Exposure to high levels of fine particle pollution produced by wildfires may have led to thousands more COVID cases and deaths, according to a new study published in the journal Science Advances.

Why it matters: Research has shown that smoke can have dangerous health impacts, a correlation that is putting more and more at risk as the pandemic collides with the climate crisis.

Details: Researchers tracked more than 90 counties in California and Washington that were ravaged by wildfires last year, and found that nearly 20% of COVID cases in certain counties were linked to elevated levels of wildfire smoke.

• In some counties, an even higher percentage of COVID deaths could be associated with wildfire smoke.
• Their models accounted for other variables, including weather, population and general COVID trends, to control for factors that might influence the findings.
• "Scientists who study air quality say it is possible that smoke particles could carry the virus," the Washington Post writes. "There are also other possible dynamics involved, such as people tending to gather indoors to avoid wildfire smoke, which could lead to more interaction with infected people."

What they're saying: "This illustrates the systemic and contingent nature of crises and how the effects of one global crisis (climate change) can have cascading effects on concurrent global crises (the COVID-19 pandemic) that play out in location-specific ways (increased COVID-19 cases and deaths due to wildfire)," the authors wrote in the study.

The big picture: Climate change is increasingly inducing wildfires, and they won't stop anytime soon. Rapid global warming is reaching across the globe and making the world a more volatile place, per a recent UN-sponsored report.

• Extreme heat and wildfires are plaguing the United States, Canada, Siberia, Europe and northern Africa.
• In some of these regions, the fires are likely to continue to burn until the onset of winter snows.

Go deeper... In photos: Where wildfires are blazing around the world