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.
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.
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.
In Asia where air quality is poor and deteriorating, there is very little local data on the long-term effects of PM2.5. The limited number of studies done suggested it can be an important cause of morbidity and mortality. This cohort study was done 1998-2001 and consisted of 66,820 participants >65 years of age who were enrolled and interviewed in 18 Elderly Centers of the Department of Health, Hong Kong. All residential addresses were geocoded and the U.S. NASA satellite data were used for proxy exposure estimates to PM2.5. Cox regression models were used to calculate hazard ratios of mortality associated with PM2.5. Results suggested that in Hong Kong, exposure to PM2.5 was associated with mortality from natural causes, cardiovascular causes, ischemic heart disease, cerebrovascular disease and respiratory causes. This study proved that NASA satellite data can be a readily accessible and affordable approach to estimate a sufficient range of PM2.5 in any single city.
Interactions between temperature and PM2.5 on mortality have not been well studied. Hence this study aimed at assessing the modification of temperature on the association between PM2.5 and cause specific mortality, by stratifying temperature into low, medium and high stratum in Hong Kong. Data retrieved from 1999-2011 were used for the study. Results showed a statistically significant interaction of PM2.5 and temperature between low and high temperature stratum for all natural mortality and mortality. Mortality effects of PM2.5 were stronger in low temperature stratum as oppose to those in high temperature stratum. In conclusion, temperature might modify mortality effects of PM2.5.
In recent years, air pollution in China especially in the Pearl River Delta (PRD) had drastically increased. The annual mean ground level concentrations of PM2.5 were modelled based on worldwide satellite information and meteorological data from 40 cities outside the PRD. In order to estimate the annual mean concentration of PM2.5 in the PRD, the spatial –temporal dimensions of the model was validated. Meta-analysis was then used to assess health impacts and pooled excess risks of mortality in China. Results from the models and analyses revealed excess death rates were 2006 and 1069 per million people and the associated deaths for all cause and cardiopulmonary diseases were 3,386 and 2,639 respectively.
Air Quality Guidelines (AQG) launched by World Health Organization (WHO) in 2006, does not provide sufficient information on health impacts and relationships between short-term and annual AQG needed for health protection. This study focused on testing whether relationships between WHO short-term and annual AQG for PM10, PM2.5 and NO2 were consistent worldwide by obtaining air pollutant data over seven years (2004-2010) in seven Asia-Pacific cities, North America and Europe. Annual limits for SO2 and O3 based on the short-term AQG were also collected. A new method was developed based on the probability distribution concept, which was used to derive limit value one from another in each paired limits for each pollutant with the capability to account for allowable exceedances. Results revealed the pool mean short-term limit for NO2 was way lower than WHO-AQG (200 µg/m3). PM10 and PM2.5 limits were similar to WHO-AQG. In conclusion, WHO needs to lower the short-term AQG for NO2 for concordance with the selected annual AQG for health protection. Unlike NO2, empirical data from all seven cities for PM10 and PM2.5 supported the distribution relationship between the current short-term and annual WHO-AQG.
In South East Asia, global marine vessels has an impact on human health. In the Pearl River Delta (PRD) health burdens from both ocean and river going vessels are not quantified. In order to quantify these health effects, this study estimated the potential health impacts using pooled relative risks of mortality and hospital admissions in China and model derived concentration of major pollutants (SO2, PM10, NO2 and O3) due to marine vessels emission. In the PRD area the number of natural deaths were less than the hospital admissions from cardiorespiratory causes attributable to the pollutants studied. In conclusion, marine emission control measures could contribute to a large reduction in mortality and hospital admissions in the PRD regions especially in Hong Kong.
A regulation was implemented restricting sulfur to 0.5% by weight in fuel. This lead to a reduction of respiratory symptoms, an improvement in bronchial hyperresponsiveness in children. This study evaluated the short-term effects on mortality of changes in the pollutant mix after sulfur intervention, particularly with changes in PM chemical species; improved the methodology for assessment of the health impact in terms of changes in life expectancy; and developd an approach for analyzing changes in life expectancy. In order to carry out the study, Poisson regression core models were used to assess the short-term effects on mortality as a result of changes in the pollutant mix. In this study, life expectancy loss was small compared to other studies due to a small observation window of three years, whereas other studies did observations for 16 years. PM10 and SO2 exposures were associated with a change in life expectancy. In conclusion, exposure to chemical species is a health hazard. In terms of changes in life expectancy, times-series is a great method to assess short- and long-term effects once you have complete daily air pollution and mortality data over a long period.
We conducted a health impact assessment of the government's proposed new air quality objectives (AQO) in Hong Kong. We based this on the 2005 WHO-AQG and used a lognormal probability density function to model possible changes in annual mean pollutant levels resulting from the new AQO. All of the proposed short-term AQO were based on WHO interim targets (IT) or AQG, but allowed additional exceedances of these single limit values. Compliance with these short-term AQO may reduce the current annual mean concentrations but the distribution proportions exceeding the annual AQG remain high. If the proposed legal limits of AQO are fully exploited by polluters, we estimated the annual number of avoidable deaths at 1860, and avoidable health care events at 5.2 million doctor visits and 92,745 hospital bed-days with a total annual community cost of US$2.6 billion. The proposed AQO may only reduce the current air pollution health impacts by 17% but could achieve 41% reduction if additional exceedances were not permitted. This analysis demonstrates problems arising from the absence of annual limits for some pollutants and the discordance between the short-term and annual AQG, suggesting that revisions based on a lognormal probability model should be considered.
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