ST. PAUL and DULUTH, Minn. — Minnesota Sea Grant researchers are helping scientists better understand how PFAS, often called "forever chemicals," move through the atmosphere and enter the Great Lakes through rain and snow.
Researchers will present three analyses from a United States Geological Survey-funded project called Tracing Atmospherically Deposited PFAS from Source to Sediment in the Great Lakes Region at an upcoming scientific conference. The work is based on two years of precipitation monitoring at five sites in Minnesota and Michigan and investigates the role atmospheric deposition plays in PFAS contamination.
"Our project is helping scientists understand not only how much PFAS is entering the Great Lakes region through precipitation, but also where it may be coming from and what current monitoring approaches may be missing," said project lead, presenter and MNSG Research and Fellowship Coordinator Alex Frie.
PFAS, or per- and polyfluoroalkyl substances, are a large group of human-made chemicals used in products such as nonstick cookware, waterproof clothing, firefighting foam and food packaging. Many PFAS break down very slowly in the environment and can accumulate in water, wildlife and people.
The research team includes Minnesota Sea Grant Postdoctoral Associate Miguel Bernardez, Graduate Research Assistant Quinn Whiting, and Frie.
Their work will be presented at the National Atmospheric Deposition Program Scientific Symposium , June 9-12, 2026, in Madison, Wisconsin. The project is a close collaboration among Minnesota Sea Grant, the University of Minnesota Natural Resource Research Institute and the National Atmospheric Deposition Program at the University of Wisconsin-Madison.
Frie's presentation will focus on the finding that PFAS was in every rain and snow sample collected during the two-year monitoring period. Researchers measured weekly precipitation samples and found that atmospheric deposition appears to be a widespread and persistent source of PFAS contamination across the region.
"We were surprised not only by the frequency of PFAS detection but also by the significant variability in its composition and concentration," said Frie. "These findings underscore the ability of continuous monitoring to capture short-term spikes and better understand the sources and extent of contamination in rain and snow."
Bernardez's presentation will focus on using atmospheric modeling to trace where air masses traveled before rain or snow events occurred. By combining those air-movement patterns with PFAS measurements, researchers are beginning to identify possible source regions and better understand how weather and atmospheric transport influence PFAS contamination.
"The most challenging aspect of modeling the atmosphere is the sheer scale we have to think about," said Bernardez. "We are attributing concentrations of nanograms per liter over areas greater than 100 square miles. It takes some very clever math and a lot of hard work to get the considerable amount of data that is needed."
Whiting's presentation will focus on whether current PFAS monitoring methods may be missing a substantial portion of fluorinated chemicals present in precipitation. Researchers compared measurements of 33 known PFAS compounds with broader measurements of extractable organic fluorine and found that standard PFAS testing explained only a small fraction of the fluorinated chemicals detected. Additional screening identified roughly 300 unique fluorinated chemical signals, including pesticides, pharmaceuticals, PFAS precursors and other compounds not routinely monitored.
"Many people assume standard testing captures all PFAS, but current monitoring only measures a small share of the thousands of PFAS that exist," said Whiting. "That approach is practical, but it can miss other chemicals contributing to contamination. By using methods such as non-target analysis, we can identify PFAS that are not usually included in routine testing and get a clearer picture of the total PFAS present in an environment."
Collectively, the studies suggest PFAS contamination is not only linked to wastewater discharges or local industrial sources. Airborne transport may carry PFAS and related fluorinated chemicals across long distances before they return to Earth in precipitation.
The findings also highlight the importance of long-term monitoring. Researchers observed seasonal differences in atmospheric contamination, with some fluorinated compounds increasing during spring and summer and decreasing during winter.
"This work will help resource managers create realistic PFAS budgets by constraining atmospheric inputs to watersheds and identifying potential contributors to local pollution," said Frie.
The presentations build on growing scientific interest in atmospheric PFAS transport and may help improve future environmental monitoring and pollution management efforts in the Great Lakes region.
Minnesota Sea Grant is a system program of the University of Minnesota and one of 34 federal-university Sea Grant partnerships across the country supported by the National Oceanic and Atmospheric Administration in Great Lakes and coastal states that encourage the wise stewardship of our marine resources through research, outreach, communication, education and technology transfer.
