To understand the effect chlorine has on our drinking water, we first have to understand the element itself. Chlorine is necessary to all forms of life and found abundantly in nature. At normal pressure and temperature, chlorine is a yellow/green gas with the strong smell of bleach. Common salt, sodium chloride, and sea salt contain components of chlorine. Ancient people dating back to 6000 B.C. used sodium chloride as rock salt and brine in preservatives. Today chlorine is used primarily as a disinfectant or bleaching agent. Molecules in the upper atmosphere containing chlorine may contribute to the depletion of the ozone layer protecting the Earth from harmful effects of ultraviolet rays.

Primarily used as a sanitizer in swimming pool water, chlorine also treats approximately 75% of the drinking water in the United States and Canada. Chlorine treatment of water has lowered the number of waterborne infectious diseases, but does not affect many parasites that are harmful to humans. Many municipalities currently using chlorine to sanitize drinking water are seeking alternatives, such as Ozone, as a more cost effective means. The federal standard for chlorine in drinking water is 4 ppm (parts per million) to reduce the spread of bacteria in the water. Human exposure to chlorine may occur when using treated water in food preparation or for drinking. Breathing, eating, drinking, or touching may expose humans to chlorine. The use of drinking water containing more than 4 ppm is not healthy. Medical experts argue the connection between high rates of colon and bladder cancer and the long term drinking of chlorinated water. Some scientists are of the opinion that chlorine alone is not the problem. They believe the problem arises from the combination of chlorine with other natural substances and pollutants found in some water.

Despite risk assessment performed by the Environmental Protection Agency, there is little official data on the health risks of chlorinated water. Carbon filters mounted on faucets will remove most chlorine from water used for drinking and cooking. Commercially available pitchers with drop in filters will accomplish the same end. Some argue that letting the water run at the tap for a minute will remove chlorine, but a more viable solution is to allow the water to set for up to twenty-four hours.

Stepping back to view the big chlorine picture, we will see the concern of chlorine in our drinking water. Adding chlorine to drinking water in very small amounts is for the particular purpose of killing microorganisms harmful to humans, but it is still a corrosive element, as well as an oxidizer. We would be remiss not to be concerned about the long-term effects on humans. Yet we have to be pro-active with regard to keeping our water supplies safe from bacteria. New hope may come in the form of the ozone water treatment systems previously mentioned. Some municipalities have found ozone far more cost effective than chlorine. Solar energy, hydrogen peroxide, ultraviolet light, and fluoride are other methods under consideration for water purification purposes.