Comparison between two districts of the effects of an air pollution intervention on bronchial responsiveness in primary school children in Hong Kong

Abstract

Study objective - This study examined the impact on children's respiratory health of a government air quality intervention that restricted the sulphur content of fuels to 0.5% from July 1990 onwards. Design/setting/participants - This study examined the changes, one and two years after the introduction of the intervention, in airway hyperreactivity of non-asthmatic and non-wheezing, primary 4, 5, and 6, school children aged 9-12 years living in a polluted district compared with those in a less polluted district. Bronchial hyperreactivity (BHR) (a 20% decrease in FEV, provoked by a cumulative dose of histamine less than 7.8 μmol) and bronchial reactivity slope (BR slope) (percentage change in logarithmic scale in FEV, per unit dose of histamine) were used to estimate responses to a histamine challenge. The between districts differences after the intervention were studied to assess the effectiveness of the intervention. Main results - In cohorts, comparing measurements made before the intervention and one year afterwards, both BHR and BR slope declined from 29% to 16% (p = 0.026) and from 48 to 39 (p = 0.075) respectively in the polluted district; and from 21% to 10% (p = 0.001) and 42 to 36 (p > 0.100) in the less polluted district. Comparing measurements made in 1991 (one year after intervention) with those in 1992 (two years after intervention), only the polluted district showed a significant decline from 28% to 12% (p = 0.016) and from 46 to 35 (p = 0.014), for BHR and BR slope respectively, with a greater decline in both responses (p = 0.018 and 0.073) than in the less polluted district. Conclusion - Bronchial hyperresponsiveness tests can be used to support the evaluation of an air quality intervention. The demonstrated reduction in bronchial hyperresponsiveness is an indication of the effectiveness of the intervention.