Its easy to get tripped up by orders of magnitude when discussing units of radiation. Both Sievert and Rem are used for dose, and 1 Sv is 100 Rem. When you start talking microsiverts and millirem, its hard to keep track. This page is mostly a reference for myself; Here's the radiation unit comparison from Wikipedia:
The yearly dose limits for radiation workers is shown below. The 1931 limit is from page 53 of On Thermonuclear War by Herman Kahn, and the rest of the limits are from A Review of the History of U.S. Radiation Protection Regulations, Recommendations, and Standards:
History of Radiation Dose Limits