Long-term fine particulate matter exposure and nonaccidental and cause-specific mortality in a large national cohort of Chinese men

Abstract

BACKGROUND: Cohort studies in North America and western Europe have reported increased risk of mortality associated with long-term exposure to fine particles (PM2.5), but to date, no such studies have been reported in China, where higher levels of exposure are experienced. OBJECTIVES: We estimated the association between long-term exposure to PM2.5with nonaccidental and cause-specific mortality in a cohort of Chinese men. METHODS: We conducted a prospective cohort study of 189,793 men 40 y old or older during 1990-91 from 45 areas in China. Annual average PM2.5levels for the years 1990, 1995, 2000, and 2005 were estimated for each cohort location using a combination of satellite-based estimates, chemical transport model simulations, and ground-level measurements developed for the Global Burden of Disease (GBD) 2013 study. A Cox proportional hazards regression model was used to estimate hazard ratios (HR) for nonaccidental cardiovascular disease (CVD), chronic obstructive pulmonary disease (COPD), and lung-cancer mortality. We also assessed the shape of the concentration-response relationship and compared the risk estimates with those predicted by Integrated Exposure-Response (IER) function, which incorporated estimates of mortality risk from previous cohort studies in western Europe and North America. RESULTS: The mean level of PM2.5exposure during 2000-2005 was 43.7 μg/m3(ranging from 4.2 to 83.8 μg/m3). Mortality HRs (95% CI) per 10-μg/m3increase in PM2.5were 1.09 (1.08, 1.09) for nonaccidental causes; 1.09 (1.08, 1.10) for CVD, 1.12 (1.10, 1.13) for COPD; and 1.12 (1.07, 1.14) for lung cancer. The HR estimate from our cohort was consistently higher than IER predictions. CONCLUSIONS: Long-term exposure to PM2.5was associated with nonaccidental, CVD, lung cancer, and COPD mortality in China. The IER estimator may underestimate the excess relative risk of cause-specific mortality due to long-term exposure to PM2.5over the exposure range experienced in China and other low-and middle-income countries.