- 3% - TABLE V Rocky Flats Exposure* °F Number of Cases Total Lung Burden (uCi) 1 0.272 0.033 137,000 1 0.160 0.019 79,000 1 0.111 0.013 54,000 3 0.064 0.008 33,000 0.024 0.003. lg / Hot Particles Lund Burden (uCi) - Number of Hot Particles : 12,500 * Mann and Kirchner presented the lung burdens as number of MPLB. These have been converted to uCi in colum two using MPLB=0.016 uCi. (For the groups with 32 and 19 cases, we selected the midpoint of the reported rance.) The hot particle burden in colum three was estimated by multiplying the total burden by 0.17, the fraction of the activity on particles above 0.6 u, and 0.70, the fraction of initial deposited activity that was involved in low, term retention in the lung. Baséd on particle size data reported by Mann and Kirchner, we estimate the average hot particle activity is about 0.24 pCi. The numbers of hot particles in the last column were obtained by dividing the hot particle burdens in colum three by the average hot particle activity (0.24 pCi). Allowing a risk of cancer equal to 1/2000 per hot particle, suggests that the individuals whose exposures are presented in Table V stand a very high chance of developing lung cancer -- the probability is essentially unity. In this respect, it.is significant to note that in the experiments