抄録
Measurements have been made on the radioactivity of dust, foodstuffs, lungs and thyroids of man and animals since October to December 1961. The concentration of 131I in air showed a maximum of 2.07 μμc/m3 on November 6 and the average for the second half of November was 0.62 which value decreased to less than 0.2 in December. Spinach samples showed remarkable contamination with fission products, the maximum being 16 mμc of 131I per fresh kg.
Average intake of 131I by population through ingestion of leafy vegetables was estimated as 100-300 μμc in November and 7-20 μμc in December. The contribution of milk in daily intake was less than 10% of that of leafy vegetables which was considered the main channel of transmittance of 131I to the human population of Japan.
A greater risk would be involved to breast-fed baby than bottle-fed one since the latter consumes canned powder milk in Japan and the former would be greatly influenced by its mother's diet composition.
The level of 131I in human thyroids from 52 persons who died during the period December 4-12 in Tokyo was less than 5.6 μμc/fresh g on the average ; the thyroid burden was estimated as 100-165 μμc of human population in the period November-December 1961.
