2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -1-

Contents

George Allen .........................................................................................................................................2

John Balmes ..........................................................................................................................................6

Joe Brain..............................................................................................................................................10

James Gauderman ...............................................................................................................................14

Rogene Henderson ..............................................................................................................................16

Philip K. Hopke...................................................................................................................................19

Michael T. Kleinman ..........................................................................................................................22

Morton Lippmann ...............................................................................................................................27

Fred Miller...........................................................................................................................................30

Lianne Sheppard..................................................................................................................................31

Frank Speizer.......................................................................................................................................32

Helen Suh ............................................................................................................................................35

James Ultman ......................................................................................................................................38

Sverre Vedal........................................................................................................................................40
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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George Allen

Caveat: With regard to the range of ozone concentrations under consideration, these comments 

assume the form of the NAAQS will remain unchanged from what was promulgated in the 2008 

rule. Any change in the form (daily average duration, percentile, multi-year averaging) will 

change the effects of a standard even if the numerical value (e.g., .060 to .070 ppm) remains the 

same.

Q 1. What is your advice on the overall strengths and limitations of the evidence from controlled 

human exposure and epidemiological studies and the results of the exposure and risk assessments, 

in the context of EPA's selection of a standard level within the proposed range that would be 

requisite to protect public health with an adequate margin of safety, including the need to protect 

susceptible populations, such as children and people with asthma?

As with nearly all other pollutants, the exposure-response relationship is stronger and more 

scientifically robust as you go to higher concentrations. This holds for both controlled human 

exposures and epidemiological studies. Both approaches have their limitations, especially toward 

the lower end of the proposed range. The controlled exposure studies usually do not include 

sensitive and vulnerable populations (SVP) as subjects; this makes it more difficult to extrapolate 

results to the SVP that the NAAQS is intended to protect. The bias here is to underestimate the 

effects of a given concentration on SVP. These types of studies do allow detailed assessment of 

physiological markers such as FEV1 and inflammatory markers that epidemiological studies can 

not (usually) assess. Epidemiological studies do include SVP, although they are usually not 

constrained to this group. These studies have much greater exposure mis-classification than 

controlled exposure studies, and potential confounding from other pollutants and uncontrolled 

variables; these factors would usually bias effect results toward the null. However, since the 

ambient ozone measurements used in epidemiological studies are reasonably specific to ozone, 

they are actually an indicator of strong oxidants in the air, and thus the health effects may be larger 

than if the exposure were only to ozone. This is different than the ozone concentrations used in 

controlled exposure studies where other strong oxidants are presumably not present; thus these 

studies may underestimate the reported ozone health effects relative to epidemiological studies. 

Another potential difference between controlled exposure and epidemiological studies is the 

reaction products from ozone once it gets indoors (Weschler, Atmospheric Environment 38 (2004) 

5715B5716); these include a wide range of gas-phase respiratory irritants and ultra-fine particles.

Q2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have 

provided evidence of other health effects, including inflammation and increased airway 

responsiveness which may occur through different physiological mechanisms than the reduction in 

FEV1, how should the results of these studies inform our understanding the health effects to 

healthy adults at exposures levels from 0.060 to 0.070 ppm? 

As noted in the background material included in these charge questions, the available data suggest 

that there probably is a reasonably Asmooth exposure-response curve@ going from .080 to .060 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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ppm. This does not imply that this holds at even lower levels, since that gets into the issue of 

thresholds. And as with all other aspects of the science, this assumption is weaker at .060 than at 

.070 ppm.

Q3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing 

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence from 

controlled human exposure studies, mentioned above, inform our understanding of the health 

effects to healthy adults at exposure levels from 0.060 to 0.070 ppm? 

These studies support the concept of a reasonably smooth exposure-response curve down to these 

levels as opposed to a health effect threshold near .060 ppm.

Q4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, 

what is the scientific importance of the small, group mean FEV1 decrements relative to the 

findings that 7 to 20% of the subjects experienced FEV1 decrements ∃ 10%? Please consider this 

question from both a public health and a clinical perspective.

For healthy adult subjects in controlled human exposure studies, these FEV1 decrements indicate 

some biological response, but the clinical significance of this is unclear especially in light of some 

studies showing inflammatory responses without FEV1 decrements. From a public health 

perspective, where SVP would be expected to have an enhanced response to exposures to these 

concentrations, these results may have more importance. Ideally, controlled human exposure 

studies would be conducted at these levels using SVP, but that has risks of adverse outcomes in the 

study subjects, making such studies difficult to do.

Q5. The evidence, including that summarized above, indicates that susceptible populations may 

have greater responses than healthy people. In light of this evidence, how can we appropriately 

use the results of controlled human exposure studies conducted on healthy adults, as well as the 

epidemiological studies of susceptible groups, to inform a judgment on the effects of ozone 

exposure on susceptible populations?

The results of controlled human exposure studies conducted on healthy adults provide a Abest 

case@ (least health effect) scenario relative to SVP. Epidemiological studies that focus on SVP 

would be expected to show greater health effects for a given concentration, but are subject to the 

confounding factors noted above. The best approach may be a Aweight of evidence@ scenario that 

assesses the consistency (or lack thereof) across these very different approaches to quantifying 

ozone health effects.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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Q6. To what extent does your confidence that the effects observed in epidemiological studies are 

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the 

proposed range as compared to the higher levels?

As noted previously, the uncertainty (or confidence if you wish) of any exposure study decreases 

as the exposure concentrations decrease. For epidemiological studies, the effects of confounders is 

likely to be larger at .060 than .070 ppm. However, it=s a reasonable assumption that this factor 

would bias observed health effects toward the null, not strengthen them.

Q7. EPA's exposure assessment quantified the number of all children and asthmatic children 

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 and 0.070 

ppm. Considering the patterns of change in the estimates of exposures of concern at and above the 

0.060 and 0.070 ppm benchmark levels, and the uncertainties and limitations in the estimates, what 

is the relative importance from a public health perspective of the estimated reductions in 

exposures of concern, as well as the exposures remaining, for alternative standards across the 

proposed range?

There is little doubt that reduced exposure, both in size of SVP exposed and the concentrations 

they are exposed to, has some public health benefit as you go from .070 to .060 ppm. However, it 

is difficult to quantify the changes in public health benefits across this range of concentrations. 

There will always be some remaining exposures with health effects across the proposed range in 

SVP.

Q8. EPA's quantitative risk assessment estimated the numbers of occurrences of various ozone 

related health effects associated with just meeting alternative standard levels down to a standard 

level of 0.064 ppm. Considering the patterns of change in the estimates of health effects in the risk 

assessment at the alternative standard levels, and the uncertainties and limitations in the estimates, 

what is the relative importance from a public health perspective of the estimated reductions in risk, 

as well as the risk remaining, for alternative standards across the proposed range? Please consider 

this question in light of the scientific evidence as a whole.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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This is really a policy question, not a science question. There is likely some risk (i.e., not 0) for 

SVP even at the low end of the proposed range. This is not unique to ozone; some residual risk is 

present for every NAAQS pollutant, since none of them (except maybe CO) have a clear effect 

threshold. The quantitative risk assessment does not provide a bright line; it only provides 

guidance to the best estimate of risk at the various ranges considered. The science can only take 

the process so far, and after that it becomes a policy judgment that weighs the estimated (and more 

uncertain at the lower end of the range) health benefits against the difficulty of implementing 

effective control strategies to meet any given NAAQS.

Additional Comments.

Although the reconsideration of the 2008 ozone NAAQS is constrained to the literature available 

during that NAAQS review process, it is worth noting that more recent studies over the last 4-5 

years support and perhaps strengthen the scientific justification for an ozone NAAQS in the range 

of .060 to .070 ppm.

Some interested parties have raised the question of the quality of the ozone data used in the 

epidemiologic studies, saying that there are common situations where the UV absorption 

measurement method normally used in the ozone monitoring network can significantly over-report 

ozone concentrations. There is evidence that this can happen, but it is unclear if this a significant 

factor in the overall ozone exposure-health effect relationship. Additionally, the difference 

between chamber studies and ambient air exposures with the additional load of strong oxidants not 

being included in the measurement further reduces the implications of a modest issue with the UV 

method. It should also be noted that nearly all ambient air measurements of NAAQS pollutants 

have various biases associated with them, sometimes positive (NO2, non-trace CO, SO2 when NO 

is elevated, sometimes negative (the PM2.5 FRM, depending how it is run), sometimes biases 

between different FRMs for PM10 (the SSI Hi-Vol Awar@ in the 1980's), and sometimes just very 

goofy (the Hi-Vol FRM for lead). Some of these biases are as large or larger than the likely 

positive bias from the UV ozone method. In this context, I am not concerned with the reported 

biases in the UV method. However, since there may be effective ways to reduce the biases in this 

method, EPA may want to consider additional specifications for the testing of UV ozone analyzers 

in the Federal Equivalent Method (FEM) regulations to assess this issue.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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John Balmes

1. What is your advice on the overall strengths and limitations of the evidence from 

controlled human exposure and epidemiological studies and the results of the exposure 

and risk assessments, in the context of EPA's selection of a standard level within the 

proposed range that would be requisite to protect public health with an adequate margin 

of safety, including the need to protect susceptible populations, such as children and 

people with asthma?

Taken together, the evidence from controlled human and epidemiological studies strongly 

supports the selection of a new primary ozone standard that is well below the 1997 standard 

of 0.08 ppm over an 8-hour averaging time. There is scientific certainty that 6.6-hour 

exposures to concentrations ≥0.08 ppm with intermittent exercise cause clinically relevant 

decrements of lung function in young, healthy volunteers. The results of multiple 

epidemiological studies also show that children and adults with asthma are at increased risk 

of acute exacerbations of this disease on or shortly after days when ozone concentrations are 

elevated above background but remain below 0.08 ppm. Given the need to protect public 

health with an adequate margin of safety and the results of EPA’s exposure and risk 

assessments, setting a new NAAQS in the range of 0.060 to 0.070 is appropriate.

 

2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have 

provided evidence of other health effects, including inflammation and increased airway 

responsiveness which may occur through different physiological mechanisms than the 

reduction in FEV1, how should the results of these studies inform our understanding the 

health effects to healthy adults at exposures levels from 0.060 to 0.070 ppm?

The results of studies that show that exposure to ozone at 0.080 ppm and above causes 

airway inflammation, increased permeability, and increased responsiveness provide 

mechanistic support for the observed epidemiological associations with regard to 

exacerbations of asthma at concentrations below 0.080 ppm. The mechanism of ozoneinduced decrements in lung function may not be related to airway inflammation. 

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, 

showing effects on FEV1 and respiratory symptoms, in the context of the larger body of 

evidence from controlled human exposure studies, mentioned above, inform our 

understanding of the health effects to healthy adults at exposure levels from 0.060 to 

0.070 ppm?

At the time of the last EPA review of the evidence on the health effects of ozone, only the 

study of Adams et al. (2006) provided data on exposures at concentrations ≤0.080 ppm. 

Although that study as published reported a non-significant group decrease (~3%) in FEV1, 

several subjects experienced decreases ≥10%, which have been previously determined to be 

of clinical relevance. These results fit well with those from multiple other studies of ozone’s 

effect on lung function at concentrations ≥0.080 ppm, which have consistently shown that 

some individuals are more sensitive to this effect of ozone than others. The selection of a 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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NAAQS for ozone needs to consider an adequate margin of safety to protect the most 

sensitive subgroup of individuals. Since the scientific evidence was reviewed for the 

preparation of the 2006 Criteria Document for Ozone, the results of the Adams et al. (2006) 

study have been carefully reanalyzed (Brown et al., 2008) and actually show a statistically 

significant group effect. In addition, two other studies have shown statistically significant 

decrements in FEV1 after 6.6-hour exposures to 0.070 ppm (Schelgele et al., 2009) and 0.060 

ppm (Kim et al., 2011), respectively.

4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, 

what is the scientific importance of the small, group mean FEV1 decrements relative to 

the findings that 7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please 

consider this question from both a public health and a clinical perspective.

From a clinical perspective, a 10% decrement in FEV1 is often associated with respiratory 

symptoms, especially in individuals with pre-existing pulmonary or cardiac disease. For 

example, people with chronic obstructive pulmonary disease have decreased ventilatory 

reserve (i.e., decreased baseline FEV1) such that a ≥10% decrement could be associated with 

moderate to severe respiratory symptoms. From a public health perspective, the exposure 

and risk assessment conducted for the last review of the ozone NAAQS clearly document that 

a substantial proportion of the U.S. population is exposed to levels of ozone at the various 

alternative standards considered. This means that even if a NAAQS of 0.060 ppm were to be 

selected, some sensitive individuals could still be exposed to concentrations that could cause 

them to have a clinically relevant decrement in lung function.

5. The evidence, including that summarized above, indicates that susceptible populations 

may have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy 

adults, as well as the epidemiological studies of susceptible groups, to inform a judgment 

on the effects of ozone exposure on susceptible populations?

Controlled human exposure studies have shown that individuals with asthma have enhanced 

responses to ozone, in terms of both airway inflammation and lung function decrements with 

exercise. Epidemiological studies have shown that such individuals are at increased risk of 

exacerbations of their disease on or shortly after days with elevated ambient ozone 

concentrations. Taken together, the results of these studies provide strong evidence that 

people with asthma are a subgroup of the population with increased susceptibility to ozone. 

Given the effects on lung function that have been documented in healthy adults exposed to 

ozone at concentrations ≤0.080 ppm, a NAAQS with a margin of safety is necessary to 

protect the susceptible population of children and adults with asthma. Older individuals 

with pre-existing lung and heart disease, who have not been adequately investigated in 

controlled human exposure studies, as well as young children who cannot participate in such 

studies, may also be more susceptible than the healthy young adults who have been studied to 

date.

6. To what extent does your confidence that the effects observed in epidemiological studies 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -8-

are attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels 

in the proposed range as compared to the higher levels?

While the effects of ozone cannot be easily isolated from the effects of other pollutants in 

epidemiological studies, health care utilization for asthma has been shown to decrease when 

ozone concentrations are decreased. For example, when traffic density was decreased during 

the Summer Olympic Games in Atlanta in 1996, there was significantly decreased use of 

pediatric care for asthma that correlated best with a reduction in peak ozone concentrations 

(Friedman et al., 2001). In this study, the relative risk of asthma events increased stepwise at 

cumulative ozone concentrations 0.060 to 0.089 ppm and 0.090 ppm or more compared with 

ozone concentrations of less than 0.060 ppm. The reduction of the adverse effects on asthma 

in this study was dependent on reduction of ozone exposures to levels below 60 ppb.

7. EPA’s exposure assessment quantified the number of all children and asthmatic children 

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 

and 0.070 ppm. Considering the patterns of change in the estimates of exposures of 

concern at and above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties 

and limitations in the estimates, what is the relative importance from a public health 

perspective of the estimated reductions in exposures of concern, as well as the exposures 

remaining, for alternative standards across the proposed range?

The cumulative evidence to date on the ozone exposure-lung function response relationship 

strongly suggests that it is linear with no threshold, at least through 0.060 ppm. Therefore, it 

is reasonable to assume a similar exposure-response relationship for exacerbations of 

asthma. Considering the patterns of change in the estimates of exposures at alternative 

standards, as well as the uncertainties and limitations of the estimates, it is likely that 

susceptible individuals would still be adversely affected at a NAAQS of 0.060 ppm, although 

the number of such individuals would be substantially lower than at higher alternate 

standards.

8. EPA’s quantitative risk assessment estimated the numbers of occurrences of various 

ozone related health effects associated with just meeting alternative standard levels down 

to a standard level of 0.064 ppm. Considering the patterns of change in the estimates of 

health effects in the risk assessment at the alternative standard levels, and the 

uncertainties and limitations in the estimates, what is the relative importance from a 

public health perspective of the estimated reductions in risk, as well as the risk 

remaining, for alternative standards across the proposed range? Please consider this 

question in light of the scientific evidence as a whole.

In addition to what I have stated in my responses to the previous seven questions, it is also 

important to consider the effect of reductions in exposures to ozone on mortality with the 

alternate standards. Although the evidence from epidemiological studies of ozone-related 

mortality published prior to 2006 was not considered sufficiently robust by CASAC to serve 

as the basis for a new NAAQS, EPA estimated effects on mortality in the exposure and risk 

assessment components of the 2007 Staff Paper. The evidence regarding the ozone exposure-
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -9-

mortality relationship has grown stronger since the publication of the Staff Paper (e.g., 

Jerrett et al., 2009) and a mortality effect was seen at concentrations below the current 

standard.

References Cited:

Brown JS, Bateson TF, McDonnell WF. 2008. Effects of exposure to 0.06 ppm ozone on FEV1 in 

humans: A secondary analysis of existing data. Environ Health Perspect 116:1023-1026.

Friedman MS, Powell KE, Hutwagner L, Graham LM, Teague WG. 2001. Impact of changes in 

transportation and commuting behaviors during the 1996 Summer Olympic Games in Atlanta on 

air quality and childhood asthma. JAMA 285:897-905.

Jerrett M, Burnett RT, Pope CA 3rd, Ito K, Thurston G, Krewski D, Shi Y, Calle E, Thun M. 2009. 

Long-term ozone exposure and mortality. N Engl J Med 360:1085-1095.

Kim CS, Alexis NE, Rappold AG, Kehrl H, Hazucha Mj, Lay JC, Schmitt MT, Case M, Devlin 

RB, Peden DB, Diez-Sanchez D. 2011. Lung function and inflammatory responses in healthy 

young adults exposed to 0.06 ppm ozone for 6.6 hours. Am J Respir Crit Care Med Jan 7 [Epub 

ahead of print].

Schelegle ES, Morales CA, Walby WF, Marion S, Allen RP. 6.6-hour inhalation of ozone 

concentration from 60 to 87 parts per million in healthy humans. 2009. Am J Respir Crit Care Med

180:265-272.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -10-

Joe Brain

What is your advice on the overall strengths and limitations of the evidence from controlled human 

exposure and epidemiological studies and the results of the exposure and risk assessments, in the 

context of EPA's selection of a standard level within the proposed range that would be requisite to 

protect public health with an adequate margin of safety, including the need to protect susceptible 

populations, such as children and people with asthma?

The quality of the controlled human exposures to ozone is extremely good. Established

investigators at distinguished institutions did their best to measure pulmonary function changes. 

There are even some bronchoalveolar lavage data. In general, there are more data here than for 

many other regulated and unregulated pollutants. 

At the same time, there are limitations worth considering. They are primarily carried out in 

healthy, young, non-smoking volunteers. Data for susceptible populations are modest at best. It 

should also be noticed that most of the studies involve exercise as a necessary component to reveal 

responses to ozone. Of course, many Americans exercise, so that’s not irrelevant. But it is 

important to keep in mind that higher levels of ventilation, and especially switching from nose to 

mouth breathing, have a substantial effect on ozone responses. Finally, the issue of adaptation has 

generally not been addressed. On the one hand, when humans are chronically exposed to steadystate levels of ozone, they may adapt, and their responses may be diminished. On the other hand, if 

they have not seen these levels of ozone recently, responses may be greater.

There is also a considerable amount of epidemiologic data as well. This has the advantage of more 

diverse subjects, but typically less invasive responses – primarily limited to pulmonary function 

studies. As noted elsewhere, in contrast to chamber studies where exposures are limited to ozone, 

epidemiologic studies inevitably involve a mixture of pollutants. Identifying changes relating to 

ozone only may be difficult or impossible.

2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have provided 

evidence of other health effects, including inflammation and increased airway responsiveness 

which may occur through different physiological mechanisms than the reduction in FEV1, how 

should the results of these studies inform our understanding the health effects to healthy adults at 

exposures levels from 0.060 to 0.070 ppm?

The database reviewed and summarized is consistent with past evaluations, but emphasizes the fact 

that responses to ozone can be seen within the proposed range of 0.06-0.07 ppm, especially when 

exercise is included.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -11-

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence from

controlled human exposure studies, mentioned above, inform our understanding of the health

effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

The data mentioned above, especially inflammation, are important. If responses to ozone were 

completely limited to reversible pulmonary function changes, we would be less concerned. 

However, chronic inflammation and the presence of increased neutrophils and neutrophil elastase 

raise concerns. Chronic inflammation and resulting increased levels of reactive oxygen species 

(ROS) may result in cumulative irreversible damage. These changes raise concerns about 

increases in morbidity and mortality caused by chronic exposure to ozone.

Unfortunately, the number of studies at 0.06 ppm of ozone are more limited than those at higher 

concentrations of ozone. Like other pollutants, our confidence about the magnitude of health 

effects increases as we go to higher levels. However, the limited studies that do exist at 0.06 ppm 

ozone demonstrate that there are responses among some individuals. Like PM2.5, there is the 

absence of a clearly defined threshold. Instead, we can always find a susceptible group that 

responds to lower and lower levels.

4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, what 

is the scientific importance of the small, group mean FEV1 decrements relative to the findings that 

7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please consider this question from 

both a public health and a clinical perspective.

We must not only look at average responses to a given pollutant exposure. We need to take into 

consideration the entire distribution of responses, particularly that of outliers. We must protect 

even a minority of exposed subjects, if they experience significant declines in pulmonary function. 

The existence of susceptible subgroups will usually drive standard setting.

5. The evidence, including that summarized above, indicates that susceptible populations may have 

greater responses than healthy people. In light of this evidence, how can we appropriately use the 

results of controlled human exposure studies conducted on healthy adults, as well as the

epidemiological studies of susceptible groups, to inform a judgment on the effects of ozone

exposure on susceptible populations?

As indicated above, the presence of susceptible populations and the magnitude of their increased 

responsiveness is a key factor in regulation setting. As the question suggests, an advantage of 

epidemiologic studies is that they usually encompass a wider range of populations including older, 

younger, and sicker individuals. In contrast, the chamber studies typically exclude these much 

more susceptible populations. Asthmatics have been studied to a certain extent. However, it is 

also true that epidemiologic studies generally don’t utilize exercise to the same degree as chamber 

studies for ozone. Moreover, the sickest individuals probably spend less time out of doors where 

ozone levels are highest. The answer to question five is that both chamber studies and 

epidemiologic studies need to be considered and integrated.

6. To what extent does your confidence that the effects observed in epidemiological studies are

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the

proposed range as compared to the higher levels?
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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As the question implies, out confidence in attributing the effects observed in epidemiologic studies 

to ozone alone is usually limited and decreases with progressively lower levels of ozone. As the 

question implies, ozone never exists by itself in outside air. There are other sources of oxidant 

injury, as well as other pollutants known to produce some of the same effects, such as decreases in 

pulmonary function. 

Ozone concentrations/exposures throughout the day definitely have a “signature” because of the 

important role of sunlight in generating ozone from other gaseous pollutants. Then the time course 

of some acute responses may be helpful in identifying the role of ozone per se. More generally, 

however, this dilemma suggests that we should be thinking more and more about the aggregate 

effects of different types of air pollution, such as those that collectively produce oxidant injury.

7. EPA’s exposure assessment quantified the number of all children and asthmatic children likely 

to be exposed to specific benchmark levels of ozone, including in particular 0.060 and 0.070 ppm. 

Considering the patterns of change in the estimates of exposures of concern at and above the 0.060 

and 0.070 ppm benchmark levels, and the uncertainties and limitations in the estimates, what is the 

relative importance from a public health perspective of the estimated eductions in exposures of 

concern, as well as the exposures remaining, for alternative standards across the proposed range?

As indicated before, focusing on susceptible individuals is appropriate. Children represent a 

familiar and important susceptible class. Even at rest. their ventilation per kilogram is higher than 

that of adults. Moreover, they tend to be much more active and more likely to be exercising. 

Moreover, if there are chronic, cumulative changes produced by ozone, there is a longer period of 

lifespan ahead for children where these effects may become manifest. The existing data and these 

considerations of children and other susceptible groups suggest that continued reduction of ozone 

exposures will produce public health benefits. Of course, attention to other sources of oxidant 

injury from other air pollutants should be emphasized as well.

8. EPA’s quantitative risk assessment estimated the numbers of occurrences of various ozonerelated health effects associated with just meeting alternative standard levels down to a standard

level of 0.064 ppm. Considering the patterns of change in the estimates of health effects in the risk 

assessment at the alternative standard levels, and the uncertainties and limitations in the estimates, 

what is the relative importance from a public health perspective of the estimated reductions in risk, 

as well as the risk remaining, for alternative standards across the proposed range? Please 

consider this question in light of the scientific evidence as a whole.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -13-

I believe that each year brings additional scientific evidence documenting the importance of ozone 

exposures, both acute and chronic, at progressively lower levels. Maintaining or perhaps lowering 

the ozone standard will reduce the numbers of people who suffer from ozone-induced adverse 

health effects. I also agree with the suggestion that even tighter regulatory standards will not 

eliminate ozone-induced changes entirely – especially in the most susceptible groups. Because of 

variations in susceptibility and exposure, no threshold for ozone effects is likely. Moreover, there is 

no plausible scenario to reduce ozone levels to zero, given the multiplicity of industrial and natural 

sources.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -14-

James Gauderman

Charge Question #4. With respect to the information from controlled human exposure 

studies at 0.060 ppm O3, what is the scientific importance of the small, group mean FEV1 

decrements relative to the findings that 7 to 20% of the subjects experienced FEV1 

decrements ≥ 10%? Please consider this question from both a public health and a clinical 

perspective.

In the re-analysis of Adams (2006) study of 30 subjects by EPA (Brown, 2007), a small 

but statistically significant decline in FEV1 was observed. Specifically, a 2.85% mean O3-

induced decline in FEV1 was observed following 6.6 hr square wave exposure to 0.060 

ppm O3 compared to 6.6 hr filtered air (FA) exposure. The statistical analysis by EPA 

was based on a straightforward paired comparison, and they conservatively used a 

nonparametric sign test to obtain a p-value of 0.002 for the 0.06 ppm vs. FA comparison. 

Alternative, more powerful analytic methods using either a Wilcoxon signed-rank test or a 

paired t-test yielded even lower p-values in the EPA analysis. The EPA comparison 

remained significant after a Bonferroni correction for multiple comparisons. The original 

analysis of the data by Adams did not find a significant difference in FEV1 between the 

0.06 and FA exposure conditions. However, that analysis was based on a Scheffe 

correction for multiple comparisons, which is known to have very low power for the type of 

pairwise comparisons conducted by Adams compared to other well-known methods for 

multiple-testing correction (Kirk, 1982). Thus, from my understanding of the statistical 

analyses that have been conducted, I would argue that the analysis by EPA should be 

preferred to that of Adams for the specific comparison of the FEV1 effects of 0.06 ppm 

exposure relative to FA exposure. 

Of the 30 study subjects in Adams, 24 showed some evidence for an O3-induced decline 

in FEV1, and 2 of the 30 (7%) experienced a decline greater than 10%. Although the 

sample size is relatively small, the consistency of effects across O3 exposure levels, as 

well as the consistency with effects observed by an earlier independent study 

(McDonnell, 2002), indicates that the observed deficits in FEV1 at the 0.060 ppm from the 

Adams study are not spurious. In other words, it is likely that prolonged exposure to 0.06 

ppm O3 causes a general shift in the distribution of FEV1 towards lower values. The 

following plot of the Adams data, derived from Figure 8-2 of Volume I of the “Air Quality 

Criteria for Ozone and Related Photochemical Oxidants, 2006” document, shows an 

approximate normal distribution in the O3-induced changes in FEV1 with exposure to 

0.06 ppm. 
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policy. Do not cite or quote.

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Although the mean decrement is less than 3% and would not be considered clinically 

important, the shift to the right in this distribution pushes a fraction of subjects into the 

region that becomes clinically interesting (>10%). All of the Adams study subjects were 

healthy volunteers. From a public health standpoint, these results suggest that a large 

number of individuals in the general population (that are otherwise healthy), are likely to 

experience FEV1 deficits greater than 10% with prolonged exposure to 0.06 ppm O3. 

Although most healthy individuals can probably sustain a short-term 10-15% decline in 

FEV1 with little or no noticeable effect, it is not clear how they might be affected in the 

longer term if they experience repeated lung function deficits due to 0.06 ppm or greater 

O3 exposures over multiple days or weeks. Based on several other controlled exposure 

studies, we might expect that O3-induced FEV1 deficits in subjects with an existing 

respiratory condition (e.g. asthma) would be shifted even further to the right compared to 

the above figure. A 10-15% (or greater) pollution-related deficit in FEV1 in an individual 

with an existing respiratory condition is large enough that it could cause a clinically 

observable response. 
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These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -16-

Rogene Henderson

February 9, 2011

1. What is your advice on the overall strengths and limitations of the evidence from controlled 

human exposure and epidemiological studies and the results of the exposure and risk assessments, 

in the context of EPA's selection of a standard level within the proposed range that would be 

requisite to protect public health with an adequate margin of safety, including the need to protect 

susceptible populations, such as children and people with asthma?

I reviewed the previous correspondence between CASAC and the Agency as well as the 

Federal Register notice of the reconsideration of the 2008 primary NAAQS for ozone and 

found that the evidence from controlled human exposures and epidemiological studies, as 

well as the results of the exposure and risk assessments, fully supported the selection of the 

primary ozone standard in the range of 0.060 to 0.070 ppm to protect public health with a 

margin of safety. Human exposure studies provide the most direct evidence of the health 

effects on humans and the studies clearly show that adverse effects occur in some healthy 

adults after exposure for 6.6 hr to 0.060 ppm ozone. This finding has recently been 

confirmed in clinical studies in 59 healthy young adults exposed to 0.060 ppm ozone for 6.6 

hours (Kim et al., dol:10.1164/rccm.201011-18130C, Lung function and inflammatory 

responses in healthy young adults exposed to 0.060 ppm ozone for 6.6 hours.) Asthmatic 

persons are known to be more sensitive to ozone than are healthy persons. Therefore, to 

provide some margin of safety, the standard must take into consideration these sensitive 

subpopulations.

2.. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have

provided evidence of other health effects, including inflammation and increased airway

responsiveness which may occur through different physiological mechanisms than the reduction in 

FEV1, how should the results of these studies inform our understanding the health effects to 

healthy adults at exposures levels from 0.060 to 0.070 ppm?

These additional health-effect endpoints should definitely be taken into account in setting the 

standards to the extent that information is available. The recent publication by Kim et al. 

(2011) provides information on both types of endpoints endpoints.

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing 

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence from 

controlled human exposure studies, mentioned above, inform our understanding of the health 

effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

The results of human controlled exposures to 0.080. 0.070. and 0.060 form a continuum of 

levels of effect that must all be considered in setting a standard with a margin of safety. The 

results of the 0.06 ppm exposures provide increased confidence and decreased uncertainty 

about the health effects of ozone exposure at that concentration. Thus it essential that the 
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policy. Do not cite or quote.

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results of the controlled human exposure studies at 0.060 ppm be taken into consideration for 

the understanding of the health effects of ozone in the range of 0.070-0.060 ppm.

4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, what 

is the scientific importance of the small, group mean FEV1 decrements relative to the findings that 

7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please consider this question from 

both a public health and a clinical perspective.

I am not a clinician, so will not comment on that aspect. From a public health viewpoint, I 

think the effect is significant. The Clean Air Act requires that a margin of safety be taken 

into account, and from a public health viewpoint, the 0.060 level does induce adverse health 

effects in a portion of the healthy community and those effects are likely to be greater in the 

asthmatic population.

5. The evidence, including that summarized above, indicates that susceptible populations may have 

greater responses than healthy people. In light of this evidence, how can we appropriately use the 

results of controlled human exposure studies conducted on healthy adults, as well as the 

epidemiological studies of susceptible groups, to inform a judgment on the effects of ozone 

exposure on susceptible populations.

The epidemiology data showing increased use of medication, school absences, and hospital 

admissions is one way to evaluate the response of sensitive populations to ozone. The 

controlled human exposures gives you a ceiling level which is higher than the level that 

would be protective of sensitive populations.

6. To what extent does your confidence that the effects observed in epidemiological studies are 

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the 

proposed range as compared to the higher levels?

For any pollutant, as one goes down the dose-response curve to lower levels of exposure, 

confidence in the effects seen decrease and uncertainties increase. However, the effects of 

ozone exposure can best be considered as a continuum, with decreasing incidence or severity 

with decreasing exposure. However, the endpoints of concern remain the same, providing 

some confidence that the effects are due mainly to ozone.

7. . EPA’s exposure assessment quantified the number of all children and asthmatic children likely 

to be exposed to specific benchmark levels of ozone, including in particular 0.060 and 0.070 ppm. 

Considering the patterns of change in the estimates of exposures of concern at and above the 0.060 

and 0.070 ppm benchmark levels, and the uncertainties and limitations in the estimates, what is the 

relative importance from a public health perspective of the estimated reductions in exposures of 

concern, as well as the exposures remaining, for alternative standards across the proposed range?

The exposure assessments were reasonable and made with the best data available. The 

assessments indicate that the number of children and asthmatic children exposed to ozone 

levels of concern is significant from a public health viewpoint.
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policy. Do not cite or quote.

Page -18-

8. . EPA’s quantitative risk assessment estimated the numbers of occurrences of various ozone 

related health effects associated with just meeting alternative standard levels down to a standard 

level of 0.064 ppm. Considering the patterns of change in the estimates of health effects in the risk 

assessment at the alternative standard levels, and the uncertainties and limitations in the estimates, 

what is the relative importance from a public health perspective of the estimated reductions in risk, 

as well as the risk remaining, for alternative standards across the proposed range? Please consider 

this question in light of the scientific evidence as a whole.

The CASAC took into account the uncertainties associated with assessing the risks to low 

levels of ozone and concluded that in a range of 0.060 to 0.070 ppm exposures, one could have 

confidence in the observed effects. I am still in agreement with that conclusion. 
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Philip K. Hopke

The charge questions provided to the ozone panel revolve primarily around the toxicological and 

epidemiological evidence for the adverse health effects of exposure to ozone and other oxidants. 

One critical aspect that I believe is generally lost in the discussion is the presence of other 

photochemical oxidants. Thus, if we are looking at controlled exposures to ozone alone, we will 

be underestimating the effects of the total collection of oxidants in the ambient atmosphere. 

Epidemiology would take these other oxidants into account to some greater or lesser extent with 

respect to the covariance of the other ambient oxidants with ozone. However, central monitors 

particularly monitors typically placed in downwind locations in urban areas to avoid significant 

titration effects of motor vehicle emissions, may not be an adequate measure of population 

exposure across that urban area. 

We also have to recognize the full extent of the change made with the promulgation of the 2008 

ozone NAAQS. By changing the reported precision of the measurements, we have effectively 

lowered the standard from 84 ppb to 75.4 ppm and not from 80 to 75 ppb. This difference is a 

relatively large reduction whose effects have not yet been fully felt. Given that there is another 

review underway and this review is not supposed to take new literature into account, my 

recommendation would be that the standard not be lowered any further than 70.0 ppb, the upper 

end of the range judged as likely to be protective of public health, and reexamine all of the body of 

information available as part of the current round of review. Then a better informed judgment can 

be rendered.

Charge Question #4. With respect to the information from controlled human exposure 

studies at 0.060 ppm O3, what is the scientific importance of the small, group mean FEV1 

decrements relative to the findings that 7 to 20% of the subjects experienced FEV1 

decrements ≥ 10%? Please considerthis question from both a public health and a clinical 

perspective.

In the re-analysis of Adams (2006) study of 30 subjects by EPA (Brown, 2007), a small 

but statistically significant decline in FEV1 was observed. Specifically, a 2.85% mean O3-

induced decline in FEV1 was observed following 6.6 hr square wave exposure to 0.060 

ppm O3 compared to 6.6 hr filtered air (FA) exposure. The statistical analysis by EPA 

was based on a straightforward paired comparison, and they conservatively used a 

nonparametric sign test to obtain a p-value of 0.002 for the 0.06 ppm vs. FA comparison. 

Alternative, more powerful analytic methods using either a Wilcoxon signed-rank test or a 

paired t-test yielded even lower p-values in the EPA analysis. The EPA comparison 

remained significant after a Bonferroni correction for multiple comparisons. The original 

analysis of the data by Adams did not find a significant difference in FEV1 between the 

0.06 and FA exposure conditions. However, that analysis was based on a Scheffe 

correction for multiple comparisons, which is known to have very low power for the type of 

pairwise comparisons conducted by Adams compared to other well-known methods for 

multiple-testing correction (Kirk, 1982). Thus, from my understanding of the statistical 

analyses that have been conducted, I would argue that the analysis by EPA should be 
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policy. Do not cite or quote.

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preferred to that of Adams for the specific comparison of the FEV1 effects of 0.06 ppm 

exposure relative to FA exposure. 

Of the 30 study subjects in Adams, 24 showed some evidence for an O3-induced decline 

in FEV1, and 2 of the 30 (7%) experienced a decline greater than 10%. Although the 

sample size is relatively small, the consistency of effects across O3 exposure levels, as 

well as the consistency with effects observed by an earlier independent study 

(McDonnell, 2002), indicates that the observed deficits in FEV1 at the 0.060 ppm from the 

Adams study are not spurious. In other words, it is likely that prolonged exposure to 0.06 

ppm O3 causes a general shift in the distribution of FEV1 towards lower values. The 

following plot of the Adams data, derived from Figure 8-2 of Volume I of the “Air Quality 

Criteria for Ozone and Related Photochemical Oxidants, 2006” document, shows an 

approximate normal distribution in the O3-induced changes in FEV1 with exposure to 

0.06 ppm. 

Although the mean decrement is less than 3% and would not be considered clinically 

important, the shift to the right in this distribution pushes a fraction of subjects into the 

region that becomes clinically interesting (>10%). All of the Adams study subjects were 

healthy volunteers. From a public health standpoint, these results suggest that a large 

number of individuals in the general population (that are otherwise healthy), are likely to 

experience FEV1 deficits greater than 10% with prolonged exposure to 0.06 ppm O3. 

Although most healthy individuals can probably sustain a short-term 10-15% decline in 

FEV1 with little or no noticeable effect, it is not clear how they might be affected in the 

longer term if they experience repeated lung function deficits due to 0.06 ppm or greater 

O3 exposures over multiple days or weeks. Based on several other controlled exposure 

studies, we might expect that O3-induced FEV1 deficits in subjects with an existing 

respiratory condition (e.g. asthma) would be shifted even further to the right compared to 

the above figure. A 10-15% (or greater) pollution-related deficit in FEV1 in an individual 

with an existing respiratory condition is large enough that it could cause a clinically 

observable response. 
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These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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Charge Question 5. The evidence, including that summarized above, indicates that susceptible 

populations may have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy adults, as 

well as the epidemiological studies of susceptible groups, to inform a judgment on the effects of 

ozone exposure on susceptible populations? 

Response -- In many ways, the lowest exposure level of 0.06 ppm showing some symptom 

changes and statistically significant lung function changes in healthy subjects in an EPA analysis 

conducted for the last O3 NAAQS review represented a greatest lower bound on the ozone 

concentration of public health concern. In all of the controlled human exposure studies at 0.08-ppm 

ozone and below, a reasonable percentage of healthy subjects have lung function changes much 

higher than the average response (e.g., FEV1 changes > 10 %). While FEV1 changes > 10% may 

still allow healthy individuals to go about their normal daily activities, individuals with 

compromised lungs, such as asthmatics, incur significant health impacts with such lung function 

changes. As CASAC has noted in the past to the Agency, evidence is accumulating that persons 

with asthma, and particularly children, are more sensitive and experience larger decrements in lung 

function due to O3 exposure than do healthy volunteers. 

This, coupled with the fact that a number of epidemiology studies discussed in the last review were 

showing O3-related effects on various health endpoints (e.g., emergency department visits, 

increased hospital emissions, and mortality increases) at relatively low exposure levels leads one to 

conclude that O3 may cause effects even below 0.06 ppm. Since strengthening such a conclusion 

would need additional data from new studies, the CASAC concluded at the last review that the 

lower range of consideration for revision of the NAAQS should be 0.060 ppm O3. By doing so, the 

CASAC felt that margin of safety considerations would better be met than at 0.070 ppm O3. 

Moreover, since the relative strength of the science is weaker as one lowers the O3 concentration 

under consideration, a range of 0.060 to 0.070 ppm O3 allows the Administrator to place her 

judgment on the weight that any uncertainties and limitations in the science play in selecting an 

exposure level protective of public health.
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Michael T. Kleinman

1. What is your advice on the overall strengths and limitations of the evidence from controlled

human exposure and epidemiological studies and the results of the exposure and risk

assessments, in the context of EPA's selection of a standard level within the proposed range that

would be requisite to protect public health with an adequate margin of safety, including the need

to protect susceptible populations, such as children and people with asthma?

a. Controlled Human Exposure:

Controlled human studies to O3 were, in large part, conducted with volunteers that were 

relatively young, in good physical condition and were non-smokers. The proposed range 

of 0.060 to 0.070 ppm was identified after a thorough and intensive review of the 

available studies and was an important part of the data used to identify that range 

(Horstman et al., 1990, Adams, 2003b, a, 2006). However that data did not stand alone 

and was view in context with population studies that showed significant effects at and 

perhaps below the selected range and mechanistic studies that provided evidence of 

biological plausibility. 

b. Epidemiological Studies: Epidemiological studies and panel studies with sensitive 

populations, e.g. asthmatic adolescents) have demonstrated significant effects at 

exposures that were within, and sometimes below, the proposed range of O3 

concentrations. There was adequate discussion of the strengths and weaknesses of these 

study in the ISA and risk documents that were previously reviewed. 

c. Advice: Given the points in a and b above, and the fact that subsequent studies (Schelegle 

et al., 2009, Kim et al., 2011) did not negate the previous conclusions, there is not 

adequate reason to alter the Panel’s prior advice to the Administrator.

2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have

provided evidence of other health effects, including inflammation and increased airway

responsiveness which may occur through different physiological mechanisms than the reduction

in FEV1, how should the results of these studies inform our understanding the health effects to

healthy adults at exposures levels from 0.060 to 0.070 ppm?

A characteristic response to low O3 levels is mucosal neutrophilic inflammation probably

mediated by phospholipid-derived products and by epithelial cell-derived chemokines and 

cytokines (Bromberg and Koren, 1995). This response may be poorly correlated with lung 

function changes because the time course of development for these responses is different from that 

for changes in FEV1. However these data provide important components of the biological 

plausibility and advance our understanding of the mechanisms by which O3 affects health. It 

should be noted that inflammatory effects are likely to be more serious for individuals with chronic 

lung diseases. This is consistent with the exposure chamber study findings that individuals with 

chronic obstructive pulmonary disease had significantly greater losses of pulmonary function (19% 

from their baseline) than did healthy controls when exposed to O3 during light exercise (Gong et 

al., 1997). While these studies are often performed at exposure concentrations higher than typical 

ambient conditions, they serve to identify disease-relevant mechanisms and also to underscore the 

inherent variability of even healthy populations with respect to their responses to O3. It is 
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policy. Do not cite or quote.

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important that we consider this variability as we examine whether the current or proposed ambient 

concentration ranges provide an adequate margin of safety for sensitive individuals in the 

population.

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence from

controlled human exposure studies, mentioned above, inform our understanding of the health

effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

As stated in the charge document, “The controlled human exposure studies at 0.060 ppm O3 are 

limited, with only two published studies (Adams 2003a and 2006) available from one investigator. 

However, the Adams studies are well-designed and employed an exposure protocol that was 

consistent with earlier studies (Horstman et al., 1990; McDonnell et al., 1991). At the 0.080 ppm 

level, the subjects did not appear to be more responsive to O3 than subjects in previous studies, as 

the observed response was similar to that of previous studies (Horstman et al., 1990, Mcdonnell et 

al., 1991, Adams, 2003b, a, 2006). Although of much smaller magnitude, the temporal pattern of 

the 0.060 ppm response was generally consistent with the temporal patterns of response to higher 

concentrations of O3 in this and other studies. These findings are not unexpected because the 

previously observed group mean FEV1 responses to 0.080 ppm were in the range of 6–9% 

suggesting that exposure to lower concentrations of O3 would result in

smaller, but real group mean FEV1 decrements, i.e., the responses to 0.060 ppm O3 are consistent

with the presence of a smooth exposure-response curve with responses that do not end abruptly

below 0.080 ppm (75 FR 2950)”.

A graph showing an exponential fit (R2=0.87) to the group mean changes in FEV1 from the Adams 

et al. (2006) study only are shown as the solid line in context with data from more recent studies 

demonstrates that the previous conclusions remain valid. The dashed linen is an exponential fit 

(R2=0.85) to all the data.
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4. With respect to the information from controlled human exposure studies at 0.060 ppm O3,

what is the scientific importance of the small, group mean FEV1 decrements relative to the

findings that 7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please consider this

question from both a public health and a clinical perspective.

The human exposure studies used relatively small populations of healthy, non-smoking young 

individuals. The within group variability of this preselected relatively homogeneous population 

might underestimate that of the population at large. The 7-20 percent of individuals with changes 

in pulmonary function that would be considered to be clinically relevant (i.e. 10%) should have 

great weight in the evaluation of potential public health risk, especially for the less homogeneous 

population at large.

5. The evidence, including that summarized above, indicates that susceptible populations may

have greater responses than healthy people. In light of this evidence, how can we appropriately

use the results of controlled human exposure studies conducted on healthy adults, as well as the

epidemiological studies of susceptible groups, to inform a judgment on the effects of ozone

exposure on susceptible populations?

There are very few controlled human studies that have been conducted with susceptible groups . 

The Gong, et al. (1997) study showed that for some outcomes individuals with COPD were 

considerably more susceptible to O3 effects than were healthy individuals, when results were 

expressed in terms of changes from their respective baseline levels. Individuals with COPD have 
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diminished respiratory reserves and are likely to have less capacity to compensate for adverse 

environmental effects. This might be intensified when such individuals are under some stress, such 

as the light exercise imposed during the Gong et al. (1997) study. Thus one should consider that 

even though the potential benefits accruing from reducing O3 exposures below the current standard 

might be considered small based on responses of healthy subjects, there might still be important 

benefits for individuals with compromised lungs and hearts. 

6. To what extent does your confidence that the effects observed in epidemiological studies are

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the

proposed range as compared to the higher levels?

It has been very difficult to apportion effects in epidemiological studies between O3 and copollutants. However some studies that examined multiple pollutant models (i.e. O3 and particulate 

matter) have shown independent effects of O3. There might be a seasonal characteristic since the 

strongest associations between O3 and health outcomes occur in the warm season months. The 

uncertainties at lower concentrations are greater. However the epidemiological studies are 

consistent with the controlled human studies which do not suffer from multiple pollutant 

interactions. Thus reducing O3 concentrations will be expected to reduce adverse effects, 

especially in more susceptible members of the population.

7. EPA’s exposure assessment quantified the number of all children and asthmatic children

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 and

0.070 ppm. Considering the patterns of change in the estimates of exposures of concern at and

above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties and limitations in the

estimates, what is the relative importance from a public health perspective of the estimated

reductions in exposures of concern, as well as the exposures remaining, for alternative standards

across the proposed range?

The exposures of concern are at levels at which controlled studies found significant pulmonary 

function changes in health adults. Asthmatic children and others with pre-existing heart and lung 

diseases are likely to be more susceptible to effects of O3 than are healthy young adults. Some 

epidemiological studies have identified effects at or below those levels. The panel’s previous 

deliberations and the EPA assessments were based on an intensive search of the scientific literature 

at the time (2005 and earlier). The conclusions drawn remain valid and are, in fact, substantiated 

by more recent studies. The reduction of ozone exposures is important from the public health 

perspective.

8. EPA’s quantitative risk assessment estimated the numbers of occurrences of various ozonerelated health effects associated with just meeting alternative standard levels down to a standard

level of 0.064 ppm. Considering the patterns of change in the estimates of health effects in the

risk assessment at the alternative standard levels, and the uncertainties and limitations in the

estimates, what is the relative importance from a public health perspective of the estimated

reductions in risk, as well as the risk remaining, for alternative standards across the proposed

range? Please consider this question in light of the scientific evidence as a whole.

The previous deliberations of this panel concluded “Beneficial effects in terms of reduction of 

adverse health effects were calculated to occur at the lowest concentration considered (i.e., 0.064 
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Page -26-

ppm). (Henderson, 10/24/06, p.4).” The potential benefits accrued to literally thousands of 

individuals when combined improvements with respect to mortality and morbidity were 

considered. This is important from the public health standpoint. (Also see previous points).

Adams WC (2003a) Comparison of chamber and face mask 6.6-hour exposure to 0.08 ppm ozone 

via square-wave and triangular profiles on pulmonary responses. Inhal Toxicol 15:265-

281.

Adams WC (2003b) Relation of pulmonary responses induced by 6.6-h exposures to 0.08 ppm 

ozone and 2-h exposures to 0.30 ppm ozone via chamber and face-mask inhalation. Inhal 

Toxicol 15:745-759.

Adams WC (2006) Comparison of chamber 6.6-h exposures to 0.04-0.08 PPM ozone via squarewave and triangular profiles on pulmonary responses. Inhal Toxicol 18:127-136.

Bromberg PA, Koren HS (1995) Ozone-induced human respiratory dysfunction and disease. 

Toxicol Lett 82-83:307-316.

Gong H, Jr., Shamoo DA, Anderson KR, Linn WS (1997) Responses of older men with and without 

chronic obstructive pulmonary disease to prolonged ozone exposure. Arch Environ Health 

52:18-25.

Horstman DH, Folinsbee LJ, Ives PJ, Abdul-Salaam S, McDonnell WF (1990) Ozone concentration 

and pulmonary response relationships for 6.6-hour exposures with five hours of moderate 

exercise to 0.08, 0.10, and 0.12 ppm. Am Rev Respir Dis 142:1158-1163.

Kim CS, Alexis NE, Rappold AG, Kehrl H, Hazucha MJ, Lay JC, Schmitt MT, Case M, Devlin RB, 

Peden DB, Diaz-Sanchez D (2011) Lung Function and Inflammatory Responses in Healthy 

Young Adults Exposed to 0.06 ppm Ozone for 6.6 Hours. Am J Respir Crit Care Med.

Mcdonnell WF, Kehrl HR, Abdulsalaam S, Ives PJ, Folinsbee LJ, Devlin RB, Oneil JJ, Horstman DH 

(1991) Respiratory Response of Humans Exposed to Low-Levels of Ozone for 6.6 Hours. 

Archives of Environmental Health 46:145-150.

Schelegle ES, Morales CA, Walby WF, Marion S, Allen RP (2009) 6.6-hour inhalation of ozone 

concentrations from 60 to 87 parts per billion in healthy humans. Am J Respir Crit Care 

Med 180:265-272.
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Morton Lippmann

1. What is your advice on the overall strengths and limitations of the evidence from controlled 

human exposure and epidemiological studies and the results of the exposure and risk 

assessments, in the context of EPA's selection of a standard level within the proposed range 

that would be requisite to protect public health with an adequate margin of safety, 

including the need to protect susceptible populations, such as children and people with 

asthma?

The strengths of the evidence from controlled human exposure and epidemiological studies 

enumerated in the Criteria Document and its update were substantial, and more than 

adequate to support the recommended range for the NAAQS of 0.060 to 0.070 ppm. The 

limitations of the evidence from controlled human exposure and epidemiological studies were 

well and appropriately stated in the Staff Paper. These limitations have subsequently been 

substantially reduced since CASAC’s last commentary of April 7, 2008 (EPA-CASAC-08-

009) concerning the “Final rule” by the findings in peer-reviewed papers that have provided 

further evidence of the risks of inhaled ozone to normal individuals (Brown et al. 2008; 

Schelegle et al. 2009; Kim et al. in press), and in children and adults with asthma at 

concentrations well below 0.080 ppm (Lin et al. 2008; Moore et al. 2008; Islam et al. 2009; 

Silverman and Ito 2010). 

2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have 

provided evidence of other health effects, including inflammation and increased airway 

responsiveness which may occur through different physiological mechanisms than the 

reduction in FEV1, how should the results of these studies inform our understanding the 

health effects to healthy adults at exposures levels from 0.060 to 0.070 ppm?

These results demonstrate that there are subclinical responses to ozone inhalation that 

contribute to the physiological responses that are more readily measured in studies focused 

on clinically-relevant indices. They also provide results that provide a mechanistic basis for 

the functional effects and increased morbidity and mortality.

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing 

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence 

from controlled human exposure studies, mentioned above, inform our understanding of 

the health effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

As discussed at length in the Criteria Document and Staff Paper, there is no evidence of a 

threshold, i.e., the magnitude of the effect diminishes with decreasing ozone concentration, 

but does not reach the functional level associated with exposure to ozone-free clean air. 

Furthermore there is a great degree of variability of response magnitude among the 

individuals studied, with some having clinically-relevant responses, even at 0.060 ppm, and 

more of them with such responses at higher concentrations. Since the numbers of subjects 

exposed in the each of the controlled chamber studies at each concentration have been small, 

extrapolation to the much larger general population indicates that a very large number of 
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individuals would have substantial responses, even though they would constitute only about 

10% of the population. Schelege et al. (2009) show that FEV1 decrements >20% can occur at 

0.060 as well as at 0.070 and 0.080 ppm.

4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, 

what is the scientific importance of the small, group mean FEV1 decrements relative to the 

findings that 7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please 

consider this question from both a public health and a clinical perspective.

See my response to #3 above.

5. The evidence, including that summarized above, indicates that susceptible populations may 

have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy 

adults, as well as the epidemiological studies of susceptible groups, to inform a judgment 

on the effects of ozone exposure on susceptible populations?

Epidemiological studies generally show responses comparable to those observed in controlled 

human exposure studies conducted on healthy adults, but at lower ozone concentrations. 

This is partly due to the presence of less healthy, i.e., more susceptible people in the general 

population, but also due, at least in part, to the influence of prior days’ exposures, and to 

evidence that ambient air containing other pollutants that can exacerbate the responses. 

Thus, the chamber studies underestimate population responses that are known to be 

associated with ozone exposures. A margin-of-safety is needed to compensate for the 

understatement of effect from the chamber exposure studies.

6. To what extent does your confidence that the effects observed in epidemiological studies 

are attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in 

the proposed range as compared to the higher levels?

I do not have confidence that the effects observed in epidemiological studies are attributable 

specifically to O3, as noted above. However, the effects are characteristic of those produced 

by ozone, and not associated with other pollutants in the ambient air, at least at the levels 

found there. Thus reduction of the adverse health effects is dependent on reduction of ozone 

exposures.

7. EPA’s exposure assessment quantified the number of all children and asthmatic children 

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 

and 0.070 ppm. Considering the patterns of change in the estimates of exposures of 

concern at and above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties 

and limitations in the estimates, what is the relative importance from a public health 

perspective of the estimated reductions in exposures of concern, as well as the exposures 

remaining, for alternative standards across the proposed range?

Since the most reasonable assumption concerning the ozone exposure response relationship is 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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linear with no threshold, it is important to reduce ozone exposures by reducing the NAAQS 

in order to reduce the adverse health effects. However, it must be kept in mind that 

reductions of the NAAQS to either 0.060 or 0.070 will only reduce the numbers of people 

with adverse health effects, and will not eliminate such effects.

8. EPA’s quantitative risk assessment estimated the numbers of occurrences of various ozone 

related health effects associated with just meeting alternative standard levels down to a 

standard level of 0.064 ppm. Considering the patterns of change in the estimates of health 

effects in the risk assessment at the alternative standard levels, and the uncertainties and 

limitations in the estimates, what is the relative importance from a public health 

perspective of the estimated reductions in risk, as well as the risk remaining, for alternative 

standards across the proposed range? Please consider this question in light of the scientific 

evidence as a whole.

See my response to #3 above.

References Cited:

Brown JS, Bateson TF, & McDonnell WF. Effects of exposure to 0.06 ppm ozone on FEV1 in 

humans: A secondary analysis of existing data. Environ. Health Perspect. 116:1023-1026 (2008).

Islam T, McConnell R, Gauderman WJ, Avol E, Peters JM, and Gilliland F, Ozone, oxidant 

defense genes, and risk of asthma during adolescence. Am. J. Respir. Crit. Care Med. 177(4):388-

395 (2009).

Kim CS, Alexis NE, Rappold AG, Kehrl H, Hazucha Mj, Lay JC, Schmitt MT, Case M, Devlin 

RB, Peden DB, Diez-Sanchez D. Lung function and inflammatory responses in healthy young 

adults exposed to 0.06 ppm ozone for 6.6 hours. Am. J. Respir. Crit. Care Med. (in press).

Lin S, Liu X, Le LH, and Hwang S-A. Chronic exposure to ambient ozone and asthma hospital 

admissions among children. Environ. Health Perspect. 116:1725-1730 (2008).

Moore K, Neugebauer R, Lurmann F, Hall J, Brajer V, Alcorn S, & Tager I. Ambient ozone 

concentrations cause increased hospitalizations for asthma in children: An 18-year study in 

Southern California. Environ. Health Perspect. 116:1063-1070 (2008).

Schelegle ES, Morales CA, Walby WF, Marion S, Allen RP. 6.6-hour inhalation of ozone 

concentration from 60 to 87 parts per million in healthy humans. Am. J. Respir. Crit. Care Med.

180:265-272 (2009).

Silverman RA, Ito K. Age related association of fine particles and ozone with severe acute asthma 

in New York City. J. Allergy and Clin. Immunol. 125:367-373 (2010).
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Fred Miller

Charge Question 5. The evidence, including that summarized above, indicates that susceptible 

populations may have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy adults, as 

well as the epidemiological studies of susceptible groups, to inform a judgment on the effects of 

ozone exposure on susceptible populations? 

Response -- In many ways, the lowest exposure level of 0.06 ppm showing some symptom 

changes and statistically significant lung function changes in healthy subjects in an EPA analysis 

conducted for the last O3 NAAQS review represented a greatest lower bound on the ozone 

concentration of public health concern. In all of the controlled human exposure studies at 0.08-ppm 

ozone and below, a reasonable percentage of healthy subjects have lung function changes much 

higher than the average response (e.g., FEV1 changes > 10 %). While FEV1 changes > 10% may 

still allow healthy individuals to go about their normal daily activities, individuals with 

compromised lungs, such as asthmatics, incur significant health impacts with such lung function 

changes. As CASAC has noted in the past to the Agency, evidence is accumulating that persons 

with asthma, and particularly children, are more sensitive and experience larger decrements in lung 

function due to O3 exposure than do healthy volunteers. 

This, coupled with the fact that a number of epidemiology studies discussed in the last review were 

showing O3-related effects on various health endpoints (e.g., emergency department visits, 

increased hospital emissions, and mortality increases) at relatively low exposure levels leads one to 

conclude that O3 may cause effects even below 0.06 ppm. Since strengthening such a conclusion 

would need additional data from new studies, the CASAC concluded at the last review that the 

lower range of consideration for revision of the NAAQS should be 0.060 ppm O3. By doing so, the 

CASAC felt that margin of safety considerations would better be met than at 0.070 ppm O3. 

Moreover, since the relative strength of the science is weaker as one lowers the O3 concentration 

under consideration, a range of 0.060 to 0.070 ppm O3 allows the Administrator to place her 

judgment on the weight that any uncertainties and limitations in the science play in selecting an 

exposure level protective of public health.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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Lianne Sheppard

February 11, 2011

Individual comments

I still fully agree with the advice provided by CASAC in its letters of October 24, 2006 (EPACASAC-07-001), March 26, 2007 (EPA-CASAC-07-002), and February 10, 2010 (EPA-CASAC10-007). My opinion has been strengthened by the experience I have gained since 2008 through 

my continued involvement in air pollution and health research; this has contributed to my updated 

understanding of the evidence available in the 2008 review.

:

Preliminary thoughts on a draft response to Charge Question 6 (for CASAC discussion)

6. To what extent does your confidence that the effects observed in epidemiological studies are 

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the 

proposed range as compared to the higher levels?

:

Possible points for CASAC’s response:

• The endpoints of concern do not change at the lower levels of the proposed range.

• Many of the epidemiological studies had mean exposures well below the proposed range of 

0.070 ppm to 0.060 ppm and found ozone-related health effects. These include time series 

studies, field studies, and panel studies. The strengths and weaknesses of these studies do not 

differ appreciably in the proposed range.

• The epidemiological evidence does not suggest a threshold exists for mean concentrations 

within or above the proposed range. 

• While it is always difficult to tease out the effects of a single pollutant in epidemiological 

studies, there is evidence regarding ozone-related health effects from epidemiological studies 

that is consistent with the evidence from controlled exposure studies. This holds for the entire 

proposed range.

• While the effects attributed to ozone in epidemiological studies may not be specific to ozone, it 

is likely that reductions in population exposures to ozone will result in fewer adverse health 

effects. Our confidence in this statement does not change at the lower levels in the proposed 

range.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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Frank Speizer

Feb 8, 2011

Charge Question 1. What is your advice on the overall strengths and limitations of the evidence 

from controlled human exposure and epidemiological studies and the results of the exposure and 

risk assessments, in the context of EPA's selection of a standard level within the proposed range 

that would be requisite to protect public health with an adequate margin of safety, including the 

need to protect susceptible populations, such as children and people with asthma?

Although the two Adams studies represent the only reported work at levels of exposure below 

0.080 ppm of Ozone what has been pointed out and what is highly significant is that first the 

studies were done in normals and second that some 7-20% of the subjects experienced what I 

would consider very significant lung function decreases (> 10%) and or moderate respiratory 

symptoms. These findings essential preclude, because of the ethics of carrying out clinical studies 

in diseased individuals, from extending these studies to what are likely to be an even more 

sensitive groups. Thus, without having specific studies among asthmatics and children at these 

levels of exposure it is most prudent that, in spite of the uncertainty—more later on this issue—that 

EPA is justified to select an exposure level below the 0.080pppm (and I would say closer to the 

0.060 ppm level) to “protect public health with an adequate margin of safety, including the need to 

protect susceptible populations...”

Charge Question 2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and 

above have provided evidence of other health effects, including inflammation and increased airway 

responsiveness which may occur through different physiological mechanisms than the reduction in 

FEV1, how should the results of these studies inform our understanding the health effects to healthy 

adults at exposures levels from 0.060 to 0.070 ppm?

Given the evidence of pathophysiologic changes in smaller airways with exposures at 0.08 ppm as 

well as the occurrence of pulmonary function changes in a substantial number of normal subjects, 

the only mechanism that would change these finding in diseased subjects if there were some way 

that the diseased airways, perhaps because of the presence of excess mucus, would be “protected” 

from the potential oxidative effects of ozone. This seems highly unlikely in that disease subjects 

studied at 0.08 ppm and higher seem to respond more than normals and thus would not likely be 

protected more at the lower levels to which normals have responded. Clearly, these experiments 

have not been done and one might argue that thus there is uncertainty; however, as indicated above 

such experiments might be considered unethical. 

Charge Question 3. How should the results of the controlled human exposure studies at 0.060 ppm 

O3, showing effects on FEV1 and respiratory symptoms, in the context of the larger body of 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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evidence from controlled human exposure studies, mentioned above, inform our understanding of 

the health effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

Because these results represent a continuum of effects and it is unlikely that there is a threshold I 

would argue that the results are informative and suggest that EPA in carrying out its obligation 

must suggest a standard in the range indicated. I would argue that because there is no threshold 

that the data are consistent with the lower end of the range being more protective than the upper 

end. 

Charge Question 4. With respect to the information from controlled human exposure studies at 

0.060 ppm O3, what is the scientific importance of the small, group mean FEV1 decrements relative 

to the findings that 7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please consider 

this question from both a public health and a clinical perspective.

Please see answer to Charge Question 1 and 3. These small numbers of up to one-fifth of normals 

of the studied populations having changes in lung function or symptoms of this magnitude strongly 

suggests that the susceptible population would respond even greater and could reach clinically 

significant responses that might result in emergency room visits and or hospitalizations. 

Charge Question 5. The evidence, including that summarized above, indicates that susceptible 

populations may have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy adults, as 

well as the epidemiological studies of susceptible groups, to inform a judgment on the effects of 

ozone exposure on susceptible populations?

It would be difficult to make an actual estimate of the difference in impact that might occur 

between 7-20% of normals responding and even a similar if not greater number of diseased 

subjects who might have similar size responses. It would be reasonable to assume that the 

responses certainly would not be less frequent and are likely to be of greater magnitude or at least 

large enough to increase the likelihood that symptomatic responses would need to be treated. 

Given the substantial number of potentially at risk adults in the population and the distributions of 

possible exposures even at the lower level of the bounded exposures

it would be prudent to argue that there will be some individuals remaining at risk. The judgment is 

how large a population is the Administrator willing to tolerate as being still at risk, not whether she 

can protect the entire population of potentially susceptible individuals. 

Charge Question 6. To what extent does your confidence that the effects observed in 

epidemiological studies are attributable specifically to O3 lessen or otherwise change, if at all, at 

the lower levels in the proposed range as compared to the higher levels?

Clearly there is greater uncertainty at the lower bound of the range of exposure; however, whether 

this is due to the mixture of addition pollutants coming into play rather than simply more 

variability in response cannot be determined. The few cities in which there are essentially no 

alternative pollutants to consider or where seasonal selection has been used to minimize alternative 

pollutants still show similar effects, and thus the likely cause of the uncertainly relates to greater 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

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variability rather than confounding by additional pollutants and thus the effects noted seem 

attributable to ozone pollution. 

Charge Question 7. EPA’s exposure assessment quantified the number of all children and 

asthmatic children likely to be exposed to specific benchmark levels of ozone, including in 

particular 0.060 and 0.070 ppm. Considering the patterns of change in the estimates of exposures 

of concern at and above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties and 

limitations in the estimates, what is the relative importance from a public health perspective of the 

estimated reductions in exposures of concern, as well as the exposures remaining, for alternative 

standards across the proposed range?

As indicated in the discussion across the 12 urban areas the assessment are considerably larger for 

the benchmark level of 0.60 ppm compared to the 0.070 ppm benchmark. However, they also note 

that the pattern of exposure is similar for all children and asthmatic school age children. The 

Administrator also stated that she must consider the public health impact in cities receiving 

considerably less protection associated with air quality just meeting the same standard. This is a 

difficult criteria to meet with a single standard. Thus it becomes prudent to weigh the impact of the 

exposure against the cost of meeting that standard. The science is clear that there will be children 

as risk at any reasonable standard chosen. Thus the public health consideration is how big a 

population the Administrator is willing to leave at risk. 

Charge Question 8. EPA’s quantitative risk assessment estimated the numbers of occurrences of 

various ozone related health effects associated with just meeting alternative standard levels down 

to a standard level of 0.064 ppm. Considering the patterns of change in the estimates of health 

effects in the risk assessment at the alternative standard levels, and the uncertainties and 

limitations in the estimates, what is the relative importance from a public health perspective of the 

estimated reductions in risk, as well as the risk remaining, for alternative standards across the 

proposed range? Please consider this question in light of the scientific evidence as a whole.

From the Fed Reg TABLE 3—NUMBER AND PERCENT OF ALL AND ASTHMATIC SCHOOL AGE CHILDREN IN 12 

URBAN AREAS ESTIMATED TO EXPERIENCE 8-HOUR OZONE EXPOSURES ABOVE 0.060 AND 0.070 PPM WHILE AT 

MODERATE OR GREATER EXERTION,ONE OR MORE TIMES PER SEASON ASSOCIATED WITH JUST MEETING 

ALTERNATIVE 8-HOUR STANDARDS BASED ON ADJUSTING 2002 AND 2004 AIR QUALITY DATA1 2

This table not reproduced here suggests a wide range of at risk children dependent upon the choice 

of levels of exposure. Unfortunately, it is not clear that 2002 is the “worse case” or 2004 is the 

“best case”. Nevertheless, with regard to protecting the public health the range of all children aged 

5-18 between 0.064-0.074 is between 4.5 million and 950, 000 in the worse case vs 350,000 and 

10,000 in the best case, with proportionately lower numbers for asthmatic children. Clearly truth 

must lay somewhere in between. Even these lower numbers represent a substantial fraction of at 

risk children. Given the evidence of the pathophysiology, the clinical studies data in normals and 

the likelihood that symptomatic subjects will respond to a greater degree, and the fact that there is 

no evidence for a threshold of effects, the prudent decision is to set a standard that is as protective 

of the public health with a margin of safety as mandated by law.
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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Helen Suh

1. What is your advice on the overall strengths and limitations of the evidence from controlled 

human exposure and epidemiological studies and the results of the exposure and risk 

assessments, in the context of EPA's selection of a standard level within the proposed range 

that would be requisite to protect public health with an adequate margin of safety, including 

the need to protect susceptible populations, such as children and people with asthma?

The scientific evidence from controlled human exposure and epidemiological studies and from 

the exposure and risk assessments supports a primary ozone standard (with a margin of safety) 

between 0.060 to 0.070 ppm. The controlled human exposure studies by Adams (2002, 2006) 

show statistically significant changes in lung function from a 6.6 hour exposure to 0.060 ppm 

ozone. While these studies were limited in number, they were well designed and results were 

consistent with those from previous studies, thus lending credibility to their findings. Of 

particular interest is the fact that a small but important fraction of the study subjects 

experienced lung function decrements greater than 10% at exposures to 0.060 ppm ozone. 

These findings suggest that the impacts of ozone exposures at these levels may be significant 

for individuals with pre-existing respiratory conditions and must be considered to ensure 

adequate margin of safety for sensitive subpopulations.

2. Recognizing that controlled human exposure studies at 0.080 ppm O3 and above have provided 

evidence of other health effects, including inflammation and increased airway responsiveness 

which may occur through different physiological mechanisms than the reduction in FEV1, how 

should the results of these studies inform our understanding the health effects to healthy adults 

at exposures levels from 0.060 to 0.070 ppm?

It is reasonable to consider findings of sub-clinical adverse impacts, such as increased 

inflammation and airway responsiveness, when considering adverse health impacts to healthy 

adults at exposures levels from 0.060 to 0.070 ppm. These findings are certainly pertinent to 

margin of safety considerations. 

3. How should the results of the controlled human exposure studies at 0.060 ppm O3, showing 

effects on FEV1 and respiratory symptoms, in the context of the larger body of evidence from 

controlled human exposure studies, mentioned above, inform our understanding of the health 

effects to healthy adults at exposure levels from 0.060 to 0.070 ppm?

These results provide important evidence that exposures to 0.060 ppm of ozone are harmful 

and are consistent with previous observations of no safe level for ozone exposures. Findings 

from Adams studies (2002, 2006) must be considered, at the least as being central to margin of 

safety determinations. 

4. With respect to the information from controlled human exposure studies at 0.060 ppm O3, 

what is the scientific importance of the small, group mean FEV1 decrements relative to the 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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findings that 7 to 20% of the subjects experienced FEV1 decrements ≥ 10%? Please consider 

this question from both a public health and a clinical perspective.

For individuals with pre-existing respiratory disease, a 10% decrement in FEV1 is significant. 

5. The evidence, including that summarized above, indicates that susceptible populations may 

have greater responses than healthy people. In light of this evidence, how can we 

appropriately use the results of controlled human exposure studies conducted on healthy 

adults, as well as the epidemiological studies of susceptible groups, to inform a judgment on 

the effects of ozone exposure on susceptible populations.

Although the sample sizes are small, the variability in the response observed for healthy adults 

in the controlled human studies can inform judgments on the effects of ozone in susceptible 

populations. For example, the 7-20% of healthy adults who were found to have large ozonemediated responses in controlled exposure studies may provide an indication of the fraction of 

individuals in the general population who may also be large responders. Ozone-mediated 

response may comprise an even greater percentage of the susceptible population. 

6. To what extent does your confidence that the effects observed in epidemiological studies are 

attributable specifically to O3 lessen or otherwise change, if at all, at the lower levels in the 

proposed range as compared to the higher levels?

The uncertainty in the epidemiological findings at low ozone levels is certainly greater than 

that at high ozone levels, with greater confidence about the existence of health effects at the 

upper end and less confidence at lower O3 levels. Confounding by other pollutants is certainly 

of concern. However, ozone mediated impacts have been observed for a variety of endpoints, 

including those such as school absences that have not been related to particulate matter (PM), 

perhaps the most important potential confounder. Further, ozone-mediated impacts have been 

demonstrated in a number of locations, with varying correlations between ozone and PM. 

Finally, additional support for epidemiological findings is provided by results from controlled 

exposure studies. 

7 . EPA’s exposure assessment quantified the number of all children and asthmatic children 

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 and 

0.070 ppm. Considering the patterns of change in the estimates of exposures of concern at and 

above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties and limitations in the 

estimates, what is the relative importance from a public health perspective of the estimated 

reductions in exposures of concern, as well as the exposures remaining, for alternative 

standards across the proposed range?

The exposure assessment shows considerable temporal and spatial variability in exposure 

estimates, which is expected and which has important implications in determinations about

adequate margin of safety. Given results from health studies, it is reasonable to assume no 

threshold in ozone-mediated impacts. As a result, even with uncertainty in the benchmark 
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policy. Do not cite or quote.

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exposures, it is likely that a significant fraction of asthmatic children will remain exposed to 

ozone exposures above the benchmark level.

8 . EPA’s quantitative risk assessment estimated the numbers of occurrences of various ozone 

related health effects associated with just meeting alternative standard levels down to a 

standard level of 0.064 ppm. Considering the patterns of change in the estimates of health 

effects in the risk assessment at the alternative standard levels, and the uncertainties and 

limitations in the estimates, what is the relative importance from a public health perspective of 

the estimated reductions in risk, as well as the risk remaining, for alternative standards across 

the proposed range? Please consider this question in light of the scientific evidence as a 

whole.

The quantitative risk assessment showed public health significant reductions in risk in going 

from a 0.074 ppm to a 0.064 ppm standard. As acknowledged by the Administrator, 

reductions in risk may be even greater, as the risk assessment examined only a fraction of the 

observed health outcomes, with many unexamined health outcomes posing greater risks for 

sensitive subgroups. These limitations may outweigh, or at the least counteract, any concerns 

regarding uncertainty in the risk estimates. 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

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James Ultman

Charge question 1:

Strengths:

1. Objective, accurate and precise measurements of exposure pattern and response 

endpoints.

2. Minimize cofounding influence of particulate matter, other oxidants and other 

copollutants on subject response.

3. Large database of forced expired response to constant ozone exposure with 

intermittent exercise using fairly consistent protocols within labs and between labs.

4. Newest studies are designed for more realistic exposure levels and concentration 

patterns.

Weaknesses:

1. Ethical limitations testing subjects that have severe respiratory and/or 

cardiovascular disease. 

2. Usually not designed to model different exercise levels or multiple daily exposures.

3. Large majority of studies on ozone concentrations at or above 0.08 ppm and on 

constant exposure patterns.

4. Are usually not specifically designed or analyzed to examine the health effect of 

ozone exposure relative to a an exposure that emulates a policy-relevant 

background.

Charge question 2:

Results from numerous studies indicate that exposure to 0.08ppm ozone and greater 

induces decrements in FEV1 and also elevates various markers of inflammation. Because 

lung function decrements and airway inflammation occur by different mechanisms, they 

are not directly related to one another. Thus, it is not feasible to use the results of 

inflammation at 0.08 ppm and above to inform our understanding of health effects at 

lower concentrations. 

There is one recent study(1)that reported a significant increase in neutrophil counts in the 

sputum of healthy subjects during the day following a 0.06 ppm, 6.6 hour, ozone exposure. 

Whether or not this observation can be confirmed in another study remains to be seen. 

Even with this scientific uncertainty, the possibility of a clinically consequential airway 

inflammation must be kept in mind when specifying a “margin of safety” in the ozone 

standard.

Charge question 3:

Data from two clinical studies, show that exposure to 0.06ppm ozone causes a significant 

pre-to-post exposure decrement in FEV1 relative to that in clean air. The reanalysis of 
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policy. Do not cite or quote.

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Adams 2006 study by Brown(2) indicates that a 6.6 hr exposure to a square-wave or 

variable ozone concentration pattern and intermittent exercise results in a 3% decrease in 

FEV1 with 2/30 subjects exhibiting a decrement greater than 10%. For a constant 0.06 

ppm exposure, Kim et et al.(2)reported a 2% decrease in the group mean FEV1 with 3/59 

subjects exhibiting a decrement greater than 10%. In a third study (3), the group mean 

FEV1 decrement during a 0.06 ppm variable ozone exposure pattern was not statistically 

different from that observed during clean air exposure. Nevertheless, 6/31 subjects had 

FEV1 decrements that were greater than 10% relative to clean air. 

Thus, the evidence for a clinically relevant decrement in lung function among a 

subpopulation of subjects is coherent among these studies even though statistical 

comparisons of the group means are equivocal. Although it is doubtful that children, 

asthmatics and other susceptible populations would achieve the high workloads employed 

in these studies (MV=20 L/m/m2 body surface for adults), some vulnerable populations 

such as outdoor laborers could would. 

 

Charge question 4:

From a clinical perspective, the observation of decrements in FEV1>10% is an important 

indicator of a possible health effect in a limited number of patients. From a public health 

perspective, the group mean effect of long exposures at high workloads on mechanical lung 

function is minimimal.

1. Kim, C., et. Al.(2011). Lung function and inflammatory responses in healthy young 

adults exposed to 0.06 ppm ozone for 6.6 hours. Am J Resp Crit Care Med. (on-line).

2. Brown,J.S. (2007) The effects of ozone on lung function at 0.06ppm in healthy adults. 

Ozone NAAQS Review Docket (OAR-2005-0172).

3. Schelegle et al (2009). 6.6-Hour inhalation of ozone concentrations from 60 to 87 

parts per billion in healthy humans. Am J Resp Crit Care Med. 180:265-272.
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policy. Do not cite or quote.

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Sverre Vedal

7. EPA’s exposure assessment quantified the number of all children and asthmatic children 

likely to be exposed to specific benchmark levels of ozone, including in particular 0.060 

and 0.070 ppm. Considering the patterns of change in the estimates of exposures of 

concern at and above the 0.060 and 0.070 ppm benchmark levels, and the uncertainties 

and limitations in the estimates, what is the relative importance from a public health 

perspective of the estimated reductions in exposures of concern, as well as the exposures 

remaining, for alternative standards across the proposed range?

The first issue is the estimated change in exposures for alternative standards across the proposed 

range of 0.060 to 0.070 ppm. Table 1 in the Proposed Rules (p. 2978 in the Federal Register 

January 19, 2010) presents modeled number and percentage of children with exposure (defined as 

at least one 8-hr average exposure per year with moderate or greater level of exercise) at each of 

three ozone benchmark levels of concern (0.080, 0.070 and 0.060 ppm) for ozone standards 

ranging from the old standard of 0.084 to a lowest standard of 0.064 ppm, for the 12 urban areas in 

aggregate. Since no estimates are presented down to the lower end of the proposed range, i.e., 

0.060 ppm, we cannot directly answer the question for the entire proposed range of the standard, 

based on these model estimates. However, at least for levels of concern of 0.070 or greater, 

because the number and percent exposed is either zero or exceedingly small when meeting a 

standard of 0.064, depending on the year, it can be inferred that even fewer are exposed were a 

standard of 0.060 to be met. For a level of concern of 0.060, for the year with the lowest 

concentrations (2004), no exposures are estimated to occur when meeting the standard of 0.064, 

whereas for the year with the higher concentrations (2002), it is estimated that around 5% of 

children will be exposed, implying that even fewer will be exposed were a standard of 0.060 to be 

met. Some individual city estimates of exposure were lower while others were higher than these 

aggregate estimates. Based on earlier uncertainty and sensitivity analyses carried out by EPA, and 

relative to uncertainty in health effect estimates, uncertainty in these exposure estimates is 

acceptable. 

The second issue relates to the public health significance of reductions in exposure for the range of 

standards from 0.070 to 0.060. Some of the public health significance is addressed by the risk 

assessment for selected endpoints (see responses to charge question #8). For endpoints for which it 

was not possible to carry out a quantitative risk assessment, we must infer public health 

significance in light of the toxicologic, human clinical and epidemiological findings. Toxicologic 

data (i.e., animal experimental data) are largely not helpful in this regard. In the absence of 

demonstrable effects in human clinical studies (in normals or those with mild disease) on other 

than lung function decrements for exposure concentrations less than 0.080 ppm, we are left 

inferring effects at lower concentrations and in the more severely diseased. Findings from 

epidemiological studies are less certain, but indicate effects at substantially lower concentrations 

than were used in the experimental studies. The benchmark levels in Table 1 correspond to greater 

degrees of uncertainty going from 0.080 down to 0.060. Part of this uncertainty relates to the 

precious little human clinical data at exposure concentrations below 0.080, and what exists is 

essentially limited to effects on lung function. Another part of the uncertainty relates to the reliance 
2-18-11 Preliminary Individual Comments on the Ozone Reconsideration

These comments are preliminary and do not represent consensus CASAC advice or EPA 

policy. Do not cite or quote.

Page -41-

on epidemiological (non-experimental) findings at the lower concentrations. Therefore, while (in 

Table 1) the predicted number exposed increases for every level of the standard as the benchmark 

level of concern is reduced, the public health impact of this increase in number exposed becomes 

less certain. One could argue that since there is no clear threshold for ozone effects, increases in 

the number exposed translates directly into increases in health effects. This ignores not just 

increasing uncertainty, but also the fact that “exposure” at the decreasing benchmark levels results 

in an increasingly smaller percentage of people affected at the decreasing levels of exposure. 

These latter percentages are difficult to estimate for endpoints other than, perhaps, acute lung 

function changes. So, the public health significance is difficult to gauge for these other endpoints.

What then can be said about the public health significance of exposures at the different levels of 

concern across the different standards? It is prudent to assume that for at least some segments of 

the population, adverse effects (in addition to acute lung function effects) occur at levels below 

0.080, and, making use of epidemiologic observations, that there is no obvious threshold for these 

effects with effects occurring even at the benchmark level of 0.060. At some concentration the 

number of individuals affected must be exceedingly small, although, because the number of days 

with lower benchmark levels is greater than with higher levels, a feature not captured by the 

exposure estimates in Table 1, the opportunities for exposure throughout the year are greater at the 

lower benchmark levels. This explains the observation from the risk assessment that the majority 

of adverse effects are due to exposures occurring at relatively lower concentrations.