"The National Institute for Occupational Safety and Health (NIOSH) has recommended prudent precautionary interim measures for reducing work-related exposures and assessing potential risk. In the hierarchy of prevention, it is important to consider where it may be of value to provide medical screening of workers who may be exposed to a potential health hazard, but who may be asymptomatic--that is, who have no identifiable symptom of an occupational disease. On the frontiers of nanotechnology, where as yet little data exist for assessing risk with confidence, it is difficult to recommend specific screening tests. NIOSH has sought a wide range of opinions on the matter and along with its own review of the scientific literature presents this interim guidance for medical screening and hazard surveillance. The evidence base on the health effects of engineered nanoparticles is rapidly growing and NIOSH will continue to monitor and assess it and will update those recommendations as more definitive information becomes available"--P. iii