Global black carbon aerosol: Spatiotemporal distributions, drivers, and health impacts

Black carbon (BC) is a key short-lived climate pollutant and a toxic component of PM_2.5. This review synthesizes global BC studies published since 2000 and evaluates its spatiotemporal distribution, source contributions, meteorological drivers, and health risks. The compiled evidence shows high concentrations are mainly found in South Asia and Africa, while low concentrations occur in Europe and North America. South American records were limited in the screened literature, and the apparent lower concentrations in this region may partly reflect sparse monitoring coverage rather than a regionwide low concentration pattern. Source evidence indicates that fossil fuel combustion is often important in urban and industrial regions, whereas biomass burning, residential solid fuel use, open waste burning, wildfire emissions, and agricultural burning can contribute substantially in fire affected and data sparse regions. Meteorological factors, including wind speed, boundary layer dynamics, and precipitation play a crucial regulatory role in the accumulation and removal of BC, driving its seasonal variations. The passive smoking equivalent results indicated that the mean decline in lung function associated with BC in children is approximately three times higher than that associated with low birth weight and cardiovascular mortality equivalents. The human health risk assessment results suggested that the lifetime carcinogenic risk of inhaling BC for adults was approximately 2.2 times that of children and was highest in rapidly industrialized areas and transportation hotspots. We further identified dermal exposure as a neglected pathway. This study provides a scientific basis for future global BC pollution control and public health protection.