Citation:

Kim, C., H. Kehrl, A. Rappold, M. Case, R. Devlin, AND D. Diaz-Sanchez. Pulmonary Function Response to Exposure to Low Concentration Ozone in Young Adults: Inter-comparison among Studies and Meta-Analysis. American Thoracic Society Annual Meeting, San Fransisco, CA, May 13 - 18, 2016.

Impact/Purpose:

It is well established that moderate ozone exposures induce decrements in spirometric lung function measurements and respiratory symptoms in healthy young adults. However, studies for low concentration ozone near the current NAAQS standard (0.070 ppm) are limited to only a few and their conclusions are not entirely unanimous. Reasons for the inconsistency may be attributed partly to differences in the number of subjects and statistical methods used in each study. Purpose of this study is 1) to present our results obtained after 6.6 hour exposure to 0.06 ppm and 0.08 ppm ozone, 2) to evaluate the present and previously reported data with the same statistical method and 3)to examine overall effects of the exposures across the studies by meta-analysis.

Description:

Rationale: It is well established that moderate ozone exposures induce decrements in spirometry volume and respiratory symptoms in healthy young adults. However, studies for low concentration ozone near the current NAAQS standard (0.070 ppm) are limited to only a few and their conclusions are not entirely unanimous. Reasons for the inconsistency may be attributed partly to differences in the number of subjects and statistical methods used in each study. In the present study we report our results obtained after 6.6 hour exposure to 0.06 ppm and 0.08 ppm ozone, compared them with previous studies and evaluated overall effects of the exposures across the studies by meta-analysis. Methods: In a controlled environment chamber 29 healthy young adults (age = 19-35 years) were exposed to 0.00 (clean air, CA), 0.06 ppm and 0.08 ppm ozone for 6.6 hours with moderate exercise. Spirometry was performed (FEV1) and symptom scores were recorded at baseline and after each hour of exposure. % changes in FEV1 after 6.6 hour exposure were obtained for CA, ozone and CA-adjusted ozone. Results were compared with previous studies for 0.06 ppm (n=3) and 0.08 ppm (n=5) exposures after analyzing them with the same statistical method. We then calculated the average drop in FEV1 across the studies and examined heterogeneity of effect size estimates using random effects meta-analysis. Results: The % FEV1 decrement at 6.6 hour exposure adjusted to CA (mean±SEM) was 2.38±0.78% and 3.92±0.93% for 0.06 ppm and 0.08 ppm ozone, respectively (p<0.05 for both). Corresponding values in previously reported studies range from 1.51-3.52% for 0.06 ppm and 6.06-7.82% for 0.08 ppm. Meta-analysis showed that for 0.06 ppm the average FEV1 decrement across the studies was 1.73±0.40% unadjusted for CA and 2.34% adjusted for CA. Both were statistically significant (p<0.0001) and did not reveal evidence of heterogeneity (I2 statistic of 0% and 13%, respectively). For 0.08 ppm FEV1 decrement was 4.72±0.82% unadjusted for CA and 5.90±0.79% adjusted for CA. Both were statistically significant (p<0.0001) and showed moderate heterogeneity (I2 = 42% and 41%, respectively). Conclusions: Exposure to ozone causes a small but statistically significant decrement of FEV1 with or without adjustment to CA at a level of 0.06 ppm in healthy young adults. Clinical implications of such small changes in FEV1, however, may not be warranted. This work was funded by EPA but does not represent EPA policy.

Record Details: