New data show widespread chemical contamination of drinking water

A newly released trove of data reveals widespread pollution of US tap water with more than 320 chemical contaminants, including industrial chemicals and farm-related pollutants.

The latest information is part of a tap water database, created by the Environmental Working Group (EWG), and incorporates information from nearly 50,000 water systems collected between 2021 and 2023.

Though few chemicals were found exceeding the federal government’s legally mandated maximum contaminant level (or MCL), almost all US water systems nation-wide contained at least one contaminant at levels that surpassed the health guidelines developed by EWG that are based on scientific research of the harms associated with the various contaminants.

“This is a wake-up call,” Tasha Stoiber, an EWG senior scientist, said in a statement. “Outdated federal regulations continue to leave millions of people at risk of exposure to harmful substances.”

Among the chemicals commonly detected were per- and polyfluoroalkyl substances (PFAS), also known as forever chemicals, which were found in the water of at least 143 million Americans. Nitrates, found in agricultural runoff and linked to colorectal cancer and thyroid disease, were also commonly detected as well as disinfection byproducts caused by using chlorine.

Many of these disinfection byproducts — including chemicals called trihalomethanes, chloroform, haloacetic acids, and more — showed up in tens of thousands of water systems at concentrations far above what many health scientists consider safe.

Heavy metals, especially arsenic, were also frequently detected, as were some volatile organic compounds such as trichloroethylene (TCE). Hexavalent chromium, a carcinogen, was found in the water of 250 million people, according to EWG. This substance was infamously released in wastewater by Pacific Gas and Electric Company in Hinkley, California, in the 50s and 60s, eventually leading to a class action lawsuit initiated by Erin Brockovich.

Many of these chemicals are likely carcinogens or endocrine disruptors, according to EWG.

Legal limits for most of these substances have not been revisited in many decades, Stoiber said. For some, such as hexavalent chromium, there are no binding legal limits.

But “legal” doesn’t mean safe, the researchers behind the database stressed. A 2019 study by scientists with the group concluded that “over 100,000 lifetime cancer cases could be due to carcinogenic chemicals in tap water.” A historic exception are new limits for six PFAS chemicals, which came into force in April 2024.

The database includes information on agricultural chemicals such as the herbicide atrazine, a widespread water contaminant banned in the European Union, which is in the process of being reviewed for re-registration by the US EPA. The database revealed atrazine in concentrations above the recommended health limit in 479 systems that serve 3 million people.

The EPA has proposed a new framework for mitigating the impact of atrazine, while also raising the proposed allowable level in streams and lakes. The public can comment on the EPA’s proposal before April 4.

The database also notes whether water systems contain fluoride, which is widely added to the water to prevent cavities. Some recent studies cast doubt on the efficacy and safety of this practice. Utah just passed a bill to ban water fluoridation, which will go into force if and when the governor signs the legislation. Health and Human Services Secretary Robert Kenndy Jr. has previously stated he opposes the practice based on the risk it poses to children’s neurodevelopment.

There’s reason to worry that water quality regulations are not likely to improve any time soon at the federal level, advocates say, with the Trump Administration focused on reducing rules general, firing hundreds of scientists, and appointing industry-friendly people to prominent posts.

For example, Lynn Dekleva, a former lobbyist at the American Chemistry Council, an industry group that spends millions of dollars on government lobbying, was just appointed to run the EPA office in charge of approving new chemicals.

Worried by potential back-tracking on laws meant to protect water quality, California and other states have introduced legislation to set new regulations that would mirror the Biden Administration’s PFAS limits.

Water quality varies widely based on location, and generally larger water systems have more resources for removing contaminants and addressing problems when they arise.

“It’s fundamentally your right to know what’s in your drinking water,” Stoiber said. “Nobody voted to have contaminants in drinking water.”

(Featured image by Jacek Dylag via Unsplash.)