Chlorine is added as part of the drinking water treatment process, as a disinfectant to reduce or eliminate microorganisms. Drinking water supplies have been greatly improved by the addition of chlorine.
Disinfecting our drinking water ensures it is free of bacteria and viruses that can cause serious and life-threatening diseases, such as cholera and typhoid fever. Chlorine remains the most commonly used drinking water disinfectant, and the disinfectant for which we have the most scientific information.
Symptom: “My water taste like I’m drinking from a swimming pool”
Along with a taste and odor that many find offensive, chlorine also reacts with organic matter in water. This chemical reaction forms a group of chemicals known as chlorination by-products. The most common of these by-products are trihalomethanes (THMs). The amount of THMs found in drinking water depends on a number of factors, including the season and the source of the water.
Several studies have found a link between long-term exposure to high levels of chlorination by-products and a higher risk of human cancer. For instance, a recent study showed an increased risk of bladder and possibly colon cancer in people who drank chlorinated water for 35 years or more.
High levels of THMs may also have an effect on pregnancy. A California study found that pregnant women who drank large amounts of tap water with high THMs had an increased risk of miscarriage. These studies do not prove that there is a link between THMs and cancer or miscarriage. However, they do show the need for further research in this area to confirm potential health effects.