Microplastics Flood Tennessee River Watershed

By Eric Halvarson

When Andreas Fath swam the Tennessee River in 2017, he was unaware that approximately 30,000 particles of microplastics could be found floating in his immediate vicinity at any given time.

Fath, a German scientist from Furtwangen University and an accomplished long-distance swimmer, partnered with Sewanee University Professor of Geology Martin Knoll for “TenneSwim.” Fath swam the entire 652 miles of the Tennessee River in 34 days while the team collected water samples along the way. Fath had completed a similar swim along the Rhine River in Europe, prompting Knoll to contact him in 2015 about researching and swimming an American river.

In 2017, a team of volunteers and students joined Fath and Knoll on their journey to test the river for contaminants and raise awareness of water quality issues.

According to the U.S. Environmental Protection Agency’s water quality data, “the river looks pretty clean,” Knoll says. The Tennessee River, a watershed with a population of 5 million people, had much lower levels of pharmaceuticals and pesticides than in the Rhine, which drains a watershed with 50 million people.

However, the “big shock,” Knoll says, came when the water samples were tested for microplastics, which are not regulated by the EPA. Results showed microplastics between 0.25 and 0.5 millimeters in size were present at a rate of 16,000 to 17,000 particles per cubic meter of water in the Tennessee River, compared to the Rhine’s 200 particles per cubic meter.

“That’s incredible,” Knoll says.

Microplastic studies on freshwater wildlife are limited, but saltwater studies have shown these plastics can weaken an organism’s ability to reproduce and digest food by interrupting hormonal functions in the body. Microplastics and toxins attached to them can accumulate in fish and eventually be consumed by humans through food or water.

Knoll noted that most microplastics sink, and the TenneSwim team only tested waters close to the surface. His samples found high levels of plastic at all points in the Tennessee River.

“It’s a problem through the watershed,” Knoll says, which leads him to believe the problem is litter. “In my mind, that’s the source of the majority of this stuff, is litter.”