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Radiation doses received during a criticality accident will be from a combination of fission spectrum neutrons and gamma rays. It is desirable to estimate the total dose, as well as the neutron and gamma doses. Present methods for dose estimation with chromosome aberrations after a criticality accident use point estimates of the neutron to gamma dose ratio obtained from personnel dosemeters and/or accident reconstruction calculations. In this paper a Bayesian approach to dose estimation with chromosome aberrations is developed which allows the uncertainty of the dose ratio to be considered. Posterior probability densities for the total and the neutron and gamma doses were derived.

The mortality pattern of women who began employment as luminizers in the radium dial industry before 1930 was followed through 1990. Hazard models with time-dependent covariates were used on mortality data either organized by individual death times or grouped into cross-classified person-year tables. These models were used to quantify trends in mortality associated with either death from or diagnosis of bone sarcoma or head carcinoma. The accumulation of skeletal doses from 226Ra and 225Ra was an important predictor of the risk of death from bone sarcoma. Women exposed to 226Ra at ages associated with active bone growth were at greater risk of bone sarcoma than women receiving even larger exposures at an age when their skeletons would have been fully developed. Exposure to only 226Ra was found to be an important predictor of risk for carcinoma of the mastoid air cells and paranasal sinuses. For the cranial sites, where adult dimensions are attained early in life, an effect of age at exposure could not be detected.

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H d t h Physics V d . 35 (July) pp. 91-101 P a w o n Press M.. 1978. Printed in Orcat Britain 0 Health Physics Society 00 I7-W78/78/070 1 -00! 3Abstract-The ICRP model, Alkaline Earth Metabolism in Adult Man, predicts that 10% of injected radium-224 atoms decay on bone surface, and that 1.5% decay in bone volume. The model was rerun for all possible values of the size of the bone surface compartment and of its rate constant in an effort to determine the reliability of the bone surface prediction. These runs together with data for 45Ca, "'Ba, and 526Ra in rabbits and dogs lead to lo+ 2% (probable error) as our best estimate for the bone surface fraction of injected '=Ra in man. This estimate corresponds to a time of maximum radium concentration at bone surface in man of 18+6hr, and a preference for radium compared to calcium in the size of the bone surface compartment of between 2 and 3. New measurements of the total surfacelvolume ratio of bone from 10 human skeletons give a preliminary value of 50 cm2/cm3. Assuming 100% retention of thoron and its daughters at bone surface, these input values, together with integrations reported by Mays, give the estimate that an intravenous injection of 1 pCi of 224Ra in a 70 kg standard man with 5 kg of bone results in an average dose to the endosteal cells 0-10 p m from bone surfaces of 1.5rad. Considering all sources of error we believe this estimate is probably good to within a factor of 2.By calculatin the ratio of the endosteal doses for equal average doses to bone for both 224Ra and ' $u relative to 226Ra in man, we give values for what we have called the Relative Distribution Factor (RDF). This factor predicts the relative toxicity of alphaemitting radionuclides in man relative to 226Ra on the assumption that the dose to endosteal cells is the causative factor. The value of RDF('"Rala6Ra) is 20, practically independently of whether endosteal dose is averaged 0-5 p m , 0-10 p m , 0-20 p m , or 0-30pm. The RDF(23%/p6Ra) is about 28 for a surface source of plutonium, and O.% for a volume source of plutonium. The reference for these factors is taken to be a volume source of 226Ra. Since endosteal doses calculated by averaging exactly 0-10 p m from bone surface are somewhat arbitrary for alpha emitters-we don't really know exactly how far from bone surfaces the target cells lie-it is reassuring to find that RDFs for alpha emitters relative to '=Ra are almost independent of distance so long as the cell targets lie within 3 0 p m of the bone surface. Therefore, the RDF with p6Ra as the standard of reference provides a more secure description of the spatial differences between the dose distributions of alpha emitters in bone than does endosteal dose itself.The observed RBE of 224Ra relative to 226Ra for the induction of osteosarcomas-the ratio of average bone doses (226Ra/mRa) for equal incidences-is about 6, a factor of 3 less than the RDF of 20. In other words, by present calculations, 224Ra appears to be a 'Work performed under the auspices of the U.S. Atomic Energy Commissi...

This paper describes a Bayesian methodology for integrating studies in experimental animals and humans to obtain a risk estimate for a radionuclide for which no data or very limited human data are available. The method is quite general and is not limited to radiation studies. In fact, it was first developed for chemical toxicants. The methodology is illustrated using studies with rats, beagles, and humans exposed to isotopes of Ra and Pu. The goal is a quantitative risk estimate for bone cancer in humans exposed to internally deposited Pu. The choice of bone cancer as an end point and of Pu as the source of exposure was made partially because of its inherent interest but also because of issues of data availability and suitability. We performed Poisson regression analyses on 13 of 15 data sets. These analyses form the basis for the unifying method of interpreting the entire ensemble of studies. Each of the studies is summarized by the estimated dose-response slope and its estimated standard error. These summary statistics are combined with other available biological and physical information about species differences, physical and metabolic characteristics of isotopes, disease mechanisms, and the like. This information enters the analysis in the form of prior assumptions about the parameters of the Bayesian model combining the studies. The posterior distribution for the bone cancer rate in man from the Bayesian analysis of the 13 studies is updated with the limited data on Pu in humans. This update gives the final probability density for the bone cancer rate in humans exposed to internally deposited Pu. This density has a median of about three cancers per 100 Gy and has a 95% probability interval from 0.8 to 11 bone cancers per 100 Gy.

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