The Dirty Secret of Outdoor Exercise
Why Exercisers Are More Vulnerable
Ironically, on high-pollution days it is exercisers who are especially vulnerable, Thurston says. "When we work out, we breathe more air in and draw deeper breaths into the lungs," he explains. Because of this, more pollutants enter the body. Additionally, when we work out, particularly at a high intensity, we tend to breathe through the mouth. "This means you lose your body's first filters, like nasal hairs and the upper respiratory tract, which keep the larger particles from entering the body," says C. Arden Pope III, PhD, an air pollution epidemiologist at Brigham Young University in Provo, Utah. "The combination of breathing more and having the particles penetrate deeper into the lungs can irritate and inflame them." Even a relatively small amount of pollutants inhaled over extended periods during exercise may cause lung damage. Joggers who ran for 30 minutes alongside a busy New York City road had blood toxin levels similar to those found in regular smokers, a study published in The Physician and Sportsmedicine found.
"For the healthy jogger or biker, unless the pollution level is really high, she probably won't even notice it," Pope says. "But prolonged exposure, day after day, year after year, will ultimately take its toll." These days most people feel the consequences when pollution climbs to 151 or more on the Air Quality Index, a scale devised by the Environmental Protection Agency to gauge air quality on any given day. "At that level, pollutants begin to irritate your throat, get into your lungs, and cause inflammation and shortness of breath," Greenbaum says.
Even the most experienced exerciser struggles on those days. Brenda St. Hilaire, 41, a Rhode Island nutritionist and lifelong exerciser, used to spend her lunch hour jogging through Providence. She recently changed to power walking because the filth coughed up by buses and the thousands of diesel trucks that cut through the city on nearby I-95 was simply too much for her lungs to handle. "On ozone-alert days, I almost felt asthmatic when I ran or biked," Brenda says. "I had a hard time with deep breaths and could feel it coming on later in the evening, too. Even when I'm walking, I still feel asthmatic because I'm breathing the poor air, but at least I'm not placing the demands of running on my body."
Instead of altering their outdoor routines, others, like 24-year-old Ashley Thomure, respond to truck fumes by holding their breath. "I know I'm supposed to inhale deeply when I run, but the exhaust from vehicles is unbearable," the nursing student in Saint Charles, Missouri, says. Unfortunately, her breath-holding habit is doing more damage than good: Muscles need that oxygen to function.
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