Safety_Series_025_1968 - gnssn - International Atomic Energy ...

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This publication is no longer validPlease see http://www.ns-iaea.org/standards/th eir stage of developm ent, the g rea ter is th eir sen sitivity. A ftersm a ll radiation d o se s, a m od erate m u ltip lication of the young redand white cells occu rs, but after large doses an overwhelm ing effectupon the m arrow is observed , leading to the com plete depopulationof the m arrow tissu e. The m arrow begins to resum e activity in thefirst or second week after irradiation and the duration of the p rocessis governed d irectly by the radiation dose. During the p rocess itself,recov ery of white-cell production is m ore rapid than eryth rocytop oiesis.It m ay be said, v e ry b roa d ly speaking, that rea ction s to ra d iation as m anifested in the p erip h eral blood depend on the radiationd ose, sp ecies sp ecificity , the life-sp a n of the different corp u scu larelem ents, their sen sitivity and pow ers of renew al and the state ofthe organ ism at the tim e.Im m ediately after irra d ia tion , a sh ort p eriod of le u k o cy to sisensues, occasion ed by the relea se of leukocytes from the bonem a rrow . Then follow s a drop in the total leu kocyte count, these v e rity and duration o f which are p rop ortion a l to the d e g re e andlength of radiation exposu re. A fall in the lym phocyte count isc h a ra cte ris tic and r e c o v e r y fro m neutropenia m ay be taken as agood prognostic sign. The eosinophil count drops only after a largerd o se. The num ber of re ticu lo cy te s is a lso reduced and early r e -ticu locy tosis is a favourable indication of re co v e ry . The r e d -corp u scle count drops only very slow ly after irra d iation . M arkedanaem ia does not o ccu r until two to fou r weeks after a la rge ra d iation dose. In cases of severe damage this turns to aplastic anaemia.A fter irradiation, the blood-platelet count also falls, the ra d iosensitivity of the p latelets being g rea ter than that of e ry th ro cy te s.The lack of blood platelets leads to a tendency to bleeding. The r e covery of the blood-platelet count is generally very slow. The m onocytesbehave in the sam e m anner as eosinophils and an in crea se inth eir num ber is a favourable indication o f re co v e ry .1.3. 1.1. 2. G a s tro -in te s tin a l s y s t e m . S m all d o s e s o f ion izin gradiation affect the m otility o f the intestine and enzym e secre tio n ,whereas large doses lead to ulceration of the intestinal m ucosa. Theintestinal bacteria penetrate the dam aged intestinal tract, enter theblood system and are ca rrie d throughout the body, causing seriou ssep tic con d ition s. Changes in the g a stro -in te stin a l tra ct a re f r e quently d e cis iv e in the ou tcom e o f radiation d is e a s e . N aturally,d ire ct irra d ia tion fro m con sid e ra b le quantities of in gested r a d io active substances in experim ental anim als may severely damage theintestinal wall in a sim ilar m anner.36
This publication is no longer validPlease see http://www.ns-iaea.org/standards/1.3. 1.2. SkinSince radiation entering the body from external sou rces has a lm ost in varia bly to p ass fir s t through the skin, the rea ction o f theskin to ion izin g radiation has been studied in great d eta il. B eforethe developm ent of accu rate d osim eters, erythem a of the skin fo llow ing external irradiation by X -r a y s was taken as the basis of theb io lo g ica l unit o f d ose. A fter la rg e r d oses this erythem a changesto pigmentation, and after still greater doses, various types of radiodermatitis appear, which m ay lead to n e cro sis and u lcera tion s andmay finally becom e malignant growths. This latter case applies particularly to the form s of derm atitis resulting from chronic low -d oseX -r a y irradiation.T h ree d e g re e s of acute ra d io d e rm a titis can be distin guish ed:(1) R adioderm atitis eryth em atosa. This m an ifests its e lf in areddening of the skin beginning on the fourth to the seventh day. Onlyin the third to fourth week d oes the skin regain its n orm al a p p ea ra n ce.Hair from head and beard may fall from the areas of reddened skinwithin two or three w eeks. The skin rem ains tem porarily coloured,peels easily, and is d ry. E pilation is one o f the m ost con spicu ou sevents even after a dose of 200 rads of soft radiation. It begins 13 to17 days a fter irradiation and m ay be rep laced by a regrow th of hairafter several months depending on the dose delivered. A dose higherthan 2000 rads leads to com plete and permanent epilation.(2) R adioderm atitis bu llosa . T his o ccu rs after la rg e r d oses,and between the second and fifth days after exposure the skin becom esdark violet in colou r and water b listers, sim ilar to those occu rrin gin se con d -d e g re e burns, a re fo rm e d . The skin itch es, burns andis painful. Within two or three weeks, the hair falls out and the lossis largely perm anent. Healing is slow , and the skin th ereafter r e m a in s d ry , w h itish and c r o s s e d with b r ig h t-r e d b lo o d v e s s e ls .(3) R adioderm atitis e sch a rotica . The skin reddening appearsas early as the second or third day after a high radiation dose. Deepand painful u lce rs and a lso a b s c e s s e s appear on the skin, healingis slow, and sca rs, interwoven with large blood v e sse ls , rem ain onthe damaged a reas. The skin is dry, since the sebaceous and sweatglands have been com pletely destroyed.37
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