How do synthetic clothes release microplastic fibers into wastewater?

Synthetic clothing releases microplastic fibers into wastewater primarily through the process of mechanical abrasion during household laundering.12

As garments made from synthetic textiles—such as nylon—are agitated in a washing machine, the friction causes tiny plastic fibers to break away from the fabric. These fibers are classified as primary microplastics, which are defined as plastic pieces less than 5 mm in length. Once detached, these fibers are flushed out of the machine and enter wastewater treatment systems along with the wash water. Because these materials are not biodegradable, they persist in the environment and can eventually accumulate in freshwater and marine ecosystems.12