Concentrations of radionuclides in imported foods from foreign countries in Japan (2000-2003)

Japanese law concerning prohibition against marketing insanitary foods, etc, has defined the limit of radioactivity level in imported foods (370 Bq/kg in total of 137Cs and 134Cs radioactivities) post Chernobyl accident and check for this has been performed by the Ministry of Health, Labor and Welfare. The present report describes results of additional examination, conducted by National Institute of Public Health, or the Kobe or Yokohama Quarantine Station, of radionuclide (γ-emitters) concentration in imported foods during the period 2000-2003. Foods examined are from northern (40 samples) and southern (8) America, Asia (66), Oceania (9), Africa (8) and Europe (12), and are 13 kinds of grains, 12 nuts/seeds, 1 potato, 17 fruits, 12 green/yellow vegetables, 13 other vegetables, 19 mushrooms, 4 seaweeds, 15 nonessential taste items like tea leaves, 19 fishes and 12 meats. Samples are those homogenized, freeze-dried or mineralized. The Ge-semiconductor detector connected with a pulse-height analyzer is used for γ-ray detection, mainly that of 137Cs and 134Cs, and for 40K as a natural radionuclide. Sample weights are 1,000-2,000 g and counting times, 100,000-300,000 seconds. Results reveal that 137Cs alone is detectable as a artificial radionuclide but its level is as low as that in similar Japanese foods. Thus the annual effective dose due to intake of 137Cs in imported foods is evaluated enough low in adults. (N.I.)