Abstract
There is a paradox in that some types of nanoparticles (a generic term for particles less than approximately 100 nm in diameter) are used in nanomedicine for imaging and therapy, whereas other types of nanoparticles produced by combustion are thought by many scientists to be responsible for the adverse health effects of air pollution. In addition, the nanotechnology industry is in the process of producing new nanoparticles whose hazard and potential for human exposure are not yet determined. Medicinal nanoparticles are being designed and tested on a case-by-case basis using testing procedures derived from biomaterials and drug safety and with due regard to risk-benefit. There are considerable differences in physical and chemical properties between medicinal nanoparticles and the industrial and combustion-derived nanoparticles studied by particle toxicologists, a recognized branch of toxicology that studies particles. Medical nanoparticles tend to be composed of materials that are similar to biological molecules and they are generally biodegradable. By contrast, combustion-derived nanoparticles are carbon-centered and contaminated with metals and organics, with a biopersistent core. To fully address the paradox that nanoparticles can be both beneficial and harmful, there is a need, over the next 10 years, to advance our understanding of the characteristics that determine acute and chronic toxicity, translocation, biodegradation and elimination of all types of nanoparticles likely to gain access to the human body.