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Safety_Series_025_1968 - gnssn - International Atomic Energy ...

Safety_Series_025_1968 - gnssn - International Atomic Energy ...

This publication is no

This publication is no longer validPlease see http://www.ns-iaea.org/standards/Chronic derm atitis occu rs after sm all doses (considerably m orethan the m axim um p e rm is s ib le d oses) when p erson s w orking withion izin g radiations r e c e iv e dam age to the skin, p a rticu la rly o f thehands, which becom es dry and of v io le t-re d colou r. Num erous telangiectaticareas are ob serv ed . Hair falls from the body, head andbeard, the skin b e co m e s thin, k era toses are subsequently form ed ,togeth er with w arts, betw een which the skin ea sily cra c k s . In advancedstages u lce rs o c c u r and in som e ca ses even ep itheliom ata.1.3. 1.3. GonadsThe sexual glands a re highly ra d iosen sitiv e, the m ale organ sbeing con sid era bly m ore sen sitive than the fem ale. With a d ose aslow as 25 rads to the te sticle s, either loca lly or as w h ole-body exposure, detectable d ecrea se in sperm count o ccu rs. A dose of about250 rads m ay p rod u ce te m p o ra ry s te r ility fo r 1 to 2 y e a r s . Thedose required to produce permanent sterility in men is approxim ately600 rads delivered acutely. In wom en this dose amounts to about800 rads.1.3. 1.4. E m bryonic developm entD evelopm ental abn orm alities m ay also occu r when the em bryoor foetus is irradiated. Particularly in the early stages of embryonicdevelopm ent a dose of a few tens of rads may be sufficient to produceseriou s abnorm alities. This fact is especially important when womenare irradiated during the first days of pregnancy. A number of caseso f m icrocep h a ly with con gen ita l im p lica tio n s have been o b s e rv e dam ong ch ildren who w ere irra d ia ted in the uterus during the atomb om b in g s.It m ay be m entioned that ra d ioactiv e substances can reach theem bryo and the developin g foetus during the period o f nourishm ent,via the placenta. P a rticu la rly in the early stages of em bryon ic d e­velopm ent, radion u clides absorbed in this m anner resu lt in what iseffectively a w h ole-bod y irradiation o f the em bryo.1.3. 1.5. SkeletonBone changes have long been ob serv ed in human bein gs and inexperim en tal anim als as a resu lt o f ion izin g ra d iation s. In youngindividuals th ese changes ran ge fro m cessa tio n o f the p r o c e s s o f38

This publication is no longer validPlease see http://www.ns-iaea.org/standards/o s s ific a tio n and grow th (on exp osu re to d o s e s o f the o r d e r of100 rem s) to com p lete n e cro s is of the bone, observ ed after d osesof se v e ra l thousands of re m s. The m a jority of these bone in ju rieso ccu r as a resu lt of in correct radiotherapeu tic treatm ent o r o f in ­corporation of radioactive substances into the bone. In both circu m ­stances, an in creased incidence of bone tumours has been observed.However, the only bone tumours observed in man have resulted fromthe in corp ora tion of radium into the bon e. It is estim ated that anindividual retaining 0. 1 iug 226Ra after 30 years would have probablyinitially absorbed 10 ng, the greater part of this amount being elim ­inated. In general it may be said that radionuclides deposited in thebones display a particular tendency to b ecom e loca lized in the g row ­ing parts of the bone (epiphyses). With regard to malignant tumours,it has been shown that they m ost frequ en tly d ev elop in the m e ta -p h y ses o f the lon g b on es and m any m ay o c c u r in on e in d iv id u a l.1.3. 1.6. N ervou s tissu eF or a long tim e nervous tissue was thought to be highly resistantto irra d ia tion , T his was due to the fact that after irra d ia tion onlym orph ological changes w ere sought, which require considerable dosesto becom e apparent. Recently, functional changes have been elicitedwith m uch sm a lle r and often v e ry low d o s e s . A m on g such m o d i­fication s, m ention m ay be made of d e cre a se s in excitability andchanges in conditioned r e fle x e s . Irradiation o f anim als with300-400 R produces changes in the electroencephalogram which mayp ersist for about one week.1. 3. 1. 7 . M odification of the immune statusD isturbances of the im m u nological m echanism can be producedby external and internal irradiation. In the latter case, disturbancesmay occu r when the ce lls of the reticulo-en doth elial system have incorporatedradioactive m aterial which may inhibit their im m unologicalfunction.In ex p erim en ts with m on k eys, a w h o le -b o d y irra d ia tio n with450 R resulted in a tem porary su ppression of the antibody resp on sewhen the irradiation was perform ed 24 hours before the beginning ofim m unization. This effect did not develop fully after irra d iation inp reviou sly im m unized anim als.39

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