International Research Collaboration Identifies Previously Unknown Chemical Compound in Drinking Water
Published December 17, 2024
Water disinfection plays a critical role in safeguarding public health by fighting against waterborne diseases such as cholera, hepatitis, and gastrointestinal illnesses. For more than a century, chlorine has been the front- runner in this battle, proving capable of inactivating disease-causing organisms present in water.
Although chlorine is an effective disinfectant, it can react with organic and inorganic material in water and form harmful disinfection byproducts (DBPs). Removing these byproducts must then be part of the water treatment process. Disinfection byproducts have been associated with bladder and colon cancer, low birth weight and reproductive effects like miscarriages. EPA’s mission to protect human health and the environment includes regulating drinking water to balance providing adequate disinfection while limiting DBP formation.
Since the discovery of DBPs in 1974 and with EPA’s subsequent Stage 1 and 2 Disinfectants and Disinfection Byproducts Rules, many public water systems transitioned to using chloramines as an alternative disinfectant to chlorine because chloramines produce lower levels of regulated DBPs. Chloramines form when chlorine combines with ammonia in drinking water. In the U.S., chloramines are the second-most commonly used disinfectants in distributed drinking water, and surveys of drinking water systems indicate around 113 million people in the U.S. receive water treated with chloramines. While chloramines produce fewer regulated DBPs compared to chlorine, they can still react with precursors in water to create additional unregulated DBPs, including nitrogen containing DBPs. Chloramines are also unstable and decompose on their own, resulting in at least one unknown, until recently, product known as the “unidentified product.”
Groundbreaking Research and Collaboration
Researchers initially detected the “unidentified product” about 40 years ago, but analytical limitations and gaps in understanding chloramine decomposition chemistry hindered early research efforts to identify it. In a research study published in Science, EPA research environmental engineer David Wahman collaborated with University of Arkansas Associate Professor of Civil Engineering Julian Fairey, ETH Zurich Professor of Environmental Chemistry Kristopher McNeill, and ETH Zurich postdoctoral researcher Juliana Laszakovits to solve this mystery. By using innovative methods, this collaborative research team identified the “unidentified product” as chloronitramide anion.
The team’s advancements in generating and isolating the compound allowed them to determine its chemical formula and structure. Chloronitramide anion contains one chlorine atom, two nitrogen atoms, two oxygen atoms, and a negative charge, and it is also surprisingly stable in drinking water. In addition, the research team created the first method to measure chloronitramide anion concentrations and found meaningful concentrations in chloraminated drinking water. Because chloronitramide anion is inherent with chloramine use, water utilities that use chloramines as a secondary disinfectant should expect chloronitramide anion in their water to some extent. Although the toxicity is currently unknown, measured chloronitramide anion concentrations and similarity to other compounds with known toxicity raise concerns.
“The innovative research and collaboration allowed us to determine that the “unidentified product” is chloronitramide anion,” said EPA researcher David Wahman. “This finding opens the way for the research community to conduct the necessary studies to understand the potential toxicity of chloronitramide anion and the factors impacting its concentration in drinking water.”
Next Steps for the Research
The study’s findings support the need for more research to understand the implications of chloronitramide anion, including its potential toxicity and factors affecting occurrence. In addition, because activated carbon was previously shown to remove the “unidentified product” by chemical reaction, point-of-use filters that use activated carbon may remove chloronitramide anion from drinking water, but further research is needed in this area. Finally, point-of-use devices to remove chloronitramide anion using anion exchange resin or ultraviolet light treatment are likely additional effective avenues of research for in-home treatment options.