668 advise the President with respect to radiation matters and to establish a national policy relative to radiation exposure and health. 109, 142, 143, 145, 150 The membership of FRC includes the Secretary of Health, Education, and Welfare, Chairman; the Secretaries of Defense, Labor, and Commerce; and the Chairman of the Atomic Energy Commission.!45 150 The FRC introduced for use by Federal agencies the concept of a Radiation Protection Guide (RPG) defined as “the radiation dose which should not be exceeded without careful consideration of the reasons for doing so; every effort should be made to encourage the maintenance of radiation doses as far below this guide as practicable.”'°6 51 Later, a “graded scale of action” was set up for three ranges of exposure for several radionuclides.*** +5? PERSPECTIVES Young and old animals have been shown to have an increased sensitivity to radiation compared with animals in the prime of adulthood. From limited data available, it appears that this situation is also generally true in the human being. Although a number of radiation effects have been shown to be greater in the young human being, there has been no good evidence for any decreased sensitivity to any radiation effects in children as compared to adults. The above statements are based on data involving relatively high doses of radiation. The extremely limited data available do not allow one to make such positive statements in regard to low dose effects. The sources of low-level radiation are from (a) natural background, (b) fallout from nuclear test explosions, (c) industrial uses of radiation, and (d) medical uses of radiation. Little can be done to alter the dose commitments associated with natural background and the existent fallout. Al- though monitoring systems exist,1** the actual application of countermeasures against effects of fallout radiation present public health problems.®141: 145, 154-159 “Jr is clear that drastic measures to control air, water and food supplies of large population Pm é October 1965 Sutow and Conard . groups might hold threats to health more immediate and serious than the increasing , risk from radiation exposures such measures were intended to reduce.”**4 Efforts toward containment of occupa- tional radiation sources and formulation of |1 health safety standards have been effective, reducing radiation exposure in radiation workers. No instance has been recorded in which a radiation worker has stayed within the permissible limits and developed a demonstrable radiation injury.'*? Estimates of radiation effects at low dose levels are based on assumptions and extrapolations, the accuracy of which must be established. “We still know very little about the frequency with which such (harmful) effects are likely to occur, particularly following small doses of radiation at low dose rates,’’16° Epidemiologic studies have reported increases in the rate of development of leukemia and malignant neoplasia among children exposed in utero to diagnostic doses of radiation. * Not all data support this finding.** The degree of risk of induction of malignant tumors by low dose radiation is not settled.‘> However, the reports of correlation of radiation exposure and later development of malignancies have made the physician much more cautious in recent years in the use of radiation in both diagnostic and therapeutic procedures. For example, the increasing evidence for development of leukemia in children who were irradiated in infancy for thymic enlargement and the development of thyroid nodules following treatment of children with I** therapy for thyrotoxicosis has resulted in greater conservatism in the use of such treatmentin infants and children. For the same reason, the physician has become more circumspect in the use of x-ray pelvimetry on pregnant women. Consequently, the incidence of such late effects of radiation should be greatly reduced in future years. The degree of conservatism in the medical uses of radiation may be somewhat altered when more is known aboutlinearity of dose response and when the question regarding the existence or nonexistence of a threshold