1931-34	US Advisory Committee on X-Ray and Radium Protection (precursor to the National Council on Radiation Protection and Measurements) adopts X-ray "tolerance dose" of 0.1 roentgen per day.
1940-41	US Advisory Committee proposes, but does not implement, lowering the X-ray tolerance dose to 0.02 roentgen per day.
1942	U. of Chicago Metallurgical Laboratory adopts a "maximum permissible exposure" standard of 0.1 roentgen per day. Becomes standard for entire Manhattan Project.
1954	Atomic Energy Commission adopts National Bureau of Standards recommended dose limit of 5 rem per year. Sets additional limits for internal exposures at 15 rem per year for most organs.
1959	Dose limit for workers remains 5 rem per year. AEC also adopts dose limts for the public equal to one-tenth of those allowed for workers: 0.5 rem for external exposure; and 1.5 rem for most organs for internal exposure."
late 1980s - 1990	Department of Energy adopts dose limit for the public of 100 millirem (0.1 rem) per year; dose limit for workers remains 5 rem per year. A new model for calculation of internal doses to workers is adopted, the "committed effective dose equivalent." (See main article.)
1991	International Committee for Radiological Protection recommends worker dose limit be reduced to 2 rem per year. Recommendation is not adopted by DOE.
NOTE: For external radiation sources, roentgen and rem are considered to be equivalent. Sources: 1931-34, 1940-41, and 1942: Barton Hacker, The Dragon's Tail, (Berkeley: University of California Press, 1987), Appendix A, pp. 163-64; 1954: US Atomic Energy Commission, AEC Manual, TN-000-22, Chapter 0522, Vol. 0000, Part 0500, AEC-0522-01, BMBP, (US AEC, Feb. 26, 1954), 0522-01.h; and National Bureau of Standards (NBS) Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissile Concentrations in Air and Water, Handbook 52, (Washington: US Dept. of Commerce, March 20, 1953); 1959: NBS, Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure, Handbook 69, (Washington: US Dept. of Commerce, June 5, 1959), pp.4-6; late 1980s - 1990: US Dept. of Energy, Office of Environmental Safety and Health, Order: DOE 5400.5, (US DOE, February 8, 1990), II.1a; 1991: International Commission on Radiological Protection, 1990 Recommendations of the International Commission on Radiological Protection, ICRP Publication 60, Annals of the ICRP, Vol. 21, No. 1-3, (Oxford, New York: Pergamon Press, 1991), p. 72, parg. (S25).