ENVIRONMENTAL EXPOSURE

Traffic related air pollution as a determinant of asthma among Taiwanese school children

B-F Hwang¹, Y-L Lee², Y-C Lin³, J J K Jaakkola⁴, Y L Guo²

¹ Department of Health Care Administration, Diwan College of Management, Tainan, Taiwan; and Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan
² Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan; and Department of Internal Medicine, National Cheng Kung University Hospital, Tainan, Taiwan
³ College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
⁴ Institute of Occupational and Environmental Medicine, University of Birmingham, Birmingham, UK

Correspondence to:
Correspondence to:
Dr Y L Guo
Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan; leonguo{at}mail.ncku.edu.tw

Background: There is evidence that long term exposure to ambient air pollution increases the risk of childhood asthma, but the role of different sources and components needs further elaboration. To assess the effect of air pollutants on the risk of asthma among school children, a nationwide cross sectional study of 32 672 Taiwanese school children was conducted in 2001.

Methods: Routine air pollution monitoring data for sulphur dioxide (SO₂), nitrogen oxides (NOx), ozone (O₃), carbon monoxide (CO), and particles with an aerodynamic diameter of 10 µm or less (PM₁₀) were used. Information on individual characteristics and indoor environments was from a parent administered questionnaire (response rate 93%). The exposure parameters were calculated using the mean of the 2000 monthly averages. The effect estimates were presented as odds ratios (ORs) per 10 ppb changes for SO₂, NOx, and O₃, 100 ppb changes for CO, and 10 µg/m³ changes for PM₁₀.

Results: In a two stage hierarchical model adjusting for confounding, the risk of childhood asthma was positively associated with O₃ (adjusted OR 1.138, 95% confidence interval (CI) 1.001 to 1.293), CO (adjusted OR 1.045, 95% CI 1.017 to 1.074), and NOx (adjusted OR 1.005, 95% CI 0.954 to 1.117). Against our prior hypothesis, the risk of childhood asthma was weakly or not related to SO₂ (adjusted OR 0.874, 95% CI 0.729 to 1.054) and PM₁₀ (adjusted OR 0.934, 95% CI 0.909 to 0.960).

Conclusions: The results are consistent with the hypothesis that long term exposure to traffic related outdoor air pollutants such as NOx, CO, and O₃ increases the risk of asthma in children.

Abbreviations: CO, carbon monoxide; NOx, nitrogen oxides; O₃, ozone; PM₁₀, particles with aerodynamic diameter 10 µm or less; SO₂, sulphur dioxide

Keywords: asthma; children; air pollution

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