- 1B = ’ Cc, NN The Hot Particle Problem It is important to recognize that the ICRP has given NO culsance with respect to nonuniform irradiation of the lung by insoluble alpha-emitters such as insoluble plutonium particles. In its Publication 9, the ICRP states: ...In the meantime there is no clear evidence to show whetner, with a given mean absorbed dose, the biological risk associated with a non-homogeneous distribution is greater or less than the risk resulting from a more Girtiuse cistribution of that dose in the lung. 29 in etiect, the ICRP is saying that there is no guidance as £9 the risx lor non-homodqeneous exposure in the lunc, hence the MPLB are meaningless for insoluble slutonitn Tae NCRP offers the following ana sixsilar statement with restect to these particles: {210) The NCRP has arbitrarily used 10 percent of tne volume of the organ as the significant volume for izradiation of the gonads. There are some casas in waick choice of a significant volume or area is virtually meaningless. For example, if a single barticle of radioactive material fixed in either lung Or iwmph neces may be carcinocenic, the averaging ci écss ¢ither over whe lung or even over one cusic ceantineter mav have little to do with this case. 30 Tnis hot sarticle problem is also well recognized in tne bioslecical community. 29/ IcRP 30/ CRP Paport No. The following is extracted froma Publication 9, Op. 39, Oo. cit., p. cit., pp. 4. 79-30. \ spony