DULUTH — We’ve already known that microplastics are floating throughout Lake Superior, that they are in our drinking water, that they are in fish we catch and that they are even in our beer.

So maybe we shouldn’t be surprised that researchers from the University of Wisconsin-Eau Claire have found tiny pieces of plastic in the Boundary Waters Canoe Area Wilderness, the most pristine area of northern Minnesota.

Researchers found microplastics in earthworms, in the water and in the soil that they collected this summer from sites within the BWCAW, said Todd Wellnitz, professor of biology and the faculty leader on the research project.

“We found 80 pieces of microplastics in one earthworm that we examined,” Wellnitz said in a statement. “That blew me away.”

Plastics that are less than five millimeters in length, about the size of a sesame seed, are known as microplastics. They can come from a variety of sources, including synthetic clothing, soaps and toothpaste and plastic packaging and containers such as water bottles.

While microplastic beads have been banned from many consumer products, hundreds, even thousands, of plastic fibers can be shed from one fleece garment every time it’s washed. And larger pieces of plastic — including water bottles, plastic bags and packaging of all sorts — eventually break down into microplastics when left out in the environment. Once they reach the micro size, they seem to persist indefinitely.

While significant research has been done on the presence of microplastics in oceans, rivers and the Great Lakes, less has been done on plastics in smaller, freshwater lakes.

"We're finding microplastics in the Boundary Waters, and that’s a big deal,” Wellnitz said. “No place is pristine now; microplastics are everywhere. It’s all over the planet, and we’re just realizing it.”

The UW-Eau Claire research team, including, from left, Megan Vaillancourt, Todd Wellnitz and Monica Dickson, is continuing to study samples of soil and water taken from the BWCAW during two trips there this summer. Photo courtesy UW - Eau Claire.
The UW-Eau Claire research team, including, from left, Megan Vaillancourt, Todd Wellnitz and Monica Dickson, is continuing to study samples of soil and water taken from the BWCAW during two trips there this summer. Photo courtesy UW - Eau Claire.

After finding microplastics in the earthworms on a June excursion, the researchers returned to the BWCAW in August, this time collecting soil, water, earthworms and crayfish samples.

The samples were collected from areas primarily near campsites, said Reed Kostelny, a junior environmental biology major from Appleton, Wis. They found the most microplastics in samples taken from the lake closest to the Boundary Waters entry site.

“We know that earthworms do consume microplastics,” Kostelny said of their findings. “Now that we have our early data, we want to know more about the worms and how the microplastics could move up the food chain.”

Since birds, fish and other wildlife consume earthworms, microplastics have likely already entered the food chain in the Minnesota wilderness area, Wellnitz said.

Earthworms are not native to the Boundary Waters area but are brought in by visitors who come to fish the many freshwater lakes found within the area, said Megan Vaillancourt, a senior microbiology major from Stillwater, Minn.

“Fishermen bring the worms in, and the worms are ingesting the plastics we bring in with us,” Vaillancourt said. “That’s a double negative for the area.”

Most visitors do embrace the “leave no trace” mantra in the BWCAW. But microplastics shed easily, so they may be coming from clothing, blankets, tarps and other supplies that visitors routinely bring into the Boundary Waters, Vaillancourt said. Since microplastics are so small that they can’t easily be seen, people have no idea they are leaving them behind.

Microplastics also can move from place to place via rain or wind, so they likely are entering the Boundary Waters in multiple ways, the researchers said.

Microplastics first made headlines in 2013 after scientists, including Lorena Rios-Mendoza, assistant professor of chemistry at the University of Wisconsin-Superior's Lake Superior Research Institute, dragged super-fine mesh across the Great Lakes and caught millions of plastic pieces.

In a study published in 2018 in the journal Plos One, Mary Kosuth, a master's graduate of the University of Minnesota School of Public Health, found that eight of nine tap water samples taken from all five Great Lakes had plastics in them. And Kosuth, a Duluth native, found that all 12 brands of beers she tested brewed with Great Lakes water had plastics inside. It's a global phenomenon, she noted, with a 2014 study reporting plastic found in 24 brands of German beer.

Kosuth also looked beyond the Great Lakes and looked at tap water from 159 municipal sources from 14 countries, with 81% carrying plastic particles.

Kosuth noted that global plastic production has skyrocketed from 30 million tons in 1970 to 322 million tons in 2015, and each year more of that stuff ends up in the environment. She echoed what researchers and conservation activists have said for years: If you want to get plastic out of the lakes and oceans, you need to get it out of your hands and your home.

A 2016 study by Rochester Institute of Technology researchers that estimated nearly 22 million pounds of plastics enter the Great Lakes every year.

Those products get blown (or thrown) into the lakes and eventually disintegrate into plastic bits, some of them smaller than grains of sand. But the plastic bits never go away, and they have spread across the Great Lakes ecosystem.

Scientists say the human health ramifications of ingesting plastic in water, beer, fish and other items remain unknown. Not only may the plastic itself be bad but the bits can also carry other contaminants.