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/the p ossib le induction of lung ca n cer by radon and its daughtersp resen t in the m in es. The average latent p eriod fo r the inductionof lung ca n ce r is ~ 17 y e a rs and a cco rd in g to approxim ate c a lc u la tio n s the d o s e d e liv e r e d d u rin g th is tim e is h u n d red s o f r a d s .Radium is a bon e-seek in g elem ent and its deposition in them ineral part of the bone induces bone m alignancy (osteogen ic s a r com as and carcin om as of the paranasal sinuses and m a stoid s). Noclin ica lly sign ifican t sign s have been o b se rv e d with re sid u a l bodyburdens of < 0 .5 juCi Ra. With in crea sin g quantity of in corp oratedm aterial the in ciden ce of these tum ours in cre a ses.E xperim ents with anim als have elucidated to a certain d egreethe m echanism of the dam age caused by b on e-seek in g (osteotrop ic)elem ents. Bone dam age appears in two fo rm s. F irst, bone is injuredthrough d estru ction of blood v e s s e ls and by d ire ct a ction onthe osteocytes. Secondly, the radiation of the internal em itter causesabnorm al activity in osteogen ic connective tissue, leading to m arkedterm inal fib rosis . With sm all d oses there is a p ossibility of rep airin bon e. It is in terestin g that the form a tion o f tu m ou rs m u st notn e c e s s a r ily be p re ce d e d by s e v e r e dam age to the b on e.The in cid en ce o f tum ours in experim en ta l an im als in c r e a s e swith accum ulated d ose and at h igher d ose ra tes. D ose ra tes varyw id ely in exp erim en ts with in tern al e m itte rs. T his com p lica te s ,am ong other fa ctors, the determ ination of the c o r r e c t relation sh ipbetw een tum our induction and absorbed d ose.The fa r g rea ter induction of bone tum ours in experim en ta lanim als overshadow s the in ciden ce of other types of tum ours, e.g.of leukaem ia. This d isea se has been rep orted in radium patients,but only in those who w ere exposed at the sam e tim e to high d oseso f external gam m a radiation.52
This publication is no longer validPlease see http://www.ns-iaea.org/standards/2. RAD IOLOGICAL HAZARDSF rom the p6int of view of m onitoring and protection , a d istin ction m ust be m ade, a ccord in g to the way in which radiation en tersthe organism , betw een:(a) E xtern al irradiation fro m a d istance, and(b) R adioactive contam ination.E xternal irradiation originates from sou rces at a distance fromthe body which em it radiations o f such nature and energy as to reachit, X - and gamma rays, beta p a rticles, n eu tron s.-R adioactive contam ination o ccu rs when radioactive substancesare brought into contact with the body, either su p erficially (externalor skin contam ination) o r within the body (internal contam inations).2.1. EXPOSURE TO NATURAL RADIATIONB efore d iscu ssin g occupational exposu re, we should r e ca ll thatw o rk e rs, like any oth er p e rso n s, a re su b ject to natural radiation .Studies devoted to natural radioactivity have thrown light on itso rig in s , the a v era g e d ose resu ltin g in the m ost d en sely inhabitedp a rts o f the w orld and its p e rio d ic flu ctu ation s.C osm ic rays originate in in terstella r sp aces and d eliv er to thehuman body a dose estim ated at 30 m illirem s a year in the P arisianarea.The soil and building m aterials around us contain tra ces of uraniumand th oriu m , som e daughter p rod u cts o f w h ich em it gam m arays; the resulting dose varies greatly from place to place. Amongthe daughter products of uranium, radon is a gas which diffuses intothe a ir; it cau ses external irradiation because of its active deposit,in which som e o f its daughter p rod u cts are gam m a e m itte rs. It isalso inhaled, thus bringing about internal (alpha, beta, gamma) con tam ination o f the body, which is accentuated by the in gestion o f tra ceso f uranium con tain ed in w ater. T he d ose resu ltin g fr o m this en viron m en ta l ex p osu re is estim ated at 50 m illir e m s a y e a r in theP a risia n a rea.A ccount m ust a lso be taken o f the natural ra d ion u clid es whichen ter the com p osition o f the bod y and a re regu la rly ren ew ed by afo od -ch a in : p ota ssiu m -4 0 and ca rb o n -1 4 d e liv e r an a vera ge doseto the body o f som e 20 m illire m s a y e a r.53
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