However this valuable resource can be easily reduced in value or eliminated as a source of supply by contaminants, that in almost all cases could be reasonably prevented. Evidence that drinking water contributed directly to disease, was based on epidemiological studies by John Snow in London, England in 1854. Snow removed pump handles from wells and as a result ended a cholera outbreak. Chlorinating, introduced in 1908, has been a very effective chemical in preventing infectious diseases such as cholera and typhoid fever. However, there is more to assuring a safe water supply than the use of chlorine.
Chlorine also has limited effectiveness against some micro-organisms and none against chemicals.
Prior to the enactment of federal legislation, which set minimum standards for public drinking water throughout the United States, each state was responsible for protecting public water supplies and the public s health. The administration of these programs was by the U. S. Public Health Service. The Public Health Service also developed a model drinking water program, and provided guidance, and technical assistance to the states. State programs varied considerably. Many did not require monitoring or inspections to assure that the drinking water was safe.