Scientists say they have identified a previously unknown, potentially toxic chemical in the treated drinking water consumed by millions of Americans.

Chloronitrimidanion is a by-product of the breakdown of chloramine, which is used by water treatment plants to disinfect drinking water and kill diseases such as Cholera and typhoid fever.

After eluding them for years, researchers reported in the journal Science this week that they detected the “mystery” anion in 40 drinking water samples from 10 US systems that use chloramines. More than 113 million Americans drink chloraminated water.

“It’s a very stable, low molecular weight chemical,” explained Julian Fairey, associate professor of civil engineering at the University of Arkansas and first co-author of the new paper. “It’s a very difficult chemical to find. The hardest part was identifying it and proving that it was the structure we said it was.”

The team observed concentrations of up to 100 micrograms per liter, exceeding typical regulatory limits for most disinfection byproducts.

The compound was not detected in ultrapure water or drinking water not treated with chlorine-based disinfectants.

Fairey synthesized the anion in the lab for the first time but could not immediately determine whether it is linked to cancer or other negative health risks. He told reporters there are “good reasons to investigate the toxicity” of the compound.

“It’s well known that when we disinfect drinking water, some toxicity is created. Chronic toxicity, really,” Fairey said.

“A certain number of people can get cancer from drinking water over several decades. But we have not identified the chemicals that drive that toxicity. An important goal of our work is to identify these chemicals and the reaction pathways by which they are formed.”

Chlorine is used to kill harmful bacteria, viruses and other microorganisms that can cause disease. Chlorine is allowed in drinking water, but the United States The Swedish Environmental Protection Agency limits the quantity.

Some studies have linked long-term exposure to chlorinated water to an increased risk of certain cancers, especially bladder cancerand concerns about birth defects and respiratory problems due to the byproducts produced when chlorine reacts with organic matter in the water.

Many municipal water supplies have switched from chlorine to chloramine – a compound created by mixing chlorine and ammonia – because chloramine is more stable, lasts longer and typically generates fewer disinfection byproducts.

But water expert Dr. David Sedlak told CNN this week that over “the last 30 years, we’ve seen a bit of buyer’s remorse for this switch from free chlorine to chloramines, as we continue to discover these chloramine disinfection byproducts.”

“The challenge is that we don’t really know about the health effects, because unlike the free chlorine disinfection byproducts, there just hasn’t been a lot of toxicology done on these compounds,” added Sedlak, vice president for graduate studies and the Platon Malozemoff Professor of Environmental Engineering at UC Berkeley, who was not involved in the new study.

As research continues, the study authors suggest using a carbon-based filter like a Brita filter if you’re worried about what’s in the water you drink.