Wildfires near cities have become commonplace in the Western United States, but this year the reach and intensity of the dangerous air pollution they produce has been the worst on record.
Many Americans in populous, urban areas endured smoke for longer than previous years. Some places experienced very unhealthy or hazardous air from wildfires for the first time ever recorded.
An NPR analysis of U.S. Environmental Protection Agency air quality data found that nearly 50 million people in California, Oregon and Washington live in counties that experienced at least one day of "unhealthy" or worse air quality during wildfire season so far this year. That's 1 in 7 Americans, an increase of more than 9 million people compared with 2018, the worst previous year.
And this year's wildfire season is far from over.
NPR's analysis looked at air quality on days from July to January of each year, specifically focusing on small inhalable particles that can lodge deep in the lungs and be harmful to humans. An EPA spokesperson said this kind of pollutant, known as PM2.5, is the most likely culprit found in the air from wildfire smoke.
The EPA publishes data going back to 1980, though much of the earlier data is missing information about PM2.5.
As the warming climate has lengthened the fire season, some places, especially in California, have grown accustomed to the related air quality problems. But the intensity and spread of this year's fires also brought dangerous smoke to big cities such as Seattle and Portland, Ore.
More than 17 million people — the most ever recorded during fire season — live in counties where air quality reached levels deemed "very unhealthy" or "hazardous." This is the range where the EPA says everyone may be at risk for serious health effects, and they recommend children, older people and those with lung disease avoid any outdoor exertion.
For many, it wasn't just a short-term inconvenience. The very unhealthy air lingered for an average of 4.1 days this year, more than twice as long as the average over the previous decade.
Some of the readings were higher than the EPA's own scale. Marion County, home to Oregon's capital, Salem, hit an air quality index of 710 on Sept. 11.
This year, 36 counties in Washington, Oregon and California experienced very unhealthy air quality due to particulate matter during wildfire season for the first time ever recorded, including Multnomah County, Ore., where Portland is located.
The immediate health effects of living in and breathing wildfire smoke are well-known to the medical community and obvious to anyone who's been exposed: Eyes sting, throats tighten, snot can turn black. Smoke pollution can raise heart rates and exacerbate respiratory problems such as asthma or chronic obstructive pulmonary disease. Recent research even suggests smoke exposure could lead to an increased risk of getting COVID-19.
Much less is known about possible health effects after the smoke clears.
"This is not well studied because this has become more of a phenomenon in the last decade, where we've had these major fires across the world," says Dr. Karthik Mahadevan, a pulmonologist in Springfield, Ore., who saw a spike of respiratory calls during last week's heavy smoke. "We don't know what the long-term impacts are going to be for our patients."
NPR's Nathan Rott contributed to this report.