Influence of gender differences in the carbon pool on dose factors for intakes of tritium and 14C-labeled compounds.

The ICRP's biokinetic models for five tritium-labeled and five 14C-labeled compounds (not including radiopharmaceutical compounds and excepting carbon monoxide) incorporate a compartment representing the body carbon pool. Using the ICRP models, as coded into the Genmod-PC internal dosimetry code, higher dose coefficients are calculated for females than for ICRP's Reference Man. The ICRP's committed effective dose coefficients for the ingestion of tritiated water and organically bound tritium by the adult male are 1.8 x 10(-11) and 4.2 x 10(-11) Sv Bq(-1), respectively. Using the Genmod-PC code, the corresponding dose coefficients for the adult female are 2.2 x 10(-11) and 6.2 x 10(-11) Sv Bq(-1), which are 25% and 46% greater than the adult male's. Similarly, the ICRP's dose coefficient is 5.8 x 10(-10) Sv Bq(-11) for an intake of organically bound 14C by the adult male, and the estimated dose coefficient using Genmod is 54% greater for the adult female. The carbon retention half-time for an average adult female is calculated as 51 d and that for an average adult male, 38 d; the latter is similar to the carbon half-time of 40 d recommended by International Commission on Radiological Protection (ICRP). The longer turnover time of whole body carbon in females is one factor that causes the dose coefficients for females to be higher than those of males; a second factor is the smaller whole body mass of ICRP's Reference Woman compared to Reference Man.