Six US states issued stay-indoors advisories on Wednesday as wildfire smoke containing fine toxic particulate matter spread across Oregon, Washington, Idaho, Wyoming, Colorado and Nevada.
Air quality dropped to unhealthy levels across the American West as fires burning in the Pacific Northwest and other regions poured smoke into the air. Shifting winds pushed the smoke across state lines, reducing visibility and prompting officials to advise residents to close doors and windows and avoid strenuous outdoor activity.
Some advisories were scheduled to expire on Thursday or Friday, but large areas of Oregon and Washington remained under warnings until further notice. Health officials warned that microscopic particles in the smoke can bypass the body's natural defenses, lodge deep in the lungs, and enter the bloodstream. Children, pregnant women, older adults and people with heart or respiratory conditions face the highest risk.
Health risks of fine particulate matter
Wildfire smoke contains a complex mixture of gases and particles created when trees, vegetation, buildings and other materials burn. The primary health threat comes from fine particulate matter known as PM2.5, which measures no more than 2.5 micrometers across, or about 30 times smaller than the width of a human hair.
While the nose and throat trap larger particles, PM2.5 travels deep into the lungs to the tiny air sacs where oxygen enters the blood. The smallest particles can cross into circulation and affect organs throughout the body.
According to the Environmental Protection Agency, short-term exposure to PM2.5 can cause coughing, wheezing, chest tightness, breathing difficulty, headaches and burning eyes. Exposure also inflames airways, reduces lung function, and worsens asthma and bronchitis. Particle pollution is also linked to heart attacks, strokes and worsening heart failure in people with existing cardiovascular conditions.
Advisories in Oregon and Washington
In Oregon, warnings covered a broad area including Portland, Eugene, Salem, Bend, Sisters, Pendleton, La Grande and The Dalles.
Eastern Douglas County, including areas near Roseburg, was placed under an advisory until further notice as smoke from the Castle Fire and other blazes lingered. Baker, Harney and Malheur counties faced high smoke concentrations through noon Thursday, with officials urging residents to remain indoors, keep windows closed, and run high-efficiency particulate air filters.
Washington state alerts covered King, Pierce, Snohomish, Kitsap, Mason, Grays Harbor and Thurston counties through 5pm Thursday, affecting Seattle and surrounding areas. Air quality was expected to range from unhealthy for sensitive groups to unhealthy for everyone.
Alerts were also issued for Clark County, including Vancouver, as well as Cowlitz, Skamania and Wahkiakum counties. Central and eastern Washington communities, including Yakima, Walla Walla, Richland, Kennewick and Ellensburg, remained under warnings until further notice as smoke caused burning eyes, runny noses, and aggravated medical conditions.
Conditions across Idaho, Wyoming, Colorado and Nevada
Idaho officials issued alerts for Ada, Boise, Canyon, Elmore, Gem, Owyhee, Payette, Valley and Washington counties, forecasting an Unhealthy Air Quality Index. Officials banned open burning, warned that everyone could experience health effects, and urged residents to avoid extended outdoor activity. Spokane, Washington, was also pictured shrouded in wildfire smoke.
Wyoming placed central, western, southeastern and northeastern regions under alerts, including Casper, Cheyenne, Laramie, Jackson, Cody, Rock Springs, Sheridan and Gillette. The Wyoming Department of Health advised everyone to avoid prolonged exposure and urged vulnerable groups to minimize outdoor time.
Colorado issued warnings of moderate to heavy smoke for dozens of counties, including Aspen, Breckenridge, Colorado Springs, Durango, Grand Junction, Pueblo and Steamboat Springs. Officials advised residents to consider temporarily relocating if smoke entered their homes and made them ill, noting that visibility below five miles indicates unhealthy pollution levels. Warm temperatures, sunshine and smoke also triggered an action day along Colorado's Front Range for ozone and fine particles.
In Nevada, southwest Elko County faced an air-quality action day with particle levels expected to become unhealthy for sensitive groups. Officials across all six states urged residents to check local air-quality readings before going outside, as smoke levels change quickly with wind and fire activity.
