United States

Environmental Protection

Agency

Summary of Public 

Comments and Responses for the

National Emissions Standards for

Hazardous Air Pollutants:

Mineral Wool Production and Wool 

Fiberglass Manufacturing 

(Risk and Technology Review)

June 2015
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NATIONAL EMISSIONS STANDARDS FOR HAZARDOUS AIR POLLUTANTS:

MINERAL WOOL PRODUCTION AND WOOL FIBERGLASS MANUFACTURING 

(RISK AND TECHNOLOGY REVIEW)

SUMMARY OF PUBLIC COMMENTS AND RESPONSES

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policies and Programs Division

Research Triangle Park, North Carolina 27711

June 25, 2015

The primary contact regarding questions or comments on this document is:

Susan Fairchild

U.S. Environmental Protection Agency

Metals and Minerals Group (D243-02)

Research Triangle Park, North Carolina 27711

Email: Fairchild.Susan@epa.gov
Summary of Public Response to Comments 

NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

TABLE OF CONTENTS

Section Page

I. INTRODUCTION............................................................................................................. 1

II. LIST OF COMMENTERS - MINERAL WOOL.......................................................... 3

III. LIST OF COMMENTERS - WOOL FIBERGLASS.................................................... 5

IV. GENERAL COMMENTS PERTAINING TO BOTH MINERAL WOOL 

PRODUCTION AND WOOL FIBERGLASS MANUFACTURING.......................... 7

A. Risk Assessment ............................................................................................................7

B. Ample Margin of Safety Analysis ...............................................................................30

C. UPL Approach to Limited Datasets.............................................................................46

D. SSM Provisions............................................................................................................54

E. Authority to Fill Data Gaps in Existing MACT Standards..........................................72

F. Monitoring, Recordkeeping and Reporting .................................................................73

G. General Approach To Calculating MACT...................................................................76

V. MINERAL WOOL PRODUCTION (SUBPART DDD)............................................. 88

A. Cupola PM Limits........................................................................................................88

B. Cupola HF and HCl Limits..........................................................................................88

C. Cupola COS Limit .....................................................................................................105

D. Collection and Curing limits......................................................................................111

E. Compliance Schedule.................................................................................................114

F. Small Business and Economic Impacts .....................................................................114

G. Environmental Benefits .............................................................................................119

H. Surrogacy ...................................................................................................................120

I. Testing and monitoring Issues...................................................................................121

J. Miscellaneous ............................................................................................................121

VI. WOOL FIBERGLASS MANUFACTURING SOURCE CATEGORY.................. 123

A. Issues Related to Both Major and Area Sources........................................................123

1. Chromium Emission Limits for Gas-Fired Glass-Melting Furnaces.................. 123

2. PM Limit for Glass-Melting Furnaces................................................................ 131

3. Testing and Monitoring Issues............................................................................ 137

B. Issues Related to Major Sources Only.......................................................................140

1. Applicability ....................................................................................................... 140

2. Technology Developments and Controls............................................................ 141

3. HCl and HF Emission Limits for Glass-Melting Furnaces................................. 141

4. Formaldehyde, Phenol, and Methanol Limits..................................................... 150

5. Compliance Schedule.......................................................................................... 156

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TABLE OF CONTENTS (Continued)

Section Page

6. Economic Impacts............................................................................................... 162

7. MACT Floor Analyses........................................................................................ 166

8. Environmental Justice......................................................................................... 170

9. Miscellaneous ..................................................................................................... 186

C. Issues Related to Area Sources Only.........................................................................189

1. EPA Decision and Authority to Regulate Area Sources..................................... 189

2. Decision to Apply GACT to Area Sources......................................................... 190

3. Glass-Melting Furnace Emission Limits ............................................................ 191

4. Economic Impacts............................................................................................... 192

5. Miscellaneous ..................................................................................................... 194

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LIST OF ACRONYMS AND ABBREVIATIONS

ATSDR Agency for Toxic Substances and Disease Registry

AEGL Acute Exposure Guideline Level

BDL Below Detection Limit (of the method)

BLDS Bag Leak Detection System

CAA Clean Air Act

CA-REL California Reference Exposure Level 

CEMS Continuous Emissions Monitoring System

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980

CL Confidence Limit

CIIT Chemical Industry Institute of Toxicology

CSEFH Child-Specific Exposure Factors Handbook

CTE Central Tendency Exposure

CWA Clean Water Act

D/F Dioxins and Furans

dscm Dry standard cubic meters

EFH Exposure Factors Handbook

EPA U. S. Environmental Protection Agency

EPCRA Emergency Planning and Community Right-to-Know Act

ERPG Emergency Response Planning Guideline

FR Federal Register

GACT Generally Available Control Technology

GEAE Generic Ecological Assessment Endpoint

HAP Hazardous Air Pollutant

HEM Human Exposure Model

HEPA High Efficiency Particulate Air Filter

HI Hazard Index

HON Hazardous Organic NESHAP

HQ Hazard Quotient

IQ Intelligence quotient

IQA Information Quality Act

IRIS Integrated Risk Information System

LOAEL Lowest Observable Adverse Effect Level

MACT Maximum Achievable Control Technology

MDL Minimum Detection Limit (of the pollutant) 

MEI Maximum Exposed Individual

MIR Maximum Individual Risk

NAAQS National Ambient Air Quality Standards

NEI National Emissions Inventory

NESHAP National Emission Standards for Hazardous Air Pollutants

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NOAEL No Observable Adverse Effect Level

OAQPS Office of Air Quality Planning and Standards

ODW Office of Drinking Water

OEHHA Office of Environmental Health Hazard Assessment

OHEA Office of Health and Environmental Assessment

PB-HAP Persistent Bioaccumulative Hazardous Air Pollutant

ppmv Parts per million by volume

PEL Probable Effect Level

PSD Prevention of Significant Deterioration

RCRA Resource Conservation and Recovery Act

RDL Representative Detection Limit (of the pollutant) 

REL Reference Exposure Level

RfC Reference Concentrations

RME Reasonable Maximum Exposure

RQ Reportable Quantity (CERCLA)

RTR Risk and Technology Review

SAB Science Advisory Board

SARA Superfund Amendments and Reauthorization Act

SIC Standard Industrial Classification

SIP State Implementation Plan

SOP Standard Operating Procedure

SSM Startup, Shutdown, and Malfunction

STEL Short-term Exposure Limit 

TEF Toxic Equivalency Factor

TOSHI Target Organ specific Hazard Index

TRI Toxic Release Inventory

UPL Upper Predictive Limit

URE Unit Risk Exposure

WHO World Health Organization

June 2015 vii
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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

I. INTRODUCTION

On June 1, 1999 (64 FR 29490), the EPA promulgated the National Emission Standards 

for Hazardous Air Pollutants (NESHAP) for the Mineral Wool Production source category (40 

CFR part 63, subpart DDD). The EPA promulgated the NESHAP for the Wool Fiberglass 

Manufacturing source category (40 CFR part 63, subpart NNN) on June 14, 1999 (62 FR 31695). 

Under section 112(d)(6) of the Clean Air Act (CAA), the EPA is required to review NESHAP no 

less frequently than every 8 years following promulgation and to revise the standards ‘‘as 

necessary, taking into account developments in practices, processes, and control technologies.’’ 

Additionally, under section 112(f)(2), the EPA must evaluate the risk to public health remaining 

after application of the technology-based standards and revise the standards, if necessary to 

provide an ample margin of safety to protect public health or to prevent, taking into 

consideration costs, energy, safety and other relevant factors, an adverse environmental effect. 

The residual risk review is also required within 8 years after promulgation of the technologybased standards. This review process is referred to as the Residual Risk and Technology Review 

(RTR).

On November 25, 2011 (76 FR 72770), EPA proposed revisions to the Mineral Wool 

Production and the Wool Fiberglass Manufacturing NESHAP to address the results of the RTR. 

In the November 2011 notice, the EPA proposed several amendments to both NESHAP and 

announced the agency’s intention to list and to regulate area sources in the wool fiberglass area 

source category pending the collection of new test data. Following the November 2011 proposal, 

the EPA obtained information regarding PM and chromium compounds that are either used in or 

emitted by glass-melting furnaces in the wool fiberglass manufacturing industry through an

information collection request (ICR) under CAA section 114. The EPA published a supplemental 

proposal on April 15, 2013 (78 FR 22369) that made corrections to the November 2011 proposal 

for the Mineral Wool Production and Wool Fiberglass Manufacturing source categories, 

addressed certain comments received on the earlier November 25, 2011 proposal, added gasfired glass-melting furnaces at area sources in the Wool Fiberglass Manufacturing source 

category to the category list, under CAA sections 112(c)(3) and 112(k)(3)(B), and proposed firsttime standards for these sources under CAA section 112(d)(5).

On November 13, 2014 (79 FR 68012), the EPA proposed, and requested comment on, 

revisions and clarifications to the following aspects addressed under previous proposals: 

• Additional explanation of the upper prediction limit (UPL) approach; 

• An explanation of our approach to limited datasets;

• An explanation of why we are withdrawing the proposed provisions establishing an 

affirmative defense to civil penalties for violations caused by malfunctions;

• Proposed basis for our determination on ecological effects of pollutants emitted from 

major sources in these source categories;

• Work practice requirements at startup and shutdown for mineral wool production and 

wool fiberglass manufacturing source categories under CAA section 112(h)(2);

• Changes to previously proposed emission limits for the mineral wool production 

source category;

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

• Changes to previously proposed standards for both major and area sources in the 

wool fiberglass manufacturing source category.

This document contains summaries of the public comments that the EPA received on the 

proposed standards. The preamble to the final rules also contains responses to significant public 

comments. Copies of all comments submitted are available at the EPA docket Center Public 

Reading Room. Comment letters and transcripts of the public hearings are also available 

electronically through http://www.regulations.gov by searching Docket IDs EPA-HQ-OAR2010-1041 and -1042.

This document does not contain comment summaries or responses to comments 

submitted in response to the following proposed regulatory changes because the EPA has already 

provided responses to these comments in the preamble to the 2013 proposal (78 FR 22370, April 

15, 2013) and the preamble to the 2014 proposal (79 FR 68011, November 13, 2014) and is not 

finalizing these changes: 

• Establishing an affirmative defense to civil penalties for violations caused by 

malfunctions, including revised compliance date for provisions related to affirmative 

defense and definition of affirmative defense (see 79 FR 68015 for explanation). 

• Establishing numerical emission limits for startup and shutdown periods (see 78 FR 

22378-22379 and 22388 for explanation). 

• Establishing numerical emission limits for hydrogen chloride (HCl) and hydrogen 

fluoride (HF) from for wool fiberglass furnaces (78 FR 22387 for explanation).

• Requiring use of EPA Method 202 when measuring particulate matter from wool 

fiberglass furnaces (78 FR 22386 for explanation).

• Using a sodium hydroxide (NaOH) scrubber as the EPA’s technology basis for 

reducing chromium emissions from wool fiberglass furnaces (79 FR 68020-69024 for 

explanation). 

• Requiring use of Method 26A or Method 320 to test HF and HCl.

In this document, we are including comment summaries of comments related to the 

formaldehyde, methanol, and phenol emissions from wool fiberglass manufacturing lines that 

use rotary spin (RS) lines. However, the EPA is not finalizing in this final rulemaking a revised 

emission limit for formaldehyde for RS lines or new emission limits for methanol and phenol for 

RS lines. The EPA will address these limits in a future rulemaking. Based on the information 

available to the EPA, the majority of wool fiberglass facilities no longer use 

phenol/formaldehyde (PF) binder and only one facility currently manufactures product using a 

PF binder. We have issued a CAA Section 114 ICR to obtain emissions and process data from 

RS production lines. See section V.H of the preamble to the final rule for a more complete 

discussion of EPA’s decision regarding PF binder production lines.

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Summary of Public Response to Comments 

NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

II. LIST OF COMMENTERS - MINERAL WOOL

Table 2-1 presents the public comment letters received by the EPA in response to the 

2011, 2013, and 2014 proposals for the mineral wool production source category. The table 

shows the commenter, affiliation, and identification number assigned to each letter in Docket 

EPA-HQ-OAR-2010-1041.

Table 2-1. Public Comments for Mineral Wool Production NESHAP, 

Proposed Rules Docket EPA EPA-HQ-OAR-2010-1041

Commenter 

ID Commenter Affiliation

November 25, 2011 Proposal

1041-0073 Russell S. Frye SSM Coalition (duplicate of 1042-0111)

1041-0074 Vinson Hellwig and Robert Colby National Association of Clean Air Agencies 

(NACAA) (duplicate of 1042-0113)

1041-0075 James and Dorothy McField Private Citizens (duplicate of 1042-0117)

1041-0076 E. Tellis Private Citizen

1041-0077 Melvin Keener Coalition for Responsible Waste Incineration 

(duplicate of 1042-0116)

1041-0078 Ann Mason American Chemistry Council (ACC) (duplicate 

of 1042-0119)

1041-0079 Mathew Todd Residual Risk Coalition (R2C)

1041-0080 Angus Crane and Christopher 

Martin

North American Insulation Manufacturers 

Association (NAIMA)

1041-0081

Emma Cheuse Earthjustice on behalf of Sierra Club and Oak 

Grove Neighborhood Association, Inc.

1041-0082

1041-0083

1041-0084

1041-0085

1041-0086

1041-0087

April 15, 2013 Supplemental Proposal

1041-0123 David T. Hudson Strategic Materials, Inc.

1041-0124 G. Vinson Hellwig and Robert H. 

Colby

NACAA (duplicate of 1042-0298)

1041-0125 Emma Cheuse Earthjustice on behalf of Sierra Club and Oak 

Grove Neighborhood Association (duplicate 

of 1042-0299)

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

Table 2-1. Public Comments for Mineral Wool Production NESHAP, 

Proposed Rules Docket EPA EPA-HQ-OAR-2010-1041

Commenter 

ID Commenter Affiliation

1041-0126 Angus E. Crane NAIMA (restatement of comments from 1041-

0080)

1041-0127 Angus E. Crane NAIMA

November 13, 2014 Supplemental Proposal

1041-0162 Ken Cammarato Roxul USA, Inc.

1041-0163 Ken Cammarato Roxul USA, Inc.

1041-0164 Angus E. Crane NAIMA

1041-0165 Emma Cheuse Earthjustice on behalf of Sierra Club

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

III. LIST OF COMMENTERS - WOOL FIBERGLASS

Table 3-1 presents the public comment letters received by the EPA received in response 

to the 2011, 2013, and 2015 proposals for the wool fiberglass manufacturing source category. 

The table presents the commenter, affiliation, and identification number assigned to each letter in 

Docket EPA-HQ-OAR-2010-1042.

Table 3-1. Public Comments for Wool Fiberglass Manufacturing NESHAP, 

Proposed Rules Docket EPA EPA-HQ-OAR-2010-1042

Commenter 

ID Commenter Affiliation

November 25, 2011 Proposal

1042-0108 Anonymous Private Citizen

1042-0111 Russell S. Frye SSM Coalition 

(duplicate of 1041-0073)

1042-0112 Marvin Robinson, II Quindaro Ruins/UGRR Exercise 2012

1042-0113 Vinson Hellwig and Robert 

Colby

NACAA (duplicate of 1041-074)

1042-0115a Richard Mabion Kansas Sierra Club

1042-0115b Rachel Jefferson Southeast Blvd & Quindaro Blvd. Family Health 

Care

1042-0115c Junette Hunter Private Citizen

1042-0115d Chester Owens Private Citizen

1042-0115e Marilyn White Private Citizen 

1042-0115f Craig Volland Private Citizen 

1042-0115g L.V. Quinn Private Citizen 

1042-0115h Marvin Robinson, II Quindaro Ruins / UGRR Exercise 2012

1042-0115i Clintel Betts Private Citizen 

1042-0115j Angus Crane NAIMA 

1042-0115k Elnora Jefferson Oak Grove Neighborhood Association 

1042-0116 Melvin Keener Coalition for Responsible Waste Incineration 

(duplicate of 1041-0077)

1042-0117 James and Dorothy McField Private Citizens (duplicate of 1041-0075)

1042-0118 Mathew Todd R2C (duplicate of 1041-0079)

1042-0119 Ann Mason ACC (duplicate of 1041-0078)

1042-0120 Angus Crane and Christopher 

Martin

NAIMA

1042-0121

Emma Cheuse

Earthjustice on behalf of Sierra Club and Oak 

Grove Neighborhood Association, Inc. (duplicate 

of 1041-0080) 

1042-0122

1042-0123 

1042-0124

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

Table 3-1. Public Comments for Wool Fiberglass Manufacturing NESHAP, 

Proposed Rules Docket EPA EPA-HQ-OAR-2010-1042

Commenter 

ID Commenter Affiliation

1042-0125

1042-0126 Lauren Alterman Saint-Gobain Corporation

1042-0127 Angus Crane and Christopher 

Martin

NAIMA

April 15, 2013 Supplemental Proposal

1042-0298 G. Vinson Hellwig and Robert 

H. Colby NACAA (duplicate of 1041-0124)

1042-0299 Emma Cheuse

Earthjustice on behalf of Sierra Club and Oak 

Grove Neighborhood Association (duplicate 

of 1041-0125) 

1042-0300 Angus E. Crane NAIMA

November 13, 2014 Supplemental Proposal

1042-0348 Angus E. Crane and 

Christopher C. Martin NAIMA

1042-0347 Emma Cheuse Earthjustice on behalf of Sierra Club

June 2015 6
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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

IV. GENERAL COMMENTS PERTAINING TO BOTH MINERAL WOOL 

PRODUCTION AND WOOL FIBERGLASS MANUFACTURING

A. Risk Assessment

1. Comment: One commenter (1041-0074/1042-0113) stated that Acute Exposure 

Guideline Levels (AEGLs) and Emergency Response Planning Guidelines (ERPGs) were 

developed for accidental release emergency planning and they are not appropriate for assessing 

daily human exposure to toxic air pollutants because they do not include adequate safety and 

uncertainty factors. The commenter stated that they are not meant to evaluate the acute impacts 

from routine emissions that occur over the life of a facility and cannot be relied upon to protect 

the public from the adverse effects of exposure to toxic air pollutants. The commenter concluded 

that their use is not appropriate in risk assessments and urged the EPA to increase its reliance on 

the California Reference Exposure Levels (RELs) to address acute exposures in the residual risk 

assessments.

Response: The acute assessment is not an assessment of daily human exposure. Rather, 

the acute assessment uses conservative estimates of maximum hourly emissions to assess 

potential impacts of short-term, acute exposures. As such, AEGLs and ERPG values are among 

the appropriate values to use in the acute assessment. The EPA does not rely exclusively upon 

AEGL or ERPG values for assessment of acute exposures. Rather, the EPA’s approach is to 

consider various acute health effect reference values, including the California REL, in assessing 

the potential for risks from acute exposures. To better characterize the potential health risks 

associated with estimated acute exposures to HAP, and in response to a key recommendation 

from the SAB’s peer review of the EPA’s RTR risk assessment methodologies,1 we generally 

examine a wider range of available acute health metrics (e.g., RELs, AEGLs) than we do for our 

chronic risk assessments. This is in response to the SAB’s acknowledgement that there are 

generally more data gaps and inconsistencies in acute reference values than there are in chronic 

reference values. In some cases, when Reference Value Arrays2 for HAP have been developed, 

we consider additional acute values (i.e., occupational and international values) to provide a 

more complete risk characterization. The exposure guidelines EPA considers depends on which 

exposure guidelines are available for the various hazardous air pollutants emitted. The EPA uses 

AEGL and ERPG values (when available) in conjunction with REL values (again, when 

available) to characterize potential acute health risks. However, it is often the case that HAP do 

not have all of these acute reference benchmark values. In these instances, the EPA describes the 

potential acute health risk in relation to the acute health values that are available. Importantly, 

when interpreting the results, we are careful to identify the benchmark being used and the health 

implications associated with any specific benchmark being exceeded.

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

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

unsigned.pdf.

2 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of 

Chemical-Specific Health Effect Reference Values for Inhalation Exposures (Final Report). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R–09/061, and available on-line at 

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

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

2. Comment: Two commenters (1042-0121 and 1041-0074/1042-0113) objected to the 

EPA’s use of the geographic centroid of the census block in the risk assessment instead of the 

closest or maximum point of exposure. One commenter explained that this approach 

underestimates exposure and could easily be remedied because HEM-AERMOD allows the 

system to make such an adjustment. The commenter noted that this conflicts with the 

recommendation of the SAB, which has urged the EPA to consider “specific locations of 

residences.” That commenter added that the EPA has regularly received comments on this issue 

from state air pollution control agencies in past rulemakings. That commenter recommended that 

in this and future rulemakings, the EPA should follow the advice of these state regulators and 

start assessing risk at the edge or fence-line of the facility – i.e., the point of maximum exposure 

– not just at the centroid of a census block. That commenter concluded that failing to do so 

would be unlawful, arbitrary and capricious, as this approach fails to assess risk for the person 

“most exposed” to the source category‘s emissions. 

The commenters stated that census blocks are not homogeneous and, even if the area near 

the property line is not developed, over time homes and businesses could locate closer to the 

facility. The commenters also believed the EPA has at other times recognized that the maximum 

exposed individual for acute risks is likely present closer to or at the fence line. 

Another commenter (1042-0115f) stated that some neighboring residents live on the 

bluffs overlooking the Fairfax industrial district (Kansas City, Kansas) at an elevation above the 

tops of some of the smoke stacks. While the EPA's model does take nearby terrain into account, 

the commenter was concerned that it makes the exposure calculation only at the center of the 

census tract. The commenter noted that this would underestimate the risk to residents living on 

the edge of the track toward the stacks. That commenter argued that the modeling would not 

adequately consider the risk to anyone working regularly just beyond the fence line of the 

CertainTeed plant. According to that commenter, the model does not fully take into account the 

lifetime of harm that can be caused when a child is exposed at an early age to toxic chemicals.

Response: In a national-scale assessment of lifetime inhalation exposures and health 

risks from facilities in a source category, it is appropriate to identify exposure locations where it 

may be reasonably expected that an individual will spend a majority of his or her lifetime. In 

determining chronic risks, it is appropriate to use census block information on where people 

actually reside, rather than points at the property line, to locate the estimation of exposures and 

risks to individuals living near such facilities. Census blocks are the finest resolution available as 

part of the nationwide population data (as developed by the U.S. Census Bureau); on average, a 

census block is comprised of approximately 40 people and about 10 households. In the EPA risk 

assessments, the geographic centroid of each census block containing at least one person is used 

to represent the location where all the people in that census block live. The census block centroid 

with the highest estimated exposure then becomes the location of maximum exposure, and the 

entire population of that census block is assumed to experience the maximum individual risk. In 

some cases, because actual residence locations may be closer or farther from facility emission 

points, this may result in an overestimate or underestimate of the actual annual concentrations 

(although there is no systematic bias for average levels). Given the relatively small dimensions 

of census block in densely-populated areas, there is little uncertainty introduced by using the 

census block centroids in lieu of actual residence locations. There is the potential for more 

uncertainty when the census block are larger, although there is still no systematic bias. The EPA 

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NESHAP: Mineral Wool Production And Wool Fiberglass Manufacturing (Risk And Technology Review)

concludes that the most appropriate locations at which to estimate chronic exposures and risks 

are the census block centroids because: (1) census blocks are the finest resolution available in the 

national census data; (2) facility fence lines do not typically represent locations where chronic 

exposures are likely (i.e., people do not typically live at the fence line of facilities); and (3) there 

is no bias introduced into the estimate of the maximum individual risk (MIR) by using census 

block centroid locations. In its peer review of the methodologies used to estimate risks as part of 

the RTR rulemaking efforts, the EPA’s Science Advisory Board (SAB) endorsed this approach.3

3. Comment: One commenter (1041-0081) stated that in assessing acute health risk, the 

EPA used a multiplier of 10 to assess the peak 1-hour emissions, compared to average emission 

rates, for Wool Fiberglass, and a factor of 3 for Mineral Wool. As a result, the commenter noted 

that the EPA found that the highest, worst-case acute hazard quotient (HQ) for the Wool 

Fiberglass source category is 30, based on the acute REL for formaldehyde, and for Mineral 

Wool it is 8, based on formaldehyde. According to the commenter, the EPA has not 

demonstrated that using a factor of 10 is high enough for Wool Fiberglass to assess the true acute 

risk to the most-exposed individual and community under the EPA’s existing standards and that 

its use is therefore not justified. 

Response: The acute risk assessment methodology uses a tiered, iterative approach that 

begins with an assessment of an approximation of a worst-case exposure. To this end, we 

assumed that peak 1-hour emissions are equal to 10 times the average 1-hour emissions rate for 

the wool fiberglass manufacturing source category and 3 times the average 1-hour emissions rate 

for the mineral wool manufacturing source category, which are only one of the worst-case 

assumptions that we made for each source category in our acute health risk screening analysis. 

Other worst-case assumptions included: 

• For facilities with multiple emission points, peak 1-hour emissions were assumed to 

occur at all emission points at the same time.

• For facilities with multiple emission points, 1-hour concentrations at each receptor 

were assumed to be the sum of the maximum concentrations due to each emission 

point, regardless of whether those maximum concentrations occurred during the same 

hour. 

• Worst-case meteorology (from one year of local meteorology) was assumed to occur 

at the same time the peak emission rates occur. The recommended EPA local-scale 

dispersion model, AERMOD, is used for simulating atmospheric dispersion.

• A person was assumed to be located downwind at the point of maximum impact 

during this same 1-hour period, but no nearer to the source than 100 meters.

3 U.S. Environmental Protection Agency, Office of the Administrator Science Advisory Board. 

Review of EPA’s draft entitled, “Risk and Technology Review (RTR) Risk Assessment Methodologies: For 

Review by the EPA’s Science Advisory Board with Case Studies – MACT I Petroleum Refining Sources and 

Portland Cement Manufacturing.” EPA-SAB-10-007. May 7, 2010. 

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

unsigned.pdf.

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The maximum impact was compared to multiple short-term health benchmarks for the 

chemical being assessed to determine if a possible acute health risk might exist. These 

benchmarks are described in section 2.6 of the Final Risk Assessment Report in the project 

dockets. 

Based on industry-specific information, we determined that a refined emissions multiplier 

of 3 better represents the peak hourly emission rates for the Mineral Wool Production source 

category. (See acute effects memorandum in the docket for a detailed description of how the 

refined emissions multiplier was developed for the Mineral Wool Production source category: 

EPA-HQ-OAR-2010-1041-0022). For the Wool Fiberglass Manufacturing source category data 

were not available to develop an industry specific refined emissions multiplier, therefore, the 

default emissions multiplier of 10 was used. In the Wool Fiberglass risk assessment, we relied 

upon the SAB guidance that the 10-fold factor was recommended because it represented a level 

that is amply conservative in the absence of such information. Also, based on an analysis of data 

on short-term emission rates relative to long-term emission rates, the EPA has determined that 

the tenfold ratio assumption for short-term releases is protective, and that the facilities for which 

it may underestimate event releases may tend to be smaller emitters. See Appendix 4 of the 

document titled “Residual Risk Assessment for the Mineral Wool Production and Wool 

Fiberglass Manufacturing Source Categories in Support of the June 2015 Final Rule,” found in 

the docket for this rulemaking, for a detailed discussion of this analysis. We therefore disagree 

with the commenters on their characterization of the acute risk factor of 10 for wool fiberglass as 

insufficient.

4. Comment: According to one commenter (1042-0121/1042-0347), the EPA‘s 

multipathway risk assessment fell short because the EPA did not use “allowable” emissions for 

this assessment and the proposed rule shows multipathway risks that are 60 times greater than 

the EPA‘s threshold. The commenter stated that the EPA acknowledged in its 2014 Risk 

Assessment that the emissions allowed by the standard may be up to 3 times greater than actual 

emissions for phenol, methanol, and formaldehyde, such that the HQ of 30 could be 3 times 

higher based on allowable emissions. The commenter stated that by using actual emissions, the 

EPA’s analysis is likely to be an underestimate of the health risks from multipathway routes of 

exposure. The commenter supports the EPA’s use of “allowable” as well as “actual” emissions to 

assess inhalation risk.

Response: Consistent with previous risk assessments, the EPA considers both allowable 

and actual emissions in assessing chronic risks under CAA section 112(f)(2). (See, e.g., National 

Emission Standards for Coke Oven Batteries (70 FR 19998-19999, April 15, 2005); proposed 

and final National Emission Standards for Organic Hazardous Air Pollutants from the Synthetic 

Organic Chemical Manufacturing Industry (71 FR 34428, June 14, 2006, and 71 FR 76603, 

December 21, 2006). This approach is both reasonable and consistent with the flexibility 

inherent in the Benzene NESHAP framework for assessing acceptable risk and ample margin of 

safety. As a general matter, modeling allowable emission levels is inherently reasonable since 

this reflects the maximum level sources could emit and still comply with national emission 

standards. But it is also reasonable to consider actual emissions, where such data are available, in 

the acceptable risk and ample margin of safety (AMOS) analyses. See National Emission 

Standards for Coke Oven Batteries, 70 FR 19992, 19998 (April 15, 2005). The commenter 

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claims that limiting our review to actual emissions would be inconsistent with the applicability 

section of part 63 rules. As explained, however, we did not limit our review to actual emissions. 

The commenter also urged the agency to rely on allowable emissions, which we estimate 

to be three times the actual emissions, for the purpose of our acute assessment. The commenter 

indicated that the estimated maximum acute HQ of 30 (REL) would then be three times higher. 

The use of allowable emissions was not considered due to the conservative assumptions used to 

gauge worst-case potential acute health effects. The conservative assumptions built into the acute 

health risk screening analysis include: (1) use of peak 1-hour emissions that are, on average, 10 

times the annual average 1-hour emission rates; (2) that all emission points experience peak 

emissions concurrently; (3) worst-case meteorology (from 1 year of local meteorology); and (4) 

that a person is located downwind at the point of maximum impact during this same 1-hour 

period. Thus, performing an acute screen based on allowable emissions would be overly 

conservative and at best, of questionable utility to decision makers.

5. Comment: One commenter (1041-0081) stated that the EPA should find the acute 

health risk from Wool Fiberglass and Mineral Wool to be unacceptable. For both Wool 

Fiberglass and Mineral Wool, the commenter noted that the EPA’s assessment found an acute 

risk of 30 for Wool Fiberglass, and 8 for Mineral Wool. The commenter challenged the EPA’s 

consideration of a HQ below 1 as safe and argued that the EPA should find the health risk from 

both source categories to be unacceptable under CAA section 112(f)(2).

The commenter stated that the EPA has a presumption that an HQ below 1 is safe, that 

the EPA has stated that a HQ less than or equal to one indicates that adverse noncancer effects 

are not likely to occur, and that exposure below that threshold level is safe. 

The commenter added that the EPA did not adequately explain why the formaldehyde 

risks were found to be acceptable although they are 30 times higher than the threshold for Wool 

Fiberglass, and 8 times the threshold for Mineral Wool.

Response: The highest acute risk is based on the reference exposure level (REL) is 20 

(formaldehyde) for Mineral Wool Production facilities and is 30 (formaldehyde) for Wool 

Fiberglass Manufacturing facilities. As explained in our 2011 proposal, we proposed to find the 

risk acceptable after consideration of various factors, including that the one mineral wool facility 

is located in a rural area with a small population, that the HQ estimates for formaldehyde based 

on the AEGL-1 and ERPG-1 values for this facility are at 1 and because the acute modeling is a 

worst-case scenario. With respect to the wool fiberglass manufacturing source category, we 

explained that the maximum acute HQ value based on the REL for formaldehyde could exceed a 

value of 1 at a total of 7 facilities with one facility indicating the potential to have an HQ up to 

30. We further explained that this maximum worst-case acute impact corresponds to maximum 

HQ of 1 based on the AEGL-1 and ERPG-1 levels for formaldehyde. We proposed to find the 

risk acceptable after consideration of various factors, including that the HQ estimates for 

formaldehyde based on the AEGL-1 and ERPG-1 values for these facilities are at 1 and because 

the acute modeling is a worst-case scenario.

We note that the REL value is not a concentration at which health effects are expected to 

be observed. That is, the REL is defined as “the concentration level at or below which no adverse 

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health effects are anticipated for specified exposure duration.” Moreover, we note that the acute 

risk assessment is a worst case assessment. For example, the acute assessment assumes worstcase meteorology, peak emissions and an individual being located at the site of maximum 

concentration for an hour. Taken together, the EPA does not believe that in all RTR reviews, HQ 

values must be less than or equal to 1. Rather, the EPA finds that acute risks must be judged on a 

case by case basis in the context of all the available health evidence and risk analyses. 

To better characterize the potential health risks associated with estimated acute exposures 

to HAP, and in response to a key recommendation from the SAB’s peer review of the EPA’s 

RTR risk assessment methodologies,4 we generally examine a wider range of available acute 

health metrics (e.g., RELs, AEGLs) than we do for our chronic risk assessments. This is in 

response to the SAB’s acknowledgement that there are generally more data gaps and 

inconsistencies in acute reference values than there are in chronic reference values. In some 

cases, when Reference Value Arrays5 for HAP have been developed, we consider additional 

acute values (i.e., occupational and international values) to provide a more complete risk 

characterization. As discussed in the preamble to the proposed OSWRO rule (79 FR 37857, July 

2, 2014), the exposure guidelines the EPA considers depends on which exposure guidelines are 

available for the various hazardous air pollutants emitted. The EPA uses AEGL and ERPG 

values (when available) in conjunction with REL values (again, when available) to characterize 

potential acute health risks. However, it is often the case that HAP do not have all of these acute 

reference benchmark values. In these instances, the EPA describes the potential acute health risk 

in relation to the acute health values that are available. Importantly, when interpreting the results, 

we are careful to identify the benchmark being used and the health implications associated with 

any specific benchmark being exceeded. By definition, the acute CA-REL represents a healthprotective 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 onehour 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 exposure6

. 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 (U.S. EPA 2009). Such is not the case when 

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

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

unsigned.pdf.

5 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of 

Chemical-Specific Health Effect Reference Values for Inhalation Exposures (Final Report). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R–09/061, and available on-line at 

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

6 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for Formaldehyde in Graphical Arrays of 

Chemical-Specific Health Effect Reference Values for Inhalation Exposures (Final Report). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-09/061, and available on-line at 

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

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comparing the available acute inhalation health effect reference values for formaldehyde (U.S.

EPA 2009).

6. Comment: One commenter (1041-0078/1042-0119) asserted that, by applying the 

outdated Integrated Risk Information System (IRIS) dose-response values in determining 

formaldehyde inhalation exposure risk, the EPA is not basing the proposed rule on the best 

available science. The commenter urged the EPA to revise the Proposed Rule to accurately 

convey the best available science and a weight-of-evidence approach in compliance with the 

Information Quality Act (IQA) Guidelines and Executive Order 13563. In particular, the 

commenter argued that the EPA should reject the 1991 IRIS dose-response value and incorporate 

the Chemical Industry Institute of Toxicology (CIIT, 1999) cancer dose-response value for 

formaldehyde. The commenter noted that President Obama issued Executive Order 13563, 

requiring agencies to improve regulation and regulatory review. According to the commenter, the 

EPA used the 1991 IRIS value without conducting a comprehensive review of the body of 

research that may suggest an alternative value is supported by the best available science.

The commenter argued that U.S. Court of Appeals for the D.C. Circuit, in Chlorine

Chemistry Council v. EPA, 206 F.3d 1286 (D.C. Cir. 2000), further underscored the importance 

of rulemaking “on the basis of the best available science at the time of the rulemaking.” Id. at 

1291 (emphasis in original). In holding that the best available science is the science available at 

the time of rulemaking, the commenter noted that the court unanimously rejected the EPA’s 

contention that it would defer the application of the best available science until after input from 

the SAB on the carcinogenic mode of action of chloroform. “The word ‘available’ would be 

senseless if construed to mean ‘expected to be available at some future date.’” Id. Similarly, the 

commenter stated that the research and data considered in the NAS Report of the Draft IRIS 

Assessment should be incorporated into this rulemaking, and that the EPA has illegally deferred 

application of the best available science.

Response: In 2002 for this rule, and at various dates for other rules, we have complied 

with the IQA which requires us to “issue guidelines” to ensure and maximize data quality. We 

disagree with the commenter that scientific information used in the EPA risk assessments does 

not adhere to a rigorous standard of quality. The EPA has an approach for selecting the most 

appropriate and scientifically defensible health benchmarks and, in general, this approach places 

greater weight on the EPA derived health benchmarks than those from other authoritative 

bodies.7 The approach of favoring the EPA benchmarks (when they exist) has been endorsed by 

the SAB and ensures the use of values most consistent with well-established and scientificallybased EPA science policy. We also disagree with the commenter that the EPA considers the CIIT 

value as a viable dose response value to be used in EPA risk assessments. In 2004, the EPA 

determined that the CIIT cancer dose-response value for formaldehyde (5.5 x 10-9 per microgram 

per cubic meter, μg/m3) was based on better science than the IRIS 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. Subsequent research published by the EPA suggested that the 

CIIT model was not appropriate and in 2010 EPA returned to using 1991 IRIS value, which is 

more health protective (U.S. EPA. 2010. Memorandum from Peter Preuss to Steve Page entitled, 

7 http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf

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“Recommendation for Formaldehyde Inhalation Cancer Risk Values” January 22, 2010.). The 

EPA is currently revising the formaldehyde IRIS assessment and 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. This approach is consistent with the EPA’s information 

guidelines and fully compliant with the IQA.

The case cited by the commenter (Chlorine Chemistry Council v. EPA) is totally 

inapplicable to this circumstance. The rule in Chlorine Chemistry Council was issued under the 

Safe Drinking Water Act, which statutorily mandates the use of the “best available science.” 

There is no such requirement under the CAA. But even if there were, EPA has fully and 

reasonably explained its decision to use the best available science in this rulemaking.

7. Comment: One commenter (1041-0081) stated that the EPA should find the chronic 

non-cancer risk from Wool Fiberglass and Mineral Wool to be unacceptable. The commenter 

believes the EPA has underestimated the risk by considering a target organ specific hazard index

(TOSHI) below 1 as acceptable. For example, the commenter did not agree that the EPA 

adequately accounted for the greater risk to children due to early exposure, facility-wide risk or 

cumulative toxic air health risk and did not consider impacts that are occurring above the critical 

dose in the development of the TOSHI. 

The commenter pointed out that the EPA found the chronic non-cancer risk (TOSHI) (0.5 

for wool fiberglass and 0.1 for mineral wool, based on allowable emissions) to be acceptable. 

The commenter recommended that the TOSHI should be no higher than 0.2, echoing an internal 

EPA draft memorandum. 

The commenter further asserted that even a 0.2 contribution should not be assumed to be 

protective, when many local communities have already experienced a long history of air 

emissions and continue to be exposed to emissions from many sources, and the EPA should 

consider an additional safety factor to reduce this risk further.

Response: First we would point out that, for the final rule, the chronic noncancer TOSHI 

is 0.1 for both categories. 

Second, we disagree with the comment that any TOSHI value greater than 0.2 should be 

considered unacceptable. We note that pollutant-specific reference concentrations (RfCs) are not 

absolute thresholds, but estimates of chronic inhalation exposures at or below which health 

effects would not be expected to occur, including in sensitive subgroups. We further note that 

these RfCs are developed using a health-protective approach (see uncertainty discussion in risk 

assessment document section 4.2), that TOSHI values of 1 or less are (like RfC levels) generally 

considered to carry no appreciable risk of adverse health effects and that there is generally no 

need to compound this protection by suggesting that any source category maximum TOSHI 

value would need to be at or below 0.2 before we would consider it to be acceptable.

We generally draw no bright lines of acceptability regarding cancer or noncancer risks 

from source category HAP emissions. It is always important to consider the specific uncertainties 

of the emissions and health effects information regarding the source category in question when 

deciding exactly what level of cancer and noncancer risk should be considered acceptable. In 

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addition, the source category-specific decision of what constitutes an acceptable level of risk 

should be a holistic one; that is, it should simultaneously consider all potential health impacts --

chronic and acute, cancer and noncancer, and multipathway -- along with their uncertainties, 

when determining the acceptable level of source category risk. In other words, we look at the risk 

numbers within the context of uncertainty associated with emissions and health benchmark 

values. The Benzene NESHAP decision framework of 1989 acknowledged this; in today’s world, 

such flexibility is even more imperative, because new information relevant to the question of risk 

acceptability is being developed all the time, and the accuracy and uncertainty of each piece of 

information must be considered in a weight-of-evidence approach for each decision. This 

relevant body of information is growing fast (and will continue to grow even faster), 

necessitating a flexible weight-of-evidence approach that acknowledges both complexity and 

uncertainty in the simplest and most transparent way possible. While this challenge is 

formidable, it is nonetheless the goal of the EPA’s RTR decision-making, and it is the goal of the 

risk assessment to provide the information to support the decision-making process. 

Finally, we note that the commenter’s source for its statement that default limits for a HI 

should or must be established at 0.2 rests on an unsigned, internal and deliberative EPA staff 

memorandum that was neither adopted as agency policy nor reviewed by either the public or any 

peer review body and, consequently, carries no precedential weight.

8. Comment: Two commenters (1041-0080/1042-0120 and 1042-0118) stated that the 

EPA does not have authority to consider “total facility” emissions in conducting the residual risk 

assessments for a given source category. The commenter argued that it would be impossible for 

the EPA to fulfill its unambiguous obligation for CAA section 112(f) standards to protect public 

health with an ample margin of safety in cases where facilities contain sources in a category 

where the 8-year deadline for conducting the CAA section 112(f) risk review precedes the 

adoption of MACT standards for other sources at the facilities. Both commenters added that 

CAA section 112(f)(2)(A) requires the EPA to promulgate standards on a source category basis. 

One commenter (1041-0080/1042-0120) continued that this provision unambiguously requires 

the CAA section 112(f) risk assessment to be focused exclusively on “emissions from a source in 

the category or subcategory”, asserting that the EPA does not have authority to consider 

emissions from any sources other than those in the source category or subcategory under review 

at that time.

Response: First, we point out that for mineral wool and wool fiberglass facilities, no 

significant sources of HAP were identified that are outside the source categories covered by 

these standards. Therefore, separate facility-wide risk estimates were not determined for the 

Mineral Wool Production or the Wool Fiberglass Manufacturing Source Categories. 

Secondly, we disagree that examining facility-wide risk in a risk assessment conducted 

under CAA section 112(f) exceeds the EPA’s authority. The development of facility-wide risk 

estimates provides additional information about the potential cumulative risks in the vicinity of 

the RTR sources, as one means of informing potential risk-based decisions about the RTR source 

category in question. While we recognize that, because these risk estimates are derived from 

facility-wide emissions estimates which have not generally been subjected to the same level of 

engineering review as the source category emission estimates, they may be less certain than our 

June 2015 15
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risk estimates for the source category in question, but they remain important for providing 

context as long as their uncertainty is taken into consideration in the process. 

Section 112(f)(2) of the CAA expressly preserves our use of the two-step process for 

developing standards to address residual risk and interpret “acceptable risk” and “ample margin 

of safety” as developed in the Benzene NESHAP (54 FR 38044, September 14, 1989). In the 

Benzene NESHAP, the EPA rejected approaches that would have mandated consideration of 

background levels of pollution in assessing the acceptability of risk, concluding that 

“...comparison of acceptable risk should not be associated with levels in polluted urban air. With 

respect to considering other sources of risk from benzene exposure and determining the 

acceptable risk level for all exposures to benzene, the EPA considers this inappropriate because 

only the risk associated with the emissions under consideration is relevant to the regulation being 

established and, consequently, the decision being made.” (54 FR 38044, 38061, September 14, 

1989). 

Although not appropriate for consideration in the determination of acceptable risk, we 

note that background risks or contributions to risk from sources outside the source category

under review could be one of the relevant factors considered in the AMOS determination, along 

with cost and economic factors, technological feasibility, and other factors. Background risks 

and contributions to risk from sources outside the facilities under review were not considered in 

the AMOS determination for this source category, mainly because of the significant uncertainties 

associated with emissions estimates for such sources. Our approach here is consistent with the 

approach we took regarding this issue in the Hazardous Organic NESHAP (HON) RTR (71 FR 

76603, December 21, 2006), which the court upheld in the face of claims that the EPA had not 

adequately considered background (NRDC v. EPA, 529 F.3d 1077 (D.C. Cir. 2008)). In our 

November 25, 2011 proposal, we explained that for these source categories, there are no other 

significant HAP emissions sources present at wool fiberglass manufacturing and mineral wool 

production facilities beyond those included in the source category. We also explained that all 

significant HAP sources have been included in the source category risk analysis. We therefore 

concluded that the facility wide risk is essentially the same as the source category risk and that 

no separate facility wide analysis was necessary. (76 FR 72783, November 25, 2011). Our 

evaluation of facility-wide risks did not change our decisions under CAA section 112(f)(2) about 

acceptability and ample margin of safety of the risks associated with the mineral wool and wool 

fiberglass source categories. 

9. Comment: One commenter (1041-0081/1042-0347) was concerned that the EPA is 

assessing noncancer hazards for lead solely through reliance on the 2008 National Ambient Air 

Quality Standards (NAAQS) for lead, which the commenter believes is not protective enough 

because the NAAQS was created to protect the average exposed member of the population from 

an intelligence quotient (IQ) point loss above 2 points and only must satisfy the test to provide an 

“adequate margin of safety.” The commenter added that the NAAQS was also designed to 

address only a single pollutant (elemental lead). In contrast, the commenter observed that CAA 

section 112(f)(2) requires the EPA to assess and address health risk and to create an “ample 

margin of safety to protect public health”, and that lead can interact with other pollutants, such as 

arsenic, to cause greater harm than lead exposure alone. The commenter (1042-0347) further 

argued that EPA’s use of the NAAQS is unlawful and arbitrary due to the EPA’s refusal to 

consider or address the most recent data that show health effects in children at exposure levels 

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lower than the lead NAAQS: Center for Disease Control (CDC) decrease in the lead exposure 

level from 10 to 5 micrograms per deciliter (μg/dL); California’s benchmark shows that increases 

in blood-lead level of 1.0 μg/dL can correlate to loss of 1 IQ point; Children’s Health Protection 

Advisory Committee (CHPAC) recognition that loss of 1 IQ point can occur at 0.01 μg/dL; 

CHPAC recommendation of protecting children from ambient lead concentration of 0.02 

μg/m3;CHPAC evidence showing a link between lead levels in maternal blood and low birth 

weight. The commenter concluded that rather than only relying on the NAAQS to assess health 

risk from lead, the EPA should use all of the best available, most current information, including 

California‘s lead health benchmark.

Response: We disagree with the comment that the lead NAAQS was designed to protect 

the average exposed member of the population from an IQ loss above 2 points. The lead NAAQS 

primary standard targets protection to the most susceptible group in the human population –

children – and is designed to protect against adverse effects to children’s most sensitive organ 

system – the developing neurological system. (See 73 FR at 66975, 66976.) It is specifically 

targeted at those children living near major sources of lead, such as secondary smelters. (See 73 

FR at 67002/3, “in applying the evidence-based framework, we are focused on a subpopulation 

of U.S. children, those living near air sources and more likely to be exposed at the level of the 

standard”; to the same effect see 73 FR 67000/3--“The framework in effect focuses on the 

sensitive subpopulation that is the group of children living near sources and more likely to be 

exposed at the level of the standard. The evidence-based framework estimates a mean air-related 

IQ loss for this subpopulation of children; it does not estimate a mean for all U.S. children”; 73 

FR 67005/1--“the air-related IQ loss framework provides estimates for the mean air-related IQ 

loss of a subset of the population of U.S. children, and there are uncertainties associated with 

those estimates. It provides estimates for that subset of children likely to be exposed to the level 

of the standard, which is generally expected to be the subpopulation of children living near 

sources who are likely to be most highly exposed.”). In addition, in reviewing and sustaining the 

lead primary NAAQS, we note that the D.C. Circuit specifically noted that the rule was targeted 

to protect children living near lead sources: “EPA explained that the scientific evidence showing 

the impact of lead exposure in young children in the United States led it ‘to give greater 

prominence to children as the sensitive subpopulation in this review’ and to focus its revision of 

the lead NAAQS on the ‘sensitive subpopulation that is the group of children living near [lead 

emission] sources and more likely to be exposed at the level of the standard.’ Given the scientific 

evidence on which it relied, the EPA’s decision to base the revised lead NAAQS on protecting 

the subset of children likely to be exposed to airborne lead at the level of the standard was not 

arbitrary or capricious.” Coalition of Battery Recyclers, 604 F.3d at 618. 

In response to the comment that the EPA is required to assess the combined effect of a 

source category on the most exposed person, we agree and consider our analysis to have done 

this. The approach used to calculate chronic non-cancer risks, developing the target-organ 

specific hazard index, specifically considers the combined effect of multiple pollutants on the 

same target organ. Any new scientific information concerning lead will be reviewed in 

accordance with the next NAAQS review process.

The commenter also makes the legal argument that the primary lead NAAQS provides an 

“adequate” margin of safety, but that CAA section 112(f)(2) requires that a residual risk standard 

provide an “ample” margin of safety, reasoning from this that a NAAQS cannot just be 

June 2015 17
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substituted as the measure for evaluating acceptability of risk and that some greater level of 

protection is required. The EPA disagrees with the commenter that CAA section 112(f)(2) 

requires that in all cases standards must be more protective than what is achieved by attainment 

of a primary NAAQS. Nothing in CAA section 112(f)(2) requires a conclusion that a standard 

that results in attainment of a primary NAAQS might not also in fact provide an ample margin of 

safety to protect public health. Further, to the extent the commenter’s argument rests on the 

difference between ‘adequate’ and ‘ample’ margin of safety, the argument is misplaced.8 The 

EPA is considering the primary lead NAAQS --which incorporates an adequate margin of safety 

-- merely to determine whether lead risks from air-borne lead from Mineral Wool Production or 

Wool Fiberglass Manufacturing facilities are acceptable or unacceptable. The actual margin-ofsafety determinations for this rule are conducted in accord with the two-step framework set forth 

in the Benzene NESHAP and the en banc opinion in the D.C. Circuit’s ruling in the Vinyl 

Chloride case. See not only Vinyl Chloride, 824 F.2d 1146, 1165-66 (D.C. Cir. 1987), but also 

NRDC v. EPA, 902 F.2d 962, 973-74 (D.C. Cir. 1990) (distinguishing the NAAQS process, 

whereby the margin of safety analysis is incorporated as part of the standard without a two-step 

analysis, from residual risk determinations).9 Using that framework, with its consideration of 

costs, cost-effectiveness, technological feasibility, and other factors set out in the Benzene 

NESHAP, at proposal we did not identify any additional controls beyond those that would need 

to be implemented to ensure an acceptable level of risk with an ample margin of safety to protect 

public health.

Regarding the comment that the NAAQS does not account for combined impacts from 

multiple source exposure, refer to comment number 15 for the EPA’s response to the issue of 

multiple source exposure.

10. Comment: One commenter (1041-0081) stated that the EPA should assess health 

risk from all pollutants, even where it has no current reference value, and must use an uncertainty 

factor to make up for the lack of a reference value. Specifically, the commenter noted that the 

docket shows that the EPA has no human health reference value for HF, trivalent chromium, 

antimony, or mercury. According to the commenter, it appears that the EPA did not account for 

the health risks posed by these pollutants, which is irrational and unlawful. 

The commenter stated that the EPA did not identify the pollutants for which reference 

values are not available or how the EPA has sought information it could use to address the data 

gaps. The commenter further stated that the EPA did not provide a transparent discussion that 

could inform public comment in a meaningful way on this issue, as required by 42 U.S.C. § 

7607(d). The commenter stated that the EPA may not treat risk as zero for a HAP simply because 

it has no reference value for the health risk of the HAP. The commenter argued that the EPA 

must address the uncertainty associated with data gaps in its risk analysis by selecting a health 

protective value based on information it does have or by using an uncertainty factor.

8 Indeed, the EPA’s utilization of a standard which also incorporates an adequate margin of safety to evaluate 

acceptability of risk, which is the first step in the CAA section 112(f)(2) residual risk assessment, is an added 

conservative (i.e. protective) element in its approach here.

9 The court was referring to the predecessor provision to the current CAA section 112(f), but its analysis is equally 

applicable to the revised provision.

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Response: The dose-response values used for HF, antimony, gaseous divalent mercury 

and particulate divalent mercury were omitted from the dose-response value tables in the risk 

assessment document in error. The tables below show the dose-response values for each of these 

pollutants that were used to evaluate human health risks. 

Dose-Response Values for Chronic Inhalation Exposure to Noncarcinogens

Pollutant

CAS 

Number

RfC

(mg/m3) Source10

Antimony 7440360 2.0E-04 IRIS - L

Hydrofluoric acid 7664393 0.014 CAL

Mercury (gaseous divalent) 201 3.0E-4 IRIS - M

Mercury (particulate divalent) 202 3.0E-4 IRIS - M

Dose-Response Values for Acute Exposure

Pollutant

CAS 

Number

AEGL-1

(1-hr)

(mg/m3)

AEGL-2

(1-hr)

(mg/m3)

ERPG-1

(mg/m3)

ERPG-2

(mg/m3) REL 

Hydrofluoric 

acid 7664393 0.82 20 1.6 16 0.24

The only HAP emitted from the Mineral Wool Production and the Wool Fiberglass 

Manufacturing source categories for which dose-response values are not available from sources 

in EPA’s hierarchy is trivalent chromium. Emissions of trivalent chromium were very low with 

0.04 tons per year (tpy) emitted from mineral wool facilities and 0.05 tpy emitted from wool 

fiberglass facilities.

In SAB’s May 7, 2010 response to the EPA Administrator11, the panel recommended 

that, for HAP that do not have dose-response values from the EPA’s list, the EPA should 

consider and utilize, as appropriate, additional sources for such values that have undergone 

adequate and rigorous scientific peer review. The SAB panel further recommended that the 

inclusion of additional sources of dose-response values into the EPA’s list should be adequately 

documented in a transparent manner in any residual risk assessment case study. We agree with 

this approach and have considered other sources of dose-response data when conducting our risk 

determinations under RTR. However, in some instances, such as for trivalent chromium, no 

sources of information beyond the EPA’s list are available. 

It is important to note, that for the Mineral Wool Production source category, carbonyl 

sulfide (COS) is emitted from cupolas and COS does not have an IRIS reference value. In this 

case, we consulted the available research literature and found a series of studies that allowed us 

to derive of a chronic noncancer screening level of 0.163 mg/m3 for COS based on a No 

Observed Adverse Effects Level of 200 parts per million by volume (ppmv) for lesions and 

10 The descriptors L (low), M (medium), and H (high) have been added for IRIS RfC values to indicate the overall 

level of confidence in the RfC value, as reported in IRIS.

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

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

unsigned.pdf.

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neurophysiological alteration in rodents.12,13,14 The EPA agrees that we should ultimately 

develop toxicity values for all HAP utilizing all credible and relevant toxicity information. The 

need to update assessments with newly available data as well as the need to complete 

toxicological assessments for all HAP lacking dose-response assessments further increases the 

importance of agency activities to streamline and fully utilize the EPA’s already overloaded IRIS 

program. To that end, the EPA has always prioritized for future IRIS assessments those HAP 

without dose-response values but with the greatest potential for public exposure. As a result of 

this prioritization, while not all HAP may have scientifically accepted dose-response values that 

can be used in residual risk assessments, it is clear that the vast majority of HAP which might 

carry the potential to significantly impact the results of residual risk assessments do, in fact, have 

credible dose-response values. Thus, while we are not yet at the point where all HAP have doseresponse values, we are generally capable of deriving reasonable risk estimates for those HAP 

which dominate the risks from any one source category. In the course of each residual risk 

assessment, should we encounter HAP without dose-response values which carry the potential to 

create significant risks, we shall clearly point those out as uncertainties and target them for future 

IRIS assessments. Moreover, as additional dose-response values become available, the EPA will 

incorporate these dose-response values into future risk assessments.

11. Comment: One commenter (1041-0081) stated that it was not clear whether there 

are HAP missing from the EPA’s risk assessments for wool fiberglass and mineral wool. The 

commenter further stated that it was not clear whether the EPA’s health risk assessments include 

the currently uncontrolled emission points for which the EPA proposed to set standards. The 

commenter also asked for confirmation that the EPA has assessed the health risk for all emitted 

HAP. 

The commenter cited CAA section 112(f)(2) text that instructs EPA to assess health risk 

for “each category or subcategory of sources,” and the commenter interpreted this text to mean 

“all HAP emissions and emission points, not just the emission points that the CAA section 

112(d) standard previously covered.” 

Response: The EPA has complied with CAA section 112(f)(2) by assessing the health 

risk for all HAP and emission points for these two categories for which emissions data and doseresponse value data were available. As indicated above, EPA cannot determine risk values for 

HAP that do not have dose-response values available, such as for trivalent chromium. Refer to 

the previous response for further discussion of the EPA’s approach to addressing HAP associated 

with the wool fiberglass manufacturing and mineral wool production source categories where 

dose-response values were not available to assess risk.

12 Morgan, D.L., Little, P.B., Herr, D.W., Moser, V.C., Collins, B., Herbert, R., Johnson, G.A., Maronpot, R.R., 

Harry, G.J., and Sills, R.C.: Neurotoxicity of carbonyl sulfide in F344 rats following inhalation exposure for up to 

12 weeks. Toxicol. Appl. Pharmacol. 200(2):131-145, 2004.

13 Herr, D.W., Graff, J.E., Moser, V.C., Crofton, K.M., Little, P.B., Morgan, D.L., and Sills, R.C.: Inhalation 

exposure to carbonyl sulfide produced altered brainstem auditory and somatosensory-evoked potentials in Fischer 

344N rats. Toxicol. Sci. 95(1):118-135, 2007.

14 Sills, R.C., Morgan, D.L., Herr, D.W., Little, P.B., George, N.M., Ton, T.V., Love, N.E., Maronpot, R.R., and 

Johnson, G.A.: Contribution of magnetic resonance microscopy in the 12-week neurotoxicity evaluation of carbonyl 

sulfide in Fischer 344 rats. Toxicol. Pathol. 32:501-510, 2004.

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12. Comment: One commenter (1041-0081) stated that an IRIS review is currently 

underway to update EPA’s toxicity information for formaldehyde, hexavalent chromium, and 

methanol, which are pollutants emitted by these source categories. The commenter further stated 

that the EPA should use the best available scientific information from the IRIS review during the 

current rulemaking and that the EPA should take a more protective approach until these 

reassessments are complete.

Response: The dose-response values that were used in this risk analysis for 

formaldehyde, hexavalent chromium, and methanol are based on the current peer reviewed IRIS 

values. The dose-response value used for methanol was updated to reflect the September 2013 

IRIS findings. At the time this analysis was performed these values were deemed to represent the 

best science and thus represent the most protective approach. 

13. Comment: One commenter (1041-0081/1042-0121/1042-0347) added that the EPA 

should perform a multipathway risk assessment for all metals emitted by this source category, 

including arsenic, chromium, nickel, and manganese. The commenter noted that California 

OEHHA has recommended multipathway assessment for these metals based on scientific 

research, and the EPA should follow its lead instead of the 2003 Risk Assessment Guidance. The 

commenter provided additional information for each of these pollutants for the EPA’s 

consideration (e.g., California OEHHA’s recommended multipathway assessment for nickel, 

arsenic, manganese, and hexavalent chromium based on scientific research). The commenter 

concluded that the EPA simply may not assume that the ingestion and other multipathway risks 

are zero for these pollutants, because doing so when science shows otherwise results in an 

underestimate of the health risks of HAP emissions from this source category and is arbitrary and 

capricious.

Response: In the Air Toxics Assessment Library, we developed the current persistent 

and bioaccumulative HAP (PB-HAP) list considering all of the available information on 

persistence and bioaccumulation (see http://www.epa.gov/ttn/fera/risk_atra_main.html). This list 

was created by reviewing HAP identified as PB-HAP by other EPA Program Offices (e.g., The 

Great Waters Program) and also used information from the PBT Profiler (see 

http://www.pbtprofiler.net). This list was peer-reviewed by the SAB, and it is reasonable to use it 

in the RTR program. Based on these sources and the limited available information on the 

persistence and bioaccumulation of other HAP, we do not believe that the potential for 

multipathway risk from other HAP rises to the level of the PB-HAP currently on the list.

14. Comment: One commenter (1042-0121/1042-0347) stated that the EPA must 

consider this science and update its risk assessment in each of the following ways before 

finalizing the rule:

• Adopt the OEHHA of the California Environmental Protection Agency childprotective scientific approach on cancer and other pollutants, and use at least an 

additional 10-fold uncertainty factor to protect children in addition to the uncertainty 

factors it already uses, when a child-specific reference value or vulnerability 

information is not available. The commenter observed that Congress recognized this 

science in toxics legislation in 1996, the Food Quality Protection Act (FQPA) for 

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pesticide chemical residue, where Congress used a ten-fold margin of safety for 

infants and children.

• Follow the lead of OEHHA by using age-dependent adjustment factors for all 

carcinogens emitted by this source, including naphthalene, polycyclic aromatic 

hydrocarbons (PAHs) and arsenic; use a 10-fold adjustment factor to account for 

prenatal susceptibility to POM; and use the OEHHA factors for prenatal susceptibility 

and exposures. 

• Use the OEHHA child-specific reference doses to assess chronic noncancer and acute 

health risk, where they are available.

Consult with multiple scientific bodies on the scientific basis of the proposed rulemaking, 

including multiple citations provided by the commenter in support of the commenter’s assertions 

about risks from POM, PAHs and arsenic. 

The commenter also provided a table of comparisons between OEHHA child-health 

reference values and those of EPA.

The commenter opined that the EPA did not provide a valid justification for not using the 

method developed by California’s Office of Environmental Health Hazard Assessment to assess 

the risks from nickel, arsenic, manganese, and hexavalent chromium.

Response: We disagree with the general comment that the EPA should adopt the Cal 

OEHHA methods to estimate cancer risk and non-cancer hazard for specific pollutants. The EPA 

has an approach for selecting appropriate health benchmarks and in general, this approach places 

greater weight on the EPA derived health benchmarks than those from other agencies (see 

http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf). Notably, this approach 

favoring EPA benchmarks (when they exist) over all others has been endorsed by the SAB. The 

EPA is currently evaluating whether it is appropriate to use specific benchmarks derived by the 

Cal OEHHA. We note that there are currently no such values for HAP inhalation, therefore their 

current utility would be limited to persistent and bioaccumulative PB-HAP, which may be 

associated with non-negligible ingestion exposures. The evaluation of the appropriateness of 

these values in the context of the RTR Program and EPA science policy is necessary prior to 

using these child-specific reference doses (RfDs).

We also disagree with the comment that a children’s default safety factor of 10 or more 

should be added to EPA’s reference values. In response to the 10X factor enacted by Congress in 

the Food Quality Protection Act (1996)15 to the EPA non-cancer reference value derivation, the 

agency evaluated their methods for considering children’s risk in the development of reference 

values. As part of their response, the U.S. EPA (i.e. the Science Policy Council and Risk 

Assessment Forum) established the RfD/RfC Technical Panel to develop a strategy for 

implementing the Food Quality Protection Act (FQPA) and examine the issues relative to 

protecting children’s health and application of the 10X safety factor. One of the outcomes of the 

Technical Panel’s efforts was an in depth review of a number of issues related to the RfD/RfC 

process (U.S. EPA 2002). The most critical aspect in the derivation of a reference value 

15 US Environmental Protection Agency, Pesticide: Regulating Pesticides. The Food Quality Protection Act (FQPA). 

1996. Available at http://www.epa.gov/pesticides/regulating/laws/fqpa/backgrnd.htm.

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pertaining to the FQPA has to do with variation between individual humans and is accounted for 

by a default uncertainty factor (UF-H) when no chemical-specific data are available. EPA 

reviewed the default UF for inter-human variability and found the EPA’s default value of 10 

adequate for all susceptible populations, including children and infants. The EPA also 

recommended the use of chemical-specific data in preference to default uncertainty factors when 

available (US EPA, 1994, 2011) and is developing agency guidance to facilitate consistency in 

the development and use of data-derived extrapolation factors for RfCs and RfDs (U.S EPA, 

2011). Additionally, the EPA also applies a database uncertainty factor (UF-D) which is intended 

to account for the potential for deriving an under-protective RfD/RfC as a result of an incomplete 

characterization of the chemical’s toxicity. In addition to the identification of toxicity 

information that is lacking, review of existing data may also suggest that a lower reference value 

might result if additional data were available.

We acknowledge that population subgroups, including children, may have a potential for 

risk that is greater than the general population due to greater relative exposure and/or greater 

susceptibility to the toxicant. As explained in previous actions, including the final HON RTR (71 

FR 76610-76611), the assessments we undertake to estimate risk account for this potential 

vulnerability. With respect to exposure, the risk assessments we perform implicitly account for 

this greater potential for exposure by assuming lifetime exposure, in which populations are 

conservatively presumed to be exposed to airborne concentrations at their residence 

continuously, 24 hours per day for a full lifetime, including childhood. With regard to children’s 

potentially greater susceptibility to non-cancer toxicants, the assessments rely on EPA (or 

comparable) hazard identification and dose-response values which have been developed to be 

protective for all subgroups of the general population, including children. In the latest review16

of the chronic reference value process EPA concluded that the EPA’s reference concentration 

(RfC) derivation processes adequately considers potential susceptibility of different subgroups 

with specific consideration of children, such that the resultant RfC values pertain to the full 

human population “including sensitive subgroups,” a phrase which is inclusive of childhood. 

With respect to cancer, the EPA uses the age-dependent adjustment factor approach referred to 

by the commenter, but limits the use of those factors only to carcinogenic pollutants that are 

known to act via mutagenic mode of action, in contrast to the OEHHA approach, which uses 

them across the board for all carcinogens regardless of mode of action (MOA). In lieu of 

chemical-specific data on which age or life-stage specific risk estimates or potencies can be 

determined, default age dependent adjustment factors can be applied when assessing cancer risk 

for early-life exposures to chemicals which cause cancer through a mutagenic MOA. With regard 

to other carcinogenic pollutants for which early-life susceptibility data are lacking, it is the 

agency’s long-standing science policy position that use of the linear low-dose extrapolation 

approach (without further adjustment) provides adequate public health conservatism in the 

absence of chemical-specific data indicating differential early-life susceptibility or when the 

16 U.S. EPA. A Review of the Reference Dose and Reference Concentration Processes. U.S. Environmental 

Protection Agency, Risk Assessment Forum, Washington, DC, EPA/630/P-02/002F, 2002. 

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mode of action is not mutagenicity.17 The basis for this methodology is provided in the 2005 

Supplemental Guidance.18

The estimated risks for this source category must also be considered in the context of the 

full set of assumptions used for this risk assessment. For example, we used a health-protective 

assumption of a 70-year exposure duration in our risk estimates; however, using the national 

average residency time of 12 years would reduce the estimate of risk by roughly a factor of 6. 

Our unit risk estimates for HAP are considered a plausible upper-bound estimate; actual potency 

is likely to be lower and some of which could be as low as zero. After considering these and 

other factors, we continue to consider the risks from emissions after application of the revisions 

to the NESHAP for this source category to provide an ample margin of safety (consistent with 

the Benzene NESHAP framework).

15. Comment: Two commenters (1041-0081/1042-0121 and 1041-0081) opined that 

the EPA should assess the cumulative burden of exposures to multiple pollutants and sources via 

multiple pathways. To do this, the commenters suggested that the EPA include the interaction of 

multiple pollutants and account for exposure to multiple emissions sources including other 

emissions sources at the facilities and from other sources of toxic air pollutants in the area. 

Another commenter (1041-0076) underscored the importance of considering other sources of 

HAP regardless of industry segment.

One commenter (1041-0081) stated EPA needs to assess the synergistic, carcinogenic, 

and other effects of different pollutants because multiple carcinogens work together to create a 

cancer risk greater than the single effect of any one pollutant. The commenter stated that EPA 

combines the risk for different pollutants in determining the cancer risk or MIR and also 

combines the chronic non-cancer risk HQ for pollutants that work in a similar way or on the 

same organ system, to create a “target organ specific hazard index or TOSHI. The commenter 

asserted that EPA does not create a combined acute risk number that would represent the total 

acute risk for all pollutants that act in a similar way on the same organ system or systems, similar 

to the chronic TOSHI, and that without that, the full acute health risk is not accounted for.

One commenter (1041-0081/1042-0121) contended that, if a source category’s risk is 

between 1-in-1 million and the presumptive limit on acceptability (currently 100-in-1 million) 

and the source category is contributing risk along with numerous other source categories, then 

CAA section 112(f)(2) requires the EPA, and gives the EPA full authority, to include in its 

residual risk analysis the risk associated with the whole cumulative health burden on the people 

living near the source category, not just the future risk for the source category. According to the 

commenter, whole cumulative health burden includes the following impacts in addition to future 

health impact: (1) cumulative impacts over time (i.e., persistent, bioaccumulative HAP and 

health risk due to past exposure, which increases the current health risk) and (2) impacts from all 

HAP-emitting sources in the local area. The commenter also suggested that, to account for these 

additional cumulative impacts including other sources, the EPA could incorporate an uncertainty 

17 Id.

18 U.S. EPA. (2005), Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens. 

EPA/630/R-03/003F. Washington, DC. Available online at: http://www.epa.gov/cancerguidelines/guidelinescarcinogen-supplement.htm. 

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factor into its residual risk analysis. The commenter also stated that this approach of accounting 

for cumulative risks in its residual risk analysis would be consistent with the SAB’s 

recommendation (made in May 2010), which stated 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.

Regarding cumulative impacts, one commenter (1041-0081/1042-0121) cited the 

CertainTeed facility in Kansas City. The commenter noted that the EPA recognized the potential 

for that facility to emit 913 pounds per year of chromium compounds, of which 840 pounds is 

hexavalent chromium. The commenter suggested that these data show that this one facility may 

have emitted 7 times 840 pounds (or over 5,000 pounds) hexavalent chromium into this one 

community during the last 7 years. The commenter surmised that the EPA did not evaluate how 

long facilities have existed at their current locations and did not calculate the impact of their past 

emissions on the current health risk of the most-exposed local communities. The commenter 

recommended that the EPA aggregate people’s risk when deciding how much additional risk is 

acceptable for a single source category. The commenter added that for the CertainTeed facility 

the acceptable level of cancer, non-cancer chronic, and acute risk from the source category 

should be adjusted (e.g., divided by an uncertainty factor) based on the number of other facilities 

contributing HAP exposure risks, over a period of 7 years.

Regarding impacts from other sources, one commenter (1041-0081/1042-0121) alleged 

that the EPA used uncertainty as the basis for focusing the risk assessment on only the sources in 

the mineral wool and wool fiberglass source categories, and added that uncertainty is not a 

rational explanation for failing to address this important element of health risk. Where public 

health is concerned, the commenter believed that uncertainties require more conservative 

assessment and more protective action, rather than inaction. The commenter suggested that the 

EPA should, at minimum, use an uncertainty factor to account for the greater health risk. The 

commenter argued that the EPA should follow the recommendations in the SAB Report stating 

that: “the Panel recommends that the Agency perform a sensitivity analysis to identify the major 

uncertainties in both the human health and ecological risk assessments. The Agency should then 

proceed to: (1) explain them clearly in the risk characterization section and (2) take steps to 

reduce them.”

The commenter argued that EPA did not adequately assess facility wide risk and vicinity 

risks from nearby communities in developing a combined impacts assessment. Per the 

commenter, EPA should more adequately address children‘s health, multiple source exposure, 

and environmental justice factors in deciding what margin is needed to provide ‘ample’ 

protection for public health.

The commenter suggested that the EPA did not consider in its residual risk analysis the 

existing baseline (cumulative impacts from persistent, bioaccumulative HAP and health risk due 

to past exposure) and impacts from all HAP-emitting sources in the local area beyond the wool 

fiberglass and mineral wool source categories. According to the commenter, that type of 

cumulative impacts analysis is a routine consideration that is also required under other provisions 

of the CAA and other environmental statutes and would characterize a full risk assessment. The 

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commenter alleged that the EPA did not fully consider such factors in this risk assessment, and 

therefore did not fulfill its obligation to provide the legally required ample margin of safety.

Response: We have combined risk assessment results to the extent that it is appropriate 

to do so. We consider the effect of mixtures of carcinogens and use a TOSHI approach for our 

chronic noncancer assessments. We do not use a TOSHI approach for our acute analyses nor do 

we combine the results of our inhalation and multipathway assessments.

For the wool fiberglass and mineral wool manufacturing source categories, the EPA 

conducted assessments of the cumulative cancer risks from emitted carcinogens and the 

cumulative noncancer hazard indices from all emitted non-carcinogens affecting the same target 

organ system for both the source category emissions. To address the effect of mixtures of 

carcinogens, our assessment used the guideline’s default assumption for mixtures of additivity of 

effects, and combined the cancer risks by summing them using the independence formula in the 

mixtures guidelines. In assessing noncancer hazard from chronic exposures for pollutants that 

have similar modes of action or that affect the same target organ, we aggregated the HQ to 

provide a TOSHI. A TOSHI is defined as the sum of HQs for individual HAP that affect the 

same organ or organ system. All TOSHI calculations presented here were based exclusively on 

effects occurring at the “critical dose” (i.e., the lowest dose that produces adverse health effects). 

We also disagree with the commenter’s assertion that additional quantitative assessment of risks 

from sources outside the source categories is required under the statute. The statute requires the 

EPA to provide the quantitative risk information necessary to inform RTR regulatory decisions, 

and to this end, the EPA conducts a comprehensive assessment of the risks associated with 

exposure to the HAP emitted by the source categories and supplements that with additional 

information that is available about other possible concurrent and relevant risks.

While the incorporation of additional background concentrations from the environment in 

our risk assessments (including those from mobile sources and other industrial and area sources) 

could be technically challenging, they are neither mandated nor barred from our analysis. In 

developing the decision framework in the Benzene NESHAP currently used for making residual 

risk decisions, the EPA rejected approaches that would have mandated consideration of 

background levels of pollution in assessing the acceptability of risk, concluding that comparison 

of acceptable risk should not be associated with levels in polluted urban air (54 FR 38044, 

38061, September 14, 1989). Background levels (including natural background) are not barred 

from the EPA’s AMOS analysis, and the EPA may consider them, as appropriate and as 

available, along with other factors, such as cost and technical feasibility, in the second step of its 

CAA section 112(f) analysis. This assessment excludes background contributions because the 

available data are of insufficient quality upon which to base a meaningful analysis.

As described in the risk assessment report (available in the docket for this action), we do 

not sum results of the acute noncancer inhalation assessment to create a combined acute risk 

number that would represent the total acute risk for all pollutants that act in a similar way on the 

same organ system or systems (similar to the chronic TOSHI). As noted in previous responses, 

the worst-case acute screen is already a conservative scenario. That is, the acute screening 

scenario assumes worst-case meteorology, peak emissions for all emission points occurring 

concurrently and an individual being located at the site of maximum concentration for an hour. 

Thus, as noted in section 2.7.2 of the Draft Residual Risk Assessment for the Mineral Wool 

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Production and Wool Fiberglass Manufacturing Source Categories (Docket Item No. EPA-HQOAR-2010-1042-0328), “because of the conservative nature of the acute inhalation screening 

and the variable nature of emissions and potential exposures, acute impacts were screened on an 

individual pollutant basis, not using the TOSHI approach.”

16. Comment: One commenter (1042-0347) disagreed with the EPA’s use of 

workplace benchmarks to justify that an HQ of 30 is acceptable because the workplace 

benchmarks do not protect the vulnerable populations (children, pregnant women, elderly, and 

those with health conditions).

Response: The commenter is responding to the EPA’s request for comment on whether 

the occupational values should be used in the interpretation of these worst-case acute screening 

exposure estimates for these source categories. The EPA thanks the commenter for providing this 

feedback. In the preamble to the 2014 supplementary proposal, the EPA did not include 

workplace benchmarks as part of its discussion of risk, but rather relied on the HQ for only REL 

and AEGL-1. The EPA considered the workplace benchmarks in assessing the acceptability of 

an HQ of 30, but did not determine acceptability based solely on this metric. In the preamble to 

the 2011 proposal (76 FR 71782, November 25, 2011), the EPA presented multiple HQ levels 

based on multiple acute dose-response values, including acute REL, AEGL, ERPG, and the 15-

minute occupational ceiling values referred to by the commenter. The EPA used all such HQ 

values in assessing the risk associated with the wool fiberglass and mineral wool production 

industries. In the preamble cited above, the EPA acknowledged that, historically, comparisons of 

the estimated maximum off-site one-hour exposure levels have not typically been made to 

occupational levels for the purpose of characterizing public health risks in RTR assessments due 

to the fact that 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.” 

17. Comment: One commenter (1042-0347) argued that the EPA’s proposed 

“acceptable” risk determination based on an HQ of 30 is arbitrary and capricious because this 

determination conflicts with the EPA’s recently proposed National Emission Standards for 

Hazardous Air Pollutants: Ferroalloys Production, 79 Fed. Reg. 60,238, 60,269-70 (October 6, 

2014) that concluded an HQ of 40 contributed to the EPA’s determination that risk is 

unacceptable for that industry, when combined with high cancer risk.

Response: The commenter is referring to the maximum chronic non-cancer TOSHI 

established as part of the EPA’s risk assessment conducted for the EPA’s review of the 

Ferroalloys Production NESHAP. In the EPA’s proposal cited by the commenter, the EPA 

specified in Table 8 of the preamble (79 FR 60266, October 6, 2014) that the maximum chronic 

non-cancer TOSHI was 40 based on allowable emissions and 4 based on actual emissions, with 

an HQ (REL) of 1. In comparison, the EPA’s risk assessment supporting the EPA’s 2014 

proposal for wool fiberglass manufacturing established a maximum chronic non-cancer TOSHI 

of 0.5 based on allowable emissions and 0.2 based on actual emissions, with an HQ (REL) of 30. 

The commenter is asking the EPA to compare the TOSHI value of 40 generated for ferroalloys to 

the HQ (REL) of 30 generated for wool fiberglass; however, these two values are not comparable 

because they represent two different measures of risk. A TOSHI, defined as the sum of HQs for 

individual HAP that affect the same organ or organ system, is used for assessing noncancer 

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hazards from chronic exposures. An HQ based on an REL is used for assessing health risks from 

acute exposures. Therefore, the TOSHI of 40 for ferroalloys would better be compared to the 

TOSHI of 0.5 for wool fiberglass. 

18. Comment: According to one commenter (1042-0121), the EPA’s risk review failed 

to assess the health risk from malfunctions or violations of the existing MACT standard because 

facilities may violate that standard and emit HAP at a level beyond what is “allowable” under the 

rule. The commenter noted that the CAA specifically requires EPA to base its risk analysis on 

the highest potential risk “to the individual most exposed to emissions from a source in the 

category or subcategory” (42 U.S.C. § 7412(f)(2)(A); § 7412(f)(1)(C)). The commenter stated 

that the EPA must consider the full potential for health risk that will occur should sources emit 

above the level the CAA section 112(d) standard allows (e.g., due to control device failure), not 

just the risk based on the amount of emissions that the standard would allow. In the commenter’s 

opinion, ignoring the potential for non-compliance is equivalent to treating additional health risk 

caused by exceedances as zero, but the EPA knows that there is additional risk from 

malfunctions and violations and it cannot ignore that risk.

Response: We disagree with the commenter that emissions that exceed standards and are 

violations, whether or not they are caused by malfunction events, should be considered as part of 

the risk analysis for purposes of determining the sufficiency of pre-existing standards, 

particularly when we are revising the standards to eliminate any excused periods of noncompliance during upset periods. The purpose of the risk review is to evaluate whether the 

emission limits -- the “standards promulgated pursuant to subsection (d),” not the noncompliance with those standards (CAA section 112(f)(2)(A)) -- should be made more stringent to 

reduce the risk posed after compliance with the underlying MACT standard. To the extent that a 

source is violating the underlying MACT standard, no tightening of the emission standard under 

the residual risk rule will avoid or militate against such violations. In other words, a source that 

is violating the emission standard promulgated under CAA section 112(d) would not be any 

more likely to be able to avoid such violations and comply with a different presumably more 

stringent standard promulgated under CAA section 112(f). Such events are violations and subject 

to enforcement by the EPA, the states or citizens, and an action for injunctive relief is the most 

effective means to address violations, whether or not they are caused by malfunctions, if an 

emissions event poses a significant health or environmental risk.

Furthermore, the conservative estimates built into the acute risk assessment are sufficient 

to gauge worst-case potential acute health effects. The conservative estimates built into the 

assessment include worst-case meteorology, emissions at 10 times the maximum peak emission 

rate from all wool fiberglass point sources simultaneously (a multiplier of 3 is used for mineral 

wool sources), and the sum of the maximum impact of each emission source, regardless of 

receptor location. Thus, even if we were to consider emissions that are in violation of the 

standard, we do not believe that they would result in any different level of control than we are 

promulgating here.

With regard to the failure of a control device, this would constitute a violation of the 

emission standard. The acute risk emissions factor is designed to account for fluctuations in 

emissions for facilities complying with the standards, not for facilities in non-compliance. 

Therefore, it would be inappropriate to use the emissions factor suggested by the commenter for 

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purposes of determining whether the NESHAP’s current requirements are in need of revision 

under CAA section 112(f)(2).

19. Comment: One commenter (1042-0115f) asserted that the EPA’s Heath Risk 

Assessment is not conservative and additional analysis is needed because the EPA has 

insufficient data as demonstrated by how many years the plants operated before the EPA 

discovered the high emissions and how much the data vary. 

Response: The EPA disagrees with the commenter that the EPA did not have sufficient

data to establish standards for the wool fiberglass source category and to conduct its risk 

analysis. The EPA began developing the original NESHAP (subpart NNN) in 1996 and the final 

rule was promulgated on June 1, 1999. Subpart NNN includes PM emission limits for glassmelting furnaces which serve as a surrogate for HAP metals, including chromium compounds. 

As part of the residual risk and technology review, the agency began collecting additional 

information related to wool fiberglass manufacturing in the 2008 – 2009 timeframe. Meetings 

with industry representatives and one of their trade associations (NAIMA) led to a voluntary 

survey being sent out in 2010. A CAA section 114 ICR was sent out in November 2011 to 

collect additional information and test data on all glass-melting furnaces. The EPA had sufficient 

data to establish standards and conduct a risk assessment for all pollutants except methanol, 

phenol, and formaldehyde for RS manufacturing lines at wool fiberglass manufacturing facilities. 

As discussed in section V.H of the preamble to the final rule, we have issued an ICR under 

section 114 of the CAA to collect updated emissions and process information from the industry 

and we will analyze the ICR data and evaluate MACT limits for RS lines at wool fiberglass 

manufacturing facilities at a future date. 

Uncertainty and the potential for bias are inherent in all risk assessments, including those 

performed for this rulemaking. Although uncertainty exists, our approach, which uses 

conservative tools and assumptions, ensures that our decisions are appropriately health protective 

and environmentally protective. A discussion of the uncertainties in the RTR emissions datasets, 

dispersion modeling, inhalation exposure estimates and dose-response relationships can be found 

in the residual risk assessment document in the rulemaking docket.

20. Comment: One commenter (1041-0076) stated that the EPA, in assessing risks in 

the Oak Grove Neighborhood in Kansas City, Kansas (and other similarly situated 

neighborhoods across the country), should consider that residents are more likely to have 24/7 

exposure to HAP than residents in geographic areas where the population is younger and more 

mobile, and where the discretionary income is higher and transportation is more accessible.

Response: Our residual risk characterization does make this health protective assumption 

that people will be in their home 24/7 for 70 years.

21. Comment: One commenter (1042-0115/1042-0120/1042-0300/1042-0348) alleged 

that potential errors in the EPA's risk and exposure assessment led the agency to overestimate the 

risk from this source category. 

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Response: The commenter did not provide any information or data to characterize the 

“potential errors” in the risk and exposure assessment conducted for the Mineral Wool 

Production or Wool Fiberglass Manufacturing source categories. 

B. Ample Margin of Safety Analysis

22. Comment: Two commenters (1041-0081/1042-0121/1042-0299 and 1042-

0300/1042-0348) opined that, for both RTRs, the EPA should provide the analysis that was 

conducted to determine whether an ample margin of safety is achieved by the standard, as well 

as all options that were considered along with the emission reductions, the risk level of each 

option, and the cost of each option. One commenter (1042-0300/1042-0348) asked whether the 

EPA identified other limits that would have also provided an AMOS with far lower costs. One 

commenter (1042-0299) also believed that for wool fiberglass, the EPA should improve the 

AMOS analysis conducted for major sources and then apply that improved AMOS analysis to 

the proposed area source standards in order to consider and provide sufficient protection for 

public health. 

One commenter (1041-0081/1042-0121) stated that the EPA does not discuss how the 

proposed rule provides an ample margin of safety, describe the ample margin, present what are 

less expensive options, or discuss why the agency considers the margin of safety as “ample”. The 

commenter contended that the EPA is not authorized to put cost of controls above health of 

people, but that the EPA has done that because it did not adequately consider health impacts of 

the most-exposed person. The commenter added that the EPA did not sufficiently explain how 

the cost-based decision on the AMOS determination was made and that the EPA should have 

considered additional options for reductions. The commenter added that the EPA did not satisfy 

its own “ample margin of safety” test because it did not consider whether the proposed rules 

provide the maximum feasible protection against health risks for the greatest number of people, 

did not discuss or analyze what the maximum feasible protection would be, or how many people 

could be protected from a greater level of risk.

Response: We agree with the commenter that the agency did not provide an explanation 

of the analysis we conducted for the AMOS review in the 2011 and 2013 proposals. These 

proposals did not contain a discussion of options for both the mineral wool and the wool 

fiberglass source categories, along with the costs, emission reductions, and associated risk of 

each option. In response to comments like this, following the 2011 and 2013 proposals, the EPA 

provided its analysis in the docket with the 2014 proposal. Our discussion and review of options 

can be found in the memoranda titled: “Mineral Wool RTR Ample Margin of Safety (AMOS) –

Analysis and Proposed Controls,” October 15, 2014 (EPA-HQ-OAR-2010-1041-0154); and 

Wool Fiberglass RTR Ample Margin of Safety – Analysis and Proposed Controls,” October 15, 

2014 (EPA-HQ-OAR-2010-1042-0334). For the Mineral Wool source category, the AMOS 

analysis did not identify any feasible options for increasing the ample margin of safety, 

considering cost and technical feasibility. For the Wool Fiberglass source category the AMOS 

analysis identified that reducing the operational life of the gas-fired furnaces from 10 years to 7 

years was the option that the EPA determined necessary to provide an ample margin of safety.

We disagree with the comment that the EPA did not sufficiently explain how the costbased decision on the AMOS determination was made. As also explained in our November 2011 

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proposal, the EPA may consider costs in its decision to set standards under the ample margin of 

safety step of CAA section 112(f)(2). This is consistent with the approach set out in the Benzene 

NESHAP framework for assessing acceptable risk and ample margin of safety. As previously 

explained, section 112(f)(2) of the CAA expressly preserves our use of the two-step process for 

developing standards to address residual risk and interpret “acceptable risk” and “ample margin 

of safety” as developed in the Benzene NESHAP (54 FR 38044, September 14, 1989). We also 

note that the U.S. Court of Appeals for the D.C. Circuit has affirmed this approach of 

implementing CAA section 112(f)(2)(A): NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008). 

Our cost considerations can be found in the memorandum “Wool Fiberglass RTR Ample Margin 

of Safety – Analysis and Controls for the Final Amendments”, which is in the docket for this 

rulemaking.

23. Comment: One commenter (1042-0300/1042-0348) opined that there is only one 

facility in the industry with elevated chromium emissions, such that all risk of chromium 

associated with this source category is attributable to the one facility that has unusually high 

emissions. The commenter suggested that the EPA consider the lower levels emitted by all other 

facilities to be an ample margin of safety to the risk posed by the one facility, and that the EPA 

address these elevated chromium emissions by addressing one facility’s high emissions, separate 

from this rulemaking.

Response: The EPA does not agree with the commenter that only one facility in the 

source category has elevated chromium emissions or that all risk of chromium associated with 

this source category is attributable to that facility. In our April 2013 proposal, we explained that 

gas-fired glass-melting furnaces can emit higher levels of metal HAP as well as higher than 

expected levels of chromium as a result of using high-chromium refractories. (78 FR 22377, 79 

FR 68024). As also documented in the memorandum “Chromium Emissions and Furnace Age” 

(EPA-HQ-OAR-2010-1042-0332), of the six gas-fired furnaces at major sources tested, three 

furnaces emit chromium at levels higher than the proposed chromium limit, and two of these 

furnaces emit chromium at significantly higher levels. Further, as the EPA stated in the preamble 

to the April 15, 2013 proposal (78 FR 22379), the EPA has determined that it is possible that the 

lower-emitting furnaces could emit higher levels of chromium, and that lower-emitting furnaces 

could be replaced with other types of furnaces that emit higher levels of chromium. For further 

discussion of these conclusions, refer to the memorandum cited above, which discusses the 

EPA’s conclusion that chromium emissions increase with furnace age, and section IV.A of the 

preamble to the April 15, 2013 proposal (78 FR 22380), which discusses the industry trend is to 

utilize oxyfuel gas-fired furnaces, which have the highest potential for elevated chromium 

emissions. In our various proposals, we have also indicated that hexavalent chromium is the 

secondary risk driver. An MIR of 3-in-1 million was attributable to hexavalent chromium from 

the facility that contributes the highest risk. Therefore, in the final rule we are finalizing emission 

limits for chromium emissions from gas-fired glass-melting furnaces of 0.00025 pounds of total 

chromium per ton of glass pulled to provide an ample margin of safety and prevent adverse 

environmental effects.

24. Comment: One commenter (1042-0300) opined that the existing risk does not 

warrant imposing the chromium emission limit in addition to the PM limit. The commenter 

(1042-0300/1042-0348) suggested that facilities with less than 1-in-1 million cancer risk should 

be exempt from the chromium limits in the rule. 

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Response: Regarding the comment that the existing risk does not warrant imposing the 

chromium emission limit in addition to the PM limit, the EPA disagrees with the commenter. In 

our November 2011 proposal, we performed an auxiliary risk characterization analysis to assess 

the potential maximum individual lifetime cancer risks in the event that all wool fiberglass 

facilities switch to high-chromium refractory. We assumed that chromium emissions for facilities 

would be the same as CertainTeed’s annual emission of 420 pounds of hexavalent chromium per 

furnace. The results of the auxiliary analysis indicated that emissions from 14 facilities could 

lead to maximum individual cancer risks greater than 100-in-1-million, with the highest emitting 

facility posing a potential MIR of 900-in-1-million. See 76 FR 72800-72801 for a complete 

discussion of the risk assessment of the Wool Fiberglass Manufacturing source category. As also 

explained in our November 2014 proposal, we limited the chromium emissions from gas-fired 

glass-melting furnaces in response to similar comments. (79 FR 68024). This is because an MIR 

of 3-in-1 million was attributable to hexavalent chromium from a gas-fired glass-melting furnace 

located at the facility that contributes the highest risk in this source category. 

Regarding the comment that facilities with less than 1-in-1 million cancer risk should be 

exempt from the chromium limits in the rule, we have no such authority under CAA section 

112(f)(2). According to CAA section 112(f)(2)(A), if the MACT standards for HAP “classified 

as a known, probable, or possible human carcinogen do not reduce lifetime excess cancer risks to 

the individual most exposed to emissions from a source in the category or subcategory to less 

than one in one million,” the EPA must promulgate residual risk standards for the source 

category (or subcategory), as necessary to provide an ample margin of safety to protect public 

health. The final chromium emissions limit applies to affected sources in the source category

(i.e., gas-fired glass-melting furnaces). If such sources have chromium emissions that fall below 

this emission limit, as many gas-fired furnaces currently do, they are in compliance with the 

chromium limits, and their only impacts are the cost of conducting emissions tests to 

demonstrate compliance with the limit. As discussed in the memorandum “Chromium Emissions 

and Furnace Age” (EPA-HQ-OAR-2010-1042-0332), available chromium emissions testing data 

and information indicate that emissions of chromium increase with furnace age; therefore a 

furnace whose chromium emissions tested at levels well below the limits (with risk below 1-in-1 

million) during a particular year’s compliance test, may test at or above the limit in subsequent 

years due to furnace degradation. Requiring emission limits for all gas-fired sources prevents all 

such furnaces from emitting chromium at the high levels similar to the gas-fired glass-melting 

furnace with the highest emissions level tested (approximately 500 pounds per year of 

hexavalent chromium) and presenting a much higher risk. 

The EPA has limited the scope of applicability of the chromium limit to only gas-fired 

glass-melting furnaces because electric-only glass-melting furnaces do not have the potential to 

emit elevated emissions of hexavalent chromium due to fundamental design, temperature, and 

fuel differences. As a result, electric glass-melting furnaces at wool fiberglass manufacturing 

facilities are subject to a PM limit, but not a chromium limit. 

25. Comment: One commenter (1041-0081) contended that EPA did not set residual 

risk standards for either source category that provide the requisite AMOS to protect public 

health, pursuant to CAA section 112(f)(2). For the Wool Fiberglass Manufacturing source 

category, the commenter supported the EPA’s recognition that a residual risk standard is needed, 

but urged the EPA to finalize stronger residual risk standards. The commenter noted that EPA’s 

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proposed chromium limit (6.0E-05 lbs per ton of glass pulled) was expected to decrease the 

cancer risk (MIR) from 40-in-1 million to 20-in-1 million, based on actual emissions. According 

to the commenter, the standards are not expected to reduce the acute or chronic noncancer health 

risks at all. According to the commenter, the requirement for an AMOS is designed to protect 

public health in light of scientific uncertainty regarding what precise level of risk is safe.

According to the commenter, the statutory term “ample” means more than adequate, 

implying a generous, health-protective approach to set a margin of safety that is copious and 

abundant, and the commenter believed that the EPA did not take such an approach, rendering the 

phrase “ample margin of safety to protect public health” superfluous and in violation of CAA 

section 112(f)(2). The commenter argued that EPA does not discuss how the health risk 

information shows that an AMOS is provided by the proposed rule or what constitutes that ample 

margin. The commenter argued that EPA also does not explain how it follows that, just because 

EPA has been unable to identify what it deems to be less expensive options, the margin of safety 

is ample. 

The commenter noted that EPA interpreted CAA section 112(f)(2) as requiring the 

agency to provide maximum feasible protection against risks to health from HAP, both by 

protecting the greatest number of persons possible from an individual lifetime risk level no 

higher than 1-in-1 million and by protecting the most-exposed person from a cancer risk of 100-

in-1 million. The commenter contended that EPA failed to satisfy even this standard, which the 

commenter characterized as not protective enough.

The commenter urged EPA to consider and require additional emission reductions at the 

ample margin stage to ensure that there is a truly ample amount of protection for affected 

communities’ health, particularly for children.

Response: As stated in the Benzene NESHAP (54 FR 38044, 38061, September 14, 

1989), in determining the need for residual risk standards, we strive to limit to no higher than 

approximately 1-in-10 thousand (100-in-1 million) the estimated cancer risk that a person living 

near a plant would have if he or she were exposed to the maximum pollutant concentrations for 

70 years and, in the AMOS decision, to protect the greatest number of persons possible to an 

individual lifetime risk level of no higher than approximately 1-in-1 million. However, in 

determining whether to require additional standards under CAA section 112(f), these levels are 

not considered rigid lines, and we weigh the cancer risk values with a series of other health 

measures. In the AMOS determination we also consider costs, energy, safety and other relevant 

factors for the available control options. We continue to believe that CAA section 112(f)(2) does 

not impose a mandatory obligation to reduce maximum lifetime cancer risk to below 1-in-1 

million. As explained in the November 2011 proposal, we believe CAA section 112(f)(2)

expressly preserves our use of the two-step process for developing standards to address any 

residual risk in our interpretation set out in the Benzene NESHAP. Section 112(f)(2)(B) of the 

CAA preserves this interpretation and the U.S. Court of Appeals for the District of Columbia 

Circuit has upheld as reasonable the EPA’s interpretation that CAA subsection 112(f)(2) 

incorporates the approach established in the Benzene NESHAP. NRDC v. EPA, 529 F.3d 1077, 

1083 (D.C. Cir. 2008) (“[S]ubsection 112(f)(2)(B) expressly incorporates the EPA’s 

interpretation of the Clean Air Act from the Benzene standard, complete with a citation to the 

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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 agree with the commenter that we did not show the options for reducing HAP 

emissions that were explored to reduce risk from these source categories in our 2011 and 2013 

proposals. As previously explained in response to comments like this, we provided the analyses 

in the docket for our 2014 proposal and have subsequently updated them for the final rule (see 

the memoranda “Mineral Wool RTR Ample Margin of Safety (AMOS) – Analysis and Proposed 

Controls” and “Wool Fiberglass RTR Ample Margin of Safety (AMOS) – Analysis and 

Proposed Controls.”) 

In our AMOS analysis for mineral wool, we evaluated several potential measures or 

options for reducing formaldehyde emissions from bonded lines, but no new technologies 

(beyond those technologies already in place) were found. A pollution prevention option (the use 

of non-HAP binders) was considered, but we found that product (performance) specifications of 

mineral wool products made this option technically infeasible. In addition, we evaluated controls 

for the collection process on bonded lines and found that controls capable of handling the high 

volume air flows characteristic of most collection processes would be cost prohibitive. The 

potential of re-routing exhaust from the collection process through existing incineration or other 

control equipment was also considered. We found that existing facilities do not have equipment 

with sufficient capacity to handle the additional flow and pollutant loading of the collection 

chamber; therefore, this option would not be technically feasible (see Section 112(d)(6) 

Technology Review for Mineral Wool NESHAP, docket item EPA-HQ-OAR-2010-1041-0111). 

Therefore, considering cost and technical feasibility, no feasible options for increasing the ample 

margin of safety were identified for mineral wool production facilities. 

In our AMOS analysis for wool fiberglass, we considered several process alternatives and 

control options for reducing chromium emissions from glass-melting furnaces which are 

summarized in the AMOS memorandum. Considering cost and technical feasibility, rebuilding 

gas-fired glass-melting furnaces before degradation of the refractory causes elevated chromium 

emissions (i.e., reducing the operational life of the gas-fired furnaces from 10 years to 7 years)

was identified as the most feasible option for increasing the ample margin of safety for wool 

fiberglass manufacturing facilities. Sources may choose to rebuild a high-emitting furnace earlier 

than its projected end-of-campaign to meet the chromium emissions limit of 2.5E-04 pounds 

total chromium per ton of glass pulled for gas-fired glass-melting furnaces. Industry identified 

other chromium emission reduction measures that may also be used, but our analyses show that 

an earlier furnace rebuild is likely to be the most cost effective way to meet the chromium 

emission limit. We also looked for potential measures or options for reducing formaldehyde 

emissions from bonded lines and no new technologies (beyond those technologies already in 

place) were found. We also evaluated the use of non-HAP binders in the wool fiberglass 

manufacturing industry and found that most facilities have already phased out the use of 

formaldehyde on bonded lines.

26. Comment: One commenter (1041-0081) asserted that, for both source categories, 

the EPA’s analysis is completely based on cost, and that the EPA may not lawfully consider cost 

in the AMOS decision, without an express authorization to consider cost in that analysis. The 

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commenter asserted that the Supreme Court precedent in Whitman v. Am. Trucking Ass’n, 531 

U.S. 457, 467 (2001), bars the EPA from considering cost absent a clear textual commitment.

It was unclear to the commenter whether the EPA considered any other control options or 

methods to further reduce emissions other than the controls for which it deems cost to be 

negligible. The commenter argued that, even assuming if cost was a factor, the EPA may 

consider in an AMOS analysis, the commenter asserted that the EPA’s proposal does not provide 

any analysis of what is, by definition, the central question in the inquiry into the AMOS to 

protect public health. The commenter contended that the EPA’s analysis does not consider the 

ample margin in terms of health or what margin would provide ample protection, particularly for 

children. 

The commenter conceded that the D.C. Circuit previously allowed the agency to consider 

cost in the HON decision, but asserted that the case was wrongly decided and that the EPA 

should not rely on it as justification to evade the statute. The commenter maintains that the 

statute prohibits the agency from considering cost in its AMOS analysis. 

Response: We disagree with the commenter that CAA section 112 prohibits us from 

considering cost when evaluating technologies for the AMOS decision. As explained in our 

November 2011 proposal, the first step in the process of evaluating residual risk is the 

determination of acceptable risk. If risks are unacceptable, the EPA cannot consider cost in 

identifying the emissions standards necessary to bring risks to an acceptable level. The second 

step is the determination of whether standards must be further revised in order to provide an 

ample margin of safety to protect public health. The ample margin of safety is the level at which 

the standards must be set, unless an even more stringent standard is necessary to prevent, taking 

into consideration costs, energy, safety and other relevant factors, an adverse environmental 

effect. As the commenter has correctly pointed out, case law precedence in the HON decision

specifically allows us to consider cost impacts, and we did that for the risk drivers in these source 

categories. However, we agree with the commenter that we should have explained our analysis 

of the ample margin of safety more completely in our 2011 and 2013 proposals. The details of 

this analysis can be found in the revised and updated risk assessment report entitled, “Residual 

Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing Source 

Categories in Support of the June 2015 Final Rule” found in the docket for this rulemaking. 

27. Comment: One commenter (1041-0081) contended that because the proposed wool 

fiberglass chromium limit is a production-based limit, rather than a health-based limit, it does not 

identify what amount of total chromium reduction is needed to provide an AMOS. Rather than 

set a limit measured only in terms of production, the commenter argued that EPA should set a 

total chromium limit to achieve an AMOS.

Response: Regarding the production-based chromium emission limit in the wool 

fiberglass rule, while the emission limits are expressed in terms of pounds of pollutant per ton of 

product manufactured, this is a metric that lends itself to direct comparison with permit limits. 

Additionally, the total annual emissions of any of the regulated pollutants for these industries 

may be calculated using the emission limits and site-specific production rate as follows: 

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Production rate (ton/yr) x Emission limit (lb/ton) = Annual Emissions (lb chromium compounds), 

and

Emissions (lb/yr)/2000 lb/ton = Annual Emissions (tons all other regulated pollutants).

Further, we did consider what the total chromium emissions would be for each facility, 

and we revisited the risk assessment based on post-RTR compliance for each plant (76 FR 

72802, November 25, 2011). For details on this reassessment of the risk, see the document 

entitled Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing 

Source Categories in Support of the June 2015 Final Rule found in the docket for this 

rulemaking.

28. Comment: One commenter (1042-0121) noted that the proposed rule for the wool 

fiberglass manufacturing source category allows a cancer risk greater than 1-in-1 million and a 

higher chronic non-cancer risk twice EPA’s safety threshold. Another commenter (1041-0081) 

stated that the EPA recognized the need for the wool fiberglass manufacturing source category to 

reduce health risk due to chromium, but did not explain why it is only requiring a standard that 

would reduce cancer risk by 20-in-1 million, and is still allowing emissions that will cause an 

MIR of 20 times the statutory goal (1-in-1 million based on allowable emissions). The 

commenter urged the EPA to set an absolute pollutant limit as measured in lbs or lbs per hour on 

chromium, not just a production-based limit and that it is possible for the EPA to set an absolute

limit in addition to a production-based limit as evidenced by the proposed limit for startup and 

shutdown.

The commenter noted that the EPA does not consider or propose any standard to reduce 

acute or chronic non-cancer risk for the wool fiberglass manufacturing source category, even 

though the acute health risk is 30 times the EPA’s safety threshold. According to the commenter, 

in the 2011 proposal, the EPA appears to be relying on the industry statement that the industry 

“has converted or . . . announced plans to convert to non-phenol formaldehyde binders.” The 

commenter asserted that the agency cannot base the current rule on an industry group’s stated 

future plans and that relying on industry’s stated plans is an unlawful evasion of the EPA’s legal 

duty. 

The commenter supported the EPA’s proposed determination to promulgate a chromium 

limit but asserted that the EPA should finalize more stringent emission limits than it has 

proposed for the Wool Fiberglass Manufacturing source category and should strengthen the 

proposed limits to achieve a cancer risk below 1-in-1 million (the statutory goal), a chronic noncancer risk below 0.2, and an acute health risk below 0.2 (per the EPA’s memorandum, Residual 

Risk Program: Selection of Hazard Index Limits (dated Oct. 4, 2002), EPA-HQ-OAR-2003-

0048-0203), a multipathway risk below 1, and a cumulative burden that ensures an ample margin 

of safety from the combined health risks to this community. 

Response: Setting an absolute pollutant emission limit, as suggested by the commenter, 

is not practical in this situation. Since risk is a function of emission rate, release height, 

meteorology and proximity to populations, establishing such an absolute emissions limit would 

require either a plant-specific emission limit for each facility based on that facility’s emissions 

and distance to the surrounding population, or identifying the one facility that is located closest 

to populations or sensitive receptors and determining the maximum emissions rate for that 

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facility and applying that rate to all facilities in the source category. In either case, the 

circumstances could change from year to year. Note that we generally do not draw bright lines 

(i.e., 1-in-1 million MIR) of acceptability regarding cancer or non-cancer risks from source 

category HAP emissions, and that it is always important to consider the specific uncertainties of 

the emissions and health effects information regarding the source category in question when 

deciding exactly what level of cancer and non-cancer risk should be considered acceptable. In 

addition, the source category-specific decision of what constitutes an acceptable level of risk 

should be a holistic one; that is, it should simultaneously consider all potential health impacts--

chronic and acute, cancer and non-cancer, and multipathway--along with their uncertainties, 

when determining the acceptable level of source category risk. Experience with source category 

rulemakings in the past tells us that this means that drawing bright lines for such decisionmaking is impossible. The Benzene NESHAP decision framework of 1989 acknowledged this; in 

today‘s world, such flexibility is even more imperative, because new information relevant to the 

question of risk acceptability is being developed all the time, and the accuracy and uncertainty of 

each piece of information must be considered in a weight-of-evidence approach for each 

decision. This relevant body of information is growing fast (and it will continue to grow faster 

and faster), necessitating a flexible weight-of-evidence approach that acknowledges both 

complexity and uncertainty in the simplest and most transparent way possible. While this 

challenge is formidable, it is nonetheless the goal of the EPA‘s RTR decision-making, and it is 

the goal of the risk assessment to provide the information to support the decision-making 

process.

Regarding the comment that we are relying on an industry statement that the industry will 

be phasing out the use of PF binders and that we are evading our legal duty, we disagree with the 

commenter. As discussed in section V.H of the preamble to the final rule, sources that use RS 

lines have been phasing out the use of PF binders, but, at the time we conducted the risk 

assessment, we did not know which lines and facilities were formaldehyde-free. We therefore, 

included the available actual emissions from the RS bonded lines in the risk assessment we 

conducted for this source category. Regarding the proposed formaldehyde, methanol, and phenol 

limits for RS lines, as noted in the preamble to the final rule, we are not establishing MACT 

standards for RS manufacturing lines at wool fiberglass manufacturing facilities in this final 

action. We have issued an ICR under CAA section 114 to collect updated emissions and process 

information from the industry and we will analyze the ICR data and evaluate MACT limits for 

RS lines at wool fiberglass manufacturing facilities at a future date. With regard to FA lines, we 

have explained that the EPA proposed to discontinue the use of formaldehyde as a surrogate for 

phenol and methanol. 76 FR 72788, 72791; 72796. The EPA may attribute characteristics of a 

subclass of substances to an entire class of substances if doing so is scientifically reasonable. 

Dithiocarbamate Task Force v. EPA, 98 F.3d 1394, 1399 (D.C. Cir. 1996). As also explained in 

the preamble to the final rule, we are establishing emission limits for formaldehyde, phenol and 

methanol at the MACT floor level of control because the existing standard for formaldehyde was 

calculated incorrectly. 

With regard to the emissions limit for chromium compounds, we evaluated the public 

comments received in response to the 2014 supplemental proposal and the available emissions 

data for gas-fired glass-melting furnaces that had been rebuilt, which is the most demonstrated 

technology for reducing chromium emissions. We received comment that, in one case, newlyrebuilt furnaces may not be able to demonstrate compliance with the proposed emission limit of 

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6.0E-05 pounds of total chromium per ton of glass, based on one specific example from the 2012 

test data in which a 1-year old furnace emitted 2.5E-04 pounds of chromium per ton of glass. We 

reevaluated the technology, and based on the data available, newly-rebuilt gas-fired glassmelting furnaces operate below an emissions level of 2.5E-04 pounds per ton of glass pulled. We 

conducted an assessment of the risk attributable to all HAP for each facility and determined that 

increasing the chromium compound emission limit from 6.0E-05to 2.5E-04 pounds total 

chromium per ton of glass pulled has a minimal effect on the post-RTR risks because these risks 

are largely driven by formaldehyde emissions. Specifically, at the chromium compounds 

emission limit of 2.5E-04 pounds total chromium per ton of glass pulled, the MIR due to only 

chromium emissions for the source category is 3-in-1 million; whereas, the MIR due to only 

formaldehyde post-RTR emissions for the source category is 60-in-1 million. As noted above, 

these post-RTR risks were determined to be acceptable. Therefore, a more stringent emissions 

limit for chromium compounds would not significantly reduce the risks.

We note that, based on information provided by the industry, the wool fiberglass industry 

has phased out the use of PF binders on 95 percent of the RS lines. However, this phase out is 

not reflected in the actual emissions data available to us. Therefore, we believe the risks from 

wool fiberglass manufacturing from actual emissions are lower than our estimated MIR of 60-in1 million for formaldehyde emissions for major sources. The emissions and risks associated with 

formaldehyde emissions will be further investigated based on industry responses to the CAA 

section 114 ICR that we have issued as mentioned in the previous paragraph. 

Further, we note that the source for the commenter’s statement that default limits for HI 

should or must be established at 0.2 rests on an internal EPA staff memorandum (from 2002) that 

was never adopted as agency policy (and never reviewed by the public or by any peer review 

body) and consequently carries no precedential weight.

29. Comment: According to one commenter (1041-0081), the EPA also must consider 

enforceability when setting standards, and the commenter urged EPA to ensure that it sets a limit 

that will allow concerned local residents to assess compliance. 

Response: Regarding the public’s ability to assess compliance with the standard,

Enforcement and Compliance History Online (ECHO) is a Web-based tool that provides public 

access to compliance and enforcement information for approximately 800,000 EPA-regulated 

facilities. ECHO allows users to find permit, inspection, violation, enforcement action, and 

penalty information covering the past three years. The site includes facilities regulated as CAA

stationary sources, Clean Water Act (CWA) direct dischargers, and Resource Conservation and 

Recovery Act hazardous waste generators/handlers. The data in ECHO are updated monthly. 

Review of the detailed facility report in ECHO lists whether a stack test was conducted 

and whether the source passed or failed their compliance demonstration. 

Regarding the enforceability of the standard, the EPA considered this aspect in both the 

November 25, 2011 proposed rule and in the April 15, 2013 supplemental proposal, and the 

Office of Enforcement and Compliance Assurance (OECA) was involved in the development of 

both proposals and the final rule so that the resulting rule could be enforced and compliance with 

the rule determined. To further aid in compliance, the final rule includes requirements (further 

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discussed in section VI.A of the preamble to the final rule) for facilities to establish the 

percentage of cullet used in the materials mix fed to the furnace during the initial performance 

test and to maintain the percentage of cullet at or below that established level.

30. Comment: One commenter (1041-0081) stated that the EPA did not provide a 

determination of the environmental effects and that EPA cannot assume there is no potential for 

environmental effects based on the health assessment.

According to the commenter, the EPA did not consider or address whether a more 

stringent limit than the existing MACT is required to protect the environment. The commenter 

noted that the EPA proposed environmental risks were deemed negligible, and evaluated the 

potential for significant ecological exposures to non PB-HAP. The commenter noted that the 

EPA based the environmental determination on the human health assessment.

The commenter observed that under CAA section 112(f)(2), the EPA is required to 

determine whether to set a standard to prevent an adverse environmental effect. According to the 

commenter, adverse environmental effect is defined as any significant and widespread adverse 

effect, which may reasonably be anticipated to wildlife, aquatic life, or other natural resources, 

including adverse impacts on populations of endangered or threatened species or significant 

degradation of environmental quality over broad areas. As the D.C. Circuit has explained (244 

Sierra Club v. EPA, 353 F.3d 976, 992 (D.C. Circuit 2004)), the commenter asserted that the 

residual risk review is the proper time for the EPA to consider these effects, including the need to 

engage in Endangered Species Act consultation under 16 U.S.C. §536. 

According to the commenter, the EPA may not rely on its human health risk assessment 

alone to satisfy its environmental duty under CAA section 112(f)(2). Although the EPA states 

that the reference doses it is using are more protective than the EPA believes is necessary to 

protect laboratory animals such as rodents, the commenter asserted that EPA gives no basis for 

why this is a sufficient way to prevent an adverse environmental effect for more sensitive 

wildlife or other environmental receptors. The commenter noted that the EPA also says nothing 

at all about ESA consultation, which provides further evidence that it has not considered or 

addressed its duty to prevent adverse environmental effects, as recognized by the D.C. Circuit.

The commenter asserted that the SAB has stated: “The assumption that ecological 

receptors will be protected if human health is protected is incorrect.” In addition to inhalation 

risk for wildlife and air impacts to plants, the commenter observed that chemicals that are 

persistent in the environment or bioaccumulative in living tissue will remain or increase over 

time, particularly in areas of high emissions. Accordingly, the commenter stated that any 

additional exposure from current activities would thus be added to a background that is likely 

unsafe already for wildlife and other environmental resources. The commenter contended that 

the EPA should perform an appropriate ecological assessment.

The commenter argued that the EPA should perform an ecological risk assessment for 

these source categories, and not simply rely only on the human health assessment. According to 

the commenter, the EPA neither carried out the required ecological risk assessment nor presented 

a reasoned explanation supported by science in the record.

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Response: We agree with the commenter that we did not evaluate environmental impacts 

independent of our human health assessment in either our November 25, 2011 or our April 15, 

2013 proposals. We also agree with the commenter that the approach used to evaluate 

environmental impacts in our 2011 and 2013 proposals did not address SAB’s concerns that 

“The assumption that ecological receptors will be protected if human health is protected is 

incorrect.” To address these issues, we developed the environmental screening methodology that 

is briefly described below. This environmental screen was used to screen for environmental 

impacts in our 2014 proposal (79 FR 68016-68017) and the final rule. 

The environmental screen focuses on the following seven environmental HAP: 

• Five persistent bioaccumulative HAP (PB-HAP) – cadmium, dioxins/furans, 

polycyclic organic matter (POM), mercury (both inorganic mercury and methyl 

mercury) and lead.

• Two acid gases - HCl, and HF. 

In the environmental risk screen we evaluate the following four exposure media: 

terrestrial soils, surface water bodies, fish consumed by wildlife, and air. Within these four 

exposure media, we evaluate nine Generic Ecological Assessment Endpoints (GEAEs). The 

GEAEs reflect the overall “health” of aquatic and terrestrial ecosystems and any important biota 

or community types that could be exposed in those ecosystems. For persistent and 

bioaccumulative (PB) HAP, the generic set of receptors includes both community-level and 

population-level endpoints; for acid gases, the receptors are terrestrial plant communities. 

Selection of species for the population-level assessments for PB-HAP was based on those 

organisms that are likely to be the most highly exposed due to bioaccumulation of the PB-HAP 

through aquatic and terrestrial food chains. 

For each HAP evaluated, we identified the available ecological benchmarks for each of 

the GEAEs. An ecological benchmark represents a concentration of HAP (e.g., 0.77 μg of HAP 

per liter of water) that has been linked to a particular environmental effect level through 

scientific study. Where possible, we identified existing ecological benchmarks for each 

ecological assessment endpoint at each of the following effect levels: Probable effect levels 

(PEL), Lowest-observed-adverse-effect level (LOAEL), and No-observed-adverse-effect levels 

(NOAEL). The benchmarks used in the environmental risk screen are shown in the Appendix to 

the final risk assessment document that is available in the docket.

For cadmium, mercury, PAHs, and dioxins/furans, the environmental screening analysis 

consists of two tiers. In Tier 1 of the screening analysis, HAP concentrations are modeled using 

facility specific HAP emissions at a hypothetical facility and using worst-case meteorology. The 

hypothetical facility includes a conceptual model for the environment surrounding the facility, 

including a conceptual lake. The Tier 1 modeling parameters are designed to encompass worstcase conditions to provide conservatively high HAP concentrations. For those facilities that 

exceed the no-effect level in the Tier 1 screening analysis, we conduct a Tier II screening 

analysis that estimates the emissions concentrations based on the actual meteorology near the 

facilities and the actual locations of lakes in the vicinity of the facilities. 

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Potential adverse environmental effects on terrestrial plant communities caused by acid 

gas emissions are screened in a single-tier. The acid gas screen utilizes HF and HCl 

concentrations that are modeled based on actual facility emissions and meteorology. We 

compare these modeled concentrations to conservative lowest observable effect level (LOEL) 

ecological benchmarks in order to evaluate the potential phytotoxicity and reduced productivity 

of plants due to chronic exposure to acid gases.

Of the seven pollutants included in the environmental risk screen, the facilities subject to 

this rulemaking emit lead, mercury (elemental and divalent), cadmium, HF and HCl. In the Tier I 

screening analysis for PB–HAP other than lead (which was evaluated differently, as noted in the 

reference above), none of the individual modeled concentrations for any facility in the source 

categories exceed any of the ecological benchmarks (either the LOAEL or NOAEL) for mercury 

or cadmium. Therefore, we did not conduct a Tier II screening assessment. For lead, we did not 

estimate any exceedances of the secondary lead NAAQS. For HCl and HF, the average modeled 

concentration around each facility (i.e., the average concentration of all off-site data points in the 

modeling domain) did not exceed any ecological benchmarks (either the LOAEL or NOAEL). In 

addition, each individual modeled concentration of HF and HCl (i.e., each off-site data point in 

the modeling domain) was below the ecological benchmarks for all facilities. 

Because our environmental risk screen does not indicate an environmental effect from 

this source category, we disagree with the commenter’s statement that the EPA must engage in 

consultations (e.g., with the U.S. Fish and Wildlife Service and the National Marine Fisheries 

Service) under 16 U.S.C. 1536(a)(2).

31. Comment: Three commenters (1042-0115f, 1042-0115k, and 1042-0126) 

questioned the validity of the emissions testing related to CertainTeed’s K2 furnace. One 

commenter (1042-0126) argued that EPA’s concern over chromium emissions are overstated 

because they are based on a single test conducted in 2010 which the commenter characterized as 

erroneous. The commenter stated that the furnace was retested in 2011 and the resulting 

hexavalent chromium emission rates were far less than the rates determined from the November 

2010 test. The commenter estimated a linear relationship between risk and emission rate would 

result in a MIR of less than 10-in-1-million which is a risk factor generally accepted by EPA as 

being within a reasonable range.

One commenter (1042-0115f) stated that subsequent testing of the same furnace showed 

much lower emissions of hexavalent chromium. The commenter stated that EPA did the right 

thing by initiating direct monitoring of the air in Garland Park just south of the plant. 

One commenter (1042- 0115k) requested further clarification on the stack testing done at 

CertainTeed, specifically whether the testing conducted by CertainTeed in November 2010 was 

of the same merit as that conducted in September of 2011; whether EPA considered both tests 

valid; and whether EPA can explain any differences between the two tests and operations at the 

company being tested.

Response: In response to the chromium testing at one facility exhibiting the highest 

hexavalent chromium emissions, EPA reviewed three tests at that facility: two tests on the K2 

furnace and one test on the K1 furnace. The test on the K1 furnace and the first test conducted on 

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the K2 furnace were done correctly and emissions were correctly calculated according to the test 

report submitted by the company. We also note that the company did not assert that an error was 

made in the K2 testing when we contacted them to discuss the results in April 2011. To the 

contrary, the company knew it had high emissions of chromium; that these emissions were 

attributed to the type of furnace, its production rate and operating temperatures; and the type of 

refractory used to construct the furnace, but that they did not realize that most of the chromium 

emitted was in the hexavalent state. The company also noted that it inspected the electrostatic 

precipitator in place on the K2 kiln and confirmed that it was working properly.

The company retested the K2 furnace using a different test contractor in October 2011 

and submitted a second source test for it to EPA. We completed a thorough review of the source 

test report submitted by the company, and conclude the following:

1. The results reported for hexavalent chromium in the report submitted by the company 

are in error, and are reported low by at least one order of magnitude. This error is due 

to the test contractor referencing the wrong lab data in calculating the hexavalent 

chromium emissions. The reported hexavalent chromium emissions are based on 

reported values from the nitric acid sample analysis from method 0061, while these 

calculations should have been derived from the potassium hydroxide samples 

analyzed and reported by the lab. Our calculations show the hexavalent chromium 

average of the three test runs to be in the neighborhood of 75 lb/yr of hexavalent 

chromium emissions, rather than the reported result of approximately 7 lbs/yr. 

2. Furthermore, the results reported for hexavalent chromium were blank-corrected 

based on the wrong lab data as well. Blank values from Method 29 nitric reagent 

analysis were used, when the appropriate blank values should have been taken from 

the potassium hydroxide blank analysis instead.

3. While the Test Protocol for this sampling stated that the testing company would send 

the method 0061 filter to the lab for total chromium analysis, this was not done (at 

least there is no lab data to support this) and so the total chromium result from the 

Method 29 multi-metals test is the total chromium number presented in the report. 

Method 29 calculations and lab data are appropriate, save the minor concern with 

barium spike recovery listed in the lab’s narrative, and some background zinc present 

in the method blank, and we expect the total chromium measured by Method 29 to be 

an accurate assessment of the emissions during the testing.

4. We found no deficiencies in the laboratory analysis, other than the omission of the 

method 0061 filter analysis; though it appears this was not submitted to them for 

analysis. 

5. Flow rate measurement indicates very low flow, with delta-p values recorded below 

the method sensitivity level of 0.05” H2O column. There are delta-P data points that 

show three significant figures which indicate the use of a gauge other than an inclined 

manometer (the test method standard) however there is no documentation in the test 

report to substantiate this. While this is a minor deviation from the method, it is not 

likely to have a significant impact on the result and indicates an effort on the part of 

the tester to improve their data quality above the method minimum. 

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a. The flow rate change (less than 40 percent) in the October testing indicates that 

the source was making process changes that would lower their chromium 

emissions for this second round of testing (versus the 2010 test results). 

b. If the source conducted the second tests with the same flow rate as the first set of 

tests they would have been emitting about 125 lb/yr of hexavalent chromium. 

This is about 25 percent of the total measured during the first testing in 2010, so 

we conclude the source is likely to have made other process changes in an effort 

to minimize the chromium emissions. Slowing the flow rate through the ESP 

particulate control device is one way to improve the collection efficiency of the 

device and lower metals emissions. This is consistent with the results as we 

calculate them, but may not be solely responsible for the lower emissions result of 

this data set. 

c. Lower CO2 emissions and lower stack temperature noted in the October tests 

generally point to an increase in dilution air for this testing; however with a lower 

flow rate measurement this is contraindicated. If the source were able to find a 

way to keep the melt at the needed temperature and use less fuel, this would seem 

to reconcile well with the results measured by the October testing.

6. Sample temperature on arrival at the laboratory was noted at 19.6°C which is higher 

than the lab method requirement of 4°C to 6°C. The impact of this is likely to be 

minimal, in the EPA’s estimation, as this requirement is meant to safeguard the 

stability of hexavalent chromium in the solution. The risk of elevated sample 

temperature prior to analysis is that it may drive the fraction of hexavalent to trivalent 

chromium in the sample toward a trivalent bias. However, after calculating the 

emissions based on the appropriate lab data we find that over 90 percent of the 

chromium emissions were measured as hexavalent, so we conclude that any impact 

this had on the stability of hexavalent chromium in the reagent solution prior to 

analysis is likely to be of minimal impact to the result.

7. The pH of the #1 impinger solution during test run 1 was listed below method 

specification at the conclusion of the test run. The solution pH is reported as being 

8.5, while the test method (SW-846 method 0061, section 5.2.2) stipulates that this 

value should be “...above 8.5 after sampling.” It is our understanding from 

conversation with the testing officials at EPA Region 7 that there was some difficulty 

reading the pH indicator in the field following this run and that it was difficult to 

determine if the value was 8, 8.5, or 9, and that 8.5 was chosen as a compromise with 

the understanding of those present that it met the method minimum. While this 

reported value technically does not meet the method minimum, we find that the data 

is likely to be representative of emissions based on the following:

a. Test run 1 results are neither the high nor low of this sample set, but the middle of 

the three samples. Emissions averages calculated with or without this number in 

the set do not markedly change the calculated emissions when the appropriate 

hexavalent chromium data are used.

b. The analytical portion of this test method, EPA method 7199, states that good 

sample stability is achieved when the pH is kept at 7 or higher (above 6.5). This 

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indicates to us that a pH of 8.5 is not likely to have had a negative impact on the 

measured hexavalent chromium emissions.

c. A sample compromised by lower pH would present itself in a shift of the result 

away from hexavalent chromium toward trivalent chromium emissions, with the 

expectation that the ratio of hexavalent to trivalent would be lower. Test run 1 still 

shows hexavalent chromium emissions to be above 90 percent of the sample 

catch, both consistent with the other test data and indicative of minimal 

interference from any pH driven chemical changes in the matrix of the solution.

In summary, we concluded that the 2011 testing was conducted properly; however, 

because the calculations done during the reporting phase were incorrect, the reported numbers 

were also incorrect and low. The corrected values presented by the test contractor were 

appropriate (and much higher than their original report). There remains the issue of discarded 

filters that were required under the method to be analyzed for hexavalent chromium; this step 

was not conducted and contributed to the low measured hexavalent emissions. While there 

appears to be no further reasons to discard the 2010 data (after corrections and assumptions of 

the level of hexavalent chromium that the discarded filter may have contained), the corrected 

2011 report confirms emissions of the same order of magnitude, though slightly lower than the 

2010 testing. This lower value may be attributed to the discarded filter. Subsequently, we issued 

a CAA section 114 ICR in December 2012, requesting test data on total chromium compounds 

emissions from all glass-melting furnaces and we were able to confirm our view of chromium

emissions from this source category in our April 2013 proposal.

32. Comment: One commenter (1042-0115) opined that the EPA had concluded that 

the health risks from this category are unacceptable and the commenter argued that the proposed 

new standard for chromium does not provide an ample margin of safety. The commenter stated 

that the higher temperature of oxyfuel design is part of the problem and this is a special concern 

in Kansas City, Kansas. The commenter believed it is likely that citizens near the plant have been 

exposed to higher hexavalent chromium emissions than was assumed in the health risk 

assessment conducted by the EPA. The commenter noted that even the EPA's limited analysis 

showed that Owens Corning plant adds about 25 percent to the risk calculated from the 

CertainTeed operation.

Response: Contrary to the statement made by the commenter, the EPA did not determine 

that risks from the Wool Fiberglass Manufacturing source category were unacceptable at 

proposal. Rather, we explained that we had conducted a risk assessment that provided estimates 

of the MIR posed by the allowable and actual HAP emissions from this source category, the 

distribution of cancer risks within the exposed populations, cancer incidence, HI for chronic 

exposures to HAP with noncancer health effects, and HQ for acute exposures to HAP with noncancer health effects. Specifically, we found that formaldehyde is the primary HAP driving the 

risks from this source category. The greatest MIR resulted from MACT-allowable formaldehyde 

emissions from one facility in the source category and was assessed at 40-in-1 million. 

Additional analyses showed that the cancer incidence and number of people with cancer risk 

over 1-in-1 million were low. We found that the residual risks to public health are acceptable. 

We also proposed emission limits for total chromium compounds that would achieve an ample 

margin of safety to protect public health and prevent adverse environmental effects. At proposal, 

we also performed an auxiliary risk characterization analysis to assess the potential maximum 

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individual lifetime cancer risks in the event that all Wool Fiberglass facilities switch to high 

chromium refractory brick. We assumed that chromium emissions for facilities would be the 

same as CertainTeed’s annual emission of 420 pounds of hexavalent chromium per furnace. The 

results of the auxiliary analysis indicated that emissions from 14 facilities could lead to 

maximum individual cancer risks greater than 100-in-1-million, with the highest emitting facility 

posing a potential maximum individual risk of 900-in-1-million. See 76 FR 72800-801 for a 

complete discussion of the risk assessment of the Wool Fiberglass Manufacturing source 

category.

Regarding the secondary risk driver, hexavalent chromium, we reevaluated the 

performance associated with rebuilding gas-fired glass-melting furnaces, based on public 

comments and the available emissions data, and determined that newly-rebuilt furnaces operate 

below an emissions level of 2.5E-04 pounds per ton of glass pulled. The final standard for 

chromium reflects this level of emissions and the cancer risk from hexavalent chromium after 

implementation of the final standards is no higher than 3-in-1 million. The results of the risk 

assessment are presented in more detail in the final residual risk memorandum titled “Residual 

Risk Assessment for the Mineral Wool Production and Wool Fiberglass Manufacturing Source 

Categories in Support of the June 2015 Final Rule”, which can be found in Docket ID No. EPAHQ-OAR-2010-1042.

Additionally, we have further evaluated the cost, emissions reductions, energy 

implications and cost-effectiveness of both the PM and total chromium compounds emission 

limits being promulgated in this final rule and have determined that they are cost effective, 

technically feasible and will provide an ample margin of safety to protect public health and 

prevent adverse environmental effects. We have further determined that there have been 

developments in practices, processes or control technologies since promulgation of the MACT 

standards that warrant revisions to the MACT standard. Therefore, to satisfy CAA sections 

112(d)(6) and 112(f)(2) of the CAA, we are promulgating a limit of 2.5E-04 pounds of 

chromium compounds per ton of glass pulled for both existing and new furnaces and lowering 

the MACT standard for PM from the current 0.50 lb PM per ton of glass pulled to 0.33 lb of PM 

per ton of glass pulled for both existing and new furnaces. 

33. Comment: One commenter (1042-0115f) suggested that air monitoring around 

Kansas City, Kansas, was conducted for the residual risk assessment, and added that such 

monitoring should be conducted for other RTR rules being proposed by the agency. 

The commenter also stated that the health risk assessment is not conservative for other 

reasons as well. The commenter noted that the EPA's model did not consider risks from other 

nearby sources of industrial pollution that included a medical waste incinerator, the General 

Motors assembly plant and the Quindaro Coal Fire Power Station. The commenter observed that 

the area is also home to large numbers of diesel trucks and trains. 

Another commenter (1042-0115k) stated that the EPA needs to rerun the risk models so 

that a full picture of the effects of the pollutants on the bluffs (Kansas City, Kansas) can be 

obtained.

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Response: We agree that ambient air monitoring, when available for specific HAP of 

concern, can be a useful tool for ground-truthing emission estimates. In this particular case, EPA 

Region 7 conducted the monitoring to determine if the levels of hexavalent chromium from any 

local sources posed health concerns for local residents. In addition to emissions of hexavalent 

chromium from wool fiberglass furnaces, other sources of HAP in the area include a coal-fired 

power plant, a medical waste incinerator, and a landfill. While the monitoring results were not 

conducted for the residual risk assessment of the wool fiberglass RTR, we note that the results of 

the ambient air monitoring generally agree with our risk assessment results for this source 

category. 

Our approach here is consistent with the approach we took regarding this issue in the 

Hazardous Organic NESHAP (HON) RTR, which the court upheld in the face of claims that the 

EPA had not adequately considered background (NRDC v. EPA, 529 F.3d 1077 (D.C. Cir. 

2008)). Questions regarding risk from industrial sources other than those specifically addressed 

by this rulemaking may be addressed to Region 7 as a part of the larger stakeholder meetings in 

which the Region may answer questions that go beyond the context of this rulemaking.

C. UPL Approach to Limited Datasets

34. Comment: One commenter (1042-0348) agreed with the EPA that an analysis of 

the uncertainty inherent in source test data is required, and agreed that the EPA’s proposed UPL 

methodology to addressing limited datasets (79 FR 68017, November 13, 2014), if correctly 

applied, is necessary and useful to account for the uncertainty associated with available emission 

data (e.g., due to the number of emission samples available and the number of samples that will 

be collected to assess compliance with the emission limit).

The commenter indicated, however, that they were not able to adequately review the 

EPA’s application of this UPL method because the EPA did not provide in the docket a detailed 

explanation of its application of the method, and, as a result, the EPA’s determinations were “far 

from clear or identifiable.” The commenter maintained that it was not possible to determine if the

UPL methodology was consistently applied and what the rationale was for the EPA’s 

results (e.g., use of data below the detection limit from testing, properly skewing of data, data 

distribution fit, use of only relevant data). The commenter provided the example that it was not 

clear if certain formaldehyde, phenol and methanol limits (e.g., those for the RS wool forming 

process) developed using the UPL method were based on data that were “clearly generated in 

accordance with the protocols that were gathered in accordance with the present MACT rule 

requirements.” Another commenter (1042-0347) stated that the EPA failed to provide adequate 

justification and factual support because the EPA’s limited datasets and UPL memoranda do not 

clearly explain EPA’s analysis.

One commenter (1042-0348) further pointed out that the UPL method for limited datasets 

was applied to every limit in the 2014 proposal except for chromium compounds, noting that 

application of the method to chromium data would yield a higher limit than proposed.

Response: We disagree with the commenters that we did not provide detailed 

explanations of the use of the UPL approach in support of the 2014 supplemental proposal. Our 

use of the UPL and the approach followed to calculate the MACT floors is clearly explained in 

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the following memoranda available in the dockets to this rulemaking: “Use of the Upper 

Prediction Limit for Calculating MACT Floors,” “Approach for Applying the Upper Prediction 

Limit to Limited Datasets,” “Revised Technical Approach for Mineral Wool MACT Floor 

Calculations,” and “Revised Technical Approach for Wool Fiberglass MACT Floor 

Calculations.” The various memorandum detail our approach to evaluating which data sets 

require additional scrutiny and what steps we now use to ensure that limited data sets are 

appropriately evaluated.

With regard to the commenter’s observation that we did not apply the UPL methodology 

in establishing the emission limit for chromium compounds, the commenter is correct. This limit 

is being finalized under CAA sections 112(d)(6) and 112(f)(2) as an outcome of both our 

technology review and our AMOS analysis. Consequently, we did not calculate a MACT floor 

and, therefore, we did not use the UPL approach which is applied when establishing emission 

limits as part of the MACT floor analysis. 

35. Comment: One commenter (1042-0347) opined that the EPA’s use of UPL is 

arbitrary and capricious, resulting in proposed MACT floors that do not reflect CAA section 

112(d)(3) language: “the average emission limitation achieved by the best performing 12 percent 

of the existing sources.” The commenter pointed out that the D.C. Circuit remanded under CAA 

section 7429(a)(2) the EPA’s use of the UPL method in NACWA v. EPA, 734 F.3d 1115, 1139-

45 (D.C. Cir. 2013) for sewage sludge incinerators. The Court found that the EPA seemed to 

have interpreted “‘average emissions limitation achieved by the best performing 12 percent’ . . . 

[to] refer to the future average of a 3-run test that the EPA predicts a source in the bestperforming 12 percent will fall below with 99 percent confidence.” It then held that the EPA 

must provide clarification on two points: 

Although EPA may be able to justify its novel interpretation that “average” means the 

average of a future 3-run compliance test, one sentence in the Federal Register is not 

enough of a basis to uphold EPA’s new approach to incorporating variability against 

arbitrary and capricious review. Accordingly, on remand, we expect EPA to clarify how

the upper prediction limit represents the “average emissions limitation achieved by the 

best performing 12 percent.” The Court also noted that the upper prediction limit 

produces an “apparently illogical result.” For example, EPA predicted a “higher MACT 

floor for an incinerator with raw test data ranging from 0.31 to 2.26 than for a group of 

incinerators with raw test data ranging from 0.31 to 40.32 and a mean of 9.38.” The Court 

remanded on this issue as well, observing “[w]e are hesitant to rubber-stamp EPA’s 

invocation of statistics without some explanation of the underlying principles or reasons 

why its formulas would produce an accurate result, particularly when the ‘facts found’ –

the MACT floor datasets – demonstrate flaws in the formula.” [footnotes omitted] 

Response: The EPA first notes that the commenters reference a court decision that 

addressed MACT standards for a different source category, which are not at issue in this 

rulemaking. Second, the commenter did not assert that the methodology resulted in an 

“apparently illogical result” in this rulemaking (the apparently illogical result was where the 

calculated limit for the best performing unit was higher than the calculated limit for the best 

performing 12 percent of units), as the court pointed out in NACWA. Rather, the commenter 

asserts that the methodology results in limits that are less stringent than they believe is required. 

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Finally, the UPL methodology used to establish the MACT standards referenced in the comment 

(from the sewage sludge incinerators rule) was not the same UPL methodology used to set the 

standards in the final action. We note that the “apparently illogical result” in the sewage sludge 

incinerators rule resulted from analysis of small datasets and the use of procedures that the EPA 

no longer follows. We included in the docket a memorandum explaining how we adjusted the 

UPL methodology to address situations in which the agency must establish MACT standards 

with limited data. That memorandum, entitled Approach for Applying the Upper Predictive 

Limit to Limited Datasets (Docket No. EPA-HQ-OAR-2010-0895-0178) (Limited Datasets 

Memorandum), provides an analysis of the use of the UPL for limited data sets and includes 

procedures to evaluate whether additional analyses beyond the use of the 99 percent UPL are 

needed. We also note that the “apparently illogical results” questioned by the court will no longer 

occur provided the procedures laid out in our UPL memorandum and limited data sets 

memorandum are followed. The EPA followed those procedures in this rulemaking. Therefore, 

this criticism of a prior rulemaking’s record is irrelevant to analyzing the record supporting the 

standards in this rulemaking. The commenter provides no analysis of the approach described in 

the limited data sets memorandum, but simply refers to a court decision addressing standards in a 

different rule that pre-dated that approach. The limited data sets memorandum outlines 

procedures for the EPA to follow to ensure that the statistical approach results in limits that 

reflect the actual performance of the best performing unit or units. Three key changes to the 

EPA’s methodology that are outlined in the limited data sets memorandum are the establishment 

of a minimum size data set for statistical analyses (3 data points), the use of improved analytical 

tools for determining the data distribution (which is key in selecting the appropriate equation to 

perform the calculations), and the establishment of qualitative criteria for comparing unit 

performance in order to inform the selection of the best performing unit.

36. Comment: One commenter (1042-0347) stated that the EPA’s claim that it has 

discretion to set standards using an UPL “is unlawful under the Act, per Chevron.” The 

commenter opined that the statute is clear, and EPA may not read ambiguity into the statute

where it does not exist, nor ignore the use of the unambiguous term “average emission 

limitation.” The commenter further argued that CAA section 7412(d)(3) unambiguously requires 

that floors reflect the “average” emission level “achieved in practice” by the best-performing 12 

percent of sources, and by using the 99-percent confidence level for calculating the UPL (to 

reasonably assure that the calculated limit can be met at all times by the best-performing 

source(s)) the EPA has proposed a floor that results in a greater-than-average level of emissions 

being achieved in practice, which fails to protect communities surrounding the wool fiberglass 

and mineral wool sources and is unlawful, arbitrary, and capricious.

Response: We disagree. Section 112(d)(3) of the CAA requires the EPA to promulgate 

standards for major sources of HAP that are based on MACT performance. For existing sources, 

MACT standards must be at least as stringent as the average emission limitation achieved by the 

best performing 12 percent of existing sources (for which the Administrator has emissions 

information) or the best performing 5 sources for source categories with less than 30 sources. For 

new sources, the MACT standards must be at least as stringent as the control level achieved in 

practice by the best controlled similar source. The reference to “sources” does not lead to the 

assumption the commenter makes that the best performing sources can only be the bestperforming sources for the entire suite of regulated HAP. Instead, the language can be reasonably 

interpreted as referring to the source as a whole or to performance as to a particular HAP. 

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Similarly, the reference in the new source MACT floor provision to “emission control achieved 

by the best controlled similar source” can mean emission control as to a particular HAP or 

emission control achieved by a source as a whole. Also, CAA section 112(d) includes language 

such as “existing source,” “best performing,” and “achieved in practice” in referring to sources’ 

actual operations, but again the language does not address the question of whether, in assessing 

which sources perform best or are best controlled, emission levels should be evaluated either 

over time or in a single test result. Thus, the EPA has discretion to interpret the phrase “average 

emission limitation achieved” by the best performing source or sources.

Further, the D.C. Circuit has held repeatedly that variability of best performing sources 

may be taken into account in establishing MACT floors. Id at 881-882. See also National Lime 

Ass’n v. EPA, 627 F.2d 416, 431 n.46, 443 (D.C. Cir. 1980). Therefore, we believe it is 

appropriate to consider statistical variability to ensure that regulated sources can meet the 

proposed limits at all times. Our analyses used the data from the best performing units to assess 

the actual performance of the units, considering the variability demonstrated by the data.

Regarding the assertion that by using the 99-percent confidence level for calculating the 

UPL (to reasonably assure that the calculated limit can be met at all times by the best-performing 

source(s)) the EPA has proposed a floor that results in a greater-than-average level of emissions, 

the commenter misunderstands the meaning of the upper prediction limit. The UPL is in fact a 

reflection of the relevant source or sources’ performance over time, and is calculated using the 

mathematical average emissions level of those sources based on stack test data, and then 

applying a factor that addresses the sources’ expected variation in emissions over time. As noted 

above, the D.C. Circuit has recognized that it is appropriate for the EPA to account for variability 

in establishing MACT standards. The data gathered through emission testing of sources in the 

ferroalloys source category are short-term measurements rather than measures of what has been 

and can be achieved over time by the best performing source or sources. The EPA also disagrees 

that it lacks discretion to use the UPL in establishing MACT standards and as earlier stated that 

the term “average emission limitation” is unambiguous. In fact, the D.C. Circuit has long 

recognized the ambiguity in this term. See NACWA v. EPA, 734 F.3d at 1131 (noting that court 

has accorded Chevron deference to EPA’s interpretation of CAA sections 129 MACT floor 

requirement) and 112 (“the phrase ‘average emissions limitation achieved by the best performing 

12 percent of units’ could be interpreted several different ways, with several different variations 

of what the MACT floor is supposed to represent”). The phrase “average emission limitation 

achieved by the best performing 12 percent of units” simply says nothing about the methodology 

the EPA should use to determine what the best performing sources are actually achieving. 

Absent a method for adjusting for variability like the UPL, a straight average of test runs for a 

unit does not capture the performance of a unit over time. As outlined in the UPL memorandum, 

we use short-term test data to determine the actual performance of the best unit or units over 

time, based on the average of the emissions data.

37. Comment: One commenter (1042-0347) stated that use of the 99-percent 

confidence level in the UPL approach results in proposed floors that are based on the EPA’s 

hypothetical emission levels that are much higher than the level in the emissions data in the 

record, and that the EPA should collect better test data if the available data do not accurately 

reflect what sources have achieved. The commenter contended that the EPA may not collect test 

data and then suggest that the data do not actually reflect source achievements.

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Response: The UPL is in fact a reflection of the relevant source or sources’ performance 

over time, and is calculated using the mathematical average emissions level of those sources 

based on stack test data, and then applying a factor that addresses the sources’ expected variation 

in emissions over time. While we acknowledge that the UPL can be calculated at different 

confidence levels, we selected the 99 percent level to provide reasonable assurance that the limit 

can be met at all times by a source with emissions at the average level achieved by the best 

performing source or sources. The emissions data submitted by the industry to support this 

rulemaking were collected following the procedures specified in EPA reference test methods and 

under normal process conditions; however, the emissions data submitted to EPA represent 

emissions over the short term (e.g., a few hours per year). The purpose of the UPL is to predict 

the level of emissions that the sources upon which the floor is based are expected to meet over 

time, considering both the average emissions level achieved as well as emissions variability and 

the uncertainty that exists in the determination of emissions variability given the available, shortterm data. As noted above, the D.C. Circuit has recognized that it is appropriate for the EPA to 

account for variability in establishing MACT standards. The data gathered through emission 

testing of sources in the ferroalloys source category are short-term measurements rather than 

measures of what has been and can be achieved over time by the best performing source or 

sources. The EPA also disagrees that it lacks discretion to use the UPL in establishing MACT 

standards and as earlier stated that the term “average emission limitation” is unambiguous. In 

fact, the D.C. Circuit has long recognized the ambiguity in this term. See NACWA v. EPA, 734 

F.3d at 1131 (noting that court has accorded Chevron deference to the EPA’s interpretation of 

CAA sections 129 MACT floor requirement) and 112 (“the phrase ‘average emissions limitation 

achieved by the best performing 12 percent of units’ could be interpreted several different ways, 

with several different variations of what the MACT floor is supposed to represent”). The phrase 

“average emission limitation achieved by the best performing 12 percent of units” simply says 

nothing about the methodology EPA should use to determine what the best performing sources 

are actually achieving. Absent a method for adjusting for variability like the UPL, a straight 

average of test runs for a unit does not capture the performance of a unit over time. As outlined 

in the UPL memorandum, we used short-term test data to determine the actual performance of 

the best unit or units over time, based on the average of the emissions data.

Finally, the EPA is tasked with setting standards using available data and, while we agree 

that more data is desirable, the standards that we proposed are based on a considerable amount of 

data that, while not perfect, provide sufficient information with which to develop standards that 

reasonably reflect the required levels of performance. (“EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a problem. We generally defer to an 

agency's decision to proceed on the basis of imperfect scientific information, rather than to invest 

the resources to conduct the perfect study.” Sierra Club v. EPA, 334 U.S. App. D.C. 421, 167 

F.3d 658, 662 (D.C. Cir. 1999) (citation omitted)). The EPA must rely on emission test methods 

that are available to the Agency and to sources. The task of selecting an appropriate test method 

is one for the technical expertise of the agency, and the approach we take to setting standards 

accounts for the accuracy of the emission test method. See NACWA at 1155. As described in the 

UPL memorandum, our standards reflect the average emission limitation achieved by the best 

source or sources as required under the statute.

38. Comment: One commenter (1042-0347) contended that the EPA violated CAA 

section 7412(d)(3) by failing to ensure that the average of emissions achieved in practice by the 

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best-performing sources is reflected in the floors it proposes based on use of Representative 

Detection Limit values (RDL). The commenter opined that the EPA’s documentation regarding 

the RDL does not clearly identify which sources contained BDL data and when the 3xRDL 

approach was used to create floors; therefore, it is not possible to provide a meaningful comment 

without a clear explanation on this.

Response: We disagree with the commenter that the documentation regarding the use of

the RDL approach (Revised Technical Approach for Wool Fiberglass MACT Floor Calculations) 

was unclear. However, because the data submitted by the industry were claimed as CBI, we were 

unable to present specific data values in the memorandum.

We note that the use of the RDL in establishing the emission limit for HCl is consistent 

with the approach approved by the court in NACWA v. EPA, 734 F.3d 1115, 1154 – 55. 

Specifically, the EPA calculated a numeric limit according to our standard UPL-based procedure, 

and then compared that result to a value equal to 3 x RDL. The 3 x RDL value is a value that the 

EPA established as the lowest level of emissions that can be accurately measured using the 

required test method. Descriptions of the development of 3 x RDL values and the rationale that 

was upheld by the court are included in Docket Item No. EPA-HQ-OAR-2010-0895-0034. Our 

standard MACT methodology includes comparing each calculated limit to the 3 x RDL value in 

order to ensure that emissions at the level of the standard can be accurately measured. For the 

emission limit being questioned by the commenter, the 3 x RDL value was greater than the UPLbased value, and we therefore set the limit at the 3 x RDL value. In the court decision cited 

above, the court stated the following regarding this methodology:

“We agree with EPA that its method of incorporating nondetect data is reasonable, and 

not arbitrary or capricious. We do not expect EPA to perform the impossible, see Cement

Kiln, 255 F.3d at 871, and that includes recording emission levels that are not accurately 

detectable with its current emissions testing technology. As EPA explains the issue, 

emission levels from zero up to some value above the method detection level cannot be 

stated with accuracy. Because any emission level EPA selects at that point will 

necessarily be an estimate, EPA adopted a method to account for measurement 

imprecision that has a rational basis in the correlation between increased emission values 

and increased testing precision.”

39. Comment: One commenter (1042-0347) contended that the EPA may not lawfully 

account for malfunctions in setting standards, and thus may not use the UPL method because it 

accounts for variability that builds in potential malfunction-caused higher emissions as a 

potential driver of the floor. The commenter opined that use of the UPL is just as likely to create 

a weaker standard due to sources operating improperly as it is to account for any other causes of 

variability. The commenter contended that use of the UPL method is unlawful and arbitrary 

because the EPA does not explain how use of the UPL method will avoid accounting for 

malfunctions in setting standards.

Response: There is nothing in CAA section 112 that directs the agency to consider 

malfunctions in determining the level “achieved” by the best performing sources when setting 

emission standards. As the D.C. Circuit has recognized, the phrase “average emissions limitation 

achieved by the best performing 12 percent of” sources “says nothing about how the 

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performance of the best units is to be calculated.” Nat'l Ass'n of Clean Water Agencies v. EPA, 

734 F.3d 1115, 1141 (D.C. Cir. 2013). As discussed above, nothing in CAA section 112 requires 

the agency to consider malfunctions as part of that analysis, accounting for malfunctions in 

setting emission standards would be difficult, if not impossible, and could lead to standards that 

are not reflective of levels achieved by a well-performing non-malfunctioning source.

Regarding the commenter’s assertion that use of the UPL is unlawful and arbitrary 

because we do not explain how to avoid accounting for malfunctions when setting standards, the 

EPA does not use emissions test data collected from processes during malfunctions to establish 

emissions standards. 

40. Comment: One commenter (1041-0081) argued that the EPA should use the 

average, not a high variability factor, in setting the MACT standards for these pollutants, as use 

of a variability factor is unsupported and results in a standard that is higher than appropriate.

The commenter noted that the EPA may consider variability in calculating the best 

sources’ performance. The commenter contended that the EPA’s method of considering 

variability seeks to assure that none of the sources among those identified as best performers 

would ever exceed the floor level which ignores the reality that sources’ emission levels are 

largely within their control. The commenter claimed that a great deal of variability may be 

statistically conceivable if the EPA chooses a high enough prediction limit (in this case the 99th 

percentile), but that does not mean that a well-run source actually would experience such 

variability. Indeed, the commenter asserted that one of the main points of having emission 

standards is to ensure that sources not only deploy the appropriate control measures, but use 

those control measures properly and consistently to minimize emissions.

Citing dicta in a 1999 D.C. Circuit decision (Sierra Club v. EPA, 167 F.3d 658, 665), the 

commenter stated that industry groups have argued that EPA should set weak standards to 

accommodate sources’ worst reasonably foreseeable performance. According to the commenter, 

those dicta have no precedential value and do not bind the EPA’s rulemaking in any way. The 

commenter further stated that even if they constituted a holding – which they do not – they do 

not apply to the EPA’s floors for existing sources. Moreover, the commenter observed that the 

underlying assumption – that if a particular standard reflects what a given source achieves in 

practice, that source will never violate the standard – is plainly flawed. No matter what level a 

given source normally achieves in practice, the commenter asserted that the source may emit far 

higher levels if it is not run properly. The commenter cited the following example: if a careless 

operator allows a combustion unit to operate outside the proper parameters for temperature and 

pressure, its emissions may increase. Likewise, the commenter observed that if a baghouse is not 

properly maintained or the pressure drop is allowed to exceed the proper parameters, emissions 

may increase.

According to the commenter, the high emissions that occur when a source is poorly 

operated must be treated as exceedances or violations of the emission standards, even though it is 

foreseeable that periods of sloppy or negligent operation may occur even at the source with the 

lowest emission tests. The commenter argued that floors should not be set at a level that the best 

performers could never exceed even when they operate poorly or fail to maintain their control 

equipment. Indeed, the commenter claimed that such an approach violates CAA section 

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112(d)(3) and frustrates its intent. The commenter asserted that floors must be set at the average 

emission level achieved by the best performers when they are operating properly. The 

commenter contended that using a UPL approach to set standards reflecting the worst 

performance these sources could have in a purely statistical sense does not yield an accurate 

picture of the best sources’ actual performance, and it is especially arbitrary in the absence of 

any explanation of why EPA thinks that the relevant best sources’ performance would ever be so 

bad, other than the fact that it is statistically possible.

Response: We disagree with the commenter that the EPA should use the short-term

average in setting MACT standards. We also disagree with the comment that using the UPL in 

MACT floor calculation does not yield an accurate picture of the best sources actual 

performance. As explained in two memoranda submitted to the docket in support of the 2014 

supplemental proposal (the limited data sets memorandum and the UPL memorandum), the UPL 

represents the average emission limitation achieved by the best performing 12 percent (or best 5 

sources for subcategories with fewer than 30 sources) as required by the statute. Section 

112(d)(3) of the CAA requires the EPA to promulgate standards for major sources of HAP that 

are based on MACT performance. For existing sources, MACT standards must be at least as

stringent as the average emission limitation achieved by the best performing 12 percent of 

existing sources (for which the Administrator has emissions information) or the best performing 

5 sources for source categories with less than 30 sources. For new sources, the MACT standards 

must be at least as stringent as the control level achieved in practice by the best controlled 

similar source. CAA Section 112(d)(3). In construing CAA section 112(d)(3), the D.C. Circuit 

has stated that “[t]hough section 7412(d)(2) does direct EPA to require the maximum emission 

reduction that it determines to be achievable, section 7412(d)(3) provides that the maximum 

degree of reduction in emissions that is deemed achievable... shall not be less stringent that what 

the best-performing sources achieve. Section 112(d)(3) therefore limits the scope of achievable 

in section 7412(d)(2).” Sierra Club v. EPA, 479 F.3d at 878. (Internal quotations omitted). As the 

Court has also explained “[i]t is reasonable to suppose that if an emissions standard is as 

stringent as the emissions control that is achieved in practice by a particular unit, then that 

particular unit will not violate the standard. This only results if “achieved in practice” in CAA

section 112(d)(3) “to mean achieved under the worst foreseeable circumstances.” Sierra Club v. 

EPA, 167 F.3d 658, 665. Moreover, the Court has further stated that “to comply with the statute, 

EPA’s method of setting emissions floors must reasonably estimate the performance of the best 

performing plants.” Id. And, that “EPA would be justified in setting the floor as a level that is a 

reasonable estimate of the performance of the best controlled similar unit under the worst 

reasonably foreseeable circumstances.” Id. Earlier, in National Lime Ass’n v. EPA, 627 F.2d 416, 

431 n.46, the Court also stated that “where a statute requires that a standard be achievable it must 

be achievable under most adverse circumstances which can reasonably be expected to recur.” As 

we have explained in various rules, CAA section 112(d)(3) does not address the question of 

whether, in assessing which sources perform best or are best controlled, emission levels should 

be evaluated either over time or in a single test result. We believe, however, that our MACT 

floor calculation should identify the best performers (i.e., the best performing 12 percent or best 

performing five sources in smaller source categories for existing sources, and the best controlled 

single source for new sources) as those sources likely to emit the least HAP over time 

considering variability. Further, the D.C. Circuit has held repeatedly that variability of best 

performing sources may be taken into account in establishing MACT floors. Sierra Club v. EPA, 

479 F.3d at 881-882. See also National Lime Ass’n v. EPA, 627 F.2d 416, 431 n.46, 443 (D.C. 

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Cir. 1980). Therefore, we believe it is appropriate to consider statistical variability in order to 

ensure that units could meet the floors at all times.

Further, in the context of development of MACT floors, the UPL is a value, calculated 

from a dataset, which identifies the average emissions level that a source or group of sources is 

meeting and would be expected to meet a specified percent of the time that the source is 

operating. As explained in our November 13, 2014 supplemental proposal, contrary to the 

commenter’s assertion, the NACWA court did not find the UPL to be an arbitrary approach, but 

simply asked for a better explanation from the Agency. The UPL memorandum provides the 

explanation of what the UPL represents sought by the NACWA Court. It also explains why the

UPL is representative of the level of performance achieved by the best performing unit or units. 

The court did not state that the “average emissions limitation achieved by the best performing 12 

percent” must be equal to the mean of the available data, as suggested by the commenter, and in 

past decisions the court has upheld that it is appropriate for EPA to account for variability when 

establishing numeric MACT standards. See Mossville Environmental Action Now v. EPA, 370 

F.3d 1232, 1241-42 (D.C. Cir. 2004).

We also refer the commenter to the proposal MACT floor memorandum, which is in the 

rulemaking docket. This memorandum provides a detailed discussion of the EPA’s authority to 

consider variability, especially given that MACT and other technology-based standards are 

necessarily derived from short term emissions test data and such data are not representative of 

the range of operating conditions that the best-performing facilities face on a day-to-day basis. In 

statistical terms, each test produces a limited data sample, not a complete enumeration of the 

available data for performance of the unit over a long period of time. The EPA, therefore, often 

needs to adjust the short-term data to account for these varying conditions in order to properly 

estimate these sources’ performance over time. The types of variability that the EPA accounts for 

include variability between and within tests at the same unit as well as between units in the pool 

of “best performing units”. This memo also describes the EPA’s selection of the UPL 

methodology to address such variability.

Additionally, the EPA has incorporated new data and data corrections received during the 

public comment period that were based on all emission stack test data of appropriate quality 

available to the EPA. (“EPA typically has wide latitude in determining the extent of datagathering necessary to solve a problem. We generally defer to an agency's decision to proceed on 

the basis of imperfect scientific information, rather than to invest the resources to conduct the 

perfect study.” Sierra Club v. EPA, 334 U.S. App. D.C. 421, 167 F.3d 658, 662 (D.C. Cir. 1999) 

(citation omitted)). As a result, we have revised the appropriate limits in the final rule. These 

calculations can be found in the memoranda “Revised MACT floor Analysis for the Wool 

Fiberglass Manufacturing Source Category” and “Revised MACT floor Analysis for the Mineral 

Wool Production Source Category,” which are in the docket for this rulemaking.

D. SSM Provisions

41. Comment: One commenter (1041-0073/1042-0111) stated that the 2011 

amendments to the SSM provisions make the rule more stringent and that the EPA does not have 

this authority. 

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The commenter supported their assertion noting that CAA section 112(d)(6) tells the EPA 

to “review and revise as necessary (taking into account developments in practices, processes, and 

control technologies), emissions standards promulgated under this section no less often than 

every 8 years.”, but that the EPA did not invoke its authority under CAA section 112(d)(6) to 

support the SSM provisions in their 2011 proposal (see, e.g., 76 Fed. Reg. at 72794 cols. 1-2). 

The commenter continued, stating that CAA section 112(d)(6) does not provide broad authority 

to reconsider aspects of previously issued MACT standards unrelated to “developments in 

practices, processes, and control technologies.” Thus, the commenter questioned the EPA’s 

authority to revise the standard as it does with the proposed SSM Provisions. 

Per the commenter, reassessing existing NESHAP that were based on the MACT floor 

now, and imposing more-stringent requirements, would be inconsistent with the statute’s 

provision of technology-review and residual-risk authority to follow establishment of MACT 

standards and with Congress’s desire for finality evident in the judicial review provisions of 

CAA section 307(b). 

The commenter stated that challenges to MACT standards needed to be raised within 60 

days of their promulgation. The commenter highlighted that this provision ensures that regulated 

entities, the EPA, and the public know what emission limitations will apply to the source, rather 

than having those limitations be subject to flux. In the instant case, the commenter contended, 

facilities regulated by the two NESHAP long ago made capital investment decisions and

developed and honed their operating procedures to meet the existing MACT standards. The 

commenter highlighted that CAA does not allow the EPA simply to revisit the analysis and 

decisions involved in developing emission standards that meet the requirements of CAA sections 

112(d)(2) and (3).

Response: In the 2011 proposal (76 FR 72775, 72794), we explained that the D.C. Court 

had recently vacated the SSM exemption contained in 40 C.F.R. sections 63.6(f)(1) and

63.6(h)(1). Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008) cert. denied, 130 S. Ct 1735 

(2010). The exemptions for startup and shutdown and for malfunctions in subpart DDD (Table 1 

and 63.1180(d)) and NNN (Table 1) are inconsistent with the holding in Sierra Club that 

emissions limitations under CAA section 112 must apply continuously. Thus, EPA is eliminating 

the SSM exemption in subparts DDD and NNN. The EPA does not claim that the Sierra Club

case constrains its authority to prescribe unique standards for startup and shutdown or 

malfunction periods. 

In the 2011 proposal, the EPA also explained that unique standards were not necessary 

for periods of startup and shutdown. Some industry representatives believe, based on 

observations, that emissions during periods of startup and shutdown are lower than emissions 

during production. Other industry representatives believe, based on observation, that startup and 

shutdown emissions may be higher for some pollutants while other pollutants are not emitted at 

all during such periods. However, with the exception noted below, no industry representatives 

provided emission monitoring, testing, or records of visual emissions observations in support of 

separate emission limits for startup or shutdown. We explained that the pollutants emitted from 

these processes are captured and controlled by the technologies in place regardless of the 

concentration of pollutant loading at the inlet to the control devices. We also explained that 

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applicable control devices are started up prior to the process units and are also operational during 

the shutdown phase of the process. (76 FR 72794). 

We therefore continue to believe that unique standards are not necessary for periods of 

startup and shutdown. In the final rule, we are establishing work practice standards that apply at 

all times.

With regard to our approach to periods of malfunctions, we explained in the 2011 

proposal that while periods of startup, normal operations and shutdown are all predictable and 

routine, malfunctions in contrast are “sudden, infrequent and not reasonably preventable failure 

of air pollution control and monitoring equipment, process equipment or a process to operate in a 

normal or usual manner.” (40 CFR 63.2) As the preamble explained, the EPA has determined 

that CAA section 112 does not require that emissions that occur during periods of malfunction be 

factored into development of CAA section 112 standards. That approach is consistent with CAA 

section 112 and is reasonable. (72 FR 72794).

Further, the commenter is incorrect that CAA section 112(d)(6) provides the exclusive 

authority to address standards that apply during SSM events. In Medical Waste Institute v. EPA,

645 F.3d 420, 425-27 (D.C. Cir. 2011), the D.C. Circuit held that the EPA may permissibly 

amend improper MACT determinations, including amendments to improperly-promulgated floor 

determinations, using its authority under CAA sections 112(d)(2) and (3). Similarly, the absence 

of standards for periods of startup and shutdown and periods of malfunction is not proper. Sierra 

Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008) cert. denied, 130 S. Ct 1735 (2010); see also 

Medical Waste Incinerator, 645 F.3d at 426 (resetting MACT floor, based on post-compliance 

data, permissible when originally-established floor was improperly established). Additionally, 

Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011) confirms that “nothing 

prohibits the EPA from reassessing its standards more often” than every 8 years under CAA 

section 112(d)(6). The commenters are thus incorrect that CAA section 112(d)(6) provides the 

exclusive authority to address standards that apply during SSM events. Here, the EPA adopted 

no MACT standard at all during SSM events, an approach soundly rejected by the D.C. Circuit 

in Sierra Club v. EPA, 551 F.3d 1019. Consequently, the emission limits of the final rule apply at 

all times, including during periods of SSM. 

42. Comment: One commenter (1041-0073/1042-0111) stated the proposed SSM 

provisions are not required in order to be consistent with Sierra Club v. EPA and that it is 

unreasonable to require sources to meet technology-based emission standards during SSM 

periods. See 40 CFR section 60.8(c). The commenter believes this opinion is supported by the 

exemption of SSM periods under and incorporation by reference of the General Provisions SSM 

requirements in numerous MACT standards, but also noted that the Mineral Wool MACT 

specifically exempts SSM events rather than relying solely on reference to the General 

Provisions.

According to the commenter, the EPA suggested that its treatment of excess emissions 

during SSM events in the 2011 proposal is appropriate, even “required,” in order to make the 

standards “consistent with” the D.C. Circuit’s decision in Sierra Club v. EPA, 551 F.3d 1019 

(D.C. Cir. 2008), cert. denied, 130 S. Ct. 1735 (2010), which vacated the exemption for excess 

emissions during SSM events contained in the 40 CFR part 63, subpart A General Provisions for 

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emission standards for HAP under CAA section 112. See, e.g., 76 Fed. Reg. at 72775, col. 3; 

72787, col. 2; 72794 col. 1-3; 72795, col. 2-3. The commenter stated that D.C. Circuit’s Sierra 

Club decision does not compel or support the proposed SSM provisions because of the 

following:

1. The Sierra Club decision interpreted the NESHAP General Provisions, but did not 

dictate what the EPA may or may not include in category-specific MACT standards. 

See 40 CFR. section 63.1180(d); see also July 22, 2009 letter to counsel from Adam 

Kushner, Director of EPA’s Office of Civil Enforcement, Table 2 (stating that 

standards in 40 CFR. part 63 subpart DDD, among others, are “not affected” by the 

Sierra Club decision).

2. The Sierra Club decision does not preclude the EPA from applying different 

standards during SSM events than apply during normal operations, adding that 

section 302(k)’s “inclusion of [the] broad phrase” “any requirement relating to the 

operation or maintenance of a source to assure continuous emission reduction” in the 

definition of “emission standard” suggests that MACT standards can be consistent 

with CAA section 112 “without necessarily continuously applying a single standard.”

The commenter added that legislative precedent, court precedence, and the language of 

CAA section 112(h) supports application of a different standard during SSM events. The 

commenter stated that the language that the D.C. Circuit considered dispositive in interpreting 

EPA’s standards-setting authority under CAA section 112 has been in the statute since 1977, that 

the language in section 302(k) of section 111 exempted SSM periods, that sources are not 

required to meet NSPS emission limits under CAA section 111, and that nothing in the 

legislative history of the 1977 amendments to the CAA that suggests Congress intended to 

overturn that practice. See 40 CFR. Section 60.8(c).

The commenter continued that court decisions both before and after the CAA 

Amendments of 1977 have affirmed that special SSM provisions are appropriate in CAA section 

111 standards despite the “continuous basis” language in the definition of “emission limitation.” 

The commenter extended the NSPS rationale to MACT continuing that the legislative history of 

the CAA Amendments of 1990 does not suggest Congress intended different meanings in both 

111 and 112 language for the same terms “emission standard” and “emission limitation,” in the 

1990 amendments directing EPA to establish MACT standards.

Additionally, the commenter cited that the Sierra Club decision did not address EPA’s 

authority to set a “design, equipment, work practice or operational standard,” in lieu of a 

numerical emission limitation under CAA section 112(h) for SSM events. The commenter stated 

EPA told the Court that the General Provisions SSM exemption struck down in Sierra Club was 

not an alternative standard based on the work practice standard authority. See 551 F.3d at 1028. 

The commenter believes EPA argued in that case that CAA section 112(h) was irrelevant to its

authority to exempt excess emissions during SSM events, contending that even the “best 

performers” may be unable to achieve the emission limits of a MACT standard established for 

normal operations during SSM events.

The commenter argued that the approach the EPA is proposing would not establish the 

required “continuous CAA section 112-compliant standards” because MACT emission standards 

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must be “achievable”, and “achieved” by the best performers. See CAA section 112(d)(3). The 

commenter continued that the courts recognize that a “technology based standard discards its 

fundamental premise when it ignores the limits inherent in technology.” NRDC v. EPA, 859 F.2d 

156, 208 (D.C. Cir. 1988). The commenter cited an example of this from the D.C. Circuit: 

Portland Cement Ass'n v. Ruckelshaus, 486 F.2d 375, 398 (D.C. Cir. 1973), in a decision 

reviewing standards under CAA section 111, that “‘start-up’ and ‘upset’ conditions due to plant 

or emission device malfunction, is an inescapable aspect of industrial life and that allowance 

must be made for such factors in the standards that are promulgated.” Id. at 399. Another 

example cited by the commenter stated that in Essex Chem. Corp. v. Ruckelshaus, 486 F.2d 427, 

432 (D.C. Cir. 1973), cert. denied, 416 U.S. 969 (1974), the court held that SSM provisions are 

“necessary to preserve the reasonableness of the standards as a whole.” Id. at 433. The 

commenter contended that in National Lime Ass’n v. EPA, 627 F.2d 416 (D.C. Cir. 1980), a third 

case reviewing emission standards promulgated under CAA section 111, the court held that the 

CAA requirement that NSPS be “achievable” means that the standards must be capable of being 

met “on a regular basis,” including “under most adverse circumstances which can reasonably be 

expected to recur,” including during periods of SSM. 627 F.2d at 431 n.46.

Arguing that the CWA in this regard is analogous to the CAA, the commenter continued 

that courts have reached a similar conclusion under the CWA requirements that the EPA 

establish technology-based effluent limitations based on the best available control technology. 

The commenter cited one such case in which the court held that where the EPA knew that there 

would be periods where a discharger, even with “exemplary use of” the identified best 

technology, would exceed the effluent limitations because of conditions “beyond the control of 

the permit holder,” the EPA had violated the CWA by failing to provide an “upset provision” to 

address those periods. Marathon Oil Co. v. EPA, 564 F.2d 1253, 1273-74 (9th Cir. 1977). See 

also, e.g., NRDC v. EPA, 859 F.2d at 207 (distinguishing between technology-based effluent 

limitations, where some provision for “upsets” is required, and water-quality-based effluent 

limitations, which are tied to achieving water quality standards rather than based on available 

technology, and therefore need not include an upset provision).

The commenter stated that, in the preamble to the 2014 proposal, the EPA acknowledges 

this precedent, but suggests that “intervening case law such as Sierra Club v. EPA and the CAA 

1977 amendments undermine the relevance of these cases today.” 76 Fed. Reg. at 72795 col. 3. 

According to the commenter, the EPA does not explain why it believes that to be the case but 

contends Sierra Club v. EPA did not address this precedent, and the 1977 CAA amendments 

support the conclusion that emission standards should account for the inability of a source to 

meet the normal emission limits during particular circumstances. Moreover, the commenter 

contended that National Lime Association decision discussed above, which relied in part on the 

cases the EPA referenced in the preamble, and which addresses the need for emission limits that 

address reasonably anticipated adverse circumstances, post-dates the CAA Amendments of 1977 

by 3 years.

The commenter also stated that the Sierra Club decision did not prohibit the EPA from 

setting a “requirement relating to the operation or maintenance of a source to assure continuous 

emission reduction” as the emission standard to apply to malfunctions. See 551 F.3d at 1027. 

The commenter contended that the Sierra Club decision only rejected the EPA’s assertion that it 

had discretion to decide not to impose any emission standard covering SSM periods. See Id. at 

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1027-28, 1030 (noting that the EPA was not claiming that the General Provisions SSM 

exemption was either an emission standard under CAA section 112(d) or a design, equipment, 

work practice, or operational standard under CAA section 112(h)).

The commenter argued that, despite implications to the contrary, the Sierra Club decision 

recognized that different standards may (and in some cases must) apply during non-standard 

operating conditions, such as SSM.

Response: As explained in our responses to other comments in this section, the 

exemptions for startup and shutdown and for malfunctions in subparts DDD and NNN 

promulgated in 1999 are inconsistent with the holding in Sierra Club that emissions limitations 

under CAA section 112 must apply continuously. As also earlier explained, we do not claim that 

the Sierra Club decision constrains our authority to prescribe unique standards or work practice 

standards during startup and shutdown periods where such standards are justified. We have 

evaluated whether different standards during startup and shutdown periods are justified, and in 

this case, we believe different standards are not warranted. We maintain that control devices, 

such as baghouses for PM and metal HAP particulate control and regenerative thermal oxidizers 

(RTOs) for control of COS, are started prior to process units in use by these sources and are also 

operational during the shutdown phase, and to require that the emission limits apply at all times. 

However, based on comments received from representatives of the wool fiberglass 

industry during a December 12, 2012 meeting discussing this and other topics, we added a 

provision in the April 15, 2013 supplemental proposal that required sources to demonstrate 

compliance with the limits during periods of startup by showing the emissions are routed to the 

control device operated at the same conditions that showed compliance with the standard during 

the most recent performance test. In the 2014 supplemental proposal, we added a requirement for 

facilities to maintain records that show that only clean fuels were used during startup and 

shutdown periods. We also added a requirement for cold-top furnaces at wool fiberglass facilities 

to maintain records that show that only cullet was used as the raw material during startup. 

With respect to periods of startup and shutdown, we agree that in some circumstances, 

separate standards for such periods may be appropriate. However, as explained in the preamble 

to the 2013 proposal (78 FR 22378), we believe our approach to periods of startup and shutdown 

is reasonable because we have taken into account these periods and expect sources will be able to 

meet emission limits during such periods based on comments the agency received on its various 

proposals. The EPA has established work practice standards in this rule that apply during startup 

and shutdown periods. 

For periods of malfunction, the EPA provided a detailed justification for its approach to 

malfunctions in the preamble to the 2011 proposed rule (76 FR 72794). As the D.C. Circuit 

noted in Sierra Club v. EPA, 167 F.3d 658 (D.C. Cir. 1999), the phrase "average emissions 

limitation achieved by the best performing 12 percent of units” in section 112 of the CAA "says 

nothing about how the performance of the best units is to be calculated.” Id. at 661. Congress has 

not directly addressed the issue of whether emissions that occur during periods of malfunction 

must be taken into account in calculating the performance of the best units and the EPA’s 

approach to malfunctions is reasonable for the reasons set out in the preamble to the proposed 

rule. The EPA further explained that the performance of units that are malfunctioning is not 

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reasonably foreseeable and cited case law supporting its approach to malfunctions. See Sierra 

Club at 665 (discussing need to take into account the worst reasonably foreseeable performance) 

and Weyerhaeuser v. Costle, 590 F.2d 1011, 1058 (D.C. Cir. 1978) (“In the nature of things, no 

general limit, individual permit, or even any upset provision can anticipate all upset situations.”).

Although the EPA bases emission standards on different manners of operations and 

circumstances, the EPA only takes into account conditions that are “foreseeable” and “which can 

reasonably be expected to recur.” Sierra Club, 167 F.3d at 665; see also Nat. Lime, 627 F.2d. at 

431, n.46. Virtually no malfunction is foreseeable in terms of its nature, timing or effect on 

emission levels and no operator knows if or when a malfunction could recur.

With respect to commenters’ suggestion that EPA consider work practice standards, the 

decision to use a work practice standard is wholly within the discretion of the EPA. See CAA 

section 112(h) (“[T]he Administrator may, in lieu [of a numeric standard], promulgate a design, 

equipment, work practice, or operational standard, or combination thereof.”). In exercising the 

option to establish a work practice standard, that standard must “in the Administrator’s judgment

[be] consistent with the provisions of subsection (d) or (f).” CAA section 112(h)(1) (emphasis 

added). These subsections make clear that the EPA is to base emission standards on the emission 

levels already achieved by the best performing sources and to ensure that public health is 

protected, as applicable. This means that work practice standards, although written in nonnumeric form, must still satisfy statutory requirements such as those applicable to MACT 

standards, including the requirement to be no less stringent than the MACT floor.

It is just as difficult to establish a work practice standard for malfunctions that can 

approximate the level of emission reduction achieved by the best performing sources during 

malfunctions as it would be to factor emission levels that occur during malfunctions into the 

numeric standards, as discussed above, the EPA would have to design a single work practice 

standard that applies equally to a tank explosion as it does to innumerable types of operator error, 

computer glitches or a myriad of other unknown events, or alternatively create innumerable work 

practice standards.

In summary, the EPA believes that, based on this rulemaking record, it would be clearly 

inappropriate to set a work practice standard for malfunctions in lieu of the otherwise applicable 

numerical emission limit. We also note that we would consider any response to violations caused 

by a malfunction on a case-by-case basis through the exercise of enforcement discretion. 

Regarding startup and shutdown periods, we do not replace the emission limits with a work 

practice standard, but we provide an option for companies to demonstrate compliance with the 

standard during periods of startup and shutdown. Thus, contrary to the commenter’s argument, 

we believe that the standards that apply during startup and shutdown periods will establish 

“continuous section 112-compliant standards” that the Sierra Club decision concluded are 

required. We also disagree with the comment that the Sierra Club decision “did not by its terms” 

concern what EPA may or may not include in category-specific MACT standards. (Citing letter 

to counsel from Adam Kushner, Director of EPA’s Office of Civil Enforcement, July 22, 2009 

(see Table 2 of the letter)). This letter, which addressed potential compliance issues arising from 

the Sierra Club court decision, contained EPA’s plans for addressing those concerns, including 

potential future revisions to CAA section 112(d) standards. As explained in the letter, our initial 

analysis indicated that certain rules, such as the mineral wool production NESHAP, included 

specific regulatory text exempting or excusing compliance during SSM events in addition to 

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cross-references to 40 CFR. Sections 63.6(f)(1) and 63.6(h)(1). At the time, we indicated that the 

vacatur in Sierra Club would have no direct impact on such source category-specific SSM 

provisions because we believed these provisions were not challenged in Sierra Club. We, 

however, also recognized that the legality of those source-category specific provisions may have 

been called into question and indicated that we were evaluating them in light of Sierra Club. 

“The tables attached to this letter are based on the EPA‘s initial analysis and are, therefore, 

subject to change.” (p. 3) [footnote omitted]. We have now evaluated the relevant provisions and 

determined that they need to be revised to address the Sierra Club decision.

We disagree with commenters claim that case law under the CAA and CWA supports its 

argument that EPA’s approach to startup and shutdown and malfunction periods is inconsistent 

with CAA section 112. As explained above and in the preamble to the 2013 and 2014 proposed 

rules, the EPA has taken into account startup and shutdown periods in determining appropriate 

standards. Further, the case law cited by commenters does not undermine the EPA’s approach to 

malfunctions. As noted in the preambles to the 2013 and 2014 proposed rules, the relevance of 

Portland Cement and Essex Chem. Corp. is questionable in light of subsequent case law and the 

1977 amendments to the CAA definition of emission standard requiring that such standards be 

continuous. As the D.C. Circuit noted in National Lime v. EPA, 627 F.2d. 416, 434 at n 54, 

“[w]hether the 1977 Amendments have effectively repealed the regulations permitting flexibility 

to account for startups, shutdowns and malfunctions regulations applauded by this court in 

Portland Cement I, 486 F.2d at 398-99 is certainly unclear.” The EPA’s approach to malfunction 

is consistent with CAA section 112 and is a reasonable interpretation. 

In any event, the EPA’s overall approach to malfunction events in this rule is consistent 

with the approach set forth in the EPA’s 1972 proposed rules cited favorably in Portland Cement 

and Essex Chemical in that both EPA’s approach today and in 1972 impart a construction of 

"reasonableness" to the standards as a whole and adopts a more flexible system of regulation 

than can be had by a system devoid of "give." Portland Cement at 399. Portland Cement and 

Essex criticized the EPA regulations that contained no specific provisions to address 

malfunctions and the EPA‘s assertion that malfunctions would be dealt with by the informal 

exercise of discretion in the agency‘s enforcement activities. Those decisions did not require 

exemptions or less stringent standards for malfunction events as the commenter suggests. 

The NRDC v. EPA (859 F.2d 156, 207(D.C. Cir. 1988)) case cited by commenter 

interprets provisions of the CWA that are different in nature than provisions governing standards 

under section 112 of the CAA. Furthermore, the discussion of technology-based standards in the 

NRDC case is dicta. Nevertheless, the EPA‘s approach to malfunctions is also consistent with 

NRDC. 

43. Comment: One commenter (1041-0073/1042-0111) stated that the EPA should 

fully justify applying the same emission limitations during startup and shutdown as during 

normal operations. 

The commenter contended that it is not apparent from the cursory treatment of this issue 

in the preamble, however, that the EPA has sufficiently justified the conclusion that emissions 

during startup and shutdown would be no greater than during normal operations, adding that a 

control device may be less efficient when the pollutant concentrations in the gases to be treated 

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are lower than during steady state operation (as they often will be when a process is starting up 

or shutting down). See, e.g., 68 Fed. Reg. 1276 at 1287-88 (January 9, 2003). The commenter 

noted that higher emissions may occur during startup and shutdown, either on a total mass basis 

or on a mass per unit of production basis. See, e.g., 76 Fed. Reg. 63878, 63883 col. 2 (October 

14, 2011). 

The commenter stated that, even if the EPA did have authority to go back and change the 

existing MACT standards, the EPA would have to justify why the decisions reflected in the 

current standards are wrong and why the new standards meet the required criteria that the EPA 

should satisfy in issuing MACT standards under CAA sections 112(d)(2) and (3). The 

commenter stated that the EPA did not make either showing in the 2011 proposal.

The commenter argued that the EPA has not analyzed sufficient data on emissions during 

startup and shutdown to justify the conclusion that the emission limits should apply at all times, 

and that the EPA should conduct a thorough analysis to determine whether the best-performing 

sources (the MACT floor) achieve the same emission limitation during startup and shutdown as 

during normal operations. 

The commenter noted that adequate data do not often exist to establish emission limits for 

periods of startups and shutdowns because regulations generally prohibit compliance testing 

during SSM conditions, instead requiring data to be obtained during normal operating conditions. 

Also, the commenter stated that atypical pollutant concentrations outside of the monitoring 

equipment’s span, stack conditions outside of QA/QC parameters, and limitations of the 

monitoring equipment may yield unusable data, or data that would understate emissions during 

startup and shutdown periods. 

The commenter added that a clear demarcation of startup, shutdown, and malfunction 

events is needed to avoid confusing one event with another in the data sets. The commenter 

surmised that the EPA may be analyzing data for malfunctions that should be included in startup 

or shutdown emission calculations.

Response: We disagree with the comment that the agency provided a “cursory” 

description of the proposed startup and shutdown provisions. As explained in the 2011 proposal 

(76 FR 72775, 72794), the D.C. Court had recently vacated the SSM exemption contained in 

NESHAP General Provisions (40 CFR sections 63.6(f)(1) and 63.6(h)(1)). Therefore, we 

eliminated the SSM exemption in subparts DDD and NNN and proposed that the emission 

limitations under CAA section 112 must apply continuously. In the April 2013 proposal, we 

withdrew our previously-proposed alternative emission limits for startup and shutdown, and 

instead proposed that sources may demonstrate compliance with the MACT floor emission limits 

during periods of startup and shutdown. Also, in our November 2014 notice, we proposed work 

practice standards for startup and shutdown periods, under CAA section 112(h), based on 

comments regarding the practices used by the best performers among mineral wool producers to 

minimize emissions during these activities. 

As explained in the 2013 and 2014 proposals, industry trade association conducted a 

voluntary survey among all owners and operators of mineral wool and wool fiberglass 

manufacturing facilities. The survey sought test data for PM, CO, and HAP emissions and 

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information on process equipment, control devices, point and fugitive emissions, practices used 

to control point and fugitive emissions. The survey also sought emissions data during periods of 

startup and shutdown. (Form D of Enclosure 1). We did not receive any relevant data for periods 

of startup and shutdown in response to the survey. We also note that although we again requested 

test data for startup and shutdown events at proposal, the EPA did not receive any relevant data 

on startup and shutdown in response to the survey. 

The EPA is allowed to set standards using available information, under CAA section 

112(d)(3)(A) (Standards are to be based on the average emissions limitation achieved by the best 

performing units “for which the Administration has information).” Further, as earlier explained, 

we do not claim that the Sierra Club decision constrains our authority to prescribe unique 

standards during SSM periods. 

We also disagree with the comment that there is no demarcation between malfunctions 

and startup and shutdown events. As explained at proposal (79 FR 68015, November 13, 2014), 

the EPA believes that malfunction events should be treated differently than periods of startup and 

shutdown, which are predictable and routine aspects of a source’s operations. As also explained, 

the EPA has determined that CAA section 112 does not require that emissions that occur during 

malfunctions be factored into development of CAA section 112 standards. Because startup and 

shutdown periods are part of a source’s standard operating procedures, the same approach to 

compliance with, and enforcement of, applicable emissions standards during those periods 

should apply as otherwise applies during a source’s operations. 

While the starting up or shutting down of a batch or continuous process is part of a 

regulated source’s standard operating procedures, it is not a period of normal production, that is, 

no mineral wool melt or usable glass is being produced during periods of startup and shutdown. 

If data were collected for either source category during periods of startup, shutdown or 

malfunction, those data would not be representative of normal operations, and would not be used 

to determine the emissions limits for normal production periods in the source categories. Such 

data would only be used to determine emission limits for periods of startup and shutdown. 

Because our emissions testing methods are currently only valid for periods of normal production, 

sources correctly tested only during such periods, and did not test for periods of startup or 

shutdown. If, in the future, new methods are developed for periods of startup and shutdown, we 

will consider amendments to these rules for such testing at that time.

As explained in response to earlier comments in this section, pollutants emitted from 

these industry processes are reduced by the control devices regardless of concentration at the 

inlet loading of the control device. Therefore, properly operated controls (that is, controls 

operated at the parameters established at the most recent successful performance test) would 

achieve the same emission limit as during normal operation. We therefore disagree with the 

commenter that even the best performers may not achieve the standards during periods of startup 

and shutdown. 

In the final rule, the EPA has established work practice standards that apply during 

startup and shutdown periods. See 40 CFR 63.1197 and 63.1388.

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44. Comment: One commenter (1042-0299) objected to the EPA proposing to allow 

sources to demonstrate compliance during startup and shutdown by showing that the emissions 

were controlled during these periods, because the commenter believes this amounts to an 

exemption from the standard--rather than compliance with the standard--during startup and 

shutdown periods. The commenter sees this requirement as only a recordkeeping exercise, not as 

a provision that limits emissions to levels that meet the limits of the proposed rule. The 

commenter believes this approach undermines enforcement of the rule and asks how the EPA 

enforces a recordkeeping provision to ensure compliance with a limit. The commenter also 

believes that this approach undermines citizen enforcement because these records cannot be 

accessed by the community. In an earlier letter submitted in response to the 2011 proposal (1041-

0081), the commenter suggested that the EPA should implement strong enforcement provisions 

to prevent emission spikes, malfunctions and other violations in a way that will be enforceable 

by citizens in the Title V permits for these source categories. The commenter asserted that the 

past exemption during periods of startup, shutdown, and malfunction shows the need for strong 

enforcement of the EPA’s standards to apply at all times.

In the more recent comments (1042-0299), the commenter asked why the EPA has not 

required work practices for startup and shutdown periods (e.g., use of certain raw materials, 

preheating empty furnace) for wool fiberglass facilities (major sources) as the EPA discussed in 

the preamble to the 2012 proposal because work practices establish specific requirements to 

ensure compliance with the emission limit. The commenter added that, to establish work practice 

standards, the EPA must demonstrate that an “alternative standard” is technologically or 

economically impracticable or is consistent with CAA subsection (d) or (f). The commenter 

noted that, in the original rule, the EPA acknowledged it has data to assess compliance during 

startup and shutdown (78 FR 22378, 22388).

Response: In the 2013 and 2014 proposals, we stated that the limits of the rule apply at 

all times. However, because emissions during startup and shut down periods are not at steady 

state (which is necessary for accurate emissions testing) and cannot be measured (as discussed in 

section VI.D of the preamble to the final rule), we considered ways in which a source could 

demonstrate that they meet the limits of the rule. One way to do this is to control the process 

emissions at all times using a control device that is operated at the same parameters as when the 

source conducted the most recent successful performance test, that is, the compliance test 

showing that the source met the limits. The control devices used in these processes are wet and 

dry electrostatic precipitators and fabric filters (baghouses). These types of controls achieve the 

same level of emission reduction regardless of loading as long as they are properly maintained 

and operated. However, to determine whether a control is properly maintained and operated, 

adequate recordkeeping must exist that documents the parameters of operation, frequency of 

maintenance and monitoring. Thus, the requirements of startup and shutdown are that sources 

must control all emissions during these periods and also must keep records of their operating, 

maintenance, and monitoring that demonstrate the controls are operational and properly 

functioning. 

Additionally, we do not believe this weakens or compromises the ability to enforce the 

rule, because it is straightforward to determine if sources can demonstrate compliance with the 

limits during startup and shutdown. Regarding citizen enforcement, failure of owners or 

operators to maintain records of control device operation during startup and shutdown periods 

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would be a violation of the standards. Under the provisions of 40 CFR 63.15, the public can 

request access to reports submitted to the regulatory agency whenever they choose, with the 

exception of information protected through 40 CFR part 2 (e.g., CBI). In addition, as discussed 

in section IV.F of this document, we are promulgating requirements for electronic reporting of 

emissions test data that will improve public access to emissions information.

Regarding work practice standards, we did not replace the emission limits with a work 

practice standard, but we provided an option for owners or operators to demonstrate compliance 

with the standard during periods of startup and shutdown. Thus, contrary to the commenter’s 

argument, we believe that the standards that apply during startup and shutdown periods will 

establish “continuous section 112-compliant standards” that the Sierra Club decision concluded 

are required.

Regarding the assertion that the EPA had previously indicated that it had data to assess 

compliance during startup and shutdown, the EPA does not have any such data. The commenter 

misinterpreted the EPA’s statement in the 2013 proposal preamble “Based on the information 

before the Agency, which includes information provided by industry, we expect facilities can 

meet the proposed emission standards during startup and shutdown.” (78 FR 22378) “The 

information before the Agency” includes the two docket items EPA-HQ-OAR-1042-0334 and 

EPA-HQ-OAR-1042-0307, which provide adequate information to establish a recordkeeping 

requirement, but not to establish emission limits during periods of startup and shutdown.

45. Comment: One commenter (1041-0126) objected to the monitoring requirements 

for control devices during startup and shutdown, adding that sources may have to install new 

control devices in order to demonstrate compliance during periods of startup and shutdown, a 

requirement that the commenter considered cost-prohibitive considering the emissions, while 

although unquantified, are likely negligible during this period of time. The commenter added that 

presumably some emissions may be higher during startup and shutdown, but that EPA does not 

have data on which to base the requirement that the emissions limit should apply during these 

periods.

Response: No data were provided by the commenter in support of statements regarding 

the magnitude of emissions during startup and shutdown. While we agree that emissions during 

startup and shutdown are likely to be negligible, emissions during this time may not be excluded 

from regulation. As addressed elsewhere in the response to comments received on the November 

25, 2011 proposed RTR, recent court decisions have made clear that sources subject to MACT 

must comply with the limits in the rule at all times, and are not exempt from regulation due to 

startup, shutdown, or malfunction. Further, according to information submitted by all mineral 

wool manufacturers, all cupolas are currently equipped with controls that can meet the limits of 

the rule, and curing and collection processes only operate when fed melt from the cupola. Thus, 

no facilities would have to purchase and install new air pollution control devices to comply with 

the startup and shutdown provisions, as alleged by the commenter. Additionally, we disagree 

with the commenter that monitoring the control device parameters is burdensome: according to 

information collected during site visits, all manufacturing processes, operating parameters and 

production processes are already monitored and recorded by sophisticated computerized systems. 

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In addition, we note that the commenter later filed an amended comment in a letter to 

EPA (EPA-HQ-OAR-2010-0142-0300) in support of the revised rule requirements for periods of 

startup and shutdown. 

46. Comment: One commenter (1041-0126) expressed concerned that mineral wool 

facilities may be in violation of the rule because their control devices may not be as effective 

during startup and shutdown as they are during steady-state normal production. While the 

commenter noted that EPA’s test methods are only used to measure emissions during steadystate operations, companies have not attempted to measure emissions that occur during startup 

and shutdown, and requested that EPA conduct further analyses to determine actual emissions 

during these periods, determine the best performing sources and evaluate whether they achieve 

the limits during startup and shutdown. The commenter also questioned whether the controls in 

use would achieve the same emissions reductions during startup and shutdown as they achieve 

during steady-state operations.

Response: We considered the air pollution control devices in use in this industry to 

determine whether a properly operated fabric filter (baghouse), ESP, thermal oxidizer or RTO 

would achieve the same reduction in emissions regardless of loading, temperature of the process 

exhaust, and stability of the emissions stream. According to the information available to us on 

the mineral wool industry, the control devices used at mineral wool facilities achieve the same 

emission reduction regardless of changes in these parameters. For these reasons, we proposed 

and are finalizing the requirement that facilities must route emissions occurring during startup 

and shutdown to the control device operating at the parameters that showed compliance with the 

rule during the most recent performance test. 

With regard to testing during startup and shutdown periods, emissions are not at steady 

state during startup and shutdown (a necessary factor for accurate emissions testing), and the 

varying stack conditions, gas compositions and low emission rates make accurate emission 

measurements impracticable. In addition, the startup period for mineral wool cupolas is usually 2 

hours, which is too short a time in which to conduct source testing.

Furthermore, as stated above, the commenter later filed an amended comment in a letter 

to EPA (EPA-HQ-OAR-2010-0142-0300) in support of the revised rule requirements for periods 

of startup and shutdown. 

47. Comment: The commenter (1041-0126) requested changes to the proposed 

definitions for startup and shutdown, closed-top cupolas, open-top cupolas, and the three 

definitions for the curing and collection subcategories. The commenter also supported the 

proposed definition of the combined collection/curing process.

Response: We met with industry representatives on July 16 and July 25, 2013 to discuss 

these issues with both the existing facility representatives and with representatives of a new 

facility undergoing construction in Mississippi. Because the new facility is planning to construct 

process equipment meeting the applicability description of subpart DDD, but of a distinctly 

unique design, we are incorporating into the final rule requirements for startup and shutdown that 

are applicable to all mineral wool facilities. Specifically, these requirements will include 

compliance demonstrations for cupolas operating in oxidizing conditions, with oxygen 

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concentrations above 24 percent. These provisions provide a means for mineral wool production 

facilities to meet the limits of the rules at all times, including during periods of startup and 

shutdown, regardless of cupola design. 

We also acknowledge the commenter’s support for the proposed definition of the 

“combined collection/curing” process. However, we disagree with the commenter’s suggestions 

regarding the definition of “closed-top cupola” and “open-top cupola,” and with the need to 

include definitions for vertical, drum, and horizontal collection. Therefore, in the final 

amendments to the Mineral Wool NESHAP, we included the definition of “combined 

collection/curing,” as proposed.

48. Comment: Three commenters (1041-0073/1042-0111, 1042-0120, and 1041-080) 

stated that EPA should take malfunctions into account when adopting emission standards, adding 

that there is nothing in CAA section 112 that allows EPA to ignore malfunctions and set MACT 

standards based on a level of emissions that even best-performing sources only achieve part of 

the time.

According to the commenters, the EPA’s rationale contravenes congressional intent that 

MACT floor standards be based on what the best sources actually achieve, and “accounting for 

malfunctions could lead to standards that are significantly less stringent than levels that are 

achieved by a well-performing non-malfunctioning source.” The commenters stated that the EPA 

acknowledges that even properly designed and operated equipment will sometimes exceed 

emission limitations that were based on steady-state operation, due to malfunctions, and 

emissions during such often are not routed to a stack where they can be measured, and upsets 

during stack testing invalidate the test results under the EPA’s approved test methods. The 

commenters agreed with the EPA’s understanding that SSM events can lead to higher emissions 

even at well-operated facilities with the best control equipment, but thought that should lead the 

EPA to prescribe alternative design, equipment, work practice or operational standards under its 

CAA section 112(h) authority (where it is not feasible to set or enforce a numerical emission 

limit). The commenters argued that the concept of “best performing” is inconsistent with a 

source experiencing a malfunction because it ignores that there are work practices – such as 

monitoring operating parameters to identify a malfunction and stopping or cutting back the 

process accordingly – that represent the best practices for minimizing emissions during a 

malfunction. The commenters noted that while the measures that represent these best practices 

will depend on facility-specific issues, such as process design, pollution control train, and other 

factors, they are nonetheless the “best technological system of continuous emission reduction ... 

adequately demonstrated.” The commenter claimed that “significant difficulties” are encountered 

by the proposed approach to malfunctions because even best-performing sources, do not achieve 

the emission limit part of the time and since the EPA agrees they may be unavoidable or “not 

reasonably preventable,” despite proper design and maintenance of equipment, the commenter 

contended that there is no basis for the EPA’s conclusion that malfunction events are not 

representative of best-performing sources. By proposing MACT standards that the EPA 

recognizes even the best performing existing sources cannot achieve part of the time, the 

commenters argued that the EPA is going beyond the MACT floor without making the 

demonstrations that those conditions are reasonable “taking into consideration the cost of 

achieving such emission reduction.” See CAA section 112(d)(2). 

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According to the commenters, the EPA does not present any substantiation for its belief 

that “[a]pplying the concept of ‘best controlled’ or ‘best performing’ to a unit that is 

malfunctioning presents significant difficulties” in setting CAA section 112 standards. See 76 

Fed. Reg. at 72794 col. 3. The commenters argued that if the EPA acknowledges that 

malfunctions are inevitable, even for the best performing sources, they should include emissions 

data representing malfunctions in calculating the MACT floor (see 76 Fed. Reg. at 72794 col. 3), 

and then require that those MACT floor limitations be met even during malfunctions. However, 

the commenters also questioned whether it is possible to obtain emissions data during periods of 

malfunction.

The commenters contended that if it is possible to gather sufficient representative data 

reflecting emissions during malfunctions, then the EPA should consider such data in its MACT 

floor calculations for steady-state operating conditions. The commenters added that, to the extent 

EPA had access to continuous monitoring data for emission units covered by the NESHAP, it 

should have conducted analyses of emissions levels during malfunction events. According to the 

commenters, many types of sources are required by many state agencies to submit deviation 

reports or malfunction reports when they experience a malfunction that causes an exceedance of 

an applicable limitation. The commenters argued that the EPA does not appear to have made any 

attempt to obtain and analyze such reports, in order to assess what type of requirement might 

reasonably apply to the subject emission units during malfunctions.

According to the commenters, there are several options the EPA could use for setting 

MACT standards under CAA section 112 that would apply during malfunction events, including 

establishing an emission limitation that applies at all times, but that has an averaging time of 

sufficient duration that short, infrequent spikes in emissions due to malfunctions would not cause 

the source to exceed the emission limit (while at the same time assuring that the source does not 

operate in a way that causes frequent, lengthy excursions above the normal controlled emission 

rate). The commenters noted that the EPA could also use the flexibility accorded by CAA section 

302(k) (defining “emission limitation” and “emission standard” to include “any requirement 

relating to the operation or maintenance of a source to ensure continuous emission reduction, and 

any design, equipment, work practice or operational standard promulgated under” the CAA) to 

address emissions during malfunction events through operational requirements. The commenters 

added that the EPA might use a combination of such approaches for malfunction events. 

Finally, if the EPA continues to conclude that it must eliminate the SSM exemption, the 

commenters stated that the limits are unsupportable. Therefore, the EPA should instead adopt 

work practice standards, specifically to require that sources only operate existing pollution 

control equipment during startup and shutdown periods consistent with current practices, with 

exemptions for maintenance.

According to the commenters, because it is unclear whether the EPA considered these 

types of options, the proposed rule is arbitrary and the EPA should develop a new proposal.

Response: The EPA has provided a detailed justification for its approach to malfunctions 

in the preambles to the 2013 and 2014 proposals. There is nothing in CAA section 112 that 

directs the agency to consider malfunctions in determining the level “achieved” by the best 

performing sources when setting emission standards. As the D.C. Circuit has recognized, the 

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phrase “average emissions limitation achieved by the best performing 12 percent of sources” 

says nothing about how the performance of the best units is to be calculated.” Nat'l Ass'n of 

Clean Water Agencies v. EPA, 734 F.3d 1115, 1141 (D.C. Cir. 2013). As discussed above, 

nothing in CAA section 112 requires the agency to consider malfunctions as part of that analysis, 

accounting for malfunctions in setting emission standards would be difficult, if not impossible, 

and could lead to standards that are not reflective of levels achieved by a well-performing nonmalfunctioning source. As the D.C. Circuit also noted in Sierra Club v. EPA, 167 F.3d 658 (D.C. 

Cir. 1999), the phrase "average emissions limitation achieved by the best performing 12 percent 

of units” in section 112 of the CAA "says nothing about how the performance of the best units is 

to be calculated.” Id. at 661. Congress has not directly addressed the issue of whether emissions 

that occur during periods of malfunction must be taken into account in calculating the 

performance of the best units and the EPA’s approach to malfunctions is reasonable for the 

reasons set out in the preamble to the proposed rule. For example, the EPA explained, and 

commenter agrees, that the factual complexity of differing processes and of the severity, 

frequency, and duration of malfunctions makes standard-setting impracticable. In fact, the 

commenter’s statement that the best work practices employed during malfunctions “will depend 

on facility-specific issues, such as process design, pollution control train, and other factors” 

highlights the impracticability of setting work practice standards that apply across all sources in 

the category for the myriad types of malfunction that could occur. The commenter does not 

explain how any of the options suggested would make it any easier or practicable for the EPA to 

set a national standard that accounts for the innumerable types of malfunctions that, as 

commenter points out, might vary depending on facility-specific issues. The EPA further 

explained that the performance of units that are malfunctioning is not reasonably foreseeable and 

cited to case law supporting its approach to malfunctions. See Sierra Club at 665 (discussing 

need to take into account the worst reasonably foreseeable performance) and Weyerhaeuser v.

Costle, 590 F.2d 1011, 1058 (D.C. Cir. 1978) (“In the nature of things, no general limit, 

individual permit, or even any upset provision can anticipate all upset situations.”).

In pointing out that “accounting for malfunctions could lead to standards that are 

significantly less stringent than levels that are achieved by a well-performing nonmalfunctioning source,” the EPA was merely pointing out one possible consequence of taking 

malfunctions into account in setting standards if such an approach were practicable. This 

theoretical consequence is not driving the EPA’s approach to malfunctions. Further, the EPA’s is 

not going beyond the MACT floor as the commenter suggests. Rather, the EPA is setting floor 

standards based on a reasonable interpretation of a statutory provision that is ambiguous as to 

how the performance of the best units is to be calculated.

The commenter argues that, if it is possible to gather sufficient representative data 

reflecting emissions during malfunctions, then the EPA is obligated to consider these data in its 

MACT floor calculations, but also makes the seemingly inconsistent point that it is often 

infeasible to gather emission data during malfunctions. 

With respect to commenters’ suggestion that the EPA consider work practice standards, 

section 112(h) of the CAA allows the EPA to set work practice standards instead of an emissions 

floor “if it is not feasible in the judgment of the Administrator to prescribe or enforce an 

emission standard.” (“[T]he Administrator may, in lieu [of a numeric standard], promulgate a 

design, equipment, work practice, or operational standard, or combination thereof.”). In 

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exercising the option to establish a work practice standard, that standard must “in the 

Administrator’s judgment [be] consistent with the provisions of subsection (d) or (f).” CAA 

section 112(h)(1) (emphasis added). Under CAA section 112(h)(2)(B), it is “not feasible” to set 

an emission standard when “the application of measurement methodology to a particular class of 

sources is not practicable due to technological and economic limitations.” Thus, section 112(h) 

“allows EPA to substitute work practice standards for emission floors only if measuring emission 

levels is technologically or economically infeasible.” Sierra Club v. EPA, 479 F.3d 875, 884 

(D.C. Cir. 2007). These subsections make clear that the EPA is to base emission standards on the 

emission levels already achieved by the best performing sources as applicable. This means that 

work practice standards, although written in non-numeric form, must still satisfy statutory 

requirements such as those applicable to MACT standards, including the requirement to be no 

less stringent than the MACT floor.

It is just as difficult to establish a work practice standard for malfunctions that can 

approximate the level of emission reduction achieved by the best performing sources during 

malfunctions as it would be to factor emission levels that occur during malfunctions into the 

numeric standards, as discussed above. The EPA would have to design a single work practice 

standard that applies equally to a tank explosion as it does to innumerable types of operator error, 

computer glitches or a myriad of other unknown events, or alternatively create innumerable work 

practice standards.

In summary, the EPA believes that based on this rulemaking record it would be clearly 

inappropriate to set a work practice standard for malfunctions in lieu of the otherwise applicable 

numerical emission limit. For all the reasons explained in the preamble to the final rule and 

above, the EPA’s approach to malfunctions is reasonable and consistent with the statute 

regardless of whether collection of certain types of malfunction data under certain circumstances 

is theoretically possible. We also note that we would consider any response to violations caused 

by a malfunction on a case-by-case basis through the exercise of enforcement discretion. 

49. Comment: One commenter (1041-0081) supported the EPA’s proposed removal of 

the startup, shutdown, and malfunction (SSM) exemption. The commenter asserted that D.C. 

Circuit struck down the SSM exemption as a violation of CAA section 112, 42 U.S.C. § 7412. 

All such exemptions are unlawful and must be removed.

Response: In the 2011 proposal, we explained that the D.C. Court had recently vacated 

the SSM exemption contained in 40 C.F.R. sections 63.6(f)(1) and 63.6(h)(1). Sierra Club v. 

EPA, 551 F.3d 1019 (D.C. Cir. 2008) cert. denied, 130 S. Ct 1735 (2010). The exemptions for 

startup and shutdown and for malfunctions in subpart DDD (Table 1 and 63.1180(d)) and NNN 

(Table 1) are inconsistent with the holding in Sierra Club that emissions limitations under CAA 

section 112 must apply continuously. Thus, EPA is eliminating the SSM exemption in subpart 

DDD and NNN. The EPA has established work practice standards in this rule that apply during 

startup and shutdown periods.

50. Comment: One commenter (1041-0081) noted that the EPA should promulgate 

specific public reporting and notification requirements for malfunctions, or any emission 

exceedance that occurs. According to the commenter, the EPA should require telephone 

reporting by the facility no later than 24 hours after the malfunction or exceedance, that such 

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notice would be made publicly available on the EPA’s website and through ECHO within 24 

hours, and that the Regional office must notify the local community on the Internet, by direct 

communication, and through all available means.

In addition, the commenter argued that the EPA should promulgate the requirement that 

when such notification is made, the facility must also provide for community notification of the 

malfunction or emission standard exceedance within 24 hours, through an appropriate public 

forum that is designed to reach residents who live near the facility, including but not limited to a 

notice on the facility’s own website (if it has one), a written notice to the local municipality and 

local school district and a press release to the local newspaper, radio, and television news station 

that contains any information community members may need to try to protect themselves and 

their families from the additional air pollution. The commenter supported the EPA’s proposal to 

require reporting of malfunctions, but prioritized this information so that the public can evaluate 

associated health risks.

According to the commenter, the EPA should also require a written report to be 

submitted within 7 days, and use the same distribution method as outlined above, including 

publication on ECHO, the EPA’s Regional website, and sending this to active local community 

members who are interested (such as through setting up an email list, a local listserv, Twitter®, 

and other media).The commenter argued that, in the written report, the EPA should require the 

facility to report: (1) the nature of the event; (2) the duration of the event; (3) estimate of 

emissions released during the event; and (4) a description and timing of corrective actions that 

were taken and any planned to be taken.

The commenter contended that the reporting of malfunctions or other exceedances is not 

enough to protect the most exposed people from high metal and other HAP emissions like those 

from the Wool Fiberglass and Mineral Wool source categories. The commenter contended that 

the EPA also should promulgate additional requirements that apply in the event of a malfunction 

or violation of the numerical emission standards. According to the commenter, the CAA requires

continuous compliance with the emission standards. The commenter provided the ECHO reports 

of a number of existing sources in the Wool Fiberglass source category for the EPA to consider 

as part of this rulemaking. The commenter stated that the EPA should take action to protect local 

communities from unacceptable risk. The commenter stated that facilities must not be able to 

emit in an unlimited manner for an unlimited period of time.

The commenter stated that, in addition to requiring reporting of exceedances and 

malfunctions, the EPA should:

1. Require automatic shut-off of the malfunctioning equipment or process for the time 

needed to take corrective action whenever an exceedance or malfunction occurs.

2. Assign responsibility and liability to the plant manager or a senior staff member that 

allows only that person to restart the equipment or process.

3. Require specific corrective measures to be taken immediately to remedy and prevent 

recurrence of the malfunction or violation.

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The commenter also stated that, for a facility that has had one or more malfunction, 

exceedance, or other violation incident in the prior month, written authorization by EPA should 

be required to restart equipment or processes. The commenter further noted that EPA should 

only authorize restart after making a public determination that provides information on the 

corrective measures that EPA is requiring. The commenter claimed that EPA should release this 

public determination on the Internet and require its Regional office to communicate this 

determination to all interested members of the public, including local community representatives. 

If a facility has more than 4 exceedances or malfunctions during the same quarter, the 

commenter urged EPA to require automatic shut down of the operation for a period of time 

needed to conduct and publish a full investigation and ensure systematic correction of the 

problems.

The commenter further claimed that the EPA should create a community complaint 

mechanism in the standards that ensures that citizen complaints of clouds, plumes, exceedances, 

odors, other air pollution incidents or health concerns receive an immediate response, in which 

EPA commits to initiate an investigation and provide a publicly available report of the result of 

the investigation, including whether it leads to an enforcement outcome from EPA’s enforcement 

division within 7 days.

Response: The final rule requires malfunction recordkeeping and reporting, including for 

each failure to meet a standard, the date, time, and duration, a list of the affected sources or 

equipment, an estimate of the volume of each regulated pollutant emitted over the standard, a 

description of the method used to estimate such emissions, and actions taken to minimize 

emissions and any corrective actions taken. Any reports submitted to the EPA are publicly 

available subject to the requirements of CAA section 114(c). We do not agree with the 

commenter that the suggested additional notification and reporting requirements are necessary, 

as they would be duplicative of the immediate notification requirements of the Superfund 

Amendments and Reauthorization Act (SARA)/Comprehensive Environmental Response, 

Compensation, and Liability Act (CERCLA)/Emergency Planning and Community Right-toKnow Act (EPCRA), would be burdensome for both facilities and agencies to review, and would 

not enhance compliance beyond that of the requirements in the rule for reporting violations of 

emission limits.

E. Authority to Fill Data Gaps in Existing MACT Standards

51. Comment: One commenter (1041-0081) stated that the EPA should set a standard 

to limit all HAP emissions. The commenter pointed out that the EPA’s dataset for both source 

categories includes mercury emissions that are currently uncontrolled by the standards. The 

commenter argued that the EPA has failed to propose a limit to control these emissions. 

According to the commenter, CAA section 112 requires the EPA to set an emission standard to 

control all HAP emitted at all times. The commenter stated that the EPA should do so, at least by 

setting the mercury limit at the detection level if emissions fall below that.

The commenter was also concerned that, because the furnaces in this source category use 

a combustion process, the source category may emit dioxin. The commenter contended that the 

EPA has not addressed dioxin and that it is unclear whether the EPA required testing for dioxin. 

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The commenter urged the EPA to ensure that it sets a limit on dioxin if these source categories 

emit this pollutant.

Response: In the 1999 NESHAP, we established emissions limits for many HAP that 

were emitted from processes under both the Mineral Wool Production and the Wool Fiberglass 

Manufacturing source categories, and we are amending those standards with emission limits for 

HAP that are emitted from the sources and which can be measured and controlled using existing 

air pollution control technology.

At this time we are not setting limits for mercury under this rulemaking. We do not 

believe that the limited data we have at this time is sufficient to set a mercury emissions limit. 

Regarding dioxin, the EPA had no information suggesting that dioxin was expected to be emitted 

from sources in either of these industries, and no information indicated that conditions conducive 

for dioxin formation were present in these source categories. In light of this, we did not require 

emission testing for dioxin from sources in these industries. Consequently, we did not propose 

emission limits for dioxin. Additionally, no information was brought to us during any of the 

three comment periods upon which we could base emission limits for dioxin, and no information 

was brought forth that would lead us to reconsider this decision. Therefore, the final emission 

limits for these industries do not include emission limits for dioxin. 

F. Monitoring, Recordkeeping and Reporting

52. Comment: One commenter (1041-0081) urged the EPA to strengthen enforcement, 

monitoring, and reporting requirements for these source categories. According to the commenter, 

EPA should take this action both under CAA section 112(f)(2) and under CAA section 

112(d)(6). The commenter also stated that, considering that the risk from the Wool Fiberglass 

source category has disproportionate effects on minority and economically disadvantaged 

communities, additional monitoring and stronger enforcement provisions would help provide 

environmental justice, especially in Kansas City.

Response: We believe that the monitoring requirements included in these rules are 

sufficient to ensure compliance with the standards regardless of whether or when a violation 

occurs. Under the provisions of 40 CFR 63.15, the public can request access to reports submitted 

to the regulatory agency whenever they choose, with the exception of information protected 

through 40 CFR part 2 (e.g., CBI). In addition, as discussed below, we are promulgating 

requirements for electronic reporting of emissions test data that will improve public access to 

emissions information. 

53. Comment: One commenter (1041-0081) asserted that the EPA should require 

periodic testing that will assure compliance and demonstrate to the EPA, states, and the public 

whether or not the facilities are in compliance. The commenter added that the EPA should write 

standards that ensure prompt compliance, pursuant to the deadlines set by the Act. Section 112 of 

the CAA includes strict compliance provisions for residual risk standards and all other CAA 

section 112(d) standards. The commenter contended that the EPA also must ensure that strict 

monitoring and enforcement provisions are part of its standards to enforce the permit condition 

requirements of the Act. The commenter noted that the CAA requires permits to contain 

―conditions as are necessary to assure compliance with applicable requirements of [the Act]. 40 

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C.F.R. Part 70 adds detail to this requirement. 40 C.F.R. § 70.6(a)(3) requires ―monitoring 

sufficient to yield reliable data from the relevant time period that are representative of the 

source’s compliance. The commenter noted that section 70.6(c)(1) requires all Part 70 permits to 

contain testing, monitoring, reporting, and recordkeeping requirements sufficient to assure 

compliance with the terms and conditions of the permit. The commenter suggested that the EPA 

should fully review the monitoring requirements it has proposed and ensure that they are 

sufficient to quickly determine the compliance status of a facility. The commenter further stated 

that the EPA should require performance tests every year instead of every 5 years to stay up-todate on the industry’s emissions and compliance status. 

Response: We believe that the monitoring requirements included in these rules are 

sufficient to ensure compliance with the standards. With regard to the frequency of performance 

tests, we agree that there are many instances in which annual performance tests can be used as a 

tool by which the citizens can be informed of the emissions of HAP from particular industrial 

sources. We also are concerned with the impact to regulated entities that annual testing imposes. 

Performance tests can interrupt production and manufacturing at a facility, and can be costly; we 

are therefore mindful to temper imposing the frequency of testing with the hazard that may be 

assessed by release of a highly toxic pollutant. Based on information from industry, we found 

that both formaldehyde and chromium compounds are highly toxic HAP emitted from wool 

fiberglass facilities. We anticipate in general that formaldehyde emissions from bonded lines at 

wool fiberglass facilities will continue to decline, but that chromium emissions from the furnaces 

will both continue and may increase rapidly and unexpectedly. We therefore are requiring annual 

testing at wool fiberglass gas-fired furnaces for chromium emissions. For the PM, formaldehyde, 

methanol and phenol emission limits for wool fiberglass facilities, the final rule requires 

performance testing initially and every 5 years. We are also requiring owners or operators of 

mineral wool facilities to conduct performance tests initially and every 5 years. 

54. Comment: One commenter (1041-0081) supported the EPA’s proposal for 

electronic reporting because it will strengthen EPA, state, and citizen enforcement, and provide 

prompt information transparency for local communities near facilities. The commenter stated 

that because the public has a right to all reports collected under the CAA, it is important that the 

EPA ensure immediate disclosure of these reports within 7 days of receipt and without 

necessitating a FOIA request. 

Response: We appreciate the commenter’s support for requiring electronic reporting in 

the NESHAP and GACT standards. However, we disagree with the commenter that reports 

submitted electronically should be available to the public within 7 days of receipt. In our 

proposed revisions to certain New Source Performance Standards (NSPS) regulations to require 

electronic reporting (80 FR 15100) and our anticipated revisions to certain part 63 NESHAP, we 

are proposing that electronic reports submitted to the Compliance and Emissions Data Reporting 

Interface (CEDRI) be stored on the EPA’s Central Data Exchange (CDX) for 60 days before 

they will be available for public access. During this 60-day processing period, the report will be 

available to the EPA or registered air agency personnel to conduct a quality review of the report 

data and supporting documentation and the report preparer may submit corrections to the report 

to CEDRI based on the air agency’s review. We believe that this processing period is necessary 

to ensure that the data available to the public are as complete and accurate as possible and we do 

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not agree with the commenter that a 7-day period is sufficient for the air agency to review the 

submissions.

55. Comment: One commenter (1041-0081) stated that the EPA should require 

continuous monitoring of emissions from this source category. The commenter noted there is 

technology available to perform continuous emissions monitoring for Hg, HCl, HF, PM, and 

opacity, among others, and asked the EPA to require the use of this technology to assure 

compliance, adding that the EPA should require immediate Internet reporting of all monitoring 

records. 

Response: We disagree with the commenter that continuous emissions monitoring 

systems (CEMS) are necessary for ensuring compliance with the final emission limits for PM 

and chromium. The final standards require that owners or operators conduct performance tests 

initially and annually thereafter to demonstrate compliance with the chromium emission limit. 

For PM, owners or operators must conduct performance tests initially and every 5 years to 

demonstrate compliance with the final emissions limits. We believe that the performance testing 

schedule specified in the final rule is appropriate for demonstrating compliance with the 

chromium and PM emission limits.

We also disagree with the commenter that the EPA should require CEMS for HCl and HF 

emissions from furnaces. As noted in our April 2013 notice, we proposed work practice 

standards for HF and HCl emissions because the test data showed that for at least 80 percent of 

the furnaces tested, emissions were lower than the detection level of the methods used to 

measure those pollutants. Section 112(h) of the CAA allows the EPA to set work practice 

standards instead of an emissions floor “if it is not feasible in the judgment of the Administrator 

to prescribe or enforce an emission standard.” Under CAA section 112(h)(2)(B), it is “not 

feasible” to set an emission standard when “the application of measurement methodology to a 

particular class of sources is not practicable due to technological and economic limitations.” 

Thus, CAA section 112(h) “allows EPA to substitute work practice standards for emission floors 

only if measuring emission levels is technologically or economically infeasible.” Sierra Club v. 

EPA, 479 F.3d 875, 884 (D.C. Cir. 2007). Because we identified technological and economic 

limitations associated with measuring HF and HCl emissions from furnaces, the EPA has the 

discretion to adopt work practice standards rather than establishing numeric emission limits.

The final rule also requires owners or operators to ensure that the cullet fed to gas-fired 

glass-melting furnaces does not contain glass from the following chloride-, fluoride-, or fluorinebearing components that would form HF or HCl in the furnace exhaust: glass from industrial 

(also known as continuous strand, or textile) fiberglass, cathode ray tubes (CRT), computer 

monitors that include CRT, and glass from microwave ovens, televisions or other electronics. 

ensure their cullet feedstock does not contain any of these chloride-, fluoride-, or fluorinebearing components by one of two approaches: (1) Require the providers of external cullet to 

verify that the cullet does not include waste glass from the chloride-, fluoride- or fluorinebearing components, or (2) Sample their raw materials to show the cullet entering the furnace 

does not contain glass from these components. To demonstrate compliance, the final rule 

requires facilities to maintain quality assurance records for raw materials and/or records of glass 

formulations indicating the facility does not process fluoride-, fluorine-, or chloride-bearing 

materials in their furnaces, and that they thereby maintain low HF and HCl emissions. The final 

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rule also requires facilities to record the percentage of cullet in the materials mix fed to the 

furnace during the performance test and to maintain the rolling 30-day average cullet percentage 

at or below the level established during the test these types of sources either by conducting their 

own internal inspection and recordkeeping program, or by receiving certification from their 

cullet suppliers. Given the low level of emissions and the monitoring and recordkeeping 

requirements of the final rule, we do not believe that CEMS are warranted for HCl and HF 

emissions from gas-fired glass-melting furnaces.

G. General Approach To Calculating MACT

56. Comment: One commenter (1042-0120/1041-0080) argued that the EPA can revise 

an existing standard only under CAA section 112(d)(6) because the NRDC v. EPA decision 

(HON RTR rule: Cf. NRDC v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008)) plainly holds that the 

EPA is not required to “correct” prior MACT standards or recalculate MACT standards under 

CAA section 112(d)(6).

Response: We disagree with the comment. The commenter mischaracterizes the HON

decision, which involved RTR revisions to existing and properly promulgated MACT standards. 

CAA section 112(d)(6) provides that the agency must review and revise “as necessary.” The “as 

necessary” language must be read in the context of the provision, which focuses on the review of 

developments that have occurred since the time of the original promulgation of the MACT 

standard and thus, should not be read as a mandate to correct flaws that existed at the time of the 

original promulgation. Further, the D.C. Circuit has held that the EPA may permissibly amend 

improper MACT determinations, including amendments to improperly promulgated floor 

determinations, using its authority under CAA sections 112 (d)(2) and (3). Medical Waste 

Institute v. EPA, 645 F.3d 420, 425-27 (D.C. Cir. 2011). (Resetting MACT floor, based on postcompliance data, permissible when originally-established floor was improperly established, and 

permissibility of the EPA’s action does not turn on whether the prior standard was remanded or 

vacated). Similarly, Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011) confirms 

that CAA section 112(d)(6) does not constrain EPA and it may reassess its standards more often, 

including revising existing floors if need be. 

As also previously explained, in several recent rulemakings, we have chosen to fix 

underlying defects in existing MACT standards under CAA sections 112(d)(2) and (3), 

provisions that directly govern the initial promulgation of MACT standards (see National 

Emission Standards for Hazardous Air Pollutants From Petroleum Refineries, October 28, 2009, 

74 FR 55670; and National Emission Standards for Hazardous Air Pollutants: Group I Polymers 

and Resins; Marine Tank Vessel Loading Operations; Pharmaceuticals Production; and the 

Printing and Publishing Industry, April 21, 2011, 76 FR 22566). We believe that our approach is 

reasonable because using those provisions ensures that the process and considerations are those 

associated with initially establishing a MACT standard, and it is reasonable to make corrections 

following the process that would have been followed if we had not made an error at the time of 

the original promulgation. 

57. Comment: One commenter (1042-0120/1041-0088/1041-0126) disagreed with the 

EPA’s interpretation of the CAA that the lowest performing sources are representative of the 

actual performance of the best performing sources. The commenter argued that the EPA is not 

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constrained by the Brick MACT to interpret “best controlled similar source” to mean “those with 

the lowest emission levels” because this Brick MACT language is an isolated statement and does 

not necessarily underpin the Brick MACT decision, is not supported by any other D.C. Circuit 

decision, and is contradicted by the technology approach endorsed by the courts for the Portland 

Cement and National Lime MACT standards. According to the commenter, Congress did not 

intend, and the courts have never required that the EPA equate the “lowest emitting” sources to the 

“best performing” sources and that the EPA is not required to set emission standards equivalent to 

the level achieved by the lowest emitting sources.19

The commenter argued that in its review of the 1999 Portland Cement MACT Standards, 

the court endorsed a “technology approach” to setting the MACT standards, whereby the EPA 

would use the relative performance of air pollution control technology to select the best 

performing sources.20

The commenter quoted the D.C. circuit:

“According to the Sierra Club, section 7412(d)(3) requires EPA to set new source floors 

at the lowest recorded emission level for which it has data and existing source floors at 

the average of the lowest twelve percent of recorded emission levels for which it has data. 

Nothing in the statute, the Sierra Club argues, permits the Agency to set floors based on 

the performance of technology as opposed to the recorded performance of plants.

In resolving this issue, we do not write on a clean slate. EPA’s technology-based 

approach to setting new source emission standards has already faced and survived a 

Chevron one challenge. In Sierra, 334 U.S. App. D.C. 421, 167 F.3d 658, we reviewed a 

new source emission standard for solid waste combustion that EPA promulgated pursuant 

to section 7429, which establishes emission requirements virtually identical to that of 

section 7412. There, as here, the Sierra Club argued that EPA’s MACT technology 

approach to setting emission standards is unambiguously forbidden by the CAA. Sierra 

rejected that argument, holding that EPA may estimate the performance of the best 

performing units and that it was not “impossible” that EPA’s methodology constituted a 

reasonable estimation technique. See 167 F.3d at 665.” [National Lime Ass’n v. EPA, 233 

F.3d 625, 631 (D.C. Cir. 2000).]”

The commenter concluded that the D.C. Circuit in National Lime endorsed the EPA’s use 

of a technology-based approach that uses the relative performance of pollution control 

technology to set the MACT floor.

The commenter observed that the EPA’s decisions to equate best performance with 

lowest emissions, rather than with other means of measuring performance, is based on a 

parenthetical phrase found in the Brick MACT decision that refers to the “best performing” 

sources as “those with the lowest emission levels.” The commenter stated that this isolated 

statement is dictum; it is not a necessary underpinning of the Brick MACT decision, nor is it 

19 See Sierra Club v. EPA, 167 F.3d 658, 661 (D.C. Cir. 1999) (CAA section 112(d) “on its own says 

nothing about how the performance of the best units is to be calculated”).

20 National Lime Ass’n v. EPA, 233 F.3d 625, 631 (D.C. Cir. 2000). 

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supported by any other D.C. Circuit decision on this issue. The commenter argued that in Brick 

MACT, the D.C. Circuit affirmed its decision in Cement Kiln that the EPA cannot redefine “best 

performing” to mean those sources with emission levels achievable by all sources:

“But EPA cannot circumvent Cement Kiln’s holding that section 7412(d)(3) 

requires floors based on the emission level actually achieved by the best 

performers (those with the lowest emission levels), not the emission level 

achievable by all sources.”

The commenter stated that the EPA’s interpretation of this dictum is to prohibit the 

adoption of any measure of “best performing” other than lowest emission levels, but this is an 

unnecessarily narrow view of the language of Brick MACT. The commenter asserted that the 

Brick MACT decision did not overrule either of the National Lime or Sierra decisions, in which 

the D.C. Circuit approved approaches that did not simply equate “best performing” sources with 

“those with the lowest emission levels.” According to the commenter, the EPA responded to the 

demonstrably contradictory yet binding precedent by electing to follow non-binding language 

that would appear to place great restraint on the EPA’s discretion. The commenter questioned 

why the EPA is willing to sacrifice its discretion on this issue when it has repeatedly asserted its 

discretion to characterize “best performing” sources by criteria other than simply the lowest 

emission level.

The commenter asserted that there is no reason to read the Brick MACT language the way 

the EPA does for purposes of the Proposed Rule when there is an alternative interpretation –

relative performance of sources and control technology – that harmonizes Brick MACT with 

prior and still binding case law.

The commenter observed that the EPA’s interpretation of Brick MACT collides with 

CAA section 112(d)(3) and other D.C. Circuit decisions requiring the EPA to take nontechnological and non-intentional factors into consideration if they impact emissions levels 

achieved in practice by sources, particularly as the EPA is advocating a “pollutant-by-pollutant” 

approach to setting the MACT floor. The commenter maintained that the EPA has the discretion 

to address factors such as technologies that lower a particular HAP but increase emissions of 

another air pollutant, and not be constrained to identify the lowest emitters of that particular HAP 

as the best performing sources regardless of any collateral negative impacts. 

The commenter noted that the EPA has, since the Brick MACT decision, acknowledged 

its discretion to define “best performing” sources in a manner that accounts for all the relevant 

factors. The commenter noted that in its Notice of the Proposed Hazardous Waste Combustor 

(“HWC”) Reconsideration Rule, the EPA justified using control efficiency rather than the 

simplistic emissions levels in defining “best controlled” and “best performing” HCl production 

furnaces, and although the final HWC rule hews to the narrow view of the Brick MACT decision, 

the commenter quoted the EPA that, “standards requiring HAP reduction of a given percent limit 

the emission quantity, rate, and (in any realistic scenario) concentration of the HAP and so falls 

squarely within the statutory definition [of emission standard].”

The commenter maintained that NESHAP standards must ‘consider emissions in the best 

performing sources as they would be under the worst foreseeable circumstances’ per instruction 

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in Sierra Club v. EPA, 167 F.3d 658, 665 (D.C. Cir. 1999). The commenter suggests that the 

EPA should use this consideration as one basis to increase the EPA’s emissions estimate of the 

performance of the sources defining the MACT floor, thereby raising the proposed emission 

limits, which the commenter believes is appropriate.

Response: Section 112(d) of the CAA requires the EPA to promulgate standards for 

major sources of HAP that are based on MACT performance. For existing sources, MACT 

standards must be at least as stringent as the average emissions limitation achieved by the best 

performing 12 percent of existing sources (for which the Administrator has emissions 

information) or the best performing 5 sources for source categories with less than 30 sources. For 

new sources, the MACT standards must be at least as stringent as the control level achieved in 

practice by the best controlled similar source. In construing CAA section 112(d)(3), the D.C. 

Circuit has stated that “[t]hough section 7412(d)(2) does direct the EPA to require the maximum 

emission reduction that it determines to be achievable, section 7412(d)(3) provides that the 

maximum degree of reduction in emissions that is deemed achievable. . . shall not be less 

stringent that what the best-performing sources achieve. Section 112(d)(3) therefore limits the 

scope of achievable in section 7412(d)(2).” Sierra Club v. EPA, 479 F.3d at 878. (Internal 

quotations omitted). The Court has also stated that “to comply with the statute, the EPA’s 

method of setting emissions floors must reasonably estimate the performance of the best 

performing plants.” Sierra Club v. EPA, 167 F.3d at 665. As also previously explained, the D.C. 

Circuit has consistently rejected the EPA’s reading of “achieved by the best performers,” in 

section 112(d)(3), as meaning achievable by all sources within a source category. “EPA’s 

rationales . . . amount to nothing more than concern about ensuring that its floor is achievable by 

all kilns in the subcategory--precisely the position we rejected in Cement Kiln.” Sierra Club v. 

EPA, 479 F.3d at 881. See also, Cement Kiln v. EPA, 255 F.3d at 861 “EPA may not deviate 

from section 7413(d)(3)’s requirement that floors reflect what the best performers actually 

achieve by claiming that floors must be achievable by all sources using MACT technology.” 

With regard to the comment that the EPA justified using control efficiency rather than the 

simplistic emissions levels in defining “best controlled” and “best performing," in more recent 

rulemakings, the EPA has not proposed an alternative standard expressed as a percent reduction 

reflecting the average of the best removal efficiencies. We have reasoned that one problem with 

a percent reduction standard is that it could downplay the role of HAP inputs on emissions by 

allowing more HAP to be emitted provided a given level of removal efficiency reflecting the 

average of best removal efficiencies is achieved. We have also explained that we believe percent 

reduction standards are not legally permissible because the Brick MACT opinion states, arguably 

in dicta, that best performers are those emitting the least HAP (see 479 F. 3d at 880 (“section 

[112 (d)(3)] requires floors based on emission levels actually achieved by best performers (those 

with the lowest emission levels)”). More important, the opinion stresses that raw material inputs 

must be accounted for in determining MACT floors. Id. at 882-83.

Thus, while the Brick MACT decision did not overrule either National Lime or Cement 

Kiln, it did reiterate prior holdings and again invalidated our prior reading of section 112(d)(3) as 

allowing factors other than the performance of the best performing sources in our MACT floor 

calculations. More recently, in Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 

2011), the Court stated “PCA also argues EPA violated the CAA when it premised the NESHAP 

standards on bare emissions data rather than on data that specifically isolated the effect of 

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technology by controlling for variations in input quality. We considered and rejected this very 

argument quite recently” in Sierra Club. (“We declined to read the Clean Air Act’s command 

that it assess the emission ‘control’ or ‘limitation’ achieved [as] refer[ring] to the deliberate steps 

kiln operators take to reduce emissions rather than to the ‘happenstance’ of being located near 

cleaner clay.” Id. at 189. (Alterations in original)). 

As explained earlier, CAA section 112(d)(3), does not address the question of whether, in 

assessing which sources perform best or are best controlled, emission levels should be evaluated 

either over time or in a single test result. We believe, however, that our MACT floor calculation 

should identify the best performers (i.e., the best performing 12 percent or best performing five 

sources in smaller source categories for existing sources, and the best controlled single source for 

new sources), as those sources likely to emit the least HAP over time considering variability. In 

other words, the EPA does not believe that the statute requires or contemplates a random sample. 

Rather, use of data from the best performing sources is specified for developing the MACT floor 

limits. The EPA also believes that the lowest emission value available from a given source is a 

reliable measure of the best performance the source has achieved. We use the lowest emission 

value to rank the different facilities and to select the best performing sources. We do not use the 

average because it is affected by extreme values, both large and small, and does not represent the 

best performance of the source. We believe that use of the lowest emissions value is consistent 

with the D.C. Circuit construct of CAA sections 112(d)(2) and (d)(3).

Thus, in calculating the MACT floor for each pollutant for the two source categories, we 

used the lowest emission value to rank the different facilities and to select the best performing 

sources. We did not assign unusually low emissions to any unit. We also used all the available 

emission data from all best performing sources to estimate the variability in the UPL, as 

discussed in the preamble to the 2011 proposal and the memorandum “Use of the Upper 

Prediction Limit for Calculating MACT Floors” (available in the docket for this action), 

accounting for within and between source variability. Additionally, where a dataset consisted of 

limited data, we used a UPL approach based on limited datasets, as discussed in more detail in 

the preamble to the 2014 proposal. We obtained the available data from emissions tests that the 

commenter submitted in accordance with the voluntary survey it conducted of wool fiberglass 

manufacturing facilities and from the CAA section 114 survey conducted to collect data for all 

furnaces not represented by the voluntary survey, in support of the 2013 proposal. As explained 

in the November 2011 proposal, industry conducted a voluntary survey that called for test data 

for HAP emissions and process equipment and processes. In lieu of testing, the EPA also 

allowed for submittal of prior existing and well documented test data that were representative of 

wool fiberglass manufacturing operations. 76 FR 72778. In certain instances, industry opted to 

submit existing test data in lieu of conducting new testing. (“EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a problem. We generally defer to an 

agency's decision to proceed on the basis of imperfect scientific information, rather than to invest 

the resources to conduct the perfect study.” Sierra Club v. EPA, 334 U.S. App. D.C. 421, 167 

F.3d 658, 662 (D.C. Cir. 1999) (citation omitted)). Thus, the limits being finalized are based on 

data representing all existing wool fiberglass manufacturing facilities and mineral wool 

production facilities, and we disagree with the comment’s assertion that EPA’s dataset for each 

of these two source categories is a “very small data set, collected during a specific time period, 

and without any historical data.” We conducted outlier analyses of these datasets and do not 

believe that the data in the resultant MACT floor pool data sets are outlier data. Thus, contrary to 

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the commenter’s assertions, we have also identified the best performers for each source category 

for purposes of the MACT floor calculation in the memoranda “Revised MACT Floor Analyses 

for Wool Fiberglass Manufacturing Source Category” and “Revised MACT Floor Analyses for 

Mineral Wool Production Source Category,” both of which are in the docket for this rulemaking. 

Further, because the D.C. Circuit has held repeatedly that variability of best performing 

sources may be taken into account in establishing MACT floors. Sierra Club, 479 F.3d at 881-

882, (See also National Lime Ass’n v. EPA, 627 F.2d 416, 431 n.46, 443(D.C. Cir. 1980)), we 

believe it is appropriate to consider statistical variability in order to ensure that units could meet 

the floors at all times.

As noted earlier, we are prohibited from setting floors on the level that can simply be 

achieved by all sources; the MACT floor emission limit must be set at the level achieved by the 

average of the best 12 percent of existing sources (and may consider variability); new source 

MACT must be the limit achieved by the best controlled similar source. 

58. Comment: One commenter (1041-0080/1041-0126/1042-0120) suggested that the 

EPA did not adequately take variability into account in its MACT floor determinations for the 

mineral wool production and wool fiberglass manufacturing source categories. 

According to the commenter, the EPA has historically demonstrated persuasively why the 

agency might in its discretion choose some other or more complex measure of what constitutes a 

“best performing” source. The data that the EPA collected for the wool fiber glass manufacturing 

industry and the mineral wool production industry indicate such an approach – which accounts 

for operational and other variability that undermines any straightforward connection between the 

“lowest emitters” and the “best performing” sources – would be justified. 

The commenter stated that the D.C. Circuit has held that NESHAP must consider 

emissions in the best performing sources as they would be “under the worst foreseeable 

circumstances.” To evaluate the emission limits achieved by existing sources, the commenter 

noted that the EPA is required to develop methodologies for estimating the variability associated 

with all factors that impact a source’s emissions, including process, operational and nontechnological variables. The commenter asserted that these factors may change on a frequent 

basis in relation to price fluctuations and availability, such as fuel type, or may only change 

slowly over time, such as by operational decisions regarding waste management and product 

specifications. While courts have affirmed the EPA’s authority to choose a methodology 

designed to estimate emissions in setting the MACT floor, the commenter noted that the courts 

have also made clear that the EPA’s method “must ‘allow a reasonable inference as to the 

performance of the top 12 percent of units.’” Accordingly, the commenter noted that the Court of 

Appeals for the D.C. Circuit has stated that “EPA must show not only that it believes its 

methodology provides an accurate picture of the relevant sources’ actual performance, but also 

why its methodology yields the required estimate.” (Sierra Club v. EPA, 167 F.3d at 663; DC 

Circuit 1999)

The commenter stated that the EPA has a clear policy of considering long-term 

variability when establishing enforceable emission rates for both Prevention of Significant 

Deterioration (PSD) permits under the CAA and Best Available Control Technology (BACT) 

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emissions limits. The commenter asserted that the Environmental Appeals Board has recognized 

the use of “safety factor[s]” in the calculation of BACT permit limits to take into account both 

the variability and fluctuation in the expected performance of pollution controls and the fact that 

setting emissions limitations for one facility at the highest control efficiency demonstrated at 

another facility would make violations of the permit unavoidable. For this reason, the commenter 

argued that the policy and common sense approach used by the EPA in PSD permitting should 

also apply in establishing MACT standards.

The commenter contended that the EPA should not rely solely on short-term data from 

similar sources and ignore the variability and long-term impact of the proposed emission rates. 

The commenter stated that the EPA has expressed caution regarding reliance on stack test and 

short-term emissions data results to derive a MACT floor due to the variability in operating 

conditions at any facility. In the EPA’s proposed rule to set a NESHAP for mercury at coal-fired 

electric utilities, the commenter noted that the agency identified a number of factors that 

contribute to the variability in emission test data that must be considered, including the (1) 

emission test method; (2) analytical method; (3) design of the unit and the control device(s); (4) 

operating conditions of the facility and the control device(s); (5) amount of constituent being 

tested in the fuel; and 6) composition of the constituents in the fuel or flue gases. The commenter 

stated that the EPA should consider these sorts of factors in this rulemaking.

Furthermore, the commenter argued that this policy and common sense approach is 

recognized and required by the D.C. Circuit. Once the “similar sources” category is established, 

the EPA should identify the lowest emission limitation that has been “achieved in practice” by 

these sources. In another MACT case, the commenter cited that the D.C. Circuit has held that the 

phrase “achieved in practice” refers to the performance of the source “under the worst 

foreseeable circumstances.” (Sierra Club, 167 F.3d at 664.)

The commenter contended that the EPA should follow its own common sense approach 

and the directive of the D.C. Circuit and develop MACT standards that consider the long-term 

emission variations in mineral wool and wool fiberglass facilities. Specifically, the commenter 

argued that HCl and HF emissions data are limited to the BTEC data collected during a single 

season, and there are no historic data. The commenter asserted that mineral wool companies are 

concerned that given the limitations of the data, consistent compliance with the EPA’s proposed 

limits will be difficult. Therefore, the commenter urged the EPA to apply liberal variation factors 

to account for the limitation of the HCl and HF data.

Response: Section 112(d)(3) of the CAA requires that the MACT standards for existing 

sources be no less stringent than the average emission limitation achieved by the best performing 

12 percent of existing sources for which the EPA has emissions information. “Section 112(d)(3) 

requires floors that are based on the emission level actually achieved by the best performers 

(those with the lowest emission levels).” Sierra Club, 479 F.3d at 880. As we have explained in 

various rules, CAA section 112(d)(3) does not address the question of whether emission levels 

should be evaluated either over time or in a single test result for assessing which sources perform 

best or are best controlled. We believe, however, that our MACT floor calculation should 

identify the best performers (i.e., the best performing 12 percent or best performing five sources 

in smaller source categories for existing sources, and the best controlled single source for new 

sources) as those sources likely to emit the least HAP over time considering variability. Further, 

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the D.C. Circuit has held repeatedly that variability of best performing sources may be taken into 

account in establishing MACT floors. Id at 881-882. See also National Lime Ass’n v. EPA, 627 

F.2d 416, 431 n.46, 443(D.C. Cir. 1980). Therefore, we believe it is appropriate to consider 

statistical variability to ensure that regulated sources can meet the proposed limits at all times.

Further, as explained in earlier responses, the EPA believes that the UPL calculation is a 

valid statistical approach to estimate a MACT floor level (including variability) that is equivalent 

to the average of the best performing sources based on future compliance tests. The EPA 

believes it is entirely appropriate to consider the variability within the best performing sources in 

developing emission limits based on the average performance of those sources. We also believe 

that if we did not account for variability in this manner, and instead set the limit based solely on 

the average (mean) performance (e.g., as measured by a single test at each source), then it would 

be reasonable to expect these same units to exceed the limit half the time or more. The EPA 

agrees with the commenter that there are alternatives to the UPL statistics. But, we believe that 

because the floor calculations represent the average of the best performing 12 percent of existing 

sources, it is reasonable for the EPA to use an appropriate statistical analysis to assess the effect 

that both intra-unit and inter-unit variability have on the emissions profiles. 

Consistent with CAA sections 112(d)(2) and (3), the MACT floors for both source 

categories were calculated using the UPL approach, which includes variability based on the 

individual test runs from the top five performing sources for which we have data. We have also 

revised and updated our calculation of the proposed limits for both source categories using 

additional test data we received in response to the proposed rules, including new data and data 

corrections from the wool fiberglass and mineral wool industries and they are based on all 

certified or independently-verifiable emission stack test data of appropriate quality available to 

the EPA. As a result, we have revised the appropriate limits in the final rule. Our calculations 

and detailed explanations can be found in the memoranda, Use of the Upper Prediction Limit for 

Calculating MACT Floors,” and “Approach for Applying the Upper Prediction Limit to Limited 

Datasets,” which are available in the dockets for this rulemaking.

Further, as explained in the 2011 proposal, the EPA and industry, as documented in the 

trade association’s (NAIMA’s) April 13, 2010 letter, agreed on the sources and emissions testing 

that would be conducted for these rules using the EPA approved test methods. In that letter, 

industry assured the EPA that these tests would provide data that would be representative of 

other mineral wool producers across the U.S. In acknowledging this agreement, the April 13, 

2010 letter indicated that the bases for representativeness would include design type and size of 

process units or equipment, fuel type, operating temperatures, control devices and raw material 

content. We note that all mineral wool producers participated in this process and agreed with the 

voluntary data collection effort initiated by the trade association. The industry conducted these 

emissions tests during 2010, submitted them to the EPA in January 2011 and submitted new 

information regarding cupola design and raw material use after the proposed rules were 

published in November 2011 and in April 2013. (“EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a problem. We generally defer to an 

agency's decision to proceed on the basis of imperfect scientific information, rather than to invest 

the resources to conduct the perfect study.” Sierra Club v. EPA, 334 U.S. App. D.C. 421, 167 

F.3d 658, 662 (D.C. Cir. 1999) (citation omitted)).

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59. Comment: One commenter (1042-0120/1042-0348/1041-0126) stated the proposed 

standards for the mineral wool production and wool fiberglass manufacturing source categories 

are based on pollutant-by-pollutant analyses that rely on different sets of best performing sources 

for each HAP standard. The commenter maintained that the EPA has “cherry-picked” the best 

performing data in setting each standard, without regard for the sources from which the data 

originated. The commenter stated that the result is a set of standards that reflect the performance 

of a hypothetical set of best performing sources that simultaneously achieve the greatest 

emission reductions for each HAP, rather than the actual performance of one or more real 

sources. The commenter asserted that this biased approach is contrary to the language of section 

112 of the CAA and produces unrealistic and impracticable standards.

The commenter (1042-0120/1042-0348) argued that the statute unambiguously directs 

the EPA to set standards based on the overall performance of sources. The commenter observed 

that sections 112(d)(1), (2), and (3) of the CAA specify that emissions standards must be 

established based on the performance of “sources” in the category or subcategory and that the 

EPA’s discretion in setting standards for such units is limited to distinguishing among classes, 

types, and sizes of sources. The commenter pointed out that these provisions make clear that 

standards must be based on actual sources, and cannot be the product of pollutant-by-pollutant 

parsing. The commenter noted that Congress also provided express limits on the EPA’s authority 

to parse units and sources for purposes of setting standards and that express authority does not 

allow the EPA to “distinguish” units and sources by individual pollutant as it has proposed in this 

rule.

The commenter (1042-0120/1042-0348) observed that in other MACT standards, the 

EPA has taken the position that the cherry-picking argument was waived if not raised in the 

original promulgation of the MACT. The commenter argued that in the original wool fiberglass 

MACT, the EPA only directly regulated one pollutant per affected facility – PM for furnaces and 

formaldehyde for forming, collection, and curing lines (either RS or FA). The commenter 

concluded that the EPA did not engage in “cherry-picking” in the original MACT rule and

neither the commenter nor the industry had the need to raise the issue in the original 1999 

rulemaking.

Response: The EPA disagrees with the commenter. Contrary to the commenter’s 

suggestion, CAA section 112(d)(3) does not mandate a total facility approach. A reasonable 

interpretation of CAA section 112(d)(3) is that MACT floors may be established on a HAP-byHAP basis, so that there can be different pools of best performers for each HAP. Indeed, as 

illustrated below, the total facility approach is not compelled by the statutory language but can 

lead to results so arbitrary that the approach may simply not be legally permissible.

Section 112(d)(3) of the CAA is ambiguous as to whether the MACT floor is to be based 

on the performance of an entire source or on the performance achieved in controlling particular 

HAP. Congress specified in CAA section 112(d)(3) the minimum level of emission reduction 

that could satisfy the requirement to adopt MACT. For new sources, this floor level is to be “the 

emission control that is achieved in practice by the best controlled similar source.” For existing 

sources, the floor level is to be “the average emission limitation achieved by the best performing 

12 percent of the existing sources” for categories and subcategories with 30 or more sources, or 

“the average emission limitation achieved by the best performing 5 sources” for categories and 

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subcategories with fewer than 30 sources. The language of the CAA does not address whether 

floor levels can be established HAP-by-HAP or by any other means. The reference to “sources” 

does not lead to the assumption the commenter makes that the best performing sources can only 

be the best-performing sources for the entire suite of regulated HAP. Instead, the language can 

be reasonably interpreted as referring to the source as a whole or to performance as to a 

particular HAP. Similarly, the reference in the new source MACT floor provision to “emission 

control achieved by the best controlled similar source” can mean emission control as to a 

particular HAP or emission control achieved by a source as a whole.

Also, CAA section 112(d) includes language such as “existing source,” “best 

performing,” and “achieved in practice” in referring to sources’ actual operations, but again the 

language says nothing about whether it is referring to performance as to individual HAP or to 

single facility’s performance for all HAP. Industry commenters also said that Congress could 

have mandated a HAP-by-HAP result. The argument that MACT floors set HAP-by-HAP are 

based on the performance of a hypothetical facility, so that the limitations are not based on those 

achieved in practice, just re-begs the question of whether CAA section 112(d)(3) refers to whole 

facilities or individual HAP. All of the limitations in the floors in this rule of course reflect 

sources’ actual performance and were achieved in practice. 

The commenter also points to EPA’s subcategorization authority, and claims that because 

Congress authorized the EPA to distinguish among classes, types, and sizes of units, the EPA 

cannot distinguish units by individual pollutant, as they allege the EPA did in the proposed rules. 

However, that statutory language addresses the EPA’s authority to subcategorize sources within 

a source category prior to setting standards. In doing so, the EPA does not distinguish within 

each subcategory based on HAP emitted. Rather, it establishes emissions standards based on the 

emissions limits achieved by units in each subcategory. Therefore, the EPA’s subcategorization 

authority is irrelevant to the question of how the EPA establishes MACT floor standards once it 

has made the decision to distinguish among sources and create subcategories.

The EPA’s long-standing interpretation of the CAA is that the existing and new source 

MACT floors are to be established on a HAP-by-HAP basis. One reason for this interpretation is 

that a whole plant approach could yield least common denominator floors – that is floors 

reflecting mediocre or no control, rather than performance which is the average of what best 

performers have achieved. See 61 FR 173687 (April 19, 1996); 62 FR 48363-64 (September 15, 

1997) (same approach adopted under the very similar language of CAA section 129 (a)(2)). Such 

an approach would allow the performance of sources that are outside of the best-performing 12 

percent for certain pollutants to be included in the floor calculations for those same pollutants, 

and it is even conceivable that the worst performing source for a pollutant could be considered a 

best performer overall, a result Congress could not have intended. Inclusion of units that are 

outside of the best performing 12 percent for particular pollutants would lead to emission limits 

that do not meet the requirements of the statute.

For example, if the best performing 12 percent of facilities for HAP metals were also the 

worst performing units for acid gas HAP, the floor for acid gases or metals would end up not 

reflecting best performance. In such a situation, the EPA would have to make some type of value 

judgment as to which pollutant reductions are most critical to decide which sources are best 

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controlled. Such value judgments are antithetical to the direction of the statute at the MACT 

floor-setting stage. 

The central purpose of the amended air toxics provisions was to apply strict technologybased emission controls on HAP. See, e.g., H. Rep. No. 952, 101st Cong. 2d sess. 338. The 

floor’s specific purpose was to assure that consideration of economic and other impacts not be 

used to “gut the standards. Although costs are by no means irrelevant, they should by no means 

be the determining factors. There needs to be a minimum degree of control in relation to the 

control technologies that have already been attained by the best existing sources.” A Legislative 

History of the Clean Air Act, Vol. II at 2897 (statement of Rep. Collins). An interpretation that 

the floor level of control must be limited by the performance of devices that only control some of 

these pollutants effectively “guts the standards” by including worse performers in the averaging 

process, whereas the EPA’s interpretation promotes the evident Congressional objective of 

having the floor reflect the average performance of best performing sources. Because Congress 

has not spoken to the precise question at issue and the agency’s interpretation effectuates 

statutory goals and policies in a reasonable manner, its interpretation must be upheld. See 

Chevron v. NRDC, 467 U.S. 837 (1984). 

The EPA notes, however, that if optimized performance for different HAP is not 

technologically possible due to mutually inconsistent control technologies (for example, if metals 

performance decreased if organics reduction is optimized), then this would have to be taken into 

account by the EPA in establishing a floor (or floors). The Senate Report indicates that if certain 

types of otherwise needed controls are mutually exclusive, the EPA is to optimize the part of the 

standard providing the most environmental protection. S. Rep. No. 228, 101st Cong. 1st sess. 

168 (although, as noted, the bill accompanying this Report contained no floor provisions). It 

should be emphasized, however, that, “the fact that no plant has been shown to be able to meet 

all of the limitations does not demonstrate that all the limitations are not achievable.” Chemical 

Manufacturers Association v. EPA, 885 F.2d at 264 (upholding technology-based standards 

based on best performance for each pollutant by different plants, where at least one plant met 

each of the limitations but no single plant met all of them).

Finally, we note that the D.C. Circuit recently found a challenge to the agency’s practice 

of setting floors based on emissions levels achieved by the best performing units on a pollutantby-pollutant basis to be barred on jurisdictional grounds. Medical Waste Institute v. EPA, 645 

F.3d 420 (D.C. Cir. 2011).

60. Comment: One commenter (1042-0115f) stated that the EPA has the duty under the 

MACT Review, CAA section 112(d)(6), both to look back and to have reductions now 

achievable and to look around at developments in the technology processes and work practices to 

update the rule to obtain all appropriate emission reductions.

Response: We agree with the commenter, and note that the final rule addresses 

technology review for these source categories. Specifically, the EPA conducted a technology 

review on the wool fiberglass MACT to determine what emission limits are appropriate due to 

improvements in technology and work practices that have developed since the MACT standard 

was promulgated in 1999. We determined that there are developments in practices, processes, 

and control technologies that warrant revisions to the MACT standards for the Wool Fiberglass 

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Manufacturing source category. Therefore, to satisfy the requirements of CAA section 112(d)(6), 

we are revising the existing MACT standards to include an emission limit for glass-melting 

furnaces of 0.33 pounds of PM per ton of glass pulled as we proposed in April 2013. In this 

action, we are also revising the proposed chromium emission limit for gas-fired glass-melting 

furnaces from 6.0E-05 to 2.5E-04 pounds of total chromium per ton of glass pulled, based on our 

re-assessment of emissions data for newly-rebuilt gas-fired glass-melting furnaces. As explained 

in the preamble to the final rule, we have adopted both standards, under CAA sections 112(f)(2) 

and 112(d)(6), but these standards rest on independent statutory authorities and independent 

rationales. Consequently, these standards remain independent and legally severable. 

We also reviewed but did not find new developments in technology within the mineral 

wool production industry, and therefore we are readopting the existing PM standards under CAA 

section 112(d)(6).

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V. MINERAL WOOL PRODUCTION (SUBPART DDD)

A. Cupola PM Limits 

61. Comment: One commenter (1041-0081) supported the EPA’s retention of 

particulate matter (PM) as a surrogate for HAP metals and the PM emission limit for mineral 

wool production. As noted by the EPA, the commenter stated that the courts have held that PM is 

an appropriate surrogate for HAP metals. Therefore, the commenter agreed that the EPA is 

correct in retaining PM as a surrogate for the Mineral Wool MACT.

Response: The agency acknowledges the commenter’s support.

B. Cupola HF and HCl Limits 

62. Comment: One commenter (1041-0164) supported the EPA's proposed emission 

limits for HF and HCl for existing sources in both cupola subcategories published on November 

13, 2014.

Response: The agency acknowledges the commenter’s support.

63. Comment: One commenter (1041-0080/1041-0126) asserted that the EPA did not 

provide complete disclosure of the way the emission limits proposed in 2011 and 2013 were 

determined, including the specific data that the EPA did and did not consider in developing the 

limits. The commenter argued that the EPA’s MACT floor calculation method for new and 

existing sources was improperly applied. The commenter argued that the EPA’s discussion in the 

preambles to the 2011 and 2013 proposed rules and the MACT floor memorandum lacked any 

details on the analysis itself. The commenter opined that, due to the insufficient detail regarding 

the data that the EPA did and did not consider, the EPA record is inadequate and, according to 

the commenter, subject to challenge. The commenter provided as an example, to determine UPL, 

the EPA should conduct statistical analysis related to the normality of the test data and possibly 

transform the data to produce a suitable distribution. The commenter noted that the MACT floor 

memorandum discusses this, but does not fully explain how the analysis was done for the 

mineral wool industry, which the commenter found to be a significant lapse. The commenter 

asserted that the EPA has a legal obligation under the CAA to include in the record a “statement 

of basis and purpose” that should include such information. The commenter maintained that its 

absence violates section 307(d)(3) of the CAA, and, if not corrected prior to promulgation, 

would render the final rule arbitrary. 

Response: We note that, in another letter (1041-0164), the commenter subsequently 

expressed support for the HCl and HF limits for existing sources that we proposed in 2014 and 

are finalizing in this action (see comment number 62). We disagree with this comment and we 

believe that we clearly presented the data sources and our approach used to calculate the MACT 

floors. In our November 25, 2011 proposal, we included a detailed explanation of our calculation 

of the MACT floors in the MACT Floor Analysis for the Mineral Wool Production 

Manufacturing Source Category memorandum that is available in the docket for this rulemaking 

(docket item number EPA-HQ-OAR-2010-1041-0019). As explained in the 2011 proposal, we 

received test data from all the mineral wool production facilities in response to a voluntary 

survey conducted by the commenter of both the mineral wool and wool fiberglass manufacturing 

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facilities. The EPA requested from the commenter, and the commenter agreed (see the May 5, 

2010 letter contained as Appendix A to docket item number EPA-HQ-OAR-2010-1041-0080), 

that the data submitted in response to the voluntary survey would include existing test data and 

test data collected from a subset of facilities that were representative of emission sources from 

certain mineral wool production facilities. In acknowledging this agreement, the commenter’s 

May 5, 2010 letter indicated that the bases for representativeness would include design type and 

size of process units or equipment, fuel type, operating temperatures, control devices and raw 

material content. We also explained in the November 25, 2011 preamble (76 FR 72778) that 

these responses included test data for most HAP metals, CO, PM, formaldehyde, methanol, and 

phenol emissions from cupolas, curing ovens and collection operations. We relied on these test 

data in calculating the MACT floor level of control for cupolas used in mineral wool production 

for the 2011 proposal.

In the April 15, 2013 supplemental proposal to the RTR (78 FR 22385) and in the 

memorandum “Technical Approach for Mineral Wool MACT Floor Calculations” (docket item 

number EPA-HQ-OAR-2010-1041-0109), we presented our rationale for developing 

subcategories for different types of cupolas and for revising the HF and HCl emission limits 

using the UPL approach. Additionally, more recently in the November 13, 2014 supplemental 

proposal (79 FR 68019) and in the memorandum “Revised Technical Approach for Mineral 

Wool MACT Floor Calculations” (docket item number EPA-HQ-OAR-2010-1041-0156), we 

subsequently proposed and discussed our decision to revise the HF and HCl emissions limits for 

cupolas based on our updated approach for evaluating limited data sets (also see the 

memorandum “Approach for Applying the Upper Prediction Limit to Limited Datasets –

Ferroalloys” (docket item number EPA-HQ-OAR-2010-1041-0129) for the updated approach for 

limited datasets).

64. Comment: One commenter (1041-0126) suggested in response to the 2013 proposal 

that one alternative approach for the EPA to use in developing the MACT floor limits for the 

acid gases HF and HCl from the two subcategories of cupolas (those that process slag and those 

that do not) is to set work practice standards instead of emission limits for HF and HCl for the 

subcategory of cupolas not processing slag.

Response: We note that, in another letter (1041-0164), the commenter subsequently 

expressed support for the HCl and HF limits for existing sources that we proposed in 2014 and 

are finalizing in this action (see comment number 62). We disagree with the commenter’s 

recommended alternative approach because it is unsupported by available test data and therefore, 

impermissible under the CAA. As explained in our 2011 and 2013 proposals, under CAA section 

112(d), the EPA is required to promulgate standards for major sources of HAP based on MACT 

performance. For existing sources, MACT standards must be at least as stringent as the average 

emissions limitation achieved by the best performing 12 percent of existing sources (for which 

the Administrator has emissions information) or the best performing 5 sources for source 

categories with less than 30 sources. For new sources, the MACT standards must be at least as 

stringent as the control level achieved in practice by the best controlled similar source (section 

112(d)(3)). The EPA is not allowed to consider costs in establishing the MACT floor standards; 

“Congress imposed minimum stringency requirements - the EPA calls them ‘emission floors’-

which apply without regard to either costs or other factors and methods listed in section 

7412(d)(2).” Sierra Club, 479 F.3d at 877. The EPA also must consider more stringent “beyondJune 2015 89
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the-floor” control options. In doing so, the EPA must take into consideration the costs of 

achieving such options, and any non-air quality health and environmental impacts and energy 

requirements (CAA section 112(d)(2)). 

Section 112(h) of the CAA allows the EPA to set work practice standards instead of an 

emissions floor “if it is not feasible in the judgment of the Administrator to prescribe or enforce 

an emission standard.” Under CAA section 112(h)(2)(B), it is “not feasible” to set an emission 

standard when “the application of measurement methodology to a particular class of sources is 

not practicable due to technological and economic limitations.” Thus, CAA section 112(h) 

“allows EPA to substitute work practice standards for emission floors only if measuring emission 

levels is technologically or economically infeasible.” Sierra Club v. EPA, 479 F.3d 875, 884 

(D.C. Cir. 2007). Because we did not identify any technological or economic limitations 

associated with measuring HF and HCl emissions from cupolas, the EPA does not have the 

discretion to adopt work practice standards rather than establishing emission limits.

65. Comment: One commenter (1041-0080/1041-0126) stated that their understanding 

was that the proposed MACT standards for HF and HCl for existing sources were calculated by 

taking the average of the top five cupolas and multiplying it by different multipliers – possibly 2, 

2.5, or 3. The commenter noted that current calculations of the EPA’s proposed emission limits 

seem to average out as follows:

• COS – 3 times the Top 5 Cupola Average

• HF – 1.5 times the average of the top five cupolas

• HCl – 1.5 times average of the top five cupolas

Pollutant

Emission Limit (lb/ton of melt)

Average of 

Top 5 

Cupolas

EPA’s Proposed Rule

Multiplied Average by 3 for 

COS and 1.5 for HF and HCl

Multiplied 

Average by 2

Multiplied 

Average by 2.5

Multiplied 

99% UPL Existing Sources Average by 3

COS 1.066979 3.30 2.1338 2.667 3.2007

HF 0.008895 0.014 0.01778 0.0222 0.02669

HCl 0.0066 0.0096 0.01316 0.0165 0.0198

The commenter urged the EPA to use a higher multiplier, where possible, for all 

pollutants to account for greater variability in emission limits.

Response: We note that this commenter subsequently expressed support for the finalized 

HCl and HF limits for existing sources, as summarized in comment number 62. Regarding the 

commenter’s understanding of the EPA’s MACT floor calculations and the EPA’s use of 

multipliers, as explained in the 2011 proposal (6 FR 72788), the 2013 supplemental proposal (78 

FR 22385-22386), and the 2014 supplemental proposal (79 FR 68017-68018, and 68109), we 

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used the UPL approach our updated approach to evaluated limited datasets to develop the HF 

and HCl emissions limits, rather than multipliers as noted by the commenter.

66. Comment: One commenter (1041-0080/1041-0126) argued that the EPA is not 

required to set limits for HCl and HF. The commenter (1041-0080) stated that the EPA is not 

required to regulate HCl and HF because, as the EPA acknowledged, HCl and HF were not 

regulated under the 1999 Mineral Wool MACT Standard and the emissions of these pollutants 

have not increased in the mineral wool industry since that time. The commenter added that the 

industry has experienced a significant reduction in the number of operating plants since 

implementation of the MACT standard. The commenter argued that because of the EPA's 

interpretation of the Brick MACT decision, the EPA believes that the court decision mandates 

imposition of emission limits for HCl and HF.

The commenter stated that the EPA’s interpretation is incorrect, and that the agency is 

not mandated to regulate HCl and HF. The commenter noted that the amount of HCl and HF 

emitted by mineral wool sources does not meet the 10 tons per year threshold required to trigger 

MACT applicability. Moreover, the commenter stated that the EPA can revise an existing 

MACT standard only under CAA section 112(d)(6). The commenter claimed that the NRDC v. 

EPA decision (HON RTR rule) plainly holds that the EPA is not required to “correct” prior 

MACT standards or recalculate MACT standards under CAA section 112(d)(6). Therefore, the 

commenter asserted, the EPA does not need to regulate HCl and HF. But if it decides to do so, 

the commenter contended that the EPA does not need to set a standard under CAA sections 

112(d)(2) and (d)(3).

The commenter (1041-0126) opined that precedent exists in the CAA section 112 MACT 

standard for utility boilers to support the premise that the EPA is not required to set emission 

limits for all HAP emitted from a source category. The commenter observed that for coal-fired 

utilities, the EPA has published AP-42 emission factors indicating that organic HAP are emitted 

from these sources, but the EPA has not regulated organic HAP emissions either directly or by 

using a surrogate. The commenter requested that the EPA refrain from setting any standard for 

HF and HCl from mineral wool production processes on the basis of this example from the coalfired utility industry.

Response: We disagree with the commenter that CAA section 112(d)(6) is the EPA’s 

sole authority for revising existing MACT standards. We believe that CAA section 112 does not 

expressly address this issue, and that the EPA has discretion in determining how to address 

potential revisions to a promulgated standard. CAA section 112(d)(6) provides that the agency 

must review and revise “as necessary.” The “as necessary” language must be read in the context 

of the provision, which focuses on the review of developments that have occurred since the time 

of the original promulgation of the MACT standard and thus, should not be read as a mandate to 

correct flaws that existed at the time of the original promulgation. Further, recent D.C. Circuit’s 

decisions support the EPA amending improper MACT determinations under CAA sections 112 

(d)(2) and (3). The D.C. Circuit held that the EPA may permissibly amend improper MACT 

determinations, including amendments to improperly promulgated floor determinations, using its 

authority under CAA sections 112(d)(2) and (3). Id. Thus, we believe that we may amend 

improper MACT determinations, including amendments to improperly promulgated floor 

determinations, under CAA sections 112 (d)(2) and (3). Medical Waste Institute v. EPA, 645 

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F.3d 420, 425-27 (D.C. Cir. 2011) (resetting MACT floor, based on post-compliance data, is 

permissible when originally-established floor was improperly established, and permissibility of 

the EPA’s action does not turn on whether the prior standard was remanded or vacated). Here, 

the EPA did not establish a MACT standard for these HAP, an approach soundly rejected by the 

D.C. Circuit in National Lime, 233 F.3d at 633-34. We also note that, in National Lime 

Association v. EPA, 233 F.3d 625 (D.C. Cir. 2000), the D.C. Circuit remanded the Portland 

Cement MACT to the EPA to establish MACT floors for HCl holding that we had a clear 

“statutory obligation to set emission standards for each listed HAP.” Therefore, we believe the 

EPA is not barred from making MACT floor determinations and issuing MACT standards 

pursuant to CAA sections 112(d)(2) and (3) for this source category. Additionally, in several 

recent rulemakings, we have chosen to fix underlying defects in existing MACT standards under 

CAA sections 112(d)(2) and (3), the provisions that directly govern the initial promulgation of 

MACT standards (see National Emission Standards for Hazardous Air Pollutants From 

Petroleum Refineries, October 28, 2009, 74 FR 55670; and National Emission Standards for 

Hazardous Air Pollutants: Group I Polymers and Resins; Marine Tank Vessel Loading 

Operations; Pharmaceuticals Production; and the Printing and Publishing Industry, April 21, 

2011, 76 FR 22566). We believe that our approach is reasonable because using those provisions 

ensures that the process and considerations are those associated with initially establishing a 

MACT standard, and it is reasonable to make corrections following the process that would have 

been followed if we had not made an error at the time of the original promulgation.

We also disagree with the comment that the EPA did not regulate (directly or by 

surrogate) any organic HAP from coal-fired utilities in the recent Utility MACT rule. To the 

contrary, the EPA established work practice standards for organic HAP under CAA section 

112(h). Additionally, in the Boilers NESHAP we established a MACT standard for HCl 

emissions. Both HCl and HF are listed HAP under CAA section 112(b), and we are statutorily 

required to establish MACT standards for all HAP emitted by major sources under CAA sections

112(d)(2) and (3).

67. Comment: One commenter (1014-0164) opposed the emission limits for HF and 

HCl for new sources in both cupola subcategories proposed on November 13, 2014. The 

commenter argued that the proposed limits were very stringent and impossible to meet with 

existing technology available to the industry, and would prohibit expansion or growth of the 

mineral wool industry. The commenter argued that the proposed new source emission limits are 

based on very limited a dataset resulting in too much uncertainty (a large standard deviation) and 

an unacceptably high MACT floor. The commenter argued that historical data are lacking 

because mineral wool facilities have not been regulated for HF and HCl emissions. The 

commenter asked that the EPA delay HF and HCl emission limits for new sources until the next 

residual risk analysis when more data are available.

The commenter (1041-0088/1041-0126) expressed a similar concern in response to the 

HF and HCl emission limits for new and existing sources proposed on November 25, 2011, and 

April 15, 2013, saying that these limits were based on a very small data set collected in a brief 

period of time and in one season of the year, and that these data failed to correctly account for 

variation in emissions over time (e.g., season to season or over the course of the year). The 

commenter added that there has been no indication that HCl and HF emissions from industry 

have increased since the 1999 NESHAP was finalized. To address this lack of data and unknown 

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variability, the commenter requested that the EPA recalculate the proposed limits using data in a 

way that maximizes variability, such as calculating emission limits based on the best performing 

sources rather the lowest emitting sources. In their comment on the 2014 proposal (1041-0164), 

the commenter expressed support for the EPA's method for addressing data variability and 

limited data availability by calculating emission HF and HCl limits using the UPL approach.

In addition to considering variability in the emissions data, the commenter emphasized 

that the EPA should also consider variability in the processing rate. Given the fact that EPA is 

using lbs per ton of melt data to calculate the MACT floor, the commenter believed that 

variability in that processing rate is equally important. 

Response: Regarding the comment that the EPA should delay finalizing HF and HCl 

emission limits, the EPA is finalizing emission limits for HF and HCl proposed in 2014 to meet 

the EPA’s statutory obligation to set emission standards for each listed HAP, as reinforced by the 

court’s decision in National Lime v. EPA (233 F.3d 625, 634 (DC Cir. 2000)) (see the 2011 

proposed rule (76 FR 72788)). Congress specified in CAA section 112(d)(3) the minimum level 

of emission reduction that could satisfy the requirement to adopt MACT. For new sources, this 

floor level is “the emission control that is achieved in practice by the best controlled similar 

source.” Thus, CAA section 112(d)(3) requires the EPA to establish the MACT floor for new 

sources differently for new sources and existing sources and the EPA is prohibited from adopting 

the same standard for new sources as for existing sources, as recommended by the commenter, 

where the available data indicate that new sources can achieve a more stringent level of control, 

which is the case here. As such, the EPA may not set limits for new sources equal to the limits 

for existing sources because the available data indicates that new sources can achieve “the 

emission control that is achieved in practice by the best controlled similar source.”

The EPA’s analysis of the available data indicate that the proposed limits for new sources 

were based on the emission controls that are achieved by the best controlled similar source, as 

discussed in the preamble to the 2014 proposed rule (79 FR 68020) and in the supporting 

memorandum in the docket for this rulemaking (EPA docket item EPA-HQ-OAR-2010-1041-

0156).

In response to the comment that the EPA’s dataset for HCl and HF is too limited and 

does not include historical data, as explained in the 2011 proposal, industry conducted a 

voluntary survey among all owners and operators of mineral wool production facilities to collect 

HCl and HF data. Further, the EPA requested and industry agreed (see the May 5, 2010 letter 

contained as Appendix A to docket item number EPA-HQ-OAR-2010-1041-0080), that a subset 

of facilities that were representative of emission sources from both the mineral wool and wool 

fiberglass industries would conduct emissions testing. The April 13, 2010 letter indicated that the 

bases for representativeness included design type and size of process units or equipment, fuel 

type, operating temperatures, control devices and raw material content. With regard to HCl and 

HF emissions data, the letter states that “[f]ive of the six companies are collecting new data. The 

Thermafiber data is representative of Amerrock Products based on the following: all of the 

cupolas are coke-fired, melting blast furnace slag and producing slag wool products.” In lieu of 

new testing, the EPA also allowed industry to submit prior existing and well-documented test 

data that were representative of wool fiberglass manufacturing operations (76 FR 72778). In 

certain instances, industry opted to submit existing test data in lieu of conducting new testing. 

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(“EPA typically has wide latitude in determining the extent of data-gathering necessary to solve 

a problem. We generally defer to an agency's decision to proceed on the basis of imperfect 

scientific information, rather than to invest the resources to conduct the perfect study.” Sierra 

Club v. EPA, 334 U.S. App. D.C. 421, 167 F.3d 658, 662 (D.C. Cir. 1999) (citation omitted)). 

Thus, we disagree with the commenter’s assertion that the EPA’s data set is a very small, 

collected during a specific time period, and without historical data. 

Further, regarding the comment that the EPA’s dataset failed to correctly account for 

variations in processing and emissions over time, the D.C. Circuit has held repeatedly that 

variability of best performing sources may be taken into account in establishing numeric MACT 

floors. See Mossville Environmental Action Now v. EPA, 370 F.3d 1232, 1241-42 (D.C. Cir. 

2004). Section 112(d)(3) of the CAA “requires that floors reflect a reasonable estimate of the 

emissions achieved in practice by the best-performing sources.” Cement Kiln Recycling 

Coalition v. EPA, 255 F.3d 855, 872-73 (D.C. Cir. 2001) (internal quotes omitted); See also, 

Sierra Club v. EPA, 479 F.3d at 881-82. Consistent with section 112(d)(2) and (3), the MACT 

floors for HCl and HF were calculated using the UPL approach, which includes variability based 

on the individual test runs from the best performing 12 percent of sources – or in this case, the 

top 5 performing sources. A more detailed explanation of how we calculated the MACT floors 

can be found in the “Technical Approach for Mineral Wool MACT Floor Calculations”

(September 15, 2011)21 and in the two memoranda updating this 2011 analysis, “Technical 

Approach for Mineral Wool MACT Floor Calculations” (February 7, 2013),22 and “Revised 

Technical Approach for Mineral Wool Production MACT Floor Calculations (September 26, 

2014).”23

Regarding the commenter’s request that the EPA address data limitations and variability 

by calculating emission limits based on the “best performing sources” rather the “lowest emitting 

sources,” the EPA uses the lowest emission value to rank the different facilities and to select the 

best performing sources (see the EPA’s response to comment number 57 for a detailed EPA 

response to this comment). 

The EPA appreciates the commenter’s support for its use of the UPL approach in the 

2014 proposal.

68. Comment: One commenter (1041-0080; 1041-0126) stated that the EPA’s 

calculation of the MACT floor for the HCl and HF emission limits proposed on November 25, 

2011 was flawed because the EPA erred in selecting and analyzing the data used in the MACT 

analysis. The commenter argued that, in selecting the top five performing sources (the Mineral 

Wool Source Category has less than 30 sources), the EPA calculated the MACT floor for HCl 

and HF with data from two facilities that are synthetic area sources. The commenter argued that 

the MACT floor can be based only on data from sources in the source category being regulated. 

The commenter noted that there are no reported legal decisions supporting the use of synthetic 

area sources in setting MACT floors under CAA section 112(d)(3), and the commenter 

challenged and objected to using synthetic area sources for this MACT determination. The 

21 EPA docket item number EPA-HQ-OAR-2010-1041-0019. 

22 EPA docket item number EPA-HQ-OAR-2010-1041-0109.

23 EPA docket item number EPA-HQ-OAR-2010-1041-0156.

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commenter argued that only major sources compose the source category, so only major sources 

should be included in the MACT floor. The commenter noted that true area sources are not 

included in MACT floor determinations, and concluded that synthetic area sources should be 

treated similarly. The commenter argued that including synthetic area sources would lead to 

controls that would be both technologically and economically infeasible, especially for specific 

plants. The commenter argued that this could lead to a result in which the "MACT floor" 

meeting the criteria in CAA section 112(d)(3) would be rejected if the criteria in CAA section 

112(d)(2) were applied.24 The commenter urged the EPA to reconsider the sources it selected to 

create the MACT floor.

Response: We disagree with the commenter’s assertion that test data for the two 

synthetic area sources may not be used to establish the MACT floor for major sources, as well as 

the commenter’s suggestion that the EPA should exclude these data, because such an exclusion 

would be impermissible under the CAA. As explained in previous rulemakings (e.g., Brick 

NESHAP, 68 FR 26697–26698, May 16, 2003), the EPA has determined that including synthetic 

area sources in calculating the MACT floor for major sources is consistent with CAA section 

112(d). We continue to believe that inclusion of synthetic area sources in MACT floor 

determinations is justified for the reasons explained below. Section 112 of the CAA does not 

specifically address the inclusion of synthetic area sources in the MACT floor calculations. 

These are sources that emit fewer than 10 tons per year of any HAP or fewer than 25 tons per 

year of any combination of HAP because they use some emission control device(s), pollution 

prevention techniques or other measures (collectively referred to as controls in this document) 

adopted under Federal or State regulations. If not for the enforceable controls they have 

implemented, synthetic area sources would be major sources under section 112 of the CAA. We

believe that the better interpretation of the CAA's plain language and legislative history requires 

that synthetic area sources be included in MACT floor determinations. 

First, the plain language of the statute makes clear that our MACT floor determinations 

are to reflect the best sources in a category. For new sources in a category or subcategory, the 

MACT floor shall not be less stringent than the emission control that is achieved in practice by 

the best-controlled similar source, as determined by the EPA. Section 112(d)(3) of the CAA 

requires that MACT floors reflect what the best controlled new sources and the best performing 

existing sources achieve in practice. These phrases contain no exemptions and are not limited by 

references to sources with or without controls. Therefore, they suggest that all of the bestcontrolled or best-performing sources should be considered in MACT floor determinations, 

regardless of whether or not such sources rely upon controls.

Second, CAA section 112(d)(3) expressly excludes certain sources that meet LAER 

requirements from MACT floor determinations for existing sources. (See CAA section 

112(d)(3)(A).) The fact that Congress expressly excluded such LAER sources but did not also 

exclude synthetic area sources suggests that no exclusion was intended for synthetic area 

sources. Indeed, nothing in the statute suggests that EPA should exclude a control technology 

from its consideration of the MACT floor because the technology is so effective that it reduces 

source emissions such that the source is no longer a major source of HAP. 

24 The commenter cited Sierra Club v. EPA, 479 F.3d 875, 884, and 885.

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Third, the EPA disagrees that the CAA contemplates that synthetic area sources must be 

treated like true area sources and excluded from MACT floor determinations. Section 112(a) of 

the CAA defines a major source as: any stationary source or group of stationary sources located 

within a contiguous area and under common control that emits or has the potential to emit 

considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 

25 tons per year or more of any combination of hazardous air pollutants * * *(See CAA section 

112(a)(1).) An area source is defined as any stationary source of hazardous air pollutants that is 

not a major source. (See CAA section 112(a)(1).) In the major source definition, the reference to 

a source's potential to emit considering controls allows the interpretation that a source's potential 

to emit before and after controls is relevant, such that synthetic area sources may be considered 

within the meaning of this definition and included in MACT floor determinations for categories 

of major sources. This is because we believe synthetic area sources, because they have already 

reduced HAP emissions below the major source threshold, they are among the best performing 

12 percent of existing sources and thus help to define the level of the MACT emission limit. 

Thus, including synthetic area sources in MACT floor determinations ensures that MACT floors 

reflect the best-performing sources, as the CAA requires. While the effect of excluding the best 

performing sources in a category from MACT floor determinations and therefore would be 

contrary to the statutory mandate that the EPA set MACT floors based on the levels the best 

controlled new sources and the best performing existing sources achieve in practice. We believe 

the statutory reference to potential to emit considering controls should be read in a manner 

consistent with the other requirements of section 112(d) of the CAA to allow for the 

consideration of synthetic area sources in MACT floor determinations for categories of major 

sources. 

Fourth, relevant legislative history for this section suggests that synthetic area sources 

should be included in MACT floor determinations. In a floor statement, Senator Durenberger 

stated that in implementing section 112(d)(3) of the CAA, "the [Senate] managers intend the 

Administrator to take whatever steps are necessary to assure that [the Administrator] has 

collected data on all of the better-performing sources within each category. [The Administrator] 

must have a data-gathering program sufficient to assure that [EPA] does not miss any sources 

that have superior levels of emission control." (See Environment and Natural Resources Policy 

Division, Congressional Research Service, 103d Cong., S.Prt. 103-38 (prepared for the U.S. 

Senate Committee on Environment and Public Works), A Legislative History of the Clean Air 

Act Amendments of 1990 at 870, Nov. 1993, emphasis added.) This statement underscores that 

Congress intended for MACT floor determinations to reflect consideration of all of the sources in 

each category with the best emission controls. We believe it would be inconsistent with 

Congress's intent and the plain language of the CAA to exclude synthetic area sources -those 

sources with superior controls which became synthetic area sources by implementing such 

controls-from MACT floor determinations. Therefore, we believe that the inclusion of synthetic 

area sources in MACT floor determinations is justified because of the reasons explained above. 

The EPA Title V Operating Permits Program (Title V) tracks the performance, 

compliance, operational status and major source status of all permitted sources, including wool 

fiberglass facilities currently in operation in the U.S. In finalizing this rule, we have not included 

sources that have been identified by the Title V program as area sources in the floor calculations. 

Therefore, true area sources (i.e., sources that do not have the potential to emit at least 10 tons 

per year of a single pollutant or at least 25 tons per year of any combination of HAP) were not 

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part of the MACT floor calculation for phenol, formaldehyde, or methanol. We note that most of 

the sources identified by the commenter as area sources were not described as area sources in the 

May 5, 2010 letter that was submitted in response to the voluntary survey conducted by the 

commenter. The letter states in pertinent part “[n]ew PM2.5 [and] total PM will be collected 

from Knauf’s Lannett, Alabama facility (621 Furnace)”(p.5);” [n]ew PM2.5 [and] total PM data 

will be collected from Johns Manville’s Richmond, Indiana facility (Melter)”(p.7);[e]xisting 

PM2.5 [data] will be provided from Knauf’s Shasta Lake, California facility” (p.7); and 

[e]xisting PM 2.5, and total PM data from Johns Manville’s Willows California facility will be 

provided.” (p. 9).” 

As explained in the 2011 proposal, industry conducted a voluntary survey among all 

owners and operators of mineral wool and wool fiberglass manufacturing facilities that were 

major sources. The survey sought test data for PM, CO and HAP emissions and information on 

process equipment, control devices, point and fugitive emissions, practices used to control point 

and fugitive emissions. Further, the EPA requested and industry agreed in a May 5, 2010 letter 

(see Appendix A of docket item number EPA-HQ-OAR-2010-1041-0080), that a subset of 

facilities that were representative of emission sources from both the mineral wool and wool 

fiberglass industries would conduct emissions testing. The May 5, 2010 letter indicated that the 

bases for representativeness included design type and size of process units or equipment, fuel 

type, operating temperatures, control devices and raw material content. The commenter did not 

identify in its May 5, 2010 letter these two synthetic area sources as synthetic area sources or as 

not representative of major sources. Rather, the letter states in pertinent part that “[n]ew 

hydrogen fluoride and hydrochloric acid data will be collected from USG Interiors’ Walworth, 

Wisconsin facility (1 Cupola) [and] [n]ew HF and HCl will be collected at USG Interiors’ Red 

Wing, MN facility.” (May 5, 2010 letter, p. 14). (“EPA typically has wide latitude in determining 

the extent of data-gathering necessary to solve a problem. We generally defer to an agency's 

decision to proceed on the basis of imperfect scientific information, rather than to invest the 

resources to conduct the perfect study.” Sierra Club v. EPA, 334 U.S. App. D.C. 421, 167 F.3d 

658, 662 (D.C. Cir. 1999) (citation omitted)).

Synthetic area sources are essentially major sources by design that agree to operate at a 

level that is synonymous with area sources. Due to their design, emissions from a synthetic area 

source are reflective of emissions from a major source. Their reduced level of operation to 

qualify to be a synthetic area source has no impact on the representativeness of their emission 

data as a major source. The commenter has argued elsewhere (see comment number 67) that the 

proposed HF and HCl emission limits are flawed due to limited data availability. Use of these 

data for the two synthetic area sources provides more data availability. For these reasons and the 

reasons stated above, the EPA has established no justification for removing the emission data for 

these two synthetic area sources from its emission dataset.

69. Comment: One commenter (1041-0080/1041-1026) argued that the EPA should 

have counted the data from two sources that share a common exhaust stack as only a single 

source, and should not have counted them twice when doing the MACT floor calculations. 

According to the commenter, the EPA should not have counted the two cupolas that share one 

exhaust stack at two of the facilities (Isolatek and USG’s Red Wing, MN) because in each case 

the single stack should count as one point source. The commenter argued that counting one point 

source as two was inaccurate, particularly when the emissions from each cupola cannot be 

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accurately ascertained. The commenter urged the EPA to count each of these facilities as one 

source, not two. As an alternative, the commenter suggested that because the EPA cannot 

distinguish the specific data for each cupola, the EPA should not include any of these data to set 

the MACT floor. The commenter stated that this approach would enable the EPA to establish a 

limit that is more representative of the actual performance of the industry.

Response: The EPA disagrees with commenter. As explained in the Industrial Boiler 

NESHAP, the EPA continues to believe that emissions from a common stack should be 

considered as representing the average emissions of process units, in this instance a cupola or 

furnace, exhausting to the common stack and thus, should be considered representative of 

emissions from both process units or cupolas or furnaces. The commenters have provided no 

data to support the contention that this assumption is false. The EPA used data from combined 

stacks where multiple cupolas or furnaces were routed to a common stack and control device. 

Emissions were allocated to each cupola or furnace based on production capacities. Similar to 

testing conducted for the voluntary survey, the EPA expects that companies will comply with the 

final rule by conducting testing at the common stack as that is usually where the sampling 

locations are (rather than in the intermediate ductwork) and will report the results as being for 

each cupola or furnace.

Further, the commenter’s May 5, 2010 letter (see Appendix A of docket item number 

EPA-HQ-OAR-2010-1041-0080) indicated that mineral wool production facilities would be 

conducting and submitting test results for the two cupolas that are the subject of this commentIsolatek and Red Wing. At the time, the commenter only identified two cupolas at the Isolatek 

facility as having “combined baghouse/combined point source." No mention was made of USG's 

Red Wing cupola as sharing common control equipment. (May 5, 2010 letter, pp. 13-14). 

Second, the EPA requested testing of all emissions points and the submission of test results as 

part of the voluntary survey. Specifically, Enclosure 2 of the survey requested testing at both the 

inlet and outlet of each cupola. "Testing should be conducted on 1) both the inlet and outlet for 

CO and COS testing on the cupola and organic HAP testing on the curing oven and 2) the outlet 

from at least one of the controls systems used to control emissions from the [each fiber collection 

operation, each curing oven and each cooling operation]. . . If the process unit you are testing 

does not have a control system, test the outlet from your process unit." Section 1.2, Enclosure 2. 

Third, as earlier explained, the EPA and industry agreed that a subset of facilities that were 

representative of emission sources from both the mineral wool and wool fiberglass industries 

would conduct emissions testing. The May 5, 2010 letter indicated that the bases for 

representativeness included design type and size of process units or equipment, fuel type, 

operating temperatures, control devices and raw material content. The EPA and industry agreed 

to submission of data that would be considered representative of other process units. The 

commenter's response in relevant part was that "“[n]ew hydrogen fluoride and hydrochloric acid 

data will be collected from USG Interiors’ Walworth, Wisconsin facility (1 Cupola) [and] [n]ew 

hydrogen fluoride and hydrochloric acid will be collected at USG Interiors’ Red Wing, MN 

facility.” (May 5, 2010 letter, p. 14). Moreover, owners or operators of these facilities certified 

the results submitted to the agency as being true, accurate, and complete. 

The EPA has reviewed the data based on comments received and does not believe that 

there are any inconsistencies in the data set used for the final rule. In the MACT floor analysis, 

the EPA used data only from stacks that were tested or for which test data were provided. 

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(“EPA typically has wide latitude in determining the extent of data-gathering necessary to solve 

a problem. We generally defer to an agency's decision to proceed on the basis of imperfect 

scientific information, rather than to invest the resources to conduct the perfect study.” Sierra 

Club v. EPA, 334 U.S. App. D.C. 421, 167 F.3d 658, 662 (D.C. Cir. 1999) (citation omitted)).

70. Comment: One commenter (1041-0080/1041-0126) recommended that data 

characterized as below-the-minimum-detection-limit (below-MDL) should not be used to set the 

MACT floor because such data are unquantifiable. The commenter (1041-0080) requested that 

the EPA remove the Industrial Insulation Group (IIG) data from the calculation for the MACT 

floor because below-MDL data are unquantifiable. The commenter expressed concern that using 

below-MDL data is likely to set limits so stringent that even the best performing sources cannot 

meet those limits. The commenter cited a memorandum from RMB Consulting and Research 

about relying on below-MDL data.25

According to the commenter, the EPA should use only values that are above the MDL 

(i.e., actual values) in calculating the MACT floor. The commenter stated that the emissions 

floor must be determined by quantifiable data, and thus, the EPA should not use the IIG data to 

set the MACT floor.

The commenter (1041-0126) said that the EPA should allow those sources whose tests 

showed results below the detection limits of the method to use work practices rather than testing 

to show compliance with the emission limits of the rule.

Response: The EPA disagrees with the commenter’s assertion that data returned from an 

ICR with a value reported as below the detection limit should be excluded from the MACT floor 

data set simply because a specific value for this data is not reported. Where no detection of an 

analyte is found across an industry sector, we find no need to regulate such pollutants as they are 

not present in measureable quantities; however, in an industry sector where the pool of best 

performing units are represented, in part, by measured and in part by values at or below the 

method detection limit, we have no discretion available with which to exclude data at or below 

the method detection limit from the pool of best performing units and, as a matter of practice, 

assign a value at the method detection limit to those data for the purposes of conducting the 

MACT floor analysis. We also disagree that use of such data would result in limits so stringent 

that they cannot be met by the best performing sources.

A small percentage of the tests at cupolas returned values for HF and HCL that were 

BDL of the method. With such data, that often represent best performing units in a data set, we 

use a procedure for identifying a representative method detection level (RDL). The procedure for 

determining an RDL starts with identifying all of the available reported pollutant specific method 

detection levels for tests of the best performing units regardless of any subcategory (e.g., existing 

or new, fuel type). By limiting the data set to those tests used to establish the floor or emissions 

limit (i.e., best performers), we believe that the result is representative also of the better 

performing testing companies and laboratories. From that combined pool of data, we calculate an 

arithmetic mean value. The averaging step would minimize the effect of a test(s) with an 

25 RMB Consulting & Research, Inc. Memorandum, Comments on Proposed EGU MACT Rule, July 19, 2011, 

p. 18.

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inordinately high method detection level (e.g., the sample volume was too small, the laboratory 

technique was insufficiently sensitive, or the procedure for determining the detection level was 

other than that specified). We then call the resulting mean of the method detection levels as the 

RDL as characteristic of accepted source emissions measurement performance. 

The second step in the process is to calculate three times the RDL to compare with the 

calculated floor or emissions limit. Using a multiplication factor of three is comparable to 

practice common among testing and analytical laboratories for defining a measurement reporting 

limit. This step is also similar to what we have used in other rulemakings, including for the 

Portland cement MACT determination. The multiplication factor of three approximates a 99-

percent upper confidence interval for a data set of 7 or more values. We then compared this value 

to the calculated floor and if three times the RDL were less than the calculated floor or emissions 

limit (e.g., calculated from the UPL), we would conclude that measurement variability was 

adequately addressed. The calculated floor or emissions limit would need no adjustment. If, on 

the other hand, the value equal to three times the RDL were greater than the UPL, we would 

conclude that the calculated floor or emissions limit does not account entirely for measurement 

variability. If indicated, we substituted the value equal to three times the RDL for the calculated 

floor or emissions limit.

We determined the RDL for each pollutant using data from tests of all the best 

performers for all of the final regulatory subcategories (i.e., pooled test data). We applied the 

same pollutant-specific RDL and emissions limit adjustment procedure to all subcategories for 

which we established emissions limits. We believe that emissions limits adjusted in this manner 

better ensure measurement variability is adequately addressed relative to compliance 

determinations than did the procedure applied for the proposal that may have been based on data 

sets smaller than seven tests and as few as one test. We also believe that the emissions testing 

procedures and technologies available now and in the future will be adequate to provide the 

measurement certainty sufficient for sources to demonstrate compliance at the levels of the 

adjusted emissions limits.

We note that the use of the RDL in establishing the emission limits for HF and HCl is 

consistent with the approach approved by the court in NACWA v. EPA, 734 F.3d 1115, 1154 –

55: 

“We agree with EPA that its method of incorporating nondetect data is reasonable, and 

not arbitrary or capricious. We do not expect EPA to perform the impossible, see Cement 

Kiln, 255 F.3d at 871, and that includes recording emission levels that are not accurately 

detectable with its current emissions testing technology. As EPA explains the issue, 

emission levels from zero up to some value above the method detection level cannot be 

stated with accuracy. Because any emission level EPA selects at that point will 

necessarily be an estimate, EPA adopted a method to account for measurement 

imprecision that has a rational basis in the correlation between increased emission values 

and increased testing precision.”

71. Comment: One commenter (1041-0080/1041-0126) recalculated the MACT floor 

for HCl and HF after eliminating the three following categories of mineral wool production 

facilities, and recommended that the EPA adopt these revised limits: (1) synthetic area sources, 

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(2) sources that share common stacks/controls that were represented by one data point (Isolatek 

and USG – Red Wing), and (3) sources with data that were below-MDL (IIG). The commenter’s 

rationale for eliminating each of these three categories of sources is summarized in comment 

numbers 68, 69, and 70. The commenter’s MACT floor calculations for HCl and HF are shown 

in the two following tables:

Facilities

HCl Emission Limit (lb/ton of melt)

Average 

of 

Cupolas

99% UPL 

Existing Sources

Multiplied 

Average by 2

Multiplied 

Average by 2.5

Multiplied 

Average by 3

Rock Wool & 

Thermafiber 0.098 0.249 0.196 0.245 0.294

Facilities

HF Emission Limit (lb/ton of melt)

Average of 

Cupolas

99% UPL 

Existing Sources

Multiplied 

Average by 2

Multiplied 

Average by 2.5

Multiplied 

Average by 3

Rock Wool, 

Thermafiber, & 

Amerrock 

0.0844 0.190 0.169 0.211 0.2532

Response: As explained in section VI.D of the preamble to this final rule and also in this 

response to comment document, we are not adopting the numerical limits proposed on November 

25, 2011 for HCl and HF emissions from cupolas. As explained in our proposal on April 15, 

2013, we are subcategorizing cupolas according to whether they use slag in the raw material 

introduced to the cupola, and are finalizing the 2014 proposed HF and HCl limits specific to 

these two different subcategories. We also note that the commenter subsequently expressed 

support for the finalized HCl and HF limits for existing sources, as summarized in comment 

number 62.

We disagree with the commenter’s recommended alternative calculations because they 

are not permissible under the CAA, as discussed in the EPA’s responses to comment numbers 

70, 71, and 72. As discussed earlier in response to comment numbers 68, 69, and 70, 

respectively, the EPA cannot exclude synthetic area sources from the MACT analysis, the EPA 

must consider sources with shared stacks and can treat them as two distinct sources, and the EPA 

must account for measures of emitted HAP that are at or below the MDL.

72. Comment: One commenter (1042-0080) urged the EPA to establish risk-based 

standards for HCl and HF emissions from the mineral wool industry. The commenter noted that 

CAA section 112(d)(4) expressly authorizes the EPA to establish risk-based standards for 

threshold pollutants for which a health threshold has been established. 42 U.S.C. § 7412(d)(4). 

The commenter asserted that this provision was established by Congress because "[f]or some 

pollutants a MACT emissions limitation may be far more stringent than is necessary to protect 

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public health and the environment" and quotes from the legislative history for the 1990 CAA 

amendments. The commenter also asserted that EPA has previously determined that HCl is a 

threshold pollutant. It also asserts that the EPA has established what the commenter 

characterized as a lack of risk. The commenter further asserted that health-based limits would be 

more reasonable and achievable and would enable the EPA to achieve the ample margin of 

safety to health and the environment.

Response: Section 112(d)(4) of the CAA provides that: "[w]ith respect to pollutants for 

which a health threshold has been established, the Administrator may consider such threshold 

level, with an ample margin of safety, when establishing emissions standards under this 

subsection." Notably, the statute confers limited discretionary authority on the EPA and does not 

mandate the use of health-based standards. The legislative history cited by the commenters 

contains similarly permissive language and does not suggest that health-based standards would 

be required in any circumstances. Specifically, the legislative history quoted by the commenter 

provides that "where health thresholds are well-established . . . and the pollutant presents no risk 

of other adverse health effects, including cancer, for which no threshold can be established, the 

administrator may use the threshold with an ample margin of safety (and not considering cost) to 

set emissions limitations for sources in the category or subcategory." S. Rep. No. 101-228, at 

144 (1989). In other words, where certain preconditions are met (i.e. health thresholds are wellestablished and the pollutant presents no other risks), the EPA has discretionary authority to set 

health-based standards. Here, the commenter urges the EPA to create risk-based limits based 

largely on their assertion that EPA has authority to do so because the pre-conditions are met. 

The commenter does not, however, offer a rationale to support their assertion that the EPA 

should exercise this discretionary authority in this rulemaking. In fact, the only rationale offered 

is a bald assertion that such limits would be more reasonable and achievable and would enable 

the EPA to achieve the ample margin of safety to health and the environment. This comment was 

offered in response to the 2011 proposal, aspects of which were modified in the 2013 proposal. 

As explained in the 2013 proposal (78 FR 22370 at 22389), the HF and HCl standards are not 

only reasonable and achievable, but will in fact have minimal impact on the mineral wool 

industry.

73. Comment: One commenter (1041-0126/1041-0164) supported the subcategories in 

the proposed rules published on April 15, 2013 and November 13, 2014, that proposed separate 

limits with respect to HF and HCl emissions for cupolas processing slag and cupolas not processing 

slag. Previously, in response to the 2011 proposal, the commenter (1041-0080) had 

recommended that the EPA subcategorize cupolas and provided a rationale for each of their 

recommended subcategory options based on six criteria: (1) permitted capacity (permitted 

maximum melt rate); (2) manufactured product (residential loose fill insulation, ceiling tiles, 

fireproofing materials, and commercial and industrial insulation); (3) raw material (i.e., recycled 

slag vs. mineral rock (non-recycled material)); (4) bonded vs. unbonded products; (5) unique 

fuels and raw materials that would put each facility in its own separate subcategory; and (6) air 

pollution control differences (i.e., cupolas with an incinerator vs. those without). The commenter 

also said that the EPA was assuming that raw material substitution could reduce the HCl, HF, 

and COS emissions to the proposed limits. According to the commenter, there are no supporting 

data, analyses, or feasibility determinations in the docket to support the EPA’s assumption, and 

therefore, the proposed standards are unsupported on the record and patently arbitrary.

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Response: The agency acknowledges the commenter’s support for HCl and HF limits 

proposed in 2013 and 2014 for two different subcategories of cupolas according to whether slag 

is among the raw materials melted in the cupola. As the EPA specified in the 2013 proposal (78 

FR 22385), the EPA considered the information provided by the commenter in response to the 

2011 proposal, and the EPA obtained and reviewed additional information from industry 

regarding which companies use slag in the cupola and which do not as well as the emissions 

characteristics of the different raw material mixtures. These data indicate that there are 

differences in the emissions of the acid gases HF and HCl depending on whether slag is used in 

the cupola to produce mineral wool. Of the 7 facilities, three reported using slag and four 

reported only using minerals (rock) and coke (e.g., no slag). Slag is a waste by-product from the 

iron and steel industry and is location-specific depending on the type of facility/process 

generating the slag. Some types of slag have residual fluorides or chlorides which vary from 

location to location and from process to process. The EPA determined that cupolas that did not 

process slag had lower emissions of acid gases than those that did not. We agreed with the 

commenter that cupolas could be subcategorized according to these raw material differences, and 

in April 2013 we proposed to subcategorize the mineral wool cupolas into two categories (those 

that process slag materials and those that do not), and we proposed revised standards for HCl and 

HF based on the cupola subcategories. Subsequently, the EPA applied its updated approach for 

evaluating limited datasets to the HF and HCl emission limits and proposed revised limits in 

November 2014 (79 FR 68017) for the same two subcategories of cupolas: those that process 

slag and those that do not. The finalized emission limits for HF and HCl reflect the same 

subcategories as proposed in 2014.

74. Comment: One commenter (1041-0080) recommended that the EPA use the 

following alternative emission limits for HCl and HF because the majority of the commenter’s 

members cannot meet the EPA’s proposed limits for HCl and HF, and none of the commenter’s 

members were confident that the proposed HCl and HF limits proposed on November 25, 2011, 

could be met on a consistent basis. The commenter also argued that raw material substitution was 

not a feasible alternative to meet the proposed limits. These alternative limits were formulated by 

the commenter as follows:

Formula for calculating X at a known cumulative probability (99.0 percent):

X = x + Z(.99)* s

Pollutant

Emission Limit (lb/ton of melt)

Existing Cupolas New and Reconstructed Cupolas

HCl 0.258 0.258

HF 0.172 0.172

COS 8.4 8.4

With a 99 percent calculated probability, the commenter recommended that these limits 

could be generally met by all mineral wool companies.

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Based on the commenter’s statistical/probability calculations using existing mineral wool 

HCl and HF data, the commenter estimated the following probabilities of failing to meet the 

EPA’s proposed limits and the commenter’s recommended limits:

• HCl – with the EPA’s proposed limit, there is a 77.1 percent chance of failure to meet 

the proposed limit.

• HCl – with the commenter’s recommended limit, there is 1.0 percent chance of 

failure to meet the limit.

• HF – with the EPA’s proposed limit, there is a 78.8 percent chance of failure to meet 

the proposed limit.

• HF – with the commenter’s recommended limit, there is 1.0 percent chance of failure 

to meet the limit.

According to the commenter, adoption of these recommended limits would: (1) eliminate 

the need to install costly wet scrubber/dry scrubber; (2) avoid costs of control equipment too 

burdensome for small businesses; (3) establish measurable/quantifiable emission limits; (4) avoid 

environmental waste caused by installation of wet scrubbers; (5) preserve the EPA’s objective of 

avoiding installation of new control equipment as stated in the Proposed Rule; and (6) establish 

limits commensurate with the low level of risk posed by HCl and HF from the mineral wool 

industry.

Response: We note that the commenter subsequently expressed support for the HCl and 

HF limits being finalized for existing sources (1041-0164), as summarized in comment number 

62. As explained in section VI.D of the preamble to the final rule and in the November 13, 2014 

supplemental proposal, we are not finalizing the numerical limits for HCl and HF emissions from 

cupolas presented in the November 25, 2011 notice, but are setting emission limits for two 

subcategories of cupolas: cupolas that process slag and those that do not process slag. Further, as 

explained in the 2014 proposal, the finalized HCl and HF limits for new and existing sources in 

each subcategory were calculated using the UPL approach to account for uncertainty and 

variability in the measured emission levels. For more information on the EPA’s approach to 

calculating the finalized limits for HCl and HF, refer to the memoranda “Revised Technical 

Approach for Mineral Wool MACT Floor Calculations” (docket item number EPA-HQ-OAR2010-1041-0156) and “Approach for Applying the Upper Prediction Limit to Limited Datasets –

Ferroalloys” (docket item number EPA-HQ-OAR-2010-1041-0129). 

The limits suggested by the commenter for existing sources, in response to the 2011 and 

2013 proposals, were not supported by the test data submitted by industry for this source 

category, and as such are not permissible under CAA section 112. To set the level of the MACT 

floor at the level suggested by the commenter would be to set the floor on the highest emitting 

source; that is, a level that could be achieved by all existing sources in the industry. As earlier 

explained, however, the D.C. Circuit has consistently rejected a reading of “achieved by the best 

performers,” in section 112(d)(3), as meaning achievable by all sources within a source category. 

“EPA’s rationales . . . amount to nothing more than concern about ensuring that its floor is 

achievable by all kilns in the subcategory--precisely the position we rejected in Cement Kiln.” 

Sierra Club v. EPA, 479 F.3d at 881. See also, Cement Kiln Recycling Coalition v. EPA, 255 

F.3d at 861 “EPA may not deviate from section 7413(d)(3)’s requirement that floors reflect what 

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the best performers actually achieve by claiming that floors must be achievable by all sources 

using MACT technology.” (“EPA cannot circumvent Cement Kiln’s holding that section 

7412(d)(3) requires floors based on the emission level actually achieved by the best performers 

(those with the lowest emission levels), not the emission level achievable by all sources, simply 

by redefining “best performing” to mean those sources with emission levels achievable by all 

sources.”). Sierra Club v. EPA, 479 F.3d at 881. (Emphasis in original).

Also, regarding the comment on the 2011 proposed rule’s potential impact to small 

businesses, while the EPA may use regulatory flexibility to ease section 112 impacts on small 

businesses such as those in the mineral wool industry, the EPA may not dismiss the requirements 

of CAA section 112 due to small business impacts.

C. Cupola COS Limit

75. Comment: One commenter (1041-0126/1041-0164) supported the subcategories in 

the proposed rules published on April 15, 2013 and November 13, 2014, that established separate 

limits with respect to COS emissions for closed top and open top cupolas.

Response: The agency acknowledges the commenter’s support.

76. Comment: One commenter (1041-0164) supported the proposed COS emission 

limits published on November 13, 2014 for existing sources within both the open-top and closedtop subcategories for cupolas.

Response: The agency acknowledges the commenter’s support.

77. Comment: One commenter (1041-0164) opposed the COS emission limits proposed 

on November 13, 2014 and being finalized in this action for new sources within both the open 

top and closed top subcategories for cupolas. The commenter argued that the proposed emission 

limits are too stringent and technology is not available to achieve compliance with those proposed 

limits.

Response: In the 2011 proposed rule, limits were proposed for COS to replace the use of 

CO as a surrogate for COS. In the 2013 and 2014 proposed rules, the proposed limits were 

revised to reflect the addition of subcategories for cupolas that are open topped and those that are 

closed topped, and to reflect the performance of the best controlled similar source as the limit for 

new sources. Congress specified in CAA section 112(d)(3) the minimum level of emission 

reduction that could satisfy the requirement to adopt MACT. For new sources, this floor level is 

“the emission control that is achieved in practice by the best controlled similar source.” The 

EPA’s analysis of the available data indicate that the proposed limits for new sources are 

achievable using the controls identified as MACT, as discussed in the preamble to the 2014 

proposed rule (79 FR 68020) and in the supporting memo in the docket for this rulemaking (EPA 

docket item EPA-HQ-OAR-2010-1041-0156).

Further, section 112(d) requires the EPA to promulgate standards for major sources of 

HAP that are based on MACT performance. For existing sources, MACT standards must be at 

least as stringent as the average emissions limitation achieved by the best performing 12 percent 

of existing sources (for which the Administrator has emissions information) or the best 

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performing 5 sources for source categories with less than 30 sources. The worst performing 

sources would have to take action to reduce their air toxic emissions. As a general matter, 

emissions standards under section 112(d) include measures that “reduce the volume of, or 

eliminate emissions of pollutants through process changes, substitution of materials or other 

modifications.”

78. Comment: One commenter (1041-0080) stated that the proposed limits for COS 

published on November 25, 2011, are not achievable for the entire industry without additional 

control equipment. Specifically, based on new and existing data, the commenter expressed 

concern that the following two existing facilities would have problems meeting the EPA’s 2011 

proposed limit for COS:

• Rockwool – New and existing data shows that the limit cannot be met.

• Amerrock – Data show that meeting the proposed limit consistently may be 

problematic.

According to the commenter, data show that the four remaining companies can meet the 

EPA’s 2011 proposed limit range. However, the commenter stated that many of these companies 

expressed concern about meeting the limits consistently, and therefore, all companies supported 

a revised limit.

The commenter asserted that COS should not be regulated as a HAP. The commenter 

argued that the majority of COS emissions originate from nature, the scientific record does not 

support COS as a significant risk, and because COS emissions do not present any threat to public 

health or the environment, imposing stringent COS emissions limitations would simply be 

regulation for regulation’s sake. The commenter stated that such an approach is not necessary 

under the law and not justifiable in light of the significant costs that would be incurred by 

affected sources. The commenter recommended alternatives to the proposed rule.

Response: We note that this commenter subsequently expressed support for the finalized 

COS limits for existing sources (for both open-top and closed-top subcategories of cupolas), as 

summarized in comment number 76.

In 2011, we proposed COS emissions limit that would apply to all cupolas in the industry 

without regard to design. In response to our 2011 proposal, we received additional information 

from industry indicating that two types of cupolas are used in the production of mineral wool: 

cupolas with closed tops and those with open tops. Based on this additional information, we 

identified that there are two operating open-top cupolas and 9 closed-top cupolas. As explained 

in the preamble to the April 15, 2013 supplemental proposal, we proposed separate subcategories 

for open-top and closed-top cupolas. 

In 2014, we proposed a limit of 3.4 lb COS/ton melt for closed-top cupolas at existing 

sources. We also proposed a limit of 6.8 lb COS/ton melt for open-top cupolas at existing 

sources. We based the COS emission limits for these two cupola subcategories on the MACT 

floor calculation as required under CAA section 112. A more detailed explanation of how we 

calculated the MACT floors can be found in the memorandum, "Revised Technical Approach for 

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Mineral Wool Production MACT Floor Calculations," which is in the docket for this rulemaking 

(see docket item number EPA-HQ-OAR-2010-1041-0156).

While the commenter contends that COS emissions also originate from nonanthropogenic sources, this does not affect that COS is a listed HAP for regulation under section 

112 of the CAA, and that the EPA must regulate such HAP under section 112 provisions. We 

also note that any individual or group may petition to add or delete a chemical from the list of 

HAP under CAA section 112(b)(3)(A). 

The EPA recognizes that the final limits would not necessarily be met by all mineral 

wool producers without the addition of either control equipment or selection of raw materials 

with lower sulfides content. As explained in detail in the EPA’s response to comment number 

57, the D.C. Circuit has consistently rejected a reading of “achieved by the best performers,” in 

CAA section 112(d)(3), as meaning achievable by all sources within a source category.

79. Comment: One commenter (1042-0080) urged the EPA to establish risk-based 

standards for COS emissions from the mineral wool industry. The commenter noted that CAA 

section 112(d)(4) expressly authorizes the EPA to establish risk-based standards for threshold 

pollutants for which a health threshold has been established. 42 U.S.C. § 7412(d)(4). The 

commenter asserted that this provision was established by Congress because "[f]or some 

pollutants a MACT emissions limitation may be far more stringent than is necessary to protect 

public health and the environment" and quotes from the legislative history for the 1990 CAA 

amendments. The commenter also asserted that the EPA has previously determined that COS is a 

threshold pollutant. It also asserts that the EPA has established what the commenter 

characterized as a lack of risk. The commenter further asserted that health-based limits would be 

more reasonable and achievable and would enable the EPA to achieve the ample margin of 

safety to health and the environment.

Response: Section 112(d)(4) of the CAA provides that: "[w]ith respect to pollutants for 

which a health threshold has been established, the Administrator may consider such threshold 

level, with an ample margin of safety, when establishing emissions standards under this 

subsection." Notably, the statute confers limited discretionary authority on the EPA and does not 

mandate the use of health-based standards. The legislative history cited by the commenters 

contains similarly permissive language and does not suggest that health-based standards would 

be required in any circumstances. Specifically, the legislative history quoted by the commenter 

provides that "where health thresholds are well-established . . . and the pollutant presents no risk 

of other adverse health effects, including cancer, for which no threshold can be established, the 

administrator may use the threshold with an ample margin of safety (and not considering cost) to 

set emissions limitations for sources in the category or subcategory." S. Rep. No. 101-228, at 

144 (1989). In other words, where certain preconditions are met (i.e. health thresholds are wellestablished and the pollutant presents no other risks), the EPA has discretionary authority to set 

health-based standards. Here, the commenter urges the EPA to create risk-based limits based 

largely on their assertion that EPA has authority to do so because the pre-conditions are met. 

The commenter does not, however, offer a rationale to support their assertion that the EPA 

should exercise this discretionary authority in this rulemaking. In fact, the only rationale offered 

is a bald assertion that such limits would be more reasonable and achievable and would enable 

the EPA to achieve the ample margin of safety to health and the environment. This comment was 

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offered in response to the 2011 proposal, aspects of which were modified in the 2013 proposal. 

As explained in the 2013 proposal (78 FR 22370 at 22389), the final COS standard is not only 

reasonable and achievable, but will in fact have minimal impact on the mineral wool industry.

80. Comment: The commenter (1041-0080) argued that the EPA is not required to set 

standards for COS emissions from the mineral wool industry, and urged the EPA to forego 

setting any COS emission limits from cupola furnaces. The commenter also stated that the EPA 

is not required to “correct” existing MACT standards when it conducts a review under CAA 

section 112(d)(6). According to the commenter, even if the EPA decides to set a standard for 

COS, it is not required under CAA section 112(d)(6) to set a “floor” when doing so. 

Response: As explained in earlier responses, the D.C. Circuit has held that the EPA may 

permissibly amend improper MACT determinations, including amendments to improperly 

promulgated floor determinations, using its authority under sections 112(d)(2) and (3). Refer to 

the EPA’s response to comment number 66 for a detailed discussion of these rulings. We also 

note that, in National Lime Association v. EPA, 233 F.3d 625 (D.C. Cir. 2000), the D.C. Circuit 

remanded the Portland Cement MACT to the EPA to establish MACT floors for HCl holding 

that we had a clear “statutory obligation to set emission standards for each listed HAP.” A 

detailed discussion of this court case and the EPA’s authority to address potential revisions to a 

promulgated standard (e.g., the fact that we used improper surrogates (such as CO) in the 1999 

NESHAP for the mineral wool production source category) is provided in the EPA’s response to 

comment number 66. The EPA further discusses its assessment of the use of surrogates in the 

1999 NESAHP in section IV.C.4 of the preamble to the final rule.

Further, in several recent rulemakings, we have chosen to fix underlying defects in 

existing MACT standards under CAA sections 112(d)(2) and (3), as discussed in the EPA’s 

response to comment number 56.

As also explained in various responses including comment number 66, we disagree with 

the comment that CAA section 112(d)(6) is the EPA’s sole authority for revising existing MACT 

standards. We believe that CAA section 112 does not expressly address this issue, and that the 

EPA has discretion in determining how to address potential revisions to a promulgated standard. 

CAA section 112(d)(6) provides that the agency must review and revise “as necessary.” The “as 

necessary” language must be read in the context of the provision, which focuses on the review of 

developments that have occurred since the time of the original promulgation of the MACT 

standard and thus, should not be read as a mandate to correct flaws that existed at the time of the 

original promulgation.

81. Comment: One commenter (1041-0080) urged the EPA to apply a more liberal 

variability factor in calculating the 2011 proposed COS limit to avoid a scenario of frequent noncompliance. According to the commenter, all mineral wool companies expressed concern about 

meeting the limit for new and reconstructed sources. At a minimum, the commenter requested 

that the EPA set the COS limits for new sources that are equal to the limits for existing sources 

identical limits, as the EPA did for HF and HCl in the November 25, 2011 proposed rule.

Further, the commenter stated that the mineral wool industry provides environmental 

benefits by creating a product that increases energy efficiency and by re-using blast furnace slag 

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as an input material. The commenter argued that the EPA should avoid directly imposing overly 

stringent or unnecessary emission limits or indirectly imposing technological requirements that 

will threaten the viability of mineral wool companies that provide such significant environmental 

benefits. Therefore, the commenter strongly urged the EPA to consider alternatives to imposing a 

COS MACT limit.

Response: Congress specified in CAA section 112(d)(3) the minimum level of emission 

reduction that could satisfy the requirement to adopt MACT. For new sources, this floor level is 

“the emission control that is achieved in practice by the best controlled similar source.” 

For existing sources, MACT standards must be at least as stringent as the average 

emissions limitation achieved by the best performing 12 percent of existing sources (for which

the Administrator has emissions information) or the best performing 5 sources for source 

categories with less than 30 sources. The worst performing sources would have to take action to 

reduce their air toxic emissions. Thus, CAA section 112(d) requires the EPA to establish the 

MACT floor for new sources differently for new sources and existing sources and the EPA is 

prohibited from adopting the same standard for new sources as for existing sources, as 

recommended by the commenter, where the available data indicate that new sources can achieve 

a more stringent level of control, which is the case here. As such, the EPA may not set the COS 

limits for new sources equal to the limits for existing sources because the available data indicates 

that new sources can achieve “the emission control that is achieved in practice by the best 

controlled similar source.”

Regarding the comment that the EPA proposed in 2011 equivalent new and existing 

source limits for HCl and HF, we acknowledge that the emission limits for new and existing 

sources were the same in the 2011 proposal. However, we revised the emission limits in the 2013 

supplemental proposal based on subcategories develop for slag and non-slag using cupolas (78 

FR 22385-22386). In the 2014 supplemental proposal (79 FR 68019), we further revised the HF 

and HCl emissions for new sources using our updated approach for evaluating limited datasets. 

This is to be consistent with CAA section 112(d)(3).

Further, regarding the comment that EPA should apply a more liberal variability factor,

we do not believe that such a factor would be consistent with our authority to set MACT 

standards under CAA section 112(d). We note that the EPA’s more recent approach in the 2014 

proposal for setting MACT standards employs a formula that accounts for variability, which was 

described in the preambles to the proposed rules published on April 15, 2013 and November 13, 

2014. See the memoranda “Approach for Applying the Upper Prediction Limit to Limited 

Datasets” (docket ID EPA-HQ-OAR-2010-1042-0331) and “Use of the Upper Prediction Limit 

for Calculating MACT Floors” (docket ID EPA-HQ-OAR-2010-1042-0333) prepared for the 

2014 supplemental proposal. As explained in the preamble to the final rule, we are promulgating 

a limit of 3.4 lb COS/ton melt for closed-top cupolas at existing sources. We are also 

promulgating a limit of 6.8 lb COS/ton melt for open-top cupolas at existing sources. These 

limits were calculated using the 99-percent UPL for existing sources.

Regarding the comment that the EPA should avoid imposing overly stringent or 

unnecessary emission limits or indirectly imposing technological requirements that will threaten 

the viability of mineral wool companies, the EPA is precluded from considering costs in 

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calculating MACT floors. National Lime Ass’n v. EPA, 233 F.3d at 640. Section 112(d) of the 

CAA requires the EPA to promulgate standards for major sources of HAP, and COS is on the list 

of HAP that can be found in CAA section 112(b). Additionally, as noted in the EPA’s response 

to comment number 78, petitions to add or delete chemicals from the list of HAP are allowed 

under CAA section 112(b)(3)(A). 

In response to the commenter’s statement that incineration of COS would create SO2 and 

NOX emissions, we note that, while several sources already incinerate COS and other sources 

could also install controls on added incinerators that would reduce SO2 and NOx, this would be 

done at great expense and for little environmental benefit. We have instead exercised our 

discretion under CAA section 112(d) to subcategorized cupolas according to whether they are 

open- or closed-top, as this design feature factors prominently into the COS emission potential of 

cupolas.

We note that the commenter subsequently expressed support (1041-0164) for the COS 

limits for existing sources in the 2014 proposal and being finalized, as summarized in comment 

number 76.

82. Comment: One commenter (1041-0080) described the EPA’s MACT floor 

calculation methods in the November 25, 2011 proposed rule as improper. According to the 

commenter, a thorough and complete analysis of the EPA’s calculation method was not possible 

because the preamble to the proposed rule and the MACT floor memorandum lacked details of 

the data the EPA relied on in its analysis and calculations. As a result, the commenter challenged 

the record as inadequate. According to the commenter, the EPA has improperly exercised its 

discretion and failed to provide an assessment of how many actual mineral wool cupolas would 

be able to meet the standards without installing further controls. The commenter highlighted the 

need for a full explanation of how the UPL was determined for the mineral wool industry, 

including the statistical analysis related to the normality of the test data and transformation of the 

data to produce a suitable distribution. The commenter argued that the absence of the identified 

data was a significant lapse, given that the CAA requires the EPA to include in the record a 

“statement of basis and purpose” that should include such information. The commenter stated 

that its absence violated CAA section 307, and, if not corrected prior to promulgation, would 

render the final rule arbitrary.

Response: We note that the commenter subsequently expressed support (1041-0164) for 

the COS limits for existing sources in the 2014 proposal and being finalized, as summarized in 

comment number 76. We disagree with this comment on the 2011 proposal that the EPA did not 

provide complete disclosure, and we believe we clearly presented the data source and our 

approach used to calculate the MACT floors. Please refer to the EPA’s response to comment 

number 78 for a detailed discussion of how the EPA provided the data sources, our approach to 

calculating all MACT floors (including a list of documents that the EPA provided in the docket), 

a description of the test data collected by the EPA, and the commenter’s indication back in 2010 

that these data were representative of industry emissions. 

In the April 15, 2013 proposal (78 FR 22385) and in the memorandum “Technical 

Approach for Mineral Wool MACT Floor Calculations” (docket item number EPA-HQ-OAR2010-1041-0109), we presented our rationale for developing subcategories for different types of 

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cupolas and for revising the COS emission limits using the UPL approach. Additionally, more 

recently in the November 13, 2014 proposal (79 FR 68019) and in the memorandum “Revised 

Technical Approach for Mineral Wool MACT Floor Calculations” (docket item number EPAHQ-OAR-2010-1041-0156), we subsequently proposed and discussed our decision to revise the 

COS emissions limits for cupolas based on our updated approach for evaluating limited data sets 

(also see the memorandum “Approach for Applying the Upper Prediction Limit to Limited 

Datasets” (docket item number EPA-HQ-OAR-2010-1041-0331) for the updated approach for 

limited datasets).

83. Comment: One commenter (1041-0080) recalculated the MACT floors for COS, 

eliminating all synthetic area sources (all USG sources), sources that share common controls and 

a stack and were represented by one data point (Isolatek and USG – Red Wing), and measured 

emissions data that were below-MDL (Thermafiber). The commenter’s rationale for eliminating 

these facility data is described in the comment summaries for HF and HCl in comment numbers 

68, 69, and 70. The same rationales summarized for HCl and HF in those comment summaries 

also apply to COS. The commenter revised the MACT floor calculations for COS as follows:

Facility

COS Emission Limit (lb/ton of melt)

Average of 

Cupolas

99% UPL 

Existing Sources

Multiplied 

Average by 2

Multiplied 

Average by 2.5

Multiplied 

Average by 3

IIG, Rock 

Wool, & 

Amerrock 

2.915 10.439 5.83 7.2875 8.745

Response: As explained in section IV.A of the preamble to the final rule and also in this 

response to comment document, we are not adopting the numerical limits proposed on November 

25, 2011 for COS from cupolas. As explained in our proposal on April 15, 2013, we are 

subcategorizing cupolas according to whether they use slag in the raw material introduced to the 

cupola, and are finalizing COS limits specific to these two different subcategories, as proposed in 

2014. We also note that the commenter subsequently expressed support for the finalized COS 

emission limits for existing sources, as summarized in comment number 76.

We disagree with the commenter’s recommended alternative calculations because they 

are not permissible under the CAA, as discussed in the EPA’s responses to comment numbers 

68, 69, and 70 for HF and HCl. We note in those responses that the EPA cannot exclude 

synthetic area sources from the MACT analysis, the EPA must consider sources with shared 

stacks and can treat them as two distinct sources, and the EPA must account for measures of 

emitted HAP that are at or below the MDL.

D. Collection and Curing limits

84. Comment: One commenter (1041-0080/1041-0126/1041-0164) strongly supported 

the EPA’s combining curing and collection sources into a single source. The commenters also 

supported the EPA’s proposed three subcategories for that source (vertical, horizontal, and drum) 

with respect to formaldehyde, phenol, and methanol emissions.

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Response: The agency acknowledges the commenter’s support.

85. Comment: One commenter (1041-0164) strongly supported the proposed revised 

emission limits for formaldehyde, phenol, and methanol for both existing and new sources within 

the Curing and Collection Source Category, and in each subcategory (vertical, horizontal, and drum).

In earlier comments, the same commenter (1041-0080) had suggested the EPA’s 2011 proposed 

emission limits on formaldehyde, phenol, and methanol were unnecessarily stringent, 

unreasonably costly, and not achievable in some cases. The commenter had recommended the 

following alternative emission limits for formaldehyde, phenol, and methanol in each of the 

proposed subcategories:

Design Pollutant

Proposed Emission 

Limit (lb/ton of melt)

Recommended Emission 

Limit (lb/ton of melt)

Vertical collection plus 

curing oven

Formaldehyde 0.46 1.2

Phenol 0.52 0.60

Methanol 0.63 0.70

Horizontal collection

plus curing oven

Formaldehyde 0.054 0.5

Phenol 0.15 0.3

Methanol 0.022 0.1

Drum collection plus 

curing oven

Formaldehyde 0.067 0.67

Phenol 0.0023 0.70

Methanol 0.00077 0.23

Vertical Collection

The commenter noted the following issues related to the proposed vertical collection 

subcategory:

• Very limited emissions data were available for the collection chamber. Engineering 

data from each of two inlet ducts to the filter house were provided. 

• For phenol and methanol, the EPA correctly summed the two data points. However, 

for formaldehyde, it appeared the EPA incorrectly averaged the two points. 

Representatives from facilities in the vertical collection subcategory have discussed 

this matter with EPA and it has been acknowledged that indeed this miscalculation 

did occur. 

• The EPA’s proposed limits would necessitate installation of additional control 

technology, which, as noted earlier, is inconsistent with the EPA’s stated position. 

• The commenter urged a liberal application of variability factors to account for very 

likely fluctuations in emissions given the very limited actual data. 

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Horizontal Collection

The commenter noted the following issues related to the proposed horizontal collection 

subcategory:

• This is a small data set – limited in volume, time, and season – and application of a 

liberal variability factor is absolutely essential to insure the company can meet 

emission limits without the installation of control equipment. New data are being 

collected for the EPA’s consideration.

• There are limited data on formaldehyde, phenol, and methanol. The data for phenol 

and methanol are limited to the BTEC data. Specifically, this facility has only 6 data 

points for methanol and 6 data points for phenol; it is new data, not historical. The 

formaldehyde data are similarly limited.

• Increasing the EPA’s limits is particularly important for this subcategory because the 

data for formaldehyde range from 0.73 lbs per ton of melt to lower numbers that are 

within the proposed limits. 

• These data points do not reflect possible fluctuations due to weather changes.

Drum Collection

The commenter noted the following issues related to the proposed drum collection 

subcategory:

• BTEC data were collected from the exhaust of the oven RTO and not the exhaust duct 

from the collection drum for this subcategory and were not properly collected. New 

data have already been provided to the EPA to show more reliable drum emissions, 

which the commenter has requested be used to set the MACT floor.

• The commenter emphasized the importance of the EPA applying variability factors.

• No plant worldwide, to the commenter’s knowledge, using a collection drum had 

previous emission testing done on its emissions. Therefore, the proposed emission 

limits for formaldehyde, phenol, and methanol need to be modified.

Response: The agency acknowledges the commenter’s support. Regarding the 

commenter’s earlier comment on the 2011proposal, the subcategorization of bonded products 

and emission limits had been based on the data available to the EPA from the voluntary survey 

industry conducted within the industry. In our November 25, 2011 proposal, we explained that 

the survey included requests for existing test data on cupolas, curing ovens and collection 

operations as well as test data for most HAP metals, CO, PM, formaldehyde, methanol and 

phenol. We also explained that all 7 mineral wool manufacturing facilities submitted existing test 

data and in some instances for multiple years. We included a detailed explanation of our 

calculation of the MACT floors in the MACT Floor Analysis for the Mineral Wool Production 

Manufacturing Source Category (EPA docket item EPA-HQ-OAR-2010-1041-0019), which was 

placed in the docket for this rulemaking.

Following the November 2011 proposal, we evaluated comments and data we received 

on the proposed emissions limits for the drum and vertical collection and curing subcategories 

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and in response we revised the MACT floor emission limits for formaldehyde, phenol and 

methanol for these two subcategories, and in our supplemental proposal on April 15, 2013, we 

corrected the MACT floor limits for these pollutants. We further revised the limits in our 2014 

proposal based on the EPA’s updated approach for limited dataset and on new test data received 

in response to our 2013 proposal. The EPA acknowledges the commenter’s more recent support 

on the 2014 proposed emission limits for the formaldehyde, phenol, and methanol being finalized 

for both existing and new sources within the Curing and Collection Source Category, and in each 

subcategory (vertical, horizontal, and drum).

E. Compliance Schedule

86. Comment: One commenter (1041-0164) supported the EPA's proposed compliance 

dates, including the three year compliance period for existing sources.

Response: The agency acknowledges the commenter’s support.

F. Small Business and Economic Impacts

87. Comment: One commenter (1041-0080) observed that the mineral wool industry 

already responded to one Advanced Notice of Proposed Rulemaking and a Notice of Proposed 

Rulemaking (October 10, 2008) on residual risk and provided the EPA extensive emissions data. 

The commenter noted that the EPA concluded in the proposed rulemaking in 2007 that additional 

controls or requirements were not necessary.

Response: The October 10, 2008 proposed rulemaking was based upon one source test 

data point from the National Emissions Inventory (NEI) from a facility that closed subsequent to 

that proposal. The EPA did not receive additional data during the comment period on which to 

support a no-risk conclusion. Moreover, the Brick MACT issues, and the General Provisions 

vacatur were not addressed by that rule. For these reasons, EPA decided to collect new data from 

operating facilities to assess risks, and re-propose a rule that addressed the other MACT 

amendments identified by recent litigation referenced above. 

88. Comment: One commenter (1041-0080, 1041-0126) disagreed with the conclusions 

of the EPA’s economic impact analysis on both the November 25, 2011 and April 15, 2013 

proposed rules. Specifically, the commenter believed some companies may have to install 

incinerators or wet or dry scrubbers to meet the emission limits, and the cost of additional control 

would be unaffordable by the companies and they would be forced out of business. The 

commenter expressed concern that when the EPA considered the economic impact of the 

proposed rule, it did so under the erroneous assumption that no new additional controls would be 

necessary.

The commenter argued that an independent analysis of the proposed 1999 standards 

conducted by Price Waterhouse for the industry association estimated that the capital cost of 

installing an incinerator would be equal to three years of income and equal to 25 percent of the 

assets of a rock and slag wool facility. (A copy of the study was attached to comment letter 

1041-0080.) The commenter reported that the study also estimated that the ratio of control costs 

to pre-tax profits would range from 94.9 to 118.5 percent depending on the elasticity of demand 

for non-bonded products. The commenter reported that the study concluded that the economic 

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impact would be substantially reduced if cupola incinerators were not needed to meet the 

standards. The commenter argued that the costs of wet and dry scrubbers would have similar 

impacts. The commenter stated that the study was not updated to address the impacts of the 2013 

proposed rule, but argued that the overall impacts estimated in 1999 would still be applicable to 

the 2013 proposed rule. 

The commenter argued that the technology needed to meet the emission limits proposed 

in 2011 and 2013 would cause the closure of some existing facilities. The commenter argued that 

the legislative history of the CAA indicates that MACT standards were not intended to force the 

shutdown of facilities.26

The commenter also argued that controls needed to achieve the proposed limits would not 

be cost effective, and would be unreasonable based on earlier EPA findings that costs above a 

specified dollar amount per ton are unreasonable.27 Therefore, according to the commenter, the 

EPA should modify the proposed emission limits to avoid requiring additional control 

equipment, as done in other NESHAP, especially with respect to emissions of COS. The 

commenter argued that the EPA should not threaten the existence of the mineral wool industry 

over the control of COS, which the commenter argued is naturally produced in abundance.

The commenter noted that the controls needed to meet the proposed limits, particularly 

incineration, would also create secondary emissions of NOx and SO2, and that these would offset 

the emission reductions and also offset the environmental benefits of mineral wool products. The 

commenter noted that SO2 has also been targeted by the EPA with a vigorous program of 

reduction. The commenter also argued that installation of control equipment would increase 

energy consumption for mineral wool companies, and thus increase greenhouse gas production.

Finally, the commenter argued that the mineral wool industry itself provides economic 

benefits in creating domestic employment opportunities and creating a quality product to meet 

both domestic and international markets, instead of relying on lesser-quality foreign products. 

Response: Section 112(d) of the CAA requires the EPA to promulgate standards for 

major sources of HAP based on the performance of the MACT. For existing sources, MACT 

standards must be at least as stringent as the average emissions limitation achieved by the best 

performing 12 percent of existing sources (for which the Administrator has emissions 

information) or the best performing 5 sources for source categories with less than 30 sources, as 

is the case here. For new sources, the MACT standards must be at least as stringent as “the 

emission control that is achieved in practice by the best controlled similar source.” 42 U.S.C. 

section 7412(d)(3). The EPA is precluded from considering costs in determining the minimum 

stringency of the MACT standards (National Lime Ass’n v. EPA, 233 F.3d at 640), but the EPA 

26 The commenter cited, H.R. Rep. No. 101-490(I) at 335 (1990) (“MACT is not intended to . . . drive

sources to the brink of shutdown.”) S. Rep. No. 101-228 at 152 (1989) (“Controls which are so 

expensive that they force closure of the source or would severely impair its continuation as an 

economic entity are not ‘available.’”

27 The commenter cited, 59 Fed. Reg. 25,387, 25,391 (May 16, 1994). 

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must consider more stringent “beyond-the -floor” control options in which cost can be 

considered. 

In the 2011 proposal (76 FR 72787), we explained that section 609(b) of the Regulatory 

Flexibility Act (RFA), as amended, requires the EPA to convene a SBAR Panel prior to 

publication of the initial regulatory flexibility analysis (IRFA) that an agency may be required to 

prepare under the RFA. We explained that an SBAR was conducted for the Mineral Wool 

Production source category along with site visits to two mineral wool facilities. As also 

explained in the 2011 proposal, the SBREFA directs federal agencies to use regulatory flexibility 

in setting standards that apply to small businesses. And under the RFA, the EPA may consider 

legal alternatives that result in lower impacts to the industry where there is a significant impact 

on a substantial number of small entities (SISNOSE).

We agree with the commenter that for some companies there were economic impacts 

associated with the November 25, 2011 proposed rule, but we note that it was not SISNOSE. (76 

FR 72810). In the 2011 proposal, therefore, to the extent allowed under CAA section 112, we 

considered the SBAR panel recommendations, and these were reflected in the proposed 

subcategorization of collection and curing processes (CAA section 112(d)) and the proposed 

compliance deadlines (CAA section 112(i)). The EPA proposed three subcategories based on the 

industry identified collection and curing processes used in the U.S. mineral wool industry to 

produce bonded products, which are: vertical, horizontal and drum collection and curing. In 

response to comments such as this one, we obtained additional information on the raw materials 

and design of cupolas in the mineral wool industry that was not included in the voluntary ICR on 

which the November 2011 proposed rule was based. We then proposed additional subcategories 

for compliance with the HF and HCl numeric limits in our April 15, 2013 proposal. At that time, 

we again found that there was no SISNOSE. (78 FR 22391).

As explained in the 2014 proposal (79 FR 68025), we revised the emission limits for 

horizontal collection and curing operations, based on additional test data received, and the 

associated cost impacts. We performed an economic impact analysis for mineral wool consumers 

and producers nationally, using the annual compliance costs estimated for this proposed rule, and 

we again found that there was no SISNOSE. (79 FR 68029).

The EPA is finalizing the standards as proposed in 2013 and 2014. As shown in section 

III.F of the preamble to the final rule, there is no SISNOSE and we believe the overall economic 

impact of the final rule is expected to be low on the affected industries and their consumers.

89. Comment: One commenter (1041-0080) expressed concern over the economic 

impacts from the EPA’s 2011 proposed rule on the mineral wool industry. The commenter 

disagreed with the EPA’s conclusion that the 2011 proposed emission limits would not 

necessitate any additional controls. The commenter stated that the majority of the industry could 

not meet some of the emission limits without installing additional air pollution controls, with 

capital cost estimates on possible controls ranging between $3 million to $6 million. According 

to the commenter, the remaining companies were concerned over their ability to consistently 

meet the emission limits going forward. In addition, according to the commenter, the investment 

to collect data and complete the research necessary to predict emission levels of HF and HCl for 

the different raw material combinations and fuel sources would cost the industry hundreds of 

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thousands of dollars. The commenter expressed concern that given the current economic 

conditions, forcing mineral wool companies to install additional equipment likely would result in 

many companies going out of business. The commenter contended that the economic downturn 

has been particularly severe for these companies since the building industry is experiencing the 

greatest downturn since building growth measurements were first taken in the 1950s.

The commenter agreed, in general, with the EPA’s characterization of the mineral wool 

industry, but corrected the EPA’s estimate of the facilities that are small businesses, and stated 

that five of the 7 facilities are owned by small businesses, and five of the six companies in the 

mineral wool source category are small businesses. The commenter pointed out that mineral 

wool industry has been reduced by more than half since the implementation of the Mineral Wool 

MACT in 1999. In addition, stated the commenter, many of the surviving plants have reduced 

the number of operating cupolas or production lines. Also, the commenter stated, no new mineral 

wool production facilities have started operations since the promulgation of the Mineral Wool 

MACT Standard, and two companies have changed owners. The commenter pointed out that the 

reduction in facilities and shut down of production lines are a permanent loss in industrial 

capacity and a permanent reduction in pollutant emissions.

The commenter (1041-0080) provided the following list of operating facilities in the 

United States: 

Company Location

Production Lines Date of 

Bonded-Product Nonbonded-Product Installation

Amerrock Nolanville, TX 0 2 1986

Isolatek Huntington, IN 0 2 1929

IIG Phenix City, AL 1 1 1990

Rock Wool Mfg Leeds, AL 1 1 1970

Thermafiber Wabash, IN 1 1 1935

USG Walworth, WI 0 1 1969

USG Red Wing, MN 0 2 1973

1979

TOTAL 3 10

The commenter indicated that it had recently learned of the construction of a new mineral 

wool production facility by a company known as Armstrong and that the new facility would 

manufacture ceiling tile fibers, which the company had previously obtained from the now-closed 

Sloss facility. 

The commenter also recommended that the EPA should follow the recommendations of 

the Small Business Advocacy Review (SBAR) Panel that could effectively reduce the impact of 

the Proposed Rule on small businesses. The recommendations highlighted by the commenter 

were:

• The Panel recommended that the EPA propose amendments to the mineral wool 

MACT that offer regulatory flexibility to the maximum extent possible.

• The SBAR Panel observed that the EPA has flexibility in the averaging method used 

for calculating the MACT floor and could use one of several averaging methods. 

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Consistent with the SBAR Panel’s admonition to “offer regulatory flexibility to the 

maximum extent possible,” the commenter strongly urged the EPA to use the 

averaging method that accurately reflects the floor level of performance, but 

minimizes cost impacts on affected sources. The commenter argued that the manner 

in which the EPA calculated the 2011 proposed limits created limits that the majority 

of the facilities could not meet, and, in many instances, may not be met on a 

consistent basis by the facilities on which the EPA based their calculation.

• The Panel recommended subcategorization wherever appropriate. The commenter 

strongly endorsed the EPA’s subcategorization of the collection and curing sources, 

and requested subcategorization of the cupolas. (In response to the EPA’s proposed 

revisions in 2014 (79 FR 68025), the commenter (1041-0164) supported the EPA’s 

final subcategories for cupolas.)

• The Panel recommended setting MACT limits for new sources equal to MACT limits 

for existing sources. The commenter supported the EPA proposing identical limits for 

HF and HCl for new and existing sources, and requested that the EPA set identical 

limits for new and existing sources for COS.

• The Panel recommended the maximum amount of compliance time (3 years) for 

existing sources. (In response to the EPA’s proposed revisions in 2014 (79 FR 

68025), the commenter (1041-0164) supported the EPA’s proposal to allow a 3 year 

compliance period for existing sources.)

• The Panel recommended modifications for affirmative defense requirements to 

address malfunctions that reflect changes made in other Section 112 rules, and to 

provide guidance on complying during startup and shutdown.

Response: As previously explained, in the 2011 proposal (76 FR 72787), we explained 

that section 609(b) of the RFA, as amended, requires the EPA to convene a SBAR Panel prior to 

publication of the IRFA that an agency may be required to prepare under the RFA. We explained 

that an SBAR was conducted for the mineral wool production source category along with site 

visits to two mineral wool facilities. We also explained that the SBAR panel is required to report 

findings on four key items that the EPA is to consider when completing the draft of the proposed 

rule. The Panel’s report addressing these key items has been placed in the docket for this 

rulemaking.

Under the RFA, the EPA may consider legal alternatives that result in lower impacts to 

the industry where there is a SISNOSE. As also explained in the 2011 proposal, the SBREFA 

directs federal agencies to consider using regulatory flexibility in setting standards that apply to 

small businesses. In the 2011 proposal, therefore, to the extent allowed under CAA section 

112(d), we considered the SBAR panel recommendations, where possible, and these are reflected 

in the proposed subcategorization of collection and curing processes and the proposed 

compliance deadlines. The EPA proposed three subcategories based on the industry identified 

collection and curing processes used in the U.S. mineral wool industry to produce bonded 

products, which are: vertical, horizontal and drum collection and curing. In response to 

comments on our November 2011 proposal, and after our review of additional data, we proposed 

in November 2013 two different subcategories for cupolas: open-top and closed-top cupolas. We 

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also proposed a 3-year compliance deadline for existing sources. As explained in the earlier 

response, none of the proposals resulted in a SISNOSE.

As also explained earlier, CAA section 112(d) requires the EPA to promulgate standards 

for major sources of HAP based on the performance of the MACT. For existing sources, MACT 

standards must be at least as stringent as the average emissions limitation achieved by the best 

performing 12 percent of existing sources (for which the Administrator has emissions 

information) or the best performing 5 sources for source categories with less than 30 sources, as 

is the case here. For new sources, the MACT standards must be at least as stringent as “the 

emission control that is achieved in practice by the best controlled similar source.” 42 U.S.C. 

section 7412(d)(3). The EPA is precluded from considering costs in determining the minimum 

stringency of the MACT standards (National Lime Ass’n v. EPA, 233 F.3d at 640), but the EPA 

must consider more stringent “beyond-the -floor” control options in which cost can be 

considered. Thus, the EPA is prohibited from adopting the same standard for new sources as for 

existing sources, as recommended by the commenter, where the available data indicate that new 

sources can achieve a more stringent level of control, which is the case here. 

We also note that the impacts of the 2014 proposed rule to mineral wool producers, 

which are associated with conducting performance tests, are estimated to be $48,800 (2013 

dollars) for the whole industry, and range from 0.006 percent to 0.1 percent, expressed as annual 

compliance costs as a percent of sales.28 The price elasticity of demand for the mineral wool 

industry is estimated at -0.829, and the price elasticity of supply for the industry is estimated at -

0.7.30 With the responsiveness of mineral wool demand and supply to be less in percentage terms 

than the change in product price as approximated by the cost to revenue ratio, since this ratio is 

the maximum price change that producers may face, and with this ratio at or below 1 percent for 

the majority of production from this industry, it is expected that mineral wool price and output 

changes in response to this final rule will be less than 1 percent.31 Given these estimates of 

expected impacts, the EPA believes there is no SISNOSE and has so certified in the preamble to 

the final rule.

G. Environmental Benefits

90. Comment: One commenter (1041-0080) stated that insulation has provided 

fundamental and very pragmatic health benefits. The commenter emphasized that rock and slag 

wool insulation resists mold, fungi, and bacteria growth because the material is inorganic. The

commenter observed that the industry’s products also offer enhanced protection against 

28 Use of this metric for economic impacts when small businesses are prevalent in an industry affected by a 

regulation is consistent with the EPA guidance on SBREFA compliance 

(http://www.epa.gov/sbrefa/documents/Guidance-RegFlexAct.pdf), chapters 2 and 3. 

29 Ho, M. S, R. Morgenstern, and J. S. Shih. 2008. “Impact of Carbon Price Policies on US Industry.” RFF 

Discussion Paper 08-37. Http://Www.Rff.Org/Publications/Pages/Publicationdetails.Aspx?. Publicationid=20680. 

Accessed August 2009. Table 8.A.6.

30 Broda, C., N. Limao, and D. Weinstein. 2008b. “Export Supply Elasticities.” <http://faculty.

chicagobooth.edu/christian.broda/website/research/unrestricted/TradeElasticities/

TradeElasticities.html.>

31 This conclusion is consistent with perfect competition for this industry. This conclusion may change somewhat to 

the extent that this industry is imperfectly competitive. 

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damaging moisture infiltration that can rob insulation of R-value. Other advantages of rock and 

slag wool insulation offered by the commenter are: 

• Thermal performance – mineral wool achieves higher R-values than other insulation 

products; higher R-values mean greater insulating power, translating into increased 

year-round comfort and more significant energy savings;

• Fire protection and life safety - mineral wool products lend enhanced fire protection 

to buildings and structures;

• Energy conservation - mineral wool makes buildings more energy efficient, in a 

highly cost effective manner, and reducing GHG and other emissions; 

• Waste reduction - Slag wool is made from blast-furnace slag, a waste by-product of 

steel manufacturing, and consumes less energy during production than using entirely 

natural rock. Many insulation manufacturers are also reducing process waste by reengineering manufacturing to incorporate production scrap back into the primary 

production process, or reprocessing it into other products.

Response: We acknowledge the comment. 

H. Surrogacy

91. Comment: One commenter (1041-0080) noted that the EPA specifically requested 

comments on the agency decision to discontinue use of formaldehyde as a surrogate for phenol 

and methanol (as well as a direct measure of formaldehyde emissions) and the use of CO as a 

surrogate for COS. The commenter and its members supported the EPA’s decision to abandon a 

surrogate for COS. With the development of EPA Test Method 318 for COS, the measurement 

will be a more accurate reflection of the actual COS emissions. While there is a correlation 

between CO emissions and formation of organic HAP emissions, COS is a single HAP, not 

multiple HAP like the metals, and the commenter argued that testing directly for that one HAP is 

preferable.

The commenter also supported the EPA’s decision to retain PM as a surrogate for the 

various metals that may be present in trace amounts in the mineral wool process. Specifically, 

there are various metals that have an identified presence in mineral wool emissions, but the 

volume is so miniscule that to test for each metal seems counterintuitive, and, given that the 

majority of mineral wool manufacturers are small businesses, the commenter noted that it also 

seems unnecessarily costly when the emissions can just as effectively be monitored with one test 

for particulate matter. The commenter also noted that, as acknowledged by the EPA, the courts 

have held that PM is an appropriate surrogate for HAP metals.32

The commenter urged the EPA to retain formaldehyde testing as a surrogate for phenol 

and methanol for the same reasons PM data is more efficient than multiple tests for separate 

metals.

32 76 Fed. Reg. at 72,775 (citing Sierra Club v. EPA, 353 F.3d 976 (D.C. Cir. 2004)).

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Response: We acknowledge the commenter’s support for our decision to discontinue the 

use of CO as a surrogate for COS and the continued use of PM as a surrogate for metals. 

However, as further discussed in section IV.C.4 of the preamble to the final rule, we disagree 

that formaldehyde should be retained as a surrogate for phenol and methanol because the control 

device does not necessarily achieve the same reduction in all three pollutants.

I. Testing and monitoring Issues

92. Comment: One commenter (1041-0080/1041-0164) supported the EPA's proposed 

performance test schedule and the modified performance test methods. The commenter also 

supported the EPA’s proposed changes that require electronic notification, recordkeeping and 

reporting requirements.

Response: The agency acknowledges the commenter’s support.

J. Miscellaneous 

93. Comment: Commenter (1041-0126) identified a correction in the record for the 

EPA regarding the acronym for their organization. The EPA erroneously identified NAIMA as 

the National Association of Insulation Manufacturers of America. The correct identification is 

the North American Insulation Manufacturers Association. 

Response: We appreciate the commenter pointing out this error on our part. The EPA 

regrets this error and will correct it in the final rule.

94. Comment: One commenter (1041-0126/1041-0164) argued that the EPA should 

delist COS from the CAA section 112 list of HAP based on three findings: no adverse health 

effects have been attributed to COS, no evidence of carcinogenicity exists, and no data 

supporting chronic toxicity have been reported to date. The commenter (1041-0164) also argued 

that there is no evidence that COS presents a risk to the environment, that COS is naturally 

present in the atmosphere, and that 43 percent of emissions are from natural sources and 35 

percent derives from atmospheric transformation of carbonyl disulfide (CS2) to COS. The 

commenter argued that all worldwide anthropogenic sources account for only 4 percent of total 

COS levels, and that U.S. mineral wool manufacturing accounts for only a small fraction of these 

emissions. The commenter also argued that mineral wool provides environmental benefits that 

increase energy efficiency that reduces emissions from other sources.

Response: The issue of delisting COS from the HAP list is outside the scope of this 

rulemaking. However, we invite the commenter to petition the EPA to delist COS. In order to do 

so, the petitioner is required to provide data showing that COS is not toxic. The absence of health 

effects data for any HAP is not the same as data showing no adverse health effects.

95. Comment: The commenter’s (1041-0126) stated that significant environmental and 

public health benefits are realized by the use of mineral wool, and requested that the agency’s 

decisions and actions regarding the standard reflect the need to preserve and protect the mineral 

wool industry as a U.S. business that supplies the insulation market without resorting to foreign 

markets.

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Response: This comment is outside the scope of CAA section 112. The EPA’s mission in 

regard to this MACT rule is to establish emission standards for all HAP emitted by sources in the 

mineral wool industry.

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VI. WOOL FIBERGLASS MANUFACTURING SOURCE CATEGORY 

A. Issues Related to Both Major and Area Sources

1. Chromium Emission Limits for Gas-Fired Glass-Melting Furnaces

96. Comment: One commenter (1042-0300/1042-0348) opined that the EPA should 

increase the chromium emission limits for oxyfuel furnaces and allow such furnaces to emit 

4.6E-4 lb hexavalent chromium per ton of glass because this would not adversely impact the 

wool fiberglass industry. The commenter further believes this emission limit would present an 

acceptable risk as has been accepted in other RTR rules.

Response: We have reviewed the available chromium test data and information provided

in comments received in response to our 2011, 2013, and 2014 proposals (76 FR 72770, 

November 25, 2011; 78 FR 22370, April 15, 2013; and 79 FR 68011, November 13, 2014), and 

based on this information we are revising the emissions limit for total chromium in this final 

rule. One such comment indicated that a newly-rebuilt furnace, which we believe is the likely 

compliance technology, may not be able to demonstrate compliance with the proposed emission 

limit. The comment was based on one specific example from 2012 test data that showed a 1-year 

old gas-fired glass-melting furnace emitting 0.00025 pounds chromium per ton of glass. We also 

reviewed comments and information, such as this one, and are revising the estimated costs of 

rebuilding the furnace as an option to comply with the chromium limit. We note that EPA may 

consider cost in revising emissions standards under CAA section 112(d)(6). (Ass'n of Battery 

Recyclers v. EPA, 716 F.3d 667, 673 (D.C. Cir. 2013). We also note in section VIII.D.1 of the 

preamble to the final rule that rebuilding the furnace has a reasonable cost per pound of 

emissions reduction. Given the fact that the 2.5E-04 emissions level is achievable and cost 

effective, and results in lower chromium emissions and lower risk, the EPA sees no reason to set 

the limit at a higher level. Thus, in the final rule, EPA is establishing a total chromium 

compound limit of 2.5E-04 pounds per ton of glass pulled.

Note that the HAP listed for regulation is chromium compounds, and is not limited only 

to the hexavalent species of the pollutant. The EPA is establishing a chromium limit that applies 

to total chromium compounds.

As further discussed in sections VI.A and B of the preamble to the final rule regarding 

major sources, and in sections VII of the preamble to the final rule regarding area sources, we 

have reviewed the available chromium test data and information provided in comments received 

in response to our 2011, 2013, and 2014 proposals (76 FR 72770, November 25, 2011; 78 FR 

22370, April 15, 2013; and 79 FR 68011, November 13, 2014), and based on this information we 

are revising the emissions limit for total chromium in these final rules. Based on comments we 

received in response to the proposed chromium compounds limits for gas-fired glass-melting 

furnaces the November 2014 supplemental proposal, we reviewed the cost and control options 

and found using new cost information that the limit, as proposed, was not as cost effective as we 

initially believed. 

One such comment indicated that a newly-rebuilt furnace, which we believe is the likely 

compliance technology, may not be able to demonstrate compliance with the proposed emission 

limit. The comment was based on one specific example from 2012 test data that showed a 1-year 

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old gas-fired glass-melting furnace emitting 0.00025 pounds chromium per ton of glass. We also 

reviewed comments and information, such as this one, and are revising the estimated costs of 

rebuilding the furnace as an option to comply with the chromium limit, as discussed in section 

VI.B of the preamble to the final rule. 

For major sources in this source category, consistent with the legislative history on CAA 

section 112(f)(2), and as discussed in sections IV and V of the preamble to the final rules, we 

conduct our risk assessment in two steps. The first step in the process of evaluating residual risk 

is the determination of acceptable risk. If risks are unacceptable, the EPA cannot consider cost in 

identifying the emissions standards necessary to bring risks to an acceptable level. The second 

step is the determination of whether standards must be further revised in order to provide an 

ample margin of safety to protect public health. The ample margin of safety is the level at which 

the standards must be set, unless an even more stringent standard is necessary to prevent, taking 

into consideration costs, energy, safety and other relevant factors, an adverse environmental 

effect.

As discussed in sections IV and V of the preamble to the final rules, in assessing risk for 

the major sources in the Wool Fiberglass Manufacturing source category, we found that risk was 

acceptable. In our ample margin of safety analysis we determined that a chromium limit was 

necessary to provide an ample margin of safety. To establish the level of the chromium limit, we 

considered costs and economic impacts, technological feasibility, and other factors.

Also for major sources in the Wool Fiberglass Manufacturing source category, we note 

that EPA may consider cost in revising emissions standards under CAA section 112(d)(6). (Ass'n 

of Battery Recyclers v. EPA, 716 F.3d 667, 673 (D.C. Cir. 2013). We also note in section VI.B of 

the preamble to the final rule that rebuilding the furnace has a reasonable cost per pound of

emissions reduction. For our technology review conducted under CAA section 112(d) (6), in 

reviewing advancements and new technology; we consider cost, availability, transferability, and 

other factors of all relevant new technology as well as improvements in technology since the 

time that the MACT standard was last amended. Our analysis is explained in section VI of the 

preamble to the final rule, and in the Technology Review Memo for the Wool Fiberglass 

Manufacturing source category. 

For area sources in the wool fiberglass manufacturing source category, consistent with 

the legislative history on CAA sections; in the Urban Air Toxics Strategy (Strategy) as defined 

by CAA sections 112(d)(5), (c) (3) and (k), in determining GACT, we may consider costs and 

economic impacts, in addition to considering technical capabilities of the facilities and the 

availability of control measures. This is particularly important when developing regulations for 

source categories ...when determining whether additional control is necessary for sources with 

emissions that are already well controlled as a result of other existing or applicable 

standards. (Senate Report Number 101-228, December 20, 1989).

We determined that it was appropriate to modify the proposed limit of 6.0E-5 pounds per 

ton of glass pulled because the cost effectiveness for the emission reduction options ($660,000 

per pound of chromium reduced for the raw material substitution option, and $620,000 per pound 

chromium reduced for the furnace rebuild) were not reasonable compared to other cases where 

the EPA has regulated highly toxic pollutants, such as hexavalent chromium. We therefore 

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reviewed the data to determine whether a higher limit than previously proposed would be more 

cost effective while still significantly reducing chromium emissions from wool fiberglass gasfired glass-melting furnaces. The EPA found that most wool fiberglass gas-fired glass-melting 

furnaces at major sources currently emit chromium compounds at rates below 2.5E-04 pounds 

chromium per ton of glass pulled. We compared the chromium emission reductions that would 

have resulted under the previously proposed emission limit of 6.0E-5 pounds chromium per ton 

of glass pulled to the reductions that result from the final limit of 2.5E-04 pounds chromium per 

ton of glass pulled. We found that the proposed limit would have reduced chromium from major 

sources by 567 pounds per year, and that the final limit reduces chromium by 524 pounds per 

year. Because these emissions reductions are comparable, we finalized the emission limit for 

2.5E-04 pounds chromium per ton of glass pulled for gas-fired glass-melting furnaces located at 

wool fiberglass facilities. Given the fact that the 2.5E-04 emissions level is achievable and cost 

effective, and results in lower chromium emissions and lower risk, the EPA sees no reason to set 

the limit at a higher level. Thus, in the final rule, EPA is establishing a total chromium 

compound limit of 2.5E-04 pounds per ton of glass pulled.

Note that the HAP listed for regulation is chromium compounds, and is not limited only 

to the hexavalent species of the pollutant. The EPA is establishing a chromium limit that applies 

to total chromium compounds.

97. Comment: Two commenters (1042-0120 and 1042-0115/1042-0120/1042-

0300/1042-0348) requested that the EPA treat furnace K2 at CertainTeed’s Kansas City facility 

as an outlier. The commenters (1042-0120; 1042-0126) stated that the EPA is attempting to 

subject the entire industry either to the existing MACT and new area source standards based on a 

single facility’s test results showing high hexavalent chromium emissions from one of several 

types of furnaces used in the industry, which is an oxyfuel melter. According to the commenters, 

this approach was flawed, as was the EPA’s understanding of the facts, and the approach lacks 

sound scientific support for its proposed regulation.

One commenter (1042-0115/1042-0120/1042-0300/1042-0348) observed that the EPA 

acknowledged during the August 31, 2011 meeting that, but for this one test result –

CertainTeed, Kansas City – chromium emissions from this industry would not be a concern on 

the part of the agency. The commenter agreed with this characterization and urged the EPA to 

treat this result as an outlier and deal with it accordingly without implicating the entire wool 

fiberglass industry. The commenter contended that the EPA should either reject the outlier 

entirely from the dataset or address it in a separate action from the RTR for the wool fiberglass 

industry. The commenter argued that the EPA, in deciding that these furnaces are not outliers, 

has not considered key information about the furnaces indicating that they are outliers (i.e., 

design and raw material variation). The commenter believed additional data would support a 

conclusion that the highest emissions should be viewed as an outlier, and not as an industry-wide 

concern. The commenter reserved the right to submit supplemental comments to provide 

additional analysis on this very point.

The commenter (1042-0115/1042-0120/1042-0300/1042-0348) continued that there is 

reason to believe that the CertainTeed data are either flawed (because emissions from this facility 

are so much greater than emissions from other tested facilities) or at least are not representative 

of the industry as a whole, and that a separate subcategory should be established for this facility 

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to assure that it (and the industry as a whole) is appropriately regulated. The commenter argued 

that it should be evident that because the second highest emission data point is less than two 

percent of the outlier from CertainTeed’s Kansas City, Kansas furnace, the CertainTeed data 

point is not statistically significant when viewed in the context of all hexavalent chromium

emitted from the industry, and should be treated as an outlier. 

Response: We disagree with the comment. As explained in our April 2013 proposal, we 

issued a CAA section 114 ICR in December 2012, requesting test data on total chromium 

compounds emissions from all glass-melting furnaces and we were able to confirm our view of 

chromium emissions from this source prior to our April 2013 proposal. In our November 2014 

proposal, we also explained that as part of the data collection effort associated with this 

rulemaking, we collected source test data on 14 furnaces with information on furnace age, last 

rebricking or repair dates, current furnace age, and anticipated or planned future furnace 

replacement. We also explained that we had obtained emissions data for repeated testing of three 

rebuilt gas-fired glass-melting furnaces. We further explained that of the 14 tested furnaces, all 

four furnaces over 12 years old exceeded the proposed chromium limit. Of the 10 furnaces under 

12 years old, three exceeded the limit (one only marginally), and seven tested in compliance with 

(i.e., below) the proposed chromium limit. (79 FR 68021). See also 72 FR 22379-82 for our 

discussion of the test data the agency used to support the proposed chromium compounds limit.

As part of our data gathering exercise, we carefully reviewed each test report conducted 

for this industry and discussed the results with company operators. We learned through that 

process that, although the Kansas City K2 emitted in 2012 at extremely high levels, when the 

furnace was less than two years old, chromium emissions measured on the same scale as other 

newer furnaces in this industry currently measure. We also confirmed that chromium emissions 

increase with furnace age as the refractories age, and that the type of furnace at the high emitter 

is an emerging new technology that is preferred across the industry where a source of industrial 

oxygen is economically available. As explained in section VI.B of the preamble for the final rule, 

we view this as a “development in practices, processes and control technologies” for this source 

category and are therefore, promulgating the chromium compounds limit under CAA section

112(d)(6). The results of our technology review can be found in the Section 112(d)(6) 

Technology Review for Wool Fiberglass NESHAP memorandum, which is in the docket for this 

rulemaking.

As explained earlier, we did obtain test data subsequent to the test data that this 

commenter describes as an “outlier.” We also note that when we conducted our review of the 

data, we learned that the company operator knew the emissions of chromium compounds were 

very high, that the source of the chromium was the refractory lining of the furnace, and that the 

emissions of chromium increased with furnace age. Only the amount of chromium that was in 

the hexavalent state (93 percent) was new information to the operator. As also explained in our 

November 2014 proposal, we also learned at industry meetings, and from our CAA section 114 

data collection, that most wool fiberglass furnaces are constructed using similar high-chromium 

refractories, and that gas-fired (oxyfuel and air-gas) furnaces have the greatest potential to emit 

chromium compounds because they have the internal temperature, the availability of oxygen, 

reactivity, and corrosivity of the furnace environment that are typical of wool fiberglass furnaces. 

(79 FR 68021).

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As explained in the November 2011 proposal, under the second step of the risk 

assessment, under CAA section 112(f)(2), the EPA also considers whether existing risk can be 

lowered, and considers the cost of those reductions. This second step of the analysis is also 

known as an ample margin of safety analysis. We are also finalizing the chromium compounds 

limit as a result of our ample margin of safety analysis. This is because in our April 2013 

proposal, we also explained that we have no reason to believe the exact process that was found at 

the Kansas City, Kansas facility could not be replicated at any wool fiberglass manufacturer 

elsewhere, and we continue to believe that the test results at issue are simply indicative of the 

potential chromium (and hexavalent chromium) emissions that can result from the combination 

of gas-fired glass-melting furnaces that are constructed using high-chromium refractories. (78 FR 

22379). In our April 15, 2013 supplemental proposal, we also explained that the elevated 

chromium emissions from gas-fired furnaces are of concern due to the toxic nature of the type of 

chromium emitted (hexavalent chromium) and the effects associated with its inhalation. For 

example, we explained that hexavalent chromium inhalation is associated with lung cancer and 

that it is classified as a Class A known human carcinogen. (76 FR 22374). In our November 

2011 proposal, we explained that we had also performed an auxiliary risk characterization 

analysis to assess the potential maximum individual lifetime cancer risks in the event that all 

wool fiberglass manufacturing facilities emitted at the level of the highest hexavalent chromium 

emitter. We also explained that the auxiliary risk analysis indicated that if other facilities were to 

emit at that high level, emissions of hexavalent chromium could potentially pose unacceptable 

risks to public health due to inhalation exposures resulting from stack emissions of hexavalent 

chromium. This is because the results of the auxiliary analysis indicated that the estimated 

emissions from 14 facilities could lead to maximum individual lifetime cancer risks greater than 

100-in-1-million, with the highest emitting facility posing a potential maximum individual risk 

of 900-in-1-million; 8,100 people would be exposed to risks greater than 100-in-1-million, 

460,000 people would be exposed to risks of greater than 10-in-1-million, and over 7 million 

people would be exposed to cancer risks of greater than 1-in-1-million. The results of the 

auxiliary risk assessment were presented in Table 9 of the preamble, which can be found at 76 

FR 72801-80.

98. Comment: One commenter (1042-0299) challenged the EPA’s authority to exclude 

electric furnaces at major sources from regulation because CAA section 112(d) requires the EPA 

to set standards for all HAP emitted from the source category, and electric arc furnaces are part 

of the source category and emit chromium, albeit at lower levels than the gas-fired furnaces. The 

commenter (1042-0299) argued that the EPA had not justified excluding electric furnaces from 

the definition of category. In the commenter’s (1042-0299) view, the EPA is not allowed to 

exempt electric-only furnaces from regulation under the RTR because electric furnaces are part 

of the source category and because they emit chromium compounds, a HAP. Another commenter 

(1042-0300) agreed with the EPA’s decision to exclude electric furnaces from the rule because, 

in the commenter’s opinion, electric furnaces do not have the design features needed to emit high 

(or frequently even measurable) levels of chromium compounds, and therefore do not warrant 

regulation. 

Response: In the final rule, we are promulgating an emission limit of 0.33 pounds of PM 

per ton of glass pulled that is applicable to all glass-melting furnaces in the Wool Fiberglass 

Manufacturing source category. Accordingly, the PM limit will apply to electric furnaces at 

major sources as a surrogate limit for non-mercury metal HAP. The EPA may use a surrogate to 

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regulate HAP if there is reasonable basis to do so and in several rulemakings, we have used PM 

as a surrogate ‘‘for HAP metals because PM control technology traps HAP metal particles and 

other particulates indiscriminately.’’ National Lime v. EPA, 233 F.3d at 639. We continue to 

believe that PM controls would be effective for chromium emissions commensurate with the 

levels from both steel and electric furnaces used by wool fiberglass manufacturing facilities.

In response to comments on our November 2011 proposal, we proposed to limit the 

applicability of the chromium compounds standards to only gas-fired glass-melting furnaces in 

our April 2013 proposal (72 FR 22386). We also retained the PM limits for all glass-melting 

furnaces that would include electric glass-melting furnaces at major sources. We explained that

electric furnaces emit metal HAP including chromium, albeit at generally lower emission levels 

than gas-fired furnaces. Our proposal was based on emissions test data collected for all furnace 

types at all facilities in the source category. As explained in the preamble to the 2013 proposal, 

furnace construction and source test data collected via CAA section 114 questionnaires show that 

electric furnaces are not constructed using high-chromium refractories above the glass-metal 

line, do not reach the temperatures necessary to transform chromium to the hexavalent state, and 

do not emit significant amounts of chromium compounds, as do the gas-fired furnaces. In fact, 

all test data for electric furnaces show that chromium emissions were below the detection limit or 

were at least one order of magnitude below the proposed limit. Refer to the preamble discussion 

to the 2013 proposal (78 FR 22379 - 22382, April 15, 2013) for further discussion about the low 

potential for metal emissions from electric glass-melting furnaces as compared to gas-fired glassmelting furnaces. We have also provided a detailed explanation on our decision to set both PM 

and total chromium standards in the memorandum “Technical Basis for Separate Chromium 

Emission Limits for Wool Fiberglass Glass-Melting Furnaces,” which is in the docket for this 

rulemaking.

Therefore, we believe that PM controls for electric glass-melting furnaces are an 

appropriate surrogate for all non-mercury HAP metals.

99. Comment: One commenter (1042-0120/1042-0300/1042-0348) argued that the 

EPA should not promulgate a chromium limit for wool fiberglass furnaces and that PM is a valid 

surrogate for all HAP metals, including chromium. The commenter (1042-0120) stated that nonoxyfuel furnaces should not have a chromium limit, but should be subject instead to a PM limit 

as surrogate for all non-mercury metal HAP including chromium. The commenter noted that 

non-oxyfuel furnaces – steel shell, cold-top electric, air-gas, and specialty – have extremely low 

to non-detectable chromium emissions. The commenter referred to the summary spreadsheet 

setting forth the chromium content of refractories and chromium emissions (provided in 

Attachment 8 of comment letter 1042-0120) and the test reports sent to the EPA. The commenter 

continued that this summary spreadsheet establishes that oxyfuel furnaces are the furnaces that 

are more likely to have different chromium emissions. The commenter stated that this conclusion 

will be substantiated by the data submitted through companies pursuant to the EPA’s CAA 

section 114 inquiry. The commenter stated that these data sets demonstrate that the other furnace 

types do not pose a chromium issue. Therefore, the commenter urged the EPA not to impose a 

chromium limit for the other furnace types. The commenter argued that because PM limits will 

remain in place, a specific chromium limit for non-oxyfuel furnaces is duplicative and certainly 

not justified by the EPA’s risk and exposure assessment for chromium emissions.

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The commenter (1042-0300/1042-0348) noted that in the original 1999 MACT standard, 

PM appropriately was considered a surrogate for all HAP metals. In the commenter’s opinion, 

the EPA should continue with this 1999 designation for this industry, as currently allowed by the 

courts. The commenter (1042-0120) stated that because the courts have recognized that PM is a 

valid surrogate for heavy metals, it should be retained as a surrogate for all heavy metals, 

including chromium.

The commenter (1042-0120) argued that, if the EPA were to retain a chromium limit, the 

EPA should not also retain PM as a surrogate.

Response: The commenter (1042-0300/1042-0348) is correct that we used PM as a 

surrogate for all non-mercury metals in the 1999 NESHAP. The commenter, however, is 

incorrect in asserting that there is no justification for a PM limit if there is also a chromium limit. 

As explained earlier, the EPA may use a surrogate to regulate HAP if there is reasonable basis to 

do so. We have used PM as a surrogate to regulate non-mercury HAP metals when (1) “HAP 

metals are invariably present . . . in PM;” (2) “PM control technology indiscriminately captures 

HAP metals along with other particulates;” and (3) “PM control is the only means by which 

facilities achieve reduction in HAP metal emissions.” National Lime v. EPA, 233 F.3d at 639. 

We have also always reasoned that “[i]f HAP metals are invariably present in ...PM, then even if 

the ratio of metals to PM is small and variable, or simply unknown, PM is a reasonable surrogate 

for the metals-assuming ... that PM control technology indiscriminately captures HAP metals 

along with other particulates.” Id. As explained earlier, we are promulgating a PM standard that 

is applicable to all glass melting furnaces in the Wool Fiberglass Manufacturing source category. 

Accordingly, the PM limit will apply to electric furnaces at major sources as a surrogate limit for 

non-mercury metal HAP. 

In response to comments on our November 2011 proposal, in April 2013 we proposed to 

limit the applicability of the chromium compounds limit to only gas-fired glass-melting furnaces

(72 FR 22386). As explained in our 2013 proposal, gas-fired furnaces have a higher chromium 

emission potential due to their technical design and operation. For example, because they operate 

at higher temperatures, gas-fired furnaces are constructed with chromium refractories at various 

parts of the furnace that are above the molten glass, including the crown. Temperatures above the 

melt in gas-fired furnaces range from 2,500 to 4,500◦

F, and these temperatures are sufficient to 

convert chromium to its hexavalent state. When chromium is available, as it is in the refractories 

above the melt in gas-fired furnaces, it may be converted to the hexavalent state by the heat of 

the gas-fired furnace. Thus, gas-fired furnaces have the potential to emit elevated levels of 

chromium, even when meeting the total PM limit. (78 FR 22379-82; 78 FR 22386). These higher 

chromium emissions do not occur with electric furnaces because they are constructed with either 

non-chromium refractories (cold-top electric) or steel in place of refractories (electric steel shell) 

above the glass/metal line. As also explained in our 2013 proposal, available test data from both 

electric and steel shell glass-melting furnaces consistently showed chromium emission below the 

detection level of the emissions measurement method. (78 FR 22379-80). Retaining a PM 

surrogate without also requiring a chromium limit for gas-fired furnaces (as in the 1999 MACT) 

would ignore the new information we have obtained from industry regarding the potentially high 

chromium emissions from gas-fired furnaces, and would not sufficiently reduce emissions of 

hexavalent chromium, a known human carcinogen, from these sources. For non-gas-fired 

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furnaces, as explained earlier, we continue to believe that the control devices used in the industry 

to reduce emissions of PM are effective for all non-mercury HAP metals.

Therefore, we are finalizing a chromium emissions limit that is applicable to all gas-fired 

furnaces in order to address the higher chromium emission potential for such furnaces, under 

both sections 112(d)(6) and (f)(2). We are also finalizing a PM limit to serve as the surrogate for 

all non-mercury metal HAP for non-gas-fired furnaces and the surrogate for all non-mercury and 

non-chromium metal HAP for gas-fired furnaces, under section 112(d)(6).

100. Comment: One commenter (1042-0115/1042-0120/1042-0300/1042-0348) asked 

why a chromium limit is needed if recent air monitoring in Kansas City shows that the 

hexavalent chromium levels in air do not indicate a health concern.

Response: The monitoring mentioned by the commenter presents a short snapshot of 

time and may not be indicative of long-term risk. In addition, it is our understanding that the 

monitoring was conducted during a time period when the furnace with the highest chromium 

emissions was shut down. 

In section VI of the preamble to the final rule, we present our RTR results, which were 

conducted under both CAA sections 112(d)(6) and (f)(2). As explained in the preamble for the 

final rule, we are promulgating the chromium compounds limit under CAA section 112(d)(6) 

because we have found that a “development in practices, processes and control technologies” for 

this source category. Additionally, as also explained in the preamble to the final rule, we are 

finalizing the chromium compounds limit under the ample margin of safety step of CAA section 

112(f)(2). The final rule requirements are based on information we have gathered from industry 

meetings and our CAA section 114 data collection, and we have established that most wool 

fiberglass furnaces are constructed using similar high-chromium refractories as the Kansas City 

facility referred to by the commenter, that emissions of chromium increase with furnace age (see 

the memorandum “Explanation of the Mechanisms of Chromium Emissions from Gas-Fired 

Furnaces” in docket EPA-HQ-OAR-2010-1042), and that gas-fired (oxyfuel and air-gas) 

furnaces have the greatest potential to emit chromium compounds because they have the internal 

temperature, the availability of oxygen, reactivity, and corrosivity of the furnace environment 

that are typical of wool fiberglass furnaces. Based on these facts (as further discussed in section 

VI.B.3 of the preamble to the final rule), we have reason to believe that there is a potential for 

gas-fired furnaces to emit chromium at levels significant enough to potentially present a health 

risk to nearby populations in the absence of chromium air emissions limits. The auxiliary risk 

analysis performed as part of this rulemaking (“Draft Residual Risk Assessment for the Mineral 

Wool Production and Wool Fiberglass Manufacturing Source Categories” and “Maximum 

Predicted HEM-3 Chronic Risks (Wool Fiberglass Manufacturing) based on Revised – What If 

Analysis,” available in the docket for this rulemaking (EPA-HQ-OAR-2010-1042-0086 and 

EPA-HQ-OAR-2010-1042-0263, respectively) specifically addressed health risks if the potential 

for high chromium emissions at other locations of wool fiberglass were realized, and these risks 

were found to be as much as 400-in-1 million. Therefore, even if one were to accept that the 

actual monitoring data from Kansas City does not indicate a health concern, that fact does not 

mean that chromium emissions from furnaces are not a national health concern sufficient to 

warrant regulation. We have also confirmed that chromium emissions increase with furnace age 

as the refractories age, and that the type of furnace at the high emitter is an emerging new 

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technology that is preferred across the industry where a source of industrial oxygen is 

economically available.

2. PM Limit for Glass-Melting Furnaces

101. Comment: One commenter (1042-0120) argued that the EPA should not have 

proposed in 2011 to reestablish the PM MACT floor for glass-melting furnaces or use postMACT compliance data. According to the commenter, the EPA issued new and existing source 

MACT standards for PM in 1999 and therefore, is not required to revisit those standards. The 

commenter contended that the 1999 PM standards are valid MACT standards when PM is used 

as a surrogate for HAP metals. The commenter argued that, even if it were appropriate to 

otherwise revise the 1999 PM standards, the EPA has not provided an explanation or asserted 

any rational basis for choosing to calculate a new MACT floor and standard for PM, as opposed 

to using its discretion under CAA section 112(d)(6) to make an appropriate adjustment without 

recalculating the floor and standard.

The commenter added that nothing in CAA section 112(d) suggests that the EPA is 

required to establish a floor under CAA section 112(d)(3) more than once in issuing or revising 

MACT standards under CAA section 112(d). The commenter contended that the structure of 

CAA section 112(d) envisions the initial setting of new and existing source MACT standards that 

are no less stringent than the formulations set forth in paragraph (d)(3). The commenter noted 

that the EPA then is to revisit those standards every 8 years when it conducts its “technology 

review” under section CAA 112(d)(6), and determines whether it is appropriate to revise the 

standards. Moreover, according to the commenter (1042-0120), the U.S. Court of Appeals for the 

D.C. Circuit upheld the position that there should not be an inexorable downward ratcheting 

effect for the MACT floors in the challenge to the Hazardous Organic NESHAP rule. The 

commenter claimed that the EPA proposed exactly such a downward ratcheting of the floors by 

setting the floor for a second time and using data gathered following compliance with the 1999 

MACT standards. According to the commenter, the “new technology development” identified by 

the EPA exists as a result of industry having to comply with the 1999 MACT standard and that 

there are no new control technologies in use in this industry beyond those used to comply with 

the 1999 standard. The commenter argued that the EPA’s proposal uses test data that have 

achieved much lower emissions levels as a result of complying with the 1999 PM standards to 

set more stringent standards now, but that the CAA does not allow the EPA to drive down the 

floors as a result of using data from sources that already have installed MACT controls.

Response: In the 2011 proposal, the EPA had intended to set a PM limit that represented 

what we considered to be the demonstrated current performance of PM controls for the entire 

population of furnaces as part of the technology review performed under the authority of CAA 

section 112(d)(6). We explained that most sources had reported PM emissions that were less than 

10 percent of the current limit with several sources achieving PM emissions that were two to 

three orders of magnitude lower than the current MACT limit. We reasoned that new furnace 

designs and improvements in control devices operations, design and bags since the 1999 MACT 

promulgation were most likely responsible for reductions in PM emissions. However, as 

explained in the preamble to the 2013 proposal (78 FR 22837), in reviewing comments related to 

the proposed PM limit, we realized that we had erred in calculating the 2011 proposed PM limit

based on the best performing 12 percent of the sources, and we proposed a revised PM limit of 

0.33 pounds per ton of glass pulled based on the level achieved by well-controlled units that we 

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evaluated, not based on recalculation of the MACT floor. Recalculating the MACT floor would 

have been the correct approach if our intent had been to establish a MACT limit under CAA 

sections 112(d)(2) and (3), but that was not our intent. We are finalizing the PM limit of 0.33 

pounds per ton of glass pulled. This standard and the results of our technology review, including 

our calculations, can be found in the memorandum “Section 112(d)(6) Technology Review for 

Wool Fiberglass NESHAP,” which is in the docket for this rulemaking. 

However, we disagree with the commenter’s view that CAA section 112(d)(6) is the 

EPA’s sole authority for revising existing MACT standards. As a general matter, an agency 

remains free to revise improperly promulgated or otherwise unsupportable rules. Further, we 

believe that Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011) confirms that the 

EPA is not constrained by CAA section 112(d)(6) and may reassess its standards more often, 

including revising existing floors if need be under the authority of CAA sections 112(d)(2) and 

(3). The commenter is, thus, incorrect that CAA section 112(d)(6) provides the exclusive 

authority to situations where (e.g., HCl and HF) the EPA did not adopt a proper MACT standard

initially. 

102. Comment: One commenter (1042-0120) suggested that the PM limits proposed by 

the EPA in 2011 cannot be met by the majority of wool fiberglass manufacturing facilities (or the 

facilities are not confident they can meet the proposed PM limits on a consistent basis with the 

controls implemented to meet the original MACT limits), even with the controls that were 

implemented as a result of the initial MACT limits. The commenter provided a list of facilities 

that, based on the available data, cannot meet the 2011 proposed PM emission limit for existing 

sources. The commenter stated that existing data provided to the EPA as part of the fiberglass 

industry’s voluntary data submission show the range for PM emissions as 0.0043 – 0.50 pounds

per ton of melt (filterable PM only). The commenter opined that the EPA should retain the 

current PM limit of 0.5 pound per ton of melt.

Response: As discussed in the preamble to the 2013 proposal, we did not intend to 

propose a PM MACT floor limit in 2011. We intended to develop a limit under CAA section 

112(d)(6) based on the level achieved by well-controlled units that we evaluated, not based on 

recalculation of the MACT floor. As noted in our response to comment number 101, we 

corrected our error by re-proposing a new PM limit in our 2013 proposal. Based on the PM data 

available to the EPA, all current furnaces can meet the final limit of 0.33 pounds per ton glass 

pulled. The results of our technology review including more information on the development of 

the PM limit can be found in the memorandum, “Section 112(d)(6) Technology Review for 

Wool Fiberglass NESHAP,” which is in the docket for this rulemaking.

103. Comment: One commenter (1042-0120) opined that because PM is not a HAP, the 

EPA lacks authority to regulate PM in a MACT standard except as a surrogate, and that the 2011 

proposal did not indicate that the EPA was retaining PM as a surrogate for HAP in this rule. 

Response: The EPA clarifies that the PM limit being finalized is a surrogate for nonmercury HAP metals. Refer to the EPA’s response to comment number 99 for a discussion of the 

EPA’s decision to finalize PM as a surrogate for non-mercury metal HAP for major sources.

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104. Comment: One commenter (1042-0115f) recommended that the EPA minimize 

the use of surrogates in all related industries to avoid situations like CertainTeed’s K2 facility in 

Kansas. 

Response: We disagree with the commenter regarding minimizing the use of surrogates. 

As outlined in our response to comment number 99, we may use surrogates to regulate HAP if 

there is a reasonable basis to do so. We do recognize, however, that in cases where a surrogate is 

not reasonable, we should regulate specific HAP as we are regulating chromium from gas-fired 

furnaces in this final rule.

105. Comment: One commenter (1042-0120) asserted that the EPA’s position that 

“synthetic area sources” may be considered in the floor determination for PM for this source 

category is unfounded because CAA section 112 expressly defines the terms “major source” and 

“area source” and provides for separate listing and regulation of major sources and area sources, 

but that the statute does not distinguish between “area sources” and “synthetic area sources.” 

Therefore, the commenter contended that “synthetic area sources” are not part of a corresponding 

major source category and cannot be used in determining the MACT floors for the major source 

category. The commenter argued that the MACT floor should be recalculated using data from 

only sources that are currently subject to the MACT.

The commenter provided a list of six area source facilities that the commenter argued 

should be eliminated from EPA’s MACT floor calculation for PM: Knauf’s Lanett, Alabama; 

Knauf’s Shasta Lake, California; Johns Manville’s Richmond, Indiana (7603); Johns Manville’s 

Richmond, Indiana (7602); Johns Manville’s Willows, California; and Owens Corning’s 

Fairburn, Georgia. 

The commenter noted that, in other MACT standards for other source categories, the 

EPA has not included true (or “natural”) area sources in establishing the MACT floor for PM. In 

the recent Portland Cement MACT, the commenter argued that the EPA conceded that it would 

be inappropriate to include true area sources in the MACT floor. See Office of Air Quality 

Planning and Standards, Development of the MACT Floors for the Final NESHAP for Portland 

Cement, August 6, 2010 at 14 (“Subsequent to proposal, we received comments that indicated 

we had inappropriately (albeit inadvertently) included certain natural area sources in the MACT 

floor analysis.”). See also 68 Fed. Reg. 26,690, 26,698 (May 16, 2003) (“EPA disagrees that the 

CAA contemplates that synthetic minor sources must be treated like true area sources and 

excluded from the MACT floor determinations.”) The commenter observed that EPA has 

interpreted the Act to require inclusion of synthetic area sources in the MACT floor 

determination. See Id. (“We believe that the better interpretation of the CAA’s plain language 

and legislative history requires that synthetic minor sources be included in MACT floor 

determinations.”)

The commenter stated that CAA section 112 expressly defines the terms “major source” 

and “area source” and provides that major sources and area sources must be separately listed and 

regulated. The commenter argued that the statute does not distinguish between “area sources” 

and “synthetic area sources” (i.e., an area source is an area source, regardless of whether 

emissions limitations or control requirements are needed). Therefore, the commenter argued that 

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“synthetic area sources” are not part of a corresponding major source category and cannot be 

used in determining the MACT floors for the major source category.

Response: As discussed in the preamble to the 2013 proposal, we did not intend to 

propose a PM MACT floor limit in 2011. We intended to develop a limit under CAA section

112(d)(6). As noted in our response to comment number 101, we corrected our error and the PM 

limit is no longer based on a MACT floor calculation. Moreover, and as explained in previously 

rulemakings (e.g., Brick NESHAP, 68 FR 26697–26698, May 16, 2003) we believe that the 

better interpretation of the plain language of section 112(d)(3) and relevant legislative history 

requires that synthetic minor sources should be included in MACT floor determinations.

106. Comment: One commenter (1042-0120) stated that five of the sources –

Guardian’s Albion, Michigan (counted as three sources for the MACT floor) and Johns 

Manville’s Richmond, Indiana (counted as two sources) – are inappropriately used to set the 

MACT floor. The commenter observed that Guardian’s Albion, Michigan facility is used as three 

sources for the MACT floor calculation. According to the commenter, this is problematic for a 

number of reasons: (1) one of three furnaces was not operating when the testing was conducted; 

(2) the emissions from all three sources are emitted to one common exhaust point, so the testing 

sampling was collected from this one exhaust point; (3) EPA did not accurately identify the 

emissions from each furnace; and (4) after testing these furnaces under these conditions for 

years, the company could not accurately identify or predict the specific emissions from each 

furnace. The commenter claimed that to count one point source as three sources when the 

emissions from each furnace cannot be accurately ascertained is incorrect. The commenter also 

stated that Johns Manville Richmond, Indiana facility is counted as two sources, but there is only 

one furnace at the Richmond, Indiana facility. The commenter contended that EPA should count 

Guardian’s Albion, Michigan facility as one source, not three, and count Johns Manville’s 

Richmond, Indiana facility as one source, not two. 

The commenter also contended that PM data from Guardian’s Albion, Michigan facility 

(counted as three sources); Johns Manville’s Willows, California facility; Johns Manville’s 

Richmond, Indiana facility (counted as two sources); and Knauf’s Lanett, Alabama facility are 

below-MDL, even though the data were generated from runs longer than the promulgated 

methods contemplate. The commenter requested that the EPA remove all seven of these sources 

from the calculation for the MACT floor because below-MDL data is unquantifiable. The 

commenter expressed concern that using below-MDL data is likely to set limits so stringent that 

the best performing sources cannot even meet those limits. The commenter cited a memorandum 

from RMB Consulting about relying on below-MDL data.33 According to the commenter, the 

EPA should only use values that are above the MDL, i.e., actual values, in calculating the MACT 

floor. The commenter stated that the emissions floor must be determined by quantifiable data.

Response: As discussed in the preamble to the 2013 proposal and as noted in response to 

comment number 101, the PM limit is no longer based on a MACT floor calculation.

33 RMB Consulting & Research, Inc. Memorandum, Comments on Proposed EGU MACT Rule, July 19, 2011, 

p. 18.

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107. Comment: One commenter (1042-0299) contended that standard developed under 

section 112(d) of the CAA must first meet the requirements of CAA sections 112(d)(2) and (3) 

for developing MACT standards, and that the provisions in CAA section 112(d)(6) for 

technology review serve to continually re-evaluate MACT and thereby ratchet down emissions 

from each source category under review to control emissions to the greatest degree possible. The 

commenter pointed out that the court recently ruled against this view in two court cases and 

upheld the EPA’s decisions. The commenter contended that the similarity between these rules’ 

issues and the recently litigated rules are insufficient for that precedent to apply, and additionally 

argues that, in the commenter’s opinion, those cases were wrongly decided.

Response: We disagree with the commenter’s view that a MACT standard should be 

recalculated each time a source category is reviewed for technology review, under CAA section 

112(d)(6). In response to a similar argument that the EPA was obligated to completely 

recalculate MACT in conducting a technology review, under CAA section 112(d)(6), the D.C. 

Cir. held “[w]e do not think the words ‘review, and revise as necessary’ can be construed 

reasonably as imposing any such obligation.” NRDC v. EPA, 529 F.3d 1077, 1084, (D.C. Cir. 

2008). The D.C. Cir affirmed this holding more recently in Ass'n of Battery Recyclers v. EPA, 

716 F.3d 667, 673 (D.C. Cir. 2013). (Section 112(d)(6) “could not be construed reasonably as 

imposing an obligation on EPA ‘to completely recalculate the maximum achievable control 

technology’ when it revises standards under that provision.”) (Internal citations omitted).

Thus, we disagree with the commenter that recent court decisions in Association of Battery 

Recyclers v. EPA and NRDC v. EPA are sufficiently dissimilar to these decisions as to render 

them not applicable, and maintain that the issues are the same.

It is, however, appropriate for the EPA to consider data showing changes in emissions 

profiles and emission levels when conducting a technology review under 112(d)(6). This section 

broadly directs the EPA to review existing standards to determine if revisions are appropriate 

considering, among other things, developments that have occurred since promulgation of the 

original MACT standard. As previously explained, the D.C. Circuit has also held that the EPA 

may permissibly amend improper MACT determinations, including amendments to improperly 

promulgated floor determinations, using its authority under CAA sections 112(d)(2) and (3). 

Medical Waste Institute v. EPA, 645 F. 3d 420, 425-27 (D.C. Cir. 2011). In doing so, the EPA is 

not constrained by post-MACT compliance data. Medical Waste Incinerator, 645 F. 3d at 426 

(resetting MACT floor, based on post-compliance data, is permissible when originallyestablished floor was improperly established, and permissibility of the EPA’s action does not 

turn on whether the prior standard was remanded or vacated). Similarly, the D.C. Circuit’s 

December 9, 2011 decision in Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 

2011) confirms that CAA section 112(d)(6) does not constrain the EPA and it may reassess its 

standards more often, including revising existing floors if need be.

108. Comment: One commenter (1042-0120) stated that a thorough and complete 

analysis of the EPA’s calculation method is not possible since the EPA’s preamble discussion 

and MACT floor memorandum lack any details on the analysis itself. The commenter stated that 

the EPA has not provided enough information in the record to support its proposed floor analysis 

and proposed standards for HCl, HF, and PM. For example, to determine UPL, the commenter 

explained that the EPA should do statistical analysis related to the normality of the test data and 

possibly transform the data to produce a suitable distribution. The commenter noted that the 

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MACT floor memorandum talks about this but does not fully explain how the analysis was done 

for the fiber glass industry. The commenter asserted that the EPA has a legal obligation under the 

CAA to include in the record a “statement of basis and purpose” that should include such 

information. According to the commenter, its absence violates Section 307, and, if not corrected 

prior to promulgation, would render the final rule arbitrary.

Response: As discussed in the preamble to the 2013 proposal and as noted in response to 

comment number 101, the PM limit is no longer based on a MACT floor calculation as proposed 

in 2011. Also, as discussed in the preamble to the 2013 proposal and as noted in the EPA’s 

response to comment numbers 117 and 118, the HF and HCl standards are no longer numerical 

limits as proposed in 2011, but are being finalized as work practices. 

With regard to HF and HCl, we proposed work practice standards in our 2013 proposal to 

reflect comments and our evaluation of test data from industry on our 2011 proposal. We 

explained that we had re-evaluated available test data that we had used to calculate the MACT 

floor limits for the HCl and HF limits proposed in 2011, and found that most of the test data 

reflected values that were below the detection limit of the test methods. Specifically, over 80 

percent of the test results were values indicating that either HF or HCl, or both pollutants in the 

exhaust gas stream were below the detection limit of the methods. We believe that such values 

are not a measurement of pollutants but rather an indication that such pollutants are not present 

in measurable concentrations. (78 FR 22387). We therefore proposed work practices standards 

for the control of HF and HCl emissions from furnaces that would require air pollution control 

equipment associated with glass-melting furnaces to be operated according to the parameters 

established in the most recent performance test. The final rule contains work practices consistent 

with our 2013 proposal.

109. Comment: One commenter (1042-0299) stated that the 2013 proposal included

weaker PM and chromium limits for the wool fiberglass source category than proposed in 2011, 

and the commenter requested that the EPA revert to the PM limits proposed in November 2011.

Response: As a practical matter, the chromium emission limits are unchanged between 

the 2011 proposal and the 2013 supplemental proposal. The value of the chromium limit is 

identical in both the 2011 and 2013 proposals, but we did propose to change the applicability of 

the chromium limits to only gas-fired furnaces, and not to electric furnaces. However, that 

proposed change does not significantly affect the stringency of the rule because all the electric 

furnaces either did not detect chromium emissions during testing, or detected chromium at least 

one order of magnitude below the proposed limit. Therefore, the change in applicability will not 

result in any chromium emissions increases. So, as a practical matter, stringency is unchanged. In 

addition, due to design and construction differences, and as supported by the source test data 

collected for the rulemaking, electric furnaces do not have the potential to emit increasing 

chromium emission over time, so we do not believe that a limit is necessary to provide assurance

against future emissions increases

Regarding the numerical limits for PM for wool fiberglass manufacturing furnaces than 

had been proposed in 2011, the EPA intended for the stringency of the limit to be unchanged. As 

explained in the 2013 supplemental proposal preamble (78 FR 22387) and our response to 

comment number 101, the changes in the numerical limit occurred because the EPA was 

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correcting an error in the 2011 proposal. In the 2011 proposal, the EPA intended to set a PM 

limit that represented what we considered to be the demonstrated current performance of PM 

controls for the entire population of furnaces as part of the technology review performed under 

the authority of CAA section 112(d)(6). So, even though the numerical limit increased, the 

stringency of the limit the EPA intended to set did not change. We believe that new furnace 

designs and improvements in control device operation, design, and baghouses are the factors that 

are responsible for the improvements in PM control performance from 0.5 lb/ton (1999 MACT) 

to 0.33 lb/ton in the industry. The results of our technology review, including our calculations 

can be found in the memorandum, “Section 112(d)(6) Technology Review for Wool Fiberglass 

NESHAP”, which is in the docket for this rulemaking.

3. Testing and Monitoring Issues

110. Comment: Two commenters (1042-0300/1042-0348; 1042-0120) requested that 

the EPA leave the testing duration of 1 hour for Method 318 unchanged from the MACT 

compliance requirements originally proposed in 2011. One commenter (1042-0300/1042-0348) 

pointed out that sources were required to test under Method 318 for a period of 1 hour, but the 

EPA is proposing to change this duration by requiring 10 spectra. 

Response: In Method 318, sample gas is continuously extracted from the source and the 

sample gas is conveyed to a Fourier transform infrared (FTIR) spectroscopy cell where a 

spectrum of the sample gas is recorded. Section 8.6.3 of Method 318 specifies that the sample 

integration time, the sample flow rate through the FTIR gas cell, and the total run time must be 

chosen so that the collected data consist of at least 10 spectra with each spectrum being of a 

separate cell volume of flue gas. The EPA is finalizing its proposed change to require 10 spectra 

for Method 318 rather than specifying a minimum sampling duration to be consistent with the 

sampling requirements of Method 318. 

111. Comment: One commenter (1042-0300/1042-0348) expressed concern about 

proposed changes to Method 316 that would increase the testing duration from 1 to 2 hours. The 

commenter noted that the increase in sampling time would not increase the accuracy or reliability 

of the method. The commenter asked that the EPA retain the original test duration of 1 hour. 

Response: We are finalizing, as proposed, the requirement to collect a minimum 

sampling volume of 2 dry standard cubic meters (dscm); however, we are not finalizing the 

proposed minimum sampling run time for EPA Method 316 of 2 hours. Method 316 is capable of 

formaldehyde detection limits as low as 0.01 ppmv with a 1-hour test run when matrix 

interferences are not present. However, where concentrations of formaldehyde may be very low, 

it may be necessary to collect additional sample volume to ensure that the in-stack detection 

capability of the test method is sufficient to demonstrate compliance with the limit in the rule. 

Although Method 316 is very sensitive, it is incumbent upon the source and tester to ensure that 

sample collection during performance testing is sufficient for compliance demonstration. To that 

end, we are finalizing the requirement to collecting 2 dscm sample volume when using Method 

316. 

112. Comment: One commenter (1042-0120) cautioned the EPA against setting the 

MACT floor based on data from one test method or testing duration and mandating compliance 

testing based on data from a different test method or testing duration. The commenter provided 

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one example in the proposed rule that the EPA set the MACT floor using Method 316 data for 

formaldehyde, but now proposes use of Method 318 for compliance testing even though no data 

were collected using Method 318. Given the very low proposed limits, the commenter was 

concerned that compliance testing would not correspond with the data used to set the floor and, 

therefore, a disparity in test methods would cause compliance issues. The commenter provided a 

second example that the EPA set the MACT floors based on data collected using Method 316 

during extended four-hour runs; whereas compliance is based on data collected using fewer runs. 

The commenter believed it would be more appropriate for economic reasons to perform 

compliance testing using the shorter runs – one to two hours, but that it is quite possible that one 

or two hour runs could result in data that are below the method detection limit (MDL), which 

when converted to a lb/ton number could exceed the MACT standard. The commenter was 

concerned with how the EPA would handle non-detects in such instances and urged the EPA to 

consider this correlation before publishing its final rule.

The commenter urged the EPA to examine the correlation between the test methods the 

EPA used for calculating the MACT floor for PM, HF, HCl, formaldehyde, phenol, and 

methanol and proposed test methods for future compliance testing to ensure that these test 

methods correlate with currently used test methods. The commenter urged the EPA to recalculate 

the MACT floor so that the same test methods are used when setting the MACT floor and for 

compliance testing.

For measuring the concentration of formaldehyde, phenol, and methanol, the commenter 

stated that the use of Method 318 can result in non-quantifiable levels that are inappropriate to 

determine the levels proposed for this regulation. In the alternative, the commenter requested the 

option to determine all organics by FTIR Method 318 or determine formaldehyde by Method 

316, determine phenol by Method 8270D, and determine methanol by Method 308.

Response: The EPA agrees that Method 316 is capable of obtaining measurements with 

enough sensitivity to demonstrate compliance for this source category. In response to this 

comment, we proposed in the April 15, 2013 supplemental notice (78 FR 22387-88) that owners 

or operators could use Method 318 for measuring concentrations of phenol, methanol, and 

formaldehyde; Method 316 or Method 318 for measuring concentrations of formaldehyde; and 

Method 318 or Method 308 for measuring concentrations of methanol. The final rule, consistent 

with the 2014 proposal, provides alternative test methods to facilities for demonstrating 

compliance with the emission limits. For measuring formaldehyde concentrations, the final rule 

continues to allow owners or operators to use EPA Methods 316 or 318. For methanol, facilities 

can use EPA Method 318 or 308. With regard to the commenter’s suggestion to allow owners or 

operators to measure phenol concentrations using Method SW-846 8270D, we will consider 

providing this alternative when we evaluate MACT limits for RS lines at wool fiberglass 

manufacturing facilities as discussed in section V.H of the preamble to the final rule.

Regarding the comment that the same sampling time should be used for both the test data 

used to establish a MACT limit and the test method used to enforce that limit, for many test 

methods the detection limit decreases with increases in sampling time (i.e., larger sample 

volume). As the sensitivity of the method increases, the detection level decreases. ICR guidance 

directs testers and laboratories to gather larger sample volumes (longer test runs) in the pursuit of 

returning detectable amounts of each analyte. The EPA has adopted a method to establish floor 

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limits based on actual emissions measurements or, in the case of detection limit issues, a 3x RDL 

(Representative Detection Limit - determined from the pool of lab information provided through 

the ICR) value. The result of this process is that, if the emission limit is not based on actual 

measured concentrations as applied with the UPL procedure, compliance may be demonstrated

with a test that includes detectable amounts of the pollutant of interest, or the data are returned as 

below the detection limit. We expect that many emissions measurements will be sufficiently 

above the detection limit such that a UPL-calculated floor value results in test durations less than 

the four hour tests required by the ICR; however, we also expect sources, testers, and 

laboratories to research method detection and carefully plan their detection limits prior to any 

compliance sampling and design their testing and analytical protocols to attain detection of the 

analytes of concern before starting any field work. In no instance should a non-detect value result 

in a non-compliance situation unless the tester and/or laboratory does not appropriately consider

the concern of detection limitations prior to sampling.

113. Comment: One commenter (1042-0120) supported the EPA’s proposed electronic 

notification, recordkeeping, and reporting requirements in the 2011 proposal (76 FR 72770, 

November 25, 2011). The commenter, however, expressed concerns regarding the recordkeeping 

and notification requirements for refractory brick composition of glass-melting furnaces. 

According to the commenter, because refractory brick composition does not have any effect on 

hexavalent chromium emissions, the data requested would be irrelevant and therefore, 

inappropriate for recordkeeping purposes. The commenter believed that, moreover, sources 

consider this information as CBI, while some sources have also indicated that such data would be 

unavailable at certain facilities or plants. The commenter noted that the proposed requirement 

would subject sources to electronic reporting after January 1, 2012 and within 60 days of 

completion of each performance testing. The commenter suggested the reporting should begin 

within 60 days of the effective date of the rule instead. 

Response: The requirement to report refractory brick composition was initially 

considered as a way to track the potential for chromium emission increases. Because we are 

establishing chromium emissions limits in this final rule, there is no longer a need for this 

information and the final rule amendments do not contain any refractory composition 

recordkeeping and notification requirements. With regard to the commenter’s suggestion to 

require electronic reporting within 60 days of the effective date of the rule instead of the 

proposed requirement for electronic reporting within 60 days of completion of each performance 

testing after January 1, 2012, we note that it was not our intent that sources would have to 

retroactively go back and report all emission tests that were performed since January 1, 2012. 

Therefore, we have changed the language in the final rule to simply require reporting within 60 

days of each performance test and deleted the reference to January 1, 2012.

Regarding the timing of reporting, we disagree with the commenter that electronic 

reporting of the results of compliance tests should be delayed until 60 days after the effective 

date of the final rule. First, the commenters’ preference would amount to submission of only one 

report while we have information that hexavalent chromium emissions are expected to increase 

over the life of a wool fiberglass furnace, as further discussed in section VI.B.3 of the preamble 

to the final rule. This alone illustrates the usefulness of timely data from industry indicating the 

levels of chromium compounds being emitted from any wool fiberglass furnace. More important 

is the likelihood that certain wool fiberglass furnaces emitting close to but below the rule limits 

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one year may exceed the limits the next year. Second, the public has a right to be aware of the 

toxic compounds emitted into the atmosphere by wool fiberglass manufacturing facilities and 

these reporting requirements assure that timely reports are made available to the public as they 

become available.

Third, we do not believe this requirement is burdensome because test results can now be 

submitted electronically, as compared to when emissions reports were only available on paper. 

Moreover, we also believe that this rule, including the reporting requirements, is cost effective 

because the costs analyses shows the entire cost of the rule (of which reporting requirements are 

a small fraction) as less than one-tenth of one percent of the industry profits.

114. Comment: One commenter (1042-0299) requested in response to the EPA’s 2013 

proposal (78 FR 22370, April 15, 2013) that the EPA require continuous monitoring of PM and 

HCl, as it has done for other source categories, or at the very least, annual testing.

Response: In the final regulation, we are requiring that owners or operators conduct 

annual emissions tests for chromium. The EPA is finalizing the requirements to conduct 

emissions tests for filterable PM initially and every five years, and to conduct continuous 

parametric monitoring of control devices used to reduce PM emissions from furnaces, as 

proposed. As discussed in the 2011 proposal (76 FR 72803), the data submitted to the EPA show 

that most, if not all, facilities are achieving much lower levels of PM emissions than the level 

allowed under the 1999 NESHAP, and this is also the case for the revised PM emission limit of 

0.33 pounds per ton glass in the final rule. We believe that the PM data collected as part of this 

rulemaking indicate that facilities are maintaining PM emission levels well below the emission 

limits by using the current parameter monitoring requirements in the rule. Therefore, we disagree 

with the commenter that CEMS and/or annual testing are necessary to ensure compliance with 

the final PM emission limits. 

For HCl, the final rule requires facilities to comply with the work practice standards and 

the final rule does not require emissions testing for HCl. As discussed in the 2013 proposal (78 

FR 22387), the test data submitted to EPA showed that HCl concentration levels were very low 

(approximately 80 percent of the test data were BDL). Therefore, we did not establish numerical 

emission limits for HCl. Based on the low levels of HCl emissions, we disagree with the 

commenter that additional requirements beyond the work practice standards in the final rule are 

justified for HCl emissions.

B. Issues Related to Major Sources Only

1. Applicability

115. Comment: One commenter (1042-0300/1042-0348) objected to footnote 3 in the 

2013 proposal (78 FR 22374, April 15, 2013) explaining that the EPA’s original intent was to 

regulate all wool fiberglass furnaces, and the commenter expressed the opinion that the EPA and 

industry had agreed prior to promulgation of the MACT rule that certain furnaces should be 

exempt from regulation. The commenter referred to the 2002 EPA Applicability Determination 

in which the EPA agreed that furnaces feeding a line that is not processing formaldehyde were 

not subject to the MACT standard. Therefore, the commenter found the footnote to be 

misleading on this matter. The commenter (1042-0348) also requested the exact citation for the

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EPA’s reference to EPA’s response indicating EPA’s original intent regarding applicability to 

non-bonded lines.

Response: The EPA’s footnote 3 in the 2013 proposal (78 FR 22374, April 15, 2013) 

was intended to clarify the EPA’s original intent in 1999 regarding the applicability of MACT to

non-bonded lines, and simply reiterated the EPA’s intent stated in the RTC to the original 1999 

rulemaking. As documented in section 2.3 of the RTC accompanying the 1999 promulgation 

preamble (“Summary of Public Comment and Responses on Wool Fiberglass Manufacturing 

NESHAP,” March 31, 1999, available in EPA-HQ-OAR-2010-1042-0244), in response to a 

comment requesting that the EPA modify the definition of “wool fiberglass” by adding “bonded” 

to the definition, we responded that “Because the EPA’s intent is to regulate all glass furnaces 

located at wool fiberglass plants that are major sources of HAP, and not just those melters that 

feed molten glass to manufacturing lines producing bonded wool fiberglass products, the EPA 

has decided to not modify the definition of “wool fiberglass” by adding “bonded” to the 

definition.”

We disagree that this clarification of the EPA’s original 1999 intent creates confusion 

about the EPA’s current intent. The EPA made it clear in the 2011 and 2013 proposals that the 

major source rule applies to non-bonded lines (regardless of the EPA’s original intent), and that 

the area source rule would apply to bonded lines. 

2. Technology Developments and Controls

116. Comment: One commenter (1042-0121) stated that the EPA had appropriately 

recognized in their 2011 proposal (76 FR 72770, November 25, 2011) that there are significant 

industry developments that require the EPA to update the PM and formaldehyde standards for 

the Wool Fiberglass Manufacturing source category. The commenter expressed support for the 

EPA’s proposed PM and formaldehyde standards and the proposal to set a chromium limit under 

CAA section 112(d)(6). The commenter urged EPA to ensure that these limits are as stringent as 

allowed under the statute. The commenter also expressed support for EPA’s decision to seek and 

obtain appropriate test data to support these proposed standards.

Response: The EPA acknowledges this comment. Regarding the proposed formaldehyde, 

methanol, and phenol limits for RS lines, as noted in section V.H of the preamble to the final 

rule, we are not establishing MACT standards for RS manufacturing lines at wool fiberglass 

manufacturing facilities in this final action. We have issued an ICR under CAA section 114 to 

collect updated emissions and process information from the industry and we will analyze the ICR 

data and evaluate MACT limits for RS lines at wool fiberglass manufacturing facilities at a 

future date. 

3. HCl and HF Emission Limits for Glass-Melting Furnaces

117. Comment: One commenter (1041-0081) supported the EPA’s decision to set 

limits for previously uncontrolled emissions of HF and HCl from glass-melting furnaces. The 

commenter noted that CAA section 112(d) requires the EPA to set emission standards for all 

emitted pollutants. According to the commenter, closing loopholes and correcting problems that 

exist in the existing standard is an important part of the EPA’s job under CAA section 112(d)(6). 

The commenter believed that EPA should ensure that these standards fully satisfy both CAA 

sections 112(d)(2) and 112(d)(3). 

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Response: As explained above, the EPA disagrees that correcting problems with existing 

MACT standards is a necessary part of a 112(d)(6) technology review conducted under CAA 

section 112(d)(6). Nonetheless, EPA is finalizing new standards under 112(d)(2) for HCl and 

HF as part of this final action. It is not, however, promulgating these standards as part of its 

112(d)(6) technology review. For the reasons discussed in the preamble to the 2013 proposal (78

FR 22387) and explained in response to comment 118, the EPA is finalizing work practice 

standards for HCl and HF. Further, the EPA is revising these work practice standards to address 

public comments received in response to the 2013 and 2014 proposals. Specifically, we are 

replacing the 2013 proposed requirement that cullet be “free of chloride-, fluoride-, and fluorinebearing constituents” with work practice standards that require wool fiberglass facilities to 

maintain records from either cullet suppliers or their internal inspections showing that cullet is 

free of the following components that would form HF or HCl in the furnace exhaust (i.e., 

chlorides, fluorides and fluorine): glass from industrial (also known as continuous strand, or 

textile) fiberglass, cathode ray tubes (CRT), computer monitors that include CRT, and glass from 

microwave ovens, televisions or other electronics. For further discussion of this revision, refer to 

section VI.D of the preamble to the final rule.

118. Comment: One commenter (1042-0120) contended that HCl and HF emissions 

from the wool fiberglass industry are both so low and present such low risk that regulation is not 

necessary. The commenter argued that, despite the EPA’s claim in the preamble to the 2011 

proposal that the Brick MACT case requires regulation of every HAP emitted (regardless of 

amount), the EPA has not followed that argument in other recent rulemakings. In the recent 

Utility MACT, the commenter noted that the EPA did not regulate, either directly or by 

surrogate, any organic HAP from coal-fired utilities. The commenter stated that this is despite 

the EPA’s own AP-42 factors that indicate significant emission factors for a number of organic 

HAP. The commenter recommended that the EPA take the same approach for the wool fiber 

glass source category because the several below-MDL results in the test data indicate that the 

numeric standard is close enough to the detection and quantification limits that companies could 

not reliably show compliance.

According to the commenter, the EPA can revise an existing MACT standard only under 

CAA section 112(d)(6). The commenter cited that the NRDC v. EPA decision (Hazardous 

Organic NESHAP RTR Rule) plainly holds that EPA is not required to correct prior MACT 

standards or recalculate MACT standards under CAA section 112(d)(6). Therefore, the EPA 

does not need to regulate HCl and HF, but, if it decides to do so, the EPA does not need to set the 

standard under CAA sections 112(d)(2) and (3).

The commenter stated that the EPA’s interpretation is incorrect and that the agency is not 

mandated to regulate de minimis HAP like HCl and HF, as demonstrated by the EPA’s decision 

not to regulate organic HAP in the recent Utility MACT. Moreover, the commenter contended 

that the amount of HCl and HF emitted by any single wool fiber glass facility does not meet the 

10 tpy and 25 tpy threshold required to trigger MACT applicability.

Response: The EPA is finalizing new standards under 112(d)(2) for HCl and HF as part 

of this final action. It is not, however, promulgating these standards as part of its 112(d)(6) 

technology review. For the reasons discussed in the preamble to the 2013 proposal (78 FR 

22387) the EPA is finalizing work practice standards for HCl and HF. Further, the EPA is 

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revising these work practice standards to address public comments received in response to the 

2013 and 2014 proposals. As explained in the preamble to the 2013 proposal (78 FR 22387), in 

response to this comment on the HCl and HF emission limits proposed in 2011, we re-evaluated 

test data that we used to calculate the MACT floor for the proposed HCl and HF standards, and 

we had found that most of the test data reflected values below the detection limit of the test 

method. Specifically, over 80 percent of the test results were values indicating that either HF or 

HCl, or both pollutants in the exhaust gas stream, were below the detection limit of the methods. 

We believe such values are not a measurement of pollutants but rather an indication that such 

pollutants are not present in measurable concentrations. We therefore proposed in 2013 work 

practices standards for the control of HF and HCl emissions to ensure that the cullet does not 

include waste materials that would form HF or HCl in the furnace exhaust. In the final rule, we 

are revising the work practice standards proposed in 2013 and 2014, as discussed in section VI.D

of the preamble to the final rule.

As explained above, the EPA disagrees that correcting problems with existing MACT 

standards is a necessary part of a 112(d)(6) technology review. We also disagree with the 

comment that CAA section 112(d)(6) is the EPA’s sole authority for revising existing MACT 

standards. As a general matter, an agency remains free to revise improperly promulgated or 

otherwise unsupportable rules, even in the absence of a remand from a Court. United Gas 

Improvement Co. v. Callery Props. Inc., 382 U.S. 223, 229 (1996) (An agency, like a court, can 

undo what is wrongfully done by virtues of its order.”). As explained in earlier responses in this 

response to comment document, we believe that CAA section 112 does not expressly address 

this issue, and the EPA has discretion in determining how to address improperly promulgated 

floor determinations. CAA section 112(d)(6) provides that the agency must review and revise “as 

necessary.” The “as necessary” language must be read in the context of the provision, which 

focuses on the review of developments that have occurred since the time of the original 

promulgation of the MACT standard and thus, should not be read as a mandate to correct flaws 

that existed at the time of the original promulgation. Further, we believe that Portland Cement 

Ass’n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011) confirms that EPA is not constrained by CAA 

section 112(d)(6) and may reassess its standards more often, including revising existing floors if 

need be. We also note that the D.C. Circuit also held that EPA may permissibly amend improper 

MACT determinations, including amendments to improperly promulgated floor determinations, 

using its authority under CAA sections 112(d) (2) and (3). Id. Thus, we believe that we may 

amend improper MACT determinations, including amendments to improperly promulgated floor 

determinations, under sections 112(d) (2) and (3). Medical Waste Institute v. EPA, 645 F.3d 420, 

425-27 (D.C. Cir. 2011) (resetting MACT floor, based on post-compliance data, permissible 

when originally-established floor was improperly established, and permissibility of the EPA’s 

action does not turn on whether the prior standard was remanded or vacated). The commenter is, 

thus, incorrect that CAA section 112(d)(6) provides the exclusive authority to address for e.g., 

HCl and HF emissions here. Put another way, if the EPA did not adopt a proper MACT standard 

initially, it is not amending a MACT standard but adopting one for the first time. Here, the EPA 

adopted no MACT standard at all for these HAP, an approach soundly rejected by the D.C. 

Circuit in National Lime, 233 F.3d at 633-34. We also note that we note that in National Lime 

Association v. EPA, 233 F.3d 625 (D.C. Cir. 2000), the D.C. Circuit remanded the Portland 

Cement MACT to EPA to establish MACT floors for HCl holding that we had a clear “statutory 

obligation to set emission standards for each listed HAP.” Therefore, we believe the EPA is not 

barred from making MACT floor determinations and issuing MACT standards pursuant to CAA 

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sections 112(d)(2) and (3) for this source category. Additionally, in several recent rulemakings, 

we have chosen to fix underlying defects in existing MACT standards under CAA sections 

112(d)(2) and (3), the provisions that directly govern the initial promulgation of MACT 

standards (see National Emission Standards for Hazardous Air Pollutants From Petroleum

Refineries, October 28, 2009, 74 FR 55670; and National Emission Standards for Hazardous Air 

Pollutants: Group I Polymers and Resins; Marine Tank Vessel Loading Operations; 

Pharmaceuticals Production; and the Printing and Publishing Industry, April 21, 2011, 76 FR 

22566). We believe that our approach is reasonable because using those provisions ensures that 

the process and considerations are those associated with initially establishing a MACT standard, 

and it is reasonable to make corrections following the process that would have been followed if 

we had not made an error at the time of the original promulgation.

We also disagree with the comment that the EPA is not mandated to regulate de minimis

HAP like HCl and HF. While the EPA’s de minimis authority exists to help avoid what might be 

perceived as excessive regulation of tiny amounts of pollutants, it is unavailable “where the 

regulatory function does provide benefits, in the sense of furthering the regulatory objectives, but 

the agency concludes that the acknowledged benefits are exceeded by the costs.” Alabama 

Power v. EPA, 636 F.2d 323, 360-61 &n.89 (D.C. Cir. 1979). According a de minimis exemption 

to CAA sections 112(d)(2) and (3) are unavailable because it would frustrate a primary 

legislative goal by carving out tons of HAP emissions from regulation. Moreover, the EPA’s 

rejection of the de minimis concept has been affirmed by the U.S. Court of Appeals for the D.C. 

Circuit in National Lime Ass’n v. EPA, 233 F.3d 625, 640 (D.C. Cir. 2000), where the court 

rejected the petitioner’s claim that in light of both high costs and low quantities of HAP at issue 

in that rule, the EPA should read a de minimis exemption into the requirement to regulate all 

HAP emitted by major sources. The Court found that “EPA reasonably rejected this argument 

on the ground that the statute ‘does not provide for exception from emissions standards based on 

de minimis principles where a MACT floor exists.’ ” National Lime Ass’n, at 640. We also 

continue to believe that CAA section 112 is replete with careful definitions of volume or effect 

based limitations on regulation, indicating that Congress has already defined what amounts of 

HAP emissions are too small to warrant MACT standards. The requirement to adopt MACT 

emission limitations, for example, applies without exception to “category or subcategory of 

major sources . . . of [HAP].” CAA section 112(d)(1). For sources below the major sources 

threshold, however, EPA has discretion to require “generally available control technologies or 

management practices.” CAA section 112(d)(5). Congress has thus defined volumetrically which 

sources’ emissions are small enough not to warrant mandatory MACT standards. 

Finally, we also disagree with the comment that the EPA did not “did not regulate, either 

directly or by surrogate, any organic HAP from coal-fired utilities,” in the recent Utility MACT 

rule. To the contrary, the EPA did set work practice standards for organic HAP, under CAA

section 112(h). Additionally, in the Boilers NESHAP we set MACT standard for HCl. As 

explained earlier above, both HCl and HF are listed HAP, under CAA section 112(b) and we are 

required to establish MACT standards for all HAP emitted by major sources, under CAA 

sections 112(d)(2) and (3). 

119. Comment: One commenter (1042-0120) urged the EPA to establish risk-based 

standards for HCl and HF emissions from the wool fiberglass industry. The commenter stated 

that CAA section 112(d)(4) expressly authorizes the EPA to establish risk-based standards for 

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threshold pollutants for which a health threshold has been established. 42 U.S.C. § 7412(d)(4). 

The commenter asserted that this provision was established by Congress because “[f]or some 

pollutants a MACT emissions limitation may be far more stringent than is necessary to protect 

public health and the environment” and quotes from the legislative history for the 1990 CAA 

amendments. The commenter also asserted that the EPA has previously determined that HCl is a 

threshold pollutant and that the EPA has established what the commenter characterized as a lack 

of risk. The commenter further asserted that health-based limits would be more reasonable and 

achievable and would enable the EPA to achieve the ample margin of safety to health and the 

environment. 

Response: Section 112(d)(4) of the CAA provides that: “[w]ith respect to pollutants for 

which a health threshold has been established, the Administrator may consider such threshold 

level, with an ample margin of safety, when establishing emissions standards under this 

subsection.” Notably, the statute confers limited discretionary authority on the EPA and does not 

mandate the use of health-based standards. The legislative history cited by the commenters 

contains similarly permissive language and does not suggest that health-based standards would 

be required in any circumstances. Specifically, the legislative history quoted by the commenter 

provides that “where health thresholds are well-established . . . and the pollutant presents no risk 

of other adverse health effects, including cancer, for which no threshold can be established, the 

administrator may use the threshold with an ample margin of safety (and not considering cost) to 

set emissions limitations for sources in the category or subcategory.” S. Rep. No. 101-228, at 144 

(1989). In other words, where certain preconditions are met (i.e., health thresholds are wellestablished and the pollutant presents no other risks), the EPA has discretionary authority to set 

health-based standards. Here, the commenter urges the EPA to create risk-based limits based 

largely on their assertion that the EPA has authority to do so because the pre-conditions are met. 

The commenter does not, however, offer a rationale to support their assertion that the EPA 

should exercise this discretionary authority in this rulemaking. In fact, the only rationale offered 

is a bald assertion that such limits would be more reasonable and achievable and would enable 

the EPA to achieve the ample margin of safety to health and the environment. This comment was 

offered in response to the 2011 proposal in which EPA had proposed to establish numeric 

emissions limits for HCl and HF for furnaces at wool fiberglass manufacturing facilities. In this 

final rule case we are setting work practice standards for HCL and HF because the emissions of 

HCl and HF are so low as to make measurement impracticable. As explained in the 2013 

proposal (78 FR 22389), these standards are not only reasonable and achievable, but will in fact 

have minimal if any impact on the wool fiberglass industry. 

120. Comment: One commenter (1042-0120) asserted that the EPA’s position that 

“synthetic area sources” may be considered in the floor determination for HCl and HF is 

unfounded because CAA section 112 expressly defines the terms “major source” and “area 

source” and provides for separate listing and regulation of major sources and area sources, but 

that the statute does not distinguish between “area sources” and “synthetic area sources.” 

Therefore, the commenter contended that “synthetic area sources” are not part of a corresponding 

major source category and cannot be used in determining the MACT floors for the major source 

category. The commenter argued that the MACT floor should be recalculated using data from 

only sources that are currently subject to the MACT. 

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Response: We disagree with the comment that our use of synthetic area sources in 

MACT floor calculations is unfounded. We believe that the better interpretation of the plain 

language of CAA section 112(d)(3) and relevant legislative history requires that synthetic minor 

sources should be included in MACT floor determinations. As explained in previous 

rulemakings (e.g., Brick NESHAP, 68 FR 26697–26698, May 16, 2003), the EPA has 

determined that including synthetic area sources in calculating the MACT floor for major 

sources is consistent with CAA section 112(d). We continue to believe that inclusion of synthetic 

area sources in MACT floor determinations is justified for the reasons explained below. Section 

112 of the CAA does not specifically address the inclusion of synthetic area sources in the 

MACT floor calculations. These are sources that emit fewer than 10 tons per year of any HAP or 

fewer than 25 tons per year of any combination of HAP because they use some emission control 

device(s), pollution prevention techniques or other measures (collectively referred to as controls 

in this preamble) adopted under Federal or State regulations. If not for the enforceable controls 

they have implemented, synthetic area sources would be major sources under CAA section 112 

of the CAA. We believe that the better interpretation of the CAA's plain language and legislative 

history requires that synthetic area sources be included in the MACT floor determinations. 

First, the plain language of the statute makes clear that our MACT floor determinations 

are to reflect the best sources in a category. For new sources in a category or subcategory, the 

MACT floor shall not be less stringent than the emission control that is achieved in practice by 

the best-controlled similar source, as determined by the EPA. Section 112(d)(3) of the CAA 

requires that MACT floors reflect what the best controlled new sources and the best performing 

existing sources achieve in practice. These phrases contain no exemptions and are not limited by 

references to sources with or without controls. Therefore, they suggest that all of the bestcontrolled or best-performing sources should be considered in MACT floor determinations, 

regardless of whether or not such sources rely upon controls.

Second, CAA section 112(d)(3) expressly excludes certain sources that meet LAER 

requirements from MACT floor determinations for existing sources. (See CAA section 

112(d)(3)(A).) The fact that Congress expressly excluded such LAER sources but did not also 

exclude synthetic area sources suggests that no exclusion was intended for synthetic area 

sources. Indeed, nothing in the statute suggests that the EPA should exclude a control technology 

from its consideration of the MACT floor because the technology is so effective that it reduces 

source emissions such that the source is no longer a major source of HAP. 

Third, the EPA disagrees that the CAA contemplates that synthetic area sources must be 

treated like true area sources and excluded from MACT floor determinations. Section 112(a) of 

the CAA defines a major source as: any stationary source or group of stationary sources located 

within a contiguous area and under common control that emits or has the potential to emit 

considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 

25 tons per year or more of any combination of hazardous air pollutants * * *(See CAA section 

112(a)(1).) An area source is defined as any stationary source of hazardous air pollutants that is 

not a major source. (See CAA section 112(a)(1).) In the major source definition, the reference to 

a source's potential to emit considering controls allows the interpretation that a source's potential 

to emit before and after controls is relevant, such that synthetic area sources may be considered 

within the meaning of this definition and included in MACT floor determinations for categories 

of major sources. This is because we believe synthetic area sources, because they have already 

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reduced HAP emissions below the major source threshold, they are among the best performing 

12 percent of existing sources and thus help to define the level of the MACT emission limit. 

Thus, including synthetic area sources in MACT floor determinations ensures that MACT floors 

reflect the best-performing sources, as the CAA requires. While the effect of excluding the best 

performing sources in a category from MACT floor determinations and therefore would be 

contrary to the statutory mandate that the EPA set MACT floors based on the levels the best 

controlled new sources and the best performing existing sources achieve in practice. We believe 

the statutory reference to potential to emit considering controls should be read in a manner 

consistent with the other requirements of section 112(d) of the CAA to allow for the 

consideration of synthetic area sources in MACT floor determinations for categories of major 

sources. 

Fourth, relevant legislative history for this section suggests that synthetic area sources 

should be included in MACT floor determinations. In a floor statement, Senator Durenberger 

stated that in implementing section 112(d)(3) of the CAA, "the [Senate] managers intend the 

Administrator to take whatever steps are necessary to assure that [the Administrator] has 

collected data on all of the better-performing sources within each category. [The Administrator] 

must have a data-gathering program sufficient to assure that [EPA] does not miss any sources 

that have superior levels of emission control." (See Environment and Natural Resources Policy 

Division, Congressional Research Service, 103d Cong., S. Prt. 103-38 (prepared for the U.S. 

Senate Committee on Environment and Public Works), A Legislative History of the Clean Air 

Act Amendments of 1990 at 870, Nov. 1993, emphasis added.) This statement underscores that 

Congress intended for MACT floor determinations to reflect consideration of all of the sources in 

each category with the best emission controls. We believe it would be inconsistent with 

Congress's intent and the plain language of the CAA to exclude synthetic area sources -those 

sources with superior controls which became synthetic area sources by implementing such

controls-from MACT floor determinations. Therefore, we believe that the inclusion of synthetic 

area sources in MACT floor determinations is justified because of the reasons explained above. 

The EPA Title V Operating Permits Program (Title V) tracks the performance, 

compliance, operational status and major source status of all permitted sources, including wool 

fiberglass facilities currently in operation in the U.S. In finalizing this rule, we have not included 

sources that have been identified by the Title V program as area sources in the floor calculations. 

Therefore, true area sources (i.e., sources that do not have the potential to emit at least 10 tons 

per year of a single pollutant or at least 25 tons per year of any combination of HAP) were not 

part of the MACT floor calculation for phenol, formaldehyde, or methanol. 

As also explained in the November 2011 proposal, the commenter conducted a voluntary 

survey among all owners and operators of mineral wool production and wool fiberglass 

manufacturing facilities. The survey sought test data for PM, and HAP emissions, such as 

hydrogen fluoride and hydrochloric acid and information on process equipment, control devices, 

point and fugitive emissions, and practices used to control point and fugitive emissions. Further, 

the EPA requested and industry agreed in a May 5, 2010 letter, that a subset of facilities that 

were representative of emission sources from wool fiberglass industries would conduct testing 

and submit existing test data. The May 5, 2010 letter indicated that the bases for 

representativeness included design type and size of process units or equipment, fuel type, 

operating temperatures, control devices and raw material content. The commenter did not 

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identify any sources as synthetic area sources in its May 5, 2010 letter. Rather, the letter states in 

pertinent part that “new hydrogen fluoride and hydrochloric acid data will be collected from 

Johns Manville, Richmond, IN facility and Knauf’s Shasta Lake, CA facility.” The letter further 

stated Owens Corning operates a Cold Top Electric furnace with batch wetting and “new 

hydrogen fluoride and hydrochloric acid data will be collected from Owens Corning Kansas 

City, KS facility.” (p. 7).

121. Comment: One commenter (1042-0120) contended that the HF and HCl data from 

the following sources that the EPA used to set the MACT floor for HCl are below-MDL, and that 

the EPA should remove all of these sources from the calculation for the MACT floor for HF and 

HCl: Owens Corning’s Kansas City, Kansas (K5); Owens Corning’s Newark, Ohio (F6); 

Knauf’s Shasta Lake, California (641); CertainTeed’s Kansas City, Kansas (K2); Guardian’s 

Mineral Wells, Mississippi; Johns Manville’s Richmond, Indiana (incorrectly split into two 

sources by EPA); and Johns Manville’s Defiance, Ohio (3 sources).

The commenter argued that below-MDL data are unquantifiable and that using belowMDL data is likely to set limits so stringent that the best performing sources cannot even meet 

those limits. The commenter observed that every source relied upon to set the MACT floor is 

below-MDL data; and the majority of HCl data points are below the detection limit. The 

commenter contended that facilities will have difficulty showing compliance with an emission 

limit that is based on data from testing that was below-MDL. According to the commenter, the 

EPA should only use values that are above the MDL (i.e., actual values) in calculating the 

MACT floor, and that the emissions floor must be determined by quantifiable data.

According to the commenter, in the Boiler MACT, the EPA reassessed the proposed 

emission limits for dioxins/furans. The commenter noted that, as explained by the EPA, a large 

amount of the emission measurement used to set the dioxin/furan limits were below the level that 

could be accurately measured. Alternatively, the commenter stated that the EPA could propose a 

work practice standard in order for facilities to show compliance. Under the Boiler MACT, the 

commenter noted that the EPA chose to regulate dioxins/furans by using a work practice 

standard. In that case, the commenter stated that 55 percent of facilities tested had dioxin/furan 

emissions below the MDL for EPA Method 23 test. The commenter stated that a work practice 

standard would allow facilities to decrease HCl and HF emissions and be able to show 

compliance.

Response: We disagree with commenter that we should disregard values less than the 

MDL in the data set used to calculate the floor. As explained in earlier responses, we evaluated 

test data that we had used to calculate the MACT floor limits for HCl and HF in response to 

comments such as this one. Industry had conducted testing in an attempt to obtain data for the 

acid gases HF and HCl, under the terms of the voluntary survey. Emissions tests were conducted 

over three 1-hour test runs, which is, for similar industries, sufficient time to detect these acid 

gases when they are emitted. However, even with 3-hour sampling times, such data were not 

obtained. Rather, we found that most of the test data reflected values that were below the 

detection limit of the test method. Specifically, more than half (80 percent) of the test results 

were values indicating that either HF or HCl in the exhaust gas stream was below the detection 

limit of the method. As earlier explained also, such values are not a measurement of the pollutant 

but indicate that the pollutant was not present in measurable concentrations. We therefore 

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proposed work practice standards for HF and HCl in our April 15, 2013 supplemental proposal to 

reflect comments and our evaluation of test data from industry on our November 2011 proposal. 

As explained in our April 15, 2013 supplemental proposal, EPA regards situations where, as 

here, the majority of measurements are below the detection limit as being a situation where 

measurement is not “technologically practicable” within the meaning of section 112(h)(2)(B). 

EPA also believes that unreliable measurements raise issues of practicability, feasibility and 

enforceability. The application of measurement methodology in this situation would also not be 

“practicable due to . . . economic limitation” within the meaning of section 112(h)(2)(B) because 

it would just result in cost expended to produce analytically suspect measurements. (78 FR 

22387). Section 112(h) of the CAA “allows EPA to substitute work practice standards for 

emission floors only if measuring emission levels is technologically or economically infeasible.” 

Sierra Club v. EPA, 479 F. 3d 875, 884 (D.C. Cir. 2007. 

Additionally, as explained in the Industrial Boiler NESHAP, the EPA continues to 

believe that emissions from a common stack should be considered as representing the average 

emissions of process units ̧ in this instance a furnace, exhausting to the common stack and thus, 

should be considered representative of emissions from either process units or furnaces. The 

commenters have provided no data to support the contention that this assumption is false. The 

EPA used data from combined stacks only where both furnaces were operating. Similar to testing 

conducted for the voluntary survey, the EPA expects that companies will comply with the final 

rule by conducting testing at the common stack as that is usually where the sampling locations 

are (rather than in the intermediate ductwork) and will report the results as being for each 

furnace.

122. Comment: One commenter (1042-0348) asked for clarification on whether the 

limits on cullet apply to the company’s own internal cullet, or only to external cullet purchased 

from third-party suppliers.

Response: The final work practice standards apply only to external cullet used at a wool 

fiberglass manufacturing facility because based on industry representations external cullet is the 

source of chloride-, fluoride-, and fluorine-bearing constituents at wool fiberglass manufacturing 

facilities. 

123. Comment: One commenter (1042-0347) argued that the HCl and HF work 

practice standards should require reporting, not just recordkeeping, to demonstrate compliance 

and enable citizen to be informed and participate in enforcement. The commenter stated that the 

EPA has not justified excluding these data from reporting.

Response: The final rule specifies recordkeeping requirements for owners or operators to 

demonstrate compliance with the work practice standards for HCl and HF emissions. We believe 

that the final rule requirements will ensure compliance. As explained in the section VI.D of the 

preamble to the final rule, we found that most of the test data reflected values that were below 

the detection limit of the test method. Specifically, approximately 80 percent of the test results 

were values indicating that either HF or HCl in the exhaust gas stream was below the detection 

limit of the method. Given the very low level of HCl and HF emitted from wool fiberglass 

facilities, we do not believe that requiring additional reporting requirements is warranted.

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4. Formaldehyde, Phenol, and Methanol Limits

124. Comment: One commenter (1042-0120/1042-0300) stated that the proposed limits 

for formaldehyde, phenol, and methanol seem superfluous given that majority of the fiberglass 

industry is no longer subject to the MACT standards since, according to the commenter, only 

“bonded” lines using PF binders are subject to the Wool Fiberglass MACT standard. According 

to the commenter, 23 facilities have switched to non-PF binders while most other facilities are in 

the process of switching to non-PF binders and would have completed that process before the 

new MACT compliance deadline, which means that there has been a virtual elimination of 

formaldehyde emissions from the binder for the vast majority of the fiber glass building 

insulation industry.

The commenter also expressed concerns regarding the EPA’s proposed limits for 

formaldehyde, phenol, and methanol in that while most of the industry has voluntarily switched 

from a PF binder to non-PF binders, certain products continue to use PF binders. Therefore, the 

commenter contended that it remains important that the limits for formaldehyde, phenol, and 

methanol be feasibly achieved when PF binder is used, and that some formaldehyde and 

methanol is created from the combustion of natural gas in the wool fiber glass production 

process even when PF binders are not used.

Response: Regarding the comment that the proposed limits for formaldehyde, phenol, and 

methanol “seem superfluous given that majority of the fiberglass industry is no longer subject to 

the MACT standards,” the EPA disagrees. The final standards are based on test data provided by 

major sources pursuant to a voluntary survey that they conducted. As explained in the preamble 

to the final rule, we are establishing emission limits for formaldehyde, phenol and methanol from 

FA lines at the MACT floor level of control even though there is an existing standard for 

formaldehyde in the current MACT rule. This is because in conducting our review, we also 

found that in the current rule we had calculated a MACT floor for formaldehyde that was 

intended to be achievable by all existing sources. This is an approach that the D.C. Circuit has 

consistently rejected. “EPA may not deviate from section 7413(d)(3)’s requirement that floors 

reflect what the best performers actually achieve by claiming that floors must be achievable by 

all sources using MACT technology.” Cement Kiln Recycling Coalition v. EPA, 255 F.3d at 861.

(“EPA cannot circumvent Cement Kiln’s holding that section 7412(d)(3) requires floors based on 

the emission level actually achieved by the best performers (those with the lowest emission 

levels), not the emission level achievable by all sources, simply by redefining “best performing” 

to mean those sources with emission levels achievable by all sources.” Sierra Club v. EPA, 479 

F. 3d at 881. (Emphasis in original). Additionally, the EPA proposed to discontinue the use of 

formaldehyde as a surrogate for phenol and methanol because we no longer believe that there is a 

correlation and therefore, reasonable bases, between formaldehyde and phenol and methanol. 76 

FR 72788, 72791:72796. (The EPA may attribute characteristics of a subclass of substances to an 

entire class of substances if doing so is scientifically reasonable. Dithiocarbamate Task Force v. 

EPA, 98 F.3d 1394, 1399 (D.C. Cir. 1996)). Based on our revised analyses, we are setting 

standards for FA lines at the MACT floor level of control for these emissions. 

We note that sources should have already installed thermal oxidizers to control emissions 

of formaldehyde in response to the existing MACT rule requirements. Thus, any further 

reductions called for in the final action may not necessitate the installation of new air pollution 

controls.

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Regarding RS manufacturing lines at wool fiberglass manufacturing facilities, we are not 

establishing in this final action standards for formaldehyde, phenol, and methanol. We have 

issued an ICR under CAA section 114 to collect updated emissions and process information from 

the industry, and we will analyze the ICR data and evaluate MACT limits for RS lines at wool 

fiberglass manufacturing facilities at a future date (see section V.H of the preamble to the final 

rule).

Comment: One commenter (1042-0120) asserted that the EPA incorrectly calculated the 

floor for FA lines because the EPA counted certain sources that share a common stack as one 

source for the curing section – Johns Manville line 81 at Defiance, Ohio and lines 92 and 93 at 

Cleburne, Texas. According to the commenter, even though there are no MACT limits for FA 

lines, the state permit imposes a bubble emission limit across the two lines, because Johns 

Manville cannot distinguish total emissions from each line. Therefore, the Cleburne, Texas lines 

should be counted as one line, not two. The commenter also urged the EPA to consider the total 

emissions from Cleburne, Texas flame attenuation and the total emissions from Defiance, Ohio 

Line 81 as either one line each, or two lines in total. By doing so, the commenter noted that the 

average (before EPA applied its confidence level analysis) should be what is reflected in the 

“Two Line” column in the table below. But even if the Cleburne, Texas lines are considered 

separate, the calculated average is still incorrect, and counting as three lines, the commenter 

argued that the average (before EPA applied its confidence level analysis) should be what is 

reflected in the “Three Line” column in the table below (all numbers in lb/ton). According to the 

commenter, these numbers are far higher than the numbers in the EPA’s spreadsheet and way 

higher than even the proposed standards. The commenter opined that it is reasonable to conclude 

that the EPA did not properly account for the scientific notation in which all stack test data were 

reported. The commenter stated that, perhaps, the EPA did not include all of the forming and 

curing stacks, though the footnote in EPA’s spreadsheet indicates that such consideration was 

intended.

Response: At the November 25, 2011 proposal, the EPA only had emissions test data for 

FA lines making heavy density products. The 1999 MACT standard for the Wool Fiberglass 

Manufacturing established two subcategories for the forming process (i.e., FA and RS lines). It 

also included no control floors for existing sources that make light density, automotive and 

heavy density products on FA line.34 But, CAA section 112(d) requires the EPA to set standards 

for all HAP. Therefore, it was our intent to eliminate the subcategories for FA lines because we 

believed that the technical or design differences that distinguished these subcategories in 1999 no 

longer existed. We, however, did not clearly state that we were eliminating the subcategories for 

FA lines. In response to comments such as this one, in our April 15, 2013 supplemental notice, 

we proposed eliminating the subcategories for FA bonded lines because we believed that the 

technical or design differences that distinguished these subcategories when the original rule was 

developed no longer exist. We also proposed establishing standards at the MACT floor level of 

control for phenol, formaldehyde and methanol emissions from FA bonded lines. As the 

34 We divided the FA lines into 4 subcategories: 1. light density, 2. automotive, 3. heavy density and 4. pipe 

products. We set standards for two subcategories--heavy density (new) and pipe product (new and existing). And we 

said "[b]ecause no controls are currently used, the MACT floor is no control and because the cost effectiveness of 

additional controls beyond the floor is not reasonable, the Agency is not setting emission limits for existing FA 

manufacturing lines producing [1] light-density, [2] automotive or [3] heavy-density products or new FA 

manufacturing lines producing [1] light-density or [2] automotive products." 61 Fed. Reg. 15239 (March 31, 1997).

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commenter notes, Johns Manville only submitted data for FA lines producing heavy density 

products and no data for FA lines producing pipe products. Additionally, we note that industry 

had indicated that the test data for this subcategory were representative of other subcategories. 

Thus, the data available to us at proposal were only emissions test data for heavy density 

products. As earlier explained, CAA section 112(d)(3) requires the EPA to promulgate standards 

that must be at least as stringent as the average emissions limitation achieved by the best 

performing 12 percent of existing sources “for which the Administrator has emissions 

information.” (The EPA typically has wide latitude in determining the extent of data-gathering 

necessary to solve a problem. NRDC v. EPA, 529 F.3d 1077, 1086) (D.C. Cir. 2008). Since both 

our November 2011 and April 15, 2013 proposals, no additional information has been provided 

to support further subcategorization of FA lines. We are therefore concluding that the limits 

developed for FA lines are representative of all products made on FA lines and that further 

subcategorization was no longer supportable. 

As also explained in our April 15, 2013 proposal, in examining the 1999 MACT rule, we 

found that we had set emissions standards for certain subcategories of the FA bonded lines. (78 

FR 22387). But, EPA has a “clear statutory obligation to set emission standards for each listed 

HAP. Although Sierra permits the agency to look at technological controls to set emissions 

standards, it does not say that EPA may avoid setting standards for HAP not controlled with 

technology.” National Lime Association v. EPA, 233 F.3d 625, 634 (D.C. Cir. 2000)(internal 

citation omitted). As explained in section VI.C of the preamble to the final rule, we are therefore, 

also finalizing emissions limits at the MACT level of control for formaldehyde, phenol and 

methanol for flame attenuation lines. 

125. Comment: One commenter (1042-0120) noted that all data used by the EPA to 

calculate emission limits for formaldehyde, methanol, and phenol for FA lines included only 

those lines producing heavy density products. The commenter stated that Johns Manville did not 

submit any data for FA lines producing pipe products, because Johns Manville only uses FA 

lines as a backup for pipe insulation products. The commenter stated that the EPA’s spreadsheet 

of the floor locations did not include anything for FA lines making pipe products. Thus, the 

commenter expressed concern that they do not know how the EPA calculated the floor for FA 

lines making pipe products.

Response: As the commenter notes, Johns Manville only submitted data for FA lines 

producing heavy density products and no data for FA lines producing pipe products. 

Additionally, we note that in the 2011 voluntary survey industry had indicated that the test data 

for this subcategory were representative of other subcategories. Thus, the data available to us at 

proposal were only emissions test data for heavy density products. As earlier explained, CAA 

section 112(d)(3) requires the EPA to promulgate standards that must be at least as stringent as 

the average emissions limitation achieved by the best performing 12 percent of existing sources 

“for which the Administrator has emissions information.” (The EPA typically has wide latitude 

in determining the extent of data-gathering necessary to solve a problem. NRDC v. EPA, 529 

F.3d 1077, 1086) (D.C. Cir. 2008)). As subsequently explained in the 2013 proposal preamble 

(78 FR 22387, April 15, 2013), though we did not clearly state in the 2011 proposal that we were 

eliminating the subcategories for FA lines, this was our intent. The reason for eliminating these 

subcategories was that we determined that there was no longer any technical basis for 

distinguishing these subcategories. 

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We also note that we confirmed with Johns Manville, who supplied all the FA line data, 

that the emission data was representative of emissions from all their FA products and thus 

suitable to use to calculate MACT floors.

126. Comment: One commenter (1042-0120/1042-0300/1042-0348) recommended 

against the EPA setting limits for phenol and methanol because available data on phenol and 

methanol are very limited and the data were collected in different seasons. The commenter 

indicated that weather conditions could impact test results. The commenter recommended that 

the EPA use formaldehyde as a surrogate for phenol and methanol or, in the alternative, use 

liberal variability factors in setting limits for phenol and methanol. 

Response: We disagree with the comment. Section 112(d)(3) of the CAA requires the 

EPA to promulgate standards for major sources of HAP that are based on MACT performance. 

For existing sources, MACT standards must be at least as stringent as the average emission 

limitation achieved by the best performing 12 percent of existing sources (for which the 

Administrator has emissions information) or the best performing 5 sources for source categories 

with less than 30 sources. For new sources, the MACT standards must be at least as stringent as 

the control level achieved in practice by the best controlled similar source. CAA Section 

112(d)(3). Section 112(d)(3) of the CAA does not address the question of whether, in assessing 

which sources perform best or are best controlled, emission levels should be evaluated either 

over time or in a single test result. We believe, however, that our MACT floor calculation should 

identify the best performers, i.e., the best performing 12 per cent or best performing five sources 

in smaller source categories for existing sources, and the best controlled single source for new 

sources, as those sources likely to emit the least HAP over time considering variability. Thus, the 

EPA does not believe that the statute requires or contemplates a random sample. Rather, use of 

data from the best performing sources is specified for developing the MACT floor limits. We 

note that the D.C. Circuit has held repeatedly that variability of best performing sources may be 

taken into account in establishing numeric MACT floors. Sierra Club, 479 F.3d at 881-882. (See 

also National Lime Ass’n v. EPA, 627 F.2d 416, 431 n.46, 443(D.C. Cir. 1980)). In general, 

MACT standards are based on short term emissions test data because such data are derived from 

emissions tests conducted in response to CAA section 114 ICR. Because data may not represent 

the range of operating conditions that best performing sources face on a day-to-day basis EPA 

adjusts these short-term data to account for the range of operating conditions. The varying 

conditions that the EPA is concerned with are variations between tests at the same unit, and 

variations between the separate test runs that comprise a single test at the same unit. (A single 

test at a unit usually includes at least three separate test runs.). Between tests variability may be 

caused by different setting for testing equipment, different people performing tests or different 

laboratories analyzing test results. These differences can lead to variations in results from 

different runs comprising the same test, which is known as within-test variability i.e., variability 

among the three separate test runs. In sum, each separate test run is a snapshot of actual 

performance that gives information about the normal and unavoidable variations in emissions 

that would be expected to occur over time. The EPA believes that the UPL calculation is a 

statistical formula designed to estimate a MACT floor level (including variability) that is 

equivalent to the average of the best performing sources based on future compliance tests. And 

that it is entirely appropriate to consider the variability within the best performing sources in 

developing emission limits based average performance of those sources. We also believe that if 

we did not account for variability in this manner and instead set the limit based solely on the

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average (mean) performance, then these units could exceed the limit half the time or more. The 

EPA agrees with the commenter that there are alternatives to the UPL statistics. But, we believe 

that because the floor calculations represent the average of the best performing 12 percent of 

existing sources, it is reasonable for the EPA to use an appropriate statistical analysis to assess 

the impact both intra-unit and inter-unit variability have on the emissions profiles.

The final standards are based on test data provided by sources pursuant to a voluntary 

survey that they conducted. As explained in the November 2011and April 2013 proposals, the 

EPA had requested and the commenter agreed in a May 5, 2010 letter, that existing test data and 

testing data from a subset of facilities that were representative of emission sources from certain 

facilities would be submitted in response to the voluntary survey. In acknowledging this 

agreement, the commenter’s statements of May 5, 2010 indicated that the bases for 

representativeness would include design type and size of process units or equipment, fuel type, 

operating temperatures, control devices and raw material content. (76 FR 72778; 78 FR 22379).

As also explained in our various proposals, the EPA proposed to discontinue the use of 

formaldehyde as a surrogate for phenol and methanol. 76 FR 72788, 72791; 72796. The EPA 

may attribute characteristics of a subclass of substances to an entire class of substances if doing 

so is scientifically reasonable. Dithiocarbamate Task Force v. EPA, 98 F.3d 1394, 1399 (D.C. 

Cir. 1996). We no longer believe that there is a correlation and therefore, reasonable bases, 

between formaldehyde and phenol and methanol.

As also explained in section VI.C of the preamble to the final rule, we are establishing 

emission limits for formaldehyde, phenol and methanol at the MACT floor level of control even 

though there is an existing standard for formaldehyde in the current MACT rule. This is because 

in conducting our review, we also found that in the current rule we had calculated a MACT floor 

for formaldehyde that was intended to be achievable by all existing sources.

In earlier responses, we have noted that we are not establishing new MACT standards for 

formaldehyde, phenol, and methanol emissions from RS manufacturing lines at wool fiberglass 

manufacturing facilities in this final action. We have issued an ICR under CAA section 114 to 

collect updated emissions and process information from the industry and we will analyze the ICR 

data and evaluate MACT limits for RS lines at wool fiberglass manufacturing facilities at a 

future date. 

With regard to the commenter’s concern related to weather effects on testing, as 

explained earlier, we note that the commenter conducted a voluntary survey among all owners

and operators of mineral wool production and wool fiberglass manufacturing facilities. The 

survey sought test data for PM, and HAP emissions, such as HF and HCl and information on 

process equipment, control devices, point and fugitive emissions, and practices used to control 

point and fugitive emissions. Further, the EPA requested and industry agreed in a May 5, 2010 

letter, that a subset of facilities that were representative of emission sources from wool fiberglass 

industries would conduct testing and submit existing test data. The requirements in the final rule 

are based on test data submitted by the commenter.

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127. Comment: One commenter (1042-0299) opined that the EPA has not sufficiently 

strengthened the formaldehyde limits, and argued that the EPA should consider the phase out of 

phenol-formaldehyde binders as a new technology under technology review.

Response: As explained in earlier responses, CAA section 112(d) requires the EPA to 

promulgate standards for major sources of HAP based on the MACT performance. For existing 

sources, MACT standards must be at least as stringent as the average emissions limitation 

achieved by the best performing 12 percent of existing sources (for which the Administrator has 

emissions information) or the best performing 5 sources for source categories with less than 30 

sources, as is the case here. For new sources, the MACT standards must be at least as stringent as 

the control level achieved in practice by the best controlled similar source. CAA Section 

112(d)(3). As also earlier explained, the final standards are based on test data provided by 

sources pursuant to a voluntary survey that they conducted, which indicate the presence of 

formaldehyde despite indications that industry is phasing out its use. Our MACT floor 

calculations are consistent with the CAA section 112(d) and can be found in the “Revised 

Technical Approach for Wool Fiberglass Manufacturing MACT Floor Calculations” which is 

available in the docket. We subsequently proposed and discussed our decision to revise these 

emissions limits for based on our updated approach for evaluating limited data sets (also see the 

memorandum “Approach for Applying the Upper Prediction Limit to Limited Datasets – Wool 

Fiberglass Manufacturing” for the updated approach for limited datasets).

128. Comment: One commenter (1041-0081) supported the EPA’s decision to set 

limits for previously uncontrolled emissions of formaldehyde, phenol and methanol for RS 

manufacturing lines and FA lines. The commenter cited that CAA section 112(d) requires the 

EPA to set emission standards for all emitted pollutants. According to the commenter, closing 

loopholes and correcting problems that exist in the existing standard is an important part of the 

EPA’s job under CAA section 112(d)(6). The commenter believes that the EPA should ensure 

that these standards fully satisfy both CAA sections 112(d)(2) and (d)(3). 

Response: The EPA acknowledges this support. Note that we are not establishing new 

MACT standards for RS manufacturing lines at wool fiberglass manufacturing facilities in this 

final action. We have issued an ICR under CAA section 114 to collect updated emissions and 

process information from the industry and we will analyze the ICR data and evaluate MACT 

limits for RS lines at wool fiberglass manufacturing facilities at a future date. Subsequent 

responses below discuss specific details on the status of emission standards for flame attenuation 

manufacturing lines.

129. Comment: One commenter (1042-0120) noted that a significant shift in the use of 

non-PF binders had reduced enormously the residual risk remaining from formaldehyde. 

Therefore, the commenter contended that EPA is not justified in revising the formaldehyde limit.

Response: We disagree with the comment. As explained in our various proposals, the 

EPA proposed to discontinue the use of formaldehyde as a surrogate for phenol and methanol. 76 

FR 72788, 72791; 72796. The EPA may attribute characteristics of a subclass of substances to an 

entire class of substances if doing so is scientifically reasonable. Dithiocarbamate Task Force v. 

EPA, 98 F.3d 1394, 1399 (D.C. Cir. 1996). We no longer believe that there is a correlation and 

therefore, reasonable bases, between formaldehyde and phenol and methanol.

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As also explained in the preamble to the final rule, we are establishing emission limits for 

formaldehyde, phenol and methanol at the MACT floor level of control because the existing 

standard for formaldehyde was calculated incorrectly. We also note that the requirement to adopt 

MACT emission limitations, for example, applies without exception to “category or subcategory 

of major sources . . . of [HAP].” CAA section 112(d)(1). Regarding emission limits for RS lines, 

as discussed in section V.H of the preamble to the final rule, we are not establishing emission 

limits for RS manufacturing lines in this final action because we believe that the data no longer 

represent current industry conditions, most notably the significant reduction in the use of PF

binders in wool fiberglass manufacturing. Consequently, we have issued a CAA section 114 ICR 

to obtain process and emissions data for RS manufacturing lines and we will evaluate MACT 

limits for these sources, based on the CAA section 114 ICR data, at a future date.

5. Compliance Schedule

130. Comment: One commenter (1042-0120/1042-0300/1042-0348) urged the EPA to 

adopt a 3-year compliance period, with an option for facilities to petition for a 1-year extension 

of time. The commenter (1042-0120) strongly objected to the EPA’s 90-day deadline for 

compliance with requirements related to total chromium compounds. According to the 

commenter, 1 year is insufficient to design, obtain capital approval, purchase, construct, and 

install any additional control equipment. The commenter stated that companies cannot begin to 

design in advance of the final rule, given the known errors in the EPA’s floor and standard 

setting process as proposed in 2011. The commenter urged the EPA to consider granting further 

time, if necessary, for the installation and implementation of control measures such as during a 

time when the furnace is idle and undergoing construction.

The commenter (1042-0300/1042-0348) contended that the EPA incorrectly concluded in 

its 2014 proposal that a furnace rebuild alone could achieve the chromium limit of 6.0E-05

pounds of chromium compounds per ton glass pulled and that proven emission controls currently 

exist. The commenter explained that compliance with this chromium limit will require additional 

time to implement the necessary experimental, unproven equipment (e.g., scrubbers) in the wool 

fiberglass industry, including facilitating research options including pilot programs, 

experimentation with different control systems, furnace design changes, and improvements to 

existing control systems. The commenter invited the EPA to fund chromium emission reduction 

research programs for wool fiberglass furnaces. 

Response: The compliance schedule for all finalized limits for existing major and area 

sources is 2 years from the effective date of this rule. The finalized chromium limit is 2.5E-04

pounds of chromium compounds per ton glass pulled, and the EPA has determined that 

rebuilding gas-fired glass-melting furnaces before degradation of the refractory causes elevated 

chromium emissions will be sufficient for facilities to meet this limit, as further discussed in 

section VI.B of the preamble to the final rule. 

In the preamble to the 2014 proposal, we explained that standards promulgated under 

CAA section 112(f)(2) do not apply until 90 days after the effective date of the final action 

amending this rule and sources may have up to 2 years after the effective date of the standard to 

comply, if the EPA finds that such period is necessary for the installation of controls. (CAA 

section 112(f)(2)(B).) We further explained that under CAA section 112(i)(3), the EPA must 

require sources to comply as expeditiously as practicable, but no later than 3 years after 

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promulgation of the standard. (Ass'n of Battery Recyclers v. EPA, 716 F.3d 667, (D.C. Cir. 

2013). To establish the compliance schedule for major and new existing sources, we consulted 

our records from voluntary ICR responses and CAA section 114 responses regarding furnace 

ages and rebuilds, as well as statements by industry regarding furnace replacements. These 

sources of information indicated that the time period required to replace furnace refractory (for a 

complete furnace deconstruction and reconstruction) ranges from a few weeks (in the case of a 

“hot repair,” done while the furnace is operating) to 20 months. According to industry 

information, existing sources subject to the phenol, formaldehyde, and methanol limits for FA 

lines are already equipped with control devices that can achieve the MACT floor limits, but may 

need to operate these devices more often than would be required to meet the limits of the 1999 

MACT. Regarding chromium emission limits for gas-fired furnaces, we are allowing the time 

period allowed by statute (up to 2 years). Existing sources may need to undertake such 

improvements as design, construction and installation of fans, ductwork, monitors and feed for 

add-on controls, or may choose to replace their furnaces earlier than the furnace’s maximum 

expected lifetime. These activities cannot be accomplished in 90 days, and 2 years is a 

reasonable amount of time to carry them out. Based on all of this information, we concluded that 

2 years would be sufficient for sources to comply with the finalized standards. We see no reason 

for furnaces at area sources to require additional time for compliance not afforded to major 

sources, as there is no difference in the operation of the furnace itself as a result of major or area 

source status. If a major or area source were to require more than 2 years to comply with the 

finalized rule, then the owner or operator may request an extension under 40 CFR 63.1387(b).

Accordingly, the EPA has corrected regulatory text to reflect the applicable compliance 

dates, including revision of 40 CFR 63.1382(d) to remove the requirement to complete the initial 

performance test within 90 days of the effective date of the rule.

131. Comment: One commenter (1042-0120) supported the proposal to provide a 

categorical 1-year compliance extension for sources covered by the CAA section 112(f)(2) 

residual risk standards. In other recent rules, the commenter stated that the EPA has adopted an 

unnecessarily constrained view of its authority to provide categorical extensions under CAA 

section 112(i)(3)(B), which is comparable to CAA section 112(f)(4)(B) in all relevant respects. 

The commenter believes that the better reading of CAA sections 112(f)(4)(B) and (i)(3)(B) is 

that, given adequate factual support, both provisions authorize the EPA to grant categorical 

compliance extensions. Therefore, the commenter supported this aspect of the proposal.

The commenter, however, contended that the EPA was mistaken in its assertion in the 

2011 preamble that compliance with the CAA section 112(f)(2) standards must be required, in 

the first instance, no later than 90 days after the effective date of the rule. Although the EPA does 

not expressly say so in the proposal, the commenter stated that this assertion appears to be 

grounded in CAA section 112(f)(4)(A), which states that a standard adopted under CAA section 

112(f) “shall not apply until 90 days after its effective date.” In contrast to the proposed wool 

fiberglass RTR, the commenter stated that the EPA set out a comprehensive and authoritative 

interpretation of CAA section 112(f)(4)(A) in the proposed RTR for the “Hazardous Organic 

NESHAP.” The commenter opined that the interpretation therein is a correct assessment of the 

law and should be adopted in this and all other RTR rules.

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In the preamble to the proposed HON RTR, the commenter stated that EPA observed that 

CAA sections 112(f)(4)(A) and (B) “are at odds with the rest of the statutory scheme governing 

compliance deadlines for section 112 rules in several respects.” The commenter noted that the 

EPA provided the following explanation of these inconsistencies:

• The 90-day compliance deadline for existing sources in CAA section 112(f)(4)(A) 

directly conflicts with the up-to-3-year deadline in CAA section 112(i)(3)(A) allowed 

for existing sources subject to “any” rule under section 112. 

• The CAA section 112(f)(4)(A) deadline results in providing a shorter deadline for 

ordinary existing sources to comply with residual risk standards than would apply 

under CAA section 112(i)(2) to new sources that are built after a residual risk 

standard is proposed but a more stringent version is promulgated. 

• While both CAA section 112(i)(1), for new sources subject to any CAA section 

112(d), (f), or (h) standard, and CAA section 112(i)(3), for existing sources subject to 

any CAA section 112(d) standard, refer to and rely upon the new title V permit 

program added in 1990 and explicitly provide for State permitting authorities to make 

relevant decisions regarding compliance and the need for any compliance extensions, 

CAA section 112(f)(4)(B) still reflects the pre-1990 statutory scheme in which only 

the Administrator is referred to as a decision-making entity, notwithstanding the fact 

that even residual risk standards under CAA section 112(f) are likely to be delegated 

to States for their implementation, and will be reflected in sources’ title V permits and 

need to rely upon the title V permit process for memorializing any compliance 

extensions for those standards.

• “While we appreciate the fact that CAA section 112(i)(3)(B) refers specifically only 

to standards under CAA subsection 112(d), which some might argue means that CAA 

subsection 112(i)(3), in general, applies only to existing sources subject to section 

112(d) standards, we believe that Congress inadvertently limited its scope and created 

a statutory conflict in need of our resolution.” 

The commenter noted that the EPA concluded that the requirements of CAA section 

112(i)(3)(B) should take precedence over the conflicting provisions of CAA section 112(f)(4) 

and, as a result, proposed in the HON RTR to provide a three-year compliance period for sources 

covered by the proposed CAA section 112(f)(2) standards.

The commenter stated that the EPA’s interpretation in the HON RTR is not only 

persuasive, but correct. The commenter argued that the requirements of CAA section 112(f)(4) 

are plainly at odds with those of CAA section 112(i)(3) and the only rational way to resolve the 

inconsistencies is to implement the comprehensive and cohesive compliance deadline scheme 

outlined in CAA section 112(i). Thus, in the 2011 proposal, the commenter contended that the 

EPA should provide in the first instance a three-year compliance period for sources covered by 

the CAA section 112(f)(2) standards and should consider granting further time if necessary for 

the installation and implementation of control measures.

Response: We acknowledge the commenter’s support for the 1-year compliance period 

proposed in 2011 in 40 CFR 63.1387(a)(2)(i). As explained in response to comment number 131, 

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the compliance date for all emission limits being finalized is 2 years from the effective date of 

this rule.

With regard to the applicability of CAA section 112(i)(3), we have explained in more 

recent rules than the HON RTR mentioned by the commenter (e.g., Primary Lead RTR) that 

CAA section 112(i)(3) does not apply where we are setting the compliance date consistent with 

CAA section 112(f)(4). The EPA’s construct has recently been upheld in Ass'n of Battery 

Recyclers v. EPA, 716 F.3d 667 (D.C. Cir. 2013). “Although section 112(i)(3)’s three-year 

maximum compliance period applies generally to ‘any emissions standard . . . promulgated under 

[section 112],’. . . section 112(f)(4)’s two-year maximum applies more specifically to standards 

‘under this section,’ i.e., section 112(f).” Id. at 672 (Alteration in original). We continue to 

believe that CAA section 112(f)(4) independently requires the agency to set a compliance date of 

90 days and, as the commenter states, specifies the basis for providing a longer compliance 

period of up to 2 years. Thus, at proposal we explained that CAA section 112(f)(4)(B) allows us 

to extend the compliance timeframe in circumstances where we believe that additional time is 

necessary for installation of equipment or other measures to reduce HAP emissions. 

We also note that we are promulgating emissions for chromium under both CAA sections 

112(f)(2) and 112(d)(6). Consistent with CAA section 112(i)(3), standards developed under

CAA section112(d)(6) would provide up to a 3-year compliance date for existing sources. 

However, as explained in the EPA’s response to comment number 131, the EPA is finalizing a 2-

year compliance period for both existing major and existing area sources.

132. Comment: One commenter (1042-0121) stated that compliance delays are 

unlawful and arbitrary. The commenter further stated that the EPA’s 2011 proposal to delay 

compliance with the new chromium limit for Wool Fiberglass for 1 year after the effective date 

would mean that local communities would have to wait until 2013 to receive protection from 

health risk. The commenter noted that the EPA proposed to delay compliance with the new 

MACT standards for both Wool Fiberglass and Mineral Wool for 3 years. The commenter 

asserted that facilities would be allowed to continue emitting manganese, lead, arsenic, nickel, 

and other HAP above the levels allowed by the proposed rules. 

The commenter asserted that the proposed 1-year compliance chromium limit date 

violates the plain text of CAA sections 112(f)(3) and (4), which require immediate compliance 

for new sources and a 90-day compliance date for existing sources. The commenter stated that 

CAA section 112(f)(3) provides that ―[a]ny emission standard established pursuant to this 

subsection [section 112(f)] shall become effective upon promulgation. According to the 

commenter, CAA section 112(f)(4) establishes a prohibition on violating the new standard, 

stating that ―[n]o air pollutant to which a standard under this subsection applies may be emitted 

from any stationary source in violation of such standard, except that in the case of an existing 

source . . . such standard shall not apply until 90 days after its effective date. Thus, the 

commenter claimed that the statute establishes an immediate compliance date for new sources 

and a 90-day compliance date for existing sources. The commenter asserted that, for existing 

sources only, the statute provides the following: the Administrator may grant a waiver permitting 

such source a period of up to 2 years after the effective date of a standard to comply with the 

standard if two statutory factors are met for a particular source. The commenter argued that the 

EPA may grant such a waiver only if (1) the Administrator finds that such period is necessary for 

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the installation of controls, and (2) that steps will be taken during the period of the waiver to 

assure that the health of persons will be protected from imminent endangerment.

The commenter observed that the statute creates a waiver process for an existing source 

to apply for an extension of the date, if it can meet the statutory factors. To implement that 

requirement, the commenter argued that the EPA’s own regulations have established an 

application process where an individual facility unable to comply with a relevant standard under 

CAA section 112(f) may file an application for a 2-year extension of compliance after the 

standard’s effective date to comply with the standard. The commenter noted that the regulation 

follows the language of the statute. The commenter asserted that the regulation also provides a 

specific list of information that an application for a compliance extension must include and that 

the EPA should consider, including specific details on the compliance plan and the need for an 

extension. 

According to the commenter, neither the statute nor the EPA’s own regulation authorize 

the EPA to use the national rulemaking process to grant a CAA section 112(f)(4) waiver to an 

entire source category of facilities, absent any application. There is no indication in this record 

that any waiver application has been submitted to the EPA. In order for the EPA to consider such 

a waiver, a facility must submit a request for that waiver with supportive evidence. The EPA 

should evaluate that request on a case-by-case basis, with full notice and comment from the local 

community. Using the national rule process to delay compliance is arbitrary and capricious and 

an abuse of discretion.

Moreover, the commenter contended that the EPA’s proposal to delay the chromium limit 

also violates CAA section 112(f)(4) because the EPA has failed to satisfy the required statutory 

factors. The commenter claimed that the EPA’s record includes no evidence that the statutory 

factors are met. The commenter noted that the proposed rule simply states that we are proposing 

that a 1-year compliance timeframe is necessary so that affected facilities have adequate time to 

install additional controls and demonstrate compliance. The commenter claimed that the 

agency’s belief is not sufficient to satisfy the statute when it has the burden of proof.

The commenter argued that the second statutory factor also bars the compliance delay 

proposed by the EPA. The commenter contended that there is no evidence in the record that 

necessary steps will be taken during the additional year to assure that the health of persons will 

be protected from imminent endangerment. According to the commenter, there is evidence of 

endangerment for this source category that makes it particularly dangerous, among major source 

categories. The commenter concluded that the EPA has the burden to prove that allowing the 

delay will avoid imminent endangerment.

Although it is not the commenter’s burden to show this, there are many reasons to be 

concerned about imminent endangerment during the year the EPA proposes to delay compliance. 

First, although the EPA has not recognized this, the commenter noted that existing health risk 

from the Wool Fiberglass Manufacturing source category is currently unacceptable, and the 

EPA’s own auxiliary analysis shows that even the EPA believes it is likely to become much 

worse if EPA does not finalize a chromium limit. Per the commenter, every additional day that 

the EPA allows children to be exposed to these unacceptable health risks is itself indefensible. 

Second, because of the history of exposure to chromium, mercury, and other PB-HAP in the 

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affected communities, the commenter contended that there is an even greater health risk from 

each additional day of exposure than there would be if none of the pollutants were PB-HAP. 

Third, the commenter asserted that there is an indication of socioeconomic disparities for the 

Wool Fiberglass Manufacturing source category which shows the affected communities are 

likely to be more vulnerable and less equipped to handle the increased health risk from this 

source category. In view of this, the commenter asserted that the EPA may not lawfully delay 

compliance without assuring public health protection during the delay period, and therefore the 

proposed rule is also unlawful on this basis.

The commenter asserted that by failing to begin this rulemaking for so long, the EPA has 

already delayed satisfying its legal duties both under CAA sections 112(f)(2) and (d)(6) to 

provide protection for affected local communities. The commenter argued that these provisions 

actually required the EPA to perform this rulemaking and set the required standards no later than 

8 years after the MACT standards were first promulgated. According to the commenter, this 

occurred in 1999, and this rulemaking duty became due in 2007. The commenter observed that 

the EPA did not propose this rule until 2011. The commenter argued that the EPA should not 

deny local communities vital protection they need for an additional 2 years when the EPA was 

obligated to promulgate this rule more than 4 years ago. According to the commenter, the EPA 

has no lawful justification, in view of the statutory context and these circumstances, to delay the 

compliance date any longer.

Per the commenter, in enacting the provision governing the compliance schedule for 

CAA section 112(d), which is 42 U.S.C. section 7412(i), Congress stated it wanted “expeditious” 

compliance. The commenter observed that this principle also applies to CAA section 112(f)(4), 

42 U.S.C. section 7412(f)(4). There, the commenter noted that the statute has established a 

“prohibition on non-compliance by existing sources after the 90-day period, unless a waiver of 

up to 2 years is specifically granted based on the statutory factors provided.” Moreover, the 

commenter asserted that Congress intended for similarly “expeditious compliance with the 

deadline set by section 112(f)(4), and ―[w]here Congress explicitly enumerates certain 

exceptions to a general prohibition, additional exceptions are not to be implied, in the absence of 

a contrary legislative intent.”

For these reasons, the commenter argued that the compliance delay for the residual risk 

standard for chromium is arbitrary and capricious, and without the required evidentiary support 

in the record.

The commenter continued that EPA’s proposed 3-year delay for the new MACT 

standards is also unlawful for reasons similar to those described above. In addition, the 

commenter argued that EPA also has not met the standard under section 112(i)(3) to demonstrate 

that a MACT compliance date for existing sources ―shall provide for compliance as 

expeditiously as practicable. According to the commenter, not only is there no evidence of this 

required determination in the record, but also EPA cannot meet this test because it is ensuring no 

additional protection for communities in the meantime.

Response: As explained in the EPA’s response to comment number 132, we believe that 

CAA section 112(i)(3) does not apply where we are setting the compliance date consistent with 

CAA section 112(f)(4). The EPA is not ignoring the requirements of CAA sections 112(f)(3) and 

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(4). Section 112(f)(4)(B) of the CAA is a direct grant of authority, which can be implemented not 

just by regulation but by other EPA action, as done here. The EPA considered how much time 

would be required by industry to comply with the finalized standards, and concluded that 2 years 

would be sufficient. 

We also note that we are promulgating emissions for chromium under both CAA sections 

112(f)(2) and (d)(6). Consistent with CAA section 112(i)(3), standards developed under CAA 

section 112(d)(6) would provide up to a 3-year compliance date for existing sources. However, 

as explained in the EPA’s response to comment number 131, the EPA is finalizing a 2-year 

compliance period for both existing major and existing area sources. 

133. Comment: One commenter (1042-0300) requested that the EPA extend the 

compliance deadline to coincide with currently planned furnace rebuilds for each facility rather 

than the compliance date one year from promulgation of the standards, due to the cost of 

unplanned furnace rebuilds. The commenter added that the cost of an oxyfuel or air-gas furnace 

rebuild is on the order of between $7-10 million, depending on size and materials. If a company 

has recently undertaken a furnace rebuild at this cost, that cost would recur for a company to 

reconstruct the furnace within a year after promulgation of this rule. 

Response: The final rule requires owners or operators to demonstrate initial compliance 

with the chromium emissions limit for existing sources within 2 years of the effective date of the 

rule and to conduct emissions test each year thereafter. A furnace rebuild would be needed only 

if a furnace can no longer achieve the chromium limit, regardless of age.

6. Economic Impacts 

134. Comment: One commenter (1042-0120) argued that the emission limits proposed 

in 2011 (76 FR 72770) for new and reconstructed sources (PM, formaldehyde (RS lines only), 

phenol (RS lines only), and methanol (RS lines only)) would have a devastating impact on many 

wool fiberglass manufacturing companies, and that the EPA’s economic impacts analysis did not 

address this cost. The commenter claimed that companies estimate $1 million or more per source 

to install this equipment. The commenter opined that the EPA was mistaken in its 2011 proposal 

in assuming that existing sources could meet the 2011 proposed limits without using additional 

controls not considered by the EPA in its cost analysis (wet or dry scrubbers in addition to the 

existing control devices). With regard to the proposed limits for phenol, formaldehyde, and 

methanol for RS manufacturing lines, the commenter stated that these limits cannot be achieved 

even by sources using non-PF binders. 

The commenter asserted that such an outcome is inconsistent with the legislative history 

of the CAA, which makes clear that the MACT standards were not intended to force the 

shutdown of facilities. H.R. Rep. No. 101-490, at 335 (1990) (“MACT is not intended to . . .

drive sources to the brink of shutdown.”) S. Rep. No. 101-228, at 152 (1989) (“Controls which 

are so expensive that they force closure of the source or would severely impair its continuation as 

an economic entity are not ‘available.”)

Response: As previously explained, CAA section 112(d) requires EPA to promulgate 

standards for major sources of HAP based on the performance of the maximum achievable 

control technology. For existing sources, MACT standards must be at least as stringent as the 

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average emissions limitation achieved by the best performing 12 percent of existing sources (for 

which the Administrator has emissions information) or the best performing 5 sources for source 

categories with less than 30 sources, as is the case here. For new sources, the MACT standards 

must be at least as stringent as the control level achieved in practice by the best controlled 

similar source. CAA Section 112(d)(3). The EPA is not allowed to consider costs in setting 

MACT standards. National Lime Ass’n v. EPA, 233 F.3d at 640.

Regarding the emission limits for formaldehyde, phenol, and methanol for RS lines 

proposed in the November 25, 2011 notice, we do not believe that the available data for RS 

manufacturing lines are sufficient for EPA to establish appropriate emission limits. 

Consequently, we have issued a CAA section 114 ICR to wool fiberglass facilities to obtain 

process and emissions data for RS manufacturing lines. We will analyze ICR data and evaluate 

MACT floor limits for RS lines at a future date. See section V.H of the preamble to the final rule 

for a more detailed discussion regarding the status of RS lines.

Regarding the comment that the EPA did not include in its economic impacts analysis the 

control technologies needed to meet the PM limit, the EPA has revised the PM limits since the 

2011 proposal (76 FR 72770, November 25, 2011). The final PM limit is 0.33 pounds per ton of 

glass pulled. As noted in the November 13 2014 supplemental proposal (79 FR 68026), we 

believe that all facilities will be able to comply with the final PM emission limit based on the 

data submitted to EPA. 

Price elasticities of demand and supply obtained by the EPA and included in the 

economic impact analysis report show that consumers of wool fiberglass products will incur 

some of the costs of this rule in the form of increases in price. Thus, producers will not incur the 

entirety of the costs of this rule, and should not bear large enough costs to lead to facilities or 

firms being at risk of closure or other substantial economic impacts based on the EPA’s 

estimates of the compliance costs. Refer to the EPA’s responses to comment number 101 for 

further discussion of the technology basis for the final PM standard and the memorandum 

“Economic Impact and Small Business Analysis – Mineral Wool and Wool Fiberglass RTRs and 

Wool Fiberglass Area Source NESHAP,” which is available in the docket, for further discussion 

of the economic analysis.

135. Comment: One commenter (1042-0120) argued that the EPA’s justifying the costeffectiveness values supporting the 2011 proposed chromium limit by comparing compliance 

costs to annual sales or revenues of the affected companies is arbitrary and fails to provide a 

reasoned basis for the proposed standards because gross sales have no necessary relationship to 

the financial viability of the affected company. The commenter cited the EPA’s rationale for the 

cost-effectiveness values for the 2011 proposed chromium limit (76 FR 72770, November 25, 

2011): “The economic impact on [affected] firms measured in annual compliance costs as a 

percent of sales or revenues, is less than 0.001 percent for each of the affected firms.” According 

to the commenter, many companies with very high sales are highly unprofitable. The commenter 

concluded that sales alone provide no insight into the ability of the affected company to 

reasonably bear the cost of compliance. In addition, the commenter argued that the use of 

revenues as a measure of cost effectiveness is arbitrary because the level of emissions control 

that might be required would depend on the profitability of the affected companies. The 

commenter concluded that, therefore, if an industry happens to be doing well financially at the 

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time the EPA conducts an RTR rulemaking, the industry could be regulated much more

stringently than if the same industry happened to be doing poorly at the time the rules are 

developed. 

Response: The economic impact analysis mentions that the change in product price 

associated with the impact of the rule is “approximated by the cost to revenue ratio, since this 

ratio is the maximum price change that producers may face” to recover from consumers all costs 

of the rule. In addition, the agency never uses revenue data as part of estimating the costeffectiveness of its rules since the cost-effectiveness is, by definition, the annualized cost of 

control divided by emissions reduction, and does not consider revenue data. The EPA used sales 

rather than profits in its economic impact analysis since the sales data is more complete and 

accurate than profit data for individual companies, data that often incorporates provisions of tax 

laws than may yield estimates of profit that do not reflect the true economic profit experienced 

by companies. Price elasticities of demand and supply obtained by the EPA are used in the 

economic impact analysis to show that consumers of wool fiberglass products will incur some of 

the costs of this rule in the form of increases in price. Thus, producers will not incur the entirety 

of the costs of this rule, and should not bear large enough costs to lead to facilities or firms being 

at risk of closure or other substantial economic impacts based on the EPA’s estimates of the 

compliance costs and our economic impact analysis. That being said, the agency is mindful of 

the potential impact of this rule upon wool fiberglass producers and their consumers regardless 

of the financial condition of such producers and consumers. 

We also note that we found $11,000 per pound chromium removed to be a reasonable 

cost in the final Chromium Electroplating RTR rulemaking, where we regulated chromium 

compounds (77 FR 59220, September 19, 2012). Thus, contrary to the commenter’s assertion the 

cost-effectiveness for this rule is not in excess of the cost effectiveness values the EPA has found 

acceptable in prior CAA section 112 cost effectiveness analyses. Moreover, CAA section 112(d) 

neither specifies nor mandates a cost methodology. In Husqvrna AB v. EPA, 254 F.3d 195, 200 

D.C. Cir. 2001), the D.C. Circuit found EPA’s chosen methodology “reasonable” because the 

statute “did not mandate a specific method of cost analysis.”

136. Comment: Two commenters (1042-0300/1042-0348, 1042-0120) argued that the 

EPA’s cost effectiveness measure for chromium using dollars per pound pollutant is 

unreasonable because in other rules the EPA has used a ‘dollars per ton pollutant removed’ 

metric to evaluate cost effectiveness. The commenter believes the EPA has artificially deflated 

the true cost effectiveness of the emission reductions by employing the dollars per pound 

pollutant metric, and if the agency used the dollars per ton metric, as in the 1999 MACT rule, the 

limits proposed by the EPA would have been rejected as too costly. 

Response: Regarding the commenter’s assertion that our cost effectiveness measure is 

unreasonable, we disagree. For highly toxic pollutants such as hexavalent chromium, mercury, 

and lead, we use unit of measure dollars spent per pound of pollutant removed. As earlier 

explained, the cost-effectiveness for the chromium compound limit in the final rule is consistent 

with the approach the EPA has taken in numerous rulemakings including the RTRs for 

chromium electroplating industry. We also note that we found $11,000 per pound chromium 

removed to be a reasonable cost in the final Chromium Electroplating RTR rulemaking, where 

we regulated chromium compounds (77 FR 59220, September 19, 2012). Thus, contrary to the 

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commenter’s assertion, the cost-effectiveness for this rule is not in excess of the cost 

effectiveness values the EPA has found acceptable in prior CAA section 112 cost effectiveness 

analyses. Moreover, CAA section 112(d) neither specifies nor mandates a cost methodology. In 

Husqvrna AB v. EPA, 254 F.3d 195, 200 D.C. Cir. 2001), the D.C. Circuit found EPA’s chosen 

methodology “reasonable” because the statute “did not mandate a specific method of cost 

analysis.”

137. Comment: One commenter (1042-0300/1042-0348) stated that the proposed 

increase in the testing duration for Method 316 from one to two hours will add cost that the EPA 

did not factor into its estimated rule cost burden. 

Response: Consistent with our proposal, we are finalizing, as proposed, the requirement 

to collect a minimum sampling volume of 2 dscm; however, we are not finalizing the proposed 

minimum sampling run time for EPA Method 316 of 2 hours. In the final rule, the EPA is 

specifying the use of Method 318 for measuring concentrations of formaldehyde, methanol, and 

phenol. The final rule also allows facilities use the options of using either (1) Method 316 for 

formaldehyde, or (2) Method 308 for methanol. The EPA’s testing cost estimate is based on the 

use of Method 318 rather than Method 316.

138. Comment: One commenter (1042-0348) argued that the EPA, in changing 

applicability for FA lines to lines not previously regulated, has not considered this expansion in 

its cost estimates, which is required by law expands applicability to lines not previously 

regulated. The EPA’s new applicability language will affect the competitiveness of lines not 

previously regulated.

Response: As previously explained, CAA section 112(d) requires the EPA to promulgate 

standards for major sources of HAP based on the performance of the maximum achievable 

control technology. For existing sources, MACT standards must be at least as stringent as the 

average emissions limitation achieved by the best performing 12 percent of existing sources (for 

which the Administrator has emissions information) or the best performing 5 sources for source 

categories with less than 30 sources, as is the case here. For new sources, the MACT standards 

must be at least as stringent as the control level achieved in practice by the best controlled 

similar source. CAA Section 112(d)(3). The EPA is not allowed to consider costs in setting 

MACT standards. National Lime Ass’n v. EPA, 233 F.3d at 640. As also earlier explained, the 

1999 MACT standard for the Wool Fiberglass Manufacturing source category included no 

control floors for existing sources making light density, automotive and heavy density products 

on FA lines. But, the EPA has a “clear obligation to set emissions standards for each listed 

HAP.” National Lime v. EPA, 233 F. 3d at 634. As also explained earlier, the existing source 

limits for formaldehyde were set at the highest measured value for each of the subcategories. 

Again, the D.C. Circuit has consistently rejected the EPA’s construct of CAA section 112(d) as 

requiring standards that can be achieved by all sources. “EPA may not deviate from section 

7413(d)(3)’s requirement that floors reflect what the best performers actually achieve by 

claiming that floors must be achievable by all sources using MACT technology.” Cement Kiln 

Recycling Coalition v. EPA, 255 F.3d at 861. Thus, in addition to setting no control floors, the 

emission limits were set not at the level defined by the MACT floor, but at a level that was 

achievable by all sources within the wool fiberglass manufacturing source category.

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We based our cost estimate for FA lines on the process and emissions data submitted by 

industry in response to voluntary surveys and information collection requests under CAA section 

114. As discussed in the April 15, 2013 supplemental proposal (78 FR 22388), based on the 

industry-supplied data, we do not believe that the subcategories for FA lines in the 1999 

NESHAP continue to have a technical basis. Based on the data submitted, we also do not believe 

that our cost estimate for FA lines did not cover all FA lines that will be subject to the final rule 

and the commenter did not provide any data or information that would substantiate the claim that 

previously-unregulated FA lines would be covered under the final rules.

7. MACT Floor Analyses

139. Comment: One commenter (1042-0120), in response to the 2011 proposal, 

highlighted that the EPA cannot simply change its mind about what standards are required to 

comply with CAA sections 112(d)(2) and (3), nor can it recalculate a MACT floor based on 

subsequent performance. Cf. NRDC v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008) (rejecting 

contention that CAA section 112(d)(6) requires the EPA to “start from scratch” and develop new 

MACT standards).

Response: We disagree with the comment. The D.C. Circuit has held that the EPA may 

permissibly amend improper MACT determinations, including amendments to improperly 

promulgated floor determinations, using its authority under CAA sections 112 (d) (2) and (3). 

Medical Waste Institute v. EPA, 645 F.3d 420, 425-27 (D.C. Cir. 2011). (Resetting MACT floor, 

based on post-compliance data, permissible when originally-established floor was improperly 

established, and permissibility of the EPA’s action does not turn on whether the prior standard 

was remanded or vacated). Similarly, Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. 

Cir. 2011) confirms that CAA section 112 (d)(6) does not constrain EPA and it may reassess its 

standards more often, including revising existing floors if need be. 

We note that in this instance, we had improperly promulgated a floor determination in 

1999 for formaldehyde as well as a surrogacy requirement that lacked correlation (76 FR 72775). 

(The EPA may attribute characteristics of a subclass of substances to an entire class of 

substances if doing so is scientifically reasonable. Dithiocarbamate Task Force v. EPA, 98 F.3d 

1394, 1399 (D.C. Cir. 1996)). Put another way, if the EPA did not adopt a proper MACT 

standard initially, it is not amending a MACT standard but adopting one for the first time. That 

was the case for formaldehyde, methanol, and phenol emissions in the 2011 proposal. Here, the 

EPA either adopted no MACT standard at all for these HAP or improperly promulgated a floor 

determination for formaldehyde, which is an approach soundly rejected by the D.C. Circuit in 

both National Lime, 233 F.3d at 633-34 and in Portland Cement Ass’n v. EPA, 665 F.3d at 189. 

Therefore, the EPA is not barred from making MACT floor determinations and issuing MACT 

standards for formaldehyde, phenol, and methanol pursuant to CAA sections 112 (d)(2) and (3). 

As also previously explained, in several recent rulemakings, we have chosen to fix 

underlying defects in existing MACT standards under CAA sections 112(d)(2) and (3), 

provisions that directly govern the initial promulgation of MACT standards (see National 

Emission Standards for Hazardous Air Pollutants From Petroleum Refineries, October 28, 2009, 

74 FR 55670; and National Emission Standards for Hazardous Air Pollutants: Group I Polymers 

and Resins; Marine Tank Vessel Loading Operations; Pharmaceuticals Production; and the 

Printing and Publishing Industry, April 21, 2011, 76 FR 22566). We believe that our approach is 

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reasonable because using those provisions ensures that the process and considerations are those 

associated with initially establishing a MACT standard, and it is reasonable to make corrections 

following the process that would have been followed if we had not made an error at the time of 

the original promulgation.

Note that we are not finalizing in this final action MACT standards for formaldehyde, 

phenol, and methanol for RS manufacturing lines at wool fiberglass manufacturing facilities. We 

have issued an ICR under section 114 of the CAA to collect updated emissions and process 

information from the industry, and we will analyze the ICR data and evaluate MACT limits for 

RS lines at wool fiberglass manufacturing facilities at a future date. Refer to section V.H of the 

preamble to the final rule for further discussion of the EPA’s rationale for postponing 

establishing MACT standards for formaldehyde, phenol, and methanol emission data for RS 

lines until a future date and for issuing an ICR for additional data.

140. Comment: One commenter (1042-0348) opined that “cherry picking” the best data 

individually for formaldehyde, phenol, and methanol results in unachievable limits because it 

does not account for the relationship among formaldehyde, phenol, and methanol and their use 

together in the insulation binding process. The commenter further argued that, according to the 

EPA’s database, very few units are best performers for more than one pollutant, meaning that the 

proposed standards reflect the performance of exceedingly few actual sources. The commenter 

claimed that the EPA has improperly exercised its discretion in this rule and has failed to provide 

an assessment of how many actual fiber glass furnaces or lines will be able to meet the proposed 

standards without taking any further control measures.

Response: The EPA disagrees with the commenter who believes MACT floors cannot be 

set on a pollutant-by pollutant basis. Regarding determination of the MACT floor, and as earlier 

explained in various responses, above, the intent of CAA section 112(d)(3) is to bring all 

industry into compliance with the emission limits achieved by the best performing sources across 

the industry. As also explained earlier, the D.C. Circuit has consistently rejected a reading of 

“achieved by the best performers,” in CAA section 112(d)(3) as meaning achievable by all 

sources within a source category. “EPA’s rationales . . . amount to nothing more than concern 

about ensuring that its floor is achievable by all kilns in the subcategory--precisely the position 

we rejected in Cement Kiln.” Sierra Club v. EPA, 479 F.3d at 881. See also, Cement Kiln 

Recycling Coalition v. EPA, 255 F.3d at 861 “EPA may not deviate from section 7413(d)(3)’s 

requirement that floors reflect what the best performers actually achieve by claiming that floors 

must be achievable by all sources using MACT technology.” (“EPA cannot circumvent Cement 

Kiln’s holding that section 7412(d)(3) requires floors based on the emission level actually 

achieved by the best performers(those with the lowest emission levels), not the emission level 

achievable by all sources, simply by redefining “best performing” to mean those sources with 

emission levels achievable by all sources.” Sierra Club v. EPA, 479 F. 3d at 881. (Emphasis in 

original)).

Contrary to the commenter’s suggestion, CAA section 112(d)(3) does not mandate a total 

facility approach. A reasonable interpretation of CAA section 112(d)(3) is that MACT floors 

may be established on a HAP-by-HAP basis, so that there can be different pools of best 

performers for each HAP. Indeed, as illustrated below, the total facility approach is not 

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compelled by the statutory language but can lead to results so arbitrary that the approach may 

simply not be legally permissible.

Section 112(d)(3) of the CAA is ambiguous as to whether the MACT floor is to be based 

on the performance of an entire source or on the performance achieved in controlling particular 

HAP. Congress specified in CAA section 112(d)(3) the minimum level of emission reduction 

that could satisfy the requirement to adopt MACT. For new sources, this floor level is to be “the 

emission control that is achieved in practice by the best controlled similar source.” For existing 

sources, the floor level is to be “the average emission limitation achieved by the best performing 

12 percent of the existing sources” for categories and subcategories with 30 or more sources, or 

“the average emission limitation achieved by the best performing 5 sources” for categories and 

subcategories with fewer than 30 sources. The language of the CAA section 112(d) does not 

address whether floor levels can be established HAP-by-HAP or by any other means. The 

reference to “sources” does not lead to the assumption commenters make that the best 

performing sources can only be the best-performing sources for the entire suite of regulated 

HAP. Instead, the language can be reasonably interpreted as referring to the source as a whole or 

to performance as to a particular HAP. Similarly, the reference in the new source MACT floor 

provision to “emission control achieved by the best controlled similar source” can mean 

emission control as to a particular HAP or emission control achieved by a source as a whole.

Also, CAA section 112(d) includes language such as “existing source,” “best 

performing,” and “achieved in practice” in referring to sources’ actual operations, but again the 

language says nothing about whether it is referring to performance as to individual HAP or to 

single facility’s performance for all HAP. The argument that MACT floors set HAP-by-HAP are 

based on the performance of a hypothetical facility, so that the limitations are not based on those 

achieved in practice, also just re-begs the question of whether CAA section 112(d)(3) refers to 

whole facilities or individual HAP. All of the limitations in the floors in this rule of course reflect 

sources’ actual performance and were achieved in practice. The commenter also points to the 

EPA’s subcategorization authority, and claims that because Congress authorized the EPA to 

distinguish among classes, types, and sizes of units, the EPA cannot distinguish units by 

individual pollutant, as they allege the EPA did in the proposed rule. However, that statutory 

language addresses the EPA’s authority to subcategorize sources within a source category prior 

to setting standards. In doing so, the EPA does not distinguish within each subcategory based on 

HAP emitted. Rather, it establishes emissions standards based on the emissions limits achieved 

by units in each subcategory. Therefore, the EPA’s subcategorization authority is irrelevant to 

the question of how the EPA establishes MACT floor standards once it has made the decision to 

distinguish among sources and create subcategories.

The EPA’s long-standing interpretation of the CAA is that the existing and new source 

MACT floors are to be established on a HAP-by-HAP basis. One reason for this interpretation is 

that a whole plant approach could yield least common denominator floors – that is floors 

reflecting mediocre or no control, rather than performance which is the average of what best 

performers have achieved. See 61 FR 173687 (April 19, 1996); 62 FR 48363-64 (September 15, 

1997) (same approach adopted under the very similar language of CAA section 129 (a)(2)). Such 

an approach would allow the performance of sources that are outside of the best-performing 12 

percent for certain pollutants to be included in the floor calculations for those same pollutants, 

and it is even conceivable that the worst performing source for a pollutant could be considered a 

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best performer overall, a result Congress could not have intended. Inclusion of units that are 

outside of the best performing 12 percent for particular pollutants would lead to emission limits 

that do not meet the requirements of the statute.

For example, if the best performing 12 percent of facilities for HAP metals were also the 

worst performing units for acid gas HAP, the floor for acid gases or metals would end up not 

reflecting best performance. In such a situation, the EPA would have to make some type of value 

judgment as to which pollutant reductions are most critical to decide which sources are best 

controlled. Such value judgments are antithetical to the direction of the statute at the MACT 

floor-setting stage. 

The central purpose of the amended air toxics provisions was to apply strict technologybased emission controls on HAP. See, e.g., H. Rep. No. 952, 101st Cong. 2d sess. 338. The 

floor’s specific purpose was to assure that consideration of economic and other impacts not be 

used to “gut the standards. Although costs are by no means irrelevant, they should by no means 

be the determining factors. There needs to be a minimum degree of control in relation to the 

control technologies that have already been attained by the best existing sources.” A Legislative 

History of the Clean Air Act, Vol. II at 2897 (statement of Rep. Collins). An interpretation that 

the floor level of control must be limited by the performance of devices that only control some of 

these pollutants effectively “guts the standards” by including worse performers in the averaging 

process, whereas the EPA’s interpretation promotes the evident Congressional objective of 

having the floor reflect the average performance of best performing sources. Because Congress 

has not spoken to the precise question at issue and the agency’s interpretation effectuates 

statutory goals and policies in a reasonable manner, its interpretation must be upheld. See 

Chevron v. NRDC, 467 U.S. 837 (1984). 

The EPA notes, however, that if optimized performance for different HAP is not 

technologically possible due to mutually inconsistent control technologies (for example, if metals 

performance decreased if organics reduction is optimized), then this would have to be taken into 

account by the EPA in establishing a floor (or floors). The Senate Report indicates that if certain 

types of otherwise needed controls are mutually exclusive, the EPA is to optimize the part of the 

standard providing the most environmental protection. S. Rep. No. 228, 101st Cong. 1st sess. 

168 (although, as noted, the bill accompanying this Report contained no floor provisions). It 

should be emphasized, however, that, “the fact that no plant has been shown to be able to meet 

all of the limitations does not demonstrate that all the limitations are not achievable.” Chemical 

Manufacturers Association v. EPA, 885 F. 2d at 264 (upholding technology-based standards 

based on best performance for each pollutant by different plants, where at least one plant met 

each of the limitations but no single plant met all of them).

Finally, we note that the D.C. Circuit recently found a challenge to the agency’s practice 

of setting floors based on emissions levels achieved by the best performing units on a pollutantby-pollutant basis to be barred on jurisdictional grounds. Medical Waste Institute v. EPA, 645 F. 

3d 420 (D.C. Cir. 2011).

We also note that the final rule limits are based on data that industry submitted to the 

agency pursuant to a voluntary survey they requested and conducted.

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Regarding the proposed formaldehyde, methanol, and phenol limits for RS lines, as noted 

in section V.H of the preamble to the final rule, we are not establishing MACT standards for RS 

manufacturing lines at wool fiberglass manufacturing facilities in this final action. We have 

issued an ICR under CAA section 114 to collect updated emissions and process information from 

the industry and we will analyze the ICR data and evaluate MACT floor limits for RS lines at 

wool fiberglass manufacturing facilities at a future date.

8. Environmental Justice

141. Comment: One commenter (1042-0121) opined that the EPA’s environmental 

justice (EJ) analysis is incomplete and the EPA should include the following additional elements 

to assess environmental justice impacts:

• Assess the baseline “overall health” status and cancer levels of individuals and 

communities.

• Follow the recommendations of the EPA’s interim guidance found in the 

Environmental Justice Strategic Enforcement Assessment Tool (EJSEAT).

• Include statistics on the percentages of population with limited English proficiency, 

infant mortality, and low birth weight.

The commenter stated that socioeconomic disparity in health risk from the Wool 

Fiberglass Manufacturing source category makes the risk the EPA has found unacceptable, and 

the EPA should finalize a rule that is consistent with the principle of environmental justice. 

According to the commenter, the EPA’s socioeconomic analysis for the Wool Fiberglass 

Manufacturing source category finds disproportionate impacts on minorities and people below 

the poverty level. The commenter noted that this document indicates that the demographic results 

for the population potentially impacted by wool fiberglass emissions indicate that the Minority, 

African American, Other and Multiracial, and Hispanic or Latino percentages are higher than 

their respective national percentages (by 11, 7, 5, and 2 percentage points, respectively).

Response: Where the agency finds risks to be acceptable, the EPA’s obligation under EO 

12898 is to ensure that no group is subject to adverse impacts. The agency conducts its risk 

assessments based on the risks posed to the general population which includes ethnic and socio 

economically disadvantaged communities. Where we find those risks to be acceptable no further 

action is warranted. For the Wool Fiberglass Manufacturing source category, we determined that 

the current health risks posed by emissions from the source category are acceptable. However, 

there are about 1,200,000 people nationwide that are currently subject to health risks which are 

non-negligible (i.e., cancer risks greater than 1-in-1 million) due to emissions from this source 

category. We performed an analysis of the demographic makeup of these 1,200,000 people. The 

demographic distribution of this ‘‘at-risk’’ population is similar to the national distribution of 

demographics for all groups except for the ‘‘minority’’ group (defined as total population minus 

the white population), which is 16 percent greater than its corresponding national percentage. 

See the Risk and Technology Review—Analysis of Socio-Economic Factors for Populations 

Living Near Wool Fiberglass Facilities dated March 23, 2015 in the docket for additional details 

on the demographic analysis. The EPA has determined that the current health risks posed by 

emissions from this source category are acceptable. 

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With respect to the EJSEAT tool, it is currently a draft tool in development and has not 

undergone a sufficient level of peer review. Additionally, EJSEAT is a simple screening tool 

whereas the aforementioned demographic distributions of “at-risk” populations reflect a much 

more thorough examination of populations. 

Regarding the comment that the EPA should assess the baseline “overall health” status 

and cancer levels of individuals and communities, in our Risk and Technology Review—Analysis 

of Socio-Economic Factors for Populations Living Near Wool Fiberglass Facilities we looked at 

the percentages of the “at-risk” population that were “Over 25 without a high school diploma” 

and that were considered to be in “Linguistic Isolation.” We found that the percentages in these 

demographic categories in the “at-risk” population were similar to the percentages in the national 

population.

Regarding the comment that the EPA should include statistics on the percentages of 

population with limited English proficiency, in our Risk and Technology Review—Analysis of 

Socio-Economic Factors for Populations Living Near Wool Fiberglass Facilities we looked at 

the percentages of the “at-risk” population that were “Over 25 without a high school diploma” 

and that were considered to be in “Linguistic Isolation.” We found that the percentages in these 

demographic categories in the “at-risk” population were similar to the percentages in the national 

population.

Regarding the comment that the EPA should include statistics on the percentages of the 

population with infant mortality and low birth weight, in our Risk and Technology Review—

Analysis of Socio-Economic Factors for Populations Living Near Wool Fiberglass Facilities we 

looked at the percentages of the “at-risk” population that were between the ages of “0 to 17.” We 

found the percentage of the population in the “0 to 17” demographic category to be identical in 

the “at risk” population and the national population. In addition, the risk assessment for this 

source category considers the groups that may be most at-risk. When the EPA derives exposure 

reference concentrations and unit risk estimates for HAP, it also considers the most sensitive 

populations identified in the available literature, and importantly, these are the values used in our 

risk assessments (see “A Review of the Reference Dose and Reference Concentration 

Processes,” U.S. EPA, Risk Assessment Forum, Washington, DC, EPA/630/P-02/002F, 2002, 

available online at http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf). For further discussion 

of the parameters considered as part of our risk assessment, refer to the final risk assessment 

document titled “Residual Risk Assessment for the Mineral Wool Production and Wool 

Fiberglass Manufacturing Source Categories in Support of the June 2015 Final Rule”, which is 

located in the docket.

142. Comment: Two commenters (1042-0121 and 1042-0113) recommended that the 

EPA conduct the demographic analysis on individuals projected to experience a risk greater than 

1-in-1-million and also on individuals living within five kilometers (km) of the facility, 

regardless of projected risk, consistent with the approach used for the Hard and Decorative 

Chromium Electroplating and Chromium Anodizing Tanks source category. One commenter 

also suggested analyzing risk as close as a 2 km radius of each facility. One commenter (1042-

0113) noted that the socio-economic analysis for this rule did not evaluate potential disparities 

within five km for cancer risk at maximum allowable emission levels. The commenter observed 

that this type of analysis is especially important in instances where a facility is located in a 

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minority and low-income community. The commenter asserted that because the EPA only 

evaluated the risk to the population within a 50-km radius, the results could be diluted by 

including populations not in the demographic groups most at risk, especially if the source is 

located in or next to a minority or low-income population. Therefore, the commenter 

recommended an analysis at the five-km distance be conducted to assess facility impacts to 

nearby environmental justice communities. 

The commenters recommended that the rule writers work with the EPA Office of 

Environmental Justice to develop criteria and specific guidance on how to interpret and apply the 

outcome of the demographics analyses in the rulemaking process.

Response: The commenter is correct that we performed the demographic analyses for the 

Wool Fiberglass Manufacturing source category differently than we did for the October 2010 

proposed RTR for the Hard and Decorative Chromium Electroplating and Chromium Anodizing 

Tanks source categories. We performed the demographic analyses for these two source 

categories using two approaches as examples of how such analyses might be developed, and 

invited public comment on the approaches used and the interpretations made from the results. In 

the first approach, we focused the analysis on the total populations residing within 5 km of each 

facility, regardless of their estimated risks, and examined the distributions across various 

demographic groups within those 5 km circles. That analysis was a “proximity” analysis in that it 

considered only the distance from the emission sources to surrounding populations, and not the 

estimated risks to those populations.

In the second approach, we focused the analysis on the populations within 5 km of any 

facility estimated to have exposures to HAP which result in cancer risks of 1-in-1 million or 

greater or non-cancer hazard indices of 1 or greater. We examined the distributions of those risks 

across various demographic groups. In each approach, we compared the percentages of particular 

demographic groups to the total number of people in those demographic groups nationwide. We 

stated in the proposed rule for the chromium source categories that in future rules we planned to 

extend the analyses to cover the entire modeled domain for a facility (50 km radius) to capture 

all individuals with risks above 1-in-1 million or greater or non-cancer hazard indices of 1 or 

greater. We also stated that generally we have found that using a 5 km radius in the analysis will 

capture more than 90 percent of the individuals with cancer risks above 1-in-1 million.

In the February 2012 supplemental proposal for the RTR for the chromium source 

categories, our demographic analyses included populations within 50 km of each source 

(including those very near the sources) with risks of 1-in-1 million or greater or non-cancer 

hazard indices of 1 or greater (77 FR 6628, Feb. 8, 2012). We did not include analyses using a 5 

km radius in that supplemental proposal nor in the RTR proposal for the Wool Fiberglass 

Manufacturing source category. We believe that, where a risk assessment has been performed, it 

is more informative to consider the demographics of all populations (including those beyond 5 

km) with elevated risks than to limit the demographics analysis to populations located within 5 

km of a facility. Where a risk assessment has been performed, these populations are identified, 

and the source parameters (like the low release height mentioned by the commenter) are taken 

into account. As discussed above, we have found that most exposure locations with the highest 

estimated risks are within 5 km of a facility, so extending the radius to 50 km has little impact on 

an analysis based on risks, but makes more sense because 50 km corresponds to the risk 

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modeling radius and includes all populations with elevated risk estimates. We also note that we 

are working with the Office of Environmental Justice in an ongoing effort to develop new tools 

for considering environmental justice in rulemakings. 

We did not perform a risk-based demographics analysis for the Mineral Wool Production 

source category because the population of individuals with risks greater than or equal to 1-in-1 

million is very small (12,000 individuals) and would not be sufficient to conduct a robust 

demographic analysis.

143. Comment: Two commenters (1042-0121 and 1042-0113) opined that the poverty 

statistics used by the EPA in its demographics analysis to identify low-income communities 

should be updated to include 2010 census data, rather than relying on older information, as 

number of people in poverty in 2010 is the largest number in the 52 years for which poverty 

estimates have been published.

Response: The risk-based demographics analysis for the Wool Fiberglass Manufacturing 

source category has been updated to use the 2010 census data. The memorandum “Risk and 

Technology Review—Analysis of Socio-Economic Factors for Populations Living Near Wool 

Fiberglass Facilities” dated March 23, 2015 summarizes the results and is available in the 

docket.

144. Comment: One commenter (1042-0121/1042-0299) requested that the EPA 

provide EJ outreach to affected communities including a plain-language statement of the health 

risks and benefits from the rule. The commenter (1042-0299) requested that this document 

include a statement and analysis of the supporting cost vs. emission reductions. The commenter 

(1042-0121) requested that this document include the types of harm to public health that the EPA 

proposes are “acceptable” or “unacceptable.”

Response: A plain-language statement of the health risks and benefits from this rule is 

provided in the preamble of this rule and more information is available in the docket. For 

information on supporting cost vs. emission reductions and EJ outreach activities, this 

information is also available in the docket. Regarding the comment that these outreach materials 

should include the types of harm to public health that the EPA proposes are “acceptable” or 

“unacceptable,” refer to section VI.A of the preamble to the final rule.

145. Comment: One commenter (1042-0081/1042-0299) opined that the EJ impacts of 

the wool fiberglass industry warrant stronger standards than proposed by the EPA in 2013. The 

commenter cited the socioeconomic analysis for the highest risk area in Kansas City, Kansas, 

which showed that although minorities comprise 25 percent of the population, they bear 41 

percent of the cancer risk above 1-in-1-million, and that African Americans comprise 12 percent 

of the national population compared to 30 percent of the population bearing the highest risk from 

the facilities in this area. 

The commenter added that EPA should consider that the baseline health status of 

Wyandotte County (which encompasses Kansas City, Kansas) is lower than the national average 

according the EPA’s EJ View Health Analysis. 

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The commenter also urged the EPA to do more than look at numbers for multiple source 

categories in a given location and actually use these data in its decision making process and 

reduce risk and health impacts to local communities beyond what is proposed. 

Response: As discussed in our response to comment number 142, where the agency finds 

risks to be acceptable, the EPA’s obligation under EO 12898 is to ensure that no group is subject 

to adverse impacts. Where we find those risks to be acceptable no further action is warranted.

Regarding the elevated chromium emissions that occurred in Kansas City, the EPA 

shares the commenters’ concerns about adverse health effects associated with indoor and outdoor 

air pollution. As further discussed in our response to comment number 152, the agency is 

committed to making environmental justice a priority. The agency has worked in the past with 

the northeast Kansas City, Kansas, neighborhoods on a number of issues, the EPA is committed 

to continuing the dialogue to help the community understand the rulemaking process for this rule 

and future rules, and provide meaningful comment in the process.

Regarding the comment that EPA should consider that the baseline health status of 

Wyandotte County is lower than the national average,” we are not able to determine the baseline 

health status of individuals or communities in a national rulemaking. Individual privacy issues as 

they relate to health records and the costs that would be associated with such an analysis make 

the analysis infeasible. Through the EPA’s interim guidance on EJ and the Action Development 

Process, the agency is encouraging rule writers and policy makers to look at the whole range of 

factors that impact communities and population groups when crafting rules. The EPA is 

continuing to discuss and pilot approaches that are consistent with the agency’s responsibilities 

regarding EJ as outlined in EO 12898. In determining the need for tighter residual risk standards, 

the EPA strives to limit to no higher than 100-in-1 million the estimated cancer risk for persons 

living near a plant if exposed to the maximum pollutant concentration for 70 years and to protect 

the greatest number of persons to an individual lifetime risk of no higher than 1-in-1 million. 

Considerations are made for all people regardless of racial or socioeconomic status, and the EPA 

does not believe it is necessary to establish a default factor to account for socioeconomic and 

other community-based stressors.

Regarding the risk caused by the Wool Fiberglass Manufacturing source category as a 

whole, we determined that the current health risks posed by emissions from the source category 

are acceptable, as discussed in refer to section VI.A of the preamble to the final rule; however, 

we have taken steps based on our AMOS analysis to ensure that these NESHAP reduce the risks 

posed by this industry. There are approximately 1,200,000 people nationwide that are currently 

subject to health risks that are non-negligible (i.e., cancer risks greater than 1-in-1 million) due to 

emissions from the Wool Fiberglass Manufacturing source category. We performed an analysis 

of the demographic makeup of these 1,200,000 people. The demographic distribution of this ‘‘atrisk’’ population is similar to the national distribution of demographics for all groups except for 

the ‘‘minority’’ group (defined as total population minus the white population), which is 16 

percent greater than its corresponding national percentage. See the Risk and Technology 

Review—Analysis of Socio-Economic Factors for Populations Living Near Wool Fiberglass 

Facilities dated March 23, 2015 in the docket for additional details on the demographic analysis.

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146. Comment: One commenter (1042-0299) advocated for the following additional 

measures due to environmental justice concerns, to assure compliance and protect the most 

exposed people:

• Immediate reporting to the public;

• Removal of the freedom of information (FOIA) request process, to allow prompt 

citizen enforcement of rule violations (including malfunctions); 

• Shorter compliance period (than the 1-year period proposed for wool fiberglass 

furnaces and the 3-year period for other sources of pollutants); 

• Public distribution of reports detailing each violation;

• Automatic shutoff of the malfunctioning equipment and associated process during the 

period of corrective action; and

• Measures to ensure a prompt and effective response by facility personnel to 

malfunctioning equipment.

Response: The EPA has evaluated the appropriate compliance assurance measures and 

the final rule includes measures that allow effective implementation of the NESHAP 

requirements, which are designed to protect the health of all populations. The compliance dates 

were selected considering the shortest amount of time that the affected sources need to achieve 

compliance. These requirements include reporting of any emissions exceedance, and 

requirements to promptly correct malfunctions. Information on exceedances and malfunctions is 

available to the public through the required reports which are required in a semiannual basis. 

Though the pollutants of concern are toxic, their effects are long term, not short term. In

situations where a release can result in an immediate public health effect, the EPA had developed 

a separate set of regulations under the authority of CAA section 112(r) that deal with 

requirements for immediate public notice. Additionally, the EPA’s enforcement office or the 

delegated state, local or tribal office will be investigating violations of the emissions limits

established in this rulemaking and will assesses penalties where appropriate. These penalties 

serve to encourage sources to minimize these exceedances by promptly responding to 

malfunctions and other types of exceedances.

147. Comment: Three commenters (1042-0115a; 0115(d); 0115(f)) stated that it 

appears that EPA knew about the high levels of hexavalent chromium emitted by CertainTeed in 

Kansas City, Kansas, but did not inform the community affected by those emissions. The 

commenters asked the EPA to explain why the community was not informed immediately after 

CertainTeed testing was conducted. 

Response: After the initial tests were conducted, follow up analyses were conducted to 

verify the accuracy of the results, after which community, stakeholders, and industry 

representatives were informed. EPA Region 7 conducted the monitoring to determine if the 

emissions posed health concerns for local residents. When Region 7 informed the public of the 

ambient air monitors at the local park, the CertainTeed facility in Kansas City idled (stopped 

production but did not shut down) the K2 high emitting furnace. 

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148. Comment: Four commenters (1042-0299; 1042-0300; 1042-0115f; and 1042-

0115k) expressed concern that the air monitoring conducted in Kansas City by EPA Region 7 

was inadequate. Two commenters (1042-0115f and 1042-0299) requested that the EPA extend 

the monitoring program in Garland Park. One commenter (1042-0115f) urged the EPA to extend 

the monitoring program to at least six months after CertainTeed's K2 furnace returns to service, 

as a matter of fairness and considering that the risk falls disproportionately on minorities and 

people who are economically disadvantaged. One commenter (1042-0299) requested the EPA to 

restart the monitoring program in this area for at least a year to inform compliance and ensure the 

rule’s effectiveness at reducing chromium emissions. One commenter (1042-0115f) pointed out 

that the six months of monitoring at Garland Park planned following the 2011 proposal was not 

sufficient because it would capture no emissions at all from the K2 furnace because the furnace 

was shut down due to unfavorable economic conditions, and thus the testing would greatly 

underestimate the risk that would occur when K2 starts up again. Another commenter (1042-

0115k) added that the EPA has gone through a lot of expense to install the air monitoring 

equipment in Garland Park. The commenter questioned whether there is adequate, ongoing 

monitoring of pollutants coming from the Fairfax industrial plants. The commenter also stated 

that the agency should conduct air quality monitoring similar to that done in Garland Park (just 

south of CertainTeed’s K2 plant) each time it proposes RTR rules. 

Response: We continue to believe that the risk modeling performed as part of the 

residual risk assessment is sufficient to determine the risks to potentially exposed populations. 

These risk assessments give a better long-term analysis of the risks as opposed to ambient 

modeling which would be a short-term snapshot of ambient levels of HAP. As a result, 

performing monitoring each time EPA proposed an RTR would simply result in a huge 

expenditure of resources for no real benefit. The other comments specifically relating to Kansas 

City are beyond the scope of this rulemaking.

149. Comment: One commenter (1042-0115k) requested clarification as to whether the 

testing conducted by CertainTeed in November 2011 was of the same merit as the testing 

conducted in September 2011 and whether the EPA considered both tests valid. The commenter 

also asked if the furnace allegedly retired by CertainTeed for 2013 was still in place at the 

facility, and if so, why? Further, the commenter asked what the penalties will be for not meeting 

the established standards when they are promulgated. 

Response: Regarding the quality of the testing, EPA Region 7 conducted the monitoring 

to determine if the emissions in Garland Park posed health concerns for local residents. After the 

initial tests were conducted, follow up analyses were conducted to verify the accuracy of the 

results, after which community, stakeholders, and industry representatives were informed. 

CertainTeed provided actual production data for both K1 and K2 furnaces located at its Kansas 

City, Kansas facility, as well as emissions testing data for the K2 furnace and from its collection 

and cooling processes on bonded lines. We have not made a comparison between these 

production data and the Region 7 monitoring data, which was initiated in December 2007. This 

is because the monitoring conducted by Region 7 was not for purposes of the risk and technology 

review for the Wool Fiberglass Manufacturing NESHAP.

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Regarding the status of the K2 furnace, that furnace was idled for several years before the 

company shut it down. CertainTeed is in the process of rebuilding the K2 furnace. The rebuilt 

furnace has not at this writing been permitted.

Regarding the penalties for not meeting the established standards, establishment of such 

penalties is outside of the scope of this rulemaking.

150. Comment: One commenter (1042-0075/1042-0117) asked if the EPA had 

collected data on CertainTeed’s production rates during the months preceding the December 

(2011) monitoring at John Garland Park. According to the commenter, such data would be used 

to determine if a comparison can be made between production rates and the monitoring and 

sampling data. 

Response: The EPA did not collect production rate data over the December 2011 

monitoring period.

151. Comment: There were several comments related to issues involving the local 

community in Kansas City, Kansas where two wool fiberglass manufacturing facilities are 

located. These local community issues have been consolidated and grouped under this comment; 

the following paragraphs summarize specific issues raised by the commenters:

1. One commenter (1042-0115a) stated that over 70 percent of African Americans live 

in counties in violation of the federal air pollution standards and that in every one of 

the 44 major metropolitan areas in the U.S., African Americans are more likely than 

whites to be exposed to a higher level of air toxic contamination. The commenter 

theorized that as a result of air toxics concentrations within predominantly African 

American communities, African Americans are nearly three times as likely to be 

hospitalized or killed. The commenter stated that emissions of air pollutants include 

lead, which has been tied to educational and behavioral challenges thereby impacting 

the learning opportunities for children of color and potentially contributing to the 

‘school-to- prison’ pipe line. The commenter added that air pollutants include 

mercury, which has been tied to negative birth outcomes in African American 

families already suffering from high rates of low birth weight and infant mortality.

The commenter added that the presence of toxic facilities in the Kansas City, Kansas 

communities have negative effects on property values, thereby negatively impacting 

the economic well-being and wealth development potential within the communities of 

color which disproportionately host facilities that emit pollution. The commenter 

stated that multiple policy initiatives have been introduced in Congress to defund, that 

is, to lessen the power of the CAA as well as to significantly reduce the authority of 

the EPA, which is tasked with monitoring and regulating pollution and other harms in 

the air that we breathe, the water we drink and the land on which we live.

The commenter noted its support for the CAA as a critical bedrock policy for the 

protection of the environment and the human health and well-being and stated that the 

NAACP will put the power and resources of the association's unit and members 

behind protecting and defending environmental policies designed to provide 

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safeguards to assure that all communities are breathing clean air, ingesting clean 

water and living and thriving on safe lands.

2. One commenter (1042-0115b) stated that as a provider of medical services in the 

neighborhood, she is very interested in the health of our community. The commenter 

asked the EPA to provide strong oversight on emissions from all manufacturing in the 

commenter’s geographic area. The commenter stated that history shows that lack of 

strong oversight often reflects harm to those who reside nearby when toxic chemicals 

are released without treatment.

3. One commenter (1042-01115c) described the air quality in the Kansas City, Kansas 

area as terrible and the cause of various health problems, including respiratory and 

pulmonary effects. The commenter further stated that she was having problems with 

her oxygen. The commenter stated that she wants EPA to take corrective action in the 

Kansas City, Kansas area to lower emissions of air toxics and other pollutants 

contributing to adverse health effects so people living in her neighborhood can have 

the same opportunity as anybody else.

4. One commenter (1042-0115d) stated that when the Kansas Health Institute in 2009 

ranked the 105 counties of Kansas as related to their health, Wyandotte County was 

ranked 105th, the last of all the counties, the lowest-rated county in the State of 

Kansas. The commenter observed that physical environment was listed as one of the 

poor health determents. Quoting from the report, the commenter stated that the 

physical environment determines the daily condition in which we live, these 

conditions, the quality of air we breathe and the water we drink among them, 

significantly affect our health.

The commenter stated he has lived in the northeast area of Kansas City, Kansas for 63 

years and he sees the smoke that comes from many of the plants in the Fairfax area of 

Kansas City, and he wonders how this is affecting his health and the health of the 

children in the area. The commenter stressed that the agency should set stronger 

standards that take into account the vulnerability of children. The commenter stated 

that the citizens who live closest to Fairfax are probably the most vulnerable persons 

in Wyandotte County. The commenter added that he must depend on agencies like the 

EPA to provide the proper controls to see that the residents of Fairfax receive the best 

protection.

The commenter added that the air quality of the Fairfax district fluctuates and that 

some days are worse than others in terms of health impacts associated with that air 

quality. The commenter requested some type of mask be made available to citizens 

for days during which poor air quality is present for persons with special pulmonary 

and/or respiratory needs due to poor air quality.

The commenter continued that it is important for the EPA to learn about the 

communities which may be more affected by air and water pollution. The commenter 

added that communication between EPA and the local community should be 

improved to form a dialogue (between EPA and the community) instead of only a 

monologue from EPA without opportunity for feedback. 

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The commenter was concerned about the toxicity of a local lake and whether it was 

safe to eat the fish from that lake. The commenter continued that although testing of 

the waters is now going on, subsistence fishing is practiced in the community and the 

community has queried EPA for a determination on whether or not it was safe for 

persons to consume fish from the lake based on their reports, but the EPA has not 

provided a definitive answer as to whether or not it is safe to eat the fish. 

5. One commenter (1042-0115e) stated that John Garland Park was a local ‘dump’ that 

was later repurposed as a landfill, permitted by EPA to be sited in the Quindaro 

township, a predominantly minority and low-income community. The commenter 

recalled that the EPA established the landfill and the clay cap for later use as a 

playground or low-income housing project because it was eventually deemed 

reasonably safe for residential use. The commenter also stated that as a longtime 

resident of Kansas City, Kansas in the vicinity of John Garland Park, she has 

experienced air pollution continually released from the John Garland Park landfill, 

and believes the landfill emissions are negatively affecting the health of persons in 

the community. 

The commenter asserted that it is unfair for the U.S. Government to work against the 

health and welfare of low-income people. The commenter added that she does not 

have much faith in government because government work is counter-productive to 

the good will of people who are less well off than others. 

6. One commenter (1042-0115f) recommended that the EPA should minimize the use of 

surrogates in all related industries. 

7. The commenter (1042-0115f) stated that EPA needs to confirm whether and when the 

wool fiberglass facilities in Kansas City, Kansas (Owens Corning and CertainTeed) 

ceased using formaldehyde in their binder ingredients, and determine if this is a 

permanent change. The commenter added that this is important because of the 

concentration of facilities in Kansas City, Kansas and the fact that formaldehyde is 

one of the risk drivers. 

8. The commenter 1042-0115g stated that she works with North East KCK Healthy Kids 

developing projects that increase physical fitness and decrease factors of childhood 

obesity. The commenter explained the relationship between physical activity, 

increased inhalation depth and frequency and reduction in childhood obesity. The 

commenter also attended three-day EPA training on “interior combatants”, which she 

described as what is dangerous in the home. The commenter explained that increased 

inhalation during physical activity exposes young people and children to additional 

risk from inhalation of toxic pollutants, including PM, formaldehyde and hexavalent 

chromium from wool fiberglass manufacturing and pollutants from many other 

industries in the area. The commenter is personally aware of children in the 

community that have started to develop different types of diseases: asthma, diabetes, 

childhood obesity, among others. The commenter suggested plant closings, an 

enclosed playground or similar activity center that could allow children to participate 

in prolonged and strenuous physical activity without the added inhalation risk from 

air toxics. 

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9. One commenter (1042-0115h) stated that when former president Bill Clinton signed 

the Executive Order for Environmental Justice, the commenter was led to believe that 

this was a great moment in time, but it now seems that the Environmental Justice 

Executive Order is without a spine. The commenter asserted that there were no 

regulatory tools or teeth or mandates to be enforce reductions in pollution. The 

commenter observed only industry-friendly provisions of the Executive Order for 

Environmental Justice are exercised. The commenter observed huge environmental 

inequities remain in the area. The commenter noted examples including the toxic 

waste sites in the northeast area of Wyandotte County, and stated that many people 

are becoming sick with asthma, respiratory cancers, and pancreatic cancer from the 

exposures to air toxics and other pollution. The commenter added that others are 

turning to drugs such as crack cocaine because it helps users to breathe and acts as an 

antidepressant.

Two commenters (1041-076; 1042-0115h) opined that the EPA should put in place a 

more effective and efficient method of communicating with the affected communities 

in order to ensure excellence in the exchange of relevant, meaningful and timely 

information. One commenter (1042-0115h) requested that the EPA take the following 

steps to make information available for the population of the Fairfax area of Kansas 

City, Kansas:

• make information available online and in other formats so that active community 

members are able to disburse that amongst the community;

• make relevant information available in a user friendly context online and in a 

format that is easily understood by the general public (i.e., the non-technical 

reader);

• provide plain language community outreach tools; 

• provide contact phone numbers and email addresses to get additional information.

10. One commenter (1042-0115i) stated that he served on the committee to help refurbish 

John Garland Park, which is a landfill in this area. The commenter observed that it 

seems like a cloud of toxic smoke is coming out of the area, and added that on a clear 

day, it is easily seen. The commenter added that several studies on the John Garland 

Park project have been undertaken but no real risk assessment of the landfill has been 

done. The commenter added that many individuals experienced pulmonary health 

effects and have died from unknown causes. 

The commenter stated that this (residual risk) assessment should have been done a 

long time ago and added that it still seems like there are health impacts to residents 

from the poor air quality of the Fairfax district. 

The commenter stated that a relative living in the Fairfax district wears a paper air 

mask to alleviate breathing problems caused by the poor air quality, and added that 

the two fiberglass plants and the medical waste incinerator are releasing emissions to 

the air, and contributing to the area’s air toxics. The commenter stated that from his 

front porch he has a perfect view of downtown Kansas City, Missouri and a perfect 

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view of the Fairfax industrial area and visually observes emissions from these sources 

as they are released into the ambient air. 

11. One commenter (1042-0115k) stated that she is the President of the Oak Grove 

Neighborhood Association. The commenter noted that the Oak Grove Neighborhood 

is the most northeast situated neighborhood in Wyandotte County. The commenter 

noted that this is the area impacted by the John Garland Park, the Fairfax industrial 

complex, coal-fired plants, the medical waste incinerator and the two wool fiberglass 

manufacturing facilities.

The commenter added that she is speaking on behalf of her neighborhood on the 

subject of environmental justice. The commenter asked EPA to relay pertinent 

information in a more timely manner to the community so that residents have an 

opportunity to get educated about the subject matter and can have meaningful 

participation. Specifically, the commenter asked that Region 7 take an opportunity to 

make all information available to the community; notify residents of information in 

the local paper, put it on the internet, and give all interested persons the opportunity 

to understand the risk assessment and impacts to the local area. 

The commenter added that despite the fact that hexavalent chromium is a carcinogen 

she doesn’t know anyone who would say let’s shut down Fairfax, let’s shut down 

Owens Corning, let’s shut down everything, because everyone needs jobs and 

opportunities. However, the commenter added that she would be a proponent or 

advocate to shut down the industries if they cannot, and will not, produce their goods 

and services in a clean and environmentally conscientious manner. 

The commenter added that the EPA has the muscle to be able to monitor and enforce 

rules and regulations. The commenter observed that the industry would itself have onsite, and as part of their payroll, the chemists and scientists and whatever else is 

needed in order to produce a safe product, and that they should have on site anyone 

and everyone that is needed to ensure the hexavalent chromium from their 

manufacturing process does not escape and cause possible harm.

The commenter (1042-0115k) asked if the CertainTeed furnace allegedly retired by 

CertainTeed for 2013 was still in place, and if so, what is the cost effectiveness of 

that? What are we looking to determine, to gain from that? 

The commenter asked the EPA to do the following: 

• to hold a meeting as soon as possible to review the technicalities in this new rule; 

• give people an opportunity to give considerable thought and logical input; 

• address specific questions including: 

- Does EPA know and ensure that this wool fiberglass industry in Fairfax has a 

process for which to identify and report all the pollutant being emitted? 

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- Does EPA have in place something to determine how long the hexavalent 

chromium was emitted prior to being reported in November of 2010? And if 

not, then why? 

- Does EPA have a method of knowing if the hexavalent chromium has been 

found in here, by, near – by any soils or water samples? 

- Does EPA know at what point in time the production process emits the most 

pollutants? 

- Does EPA know the short and long-term risks of the pollutants on our 

children and adults and the elderly? 

- Does the EPA have an obligation to indirectly use its influence to correct 

environmental justice inequities?

12. Another commenter (1042-0115k) raised the issue of other sources of air toxics and 

particulate matter, sulfur dioxide and nitrogen oxides the coal-fired plant that are 

added with the hexavalent chromium, the methane coming from the John Garland 

Park and whatever is emitted from the medical waste incinerator that are mixing in 

the air. 

13. The commenter (1042-0115k) wanted EPA to consider whether or not the Oak Grove 

community and the northeast area neighborhoods, which are predominantly minority 

communities, have really been the subject over time of environmental injustice. The 

commenter explained that environment injustice is one component of a system of 

external forces, including laws, rules and regulations that have been in place since 

there was slavery in the U.S. The commenter further stated that when people who 

looked like her were denied certain opportunities, education opportunities, housing 

opportunities and so forth and so on. The commenter continued that during the '50s 

and in the '60s and in the '70s there was an ushering in of all kinds of rules and new 

laws purported to correct the errors of slavery, but these laws and rules and 

regulations not necessarily did the right thing, and acted not to improve, but to keep 

the same level of low income, the same level of low attainment and the same level of 

low quality of life. It is the commenter’s opinion that, as a result, there has been no 

improvement in the Oak Grove community from 1995 until now. 

The commenter accessed a website with information regarding the Federal 

Interagency Working on Environmental Justice, which includes not only the EPA, but 

also HUD, the Department of Labor, the Department of Energy, and the Department 

of Transportation. The commenter added that all Federal Agencies are supposed to 

address environmental justice in their rules and regulations to make sure that 

communities don't turn into communities like hers; and specify corrective action 

under which communities like hers can be improved under the Environmental Justice 

rules and regulations. To that end, the commenter requested the EPA to use its 

influence to improve and correct environmental injustice issues in the Oak Grove and 

the Northeast neighborhood communities. Specifically, the commenter asked the EPA 

to secure funding and other resources needed to educate the community and improve 

the lives of residents through communication, an information exchange and a virtual 

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call center. The commenter also suggested the following supplemental environmental 

projects (SEP) projects: 

• A tilapia fishery;

• Investment in the Parkwood Learn to Earn, for youth ages 12 to 14; 

• A youth camp; and 

• A curb and sidewalk program to train youth and adults how to construct and pour 

sidewalks and curbs 

Response: The EPA shares the commenters’ concerns about adverse health effects 

associated with indoor and outdoor air pollution. The agency is committed to making 

environmental justice a priority. The agency has worked in the past with the northeast Kansas 

City, Kansas, neighborhoods on a number of issues, some of which have been raised in 

comments on this proposed rule. The EPA is committed to continuing the dialogue to help the 

community understand the rulemaking process for this rule and future rules, and provide 

meaningful comment in the process. The final rule requirements are based on all data collected 

during the project and those requirements apply to all major sources located in the U.S.

We agree that is critically important to provide sufficient information so that affected 

communities have a meaningful opportunity to participate in EPA rulemakings. In order to 

disseminate information to the public the agency works with state and local agencies, regional 

offices and community-based partners. Additionally, the agency continues to think of and pilot 

new ways to disseminate information to the public.

The Wool Fiberglass rulemaking seeks to minimize adverse health effects by decreasing 

emissions associated the hazardous air pollutants emitted from this industry. Furthermore, the 

EPA has met with various community stakeholders to listen to their environmental justice and 

other concerns and is involved in an ongoing process with these stakeholders. The issues raised 

in these comments address source categories that are outside the scope of this rulemaking. 

However, meetings with stakeholders and the development of actions to address the 

community’s environmental justice concerns are ongoing as part of the local community 

stakeholder process.

As explained in the preamble to the final rule, we are promulgating requirements under 

CAA section 112(f)(2) for the Wool Fiberglass Manufacturing source category. These standards 

will result in reductions of chromium compound emissions, compared to the 2010 baseline 

estimates. We are also promulgating standards for formaldehyde, methanol and phenol because 

the 1999 standard was based on an illegal MACT floor calculation as well as served an illegal 

surrogate. We will address reductions in formaldehyde, phenol, and methanol emissions from RS 

lines in a separate rulemaking. Detailed documentation of the analysis can be found in: Cost 

Impacts of the Revised NESHAP for the Wool Fiberglass Manufacturing Source Category (see 

docket EPA-HQ-OAR-2010-1042). Further, we have determined that the current health risks 

posed to anyone by emissions from this source category are acceptable. Because there are about 

1,200,000 people nationwide that are currently subject to health risks which are non-negligible 

(i.e., cancer risks greater than 1-in-1 million) due to emissions from this source category, we 

have performed an analysis of the demographic makeup of these 1,200,000 people. See section 

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VIII.F of the preamble to the final rule and the Risk and Technology Review – Analysis of 

Socio-Economic Factors for Populations Living near Wool Fiberglass Facilities (dated March 23, 

2015) in the docket for additional details on the demographic analysis.

152. Comment: One commenter (1042-0115f) added that it is critical that the EPA 

follow through on their intention to regulate area sources in this category because the elimination 

of formaldehyde emissions may allow a plant to become technically a minor source while still 

posing a serious risk from highly dangerous pollutants like hexavalent chromium. The 

commenter also urged the EPA to set the strongest chromium limits and to set robust limits on all 

other toxic air pollutants to insure that the Kansas City community receives the required ample 

level of health protection. One commenter (1042-0121) strongly supported the EPA’s 

announcement of plans to regulate wool fiberglass area sources in a future action. According to 

the commenter, the EPA appropriately recognizes that local communities near wool fiberglass 

facilities need protection from high chromium emissions, and urged the EPA to promulgate 

requirements that should also ensure full protection for the most exposed people near these 

facilities from all HAP and other high risks, including acute health risk. The commenter urged 

the EPA to propose this rule as soon as possible during 2012, without delay.

Response: Regarding the comments on area sources, the EPA is finalizing standards for 

area sources. Regarding the comment on chromium limits, the EPA is finalizing chromium 

standard for this source category to provide an ample margin of safety, as discussed in the 

preamble to the final action. 

153. Comment: One commenter (1041-0076) stated that, because the EPA (along with 

other federal agencies) is charged with affecting environmental justice for all and because an 

ecological balance is a desired outcome of a sustainable community, the EPA should exercise 

due diligence in strongly encouraging and promoting resource partnerships (along the lines of 

SEPs (Supplemental Environmental Projects)) that will significantly accelerate the rate at which 

the affected community sustainably heals from the wounds inflicted by HAP producing decisions 

and processes.

Response: The agency agrees with the commenter and supports partnerships across 

multiple stakeholders. In the case of this specific rule, the EPA regional offices, in particular 

Region 7 has provided technical support as a means to assist collaboration between communitybased organizations and governmental entities. Additionally, the agency also recommends that 

public work with their regional EPA office and local and state departments of health and 

environmental quality to devise a community involvement strategy to address local air pollution 

health issues.

154. Comment: One commenter (1041-0080/1042-0120) stated that while the EPA 

reasonably interprets the term “public health” as used in CAA section 112(f) to include 

consideration not only of potential impacts to the population as a whole, but also to sensitive 

subpopulations, those populations should be identified according to their particular health-based 

sensitivities (e.g., asthmatics) rather than demographic classifications unrelated to particular 

health-based sensitivities (e.g., population without a high school diploma). In the commenter’s 

opinion, injecting “environmental justice” considerations into CAA section 112(f) standard 

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setting would inappropriately cause arbitrary policy and political considerations to trump 

objective scientific analysis and would not be a supportable interpretation of CAA section 112(f).

Two commenters (1041-0080/1042-0120 and 1042-0118) asserted that the EPA does not 

have authority to consider demographics in conducting residual risk assessments. The 

commenters stated that it would not be reasonable to construe the term “public health” as used in 

CAA section 112(f) as allowing consideration of demographic classifications that bear no 

relationship to the potential health effects presented by the HAP at issue for the given source 

category or subcategory. The commenters added that the EPA’s proposal would unreasonably 

inject racial, ethnic, and other policy considerations into a program designed to provide 

protection for the public at large, thus inappropriately causing arbitrary policy and political 

considerations to trump objective scientific analysis.

Response: Through the EPA’s interim guidance on Environmental Justice and the Action 

Development Process, the agency is encouraging rule writers and policy makers to look at the 

whole range of factors that impact communities and population groups when crafting rules. The 

EPA is continuing to discuss and pilot approaches that are consistent with the agency’s 

responsibilities regarding environmental justice as outlined in EO 12898. In determining the 

need for tighter residual risk standards, the EPA strives to limit to no higher than 100-in-1 

million the estimated cancer risk for persons living near a plant if exposed to the maximum 

pollutant concentration for 70 years and to protect the greatest number of persons to an 

individual lifetime risk of no higher than 1-in-1 million. Considerations are made for all people 

regardless of racial or socioeconomic status, and the EPA does not believe it is necessary to 

establish a default factor to account for socioeconomic and other community-based stressors. 

The EPA defines “environmental justice” to mean fair treatment and meaningful involvement of 

all people, and this definition represents a commitment to ensuring that the EPA works to 

improve conditions affecting the public health of all Americans so that everyone has access to 

clean water, clean air, and healthy communities.

As stated in the Benzene NESHAP ((54 FR 38044, 38061, September 14, 1989), in 

determining the need for residual risk standards, we strive to limit to no higher than 

approximately 1-in-10 thousand (100-in-1 million) the estimated cancer risk that a person living 

near a plant would have if he or she were exposed to the maximum pollutant concentrations for 

70 years and, in the AMOS decision, to protect the greatest number of persons possible to an 

individual lifetime risk level of no higher than approximately 1-in-1 million. These 

considerations are made for all people, regardless of racial or socioeconomic status. However, in 

determining whether to require additional standards under the second step of the Benzene 

analyses, we are allowed to weigh the cancer risk value with series of other health measures and 

factors such as control costs and demographic analyses. This is consistent with the position 

presented in the Residual Risk Report to Congress where we explained that the Agency typically 

uses population and demographic data that are based on the census block level in its air toxic 

exposure assessments. (p. 42). As previously explained, section 112(f)(2) of the CAA expressly 

preserves our use of the two-step process for developing standards to address residual risk and 

interpret “acceptable risk” and “ample margin of safety” as developed in the Benzene NESHAP 

(54 FR 38044, September 14, 1989). And the U.S. Court of Appeals for the D.C. Circuit has 

affirmed this approach of implementing CAA section 112(f)(2)(A): NRDC v. EPA, 529 F.3d 

1077, 1083 (D.C. Cir. 2008).

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As explained at proposal and in various responses to comments in this document, we 

conducted a risk-based demographic analysis for the Wool Fiberglass Manufacturing source 

category as part of the risk assessment. We determined that the current health risks posed by 

emissions from the source category are acceptable for all population groups. However, because 

there are about 1.2 million people nationwide that are currently subject to health risks which are 

non-negligible (i.e., cancer risks greater than 1-in-1 million) due to emissions from this source 

category, we performed an analysis of the demographic makeup of these 1.2 million people. The 

demographic distribution of this ‘‘at-risk’’ population is similar to the national distribution of 

demographics for all groups except for the ‘‘minority’’ group (defined as total population minus 

the white population), which is 16 percent greater than its corresponding national percentage. 

See the document titled “Risk and Technology Review—Analysis of Socio-Economic Factors 

for Populations Living Near Wool Fiberglass Facilities” dated March 23, 2015 in the docket for 

additional details on the demographic analysis. In summary, while we analyzed the demographic 

makeup of the at-risk populations surrounding the facilities with source categories addressed by 

this rule making, we ultimately reaffirm our initial findings that the risks from each source 

category are acceptable for all population groups and protect public health with an ample margin 

of safety.

Regarding the comment that the EPA does not have authority to consider demographics 

in conducting residual risk assessments, we note that in this rulemaking the risk considerations 

were made for all people regardless of racial or socioeconomic status. Therefore this comment is 

moot. However, because there are about 849,000 people nationwide that are currently subject to 

health risks which are non-negligible (i.e., cancer risks greater than 1-in-1 million) due to 

emissions from this source category, we performed an analysis of the demographic makeup of 

these 849,000 people. The demographic distribution of this ‘‘at-risk’’ population is similar to the 

national distribution of demographics for all groups except for the ‘‘minority’’ group (defined as 

total population minus the white population), which is 11 percent greater than its corresponding 

national percentage. See the Risk and Technology Review—Analysis of Socio-Economic Factors 

for Populations Living Near Wool Fiberglass Facilities in the docket for additional details on the 

demographic analysis. 76 FR 72807. In sum, while we analyzed the demographic makeup of the 

at-risk populations surrounding the facilities with source categories addressed by this rule 

making, we ultimately reaffirm our initial findings that the risks from each source category are 

acceptable and protect public health with an ample margin of safety.

9. Miscellaneous

155. Comment: One commenter (1042-0348) requested that the EPA modify those 

instances in the 2014 proposal where furnace rebuilds are characterized as reconstruction, 

explaining that fiber glass furnaces are “rebuilt,” not “reconstructed,” which has a very specific 

meaning in 40 C.F.R. section 63.2.

Response: There is only one instance in the 2014 proposal where “reconstruction” was 

used in place of “rebuild” in the preamble, and there were no instances in the rule. In the final 

proposal, the EPA does not confuse these terms.

156. Comment: One commenter (1041-0075/1042-0117) asked if CertainTeed would 

be required to utilize the less toxic type of refractory bricks in its glass-melting furnaces.

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Response: We are not imposing requirements on the kind of bricks to be used in glassmelting furnaces as part of the final rule. As explained in section VI.B of the preamble to the 

final rule, we are promulgating a limit of 2.5E-04 lb chromium compounds per ton of glass 

pulled for both existing and new furnaces. The final rule does not specify the actions owners or 

operators must take to comply with this limit. 

157. Comment: Two commenters (1042-0115j and 1042-0120) stated that wool 

fiberglass industry provides significant environmental benefits and is proud of the public health 

and environmental benefits realized by the use of fiber glass insulation products. The 

commenters emphasized that their products save energy and prevent pollution, including GHG, 

and reduce waste by the industry’s reuse of waste materials. One commenter (1042-0115j) also 

noted other benefits of insulation, such as its cost effectiveness in saving energy, comfortable 

buildings, and health benefits. 

One commenter (1042-0115j) noted that the wool fiberglass industry is a strong advocate 

for responsible product stewardship, citing the voluntarily reformulation to non-PF binders and 

that the entire industry will have phased out PF binders within the next couple of years. The 

commenter added that research conducted by the International Agency for Research on Cancer, 

the National Toxicology Program and the California Office of Environmental Health, has 

resulted in a determination that wool fiberglass is not a carcinogen. 

Response: The agency acknowledges the comment.

158. Comment: One commenter (1042-0108) stated that the government is going to 

enact a new law that would not allow people 16 and younger to work. According to the 

commenter, horse owners would be unable to take care of them. The commenter further stated if 

the government were to pass this law, people could not participate in 4-H, an organization that 

works with youths. As a result, many would have spare time which they would use in nonproductive ways and therefore the government would have created more problems than 

solutions. The commenter requested that the government please take this into consideration. 

Response: This comment is beyond the scope of this rulemaking.

159. Comment: One commenter (1042-0115f) requested that the EPA confirm whether 

the Owens Corning and CertainTeed facilities in Kansas City, Kansas have ceased using PF

binders, and if not, when and whether this is a permanent change. The commenter stated that this 

is important because of the concentration of facilities in Kansas City, Kansas and the fact that 

formaldehyde is one of the risk drivers. 

Response: We are not requiring that any wool fiberglass facilities cease using PF 

binders. Facilities that use PF binders are subject to the major source standards being finalized. 

Facilities that do not use PF binders are subject to the area source standards being finalized.

160. Comment: One commenter (1042-0120) stated that sources in the wool fiberglass 

source category do not emit COS in response to preamble language (at page 72791) that stated 

“We are proposing to replace CO as a surrogate for COS with COS emission limits. We are, 

therefore proposing to add emission limits for COS.” The commenter requested that this text 

should be deleted. 

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Response: We agree and have revised the final rule text accordingly.

161. Comment: One commenter (1042-0120) stated that the emissions inventory data 

the EPA used for modeling risks contained several inaccuracies. Specifically, the commenter 

stated that several sources are incorrectly described as having FA lines when in fact they have 

RS lines. According to the commenter some manufacturing lines at the OCIS Eloy, Kansas City, 

and Santa Clara facilities are described with an SCC code for flame attenuation lines. The 

commenter suggested that the SCC codes and descriptions should be updated to denote the 

correct status of the manufacturing lines. The commenter recommended that the EPA should 

check the coding for all fiber glass facilities for accuracy. The commenter asked that the EPA 

also check to be sure that similar misclassifications did not occur with respect to the 

manufacturing facilities in other analyses performed by the EPA for rulemaking purposes.

Response: We have noted and verified the commenter’s information and made the 

appropriate changes to the project data base and modeling file. 

162. Comment: One commenter (1042-0120) formally requested that the EPA provide 

a second public comment period, which would allow sufficient time, such as 60 days, to review a 

revised proposal. As these comments illustrate, the commenter asserted, there are issues that the 

EPA has yet to resolve as to the legal viability of the 2011 proposed rule and that will impact the 

ability of the wool fiberglass manufacturers to conduct business. Specifically, the commenter 

listed the following: (1) the EPA’s collection and consideration of data not available during the 

public comment period, especially the latest data from the CAA section 114 information request; 

(2) the EPA’s use of non-PF emissions data, use of below the minimum detection limit data and 

use of data from area sources to set the MACT floor; (3) the EPA’s representation that all 

companies could meet the proposed emission limits, when in reality the majority of fiber glass 

manufacturers cannot meet, at a minimum, the proposed PM, HF, HCl, formaldehyde, phenol, 

and methanol limits; (4) improper consideration of the facts surrounding hexavalent chromium 

emissions due to a rush to issue the 2011 proposal; and (5) various other concerns articulated in 

its comments. 

Response: The commenter provided comment during the comment period, provided 

comment after the close of the comment period, and initiated several meetings with the EPA to 

discuss the issues mentioned above. We addressed these and other comments in our 

supplemental proposal on April 15, 2013. Our responses to comments received on the 

supplemental proposal are included in this document. 

163. Comment: One commenter (1042-0300/1042-0348) opined that the health and 

environmental benefits of their manufactured product (i.e., use of waste glass as a raw material, 

cost effectiveness of energy efficiency achieved as a result of insulation use, and pollution 

prevention achieved through energy efficiency) should factor more significantly into EPA’s costeffectiveness value. 

Response: We note that the CAA does not mandate a specific method of cost analysis. 

However, the factors cited by the commenter are beyond the scope of the types of cost analyses 

that EPA typically performs to support rulemaking under the CAA. The EPA believes that in 

order to promote consistency in the types of economic burdens we impose on regulated 

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industries, we should use a consistent set of criteria to determine costs and benefits. In addition, 

the commenter did not provide data that the EPA could use to include the cited product benefits 

in our cost analysis.

C. Issues Related to Area Sources Only 

1. EPA Decision and Authority to Regulate Area Sources

164. Comment: One commenter (1042-0120/1042-0300/1042-0348) contended that, 

because chromium emissions do not exceed 10 tons per year from any one facility, a MACT 

standard for chromium is not appropriate for area sources. 

Response: The EPA in finalizing a GACT standard for gas-fired glass-melting furnaces 

located at wool fiberglass manufacturing facilities that are area sources, not a MACT standard. 

Section 112(a) of the CAA defines major sources as those that have the potential to emit at least 

10 tons of HAP per year or 25 tons of any combination of HAP per year. The requirement to 

adopt MACT standards applies to each category or subcategory of major sources of HAP, under 

CAA section 112(d)(1). For sources below the major source threshold, the EPA has the 

discretion to require GACT under CAA section 112(d)(5). Only major sources are subject to a 

MACT standard under 40 CFR part 63, subpart NNN, and area sources producing wool 

fiberglass are subject to a GACT standard in 40 CFR part 63, subpart NN. Refer to the EPA’s 

response to comment number 167 for further discussion of the EPA’s decision to establish a 

GACT standard for chromium emissions from gas-fired furnaces at area sources.

165. Comment: One commenter (1042-0120) noted that the EPA has recognized that 

the majority of wool fiber glass manufacturing is no longer subject to the MACT standard, yet 

the EPA has allowed a single facility’s test results in an oxyfuel furnace showing elevated 

hexavalent chromium emissions to trigger pulling the entire industry back into the MACT or area 

source standards. The commenter stated that this decision ignores the significant – near 

elimination – reduction of the only specific HAP regulated under the Wool Fiberglass MACT 

and would bring all the wool fiber glass facilities back under the MACT when virtually all 

facilities’ testing showed very low hexavalent chromium emissions. 

Response: We disagree with this comment. As explained in our April 2013 proposal and 

further discussed in section VII.A.3 of the preamble to the final rule, we issued a CAA section 

114 ICR in December 2012 requesting test data on total chromium compounds emissions from 

all glass-melting furnaces and we were able to confirm our view of chromium emissions from 

this source prior to our April 2013 proposal. In our November 2014 proposal, we also explained 

that as part of the data collection effort associated with this rulemaking, we collected source test 

data on 14 furnaces with information on furnace age, last rebricking or repair dates, current 

furnace age, and anticipated or planned future furnace replacement. We also explained that we 

had obtained repeat testing for three rebuilt gas-fired glass-melting furnaces. We further 

explained that of the 14 tested furnaces, all four furnaces over 12 years old exceeded the 

proposed chromium limit. Of the 10 furnaces under 12 years old, three exceeded the limit (one 

only marginally), and seven tested in compliance with (i.e., below) the proposed chromium limit. 

(79 FR 68021). See also 72 FR 22379-82 for our discussion of the test data the agency used to 

support the proposed chromium compounds limit. 

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As part of our data gathering exercise, we carefully reviewed each test report conducted 

for this industry and discussed the results with company operators. We learned that although the

Kansas City K2 emitted in 2012 at extremely high levels, when the furnace was less than two 

years old, chromium emissions measured on the same scale as other newer furnaces in this 

industry currently measure. We also confirmed that chromium emissions increase with furnace 

age as the refractories age, and that the type of furnace at the high emitter is an emerging new 

technology that is preferred across the industry where a source of industrial oxygen is 

economically available. 

As explained earlier, we did obtain test data subsequent to the test data that this 

commenter describes as an “outlier.” We also note that when we conducted our review of this 

data, we learned that the company operator knew the emissions of chromium compounds were 

very high, that the source of the chromium was the refractory lining of the furnace, and that the 

emissions of chromium increased with furnace age. Only the amount of chromium that was in 

the hexavalent state (93 percent) was new information to the operator. Thus, contrary to the 

commenter’s opinion, the EPA’s decision to regulate area sources was not based on the 

performance of a single facility. Furnace emissions test data were collected from all wool 

fiberglass manufacturing facilities to determine the scope and extent of the area source emission 

levels. The data collected for gas-fired furnaces demonstrate the current and potential future high 

levels of chromium emitted from multiple gas-fired glass-melting furnaces located at wool 

fiberglass manufacturing facilities that are area sources.

The EPA acknowledged in the 2011 proposal (76 FR 72778) and 2013 proposal (78 FR 

22375) the significant effect that binder change has had on reducing HAP emissions from the 

source category; however, as discussed in section II.B of the preamble to the 2013 proposal, 

chromium emissions from furnaces are not affected by the reformulation of the binder (78 FR 

22373-22374, 22375). Further, as discussed in the preamble to the 2013 proposal (78 FR 22375), 

the Urban Air Toxics Strategy (Strategy) requires the EPA to ‘‘assure that sources accounting for 

90 percent or more of the 30 identified hazardous air pollutants are subject to standards.’’ These 

are the HAP that pose the greatest potential health threat in urban areas, including chromium 

compounds. It is under this Strategy that the EPA is establishing a chromium standard for area 

sources.

2. Decision to Apply GACT to Area Sources

166. Comment: One commenter (1042-0299) contended that a GACT limit for area 

sources is not justified and the EPA should set a MACT standard. The commenter argued that 

the EPA must establish a MACT standard, not technology review, for area sources because this 

rulemaking is the first time the EPA is setting standards for chromium for area sources in this 

source category, and a technology review is a post-MACT compliance review. The commenter 

also opined that the EPA is not prohibited from setting MACT standards for area sources, and 

the EPA has this opportunity to achieve additional public health protection.

The commenter (1042-0299) noted that the EPA’s socioeconomic analysis for Wool 

Fiberglass showed that this source category’s emissions have disproportionate impacts on 

minorities and people below the poverty level; and that the EPA’s socioeconomic analysis for the 

high-risk CertainTeed facility shows an even more extreme, disproportionate impact of its 

pollution on minority communities. The commenter argued that, because of the environmental 

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justice effects of this rule and the need to protect public health, the EPA should apply CAA 

sections 112(d)(2) and (3) instead of CAA section 112(d)(5) to set the area source standards. The 

commenter maintained that the EPA has full authority under CAA section 112(d)(5) to use the 

MACT analysis to set these standards, instead of setting standards based on GACT. 

Response: We disagree with the comment. Under CAA section 112(d)(5), the 

Administrator may, in lieu of standards requiring MACT under CAA section 112(d)(2), elect to 

promulgate standards or requirements for area sources "which provide for the use of generally 

available control technologies or management practices by such sources to reduce emissions of 

hazardous air pollutants." Section 112 of the CAA gives us discretion in addressing area sources, 

providing in section (d)(5) an alternative standard for area sources for categories listed pursuant 

to subsection (c), we may, in lieu of a MACT standard, elect to promulgate GACT standards or 

management practices by such sources to reduce emissions of HAP. Thus, we are not required to 

conduct a MACT analysis for area sources under section 112 of the CAA as the commenter has 

suggested, but have elected to propose and promulgate GACT standards, as is our discretion to 

do so. As the commenter notes, we did consider what the MACT limits would be in making this 

election, and rejected that option based on both the cost of the option and the absence of 

environmental benefits for the cost. 

Beginning in 1999, the agency set MACT standards for the wool fiberglass 

manufacturing source category. As explained in our April 2013 proposal, in the conducting the 

mandatory RTR for this source category we determined that there were elevated chromium 

emissions from gas-fired glass-melting furnaces. Under existing regulations, major sources 

become area sources by virtue of eliminating formaldehyde from their processes. There are no 

differences between gas-fired glass-melting furnaces in use at area and major sources. Area 

sources were largely unregulated until this final action. Our April 2013 contains a lengthy 

discussion on the industry trend for this source category. (78 FR 22374-76).

Additionally, we note that while we have no obligation under CAA section 112(f)(2) to 

evaluate risk for area sources in standards developed under the Urban Air Toxics Strategy, we 

also included area sources in the risk assessment conducted for this source category to support 

the 2011, 2013, and 2014 proposals, and therefore, we reviewed the risk from area sources at 

their current emissions levels. Finally, we are setting the same chromium compound limits for 

glass-melting furnaces at area and major sources.

Based on this review, we believe we have achieved both the requirements for an area 

source rule and protection of public health with the final chromium limits for wool fiberglass 

furnaces located at area sources.

3. Glass-Melting Furnace Emission Limits

167. Comment: One commenter (1042-0347) contended that the EPA failed to comply 

with the Act (42 U.S.C. § 7412(d)(1), 7412(d)(5); 42 U.S.C. § 7412(k); Nat’l Lime Ass’n v. EPA, 

233 F.3d 626, 633 (D.C. Cir. 2000) in not regulating all listed HAP for listed area sources. The 

commenter supported the EPA’s addition of a chromium limit but expressed concern that the 

EPA’s removing PM as a surrogate for metal HAP has removed protections from emissions of 

non-chromium metals (e.g., arsenic, nickel, manganese, lead, selenium, cadmium, cobalt, 

beryllium, and antimony) that are not already controlled by the chromium limit. The commenter 

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also contended that the EPA has failed to fulfill the requirement to provide a reasonable 

explanation for not setting a limit on area sources’ emissions of these other metals.

Response: We disagree with the comment. As explained in section VII.A of the 

preamble to the final rule, under CAA sections 112(c)(3), (d)(5), and (k)(3), we regulate 

emissions of the 30 most toxic HAP emitted by area sources. These provisions do not require the 

EPA to regulate all HAP from all HAP-emitting processes as we must do when setting MACT 

standards. For the reasons stated in section III.E of the preamble to the 2014 proposal, the EPA 

determined that a PM limit is not warranted for area sources. As stated therein, 

“setting emission limits for chromium alone achieves the objectives of the Strategy 

because controls needed to meet the chromium limit will reduce both total PM and its 

chromium component as the furnace emissions pass through operational PM controls. We 

also note that for gas-fired glass-melting furnaces, chromium and PM reductions are 

achieved due to the co-control characteristics of the existing controls (the DESP). 

Because owners/ operators must maintain PM controls in order to continue to meet the 

chromium limits in the rule, PM co-control benefits are realized from the reduction in 

chromium compounds.” 

The EPA has determined that a chromium limit is sufficient for the EPA to achieve its 

goals under the Urban Air Toxics Strategy (Strategy), which was discussed at length in the 2013 

proposal (78 FR 22375 – 22378).

4. Economic Impacts

168. Comment: One commenter (1042-0299) contended the EPA failed to explain why 

pound per dollar of reduction is an appropriate metric of cost effectiveness because it does not 

assess the value of health protection including reductions in cancer incidence and non-cancer 

risks, toxicity and health hazards reduced for children’s health and early life exposures, and 

environmental justice considerations. The commenter argued that the EPA must consider how 

much emission reduction is needed to reduce the high cancer risk numbers and protect public 

health, as required by the CAA.

Response: Regarding the commenter’s assertion that our cost effectiveness measure is 

unreasonable, we disagree as explained in the response to comment number 137. Section 112(d) 

of the CAA neither specifies nor mandates a cost methodology. In Husqvrna AB v. EPA, 254 

F.3d 195, 200 D.C. Cir. 2001), the D.C. Circuit found EPA’s chosen methodology “reasonable” 

because the statute “did not mandate a specific method of cost analysis.”

Regarding the comment that the EPA must consider how much emission reduction is 

needed to reduce the high cancer risk numbers and protect public health, as we explained in the 

Benzene NESHAP, in determining the need for residual risk standards, we strive to limit to no 

higher than approximately 1-in-10 thousand (100-in-1 million) the estimated cancer risk that a 

person living near a plant would have if he or she were exposed to the maximum pollutant 

concentrations for 70 years and, in the AMOS decision, to protect the greatest number of persons 

possible to an individual lifetime risk level of no higher than approximately 1-in-1 million. These 

considerations are made for all people regardless of racial or socioeconomic status. 

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However, in determining whether to require additional standards under CAA section 

112(f), these levels are not considered rigid lines, and we weigh the cancer risk values with a 

series of other health measures and factors in both the decision regarding risk acceptability and 

in the AMOS determination. We also consider cost of controls in the AMOS determination. 

While we analyzed the demographic makeup of the at-risk populations surrounding the facilities 

within the source category addressed by this rule making, we ultimately concluded that the risks 

were acceptable for all population groups and that they would protect public health with an 

ample margin of safety.

Regarding the risk caused by the Wool Fiberglass Manufacturing source category as a 

whole, we determined that the current health risks posed by emissions from the source category 

are acceptable (79 FR 68020); however, we have taken steps based on our AMOS analysis to 

ensure that these NESHAP reduce the risks posed by this industry. There are about 1,200,000 

people nationwide that are currently subject to health risks that are non-negligible (i.e., cancer 

risks greater than 1-in-1 million) due to emissions from the Wool Fiberglass Manufacturing 

source category. We performed an analysis of the demographic makeup of these 1,200,000 

people. The demographic distribution of this ‘‘at-risk’’ population is similar to the national 

distribution of demographics for all groups except for the ‘‘minority’’ group (defined as total 

population minus the white population), which is 16 percent greater than its corresponding 

national percentage. See the Risk and Technology Review—Analysis of Socio-Economic Factors 

for Populations Living Near Wool Fiberglass Facilities dated March 23, 2015 in the docket for 

additional details on the demographic analysis.

169. Comment: One commenter (1042-0300/1042-0348) indicated that facilities will 

need to install control equipment to achieve the chromium standard for area sources and that the 

EPA has grossly underestimated the cost of this equipment for area sources in both the 2013 

proposal (78 FR 22370, April 15, 2013) and 2014 proposal (79 FR 68011, November 13, 2014). 

The commenter provided cost-effectiveness estimates (in dollars per pound of chromium 

emission reduction) developed by Trinity Consultants for various technologies: HEPA filter 

would be $18,500 to $24,100; venturi scrubber would be $29,700 to 41,700; 3-stage filter after 

dry ESP would be $49,100 to $63,900. 

Response: In response to comments such as this one, the EPA has amended the proposed 

chromium limit for gas-fired glass-melting furnaces at major sources and is establishing a limit 

of 2.5E-04 pounds chromium per ton of glass pulled in the final rule. Section VII.A of the 

preamble to the final rule also contains the discussion on the cost considerations based on 

comments the agency received on the November 2014 proposal. Based on emissions data 

submitted in 2010 and 2012 by all area source wool fiberglass manufacturers on every furnace 

type, the EPA believes that all area source furnaces currently meet this chromium limit. 

Therefore, we disagree with the commenter that area source facilities will need to install control 

equipment to comply with subpart NN. As also previously explained, we found $11,000 per 

pound chromium removed to be a reasonable cost in the final Chromium Electroplating RTR 

rulemaking, where we regulated chromium compounds (77 FR 59220, September 19, 2012). 

Thus, contrary to the commenter’s assertion the cost-effectiveness for this rule is not in excess of 

the cost effectiveness values the EPA has found acceptable in prior CAA section 112 cost 

effectiveness analyses. Moreover, CAA section 112(d) neither specifies nor mandates a cost 

methodology. In Husqvrna AB v. EPA, 254 F.3d 195, 200 D.C. Cir. 2001), the D.C. Circuit 

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found the EPA’s chosen methodology “reasonable” because the statute “did not mandate a 

specific method of cost analysis.” We consider these costs reasonable because chromium is a 

toxic HAP.

5. Miscellaneous

170. Comment: One commenter (1042-0299) opined that the EPA has not shown that it 

has met the 90 percent requirement for chromium under the Urban Air Toxics Strategy 

(Strategy). The commenter asserted that the EPA has full authority to regulate wool fiberglass 

area sources for chromium emissions and should do so.

Response: The EPA has documented in the following memorandum that is has achieved 

the 90 percent reduction of chromium emissions required by the Strategy: memorandum 

“Technical Memorandum - Emission Standards for Meeting the 90 Percent Requirement under 

Section 112(c)(3) and Section 112(k)(3)(B) of the Clean Air Act” (February 18, 2011 )(EPAHQ-OAR-2010-1042-0262), the EPA. The EPA also indicated in the preamble to the 2013 

proposal (78 FR 22375, April 15, 2013) that it had achieved the 90 percent target. Further, we 

agree with the commenter that the EPA has full authority to regulate wool fiberglass area sources 

for chromium emissions because nothing prevents us from going beyond the minimum 90

percent and subjecting more categories of area sources to regulation under this program, and we 

are doing so in the final rule.

171. Comment: One commenter (1042-0299) opined that the EPA is not allowed under 

the CAA sections 112(d)(5) and (6) to consider cost-effectiveness of the rule as part of its 

analyses and conclusions on technology review, AMOS, and GACT, especially for wool 

fiberglass because CAA section 112(d)(5) already includes the consideration of “economic 

impacts.” The commenter argued that this reading of the CAA is supported by a Senate Report 

(S. REP. NO. 101-228, at 144 (1989)), which states that “generally available” includes 

“methods, practices and techniques which are commercially available and appropriate for 

application by the sources in the category considering economic impacts and the technical 

capabilities of the firms to operate and maintain the emissions control systems.” 

The commenter further argues that, even if the EPA could use cost-effectiveness to set 

standards, it has failed to justify such weak levels given that the EPA’s selection of acceptable 

cost-effectiveness is arbitrary, especially considering that the costs represent such a small 

fraction of the wool fiberglass industry’s profits.

Response: The EPA disagrees that the Senate Report cited by the commenter means that 

the EPA cannot consider cost in establishing GACT. This Senate Report describes GACT as 

standards or requirements reflecting application of generally available control technology or 

management practices, that is, “methods, practices and techniques which are commercially 

available and appropriate for application by the sources in the category considering economic 

impacts and the technical capabilities of the firms to operate and maintain the emissions control 

systems” (Senate Report Number 101-228, December 20, 1989). Consistent with the legislative 

history, in addition to considering technical capabilities of the facilities and the availability of 

control measures, we may consider costs and economic impacts in determining GACT, which is 

particularly important when developing regulations for source categories that may have few 

establishments and many small businesses, or when determining whether additional control is 

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necessary for sources with emissions that are already well controlled as a result of other existing 

or applicable standards. 

As also explained in our November 2011 proposal, the EPA may consider costs in its 

decision to set standards under the ample margin of safety step of CAA section 112(f)(2). This is 

consistent with the approach set out in the Benzene NESHAP framework for assessing 

acceptable risk and ample margin of safety. As previously explained, section 112(f)(2) of the 

CAA expressly preserves our use of the two-step process for developing standards to address 

residual risk and interpret “acceptable risk” and “ample margin of safety” as developed in the 

Benzene NESHAP (54 FR 38044, September 14, 1989). We also note that the U.S. Court of 

Appeals for the D.C. Circuit has affirmed this approach of implementing CAA section 

112(f)(2)(A): NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008). We also believe that the 

EPA may consider cost in revising emissions standards under CAA section 112(d)(6). (Ass'n of 

Battery Recyclers v. EPA, 716 F.3d 667, 673 (D.C. Cir. 2013).

We evaluated the costs of the chromium compounds limits and presented our analyses in 

the various proposals. As explained earlier, section VII.A of the preamble to the final rule also 

contains detailed discussions of the cost considerations based on comments the agency received 

on the November 2014 proposal. Refer to our AMOS analysis memorandum for a discussion of 

the other options we considered, the cost impacts of those options, and the associated risk results, 

which is available in the docket to this rule. 

172. Comment: One commenter (1042-0299) contended that the EPA must consider

public health in setting area source standards under CAA sections 112(c)(3) and (k), as follows: 

(1) whether the rule achieves (or contributes to) achievement of “a substantial reduction in 

emissions of HAP from area sources,” which is a key purpose of the area source program 42 

U.S.C. § 7412(k)(1); (2) what potential reductions in cancer and non-cancer risks are associated 

with lower emissions, and does the rule achieve or contribute to the achievement of the reduction 

of cancer incidence by 75 percent, which is a major purpose of the area source program? 42 

U.S.C. § 7412(k)(1); (3) use the best available science in considering health hazards created by 

the specific emitted HAP and the National Academy of Sciences recommendations toxicity 

(including children’s health and early-life exposure); and (4) follow EPA’s environmental justice 

plan (Draft Technical Guidance for Assessing Environmental Justice in Regulatory Analysis 

(May 1, 2013); EJ Plan 2014, http://www.epa.gov/environmentaljustice/plan-ej/).

Response: We disagree with the comment. The agency listed gas-fired glass-melting 

furnaces at areas sources and proposed emissions standards for some of the 30 urban HAP, under 

CAA sections 112(c)(3), (d)(5), and (k)(3). (78 FR 22376).

Section 112 of the CAA contains several provisions that authorize the agency to regulate 

area sources. As explained in our April 2013 proposal, CAA sections 112(c)(3) and (k) require 

the EPA to identify and list the area source categories that represent 90 percent of the emissions 

of the 30 urban air toxics associated with area sources and then set standards for them under 

CAA section 112(d). We also explained that CAA section 112(k)(3), which cross-references 

CAA section 112(c)(3), requires the EPA to identify a list of at least 30 air toxics that pose the 

greatest potential health threat in urban areas (the “urban” HAP). This is considered the Urban 

Air Toxics Strategy. (CAA Section 112(k)(3)(B)(i) and (ii); 64 FR 38706 (July 19, 1999)).

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We acknowledge that CAA section 112(c) also authorizes the agency to list area sources 

pursuant to a finding of a threat of adverse health effect. 

Additionally, as previously explained, while we have no obligation under CAA section 

112(f)(2) to evaluate risk for area sources in standards developed under the Urban Air Toxics 

Strategy, we also included area sources in the risk assessment conducted for this source category. 

All wool fiberglass facilities were major sources at the time of the MACT standard and all 

facilities are included in the source category.

173. Comment: One commenter (1042-0299) contended that the EPA must do the 

following in setting area source standards: (1) collect and consider the starting point or baseline 

“overall health” status of the affected individuals and communities as part of its Environmental 

Justice (EJ) analysis; (2) include in its EJ analysis an assessment of the percent of the population 

with limited English proficiency, infant mortality, and low birth-weight births; (3) analyze those 

who are the most exposed, within 3 miles of existing plants; for urban areas like Kansas City; 

and (4) assess the demographics within 1 mile of each plant; and use the most recent census data 

from 2010 (as available), rather than data from 2000. 

Response: Our risk-based demographic analysis for the Wool Fiberglass Manufacturing 

source category included both area and major sources. With regard to the commenter’s 

suggestion regarding overall health and elements to include in the EJ analysis, see our response 

to comments in section VI.B.8 of this document. We also note that we updated the demographics 

analysis to use the 2010 census data. The memorandum “Risk and Technology Review—Analysis 

of Socio-Economic Factors for Populations Living Near Wool Fiberglass Facilities” dated 

March 23, 2015 summarizes the results and is available in the docket. 

174. Comment: One commenter (1042-0299) expressed concern that the EPA’s 

residual risk assessment (docket ID EPA-HQ-OAR-2010-1042-0263) does not explain how the 

EPA calculated the results that showed that emissions from some facilities could cause cancer 

risk of 200-400-in-1 million, and emissions from almost all other facilities cause a cancer risk of 

1-in-1 million or higher.

Response: The EPA described the auxiliary risk characterization in section 4.3 of the 

2011 memorandum “Draft Residual Risk Assessment for the Mineral Wool Production and Wool 

Fiberglass Manufacturing Source Categories,” (available in the docket for this rulemaking as 

EPA-HQ-OAR-2010-1042-0086). For the 2013 proposal, we revised our analysis to incorporate 

new emissions data that we received for one of the furnaces at the facility with the highest 

hexavalent chromium emissions, and we prepared a table of our results for each of 28 area and 

major source facilities “Maximum Predicted HEM-3 Chronic Risks (Wool Fiberglass 

Manufacturing) based on Revised – What If Analysis,” available in the docket for this 

rulemaking (EPA-HQ-OAR-2010-1042-0263).

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