Analysis of the concentration–respiratory response among asthmatics following controlled short-term exposures to sulfur dioxide

Some of the most compelling evidence of sulfur dioxide (SO2)-induced respiratory morbidity is derived from a large body of studies involving controlled short-term exposures among groups of asthmatic volunteers. These studies were extensively cited in the recently completed review of the primary National Ambient Air Quality Standards for SO2. Although it is clear from these investigations that exposure to SO2 may result in a significant increase in bronchoconstriction, there is uncertainty regarding the range of concentrations over which this respiratory response occurs. The objective of this study was to better characterize the concentration–response relationship between SO2 and measures of bronchoconstriction using individual subject lung function response data. In reviewing studies of asthmatics exposed to SO2 during 5- to 10-min periods of elevated ventilation, we observed clear and consistent evidence of an increase in the bronchoconstrictive response to SO2 with increasing exposure concentrations bet...