A probabilistic long-term health risk assessment framework for wildfires: the case of California

The increased wildfire activity across the Western United States in recent decades has amplified the health risk from wildfire smoke. Existing risk assessment frameworks, however, remain at the conceptual level or target immediate and direct economic and health consequences. Here, we develop a probabilistic risk assessment (PRA) framework to estimate the health impacts of wildfires in California, integrating (1) wildfire probability, (2) fire spread, (3) emissions, (4) PM 2.5 transport, and (5) long-term mortality from degraded air quality. The findings reveal that the frequency-mortality curve due to PM 2.5 exposure from wildfires follows a power law distribution with exponent \(β =1.44\) , emphasizing the dominant influence of extreme wildfire events. Wildfires originating in the northwestern parts of California are found to be the most significant contributor to mortality from PM 2.5 exposure, due to the high vegetation density as well as the dominant winds directing the emissions towards densely populated regions. Additionally, our results show that wildfire fatality risk is comparable to that of California earthquakes and significantly higher than the risk associated with nuclear energy generation in the state.