How to Work Out When Air Pollution is Bad

Kelly O'Mara
by Kelly O'Mara
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How to Work Out When Air Pollution is Bad

When we go for a run or a bike ride outside, it’s largely because we want to stay healthy and enjoy the outdoors. Unfortunately, if the air is filled with smoke from wildfires or pollution, it makes both those things harder to achieve.

A growing body of research has found the health costs associated with breathing in bad air can counteract the benefits of exercising. With large wildfires blowing smoke across many parts of the country, there’s been an increased awareness of the short-term costs of breathing in that smoke. It can trigger acute problems, like asthma, bronchitis or even heart attacks. But there’s also danger in the long run — and not just from smoke, but also from breathing in diesel exhaust or pollution. Breathing in air pollution for more than a few weeks can lead to strokes, chronic lung problems, lung cancer and even early death.

Obviously, any benefits from exercising in those conditions becomes moot. “At some point, the damage exceeds the benefit,” said George Thurston, a professor of environmental medicine at NYU who has studied the health effects of air quality.

Where exactly that point occurs is “a sliding scale,” he said, depending on your health and any existing conditions. It’s also true that “not all particles are the same”— some air pollution is worse for you than other kinds.


Sure, the air is smoky or hazy or dirty, but you’re thinking, ‘It can’t be that bad, right?’ Wrong.

Ozone is an irritant and affects your lungs more acutely, while particulate matter has a bigger impact on your heart, said Thurston. Particulate matter (PM) less than 10 microns wide travels deep into your lungs and even into your bloodstream. PM 2.5 means it’s less than 2.5 microns wide.

At first, it simply triggers inflammatory reactions in your lungs or heart, but over time it can cause long-term problems. Since the federal government began tracking the amount of particulate matter and regulating air quality, the mortality rate as a result of air pollution has decreased.

Even if the air doesn’t look bad, that doesn’t mean you aren’t breathing in bad particles. (And if looks bad, then you are almost definitely breathing stuff in.) And when you exercise, you’re breathing in large amounts of air.

But here’s the good news: Unless you live in a highly polluted city, the benefits of exercising still outweigh not exercising. Just take the right precautions.

Here’s what you can do to make sure you stay healthy while trying to get healthy:



The first step to fixing any problem is recognizing you have a problem.

Check the EPA’s AirNow website to see what the air pollution levels are in your area. When you type in your zip code, the site will tell you the most recent measured ozone and particles (PM 2.5) levels. It also gives a general number for the air quality index (AQI). Anything over 100 is considered unhealthy for sensitive groups and over 150 is very unhealthy. These numbers are all color-coded, too.

“Red means stop,” said Thurston.

If that doesn’t go into enough granular detail for you, there are personal air-quality monitors you can purchase, and some of the companies selling them also provide their own public detailed air quality maps.



When the AQI or air pollution is high, it’s worth heading indoors for your workout. It’s also good to plan ahead — planning to hit the outdoor trails when the air will be at its best.

In the summer, said Thurston, the air pollution levels are the highest later in the day — so you should do your workouts in the morning. In the winter, the pollution is highest in the morning because it builds up overnight — so work out later in the day.

It’s also important to avoid busy traffic routes and rush hour times if possible. While smoke, sand and wind-blown particles are bad, “fossil fuel particles are much worse,” said Thurston. Even just running through a park or less busy road can be better. And tall buildings that trap the car exhaust are worse. One study tracked walkers in London — some of whom were picked to walk on busy, trafficked roads and some of whom did their regular walks through Hyde Park. Walking on the heavily trafficked road counteracted any cardiac or respiratory benefits from the exercise.



If you head outside, know a simple surgical mask is not going to keep out pollution particles. There are, however, higher-rated masks that filter out various amounts of pollutants. An N-95 mask filters out about 95% of particulate, or PM 2.5 matter, and an N-99 mask filters out 99%. However, neither filter oil-based pollutants. A P-95 mask can filter out oil-based pollutants and 95% of particulate matter. But all these higher-end masks make it much harder to breathe, which can make exercise exceptionally difficult. (These are commonly used by construction workers or others who work with high levels of dust.)

There are also special portable HEPA (High-Efficiency Particulate Air) filters that you can carry on your waist and can breathe in through a connected mask. These can be slightly expensive, however, and difficult to exercise in.

If you go outside in less-than-ideal conditions, then there is also some evidence it helps to shower the particles off when you return home — rinse out your nose and gargle. This isn’t going to stop you from having breathed them in when you’re running, however.



It doesn’t do a lot of good to stay inside (and exercise inside), if the polluted air is just following you in through open windows and air systems.

If you buy a filter for inside your house, then you want a HEPA-level filter. Be sure to replace the filters on your air conditioner or heating systems (depending on the weather). You also want to reduce amount of activities inside that can increase indoor air pollution — like burning candles.

The same is true if you decide to head to the gym instead of outside: On one hand, there are people trekking in and out and opening doors; on the other hand, a commercial gym is likely to have heavier duty air filtration systems.

About the Author

Kelly O'Mara
Kelly O'Mara
Kelly is a professional triathlete and reporter outside San Francisco, where she is an on-call producer for the local NPR station. Her works appears regularly in espnW, Competitor, Triathlete and California Magazine. She also co-hosts the podcast, Locker Room Talk, for WiSP: The Global Women’s Sports Network. And she trains. A lot.


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