**New Study Raises Concerns Over Unidentified Chemical in U.S. Tap Water**

A recently identified chemical byproduct found in the tap water of approximately one-third of U.S. residents is drawing concerns from scientists about its potential toxicity. The substance, named chloronitramide anion, forms when water is treated with chloramine—a disinfectant made by combining chlorine and ammonia. Chloramine is commonly used in municipal water treatment systems to eliminate viruses and bacteria.

Researchers discovered the existence of chloronitramide anion about 40 years ago, but only now has it been clearly identified thanks to advancements in analytical techniques. Determining if this chemical poses a danger could take years, as no prior studies have examined its toxicity. The researchers published their findings in the journal Science, aiming to prompt further investigation into the substance's safety.

David Wahman, a study co-author and research environmental engineer at the Environmental Protection Agency (EPA), indicated that the compound shares similarities with other known toxic chemicals. "It has similarity to other toxic molecules," Wahman said. "We looked for it in 40 samples from 10 U.S. chlorinated drinking water systems across seven states and found it in all the samples."

The chemical, which forms as chloramine decays over time, is likely prevalent in all water systems treated with chloramine. This revelation highlights questions regarding the health effects of chemicals used in tap water treatment. Currently, around 113 million Americans receive water treated with chloramine, which has been in use for about a century to disinfect water.

David Reckhow, a professor in civil and environmental engineering at the University of Massachusetts, Amherst, viewed the discovery as a significant development towards understanding the potential hazards of chloronitramide anion. "It's a pretty small molecule, and it can probably enter into biological systems and cells," Reckhow remarked, "Those are the kinds of things you worry about."

The research team, led by Julian Fairey, an associate professor at the University of Arkansas, developed a method to formulate high concentrations of the chemical for laboratory testing. This advancement allows scientists to now begin the challenging task of researching its toxicological significance. Fairey noted past studies suggesting a link between disinfected water and higher cancer rates, though he clarified that the specific role of chloronitramide anion remains unknown.

Although any definitive conclusions about the chemical’s toxicity and subsequent regulations might be years away, Alan Roberson, the executive director of the Association of State Drinking Water Administrators, stressed the need for immediate response. Considering the urgency, he emphasized the importance of ongoing research and reduction strategies to minimize exposure.

David Andrews, a senior scientist at the Environmental Working Group, argued that the study questions the safety of chloramine as a water disinfectant from a health perspective. Despite the existence of hundreds of disinfection byproducts, Andrews believes this one necessitates particular scrutiny due to its widespread detection and potential risks.

Roberson highlighted the inherent trade-offs in any water disinfection process, as these processes have been crucial in eradicating waterborne diseases like cholera and typhoid. However, they also carry risks, with some byproducts associated with cancer and miscarriage. Wahman suggested that active carbon filters used in home water purification systems could potentially remove such byproducts, although more research is needed to confirm this.

The findings underscore the complexity and balance required in managing public health through water treatment practices, as researchers continue to probe the long-term effects of newly identified contaminants like chloronitramide anion.