Aldridge Creek in Huntsville, Alabama is a tributary of the Tennessee River, which is one of the most heavily polluted by microplastics in the world. Credit: Megan Jamerson

Hillary McKnight stomped along the banks of Aldridge Creek in Huntsville, Alabama on a cloudy March morning, trying to scare off snakes before she picked up a plastic water bottle on the water’s edge.

It was her second creek cleanup in two weeks after learning the bottles break down over time into microplastics — tiny plastic pieces less than 5 millimeters in length — that pollute waterways. Conservation group Tennessee Riverkeeper organized the event as part of their campaign to respond to growing concerns over plastic pollution in Southeastern waterways. A 2018 study identified the Tennessee River as one of the most heavily polluted by plastics in the world.  

Microplastics from bags, bottles, cosmetics, and even toothpaste have been found in the ocean, freshwater lakes, and arctic sea ice. They’re known to affect marine bacteria vital to producing oxygen and harm fish, insects, and potentially other organisms higher up the food chain.

Now, scientists are researching how they could threaten rivers, endangered species, and drinking water quality throughout the U.S. South.

“Microplastics are one of many sources of pollution that can really disrupt this aquatic ecosystem,” said Bernie Kuhajda, science program manager at the Tennessee Aquarium Conservation Institute. “Not only could it destroy this wonderful array of animals, it can also break that aquatic ecosystem and now we don’t feel safe swimming in our rivers, we don’t feel safe eating fish from our rivers, or we [will] have to pay a lot more to get clean drinking water.”

The 652-mile long Tennessee River is the largest tributary of the Ohio River. The main stem of its headwaters begin in Knoxville, and it winds through East Tennessee, down to Alabama and Mississippi, and then back up to Kentucky. Its reservoir system has an annual recreation value of $12 billion and its more than 40,000 square mile watershed is a freshwater source for 5 million people.

Microplastic levels were at 16,000 parts per cubic meter on the Tennessee River’s surface in 2017, according to the study by a German researcher who swam the length of the river and released a report last year. The samples, analyzed by the University of Georgia River Basin Center, revealed these levels were 80 times higher than Germany’s Rhine River, one of the most polluted in the world, and nearly twice as high as China’s Yangtze River, the third longest river in the world.

The Tennessee River dumps 32 million microplastic particles into the Ohio River every second, many of which travel down the Mississippi River to the Gulf of Mexico. That could have major ripple effects throughout the Southeast, where dense forests and intricate fresh and saltwater systems form biodiversity hotspots. Over a quarter of the species in the region are found nowhere else in the world: nearly two-thirds of U.S. fish, 90% of mussel species, and nearly half of the global total of crayfish call it home, according to a National Fish and Wildlife Federation report. Many of these species are already at risk of extinction, according to the U.S. Fish and Wildlife Service, and pollution threatens to exacerbate the problems they’re facing as the region urbanizes and develops.

“The more complex the ecosystem, the harder it’s going to be to figure out what a really widespread pollutant like microplastics could do to it,” Kuhajda said. “And if it does do something negative, it’s just going to affect a lot more species.”

Jill Jenkins, a microbiologist with the U.S. Geological Survey’s Wetland and Aquatic Research Center, said microplastics are “definitely going up the food chain and affecting the reproduction [cycles]” of marine life. Studies have shown microplastics reduce reproduction rates in oysters, which filter water as they feed; plastic pollution has caused dolphins and whales along the Florida coast to die.   

Hillary McKnight picks up a plastic bag in Aldridge Creek at a volunteer event organized by a local nonprofit. Credit: Megan Jamerson

Researchers’ work on the effects of microplastics in the region is complicated by a number of factors, including a lack of data about plastics in river ecosystems. Dr. Anna George, vice president of conservation science and education at the Tennessee Aquarium, said that without a “scientific consensus on exactly what the protocols are for looking at levels of microplastics,” it’s difficult to decipher what data from elsewhere around the world means for local ecosystems. She added that limited funding means fewer studies in an emerging field where much more attention is going to plastics in oceans.

The Environmental Protection Agency does not currently regulate microplastics or have a standard method for testing for them, leaving it up to states to create regulations. But industry interests have successfully lobbied against recent efforts to address plastic pollution.

In March, Tennessee became one of 12 states in the U.S., alongside Mississippi and South Carolina, to pass legislation that prevents local governments from banning items like plastics bags, straws, and take-out containers. It halted a growing movement in cities like Nashville that were considering stricter single-use plastics regulations similar to those in California, New York, and Washington D.C.

The Tennessee legislation matched the conservative American Legislative Exchange Council (ALEC) model bill nearly word-for-word and had the backing of Tennessee retail, grocery, and beverage organizations. ALEC has led a national effort to limit legislation banning or taxing single-use plastic items, arguing it adds an inconvenience and expense to shopping. ALEC did not respond to multiple requests for comment about the bill.

Tennessee State Sen. Richard Briggs, a Republican, backed the bill. “We did not need a hodgepodge of regulations around the state,” he said. “By having a statewide standard, it would make it easier to make a statewide ban in the future.”

He said he would like to sponsor that legislation in 2020 if he can get at least one major retailer like Kroger or Walmart on board.

A plastic bag ban is only part of the answer, said Marcus Eriksen, environmental scientist and co-founder of the 5 Gyres Institute, a nonprofit that consults with the United Nations about plastic pollution. Currently, the responsibility for plastic waste reduction falls on municipalities and individuals, not companies, since cities subsidize taxes paid by citizens for waste management, collection and recycling. As of 2015, the U.S. only recycled 9% of plastics, and some cities are backing out of recycling programs since China is no longer taking U.S. recycling.

“To make a product, you have to own the material through its entire life cycle all the way to its end game — the waste,” Eriksen said.

That means implementing policies that make industry responsible for their waste and encouraging them to use more efficient products and systems, he added. There are plenty of experiments to reduce plastics in the works, including chemical recycling, which breaks down plastics; bacteria that could help degrade plastics in landfills; and membranes in wastewater removal systems that capture and remove plastic particles.

Some experts say local efforts in the South can make a dent. Most surface level microplastics in the Tennessee River are from chemicals in plastic bags and packaging found in aging and leaking landfills and roadside litter, according to Dr. Martin Knoll, a geology professor at Sewanee University of the South who worked on the study. So not using plastic bottles — or picking them up off the river’s edge — is a way to start.

McKnight said she felt moved to participate as someone who enjoys the outdoors and is disturbed by how much trash she sees going to a local lakeside park everyday with her daughter. She uses the daily trips to teach her about pollution.

“It’s surprising and scary and disgusting,” McKnight said. “I don’t want my daughter to be exposed to that.”

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