Indoor pools are pretty popular this time of year, a good way to get some exercise without having to jog in slushy weather or bike through puddles or over ice and snow. Plenty of people, however, are concerned about chlorine levels in public pools and the possible health risks involved in soaking in it.
Chlorine has allegedly been linked to all kinds of diseases, including cancer (especially breast) and asthma, even though we gulp it down in our drinking water and use it to clean our houses.
Is it really as scary as some make it out to be? And what can we do to protect ourselves?
What the experts say
"The risks of microbial disease are much greater than the risks associated with chemical exposures. A couple of studies have suggested that indoor pools might have some connection with respiratory health, but there has never been a demonstrated connection with asthma. [The culprit] isn't chlorine itself but the chloramines caused by chlorine combining with contaminants that swimmers bring into the pool by not showering. That's what gives you the chemical smell you might associate with the pool. The way to control chloramine compounds is to add additional chlorine. Swimmers really need to practise proper hygiene, and the people maintaining the pool have to keep the right PH level and have proper ventilation."
JEFF SLOAN , director of sustainability programs, Chlorine Chemistry Council, Arlington, Virginia
"Chlorination of water has protected human health for the best part of a century. Some toxicology and epidemiology studies infer a linkage between chlorination and chloramines or THMs [compounds formed when chlorine is combined with organic elements] and diseases such as bladder cancer. But Health Canada recommends chlorination because without it we will end up with another situation like Walkerton. There are other methods, such as ozone, UV and membrane filtration, but chlorination is the only technique available at present. If people have concerns about water, carbon filtration can remove chlorinated organics."
ALLAN JONES , executive director, Canadian Chlorine Chemistry Council, Toronto
"Chlorine itself is non-carcinogenic. However, chlorine as a disinfectant in drinking water can cause cancer. In general, the concentration of THMs in drinking water is directly related to the concentration of synthetic organic industrial pollutants. In addition, there are natural organics in water from things like decaying vegetable matter. It's unarguable that chlorination of water contaminated with organic materials is a source of avoidable carcinogenic exposures. The [U.S.] National Toxicology Program recognized that there is overwhelming evidence that THMs produce cancers in a range of animal systems. We found increased levels of a variety of chlorinated carcinogens in the breast."
SAMUAL EPSTEIN , professor emeritus of environmental and occupational medicine, University of Illinois at Chicago School of Public Health, chair, the Cancer Prevention Coalition, Chicago
"THMs can be absorbed through the skin or inhaled when they evaporate into the air. If you're swimming for half an hour, you're breathing it and absorbing it though your entire body. It can be carcinogenic. I've seen research involving bladder and pancreatic cancer. It can also affect the liver, kidneys and nervous system. I advise people to weigh the risks and benefits of swimming. I do caution pregnant women, though, because the by-products can pass through the placental barrier. I think the benefits may outweigh the risks, but I definitely would limit it. Cleaning products are a no-brainer because there are so many safe, simple alternatives. You can also limit your shower and bath time and make sure you're ventilating the bathroom and filtering your tap water."
KAREN THOMPSON , naturopath, Toronto
"[Alternatives for pools might include] silver-copper ion generators. Copper ions act as an algaecide and silver ions act as a bactericide. They're really not a stand-alone system; generators are typically used in conjunction with low levels of chlorine, bromine or oxidizing agents such as ozone. Another choice is ultraviolet, which will eliminate 99.9 per cent of micro-organisms; but again you must use a sanitizer such as chlorine. If you use a salt chlorine generator, the water will be free of chloramines. Bromine is an alternative to chlorine in an indoor pool. Outside it is easily destroyed by sunlight. If you want to eliminate chlorine it's going to take more than one product."
ALAN SCHUSTER , chemist, pool consultant, Boca Raton, Florida