It kills more people each year than car accidents, war or drugs. This invisible killer is air pollution from sources such as cars and trucks or factory smokestacks.
But as wildfires intensify and become more frequent in a warming world, smoke from these fires is emerging as a new source of deadly pollution, health experts say. By some estimates, wildfire smoke – which contains a mix of dangerous air pollutants like particulate matter, nitrogen dioxide, ozone and lead – is already causing up to 675,000 premature deaths per year worldwide, as well as a range of respiratory, heart and other diseases.
Research shows that smoke from wildfires begins to erode world progress in cleaning pollution from tailpipes and chimneys, as climate change makes fires worse.
“It’s really heartbreaking,” said Dr. Afif El-Hasan, a pediatrician specializing in asthma care at Kaiser Permanente in Southern California and a board member of the American Lung Association. Wildfires “put our homes at risk, but they also put our health at risk,” Dr. El-Hasan said, “and it will only get worse.”
These health concerns emerged this week as wildfires ravaged the Los Angeles area. Residents began returning to their neighborhoods, many of which were strewn with ash and rubble, to survey the damage. Air pollution levels remained high in many areas of the cityincluding on the northwest coast of Los Angeles, where the air quality index reached “hazardous” levels.
Los Angeles, in particular, has experienced air pollution at levels that could increase daily mortality by 5 to 15 percent, said Carlos F. Gold, an expert on the effects of air pollution on health at the University of California, San Diego.
This means the current number of deaths, “while tragic, is likely greatly underestimated,” he said. People with underlying health conditions, as well as the elderly and children, are particularly vulnerable.
The rapid spread of this week’s fires through dense neighborhoods, where they burned homes, furniture, cars, electronics and materials like paint and plastic, made the smoke more dangerous, Dr. Lisa Patel, a San Francisco Bay Area pediatrician and executive director of the Medical Society Consortium on Climate and Health.
A recent study found that even in homes spared from destruction, smoke and ash blown indoors could stick to carpets, sofas and drywall. creating health risks which can persist for months. “We are breathing this toxic mixture of volatile organic compounds, polycyclic aromatic hydrocarbons and hexavalent chromium,” Dr Patel said. “All of this is harmful.”
Meanwhile, the intensification and frequency of fires are shaking up experts’ understanding of the health effects of smoke. “Wildfire season is no longer a season,” said Colleen Reid, who studies the health effects of air pollution from wildfires at the University of Colorado Boulder. “We have fires all year round that repeatedly affect the same population. »
“The health impacts are not the same as if you were exposed once and then again for 10 years,” she said. “The effects of that are something we don’t really know yet.”
A 2022 United Nations report concluded that the risk of devastating wildfires around the world would increase in the coming decades. Warming and drying caused by climate change, as well as the development of fire-vulnerable areas, are expected to intensify a “global wildfire crisis,” the report said. The frequency and intensity of extreme wildfires have more than doubled over the past two decades. In the United States, the average the area burned per year has exploded since the 1990s.
Today, pollution from wildfires is reversing what was a decades-long improvement in air quality thanks to cleaner cars and electricity generation. Since at least 2016, in nearly three-quarters of the continental United States, smoke from wildfires has eroded about 25% of the progress made in reducing concentrations of a type of particulate matter called PM 2.5. a Nature study in 2023 found.
In California, the effect of wildfire smoke on air quality reverses public health gains caused by a drop in air pollution from automobiles and factories, state health officials found. (By releasing carbon dioxide and other planet-warming gases into the atmosphere, wildfires themselves contribute greatly to climate change: The wildfires that ravaged Canada’s boreal forests in 2023 produced more greenhouse gases than burning fossil fuels in all but three countries.
“It’s not a pretty picture,” said Dr. Gold of UC San Diego, who participated in the Nature study. If greenhouse gas emissions continue at current levels, “we have work that suggests that mortality from wildfire smoke in the United States could increase by 50 percent,” he said. .
The silver lining is that the Santa Ana winds, which have fueled the flames so fiercely in recent days, have blown some of the smoke out to the ocean. That contrasts with smoke from 2023 Canadian wildfires that spread toward New York and other U.S. states hundreds of miles away, causing pollution spikes. 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 alerts due to smoke from Canadian wildfires. “We’re seeing new threats that are getting worse in places that aren’t used to them,” said Dr. Patel, a pediatrician.
The new normal is driving changes in health care, Dr. Patel said. More health systems are sending air quality alerts to vulnerable patients. At the small community hospital where she works, “to every child who comes in with wheezing or asthma, I talk to them about how air pollution is getting worse because of wildfires and changing climate,” she said.
“I teach them how to check the air quality and tell them they should ask for an air purifier,” added Dr. Patel. She also warns that children should not participate in cleaning up after a wildfire.
Scientists are still trying to understand the full health effects of wildfire smoke. A big question is how much of what researchers know about vehicle exhaust and other forms of air pollution applies to wildfire smoke, said Mark R. Miller, a researcher at the Center for Cardiovascular Sciences at the University of Edinburgh who led a recent global survey climate change, air pollution and forest fires.
For example, exhaust particles “are so small that when we breathe them in, they go deep into our lungs and are actually small enough that they can pass from our lungs into our bloodstream,” he said. “And once they’re in our blood, they can be transported into our body and start to build up.”
This means that air pollution affects our entire body, he said. “It has effects on people with diabetes, on the liver and kidneys, on the brain and on pregnancy,” he said. What’s still unclear is whether pollution from wildfires has the same effects. “But it’s likely,” he said.
Experts offer a range of advice to people living in smoky areas. Keep an eye on air quality alerts and follow evacuation orders. Stay indoors as much as possible and use air purifiers. When venturing outside, wear N95 masks. Do not do strenuous exercise in stale air. Keep children, the elderly and other vulnerable groups away from the worst smoke.
Ultimately, fighting climate change and reducing all kinds of air pollution is the way to reduce the overall health burden, said Dr. El-Hasan of the American Lung Association. “Can you imagine how much worse things would be if we hadn’t started cleaning up the emissions from our cars? » he said. “I try to think, the glass is half full, but it breaks my heart and it worries me.”
