Long-term exposure to fine particulate constituents and cardiovascular diseases in Chinese adults

Abstract Background Ambient fine particulate matter (PM2.5) has been linked to various cardiovascular disease (CVD) endpoints. However, little is known regarding the health effects of PM2.5 constituents. This study aimed to assess the associations of long-term exposures to PM2.5 constituents with the incidence of CVD in China, including black carbon (BC), organic matter (OM), sulfate (SO42−), nitrate (NO3−) and ammonium (NH4+). Methods A nationwide cohort of 14,331 adults were drawn from the China Family Panel Study, a high-quality longitudinal survey initiated from 2010 over 25 provincial regions in China. We used the baseline survey and the ensuing three waves of follow-up data during 2010–2017 to conceive our study cohort. Annual county-level exposures of PM2.5 and constituents for each participant was assessed by aggregating satellite-derived estimates at a monthly time-scale and 1 km-resolution. A directed acyclic graph (DAG) was developed to identify confounding variables. Cox proportional hazards models with time-varying exposures and province-level random intercepts were employed to quantify associations of CVD incidence with long-term exposures to PM2.5 and its constituents. Results During 84162.4 person-years’ follow-up, a total of 1575 CVD, 953 hypertension and 342 stroke incidents occurred. DAG-based Cox model estimated a hazard ratio (HR) of 1.291 (95% confidence interval: 1.147–1.454) for total CVD and 1.326 (1.151–1.528) for hypertension, associated with per interquartile range (IQR=27.9 μg/m3) increase in exposure to PM2.5 mass. Elevated CVD risks were also significantly related to several PM2.5 constituents, with the largest HRs observed in SO42− (1.721 [1.517–1.951], IQR=5.67 μg/m3), followed by NH4+ (1.537 [1.341–1.762], IQR=4.44 μg/m3), NO3− (1.311 [1.128–1.523], IQR=8.92 μg/m3) and BC (1.294 [1.158–1.446], IQR=2.28 μg/m3). No associations were identified between long-term exposures to particulate constituents and incidence of stroke. Associations with PM2.5 and constituents (BC, NO3−, NH4+ and SO42−) were more pronounced among adults aged over 50 years, and residents in southern region. Conclusions Long-term exposures to PM2.5 mass and specific constituents (i.e., BC, NO3−, NH4+ and SO42−) were associated with increased risks of total CVD and hypertension incidence in Chinese adults. Findings may have implications for in-depth understandings of biological mechanisms in chronic impacts of ambient PM2.5 on cardiovascular health.