Are Indoor Pools Bad for Your Lungs?

Are Indoor Pools Bad for Your Lungs?


swimmerGetty Images/Purestock

A 2006 study of youth athletes in Quebec City turned up the provocative finding that young, high-level swimmers wheezed and coughed far more often than young, indoor soccer players. The swimmers, mostly 8-12 years old, reported in a questionnaire that they frequently suffered from upper and lower respiratory symptoms, lung congestion, breathing difficulties, and sneezing. More than 15 percent had asthma. To ensure that these self-reported symptoms were accurate, the scientists monitored 72 of the young swimmers and 73 of the soccer players over the course of five practices. They found that the swimmers definitely struggled with more breathing problems than the soccer players. Notably, the young swimmers’ difficulties were closely correlated to the levels of chlorine and chlorine byproducts in their pools. More chemicals meant more symptoms.

Phys Ed

Is swimming good or bad for the lungs? The question has particular relevance now, with the swimming World Championships getting underway this week in Rome, and the summertime, lazing-around-the-swimming-pool season reaching its zenith. Many doctors consider swimming an ideal sport for people with breathing problems. “The pool environment is humid, and your oxygen delivery system improves when you’re lying down,” says Dr. Jim Miller, one of the team physicians for USA Swimming.

On the other hand, asthma and other severe breathing difficulties seem to be almost epidemic among competitive swimmers, with most of the problems developing after the athletes took up swimming, according to the latest research. In a study of 50 elite athletes published last year in the British Journal of Sports Medicine, almost all of the swimmers had inflamed lung tissue, with those who spent the most time at the pool showing the most changes. In another study, published earlier this year in the European Respiratory Journal, almost 70 percent of a group of 32 elite swimmers suffered from a condition known as airway hyper-responsiveness, in which the bronchial tubes twitch or spasm excessively in response to cold air and other stimuli. Airway hyper-responsiveness can be a precursor to asthma. Meanwhile, by some estimates, one-third of all elite swimmers have full-blown asthma, 80 percent of which began after they took up swimming. “The US National Team has a bunch of asthmatics on it,” says Miller.

Is chlorine to blame? The chemical disinfectant, source of the distinctive, pungent, swimming-pool smell, is lethal in large amounts. But it’s not just chlorine “that is the issue,” says Dr. Louis-Philippe Boulet, a professor of medicine at the Quebec Heart & Lung Institute, and the author of multiple studies of swimmers’ lungs. Instead, problems arise when chlorine mixes with proteins in the water, such as shredded skin or hair, creating chloramines. The more chlorine and the more protein you have in a pool the more chloramines. These toxic byproducts tend to settle just above the water’s surface — where swimmers breathe — and are inhaled deep into the lungs. “There are increasing numbers of studies that suggest that exposure to chloramines may have a major effect on bronchial health,” Boulet says.

Many of the affected swimmers have no idea that their lungs are unhealthy. Often, they have no symptoms or, as Boulet says, “they think that the symptoms”, such as coughing or tightness in the chest, “are a normal part of hard training.” Others realize that they have breathing problems when they try to exercise outside of the humid pool environment. In Boulet’s latest studies, elite swimmers with no symptoms of airway hyper-responsiveness in the pool were positive for the condition during testing on land.

Casual swimmers don’t seem to face much risk. “The evidence so far leads me to think that recreational swimming is not detrimental,” Boulet says —especially if you swim outdoors. Although one study from last year found that asthma was more common among 847 European schoolchildren who’d frequented outdoor pools, Miller says that, in his work, “we hardly ever see problems among the swimmers at outdoor pools.”

Anyone who trains several times a week or more at an indoor pool, however, might want to start “paying attention to chest health,” Miller says. If you often feel tightness or shortness of breath, in or out of the pool, “consider getting a pulmonary function test,” he says. This advice also holds true if you’re the parent of a young, competitive swimmer. In some studies, the youngest swimmers seemed to absorb the most chloramines. “If your child complains of a heavy chest or is often coughing, have him checked out,” Miller says. In addition, some emerging research suggests the possibility that babies and toddlers, with their rapidly developing lungs, shouldn’t be exposed to indoor swimming pools; in some small but intriguing studies toddlers who’d frequently been taken to indoor pools had lung damage “similar to that observed in current smokers,” a review by Boulet and others pointed out. But Boulet cautions that more testing is needed. In any case, if pulmonary testing shows airway hyper-responsiveness talk to your physician about treatments such as bronchial dilators, which helps to open the airway and “which are very effective for most swimmers” with breathing problems, Miller says. Though swimmers with existing allergies — who can have a more pronounced reaction to the chloramines — can be harder to treat, he adds.

You might also look for a different pool. “When some of our high-school swimmers are going on college recruiting trips, we tell them to follow one simple rule,” Miller says. “If you walk into the building and can find your way to the pool without directions, don’t go to that school. A smelly pool is, chemically, way out of balance.” If your favorite pool is easy to find, blind-folded, talk to the manager about re-calibrating the amount of chlorine being used or improving the air flow in the facility to circulate the air above the surface of the water.

In the meantime, if you sometimes wheeze, don’t panic. Active swimmers’ breathing problems “are probably not permanent,” Boulet says. In the largest study of its kind to date, the lungs of 26 elite swimmers from Finland were tested during and after their competitive careers. Twenty-three percent of them suffered from asthma while racing; only 4 percent still had the condition within five years after retirement.

Overall, researchers say, the benefits of swimming for exercise outweigh the risks. As the authors of the Quebec City study of youthful swim racers were careful to point out, only one of the 72 swimmers they studied smoked and none were obese, making them statistical anomalies among the young. “Breathing problems do sometimes develop,” Miller says. “But with rare exceptions, they can be controlled. Swimming remains, in general, very good for you.”


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