Abstract
The first section of this concluding part reviews epidemiological studies relating to oxidant exposures. There are convincing data from the eastern section of the continent that ozone, in combination with aerosol sulphates and acid aerosols, is strongly associated with hospital emergency visits and in-patient admissions for acute respiratory disease, including asthma. There is some evidence that long term exposures may be associated with an increased prevalence of asthma; disturbing initial observations suggest the possibility that a chronic respiratory bronchiolitis may be induced. The second section of this article reviews the totality of information on ozone in the light of customary criteria of ‘causality’. It is concluded that the present evidence justifies the conclusion that exist ing levels of tropospheric ozone are aggravating existing human disease, and probably increasing the prevalence and incidence of some diseases; however, it is uncertain whether this effect is being magnified by the concomitant presence of other pollutants. Although a great deal is known about the effects of ozone, there are still many important unresolved questions in relation to it.