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The energy dependence of film blackening is discussed and shown graphically. The exposure range of films is discussed, and blackening is plotted vs exposure for DuPont No. 502, and for the less sensitive DuPont No. 351. A plan is then described for monitoring radiation exposure to workers by requiring the worker to carry an x-ray film of dental packet size in a badge designed for the purpose. (LEW)

This letter was written in 1944 and applies to the amount of radiation a person could be subjected to under emergency, wartime conditions. Mr. Stone recommends to Dr. Norwood that no man should be ordered to expose himself to more than a tolerance dose (0.1r in a 24 hr period) except in the case of an extreme emergency in which time is of the essence. And that before any man is asked to exceed tolerance that a radiation trained physician be called in for consultation. His recommendations to said physician are that: (a) a single exposure of 1r would cause no harm and could be repeated at long intervals, (b) an exposure of 5 to 10r would produce loss of appetite and nausea and would increase the chances of genetic change but would cause no clinically detectable changes after the incident, (C) an exposure of 25r would do the same as (b) but with greater probability -- he would be personally willing to take a 25r exposure to accomplish an extremely important job, (4) in general keep exposures well below tolerance, (5) due to the genetic effects, women of childbearing age and younger men should be subjected to none and …