Is it safe and sound to exercise outdoors when there is a lot of smoke in the air from forest fires?

This week, smoke from wildfires raging across the western United States and Canada is affecting air quality as far north as Fresh England. With the air smoky, it’s vital to consider whether it’s safe and sound to exercise outside — and how to protect yourself if you do decide to venture out.

There is very little research on the health effects of short-term exposure to wildfire smoke, including during exercise. So when it comes to estimating what smoke does to the body, there are not 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, given what we know about the types of particles found in wildfire smoke and their potential health impacts, experts say it’s vital to monitor air quality and, when conditions are indigent, avoid outdoor exercise or limit it to low periods.

People who may be more sensitive to smoke exposure should exercise extra caution — including children, older adults, and pregnant women or people with lung or circulatory system 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 climate changes, the forest fire season it’s getting longer and is affecting more regions of the United States. Here’s what you need to know to stay safe and sound.

How does forest fire smoke affect the body?

Wildfire smoke is a mix of different types of particles and gases — including trace elements, carbon dioxide, carbon monoxide, hydrocarbons and other organic chemicals — that are released into the air during a fire. It contains “really, really tiny particles that can get deep into the lungs,” Dr. Christenson said. These particles, some of which are about 100 mm in diameter 30 times smaller than a single human hair, can get into small air sacs in the lungs known as alveoli and affect how they function, she explained. From there, they can also enter the bloodstream and cause damage to other parts of the body.

People who exercise in smoky conditions may have varying reactions. Some may experience coughing, shortness of breath or chest tightness, said Dr. Gillian Wooldridge, a sports medicine physician at Houston Methodist Hospital. People with lung conditions such as asthma and COPD may experience worsening symptoms, she added.

It’s also vital to remember that wildfire smoke can cause harm, even if you don’t notice any immediate effects, Dr. Koehle said. “I don’t want people to get the message that because you feel fine, pollution isn’t bad for you, don’t worry about it,” Dr. Koehle said.

For example, studies have shown that chronic exposure to diesel exhaust, a pollutant similar to wildfire smoke, damages blood vessels in a way that can increase the risk heart attacks and strokes. Long-term exposure to pollutants such as smoke from forest fires is also associated with an increased risk COPD., lung cancer, Type 2 diabetes AND dementiaDr. Koehle said.

These problems usually develop after years of exposure to smoke. If you go for a bike ride or two in foggy weather, you’ll likely experience only short-term symptoms, such as a cough, if any at all. “It’s probably not a large problem every now and then,” Dr. Wooldridge said, although it’s unclear how much smoke exposure could cause long-term problems. It’s wise to take precautions, especially as exposure to wildfire smoke becomes more common.

How to interpret air quality levels

If you’re considering exercising outside, check the air quality in your area. Because the particles in wildfire smoke are so tiny, they’re not always noticeable, Dr. Christenson said — don’t just go by what you see.

In the United States, the Environmental Protection Agency rates air quality according to Air quality index (AQI) ranging from 0 to 500. The Environmental Protection Agency (EPA) considers an AQI of 151 or higher to be unhealthy, however sensitive individuals may experience adverse health effects at lower levels.

Dr. Koehle recommends Plume Labs Appwhich includes three-day air quality forecasts, as well as recommendations for specific exercises, such as whether it is safe and sound to run outside or cycle in your area. The AirVisual app also offers air quality forecasts, along with AirNow.gov, he said.

When air quality guidelines recommend avoiding outdoor exercise, it’s best to close your windows and exercise indoors, Dr. Christenson said — ideally in a room with an air purifier that includes a HEPA filter. You can also make your own air purifier with a HEPA filter and a standard box fan, Dr. Koehle said.

Stay safe and sound outdoors

If you’re exercising outside when the air quality is indigent, experts advise against wearing a mask. The only face masks that are effective at reducing exposure to the small particles in wildfire smoke are tight-fitting respirators, such as N95s, which are notoriously hard to exercise in. “They can be very, very uncomfortable,” Dr. Wooldridge said.

Your potential risk also depends on the form of exercise you choose. Research suggests that intense but low outdoor workouts are safer than long but low-intensity ones. “The worst is a six-hour hike,” Dr. Koehle said

In a 30-minute HIIT workout, by comparison, “you can breathe twice as challenging, but your dose is still a sixth of that augment,” Dr. Koehle said. “That’s super counterintuitive.”