COVID-19 and wildfire smoke: A dangerous combo coming for Californians

31 July 2020

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USA – The coronavirus pandemic is already stressful for most Californians. Add the threat of wildfires, and the situation looks even more dire.

In recent years, smoke from huge Northern California wildfires has sometimes choked the Bay Area, creating unhealthy air quality. With fire season under way this year, how will smoke affect people who have or are recovering from COVID-19, or those with chronic lung diseases?

“It’s concerning because we don’t need yet another problem to contend with,” said Dr. Vinayak Jha, a pulmonologist in San Francisco affiliated with Sutter Health’s California Pacific Medical Center.

“People are already worried about catching the virus and becoming ill. Having respiratory problems and other problems, and then having a natural disaster to deal with or multiple fires going on during fire season is not pleasant,” he said.

In July, Gov. Gavin Newsom weighed in on the added challenges that wildfire evacuations bring to California during the pandemic, especially at shelters and fire camps.

According to the Centers for Disease Control and Prevention, those particularly vulnerable to wildfire smoke are: 65 and older, youths 18 and younger, people with chronic health conditions, and those who are pregnant, work outdoors or have low incomes. Some of them overlap with groups also susceptible to COVID-19.

Early clues about risk

While there aren’t definitive answers yet about the effects of wildfire smoke on COVID-19 patients, experts can look to research on smoking and air pollution to draw preliminary conclusions.

“Wildfire smoke is kind of like tobacco smoke without the nicotine,” said Dr. John Balmes, a professor of medicine at UCSF and environmental health sciences at UC Berkeley. “It’s plant-based material that when burned, produces carbon particles with nasty hydrocarbons that are toxic.”

He used the 2018 Camp Fire as an example. That blaze caused fine particulate matter known as PM2.5 particles to travel from the northern part of the Central Valley all the way down to the Bay Area. A thick haze blanketed the region for weeks, shutting down schools and businesses, with Northern California’s air quality rated the worst in the world for several days.

“Fine particles are small enough to make it down to the deep lung and can cause inflammation,” he said. “The acute effect of wildfire smoke on firefighters’ lungs have been studied and there is evidence of inflammation. … The closer you are to the fire, the greater the risk of inflammation.”

Jha said wildfires and air pollution from vehicles and factories share some of the same PM2.5 particles.

“There are growing reports out of China, Europe and the U.S. that the more air pollution there is, the more COVID deaths and cases there are,” Jha said. “So there’s some reason for concern that wildfire smoke, besides being bad for people in general, may affect people’s susceptibility to getting the virus.”

Breathing in wildfire smoke can cause shortness of breath, coughing and sore throat. So having the coronavirus also “could definitely make their symptoms worse,” Jha said.

One thing that particularly worries Dr. Monica Minguillon, a pulmonologist at Kaiser Permanente Santa Rosa Medical Center, is the long-term effects of COVID-19, especially those with severe cases and who are hospitalized.

“One of the things we’re seeing … is it can take a very long time to recover,” she said. “It will be months and years before we know the long-term consequences. Anybody recovering from chronic lung disease has to be on hyper-alert during wildfire season.”

Tips for dealing with wildfire smoke

So what should people recovering from COVID-19 or living with other respiratory illnesses do if wildfire smoke becomes a problem?

All the experts agree that unless there are mandatory evacuations, the best course of action is to stay inside with the windows closed — a step made easier with most people already sheltering in place in the pandemic.

But that also means keeping your home as clean and pollutant-free as possible. Balmes said to install a high-quality air filter in the HVAC system with a minimum efficiency reporting value (MERV) rating of 13 or higher, which he said filters out the particles that can get into the deep lung.

For those without a ventilation system, Balmes recommends a portable HEPA filter air purifier certified by the California Air Resources Board, which can range in cost from $200 to $1,000.

One purifier cleans one room, so people may want to consider additional purifiers for rooms where they spend the most time. If purchasing an air purifier is too costly, experts said people can make a DIY version with a box fan and air filter.

Jha said COVID-19 patients should keep close contact with their health care provider and avoid exerting themselves, especially at the beginning of the illness.

How to track air quality

Experts also recommend checking the current air quality conditions regularly at the federal Air Quality Index and the Bay Area’s Spare the Air website. The Chronicle’s Air Quality Tracker also shows current fire-emitted fine-particulate matter in the Bay Area and state.

More information about air quality and wildfire smoke is available at For more resources, visit the CDC web page about wildfire smoke and coronavirus.

If you have to leave the house when wildfire smoke is in the air, and you have a pre-existing condition or have recovered from COVID-19, an N95 respirator is the best way to protect against smoke and coronavirus. Because those are needed by health care workers, they have been in short supply.

Experts say cloth coverings and surgical masks do not offer protection against wildfire smoke, but Balmes said most healthy individuals do not need to get a special type of mask.

Two UC Berkeley students walk through Sproul Plaza wearing protective breathing masks on Nov. 16, 2018. The plaza was largely deserted after university officials canceled classes because of unhealthy air conditions caused by heavy smoke from the Camp Fire in Butte County.

Jha said staying vigilant in the pandemic and being as prepared as possible for a wildfire are important.

“Continue to socially distance, and continue to wear a mask in public,” he said. “Have precautions in place: knowing how to check the Air Quality Index, checking their own home system, and having a plan in case they need to leave the area.”

The Chronicle’s Fire Map and Tracker provides information on wildfires currently burning in California.

Kellie Hwang is a San Francisco Chronicle staff writer. Email: Twitter: @KellieHwang

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