Assessing public health burden associated with exposure to ambient black carbon in the United States

Abstract

Black carbon (BC) is a significant component of fine particulate matter (PM2.5) air pollution, which has been linked to a series of adverse health effects, in particular premature mortality. Recent scientific research indicates that BC also plays an important role in climate change. Therefore, controlling black carbon emissions provides an opportunity for a double dividend. This study quantifies the national burden of mortality and morbidity attributable to exposure to ambient BC in the United States (US). We use GEOS-Chem, a global 3-D model of atmospheric composition to estimate the 2010 annual average BC levels at 0.5×0.667° resolution, and then re-grid to 12-km grid resolution across the continental US. Using PM2.5 mortality risk coefficient drawn from the American Cancer Society cohort study, the numbers of deaths due to BC exposure were estimated for each 12-km grid, and then aggregated to the county, state and national level. Given evidence that BC particles may pose a greater risk on human health than other components of PM2.5, we also conducted sensitivity analysis using BC-specific risk coefficients drawn from recent literature. We estimated approximately 14,000 deaths to result from the 2010 BC levels, and hundreds of thousands of illness cases, ranging from hospitalizations and emergency department visits to minor respiratory symptoms. Sensitivity analysis indicates that the total BC-related mortality could be even significantly larger than the above mortality estimate. Our findings indicate that controlling BC emissions would have substantial benefits for public health in the US.

Keywords: Air pollution; Black carbon; Mortality; Public health burden.

Fig. 1

Simulated annual average black carbon concentrations in 2010: (a) At 0.5 × 0.667° resolution; (b) Aggregated to State; and (c) Aggregated to county (Unit: µg/m³).

Fig. 2

Evaluation of the modeled BC concentrations compared to measurements: (a) Results of a regression fit; and (b) The spatial plot of the model error.

Fig. 3

Ratio of BC to PM_2.5 annual average concentration in 2010.

Fig. 4

Ranking annual BC-related mortality by State: (a) Ranked by annual number of death; (b) Ranked by percent of baseline mortality.

Fig. 5

Spatial distribution of annual BC-related mortality at the county level: (a) Number of deaths; and (b) Percent of baseline mortality.