Chlorine belongs to the group of elements called halogens. The halogens combine with metals to form compounds called halides. Chlorine is manufactured commercially by running an electric current through salt water. This process produces free chlorine, hydrogen, and sodium hydroxide. Chlorine is changed to its liquid form by compressing the gas, the resulting liquid is then shipped.
Liquid chlorine is mixed into drinking water and swimming pools to destroy bacteria.
Until recently, concerns about drinking water focused on eliminating pathogens. The chlorine used to reduce the risk of infectious disease may account for a substantial portion of the cancer risk associated with drinking water. Chlorination of drinking water was a major factor in the reduction in the mortality rates associated with waterborne pathogen. The use of chlorine was believed to be safe. This view is evident in an article, which appeared on the back page of the New York Times .