Climate-driven wildfire smoke killed thousands in U.S. over 15 years

Wildfires driven by climate change contribute to as many as thousands of annual deaths and billions of dollars in economic costs from wildfire smoke in the United States, according to a new study.

The paper, published on May 2 in the journal Nature Communications Earth & Environment, found that from 2006 to 2020, climate change contributed to about 15,000 deaths from exposure to small particulate matter from wildfires and cost about $160 billion. The annual range of deaths was 130 to 5,100, the study showed, with the highest in states such as Oregon and California.

The paper's researchers focused on deaths linked to exposure to fine particulate matter, or PM2.5, the main concern from wildfire smoke.

These particles can lodge deep into lungs and trigger coughing and itchy eyes with short-term exposure. In the long term, they can make existing health problems worse and lead to a range of chronic and deadly health issues. Children, pregnant people, the elderly and outdoor workers are among the most vulnerable. The Health Effects Institute estimated the pollutant caused 4 million deaths worldwide.

Evidence is emerging that PM2.5 from wildfire smoke is more toxic than other pollution sources. When wildfires encroach into cities, burning cars and other toxics-containing materials, it adds to the danger.

Numerous studies have tied human-caused climate change – caused by the burning of coal, oil and gas – to a growth in fires in North America. Global warming is increasing drought, especially in the West, and other extreme weather. Drier conditions suck moisture from plants, which act as fuel for fires. When drier vegetation and seasons are mixed with hotter temperatures, that increases the frequency, extent and severity of wildfires and the smoke they spew.

The study's authors drew on modeled and existing data to reach their findings. First, they sought to understand how much area burned by wildfires was attributable to climate change. They did that by analyzing the real climate conditions – heat and rain, for instance – when wildfires erupted from 2006 to 2020, and compared that to a scenario where weather measurements would be different without climate change.

From there, they estimated the levels of PM2.5 from wildfire smoke tied to climate change using the same approach. Lastly, integrating the current understanding of how particulate matter affects mortality based on published research, they quantified the number of deaths related to PM2.5 from wildfires and calculated their economic impact.

This framework showed that of 164,000 deaths related to wildfire-PM2.5 exposure from 2006 to 2020, 10 percent were attributable to climate change. The mortalities were 30 to 50 percent higher in some western states and counties.

Ultimately, the study notes, the problem of deaths from wildfire smoke will only get worse without the reduction of greenhouse gas emissions.

(Cover: A fire burns near Waretown, New Jersey, U.S., April 22, 2025. /VCG)