American children are increasingly exposed to air pollution as wildfire smoke becomes more common, and some schools and childcare centers struggle to keep indoor breathing conditions clean, a new national study shows.
The researchers note that components of wildfire smoke, including PM2.5, which is fine particulate matter with a diameter of 2.5 micrometers or smaller, are known health hazards, especially for adolescents and younger children.
For the study, published in Environmental Research, scientists looked at air quality data from across the United States from 2006 through 2023 and found some alarming trends, said co-author Molly Kile of Oregon State University.
"The average number of annual smoke days at public schools rose from 6.8 to 54.4 between the beginning and end of the study period," said Kile, an environmental epidemiologist in the OSU College of Health. "Childcare centers experienced an increase from 9.4 to 112.2 days. Our children are collectively experiencing billions of days of smoky air each year."
Four decades of data from the National Interagency Fire Center show that the number of U.S. wildfires per year has remained relatively stable - generally in the range of 70,000 - but the intensity of those fires and the acreage burned have increased.
And while the western part of the country tends to see more fires and heavier smoke, the issue is a national one, Kile emphasizes.
"Yes, there is more severe wildfire smoke in the West, but fine particulate matter travels hundreds and thousands of miles," she said. "And the prevailing wind blows from west to east, so it all goes downwind."
PM2.5 can be inhaled deeply into the lungs and even enter the bloodstream, is a known cause of cardiovascular disease and is linked to the onset and worsening of respiratory illness.
As climate change exacerbates wildfire risk, PM2.5 emissions from fires have surged to the point that wildfires now account for almost half of all PM2.5 across the United States and have negated air quality improvements in multiple regions.
"We are often told to stay indoors when air pollution gets severe but being indoors does not guarantee clean air," Kile said, noting that indoor air quality measurements showed substantial variation in how well buildings protected occupants from outdoor fine particulate pollution.
"Some schools had higher indoor PM2.5 concentrations than nearby outdoor measurements during smoke days," she said. "This is a particularly actionable finding and emphasizes the need for investment in improving indoor air quality in schools through HVAC upgrades, which can be expensive, or portable HEPA filters, which can be a more affordable approach."
Stephanie Foster, the study's corresponding author, notes because of the amount of time students spend in schools and childcare centers, those places are important settings for safeguarding children's health.
"We found that the buildings where children spend much of their day do not consistently protect them from air pollution," said Foster, scholarly activity program manager in Samaritan Health Services' Research Development Office. "But educational facilities are places where coordinated preparedness plans, air filtration, indoor air quality monitoring and changes to activities during smoke events could reduce exposure."
Joining Foster and Kile on the study were Andrew Larkin, Megan MacDonald, Megan McClelland and Perry Hystad of the OSU College of Health and Parichehr Salimifard of the OSU College of Engineering. The National Institute of Environmental Health Sciences supported the research.
