The thermoplastics included in these source categories 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 these polymers 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) material recovery; and (4) finishing (

i.e.,

blending, aging, coagulation, washing and drying).

Sources of HAP emissions from thermoplastics production include raw material storage vessels, continuous and batch process vents, wastewater operations, heat exchangers and equipment leaks. The Group IV Polymers and Resins MACT standards include a combination of equipment standards and emission limits for the various emission sources, which vary in stringency in some cases among the source categories.

To meet the requirements of the Group IV Polymers and Resins MACT standards, the typical control devices used to reduce organic HAP emissions from process vents include flares, incinerators, absorbers, carbon adsorbers and condensers. In addition, emissions of hydrochloric acid (HCl) are controlled using scrubbers. Emissions from storage vessels are controlled by fixed roofs with closed vent systems routed 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 and heat exchangers are typically reduced by leak detection and repair (LDAR) work practice programs and, in some cases, by equipment modifications. Each of the five Group IV Polymers and Resins source categories addressed in this proposal are discussed further below. Two of the Group IV Polymers and Resins source categories, MABS and nitrile resins, no longer have any operating facilities in the U.S. and we do not anticipate any will begin to operate in the future. Therefore, this proposal does not address these source categories.

It is the EPA's practice in these circumstances to not conduct unnecessary risk and technology reviews for source categories that will no longer have sources operating in the U.S. See,

e.g.,

75 FR 65068, 65075, n.5 (Oct. 21, 2010) and 76 FR 22566, 22575, n.5 (Apr. 21, 2011).

a. Acrylonitrile Butadiene Styrene Resin (ABS)

ABS consist of a terpolymer of acrylonitrile, butadiene and styrene and can be synthesized by emulsion, suspension and continuous mass polymerization. The majority of ABS resin production is by batch emulsion. Typical products made from ABS resins are piping, refrigerator door liners and food compartments, automotive components, telephones, luggage and cases, toys, mobile homes and margarine tubs.

We identified five currently operating ABS facilities subject to the Group IV Polymers and Resins MACT standards. Styrene, acrylonitrile and 1,3-butadiene account for the majority of the HAP emissions from the ABS production processes at these facilities (approximately 156 tpy and 76 percent of the total HAP emissions by mass). These facilities also reported relatively small emissions of 23 other HAP. We estimate that the MACT-allowable emissions (

i.e.,

the maximum emission levels allowed if in compliance with the MACT standards) from this source category are approximately equal to the reported, actual emissions. For more detail about this estimate of the ratio of actual to MACT-allowable emissions and the estimation of MACT-allowable emission levels and associated risks and impacts, see the memorandum,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

b. Styrene Acrylonitrile Resin (SAN)

SAN resins are copolymers of styrene and acrylonitrile, and they may be synthesized by emulsion, suspension and continuous mass polymerization; however, the majority of production is by batch emulsion. Typical uses include automobile instrument panels and interior trim and housewares.

We identified two currently operating SAN facilities subject to the Group IV Polymers and Resins MACT standards. Ethyl benzene and styrene account for the majority of the HAP emissions from the SAN production processes at these facilities (approximately 2 tpy and 82 percent of the total HAP emissions by mass). These facilities also reported relatively small emissions of methylene chloride and acrylonitrile. We estimate that the MACT-allowable emissions (

i.e.,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

c. Methyl Methacrylate Butadiene Styrene Resin (MBS)

MBS resins are prepared by grafting methyl methacrylate and styrene onto a styrene-butadiene rubber in an emulsion process. The product is a two-phase polymer used as an impact modifier for rigid polyvinyl chloride products. These products are used for applications in packaging, building and construction.

We identified two currently operating MBS facilities subject to the Group IV Polymers and Resins MACT standards. Methyl methacrylate and 1,3-butadiene account for the majority of the HAP emissions from the MBS production processes at these facilities (approximately 4 tpy and 75 percent of the total HAP emissions by mass). These facilities also reported relatively small emissions of ethyl acrylate, methanol, styrene and HCl. We estimate that the MACT-allowable emissions (

i.e.,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

d. Polystyrene Resin

Polystyrene resins are those produced by the polymerization of styrene monomer. This type of resin can be produced by three methods: (1) Suspension polymerization (operated in batch mode); (2) mass (operated in a continuous mode); and (3) emulsion process (operated in a continuous mode). The mass and suspension methods are the most commercially

significant, whereas use of the emulsion process has decreased significantly since the mid-1940s. The uses for polystyrene resin include packaging and one-time use, expandable polystyrene beads, electronics, resellers and compounding, consumer and institutional products and furniture, building or construction uses. A wide variety of consumer and construction products are made from polystyrene resins, including disposable dinnerware, shower doors, light diffusers, soap dishes, insulation board, food containers, drain pipes, audio and video tape, picnic coolers, loose fill packaging and tubing.

We identified 11 currently operating polystyrene resin facilities subject to the Group IV Polymers and Resins MACT standards. Styrene accounts for the majority of the HAP emissions from the polystyrene resin production processes at these facilities (approximately 85 tpy and 94 percent of the total HAP emissions by mass). These facilities also reported relatively small emissions of eight other HAP. We estimate that the MACT-allowable emissions (

i.e.,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

e. Poly (Ethylene Terephthalate) Resin (PET)

Three different types of resins are made by sources covered by the PET source category: Solid-state resins (PET bottle grade resins), polyester film and engineering resins. They are all thermoplastic linear condensation polymers based on dimethyl terephthalate or terephthalic acid (TPA). PET meltphase polymer is used in the production of all three of these resins. PET production can occur via either a batch or continuous process. The most common use of PET solid-state resins is in soft drink bottles, and some industrial fiber-graded polyester (

e.g.,

for tire cord) is also produced from PET solid-state resins. The most common uses of PET film are photographic film and magnetic media. PET is used extensively in the manufacture of synthetic fibers (

i.e.,

polyester fibers), which compose the largest segment of the synthetic fiber industry. The most common uses of polyester fibers are apparel, home furnishings, carpets, fiberfill and other industrial processes.

We identified 15 currently operating PET facilities subject to the Group IV Polymers and Resins MACT standards. Ethylene glycol, acetaldehyde and methanol account for the majority of the HAP emissions from the PET production processes at these facilities (approximately 1,048 tpy and 89 percent of the total HAP emissions by mass). These facilities also reported relatively small emissions of 34 other HAP. We estimate that the MACT-allowable emissions (

i.e.,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

2. Pesticide Active Ingredient Production

The National Emission Standards for Hazardous Air Pollutants for Pesticide Active Ingredient Production were promulgated on June 23, 1999 (64 FR 33549), and codified at 40 CFR part 63, subpart MMM. The Pesticide Active Ingredient (PAI) MACT standards apply to major sources and regulate HAP emissions resulting from the production of active ingredients in insecticides, herbicides, fungicides and related products. Typically, the active ingredients subject to the PAI MACT standards are subsequently formulated with inert ingredients to create end-product pesticides for application. The MACT standards do not apply to the formulation of end-product pesticides or to other types of active ingredients, such as biocides.

PAI are made from a number of raw materials in a variety of processes. A process often consists of several steps, which may include reaction, crystallization, washing, solvent extraction, distillation and/or drying.

The HAP emission sources at PAI production facilities include storage vessels, process vents, equipment leaks, wastewater systems, heat exchange systems, bag dumps and product dryers. In the production of PAI, HAP are used primarily as reactants or extraction solvents; some of the PAI products are also HAP. The MACT standards for PAI production include a combination of equipment standards and emission limits for the various emission sources.

To meet the requirements of the PAI MACT standards, the typical control devices used to reduce emissions from process vents include flares, incinerators, absorbers, carbon adsorbers and condensers. In addition, emissions of HCl are controlled using scrubbers. Emissions from storage vessels are controlled by fixed roofs with closed vent systems routed to a control device. Emissions from wastewater are controlled by a variety of methods, including equipment modifications (

e.g.,

We identified 17 currently operating facilities subject to the PAI MACT standards. Toluene, methanol and methylene chloride account for the majority of the HAP emissions from the PAI production processes at these facilities (approximately 177 tpy and 51 percent of the total HAP emissions by mass). A variety of chemicals are used in the production of PAI, and these facilities also reported emissions of 67 other HAP. We estimate that the actual emissions level is representative of the MACT-allowable level (

i.e.,

the maximum emission levels allowed if in compliance with the MACT standards) for all emissions sources except process vents. 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 for process vents, the MACT-allowable level for organic HAP emissions could be up to five times the actual emissions and the MACT-allowable level for chlorine and HCl emissions could be up to six times the actual emissions from this source category. For more detail about this estimate of the ratio of actual to MACT-allowable emissions and the estimation of MACT-allowable emission levels and associated risks and impacts, see the memorandum,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

3. Polyether Polyols Production

The National Emission Standards for Hazardous Air Pollutant Emissions for Polyether Polyols Production were promulgated on June 1, 1999 (64 FR 29419), and codified at 40 CFR part 63, subpart PPP. The Polyether Polyols (PEPO) MACT standards apply to major sources and regulate HAP emissions resulting from the production of chemical products with repeating ether linkages (

i.e.,

-R-O-R-) formed by the reaction of ethylene oxide, propylene oxide or other cyclic ethers with compounds having one or more reactive hydrogens. (This definition excludes materials regulated as glycols or glycol ethers under the National Emission Standards for Organic Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry (HON).) PEPO do not have significant uses of their own but are used to make a variety of other products. Urethane grade PEPO (

i.e.,

those that are free of water) are used as raw material in the production of polyurethanes, including slabstock and molded flexible foams, rigid foams and other polyurethanes, including microcellular products, surface coatings, elastomers, fibers, adhesives and sealants. Nonurethane PEPO are used as surfactants, lubricants, degreasing agents, hydraulic fluids, cosmetics and pharmaceuticals.

PEPO can be produced by either polymerization of epoxides (

i.e.,

a three-membered cyclic ether, such as ethylene oxide or propylene oxide) or tetrahydrofuran (THF). The former process is usually conducted as a batch process, while production of polyols using THF is generally a continuous process. Ethylene oxide and propylene oxide are both HAP, but THF is not. For the MACT regulation, two subcategories of PEPO were created based on the use of either epoxides or THF in polymerization.

The HAP emission sources at PEPO production facilities include process vents, storage vessels, equipment leaks and wastewater, and some facilities have cooling towers or other heat exchangers. In the production of PEPO, HAP are used primarily as reactants or extraction solvents; some of the PEPO products are also HAP compounds. The MACT standards for PEPO production include emission limits for process vents, a combination of equipment standards and work practices for storage vessels, wastewater and equipment leaks, and work practice standards for cooling towers.

To meet the requirements of the PEPO MACT standards, the typical control devices used to reduce emissions from storage vessels are fixed roofs with closed vent systems routed 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 and heat exchangers are typically reduced by LDAR work practice programs and, in some cases, by equipment modifications. Controls for process vents for facilities that use THF as a reactant generally use scrubbers. Epoxide emissions from process vents are typically controlled by scrubbers or combustion devices, but some facilities use extended cookout as a pollution prevention technique. Extended cookout reduces the amount of unreacted ethylene oxide and/or propylene oxide (epoxides) in the reactor. This is accomplished by allowing the product to react for a longer time period, thereby having less unreacted epoxides and reducing epoxides emissions that may have otherwise occurred. Emissions from catalyst extraction and other processes are generally vented to the same control device as the epoxide emissions or are minimal if the extended cookout practice is used.

We identified 23 currently operating facilities subject to the PEPO MACT standards. Ethylene glycol, ethylene oxide and propylene oxide account for the majority of the HAP emissions from the PEPO production processes at these facilities (approximately 269 tpy and 61 percent of the total HAP emissions by mass). A variety of chemicals are used in the production of PEPO, and these facilities also reported emissions of 81 other HAP. We estimate that the actual emissions level is representative of the MACT-allowable level (

i.e.,

the maximum emission levels allowed if in compliance with the MACT standards) for all emissions sources except batch process vents and process vents that use organic HAP in catalyst extraction at units producing PEPO products using epoxides. As it is possible that the capture systems and control devices used at some facilities achieve greater emission reductions in the organic non-epoxide HAP than what is required by the NESHAP for these process vents, the MACT-allowable level for organic non-epoxide HAP emissions could be up to five times the actual emissions from this source category. For more detail about this estimate of the ratio of actual to MACT-allowable emissions and the estimation of MACT-allowable emission levels and associated risks and impacts, see the memorandum,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

B. What data collection activities were conducted to support this proposed action?

To perform the risk assessments for these source categories, we developed data sets for these seven source categories (five Group IV Polymers and Resins categories, PAI and PEPO) based on information in the 2005 National Emissions Inventory (NEI) (available at

http://www.epa.gov/chief/net/2005inventory.html

). The NEI is a database that contains information about sources that emit criteria air pollutants, 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. The EPA collects this information and releases an updated version of the NEI database every 3 years. We reviewed the NEI data and made changes where necessary to ensure the proper facilities were included and to ensure the proper processes were allocated to each source category. We also reviewed the emissions and other data to identify data anomalies that could affect risk estimates, such as whether a pollutant was expected to be emitted from facilities in a source category or whether an emission point was located within a facility's fenceline. The NEI data were also reviewed by industry trade groups, including the American Chemistry Council and the Society of Chemical Manufacturers and Affiliates. Where the EPA received new information in response to these data review by industry, including updated emissions data and process information, facility closure information and information that some facilities were not subject to the PAI, PEPO or Group IV Polymers and Resins MACT standards, we revised the NEI data where we concluded the comments supported such adjustment. We obtained updated emissions data and process information, found that some facilities had closed and that others were no longer subject to the PAI, PEPO or Group IV Polymers and Resins MACT standards. In general, we found that emissions from these source categories had decreased from the values reported in the 2005 NEI, due to factors such as the installation of additional controls at the facility,

duplication of emissions in the inventory, or emissions misappropriated to the wrong source category. We used this reviewed and revised data set to conduct the risk assessment and other analyses for each source category. Due to the uncertainties in the data (

e.g.,

most emission estimates in the data set are the result of emission factors rather than test data), along with our general finding that emissions were less than those reported in the 2005 NEI, we believe that the data set provides a conservative estimate of the risk from these source categories. Further details on the changes made to the 2005 NEI data can be found in the memorandum,

Emissions Data and Acute Risk Factor Used in Residual Risk Modeling: Pesticide Active Ingredients, Polyether Polyols, and Group IV Polymers and Resins,

which is in the docket for this rulemaking.

To conduct the technology review, we primarily relied on information downloaded from the reasonably available control technology (RACT)/best available control technology (BACT)/lowest achievable emission rate (LAER) Clearinghouse (RBLC) for processes in Agricultural Chemical Manufacturing (for PAI controls), Polymer and Resin Production (for Group IV Polymers and Resins controls) and the Synthetic Organic Chemical Manufacturing Industry (SOCMI) (for PAI, PEPO and Group IV Polymers and Resins controls) with permits dating back to the promulgation dates of each MACT regulation.

To evaluate unregulated emission points in the Group IV Polymers and Resins MACT standards, we relied on existing data submitted to the EPA during development of the MACT, information submitted after proposal of the MACT standards and information submitted with requests for reconsideration of standards.

III. Analyses Performed

A. How did we address unregulated emissions sources?

For the Group IV Polymers and Resins source categories, we identified one subcategory—PET sources using a continuous TPA high viscosity multiple end finisher process—consisting of one facility that was not subject to standards for process contact cooling towers (PCCT) or equipment leaks. While the promulgated rule includes provisions for PCCT for this subcategory, the facility is not required to comply with these provisions due to an indefinite stay in the compliance date provisions issued by the EPA in response to a request to reconsider the emission limits for this equipment. For this facility, we also identified the absence of a standard for equipment leaks, which in the absence of an enforceable standard is a potential significant emissions source for this facility, even though its operators currently voluntarily conduct their own LDAR program. For the one facility in this subcategory, we are proposing to set standards for PCCT and equipment leaks under CAA section 112(d)(2) and (d)(3) in this action. The results and proposed decisions based on the analyses performed pursuant to CAA section 112(d)(2) and 112(d)(3) are presented in section IV.E.1 of this preamble. While we also identified the absence of a standard for wastewater for the acrylonitrile styrene resin/alpha methyl styrene acrylonitrile resin (ASA/AMSAN) subcategory of the SAN source category, the only facility in this subcategory has permanently closed, and no new ASA/AMSAN operations are expected to begin operation in the United States. As stated previously and as established in prior risk and technology review rulemakings, it is not EPA's practice to unnecessarily conduct risk and technology reviews for source categories that will no longer have sources operating in the United States. Therefore, we are not addressing this emission point in this proposed action.

B. How did we estimate risks posed by the source categories?

The EPA conducted risk assessments that provided estimates of the MIR posed by the HAP emissions from each source in each source category, the hazard index (HI) for chronic exposures to HAP with the potential to cause noncancer health effects and the hazard quotient (HQ) for acute exposures to HAP with the potential to cause noncancer health effects. The assessments also provided estimates of the distribution of cancer risks within the exposed populations, cancer incidence and an evaluation of the potential for adverse environmental effects for each source category. The risk assessments consisted of seven primary steps, as discussed below. The docket for this rulemaking contains the following document which provides more information on the risk assessment inputs and models:

Draft Residual Risk Assessment for 7 Source Categories.

The methods used to assess risks (as described in the seven primary steps below) are consistent with those peer-reviewed by a panel of the EPA's Science Advisory Board (SAB) in 2009 and described in their peer review report issued in 2010; they are also consistent with the key recommendations contained in that report.

1. Establishing the Nature and Magnitude of Actual Emissions and Identifying the Emissions Release Characteristics

As discussed in section II.B, we created the preliminary data sets for the seven source categories using data in the 2005 NEI, supplemented by data collected from industry or industry trade associations when available.

2. Establishing the Relationship Between Actual Emissions and MACT-Allowable Emissions Levels

The available emissions data in the NEI and from other sources typically represent the mass of HAP actually emitted during the specified annual time period. These “actual” emission levels can be lower than the emission levels a facility might be allowed to emit and still comply with the MACT standards. The emissions level allowed to be emitted by the MACT standards is referred to as the “MACT-allowable” emissions level. This represents the highest emissions level that could be emitted by facilities without violating the MACT standards.

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 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 risks at the MACT-allowable level is inherently reasonable because these risks reflect the maximum level sources could emit and still comply with national emission standards. We continue to take this view, for the reasons presented in those discussions. 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.) We also continue to take this view, for the reasons explained in those prior discussions.

As described above, the actual emissions data were compiled based on the NEI and information gathered from facilities through industrial trade associations. To estimate emissions at the MACT-allowable level, we developed a ratio of MACT-allowable to actual emissions for each emissions source type in each source category, based on the level of control required by the MACT standards compared to the level of reported actual emissions and

available information on the level of control achieved by the emissions controls in use. For example, if there was information to suggest several facilities in a source category were controlling storage tank emissions by 98 percent, while the MACT standards required only 92-percent control, we would estimate that MACT-allowable emissions from these emission points could be as much as four times higher (8-percent allowable emissions compared with 2 percent actually emitted), and the ratio of MACT-allowable to actual would be 4:1 for this emission point type at the facilities in this source category. After developing these ratios for each emission point type in each source category, we next applied these ratios on a facility-by-facility basis to the maximum chronic risk values from the inhalation risk assessment to obtain facility-specific maximum risk values based on MACT-allowable emissions. Further explanation of this evaluation is provided in the technical document,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

which is available in the docket for this action.

3. Conducting Dispersion Modeling, Determining Inhalation Exposures, and Estimating Individual and Population Inhalation Risks

Both long-term and short-term inhalation exposure concentrations and health risks from each facility in the source categories addressed in this proposal were estimated using the Human Exposure Model (HEM) (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 the EPA's preferred models for assessing pollutant concentrations from industrial facilities.

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 (1991) of hourly surface and upper air observations for 189 meteorological stations, selected to provide 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 (U.S. 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 the 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.

U.S. EPA. Revision to the

Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions

(70 FR 68218, November 9, 2005).

A census block is generally the smallest geographic area for which census statistics are tabulated.

In developing the risk assessment for chronic exposures, we used the estimated annual average ambient air concentration of each of the HAP emitted by each source for which we have emissions data in the source category. The air concentrations at each nearby census block centroid were used as a surrogate for the chronic inhalation exposure concentration for all people who reside in that census block. We calculated the MIR for each facility as the cancer risk associated with a continuous lifetime (24 hours per day, 7 days per week and 52 weeks per year for a 70-year period) exposure to the maximum concentration at the centroid of inhabited census blocks. Individual cancer risks were calculated by multiplying the estimated lifetime exposure to the ambient concentration of each of the HAP (in micrograms per cubic meter (µg/m

)) 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 1 microgram of the pollutant per cubic meter of air. For residual risk assessments, we generally use URE values from the 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 EPA (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 the EPA, we may use such dose-response values in place of, or in addition to, other values, if appropriate.

The IRIS information is available at

http://www.epa.gov/IRIS.

We note here that several carcinogens have a mutagenic mode of action.

Of these compounds, polycyclic organic matter (POM) is emitted by facilities in the PEPO and PET source categories, and vinyl chloride is emitted by facilities in the PEPO and the PAI source categories. For these compounds, the age-dependent adjustment factors (ADAF) described in the EPA's

Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens

were applied. This adjustment has the effect of increasing the estimated lifetime risks for these pollutants by a factor of 1.6.

In addition, the EPA expresses carcinogenic potency for compounds in the POM 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, the EPA's Science Policy Council

recommends applying the

Supplemental Guidance

to all carcinogenic polycyclic aromatic hydrocarbons for which risk estimates are based on relative potency. Accordingly, we have applied the ADAF to benzo[a]pyrene equivalent portion of all POM mixtures.

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:

Memorandum from W.H. Farland, dated June 14, 2006.

http://epa.gov/osa/spc/pdfs/CGIWGCommunication_II.pdf.

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.

Only one of these mutagenic compounds, benzo[a]pyrene, is emitted by any of the sources covered by this proposal.

U.S. EPA, 2005.

Science Policy Council Cancer Guidelines Implementation Workgroup Communication I:

Memorandum from W.H. Farland, dated October 4, 2005, to Science Policy Council.

http://www.epa.gov/osa/spc/pdfs/canguid1.pdf.

Incremental individual lifetime cancer risks associated with emissions from the source categories were estimated as the sum of the risks for each of the carcinogenic HAP (including those classified as carcinogenic to humans, likely to be carcinogenic to humans, and suggestive evidence of

carcinogenic potential

) emitted by the modeled sources. Cancer incidence and the distribution of individual cancer risks for the population within 50 km of any source were also estimated for the source categories as part of these assessments by summing individual risks. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian dispersion models, including AERMOD.

These classifications also coincide with the terms “known carcinogen, probable carcinogen, and possible carcinogen,” respectively, which are the terms advocated in the EPA's previous

Guidelines for Carcinogen Risk Assessment,

published in 1986 (51 FR 33992, September 24, 1986). Summing the risks of these individual compounds to obtain the cumulative cancer risks is an approach that was recommended by the EPA's SAB in their 2002 peer review of the EPA's National Air Toxics Assessment (NATA) entitled,

NATA—Evaluating the National-scale Air Toxics Assessment 1996 Data—an SAB Advisory,

available at:

http://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.

To assess risk of noncancer health effects from chronic exposures, we summed the HQ for each of the 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 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 from the EPA's IRIS database is not available, a value from the following prioritized sources for chronic dose-response values: (1) The Agency for Toxic Substances and Disease Registry Minimum Risk Level, 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”; (2) 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 (3) as noted above, a scientifically credible dose-response value that has been developed in a manner consistent with the EPA guidelines and has undergone a peer review process similar to that used by the EPA, in place of or in concert with other values.

Screening estimates of acute exposures and risks were also evaluated for each of the HAP at the point of highest off-site exposure for each facility (

i.e.,

not just the census block centroids), assuming that a person is located at this spot at a time when both the peak (hourly) emission rates from each emission point at the facility and worst-case dispersion conditions occur. The acute HQ is the estimated acute exposure divided by the acute dose-response value. In each case, acute HQ values were calculated using best available, short-term health threshold values. These acute dose-response values, which are described below, include the acute REL, acute exposure guideline levels (AEGL) and emergency response planning guidelines (ERPG) for 1-hour exposure durations. As discussed below, we used conservative assumptions for emission rates, meteorology and exposure location for our acute analysis.

As described in the CalEPA's

Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants,

an acute REL value (

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.” Acute REL values are based on the most sensitive, relevant, adverse health effect reported in the medical and toxicological literature. Acute REL values are designed to protect the most sensitive sub-populations (

e.g.,

asthmatics) by the inclusion of margins of safety. Because margins of safety are incorporated to address data gaps and uncertainties, exceeding the REL value does not automatically indicate an adverse health impact.

AEGL values were derived in response to recommendations from the National Research Council (NRC). 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

“the NRC's previous name for acute exposure levels—community emergency exposure levels—was replaced by the term AEGL 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 that AEGL values “represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to 8 hours.” The document lays out the purpose and objectives of AEGL by stating (page 21) that “the primary purpose of the AEGL program and the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances 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 “[i]t 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.”

NAS, 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 milligrams per cubic meter (mg/m

) 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 values are derived for use in emergency response, as described in the American Industrial Hygiene Association's document titled,

Emergency Response Planning Guidelines (ERPG) Procedures and Responsibilities

(

http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf

), which states that, “Emergency Response Planning Guidelines were developed for emergency planning and are intended as

health-based guideline concentrations for single exposures to chemicals.”

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 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 or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.”

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, a severity level 1 value AEGL or ERPG has not been developed because the types of effects for these chemicals are not consistent with the AEGL-1/ERPG-1 definitions; 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. When AEGL-1/ERPG-1 values are available, they are used in our acute risk assessments.

Acute REL values for 1-hour exposure durations are typically lower than their corresponding AEGL-1 and ERPG-1 values. Even though their definitions are slightly different, AEGL-1 values are often similar to the corresponding ERPG-1 values, and AEGL-2 values are often similar to ERPG-2 values. Maximum HQ values from our acute screening risk assessments typically result when basing them on the acute REL value 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 dose-response value (usually the AEGL-1 and/or the ERPG-1 value).

To develop screening estimates of acute exposures in the absence of hourly emissions data, generally we first develop estimates of maximum hourly emissions rates by multiplying the average actual annual hourly emission rates by a default factor to cover routinely variable emissions. We choose the factor to use based on process knowledge and engineering judgment and with awareness of a Texas study of short-term emissions variability, which showed that most peak emission events in a heavily-industrialized 4-county area (Harris, Galveston, Chambers and Brazoria Counties, Texas) were less than twice the annual average hourly emission rate. The highest peak emissions event was 74 times the annual average hourly emission rate, and the 99th percentile ratio of peak hourly emissions rate to the annual average hourly emissions rate was 9.

This analysis is provided in the

Draft Residual Risk Assessment for 7 Source Categories

report, which is available in the docket for this action. Considering this analysis, to account for more than 99 percent of the peak hourly emissions, we apply a conservative screening multiplication factor of 10 to the average annual hourly emissions rate in our acute exposure screening assessments as our default approach. However, we use a factor other than 10 if we have information that indicates that a different factor is appropriate for a particular source category. For these source categories, a factor of 10 was applied to all emissions, with two exceptions. For certain facilities with volatile organic compound (VOC) emissions greater than 876 tpy and for several facilities with emissions from equipment leaks, a factor of two was applied. A further discussion of why this factor was chosen can be found in the memorandum,

Emissions Data and Acute Risk Factor Used in Residual Risk Modeling: Pesticide Active Ingredients, Polyether Polyols, and Group IV Polymers and Resins,

available in the docket for this rulemaking.

See

http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html

or docket to access the source of these data.

As part of our acute risk assessment process, for cases where 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 include using a peak-to-mean hourly emissions ratio based on source category-specific knowledge or data (rather than 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. Such an evaluation could include a more complete statistical treatment of the key parameters and elements adopted in this screening analysis. However, we recognize that having this level of data is rare, hence our use of the multiplier approach.

To better characterize the potential health risks associated with estimated acute exposures to HAP, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies,

we generally examine a wider range of available acute health metrics (

e.g.,

REL, AEGL) than we do for our chronic risk assessments. This is in response to the SAB's acknowledgement that there are generally more data gaps and inconsistencies in acute reference values than there are in chronic reference values. In some cases, when Reference Value Arrays

for HAP have been developed, we consider additional acute values (

i.e.,

occupational and international values) to provide a more complete risk characterization.

The SAB peer review of RTR Risk Assessment Methodologies is available at:

http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.

U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of Chemical-Specific Health Effect Reference Values for Inhalation Exposures (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/061, and available on-line at

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003.

4. Conducting Multipathway Exposure and Risk Screening

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 process. In the first step, we determined whether any facilities emitted any HAP known to be persistent and bio-accumulative in the environment (PB-HAP). There are 14 PB-HAP compounds or compound classes identified for this screening in the EPA's Air Toxics Risk Assessment Library (available at

http://www.epa.gov/ttn/fera/risk_atra_vol1.html

). They are cadmium compounds, chlordane, chlorinated dibenzodioxins and furans, dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene, hexachlorocyclohexane, lead compounds, mercury compounds, methoxychlor, polychlorinated biphenyls (PCB), POM, toxaphene and trifluralin.

In the second step of the screening process, we determined whether the facility-specific emission rates of each of the emitted PB-HAP were large enough to create the potential for significant non-inhalation human or environmental risks under reasonable worst-case conditions. To facilitate this step, we have developed emission rate thresholds for several of these PB-HAP using a hypothetical worst-case screening exposure scenario developed for use in conjunction with the EPA's Total Risk Integrated Methodology Fate, Transport and Ecological Exposure (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 negatives 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 of the PB-HAP in each source category were compared to the TRIM-Screen emission threshold values for each of these PB-HAP to assess the potential for significant human health risks or environmental risks via non-inhalation pathways.

5. Assessing Risks Considering Emissions Control Options

In addition to assessing baseline inhalation risks and screening for potential multipathway risks, for some source categories, we also estimated risks considering the potential emission reductions that would be achieved by the particular control options under consideration. In these cases, the expected emissions reductions were applied to the specific HAP and emission points in the source category dataset to develop corresponding estimates of risk reductions.

6. Conducting Other Risk-Related Analyses: Facility-Wide Assessments

To put the source category risks in context, we examined the risks from the entire “facility,” where the facility includes all HAP-emitting operations within a contiguous area and under common control. In other words, for each facility that includes one or more sources from a source category under review, we examined the HAP emissions not only from that source category, but also emissions of HAP from all other emission sources at the facility. The emissions data for generating these “facility-wide” risks were obtained from the 2005 NEI. We analyzed risks due to the inhalation of HAP that are emitted “facility-wide” for the populations residing within 50 km of each facility, consistent with the methods used for the source category analysis described above. For these facility-wide risk analyses, the modeled source category risks were compared to the facility-wide risks to determine the portion of facility-wide risks that could be attributed to each of the seven source categories addressed in this proposal. We specifically examined the facility that was associated with the highest estimate of risk and determined the percentage of that risk attributable to the source category of interest. The risk documentation available through the docket for this action provides all facility-wide risks and the percentage of source category contribution for all source categories assessed.

The methodology and results of the facility-wide analyses for each source category are included in the residual risk documentation as referenced in sections IV though VI of this preamble, which is available in the docket for this action.

7. Considering Uncertainties in Risk Assessment

Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for the source categories addressed in this proposal. Although uncertainty exists, we believe the approach taken, which used conservative tools and assumptions, ensures that our decisions are health-protective. A brief discussion of the uncertainties in the emissions data sets, dispersion modeling, inhalation exposure estimates and dose-response relationships follows below. A more thorough discussion of these uncertainties is included in the risk assessment documentation (

Draft Residual Risk Assessment for 7 Source Categories

(September 2011)), which is available in the docket for this action.

a. 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, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the data sets are accurate, errors in estimating emissions values and other factors. The emission values considered in this analysis generally are annual totals that do not reflect short-term fluctuations during the course of a year or variations from year to year. In contrast, the estimates of peak hourly emission rates for the acute effects screening assessment were based on emission adjustment factors applied to the average annual hourly emission rates (the default factor is 10 for the initial screening), which are intended to account for emission fluctuations due to normal facility operations. In some cases, more refined estimates, using lower emission adjustment factors that reflected consideration of category-specific information, were used for source categories where the screening estimates did not “screen out” all sources and more specific information was available.

b. Uncertainties in Dispersion Modeling

While the analysis employed the EPA's recommended regulatory dispersion model, AERMOD, we recognize that there is uncertainty in ambient concentration estimates associated with any model, including AERMOD. Where possible, model options (

e.g.,

rural/urban, plume depletion, chemistry) were selected to provide an overestimate of ambient air concentrations of the HAP rather than underestimates. 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 HAP concentrations.

c. 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 between census blocks in the modeling domain were not considered.

Not considering short or long-term population mobility does not bias the estimate of the theoretical MIR, nor does it affect the estimate of cancer incidence because the total population number remains the same. It does, however, affect the shape of the distribution of individual risks across the affected

population, shifting it toward higher estimated individual risks at the upper end and reducing the number of people estimated to be at lower risks, thereby increasing the estimated number of people at specific high risk levels (

e.g.,

1-in-1 million).

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.

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. Using the census block centroid to predict chronic exposures tends to over-predict exposures for people in the census block who live farther from the facility and under-predict 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 it is an unbiased estimate of average risk and incidence.

The assessments evaluate the cancer inhalation risks associated with continuous pollutant exposures over a 70-year period, which is the assumed lifetime of an individual. 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, in most cases, result in an overestimate both in individual risk levels and in the total estimated number of cancer cases. However, in rare cases, where a facility maintains or increases its emission levels beyond 70 years, residents live beyond 70 years at the same location, and the residents spend most of their days at that location, then the risks could potentially be underestimated. 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 as high, depending on the 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.

U.S. EPA.

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 other factors specific to the acute exposure assessment. 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 be worst-case actual exposures, as it is unlikely that a person would be located at the point of maximum exposure during the time of worst-case impact.

d. 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 on dose-response uncertainty that is brought out in the 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 residual risk documentation, which is available in the docket for this action.

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).

In some circumstances, the true risk could be as low as zero; however, in other circumstances the risk could be greater.

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. To err on the side of ensuring adequate health protection, the EPA typically uses the upper bound estimates rather than lower bound or central tendency estimates in our risk assessments, an approach that may have limitations for other uses (

e.g.,

priority-setting or expected benefits analysis).

IRIS glossary (

http://www.epa.gov/NCEA/iris/help_gloss.htm

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 reference dose (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. The UF are applied to derive reference values that are intended to protect against appreciable risk of deleterious effects. The UF are commonly default values,

e.g.,

factors of 10 or 3, used in the absence of compound-specific data; where data are available, UF may also be developed using compound-specific information. When data are limited, more assumptions are needed and more UF 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.

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 the 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.

While collectively termed “UF,” these factors account for a number of different quantitative considerations when using observed animal (usually rodent) or human toxicity data in the development of the RfC. 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 sub-chronic 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 they more often use 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 lowest observed adverse effect (exposure) level to no observed adverse effect (exposure) level 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 short-term dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties.

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, chronic noncancer 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. For a group of compounds that are either unspeciated or do not have reference values for every individual compound (

e.g.,

glycol ethers) we conservatively use the most protective reference value to estimate risk from individual compounds in the group of compounds.

Additionally, chronic reference values for several 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 may re-evaluate residual risks for the final rulemaking if these reviews are completed prior to our taking final action for these source categories and if a dose-response metric changes enough to indicate that the risk assessment supporting this notice may significantly understate human health risk.

e. Uncertainties in the Multipathway and Environmental Effects Screening Assessment

We generally assume that when exposure levels are not anticipated to adversely affect human health, they also are not anticipated to adversely affect the environment. For each source category, we generally rely on the site-specific levels of PB-HAP emissions to determine whether a full assessment of the multipathway and environmental effects is necessary. Our screening methods use worst-case scenarios to determine whether multipathway impacts might be important. The results of such a process are biased high for the purpose of screening out potential impacts. Thus, when individual pollutants or facilities screen out, we are confident that the potential for multipathway impacts is negligible. On the other hand, when individual pollutants or facilities do not screen out, it does not mean that multipollutant impacts are significant, only that we cannot rule out that possibility.

C. How did we consider the risk results in making decisions for this proposal?

As discussed in the previous section of this preamble, we apply a two-step process for determining whether to develop standards to address residual risk. In the first step, the EPA determines whether risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive level on maximum individual lifetime [cancer] risk (MIR)

of approximately one in 10 thousand [

i.e.,

100 in 1 million].” 54 FR 38045. In the second step of the process, the EPA determines what level of the standard is needed to provide an ample margin of safety “in consideration of all health information, including the number of persons at risk levels higher than approximately one in one million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.”

Id.

Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk were an individual exposed to the maximum level of a pollutant for a lifetime.

In past residual risk actions, the EPA presented and considered a number of human health risk metrics associated with emissions from the category under review, including: The MIR; the numbers of persons in various risk ranges; cancer incidence; the maximum noncancer HI; and the maximum acute noncancer hazard. See,

e.g.,

75 FR 65068, 65072-74 (Oct. 21, 2010), and 76 FR 22566, 22575 (Apr. 21, 2011). In estimating risks, the EPA considered sources under review that are located near each other and that affect the same population. The EPA developed risk estimates based on the actual emissions from the source category under review as well as based on the maximum emissions allowed pursuant to the source category MACT standards. The EPA also discussed and considered risk estimation uncertainties. The EPA is providing this same type of information in support of these actions.

The agency is considering all available health information to inform our determinations of risk acceptability and ample margin of safety under CAA section 112(f). Specifically, as explained in the Benzene NESHAP, “the first step judgment on acceptability cannot be reduced to any single factor” and thus “[t]he Administrator believes that the acceptability of risk under [previous] section 112 is best judged on the basis of a broad set of health risk measures and information.” 54 FR 38046.

Similarly, with regard to making the ample margin of safety determination, as stated in the Benzene NESHAP, “[i]n 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 cost and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors.”

Id.

The agency acknowledges that the Benzene NESHAP provides flexibility regarding what factors the EPA might consider in making our determinations and how they might be weighed for each source category. In responding to comment on our policy under the Benzene NESHAP, the EPA explained that: “The policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of noncancer health effects and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the Vinyl Chloride mandate that the Administrator ascertain an acceptable level of risk to the public by employing [her] expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations and, thereby, implicitly permits consideration of any and all measures of health risk which the Administrator, in [her] judgment, believes are appropriate to determining what will `protect the public health.' ” 54 FR 38057.

Thus, the level of the MIR is only one factor to be weighed in determining acceptability of risks. The Benzene NESHAP explains “an MIR of approximately one in 10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an overall judgment on acceptability. Or, the agency may find, in a particular case, that a risk that includes MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors.”

Id.

at 38045. Similarly, with regard to the ample margin of safety analysis, the Benzene NESHAP states that: “EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category.”

Id.

at 38061.

D. How did we perform the technology review?

Our technology review is focused on the identification and evaluation of “developments in practices, processes, and control technologies.” If a review of available information identifies such developments, then we conduct an analysis of the technical feasibility of requiring the implementation of these developments, along with the impacts (costs, emission reductions, risk reductions,

etc.

). We then make a decision on whether it is necessary to amend the regulation to require compliance with revised standards in light of these developments. This has become our standard practice in conducting technology reviews. See,

e.g.,

75 FR 65068, 65083 (October 21, 2010).

Based on specific knowledge of each source category, we began by identifying known developments in practices, processes and control technologies. For the purpose of this exercise, we considered any of the following to be a “development”:

• Any add-on control technology or other equipment that was not identified and considered during MACT development;

• Any improvements in add-on control technology or other equipment (that was identified and considered during MACT development) that could result in significant additional emission reduction;

• Any work practice or operational procedure that was not identified and considered during MACT development; and

• Any process change or pollution prevention alternative that could be broadly applied that was not identified and considered during MACT development.

In addition to looking back at practices, processes or control technologies reviewed at the time we developed the MACT standards, we reviewed a variety of sources of data to aid in our evaluation of whether there were additional practices, processes or controls to consider. One of these sources of data was subsequent air toxics rules. Since the promulgation of the MACT standards for the source categories addressed in this proposal, the EPA has developed air toxics regulations for a number of additional source categories. In these subsequent air toxic regulatory actions, we consistently evaluated any new practices, processes and control technologies. We reviewed the regulatory requirements and/or technical analyses associated with these subsequent regulatory actions to identify any practices, processes and control technologies considered in these efforts that could possibly be applied to emission sources in the source categories under this current RTR review.

We also consulted the EPA's RBLC. The terms “RACT,” “BACT” and “LAER” are acronyms for different program requirements under the CAA provisions addressing the national ambient air quality standards. Control technologies classified as RACT, BACT or LAER apply to stationary sources depending on whether the sources are existing or new and on the size, age and location of the facility. BACT and LAER (and sometimes RACT) are determined on a case-by-case basis, usually by state or local permitting agencies. The EPA established the RBLC to provide a central data base of air pollution technology information (including technologies required in source-specific permits) to promote the sharing of information among permitting agencies and to aid in identifying future possible control technology options that might apply broadly to numerous sources within a category or apply only on a source-by-source basis. The RBLC contains over 5,000 air pollution control permit determinations that can help identify appropriate technologies to mitigate many air pollutant emission streams. We searched this database to determine whether any practices, processes or control technologies are included for the types of processes used for emission sources (

e.g.,

tanks or vents) in the source categories under consideration in this proposal.

We also reviewed other information sources, such as state or local permitting agency databases and industry-supported databases.

E. What other issues are we addressing in this proposal?

In addition to the RTR performed regarding the NESHAP, we are also proposing revisions to the NESHAP to address emissions during periods of startup, shutdown and malfunction (SSM) and revisions to require electronic reporting of emissions test results.

1. Startup, Shutdown and Malfunction (SSM)

The United States Court of Appeals for the District of Columbia Circuit vacated portions of two provisions in the EPA's CAA Section 112 regulations governing the emissions of HAP during periods of SSM.

Sierra Club

EPA,

551 F.3d 1019 (DC Cir. 2008),

cert. denied,

130 S. Ct. 1735 (U.S. 2010). Specifically, the Court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), that are part of a regulation, commonly referred to as the “General Provisions Rule,” that the EPA promulgated under section 112 of the CAA. When incorporated into CAA section 112(d) regulations for specific source categories, these two provisions exempt sources from the requirement to comply with the otherwise applicable CAA section 112(d) emission standard during periods of SSM.

As we have done in other recent risk and technology review rulemakings, we are proposing the elimination of the SSM exemption in each of the three MACT standards addressed by this rule. See,

e.g.,

76 FR 22568, 22573 (Apr. 21, 2011). Consistent with

Sierra Club

EPA,

the EPA is proposing standards in these rules that apply at all times. We are also proposing several revisions to the General Provisions Applicability table in each of the MACT standards. For example, we are proposing to eliminate the incorporation of the General Provisions' requirement that the source develop an SSM plan. We also are proposing to eliminate or revise certain recordkeeping and reporting related to the SSM exemption. The EPA has attempted to ensure that we have not included in the proposed regulatory language any provisions that are inappropriate, unnecessary or redundant in the absence of the SSM exemption. We are specifically seeking comment on whether there are any such provisions that we have inadvertently incorporated or overlooked.

In proposing the standards in these rules, the EPA has taken into account startup and shutdown periods and has not proposed different standards for those periods because we expect the difference in emission levels during periods of startup and shutdown are insignificant and that facilities in these source categories should be able to comply with the standards during these times.

Periods of startup, normal operation and shutdown are all predictable and routine aspects of a source's operations. However, by contrast, malfunction is defined as a “sudden, infrequent, and not reasonably preventable failure of air pollution control and monitoring equipment, process equipment or a process to operate in a normal or usual manner * * *.” (40 CFR 63.2). The EPA has determined that CAA section 112 does not require that emissions that occur during periods of malfunction be factored into development of CAA section 112 standards. Under section 112, emissions standards for new sources must be no less stringent than the level “achieved” by the best controlled similar source and for existing sources generally must be no less stringent than the average emission limitation “achieved” by the best performing 12 percent of sources in the category. There is nothing in section 112 that directs the agency to consider malfunctions in determining the level “achieved” by the best performing or best controlled sources when setting emission standards. Moreover, while the EPA accounts for variability in setting emissions standards consistent with the CAA section 112 caselaw, nothing in that caselaw requires the agency to consider malfunctions as part of that analysis. Section 112 uses the concept of “best controlled” and “best performing” unit in defining the level of stringency that CAA section 112 performance standards must meet. Applying the concept of “best controlled” or “best performing” to a unit that is malfunctioning presents significant difficulties, as malfunctions are sudden and unexpected events.

Further, accounting for malfunctions would be difficult, if not impossible, given the myriad different types of malfunctions that can occur across all sources in the category and given the difficulties associated with predicting or accounting for the frequency, degree and duration of various malfunctions that might occur. As such, the performance of units that are malfunctioning is not “reasonably” foreseeable. See,

e.g., Sierra Club

EPA,

167 F. 3d 658, 662 (DC Cir. 1999) (The EPA typically has wide latitude in determining the extent of data-gathering necessary to solve a problem. We generally defer to an agency's decision to proceed on the basis of imperfect scientific information, rather than to “invest the resources to conduct the perfect study.”). See also,

Weyerhaeuser

Costle,

590 F.2d 1011, 1058 (DC Cir. 1978) (“In the nature of things, no general limit, individual permit, or even any upset provision can anticipate all upset situations. After a certain point, the transgression of regulatory limits caused by `uncontrollable acts of third parties,' such as strikes, sabotage, operator intoxication or insanity, and a variety of other eventualities, must be a matter for the administrative exercise of case-by-case enforcement discretion, not for specification in advance by regulation.”). In addition, the goal of a best controlled or best performing source is to operate in such a way as to avoid malfunctions of the source, and accounting for malfunctions could lead to standards that are significantly less stringent than levels that are achieved by a well-performing non-malfunctioning source. The EPA's approach to malfunctions is consistent with section 112 and is a reasonable interpretation of the statute.)

In the event that a source fails to comply with the applicable CAA section 112(d) standards as a result of a malfunction event, the EPA would determine an appropriate response based on, among other things, the good faith efforts of the source to minimize emissions during malfunction periods, including preventative and corrective actions, as well as root cause analyses to ascertain and rectify excess emissions. The EPA would also consider whether the source's failure to comply with the CAA section 112(d) standard was, in fact, “sudden, infrequent, not reasonably preventable” and was not instead “caused in part by poor maintenance or careless operation.” 40 CFR 63.2 (definition of malfunction).

Finally, the EPA recognizes that even equipment that is properly designed and maintained can sometimes fail and that such failure can sometimes cause an exceedance of the relevant emission standard. (See,

e.g.,

State Implementation Plans: Policy Regarding Excessive Emissions During Malfunctions, Startup, and Shutdown (Sept. 20, 1999); Policy on Excess Emissions During Startup, Shutdown, Maintenance, and Malfunctions (Feb. 15, 1983)). The EPA is, therefore, proposing to follow its recently established practice (see,

e.g.,

76 FR 22566, 22573-74 (Apr. 21, 2011)) and add to the rules an affirmative defense to civil penalties for exceedances of emission limits that are caused by malfunctions. See proposed 40 CFR 63.1312 (Group IV Polymers and Resins), 40 CFR 63.1361 (PAI) and 40 CFR 63.1423 (PEPO). The regulations define “affirmative defense” to mean, in the context of an enforcement proceeding, a response or defense put forward by a defendant, regarding which the defendant has the burden of proof, and the merits of which are independently and objectively evaluated in a judicial or administrative proceeding. We also are proposing other regulatory provisions to specify the

elements that are necessary to establish this affirmative defense; the source must prove by a preponderance of the evidence that it has met all of the elements set forth in proposed 40 CFR 63.1310(k) (Group IV Polymers and Resins), 40 CFR 63.1360(k) (PAI) and 40 CFR 63.1420(i) (PEPO). (See 40 CFR 22.24). The criteria ensure that the affirmative defense is available only where the event that causes an exceedance of the emission limit meets the narrow definition of malfunction in 40 CFR 63.2 (sudden, infrequent, not reasonable preventable and not caused by poor maintenance and or careless operation). For example, to successfully assert the affirmative defense, the source must prove by a preponderance of the evidence that excess emissions “[w]ere caused by a sudden, infrequent, and unavoidable failure of air pollution control and monitoring equipment, process equipment, or a process to operate in a normal or usual manner * * *.” The criteria also are designed to ensure that steps are taken to correct the malfunction, to minimize emissions in accordance with proposed 40 CFR 63.1310(j)(4) (Group IV Polymers and Resins), 40 CFR 63.1362(i) (PAI) and 40 CFR 63.1420(h)(4) (PEPO) and to prevent future malfunctions. For example, the source must prove by a preponderance of the evidence that “[r]epairs were made as expeditiously as possible when the applicable emission limitations were being exceeded * * *” and that “[a]ll possible steps were taken to minimize the impact of the excess emissions on ambient air quality, the environment and human health * * *.” In any judicial or administrative proceeding, the Administrator may challenge the assertion of the affirmative defense and, if the respondent has not met its burden of proving all of the requirements in the affirmative defense, appropriate penalties may be assessed in accordance with section 113 of the CAA (see also 40 CFR 22.27).

The EPA included an affirmative defense in these proposed rules in an attempt to balance a tension, inherent in many types of air regulation, to ensure adequate compliance while simultaneously recognizing that despite the most diligent of efforts, emission limits may be exceeded under circumstances beyond the control of the source. The EPA must establish emission standards that “limit the quantity, rate, or concentration of emissions of air pollutants on a continuous basis.” 42 U.S.C. 7602(k) (defining “emission limitation and emission standard”). See generally,

Sierra Club

EPA,

551 F.3d 1019, 1021 (D.C. Cir. 2008). Thus, the EPA is required to ensure that section 112 emissions limitations are continuous. The affirmative defense for malfunction events meets this requirement by ensuring that even where there is a malfunction, the emission limitation is still enforceable through injunctive relief. While “continuous” limitations, on the one hand, are required, there is also caselaw indicating that in many situations it is appropriate for the EPA to account for the practical realities of technology. For example, in

Essex Chemical

Ruckelshaus,

486 F.2d 427, 433 (D.C. Cir. 1973), the District of Columbia Circuit acknowledged that, in setting standards under CAA section 111, “variant provisions” such as provisions allowing for upsets during startup, shutdown and equipment malfunction “appear necessary to preserve the reasonableness of the standards as a whole and that the record does not support the `never to be exceeded' standard currently in force.” See also,

Portland Cement Association

Ruckelshaus,

486 F.2d 375 (D.C. Cir. 1973). Though intervening caselaw such as

Sierra Club

EPA

and the CAA 1977 amendments undermine the relevance of these cases today, they support the EPA's view that a system that incorporates some level of flexibility is reasonable. The affirmative defense simply provides for a defense to civil penalties for excess emissions that are proven to be beyond the control of the source. By incorporating an affirmative defense, EPA has formalized its approach to upset events. In a Clean Water Act setting, the Ninth Circuit required this type of formalized approach when regulating “upsets beyond the control of the permit holder.”

Marathon Oil Co.

EPA,

564 F.2d 1253, 1272-73 (9th Cir. 1977). See,

Weyerhaeuser Co.

Costle,

590 F.2d 1011, 1057-58 (D.C. Cir. 1978) (holding that an informal approach is adequate). The affirmative defense provisions give the EPA the flexibility to both ensure that its emission limitations are “continuous” as required by 42 U.S.C. section 7602(k), and account for unplanned upsets and thus support the reasonableness of the standard as a whole.

In addition to these changes in the provisions related to SSM, we are also proposing that there be no discharge to the atmosphere from any pressure relief device (PRD) on any equipment in HAP service within the process units for these seven source categories. To ensure compliance with this requirement, facility owners or operators would be required to install electronic indicators on each PRD that would be able to identify and record the time and duration of each pressure release and notify operators that a pressure release has occurred. While pressure release events may be associated with unplanned, nonroutine discharges that result from operator error, malfunctions or other unexpected causes that require immediate venting of gas from process equipment in order to avoid safety hazards or equipment damage, we are concerned that a large number of these releases that occur may emit large quantities of HAP, may not be identified and controlled in a timely manner and may be due to repeat problems that have not been corrected. These proposed provisions will clarify that such release events would be violations of the emissions standards of these rules. If any pressure release events that occur are related to a process or control device malfunction, the owner or operator could claim the affirmative defense described above.

2. Electronic Reporting

We are proposing to add electronic reporting requirements to the PAI, PEPO and the Group IV Polymers and Resin Production NESHAP. The EPA must have performance test data to conduct effective reviews of CAA section 112 standards, as well as for many other purposes including compliance determinations, emission factor development and annual emission rate determinations. In conducting these required reviews, the EPA has found it ineffective and time consuming, not only for us, but also for regulatory agencies and source owners and operators, to locate, collect and submit performance test data because of varied locations for data storage and varied data storage methods. In recent years, though, stack testing firms have typically collected performance test data in electronic format, making it possible to move to an electronic data submittal system that would increase the ease and efficiency of data submittal and improve data accessibility.

Through this proposal, the EPA is presenting a step to increase the ease and efficiency of data submittal and improve data accessibility. Specifically, the EPA is proposing that owners and operators of PAI, PEPO and Group IV Polymers and Resins facilities submit electronic copies of required performance test reports to the EPA's WebFIRE database. The WebFIRE database was constructed to store performance test data for use in developing emission factors. A description of the WebFIRE database is

available at

http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main.

As proposed above, data entry would be through an electronic emissions test report structure called the Electronic Reporting Tool (ERT). The ERT would generate electronic report which would be submitted using the Compliance and Emissions Data Reporting Interface (CEDRI). The submitted report would be transmitted through the EPA's Central Data Exchange (CDX) network for storage in the WebFIRE database making submittal of data very straightforward and easy. A description of the ERT can be found at

http://www.epa.gov/ttn/chief/ert/index.html

and CEDRI can be accessed through the CDX Web site (

http://www.epa.gov/cdx

The proposal to submit performance test data electronically to the EPA would apply only to those performance tests conducted using test methods that will be supported by the ERT. The ERT contains a specific electronic data entry form for most of the commonly used EPA reference methods. A listing of the pollutants and test methods supported by the ERT is available at

http://www.epa.gov/ttn/chief/ert/index.html.

We believe that industry would benefit from this proposed approach to electronic data submittal. Having these data, the EPA would be able to develop improved emission factors, make fewer information requests and promulgate better regulations.

One major advantage of the proposed submittal of performance test data through the ERT is a standardized method to compile and store much of the documentation required to be reported by this rule. Another advantage is that the ERT clearly states what testing information would be required. Another important proposed benefit of submitting these data to the EPA at the time the source test is conducted is that it should substantially reduce the effort involved in data collection activities in the future. When the EPA has performance test data in hand, there will likely be fewer or less substantial data collection requests in conjunction with prospective required residual risk assessments or technology reviews. This would result in a reduced burden on both affected facilities (in terms of reduced manpower to respond to data collection requests) and the EPA (in terms of preparing and distributing data collection requests and assessing the results).

State, local and tribal agencies could also benefit from more streamlined and accurate review of electronic data submitted to them. The ERT would allow for an electronic review process rather than a manual data assessment making review and evaluation of the source provided data and calculations easier and more efficient. Finally, another benefit of the proposed data submittal to WebFIRE electronically is that these data would greatly improve the overall quality of existing and new emissions factors by supplementing the pool of emissions test data for establishing emissions factors and by ensuring that the factors are more representative of current industry operational procedures. A common complaint heard from industry and regulators is that emission factors are outdated or not representative of a particular source category. With timely receipt and incorporation of data from most performance tests, the EPA would be able to ensure that emission factors, when updated, represent the most current range of operational practices. In summary, in addition to supporting regulation development, control strategy development and other air pollution control activities, having an electronic database populated with performance test data would save industry, state, local, tribal agencies and the EPA significant time, money and effort while also improving the quality of emission inventories and, as a result, air quality regulations.

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

A. Acrylonitrile Butadiene Styrene Resin (ABS)

1. What are the results of the risk assessments?

a. Inhalation Risk Assessment Results

Table 3 provides an overall summary of the inhalation risk assessment results for the source category.

Table 3—ABS Inhalation Risk Assessment Results

Number of

facilities

Maximum

individual

cancer risk

(in 1 million)

Actual emissions level

Allowable emissions level

Population

at risk

≥

1-in-1 million

Annual cancer incidence

(cases per year)

Maximum

chronic noncancer

TOSHI

Actual emissions level

Allowable emissions level

Maximum off-site acute noncancer

32,000

0.003

0.2

REL

= 2 acetaldehyde.

ERPG-1

= 0.04 acetaldehyde.

Number of facilities evaluated in the risk analysis.

Maximum individual excess lifetime cancer risk.

Maximum TOSHI. The target organ with the highest TOSHI for the ABS source category is the reproductive system.

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

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

more detail about this estimate of the ratio of actual to MACT-allowable emissions and the estimation of MACT-allowable emission levels and associated risks and impacts, see the memorandum,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

There were no reported emissions of PB-HAP; therefore, we do not expect potential for human health multipathway risks or adverse environmental impacts as a result of PB-HAP.

b. Facility-Wide Risk Assessment Results

Table 4 displays the results of the facility-wide risk assessment. This assessment was conducted based on actual emission levels. For detailed facility-specific results, see Appendix 4 of the

Draft Residual Risk Assessment for 7 Source Categories

in the docket for this rulemaking.

Table 4—ABS Facility-Wide Risk Assessment Results

Number of facilities analyzed

Cancer Risk:*

Estimated maximum facility-wide individual cancer risk (in 1 million)

Number of facilities with estimated facility-wide individual cancer risk of 100-in-1 million or more

Number of facilities at which the ABS source category contributes 50 percent or more to the facility-wide individual cancer risks of 100-in-1 million or more

Number of facilities at which the ABS source category contributes 50 percent or more to the facility-wide individual cancer risk of 1-in-1 million or more

Chronic Noncancer Risk:

Maximum facility-wide chronic noncancer TOSHI

< 1

Number of facilities with facility-wide maximum noncancer TOSHI greater than 1

Number of facilities at which the ABS source category contributes 50 percent or more to the facility-wide maximum noncancer TOSHI of 1 or more

The facility-wide MIR from all HAP emissions at a facility that contains sources subject to the Group IV Polymers and Resins MACT standards for ABS resins is estimated to be 30-in-1 million, based on actual emissions. Of the 5 facilities included in this analysis, none have a facility-wide MIR of 100-in-1 million. There are 4 facilities with facility-wide MIR of 1-in-1 million or greater (MIR ranging from 10 to 30 in a million). Each of these facilities has ABS production operations that contribute greater than 50 percent to the facility-wide risks.

The facility-wide maximum individual chronic noncancer TOSHI is estimated to be less than 1, based on actual emissions. Of the 5 facilities included in this analysis, none have facility-wide maximum chronic noncancer TOSHI values greater than 1.

c. What is our proposed decision regarding risk acceptability?

As noted in section III.C of this preamble, we weigh all health risk factors in our risk acceptability determination, including the MIR; the number of persons in various cancer and noncancer risk ranges; cancer incidence; the maximum noncancer HI; the maximum acute noncancer HQ; the extent of noncancer risks; the potential for adverse environmental effects; distribution of cancer and noncancer risks in the exposed population; and risk estimation uncertainty (54 FR 38044, September 14, 1989).

For the ABS source category, the risk analysis we performed indicates that the cancer risks to the individual most exposed could be up to 30-in-1 million due to both actual and allowable emissions. This value is considerably less than 100-in-1 million, which is the presumptive level of acceptability. The risk analysis also shows low cancer incidence (1 in every 333 years), no potential for human health multipathway effects, and that chronic noncancer health impacts are unlikely.

We estimate that the worst-case acute HQ value could exceed a value of 1 for one HAP, acetaldehyde, with a potential maximum HQ up to 2 based on the acute REL dose-response value. Only one of the five facilities in this source category had an estimated HQ greater than 1 (REL of 2 for acetaldehyde). All other facilities modeled had an HQ less than 1. The maximum HQ based on an AEGL-1 or ERPG-1 dose-response value is 0.04 for acetaldehyde based on the ERPG-1. As described earlier in this preamble, the acute assessment includes some conservative assumptions and some uncertainties. Moreover, the REL are protective and designed to protect the most sensitive individuals in the population by inclusion of margins of safety and exposures above the REL do not necessarily indicate that adverse effects will occur. Considering the improbable assumption that worst-case meteorological conditions are present at the same time that maximum hourly emissions of acetaldehyde exceed the average hourly emission rate by a factor of 10 at all emission points simultaneously, coincident with individuals being in the location of maximum impact, and considering the low acute HQ values based on the AEGL-1 and ERPG-1 dose-response values collectively with the REL value, we believe it is unlikely that HAP emissions from this source category would result in acute health effects.

Our additional analysis of facility-wide risks showed that the maximum facility-wide cancer risk is 30-in-1 million and that the maximum chronic exposures are expected to be without appreciable risk of adverse noncancer health effects.

The EPA has weighed the various health risk measures and health factors, including risk estimation uncertainty, discussed above and in section III.B.7 of this preamble, and we are proposing that the risks from the ABS source category are acceptable.

d. What is our proposed decision regarding ample margin of safety?

We considered whether the MACT standards provide an ample margin of safety to protect public health. In this analysis, we investigated available emissions control options that might reduce the risk associated with emissions from the source category and considered this information along with all of the health risks and other health information considered in the risk acceptability determination.

For the ABS source category, we identified only one control option to further address risks from equipment leaks. This control option would require sources to install leakless valves to prevent leaks from those components.

While approximately 15 percent of the emissions from this source category are due to equipment leaks, these emissions do not contribute to the maximum individual cancer risks estimated for the source category.

We estimated HAP reduction resulting from this control option is approximately 6 tpy from the baseline actual emissions level. We estimated that achieving these reductions would involve a capital cost of approximately $11,000,000, a total annualized cost of about $1,500,000 and a cost effectiveness of $244,000 per ton of HAP emissions reduced. The additional control requirement would not achieve a reduction in the maximum individual cancer risks. We estimate that the MACT allowable emissions from this source category are approximately equal to the reported, actual emissions. Therefore, the estimated emission reduction, risk reduction and costs discussed above would also be applicable to the MACT allowable emissions level. We believe that the costs of this option are not reasonable, given the level of emission and risk reduction.

In accordance with the approach established in the Benzene NESHAP, the EPA weighed all health risk measures and information considered in the risk acceptability determination, along with the costs and economic impacts of emissions controls, technological feasibility, uncertainties and other relevant factors in making our ample margin of safety determination. Considering the health risk information and the unreasonable cost effectiveness of the option identified, we propose that the existing MACT standards provide an ample margin of safety to protect public health and prevent an adverse environmental effect.

2. What are the results of the technology review?

In the decade since the Group IV Polymers and Resins MACT standards were promulgated, the EPA has developed 19 air toxics regulations for source categories that emit organic HAP from the same type of emissions sources that are present in the five Group IV Polymers and Resins source categories addressed in this proposed action. We reviewed the regulatory requirements and/or technical analyses for these 19 regulations for new practices, processes and control technologies. We also conducted a search of the RBLC for controls for VOC-SOCMI categories with permits dating back to 1997.

We identified no advancements in practices, processes, and control technologies applicable to the emission sources in the Group IV Polymers and Resins source categories in our technology review.

3. What other actions are we proposing?

a. SSM Provisions

We are proposing to eliminate the SSM exemption in the Group IV Polymers and Resins MACT standards. Consistent with

Sierra Club

EPA,

the EPA is proposing that standards in this rule would apply at all times. We are proposing several revisions to 40 CFR part 63, subpart JJJ. Specifically, we are proposing to revise Table 1 to indicate that the requirements of 40 CFR 63.6(e) of the General Provisions do not apply. The 40 CFR 63.6(e) requires the owner or operator to act according to the general duty to “operate and maintain any affected source, including associated air pollution control equipment and monitoring equipment, in a manner consistent with safety and good air pollution control practices for minimizing emissions.” We are separately proposing to incorporate this general duty to minimize into 40 CFR 63.1310(j)(4). The 40 CFR 63.6(e) also requires the owner or operator of an affected source to develop a written SSM plan. We are proposing to remove the SSM plan requirement. We are proposing to remove the explanation of applicability of emissions standards during periods SSM in 40 CFR 63.1310(j); remove the malfunction plan from 40 CFR 63.1335(b); clarify that representative conditions do not include periods of SSM throughout the rule; remove references to periods of SSM in monitoring; remove the provisions for excused excursions from 40 CFR 63.1334(g); and revise the SSM-associated recordkeeping and reporting requirements in 40 CFR 63.1335(b) to require reporting and recordkeeping for periods of malfunction. We are also proposing to revise Table 1 to indicate that SSM-related provisions in 40 CFR 63.6(e)(1), 63.6(e)(3), 63.6(f)(1); 40 CFR 63.7(e)(1); 40 CFR 63.8(c)(1); and 40 CFR 63.10(d)(5) of the General Provisions do not apply. We are also proposing to add requirements in 40 CFR 63.1331(a)(9)) to clarify that PRD releases to the atmosphere are violations of the emissions standards and to require pressure release alarms and to add requirements in 40 CFR 63.1335(e)(9) to require reporting of any pressure device releases to the atmosphere with the periodic report. In addition, we are proposing to promulgate an affirmative defense against civil penalties for exceedances of emission standards caused by malfunctions, as well as criteria for establishing the affirmative defense.

b. Electronic Reporting

To increase the ease and efficiency of data submittal and improve data accessibility, we are proposing to require the submission of electronic copies of required performance tests for test methods that are supported by the ERT to EPA's WebFIRE database. These provisions are added in 40 CFR 63.1335(e)(10).

B. Styrene Acrylonitrile Resin (SAN)

1. What are the results of the risk assessments?

a. Inhalation Risk Assessment Results

Table 5 provides an overall summary of the inhalation risk assessment results for the source category.

Table 5—SAN Inhalation Risk Assessment Results

Number of

facilities

Maximum individual cancer risk

(in 1 million)

Actual emissions level

Allowable emissions level

Population at risk ≥ 1-in-1 million

Annual cancer incidence (cases per year)

Maximum chronic noncancer TOSHI

Actual emissions level

Allowable emissions level

Maximum off-site acute noncancer HQ

0.03

0.000006

0.0002

REL

= 0.007 methylene chloride.

Number of facilities evaluated in the risk analysis.

Maximum individual excess lifetime cancer risk.

Maximum TOSHI. The target organ with the highest TOSHI for the SAN source category is the respiratory system.

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

The inhalation risk modeling was performed using actual emissions level data. As shown in Table 5, the results of the inhalation risk assessment indicated the maximum lifetime individual cancer risk could be up to 0.03-in-1 million, the maximum chronic noncancer TOSHI value could be up to 0.0002, and the maximum off-facility site acute HQ value could be up to 0.007, based on the actual emissions level and the REL value for methylene chloride. The total estimated national cancer incidence from these facilities based on actual emission levels is 0.000006 excess cancer cases per year or one case in every 166,666 years.

Based on our analysis, we believe that actual emissions approximate emissions allowable under the MACT standards. Therefore, the risk results for MACT-allowable emissions are approximately equal to those for actual emissions. For more detail about this estimate of the ratio of actual to MACT-allowable emissions and the estimation of MACT-allowable emission levels and associated risks and impacts, see the memorandum,

MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV Production Source Categories,

in the docket for this rulemaking.

There were no reported emissions of PB-HAP; therefore, we do not expect potential for human health multipathway risks or adverse environmental impacts as a result of PB-HAP.

b. Facility-Wide Risk Assessment Results

Table 6 displays the results of the facility-wide risk assessment. This assessment was conducted based on actual emission levels. For detailed facility-specific results, see Appendix 4 of the

Draft Residual Risk Assessment for 7 Source Categories

in the docket for this rulemaking.

Table 6—SAN Facility-Wide Risk Assessment Results

Number of facilities analyzed

Cancer Risk:

Estimated maximum facility-wide individual cancer risk (in 1 million)

Number of facilities with estimated facility-wide individual cancer risk of 100-in-1 million or more

Number of facilities at which the SAN source category contributes 50 percent or more to the facility-wide individual cancer risks of 100-in-1 million or more

Number of facilities at which the SAN source category contributes 50 percent or more to the facility-wide individual cancer risk of 1-in-1 million or more

Chronic Noncancer Risk:

Maximum facility-wide chronic noncancer TOSHI

Number of facilities with facility-wide maximum noncancer TOSHI greater than 1

Number of facilities at which the SAN source category contributes 50 percent or more to the facility-wide maximum noncancer TOSHI of 1 or more

The facility-wide MIR from all HAP emissions at a facility that contains sources subject to the Group IV Polymers and Resins MACT standards for SAN resins is estimated to be 20-in-1 million, based on actual emissions. Of the 2 facilities included in this analysis, none have a facility-wide MIR of 100-in-1 million. There are 2 facilities with facility-wide MIR of 1-in-1 million or greater (MIR of 20 and 10 in a million). Neither of these facilities have SAN production operations that contribute greater than 50 percent to the facility-wide risks.

The facility-wide maximum individual chronic noncancer TOSHI is estimated to be 2, based on actual emissions. Of the 2 facilities included in this analysis, only one facility has a facility-wide maximum chronic noncancer TOSHI value greater than 1 (TOSHI of 2).

c. What is our proposed decision regarding risk acceptability?

For the SAN source category, the risk analysis we performed indicates that the cancer risks to the individual most exposed could be up to 0.03-in-1 million due to both actual and allowable emissions. This value is less than 1-in-1 million. The risk analysis also shows low cancer incidence (1 in every 166,666 years), no potential for human health multipathway effects and that chronic noncancer and acute health effects are unlikely.

Our additional analysis of facility-wide risks showed that the maximum facility-wide cancer risk is 20-in-1 million. The maximum chronic noncancer TOSHI is estimated to be 2, but the source category contributes less than 1 percent to the maximum facility-wide TOSHI.

d. What is our proposed decision regarding ample margin of safety?

The SAN source category emits HAP which are known, probable or possible carcinogens. The EPA evaluated the emissions of these HAP and determined that the cancer risks to the individual most exposed are less than 1-in-1 million. Our analysis demonstrated that chronic noncancer risks are expected to be low, based on actual and MACT allowable emissions. We determined that emissions from the SAN source category would result in a chronic noncancer TOSHI less than 1 and an acute HQ less than 1 for the individual most exposed. The EPA undertook further analysis to assess whether environmental effects might result from

emissions from this source category. We assume that human toxicity values for the inhalation pathway are generally protective of terrestrial mammals and plants, and thus, we do not anticipate that actual or MACT allowable emissions would result in acute or chronic noncancer health effects to these mammals. While we believe this to be generally true, we acknowledge that there is some associated uncertainty with this assumption. In addition, this source category had no reported emissions of PB-HAP and, therefore, no potential for an adverse environment effect via multipathway exposures was identified as a result of PB-HAP.

2. What are the results of the technology review?

The results of the technology review for the Group IV Polymers and Resins MACT standards are discussed above in section IV.A.2. We identified no advancements in practices, processes, and control technologies applicable to the emission sources in the Group IV Polymers and Resins source categories in our technology review.

3. What other actions are we proposing?

a. SSM Provisions

The proposed changes to the SSM provisions for the Group IV Polymers and Resins MACT standards, which apply to the SAN source category, are discussed above in section IV.A.3.a.

b. Electronic Reporting

The proposed addition of electronic reporting requirements for performance tests for the Group IV Polymers and Resins MACT standards, which apply to the SAN source category, is discussed above in section IV.A.3.b.

C. Methyl Methacrylate Butadiene Styrene Resin (MBS)

1. What are the results of the risk assessments?

a. Inhalation Risk Assessment Results

Table 7 provides an overall summary of the inhalation risk assessment results for the source category.

Table 7—MBS Inhalation Risk Assessment Results

Number of

facilities

Maximum individual cancer risk

(in 1 million)

Actual emissions level

Allowable emissions level

Population at risk ≥ 1-in-1 million

Annual cancer incidence (cases per year)

Maximum chronic noncancer TOSHI

Actual emissions level

Allowable emissions level

Maximum off-site acute noncancer HQ

0.4

0.00003

0.007

ERPG-1

= 9 ethyl acrylate.

AEGL-1

= 0.01 ethyl a

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