-~ 51- VIII Summary of Recommendations The following recommendations aoply to alpha-emitting hot particles where a hot particle is defined as a particle that contains sufficient activity to deliver at least 1000 rem/yr to the surrounding lung tissue. For isotopes having half-lives greater than cone year, this would correspond to particles containing at least 0.07 pCi of alpha activity. 8? It is recommended that: 1. For occupational exposure MPLPB = 2 hot particles MPCa for Py-239 2. = 3.5x1o716 uci /m1 88 For non-orcupational exposure MPLPB ='0.2 hot particles MPCa for Pu-239 = 9x10-18 uci/m®? 877 These particulates would consist of compounds of Pu and the other actnides which fall into Class Y material in the ICRP Task Group Lung Model. These materials would be retained for years in the lung. See tor example, iCRP Publication 19, Op. cit., p. 6. Since only particles in the size range of 5 u and below in diameter would be deposited in the deep respiratory tissue, this in effect sets an upper limit for the particle size of interest here. If the half-life is less than or close to 1 year the limit of 0.07 pCi can be adjusted upward through appropriate calculations. 88/ This MPCa applies Pu-239. for particles containing 0.07 pci of For particles containing more than 0.07 pCi the MPCa could be increased proportionately. For particles containing less than 0.07 pCi the existing MPCa=4xlo71l1l pci/ml would apply. The MPCa for hot particles of other isotopes and mixtures of isotopes should be established on a Similar basis with consideration given to the half-life of the isotope. 89/ Ibid.