U.S. Geological Survey and State University of New York Fredonia scientists sampled rivers flowing into the Great Lakes3 to find out which kinds of microplastics are most commonly found in rivers, and which rivers contain the most microplastics particles.

These scientists found that rivers carry many different kinds of microplastics, and were surprised to learn that plastic microbeads make up only a small fraction of all microplastics.

The USGS scientists found that fibers composed an average of 71% of the total number of microplastics particles found in samples of river water.