Background

Two-thirds of complaints received by the Hong Kong Environmental Protection Department in 1988 were related to poor air quality.

In July 1990 legislation was implemented to reduce fuel sulphur levels.

The objective of this study was to measure the impact of the intervention on respiratory health in primary school children.

Methods

In all, 3521 children, mean age 9.51 years (SD=0.78), from two districts with good and poor air quality respectively before intervention were followed yearly from 1989 to 1991.

Children and parents reported the children's respiratory symptoms using self-completed questionnaires.

Factor analysis was used to derive independent scores from 12 symptoms.

Four groups of related symptoms were identified and binary variables (presence of any symptom in each group) were treated as dependent variables in modelling using generalized estimating equations procedures.

Results

In 1989 and 1990 an excess of respiratory symptoms was observed in the polluted compared with unpolluted district.

The significant effects (odds ratio [OR], 95% confidence interval [CI], P value) associated with living in the polluted district were : cough and sore throat (OR=1.22,95% CI : 1.04-1.43, P<0.01) and wheezing (OR=1.35,95% CI : 1.10-1.66, P<0.01).

After the intervention, in the polluted district only, sulphur dioxide levels fell by up to 80% and sulphate concentrations in respirable particulates by 38%. (...)