previous controlled studies have indicated that asthma medication modifies the adverse effects of sulfur dioxide ( so2 ) on lung function and asthma symptoms . 
 the present report analyzed the role of medication use in a panel study of children with mild asthma . 
 children from sokolov ( n = 82 ) recorded daily peak expiratory flow ( pef ) measurements , symptoms , and medication use in a diary . 
 linear and logistic regression analyses estimated the impact of concentrations of sulfate particles with diameters less than 2.5 microns , adjusting for linear trend , mean temperature , weekend ( versus weekday ) , and prevalence of fever in the sample . 
 fifty - one children took no asthma medication , and only 31 were current medication users . 
 most children were treated with theophylline ; only nine used sprays containing beta - agonist . for the nonmedicated children , 
 weak associations between a 5-day mean of sulfates and respiratory symptoms were observed . 
 medicated children , in contrast , increased their beta - agonist use in direct association with an increase in 5-day mean of sulfates , but medication use did not prevent decreases in pef and increases in the prevalence of cough attributable to particulate air pollution . 
 medication use was not a confounder but attenuated the associations between particulate air pollution and health outcomes.imagesfigure 1.figure 1.figure 2 . 
 afigure 2 . 
 b