“We were surprised by the small amount of plastic beads and high amount of fibers found in the samples,” USGS scientist Austin Baldwin said in a press release about the sampling results released Sept. 15. “These unexpected findings demonstrate how studies like ours are critical to better understanding the many forms and fates of microplastics in the environment.”
If ingested, microplastics can cause digestive and reproductive problems, and even death, in fish, birds and other animals. Also, pollutants, such as pesticides, can build up on plastic pieces floating in the water.
“These microplastics, which are harmful to animal and possibly human health, will continue to accumulate in the Great Lakes well into the future,” Baker said. “Our findings can help water managers better understand the types and sources of microplastics in rivers, and which rivers are the most polluted with microplastics.”
The water sample with the highest concentration of microplastics — 32 particles per cubic meter — was taken from a part of the Huron River that flows through Ann Arbor, Mich., while the median concentration was 1.9 particles per cubic meter in all samples.
Other high concentrations were found in samples from the Buffalo River in Buffalo, N.Y. (31 particles per cubic meter); the Ashtabula River in Ashtabula, Ohio (23 particles per cubic meter); and the Clinton River in Mount Clemens, Mich. (21 particles per cubic meter).
The study was funded by the Great Lakes Restoration Initiative, which was started in 2010 to protect the largest surface fresh water system in the world. The 29 tributaries studied make up about 22 percent of the total river water that flows into the Great Lakes.
Previous studies of water samples and fish taken from the five Great Lakes by other researchers and universities also have raised concerns about the prevalence of microfibers, which scientists said probably originate from household washing machines.