Lea [Vo.L. 91 al effect on iton human it small inthe average ations, leuf detrimenviduals. In la ease per = 3000 peo‘emely diffiizing radialants) were imental efperimenter pontaneous ‘ to obtain t would be / IS usually 1umbers of people has 's who had ation were [to higher tically, for — cher physian populadents such the Lucky ds in 1954 Test Site, zattle, but on native or animals aluate the ions from rapolation diation or ie (1958), 1964] MARTIN : RADIOECOLOGY AND STUDY OF ENVIRONMENTAL RADIATION 319 estimates of the potential genetic effects of fallout are probably morereliable than estimates of potential somatic effects. If there is no threshold for the induction of mutations by ionizing radiation, any increase in the exposure of gametes to radiation will result in an increase in the number of mutant genes: and the incidence of mutations will be proportional to the amount of radiation received by gametes. In this situation, it is a relatively simpie matter to extrapolate from higher to lower levels of gametic exposure to ionizing radiation. Extrapolations from clinical and experimental evidence of somatie effects are often confounded and madeunreliable bya variety of uncertainties. For example, the mechanisms by which ionizing radiation may cause leukemia or bone tumorsor result in the shortening of human life are not clearly understood. In most cases, the possibility that radiation below somecritical threshold may produce no increase in the incidence of a given somatic effect can neither be affirmed nor denied. According to Dunham (1958), ‘‘ Atomie energylike the other great technological advances is bound to exact some price of the society which makes use of it whether in peaceful pursuits or in its national defense effort. Our present knowledge of the hazards of radiation though incomplete is greater than for any other environmental hazard. It is for the radiobiologist to continue to define the cost in more and more precise terms while it is up to society to decide whether the price is acceptable, and if the answeris in the affirmative, it must make certain that the cost is kept at a minimum.”’ Radioecology can contribute to the solution of these problems by continuing to study the fate of fission products in the biosphere, and by the establishment of long-term ecological studies to determine the consequences, if any, of the chronic exposure of plant and animal populations and com- munities in their natural environments to low levels of ionizing radiation from external and internal sources. Studies of the former kind have been described in this paper. Some long-term ecological studies have already been inaugurated (Wolfe 1961) but significant results from these studies maynot be forth-coming for 10, 20 or 50 years. In order to gain a thorough understanding of the long-term effects of fallout and other sources of ionizing radiation on the biosphere, it would be desirable, as soon as possible, to begin continuing studies of fundamental ecology and radiation effects in every major part of the biosphere. Accord- ing to Wolfe (1961), the ecological effects of increased environmental radiation are not known. ‘‘Nor can they be determined by experiment alone, nor by considering only a single source of increased radiation, such as fallout. Determination of the total impact of this factor on man’s biotic environment, and the evolution of living organisms therein, is a continuing problem.’ It is this problem, and its many ramifications, that justifies the description of radioecology as an application of fundamental biology to the needs of man.