Evaluating differential air quality impacts of prescribed fire and wildfire in the United States

RESUMO

Increasing wildfire activities in the United States have generated far-reaching effects on air pollution and human health. While prescribed fires are used as a preventive strategy to reduce wildfire risks, the health impacts of their smoke remain uncertain. Small-scale case studies indicate that prescribed fires generally produce lower pollutant emissions than uncontrolled wildfires, potentially benefiting air quality. However, the extent to which this translates into reduced population-level smoke exposure remains uncertain due to a lack of robust, large-scale quantitative evidence. Moreover, the factors driving differences in air quality impacts between prescribed fires and wildfires were underexplored. Using fire data in California, Florida, and Georgia (2006-2020) and a causal forest approach, we quantified and compared the impacts of prescribed fires and wildfires on air quality, assessed their differences in population-level smoke exposure, and identified key factors influencing their smoke exposure levels. On a per square-kilometer basis, prescribed fires resulted in over six times less population-level smoke exposure compared to wildfires. Additionally, prescribed fires were associated with lower smoke exposure in regions with higher relative humidity and precipitation. This work could enable the broad risk-benefit assessment to guide the judicious use of prescribed fires and optimize public health outcomes while mitigating wildfire threats.