The early 1950s saw major concern developing in all countries about the effects of ionizing radiation. Not only was the horror of the Hiroshima and Nagasaki bombings fresh in everybody's memory, but three countries, by testing new nuclear devices in the atmosphere, had started to spread radioactive material world-wide. The effects of such radioative fall-out were largely unknown and speculation was rife about the health consequences of that widespread exposure to radiation.
From the Foreword.