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Residents of Vienna, Austria were whole-body counted for radiocesium content due to fallout deposited after the Chernobyl accident. Data for a 2-y period were compared with prior estimates of radiocesium body burden based on food consumption. Our results suggest that the prior estimates be revised and the rejection limit be increased by a factor of 2 for contaminated food.
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Levels of fallout radiocesium in vegetation were examined on three granite outcrops and a forested area in the Georgia piedmont during 1976-1980. Mean values averaged 4.3 times higher in three species collected on an outcrop than in the same species collected on clay soils in a nearby pine-hardwood forest. Levels in reindeer moss (Cladonia spp.) were significantly (p less than 0.01) lower in species that formed deep, entangled tufts with abundant, slender branches. Cesium levels decreased by as much as 90% from the mid-1960s but were virtually unchanged in the late 1970s. Dry-weight levels in mushrooms reached 18,470 Bq kg-1 (499.2 pCi g-1). Radiation levels in outcrop vegetation were higher than values found anywhere in the piedmont and were comparable to levels reported in plants from the sterile sandy soils of the temperate region coastal plains. These data fit well with earlier reported values and correlate well with the availability of atmospheric fallout. Outcrops can be used as sensitive environmental barometers for some contaminants.
The bioavailability of Chernobyl-derived radiocesium in hay, fungal fruit bodies, willow bark, and soil was compared to tracer radiocesium (134CsCl) by measuring transfer coefficients (Fm) to goat milk. The average Fm value from 134CsCl of 11.9 x 10(-2) d L-1 was taken to represent the maximal transfer to milk on the provided diet. In 1986, the Fm value from hay was 35% of that from 134CsCl, thus demonstrating the low bioavailability of recently deposited radiocesium. Values in 1987 were also lower, with a mean of 76% of that from tracer Cs. During 1988 and 1989, maximal Fm values were observed, suggesting increased bioavailability from the year of fallout to the following years. Transfer of radiocesium from two fungal species harvested in 1988 and 1989 were 78% and 87%, respectively, of that from tracer Cs, while bark was lower (62%). Transfer from organic soil was only 7% of tracer radiocesium, and therefore contribution from soil ingestion could only have a small impact on the content of radiocesium in animals. Live monitoring measurements and the excretion of 134Cs in milk, urine, and feces during a 50-d period was adequately described by a two-exponential equation.
In order to obtain the biological half-life (Tb) of iodine deposited on rough rice grains, rice plants of four different growing stages--heading, milky, dough, and yellow ripe--were exposed to elemental gaseous iodine. After the exposure, the rough rice samples were collected at different intervals and analyzed for iodine to estimate the value of Tb. The average value of Tb obtained by the experiments at the dough and yellow ripe stages was about 200 d. This value is considerably larger than those for pasture grass and leafy vegetables.
A review of studies conducted before and after the Chernobyl accident is presented, showing that both the duration and the extent of radiocesium contamination of ruminants will be more severe in unimproved ecosystems compared with agricultural areas. Although such unimproved ecosystems provide comparatively small quantities of food for human consumption, the integrated dose from these areas to the human population can be large. Ecological characteristics that make unimproved ecosystems particularly vulnerable to this form of pollution include the presence of (1) soils that do not immobilize radiocesium and therefore allow its uptake into vegetation; (2) vegetation species with high uptake rates of radiocesium; (3) the predominant utilization by small ruminants which attain higher muscle radiocesium levels than cattle. Unimproved ecosystems, which often are located at high altitudes, are predisposed to receiving higher fallout because of high precipitation rates which enhance the likelihood of deposition. Countermeasures have been developed and used successfully to reduce radiocesium levels in ruminants grazing in unimproved ecosystems. Apart from decontamination by altering farming practices and providing uncontaminated feeds, sustained reductions of 50% to 80% in the radiocesium concentrations of both milk and meat have been achieved in many ruminant species when AFCF is given via a sodium chloride lick or as a sustained-release bolus. Food production in unimproved ecosystems must be evaluated separately from that of ordinary agricultural systems. In addition to detailed studies on the behavior of radiocesium, consideration should be given to the collection of aggregated transfer coefficients from various ecosystems which were affected by Chernobyl fallout. By combining bioavailability estimates and aggregated transfer coefficients, based on Chernobyl and nuclear weapons test fallout data, it may in the future be possible to make a rapid assessment of both the immediate and the long-term impact of a future nuclear accident on food production in unimproved ecosystems.
Plants growing on soil contaminated with 14C can receive the radionuclide from both direct uptake through the roots or indirect uptake from the atmosphere. The contribution from the atmosphere depends on the rate of volatilization from the soil, the size of the source area, and the meteorological dispersion conditions. An atmospheric dispersion relationship was used to calculate the air concentration for a given area source term. The air concentration was then used to estimate the flux to foliage, which was compared with direct plant uptake through the roots. The ratio of atmospheric to root uptake pathways depended on plant height and source area, exceeding unity when the fetch was greater than a few meters for bean plants, but much greater for maize. A very large fetch, greater than 1000 m, is required before a uniform specific activity throughout the local biosphere can be assumed for a soil source. This quantitative analysis describes the limitations for calculations and experiments used to define simplified transfer coefficients for 14C from soil to vegetation.
Contamination of fruits and leaves from various trees with 137Cs from the Chernobyl accident was systematically studied from 1987 to 1990 on two farms in Northern Greece. Measured biological half-lives for 137Cs are in good agreement with a recently presented model. Contamination of leaves and fruits of trees planted before the accident decays exponentially with time. Contamination of trees planted after the Chernobyl accident was also studied.
Whole-body counting measurements were conducted to monitor the 137Cs biological half-life of 14 individuals in Athens during the period June 1988 to June 1989. The results and the solution of a 137Cs retention model showed that the individuals examined were receiving 0-3.7 Bq d-1 of 137Cs through the food chain during the period investigated.
Results are presented on monthly measurements of 137Cs content in cows' milk over a 3-y period after the Chernobyl reactor accident. It was observed that, in an annual cycle of measurements, the 137Cs concentration of milk increased between December and August, peaking in April each year, due to the dependency of the 137Cs content of cattle feed on the fallout activity of 137Cs. There was a consistent correlation between the 137Cs concentration of milk and surface air.
Routine operations at the Savannah River Site (SRS) in Western South Carolina result in radionuclide releases to the atmosphere and to the Savannah River. The resulting radiation doses to the off-site maximum individual and the off-site population within 80 km of the SRS are estimated on a yearly basis. These estimates are currently generated using dose models prescribed for the commercial nuclear power industry by the Nuclear Regulatory Commission (NRC). The NRC provides default values for dose-model parameters for facilities without resources to develop site-specific values. A survey of land- and water-use characteristics for the Savannah River area has been conducted to determine site-specific values for water recreation, consumption, and agricultural parameters used in the NRC Regulatory Guide 1.109 (1977) dosimetric models. These site parameters include local characteristics of meat, milk, and vegetable production; recreational and commercial activities on the Savannah River; and meat, milk, vegetable, and seafood consumption rates. This paper describes how parameter data were obtained at the Savannah River Site and the impacts of such data on off-site dose. Dose estimates using site-specific parameter values are compared to estimates using the NRC default values.
The soils of Bikini Atoll (11 degrees 35'N, 165 degrees 25'E) were contaminated by fallout from a thermonuclear explosion in 1954. Today, in the absence of any treatment, intake of 137Cs via the terrestrial food chain could account for 70% of the radiological dose received by a returning population. Therefore, we examined the effectiveness of potassium applications, alone and combined with nitrogen and phosphorus, in reducing 137Cs uptake by coconut (Cocos nucifera L.), a major food crop. Mean pretreatment concentrations of 137Cs in "drinking-nut" meat of approximately 17-y palms ranged from approximately 0.5 to 7.0 kBq kg-1 (approximately 14 to 190 pCi g-1) (wet mass) in the seven primary experiments reported. These values were reduced to approximately 0.06 to approximately 1.0 kBq kg-1 (approximately 1.6 to approximately 27 pCi g-1) following soil additions of potassium-chloride at rates from 670 to 6270 kg potassium ha-1. Major reductions were complete within 9-12 mo after single large applications and persisted for at least 3 y. Proportional reductions in associated drinking-nut fluid and in mature "copra nut" meat from the same palm also occurred. Comparable but shorter-lived reductions occurred in grass and herbaceous species beneath the palms. A combined nitrogen-phosphorus treatment had no additive effect in the presence of potassium but, by itself, reduced plant uptake by about 50%. The persistence of this effect suggested that phosphorus alone was the major factor. Periodic addictions of potassium at rates of approximately 1000 kg ha-1 would provide a feasible and highly effective means of reducing 137Cs in coconut food products.
On the basis of experimental data on the fallout of 137Cs from the Chernobyl accident, a statistical analysis was made of possible values of the coefficients of transfer via the soil-grass pathway. Model calculations of the possible radionuclide concentration in milk are performed by the Monte Carlo method using the probability distribution function obtained. It is shown that not only our limited knowledge and the possible diversity of the external conditions, but also the very nature of the phenomenon under consideration, make it desirable to switch from a deterministic to a stochastic formulation of the model. The fact that the dependence of the soil-to-grass radionuclide transfer coefficients on the initial concentration in soil might be non-linear in character is an indication of the limitation of the conventional linear model.
Dietary studies and whole-body measurements were used to estimate the intake of radiocesium and the radiation dose received by different groups of people in Norway after the Chernobyl accident. Freshwater fish, milk, and reindeer meat were the major sources for radiocesium intake. Dietary advice, together with agricultural decontamination measures, resulted in a considerable reduction in the exposure level of the population. A majority (40-80%) of the specially selected groups (farmers-hunters and Sami reindeer herdsman) changed its diet significantly after the accident. Without dietary changes, specifically a reduction in the consumption of freshwater fish and reindeer meat, the Sami group would have had a 400-700% higher radiocesium intake, and the farmers-hunters' intake would have been up to 50% higher than what they actually had experienced.
The 3H concentration in the diet of residents in Akita City, northern Japan, during autumn of 1987 and winter of 1988 was analyzed. Results were similar to those for spring and summer samples previously reported. No significant seasonal change of 3H concentration was observed. A simple model was constructed for estimating the mean residence time for organically-bound 3H in diet. However, more data about diet in the 1960s or 1970s are necessary for the estimation.
After the Chernobyl accident, the activity concentrations of radiocesium were measured in both the meals served at the cafeteria of a research center and in the employees eating there. The time-dependent means of monthly 137Cs activities in meals and people show a similar distribution pattern with highest values between March and July 1987, i.e., only 1 y after the accident. In meals, the highest activities were found when the menu consisted of pork, milk, or milk products. The 50-y cumulative effective dose calculated from the whole-body measurements is 0.21 mSv for male and 0.15 mSv for female employees. Cafeteria food contributed only a small share to this exposure.
Soil, prairie plants, and milk samples were collected at 39 dairy farms in the 9th and 10th Region in Southern Chile (38 degrees 44'-41 degrees 08' S) between 1982 and 1990. 137Cs concentrations found in soil, plant, and milk samples ranged from 3.8-17.1 Bq kg-1 for soil, from < 0.3-20 Bq kg-1 dry mass for plants, and from 0.10-0.71 Bq kg-1 for milk. Cesium concentration levels resulting from soil sample measurements exhibit a close similarity with corresponding values found in soils from Central Europe before 1986. The concentration ratio prairie plants:soil ranged from 0.05-0.62, 0.52-5.0, and < 0.02-0.40 corresponding to Dystrandepts, Placandepts, and Palehumults soil groups, respectively. At seven selected dairy farms in the vicinity of Valdivia city (10th Region), soil, prairie plant, and milk samples were taken yearly during the grazing period between 1982 and 1990. Results obtained from soil samples taken after April 1986 show no significant increase of the 137Cs concentration. Concentrations in plants and milk for 137Cs decreased during the observation time. 134Cs (as an indicator of Chernobyl fallout) was not found in soil, plant, or milk samples during 1986-1990.
A number of winter and spring barley (Hordeum vulgare L) varieties were tested for sensitivity to direct cesium contamination in Denmark arising from the Chernobyl accident. Significant differences among varieties were revealed which were independent of crop growing conditions. Results indicate that different sensitivities among varieties result from genetic or morphological differences.