"Scientists Discover Long-Sought By-Product of Drinking Water Treatment"

The potential toxicity of this by-product, which is formed during certain chlorine-based water treatments, has not been fully explored yet.

A new study reveals that about one-third of people in the U.S. could be exposed to a newly discovered by-product from some chlorine-based water treatments.

A new study reveals that around one-third of Americans may be exposed to a newly discovered by-product that forms when chlorine is used in water treatments. This by-product, an electrically charged molecule, has long been sought by scientists, but its potential health impacts are still unknown. While researchers have yet to fully understand the toxicity of the compound, early analyses suggest it could pose a range of health risks. What makes this especially concerning is that in certain water systems, this substance is found in concentrations higher than the safety limits set for other harmful breakdown products.

This new finding has already sparked significant attention within the scientific community. Daniel McCurry, an environmental engineer at the University of Southern California, who was not involved in the study but wrote a perspective on it for Science, notes that the paper is likely to generate considerable debate and concern. The study, published on November 21, raises important questions about the safety of drinking water and underscores the need for further research into the health effects of this newly identified compound.

Most water systems in the United States use chlorine to disinfect water because it effectively kills germs. However, chlorine can react with other substances in the water, creating hundreds of by-products, some of which can be harmful. To reduce these risks, many cities switched to using chemicals called chloramines for water treatment decades ago, says Julian Fairey, an environmental engineer at the University of Arkansas.

Today, about 113 million people in the U.S. get their drinking water from systems that use chloramines. While chloramines also produce by-products, they tend to form at much lower levels than chlorine does. Many of these chloramine by-products are well-known, but one particular by-product has remained a mystery for decades.

For years, scientists have been aware of mysterious by-products in water treatment systems, substances that contained nitrogen and absorbed specific wavelengths of light. However, isolating and identifying these compounds from the complex mixture of other breakdown products proved difficult. That was until Fairey and her team, using a sophisticated blend of analytical techniques, succeeded in identifying the elusive substance — a negatively charged molecule they named chloronitramide.

Chloronitramide is a small molecule, composed of just five atoms, which contributed to its ability to remain hidden among the many other by-products produced during water treatment. This molecular size, combined with its chemical characteristics, made it a challenge to identify in previous studies. But Fairey’s breakthrough finally shed light on its presence, adding a new layer of complexity to the understanding of water treatment processes.

Importantly, the presence of chloronitramide appears to be linked to the use of chloramines, a common disinfectant in U.S. water treatment systems. The research team found that in 10 water systems across the United States using chloramines, 40 out of 40 samples contained chloronitramide, with concentrations averaging 23 micrograms per liter. Some samples even had concentrations as high as 120 micrograms per liter — a significant finding, given that the U.S. Environmental Protection Agency (EPA) sets a maximum limit of 80 micrograms per liter for certain harmful water by-products.

In contrast, chloronitramide was not found in water treatment systems in Switzerland that do not use chlorine or chloramine disinfectants, suggesting that chloramine use is a key factor in its formation. This discovery raises new questions about the safety of water treated with chloramines and highlights the importance of further research to assess the potential health impacts of chloronitramide and other similar compounds. The study is an important step in understanding the unintended consequences of water disinfection practices and underscores the need for continuous monitoring and improvement of water treatment technologies.

The health effects of chloronitramide haven’t been studied in detail yet, so it’s not regulated. A preliminary check using a web app suggests there could be concerns, like toxicity or potential risks during pregnancy. However, Beate Escher, a toxicologist, explains that it's hard to know which chemicals in treated water are actually causing harm since many are produced during the treatment process. She says more detailed research is needed to understand whether chloronitramide is harmful.

While the risks could be a concern for large populations, they’re probably not a big issue for individuals, says McCurry. He drinks tap water regularly and doesn’t think the potential risks from chloronitramide are enough to stop him from doing so.