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Uranium and thorium daughters are ten times more concentrated in thyroids from some bovine animals than in the teeth of the same animals. These radioactive isotopes are believed to be from natural sources, but their resulting annual dosage of thyroid radiation has exceeded that from iodine-131 fallout.
The investigation was conducted to determine the radioactivities of fodder mixtures and their components for poultry and swine. The total radioactivity, concentrations of potassium, potassium radioisotopes radium and thorium in 273 fodder mixture samples for poultry, 131 fodder mixture samples and concentrates for swine, and 915 component samples of the mixtures were estimated. The radioactivities of fodder mixtures for poultry, swine, and protein concentrates ranged from 212.0 (DKM-2) to 269.0 Bq/kg (DKA-starter), from 206.0 (PT-1) to 233.0 (PP-prestarter), and from 444.0 (KT-1) to 557.0 Bq/kg (Provit), respectively. As to the components of fodder mixture, the radioactivities ranged from 18.0 (fodder phosphate) to 1104.0 Bq/kg (fodder yeasts). The potassium concentrations in fodder mixtures for poultry ranged from 0.82 g/100 g (DKA-starter) to 0.62 g/100 g (KB-1); for swine ranged from 1.97 g/100 g (Provit) to 0.63 g/100 g (PT-1). The highest concentration of potassium was found in fodder yeasts (3.85 g/100 g), and the lowest one in fodder phosphate (0.01 g/100 g). The analysis of the data showed that the radioactivity of the mixtures and their components was mostly conditioned by radiopotassium and revealed correlations between the radioactivities and the total concentrations of potassium. The contamination with the natural radioelements (potassium, radium, thorium) as well as their limited absorption by the gastrointestinal tract, their metabolism in organism, and their radiotoxicological characteristics do not create radiological threat to animals.
Both the farm-specific and regional costs of clean feeding as a countermeasure to reduce ingestion of contaminated grass when there is insufficient supply of other types of roughage were estimated for dairy farming in Finland in the first year after contamination. The cost estimation considered expenditures and revenues associated with milk production and were calculated using farm models developed for economic planning. A hypothetical contamination scenario was designed using RODOS models for atmospheric dispersion and transfer in terrestrial food chains. Costs for intervention after two similar hypothetical atmospheric dispersion and deposition scenarios in early June and in July were estimated. As a reference, the cost of complete replacement of fodder throughout the area was also calculated. Feed substitution costs were higher in June than in July, due to the availability of some harvested silage in the later scenario. In the first case, the additional costs of clean feeding amounted to one-fifth of the normal production costs. Effective advisory/support services, available to farmers, can substantially improve the implementation of countermeasures. However, high costs and insufficient sources of clean feed would restrict the use of clean feeding as the sole countermeasure after serious contamination during the growing season.
Effects of incorporated 131I in combination with intake of fodder contaminated with 134,137Cs on triiodothyronin reception by peripheral blood lymphocytes in rats aged 2 and 6 months were examined. Incorporation of 131I was found to cause specific binding of the hormone, particularly marked in young animals.
Radioactive fallout presents a short-term risk due to its direct deposition on agricultural crops, as well as a long-term risk resulting from its deposition on soil and subsequent uptake by crops. A dynamic model, RADFOOD, was developed, based on different existing models. It simulates transport of fallout radionuclides through agricultural food chains to man and evaluates the radiation doses resulting from consumption of contaminated food. Transport was modeled through compartments representing various environmental elements of food products. Internal radiation doses (whole-body weighted doses) following ingestion of contaminated foodstuffs were then estimated. Specific types of crops, soils and diet of man and livestock were considered. A sample calculation was performed in which individual and collective radiation doses, as well as associated health effects, resulting from fallout contamination were evaluated. They were estimated for food consumption beginning at various times after the fallout deposition and for different consumption durations. A sensitivity analysis, performed for the main model parameters, showed that the radiation dose is sensitive, for the short-term period, to changes in initial deposition levels and in the parameters characterizing initial fallout interception and resuspension.
The radionuclides in milk, which result from exposure of dairy cows to radioactive fallout, are a major factor in assessment of internal radiation of humans. To evaluate the radionuclide intake of people from fallout-contaminated milk requires information about feed sources and milk distribution. Pasture intake and the shelf-life of milk are important factors in the case of a short-lived radionuclide like 131I. Large-scale human radiation assessment studies are underway, all of which consider the dairy food chain as a critical component. These include retrospective studies of fallout from nuclear weapons testing at the Nevada site in the 1950s and the impact of the Chernobyl accident on April 26, 1986.
Today the most important anthropogenic radiation comes from atmospheric testing of nuclear weapons carried out 20-30 years ago, authorized discharges to the sea from nuclear reprocessing plants, and from the Chernobyl accident in 1986. In the past decade the International Union of Radioecologists (IUR) has contributed to improved international co-operation among radioecologists from all parts of the world through its creation of a number of working groups for specific radioecological problems. More than 30 years of radioecological studies have probably made the radioactive contamination of our environment the best-understood of all present pollution problems. This review indicates the doses to man received from the important anthropogenic sources, as well as those from natural background radiation. It appears that in a global perspective the latter is by far the most important contributor.
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.
Within the framework of the "International Chernobyl Project," selected areas in the Republics of Ukraine, Belarus, and Russia of the former USSR, contaminated by radioactive fallout from the Chernobyl accident in 1986, were investigated by international teams. In addition, environmental studies were carried out in areas officially declared as "uncontaminated regions" in order to corroborate this classification and to provide reference baseline data for the simultaneously performed medical investigations on health effects in the contaminated areas. Altogether, 141 measurements of the gamma dose rate, both outdoors and indoors, were carried out. Also, the radionuclide concentration in 58 soil and food sample was determined. In addition, results from 1,620 individual film dosimeter readings were analyzed. The results show that, in areas adjacent to those officially designated as contaminated regions (137Cs surface ground contamination > or = 37 kBq m-2), levels of environmental fallout contamination are insignificant. The additional resulting committed effective dose over the next 70 years due to the fallout is only a fraction of the corresponding value from the natural radiation environment.
After the Chernobyl nuclear accident, game meat and, in particular, sheep meat in the Republic of Croatia showed a high degree of radioactive contamination compared to large livestock. The activity concentrations of 131I, 134Cs, and 137Cs were measured in meat and internal organs (i.e., lung, liver, kidney, and heart) of game (e.g., venison, hare, and wild boar) and sheep that were used as biological indicators of radioactive contamination. In order to estimate the importance of game and sheep as a dietary source of radioactivity, the effective dose equivalent for the average and critical population (hunters and livestock raising families) were calculated. The data indicated that sheep meat represents greater risk for the human population, in case of a nuclear accident, than game meat. The share of meat from sheep (4.4%) prevailed over the share of meat from game (0.5%) when comparing the average intake of meat per inhabitant in Croatia. This result pointed to an increased risk for families who depend mostly on sheep meat in the case of a nuclear accident.
Measurements of natural radioisotopes present in some of the foodstuffs which form the main components of the composite Indian diet are presented. Assessment of daily intake of these natural radionuclides has been made on the basis of the average daily intake of these food-items by the population of Bombay and its environment. The content of 40K, 226Ra and 228Th radioactivity varies from 45.9 to 649.0 Bq/kg, 0.01 to 1.16 Bq/kg and 0.02 to 1.26 Bq/kg, respectively. The average daily intakes of 40K, 226Ra and 228Th have been estimated as 105.6, 0.17 and 0.18 Bq d(-1), respectively for the period 1970-1982.
The paper gives averages of 137Cs deposition densities in soils from three areas in Northern Ukraine measured 12 to 15 y following the Chernobyl accident: in an area near Narodici (75 km west of the Chernobyl nuclear power plant in the so-called zone II) heavily contaminated by the Chernobyl fall-out and in areas around Korosten and Zhitomir showing contamination levels to be much lower. The three areas exhibited very different 137Cs deposition densities of 2.2 MBq m(-2), 400 kBq m(-2), and 5 kBq m(-2), respectively. During a 1-y observation, measurements of the 137Cs transfer in the food chain to humans and 137Cs whole body contents dependent on the 137Cs daily intake were carried out under realistic conditions of the rural inhabitants who lived in settlements within zone II. Detailed investigations of components of the daily diet showed that the high 137Cs contamination levels found in soils of zone II do not affect in any way low 137Cs concentrations of all important agricultural products harvested and consumed by villagers. With regard to consumption habits of the population of zone II, mushrooms and wild berries were found to contribute more than 95% of the 137Cs daily intake to the 137Cs whole body content of about 12 kBq (with maximum values up to 760 kBq) measured in a group of inhabitants of zone II during a period from July 1998 to July 1999. The median of the annual dose of these inhabitants from external and internal exposures was 1.2 mSv y(-1) with a geometric standard deviation of 2.6. Excluding extreme habits, the geometric mean of the total exposure was 1.0 mSv y(-1) with a geometric standard deviation of 1.3.
The daily dietary intakes and total contents of Cs and I in skeletal muscle and thyroid, respectively, for an average Indian adult were estimated by determining their concentrations in the total cooked diet and tissue samples using instrumental neutron activation analysis. These data were then used to predict the biological half-lives of Cs and I and their radioactive counterparts for the Reference Indian Man. The predicted biological half-lives of Cs and I for Reference Indian Man were found to be comparable with the reported values for the ICRP Reference Man.
Noninbred female white rats were fed for 30 days with diets containing 137Cs and 85Sr in indicative doses. After that the animals received some sea products to investigate their radioprotective properties. Natural sea products proved able to influence the kinetics of the radionuclides metabolism. Laminaria salad "Dalnevostochny" given in the dose 20 g per animal reduced the accumulation of radioactive Cs and Sr by 76.7 and 57.6%, respectively. Moreover, sea products stabilize functional activity of peripheral blood natural killers which are important in immunological defense of the body.
The nature of the radionuclide contamination resulting from Chernobyl disaster is in its spatial and aggregate heterogeneity determined by the interaction of systematic and incidental factors. To study the radionuclide migration in the soil-plant system, an independent statistical index of contamination heterogeneity H = RAsAp is proposed which is calculated as a Brave-Pirsens coefficient of linear correlation between radioactivity of soil and dry biomass of plants grown on it and which allows to determine relative range of contamination that appears in the form of "hot particles". An adequacy of this index is substantiated, and it is used to analyze the experimental results on radionuclide migration.
Dose assessments, both retrospective and prospective, comprise one important function of a radiological study commissioned by the Republic of the Marshall Islands (RMI) government in late 1989. Estimating past or future exposure requires the synthesis of information from historical data, results from a recently completed field monitoring program, laboratory measurements, and some experimental studies. Most of the activities in the RMI to date have emphasized a pragmatic rather than theoretical approach. In particular, most of the recent effort has been expended on conducting an independent radiological monitoring program to determine the degree of deposition and the geographical extent of weapons test fallout over the nation. Contamination levels on 70% of the land mass of the Marshall Islands were unknown prior to 1994. The environmental radioactivity data play an integral role in both retrospective and prospective assessments. One recent use of dose assessment has been to interpret environmental measurements of radioactivity into annual doses that might be expected at every atoll. A second use for dose assessment has been to determine compliance with a dose action level for the rehabilitation of Rongelap Island. Careful examination of exposure pathways relevant to the island lifestyle has been necessary to accommodate these purposes. Examples of specific issues studied include defining traditional island diets as well as current day variations, sources of drinking water, uses of tropical plants including those consumed for food and for medicinal purposes, the nature and microvariability of plutonium particles in the soil and unusual pathways of exposure, e.g., that which might be associated with cooking and washing outdoors and inadvertent soil ingestion. A study on the prevalence of thyroid disease is also being conducted and the geographic pattern of disease may be useful as a bioindicator of the geographic pattern of exposure to radioiodine. Finally, an examination is underway of gummed film, fixed-instrument, and aerial survey data accumulated during the 1950's by the Health and Safety Laboratory of the U.S. AEC. This article gives an overview of these many different activities and a summary of recent dose assessments.
One of the three goals of the United Nations for sustainable food security is to ensure that all people have access to sufficient, nutritionally adequate, and safe food. Decades of tin mining in the Bitsichi area of the Jos Plateau, Nigeria, have left a legacy of polluted water supplies, impoverished agricultural land, and soil containing abnormally high levels of naturally occurring radioactive elements. In order to ascertain the radiological food safety of the population, different crops that constitute the major food nutritive requirements were collected directly across farmlands in the area. The activity concentrations of (226)Ra, (228)Th, and (40)K were determined in the food and soil samples using gamma-ray spectrometry. Additionally, in situ gamma dose rate measurements were performed on the farms using a pre-calibrated survey meter. The corresponding activity concentrations in the food crops ranged from below detection limit (BDL) to 684.5 Bq kg(-1) for (40)K, from BDL to 83.5 Bq kg(-1) for (226)Ra, and from BDL to 89.8 Bq kg(-1) for (228)Th. Activity concentrations of these radionuclides were found to be lower in cereals than in tubers and vegetables. As for the soil samples, activity concentrations of these radionuclides varied from BDL to 166.4 Bq kg(-1), from 10.9 to 470.6 Bq kg(-1), and from 122.7 to 2,189.5 Bq kg(-1) for (40)K, (226)Ra, and (228)Th, respectively. Average external gamma dose rates were found to vary across the farms from 0.50 +/- 0.01 to 1.47 +/- 0.04 microSv h(-1). Due to past mining activities, the soil radioactivity in the area has been modified and the concentration level of the investigated natural radionuclides in the food crops has also been enhanced. However, the values obtained suggest that the dose from intake of these radionuclides by the food crops is low and that harmful health effects are not expected.
The consumption rate of bottled mineral water in Japan has increased due to changes in eating habits and contamination of water sources. Radioactivity levels of 238U and 232Th in imported mineral water were checked from the viewpoint of internal radiation for Japanese subjects. Concentration ranges of 238U and 232Th in imported bottled mineral water, domestic bottled mineral water, domestic tap water, and domestic soft drinks were as follows: for U, N.D to 7.48 x 10(3), 1.07 to 344, 0.66 to 104, and 3.04 to 46.2 ng dm (ppt); for Th, 0.60 to 5.12, 0.65 to 22.4, 0.64 to 22.1, and 11.0 to 48.5 ng dm, respectively. In some brands of imported bottled mineral water, U concentration was sometimes much higher than domestic bottled mineral water and domestic tap water. The annual effective dose (1.5 x 10(-3) mSv y(-1) estimated from intake of 238U was approximately 7 times higher than that through dietary intake in Japanese. However, the internal dose added by drinking the imported portable water is negligible compared with total annual internal dose. Concentrations of non-radioactive elements were also compared between imported and domestic bottled water. Geometric means of cobalt, arsenic, strontium, cesium, phosphorous, and calcium in imported bottled water were higher compared with those of domestic bottled mineral water and domestic tap water. Maximum values of 11 elements (arsenic, rubidium, strontium, cesium, barium, sodium, magnesium, potassium, calcium, and manganese) were also found in imported bottled water.