One more thing to know about Co-60: its half-life of 5.27 years, combined with the radiation it emits, makes it particularly dangerous. The half life being so l

One more thing to know about Co-60: its half-life of 5.27 years, combined with the radiation it emits, makes it particularly dangerous. The half life being so long means it's a 30 year problem (after 5 half lives you're at about 3% of original activity), while its being so short (many metals are thousands of years) means that a small mass can have a high activity. Its gammas that it radiates are fairly energetic compared to most (a problem not encapsulated by the Ci unit) and it bioaccumulates so that small amounts inhaled or ingested can provide huge doses over the subsequent decades.