Are There Long-Term Side Effects of Breathing In Wildfire Smoke?

If you’re still processing January’s Palisades and Eaton fires, you’re not alone—many people are going through an eco-anxiety spiral right now. It’s clearer than ever that the wrath of climate change contributes to elongated droughts in Los Angeles, increasing the likelihood of devastating fires ravaging various neighborhoods. In recent years, climate experts have shown through research that wildfires are occurring more frequently than ever in western states—and many areas within Southern California are considered to have significant fire risk. 

A recent observational study from the World Weather Attribution (WWA) suggests that LA’s dry and hot conditions could lead to wildfires of the same caliber every 17 years. “The frequency and intensity of fires are escalating, and that’s been documented and described in research, but I certainly feel it in a visceral way here,” says May-Lin Wilgus, M.D., an associate clinical professor of medicine at UCLA and pulmonologist in Thousand Oaks, CA. 

As wildfires continue to become our new normal, it’s not surprising that many people (especially LA and San Diego residents) are concerned about the health impact of repeated smoke exposure.

Right now, the acute, or immediate and severe, effects of breathing in wildfire smoke are far more well-known than the long-term effects. Mary Johnson, M.D., Ph.D., the principal research scientist in the Department of Environmental Health at the Harvard T.H. Chan School of Public Health in Boston, MA, says that after a wildfire, hospitals often see an increase in emergency room visits for heart arrhythmias, heart attacks, sudden cardiac arrest, and even stroke. (According to the county Department of Public Health, fire-related hospital visits spiked 16-fold after the January wildfires.)

There’s still a lot we don’t know about the long-term impact of the recent fires, which some have called the “9/11 of LA” due to concerns about asbestos and smoke exposure. In response, researchers are closely monitoring residents’ health over the coming years. “People are rapidly mobilizing right now to gather a lot of data about the current fires and prospectively follow people after the LA fires,” Wilgus says. 

The LA Fire Study, a collaboration between researchers across multiple universities, including Harvard and UCLA, recently launched a 10-year study of the fires to find out what pollutants are present in the environment, at what levels, and the long-term respiratory, neurological, cardiovascular, reproductive, and immune system impact.

While we wait for more answers, leading experts share what the current research can tell us about the potential dangers of living in an area recently devastated by wildfires.

The Biggest Health Concern for Californians Right Now

One of the biggest concerns for LA residents is coming into contact with residual ash. Wilgus explains that this ash, which may linger on beaches or in neighborhoods destroyed by wildfires, could contain traces of asbestos, which can pose serious health risks.

Materials like pulverized concrete and tile can all release asbestos when burned, says Raja Flores, M.D., the chairman of the Department of Thoracic Surgery at Mount Sinai School of Medicine. Asbestos can look like a crystallized white powder, almost like talc. Once airborne, it can linger, where it’s no longer invisible to the human eye, Flores says. “That’s when you can inhale it unknowingly, and then it implants itself in your lungs and can cause lung cancer and mesothelioma.” Given that schools and other large buildings were damaged by the LA fires, it’s not surprising that asbestos has been detected in the debris.

In addition to asbestos, Johnson says wildfire smoke can contain hundreds of other carcinogens, depending on what’s burning. For example, toxic metals, including mercury, lead, and cadmium, may also be present in the ash. “Toxic metals tend to stay in our body, and enough exposure to them is associated with various types of cancer,” Johnson says.“There is pretty solid, growing evidence that wildfire smoke is more toxic than urban air pollution that largely comes from vehicles,” says Suzanne E. Paulson, Ph.D., professor of atmospheric and oceanic sciences at UCLA and director for its Center for Clean Air. In other words, when houses burn down from wildfires, you breathe in both the toxins from the smoke and all of the chemicals that are released from those burning homes and buildings. 

The scary thing is that those latter chemicals aren’t often accounted for in the Air Quality Index (AQI) that you see on most weather apps. That’s because standard AQI measurements are typically designed to detect only certain pollutants in the air, like PM2.5—microscopically small particulate matter. According to the Environmental Protection Agency (EPA), PM2.5 is the main pollutant emitted from wildfire smoke and is known to increase the risk of cardiovascular events.

While the immediate dangers of wildfire exposure are more clear, the long-term health consequences are still being uncovered.

What We Do—and Don’t—Know About Long-Term Health Effects

Inhaling anything that’s burning isn’t good for your health, says Flores. “Burn smoke contains polycyclic aromatic hydrocarbons (PAHs),” he says, which the EPA classifies as cancer-causing chemicals. “Whether you’re burning wood, tobacco, cigarettes, or weed, anytime you burn something and you inhale it, and that’s a bad thing—both for long-term cancer carcinogenesis and for short-term injuries to the lung, which can give you respiratory problems like COPD, [chronic obstructive pulmonary disease], and emphysema,” Flores says. 

In fact, a 2020 analysis from Stanford experts equated breathing wildfire smoke in an area where the Air Quality Index (AQI) is 150 or higher—typical during a wildfire—to smoking seven cigarettes a day. 

The question is, what about the long-term risk for the average healthy person who’s exposed to wildfire smoke for just a few days or weeks? “That’s a harder question to answer,” Johnson says. “That’s a big area that deserves more research outside of the respiratory effects,” Wilgus adds. “There are a lot of unknowns.”

That’s because researchers have typically studied populations like firefighters who have had chronic smoke exposure, Johnson says. For example, Wilgus points to a small 2021 study that identified an association between wildfire smoke exposure and new-onset asthma in firefighters. Another small study found that firefighters are at higher risk of developing lung cancer and cardiovascular disease after continuous wildfire smoke exposure. 

While we wait for answers from the LA Fire Study, emerging research suggests that wildfire smoke may impact cognitive function and mental health. Research from 2023, which looked at Californians who lived through the 2018 Camp Fire (the deadliest wildfire in U.S. history in the past 100 years), found that those who were exposed to the fires struggled to focus or handle distractions in their everyday lives. Their brains had to work harder to compensate—a change in cognitive processing that mirrors symptoms of post-traumatic stress disorder (PTSD).

Wildfire smoke has also been linked to pregnancy complications. Most recently, a 2024 study in the journal Public Health revealed that exposure to PM2.5—the main pollutant released from wildfires—may increase the risk of preterm birth and low birth weight.

How to Protect Yourself Right Now

“Ash can be suspended in the air during cleanup efforts, and that poses some risk of breathing it in or getting into contact with toxins in the ash,” Wilgus says. Wearing a tight-fitting N95 mask when walking through debris-ridden areas can help reduce your exposure.

Protecting your skin is also crucial when you’re walking through areas where ash may be lying around. “If there’s visible ash in your home returning after evacuation, use masks and gloves and wear long sleeves and pants to clean that up,” Wilgus says.

You also don’t want to accidentally disperse ash in the air as you clean it up. If you see some on your kitchen floor for example, consider misting it down or wetting the area so you can safely wipe it up and throw it away immediately. Using a duster, for example, could launch ash particles (aka toxins) into your breathing air. “If your pet’s out in the yard and there’s ash, you’d also want to wipe them off before they come back into the house,” Johnson adds.

Because there is no escaping future wildfires, any preparations you can do now to get ahead of the next tragedy may be a good idea. Installing an air filtration system in your home or getting portable air purifiers can help keep the air quality in your home clean and safe, the experts say.

If the air quality is poor outside, stay indoors until it improves. When a wildfire is active, Paulson recommends checking the AQI on various sites, including PurpleAir, AirNow, or Fire.airnow.gov for real-time readings, as they are more accurate than the AQI measurement you’d find on your weather app. That’s because these sites use real-time sensor networks that show you the particle concentrations in your neighborhood at that very moment, she explains.

Beyond taking precautions and staying vigilant of your surroundings, try to stay hopeful. Experts are optimistic that the research underway will uncover crucial insights into the effects of wildfire smoke as we adjust to this new normal. “I’m hopeful that the national attention on the LA fires will instigate more research, allowing us to answer a lot of these questions about the long-term impacts on both the environment and our health,” Wilgus says.