The new chemical compound—observed in tap water by scientists for decades—had remained unidentified, due to difficulties separating it from the high-salinity (saltier) water it was found in. But dogged researchers found a way, and now, according to a Nov. 21 research article published in the journal Science, there is a name for the compound: chloronitramide. 

That’s a byproduct of naturally occurring chemicals and chloramine—a disinfectant formed when ammonia is added to chlorine, added to drinking water since the 1930s to help stop the presence of harmful organisms, according to the Environmental Protection Agency. In the U.S. alone, notes the article, chloraminated water systems serve more than 113 million people.

But is it toxic? That part, unfortunately, remains a mystery.

“Although toxicity is not currently known, the prevalence of this by-product and its similarity to other toxic molecules is concerning,” writes editor Michael A. Funk in the article’s summary. 

The chloronitramide was detected in 40 drinking water samples from 10 U.S. drinking water systems using chloramines, according to the article. In some cases, researchers found it at levels higher than the EPA limit on most disinfection byproducts. It was not detected in ultrapure water or drinking water not treated with chlorine-based disinfectants—in Switzerland, for example, where ozone is used for disinfection. 

A bit of good news is that the authors identified a way for consumers to remove the chemical byproduct from water: activated carbon. “It’s been shown to be removed by activated carbon in the literature,” study co-author and EPA researcher David Wahman said in a press conference about the findings on Thursday. “There probably needs to be a little bit more work done to figure out what it’s being broken down into…But I think a Brita filter, or…any kind of carbon based filter that you’d have in your refrigerator would probably remove it.”

The news about chloronitramide comes on the heels of Robert F. Kennedy Jr., president elect Donald Trump’s pick to lead the Health and Human Services Department, raising concerns about fluoride in drinking water. He has said that Trump will rid tap water of the chemical ion—which has been added to water on a widespread basis since 1962 to prevent tooth decay—on his first day in office, citing a range of health risks. The Centers for Disease Control and Prevention maintains that fluoridated drinking water is safe. 

Regarding the chloramines, water expert David Sedlak, Plato Malozemoff Professor of Environmental Engineering at UC Berkeley, told CNN, “The challenge is, we don’t really know about the health impacts, because unlike the free chlorine disinfection byproducts, there just hasn’t been as much toxicology done on these compounds.” And because local water systems cannot afford to investigate these byproducts, it will be up to the federal government, Sedlak said.

“It’s the kind of thing that, when government is functioning well, it does a good job protecting us by looking at these things. But I don’t think the EPA or CDC or NIH has the funding needed to answer these questions,” he said.

Susan D. Richardson, an expert in drinking water disinfection by-products at the University of South Carolina, told Chemical & Engineering News that the findings were groundbreaking. “It will be important to quantify this new disinfection byproduct in drinking water distribution systems to determine whether it increases or decomposes over time before it reaches consumers’ taps,” she said, adding that she suspects the chloronitramide is toxic but that the idea that activated carbon would remove it is “great.” 

Meanwhile, University of Southern California environmental engineering professor Daniel McCurry said in a Science journal commentary that the identification of chloronitramide, regardless of whether it’s found to be toxic or not, “warrants a moment of reflection for water researchers and engineers.”

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