New research suggests that tribal communities that rely heavily on traditional food harvesting may face greater exposure to PFAS contamination, highlighting the need for a more holistic approach to environmental and public health research.
Gavin Dehnert of Wisconsin Sea Grant at the University of Wisconsin–Madison began the research at the request of the Voigt Intertribal Task Force after contaminants were discovered in the livers of several wolves. That initial work expanded into a broader investigation of PFAS movement through ecosystems commonly relied upon by tribal communities for food, using a “One Health” framework that examines human, environmental and wildlife health together.
Dehnert said PFAS exposure is not evenly distributed across landscapes and that communities relying on traditional foods may face higher risks in areas with elevated contamination. His findings were recently presented at the Great Lakes PFAS Summit.
One focus of the research was maple sap and syrup production. Dehnert examined whether different sap collection methods affected PFAS levels and found little difference between buckets, sap bags and tubing systems. PFAS was detected in seven of 10 sap samples, primarily short-chain compounds PFBA and PFPeA, which are more soluble in water and easily taken up by trees.
When sap was processed into syrup, however, PFAS concentrations increased dramatically. Because approximately 40 gallons of sap are required to produce one gallon of syrup, researchers tested whether PFAS would concentrate during boiling. Syrup samples showed PFAS levels 25 to 30 times higher than in sap, and a wider range of PFAS compounds was detected.
“We can listen to sugar bush trees and let nature tell the story,” Dehnert said.
The research also examined aquatic ecosystems in the Ceded Territory, focusing on 60 lakes selected based on tribal harvest activity. While many lakes showed low PFAS levels, some contained elevated concentrations. Dehnert said water sampling can provide rapid insight into contamination that may affect tribal harvest.
At Wild Rice Reservoir, PFAS levels in water were consistent across the lake, while sediment samples varied widely by location and by PFAS type. This suggests that contamination patterns in water and sediment can differ significantly.
Dehnert also studied wild rice (manoomin) and arrowhead (duck potato). While PFAS levels were higher in soils surrounding arrowhead plants than in nearby water, no PFAS was detected in the plant roots or leaves. Overall, aquatic plants appeared to absorb less PFAS than terrestrial plants.
Fish sampling revealed PFAS in all fish tested in Wild Rice Reservoir, with PFOS as the dominant compound. Walleye and northern pike showed similarly high concentrations, approaching or exceeding “do not eat” thresholds. In contrast, fish from Turtle Flowage, where PFAS levels were lower, showed limited bioconcentration.
Dehnert said these differences suggest that not all lakes with PFAS contamination will show elevated levels in fish, indicating the need for further research.
Current consumption guidelines exist primarily for fish, but not for other traditional foods such as maple syrup, wild rice, arrowhead, cranberries or mushrooms. Dehnert warned that tribal consumption patterns may not align with state guidelines, which often assume lower reliance on harvested foods.
“We want to make sure that these tribes are still going out, still harvesting food, still practicing their treaty rights,” Dehnert said. “So how do we balance protecting human health while also protecting treaty rights?”
He emphasized that PFAS contamination affects entire ecosystems, not just people, and called for collaborative research across disciplines to better understand how PFAS moves through interconnected natural systems.