Wildfire smoke increases assaults: evidence from Seattle

Abstract Wildfires are increasing in frequency and severity due to climate change, becoming a major contributor to particulate matter air pollution (PM 2.5 ) in many regions of the globe. This study investigates whether daily exposure to wildfire-derived PM 2.5 increases violent assaults in Seattle, Washington, between 2013 and 2023. Using ground-level wildfire smoke presence as an instrument for PM 2.5 and crime report data from the Seattle Police Department, this study estimates a robust relationship between air pollution and urban violence. Over the study period, an average smoke-impacted day increased mean ambient PM 2.5 by 7.0 μ g m −3 , which corresponds to 3.6% more assaults. The findings contribute to the emerging literature linking environmental change to social tensions and demonstrate that climate-driven pollution may increase violence even in relatively low-pollution, high-capacity urban settings like Seattle. The study establishes the first direct estimate of a causal effect of wildfire smoke on assaults, leveraging eleven years of daily data and high-resolution smoke exposure data. As wildfires become a globally relevant source of pollution under future climate scenarios, these results underscore the societal benefits of climate change mitigation.