The International Joint Commission, a treaty organization that advises the United States and Canada, says the two countries should do more to keep microplastics out of the lakes. Microplastics are tiny pieces of plastic that are five millimeters or smaller. Microbeads are used in things like soap and toothpaste. Microfibers are tiny fibers that wash off our synthetic clothing, like fleece. Those tiny plastics can end up in the Great Lakes and can get into fish.