Fat soluble compounds accumulate in fatty tissue, while I imagine water soluble compounds could accumulate in e.g. muscle tissue.

It’s not in the same sense as microplastics, as these compounds are released when their storage medium is processed. That’s actually a beneficial mechanism as it means that fat is also a store of essential nutrients rather than just calories, released steadily when fat is burned. It’s just bad when things accumulate in excess.

Cocaine might be able to accumulate in small amounts in tissue this way.