| Summary: | <p><b>Background:</b> A limited number of studies on long-term effects of particulate matter with aerodynamic diameter <2.5 µm (PM<sub>2.5</sub>) on health suggest it can be an important cause of morbidity and mortality. In Asia where air quality is poor and deteriorating, local data on longterm effects of PM<sub>2.5</sub> to support policy on air quality management are scarce.</p> <p><b>Objectives:</b> We assessed long-term effects of PM2.5 on the mortality in a single Asian city.</p> <p><b>Methods:</b> We followed up for 10–13 years a cohort of 66,820 participants aged ≥65 who were enrolled and interviewed in all 18 Elderly Health Centres of the Department of Health, Hong Kong in 1998–2001. Their residential addresses were geo-coded into x- and y- coordinates and their proxy exposures to PM<sub>2.5</sub> at their addresses in 1×1 km grids were estimated from the US National Aeronautics and Space Administration (NASA) satellite data. We used Cox regression models to calculate hazard ratios (HRs) of mortality associated with PM2.5.</p> <p><b>Results:</b> Mortality HRs per 10-µg/m<sup>3</sup> increase in PM<sub>2.5</sub> were 1.14 (95% CI: 1.07, 1.22) for all natural causes, 1.22 (95% CI: 1.08, 1.39) for cardiovascular causes, 1.42 (95% CI: 1.16, 1.73) for ischemic heart disease, 1.24 (95% CI: 1.00, 1.53) for cerebrovascular disease, and 1.05 (95% CI: 0.90, 1.22) for respiratory causes.</p> <p><b>Conclusions:</b> Our methods in using NASA satellite data provide a readily accessible and affordable approach to estimation of a sufficient range of individual PM<sub>2.5</sub> exposures in a single city. This approach can expand the capacity to conduct environmental accountability studies in areas with few measurements of fine particles.</p>
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