Harvard researchers: Wildfire smoke linked with increase in COVID-19 cases, deaths

Summer brought with it a double-edged threat to the lungs: not only the continuation of the pandemic but another wildfire smoke season.

A new study from Harvard University found that wildfires, which produce particulate matter, were associated with an increase in COVID-19 cases and deaths on the West Coast.

“Our research suggests that people breathing smoke from wildfires are more vulnerable to coming down with COVID-19,” said Loretta Mickley, an atmospheric chemist and research scientist who was one of the researchers on the study.

And while the study did not show that wildfire smoke containing fine particulate matter – called PM 2.5 – actually caused an increase in COVID-19 cases, there was strong enough data to show the relationship between the two.

As Mickley said, these results are not necessarily surprising, based on what research says about the short-term effects of wildfire smoke.

“We’ve known for a long time that particulate matter, (which are) tiny particles, in the air can work their way deep into the lungs and irritate the lungs, called inflammation,” Mickley said.

On average across all the counties studied, a certain increase in PM 2.5 each day for 28 days in a row was associated with a nearly 12% increase in COVID-19 cases and an 8% increase in COVID-19 deaths.

Other research, as well as climate change, suggests that the increase in particulate matter due to wildfire smoke is a phenomenon projected to increase in the West.

“Even without COVID it’s a grim picture,” Mickley said. “And if you layer on COVID, it’s horrible.”

The Harvard study took weather patterns, population size and long-term trends into consideration, but may have missed other mitigating factors.

For instance, researchers found that Whitman County had a 72% increase in COVID-19 cases associated with an increase in PM 2.5 levels over 28 days; however, those numbers might not tell the whole story. As The Spokesman-Review reported last year, college students were returning to Pullman at the same time, and case counts began to spike as a result.

The study found the strongest association between wildfire smoke and COVID-19 increases in California’s Central Valley, near Fresno and Sacramento.

The study of wildfire smoke and its relationship to COVID-19 will continue, and while there’s no proven cause-effect link, wildfire smoke can affect people’s ability to breathe.

“I think anyone with bad lung disease or bad cardiovascular disease, those patients have a poor reserve to tolerate anything, whether that’s pneumonia, a cold or COVID and wildfire smoke, which we know worsens respiratory symptoms,” said Dr. Ben Arthurs, a pulmonologist at MultiCare.

One day of wildfire smoke might not be entirely detrimental, he said, although he noted that people with pre-existing lung conditions are at higher risk for irritation.

“Degree of exposure matters, and spending one day outside exposed to wildfire smoke is not the end of the world for anybody, necessarily,” Arthurs said.

Julie Postma, associate dean for research at the WSU College of Nursing, is studying young adults’ awareness of the dangers of wildfire smoke, particularly those diagnosed with asthma.

Her 2020 research found college-age students with asthma recognized that wildfire smoke was common, and that even a few hours could impact their health.

The WSU study, which has been submitted for publication, looked at an enhanced phone app that had participants use a bluetooth-based spirometer to measure their lung air volume and record their levels. The app then created a map of these results that all users could see, effectively crowd-sourcing how impactful the smoke was for peers with a similar condition, in this case asthma.

That crowd-sourcing, Postma said, appeared to be useful.

“If people can better understand how this impacts their health and what ideas their peers have,” Postma said, they can change their behavior according to what their peers are reporting, whether that be rescheduling an event or choosing to not go hiking that day.

Postma plans to continue her research and has applied for a National Institutes of Health grant to continue studying awareness and effectiveness of tools to help young adults gauge their risk in wildfire season, something that is becoming much more noticeable in urban centers, including Spokane.

“If you live out in a rural environment where fields are burned seasonally, you’re more used to periodic smoke, but I don’t think people in urban environments have seen this in the past,” Postma said.

During the height of the smoke this summer, Arthurs said he saw more patients in the ICU needing ventilators to breathe after an asthma episode than in a normal year, and he suspects that it had to do with this year’s wildfire smoke, which lingered at times for days.

Postma’s further research will look at more people for a longer period of time to see how awareness of air quality, and crowdsourced, real-time data, affect people’s behaviors.

The 2020 Harvard study likely applies beyond the first year of the pandemic, especially with the delta variant, which is much more transmissible, said Kevin Josey, a fellow at Harvard who worked on the study.

“I think, especially with the delta variant out there, this association we’re observing is as bad or worse among those who are unvaccinated,” Josey said.