Unveiling global population exposure to biomass burning: index development and its drivers over two decades

Biomass burning is an important source of global greenhouse gases, trace gases and aerosols. With global climate warming, biomass burning poses escalating risks to human health and ecosystems. However, rapidly and comprehensively assessing global exposure burden from biomass burning remains challenging. Here, we introduce the Biomass Burning Exposure Index (BBEI), a composite metric that integrates satellite-based fire observations, PM_2.5 emission factors, land use types, and pollutant dispersion effects to quantify global population exposure burden to biomass burning related pollutants. By analyzing six different types of biomass burning over two decades (2003-2022), this study reveals critical spatial and temporal trends in exposure risks and systematically identifies contribution of key driving factors, including population growth, land use changes, and fire frequency variations. We found that despite a slightly global decline (-1.90 %) in fire pixel counts, exposure burden has risen by 10.32 % from 2003 to 2012 to 2013-2022. A decomposition analysis reveals that population growth attributes 181.20 % of the rising exposure burden from 2003 to 2012 to 2013-2022. In contrast, the variation of land use and fire frequency account for -9.91 % and -71.29 %, respectively, of the change in exposure burden. The study also identifies pronounced socioeconomic disparities in exposure burden, with low- and lower middle-income countries bearing 90.60 % of the average global exposure burden. Overall, the burden of global population exposure to biomass burning continues to rise. The BBEI framework offers valuable insights for enhancing air quality modeling, forecasting systems, and evidence-based policy development aimed at mitigating health risks associated with biomass burning, supporting more precise and effective prevention strategies.