MEMORANDUM

Date: December 20, 2018

From: Bill Schrock

To: Docket No EPA-HQ-OAR-2003-0194

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Subject: Summary of Public Comments and EPA's Responses for the Proposed Risk and Technology Review and Amendments for the Leather Finishing Operations NESHAP
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1.0	Introduction

On March 14, 2018, the U.S. Environmental Protection Agency (EPA) proposed revisions to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Leather Finishing Operations source category (83 Federal Register (FR) 11314). This memorandum contains summaries of all the public comments that EPA received on the proposed standards. Certain significant comments and responses appear in the preamble to the final rule. Copies of all comments submitted are available at EPA Docket Center Public Reading Room. Comment letters are also available electronically through https://www.regulations.gov/ by searching Docket ID No. EPA-HQ-OAR-2003-0194. 

EPA received 17 comment letters after March 14, 2018 on the proposed revisions to the NESHAP for the Leather Finishing Operations source category. Table 1 lists the name and affiliation, if available, of each commenter providing written comment, and the document identification number assigned to the comment. All comment letters are contained in Docket Number EPA-HQ-OAR-2003-0194. For simplicity, only the last four digits of the document identification number are presented in this document (e.g., 0102, instead of EPA-HQ-OAR-2003-0194-0102). 
                                       
Table 1. List of Public Commenters on the March 14, 2018 Proposed Risk and Technology Review and Amendments to the Leather Finishing Operations NESHAP (83 FR 11314) 
Commenter Name and Affiliation
Document Number EPA-HQ-OAR-2003-0194-
Anonymous
0087 through 0097
Nicholas Ancona
0098
John L. Wittenbom, Leather Industries of America
0099
Emma Cheuse, Earth Justice, submitted on behalf of Sierra Club
0100
Anonymous
0101
Frank L. Kohlasch, Minnesota Pollution Control Agency
0102
Emma Cheuse and Michelle Mabson, Earth Justice, submitted on behalf of Sierra Club
0105
   
Of the 17 comment letters (letters 0100 and 0105 are from the same organization), 11 letters (0087, 0088, 0089, 0090, 0091, 0093, 0094, 0095, 0096, 0097, 0101) provided comment that does not pertain to the Leather Finishing Operations NESHAP proposed rulemaking. These comments are not discussed further in this memorandum. Refer to the docket for this rulemaking for these comment letters. Six of the 17 comment letters (0092, 0098, 0099, 0100/0105, and 0102) provided comment that pertains to the Leather Finishing Operations source category and the proposal. The following sections of this memorandum summarize these public comments and present EPA's responses to the comments:

   Section 2.0 - Risk Assessment
   Section 3.0 - Startup, Shutdown, or Malfunction
   Section 4.0 - Miscellaneous Comments
   
2.0 Risk Assessment

Section 2.0 provides comment summaries and responses on the following aspects of EPA's risk assessment:  risk assessment inputs, risk assessment methods, risk assessment results, and demographic and environmental justice analysis.

2.1 Risk Assessment Inputs

2.1-01 Comment: Commenter 0100 contended that EPA likely underestimates both emissions and exposure because the data used for this review are based on estimates that assume hypothetical perfect compliance and operation, not those that may arise during startup/shutdown processes. Commenter 0100 asserted that EPA must account for the health risks from emissions during periods of malfunction, stating that EPA ignores these risks. According to the commenter, these completely uncontrolled and unlimited emissions pose significant health risks to nearby communities. The commenter stated that, where control equipment fails, emissions could be at least 100 times greater (e.g., in the circumstance where a control device has 99% efficiency, such that an uncontrolled release would cause 100 times the usual amount of emissions).

The commenter contended that failing to look at the true potential for spikes in emissions over a person's lifetime may underestimate acute risk, cancer risk and the amount of chronic risk based on pollutants that persist in the environment, such as polychlorinated biphenyls (PCBs), polycylic organic matter (POM), lead, and cadmium. The commenter asserted that ignoring these emission spikes is equivalent to treating additional health risk caused by exceedances as zero. The commenter stated that EPA knows that there is additional risk from malfunctions and violations, and that this additional risk should not be ignored in risk assessments.

The commenter pointed out that, to assess the health risk from malfunctions, EPA has information available or can collect information on major sources' malfunction and violation histories. The commenter further pointed out that EPA regularly uses statistical methods and probability factors, which are readily available tools that EPA can also use to assess health risk due to malfunctions, to set clean air standards. The commenter further pointed out that, to calculate acute health risk, EPA uses what it calls a "worst case" scenario approach that attempts to account for some variability under the existing standard, which shows that the agency could similarly add a factor to account for malfunctions for acute and other types of health risk. 

Response: While we appreciate the additional information provided by the commenter about specific emissions events in violation of the standards, we disagree with the commenter that such emissions, whether or not they are caused by malfunction events, should be considered as part of the risk analysis. The purpose of the risk review (Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule; Docket Item No. EPA-HQ-OAR-2003-0194-0011) is to evaluate whether the emission limits - the "standards promulgated pursuant to subsection (d)" not the non-compliance with those standards [ U.S.C. § 7412 (f)(2)(A)] - should be made more stringent to reduce the risk posed after compliance with the underlying maximum achievable control technology (MACT) standard. To the extent that a source is violating the underlying MACT standard, no tightening of the emissions standard under the residual risk review will prevent or mitigate against such violations. In other words, a source that is violating the MACT emissions standard promulgated under section 112(d) would not be any less likely to violate under a different, presumably more stringent, standard promulgated under section 112(f). Violations of the standard are subject to enforcement by EPA, the States or citizens. An action for injunctive relief is the most effective means to address such violations, whether or not they are caused by malfunctions, if an emissions event poses a significant health or environmental risk. The original Leather Finishing NESHAP (65 FR 58703, October 2, 2000) requires that the standards apply at all times, consistent with Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir. 2008).. The proposed amendments related to malfunctions are intended to clarify this original requirement. Further discussion of these amendments is provided in the preamble to the proposed amendments (83 FR 11314, March 14, 2018). 

2.1-02 Comment: Commenter 0099 stated that they are not aware of any additional "major" sources other than the four identified by EPA in the current risk and technology review (RTR) analysis. The commenter added that "most, if not all" of the four sources identified by EPA in the current RTR analysis would not qualify as a "major" source of hazardous air pollutants (HAPs) today based on actual HAP emissions," explaining that this is due to the significant reduction in the use of HAP VOC-containing finishes. The commenter pointed out that the industry has been moving away from solvent finishes to water-based finishes since before adoption of the NESHAP, as well as moving away from the use of regulated glycol ethers since adoption of the NESHAP.

Response: The determination whether a source is major is dependent on the potential to emit 10 tons per year of any one HAP or 25 tons per year of all HAPs, and not on actual emissions. Residual risk reviews do not look at potential to emit, but analyze actual, allowable, and short-term emissions. Allowable emissions are somewhat analogous to potential to emit in that they represent the maximum amount of HAP which the facility can emit and still be in compliance with the MACT standards. Allowable emissions calculations also consider emission limits and control requirements. For the four major sources identified in this source category the allowable emissions are either above the 25 tons per year level for all HAP or the 10 tons per year level for at least one HAP.

2.1-03 Comment: Commenter 0100 asserted that the proposal is unlawful and arbitrary because it is based on production-based estimates to evaluate emissions, rather than on actual monitoring or measurement. The commenter stated that an emission inventory based on production-based estimates is "irrational" because it underestimates exposure and risk, assuming hypothetical perfect compliance and operation and not real-world emissions as reported by each facility, and leaves commenters with no actual emissions data to check EPA's estimates or to calculate "allowable" emissions estimates. The commenter further stated that EPA has not justified using this approach, noting that EPA's rule proposal explains that it has used ad hoc methodologies to estimate allowable emissions for each individual facility and acknowledges that it does not have actual production data because EPA chose not to require the four facilities to submit data through an information collection request. 

Response: We disagree that not using monitoring data to calculate allowable emissions is unlawful or arbitrary. Under the Clean Air Act (CAA) (42 U.S.C. § 7412(f)(2)), EPA has a legal obligation to conduct the risk and technology review using the best available data and tools. The risk modeling file contains emissions, by pollutant, for each emission release point from each leather finishing operation. For the four affected facilities, "actual" emissions and release parameters in our risk analysis are based on actual emission data available in the 2014 National Emissions Inventory (2014 NEI), facility operating permits and permit applications, facility annual emission reports, Google Earth satellite and street view imagery, and communication with facility representatives. Allowable emissions are calculated to represent the maximum amount of emissions which the facility is permitted to release each year. Given that the Leather Finishing NESHAP establishes the maximum allowable emission level based on a ratio tied to production, and we do not have production data for all four facilities, we developed methods using available data to calculate conservative estimates of allowable emissions of organic HAP for each facility. We used a production-based approach to estimate allowable organic HAP emissions for only one of the four facilities subject to the Leather Finishing NESHAP, and we disagree with the commenter that this method "underestimates exposure and risk, assuming hypothetical perfect compliance and operation and not real-world emissions as reported by each facility." Our estimate is based on real-word data about the leather finishing operation, and it overestimates emissions by assuming worst-case conditions with regards to production level. As discussed in the proposal preamble, we calculated allowable organic HAP emissions for Alliance Leather as the product of the NESHAP HAP limit of 3.7 pounds per 1,000 square feet of leather processed, the design production capacity of the leather finishing process (16,200 square feet per hour), and the annual operating schedule contained in the 2014 NEI (2,000 hours per year). Using design production capacity in place of actual production is a more conservative approach, yielding a higher estimate for allowable organic HAP emissions. For SB Foote Tanning Co. and Pearl Leather Finishers, we did not use a production-based approach to estimate allowable organic HAP emissions. Rather, we estimated allowable organic HAP emissions as the product of the actual organic HAP emission rate and the ratio of each facility's permitted VOC emission limit to its reported annual VOC emissions. For Tasman Leather Group LLC., we estimated allowable organic HAP emissions as the product of the actual organic HAP emission rate and the ratio of 10 tpy (i.e., the maximum HAP emissions allowed for this area source) to actual facility emissions of HAP. Refer to the proposal preamble and to memorandum titled Leather Finishing: Residual Risk Modeling File Supporting Documentation (available in Docket ID No. EPA-HQ-OAR-2003-0194) for more detailed discussions of the data and methods we used to calculate allowable organic HAP emissions for these four facilities.

In estimating allowable chromium (III) emissions from buffing operations, we used a production-based approach for two of the four facilities. For Pearl Leather Finishers and Tasman Leather Group, we calculated allowable chromium III emissions based on an uncontrolled particulate emission factor presented in the S.B. Foot permit TSD and assuming maximum finishing capacity and 90-percent control efficiency for dust capture. Given that the buffing operations do not typically operate at maximum capacity (e.g., Pearl Leather Finishers typically operates at two-thirds of capacity) and dust capture systems can achieve better than 90% control (e.g., Pearl Leather has a reported 100% control efficiency), our production-based approach for these facilities yield conservative estimates of allowable chromium III emissions. For the S.B. Foot facility, the allowable rate for each chromium-emitting emission release point was set equal to the potential to emit value in the facility's permit technical support document (TSD). We did not estimate chromium (III) emissions from Alliance Leather because we identified no buffing operations at Alliance Leather. Refer to the proposal preamble and to memorandum titled Leather Finishing: Residual Risk Modeling File Supporting Documentation (available in Docket ID No. EPA-HQ-OAR-2003-0194) for more detailed discussions of the data and methods we used to calculate allowable chromium emissions from buffing operations for these facilities.

We also disagree with the comment that our method of calculating allowable emissions for these four facilities does not provide sufficient data for the commenter to check EPA's estimates or to calculate "allowable" emissions estimates, as claimed by the commenter. All data that we used to calculate allowable emissions, and further discussion of our method for calculating allowable emissions, is provided in the document titled Leather Finishing: Residual Risk Modeling File Supporting Documentation (available in Docket ID No. EPA-HQ-OAR-2003-0194). 
	
2.1-04 Comment: Commenter 0102 suggested that EPA's factor of annual to hourly emissions of 1.8 used in the risk assessment accounts for most of the variation in production levels and actual HAP emissions from S.B. Foot, but asserted that data of actual monthly HAPs use shows that hourly emissions can be up to 1.5 times greater than that emissions rate used to estimate acute exposures, which raises the acute hazard quotient (HQ) proportionately, greater than EPA's proposed estimate of 3. The commenter explained that S.B. Foot tracks the amount of coatings used and their formulation to determine actual HAP emissions on a monthly basis as required by their air emissions permit and the NESHAP. The Minnesota Pollution Control Agency (MPCA) requested and received detailed HAP compliance information from S.B. Foot in order to determine the accuracy of EPA's estimates of HAP emissions used in the risk analysis. The commenter provided the collected data is in an Excel spreadsheet titled "HAPs emissions from SB Foot." 

The commenter asserted that MPCA's data, which shows that hourly emissions could be well above EPA's estimated emissions, contradicts (1) EPA's assumption that residential areas are currently expected to be below the threshold for acute exposures, and (2) EPA's claim that the acute exposure assessment is "biased high", and, thus, might already provide an ample margin of safety.

Response: Refer to section IV.A.3 of the preamble to the final rule for EPA's response to this comment.
	
2.2 Risk Assessment Methods

2.2-01 Comment: Commenter 0100 contended that EPA's risk assessment is far behind prevailing scientific approaches in that it fails to account for early-life risks that threaten children's development. The commenter asserted that EPA must strengthen its risk assessment before it can lawfully and rationally determine whether or not the residual health risks to the most-exposed person are "acceptable" or not, and before it can determine what is required to provide the requisite "ample margin of safety to protect public health" under CAA § 7412(f)(2).

In the commenter's opinion, EPA's cancer risk assessments do not adequately account for early-life exposure or the greater risk to and susceptibility of children. According to the commenter, EPA must account for increased early-life susceptibility by applying age-dependent adjustment factors for all carcinogens emitted by a source category. The commenter noted that EPA has restricted its application of age-dependent adjustment factors to those HAP included in EPA's list of carcinogens that act by a mutagenic mode of action (MOA). The commenter pointed out that EPA's 2005 Guidelines recognized that updates would be needed if more data became available, and claimed that such data are now available from the National Academy of Sciences (NAS) and the California Office of Environmental Health Hazard Assessment (OEHHA), yet EPA has not issued such updates to implement age-dependent adjustment factors for all carcinogens. The commenter further pointed out that the NAS recognized this as a "missing" default in EPA's approach that it should address and account for. 

Regarding pre-natal cancer risk, the commenter asserted that EPA's risk assessment should account for increased susceptibility to carcinogens due to pre-natal exposures, by using a pre-natal adjustment factor for all carcinogens of at least 10X. The commenter pointed out that the 2005 Supplemental Guidance recognized the scientific findings of increased susceptibility to carcinogens resulting from pre-natal exposure, but did not develop adjustment factors to account for increased cancer risk resulting from prenatal exposures. The commenter further pointed out that the NAS recognized this as a major omission in EPA's 2005 cancer guidelines. The commenter explained that OEHHA has reviewed the scientific literature to account for pre-natal susceptibility and exposures and has developed methods and adjustment factors to account for this susceptibility and exposures, and the commenter asserted that EPA should consult this information and use the factors, including procedures for exposure assessment during fetal development and use of a 10X adjustment factor for cancer risk due to pre-natal to age 2 exposures.

Regarding chronic noncancer risk, the commenter asserted that EPA should consult and apply child-specific reference values, noting that exposure to toxic agents in the intrauterine stage of life has one of the most important, potentially irreversible impacts on life-long health, and that EPA's rules are insufficient to protect human health at the critical stage of embryonic development. The commenter further stated that most of EPA's IRIS toxicity threshold values (reference concentrations and reference doses) used for chronic noncancer risk assessment do not incorporate the latest science on increased susceptibility of children. The commenter asserted that until the IRIS values fully account for the increased risk caused by early-life exposure to an emitted pollutant, EPA should use the OEHHA child-specific reference doses or benchmarks (based on the latest science to take into account children's greater exposure and greater vulnerability), available to assess chronic noncancer health risk from ingestion for certain pollutants, assessing such risk from inhalation by using standard methods to translate these values into child-specific reference concentrations to assess inhalation-based risk.

	The commenter further contended that, if child-specific reference values are unavailable, EPA should consult science on early exposure impacts, and use an additional default or uncertainty factor of at least 10X to account for increased risk from early-life exposures for noncancer risk assessments. The commenter pointed out that this approach would be consistent with the NAS recommendation on the need for EPA to use default factors to account for greater risk, with the science developed and considered by OEHHA, and with the 10X factor enacted by Congress in the Food Quality Protection Act. In the commenter's opinion, it would be appropriate and within EPA's authority under CAA section 112(f)(2) to determine that EPA must similarly use a children's ten-fold margin of safety factor here, consistent with the CAA's "margin of safety" requirement. The commenter further pointed out that EPA's current reference values are generally one order of magnitude less protective (i.e., larger) than the child-specific reference doses that OEHHA has created for some pollutants, which support the use of an additional Ten-fold Margin of Safety Factor.

Response: We disagree with the comment that this risk assessment underestimates risk to children and lacks consideration of early-life susceptibility. 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. In our risk assessments, we take steps to account for early-life exposure and to consider susceptible groups. With respect to exposure, we use a health-protective assumption of a 70-year exposure duration, 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. In addition, when deriving reference concentrations and unit risk estimates for hazardous air pollutants, we also consider the most sensitive populations identified in the available literature, and importantly, these are the values used in our risk assessments.  

For example, a review of the chronic reference value process concluded that 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, 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 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 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 MOA is not mutagenicity. The basis for this methodology is provided in the 2005 Supplemental Guidance. 

We also disagree with the comment that the risk assessment for this source category did not consider the groups that may be most at risk (e.g., pregnant women and children). When EPA derives exposure RfCs and UREs for HAP, it also considers the most sensitive populations identified in the available literature, and importantly, these are the values used in our risk assessments. With regard to consideration of a potential vulnerability of a specific life-stage, including time period before conception, EPA includes this information in its derivation of cancer and noncancer toxicity values. For example, prenatal developmental studies in rodents, when available, are regularly considered in IRIS toxicity assessments and data are then extrapolated to predict effects in humans. In some instances, the available literature is unavailable for a robust characterization of risk during a specific life-stage and, in that case, the potential susceptibilities are accounted for by applying the appropriate uncertainty factors. 

We disagree with the general comment that EPA should adopt the California OEHHA child-protective scientific approach for deriving health benchmarks. EPA has an approach for selecting appropriate health benchmark values and in general, this approach places greater weight on EPA-derived health benchmarks than those from other agencies. The approach of 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. EPA is currently evaluating the most appropriate use for the California OEHHA child-specific reference doses (RfDs). We note that there are currently no such values for HAP inhalation, therefore the current utility may be limited to persistent and bioaccumulative-HAP (PB-HAP) ingestion. 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 RfDs. 

The estimated risks must also be considered in the context of the full set of assumptions used for this risk assessment. The UREs for HAP are considered a plausible upper-bound estimate with an appropriate age dependent adjustment; actual potency is likely to be lower and 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 10X uncertainty factor, as suggested by the commenter, is not needed in the RfC/RfD methodology because the currently available factors are considered sufficient to account for uncertainties. After considering these and other factors, we continue to find that the NESHAP provides an ample margin of safety to protect public health. 

EPA disagrees with the commenter 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 (FQPA), the Agency evaluated their methods for considering children's risk in the development of reference values. As part of their response, EPA (i.e., the Science Policy Council and Risk Assessment Forum) established the RfD/RfC Technical Panel to develop a strategy for implementing the 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. 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 uncertainty factor for inter-human variability and found EPA's default value of 10 adequate for all susceptible populations, including children and infants. EPA also recommended the use of chemical-specific data in preference to default uncertainty factors when available, and is developing Agency guidance to facilitate consistency in the development and use of data-derived extrapolation factors for RfCs and RfDs. Additionally, 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, an additional 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 (and does not exclude the possibility that these uncertainty factors may be decreased or increased from the default value of 10).

2.2-02 Comment: Commenter 0100 argued that EPA must assess the combined impact of multiple pollutants. The commenter cited a California OEHHA report on arsenic, stating that EPA's assessment should evaluate the combined impact of each type of risk from multiple pollutants and assess the total cumulative risk burden from all pollutants to make an ample margin of safely determination. The commenter noted that in the Leather Finishing Operations risk assessment, EPA only assesses the combined impact of cancer risk and chronic noncancer risk that operates on the same target organ, while the commenter argued that EPA should assess the total and synergistic cancer risk and total chronic noncancer risk for different pollutants. In addition, the commenter noted that EPA should apply these same principles to create a mechanism for assessing the total acute risk to chemical mixtures, such as the target-organ-specific hazard index (TOSHI) for chronic risk that aggregates the acute impacts on the same organ systems for all pollutants. 

The commenter asserted that, consistent with NAS recommendations, EPA must create a metric to assess the total and cumulative risk burden, rather than only looking at each type of risk separately. After first assessing the total cancer, chronic noncancer, and acute risks, for both inhalation and multipathway exposure, the commenter argued that EPA also must create a metric to assess the total risk. The commenter continued that EPA must aggregate health risk for each pollutant, and each type of health risk, according to the commenter, to create a cumulative risk determination for the individual "most exposed" to emissions as section 112(f)(2) of the CAA requires. The commenter asserted that without performing this cumulative assessment, EPA has failed to gather the information needed to assess whether the risk to public health is acceptable under CAA section 112(f)(2).

Response: EPA has combined risk assessment results to the extent that it is appropriate to do so. We sum the inhalation risk posed by carcinogens and use a TOSHI approach for our chronic noncancer assessments. We do not use a TOSHI approach for our acute analyses, nor do we combine the results of our inhalation and multipathway assessments. 

For the Leather Finishing Operations source category, EPA conducted an assessment of the cumulative cancer risks from emitted carcinogens and the cumulative noncancer hazard indices from all emitted non-carcinogens affecting the same target organ system for both the source category emissions and the facility-wide emissions. 

Concerning comments that we should consider aggregate risks from multiple pollutants and sources, we note that we have done this to the extent it is appropriate to do so. We modeled whole-facility risks for both chronic cancer and noncancer impacts to understand the risk contribution of the sources within the Leather Finishing Operations source category. The individual cancer 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 (where this information is absent) that affect the same target organ, we aggregated the HQs. This process creates, for each target organ, a TOSHI, defined as the sum of the HQs for individual HAP that affect the same organ or organ system. Facility-wide risks were estimated based on emission and modeling data from version 1 of the 2014 National Emissions Inventory (NEI). Facility-wide data were available in the NEI for 3 of the 4 facilities.

As described in the Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011), 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 Section 2.8.2 of the Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011), "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." 

We did not combine the inhalation and multipathway risk assessment results for each pollutant because it is inappropriate to do so. EPA is not aware of emission of PB-HAP being emitted from the four affected sources covered by the Leather Operations NESHAP, and the commenters have provided no data to suggest otherwise.

2.2-03 Comment: Commenter 0100 contended that EPA should evaluate the use of perfluorooctyl sulfonate or perfluoroctane sulfonic acid-based fume suppressants (PFOS) and per- and polyfluoroalkyl substances (PFAS)-related chemicals and resulting emissions from leather finishing operation facilities to ensure that any such use (including as a potential pollution control method) is not causing health threats, as it has done previously where it found the use of a PFOS-based fume suppressant was causing harm.

Response: EPA found no evidence that PFAS or PFOS are emitted by this source category. The commenter provided no data or information to demonstrate that PFAS or PFOS are emitted by this source category. Based on this information, we see no reason to further evaluate the presence of PFAS/PFOS emissions for this source category.

2.2-04 Comment: Commenter 0105 pointed out that both the Occupational Health and Safety Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have developed chronic reference values for chromium III and contended, therefore, that EPA has the means to both identify a reference value and to evaluate and quantify the chronic noncancer risk resulting from chromium III exposure.

Commenter 0098 objected to EPA's statement in the proposed rule amendments declaring that there are no public environmental health risks associated with Leather Finishing Operations. The commenter acknowledged that airborne exposure to chromium (III) emissions from buffing operations outside the facility was evaluated as part of the RTR, but argued that EPA failed to mention occupational health hazards of the industry in the environmental risk. The commenter cited a 2011 OSHA press release regarding 20 health and safety hazards following a serious injury sustained by a worker at Pearl Leather Finishers, Inc. of Johnstown, NY. The commenter also cited a study published by the Indian Journal of Occupational Medicine in which leather industry workers were found to have increased respiratory disease morbidity and elevated blood/urine chromium (III), a known carcinogen. The commenter pointed out that the study indicated that workers involved in coloring and producing surface effects that enhance brightness, durability, and softness of the finished leather product, similar to the leather coating procedures at the four facilities subject to the rule, were exposed to formaldehyde, a probable carcinogen. The commenter further cited a study published in the Archives of Environmental & Occupational Health that noted that adverse dermatological and respiratory conditions were associated with occupational chromium (III) exposure amongst Pakistani workers. 

Response: As noted in our response to comment 2.2-11, it is the Occupational Safety and Health Administration (OSHA), working under the authority of the Occupational Safety and Health Act of 1970, that is tasked with assuring safe and healthful workplaces by setting and enforcing occupational standards. Further, the 2011 OSHA press release cited by the commenter "regarding 20 health and safety hazards following a serious injury sustained by a worker at Pearl Leather Finishers, Inc. of Johnstown, NY" is unrelated to air emissions from the facility.
      
Commenter 0098 argued that EPA failed to mention occupational health hazards of the industry in the environmental risk, citing various studies to demonstrate their contention that EPA failed to address occupational health hazards of the industry in the environmental risk assessment, including exposure to chromium (III); however, the studies cited by the commenter do not address air emissions from leather finishing operations. The cited OSHA press release discusses physical injuries due to embossing press and absent machine guarding, but it does not address air emissions. The cited studies published by the Indian Journal of Occupational Medicine and in the Archives of Environmental & Occupational Health address leather tanning operations; however, none of the four affected sources under the Leather Finishing NESHAP conduct leather tanning, and leather tanning operations are not covered under the Leather Finishing NESHAP.

2.2-05 Comment: Commenter 0100/0105 contended that that EPA must evaluate emissions and health risks of hexavalent chromium (CrVI), and set emission limits for the listed HAP, in order to fulfill its obligations for this rulemaking under § 7412(f)(2), 7412(d)(1), 7412(d)(2), 7412(d)(6), and Nat'l Lime Ass'n v. EPA. Commenter 0105 emphasized that the CAA unambiguously requires EPA's §112(d) rules to include emission standards for each listed HAP that a source category emits, and that the D.C. Circuit so held Nat'l Lime Ass'n v. EPA , and it confirmed that ruling repeatedly in the years that followed.

Commenter 0100/0105 asserted that EPA, unlawfully and arbitrarily, did not evaluate the cancer risk, or other health threats, from CrVI emissions, a known carcinogen, for which there is evidence of emissions from leather finishing operations[,][,] and evidence of the creation or presence of CrVI in leather tanning processes and products, noting that EPA itself acknowledged the presence of CrVI in effluent from leather tanning operations. The commenter questioned why EPA did not use the referenced NEI data to evaluate CrVI (or any other emitted HAPs) for this rulemaking. Commenter 0105 asserted that EPA is not consulting valuable updates in the science, such as the NEI's suggestion that CrVI is emitted from leather finishing facilities. The commenter provided an example of EPA failing to account for valuable updates in the science when EPA referenced the 1984 version of its document titled Locating and Estimating Air Emissions from Sources of Chromium, (EPA-450/4-84-007g) in reference to chromium III emissions (to support EPA's approach of including leather buffing emission units in the risk modeling file), when EPA should have referenced the 2003 version of the document Locating and Estimating Air Emissions From Sources of Chromium, which states: "[t]he buffing of tanned hides during the suede finishing process is a possible source of chromium emissions. The repeated brushing, or buffing, of the leather dislodges small particles of leather which contain trivalent chromium."
      
The commenter asserted that EPA has no lawful or rational basis to ignore the information on CrVI provided by commenters, and that EPA must review the information regarding CrVI use and formation for this source category and set a limit for this pollutant because the CAA requires emission limits for all emitted HAPs that must meet the statutory test enacted by Congress to protect public health and the environment from these HAPs. 42 U.S.C. § 7412(d)(1)-(3), (6), (f)(2). 
      
Commenter 0105 pointed out that CAA § 112(d)(6) requires EPA to review its § 112(d) rules every 8 years and revise them "as necessary." The commenter asserted that it is "necessary" that EPA's § 112(d) rules comply with the law, stating that in the current proposed rule, not only did EPA fail to propose any emissions standards for CrVI, but it did not evaluate these emissions at all to fulfill its § 7412(d)(6) or (f)(2) responsibilities (as discussed above), thereby contravening the plain language of the statute. The commenter stated that EPA has provided no explanation for why it has continued to fail to set any emissions standards for this emitted pollutant. 

Commenter 0100 added that, because EPA did not evaluate CrVI, it is likely that EPA did not evaluate all major sources of HAPs as part of this rulemaking, and thus has further underestimated the source category risks as a whole. In the commenter's opinion, EPA must reevaluate the source category and assess health risks after adding hexavalent chromium and any other emitted HAPs into its emission inventory.

Response: We disagree that there is any basis for EPA to evaluate emissions and health risks of CrVI and to set emission limits for the pollutant in order to fulfill its obligations for this rulemaking under § 7412(f)(2), 7412(d)(1), 7412(d)(2), 7412(d)(6), and Nat'l Lime. Refer to section IV.A.3 of the preamble to the final rule for EPA's response to this comment.

Regarding the comment that EPA should have referenced the 2003 version of the document Locating and Estimating Air Emissions From Sources of Chromium[50] instead of the 1984 version of the document (EPA-450/4-84-007g), to support EPA's approach of including leather buffing emission units in the risk modeling file,[49] we acknowledge that it would be more appropriate to cite the more recent version of the document; however, we have reviewed the newer version of the document and the relevant information about potential chromium III emissions from buffing operations has not changed since the older version of the document. As a result, we disagree that we have missed a "valuable update," and it is not clear how this reference demonstrates EPA's failure to "consult valuable updates in the science" as stated by the commenter.
	
2.2-06 Comment: Commenter 0102 contended that EPA must conduct further review of the toxicity of propyl cellosolve (Ethylene Glycol Mono-n-propyl Ether I CAS 2807-30-9) before concluding the NESHAP is health protective. The commenter pointed out that EPA used the toxicity value for ethylene glycol monomethyl ether as a surrogate for propyl cellosolve since there is no specific acute inhalation health benchmark for this glycol ether, but stated that ethylene glycol monomethyl ether is the most toxic compared to other glycol ethers, and so the use of this surrogate is a health protective choice in EPA's risk assessment. The commenter also pointed out that EPA does not provide a specific discussion of the relative toxicity of propyl cellosolve, and so the reader has no basis to determine if and how much less toxic propyl cellosolve is in comparison to ethylene glycol monomethyl ether. The commenter noted that glycol ethers generally have acute inhalation health benchmarks from approximately 93 to 14,000 (ug/m3). The commenter asserted that, without additional revision of the NESHAP, or at least a more expansive evaluation of the toxicity of the primary risk driver at SB Foot (propyl cellosolve), the existing NESHAP fails to meet the requirement of the CAA to provide an ample margin of safety.
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Response: In its May 7, 2010 response to the EPA Administrator, the SAB panel recommended that, for HAP that do not have dose-response values from EPA's list, 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 EPA's list should be adequately documented in a transparent manner in any residual risk assessment case study. We agree with this approach and have considered other sources of dose-response data when conducting our risk determinations under RTR. In some instances, no sources of information beyond EPA's list are available. 

In cases where there are glycol ether emissions of unspecified composition, as for this source category, to avoid underestimating the health hazard associated with glycol ethers, we protectively apply the reference value for ethylene glycol methyl ether (the most toxic glycol ether for which an assessment exists) to propyl cellosolve and other glycol ethers for which there is not a dose-response value. For a tabular summary of HAP that have dose-response values for which an exposure assessment was conducted, refer to Table 3.1-1 of the Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011).

EPA agrees that it is important to develop toxicity values for all HAP using all credible and relevant toxicity information. Refer to EPA's response to comment number 2.2-12 for further discussion on this topic.

2.2-07 Comment: Commenter 0102 asserted that the risk assessment process neglected to review or assess the remaining Volatile Organic Compounds (VOCs) that are not classified as HAPs, but which have health effects and are not without risk. The commenter stated that, in 1990, these VOCs had not been identified as HAPs and were therefore not subject to regulation nor review of their potential hazard in this assessment. The commenter pointed out that, based on the ratio of HAPs to VOCs emitted in 2014 (16.2 tons vs 88.61 tons), only 18.2 percent of total chemical emissions were evaluated. The commenter stated that this omission contradicts EPA's claim that the acute exposure assessment is "biased high" and thus might already provide an ample margin of safety.

Response: Section 112(f) of the CAA evaluates risks associated with emissions of HAP listed under section 112 (b)(1) or those added to this list under section 112(b)(2). EPA does not regulate VOC, particulate matter (PM), NOx, or SO2 under section 112 except to the extent that individual HAP are also VOC (e.g., for this RTR we evaluated propyl cellosolve among other individual HAP that are also VOC) or PM (e.g., under this RTR we evaluated chromium III). Criteria pollutants (e.g. PM, SO2) and their precursors (e.g. VOCs) are regulated under Title 1 of the CAA through the ambient air quality standards (NAAQS). Therefore, they are not subject to this residual risk review under section 112.
	
2.2-08 Comment: Commenter 0100 asserted that EPA's multipathway risk assessment (i.e., non-inhalation) is incomplete and underestimates risks. The commenter supported performing a multipathway risk assessment but stated that EPA's multipathway analysis is deficient and could be improved by incorporating the following suggestions.

The commenter argued that EPA must assess non-inhalation-based risk for all metals and all other pollutants with a persistent or bioaccumulative impact, as OEHHA does, both individually and cumulatively, to avoid underestimating the health risks of HAP emissions, instead of restricting the assessment to the 14 contaminants identified in the 2003 Risk Assessment Guidance as PB-HAPs,[,] which recognized deposition of persistent HAPs as a source of soil contamination presenting a potentially significant route of exposure, particularly for children.[,] The commenter specifically recommended that six other toxic metals be included in the assessment (arsenic, hexavalent chromium, nickel, diethylhexylphthalate, beryllium, and selenium). The commenter asserted that these six pollutants have been shown to have a significant potential for deposition and retention within the environment and present a risk to nearby communities. The commenter cited the California 2012 Guidelines for Exposure Assessment as the rationale for including these six HAP in the assessment and recommended that EPA review and adopt the methods in these guidance documents. In addition to the six metals listed by OEHHA, the commenter stated that manganese is a pollutant to which children are particularly vulnerable, and there is evidence that it can pose a multipathway risk due to elevated levels in soils around major emission sources. The commenter also stated that naphthalene has been demonstrated to be persistent and bioaccumulative and is a PAH, and as such must be considered in the POM category which is already listed as a PB-HAP. 
The commenter also asserted that EPA must perform its multipathway assessment for all pathways of exposure, including those that particularly affect children. The commenter stated that EPA has been relying on outdated estimates of incidental soil ingestion exposures and EPA must update these values to ensure that it considers the urban child scenario in its multipathway risk assessment. The commenter asserted that EPA must recognize the deposition of persistent HAP as a source of soil contamination presenting a potentially significant route of exposure, particularly for children. The commenter asserted that the risk assessment of exposure to soil contaminants should evaluate both direct exposure, hand-to-mouth, and indirect, object-to-mouth exposure as a study has found a statistically significant positive correlation between the frequency of object or food in mouth activity and blood lead levels, according to the commenter. The commenter added that the 2011 update to EPA's Exposure Factors Handbook includes more recent studies and estimates of hand-to-mouth behavior, which must be used to assess risks from exposures to contaminated soils.
                                       
The commenter further asserted that EPA must account for the aggregate impact of inhalation and multipathway cancer and chronic noncancer risk by adding each type of similar risk together for all pollutants. The commenter stated that the purpose of the multipathway assessment is to allow EPA to look at a person's exposure overall - not just inhalation or other exposure pathways, in isolation. According to the commenter, failing to add up each type of risk in order to come up with a total cancer risk number and a total noncancer number, and then a cumulative burden metric, makes EPA's overall risk assessment incomplete. 

Response: EPA is not aware of emission of PB-HAP being emitted from the four affected sources covered by the Leather Operations NESHAP, and the commenters have provided no data to suggest otherwise. Furthermore, EPA is not aware of emissions of the six other toxic metals or naphthalene the commenter recommended be included in a multipathway assessment from the four affected sources. Therefore a multipathway risk assessment for this source category was not warranted and the comment is outside the scope of this rulemaking.

 2.2-09 Comment: Commenter 0100 stated that EPA must assess and account for the cumulative impact and risk caused by exposure to multiple source categories' toxic air emissions. The commenter asserted that, in addition to performing a cumulative assessment from nearby leather finishing operations alone, EPA must perform a cumulative analysis which aggregates or adds the emissions for the most-exposed communities coming from: (1) the source category (including all individual sources within it); (2) facility-wide risk from collocated sources outside of this category; and (3) all other sources of toxic air pollution in the area. The commenter noted that EPA has recognized this need in its recent risk report, yet has failed to propose any changes to the emissions standards based on the combined exposure with any other sources. In support of their argument, the commenter also cited recommendations from the SAB and NAS which called for the incorporation of cumulative health risk into its residual risk analysis.  The commenter supported EPA's recognition of the need to assess whether the maximum exposed individual is exposed to emissions from more than one source within each source category. The commenter also appreciated that EPA had considered facility-wide risk in some way in this rulemaking. However, according to the commenter, those assessments offer only part of the picture. And, even on both of these issues, the commenter stated that EPA has provided very little information about what it included in such assessments, only stating numbers found for facility-wide risk, without explaining where those numbers came from, how they were calculated, or what emission sources they covered.

The commenter noted that EPA has acknowledged the importance of addressing multiple source exposures, by stating that it "understands the potential importance of considering an individual's total exposure to HAP in addition to considering exposure to HAP emissions from the source category and facility," and that it is "interested in placing source category and facility-wide HAP risks in the context of total HAP risks from all sources combined in the vicinity of each source." The commenter also noted that, although EPA has calculated what it calls "facility-wide" risk for different sources collocated at the same address, EPA has not used its calculated "facility-wide" risk for collocated sources to set standards, and it has ignored different sources across the street or in close proximity in its draft risk assessment. 

Commenter 0100 stated that, as a scientific and policy matter, where there is exposure to air toxic emissions beyond the individual source category, the level of total risk that is occurring, including the baseline health risk and the risk from other sources, is greater. The commenter continued that, thus, the total risk that is unacceptable for the most-exposed person must in fact be lower for each source category that person is exposed to, because it combines with other risks to create a total risk from all regulated source categories which must be minimized. The commenter contended that looking at a source category's contribution of risk in isolation is equivalent to ignoring the facts and pretending other health risks are not occurring. The commenter asserted that EPA may not decide that it is okay for a person to be exposed at a higher level simply because they live in a community where they are exposed to multiple sources of air pollution. In the commenter's opinion, that is the opposite of what EPA is required to do  -  protect the people in local communities who are most exposed and most vulnerable to air pollution. It also conflicts with EPA's own commitment to consider and provide environmental justice to overburdened communities. The commenter also suggested that EPA consider the existing research regarding health risk from toxic air pollution in urban communities nationwide as well as the OEHHA cumulative assessment approach and apply a similar science-based approach in this residual risk assessment. 

In addition, the commenter noted that the NAS has recommended that EPA evaluate "background exposures and vulnerability factors," as well as use "epidemiologic and toxicologic evidence" in its risk assessments. Rather than separating an environmental justice (EJ) analysis and considerations of inequality from the risk assessment, considering these factors as part of the cumulative risk assessment - because of the increased vulnerability created - would be a more effective, meaningful, and scientific approach, according to the commenter. The commenter asserted that, in assessing a source category's emission contributions in affected communities and considering whether these contributions cause the most-exposed people to experience an unacceptable level of public health risk when combined with the existing baseline from past emissions, other HAP emissions, and the community's health status, EPA can describe and manage uncertainties, similar to many other analyses. 
	
The commenter concluded that until EPA develops a data-driven approach to comprehensively model cumulative risk or impacts from multiple sources, EPA must incorporate a default or uncertainty factor to adjust the degree to which each individual source category is contributing to the total risk experienced by the most-exposed individuals. For example, according to the commenter, for a source category in an area with up to 10 other HAP-emitting facilities, this default uncertainty factor should equal at least 10, consistent with the common scientific use of this factor for other kinds of vulnerability. This commenter suggested that wherever there is a history of other exposures or other source categories, the "unacceptable" level of cancer, noncancer chronic, and acute risk from the source category must be adjusted downward (such that no single source category could constitute all acceptable risk, when the most-exposed person is exposed to many other source categories).

Response: We disagree with the claim that additional quantitative assessment of risks from sources outside the source category is required under the statute. CAA section 112(f) requires 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, 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, 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). Although EPA rejected such approaches for considering the acceptable level of risk, EPA recognized in the Benzene NESHAP that background levels (including natural background) could be considered as part of EPA's ample margin of safely analysis, as appropriate and as available, along with other factors, such as cost and technical feasibility. 

For the Leather Finishing Operations source category, EPA conducted an assessment of the cumulative cancer risks from emitted carcinogens and the cumulative noncancer hazard indices from all emitted non-carcinogens affecting the same target organ system for both the source category emissions and the facility-wide emissions. The emissions for the source category and facility-wide emissions have been collected from a variety of sources, including the 2014 NEI, facility annual emission reports, facility operating permits, and operating permit applications. The emission sources covered in our facility-wide beyond the source category included on-site stationary sources outside the source category for which we have data, such as boilers. Off-site emission sources and mobile sources were not included. As stated in the Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011), emissions data and other modeling parameters for the facility-wide assessment came from version 1 of the 2014 National Emissions Inventory (NEI),  and  the development of the source data, emissions, and associated uncertainties in the data for the leather finishing operations source category are summarized in section 3 of the memorandum and provided in more detail in Appendix 1 of the memorandum (Emissions Inventory Support Documents).

The risk assessment modeling for the Leather Finishing Operations MACT accounted for the effects of multiple facilities within the source category that may be in close proximity when estimating concentration and risk impacts at each block centroid. When evaluating the risks associated with a particular source category, we combined the impacts of all facilities within the same source category and assessed chronic exposure and risk for all census blocks with at least one resident (i.e., locations where people may reasonably be assumed to reside rather than receptor points at the fence-line of a facility). The MIR considers the combined impacts of all sources in the category that may be in close proximity. We do not agree with the idea that we should apply an uncertainty factor related to the number of non-leather finishing operations near leather finishing operations.

2.2-10 Comment: Commenter 0100 asserted that EPA should end its longstanding policy of assuming that it is possible to find a safe or acceptable level of cancer and other kinds of health risks, and should instead account for cumulative impacts of multiple exposures vulnerabilities by shifting the level of risk which triggers policy action, reforming risk assessments to support reducing risks to the lowest possible level, to protect public health, rather than suggesting that there is a safe or acceptable level. The commenter suggested that, as an example, EPA should recognize that cancer risk from a major industrial source category of toxic air pollution (listed under CAA § 112) that is 100-in-1 million or less cannot be presumed safe or "acceptable," as EPA has assumed since 1990, basing this assumption not on scientific information about cancer risk, but on an unusual study of people's perceptions of their own risk from 1988, known as the Survey of Societal Risk (July 1988), to consider various types of health risks at that time. The commenter claimed that EPA, using a comparison of cancer risk to other kinds of hazards Americans then faced in their daily lives, effectively chose a number out of a hat that it would consider acceptable, looking at an odd collection of risks, such as dangers from driving a car, and finding 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.'" The commenter asserted that EPA has failed to revisit or update this number for the decades since, even though scientists have made breakthroughs on early-life exposure and children's vulnerability; biomonitoring and other data on adult body burdens of chemicals; the vulnerability of overburdened communities, including socioeconomic disparities; and on ways to analyze and control the impacts of pollutants on human health.

The commenter further asserted that EPA should also reform how it evaluates chronic and acute hazard indices, in which a risk number below 1 does not result in policy changes or standards, stating that EPA should instead factor in uncertainties and vulnerability factors that adjust the "acceptable level of risk." The commenter pointed out that this is currently done under 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.

Response: EPA disagrees that we should move away from our approach for determining risk acceptability. Section 112(f)(2) of the CAA requires the EPA Administrator to "...promulgate standards for such category or subcategory if promulgation of such standards is required in order to provide an ample margin of safety to protect public health in accordance with this section (as in effect before November 15, 1990)..." As stated in the Benzene NESHAP (54 FR 38044, 38061, September 14, 1989), in determining the need for residual risk standards, we strive to limit to no higher than approximately 1-in-10 thousand (100-in-1 million) the estimated cancer risk that a person living near a plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years and, in the ample margin of safety decision, to protect the greatest number of persons possible to an individual lifetime risk level of no higher than approximately 1-in-1 million. The 100-in-1 million presumptive limit for risk acceptability was established in the Benzene NESHAP (54 FR 38044, September 14, 1989), which Congress specifically referenced in CAA section 112(f)(2)(B). In its March 1999 Residual Risk Report to Congress, EPA documented its planned use of this approach in the residual risk reviews of the NESHAP.

While the presumptive level (i.e., 100-in-1 million) provides a benchmark for judging the acceptability of the maximum individual risk (MIR), it is important to recognize that it does not constitute a rigid line for making that determination. EPA considers the specific uncertainties of the emissions, health effects and risk information for the source category in question when deciding whether the risk posed by that source category is acceptable. In addition, the source category-specific decision of what constitutes an acceptable level of risk is a holistic one; that is, EPA considers all potential health impacts - chronic and acute, cancer and noncancer, and multipathway - along with their uncertainties, when determining whether the source category presents an unacceptable risk.

In our risk assessments, we take steps to account for early-life exposure and to consider susceptible groups in our risk assessments. With respect to exposure, we use a health-protective assumption of a 70-year exposure duration, 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. In addition, when deriving reference concentrations and unit risk estimates for HAPs, we also consider the most sensitive populations identified in the available literature, and importantly, these are the values used in our risk assessments. With respect to cancer, when chemical-specific data are available on which age or life-stage specific risk estimates or potencies can be determined, EPA applies default age-dependent adjustment factors when assessing cancer risk for early-life exposures to chemicals that cause cancer through a mutagenic mode of action. 

For chronic noncancer effects, EPA applies inhalation reference concentrations (RfCs), where available. By definition, RfCs are designed to protect susceptible groups, which may refer to life stages (e.g., children or the elderly) or to other segments of the population (e.g., asthmatics or the immune-compromised), from an appreciable risk of adverse health effects over a lifetime of continuous exposure. Values are derived using 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. Uncertainty factors are commonly default values (e.g., factors of 10 or 3) used in the absence of compound-specific data; where data are available, data-derived extrapolation factors may also be developed using compound-specific information. 

The Agency has evaluated the methods for considering children's risk in the development of reference values. In developing a strategy for implementing the Food Quality Protection Act (FQPA) and examining the issues relative to protecting children's health and application of the 10X safety factor, EPA (i.e., the Science Policy Council and Risk Assessment Forum) established the RfD/RfC Technical Panel. 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 EPA's default value of 10 adequate for all susceptible populations, including children and infants. EPA also recommended the use of chemical-specific data in preference to default uncertainty factors when available (US EPA, 1994, 2011), and is developing Agency guidance to facilitate consistency in the development and use of data-derived extrapolation factors for RfCs and RfDs (U.S EPA, 2011). Additionally, 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. 

As new science and new chemical-specific data become available, the Agency continues to revise its approaches and its toxicity assessments. When new or revised peer-reviewed toxicity assessments and approaches become available, we apply these in our risk assessments.

For this source category, EPA assessed whether there were disproportionate impacts to people living within 50 km of the facilities, as documented in Risk and Technology Review  -  Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations (available in Docket ID No. EPA-HQ-OAR-2003-0194). EPA determined that there are no disproportionate impacts to minority populations, low-income populations, and/or indigenous peoples from HAP emissions from the four facilities. There are no known cancer risks by the HAP emissions from the four facilities. In addition, of the 4,600,000 people living within 50 kilometers of these facilities, based on our assessment of actual emissions of HAP from this source category, none are exposed to a noncancer hazard index above 1. 

2.2-11 Comment: Commenter 0098 stated that although EPA does not have regulatory authority over occupational health, EPA and OSHA should collaborate when examining, revising, and implementing policies, addressing risks to workers, the general public, and the natural environment. The commenter argued that EPA should acknowledge the linkages between environmental conditions and occupational settings when making regulatory decisions that impact the public's health.
 
Response: It is the Occupational Safety and Health Administration (OSHA), working under the authority of the Occupational Safety and Health Act of 1970, that is tasked with assuring safe and healthful workplaces by setting and enforcing occupational standards. As noted in our response to comment 2.2-04, OSHA PELs are developed to protect workers (presumed healthy adults) for specific exposure duration scenarios (e.g., 8-hour work shift of a 40-hour work week, for a less-than-lifetime exposure duration). These values are not considered protective for the general public, particularly for sensitive groups, such as children and asthmatics, and for lifetime exposures. In developing dose-response values for a chemical, EPA considers available data on adverse effects associated with exposure to that chemical, including occupational exposure data.

2.2-12 Comment: Commenter 0100/0105 disagreed with EPA's risk assessment results on the premise that the risk assessment treats health risk as zero for some pollutants. The commenter contended that EPA's conclusion that the risks from this source category's emissions are "acceptable" is unlawful and arbitrary under 42 U.S.C. § 7412(f)(2) because EPA treated some health risks as zero. Commenter 0105 asserted that, for ethylene glycol and methyl isobutyl ketone, EPA treated the acute health risks as zero and thus ignored certain health threats completely, despite the Act's requirement that EPA complete the risk assessment for the person most-exposed to all HAP emitted in order to fulfill its obligations under § 7412(f)(2) and (d)(1)-(3) and (6). The commenter stated that, for these pollutants, EPA identified no reference values for acute noncancer risks. The commenter asserted that EPA cannot finalize action on this source category until it sets a limit for all HAP emitted, as the Act directs, and perform all other obligations required as part of this rulemaking. The commenter further contended that, at the very least, EPA should commit to evaluate the risks posed by this source category when these reference values are updated and should plan to take notice and comment on the § 7412(f)(2) issues at that time using the new values.

Commenter 0100/0105 disagreed with EPA treating health risks as zero for chromium III, considering that the Office of Health Hazard Assessment has recognized, and robust scientific evidence shows, that metals including chromium III persist in the environment and thus can cause exposure through other pathways, beyond and after initial inhalation exposure. Commenter 0105 asserted that EPA failed to identify reference values for any risk category for chromium III, despite it being known to cause respiratory irritation. The commenter stated that EPA thus ignored certain health threats completely even though there is evidence showing it must assess them. The commenter stated that EPA underestimated health risks by not using the best available information on pollutants and by treating various types of risk as zero when the science shows risk is present. The commenter asserted that, just because EPA has not yet developed a reference value for a pollutant, type of exposure, or type of risk, does not mean risk does not exist and can be ignored. The commenter asserted that the absence of a reference value means that EPA does not know by how much it is underestimating risk to human health, but it does know that its assessment is an underestimation. The commenter quoted EPA as stating, "an understatement of risk for these pollutants at environmental exposure levels is possible," in its rulemakings due to the lack of reference values. The commenter suggested that, consistent with NAS recommendations, EPA should, at a minimum, develop default approaches to support the evaluation of risk from chemicals which lack chemical-specific data. One of the approaches detailed by the commenter is the inclusion of an uncertainty factor to account for the additional risk that a HAP likely causes, until such time as EPA does have a reference value to use, which the commenter stated would allow EPA to satisfy its legal duty under section 112(f)(2) to prevent unacceptable health risk, and ensure an "ample margin of safety to protect public health." The commenter quoted the NAS as stating "for virtually all chemicals, it is possible to say something about the uncertainty distribution regarding dose-response relationships," such as information on chemical structure, available toxicologic tests and model or experimental data, and data on similar chemicals that have been well-studied. 

Commenter 0100/0105 also argued that some pollutants continue to have no reference values over 20 years after the CAA was amended and that the Integrated Risk Information System (IRIS) review process has been bogged down for many pollutants. The commenter expressed support for the Center for Progressive Reform's recognition that EPA should prevent the delay in this process from undermining its residual risk analysis for source categories under review. The commenter asserted that, for pollutants currently under IRIS assessment, EPA must use the best available scientific information from the IRIS review during current rulemakings. At minimum, the commenter concluded that EPA must account for the lack of reference values or the lack of an up-to-date final IRIS assessment rather than not including any consideration of health risks caused by such pollutants.

Commenter 0105 referenced an 8-hour time weighted average NIOSH recommended exposure limit (REL) for chromium III of 0.5 milligrams (mg)/cubic meter (m[3]) and an OSHA permissible exposure limit (PEL) of 0.5 mg/m[3] (8-hour TWA). 

Response: Commenter 0100/0105 indicated that EPA treated some health risks as zero, effectively indicating that EPA must assess health risk from all pollutants, even where there is no current reference value. This issue was addressed by EPA's Science Advisory Board (SAB) in their May 7, 2010 response to the EPA Administrator (EPA-SAB-10-007). In that response, the SAB Panel recommended that, for HAP that do not have dose-response values from EPA's list, 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 EPA's list should be adequately documented in a transparent manner in any residual risk assessment case study. We agree with this approach and have considered other sources of dose-response data when conducting our risk determinations under RTR. However, in some instances no sources of information beyond those included in EPA's list are available. 

Commenter 0105 referenced an 8-hour time weighted average NIOSH recommended exposure limit (REL) for chromium III of 0.5 milligrams (mg)/cubic meter (m[3]) and an OSHA permissible exposure limit (PEL) of 0.5 mg/m[3] (8-hour TWA). These values are levels that must not be exceeded during any 8-hour work shift of a 40-hour work week. Because these values are developed to protect workers (presumed healthy adults) for specific exposure duration scenarios, these values are not considered protective for the general public and are not used in our acute (1-hour) or chronic (lifetime) exposure assessments. That said, the maximum predicted chromium III acute concentration from the source category was 0.03 mg/m[3], 17 times lower than the NIOSH and OSHA exposure limits.

EPA agrees that we should ultimately develop toxicity values for all HAP utilizing all credible and relevant toxicity information. The need to update assessments to be consistent with EPA guidelines, and to incorporate the best 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 EPA's already overloaded IRIS program. To that end, EPA includes in its prioritization for future IRIS assessments those HAP without dose-response values and with the greatest potential for public exposure and potential adverse effects. As a result of this prioritization, while not all HAP have scientifically accepted dose-response values that can be used in residual risk assessments, it is clear that the vast majority of HAP that 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 which carry the potential to create significant risks, we clearly point those out as uncertainties and target them for future IRIS assessments. In general, we strive to strike a balance in our assessments; while some factors likely lead to underestimates of risk, others likely lead to overestimates of risk. We conclude that the risk assessment for this source category is sufficient to support a decision on the acceptability of the risk and ample margin of safety. 

Regarding the comment that, once EPA develops acute reference values for ethylene glycol and methyl isobutyl ketone, EPA should commit to evaluate the risk for this source category using the new values and take notice and comment on the evaluation at that time, we plan to finalize the residual risk assessment for this source category using the available information. It would not be reasonable to commit to reopen every rule every time the science changes, but we note that if new science identifies a risk issue, we could revisit the project in the future. 

      Regarding the comment that EPA must set emission limits for all HAP in order to fulfill its obligations under § 7412(f)(2) for this rulemaking, the Leather Finishing Operations NESHAP sets a limit on all HAP emitted, regardless of whether risk reference values have been set for any specific HAP being emitted. Therefore, EPA disagrees with any implication that any additional HAP limits for this source category are needed in order to regulate HAP emitted by leather finishing operations. 

2.2-13 Comment: Commenter 0105 asserted that EPA arbitrarily underestimated risk in violation of CAA §  7212(f)(2) by failing to assess risks for the most exposed individual. 
      
The commenter contended that the purpose of the CAA is to protect public health by preventing air pollution. Stating that the statutory test for the health risk rulemaking under § 7412(f)(2) is two-fold: (1) EPA must prevent all unacceptable health risks; and (2) EPA must assure an "ample margin of safety to protect public health" and "prevent ... an adverse environmental effect." The commenter stated that under section 112(f), EPA must first assess the health risk created by toxic air emissions from a source category which remains once an existing MACT standard is in place and determine whether this risk is "acceptable" or not. The commenter continued that, if health risk is unacceptable, EPA must set a standard to prevent unacceptable risk, and then, EPA is required to consider whether further health risk and emission reductions are needed to provide an additional, "ample margin of safety to protect public health," in view of scientific uncertainty regarding its own risk assessment. The commenter argued that this provision requires EPA both to prevent unacceptable risk and provide a buffer or cushion, between the line of acceptability EPA draws, and the emission limit  -  to ensure that in the event EPA's acceptability line is incorrect, facilities will not be allowed to emit right up to the line of what is unacceptable, and must instead emit at levels lower than that. The commenter stated that the difference between the two is the "ample margin of safety" required by the Act.

The commenter contended that, under § 112(f)(2)(A) of the CAA, EPA is required to account for the "risks to the individual most exposed to emissions from a source in the category" in its residual risk assessment. The commenter continued that, as the Act directs, if EPA finds cancer risk is one in one million or more, it must promulgate standards under this subsection. The commenter further stated that the D.C. Circuit relied on this language in finding that this requires EPA at least to perform such a residual risk rulemaking, and held, further, that reducing cancer risk of one-in-one million for the most-exposed person is the "aspirational goal" of the rulemaking directive, based on EPA's own interpretation of this language in the 1989 Benzene Rule. The commenter argued that the CAA and binding Circuit precedent thus require EPA in these proposed amendments to assess health risks for the most-exposed person, to determine whether or not to promulgate stronger emission standards pursuant to § 7412(f)(2). 
      
The commenter referred to an EPA statement in its risk assessment for chronic exposures, "the estimated annual average ambient air concentration of each HAP at each census block centroid or user-defined receptor as a surrogate for the lifetime inhalation exposure concentration of all the people who reside in the census block." without further explanation. The commenter argued that using census block centroids as surrogates is insufficient as a matter of science and law, as it understates cancer and other chronic health risk by assuming that exposure to HAP occurs only at the census block centroid and not at the facility fence or property line, even though people often do live or spend significant time at or near those locations. The commenter stated that the Science Advisory Board ("SAB") urged EPA to consider "specific locations of residence" when conducting the scientific review of health risks required under the CAA. The commenter contended that taking geographic variation out of the equation fails to properly account for exposure to the "individual most exposed to emissions" as required by section 7412(f)(2)(A), and fails to provide an accurate accounting of risks. 

The commenter noted that, while EPA has made some changes to its methodology, the SAB has found that EPA's report "does not provide enough information about the efficacy of the tool, especially regarding criteria that would determine the number and placement of new receptors." The commenter stated that, like the SAB panel, commenters are concerned that the Census Block Receptor Check Tool would not be reproducible and the application of the Tool would vary from risk assessor to risk assessor when conducting modeling on an individual facility, introducing bias and potential for human error. The commenter stated that it is imperative that EPA has verification metrics in place to ensure that the locations of specific receptors is actually representative of those living near the facility or that it adopts the SAB's land use-based procedure making use of national land cover data.

Response: In a national-scale assessment of lifetime inhalation exposures and health risks from facilities in a source category, it is appropriate to identify exposure locations where it may be reasonably expected that an individual will spend a majority of his or her lifetime. In determining chronic risks, it is appropriate to use census block information on where people actually reside, rather than points at the property line, to locate the estimation of exposures and risks to individuals living near such facilities. Census blocks are the finest resolution available as part of the nationwide population data (as developed by the U.S. Census Bureau); on average, a census block is comprised of approximately 40 people and about 10 households. In EPA's 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 blocks are larger, although there is still no systematic bias. 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 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, EPA's SAB endorsed this approach.

In addition to the approach described above, 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 Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the December, 2017 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011) (and in more detail in Appendix 4 "Dispersion Model Receptor Revisions and Additions" of that document), EPA employed the Census Block Receptor Check Tool to identify census blocks surrounding the four facilities and ensure centroids were representative of the population living near each. 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 additional receptors for residences nearer to the facility than the centroid. For this source category, we relocated 3 census blocks that appeared to be on facility property (leather finishing or other industry) or were otherwise not representative of the surrounding population. In addition, we added 3 user receptors to represent the surrounding population. Appendix 4 of the risk assessment Residual Risk Assessment cited above provides additional information about these changes.

2.2-14 Comment: Commenter 0100 asserted that EPA must involve community stakeholders in strengthening its risk assessment approach overall, especially local organizations and citizens in communities that will be affected by a given risk assessment. The commenter further asserted that for EPA to fulfill its commitment to environmental justice it also must listen to and engage with affected communities. The commenter clarified that this means not just publishing something in the Federal Register and on the Internet, but finding community members, leaders, and representatives, and making phone calls to discuss the substantive issues in person and by phone, in a way that allows communities to provide meaningful input. The commenter referenced NAS recommendations urging EPA to expand "stakeholder involvement" and community outreach in the planning, scoping, and problem formulation of risk assessments, and to better explain and provide information to affected communities on the considerations and conclusions of risk assessments.

The commenter also asserted that the "very short" comment deadline on EPA's notice on cumulative risk assessment and the lack of direct outreach from EPA mean that the agency, thus far, has not provided affected communities with a meaningful opportunity to engage in this process. The commenter added that the lack of advance notice and short comment period also have made it difficult for communities to engage with scientists in the academic field.

Response: EPA initially provided a 30-day public comment period for the proposed rulemaking. As discussed in our response to comment 4.0-01, we extended the comment period to provide an additional 30 days for public review and comment on the proposed rule, providing a new deadline of June 14, 2018. 

We proposed that the risks for this source category to be acceptable. In addition, due to our determinations that cancer risks are below 1-in-1 million, that the maximum chronic noncancer TOSHI value is below 1, and recognizing the uncertainties associated with the acute screening risk estimate and the substantial costs associated with the control options, we proposed that additional standards for this source category are not required to provide an ample margin of safety to protect public health, and that the current standards provide an ample margin of safety to protect public health. The commenters have not identified any statute or regulation that requires more notice or outreach than the 60 days of public comment which EPA provided. In addition, considering the results of EPA's analyses, the proposed rule, and the fact that no party requested a public hearing as provided for in the proposal (83 FR 11314), EPA determined that, given its limited resources, that additional methods of outreach and notice were not required or warranted.

2.3 Risk Assessment Results

2.3-01 Comment: Commenters 0100 and 0102 contended that cost of control cannot be a sole factor in determining the appropriate risk management response considering that EPA identified an acute HQ of 3. Commenter 0100 asserted that using cost alone as its sole basis for not strengthening the emission limits pursuant to § 7412(d)(6), even though EPA identified two significant and feasible control developments, is not lawful or rational when the record shows developments have occurred that EPA must "tak[e] into account" under § 7412(d)(6). The commenter asserted that EPA should strengthen the standards to account for the developments that it found are feasible, and that would reduce toxic air emissions from these facilities. 

Commenter 0100 explained that Congress enacted the 1990 Amendments of the CAA to prevent and reduce cancer and other adverse health effects from toxic air pollution, and to do so especially in communities overburdened by such pollution. The commenter continued that the CAA Act requires EPA to review and update the emission standards both to protect public health and the environment, and to ensure sources apply up-to-date pollution control methods, technologies, and practices, rather than freezing protection at the level established when EPA first evaluated and set standards for a source category.

Commenter 0102 argued that cost of control cannot be a sole factor in determining the appropriate risk management response. The commenter stated that it appears that the only additional factor involved in EPA's determination of ample margin of safety is the cost of control. The commenter referred to EPA's estimated cost of equipment for additional controls to reduce risk at SB Foot of $30,000 per ton of pollutant removed, which is lower than the average cost calculated by EPA of $43,000. The commenter argued that a more thorough analysis of the cost of controls and an evaluation of economic impact should be conducted to determine whether this represents an unreasonable impact to the company and/or the industry before it was determined to be too costly. The commenter asserted that without additional revision of the NESHAP or a more expansive evaluation of economic impacts of additional air pollution controls, the existing NESHAP fails to meet the requirement of the CAA to provide an ample margin of safety.

Commenter 0099 agreed with EPA's primary conclusion that any identified risks are "acceptable from this source category and ... that the current NESHAP provides an ample margin of safety to protect public health." The commenter also agreed with the conclusion that, based on the technology review, there are "no new cost-effective controls ... to achieve further emissions reductions." The commenter recognized that the agency's analysis is based on conservative assumptions related to the emissions dataset, dispersion modeling, inhalation exposure estimates, and dose-response relationships, and, therefore, tends to overstate any potential risks to ensure protection of human health and the environment. Based on these conclusions, the commenter expressed support for EPA's proposal to maintain the numerical emission limits in the current Leather Finishing NESHAP.

Response: We disagree that the cost of controls was the sole factor in our proposing not to strengthen the emission limits pursuant to § 7412(d)(6). We weigh all health risk factors in our risk acceptability determination, including the cancer MIR, the number of people in various cancer risk ranges, cancer incidence, the maximum noncancer TOSHI, the maximum acute noncancer HQ, the extent of noncancer risks, the distribution of cancer risks in the exposed population, and risk estimation uncertainties (54 FR 38044, September 14, 1989). We proposed that additional standards for this source category are not required to provide an ample margin of safety to protect public health, and that the current standards provide an ample margin of safety to protect public health, due to a number of factors:  our determinations that cancer risks are below 1-in-1 million and that the maximum chronic noncancer TOSHI value is below 1; uncertainties associated with the acute screening risk estimate that make the estimate conservative, as further discussed in our response to comment 2.3-02; and the substantial costs associated with the control options. 

Regarding the comment that EPA's estimated cost of equipment for additional controls to reduce risk at S.B. Foot of $30,000 per ton of pollutant removed is lower than the average cost calculated by EPA of $43,000, and the assertion that EPA must conduct a more thorough analysis of the cost of controls, including an evaluation of economic and impact to determine whether requiring additional control would represent an unreasonable impact to the company and/or the industry, we did conduct a thorough analysis of the cost of controls, as documented in the memorandum titled CAA section 112(d)(6) Technology Review for the Leather Finishing Source Category (available in Docket ID No. EPA-HQ-OAR-2003-0194). As specified in the memorandum, EPA determined that the cost of requiring biofiltration for control of HAP emissions from the four leather finishing facilities subject to the rule would vary from $30,360 to $110,135 per ton of HAP reduced, depending on the facility. Also, as discussed in the memorandum, EPA determined that the cost-effectiveness of a concentrator at model leather finishing facility would vary from $54,172 to $62,457, depending on whether it was paired with an RTO or biological treatment unit. Note that, as stated in the preamble to the proposed amendments (83 FR 11314, March 14, 2018), these dollar values only represent the cost of operating the concentrator and not the RTO or biological treatment process. Due to our determinations that cancer risks are below 1-in-1 million and that the maximum chronic noncancer TOSHI value is below 1, uncertainties associated with the acute screening risk estimate as discussed above, and the substantial costs associated with the control options, we concluded that additional standards for this source category are not required to provide an ample margin of safety to protect public health, and that the current standards provide an ample margin of safety to protect public health.
      
2.3-02 Comment: Commenters 0100 and 0102 asserted that EPA has not sufficiently justified that the acute risk (HQ of 3) is acceptable, given the toxicity of propyl cellosolve. Commenter 0102 stated that the HQ for acute exposure to propyl cellosolve is concerning because short-term outdoor human exposures have a high potential of occurring and the highest HQ was predicted well within residential areas. Commenter 0100 asserted that EPA provides no rational justification for ignoring the acute risk (HQ of 3) and the finding that there are chronic noncancer risks to the reproductive system. The commenter listed various human health effects from the toxicity of levels propyl cellosolve, and cited references for these health effects.[,] The commenter contended that EPA unlawfully and arbitrarily proposed not strengthening the emission standards to reduce health risks pursuant to CAA § 7412(f)(2), under which EPA must set health-risk reduction limits that ensure that no community near leather finishing operations faces unacceptable health risks and require emission reductions that assure an ample margin of safety to protect public health, particularly to protect children and vulnerable communities.

      Response: Refer to section IV.A 3 of the preamble to the final rule for EPA's response to this comment.	
2.3-03 Comment: Commenter 0102 disagreed with EPA's rationale that summing the maximum emission locations, even if they were not paired in space and time, caused the risk assessment to be over protective, thus providing an ample margin of safety. The commenter explained that S.B. Foot is a somewhat small industrial facility without significant property to provide distance from emissions to the fence line. 

Response: We disagree that standards, considering all health information including the acute exposure risk screen, do not provide an ample margin of safety. As mentioned earlier, the risk analysis for the proposed rule amendments indicated that the cancer risks to the individual most exposed are below 1-in-1 million from both actual and allowable emissions. These risks are considerably less than 100-in-1 million, which is the presumptive upper limit of acceptable risk. The risk analysis also showed no cancer incidence, as well as maximum chronic noncancer TOSHI value of 0.04, which is significantly below 1. In addition, the risk assessment indicated no significant potential for multi-pathway health effects. Regarding the acute exposure risk screen, the screen has multiple conservative assumptions built in, and the commenters point that the facility has minimal distance to the fence line is also taken into account by the screen. We note that in this case, the information relied upon included a combination of the 2014 National Emissions Inventory (NEI) and satellite imagery. 

2.3-04 Comment: Commenter 0102 disagreed with EPA's claim that the acute exposure assessment is "biased high" and thus might already provide an ample margin of safety, arguing that, though there is uncertainty in dispersion modeling results, there is "considerable certainty" in EPA's short-term estimate of ambient concentration of HAPs because AERMOD was developed to be a model to predict realistic ambient air concentrations and not to bias high for conservatism. The commenter stated that, for the S.B. Foote facility, it is reasonable to assume that 1) a person could be at a location for an hour at the worst-case meteorological conditions, as residential areas are close to the facility, and (2) most processes are operating simultaneously because this industry has fairly steady production.

The commenter also asserted that EPA's estimate of hourly emissions closely approximates the temporal emissions from the facility, given that it is not overly conservative as discussed above. The commenter stated that, based on the information and assumptions in EPA's assessment, acute exposures from the S.B. Foot facility to residents in Red Wing, MN are likely to occur and that the potential health risks to these communities are at a level of concern. In the commenter's opinion, EPA should perform an adequate review of the toxicity of the risk driving chemicals and complete an assessment of the economics of further controls.
      
Response: For the residual risk analyses, we estimate both long- and short-term inhalation exposure concentrations and associated health risks from each facility in the source category using the Human Exposure Model 3 (HEM-3 or HEM-AERMOD) modeling system  -  which combines the Human Exposure Model (HEM) with the American Meteorological Society/EPA Regulatory Model (AERMOD) dispersion modeling system. EPA uses AERMOD (version 16216r) to develop annual average ambient concentrations through the simulation of hour-by-hour dispersion from the emission sources into the surrounding atmosphere, which is a state-of-the-science Gaussian plume dispersion model that is preferred by EPA for modeling point, area, and volume sources of continuous air emissions from facility applications. We agree with the commenter that this model was developed to predict "realistic" ambient air concentrations for short-term acute emissions, and we agree that the model itself "is not biased high for conservatism"; however, the model allows the user to elect to enter data or use default values that effectively bias the results high for conservatism. For example, as further discussed in EPA's response to comment 2.3-02, in the case of propyl cellosolve, we used the acute toxicity value for ethylene glycol monomethyl ether as a surrogate for propyl cellosolve since there is no specific acute inhalation health benchmark for this glycol ether. Given that ethylene glycol monomethyl ether is the most toxic compared to other glycol ethers, the use of this surrogate is a health protective choice in EPA's risk assessment. As another example, we use a worst-case hourly emission multiplier of 1.8 to account for most of the variation in production levels and actual HAPs emissions from SB Foot. Refer to EPA's response to comment 2.1-04 for a discussion of how hourly data submitted by commenter 0102 supports this worst-case hourly emission multiplier of 1.8. These approaches effectively bias the acute screening risk results high for conservatism. 

The uncertainties in virtually all of the RTR risk assessments can be divided into three areas: 1) uncertainties in the emission data sets, 2) exposure modeling uncertainties, and 3) uncertainties in the dose-response relationships. Uncertainties in the emission estimates and in the air quality models lead to uncertainty in air concentrations. Uncertainty in exposure modeling can arise due to uncertain activity patterns, the locations of individuals within a census tract, and the microenvironmental concentrations as reflected in the exposure model. Finally, uncertainty in the shape of the relationship between exposure and effects, the unit risk estimate (URE) and the RfC, also contributes to uncertainties in the risk assessment. In the acute screening assessment that we conduct under the RTR program, we assume that peak emissions from the source category and worst-case meteorological conditions co-occur, thus resulting in maximum ambient concentrations. Refer to EPA's response to comment 2.3-02 and the Residual Risk Assessment for the Leather Finishing Operations Source Category in Support of the Risk and Technology Review December 2017 Proposed Rule (Docket Item No. EPA-HQ-OAR-2003-0194-0011) for further discussion of these uncertainties associated with our acute health risk screening assessment, which yielded conservative results due to our handing of the uncertainties.

The commenter also contended that, for the S.B. Foote facility, it is reasonable to assume that a person could be at a location for an hour at the worst-case meteorological conditions, because residential areas are close to the facility and most processes are operating simultaneously because this industry has fairly steady production. In the preamble to the proposed amendments, we stated that it "would tend to be worst-case actual exposures, and that it would be unlikely" for three conditions to occur simultaneously: (1) peak emissions from the source category, (2) worst-case meteorological conditions, and (3) a person located at the point of maximum exposure. In fact, our risk assessment modeling indicated that when assuming the peak hourly emissions (1.8 times higher than annual average emissions) for all operating hours, worst-case meteorological conditions that produce an acute exposure occurred during 0.1% of all operating hours (6 out of 6,240 hours). Therefore, for an acute exposure to occur, the actual peak emissions would have to coincide with the 6 hours of the worst-case meteorological conditions (out of 6,240 operating hours), and a person would need be located at the point of maximum exposure. Furthermore, modeling indicated the location of potential acute exposures were in wooded areas near the facility and not in residential areas. Therefore, we disagree that acute exposures from the S.B. Foot facility to residents in Red Wing, MN are likely to occur and that the potential health risks to these communities are at a level of concern, and we disagree with the comment that EPA has not performed an adequate review of the toxicity of the risk driving chemicals or completed an assessment of the economics of further controls. As we stated in the preamble to the proposed amendments (83 FR 11314, March 14, 2018), the current standards provide an ample margin of safety to protect public health. Refer to EPA's response to comment 2.3-02 for further EPA response to the comment on EPA's assessment of the economics of further controls, and refer to the response to comment 2.3-03 for further discussion on EPA's conclusion that, in acute health risk screening assessment, we used conservative tools and assumptions to ensure that our decisions are health and environmentally protective.

2.4 Demographic and Environmental Justice

2.4-01 Comment: Commenter 0100 stated that there is a discrepancy between the preamble (83 FR 11337) and the supporting document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations, and that it is unclear which is correct. The commenter explained that EPA stated in the preamble that its demographic analysis shows disproportionate exposure for Native Americans and people ages 65 and older; whereas the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations states that the percentage of the Native American population exposed to the source category is lower for the source category than nationwide; but that "other and multiracial" individuals are exposed at a higher rate than represented in the national population (i.e., 9% instead of 7%). 

Response: The commenter is correct that there is a discrepancy between the preamble to the proposed amendments (83 FR 11314, March 14, 2018) and the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations. This discrepancy is due to an error in transferring information from the document cited above to the preamble. The information in the document cited above is correct:  Within HEM-3 Model Domain (50 km), the percentage of the Native American population exposed to the source category is lower for the source category than nationwide, and "other and multiracial" individuals are exposed at a higher rate than represented in the national population (i.e., 9% instead of 7%). The proposal preamble incorrectly stated: "The proximity results indicate that the population percentage for the "Native American" demographic group within 5 km of leather finishing operations emissions is slightly greater than the corresponding nationwide percentage for that same demographic." The correct sentence reads: "The proximity results indicate that the population percentage for the "Other and Multiracial" demographic group within 50 km of leather finishing operations emissions is slightly greater than the corresponding nationwide percentage for that same demographic." This revision has no impact on our conclusion that the proposed rule does "not have disproportionately high and adverse human health or environmental effects on minority populations, low-income populations, and/or indigenous peoples." There are no known cancer risks posed by HAP emissions from the four facilities, as the HAP emitted have no known cancer risks. In addition, of the 4,600,000 people living within 50 kilometers of these facilities, based on our assessment of actual emissions of HAP from this source category, no one is exposed to a noncancer hazard index above 1.The proposed rule would maintain or increase the level of environmental protection for all affected populations without having any disproportionately high and adverse human health or environmental effects on any population, including any minority, low-income, or indigenous populations.  EPA found the overall level of risk from the source category to be acceptable and that the current standards provide an ample margin of safely for all populations in close proximity to these sources, including minority and low-income populations, as discussed in EPA's response to comment 2.4-05.
2.4-02 Comment: Commenter 0102 asserted that the population exposed to emissions from S.B. Foot reside in a potential environmental justice area. The commenter defined potential environmental justice areas based on the census tract geography with residents as either low income or a majority of Persons of Color, with the low-income indicator defined as over 40% of the population living under 185% of the Federal Poverty Level, and the majority Persons of Color indicator as defined as over 50% of the population not identified as white or Caucasian in the US Census. The commenter indicated that, based on this definition, the area falls within the low-income potential environmental justice area identifier. The commenter cited the MPCA's "Life and Breath report," stating that it indicates that people of lower socio-economic status and people of color are more vulnerable to adverse health effects from exposure to air pollution.

Response: As discussed in the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations (available in Docket ID No. EPA-HQ-OAR-2003-0194), EPA used its Environmental Justice Risk and Proximity Analysis Tool ("EJ Tool") to link HEM-3/AERMOD modeling results for the Leather Finishing Operations source category with detailed census data, in order to evaluate the distribution of cancer and noncancer risks for different demographic factors (including racial, ethnic, age, economic, educational, and linguistically isolated population categories). In addition to evaluating risk distribution, this analysis also presents the demographic composition of the population located within close proximity (5 km) and within the overall HEM-3/AERMOD model domain (50 km) of the source category emissions (irrespective of risk). The following demographic groups were included in this risk and proximity analysis:
 Total population;
 White;
 Minority;
 African American (or Black);
 Native Americans;
 Other races and multiracial;
 Hispanic or Latino;
 Children 17 years of age and under;
 Adults 18 to 64 years of age;
 Adults 65 years of age and over;
 Adults without a high school diploma;
 People living below the poverty level;
 People living below two times the poverty level, and
 Linguistically isolated people.
      
The total population statistics near facilities in the source category, irrespective of risk (i.e., at all risk levels) are provided in Table 2 of the Analysis of Demographic memorandum cited above. These results indicate that the demographic composition of the population located within close proximity (5 km) and within the overall HEM-3/AERMOD model domain (50 km) of the source category emissions are the same or lower than the nationwide average for all minority groups listed above except "Other and Multiracial, which was slightly higher (9%) than then national average (7%). When compared to the MPCA's definition of "Persons of Color," defined as over 50% of the population not identified as white or Caucasian in the US Census, these results indicate that the total minority population is 25% within 50 km of the facilities and 13% within 5 km of the facilities, both of which are less than the MPCA's cutoff of 50%, so that these results do not meet the first criteria for these areas being considered environmental justice areas. Please see the responses to comments 2.2-10 and 2.4-01 for further explanation of the risk assessment results and the results of the demographic analysis.

Refer to sections 2 and 3 of the document cited above for details on the census data used in this analysis, the algorithms used to compute the risk distributions for the total population and for each demographic category analyzed are presented. Sections 3.2 through 3.5 of the document cited above provide detailed discussions on the source of data on race/ethnicity statistics for each census block group nationwide, level of education, poverty level, and linguistic isolation.

EPA continues to evaluate and refine our methods for analyzing Environmental Justice, such as the proximity analysis performed for Leather Finishing Operations. The draft EPA document titled Technical Guidance for Assessing Environmental Justice in Regulatory Analysis is currently undergoing SAB review. The Office of Air and Radiation is a contributor to this draft document and cites numerous examples of Environmental Justice analysis performed in agency rulemakings. Environmental justice considerations are a part of the rulemaking process; however, various factors influence the scope and complexity of an assessment. These factors may include, but are not limited to statutory mandates, data availability, resources and/or timeframe limitations.

In the Urban Air Toxics Strategy Report to Congress, we acknowledge that national rules and standards can address part of the risk to communities, but because the assessments did not include background risks or contributions to risk from sources outside the facilities more needs to be done at the community level with other tools available within the CAA and within state, local, and other federal programs. EPA is committed to our efforts to make a difference in communities of concern and is developing an integrated strategy focusing work in communities with the most need for EPA's assistance. This effort to enhance coordination across our EPA programs and with other federal agencies will improve how we support community needs. We will focus on those communities where we think we have opportunities to leverage resources and actions to make a real difference. As we learn lessons on coordinating and focusing our efforts, we will use these lessons to help more communities in the future.
Under EO 12898, 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 U.S. Consistent with EO 12898 and the Presidential Memorandum that accompanies it, EPA's Environmental Justice policies promote justice by focusing attention and EPA efforts on addressing the types of Environmental Justice harms and risks that are prevalent among minority, low-income, and indigenous populations. EO 12898 and EPA's Environmental Justice policies do not mandate particular outcomes from an action, but they require that decisions involving the action be informed by a consideration of Environmental Justice issues. With respect to this rule, EPA found the overall level of risk from the source category to be acceptable and that the standards provide an ample margin of safely for all populations in close proximity to these sources, including minority and low-income populations.

2.4-03 Comment: Commenter 0098 stated that it is not clear whether or not facility workers who live between 5 and 50 km of each of the four facilities were included in the demographic analysis, or if any workers lived within this area. Commenter 0098 contended that the environmental justice analysis component of the RTR should have examined workers living within a close proximity to the facilities, both as part of the demographic groups included in the analysis and separately as a group, to determine if workers experience a higher amount of environmental justice-related burden due to emissions exposure both at work and at home. 

Response: As noted in our response to comment 2.2-11, EPA does not have regulatory authority to include occupational health requirements and standards in NESHAP or RTRs. As a result, the demographic analysis does not focus on facility workers. As discussed in the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations (available in Docket ID No. EPA-HQ-OAR-2003-0194), we evaluate the distribution of cancer and noncancer risks for different demographic factors (including racial, ethnic, age, economic, educational, and linguistically isolated population categories). In addition to evaluating risk distribution, we present the demographic composition of the population located within close proximity (5 km) and within the overall HEM-3/AERMOD model domain (50 km) of the source category emissions. Also note that any workers who live in census blocks within 50 km from a facility are included in the population count for the census block. Please refer to our response to comment 2.4-02 for a discussion of our Environmental Justice Risk and Proximity Analysis and the demographic factors that are considered.

2.4-04 Comment: Commenter 0100 asserted that EPA's risk assessment must account for increased vulnerability based on demographic differences, using socioeconomic factors as core elements of the risk assessment to address vulnerability and variability, consistent with NAS recommendations. The commenter pointed out that a NAS report identified significant flaws in EPA's assessment of individual variability in risk assessments that could result in significant underestimation of risk, indicating 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, which causes them to experience greater health risk from the same amount of a toxic chemical exposure as well as a lack of access to health care. The commenter added that NAS has observed that performing risk assessment that is meaningful for communities that already face a significant amount of pollution and communities concerned about environmental justice "requires an ability to evaluate multiple agents or stressors simultaneously, considering exposures not in isolation but in the context of other community exposures and risk factors." The commenter acknowledged and supported EPA's current policy of assessing the demographics of affected communities, pursuant to CAA § 112(f) and the Environmental Justice Executive Order 12898; however, the commenter asserted that, in addition to looking at the demographic census data on race, ethnicity, poverty level, and similar factors, EPA must also assess the starting point or baseline overall health status of the affected individuals and communities using the best available data at a local and national level, including the baseline cancer levels, respiratory problems, and health problems associated with the toxic chemicals emitted by a source category. The commenter pointed out that doing so would be consistent with the 1999 Residual Risk Report. In the commenter's opinion, EPA has significant research available on which it must draw to incorporate "overall health" into its risk assessments, referencing one example by the American Lung Association.

The commenter asserted that, where a rule affects communities that are disproportionately minority or lower income, EPA cannot ignore this greater risk in its assessment, as mandated by Exec. Order 12898. The commenter referenced additional sources indicating that communities with minority and lower income populations, and communities with higher than average levels of cancer, respiratory, and other health problems, as well as a lack of access to health care, are likely to be more vulnerable to the impact of toxic air pollution. The commenter recommended that EPA assess the greater health risk based on socioeconomic status found in epidemiological research studies, consistent with NAS studies. The commenter pointed out that data describing these factors are available from the Center for Disease Control's Environmental Public Health Tracking ("EPHT") Program, the U.S. Agency for Toxic Substances and Disease Registry, state and local health agencies, and academic researchers, and asserted that EPA must consider and use such information in its risk assessments.

The commenter added that EPA should develop and use a default factor to account for socioeconomic and other community-based stressors, just as it does to account for intrinsic biological factors. The commenter pointed out that EPA traditionally uses a factor of 100 to account for the use of animal studies, when translating such studies to assess human impacts. The commenter further pointed out that the Food Quality Protection Act directed EPA to use a factor of 10 to account for in utero exposure. California's Office of Environmental Health Hazard Assessment uses a similar factor to account for in utero exposure. 

Response: EPA continues to evaluate and refine environmental justice analyses. The draft EPA document titled Technical Guidance for Assessing Environmental Justice in Regulatory Analysis is currently undergoing SAB review. The Office of Air and Radiation is a contributor to this draft document and cites numerous examples of environmental justice analysis performed in agency rulemakings. Environmental justice considerations are a part of the rulemaking process; however, various factors influence the scope and complexity of an assessment. These factors may include, but are not limited to statutory mandates, data availability, resources and/or timeframe limitations. 

In the Urban Air Toxics Strategy Report to Congress, we acknowledge that national rules and standards can address part of the risk to communities, but because the assessments do not include background risks or contributions to risk from sources outside the facilities more needs to be done at the community level with other tools available within the CAA and within state, local, and other federal programs. EPA is committed to our efforts to make a difference in communities of concern and developing an integrated strategy focusing work in communities with the most need for EPA's assistance. This effort to enhance coordination across our EPA programs and with other federal agencies will improve how we support community needs. We will focus on those communities where we think we have opportunities to leverage resources and actions to make a real difference. As we learn lessons on coordinating and focusing our efforts, we will use these lessons to help more communities in the future. Refer to EPA's response to comment 2.4-05 for a discussion on EPA's actions to fulfill its obligations under Executive Order 12898.

2.4-05 Comment: Commenter 0100 asserted that EPA must fully integrate the findings of its environmental justice analysis into this risk assessment and rulemaking and set stronger pollution limits to provide environmental justice.

Response: Under Executive Order (EO) 12898, 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 U.S. Consistent with EO 12898 and the Presidential Memorandum that accompanies it, EPA's environmental justice policies promote justice by focusing attention and EPA efforts on addressing the types of environmental justice harms and risks that are prevalent among minority, low-income, and indigenous populations. EO 12898 and 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, EPA found the overall level of risk from the source category to be acceptable and to provide an ample margin of safely for all populations in close proximity to these sources, including minority and low-income populations.

3.0  Startup, Shutdown, or Malfunction

3.0-01 Comment: Commenter 0100 contended that EPA has no lawful basis or authority to create a "force majeure event" exemption to reporting, or any other requirements, as it proposes to do, as the D.C. Circuit has previously explained in rejecting a similar "affirmative defense" to civil penalties for malfunctions. NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014). The commenter explained that adding such an exemption would also be arbitrary and unlawful because it would undermine the reporting requirements by providing a justification to delay reporting, and thus undermine compliance, enforcement, and fulfillment of the emissions standards designed to protect public health and the environment at the core of the Act's and § 7412's purpose. See, e.g., 42 U.S.C. § 7401 (emphasizing objective of pollution prevention to protect public health and welfare). The commenter suggested that, if an event occurs that delays reporting, EPA and/or a court may address the implications of that event in an administrative or judicial enforcement proceeding, as part of the penalty assessment tests applicable under 42 U.S.C. § 7413(d) (EPA) and (e) (court).

Response: Refer to section IV.C.3 of the preamble to the final rule for EPA's response to this comment.

3.0-02 Comment: Commenter 0100 expressed support for EPA's removal of regulatory language that violated the Act's requirements and D.C. Circuit precedent directing that emission standards apply at all times. The commenter supported EPA's finalizing the provisions as proposed to ensure that it is clear that they apply at all times, and are continuous, without any exemptions because this revision would strengthen the compliance and enforcement regulatory provisions applicable to these facilities. 

Response: EPA acknowledges the commenter for supporting removal of regulatory language to ensure that it is clear that the standards apply at all times. The Leather Finishing NESHAP currently requires that the standards apply at all times, consistent with Sierra Club v. EPA. The NESHAP specifies in 40 CFR 63.5320(a) "All affected sources must be in compliance with the requirements of this subpart at all times, including periods of startup, shutdown, and malfunction." However, the NESHAP refers to General Provisions (40 CFR 63, subpart A) that include provisions related to SSM that are not consistent with Sierra Club v. EPA or 40 CFR 63.5320(a). In order to remove these inconsistencies within the NESHAP, to clarify EPA's original intent that the standards apply at all times, and to ensure that the subpart requirements are consistent with the court decision cited above, we proposed and are finalizing the un-incorporation of all General Provisions related to the SSM exemption and move any applicable portion of these General Provisions to the NESHAP. A detailed discussion of this decision is provided in the preamble to the proposed rule.

4.0 Miscellaneous Comments

4.0-01 Comment: Commenter 0100 stated that EPA's failure to include the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations was a violation of notice-and-comment requirements because EPA had not published this document for public review and comment, nor had it provided the statutorily-required thirty-day comment period to review the proposed rule and supporting material on which the agency relied for that proposed rule. See, e.g., 42 U.S.C. § 7607(d)(3)-(6). The commenter further suggested that exclusion from the public docket of this one document raises a serious concern that EPA has failed to publish additional information on which it relies for the proposed rule.

Response: We added the document titled Analysis of Demographic Factors for Populations Living Near Leather Finishing Operations to docket No. EPA-HQ-OAR-2003-0194 and published a notice on May 15, 2018 (83 FR 22438) explaining the inadvertent omission from, and subsequent addition of, this document to the docket for the proposed rule. In addition, we re-opened the comment period on May 15, 2018 (83 FR 22438) to provide an additional 30 days for public review and written comment on the proposed rule, extending the deadline to June 14, 2018. As such, EPA has complied with its statutory obligations under 42 U.S.C. § 7607(d)(3)-(6). Further, we disagree with the comment that EPA may have failed to publish additional information on which it relies for the proposed rule. Upon notification of the inadvertent omission of the above referenced document from the docket, EPA took prompt action to include add it to the docket and reopened the comment period for an additional 30 days, commenters provided no evidence that additional relevant documents were not provided in the docket for this rulemaking.

4.0-02 Comment: Commenter 0092 contended that the rule created "potentially unduly burdensome requirements." The commenter added that EPA's analysis shows limited pollutant loadings and relative high costs to control. The commenter stated that, consequently, EPA should substantially reduce or eliminate the burdensome requirements. The commenter concluded that the entire subcategory should be excluded given the de minimis amount of pollution.

Response: The commenter did not specify to which "potentially unduly burdensome requirements" they were referring. We disagree with the commenter that these amendments create any unduly burdensome requirements. As documented in the memorandum titled Costs for the Leather Finishing Operations Source Category Risk and Technology Review (available in Docket ID No. EPA-HQ-OAR-2003-0194), the total national cost of the proposed rules is $705, associated with reviewing the promulgated standards. The proposed rule amendments include additional recordkeeping and reporting requirements for any leather operation that elects to comply with the standard using an emission control device; however, none of the four existing leather operations currently use an emission control device to comply with subpart TTTT, and we are not aware of any planned or potential new or reconstructed leather finishing operations. As a result, no leather finishing operations will comply with these new requirements, which will result in no added cost to the industry. Further, the proposed rule amendments include revised recordkeeping and reporting requirements for any leather finishing operation that deviates from the standards; however, these revised records and reports add no additional burden because EPA anticipate that no facilities will deviate from the standards during the three years of this information collection.

4.0-03 Comment: Commenter 0092 asserted that EPA must give serious attention to impacts on small entities caused by rulemakings. The commenter cited the Regulatory Flexibility Act (RFA), the Small Business Regulatory Enforcement Fairness Act, the Improper Payments Information Act of 2002, and the Regulatory Right-to-Know- Act. The commenter noted that EPA must conduct an initial regulatory flexibility analysis with the proposed rule and a final regulatory flexibility analysis with the final rule.

Response: The RFA generally requires an agency to prepare a regulatory flexibility analysis of any rule subject to notice and comment rulemaking requirements under the APA or any other statute, unless the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities. The impact of concern is any significant adverse economic impact on small entities directly regulated by the rule. EPA made such a certification and, thus, a regulatory flexibility analysis is not required. We concluded that the proposed and final rule will not have a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act. We determined that each of the three small entities impacted by this action may experience an impact of less than 0.01 percent of sales. Details of this analysis are presented in the memorandum titled Proposal Economic Impact Analysis for the Reconsideration of the Risk and Technology Review: Leather Finishing Operations Source Category (available in Docket ID No. EPA-HQ-OAR-2003-0194). The Small Business Regulatory Enforcement Fairness Act amended the RFA to require EPA to convene a Small Business Advocacy Review (SBAR) Panel for most proposed rules unless the agency can certify that a rule will not have a significant economic impact on a substantial number of small entities. As previously discussed, EPA has made such a certification, and, thus, this requirement is not applicable to this rulemaking. Further, the EPA is not aware of, nor has the commenter provided, any provisions of the Improper Payments Information Act of 2002, and the Regulatory Right-to-Know- Act which are applicable to this rulemaking in regard to its to impacts on small entities.  

4.0-04 Comment: Commenter 0100 expressed support for requiring electronic reporting and urged EPA to extend this requirement to all covered facilities. The commenter stated that EPA provided no lawful or rational justification for not requiring all sources to report electronically. 

Response: EPA acknowledges the commenter for supporting electronic reporting. The proposed requirement to electronically report test reports applies to all sources subject to the Leather Finishing Operations NESHAP. However, none of the four existing facilities are using control devices to comply with the NESHAP, so none will conduct any periodic performance testing that would trigger electronic reporting. Note that leather finishing operations subject to the NESHAP that comply without using a control device are required to conduct performance tests only once as part of the initial compliance determination, and that all four facilities subject to the NESHAP have already conducted this required test and submitted the required test data, prior to this requirement to electronically submit such data. 
