Limited evidence exists about the long-term effects of fine particulate matter (PM_2.5) constituents on mortality, especially in developing regions with moderate-to-high pollution levels. Hence, we aimed to assess the associations of long-term exposure to PM_2.5 constituents with all-cause mortality in China.

We designed a nationwide cohort study of 30,524 adults from the China Family Panel Studies with follow-ups through the years 2010 to 2017. Annual county-level exposures of PM_2.5 mass and its 5 constituents (black carbon [BC], organic matter [OM], nitrate [NO₃⁻ ], ammonium [NH₄⁺] and sulfate [SO₄²⁻]) were assessed by satellite-derived estimates across the 162 counties where participants resided at baseline. Cox proportional hazards models with time-varying exposures were employed to quantify associations of all-cause mortality with long-term exposure to PM_2.5 and constituents.

A total of 1210 death events occurred during the 172,297.7 person-years of follow-up. Multi-adjusted

Cox model estimated an hazard ratio (HR) of 1.125 (95% confidence interval: 1.058–1.197) for all-cause

mortality, associated with per interquartile range (IQR = 26.7 μg/m³) increase in exposure to PM_2.5

mass. Highly comparable associations were found among all PM_2.5 constituents of study, with HRs

ranging from 1.113 [1.006–1.231] for SO₄^2- (IQR = 5.6 μg/m³ ) to 1.141 [1.048–1.243] for NO₃^- (IQR = 8.7 μg/m³). PM_2.5 constituents-mortality associations varied by subpopulations and regions, with larger magnitudes in males, smokers, alcohol drinkers, and urban residents.

Long-term exposure to specific PM_2.5 constituents (i.e., BC, OM, NO₃^-, NH₄⁺ and SO₄^2-) were associated

with all-cause mortality in Chinese adults. These associations were more pronounced in males,

smokers, alcohol drinkers, and urban residents. Our study provides the brand-new evidence for chronic

health effects of PM_2.5 constituents on human mortality in China.