The maximum permissible level of occupational exposure to radiation is...per year –: (A) 5 rad., (B) 2 rad., (C) 10 rad., (D) 50 rad.
Answer is A. The amount of radiation received from outer space and background radiation has been estimated to be 0.1 rad a year. Apparently, this does not at present constitute a hazard. The additional permissible dose from man made sources should not exceed 5 rad a year.