  Sulfuric acid aerosol is suspected to be a major contributor to mortality and
morbidity associated with air pollution. The objective of the study is to
determine if exposure of human participants to anticipated levels of sulfuric
acid aerosol ($\sim 100\mu g/m^3 $) in the near future would have an adverse
effect on respiratory function. We used data from 28 adults exposed to sulfuric
acid for 4 hours in a controlled exposure chamber over a 3 day period with
repeated measures of pulmonary function (FEV1) recorded at 2-hour intervals.
Measurements were also recorded after 2 and 24 hours post exposure. We
formulated a linear mixed effect model for FEV1 with fixed effects (day of
treatment, hour, day-hour interaction, and smoking status), a random intercept
and an AR1 covariance structure to estimate the effect of aerosol exposure on
FEV1. We further assessed whether smoking status modified the exposure effects
and compared the analysis to the method used by Kerr et al.,1981. The findings
of the study show that the effect of day 3 exposure is negatively associated
with lung function (coefficient ($\beta$), -0.08; 95% CI, -0.16 to -0.01). A
weak negative association is also observed with increasing hours of exposure
($\beta$, -0.01; 95% CI, -0.03 to 0.00). Among the smokers, we found a
significant negative association with hours of exposure ($\beta$, -0.02; 95%
CI, -0.03 to -0.00), day 3 exposure ($\beta$, -0.11; 95% CI, -0.14 to -0.02)
and a borderline adverse effect for day 2 treatment ($\beta$, -0.06; 95% CI,
-0.14 to 0.03) whilst no significant association was observed for nonsmokers.
In conclusion, 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.
