StaffScientist NaturalResourcesDefenseCouncil 111SutterStreet,20 th Floor SanFrancisco,California94104 ReneeSharp Director,CaliforniaOffice EnvironmentalWorkingGroup 2201BroadwayStreet,Suite308 Oakland,Californi
Human exposure to natural ionizing radiation is due to both internal sources such as ingestion and inhalation of radioactive isotopes, and external sources from cosmic radiation and primordial radionuclides present in the Earth crust. Primordial radionuclides are40K and radioisotopes of the decay series ...