# Comments to the CASAC Ozone Review Panel for the

Reconsideration of the 2008 NAAQS

Julie E. Goodman, Ph.D., DABT

Prepared on behalf of American Petroleum Institute 1220 L Street NW Washington DC 20005-4070

February 7, 2011G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 1 Gradient 

## Background

In reconsidering the 2008 ozone standard, th e United States Environmental Protection Agency (US EPA) proposed the primary 8-hour ozone National Ambient Air Quality Standard (NAAQS) be set in the range of 0.060 to 0.070 parts per million (ppm). In its deliberations, the agency is weighing the evidence favoring the upper or lower ends of this range with respect to the uncertainties and limitations in
the data available at the time of the 2008 ozone NAAQS review. These comments address the body of evidence comprising controlled exposure studies of young, healthy adults at an ozone concentration at 0.060 ppm for 6.6 hours. Specifically, this evidence was reported in three studies by Adams (1998, 2002, 2006). Below, this evidence is discussed in relation to charge questions 2, 3, and 4 that were attached to the January 26, 2011 memorandum, in which US EPA solicited the CASAC's advice on the reconsideration of the primary ozone NAAQS (W egman, 2011). Overall, this evidence supports maintaining the existing primary ozone 8-hour NAAQS pe nding a thorough review of scientific evidence
that has become available since the 2008 review of the primary ozone NAAQS.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 2 Gradient CASAC Charge Question 2. Recognizing that controlled human exposure studies at 0.080 ppm O 3 and above have provided evidence of other health effects, including inflammation and increased airway responsiveness which ma y occur through different physiological mechanisms than the reduction in FEV 1 , how should the results of these studies inform our understanding the health effects to health y adults at exposures levels from 0.060 to 0.070 ppm?

Human exposure studies with exposures of ≥ 0.080 ppm ozone have provided valuable evidence of the exposure-response re lationship for respiratory health effect s. At lower ozone concentrations, particularly ≤ 0.060 ppm, similar studies have yielded only limite d evidence of adverse respiratory effects, specifically of decrements in forced expiratory volume in one second (FEV 1 ). Indeed, there appears to be a threshold below 0.070 ppm ozone where there are no si gnificant effects of ozone exposure. Because of this discontinuity in the exposure-response relationship, FEV 1 decrements at exposures ≥ 0.080 ppm ozone may not be appropriate for inferring effects at the lower end of the proposed ozone range of 0.060 to 0.070 ppm. Regarding respiratory health endpoints of interest other than FEV 1 at ozone concentrations <0.080 ppm, there were no data available at the time of the 2008 ozone NAAQS review, but a recent study (Kim et al ., 2011) may shed some light on inflammatory responses at a lower concentration. Kim
et al . (2011) reported elevated polymorphonuclear neut rophils (PMNs) in the induced sputum of 24 subjects at a time point of 16-18 hours after exposure to 0.060 ppm ozone for 6.6 hours, and, although the elevation was statistically significant, it is not clear wh ether this effect is clinically significant. Thus, studies of elevations in this outcome at higher exposures should not be used to infer lung function responses, especially at relatively low ozone le vels in the range of 0.060 to 0.070 ppm.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 3 Gradient CASAC Charge Question 3. How should th e results of the controlled human exposure studies at 0.060 ppm O 3 , showing effects on FEV 1 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?

Although the controlled chamber experiments by Adams (2006) demonstrated statistically significant decrements in FEV 1 at 0.080 ppm ozone for 6.6 hours relative to fresh air exposure, statistically significant decrements were not demonstr ated at 0.060 ppm ozone. Dr. Adams reiterated this result in the March 5, 2007 CASAC teleconference, when he affirmed that data from Adams (2006) should not be interpreted as demonstrating respir atory effects at ozone exposures of 0.060 ppm. Moreover, the FEV 1 decrement reported in Adams (2006) was only 3.52%, which was attributable in part
to FEV 1 reductions of >10% in only two of the 30 stud y subjects. Similarly, two face-mask exposure studies by Adams (1998, 2002) did not report statistically significant decrements in pulmonary function at or below 0.060 ppm ozone after 6.6 hours of exposure , although it was noted that six of 30 subjects had
an FEV 1 decrement greater than 10%.

The null results at 0.060 ppm ozone in the Adam s (2006) study are not necessarily due to small sample size or lack of statistical power. In reality, one cannot know whether a lack of effect is the result of small sample size or because there is actually no asso ciation. Using non-statistically significant results as evidence for an association essentially ignores the results obtained using statistics. If future studies demonstrate an association at 0.060 ppm ozone that is both statistically significant and clinically relevant, they would contribute to the weight of evidence in favor of the lower end of the proposed range of the 8- hour primary ozone standard. In the absence of such evidence, CASAC should conclude that the available data do not support an association be tween lung function eff ects and 0.060 ppm ozone.

US EPA conducted an internal reanalysis (Brown , 2007) of a small portion of the data reported in Adams (2006), which, in contrast to the original published results, found a statistically significant
decrement in FEV 1 at 0.060 ppm ozone. This was primarily based on a t-test of FEV 1 applied to the 6.6 hour data only from the square wave profile versus that of controls. This is inappropriate because it was based on only a small subset of the available FEV 1 data ( i.e. , the analysis excluded all measurements taken at 1, 2, 3, 4.6, and 5.6 hours) and did not account for all the other responses from different exposure
scenarios.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 4 Gradient Given the choice between discarding data versus using all available data, the general preference
should be to use the most information with the most powerful statistical technique suitable for the study design. Hence, the statistical approach by Brown (200 7) is curious because the data were discarded rather than being analyzed in a more powerful, albeit more complex, statistical model, such as mixed effects models. Discarding data is not only inefficient, but is generally inappropriate because such post hoc
selection of a data subset when valid and otherwise non-problematic observations exist calls into question the rationale for such action. The primary rationa le for Brown (2007) to remove data from other experimental conditions was apparently to avoid stringent reductions in the critical p-value for statistical significance due to multiple comparisons procedures. The intention of multiple comparisons procedures, however, should not be to deter researchers from anal yzing available data. Or, as Rothman (1990) noted in questioning the general necessity of multiple comp arisons procedures, "The more that one observes, the stiffer the penalty exacted for the privilege of observing." It is also notable that US EPA investigators, as well as other research groups who perform human clinical studies of prolonged ozone exposure, do not routinely exclude time-varying pulmonary function data in order to focus their analysis on only the final data point. Rather, these research groups use statistical procedures that utilize all of the data, similar to the approach used by Adams (2006) ( e.g. , McDonnell et al ., 1997; Liu et al ., 1999; Gong
et al ., 1998; Vincent et al ., 1997; Torres et al ., 1997; Wang and Petsonk, 2004).

Even though the observed effects for lung function were not statistically significant, it is also worth considering whether the decrements were clini cally relevant with respect to broadly recognized clinical guidelines (Goodman et al ., 2010). The American Thoracic Society (ATS) judges a reversible loss of lung function in combination with symptoms to be adverse (ATS, 2000). Although Adams (2006) reported a statistically significant increase in total symptom severity (TSS) after 6.6 hours of exposure to 0.060 ppm ozone compared to pre-exposure baseline, there was no significant difference when compared to filtered air exposure (in contrast to US EPA's claims that this difference was statistically significant). Hence, not only was the decrement in lung function no t statistically significant at 0.060 ppm ozone for 6.6 hours, but also symptom scores were not statistically different from those for filtered air exposure, indicating that the observations at 0.060 ppm ozone by Adams (2006) were not clinically adverse according to ATS guidelines. The European Respirat ory Society (ERS) suggests that only short-term changes in FEV 1 exceeding 12% "may be clinically important," and that changes in FEV 1 measurements should exceed 5% to overcome the intra-day variability of FEV 1 in normal subjects (Pellegrino et al ., 2005). The FEV 1 decrement of 3.52% reported in Adams (2006) is below potential clinical relevance, and, according to ERS guidelines, is within the bounds of intra- individual variabi lity for daily FEV 1 .G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 5 Gradient While US EPA has requested that CASAC consider only the data available at the time of the 2008 ozone NAAQS review, CASAC should at least be aw are of the general results of highly relevant studies recently published in the peer-reviewed scientif ic literature, which US EPA has summarized in the draft Integrated Science Assessment document for the next review of the primary ozone NAAQS (US EPA, 2010). In particular, CASAC should recognize that these studies cast further uncertainty on the existence of clinically relevant decrements in FEV 1 at 0.060 ppm. Schelegle et al . (2009) conducted a series of controlled exposure chamber studies on 31 healthy young adults at mean ambient ozone concentrations of 0.063, 0.072, 0.081, and 0.088 ppm (Schelegle et al ., 2009, Table 2), as well as filtered air (control), with FEV 1 measurements at multiple time points up to 6.6 hours of exposure and four hours post-exposure. Subjects exercised during the exposure, with periodic breaks. The researchers' stated goal was to identify the lowest ozone concentration that induced a statistically significant decrement in FEV 1 . Their findings indicate that the lowest mean ambient ozone concentration associated with a statistically significant decrease in FEV 1 from filtered air control after 6.6 hours of exposure was 0.072 ppm. The researchers, however, were clearly mindful of the interest in FEV 1 effects at 0.063 ppm ozone, as they discussed with particular attention the statistical an alyses of data at this concentration (Schelegle et al ., 2009, Table 4). The researchers used no less than thre e different statistical techniques to address different analytic issues, such as repeated measurements, multiple comparisons, a nd non-normally distributed data. These techniques were mixed effects two-way (with ozone concentration and time as factors) ANOVA with Tukey's adjustment for multiple comparisons (also known as the Tukey-Kramer adjustment), mixed effects one-way (with ozone concentration as the fa ctor) ANOVA with Dunnett's adjustment for multiple comparisons against a single control (fresh air), and Friedman's nonparametr ic test with Dunnett's adjustment. For the latter two techniques, in order to avoid stringent reductions in the critical value for statistical significance due to excessive multiple comparis ons, the researchers restricted statistical analysis
to the FEV 1 decrements at 6.6 hours, ignoring data collect ed at other time points. None of these techniques yielded a statistically significant FEV 1 decrement at an exposure of 0.063 ppm ozone for 6.6 hours, yet all were statistically significant at 0.072 ppm. After 6.6 hours of exposure at 0.063 ppm ozone,
the researchers observed a mean FEV 1 decrement from baseline of 2.72% (standard error: 0.27) versus 5.34% (0.25) at 0.072 ppm ozone. For comp arison, the mean percent-change in FEV 1 for filtered air after 6.6 hours was 0.80% (0.16).

Kim et al . (2011) exposed 59 healthy, exercising young adults to 0.060 ppm ozone for 6.6 hours
under controlled chamber conditions and observed a statistically signifi cant mean percent-change in FEV 1 (clean-air adjusted) of -1.75 (95% CI: -3.0, -0.5 ) and an increase in neutrophilic inflammation of the airways, with no statistically significant increase in total symptom score. The decrement reported by KimG:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 6 Gradient et al . (2011) is much smaller than the ATS and ERS c linical guidelines reported a bove, and is also smaller than the previously reported decrements of Adams (2006) and Schelegle et al . (2009), neither of which were statistically significant. Hence, the results of Kim et al . (2011) are consistent with earlier reports that the effect of 0.06 ppm ozone exposure for 6.6 hours is not clinically adverse. In view of the lack of clinically significant lung function effects at 0.060 ppm for 6.6 hours demonstrated by these recent studies, the weight of evidence clearly favors maintaining the existing primary ozone NAAQS.

Results from controlled human exposure studies at 0.060 ppm ozone (Adams 1998, 2002, 2006) provide the best evidence for whether respiratory hea lth effects in healthy adults are associated with ozone exposures at the lower end of the range proposed for the primary ozone NAAQS. Clearly, the data do not support adverse health effects at 0.060 ppm oz one. As a consequence, the available evidence for health effects in healthy adults from relatively low ozone exposure levels supports maintaining the existing primary ozone NAAQS pending a thorough revi ew of the scientific ev idence that has become available since the 2008 review of the primary ozone NAAQS.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 7 Gradient CASAC Charge Question 4. With respect to the information from controlled human exposure studies at 0.060 ppm O 3 , what is the scientific importance of the small, group mean FEV 1 decrements relative to the findings that 7 to 20% of the subjects experienced FEV 1 decrements ≥ 10%? Please consider this question from both a public health and a clinical perspective.

In the charge questions attached to the January 26, 2011 memorandum soliciting the CASAC's advice on the primary ozone NAAQS, US EPA writes:

The CASAC panel indicated that a focus on the lower end of the range of moderate levels of functional responses ( e.g ., FEV 1 decrements ≥ 10%) is most appropriate for estimating potentially adverse lung function decrements in people with lung disease. (Wegman, 2011)

As already noted above, ERS considers a decrement of at least 12% in FEV 1 as only potentially clinically important. In addition, clinical studies ha ve often used a cut-off value of at least 20% for a
decline in FEV 1 as the definition of a "mild" asthma exacerbation (Reddel et al ., 2009). CASAC's suggested cut-off of 10% would appear to be overly conservative with respect to clinical guidelines.

CASAC also seems to be suggesting that, b ecause a proportion of subjects in the studies by Adams (2002, 2006) had an FEV 1 decrement >10%, a similar proportion of the healthy young adult population and a larger proportion of the population with lung disease will have comparable FEV 1 decrements at 0.060 ppm ozone. Not only is the number of subjects far too small to support such generalizations, but the study sample (young, healthy adults) is not suitable for extrapolation to the population with lung disease ( e.g. , asthmatics may not be able to achie ve the total cumulative ozone doses in Adams, 2006 because of the inabilit y to exercise strenuously for long durations). Thus, the proportion of subjects with FEV 1 decrements ≥ 10% is an inappropriate estimate of the decrements that would be faced by the population with lung disease at 0.060 ppm ozone.

The findings of small, group mean FEV 1 decrements and the observation that 7 to 20% of subjects experienced FEV 1 decrements ≥ 10% are related insofar as they represent two characteristics of
the distribution of FEV 1 decrements in healthy subjects expo sed to 0.060 ppm ozone. The mean FEV 1 decrements represent the central tendency of the di stribution and are only significant — both from public health and clinical standpoints — if they exceed clinic ally relevant levels, whic h they do not at 0.060 ppm ozone. In contrast, the proportion of subjects with FEV 1 decrements ≥ 10% represent the extreme lower tail of the distribution, and hence are associated wi th the degree of variation and are not necessarily attributable to ozone exposure. In the case of FEV 1 measurements, it has been well-established that thereG:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 8 Gradient is substantial inter-individual variati on that is largely unexplained (McDonnell et al ., 1993, 1997), except for its dependence on age and elevated ozone exposure. In fact, at such relatively low levels of ozone exposure, it is likely that the apparent variation is a ttributable to a substantial intra-individual variation,
which ERS estimates to be about 5% for intra-day variation (Pellegrino et al ., 2005). It is therefore inappropriate to ascribe to the entire population with lung disease the result s from a relatively small number of healthy adults at the lower tail of the distribution.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 9 Gradient 

## Conclusions

In his experimental chamber study, Adams (2006) analyzed the data using accepted statistical
methods and found that FEV 1 decrements in young, healthy adults exposed to ozone were not statisticallysignificantly different from those in subjects exposed to fresh air at 0.060 ppm ozone. Although this nonstatistically significant finding has been the subject of some debate, it is also important to consider whether the observed decrements in lung function are significant with respect to broadly recognized clinical guidelines (Goodman et al ., 2010). ATS judges a reversible loss of lung function in combination with symptoms to be adverse (ATS, 2000). Adams (2006) found no statistically significant increase in TSS after 6.6 hours of exposure to 0.060 ppm ozone compared to fresh air exposure. Hence, the observations at 0.060 ppm ozone in Adams (2006) were not clinically adverse according to ATS guidelines. In addition, ERS suggests that only short-term changes in FEV 1 exceeding 12% "may be clinically important," and that changes in FEV 1 measurements should exceed 5% to overcome the intraday variability of FEV 1 in normal subjects (Pellegrino et al ., 2005). The FEV 1 decrement of 3.52% reported in Adams (2006) is below potential clinical relevance, and, according to ERS guidelines, is within the bounds of intra-individual variability for daily FEV 1 .

Adams (2002, 2006) also noted that a proportion of subjects — 20% and 7%, respectively — had
an FEV 1 decrement greater than 10%. CASAC has sugg ested that a similar proportion of the healthy young adult population will have comparable FEV 1 decrements at 0.060 ppm ozone, but the number of subjects is far too small ( i.e. , 30) for such a generalization. Hence, the proportion of subjects with FEV 1 decrements greater than 10% should not be the b asis for claims about the population-wide risks of exposure to 0.060 ppm ozone.

Because lung function effects at 0.060 ppm ozon e were neither statistically nor clinically significant (Adams 2006), and effects at 0.040 ppm ozone were clearly not significant (Adams, 2002), the exposure-response curve for FEV 1 flattens out in the 0.040 to 0.060 ppm ozone range. This is suggestive of a threshold for a clinically adverse response. He nce, effects at 0.080 ppm oz one and above may not be appropriate for inferring effects at the lower end of the proposed 0.060 to 0.070 ppm ozone range.

In view of the evidence, and, in particular, the uncertainties surrounding possible decrements in lung function at 0.060 ppm ozone, the primary ozon e 8-hour NAAQS should be maintained pending aG:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 10 Gradient thorough review of scientific evidence that has beco me available since the 2008 review of the primary ozone NAAQS.G:\PROJECTS\210153_Ozone\TextProc\r020711a.docx 11 Gradient 

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