Chronic exposure to particulate matter is associated with increased cardiovascular risk

1. Long-term exposure to particulate matter with diameter ≤2.5 μm (PM2.5) was significantly associated with elevated cardiovascular (CVD) risk, with Cl−, BC, or SO42− having particularly hazardous profiles.

Evidence Rating Level: 2 (Good)

PM2.5 exposure is a known independent risk factor for CVD. However, it is not only PM2.5 mass concentration that worsens health outcomes. Certain chemical components of PM2.5 have been found to have varying levels of oxidative stress and cytotoxicity. This study sought to investigate the associations between CVD and long-term exposure to PM2.5 components, considering both absolute and relative concentrations. The authors utilized data from the China Kadoorie Biobank (CKB) cohort, which recruited 512 724 participants aged 30 to 79 years from 2004-2008. After excluding patients with heart disease, stroke, or cancer at baseline, 487 037 patients (mean [SD] age, 51.5 [10.5] years; 59.1% female) were included in the final analysis. The daily mean concentrations of PM2.5 and its 6 key chemical components (organic matter (OM), black carbon (BC), Cl−, NO3−, SO42−, and NH4+) were obtained from the ChinaHighAirPollutants (CHAP) data sets. Individuals who moved out of their baseline cities were considered lost to follow-up, with a proportion of <1%. The average composition of PM2.5 was 38.8% OM, 19.8% SO42−, 17.6% NO3−, 12.0% NH4+, 7.9% BC, and 3.9% Cl−. Those exposed to median or higher levels of PM2.5 were more likely to live in rural areas. After stratifying by PM2.5 levels, the HRs for total CVD per IQR increase were 1.15 (95% CI: 1.13-1.17) for BC, 1.17 (95% CI: 1.15-1.18) for OM, 1.28 (95% CI: 1.25-1.32) for Cl−, 1.29 (95% CI: 1.24-1.33) for NO3−, and 1.23 (95% CI: 1.20-1.25) for SO42−. Increasing quartiles were also significantly associated with higher rates of ischemic heart disease and ischemic stroke, but only BC, Cl−, NO3−, and SO42− were significantly associated with higher rates of hemorrhagic stroke. Increasing the relative proportions of Cl−, BC, and SO42− was associated with higher CVD risk, while increasing the relative proportions of NO3− and OM were associated with a reduced risk for ischemic heart disease and stroke.

Click here to read this study in the Journal of the American College of Cardiology

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