I'll admit I didn't read the study because its paywalled and the preview gives absolutely zero useful information.

If the goal is to reduce microplastics in the environment all of these researchers should immediately pivot to researching alternatives to plastic tires, and find a way to convince the world to move away from synthetic fibers.

In other words if they managed to stop this sewer practice they would reduce microplastics by .001% (or whatever the study claims it is)