Estimation of internal radiation dose to the adult Asian population from the dietary intakes of two long-lived radionuclides

Daily dietary intakes of two naturally occurring long-lived radionuclides, ²³²Th and ²³⁸U, were estimated for the adult population living in a number of Asian countries, using highly sensitive analytical methods such as instrumental and radiochemical neutron activation analysis (INAA and RNAA), and inductively coupled plasma mass spectrometry (ICP-MS). The Asian countries that participated in the study were Bangladesh (BGD), China (CPR), India (IND), Japan (JPN), Pakistan (PAK), Philippines (PHI), Republic of Korea (ROK) and Vietnam (VIE). Altogether, these countries represent more than 50% of the world population. The median daily intakes of ²³²Th ranged between 0.6 and 14.4 mBq, the lowest being for Philippines and the highest for Bangladesh, and daily intakes of ²³⁸U ranged between 6.7 and 62.5 mBq, lowest and the highest being for India and China, respectively. The Asian median intakes were obtained as 4.2 mBq for ²³²Th and 12.7 mBq for ²³⁸U. Although the Asian intakes were lower than intakes of 12.3 mBq (3.0 ug) ²³²Th and 23.6 mBq (1.9 ug) ²³⁸U proposed by the International Commission on Radiological Protection (ICRP) for the ICRP Reference Man, they were comparable to the global intake values of 4.6 mBq ²³²Th and 15.6 mBq ²³⁸U proposed by the United Nation Scientific Commission on Effects of Radiation (UNSCEAR). The annual committed effective doses to Asian population from the dietary intake of ²³²Th and ²³⁸U were calculated to be 0.34 and 0.20 μSv, respectively, which are three orders of magnitude lower than the global average annual radiation dose of 2400 μSv to man from the natural radiation sources as proposed by UNSCEAR.