A biokinetic model for carbon dioxide and bicarbonate.

A systemic biokinetic model is presented for radiocarbon taken into the body as carbon dioxide or bicarbonate. Parameter values describing retention and excretion of carbon during the first few weeks after administration are based on studies of the fate of radiocarbon in human subjects after injection of labelled bicarbonate or inhalation of carbon dioxide. Data on laboratory animals administered labelled bicarbonate, carbonate or carbon dioxide provide information on the tissue distribution and long-term retention of carbon. Model predictions of the time-dependent distribution and retention of carbon differ considerably from those of models recommended by the International Commission on Radiological Protection.