# National Emission Standards for Hazardous Air Pollutants for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2016-30758 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** December 30, 2016 - **Citation:** 81 FR 97046 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 63 [EPA-HQ-OAR-2014-0741; FRL-9957-07-OAR] RIN 2060-AS46 National Emission Standards for Hazardous Air Pollutants for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills to address the results of the residual risk and technology review (RTR) that the EPA is required to conduct under the Clean Air Act (CAA). These proposed amendments include revisions to the opacity monitoring provisions; addition of electrostatic precipitator (ESP) parameter monitoring provisions; a requirement for 5-year periodic emissions testing; revisions to provisions addressing periods of startup, shutdown, and malfunction (SSM); and technical and editorial changes. The EPA is proposing these amendments to improve the effectiveness of the rule. DATES: Comments. Comments must be received on or before February 28, 2017. Under the Paperwork Reduction Act (PRA), comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of your comments on or before January 30, 2017. Public Hearing. A public hearing will be held if requested by January 4, 2017. ADDRESSES: Comments. Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2014-0741, at http://www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov . The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (i.e., on the Web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets. Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-2014-0741. 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 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 not include special characters or 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/dockets. Docket. The EPA has established a docket for this rulemaking under Docket ID No. EPA-HQ-OAR-2014-0741. All documents in the docket are listed in the 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 Regulations.gov or in hard copy at the EPA Docket Center, Room 3334, EPA WJC West Building, 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. A public hearing will be held, if requested by January 4, 2017, to accept oral comments on this proposed action. If a hearing is requested, it will be held at the EPA's Washington, DC campus located at 1201 Constitution Avenue NW., Washington, DC. The hearing, if requested, will begin at 9:00 a.m. (local time) and will conclude at 5:00 p.m. (local time) on January 17, 2017. To request a hearing, to register to speak at a hearing, or to inquire if a hearing will be held, please contact Ms. Aimee St. Clair at (919) 541-1063 or by email at stclair.aimee@epa.gov. The last day to pre-register to speak at a hearing, if one is held, will be January 12, 2017. Additionally, requests to speak will be taken the day of the hearing at the hearing registration desk, although preferences on speaking times may not be able to be fulfilled. Please note that registration requests received before the hearing will be confirmed by the EPA via email. The EPA will make every effort to accommodate all speakers who arrive and register. Because the hearing will be held at a United States governmental facility, individuals planning to attend the hearing should be prepared to show valid picture identification to the security staff in order to gain access to the meeting room. Please note that the REAL ID Act, passed by Congress in 2005, established new requirements for entering federal facilities. If your driver's license is issued by Alaska, American Samoa, Arizona, Kentucky, Louisiana, Maine, Massachusetts, Minnesota, Montana, New York, Oklahoma or the state of Washington, you must present an additional form of identification to enter the federal building. Acceptable alternative forms of identification include: Federal employee badges, passports, enhanced driver's licenses and military identification cards. In addition, you will need to obtain a property pass for any personal belongings you bring with you. Upon leaving the building, you will be required to return this property pass to the security desk. No large signs will be allowed in the building, cameras may only be used outside of the building and demonstrations will not be allowed on federal property for security reasons. Please note that any updates made to any aspect of the hearing, including whether or not a hearing will be held, will be posted online at https://www.epa.gov/stationary-sources-air-pollution/kraft-soda-sulfite-and-stand-alone-semichemical-pulp-mills-mact-ii. We ask that you contact Ms. Aimee St. Clair at (919) 541-1063 or by email at stclair.aimee@epa.gov or monitor our Web site to determine if a hearing will be held. The EPA does not intend to publish a notice in the Federal Register announcing any such updates. Please go to https://www.epa.gov/stationary-sources-air-pollution/kraft-soda-sulfite-and-stand-alone-semichemical-pulp-mills-mact-ii for more information on the public hearing. FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Dr. Kelley Spence, Sector Policies and Programs Division (Mail Code: E143-03), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-3158; fax number: (919) 541-3470; and email address: spence.kelley@epa.gov. For specific information regarding the risk modeling methodology, contact Mr. James Hirtz, Health and Environmental Impacts Division (Mail Code: C539-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-0881; fax number: (919) 541-0840; and email address: hirtz.james@epa.gov. For information about the applicability of the NESHAP to a particular entity, contact Ms. Sara Ayres, Office of Enforcement and Compliance Assurance, U.S. Environmental Protection Agency, USEPA Region 5 (Mail Code: E-19J), 77 West Jackson Boulevard, Chicago IL 60604; telephone number: (312) 353-6266; and email address: ayres.sara@epa.gov. SUPPLEMENTARY INFORMATION: Preamble Acronyms and Abbreviations. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here: AEGL acute exposure guideline levels AERMOD air dispersion model used by the HEM-3 model ANSI American National Standards Institute ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATSDR Agency for Toxic Substances and Disease Registry BACT best available control technology BAT best available technology BLO black liquor oxidation BLS black liquor solids CAA Clean Air Act CaCO 3 calcium carbonate CalEPA California EPA CBI Confidential Business Information CEDRI Compliance and Emissions Data Reporting Interface CFR Code of Federal Regulations CMS continuous monitoring system COMS continuous opacity monitoring system CPMS continuous parameter monitoring system DCE direct contact evaporator EJ environmental justice EPA Environmental Protection Agency ERPG Emergency Response Planning Guidelines ERT Electronic Reporting Tool ESP electrostatic precipitator FR Federal Register gr/dscf grains per dry standard cubic foot HAP hazardous air pollutant HCCPD hexachlorocyclopentadiene HCl hydrochloric acid HEM-3 Human Exposure Model, Version 1.1.0 HF hydrogen fluoride HI hazard index HQ hazard quotient IBR incorporation by reference ICR Information Collection Request IRIS Integrated Risk Information System km kilometer LAER lowest achievable emission rate lb/hr pounds per hour lb/ton pounds per ton LOAEL lowest-observed-adverse-effect level MACT maximum achievable control technology mg/kg-day milligrams per kilogram per day mg/m 3 milligrams per cubic meter MIR maximum individual risk Na 2 CO 3 sodium carbonate Na 2 S sodium sulfide NAAQS National Ambient Air Quality Standards NAC National Advisory Committee NAICS North American Industry Classification System NaOH sodium hydroxide NAS National Academy of Sciences NATA National Air Toxics Assessment NCASI National Council for Air and Stream Improvement NDCE nondirect contact evaporator NEI National Emissions Inventory NESHAP National Emission Standards for Hazardous Air Pollutants NH 3 ammonia NOAA National Oceanic and Atmospheric Administration NOAEL no-observed-adverse-effect level NRC National Research Council NRDC Natural Resources Defense Council NSPS New Source Performance Standards NTTAA National Technology Transfer and Advancement Act O&M operation and maintenance O 2 oxygen OAQPS Office of Air Quality Planning and Standards OMB Office of Management and Budget PAH polycyclic aromatic hydrocarbons PB-HAP hazardous air pollutant known to be persistent and bio-accumulative in the environment PDF portable document format PEL probable effects level PM particulate matter PM 2.5 fine particles (particulate matter with particles less than 2.5 micrometers in diameter) POM polycyclic organic matter ppm parts per million PRA Paperwork Reduction Act PTC Performance Test Code QA quality assurance RACT reasonably available control technology RBLC RACT/BACT/LAER Clearinghouse REL reference exposure level RFA Regulatory Flexibility Act RfC reference concentration RfD reference dose RTO regenerative thermal oxidizer RTR residual risk and technology review SAB Science Advisory Board SCC source classification code SDT smelt dissolving tank SOP standard operating procedure SSM startup, shutdown, and malfunction STAPPA/ State and Territorial Air Pollution Program ALAPCO Administrators/Association of Local Air Pollution Control Officers TEQ toxic equivalent THC total hydrocarbon TOSHI target organ-specific hazard index tpy tons per year TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model TRS total reduced sulfur UF uncertainty factor μg/m 3 micrograms per cubic meter UMRA Unfunded Mandates Reform Act URE unit risk estimate yr year Organization of this Document. The information in this preamble is organized as follows: I. General Information A. Executive Summary 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 is the statutory authority for this action? B. What is this source category and how does the current NESHAP regulate its HAP emissions? C. What data collection activities were conducted to support this action? D. What other relevant background information and data are available? III. Analytical Procedures A. How did we estimate post-MACT risks posed by the source category? B. How did we consider the risk results in making decisions for this proposal? C. How did we perform the technology review? IV. Analytical Results and Proposed Decisions A. What are the results of the risk assessment and analyses? B. What are our proposed decisions regarding risk acceptability, ample margin of safety, and adverse environmental effects? C. What are the results and proposed decisions based on our technology review? D. What other actions are we proposing? E. What compliance dates are we proposing? V. 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? VI. Request for Comments VII. Submitting Data Corrections VIII. 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 (PRA) C. Regulatory Flexibility Act (RFA) D. Unfunded Mandates Reform Act (UMRA) 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 (NTTAA) and 1 CFR part 51 J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations I. General Information A. Executive Summary 1. Purpose of the Regulatory Action Section 112(f)(2) of the CAA requires the EPA to analyze and address the residual risk associated with hazardous air pollutant emissions from source categories subject to maximum achievable control technology (MACT) standards. This review, known as the residual risk review, is a one-time review that the statute provides will be done within 8 years of issuance of the MACT standard. Section 112(d)(6) of the CAA requires the EPA to review and revise CAA section 112 emissions standards, as necessary, taking into account developments in practices, processes, and control technologies. Emission standards promulgated under CAA section 112 are to be reviewed no less often than every 8 years. The EPA issued the NESHAP for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Mills (40 Code of Federal Regulations (CFR) part 63, subpart MM) in 2001. The 2001 emission standards are due for review under CAA sections 112(d)(6) and 112(f)(2). In addition to conducting the RTR for subpart MM, we are evaluating the SSM provisions in the rule in light of the United States Court of Appeals for the District of Columbia Circuit decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008). As explained in section IV of this preamble, in the Sierra Club case, the D.C. Circuit vacated the SSM exemption provisions in the General Provisions for nonopacity and opacity standards. Finally, the EPA evaluated the rule to determine if additional amendments were warranted or necessary to ensure continuous compliance with the standard and to promote consistency with other standards. 2. Summary of the Major Proposed Revisions The EPA is not proposing to make any changes pursuant to 112(f)(2) as a result of its residual risk review. The EPA is proposing to reduce opacity limits as a result of the technology review under CAA section 112(d)(6). In addition, we are proposing the following as part of the technology review: Revising the opacity monitoring provisions, requiring ESP parameter monitoring for processes equipped with ESPs, clarifying the monitoring for combined ESP/wet scrubber controls, and providing alternative monitoring for smelt dissolving tank (SDT) wet scrubbers. As an additional action, we are proposing to improve the compliance provisions of the subpart by proposing to require periodic air emissions performance testing once every 5 years for facilities subject to the standards for Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills. To address the SSM exemptions, we are proposing amendments to subpart MM that will (1) require facilities to meet the standard at all times, including during periods of SSM, and (2) provide alternative monitoring parameters for wet scrubbers and ESPs during these periods. We are also proposing changes to the subpart MM NESHAP and the General Provisions applicability table to eliminate the SSM exemption. To increase the ease and efficiency of data submittal and improve data accessibility, we are proposing to require mills to submit electronic copies of compliance reports, which includes performance test reports. We are also proposing a number of technical and editorial changes. These changes include the following: Clarifying the location in 40 CFR part 60 of applicable EPA test methods; updating the facility name for Cosmo Specialty Fibers; revising the definitions section in 40 CFR 63.861; corrected misspelling in 40 CFR 63.862(c), revising multiple sections to remove reference to former smelters and former black liquor gasification system at Georgia-Pacific's facility in Big Island, Virginia; revising the monitoring requirements section; revising the performance test requirements section to specify the conditions for conducting performance tests and to revise the ambient O2 concentration in Equations 7 and 8; revising the recordkeeping requirements section in 40 CFR 63.866 to include the requirement to record information on failures to meet the applicable standard; revising the terminology in the delegation of authority section in 40 CFR 63.868 to match the definitions in 40 CFR 63.90; and revising the General Provisions applicability table (Table 1 to subpart MM of part 63) to align with those sections of the General Provisions that have been amended or reserved over time. 3. Costs and Benefits Table 1 summarizes the costs of this action. See section V of this preamble for further discussion. Table 1—Summary of the Costs of This Proposed Action Requirement Capital cost, $ million Annual cost, $ million Change in opacity monitoring provisions for recovery furnaces and lime kilns 42 8.8 ESP parameter monitoring 5.7 1.4 Periodic emissions testing 1.1 Incremental reporting/recordkeeping 0.50 1.9 Total nationwide 48 13 The EPA estimates that the proposed changes to the opacity limits and monitoring allowances will reduce PM emissions by approximately 235 (tons per year) tpy and fine particle (PM 2.5 ) emissions by approximately 112 tpy. Periodic testing will tend to reduce emissions by providing incentive for facilities to maintain their control systems and make periodic adjustments to ensure peak performance. Eliminating the SSM exemption will reduce emissions by requiring facilities to meet the applicable standard during SSM periods. See section V of this preamble for further discussion. B. Does this action apply to me? Table 2 of this preamble lists the NESHAP and associated regulated industrial source categories that are the subject of this proposal. Table 2 is not intended to be exhaustive, but rather provides a guide for readers regarding the entities that this proposed action is likely to affect. The proposed standards, once promulgated, will be directly applicable to the affected sources. Federal, state, local, and tribal government entities would not be affected by this proposed action. As defined in the Initial List of Categories of Sources Under Section 112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR 31576, July 16, 1992), the “Pulp and Paper Production” source category is any facility engaged in the production of pulp and/or paper. The EPA developed the NESHAPs for the source category in phases. This NESHAP, 40 CFR part 63, subpart MM, regulates chemical recovery combustion sources at kraft, soda, sulfite, and stand-alone semichemical pulp mills. The NESHAP for non-combustion sources (40 CFR part 63, subpart S) regulates non-combustion processes at mills that (1) chemically pulp wood fiber (using kraft, sulfite, soda, and semichemical methods), (2) mechanically pulp wood fiber ( e.g., groundwood, thermomechanical, pressurized), (3) pulp secondary fibers (deinked and non-deinked), (4) pulp non-wood material, and (5) manufacture paper. This proposal only addresses the RTR for subpart MM, and does not propose any amendments to subpart S. Table 2—NESHAP and Industrial Source Categories Affected by This Proposed Action Source category NESHAP NAICS code a Pulp and Paper Production Chemical Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone Semichemical Pulp Mills 32211, 32212, 32213 a North American Industry Classification System. 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 action is available on the Internet through the EPA's Stationary Sources of Air Pollution Web site, a forum for information and technology exchange in various areas of air pollution control. A redline version of the regulatory language that incorporates the proposed changes in this action is available in the docket for this action (Docket ID No. EPA-HQ-OAR-2014-0741). Following signature by the EPA Administrator, the EPA will post a copy of this proposed action at: https://www.epa.gov/stationary-sources-air-pollution/kraft-soda-sulfite-and-stand-alone-semichemical-pulp-mills-mact-ii. Following publication in the Federal Register , the EPA will post the Federal Register version of the proposal and key technical documents at this same Web site. Information on the overall RTR program is available at http://www3.epa.gov/ttn/atw/rrisk/rtrpg.html. 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 comments that includes information claimed as CBI, you must submit a copy of the comments that does not contain the information claimed as CBI 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: OAQPS Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2014-0741. II. Background A. What is the statutory authority for this action? Section 112 of the CAA establishes a two-stage regulatory process to address emissions of hazardous air pollutants (HAPs) from stationary sources. In the first stage, after the EPA has identified categories of sources emitting one or more of the HAPs listed in CAA section 112(b), CAA section 112(d) requires the Agency to promulgate technology-based NESHAPs for those sources. “Major sources” are those that emit or have the potential to emit 10 tpy or more of a single HAP or 25 tpy or more of any combination of HAPs. For major sources, the technology-based NESHAP must reflect the maximum degree of emission reductions of HAPs achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts) and are commonly referred to as MACT standards. MACT standards must reflect 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 pollutant, 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 section 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 floor for existing sources can be less stringent than floors for new sources, but not 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, the EPA 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 emission 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. CAA section 112(d)(6). In conducting this review, the EPA is not required to recalculate the MACT floor. Natural Resources Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013). The second stage in standard-setting focuses on reducing any remaining ( i.e., “residual”) risk according to CAA section 112(f). Section 112(f)(1) of the CAA required 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 the Residual Risk Report to Congress, EPA-453/R-99-001 ( Risk Report ) in March 1999. Section 112(f)(2) of the CAA then provides that if Congress does not act on any recommendation in the Risk Report, the EPA must analyze and address residual risk for each category or subcategory of sources 8 years after promulgation of such standards pursuant to CAA section 112(d). Section 112(f)(2) of the CAA requires the EPA to determine for source categories subject to MACT standards whether promulgation of additional standards is needed to provide an ample margin of safety to protect public health. Section 112(f)(2)(B) of the CAA expressly preserves the EPA's use of the two-step process for developing standards to address any residual risk and the Agency's 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 EPA notified Congress in the Risk Report that the Agency intended to use the Benzene NESHAP approach in making CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently adopted this approach in its residual risk determinations and, in a challenge to the risk review for the Synthetic Organic Chemical Manufacturing source category, the United States Court of Appeals for the District of Columbia Circuit upheld as reasonable the EPA's interpretation that CAA section 112(f)(2) incorporates the approach established in the Benzene NESHAP. See NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008) (“[S]ubsection 112(f)(2)(B) expressly incorporates the 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, vol. 1, p. 877 (Senate debate on Conference Report). The first step in the process of evaluating residual risk is the determination of acceptable risk. If risks are unacceptable, the EPA cannot consider cost in identifying the emissions standards necessary to bring risks to an acceptable level. The second step is the determination of whether standards must be further revised in order to provide an ample margin of safety to protect public health. The ample margin of safety is the level at which the standards must 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. 1. Step 1—Determination of Acceptability The Agency in the Benzene NESHAP concluded that “the acceptability of risk under section 112 is best judged on the basis of a broad set of health risk measures and information” and that the “judgment on acceptability cannot be reduced to any single factor.” Benzene NESHAP at 38046. 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” ( Risk Report at 178, quoting NRDC v. EPA, 824 F. 2d 1146, 1165 (D.C. Cir. 1987) ( en banc ) (“Vinyl Chloride”), recognizing that our world is not risk-free. In the Benzene NESHAP, we stated that “EPA will generally presume that if the risk to [the maximum exposed] individual is no higher than approximately one in 10 thousand, that risk level is considered acceptable.” 54 FR at 38045, September 14, 1989. 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 acknowledged 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 the MIR as a metric for determining acceptability, we acknowledged in the Benzene NESHAP that “consideration of maximum individual risk . . . must take into account the strengths and weaknesses of this measure of risk.” Id. Consequently, the presumptive risk level of 100-in-1 million (1-in-10 thousand) provides a benchmark for judging the acceptability of maximum individual lifetime cancer risk, but does not constitute a rigid line for making that determination. Further, in the Benzene NESHAP, we noted that: “[p]articular 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 Benzene NESHAP that: “[i]n 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 km exposure radius around facilities, the science policy assumptions and estimation uncertainties associated with the risk measures, weight of the scientific evidence for human health effects, other quantified or unquantified health effects, effects due to co-location of facilities, and co-emission of pollutants.” Id. at 38045. 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 noted earlier, in NRDC v. EPA, the court held that CAA section 112(f)(2) “incorporates the EPA's interpretation of the Clean Air Act from the Benzene Standard.” The court further held that Congress' incorporation of the Benzene standard applies equally to carcinogens and non-carcinogens. 529 F.3d at 1081-82. Accordingly, we also consider non-cancer risk metrics in our determination of risk acceptability and ample margin of safety. 2. Step 2—Determination of Ample Margin of Safety Section 112(f)(2) of the CAA requires the EPA to determine, for source categories subject to MACT standards, whether those standards provide an ample margin of safety to protect public health. As explained in the Benzene NESHAP, “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 section 112.” 54 FR at 38046, September 14, 1989. According to CAA section 112(f)(2)(A), 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 ( i.e., the MACT standards) are sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008) (“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, 1 but must consider cost, energy, safety, and other relevant factors in doing so. 1 “Adverse environmental effect” is defined 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. CAA section 112(a)(7). The CAA does not specifically define the terms “individual most exposed,” “acceptable level,” and “ample margin of safety.” In the Benzene NESHAP, 54 FR at 38044-38045, September 14, 1989, the Agency stated as an overall objective: In protecting public health with an ample margin of safety under section 112, EPA strives 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 plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years. The Agency further stated that “[t]he 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.” Id. at 38045. 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, including the incremental risk reduction associated with standards more stringent than the MACT standard or a more stringent standard that the EPA has determined is necessary to ensure risk is acceptable. In the ample margin of safety analysis, the Agency considers additional factors, 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, September 14, 1989. B. What is this source category and how does the current NESHAP regulate its HAP emissions? The “Pulp and Paper Production” source category includes any facility engaged in the production of pulp and/or paper. The EPA developed the NESHAPs for the source category in two phases. The first phase, 40 CFR part 63, subpart S, regulates pulping and paper production processes, and was originally promulgated in 1998. The second phase, 40 CFR part 63, subpart MM, regulates chemical recovery combustion sources at kraft, soda, sulfite, and stand-alone semichemical pulp mills, and was originally promulgated in 2001. Another separate NESHAP, 40 CFR part 63, subpart DDDDD, covers other combustion sources located at pulp mills, such as industrial boilers. This proposal focuses exclusively on the RTR for subpart MM. The EPA is not proposing any amendments to Subpart DDDDD or subpart S in this notice. Subpart MM of 40 CFR part 63 was promulgated on January 12, 2001 (66 FR 3180). As promulgated in 2001, the subpart MM MACT standard applies to major sources of HAP emissions from chemical recovery combustion sources at kraft, soda, sulfite, and stand-alone semichemical pulp mills. The chemical recovery combustion sources include kraft and soda recovery furnaces, SDTs, and lime kilns; kraft black liquor oxidation (BLO) units; sulfite combustion units; and semichemical combustion units. Subpart S was promulgated on April 15, 1998 (63 FR 18504), and underwent a RTR, with final amendments to subpart S promulgated on September 11, 2012 (77 FR 55698). This proposal includes both a risk assessment and a technology review of the emission sources in 40 CFR part 63, subpart MM, as well as a risk assessment of the whole facility. The whole facility risk assessment includes emissions from all sources of HAP at the facility, including sources covered by other NESHAP ( e.g., boilers covered under 40 CFR part 63, subpart DDDDD; pulp and paper production processes covered under 40 CFR part 63, subpart S; paper coating operations covered under 40 CFR part 63, subpart JJJJ). According to results of the EPA's 2011 pulp and paper information collection request (ICR), and updates based on more recent information, there are a total of 108 major sources in the United States that conduct chemical recovery combustion operations, including 97 kraft pulp mills, 1 soda pulp mill, 3 sulfite pulp mills, and 7 stand-alone semichemical pulp mills. Subpart MM of 40 CFR part 63 includes numerical emission limits for recovery furnaces, SDTs, lime kilns, and sulfite and semichemical combustion units. The control systems used by most mills to meet the subpart MM emission limits are as follows: • Recovery furnaces: ESPs, wet scrubbers, and nondirect contact evaporator (NDCE) furnace design with dry-bottom ESP, and dry particulate matter (PM) return system. • Smelt dissolving tanks: Wet scrubbers, mist eliminators, and venting to recovery furnace. • Lime kilns: ESPs and wet scrubbers. • Sulfite combustion units: Wet scrubbers and mist eliminators. • Semichemical combustion units: Wet scrubbers, ESPs, and regenerative thermal oxidizers (RTOs). C. What data collection activities were conducted to support this action? In February 2011, the EPA issued an ICR, pursuant to CAA section 114, to United States pulp and paper manufacturers to gather information needed to conduct the regulatory reviews required under CAA sections 112(d)(6) and (f)(2). The EPA divided the ICR into three parts. Part I requested available information regarding 40 CFR part 63, subpart S process equipment, control devices, pulp and paper production, bleaching, and other aspects of facility operations to support the subpart S technology review and the review of the Kraft Pulp Mills New Source Performance Standards (NSPS) under 40 CFR part 60, subpart BB. Part II requested updated inventory data for all pulp and paper emission sources to support the residual risk assessment for the pulp and paper sector (including 40 CFR part 63, subparts S and MM) and to supplement the National Emissions Inventory (NEI) for the source category for purposes of detailed residual risk modeling. Part III requested available information on subpart MM chemical recovery combustion equipment, control devices, and other pertinent information, to support the subpart MM technology review and the subpart BB NSPS review. The response rate for the ICR was 100 percent. D. What other relevant background information and data are available? In addition to ICR responses, the EPA reviewed a number of other information sources to determine if there have been developments in practices, processes, or control technologies by chemical recovery combustion sources. These include: • Permit limits from permits submitted with ICR responses and collected from state agencies. • Information on air pollution control options in the pulp and paper industry from the RACT/BACT/LAER Clearinghouse (RBLC). • Information on best available techniques in the pulp and paper industry from a 2015 European Commission document, titled Best Available Techniques (BAT) Reference Document for the Production of Pulp, Paper and Board. • Information on the most effective ways to control emissions of PM 2.5 and PM 2.5 precursors from sources in various industries, including the pulp and paper industry, from a 2006 State and Territorial Air Pollution Program Administrators/Association of Local Air Pollution Control Officers (STAPPA/ALAPCO) document, titled Controlling Fine Particulate Matter under the Clean Air Act: A Menu of Options. • Stack test data submitted with ICR responses. • Emissions factors from technical bulletins prepared by the National Council for Air and Stream Improvement, Inc. (NCASI), a major source of environmental data affecting the pulp and paper industry. III. Analytical Procedures In this section, we describe the analyses performed to support the proposed decisions for the RTR and other issues addressed in this proposal. A. How did we estimate post-MACT risks posed by the source category? The EPA conducted a risk assessment that provides estimates of the MIR posed by the HAP emissions from each source in the source category, the hazard index (HI) for chronic exposures to HAPs with the potential to cause non-cancer health effects, and the hazard quotient (HQ) for acute exposures to HAPs with the potential to cause non-cancer health effects. The assessment also provides estimates of the distribution of cancer risks within the exposed populations, cancer incidence, and an evaluation of the potential for adverse environmental effects. The seven sections that follow this paragraph describe how we estimated emissions and conducted the risk assessment. The docket for this rulemaking contains the following document which provides more information on the risk assessment inputs and models: Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule. 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; 2 they are also consistent with the key recommendations contained in that report. 2 U.S. EPA SAB. Risk and Technology Review (RTR) Risk Assessment Methodologies: For Review by the EPA's Science Advisory Board with Case Studies—MACT I Petroleum Refining Sources and Portland Cement Manufacturing, May 2010. 1. How did we estimate actual emissions and identify the emissions release characteristics? As discussed in section II.C of this preamble, we used data from Part II of the Pulp and Paper Sector ICR as the basis for the risk assessments for the pulp and paper sector (including 40 CFR part 63, subparts S and MM). Part II of the ICR, which concluded in June 2011, targeted facilities that are major sources of HAP emissions and involved an update of pre-populated NEI data spreadsheets (or creation of new datasets). The NEI is a database that contains information about sources that emit criteria air pollutants, their precursors and HAPs. The NEI database includes estimates of actual annual air pollutant emissions from point and volume sources; emission release characteristic data such as emission release height, temperature, diameter, velocity, and flow rate; and locational latitude/longitude coordinates. We asked pulp and paper mills to refine (or create new) inventories based on their NEI datasets for purposes of detailed residual risk modeling. Refinements included providing additional details for HAP emission sources, providing more specific information on the location and characteristics of emission points ( e.g., updating emission release coordinates and parameters), and adding or updating HAP emissions data for each emission release point. We compiled the updated datasets for each individual mill into a pulp and paper Part II emissions database to create the whole facility and MACT source category residual risk modeling files. The actual annual emissions data in the pulp and paper emissions database include limited data from actual emissions tests and, in most cases, estimates of actual emissions (based on emissions factors) provided by sources surveyed in Part II of the ICR. We received a comprehensive set of emissions test data and emissions estimates that enabled us to conduct risk modeling of detectable HAP emissions for all major source facilities in the MACT source category. We conducted two substantial quality assurance (QA) efforts on the Part II data in order to create the modeling files needed for the 40 CFR part 63, subpart S residual risk assessment, which included: (1) QA of the updated inventory spreadsheets submitted by each mill prior to import into the compiled database; and (2) QA and standardization of the compiled database. 3 We needed modeling files for both the subpart S category and the whole facility, so our QA efforts focused on data for all emission sources at pulp and paper facilities, including 40 CFR part 63, subpart MM emission sources. 3 These QA efforts are discussed in a November 11, 2011 memorandum in the docket, titled Inputs to the Pulp and Paper Industry October 2011 Residual Risk Modeling. We reviewed the Part II datasets to ensure that the major pulp and paper processes and pollutants were included and properly identified, to ensure that emissions from the various processes were allocated to the correct source category, and to identify emissions and other data anomalies. We also standardized the various codes ( e.g., source classification codes (SCCs), pollutant codes), eliminated duplicate records, and checked geographic coordinates. We reviewed emissions release parameters for data gaps and errors, assigned the proper default parameters where necessary, assigned emission process groups to distinguish between processes with related SCCs, and ensured that fugitive release dimensions were specified or given default values where necessary. We requested comments on the inventory in the preamble to the December 27, 2011, 40 CFR part 63, subpart S proposal. We requested further updates to the mill-specific HAP emissions data used in the risk modeling, if needed. In 2012, we received revisions to inventories for 81 facilities following proposal of the subpart S residual risk review. 4 4 Review of the inventory revisions performed prior to promulgation of 40 CFR part 63, subpart S is documented in a May 8, 2012, memorandum in the subpart S docket (EPA-HQ-OAR-2007-0544), titled Recommendations Concerning Residual Risk Remodeling for the Pulp and Paper Industry. While most of the inventory revisions that we received after the proposal made additional refinements to emissions levels and release point details for 40 CFR part 63, subpart S sources, some inventory revisions also made refinements to data for 40 CFR part 63, subpart MM sources. We incorporated revisions to all process types into the inventory to remodel facility-wide risk and perform the complete scope of residual risk modeling for subpart MM emissions sources. We checked the 81 individual revision files to ensure they were incorporated into the main database correctly, and then further reviewed the entire database. We began compiling an initial draft residual risk modeling input file for use in the 40 CFR part 63, subpart MM residual risk review in September 2014. 5 We made updates to the mill list to account for facilities that recently closed or reopened, and to mill equipment configurations for facilities that recently upgraded equipment. We reviewed the inventory to ensure that each record contained a facility ID, emission unit ID, process ID, and emission release point ID. We cross-walked regulatory codes, SCCs, and emission process groups to identify and correct any inconsistencies that may have been introduced with the inventory updates. 5 For more information, see the September 30, 2014 memorandum in the docket, titled Preparation of Residual Risk Modeling Input File for Subpart MM. The September 2014 memorandum describes the source of the inventory data, discusses quality assurance of the 40 CFR part 63, subpart MM data, provides actual versus allowable and acute risk multipliers for subpart MM sources, and identifies potential outliers and suspect data for further review. In addition to retaining the emission process groups used in the previous 40 CFR part 63, subpart S modeling effort, we added new emission process groups for 40 CFR part 63, subpart MM sources where necessary. We compared the subpart MM emission process groups with the Part III ICR database to ensure that we included all known recovery furnaces and lime kilns in the inventory for the residual risk modeling. In addition, we reviewed the presence or absence of BLO systems ( i.e., because BLO systems are only expected to be present at mills with direct contact evaporator (DCE) recovery furnaces). Finally, we checked the mills to ensure emission process groups included SDTs and sulfite and semichemical recovery equipment, as expected. We reviewed the pollutant codes in the inventory to ensure the codes and descriptions matched the latest NEI lookup table used by the EPA for risk model input files. We performed extensive QA of the pollutant codes prior to the 40 CFR part 63, subpart S risk modeling, so few updates were required. We speciated data for a number of HAPs, including chromium, mercury, radionuclides, polycyclic organic matter (POM), and dioxins/furans to facilitate risk modeling. We speciated chromium emissions as hexavalent chromium (chromium VI) and trivalent chromium (chromium III). 6 We speciated mercury emissions as particulate divalent mercury, gaseous divalent mercury, and gaseous elemental mercury. We speciated total POM emissions differently for each emission unit type based on the most common POM compounds emitted from that unit. We speciated dioxin/furan emissions based on published emissions data in the EPA's dioxin/furan inventory report 7 or, if no speciation profile was available, recalculated the emissions using published emissions factors. 8 Where needed, we added/replaced emissions estimates that were omitted, outdated, out-of-scope, or inconsistent with changes to mill equipment configurations. 6 For more information on pollutant speciation, see the September 30, 2014 memorandum in the docket, titled Preparation of Residual Risk Modeling Input File for Subpart MM. 7 U.S. Environmental Protection Agency. An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000. Publication No. EPA/600/P-03/002F. Available at: http://www.epa.gov/ncea/pdfs/dioxin/2006/dioxin.pdf. November 2006. Tables 4-14, 4-25, and 5-13. 8 National Council for Air and Stream Improvement (NCASI). Compilation of `Air Toxic' and Total Hydrocarbon Emissions Data for Pulp and Paper Mill Sources—A Second Update. Technical Bulletin No. 973. February 2010. Table 9.9. We reviewed all records for consistency with respect to the emission release point to ensure each record was characterized by one set of coordinates (latitude and longitude) and one set of stack or fugitive parameters. We checked fugitive parameters to ensure there were no blanks and that the values provided were reasonable and consistent with the required national defaults or other criteria. We reviewed emission points labeled as stacks to ensure no fugitive parameters were identified. We checked exit gas flow rate values against the stack velocity provided to ensure there were no inconsistencies. We mapped the emission point coordinates for each facility to determine if they were properly placed on the mill site. We also added control information from the Part III ICR database or mills' title V permits to the input file for 40 CFR part 63, subpart MM sources. The emissions inventory for 40 CFR part 63, subpart MM sources identifies emissions of the following HAP known to be persistent and bio-accumulative in the environment (PB-HAPs): Cadmium compounds, lead compounds, mercury compounds, POM, dioxins/furans, and hexachlorobenzene. Risk-based screening levels are available for Tier 1 screening for all of the above PB-HAPs, with the exception of hexachlorobenzene. Consistent with the EPA's standard practice in conducting risk assessments for source categories, we conducted a two-step process to determine: (1) Whether PB-HAPs are being emitted; and (2) whether they are being released above screening levels. If these releases are significantly above the screening levels and the EPA has detailed information on the releases and the site, a complete multipathway analysis of the site is conducted to estimate pathway risks for the source category. We considered actual emissions of the ecological HAPs emitted from the 40 CFR part 63, subpart MM source category in the ecological HAP analysis. In addition to the PB-HAPs emitted from the subpart MM source category (except hexachlorobenzene), we considered hydrochloric acid (HCl) and hydrogen fluoride (HF) for ecological HAP modeling. Further information about the multipathway analysis performed for this category follows in section III.B.4 of this preamble. In 2015, we posted the initial draft risk model input file on our Technology Transfer Network for additional review by interested parties. This review resulted in the submittal of additional mill-specific inventory and receptor revisions. As part of the review, we identified potential outliers and suspect data for 40 CFR part 63, subpart MM sources in the emission inventory and notified facilities to provide an opportunity to review and revise their emissions data, if needed. A total of 40 mills reviewed their emissions data, with 38 of those mills submitting inventory revisions to the EPA. 9 9 For further information, see the October 16, 2015 memorandum in the docket, titled Review of Pulp Mill Inventory Revisions Received in 2015. Inventory revisions primarily included mill name changes; revisions to HAP metal, POM, and dioxin/furan inventory data; and requests for removal of hexachlorocyclopentadiene (HCCPD) data from inventories, particularly for SDTs, since HCCPD is not expected from pulp mill sources. Where necessary, we speciated the revised chromium, mercury, and POM data that the mills provided, using the approaches described above. As part of the review, we identified risk modeling receptors improperly located on mill property for correction in the Human Exposure Model (Community and Sector HEM-3 version 1.1.0) input files before we performed risk modeling for 40 CFR part 63, subpart MM. After we incorporated the revisions into the input file, we conducted an additional review of the file, which included the following: • Identified non-40 CFR part 63, subpart MM mills in the inventory and removed them. • Identified additional mill name changes and incorporated them in the inventory. • Reviewed fugitive parameters for missing data. • Identified missing speciated mercury and chromium data and restored the data to the inventory. • Reviewed location data for mills that submitted inventory revisions and corrected coordinates, as needed. • Identified records for emissions points with zero emissions for a given pollutant and removed those records from the inventory. • Conducted emission process group checks, resulting in a revision to an emission process group that reflects a change in SCC, and removal of records with an emission process group no longer applicable (specifically a BLO unit for a mill that no longer operates any DCE recovery furnaces that require a BLO unit). • Checked mills to ensure they had the expected 40 CFR part 63, subpart MM equipment, comparing the number of recovery furnaces, lime kilns, and SDTs to Part III ICR data to ensure each emission unit was represented in the inventory. • Reviewed each emission unit for the presence of an emissions value for key expected pollutants ( e.g., HAP metals, HCl, methanol, dioxins/furans, POM) and added emissions estimates for those pollutants where needed. 10 10 For further information, see the February 16, 2016 memorandum in the docket, titled Approach for Populating Missing and Erroneous Emissions Estimates for Key HAP in the Subpart MM Residual Risk Modeling Inventory. • Replaced obviously errant emissions data (particularly dioxins/furans) with revised estimates calculated based on ICR-reported throughput and emissions factors. • Rechecked IDs, SCCs, regulatory codes, pollutant codes, duplicate pollutants, and HCCPD deletions. 2. How did we estimate MACT-allowable emissions? The available emissions data in the RTR emissions dataset include estimates of the mass of HAPs emitted during the specified annual time period. In some cases, these “actual” emission levels are lower than the emission levels required to comply with the current MACT standards. The emissions level allowed to be emitted by the MACT standards is referred to as the “MACT-allowable” emissions level. We discussed the use of both MACT-allowable and actual emissions in the final Coke Oven Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed and final Hazardous Organic NESHAP RTRs (71 FR 34428, June 14, 2006, and 71 FR 76609, December 21, 2006, respectively). In those actions, we noted that assessing the risks at the MACT-allowable level is inherently reasonable since these risks reflect the maximum level facilities could emit and still comply with national emission standards. 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 approach. (54 FR 38044, September 14, 1989.) It is reasonable to consider actual emissions because sources typically seek to perform better than required by emissions standards to provide an operational margin to accommodate the variability in manufacturing processes and control device performance. Facilities' actual emissions may also be significantly lower than MACT-allowable emissions for other reasons such as state requirements, better performance of control devices than required by the MACT standards, or reduced production. We estimated actual emissions based on the Part II emissions inventory and subsequent site-specific inventory revisions provided by mills. To estimate emissions at the MACT-allowable level, we developed a ratio of MACT-allowable emissions to actual emissions for each source type for the facilities in the 40 CFR part 63, subpart MM source category. We developed this ratio based on the level of control required by the subpart MM MACT standards compared to the level of reported actual emissions from stack test reports provided with Part III survey responses. For example, stack test data indicated that SDTs achieve PM levels of 0.108 pounds per ton (lb/ton) black liquor solids (BLS), on average, while the PM emission limit for existing SDTs is 0.20 lb/ton BLS, so we estimated that MACT-allowable emissions of HAP metals from SDTs (where PM is used as a surrogate) could be as much as 1.8 times higher, and the ratio of MACT-allowable to actual emissions used was 1.8:1 for SDTs. 11 11 For more information, see the September 30, 2014 memorandum in the docket, titled Preparation of Residual Risk Modeling Input File for Subpart MM. After developing these ratios for each emission point type in this source category, we next applied these ratios on an emission unit basis to the Part II actual emissions data to obtain risk estimates based on MACT-allowable emissions. 3. How did we conduct dispersion modeling, determine inhalation exposures and estimate individual and population inhalation risks? Both long-term and short-term inhalation exposure concentrations and health risks from the source category addressed in this proposal were estimated using HEM-3. The HEM-3 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAPs in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 kilometers (km) of the modeled sources, 12 and (3) estimating individual and population-level inhalation risks using the exposure estimates and quantitative dose-response information. 12 This metric comes from the Benzene NESHAP. See 54 FR 38046. The air dispersion model used by the HEM-3 model (AERMOD) is one of the EPA's preferred models for assessing pollutant concentrations from industrial facilities. 13 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 (2014) of hourly surface and upper air observations for more than 800 meteorological stations, selected to provide coverage of the United States and Puerto Rico. A second library of United States Census Bureau census block 14 internal point locations and populations provides the basis of human exposure calculations (U.S. Census, 2010). In addition, for each census block, the census library includes the elevation and controlling hill height, 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 HAPs and other toxic air pollutants. These values are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants and are discussed in more detail later in this section. 13 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). 14 A census block is 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 concentrations of each 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 the 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 3 )) by its unit risk estimate (URE). The URE 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 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 the 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 EPA estimated incremental individual lifetime cancer risks associated with emissions from the facilities in the source category 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 15 ) emitted by the modeled sources. Cancer incidence and the distribution of individual cancer risks for the population within 50 km of the sources were also estimated for the source category as part of this assessment by summing individual risks. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044, September 14, 1989) and the limitations of Gaussian dispersion models, including AERMOD. 15 These classifications also coincide with the terms “known carcinogen, probable carcinogen, and possible carcinogen,” respectively, which are the terms advocated in the EPA's Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 33992, September 24, 1986). In August 2000, the document Supplemental Guidance for Conducting Health Risk Assessment of Chemical Mixtures (EPA/630/R-00/002) was published as a supplement to the 1986 document. Copies of both documents can be obtained from https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. 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) titled, 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 the risk of non-cancer 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 value, which is a value selected from one of several sources. First, the chronic reference level can be the EPA reference concentration (RfC) ( https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary ), 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.” Alternatively, in cases where an RfC from the EPA's IRIS database is not available or where the EPA determines that using a value other than the RfC is appropriate, the chronic reference level can be a value from the following prioritized sources: (1) The Agency for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Level ( http://www.atsdr.cdc.gov/mrls/index.asp ), which is defined as “an estimate of daily human exposure to a hazardous substance that is likely to be without an appreciable risk of adverse non-cancer health effects (other than cancer) over a specified duration of exposure”; (2) the CalEPA Chronic Reference Exposure Level (REL) ( http://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0 ), which is defined as “the concentration level (that is expressed in units of micrograms per cubic meter (μg/m 3 ) for inhalation exposure and in a dose expressed in units of milligram per kilogram-day (mg/kg-day) for oral exposures), 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. As mentioned above, in order to characterize non-cancer chronic effects, and in response to key recommendations from the SAB, the EPA selects dose-response values that reflect the best available science for all HAPs included in RTR risk assessments. 16 More specifically, for a given HAP, the EPA examines the availability of inhalation reference values from the sources included in our tiered approach ( e.g., IRIS first, ATSDR second, CalEPA third) and determines which inhalation reference value represents the best available science. Thus, as new inhalation reference values become available, the EPA will typically evaluate them and determine whether they should be given preference over those currently being used in RTR risk assessments. 16 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. The EPA also evaluated screening estimates of acute exposures and risks for each of the HAP (for which appropriate acute dose-response values are available) at the point of highest potential off-site exposure for each facility. To do this, the EPA estimated the risks when both the peak (hourly) emissions rate and worst-case dispersion conditions occur. We also assume that a person is located at the point of highest impact during that same time. In accordance with our mandate in section 112 of the CAA, we use the point of highest off-site exposure to assess the potential risk to the maximally exposed individual. The acute HQ is the estimated acute exposure divided by the acute dose-response value. In each case, the EPA calculated acute HQ values using best available, short-term dose-response 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 emissions rates, meteorology, and exposure location. 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://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary ) is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.” Id. at page 2. Acute REL values are based on the most sensitive, relevant, adverse health effect reported in the peer-reviewed medical and toxicological literature. Acute REL values are designed to protect the most sensitive individuals in the population through the inclusion of margins of safety. Because margins of safety are incorporated to address data gaps and uncertainties, exceeding the REL does not automatically indicate an adverse health impact. Acute exposure guideline level values were derived in response to recommendations from the National Research Council (NRC). The National Advisory Committee (NAC) for the Development of Acute Exposure Guideline Levels for Hazardous Substances—usually referred to as the AEGL Committee or the NAC/AEGL committee developed AEGL values for at least 273 of the 329 chemicals on the AEGL priority chemical list. The last meeting of the NAC/AEGL Committee was in April 2010, and its charter expired in October 2011. The NAC/AEGL Committee ended in October 2011, but the AEGL program continues to operate at the EPA and works with the National Academies to publish final AEGLs ( https://www.epa.gov/aegl ). As described in Standing Operating Procedures (SOP) for Developing Acute Exposure Guideline Levels for Hazardous Substances, “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” ( https://www.epa.gov/aegl/process-developing-acute-exposure-guideline-levels-aegls ) Id. at 2. 17 The AEGL values represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to 8 hours. “The primary purpose of the AEGL program is to develop guideline levels for once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.” Id. at 21. “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.” Id. at 31. 17 National Academy of Sciences (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 (expressed as ppm (parts per million) or mg/m3 (milligrams per cubic meter)) 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.” Id. at 3. The document also notes 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.” Id. Similarly, the document defines AEGL-2 values as “the airborne concentration (expressed as parts per million or milligrams per cubic meter) 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.” Id. Emergency response planning guideline values are derived for use in emergency response, as described in the American Industrial Hygiene Association's Emergency Response Planning (ERP) Committee document titled, ERPGS Procedures and Responsibilities ( https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.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.” 18 Id. at 1. The ERPG-1 value is defined as “the maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing more than mild, transient health effects or without perceiving a clearly defined, objectionable odor.” Id. at 2. Similarly, the ERPG-2 value is defined as “the maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious adverse health effects or symptoms that could impair an individual's ability to take protective action.” Id. at 1. 18 ERP Committee Procedures and Responsibilities. November 1, 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, we compare higher severity level AEGL-2 or ERPG-2 values 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 the same as the corresponding ERPG-1 values, and AEGL-2 values are often equal to ERPG-2 values. Maximum HQ values from our acute screening risk assessments typically result when basing them on the acute REL 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 emissions rates by a default factor to cover routinely variable emissions. We choose the factor to use partially based on process knowledge and engineering judgment. The factor chosen also reflects a Texas study of short-term volatile organic compound (VOC) emissions variability, which showed that most peak emission events in a heavily-industrialized four-county area (Harris, Galveston, Chambers, and Brazoria Counties, Texas) were less than twice the annual average hourly emissions rate. The highest peak emissions event was 74 times the annual average hourly emissions rate, and the 99th percentile ratio of peak hourly emissions rate to the annual average hourly emissions rate was 9. 19 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 this source category, median peak-to-mean multipliers ranging from 1.1 to 4.7 were developed for 40 CFR part 63, subpart MM emission process groups based on the routine annual emissions data and peak hourly emissions data obtained from Part II survey data. A further discussion of why these factors were chosen can be found in the memorandum, Preparation of Residual Risk Modeling Input File for Subpart MM, available in the docket for this rulemaking. 19 Allen, et al., 2004. Variable Industrial VOC Emissions and their impact on ozone formation in the Houston Galveston Area. Texas Environmental Research Consortium. https://www.researchgate.net/publication/237593060_Variable_Industrial_VOC_Emissions_and_their_Impact_on_Ozone_Formation_in_the_Houston_Galveston_Area. 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 (even under the conservative assumptions of the screening analysis), acute impacts were deemed negligible and no further analysis was performed for these HAPs. See the Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule for more details. 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 emissions 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. Recognizing that this level of data is rarely available, we instead rely on the multiplier approach. To better characterize the potential health risks associated with estimated acute exposures to HAPs, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies, 20 we generally examine a wider range of available acute health metrics ( e.g., RELs, 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 21 for HAPs have been developed, we consider additional acute values ( i.e., occupational and international values) to provide a more complete risk characterization. 20 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. 21 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, 2009, and available online at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003. 4. How did we conduct the multipathway exposure and risk screening? The EPA conducted a screening analysis examining the potential for significant human health risks due to exposures via routes other than inhalation ( i.e., ingestion). We first determined whether any sources in the source category emitted PB-HAP. The PB-HAP compounds or compound classes are identified for the screening from the EPA's Air Toxics Risk Assessment Library (available at http://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library ). For the 40 CFR part 63, subpart MM source category, we identified emissions of cadmium compounds, lead compounds, mercury compounds, POM, dioxins/furans, and hexachlorobenzene. Because one or more of these PB-HAPs are emitted by at least one facility in the subpart MM source category, we proceeded to the next step of the evaluation. In this step, we determined whether the facility-specific emissions rates of the emitted PB-HAP were large enough to create the potential for significant non-inhalation human health risks under reasonable worst-case conditions. To facilitate this step, we have developed emissions rate screening levels for several PB-HAPs using a hypothetical upper-end 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 PB-HAPs with emissions rate screening levels are: Lead, cadmium, dioxins/furans, mercury compounds, and POM. We conducted a sensitivity analysis on the screening scenario to ensure that its key design parameters would represent the upper end of the range of possible values, such that it would represent a conservative, but not impossible, scenario. The facility-specific emissions for each PB-HAP were compared to the emission rate screening levels for these PB-HAPs to assess the potential for significant human health risks via non-inhalation pathways. We call this application of the TRIM.FaTE model the Tier 1 TRIM-screen or Tier 1 screen. For the purpose of developing emission rate screening values for our Tier 1 TRIM-screen, we derived emission levels for these PB-HAPs (other than lead compounds) at which the maximum excess lifetime cancer risk would be 1-in-1 million ( i.e., for dioxins/furans and POM) or, for HAPs that cause non-cancer health effects ( i.e., cadmium compounds and mercury compounds), the maximum HQ would be 1. If the emissions rate of any PB-HAP included in the Tier 1 screen exceeds the Tier 1 screening emissions level for any facility, we conduct a second screen, which we call the Tier 2 TRIM-screen or Tier 2 screen. In the Tier 2 screen, the location of each facility that exceeded the Tier 1 emission level is used to refine the assumptions associated with the environmental scenario while maintaining the exposure scenario assumptions. A key assumption that is part of the Tier 1 screen is that a lake is located near the facility; we confirm the existence of lakes near the facility as part of the Tier 2 screen. We then adjust the risk-based Tier 1 screening value for each PB-HAP for each facility based on an understanding of how exposure concentrations estimated for the screening scenario change with meteorology and environmental assumptions. PB-HAP emissions that do not exceed these new Tier 2 screening levels are considered to pose no unacceptable risks. If the PB-HAP emissions for a facility exceed the Tier 2 screening levels and data are available, we may decide to conduct a more refined Tier 3 multipathway assessment. There are several analyses that can be included in a Tier 3 screen depending upon the extent of refinement warranted, including validating that the lake is fishable and considering plume-rise to estimate emissions lost above the mixing layer. If the Tier 3 screen is exceeded, the EPA may further refine the assessment. In evaluating the potential multipathway risk from emissions of lead compounds, rather than developing a screening emissions rate for them, we compared maximum estimated chronic inhalation exposures with the level of the current National Ambient Air Quality Standard (NAAQS) for lead. 22 Values below the level of the primary (health-based) lead NAAQS were considered to have a low potential for multipathway risk. 22 In doing so, the EPA notes that the legal standard for a primary NAAQS—that a standard is requisite to protect public health and provide an adequate margin of safety (CAA section 109(b))—differs from the CAA section 112(f) standard (requiring among other things that the standard provide an “ample margin of safety”). However, the primary lead NAAQS is a reasonable measure of determining risk acceptability ( i.e., the first step of the Benzene NESHAP analysis) since it is designed to protect the most susceptible group in the human population—children, including children living near major lead emitting sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, applying the level of the primary lead NAAQS at the risk acceptability step is conservative, since that primary lead NAAQS reflects an adequate margin of safety. For further information on the multipathway analysis approach, see the document titled Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule , which is available in the docket for this action. 5. How did we conduct the environmental risk screening assessment? a. Adverse Environmental Effect The EPA conducts a screening assessment to examine the potential for adverse environmental effects as required under section 112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines “adverse environmental effect” as “any significant and widespread adverse effect, which may reasonably be anticipated, to wildlife, aquatic life, or other natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental quality over broad areas.” b. Environmental HAPs The EPA focuses on seven HAPs, which we refer to as “environmental HAPs,” in its screening analysis: Five PB-HAPs and two acid gases. The five PB-HAPs are cadmium, dioxins/furans, POM, mercury (both inorganic mercury and methyl mercury) and lead compounds. The two acid gases are HCl and HF. The rationale for including these seven HAPs in the environmental risk screening analysis is presented below. The HAPs that persist and bioaccumulate are of particular environmental concern because they accumulate in the soil, sediment, and water. The PB-HAPs are taken up, through sediment, soil, water, and/or ingestion of other organisms, by plants or animals ( e.g., small fish) at the bottom of the food chain. As larger and larger predators consume these organisms, concentrations of the PB-HAPs in the animal tissues increases as does the potential for adverse effects. The five PB-HAPs we evaluate as part of our screening analysis account for 99.8 percent of all PB-HAP emissions nationally from stationary sources (on a mass basis from the 2005 EPA NEI). In addition to accounting for almost all of the mass of PB-HAPs emitted, we note that the TRIM.FaTE model that we use to evaluate multipathway risk allows us to estimate concentrations of cadmium compounds, dioxins/furans, POM, and mercury in soil, sediment and water. For lead compounds, we currently do not have the ability to calculate these concentrations using the TRIM.FaTE model. Therefore, to evaluate the potential for adverse environmental effects from lead compounds, we compare the estimated exposures from the source category emissions of lead with the level of the secondary NAAQS for lead. 23 We consider values below the level of the secondary lead NAAQS to be unlikely to cause adverse environmental effects. 23 The Secondary Lead NAAQS is a reasonable measure of determining whether there is an adverse environmental effect since it was established considering “effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal comfort and well-being.” Due to their well-documented potential to cause direct damage to terrestrial plants, we include two acid gases, HCl and HF, in the environmental screening analysis. According to the 2005 NEI, HCl and HF account for about 99 percent (on a mass basis) of the total acid gas HAPs emitted by stationary sources in the United States. In addition to the potential to cause direct damage to plants, high concentrations of HF in the air have been linked to fluorosis in livestock. Air concentrations of these HAPs are already calculated as part of the human multipathway exposure and risk screening analysis using the HEM3-AERMOD air dispersion model, and we are able to use the air dispersion modeling results to estimate the potential for an adverse environmental effect. The EPA acknowledges that other HAPs beyond the seven HAPs discussed above may have the potential to cause adverse environmental effects. Therefore, the EPA may include other relevant HAPs in its environmental risk screening in the future, as modeling science and resources allow. The EPA invites comment on the extent to which other HAPs emitted by the source category may cause adverse environmental effects. Such information should include references to peer-reviewed ecological effects benchmarks that are of sufficient quality for making regulatory decisions, as well as information on the presence of organisms located near facilities within the source category that such benchmarks indicate could be adversely affected. c. Ecological Assessment Endpoints and Benchmarks for PB-HAP An important consideration in the development of the EPA's screening methodology is the selection of ecological assessment endpoints and benchmarks. Ecological assessment endpoints are defined by the ecological entity ( e.g., aquatic communities including fish and plankton) and its attributes ( e.g., frequency of mortality). Ecological assessment endpoints can be established for organisms, populations, communities or assemblages, and ecosystems. For PB-HAPs (other than lead compounds), we evaluated the following community-level ecological assessment endpoints to screen for organisms directly exposed to HAPs in soils, sediment, and water: • Local terrestrial communities (i.e., soil invertebrates, plants) and populations of small birds and mammals that consume soil invertebrates exposed to PB-HAPs in the surface soil; • Local benthic (i.e., bottom sediment dwelling insects, amphipods, isopods, and crayfish) communities exposed to PB-HAPs in sediment in nearby water bodies; and • Local aquatic (water-column) communities (including fish and plankton) exposed to PB-HAP in nearby surface waters. For PB-HAPs (other than lead compounds), we also evaluated the following population-level ecological assessment endpoint to screen for indirect HAP exposures of top consumers via the bioaccumulation of HAPs in food chains: • Piscivorous ( i.e., fish-eating) wildlife consuming PB-HAP-contaminated fish from nearby water bodies. For cadmium compounds, dioxins/furans, POM, and mercury, we identified the available ecological benchmarks for each assessment endpoint. An ecological benchmark represents a concentration of HAPs ( e.g., 0.77 μg of HAP per liter of water) that has been linked to a particular environmental effect level through scientific study. For PB-HAPs we identified, where possible, ecological benchmarks at the following effect levels: • Probable effect levels (PEL): Level above which adverse effects are expected to occur frequently; • Lowest-observed-adverse-effect level (LOAEL): The lowest exposure level tested at which there are biologically significant increases in frequency or severity of adverse effects; and • No-observed-adverse-effect levels (NOAEL): The highest exposure level tested at which there are no biologically significant increases in the frequency or severity of adverse effect. We established a hierarchy of preferred benchmark sources to allow selection of benchmarks for each environmental HAP at each ecological assessment endpoint. In general, the EPA sources that are used at a programmatic level ( e.g., Office of Water, Superfund Program) were used in the analysis, if available. If unavailable, the EPA benchmarks used in regional programs ( e.g., Superfund) were used. If benchmarks were not available at a programmatic or regional level, we used benchmarks developed by other federal agencies ( e.g., National Oceanic and Atmospheric Administration (NOAA)) or state agencies. Benchmarks for all effect levels are not available for all PB-HAPs and assessment endpoints. In cases where multiple effect levels were available for a particular PB-HAP and assessment endpoint, we use all of the available effect levels to help us to determine whether ecological risks exist and, if so, whether the risks could be considered significant and widespread. d. Ecological Assessment Endpoints and Benchmarks for Acid Gases The environmental screening analysis also evaluated potential damage and reduced productivity of plants due to direct exposure to acid gases in the air. For acid gases, we evaluated the following ecological assessment endpoint: • Local terrestrial plant communities with foliage exposed to acidic gaseous HAPs in the air. The selection of ecological benchmarks for the effects of acid gases on plants followed the same approach as for PB-HAPs ( i.e., we examine all of the available chronic benchmarks). For HCl, the EPA identified chronic benchmark concentrations. We note that the benchmark for chronic HCl exposure to plants is greater than the reference concentration for chronic inhalation exposure for human health. This means that where the EPA includes regulatory requirements to prevent an exceedance of the reference concentration for human health, additional analyses for adverse environmental effects of HCl would not be necessary. For HF, the EPA identified chronic benchmark concentrations for plants and evaluated chronic exposures to plants in the screening analysis. High concentrations of HF in the air have also been linked to fluorosis in livestock. However, the HF concentrations at which fluorosis in livestock occur are higher than those at which plant damage begins. Therefore, the benchmarks for plants are protective of both plants and livestock. e. Screening Methodology For the environmental risk screening analysis, the EPA first looked at whether any facilities in the 40 CFR part 63, subpart MM source category emitted any of the seven environmental HAPs. Because we found that one or more of the seven environmental HAPs evaluated are emitted by at least one facility in the source category, we proceeded to the second step of the evaluation. f. PB-HAP Methodology For cadmium, mercury, POM, and dioxins/furans, the environmental screening analysis consists of two tiers, while lead compounds are analyzed differently as discussed earlier. In the first tier, we determined whether the maximum facility-specific emission rates of each of the emitted environmental HAPs were large enough to create the potential for adverse environmental effects under reasonable worst-case environmental conditions. These are the same environmental conditions used in the human multipathway exposure and risk screening analysis. To facilitate this step, TRIM.FaTE was run for each PB-HAP under hypothetical environmental conditions designed to provide conservatively high HAP concentrations. The model was set to maximize runoff from terrestrial parcels into the modeled lake, which in turn, maximized the chemical concentrations in the water, the sediments, and the fish. The resulting media concentrations were then used to back-calculate a screening level emission rate that corresponded to the relevant exposure benchmark concentration value for each assessment endpoint. To assess emissions from a facility, the reported emission rate for each PB-HAP was compared to the screening level emission rate for that PB-HAP for each assessment endpoint. If emissions from a facility do not exceed the Tier 1 screening level, the facility “passes” the screen, and, therefore, is not evaluated further under the screening approach. If emissions from a facility exceed the Tier 1 screening level, we evaluate the facility further in Tier 2. In Tier 2 of the environmental screening analysis, the emission rate screening levels are adjusted to account for local meteorology and the actual location of lakes in the vicinity of facilities that did not pass the Tier 1 screen. The modeling domain for each facility in the Tier 2 analysis consists of 8 octants. Each octant contains 5 modeled soil concentrations at various distances from the facility (5 soil concentrations × 8 octants = total of 40 soil concentrations per facility) and 1 lake with modeled concentrations for water, sediment and fish tissue. In the Tier 2 environmental risk screening analysis, the 40 soil concentration points are averaged to obtain an average soil concentration for each facility for each PB-HAP. For the water, sediment, and fish tissue concentrations, the highest value for each facility for each pollutant is used. If emission concentrations from a facility do not exceed the Tier 2 screening level, the facility passes the screen, and typically is not evaluated further. If emissions from a facility exceed the Tier 2 screening level, the facility does not pass the screen and, therefore, may have the potential to cause adverse environmental effects. Such facilities are evaluated further to investigate factors such as the magnitude and characteristics of the area of exceedance. g. Acid Gas Methodology The environmental screening analysis evaluates the potential phytotoxicity and reduced productivity of plants due to chronic exposure to acid gases. The environmental risk screening methodology for acid gases is a single-tier screen that compares the average off-site ambient air concentration over the modeling domain to ecological benchmarks for each of the acid gases. Because air concentrations are compared directly to the ecological benchmarks, emission-based screening levels are not calculated for acid gases as they are in the ecological risk screening methodology for PB-HAPs. For purposes of ecological risk screening, the EPA identifies a potential for adverse environmental effects to plant communities from exposure to acid gases when the average concentration of the HAP around a facility exceeds the LOAEL ecological benchmark. In such cases, we further investigate factors such as the magnitude and characteristics of the area of exceedance ( e.g., land use of exceedance area, size of exceedance area) to determine if there is an adverse environmental effect. For further information on the environmental screening analysis approach, see the Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule , which is available in the docket for this action. 6. How did we conduct facility-wide assessments? To put the source category risks in context, we typically examine 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, we examine the HAP emissions not only from the source category emission points of interest, but also emissions of HAPs from all other emission sources at the facility for which we have data. There are currently 108 major sources subject to the 40 CFR part 63, subpart MM source category which includes chemical recovery combustion sources ( e.g., recovery furnace, SDT, lime kiln). Nearly all major sources also have boilers on site. These facilities engage in chemical or mechanical pulping, papermaking, paper coating, landfills, petroleum storage and transfer, and other operations. Therefore, where data were available, we performed a facility-wide risk assessment for these major sources as part of this action. For this source category, we conducted the facility-wide assessment using the data from Part II of the Pulp and Paper Sector ICR. We analyzed risks due to the inhalation of HAPs 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 the source category 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 document titled Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule, available in the docket for this action, provides the methodology and results of the facility-wide analyses, including all facility-wide risks and the percentage of source category contribution to facility-wide risks. 7. How did we consider uncertainties in risk assessment? In the Benzene NESHAP, the Agency concluded that risk estimation uncertainty should be considered in our decision-making under the ample margin of safety framework. Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this proposal. Although uncertainty exists, we believe that our approach, which used conservative tools and assumptions, ensures that our decisions are health-protective and environmentally protective. A brief discussion of the uncertainties in the RTR emissions dataset, dispersion modeling, inhalation exposure estimates, and dose-response relationships follows below. 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. A more thorough discussion of these uncertainties is included in the document titled Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule, which is available in the docket for this action. a. Uncertainties in the RTR Emissions Dataset Although the development of the RTR emissions dataset involved quality assurance/quality control processes, various uncertainties exist. Thus, 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 datasets are accurate, errors in emission estimates, and other factors. The emission estimates considered in this analysis generally are annual totals for certain years, and they do not reflect short-term fluctuations during the course of a year or variations from year to year. The estimates of peak hourly emission rates for the acute effects screening assessment were based on an emission adjustment factor applied to the average annual hourly emission rates, which are intended to account for emission fluctuations due to normal facility operations. b. Uncertainties in Dispersion Modeling We recognize there is uncertainty in ambient concentration estimates associated with any model, including the EPA's recommended regulatory dispersion model, AERMOD. In using a model to estimate ambient pollutant concentrations, the user chooses certain options to apply. For RTR assessments, we select some model options that have the potential to overestimate ambient air concentrations ( e.g., not including plume depletion or pollutant transformation). We select other model options that have the potential to underestimate ambient impacts ( e.g., not including building downwash). Other options that we select have the potential to either under- or overestimate ambient levels ( e.g., meteorology and receptor locations). On balance, considering the directional nature of the uncertainties commonly present in ambient concentrations estimated by dispersion models, the approach we apply in the RTR assessments should yield unbiased estimates of ambient HAP concentrations. c. Uncertainties in Inhalation Exposure The EPA did not include the effects of human mobility on exposures in the assessment. Specifically, short-term mobility and long-term mobility between census blocks in the modeling domain were not considered. 24 The approach of not considering short or long-term population mobility does not bias the estimate of the theoretical MIR (by definition), 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-10 thousand or 100-in-1 million). 24 Short-term mobility is movement from one micro-environment 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 is an unbiased estimate of average risk and incidence. We reduce this uncertainty by analyzing large census blocks near facilities using aerial imagery and adjusting the location of the block centroid to better represent the population in the block, as well as adding additional receptor locations where the block population is not well represented by a single location. The assessment evaluates the cancer inhalation risks associated with pollutant exposures over a 70-year period, which is the assumed lifetime of an individual. In reality, both the length of time that modeled emission 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 domestic facilities) will influence the future risks posed by a given source or 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 the unlikely scenario where a facility maintains, or even increases, its emissions levels over a period of more than 70 years, residents live beyond 70 years at the same location, and the residents spend most of their days at that location, then the cancer inhalation risks could potentially be underestimated. However, annual cancer incidence estimates from exposures to emissions from these sources would not be affected by the length of time an emissions source operates. The exposure estimates used in these analyses assume chronic exposures to ambient (outdoor) 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 of the HAPs, indoor levels are roughly equivalent to ambient levels, but for very reactive pollutants or larger particles, indoor levels are typically lower. This factor has the potential to result in an overestimate of 25 to 30 percent of exposures. 25 25 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 factors specific to the acute exposure assessment that the EPA conducts as part of the risk review under section 112 of the CAA that should be highlighted. The accuracy of an acute inhalation exposure assessment depends on the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and the present of humans at the location of the maximum concentration. In the acute screening assessment that we conduct under the RTR program, we assume that peak emissions from the source category and worst-case meteorological conditions co-occur, thus, resulting in maximum ambient concentrations. These two events are unlikely to occur at the same time, making these assumptions conservative. We then include the additional assumption that a person is located at this point during this same time period. For this source category, 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 when peak emissions and worst-case meteorological conditions occur simultaneously. d. Uncertainties in Dose-Response Relationships There are uncertainties inherent in the development of the dose-response values used in our risk assessments for cancer effects from chronic exposures and non-cancer 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's 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 variability in dose-response relationships is given in the Residual Risk Assessment for Pulp Mill Combustion Sources in Support of the December 2016 Risk and Technology Review Proposed Rule, 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). 26 In some circumstances, the true risk could be as low as zero; however, in other circumstances the risk could be greater. 27 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). 26 IRIS glossary ( https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary ). 27 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 non-cancer 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 a continuous inhalation exposure ( i.e., the RfC) or a daily oral exposure ( i.e., the RfD) 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 and 1994) which considers uncertainty, variability and gaps in the available data. The UFs are applied to derive reference values that are intended to protect against appreciable risk of deleterious effects. The UFs are commonly default values, 28 e.g., factors of 10 or 3, used in the absence of compound-specific data; where data are available, UFs may also be developed using compound-specific information. When data are limited, more assumptions are needed and more UFs 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 po [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2016-30758. Public record. Not legal advice.