UCLA-led research reveals extent of L.A. and California wildfires’ impact on air quality

Two related and recently published studies by teams led by UCLA Fielding School of Public Health researchers focused on the public health impact of wildfires, including whether publicly available data sources captured an increase in air pollution during the fires and how air quality changed over space and time.

"Wildfires can degrade air quality in downwind communities," said Miriam Marlier, assistant professor in the Fielding School's department of environmental health sciences and a co-author of both studies. "By integrating data from multiple sources - ground monitors, atmospheric models, and satellites - our research aims to provide a more complete picture of smoke exposure during wildfire events."

The peer-reviewed studies, whose authors included researchers affiliated with UCLA, UC Merced and/or the University of British Columbia (Canada), are "Air Quality Impacts of the January 2025 Los Angeles Wildfires: Insights from Public Data Sources," in Environmental Science & Technology Letters and "Contribution of Large Wildfire Events and Burn Severity Classes to Air Pollution in California in 2018," in Environmental Science & Technology Air, both published by the American Chemical Society.

The researchers looked at measurements of dangerous airborne particles that are less than 2.5 micrometers in diameter, or 30 times smaller than a human hair, known as PM2.5.

"Because these particles are so small, they can travel deep into your lungs and even enter your bloodstream - potentially leading to serious problems like heart or lung disease," said Michael Jerrett, professor of environmental health sciences at the Fielding School, co-director of the UCLA Center for Healthy Climate Solutions and a co-author on both studies. "For anyone, exposure to fine particles can contribute to health issues, and for those with existing conditions or heightened sensitivity, the risks are even greater."

The study of the January 2025 fires in Los Angeles County analyzed the air quality data from federal monitoring stations, satellites and low-cost sensors, and found that each data source has its advantages and disadvantages: The monitoring stations yielded highly accurate data but are limited in number; the low-cost sensors are less accurate but more prolific; and the satellite imagery covers larger areas but do not always reflect the conditions on the ground.

Read the full story on the Fielding School's website.