There Isn’t One Groundwater Problem in the Midwest

Midwesterners frequently hear about nitrate contamination in groundwater. It’s discussed in town halls and classrooms from northern Minnesota to southern Missouri and everywhere in between. But groundwater contamination varies substantially, depending on where you live and where your water comes from.

Someone using a shallow well near an industrial contamination site could face a very different concern than someone whose municipal water system draws from a deep aquifer. 

David Cwiertny, professor of civil and environmental engineering and chemistry at the University of Iowa and director of the Center for Health Effects of Environmental Contamination, says understanding local differences is the first step toward protecting yourself and your community. “We have to be very careful when we talk about environmental contamination that has impacts on human health [not] to make Iowans think it’s going to be one thing everywhere,” Cwiertny says.

PCE and TCE

PCE, or tetrachloroethylene, and its degradation product TCE, or trichloroethylene, are chemicals historically used as cleaning solvents. 

PCE was historically used in dry cleaning, and TCE was used to degrease machinery in industrial and military settings. Cwiertny says that large vats of these solvents were historically used to clean machine parts. 

When the chemicals spilled, they could seep into groundwater. Because they are heavier than water, they sink and accumulate in bedrock, where they can slowly leach into the water over time. The Environmental Protection Agency classifies PCE and TCE as known human carcinogens with links to things like kidney cancer, liver cancer and non-Hodgkin lymphoma.

Cwiertny also discussed concerns about organ damage, including the liver, kidneys and central nervous system. In December 2024, the EPA finalized rules that prohibit the use of TCE and prohibit or phase out many uses of PCE. But chemicals already in the ground can remain a problem.

Cleaning them up can also create another environmental concern: As these chemicals break down during treatment, they can form substances such as vinyl chloride, which also poses serious health risks.

PFAS

PFAS, or per- and polyfluoroalkyl substances, are a family of thousands of different chemicals used in industrial and commercial products since the mid-1900s. Two of the most common PFAS found in groundwater contamination are PFOS, or perfluorooctane sulfonate, and PFOA, or perfluorooctanoic acid.

PFAS are often called “forever chemicals” because they can persist in the environment and human bodies for decades or longer. Cwiertny describes them as “bioaccumulative,” meaning they can build up in our bodies and be “problematic for health at really low levels.” One source of PFAS exposure is firefighting foam. Due to exposure to the foam, “firefighters have had a higher incidence of things like testicular cancer,” Cwiertny says.

PFAS can be difficult to remove from groundwater. Even when treatment pulls the chemicals out of the water, Cwiertny says, “you still have a waste stream that you have to manage, and that can be difficult.”

Minnesota has one of the largest PFAS pollution plumes in the United States. The Minnesota Center for Environmental Advocacy says the plume is connected to decades of PFAS manufacturing and disposal by companies including 3M and describes PFAS as “one of the most toxic and pervasive public health threats of our time.”

Radium

Not every groundwater contaminant comes from something we put into the environment. Radium occurs naturally in some areas because of the underlying geology. Radium is a radioactive product of the decay of thorium, which is present in the bedrock of some areas, including northern Iowa and Wisconsin.

“We tend to think of it as a municipal water system issue because municipal wells tend to be deeper and can access the deeper aquifers,” Cwiertny says. The EPA began regulating radium in the 1970s because of health concerns, including an increased risk of bone cancer.

Unlike an industrial chemical, radium cannot simply be removed from the environment at its source because it is naturally present in the geology. One way communities can remove radium from drinking water is through water softening, which uses ion exchange to capture things that are positively charged, including radium.

In Grinnell, Iowa, municipal water comes from the Jordan Aquifer, which contains trace amounts of radium. The city took its municipal water softener offline in 2021 because of deteriorating equipment, and radium levels have since climbed above the EPA’s regulatory standard of 5 pCi/L.

The city is building a new water treatment plant designed to reduce radium levels below the federal standard, with the plant expected to be operational in early 2027.

What’s in Your Water?

There is no single groundwater problem affecting the entire Midwest. Water quality can vary from state to state and town to town.

“You need to know what’s in your water and prioritize the things that are your greatest risks,” Cwiertny says. “Just get your water tested to know whether or not it’s contaminated and what it’s contaminated with.”

For people on public water systems, that can also mean looking at information from their local water provider. “If you’re on a public water supply and you’re concerned about what’s in your water, talk to your public water provider,” Cwiertny says. “They know what’s regulated. They are required by law to meet those regulations. They do testing. They should be able to share a wealth of information with you about what you’re drinking.”

Knowing what is in your water can help you understand which contaminants are relevant to your community and what questions to ask about treatment.