Previously unknown compound in chloraminated drinking water identified

A team of researchers from the United States and Switzerland have reported the discovery of a previously unknown compound in chloraminated drinking water. Inorganic chloramines are commonly used to disinfect drinking water to safeguard public health from diseases like cholera and typhoid fever. It’s estimated that more than 113 million people in the United States alone drink chloraminated water.

The researchers have now identified chloronitramide anion, chemically expressed as Cl–N–NO2⁻, as an end product of inorganic chloramine decomposition. While its toxicity is not presently known, its prevalence and similarity to other toxic compounds is concerning and warrants further study to assess its public health risk.

Simply identifying the compound has been both a challenge and breakthrough write the authors in a paper published in the journal, Science. “The compound has been known to form in chloraminated drinking water since the early 1980’s. Later studies in the 1990’s tried to determine its structure, but were not successful due to an incomplete understanding of the chemistry surrounding chloramine decomposition and limitations in analytical instrumentation,” notes Kristopher McNeill, Professor of Environmental Chemistry at ETH Zurich and one of the lead authors of the study.

His colleague Julian Fairey, an Associate Professor of Civil Engineering at the University of Arkansas, adds, “It’s a very stable chemical with a low molecular weight. And it’s a very difficult chemical to find. The hardest part was identifying it and proving it was the structure we were saying it was – Fairey himself began trying to unravel the mystery 10 years ago.

This included being able to synthesize the compound in his lab, which had never been done before. Samples were then sent for analysis to his colleague and co-first author on the paper, Juliana Laszakovits, a postdoctoral researcher in the McNeill lab at ETH Zurich. In 2022, Fairey visited McNeill at ETH Zurich as part of his sabbatical where they worked with Laszakovits on this study.

“Chloraminated drinking water is common in North America, but chloramination is not really practiced in Switzerland, and there’s no chloronitramide anion in Swiss waters”, Laszakovits says. “This actually allowed us to use Swiss tap water as a control in the study,” McNeill adds.

The current paper focused on water systems in the US. However, Italy, France, Canada, and other countries also use chloramination and could be potentially affected as well, according to McNeill.

Toxicity is unknown at this point

Inevitably, there will be questions about the health risks posed by this new compound, which could not be previously evaluated in any toxicity studies.

Fairey, who studies the chemistry of drinking water disinfectants, explains: “It's well recognized that when we disinfect drinking water, there is some toxicity that's created. Chronic toxicity, really. A certain number of people may get cancer from drinking water over several decades. But we haven't identified what chemicals are driving that toxicity.”

Identifying this compound is an important step in that process. Whether chloronitramide anion will be linked to any cancers or has other adverse health risks will be assessed in future work by academics and regulatory agencies, such as the U.S. Environmental Protection Agency. At the very least, toxicity studies can now be completed on this compound thanks to this discovery.