Step aside tobacco, chlorine could be man's next great carcinogen.

Med Hypotheses. 2009 Jun;72(6):759. doi: 10.1016/j.mehy.2009.01.010. Epub 2009 Mar 12. Step aside tobacco, chlorine could be man's next great carcinogen. Katona S. Step aside tobacco, chlorine could be manﾒs next great carcinogen. Is it a coincidence that the Western world disinfects its drinking water with chlorine, and a high proportion of the population develop bowel cancer and inflammatory bowel disease ? Perhaps we should start to question the health risks due to a chemical capable of killing most organisms in our water supply. Consider what many carcinogens have in common, namely that they are toxic to cells. Any chemical which damages cells makes them divide more often. During each cell division there is a chance a mistake may result in a cancer cell being formed. Any gas is most soluble in a cold liquid. When chlorinated water is ingested, the water warms up, and chlorine will come out of the water, and be trapped in the bowel. Most gas ends up in the large intestine which is most affected by bowel cancel and inflammatory bowel disease. Patients who have a long bowel transmit time, a known association with bowel cancer, would be expected to have chlorine trapped in the bowel for the longest period of time. The caecum and splenic flexure are sites where gas might be expected to collect, and are also common places to find bowel cancer. Persistent exposure to chlorine could be expected to kill mucosal cells, and both initiate, and perpetuate the kind of inflammation seen in inflammatory bowel disease, whose presence is already known to increase the risk of bowel cancer. A case control study in Ontario compared 767 patients with colon cancer, and 661 with rectal cancer, with 1545 controls with exposure information to chlorination bi-products (trihalomethanes or THMs) for at least 30 years. Males exposed to the highest levels of THMs had double the risk of colon cancer [1], although no association was found in a study in Iowa [2]. Interestingly there was no increased risk of rectal cancer in the Ontario study [1] but those with a low fibre intake had over twice the relative risk in Iowa [2]. A meta-analysis concluded there was a positive association between chlorination by-products in drinking water and bladder and rectal cancer in humans [3]. There may be health risks caused by consumption of chlorinated water, such as bladder cancer [4]. More studies are needed, but in the meantime the public should be warned to boil tap water, or let it stand overnight before consumption, to allow chlorine to evaporate. Even these measures may not remove THMs sufficiently. Cutaneous, mucosal and inhalation exposure may also be sufficient to cause a significant risk to health [5-6]. It took decades to establish, and publicise the link between tobacco and cancer. Lets not make the same mistake twice. [1] Case-control study of colon and rectal cancers and chlorination by-products in treated water. Cancer Epidemiol Biomarkers Prev. 2000 Aug;9(8):813-8. King WD, Marrett LD, Woolcott CG. [2] Drinking water source and chlorination byproducts. II. Risk of colon and rectal cancers. Epidemiology. 1998 Jan;9(1):29-35. Hildesheim ME, Cantor KP, Lynch CF, Dosemeci M, Lubin J, Alavanja M, Craun G. [3] Chlorination, chlorination by-products, and cancer: a meta-analysis. Am J Public Health. 1992 Jul;82(7):955-63. Morris RD, Audet AM, Angelillo IF, Chalmers TC, Mosteller F. [4] Drinking water source and chlorination byproducts. I. Risk of bladder cancer. Epidemiology. 1998 Jan;9(1):21-8. Cantor KP, Lynch CF, Hildesheim ME, Dosemeci M, Lubin J, Alavanja M, Craun G. [5] Risk from exposure to trihalomethanes during shower: Probabilistic assessment and control. Sci Total Environ. 2009 Jan 6. [Epub ahead of print] Chowdhury S, Champagne P. [6] Cancer risk assessment from exposure to trihalomethanes in tap water and swimming pool water. J Environ Sci (China). 2008;20(3):372-8. Panyakapo M, Soontornchai S, Paopuree P.