Mean Lung Function Research Articles

Respiratory effects of mixed nitrogen dioxide and sulfur dioxide in human volunteers under simulated ambient exposure conditions

Normal and asthmatic volunteers ( N = 24 and 19, respectively) were exposed to mixed nitrogen dioxide (NO 2) and sulfur dioxide (SO 2) in purified background air in an environmental chamber under conditions simulating an ambient pollution episode. The NO 2 concentration was 0.5 ppm; the SO 2 concentration was 0.5 ppm for normals and 0.3 ppm for asthmatics. Exposures lasted 2 hr and included intermittent exercise and heat stress. Control studies consisted of similar exposures to purified air alone. The mixed pollutant gases may have reacted chemically in the exposure chamber, but no appreciable amounts of sulfate or nitrate aerosol were detected there. Group mean lung function changes during exposure generally were not significantly different from control for normals or for asthmatics. Symptoms reported by the normal group showed a small significant overall increase during pollutant exposure and later the same day relative to the corresponding control periods; the asthmatics showed a small significant increase later in the day but not during exposure. The increased symptom reporting showed little consistency from subject to subject: there were small increases for most individual symptom categories evaluated, none of them statistically significant. The results are not sufficient to establish whether this slight and nonspecific clinical response should be attributed to the pollutant mixture or to some other aspect of the exposure protocol.

Air pollution and health in three urban communities.

A health study was conducted in three communities in the greater Montreal region; the first two were characterized by relatively high particulate and sulfur dioxide levels, respectively, and a third community without major industrial pollution. In each community, 300 men and women 45 to 64 yr of age were studied. Residents of the two more polluted communities exhibited a higher prevalence of respiratory symptoms and mean lung function evaluated by various tests was lower than in residents of the less polluted community. When intercity differences in age and smoking were accounted for, no statistically significant intercity differences in health status could be shown. Given the limitations of this study, the results provide no evidence to suggest that current Canadian standards for sulfur dioxide adequately protect human health as measured by the indices used in the study, for adults in the age range of 45 to 64 yr.