GRAND PORTAGE 鈥� Dozens of chemicals, from DEET bug spray to antidepressants, hormones, antifungals, antihistamines, antibiotics and heart medications, are showing up in fish in even remote lakes across Northeastern Minnesota and are impacting the health of those fish.
That was the finding of a lengthy research project by the University of Minnesota and Grand Portage Band of Lake Superior Chippewa published last month in the journal .
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Researchers took samples from hundreds of fish from two dozen lakes and rivers in developed, urban areas as well as lakes with a few cabins and homes and lakes with little or no human impact.
Many of the substances found in those samples are 鈥渃hemicals of emerging concern,鈥� which scientists suspect can cause health issues such as cancer in fish, wildlife and humans. And fish in remote lakes showed as many or more signs of health issues as those in urban areas.
鈥淥ur results suggest that the health of fish is adversely affected in lakes in various ways across a spectrum of鈥� human development, the study concluded, 鈥渇rom remote, undeveloped wilderness to lakes directly impacted by wastewater effluent.鈥�
The study found 鈥減otentially concerning health effects at the organism level and the presence of some (chemicals of emerging concern) that could lead to potential population-level effects.鈥�
"We found them in every system we looked in. We tested for 140 possible chemicals and found 117 of them," Seth Moore, environment and natural resources director for the Grand Portage Band, told the Duluth News Tribune.
While previous studies have looked at the distribution of chemicals, and others the impact of chemicals on fish in labs, this is the first to look at how chemicals in widespread Minnesota lakes and rivers are impacting wild fish. It's a follow-up to a 2020 report by the same researchers that outlined where the chemicals are showing up.
Some of the chemicals were found at low doses, but every fish was carrying some and even fish in remote lakes were found to have health issues. How much those health issues in individual fish may be impacting fish populations remains unclear, said Tiffany Wolf, a University of Minnesota researcher in the College of Veterinary Sciences.
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While scientists expected to find many or most of the chemicals in the St. Louis River Estuary, for example, where the Western Lake Superior Sanitary District discharges treated wastewater from the Twin Ports area, they didn't expect to find so many chemicals in remote lakes to the north. From Lake Vermilion to Shagawa to Trout to Devilfish to Lake Superior and many others, the chemicals were ubiquitous in both the water and the fish.
鈥淭he fact that we found most of the contaminants we were looking for even in very remote lakes, with little human impact, that was very surprising,鈥� Wolf said. 鈥淭here wasn't a site we tested where we didn鈥檛 find something.鈥�
Fish exposed to chemicals had tissue and organ abnormalities, although it couldn鈥檛 be proven what caused those issues.
An antifungal chemical that is known to have impacts on estrogen production was found in many fish and may be impacting egg production in female fish. Other chemicals may be impacting fish livers or growth. Antidepressants may be making some fish act less aggressively, meaning they may be more likely to get eaten by another fish. In some cases, yellow perch carrying some chemicals were found to have more parasites.
鈥淲e know how some of these chemicals are getting into the developed systems, those affected by wastewater treatment plants. But I suspect it鈥檚 getting into the undeveloped systems by airborne deposition,鈥欌�� Moore said.
Indeed other studies have found many of the same chemicals in rainwater and snow, and it follows an insidious pattern like mercury, microplastics and PFAS 鈥渇orever chemicals鈥� 鈥� all of them are showing up in lakes and fish everywhere, far from any point source, some of them blowing in the wind from local, regional and even global sources.
鈥淭he chemicals we found are getting into the atmosphere,鈥� Wolf added.
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DEET, the common ingredient in most mosquito repellents, was found in every single test sample. It鈥檚 unclear if it鈥檚 simply washing off humans or getting into the lakes some other way. It is entirely unknown what impact DEET might have on fish.
鈥淚t just shows how large our human footprint is,鈥� Moore said, adding that chemicals intended to help humans are having major unintended consequences, passing onto fish and likely back to humans who eat those fish.
鈥淚鈥檇 suspect that the people who eat fish are acquiring some level of those contaminants. Probably in low doses. Maybe with no impact. But we really don鈥檛 know,鈥� Moore said.
Efforts have been underway for 20 years to convince people to dispose of their pharmaceuticals properly by recycling them at a pharmacy or other facility and not to flush them down the drain or toilet. Wastewater treatment plants are designed to remove biological impurities but not chemicals such as pharmaceuticals. Moore called for tougher laws, not just voluntary programs, requiring safe disposal of pharmaceuticals.
Wolf said much more research is needed on the impact of the 鈥渃ocktail of chemicals鈥� that are being found in northern Minnesota fish, and then ways to keep those chemicals from getting into our lakes.
Moore said researchers hope to move on to look at chemical buildup in terrestrial animals like grouse, deer and moose that many Grand Portage Band members rely on for food.
Researchers noted that the results are especially important for members of the Grand Portage Band who rely heavily on subsistence fishing, hunting and gathering for their food and traditional way of life. Band members should have the right to harvest and eat food that isn鈥檛 tainted by human toxins, Moore said.
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Funding for the research came from tribal, state and federal sources.
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