eo reported by Park, et al, the beagle dog with the smallest lung burden, i.e., 0.2 uCi, developed lung cancer.°" The highest Durden in Tabie V is comparable to the lowest beagle exposure; the lowest exposure in Table V, the 19 cases with lung burdens in the 0.024 uCi range are only an order of magnitude less than the lowest beagle exposure. We would suggest that tnis is potentially a serious situation. As of this time, none of these individuals has developed lung cancer.”” However, it is only 9 years Since the exposure and there is good reason to sugcest that the latent period (the time between exposure and the development of cancer) is much loncer than this.” In the beagle dog experiments, the lowest lung burden was associated with a latent period of 11 years. The latent period may be longer in man and particularly at these cases involved. 4 ; lower dosacaes and the small number of Therefore, while these exposed individuals will be expected to supply pertinent data relative to this hot particle cancer risk over the next 10 to 20 years, these exposures give us no information at this time that would warrant modifying the risk per particle or the critical particle activity. 64/ Park, J.F., et al, Health Physics, Op. cit. p. 805. 65/ Richmond, Chet, Op. cit., p. 320.