[Long term survey on food pollution and contamination by radioactive fallout in Fukuoka, Japan (1961-1976) (author's transl)].
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.
[Experimental studies on the effect of 95Zr-95Nb in albino rats. 3. Distribution of 95Zr-95Nb among organs. Micro-autoradiography of the lung on intratracheally intubated albino rats].
Distribution and excretion of 95Zr-95Nb, which was administrated subcutaneously and orally in rats, had been studied from time to time, for the same experimental period as previous reports. At this time, 95Zr-95Nb were administered to rats of the Wister strain, by intra-tracheal intubation and time trends of distribution in organs as well as excretion in urine and feces of these experimental animals were observed. In addition an autoradiography of lung was performed using the dipping technique in order to observe a finer distribution of 95Zr-95Nb in lung when administered by inrta-tracheal intubation. The results are as follows.1) When 95Zr-95Nb were intubated into the lung, a great amount was retained in and deposited into lung 24 hours after administration and the amount of them decreased considerably after the 7th experimental day. But, it was observed that the amount of 95Zr-95Nb at any time during the experimental period of lung was greater than that for other organs. 63 days after administration, deposition ratio of 95Zr-95Nb for lung held the some level as that of bone which would be considered to be the highest affinity for 95Zr-95Nb among organs.2) The amount of 95Zr-95Nb of tibia increased considerably for 7 days from administration and then began to decrease toward the final experimental day. The rate of decreasing radioactivity in the tibia was considerably slow after the 14th experimental day and the deposition ratio of tibia was the highest among organs excluding the lungs. Therefore, when 95Zr-95Nb was administered into the body, it was considered that bony tissue had strongest affinity of all organs.3) After administrating 95Zr-95Nb, the largest amount was excreted in urine and especially in the feces the first 24 hours through the experimental period. And, 49.86% of 95Zr-95Nb intubated into the lung was excreted in feces until the 63th experimental day and half of the amount of them was contains in the feces excreted until 24 hours after administration. After that, the amount of 95Zr-95Nb excreted in feces suddenly decreased and difference of the amount between feces and urine gradually became less and less toward the final experimental day.4) A micro-autoradiography of the lung at the 63th experimental day revealed the fact there were still a number of blackening spot caused by 95Zr-95Nb in the alveolar wall and some spots were also likely to be in cells in the wall.
[Observations of fallout related to radioactive air-borne dust particles on vegetables].
Studies were made of the chemical and physical properties of large particles of radioactive fallout removed from various vegetables between Dec. 1961 and March 1962. The particles were between 50 and 200 mu in dameter and were very stable against heating and mechanical pressure. Their radioactivity was about 3,000 to 4,000 mu mu c/particle and was characterized by the Nb/sup 95/ + Zr/sup 95/ peak with about 5% Sr/sup 90/. Measurements were made with a gamma spectrometer. (C.H.)