Contributions of 18 food categories to intakes of Th-232 and U-238 in Japan

Daily intakes of Th-232 and U-238 and contributions of food categories to those nuclide intakes in Japanese were estimated using a market basket study for 18 food categories. Food categories having higher U-238 contents (per g-fresh) were found to be as follows: seaweeds 1,140 mu Bq; fishes and shellfishes 37 mu Bq; nuts and seeds 11 mu Bq; bean products 8.6 mu Bq; and cooked meals 7.3 mu Bq. Big contributors to the daily U-238 intake in Japan were as follows: seaweeds (50%); fishes and shellfishes (26%); and bean products (4.3%), For Th-232, higher contents (per g-fresh) were found as follows: seaweeds 28 mu Bq; fishes and shellfishes 13 mu Bq; mts and seeds 8.2 mu Bq; green vegetables 3.9 mu Bq; cooked meals 3.5 mu Bq; and bean products 2.9 mu Bq. Big contributors to the daily Th-232 intake were as follows: fishes and shellfishes (44%); green vegetables (11%); bean products (7.4%); and seaweeds (6.0%). For both nuclides, marine food products were big contributors, while minor contributors were oil and fats, eggs, and cooked meals Daily intakes of Th-232 and U-238 in Japan were estimated to be 2.7 mBq and 14 mBq per person from the intakes of the 18 categories, respectively. Annual effective doses were estimated to be Th-232, 2.2 X 10(-7) Sv, and U-238 2.2 x 10-7 Sv.