In two-pollutant models, the associations between hospital
admission for asthma and SO2 as well as NO2 were robust after
adjustment for PM10. The effect of NO2 did not alter much after
adding SO2 into the models; however, when adjusted for NO2, the
effect of SO2 decreased and became nonsignificant. The relationship
between asthma and PM10 remains nonsignificant after adjusting
for SO2 or NO2.