How Wildfire Smoke Affects Your Health—and How You Can Protect Yourself

As a series of massive fires continues to blaze through the Los Angeles area, blanketing neighborhoods with smoke and forcing thousands of people to evacuate their homes, air quality remains unhealthy throughout many parts of the county.

Wildfire smoke is a mixture of water vapor, gases, and microscopic particles known as particulate matter. The smallest of these particles, known as PM2.5 because they have a diameter of less than 2.5 micrometers, pose the most danger to human health. They can lodge deep in the lungs and sometimes enter the bloodstream. Earlier this week, PM2.5 around Los Angeles rose to “hazardous” levels, the highest warning on the US Air Quality Index.

“Wildfire smoke is risky for everybody, especially when the particulate matter that is being released is in large quantities for long periods, like what is happening in California right now,” says Zachary Rubin, a Chicago-area pediatric allergist and spokesperson for the American College of Allergy, Asthma, and Immunology.

When fine particulate matter is inhaled, it can trigger inflammation in the body. Symptoms can range from the mild, such as burning or itchy eyes, runny nose, scratchy throat, and headache, to severe respiratory issues, including difficulty breathing, wheezing, coughing, fatigue, and chest pain. It can take anywhere from a few hours to days after exposure for symptoms to appear. In the most serious of cases, it increases the risk of premature death.

Children, older adults, pregnant individuals, and those with heart or lung conditions or weakened immune systems are at higher risk of developing severe side effects. But Rubin says it’s possible for anyone, regardless of their health status, to have respiratory effects from exposure to wildfire smoke.

“Any level of air pollution, including from wildfires, can be dangerous for your health,” says Laura Corlin, an environmental epidemiologist at Tufts University School of Medicine. Just how dangerous depends on many factors, including your existing health status, your proximity to the fire, and the duration of exposure. “A good rule of thumb is that more exposure is worse,” she says.

The composition of a wildfire can also have an impact on human health. With the California fires engulfing homes and businesses, smoke in the region is likely carrying chemicals released from synthetic building materials that are more toxic than those emitted from burning vegetation.

People in Los Angeles County and elsewhere in the US can check airnow.gov to learn more about the current air quality in their area. As air quality can change quickly during the day, you should monitor readings regularly if there is a fire burning in your area, and try to limit your exposure to outdoor air when the quality is poor. The Watch Duty app is a good resource for checking if there are fires burning close to where you are.

How to Protect Yourself and Others

“The lungs purify the air that we breathe in and sends it to the heart, and the heart pumps it to the rest of the body,” says Shazia Jamil, a pulmonologist and professor of medicine at the Scripps Clinic and University of California, San Diego. Jamil helped develop a guide for the American Thoracic Society on how to stay healthy during wildfires.

She says if someone is short of breath, wheezing, or has an elevated respiratory rate from inhaling smoke, that makes the heart beat faster and can exacerbate preexisting heart problems. Even healthy people can experience chest pain and shortness of breath due to smoke inhalation.

It’s why health officials in Los Angeles County are urging everyone in areas with unhealthy air quality to stay indoors as much as possible. They should also limit exercise and other kinds of physical exertion, even when indoors. “When we do any strenuous physical activity, we are actually breathing deeper and we are breathing faster,” Jamil says. Coupled with air pollution, physical activity can lead to breathing problems.

When indoors, close windows and doors. Wet towels can be used to seal off any potential cracks. Avoid using air conditioners that only bring in outside air and don’t recirculate. Air purifiers that use a HEPA (high efficiency particulate air) filter can help reduce fine particles indoors. Fireplaces, candles, vacuums, gas stoves, and aerosols should be avoided, since they emit fine particles and can worsen indoor air quality.

If you must go outside, experts recommend wearing an N95 or P100 mask, which will block out 95 percent or more of very small particles. Bandanas and cloth masks are not effective against wildfire smoke. When traveling in a car, you can reduce smoke exposure by keeping the windows closed, turning on the air conditioner, and setting the air to recirculate.

While healthy people can have reactions to particulate matter, those with asthma and chronic obstructive pulmonary disease, or COPD, are most sensitive to it. Fine particulate matter can travel into the small airways of the lungs, exacerbating their condition. People with asthma and COPD should take their inhalers or other medications as prescribed.

Babies and children are at risk because their lungs are still developing. And as people age, their lung function naturally declines, so those 65 and older are also vulnerable. Wildfire smoke can aggravate heart problems as well.

Beware of the Lingering Threat

Even after the initial blaze has passed or been extinguished, wildfire smoke can continue to cause health issues. A 2023 study found that even after an initial cleaning by air purifiers, wildfire smoke can attach to home surfaces like carpet, drapes, and countertops, potentially prolonging exposure for people inside. Simple surface cleaning, like vacuuming, dusting, and mopping, can reduce exposure and limit risk.

In the coming days and weeks, more people outside the Los Angeles area may be at risk of smoke-related health issues. Wildlife smoke can travel hundreds of miles through the atmosphere. During the record-setting 2023 wildfires in Western Canada, some parts of the Eastern United States, including New York City and Philadelphia, were temporarily ensconced in smoke. “Smoke winds can travel over surprisingly long distances and time periods,” Corlin says.

And that smoke can cause health problems hundreds of miles from the fire itself. In a study published in December, researchers at the University of Maryland found that medical visits for heart and lung problems rose by nearly 20 percent during six days in June 2023, when smoke from the Western Canadian wildfires drifted across the country, leading to poor air quality days in Baltimore and the surrounding region.