What to know about the newly identified chemical in U.S. drinking water

Researchers have identified a chemical in certain tap water across the United States, prompting questions about what it means for drinking water safety and Americans’ health. 
In the study, published in the journal Science Thursday, researchers detected the compound, called chloronitramide anion, in 40 drinking water samples from 10 U.S. drinking water systems using chloramines, a type of disinfectant. 
The levels of the newly identified chemical were also notable, as high as about 100 micrograms per liter (μg/l), which surpasses the typical regulatory limits of 60 to 80 μg/l for many disinfection by-products.
The compound was not detected in ultrapure water or drinking water treated without chlorine-based disinfectants. 
While the existence of chloronitramide anion has been known for about 30 years, this new research identifies it, shedding light on just how prevalent it is in U.S. drinking water and making the way for further testing. 
Chloronitramide anion is a by-product of chloramine decomposition. Chloramines are used to disinfect drinking water. 
“For over a century, chemical disinfection of public water supplies has effectively reduced waterborne disease by killing pathogens in drinking water,” a news release for the study notes. “Inorganic chloramines, like monochloramine (NH22Cl) and dichloramine (NHCl2), have become widely used in the U.S. for this purpose and are used to treat the tap water of nearly one-third Americans.”
More precisely, chloraminated water systems serve more than 113 million people in the U.S. alone, the study notes. For decades though, chloramine decomposition has been suspected of producing elusive chemical by-products.
Some still consider chloramine a better option, however, than chlorine, the most common drinking water disinfectant used, due to known health concerns. 
“Since the 1970s, we’ve known that chlorine reacts with constituents in the water to form disinfection by-products which have been associated with bladder and colon cancer, low birth, weight and miscarriage,” author Julian Fairey said in a press briefing, adding the most predominant chlorine disinfection by-products are regulated by the Environmental Protection Agency.
This prompted many public water systems to switch from chlorine to chloramines, Fairey said, because they form lower concentrations of these regulated disinfection by-products.
But chloramines still decompose into products that aren’t well studied, like the latest identified compound. 
The study underlines that any potential toxicity is not currently known, but adds the prevalence of the compound and its similarity to other toxic molecules is concerning.
“Detected in the tap water of millions of Americans, this compound’s toxicity remains untested, prompting calls for immediate toxicological evaluation and raising questions about the safety of chloramine in public water supplies,” the release added. 
In a related commentary published alongside the study, civil and environmental engineering professor Daniel McCurry writes the findings may trigger a reevaluation of how water supplies are treated. 
“Regardless of whether chloronitramide anion is found to be toxic or not, its discovery warrants a moment of reflection for water researchers and engineers,” he writes. 
In the news briefing, the study’s authors reiterated that further testing is needed to understand any potential health implications of chloronitramide anion in drinking water.
Still, if people are currently concerned about their drinking water while any potential toxicity is yet to be evaluated, study author David Wahman said in the briefing that previous literature has shown the by-product to be removed by activated carbon. 
“A Brita filter, or something like that, is probably logical … Any kind of carbon-based filter that you’d have in your refrigerator would probably remove it. If someone was concerned, that would be the one thing that maybe they could think about doing,” he said.