Association of indoor air quality and preschool children's respiratory symptoms

Background: This study aimed to assess the association between exposure to indoor air pollution in DCCs (Child Day Care Centers) and the respiratory symptoms of children under 6 years old. Methods: Air quality data were collected three times regarding to seasonal variation. Pollutants measured in 11 DCCs included PM10, CO, NO2, SO2, O-3, benzene, bacteria, fungi, and dust mite. The frequency of respiratory symptoms including coughing, rhinitis, and dyspnea were recorded via teacher and parent-report questionnaires. Fractional exhaled nitric oxide (FENO) levels were measured to assess airway inflammation. Results: 436 children participated in the study. 83% completed data collection in all 3 seasons. The frequency of rhinitis correlated with PM, 0 (IRR=70.3, 95% CI=12.4-399.7, p<0.001), CO (IRR=3.2, 95% CI=2.4-4.2, p<0.001), benzene (IRR=2.3, 95% CI=1.8-3.2, p<0.001) and D. Pteronyssinus level (IRR=2.1, 95% CI=1.7-2.7, p<0.001). The frequency of coughingcorrelated with levels of PM10 (IRR=15.2, 95% CI=3.0-78.2, p<0.001), CO (IRR=2.8, 95% CI=2.1-3.7, p<0.001), benzene (IRR=1.4, 95% CI=1.1-1.9, p=0.02). The frequency of dyspnea correlated with D. Pteronyssinus level (IRR=3.9, 95% CI=1.7-9.1, p=0.001). FENO levels associated with high benzene levels (OR=5.9, 95% CI=1.5-22.9, p=0.01). The majority of DCCs had at least one PM10 measurement above the standard level, and these high levels were noted in all 3 seasons. Three DCCs had PM10 levels above the standard level in all seasons. 64% of the DCCs had indoor bacterial counts above the standard level in all seasons. Conclusions: PM10 and bacterial count is a significant problem in Bangkok metropolitan DCCs. The respiratory symptoms of children positively associated with PM10, CO, benzene and dust mite levels.