# Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2014-25872 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** November 7, 2014 - **Citation:** 79 FR 66512 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 60 and 63 [EPA-HQ-OAR-2012-0522; FRL-9912-61-OAR] RIN 2060-AQ20 Phosphoric Acid Manufacturing and Phosphate Fertilizer Production RTR and Standards of Performance for Phosphate Processing AGENCY: Environmental Protection Agency. ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing amendments to the National Emission Standards for Hazardous Air Pollutants for the Phosphoric Acid Manufacturing and Phosphate Fertilizer Production source categories and to new source performance standards (NSPS) for several phosphate processing categories. The proposed amendments address the results of the residual risk and technology reviews (RTR) conducted as required under the Clean Air Act (CAA), as well as other actions deemed appropriate during the review of these standards. The proposed amendments include numeric emission limits for mercury and work practice standards for hydrogen fluoride (HF) from calciners; work practice standards for hazardous air pollutant (HAP) emissions from gypsum dewatering stacks and cooling ponds; emission standards requiring HF testing from various affected sources; clarifications to the applicability and monitoring requirements for both source categories to accommodate process equipment and technology changes; changes to remove the exemptions for startup, shutdown and malfunction; work practice standards for periods of startup and shutdown; and revised provisions to address recordkeeping and reporting requirements applicable to periods of startup, shutdown and malfunction. The proposed amendments will reduce mercury emissions, thereby reducing potential mercury exposure to children, including the unborn. Further, the EPA has conducted an 8-year review of the current NSPS for these source categories, and is proposing that no revisions to the numeric emission limits for these standards are appropriate. DATES: Comments . Comments must be received on or before December 22, 2014. A copy of comments on the information collection provisions should be submitted to the Office of Management and Budget (OMB) on or before December 8, 2014. Public Hearing. If anyone contacts the EPA requesting to speak at a public hearing by November 12, 2014, we will hold a public hearing on November 24, 2014 on the EPA campus at 109 T.W. Alexander Drive, Research Triangle Park, North Carolina. ADDRESSES: Comments. Submit your comments, identified by Docket ID Number EPA-HQ-OAR-2012-0522, by one of the following methods: • Federal eRulemaking Portal: http://www.regulations.gov : Follow the online instructions for submitting comments. • Email: A-and-R-Docket@epa.gov . Include Attention Docket ID No. EPA-HQ-OAR-2012-0522 in the subject line of the message. • Fax: (202) 566-9744, Attention Docket ID No. EPA-HQ-OAR-2012-0522. • Mail: Environmental Protection Agency, EPA Docket Center (EPA/DC), Mail Code 28221T, Attention Docket ID No. EPA-HQ-OAR-2012-0522, 1200 Pennsylvania Ave. NW., Washington, DC 20460. In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th Street NW., Washington, DC 20503. • Hand/Courier Delivery: EPA Docket Center, Room 3334, EPA WJC Building, 1301 Constitution Ave. NW., Washington, DC 20004, Attention Docket ID Number EPA-HQ-OAR-2012-0522. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information. Instructions. Direct your comments to Docket ID Number EPA-HQ-OAR-2012-0522. The EPA's policy is that all comments received will be included in the public docket without change and may be made available online at http://www.regulations.gov , including any personal information provided, unless the comment includes information claimed to be confidential business information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through http://www.regulations.gov , your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should 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 Number EPA-HQ-OAR-2012-0522. All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g. , CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy. Publicly available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the EPA Docket Center, Room 3334, EPA WJC West Building, 1301 Constitution Avenue NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742. Public Hearing. If anyone contacts the EPA requesting a public hearing by November 12, 2014, the public hearing will be held on November 24, 2014 at the EPA's campus at 109 T.W. Alexander Drive, Research Triangle Park, North Carolina. The hearing will begin at 10:00 a.m. (Eastern Standard Time) and conclude at 5:00 p.m. (Eastern Standard Time). There will be a lunch break from 12:00 p.m. to 1:00 p.m. Please contact Ms. Pamela Garrett at 919-541-7966 or garrett.pamela@epa.gov to register to speak at the hearing, or to inquire about whether a hearing will be held. The last day to pre-register in advance to speak at the hearings will be November 19, 2014. 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. If you require the service of a translator or special accommodations such as audio description, please let us know at the time of registration. If you require an accommodation, we ask that you pre-register for the hearing, as we may not be able to arrange such accommodations without advance notice. The hearing will provide interested parties the opportunity to present data, views or arguments concerning the proposed action. The EPA will make every effort to accommodate all speakers who arrive and register. Because this hearing is being held at U.S. government facilities, 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. The EPA may ask clarifying questions during the oral presentations, but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral comments and supporting information presented at the public hearing. Commenters should notify Ms. Garrett if they will need specific equipment, or if there are other special needs related to providing comments at the hearings. Verbatim transcripts of the hearing and written statements will be included in the docket for the rulemaking. The EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearing to run either ahead of schedule or behind schedule. Again, a hearing will only be held if requested by November 12, 2014. Please contact Ms. Pamela Garrett at 919-541-7966 or at garrett.pamela@epa.gov or visit http://www.epa.gov/ttn/atw/phosph/phosphpg.html to determine if a hearing will be held. If the EPA holds a public hearing, the EPA will keep the record of the hearing open for 30 days after completion of the hearing to provide an opportunity for submission of rebuttal and supplementary information. FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Ms. Tina Ndoh, Sector Policies and Programs Division (D243-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-2750; fax number: (919) 541-5450; and email address: Ndoh.Tina@epa.gov . For specific information regarding the risk modeling methodology, contact James Hirtz, Health and Environmental Impacts Division (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) 541-0359; and email address: Hirtz.James@epa.gov . For information about the applicability of the national emissions standards for hazardous air pollutants (NESHAP) or the NSPS to a particular entity, contact Scott Throwe, Office of Enforcement and Compliance Assurance, U.S. Environmental Protection Agency, William Jefferson Clinton Building, Mail Code 2227A, 1200 Pennsylvania Avenue NW., Washington, DC 20460; telephone number: (202)562-7013; and email address: Throwe.Scott@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: ACI Activated Carbon Injection AEGL Acute exposure guideline levels AERMOD Air dispersion model used by the HEM-3 model AFPC Association of Fertilizer and Phosphate Chemists AOAC Association of Official Analytical Chemists APF Ammonium phosphate fertilizer BACT Best available control technology BDL Below the method detection limit BSER Best System of Emissions Reduction CAA Clean Air Act CalEPA California EPA CA-REL California Reference Exposure Level CBI Confidential Business Information CDX Central Data Exchange CEDRI Compliance and Emissions Data Reporting Interface CEMS Continuous emissions monitoring system CFR Code of Federal Regulations CMS Continuous monitoring system CPMS Continuous parameter monitoring system DAP Diammonium phosphate EPA Environmental Protection Agency ERPG Emergency Response Planning Guidelines ERT Electronic Reporting Tool F Fluoride FaTE Fate, Transport, and Ecological Exposure FR Federal Register FTIR Fourier transform infrared spectroscopy gr/dscf Grams per dry standard cubic feet GTSP Granular triple superphosphate H Hydrogen HAP Hazardous air pollutants HCl Hydrogen chloride HEM-3 Human Exposure Model, Version 1.1.0 HF Hydrogen fluoride Hg Mercury HI Hazard index HQ Hazard quotient ICR Information Collection Request IRIS Integrated Risk Information System km Kilometer LAER Lowest achievable emissions rate LOAEL Lowest-observed-adverse-effect level MACT Maximum achievable control technology MAP Monoammonium phosphate mg/dscm Milligrams per dry standard cubic meter mg/kg-day Milligrams per kilogram-day mg/m 3 Milligrams per cubic meter MIBK Methyl isobutyl ketone MIR Maximum individual risk MRL Minimum risk level NAAQS National Ambient Air Quality Standards NAICS North American Industry Classification System NATA National Air Toxics Assessment NEI National Emissions Inventory NESHAP National Emissions Standards for Hazardous Air Pollutants NOAA National Oceanic and Atmospheric Administration NOAEL No-observed-adverse-effect level NRC National Research Council NTTAA National Technology Transfer and Advancement Act OAQPS Office of Air Quality Planning and Standards OECA Office of Enforcement and Compliance Assurance OMB Office of Management and Budget P 2 O 5 Phosphorus pentoxide PB-HAP Hazardous air pollutants known to be persistent and bio-accumulative in the environment PEL Probable effect levels PM Particulate matter POM Polycyclic organic matter PPA Purified phosphoric acid ppm Parts per million QA/QC Quality assurance/quality control RACT Reasonably available control technology RATA Relative accuracy test audit RBLC RACT/BACT/LAER Clearinghouse REL Reference exposure level RFA Regulatory Flexibility Act RfC Reference concentration RfD Reference dose RTR Residual risk and technology review SAB Science Advisory Board SBA Small Business Administration SiF4 Silicon tetrafluoride SPA Superphosphoric acid SSM Startup, shutdown and malfunction TOSHI Target organ-specific hazard index tpy Tons per year TRIM Total Risk Integrated Modeling System TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model TTN Technology Transfer Network UF Uncertainty factor μg/m 3 Micrograms per cubic meter UMRA Unfunded Mandates Reform Act UPL Upper prediction limit URE Unit risk estimate VCS Voluntary consensus standards WESP Wet electrostatic precipitator WPPA Wet-process phosphoric acid WWW World Wide Web Organization of this Document. The information in this preamble is organized as follows: I. General Information A. Does this action apply to me? B. Where can I get a copy of this document and other related information? C. What should I consider as I prepare my comments for the EPA? II. Background A. What are the statutory authorities for this action? B. What are the source categories and how do the current NESHAP and NSPS regulate 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 categories? B. How did we consider the risk results in making decisions for this proposal? C. How did we perform the technology reviews for the NESHAP and NSPS? IV. Analytical Results and Proposed Decisions for the Phosphoric Acid Manufacturing Source Category A. What actions are we taking pursuant to CAA sections 112(d)(2) and 112(d)(3) for the Phosphoric Acid Manufacturing source category? B. What are the results of the risk assessment and analyses for the Phosphoric Acid Manufacturing source category? C. What are our proposed decisions regarding risk acceptability, ample margin of safety and adverse environmental effects for the Phosphoric Acid Manufacturing source category? D. What are the results and proposed decisions based on our technology review for the Phosphoric Acid Manufacturing source category? E. What other actions are we proposing for the Phosphoric Acid Manufacturing source category? F. What are the notification, recordkeeping and reporting requirements for the Phosphoric Acid Manufacturing source category? G. What compliance dates are we proposing for the Phosphoric Acid Manufacturing source category? V. Analytical Results and Proposed Decisions for the Phosphate Fertilizer Production Source Category A. What are the results of the risk assessment and analyses for the Phosphate Fertilizer Production source category? B. What are our proposed decisions regarding risk acceptability, ample margin of safety and adverse environmental effects for the Phosphate Fertilizer Production source category? C. What are the results and proposed decisions based on our technology review for the Phosphate Fertilizer Production source category? D. What other actions are we proposing for the Phosphate Fertilizer Production source category? E. What are the notification, recordkeeping and reporting requirements for the Phosphate Fertilizer Production source category? F. What compliance dates are we proposing for the Phosphate Fertilizer Production source category? VI. 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? VII. Request for Comments VIII. Submitting Data Corrections IX. Statutory and Executive Order Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review B. Paperwork Reduction Act C. Regulatory Flexibility Act D. Unfunded Mandates Reform Act E. Executive Order 13132: Federalism F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use I. National Technology Transfer and Advancement Act J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations I. General Information A. Does this action apply to me? Table 1 of this preamble lists the industrial source categories that are the subject of this proposal. Table 1 is not intended to be exhaustive but rather to provide 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. 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 “Phosphoric Acid Manufacturing” source category is any facility engaged in the production of phosphoric acid. The category includes, but is not limited to, production of wet-process phosphoric acid (WPPA) and superphosphoric acid (SPA). The “Phosphate Fertilizer Production” source category includes any facility engaged in the production of phosphate-based fertilizers including, but not limited to, plants with bulk-blend processes, fluid-mix processes or ammonia granulation processes. Examples of phosphate fertilizers are: Monoammonium phosphates (MAP) and diammonium phosphates (DAP) (or ammonium phosphate fertilizer (APF)), and triple superphosphates (TSP). 1 1 U.S. EPA. Documentation for Developing the Initial Source Category List—Final Report, USEPA/OAQPS, EPA-450/3-91-030, July, 1992. Table 1—Industrial Source Categories Affected by This Proposed Action Source category NAICS Code a Examples of regulated entities Industrial 325312 Phosphoric Acid; and Phosphate Fertilizers. a North American Industry Classification System. B. 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 Technology Transfer Network (TTN) Web site, a forum for information and technology exchange in various areas of air pollution control. Following signature by the EPA Administrator, the EPA will post a copy of this proposed action at: http://www.epa.gov/ttn/atw/phosph/phosphpg.html. Following publication in the Federal Register, the EPA will post the Federal Register version of the proposal and key technical documents at the same Web site. Information on the overall residual risk and technology review program is available at the following Web site: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. C. 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 Code of Federal Regulations (CFR) part 2. Send or deliver information identified as CBI only to the following address: Roberto Morales, OAQPS Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID Number EPA-HQ-OAR-2012-0522. II. Background A. What are the statutory authorities for this action? 1. NESHAP Authority 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 HAP listed in CAA section 112(b), CAA section 112(d) requires us to promulgate technology-based NESHAP for those sources. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of 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 maximum achievable control technology (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 eight years. CAA section 112(d)(6). In conducting this review, the EPA is not required to recalculate the MACT floor. 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). CAA section 112(f)(1) 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. CAA section 112(f)(2) 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). CAA section 112(f)(2) of the CAA requires the EPA to determine for source categories subject to MACT standards whether the emission standards provide an ample margin of safety to protect public health. CAA 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. a. 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. b. Step 2-Determination of Ample Margin of Safety CAA section 112(f)(2) 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, 2 but must consider cost, energy, safety and other relevant factors in doing so. 2 “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, we 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, September 14, 1989. 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 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. 2. NSPS Authority New source performance standards implement CAA section 111, which requires that each NSPS reflect the degree of emission limitation achievable through the application of the best system of emission reduction (BSER) which (taking into consideration the cost of achieving such emission reductions, any nonair quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated. Existing affected facilities that are modified or reconstructed are also be subject to NSPS. Under CAA section 111(a)(4), “modification” means any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted. Changes to an existing facility that do not result in an increase in emissions are not considered modifications. Rebuilt emission units would become subject to the NSPS under the reconstruction provisions in 40 CFR 60.15, regardless of changes in emission rate. Reconstruction means the replacement of components of an existing facility such that: (1) The fixed capital cost of the new components exceeds 50 percent of the fixed capital cost that would be required to construct a comparable entirely new facility; and (2) it is technologically and economically feasible to meet the applicable standards (40 CFR 60.15). Section 111(b)(1)(B) of the CAA requires the EPA to periodically review and, if appropriate, revise the standards of performance as necessary to reflect improvements in methods for reducing emissions. The EPA need not review an NSPS if the agency determines that such review is not appropriate in light of readily available information on the efficacy of the standard. When conducting the review under CAA section 111(b)(1)(B), the EPA considers both (1) whether developments in technology or other factors support the conclusion that a different system of emissions reduction has become the “best system of emissions reduction” and (2) whether emissions limitations and percent reductions beyond those required by the current standards are achieved in practice. B. What are the source categories and how do the current NESHAP and NSPS regulate emissions? 1. Description of Phosphoric Acid Manufacturing Source Category In 2014, 12 facilities in the United States manufacture phosphoric acid. The basic step for producing phosphoric acid is acidulation of phosphate rock. Typically, sulfuric acid, phosphate rock and water are combined together and allowed to react to produce phosphoric acid and gypsum. When phosphate rock is acidulated to manufacture WPPA, fluorine contained in the rock is released. Fluoride (F) compounds, predominately HF, are produced as particulates and gases that are emitted to the atmosphere unless removed from the exhaust stream. Some of these same F compounds also remain in the product acid and are released as air pollutants during subsequent processing of the acid. Gypsum is pumped as a slurry to ponds atop stacks of waste gypsum where the liquids separate from the slurry and are decanted for return to the process. The gypsum, which is discarded on the stack, is a solid waste stream produced in this process. Five facilities concentrate WPPA to make SPA, typically using the vacuum evaporation process. While one manufacturer is permitted to use a submerged combustion process for the production of SPA, that process was indefinitely shutdown on June 1, 2006. The majority of WPPA is used to produce phosphate fertilizers. Additional processes may also be used to further refine phosphoric acid. At least two facilities have a defluorination process to remove F from the phosphoric acid product, and one company uses a solvent extraction process to remove metals and organics and to further refine WPPA into purified phosphoric acid (PPA) for use in food manufacturing or specialized chemical processes. In addition, four facilities have processes to remove organics from the acid (i.e., the green acid process). Sources of HF emissions from phosphoric acid plants include gypsum dewatering stacks, cooling ponds, cooling towers, calciners, reactors, filters, evaporators and other process equipment. 2. Federal Emission Standards Applicable to the Phosphoric Acid Manufacturing Source Category The following federal emission standards are associated with the Phosphoric Acid Manufacturing source category and are subject of this proposed rulemaking: • National Emission Standards for Hazardous Air Pollutants from Phosphoric Acid Manufacturing Plants (40 CFR part 63, subpart AA); • Standards of Performance for the Phosphate Fertilizer Industry: Wet-Process Phosphoric Acid Plants (40 CFR part 60, subpart T); and • Standards of Performance for the Phosphate Fertilizer Industry: Superphosphoric Acid Plants (40 CFR part 60, subpart U). a. Phosphoric Acid Manufacturing NESHAP Emission Regulations The EPA promulgated 40 CFR part 63, subpart AA for the Phosphoric Acid Manufacturing source category on June 10, 1999 (64 FR 31358). The NESHAP established standards for major sources to control HAP emissions from phosphoric acid facilities. Total F emission limits, as a surrogate for the HAP HF, were set for WPPA process lines and SPA process lines. For new sources, WPPA process lines are limited to 0.0135 pounds (lb) total F per ton (lb total F/ton) of equivalent phosphorus pentoxide (P 2 O 5 ), and SPA process lines are limited to 0.00870 lb total F/ton of equivalent P 2 O 5 . For existing sources, WPPA process lines are limited to 0.020 lb total F/ton of equivalent P 2 O 5, SPA process lines using a vacuum evaporation process are limited to 0.010 lb total F/ton of equivalent P 2 O 5 , and SPA process lines using a submerged combustion process are limited to 0.020 lb total F/ton of equivalent P 2 O 5 . The NESHAP established emission limits for PM from phosphate rock dryers and phosphate rock calciners as a surrogate for metal HAP. For new sources, phosphate rock dryers are limited to 0.060 pounds PM per ton (lb PM/ton) of phosphate rock feed, and phosphate rock calciners are limited to 0.040 grains of PM per dry standard cubic feet (gr/dscf). For existing sources, phosphate rock dryers are limited to 0.2150 lb PM/ton of phosphate rock feed, and phosphate rock calciners are limited to 0.080 gr/dscf. Also, the NESHAP established an emission limit for methyl isobutyl ketone (MIBK) for PPA process lines and work practices for cooling towers. For new and existing sources, each product acid stream from PPA process lines is limited to 20 parts per million (ppm) of MIBK, and each raffinate stream from PPA process lines is limited to 30 ppm of MIBK (compliance is based on a 30-day average of daily concentration measurements). b. Phosphoric Acid Manufacturing NSPS Emission Regulations The EPA promulgated 40 CFR part 60, subpart T for Wet-Process Phosphoric Acid Plants on August 6, 1975 (40 FR 33154). The NSPS established standards to control total F emissions from WPPA plants, including reactors, filters, evaporators and hot wells. For new, modified, and reconstructed sources WPPA plants are limited to 0.020 lb total F/ton of equivalent P 2 O 5 . The EPA promulgated 40 CFR part 60, subpart U for Superphosphoric Acid Plants on August 6, 1975 (40 FR 33155). The NSPS established standards to control total F emissions from SPA plants, including evaporators, hot wells, acid sumps and cooling tanks. For new, modified and reconstructed sources, SPA plants are limited to 0.010 lb total F/ton of equivalent P 2 O 5 . 3. Description of Phosphate Fertilizer Production Source Category In 2014, there are 11 operating facilities that produce phosphate fertilizers, and most facilities can produce either MAP or DAP in the same process train. However, approximately 80 percent of all ammonium phosphates are produced as MAP. MAP and DAP plants are generally collocated with WPPA plants since it is manufactured from phosphoric acid and ammonia. The MAP and DAP manufacturing process consists of three basic steps: Reaction, granulation and finishing operations such as drying, cooling and screening. In addition, some of the fluorine is liberated as HF and silicon tetrafluoride (SiF 4 ), with the majority being emitted as HF. Sources of F emissions from MAP and DAP plants include the reactor, granulator, dryer, cooler, screens and mills. TSP is made as run-of-the-pile-TSP (ROP-TSP) and granular TSP (GTSP) by reacting WPPA with ground phosphate rock. The phosphoric acid used in the GTSP process is appreciably lower in concentration (40- percent P 2 O 5 ) than that used to manufacture ROP-TSP product (50- to 55- percent P 2 O 5 ). The GTSP process yields larger, more uniform particles with improved storage and handling properties than the ROP-TSP process. Currently, no facilities produce ROP-TSP or GTSP, 3 although one facility retains an operating permit to store GTSP. 3 According to 2014 production and trade statistics issued by International Fertilizer Industry Association (IFA). 4. Federal Emission Standards Applicable to the Phosphate Fertilizer Production Source Category The following federal emission standards are associated with the Phosphate Fertilizer Production source category and are subject of this proposed rulemaking: • National Emission Standards for Hazardous Air Pollutants from Phosphate Fertilizers Production Plants (40 CFR part 63, subpart BB); • Standards of Performance for the Phosphate Fertilizer Industry: Diammonium Phosphate Plants (40 CFR part 60, subpart V); • Standards of Performance for the Phosphate Fertilizer Industry: Triple Superphosphate Plants (40 CFR part 60, subpart W); and • Standards of Performance for the Phosphate Fertilizer Industry: Granular Triple Superphosphate Storage Facilities (40 CFR part 60, subpart X). a. Phosphate Fertilizer Production NESHAP Emission Regulations The EPA promulgated 40 CFR part 63, subpart BB for the Phosphate Fertilizer Production source category on June 10, 1999 (64 FR 31358). The NESHAP established standards for major sources to control HAP emissions from phosphate fertilizer facilities. As a surrogate for HF, the NESHAP set total F emission limits for DAP and/or MAP process lines and GTSP process lines and storage buildings. The NESHAP also established work practices for GTSP production. For new sources, DAP and MAP process lines are limited to 0.058 lb total F/ton of equivalent P 2 O 5 feed. For existing sources, DAP and MAP process lines are limited to 0.06 lb total F/ton of equivalent P 2 O 5 feed. For new sources, GTSP process lines are limited to 0.1230 lb total F/ton of equivalent P 2 O 5 feed. For existing sources, GTSP process lines are limited to 0.150 lb total F/ton of equivalent P 2 O 5 feed. For new and existing sources, GTSP storage buildings are limited to 5.0×10 −4 pounds of total F per hour per ton of equivalent P 2 O 5 stored. b. Phosphate Fertilizer Production NSPS Emission Regulations The EPA promulgated 40 CFR part 60, subpart V for Diammonium Phosphate Plants on July 25, 1977 (42 FR 37938). The NSPS established standards to control total F emissions from granular DAP plants, including reactors, granulators, dryers, coolers, screens and mills. For new, modified and reconstructed sources, granular DAP plants are limited to 0.06 lb total F/ton of equivalent P 2 O 5 feed. The EPA promulgated 40 CFR part 60, subpart W for Triple Superphosphate Plants on July 25, 1977 (42 FR 37938). The NSPS established standards to control total F emissions from the production of ROP-TSP and GTSP, and the storage of ROP-TSP. For new, modified and reconstructed sources, production of ROP-TSP and GTSP and the storage of ROP-TSP is limited to 0.20 lb total F/ton of equivalent P 2 O 5 feed. The EPA promulgated 40 CFR part 60, subpart X for Granular Triple Superphosphate Storage Facilities on July 25, 1977 (42 FR 37938). The NSPS established standards to control total F emissions from the storage of GTSP, including storage or curing buildings (noted as “piles” in subpart X), conveyors, elevators, screens and mills. For new, modified and reconstructed sources, the storage of GTSP is limited to 5.0×10 −4 pounds of total F per hour per ton of equivalent P 2 O 5 stored. C. What data collection activities were conducted to support this action? In April 2010, the EPA requested data, pursuant to CAA section 114, from the seven companies that own and operate the 12 Phosphoric Acid facilities and 11 Phosphate Fertilizer facilities. The EPA requested available information regarding process equipment, control devices, point and fugitive emissions, and other aspects of facility operations. The seven companies completed the surveys for their facilities and submitted the responses to the EPA in the fall of 2010. Additionally, the EPA requested that the facilities conduct emissions tests in 2010 for certain HAP from specific processes. Pollutants tested included HF, total F, PM and HAP metals. The facilities also conducted analyses of the phosphate rock used in the manufacture of phosphoric acid. The facilities submitted the results of these tests to the EPA in the fall of 2010. The test results are available in the docket for this action. On January 24, 2014, the EPA issued another CAA section 114 survey and testing request to certain facilities in order to gather additional mercury (Hg) and HF emissions data from calciner operations, and additional total F and HF emissions data from certain WPPA, SPA and APF lines. The selection of WPPA, SPA and APF lines to be tested was based on a review of the data received from the April 13, 2010 CAA section 114 survey request. In addition to the testing, the EPA requested process production rate data concurrent with the duration of the emissions testing (e.g., phosphoric acid production in tons per hour of P 2 O 5 ). For more information regarding the April 2010 CAA section 114 and January 2014 CAA section 114 requests, refer to the memorandum, “Information Collection and Additional Data Received for the Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action. D. What other relevant background information and data are available? To support this proposed rulemaking, the EPA used information from the EPA's National Emissions Inventory (NEI), and the RACT/BACT/LAER Clearinghouse (RBLC) when performing the technology review and other analyses. If emissions for a specific emission point were available in the NEI, but test data were not available, we used the NEI data to estimate emissions. This approach was primarily applicable to combustion emissions. The EPA utilized the RBLC as a reference for additional control technologies when performing the technology review. See sections III.C, and IV.D, and V.C of this preamble for further details on the use of these sources of information. Table 2 of this preamble summarizes the emissions data collected for point sources and fugitive sources at phosphoric acid manufacturing and phosphate fertilizer production facilities of HF, Total PM, Hg and other HAP Metals. This includes emissions data from stack tests, fugitive emission reports, and the NEI. Table 2—Summary of Emissions Data Collected for Point Sources and Fugitive Sources at Phosphoric Acid Manufacturing and Phosphate Fertilizer Production Facilities Source category and emission point type HF (tpy) Total PM (tpy) Hg (tpy) HAP Metals (tpy) a Phosphoric Acid Manufacturing: Point Sources 38 162 0.019 1.07 Fugitive Sources 2,155 0 0 0 Total 2,193 162 0.019 1.07 Phosphate Fertilizer Production: Point Sources 85.0 907 0.13 0.40 Fugitive Sources 0.0051 0 0 0 Total 85.0 907 0.13 0.40 a HAP metals includes: antimony, arsenic, beryllium, cadmium, chromium (VI), chromium III, cobalt, lead, manganese, nickel, and selenium. 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 categories? 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 HAP with the potential to cause non-cancer health effects, and the hazard quotient (HQ) for acute exposures to HAP 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 risk assessment consisted of seven primary steps, as discussed below. The docket for this rulemaking contains the following document, which provides more information on the risk assessment inputs and models: Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing. 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; 4 they are also consistent with the key recommendations contained in that report. 4 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? a. Estimation of Actual Emissions Data from our April 2010 CAA section 114 request were used for this assessment. The EPA performed a review and thorough quality assurance/quality control (QA/QC) of the data to identify any limitations and issues. The EPA also contacted facility and industry representatives to clarify details and resolve issues with their data submissions. The EPA updated the 2005 NEI data for the Phosphate Fertilizer Production and Phosphoric Acid Manufacturing source categories with the emissions data and corrections to facility and emission point locations that we received from industry through the CAA section 114 request. The data incorporation procedures are discussed in the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action. In a few limited instances, test data were not available for an emission point available in the NEI, in which case the existing emissions data in the 2005 NEI were used. The following sections of this preamble describe each of the source categories, including a discussion of the applicable information sources used to estimate emissions. b. Phosphoric Acid Manufacturing Phosphate rock is the starting material for the production of all phosphate products. Once the rock reaches the phosphoric acid production facility, phosphoric acid is typically produced using the wet method, in which beneficiated ground phosphate rock (i.e., phosphate rock that has been processed to remove impurities) is reacted with sulfuric acid and weak phosphoric acid to produce phosphoric acid and phosphogypsum, a waste product. The phosphogypsum is disposed of on site in waste piles known as gypsum dewatering stacks (which are also referred to as “gypsum stacks” or “gypstacks”). Phosphoric acid facility emissions are both point sources and fugitive sources. Point source emissions originate from equipment (e.g., reactors, filters, evaporators and calciners) associated with phosphoric acid manufacturing processes including WPPA process lines, SPA process lines and PPA process lines. Fugitive emissions are released from cooling ponds, cooling towers and gypsum dewatering stacks. In 2014, there are 12 phosphoric acid manufacturing facilities operating in the United States. Based on the emissions dataset (see the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action), all 12 of these facilities are, or show the potential to be, major sources of HAP even though two of these facilities identified themselves as area sources of HAP in their response to our April 2010 CAA section 114 request. Ten of these 12 facilities are collocated with phosphate fertilizer production facilities. Based on the emissions data provided with the CAA section 114 request or available in the NEI, the total HAP emissions for the Phosphoric Acid Manufacturing source category are approximately 2,230 tpy. HF is the HAP emitted in the largest quantity across these 12 facilities, accounting for approximately 98 percent of the total HAP emissions by mass. Persistent and bioaccumulative HAP (PB-HAP) emissions reported from these facilities include Hg, Pb, dioxin, polycyclic organic matter (POM) and cadmium compounds. c. Phosphate Fertilizer Production Phosphate fertilizer operations are generally collocated with phosphoric acid manufacturing facilities, which provide the feedstock (phosphoric acid) for phosphate fertilizer production facilities. Phosphate fertilizer is produced by reacting phosphoric acid and ammonia, followed by granulation, drying, cooling and screening. Emissions from each of these steps are included in the estimated point source emissions for each facility. Phosphate fertilizer facilities also send water to cooling ponds and, thus, contribute to the fugitive emissions from these sources. However, the contribution from phosphate fertilizer production sources to the fugitive emissions from the cooling ponds is minimal. Therefore, we have assigned fugitive emissions from cooling ponds to the Phosphoric Acid Manufacturing source category. In 2014, there are 11 phosphate fertilizer production facilities operating in the United States. Based on the emissions dataset (see the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action), all 11 of these facilities are, or show the potential to be, major sources of HAP even though one of these facilities identified itself as an area source of HAP in their response to our April 2010 CAA section 114 request. Ten of these 11 facilities are collocated with phosphoric acid manufacturing facilities. Based on the emissions data provided with the CAA section 114 request or available in the NEI, the total HAP emissions for the Phosphate Fertilizer Production source category are approximately 86 tpy. The HAP emitted in the largest quantity across these 11 facilities is HF. HF accounts for 99 percent of the total emissions by mass. PB-HAP emissions reported from these facilities include Hg, Pb, and cadmium compounds. 2. How did we estimate MACT-allowable emissions? The available emissions data in the RTR emissions dataset include estimates of the mass of HAP 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 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 residual risk rule (70 FR 19998-19999, April 15, 2005) and in the proposed and final Hazardous Organic NESHAP residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609, December 21, 2006, respectively). In those previous actions, we noted that assessing the risks at the MACT-allowable level is inherently reasonable 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.) Details on the methodologies for calculating allowable emissions, as discussed below, are provided in the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action. a. Phosphoric Acid Manufacturing In the case of this particular source category, point sources contribute only a small percentage of overall emissions. Therefore, as a conservative approach, we used the emission limits and the permitted production capacity specified in the title V permit for each facility to calculate allowable emissions for point sources. Because emission limits are in terms of total F (pounds of total F per ton of P 2 O 5 production), and not the HAP HF, emissions for total F were used as a surrogate for HF when calculating allowable emissions. If emissions limits were not available in the title V permit, we used the emission limits for existing sources in the current NESHAP subpart AA. Because emissions limits for metals and MIBK are not listed in the permits, we calculated allowable emissions using the emissions as measured in the stack tests for the CAA section 114 request, and scaled these emissions up using the permitted capacity. Allowable point source emissions are as much as 59 times higher than actual total F emissions, about 8 times higher than actual metal emissions, and about 2 times higher than actual MIBK emissions at phosphoric acid manufacturing processes. For fugitive emissions of HF from gypsum dewatering stacks, cooling ponds and cooling towers, the EPA estimated that actual emissions were equivalent to allowable emissions. We do not expect fugitive emissions to increase from these sources with an increase in production rate, or increase significantly during a process upset, as emissions from these large fugitive sources are the cumulative result of many decades of stacking gypsum waste product and re-circulating cooling water. Because of their general homeostatic nature, we expect only minor changes in cooling pond emissions over time. We also anticipate that emissions are higher during daylight hours and warmer months due to the increased evaporation rate associated with higher ambient temperatures. Test data for these sources were obtained during the spring and summer seasons and during daylight hours. Therefore, emissions would not be expected to increase significantly beyond the levels measured during the tests. We expect that the emission factors and range of estimates (high, medium and low) that we developed, based on the test data for the spring and summer seasons obtained from industry, account sufficiently for any changes to emissions as ambient conditions change. For more information on the development of emission factors, see the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid and Phosphate Fertilizer Production Source Categories,” which is available in the docket for this action. b. Phosphate Fertilizer Production Similar to phosphoric acid manufacturing, point sources contribute only a small percentage of overall emissions from this particular source category. Therefore, as a conservative approach, we used the emission limits (expressed in pounds of total F per ton of P 2 O 5 production) and the permitted production capacity specified in the title V permit for each facility to calculate point source allowable emissions for total F, as a surrogate for HF. If emissions limits were not available in the title V permit, we used the limits for existing sources in the current NESHAP subpart BB. Because emissions limits for metals are not listed in the permits, we calculated allowable emissions using the emissions test data collected by the CAA section 114 request, and scaled these emissions up using the permitted capacity. Allowable point source emissions are as much as 11 times higher than actual total F emissions and about 2 times higher than actual metal at phosphate fertilizer production processes. 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 the Human Exposure Model (Community and Sector HEM-3 version 1.1.0). The HEM-3 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 kilometers (km) of the modeled sources, 5 and (3) estimating individual and population-level inhalation risks using the exposure estimates and quantitative dose-response information. 5 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. 6 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 (2011) 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 7 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 HAP and other toxic air pollutants. These values are available at: http://www.epa.gov/ttn/atw/toxsource/summary.html and are discussed in more detail later in this section. 6 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). 7 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 EPA IRIS values, we look to other reputable sources of cancer dose-response values, often using California EPA (CalEPA) URE values, where available. In cases where new, scientifically credible dose response values have been developed in a manner consistent with 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 8 ) 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. 8 These classifications also coincide with the terms “known carcinogen, probable carcinogen, and possible carcinogen,” respectively, which are the terms advocated in the EPA's previous Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 33992, September 24, 1986). Summing the risks of these individual compounds to obtain the cumulative cancer risks is an approach that was recommended by the EPA's SAB in their 2002 peer review of EPA's National Air Toxics Assessment (NATA) entitled, NATA—Evaluating the National-scale Air Toxics Assessment 1996 Data—an SAB Advisory, available at: http://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf. To assess 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 either the EPA reference concentration (RfC) ( http://www.epa.gov/riskassessment/glossary.htm ), defined as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime,” or, in cases where an RfC from the EPA's IRIS database is not available, a value from the following prioritized sources: (1) The Agency for Toxic Substances and Disease Registry 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://www.oehha.ca.gov/air/hot_spots/pdf/HRAguidefinal.pdf ), 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. The EPA also evaluated screening estimates of acute exposures and risks for each of the HAP 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 for our acute analysis. As described in the CalEPA's Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants, an acute REL value ( http://www.oehha.ca.gov/air/pdf/acuterel.pdf ) is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.” 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. AEGL values were derived in response to recommendations from the National Research Council (NRC). As described in Standing Operating Procedures (SOP) of the National Advisory Committee on Acute Exposure Guideline Levels for Hazardous Substances ( http://www.epa.gov/oppt/aegl/pubs/sop.pdf ), 9 “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.” Id. at 2. 9 National Academy of Sciences (NAS), 2001. Standing Operating Procedures for Developing Acute Exposure Levels for Hazardous Chemicals, page 2. This document also states that AEGL values “represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to eight hours.” Id. at 2. The document lays out the purpose and objectives of AEGL by stating that “the primary purpose of the AEGL program and the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances is to develop guideline levels for once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.” Id. at 21. In detailing the intended application of AEGL values, the document states that “[i]t is anticipated that the AEGL values will be used for regulatory and nonregulatory purposes by U.S. federal and state agencies and possibly the international community in conjunction with chemical emergency response, planning, and prevention programs. More specifically, the AEGL values will be used for conducting various risk assessments to aid in the development of emergency preparedness and prevention plans, as well as real-time emergency response actions, for accidental chemical releases at fixed facilities and from transport carriers.” Id. at 31. The AEGL-1 value is then specifically defined as “the airborne concentration (expressed as ppm (parts per million) or mg/m 3 (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. ERPG values are derived for use in emergency response, as described in the American Industrial Hygiene Association's ERP Committee document titled, ERPGS Procedures and Responsibilities ( http://sp4m.aiha.org/insideaiha/GuidelineDevelopment/ERPG/Documents/ERP-SOPs2006.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.” 10 Id. at 1. The ERPG-1 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or without perceiving a clearly defined, objectionable odor.” Id. at 2. Similarly, the ERPG-2 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.” Id. at 1. 10 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 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. 11 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, we applied a multiplication factor of 10 to all emission sources except for HF emissions from the gypsum dewatering stacks and cooling ponds. The EPA used a multiplication factor of 1 for gypsum dewatering stacks and cooling ponds based upon the stability of HF releases from this emission source. Section III.A.2.a of this preamble as well as the memorandum, “Emissions Data Used in Residual Risk Modeling: Phosphoric Acid Manufacturing and Phosphate Fertilizer Production,” which is available in the docket for this rulemaking, discusses our rationale for choosing this factor. 11 See http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html or docket to access the source of these data. As part of our acute risk assessment process, for cases where acute HQ values from the screening step were less than or equal to 1 (even under the conservative assumptions of the screening analysis), acute impacts were deemed negligible and no further analysis was performed. In cases where an acute HQ from the screening step was greater than 1, additional site-specific data were considered to develop a more refined estimate of the potential for acute impacts of concern. For these source categories, the data refinements employed consisted of, in some cases, the use of a refined emissions multiplier for individual emission process groups to estimate the peak hourly emission rates in lieu of using the default emission multiplier of 10(x) the annual average 1-hour emission rate. For the two source categories, we conducted a review of the layout of emission points at the facilities to ensure they were located within the facility boundaries as well as to identify the maximum off-site acute impact receptor for the facilities that did not screen out during the initial base model run. 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 HAP, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies, 12 we generally examine a wider range of available acute health metrics (e.g., RELs, AEGLs) 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 13 for HAP have been developed, we consider additional acute values (i.e., occupational and international values) to provide a more complete risk characterization. 12 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. 13 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of Chemical-Specific Health Effect Reference Values for Inhalation Exposures (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/061, and available 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 categories emitted any hazardous air pollutants known to be persistent and bioaccumulative in the environment (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 Phosphoric Acid Manufacturing source category, we identified PB-HAP emissions of cadmium compounds, Pb compounds, Hg compounds, POM and dioxin. For the Phosphate Fertilizer Production Source Category, we identified PB-HAP emissions of cadmium compounds, Pb compounds, and Hg compounds. Because one or more of these PB-HAP are emitted by at least one facility in the two source categories, 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 developed emissions rate screening levels for several PB-HAP 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-HAP with emissions rate screening levels are: Pb, cadmium, chlorinated dibenzodioxins and furans, Hg 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 rates of each of these PB-HAP were compared to the emission rate screening levels for these PB-HAP to assess the potential for significant human health risks via non-inhalation pathways. We call this application of the TRIM.FaTE model the Tier I TRIM-screen or Tier I screen. For the purpose of developing emissions rates for our Tier I TRIM-screen, we derived emission levels for these PB-HAP (other than Pb compounds) at which the maximum excess lifetime cancer risk would be 1-in-1 million (i.e., for polychlorinated dibenzodioxins and furans and POM) or, for HAP that cause non-cancer health effects (i.e., cadmium compounds and Hg compounds), the maximum HQ would be 1. If the emissions rate of any PB-HAP included in the Tier I screen exceeds the Tier I screening emissions rate for any facility, we conduct a second screen, which we call the Tier II TRIM-screen or Tier II screen. In the Tier II screen, the location of each facility that exceeded the Tier I emission rate is used to refine the assumptions associated with the environmental scenario while maintaining the exposure scenario assumptions. We then adjusted the risk-based Tier I screening level 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 II screening levels are considered to pose no unacceptable risks. When facilities exceed the Tier II screening levels, it does not mean that multipathway impacts are significant, only that we cannot rule out that possibility based on the results of the screen. These facilities may be further evaluated for multipathway risks using the TRIM.FaTE model. In evaluating the potential multi-pathway risk from emissions of Pb compounds, rather than developing a screening emissions rate for them, we compared maximum estimated chronic inhalation exposures with the level of the current NAAQS for Pb. 14 Values below the level of the primary (health based) Pb NAAQS were considered to have a low potential for multi-pathway risk. 14 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 Pb 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 Pb NAAQS at the risk acceptability step is conservative, since that primary Pb NAAQS reflects an adequate margin of safety. For further information on the multipathway analysis approach, see the memorandum, “Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing,” 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 has developed a screening approach 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 HAP The EPA focuses on seven HAP, which we refer to as “environmental HAP,” in its screening analysis: Five PB-HAP and two acid gases. The five PB-HAP are cadmium, dioxins/furans, POM, Hg (both inorganic mercury and methyl mercury) and Pb compounds. The two acid gases are HCl and HF. The rationale for including these seven HAP in the environmental risk screening analysis is presented below. HAP that persist and bioaccumulate are of particular environmental concern because they accumulate in the soil, sediment and water. The PB-HAP 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-HAP in the animal tissues increases as does the potential for adverse effects. The five PB-HAP 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 NEI). In addition to accounting for almost all of the mass of PB-HAP emitted, we note that the TRIM.FaTE model that we use to evaluate multipathway risk allows us to estimate concentrations of for cadmium compounds, dioxins/furans, POM and Hg in soil, sediment and water. For Pb 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 Pb compounds, we compare the estimated HEM-modeled exposures from the source category emissions of Pb with the level of the secondary NAAQS for Pb. 15 We consider values below the level of the secondary Pb NAAQS to be unlikely to cause adverse environmental effects. 15 The secondary Pb 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 HAP emitted by stationary sources in the U.S. 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 HAP 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 HAP beyond the seven HAP discussed above may have the potential to cause adverse environmental effects. Therefore, the EPA may include other relevant HAP in its environmental risk screening in the future, as modeling science and resources allow. The EPA invites comment on the extent to which other HAP emitted by the source categories 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-HAP (other than Pb compounds), we evaluated the following community-level ecological assessment endpoints to screen for organisms directly exposed to HAP 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-HAP in the surface soil. • Local benthic (i.e., bottom sediment dwelling insects, amphipods, isopods and crayfish) communities exposed to PB-HAP in sediment in nearby water bodies. • Local aquatic (water-column) communities (including fish and plankton) exposed to PB-HAP in nearby surface waters. For PB-HAP (other than Pb compounds), we also evaluated the following population-level ecological assessment endpoint to screen for indirect HAP exposures of top consumers via the bioaccumulation of HAP 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 Hg, we identified the available ecological benchmarks for each assessment endpoint. An ecological benchmark represents a concentration of HAP (e.g., 0.77 ug of HAP per liter of water) that has been linked to a particular environmental effect level (e.g., a no-observed-adverse-effect level (NOAEL)) through scientific study. For PB-HAP 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. • 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, if available. If not, 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-HAP 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 HAP in the air. The selection of ecological benchmarks for the effects of acid gases on plants followed the same approach as for PB-HAP (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 determined whether any facilities in the Phosphoric Acid Manufacturing source category and Phosphate Fertilizer Production source category emitted any of the seven environmental HAP. For the Phosphoric Acid Manufacturing source category, we identified emissions of cadmium, dioxin, Hg, Pb, POM, HCl and HF. For the Phosphate Fertilizer Production source category, we identified emissions of cadmium, Hg, Pb and HF. Because one or more of the seven environmental HAP evaluated are emitted by at least one facility in the source categories, we proceeded to the second step of the evaluation. f. PB-HAP Methodology For cadmium, Hg, POM and dioxins/furans, the environmental screening analysis consists of two tiers, while Pb 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 HAP 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 sediment 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 I 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 I screening level, we evaluate the facility further in Tier II. In Tier II 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 I screen. The modeling domain for each facility in the Tier II analysis consists of eight 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 II 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 II screening level, the facility passes the screen, and is typically not evaluated further. If emissions from a facility exceed the Tier II 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 “Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing”, 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 HAP from all other emission sources at the facility for which we have data. We examined “facility-wide” risks using 2005 NEI data and modeling as described in sections IV.B.5 and V.A.5 of this preamble. We analyzed risks due to the inhalation of HAP that are emitted “facility-wide” for the populations residing within 50 km of each facility, consistent with the methods used for the source category analysis described above. For these facility-wide risk analyses, the modeled source category risks were compared to the facility-wide risks to determine the portion of facility-wide risks that could be attributed to each of the source categories addressed in this proposal. For the facilities in these source categories, we estimated the maximum inhalation cancer and chronic non-cancer risks associated with all HAP emissions sources at the facility, including emissions sources that are not part of the source categories but are located within a contiguous area and are under common control. 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 results of these facility-wide assessments are summarized in sections IV and V of this preamble. The “Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing” available through 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, we 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 datasets, dispersion modeling, inhalation exposure estimates and dose-response relationships follows below. A more thorough discussion of these uncertainties is included in the Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing, which is available in the docket for this action. a. Uncertainties in the RTR Emissions Datasets Although the development of the RTR emissions datasets involved quality assurance/quality control processes, the accuracy of emissions values will vary depending on the source of the data, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the 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 estimated 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. 16 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 1-in-1 million). 16 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 HAP, 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. 17 17 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 presence 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; 18 namely, that “the primary goal of EPA actions is protection of human health; accordingly, as an Agency policy, risk assessment procedures, including default options that are used in the absence of scientific data to the contrary, should be health protective” ( EPA 2005 Cancer Guidelines, pages 1-7). This is the approach followed here as summarized in the next several paragraphs. A complete detailed discussion of uncertainties and variability in dose-response relationships is given in the Draft Residual Risk Assessment for Phosphate Fertilizer Production and Phosphoric Acid Manufacturing, which is available in the docket for this action. 18 Guidelines for Carcinogen Risk Assessment, EPA/630/P-03/001F, March 2005, Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. 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). 19 In some circumstances, the true risk could be as low as zero; however, in other circumstances the risk could be greater. 20 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). 19 Upper bound, IRIS glossary ( http://www.epa.gov/NCEA/iris/help_gloss.htm ). 20 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 (RfC) or a daily oral exposure (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, 1994) 21 22 which considers uncertainty, variability and gaps in the available data. The UF are applied to derive reference values that are intended to protect against appreciable risk of deleterious effects. The UF are commonly default values, 23 e.g., factors of 10 or 3, used in the absence of compound-specific data; where data are available, UF may also be developed using compound-specific information. When data are limited, more assumptions are needed and more UF are used. Thus, there may be a greater tendency to overestimate risk in the sense that further study might support development of reference values that are higher ( i.e., less potent) because fewer default assumptions are needed. However, for some pollutants, it is possible that risks may be underestimated. 21 U.S. EPA. Reference Dose (RfD): Description and Use in Health Risk Assessments. Dated March 1993. 22 U.S. EPA. Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry. EPA/600/8-90/066F. Dated October 1994. 23 According to the NRC report, Science and Judgment in Risk Assessment (NRC, 1994) “[Default] options are generic approaches, based on general scientific knowledge and policy judgment, that are applied to various elements of the risk assessment process when the correct scientific model is unknown or uncertain.” The 1983 NRC report, Risk Assessment in the Federal Government: Managing the Process, defined default option as “the option chosen on the basis of risk assessment policy that appears to be the best choice in the absence of data to the contrary” (NRC, 1983a, p. 63). Therefore, default options are not rules that bind the agency; rather, the agency may depart from them in evaluating the risks posed by a specific substance when it believes this to be appropriate. In keeping with the EPA's goal of protecting public health and the environment, default assumptions are used to ensu [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%3A2014-25872. Public record. Not legal advice.