Swimming in Chlorinated Pools May Increase Cancer Risk

Chlorination is the most commonly used method of disinfecting the water in swimming pools. Levels of disinfection by-products (DBPs) in swimming pool water are not necessarily higher than those in drinking water, however swimming in an indoor pool is known to lead to a greater uptake of compounds such as trihalomethanes (THMs), which are inhaled and absorbed by the skin. Thus, there has been concern that swimming in an indoor chlorinated pool could increase a person’s risk of developing cancer. Researchers collected blood, urine, and exhaled air samples from 49 non-smoking adults before and after they swam for 40 minutes in an indoor chlorinated pool. Evidence of genotoxic (DNA damaging) effects was observed in all participants – micronuclei in blood lymphocytes, and urine mutagenicity (Ames assay). Results also showed that the total concentration of the four most common THMs in exhaled breath was seven times higher after swimming. The authors concluded: “Our findings support potential genotoxic effects of exposure to DBPs from swimming pools. The positive health effects gained by swimming could be increased by reducing the potential health risks of pool water.”