A peer-reviewed study published June 4, 2026 in the journal Science has found that wildfire smoke has effectively reversed years of hard-won air quality improvements in the United States — particularly in Western states including Oregon, Washington, and Idaho. The research found that since approximately 2015, worsening wildfire smoke has undone efforts to reduce ground-level ozone pollution, a pollutant with serious health consequences.

What the Research Found

The study, which analyzed air quality monitoring data from across the United States over several decades, found that despite significant reductions in industrial and vehicle emissions — the traditional targets of clean air regulation — ozone concentrations in many Western communities have stopped improving or have actually worsened. The culprit: wildfire smoke, which releases precursor gases that react in the atmosphere to produce ozone.

Ground-level ozone is not the same as the protective ozone layer high in the stratosphere. At ground level, ozone is a lung irritant that can trigger asthma attacks, reduce lung function, aggravate chronic respiratory disease, and cause chest pain and throat irritation. Long-term exposure is associated with increased risk of respiratory disease and premature death.

Why It Matters for the Pacific Northwest

For Pacific Northwest residents — particularly those in the Willamette Valley, Puget Sound corridor, and Central Oregon — the findings are especially significant. These areas have historically struggled with wood smoke and vehicle emissions but had seen gradual air quality improvements through regulatory action over the past two to three decades.

As wildfire smoke events have become more frequent, longer-lasting, and more geographically widespread, those gains are being eroded. Communities that once confidently reported improving air quality trends are now experiencing some of their worst air quality readings in years during heavy smoke summers.

Implications for Public Health Policy

The study's findings present a fundamental challenge to conventional air quality management: regulations designed to control emissions from factories, vehicles, and other stationary sources cannot address wildfire smoke, which is driven by fire behavior and climate conditions largely beyond regulatory reach.

Researchers and public health advocates say the findings underscore the need for:

  • Increased investment in prescribed fire and forest management to reduce fuel loads and the intensity of future wildfires.
  • Greater public health infrastructure for protecting vulnerable populations during smoke events, including clean air shelters and distribution of N95 masks.
  • Updated federal air quality standards that account for wildfire smoke as a distinct and growing source of pollution.
  • Climate adaptation strategies that anticipate continued increases in wildfire-driven smoke.

What You Can Do

During smoke events, the best protection for individuals remains staying indoors with windows closed, using air purifiers with HEPA filters, and wearing N95 respirators when outdoor exposure is unavoidable. Track air quality daily at AirNow.gov and sign up for smoke alerts from your local air quality management district.