A common source for microplastic is the abration of synthetic textiles and rubber. So unless you only wear unmixed nature fibre and walk in straw sandals you have to assume that you might also produce microplastic even if you never drive a car, take a bus or anything with wheels not made of steel or wood.

This is why we need to deal with the issue as a society, instead of blaming it onto individuals. We did precisely that for decades now and it doesn’t seem to work.