The invisible problem

Microplastics are clogging our rivers — and have for decades

by Sydney Cromwell

Plastic pollution is easy to spot: takeout containers on the side of the road, plastic bottles bobbing down a river.

There’s far more plastic, however, than meets the eye. Microplastics (plastic particles under five millimeters long) are in the water we drink, the clothes we wear and even the air we breathe. Some are created intentionally, while others are broken down from larger pieces by sunlight, water and other environmental wear and tear.

“If you’ve ever used a single-use plastic item in your life, you’re part of this problem,” Tennessee Riverkeeper Executive Director David Whiteside said.

Research in the Tennessee River is showing that microplastics are abundant, and they’ve been around for a long time. Their health impacts — for fish or for humans — are still unclear.

A wide shot of the Tennessee River taken from above, with woodland areas and a bridge visible in the background.
The Tennessee River as seen from the top of the Wilson Dam, near Florence. Photo courtesy of the Tennessee Valley Authority.


In August 2017, Andreas Fath stepped into the Tennessee River in Knoxville. Thirty-four days later, the professor and chemist from Germany’s Furtwangen University emerged from the river in Paducah, Kentucky, with startling new data on river pollution.

Fath swam the entire 652-mile river, including the portion that loops through northern Alabama and feeds Guntersville, Wheeler, Wilson and Pickwick lakes. During the “Tenneswim,” he attached a passive sampling device to his body to measure the amount of microplastics and man-made chemicals he encountered.

“This was sport meets science project,” Fath said.

What he found, from one end of the river to the other: 16,000 to 18,000 microplastic particles per cubic meter.

“It was shocking to measure these high amounts of microplastics in the Tennessee River,” he said.

A similar swim he had done in the Rhine River in 2014, by comparison, had only 200 particles per cubic meter.

“Rivers are a mirror image of society, and society in the U.S. lives different … than in Germany,” Fath said.

The Tennessee River and its tributaries are home to hundreds of aquatic species and provide drinking water for 5 million people in Tennessee and northern Alabama. The microplastic pollution that Fath found earned coverage in National Geographic, prompted proposals for plastic bottle regulation in Knoxville and caused the Tennessee Riverkeeper to make macro- and microplastics a top priority for advocacy and education.

“The Tennessee River has become the poster child for freshwater microplastic pollution in the world, certainly in the country,” Whiteside said.


While Fath’s Tenneswim painted a picture of the Tennessee River’s modern microplastic pollution, biologist Ben Keck recently decided to take a look into the past.

Keck is the director and curator of the David A. Etnier Icthyological Collection, a library of 450,000 pickled fish specimens collected by the University of Tennessee, Knoxville and the Tennessee Valley Authority since the 1960s.

Keck and UTK students are currently dissecting fish specimens gathered upstream of Chattanooga. They are focusing mainly on three species with different food sources: the stoneroller, the whitetail shiner and black bass, to see how diet affects their plastic exposure.

A fish specimen has been removed from its jar and set on a table. The jar is visible in the background, identifying the fish as Micropterus dolomieu lacepede (smallmouth bass), captured in October 1988 from Abrams Creek.
A pickled bass specimen from the Etnier Icthyological Collection, waiting to be examined as part of a study on microplastics in the Tennessee River. This specimen was originally collected in 1988. Photo courtesy of Ben Keck.

Some of the earliest specimens they’ve looked at were gathered in Abrams Creek, a tributary of the Tennessee River, in the 1970s.

“Right away, we found microplastics covering the gills and the gut,” Keck said.

Most of the plastics they have found so far have been fibers, likely from clothing. While their work is still in progress, he said the amount of microplastics they’ve found so far is “honestly quite shocking.”

Keck plans to publish the results of his research this fall. Eventually, he would like to study samples from the entire Tennessee River to see if fish have differing levels of microplastics in urban and rural portions of the river.

Keck said study of microplastics is still in the “discovery” stage and a lot more research is needed to understand the role microplastics are playing in local ecosystems.

“It spurs a whole lot more questions,” he said.

For his part, Fath will be exploring some of those questions with an expedition to sample snow and ice in the Norwegian wilderness for microplastics in January 2022. He will follow this up with another swim next May and June, this time carrying his sampling device down the length of the Danube River.


Microplastics are ubiquitous, from glacial ice to the Marianas Trench. Fath has even found them in the remote Alps, where the Rhine River gets its start.

And the fact that microplastic levels are consistent throughout the Tennessee River means that the pollution isn’t coming from one particular source; it’s an inescapable byproduct of human life.

Fish and other aquatic species can take in microplastics through their gills or by confusing the particles with their regular food sources. Most of those plastics do not accumulate in the fish and pass out of their systems in a matter of days, Keck said.

However, Keck said he is particularly concerned by fibers that get trapped in gills, which can hinder the animals’ ability to breathe.

Plastics also have the potential to cause internal injuries, and larger pieces may not pass through an animal’s system successfully. Some studies are showing changes in the way fish and oysters behave, including feeding and reproduction, after plastic consumption.

“Microplastic is like a Trojan horse, which brings pollutants into our bodies.”

Andreas Fath, Furtwangen University

But microplastics can also carry hitchhikers with them, in the form of toxic chemicals that attach to the surface of the plastic, Fath said. He put the microplastics caught in his sampling device under a microscope and found that the particles acted “like a magnet” for chemicals from pesticides, household cleaners and even medications that wind up in the water system.

“[It’s] like a brain, … very high surface areas, a lot of parking places for chemicals which are not that soluble in water, which prefer the surface of microplastics,” he said.

Keck said microplastics that stick to a fish’s gills create a good opportunity for those hitchhiking chemicals to be absorbed. Some can be absorbed through digestion as well.

“At the end of the day, this plastic will turn up on your plate,” Fath said.

Microplastics are also making their way into human bodies through the air we breathe, the food we eat and household items. A 2020 study published in Environmental Science and Technology estimated that adults and children consume or inhale anywhere from 74,000 to 114,000 microplastic particles every year. 

A report commissioned by the World Wildlife Fund International estimated in 2019 that people consume an average of five grams of plastic every week, about the weight of a credit card.

“Our water treatment filtration plants are not designed to filter these plastics out. So we are ingesting an alarming amount of these microplastics,” Whiteside said.

Fath is concerned by the potential health effects of the unwitting chemical consumption that happens due to microplastics.

“Microplastic is like a Trojan horse, which brings pollutants into our bodies,” he said.

There isn’t enough research yet to definitively say whether the plastics and chemicals we consume are passing harmlessly through our bodies or whether they’re hurting our health in ways we don’t yet understand. As with studying the ecological effects of microplastics, Keck said the research being done now is just the starting point.

Continuing study on microplastics will be important, but Fath said he doesn’t want to wait around to act.

“I think it’s time to react before we have the proof on the impact to the ecosystem, because then it is too late to turn the wheel,” Fath said.


Due to their size, microplastics are difficult to filter and remove from the water, and that’s before they break down even further into “nanoplastics,” particles less than .001 millimeters long.

The better solution is to prevent plastics from reaching the Tennessee River — and other rivers — in the first place.

The Tennessee Riverkeeper organizes cleanups of cigarette butts, bottles, shopping bags, single-use wrappers and other plastics along the river as “one of the obvious solutions that we can do,” Whiteside said.

“Those are an obvious eyesore. The litter, it’s unsightly. It’s not something people want to look at, especially when they go down to the beautiful creek or river.”

David Whiteside sits among garbage bags of collected litter, along with tires and a traffic cone, during a river cleanup.
Tennessee Riverkeeper Executive Director David Whiteside at a litter cleanup event. Photo courtesy of David Whiteside.

He also hailed the city of Decatur, which contracted a Mobile-based company called Osprey Initiative to install litter collection devices in waterways around the city. Osprey has also installed “Litter Gitters” in communities around Birmingham and the Gulf Coast.

Where those litter traps have been installed in Decatur, Whiteside said, “the litter is reduced significantly, to the point where we almost don’t have to do cleanups at all.”

Fath said he would like to see total plastic recycling. In Germany, he said, there is an annual cleanup day along the Rhine River. The most recent cleanup removed 200 tons of litter, preventing that plastic from being broken down by the river into microplastics.

“Plastic is not a bad material, it is very smart as long as it stays in the loop of use,” Fath said.

Whiteside said the Tennessee Riverkeeper has a public education program on microplastics, to show consumers the impact of the styrofoam takeout container or the plastic fork or straw that they may not think about.

“Telling as many people as we can, that is a very significant tool in this battle,” he said.

Keeping the public’s attention on the issue is part of the problem. The plastic bottle regulations that were proposed in Knoxville after Fath’s 2017 Tenneswim were never actually passed.

Solving microplastic pollution will take more than individual behavior changes, however. Industrial and commercial businesses will also have to move away from the ever-present single-use and disposable plastics.

Whiteside said that can include tightening pollution regulations or “common-sense rules” like making single-use plastics available by request only.

“If we did that one change in this country, [it] would reduce hundreds of thousands of single-use plastics from going to the landfill every day,” he said.

Removing these near-invisible pieces of plastic from our ecosystems — and our bodies — will likely require a total cultural shift in the way we view plastic use.

“We all are a little bit guilty,” Whiteside said.

The Tennessee River has a “grim litany” of pollution issues — including microplastics, industrial and agricultural chemicals, raw sewage, pharmaceuticals and other substances — according to Tennessee Riverkeeper Executive Director David Whiteside.
You can learn more about some of the sources and impacts of these pollutants here.

Main article image courtesy of Oregon State University, via Wikimedia Commons.

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