Toshihiro Takatsuji

Measurement of soil contamination by radionuclides due to the Fukushima Dai-ichi Nuclear Power Plant accident and associated estimated cumulative external dose estimation

Soil sampling was carried out at an early stage of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Samples were taken from areas around FDNPP, at four locations northwest of FDNPP, at four schools and in four cities, including Fukushima City. Radioactive contaminants in soil samples were identified and measured by using a Ge detector and included (129 m)Te, (129)Te, (131)I, (132)Te, (132)I, (134)Cs, (136)Cs, (137)Cs, (140)Ba and (140)La. The highest soil depositions were measured to the northwest of FDNPP. From this soil deposition data, variations in dose rates over time and the cumulative external doses at the locations for 3 months and 1y after deposition were estimated. At locations northwest of FDNPP, the external dose rate at 3 months after deposition was 4.8-98 μSv/h and the cumulative dose for 1 y was 51 to 1.0 × 10(3)mSv; the highest values were at Futaba Yamada. At the four schools, which were used as evacuation shelters, and in the four urban cities, the external dose rate at 3 months after deposition ranged from 0.03 to 3.8μSv/h and the cumulative doses for 1 y ranged from 3 to 40 mSv. The cumulative dose at Fukushima Niihama Park was estimated as the highest in the four cities. The estimated external dose rates and cumulative doses show that careful countermeasures and remediation will be needed as a result of the accident, and detailed measurements of radionuclide deposition densities in soil will be important input data to conduct these activities.

FALLOUT RADIOACTIVITY IN SOIL AND FOOD SAMPLES IN THE UKRAINE : MEASUREMENTS OF IODINE, PLUTONIUM, CESIUM, AND STRONTIUM ISOTOPES

To estimate the level and distribution of fallout attributable to the 26 April 1986 Chernobyl nuclear power station accident in the Ukraine, we sampled several kinds of substances at Korosten, Zhitomir and at Katyuzhanka, Vishgorod, Kiev in the Ukraine, and measured the radioactivity of 137Cs, 134Cs, 90Sr, 129I, 238Pu, 239,240Pu, and the density of 127I (stable). The substances investigated were soil, dry milk, wheat, rye, drinking water, and mushrooms. Except for the mushrooms collected, which were sampled at Katyuzhanka, Vishgorod, and at Kiev, all substances were at Korosten, Zhitomir. The activity of 137Cs, 134Cs, 90Sr, 238Pu, and 239,240Pu were all higher in soil and mushrooms than in the other four substances. The activity of 137Cs was 960 and 1,210 Bq kg-1 in the two soil samples and 6,110 Bq kg-1 in the mushrooms. The activity of 134Cs was approximately 15% of 137Cs in the two soil samples while < 3% of 137Cs in the mushrooms. The activity concentration level of 90Sr as compared to 137Cs concentration was 15-31% in food samples other than mushrooms but only 1.9% in mushrooms and 1.4 and 1.2% in the two soil samples. The radioactivity ratios, 238Pu: 239,240Pu and 239,240Pu: 137Cs, suggested that the proportion of cesium radioisotopes and 239,240Pu in the soil attributable to the Chernobyl accident was approximately 100% and 10-20%, respectively, while approximately 100% of 239,240Pu in the mushrooms was attributable to the accident. The activity of 129I was small but the ratio of 129I: 127I in the two soil samples was 4.3 x 10(-8) and 1.0 x 10(-7), which is approximately 10 times larger than that in the global fallout. These results suggest that the areas where the soil was sampled are iodine-deficient and were contaminated slightly by the Chernobyl accident.

The F value cannot be ruled out as a chromosomal fingerprint of radiation quality.

The F value, the ratio of inter- to intrachromosomal interchanges, as a biomarker for densely ionizing radiation which was proposed by Brenner and Sachs (Radiat. Res. 140, 134-142, 1994) has been a matter of repeated discussion. We examined our experimental data on radiation-induced chromosome aberrations in human peripheral blood lymphocytes for the F value as measured by the ratio of dicentrics to centric rings. Because of the rarity of aberrations, the F value showed a considerable variability, with a large error range particularly in the low-dose range of low-LET radiation. However, the data showed a general trend that the F value tended to be lower for high-LET than low-LET radiations. The differential F value was more pronounced at low doses and diminished with increasing dose; the F values of all radiations tended to converge toward a similar value at high doses. The limiting F value at the lowest doses, or the F0 value, was dependent on LET for high-energy radiations that can produce an array of DNA double-strand breaks along the track of the charged particle. However, LET and dose dependence were not seen for the low-energy photons, where spatially uncorrelated random breaks were produced by independent photoabsorption events.

Chromosome aberration frequency and radiation dose to lymphocytes by alpha-particles from internal deposit of Thorotrast

SummaryFrequencies of chromosome aberrations in peripheral blood lymphocytes from 63 Thorotrast patients were analysed basing on the age distribution of lymphocytes. The frequency and distribution of chromosome aberrations among lymphocytes are best explained if we assume that the lymphocytes are renewed as an exponential function of time and spend most of their lifetime in the distributive pool where, while exchange of lymphocytes is taking place, the lymphocytes are hit byα-particles from Thorotrast aggregates resulting in the formation of chromosome aberrations and killing at specific rates per hit. The model predicts that the aberration frequency is rather insensitive to the fluence rate because of modulation by cell killing by hit. Fitting the observed data to the model showed that approximately 0.8 dicentrics and rings were produced by a single path ofα-particle and average fluence rate to lymphocytes in a group of patients with the highest aberration frequency was estimated to be about 1.5 hits or 87 rad/lymphocyte/year.

Relationship between the 137Cs whole-body counting results and soil and food contamination in farms near Chernobyl

We measured the radioactivity in the soil and child food samples from farms near Mogilev (56-270 GBq km(-2) 137Cs), Gomel (36-810 GBq km(-2) 137Cs), and Klincy (59-270 GBq km(-2) 137Cs), who had whole-body 137Cs counting results measured as part of a health examination in the Chernobyl Sasakawa Health and Medical Cooperation Project. Soil contamination on the family farm seems to be the main source of human contamination because most of the people in the area live on small farms and they and their domestic animals eat crops from the farms. A clear correlation was found between the childrens whole-body 137Cs counting results and the radioactivity in their food (correlation coefficient: 0.76; confidence level of correlation: 3.2 x 10(-9)). There were also significant correlations between the whole-body 137Cs counting results and both the radioactivity of the soil samples (correlation coefficient: 0.22; confidence level of correlation: 0.0107) and the average contamination level of their current residence (correlation coefficient: 0.20; confidence level of correlation: 0.0174).

Ingestion of radioactively contaminated diets for two generations in the pale grass blue butterfly

BackgroundThe release of radioactive materials due to the Fukushima nuclear accident has raised concern regarding the biological impacts of ingesting radioactively contaminated diets on organisms. We previously performed an internal exposure experiment in which contaminated leaves collected from polluted areas were fed to larvae of the pale grass blue butterfly, Zizeeria maha, from Okinawa, which is one of the least polluted localities in Japan. Using the same experimental system, in the present study, we further examined the effects of low-level-contaminated diets on this butterfly. Leaves were collected from two localities in Tohoku (Motomiya (161 Bq/kg) and Koriyama (117 Bq/kg)); two in Kanto (Kashiwa (47.6 Bq/kg) and Musashino (6.4 Bq/kg)); one in Tokai (Atami (2.5 Bq/kg)); and from Okinawa (0.2 Bq/kg). In addition to the effects on the first generation, we examined the possible transgenerational effects of the diets on the next generation.ResultsIn the first generation, the Tohoku groups showed higher rates of mortality and abnormalities and a smaller forewing size than the Okinawa group. The mortality rates were largely dependent on the ingested dose of caesium. The survival rates of the Kanto-Tokai groups were greater than 80%, but the rates in the Tohoku groups were much lower. In the next generation, the survival rates in the Tohoku groups were below 20%, whereas those of the Okinawa groups were above 70%. The survival rates in the second generation were independent of the locality of the leaves ingested by the first generation, indicating that the diet in the second generation was the determinant of their survival. Moreover, a smaller forewing size was observed in the Tohoku groups in the second generation. However, the forewing size was inversely correlated with the cumulative caesium dose ingested throughout the first and second generations, indicating that the diet in the first generation also influenced the forewing size of the second generation.ConclusionsBiological effects are detectable under a low ingested dose of radioactivity from a contaminated diet. The effects are transgenerational but can be overcome by ingesting a non-contaminated diet, suggesting that at least some of the observed effects are attributable to non-genetic physiological changes.

Long Incubation Period for the Induction of Cancer by Thorotrast is Attributed to the Uneven Irradiation of Liver Cells at the Microscopic Level

Abstract Yamamoto, Y., Usuda, N., Takatsuji, T., Kuwahara, Y. and Fukumoto, M. Long Incubation Period for the Induction of Cancer by Thorotrast is Attributed to the Uneven Irradiation of Liver Cells at the Microscopic Level. Radiat. Res. 171, 494– 503 (2009). Irradiation from internally deposited radionuclides induces malignant tumors. Ingested long-lived radionuclides accumulate in specific organs that are irradiated throughout life. To elucidate why the development of malignant tumors requires long-term internal exposure, of the order of decades, despite the fact that irradiation is continuous over this period, we analyzed intrahepatic cholangiocarcinoma in Thorotrast patients (Th-ICC). Autoradiography showed that the density of α-particle tracks was 50 times more concentrated than would be expected if Thorotrast were evenly distributed throughout the liver. The age–incidence curves revealed that while the incidence of hepatobiliary cancer in Japan increased in proportion to the 7th power of age, that of Th-ICC increased to the 6th power. Internal radiation significantly increased the randomness of hepatocyte distribution but not the density. Three major factors are considered to be responsible for the long incubation time: the uneven distribution of radionuclides, the limited range of radiation, and the movement of tumor precursor cells. Target cells susceptible to malignant transformation may undergo one event and may then migrate outside of the range of α particles, thereby avoiding immediate induction of successive additional events that would lead to cell death or neoplastic changes.

Cohort study for prevention of atopic dermatitis using hair mineral contents

We undertook a cohort study to determine the association between hair mineral content and the onset of atopic dermatitis (AD) in infants. Eight hundred and thirty-four mother-infant pairs, who donated hair samples during one and ten-month health checkups, had their samples analyzed by proton induced X-ray emission (PIXE) for 32 mineral concentrations, and these mineral concentration data together with their AD family history were statistically examined for any relationships between them. Results indicated that of all minerals, only selenium (Se) and strontium (Sr) showed statistically significant associations for infants, while the same two elements were only marginally significant for mothers. Se deficiency in either infant or mother increased the AD risk. A Sr deficiency in infants increased AD risk, while the same deficiency in mothers decreased the risk. To predict the probability of AD development using this data, we performed logistic regression analysis, which provided a sensitivity of 65.9%, a specificity of 70.5%, a positive predictive value (PPV) of 10.3%, a negative predictive value (NPV) of 97.6% and a relative risk (RR) of 4.2, all far better than any corresponding figures explicitly mentioned in previously published papers.

Measuring The External Exposure Dose In The Contaminated Area Near The Chernobyl Nuclear Power Station Using The Thermoluminescence Of Quartz In Bricks

We collected bricks from buildings in the heavily contaminated evacuated area of Belarus in a 30-km zone around the Chernobyl nuclear power station and the Gomel-Bryansk area of 150–250 km from Chernobyl and estimated the cumulative radiation dose caused by the reactor accident by measuring the thermoluminescence (TL) of the bricks. The annual dose at each location was measured using glass dosimeters and thermoluminescence dosimeters (TLD). The dose rate was measured using an energy-compensated NaI scintillation survey meter. The soil contamination near the location of each brick was measured using a germanium semiconductor detector. The main purpose of the project was to extrapolate the relation between the cumulative external dose and the present dose rate or contamination level to the lower contaminated areas. The results of the glass dosimeter, TLD, and survey meter determinations were almost identical. For a determination of the annual dose higher than 10 mGy y−1, the cumulative dose by TL (TL dose) was roughly proportional to the annual dose and about 1.5 times larger than the cumulative dose calculated from the annual dose and 137Cs half life. The difference is expected due to the contribution of short-lived nuclides immediately after the accident or localized heavy contamination of the ground surface with 137Cs that migrated afterwards. For annual dose smaller than 10 mGy y−1, the proportionality was not observed and most of the locations facing indoors showed TL doses very much larger than that expected from the proportionality. The cumulative dose outdoors by TL was also roughly proportional to the regional 137Cs contamination level and the proportional constant is about 10−1 mGy per GBq km−2, and is about 250 times larger than the present annual internal dose derived from published results. The correlation between the present dose rate where the brick was sampled and the average 137Cs concentration in the ground soil near the point is not clear, possibly because of the large spatial fluctuation in the 137Cs concentration in the soil.

ESTIMATION OF HAIR ARSENIC AND STATISTICAL NATURE OF ARSENICOSIS IN HIGHLY ARSENIC EXPOSED BANGLISH VILLAGE IN COMILLA DISTRICT OF BANGLADESH

This study was carried out to investigate biological and statistical nature of arsenicosis risks on a severely arsenic (As) affected population in the Banglish village in Comilla district of Bangladesh. Subjects hair As and vegetables As levels were estimated by PIXE method, and arsenicosis status of the subject was examined by a physician. Arsenicosis was found in 45% female and 61% male subjects. Arsenic levels > 0.50 ppm showed greater arsenicosis risks that significantly varied with subjects sex and age. Unlike children, young (≥10 years) to middle aged (~49 years) population were significantly affected by arsenicosis. Logistic regression model analysis showed that arsenicosis risks are not only the devastating toxicity of As accumulation in human body through ingestion of contaminated drinking water, but the summation of all sources of As accumulation. Human hair As levels were found as the biomarker ranging from 0.03-8.3 μg/g in stage I arsenicosis patients, and from 1.1-56.9 ppm in the stage II patients up to 49 age. Hair As level was declined to 2.2-25.5 ppm at > 49 aged population. The findings inferred that groundwater As affecting the public health through contaminating total environment, that in turn posing an alarming situation in the study area.