Is swimming in chlorinated swimming pools dangerous to your health?

Swimming has long been advocated as an ideal exercise for people with asthma. Breathing moist air helps keep an asthmatic's lung secretions moist, and studies in the 1970's and 80's showed that swimmers with asthma had improvements in their asthma symptoms. But in the last few years, some researchers have suggested that swimming in chlorinated pools might be harmful, and could even cause asthma. In an April 2009 article in Environmental Health Perspectives, the authors conclude that we simply do not have enough information to conclude that there is any harm from chlorinated swimming pools.

Because chlorine can cause skin and respiratory irritation when people are exposed to it in high concentrations, researchers theorized that chronic, low grade exposure to chlorine in swimming pools may cause respiratory problems. So far, however, most of the studies done are far from conclusive. For instance, some studies asked families to answer questionnaires regarding symptoms and amount of swimming pool exposure over the previous decade or more. These surveys have suggested there may be an association between swimming pool exposure and asthma, but they are too inaccurate to demonstrate that chlorine exposure from swimming pools actually causes asthma. In fact, another study done in Spain showed that children who swam regularly actually had a decreased incidence of asthma, although they seemed to have a higher rate of eczema, a skin condition. Further, the Occupational Safety and Health Administration (OSHA) notes that studies of workers exposed to chlorine daily for 10 years found that with exposure of less than or equal to one part per million, none of the workers experienced lung damage. The chlorine concentration recommended for swimming pools is between 0.5 and 2 parts per million. There is inadequate research looking at whether the concentration of chlorine in the pools of the swimmers may be related to symptoms, or comparing different methods of disinfection.

Chlorine has been used to disinfect swimming pools for over 100 years. It not only keeps the pool water clear and clean, but it kills the pathogens bacteria and viruses that cause potentially serious illness, such as polio, pneumonia, gastroenteritis, parasite infections, ear infections, eye infections, skin infections and other problems from swimming in non-treated water. The chlorination of public swimming pools has eliminated the vast majority of these health risks. Chlorine's effectiveness varies depending on the pH of the water and the amount of other contaminants in the water. It breaks down fastest in sunlight, so the level in outdoor pools must be monitored closely. As it breaks down, it turns to a gas, which can cause lung irritation in poorly ventilated indoor pools.

Should you be concerned about allowing your children to swim in chlorinated pools? The evidence available now says no. The health benefits of swimming appear to far outweigh any theoretical risk from the chlorine itself. You should, however, monitor the chlorine concentration, especially for home pools that are used daily, and maintain it at the lower recommended range. There appears to be little risk for occasional, recreational swimmers. Also make sure that when using indoor pools, there is food air circulation.

Other pool sterilization products, such as bromine or ozone, either carry the same potential risks as chlorine (bromine) or have not been adequately studied to know what their risks might be. They tend to be much more expensive than chlorination, and at present, are without clear benefit to justify the added cost.

Learn more about this author, Harriet Squier.
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