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, PM, in wildfire smoke adversely impacts human health. Recent toxicological studies suggest that wildfire particulate matter may be more toxic than equal doses of ambient PM. Air quality regulations however assume that the toxicity of PM does not vary across different sources of emission. Assessing whether PM from wildfires is more or less harmful than PM from other sources is a pressing public health concern. Here, we isolate the wildfire-specific PM using a series of statistical approaches and exposure definitions. We found increases in respiratory hospitalizations ranging from 1.3 to up to 10% with a 10 μg m increase in wildfire-specific PM, compared to 0.67 to 1.3% associated with non-wildfire PM. Our conclusions point to the need for air quality policies to consider the variability in PM impacts on human health according to the sources of emission.