Dr. Mark D. Hoover is a senior research scientist in the Division of Respiratory Disease Studies at the CDC’s National Institute for Occupational Safety and Health, in Morgantown, West Virginia. Mark is a critical area leader in the NIOSH Nanotechnology Research Center and also serves as coordinator of the NIOSH Exposure Assessment Cross-sector Research Program. NIOSH is the leading federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanotechnology. Mark earned a BS degree in mathematics and English in 1970 from Carnegie Mellon University and MS and PhD degrees in engineering in 1975 and 1980 from the University of New Mexico. He is board certified in the comprehensive practice of health physics and in the comprehensive practice of industrial hygiene. Mark has developed improved approaches, techniques, and instrumentation for aerosol characterization, generation, and control; served as chairman or contributor to the development of many national and international standards; is a past chairman of the AIHA Nanotechnology Working Group; and is author or co-author of more than 180 open literature publications. He recently completed co-editing and writing a new CRC Press handbook on Radioactive Air Sampling Methods. Special emphasis areas for Mark’s work in nanotechnology include a graded approach to exposure assessment and characterization of nanoparticles in the workplace, development of a prototype Nanoparticle Information Library, and promotion of opportunities to apply performance-based occupational exposure limits or control banding approaches to nanotechnology. Detailed information about the NIOSH nanotechnology health and safety research program is available at www.cdc.gov/niosh/topics/nanotech/.