Dosimetric quantities in radiological protection and risk assessment

Abstract

Central to the application of the system of protection recommended by the InternationalCommission on Radiological Protection (ICRP) are the physical quantity, absorbed dose,and the protection quantities, equivalent and effective dose. These protection quantities areused to set dose limits, constraints and reference levels and to test compliance in thevarious activities of occupational and public exposure. They are also used inthe assessment of doses from medical procedures. Effective dose in particularhas proved to be a very valuable quantity that allows the summation of dosesfrom external radiation and internal doses from different radionuclides in a singlerisk-related value. However, while it is possible to measure external radiation exposuresand estimate internal exposures down to very low levels of dose, the associatedrisks, principally of cancer, are much less certain. Equivalent and effective dosesare calculated using simplifying assumptions to apply to reference workers andmembers of the public for the purpose of control of exposures. Risks to individuals orspecific population groups should be calculated not using these quantities butusing best scientific information. The purpose of this note is to provide a shortand readily accessible account of the purpose of the ICRP dosimetric quantities,how they are calculated, how they should be used, and how they relate to riskestimation.