researchers have found an increased risk of bladder cancer due to exposure to chlorinated water through drinking, swimming and bathing. The study was published online in the January 15, 2006, issue of American Journal of Epidemiology. The study found that exposure also occurs through inhalation and dermal absorption of trihalomethanes (thms) during such activities. thms are substances formed when natural organic material, such as the decaying vegetation commonly found in lakes and reservoirs, reacts with chlorine used to treat water. The most common thm is chloroform--usually comprising more than 90 per cent of the total thms.
The study, conducted in Spain between 1998 and 2001, shows a doubling of the risk of bladder cancer at thm levels of 50 micro grams per liter--well below the levels found in industrialised countries. The standards set by the us Environmental Protection Agency are 80 micro grams per liter. According to scientist Neeta P Thacker, "the Bureau of Indian Standards has not set any norms for thms yet. It is in the process of doing so."
Discovery of disinfection byproducts during the 1970s led to concerns and then stimulated investigations on their chemical and biological properties. A drinking water disinfection by-product is formed when the chemical used for disinfecting the drinking water reacts with natural organic matter and/or bromide/iodide in the source water.Making water fit for human consumption then becomes a balancing act between biological and chemical contamination: disinfection reduces the former but increases chemical contamination. And the authors say this may lead to long-term illnesses like cancers.
Chlorine has been used to disinfect water for over a century. It has properties to kill bacteria and viruses present in water. Its prime advantage is that it continues to combat pathogens over a sustained period of time.
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