The contribution of fires to PM2.5 and population exposure in the Asia Pacific region

Abstract

Forest and vegetation fires are major sources of air pollution and have triggered air quality issues in many regions of Asia. Measures to reduce fires may be a significant yet under-recognized option for efficiently improving air quality and preventing related premature deaths. Here we isolate fire-specific fine particulate matter (PM2.5) from monitoring concentrations using an observation-driven approach in the region. Fire-specific PM2.5 concentrations average 2-15 μg m-3 during the fire season, with higher values in Southeast Asia (SEA), Northeast Asia (NEA), and northern India. The total PM2.5 in the Asia Pacific region exhibits a rapid declining trend from 2014 to 2021, while fire-specific PM2.5 decreases in early years but begins to reverse in SEA and NEA. The proportions of fire-specific PM2.5 increase in NEA from 0.2 to 0.3 during the fire season and increase in SEA from 0.2 in 2018 to 0.4 in 2021. Fire-specific PM2.5 exposure caused 58 000 (95 % confidence interval (CI) of 32 600-82 600), 90 000 (95 % CI of 63 700-106 000), 157 000 (95 % CI of 110 000-186 000), and 29 300 (95 % CI of 18 000-39 700) premature deaths annually in SEA, East Asia (EA), Central Asia (CA), and NEA, respectively, accounting for 40.9 % (95 % CI of 22.8 %-57.7 %), 14.9 % (95 % CI of 10.5 %-17.6 %), 19.4 % (95 % CI of 13.5 %-24.5 %), and 24.1 % (95 % CI of 14.8 %-32.5 %) of the numbers caused by the total PM2.5. Analysis of infant mortality rate data and PM2.5 exposure indicates that the total PM2.5 exposure had a greater impact in richer areas, while fire-specific PM2.5 exposure affected more populations in poorer regions. Based on the positive correlation between vapor pressure deficit and fire-specific PM2.5, this study suggests that, without further regulation and policy intervention, the emerging growth trend of fire-specific PM2.5 in the Asia Pacific region is likely to continue under the influence of future climate change.