<prompt> The maximum permissible level of occupational exposure to radiation is...per year5 rad.2 rad.10 rad.50 rad.  <response>: 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. 