By midsummer, it was clear the western United States would have another record-breaking fire season. Wildfires had burned through nearly 2 million acres (810,000 hectares) and consumed thousands of structures in California alone. Smoke from the fires reached all the way to the East Coast, carrying particulate matter 2.5 micrometers or less in width (PM2.5) and other pollutants across the country. Although PM2.5 is known to harm human health, less is known about the specific effects of wildfire smoke on health across regions. However, knowledge of wildfire smoke impacts is critical for researchers and public health experts going forward, as climate change continues to produce a warmer, drier western United States and the fire season is expected to become only longer and more intense.
To fill this gap, O’Dell et al. looked at smoke exposure across seasons and regions in the United States between 2006 and 2018. The team combined observation-based estimates of smoke-related PM2.5 and gas phase hazardous air pollutants, or HAPs, with data on asthma hospital admissions and emergency department visits to determine the impacts of both acute and chronic smoke exposure.
The authors found that smoke caused between 1,300 and 5,900 asthma-related emergency department visits per year, and these were more likely to occur in the spring and summer. Chronic exposure to PM2.5 from smoke was linked to as many as 6,300 deaths per year, the study found.
Although most large wildfires originated in the western United States, nearly 75% of the emergency department visits and hospital admissions due to smoke occurred in nonwestern states. This is due largely to the higher population in the eastern United States, according to the study’s authors. Comparing the relative health effects of PM2.5 and HAPs in smoke, the authors found that the former had more long-term health impacts on individuals than the latter, but they note that the health impacts of HAPs are more uncertain.
The results highlight the importance of understanding the impacts of wildfire smoke on human health for populations across the country, not just those in states typically thought of as the most affected by wildfires. Insights into wildfire-related human health effects will be especially important as wildfire conditions continue to worsen under climate change. (GeoHealth, https://doi.org/10.1029/2021GH000457, 2021)
—Kate Wheeling, Science Writer