SCA Learns What Microplastics Are: Toxin Magnets
by Leslie Lytle, Messenger Staff Writer
The Feb. 20 Sewanee Civic Association (SCA) dinner meeting began with an update on the Community Chest and other projects. Martin Knoll gave a presentation on the insidious danger of microplastics, tiny pieces of plastic from grocery bags, packaging and bottles invading Tennessee waterways.
SCA President Brandon Barry announced the Community Chest had reached 57 percent of the $105,000 goal. This year’s campaign has pledged support to 25 local initiatives, among them Scouts, recreation opportunities, animal welfare, food and nutrition assistance, and help for the elderly. Join in enhancing the quality of life on the Plateau by contributing at
At the April 23 annual meeting, the SCA will elect officers, vote on a bylaws change removing language pertaining to parks, and approve the budget. The 2020-21 budget will remain the same as last year except for a reduction in insurance premiums due to the SCA’s release from responsibility for parks.
On March 21, at St. Mark’s Hall, 10-11:30 a.m., the SCA will host a Technical Support and Classifieds Q & A session led by Sewanee Classifieds Director Bentley Cook. The session will focus on safe use of the Internet.
Speaker Knoll took the audience on a tour into the world of microplastics following the journey of Andreas Fath, athlete and scientist, who swam the full length of the Tennessee River in the summer of 2017 to draw attention to a research study called TenneSwim. Knoll, professor of hydrology and geology, directed the project. Researchers took hundreds of water samples and tested for more than 600 chemicals. Two years before, Fath swam the German Rhine River with the same sampling done allowing for comparison of these similar-size rivers.
What did the Tenneswim researchers learn? Heavy metal levels were relatively low except around areas frequently using road de-icing agents. Herbicide and pharmaceutical levels were high, but the Rhine had even higher pharmaceutical levels. Knoll speculated this resulted because 10 times more people live in the Rhine watershed. High PFC levels in the Tennessee correlated with metal plating industry locals. In addition, artificial sweeteners’ concentration was higher in the Tennessee than the Rhine, possibly due to their use in animal feed.
Overall, though, the Tennessee River scored fairly well on water quality, Knoll said, except for one factor.
The Tennessee River had far higher levels of microplastics, plastic particles five millimeters or smaller in diameter. Tennessee samples showed 16,000 particles for every cubic foot of water compared to 200 for every cubic foot in the Rhine. The microplastics were primarily polyethylene, the stuff of grocery bags and packaging. The researcher sampled only the top two feet of water. Microplastics from PET products like bottles are heavier, Knoll said, and sink to the bottom.
Why are microplastics bad? The other toxic chemicals in the river—heavy metals, herbicides, pharmaceuticals, and PFCs—are drawn to the surface of microplastics, according to Knoll. The microplastics act like toxin magnets. Although the impact on humans is not known, in filter fish the toxin-laden microplastic impede digestion and cause endocrine disruption, which affects the expression of sex genes. Examination with a high-powered microscope showed microplastics clinging to the gills of carp and intestines of shad.
The TenneSwim research has prompted the Tennessee legislature to consider a bill banning all single-use plastic bags. Knoll stressed avoiding single-use plastic and practicing reuse. He pointed to Germany’s vigorous litter control and recycling as a model for how to clean up the Tennessee River, insisting, “We can get there.”