The increasing number of media reports in the 1980s on the pollution of the environment in Hong Kong reflected the growing concern of people about the impact of that environment on their quality of life. In 1988, 66% of all complaints to the Hong Kong Environmental Protection Department were about air pollution. In 1989, in Kwai Tsing District, a relatively polluted area in Hong Kong, the 24-hour mean and annual mean concentrations were respectively: 350 µg/m 3 and 80 µg/m 3 for sulphur dioxide

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... (SO 2 ); 260 µg/m 3 and 80 µg/m 3 for total suspended particulates (TSP); 180 µg/m 3 and 55 µg/m 3 for respirable suspended particulates (RSP); and 150 µg/m 3 and 80 µg/m 3 for nitrogen dioxide (NO 2 ). These concentrations exceeded the air quality objectives for air pollutants in Hong Kong. 1 Early air pollution studies showed that high concentrations in ambient air of particulates and SO 2 , which resulted from coal burning, were harmful to respiratory health. 2 Although the concentration levels of particulates and SO 2 have been reduced after implementation of legislation on air pollution in most western countries, at relatively low concentration level, they might still adversely affect human health. 3-6 A review of recent 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 intervention led to a reduction in respiratory symptoms and bronchial hyperresponsiveness of primary school children. The objectives of this study were to investigate the differences in respiratory health between non-smoking women living in the more polluted district (Kwai Tsing) and those living in the less polluted district (Southern); to assess the impact of the government air quality intervention; and to study the effect of environmental tobacco smoke on respiratory health in non-smoking women in both districts. Method A total of 3405 non-smoking women, aged 36.5 years (standard deviation = 3.0), from two districts with good and poor air quality respectively before the intervention were followed yearly from 1989 to 1991. Binary latent variable modelling was used to summarize the six respiratory symptoms and to estimate the effects of risk factors. Results In 1989, living in the polluted district was associated with poor respiratory health (odds ratio [OR] = 1.55, 95% confidence interval [CI] : 1.11-2.17, P Ͻ 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%. Between 198938%. Between and 199038%. Between -1991 was no significantly greater decline (P Ͼ 0.241) in the more polluted compared with the less polluted district for poor respiratory health. In 1989, the effects on poor respiratory health for exposure to two or more categories of smokers relative to none in the home (OR = 1.80, 95% CI : 1.15-2.83, P Ͻ 0.01) were higher but not significantly than those for living in polluted relative to less polluted district (95% CI of the two effects overlapping each other). Conclusions Environmental tobacco smoke (ETS) and outdoor air pollution had independent adverse effects on respiratory health of non-smoking women and improvement in air quality had produced some but non-significant benefits.