678e89c5___CTBTO_Preparatory_Commission__Health_hazards
[Radionuclide] Caesium-137 (137Cs) [Half-life*] 30 years [Health hazards] 
After entering the body, caesium is distributed fairly uniformly through the body, with higher concentration in muscle tissue and lower concentration in bones. Can cause gonadal irradiation and genetic damage.
General overview of the effects of nuclear testing: CTBTO Preparatory Commission
Health hazards