Microplastics are chemically active and could cause biological harm
Plastics are supposed to be chemically inert. It's the reason they're used so frequently to package food, bottle water and create children's toys: They're safe. But something important happens when a large piece of plastic fragments into micro- and nanoparticles. Its surface area increases dramatically relative to its volume. Vastly more of the material is now exposed to its surroundings.
We haven't written up this one. Phys.org has the full story — the link below goes straight to it.