[General environmental pollutants: effect on at-risk groups]

A number of epidemiologic studies have emphasized the relationship between air pollution and the frequency of respiratory symptoms in patients with underlying airway diseases. On the basis of acute controlled exposure studies, SO2 causes transient airflow obstruction in patients with asthma, but not necessarily in patients with bronchitis or lung fibrosis. The photochemical oxidants (ozone, NO2) induce an increase in airway responsiveness, ozone being of greater potential hazard than NO2. These effects have been described for healthy subjects and asthmatics. Acid aerosols may produce transient bronchoconstriction in asthmatics. In general, the harmful effects of polluted air will first affect the most sensitive persons in the population, such as asthmatics.