Assessing the effects of exposure to sulfuric acid aerosol on respiratory function in adults
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Background: Sulfuric acid aerosol is suspected to be a major contributor to mortality and morbidity associated with air pollution. Objective: To determine if exposure of human participants to anticipated levels of sulfuric acid aerosol (∼ 100μ g/m^3 ) in the near future would have an adverse effect on respiratory function. Methods: We used data from 28 adults exposed to sulfuric acid for 4 hours in a controlled exposure chamber over a 3 day period with repeated measures of pulmonary function (FEV1) recorded at 2 hour intervals. Measurements were also recorded after 2 and 24 hours post exposure. We formulated a linear mixed effect model for FEV1 with fixed effects (day of treatment, hour, day-hour interaction, and smoking status), a random intercept and an AR1 covariance structure to estimate the effect of aerosol exposure on FEV1. We further assessed whether smoking status modified the exposure effects and compared the analysis to the method used by Kerr et al.,1981. Results: The effect of day 3 exposure is negatively associated with lung function (coefficient (β), -0.08; 95 negative association is observed with increasing hours of exposure (β, -0.01; 95 negative association with hours of exposure (β, -0.02; 95 -0.00), day 3 exposure (β, -0.11; 95 borderline adverse effect for day 2 treatment (β, -0.06; 95 0.03) whilst no significant association was observed for nonsmokers. Conclusions: Anticipated deposits of sulfuric acid aerosol in the near would adversely affect respiratory function. The effect observed in smokers is significantly more adverse than in nonsmokers.
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