Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California

Wildfires are becoming more frequent and destructive in a changing climate. Fine particulate matter (PM2.5) in wildfire smoke adversely impacts human health, and recent toxicological studies suggest wildfire particulate matter may be more toxic than equal doses of ambient PM2.5. Air quality regulations, however, generally assume toxicity does not vary by source. Using several statistical approaches and exposure definitions to isolate wildfire-specific PM2.5 in Southern California, we found increases in respiratory hospitalizations ranging from 1.3% up to 10% per 10 µg m−3 increase in wildfire-specific PM2.5, compared to 0.67% to 1.3% associated with non-wildfire PM2.5. These findings suggest air quality policies should consider source-specific variability in PM2.5 health impacts.