A new study has found that climate change has significantly contributed to wildfire smoke in the U.S., leading to thousands of deaths and billions in economic damages over a 15-year period.
Published in Nature Communications Earth & Environment, the study estimates that from 2006 to 2020, climate change was responsible for approximately 15,000 deaths due to fine particulate matter (PM2.5) from wildfire smoke, with an associated economic cost of around $160 billion. Annual deaths linked to this pollution ranged from 130 to 5,100, with the highest numbers in states like California and Oregon.
According to co-author Nicholas Nassikas, a physician and Harvard professor, the team aimed to understand how rising wildfire smoke exposure in a warming climate affects mortality — the most severe health outcome.
Lisa Thompson, an Emory University professor not involved in the study, said it stands out for isolating the impact of climate change on deaths and for analyzing these effects over time and across regions.
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The research focused on PM2.5 particles, which can deeply penetrate the lungs and, with long-term exposure, worsen existing health conditions and cause chronic diseases. Vulnerable populations include children, older adults, pregnant people, and outdoor workers. Globally, PM2.5 is responsible for about 4 million deaths annually, according to the Health Effects Institute.
Evidence suggests wildfire-sourced PM2.5 may be more harmful than other pollution due to the burning of man-made materials during urban fires. Climate change, driven by fossil fuel use, has intensified droughts and extreme heat — conditions that dry out vegetation and increase fire risk.
Jacob Bendix, professor emeritus at Syracuse University, said the findings were alarming but expected. He emphasized that even those far from wildfires are impacted, showing the wide-reaching effects of climate change.
To determine the number of climate-related deaths, researchers compared wildfire conditions with and without climate change influences, then estimated PM2.5 levels and resulting fatalities using established health risk data. They found that 10% of 164,000 wildfire-related deaths over the study period could be attributed to climate change, with even higher rates in parts of the western U.S.
Some experts, like Stanford’s Marshall Burke, affirmed the study's methods in linking climate change to burned areas but noted challenges in tracking smoke dispersion. Patrick Brown from Johns Hopkins raised concerns that non-climate wildfire factors were underrepresented, cautioning against assuming that carbon emission reductions are the sole solution. He suggested practical actions like controlled burns and ignition controls as additional strategies.
While land management can reduce risk, Nassikas stressed that cutting greenhouse gas emissions is essential to prevent worsening health impacts from wildfire smoke.
“We need awareness,” Nassikas said, “but we also need action — at every level, from individuals to global policy.”