Background Humans have been exposed to fine and ultrafine particles throughout their
history. Since the Industrial Revolution, sources, doses, and types of nanoparticles have
changed dramatically. In the last decade, the rapidly developing field of nanotechnology has
led to an increase of engineered nanoparticles with novel physical and chemical properties.
Regardless of whether this exposure is unintended or not, a careful assessment of possible
adverse effects is needed. A large number of projects have been carried out to assess the …