A previously unidentified chemical has been discovered in the tap water of about one-third of U.S. homes, a new study has found, and scientists are actively investigating whether it's toxic.

The chemical, called chloronitramide anion, forms when "water is treated with chloramine, a chemical formed by mixing chlorine and ammonia. Chloramine is often used to kill viruses and bacteria in municipal water treatment systems," NBC News reported.

About 40 years ago, researchers became aware of a chemical byproduct from water being treated with chloramine, but only with new testing have researchers been able to identify exactly what it is.

Chloronitramide anion has never been studied before, so it may be years before scientists are able to understand whether it's dangerous to consume. The study was published to call attention to potential safety concerns and encourage additional research.

While there is currently no conclusive evidence to suggest chloronitramide anion is harmful to health, it has some resemblances to other "toxic molecules," David Wahman, Ph.D., study author and research environmental engineer at the Environmental Protection Agency, told NBC News.

Part of the reason for the concern over the chemical's potential toxicity is that it appears to be widespread in U.S. drinking water.

"We looked for it in 40 samples in 10 U.S. chlorinated drinking water systems located in seven states. We did find it in all the samples," Wahman said.

He added that it's likely to be found in all water treated with chloramine, which about 113 million U.S. residents get in their taps.

The study also calls attention the possible health impact of using certain chemicals to treat tap water, not just chloramine. Some research has linked disinfected drinking water with increased rates of certain types of cancers.

“We don’t know what’s driving these. We have no idea if this compound is in any way related to those outcomes,” Julian Fairey, the study's lead author and associate professor at the University of Arkansas, told NBC News. “But we have unexplained incidents of certain types of cancer from treated drinking water.”

However, treating drinking water with chemicals does reduce the presence of dangerous bacteria, especially those that cause cholera and typhoid, Alan Roberson, executive director of the Association of State Drinking Water Administrators, said.

“The reason you’re adding the chloramine — you want to kill the bacteria and viruses, you have a real risk-risk trade-off,” he explained. 

So, is tap water safe to drink? Is it time for you to invest in a water filter? Here's what to know.

Do I need a water filter?

The U.S. Centers for Disease Control and Prevention recommend testing your home's tap water for the presence of harmful germs or chemicals. Then you can purchase a water filter designed to remove what you found specifically in your water.

If your water does not have any harmful germs or chemicals, you may decide not to use a filter. The CDC also points out that most home filters, like those in your fridge or in a pitcher, do not remove germs and typically only remove heavy metals and make the water taste better.

If you get your water from a well or rain, you should test it regularly for the presence of harmful germs or chemicals. For people who get their water from a public system, your utility company must provide a water safety report every year.

Before purchasing a water filter, check for an NSF International certification to make sure the product works and the NSF International database to see what types of germs and chemicals your filter is certified to remove.

When it comes to chloronitramide anion, the chemical the recent study identified, you can check your utility company's website to see if they use chlorine or chloramine. An activated carbon filter, found in many fridge and pitcher filters, may remove the byproducts of chemicals used to disinfect tap water, but more research is needed, Wahman said.

This story first appeared on TODAY.com. More from Today:

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