Effects of single- and multiday ozone exposures on respiratory function in active normal children.

Ventilatory function was measured twice daily on 46 healthy children aged 8-14 years on at least 7 days for each child during a 4-week period at a northwestern New Jersey residential summer camp in 1988. The highest 1-hr O3 concentration was 150 ppb, while the highest 12-hr H+ concentration (as H2SO4) was 18.6 micrograms/m3. The highest temperature-humidity index was 81 degrees F. The regressions of FVC, FEV1, FEF25-75, and PEFR on O3 in the hour preceding the afternoon function measurements yielded slopes essentially the same as those measured on other children at the same camp in 1984. Regressions of the changes in function between the late morning and late afternoon function measurements on average O3 concentration between them produced significant, but somewhat smaller effects, while regressions of morning function on O3 during the previous day indicated small but still significant effects. There were no significant correlations with other measured environmental variables including H+. Based on the results of this study and similar previous studies, we conclude that O3 exposures in ambient air produce greater lung function deficits in active young people in natural settings then does pure O3 in controlled chamber exposure studies because of: (1) longer exposures; (2) potentiation by other factors in the ambient exposures; (3) the persistence of effects from prior day's exposures; and (4) the persistence of a transient response associated with the daily peak of exposure. It follows that projections of likely effects in the real world from controlled chamber exposure studies should either have a large margin of safety, or the judgment of the extent of effects likely to occur among populations should be based directly on the effects observed in field studies.