It kills more people each year than car accidents, wars or drugs. This invisible killer is air pollution from sources such as cars and trucks or factory smokestacks.
But as wildfires intensify and grow more frequently in the tropical world, smoke from these fires is emerging as a new source of deadly pollution, health experts say. According to some estimates, wildfire smoke – which contains a mixture of harmful air pollutants such as particulate matter, nitrogen dioxide, ozone and lead – already causes 675,000 premature deaths a year worldwide, as well as a host of respiratory, heart and other diseases. .
Research shows that wildfire smoke is beginning to undermine the world’s progress in cleaning up pollution from tailpipes and smokestacks, as climate change exacerbates fires.
“It’s sad, it’s really sad,” said Dr. Afif El-Hasan, a pediatrician who specializes in asthma care at Kaiser Permanente in Southern California and a board director of the American Lung Association. Wildfires “put our homes at risk, but they also put our lives at risk,” said Dr. El-Hasan, “and it will only get worse.”
Those health concerns were highlighted this week as wildfires ravaged the Los Angeles area. Residents began returning to their homes, many strewn with smoldering ash and debris, to assess the damage. Air pollution levels remain high in many parts of the city, including the northwest coast of Los Angeles, where the air quality index has risen to “hazardous” levels.
Los Angeles, in particular, has seen air pollution at levels that could increase daily deaths by between 5 and 15 percent, said Carlos F. Gold, an expert on the health effects of air pollution at the University of California, San Diego.
That means the current death toll, “while grim, may be an overestimate,” he said. People with underlying health problems, as well as the elderly and children, are at greater risk.
The rapid spread of this week’s fires in crowded areas, where houses, furniture, cars, electrical appliances and things like paint and plastic burned, made the smoke very dangerous, said Dr. Lisa Patel, a pediatrician in the San Francisco Bay Area and executive director of the Medical Society Consortium on Climate and Health.
Recent studies have found that even in homes that are not destroyed, smoke and ash blown in can cling to rugs, sofas and drywall, causing health hazards that can last for months. “We are breathing in this toxic intake of volatile organic compounds and polycyclic aromatic hydrocarbons and hexavalent chromium,” said Dr. Patel. “Everything is dangerous.”
More intense and more frequent fires, on the other hand, increase experts’ understanding of the health effects of smoke. “The wildfire season is no longer a season,” said Colleen Reid, who studies the effects of air pollution from wildfires on campus at the University of Colorado Boulder. “We have fires throughout the year that affect the population over and over again.”
“The health effects are not the same as if you were exposed once, then you don’t have it again for 10 years,” she said. “The consequences of that are something we don’t really know yet.”
A 2022 United Nations report concluded that the risk of devastating wildfires worldwide will increase in the coming decades. Warming and drying caused by climate change, as well as development in fire-prone areas, is expected to intensify “the global wildfire crisis,” the report said. Both the frequency and severity of extreme wildfires have more than doubled over the past two decades. In the United States, acreage burned annually has increased since the 1990s.
Now, wildfire pollution is reversing decades of improvements in air conditions brought about by cleaner cars and electricity generation. Since at least 2016, in about three-quarters of states in the continental US, wildfire smoke has eroded about 25 percent of the progress in reducing concentrations of a type of particulate matter called PM 2.5, a study by Environment 2023 found.
In California, the effect of wildfire smoke on air quality offsets the public health benefits of reduced air pollution from cars and factories, state health officials have found. (By releasing carbon dioxide and other planet-warming gases into the atmosphere, wildfires themselves are a major contributor to climate change: The wildfires that destroyed Canada’s boreal forests in 2023 produced more greenhouse gases than the burning of fossil fuels in all but three countries. )
“It’s not a good picture,” said Dr. Gold from UC San Diego, who participated in the Nature study. If greenhouse gas emissions continue at current levels, “we have some work suggesting that deaths from wildfire smoke in the US could increase by 50 percent,” he said.
Another silver lining is that the Santa Ana winds that have fueled the flames in recent days have been blowing more smoke out to sea. That’s in stark contrast to the smoke from the 2023 Canadian wildfires that drifted into New York and other US states miles away, causing a spike in emergency room visits for asthma.
At one point that year, more than a third of Americans, from the East Coast to the Midwest, were under air quality warnings from Canadian wildfire smoke. “We are seeing new threats that are getting worse in places we are not familiar with,” said Dr. Patel, a pediatrician.
The new normal is bringing changes to health care, said Dr. Patel. Many health systems send air quality alerts to at-risk patients. At the small community hospital where she works, “all the children who come in with asthma or asthma, I talk to them about how air pollution is getting worse because of wildfires and climate change,” she said.
“I teach them how to check the air quality, and I say they should ask for an air purifier,” added Dr. Patel. He also warns that children should not participate in cleaning up after a wildfire.
Scientists are still trying to understand the full range of health effects of wildfire smoke. One big question is how much researchers know about the emissions of vehicle debris and other forms of active air pollution in wildfire smoke, said Mark R. Miller, a researcher at the Center for Cardiovascular Sciences at the University of Edinburgh who is leading a recent global survey of climate change, air pollution and wildfires. .
For example, exhaust particles “are so small that when we breathe them in, they go deep into our lungs and are actually small enough to pass from our lungs into our blood,” he said. And once they’re in our blood, they can be carried around our bodies and start building.”
That means air pollution affects our entire body, he said. “It has an effect on people with diabetes, it has an effect on the liver and kidneys, it has an effect on the brain, on pregnancy,” he said. What is not clear is whether wildfire pollution has all those same effects. “But it’s possible,” he said.
Experts have a list of advice for people living in smoky areas. Check for air quality alerts, and follow evacuation orders. Stay indoors as much as possible, and use air purifiers. When going outside, wear an N95 mask. Don’t do hard work in a bad mood. Keep children, the elderly and other vulnerable groups away from harmful fumes.
Ultimately, addressing climate change and reducing all forms of air pollution is a way to reduce the burden on health, said Dr. El-Hasan of the American Lung Association. “Can you imagine how bad things would be if we didn’t start cleaning the gas coming out of our cars?” he said. “I try to think, the glass is half full, but it breaks my heart and worries me.”
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