TABLE V Occupational Exvesure Guidance for Insoluble Alpha Emitters, ; -_, ; . Maximum Permissible Lung Particle Burden Cancer risk due to 5 rem/yr whole body exposure (MPLPB) 77 Assumed Risk in Particle 1/1000 1/2000 1/10,000 4.5x1074 0.45 0.9 1073 (best estimate) 1. 2. 10. 2.3x1073 2.3 4.6 23. largest MPLEB in Table V, 23 particles, 4.5 represent a reduction of the existing MPLB and MPC, by a factor of 10,000. It is recommended here that the best estimate of the effects of uniform exposure by the BEIR Committee be used together with a risk of cancer induction of 1/2000 per hot particle in determining the MPLPB for insoluble alphaemitting radionuclides in hot particles. This is a somewhat arbitrary compromise and is not the most conservative value that could be recommended. for occupational exposure Thus, the recommended MPL?PB from hot particles of alpha- 77/ The number of particles required to give a cancer risk 78/ Source: equal to that from uniform radiation. BEIR Report, Op. cit., p. 91. The MPLPB corresponding to a lung cancer risk of 3xl07> due to 15 rem/yr lung dose [BEIR Report, Op. cit., p. 156] are 0.03, 0.06 and 0.3 for assumed particle risks of 1/1000, 1/2000 and ~~ ¢ on . * ~ 1/10 ,000 respectively.