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PubMed1990

Tritium concentration in Japanese rice.

Polished rice samples harvested in 1985 were collected from 25 prefectures throughout Japan. Concentrations of both tissue free water tritium (TFWT) and organically bound tritium (OBT) were determined. Nearly uniform distribution of the TFWT and OBT concentrations was observed in Japan, taking into account a relatively large counting error. The average values for all Japanese polished rice were 2.69 +/- 0.74 Bq/L for the TFWT concentration, 2.01 +/- 0.78 Bq/L for the OBT concentration and 0.83 +/- 0.32 for the specific activity ratio. The TFWT concentration was within the range of tritium concentration of the land water reported by other researchers. The specific activity ratio below unity also confirmed by analyses of the 4 Chinese polished rice samples suggests that OBT in the rice is not equilibrated with TFWT or HTO in the environment because of isotope discrimination.

Food Contamination, Radioactive↗
PubMed1991

Tritium concentration in unpolished rice.

Inoue and Iwakura recently reported that the specific activity ratio of organically-bound 3H to free water 3H in polished rice samples collected in Japan and China was lower than unity. Their paper was the first to report the systematic apparent elimination of 3H for incorporation to organically-bound form in samples collected from the general environment. To confirm their result, seven unpolished rice samples obtained just after harvesting were analyzed for 3H. The mean specific activity ratio of organically-bound 3H to free water 3H was found to be 0.57, somewhat lower than the data by Inoue and Iwakura. This small difference may be caused by the different sampling years and/or the possible replacement of free water by atmospheric water vapor after harvesting.

Food Contamination, Radioactive↗
PubMed1992

Incorporation and distribution of tritium in rats exposed to tritiated rice or tritiated soybean.

The incorporation and distribution of tritium were examined in rats exposed to tritiated rice or tritiated soybean by single ingestion or continuous feeding. Results were compared with those for tritiated wheat and tritiated water in a previous study done under the same experimental conditions. All the tritiated crops examined were more efficiently incorporated into rat tissues than was tritiated water, the extent of incorporation depending on the kind of crop. The differences in incorporation were clear in organically bound tritium determined as tritium in dried tissue. The respective concentrations of organically bound tritium after a single ingestion of tritiated rice, tritiated wheat or tritiated soybean were about 10-20, 20-30 and 25-60 times higher than after the ingestion of tritiated water. After continuous feeding for 22 days with tritiated rice, tritiated wheat or tritiated soybean, the respective concentrations of organically bound tritium were 5-8, 6-11 and 10-25 times the values after continuous ingestion of tritiated water. At the end of continuous ingestion, the radiation dose rates to almost of the tissues from all three tritiated crops were estimated to be 2-3 times that for tritiated water.

Animals↗
PubMed2003

Transfer factors of radioiodine from volcanic-ash soil (Andosol) to crops.

In order to obtain soil-to-plant transfer factors (TFs) of radioiodine from volcanic-ash soil to agricultural crops, we carried out radiotracer experiments. The mean values of TFs (on a wet weight basis) of radioiodine from Andosol to edible parts of crops were as follows: water dropwort, 0.24; lettuce, 0.00098; onion, 0.0011; radish, 0.0044; turnip, 0.0013 and eggplant, 0.00010. The mean value of the TFs of radioiodine for edible parts of wheat (on a dry weight basis) was 0.00015. We also studied the distributions of iodine in crops. There was a tendency for the TFs of leaves to be higher than those of tubers, fruits and grains. A very high TF was found for water dropwort, because this plant was cultivated under a waterlogged condition, in which iodine desorbed from soil into soil solution with a drop in the Eh value. The data obtained in this study should be helpful to assess the long-lived 129I (half life: 1.57 x 10(7) yr) pathway related to the fuel cycle.

Crops, Agricultural↗
PubMed2003

Uranium concentration in typical Pakistani diet.

To strengthen the radiation protection infrastructure in Pakistan, the uranium concentration in daily diet was measured and its associated radiation risks were estimated for the adult population. Food samples were collected from major cities and districts of the country by the market basket method, from which daily diets were prepared. These diet samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) at the National Institute of Radiological Sciences, Japan, the regional Central Reference Laboratory of the Reference Asian Man Project. The measured values of the uranium content were found to vary from 2.3 ng (g dry)(-1) to 11 ng (g dry)(-1). The geometric mean concentration and geometric standard deviation were 4.5 x//1.7 ng (g dry)(-1). This leads to a daily dietary intake of 2.6 x// 1.7 microg d(-1) or 33 x// 1.7 mBq d(-1), which is approximately 40% higher than the ICRP value. The measured value, i.e. 33 mBq d(-1), contributes 12 Bq y(-1) to annual intake of 238U activity and 0.54 microSv to the committed effective dose to the adult population. This is a very small fraction of the ICRP annual effective dose limit of 1 mSv for the general public. Therefore, it would pose no significant health hazard.

Diet↗
PubMed2004

Concentrations of 137Cs and 40K in mushrooms consumed in Japan and radiation dose as a result of their dietary intake.

Mushrooms are known to accumulate radiocesium. To estimate the intake of radiocesium through the eating of mushrooms, about 30 samples belonging to 4 commonly consumed species (Lentinula edodes, Hypsizigus marmoreus, Grifola frondosa, and Tricholoma matsutake), were analyzed for (137)Cs and (40)K. The concentration ranges were 0.060-29 Bq kg(-1) (wet wt) for (137)Cs and 38-300 Bq kg(-1) (wet wt) for (40)K. The geometric mean concentration for (137)Cs was 0.56 Bq kg(-1) (wet wt), and the mean concentration for (40)K was 92 Bq kg(-1) (wet wt). The (137)Cs concentrations in L. edodes cultivated in mushroom beds (sawdust-rice bran media) were lower than those cultivated on bed logs (natural wood with bark). The annual intake of (137)Cs per person through mushrooms was calculated, by using the current analytical results and food consumption data in Japan, to be 3.1 Bq for (137)Cs, which is about 28% of the total dietary intake of this nuclide. The effective dose equivalent of (137)Cs through mushrooms was estimated to be 4.0 currency 10(-8) Sv, which is about the half the value obtained in our previous study. The decrease of the (137)Cs intake through mushrooms is probably related to changes in cultivation methods in recent years, from the use of bed logs to mushroom beds.

Agaricales↗
PubMed2006

Retrospective dose assessment for the population living in areas of local fallout from the Semipalatinsk Nuclear Test Site Part II: Internal exposure to thyroid.

A methodology to assess internal exposure to thyroid from radioiodines for the residents living in settlements located in the vicinity of the Semipalatinsk Nuclear Test Site is described that is the result of many years of research, primarily at the Moscow Institute of Biophysics. This methodology introduces two important concepts. First, the biologically active fraction, is defined as the fraction of the total activity on fallout particles with diameter less than 50 microns. That fraction is retained by vegetation and will ultimately result in contamination of dairy products. Second, the relative distance is derived as a dimensionless quantity from information on test yield, maximum height of cloud, and average wind velocity and describes how the biologically active fraction is distributed with distance from the site of the explosion. The parameter is derived in such a way that at locations with equal values of relative distance, the biologically active fraction will be the same for any test. The estimates of internal exposure to thyroid for the residents of Dolon and Kanonerka villages, for which the external exposure were assessed and given in a companion paper (Gordeev et al. 2006) in this conference, are presented. The main sources of uncertainty in the estimates are identified.

Body Burden↗
PubMed2006

An overview on GSF activities at the Semipalatinsk Test Site, Kazakhstan.

The Semipalatinsk Test Site (STS) in Kazakhstan was one of the major sites used by the former USSR for testing nuclear weapons for more than 40 years. Since the early 1990s, agricultural activities have been re-established there by neighbouring collective and private farms. Therefore, it has become important to evaluate the radiological situation and the current and future risk to people living on and using the contaminated area. During the last eight years, GSF has participated in many international projects performed on the STS to evaluate the radiological situation. A large number of soil, vegetation and food samples has been collected and analysed. Internal dose is one of the main components of the total dose when deriving risk factors for a population living within the test site. Internal doses, based on food monitoring and whole body measurements, were calculated for adults and were in the range of 13-500 microSv/y due to radiocaesium and radiostrontium.

Animals↗
PubMed1999

Radionuclides in the lichen-caribou-human food chain near uranium mining operations in northern Saskatchewan, Canada.

The richest uranium ore bodies ever discovered (Cigar Lake and McArthur River) are presently under development in northeastern Saskatchewan. This subarctic region is also home to several operating uranium mines and aboriginal communities, partly dependent upon caribou for subsistence. Because of concerns over mining impacts and the efficient transfer of airborne radionuclides through the lichen-caribou-human food chain, radionuclides were analyzed in tissues from 18 barren-ground caribou (Rangifer tarandus groenlandicus). Radionuclides included uranium (U), radium (226Ra), lead (210Pb), and polonium (210Po) from the uranium decay series; the fission product (137Cs) from fallout; and naturally occurring potassium (40K). Natural background radiation doses average 2-4 mSv/year from cosmic rays, external gamma rays, radon inhalation, and ingestion of food items. The ingestion of 210Po and 137Cs when caribou are consumed adds to these background doses. The dose increment was 0.85 mSv/year for adults who consumed 100 g of caribou meat per day and up to 1.7 mSv/year if one liver and 10 kidneys per year were also consumed. We discuss the cancer risk from these doses. Concentration ratios (CRs), relating caribou tissues to lichens or rumen (stomach) contents, were calculated to estimate food chain transfer. The CRs for caribou muscle ranged from 1 to 16% for U, 6 to 25% for 226Ra, 1 to 2% for 210Pb, 6 to 26% for 210Po, 260 to 370% for 137Cs, and 76 to 130% for 40K, with 137Cs biomagnifying by a factor of 3-4. These CRs are useful in predicting caribou meat concentrations from the lichens, measured in monitoring programs, for the future evaluation of uranium mining impacts on this critical food chain.

Animals↗
PubMedDate not supplied

Cesium-134 and strontium-85 in strawberry plants following wet aerial deposition.

The understanding of the processes that control the behavior of radionuclides in crops can support policymakers to take actions to protect the environment and safeguard human health. Data concerning the behavior of radionuclides in fruits are limited. Strawberry (Fragaria x ananassa Duchesne) plants were contaminated on the aboveground part by sprinkling an aqueous solution of 134Cs and 85Sr at three growing stages: predormancy, anthesis, and beginning of ripening. Intercepted activity was more affected by the posture and physical orientation of leaves rather than by leaf area or biomass. Fruit interception ranges from 0.2 to 1.2% of the sprinkled activity. Translocation coefficients from leaf to fruit are on the order of 10(-4) for 134Cs and 10(-5) for 85Sr. Translocation reaches its highest intensity between anthesis and ripening. If deposition occurs when plants are bearing fruits, the fruit activity will be affected by the activity initially deposited on the fruit surfaces. This is important for 85Sr as it is not translocated in the phloem. The loss of the dead leaves at the resumption of growth causes high plant decontamination, but a fraction of both radionuclides remains in the storage organs, roots, and shoots, which is retranslocated to fruits in the following spring. The values of the environmental half-time, t(w), after deposition at predormancy are 114 d for 134Cs and 109 d for 85Sr. Cesium-134 tends to be allocated to fruits, while 85Sr remains in leaves and crowns. Translocation of radionuclides to roots results in soil contamination.

Cesium Radioisotopes↗