Se hundred roentgens at a single exposure, The British report is totally reassuring on the effects of occupational exposures on fertility, Chapter IV 1s a very lengthly genetics effects discussion with many figures, tables and calculations and a critique of the Atomic Bomb Casualty Commission genetics study in Japan, This is a highly technical discussion and comes out with the same conclusions as does the National Academy of Sciences, namely that a dose of radiation which would double the mutation rate of a relatively small group of prospective parents would produce no noticeable effects, 'For levels of radiation up to the doubling dose, and even some way beyond, the genetics effects of radiation are only appreciable when reckoned over the population as a whole and need cause no alarm to the individual on his own account," Chapter V discusses natural radioactivity - radiation from appurtenances of civilization and occupational exposure to radiation, The report concludes that diagnostic medical x-rays produce exposures to the germ cells of the order of 22% that of background and constitute the most important source of man made irradiation, It is estimated that the United Kingdom Atomic Energy Authority's employees receive an average dose of 0.4 per year, The estimated external radiation exposure to people in Great Britain from fallout from all past nuclear tests has been quite minimal, "“~---Including all ordinary atomic bombs exploded before December 1955, and calculating all the radioactivity which they have contributed and will contribute over the next 50 years, it is found that the total dose which a man, continuously out of doors, night and day, would receive is 0,005r. To this dose from ordinary atomic bombs must be added the dose of thermonuclear -~ 19 - Enclosure IIT