The contribution of fires to PM_2.5 and population exposure in Asia Pacific

Abstract. Forest and vegetation fires are important sources of air pollution in many regions. Reducing fires may be a significant yet under-recognized option for improving air quality and preventing premature deaths. This study isolates fire-specific PM_2.5 from monitoring data using an observation-driven approach. Fire-specific PM_2.5 concentrations average 2–15 µg/m³ during the fire season, with higher levels in Southeast Asia (ESA), Northeast Asia (NA), and northern India. Total PM_2.5 in Asia Pacific shows a rapid decline from 2014 to 2021, while fire-specific PM_2.5 decreases initially but begins to rise in ESA and NA. The proportion of fire-specific PM_2.5 in NA increases from 0.2 to 0.3 during the fire season, and in ESA from 0.2 in 2018 to 0.4 in 2021. Fire-specific PM_2.5 exposure caused 58,000, 90,000, 157,000, and 29,300 premature deaths annually in ESA, East Asia, Central Asia, and NA, respectively, accounting for 40.9 %, 14.9 %, 19.4 %, and 24.1 % of numbers caused by total PM_2.5. Analysis shows that total PM_2.5 exposure impacts more in wealthier areas, while fire-specific PM_2.5 affects poorer populations more. Given the positive correlation between vapor pressure deficit and fire-specific PM_2.5, this study suggests that without regulation and policy intervention, the emerging growth trend of fire-specific PM_2.5 in Pacific Asia will likely to continue influenced by future climate change.