This is an updated radiation chart courtesy of reader Goatguy
Note: the cancer risk probably starts after 100 milliSieverts.
If a over 40 years of less than 1 or 2 in 1000 is tolerable (2-4 weeks average life expectancy, a hundred times smaller than that due to smoking), then
•in the case of leukaemia a radiation dose of 200 mSv is harmless
•in the case of solid cancers a dose of 100 mSv is harmless
•studies of other abnormalities show no significant effects at these low doses (not discussed here).