Long term survey on food pollution and contamination by radioactive fallout in Fukuoka, Japan (1961 - 1976)

The contamination and the pollution of foodstuffs by radioactive fallout have been investigated since 1961 in Fukuoka city and its suburban area. The results obtained were as follows. 1) Recently, the degree of the contamination of greens by radioactive fallout which fell on the leaves decreased to one thousandth in the early stage of the investigation (1961 - 1962). In the period of the investigation, the remarkable increase of the radioactivity of fallout was observed within a week after the Chinese nuclear bomb explosion in the atmosphere (1st, 2nd, 5th, 12th, 13th, and 15th). The radioactivity was 2 to 300 times higher than the usual level. 2) The radioactivity was not remarkable in vegetables which were washed with soap, but it decreased gradually year by year. The increase of the radioactivity was also observed a few days after the atmospheric nuclear explosion. 3) In milk, there were no remarkable yearly decreases of the radioactivity from the beginning of the investigation, but the seasonal variations of the radioactivity, such as higher in April and May, were observed. 4) The radioactivity in diets based on the standard food production in Japan was the highest in 1967. It decreased gradually from 1967 to 1971 and after that the remarkable variation of the activity was not observed. 5) 137Cs contamination of foodstuffs has been observed quantitatively by the method of gamma spectrometry, while sometimes 95Zr-95Nb, 103Ru, and 131I were also detected from the specimens obtained immediately after the nuclear explosions. (auth.)