Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

1

 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.

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? 

Page 163: 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

2

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). 

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. 

Page 167

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. 

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,1 and lung 

 

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 [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? 

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 Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

3

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).

Page 180

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. 

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) 

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 Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

4

estimated to experience at least two O3 exposure concentrations at or above 60 ppb during a 

single O3 season. 

(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).

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 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

5

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: 

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 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. 

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). 

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. 

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 Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

6