Dr. David Brenner, Director of the Center for Radiological Research at the Columbia University Medical Center, provides a 30 minute primer on radiation exposure, addressing the scientific facts and common misconceptions. He describes how a nuclear reactor works and how the Dai-ichi plant in Japan began to leak radiation after the 2011 earthquake and tsunami. He also outlines the potential health hazards posed by radiation, as well as risk communication strategies that the U.S. public health sector should take note of.