Inorganic chloramines have been used for decades to remove pathogens from public water supplies.

Though chlorine remains the most widely used disinfectant in the US and globally, chloramines have increasingly replaced it in many systems to reduce certain byproducts linked to bladder and colon cancer, low birth weight, and miscarriage.

Today, more than 113 million Americans rely on chloraminated drinking water, with the compound also in use across Canada, Asia, and Europe.

"However, chloramines themselves decompose into products that are poorly characterized," said Julian Fairey, lead author of the study published in the journal Science, during a press briefing.

One such product, identified more than 40 years ago but left chemically unresolved, was simply dubbed the "unidentified product."

Fairey and his team have finally cracked the mystery.

Using a combination of traditional chemistry methods and modern tools like high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, they identified the compound as "chloronitramide anion."

The compound was detected in all 40 chloraminated drinking water samples tested, with concentrations reaching up to 100 micrograms per liter -- exceeding typical regulatory limits for disinfection byproducts, which range between 60 and 80 micrograms per liter.

Although toxicological studies have yet to be conducted, the researchers sounded a warning.

"The chemical structure looks concerning, as does the concentrations at which this compound is forming, so we certainly think health effects studies are warranted," Fairey said.

Their study calls for the compound to be "an immediate candidate" for quantification in public waters and for closer health and toxicity studies.

Water utilities could consider reverting to chlorine, Fairey suggested, though this would require secondary disinfectants to neutralize the known toxic byproducts chlorine produces.

With further study and regulatory action likely years away, the researchers recommended home filtration systems using activated carbon blocks for people who are concerned.