A generic age-specific biokinetic model for calcium-like elements

Publication No.56 of the International Commission on Radiological Protection (ICRP) introduces a generic model structure to address the age-specific biokinetics of 'calcium-like' radionuclides, including Sr, Ba, and Ra, and less complete physiological analogues of Ca, such as Pb and U, in humans. This paper outlines the conceptual basis for the model, summarises the selection of parameter values for the alkaline earth elements, and describes special features of the model included for consideration of Pb. The model differs in form from the alkaline earth model for adult man described in Publication No.20 of the ICRP but depicts similar processes of skeletal uptake and removal. In contrast to the earlier alkaline earth model, parameter values are age specific, redeposition of biologically removed activity is treated explicitly, diminution of activity in bone volume is assumed to be a first-order process, and soft tissues are addressed explicitly rather than as the whole body minus bone and blood.