Tap water contaminants cause an estimated 105,000 lifetime cancer cases, study finds

A drinking glass is filled from the tap. A new study found that contaminants in tap water cause an estimated 105,000 lifetime cancer cases in the U.S. ( Patrick Pleul/picture alliance via Getty Images )

Carcinogenic chemicals in tap water could be causing an estimated 105,000 lifetime cancer cases, according to a new study.

That means that for the 86 percent of the U.S. population served by community water systems, the overall cumulative lifetime risk is equivalent to four lifetime cancer cases per 10,000 people.

The study comes from scientists with the Environmental Working Group and was published in the peer-reviewed journal Heliyon.

Arsenic and disinfectant products were found to be the cause of 87 percent of the total number of estimated lifetime cancer cases. The rest of the cases were due to hexavalent chromium, carcinogenic Volatile Organic Compounds (VOCs) and radioactive chemicals.

The researchers behind the study say it’s important to note that the significant majority of community water systems analyzed for the study were in compliance with U.S. national drinking water standards.

“Compliance with national drinking water standards does not mean that water contaminant levels are reduced to concentrations that, according to the latest research, are entirely without health risk,” the study’s authors warned, “The majority of the cancer risk and estimated lifetime cancer cases correspond to community water systems that are in full compliance with drinking water standards.”

Researchers analyzed data from a multi-year research project that recorded the contaminant occurrence in community water systems in the U.S. They analyzed water quality profiles for 48,363 community water systems.

National attributable cancer risk due to tap water contamination was found to be approximately two orders of magnitude higher than the acceptable minimum risk set forth by the EPA. The study found that current contamination levels in tap water would result in four lifetime cancer cases per 10,000, but the EPA’s acceptable baseline of contamination would yield only one lifetime cancer case per million.

The study’s authors warn that their analysis could be conservative because of limitations to their data, which means that the cumulative risk might be even greater. They clarify that there are numerous other contaminants, “such as nitrosamines, unregulated disinfection byproducts, per- and polyfluoroalkyl substances (PFAS) and a variety of industrial and agricultural chemicals,” which are rarely monitored in community water systems, if ever.

What’s more, regulations for monitoring and reporting water contaminants are not always fully followed, and non-carcinogenic contaminants in tap water may also increase risk. Some research suggests that certain chemicals may act together to promote the formation of cancer.

Those concerned about their tap water can check local water reports and select a suitable filter, if necessary, which can be done quickly and easily through the Environmental Working Group’s drinking water database.