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Disinfection

Fighting disease

Chlorine saves lives. Chlorination and disinfection of water supplies are the public health success stories of the century.

Chlorine was first used in drinking water in the late 19th century to control the spread of water-borne diseases such as typhoid, cholera, dysentery and gastro-enteritis, which have killed more people than all the wars in history. Fighting these diseases remains vital today; the World Health Organization estimates that more than three million people still die each year as a direct result of drinking unsafe water.

Chlorine acts as a powerful disinfection agent when used either on its own or as sodium hypochlorite (bleach). Added to water in minute quantities, it quickly kills bacteria and other microbes. Chlorine has the major advantage of ensuring clean water right up to the tap, whereas the action of other disinfectants - such as ozone, ultraviolet light and ultrafiltration - is only temporary. In addition to purifying water, chlorine helps remove tastes and odours, controls the growth of slime and algae in mains pipes and storage tanks, and helps to remove unwanted nitrogen compounds from water. Today, 98% of Western Europe's drinking water is chlorinated.

Proven life saver

Many events testify to the importance of chlorine in water purification:

• In the US, annual deaths from cholera totalled 25,000 in 1900. By 1960, this figure had fallen to fewer than 20;
• In 1991, a misinterpretation of US law resulted in a voluntary suspension by Peru's government of chlorination of water supplies. The resulting cholera epidemic spread to neighbouring countries causing 1,000,000 cases of cholera and more than 10,000 deaths;
• In 1986, 4,000 people in Tenerife were hospitalised due to water contamination which followed the temporary withdrawal of chlorine for disinfection.

Chlorine products are effective and economical as household bleach and as disinfectants to destroy and deactivate a wide range of dangerous microbes in homes, hospitals, swimming pools and spas, hotels, restaurants and other public places.

A range of chlorine compounds - including ferric chloride (FeCl₃6H₂O) and hydrochloric acid (HCl) - are used to purify waste water and sewage.

In the home and public swimming pools

In the home, chlorine-based products are used in laundry bleach, dishwasher detergents, scouring powders and paper towels, and as all-purpose disinfectants to kill common germs (including Staphylococcus, Salmonella, Pseudomonas and athlete's foot fungus).

Swimming remains a very popular, healthy leisure pastime thanks in part to the benefits of chlorine. Disinfectants based on this element keep swimming pool water safe by killing a range of dangerous microbes which could otherwise threaten health.