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PubMedDate not supplied

Investigation of food contamination since the Chernobyl fallout in Austria.

In a large-scale investigation the decrease of the activity concentration of 137Cs in foodstuffs after the widespread Chernobyl fallout was determined. At different times after the deposition in 1986 more than 1000 samples of various foodstuffs in Austria were taken and investigated with regard to their activity concentration. The investigation showed that in the first year after deposition, the activity concentration decreased to about 6-10% (milk, fruit), and 3-6%, respectively (grain, potatoes, vegetables) of the values in the fallout maximum. The calculated effective half-lives are significantly shorter than observed after nuclear weapon test series and result in a smaller long-term exposure than estimated before. The effective ingestion dose in the 50 years following of a one-time nuclear fallout amounts to about 1.3 times of the first year ingestion dose. In 2002, the ingestion dose in Austria amounts to 2.24 microSv (adult), or 0.88 microSv (5-year infant) respectively, which is less than 0.5% of the ingestion dose of the first year and amounts to 0.7% of the ingestion dose from natural radionuclides.

Austria↗

PubMed2001

Distribution of 137Cs in the Lena River estuary-Laptev Sea system.

Surface sediment samples in the Laptev Sea have average 137Cs content of 7.1 Bq kg(-1), a value intermediate between that of the western Kara Sea (23 Bq kg(-1) and the East Siberian Sea (4.2 Bq kg-'). Both surface sediment content and sediment inventory of 137Cs in the Laptev Sea sediments show significant variability, and the influence of a variety of environmental factors.137Cs concentrations in the Laptev Sea surface sediments range from 0.8 to 16 Bq kg(-1). There is a marked increase in 137Cs content of surface sediment samples collected near the Lena River delta, and a local enrichment in the 137Cs inventories at these sites is also evident. Fine-grained mixed-layer illite/ smectite rich sediments in the estuary provide effective adsorption sites to fix 137Cs, in spite of desorption processes associated with low salinities in estuarine mixing. The Lena River-Laptev Sea mixing zone is a major site of sea-ice production. River and shelf sediments are incorporated into sea-ice formed in this region (Holmes and Creager, 1974). The irregular 137Cs activity profiles of the Lena River estuary cores indicate disturbance or removal of 137Cs-laden sediments via sea-ice related processes. Lena River and Estuary sediments may have served as a secondary source (i.e. other than direct fallout) of 137Cs in sea-ice. North-east of the Lena River estuary, sediment contains a thin layer of 137Cs-bearing material over an erosion surface. The 137Cs-laden surface layer may be the result of transient deposition of estuarine sediments being delivered by sea-ice or spring floods.

Cesium Radioisotopes↗

PubMed2003

Thyroid cancers in France and the Chernobyl accident: risk assessment and recommendations for improving epidemiological knowledge.

From 1975 to 1995, the incidence of thyroid cancer in the French population increased by a factor of 5.2 in men and 2.7 in women, thereby raising public concerns about its association with the nuclear accident at Chernobyl. A study performed at the request of French health authorities sought to quantify the potential risk of thyroid cancer associated with the Chernobyl fallout in France in order to determine if this risk could be observed through an epidemiological approach. The study focused on the most exposed population: those living in eastern France and younger than 15 y at the time of the Chernobyl nuclear power plant accident (26 April 1986). The number of spontaneous thyroid cancers in this population was predicted from French cancer registry data, and the thyroid doses were estimated from all available data about contamination in France. Associated risks were calculated with different risk models, all based on a linear no-threshold dose-effect relationship. Under this hypothesis, from 1.3 to 22 excess thyroid cancer cases were predicted for the 1991-2000 period, compared with the 212 spontaneous cases (0.5 to 10.5%) predicted, and from 11.2 to 55.2 excess cases were predicted for 1991-2015, compared with the 1,342 spontaneous cases (0.8 to 4.1%) predicted. These risk calculations indicate that the Chernobyl fallout cannot explain the entire increase in thyroid cancers in France, and that it is improbable that an epidemiological study could demonstrate such an excess. The surveillance of thyroid cancers in France should be enhanced.

Adolescent↗

PubMed1998

Variation in the metabolism of radiocaesium between individual sheep.

Considerable variability has been recorded in the radiocaesium activity concentration of muscle between individual sheep in the same flocks in upland areas that received fallout from the Chernobyl accident. In a previous paper we demonstrated that there is a propensity for certain sheep within a flock to be always amongst the most contaminated and others to be consistently the least contaminated. Here we report a study to determine the extent to which variation in the metabolism of radiocaesium by individual sheep may contribute to the observed variability within sheep flocks. The transfer coefficient and biological half-life of orally administered ionic radiocaesium in muscle were determined under controlled conditions in 22 ewes from an upland farm in an area of the UK which received comparatively high levels of Chernobyl fallout. There was considerable variation between individuals in both the transfer coefficient (0.19-0.56 day x kg(-1); mean 0.34 day x kg(-1)) and biological half-life in muscle (5.2-18.7 days; mean 9.8 days). Changes in liveweight during the study and feed intake together accounted for 72% of the variation in the derived transfer coefficients; liveweight change also accounted for 56% of the observed variation in biological half-life. In a subsequent study, the true absorption coefficient of radiocaesium was determined in 12 of the ewes. There was a positive correlation between transfer and true absorption coefficients (R = 0.57). We conclude that differences in the metabolism of radiocaesium will contribute to the observed variability in radiocaesium activity concentrations within sheep flocks in areas which were contaminated by Chernobyl fallout. We also suggest that for growing animals, the influence of liveweight change and feed intake on radiocaesium transfer may be greater than observed here. Similarly, in dairy cattle, for which feed intake changes considerably during the course of a lactation, large temporal variation in radiocaesium transfer to milk could be expected.

Animals↗

PubMed2005

Investigating Pu and U isotopic compositions in sediments: a case study in Lake Obuchi, Rokkasho Village, Japan using sector-field ICP-MS and ICP-QMS.

The objectives of the present work were to study isotope ratios and the inventory of plutonium and uranium isotope compositions in sediments from Lake Obuchi, which is in the vicinity of several nuclear fuel facilities in Rokkasho, Japan. Pu and its isotopes were determined using sector-field ICP-MS and U and its isotopes were determined with ICP-QMS after separation and purification with a combination of ion-exchange and extraction chromatography. The observed (240)Pu/(239)Pu atom ratio (0.186 +/- 0.016) was similar to that of global fallout, indicating that the possible early tropospheric fallout Pu did not deliver Pu from the Pacific Proving Ground to areas above 40 degrees N. The previously reported higher Pu inventory in the deep water area of Lake Obuchi could be attributed to the lateral transportation of Pu deposited in the shallow area which resulted from the migration of deposited global fallout Pu from the land into the lake by river runoff and from the Pacific Ocean by tide movement and sea water scavenging, as well as from direct soil input by winds. The (235)U/(238)U atom ratios ranged from 0.00723 to 0.00732, indicating the natural origin of U in the sediments. The average (234)U/(238)U activity ratio of 1.11 in a sediment core indicated a significant sea water U contribution. No evidence was found for the release of U containing wastes from the nearby nuclear facilities. These results will serve as a reference baseline on the levels of Pu and U in the studied site so that any further contamination from the spent nuclear fuel reprocessing plants, the radioactive waste disposal and storage facilities, and the uranium enrichment plant can be identified, and the impact of future release can be rapidly assessed.

Environmental Monitoring↗

PubMedDate not supplied

Fallout from the Chernobyl nuclear disaster and congenital malformations in Europe.

Investigators estimate that the population exposure that resulted from the Chernobyl fallout is in the range of natural background radiation for most European countries. Given current radiobiologic knowledge, health effects-if any-would not be measurable with epidemiologic tools. In several independent reports, however, researchers have described isolated peaks in the prevalence of congenital malformations in the cohort conceived immediately after onset of the fallout. The consistency of the time pattern and the specific types of malformation raise concern about their significance. In this study, the author summarizes findings from Turkey, Belarus, Croatia, Finland, Germany, and other countries, and implications for radiation protection and public health issues are discussed.

Abnormalities, Radiation-Induced↗

PubMed1997

Direct determination of 90Sr and 147Pm in Chernobyl hot particles collected in Kiev using beta absorption method.

59 hot particles were collected in Kiev, Ukraine, in 1987. All but one were prepared from a moss carpet of 360 cm2 area. Radionuclide composition of the hot particles was investigated by gamma-spectrometry and beta absorption method. Pure beta emitters 90Sr and 147Pm were determined in 25 hot particles measuring the beta absorption curves of the hot particles with an end-window Geiger-Müller counter and decomposing the curves in order to obtain the contributions of 90Sr and 147Pm to the total beta counting rate. All but one of the hot particles were found to be the debris of the fuel. The activity ratio 90Sr:l44Ce was 0.052 in good agreement with theoretical calculations on core inventories. This means that strontium behaved as a nonvolatile element in the process of the formation of the hot particles investigated. The activity ratio 147Pm:144Ce was 0.078 which is half of the theoretical result. Although 147Pm is considered to be a refractory nuclide, it seems that significant part of 147Pm went to the homogeneous fraction of the general fallout. The surface density of hot particles (of higher than about 50 Bq activity) was about 1,600 m(-2) and that of the activities of the nuclides 90Sr, 106Ru, 134Cs, 137Cs, 144Ce and 147Pm as components of hot particles was 12.2, 54.3, 5.9, 9.7, 234 and 18.3 kBq m(-2) (activity values counted for 26 April 1986), respectively, in downtown Kiev city in 1987.

Beta Particles↗

PubMed2002

Food chains and biogeochemical pathways: contributions of fallout and other radiotracers.

This paper reviews examples of how measurements of global fallout in the environment and related tracer radionuclides have been used to enhance our basic knowledge of biogeochemical processes and food-chain pathways. Because it is these fundamental, natural processes that control the transport and accumulation of such trace substances in the environment, direct measurements of trace substances over time and space reveal strong insights into these processes. The necessity to monitor global fallout transport, although largely motivated by human health concerns, gave rise to a plethora of new information about plants, animals, and natural and agricultural ecosystems and how they function. This review provides a small selection of examples in the areas of plant and animal physiology, productivity and energy transfer in food chains, biogeochemical cycles of certain elements and their analogues, feeding relationships and movements of organisms, and the agriculture-based human food chain. It is concluded that if society is to cope successfully with continued growth of the human population and resource consumption, more knowledge is still required about these fundamental processes. The use of radiotracers can contribute greatly to this need, but current funding priorities, societal attitudes, and onerous regulations on the use of radioactivity may continue to limit such applications.

Animals↗

PubMed2005

Distribution of 137Cs, 238Pu and 239+240 Pu in sediments of the southeastern Brazilian shelf-SW Atlantic margin.

In this work levels of 137Cs, 238Pu and 239+240 Pu as well as activity ratios of anthrophogenic radionuclides in sediment samples from the southeastern Brazilian shelf are presented. Instrumental gamma spectrometry was used to determine 137Cs and alpha spectrometry to determine 238Pu and 239+240 Pu after a radiochemical procedure. The levels ranged from 0.30 to 1.79 Bq kg(-1) for 137Cs, from 15 to 150 mBq kg(-1) for 238Pu and, from 18 to 117 mBq kg(-1) for 239+240 Pu. There was a bathymetric differentiation in the radionuclides distribution. 137Cs values were generally higher in the samples collected at water depths of less than 100 m. On the other hand, plutonium isotopes exhibit higher values at greater depths. The mean ratio of 239+240 Pu/137Cs obtained was 0.112+/-0.072 which is in agreement with the value reported for the Atlantic from atmospheric fallout of nuclear explosions in the past. The 238Pu/230+240 Pu ratios varied widely (from 0.339 to 2.088) and showed the influence of the SNAP-9A accident in the 238Pu levels for this area. The main goal of this work was to present unpublished anthropogenic radionuclide levels and activity ratios related to the contamination of the southeastern Brazilian shelf.

Atlantic Ocean↗

PubMed1999

Pu-241 in samples of forest soil from Poland.

241Pu activity measurements in coniferous forest soil samples from Poland are presented. The results were obtained in two ways: by alpha spectrometric remeasurements of the plutonium sources 3-4 years after their preparation (i.e. by the 241Am ingrowth) and by direct measurements of 241Pu using liquid scintillation (LS) spectrometry. Both methods gave consistent results. The maximum observed activity concentration obtained by the 241Am ingrowth was (254 +/- 43) Bq/kg, and by direct measurements it was (284 +/- 31) Bq/kg (the same sample, activities calculated for May 1, 1986). Enhanced levels of 241Pu were observed in all samples from the farthest north-eastern Poland. The estimated 241Pu maximum deposition from Chernobyl fallout in this area (sum of deposition for two examined layers of one site) was (1.025 +/- 0.110) kBq/m2. This will result after 70 years in an additional 241Am activity of about (30.1 +/- 3.2) Bq/m2. The average ratio for 241Pu to total 238,239,240Pu was of the order of 25. The obtained average Chernobyl ratios for 241Pu to 239,240Pu were about 86, and those for 241Pu to 238,239,240Pu were 56.

Plutonium↗

PubMedDate not supplied

Association of nuclear fallout with leukemia in the United States.

The world population has been exposed to low levels of fission products from nuclear testing. Has this had any health effects? Six different epidemiological associations are demonstrated between leukemia and nuclear fallout in the general population. The strongest association is with acute and myeloid types of leukemia among children. They peaked at approximately 5.5 yr (among 5-9 yr olds) after the peaks in fallout. The entire United States population exhibited an increasing leukemia rate during and for several years after the open air nuclear testing and fell sharply thereafter. Regional differences in leukemia rates correspond to a composite exposure index that used 90Sr concentrations in food, cow's milk, and human bone. The calculated leukemia risk per rad for children was similar to that calculated for Japanese A-bomb children survivors.

Animals↗

PubMed2001

Effect of origin of radiocaesium on the transfer from fallout to reindeer meat.

Data on radiocaesium contamination of reindeer from five regions in Sweden have been used, together with interpolated radiocaesium deposition data, to quantify spatial variation in transfer to reindeer meat and to consider how it changes with time in different areas. Since the regions were contaminated to different extents by global and Chernobyl fallout, it was also possible to determine the influence of the origin or age of radiocaesium fallout on the transfer to reindeer meat. The regions differed significantly with regard to transfer of radiocaesium to reindeer meat. In two regions in the North of Sweden, where there was less Chernobyl 137Cs, aggregated transfer coefficients (Tag), estimated for the main slaughter period in the first year after the Chernobyl fallout, were low (0.15 and 0.36 m2 kg(-1) in January-April). Average Tag values calculated for the winter period (January-April) in two regions in the middle of Sweden, where deposition from Chernobyl dominated (83 and 94%, respectively, of the total deposition), were 0.78 and 0.84 m2 kg(-1), respectively with a maximum Tag for an individual reindeer of 1.87 m2 kg(-1). There was a threefold increase in Tag values from early autumn to late winter reflecting the change in the reindeer diet from less contaminated vascular plants to more contaminated lichens. The decline of 137Cs in reindeer meat from 1986 to 2000 differed between regions with longer effective half-lives (Tef) in the northerly regions (11.0 and 7.1 years, respectively) with less Chernobyl fallout, and shorter half-lives in the other three regions (3.5-3.8 years). This observation, together with a lack of a decline in early autumn in the region with least Chernobyl fallout, supports the theory of a gradual, but reversible, fixation of radiocaesium in the soil over the mid-long term. The results suggest that both the extent of transfer of 137Cs to reindeer meat, and its subsequent decline with time, are affected by the differing origins of radiocaesium and that previous contamination may substantially influence radiocaesium transfer in the event of a further accident.

Animals↗

PubMed1996

A post-Chernobyl rise in thyroid cancer in Connecticut, USA.

Recent analyses of children in Belarus and the Ukraine are the first to document large numbers of excess thyroid cancer cases only 4 years after exposure to radiation. In Connecticut (USA), a thyroid cancer increase of a much smaller magnitude occurred in 1990-93, 4-7 years after the Chernobyl accident, for both children and adults. Similar changes also occurred in the states of Iowa and Utah, which like Connecticut were exposed to low levels of radionuclides from Chernobyl fallout during May and June of 1986. Historical data from Connecticut also reveal substantial increases in thyroid cancer incidence about 5 years after large releases of iodine-131 from distant US nuclear weapons plants, after the largest atmospheric US atomic weapons tests in Nevada, and after substantial releases of iodine-131 from the Millstone nuclear power plant in Connecticut. Further analysis of this apparent 5-year latency period will enhance understanding of ionizing radiation's effects on thyroid function and on human health in general.

Adolescent↗

PubMed2002

A comparison of 90Sr and 137Cs uptake in plants via three pathways at two Chernobyl-contaminated sites.

Foliar absorption of resuspended 90Sr, root uptake and contamination adhering to leaf surfaces (i.e. soil loading) were compared at two Chernobyl-contaminated sites, Chistogalovka and Polesskoye. Although foliar absorption of resuspended 90Sr was quantifiable, its contribution amounted to less than 10% of the plants' total, above-ground contamination. Root uptake was 200 times greater than foliar absorption at the near-field site of Chistogalovka and eight times greater at Polesskoye, where the fallout consisted of the more soluble condensation-type, rather than fuel particles. Strontium's bioavailability exceeded that of 137Cs (analyzed in the same plants) by orders of magnitude when compared using concentration ratios. Simplistic, cumulative effective dose calculations for humans ingesting 90Sr- and 137Cs-contaminated plants revealed that the dose at Chistogalovka was greater from 90Sr (185 mSv vs. 3 mSv from 137Cs), while at Polesskoye the dose from 137Cs (66 mSv) was 30 times greater than from 90Sr (2 mSv).

Absorption↗

PubMed1999

The spatial variability of Chernobyl-derived 137Cs inventories in a small agricultural drainage basin in central Russia.

Little information currently exists regarding the small-scale spatial variability of Chernobyl radiocaesium fallout and associated inventories. This contribution reports the results of a study of the variability of 137Cs inventories within the 2.18-km2 Lapki balka catchment located near Tula in central Russia. The local area was characterized by 137Cs inventories in excess of 200 kBq m-2 immediately after the Chernobyl accident and pre-existing bomb-derived inventories can be ignored in view of their very low magnitude. Field sampling and measurements included both collection of soil cores for subsequent laboratory analysis and in situ field measurements using a CORAD portable detector. The results obtained show evidence of a systematic south-north increase in the reference inventory across the basin, which must be taken into account when interpreting subsequent radiocaesium redistribution within the basin. Random spatial variability of 137Cs inventories of a similar magnitude to that reported for bomb-derived fallout was also documented. The extent of random spatial variability varied between different geomorphological units. Maximum variability, with coefficients of variation up to 20%, was associated with areas of sediment accumulation within the balka bottoms. Substantial variability (cv. typically ca. 15%) was found within flat cultivated areas and undisturbed areas both on the interfluves and on the balka sides, all of which could serve as reference sites. Minimum variability (cv. typically ca. 12%) was associated with the cultivated slopes with no evidence of sediment accumulation.

Agriculture↗

PubMed1998

Variability of water content and of depth profiles of global fallout 137Cs in grassland soils and the resulting external gamma-dose rates.

137Cs from global fallout of nuclear weapon testings in the 1950s and 1960s was determined in successive layers (0-30 cm) of eight undisturbed grassland soils in Bavaria, Germany. The maximum activity concentration was found in soil layers between 4 and 15 cm below the surface. Using the vertical distribution of the cesium activity, which varied considerably from site to site, the mean residence half-time of 137Cs from global fallout in each soil layer was evaluated with a compartment model. These values ranged from 1.0 to 6.3 years/cm. The mean residence half-time averaged over all soil layers and all sites was 2.7 +/- 1.4 years/cm and, thus, about twice the corresponding residence half-time of the Chernobyl-derived 137Cs as determined in the same soil layers (also in 1993). The dose rate of the external gamma-radiation due to 137Cs from global fallout in the soil determined from the depth distributions varied between 0.34 and 0.57 (mean: 0.45 +/- 0.07) nGy/h per kBq/m2. The effect of soil water content on the dose rate was studied by considering four states of the soil, from water content zero to complete water saturation of the total pore volume. It was shown that the difference between the dose rates at the permanent wilting point and the field capacity, which both represent the most relevant water contents of soils, was only 10% of the dose rate at the permanent wilting point for all sites.

Cesium Radioisotopes↗

PubMed2000

137Cs distribution and geochemistry of Lena River (Siberia) drainage basin lake sediments.

The Lena River is the second largest river that discharges into the Arctic Ocean. It is therefore important to determine not only the direct impact its discharge has on the 137Cs concentration of the Arctic, but also the potential its drainage basin has as a 137Cs source. 137Cs surface sediment concentrations and inventory values, which range from 4.97 to 338 Bq kg(-1) and 357 to 1732 Bq m(-2), respectively, were determined for the Lena River drainage basin lake samples, via gamma analysis. The average geochemical and mineralogical composition of a subset of samples was also determined using neutron activation analysis, X-ray diffraction and X-ray fluorescence spectrometry techniques. Results of these geochemical analyses allowed for the identification of key geochemical factors that influence the distribution of 137Cs in the Lena River drainage basin. 137Cs profiles indicate that Lena River drainage basin lacustrine sediments serve as a record of 137Cs fallout. Based on the downcore 137Cs, %illite, %smectite, %Al and %Mn distribution patterns, it was concluded that a small fraction of non-selectively bound 137Cs was remobilized at depth in some cores. Inconsistencies between the actual 137Cs fallout record and the 137Cs profiles determined for the lake sediments were attributed to 137Cs remobilization in subsurface sediments. In addition to establishing the agreement between the global atmospheric fallout record and the downcore 137Cs distribution patterns determined for these sediments, results indicate that 137Cs deposited during periods of maximum atmospheric release was buried and is not susceptible to surface erosion processes. However, mean 137Cs concentrations of the lacustrine surface sediments (125 Bq kg(-1)) are still significantly higher than those of the nearby Lena River estuary (11.22 Bq kg(-1)) and Laptev Sea (6.00 Bq kg(-1)). Our study suggests that the Lena River drainage basin has the potential to serve as a source of 137Cs to the adjacent Arctic Ocean.

Cesium Radioisotopes↗

PubMed2005

Uncertainty and sensitivity analysis in assessment of the thyroid cancer risk related to Chernobyl fallout in Eastern France.

The increase in the thyroid cancer incidence in France observed over the last 20 years has raised public concern about its association with the 1986 nuclear power plant accident at Chernobyl. At the request of French authorities, a first study sought to quantify the possible risk of thyroid cancer associated with the Chernobyl fallout in France. This study suffered from two limitations. The first involved the lack of knowledge of spontaneous thyroid cancer incidence rates (in the absence of exposure), which was especially necessary to take their trends into account for projections over time; the second was the failure to consider the uncertainties. The aim of this article is to enhance the initial thyroid cancer risk assessment for the period 1991-2007 in the area of France most exposed to the fallout (i.e., eastern France) and thereby mitigate these limitations. We consider the changes over time in the incidence of spontaneous thyroid cancer and conduct both uncertainty and sensitivity analyses. The number of spontaneous thyroid cancers was estimated from French cancer registries on the basis of two scenarios: one with a constant incidence, the other using the trend observed. Thyroid doses were estimated from all available data about contamination in France from Chernobyl fallout. Results from a 1995 pooled analysis published by Ron et al. were used to determine the dose-response relation. Depending on the scenario, the number of spontaneous thyroid cancer cases ranges from 894 (90% CI: 869-920) to 1,716 (90% CI: 1,691-1,741). The number of excess thyroid cancer cases predicted ranges from 5 (90% UI: 1-15) to 63 (90% UI: 12-180). All of the assumptions underlying the thyroid cancer risk assessment are discussed.

Adolescent↗