Children across the United States are breathing unhealthy wildfire smoke for dramatically longer periods than they were two decades ago, and the trend shows no signs of reversing — that is the stark conclusion of a new study published by Oregon State University's College of Health.

The research, published earlier this month in the journal Environmental Research, analyzed air quality data from across the country from 2006 through 2023. Researchers found that the average number of annual smoke-impacted days at public schools rose from 6.8 to 54.4 — a nearly eightfold increase. Childcare centers saw an even steeper rise, with average annual smoke days climbing from 9.4 to 112.2.

"Billions of Days of Smoky Air"

"Our children are collectively experiencing billions of days of smoky air each year," said Molly Kile, a lead researcher and environmental epidemiologist at Oregon State University. Kile emphasized that while the total number of U.S. wildfires per year has remained relatively stable at around 70,000, the intensity and scale of those fires has increased dramatically — meaning smoke travels farther and lingers longer.

The Pacific Northwest has borne a disproportionate share of that smoke burden. Oregon's 2026 wildfire season alone scorched more than 2.5 million acres, shattering the previous state record set in 2024 when 1.9 million acres burned. Communities across the Willamette Valley, central Oregon, and the Columbia River Gorge experienced repeated multi-day air quality events that pushed AQI readings into the Very Unhealthy and Hazardous categories.

Smoke Doesn't Stop at the Schoolhouse Door

One of the study's most actionable findings concerns indoor air quality. Researchers discovered that some schools actually had higher indoor PM2.5 concentrations than nearby outdoor measurements during heavy smoke events — meaning that simply keeping children inside provides little protection in inadequately filtered buildings.

"Some schools had higher indoor PM2.5 concentrations than nearby outdoor measurements during smoke days," Kile 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."

PM2.5 — fine particulate matter small enough to be inhaled deeply into the lungs and enter the bloodstream — is a known driver of cardiovascular disease and is linked to the onset and worsening of respiratory illness. Wildfires account for nearly half of all PM2.5 pollution across the United States.

What Schools and Parents Can Do

The researchers called for coordinated preparedness planning at educational facilities, including:

  • HVAC system upgrades with high-efficiency filtration (MERV-13 or higher)
  • Portable HEPA air purifiers in classrooms as a cost-effective near-term solution
  • Indoor air quality monitoring to enable real-time decision-making
  • Written smoke response protocols that define thresholds for moving activities indoors or canceling outdoor time

The study's findings carry particular weight as Oregon, Washington, and Idaho school districts face increasing pressure to respond to smoke events without comprehensive guidance or dedicated funding. Advocates say the research strengthens the case for state-level legislation requiring air quality infrastructure in schools — and for federal funding to help districts in high-smoke-exposure regions meet that standard.