Do pools expose swimmers to potentially harmful chemicals?

Swimmers have detectable levels of a potentially dangerous chlorine by-product called haloacetic acids (HAAs) in their urine within 30 minutes of a swim, a study shows.

The Environmental Protection Agency limits HAA levels in drinking water because high amounts may be linked to birth defects and cancer. Chlorine is used in drinking water and swimming pool water to kill harmful bacteria. By-products such as HAA occur when disinfectants such as chlorine react with impurities in the water.

The new study is published in Environmental Science & Technology.

Researchers tested the urine of 49 volunteers who swam in or worked around an indoor and outdoor pool. Study volunteers included adults and children.

The researchers found that HAAs appeared in the urine 20 to 30 minutes after exposure and were eliminated from the body within three hours.

Swallowing pool water

More than 90% of the HAA exposures likely occurred as a result of swallowing pool water; the remaining were due to inhalation or were absorbed through the skin, the study showed.

Children were more likely than adults to have a high concentration of HAAs after swimming. And swimmers accumulated HAAs almost four times as fast as pool workers. Concentrations of HAAs were higher in outdoor pools compared with indoor pools, the study showed.

Concentration of these by-products in swimming pools may be higher than in drinking water because pools use a water recirculation system for long periods to enhance the chlorination of the water, the researchers write.

The implications of the new findings for the health of swimmers are unclear, as this research is in its infancy. "There is little data about HAAs in swimming pools since they are still not regulated in many parts of the world," the researchers conclude.

Proper pool maintenance

"Chlorine disinfects swimming pool water," says Mary Ostrowski, director of chlorine issues for the American Chemistry Council in Washington, D.C. Well-managed pools should have concentrations that are less than what is found in drinking water, she says. "In a properly-maintained pool, any risk is likely to be very small."

Swimmers also can play a role in reducing their exposure to HAAs, she says. "Swimmers should not ingest pool water and should be taught to keep their mouth closed in the pool."

Test strips are commercially available that can measure chlorine and pH or acidity levels in pools. Pool managers should be informed if any of the readings do not fall within the acceptable range, she says.

Andy Igrejas, national campaign director of Safer Chemicals, Healthy Families in Washington, D.C., says that this issue has been around for a while. "We have drinking water and air regulations regarding the use of chemicals, but there is a big gap with what is happening with chemicals in general when they are used the way they are supposed to be used."

By Denise Mann

Reviewed by Laura J. Martin, MD