- For more than a century, U.S. utility companies have safely disinfected drinking water with chlorine and chloramine to prevent waterborne diseases such as typhoid.
- New research from Stevens Institute of Technology suggests that these disinfectants can react with organic matter to form hundreds of potential byproducts, many of which remain unstudied and may be more toxic than those currently regulated by the EPA.
- While the study emphasizes that tap water in the U.S. remains safe to drink, researchers note that home filtration or boiling can further reduce trace chemical byproducts.
A lot of work goes into ensuring the water that comes out of your tap is safe to drink. For more than 100 years, U.S. utility companies have used small doses of chemicals to disinfect water and prevent dangerous waterborne diseases before it reaches your glass. These include chlorine, “a disinfectant that kills germs in water,” and chloramine, “a group of chemical compounds that contain chlorine and ammonia.” The Centers for Disease Control and Prevention (CDC) explains that the type of chloramine used to disinfect drinking water is called monochloramine.
This is, by and large, beneficial and has helped prevent diseases such as typhoid from causing illness or mortality. However, according to recent research from Stevens Institute of Technology in New Jersey, these disinfecting chemicals could, in theory, create byproducts we don’t yet know about that could harm human health.
In January, the researchers published their study in the journal Environmental Science & Technology Letters, which examined how common disinfectants could react with organic matter in water to form potentially harmful byproducts.
One critical point the researchers put right out front in a press release about their study is that “Disinfecting drinking water is one of the most important public health achievements in human history.” That said, they also noted that some byproducts created by the chemicals added to water, such as “trihalomethanes and haloacetic acids,” have been linked to increased risks of bladder cancer as well as impaired fetal development.”
They also explained that the Environmental Protection Agency (EPA) sets safety standards for certain byproducts produced by the chemicals. But according to the researchers, there are many more that the EPA may not even be aware of.
“There are 11 such byproducts regulated by the EPA,” said assistant professor Tao Ye. “However, so far, research has identified several hundred more, which we don’t know much about — and they may be more toxic than the ones that are regulated.”
As Ye further explained, traditional toxicology can be costly and time-consuming. His team wanted to see whether AI could identify all possible byproducts and their potential harm to humans. “AI and machine learning are fundamentally transforming this process by enabling rapid, scalable toxicity screening, allowing us to assess hundreds of compounds that would otherwise be impractical to test experimentally,” Ye said.
So, Ye, along with his PhD student, Rabbi Sikder, and their collaborator Peng Gao at Harvard T.H. Chan School of Public Health, first examined toxicology data from studies of more than 200 chemicals, then trained an AI model on that data to predict the potential toxicity of other chemicals. While they already knew about 227 chemicals, their AI model predicted toxicity for a total of 1,163 byproducts, some of which had toxicity levels 10 times higher than those of chemicals already regulated by the EPA.
What’s in your tap water? Here’s how to find out
If you’re curious about exactly what’s in your tap water, you don’t have to guess. Every public water utility in the United States is required to publish an annual Consumer Confidence Report (CCR) — also called the annual drinking water quality report — detailing what’s been detected in your local supply. The report lists contaminants and compares their levels with EPA safety standards.
The team wanted to make it clear that this doesn’t mean your drinking water is unsafe, explaining that your “average glass of tap water will never have all these harmful byproducts together.” That 1,163 number is simply the number of compounds that could “theoretically” form, depending on whatever organic matter may be in your water and the chemicals used to clean it.
To be clear: The study doesn’t suggest Americans are drinking unsafe water — instead, it offers regulators a faster way to identify chemicals that may warrant future scrutiny.
“What we are doing here is our due diligence to see what else may need to be regulated, depending on what’s in the water and what you use to clean it,” Ye said. “All in all, our tap water is safe to drink, and our research intends to make it even safer.”
But if you’re still a little concerned about the idea of all this lurking in your water, Ye shared that it’s easy to filter out much of it with any widely available filter, or “you can boil it because when you boil it, these chemicals evaporate,” Ye said. “Both methods are easy to do at home.”
