First detected 40 years ago, a byproduct in chloraminated drinking water has finally been identified
The nature of an ‘unidentified product’ in drinking water disinfected with chloramines, which serves over 113 million people in the US alone, has finally been revealed by researchers in the US and Switzerland. Despite First detected almost 40 years ago, the molecular ion, called chloronitramide, has never been characterised before, so its toxicology is unknown. However, its concentration in some samples of tap water taken in areas such as California and Texas and its similarity to harmful molecules warrant investigation, the researchers warn. The discovery could also add to previous concerns about the use of chloramines to sterilise tap water.
Chlorine, a low-cost and highly effective disinfectant, is the most widely used chemical for steralising drinking water across the world. But in the 1970s, scientists found that it could react with organic matter to produce harmful chemicals such as trihalomethanes and haloacetic acids. The US Environmental Protention Agency (EPA) subsequently regulated the maximum permissible concentrations of several of these in tap water. To reduce the production of these disinfection by-products, many water treatment authorities in the US and some other countries including the UK have partially or totally switched to disinfecting water with chloramines, which are formed by combining chlorine with ammonia.
In the early 1980s the signal of a mysterious molecule was observed in UV absorbance spectra of chloraminated water. Environmental engineer Richard Valentine at the University of Iowa, US, and his colleagues conducted extensive investigations in the 1980s and 1990s, showing the circumstances under which it formed. However, the molecule’s exact structure remained unclear.
