$/30 /s9 ie frir 407940 BACKGROUND VS. Sr? IN MILK 7 N. Irving Sax via (From the Division of Laboratories and Research, New York State Department of Health, Albany) One of the chief difficulties which arises when attempts are made to set up acceptable mpl of radioactive contamination in population vectors of exposure is the necessity to decide just how much radiation damage a given population is willing to sustain in order to get the “good things" that the environmental contaminating processes may produce. These "good things" include strengthened national defense, cheaper and more plentiful power, and advances in medicine, agriculture, and industry. Many theoreticians in the field of public health who have come up against the nearly insoluble problem of equating damage to life with the advantages of the atomic age are now resorting to the device of comparing a given exposure to the universally sustained exposure to background radiation. This background radiation consists of contributions from cosmic rays from outer space, external radiations from possibly 50 naturallyoccurring radioisotopes in the air and lithosphere, and finally from the naturally-occurring radioisotopes inside the body. Dr. Willard F. Libby, Commissioner, United States Atomic Energy 1) Commission, has stated: ‘