The study is part of a growing collection of research that links exposure to heavy wildfire smoke with a greater risk of becoming infected with the coronavirus.
“Our results showed a substantial increase in the COVID-19 [the disease caused by the coronavirus] positivity rate in Reno during a time when we were affected by heavy wildfire smoke from California wildfires,” said study lead author Daniel Kiser.
“This is important to be aware of as we are already confronting heavy wildfire smoke from the Beckwourth Complex Fire, and with COVID-19 cases again rising in Nevada and other parts of the western US.”
The research raises concerns that the wildfire smoke currently blowing across the United States could cause a surge in coronavirus cases.
In northern California, ongoing wildfires have burned more than 190,000 acres. The fires corresponded with a recent spike in the state’s coronavirus cases. Infections jumped by 43 percent in just 24 hours, increasing from 5,577 on July 22 to 7,984 on July 23.
The DRI team set out to investigate whether western wildfires in 2020 were linked to coronavirus cases in Reno. The researchers measured the amount of fine particle pollution circulating in the air as a result of wildfire smoke from May 15 to October 20.
Exposure to fine particle pollution (PM2.5) has been linked to an increased risk of catching a respiratory virus due to modified immune responses such as inflammation. According to the DRI scientists, PM 2.5 may also “enhance the spread and survival” of aerosols that carry the coronavirus.
The researchers compared levels of PM 2.5 in Reno to confirmed coronavirus cases in one of the city’s hospitals. The results indicate that there was a three percent rise in coronavirus cases for every 10-microgram increase in PM 2.5 levels per cubic meter.
“This corresponded to an estimated 17.7% increase in the number of cases during the time period most affected by wildfire smoke, from 16 Aug to 10 Oct,” wrote the study authors.
The experts found that residents of Reno were exposed to higher levels of PM2.5 that persisted for longer periods of time compared to neighboring cities. During the study period, PM2.5 levels were elevated for 43 days in Reno versus 26 days in San Francisco.
“We had a unique situation here in Reno last year where we were exposed to wildfire smoke more often than many other areas, including the Bay Area,” said study co-author Dr. Gai Elhanan.
“We are located in an intermountain valley that restricts the dispersion of pollutants and possibly increases the magnitude of exposure, which makes it even more important for us to understand smoke impacts on human health.”
“We believe our study greatly strengthens the evidence that wildfire smoke can enhance the spread of the coronavirus.”
The study is published in the Journal of Exposure Science and Environmental Epidemiology.