WORLDWIDE EFFECTS OF ATOMIC WEAPONS BIOMEDICAL CONSIDERATIONS cortex, is probably quite inactive and the calcium and strontium that reside there are probably turned over in negligible quantities. It is this aspect of bone metabolism that renders the quantitative considerations of most recent tracer work inapplicable to the problem we are considering. The tracer experiments that have been reported are dealing with a relatively high concentration of strontium deposited in the bone and are followed for short periods of time. Thus, in absolute terms, the bulk of the material of cell division. In fact, a direct comparison between the effects on adults 42 is followed while it is present in the “high turnover’ structures and is not a true quantitative picture for considering the same amount of material deposited largely in the “low turnover” portions of mineralized bone. An experiment reported by Pecher’ supports this contention. He injected radioactive calcium and radioactive strontium intravenously into mice and after 24 hr he recovered 58 per cent of the calcium and 33 per cent of the strontium. However, when he reduced the amountof strontium injected, 43 and the effects on growing children presents a high degree of quantitative uncertainty at this time. MAXIMUM PERMISSIBLE BODY BURDEN FOR STRONTIUM 90 This study is attempting to define the hazard involved relative to the production of Sr°° by atomic bombs. In order to provide a reference standatd for quantitative comparisons and evaluations of risk, it is suggested that the maximum permissible body concentration of 1 pc (i.e., 5 X 10° wg) of Sr°° as established by the International Commission on Radiological Protection (1950) be used. Anycalculations referring to the number of bombs exploded, the fallout problem, etc., may then be extrapolated to this reference point. In this manner we may then estimate, for a given set of conditions, the number of people who have been brought to this level. Or, alternatively, we can. estimate the percentage ofthis level to which a!! people at risk have been brought. the recovery percentage more closely approximated the calcium values. Thus, we are probably further supported when we insist that at the low levels of natural strontium intake we assume that calcium and strontium will behave quantitatively in the same way. This supports the use of the calcium and strontium deposition graphs described earlier. This quantitative behavioral difference at different ranges of concentration again points out the inapplicability of the tracer experiments being sible body burden) has important implications relative to the amount of Sr’ one can calculate as being nonhazardous when released. The dependa- also brings to mind an important quantitative aspect relative to the mass matter of vital concern in any quantitative consideration regarding the release of Sr°° into the earth’s atmosphere. A few remarksrelating to how reported in the literature. This brief discussion of the deposition of calcium and strontium in bone of tissue at risk. If we are discussing the gradual accumulation of a per- This figure of 1 pc, or 5 X 10° pg, of Sr°° (as the maximum permis- bility of this standard in predicting what it is supposed to predict is a missible body concentration over the growth years, we can safely assume this standard came into being and to some of the limitations involved wouldseem to be in order. if we are discussing the accumulation of radioactivity in adults, a sraaller in man. It has, therefore, been necessary to compare the effects of Sr°° in that the total mass of the skeleton will be uniformly exposed. However, mass of tissue is involved, probably on the order of one-tenth of thetotal skeleton. Other factors also enter into consideration. The 10 per cent of the skeleton involved in the adult 1s in the region of high turnover with regard to dynamic equilibrium, and retention may be quantitatively different over a period of years.when compared with that in a young growing person. On a comparative basis we must also bear in mind that young growing tissue is more radiosensitive than adult tissue having lower rates Thereis no direct experimental evidence that Sr°° is a carcinogenic agent animals with those of radium and then to estimate the equivalent response in man from the known radium effects in man. The generally accepted maximum permissiple amount or radium Tinea Mm the Motta SReTeTOT fs 0.1 ug, and the St”® value given above is supposed to be equivalentto this. (This method of approach was accepted for the bone-seeking elements in preference to the calculation in terms of a permissible amountof radiation equivalent to 0.3 r/week to the critical tissues. Because of the distribution