Things can get weird at very small sizes because of the huge ratio of surface area to mass. An amount of plastic that is safe to place against your skin as one

Things can get weird at very small sizes because of the huge ratio of surface area to mass. An amount of plastic that is safe to place against your skin as one object, might have more significant chemical interactions as a collection of particles in your digestive system--which specializes in leaching complex chemicals out the materials that pass through it.