Acute effects of air pollution on respiratory health of children in Maemoh, Thailand

Epidemiological studies to evaluate the acute effect of ambient SO ₂ on respiratory health are still inconclusive and studies in Asian countries are still limited. This study examined the association of short-term exposure to sulfur dioxide with occurrence of acute respiratory symptoms and changes in pulmonary function among children in the Maemoh district of Thailand. A panel study was conducted on 196 asthmatic and non-asthmatic children aged 6–14 yrs who resided in a community near a power plant during Oct 1, 1997–Jan 15, 1998. The children were interviewed daily and coached for performing pulmonary function tests. Air pollution concentration, expressed as 24-hr average SO₂ and PM₁₀, were obtained from outdoor fixed monitoring stations in the community; ranged from 1.8 to 128 μg/m 3 and from 4.2 to 153.2 μg/m3 respectively. For asthmatic children, we observed a weak negative association of SO₂ with pulmonary function but not with respiratory symptoms. On a microgram per cubic meter basis, stronger associations of daily particulate air pollution concentrations with respiratory health outcomes were observed. A 10 μg/m 3 increment in PM₁₀ was associated with changes in FVC (−4.4 ml, 95%CI −11.4, 2.6), FEV₁ (−3.1 ml, 95% CI −9.4, 3.2), PEFR (−18.3 ml.sec−1, 95% CI −31.8, −4.8) and FEF_25–75% (−3.4 ml.sec −1, −13.7, 6.9) and modestly associated with increases of similar magnitude in both prevalence and incidence of lower respiratory symptoms (eg. Prevalence odds ratio, POR = 1.02, 95%CI = 0.98, 1.06) and cough (eg. POR = 1.03, 95% CI = 1.00, 1.06) in asthmatic children. No consistent direction of association between daily air pollution and pulmonary function or respiratory symptoms was observed in non-asthmatic children. In conclusion, at the air pollution levels observed during the study, daily decrement in pulmonary function and increased prevalence and incidence of respiratory symptoms are more likely to be associated with particulate air pollution rather than with SO₂ on a μg/m3 basis. Evidence of variation in association of SO₂ and PM₁₀ with pulmonary function changes across children (heterogeneous response) was observed among asthmatics.