Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

1

I. Responses to Interagency Comments Submitted to EPA on November 19, 2014

(1) Comment

For insertion on pg 33 of the preamble: 

Wildfires pose a direct threat to public safety – a threat that can be mitigated through 

management of wildland vegetation. Besides the physical threat to life and property 

posed by wildfires, they also affect air quality. Wildfire emissions do significantly 

contribute to periodic high levels and affects background levels of ozone (Jaffe, D.A. and 

N.L. Wagner, 2012), especially as standards approach background levels (Emery, C. et 

al., 2012). As has been acknowledged by EPA previously, fires play an important 

ecological role across the globe. Wildfire benefits those plant and animal species that 

depend upon natural fires for propagation, habitat restoration, and reproduction, as well 

as myriad ecosystem functions (e.g., carbon sequestration). Attempts to exclude wildland 

fire have resulted in unintended consequences, including increased risks to both humans 

and ecosystems. Indeed, “Fire policy that focuses on [wildfire] suppression only, delays 

inevitable, promising more dangerous and destructive future...fires” (Stephens, S. et al., 

2013). Most North American plant communities evolved with recurring fire and are 

dependent on recurring fire for maintenance. Fires also reduce fuel load, unnatural 

understory, and tree density, helping to reduce the risk of catastrophic wildfires. The use 

of prescribed fire can influence the occurrence of catastrophic wildfires which will have 

direct impacts on high level impacts to ozone, background levels and subsequent public 

health effects. Wildfire and prescribed fire are both part of the natural background that 

will need further consideration during development of implementation rules for this 

standard. EPA has policies that allow for the exclusion of air quality monitoring data 

from design value calculations when they are substantially affected by certain 

background influences. However, the CAA requires the EPA to set the NAAQS at levels 

requisite to protect public health and welfare without regard to the source of the pollutant.

The EPA is committed to working with Federal land managers, Tribes and the States, 

between this draft proposal and the final rule, to refine actions that address ozone impacts 

while protecting and improving vegetation health and resilience to wildfire and climate 

risks.

EPA Response: The suggested new paragraph is a discussion of implementation-related 

policies specific to wildfire and wildland fire, and does not belong within the overall 

context of this preamble section. The section, titled “E. Ozone Air Quality” is intended 

to be a brief overview of ozone in the U.S. (e.g., monitoring, atmospheric chemistry, 

emissions and other sources, meteorology, past trends, and possible futures). This section 

does not either logically or appropriately cover implementation-related policy issues 

other than to describe generally the types of issues that are addressed in the 

implementation phase rather than standard setting phase. If we were to incorporate the 

issues from the above paragraph, EPA believes they would be more appropriately 

addressed in section VII.F covering Background Ozone. We recommend that a revised 
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

2

version of the above paragraph could be inserted in section VII.F.2, titled Exceptional 

Events Exclusions.

EPA recommends that the following revised text could be included in section VII.F.2 as 

the last paragraph, beginning with the sentence that is currently the last sentence:

Additionally, the EPA intends to develop guidance to address implementing the 

Exceptional Events Rule criteria for wildfires that affect ambient O3 concentrations. 

Wildfire emissions are a component of background ozone (Jaffe, D.A. and N.L. Wigder, 

2012) and can significantly contribute to periodic high ozone levels (Emery, C. et al., 

2012). Besides their effect on air quality, wildfires pose a direct threat to public safety – a 

threat that can be mitigated through management of wildland vegetation. Attempts to 

suppress wildfires have resulted in unintended consequences, including increased risks to 

both humans and ecosystems. Indeed, “Fire policy that focuses on [wildfire] suppression 

only, delays inevitable, promising more dangerous and destructive future...fires” 

(Stephens, S. et al., 2013). The use of prescribed wildland fire can influence the 

occurrence of catastrophic wildfires which may help manage the contribution of wildfires 

to background ozone levels and periodic peak ozone events. Additionally prescribed fires 

can have benefits to those plant and animal species that depend upon natural fires for 

propagation, habitat restoration, and reproduction, as well as myriad ecosystem functions 

(e.g., carbon sequestration). As previously indicated, the CAA and EPA’s implementing 

regulations allow for the exclusion of air quality monitoring data from design value 

calculations when they are substantially affected by certain background influences. 

However, the CAA requires the EPA to set the NAAQS at levels requisite to protect 

public health and welfare without regard to the source of the pollutant. The EPA is 

committed to working with Federal land managers, Tribes and the States to address the 

impact of fire-related emissions on ozone through appropriate implementation policies.

(2) Comment

Table 3, Page 162: 

There is a lot of good information here, but there is not enough explanation to help the 

reader understand it. The title needs some work for clarity. Maybe some of the 

information goes in footnotes. We recommend stating in the title whether this table 

refers to long term or short term exposure. Can footnotes to be used to provide the source 

of the concentration response function – we assume this is Jerrett et al? 

EPA Response: We have added clarifying information to footnote 85 describing the 

information in Table 3. 

(3) Comment
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

3

Page 163: 

The HREA also concludes that lower confidence should be placed in the results of the 

assessment of respiratory mortality risks associated with long-term O3, primarily because 

that analysis is based on only one study, though that study is well-designed, and because 

of the uncertainty in that study about the existence and identification of a potential 

threshold in the concentration-response function (U.S. EPA, 2014a, section 9.6). 

EPA Response: We have added a new footnote (number 88) clarifying that there is 

uncertainty about the extent to which mortality risk estimates based on the long-term 

metric used in the study by Jerrett et al. (2009) (i.e., seasonal average of 1-hour daily 

maximum concentrations) reflects associations with long-term average O3 versus 

repeated occurrences of elevated short-term concentrations

(4) Comment

Page 164:

To evaluate the second issue, the HREA conducted national air quality modeling 

analyses. These analyses estimated the proportion of the U.S. population living in 

locations where seasonal averages of daily O3 concentrations are estimated to decrease in 

response to reductions in NOX emissions, and the proportion living in locations where 

such seasonal averages are estimated to increase. Given the close relationship between 

changes in seasonal averages of daily O3 concentrations and changes in seasonal 

mortality and morbidity risk estimates, this analysis informs consideration of the extent to 

which the risk results in urban study areas represent the U.S. population as a whole. This 

representativeness analysis indicates that the majority of the U.S. population lives in 

locations where reducing NOX emissions would be expected to result in decreases in 

warm season averages of daily maximum 8-hour ambient O3 concentrations. 

EPA Response: Several parts of the notice discuss EPA’s consideration of this issue, 

including p. 158; bottom of p. 201 to top of p. 202; p. 204; p. 217; bottom of p. 179 to p. 

183; p. 217 to top p. 218; and p. 312 to 313 (page numbers refer to the track changes 

version of the notice sent by EPA to OMB on November 21, 2014). The notice also cites 

to HREA analyses that evaluated this issue. 

(5) Comment

Page 167

Commented [A1]: Isn’t another key with the long term 

studies the potential for double counting? 

Commented [A2]: Are there any environmental justice 

implications associated with the areas where there are NOx 

sources, and thus ozone levels expected to get higher? 
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

4

To the extent adverse O3-attributable effects are more strongly supported for higher 

ambient concentrations (which are consistently reduced upon air quality adjustment), the 

impacts on risk estimates of increasing low O3 concentrations reflect an important source 

of uncertainty. 

EPA Response: The views of the Administrator regarding the relative weight it is 

appropriate to place on the various exposure and risk metrics are discussed in detail in 

sections II.D.5 and II.E.4.d. 

(6) Comment

Page 172:

In addition to lung function decrements, aAvailable studies have also evaluated either 

most of these effects (i.e., lung function decrements, respiratory symptoms or, airway 

inflammation) following exposures to O3 concentrations below 75 ppb. Table 3-1 in the 

PA highlights the group mean results of individual controlled human exposure studies 

that have evaluated exposures of healthy adults to O3 concentrations below 75 ppb (U.S. 

EPA, 2014c). The studies included in Table 3-1 of the PA indicate that some subjects 

experience a combination of lung function decrements and respiratory symptoms (after 

the fifth and sixth exercise period) following exposures to O3 concentrations as low as 72 

ppb,1and lung function decrements and airway inflammation following exposures to O3

concentrations as low as 60 ppb. 

The PA also notes consistent results in some panel studies of O3-associated lung function 

decrements. In particular, Tthe PA notes that epidemiologic panel studies in children and 

adults consistently indicate O3-associated lung function decrements when on-site 

monitored concentrations were below 75 ppb, althoughwith the evidence becomesing less 

consistent at lower O3 concentrations (U.S. EPA, 2014c, section 3.1.4.1).

EPA Response: We have made edits to these paragraphs that are consistent with 

interagency comments, and that are consistent with our responses to similar comments 

submitted to EPA on November 12 and November 18. 

(7) Comment

Page 180

 

1 As noted above, for the 70 ppb exposure concentration Schelegle et al. (2009) reported that 

the actual 6.6-hour mean exposure concentration was 72 ppb.

Commented [A3]: Again, did EPA look at any EJ 

implications – this is a risk-risk trade off.

Commented [A4]: Consider edits to this paragraph for 

transparency and clarity.

Commented [A5]: Per prior question about if these are 

the same people showing both stat sign diff in FEV1 and 

symptoms.
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

5

iii. Important Uncertainties 

The PA also notes that there are important uncertainties associated with analyses 

of air quality in locations of epidemiologic studies. For example, the PA notes that while 

multicity studies generally have greater statistical power and geographic coverage than 

single-city studies, there is often greater uncertainty in conclusions about the extent to 

which multicity effect estimates reflect associations with air quality meeting the current 

standard (U.S. EPA, 2014c, section 1.3.1.2.1). This is particularly the case for the 

multicity studies evaluated in this review with some study locations meeting the current 

standard and others violating that standard. Specifically for the four Canadian multicity 

studies discussed above, the PA notes that interpretation of air quality information is 

complicated by uncertainties in the extent to which multicity effect estimates can be 

attributed to ambient O3 in the majority of locations, which would have met the current 

standard, versus O3 in the smaller number of locations that would have violated the 

standard. 

EPA Response: A new introductory paragraph has been added to this section to clarify 

the consideration of uncertainties in developing the PA conclusions. 

(8) Comment

Beginning on page 185: 

For exposures of concern at or above 60 ppb, the PA highlights the following key 

observations at a standard of 75 ppb:

(1) On average over the years 2006 to 2010, the current standard is estimated to allow 

approximately 10 to 18% of children in urban study areas to experience one or more 

exposures of concern at or above 60 ppb. Summing across urban study areas, these 

percentages correspond to almost 2.5 million children experiencing approximately 4 

million exposures of concern at or above 60 ppb during a single O3 season. Of these 

children, almost 250,000 are asthmatics. 

(2) On average over the years 2006 to 2010, the current standard is estimated to allow 

approximately 3 to 8% of children in urban study areas to experience two or more 

exposures of concern to O3 concentrations at or above 60 ppb. Summing across the urban 

study areas, these percentages correspond to almost 900,000 children (including almost 

90,000 asthmatic children) estimated to experience at least two O3 exposure 

concentrations at or above 60 ppb during a single O3 season. 

Commented [A6]: Some commenters are confused by the 

placement of this section (after the discussion of the 

“conclusions” of the PA. Is this section outlining the 

uncertainties in the conclusions or were these uncertainties 

taken into account when the conclusions we developed?

Commented [A7]: See parallel requests for adding “at a 

standard of 75 ppb” throughout pages 195-192 (for brevity, 

not all instances copied here)

Commented [A8]: Please develop a standard footnote 

that is used whenever EPA refers to the number of children. 

These numbers assume all children respond, extrapolated 

from the fact that only 10% of the healthy adults in the 

clinical studies responded gt 10% change in FEV. Given the 

assumption is that for children that would be adverse, there 

is margin of safety built in on a variety of levels, from a) the 

% responding; b) the severity of the re response. These are 

influenced by how severe the child’s asthma is and the 

extent of proper medical management of the child’s 

asthma. Thus, with increasing health care coverage, these 

numbers might be substantial over estimates. 
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

6

(3) In the worst-case years (i.e., those with the largest exposure estimates), the current 

standard is estimated to allow approximately 10 to 25% of children to experience one or 

more exposures of concern at or above 60 ppb, and approximately 4 to 14% to experience 

two or more exposures of concern at or above 60 ppb. 

For exposures of concern at or above 70 ppb, the PA highlights the following key 

observations at a standard of 75 ppb: 

(1) On average over the years 2006 to 2010, the current standard is estimated to allow up to 

approximately 3% of children in urban study areas to experience one or more exposures 

of concern at or above 70 ppb. Summing across urban study areas, almost 400,000 

children (including almost 40,000 asthmatic children) are estimated to experience O3

exposure concentrations at or above 70 ppb during a single O3 season. 

(2) On average over the years 2006 to 2010, the current standard is estimated to allow less 

than 1% of children in urban study areas to experience two or more exposures of concern 

to O3 concentrations at or above 70 ppb. 

(3) In the worst-case years, the current standard is estimated to allow approximately 1 to 8% 

of children to experience one or more exposures of concern at or above 70 ppb, and up to 

approximately 2% to experience two or more exposures of concern, at or above 70 ppb. 

For exposures of concern at or above 80 ppb, the PA highlights the observation that the 

current standard is estimated to allow about 1% or fewer children in urban study areas to 

experience exposures of concern at or above 80 ppb, even in years with the highest 

exposure estimates. 

b. Lung function risk assessment – key observations

As discussed above (II.C.3.a), the HREA estimates risks of moderate to large lung 

function decrements (i.e., FEV1 decrements > 10%, 15%, or 20%) in school-aged 

children (ages 5 to 18), asthmatic school-aged children, and the general adult population 

for 15 urban study areas. As for exposures of concern, the PA focuses on lung function 

risk estimates in children (including children with asthma). 

Compared to risks associated with recent air quality, risk estimates for air quality 

just meeting the current standard are consistently smaller across urban study areas (U.S. 

EPA, 2014a, Appendix 6B). When averaged over the years evaluated in the HREA, risk 

reductions of up to about 40% were estimated compared to recent air quality. These 

reductions reflect the consistent decreases in relatively high ambient O3 concentrations 

upon adjustment to just meet the current standard (U.S. EPA, 2014a, Chapter 4). Such 

reductions in estimated lung function risks are evident throughout urban study areas, 

including in urban cores and in surrounding areas (U.S. EPA, 2014, Appendix 9A).
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

7

Based on Figures 3-11 to 3-14 in the PA (U.S. EPA, 2014c), and the associated 

details described in the HREA (U.S. EPA 2014a, chapter 6), the PA highlights key 

observations with regard to lung function risks estimated in children for air quality 

adjusted to just meet the current standard. These key observations are presented below for 

FEV1 decrements > 10, 15, and 20%. 

With regard to decrements > 10%, the PA highlights the following key 

observations at a standard of 75 ppb: 

With regard to decrements > 15%, the PA highlights the following key observations at a 

standard of 75 ppb: 

With regard to decrements > 20%, the PA highlights the following key observations at a 

standard of 75 ppb: 

With regard to total mortality or morbidity associated with short-term O3, the PA 

notes the following at a standard of 75 ppb:

With regard to respiratory mortality associated with long-term O3, the PA notes the 

following at a standard of 75 ppb: 

EPA Response: We have added text to clarify that exposure and risk estimates are for air 

quality adjusted to just meet the current O3 standard. We have also added a footnote 

reiterating the due to variability in responsiveness, only a subset of individuals who 

experience exposures at or above a benchmark concentration can be expected to 

experience adverse health effects. 

(9) Comment

Page 201 (same with footnote 89 on page 203)

Reductions in O3 precursor emissions (i.e., NOX) could also increase public health 

protection by reducing the ambient concentrations of pollutants other than O3. For 

example, in their advice on the second draft HREA CASAC acknowledged the potential 

for ambient NO2 concentrations to be affected by changes in NOX emissions (Frey, 

2014a, p. 10). Consistent with this, the PA notes that NOX emissions contribute to 

ambient NO2, and NOX and VOCs can contribute to secondary formation of PM2.5 

constituents, including ammonium sulfate (NH4SO4), ammonium nitrate (NH4NO3), and 

Commented [A9]: It is not clear why this paragraph is 

here – why it is part of the argument about the choice of a 

standard for ozone vs. in the benefits analysis. 
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

8

organic carbon (OC). Therefore, at some times and in some locations, control 

strategies that would reduce NOX emissions (i.e., to meet an O3 standard) could 

reduce ambient concentrations of NO2 and PM2.5, resulting in health benefits 

beyond those directly associated with reducing ambient O3 concentrations. 

EPA Response: While it is not the basis for the proposed decisions reached by the 

Administrator, this is an issue that is acknowledged in the PA and that was discussed by 

CASAC. The text indicated reflects that acknowledgment in the PA and the discussion of 

this issue in CASAC’s letter to the Administrator. 

(10) Comment

Page 204:

In addition, based on the consistency of findings across studies and evidence for the 

coherence of results from different scientific disciplines, strong evidence indicates that 

certain populations are at increased risk of experiencing O3-related effects, including the 

most severe effects. These include populations and lifestages identified in previous 

reviews (i.e., people with asthma, children, older adults, outdoor workers) and 

populations identified since the last review (i.e., people with certain genotypes related to 

antioxidant and/or anti-inflammatory status; people with reduced intake of certain 

antioxidant nutrients, such as Vitamins C and E). 

EPA Response: To avoid confusion with the ISA conclusions, the word “strong” has 

been removed. 

II. Responses to Additional Interagency Comments Submitted to EPA 

(1) This is a follow-up to EPA’s prior 11-14-2014 response to General Conformity related 

issues raised by interagency commenters. 

EPA’s understanding of the most recent issues raised by USDA: USDA would like EPA 

to extend the grace period for general conformity applicable to federal activities in 

designated nonattainment areas, and address a concern they have about the viability of 

the “emissions inventory option” for “presumed conformity” in the General Conformity 

Rule. On the latter, the concern is that this option is not realistically available to federal 

agencies prior to states establishing approved emissions inventories for newly designated 

nonattainment areas.

EPA Response: Regarding the extension of the grace period, as EPA indicated in an 

earlier response, the CAA establishes the requirement that conformity applies 1 year after 

Commented [A10]: Please clarify the difference between 

“adequate evidence” as stated earlier in the document (e.g., 

page 134 states:

Overall, the factors for which the ISA concludes there is 

adequate evidence of increased risk for experiencing O3-

related effects were related to asthma, lifestage (children 

and older adults), genetic variability, dietary factors, and 

working outdoors. 
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

9

an area is designated nonattainment. The CAA does not provide discretion for EPA to 

revise this requirement to extend the grace period beyond 1 year. Regarding the options 

for federal actions in nonattainment areas to be deemed to conform, the General 

Conformity Rule, which EPA last revised in 2010 with considerable input from federal 

agencies (including USDA) provides several methods. A method that was added in the 

2010 revision allowing prescribed burns to be considered “presumed to conform” when 

conducted under approved smoke management plans or by using basic smoke 

management practices deemed to satisfy the general conformity requirement.

Another method for satisfying these requirements involves comparing the sum of 

the total emissions from the federal actions plus other emissions in the area to the 

emissions budget in the applicable SIP. In cases where the SIP has not been developed 

yet there is an emissions inventory option. This option allows federal emissions activities 

to conform if they do not increase the total area’s emissions above the nonattainment 

area’s baseline emissions inventory. The baseline emissions inventory can be the most 

current calendar year with a complete emissions inventory available before an area is 

designated. This method was also available prior the 2010 revision to the General 

Conformity Rule, and continues to be available. Federal agencies should recognize that 

this emissions inventory option is not available until states have submitted approved areawide inventories. Since this option relies on states to timely develop these inventories, 

EPA encourages potential federal stakeholders to work with states as soon as possible if a 

nonattainment designation is anticipated to ensure the federal activities they are 

concerned about are adequately accounted for in state inventories if the federal actors 

intend to use the emissions inventory method to demonstrate conformity. 

There are several other flexible approaches available for federal agencies to comply with 

their general conformity responsibilities not mentioned in this response. The EPA is 

available to assist federal agencies in using these approaches when federal actions are 

being planned. The EPA does not at this time have specific plans to review the General 

Conformity Rule for purposes of exploring additional presumptive conformity methods 

as a result of a potential revision to the existing ozone NAAQS, but will consider whether 

a revised NAAQS creates new challenges not already addressed by the recent 2010 

revision to those rules.

(2) Revisions related to the secondary standard made in response to interagency comments 

(beyond editorial, simple clarifications), beyond that noted in responses sent to OMB on 

November 13, 2014:
Summary of EPA Responses to Interagency Working Comments on Draft 

Language under EO12866/13563 Interagency Review. 

10

a. revision regarding solicitation of comment on retaining current standard and associated 

rationale– section IV.F

b. clarification for text regarding crop yield loss impacts in Administrator’s conclusions 

section – section IV.D.5

c. Revisions to reduce extraneous discussion wrt crops – sections IV. B.1.c, IV.D.1., 

IV.E.2

d. Clarification of the framework used for decision-making on the secondary standard –

beginning of section IV