The distinction between “engineered,” “incidental,” and “natural” nanoparticles is beginning to blur. A vocal contingent advocates regulation of the first category without much focus on the later two. We recently asked whether this distinction is meaningful for certain EHS purposes. The human body may not differentiate between exposure to the three categories of materials. On the other hand, it makes sense to be concerned with reducing man-made risks first.
Here is a related question: What happens to this definitional scheme when naturally occurring nanomaterials (ex/ carbon nanotubes and fibers) are harvested/mined and then used for commercial purposes? While they are not “man-made” in the traditional sense, they presumably pose the same exposure risks as engineered nanomaterials created in a lab. The industry is currently exploring cheaper ways to mass-produce nanomaterials. Consequently, we will undoubtedly see more "natural" nanomaterials being used in commercial applications. This issue merits serious consideration in any attempt to regulate nanotechnology and/or create uniform standards and nomenclature.
"Engineered" = purposefully created; man-made. "Incidental" = unintentionally created; by-product of human activity. "Natural" = found in nature; volcanic rock; smoke.