Document text
Machine-read from the scan, so expect some errors. Lines that couldn’t be read are left out.
Page 1
DEPARTMENT OF PHYSICS Yany thanks for your d e t a h d an thoughtf'ul letter of 7 January 1958 about the design of the Dpois Srb oxperhent. I understand from Dave Bruner that we wlll be meeting In Ben Pork next month. In the meantime here a r e some commonts whlch may speed up discus8ion o f some questions raised i n your letter. When retrsined dose is pu on a basis of ppc Sr90 per g of skeletal calcium instead of (rc &/kg body weight, there i s substantial agreement between your revised levels and those originally proposed a t Davis, This i s because at Davis we assuned that the beagle, like man, I s 1/70 calcium andtherefore that a l2-Q beagle contains about 170 g Ca. Your table and discussion a r e basod on pour assumed value of 500 g Ca per 12-kg beagle, assumptions means that your proposed l / a pc/kg level (8,000 ppc/g Ca) i s roughly sirnilat. t o the original 1/6 pcJkg level (12,000 ppc/g CO) l n the sense that both of them are Intended to b8 about 10,000 p p d g CaO Similarly the original 1/70 pc/kg level was intended t o correspond t o industrial HPL, as mentioned In the text on page a, and therefore ppc/g Ca as your proposed 1/27 )rc/kg level for bony beagles w i t h the skeleton o f a beagle. The factor of 3 between these t w o It i s therefore the same, i n terms of intended Clearly, w e are a511 thinking alike in terms We just need to learn how much calcium really I s In You asked on p. 5 about dropping the highest dose level. think it I s needed. tained dose, 6'"" less than 0.1 pg Ra to more than 100 pg Ra. range of dosage, because the may well prove t o be a function of ggse level. we want the complete wladder" of Sr re did a t Utah for plutonium and other nuclides, The hunen Ra cases cover a wide range of reand Ra levels in the dogs should also cover a wide pathology and the relative toxicity Th9.s is why I feel dose levels at Davis, Just as
Page 2
The recomabation of only 12 animals per point in the radium series was based on economy. ctould be Interlocked with the Utah 12-anlsal radltm ladder, and i f SO that12 animals per radium level might suffice e t Davis. protectioan, .country doctorn, etc., when Austin and you and I overrode Brandtls equations and s e t up double control groups in the U t a h experlment, !Rm point is there may be no clean regression relationship between dose and pathology, you have in mind in pour p, 5 0 p, 4 where threshold VS. nonthreshold inferences a r e hoped for (without illustration of extrapolation i n the sense of your p, 5, perheps by using hypothetical results and "extrapolating" them, t o agreement on how to begin the Davis experiment. It would be better to have 50 as in We thought that the ladder of Davis radium groups ! Tha double-sized control group I s thm old Chfcago story which Ifind it difficult to visualize what kind of extrapolations Apparently not the same as When we meet, or before, could you give me an I think your letter is excellent, end that we are 611 closer Kith every good wish. Robley Do Evans Professor of Physics