- 39 - Positive counts were obtained for 14 of 21 persons measured. These counts suggested chest burdens ranging from 3 to about 10 nCi. However, in no case did the estimated chest burden exceed the MDA at the 95% con- fidence level. Seven of the 14 subjects with positive chest counts had estimated chest burdens of 7 nCi or greater and may be considered (at the 68% level of confidence) to have statistically significant chest burdens of from 7 to 10 nci.68 Since the plutonium is still in the lung cavity, 27 years post-exposure, it is correct to assume that it was initially in the insoluble form and hence pertinent here. 69 At the time of this measurement, however, most of the material would be expected to be in the lymph nodes. Nevertheless, we could estimate the initial particle burden in these subjects from these data if we knew the initial particle size at the time of contamination. This particle size data is unavailable. The nature of the contaminating events Sugcest that the = particle size might have been somewhat larger than those that result from plutonium fires where most of the respirable activity resides on particles in the size range of 0.1 u to 0.5 u in diameter. 70 Much of the contamination of the 69/ ICKP Publication 70/ Mann, J.R. Op. 19, cit., Dp. 474. The Metabolism of Compounds of Plutonium and Other Actnides, Pergamon Press, New York, and A.R. Kirchner, Op. cit., p. 880. 127 rey Hemplemann, L.H., ty 68/