How Air Quality Affects Asthma—and What to Do About It

8 minute read

Alana Yañez’s severe asthma had been completely under control for years. But when the 2020 wildfires started pumping thick plumes of ugly black smoke into the southern California sky, the 41-year-old Los Angeles resident began to wheeze. 

She felt her chest tighten and then become painful. Yañez shut all the windows in her house, cranked the air conditioner, and turned on an air filter. But those measures barely made a dent in her symptoms.   

“I was sucking on my inhaler every couple of hours,” Yañez says, adding that no matter what medications she was given, the pain in her chest persisted.  

After several miserable days, Yañez remembered that she’d always breathed easier on the coast. When she checked local air quality maps, she saw that the air was far cleaner by the ocean. So she packed up her work and her little boy and headed for Redondo Beach.

“With every mile, my lungs felt better,” she says. “By the time I took the exit for the beach, I was able to breathe without pain.”

While dirty air—whether it’s due to diesel exhaust, traffic fumes, industrial pollution, or wildfires—can make breathing difficult for anyone, it hits people with severe asthma much harder, with some ending up in the emergency room or even hospitalized.

During the spring and summer of 2023, when Canadian wildfires were shooting thick clouds of smoke into the air, asthma-associated emergency room visits in the U.S. spiked 17% higher than what would normally be expected. 

The research linking air pollution exposure to asthma attacks “is very consistent,” says Dr. Akhgar Ghassabian, an associate professor of pediatrics and population health at the NYU Grossman School of Medicine. Even low levels of exposure can trigger an exacerbation, she says, and the most at-risk groups are children and seniors.

Read More: What to Know About the Latest Advances in Managing Severe Asthma

How does dirty air harm the respiratory system and exacerbate asthma?

Over the past few decades, volunteers, one at a time, have entered a small chamber in a lab at the University of North Carolina and either pedaled on a stationary bike or sat quietly while components of diesel exhaust or smoke from burning wood were pumped into the room.  

The volunteers had been carefully selected to avoid any severe reactions. They were all relatively young, under 45, and healthy overall, although some had mild asthma. After a few hours in the chamber, the study participants gave sputum samples, which helped researchers identify those who were sensitive to the fumes and exactly how their airways and lungs were being affected.

Early experiments by the researchers from UNC and the U.S. Environmental Protection Agency (EPA) looked at the impact of exposure to diesel exhaust components, which included fine particles (PM2.5), ozone, and other gases. In some volunteers, the fumes sparked increases in airway inflammation, says Dr. David Peden, senior associate dean of translational research and medical director of the Center for Environmental Medicine, Asthma and Lung Biology at the University of North Carolina School of Medicine.  

“Our studies are designed to get an idea of the underlying biology, and to use this information and these methods to identify particular interventions,” Peden says. Inhaling exhaust constituents sparked neutrophilic and eosinophilic inflammation. “The most important thing we find with most air pollution is that it irritates the airway epithelium.”

Most people will acutely experience some degree of airway inflammation when they encounter air pollution or wildfire smoke, Peden says. “For many, it’s simply an annoyance, and they may not worry about it,” he adds.

But for those with severe asthma, the impact can be much greater, Peden says. That’s especially true for children: Their respiratory rates tend to be higher than those of adults, so even a small amount of polluted air can make a big impact.

The center’s most recent research has focused on potential treatments for exposure to pollution and wildfire smoke in the volunteers who were found to be sensitive. It’s yielded promising results. For example, people who overproduce mucus in response to dirty air may be helped by inhaling hypertonic saline solution. “When they inhale the solution, it loosens up the mucus,” Peden explains. 

The research has also suggested a role for a certain type of vitamin D (gamma-tocopherol) that appears to calm the eosinophil response to pollution. But, Peden cautions, “this is a very early phase study. It’s not definitive.”

Ongoing research is examining the genetics that impact sensitivity to wildfire smoke and air pollution, as well as ways to protect people with respiratory diseases, such as studies to determine the efficacy of N95 masks.

Read More: An N95 Mask Is Your Best Outdoor Defense Against Wildfire Smoke

Dirty air’s impact on people with severe asthma

Exposure to any kind of dirty air can make asthma a lot worse, says Dr. Stokes Peebles, section chief for allergy and immunology at Vanderbilt University Medical Center. “It can lead to a feeling of tightness in the chest, coughing and shortness of breath,” he says. “The fine particulate matter, PM2.5, can get down into the very lowest parts of the airways.”

Those ultrafine particles can also get deep inside the lungs, says Dr. Barbara Mann, an associate professor of medicine in the division of pulmonary, critical care and sleep medicine at the Icahn School of Medicine and at Mount Sinai in New York City. “They can evade most of the body’s defenses and wreak havoc.”

Air pollution can cause two airway issues: constriction and inflammation. And it doesn’t stop there, Mann says. The tiniest particles can leach into the bloodstream and cause systemic inflammation. The more severe a person’s asthma is at baseline, the smaller the dose of polluted air it takes to kick off an exacerbation, and the worse those flare-ups might be.

Wildfire smoke: an urgent danger 

Wildfire smoke is an especially troublesome type of air pollution. It “dwarfs other kinds of air pollution," Mann says. “It’s a toxic mix of both organic and inorganic materials that have been burned.”

As Peden points out, wildfires can significantly raise the amount of fine particles in the atmosphere. “In 2018, when the Camp Fire was burning, the amount of fine particles in San Francisco was up three- to five-fold,” he says. 

Unlike industrial and traffic related air pollution, wildfire smoke is likely to also contain fumes from the burning of manmade items, such as houses and vehicles. That can be a nefarious combination.

Read More: What Wildfire Smoke Does to the Human Body

New asthma kicked off by air pollution

Along with exacerbating asthma, air pollution can spark new onset airway disease in those who are exposed, says Matt Perzanowski, an associate professor of environmental health sciences at the Columbia University Mailman School of Public Health. 

Moreover, studies done at Columbia have shown that when people are exposed to diesel smoke, they can develop allergies to proteins they weren’t previously allergic to. “We study children in the South Bronx,” Perzanowski says. “When they’re exposed to cockroaches and diesel exhaust, they are more likely to develop an allergy to cockroaches.”

Perzanowski recommends that parents limit their children’s exposure to pollution, especially wildfire smoke. 

How to protect yourself

If you have asthma, the most important step you can take to avoid an exacerbation due to wildfire smoke and pollution is to check local air quality reports daily. “There’s good data available in real time,” Ghassabian says., for example, is a terrific resource.

On bad air quality days, take precautions to protect yourself from exposure to the dirty air. These are doctors' favorite strategies:

  • Check ozone levels online and stay inside if they’re high. Close all the windows and block other spots where outside air could seep in.
  • Invest in a HEPA filter. According to the EPA, these can remove at least 99.97% of dust, pollen, mold, bacteria, and other airborne particles.
  • If the air quality index goes over 100, don’t exercise outside. If it’s over 150, don’t exercise at all. 
  • When the index is lower than 100 but still relatively high, you can exercise outside, but only in the early morning or evening.
  • Switch the setting on your home and car air conditioners to recycle, so you’re not bringing in outside air.
  • Use an N95 mask when you go outside.
  • When wildfire smoke is at high levels, consider temporarily relocating to a spot where air quality is better.

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