Following WWII, scientists needed a license from what later became the Nuclear Regulatory Commission to work with radioisotopes. This FDA scientist is wearing a dosimeter to check his radiation exposure levels and working in a lead barrier. Following the detonation of the first atomic bomb, pre-war steel became a valuable commodity for scientists since it was the only steel not contaminated by radiation. Dosimeters measure an individual's exposure to something in the environment, particularly to a hazard inflicting cumulative impact over long periods of time, or over a lifetime. No date given for this photograph.