Chlorine is the chemical that effectively kills water-borne critters that can cause typhoid, cholera and dysentery. Chlorine reacts with other substances in water to form chloroform, carbon tetrachloride and other cancer-causing compounds. There are several bugs that are resistant to chlorine such as the one that causes Legionnaire's disease. Most every outbreak since 1982 has been linked back to a water system. Flouride There has been great controversy as far as whether fluoride should be added to drinking water.
Proponents say that fluoride helps build strong bones and teeth.
Many ailments have been linked to fluoride in the water such as Mottled teeth, cancer and even Down's Syndrome. Most of the lead problems in water come from the pipes, this is especially true in older cities and homes. Lead has been shown to negatively affect the brain and other systems of the body. Other Things to Complain About Industrial and agricultural pollutants are now showing up in water supplies. Nitrate contamination has required the closing of many wells.