The record-setting 2020 wildfire season scorched millions of acres, forcing the evacuation of hundreds of thousands of people and costing billions of dollars in insured losses.
But the damage didn’t stop there.
A study, published Friday in the peer-reviewed journal Science Advances, says thousands of COVID-19 cases and hundreds of deaths in California, Oregon and Washington state from March to December 2020 may be linked to wildfire smoke.
Researchers at Harvard T.H. Chan School of Public Health used a statistical model to measure the connection between high levels of fine particulate air pollution, or PM2.5, produced by the wildfires and the number of COVID-19 cases and deaths in 92 counties.
They found a daily increase of 10 micrograms in PM2.5 per cubic meter of air for 28 days was associated with an 11.7% increase in COVID-19 cases and an 8.4% increase in death. Across the three states studied, researchers determined nearly 19,700 COVID-19 cases and 750 deaths were attributable to daily increases in PM2.5 from wildfires.
“The year 2020 brought unimaginable challenges in public health, with the convergence of the COVID-19 pandemic and wildfires across the western United States,” said senior author Francesca Dominici, professor of biostatistics, population and data science at Harvard Chan School. “Climate change – which increases the frequency and the intensity of wildfires – and the pandemic are a disastrous combination.”
COVID-19 cases had the biggest increase in Sonoma County, California, and Whitman County, Washington – 65.3% and 71.6%, respectively – sites of the Glass Fire and Babb-Malden Fire.
The Glass Fire burned more than 67,000 acres in Napa and Sonoma counties in 2020, according to Cal Fire, the state’s firefighting agency. The Babb-Malden Fire burned more than 15,000 acres in Whitman County, KING-TV reported.
High levels of PM2.5 have been associated with a host of negative health outcomes, including premature death, asthma, chronic obstructive pulmonary diseases and other respiratory illnesses. Other studies have found a link between short- and long-term exposure to PM2.5 and COVID-19 cases and deaths.
“That small particle is small enough to burrow into the lung in a way that sets it up for any respiratory disease,” said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City. “It can burrow past the epithelium and create inflammation. It’s a setting for any respiratory disease, including COVID, to exacerbate.”
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Wildfire smoke can temporarily compromise the immune system, said Dr. Kari Nadeau, director of the Sean N. Parker Center for Allergy and Asthma at Stanford University.
“When you breathe in smoke, those particulates get into the lungs … they can get into your bloodstream, and they damage your immune system,” she said. “COVID affects your immune system, your lungs and your blood vessels. So you’re getting doubled up targeting of these organs in a very pathological way. It’s like a double hit.”
Although the damage is typically reversible, Nadeau said, it can become permanent in residents who have lived for decades where wildfires are common and have been repeatedly exposed to high levels of PM2.5.
It isn’t just western Americans affected by wildfire smoke. A satellite video published by the National Oceanic and Atmospheric Administration in July shows how smoke produced in the West blankets much of the USA and Canada.
This year’s fire season is on pace to race past 2020. As of Aug. 12, 6,272 fires in California have burned about 1,432 square miles, according to Cal Fire.
Health experts worry the wildfires may lead to another rise in coronavirus cases this year. Unvaccinated Americans make up more than 90% of COVID-19 hospitalizations, and if the body’s defenses are further weakened by smoke, they stand little chance against the highly contagious delta variant.
They urge Americans to not only protect themselves from COVID-19 but also from wildfire smoke by staying indoors and wearing N95 masks that help block PM2.5.
“We need to try to prevent the wildfires, and we need to prevent COVID, and luckily, we have that knowledge in our hands,” Nadeau said. “We just have to do something actionable about it.”
Contributing: David Benda and Mike Chapman, Redding Record Searchlight
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