-~2Using this concept a simple approach miaht involve assigning probabilities to various values of the aut transfer coefficient. This would result in a distribution of dose estimates, j.e., different doses result with probabilities assigned to the liklihood of each. The distribution of dose estimates depends, of course, on the assigned probabilities to the various gut transfer coefficients. An important aspect of the study would be to determine the sensitivity of the distribution of dose estimates to the distribution of transfer coefficients. Estimated time: J-2 months. (3) The dose estimates are based on average soil concentrations obtained using the IMP and soil samples. The conversion of IMP readings into soil concentrations is obviously an important link in obtaining dose estimates. Also important is the calibration of the IMP with Am sources to insure that correct readings are being obtained. The entire calibration and conversion procedure should be reviewed to evaluate whether brases are present in the procedure that could materially affect dose estimates. As you know, I am attending a general review of these aspects in Las Vegas April 26. ] month. Estimated time to complete: (4) EPA proposed guidelines using a soil screening level concentration that is applicable to the top 1 cm of soil, < 2 mm soil size fraction. To my knowledge, the thinest layer sampled on the atoll has been 0-2 cm (profile samples collected during the 1972-73 survey). I suggest that a soil sampling study be conducted to evaluate the transuranic concentrations in the 0-1, 1-2, and 2-3 cm regions. It may be advisable to take IMP readings in conjunction with these samples. I expect to obtain more information on these points at the meeting on April 26. Estimated time to complete: 2 weeks. (5) The version of the LLL dose assessment handed out to us at the Las ‘yegas meeting on April 13-14 contained recommendations for additions or continued research to better define parameters for the dose estimation model. I urge that these be implemented as soon as possible, particularly since some are long range studies. These studies involved (in the order of importance assigned by the authors) estimating gut transfer coefficients, resuspension and dust loading factors, terrestrial and marine food concentration factors, residence times of transuranics in the atoll] environment, impact of vegetation removal on groundwater quality, transport of "hot" Pu particles from the lagoon to the terrestrial environment, concentrations in clams and shellfish, and the expected diet for each island and population group with some idea of potential variation over time. Estimated time to complete: Question 2: greater than 2 months for most studies. If the above (and other) activities suggest the "40 pCi/g soil level" approach result in doses above EPA guidelines, what do we recommend? The answer to this will depend on the answers to the research. cannot give an informed opinion at this point in time. I, personally,