The prospective effects of long-term exposure to ambient PM_2.5 and constituents on mortality in rural East China

Few cohort studies explored the associations of long-term exposure to ambient fine particulate matter with an aerodynamic diameter of 2.5 μm or less (PM_2.5) and its chemical constituents with mortality risk in rural China. We conducted a 12-year prospective study of 28,793 adults in rural Deqing, China from 2006 to 2018. Annual mean PM_2.5 and its constituents, including black carbon (BC), organic carbon (OC), ammonium (NH₄⁺), nitrate (NO₃⁻), sulfate (SO₄²⁻), and soil dust were measured at participants’ addresses at enrollment from a satellite-based exposure predicting model. Cox proportional hazard model was used to estimate hazard ratios (HRs) and 95% confidence intervals (95%CIs) of long-term exposure to PM_2.5 for mortality. A total of 1960 deaths were identified during the follow-up. We found PM_2.5, BC, OC, NH₄⁺, NO₃⁻, and SO₄²⁻ were significantly associated with an increased risk of non-accidental mortality. The HR for non-accidental mortality was 1.17 (95%CI: 1.07, 1.28) for each 10 μg/m³ increase in PM_2.5. As for constituents, the strongest association was found for BC (HR = 1.21, 95%CI: 1.11, 1.33), followed by NO₃⁻, NH₄⁺, SO₄²⁻, and OC (HR = 1.14–1.17 per interquartile range). A non-linear relationship was found between PM_2.5 and non-accidental mortality. Similar associations were found for cardio-cerebrovascular and cancer mortality. Associations were stronger among men and ever smokers. Conclusively, we found long-term exposure to ambient PM_2.5 and its chemical constituents (especially BC and NO₃⁻) increased mortality risk. Our results suggested the importance of adopting effective targeted emission control to improve air quality for health protection in rural East China.