Contributions of Acute Wildfire Smoke Exposure to Excess Mortality from the 2025 Los Angeles Fires

In January 2025, a series of severe wildfires in Los Angeles County burned over 50000 acres, destroyed over 16000 structures, and caused 30 fatalities. These fires, driven by intense Santa Ana winds, rank among the most destructive and deadliest fires in California’s history. Beyond the destruction and loss of lives, these fires also contributed to unhealthy levels of pollutants, such as fine particulate matter (PM 2.5 ), which cause increased respiratory and cardiopulmonary morbidity, yet this smoke-specific mortality burden is not routinely documented in official reports of wildfire damage and losses. By employing high-resolution air-quality forecast data, we quantify the excess mortality from smoke exposure during a wildfire episode in Los Angeles County in 2025. We found unhealthy air quality in the most populous census tracts immediately after the fire outbreak that persisted for several days. We estimated a total of 14 unaccounted excess deaths from acute wildfire smoke exposure, which is equivalent to 47% of direct fire fatalities. Our study shows that excess mortality from smoke exposure, even for a few days, causes increased mortality, which requires consideration for a comprehensive assessment of wildfires.