A Toxic Chemical Could Be Lurking In Our Tap Water, According To A New Study

You might think twice before drinking water straight from your tap. Researchers have discovered a new chemical called chloronitramide in 40 U.S. water samples from 10 water systems, with some of those samples testing moderately high for this substance, according to a 2024 study in Science. Ultrapure water and water untreated by the disinfectant chloramine didn't have this chemical (here are signs your tap water isn't safe to drink).

Chloronitramide is a byproduct of chloramine, which is used to treat water systems used by more than 113 million people in the United States. The researchers still aren't sure if chloronitramide is toxic. However, the chemical makeup of this byproduct is similar to other toxic chemicals.

Study author and Associate Professor of Civil Engineering at the University of Arkansas, Julian Fairey, said that scientists have known about chloronitramide for a long time but have had a hard time identifying it. His work has centered on finding out which chemicals in drinking water could be toxic over time. "It's well recognized that when we disinfect drinking water, there is some toxicity that's created," Fairey said in a news release. "Chronic toxicity, really. A certain number of people may get cancer from drinking water over several decades."

If treating drinking water might be toxic over time, it might seem to make sense not to add chloramine to the tap water. Yet your drinking water comes from fresh surface waters and groundwater aquifers that have many contaminants, according to the Environmental Protection Agency. Pesticides, petroleum, and heavy metals from farming and other industries can find their way to aquifers. Animal and human waste carry Giardia, Cryptosporidium, and E. coli, and these microbes enter sewage and septic systems. Groundwater can be contaminated with arsenic or other heavy metals.

The EPA says chloramine is preferred over chlorine because it continues to disinfect the water as it moves to the taps in your home. Chloramines are used to treat the water consumed by about one in five U.S. residents. The EPA is continually researching the safety of chloramines and their byproducts.

Now that this byproduct has been identified, researchers like Fairey can study chloronitramide's potential toxicity. "Even if it is not toxic, finding it can help us understand the pathways for how other compounds are formed, including toxins," Fairey said. "If we know how something is formed, we can potentially control it." In the meantime, Fairey suggests purifying your drinking water using a home water filter. Waterdrop's Reverse Osmosis countertop water filter has a five-step filter that reduces 99% of impurities from your tap water.