Wildfire smoke linked to thousands of coronavirus cases on West Coast – San Francisco Chronicle

The presence of wildfire smoke last year during the pandemic may have been responsible for at least 19,000 additional coronavirus cases on the West Coast, and 700 subsequent deaths, a new study shows.

The study, published Friday in the journal Science Advances, offers the most detailed accounting yet of how the devastating 2020 wildfire season is believed to have amplified the coronavirus outbreak.

It traces increases in infections to periods of smoke in more than 50 counties in California, Oregon and Washington.

Some of the biggest smoke-related spikes were in the Sierra foothills and Central Valley, according to the study, but parts of the Bay Area also saw jumps. In Sonoma County, 13.1% of the cases from March to December last year were linked to smoke, or 1,754. This compares to 17.3% of the cases in Butte County, which had the largest percentage of smoke-associated cases of any California county.

Calaveras County fared the worst in terms of per-capita deaths. More than half of the countys 22 coronavirus fatalities were tied to smoke. The highest number of overall COVID-19 deaths associated with smoke were in Fresno and Alameda counties, with 131 and 110 people dying, respectively.

While a correlation between wildfire smoke and COVID-19 doesnt prove causation, the studys authors say the tie is no coincidence. Plenty of research since the start of the pandemic has suggested that exposure to smokes primary unhealthy component PM 2.5, which refers to particulate matter that is 2.5 micrometers in size or smaller, compromises peoples immunity and increases susceptibility to COVID-19. Scientists also hypothesize that the virus may be spread by the particles.

The new findings come as the delta variant fuels yet another surge of coronavirus infections across the country while fire season is again in high gear in the West. Parts of California are already blanketed in smoke, with bad air recently reported as far away as New York and North Carolina.

Its a horrible combination, said Francesca Dominici, one of the authors of the study and a biostatistician at Harvard Universitys T.H. Chan School of Public Health. Together, the wildfires and COVID-19 make us even sicker.

The new research is based on statistical modeling done by Dominici and her colleagues at Harvard University and Californias Environmental Systems Research Institute in San Bernardino County.

The teams models crunched coronavirus numbers in 92 counties during non-smoky periods from March 15 to Dec. 16 and how these numbers changed when wildfire smoke brought particulate pollution. The area the researchers examined covered 95% of the population in California, Oregon and Washington. They excluded areas that did not have sufficient data for modeling.

The models took into consideration lag times between viral exposure and testing, and they adjusted for several variables, including changes in weather and population.

Areas with the most coronavirus cases and deaths linked to smoke last year were often those closest to the fires.

The researchers found that across the counties a daily increase in PM 2.5 concentrations of 10 micrograms per cubic meter of air in smoke over 28 days correlated with an average 11.7% increase in coronavirus cases and 8.4% increase in COVID-19 deaths. The 24-hour concentration of PM 2.5 is generally considered unhealthy for some people when it gets above 35 micrograms per cubic meter of air.

In California, Sutter County followed Butte County in tallying the largest percentage of smoke-related coronavirus cases: 16.2% of all infections. Both are north of Sacramento, where bad air from several Sierra fires collected. In Mendocino County, where Californias largest fire in history burned, the August Complex fires, 14.6% of cases were associated with smoke.

Sacramento County, meanwhile, counted the most overall coronavirus cases tied to wildfires in the state: 4,639.

Beyond proximity to fires, the researchers said that the same factors resulting in some areas having more coronavirus cases than others racial makeup, pre-existing medical conditions and access to health care, for example explain why certain areas may be more vulnerable to smoke.

In some counties, including San Francisco, the number of coronavirus cases tied to smoke was actually less than what it would have been without a smoky fire season, according to the study. The researchers presumed that residents in these areas took extra precautions because of the wildfires, such as staying indoors as much as possible, buying air filters and wearing masks while outside. This could have boosted their level of protection to the virus.

The 2020 fire season went down as one of the nations worst, with a record 4.1 million acres burned in California. Many remember the eerie orange sky that emerged over the Bay Area because of wildfire smoke last September.

John Balmes, a professor of medicine at UCSF who was not affiliated with the new paper, said the research both helps validate the connection between wildfires and COVID-19 and underscores the need to do something about it.

This study is just one more set of evidence that we have to be doubling down on our efforts to reduce catastrophic wildfire risk, he said.

In the meantime, Balmes and the studys authors advise people to avoid exposure to smoke as best they can.

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander

Originally posted here:

Wildfire smoke linked to thousands of coronavirus cases on West Coast - San Francisco Chronicle