How do you like your credit cards?  Warm and dripping with butter, or cold and loaded with ranch dressing?

Every week on average we ingest a “credit card’s worth” of tiny plastic particles in drinking water, officials of the Cumberland River Compact told members of The Rotary Club of McMinnville on Thursday.

And what’s the source of these omnipresent plastic microparticles in our diet? The disposable beverage bottles, plastic shopping bags, and other consumer waste we let go into the environment and waterways, the Rotary presenters said.

“We ingest a credit card’s worth of plastic a week,” said Ross Miller, stream and field program manager at the Cumberland River Compact, a Nashville-based nonprofit engaged in environmental activism.   

The Caney Fork River and its tributaries contribute to the flow of the Cumberland River, which eventually goes in the Mississippi River and empties into the Gulf of Mexico.

Plastic products when released to the environment break down into microscopic particles but do not completely dissolve into the non-toxic chemicals from which they’re made — carbon, hydrogen and oxygen. These tiny remnants of our consumer-driven, throw-away lifestyle are much smaller than the width of a human hair.

A familiar example is the single-use plastic shopping bag littering roadways and parking lots. Rainfall washes the bags into streams and storm water drains, then into rivers like the Barren Fork which serves as the drinking water source for McMinnville and much of Warren County. The decomposing plastic grains are so small they pass through the normal filtration process and into the pipes in our homes, schools and restaurants.

In a WCPI 91.3 “FOCUS” interview recording following their Rotary appearance, Miller and CRC associate Jed Grubbs cited studies into the human health effects of the microplastics. While scientific investigations are ongoing into the possible toxicity of the plastic itself, a report from the World Health Organization in 2018 cautioned that the particles attract “microorganisms that may attach and colonize on microplastics, known as biofilms.”

Municipal water suppliers are required by law to publish annually a standardized analysis of what’s in our drinking water.  Those reports are filed with the Tennessee Department of Environment and Conservation and may be viewed online.

McMinnville Water Department has consistently passed all requirements — routinely with flying colors — on the yearly studies, including those for biologically sensitive metals like lead and trihalomethanes, an artifact of the antimicrobial treatment of water and a potential carcinogen.  The uniform Tennessee water testing mandate doesn’t call for testing for plastic microparticles.

On a more cheerful note, Warren County’s nursery products earn high marks among environmental scientists and landscape architects, the Rotary speakers said. The planting of native species is strongly recommended to secure biological resiliency in face of climate change and as a natural cleansing system for rainwater runoff.  

The “FOCUS” interview with Grubbs and Miller airs on public radio 91.3 FM this Tuesday at 5 p.m., with repeats Wednesday at 5 a.m., Thursday at 1 p.m., and Friday at 1 a.m.