National Cohort Study of Long-Term Exposure to PM_2.5 Components and Mortality in Medicare American Older Adults

Abstract

There is increasing evidence linking long-term fine particulate matter (PM_2.5) exposure to negative health effects. However, the relative influence of each component of PM_2.5 on health risk is poorly understood. In a cohort study in the contiguous United States between 2000 and 2017, we examined the effect of long-term exposure to PM_2.5 main components and all-cause mortality in older adults who had to be at least 65 years old and enrolled in Medicare. We estimated the yearly mean concentrations of six key PM_2.5 compounds, including black carbon (BC), organic matter (OM), soil dust (DUST), nitrate (NO₃^-), sulfate (SO₄^2-), and ammonium (NH₄⁺), using two independently sourced well-validated prediction models. We applied Cox proportional hazard models to evaluate the hazard ratios for mortality and penalized splines for assessing potential nonlinear concentration-response associations. Results suggested that increased exposure to PM_2.5 mass and its six main constituents were significantly linked to elevated all-cause mortality. All components showed linear concentration-response relationships in the low exposure concentration ranges. Our research indicates that long-term exposure to PM_2.5 mass and its essential compounds are strongly connected to increased mortality risk. Reductions of fossil fuel burning may yield significant air quality and public health benefit.