Satellite-based estimates of long-term exposure to fine particles and association with mortality in elderly Hong Kong residents

Background: A limited number of studies on long-term effects of particulate matter with aerodynamic diameter < 2.5 μm (PM_2.5) 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 long-term effects of PM_2.5 to support policy on air quality management are scarce. Objectives: We assessed long-term effects of PM_2.5 on the mortality in a single Asian city. Methods: For 10–13 years, we followed up a cohort of 66,820 participants ≥ 65 years of age 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 geocoded into x- and y-coordinates, and their proxy exposures to PM_2.5 at their addresses in 1 × 1 km grids were estimated from the U.S. National Aeronautics and Space Administration (NASA) satellite data. We used Cox regression models to calculate hazard ratios (HRs) of mortality associated with PM_2.5. Results: Mortality HRs per 10-μg/m³ increase in PM_2.5 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 cerebro vascular disease, and 1.05 (95% CI: 0.90, 1.22) for respiratory causes. conclusions: Our methods in using NASA satellite data provide a readily accessible and affordable approach to estimation of a sufficient range of individual PM_2.5 exposures in a single city. This approach can expand the capacity to conduct environmental accountability studies in areas with few measurements of fine particles.