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

Forest and vegetation fires are one of the major sources of air pollution and have triggered air quality issues in many regions of Pacific Asia. Here we isolate the fire-specific PM_2.5 from monitoring concentrations using an observation-driven approach in the region. The total PM_2.5 in Pacific Asia exhibited a rapid declining trend from 2014 to 2021, while fire-specific PM_2.5 decreased in early years but begun to reverse, leading to an increasing proportions of fire-specific PM_2.5 in recent years. The inconsistency between the decreasing number of fire points and the rising levels of fire-specific PM_2.5 may be attributed to a shift in dominant sources of fire emissions in Pacific Asia, moving from anthropogenic agriculture fires to wildfires. Fire-related PM_2.5 poses a significant public health threat in Pacific Asia, contributing to approximately 334,300 premature deaths each year. Our assessment highlights the disproportionate impact of fire-specific PM_2.5 on poverty populations, indicating a pressing need for more attentions and researches in these regions. Based on the positive correlation between vapor pressure deficit and fire-specific PM_2.5, this study suggests that without further regulation and policy intervention, the contributions of fire-specific PM_2.5 to air pollution in Pacific Asia are likely to continue increasing under the influence of future climate change.