. rg wa 40. ‘She probic ms of high lceal concent ton wWeterat (irantialy Gl¢ of cose ace at these moot sovere wie: rad IRCLIVS Det Vaile some sol merry Ce“ussion} de pariteclate angie: lab bv the feo uy CU cay wile fang adaotiyyhaces, ad fart Pe‘esis based ecetrdttecs. Here the locnh Coco can reach very on dose Cstecminatioa encounters prifonad high valucs even theugh the Incan tissue dase ypstucel toute“s my be very low. Gereintyii Canuat be assured “acu! Ties, onoilering onty che yey there is first the pioblaa of lack off newledes of thathacacny ofe sc aud efcctwill hold at these the sensitivity to radintion-induced matizaant Richt doses aud @os.c rates, On the ather ha:nd, there m: chanze of the reticulum cclis presant, aud poss- bea gecat deal of cell death, nnd par- az ibly also of lysaphocytes thensh+ e3. Also ay calculation of Coan NoriLation to t! 2 WARDrion. chements ct tac lympioid tissue wool TSae] ive ticuladly with c-errission, withits snore nad well- oe defined ranges, the sunnber of a® “ue sinble i eels raoy besmall sorapared with thhe numb er at: Rilled! celis. Flow= = eer, this ratio w ul deosad on Lvvormatio ubjects as : the size and activityof the particles, the extent resent RAY to which they agcregate, and their movearent culate im 41. Oa the basis of general considerations and of some experimenveul data and clinical experi- particles within. the lymph nodes.“Tn addition there is very little reported work on Uhe distribution of the material withia fie nedes, which within the tissue, aad the movementof the cells pest them. clsRe u ence the ‘Disk Gro:op were of the opinion that, could be obtained by autoradiographic study, the SAMS I“ACiciiva NCrey ab- ; or on the deeres of fibrast sis and ether lastolozical sorption nucht welk Deiiess Chective when distri- bated as 2 series of “hot spots” than whea uai- oo for date cfiec ts, farmly distributed. Fhus, with particulate= racliovc.. a . Mowevec, @ savers praciical problem alld hes now been rccogauized in coanecition with the ishala ae tion ofplutconiuim pacticutates, and is now being coasilered in cciait by a Task Group of Corm- mittee 1 of ICRP. 42. From dog experiments bein. carried out in the United States and Som limited sstudies in made the Task Group coagidered that they should, for consistency \ithia, the recomunenaations, refer to the whole lymph tissns and not only to the respiratory lymph nodes. However, human subjects it hzs become clear that inhalation of plutonium pxrticulates can leadto hin concentrations of the particulate matecial in the pulmonary lymph rodes, and thet the mean radiation dose to ths© pulmontary lymph nodes until more information becomes available on some of the subjects mentioned above, litds and indeed to lympmhonl tissue 2s a whole is Nkely to be greatly ic excess of that to the lang, which is at present receded a3 the critical orza for inhaled particulans matter. 45. The actual dose ratio; are not yet known with anyprecision bat the Task Group underston] that the mean cose to lymphoid tiiue a3 “R® whole might excee:i that to the hing by a factor of 10 or marc, and, if the respiratory lyznph nodes were atanc teken into consideration, the facter cou Be 109 ov perhans much | Rreater, Lhe problent &s whether lympiroiel tissue he as the critical organ, and, if su, achother the dose "sie (MU, foe phvteslaa ino putentets foc Snow’ be sebstuvieds seduccd Latow the cure XC reet valicn weirht can be put on dose calculations. Data on tumour productioa from animal experiments ave of more significance, 7and the results of pyresent work with dogs, particularly those with lower amounts ofplut onium, are awaited with interest. In the meantime, the Task Group 3ve OF aed es a whole or respteaeecy lyrapt: rode isaunc ds particuler showd bs teben on the residence times of the particulate maaterial particulate matecial over reauy years. Another factor to befhen inte cousideration, corna.aa to all particel ic deposition and espacially to those involving eoerediters, is that the nurnber of cells irradiatediis, for the samemeantissns dose, Very dependent on the purticle size, Minalty, ly:nphocyte migration ts a factor that should be taken . into consideration. can! ions calculat se 45, Inso far a3 meanco active sources withic a tissue, 2 mean tis: 12 dose would .probably i: Lat ottce changes oroduced. Better data ave zlso reauired ia the Jymph nodes and the solubiliy of the the opinion that any Immediate change Jja the dos lisnit for plutonium ou thes basis of visk to lym phoid tissue is not warranted. so meee ome II. -13- a on . ICRP Publication 14 Radiation Sensitivity and Spatial Distribution of Dose (Publication 14 app2ars as a report of two Task Groups, and not as the official recormondations of the ICRP.)