Chlorine is a highly reactive element that is seldom found in its natural state. It comprises about 2 per cent of the earth's surface material, mostly in the form of sodium chloride dissolved in seawater. Its reactivity makes it valuable as a disinfectant, and it has been widely used to decontaminate drinking water and swimming pools. Though it is generally thought to be safe in small concentrations, many studies indicate this is not so.
Chlorine gas is a respiratory irritant that can cause coughing, sneezing, throat irritation and salivation. In high concentrations it is fatal; for this reason chlorine gas has been used as a weapon. According to a 1999 publication of the Chlorine Institute, a trade organisation of chlorine manufacturers, the concentrations in water used for drinking and swimming pools are seldom high enough to produce respiratory discomfort. Dr. Andrew Weil, however, writing in 2009, cites a Belgian study that shows that children who swim in chlorinated water are eight times more likely to develop asthma, a respiratory illness. They are also more likely to develop hay fever and other allergies.
Chlorine and Cancer
A link between chlorine ingestion and various forms of cancer has long been suspected, and research shows that chlorine reacts with organic matter in water to produce trihalomethanes, which encourages the growth of free radicals that can damage vital cells. This can lead to bladder, rectal and breast cancer, according to the editors of The Environmental Magazine at Journal Times.com. The link between chlorine and these forms of cancer is also noted by D. Weil. In addition, there is wide agreement on the carcinogenic properties of dioxin, a complex molecule of chlorine.
Chlorine and Heart Disease
Although studies linking chlorine to heart disease are not conclusive, there is evidence to suggest a causal relationship. Joseph Hattersley reported in the Journal of Orthomolecular Medicine in 2000 that residents of a small town in Pennsylvania had no incidence of heart disease until they began drinking chlorinated water. He also noted that autopsies of 300 GIs who fought in the Korean War showed evidence of arteriosclerosis in the coronary arteries. The water the GIs drank in Korea was so chlorinated that they could hardly stand it, according to Hattersley. Autopsies performed on soldiers who fought in Vietnam, another locality with heavily chlorinated water, yielded similar results.
Other Side Effects
Chlorine is a bleaching agent, and swimming in chlorinated water can dry hair and cause skin problems. It also has a strong odour that is detectable at low concentrations. Chlorinated water consequently has an unpleasant taste and aroma that make it unpalatable to some.