More than 50,000 people in North America died of typhoid fever due to contaminated water in a five year period from 1900 to 1904. The use of chlorine compounds for disinfection of water began in 1908 in the US and chlorine gas was introduced for this purpose in 1911. By the 1930s, due both to better protection of sources of water and to chemical disinfection, waterborne diseases were largely eliminated from the cities of developed countries. Unfortunately, to this day, large parts of our world do not have adequate supplies of clean infection-free water. The World Health Organization calculates that thousands of humans die each day as a result of preventable water-borne diseases.
Chlorine is a highly reactive element.
For this reason, it combines with organic compounds to form chlorinated organic compounds. The presence of a chlorine in an organic molecule results in changes in the properties of the molecule. Chlorine in a molecule increases stability and, for example, makes the substance harder to burn. This increase in the chemical stability of the molecule also increases the biological and environmental persistence of the substance. Because the chlorine atom has a large size and because it usually replaces the much smaller hydrogen atom when it combines with organic compounds, chlorinated organic compounds have a larger volume than their nonchlorinated counterparts.