 It is used in external beam radiotherapy , sterilization of medical supplies and medical waste , radiation treatment of foods for sterilization ( cold pasteurization ) , industrial radiography ( e.g. weld integrity radiographs ) , density measurements ( e.g. concrete density measurements ) , and tank fill height switches . The metal has the unfortunate property of producing a fine dust , causing problems with radiation protection . Cobalt from radiotherapy machines has been a serious hazard when not discarded properly , and one of the worst radiation contamination accidents in North America occurred in 1984 , when a discarded radiotherapy unit containing cobalt @-@ 60 was mistakenly disassembled in a junkyard in Juarez , Mexico . 
