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Environmental Protection Agency (EPA): Final Rule 

Review of National Ambient Air Quality Standards for Ozone 

RIN 2060-AP38 

General Comments 

1. Reviewer recommends EPA conduct a review of health and welfare improvements 

achieved in meeting previous versions of the NAAQS in subsequent NAAQS setting 

efforts in order to provide a real-world context to EPA’s decision making. EPA’s 

historical and current approach has been quite experimental, theoretical, and statistical, 

without conducting a retrospective analysis of actual ozone concentration improvements 

to verify that the expected improvement in public health and welfare matches that which 

was achieved. EPA has revised the O3 NAAQS a number of times since 1979, and there 

have been many areas that have achieved attainment and/or made progress toward 

achieving previous NAAQS. It would seem reasonable that EPA could incorporate 

information related to the air quality improvement and resulting improvement in public 

health and welfare to verify that the assumptions and procedures used in setting the 

NAAQS actually make sense and accurately predict the actual improvement that has 

been observed. For example, EPA could look at a number of nonattainment areas for O3

that have achieved the standard and answer the following: “We expected __ 

improvement in O3 concentrations due to the implementation and attainment of a certain 

NAAQS level in area __ and thus we expected to achieve __ improvement in public 

health (choose various public health metrics used in setting the standards, such as 

expected reduced mortalities, expected reduced hospital visits, etc.) and welfare (choose 

various public welfare metrics used in setting the standards, such as expected 

improvement in biomass loss, expected improvement in crop yield loss, etc.). After 

implementing the regulations and achieving O3 concentrations of __, we actually saw __ 

improvement in public health and welfare.” Conducting such an analysis would lend 

credibility and a valuable means of verifying initial assumptions, as well as verifying 

those data obtained from chamber studies and other experimental work matched reality. 

2. Reviewer recommends addressing the effects of the Ozone NAAQS on Outer 

Continental Shelf (OCS) oil and gas development. The rule does not currently address 

requirements for offshore oil and gas operators with respect to their emissions or the 

effects of offshore emissions to the onshore environment. It also does not appear to 

provide any additional information or guidance regarding the treatment of OCS air 

quality plans or permits submitted to the EPA for such facilities. Reviewer also 

recommends discussing to what extent the EPA intends to address implications of 

offshore air pollutant emissions in 40 CFR parts 51 or 60 or to change the permitting 

requirements for OCS lessees and operators. 

3. In order to establish appropriate background concentrations for ozone and applicable 

precursors that could be used in conjunction with an analysis of potential impacts 

originating from facilities on the OCS, reviewer recommends EPA establish guidelines 

or requirements for monitoring locations along the coasts, particularly for areas in the 

Gulf of Mexico that could be classified as potentially nonattainment areas under this 

rule. Currently, the rule proposed various guidelines for monitoring but does not list any 
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specific or special requirements related to locating monitors along the coasts or in any 

locations that would be relevant to measuring ozone on the OCS. 

4. Reviewer recommends considering that evaluations of air quality used to make welfare 

effects determinations should be based on creating a surface for each year and then 

averaging across years at each grid cell, rather than be created from the three-year 

average at the monitor location. If a three-year average is used, reviewer recommends a 

lower level standard should be set to account for the greater variability in the shorter 

term numbers. 

5. Reviewer recommends limiting grandfathering of PSD limits in time and not making 

them permanent for this rulemaking. Currently, the proposed grandfathering provisions 

under either 40 CFR 52.21 or 51.166 would exempt certain pending PSD permit 

applications from having to address the revised ozone NAAQS. The net result would be 

to put an excessive burden for achieving attainment on new applicants for PSD or 

NNSD approval. This could also have potentially adverse effects on new economic 

development and would potentially ignore the disproportional impact caused by older 

facilities. Reviewer recommends at a minimum that the final should make clear that 

applications for modifications to existing permits would be required to comply with the 

new standards. 

6. Reviewer recommends that the secondary standard be set independently of the primary 

standard based on an appropriate analysis of the welfare effects of ozone emissions, 

regardless of whether that standard ultimately ends up being higher, lower, or the same 

as the primary standard. 

7. Reviewer recommends revising the major source criteria to include an evaluation of the 

location of the proposed major source in relation to existing or likely nonattainment 

areas. Rather than using a fixed number, it may be more appropriate to establish a 

formula to determine whether the proposed facility emissions of precursors are likely to 

constitute a major source. 

8. Reviewer recommends evaluating the potential for methane emissions within the new 

source review program. 

9. Reviewer recommends updating the general conformity provisions as they appear to be 

largely out of date and should be updated either in conjunction with this rulemaking or 

as a separate but related effort. 

10. Reviewer recommends that EPA add language indicating that simply moving from 

“good” to “moderate” Air Quality Index (AQI) category should not necessitate the 

implementation of curtailment or management of emissions and activities given that the 

break between good and moderate has historically been significant for some planning 

purposes. In this ozone NAAQS preamble, EPA states on p. 276 that “An AQI value of 

50 is set at 54 ppb”. This level was seemingly determined (p. 273) because it is 

approximately 15 ppb below the level of the standard of 70 ppb in order to allow for 

having AQI categories “span ranges large enough to support accurate forecasting” and is 

“consistent with past practice of making a proportional adjustment to this AQI 

breakpoint, relative to an AQI value of 100 (i.e., 70 ppb)”. It should be noted that an 

AQI value of 50 is intended to be the breakpoint between the good and moderate 

categories, and that a level of 54 ppb is well below the lowest concentration (i.e., 60 

ppb) that has been shown in controlled human exposure studies of healthy adults to 
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cause moderate lung function decrements (i.e., FEV1 decrements ≥ 10%, which could be 

adverse to people with lung disease) and airway inflammation in some people. 

11. Reviewer recommends clarifying whether the changes in the ozone monitoring season 

will impact the “attainment year” for SIP and conformity analysis. This is especially 

important for meeting conformity requirements (see 40 CFR 93.118). 

Specific Comments 

1. Page 16, footnote 5 – Reviewer recommends modifying the footnote to state the 

following to reflect the D.C. Circuit’s decision on remand in the Cross-State Air 

Pollution Rule case: 

a. The Cross-State Air Pollution Rule was upheld by the Supreme Court in 

Environmental Protection Agency v. EME Homer City Generation, L.P., 134 S. Ct. 

1584 (2014), and remanded to the D.C. Circuit for further proceedings. The D.C. 

Circuit issued its decision on remand from the Supreme Court on July 28, 2015, 

remanding CSAPR to EPA, without vacating the rule, for EPA to reconsider certain 

emission budgets for certain States. EME Homer City Generation, L.P. v. 

Environmental Protection Agency, No. 11-1302, 2015 WL 4528137 (D.C. Cir. July 

28, 2015). 

2. Page 32 – Reviewer recommends retaining the effects of climate change described in the 

Endangerment Finding by the Administrator. Reviewer also recommends that more 

recent scientific findings should supplement the current references, particularly the EPA 

CIRA report. 

3. Pages 278-314 – In the discussion of the secondary standard and effects of ozone on 

vegetation, EPA discusses the degradation of ecosystem services and the ability of 

ecosystems to sequester carbon with increased ozone and climate change. Reviewer 

recommends EPA add specific mention that increased temperature, which is known to 

increase ozone levels, will also likely lead to increased wildfires, which will result in 

additional increases in emissions of ozone and especially ozone precursors (EPA could 

also reference the CIRA report). 

4. Page 308 – Reviewer recommends using the phrase “restoration of desired fire regimes 

and fire-adapted ecosystems” instead of the term “fire regime stabilization.” The term 

“landscapes” could also be used in place of “fire-adapted ecosystems,” and implies a host 

of related ecological services and desirable ecological conditions. 

5. Page 515-518 – Reviewer recommends noting that while it is the role of the States to 

proposed the designation of nonattainment areas, and that EPA evaluated these proposals, 

that federal agencies and non-federal stakeholders are not precluded from participating in 

the designation process. 

6. Page 522 – Reviewer recommending inserting at the end of the paragraph on EER: 

a. A number of commenters expressed concern regarding the new standards and use of 

prescribed fire. Currently prescribed fires can be an exceptional event upon meeting 

the required criteria. EPA further intends to address these requirements surrounding 

use of the Exceptional Events Rule with regard to prescribed fires in its upcoming 

rulemaking. 

7. The section on Implementation does not seem to utilize wording previously used in 

Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State 
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Implementation Plan Requirements, March 6, 2015 in 80 FR 12264 and other recent rules 

where wildland fire has been discussed. Therefore, reviewer recommends the following 

changes: 

a. Page 534 – add a new paragraph after paragraph 1 and before the next paragraph 

starting with “If this is . . .” that states: 

i. Significant tracts of land under federal management may also be included in 

nonattainment area boundaries. The role of fire in these areas should be assessed 

and emissions budgets developed in concert with those federal land management 

agencies. In such areas the EPA encourages states to consider in any baseline, 

modeling and SIP attainment inventory used and/or submitted to include emissions 

expected from projects subject to general conformity, including emissions from 

wildland fire that may be reasonably expected in the area. Where appropriate, states 

may consider developing plans for addressing wildland fuels in collaboration with 

land managers and owners. Information is available from DOI and USDA Forest 

Service on the ecological role of fire and on smoke management programs and 

basic smoke management practices.1

b. Page 535 – add the following at the end of the 1st paragraph: 

i. EPA intends to develop guidance to address implementing the Exceptional Events 

Rule criteria for wildfires that could affect ambient ozone concentrations. 

Depending on the nature and scope of interstate emission events affecting 

downwind air quality, the EPA may be able to assist states in developing 

approvable exceptional events demonstrations. 

c. Page 537 – add the following at the end of the 3rd paragraph before the examples 

paragraph: 

i. Depending on the nature and scope of international emissions events affecting air 

quality in the U.S., the EPA may be able to assist states in developing approvable 

exceptional events demonstrations. More generally, the EPA believes that the best 

approach for evaluating the potential impacts of international transport on 

nonattainment is for states to work with the EPA on a case-by-case basis to 

determine the most appropriate information and analytical methods for each area’s 

unique situation. The EPA will work with states that are developing attainment 

plans for which section 179B is relevant, and ensure the states have the benefit of 

the EPA's understanding of international transport of ozone and ozone precursors. 

Regulatory Impact Analysis 

1. Reviewer recommends providing uncertainty bounds around the costs throughout the 

RIA. This would greatly help communicate that there is uncertainty about these 

estimates in addition to the benefits estimates, which have upper and lower bounds. This 

is particularly relevant for the unidentified controls. The approaches discussed in 

Chapter 4 (e.g., regression, simulation) have confidence intervals around them, so there is 

even an analytical basis for including uncertainty bounds. In addition to unidentified 

 

1 USDA Forest Service and Natural Resources Conservation Service, Basic Smoke Management 

Practices Tech Note, October 2011, 

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046311.pdf. 
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controls, it is also relevant for identified technologies where there is clearly uncertainty in 

the cost curves. 

2. Reviewer recommends listing more unidentified controls. While it may not be possible 

to quantify them, listing more potential unidentified controls seems essential. This is 

particularly important for California, where it appears that 100% of the emission 

reductions are coming from unidentified NOx sources for the post-2025 period (see Table 

3-10). Reviewer also recommends clarifying how EPA expects California to comply. 

3. Reviewer recommends confirming in the title for Table 4-9 that this is a 7% discount rate. 

4. Reviewer recommends confirming in the title for Table 4-10 that this is a 7% discount 

rate. 

5. Reviewer recommends clarifying what the benefit is of including the 3% discount rate in 

some of the main tables, given that it can’t be included in most cases (e.g., Table 6-1). It 

is a bit confusing to see these numbers in some places, but then not see them in the 

headline numbers and really have no points for comparison. 

6. Reviewer recommends clarifying why is there a “+B” caveat in total benefits in tables 6-1 

and 6-2, but not in the headline cost/benefit tables in the executive summary or in tables 

8-1 and 8-2. Reviewer recommends being consistent. 

7. The coefficients cited from the Smith and Zanobetti papers are the “national average” 

coefficients. However, in the table that has the baseline incidence and prevalence 

estimates (Table 6-4 in the RIA) it is stated that the baseline rates are age, cause, and 

county-specific. Does this imply that EPA used something other than the national 

coefficient from the studies, or did they use the national coefficient and apply it 

separately to each group? Reviewer recommends clarifying as the estimates are very 

difficult to replicate and verify without this information. 

8. Reviewer recommends clarifying whether the damage function written out in Section 

6.4.1 is the actual functional form that is used or is it meant to just be an example? In 

general, it would help to have further clarity on exactly how EPA applies the coefficients 

in the literature to estimate the benefits. 

9. Reviewer recommends modifying Table 6-7 as the coefficients for Zanobetti et al. and 

Smith are flipped. 

10. EPA states that they use a benefits-per-ton method to assess the PM benefits, but then 

also outlines a similar health-impact valuation to the one that is done for ozone. Do these 

map onto one another? If not, reviewer recommends clarifying which methodology is 

actually used and how they relate. 

11. Reviewer recommends modifying Table 8-1 as $15 - $15.5 = -$0.5, not -$1.0. Similarly 

for $14.5 versus the $14 that is in the table. If the difference is due to rounding, reviewer 

recommends providing that information within the table. 

12. Reviewer recommends modifying the impact to forest product facilities, which are 

described by EPA as most indirect, as there are direct impacts associated with installing 

mandated emissions reductions technologies. Specifically, one commenter estimated the 

direct costs of the 70 ppb target to forest product facilities at $123M in capital costs and 

$24M in annual costs. For an affected facility and its local economy, the economic 

impacts of bringing a nonattainment area into compliance could be significant. 

13. Reviewer recommends providing a quantitative analysis or qualitative discussion of 

differences between using the proposed Clean Power Plan versus the finalized Clean 

Power Plan for the RIA and how this may affect the baseline. Reviewer also 
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recommends providing a quantitative analysis or qualitative discussion regarding the use 

of IPM v 5.14 instead of IPM v 5.15 that was used in the Clean Power Plan. 

14. Reviewer recommends providing additional analysis or discussion in relation to a 

scenario where the intended regulations (e.g., Cross-State Air Pollution Rule, Clean 

Power Plan) do not provide the ozone reductions that are expected and how it would 

affect the benefits and costs of the rule. 

15. Reviewer recommends providing additional rationale for the logic that the unidentified 

control costs would be based on the on the identified control costs. As a sensitivity, EPA 

should assume that there is a steeper control curve for unidentified controls and that 

unidentified control costs would be higher. 

16. Reviewer recommends providing additional clarification why the use of unidentified 

controls are not in the same ratio as identified controls within an area. For example, an 

area that is 40% NOx controls and 60% VOC controls for identified controls, should 

assume that 40% of unidentified controls are NOx controls and 60% of unidentified 

controls are VOC controls. Based on the logic presented as to why only unidentified 

NOx controls would be used could be made in relation to applying any identified VOC 

controls.