Water disinfection has reduced significantly the occurrence of lethal diseases, such as cholera in many parts of the world. However, according to Michael Smith, a microbiologist in the School of Public Health, at Griffith University, in Queensland, Australia, some disinfection compounds release potentially dangerous chemicals into the water. Writing in the International Journal of Water, Smith suggests that several by-products of water disinfection have halogen-containing chemicals such as chloroform, commonly referred to as trihalomethanes. However, how these compounds interact with natural and non-natural organic matter in water is unclear.

The main source of natural organic matter in drinking water is so-called humic substances, which are formed from the chemical degradation of plant and animal matter such as proteins, amino acids, lignins, fatty acids, complex sugars, humic acids, fulvic acids, hydrocarbons, and microbial metabolites. Non-natural organic matter from agricultural and industrial runoff may also be present in small amounts in water. How each of these small quantities of impurities interact with disinfect compounds is not understood in detail.

Chlorine, chloramine, ozone and chlorine dioxide are the most widely used disinfectants in drinking water treatment. Each of these compounds can lead to the formation of by-products, such as haloacetic acids, haloacetonitriles, haloketones, haloalkenes, and haloaldehydes, as well as nitrosamines. All of these compounds and others have health effects above a certain concentration whether ingested, inhaled, or absorbed through the skin.

Because of the general lack of information in this area, Michael Smith is calling for urgent research to establish what derivative compounds might be present in the water we drink and how these might affect our long-term health.

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First Published in January 2008

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