Disinfected Water: Unintended Consequences

Summer 2020

Toxic byproducts in waterMixing drinking water with chlorine, the United States’ most common method of disinfecting drinking water, creates previously unidentified toxic byproducts, according to a team led by Carsten Prasse, an assistant professor of environmental health and engineering.

“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,” says Prasse. “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.”

Phenols—chemical compounds that occur naturally in the environment and are abundant in personal care products and pharmaceuticals—are commonly found in drinking water. When they mix with chlorine, a large number of byproducts are created. Current analytical chemistry methods are unable to detect and identify all of these byproducts, some of which may be harmful and can cause long-term health consequences, according to Prasse.

In a study published in Environmental Sciences & Technology, Prasse’s team used a technique adapted from the field of toxicology to identify compounds based on their reaction with biomolecules, such as DNA and proteins. They added N-α-acetyl-lysine, which is almost identical to the amino acid lysine that makes up many proteins in our bodies, to detect reactive electrophiles. Previous studies show that electrophiles are harmful compounds that have been linked to a variety of diseases, including cancer.

The researchers first chlorinated water utilizing the same methods used commercially for drinking water. After that, the team added the aforementioned amino acid, let the water incubate for one day, and used mass spectrometry, a very sensitive and selective method of analyzing chemicals, to detect the electrophiles that reacted with the amino acid.

Their experiment found the 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, until this study, scientists had not detected in chlorinated water before.

While Prasse stresses that this is a lab-based study and the presence of these novel byproducts in real drinking water has not been evaluated, the findings also raise the question about the use of alternative methods to disinfect drinking water, including the use of ozone, UV treatment, or simple filtration.

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