# National Emissions Standards for Hazardous Air Pollutants: Ferroalloys Production > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-29455 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** November 23, 2011 - **Citation:** 76 FR 72508 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 63 [EPA-HQ-OAR-2010-0895; FRL-9491-8] RIN 2060-AQ-11 National Emissions Standards for Hazardous Air Pollutants: Ferroalloys Production AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The EPA is proposing amendments to the national emissions standards for hazardous air pollutants for Ferroalloys Production to address the results of the residual risk and technology review that the EPA is required to conduct under the Clean Air Act. These proposed amendments include revisions to particulate matter standards for electric arc furnaces, metal oxygen refining processes, and crushing and screening operations. The amendments also add emission limits for hydrochloric acid, mercury, polycyclic aromatic hydrocarbons, and formaldehyde from electric arc furnaces. Furthermore, the amendments expand and revise the requirements to control fugitive emissions from furnace operations and casting. Other proposed requirements related to testing, monitoring, notification, recordkeeping, and reporting are included. We are also proposing to revise provisions addressing periods of startup, shutdown, and malfunction to ensure that the rules are consistent with a recent court decision. DATES: Comments must be received on or before January 9, 2012. Under the Paperwork Reduction Act, comments on the information collection provisions are best assured of having full effect if the Office of Management and Budget (OMB) receives a copy of your comments on or before December 23, 2011. Public Hearing. If anyone contacts the EPA requesting to speak at a public hearing by December 5, 2011, a public hearing will be held on December 8, 2011. ADDRESSES: Submit your comments, identified by Docket ID Number EPA-HQ-OAR-2010-0895, by one of the following methods: • http://www.regulations.gov: Follow the on-line instructions for submitting comments. • Email: a-and-r-docket@epa.gov, Attention Docket ID Number EPA-HQ-OAR-2010-0895. • Fax: (202) 566-9744, Attention Docket ID Number EPA-HQ-OAR-2010-0895. • Mail: U.S. Postal Service, send comments to: EPA Docket Center, EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR-2010-0895, U.S. Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460. Please include a total of two copies. In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th Street, NW., Washington, DC 20503. • Hand Delivery: U.S. Environmental Protection Agency, EPA West (Air Docket), Room 3334, 1301 Constitution Ave. NW., Washington, DC 20004, Attention Docket ID Number EPA-HQ-OAR-2010-0895. 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-2010-0895. The EPA's policy is that all comments received will be included in the public docket without change and may be made available on-line at http://www.regulations.gov, including any personal information provided, unless the comment includes information claimed to be confidential business information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through http://www.regulations.gov, your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at epa.gov/epahome/dockets.htm. Docket. The EPA has established a docket for this rulemaking under Docket ID Number EPA-HQ-OAR-2010-0895. All documents in the docket are listed in the regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy. Publicly available docket materials are available either electronically in regulations.gov or in hard copy at the EPA Docket Center, EPA West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742. Public Hearing. If a public hearing is held, it will begin at 10 a.m. on December 8, 2011 and will be held at the EPA's campus in Research Triangle Park, North Carolina, or at an alternate facility nearby. Persons interested in presenting oral testimony or inquiring as to whether a public hearing is to be held should contact Ms. Virginia Hunt, Office of Air Quality Planning and Standards (OAQPS), Sector Policies and Programs Division, (D243-02), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-0832. FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Mr. Conrad Chin, 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 (919) 541-1512; fax number: (919) 541-3207; and email address: chin.conrad@epa.gov. For specific information regarding the risk modeling methodology, contact Ms. Darcie Smith, 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) 541-2076; fax number: (919) 541-0840; and email address: smith.darcie@epa.gov. For information about the applicability of the National Emissions Standards for Hazardous Air Pollutants (NESHAP) to a particular entity, contact the appropriate person listed in Table 1 of this preamble. Table 1—List of EPA Contacts for the NESHAP Addressed in This Proposed Action NESHAP for: OECA contact 1 OAQPS contact 2 Ferroalloys Production Cary Secrest, (202) 564-8661 secrest.cary@epa.gov Conrad Chin, (919) 541-1512, chin.conrad@epa.gov. 1 EPA Office of Enforcement and Compliance Assurance. 2 EPA Office of Air Quality Planning and Standards. SUPPLEMENTARY INFORMATION: Preamble Acronyms and Abbreviations Several acronyms and terms used to describe industrial processes, data inventories, and risk modeling are included in this preamble. While this may not be an exhaustive list, to ease the reading of this preamble and for reference purposes, the following terms and acronyms are defined here: ACI Activated Carbon Injection ADAF age-dependent adjustment factors AEGL acute exposure guideline levels AERMOD air dispersion model used by the HEM-3 model ATSDR Agency for Toxic Substances and Disease Registry BLDS bag leak detection system BPT benefit-per-ton CAA Clean Air Act CalEPA California EPA CBI Confidential Business Information CFR Code of Federal Regulations CIIT Chemical Industry Institute of Toxicology CO 2 carbon dioxide EJ environmental justice EPA Environmental Protection Agency ERPG Emergency Response Planning Guidelines ERT Electronic Reporting Tool FR Federal Register gr/dscf grains per dry standard cubic foot HAP hazardous air pollutants HCl hydrochloric acid HEM-3 Human Exposure Model, Version 1.1.0 HI Hazard Index HON hazardous organic national emissions standards for hazardous air pollutants HQ Hazard Quotient ICR information collection request IRIS Integrated Risk Information System kg/hr kilograms per hour kg/hr/MW kilograms per hour per megawatt km kilometer lb/hr pounds per hour lb/hr/MW pounds per hour per megawatt lb/yr pounds per year LML lowest measured level MACT maximum achievable control technology MACT Code Code within the National Emissions Inventory used to identify processes included in a source category MDL method detection limit mg/dscm milligrams per dry standard cubic meter MIR maximum individual risk MM millions MW megawatt NAC/AEGL Committee National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances NAICS North American Industry Classification System NAS National Academy of Sciences NATA National Air Toxics Assessment NESHAP National Emissions Standards for Hazardous Air Pollutants 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 PAH polycyclic aromatic hydrocarbons PB-HAP hazardous air pollutants known to be persistent and bio-accumulative in the environment PM particulate matter POM polycyclic organic matter QA quality assurance RCRA Resource Conservation and Recovery Act RDL representative detection level REL reference exposure level RFA Regulatory Flexibility Act RfC reference concentration RfD reference dose RIA Regulatory Impact Analysis RTR residual risk and technology review SAB Science Advisory Board SBA Small Business Administration SOP standard operating procedures SSM startup, shutdown, and malfunction TOSHI target organ-specific hazard index TPY tons per year TRIM.FaTE  Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model TTN Technology Transfer Network UF uncertainty factor μg/m 3 microgram per cubic meter UMRA Unfunded Mandates Reform Act UPL upper predictive limit URE unit risk estimate VCS voluntary consensus standards WWW world wide web Organization of this Document. The information in this preamble is organized as follows: I. General Information A. Summary of Costs and Benefits B. What are NESHAP? C. Does this action apply to me? D. Where can I get a copy of this document and other related information? E. What should I consider as I prepare my comments for the EPA? II. Background A. What is this source category and how did the 1999 MACT standards regulate its HAP emissions? B. What data collection activities were conducted to support this action? C. What other relevant background information from previous studies on ferroalloys emissions is available? III. Analyses Performed A. How did we address unregulated emissions sources? B. How did we estimate risks posed by the source category? C. How did we consider the risk results in making decisions for this proposal? D. How did we perform the technology review? E. What other issues are we addressing in this proposal? IV. Analytical Results and Proposed Decisions A. What are the results of our analyses and proposed decisions regarding unregulated pollutants? B. What are the results of the risk assessment and analyses? C. What are our proposed decisions based on risk acceptability and ample margin of safety? D. What are the results and proposed decisions based on our technology review? E. What other actions are we proposing? F. What compliance dates are we proposing? V. Summary of Cost, Environmental, and Economic Impacts A. What are the affected sources? B. What are the air quality impacts? C. What are the cost impacts? D. What are the economic impacts? E. What are the benefits? F. What demographic groups might benefit from this regulation? VI. Request for Comments VII. Submitting Data Corrections VIII. Statutory and Executive Order Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review B. Paperwork Reduction Act 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. Summary of Costs and Benefits Consistent with the recently issued Executive Order 13563, “Improving Regulation and Regulatory Review,” we have estimated the costs and benefits of the proposed rule. The estimated net benefits of the proposed rule at a 3 percent discount rate are $67 to $170 million or $59 to $150 million at a 7 percent discount rate. The monetized benefits in this analysis are due to PM 2.5 co-benefits, as HAP benefits are not monetized. Table 2 presents a summary of the results of the analysis. Table 2—Summary of the Estimated Annual Monetized Benefits, Social Costs, and Net Benefits for the Proposed Rule in 2015 [Millions of 2010$] a 3% Discount rate 7% Discount rate Total Monetized Benefits b $71 to $170 $63 to $160. Total Social Costs c $4.0 $4.0. Net Benefits $67 to $170 $59 to $150. Non-monetized Benefits Reduced exposure to Hazardous Air Pollutants (HAP), including Manganese, polycyclic aromatic hydrocarbons (PAH), Chromium, Arsenic, Nickel, and Mercury. a All estimates are for implementation year 2015 (the benefit estimates use 2016 values as an approximation); and are rounded to two significant figures so numbers may not sum across columns. All fine particles are assumed to have equivalent health effects, but the benefit-per-ton (BPT) estimates vary because each ton of precursor reduced has a different propensity to become particulate matter (PM) 2.5. These benefits incorporate the conversion from precursor emissions to ambient fine particles. The BPT estimates are based on recent air quality modeling specific to the ferroalloys sector. b All estimates are for 2016, which we use as an approximation for impacts in 2015. c The compliance costs of the proposal serve as a proxy for the social costs. The compliance costs are estimated using a 7% interest rate. Under the proposed amendments, ferroalloys production facilities are expected to incur $11.4 million in capital costs to install new air pollution controls and new or improved monitoring systems. We have estimated the annualized costs to be $4.0 million, which includes estimated monitoring and testing costs. Section V.C of this preamble contains more detail on these estimated cost impacts. B. What are NESHAP? 1. What is the statutory authority for this action? Section 112 of the Clean Air Act (CAA) establishes a two-stage regulatory process to address emissions of HAP from stationary sources. In the first stage, after the EPA has identified categories of sources emitting one or more of the HAP listed in CAA section 112(b), CAA section 112(d) calls for us to promulgate national technology-based emission standards for hazardous air pollutants (NESHAP) for those sources. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP. For major sources, these technology-based standards must reflect the maximum degree of emissions reductions of HAP achievable (after considering cost, energy requirements, and nonair quality health and environmental impacts) and are commonly referred to as maximum achievable control technology (MACT) standards. MACT standards must require the maximum degree of emissions reduction achievable through the application of measures, processes, methods, systems, or techniques, including, but not limited to, measures that (1) Reduce the volume of or eliminate pollutants through process changes, substitution of materials or other modifications; (2) enclose systems or processes to eliminate emissions; (3) capture or treat pollutants when released from a process, stack, storage, or fugitive emissions point; (4) are design, equipment, work practice, or operational standards (including requirements for operator training or certification); or (5) are a combination of the above. CAA section 112(d)(2)(A)-(E). The MACT standards may take the form of design, equipment, work practice, or operational standards where the EPA first determines either that, (1) a pollutant cannot be emitted through a conveyance designed and constructed to emit or capture the pollutants, or that any requirement for, or use of, such a conveyance would be inconsistent with law; or (2) the application of measurement methodology to a particular class of sources is not practicable due to technological and economic limitations. CAA sections 112(h)(1)-(2). The MACT “floor” is the minimum control level allowed for MACT standards promulgated under CAA section 112(d)(3), and may not be based on cost considerations. For new sources, the MACT floor cannot be less stringent than the emissions control that is achieved in practice by the best-controlled similar source. The MACT floors for existing sources can be less stringent than floors for new sources, but they cannot be less stringent than the average emissions limitation achieved by the best-performing 12 percent of existing sources in the category or subcategory (or the best-performing five sources for categories or subcategories with fewer than 30 sources). In developing MACT standards, we must also consider control options that are more stringent than the floor. We may establish standards more stringent than the floor based on considerations of the cost of achieving the emissions reductions, any non-air quality health and environmental impacts, and energy requirements. The EPA is then required to review these technology-based standards and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less frequently than every 8 years, under CAA section 112(d)(6). In conducting this review, the EPA is not obliged to completely recalculate the prior MACT determination. NRDC v. EPA, 529 F.3d 1077, 1084 (DC Cir., 2008). The second stage in standard-setting focuses on reducing any remaining ( i.e., “residual”) risk according to CAA section 112(f). This provision requires, first, that the EPA prepare a Report to Congress discussing (among other things) methods of calculating the risks posed (or potentially posed) by sources after implementation of the MACT standards, the public health significance of those risks, and the EPA's recommendations as to legislation regarding such remaining risk. The EPA prepared and submitted this report ( Residual Risk Report to Congress, EPA-453/R-99-001) in March 1999. Congress did not act in response to the report, thereby triggering the EPA's obligation under CAA section 112(f)(2) to analyze and address residual risk. CAA section 112(f)(2) requires us to determine for source categories subject to certain MACT standards, whether those emissions standards provide an ample margin of safety to protect public health. If the MACT standards for HAP “classified as a known, probable, or possible human carcinogen do not reduce lifetime excess cancer risks to the individual most exposed to emissions from a source in the category or subcategory to less than one in one million,” the EPA must promulgate residual risk standards for the source category (or subcategory), as necessary to provide an ample margin of safety to protect public health. In doing so, the EPA may adopt standards equal to existing MACT standards if the EPA determines that the existing standards are sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (DC Cir. 2008). (“If EPA determines that the existing technology-based standards provide an “ample margin of safety,” then the Agency is free to readopt those standards during the residual risk rulemaking.”) The EPA must also adopt more stringent standards, if necessary, to prevent an adverse environmental effect, 1 but must consider cost, energy, safety and other relevant factors in doing so. 1 “Adverse environmental effect” is defined in CAA section 112(a)(7) as any significant and widespread adverse effect, which may be reasonably anticipated to wildlife, aquatic life or natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental qualities over broad areas. Section 112(f)(2) of the CAA expressly preserves our use of the two-step process for developing standards to address any residual risk and our interpretation of “ample margin of safety” developed in the National Emissions Standards for Hazardous Air Pollutants: Benzene Emissions From Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants (Benzene NESHAP) (54 Federal Register (FR) 38044, September 14, 1989). The first step in this process is the determination of acceptable risk. The second step provides for an ample margin of safety to protect public health, which is the level at which the standards are to be set (unless an even more stringent standard is necessary to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect). The terms “individual most exposed,” “acceptable level” and “ample margin of safety” are not specifically defined in the CAA. However, CAA section 112(f)(2)(B) preserves the EPA's interpretation set out in the Benzene NESHAP, and the United States Court of Appeals for the District of Columbia Circuit in NRDC v. EPA, 529 F.3d 1077, concluded that the EPA's interpretation of subsection 112(f)(2) is a reasonable one. See NRDC v. EPA, 529 F.3d at 1083 (DC Cir. 2008), which says “[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, volume 1, p. 877 (Senate debate on Conference Report). We also notified Congress in the Residual Risk Report to Congress that we intended to use the Benzene NESHAP approach in making CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p. ES-11). In the Benzene NESHAP, we stated as an overall objective: * * * in protecting public health with an ample margin of safety, we strive to provide maximum feasible protection against risks to health from hazardous air pollutants by (1) protecting the greatest number of persons possible to an individual lifetime risk level no higher than approximately 1 in 1 million; and (2) limiting to no higher than approximately 1-in-10 thousand [ i.e., 100 in 1 million] the estimated risk that a person living near a facility would have if he or she were exposed to the maximum pollutant concentrations for 70 years. The Agency also stated that, “The EPA also considers incidence (the number of persons estimated to suffer cancer or other serious health effects as a result of exposure to a pollutant) to be an important measure of the health risk to the exposed population. Incidence measures the extent of health risks to the exposed population as a whole, by providing an estimate of the occurrence of cancer or other serious health effects in the exposed population.” The Agency went on to conclude that “estimated incidence would be weighed along with other health risk information in judging acceptability.” As explained more fully in our Residual Risk Report to Congress, the EPA does not define “rigid line[s] of acceptability,” but rather considers broad objectives to be weighed with a series of other health measures and factors (EPA-453/R-99-001, p. ES-11). The determination of what represents an “acceptable” risk is based on a judgment of “what risks are acceptable in the world in which we live” ( Residual Risk Report to Congress, p. 178, quoting the Vinyl Chloride decision at 824 F.2d 1165) recognizing that our world is not risk-free. In the Benzene NESHAP, we stated that “EPA will generally presume that if the risk to [the maximum exposed] individual is no higher than approximately one in 10 thousand, that risk level is considered acceptable.” 54 FR 38045. We discussed the maximum individual lifetime cancer risk (or maximum individual risk (MIR)) as being “the estimated risk that a person living near a plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years.” Id. We explained that this measure of risk “is an estimate of the upper bound of risk based on conservative assumptions, such as continuous exposure for 24 hours per day for 70 years.” Id. We acknowledge that maximum individual lifetime cancer risk “does not necessarily reflect the true risk, but displays a conservative risk level which is an upper-bound that is unlikely to be exceeded.” Id. Understanding that there are both benefits and limitations to using maximum individual lifetime cancer risk as a metric for determining acceptability, we acknowledged in the 1989 Benzene NESHAP that “consideration of maximum individual risk * * * must take into account the strengths and weaknesses of this measure of risk.” Id. Consequently, the presumptive risk level of 100 in one million (one in 10 thousand) provides a benchmark for judging the acceptability of maximum individual lifetime cancer risk, but does not constitute a rigid line for making that determination. Further, in the Benzene NESHAP, we noted that, “Particular attention will also be accorded to the weight of evidence presented in the risk assessment of potential carcinogenicity or other health effects of a pollutant. While the same numerical risk may be estimated for an exposure to a pollutant judged to be a known human carcinogen, and to a pollutant considered a possible human carcinogen based on limited animal test data, the same weight cannot be accorded to both estimates. In considering the potential public health effects of the two pollutants, the Agency's judgment on acceptability, including the MIR, will be influenced by the greater weight of evidence for the known human carcinogen.” Id. at 38046. The Agency also explained in the 1989 Benzene NESHAP the following: “In establishing a presumption for MIR, rather than a rigid line for acceptability, the Agency intends to weigh it with a series of other health measures and factors. These include the overall incidence of cancer or other serious health effects within the exposed population, the numbers of persons exposed within each individual lifetime risk range and associated incidence within, typically, a 50-kilometer (km) exposure radius around facilities, the science policy assumptions and estimation uncertainties associated with the risk measures, weight of the scientific evidence for human health effects, other quantified or unquantified health effects, effects due to co-location of facilities, and co-emissions of pollutants.” Id. In some cases, these health measures and factors taken together may provide a more realistic description of the magnitude of risk in the exposed population than that provided by maximum individual lifetime cancer risk alone. As explained in the Benzene NESHAP, “[e]ven though the risks judged `acceptable' by EPA in the first step of the Vinyl Chloride inquiry are already low, the second step of the inquiry, determining an `ample margin of safety,' again includes consideration of all of the health factors, and whether to reduce the risks even further * * *. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including costs and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors. Considering all of these factors, the Agency will establish the standard at a level that provides an ample margin of safety to protect the public health as required by section 112.” In NRDC v. EPA, 529 F.3d 1077, 1082 (DC Cir. 2008), the Court of Appeals held that section 112(f)(2) “incorporates EPA's `interpretation' of the Clean Air Act from the Benzene Standard, and the text of this provision draws no distinction between carcinogens and non-carcinogens.” Additionally, the Court held there is nothing on the face of the statute that limits the Agency's section 112(f) assessment of risk to carcinogens. Id. at 1081-82. In the NRDC case, the petitioners argued, among other things, that section 112(f)(2)(B) applied only to non-carcinogens. The DC Circuit rejected this position, holding that the text of that provision “draws no distinction between carcinogens and non-carcinogens,” id., and that Congress' incorporation of the Benzene standard applies equally to carcinogens and non-carcinogens. In the ample margin of safety decision process, the Agency again considers all of the health risks and other health information considered in the first step. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including costs and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors. Considering all of these factors, the Agency will establish the standard at a level that provides an ample margin of safety to protect the public health, as required by CAA section 112(f). 54 FR 38046. 2. How do we consider the risk results in making decisions? As discussed in the previous section of this preamble, we apply a two-step process for developing standards to address residual risk. In the first step, the EPA determines if risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR) 2 of approximately one in 10 thousand [ i.e., 100 in one million].” 54 FR 38045. In the second step of the process, the EPA sets the standard at a level that provides an ample margin of safety “in consideration of all health information, including the number of persons at risk levels higher than approximately one in one million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.” Id. 2 Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk were an individual exposed to the maximum level of a pollutant for a lifetime. In past residual risk determinations, the EPA presented a number of human health risk metrics associated with emissions from the category under review, including: The MIR; the numbers of persons in various risk ranges; cancer incidence; the maximum noncancer hazard index (HI); and the maximum acute noncancer hazard. In estimating risks, the EPA considered sources under review that are located near each other and that affect the same population. The EPA developed risk estimates based on the actual emissions from the source category under review as well as based on the maximum emissions allowed pursuant to the source category MACT standard. The EPA also discussed and considered risk estimation uncertainties. The EPA is providing this same type of information in support of these actions. The Agency acknowledges that the Benzene NESHAP provides flexibility regarding what factors the EPA might consider in making our determinations and how they might be weighed for each source category. In responding to comment on our policy under the Benzene NESHAP, the EPA explained that: “The policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of noncancer health effects, and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the Vinyl Chloride mandate that the Administrator ascertain an acceptable level of risk to the public by employing [her] expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations, and, thereby, implicitly permits consideration of any and all measures of health risk which the Administrator, in [her] judgment, believes are appropriate to determining what will `protect the public health.' ” For example, the level of the MIR is only one factor to be weighed in determining acceptability of risks. The Benzene NESHAP explains “an MIR of approximately one in 10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an overall judgment on acceptability. Or, the Agency may find, in a particular case, that a risk that includes MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors.” Similarly, with regard to the ample margin of safety analysis, the Benzene NESHAP states that: “EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category.” C. Does this action apply to me? The regulated industrial source category that is the subject of this proposal is listed in Table 3. Table 3 of this preamble is not intended to be exhaustive, but rather provides a guide for readers regarding the entities likely to be affected by this proposed action. The proposed standards, once finalized, will be directly applicable to affected sources. Federal, state, local, and tribal government entities are not affected by this proposed action. As defined in the MACT (major source) source category listing report published by the EPA in 1992, the “Ferroalloys Production” source category is any facility engaged in producing ferroalloys such as ferrosilicon, ferromanganese, and ferrochrome. 3 Subsequently, the EPA redefined the MACT source category when it promulgated the Ferroalloy MACT standard so that it now includes only major sources that produce products containing manganese. (64 FR 27450, May 20, 1999) The MACT standard applies specifically to two ferroalloy product types: ferromanganese and silicomanganese. 3 EPA. Documentation for Developing the Initial Source Category List—Final Report, EPA/OAQPS, EPA-450/3-91-030, July, 1992. Table 3—NESHAP and Industrial Source Categories Affected by This Proposed Action Source category NESHAP NAICS code 1 MACT code 2 Ferroalloys Production Ferroalloys Production 331112 0304 1 North American Industry Classification System. 2 Maximum Achievable Control Technology. D. Where can I get a copy of this document and other related information? In addition to being available in the docket, an electronic copy of this proposal will also be available on the World Wide Web (WWW) through the EPA's Technology Transfer Network (TTN). Following signature by the EPA Administrator, a copy of this proposed action will be posted on the TTN's policy and guidance page for newly proposed or promulgated rules at the following address: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The TTN provides information and technology exchange in various areas of air pollution control. Supporting documents and other relevant information including a version of the regulatory text showing specific proposed changes is located in the docket (EPA-HQ-OAR-2010-0895). Additional information is available on the residual risk and technology review (RTR) Web page at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. This information includes source category descriptions and detailed emissions estimates and other data that were used as inputs to the risk assessment. E. 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, a copy of the comments that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. If you submit a CD-ROM or disk that does not contain CBI, mark the outside of the disk or CD-ROM clearly that it does not contain CBI. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 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-2010-0895. II. Background A. What is this source category and how did the 1999 MACT standards regulate its HAP emissions? The NESHAP (or MACT rule) for Ferroalloys Production: Ferromanganese and Silicomanganese was promulgated on May 20, 1999 (64 FR 27450) and codified at 40 CFR part 63, subpart XXX. 4 The 1999 NESHAP applies to all new and existing ferroalloys production facilities that manufacture ferromanganese or silicomanganese and are major sources or are co-located at major sources of HAP emissions. The rule's product-specific applicability reflected the fact that there was only one known major source within the Ferroalloys Production source category at the time of promulgation. Since then, one other major source of silicomanganese has started production, but it was permitted as an existing source. 4 The emission limits were revised on March 22, 2001 (66 FR 16024) in response to a petition for reconsideration submitted to the EPA following promulgation of the final rule, and a petition for review filed in the U.S. Court of Appeals for the District of Columbia Circuit. Today, there are two ferroalloys production facilities subject to the MACT rule. No greenfield manganese ferroalloys production facilities have been built in over 20 years, and we anticipate no greenfield manganese ferroalloys production facilities in the foreseeable future, although one facility is currently exploring expanding operations through the addition of a new furnace. Ferroalloys are alloys of iron in which one or more chemical elements (such as chromium, manganese, and silicon) are added into molten metal. Ferroalloys are consumed primarily in iron and steel making and are used to produce steel and cast iron products with enhanced or special properties. Ferroalloys within the scope of this source category are produced using submerged electric arc furnaces, which are furnaces in which the electrodes are submerged into the charge. The submerged arc process is a reduction smelting operation. The reactants consist of metallic ores (ferrous oxides, silicon oxides, manganese oxides, etc.) and a carbon-source reducing agent, usually in the form of coke, charcoal, high- and low-volatility coal, or wood chips. Raw materials are crushed and sized, and then conveyed to a mix house for weighing and blending. Conveyors, buckets, skip hoists, or cars transport the processed material to hoppers above the furnace. The mix is gravity-fed through a feed chute either continuously or intermittently, as needed. At high temperatures in the reaction zone, the carbon source reacts with metal oxides to form carbon monoxide and to reduce the ores to base metal. 5 The molten material (product and slag) is tapped from the furnace, sometimes subject to post-furnace refining, and poured into casting beds on the furnace room floor. Once the material hardens, it is transported to product crushing and sizing systems and packaged for transport to the customer. 5 EPA. AP-42, 12.4. Ferroalloy Production. 10/86. HAP generating processes include electrometallurgical (furnace) operations (smelting and tapping), other furnace room operations (ladle treatment and casting), building fugitives, raw material handling and product handling. HAP are emitted from ferroalloys production as process emissions, process fugitive emissions, and outdoor fugitive dust emissions. Process emissions are the exhaust gases from the control devices, primarily the furnace control device, metal oxygen refining control device and crushing operations control device. The HAP in process emissions are primarily composed of metals (mostly manganese, arsenic, nickel, lead, mercury and chromium) and also may include organic compounds that result from incomplete combustion of coal, coke or other fuel that is charged to the furnaces as a reducing agent. There are also process metal HAP emissions from the product crushing control devices. Process fugitive emissions occur at various points during the smelting process (such as during charging and tapping of furnaces and casting) and are assumed to be similar in composition to the process emissions. Outdoor fugitive dust emissions result from the entrainment of HAP in ambient air due to material handling, vehicle traffic, wind erosion from storage piles, and other various activities. Outdoor fugitive dust emissions are composed of particulate metal HAP only. The MACT rule applies to process emissions from the submerged arc furnaces, the metal oxygen refining process, and the product crushing equipment, process fugitive emissions from the furnace and outdoor fugitive dust emissions sources such as roadways, yard areas, and outdoor material storage and transfer operations. For process sources, the NESHAP specifies numerical emissions limits for particulate matter (as a surrogate for non-mercury (or particulate) metal HAP) from the electric (submerged) arc furnaces (including smelting and tapping emissions), with the specific limits depending on furnace type, size, and product being made. Particulate matter emission limits (again as a surrogate for particulate metal HAP) are also in place for process emissions from the metal oxygen refining process and product crushing and screening equipment. Table 4 is a summary of the applicable limits. Table 4—Emission Limits in Subpart XXX New or reconstructed or existing source Affected source Applicable PM emission standards Subpart XXX reference New or reconstructed Submerged arc furnace 0.23 kilograms per hour per megawatt (kg/hr/MW) (0.51 pounds per hour per megawatt (lb/hr/MW) or 35 milligrams per dry standard cubic meter (mg/dscm) (0.015 grains per dry standard cubic foot (gr/dscf) 40 CFR 63.1652(a)(1) and (a)(2) Existing Open submerged arc furnace producing ferromanganese and operating at a furnace power input of 22 megawatts (MW) or less 9.8 kg/hr (21.7 lb/hr) 40 CFR 63.1652(b)(1) Existing Open submerged arc furnace producing ferromanganese and operating at a furnace power input greater than 22 MW 13.5 kg/hr (29.8 lb/hr) 40 CFR 63.1652(b)(2) Existing Open submerged arc furnace producing silicomanganese and operating at a furnace power input greater than 25 MW 16.3 kg/hr (35.9 lb/hr) 40 CFR 63.1652(b)(3) Existing Open submerged arc furnace producing silicomanganese and operating at a furnace power input of 25 MW or less 12.3 kg/hr (27.2 lb/hr) 40 CFR 63.1652(b)(4) Existing Semi-sealed submerged arc furnace (primary, tapping, and vent stacks) producing ferromanganese 11.2 kg/hr (24.7 lb/hr) 40 CFR 63.1652(c) New, reconstructed, or existing Metal oxygen refining process 69 mg/dscm (0.03 gr/dscf) 40 CFR 63.1652(d) New or reconstructed Individual equipment associated with the product crushing and screening operation 50 mg/dscm (0.022 gr/dscf) 40 CFR 63.1652(e)(1) Existing Individual equipment associated with the product crushing and screening operation 69 mg/dscm (0.03 gr/dscf) 40 CFR 63.1652(e)(2) The 1999 NESHAP established a building opacity limit of 20 percent that is measured during the required furnace control device performance test. The rule provides an excursion limit of 60 percent opacity for one 6-minute period during the performance test. The opacity observation is focused only on emissions exiting the shop due solely to operations of any affected submerged arc furnace. In addition, blowing taps, poling and oxygen lancing of the tap hole; burndowns associated with electrode measurements; and maintenance activities associated with submerged arc furnaces and casting operations are exempt from the opacity standards specified in § 63.1653. For outdoor fugitive dust sources, as defined in § 63.1652, the 1999 NESHAP requires that plants prepare and operate according to an outdoor fugitive dust control plan that describes in detail the measures that will be put in place to control outdoor fugitive dust emissions from the individual outdoor fugitive dust sources at the facility. The owner or operator must submit a copy of the outdoor fugitive dust control plan to the designated permitting authority on or before the applicable compliance date. B. What data collection activities were conducted to support this action? In April 2010, we issued an information collection request (ICR), pursuant to CAA section 114, to the two companies that own and operate the two known ferroalloys production facilities producing ferromanganese and silicomanganese. The ICR requested available information regarding process equipment, control devices, point and fugitive emissions, practices used to control fugitive emissions, and other aspects of facility operations. The two companies completed the surveys for their facilities and submitted the responses to us in the fall of 2010. We also requested that the two facilities conduct additional emissions tests in 2010 for certain HAP from specific processes that were considered representative of the industry. Additional emissions testing was performed for most HAP metals (e.g., manganese, arsenic, chromium, lead, nickel and mercury), hydrochloric acid (HCl), formaldehyde, and PAH. The results of these tests were submitted to the EPA in the fall of 2010 and are available in the docket for this action. During the development of this regulation we discovered other types of ferroalloys production facilities (e.g., non-manganese ferroalloy production) that are not subject to this NESHAP. We plan to gather additional information on these other types of sources, and then evaluate whether we need to establish MACT standards for these sources. C. What other relevant background information from previous studies on ferroalloys emissions is available? In addition to the emissions information and risk assessment described in this preamble, other sources of publicly available data exist. Based on historical emissions data from the EPA's Toxics Release Inventory, one of the manganese ferroalloys facilities in this source category 6 has been one of the highest-emitters of manganese in the country for at least 15 years ( http://www.epa.gov/enviro/facts/tri/index.html ). Several agencies have conducted studies of the emissions from this facility and potential health effects of those emissions. 6 Eramet Marrietta, located in Marietta, Ohio. The Agency for Toxic Substances and Disease Registry (ATSDR), of the U.S. Department of Health and Human Services, along with the Ohio Department of Health and the Ohio Environmental Protection Agency conducted two health consultations in the communities surrounding this manganese ferroalloys facility between 2004 and 2007. The investigations found average ambient concentrations of manganese at levels higher than background concentrations and higher than health benchmark concentrations. More information about these studies can be found at http://www.atsdr.cdc.gov/sites/washington_marietta/index.html. As a result of these findings, a health study of chronic adult exposure to ambient manganese in the communities surrounding the facility was funded by the EPA. Available results show no significant differences in blood manganese concentrations or major health outcomes between residents living near the facility and residents in a comparison town; however some subtle, subclinical motor (movement) differences were found in residents in the town with the facility. 7 7 In press: Kim Y et al. Motor function in adults of an Ohio community with environmental manganese exposure. 2011 Neurotoxicology, doi: 10.1016/j. neuro.2011.07.011. In addition, under the EPA's School Air Toxics Initiative, ambient concentrations of manganese were monitored at three schools located near the ferroalloys production facility in late 2009. At these locations, mean manganese concentrations above the health benchmark value were observed. We note that the daily monitored values were in some cases above the RfC and in some cases below. The daily values were highly variable as they were likely influenced by wind direction and speed. More information about the health benchmark value is available in section III.B. More information on the School Air Toxics Initiative can be found at http://www.epa.gov/schoolair/index/html, while the study including the area around this facility can be found at http://www.epa.gov/schoolair/pdfs/MariettaTechReport.pdf. The monitoring was conducted for the School Air Toxics Initiative; however we do present a comparison of modeled concentrations to monitored concentrations in the Risk Assessment document, which is available in the docket. III. Analyses Performed In this section, we describe the analyses performed to support the proposed decisions for the RTR for this source category. A. How did we address unregulated emissions sources? In the course of evaluating the Ferroalloys Production source category, we identified certain HAP for which we failed to establish emission standards in the original MACT. See National Lime v. EPA, 233 F. 3d 625, 634 (DC Cir. 2000) (EPA has “clear statutory obligation to set emissions standards for each listed HAP”). Specifically, we identified and evaluated emissions standards for four HAP (or groups of HAP), described below, that are not specifically regulated in the existing 1999 MACT standard, or are only regulated for certain emissions points. As described below, for these HAP (or groups of HAP), we are proposing emissions limits pursuant to section 112(d)(2) and 112(d)(3). The results and proposed decisions based on the analyses performed pursuant to CAA section 112(d)(2) and 112(d)(3) are presented in section IV.A of this preamble. 1. Hydrochloric acid We were unaware of the potential for hydrochloric acid (HCl) emissions when we developed the 1999 NESHAP. As a result, we did not establish standards for HCl for these sources in the 1999 NESHAP. We recently received HCl emissions data in response to the ICR. Therefore, we are proposing a standard pursuant to section 112(d)(2) and (d)(3) (as described further in section IV.A of this preamble). 2. Mercury The 1999 NESHAP specified emissions limits for particulate metal HAP ( e.g., manganese, arsenic, nickel, chromium) in terms of a particulate matter emissions limit ( i.e., particulate matter is used as a surrogate for metal HAP that are mainly emitted in particulate form). There is no explicit standard for mercury, and a significant fraction of the mercury emissions are expected to be in gaseous mercury forms ( e.g., gaseous elemental mercury or gaseous oxidized mercury) with a smaller fraction in particulate form. Therefore, we are proposing a standard specifically for mercury pursuant to section 112(d)(2) and (d)(3) (as described further in section IV.A of this preamble). 3. Polycyclic Aromatic Hydrocarbons As described above, the 1999 NESHAP only regulated particulate metal HAP emissions and did not establish standards for PAH. Since then, we have determined that electric arc furnaces emit PAH, and we are proposing a standard pursuant to section 112(d)(2) and (d)(3) (as described further in section IV.A of this preamble). 4. Formaldehyde As described above, the 1999 NESHAP only regulated particulate metal HAP emissions and did not establish standards for formaldehyde. Since then, we have determined that electric arc furnaces emit formaldehyde, and we are proposing a standard pursuant to section 112(d)(2) and (d)(3) (as described further in section IV.A of this preamble). B. How did we estimate risks posed by the source category? The EPA conducted a risk assessment that provided estimates of the MIR posed by the HAP emissions from each source in the source category, the HI for chronic exposures to HAP with the potential to cause noncancer health effects, and the hazard quotient (HQ) for acute exposures to HAP with the potential to cause noncancer health effects. The assessment also provided estimates of the distribution of cancer risks within the exposed populations, cancer incidence and an evaluation of the potential for adverse environmental effects for each source category. The risk 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 the Ferroalloys Production Source Category. 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; 8 they are also consistent with the key recommendations contained in that report. 8 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. Establishing the Nature and Magnitude of Actual Emissions and Identifying the Emissions Release Characteristics The two existing ferromanganese and silicomanganese production facilities constitute the dataset that is the basis for the risk assessment. We estimated the magnitude of emissions using data collected through the ICR. In addition to the quality assurance (QA) of the source data for the facilities contained in the dataset, we also checked the coordinates of every emission source in the dataset through visual observations using tools such as GoogleEarth and ArcView. Where coordinates were found to be incorrect, we identified and corrected them to the extent possible. We also performed QA of the emissions data and release characteristics to ensure the data were reliable and that there were no outliers. 2. Establishing the Relationship Between Actual Emissions and MACT-Allowable Emissions Levels The emissions data in the MACT dataset include estimates of the mass of emissions actually emitted during the specified annual time period. These “actual” emission levels are often lower than the emission levels that a facility might be allowed to emit and still comply with the MACT standards. The emissions level allowed to be emitted by the MACT standards is referred to as the “MACT-allowable” emissions level. This represents the highest emissions level that could be emitted by facilities without violating the MACT standards. We discussed the use of both MACT-allowable and actual emissions in the final Coke Oven Batteries residual risk rule (70 FR 19998-19999, April 15, 2005) and in the proposed and final 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 because these risks reflect the maximum level sources could emit and still comply with national emission standards. But we also explained that it is reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis, in accordance with the Benzene NESHAP. (54 FR 38044, September 14, 1989.) For the Ferroalloys Production source category, we evaluated allowable stack emissions, based on the level of control required by the MACT standards compared to the level of reported actual emissions and available information on the level of control achieved by the emissions controls in use. Further explanation is provided in the technical document: Draft Development of the RTR Emissions Dataset for the Ferroalloys Production Source Category, which is available in the docket. 3. Conducting Dispersion Modeling, Determining Inhalation Exposures, and Estimating Individual and Population Inhalation Risks Both long-term and short-term inhalation exposure concentrations and health risks from 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 of the primary risk assessment activities listed above: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 km of the modeled sources, and (3) estimating individual and population-level inhalation risks using the exposure estimates and quantitative dose-response information. The 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. 9 To perform the dispersion modeling and to develop the preliminary risk estimates, HEM-3 draws on three data libraries. The first is a library of meteorological data, which is used for dispersion calculations. This library includes 1 year of hourly surface and upper air observations for 189 meteorological stations, selected to provide coverage of the United States and Puerto Rico. A second library, of United States Census Bureau census block 10 internal point locations and populations, provides the basis of human exposure calculations (Census, 2000). 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. 9 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). 10 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 of the HAP emitted by each source for which we have emissions data in the source category. The air concentrations at each nearby census block centroid were used as a surrogate for the chronic inhalation exposure concentration for all 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), which is an upper bound estimate of an individual's probability of contracting cancer over a lifetime of exposure to a concentration of 1 microgram of the pollutant per cubic meter of air. For residual risk assessments, we generally use URE values from the EPA's Integrated Risk Information System (IRIS). For carcinogenic pollutants without the 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. In the case of nickel compounds, to provide a health protective estimate of potential cancer risks, we used the URE value for nickel subsulfide in this assessment. Based on past scientific and technical considerations, the determination of the percent of nickel subsulfide was considered a major factor for estimating the extent and magnitude of the risks of cancer due to nickel-containing emissions. Nickel speciation information for some of the largest nickel-emitting sources (including oil combustion, coal combustion, and others) suggested that at least 35 percent of the total nickel emissions may be soluble compounds and that the URE for the mixture of inhaled nickel compounds (based on nickel subsulfide, and representative of pure insoluble crystalline nickel) could be derived to reflect the assumption that 65 percent of the total mass of nickel may be carcinogenic. Based on consistent views of major scientific bodies (i.e., National Toxicology Program in their 12th Report on Carcinogens, 11 International Agency for Research on Cancer, 12 and other international agencies) 13 that consider all nickel compounds to be carcinogenic, we currently consider all nickel compounds to have the potential of being carcinogenic to humans. The major scientific bodies mentioned above have also recognized that there are differences in toxicity and/or carcinogenic potential across the different nickel compounds. More discussion of the nickel URE can be found in the risk assessment report in the docket for this action. For this analysis, to take a more health-protective approach, we considered all nickel compounds to be as carcinogenic as nickel subsulfide in our inhalation risk assessments and have applied the IRIS URE for nickel subsulfide without a factor to reflect the assumption that 100 percent of the total mass of nickel may be as carcinogenic as pure nickel subsulfide. In addition, given that there are two URE values 14 derived for exposure to mixtures of nickel compounds, as a group, that are 2-3 fold lower than the IRIS URE for nickel subsulfide, we also consider it reasonable to use a value that is 50 percent of the IRIS URE for nickel subsulfide for providing an estimate of the lower end of a plausible range of cancer potency values for different mixtures of nickel compounds. 11 National Toxicology Program (NTP), 2011. Report on carcinogens. 12th ed. Research Triangle Park, NC: U.S. Department of Health and Human Services (DHHS), Public Health Service. Available online at http://ntp.niehs.nih.gov/ntp/roc/twelfth/roc12.pdf. 12 International Agency for Research on Cancer (IARD), 1990. IARC monographs on the evaluation of carcinogenic risks to humans. Chromium, nickel, and welding. Vol. 49. Lyons, France: International Agency for Research on Cancer, World Health Organization Vol. 49:256. 13 World Health Organization (WHO, 1991) and the European Union's Scientific Committee on Health and Environmental Risks (SCHER, 2006). 14 Two UREs (other than the current IRIS values) have been derived for nickel compounds as a group: one developed by the California Department of Health Services ( http://www.arb.ca.gov/toxics/id/summary/nickel_tech_b.pdf ) and the other by the Texas Commission on Environmental Quality ( http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf ). We also note that polycyclic organic matter (POM) (of which PAH are a subset), a carcinogenic HAP with a mutagenic mode of action, is emitted by the facilities in this source category. 15 For this compound group, 16 the age-dependent adjustment factors (ADAF) described in the EPA's Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens 17 were applied. This adjustment has the effect of increasing the estimated lifetime risks for POM by a factor of 1.6. In addition, although only a small fraction of the total POM emissions were not reported as individual compounds, the EPA expresses carcinogenic potency for compounds in this group in terms of benzo[a]pyrene equivalence, based on evidence that carcinogenic POM has the same mutagenic mechanism of action as benzo[a]pyrene. For this reason, the EPA's Science Policy Council 18 recommends applying the Supplemental Guidance to all carcinogenic PAH for which risk estimates are based on relative potency. Accordingly, we have applied the ADAF to the benzo[a]pyrene equivalent portion of all POM mixtures. 15 U.S. EPA. Performing risk assessments that include carcinogens described in the Supplemental Guidance as having a mutagenic mode of action. Science Policy Council Cancer Guidelines Implementation Work Group Communication I: Memo from W.H. Farland, dated October 4, 2005. 16 See the Risk Assessment for Source Categories document available in the docket for a list of HAP with a mutagenic mode of action. 17 U.S. EPA Supplemental Guidance for Assessing Early-Life Exposure to Carcinogens. EPA/630/R-3/003F, 2005. http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf. 18 U.S. EPA Science Policy Council Cancer Guidelines Implementation Workgroup Communication II: Memo from W.H. Farland, dated June 14, 2006. Incremental individual lifetime cancer risks associated with emissions from the two facilities in the source category were estimated as the sum of the risks for each of the carcinogenic HAP (including those classified as carcinogenic to humans, likely to be carcinogenic to humans, and suggestive evidence of carcinogenic potential 19 ) emitted by the modeled source. 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) and the limitations of Gaussian dispersion models, including AERMOD. 19 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 Science Advisory Board (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), 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, the EPA will utilize the following prioritized sources for our chronic dose-response values: (1) The Agency for Toxic Substances and Disease Registry Minimum Risk Level, which is defined as “an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (other than cancer) over a specified duration of exposure”; (2) the CalEPA Chronic Reference Exposure Level (REL), which is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration”; and (3), as noted above, in cases where 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 those dose-response values in place of or in concert with other values. Screening estimates of acute exposures and risks were also evaluated for each of the HAP at the point of highest off-site exposure for each facility (i.e., not just the census block centroids), assuming that a person is located at this spot at a time when both the peak (hourly) emission rate and worst-case dispersion conditions (1991 calendar year data) occur. The acute HQ is the estimated acute exposure divided by the acute dose-response value. In each case, acute HQ values were calculated using best available, short-term 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 emission rates, meteorology and exposure location for our acute analysis. As described in the CalEPA's Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants, an acute REL value ( http://www.oehha.ca.gov/air/pdf/acuterel.pdf ) is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.” Acute REL values are based on the most sensitive, relevant, adverse health effect reported in the medical and toxicological literature. Acute REL values are designed to protect the most sensitive individuals in the population by 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/opptintr/aegl/pubs/sop.pdf ), 20 “the NRC's previous name for acute exposure levels—community emergency exposure levels—was replaced by the term AEGL to reflect the broad application of these values to planning, response, and prevention in the community, the workplace, transportation, the military, and the remediation of Superfund sites.” This document also states that AEGL values “represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to eight hours.” The document lays out the purpose and objectives of AEGL by stating (page 21) that “the primary purpose of the AEGL program and the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances is to develop guideline levels for once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.” In detailing the intended application of AEGL values, the document states (page 31) that “[i]t is anticipated that the AEGL values will be used for regulatory and nonregulatory purposes by U.S. Federal and state agencies and possibly the international community in conjunction with chemical emergency response, planning, and prevention programs. More specifically, the AEGL values will be used for conducting various risk assessments to aid in the development of emergency preparedness and prevention plans, as well as real-time emergency response actions, for accidental chemical releases at fixed facilities and from transport carriers.” 20 NAS, 2001. Standing Operating Procedures for Developing Acute Exposure Levels for Hazardous Chemicals , page 2. The AEGL-1 value is then specifically defined as “the airborne concentration of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.” The document also notes (page 3) that, “Airborne concentrations below AEGL-1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects.” Similarly, the document defines AEGL-2 values as “the airborne concentration (expressed as 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.” ERPG values are derived for use in emergency response, as described in the American Industrial Hygiene Association's document entitled, Emergency Response Planning Guidelines (ERPG) Procedures and Responsibilities ( http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf ) which states that, “Emergency Response Planning Guidelines were developed for emergency planning and are intended as health based guideline concentrations for single exposures to chemicals.” 21 The ERPG-1 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or without perceiving a clearly defined, objectionable odor.” Similarly, the ERPG-2 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.” 21 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, higher severity level AEGL-2 or ERPG-2 values are compared to our modeled exposure levels to screen for potential acute concerns. When AEGL-1/ERPG-1 values are available, they are used in our acute risk assessments. Acute REL values for 1-hour exposure durations are typically lower than their corresponding AEGL-1 and ERPG-1 values. Even though their definitions are slightly different, AEGL-1 values are often 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. For the Ferroalloys Production source category hourly emissions estimates were available for individual emissions points, so we did not use the default factor of 10. Using emission test data, hourly emission rates were developed for those processes considered to operate continuously (i.e., steady-state operations for 8,760 hours per year) and for those processes considered to operate intermittently (i.e., non-steady-state operations for less than 8,760 hours per year). A discussion of the hourly emissions estimates is provided in the Methodology for Estimation of Maximum Hourly Emissions for Ferroalloy Sources, which is available in the docket for this action. As part of our acute risk assessment process, for cases where acute HQ values from the screening step were less than or equal to 1, acute impacts were deemed negligible and no further analysis was performed. In 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 this source category, the data refinements employed consisted of using the site-specific facility layout to distinguish facility property from an area where the public could be exposed. These refinements are discussed in the draft risk assessment document, which is available in the docket for this source category. Ideally, we would prefer to have continuous measurements over time to see how the emissions vary by each hour over an entire year. Having a frequency distribution of hourly emission rates over a year would allow us to perform a probabilistic analysis to estimate potential threshold exceedances and their frequency of occurrence. Such an evaluation could include a more complete statistical treatment of the key parameters and elements adopted in this screening analysis. However, we recognize that having this level of data is rare, hence our use of the multiplier approach. To better characterize the potential health risks associated with estimated acute exposures to HAP, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies, 22 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 23 for HAP have been developed, we consider additional acute values (i.e., occupational and international values) to provide a more complete risk characterization. 22 The SAB peer review of RTR Assessment Methodologies is available at: http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf 23 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of Chemical-Specific Health Effect Referenhce Values for Inhalation Exposures (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/r-09/061, and available on-line at http://cfpub.epa.gov/ncea/dfm/recordisplay.cfm?deid=211003. 4. Conducting Multipathway Exposure and Risk Screening The potential for significant human health risks due to exposures via routes other than inhalation (i.e., multipathway exposures) and the potential for adverse environmental impacts were evaluated in a two-step process. In the first step, we determined whether any facilities emitted any PB-HAP (HAP known to be persistent and bio-accumulative in the environment). There are 14 PB-HAP compounds or compound classes identified for this screening in the EPA's Air Toxics Risk Assessment Library (available at http://www.epa.gov/ttn/fera/risk_atra_vol1.html ). They are cadmium compounds, chlordane, chlorinated dibenzodioxins and furans, dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene, hexachlorocyclohexane, lead compounds, mercury compounds, methoxychlor, polychlorinated biphenyls, POM, toxaphene and trifluralin. Because one or more of these PB-HAP are emitted by at least one facility in the source category, we proceeded to the second step of the evaluation. In this step, we determined whether the facility-specific emission rates of each of the emitted PB-HAP were large enough to create the potential for significant non-inhalation human or environmental risks under reasonable worst-case conditions. To facilitate this step, we have developed emission rate thresholds for each PB-HAP using a hypothetical worst-case screening exposure scenario developed for use in conjunction with the EPA's Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure (TRIM.FaTE) model. The hypothetical screening scenario was subjected to a sensitivity analysis to ensure that its key design parameters were established such that environmental media concentrations were not underestimated ( i.e., to minimize the occurrence of false negatives or results that suggest that risks might be acceptable when, in fact, actual risks are high) and to also minimize the occurrence of false positives for human health endpoints. We call this application of the TRIM.FaTE model TRIM-Screen. The facility-specific emission rates of each of the PB-HAP in the source category were compared to the TRIM-Screen emission threshold values for each of the PB-HAP identified in the source category datasets to assess the potential for significant human health risks or environmental risks via non-inhalation pathways. 5. Assessing Risks Considering Emissions Control Options In addition to assessing baseline inhalation risks and screening for potential multipathway risks, we also estimated risks considering the potential emissions reductions that would be achieved by the main control options under consideration. In these cases, the expected emissions reductions were applied to the specific HAP and emissions points in the source category dataset to develop corresponding estimates of risk reductions. 6. Conducting Other Risk-Related Analyses: Facilitywide 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 of interest, but also emissions of HAP from all other emissions sources at the facility for which we have data. However, for the Ferroalloys Production source category, there are no other significant HAP emissions sources operating at present. Thus, there was no need to perform a separate facility wide risk assessment. 7. Considering Uncertainties in Risk Assessment Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for the source category addressed in this proposal. Although uncertainty exists, we believe that our approach, which used conservative tools and assumptions, ensures that our decisions are health-protective. A brief discussion of the uncertainties in the emissions dataset, dispersion modeling, inhalation exposure estimates and dose-response relationships follows below. A more thorough discussion of these uncertainties is included in the risk assessment documentation ( Draft Residual Risk Assessment for the Ferroalloys Production Source Category ) available in the docket for this action. a. Uncertainties in the Emissions Dataset Although the development of the RTR dataset 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 were made in estimating emissions values and other factors. The emission estimates considered in this analysis generally are annual totals for certain years that do not reflect short-term fluctuations during the course of a year or variations from year to year. The estimates of peak hourly emissions rates from stacks for the acute effects screening assessment were based on actual maximum hourly emissions estimates for individual emission points, which is intended to account for emissions fluctuations due to normal facility operations. b. Uncertainties in Dispersion Modeling While the analysis employed the EPA's recommended regulatory dispersion model, AERMOD, we recognize that there is uncertainty in ambient concentration estimates associated with any model, including AERMOD. In circumstances where we had to choose between various model options, where possible, model options ( e.g., rural/urban, plume depletion, chemistry) were selected to provide an overestimate of ambient air concentrations of the HAP rather than underestimates. However, because of practicality and data limitation reasons, some factors ( e.g., meteorology, building downwash) have the potential in some situations to overestimate or underestimate ambient impacts. For example, meteorological data were taken from a single year (1991) and facility locations can be a significant distance from the site where these data were taken. Despite these uncertainties, we believe that at off-site locations and census block centroids, the approach considered in the dispersion modeling analysis should generally yield overestimates of ambient HAP concentrations. c. Uncertainties in Inhalation Exposure The effects of human mobility on exposures were not included in the assessment. Specifically, short-term mobility and long-term mobility between census blocks in the modeling domain were not considered. 24 The assumption of not considering short or long-term population mobility does not bias the estimate of the theoretical MIR, nor does it affect the estimate of cancer incidence because the total population number remains the same. It does, however, affect the shape of the distribution of individual risks across the affected population, shifting it toward higher estimated individual risks at the upper end and reducing the number of people estimated to be at lower risks, thereby increasing the estimated number of people at specific high risk levels ( e.g., one in 10,000 or one in one million). 24 Short-term mobility is movement from one micro-environment to another over the course of hours or days. Long-term mobility is movement from one residence to another over the course of a lifetime. In addition, the assessment predicted the chronic exposures at the centroid of each populated census block as surrogates for the exposure concentrations for all people living in that block. Using the census block centroid to predict chronic exposures tends to over-predict exposures for people in the census block who live farther from the facility and under-predict exposures for people in the census block who live closer to the facility. Thus, using the census block centroid to predict chronic exposures may lead to a potential understatement or overstatement of the true maximum impact, but is an unbiased estimate of average risk and incidence. 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 emissions sources at facilities actually operate ( i.e., more or less than 70 years), and the domestic growth or decline of the modeled industry ( i.e., the increase or decrease in the number or size of United States facilities), will influence the 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 rare cases, where a facility maintains or increases its emissions levels beyond 70 years, residents live beyond 70 years at the same location, and the residents spend most of their days at that location, then the risks could potentially be underestimated. Annual cancer incidence estimates from exposures to emissions from these sources would not be affected by uncertainty in the length of time emissions sources operate. The exposure estimates used in these analyses assume chronic exposures to ambient levels of pollutants. Because most people spend the majority of their time indoors, actual exposures may not be as high, depending on the characteristics of the pollutants modeled. For many of the HAP, indoor levels are roughly equivalent to ambient levels, but for very reactive pollutants or larger particles, these levels are typically lower. This factor has the potential to result in an overstatement of 25 to 30 percent of exposures. 25 25 U.S. EPA. National-Scale Air Toxics Assessment for 1996. (EPA 453/R-01-003; January 2001; page 85.) In addition to the uncertainties highlighted above, there are several factors specific to the acute exposure assessment that 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 human activity patterns. In this assessment, we assume that individuals remain for 1 hour at the point of maximum ambient concentration as determined by the co-occurrence of peak emissions and worst-case meteorological conditions. These assumptions would tend to be worst-case actual exposures as it is unlikely that a person would be located at the point of maximum exposure during the time of worst-case impact. d. Uncertainties in Dose-Response Relationships There are uncertainties inherent in the development of the dose-response values used in our risk assessments for cancer effects from chronic exposures and non-cancer effects from both chronic and acute exposures. Some uncertainties may be considered quantitatively, and others generally are expressed in qualitative terms. We note as a preface to this discussion a point on dose-response uncertainty that is brought out in the EPA's 2005 Cancer Guidelines; namely, that “the primary goal of EPA actions is protection of human health; accordingly, as an Agency policy, risk assessment procedures, including default options that are used in the absence of scientific data to the contrary, should be health protective” ( EPA 2005 Cancer Guidelines, pages 1-7). This is the approach followed here as summarized in the next several paragraphs. A complete detailed discussion of uncertainties and variability in dose-response relationships is given in the residual risk documentation which is available in the docket for this action. Cancer URE values used in our risk assessments are those that have been developed to generally provide an upper bound estimate of risk. That is, they represent a “plausible upper limit to the true value of a quantity” (although this is usually not a true statistical confidence limit). 26 In some circumstances, the true risk could be as low as zero; however, in other circumstances the risk could be greater. 27 When developing an upper bound estimate of risk and to provide risk values that do not underestimate risk, health-protective default approaches are generally used. To err on the side of ensuring adequate health protection, the EPA typically uses the upper bound estimates rather than lower bound or central tendency estimates in our risk assessments, an approach that may have limitations for other uses ( e.g., priority-setting or expected benefits analysis). 26 IRIS glossary ( http://www.epa.gov/NCEA/iris/help_gloss.htm ). 27 An exception to this is the URE for benzene, which is considered to cover a range of values, each end of which is considered to be equally plausible, and which is based on maximum likelihood estimates. Chronic non-cancer reference (RfC) and reference dose (RfD) values represent chronic exposure levels that are intended to be health-protective levels. Specifically, these values provide an estimate (with uncertainty spanning perhaps an order of magnitude) of 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) 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, 28 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. 28 According to the NRC report, Science and Judgment in Risk Assessment (NRC, 1994) “[Default] options are generic approaches, based on general scientific knowledge and policy judgment, that are applied to various elements of the risk assessment process when the correct scientific model is unknown or uncertain.” The 1983 NRC report, Risk Assessment in the Federal Government: Managing the Process, defined default option as “the option chosen on the basis of risk assessment policy that appears to be the best choice in the absence of data to the contrary” (NRC, 1983a, p. 63). Therefore, default options are not rules that bind the Agency; rather, the Agency may depart from them in evaluating the risks posed by a specific substance when it believes this to be appropriate. In keeping with EPA's goal of protecting public health and the environment, default assumptions are used to ensure that risk to chemicals is not underestimated (although defaults are not intended to overtly overestimate risk). See EPA, 2004, An Examination of EPA Risk Assessment Principles and Practices, EPA/100/B-04/001 available at: http://www.epa.gov/osa/pdfs/ratf-final.pdf. While collectively termed “UF,” these factors account for a number of different quantitative considerations when using observed animal (usually rodent) or human toxicity data in the development of the RfC. The UF are intended to account for: (1) Variation in susceptibility among the members of the human population ( i.e., inter-individual variability); (2) uncertainty in extrapolating from experimental animal data to humans ( i.e., interspecies differences); (3) uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure ( i.e., extrapolating from sub-chronic to chronic exposure); (4) uncertainty in extrapolating the observed data to obtain an estimate of the exposure associated with no adverse effects; and (5) uncertainty when the database is incomplete or there are problems with the applicability of available studies. Many of the UF used to account for variability and uncertainty in the development of acute reference values are quite similar to those developed for chronic durations, but they more often use individual UF values that may be less than 10. The UF are applied based on chemical-specific or health effect-specific information ( e.g., simple irritation effects do not vary appreciably between human individuals, hence a value of 3 is typically used), or based on the purpose for the reference value (see the following paragraph). The UF applied in acute reference value derivation include: (1) Heterogeneity among humans; (2) uncertainty in extrapolating from animals to humans; (3) uncertainty in lowest observed adverse effect (exposure) level to no observed adverse effect (exposure) level adjustments; and (4) uncertainty in accounting for an incomplete database on toxic effects of potential concern. Additional adjustments are often applied to account for uncertainty in extrapolation from observations at one exposure duration ( e.g., 4 hours) to derive an acute reference value at another exposure duration ( e.g., 1 hour). Not all acute reference values are developed for the same purpose and care must be taken when interpreting the results of an acute assessment of human health effects relative to the reference value or values being exceeded. Where relevant to the estimated exposures, the lack of short-term dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties. Although every effort is made to identify peer-reviewed reference values for cancer and noncancer effects for all pollutants emitted by the sources included in this assessment, some HAP continue to have no reference values for cancer or chronic noncancer or acute effects. Because exposures to these pollutants cannot be included in a quantitative risk estimate, an understatement of risk for these pollutants at environmental exposure levels is possible. For a group of compounds that are either unspeciated or do not have reference values for every individual compound ( e.g., glycol ethers), we conservatively use the most protective reference value to estimate risk from individual compounds in the group of compounds. Additionally, chronic reference values for several of the compounds included in this assessment are currently under the EPA IRIS review and revised assessments may determine that these pollutants are more or less potent than the current value. We may re-evaluate residual risks for the final rulemaking if these reviews are completed prior to our taking final action for this source category and a dose-response metric changes enough to indicate that the risk assessment supporting this notice may significantly understate human health risk. e. Uncertainties in the Multipathway and Environmental Effects Assessment We generally assume that when exposure levels are not anticipated to adversely affect human health, they also are not anticipated to adversely affect the environment. For each source category, we generally rely on the site-specific levels of PB-HAP emissions to determine whether a full assessment of the multipathway and environmental effects is necessary. Our screening methods use worst-case scenarios to determine whether multipathway impacts might be important. The results of such a process are biased high for the purpose of screening out potential impacts. Thus, when individual pollutants or facilities screen out, we are confident that the potential for multipathway impacts is negligible. On the other hand, when individual pollutants or facilities do not screen out, it does not mean that multipollutant impacts are significant, only that we cannot rule out that possibility. C. How did we consider the risk results in making decisions for this proposal? In evaluating and developing standards under section 112(f)(2), as discussed in section I.B of this preamble, we apply a two-step process to address residual risk. In the first step, the EPA determines whether risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR) 29 of approximately one in 10 thousand [ i.e., 100 in one million]” (54 FR 38045). In the second step of the process, the EPA sets the standard at a level that provides an ample margin of safety “in consideration of all health information, including the number of persons at risk levels higher than approximately one in one million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.” ( Id. ) 29 Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk were an individual exposed to the maximum level of a pollutant for a lifetime. In past residual risk actions, the EPA has presented and considered a number of human health risk metrics associated with emissions from the category under review, including: the MIR; the numbers of persons in various risk ranges; cancer incidence; the maximum non-cancer HI; and the maximum acute non-cancer hazard (72 FR 25138, May 3, 2007; 71 FR 42724, July 27, 2006). In most recent proposals (75 FR 65068, October 21, 2010; 75 FR 80220, December 21, 2010; and 76 FR 29032, May 19, 2011), the EPA also presented and considered additional measures of health information, such as estimates of the risks associated with the maximum level of emissions which might be allowed by the current MACT standards (see, e.g., 75 FR 65068, October 21, 2010 and 75 FR 80220, December 21, 2010). The EPA also discussed and considered risk estimation uncertainties. The EPA is providing this same type of information in support of the proposed actions described in this Federal Register notice. The Agency is considering all available health information to inform our determinations of risk acceptability and ample margin of safety under CAA section 112(f). Specifically, as explained in the Benzene NESHAP, “the first step judgment on acceptability cannot be reduced to any single factor” and thus “[t]he Administrator believes that the acceptability of risk under [previous] section 112 is best judged on the basis of a broad set of health risk measures and information” (54 FR 38046). Similarly, with regard to making the ample margin of safety determination, as stated in the Benzene NESHAP “[in the ample margin decision, the Agency again considers all of the health risk and other health information considered in the first step. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including cost and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors.” Id. The Agency acknowledges that the Benzene NESHAP provides flexibility regarding what factors the EPA might consider in making determinations and how these factors might be weighed for each source category. In responding to comment on our policy under the Benzene NESHAP, the EPA explained that: “The policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of non-cancer health effects, and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the Vinyl Chloride mandate that the Administrator ascertain an acceptable level of risk to the public by employing [her] expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations, and, thereby, implicitly permits consideration of any and all measures of health risk which the Administrator, in [her] judgment, believes are appropriate to determining what will `protect the public health' ” (54 FR at 38057). Thus, the level of the MIR is only one factor to be weighed in determining acceptability of risks. The Benzene NESHAP explained that “an MIR of approximately one in 10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an overall judgment on acceptability. Or, the Agency may find, in a particular case, that a risk that includes MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors” ( Id. at 38045). Similarly, with regard to the ample margin of safety analysis, the EPA stated in the Benzene NESHAP that: “* * * EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category” ( Id. at 38061). The EPA wishes to point out that certain health information has not been considered to date in making residual risk determinations. In assessing risks to populations in the vicinity of the facilities in each category, we present estimates of risk associated with HAP emissions from the source category alone (source category risk estimates), and generally we have also assessed risks due to HAP emissions from the entire facility at which the covered source category is located (facilitywide risk estimates). We have not, however, attempted to characterize the risks associated with all HAP emissions impacting the populations living near the sources in these categories. That is, at this time, we do not attempt to quantify those HAP risks that may be associated with emissions from other facilities that do not include the source categories in question, mobile source emissions, natural source emissions, persistent environmental pollution, or atmospheric transformation in the vicinity of the sources in these categories. The Agency understands the potential importance of considering an individual's total exposure to HAP in addition to considering exposure to HAP emissions from the source category and facility. This is particularly important when assessing non-cancer risks, where pollutant-specific exposure health reference levels ( e.g., RfCs) are based on the assumption that thresholds exist for adverse health effects. For example, the Agency recognizes that, although exposures attributable to emissions from a source category or facility alone may not indicate the potential for increased risk of adverse non-cancer health effects in a population, the exposures resulting from emissions from the facility in combination with emissions from all of the other sources ( e.g., other facilities) to which an individual is exposed may be sufficient to result in increased risk of adverse non-cancer health effects. In May 2010, the EPA SAB advised us “* * * that RTR assessments will be most useful to decision makers and communities if results are presented in the broader context of aggregate and cumulative risks, including background concentrations and contributions from other sources in the area.” 30 30 EPA's responses to this and all other key recommendations of the SAB's advisory on RTR risk assessment methodologies (which is available at: http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf ) are outlined in a memo to this rulemaking docket from David Guinnup entitled, EPA's Actions in Response to the Key Recommendations of the SAB Review of RTR Risk Assessment Methodologies. Although we are interested in placing source category and facilitywide HAP risks in the context of total HAP risks from all sources combined in the vicinity of each source, we are concerned about the uncertainties of doing so. At this point, we believe that such estimates of total HAP risks will have significantly greater associated uncertainties than for the source category or facilitywide estimates, and hence would compound the uncertainty in any such comparison. This is because we have not conducted a detailed technical review of HAP emissions data for source categories and facilities that have not previously undergone an RTR review or are not currently undergoing such review. We are requesting comment on whether and how best to estimate and evaluate total HAP exposure in our assessments, and, in particular, on whether and how it might be appropriate to use information from the EPA's NATA to support such estimates. We are also seeking comment on how best to consider various types and scales of risk estimates when making our acceptability and ample margin of safety determinations under CAA section 112(f). D. How did we perform the technology review? Our technology review focused on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the 1999 NESHAP was promulgated. In cases where the technology review identified such developments, we conducted an analysis of the technical feasibility of applying these developments, along with the estimated impacts (costs, emissions reductions, risk reductions, etc.) of applying these developments. We then made decisions on whether it is necessary to propose amendments to the 1999 NESHAP to require any of the identified developments. Based on our analyses of the data and information collected by the ICR and our general understanding of the industry and other available information on potential controls for this industry, we identified several potential developments in practices, processes, and control technologies. For the purpose of this exercise, we considered any of the following to be a “development”: • Any add-on control technology or other equipment that was not identified and considered during development of the 1999 NESHAP. • Any improvements in add-on control technology or other equipment (that were identified and considered during development of the 1999 NESHAP) that could result in significant additional emissions reduction. • Any work practice or operational procedure that was not identified or considered during development of the 1999 NESHAP. • Any process change or pollution prevention alternative that could be broadly applied to the industry and that was not identified or considered during development of the 1999 NESHAP. In addition to reviewing the practices, processes, or control technologies that were not considered at the time we developed the 1999 NESHAP, we reviewed a variety of data sources in our evaluation of whether there were additional practices, processes, or controls to consider for the Ferroalloys Production industry. Among the data sources we reviewed were the NESHAP for various industries that were promulgated after the 1999 NESHAP. We reviewed the regulatory requirements and/or technical analyses associated with these regulatory actions to identify any practices, processes, and control technologies considered in these efforts that could possibly be applied to emissions sources in the Ferroalloys Production source category, as well as the costs, non-air impacts, and energy implications associated with the use of these technologies. Additionally, we requested information from facilities regarding developments in practices, processes, or control technology. Finally, we reviewed other information sources, such as State or local permitting agency databases and industry-supported databases. E. What other issues are we addressing in this proposal? In addition to the analyses described above, we also reviewed other aspects of the MACT standards for possible revision as appropriate and necessary. Based on this review we have identified aspects of the MACT standards that we believe need revision. This includes proposing revisions to the startup, shutdown, and malfunction (SSM) provisions of the MACT rule in order to ensure that they are consistent with a recent court decision in Sierra Club v. EPA, 551 F. 3d 1019 (DC Cir. 2008). In addition, we are proposing various other changes to monitoring and testing requirements to ensure that this rule includes the measures needed to ensure continuous compliance at major sources subject to the revised NESHAP for the Ferroalloys Production source category. Our analyses and proposed decisions related to SSM and other testing and reporting requirements for this source category are presented in section IV.E of this preamble. IV. Analytical Results and Proposed Decisions This section of the preamble provides the results of our review of the MACT rule including the RTR for the Ferroalloys Production source category and our proposed decisions concerning changes to the 1999 NESHAP. A. What are the results of our analyses and proposed decisions regarding unregulated pollutants? In this section, we describe how we addressed unregulated emissions, including how we calculate MACT floors, how we account for variability in those floor calculations, and how we consider beyond the floor options. As described previously, the CAA section 112(d) requires the EPA to promulgate national technology-based emission standards for hazardous air pollutants (NESHAP) for listed source categories, including this source category. For more information on this analysis, see the Draft MACT Floor Analysis for the Ferroalloys Production Source Category which is available in the docket for this proposed action. Based on the ICR data that we collected, we conducted a MACT Floor analysis. Section 112(d)(3)(B) of the CAA requires that the MACT standards for existing sources be at least as stringent as the average emissions limitation achieved by the best performing five sources (for which the Administrator has or could reasonably obtain emissions information) in a category with fewer than 30 sources. The Ferroalloy Production source category consists of fewer than 30 sources. Where, as here, there are five or fewer sources, we base the MACT floor limit on the average emissions limitation achieved by those sources for which we have data. The EPA must exercise its judgment, based on an evaluation of the relevant factors and available data, to determine the level of emissions control that has been achieved by the best performing sources under variable conditions. It is recognized in the case law that the EPA may consider variability in estimating the degree of emissions reduction achieved by best-performing sources and in setting MACT floors. See Mossville Envt'l Action Now v. EPA, 370 F.3d 1232, 1241-42 (DC Cir 2004) (holding the EPA may consider emissions variability in estimating performance achieved by best-performing sources and may set the floor at a level that a best-performing source can expect to meet “every day and under all operating conditions”). With regard to data used to determine the MACT limits, we received detailed emissions data for multiple HAP from one furnace and one crushing system baghouse at each plant (collected at the outlet of the control device) based on an ICR sent to the two companies in 2010. We are soliciting additional emissions data for the operating furnaces and crushing system baghouses for which we do not have data and any other emissions sources at ferroalloys production facilities including available information on the quantity and composition of process fugitive emissions. 1. Mercury Emissions The raw materials used to produce ferroalloys contain various amounts of mercury, which is emitted during the smelting process. These mercury emissions are derived primarily from the manganese ore although there may be trace amounts in the coke or coal used in the smelting process. While some of the mercury that is in particulate or oxidized forms is captured by the particulate control devices, the more volatile elemental mercury is largely emitted to the atmosphere. We found that mercury emissions are emitted from the furnaces as measured during the ICR test program (estimated to be 540 pounds per year (lb/yr) at one plant and 140 lb/yr at the other plant). Pursuant to CAA section 112(d)(2) and 112(d)(3), we are proposing to revise the 1999 NESHAP to include emission limits for mercury. As discussed above, the MACT floor limit is calculated based on the average performance of the units in each category plus an amount to account for these units' variability. To account for variability in the operation and emissions, the stack test data were used to calculate the average emissions and the 99 percent upper predictive limit (UPL) to derive the MACT floor limit. For more information on how we calculated the MACT floors and other emission limits, see the Ferroalloys Production MACT Floor Analysis document, which is available in the docket. Using this method, the MACT floor (or 99 percent UPL) for exhaust mercury concentrations from existing furnaces is 80 µg/dscm at 2 percent carbon dioxide (CO 2 ). This MACT floor limit is higher than the actual emissions measured during the ICR performance tests at each plant. Therefore, we anticipate that both of the existing sources would be able to meet this limit without installing additional controls. With regard to new sources, as described above, the MACT floor for new sources cannot be less stringent than the emissions performance that is achieved in practice by the best-controlled similar source. A variability analysis similar to that used for existing sources was then performed to calculate a 99 percent UPL using the three run test data from the top source. For this source category, we calculate that the UPL MACT floor limit for new sources is 16 µg/dscm at 2 percent CO 2 . This limit is based on the performance of the best performing source. The next step in establishing MACT standards is the beyond the floor analysis. In this step, we investigate other mechanisms for further reducing HAP emissions that are more stringent than the MACT floor level of control in order to “require the maximum degree of reduction in emissions” of HAP. In setting such standards, section 112(d)(2) requires the Agency to consider the cost of achieving the additional emission reductions, any non-air quality health and environmental impacts, and energy requirements. Historically, these factors have included factors such as solid waste impacts of a control, effects of [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%3A2011-29455. Public record. Not legal advice.