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  • Author or Editor: S. Hisamatsu x
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Abstract  

The direct transfer of organically-bound3H (OBT) of diet to that in the human body is reasonable, since the human body needs essential amino acids and fatty acids. Metabolic models of3H which were recently developed for the human body took this direct incorporation into account. Data for fallout3H in diet and human tissues were used to validate model parameters, although such data are relatively scarce. However, a simple equilibrium between dietary3H and human body3H was assumed for such validations. The simple equilibrium assumption means completely neglecting past3H concentration in the human body. When the model consists of compartments which have long mean residence times, estimated3H concentrations in the human body from the simple equilibrium assumption can differ significantly from results of adequate calculation considering contribution of past human3H concentrations. The examples of such calculations are described in this paper. Results of the calculations show that suitable environmental3H transfer models are necessary to use fallout3H data for the validation of3H metabolism models.

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Abstract  

The soil-to-grass transfer factors and grass-to-milk transfer coefficients were determined for 137Cs and stable Cs in soil, grass and milk samples collected in Aomori Prefecture, Japan. The concentrations of 137Cs in the soil and grass samples collected from 25 sampling sites were 13±12 Bq.kg-1 and 2.0±2.1 Bq.kg-1 dry wt., respectively. The geometric mean of soil-to-grass transfer factor of 137Cs was 0.13 and its 95% confidence interval was 0.017-0.98. The transfer factor of 137Cs was higher than that of stable Cs, and they had a positive correlation. The concentration of K in the soil affected both transfer factors. The concentration of 137Cs in milk samples collected from 16 sites was 76±43 mBq.kg-1 fresh wt. and had a good correlation with that of stable Cs. The geometric mean of grass-to-milk transfer coefficient of 137Cs was 0.0027, assuming that a cow's total daily intake was 20 kg of dry grass. The transfer coefficient of 137Cs was positively correlated with that of stable Cs.

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Abstract  

The paper describes the recent plutonium measurements on tissues taken at human autopsy on foodstuffs collected in northern Japan. Estimates of plutonium concentrations are made using the ICRP 30 metabolic model and is compared with the results of our measurements.

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Abstract  

Tritium (3H) concentrations in diet samples from Akita City, northern Japan, and in human tissue samples from the general population of Akita Prefecture were analyzed to study fallout3H transfer.3H concentrations in human soft-tissue samples have been previously found to be similar to those in diet samples. In this study, higher organically-bound3H (OBT) concentrations were found in human costal cartilage and sternum samples than in the soft-tissues. Mean residence times of OBT in the cartilage and sternum were estimated to be 57 years and <6 years, respectively, with a single compartment model which took into account compartment growth.

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Abstract  

Americium and plutonium concentrations in food samples and human tissue samples were determined using alpha-ray spectrometry.Food samples, representative of the average dietar intake over a period of 30d in Japan, were pruchased in Akita during 1985 and 1986. The food was divided into six groups: cereals, vegetable, fruits/beans, seaweeds, fish/shellfish, and meats/eggs/milk. Most of the. total ingestion of both Pu and Am was contributed by seaseed and fish/shellfish. The concentration of Am in the other food groups was low.A compoarison of the measured241Am/239+240Pu ratio in human liver with the predicted value of the ICRP-30 or ICRP-48 model showed that the half-life of Am in the liver is approximately 2–10y. The human tissue samples were obtained from subjects who died in Akita and Niigata Prefectures in northern Japan during 1981–1984. The median concentration of241Am was 1.4 mBq/kg-wet in the stemum (n=11), 3.4 mBq/kg-wet in the liver (n=19), and 0.5 mBq/kg-wet in the lung (n=15). The ratio of241Am/239+240Pu was 0.34 in the sternum, 0.12 in the liver, and 0.14 in the lung.

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Abstract  

High specific activity ratios of tissue-bound3H to free water3H were reported for foods in Europe und USA during 1970s and 1980s. To examine these high specific activity ratios, small number of some recent food samples imported from European countries were previously analyzed in our laboratory. The specific activity ratios obtained were around unity, and not so high as those reported by other investigators. To confirm our results, additional food samples were collected during 1988–90 and analyzed for3H. The specific activity ratios in the food samples were found to be around unity, and the previous results was confirmed.

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Abstract  

Radioactive fallout constitutes the major source of contamination of the environment with fission products. Our primary interest was in selected fission products, such as 131I, 89Sr, 90Sr, and 137Cs, and neutron activation products, such as 3H and 14C. Plutonium-239,240, 241Am and 90Tc are generated from nuclear tests, and they are important by-products of nuclear industries. Polonium-210, 210Pb and 232Th, 230Th and 228Th occur widely in nature. These radionuclides enter the human body through inhalation and the ingestion through food and water. These nuclides may cause radiation doses to certain organs of the body. Assessment of the resulting health hazards is an essential public health activity, which demands reliable techniques for the assay of the various radionuclides in man and his environment. In this paper, we present the accumulation of radionuclides from man-made sources and primordial radionuclides in various tissues of the Japanese population. The studies were performed at the Department of Public Health, Akita University School of Medicine, during the periods from 1973 to 1995.

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Abstract  

Rice grain samples and surface paddy soil samples were collected from 20 sites throughout Aomori Prefecture, Japan, and the concentrations of 25 elements in the polished rice and 33 elements in the soils were determined by neutron activation analysis, inductively coupled plasma-mass spectrometer or atomic adsorption spectrometer. The range of essential element concentrations in the polished rice was within one order of magnitude, however, the range for most of the trace elements was more than one order of magnitude. The range of element concentrations, except for I, in the paddy soils was within one order of magnitude. The ±95% confidence intervals of the soil-to-polished rice transfer factors for all elements, except for Pb, were within two orders of magnitude, and the geometric mean values were as follows: Cl, Mo and Zn (0.1–1); K, Cu, Cd, Rb, Mg, Mn, and Ag (0.01–0.1); Ni, As, Ca, Se and I (0.001–0.01); Na, Cs, Sr, Co, Cr, V, Ba, Pb, Fe and Al (<0.001).

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Abstract  

The concentration of232Th,230Th and228Th in various human tissues of Japanese subjects obtained at autopsies are reported. The tissue samples were weighed, spiked with234Th tracer and ashed by acid. The solution was dried on a hot-plate. Separation of thorium radionuclides was accomplished through cation-exchange resin chromatography and electrodeposition. The concentrations of thorium isotopes were measured by -spectrometry. Thorium-232 and230Th concentrations were found to be highest in lung, followed by bone. The maximum concentration of228Th was in bone. The lowest concentrations of thorium isotopes were in muscle.

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