These concerns about cancer risks associated with chemical contamination from chlorination by-products have resulted in numerous epidemiological studies. These studies generally support the notion that by-products of chlorination are associated with increased cancer risks.
Chlorine is used to combat microbial contamination, but it can react with organic matter in the water and form dangerous, carcinogenic Trihalomethanes. According to Dr. Joseph M. Price, MD, in Moseby’s Medical Dictionary, “Chlorine is the greatest crippler and killer of modern times. It is an insidious poison”.
In a 1992 study that made front-page headlines, and was reported on in the July issue of the American Journal of Public Health researchers at the Medical College of Wisconsin in Milwaukee found that people who regularly drink tap water containing high levels of chlorine by-products have a greater risk of developing bladder and rectal cancers than people who drink unchlorinated water. The study estimates that about 9 percent of all bladder cancer and 18 percent of all rectal cancer cases are associated with long-term consumption of these by-products. This amounts to over 20,000 new cases each year.