6560-50-P
                        ENVIRONMENTAL PROTECTION AGENCY
                                40 CFR Part 63
           [EPA-HQ-OAR-2010-1041, EPA-HQ-OAR-2010-1042; FRL-9303-4]
                                 RIN 2060-AQ90
National Emissions Standards for Hazardous Air Pollutants: Mineral Wool Production and Wool Fiberglass Manufacturing

AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
SUMMARY: The EPA is proposing amendments to the national emissions standards for hazardous air pollutants for Mineral Wool Production and Wool Fiberglass Manufacturing to address the results of the residual risk and technology review that the EPA is required to conduct by the Clean Air Act. The proposed Mineral Wool Production amendments include emissions limits for carbonyl sulfide, hydrogen fluoride and hydrochloric acid for cupolas; add combined collection and curing processes as new regulated sources; and include emissions limits for formaldehyde, phenol and methanol for combined collection and curing operations. Modifications to the testing and monitoring and related notification, recordkeeping and reporting requirements are also proposed.
The proposed amendments for the Wool Fiberglass Manufacturing source category include emissions limits for chromium compounds, hydrogen fluoride, hydrochloric acid and particulate matter for glass-melting furnaces at major sources; revised emissions limits for formaldehyde, and the addition of emissions limits for phenol and methanol for bonded product lines at major sources; and modifications to testing and monitoring and related notification, recordkeeping and reporting requirements.
These proposed rules only apply to major sources, but we plan to regulate wool fiberglass area sources in a future action.

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 [INSERT THE DATE 60 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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 receives a copy of your comments on or before [INSERT THE DATE 30 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER].
Public Hearing. If anyone contacts the EPA requesting to speak at a public hearing by [INSERT THE DATE 10 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER], a public hearing will be held on [INSERT THE DATE 15 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER].
ADDRESSES: Submit your comments, identified by Docket ID Numbers EPA-HQ-OAR-2010-1041 and EPA-HQ-OAR-2010-1042, by one of the following methods:
http://www.regulations.gov: Follow the on-line instructions for submitting comments.
Email<EMAIL_ADDRESS>Attention Docket ID Number EPA-HQ-OAR-2010-1041 and EPA-HQ-OAR-2010-1042.
Fax:<PHONE_NUMBER>, Attention Docket ID Number EPA-HQ-OAR-2010-1041 or EPA-HQ-OAR-2010-1042.
Mail: U.S. Postal Service, send comments to: EPA Docket Center, EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR-2010-1041 or EPA-HQ-OAR-2010-1042, 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, Attn: Desk Officer for EPA, 725 17[th] 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-2010-1041 or EPA-HQ-OAR-2010-1042. 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 on the Mineral Wool RTR to Docket ID Number EPA-HQ-OAR-2010-1041 and direct your comments on the Wool Fiberglass RTR to Docket ID Number EPA-HQ-OAR-2010-1042. 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 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 website is an "anonymous access" system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through http://www.regulations.gov, your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
Docket. The EPA has established dockets for this rulemaking under Docket ID Number EPA-HQ-OAR-2010-1041 (Mineral Wool Production) and EPA-HQ-OAR-2010-1042 (Wool Fiberglass Manufacturing). All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy. Publicly available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the EPA Docket Center, EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is<PHONE_NUMBER>, and the telephone number for the EPA Docket Center is<PHONE_NUMBER>.
FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Ms. Susan Fairchild, Sector Policies and Programs Division (D243-04), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, telephone<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>For specific information regarding the risk modeling methodology, contact Mr. Chris Sarsony, 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 - 4843; fax number: (919) 541 - 0840; and email address<EMAIL_ADDRESS>For information about the applicability of the NESHAP to a particular entity, contact Scott Throwe, Office of Enforcement and Compliance Assurance; US EPA Headquarters Ariel Rios Building; 1200 Pennsylvania Avenue, N. W.; Mail Code: 2227A; Washington, DC 20460; telephone number: (202) 564 - 7013; fax number: (202) 564 - 0050; email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
Organization of this Document. The information in this preamble is organized as follows:
Toc304992158I. Preamble Acronyms and Abbreviations
Toc304992159II. General Information
Toc304992160A. Does this action apply to me?
Toc304992161B. Where can I get a copy of this document and other related information?
Toc304992162C. What should I consider as I prepare my comments for the EPA?
Toc304992163D. When will a public hearing occur?
Toc304992164III. Background Information
Toc304992165A. What are NESHAP?
Toc304992166B. What litigation is related to this proposed action?
Toc304992167IV. Mineral Wool and Wool Fiberglass Source Categories
Toc304992168A. Overview of the Mineral Wool Production Source Category and MACT Standards.
Toc304992169B. Overview of the Wool Fiberglass Manufacturing source category and 1999 MACT rule.
Toc304992170C. What data collection activities were conducted to support this action?
Toc304992171V. Analyses Performed
Toc304992172A. How did we estimate risks posed by the source categories?
Toc304992173B. How did we consider the risk results in making decisions for this proposal?
Toc304992174C. How did we perform the technology review?
Toc304992175D. What other issues are we addressing in this proposal?
Toc304992176E. What analyses were performed for the Mineral Wool Production Source Category under the Regulatory Flexibility Act?
Toc304992177VI. Summary of Proposed Decisions and Actions
Toc304992178A. What are the proposed decisions and actions related to the Mineral Wool Production NESHAP?
Toc304992179B. What are the proposed decisions and actions related to the Wool Fiberglass Manufacturing NESHAP?
Toc304992180C. What are the proposed decisions and actions related to startup, shutdown and malfunction?
Toc304992181D. What are the proposed decisions and actions related to electronic reporting?
Toc304992182VII. Rationale for the Proposed Actions for the Mineral Wool Production Source Category
Toc304992183A. What data were used for the NESHAP analyses?
Toc304992184B. What are the proposed decisions regarding surrogacy relationships?
Toc304992185C. What are the proposed decisions regarding certain unregulated emissions sources?
Toc304992186D. What are the proposed decisions regarding subcategorization?
Toc304992187E. What are the results from the risk assessments performed and the proposed decisions for the Mineral Wool Production Source Category?
Toc304992188F. What are our proposed decisions for the Mineral Wool Production source category based on risk acceptability and ample margin of safety?
Toc304992189G. What are the results from the technology review and proposed decisions?
Toc304992190VIII. Rationale for the Proposed Actions for the Wool Fiberglass Manufacturing Source Category
Toc304992191A. What data were used for the NESHAP analyses?
Toc304992192B. What are the proposed decisions regarding surrogacy relationships?
Toc304992193C. What are the proposed decisions regarding certain unregulated emissions sources?
Toc304992194D. What are the results from the risk assessments and analyses and the proposed decisions for the Wool Fiberglass Manufacturing Source Category?
Toc304992195E. What are our proposed decisions for the Wool Fiberglass Manufacturing source category based on risk acceptability and ample margin of safety?
Toc304992196F. What are the results from the technology review and proposed decisions?
Toc304992197IX. Summary of Cost, Environmental, and Economic Impacts for the Mineral Wool Source Category
Toc304992198A. What are the affected sources in the Mineral Wool Production source category?
Toc304992199B. How are the impacts for this proposal evaluated?
Toc304992200C. What are the air quality impacts for the Mineral Wool Production source category?
Toc304992201D. What are the water quality and solid waste impacts?
Toc304992202E. What are the secondary impacts?
Toc304992203F. What are the energy impacts?
Toc304992204G. What are the cost impacts for the Mineral Wool Production source category?
Toc304992205H. What are the economic impacts for the Mineral Wool Production source category?
Toc304992206I. What are the benefits for the Mineral Wool Production source category?
Toc304992207J. What demographic groups might benefit the most from this regulation?
Toc304992208X. Summary of Cost, Environmental, and Economic Impacts for the Wool Fiberglass Manufacturing Source Category
Toc304992209A. What are the affected sources in the Wool Fiberglass Manufacturing source category?
Toc304992210B. How are the impacts for this proposal evaluated?
Toc304992211C. What are the air quality impacts?
Toc304992212D. What are the water quality and solid waste impacts?
Toc304992213E. What are the secondary impacts?
Toc304992214F. What are the energy impacts?
Toc304992215G. What are the cost impacts?
Toc304992216H. What are the economic impacts?
Toc304992217I. What are the benefits?
Toc304992218J. What demographic groups might benefit the most from this regulation?
Toc304992219XI. Request for Comments
Toc304992220XII. Submitting Data Corrections
Toc304992221XIII. Statutory and Executive Order Reviews
Toc304992222A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review
Toc304992223B. Paperwork Reduction Act.
Toc304992224C. Regulatory Flexibility Act.
Toc304992225D. Unfunded Mandates Reform Act.
Toc304992226E. Executive Order 13132: Federalism.
Toc304992227F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments.
Toc304992228G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks.
Toc304992229H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use.
Toc304992230I. National Technology Transfer and Advancement Act.
Toc304992231J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations.

I. 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:

ACGIH	American Conference of Governmental Industrial Hygienists
AEGL	acute exposure guideline levels
AERMOD	air dispersion model used by the HEM-3 model

ATSDR	Agency for Toxic Substances and Disease Registry
BACT	best available control technology
BLDS	bag leak detection systems
BTF	beyond the floor
CAA	Clean Air Act
CalEPA	California EPA
CA-REL	California reference exposure level
CBI	Confidential Business Information

CFR	Code of Federal Regulations
CIIT	Chemical Industry Institute of Toxicology
CO	carbon monoxide
COS	Carbonyl sulfide

EJ	environmental justice
EPA	Environmental Protection Agency
ERPG	Emergency Response Planning Guidelines
ERT	Electronic Reporting Tool
ESP	electrostatic precipitators
FA	flame attenuation
GP	General Provisions
GHG	Greenhouse Gases
HAP	hazardous air pollutants
HCl	Hydrogen chloride
HEM	Human Exposure Model
HEM-3	Human Exposure Model, Version 3

HF	Hydrogen fluoride

HI	Hazard Index

HQ	Hazard Quotient

IRFA	Initial Regulatory Flexibility Analysis
IRIS	Integrated Risk Information System
kg/MG	kilogram/megawatt
km	kilometer
LAER	lowest achievable emissions rate
lb/ton	pounds per ton
lb/yr	pounds per year
MACT	maximum achievable control technology

mg/L	milligrams per liter
mg/m3	milligrams per cubic meter
MIR	maximum individual risk

NAAQS	National Ambient Air Quality Standard

NAICS	North American Industry Classification System
NaOH	sodium hydroxide
NAS	National Academy of Sciences
NATA	National Air Toxics Assessment

NESHAP	National Emissions Standards for Hazardous Air Pollutants
NIOSH	National Institutes for Occupational Safety and Health
NRC	National Research Council
NTTAA	National Technology Transfer and Advancement Act

OAQPS	Office of Air Quality Planning and Standards

OMB	Office of Management and Budget
PB-HAP	hazardous air pollutants known to be persistent and bio-accumulative in the environment

PM	particulate matter

RACT	reasonably available control technology
RBLC	RACT/BACT/LAER Clearinghouse
RCRA	Resource Conservation and Recovery Conservation
REL	reference exposure level
RFA	Regulatory Flexibility Act
RfC	reference concentrations
RfD	reference dose

RS	rotary spin
RTO	regenerative thermal oxidizers
RTR	residual risk and technology review
SAB	Science Advisory Board
SBA	Small Business Administration
SBAR	Small Business Advocacy Review
SCC	Source Classification Codes

SER	Small Entity Representatives
SO2	sulfur dioxide
SSM	startup, shutdown, and malfunction
TC	Toxicity Characteristics
TCLP	Toxicity Characteristic Leaching Procedure

TLV	threshold limit value
TOSHI	target organ-specific hazard index
tpy	tons per year
TRIM	Total Risk Integrated Modeling System

TTN	Technology Transfer Network
UF	uncertainty factors
ug/m3	microgram per cubic meter

UMRA	Unfunded Mandates Reform Act
UPL	upper predictive limit
URE	unit risk estimate

WHO	World Health Organization
WWW	worldwide web

II. General Information
A. Does this action apply to me?
The regulated industrial source categories that are the subject of this proposed rule are listed in Table 1 of this preamble. Table 1 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. These standards, once finalized, will be directly applicable to affected sources. Federal, state, local, and tribal government entities are not affected by this proposed action.
In 1992 the EPA defined the Mineral Wool Production source category as any facility engaged in producing mineral wool fiber from slag or rock. Mineral wool is a material used mainly for thermal and acoustical insulation. This category includes, but is not limited to, the following process units: a cupola furnace for melting the mineral charge; a blow chamber in which air and, in some cases, a binder is drawn over the fibers, forming them to a screen; a curing oven to bond the fibers; and a cooling compartment.
In 1992 the EPA defined the Wool Fiberglass Manufacturing source category as any facility engaged in producing wool fiberglass from sand, feldspar, sodium sulfate, anhydrous borax, boric acid or any other materials. In the wool fiberglass manufacturing process, molten glass is formed into fibers that are bonded with an organic resin to create a wool-like material that is used as thermal or acoustical insulation. The category includes, but is not limited to the following processes: glass-melting furnace, marble forming, refining, fiber forming, binder application, curing and cooling.
Table 1. NESHAP and Industrial Source Categories Affected By This Proposed Action
                                Source Category
                                    NESHAP
                                  NAICS code1
Mineral Wool Production
Mineral Wool Production
327993
Wool Fiberglass Manufacturing
Wool Fiberglass Manufacturing
327993
[1] North American Industry Classification System

B. Where can I get a copy of this document and other related information?
In addition to being available in the docket, an electronic copy of this proposal will also be available on the WWW through the EPA's 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. In addition, a copy of each rule showing specific changes proposed under this action is available in their respective dockets. The TTN provides information and technology exchange in various areas of air pollution control.
C. What should I consider as I prepare my comments for the EPA?
Submitting CBI. Do not submit information containing CBI to the EPA through http://www.regulations.gov or email. Clearly mark the part or all of the information that you claim to be CBI. For CBI information on a disk or CD ROM that you mail to the EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. If you submit a CD ROM or disk that does not contain CBI, mark the outside of the disk or CD ROM clearly indicating that it does not contain CBI. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. Send or deliver information identified as CBI only to the following address: Roberto Morales, OAQPS Document Control Officer (C404-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID Number EPA-HQ-OAR-2010-1041 (Mineral Wool RTR) or Attention Docket ID Number EPA-HQ-OAR-2010-1042 (Wool Fiberglass RTR).
D. When will a public hearing occur?
If a public hearing is held, it will begin at 10:00 a.m. on [INSERT DATE 15 DAYS AFTER THE DATE OF PUBLICATION IN THE FEDERAL REGISTER] and will be held at a location to be determined. Persons interested in presenting oral testimony or inquiring as to whether a public hearing is to be held should contact Ms. Pamela Garrett, Office of Air Quality Planning and Standards, Sector Policies and Programs Division, (D243-01), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541 - 7996; email address<EMAIL_ADDRESS>
III. Background Information
A. What are NESHAP?
1. What is the statutory authority for NESHAP?
Section 112 of the 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 NESHAP for those sources. "Major sources" are those that emit or have the potential to emit 10 tpy or more of a single HAP or 25 tpy or more of any combination of HAP. For major sources, these technology-based standards must reflect the maximum degree of emissions reductions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts) and are commonly referred to as MACT standards. Area sources are those that emit less than major amounts of HAP.
MACT standards must require the maximum degree of emissions reduction through the application of measures, processes, methods, systems, or techniques, including, but not limited to, measures that (A) reduce the volume of or eliminate pollutants through process changes, substitution of materials or other modifications; (B) enclose systems or processes to eliminate emissions; (C) capture or treat pollutants when released from a process, stack, storage or fugitive emissions point; (D) are design, equipment, work practice or operational standards (including requirements for operator training or certification); or (E) 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, (A) 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 (B) 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 5 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, and, in particular, is not obligated to recalculate the MACT floors. NRDC v. EPA, 529 F.3d 1077, 1084 (D. C. Cir., 2008).
The second stage in standard-setting focuses on reducing any remaining "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.
Section 112(f)(2) of the CAA 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 that apply to a source category emitting a HAP that is "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 (CAA section 112(f)(2)(A)). This requirement is procedural. It mandates that the EPA establish CAA section 112(f) residual risk standards if certain risk thresholds are not satisfied, but does not determine the level of those standards (NRDC v. EPA, 529 F. 3d at 1083). The second sentence of CAA section 112(f)(2) sets out the substantive requirements for residual risk standards: protection of public health with an ample margin of safety based on the EPA's interpretation of this standard in effect at the time of the CAA amendments. Id. This refers to the National Emissions Standards for Hazardous Air Pollutants: Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants (Benzene NESHAP),(54 FR 38044, September 14, 1989), described in the next paragraph.
The EPA may adopt residual risk standards equal to existing MACT standards if the EPA determines that the existing standards are sufficiently protective, even if (for example) excess cancer risks to a most exposed individual are not reduced to less than one-in-one million. Id. at 1083, ("If the 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"). Section 112(f)(2) of the CAA further authorizes the EPA to adopt more stringent standards, if necessary "to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect."
CAA section 112(f)(2) 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 Benzene NESHAP. The first step in this process is the determination of acceptable risk. This determination "considers all health information, including risk estimation uncertainty, and includes a presumptive limit on MRI [cancer] of approximately 1-in-10 thousand [i.e., 100-in-1 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 1-in-1 million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision" (Id.)
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 Court in NRDC v. EPA concluded that the EPA's interpretation of CAA section 112(f)(2) is a reasonable one. See NRDC v. EPA, 529 F.3d at 1083 (D.C. Cir. 2008), which says "[S]ubsection 112(f)(2)(B) expressly incorporates the EPA's interpretation of the CAA 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 D.C. Circuit's en banc Vinyl Chloride decision at 824 F.2d 1165) recognizing that our world is not risk-free.
In the Benzene NESHAP, we stated that "the EPA will generally presume that if the risk to [the maximum exposed] individual is no higher than approximately 1-in-10 thousand, that risk level is considered acceptable." 54 FR 38045. We discussed the maximum individual lifetime cancer risk as being "the estimated risk that a person living near a plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years." Id. We explained that this measure of risk "is an estimate of the 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-1 million (1-in-10 thousand) provides a benchmark for judging the acceptability of maximum individual lifetime cancer risk, but does not constitute a rigid line for making that determination.
The agency also explained in the 1989 Benzene NESHAP the following: "In establishing a presumption for MIR [maximum individual cancer risk], rather than a rigid line for acceptability, the agency intends to weigh it with a series of other health measures and factors. These include the overall incidence of cancer or other serious health effects within the exposed population, the numbers of persons exposed within each individual lifetime risk range and associated incidence within, typically, a 50- km exposure radius around facilities, the science policy assumptions and estimation uncertainties associated with the risk measures, weight of the scientific evidence for human health effects, other quantified or unquantified health effects, effects due to co-location of facilities, and co-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 the EPA in the first step of the Vinyl Chloride inquiry are already low, the second step of the inquiry, determining an `ample margin of safety,' again includes consideration of all of the health factors, and whether to reduce the risks even further." In the 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 and prevent adverse environmental effects, taking into consideration costs, energy, safety, and other relevant factors, as required by CAA section 112(f) (54 FR 38046).
2. How do we consider the risk results in making decisions?
      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 HI; and the maximum acute noncancer hazard. In estimating risks, the EPA considered source categories under review that are located near each other and that affect the same population. The EPA provided estimates of the expected difference in actual emissions from the source category under review and 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 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 1-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 an 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: "the 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."
B. What litigation is related to this proposed action?
In 2007, the D.C. Circuit (Court) found that the EPA had erred in establishing emissions standards for sources of HAP in the NESHAP for Brick and Structural Clay Products Manufacturing and Clay Ceramics Manufacturing, 67 FR 26,690 (May 16, 2003), and consequently vacated the rule. These errors included incorrectly calculated MACT emission limits, instances where EPA failed to set emission limits, and instances where EPA failed to regulate processes that emitted HAP. We are taking action to correct errors in both the Mineral Wool and Wool Fiberglass NESHAP for HAP that are not regulated. Some pollutants were represented in the 1999 MACT rules by surrogates; other pollutants were not regulated at all in the rule. In both these cases, we are establishing pollutant-specific emission limits. With the exception of PM as a surrogate for all HAP metals, where surrogacy relationships exist, we are proposing to remove that surrogacy. We are also correcting one unregulated HAP-emitting process in the Mineral Wool NESHAP.
      In two earlier court decisions[,] the court found EPA had erred in not setting MACT standards for every HAP emitted from a source. Therefore, with the exception of PM as a surrogate for HAP metals,in this action we are proposing emission limits for all HAP emitted from Mineral Wool and Wool Fiberglass. We note that we have established through previous analyses upheld by the court that PM is an appropriate surrogate for HAP metals, therefore, we retain that surrogacy relationship in these proposed rules.
      In separate litigation, the Court vacated portions of two provisions in EPA's CAA section 112 regulations that govern emissions of HAP during periods of SSM. Specifically, the Court vacated the SSM exemption contained in 40 CFR §§ 63.6(f)(1) and 63.6(h)(1) that are part of regulations commonly referred to as the GP rule. When incorporated into section 112(d) regulations for specific source categories, these two provisions exempt sources from the requirement to comply with otherwise applicable MACT standards during periods of SSM. Because both of the Mineral Wool and Wool Fiberglass NESHAP relied on the GP rule for startup and shutdown provisions (40 CFR §§ 63.1194 and 63.1386(c)), we are also proposing to revise these provisions for both of the Mineral Wool and Wool Fiberglass source categories.

Recent litigation led to a consent decree under which we must propose these amendments no later than October 31, 2011; and promulgate no later than June 29, 2012.
IV. Mineral Wool and Wool Fiberglass Source Categories
A. Overview of the Mineral Wool Production Source Category and MACT Standards.
The NESHAP (or MACT rule) for the Mineral Wool Production source category was promulgated on June 1, 1999 (64 FR 29490), and codified at 40 CFR part 63, subpart DDD. As promulgated in 1999, the NESHAP applies to affected sources of HAP emissions at mineral wool production facilities. As defined in the 1992 EPA report, "Documentation for Developing the Initial Source Category List" (EPA-450/3/91/030, July 1992), a "mineral wool facility" is "any facility engaged in producing mineral wool fiber from slag, rock or other materials, excluding sand or glass."
The MACT rule for the Mineral Wool Production source category does not apply to facilities that manufacture wool fiberglass from sand, feldspar, sodium sulfate, anhydrous borax, boric acid or other similar materials. Although there are some similarities among rock that may be used for both mineral wool and wool fiberglass production, the two industries are distinct. Mineral wool is used in cases in which fireproofing, structural strength and sound attenuation are needed, such as in high occupancy commercial and industrial buildings. Wool fiberglass is used primarily for insulation, in residential and small commercial buildings. Some wool fiberglass facilities also operate a ceiling tile or pipe product manufacturing line. The manufacturing of ceiling tile is not regulated under the Wool Fiberglass Manufacturing MACT Standard.
Today, there are seven mineral wool facilities that are subject to the MACT rule. No new mineral wool facilities have been built in the last 21 years and the agency does not anticipate new mineral wool facilities will be built in the foreseeable future. According to the size definition applied to this industry by the U.S. SBA(750 company employees or less), 5 of the 7 firms, employing 540 employees altogether, are classified as a small business.
Mineral wool is a fibrous, glassy substance consisting of silicate fibers typically 4 to 7 micrometers in diameter, made from natural rock (such as basalt, granite and other rock), blast furnace slag, glass cullet, coke and other similar materials. Products made from mineral wool are widely used in thermal and acoustical insulation and other products where mineral wool fiber is added to impart structural strength or fire resistance. In the mineral wool manufacturing process, raw materials (e.g., rock and slag) are melted in a cupola using coke as fuel; the molten material is then formed into fiber. In the production of mineral wool products that do not require high rigidity, oil is typically applied to suppress dust and add some strength to the fiber; the fiber is then sized and bagged or baled. This is known as a "nonbonded" product which is manufactured on a "nonbonded" production line.
For mineral wool products requiring a higher structural rigidity, typically a phenol/formaldehyde binder may be applied to the fiber. The binder-laden fiber mat is then thermoset in a curing oven and cooled. This is known as a "bonded" product which is made on a "bonded product" line. The major differences between the "nonbonded" and "bonded" production lines are the application of binder during fiber collection and the use of a curing oven. Four facilities only manufacture nonbonded products, while the other three facilities operate both bonded and nonbonded production lines. A total of 11 cupolas and 3 curing ovens are operated by the facilities in this source category.
HAP emission sources at mineral wool production facilities include the cupola where the mineral charge is melted; a collection chamber, in which air and a binder are drawn over the fibers, forming them into a mat against a screen; and a curing oven that bonds the fibers (for bonded products). HAP are emitted from the cupolas, curing ovens and collection operations when collection occurs with curing. Collection at nonbonded product lines does not emit HAP. COS accounts for the majority of the HAP emissions from these facilities (approximately 224 tpy and 51 percent of the total HAP emissions by mass). The majority of HAP emissions (approximately 58 percent of the total HAP by mass, including HF and HCl are from the cupolas. The remainder of the HAP are from bonded lines, including phenol, formaldehyde, and methanol. Although the majority of HAP are emitted from the cupola, the emissions (primarily formaldehyde and phenol) that were significant in evaluating risk are from the collection chambers on the bonded lines. Formaldehyde and phenol are emitted only from bonded mineral wool production lines; these lines include emissions from the application of the binder during collection and curing.
The current NESHAP requires control of PM emissions, as a surrogate for HAP metals, from the cupolas and formaldehyde emissions from the curing ovens. Fabric filters are the control devices used by this industry to reduce both PM and HAP metal emissions from cupolas. Emissions from collection operations are not regulated under the current NESHAP, but collection and curing ovens are generally controlled using RTOs and fabric filters.
The existing MACT rule applies to each existing, new and reconstructed cupola or curing oven in a mineral wool production facility. All mineral wool production facilities that are major sources are subject to the standards. For all cupolas, the 1999 MACT rule specifies a numerical emission limit for PM, as a surrogate for metal HAP. For new and reconstructed cupolas, emissions limits are specified for CO, as a surrogate for COS. Emissions limits for formaldehyde are also specified (as a surrogate for phenol emissions) for each existing, new, and reconstructed curing oven. Under the 1999 MACT rule, a mineral wool production facility may elect to comply with a numerical formaldehyde or CO emission limit expressed in mass of emissions per unit of production (kg/MG of melt or lb/ton of melt) or a percent reduction standard. PM emissions from existing, new, and reconstructed cupolas are limited to an outlet concentration of 0.05 kg/Mg (0.10 lb/ton) of melt, 40 CFR 63.1178(a). CO emissions limits from new and reconstructed cupolas are limited to an outlet concentration of 0.05 kg/Mg (0.10 lb/ton) of melt or 99 percent CO removal, 40 CFR 63.1178(a). Formaldehyde emissions limits from existing, new, and reconstructed curing ovens are limited to an outlet concentration of 0.03 kg/Mg (0.06 lb/ton) of melt or 80 percent formaldehyde removal, 40 CFR 63.1179(a).
B. Overview of the Wool Fiberglass Manufacturing source category and 1999 MACT rule.
The NESHAP (or MACT rule) for the Wool Fiberglass Manufacturing source category was promulgated on June 14, 1999 (62 FR 31695), and codified at 40 CFR part 63, subpart NNN. As promulgated in 1999, the MACT rule applies to affected sources of HAP emissions at wool fiberglass manufacturing facilities. Although the source category definition includes all manufacturers of wool fiberglass, the 1999 MACT rule (40 CFR 63.1381) defines a "wool fiberglass manufacturing facility" as "any facility manufacturing wool fiberglass on a RS manufacturing line producing bonded building insulation or on a FA manufacturing line producing bonded pipe insulation and bonded heavy-density products." The MACT rule for the Wool Fiberglass Manufacturing source category does not apply to facilities that manufacture mineral wool from rock, slag, and other similar materials. In addition, RS and FA manufacturing lines that produce nonbonded products (in which no phenol-formaldehyde binder is applied) are not subject to the current standards.
Wool fiberglass products are primarily used as thermal and acoustical insulation for buildings, automobiles, aircraft, appliances, ductwork and pipes. Other uses include liquid and air filtration. Approximately 90 percent of the wool fiberglass currently produced is used for residential and commercial building insulation products. Today, wool fiberglass is currently manufactured in the United States by 5 companies operating 29 facilities across 16 states. According to the size definition applied to this industry by the U.S. SBA (750 company employees or less), none of these companies are classified as a small business. One new wool fiberglass facility was recently built in 2007 and one wool fiberglass facility closed in 2010. Because several furnaces have been idled across the industry, current production of wool fiberglass is below production levels from previous years, and several months of stockpiled products exist at wool fiberglass companies, we do not expect new wool fiberglass facilities to be built in the near future.
Wool fiberglass is manufactured in a process that forms thin fibers from molten glass. Over 90 percent of the wool fiberglass industry produces insulation; two plants also operate a pipe product line and one plant operates a ceiling tile line (although the production of ceiling tile is not part of this MACT standard). A typical wool fiberglass manufacturing line consists of the following processes: (1) heating of raw materials and/or cullet in a furnace to a molten state, (2) preparation of molten glass for fiberization, (3) formation of fibers into a wool fiberglass mat or pipe insulation product, (4) curing the binder-coated fiberglass mat, (5) cooling the mat (this process is not always present) and (6) backing, cutting, and packaging.
The primary component of most types of wool fiberglass is silica sand, but wool fiberglass also includes varying quantities of feldspar, sodium sulfate, anhydrous borax, boric acid, and may be made entirely of glass cullet, crushed recycled glass. Wool fiberglass manufacturing plants typically operate one or more manufacturing lines. Refined raw materials for the glass batch are weighed, mixed, and conveyed to the glass-melting furnace, which may be gas-fired, electric, oxygen-enriched or a combination of gas and electric.
Two methods of forming fibers are used by the industry, RS and FA. In the RS process, centrifugal force causes molten glass to flow through small holes in the wall of a rapidly rotating cylinder. In the FA process, molten glass flows by gravity from a small furnace, or pot, to form threads that are then attenuated (stretched to the point of breaking) with air and/or flame.
After the fibers are formed, they are sprayed with a binder to hold the fibers together. These bonded fibers are then collected as a mat on a conveyor. Binder compositions vary with product type. At the time of development of the MACT standard, wool fiberglass mat was typically made using a phenol-formaldehyde resin based binder. According to the trade organization, only a few insulation products are currently made using a formaldehyde-based binder because new formaldehyde- and HAP-free binder formulations have been developed in recent years. Most new binder formulations are now HAP-free. According to the information collected through a survey by the industry, a few pipe insulation products made from wool fiberglass are still made at two facilities using a phenol-formaldehyde based binder.
After application of the binder and formation of the mat, the conveyor carries the newly formed mat through an oven to cure the thermosetting resin and then through a cooling section. Some products, such as those made on FA manufacturing lines, do not require curing and/or cooling.
Process emissions sources include the furnace where the charge is melted; the collection process, in which air carrying a binder is drawn over the fibers, forming them into a mat; and the curing oven that bonds the fibers (for bonded products only).
HAP, including chromium compounds, are emitted from glass-melting furnaces. Glass-melting furnaces are constructed using refractory bricks or blocks (commonly called refractories), that provide thermal insulation and corrosion protection. The refractory bricks re-direct the heat of the furnace back into the melt. Refractories are produced to withstand the extreme corrosive thermal conditions of a furnace and may contain a variety of mineral materials, including chromium, and more specifically chromic oxide.
In a wool fiberglass glass-melting furnace, sufficient temperatures are reached to drive the transformation of chromium from the trivalent to the hexavalent valence state. Because of the corrosive properties of the molten glass and the fining agents (salts added to the top of the molten glass layer which act to draw the gas bubbles out of the molten glass), the refractory of the inner furnace walls are eroded and fresh refractory is continually exposed along the metal/glass line within the furnace. As a result, when the glass-melting furnace is constructed using refractories containing high percentages of chromium, the emission levels of chromium compounds continuously increase over the life of the furnace according to the increasingly exposed refractory surface area.[,][,]
In addition, organic HAP (formaldehyde, phenol, and methanol) may be released from RS forming and curing processes and FA forming and curing processes.
The 1999 MACT rule applies to process emissions from each of the following existing, newly constructed, and reconstructed sources: glass-melting furnaces located at a wool fiberglass manufacturing plant, RS manufacturing lines that produce building insulation, and FA manufacturing lines producing pipe insulation. The MACT rule also applies to FA manufacturing lines producing heavy-density products.
The 1999 MACT rule requires control of PM emissions from the glass-melting furnaces and formaldehyde emissions from the RS and FA lines. Typical control devices to reduce PM and HAP emissions from furnaces include both wet and dry ESP and fabric filters. Low and high-temperature thermal oxidizers are used to control phenol, formaldehyde, and methanol from curing operations on bonded lines.
The 1999 MACT rule limits PM emissions to an outlet concentration of 0.50 lb of PM per ton of glass pulled for both existing and new furnaces, 40 CFR 63.1382. Emissions of formaldehyde from RS manufacturing lines are limited to an outlet concentration of 1.2 lb/ton of glass pulled for existing sources and 0.80 lb/ton of glass pulled for new sources. Emissions of formaldehyde from FA manufacturing lines producing pipe insulation are limited to an outlet concentration of 6.8 lb/ton of glass pulled from both existing and new sources, 40 CFR 63.1382. Emissions of formaldehyde from FA manufacturing lines producing heavy-density products are limited to an outlet concentration of 7.8 lb/ton of glass pulled for new sources; no emission limit is specified for existing FA manufacturing lines producing heavy-density products, 40 CFR 63.1382. A surrogate approach, where PM serves as a surrogate for HAP metals and formaldehyde serves as a surrogate for organic HAP, was used in the 1999 MACT rule to allow for easier and less expensive testing and monitoring requirements.
The industry trade association has advised us that because the wool fiberglass industry has voluntarily phased out most uses of phenol-formaldehyde based binders, there may now be only two wool fiberglass facilities that are subject to the current MACT rule. If this is accurate, 27 of the 29 facilities manufacturing wool fiberglass may not be considered major sources due to the phaseout of phenol-formaldehyde based binders. We are soliciting comment on our understanding that there will be no major sources in the wool fiberglass insulation source category (other than pipe insulation products)by the end of the 2012 calendar year.
C. What data collection activities were conducted to support this action?
In June 2010, the industry conducted a voluntary survey among all companies that own and operate mineral wool production and wool fiberglass manufacturing facilities. The survey sought test data for PM, CO and HAP emissions and information on the process equipment, control devices, point and fugitive emissions, practices used to control point and fugitive emissions, and other aspects of facility operations. Facilities were asked to seek and obtain prior EPA approval where new test data for a subset of processes, control devices and operations would be submitted as representative of an untested subset of processes, control devices and operations. In addition, facilities were allowed, in lieu of conducting new testing and with prior EPA approval, to submit existing and well-documented test data that were representative of current operations using the recommended test methods in the industry survey. Furthermore, the EPA requested, and industry agreed, that a subset of the facilities that were thought to be representative of emission sources from both the mineral wool and wool fiberglass industries would conduct additional emissions testing for certain HAP from specific processes. The bases for representativeness included design type and size of process units or equipment; fuel type; operating temperatures; control devices; and raw material content. Facilities completed and submitted responses to the industry survey in the spring of 2011.
In summary, the EPA received existing emissions test data from all 7 mineral wool facilities and 26 of the 29 wool fiberglass facilities, with some facilities submitting data for multiple years. Mineral wool facilities provided existing test data on cupolas, curing ovens, and collection operations. Wool fiberglass facilities provided existing test data on one or more of the following emission sources: glass-melting furnaces, curing ovens, forming, and collection operations. Emissions test data provided by facilities in both source categories, including the emission unit and pollutant tested, varied widely by facility.
The mineral wool industry included testing for most HAP metals, CO, PM and certain organic HAP (formaldehyde, phenol, methanol and COS). Pollutants tested for by the wool fiberglass manufacturing source category included most HAP metals, including chromium and hexavalent chromium, PM, formaldehyde, phenol and methanol. The EPA completed the dataset by assigning emission estimates from tested processes and their known production rates to the similar represented processes based on production rates at the untested processes. A copy of the dataset can be found in the docket to this proposed rule.
The results of these emission tests were compiled into a database for each source category, which is available in the docket for this action.
V. Analyses Performed
A. How did we estimate risks posed by the source categories?
The EPA conducted a risk assessment that provided estimates of (1) the MIR posed by the HAP emissions from the 7 mineral wool facilities and 29 wool fiberglass manufacturing facilities in the source categories, (2) the distribution of cancer risks within the exposed populations, (3) the total cancer incidence, (4) estimates of the maximum TOSHI for chronic exposures to HAP with the potential to cause chronic non-cancer health effects, (5) worst-case screening estimates of HQ for acute exposures to HAP with the potential to cause non-cancer health effects, and (6) an evaluation of the potential for adverse environmental effects. In June of 2009, the EPA's SAB conducted a formal peer review of the risk assessment methodologies used in its review of the document entitled, "Risk and Technology Review Assessment Methodologies." We received the final SAB report on this review in May of 2010. Where appropriate, we have responded to the key messages from this review in developing the current risk assessment; we will be continuing our efforts to improve our assessments by incorporating updates based on the SAB recommendations as they are developed and become available. 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 Mineral Wool Production and Wool Fiberglass Manufacturing Source Categories.

1. Establishing the Nature and Magnitude of Actual Emissions and Identifying the Emissions Release Characteristics.
For each facility in the Mineral Wool Production and Wool Fiberglass Manufacturing source categories, we developed and compiled an emissions profile (including emissions estimates, stack parameters, and location data) based on the information provided by the industry survey, the emissions test data, and various calculations. We used the production rates of tested processes to assign emissions to untested but similar processes based on known production rates at the untested processes. The site-specific emissions profiles include annual estimates of process emissions for the 2010 timeframe, as well as emissions release characteristics such as emissions release height, temperature, velocity, and location coordinates. We are requesting comment on the assumptions used to complete the dataset, including assumptions we made to assign emission rates.
The primary risk assessment is based on estimates of the actual emissions (though we also analyzed allowable emissions and the potential risks due to allowable emissions). We received a substantial amount of emissions test data and other information from the industry survey that enabled us to derive estimates of stack emissions of certain HAP for all of the facilities in both source categories. The wool fiberglass industry provided emission testing on all known pollutants, including total chromium and hexavalent chromium, PM, and other metals at furnaces they considered to be representative of other furnaces operated by the company. Where different furnace types were used to melt fiberglass, industry usually tested representative furnaces for each furnace type. The representative furnaces were chosen by industry according to production rates and furnace type. For untested furnaces, industry provided the normal operating rate in terms of tons of glass produced per hour. We estimated emissions at untested furnaces by using data from the representative tested furnaces. To do this, we used test data from representative furnaces that provided emissions rates of all tested pollutants on a pound per hour basis. We applied this pound per hour basis to the untested furnaces with the known production rates of those furnaces to estimate pounds per hour of pollutants. We considered furnace type and company when making these assignments.
We consider these estimates to be very good because they are based upon known emission test methods, have test reports that verify the results, were signed as being true and accurate by authorized company representatives, and also signed as being accurate by the testing company. In addition, one testing company was used by the industry to conduct all the emissions testing using approved EPA methods. We are requesting comment on our use of the available test data to assign emission estimates to untested emission points.
2. Establishing the Relationship between Actual Emissions and MACT-Allowable Emissions Levels.
The emissions data in our data set consists of actual stack emissions and, where we did not have actual emissions data, estimates of emissions based on a subset of operations that were representative of such emission points. In the EPA's experience, with most source categories, we generally have found that "actual" emissions levels are lower than the emissions levels that a facility is allowed to emit under the MACT standards. The emissions levels allowed to be emitted by the MACT standards are referred to as the "MACT-allowable" emissions levels. This represents the highest emissions level that could be emitted by facilities without violating the MACT standards.
As we discussed in prior residual risk and technology review rules, assessing the risks at the MACT-allowable level is reasonable since these risks reflect the maximum level at which sources could emit while still complying with the MACT standards. However, 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). Considering actual emissions is reasonable because source categories typically seek to perform better than required by emissions standards to provide an operational cushion and to accommodate the variability in manufacturing processes and control device performance. Facilities' actual emissions may also be significantly lower than MACT-allowable emissions for other reasons such as State requirements, improvements in performance of control devices since by the MACT standards, or reduced production. In this case, we are reducing the allowable emissions limits to the levels of actual emissions. For this reason, for the pollutants emitted, we are using only actual emissions in our risk analysis.
For both the Mineral Wool Production and Wool Fiberglass Manufacturing source categories, we evaluated actual and allowable stack emissions. Appendices 1a and 1b of the Draft Residual Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing Source Categories, available in the docket, further describe the estimates of MACT-allowable emissions and the estimates of risks due to allowable emissions.
      a. Actual and allowable emissions for the Mineral Wool Production source category.
The analysis of allowable emissions for the Mineral Wool Production source category was largely focused on formaldehyde emissions, which we considered the most important HAP emitted from this source category based on our screening level risk assessment and the HAP for which we had the most data. However, we also considered allowable emissions for other HAP, including HAP metals and COS. To estimate the difference between the actual and allowable emissions, we averaged the actual formaldehyde emission rates of manufacturing lines provided by facilities and compared those values to the maximum level allowed by the existing MACT standard (i.e., 0.06 pounds of formaldehyde per ton of melt) from all curing ovens.
 We realize that these estimates of allowable emissions are theoretical high-end estimates as facilities must maintain average emissions levels at some level below the MACT limit to ensure compliance with the standard at all times because of the day-to-day variability in emissions. Nevertheless, these high-end estimates of allowable emissions were adequate for us to estimate the magnitude of allowable emissions and the differences between the estimates of actual emissions and the MACT allowable emissions.
Based on this analysis, we conclude that all facilities in the mineral wool source category are emitting formaldehyde at levels lower than allowable and that the differences between actual and allowable emissions are significant. For the facilities producing bonded product, the estimated actual emissions were up to three times lower than allowable emissions. That is, MACT-allowable emissions were determined to be three times the actual emissions for all pollutants in the Mineral Wool Production category. Therefore, we multiplied the actual stack emissions from each facility by a factor of 3 to derive estimates of allowable emissions for modeling (whether these emissions were measured by testing or calculated based on representative emission tests).
      b. Analysis of allowable and actual emissions for the Wool Fiberglass Manufacturing source category.
The analysis of allowable emissions for the Wool Fiberglass Manufacturing source category was largely focused on emissions of chromium compounds and formaldehyde because these are the only pollutants emitted with significant health risks. To estimate the difference between the actual and allowable emissions, we averaged the actual formaldehyde emission rates of manufacturing lines provided by facilities and compared those values to the maximum level allowed by the existing MACT standard (i.e., 1.2 or 0.8 lb/ton of glass pulled for formaldehyde).
We realize that these estimates of allowable emissions are theoretical high-end estimates as facilities must maintain average emissions levels at some level below the MACT limit to ensure compliance with the standard at all times because of the day-to-day variability in emissions. Nevertheless, these high-end estimates of allowable emissions were adequate for us to estimate the magnitude of allowable emissions and the differences between the estimates of actual emissions and the MACT allowable emissions. Based on this analysis, we conclude that allowable emissions are estimated to be three times higher than actual emissions. Therefore, to develop the MACT-allowable emissions, the actual stack emissions for formaldehyde, phenol and methanol were multiplied by a factor of 3. The range of differences between actual and allowable formaldehyde emission levels is significant, that is, for some sources there was little difference between actual and allowable emission levels, other times, allowable emissions were up to 5 times greater than actual emissions. MACT-allowable emissions for chromium compounds were determined to be equal to actual emissions since there is currently no emissions limit for chromium compounds.
3. Conducting Dispersion Modeling, Determining Inhalation Exposures, and Estimating Individual and Population Inhalation Risks.
      Both long-term and short-term inhalation exposure concentrations and health risks from each source in both the source categories addressed in this proposal were estimated using the HEM (Community and Sector HEM - 3 version 2.1 Beta). The HEM - 3 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 km of the modeled sources, and (3) estimating individual and population-level inhalation risks using the exposure estimates and quantitative dose-response information.
      The dispersion model used by HEM - 3 is AERMOD, which is one of the EPA's preferred models for assessing pollutant concentrations from industrial facilities. HEM - 3 draws on three data libraries to perform the dispersion modeling and to develop the preliminary risk estimates. 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 more than 200 meteorological stations, selected to provide coverage of the United States and Puerto Rico. A second library of United States Census Bureau census block internal point locations and populations provides the basis of human exposure calculations (Census, 2000). In addition, for each census block, the Census library includes the elevation and controlling hill height, which are 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.
      In developing the risk assessment for chronic exposures, we used the estimated annual average ambient air concentration of each of the HAP emitted by each source for which we have emissions data in the source category. The air concentrations at each nearby census block centroid were used as a surrogate for the chronic inhalation exposure concentration for all the people who reside in that census block. We calculated the MIR for each facility as the cancer risk associated with a continuous lifetime exposure (24 hours per day, 7 days per week, and 52 weeks per year for a 70-year period) to the maximum concentration at the centroid of an inhabited census block. 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) by its 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 an EPA IRIS value, we look to other reputable sources of cancer dose-response values, often using CalEPA URE values, where available. We may use dose-response values in place of or in addition to other values, if appropriate, 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.
	With regard to formaldehyde, the EPA determined in 2004 that the CIIT cancer dose-response value for formaldehyde (5.5 x 10-9 per μg/m3) was based on better science than the IRIS cancer dose-response value (1.3 x 10-5 per μg/m3) and we switched from using the IRIS value to the CIIT value in risk assessments supporting regulatory actions. Based on subsequent published research, however, EPA changed its determination regarding the CIIT model and in 2010 the EPA returned to using the 1991 IRIS value. The EPA has been working on revising the formaldehyde IRIS assessment and the NAS completed its review of the EPA's draft in May of 2011. The EPA is reviewing the public comments and the NAS independent scientific peer review. The EPA will follow the NAS Report recommendations and will present results obtained by implementing the biologically based dose-response (BBDR) model for formaldehyde. The EPA will compare these estimates with those currently presented in the External Review draft of the assessment and will discuss their strengths and weaknesses.  As recommended by the NAS committee, appropriate sensitivity and uncertainty analyses will be an integral component of implementing the BBDR model. The draft IRIS assessment will be revised in response to the NAS peer review and public comments and the final assessment will be posted on the IRIS database. In the interim, we will present findings using the 1991 IRIS value as a primary estimate, and may also consider other information as the science evolves. As described in the risk assessment, the IRIS URE for formaldehyde is 1.3 x 10[-5] ug/m[3], whereas, the CIIT URE for formaldehyde is 5.5 x 10[-9] ug/m[3].
	Incremental individual lifetime cancer risks associated with emissions from 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) emitted by the modeled source. Cancer incidence and the distribution of individual cancer risks for the population within 50 km of any source were also estimated for the source category as part of these assessments by summing individual risks. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian dispersion models, including AERMOD.
      To assess risk of noncancer health effects from chronic exposures, we summed the HQ for each of the HAP that affects a common target organ system to obtain the HI for that target organ system (or TOSHI). The HQ for chronic exposures is the estimated chronic exposure divided by the chronic reference level, which is either the EPA 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 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, AEGL and 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. Since margins of safety are incorporated to address data gaps and uncertainties, exceeding the acute REL does not automatically indicate an adverse health impact.
      AEGL values were derived in response to recommendations from the NRC. As described in Standing Operating Procedures of the National Advisory Committee on Acute Exposure Guideline Levels for Hazardous Substances (http://www.epa.gov/opptintr/aegl/pubs/sop.pdf), "the NRC's previous name for acute exposure levels -- community emergency exposure levels -- was replaced by the term AEGL to reflect the broad application of these values to planning, response, and prevention in the community, the workplace, transportation, the military, and the remediation of Superfund sites." This document also states that AEGL values "represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to 8 hours." The document lays out the purpose and objectives of AEGL by stating (page 21) that "the primary purpose of the AEGL program and the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances is to develop guideline levels for once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals." In detailing the intended application of AEGL values, the document states (page 31) that "[i]t is anticipated that the AEGL values will be used for regulatory and nonregulatory purposes by U.S. Federal and state agencies and possibly the international community in conjunction with chemical emergency response, planning and prevention programs. More specifically, the AEGL values will be used for conducting various risk assessments to aid in the development of emergency preparedness and prevention plans, as well as real-time emergency response actions, for accidental chemical releases at fixed facilities and from transport carriers."
      The AEGL - 1 value is then specifically defined as "the airborne concentration of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure." The document also notes (page 3) that, "Airborne concentrations below AEGL - 1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects." Similarly, the document defines AEGL - 2 values as "the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape."
      ERPG 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." 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."
      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; in these instances, higher severity level AEGL - 2 or ERPG - 2 values are compared to our modeled exposure levels to screen for potential acute concerns.
      Acute REL values for 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, we developed estimates of maximum hourly emission rates by multiplying the average actual annual hourly emission rates by a factor to cover routinely variable emissions. We chose the factor based on process knowledge and engineering judgment and with awareness of a Texas study of short-term emissions variability, which showed that most peak emission events, in a heavily-industrialized four county area (Harris, Galveston, Chambers and Brazoria Counties, Texas) were less than twice the annual average hourly emission rate. The highest peak emission event was 74 times the annual average hourly emission rate, and the 99th percentile ratio of peak hourly emission rate to the annual average hourly emission rate was 9. This analysis is provided in Appendix 4 of the Draft Residual Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing Source Categories, which is available in the docket for this action. Considering this analysis, unless specific process knowledge or data are available to provide an alternate value, to account for more than 99 percent of the peak hourly emissions, we apply a conservative screening multiplication factor of 10 to the average annual hourly emission rate in these acute exposure screening assessments. The factor of 10 was used for the Wool Fiberglass Manufacturing source category, but we determined that a factor of 3 is more appropriate for the Mineral Wool Production source category (for more details see the Acute Effects Factor for Mineral Wool Manufacturing Operations document in the docket for this rulemaking).
      For the mineral wool source category, we used data from the highest formaldehyde emitting source among the mineral wool producers. That company also presented the highest risk due to formaldehyde emissions. This company provided the agency with 10 years of measurements of binder formulation, formaldehyde content in binders, binder application rates, and binder retention rates. Because the industry must manufacture their product for use in fireproofing, they must keep meticulous records of production specifics. These data are used to show compliance with Underwriters Laboratories and other building construction safety standards. From this specific 10-year data set, the EPA determined that, on a worst-case possible basis, formaldehyde could be emitted at levels no more than three times the actual rate. The worst-case scenario is possible if the binder contained the maximum amount of resin possible, the resin contained the maximum amount of formaldehyde possible, was sprayed at the maximum rate possible, and retained in the product at the minimum level possible. These data were used to in the risk assessment to determine the acute health effects hazard index. For Mineral Wool Production, the plant-specific acute factors were calculated and ranged from 1.0 to 1.6. Based on these results, and to allow for additional uncertainty in emissions, we used an acute factor of 3.0. The calculation we used to determine this acute factor is available in the docket to this rule.
      In 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. The data refinements employed for these source categories 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 each of these source categories. Ideally, we would prefer to have continuous measurements over time to see how the emissions vary 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 worst-case acute exposures to HAP, and in response to a key recommendation from the SAB's peer review of EPA's RTR risk assessment methodologies, we examine a wider range of available acute health metrics than we do for our chronic risk assessments. This is in response to the acknowledgement that there are generally more data gaps and inconsistencies in acute reference values than there are in chronic reference values. By definition, the acute CA-REL represents a health-protective level of exposure, with no risk anticipated below those levels, even for repeated exposures; however, the health risk from higher-level exposures is unknown. Therefore, when a CA-REL is exceeded and an AEGL-1 or ERPG-1 level is available (i.e., levels at which mild effects are anticipated in the general public for a single exposure), we have used them as a second comparative measure. Historically, comparisons of the estimated maximum off-site one-hour exposure levels have not been typically made to occupational levels for the purpose of characterizing public health risks in RTR assessments. This is because occupational ceiling values are not generally considered protective for the general public since they are designed to protect the worker population (presumed healthy adults) for short duration (<15 minute) increases in exposure. As a result, for most chemicals, the 15-minute occupational ceiling values are set at levels higher than a one-hour AEGL-1, making comparisons to them irrelevant unless the AEGL-1 or ERPG-1 levels are exceeded (US EPA 2009). Such is not the case when comparing the available acute inhalation health effect reference values for formaldehyde (US EPA 2009).
      The worst-case maximum estimated 1-hour exposure to formaldehyde outside the facility fence line for the mineral wool source category is 0.47 mg/m[3]. This estimated worst-case exposure exceeds the 1-hour REL by a factor of 8 (HQREL = 8) and is below the 1-hour AEGL-1 (HQAEGL-1 = 0.4). This exposure estimate does not exceed the AEGL-1, or exceed the workplace ceiling level guideline for the formaldehyde value developed by the NIOSH "for any 15 minute period in a work day" (NIOSH REL-ceiling value of 0.12 mg/m[3]; HQNIOSH = 4). The estimate is at the value developed by the ACGIH as "not to be exceeded at any time" (ACGIH TLV-ceiling value of 0.37 mg/m[3]; HQACGIH = 1). Additionally, the estimated maximum acute exposure exceeds the Air Quality Guideline value that was developed by the World Health Organization for 30-minute exposures (0.1 mg/m[3]; HQWHO = 5).
      For the wool fiberglass manufacturing source category, the worst-case maximum estimated 1-hour exposure to formaldehyde outside the facility fence line is 1.92 mg/m[3]. This estimated worst-case exposure exceeds the 1-hour REL by a factor of 30 (HQREL = 30) and the 1-hour AEGL-1 (HQAEGL-1 = 2). This exposure estimate also exceeds multiple workplace ceiling level guidelines for formaldehyde, including the value developed by the American Conference of Governmental Industrial Hygienists (ACGIH) as "not to be exceeded at any time" (ACGIH TLV-ceiling value of 0.37 mg/m[3]; HQACGIH = 5), and the value developed by the National Institutes for Occupational Safety and Health (NIOSH) "for any 15 minute period in a work day" (NIOSH REL-ceiling value of 0.12 mg/m[3]; HQNIOSH = 16). Additionally, the estimated maximum acute exposure exceeds the Air Quality Guideline value that was developed by the World Health Organization for 30-minute exposures (0.1 mg/m[3]; HQWHO = 19). Id.
      We solicit comment on the use of the occupational values described above in the interpretation of these worst-case acute screening exposure estimates for both the Mineral Wool Production and Wool Fiberglass Manufacturing source categories.
4. Conducting Multipathway Exposure and Risk Modeling.
      The potential for significant human health risks due to exposures via routes other than inhalation (i.e., multi-pathway exposures) and the potential for adverse environmental impacts were evaluated in a three-step process. In the first step, we determined whether any facilities emitted any PB-HAP 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, polycyclic organic matter, toxaphene and trifluralin.
      Since three of these PB-HAP (lead, cadmium, and mercury compounds) are emitted by at least one facility in both source categories, 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 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 TRIM.FaTE model. The hypothetical screening scenario was subjected to a sensitivity analysis to ensure that its key design parameters were established such that environmental media concentrations were not underestimated (i.e., to minimize the occurrence of false negatives or results that suggest that risks might be acceptable when, in fact, actual risks are high) and to also minimize the occurrence of false positives for human health endpoints. We call this application of the TRIM.FaTE model TRIM-Screen. The facility-specific emission rates of each of the PB - HAP in each source category were compared to the TRIM-Screen emission threshold values for each of 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.
      None of the facilities in the Mineral Wool Production and Wool Fiberglass Manufacturing source categories reported emissions of PB-HAP that were greater than the de minimis threshold levels, indicating no potential for significant multi-pathway risks from these facilities. Therefore, multi-pathway exposures and environmental risks were deemed negligible and no further analysis was performed. This analysis is provided in the Draft Residual Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing Source Categories, which is available in the docket for this action.
5. Assessing Risks After Control Options.
      In addition to assessing baseline inhalation risks and screening for potential multi-pathway risks, where appropriate, we also estimated risks considering the potential emission reductions that would be achieved by the particular control options under consideration. In these cases, the expected emissions reductions were applied to the specific HAP and emissions sources in the source category dataset to develop corresponding estimates of risk reductions. More information on the risks remaining after controls are in place to meet the emissions limits is available in the Draft Residual Risk Assessment for the Mineral Wool Production and Wool fiberglass Manufacturing Source Categories, which is available in the docket for this action.
6. Conducting Facility Wide Risk Assessments
      To put the source category risks in context, we also 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, for each facility that includes one or more sources from one of the source categories under review, we examine the HAP emissions not only from the source category of interest, but also from all other emission sources at the facility. For both source categories, all significant HAP sources have been included in the source category risk analysis and there are no other significant HAP emissions sources present. Therefore, we conclude that the facility wide risk is essentially the same as the source category risk for both the mineral wool and wool fiberglass source categories and that no separate facility wide analysis is necessary.
7. Considering Uncertainties in Risk Assessment.
      Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for the source categories addressed in this proposal. Although uncertainty exists, we believe that our approach, which uses conservative tools and assumptions, ensures that our decisions are health-protective. A brief discussion of the uncertainties in the emissions datasets, dispersion modeling, inhalation exposure estimates and dose-response relationships follows below. A more thorough discussion of these uncertainties is included in the draft risk assessment documentation (referenced earlier) available in the docket for this action.
      a. Uncertainties in the Emissions Datasets.
      Although the development of the MACT datasets involved quality assurance/quality control processes, the accuracy of emissions values will vary depending on the source of the data, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the datasets are inaccurate, errors 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 emission rates for the acute effects screening assessment were based on a multiplication factor of 10 applied to the average annual hourly emission rate, which is intended to account for emission 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 the approach considered in the dispersion modeling analysis for off-site locations and census block centroids 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. 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 since 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 risk levels.
	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 further 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 assessments evaluate the cancer inhalation risks associated with continuous pollutant exposures over a 70-year period, which is the assumed lifetime of an individual. In reality, both the length of time that modeled emissions sources at facilities actually operate (i.e., more or less than 70 years), and the domestic growth or decline of the modeled industry (i.e., the increase or decrease in the number or size of United States facilities), will influence the risks posed by a given source category. Depending on the characteristics of the industry, these factors will, in most cases, result in an overestimate both in individual risk levels and in the total estimated number of cancer cases. However, in rare cases, where a facility maintains or increases its emission levels beyond 70 years, residents live beyond 70 years at the same location, and the residents spend most of their days at that location, then the risks could potentially be underestimated. Annual cancer incidence estimates from exposures to emissions from these sources would not be affected by uncertainty in the length of time emissions sources operate.
      The exposure estimates used in these analyses assume chronic exposures to ambient levels of pollutants. Because most people spend the majority of their time indoors, actual exposures may not be as high, depending on the characteristics of the pollutants modeled. For many 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.
      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 overestimate actual exposures since it is unlikely that a person would be located at the point of maximum exposure during the time of worst-case impact.
      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 noncancer effects from both chronic and acute exposures. Some uncertainties may be considered quantitatively, and others generally are expressed in qualitative terms. We note as a preface to this discussion a point on dose-response uncertainty that is brought out in the EPA 2005 Cancer Guidelines; namely, that "the primary goal of the 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). In some circumstances, the true risk could be as low as zero; however, in other circumstances, the risk could also be greater. When developing an upper bound estimate of risk and to provide risk values that do not underestimate risk, health-protective default approaches are generally used. To err on the side of ensuring adequate health-protection, the EPA typically uses the upper bound estimates rather than lower bound or central tendency estimates in our risk assessments, an approach that may have limitations for other uses (e.g., priority-setting or expected benefits analysis).
      Chronic noncancer reference (RfC and RfD) values represent chronic exposure levels that are intended to be health-protective levels. Specifically, these values provide an estimate (with uncertainty spanning perhaps an order of magnitude) of daily oral exposure (RfD) or of a continuous inhalation exposure (RfC) to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. To derive values that are intended to be "without appreciable risk," the methodology relies upon an UF approach (U.S. EPA, 1993, 1994) which includes consideration of both uncertainty and variability. When there are gaps in the available information, UF are applied to derive reference values that are intended to protect against appreciable risk of deleterious effects. The UF are commonly default values, e.g., factors of 10 or 3, used in the absence of compound-specific data; where data are available, UF may also be developed using compound-specific information. When data are limited, more assumptions are needed and more UF are used. Thus, there may be a greater tendency to overestimate risk in the sense that further study might support development of reference values that are higher (i.e., less potent) because fewer default assumptions are needed. However, for some pollutants, it is possible that risks may be underestimated. While collectively termed "uncertainty factor," these factors account for a number of different quantitative considerations when using observed animal (usually rodent) or human toxicity data in the development of the RfC. The UF are intended to account for: (1) variation in susceptibility among the members of the human population (i.e., inter-individual variability); (2) uncertainty in extrapolating from experimental animal data to humans (i.e., interspecies differences); (3) uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure (i.e., extrapolating from sub-chronic to chronic exposure); (4) uncertainty in extrapolating the observed data to obtain an estimate of the exposure associated with no adverse effects; and (5) uncertainty when the database is incomplete or there are problems with the applicability of available studies. Many of the UF used to account for variability and uncertainty in the development of acute reference values are quite similar to those developed for chronic durations, but they more often use individual UF values that may be less than 10. UF are applied based on chemical-specific or health effect-specific information (e.g., simple irritation effects do not vary appreciably between human individuals, hence a value of 3 is typically used), or based on the purpose for the reference value (see the following paragraph). The UF applied in acute reference value derivation include: (1) Heterogeneity among humans; (2) uncertainty in extrapolating from animals to humans; (3) uncertainty in lowest observed adverse effect (exposure) level to no observed adverse effect (exposure) level adjustments; and (4) uncertainty in accounting for an incomplete database on toxic effects of potential concern. Additional adjustments are often applied to account for uncertainty in extrapolation from observations at one exposure duration (e.g., 4 hours) to derive an acute reference value at another exposure duration (e.g., 1 hour).
      Not all acute reference values are developed for the same purpose and care must be taken when interpreting the results of an acute assessment of human health effects relative to the reference value or values being exceeded. Where relevant to the estimated exposures, the lack of short-term dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties.
      Although every effort is made to identify peer-reviewed reference values for cancer and noncancer effects for all pollutants emitted by the sources included in this assessment, some HAP continue to have no reference values for cancer or chronic noncancer or acute effects. Since exposures to these pollutants cannot be included in a quantitative risk estimate, an understatement of risk for these pollutants at environmental exposure levels is possible. For a group of compounds that are either unspeciated, or do not have reference values for every individual compound (e.g., glycol ethers), we conservatively use the most protective reference value to estimate risk from individual compounds in the group of compounds.
      Additionally, chronic reference values for several of the compounds included in this assessment are currently under 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 these source categories and if dose-response metric changes enough to indicate that the risk assessment supporting this notice may significantly understate human health risk.
      When we identify acute impacts which exceed their relevant benchmarks, we pursue refining our acute screening estimates. For the Mineral Wool Production source category, we used a refined emissions multiplier of 3 to estimate the peak hourly emission rates from the average rates. For a detailed description of how the refined emissions multiplier was developed for the Mineral Wool Production source category see the memo on the Acute Effects Factor for Mineral Wool Manufacturing Operations, which is in the docket for this action. For the Wool Fiberglass Manufacturing source category, data were not available to develop a refined emissions multiplier; therefore, the default emissions multiplier of 10 was used.
      e. Uncertainties in the Multi-Pathway 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 multi-pathway and environmental effects is necessary. As discussed above, we conclude that the potential for these types of impacts is low for these source categories.
      f. Uncertainties in the Facility Wide Risk Assessment.
Given that the same general analytical approach and the same models were used to generate facility wide risk results as were used to generate the source category risk results, the same types of uncertainties discussed above for our source category risk assessments apply to the facility wide risk assessments. Because the source category processes are the only processes at each facility, there is no greater uncertainty for facility wide emissions.
B. How did we consider the risk results in making decisions for this proposal?
Based on our risk assessment we are proposing that risks due to hexavalent chromium and formaldehyde are acceptable, with a maximum individual cancer risk for the source category at 40-in-one million. Emissions testing at the facility presenting this risk indicated that 92 percent of the total chromium compounds were hexavalent chromium. In the second step of the process, the EPA sets the standard at a level that provides an ample margin of safety.
We found from our risk assessment that risks due to hexavalent chromium were acceptable at 40-in-one million. In the second step of our risk assessment, we considered whether any cost-effective measures, technologies or practices are available to reduce risks further to an "ample margin of safety". We found two methods whereby hexavalent chromium emissions can be reduced at wool fiberglass facilities and we are proposing in this action emission limits for hexavalent chromium from wool fiberglass facilities that will provide an ample margin of safety to protect the public health and prevent adverse environmental effects. We discuss these methods further in Sections V.A., VIII. D and VIII. E of this preamble.
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 our most recent proposals (75 FR 65068, October 21, 2010 and 75 FR 80220, December 21, 2010), 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). 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. Thus, the level of the MIR is only one factor to be weighed in determining acceptability of risks.
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 risk estimates associated with HAP emissions from the source category alone (source category risk estimates) and the risks due to HAP emissions from the entire facility at which the covered source category is located (facility wide risk estimates). We have not 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 are not included in the source categories in question, including mobile source emissions, natural source emissions, persistent environmental pollution, and 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., RfC) 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."
Although we are interested in placing source category and facility wide 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 facility wide 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.
C. How did we perform the technology review?
For our technology review, we identified and evaluated the developments in practices, processes and control technologies that have occurred since the 1999 MACT rules were promulgated. In cases where we identified such developments, we analyzed the technical feasibility of and the estimated impacts (costs, emissions reductions, risk reductions, etc.) of applying these developments. We then decided, based on impacts and feasibility, whether it was necessary to propose amendments to the regulation to require any of the identified developments.
Based on our analyses of the data, information collected under the voluntary industry survey, our general understanding of both of the industries and other available information on potential controls for these industries, we identified 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 MACT rules.
   * Any improvements in add-on control technology or other equipment (that were identified and considered during development of the 1999 MACT rules) 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 MACT rules.
   * 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 MACT rules.
   * Any development in equipment or technology that could result in increased HAP emissions.
In addition to reviewing the practices, processes, and technologies that were not considered at the time we developed the 1999 MACT rules, we reviewed a variety of data sources for the mineral wool and wool fiberglass industries. Among the data sources we reviewed were the NESHAP for various industries that were promulgated after the 1999 MACT rules. 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 Mineral Wool Production and Wool Fiberglass source categories, as well as the costs, non-air impacts, and energy implications associated with the use of these technologies. We reviewed scientific and technical literature regarding refractory products including high chrome refractories and consulted experts in the refractory manufacturing field.
Control technologies, classified as RACT, BACT, or LAER apply to stationary sources depending on whether the sources are existing or new, and on the size, age and location of the facility. We consulted the EPA's RBLC to identify potential technology advances. BACT and LAER (and sometimes RACT) are determined on a case-by-case basis, usually by state or local permitting agencies. The EPA established the RBLC to provide a central database of air pollution technology information (including technologies required in source-specific permits) to promote the sharing of information among permitting agencies and to aid in identifying future possible control technology options that might apply broadly to numerous sources within a category or apply only on a source-by-source basis. The RBLC contains over 5,000 air pollution control permit determinations that can help identify appropriate technologies to mitigate many air pollutant emissions streams. We searched this database to determine whether it contained any practices, processes, or control technologies for the types of processes covered by the Mineral Wool Production and Wool Fiberglass Manufacturing MACT rules.
Additionally, we requested information from facilities regarding developments in practices, processes, or control technology. Finally, we reviewed other information sources, such as State and local permitting agency databases and industry-supported databases.
D. 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. Based on this review we have identified several aspects of the MACT standards that we believe need revision. This includes proposing revisions to the startup, shutdown, and malfunction 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 (D.C. Cir. 2008).
We are proposing HAP-specific emission limits for COS, phenol, and methanol in place of surrogacy in the MACT standards. The proposed rule also would regulate the collection process as a source of HAP emissions of phenol, methanol and formaldehyde that were not included in the 1999 Mineral Wool MACT standard.
In addition, we are proposing other various minor changes with regards to editorial errors and other revisions to promote the use of plain language. The analyses and proposed decisions for these actions are presented in Section VI of this preamble.
E. What analyses were performed for the Mineral Wool Production Source Category under the Regulatory Flexibility Act?
      Section 609(b) of the RFA requires a Panel to be convened prior to publication of the IRFA that an agency may be required to prepare under the RFA. The RFA directs the Panel to report on the comments of small entity representatives and make findings on the following elements:
   *          a description and estimate of the number of small entities to which the proposed rule will apply;
   *          a description of projected reporting, recordkeeping and other compliance requirements of the proposed rule, including an estimate of the classes of small entities that will be subject to the requirements and the type of professional skills necessary for preparation of the report or record;
   *          an identification, to the extent practicable, of all relevant federal rules which may duplicate, overlap, or conflict with the proposed rule; and
   *          descriptions of any significant alternatives to the proposed rule which accomplish the stated objectives of applicable statutes and which minimize any significant economic impact of the proposed rule on small entities. This analysis must discuss any significant alternatives such as:
         *          o          the establishment of differing compliance or reporting requirements or timetables that take into account the resources available to small entities;
         *          o          the clarification, consolidation, or simplification of compliance and reporting requirements under the rule for such small entities;
         *          o          the use of performance rather than design standards; and
         *          o          an exemption from coverage of the rule, or any part thereof, for such small entities.
      Once completed, the Panel Report presents the results of the analyses identified in the above list, and is provided to the agency issuing the proposed rule and is included in the rulemaking record. The agency is to consider the Panel's findings when completing the draft of the proposed rule. In light of the Panel Report, and where appropriate, the agency is also to consider whether changes are needed to the IRFA for the proposed rule or the decision on whether an IRFA is required.
      The Panel's findings and discussion are based on the information available at the time the final Panel Report is published. The EPA will continue to conduct analyses relevant to the proposed rule, and additional information may be developed or obtained during the remainder of the rule development process.
      Any options identified by the Panel for reducing the rule's regulatory impact on small entities may require further analysis and/or data collection to ensure that the options are practicable, enforceable, environmentally sound and consistent with the CAA and its amendments. The Mineral Wool SBAR Panel convened on June 2, 2011, to address regulatory flexibility alternatives and opportunities for the mineral wool industry.
VI. Summary of Proposed Decisions and Actions
Pursuant to CAA sections 112(d)(2), 112(d)(6) and 112(f), we are proposing to revise the 1999 MACT rules relative to mineral wool production and wool fiberglass manufacturing to include the standards and requirements summarized in this section. More details of the rationale for these proposed standards and requirements are provided in Sections VII and VIII of this preamble. In addition, as part of these rationale discussions, we solicit public comment and data relevant to several issues. The comments we receive during the public comment period will help inform the rule development process as we work toward promulgating a final action.