Scientists say Pacific Northwest wildfires are altering air pollution patterns across the U.S.

Scientists warn that the increasingly large and intense wildfires that rage in the Pacific Northwest each summer are causing a spike in air pollutants during August, which they say undermines clear air gains and could be harmful to millions of people. 

The warning comes in a study recently published in Nature Communications, a peer-reviewed scientific journal. In that study, scientists with the National Center for Atmospheric Research found that amount of carbon monoxide in the air in August increased dramatically between 2002 and 2018.  

That’s significant because carbon monoxide levels are typically lower during the summer. Scientists say wildfire smoke is likely the reason for the detected increase. 

“Wildfire emissions have increased so substantially that they’re changing the pattern of air quality across North America,” Rebecca Buchholz, the lead author of the study, said in a news release. “It’s quite clear that there is a new peak of air pollution in August that didn’t used to exist.”

Nearly 3,500 wildfires have burned more than 1 million acres of land in Washington during the last two years, according to the Washington Forest Protection Association. State leaders warn the problem will likely get worse as our years get hotter, which will increase the length and intensity of Washington’s wildfire season. 

To determine whether the higher pollution levels were caused by smoke, the scientists eliminated other sources of emissions. They found that carbon monoxide levels over the Pacific Ocean were lower in August — a sign that the pollutants were not coming from Asia — and determined that the more tame wildfire seasons in the central and eastern portions of the U.S. did not coincide with as dramatic of an increase in carbon monoxide levels in those regions. 

They also studied a pair of fossil fuel emission inventories, which showed that carbon monoxide emissions from human activity did not increase in the Pacific Northwest during the study period. 

“Multiple lines of evidence point to the worsening wildfires in the Pacific Northwest as the cause of degraded air quality,” Buchholz said. “It’s particularly unfortunate that these fires are undermining the gains that society has made in reducing pollution overall.” 

That degraded air quality has large health implications for Pacific Northwest residents. Prolonged exposure to smoke pollutants has been linked to significant respiratory problems, and can affect the cardiovascular system. Such exposure has also been known to “worsen pregnancy outcomes,” scientists say. 

Buchholz also warned that the smoke pollution can have health implications for those living downwind of the Pacific Northwest. 

“It’s clear that more research is needed into the health implications of all this smoke,” she said. “We may already be seeing the consequences of these fires on the health of residents who live hundreds or even thousands of miles downwind.”