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“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.”…