Climate change is making wildfire smoke more deadly

Human-caused climate change is already cutting lives short in the United States, and now scientists can attach a grim number to one key pathway. A new study shows that wildfire smoke intensified by climate change triggered about 15,000 additional deaths between 2006 and 2020.

The work, led by Oregon State University (OSU) researcher Bev Law, is the first to tie a death toll directly to climate-driven increases in fine particulate matter from wildfires.

Smoke is deadlier than storms

Wildfires emit PM2.5 – sooty particles smaller than 2.5 micrometers that slip deep into the lungs and even the bloodstream.

Using climate projections, fire-behavior models, smoke-dispersion simulations, and county-level health data, the team found that wildfire PM2.5 killed an estimated 164,000 people in the lower forty-eight states during the 15-year window.

The researchers calculate that 15,000 of those lives were lost because rising temperatures and drier landscapes made fires larger or more intense. The average annual death rate came to 5.14 per 100,000 people – roughly twice the national rate from hurricanes and other tropical cyclones.

Billions lost to wildfire smoke

The human cost is only part of the burden. Factoring in lost productivity, medical bills, and the federally accepted “value of a statistical life,” the researchers peg the economic damage from those extra smoke deaths at $160 billion.

“Without efforts to address climate change, wildfires and associated fine particulate matter will continue to increase,” said Law, professor emerita in the OSU College of Forestry.

According to Professor Law, smoke-related deaths could climb at least 50% by mid-century and push annual damages to $244 billion.

Western U.S. is hit the hardest

Although the analysis spans every county in the continental United States, the heaviest mortality and economic losses fell on California, Oregon, and Washington.

About 35% of the climate-linked deaths occurred in 2020 alone, a year dominated by California’s record fire season and the unprecedented Labor Day blazes that swept through the Pacific Northwest. Major fires in Colorado and Arizona added to the smoke plume that summer and fall.

Tracking a hidden killer

Law’s group pulled together about 44,000 documented fire-smoke events dating back to 1958, then used the subset from 2006 onward to match modern satellite and ground-sensor coverage.

They fed those fire fingerprints into atmospheric transport models that estimate surface PM2.5 concentrations downwind. Finally, they applied health-risk functions from the Environmental Protection Agency to translate the exposure into mortality.

By rerunning the chain with and without the climate-induced boost in fire activity, the researchers isolated the share of deaths attributable to global warming.

Smoke erodes air-quality gains

For decades, regulators had chipped away at urban smog and tailpipe emissions, steadily lowering average PM2.5 across the nation. Wildfire smoke is reversing those gains.

The authors note that fires now account for almost half of all fine-particle pollution in the United States, a proportion likely to grow as hotter, drier summers extend burning seasons and speed up daily fire growth.

“Exposure to PM2.5 is a known cause of cardiovascular disease and is linked to the onset and worsening of respiratory illness,” Law said.

She pointed to climate fingerprints that have already increased fires: earlier snowmelt leaves forests drier by midsummer; heat waves stress trees; and low humidity turns lightning ignitions into runaway blazes. Those same conditions are projected to intensify unless greenhouse-gas emissions fall sharply.

Preventing more smoke deaths

The study arrives as fire-prone states weigh investments in forest thinning, prescribed burning, and community protection.

By putting a dollar value on smoke mortality, the work gives lawmakers a fresh metric to compare against the price of mitigation. It also highlights the need for national strategies to alert vulnerable groups – such as people with heart or lung disease – when smoke plumes threaten.

Smoke travels nationwide

While western states dominate the tally, the models show that smoke travels far, bringing elevated PM2.5 to the Midwest and even the East Coast on certain wind patterns.

Communities hundreds of miles from a flame front can still see emergency-room visits rise when fine-particle concentrations spike.

Smoke’s future looks worse

Law and colleagues plan to refine their estimates with newer satellite instruments and higher-resolution health data. They also hope to model how different climate-policy scenarios would change future smoke impacts.

Their message is stark though. The deaths tallied through 2020 reflect atmospheric conditions already locked in by past emissions. If warming continues on its present course, today’s lethal smoke seasons may soon look mild by comparison.

The study turns a statistical spotlight on a threat many people only smell or glimpse as a haze on the horizon.

By counting lives lost to smoke intensified by climate change, the research underscores how quickly the abstract math of global warming translates into human tragedy  – and why cutting emissions now could spare thousands of lives in the decades to come.

The study is published in the journal Nature Communications Earth & Environment.

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