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The standards promulgated by the Environmental Protection Agency under the Clean Air Act must protect the health of all persons, regardless of individual susceptibility. To provide the data needed to set such standards, both clinical and short-term epidemiological investigations of subjects considered to be susceptible have been undertaken. Recent clinical studies involving the exposure of asthmatics to sulfer dioxide, nitrogen dioxide, and ozone were reviewed to determine the characteristics of the study subjects. The subjects in these investigations tended to be young adults with mild asthma, frequently not requiring medications. In most of the studies, only a minority of the subjects had airflow obstruction at the time of testing. In contrast, data from general population surveys show that asthma is equally common among younger and older persons and that many asthmatics in the general population have clinically significant impairment of lung function. The clinical studies thus provide information about the responses of a susceptible group, but not about the members of the group who may have the greatest susceptibility. To characterize the representativeness of subjects in clinical and epidemiological studies of asthma, the characteristics of individual subjects should be provided in reports. Appropriate instruments should be developed for this task.
air pollution, asthma, experimental design, host factors, susceptibility
Professor of medicine, Cancer Center, University of New Mexico, Albuquerque, NM