Fitness benefits tempered by pool cleaning chemicals?
Kogevinas, M, CM Villanueva, L Font-Ribera, D Liviac, M Bustamente, F Espinoza, MJ Nieuwenhuijsen, A Espinosa, P Fernandez, DM DeMarini, JO Grimalt, T Grummt and R Marcos. Genotoxic effects in swimmers exposed to disinfection by-products in indoor swimming pools. Environmental Health Perspectives http://dx/doi.org/10.1289/ehp.1001959.
Swimmers exposed to chemical by-products of chlorine used to disinfect indoor swimming pools experienced increased cell damage associated with a higher risk of cancer, according to a study authored by a team of researchers in Spain.
Prior laboratory cell studies and animal studies report similar findings, but this is the first one to look experimentally at how exposure to these by-products through swimming may be detrimental.
Although little is known about how they may affect swimmers' long-term health in particular, some of the by-products – including the most common ones found in the study, the trihalomethanes – are found at similar levels in drinking water where they have been associated with increased risk of bladder cancer. Whether exposure through swimming might contribute to similar cancer risks is unknown thus far.
People who use the pools may be at risk simply because they could inhale the chemicals, swallow them or absorb them through the skin, thus increasing exposure and body levels of the toxic chlorine by-products. Once in the body they may damage cell genetic material and increase the risk of certain cancers. The exposures could negate the positive health benefits of increased exercise and aerobic workouts swimming offers, the authors suggest.
Chlorine is widely used as a disinfectant in swimming pools to protect swimmers from harmful bacteria and other microbes. When chlorine mixes with dirt and other contaminants in the water, hundreds of different by-products may form.
Researchers recruited 50 non-smoking adults and asked them to swim for 40 minutes in an indoor pool in Barcelona, Spain, during four months in the summer and fall of 2007. They gathered personal information via a questionnaire and recorded time in the water and distance swum. Air, water and physical markers – exhaled breath, urine and blood – were sampled before and after the test and analyzed for chemical byproducts. They also measured several well-established indicators of DNA damage and increased cancer risk in cells found in blood and urine. Personal, social and other factors were statistically controlled in the study.
The researchers found that levels of trihalomethanes in exhaled air were seven times higher after a 40-minute swim than before. This indicates similar levels would be found in the bloodstream. Levels of some trihalomethanes – especially those with bromine – were associated with cell signs of increased cancer risk.
These results suggest that the current practice of using chlorine to minimize microbial risk may have inadvertent negative health consequences for people who use pools. More research is needed to fully understand if the cell changes found in the swimmers are linked to more serious health concerns, such as cancer.
