Nanoparticles differ from the same material at larger scale in chemical and physical properties. Evidence from studies of fibres leads to the conclusion that inhalation of nanotubes could be dangerous and should be regulated. Air pollution research has suggested that particles may be more toxic to cells at the nanoscale. At present the marketing of nanoparticles is advancing more rapidly than research into their safety and toxicology, and one serious inhalation episode has been reported in Germany from apparent use of a nanoproduct. This rapidly developing industry will make an impact on the work of occupational physicians, first in universities and small concerns but later more widely. The future safety of workers and consumers is dependent on research into hazard and risk, an area in which the UK and most other countries are dragging their feet. However, a resource, the Safety of Nanomaterials Interdisciplinary Research Consortium, has been established in the UK to assist those active in this field.