Study: Plastic pollution prevalent in St. Croix and Namekagon Rivers

Researchers find tiny pieces of plastic in the water from Seeley to Prescott.




3 minute read


The St. Croix and Namekagon Rivers have a plastic problem.

Like many waters around the world, synthetic materials are contaminating the Wild & Scenic Rivers.

Scientists with the U.S. Geological Survey and the National Park Service recently collected samples from four locations in the St. Croix and Namekagon, as well as in the Mississippi River in the Twin Cities. They made some startling discoveries.

“Microplastics” were found in every single water, fish, mussel, and sediment sample.

Across all locations sampled, smallmouth bass had 17.5 plastic particles on average, while three-ridge mussels had 6.7 particles per specimen. A cubic meter of water had an average of two particles, and a liter of mud had an average of 600 particles in it.

Clothes are a major cause

The pollution comes from numerous human sources.

Styrofoam and plastic litter such as bottles and bags break down in the natural environment to create microscopic particles. Before President Obama signed the Microbeads Free Waters Act two years ago, which barred plastic particles used in soaps, they would go down the drain and pass through wastewater treatment facilities before gradually break down in water.

Currently, the primary culprit is clothing and washing machines. Most of the plastic the researchers found came from textiles like fleece. A single fleece jacket can release up to 250,000 fibers in its lifetime, according to a a study commissioned by apparel-maker Patagonia.

Sixty percent of the clothes on Earth are made from such materials.

Watch this quick video from the “Story of Stuff” for more information on microfibers:

A threat to living things

The tiny pieces of plastic can harm everything from fish down to plankton.

The fibers from fleece and other materials “tangle into tight balls and become lodged in an organism’s gut,” according to the researchers.

Other particles might contain toxic substances like flame retardants, antibacterial chemicals, and other dangerous compounds. Plastics also soak up other contaminants from the water, including PCBs, hydrocarbons, pesticides, and heavy metals.

The specific harm that such pollution causes to fish and other living things is not yet fully understood, but several studies are underway to determine those effects.

It is also not known if the chemicals can be transferred from fish tissue to humans if people eat contaminated fish. That threat is also being studied.

Because most particles are smaller than the researchers were able detect, they believe actual concentrations could be much higher.

The samples were taken at four sites on the Saint Croix National Scenic Riverway: Seeley, Wis. (on the upper Namekagon); Danbury, Wis. (on the upper St. Croix); St. Croix Falls, Wis.; and Prescott, Wis. They were highest in the St. Croix at Prescott. Levels were generally higher in the Mississippi River than the St. Croix. Read the full report (PDF) here »

Take action:

Anybody can have a positive impact on this problem.

Sign the “4Rs Pledge” to Refuse, Reduce, Reuse, and Recycle displosable plastic.

Add your name to the petition calling on the clothing industry to address its microplastic problem.

Here are more suggested steps from the Plastic Pollution Coalition:

  • Wash synthetic clothes less frequently and for a shorter duration.
  • Fill up your washing machine. Washing a full load results in less friction between the clothes and fewer fibers released.
  • Consider switching to liquid laundry soap. Laundry powder “scrubs” and loosens more microfibers.
  • Use a colder wash setting. Higher temperature can damage clothes and release more fibers.
  • Dry spin clothes at low revs. Higher revolutions increase the friction between the clothes.
  • When you clean out your dryer, place lint in the trash instead of washing it down the drain.
  • Consider purchasing a Guppy Friend wash bag. In tests, the bag captured 99 percent of fibers released in the washing process. The bags will soon be available for purchase at Patagonia for $20-30.

Here are two more from St. Croix 360:

  • Don’t litter.
  • Pick up trash when enjoying the river.

Top image: Microplastics, courtesy Oregon State University


2 responses to “Study: Plastic pollution prevalent in St. Croix and Namekagon Rivers”

  1. Sara Avatar

    I think the link to the full report is broken…

    1. Greg Seitz Avatar

      Thanks, got that fixed now!


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Study: Plastic pollution prevalent in St. Croix and Namekagon Rivers