Study: Mixing chlorine and drinking water can be toxic

Researchers find previously undetected byproducts that can cause long-term health problems

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Chlorine is the most commonly used chemical to disinfect water supplies and has been used as such since the early 1900s, according to the National Center for Biotechnology Information.

A new study by researchers at Johns Hopkins University, however, finds there are unintended and toxic byproducts produced through this process.

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"There's no doubt that chlorine is beneficial; chlorination has saved millions of lives worldwide from diseases such as typhoid and cholera since its arrival in the early 20th century," wrote lead author Carsten Prasse, an assistant professor of environmental health and engineering at Johns Hopkins University.

“But that process of killing potentially fatal bacteria and viruses comes with unintended consequences. The discovery of these previously unknown, highly toxic byproducts, raises the question how much chlorination is really necessary.”

According to the study, when chlorine mixes with phenols — which are chemical compounds that occur naturally in the environment and are commonly found in drinking water — a “large number of byproducts” are created.

The problem, Prasse wrote, is that analytical chemistry methods can’t detect all of those byproducts, and some could cause long-term health problems.

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For their study, researchers chlorinated water using the same process employed for commercial drinking water. Next they added an amino acid that is almost identical to lysine, which is found in the human body. After allowing the water to incubate, the researchers used mass spectrometry to see which electrophiles — harmful compounds linked to a variety of diseases — reacted to the amino acid.

They found two compounds: 2-butene-1,4-dial (BDA) and chloro-2-butene-1,4-dial (or BDA with chlorine attached). BDA is a very toxic compound and a known carcinogen that Prasse said had not been detected in chlorinated water before this study.

Although the presence of these byproducts in actual drinking water hasn’t been evaluated, Prasse raises the prospect of using a different methode to disinfect drinking water.

“In other countries, especially in Europe, chlorination is not used as frequently, and the water is still safe from waterborne illnesses. In my opinion, we need to evaluate when chlorination is really necessary for the protection of human health and when alternative approaches might be better,” Prasse wrote.

“Our study also clearly emphasizes the need for the development of new analytical techniques that allow us to evaluate the formation of toxic disinfection by-products when chlorine or other disinfectants are being used. One reason regulators and utilities are not monitoring these compounds is that they don’t have the tools to find them.”

The study was published earlier this month in Environmental Science & Technology.

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