Fine Pollutants From ‘New Normal’ of Wildfires Affects Much of US

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by Shayna Korol |

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Life in the wake of the COVID-19 pandemic isn’t the only “new normal.”

Wildfires in the northwestern U.S. and Canada have become regular summertime occurrences in the northern hemisphere, with more than half of U.S. states being affected by the particulate matter that blows over from the fires, according to a recent study.

These findings are of particular concern for people living with lung diseases, including chronic obstructive pulmonary disease (COPD).

The study, “Satellite-based estimation of the impacts of summertime wildfires on PM2.5 concentration in the United States,” was published in Atmospheric Chemistry and Physics.

“Wildfire smoke exposure can cause small particles to be lodged in lungs, which may lead to exacerbations of asthma, chronic obstructive pulmonary disease (COPD), bronchitis, heart disease, and pneumonia,” Zhixin Xue, a PhD candidate in atmospheric science at the University of Alabama in Huntsville and the study’s first author, said in a university press release.

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The research team assessed how the wildfires are affecting U.S. air quality using surface PM2.5 concentration as a metric. The Environmental Protection Agency defines PM2.5 as fine inhalable particles with diameters of 2.5 micrometers or less. (PM stands for particulate matter or particle pollution, a mixture of solid particles and liquid droplets found in the air; at 2.5 micrometers, they are 30 times smaller than a strand of human hair.)

With the support of a National Aeronautics and Space Administration (NASA) grant, the researchers used NASA satellite data, ground observations, and several meteorological datasets to determine surface PM2.5 concentrations.

“Most of the data used in our study is publicly available,” Xue said. “It is important to note that ground measurements of PM2.5 are not available everywhere and therefore satellite data provides an excellent opportunity to map the spatial distribution of air pollution.”

Using a statistical model — known as a geographically weighted regression method — the researchers estimated surface PM2.5 between low (in 2011) and high (in 2018) fire activity years. A specific 17-day period, Aug. 9 to 25, was analyzed for both periods.

Major wildfires in 2018 were reported in British Columbia, Canada, (the Tweedsmuir Complex fire) and Washington state (the Cougar Creek, Crescent Mountain, and Gilbert fires) beginning in late July and continuing until mid-September, the study noted.

Results showed that aerosols from smoke caused significant pollution across more than half of the U.S.

In 2018 relative to 2011, PM2.5 levels rose in 29 states, and 15 of those states had more than twice the PM2.5 concentrations recorded in 2011, the team estimated. The most affected states were Washington, California, Wisconsin, Colorado, and Oregon, each of which have more than 4 million residents.

“The PM2.5 values in Oregon increase from 4.97 in 2011 to 33.3 mcg m−3 [micrograms per cubic meter of air] in 2018, which is nearly a 7-fold increase,” the researchers wrote. They rose by a magnitude of eight times in Washington, from 5.87 to 46.47 mcg m−3.

A single 2018 wildfire event exposed up to 52% of people living in the U.S. and Canada to particulate matter, they added, suggesting this should be a matter of concern to policymakers from a health perspective.

Researchers also noted previous studies, showing that from 2013 to 2016 more than 69% of Americans and 76% of Canadians were at least partly affected by wildfire smoke.

Based on data from the Centers for Disease Control and Prevention (CDC), suggesting that about 8% of the U.S. population is asthmatic, the researchers estimated that wildfire smoke impacts 3 million Americans with asthma. Healthy people can also develop respiratory issues from smoke exposure.

People with COPD —  one of the leading causes of death in the U.S., estimated to affect about 16 million residents — are especially vulnerable to the wildfires’ effects as they have chronically blocked airways. The CDC recommends that COPD patients talk to their healthcare provider about steps to take to protect against wildfire smoke.

“With wildfires becoming more frequent during recent years, more effort is needed to predict and warn the public about the long-range transported smoke from wildfires,” the researchers wrote.

The PM2.5 aerosols are eroding gains in U.S. air quality made since the 1970, with the passage of the Clean Air Act, Xue said.

“Furthermore, in a changing climate, as surface temperature increases and humidity decreases, the flammability of land cover also increases and thus accelerates the spread of wildfires, leading to increase in PM2.5 concentrations,” Xue added. “The smoke aerosols from these fires increase fine particulate matter concentrations and degrade air quality.”