Air quality has deteriorated in Hong Kong over more than 15 years. As part of a program of public accountability, photographs on Poor and Better visibility days were used as representations of the relationships among visibility, air pollution, adverse health effects, and community costs for health care and lost productivity. Coefficients from time-series models and gazetted costs were used to estimate the health and economic impacts of different levels of pollution. In this population of 6.9 million, air quality improvement from the annual average to the lowest pollutant levels of Better visibility days, comparable to the WHO-AQG, would avoid 1335 deaths, 60,587 hospital bed days, and 6.7 million doctor visits for respiratory complaints each year. Direct costs and productivity losses avoided would be over US$240 million a year. The dissemination of these findings led to increased demands for pollution controls from the public and legislators, but denials of the need for urgent action arose from the government. The outcome demonstrates the need for more effective translation of the scientific evidence base into risk communication and public policy.

We assessed the long-term effects of PM2.5 on cancer mortality for multiple causes. In Hong Kong, most people live and work in urban/suburban areas with high-rise buildings. This facilitates the estimation of PM2.5 exposure of individuals, taking into account the height of residence for assessment of long-term health effects with sufficient statistical power. Annual concentrations of PM2.5 at 66,820 recruited persons' (aged ≥65) residential addresses were estimated using PM2.5 concentrations measured at fixed-site monitors, horizontal-vertical locations, and satellite data. Cox regression models were used assess the hazard ratios of cancer mortality associated with PM2.5. We found that PM2.5 was associated with mortality from all causes of cancer, and from digestive cancer in all subjects; breast cancer in females; and lung cancer in males. This study is particularly timely in China, where compelling evidence is needed to support the pollution control policy to ameliorate the health damages associated with economic growth.

We have developed a simple and concise method to construct an air quality index (AQI) that accounted for additive effects of multiple pollutants to quantify air quality conditions for Hong Kong. We obtained concentrations of four criteria pollutants (PM₁₀, SO2, NO2 and O3) and daily cardio-respiratory hospital admissions in Hong Kong for all ages and aged ≥ 65 from 2001 to 2012. We derived sub-indices of the four criteria pollutants, calculated by normalizing pollutant concentrations to their respective short-term WHO AQG. The combined condition of observed high-pollution days as either at least one pollutant >1.5×WHO AQG or at least two pollutants >1.0×WHO AQG to characterize the typical pollution profiles was identified. We aggregated the sub-indices using the root-mean-power function with the resulted optimal power=3 to form an overall AQI. Using a time-stratified case-crossover design, significant associations were found between hospital admissions and the pollution bands of the index. The trends of increasing pollution bands in relation to increasing excess risks of hospital admissions were significant, suggesting a dose-response relation.

Little is known about the effect of air pollution on the gastrointestinal system. We studied the association between long-term exposures to outdoor PM2.5 and hospitalization for peptic ulcer diseases (PUD) in a large cohort of 66,820 Hong Kong Chinese elderly (aged ≥65). PM2.5 exposure at residence of individuals were estimated by satellite data through linkage with address details including floor level. Hospital admission records of the participants up to December 31, 2010 were retrieved from the central database of Hospital Authority. Cox regression was used to estimate the hazard ratio for PUD hospitalization associated with PM2.5 exposures. During the follow-up period, 1991 (3.3%) subjects had been hospitalized for PUD. It was found that PM2.5 exposure was associated with PUD hospitalization. Further analysis showed that the associations were significant for gastric ulcers but not for duodenal ulcers. The mechanism underlying the PM2.5 in the development of gastric ulcers warrants further research.