MINNEAPOLIS-We've known for years that tiny bits of plastic, called microplastics, have become ubiquitous in the oceans and across the Great Lakes. We've also known that so many of these tiny plastic particles are floating around that they are ending up inside fish.

Another recent study found plastic particles in many popular brands of supposedly filtered and purified bottled water drawn from multiple sources, including wells and springs.

Now, a Minnesota researcher says she's tested municipal tap water taken from all of the Great Lakes and, not surprisingly, found plastic particles in almost all of them. The microplastics are even showing up in the plethora of beers now being brewed with Great Lakes water.

In a study published this month in the journal Plos One, Mary Kosuth - a masters graduate of the University of Minnesota School of Public Health who now teaches environment courses at Dunwoody College of Technology in Minneapolis - 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.

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To confuse the issue, however, Kosuth said she found no correlation between how much plastic was in the tap water in the city supply and how much was in the local beer.

"I tested a couple of beer brands from Chicago, and one of them had the highest number of plastic of all 12 beers tested and one had the lowest,'' she said. "So maybe it's not coming from the water source, or all of it isn't from the water. Maybe it's getting in during the brewing process. We don't know."

Plastic is so ubiquitous that Kosuth was even finding microscopic particles in the experiment's so-called "lab blanks,'' control samples of water that were ultra-filtered. It's not clear if the particles were simply in the laboratory's air and settled into the water.

"Our study basically confirmed that this stuff is everywhere,'' Kosuth said, noting that the same thing that makes plastic good for packaging-it's durability-makes it a serious problem in the environment.

In the study, a dozen brands of Great Lakes beer were purchased between January and April 2017. All of the beer manufacturers used municipal water - three from Lake Superior, four from Lake Michigan, one from Lake Huron, two from Lake Erie and two from Lake Ontario. All beers were packaged in 12- or 16-ounce aluminum cans, 12-ounce glass bottles or larger glass growlers.

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

Cosmetics, bags and clothing

Kosuth notes 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 echos what Northland 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 homes.

"We need to change behavior among people and industries, and improve policies to reduce the amount of single-use plastic," Kosuth said.

Kosuth hopes to continue her research to pinpoint the specific sources of microplastics in municipal water and beer.

Lawmakers at the state and federal level already have moved to get tiny plastic beads out of cosmetics, soaps and other home health care products, and many manufacturers agreed early to stop using the beads as scrubbing particles.

But it turns out many of the tiny plastic particles in the ocean and lakes started out as bigger plastic items - shopping bags, six-pack rings, food wrappers and other products. The Duluth News Tribune in 2016 reported a 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.

Other studies have found plastic fibers from synthetic clothing - think how many fleece clothing pieces you own - are flowing into the Great Lakes through sewage systems. Every time we wash our fleece sweaters and vests, tiny particles slough off into the washing machine and down the drain. Sewage treatment plants are not designed to remove them, so they flow into the lakes.

Each washing can slough thousands of plastic fibers into the environment, Kosuth said.

"Some of the fibers also are airborne,'' she noted, and fall from the sky into waterways.

The type of plastic can differ in each water source. In bottled water samples in other studies, most of the plastic found was in tiny chunks and was the same kind of plastic used to make the bottles. In Great Lakes tap water, Kosuth found, nearly all the plastic was in the form of fibers.

Human health impacts unknown

There has been little peer-reviewed research published on the potential health effects of microplastic buildup in humans. In a 2015 report by the science advisory panel to the New Jersey Department of Environmental Protection, physicians and scientists said more research needs to be done on human health related to toxins in plastic.

"Human health may ultimately be affected due to the transfer of these plastics and/or contaminant chemicals - absorbed pollutants, plastic additives - through the food web,'' the report concluded. "The current state of science regarding microplastics and nanoplastics, specifically with reference to ecological effects, suggests that it is plausible that human exposures are occurring and may lead to adverse health effects."

Kosuth said toxic chemicals, bacteria and even heavy metals often bind to plastics. And she noted plastics are made of chemicals - like BPA - that can leach into foods.

"There's all sort of exposure we may be getting from chemicals in the plastic and on the plastic,'' Kosuth said. "It's something that needs to be looked at much closer."

A Minnesota Department of health spokesman Wednesday said there is concern regarding the potential passing of toxins from plastics to people, but the agency has very little hard data on the effects of plastics ingested by humans.