DETROIT — PFAS pollutants ride rivers across the Midwest and Canada to get to the Great Lakes. But not in the way a pair of University of Wisconsin-Madison researchers studying the forever chemicals expected, and that could impact how environmental officials regulate the chemicals.
Christy Remucal, a professor of civil and environmental engineering, and Sarah Balgooyen, a postdoctoral researcher, expected to find the most PFAS in waterways that run through heavily polluted places, like small streams that travel through Marinette where PFAS used at Tyco's Fire Technology Center contaminated groundwater, ponds and ditches.
The streams flowing through well-known polluted sites did carry PFAS, but Remucal and Balgooyen were surprised to find a concerning amount of PFAS in the samples they took from big rivers: specifically the Fox, Peshtigo and Menominee.
While those rivers carry less PFAS pollution per gallon of water, they also dump a lot of water into the bay.
"When we did the math on the loadings, combining the concentrations and the flow rates, we found out 'hey, these big rivers contribute two-thirds of the tributary loading to Green Bay.' That was a really surprising finding," Remucal said. "You look at the concentrations and they're not that bad, but they actually really, really matter."
To find PFAS, Balgooyen and Remucal spent five days in 2020 driving around the Bay of Green Bay, the narrow, 120-mile-long bay on Lake Michigan's Wisconsin side, collecting samples of water and sediment from 41 tributaries to the bay. They took the samples to a lab to analyze them and measure how much, if any, of 10 specific PFAS chemicals each one contained. They published their research in the journal ACS ES&T Water in February.
The big takeaway: Big rivers are a significant source of PFAS pollution into the Great Lakes, but not one that would be noticed by regulators who focus on cleaning sites with high concentrations of the pollution.
"Right now, we focus on sites that have high concentrations, and that makes a lot of sense," she said. "You don't want to be eating fish from those really impacted rivers or letting your dogs swim in that water.
"But if we want to think about protecting the Great Lakes, we have to think about these large rivers that have modest PFAS concentrations because they're a really important source."
PFAS, synthetic substances known as "forever chemicals," don't break down in the environment. They're used in lots of consumer products, from nonstick cookware to stain-resistant carpet to dental floss, and are known or suspected to pollute groundwater at hundreds of sites in Michigan, often near manufacturing facilities and landfills.
It's not a surprise that they reach the Great Lakes, said Daniel Jones, associate director of Michigan State University's Center for PFAS Research.
"The nature of most of these chemicals is that they’re water-soluble enough that water will carry them downward through soil until they reach the water table, and this water eventually flows into streams and lakes," Jones said. "Once the chemicals reach a body of water, they will be absorbed by creatures that live in the water."
Doctors are still investigating the health impacts of PFAS exposure, but the U.S. Centers for Disease Control and Prevention officials said exposure might lead to increased cholesterol levels, decreased vaccine response in children, changes in liver enzymes, increased risk of high blood pressure or pre-eclampsia in pregnant women, small decreases in infant birth weights and increased risk of kidney or testicular cancer.
Last week, the Michigan Department of Health and Human Services renewed its precautionary consumption advisory for Lake Superior smelt, recommending people eat no more than one serving per month after finding they contained elevated levels of a PFAS chemical, perfluorooctane sulfonate, or PFOS.
The Wisconsin Department of Natural Resources first discovered the PFOS levels in Lake Superior smelt early last year, which prompted Michigan's health department to issue its initial consumption advisory.
"There's more and more information coming out about (PFAS exposure) health effects," said Frank Bove, senior epidemiologist with the CDC's Agency for Toxic Substances and Disease Registry.
"I think eventually they'll be at least as important as the well-known chemicals, like asbestos, like lead, like trichloroethylene. I think it's an important contaminant. Like PCBs, they last forever, or almost forever, in the environment, so that makes them very dangerous for that reason alone."
PFAS in Detroit rivers
PFAS chemicals are not just a Green Bay problem. Balgooyen and Remucal said their work has implications throughout the Great Lakes basin, including Metro Detroit.
Tracie Baker, director of the Baker Water Lab at Wayne State University, agreed. She and a team of WSU researchers recently published a study in the Journal of Great Lakes research that documented some of the concerning chemicals that end up in Lake Ontario, Lake Erie and the surrounding rivers.
They found 50 compounds, including chemicals and products such as caffeine, nicotine, pesticides, antibiotics, fragrances and insect repellants.
PFAS pollution was most troubling, Baker said. The team found a mix of PFAS chemicals in five of the six sites they surveyed. Some of the chemicals they discovered have been phased out of production because of health concerns, but they stick around in the environment.
"They are forever compounds that are staying in the environment for a long time," Baker said. "The fact that they're in the sediment where they can potentially redistribute into the water, I find that concerning."
The research team collected water samples from six locations around Metro Detroit: the mouth of the Clinton River, Lake St. Clair Metropark, northeast Belle Isle, southwest Belle Isle, the mouth of the Rouge River and the Detroit River International Wildlife Refuge in the Trenton Channel.
They found some mixture of PFAS chemicals in water all of the sites except southwest Belle Isle.
They also looked for PFAS in the sediment at Lake St. Clair Metropark and the mouth of the Rouge River. They found it at both sites, Baker said.
While conducting follow-up sampling for a more comprehensive study of sediment pollution, the research team found PFAS in the sediment at more sites along the Detroit River, Baker said, including multiple sites in the Rouge River, the mouth of the Clinton River and again at Lake St. Clair Metropark.
The mouth of the Rouge River had the highest number of PFAS chemicals detected in its surface water, which the research team said may be related to its proximity to wastewater treatment plants, "a major source of PFAS in the eastern Great Lakes." It also is a heavily industrialized area, she said.
None of the sites had high enough PFAS concentrations in the water to trigger a state or federal cleanup action, Baker said, and PFAS in sediment is not regulated.
The Clinton River and Rouge River appeared to be primary sources of PFAS contamination, Baker said.
Researchers checked for about 30 PFAS compounds, Baker said, but there could be as many as 3,000-5,000 of those compounds that exist and maybe circulate undetected in the Great Lakes.
"Knowing what's there, knowing that it's in the sediment and the water and at the levels that we're seeing, I think hopefully can be used to help inform both the public and policy," Baker said.
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