Safety_Series_025_1968 - gnssn - International Atomic Energy ...

This publication is no longer validPlease see http://www.ns-iaea.org/standards/tration s’ fo r about 250 radionuclides based on radioactive ch aracteristicsof these nuclides and their m etabolism in the 'standard man'(see part 3).The deposition o f internal em itters has been extensively studiedon experim ental anim als and also in man whenever adequate data hasbeen available.A lkaline earths like strontium and radium a re m etabolized likeca lciu m . T hey a re d eposited and retained in the bon es. T hey a renot even ly d istribu ted , but m ay fo r m sm a ll fo c i o f unusually highlo c a l con cen tra tion .The tox icity o f radium fo r man is quite w ell establish ed and ithas been used fo r estim ating the potential toxicity of other osteotropicn u clides. The sym ptom s o f radium poisoning appear 20 - 30 yea rsafter exposure to radium . An individual having 0.1 ng 226Ra 30 yearsa fter a sin gle exp osu re m ust have absorbed m uch m o re radiumin itia lly .S trontium -90 fo rm s a part of the b iosp h ere and it follow s c a l­cium in ca lciu m -ric h food s, esp ecia lly m ilk . It is deposited intensively in the bones of infants, together with ca lciu m . A fter then uclear tests great quantities o f stron tiu m -90 w ere introduced intothe food -ch ain s and as a resu lt a con sid era b le in crea se in the ratio90S r /C a has been o b serv e d . A s dem on strated in F ig . 16, this in ­c r e a s e is g reat, e sp e cia lly in infants.AGE (yr)FIG. 16. Age distribution o f 90Sr/Ca ratio in human bones [ 7 ],O 1961 ■ 196247