Field Studies of Health Effects from Acute Exposures to Secondary Ambient Air Pollutants

ABSTRACT

A series of field studies involving repetitive functional measurements in relatively small populations of healthy children and adults engaged in normal outdoor activities has shown that significant decrements in respiratory function are associated with exposures to ozone (O₃) at concentrations well below the current U.S. National Ambient Air Quality Standard (NAAQS). The ability to detect such effects can be attributed, at least in part, to the study design used, which emphasized maximization of signal-to-noise ratios. Locations were selected to ensure relatively high exposures to relatively uniformly distributed secondary pollutants such as ozone and acidic aerosols, with minimal exposure to local sources of primary pollutants. Populations were selected that would be engaged in active recreation out-of-doors. Populations of healthy persons were used to minimize variability in baseline function. The magnitude of the O₃ associated decrements in respiratory function is dependent on the sensitivity to O₃ among the members of the population, the minute ventilation during outdoor activity, and the duration of the outdoor exposure. Furthermore, a comparison of the results from these field studies with those from controlled chamber exposure studies suggests that the O₃ associated responses are potentiated by the presence of other air pollutants.