Variation of Internal Doses Caused by Differences in Physical Characteristics between the Average Japanese and the ICRP’s Reference Man Which Is Based on the Standard Data of Caucasians in the Dosimetric Methodology in Conformity to the 2007 Recommendations

This paper describes a systematic analysis of the variation of internal doses derived from differences in physical characteristics in a dosimetric methodology fully based on the 2007 Recommendations of the International Commission on Radiological Protection (ICRP), including biokinetic models revised recently. Effective dose coefficients were estimated for the intakes of radionuclides reflecting the average physical characteristics of the adult Japanese, and compared with those provided by the ICRP, which have been evaluated using the physical constitution of the standard adult Caucasian (ICRP reference phantoms). Japanese dose coefficients were calculated using a dataset of specific absorbed fractions for the average adult Japanese, which was prepared by modification of the existing data with additional radiation transport calculations, combined with the current nuclear decay data and biokinetic models of ICRP. Comparison was made on 1339 conditions of intakes for 284 nuclides, which showed discrepancies in dose coefficients ranging from −37% to 44%. However, the discrepancies were smaller than 10% in 78% of all conditions. The extent of the variation in the dose coefficients will be acceptable for using the ICRP’s dose coefficients for the purpose of radiation protection for the Japanese.