Mortality and long-term exposure to source-specific PM2·5: evidence from a national cohort study in China

Background

The hazardous effects of fine particulate matter (PM2·5) could vary by source. However, evidence regarding the long-term effects of source-specific PM2·5 on mortality is scarce, particularly in countries with high levels of pollution. We aimed to assess the associations between long-term exposure to source-specific PM2·5 and mortality in China, a low-income and middle-income country with high concentrations of PM2·5.

Methods

This nationwide cohort study used data from the 2010–11 wave of the China Chronic Disease and Risk Factor Surveillance (CCDRFS) project, which surveyed a geographically and socioeconomically representative sample of participants aged 18 years and older across mainland China. Participants were followed up through mortality information from the national Disease Surveillance Point system. Source-specific PM2·5 concentrations were estimated by combining high-resolution concentration predictions generated by a random forest model with estimates of the proportions contributed by each of six PM2·5 sources—industry, energy, transportation, residential, agriculture, and other—derived from the Community Multiscale Air Quality model. A Cox proportional hazards model, in which exposures were treated as time-varying covariates, was used to evaluate the associations between long-term exposure to source-specific PM2·5 and mortality from total non-accidental causes, cardiopulmonary disease, and lung cancer.

Findings

98 058 participants were followed from the date of their CCDRFS survey, conducted between January, 2010, and December, 2011, until death or Dec 31, 2020, whichever was earliest. Of these 98 058 participants, 96 955 were included in the analyses. The mean age was 46·5 years (SD 15·0); 52 631 (54·3%) participants were female and 44 324 (45·7%) were male. Almost all anthropogenic sources of PM2·5 were significantly associated with mortality. For each IQR increase, PM2·5 from industry (hazard ratio 1·079 [95% CI 1·024–1·137]), transportation (1·076 [1·034–1·119]), and residential (1·075 [1·029–1·124]) sources had the strongest associations with mortality from total non-accidental causes. For mortality from cardiopulmonary diseases, PM2·5 from transportation (1·106 [1·049–1·165]), industrial (1·085 [1·011–1·163]), and residential (1·070 [1·012–1·130]) sources had the strongest associations, and for mortality from lung cancer, the strongest associations were observed for PM2·5 from agricultural (1·256 [1·089–1·449]), industrial (1·235 [1·049–1·454]), and transportation (1·204 [1·048–1·384]) sources.

Interpretation

We show that the mortality risks of PM2·5 exposure can vary according to the source. These findings could contribute evidence for the development of health-oriented policies to enhance the effectiveness of clean air initiatives.