Biologic responses to nanomaterials depend on exposure, clearance, and material characteristics

Nanomaterials create challenges for the toxicology and risk assessment communities. While some nanomaterials are not new, such as colloids and the nano fractions of polydisperse aerosols such as welding fume, others are novel and unexplored. In addition to elucidating biologic responses, we also need to characterize human exposure, and to better understand the pharmacokinetics and translocation potential of nanomaterials. For example, do the smallest nanoparticles cross the air-blood barrier more readily, and can they enter cells via non-endocytic mechanisms? To what extent do nanofibers share the remarkable properties of asbestos fibers? Can carbon nanotubes find their way to the pleural space or not? More generally, we need to craft the laws of nanotoxicology. How do the size, shape, and surface chemistry of nanoparticles influence their anatomic fate and biologic consequences? Parallel to the rapid growth of nanotechnology must be a thoughtful development of the field of nanotoxicology.