Scientists identify a long-sought byproduct of some drinking water treatments

Roughly a third of Americans may be exposed to a long-sought, newly identified breakdown product of some chlorine-based water treatments.

Although the toxicity of the byproduct, an electrically charged molecule, has yet to be determined, analysis suggests the substance may have some harmful health effects. That’s a concern because in some aquatic systems the chemical appears in concentrations above the threshold allowed for other harmful breakdown products, researchers report Nov. 21 in Science.

“This paper is going to cause a lot of buzz,” says Daniel McCurry, an environmental engineer at the University of Southern California in Los Angeles, who was not involved in the research but wrote a perspective on the study for the same issue. Science.

Most water systems in the United States disinfect water with chlorine; dissolved gas effectively kills microbes, but it can react with other substances in the water to create hundreds of byproducts, some of them harmful. As a result, some municipalities decades ago switched to treating their water with chemicals called chloramines, says Julian Fairey, an environmental engineer at the University of Arkansas in Fayetteville.

Nationwide, about 113 million people get their drinking water from systems that use chloramine as a disinfectant. These nitrogen-chlorine compounds also form decomposition products, but generally do so at much lower rates than chlorine. Many byproducts of chloramine in drinking water are easily identified, but one has remained elusive for decades.

Laboratory experiments to date have hinted at the presence of another byproduct—something that contained nitrogen and absorbed specific wavelengths of light—but the researchers could not isolate it from the other byproducts to identify it. Using a combination of analytical techniques, Fairey and colleagues finally identified the enigmatic substance: a negatively charged molecule called chloronitramide. Its small size — just five atoms — among other factors helped it remain hidden among other decay products, Fairey says.

Chloronitriamide was not detected in Swiss water treatment systems that do not use chlorine or chloramine disinfectants, the team’s field studies show. But in 10 systems in the United States that use chloramine to treat their water, 40 samples contained an average of 23 micrograms per liter, with the highest concentration measuring 120 µg/l. By comparison, the US Environmental Protection Agency regulates the concentrations of some degradation products known to be harmful to be no higher than 80 µg/l.

The potential health effects of chloronitramine have not yet been studied in detail, the team notes. As such, the substance is not regulated. But using an online application to make a preliminary assessment of the newly identified substance suggests there may be dozens of issues of concern, including toxicity and adverse effects that occur during prenatal development.

“Many, many chemicals are formed from the chlorination and fluoridation processes, and it’s hard to say which are the causes” of the disease, says Beate Escher, a toxicologist at the Helmholtz Center for Environmental Research in Leipzig, Germany, who was not involved. in new study. Detailed laboratory studies are needed to understand whether chloronitramide could be harmful, she notes.

While the health risks may be worth worrying about across the population at large, because of the large numbers involved, they’re probably not worth worrying about on an individual basis, McCurry says. “I drink tap water at home and everywhere else I go,” he says. The potential dangers from chloronitramide, he says, “are not enough to make me stop drinking tap water.”