New CIRES research finds air quality in the United States worsens when natural hazards co-occur, such as when wildfires overlap with droughts or heatwaves. The results show these situations exacerbate existing air quality inequities: rural communities experience disproportionately higher fine particulate matter during simultaneous natural hazards than urban areas do. 

The findings can inform hazard response agencies, air quality managers, and public health researchers aiming to better understand and forecast air pollution risks after disasters, according to Min Gon Chung, a CIRES postdoctoral researcher who will present the work tomorrow, December 18, at the 2025 AGU Annual Meeting in New Orleans. 

“My approach can strengthen early warning tools that can help federal or state agencies and local communities know when and where the air is the most dangerous,” Chung said. 

Nearly half of Americans live in places with unhealthy levels of ozone or particulate matter, according to the American Lung Association’s 2025 State of the Air report. Extreme heat, drought, and wildfires are worsening air pollution across much of the United States, exposing more individuals to pollution that can damage their health. 

In the new study, Chung and his colleagues analyzed how hazards like wildfires, droughts, and floods impacted air quality across the United States from 2014 to 2024. They combined data from regulatory air monitoring stations, low-cost air quality sensors, satellite observations, and NOAA hazard reports to measure changes in fine particulate matter during these events. Fine particulate matter refers to tiny pollution particles (smaller than 2.5 microns) that can penetrate deep into human lungs and enter the bloodstream. 

The findings show the U.S. West experiences much higher hazard-related particulate matter increases than the East, both in urban and rural areas. In addition, fine particulate matter concentrations rise substantially when wildfires occur during heatwaves or droughts, especially in western rural areas. 

Interestingly, the results also show particulate matter pollution doesn’t increase on days when there are major floods but instead rises after the flood recedes. Outdoors, fine particulate matter increases for about a week after a flood, but indoors it stays elevated for about 10 days. The researchers aren’t sure why this happens, but one explanation could be mold growth and dust from dried sediment and building materials after a flood.

Next, the researchers aim to extend their analysis through 2025 and link these hazard-related increases in particulate matter pollution to specific health impacts. 

“Many rural residents work outdoors and live in homes with less protection from fine particulate pollution, so I hope these results will guide practical investments in cleaner air indoors and outdoors for the communities most exposed,” Chung said. 

Chung will present the results tomorrow (Thursday, December 18, 2025) in a poster session from 2:15 to 5:45 pm CST at AGU25. The work has not yet been published.