‘Mystery’ chemical found in millions of Americans’ tap water could be toxic: ‘Good reason to investigate’

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

Chloronitramide anion is a byproduct of the decomposition of chloramine, which is used by treatment plants to disinfect drinking water and kill diseases like 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 chemical with a low molecular weight,” explained Julian Fairey, an 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 it was the structure we were saying it was.”

The team observed concentrations of up to 100 micrograms per liter, surpassing the typical regulatory limits on 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’s linked to any cancers or other adverse health risks. He told reporters there’s “good reason to investigate the toxicity” of the compound.

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

“A certain number of people may get cancer from drinking water over several decades. But we haven’t identified what chemicals are driving that toxicity. A major goal of our work is to identify these chemicals and the reaction pathways through which they form.”

Chlorine is used to kill harmful bacteria, viruses and other microorganisms that could cause illness. Chlorine is allowed in drinking water, but the US Environmental Protection Agency limits the amount.

Some studies have linked long-term exposure to chlorinated water to an increased risk of certain cancers, particularly bladder cancer, and concerns about birth defects and respiratory problems because of 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 in “the last 30 years we’ve seen a little bit of buyer’s remorse for this switch from free chlorine to chloramines, because we keep discovering these chloramine disinfection byproducts.”

“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,” added Sedlak, vice chair for graduate studies and the Plato Malozemoff Professor of Environmental Engineering at UC Berkeley, who was not involved with the new study.

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