ee ee wees = ees ee ed calculations and the great range of the experimental data, the close apreement is fortuitous, IV, Conclusion It must be concluded that because of the dif2iculties in Finally, the data presented here may be used to estimate the internel dose rate dus to RaD and its daughters relative to that from the Rrae@ chain, Pig. 1 (Slide 1}. The effective aose is given Ly the product of the average energies of the emitted particles, an RBE of four fur alpina particles and the fracticnal retention of the nuclides. For Rab and its daugnters and for Re*”, the retention is one; for Face? and its da._cters, it is 0.3.23) Consequently, for a given activity determining the RaD and RaF conteats of the skeleton, the total dose-rate therein may be difficult to estimate. Moreover, because of the lack of correlation between the RaD and the paee6 concentrations, the relative dose rates cannot be defined as a funetion of geography. The statistical uncertainties in any associated epiderioloyicai study would thereby be increased,‘(38) Some of the difficulties might be alleviated if further studies make other correlations apparent. of each parent nuclide, the ratio of effective dose rates of RaD to Rae* is 0.5. Table & (Slide 10) shows the average RaD concentration of 0.246 pe/g ash is equivalent to a rato concentration of 0.673 pe/g ash. This is about twice the measured pareo soncentration in cur senples. It mast be noted that this vector of 2 is actually @ minimum sinec these camples include a relatively iarge frection from people residing in areas with high Fa 22 6 drinking water. in low-level areas, such as Chicago. (12) . Most people live Consequently, over the whole country the RaD dose-rate levels are ectually about 5 times those cf Ra““°. Acknowledgements Special thanks are due to Dr. A. J. Finkel and Mr. E. F. Luces, Jr. for obtaining the majority of the samples and to Dr. J. B. Hursh for the sets af bone specimens. Mr. Lucas also kindly supplied much of the parce deta and his discussions were very tLelpful. Technical essistanc. was supplicd by Messieurs F. W. Ilcewicz and R. P. Burke. fam particularly indebted to Mr. L. D. Marinelli for the many helpful suggestions and discussions during the preparation of this paper. Since the dose due to Ra2e" in the body is about equal to thet of Rae?® (16) the Rad dose is about 2-1/2 times that of the two Ra nuclides, The radiation levely of Ra? may be also compared to tnose of sr?? If an RBE of 4 is assumed for a]lpha tarticles relative to that of betas, and the gr? concentration is about 0.5 pe/g asnt7) then the RaD dose is about 10 times thet due to sr”? ~6- rhea ee fe es : . FN hae ReaDEKno vey TO ale mannwear2A. we .