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Evaluation of annual committed effective doses to members of the public in Morocco due to 238U and 232Th in various food materials.

Uranium (238U) and thorium (232Th) concentrations were measured in different foods widely consumed in Morocco by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). Annual committed effective doses due to 238U and 232Th intakes from the ingestion of the studied food materials were evaluated for different age groups of individuals, using the ICRP ingestion dose coefficients. The influence of the 238U and 232Th intakes and ages of individuals on the committed effective dose was investigated. Total annual intakes of 238U and 232Th for a typical food basket for adult members of the Moroccan population were estimated to be 451 +/- 27 Bq y(-1) and 359 +/- 20 Bq y(-1), corresponding to committed effective doses of (20 +/- 1) x 10(-6) Sv y(-1) and (83 +/- 5) x 10(-6) Sv y(-1), respectively.

Food Contamination, Radioactive↗

Doses from the consumption of Cardiff Bay flounder containing organically bound tritium.

ICRP dose coefficients for the ingestion of organically bound tritium (OBT) by adults and children are intended for general application to unspecified forms in diet and may not be applicable to intakes of a specific form of OBT. To obtain information relating to OBT in fish from Cardiff Bay, the retention of tritium in adult rats was determined after administration as either tritiated water (HTO) or dried flounder flesh containing OBT. Two components of retention were obtained in each case. The first component, attributable to tritium equilibrating with body water, had a half-time of retention of 3 days in each case, and accounted for 97% of the intake as HTO and 70% after intake of OBT in flounder. Results were consistent with rapid catabolism of a large proportion of flounder OBT to HTO. The second component of retention, attributable to OBT in rat tissues, accounted for 3% of tritium intake as HTO and 30% after intake as flounder OBT; the half-times of retention were 10 days and 25 days, respectively. The results obtained after administration as HTO are consistent with published animal data and correlate with the ICRP assumptions for adult man of half-times of 10 days for 97% behaving as HTO in body tissues and 40 days for 3% incorporated into OBT in body tissues. The results obtained after administration of flounder OBT suggest that appropriate assumptions for retention in adult man are 70% with a 10 day half-time and 30% with a 100 day half-time. These assumptions result in an ingestion dose coefficient of 6 x 10(-11) Sv Bq(-1). This compares with the ICRP value for OBT ingestion by adults of 4.2 x 10(-11) Sv Bq(-1), based on half-times of 10 days and 40 days applied to equal proportions of retained tritium. It is proposed that a dose coefficient of 6 x 10(-11) Sv Bq(-1) should be applied to tritium in flounders from Cardiff Bay. It is further proposed that this dose coefficient should be applied to all ingestion intakes by adults relating to this source of exposure, unless specific information is available showing that a significant proportion of the intake is HTO. The same proposals apply to dose coefficients derived here for flounder OBT consumption by children.

Animals↗

Variations in radiation exposures of adults and children in the UK.

Members of the UK population receive radiation doses from a number of sources including cosmic radiation, from uranium, thorium and their decay products, particularly radon, and from medical sources. On average, members of the UK population receive an effective dose of about 200 mSv over their lifetime. This results in a risk of fatal cancer of about 1%. However, the radiation dose is not the same to all individuals. Some components give doses that vary systematically from one region to another. Doses may also vary greatly from one individual to another. The rate at which the dose is accumulated may vary as the individual ages. Different organs and tissues do not necessarily receive the same dose. This paper discusses these factors and attempts to quantify them. Cosmic rays deliver doses which vary little across the body or between individuals. Terrestrial gamma rays also deliver more or less uniform whole-body doses, but the difference between individuals can be greater. Radionuclides in food deliver doses which vary both across the body and between individuals. These variations are even more marked in the case of doses from radon and from medical exposures.

Adult↗

Twenty years' application of agricultural countermeasures following the Chernobyl accident: lessons learned.

The accident at the Chernobyl NPP (nuclear power plant) was the most serious ever to have occurred in the history of nuclear energy. The consumption of contaminated foodstuffs in affected areas was a significant source of irradiation for the population. A wide range of different countermeasures have been used to reduce exposure of people and to mitigate the consequences of the Chernobyl accident for agriculture in affected regions in Belarus, Russia and Ukraine. This paper for the first time summarises key data on countermeasure application over twenty years for all three countries and describes key lessons learnt from this experience.

Agriculture↗

Doses and risks from the ingestion of Dounreay fuel fragments.

The radiological implications of ingestion of nuclear fuel fragments present in the marine environment around Dounreay have been reassessed by using the Monte Carlo code MCNP to obtain improved estimates of the doses to target cells in the walls of the lower large intestine resulting from the passage of a fragment. The approach takes account of the reduction in dose due to attenuation within the intestinal wall and self-absorption of radiation in the fuel fragment itself. In addition, dose is calculated on the basis of a realistic estimate of the anatomical volume of the lumen, rather than being based on the average mass of the contents, as in the current ICRP model. Our best estimates of doses from the ingestion of the largest Dounreay particles are at least a factor of 30 lower than those predicted using the current ICRP model. The new ICRP model will address the issues raised here and provide improved estimates of dose.

Administration, Oral↗

Current status of internal dosimetry in Lithuania.

After Lithuania regained independence, the legal basis for existing radiation protection was modified radically according to the IAEA, ICRP recommendations and the requirements of legislation of the European Community. The legal basis for internal dosimetry and a functioning system of assessment of exposure to intake of radionuclides have been created in the Radiation Protection Centre (regulatory authority in radiation protection). Direct and indirect measurements of concentrations of radionuclides are used for the assessment of internal doses of workers and the public.

Air Pollution, Indoor↗

Uranium gastrointestinal absorption: the f1 factor in humans.

The present investigation was undertaken by the Department of Health, Canada, to determine the most appropriate value to use for uranium gastrointestinal absorption (f1) in setting the guideline for drinking water. Fifty participants, free from medical problems, were recruited from two communities: a rural area where drinking water, supplied from drilled wells, contained elevated levels of uranium and an urban area where the water supplied by the municipal water system contained < 1 microg l(-1). Uranium intake through food, drinking water and other beverages was monitored using the duplicate diet approach. Intake and excretion were measured by inductively coupled plasma-mass spectrometry (ICP-MS) in samples collected concurrently from the same individuals over a 3 d period. The range of f1 values was between 0.001 and 0.06, with a median of 0.009. These values were independent of gender, age, duration of exposure, daily total uranium intake and allocation of intake between food and water. Consistent with the recommendation of ICRP Publication 69, 78% were below 0.02.

Absorption↗

Intake and excretion of 99Tc in a common sea alga, hijiki (Hizikia fusiforme), as ingested in the daily diet--a measurement in an adult male.

Ingestion and excretion of environmental 99Tc was measured in an adult male who ingested 'hijiki' food in his diet that contained a sub-bequerel activity per kg, and which was prepared from a marine alga, Hizikia fusiforme, or hijiki in Japanese, traditionally eaten in the Japanese diet. Harvested hijiki was boiled, dried and cooked. This was eaten at each meal five times over 2 d. All faeces and 24-h urine samples were collected during the 3 d before and subsequent 11 d starting from the day when the intake began. The ingestion intake was measured by analysing the dried hijiki material. 99Tc was determined by using liquid-liquid extraction and low-background beta ray spectrometry. The excreta were also analysed for minerals by atomic absorption spectrometry. The apparent absorption rate in the gastrointestinal tract for 99Tc under these conditions was calculated to be approximately 0.5. The present result from a single subject indicates the need for further studies.

Administration, Oral↗

Seasonal and long-term variations in 137Cs among adults from Swedish hunter families.

To study seasonal variations in 137Cs, whole-body content measurements of adults from Swedish hunter families have been performed in autumn 1997 and spring 1998. Measurements were performed in three locations, By, Harbo and Gävle, geographically close (within 100 km of each other) but with large differences in ground deposition levels. The hunter families at these three locations were previously measured in 1994. The measured persons were also asked for their frequency of intake of moose, roe-deer, reindeer, freshwater fish, mushrooms and berries. A statistically significant lower frequency of intake of mushrooms and berries in By, moose, roe deer and mushrooms in Harbo, and moose in Gävle was found in springtime compared to autumn. In one of the locations, there was a statistically significant lower average 137Cs whole-body content in spring 1998 than in autumn 1997 while in the other two locations no such effects could be seen. The 137Cs whole-body content has decreased by 37% from 1994 and to 1998 (including physical decay) correlated to an effective ecological half time of 6 years.

Adult↗

Foods found in the wild around nuclear sites: an evaluation of radiological impact.

Habit surveys were carried out around four licensed nuclear sites to identify people who collect foodstuffs from the wild (so-called 'free foods'). In total, around 800 collectors were readily identified, most of whom collected more than one free food. The data indicated that estimates of higher than average doses could reasonably be based on the three foodstuffs of most importance. Foods were selected for further study on the basis of either the number of collectors or the amount consumed. The radionuclides of interest were identified using published information on the discharges from each site. The resultant average and higher than average doses were estimated using the site-specific habit data. For all sites, doses from the consumption of free foods were low and of no radiological importance. Assessments based solely on data for cultivated foods would not therefore have underestimated radiological impact significantly. However, given the wide utilisation of free foods found in this study, for rigorous assessments it would be prudent to take account of the consumption of foods from the wild.

England↗

Contribution of different foodstuffs to the internal exposure of rural inhabitants in Russia after the Chernobyl accident.

In a large village, Veprin of the Bryansk region of Russia contaminated with radionuclides as a result of the Chernobyl accident, 137Cs concentration in food products of agricultural produce and natural origin was regularly measured, local inhabitants were polled on the composition of their diet, and the 137Cs content in their bodies was measured at the same time. These results were used as the basis for calculation of annual effective doses of internal exposure to inhabitants and for reconstruction of the dose during the entire period after the accident (1986-1996). The efficiency of countermeasures performed for reduction of the internal dose was assessed. The internal dose in inhabitants during the 10 years after the accident was shown to be reduced by countermeasures by a factor of 2, namely down to 35 mSv instead of the expected 70 mSv. The dose of external gamma radiation during the same time period is close to the obtained dose of internal exposure. The presence of peat and water-meadow soils in the vicinity of this village that are characterised by high transfer factors for radionuclides from soil to vegetation causes a high contribution of internal exposure to the total dose of population exposure. The contribution of natural products to the internal dose increased from 6% in 1987 increased to 25% in 1996. The individual content of 137Cs in the body of inhabitants reliably correlates with consumption of milk in the initial period after the accident and with consumption of forest mushrooms in the subsequent period.

Adult↗

Human absorption and retention of polonium-210 from caribou meat.

The gastrointestinal (GI) absorption factors and the biological retention times for polonium were determined for a group of 14 volunteers--seven men and seven women--from Saskatoon, Saskatchewan, Canada. Each volunteer consumed 2.0 kg of caribou meat containing known amounts of naturally occurring 210Po. Urine and faecal samples were collected for up to 65 days after meat consumption and analysed for 210Po. The average GI absorption factor for the 14 volunteers was 56 +/- 4% (range = 31-71%), not significantly different from the ICRP value of 50%. About 3% of absorbed polonium underwent prompt excretion by the urinary pathway. The remainder was retained by the body with a half-time >100 days, compared to the ICRP value of 50 days. The effect of these findings increases the dose estimate for ingestion of 210Po in food by a factor of 1.5 to 3.5. Thus, background doses to people consuming caribou and reindeer may be higher than previously thought.

Administration, Oral↗

Determination of uranium isotopes in food and environmental samples by different techniques: a comparison.

The uranium concentration in 59 samples of bottled and tap water, mainly from northern Italy, was measured by different techniques. Results obtained by inductively coupled plasma mass spectrometry (ICP-MS), semiconductor alpha spectrometry and low level liquid scintillation counting with alpha/beta discrimination (LSC) have been compared. High resolution gamma spectrometry and semiconductor alpha spectrometry have been used to analyse uranium in a variety of organic and inorganic samples. Isotopic secular equilibrium in the 238U series may be lacking or hidden by auto-absorption phenomena, so caution should be used in evaluating gamma spectrometry data. Alpha spectrometry has also been used to ascertain the possible pollution from depleted uranium in the environment.

Food Contamination, Radioactive↗

Uncertainties on predicted concentrations of radionuclides in terrestrial foods and ingestion doses.

Models are routinely used to calculate doses following routine releases and potential accidental releases of radionuclides. These models contain a number of parameters. Values for many of these are not accurately known. The primary aim of this study was to determine the level of uncertainty on predicted concentrations of radionuclides in foods, and doses to individuals consuming those foods, arising from uncertainties on the model input parameter values. A secondary objective was to identify those input parameters whose uncertainty makes a major contribution to the overall uncertainty on the predicted endpoints. The methodology adopted and results obtained are presented for the following radionuclides: 90Sr, 131I, 137Cs and 239Pu. The estimated uncertainty ratios (the ratio of the 95th to the 5th percentile) are frequently very large, often two to three orders of magnitude. The results of this study may be used to identify areas where further research could improve assessment capabilities.

Accidents↗

Overview of the wisdom stakeholder workshop on restoration management.

A Workshop to extend the Involvement of Stakeholders in Decisions On restoration Management (WISDOM) was held at New College, Oxford from 15 to 17 September 2003. The aim was to promote awareness and interest in the wider application of stakeholder involvement in the formulation of strategies for the management of contaminated agricultural land and produce following a nuclear accident. The workshop, through 25 plenary papers and a set of two facilitated discussion sessions, provided valuable feedback on a wide range of issues including technical and social factors affecting countermeasure selection, acceptability of intervention levels, the challenges of rural waste disposal and crisis management. The workshop achieved its aim and the findings will be disseminated widely. Stakeholder groups are already active in the UK, Finland, Belgium, France and Greece; there was commitment from participants to establish further, similar groups in other member states within the European Union.

Decision Support Systems, Management↗

Activity concentrations and mean annual effective dose of foodstuffs on the island of Tenerife, Spain.

A total of 26 different food types and 12 elaborated diets were analysed by low-level gamma spectrometry to measure their content of 238U(234Th), 228Ra(228Ac), 226Ra(214Pb), 210Pb, 137Cs and 40K. The concentrations of these radionuclides measured in some imported foodstuffs were compared with those measured in some locally produced ones. Moreover, the concentrations found in the analysed foodstuffs and composite diets were compared with the data available in literature from other locations, such as Egypt, Brazil, Poland and Hong Kong. 40K contributed highest to the daily dose produced by the intake of comestibles. The largest 40K concentrations were measured in the chickpeas and beans with 380 +/- 30 and 380 +/- 20 Bq kg(-1) fresh weights, respectively. The artificial radionuclide 137Cs was measured only above detection limits in the potatoes and sweet potatoes. A mean annual effective dose of 362 microSv with a standard deviation of 110 microSv was calculated from the composite diets.

Body Burden↗