was a Professor and Chief of the Epidemiology Division at New York University Grossman School of Medicine before going to the Radiation Effects Research Foundation in Hiroshima-Nagasaki as Vice Chairman and Chief of Research. He is an author of over 100 radiation-related publications.

He has served on numerous governmental and scholarly committees, including as a long-time member of the International Commission on Radiological Protection and NCRP, and has served on various committees or task groups for the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the World Health Organization, the National Academy of Sciences, the National Cancer Institute, and the U.S. Environmental Protection Agency, among others. Most recently, he evaluated the projected health effects of the Fukushima radiation accident for UNSCEAR. His interests include the effects of radiation on both cancer and noncancer disease incidence, and understanding the epidemiologic and biological modification of radiation effects by various environmental, genetic and age factors. Recent publications have particularly focused on the effects of low-dose and low dose-rate radiation.