This week, wildfire smoke from Canada and a plume of desert dust are affecting air quality levels across many parts of the United States. When the air is smoky, it’s important to consider whether it’s safe to exercise outdoors — and how to protect yourself if you choose to head out.
There is very little research on the health effects of short-term exposure to wildfire smoke, including during exercise. So, when estimating what the smoke does to the body, there aren’t always clear answers, said Dr. Michael Koehle, a kinesiologist at the University of British Columbia who studies the interaction between environmental pollution and exercise.
Still, based on what we know about the kinds of particles found in wildfire smoke and their potential health effects, experts say it’s important to monitor air quality and, when conditions are bad, to avoid outdoor workouts or keep them short.
Individuals who may be more sensitive to the effects of smoke should be especially careful — including children, older adults and those who are pregnant or have underlying lung or cardiovascular conditions such as asthma, chronic obstructive pulmonary disease or heart disease, said Dr. Stephanie Christenson, a pulmonologist at the University of California, San Francisco School of Medicine.
As the climate changes, wildfire season is getting longer and affecting more regions of the United States. Here’s what you need to know to stay safe.
What wildfire smoke does to the body
Wildfire smoke is a mixture of various kinds of particles and gases — including trace minerals, carbon dioxide, carbon monoxide, hydrocarbons and other organic chemicals — that are released into the air as a fire burns. It contains “really, really small particles that can lodge deeply into your lungs,” Dr. Christenson said. These particles, some of which have a diameter 30 times smaller than that of a single human hair, can get into the tiny air sacs known as alveoli, and affect how well they function, she explained. From there, they can also enter the bloodstream and cause harm elsewhere in the body.
People who exercise in smoky conditions can have different reactions. Some may experience coughing, shortness of breath or chest tightening, said Dr. Gillian Wooldridge, a sports medicine physician at Houston Methodist Hospital. Individuals with lung-related conditions such as asthma and C.O.P.D. may experience a worsening of their symptoms, she added.
It’s also important to keep in mind that wildfire smoke can cause harm even if you don’t notice any immediate effects, Dr. Koehle said. “I don’t want people getting the message that because you feel fine, pollution is not bad for you, don’t worry about it,” Dr. Koehle said.
For instance, research has found that chronic exposure to diesel exhaust, a pollutant similar to wildfire smoke, harms blood vessels in ways that could increase the risk of heart attacks and strokes. Long-term exposure to pollution like wildfire smoke has also been linked to an increased risk for C.O.P.D., lung cancer, type 2 diabetes and dementia, Dr. Koehle said.
These issues typically arise after years of smoke exposure. If you go on a bike ride or two in hazy weather, you’re likely to only experience short-term symptoms such as coughing, if you experience any symptoms at all. “Every once in a while is probably not going to be a big deal,” Dr. Wooldridge said, though it’s unclear exactly how much smoke exposure might cause long-term problems. It’s wise to take precautions, especially because wildfire smoke exposure is becoming more and more common.
How to interpret air quality levels
If you’re considering exercising outside, check the air quality levels in your area. Because the particles in wildfire smoke are so tiny, they aren’t always visible, Dr. Christenson said — don’t just go by what you see.
In the United States, the Environmental Protection Agency rates air quality according to the Air Quality Index (A.Q.I.), ranging from 0 to 500. The E.P.A. considers an A.Q.I. of 151 or above unhealthy, but sensitive individuals may experience health effects at lower levels.
Dr. Koehle recommends the Plume Labs app, which includes three-day air quality forecasts as well as exercise-specific recommendations, such as whether it’s safe to run outdoors or go on a bike ride in your area. The AirVisual app also offers air quality forecasting, along with AirNow.gov, he said.
When air quality recommendations advise you to avoid outdoor physical activity, it’s best to close your windows and exercise indoors, Dr. Christenson said — ideally in a room with an air purifier containing a HEPA filter. You can also make your own air purifier with a HEPA filter and a standard box fan, Dr. Koehle said.
Staying safe outdoors
If you do exercise outside when the air quality is bad, experts advised against masking. The only face masks that effectively reduce exposure to the small particles in wildfire smoke are well-fitting respirators such as N95s, which are extremely difficult to exercise in. “It can be very, very uncomfortable,” Dr. Wooldridge said.
Your potential risk also depends on the form of exercise you choose. Research suggests that high-intensity but brief outdoor workouts are safer than low-intensity, long ones. “The worst thing is the six-hour hike,” Dr. Koehle said
In a 30-minute HIIT workout, by comparison, “you may be breathing twice as hard, but your dose is still a sixth of that hike,” Dr. Koehle said. “It’s super counterintuitive.”
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