Safety_Series_025_1968 - gnssn - International Atomic Energy ...

This publication is no longer validPlease see http://www.ns-iaea.org/standards/The in gestion o f ra d ioactiv e m a teria ls by m an can take p la ceeither with drinking w ater, with food, by sw allow ing of inhaled p a r­tic le s , o r by acciden tal penetration into the mouth cavity.F ood -ch ain s are of great im portance in evaluating potential con ­tam ination o f the body by ra d ioa ctiv e m a teria ls p resen t in the environm en t. One of the m ost com m on routes to man fo r ra d ioactivefa ll-ou t is as follow s:F a ll-ou t ---------* plant ---------* cattle ---------* meat (m ilk)-------- > manMilk is a v ery im portant food -ch ain path, esp ecially fo r radioactivestrontium and iodine.1.4. 2. 2. A bsorption through inhalationIn the atom ic industry the m ost usual entry of radioa ctive m a­te r ia ls in the hum an bod y du rin g rou tin e op era tion s is that o f in ­halation. The inhaled radioactive p a rticles may be tran sferred intothe circu la tion and deposited in a c r itic a l organ . They m ay in ju red ire ctly the r e s p ira to ry su rfa ce s o f the lungs o r be ab sorb ed bybronchial lymph nodes. The depth of penetration into the respiratorysystem depends on p a rticle s iz e . S m all p a rticle s fr e e ly enter thelo w e r p ortion s o f the lungs; la rg e p a rticle s a re d ep osited m ainlyin the upper re s p ir a to r y tra ct and a re ea sily c le a r e d .Usually p a rticles are heterogeneous in size. V ery often radioactivem aterial is attached to p a rticles of inert m aterial.The fu rth er fate o f inhaled p a rticle s depends upon th eir solu ­bility in body fluids. It determ ines to a large extent their depositionand subsequent excretion (see F ig. 15).1.4. 2. 3. A bsorption through the skin ^The intact skin absorbs v ery little radioactive m aterial. Tritium ,h ow ever, and som e oth ers can be so ab sorb ed . The p erm ea b ilityo f skin w hich has been in ju red even by su rfa ce a b ra sion s is v e rycon sid era b ly in cre a se d . Wounds p erm it open entry of ra d ioa ctiv em a teria l. The p re s e n ce o f org a n ic solven ts on the su rfa ce o f theskin a ls o a c c e le r a t e s the p e n e tra tio n o f r a d io a c t iv e m a t e r ia ls .When la rge quantities of rad ioactive m aterial com es in contactwith the skin, e.g. during an industrial accident, the skin absorptionshould be taken into consideration.45'