o B. Nannattan Lrotect workers Another study of human respiratory exposure to plutonium relates to 22 young men exposed to plutcnium during tne Manhattan Project. found them te be states, 66 . . The latest examination of this qroup free of lung cancer altnouagn the report "The bronchial cells of several subjects showed moderate to marked metaplastic changes, but the significance of these changes is not clear." Such metaplastic changes are a possible indicator for detecting incipient or actual cancer. lung In one case the report indicates that the subject was a heavy smoker (3 packs/day) tributed to the cnances. suggest that and undoubtedly this con- Nevertheless, these findings lung cancer may become manit est in some of these subjects in the future. Indeed, one would not be Surprised to find one lung cancer even in such a group of non-exposed suojects. During the latest examination of these a workers, in vivo measurement of the plutonium lung burdens f were conducted with these results: An average MDA for a 2000-sec counting time is about 7 nCi if one uses the 95% confidence level.®? For the 68% , confidence level and a Similar counting time, the comparable value is about 3.5 nci. 66/ Hemplemann, L.H., et al, “Manhattan Project Plutonium Workers; 67/ A Twenty-Seven “Year Follow- Up Study of Selected Cases." MDA refers to the minimum detectable amount. Mca ht al e ace