There is the chemistry of substances and the chemistry (dynamics) of particles: diffusion, density, and volume. How just having them at some concentration participates in existing mechanisms.

If nanoplastics can help model inflammation of nanoparticles in general, stuff like graphene can also be more closely scrutinized. As well, not to overlook the combined effects of different nanoparticles in situ: adhesion, statics, or disintegrating.

Technology in wearables may advance to sprays: air becomes this composite mixture of synthetics, all just circulating around.