Application of dose coefficients for internal exposures based on Caucasian physique to Japanese

Manabe, Kentaro   ; Sato, Kaoru   ; Takahashi, Fumiaki  

Effective doses based on ICRP 2007 Recommendations are evaluated from sex averaged equivalent doses obtained by using reference male and female phantoms (male: RCP-AM, female: RCP-AF) whose physique and organ masses (physical characteristics) are adjusted to the reference values of Caucasians. ICRP is revising dose coefficients for internal exposure (committed effective doses per unit intake of radionuclides) conforming to the Recommendations. It is important to comprehend the extent of underestimate or overestimate of doses for Japanese males and females, whose physical characteristics are different from those of Caucasians, when the dose coefficients revised by the ICRP are adopted to the Japanese system of radiation protection. In this study, we evaluated the dose coefficients for ingestion and inhalation of radionuclides based on the average adult Japanese male and female phantoms (male: JM-103, female: JF-103), which have the average physical characteristics of Japanese males and females, and compared the Japanese dose coefficients with sex-averaged dose coefficients based on RCP-AM and RCP-AF. As a result, the differences in dose coefficients were within plus or minus 10% in cases of 87% and 73% for JM-103 and JF-103, respectively. Therefore, the cases that lead considerable underestimation or overestimation from the point of view of radiation protection are limited even if the sex-averaged dose coefficients based on Caucasian physical characteristics are applied to Japanese males and females.