` 

Summary of Public Comments and 

Responses for Aerospace 

Manufacturing and Rework Facilities 

Risk and Technology Review 
October 2015

Summary of Public Comments and Responses for 

Aerospace Manufacturing and Rework Facilities Risk 

and Technology Review 

U. S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Sector Policies and Programs Division (D243-02) 

Research Triangle Park, North Carolina 27711 
iii 

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

Kim Teal (919) 541-5580 

U.S. Environmental Protection Agency 

OAQPS/Sector Policies and Programs Division (D243-02) 

Research Triangle Park, North Carolina 27711 

Email: Teal.Kim@epa.gov
iv 

TABLE OF CONTENTS 

Page 

1.0 Introduction ...................................................................................................................1

2.0 List of Commenters .......................................................................................................2

3.0 General Support ............................................................................................................3

4.0 Modeling Data Files .......................................................................................................3

5.0 Risk Modeling and Determination ................................................................................3

6.0 Technology Review ...................................................................................................... 35

7.0 Proposed Regulation of Specialty Coatings ................................................................ 40

7.1 Legal Basis to Regulate Specialty Coatings ........................................................ 40

7.2 Determination of Specialty Coating Limits and Definitions ................................ 45

7.3 Specialty Coating Application Equipment Requirements .................................... 53

7.4 Specialty Coating Inorganic HAP Control Requirements .................................... 56

7.5 Specialty Coating Compliance Deadline............................................................. 61

7.6 Complying with the Proposed Specialty Coating Limits ..................................... 62

8.0 Startup, Shutdown, Malfunction Provisions .............................................................. 68

9.0 Electronic Reporting Provisions ................................................................................. 72

10.0 Alternative Compliance Demonstration ..................................................................... 73

11.0 Other Emission Sources Not Currently Regulated .................................................... 77

12.0 Estimated Cost, Economic, and Environmental Impacts ........................................... 79

13.0 Technical Corrections.................................................................................................. 87

14.0 Comments Outside the Scope of the Proposal ............................................................ 89

 
v 

List of Acronyms and Abbreviations 

AEGL Acute Exposure Guideline Levels 

ASTM American Society of Testing and Materials 

ATSDR Agency for Toxic Substances and Disease Registry

BACT Best Available Control Technology 

CAA Clean Air Act 

CFR Code of Federal Register 

DoD U.S. Department of Defense 

EA Environmental Assessment 

EJ Environmental Justice 

EMP Environmental Monitoring Program 

EO Executive Order 

EPA U. S. Environmental Protection Agency 

ERPG Emergency Response Planning Guidelines 

ERT Electronic Reporting Tool 

FR Federal Register 

GACT generally available control technologies 

GHG greenhouse gas x 1 

HAP Hazardous Air Pollutant 

HEM-3 Human Exposure Model, version 3 

HON Hazardous Organic NESHAP 

HQ Head Quarters 

ICR Information Collection Request 

IRIS Integrated Risk Information System 

LAER Lowest Achievable Emission Rate 

MACT Maximum Achievable Control Technology 

MIR Maximum Individual Risk 

μg/dL micrograms per deciliter 

NAAQS national ambient air quality standard 

NAS National Academy of Sciences 

NEI National Emissions Inventory 

NESHAP National Emission Standards for Hazardous Air Pollutants 

NRC National Research Council 

NSPS New Source Performance Standards 

OAQPS Office of Air Quality Planning and Standards 

OMB Office of Management and Budget 

PM particulate matter 

POM Polycyclic Organic Matter 

PRA Paperwork Reduction Act 

RACT Reasonably Available Control Technology 

RBLC RACT/BACT/LAER Clearinghouse 

RCRA Resource Conservation and Recovery Act 

REL CalEPA Reference Exposure Level 

RfC Reference Concentration 

RfD Reference Dose 
vi 

RTR Residual Risk and Technology Review 

SAB Science Advisory Board 

SBA Small Business Administration 

SSM startup, shutdown, and malfunction 

TOSHI Target Organ-Specific Hazard Index 

tpy tons per year 

USGS U.S. Geological Survey 

VOC volatile organic compound 

XML eXtensible Markup Language 
1 

1.0 Introduction 

On February 17, 2015, the Environmental Protection Agency (EPA) proposed revisions to the 

National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Aerospace 

Manufacturing and Rework Facilities source category. Some significant comments and responses 

appear in the preamble to the final rule. This document contains summaries of all the public 

comments that the EPA received on the proposed standards (comments that are summarized and 

addressed in the preamble to the proposed rule are also summarized in this document for 

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

Reading Room. Comment letters are also available electronically through 

http://www.regulations.gov by searching Docket ID No. EPA-HQ-OAR-2014-0830. 

 
2 

2.0 List of Commenters 

The EPA received 14 comment letters after February 17, 2015 on the proposed revisions to the 

NESHAP for the aerospace manufacturing and rework source category. All comment letters are 

contained in Docket EPA-HQ-OAR-2014-0830. The commenter, affiliation, and item number in 

Docket EPA-HQ-OAR-2014-0830 are listed in Table 2-1. 

Table 2-1. Public Comments Received after the Proposed Rule for Aerospace 

Manufacturing and Rework Facilities Risk and technology Review, Proposed Rule Docket 

EPA-HQ-OAR-2014-0830 

Commenter Identification Code Commenter and Affiliation 

EPA-HQ-OAR-2014-0830-0021 Anonymous public comment 

EPA-HQ-OAR-2014-0830-0022 John D. Conway, EHS Compliance Manager, Sikorsky 

Aircraft Corporation 

EPA-HQ-OAR-2014-0830-0023 Thelma Latimer-Davis, Manager Environmental 

Engineering, American Airlines, Inc. 

EPA-HQ-OAR-2014-0830-0024 

(duplicate of 0022) 

John D. Conway, EHS Compliance Manager, Sikorsky 

Aircraft Corporation 

EPA-HQ-OAR-2014-0830-0025 Donald R. Schregardus, Deputy Assistant Secretary of the 

Navy, Department of the Navy, U.S. Department of 

Defense 

EPA-HQ-OAR-2014-0830-0026 Nancy N. Young, Esq., Vice President, Environmental 

Affairs, Airlines for America 

EPA-HQ-OAR-2014-0830-0027 David Darling, P.E., Senior Director, Environmental 

Affairs; Timothy Serie, Esq., Counsel, Government 

Affairs, American Coatings Association 

EPA-HQ-OAR-2014-0830-0028 Leslie Riegle, Director of Environmental Policy, Aerospace 

Industries Association 

EPA-HQ-OAR-2014-0830-0029 LMS Technologies, Inc. 

EPA-HQ-OAR-2014-0830-0030 Earth Justice, on behalf of California Communities 

Against Toxics and Sierra Club 

EPA-HQ-OAR-2014-0830-0031 G. Vinson Hellwig, Michigan, and Robert H. Colby 

Chattanooga, Tennessee, Co-Chairs, Air Toxics 

Committee, National Association of Clean Air Agencies 

EPA-HQ-OAR-2014-0830-0032 

(duplicate of 0028) 

Leslie Riegle, Director of Environmental Policy, Aerospace 

Industries Association 

 
3 

3.0 General Support 

Comment: One commenter s0830-0021) supported the proposed rule. The commenter argued 

that hazardous air pollutants (HAP) are very harmful to the global population's health because 

certain HAP can cause cancer or other serious health effects such as reproductive defects or birth 

defects, or have adverse effects on the environment. 

Response: The EPA acknowledges the commenter's support. 

4.0 Modeling Data Files 

Comment: One commenter (0830-0022) submitted two corrections for their facility. The first 

was to apply an assumed scrubber efficiency of 95 percent for control of sodium dichromate on a 

metal finishing tank, and the second was a refined estimate of the chromium trioxide emissions 

from a stack serving chromic acid strip and pickle tanks with the emissions being for the two 

tanks combined instead of separately for each tank. 

Response: The EPA acknowledges the commenter's corrections. These were the only corrections 

received during the public comment period, and they both lowered the estimated emissions from 

this facility. Because the residual risk analysis performed before proposal already found that the 

risks were acceptable with an ample margin of safety, the EPA did not repeat the analyses using 

these new data. 

5.0 Risk Modeling and Determination 

Comment: One commenter (0830-0028) confirmed, after having risk modeling experts run 

EPA's risk model using EPA data, that EPA's conclusion that risks are approximately an order of 

magnitude below the level considered acceptable under CAA section 112 and EPA regulations. 

The commenter also argued that they determined that EPA likely overstated risks due to the 

conservative nature of risk modeling, including mis-located sources, suspect emission outliers, 

and non-representative receptors. 

The commenter also stated that EPA’s risk estimates may overstate the risk at the highest-risk 

facilities because of suspect data issues in the risk calculations. Based on their review of the ten 

facilities that EPA calculated as having the highest facility-wide cancer risk, the commenter 

identified data and methodological issues (e.g., mis-located sources, emission outliers, and nonrepresentative risk receptors) that would affect the calculated risk numbers at five of the ten 

facilities. The commenter noted that correction of these issues would likely result in substantially 

lower risk at several of the facilities, and in no cases would corrections result in higher modeled 

risk. The commenter concluded that the issues identified at the highest-risk sources uniformly 

bias the modeling results to overstate the risk. 

The commenter stated that EPA’s modeled hazard quotient (HQ) value of 2 at one facility is 

likely the result of errors in the modeling or input data for this facility. The commenter argued 

that EPA should have compared the California EPA 6-hour benchmark for ethylene glycol ethyl 

ether acetate (EGEEA) to the calculated maximum 6-hour average emission concentration for 

this facility instead of to the calculated maximum 1-hour average emission concentration for the 
4 

facility, stating that this correction alone would reduce the HQ to approximately 1. The 

commenter further noted that the EGEEA emissions for this facility are likely significantly 

overstated because the stated emissions are more than 10 times the EGEEA emissions of much 

larger facilities, and correcting the facility’s emissions to reflect the industry average would 

reduce the HQ value to well below 1. 

If EPA assumed significantly higher hourly emissions (as much as 5 times higher), the highest 

estimated acute risk level, including corrected errors, would still remain below an HQ value of 2. 

Therefore, the commenter agreed with EPA’s finding that acute risk from this source category is 

acceptable, even when using the modeled HQ of 2. 

Response: The commenter suggested that the EPA has over estimated risks as a result of data 

and/or modeling errors. As noted in the risk report, the model inputs for risk modeling were 

derived from 2011 survey data from an information collection request (ICR) as well as emission 

data updated in 2013 and 2014. The more recent and/or corrected data that the commenter 

references was not available at the time that the risk modeling was performed. EPA disagrees 

that methodological issues are present in the risk modeling. Receptors around each facility are 

based on USGS census block locations and are adjusted in cases where a census block is 

identified on property. As exact property lines are not provided as part of the ICR data set EPA 

conservatively leaves questionable receptors in the modeling analysis, and it is only in a situation 

where a facility shows the potential to pose a significant risk that EPA may further explore 

whether a resident is located at that particular location. 

EPA disagrees that the acute value for EGEAA was in error. As noted above, inputs were based 

on the ICR data available at the time of the assessment. Further, EPA compares 1-hour acute 

concentrations from the dispersion model with the California Reference Exposure Levels (RELs) 

as a first-level acute screening value. As noted, EPA agrees that the HQ value of 2 is not 

expected to result in any negative health impacts. 

Comment: One commenter (0830-0028) argued that while the risk from MACT-allowable 

emissions is low and that risks are acceptable, this risk factor is not required for such a finding as 

evidenced in both the Coke Oven NESHAP [70 Fed. Reg. 19992, 19998 (April 15, 2005)] and 

the Hazardous Organic NESHAP (HON) [71 Fed. Reg. 76603, 76609 (December 21, 2006)]. In 

regards to these two rules [70 Fed. Reg. 19998-99; 71 Fed. Reg. 34422, 34428-29] in which EPA 

stated that the use of MACT-allowable emissions was reasonable, the commenter pointed out 

that EPA chose to use actual emissions to determine risk because those were the most accurate 

data available. 

The commenter stated that the use of actual emissions in risk assessments is more accurate than 

MACT-allowable emissions and is supported by the language of CAA Section 112(f) because 

the statute limits the risk review to consider risks to the individual most exposed to the emissions 

from a particular source and does not include words such as “maximum allowable” or 

“potential.” The commenter further noted that not using MACT-allowable emissions is 

reasonable as they represent a hypothetical, worst-case emissions level to which an individual is 

unlikely to ever be exposed, plus (similar to the HON [71 Fed. Reg. at 76610]) there is no reason 

to conclude that sources in this source category could make changes that significantly increase 

their emissions and risks while still complying with MACT requirements. The commenter stated 
5 

that actual emissions are the most reasonable to use in risk approximation for this source 

category because aerospace manufacturers are constrained in terms of the ability to change the 

coatings and materials used, face relatively stable market conditions, and have limited excess 

capacity. The commenter also noted that basing the emission standard on unlikely, worst-case 

scenarios could lead to costly and unnecessary controls which do little to reduce risk. 

The commenter concluded that because EPA has actual emissions data from aerospace 

manufacturing and rework facilities, the Agency can choose to base its risk assessments solely 

on these data and the risk assessment would be reasonable, given the other conservative 

assumptions in the risk analysis. 

Response: The EPA disagrees with the commenter's objection to the EPA’s use of allowable 

emissions in characterizing risks from the source category. The EPA believes in cases where we 

are able to quantify allowable emissions that the risk characterization should include such an 

analyses to help determine the remaining risks (residual risks) associated with the existing 

MACT standard. This analysis is necessary to help determine the potential risks to the public as 

nothing precludes a facility from emitting at the allowable level. 

Comment: One commenter (0830-0028) agreed with the approach and rationale EPA used in 

calculating MACT-allowable emissions for the aerospace industry. The commenter agreed that 

there have been no advances in control technologies since the initial rulemaking and therefore 

EPA reasonably concluded that actual emissions generally reflect the highest emissions rate 

expected for modeling purposes. The commenter also agreed with EPA’s use of a scaling factor 

that accounts for the potential for increases in production but also caps the effects of increased 

production at levels that are reasonably expected given aerospace industry market conditions. 

The commenter stated that scaling emissions any higher than this would result in inaccurately 

high and speculative MACT-allowable risk values. However, the commenter further noted that 

even if much higher MACT-allowable scaling factors were used, the calculated risk would still 

remain below the presumptively acceptable threshold, for example if the modeling assumed 100 

percent production utilization the MIR would remain below 20-in-1 million. 

Response: EPA agrees with the commenter that maximum emissions allowable under the 

MACT standards (i.e., MACT-allowable emissions) from the inhalation risk assessment indicate 

that the maximum lifetime individual cancer risk could as high as 10 in a million, and that the 

maximum chronic non-cancer Hazard Index value is about 0.5. 

Comment: One commenter (0830-0028) agreed that EPA’s finding on facility-wide risk is well 

below acceptable levels, but stated that this risk should not be considered by EPA because CAA 

Section 112 limits the residual risk review to the regulated source category and requires that each 

source category be evaluated and regulated separately. 

The commenter noted that the statutory language clearly refers only to the specific MACT source 

category (or subcategories within that category) being considered, not to the general risks 

associated with a particular HAP. The commenter further pointed out that the second source of 

reference established by the Supreme Court is the Conference Report that accompanies 

legislation at final passage (Nat’l Assn of Greeting Cards Publishers v. U.S. Postal Serv. [462 

U.S. 810, 832 n.28 (1983)]), noting that this Report does not include language on conducting 
6 

facility-wide residual risk determinations but rather mirrors the statute in referring exclusively to 

source categories or subcategories [H.R. CONF. REP. NO. 101-952, at 338 (1990)]. 

The commenter further stated that CAA Section 112(c)(9) shows that Congress was concerned 

with emissions from specific sources, not facilities, in conducting the residual risk reviews, and 

therefore EPA cannot exceed its authority by imposing a more stringent requirement to address 

potential and uncertain risks not caused by the sources contemplated by Congress. 

Response: We disagree that examining facility-wide risk in a risk assessment conducted under 

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 were derived from facilitywide 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 

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, EPA considers this inappropriate because only the risk 

associated with the emissions under consideration are 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 ample margin of safety 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 ample margin of safety 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 concentrations. 

(NRDC v. EPA, 529 F.3d 1077 (D.C. Cir. 2008)). 

Comment: One commenter (0830-0028) stated that EPA is appropriate in using the 100-in-1 

million acceptable risk level as a threshold for determining whether additional regulation is 

needed, referencing the 1987 Vinyl Chloride decision [NRDC, Inc. v. EPA, 824 F.2d 1146 (D.C. 

Cir. 1987)] and the decision framework established in the 1989 Benzene NESHAP [54 Fed. Reg. 

38044, September 14, 1989]. 
7 

The commenter also noted that EPA appropriately weighed the costs of increased controls (e.g., 

add-on controls for primer and topcoat application operations) against the potential benefits of 

any further reductions in risks in determining whether public health is protected within an ample 

margin of safety. 

The commenter further stated that EPA appropriately concluded that the risks were acceptable 

and the current standards are protective within an ample margin of safety such that no additional 

regulations are necessary under CAA Section 112(f). 

Response: The EPA agrees with the commenter that EPA appropriately concluded that the risks 

were acceptable and the current standards are protective within an ample margin of safety. 

Comment: One commenter (0830-0028) stated that EPA’s approach to risk analyses results in a 

hypothetical, upper-bound scenario likely significantly higher than the risk an actual person 

would face. The commenter agreed that maximum individual risk (MIR) is an estimate of the 

upper bound of risk based on conservative assumptions, and noted that EPA’s MIR approach is 

conservative at several levels. The commenter further noted that EPA used conservative 

assumptions and procedures in conducting the acute inhalation exposure assessment, for example 

assuming that peak emissions will coincide with the worst-case wind and atmospheric 

conditions. 

Response: EPA acknowledges the support of the commenter. For this source category, the risk 

assessment report included in the docket includes a general discussion of uncertainties and how 

they have been addressed in the risks characterization. 

Comment: One commenter (0830-0030) noted an overall problem that EPA’s entire analysis 

seem to be incorrect as it refers to “refineries” instead of aerospace facilities. EPA must perform 

a multipathway risk assessment for aerospace facilities in this rulemaking. 

Response: EPA disagrees with the commenter that the analysis is based on refineries. The risk 

characterization, including the multipathway analysis, is based on emissions from the Aerospace 

source category. Any references to “refineries” in any of the risk analysis documentation is in 

error. 

Comment: One commenter (0830-0030) argued that EPA should also consider reforming risk 

assessments to support reducing risks to the lowest possible level to protect public health. The 

commenter argued that currently available science challenges EPA’s assumption because there is 

so much uncertainty built into the risk assessment, and because EPA lacks information on so 

many pollutants. The commenter stated that this policy is especially problematic for 

communities overburdened by pollution. 

The commenter believed that 100-in-1 million lifetime cancer risk cannot be considered safe or 

“acceptable.” The commenter disagreed with EPA basing various types of health risks at that 

time on an unusual study of people’s perceptions of their own risk from 1988, known as the 

Survey of Societal Risk (July 1988) and should instead be based on scientific information about 
8 

cancer risk.1 The commenter stated that EPA looked at an odd collection of risks, such as 

dangers from driving a car, and found that “the presumptive level established for MIR 

[maximum individual risk of cancer] of approximately 1 in 10 thousand is within the range for 

individual risk in the survey, and provides health protection at a level lower than many other 

risks common ‘in the world in which we live.’”2

The commenter recommended that the EPA revisit or update its presumed acceptable level of 

cancer risk considering information learned about children’s and overburdened community’s 

vulnerability, biomonitoring and other data on adult body burdens of chemicals, and new 

information on ways to analyze and control the impacts of pollutants on human health. 

The commenter cited various sources, such as the National Academy of Science's 2009 Science 

and Decisions report, which included new information. 

The commenter also suggested that EPA review EPA’s Children’s Health Protection Advisory 

Committee (CHPAC) which recommended addressing the developmental origins of adult disease 

that come from childhood exposure to air pollution and other environmental contaminants.3 The 

commenter also suggested that EPA heed CHPAC’s recommendation that EPA incorporate a 

more robust analysis of childhood and pre-natal exposure to environmental contaminants into its 

risk assessment method.4

As urged by the EPA’s Science Advisory Board (SAB), the commenter recommended that EPA 

address the greater risk to children from hazardous air pollution.5 The commenter added that 

SAB also further explained: “California’s Office of Environmental Health Hazard Assessment 

(OEHHA) has very recently updated its methodology in ways that could affect the development 

of RfC and URE (unit risk estimate) values. EPA should examine these developments to make 

sure that the RTR process adequately covers children’s risks.”6

 

1 Benzene Rule Docket No. OAQPS 79-3, Part I, Docket Item X-B-1, EPA Air Docket (cited at Nat’l Emission 

Standards for Hazardous Air Pollutants; Benzene Emissions from Maleic Anhydride Plants, 

Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product 

Recovery Plants, 53 Fed. Reg. 28,496, at 28,512-13 (July 28, 1988)). 

2

54 Fed. Reg. 38,044, 38,046 (Sept. 14, 1989) (quotation omitted). 

3

 EPA, Report of the Task Group of the Children’s Health Protection Advisory Comm. on America’s Children & the 

Environment, 3d Ed. (2010), available at http://www2.epa.gov/sites/production/files/2014- 

05/documents/ace_task_group_report.pdf. 

4 Letter from Pamela Shubat, Chair, Children’s Health Protection Advocacy Council, CHPAC to Lisa Jackson, 

Administrator, U.S. EPA, (Oct. 21, 2010) (“CHPAC recommends that EPA staff scientists participating in the 

upcoming discussions bring the concern of early life stage exposure and sensitivity to the conversations that will 

take place concerning optimizing risk assessment practice.”), 

http://yosemite.epa.gov/ochp/ochpweb.nsf/content/CHPAC_NRC_Report.htm. 

5

SAB May 2010 at 7, supra note 77 (stating that “an overarching concern with the Agency’s chronic inhalation 

exposure estimates is that children’s exposures do not appear to have been adequately addressed”); see also id. at 

34 n.13 (“In particular is the question of whether the interindividual variability factor for non-carcinogens and the 

standard cancer unit risk derivation adequately covers children. If it does not, it is a potentially significant 

uncertainty given the greater intake rate of children via inhalation and sensitivity to carcinogens and other 

toxicants.”). 

6

Id. at 6 
9 

The commenter recommended that EPA consider and address children’s health, early life 

exposure, and cumulative impacts by examining a number of groundbreaking scientific 

determinations and protocols released by OEHHA during the last decade, including three final 

Technical Support Documents on risk assessment and a new 2015 Risk Assessment Manual.7 

The commenter recommended that EPA scientists and science policymakers revisit the outdated 

assumption EPA makes regarding what level of cancer risk triggers policy interventions. The 

commenter supported EPA’s own policy regarding carcinogens recognizes that they have no safe 

threshold of exposure and EPA’s recognition that cancer risks add up to increase lifetime risk. 

Response: As an initial matter, we note that in 1990 Congress codified in section 112(f)(2)(B) of 

the Clean Air Act the approach we use for our residual risk analyses. Under that approach, the 

100 in 1 million cancer risk is not a bright line indicating that risk is “acceptable.” Rather, we 

consider this health metric in conjunction with a variety of health factors and their associated 

uncertainties to determine whether the risk is acceptable Where we conclude that the risk is not 

acceptable, we cannot and do not consider costs in requiring controls to bring risks down to an 

acceptable level. However, the analysis of whether risk is acceptable is not the endpoint. Once 

we determine that controls are sufficient to ensure that risk is acceptable, we again review the 

health metrics (e.g., cancer and chronic non-cancer risks) and their associated uncertainties in 

conjunction with the costs of controls, technical feasibility, and other relevant factors, to 

determine whether additional controls should be required to provide an ample margin of safety. 

We further note that we generally draw no bright lines of acceptability regarding cancer or noncancer 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 all their uncertainties, when determining the acceptable level of source category risk. 

Experience with source category rulemakings in the past tells us that this means drawing bright 

lines for such decision-making 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-ofevidence 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. 

 

7

See Cal. EPA, OEHHA, 2015 Health Risk Assessments Manual, supra note 151; Cal. EPA, OEHHA Technical 

Support Documents, http://oehha.ca.gov/air/hot_spots/riskguidancedraft2014.html#download. 
10 

We disagree with the general comment that the EPA should adopt the Cal OEHHA childprotective scientific approach on deriving health benchmarks. The EPA has an approach for 

selecting appropriate health benchmark values and in general, this approach places greater 

weight on the EPA-derived health benchmarks than those from other agencies.8 The approach 

favoring EPA benchmarks (when they exist) has been endorsed by the SAB and ensures use of 

values most consistent with well-established and scientifically-based EPA science policy. The 

EPA is currently evaluating the most appropriate use for the Cal OEHHA child- specific 

reference doses. We note that there are currently no such values for HAP inhalation, therefore, 

the current utility may be limited to persistent and bioaccumulative (PB)-HAP, which may be 

associated with non-negligible ingestion exposures. This evaluation on 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 the risk assessment for this source category does not 

consider the groups that may be most at-risk (e.g., children). When the EPA derives exposure 

reference concentrations and unit risk estimates for metal 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 US EPA, 2002, A Review of the Reference Dose and Reference 

Concentration Processes. EPA/630/P-02/002F. Risk Assessment Forum, Washington, DC. 

Available online at http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf.) With respect to 

maternal exposure in utero specifically, we are unaware of literature that would allow for a 

robust characterization of risk during this stage of development. 

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. 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 that have been developed to be 

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

For example, a review9 of the chronic reference value process concluded that the EPA’s 

reference concentration (RfC) derivation processes adequately considered 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 (MOA), in contrast to the OEHHA 

approach, which uses them across the board for all carcinogens regardless of MOA. In lieu of 

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

 

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

9

 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. 
11 

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. 

The estimated risks must be considered in the context of the full set of assumptions used for this 

risk assessment. Our unit risk estimates for HAP are considered a plausible upper-bound estimate 

with an appropriate age dependent adjustment; actual potency is likely to be lower and some of 

which could be as low as zero. Our chronic noncancer reference values have been derived 

considering the potential susceptibility of different subgroups, with specific consideration of 

children. In addition, an extra uncertainty factor is not needed in the RfC/RfD methodology 

because the currently available factors are considered sufficient to account for uncertainties in 

the database from which the reference values are derived. After considering these and other 

factors, we continue to consider the risks from emissions for this source category to provide an 

ample margin of safety (consistent with the Benzene NESHAP framework). 

Comment: One commenter (0830-0030) stated that EPA has underestimated health risks by 

underestimating HAP emissions, claiming that EPA did not collect emission test data from the 

majority of sources in the aerospace source category and has given no reasonable explanation for 

not doing so. The commenter claimed the sources from which data were collected comprise less 

than 10 percent of the existing sources and as a result, EPA’s data inventory memo shows 

significant reliance on assumptions, some of which have no real-world basis. The commenter 

also noted that the EPA asked the facilities to provide a factor to compare their actual and 

“allowable” emissions, and then argued that rather than perform its regulatory responsibility, the 

EPA allowed the regulated entities to provide their own number that EPA then used to regulate. 

The commenter asserted that EPA must provide a reasonable explanation of how its estimates 

represent real-world emissions from aerospace facilities or collect additional emission test data to 

assure its inventory is accurate. 

Response: We disagree with the commenter that we have underestimated the health risks by 

underestimating HAP emissions. The EPA’s method of collecting the emissions data for the 

facilities is explained in the memorandum in the docket documenting the development of the risk 

modelling database.10 The emissions of organic HAP from coating operations (including primers, 

top coats, chemical milling maskants, and specialty coatings) were based on the organic HAP 

content of the coatings and the conservative assumption that 100 percent of the organic HAP 

would be emitted, except in cases where add-on controls were used. In the latter cases, the EPA 

made conservative assumptions for the capture and control efficiency of the spray booths and 

add-on controls consistent with prior EPA experience with these types of controls in other 

surface coating source categories. The emissions of inorganic HAP from coating operations were 

based on the inorganic HAP content of the coatings, and assumptions for the transfer efficiency 

of spray guns, the capture efficiency of spray booths, and the control efficiency of spray booth 

filter systems, again consistent with prior EPA experience with these types of controls in other 

surface coating source categories. 

We also disagree with the commenter’s implication that the EPA had incomplete data for the risk 

assessment. Although the EPA requested stack testing data only from select facilities 

 

10 Memorandum: Aerospace Manufacturing and Rework Facilities RTR Modeling File Preparation, December 2014. 

EPA Docket Item Number EPA-HQ-OAR-2014-0830-0006. 
12 

representing less than 10 percent of existing source facilities, the EPA collected detailed 

emissions data from all known facilities in the source likely to be subject to subpart GG through 

the ICR. The EPA supplemented these data with the stack testing data and through data from 

other sources, such as the National Emission Inventory (NEI) as described in the RTR Modeling 

File Preparation memo described above. Further, as explained in the preamble for the final rule, 

in response to our proposal, EPA received only two corrections affecting two emission sources at 

one facility in the risk modeling database and both corrections reduced the emissions from that 

one facility. We note that the commenter did not provide any additional emissions data. 

Finally, as explained in the modelling file documentation memo, the EPA did not use the scaling 

factors reported by facilities to develop the allowable emission levels. Instead, the EPA 

multiplier to estimate maximum allowable emissions was based on the ratio between the 2008 

production utilization rate of 83.1 percent and the 20-year historical maximum production 

utilization rate of 85 percent. 

Comment: One commenter (0830-0030) stated that EPA underestimates health risks by not 

using the best available information on pollutants. The commenter claimed that EPA has treated 

the risk of certain pollutants as zero just because they have not developed a risk measurement for 

that pollutant – when the science shows there is a risk present. The commenter provided the 

example that EPA failed to evaluate cancer risks from lead and chloroform despite cancer 

potency factors that are available from California EPA and has given no reasoned explanation for 

ignoring the carcinogenic risks of these or other pollutants. In some cases, the commenter 

claimed EPA inappropriately used values designed for emergency exposure response – values 

which should not be considered health protective. 

The commenter also stated that EPA did not provide public notice of the HAPs for which it is 

aware of cancer, chronic non-cancer, acute, or multipathway risk, for which it did not evaluate 

such risk. The commenter claimed this is a violation of notice and comment requirements, and it 

is unlawful under CAA § 7412(f)(2) for EPA not to assess risk at all from any HAP because it 

ignores risks EPA knows to exist. The commenter stated that where there is no reference value 

for a pollutant, EPA must at a minimum add an uncertainty factor to account for the additional 

risk a HAP likely causes, until such time as EPA has a reference value to use. Using a protective 

uncertainty factor would allow EPA to satisfy its legal duty under CAA § 7412(f)(2). 

Response: This issue was addressed by the EPA’s Science Advisory Board (SAB) in their May 

10, 2010, (EPA-SAB-10-007) response to the EPA Administrator.11 In that response, the SAB 

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 

 

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
13 

conducting our risk determinations under RTR. However, in some instances no sources of 

information beyond the EPA’s list are available. 

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 that 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 dose-response values, we are generally capable of deriving reasonable 

risk estimates for those HAP that dominate the risks from any one source category. In the course 

of each residual risk assessment, should we encounter HAP without dose-response values that 

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. 

The EPA notes that we did state which HAP currently have no reference value. In the risk 

assessment document, Table 3.1-1 lists all the HAP emitted by the source category, and indicates 

whether there is an available cancer, chronic noncancer, and/or acute dose-response value. 

The EPA disagrees with the comment that EPA inappropriately uses values designed for 

emergency exposure response. The reference values used in this risk assessment for the acute 

assessments were deemed to represent the best science available to provide an accurate estimate 

of potential health risks. Our approach is consistent across exposure durations in selecting 

conservative tools and assumptions to ensure that our decisions are protective of human health 

and the environment. However, only one set of acute reference values are most appropriately 

designed for use in the RTR Program: the acute Reference Exposure Levels (RELs) from 

California OEHHA which are developed for their Air Toxics Hot Spots program – a program 

similar in scope and context to the RTR assessments of risk. The one-hour emergency response 

values available from the Acute Exposure Guideline Level (AEGL) program of EPA and the 

Emergency Response Planning Guideline (ERPG) value developed by the American Industrial 

Hygiene Association provide other values that have been considered for use as comparison 

values when an acute REL is available, or as the only viable alternative for use when there is no 

acute REL value for a chemical. When weighing the most appropriate reference values to use on 

a chemical-specific basis (when more than one is available), EPA judges the merits of the values 

on both critical aspects: (1) scientific accuracy and (2) being appropriately health protective 

based on the scientific evidence (i.e., striving to be neither under- nor over-protective). 

We disagree with the general comment that the EPA should adopt the California OEHHA acute 

RELs by default as the best science. The EPA has an approach for selecting appropriate health 

effect reference benchmark values and in general, this approach prioritizes according to (1) 

conceptual consistency with EPA risk assessment guidelines and (2) level of review received that 
14 

is consistent with EPA standards.12 Notably, this prioritization approach, which favors EPA 

benchmarks (when they exist), has been endorsed by the SAB; however, SAB also encourages 

EPA to review and consider all of the available reference values from agencies that employ a 

derivation method and review process similar to EPA’s. The EPA is currently evaluating whether 

it is appropriate to use specific benchmarks values derived by OEHHA on a chemical-bychemical basis by considering: (1) use of the most relevant scientific evidence as the basis for the 

value; (2) use of the most appropriate derivation methods (including use of appropriate models, 

scientifically-based adjustments, and application of uncertainty factors); and (3) selecting the 

most appropriate values for the exposure context. 

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 

(see 80 FR 8402), 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,13 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 Arrays14 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 rule (80 FR 8402), 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. Further, when there are gaps in the available information, 

uncertainty factors (UFs) are applied to derive reference values that are intended to be protective 

against appreciable risk of deleterious effects. Uncertainty factors are commonly default values15

 

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

13 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.

14 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.

15 According to the NRC report Science and Judgment in Risk Assessment (NRC, 1994) “[Default] options are 

generic approaches, based on general scientific knowledge and policy judgment, that are applied to various elements 

of the risk-assessment process when the correct scientific model is unknown or uncertain.” The 1983 NRC report 

Risk Assessment in the Federal Government: Managing the Process defined default option as “the option chosen on 

the basis of risk assessment policy that appears to be the best choice in the absence of data to the contrary” (NRC, 

1983a, p. 63). Therefore, default options are not rules that bind the agency; rather, the agency may depart from them 

in evaluating the risks posed by a specific substance when it believes this to be appropriate. In keeping with EPA’s 
15 

(e.g., factors of 10 or 3) used in the absence of compound-specific data; where data are available, 

uncertainty factors may also be developed using compound-specific data; where data are 

available, data-derived extrapolation factors may also be developed using compound-specific 

information. When data are limited, more assumptions are needed and more default factors are 

used. Thus there may be a greater tendency to overestimate risk—in the sense that further study 

might support development of reference values that are higher (i.e., less potent) because fewer 

default assumptions are needed. However, for some pollutants it is possible that risks may be 

underestimated.

Comment: One commenter (0830-0030) stated that EPA must recognize that chronic (noncancer) risk-causing pollutants, in the same way as carcinogens, have no safe level of human 

exposure. The commenter asserted that NAS recommends cancer and chronic non-cancer risk 

assessments use the same approach in order to address the fact that very low levels of noncarcinogen exposures can pose health risks. The commenter provided multiple references to 

scientific and medical publications supporting this assertion, including in utero research 

illustrating the high sensitivity a developing fetus has to toxic agents at extremely small doses. 

The commenter concluded, saying EPA needs to evaluate non-cancer chronic risk similarly to 

cancer risk: recognizing there is no safe level of human exposure. 

Response: Chronic non-cancer reference values represent chronic exposure levels that are 

intended to be health-protective. That is, EPA and other organizations which develop non-cancer 

reference values (e.g., the Agency for Toxic Substances and Disease Registry – ATSDR) utilize 

an approach that is intended not to underestimate risk in the face of uncertainty and variability. 

As previously explained, when there are gaps in the available information, uncertainty factors 

(UFs) are applied to derive reference values that are intended to be protective against appreciable 

risk of deleterious effects. Uncertainty factors are commonly default values16 (e.g., factors of 10 

or 3) used in the absence of compound-specific data; where data are available, uncertainty 

factors may also be developed using compound-specific data; where data are available, dataderived extrapolation factors may also be developed using compound-specific information. 

When data are limited, more assumptions are needed and more default factors are used. Thus 

there may be a greater tendency to overestimate risk—in the sense that further study might 

support development of reference values that are higher (i.e., less potent) because fewer default 

 

goal of protecting public health and the environment, default assumptions are used to ensure that risk to chemicals is 

not underestimated (although defaults are not intended to overtly overestimate risk). See EPA 2004 An examination 

of EPA Risk Assessment Principles and Practices, EPA/100/B-04/001 available at: 

http://www.epa.gov/osa/pdfs/ratf-final.pdf. 

16 According to the NRC report Science and Judgment in Risk Assessment (NRC, 1994) “[Default] options are 

generic approaches, based on general scientific knowledge and policy judgment, that are applied to various elements 

of the risk-assessment process when the correct scientific model is unknown or uncertain.” The 1983 NRC report 

Risk Assessment in the Federal Government: Managing the Process defined default option as “the option chosen on 

the basis of risk assessment policy that appears to be the best choice in the absence of data to the contrary” (NRC, 

1983a, p. 63). Therefore, default options are not rules that bind the agency; rather, the agency may depart from them 

in evaluating the risks posed by a specific substance when it believes this to be appropriate. In keeping with EPA’s 

goal of protecting public health and the environment, default assumptions are used to ensure that risk to chemicals is 

not underestimated (although defaults are not intended to overtly overestimate risk). See EPA 2004 An examination 

of EPA Risk Assessment Principles and Practices, EPA/100/B-04/001 available at: 

http://www.epa.gov/osa/pdfs/ratf-final.pdf. 
16 

assumptions are needed. However, for some pollutants it is possible that risks may be 

underestimated.

Unlike linear dose-response assessments for cancer, non-cancer health hazards generally are not 

expressed as a probability of an adverse occurrence. Instead, “risk” for non-cancer effects is 

expressed by comparing an exposure to a reference level as a ratio. The “hazard quotient” (HQ) 

is the estimated exposure divided by a reference level (e.g., the RfC). For a given HAP, 

exposures at or below the reference level (HQ≤1) are not likely to cause adverse health effects. 

As exposures increase above the reference level (HQs increasingly greater than 1), the potential 

for adverse effects increases. For exposures predicted to be above the RfC, the risk 

characterization includes the degree of confidence ascribed to the RfC values for the 

compound(s) of concern (i.e., high, medium, or low confidence) and discusses the impact of this 

on possible health interpretations. 

The risk characterization for chronic effects other than cancer is expressed in terms of the HQ for 

inhalation, calculated for each HAP at each census block centroid. As discussed above, RfCs 

incorporate generally conservative uncertainty factors in the face of uncertain extrapolations, 

such that an HQ greater than one does not necessarily suggest the onset of adverse effects. The 

HQ cannot be translated to a probability that adverse effects will occur, and is unlikely to be 

proportional to adverse health effect outcomes in a population. 

Comment: One commenter (0830-0030) claimed that EPA underestimates risks to children and 

from early-life exposure and that EPA must follow the science and account for increased earlylife susceptibility by using age-dependent adjustment factors for all carcinogens emitted by a 

source category. The commenter stated that currently, EPA only applies these factors to those 

HAP included in EPA’s list of carcinogens that act by a mutagenic mode of action and that NAS 

recognized this as a “missing” default in EPA’s approach that it should address and account for. 

Response: 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 (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 mode of action is not 

mutagenicity.17 The basis for this methodology is provided in the 2005 Supplemental 

Guidance.18

 

17U.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.

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. 
17 

The estimated risks must also be considered in the context of the full set of assumptions used for 

this risk assessment. Our unit risk estimates for HAP are considered a plausible upper-bound 

estimate with an appropriate age dependent adjustment; actual potency is likely to be lower and 

some of which could be as low as zero. 

Comment: One commenter (0830-0030) claimed that EPA’s risk assessment does not take into 

account increased susceptibility to carcinogens due to pre-natal exposures, even for known 

mutagenic carcinogens. The commenter stated that NAS identified the lack of accounting for in 

utero periods of exposure as a major omission in the EPA’s 2005 cancer guidelines. Similarly, 

the commenter noted that OEHHA conducted its own review of scientific literature on pre-natal 

susceptibility and exposures, which EPA should also consult and use. The OEHHA discusses the 

use of a 10X adjustment factor for cancer risk to account for pre-natal to age 2 exposures and the 

commenter asserts EPA should use that same factor to assess health risk due to pre-natal 

exposure. 

Response: We disagree with the commenter in that the risk assessment for this source category 

does not consider the groups that may be most at-risk (e.g., children). When the EPA derives 

exposure reference concentrations and unit risk estimates for hazardous air pollutants, it also 

considers the most sensitive populations identified in the available literature, and importantly, these 

are the values used in our risk assessments.19 With respect to maternal exposure in utero specifically, 

we are unaware of literature that would allow for a robust characterization of risk during this stage of 

development. 

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. 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. When the EPA derives exposure reference concentrations

and unit risk estimates for hazardous air pollutants, it considers the most sensitive populations 

identified in the available literature, and importantly, these are the values used in our risk 

assessments.20 We also disagree with the general comment that the EPA should adopt the Cal 

OEHHA child-protective scientific approach for deriving health benchmarks. The EPA has an 

approach for selecting appropriate health benchmark values and in general, this approach places 

greater weight on the EPA derived health benchmarks than those from other agencies.21 

Additionally, the approach of favoring 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. 

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 

 

19 US EPA. (2002). A review of the reference dose and reference concentration processes. EPA/630/P-02/002F. Risk 

Assessment Forum, Washington, DC. Available online at http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf

20 Id.

21 http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf 
18 

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 

mode of action is not mutagenicity.22 The basis for this methodology is provided in the 2005 

Supplemental Guidance.23

Comment: One commenter (0830-0030) stated that most of EPA’s IRIS toxicity values used for 

chronic non-cancer risk assessment do not incorporate the latest science on the increased 

susceptibility of children and EPA should apply child-specific reference values, where available, 

to evaluate chronic non-cancer risks. Specifically, the commenter points to nickel, cadmium, 

manganese, and lead; all of which EPA has recognized are emitted by aerospace facilities. The 

commenter claimed that OEHHA has generated child-specific reference values for several 

pollutants based on the latest science to take into account children’s greater exposure and greater 

vulnerability and EPA should use these values in its risk assessments. 

The commenter also stated that where child-specific reference values are unavailable, EPA must 

consult science on early exposure impacts and use an additional default or uncertainty factor to 

account for increased risk from early-life exposures for non-cancer risk. The commenter pointed 

to the 10X factor enacted by Congress in the Food Quality Protection Act (FQPA) of 1996 and 

stated that it would be appropriate and within EPA’s authority under CAA § 7412(f)(2) to 

similarly use a children’s ten-fold margin of safety factor to fulfill the CAA’s “margin of safety” 

requirement. The commenter went on to state that EPA can have no valid basis for ignoring 

science showing that pollutants other than carcinogens also can cause substantial harm even at 

low doses if exposure occurs in utero and during the early years of vulnerability. 

Response: We disagree with the commenter in that the risk assessment for this source category 

does not consider the groups that may be most at-risk (e.g., children). When the EPA derives 

exposure reference concentrations and unit risk estimates for hazardous air pollutants, it 

considers the most sensitive populations identified in the available literature, and importantly, 

these are the values used in our risk assessments.24 We also disagree with the general comment 

that the EPA should adopt the Cal OEHHA child-protective scientific approach for deriving 

health benchmarks. The EPA has an approach for selecting appropriate health benchmark values 

and in general, this approach places greater weight on the EPA derived health benchmarks than 

those from other agencies.25 Additionally, the approach of favoring EPA benchmarks (when they 

 

22 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 

23 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. 

24 US EPA. (2002). A review of the reference dose and reference concentration processes. EPA/630/P-02/002F. Risk 

Assessment Forum, Washington, DC. Available online at http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf

25 http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf 
19 

exist) has been endorsed by the SAB and ensures the use of values most consistent with wellestablished and scientifically-based EPA science policy. The EPA is currently evaluating the 

most appropriate use for the Cal OEHHA child-specific reference doses. 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). 

The EPA also disagrees with the commenter in 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)26 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 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)27 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) 28. 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. 

In conclusion, our chronic noncancer reference values have been derived considering the 

potential susceptibility of different subgroups, with specific consideration of children. In 

addition, an extra 10X uncertainty factor is not needed in the RfC/RfD methodology because the 

currently available factors are considered sufficient to account for uncertainties in the database 

from which the reference values are derived. After considering these and other factors, we 

continue to consider the risks from emissions after application of the revisions to the NESHAP 

 

26 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. 

27 U.S. EPA (1994). Methods for derivation of inhalation reference concentrations and application of inhalation 

dosimetry. (EPA/600/8-90/066F). Research Triangle Park, NC. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=71993

28 U.S. EPA (2011) External Review Draft of Guidance for Applying Quantitative Data to Develop Data-Derived 

Extrapolation Factors for Interspecies and Intraspecies Extrapolation http://www.epa.gov/raf/DDEF/index.htm
20 

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

NESHAP framework). 

Comment: One commenter (0830-0030) stated that EPA should utilize the best science on 

assessing children’s health risk of exposure to lead, rather than considering only the 2008 Lead 

NAAQS. The commenter stated that aerospace facilities emit at least 200 pounds per year of lead 

according to EPA’s inventory, yet EPA has assessed health risks from lead only by comparison 

with the 2008 Lead NAAQS. This ignores current data showing that harm, particularly to 

children, can occur at levels below the 2008 Lead NAAQS. The commenter pointed to several 

sources of new data on lead exposure levels and stated that EPA’s sole reliance on the 2008 Lead 

NAAQS is both unlawful and arbitrary due to EPA’s refusal to consider or address the newer 

science since 2008 showing harm to children below the exposure level of the 2008 Lead 

NAAQS. The commenter claimed EPA has no valid basis or reasoned explanation for not 

recognizing the need to consider information showing the need to address harm to children at 

ambient air levels of lead below what the 2008 Lead NAAQS allows. 

Further, the commenter stated that EPA found a NAAQS exceedance on-site at one facility (but 

no exceedance off-site), suggesting the potential for exceedances at facilities in nearby 

communities, and that EPA must require emission reductions of lead to prevent unacceptable 

levels of risk from lead. 

Response: We disagree with the comment that the use of the lead NAAQS does not sufficiently 

protect children. While recognizing that lead has been demonstrated to exert “a broad array of 

deleterious effects on multiple organ systems,” the lead NAAQS targets the effects associated 

with relatively lower exposures and associated blood lead levels, specifically nervous system 

effects in children including cognitive and neurobehavioral effects (73 FR 66976). EPA 

establishes the NAAQS at a level to protect sensitive sub-populations, such as children and 

pregnant women. The 2008 decision on the lead NAAQS was informed by an evidence-based 

framework for neurocognitive effects in young children. In applying the evidence-based 

framework, we 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 evidencebased 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 
21 

airborne lead at the level of the standard was not arbitrary or capricious.” Coalition of Battery 

Recyclers, 604 F. 3d at 618. 

As noted in the risk assessment document, there is no RfD or other comparable chronic health 

benchmark value for lead compounds. In 1988, the EPA’s IRIS program reviewed the health 

effects data regarding lead and its inorganic compounds and determined that it would be 

inappropriate to develop an RfD for these compounds, stating:29 

A great deal of information on the health effects of lead has been obtained through 

decades of medical observation and scientific research. This information has been 

assessed in the development of air and water quality criteria by the Agency’s Office of 

Health and Environmental Assessment (OHEA) in support of regulatory decision-making 

by the Office of Air Quality Planning and Standards (OAQPS) and by the Office of 

Drinking Water (ODW). By comparison to most other environmental toxicants, the 

degree of uncertainty about the health effects of lead is quite low. It appears that some of 

these effects, particularly changes in the levels of certain blood enzymes and in aspects of 

children’s neurobehavioral development, may occur at blood lead levels so low as to be 

essentially without a threshold. The Agency’s RfD Work Group discussed inorganic lead 

(and lead compounds) at two meetings (07/08/1985 and 07/22/1985) and considered it 

inappropriate to develop an RfD for inorganic lead. 

With regard to the information identified by the commenters, much of this information was 

similar to information available at the time of the 2008 NAAQS decision. For example, in 2005, 

the CDC recognized the evidence of adverse health effects in children with blood lead levels 

below 10 micrograms per deciliter (μg/dL), and that there is no safe level of blood lead in young 

children (CDC, 2005). The commenter also cites a benchmark analysis by California OEHHA 

that was completed during the time of the last lead NAAQS review (Carlisle and Dowling, 

2007). The quantitative relationship from this analysis is a correlation of 1 IQ point change with 

a 1.0 μg/dL change in blood lead is actually a substantially smaller change in IQ per μg/dL blood 

lead than the slope of 1.75 IQ points per μg/dL blood lead used in the evidence-based framework 

that the Administrator relied upon in his 2008 decision on a revised level for the lead NAAQS in 

2008 (73 FR 66964). Regarding the CHPAC recommendation on the level and averaging time 

for the revised NAAQS referenced by the commenter, the same comment was made to EPA in 

January of this year in the context of the current NAAQS review and the same comment was 

made and considered in the 2008 review, that concluded with the current lead NAAQS. 

Comment: One commenter (0830-0030) stated that EPA must fully account for the fact that 

people can be more vulnerable to toxic pollution due to various physiological, societal, 

demographic, and exposure history differences, and can therefore experience greater health risk 

from the same amount of a toxic chemical exposure. EPA found and acknowledged disparity in 

the risks that aerospace facilities create, with disproportionate exposure, and thus risks, falling on 

African-American and lower income communities. But EPA has not considered the variability 

and possible increased vulnerability of different socioeconomic groups into its risk assessment. 

 

29 The EPA’s IRIS assessment for lead and compounds (inorganic) (CASRN 7439-92-1) can be found at 

http://www.epa.gov/iris/subst/0277.htm. 
22 

Because aerospace facilities affect communities that are disproportionately people of color or 

lower income, EPA cannot ignore this greater risk in its assessment. 

Response: We disagree with the commenter that the EPA has ignored variability of different 

socioeconomic groups in their exposure and vulnerability to air pollution in the residual risk 

analysis. The EPA considers all people regardless of racial or socioeconomic status in the 

analysis. However, 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 Environmental Justice and the Action Development 

Process, the agency rule writers and policy makers could look at the whole range of factors that 

impact communities and population groups when crafting rules. The EPA is continuing to 

discuss and develop 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. 

Under EO 12898, the EPA is directed to the greatest extent practicable and permitted by law, to 

make environmental justice part of its mission by identifying and addressing, as appropriate, 

disproportionately high and adverse human health or environmental effects of its programs, 

policies and activities on minority populations and low-income populations in the United States. 

Consistent with EO 12898 and the Presidential Memorandum that accompanies it, the EPA’s 

environmental justice policies promote justice by focusing attention and EPA efforts on 

addressing the types of environmental harms and risks that are prevalent among minority, lowincome and indigenous populations. EO 12898 and the EPA’s environmental justice policies do 

not mandate particular outcomes from an action, but they demand that decisions involving the 

action be informed by a consideration of environmental justice issues. With respect to this rule, 

the EPA found the overall level of risk from the source category to be acceptable and to provide 

an ample margin of safety for all populations in close proximity to these sources, including 

minority and low-income populations. 

Comment: One commenter (0830-0030) stated that EPA must follow the best available science 

to assess multipathway risk. Specifically, the commenter added that EPA must assess the noninhalation-based risk by aerospace facilities’ emissions of all persistent and all bioaccumulative 

pollutants. The commenter stated that EPA has restricted its multipathway risk screening 

assessment to only those contaminants identified in the “outdated” 2004 Risk Assessment 

Guidance as persistent and bioaccumulative in the environment (PB-HAPs). This decision is not 

supported by EPA’s own 2004 Guidance which states that “multipathway risk assessment may 

be appropriate generally when air toxics that persist and which also may bioaccumulate and/or 

biomagnify are present in releases.” The commenter concluded that EPA’s list of 14 PB-HAPs 

is incomplete, however, because it ignores other HAPs which present a multipathway risk. 

The commenter stated the following pollutants have been shown to have a significant potential 

for deposition and retention within the environment: arsenic, hexavalent chromium, nickel, 
23 

beryllium, selenium, and naphthalene. The commenter explained that air emissions of these 

compounds therefore present a risk to nearby communities via dermal, ingestion, and other noninhalation pathways that are currently not being considered in the residual risk assessment. The 

commenter argued that the choice to exclude those contaminants which persist and accumulate in 

soils underestimates risks from HAP emissions. In addition, the commenter stated that 

manganese is a pollutant to which children have particular exposure and vulnerability due to 

elevated levels in soils around major emission sources. 

The commenter (0830-0030) stated that EPA must perform multipathway assessments for all 

pathways of exposure, including those that particularly affect children. The commenter further 

stated that EPA should recognize that science shows additional pathways that it has not 

addressed for certain pollutants for which it does not recognize the need for a multipathway 

assessment. According to the commenter, science shows that EPA has relied on outdated 

estimates of incidental soil exposures. The commenter added that risk assessments of exposure to 

soil contaminants should evaluate both direct exposure, hand-to-mouth, and indirect, object-tomouth exposure. The commenter cited multiple studies showing the rates of hand-to-mouth and 

object-to-mouth exposure in children toddlers and children, including the 2011 update to EPA’s 

Exposure Factors Handbook which includes more recent estimates of hand-to-mouth behavior 

and should be used by EPA to assess risks from exposures to contaminated soils. 

Response: We believe our multipathway assessment is a reasonable technical analysis of risk to 

human health from aerospace emissions of HAP via non-inhalation pathways. We currently do 

not have screening values for some persistent and bioaccumulative hazardous air pollutants (PBHAP), but we disagree that the multipathway assessment is inadequate because it did not include 

some hazardous air pollutants. In the Air Toxics Risk Assessment Reference Library, we 

developed the current PB-HAP list considering all of the available information on persistence 

and bioaccumulation.30 In developing the list we considered HAP identified as PB-HAP by 

other EPA Program Offices (e.g., the Great Waters Program), as well as information from the 

persistent, bioaccumulative and toxic (PBT) profiler (see http://www.pbtprofiler.net). 

Considering this list was peer-reviewed by the SAB and found to be acceptable, we believe it to 

be reasonable for use 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. However, in the future we may add more pollutants to the multipathway analysis if we 

determine it is appropriate to do so. 

We disagree with the comment that our multipathway risk assessment does not consider children. 

The multipathway screening scenario is intended to represent a high-end exposure for children 

via incidental soil ingestion. The 2011 Exposure Factors Handbook recommended “upperpercentile” soil ingestion rate (numeric percentile not specified) for children aged 3 to <6 years is 

200 mg/d. The EPA also published the Child-Specific Exposure Factors Handbook (2008). No 

additional data or recommendations for child soil ingestion are presented in this source, and in 

fact an “upper percentile” value for this parameter is not provided. Based on these sources, a 

 

30 Air Toxics Risk Assessment Library, Volume I available at http://www2.epa.gov/fera/air-toxics-risk-assessmentreference-library-volumes-1-3 
24 

value of 200 mg/d is used in the current RTR multipathway screening scenario for the child 

incidental soil ingestion rate. 

The multipathway risk assessment conducted for this source category was a screening-level 

assessment. (80 FR 8403-06, 8410, 8415, February 17, 2015). The screening assessment used 

highly conservative assumptions designed to ensure that facilities with results below the 

screening threshold values did not have the potential for multipathway impacts of concern. The 

screening scenario is a hypothetical scenario, and due to the theoretical construct of the screening 

model, exceedances of the thresholds are not directly translatable into estimates of risk or hazard 

quotients for these facilities. The tiered screening approach used the full multipathway 

assessment conducted to develop the screening thresholds, but incorporated some site-specific 

information to replace some default parameters, such as distance to the lake and local 

meteorological data. The scope of the assessment did not change across the tiers in the 

multipathway screening assessment and are described in the risk assessment document (and 

related appendices) available in the docket. 

Further, regarding incidental soil contamination, the EPA has estimated risks from both direct 

and indirect pathways. Direct routes of exposure include direct ingestion of soil and exposure 

through dermal contact. However, because it has been demonstrated in past analyses that 

exposure levels associated with dermal contact are but a small fraction of exposure levels 

associated with ingestion and inhalation pathways, dermal exposures were not assessed for this 

source category. 

Comment: One commenter (0830-0030) stated that EPA must assess multipathway risk based 

on allowable emissions, not just the so-called actual emissions which are likely underestimated. 

EPA has recognized greater amounts of inhalation-based pollutants but has not recognized or 

assessed the full potential for persistent or bioaccumulative emissions by failing to assess the 

potential for greater amounts of other PB-HAP emissions. Intermittent or short spikes of PBHAPs can represent a significant health risk because the contaminants stay in the environment 

and can accumulate over time. For this reason, the commenter stated that EPA’s analysis likely 

underestimates the health risks from multipathway routes of exposure. 

Response: We disagree with the commenter’s assertion that we should base the multipathway 

risk assessment on allowable emissions and maintain that it is reasonable for the multipathway 

risk assessment to be based on actual emissions for this source category, and not the allowable 

level of emissions that facilities are permitted to emit. The uncertainties associated with the 

multipathway screening analysis along with uncertainties in the allowable emissions estimates, 

would make a quantitative multipathway risk assessment based on allowable emissions highly 

uncertain. However qualitatively, as seen when examining the risk analysis for inhalation, 

because emissions for both actual and allowable are comparable, we would expect a 

multipathway analysis considering allowable to be similar to that for actual emissions (all 

facilities passed the Tier 1 screening analysis).

Comment: One commenter (0830-0030) stated that EPA must account for the aggregate impact 

of inhalation and multipathway cancer and chronic non-cancer risk by adding each type of 

similar risk together for all pollutants. The multipathway assessment allows EPA to look at a 

person’s overall exposure – not just inhalation. EPA must add multipathway and inhalation risk. 
25 

Failing to determine cancer risks, non-cancer risks, and a cumulative burden metric makes 

EPA’s overall analysis incomplete. 

Response: We disagree with the commenter’s assertion that our risk analysis is incomplete and 

have combined risk to the extent that it is appropriate to do so. We consider the effect of 

mixtures of carcinogens consistent with EPA guidelines and use a target organ-specific hazard 

index (TOSHI) approach for our chronic non-cancer assessments. We do not use a TOSHI 

approach for acute analyses nor do we combine the results of our inhalation and multipathway 

assessments. We did not find it reasonable to combine the results of our inhalation and 

multipathway risk assessment for this source category. The multipathway risk assessment was a 

screening-level assessment. The screening assessment used highly conservative assumptions 

designed to ensure that facilities with results below the screening threshold values did not have 

the potential for multipathway impacts of concern. The screening scenario is a hypothetical 

scenario, and due to the theoretical construct of the screening model, exceedances of the 

thresholds are not directly translatable into estimates of risk or hazard quotients for these 

facilities. Rather, it represents a high-end estimate of what the risk or hazard may be. For 

example, an exceedance of two for a non-carcinogen can be interpreted to mean that we have 

high confidence that the hazard would be less than two. Similarly, an exceedance of 30 for a 

carcinogen means that we have high confidence that the risk is lower than 30-in-1 million. Our 

confidence comes from the conservative, health-protective assumptions that are in the screens: 

we choose inputs from the upper end of the range of possible values for the influential 

parameters used in the screens; and we assume that the exposed individual exhibits ingestion 

behavior that would lead to a high total multipathway exposure. We do not sum the risk results 

from chronic inhalation assessment and the screening multipathway assessment because it is 

inappropriate to do so based on the differences in the two types of assessments. In addition to the 

constraints in the screening-level multipathway assessment described above, it is highly unlikely 

that the same receptor has the maximum results in both assessments. In other words, it is unlikely 

that the person with the highest chronic inhalation cancer risk is also the same person with the 

highest individual multipathway cancer risk. We agree, in concept, with the commenter that we 

should consider overall risk, but we do so by assessing cancer and chronic non-cancer inhalation 

risk, acute risk, multipathway risk and by combining risk results where appropriate, not by 

arbitrarily summing risk measures in the absence of a valid technical basis. 

Comment: One commenter (0830-0030) disagreed with the findings that the health risks 

presented by aerospace facilities are acceptable. The commenter stated that EPA findings of at 

least 10-in-1 million lifetime cancer risk, with 180,000 people exposed to a risk of 1-in-1 million 

or more, is an extra cancer case at least every 50 years. The commenter argued that EPA should 

not find that this extra cancer case is “acceptable” and no community member should have to 

have their child or other loved one become this statistic. 

The commenter added that the acute risk hazard quotient (“HQ”) of 2, which is twice the HQ 

where EPA believes no harm occurs, is under-protective and unreliable. The commenter argued 

that there is a good chance that this high acute risk also occurs in other communities near other 

facilities that are located nearer to people and EPA has provided no evidence showing this is not 

the case. 
26 

The commenter stated that all of these risks occur disproportionately in communities of color and 

lower income communities – many of whom are experiencing other toxic pollution 

simultaneously on top of this pollution. 

Response: In 1990, Congress codified in section 112(f) of the CAA the approach we use for our 

residual risk analyses (i.e., the Benzene NESHAP, 54 FR 38044). Under that approach, the 100-

in-1 million cancer risk is not a bright line indicating that risk is “acceptable.” Rather, we 

consider this health metric in conjunction with a variety of health factors and their associated 

uncertainties to determine whether the risk is acceptable. Where we conclude that the risk is not 

acceptable, we cannot and do not consider costs in requiring controls to bring risks down to an 

acceptable level. However, the analysis of whether risk is acceptable is not the endpoint. Once 

we determine that the existing MACT standards or controls are sufficient to ensure risk is 

acceptable, we again review the health metrics (e.g., cancer and chronic non-cancer risks) and 

their associated uncertainties in conjunction with the costs of controls, technical feasibility, and 

other relevant factors, to determine whether additional controls should be required to provide an 

ample margin of safety. As explained at proposal, EPA has adopted the Benzene NESHAP 

approach in its residual risk determinations and the D.C. Circuit has upheld as reasonable the 

EPA’s interpretation that section 112(f)(2) incorporates this approach. 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 the citation to the 

Federal Register.”). 

We generally draw no bright lines of acceptability regarding cancer or non-cancer risks from 

source category HAP emissions, and 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. 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. 

Comment: One commenter (0830-0031) recommended that the EPA consider allowable or 

potential emissions, rather than actual emissions, as much as possible for evaluating risks 

because actual emissions could increase over time and could underestimate residual risk. The 

commenter supported the EPA's use of allowable emissions in parts of the rulemaking, but noted 

that EPA used actual emissions in other parts, and encouraged EPA to use allowable emissions, 

including in assessing acute health risks. 
27 

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 analyses. See National Emission Standards for 

Coke Oven Batteries, 70 FR 19992, 19998 (April 15, 2005). The risk assessment for the 

aerospace manufacturing and rework (surface coating) source category was conducted using 

actual and allowable emissions, and all of the results were considered in determining risk 

acceptability and ample margin of safety. See the Residual Risk Assessment for the Aerospace 

Manufacturing and Rework Facilities Source Category in Support of the November, 2015 Risk 

and Technology Review – Final, available in the docket for this rulemaking. 

The commenter also urges the Agency to rely on allowable emissions for the purpose of our 

acute assessment. We did not rely on allowable emissions for the acute screening assessment 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 ten 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. 

Comment: One commenter (0830-0031) recommended that the EPA consider the emission 

concentration at the fenceline of the facility, rather than at the centroid of the most highly 

affected census block when assessing the cancer risk. The commenter noted that the point of 

maximum impact could be located far from the centroid of the census block, depending on the 

size and population density of the census block. The commenter also noted that over time homes 

and businesses could be built closer to the facility. The commenter also noted that using HEM-3, 

the EPA can locate the maximum individual risk at any point in the census block and 

recommended that the EPA should use the truly maximum individual risk, rather than the risk at the 

centroid of the census block as a surrogate for exposure to all people in the census block, in the 

EPA's CAA section 112(f)(2) risk assessments. 

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 US Census Bureau); on average, a census 
28 

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 to 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 

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.31

This has been the EPA’s approach for estimating chronic maximum individual exposures and 

risks throughout the RTR program. In addition, 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. 

In addition to the approach described above, the EPA recognizes that where a census block 

centroid is located on industrial property or is large and the centroid is less likely to be 

representative of the block’s residential locations, the block centroid may not be the appropriate 

surrogate. For this source category, as described in the risk assessment document available in the 

docket, in cases where a census block centroid was within 300 meters of any emission source 

(and, therefore, possibly on facility property), we viewed aerial images of the facility to 

determine whether the block centroid was likely located on facility property. Likewise, we 

examined aerial images of all large census blocks within one kilometer of any emission source. If 

the block centroid did not represent the residential locations within that block, we relocated it to 

better represent them and/or we added receptors for residences nearer to the facility than the 

centroid. 

In the case of military operations the census block could be located within the facility boundary 

(i.e., on the military base) in the form of on-base residential housing, and this fact was taken into 

account in the risk assessment. 

 

31 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.
29 

For this source category, we added several receptors for census blocks where the centroid 

location was not representative of the residential locations. Appendix 4 of the risk assessment, 

entitled "Residual Risk Assessment for the Aerospace Manufacturing and Rework Facilities 

Source Category in Support of the November, 2015 Risk and Technology Review – Final," 

provides additional information on these changes. 

Comment: One commenter (0830-0031) shared the EPA's concern about the disproportionate 

impact on certain social, demographic, and economic groups, but recommended that EPA 

improve the methods of evaluating environmental justice and asked EPA to consider these 

factors in developing the final rule. The commenter 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 5 kilometers (km) of the facility, regardless of projected 

risk. The commenter stated that this would be consistent with the approach used for the Hard and 

Decorative Chromium Electroplating and Chromium Anodizing Tanks source category.32 The 

commenter noted that the socio-economic analysis for the proposed Aerospace NESHAP did not 

evaluate potential disparities within 5 km for cancer risk at maximum allowable emission levels 

and argued that this type of analysis is especially important in instances where a facility is 

located in a minority and low-income community. The commenter noted that the EPA only 

evaluated the risk to the population within a 50 km radius, and argued that this could dilute the 

results by including populations not in the demographic groups most at risk, especially the case if 

the source is located in or next to a minority or low-income population. Therefore, the 

commenters recommended that EPA conduct an analysis at the 5 km distance to assess facility 

impacts to nearby environmental justice communities and 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 these types of analyses in the rulemaking process. 

Response: The commenter is correct that we performed the demographic analyses for the 

aerospace 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 both 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 that result in cancer risks of 1-in-1 million or greater or noncancer 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 Hard and Decorative Chromium Electroplating and Chromium Anodizing 

 

32 National Emission Standards for Hazardous Air Pollutant Emissions: Hard and Decorative Chromium 

Electroplating and Chromium Anodizing Tanks; Proposed Rule. 75 FR 65068, October 21, 2010. 75 FR 65089. 
30 

Tanks 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 Hard and Decorative Chromium 

Electroplating and Chromium Anodizing Tanks 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 aerospace 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 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 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. 

Comment: One commenter (0830-0031) expressed concern with the EPA’s past and current use 

of Acute Exposure Guideline Levels (AEGLs) or Emergency Response Planning Guidelines 

(ERPGs) values to address acute exposures in the residual risk assessments. The commenter 

argued that these limits were developed for accident release emergency planning, and are not 

appropriate for assessing daily human exposure scenarios. The commenter noted that in the 

December 2002 EPA document, "A Review of the Reference Dose and Reference Concentration 

Processes," EPA stated that the primary purpose of the AEGL program is to develop guidelines 

for once-in-a-lifetime short-term exposures to airborne concentrations of acutely toxic chemicals, 

and they are not meant to evaluate the acute impacts from routine emissions that occur over the 

life of a facility. The commenter argued that, unlike the reference concentrations (RfCs) for 

chronic exposures, the AEGLs and ERPGs do not include adequate safety and uncertainty factors 

and cannot be relied upon to protect the public from the adverse effects of exposure to toxic air 

pollutants. The commenter argued that AEGLs and ERPGs should not be used in residual risk 

assessments because they do not ensure that public health is adequately protected from the acute 

impacts of HAP exposure. The commenters supported EPA's increased use of California 

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

and urged EPA to use the RELs for these assessments. 

Response: 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 (see 80 FR 8402), 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 
31 

EPA’s RTR risk assessment methodologies,33 we generally examine a wider range of available 

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

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

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

cases, when Reference Value Arrays 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 rule (80 FR 8402), 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. 

Comment: One commenter (0830-0030) argued that the EPA should reform how it evaluates 

chronic and acute hazard indices, in which a risk number below 1 does not result in policy 

changes or standards. The commenter stated that the EPA should instead factor in uncertainties 

and vulnerability factors to adjust the level of non-cancer risk considered acceptable for both 

chronic and acute exposure. The commenter added that this is currently done under the Food 

Quality Protection Act (FQPA) when EPA uses factors to determine a Target Margin of 

Exposure and risks below this level warrant increased scrutiny and changes to allowable 

exposures.34

Response: The EPA’s approach to performing risks assessments in support of the residual risk 

program has been reviewed and supported by the Science Advisory Board (SAB) several times 

over the past 17 years.35 Hazard for non-cancer effects is expressed by comparing an exposure 

to a reference level as a ratio. The “hazard quotient” (HQ) is the estimated exposure divided by a 

reference level (e.g., the RfC). For a given HAP, exposures at or below the reference level 

(HQ≤1) are not likely to cause adverse health effects. For example, chronic non-cancer reference 

values represent chronic exposure levels that are intended to be health-protective. That is, EPA 

and other organizations which develop non-cancer reference values (e.g., the Agency for Toxic 

Substances and Disease Registry – ATSDR) utilize an approach that is intended not to 

underestimate risk in the face of uncertainty and variability. When there are gaps in the available 

information, uncertainty factors (UFs) are applied to derive reference values that are intended to 

be protective against appreciable risk of deleterious effects. 

 

33 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

34 See, e.g., EPA, Sulfuryl Fluoride; Proposed Order Granting Objections to Tolerances and Denying Request for a 

Stay, Proposed Rule, 76 Fed. Reg. 3422, 3427 (Jan. 19, 2011) (explaining use of MOE). 

35 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
32 

We generally draw no bright lines of acceptability regarding cancer or non-cancer 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 

decided 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 all their uncertainties, 

when determining the acceptable level of source category risk. 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. 

Comment: One commenter (0830-0030) stated that while EPA assesses the combined impact of 

cancer risks and chronic non-cancer risk, EPA must also combine and look at the whole picture 

of all other kinds of risk from multiple pollutants. In particular, EPA must assess the total and 

synergistic cancer risk and total chronic non-cancer risk for different pollutants. Additionally, the 

commenter stated EPA should apply these same principles to create a mechanism for assessing 

the total acute risk to chemical mixtures. The commenter also stated EPA must create a metric to 

assess the total and cumulative risk burden rather than only looking at each type of risk in a 

discrete, separate way. Unless EPA creates a combined health risk metric, it cannot make an 

ample margin of safety determination that is based on the full picture of health risk for a source 

category. EPA must assess the cumulative burden for public health. The commenter further 

stated that in addition to performing a cumulative assessment from multiple sources within the 

aerospace source category, EPA also must perform a cumulative analysis that considers the 

additional risk people face as a result of being exposed to aerospace and also different nearby 

source categories (not necessarily collocated). The commenter claimed EPA has recognized this 

need but has failed to follow through on evaluating all multiple sources. The commenter stated 

that while EPA has calculated a “facility-wide” risk for different sources collocated at the same 

address, it has not used that number to set standards and has ignored different sources across the 

street or in close proximity, even though all these sources’ emissions are combining to affect the 

person most-exposed to aerospace facilities’ emissions. Additionally, EPA has provided no 

information on how it reached the “facility-wide” risk number. The commenter provided 

multiple references (e.g., NAS, OEHHA) and discussion for performing this type of multi-source 

analysis. 

Response: We have combined risk assessment results to the extent that it is appropriate to do so 

and disagree with comment that we failed to consider or account for cumulative risk. The EPA 

conducted an assessment of the cumulative cancer risks from all emitted carcinogens and the 

cumulative noncancer hazard indices from all emitted non-carcinogens that are hazardous air 

pollutants affecting the same target organ system for both the source category emissions and the 

facility-wide emissions. To address the effect of mixtures of carcinogens, the individual cancer 
33 

risks for the source category were aggregated for all carcinogens. 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 hazard quotients (HQ) to provide a target organ-specific hazard 

index (TOSHI). We do not use a TOSHI approach for our acute analyses nor do we combine the 

results of our inhalation and multipathway assessments. We further modeled whole-facility risks 

for both chronic cancer and non-cancer impacts to understand the risk contribution of the sources 

within the aerospace source category. 

For this source category, the EPA conducted an assessment of the cumulative cancer risks from 

all emitted carcinogens and the cumulative noncancer hazard indices from all emitted noncarcinogens that are hazardous air pollutants affecting the same target organ system for both the 

source category emissions and the facility-wide emissions. 

The EPA modeled whole-facility risks for both chronic cancer and non-cancer impacts to 

understand the risk contribution of the sources within the aerospace source category. The 

individual cancer risks for the source categories were aggregated for all carcinogens. In assessing 

noncancer hazard from chronic exposures for pollutants that have similar modes of action or 

(where this information is absent) that affect the same target organ, we aggregated the hazard 

quotients (HQ). This process creates, for each target organ, a TOSHI, defined as the sum of 

hazard quotients 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). 

As described in the risk assessment document available in the docket, 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). The worst-case acute screen is 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 “Residual Risk Assessment for the 

Aerospace Manufacturing and Rework Facilities Source Category in Support of the November, 

2015 Risk and Technology Review - Final”, 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.” 

Also, we did not combine the inhalation and multipathway risk assessment results for each 

pollutant because it is inappropriate to do so. The multipathway risk assessment conducted for 

proposal was a screening-level assessment followed by a more refined site-specific assessment. 

The screening assessment used highly conservative assumptions designed to ensure that facilities 

with results below the screening threshold values did not have the potential for multipathway 

impacts of concern. The screening scenario is a hypothetical scenario, and due to the theoretical 

construct of the screening model, exceedances of the thresholds are not directly translatable into 

estimates of risk or hazard quotients for these facilities. Further, it is unlikely that the person with 

the highest chronic inhalation cancer risk is also the same person with the highest individual 

multipathway cancer risk. 
34 

We disagree with the claim that additional quantitative assessment of risks from sources outside 

the source category is required for this rulemaking. Section 112(f) requires the EPA to perform a 

review of whether there is risk remaining from emissions from a source category after 

promulgation of the technology based MACT standards for that source category. To this end, the 

EPA conducts a comprehensive assessment of the risks associated with exposure to the HAP 

emitted by the source category 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 ample margin 

of safety (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 section 

112(f) analysis. This assessment excludes background contributions because the available data 

are of insufficient quality upon which to base a meaningful analysis. Further, as explained at 

proposal, our approach here is also 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 

concentrations. (NRDC v. EPA, 529 F.3d 1077 (D.C. Cir. 2008)). 

Comment: One commenter (0830-0030) claimed EPA failed to use the best available reference 

values for a number of key HAPs including benzene, and thus underestimated risk from these 

pollutants. The commenter provided a comparison table of cancer potency factors utilized by 

EPA and those published by California EPA in July 2014. These comparison showed a 

significantly lower potency in EPA’s values, ranging from 57 percent to 92 percent lower. The 

commenter asserted that EPA must use the latest reference values in its analysis. 

Similarly, the commenter stated that EPA has used some out of date and less health protective 

reference inhalation factors for chronic exposure to benzene and several other important highexposure HAPs and provided another comparison table showing the differences between EPA’s 

reference concentrations and California EPA’s values published in June 2014. The commenter 

also pointed out that the acute reference value used to evaluate benzene exposure is two orders of 

magnitude too high, leading to a very significant underestimate of the acute non-cancer health 

hazards of benzene emissions from aerospace facilities.

Response: EPA’s chemical-specific toxicity values are derived using risk assessment guidelines 

and approaches that are well established and vetted through the scientific community, and follow 

rigorous peer review processes.36 The RTR program gives preference to EPA values for use in 

 

36 Integrated Risk Information System (IRIS). IRIS Guidance documents available at 

http://www.epa.gov/iris/backgrd.html 
35 

risk assessments and uses other values, as appropriate, when those values are derived with 

methods and peer review processes consistent with those followed by the EPA. The approach for 

selecting appropriate toxicity values for use in the RTR Program has been endorsed by the 

SAB.37

The commenter recommended that EPA use California OEHHA’s new toxicity values for several 

chemicals and provided some references for the approaches used to derive those values. EPA 

scientists reviewed the information provided by the commenter and concluded that further 

information is needed to evaluate the scientific basis and rationale for the recent changes in 

California OEHHA risk assessment methods. As previously explained, only one set of acute 

reference values from California OEHHA are most appropriately designed for use in the RTR 

Program: the acute Reference Exposure Levels (RELs), which are developed for their Air Toxics 

Hot Spots program – a program similar in scope and context to the RTR assessments of risk. The 

EPA will work on gathering the necessary information to conduct an evaluation of the scientific 

merit and the appropriateness of the use of California OEHHA’s new toxicity values in the 

context of the RTR program. Therefore, EPA did not use the new California OEHHA toxicity 

values and continued to follow the SAB-endorsed approach to select the most appropriate 

toxicity values for this rule making. 

6.0 Technology Review 

Comment: One commenter (0830-0028) stated that EPA’s conclusion of no new developments 

in practices, processes, and control technologies that warrant revisions of the standard is correct 

and are appropriately supported by a review of current technology and limits in EPA’s 

RACT/BACT/LAER Clearinghouse and MACT standards for other source categories. 

The commenter noted that even if EPA were to re-review technologies rejected during the initial 

rulemaking, the Agency would reach similar conclusions to not adopt them today, as these 

control options are limited to unique operations in the industry, are not cost-effective, and result 

in the creation of other pollutants. 

The commenter agreed that there are no demonstrations of add-on controls to control organic 

HAP emissions from the coating of assembled aerospace vehicles, and further noted that a recent 

BACT analysis showed that add-on controls are not cost-effective for large aerospace 

components. The commenter recommended that EPA should finalize that there are no revisions 

needed to the standards for primers, topcoats, depainting, chemical milling maskants, cleaning, 

and waste handling operations. 

Response: The EPA acknowledges the commenter’s agreement with the results of EPA’s 

technology review and the conclusion that there are no new developments in practices, 

processes, and control technologies for primers, topcoats, depainting, chemical milling maskants, 

cleaning, and waste handling operations.

Comment: One commenter (0830-0030) argued that EPA may not exempt waste handling and 

storage operations from the technology review because doing so would violate CAA § 

 

37 http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf
36 

7412(d)(6) and disagreed with EPA’s basis for not doing a technology review in the current 

rulemaking. 

First, the commenter argued that the Act requires a review of the existing emission standards at 

least every 8 years after promulgation, including reviewing developments in practices, processes, 

and control technologies.38 The commenter added that EPA argued that “there is no need to do a 

technology review” in the current rulemaking39 because EPA sets standards for wastes not 

covered by RCRA and EPA stated that “[t]he practical effect of [this rule] is that all HAPcontaining wastes generated by aerospace manufacturing and rework operations are subject to 

RCRA and are exempt from the requirements of 40 CFR 63.748.”40 The commenter added that 

in 1994, for waste that are not subject to the provisions of RCRA, the agency promulgated 

standards that required HAP-containing waste to be handled in such a manner that spills are 

minimized for waste handling and storage operations.41 The commenter added that EPA 

recognizes that it must perform the first required 8-year review of the 1994 standards.42 

In addition, the commenter argued that EPA has not provided any data or other evidence 

showing that all aerospace waste is exempt from the current standards that apply to aerospace 

facilities nor has it shown that aerospace waste and storage handling is actually regulated by 

RCRA. The commenter stated that EPA cites no RCRA regulations that regulate the emissions of 

these operations, including their hazardous air emissions, much less any such regulations that do 

so effectively. The commenter argued that unless EPA can show that all aerospace waste storage 

and handling operations’ air emissions are appropriately regulated by RCRA, at least as 

stringently as CAA § 112(d) and (f) require, then its refusal to review these standards is arbitrary 

and capricious. 

The commenter argued that EPA’s stated reason for originally exempting certain waste (that is 

subject to RCRA) from the Clean Air Act waste handling and storage standards conflicts with 

and does not support a refusal to do a CAA § 112(d)(6) review now. The commenter noted that 

EPA states in the current rule preamble that it promulgated the original exemption to try to avoid 

creating “potential conflicts” with RCRA.43 However, the commenter argued that the agency’s 

explanation for the original exemption was actually more nuanced as EPA stated that it was 

promulgating the exemption “so that the ... standards would not require less strict handling and 

storage of waste than the RCRA requirements.”44 The commenter argued that there is no 

indication that it would create “potential conflicts” for EPA to review the existing CAA 

standards to see if there are “developments” that it should account for in revised standards, as the 

CAA requires, to assure stronger standards than currently apply under either CAA or RCRA. The 

commenter explained that it would be fully consistent with the originally stated objective of 

assuring sufficiently strict requirements for EPA to perform the requisite review now and would 

allow EPA to assess and determine whether the CAA standards are up to date and sufficiently 

stringent. The commenter added that if EPA performs the requisite CAA review and finds that 

 

38 42 U.S.C. § 7412(d)(6). 

39 80 Fed. Reg. at 8419 (citing 59 Fed. Reg. 29,216). 

40 Id. 

41 Id. (citing 40 CFR 63.748). 

42 Id. at 8395; Consent Decree, Sierra Club v. Jackson, Case No. 09-cv-00152-SBA (N.D. Cal. Sept. 26, 2011). 

43 80 Fed. Reg. at 8419. 

44 1994 Proposed Rule, 59 Fed. Reg. at 29,223 (emphasis added). 
37 

there are “developments” in waste storage and handling, EPA will then need to revise the 

standards to assure that they satisfy CAA § 112(d), including § 112(d)(2) and (3). As part of this 

analysis, EPA can ensure the standards are not less stringent than what is required under RCRA, 

and thus avoid any potential conflicts, according to the commenter. 

The commenter argued that the reviews required by CAA § 7412(d)(6) and (f)(2) are both 

necessary in part to assure that there are appropriate emission standards in place for hazardous 

air pollutants emitted by aerospace waste storage and handling operations. The commenter stated 

that EPA has no authority to exempt major sources from CAA § 7412 standards. The commenter 

noted that EPA acknowledged that it also may not set no control standards.45 The commenter 

added that these must meet a particular stringency test as defined by CAA § 7412(d)(2) and (3). 

The commenter argued that EPA may not evade these CAA responsibilities by referring to a 

different statute (i.e., RCRA) that does not include and cannot substitute for the § 7412 

requirements. The commenter argued that EPA must ensure that the required CAA § 7412(d)(6) 

review is satisfied and that any HAPs emitted from waste storage and handling operations are 

subject to CAA § 7412(d) standards that assure the “maximum achievable” degree of emission 

reductions. 

The commenter noted that it is unclear whether EPA included waste handling and storage 

operations in its CAA § 7412(f)(2) risk assessment. The commenter argued that EPA did not 

state whether it included emissions from waste storage and handling operations in the CAA § 

7412(f)(2) review which requires assessing risks to public health and the environment under the 

existing standards. 

Finally, the commenter argued that EPA may not rely on the original exemption for certain waste 

operations because that, in turn, is unlawful under CAA § 7412(c) and (d). Where Congress 

intended to allow EPA to exempt sources from CAA § 7412 standards based on the existence of 

standards under other statutes, it did so expressly, according to the commenter. See, e.g., CAA § 

7412(d)(9) (radionuclide emissions provision). The commenter added that there is no such 

exemption for aerospace sources, or any part of their emissions. 

Response: The EPA disagrees with the commenter. The complete response to this comment can 

be found in section IV.K.3 of the preamble to the final rule. 

Comment: One commenter (0830-0028) requested that EPA clarify in the final rule that HAPcontaining solvent wipes subject to the Resource Conservation and Recovery Act (RCRA) 

requirements are exempted from waste handling requirements of the Aerospace NESHAP. The 

commenter referenced recent RCRA rule changes including Conditional Exclusions from Solid 

Waste and Hazardous Waste for Solvent-Contaminated Wipes [78 Fed. Reg. 46448 (July 31, 

2013)], and noted that although these wipes are conditionally excluded from the definition of 

solid waste or hazardous waste, they are subject to RCRA management and emission control 

requirements in order to retain the solid or hazardous waste exclusion. The commenter expressed 

concern that additional regulation of these wipes under the Aerospace NESHAP may result in 

conflicting requirements. 

 

45 80 Fed. Reg. at 8419. 
38 

Response: The EPA proposed no revisions to the standards in 40 CFR 63.748 for handling and 

storage of waste that would potentially affect HAP-containing solvent wipes. Because no issues 

were raised with respect to the current provisions and the use of solvent wipes since 

promulgation of the original aerospace NESHAP in 1995 we see no need to provide clarification 

at this time. However, the EPA has revised 40 CFR 63.741 to remove and reserve paragraph (e), 

and has revised 40 CFR 63.744(a) and 63.748 to clarify the relationship between subpart GG and 

the regulations to implement RCRA (40 CFR parts 260 through 268). Under these clarifications 

in the final rule, solvent laden materials that are complying with the requirements in 40 CFR 

parts 262 through 268 are not subject to the requirements in 40 CFR 63.744(a) and 63.748. 

Comment: One commenter (0830-0030) stated that EPA has not reviewed how and if the 

existing standards control polycyclic organic matter (POM) or addressed whether the standards 

are currently adequate to do so under CAA § 7412(d) or (f) as part of the required reviews in this 

rulemaking. The commenter added that EPA has not addressed what emission standards are 

needed for specialty coating operations to restrict POM as required by CAA § 7412(d)(2) and 

(3), by assuring the maximum achievable degree of emission reductions of POM. The 

commenter argued that EPA has not performed any risk assessment for POM, which is a 

multipathway, persistent bioaccumulative toxic pollutant, or shown that it has satisfied CAA § 

7412(f)(2) for this pollutant.46 The commenter explained that EPA is legally required to regulate 

and restrict all pollutants emitted by aerospace sources.47 Thus, EPA’s failure to assess health 

risks from POM violates CAA § 7412(f)(2), and EPA’s failure to address and limit POM 

emissions from specialty coating operations also violates CAA § 7412(d), including CAA § 

7412(d)(2), (d)(3), and (d)(6). 

Response: The EPA disagrees with the commenter. As explained at proposal and in the 

preamble to the final rule, the EPA has completed a technology review and risk assessment for 

surface coatings operations of the Aerospace Manufacturing and Rework facilities source 

category, under CAA sections 112(d)(6) and (f)(2), respectively. Additionally, as proposed, EPA 

is finalizing MACT standards for the specialty coating subcategory, under CAA section 

112(d)(3). POM is an organic HAP and the EPA established a total organic HAP standard for 

primer, topcoat, and chemical milling maskant operations in subpart GG promulgated in 1995 

(60 FR 45956, September 1, 1995). The primary source of POM is formation during fossil fuel 

combustion, and in the production of coke, asphalt, and coal tar.48 The only POM compound the 

EPA identified from the surface coating operations is naphthalene. This is supported by the data 

collected for the risk assessment using the 2011 ICR. The 2011 ICR data, which are in the EPA's 

risk modeling file, included emissions of POM from non-surface coating operations at only two 

facilities and from surface coating operations at 23 facilities. As stated previously, the POM from 

surface coating operations is naphthalene emissions from currently regulated surface coating 

operations and from specialty coating operations. These data for naphthalene were included in 

the risk assessment for the surface coating operations. No other forms of POM were reported 

from surface coating operations. 

 

46 Residual Risk Assessment for Aerospace, EPA-HQ-OAR-2014-0830-0004 (does not include POM risk review). 

47 42 U.S.C. § 7412(d); Nat’l Lime Assn., 233 F.3d at 633. 

48 http://www3.epa.gov/airtoxics/hlthef/polycycl.html 
39 

The MACT standards applicable to certain subcategories in the aerospace surface coating source 

category are in place to control HAP emissions, including naphthalene (40 CFR Part 63, Subpart 

GG). In our February 2015 proposal, we explained that EPA had originally set a MACT floor of 

“no control” for specialty coatings in subpart GG when first promulgated in 1995, which is not 

allowed under Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007). We therefore proposed 

revisions that would set limits for specialty coatings (80 FR 8399, February 17, 2015). In the 

final rulemaking EPA is promulgating a total organic HAP standard for specialty coating 

operations similar to the other subcategories for this source category. A reduction in total organic 

HAP includes a reduction in the naphthalene emitted from aerospace coating operations. 

The EPA also disagrees with the commenter’s statement that the EPA has not reviewed how and 

if the existing standards control POM and whether they are adequate to control POM or whether 

the proposed specialty coating standards are sufficient to address POM emissions. As previously 

explained, the EPA performed both a risk assessment and technology review for the Aerospace 

Manufacturing and Rework facilities source category. As also previously explained, under the 

CAA Section 112(d)(6) technology review, we must review the technology-based standards and 

revise them “as necessary (taking into account developments in practices, processes, and control 

technologies)” no less frequently than every 8 years.” As part of the technology review of the 

aerospace MACT standards, EPA found that surface coating operations can be controlled 

through coating reformulation, and emissions can also be captured using hoods, spray booths, 

and ventilation systems which can then route captured pollutants to control devices like thermal 

oxidizers. The standards for primer, topcoat, chemical milling maskant, and specialty coating 

operations, in fact, include multiple ways to control organic HAP emissions, such as 

reformulation and add-on controls or a combination of the two. However, as with most surface 

coating operations, the predominant strategy for meeting the standards remains reformulation 

because the surface coating operations are typically performed manually by painters in 

conditions that create large air flow rates and low pollutant concentrations. Add-on controls are 

not cost effective in these situations with large air flows and low pollutant concentrations. Addon control devices are typically seen at sources using either robotic surface coating operations or 

when the surface coating operations are vented with other HAP-emitting processes to provide a 

concentrated emissions stream. 

As also explained earlier, as part of the CAA section 112(f)(2) residual risk review, the EPA 

developed a risk modeling file. As noted above, two facilities reported emissions of POM from 

non-surface coating operations and these emissions were included in the risk assessment on the 

basis of whole-facility emissions. Naphthalene emissions were reported from surface coating 

operations at 23 facilities, including currently regulated surface coating operations and from 

specialty coating operations. These data for naphthalene were included in the risk assessment for 

the surface coating operations. No other forms of POM were reported from surface coating 

operations. For further information on the risk assessment approach, see the Residual Risk 

Assessment for the Aerospace Manufacturing and Rework Facilities Source Category in Support 

of the January, 2015 Risk and Technology Review Proposal, January 2015, which is available in 

the docket for this action. 

The EPA also compared the 1990 naphthalene baseline emission inventory for the aerospace 

industry (79 FR 74661, December 16, 2014) to the more recent naphthalene emissions from the 

risk modeling file. When the aerospace manufacturing and rework facilities MACT standard was 
40 

promulgated, the anticipated emission reductions from surface coating operations was 59 percent 

(60 FR 45952, September 1, 1995). From this comparative analysis between the 1990 baseline 

inventory and the risk modeling file, we found that emissions of total naphthalene for all 

manufacturing and rework operations in the aerospace source category have been reduced by 

99.96 percent since the updated 1990 baseline inventory. The results show that the MACT 

standards for aerospace coating operation, including the limits for total organic HAP, have 

resulted in naphthalene reductions of a magnitude that is typically associated only with the use of 

add-on controls. This result also demonstrates that the current approach of regulating total 

organic HAP and providing the option of using add-on controls are adequate to address 

naphthalene emissions under CAA § 7412(d) and (f). In addition, the current RTR modeling file, 

which has been updated with the latest available information, shows no POM emissions other 

than naphthalene from aerospace surface coating operations. 

As noted above, POM is an organic compound with more than one benzene ring and a boiling 

point greater than or equal to 100 degrees Celsius. As explained at proposal, we conducted a 

multipathway screening analysis of seven PB-HAP, which included POM. (80 FR 8403-06, 

8410; February 17, 2015). We also explained that this screening analysis indicated that PB-HAP 

emissions from this source category did not exceed the screening emissions rates for any of the 

compounds we had evaluated. (80 FR 8415). We did not receive any comments disagreeing with 

either these results or our conclusion. This multipathway risk analysis did not consider 

naphthalene because naphthalene, unlike the other POM chemicals modeled in the multipathway 

analysis, is short-lived in environmental media due to its tendency to volatilize and biodegrade 

and, consequently, will not build up in environmental media over time.49 It has a moderate 

affinity for lipids and will undergo short-term bioaccumulation in tissues; however, biochemical 

processes lead to its biodegradation and elimination. We believe that its inclusion would have 

resulted in less accurate and less meaningful estimates of media concentrations and 

multipathway risk. 

7.0 Proposed Regulation of Specialty Coatings 

7.1 Legal Basis to Regulate Specialty Coatings 

Comment: One commenter (0830-0030) agreed with the EPA that the proposed regulation of 

specialty coatings is legally required, but argued that the proposed standards themselves are too 

weak. The commenter noted that EPA acknowledged that it may not leave unregulated any 

hazardous air pollutants emitted by these sources, or set a “no control” standard.50 The 

commenter agreed that while setting organic HAP standards for specialty coating operations that 

follow the Control Techniques Guidelines (“CTG”)51 for VOCs and applying the existing 10-90 

percent efficiency requirements applicable to other operations to control metals and inorganic 

 

50 Nat’l Lime Assn., 233 F.3d at 633-34 (D.C. Cir. 2000); Sierra Club v. EPA, 479 F.3d at 878, 883. 

51 EPA, Guideline Series, Control of Volatile Organic Compound Emissions from Coating Operations at Aerospace 

Manufacturing and Rework Operations, EPA 453/R-97-004 at B-4 (Dec. 1997), EPA-HQ-OAR-2014-0830-0020. 
41 

HAPs from specialty coating operations are improvements to the current no-control status for 

these sources, it is insufficient to satisfy the Act.

The commenter further argued that the EPA is required by CAA § 7412(d)(3) to use available 

data and set standards requiring at least the average emission limitation that has been achieved 

by the best 12 percent of existing sources52 and not base it on emission reductions achieved by 

the best 32 percent of sources (35 of the 109 facilities that reported specialty coatings are located 

in ozone non-attainment areas and are likely complying with VOC limits based on the CTG).53

The commenter added that if EPA had fulfilled this requirement, it is likely to require more than 

the small HAP reduction it predicts its proposed rule would achieve (16 percent, or 58 of 360 

tons per year). 

Response: The EPA acknowledges the commenters support for the EPA’s determination that the 

regulation of specialty coatings is required under CAA § 7412. 

However, the EPA disagrees with the comment that the standards should be more stringent. For 

MACT standards, the statute specifies certain minimum stringency requirements, which are 

referred to as MACT floor requirements. See CAA section 112(d)(3). National Lime Assn. v. 

EPA, 233 F.3d 625 (D.C. Cir. 2000). For new sources, the MACT floor cannot be less stringent 

than the emission control achieved in practice by the best-controlled similar source. The MACT 

standards for existing sources can be less stringent than floors for new sources, but they cannot 

be less stringent than the average emission limitation achieved by the best-performing 12 percent 

of existing sources in the category or subcategory (or the best-performing five sources for 

categories or subcategories with fewer than 30 sources). In setting MACT, 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.” Our approach to use of available data is also supported by 

NRDC v. EPA, 529 F.3d 1077, 1086) (D.C. Cir. 2008). (The EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a problem.). 

As the EPA explained in the preamble to the proposed rule (80 FR 8420), the EPA does not 

believe that any substantial difference exists among the state rules that are based on the CTG that 

would be the basis for EPA’s calculation of the MACT floor. Therefore, the 35 facilities located 

in ozone non-attainment areas represent the best performers, and therefore fulfill the CAA’s 

requirement to determine the MACT floor based on the average emission limitation achieved by 

the top 12 percent of sources. Furthermore, the EPA believes that those 35 facilities subject to 

state rules are all complying with essentially equivalent emission limitations for purposes of 

setting emission limitations under CAA section 112(d)(3). The EPA would not reach a different 

determination of MACT for specialty coatings if the EPA looked at a smaller subset of facilities 

than the 35 that are in ozone non-attainment areas and subject to specialty coating limits based 

on the CTG. 

The EPA's approach for the determination of the MACT floor and the results of the MACT 

analysis, including the analysis of options beyond the MACT floor, are documented in the 

memorandum, Determination of Maximum Achievable Control Technology (MACT) for 

 

52 42 U.S.C. § 7412(d)(3). 

53 80 Fed. Reg. at 8420. 
42 

Specialty Coating Operations in the Aerospace Manufacturing and Rework Facilities Source 

Category, that is found in the docket for this rule making. As documented in that memorandum, 

the EPA determined that MACT was equivalent to the MACT floor for both organic HAP and 

inorganic HAP, and the EPA identified no control options that were more stringent than the 

MACT floors for organic and inorganic HAP. 

Comment: One commenter (0830-0028) noted that the EPA's risk modeling has shown that 

specialty coatings account for less than 2 percent of the risk from the facility with the highest 

modeled risk, and the maximum cancer risk from specialty coatings is less than 1-in-1 million at 

over 90 percent of facilities and less than 10-in-1 million at all facilities. As a result, specialty 

coatings do not warrant regulation based on risk. 

The commenter argued that in light of the fact that the current standards are already protective 

with an ample margin of safety, the EPA should not regulate specialty coatings. The commenter 

argued that using EPA's $590,000 per year cost estimate, the cost of regulation would be 

equivalent to $67 million to avoid a single additional expected cancer case. 

The commenter argued that EPA is not compelled to regulate specialty coatings, based on EPA 

decisions to not regulate other unregulated sources in other source categories during the RTR 

process. The commenter argued that specialty coatings should not be regulated because of their 

specialized functions and the limited quantities in which they are used, similar to the reasons 

they were not regulated in the 1995 NESHAP or subsequent amendments. 

The commenter argued that EPA should not regulate specialty coating operations or at least defer 

such regulation until such time that costs would be reasonable and EPA can be certain that 

critical specialty coatings will not be eliminated without a qualified replacement. The commenter 

stated that the decision to regulate these operations at this time is discretionary because the risk is 

acceptable (because there have been no advances in technology) and no one challenged EPA’s 

decision not to regulate them in the original rule or in previous amendments to subpart GG. The 

commenter further stated that proceeding to regulate, given the potential costs and impacts on the 

industry, would be inconsistent with EPA’s obligations to engage in reasoned decision-making 

and would be arbitrary, capricious, and an abuse of discretion. 

The commenter argued that EPA is not required to correct any perceived deficiencies found in a 

MACT during a CAA Section 112(d)(6) review, rather EPA’s only obligation in this rulemaking 

is to satisfy the requirements of CAA Section 112(d)(6) and (f), similar to EPA’s decision for the 

Pulp and Paper NESHAP.54 The commenter further noted that even if EPA decided that it should 

have regulated specialty coating operations, EPA should decline to do so since it is not required 

to correct any deficiency in an underlying MACT standard when conducting the technology 

review. The commenter stated that this approach would be consistent with recently-upheld EPA 

decisions to decline to conduct rulemaking for greenhouse gas emissions from coal mines.55

 

54 EPA, National Emission Standards for Hazardous Air Pollutants from the Pulp and Paper Industry (40 CFR Part 

63, Subpart S) Residual Risk and Technology Review, Final Amendments Response to Public Comments on 

December 27, 2011 Proposal, at 107 (July 2012) (Pulp and Paper RTC). 

55 WildEarth Guardians v. EPA, 751 F.3d 649 (D.C. Cir. 2014).
43 

The commenter argued, finally, that recent case precedent regarding uncontrolled sources56 does 

not compel EPA to revise longstanding regulatory exclusions that are justified by legitimate de 

minimis principles and that were never previously challenged by any party particularly when 

there will not be a meaningful benefit to the public health from such regulation and the cost of 

regulating will be high. 

Response: The EPA is finalizing standards to address organic and inorganic HAP emissions 

from specialty coating operations, which are currently unregulated emission sources, under CAA 

112(d)(2) and (d)(3). The EPA is not, however, promulgating these standards as part of its 

112(d)(6) technology review. 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 

Assn. 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 HAP 

emissions from specialty coatings 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 disagree with the comment that the EPA is not mandated to regulate de minimis HAP. 

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 

 

56 UARG v. EPA, 134 S. Ct. 2427, 2449 (2014) 
44 

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 

Assn. 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 Assn., 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. 

The EPA also disagrees with the commenter’s interpretation of EPA’s response to the question 

of establishing standards for unregulated sources in a comment on the proposed RTR for the 

Pulp and Paper NESHAP. In the pulp and paper response, the EPA was, as the commenter 

correctly noted, arguing only that the EPA is not required to establish standards for previously 

unregulated sources under CAA section 112(d)(6) as explained above. However, there is nothing 

in EPA’s pulp and paper response to support the commenter’s argument that the EPA is not 

required to regulate specialty coatings under CAA 112(d)(2) and (d)(3). In fact, in the same EPA 

response cited by the commenter, the EPA states that, “We intend to further investigate 

potentially deficient standards and plan to address them in a future sector rule proposed under 

section 112(d)(2) and (3).” 

The Supreme Court case cited by the commenter, UARG v. EPA, is not relevant to the decision to 

regulate HAP from specialty coatings because it dealt with the question of whether sources 

should be required to determine BACT for greenhouse gas emissions as part of the new source 

review permitting process. It did not deal with the regulation of HAP and the determination of 

MACT under CAA section 112. 

Comment: One commenter (0830-0026) argued that the EPA is not compelled to regulate 

specialty coatings under CAA Section 112(d)(2) and (3) by the "Brick MACT" decision.57 The 

commenter argued that the situation in the Aerospace NESHAP is different from the situation in 

the Brick MACT case. According to the commenter, the EPA erred in the Brick MACT case "by 

failing to regulate processes that emitted HAP, in some instances by establishing a MACT floor 

of 'no control.'"58 The commenter argued that in the Aerospace NESHAP, in contrast, the EPA 

did not establish a MACT floor of “no control,” but instead excluded specialty coatings from that 

MACT floor because the amount of organic HAP emissions generated by coating-related 

 

57 Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007). 

58 Id. at 8399. 
45 

operations is “relatively small,” the coatings are highly specialized, and subcategorization for 

specialty coatings “can be significant,” “resulting in lower potential emission reductions.”59 The 

commenter argued that the exclusion for specialty coatings is lawful under the Brick MACT 

decision, and that if EPA’s interpretation was taken to its logical conclusion, it would be 

unlawful for the Agency to exempt any subcategory of source from any MACT standard, and 

this is a result that is not mandated by the Brick MACT decision. 

Response: The EPA disagrees with the commenter’s interpretation of the “Brick MACT” 

decision relative to the regulation of specialty coatings. The EPA's complete response to this 

comment can be found in section IV.C.3 in the preamble to the final rule amendments. 

7.2 Determination of Specialty Coating Limits and Definitions 

Comment: Two commenters (0830-0027, 0830-0028) agreed that, if the EPA decides to regulate 

specialty coatings, the Aerospace CTG limits are the most appropriate basis for determining the 

floor and represent MACT. 

One commenter (0830-0027) agreed that the EPA correctly based the MACT floor analysis on 

the CTG limits as the basis for a national rule because more stringent limits that were identified 

were developed for areas with specific climate conditions. The commenter noted that the more 

stringent limits also rely on alternative compliance mechanisms, such as exemptions and 

variances, which were not included in the CTG and were not proposed for the Aerospace 

NESHAP. 

Another commenter (0830-0028) argued that the EPA’s decision to rely on the use of the CTG’s 

VOC limits for MACT was justified because the data collected by the 2008 ICR was insufficient 

for determining MACT. The commenter argued that the ICR did not collect the data that would 

be necessary to classify similar sources so that the top performing operations in each 

classification could be identified. This information would have included: detailed information on 

the coatings and specifications to determine whether the coating operations in which they are 

used are similar; data on coatings that may be used in several specialty coating classifications; 

and data on all specialty coatings used over several years. The commenter cited, as an example, 

the category of “nonstructural adhesives” and noted that even within this category there are 

numerous different adhesive formulations for different substrates and different performance 

requirements that result in different HAP contents. The ICR did not collect sufficient information 

to differentiate these applications for different HAP contents. The commenter also noted that the 

ICR did not collect information to identify specialty coatings that are used across multiple 

coating categories, because the ICR asked users to choose a single classification for each coating. 

The commenter agreed with and supported the EPA’s determination that the VOC limits 

developed under the CTG represent the MACT because these limits represent the emission levels 

achieved by the top 12 percent of sources. The commenter noted that the courts have determined 

that emission limits may be used to provide a reasonable estimate of the performance of the best 

 

59 59 Fed. Reg. 29,216, 29,239 (June 6, 1994). 
46 

performing facilities.60 The commenter also noted that the limits-based approach was supported 

by the D.C. Circuit in Mossville Environmental Action Now v. EPA, where the court found that 

EPA met the burden of supporting the use of regulatory limits in setting a MACT floor when the 

Agency “cited the great variability of emission levels, even within the same plants, and the 

inherent difficulty in other standards it considered.”61

The same commenter also argued that the fact that no state or regional specialty limits are more 

stringent than the CTG limits supports the EPA’s determination that the CTG limits can be used 

to reasonably estimate the performance of the best performing facilities. The commenter argued 

that although some states and regions have adopted limits for certain types of specialty coating 

operations that differ from the CTG limits, the state and regional rules are not more stringent 

because these rules typically provide different exemptions, different definitions to classify 

specialty coatings, or additional classes or subclasses with VOC limits different than the CTG. 

The commenter also argued that the EPA also does not have sufficient data to determine whether 

any of the more stringent limits are actually being achieved in practice. 

The commenter also argued that the determination that RACT limits from a CTG also represent 

MACT is not unique, and cited examples from the Shipbuilding and Repair Surface Coating 

NESHAP (subpart II), and the Miscellaneous Metal Parts and Products Surface Coating 

NESHAP (subpart MMMM). Finally, the commenter argued that the legislative history of the 

CAA62 and the language of section 183(b)(3), which directs the EPA directs EPA to “take into 

account the applicable requirements” of section 112 when developing the CTG, support the 

overall concept of harmonizing the NESHAP limits with the CTG limits. 

The same commenter also argued that the EPA’s decision to use an alternative approach for 

determining MACT was justified by the diversity of specialty coating operations and 

formulations needed by those operations. The commenter noted that the determination of MACT 

for new and existing sources according to CAA section 112 is based on the comparison of 

performance among similar sources for which the EPA has data. The commenter argued that 

given the diversity of specialty coating operations in the aerospace industry, and the number of 

different coating categories and formulations, and the safety considerations needed, it would be 

difficult and impractical to identify and classify similar sources to conduct a straightforward 

determination of MACT floors. The commenter argued that taking all of these factors into 

account to create homogenous grouping of similar sources could lead to the creation of hundreds 

of classifications, many of which would be likely to have only a single facility. Thus, the 

commenter argued, the EPA’s decision to use an alternative approach to determining MACT is 

justified. 

Response: The EPA acknowledges the commenter’s support of the EPA’s use of the CTG limits 

as the basis for MACT and the determination that the CTG’s VOC limits present MACT for the 

control of HAP from specialty coatings. As earlier explained, CAA section 112(d)(3) requires the 

 

60 Cement Kiln Recycling Coal. v. EPA, 255 F.3d 855, 861-62 (D.C. Cir. 2001); Sierra Club v. EPA, 167 F.3d 658, 

661 (D.C. Cir. 1999).

61 370 F.3d 1232, 1242 (D.C. Cir. 2004). 

62 H.R. REP. NO. 101-490 at 249 (1990) (Rep. accompanying on H.R. 3030) reprinted in 2 SENATE COMM. ON 

ENV'T AND PUB.WORKS, 103D CONG., A LEGISLATIVE HISTORY OF THE CLEAN AIR ACT AMENDMENTS OF 1990, at 

3273 (1993).
47 

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.” Our approach to use of available data is also supported by NRDC v. EPA, 

529 F.3d 1077, 1086) (D.C. Cir. 2008). (The EPA typically has wide latitude in determining the 

extent of data-gathering necessary to solve a problem.). 

Comment: One commenter (0830-0030) argued that the EPA cannot propose to apply the 

existing source requirement to new sources. The commenter added that CAA § 7412(d)(3) 

requires EPA to match the emission limitation achieved by the single best-performing source but 

EPA has not addressed or met this requirement. 

The same commenter also argued that for all sources, EPA must perform the requisite beyondthe-floor analysis to consider setting standards that are more stringent than the floor and, 

ultimately, must require the “maximum achievable” degree of emission reduction from all 

sources, as required by CAA § 7412(d)(2). The commenter argued that EPA has not performed 

the required beyond-the-floor analysis for specialty coating operations. The commenter argued 

that for this type of source – where EPA is requiring only 58 tons per year of reductions, of a 

total of 360 tons per year it knows are emitted – it is highly likely that a beyond-the-floor 

analysis will show significant additional reductions are achievable. 

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, MACT “shall not be less 

stringent than 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. Thus, CAA section 112(d) requires the EPA to establish the MACT floor for 

new sources differently than for existing sources. But the EPA is prohibited from adopting the same 

standard for new sources as for existing sources only where the available data indicate that the 

emission control that is achieved in practice by the best controlled similar source is in fact more 

stringent than the standards set for existing sources. As the EPA explained in the MACT memo for 

specialty coatings63 and in the preamble to the proposed rule64 the EPA did identify some cases 

in which facilities are in locations with different VOC limits than in the CTG. However, the EPA 

also determined that those limits could not be compared directly to the CTG limits because of 

different applicability criteria and additional VOC limits for related specialty categories (i.e., in 

some cases where the CTG limit applied to one type of coating, the state rule would have limits 

for two sub-types of the coating). In addition, the EPA could not confirm whether any facilities 

located in areas with these different limits were actually performing specialty coating operations 

subject to limits that were lower than in the CTG. As a result, the EPA also could not determine 

whether new source MACT could be based on those lower VOC limits for all new sources or for 

a readily identified subcategory of new sources for both the MACT floor analysis and for a 

beyond-the-floor analysis. Therefore, the CTG limits that were the basis for the MACT for 

existing sources was also the MACT for new sources. 

 

63 EPA docket item EPA-HQ-OAR-2014-0830-0012. 

64 80 FR 8420 – 8421. 
48 

Similarly, as part of the beyond-the-floor MACT analysis, the EPA identified some facilities that 

reported using add-on controls for some specialty coating operations. However, the use of addon controls is not widely used and the facilities using the add-on controls did not achieve greater 

emission reductions than facilities using coatings meeting the VOC content limits, based on an 

analysis of the EPA’s ICR data. Finally, the EPA searched the EPA’s RACT/BACT/LAER 

Clearinghouse, and the California Statewide Best Available Control Technology (BACT) 

Clearinghouse, and found no cases in which add-on controls were determined to be BACT or 

LAER for specialty coating operations. 

Comment: One commenter (0830-0028) argued that the EPA should not issue dual limits for 

VOC and HAP for specialty coatings, and should clarify that the VOC limits are not separately 

enforceable and are used only as a surrogate for HAP. The commenter argued that the EPA 

should make clear in the final rule that: 

(1) Only the organic HAP limits are enforceable; 

(2) Coatings that do not contain organic HAP are not covered by the rule; and 

(3) For coatings that do not contain exempt solvents that are also HAP, VOC content may be 

used to demonstrate compliance with the organic HAP limits as an alternative to determining 

organic HAP content directly. 

The commenter argued that CAA section 112 does not allow for the setting of VOC limits, 

except as a surrogate for HAP content, and then only in situations in which the HAP content 

could not exceed the VOC content. Therefore, the use of the VOC content to demonstrate 

compliance with the HAP content limits can only apply when the coating does not contain any 

exempt solvents that are HAP. The commenter argued that the VOC content would effectively 

cap the HAP content in those coatings with no exempt solvents. 

The commenter also argued that under either approach, coatings that do not contain any organic 

HAP cannot be subject to the HAP content limits or the VOC limits as a surrogate for HAP, and 

the rule should include a provision to clarify this. The commenter argued that facilities can use 

coating formulation information to establish whether or not the coatings contain organic HAP. 

Response: The EPA agrees with the commenter’s recommendations to clarify the relationship 

between the VOC content of coatings and the HAP emission limits. The EPA's complete 

response to this comment can be found in section IV.D.3 in the preamble to the final rule 

amendments. 

Comment: One commenter (0830-0030) argued that EPA’s VOC-based limit for organic HAPs 

is flawed because EPA is proposing to use VOCs generally as a surrogate for HAP content limits 

from specialty coatings without meeting the required test to use a surrogate instead of direct 

HAP regulation. The commenter disagreed with EPA’s statement that “there is a positive 

correlation: between the average volatile contents of the coating categories and the CTG VOC 

limits, between the average HAP contents per category and the CTG VOC limits, and between 

the average HAP contents and the average volatile contents per category.” The commenter 

argued that this conclusory statement is arbitrary and capricious because it does not explain how 
49 

EPA believes this is true. The commenter added that it is also unlawful and arbitrary because 

EPA has not met the legal test to use a pollutant like VOCs as a surrogate for a HAP. 

The commenter pointed out that the D.C. Circuit has recognized that EPA must justify the use of 

a surrogate based on facts in the record that show surrogate regulation will assure proper control 

of the listed HAPs themselves. The commenter added that EPA has neither attempted to meet nor 

has it met the test to use a single pollutant to control other emitted hazardous air pollutants, as it 

is legally required to do. The commenter argued that a surrogate is reasonable only if it meets 

three conditions: (1) the target pollutant(s) must invariably be present in the surrogate; (2) the 

control technology used to control the surrogate must indiscriminately capture both the surrogate 

and the target pollutant(s); and (3) control of the surrogate must be “the only means by which 

facilities achieve reductions in the target pollutant.” The commenter added that the EPA has not 

shown that coating content correlations between VOCs and organic HAPs (even assuming those 

exist) would also translate into actual emissions control correlation between these pollutants, or 

do so at a close enough rate to allow use of VOCs as a surrogate. According to the commenter, 

EPA has not shown that control of VOCs is “the only means by which facilities achieve 

reductions in the target [HAP]” and must directly regulate these HAPs or meet the surrogate test. 

Response: The EPA disagrees with the commenter that the EPA has failed to meet the 

requirements set out in National Lime Assn., 233 F.3d at 639, on the use of VOC as a surrogate 

for demonstrating compliance with the limits for organic HAP for the following reasons: 

1. The target pollutant(s) must invariably be present in the surrogate: all HAP are also VOC, 

with the exception of three chlorinated-organic HAP that are excluded from the definition of 

VOC because they are minimally photochemically reactive. These three HAP are not 

commonly used as solvents in specialty coatings, and for those coatings that contain those 

HAP, sources cannot use the VOC content to demonstrate compliance with the HAP content 

limits. 

2. The control technology used to control the surrogate must indiscriminately capture both the 

surrogate and the target pollutant(s): The EPA is setting the same limit for VOC and organic 

HAP so that the organic HAP content cannot exceed the VOC limit, even if the coating 

contains organic HAP that are exempt from the definition of VOC. In the case of facilities 

that are using add-on controls to achieve compliance, VOC controls will have the same 

emission reduction efficiency for organic HAP. 

3. Control of the surrogate must be “the only means by which facilities achieve reductions in 

the target pollutant:” The limits for specialty coatings are for organic HAP, not VOC. As the 

EPA explained in the MACT memo for specialty coatings65 the only other potential source of 

data for the MACT analysis of specialty coatings was the limited 2011 ICR that requested 

coating data for 2008. (As earlier explained, our approach to use of available data is also 

supported by NRDC v. EPA, 529 F.3d 1077, 1086) (D.C. Cir. 2008). (The EPA typically has 

wide latitude in determining the extent of data-gathering necessary to solve a problem.)). 

Therefore, we used the VOC limits in the CTG, as applied to organic HAP content, as a 

suitable alternative for the proposed organic HAP limits for specialty coatings. Because of 

the similarity between the CTG VOC limits and the organic HAP limits, facilities may use 

 

65 EPA docket item EPA-HQ-OAR-2014-0830-0012. 
50 

the VOC content of their coatings to demonstrate compliance with the organic HAP content 

limits, but they may not use the VOC content for coatings that contain certain chlorinated 

organic HAP that are excluded from the definition of VOC. As we noted earlier, though, 

these three chlorinated-organic HAP are not commonly used as solvents in specialty 

coatings. 

Thus, EPA disagrees with the commenter that EPA has failed to demonstrate that VOC is a 

suitable surrogate for HAP. The MACT memo, which is in the docket for this rulemaking, 

explained that there are positive correlations between the industry weighted-average volatile 

contents of the coating categories and the CTG VOC limits, between the industry weightedaverage HAP contents per category and the CTG VOC limits, and between the industry 

weighted-average HAP contents and the average volatile contents per category. 

The correlations were based on industry-weighted averages per specialty coating category 

because of the large number of data points in each category from the ICR data. Basing the 

correlations on industry-weighted averages simply accounts for the fact that many of the reported 

specialty coatings are used in small quantities at numerous facilities, but do not actually 

represent the bulk of the emissions from each specialty category. 

It is also important to note that the HAP content values used in the analysis were not corrected to 

remove water, and the volatiles content values were also not corrected to remove water or 

exempt solvents, in both cases because the ICR data did not include water content of the 

coatings. It is also important to note that the data were screened to remove cases in which the 

calculated organic HAP content was greater than the calculated volatiles content. These cases 

indicate a problem with the data that is likely due to the fact that HAP content may be reported 

as a range on coating data sheets (e.g., MSDS), and some facilities may have used the upper end 

of each range in calculating the total HAP content of the coatings, such that the total reported 

HAP content was greater than the volatiles content. 

Comment: One commenter (0830-0025) representing the Department of Defense (DoD) 

commented that most of the coatings used at DoD facilities have military specifications that 

already meet the VOC limits in the CTG, so they will meet the proposed HAP and VOC content 

limits. However, the commenter argued that DoD will be unable to certify compliance with the 

HAP/VOC limits for some materials whose composition is classified as national security 

information. The materials have properties with specific, classified characteristics based on their 

use such as radiation-effect coating, according to the commenter. Disclosure of the composition 

of these materials would risk undermining the function of the coating or could provide sufficient 

information that could be used to counter the effect of the coating, according to the commenter. 

The commenter requested that the proposed rule be modified to continue to exempt materials that 

meet the definition of “Classified National Security Information.” 

The commenter recommended that EPA amend 40 CFR 63.742 with an additional definition for 

the term “Classified National Security Information” to read as follows: 

Classified National Security Information means information that has been determined 

pursuant to this Executive Order 13526, “Classified National Security Information,” 

December 29, 2009 or any successor order to require protection against unauthorized 

disclosure and is marked to indicate its classified status when in documentary form. The 
51 

term “Classified Information” is an alternative term that may be used instead of 

“Classified National Security Information”. 

The commenter also recommended that the EPA revise the definition of “Electric or radiationeffect coating” in Appendix A to Subpart GG of Part 63 - Specialty Coating Definition to read as 

follows: 

Electric or radiation-effect coating - A coating or coating system engineered to interact, 

through absorption or reflection, with specific regions of the electromagnetic energy 

spectrum, such as the ultraviolet, visible, infrared, or microwave regions. Uses include, 

but are not limited to, lightning strike protection, electromagnetic pulse (EMP) 

protection, and radar avoidance. Coatings that have been designated as “Classified 

National Security Information’’ by the Department of Defense are exempt from 

compliance with 40 CFR 63 Subpart GG. 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.D.3 in the preamble to the final rule amendments. 

Comment: One commenter (0830-0028) argued that the current definition of electrostatic 

discharge and electromagnetic interference (EMI) coating in Appendix A of Subpart GG appears 

to limit the use of these coatings on aircraft radomes, but these coatings are commonly used on 

several parts of the non-metallic exterior portions of the aircraft to dissipate electrical charge—

not just the composite radome. The commenter recommended that the EPA should change the 

definition to reflect all of the uses of coatings on aircraft to state the following: 

Electrostatic discharge and electromagnetic interference (EMI) coating—A coating 

applied to space vehicles, missiles, aircraft radomes, and helicopter blades aerospace 

vehicles or components to disperse static electricity or reduce electromagnetic 

interference. 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.D.3 in the preamble to the final rule amendments. 

Comment: One commenter (0830-0023) argued that the proposed rule is deficient because it 

would effectively limit the definition of specialty coatings to include only those coatings that fall 

within the categories listed in Table 1. The commenter argued that the list of specialty coatings 

included in Appendix A to subpart GG was not intended to represent the universe of all specialty 

coatings, because the EPA also included the general definition of specialty coatings, and did not 

include any indication that the list in Appendix A was intended to be exclusive. The commenter 

also argued that new specialty coatings could be allowed for under the blanket exemption for 

specialty coatings under 40 CFR 63.741(f). 

The commenter argued that now that the exemption under 40 CFR 63.741(f) has been removed, 

the proposal makes no provision for the development and use of new specialty coatings that are 

not covered by the existing categories. The commenter argued that because of advancements in 

the use of composites and other materials, it is inevitable that new classes of specialty coatings 

will be developed that are required to meet FAA regulations, and airlines would then have no 
52 

choice but to use the new specialty coatings and risk non-compliance with the Aerospace 

NESHAP. 

To address this situation, the commenter recommended that the EPA include a provision in the 

final rule that would specify how any new categories of specialty coatings are to be added to 

Table 1 and what requirements would apply in the interim while EPA developed final control 

requirements for those coatings. The commenter offered the following recommendations: 

If a new specialty coating is required in a maintenance or repair operation and there is no existing 

category in proposed Table 1 that includes the new coating, the affected source could be allowed 

to use the specialty coating as formulated by the manufacturer, subject to the filing of a request 

with EPA to add the new category to Table 1 and until a determination is made by the EPA as to 

the requested addition to Table 1 and corresponding HAP limit. 

As a further alternative, upon filing of the above described request with EPA, an interim HAP 

limit for the new coating could be set at the highest HAP limit in Table 1 for similar types of 

specialty coatings. For example, if the new specialty coating is a topcoat with added functional 

characteristics that cause it to be in a new specialty coating category, the interim HAP limit for 

such new specialty topcoat would be the highest HAP content allowable for any other specialty 

coating listed in Table 1 that also functions as a topcoat. This same approach could also apply to 

primers, adhesives and other “classes” of specialty coatings. The commenter suggested that this 

approach could also be facilitated by adding generic categories for “unlisted specialty topcoats,” 

“unlisted specialty primers,” “unlisted specialty adhesives,” etc. to Table 1 with a HAP level equal to 

that of the existing specialty coating in the same class (e.g., topcoat, primer, adhesive, maskant, etc.) 

with the highest HAP limit. The generic HAP limit would then apply until EPA could formally 

amend Table 1 to include the new specialty coating and set a final HAP limit. 

Response: The EPA disagrees with the commenter that the rule should be revised to include 

provisions for coatings that do not meet the definitions of any of the existing specialty coating 

categories. As noted earlier, the Aerospace CTG that is the basis for the proposed specialty coating 

categories was published by the EPA in 1997, and since then numerous states have developed state 

rules to reduce VOC emissions based on the CTG. In the EPA’s review of state rules based on the 

Aerospace CTG, the EPA did not found any rules with specialty coating categories that differed 

substantially from the categories in the CTG or in the table of specialty coatings in the proposed rule. 

In the preamble to the proposed rule, the EPA specifically solicited comment and additional data on 

any changes needed to the definitions of specialty coating categories and the proposed organic HAP 

and VOC limits. The EPA received comments to revise only two of the current specialty coating 

category definitions, and received no requests to add any new specialty coating categories. Therefore, 

we do not even know if any new specialty coating would be used by sources in this source category. 

Under section 112(d)(1), EPA is required to “promulgate regulations establishing emissions 

standards for each category or subcategory of major sources ...of listed hazardous air pollutants.” 

Because of the observed agreement between state VOC rules and the Aerospace CTG, and because 

there were no requests to add new specialty coating categories, the EPA assumes that the current 

categories are sufficient to accommodate the range of coatings currently in use by major sources in 

this source category. 
53 

Therefore, the EPA is not adopting the commenters suggestion to include a provision in the final 

rule that would specify how new categories of specialty coatings could be added to Table 1 and 

what requirements would apply in the interim while EPA developed final control requirements 

for those coatings. Aerospace industry members and coating manufacturers have the ability to 

petition the EPA at any time to amend subpart GG through standard rule making procedures if that is 

needed to address newly developed coatings that do not fit into any of the current coating category 

definitions. The EPA is also required by CAA section 112(d)(6) to review and revise, as necessary, 

the promulgated emission standards for specialty coatings no less often than every 8 years after 

promulgation.

7.3 Specialty Coating Application Equipment Requirements 

Comment: Two commenters (0830-0028, 0830-0030) supported the EPA’s determination that 

the standards for specialty coating application equipment and inorganic HAP emissions should 

be proposed under CAA section 112(h). One commenter (0830-0028) argued that the 112(h) 

standards are justified because it may not be feasible to have the emissions conveyed by a stack 

or captured by a spray booth; the application of measurement methodology may not be feasible 

(e.g., measuring the emission reductions achieved by high efficiency coating application 

equipment), or the application of measurement technology (such as that for inorganic HAP from 

a spray booth) may not be economically feasible. 

Response: The EPA acknowledges the commenters’ support. 

Comment: One commenter (0830-0028) argued that the 40 CFR 63.745(f) should be revised to 

clarify that the proposed specialty coating application equipment requirements allow the use of 

any non-spray application equipment. The commenter argued that the rule allows the use of 

alternatives to the methods listed in 40 CFR 63.745(f)(1), but only if they are demonstrated to be 

equivalent to high-volume low-pressure (HVLP) spray or electrostatic spray, according to 40 

CFR 63.750(i). The commenter argued that the rule should be revised to allow all hand 

application methods and non-spray methods allowed in the California rules, and to require the 

equivalency demonstration only for spray application methods. The commenter argued that 

because the rule is based on California standards as MACT, it must be amended to reflect those 

requirements; otherwise the EPA would need to propose a beyond the floor determination 

according to CAA section 112(d)(2). 

The commenter recommended that the EPA add the following language to Section 63.745(f)(1) 

to clarify that other methods are allowed: 

In addition to the methods in (f)(1)(i) through (f)(1)(ix), specialty coatings may be 

applied by flow coating, web coating, coil coating, touch-up markers, marking pens, 

trowels, spatulas, daubers, rags, sponges, and mechanically and/or pneumatic-driven 

syringes. 

Response: The EPA agrees with the commenter that any hand or non-spray application methods 

should be allowed as a clarification of the current requirements, which are intended to minimize 

emissions from the spray application of coatings. The EPA's complete response to this comment 

can be found in section IV.E.3 in the preamble to the final rule amendments. 
54 

Comment: One commenter (0830-0028) argued that adhesives, sealants, maskants, caulking 

materials, and inks are not atomized even when applied with spray application equipment; 

therefore, the application of these specialty coatings is not a spray-application operation and 

should not be subject to the high efficiency application equipment requirements. The commenter 

argued that the EPA should clarify that the application of adhesives, sealants, and maskants, 

caulking materials, and inks are not subject to the application equipment requirements by the 

following addition 40 CFR 63.745(f)(3): 

(3) The following situations are exempt from the requirements of paragraph (f)(1) of this 

section: 

... 

(vii) Adhesives, sealants, maskants, caulking materials, and inks.

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.E.3 in the preamble to the final rule amendments. 

Comment: One commenter (0830-0028) argued that 40 CFR 63.745(f)(3)(ii), which is an 

exemption from the high-efficiency application requirement in 40 CFR 63.745(f)(1), should be 

revised for two specific cases to remove the requirement for permitting agency approval. In the 

first, the commenter argued that in the California South Coast AQMD and Antelope Valley 

AQMD aerospace rules on which MACT is based, there is an exemption for coatings that contain 

less than 20 grams of VOC per liter of coating.66 The commenter argued that this exemption 

accommodates spray application of low VOC coatings with high solid contents that are not 

practical to apply with high-efficiency equipment, such as high solid/low VOC ceramic coatings 

applied to reduce the infrared signature of military aircraft are classified as electric or radiationeffect specialty coatings. These coatings are not water-reducible and, due to high viscosity, 

cannot be spray applied using high-efficiency application equipment, according to the 

commenter. 

In the second case, the commenter argued that coatings with a viscosity of 200 centipoise or 

greater should be exempt from the spray application equipment requirements. The commenter 

noted that South Coast AQMD Rule 1168, Adhesive and Sealant Applications, contains the same 

exemption.67 According to the commenter, these high-viscosity coatings have poor flow 

characteristics and low VOC and organic HAP content. The commenter argued that VOC 

solvents would have to be added to these compounds to lower the viscosity and allow for 

spraying with an HVLP or equivalent spray gun, and the addition of VOC solvents to these 

coatings would likely result in greater emissions than if a conventional spray gun were used. 

Response: The EPA agrees with the commenter on the need for an exemption from the 

application equipment rules for coatings that contain less than 20 grams of VOC per liter of 

coating. The EPA's complete response to this part of the comment can be found in section IV.C.3 

in the preamble to the final rule amendments. 

 

66 South Coast AQMD Rule 1124(l)(13); Antelope Valley AQMD Rule 1124(l)(13). 

67 South Coast AQMD Rule 1168(c)(5)(H). 
55 

The EPA disagrees with the commenter on the need for the exemption from application 

equipment requirements for coatings with a viscosity of 200 centipoise or greater and this 

exemption is not being included in the final rule. The South Coast AQMD Rule 1168 cited by the 

commenter applies specifically to adhesive and sealant application operations, and it also 

specifically exempts coating of aerospace components that are subject to South Coast AQMD 

Rule 1124 (see South Coast AQMD Rule 1168(j)(2)). South Coast AQMD Rule 1124 does not 

contain an exemption from the application equipment requirements for coatings with a viscosity 

of 200 centipoise or greater. In addition, the EPA is including in the final rule, at the request of 

the same commenter, an exemption from the application equipment requirements for adhesives, 

sealants, maskants, caulking materials, and inks, consistent with other more recent surface 

coating NESHAP. Therefore, the commenter has not identified a technical basis for the 

additional exemption for high viscosity coatings that would be needed in addition to the 

exemption from the application equipment requirements for adhesives and sealants (among other 

materials) added to the final rule. 

Comment: One commenter (0830-0028) argued that 40 CFR 63.745(f)(3) should be revised to 

allow the use of detailing guns or airbrushes for all specialty coating application operations, and 

not just the two exemptions currently in the rule at 40 CFR 63.745(f)(3)(i) and (iv). The 

commenter argued that several California rules allow the use of small detailing guns and 

airbrushes for all specialty coating operations,68 and because these rules are the basis for the 

EPA’s MACT determination, the final EPA rule should be consistent with these rules. 

Response: The EPA agrees that the use of airbrushes and detailing guns should be allowed for 

all specialty coating operations. The EPA's complete response to this comment can be found in 

section IV.E.3 in the preamble to the final rule amendments. 

Comment: One commenter (0830-0028) argued that 40 CFR 63.745(f)(1) should be revised to 

allow the use of high-efficiency air-assisted airless spray guns, airless spray guns, screen 

printing, and inkjet printing for application of specialty coatings because these technologies are 

equivalent to or better than HVLP. The commenter argued that under CAA Section 112(h)(3), 

the Agency must allow alternative equipment that achieves equivalent emission reductions to the 

equipment prescribed as MACT. The commenter also noted that under other NESHAP (e.g., 40 

CFR 63, subparts JJ and HHHHHH), the EPA has determined that air-assisted airless and airless 

spray guns are equivalent to HVLP and electrostatic spray, which EPA has designated as the 

MACT for aerospace specialty coatings. The commenter also noted that subpart HHHHHH 

allows the use of air-assisted airless spray guns and airless spray guns (in addition to HVLP) for 

aerospace surface coating operations at area sources. Finally, the commenter noted that several 

state and regional air agencies allow the use of air-assisted airless spray guns and airless spray 

guns as equivalent to HVLP and included copies of two permits from the Antelope Valley 

AQMD and the Georgia Environmental Protection Division. 

 

68 Antelope Valley AQMD Rule 1124(G)(12); Mojave AQMD Rule 1118(c)(1); Bay Area AQMD Rule 8-29- 

310.3; South Coast AQMD Rule 1124(l)(14). 
56 

Finally, the commenter argued that screen printing and ink jet technology should be listed as 

approved application methods because they each achieve nearly 100 percent transfer efficiency, 

which is higher than the transfer efficiency of HVLP spray guns. 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.E.3 in the preamble to the final rule amendments. 

Comment: One commenter (0830-0028) argued that the EPA should provide an alternative to 

using the equivalency demonstration requirements in 40 CFR 63.750(i). The commenter argued 

that the method in 40 CFR 63.750(i) is overly burdensome, especially for specialty coatings, 

because it requires testing on parts of a similar configuration to the actual parts being coated, and 

because of the number of specialty coatings used at most facilities. The commenter 

recommended that for specialty coatings, the EPA should allow a facility to use any application 

method that achieves emission reductions or a transfer efficiency equal to or better than the 

methods approved in the rule (HVLP, electrostatic spray, air-assisted airless, and airless), and 

that EPA should allow facilities to use a method of its choice to demonstrate equivalency. The 

commenter argued that clarifying that facilities may demonstrate either equivalent emission 

reductions or transfer efficiency would increase flexibility in the rule by allowing the use of 

either type of equivalency method. The commenter recommended that the following language be 

added to 40 CFR 63.745(f): 

For specialty coatings, any other coating application method capable of achieving 

emission reductions or a transfer efficiency equivalent to or better than that provided by 

HVLP, electrostatic spray, air-assisted airless, or airless application. Any owner or 

operator using an application method pursuant to this subparagraph shall maintain 

records demonstrating the transfer efficiency achieved.

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.E.3 in the preamble to the final rule amendments. 

7.4 Specialty Coating Inorganic HAP Control Requirements 

Comment: One commenter (0830-0028) argued that the EPA should clarify the operations 

subject to the inorganic HAP requirements by defining “spray-applied coating operation.” The 

commenter noted that the term “spray gun” is defined in the current rule as “a device that 

atomizes a coating or other material and projects the particulates or other material onto a 

substrate.” The commenter noted that 40 CFR 63, subpart HHHHHH, which applies to area 

source aerospace facilities, excludes some specialty coating materials (including adhesives, 

sealants, maskants, and caulking materials) from the definition of spray applied coating operation 

because they are not spray applied or are not atomized even when they are applied with a spray 

gun, and instead are emitted in larger particles that settle near the source and are not emitted. The 

commenter also noted that certain application methods were excluded from the definition of 

“spray-applied coating operation” in subpart HHHHHH, including the following: powder 

coating, hand-held, non-refillable aerosol containers, or non-atomizing application technology, 

including, for example, paint brushes, rollers, hand wiping, flow coating, dip coating, 

electrodeposition coating, web coating, coil coating, touch-up markers, and marking pens. 
57 

The commenter recommended that the operations subject to the inorganic HAP control 

requirements be clarified by adding the following definition to 40 CFR 63.742: 

Spray-Applied Coating Operations means operations that apply coatings using a device 

that creates an atomized mist of coating and deposits the coating on a substrate. For the 

purposes of this subpart, spray-applied operations do not include the following materials 

or activities: 

(1) Application of coating using powder coating, hand-held non-refillable aerosol 

containers, or non-atomizing application technology, including, but not limited to paint 

brushes, rollers, flow coating, dip coating, electrodeposition coating, web coating, coil 

coating, touch-up markers, marking pens, trowels, spatulas, daubers, rags, sponges, 

mechanically and/or pneumatic-driven syringes, and inkjet machines. 

(2) Application of adhesives, sealants, maskants, caulking materials, and inks. 

Response: The EPA agrees with the commenter that certain operations, which are often 

performed with specialty coatings, should be specifically excluded from the inorganic HAP 

control requirements for spray applied coating operations because they are not, in fact, applied 

with atomizing spray application equipment. Therefore, the EPA is adopting the definition that 

was suggested by the commenter. The suggested definition is consistent with the provisions in 40 

CFR 63, subpart HHHHH for defining coating operations subject to the inorganic HAP control 

requirements in subpart HHHHHH. 

Comment: One commenter (0830-0028) argued that the rule should include additional 

exemptions from the inorganic HAP requirements for specialty coatings in 40 CFR 63.745(g)(4), 

and that these exemptions should not require approval from a permitting authority, and the 

location of these operations should not be specified in the facility’s Title V operating permit 

because they may be transitory in nature. The additional exemptions are the following: 

• Spray-application of specialty coatings where it is impractical to perform the 

operation inside a spray booth. The current rule provides an exemption for operations 

where it is impractical to perform the coating in a spray-booth, but requires 

identification of these areas in the Title V permit. To accommodate the nature and 

variety of specialty coating operations and to provide flexibility, EPA should allow 

facilities to use this exemption without designating an area in the Title V permit. 

• Spray-application of specialty coatings controlled by equipment and/or work 

practices and vented indoors. Some facilities apply specialty coatings outside of spray 

booths, but use work practices and other equipment (including filters) to control the 

inorganic HAP emissions to the atmosphere to levels that are equivalent to what 

would be achieved in a spray booth with filtration exhausted to the atmosphere. 

• Spray application of three gallons per day or less at a single location at a facility. 

California air district rules, including South Coast AQMD Rule 481(e)(1) and 

Antelope Valley AQMD Rule 481(b)(1) provide this low use exemption that is 

necessary to accommodate very small operations that result in little or no HAP 
58 

emissions.69 Facilities in these regions use this exemption to apply small volumes of 

specialty coatings when it is impractical to move the aircraft or part to a coating 

booth. Often, these coatings are applied during the final assembly of an aircraft or 

rework of a fully assembled aircraft that are too large to fit in an available coating 

booth or otherwise cannot be easily moved. Inorganic HAP emissions from these 

operations are very low due to the small volume of coatings applied and work 

practices used to reduce or control overspray. 

• Coatings applied from a hand-held device with a paint cup capacity that is equal to or 

less than 3.0 fluid ounces (89 cubic centimeters). This exemption is provided in 

Subpart HHHHHH to accommodate low volume applications, including operations 

that use airbrushes, which may occasionally occur in various locations throughout the 

assembly facility where it is impractical to relocate the aircraft or part to a coating 

booth. Because the paint cup capacity is limited to 3.0 fluid ounces, operations of this 

type are inherently limited and, result in little or no inorganic HAP emissions. 

Providing this exemption for specialty coatings would allow operational flexibility 

without creating extra HAP emissions. 

Response: In addition to our prior responses on our inability to provide exemptions given that 

Congress has not defined volumetrically which sources’ emissions are small enough not to warrant 

mandatory MACT standards, the EPA disagrees with the commenter on the need for three out of 

the four suggested exemptions, as explained in the following paragraphs. 

Spray-application of specialty coatings where it is impractical to perform the operation inside a 

spray booth: The EPA is not including this exemption in the final rule because it is important 

that permitting authorities review and approve the determinations that it is impractical to perform 

a coating operation inside a spray booth. The rule currently provides flexibility through other 

mechanisms provided in 40 CFR 63.741(f) and in other provisions included in the final rule such 

that the need for the additional flexibility for specialty coatings requested by the commenter has 

not been demonstrated by the commenter. 

Spray-application of specialty coatings controlled by equipment and/or work practices and 

vented indoors: The EPA is not incorporating this change into the rule for specialty coatings 

because it is not permitted for the currently regulated coating operations. The current 

specifications in 40 CFR 63.745(g) ensure that all spray applied coating operations achieve 

MACT for the control of inorganic HAP emissions. If the rule included an exclusion for spray 

applied coatings that are vented indoors, then the control of inorganic HAP emissions would be 

dependent on the configuration of the building and the ventilation system of that building, and 

the EPA would have no assurance that inorganic HAP emissions would be controlled to a level 

equal to MACT. 

Spray application of three gallons per day or less at a single location at a facility: The EPA is 

not incorporating this change into the final rule for specialty coatings because it is not permitted 

for the currently regulated coating operations. In the two California AQMD rules cited by the 

commenter, these applicability exemptions apply to the total amount of coating applied per day 

at a location (i.e., facility), and not to any single coating operation or use of a specialty coating, 

 

69 South Coast AQMD Rule 481(e)(1); Antelope Valle AQMD Rule 481(b)(1). 
59 

as the commenter suggested. The EPA believes that it is unlikely that any facility that is a major 

source and subject to subpart GG would have such low daily coating consumption. 

Coatings applied from a hand-held device with a paint cup capacity that is equal to or less than 

3.0 fluid ounces (89 cubic centimeters): The EPA agrees with the commenter. The EPA's 

complete response to this comment can be found in section IV.E.3 of the preamble to the final 

rule. 

Comment: One commenter (0830-0030) supported EPA setting inorganic HAP standards but 

opposed the proposed standards which is just to apply the same standards applicable to other 

spray-applied coatings to specialty coatings – i.e., filtration efficiency requirements based on the 

use of a spray booth with a particulate filter. 

The commenter argued that the EPA has not met the Act’s stringency requirements for inorganic 

HAP standards for specialty coating operations because EPA has not considered or proposed 

standards that would require the “maximum achievable” degree of inorganic HAP reductions, as 

CAA § 7412(d)(2) requires. The commenter added that EPA has not considered or assured that it 

is setting a floor that requires at least the average emission limitation “achieved” by the bestperforming 12 percent, for existing sources, and the best-performing single source, for new 

sources, as CAA § 7412(d)(3) requires. The commenter noted that EPA must perform the 

requisite floor and beyond-the-floor analysis, based on the emission reductions actually achieved 

for the inorganic HAPs, including all HAP metals which include cadmium and lead, among 

others. The commenter explained that this would assure that, at least, EPA is requiring a 99 

percent control efficiency, rather than a range of 10-90 percent efficiency as the proposed rule 

appears to allow. The commenter disagreed with EPA’s statement that it is doing this because 

this is the “predominant method used” by those other sources. According to the commenter, 

EPA has admitted “the predominant method used to control inorganic HAP emissions from all 

spray-applied coating operations (including specialty coatings) is the use of a spray booth with a 

particulate filter which generally achieves a high (i.e., greater than 99 percent) control 

efficiency” which would suggests that at least the top 12 percent best performing sources are 

achieving a 99 percent control efficiency – and this is likely to be the average emission limitation 

these sources have achieved. The commenter argued that EPA may not, therefore, set standards 

that are any less stringent than 99 percent control efficiency for existing sources or for new 

sources, as it proposes to do in violation of CAA § 7412(d)(3) and must assure the “maximum 

degree” of emission reduction that is “achievable.” 

The commenter further noted that EPA has not shown that just applying the efficiency control 

standards for inorganic HAPs will assure the requisite level of control of all HAPs, particularly 

all metal HAPs. The commenter added that EPA must directly regulate or show that an 

“inorganic HAP”-focused surrogate standard is sufficient to control these pollutants. The 

commenter noted that EPA has not shown that it has met the surrogacy test or shown that this 

proposed standard would adequately control all emitted HAP metals, as required. 

Response: The EPA acknowledges the commenters support for establishing inorganic HAP 

emission standard for specialty coating operations. However, we disagree with the commenter’s 

assessment of the MACT analysis and stringency requirements for inorganic HAP emissions 

from specialty coating operations. The information that the EPA had available for the proposed 
60 

inorganic HAP requirements for specialty coatings is based on compliance with the current 

standards in 40 CFR 63.745(g). In the analysis of the ICR data and in the search of different 

information sources described in the MACT memo for specialty coatings, the EPA found no 

information indicating that any facilities were complying with more stringent emission 

limitations than those in 40 CFR 63.745(g). 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.” Our approach to use of available data is supported by NRDC v. EPA, 529 

F.3d 1077, 1086) (D.C. Cir. 2008). (The EPA typically has wide latitude in determining the extent of 

data-gathering necessary to solve a problem.). 

The EPA acknowledges that we erred by referring to 99-percent control efficiency in the 

proposal preamble (80 FR 8421) because this was a reference to overall overspray arrestor 

efficiency, which is readily achievable by good quality spray booth filters. However, this overall 

overspray arrestor efficiency should not be compared to the arrestor efficiency requirements for 

the different aerodynamic particle size ranges in Tables 2 through 5 in 40 CFR 63.745 in the 

proposed amendments. The same filters that can comply with the requirements in Tables 2 

through 5 should also be able to achieve 99 percent efficiency of total paint overspray because 

most of the paint overspray particles are much larger than the largest particle size ranges in 

Tables 2 through 5. To avoid confusion, the EPA should have referred to the arrestor 

requirements in Tables 2 through 5 in the proposed amendments when discussing the types of 

controls currently in use that were the basis of MACT for specialty coatings. 

We also disagree with the comment that we have not shown that the standard for inorganic HAP 

will control all HAP, including metal HAP, and that we have not shown that we have met the 

surrogacy test. As previously explained, the EPA may use a surrogate to regulate HAP if there is 

a reasonable basis to do so. We have used PM as a surrogate to regulate non-mercury metal HAP 

because “(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. Here, the filtration controls in the current rule and which we proposed to 

extend to specialty coating operations are equally effective for all inorganic HAP that are emitted 

from spray applied coating operations. All of the inorganic HAP emitted, including metal HAP, 

are “invariably present” in PM, and the arrestor efficiency standards will, therefore, 

“indiscriminately capture” all of the inorganic HAP that are emitted. 

Comment: One commenter (0830-0028) stated that EPA should allow interlock systems as an 

alternative to daily pressure drop and water flow readings on coating booths, as this type of 

system automatically shuts off the air supply to the spray guns if the monitored parameters are 

out of range. The commenter referenced EPA’s proposed interlock option for the Secondary 

Aluminum NESHAP [79 Fed. Reg. 72874, 72904 (December 8, 2014)], noting that EPA should 

provide a similar option in this rule. The commenter also noted that manual recordkeeping or 

automatic data-logging to meet the requirements are time-consuming and expensive, so the 

interlock system option would reduce the monitoring and recordkeeping burden for regulated 

facilities while ensuring that coating operations cease when the parameters are out of range. 
61 

Response: The EPA agrees that these types of interlock systems can reduce the monitoring and 

recordkeeping burden associated with the use of spray booths to control inorganic HAP 

emissions from spray-applied coating operations and has included this option in the final rule. 

7.5 Specialty Coating Compliance Deadline 

Comment: Several commenters (0830-0026, 0830-0027, and 0830-0028) argued that the EPA

should provide a three-year compliance period for specialty coatings rather than the proposed 

one-year period. All commenters argued that additional time is needed to ensure the replacement 

specialty coatings meet the needed performance requirements specified by aircraft 

manufacturers, DoD, FAA, NASA, or other countries' government agencies. 

One commenter (0830-0027) argued that additional time is needed for coating manufacturers to 

develop reformulated coatings to meet the proposed limits based on the CTG, to test the coatings 

to meet customer performance specifications, and to implement changes to raw material supply 

chains, product lines, and distribution channels to ensure compliance by the deadline and to 

mitigate the effect of obsolete products and product information. 

One commenter (0830-0026) argued that more time is needed to determine whether each coating 

is compliant, engineer new coating formulations, test the new formulation to ensure it meets the 

requirements of the aircraft manufacturers, and incorporate the new formulation into the material 

specifications and add the coating to the qualified product list for the aircraft. The commenter 

noted that the EPA acknowledged the lengthy period of time needed to qualify new coatings with 

respect to the technology review performed for primer and topcoat operations. 

One commenter (0830-0028) argued that one year is shorter than has been provided in any other 

surface coating NESHAP. The commenter noted that the CTG limits generally have been applied 

only to facilities in non-attainment areas, and facilities in attainment areas may be faced with the 

need to reformulate some coatings. The commenter also argued that the application equipment 

and spray booth filtration requirements for specialty coatings will also be new requirements for 

all facilities using specialty coatings, and additional time may be needed to revise Title V 

operating permits for new or upgraded spray booths, or to allow for averaging or alternative 

compliance demonstrations. The commenter added that, because of the large number of specialty 

coatings, additional time is also needed to develop compliance systems (even for facilities that 

previously were required to comply with the primer and topcoat operation standards), determine 

the VOC and HAP content of these coatings, and setting up recordkeeping and reporting 

systems. 

One commenter (0830-0027) argued that the original surface coating NESHAP and the recent 

RTR rules for surface coating have all included three-year compliance dates for the standards or 

for any significant changes to the existing standards. The commenter argued that this time is 

needed by both the coating manufacturers to reformulate coatings and for the regulated 

operations to procure compliant products and implement new control techniques. 

Response: We agree with the commenters on the need for the three-year compliance period. The 

EPA's complete response to this comment can be found in section IV.J.3 in the preamble to the 

final rule amendments.
62 

Comment: One commenter (0830-0027) asked EPA to include in the final rule a sell-through 

provision that will allow aerospace facilities to use existing products for a period of up to 2 years 

beyond the compliance date. The commenter argued that in addition to the time needed for 

product reformulation and requalification, coating manufacturers will still need to supply the 

industry with current products that meet customer specifications prior to the compliance date of 

the final rule. 

Response: The EPA is not including the 2-year sell through provision suggested by the 

commenter in the final rule. As previously explained, under CAA section 112(i)(3), the EPA must 

require sources to comply as expeditiously as practicable, but no later than 3 years after promulgation 

of the standard. The EPA’s construct has recently been upheld in Assn. 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). Allowing a 2-year sell through provision would 

mean that some facilities may not be achieving MACT for a period of up to 2 years after the 

compliance date for existing sources. Aerospace facilities will need to begin transitioning to 

compliant coatings in advance of the 3-year compliance deadline so that they have depleted their 

inventories of non-compliant coatings by that deadline. 

7.6 Complying with the Proposed Specialty Coating Limits 

Comment: One commenter (0830-0028) requested that the EPA include a mechanism to obtain 

approval to use essential coatings for which reformulation cannot be achieved. The commenter 

argued that it is not possible to determine whether each and every specialty coating can comply 

with the proposed limits because of the large number of specialty coatings, the lack of 

formulation data available to aerospace facilities, the need to assign each coating into one or 

more of the specialty coating classifications, and the length of the comment period. The 

commenter argued that the need for the suggested mechanism would not be eliminated by the 

averaging provisions because the averaging provisions do not allow averaging between specialty 

coatings and primers or topcoats, and it would not benefit facilities that use only a few coatings. 

The commenter also noted that once an aircraft is certified, it is difficult to change the coatings 

used without having to repeat at least part of the certification process. 

Response: The EPA is not including this mechanism in the final rule. It is not included in the 

CTG, nor is it included in the various state rules that have adopted the CTG and which are the 

basis for MACT for specialty coatings. 

Comment: One commenter (0830-0028) stated that industry members will continue to review 

specialty coatings to determine if they can meet the proposed limits and the commenter will 

submit that information to the EPA, even if it is outside the public comment period, so that the 

EPA can address those coatings in the final rule or indicate how they can be addressed in a caseby-case mechanism to address coatings that cannot meet the standards. 

Response: As earlier explained, CAA section 112(d)(3) requires the EPA to promulgate standards 

that are based on emission limitations achieved by the best performing sources “for which the 

Administrator has emissions information.” Our approach to use of available data is also supported by 
63 

NRDC v. EPA, 529 F.3d 1077, 1086) (D.C. Cir. 2008). (The EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a problem.). 

Consistent with CAA section 307(d)(3), the EPA has provided the “comment period” for the 

proposed rule. (80 FR 8392). Any information or data that are submitted after the end of the 

public comment period cannot be considered in the final rulemaking for this action. Additionally, 

we note that the EPA is bound by a consent decree to sign a final rule by November 19, 2015, 

and any additional notice and public comment period based on new data would make it 

impossible to comply with that deadline. Parties can always petition for reconsideration under 

CAA section 307(d)(7)(B). 

Comment: One commenter (0830-0028) recommended that the organic HAP and VOC 

standards should not apply to the recoating of assembled aircraft if original formulations are 

used. The commenter argued that as long as an aircraft is in service, it must be maintained in 

accordance with the instructions of the original equipment manufacturer (OEM) with materials 

that conform to its certified configuration to maintain airworthiness. The commenter argued that 

aerospace facilities occasionally work on an older aircraft that was assembled with specialty 

coatings that would not meet the proposed organic HAP or VOC standards and for which there 

will not be a replacement coating that meets the specifications for the aerospace vehicle or 

component, including compatibility with the substrate and existing coatings, and it will likely be 

economically impractical to reformulate a coating that may be sparingly used on reworked 

aircraft. The commenter noted that South Coast AQMD Rule 1124 exempts such operations from 

its limits. The commenter recommended that EPA should provide this limited allowance to the 

organic HAP and VOC standards for specialty coatings by adding the following provision to 40 

CFR 63.741: 

The provisions of Section 63.745(c)(5) and (6) shall not apply to the recoating of 

assembled aircraft at rework facilities if original coating formulations are used. 

Response: The EPA disagrees with the commenter on the need for this provision. Subpart GG 

currently does not regulate the rework of aircraft or aircraft components if the holder of the 

Federal Aviation Administration (FAA) design approval, or the holder's licensee, is not actively 

manufacturing the aircraft or aircraft components. (See 40 CFR 63.741(f).) The EPA believes 

that this provision in the current addresses the issues associated with older aircraft raised by the 

commenter. 

Comment: One commenter (0830-0028) recommended that compliance averaging should be 

permitted between and among specialty coating classifications. The commenter noted that the 

EPA proposed that instead of complying with the individual organic HAP and VOC specialty 

coating limits at 40 CFR 63.745(c), facilities may use the monthly volume-weighted average of 

specialty coatings to demonstrate compliance with these limits, but averaging would be 

prohibited between different classifications of specialty coatings. The commenter argued that 

averaging should be allowed between all classifications of specialty coatings, as the current rule 

allows averaging between types of primers (e.g., averaging is allowed between primers applied 

to large commercial aircraft and general primers). The commenter noted that Under the 

Miscellaneous Metal Parts and Products NESHAP (40 CFR 63, subpart MMMM), facilities are 
64 

allowed to demonstrate compliance with the coating limits by developing a facility-wide 

emission rate calculated as the weighted average of the four different limits. 

Response: The EPA did not propose to allow emissions averaging among specialty coatings in 

different categories and subject to different emission limits, and did not discuss such an approach 

in the proposal preamble or other supporting documents, and therefore, this comment is beyond 

the scope of this rulemaking. 

The averaging language in 40 CFR 63.743(d) specifically prohibits averaging between Type I 

and Type II chemical milling maskants. In addition, the rule does not include any method or 

equation for calculating the limit with which a facility would need to comply if it were averaging 

among coating types that were subject to different limits. 

The averaging language in 40 CFR 63.743(d) was added in the amendments that were finalized 

on March 27, 1998 (63 FR 15006), and the EPA did not, through this rulemaking, reopen the 

opportunity for comments on previous actions taken. As also earlier noted, EPA considers these 

comments as beyond the scope of today’s action. The language of that section reflects the primer 

and top coat categories that were in the rule at that time in 40 CFR 63.745: primers, topcoats, and 

self-priming topcoats. The preamble to the final rule included the following discussion of the 

feasibility of averaging across coating categories (63 FR 15012): 

“A workable scheme for averaging across coating types was not developed because the 

format of the coating limits in the rule as originally promulgated creates inherent 

difficulties in making equitable comparisons/calculations of actual emissions from 

coating categories with different limits. In order to include effective emissions averaging 

provisions for different coating categories (e.g., primers, topcoats, and maskants) or other 

emission sources, the format of the entire rule would have to be overhauled. Such 

changes are now beyond the scope of the work involved in finalizing these amendments 

to the aerospace rule.” [Emphasis added.] 

Comment: One commenter (0830-0028) recommended that the rule should allow addition of 

HAP-free solvents to specialty coatings that meet the organic HAP and VOC limits as supplied 

by the coating manufacturer. The commenter argued that industry members have identified 

several specialty coatings that meet the organic HAP and VOC content limits as supplied by the 

manufacturer but that would no longer meet the VOC limit “as applied” when solvents are added 

as recommended in the manufacturing specification. In those cases, the solvents added contain 

VOC, but no HAP, such as primers that are applied in warm weather. The commenter suggested 

that facilities would be required to keep records demonstrating compliance with the limits as 

supplied and that the solvents added do not contain HAP. The commenter argued that such a 

change would be equivalent to the proposed standards because (1) the coatings meet the organic 

HAP and VOC content limits as supplied, thereby effectively limiting the HAP content of the 

coating, and (2) the solvents added do not contain HAP, such that the coatings would remain 

complaint with the organic HAP limit “as applied.” 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.E.3 in the preamble to the final rule amendments. 
65 

Comment: One commenter (0830-0028) recommended that where the EPA has found in 

approving a RACT limit for a State or region that it is equivalent to the CTG, the EPA should 

allow in the final rule that compliance with the RACT limit is equivalent to the MACT for 

complying with the specialty coatings limits. The commenter also recommended that the EPA 

should encourage states and local governments to submit their RACT or other regulations to 

EPA for equivalency determinations pursuant to Section 112(l) of the Act and Subpart E of Part 

63. The commenter noted that, under 40 CFR 63.93, a State may seek approval of State 

requirements that differ from a Section 112 NESHAP for which they would substitute. The 

commenter argued that the EPA should provide for streamlined approval in the final rule for 

state rules that have been approved as RACT, and that such an approach would be consistent 

with the intent of Section 112(l) of the CAA and would also fulfill Congress’ direction to 

harmonize aerospace industry CTG-based standards with the NESHAP requirements.70

Response: The EPA disagrees with the commenter that state approved RACT limits equivalent 

to the CTG should be allowed as equivalent to MACT for complying with the specialty coating 

limits. As previously explained, Section 112(d)(3) of the CAA requires the EPA to promulgate 

standards for major sources of HAP that are based on control technology 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). Thus, the EPA is required to 

establish uniform limits equal to MACT under section 112 of the CAA. The CTG is a guideline 

document, and state may deviate from it in developing RACT standards for controlling VOC 

emissions. Therefore, the EPA cannot determine if all approved RACT standards are equal to 

MACT. If the approved RACT standards are equal to the CTG limits that are being promulgated 

as MACT in the final rule, then there is no clear benefit to facilities or states to justify the 

additional administrative burden on facilities, states, or the EPA in the equivalency 

determinations recommended by the commenter. 

Comment: One commenter (0830-0028) argued that the EPA should expand the low-volume 

exemption in 40 CFR 63.741(g) to allow a total of 200 gallons of specialty coatings in addition 

to the 200 gallons of primers, topcoats, and chemical milling maskants. The commenter noted 

that in the rule the exemption would not be expanded from the current total of 200 gallons. The 

commenter argued that the low volume exemption is critical for the aerospace industry because 

for many applications subject to detailed specifications, only one formulation is available, and 

the small volume of coating used does not justify the cost to reformulate. 

The commenter argued that because of the total number of specialty coatings, an additional 200 

gallons is needed separate from the exemption for primers, topcoats, and chemical milling 

maskants. The commenter argued that the original 200 gallon exemption was considered part of 

MACT for primers, topcoats, and chemical milling maskants, and forcing facilities to allocate 

part of that exemption to specialty coatings would make the MACT for primers, topcoats, and 

 

70 42 U.S.C. § 7511b(b)(3); H.R. Rep. No. 101-490 At 249 (1990) (Rep. Accompanying H.R. 3030) Reprinted In 2 

Senate Comm. On Env’t and Pub. Works, 103d Cong., A Legislative History of the Clean Air Act Amendments of 

1990, At 3273 (1993).
66 

chemical milling maskants more stringent. The commenter argued that a change to the MACT 

standard can be made only if there is a finding of a technological advancement under CAA 

section 112(d)(6) or of unacceptable risk under CAA section 112(f). The commenter noted that 

the EPA has made neither of those findings. 

The commenter also noted that the CTG that is the basis for the specialty coating limits includes 

a 200-gallon low-volume exemption for specialty coatings, separate from the 200-gallon 

exemption for primers, topcoats, and chemical milling maskants. 

The commenter recommended the following changes to the proposed language in 40 CFR 

63.741(g): 

The requirements for primers, topcoats, specialty coatings and chemical milling maskants 

in §§ 63.745 and 63.747 do not apply to the use of low-volume coatings in these 

categories for which the annual total of each separate formulation used at a facility does 

not exceed 189 liters (50 gal), and the combined annual total of all such primers, 

topcoats, specialty coatings and chemical milling maskants used at a facility does not 

exceed 757 liters (200 gal). The requirements for specialty coatings in § 63.745 do not 

apply to the use of low-volume coatings in this category for which the annual total of 

each separate formulation used at a facility does not exceed 189 liters (50 gal), and the 

combined annual total of all such specialty coatings used at a facility does not exceed 757 

liters (200 gal). Primers, topcoats and specialty coatings exempted under paragraph (f) of 

this section and under § 63.745(f)(3) and (g)(4) are not included in the 50 and 200 gal 

limits. Chemical milling maskants exempted under § 63.747(c)(3) are also not included in 

these limits. 

Response: The EPA is not expanding the low-volume exemption in 40 CFR 63.741(f) to include 

a 200 gallon exemption for specialty coatings, in addition to the existing 200 gallon exemption 

for primers, topcoats, and chemical milling maskants. The exemption recommended by the 

commenter is not included in the Aerospace CTG, nor is it included in any of the state and 

regional rules based on the CTG. The commenter did not provide any data or information on 

specific examples of specialty coatings used in applications subject to detailed specifications 

where only one formulation is available. 

We also disagree with the commenter that the basis for MACT for primers, topcoats, and 

chemical milling maskants included a 200 gallon per year low volume exemption for just those 

coatings, and that the addition of specialty coatings would make the MACT for primers, 

topcoats, and chemical milling maskants more stringent. As described in section 3.4 of the 1995 

background information document for the proposed NESHAP,71 the California rules on which 

the EPA based the MACT determination included exemptions of no more than 250 gallons of 

coating per year, and no more than 20 gallons per year of individual coatings, for all surface 

coating operations, including primers, topcoats, and chemical milling maskants, and specialty 

coatings. These California rule do not presently include separate low volume exemptions for 

 

71 National Emission Standard for Hazardous Air Pollutants (NESHAP) for the Aerospace Industry - Background 

Information for Proposed Standards. Draft. May 1994. EPA Publication No. EPA-453-R94-036a. 
67 

specialty coatings. The Aerospace CTG also does not include a separate low-volume exemption 

for specialty coatings. 

Comment: One commenter (0830-0028) argued that the rule should be revised to clarify that it 

does not apply to specialty coatings that do not contain HAP. The commenter noted that 

proposed 40 CFR 63.741(f) includes the following sentence (emphasis added): 

The requirements of this subpart also do not apply to primers, topcoats, specialty 

coatings, chemical milling maskants, strippers, and cleaning solvents containing HAP 

and VOC at concentrations less than 0.1 percent by mass for carcinogens or 1.0 percent 

by mass for non-carcinogens, as determined from manufacturer’s representations, such as 

in a material safety data sheet or product data sheet, or testing. 

The commenter argued that this could be interpreted to mean that the rule would regulate 

coatings that contain no HAP, if they contained VOC above the levels specified in that sentence. 

The commenter argued that this is likely to have been unintentional because the EPA has the 

authority to regulate only sources of HAP under section 112, and EPA cannot regulate sources of 

VOC that are not sources of HAP. The commenter argued however, that aerospace facilities 

should have the option to use coating with no HAP to demonstrate compliance using the coating 

content averaging provisions of 40 CFR 63.750(d) and (f) to encourage the development and use 

of non-HAP coatings. The commenter recommended that the following provision should be 

added to 40 CFR 63.741(f) to clarify the exemption: 

The requirements of this subpart also do not apply to specialty coatings containing HAP 

at concentrations less than 0.1 percent by mass for carcinogens or 1.0 percent by mass for 

carcinogens, as determined from manufacturer’s representations, such as in a material 

safety data sheet or product data sheet, or testing, except that if an owner or operator 

chooses to include one or more such coatings in averaging under § 63.743(d), then the 

recordkeeping requirements of § 63.752(c)(4) shall apply. 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.G.3 in the preamble to the final rule amendments. 

Comment: One commenter (00830-0028) argued that the EPA should revise the definition of 

“coating” in 40 CFR 63.742 to be consistent with other surface coating NESHAP. The 

commenter argued that the current definition is vague, and with the proposed regulation of 

specialty coatings, it could be read to include products that are not considered coating products 

under other EPA surface coating rules. The commenter argued that the definition should limit 

coatings to liquid or mastic materials (consistent with the American Society of Testing and 

Materials definition of coating) and exclude materials that are excluded from the definition of 

coating in other EPA rules. The commenter recommended the following definition of coating: 

Coating means a liquid, liquefiable, or mastic composition that is applied to the surface 

of an aerospace vehicle or component and converted by evaporation, cross-linking, or 

cooling, to form a decorative, protective, or functional solid film or the solid film itself. 

Coating application with handheld, non-refillable aerosol containers, touch-up markers, 

marking pens, or the application of paper film or plastic film which may be pre-coated 
68 

with an adhesive by the manufacturer are not coating operations for the purposes of this 

subpart. 

Response: The EPA agrees with the commenter. The EPA's complete response to this comment 

can be found in section IV.G.3 in the preamble to the final rule amendments. 

8.0 Startup, Shutdown, Malfunction Provisions 

Comment: One commenter (0830-0030) supported the removal of the exemptions for emissions 

during startup, shutdown and malfunction periods. The commenter agreed that emission 

standards must apply at all times, as the Clean Air Act requires, which EPA has recognized, and 

the D.C. Circuit has held.72 Further, the commenter also supported that EPA appropriately 

recognizes that it may not promulgate any affirmative defense for civil penalties in the event of a 

malfunction73 because such provisions are also unlawful, as the D.C. Circuit has held.74

Response: The EPA acknowledges the commenter’s support. 

Comment: One commenter (0830-0028) noted that while EPA’s intent for the proposed 

recordkeeping and reporting requirements at 40 CFR 63.752(a)(1) to (3) and 63.753(a)(5) is to 

apply only to malfunctions of equipment, they could be interpreted more broadly to require 

reporting of deviations from any applicable requirement. If finalized as proposed, the commenter 

stated they could result in unnecessary and burdensome requirements that overlap with detailed 

recordkeeping and reporting provisions in the current rule and deviation reporting requirements 

in the facilities’ Title V permits. The commenter further noted that EPA should remove the 

proposed additions and simply require malfunction reporting under General Provisions, or if 

EPA keeps the new provisions it must modify them to clearly indicate that they apply only to 

malfunctions. 

Response: The commenter is incorrect. The EPA does not intend that the requirements in 40 

CFR 63.752(a)(1) to (3) and 63.753(a)(5) should apply only to malfunctions of equipment. 

Instead, the EPA intends that recordkeeping and reporting requirements that would be applicable 

to normal operations should also apply to startup and shutdown. They are general requirements 

to report deviations, and more specific requirements, such as creating and retaining records of 

occurrences and durations of malfunctions, that are included in the other paragraphs of 40 CFR 

63.752. As described in section IV.E.3 of the proposal preamble, the EPA is required by recent 

court decisions to revise the provisions of the NESHAP regarding emissions during periods of 

startup, shutdown, and malfunction, and these changes require provisions that differ from the 

current General Provisions, and which may differ from a facility’s Title V permit requirements. 

(80 FR 8425). 

Comment: One commenter (0830-0028) stated that the existing reporting requirements in the 

Aerospace NESHAP and Title V permit require only the information that is readily attainable 

and necessary to determine compliance, for example, reporting instances when a coating 

 

72 42 U.S.C. §§ 7602(k), 7412; 80 Fed. Reg. at 8423; Sierra Club, 551 F.3d 1019. 

73 80 Fed. Reg. at 8424. 

74 42 U.S.C. §§ 7413, 7604; NRDC v. EPA, 749 F.3d 1055, 1057 (D.C. Cir. 2014).
69 

operation was not immediately shut down when the pressure drop across the particulate filter was 

outside of recommended parameters. The commenter noted that the proposed requirements will 

now also require a facility to provide an estimate of the quantity of each pollutant emitted over 

the emission limit, but it is not practical for a facility to determine or even estimate the volume of 

excess emissions from a coating booth, so this should not be required. 

Response: The EPA disagrees with the commenter and we are retaining the requirement as 

proposed to report an estimate of the quantity of each regulated pollutant emitted over any 

emission limit and a description of the method used to estimate the emissions over the emission 

limit. This requirement will ensure that there is adequate information to allow the EPA to 

determine the severity of the failure to meet an applicable standard and to provide data that may 

document how the source met the general duty to minimize emissions during an exceedance 

event. We disagree with the commenter that it is not possible to estimate emissions during these 

types of events. The rule provides facilities the flexibility to select the most appropriate method 

to estimate emissions based on process knowledge and the circumstances of each situation. 

Examples of such methods would include mass balance calculations, measurements when 

available or engineering judgment based on known process parameters (e.g., coating HAP 

content and application rate or control device efficiencies). 

Comment: One commenter (0830-0028) argued that the proposed recordkeeping and reporting 

requirements are contrary to the Clean Air Act in that they appear to require reporting of 

violations per inclusion of the wording “failure to meet an applicable standard.” The commenter 

stated that CAA Section 504(c) provides that Title V facilities are required to report deviations 

from—not failure to meet—permit requirements. The commenter further noted that EPA should 

use the statutory language instead of adopting a new term which has not been defined. The 

commenter explained that a deviation from a particular permit term might be excused such that it 

is not a violation, and stated that requiring a source to concede a violation is contrary to the 

statute. If EPA keeps the new provisions, it must revise them to state that facilities are only 

required to report deviations and not failures to meet the standard. 

Response: The EPA disagrees with the commenter. As previously explained in the preamble to 

the proposed rule (80 FR 8426, February 17, 2015), the EPA intends that these requirements 

would apply to the failure to meet any applicable standard in subpart GG. They are general 

requirements to report deviations, and more specific requirements are included in the other 

paragraphs of 40 CFR 63.752. The EPA will use the reported information to determine 

compliance, the severity of the failure to meet an applicable standard, and whether the facility 

met the general duty to minimize emissions during a malfunction The language in the proposed 

rule does not affect the EPA’s discretion to evaluate each case of an exceedance of an emission 

limit or failure to meet an applicable standard on a case-by-case basis, as described in section 

IV.E.3 of the proposal preamble. 

Comment: One commenter (0830-0028) stated that EPA should not require compliance with 

emission limits during malfunctions, or if so, should develop standards for malfunctions based 

on appropriate data. The commenter further noted that the court decisions EPA used to justify 

requiring compliance during malfunctions do not stand for the proposition that standards based 

on normal operations should be applied during periods of abnormal operation. 
70 

A second commenter (0830-0026) argued that the EPA's proposal to eliminate the exemption for 

startup, shutdown, and malfunction events is based on an incorrect reading of Sierra Club v. 

EPA, 551 F.3d 1019 (D.C. Cir. 2008) (hereinafter “Sierra Club”) and that the EPA is in fact 

required to provide achievable emission standards for malfunctions under the CAA. The 

commenter also argued that Sierra Club does not bar EPA from implementing different 

emissions standards during startup and shutdown periods, and work practice standards for 

malfunction events. 

The second commenter (0830-0026) argued that Sierra Club does not require EPA to eliminate 

malfunction provisions, and instead only requires that standards promulgated under Section 112 

of the Clean Air Act must apply at all times. The commenter argued that the Sierra Club Court 

held that Congress “required that there must be continuous section 112-compliant standards,” 

and that the “general duty” requirements of 40 CFR 63.6 were not sufficient because they were 

not contained in Section 112.75 The commenter argued that the Court therefore found the SSM 

exemption to be in violation of the CAA’s requirement “that some section 112 standard apply 

continuously.”76 

The second commenter (0830-0026) argued that the court specifically noted that, although the 

blanket SSM exemption was illegal, “continuous emission reduction” could be achieved 

“without necessarily continuously applying a single standard.”77 The commenter argued that the 

court found that Congress’s primary purpose in requiring “continuous” regulations was to ensure 

that regulation was not “intermittent” and that Congress did not intend to require that one 

uniform standard apply at all times. The commenter noted that the court pointed to Section 

112(h) as an option to allow implementation of work practice standards rather than numeric 

emissions limits as a 112-compliant option for regulating SSM events, by noting that EPA had 

“not purported to act under section 112(h),” though it could have.78

The second commenter (0830-0026) argued that the EPA is still authorized to promulgate 

emissions standards that would apply during periods of malfunction, so long as the standards are 

rooted in Section 112. The commenter pointed to a memorandum issued by the EPA’s Office of 

Civil Enforcement79 that the commenter argued indicated that the vacatur of the SSM exemption 

would not impact rules that “include specific regulatory text that exempts or excuses compliance 

during SSM events, and such regulatory text is in addition to, or in lieu of, a cross-reference to” 

the general duty provisions in 40 CFR 63.6, and the Sierra Club decision would only affect 

specific rules if the rule did not contain independent SSM provisions. 

The second commenter (0830-0026) argued that EPA's rationale that the EPA cannot account for 

malfunctions in setting emission standards because of the different types of malfunctions that can 

occur and the difficulty of predicting or accounting for the frequency, degree and duration of 

various malfunctions that might occur, is not valid because Section 112(h) provides option for 

accounting for malfunctions. The commenter argued that Section 112(h) work practice standards 

 

75 Sierra Club, 551 F.3d at 1027-1028. 

76 Id. at 1028. 

77 Id. at 1027. 

78 Id. at 1028. 

79 See U.S. EPA Memorandum re Vacatur of Startup, Shutdown, and Malfunction (SSM) Exemption (40 

C.F.R. §§ 63.6(f)(1) and 63.6(h)(1)) (“Kushner Memo”) (July 22, 2009).
71 

are permitted where it is “not feasible...to prescribe or enforce an emission standard,” including 

where “the application of measurement methodology to a particular class of sources is not 

practicable,” and can be used to address the difficulties described in EPA's rationale. The 

commenter argued that Section 112(d)(1)(E) authorizes EPA to establish emission standards that 

combine numeric elements with work practice elements so that some Section 112 standard would 

apply at all times as required by the Sierra Club decision. 

A third commenter (0830-0026) argued that the EPA is required to account for malfunctions in 

setting achievable technology based standards under Section 112(d), and that these standards 

must be based on actual performance.80 The commenter argued that the EPA has acknowledged 

that malfunctions are not reasonably preventable and can result in emissions that are above 

normal levels, but notes that the EPA has argued that nothing in section 112 directs the Agency 

to consider malfunctions in determining the level “achieved” by the best performing sources 

when setting standards. The commenter argued that the EPA is incorrect to assume that it has no 

obligation to consider malfunctions in setting emission standards, and that instead, the EPA must 

consider emissions during malfunctions in order to set standards that reflect actual performance. 

The commenter argued that this conclusion is supported by judicial precedent81 that requires the 

EPA to consider malfunctions and implement different emission standards or work practice 

standards for startup, shutdown, and malfunction events. 

Response: As explained at proposal, in Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the 

United States Court of Appeals for the District of Columbia Circuit vacated the startup, 

shutdown, and malfunction (SSM) exemptions contained in section 63.6(f)(1) and (h)(1) of the 

Part 63 General Provisions. (80 FR 8423-24, February 17, 2015). When incorporated into CAA 

section 112(d) regulations for specific source categories, these two provisions exempted sources 

from the requirement to comply with the otherwise applicable section 112(d) emission standard 

during periods of SSM. In Sierra Club, the court explained that under section 302(k) of the 

CAA, emissions standards or limitations must be continuous in nature. The court then held that 

the SSM exemption violates the CAA's requirement that some section 112 standard apply 

continuously. 

To ensure that some section 112 standard applies at all times, we are specifying that the SSM 

exemption in the 40 CFR part 63 General Provisions does not apply to subpart GG and clarifying 

that the emission limits apply at all other times, including during periods of malfunction. 

Regarding periods of malfunction, the Clean Air Act does not allow EPA to provide “affirmative 

defense” provisions into NESHAP. In NRDC v. EPA, 749 F.3d 1055(D.C. Cir. 2014) the D.C. 

Circuit vacated a regulatory provision establishing an affirmative defense to civil penalties for 

 

80 See Nat’l Assn. of Clean Water Agencies v. EPA, 734 F.3d 1115, 1158 (D.C. Cir. 2013) (“[I]t is reasonable to 

expect that the incinerator on which the MACT floors are based should be able to ‘achieve’ the MACT floor ‘in 

practice,’ which it could not do unless ‘achieved in practice’ meant ‘achieved under the worst foreseeable 

circumstances.’”).

81 For example, the commenter argued that the D.C. Circuit acknowledged that malfunctions were an “inescapable 

aspect of industrial life” and agreed that EPA must allow for malfunctions in setting technology-based emission 

standards. Portland Cement Assn. v. Ruckelshaus, 486 F.2d 375, 398-99 (D.C. Cir. 1973) 
72 

violations of emission standards caused by unavoidable malfunctions. The court found that the 

authority under the CAA to determine penalty amounts lies exclusively with the courts. 

In light of NRDC, the EPA is no longer including regulatory affirmative defense provisions in its 

rules. However, if a source is unable to comply with an emission standard as a result of a 

malfunction, the EPA may use its case-by-case enforcement discretion to provide flexibility in 

deciding if a penalty is appropriate. Further, in an EPA or citizen enforcement action, the court 

has the discretion to consider any defense raised and determine whether penalties are 

appropriate. 

9.0 Electronic Reporting Provisions 

Comment: One commenter (0830-0030) supported the EPA's proposal that requires 

performance test and other compliance information to be submitted through electronic reporting 

using the portal and software developed for this purpose.82 The commenter added that the EPA 

must ensure this information is also promptly made available online to the public in an accessible 

format and supported the WebFIRE data being publicly available. However, the commenter 

noted that it is not in a form that most members of the public can understand or interpret. The 

commenter recommended that the EPA should strengthen the electronic portal to synthesize the 

data and assist the public in analyzing the raw data and reports that facilities submit. The 

commenter argued that updating the electronic reporting system to assist the public in reviewing 

and understanding the reported data would be consistent with the 1994 Environmental Justice 

Executive Order (No. 12898) and EPA’s renewed commitment to strengthen the public 

availability of information for affected communities, as part of Plan EJ 2014.83

Response: The EPA acknowledges the commenter’s support for the proposal to require 

performance test reports to be submitted through electronic reporting. However, the structure and 

format of the data provided in WebFIRE is beyond the scope of this rulemaking. The EPA notes 

that currently the WebFIRE database has over 3500 reports available for public review. Most of 

these reports are a portable document format (pdf) file, which is a format that can be easily 

reviewed by anyone. Performance test and performance evaluation reports are available as both 

an extensible markup language (XML) file and an Electronic Reporting Tool (ERT) file. The 

ERT is a free download available from the EPA at http://www3.epa.gov/ttnchie1/ert/. The 

current version of the ERT is a Microsoft Access database program, and as such, users must own 

a copy of Microsoft Access in order for the program to work. For users who do not own a copy 

of Microsoft Access, a runtime version is available through Microsoft. In order to view ERT 

files, the user must open the file in the ERT program. If a user does not wish to review the data 

in the ERT, once the ERT file is opened in Microsoft Access, a pdf file of the entered data can be 

created. Additionally, a majority of the ERT files have a pdf file of the entire stack test report 

attached. This can be obtained by opening the file in the ERT program and looking at the list of 

attachments. 

 

82 80 Fed. Reg. at 8422.

83 Plan EJ 2014, supra note 6. 
73 

10.0 Alternative Compliance Demonstration 

Comment: Two commenters (0830-0027, 0830-0028) supported the use of VOC content as a 

surrogate for HAP content and argued that it is at least as protective as using HAP content and is 

less burdensome. The two commenters added that the current NESHAP addresses the issue of 

solvents that are HAP, but exempt from the definition of VOC (methylene chloride, 

perchloroethylene, and 1,1,1-trichloroethane), by allowing sources to rely on VOC only as long 

as the coating does not contain exempt solvents (see 40 CFR 63.750(c)(1)). The commenters 

recommended that the same approach be used with the VOC limits for specialty coatings to 

address any discrepancy between VOC and HAP content while reducing the regulatory burden of 

the rule. 

Response: The EPA agrees with the commenters that facilities should have the option to use 

VOC content as a surrogate for HAP content and will include it in the final rule for specialty 

coatings that do not contain certain halogenated solvents that are excluded from the definition of 

VOC. As previously explained, EPA may use a surrogate to regulate HAP if there is a reasonable 

basis to do so. National Lime Assn., 633 F.3d at 639. As also previously explained, with the 

exception of the three halogenated solvents, all HAP are also VOC and we are setting the same 

limit for VOC and organic HAP such that the organic HAP content cannot exceed the VOC 

limit. 

Specialty coatings that contain these halogenated solvents will have to use HAP content to 

demonstrate compliance, but they will have the option to still use manufacturer’s supplied data 

on the HAP content to demonstrate compliance. Additionally, in order to verify the HAP content 

of such coatings, the EPA is also adding EPA Method 311, Analysis of Hazardous Air Pollutant 

Compounds in Paints and Coatings by Direct Injection Into a Gas Chromatograph, to 40 CFR 

63.750 as the EPA reference method to confirm the HAP content of coatings. In the event of any 

inconsistency between the EPA Method 311 test data and manufacturer’s supplied formulation 

data, that is, if the EPA Method 311 value is higher, the EPA Method 311 test will govern unless 

after consultation, the facility can demonstrate to the satisfaction of the enforcement agency that 

the formulation data were correct. 

Comment: Two commenters (0830-0027, 0830-0028) agreed that manufacturer’s 

documentation of the HAP or VOC content of the coatings, such as MSDS and product data 

sheets, should be accepted for demonstrating compliance for specialty coatings as proposed in 40 

CFR 63.750(c), (e), (k), and (m). One commenter (0830-0027) added that this approach has been 

adopted in other national, state, and local VOC regulations and noted that coating manufacturers 

have the best understanding of their products because they have to collect information on each of 

their raw materials and their coating formulations for other regulatory purposes, such as the 

preparation of MSDS to comply with OSHA's Hazard Communication Standard. The same 

commenter argued that this would also be more cost effective than performing EPA Method 24 

testing on each coating formulation. 

Response: The EPA acknowledges the commenter’s support. 

Comment: One commenter (0830-0028) argued that certain clarifications are needed to reduce 

compliance costs and bring them closer to the EPA's estimated compliance costs. The 
74 

commenter argued that first, the rule should confirm that facilities should be able to rely 

conclusively on coating manufacturer VOC data to demonstrate compliance with the VOC 

content limits. The commenter noted that, because the only reason to provide VOC content data 

is for regulatory purposes, one can assume that the VOC content listed is the regulatory VOC 

content (that is, less water and exempt solvents). The commenter suggested that this assumption 

could be made explicit in the rule by adding the following sentence or an equivalent clarification 

to 40 CFR 63.750(e), (f)(1)(iii), (m), and (n)(1): 

Unless stated otherwise on coating manufacturer documentation, coating manufacturer 

supplied VOC content provided in grams/liter (lb/gal) is deemed consistent with the 

definition of VOC in 40 CFR 51.100(s) (i.e., less water and exempt solvents). 

Second, the commenter (0830-0028) argued that the rule should confirm that facilities may use 

the VOC content data supplied by the coating manufacturer to demonstrate compliance with the 

organic HAP limits when the coating does not contain exempt solvents that are also organic 

HAP. The commenter noted that this clarification is needed to simplify the compliance 

demonstration because coating manufacturers rarely provide the HAP content on product data or 

MSDS sheets. The commenter argued that the following sentence should be added to the end of 

40 CFR 63.750(c), (d), (k), and (l): 

The coating manufacturer’s supplied VOC content may be used as a surrogate for organic 

HAP content if the coating does not contain exempt solvents that are HAP. 

The commenter (0830-0028) argued that these two changes are needed for the EPA to assume in 

the cost impact analysis for specialty coatings that facilities will not need to perform testing to 

determine the VOC or HAP content of coatings. 

The commenter (0830-0028) argued also that the rule must clarify that facilities will not be 

subject to enforcement action if laboratory testing reveals a value over the limit when the 

manufacturer data shows values that are compliant and no additional solvents were added by the 

facility. The commenter argued that EPA needs to provide a safe harbor for companies that 

reasonably rely on the data supplied by the manufacturer in order to support the EPA’s 

recordkeeping and reporting burden estimate, consistent with the Paperwork Reduction Act (44 

U.S.C. § 3506(c)(1)). 

Response: As previously explained, the EPA agrees with the commenter that with the exception 

of certain halogenated solvents, the VOC content may be used as a surrogate for HAP content in 

coatings and has added the clarifying information to 40 CFR 63.750(c), (d), (k), and (l). The 

EPA has also added language to clarify that, unless stated otherwise on the manufacturer’s 

documentation, the VOC content is assumed to be less water and exemption solvents. 

As also previously explained in order to verify the HAP content of such coatings, the EPA is also 

adding EPA Method 311, Analysis of Hazardous Air Pollutant Compounds in Paints and 

Coatings by Direct Injection Into a Gas Chromatograph, to 40 CFR 63.750 as the EPA reference 

method to confirm the HAP content of coatings. In the event of any inconsistency between the 

EPA Method 311 test data and the manufacturer's supplied formulation data, that is, if the EPA 

Method 311 value is higher, the EPA Method 311 test will govern unless after consultation, the 
75 

facility can demonstrate to the satisfaction of the enforcement agency that the formulation data 

were correct.

However, the EPA disagrees with the commenter that facilities should not be subject to 

enforcement action if laboratory testing reveals a value over the limit when the manufacturer 

data shows values that are compliant and no additional solvents were added by the facility. If the 

EPA adopted the commenter’s recommendation, then the EPA would have no method to enforce 

the VOC and HAP content standards in cases where a coating applicator adds HAP containing 

solvent to the coating. Laboratory testing of the VOC and HAP content of coating samples 

collected in an “as applied” condition using EPA Methods 24 (for VOC) and 311 (for HAP) is 

needed to ensure compliance with the requirements of surface coating NESHAP and to ensure 

that coatings are not in violation due to excessive HAP containing solvent added by the coating 

applicator. 

Comment: One commenter (0830-0030) was opposed to allowing facilities to rely on coating 

manufacturer's supplied information, regardless of the amount of emissions, because it would be 

unlawful and arbitrary. The commenter argued that authorizing sources to avoid any emission 

testing to assure compliance would violate the Act’s requirement that standards apply at all 

times, and the requirement that emission limits and permit limits be sufficient to assure 

compliance.84 The commenter explained that this is arbitrary and capricious because EPA has not 

shown that such documentation is reliable or a reasonable substitute for an actual compliance 

demonstration in regard to a source’s actual emissions. The commenter argued that EPA has not 

shown (1) test data showing that the manufacturer’s data product sheets indeed match the air 

emissions; (2) how such “supplied formulation data” could “indicate” that coatings meet the 

standards; (3) how other factors, such as the amount of coatings, the use of different kinds of 

coatings, the application of coatings, and other steps in the maintenance and use of equipment 

would not possibly affect the amount of actual HAP emissions in the air; and (4) how it will 

prevent inaccurate manufacturer documentation from circumventing the emission limits. 

The commenter argued that a coating manufacturer’s product supply document is insufficient to 

assure compliance because it may be outdated or inaccurate and may not actually reflect the 

amount of HAPs or VOCs in a coating. Instead, to ensure sources actually comply with emission 

limits, the commenter recommended that EPA must require the regulated sources themselves to 

test, report, and keep records on their actual HAP emissions. 

The commenter argued that manufacturers are not subject to the emission limits and EPA has not 

outlined how an enforcement action for a false HAP/VOC-content report could be brought to 

give them incentive to ensure accuracy of their documentation. To the contrary, knowing that 

they are more likely to be able to sell more product if they submit documentation that says the 

HAP/VOC content limit is below EPA’s standards will provide more incentive for them to do so 

– regardless of the actual content, and without appropriate quality control to assure all of their 

product indeed meets the specifications. The commenter argued that even if the content is 

accurate, a facility may be using it incorrectly or emissions may be combining to increase the 

 

84 42 U.S.C. § 7602(k); id. § 7661c(a) and implementing regulations.
76 

actual HAP content in the air above the levels of the standards and EPA has not shown how 

relying only on this will assure compliance with the emission limits. 

The commenter stated that this would create significant enforcement problems for EPA, states, 

and affected community members because the requirement to avoid HAP emissions falls on 

sources regulated under the Clean Air Act, not coating manufacturers. The commenter added that 

if a source retains documentation from a manufacturer that does not reflect the correct HAP 

emissions, that source may continue emitting HAPs no matter how high its actual emissions may 

be. The commenter argued that community members will have no information to be able to 

assess whether, in fact, a source’s emissions meet the standards and would make it impossible 

for communities to receive relief if emissions were higher than predicted by manufacturer's 

documents. It is unclear to the commenter how EPA or states could assure this either. The 

commenter opposed finalizing provisions that will, by default, exempt emissions from the limits, 

no matter how much HAP they put into the air of nearby communities. 

Response: The EPA disagrees with the commenter that more testing of coating should be 

required and that facilities should not be allowed to use coating manufacturer’s documentation to 

demonstrate compliance. The EPA has included the use of coating manufacturer's formulation 

data to demonstrate compliance with HAP and VOC content limits in numerous surface coating 

NESHAP. The EPA has not experienced the enforcement issues described by the commenter as a 

result of this approach. 

The EPA has compared emissions predicted from coating manufacturer's product data sheets 

with measured emissions. As part of developing the risk modelling database for the residual risk 

analysis for this source category, the EPA requested that certain facilities also test their air 

emissions from surface coating operations.85 These data showed that the air emissions were no 

higher than the emissions that were estimated from the coating manufacturers' product data 

sheets, and coating manufacturers' product data sheets, in fact, tended to significantly overstate 

the emission potential of the coatings. 

This testing has also shown that other factors, such as the amount of coatings, the use of different 

kinds of coatings, the application of coatings, and other steps in the maintenance and use of 

application equipment do not affect the amount of actual HAP emissions in the air in such a way 

that they would exceed the HAP emissions estimated from the coating manufacturer's 

formulation data. 

Even though coating manufacturers are not the entities that must comply with subpart GG, they 

still have many economic and regulatory incentives to provide accurate information on the VOC 

and HAP content to their customers. Coating manufacturers are required by Occupational Safety 

and Health Administration (OSHA) regulations to provide a Material Safety Data Sheet (MSDS) 

for each coating they manufacture. These MSDS are required to show the hazardous constituents 

of those coatings, and as part of the hazard communication to their coating users, many coating 

suppliers are also indicating the regulatory VOC level of the coatings (i.e., grams VOC per liter 

of coating less water and exempt solvents). Some manufacturers are also providing the HAP 

 

85 See the memorandum, Aerospace Manufacturing and Rework Facilities RTR Modeling File Preparation, in docket 

EPA-HQ-OAR-2014-0830. 
77 

content. Coating manufacturers have a strong incentive to ensure that this information is accurate 

because they know that their customers will be using it to demonstrate compliance, and they 

know that the EPA also has the authority to test samples of coatings using EPA methods 24 

(Determination of Volatile Matter Content, Water Content, Density, Volume Solids, and Weight 

Solids of Surface Coatings) and 311 (Analysis of Hazardous Air Pollutant Compounds in Paints 

and Coatings by Direct Injection Into a Gas Chromatograph). Coating manufacturers are likely to 

face civil lawsuits and the loss of business if they provide faulty documentation that results in an 

EPA violation for one of their customers. They may also face enforcement by OSHA if it is 

shown that MSDS included inaccurate information on hazardous constituents in coatings. 

Finally, the EPA can still inspect aerospace manufacturing facilities to collect samples of 

coatings and test them to measure the VOC and HAP content to compare them to the 

manufacturer’s documentation of the VOC and HAP content, and other records kept at the 

facility. In addition, many state and local air pollution control agencies that have VOC content 

limits for aerospace coatings that are the same as the VOC content limits in subpart GG perform 

compliance testing. 

11.0 Other Emission Sources Not Currently Regulated 

Comment: One commenter (0830-0030) argued that the EPA must set emission standards for all 

other currently uncontrolled emission points in the aerospace source category. The commenter 

noted that EPA argued in 1994 that control of organic HAP emissions from the four non-coating 

related operations that are uncontrolled (chemical milling, metal finishing, electrodeposition, and 

composite processing) was “not feasible because no demonstrated control measures could be 

identified.”86 However, the commenter argued that EPA has a “clear statutory obligation to set 

emission standards for each listed HAP”87 regardless of whether the best-performing sources in 

a given category are currently using air pollution control technology to limit their emissions.88 

The commenter argued that the Agency must regulate emissions from all the emission points that 

are part of the affected source. The commenter disagreed with EPA’s claims about the relative 

significance of HAP emissions from the four non-coating-related operations, and the agency’s 

failure to identify control measures cannot justify failing to set emission standards for these 

operations. The commenter concluded that EPA must set standards for these currently 

uncontrolled sources for the same reason that it is proposing to set standards for specialty coating 

operations. 

The same commenter argued that EPA lacks authority simply to declare that sources of HAP 

emissions are not worth controlling89 even if emissions from a non-coating operations constitute 

less than 1 percent of the total organic HAP emissions from aerospace facilities. 

The commenter added that EPA has failed to regulate three coating-related operations: 

adhesives, adhesive bonding primers, and sealants. According to the commenter, EPA previously 

 

86 59 Fed. Reg. 29,216, 29,239 (June 6, 1994) (“1994 Proposed Rule”). 

87 Nat’l Lime Assn., 233 F.3d at 634. 

88 Id.

89 Id.
78 

argued that the organic HAP emissions from these processes are “relatively small” and that many 

of the coatings in use are already applied using efficient techniques, and thus there was little 

room to reduce emissions further.90 EPA discussed the possibility of using coatings with lower

organic HAP content, but asserted that it lacked data on organic HAP content of coatings at the 

time of the proposal, and it did not have time to collect any, according the commenter. The 

commenter argued that as EPA has shown for specialty coatings – emissions are quite large from 

that type of emission point (360 tpy from that subset of the source category alone), which 

suggests other uncontrolled emission points may also have substantially more emissions than 

EPA had previously believed. The commenter pointed that EPA has collected some new data on 

emissions from the source category that should allow it to address the other operations that are 

currently uncontrolled in the same way that it is proposing to set standards for specialty coating 

operations. 

The commenter stated that EPA must set emission standards for each HAP emitted by a source 

category to satisfy its responsibility under CAA § 7412 and therefore, cannot fulfill its obligation 

by setting standards for some parts of the source category and not others. The commenter argued 

that EPA must evaluate new data that were collected and set standards that close significant gaps 

in the standards for this source category and thus lack of data on the effects of non-technology 

factors on emissions cannot excuse the failure to set a floor.91

Response: We disagree with the commenter that the EPA is required to establish standards for 

the four operations cited by the commenter (i.e., chemical milling, metal finishing, 

electrodeposition, and composite processing). This is because they are not part of the surface 

coating source category regulated by the Aerospace Manufacturing and Rework NESHAP. In the 

initial list of categories published in 1992 and the revised list published in 1996, the EPA 

identified Aerospace Manufacturing and Rework Facilities as a “surface coating source 

category.”92 Chemical milling, metal finishing, and electrodeposition are not part of the 

Aerospace Manufacturing and Rework surface coating source category and are not unique to 

aerospace manufacturing facilities. For example, at area sources, but not major sources, these 

operations are regulated by subpart XXXXXX, the NESHAP for Nine Metal Fabrication and 

Finishing Area Source Categories. Composite processing at major sources is regulated by 

subpart WWWW, the NESHAP for Reinforced Plastic Composites Production. 

Comment: One commenter (0830-0028) agreed with the EPA’s decision to not regulate 

additional emission sources (chemical milling, metal finishing, waste water, storage tanks, and 

composite operations) because they are not surface coating operations and are outside of the 

source category, based on the CAA Section 112(c)(1) listing of categories and subcategories of 

major sources of HAP. The commenter noted that in both the initial list of categories published 

in 1992 and the revised list published in 1996, EPA identified Aerospace Manufacturing and 

Rework Facilities as a “surface coating source category.” 

Response: The EPA acknowledges the commenter’s support. 

 

90 1994 Proposed Rule, 59 Fed. Reg. at 29,239.

91 Sierra Club, 479 F.3d at 882. 

92 Final Report: Documentation for Developing the Initial Source Category List, EPA-450/3-91-030; (July 1992) 
79 

12.0 Estimated Cost, Economic, and Environmental Impacts 

Comment: One commenter (0830-0028) contended that the proposed rule does not provide a 

detailed explanation of the basis for EPA’s finding that the proposed action is not a significant 

regulatory action and, therefore, was not submitted for review by the Office of Management and 

Budget (OMB) as an action having an annual effect on the economy of $100 million or more, as 

required by Executive Order 12866. The commenter stated that this detailed explanation was 

likely not provided because EPA greatly underestimated the total annual cost of the proposal at 

$590,000. The commenter noted that, as a significant regulatory action, the EPA would also be 

required to include more detailed underlying assessments of the costs and benefits of the 

proposed action and potentially effective and reasonably feasible alternatives as well as provide 

information about the regulatory action to the Office of Information and Regulatory Affairs. 

Response: The EPA disagrees with the commenter that the EPA did not provide a detailed 

explanation of the basis of the cost and burden estimates. The EPA’s detailed costs and burden 

estimates were documented in the items that are included in the docket for this rulemaking. The 

cost estimate methodology and assumptions are included in the memo, Estimated Cost Impacts 

for Proposed Amendments to 40 CFR 63, Subpart GG, National Emission Standards for

Aerospace Manufacturing and Rework Facilities (docket item EPA-HQ-OAR-2014-0830-0005) 

and the burden estimate under the Paperwork Reduction Act are included in the Aerospace 

NESHAP Risk and Technology Review Information Collection Request Supporting Statement and 

Tables (docket item EPA-HQ-OAR-2014-0830-0009). 

The EPA also disagrees with the commenter’s assessment that the cost impacts of the final rule 

would have an effect on the economy of $100 million or more, and that the rule should be 

submitted to the OMB for review, as required by Executive Order 12866. As explained in the 

responses to the more detailed comments, below in this section, even if the EPA accepts the 

commenters estimates’ of the costs for complying with subpart GG and applies them to EPA’s 

estimate of the number and size of facilities with specialty coating operations, the costs are well 

below the $100 million threshold for OMB review. 

Comment: Two commenters (0830-0027, 0830-0028) argued that the EPA did not account for 

the cost of reformulating coatings and bringing new products to market to comply with the 

proposed organic HAP and VOC limits, and the costs account only for recordkeeping and 

reporting costs. One commenter (0830-0027) argued that although specialty coatings that meet 

the CTG limits exist, the CTG has not been widely adopted and not all coating manufacturers 

sell coatings in the market areas that are subject to specialty coating limits based on the CTG. 

The commenter argued that because specialty coatings are used in smaller volumes, the cost to 

reformulate and test compliant coatings is higher per unit than for higher volume coatings. The 

commenter added that compliance with the performance specifications for aircraft, and for 

compliance with other regulatory programs, such as OSHA, adds other layers of testing and cost 

to reformulation that have not been accounted for by EPA. 

One commenter (0830-0028) noted that of the two-thirds (74) of the facilities using specialty 

coatings that will be required to take actions to comply with the proposed organic HAP and VOC 

standards, it is likely that some of these facilities will need to find replacement coatings or 

reformulate current coatings. The commenter stated that the approval process for replacement 
80 

coatings is lengthy and costly and may reach $1 million per coating. The commenter stated that 

reformulating and implementing new coatings in cases where no replacement coatings are 

available may be as high as $5 million to $10 million per specialty coating, depending on the 

coating type and level of testing. The commenter added that recent experiences with replacing 

obsolete specialty coatings demonstrate that suppliers may not be willing to spend resources 

reformulating small volume specialty coatings with demanding technical requirements and that 

fewer coating manufacturers are willing to certify conformity to aerospace specifications and 

submit their products to the aerospace industry’s lengthy and expensive inspection and testing 

process. The commenter suggested costs to replace or reformulate specialty coatings could be 

significantly reduced if EPA provides a mechanism to approve these coatings that do not meet 

the proposed standards. The commenter added that costs for low volume and highly specialized 

formulations would be reduced by providing an additional 200 gallons to the total volume of 

coatings that may use the low volume exemption. 

Response: The EPA disagrees with the commenter that the EPA underestimated the cost impact 

of the proposed rules. The commenter did not provide any data on specific specialty coatings that 

could not meet the proposed VOC content limits or to support an estimate of the number of 

coatings that would need to be reformulated to comply with the proposed limits. 

In the absence of any specific data from the commenters to demonstrate otherwise, the EPA still 

believes that compliant coatings are available for all applications in all of the specialty categories 

and that these compliant coatings are likely to already be certified or approved to meet current 

performance standards for those coatings. 

The EPA has estimated that the vast majority of the specialty coatings in use already meet the 

proposed HAP content limits, based on both the number of coatings used and on the volume of 

coatings used. The EPA received data from the 2011 ICR that allowed the EPA to estimate the 

HAP content of 5,173 specialty coating “applications.” For this analysis, an “application” 

represents one row of data from the ICR and generally represents one specialty coating reported 

at one facility; some specialty coatings were reported at multiple facilities, and some facilities 

reported the same coating multiple times to represent each operation using that coating; in the 

latter case, each operation would represent one application. The EPA estimated the HAP content 

in units of grams of HAP per liter of coating because the EPA did not have data to correct the 

HAP content to g/liter less water, but very few of these coatings are believed to be waterborne 

formulations. 

Of the 5,173 coating applications for which the EPA was able to estimate the HAP content, about 

96 percent of coating applications, also representing about 96 percent of coating volume, were 

already below the proposed HAP content limits. The EPA estimated that only 225 coating 

applications were non-compliant. The EPA found no cases in which all the coatings in a 

specialty category (even in those categories with very few coatings reported) were noncompliant. For 75 of the non-compliant applications, the manufacturer and the product were not 

reported, so the EPA could not determine if these were duplicates of other coatings. Finally, 

some of the non-compliant materials were thinners, activators, or other types of additives that are 

not used as coatings by themselves, but would be mixed with other components to form the 

complete coating and would then likely have a lower HAP content. 
81 

Comment: One commenter (0830-0028) stated that EPA underestimated the effort required to 

determine coating content of specialty coatings and therefore the proposed ICR estimates are 

very low and fundamentally incorrect. The commenter noted that there are costs that EPA did not 

take into consideration and EPA should adjust its cost estimates accordingly. 

The commenter stated that EPA’s estimate of one hour per coating may be reasonable for 

coatings where the manufacturer supplies all the needed data in the proper format and the facility 

can rely on the data to demonstrate compliance, but while manufacturers commonly supply VOC 

content in the same format as the proposed VOC limit, total HAP content is either rarely 

provided or is often expressed as a range of the percent weight of HAP compounds or as an “up 

to” amount. The commenter stated that demonstrating compliance could be time-consuming and 

burdensome because in these situations a facility would need to perform multi-step calculations 

to convert the manufacturer’s HAP content into the proper units or perform additional laboratory 

analyses. The commenter noted that some percentage of the coatings must be assumed to require 

data gathering beyond already available information and these additional costs should be 

included in the ICR analysis and burden analysis. The commenter suggested that EPA could 

reduce burden for coating content determinations by clarifying that facilities can definitively rely 

on coating manufacturer VOC data and use VOC content as a surrogate for organic HAP content 

for coatings that do not contain exempt solvents that are also HAP. 

The commenter also stated that the current provisions which require facilities to calculate coating 

VOC content using formulas or laboratory analyses are being retained as the base compliance 

option and therefore costs for this should have been estimated in the ICR but do not appear to 

have been. The commenter argued that EPA is effectively basing its entire analysis on the 

alternative compliance option, but cannot assume that facilities will not use the base compliance 

approach. 

The commenter estimated that performing content calculations, requesting additional information 

from manufacturers, and performing analyses would require 5 to 10 hours of labor per specialty 

coating, plus analytical service fees of $575 per coating (for VOC content by Method 24) and a 

minimum of $3,000 per coating (for HAP content by Method 311). 

The commenter also questioned EPA’s assumption of approximately 30 coatings per facility, 

stating that this underestimates burden at larger facilities as they typically use approximately 200 

to 1,000 specialty coating formulations. 

The commenter also noted that when manufacturers make changes to coating compositions or 

otherwise update their documentation, the coating content calculations and analyses for the base 

compliance option need to be repeated and/or verified by the facility and computer systems will 

need to be updated to reflect new data for the alternative compliance option. 

Response: As noted in the response to the previous comment, the EPA does not believe that the 

compliance costs have been underestimated. As noted by the commenter, the EPA is allowing 

facilities to use the coating manufacturer’s VOC content determined from formulation data to 

demonstrate compliance with the HAP content limits for coatings that do not contain the exempt 

solvents that are also HAP. For coatings that contain exempt solvents that are also HAP, 
82 

facilities can use the coating manufacturer’s documentation of the HAP content based on coating 

formulation to demonstrate compliance. 

The EPA did not estimate the compliance costs based on the other compliance calculations and 

analytical methods in the rule because the most likely compliance option for the vast majority of 

coatings used by facilities is to use the manufacturer’s documentation of HAP or VOC content 

for each coating. 

However, if one were to make a “worst-case” assumption that the industry would need to 

perform EPA Method 24 testing for 5,000 coatings in one year (based on the approximate 

number of specialty coatings reported in the 2011 ICR), and assumed that facilities needed 7.5 

hours of labor at a cost of $100 per hour to perform calculations and arrange for VOC testing, 

and a cost of VOC testing of $575 per coating, the total cost for the industry in that one year 

would be about $6.6 million. These costs would not be annual costs because facilities would not 

have to test that many new coatings in any one year. 

The EPA identified only 45 coatings being used at 21 facilities that contained HAP that were not 

VOC. If one assumed that facilities needed 7.5 hours of labor at a cost of $100 per hour to 

perform calculations and arrange for HAP testing, and a cost of HAP testing of $3,000 per 

coating, the total cost for the industry in that one year would be about $170,000. These costs 

would not be annual costs because facilities would not have to test that many new coatings in 

any one year. 

The EPA agrees with the commenter that larger facilities may use more specialty coatings than 

an average of 30 coatings per facility. However, the total burden and cost impact estimated by 

the EPA did not use the 30 coating per facility average, but instead used the actual number of 

specialty coatings reported per facility in the 2011 ICR. The 30 coatings average is just that, an 

average that is useful for estimating impacts to the “average” facility. 

Because the EPA expects that facilities will use the manufacturers’ documentation of the VOC or 

HAP content to demonstrate compliance, that documentation will most likely be updated by the 

coating manufacturers and provided to the facilities with purchases of any reformulated coatings. 

Therefore, it is unlikely that facilities will need to repeat or update the compliance calculations. 

Comment: One commenter (0830-0028) stated that the tracking of coating usage and 

maintaining records for compliance imposes significant initial capital and labor costs as well as 

ongoing labor burdens. The commenter argued that EPA’s estimate of 27 labor hours per facility 

in the initial year and no capital expenses is incorrect and unsustainable. The commenter 

disagreed that all facilities will use existing tracking systems because, while aerospace facilities 

that are currently subject to state and regional specialty coating regulations may have tracking 

systems, the majority of facilities (approximately 74) do not and therefore must design, purchase, 

and install a system. In addition, the commenter further noted that due to the large number and 

variety of applications for specialty coatings, the existing systems for primers and topcoats may 

not even work and will either need to be modified or replaced. 
83 

The commenter explained that tracking systems for specialty coating application operations are 

far more complex and expensive than systems developed to track other coating applications at 

aerospace facilities or in other surface coating source categories. 

The commenter noted that many facilities will expend a considerable amount of effort to identify 

all the materials they use that EPA would consider a specialty coating because this proposal 

includes in the specialty coating definition a wide variety of previously unregulated materials 

that are applied outside of spray-coating booths and hangars. The facilities must then identify 

current and potential uses of each specialty coating and determine if the coating meets the 

standard for each applicable classification. The commenter further noted that additional tracking 

is necessary if a single coating is used in more than one classification, which is different than 

other EPA coating standards which have at most six coating classifications and also different 

than the current primary and topcoat standards which provide a limited number of content 

restrictions that are easier to track. 

The commenter stated that a facility must also continuously track use of specialty coatings to 

ensure each coating is used only for applications for which it meets the applicable limits. This 

could require expansion of material control protocols and worker training. In addition, the 

commenter noted that the tracking of coatings may have to reach the individual part level, adding 

a further level of complexity to the tracking system. 

The commenter stated that to accommodate complex tracking, facilities would have to purchase 

or invest in upgrades to existing systems to monitor and control purchasing and use of specialty 

coatings. These systems would be in addition to existing purchase controls because those 

systems do not track internal deliveries to specific specialty coating operations; these systems 

must be integrated across departments to ensure that appropriate coatings that meet the content 

limits are included in the aircraft design, are purchased, and are used for the appropriate 

applications. 

The commenter stated that the initial capital costs and labor to purchase and install these systems 

will be significant, as will the operating labor costs because any type of tracking system will 

require labor and training to maintain and audit. The commenter further noted that these costs are 

significantly higher than for a system to track just primers and topcoats as that focuses on just the 

paint shops. 

The commenter stated that larger facilities in Southern California had costs of $5 to $7 million as 

they implemented systems for daily compliance/tracking, and argued that these were similar to 

costs for several facilities in other states subject to specialty coating regulations. These costs 

include up to $1.5 million to purchase a tracking software system and for labor costs to 

implement the system and train employees. The commenter argued that annual costs going 

forward will decrease but will still involve ongoing software and labor costs and that one 

California facility with daily tracking requirements estimated costs at $3 million per year. The 

commenter concluded that because many aerospace facilities are not currently subject to state or 

regional specialty coating regulations, their expected costs would be similar to these example 

costs. Although these estimates are from facilities with daily tracking requirements, the 

commenter stated that the burden to track specialty coatings in accordance with the 

annual/monthly requirements in the proposed rule vastly exceeds EPA’s 27 hour estimate. 
84 

Response: The EPA disagrees with the commenter. The costs for a facility complying with daily 

tracking for all coating operations are not comparable to nor representative of the costs of 

complying with the subpart GG amendments to add specialty coatings. First, subpart GG does 

not require daily tracking of coating usage for any compliance option, and the final rule will only 

require monthly tracking if a facility is using the averaging provisions. Otherwise, only annual 

tracking of consumption is required, and this can be accomplished through the use of annual 

purchase records. Second, the amendments would add only requirements for specialty coatings, 

whereas most facilities are already complying with requirements for primers and topcoats. 

The EPA also disagrees with the commenter that coating use would need to be tracked 

continuously or to the level of the individual part. Nearly all of the specialty coating categories 

are defined by the functional characteristics of the coating, and only a few coatings (e.g., rocket 

motor nozzle coatings and fuel tank coatings) are defined by the types of parts to which they are 

applied. 

The costs reported by the commenter are also for larger facilities and are not expected to be 

representative of the majority of facilities that would need to begin tracking specialty coatings. 

The commenter reported that the larger facilities for which they cited costs use 200 to 1,000 

specialty coating formulations, whereas the average facility reported to the EPA in the 2011 ICR 

using only 30 specialty coatings per facility. Therefore, even if new tracking systems are needed 

for some facilities, their capital and annual costs are likely to be one to two orders of magnitude 

(that is, 1/10th to 1/100th) of the costs reported by the commenter. This is especially true given 

that the complexity of tracking systems is likely to grow exponentially at larger facilities as the 

number of coatings and coating operations increase at a facility, subpart GG does not require 

daily coating usage tracking and, in the final rule amendments, requires monthly coating usage 

tracking only if the facility is using the averaging provisions. 

If one assumes that the costs for tracking specialty coatings at a facility using an average of 30 

specialty coatings were 1/10th of the capital and annual costs cited by the commenter a large 

facility and applied them to the 74 facilities using specialty coatings that are not already subject 

to a VOC rule based on the CTG, the total industry costs are much lower than implied by the 

commenter. For 74 facilities, assuming a capital cost of $150,000 and annual costs of $300,000, 

the total capital costs would be $11.1 million, and the annual costs would be $22.2 million. 

Comment: One commenter (0830-0028) stated that EPA’s assumption that costs of upgrading 

high-efficiency application equipment for specialty coatings will be completely offset by 

reductions to the amount of coating used is incorrect for many facilities where changes to the 

manufacturing process to accommodate this equipment will more than offset savings from 

reduced paint use. The commenter noted that, based on EPA’s understanding that 11 California 

facilities are already required to meet these equipment standards, 98 of the 109 facilities affected 

by this new requirement may need to purchase or upgrade equipment and adjust manufacturing 

processes to comply, which results in a significant cost to industry. The commenter added that 

although the cost of new HVLP equipment and training may eventually be offset by savings in 

coating usage, for many applications HVLP is not the most efficient application method and it is 

very unlikely that the cost offsets identified by EPA will be achieved. 
85 

Response: The EPA disagrees with the commenter’s interpretation of the EPA cost estimates for 

high efficiency application methods. The EPA cited the fact that 11 California facilities are 

already required to meet requirements for high efficiency application methods for specialty 

coatings as the basis for establishing these as MACT for applying specialty coatings. In the cost 

memo in the docket (docket item EPA-HQ-OAR-2014-0830-0005), the EPA did not estimate the 

actual number of facilities that would need to upgrade their application equipment, but only 

estimated the cost impact and savings for an average facility based on the information in the 

ICR. In the cost memo, the EPA noted that many facilities have already likely switched to high 

efficiency application methods for economic reasons that were illustrated by the analysis in the 

cost memo. 

The EPA agrees with the commenter that HVLP spray guns are not the most efficient application 

method for certain coating operations and, as result, has adopted many of the commenter’s 

recommendations into the final rule requirements related to the application of specialty coatings. 

These changes are described in the section on “Specialty Coating Application Equipment 

Requirements” in this document. 

Comment: One commenter (0830-0028) stated that EPA’s cost estimate excludes costs for the 

installation, expansion, or upgrade of paint booths to accommodate spray-applied specialty 

coating operations. The commenter explained that although the majority of specialty coating 

operations may be conducted in booths controlled by filters meeting the proposed standards, this 

is not true for all specialty coating spray application operations. The commenter argued that 

requiring all of these operations into spray booths, particularly operations already well controlled 

by alternate work practices and equipment, would result in significant costs across the aerospace 

industry. The commenter urged EPA to consider including costs for installing new booths or 

upgrading or expanding existing booths to accommodate all specialty coating operations that 

contain inorganic HAP to meet the proposed requirements in Section 63.745(g)(2)(ii)(A). The 

commenter added that a new booth with a filtration system meeting these requirements for new 

sources costs approximately $400,000 (including $250,000 for the booth and $150,000 for labor) 

and may range much higher depending on the booth size. 

Response: The EPA did not include costs for additional spray booths for specialty coating 

operations because the EPA assumed that specialty coating operations that were not already 

performed in spray booths would be able to use spray booths that were already present for primer 

and topcoat application operations. Even if there are spray-applied specialty coating operations 

that cannot use existing primer and topcoat spray booths, the EPA believes that the spray booth 

requirements for specialty coating operations will have a minimal cost impact on aerospace 

facilities for several reasons. First, the EPA has revised the spray booth requirements that apply 

to all coating operations, based on public comments, to clarify that the use of portable enclosures 

that meet the same filtration requirements as for spray booths can be used to comply. Second, the 

spray booth requirements apply only to the spray application of coatings that contain inorganic 

HAP, and fewer than 10 percent of all the specialty coatings reported in the 2011 ICR (including 

those that are spray and non-spray applied) contained inorganic HAP. Finally, spray applied 

coating operations that are of sufficient size to require the construction of the spray booth 

described by the commenter (for example, greater than one gallon of coating spray applied in an 

8-hour work period) are already being required to be in a spray booth to comply with OSHA 

regulations to minimize worker exposure and to prevent fires (see, for example, 29 CFR 
86 

1910.107 and National Fire Protection Association standard 33, which both address spray 

finishing using flammable and combustible materials). Given these factors, the EPA believes that 

the cost for additional spray booths as a result of the rules for specialty coating operations is 

expected to be minimal. 

Comment: One commenter (0830-0028) argued that compliance costs can be reduced if EPA 

minimized the requirement for monthly records of coating usage. The commenter noted that the 

current rule requires facilities to maintain records of the volume of each coating formulation used 

each month, and the proposed rule changes to 40 CFR 63.752(c) and (f) would allow facilities to 

use annual purchase records only if they are using manufacturer’s documentation of the VOC or 

HAP content. The commenter argued that keeping the requirement to keep monthly usage 

records for any coating not used in an average places an unnecessary burden on facilities to track 

the volume of these coatings used at each operation and does not meet the Paperwork Reduction 

Act requirement to require collection of only information that “is necessary for the proper 

performance of the functions of the Agency, including whether the information shall have 

practical utility.”93 The commenter argued that the monthly volume of coating used is irrelevant 

to the compliance demonstration if the facility is using records of which coatings are used and 

the VOC and HAP content of the coatings, and are only needed if the facility is using the 

averaging provisions. The commenter argued the rule should be revised so that all facilities that 

are not using averaging should be required to maintain only annual purchase records instead of 

monthly usage records. 

Response: The EPA agrees with the commenter and is revising the requirements in 40 CFR 

63.752(c) and (f) to require monthly usage only if the coatings are being averaged. The EPA 

agrees that monthly usage records are only needed if averaging is being performed. Otherwise, 

none of the compliance demonstration requirements uses monthly coating consumption and a 

record of annual consumption of each coating is sufficient. 

Comment: One commenter (0830-0028) argued that EPA can reduce the recordkeeping and 

reporting burden by requiring that all coating manufacturers supply the information necessary to 

demonstrate compliance using manufacturer supplied data. The commenter argued that market 

forces are not sufficient to cause all coating manufacturers to provide the VOC content on their 

documentation, especially small manufacturers of specialty coatings that may not have been 

subject to VOC regulations. The commenter argued that the EPA should require all coating 

manufacturers to provide VOC content data, as grams per liter (less water and exempt solvents), 

under EPA’s authority to request air emissions information under section 114 of the CAA and 

provide that data on the product label, product data sheet, or MSDS. 

The commenter argued that Section 114 of the Clean Air Act provides the Agency the authority 

to require coating manufacturers to provide coating content data. Under Section 114, “[f]or the 

purpose” of “carrying out any provision of this chapter,” the Agency may require “any person ... 

who the Administrator believes may have information necessary for the purposes set forth in this 

subsection,” to “provide such other information as the Administrator may reasonable require.” 

The commenter argued it is also reasonable for EPA to require coating manufacturers to supply 

these data because these companies have ready access to these data as the manufacturers of the 

 

93 44 USC § 3508. 
87 

coatings, and could provide it at minimal cost, compared to the cost to the regulated industry to 

determine the VOC content through testing. 

Response: The EPA agrees that the burden on aerospace facilities would be reduced if coating 

manufacturers provided VOC or HAP content documentation that met the compliance needs of 

the aerospace facilities. However, the EPA does not have the authority under CAA Section 114 

to compel the coating manufacturers to provide that information to the aerospace facilities in the 

form of information on product labels, product data sheets, or MSDS so that information could 

then be provided by aerospace facilities to EPA for compliance purposes. 

As previously explained, coating manufacturers are required by Occupational Safety and Health 

Administration (OSHA) regulations to provide MSDS for each coating they manufacture. These 

MSDS are required to show the hazardous constituents of those coatings, and as part of the 

hazard communication to their coating users, many coating suppliers are also indicating the 

regulatory VOC level of the coatings (i.e., grams VOC per liter of coating less water and exempt 

solvents). Some manufacturers are also providing the HAP content. We believe coating 

manufacturers have a strong incentive to ensure that this information is accurate because they 

know that their customers will be using it to demonstrate compliance, and they know that the 

EPA also has the authority to test samples of coatings using EPA methods 24 (Determination of 

Volatile Matter Content, Water Content, Density, Volume Solids, and Weight Solids of Surface 

Coatings) and 311 (Analysis of Hazardous Air Pollutant Compounds in Paints and Coatings by 

Direct Injection Into a Gas Chromatograph). 

13.0 Technical Corrections 

Comment: One commenter (0830-0027) provided the following technical corrections: 

§ 63.750 Test methods and procedures. 

(k) Organic HAP content level determination–compliant chemical milling maskants 

(k)(2) [Reserved] 

With the clarifications within 40 CFR 63.750(k), the commenter suggested that paragraph (k)(2) 

should be deleted. 

§ 63.753 Reporting requirements. 

(c) Primer, topcoat and specialty coating application operations 

Each owner or operator of a primer or topcoat application....

The commenter suggested modifying this language to read: “Each owner or operator of a primer, 

topcoat, or specialty coating application....” to clarify that this section applies to specialty coating 

applications.

Response: The EPA acknowledges that with amendments being made to 40 CFR 63.750(k), this may 

seem to be a convenient time to remove reserved paragraph (k)(2). However, the EPA is making no 

other changes to 40 CFR 63.750(k), so the EPA is keeping the placeholder for paragraph (k)(2) to 

maintain the current paragraph numbering of this section.
88 

The EPA agrees with the change to 40 CFR 63.753(c) and has made that change in the final rule.

Comment: One commenter (0830-0028) requested that EPA change specialty coating 

“Corrosion Prevention System” in Appendix A of subpart GG to “Corrosion Prevention 

Compound” to match the naming convention used in Table 1. 

Response: The EPA acknowledges this difference within subpart GG, but in the final rule is 

changing the name used in Table 1 to match the category definition in Appendix A because that 

definition specifically uses the word “system,” instead of “compound,” in the body of the definition.

Comment: One commenter (0830-0028) stated that monitoring of dry particulate filters, HEPA 

filters, and waterwash systems should only be required during spray-application of coatings 

containing inorganic HAP. The commenter noted that because the inorganic HAP standards in 

Section 63.745(g) apply only to the spray-application of coatings with inorganic HAP, the EPA 

should clarify that these monitoring provisions are only required once per shift when primer, 

topcoat, or specialty coatings containing inorganic HAP are being spray-applied. 

Response: The EPA did not propose any changes to the filter monitoring requirements in 40 

CFR 63.745(g)(2)(iv) and (v). Therefore, the EPA did not, through this rulemaking, reopen the 

opportunity for comments on previous actions taken and EPA considers these comments as 

beyond the scope of today’s action. 

Comment: One commenter (0830-0028) noted that EPA should state in Section 63.752(a) that 

facilities are not required to keep records in accordance with Section 63.10(d)(5), to be consistent 

with the removal of startup, shutdown, and malfunction requirements in Section 63.753(a) and 

Table 1 of subpart GG. 

Response: The EPA agrees and has added 40 CFR 63.10(d)(5) to the list of paragraphs in 40 

CFR 63.10 that do not apply. 

Comment: One commenter (0830-0028) noted that the term “affected unit” should be changed 

to “affected source” in Sections 63.752(a)(1) to (3), for consistency with other sections of the 

rule. 

Response: The EPA agrees and has made that change. 

Comment: One commenter (0830-0028) requested that EPA correct Table 1 of subpart GG to 

indicate that Sections 63.10(c)(7) and (8) are not applicable to the Aerospace NESHAP because 

subpart GG does not require continuous monitoring systems. 

Response: The EPA disagrees that subpart GG does not require continuous monitoring systems. 

If a facility uses an add on control device for controlled coating operations, continuous 

monitoring may be required, such as temperature monitoring for combustion devices as specified 

in 40 CFR 63.751(b)(6) through (b)(12). 

Comment: One commenter (0830-0028) requested that EPA clarify in the final rule if Sections 

63.10(b)(2)(vii) to (xiv) are applicable to the Aerospace NESHAP. 
89 

Response: The EPA acknowledges that in the version of Table 1 to subpart GG published in the 

Federal Register (80 FR 8438), the row for 40 CFR 63.10(b)(2)(vii) to (xiv) in the amended 

Table 1 to subpart GG was inadvertently left blank in the second column, and this should have 

been marked “Yes” that these requirements still apply. The amendments to Table 1 changed only 

certain elements in Table 1 and those changes were explained in the preamble. Before the 

amendments, all of paragraph 63.10(b) applied to subpart GG. Sub-paragraphs 40 CFR 

63.10(b)(2)(vii) to (xiv) are not being amended, and they still apply to subpart GG. 

14.0 Comments Outside the Scope of the Proposal 

Comment: One commenter (0830-0029) argued that EPA Method 319, Determination of 

Filtration Efficiency for Paint Overspray Arrestors, does not accurately predict the real world 

efficiency of paint overspray arrestors to filter out chromate paint particles from facility exhaust 

emissions. The commenter argued that the lack of accuracy is due to the fact that the filtration 

efficiency is measured using potassium chloride and oleic oil particles instead of actual paint 

overspray particles. The commenter argued that in some cases, the fractional efficiencies of 3-

stage filter systems using paint overspray were nearly 80 percent lower in the micro-particle size 

ranges compared to those obtained from Method 319. (The commenter did not provide any 

supporting data or test results.) 

The commenter argued that the EPA’s Environmental Technology Verification program 

mandates the use of only the most advanced and credible technologies in the development of 

standards and regulations, and that the technology to count and size paint overspray particles 

existed for many years prior to the establishment of Method 319. The commenter argued that the 

regulation of chromate-based paints should have been developed with the use of paint overspray 

as challenge particulates but the commenter blamed unspecified internal and external politics for 

this oversight. 

The commenter argued that a dangerous gap exists between Method 319 certified filters and their 

real world performance in filtering out chromate paint particles from facility exhaust systems, 

and that the inflated filter efficiency data generated by Method 319 provides a false sense of 

confidence in the filtration market. The commenter argued that neighborhoods in the vicinity of 

industrial complexes that exhaust chromate-based paints may be subjected to increased risks of 

cancer-causing agents, and recommended that the regulations on paint filter exhaust systems be 

updated to require the use of paint particle technology in determining the true efficiencies of 

filtration systems. 

Response: The EPA did not propose any changes to EPA Method 319 in this rule making, so 

this comment is outside the scope of this rulemaking.