A simple model to estimate deposition based on a statistical reassessment of global fallout data

Atmospheric testing of nuclear weapons began in 1945 and largely ceased in 1963. Monitoring of the resulting global fallout was carried out globally by the Environmental Measurements Laboratory and the UK Atomic Energy Research Establishment as well as at national level by some countries. A correlation was identified between fallout deposition and precipitation and an uneven distribution with latitude. In this study, the available data from 1954 to 1976 for (90)Sr and (137)Cs were reanalysed using analysis of covariance (ANCOVA) and logarithmically transformed values of the monthly deposition density as the response variable. Generalized additive models (GAM) were used to explore the relationship of different variables to the response variable and quantify the explanatory power that could be achieved. The explanatory variables which consistently explained most of the variability were precipitation at each site, latitude and change with time and a simple linear model was produced with similar explanatory power as the GAM. The estimates improved as the temporal resolution of the precipitation data increased. A good log-log fit could be obtained if a bias of about 1-6 mm precipitation per month was added, this could be interpreted as dry deposition which is not otherwise accounted for in the model. The deposition rate could then be explained as a simple non-linear power function of the precipitation rate (r(0.2-0.6) depending on latitude band). A similar non-linear power function relationship has been the outcome of some studies linking wash-out and rain-out coefficients with rain intensity. Our results showed that the precipitation rate was an important parameter, not just the total amount. The simple model presented here allows the recreation of the deposition history at a site, allowing comparison with time series of activity concentrations for different environmental compartments, which is important for model validation.

Tracking of airborne radionuclides from the damaged Fukushima Dai-ichi nuclear reactors by European networks

Radioactive emissions into the atmosphere from the damaged reactors of the Fukushima Dai-ichi nuclear power plant (NPP) started on March 12th, 2011. Among the various radionuclides released, iodine-131 ((131)I) and cesium isotopes ((137)Cs and (134)Cs) were transported across the Pacific toward the North American continent and reached Europe despite dispersion and washout along the route of the contaminated air masses. In Europe, the first signs of the releases were detected 7 days later while the first peak of activity level was observed between March 28th and March 30th. Time variations over a 20-day period and spatial variations across more than 150 sampling locations in Europe made it possible to characterize the contaminated air masses. After the Chernobyl accident, only a few measurements of the gaseous (131)I fraction were conducted compared to the number of measurements for the particulate fraction. Several studies had already pointed out the importance of the gaseous (131)I and the large underestimation of the total (131)I airborne activity level, and subsequent calculations of inhalation dose, if neglected. The measurements made across Europe following the releases from the Fukushima NPP reactors have provided a significant amount of new data on the ratio of the gaseous (131)I fraction to total (131)I, both on a spatial scale and its temporal variation. It can be pointed out that during the Fukushima event, the (134)Cs to (137)Cs ratio proved to be different from that observed after the Chernobyl accident. The data set provided in this paper is the most comprehensive survey of the main relevant airborne radionuclides from the Fukushima reactors, measured across Europe. A rough estimate of the total (131)I inventory that has passed over Europe during this period was <1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe.

Assessing deposition levels of 55Fe, 60Co and 63Ni in the Ignalina NPP environment

Two RBMK-1500 reactor units operated in Lithuania in the 1987-2004 period (one of them was stopped for decommissioning in 2004). This study presents a preliminary investigation of surface deposition density levels of (55)Fe and (63)Ni in moss samples collected in the close vicinity of the Ignalina NPP. Non-destructive analysis by the HPGe gamma-spectrometry was followed by radiochemical separation. Radiochemical analysis was based on anion-exchange and extraction chromatography. (55)Fe and (63)Ni activities were measured by liquid scintillation counting (LSC). The results indicate that the deposition values of (55)Fe are generally higher than those of (60)Co and (63)Ni.

Requirements for estimation of doses from contaminants dispersed by a 'dirty bomb' explosion in an urban area

The ARGOS decision support system is currently being extended to enable estimation of the consequences of terror attacks involving chemical, biological, nuclear and radiological substances. This paper presents elements of the framework that will be applied in ARGOS to calculate the dose contributions from contaminants dispersed in the atmosphere after a 'dirty bomb' explosion. Conceptual methodologies are presented which describe the various dose components on the basis of knowledge of time-integrated contaminant air concentrations. Also the aerosolisation and atmospheric dispersion in a city of different types of conceivable contaminants from a 'dirty bomb' are discussed.

Root uptake of lead by Norway spruce grown on 210Pb spiked soils

The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead (210Pb) were determined in needles and twigs and in the pot soil spiked with 210Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition.

Estimation of health hazards resulting from a radiological terrorist attack in a city

In recent years, the concern for protection of urban populations against terror attacks involving radiological, biological or chemical substances has attracted increasing attention. It sets new demands to decision support and consequence assessment tools, where the focus has traditionally been on accidental exposure. The aim of the present study was to illustrate issues that need to be considered in evaluating the radiological consequences of a 'dirty bomb' explosion. This is done through a worked example of simplified calculations of relative dose contributions for a specific 'dirty bomb' scenario leading to atmospheric dispersion of 90Sr contamination over a city area. Also, the requirements of atmospheric dispersion models for such scenarios are discussed.

New developments to support decision-making in contaminated inhabited areas following incidents involving a release of radioactivity to the environment

The Chernobyl accident demonstrated that releases from nuclear installations can lead to significant contamination of large inhabited areas. A new generic European decision support handbook has been produced on the basis of lessons learned on the management of contaminated inhabited areas. The handbook comprises detailed descriptions of 59 countermeasures in a standardised datasheet format, which facilitates a comparison of features. It also contains guidance in the form of decision flowcharts, tables, check lists and text to support identification of optimised solutions for managing the recovery of inhabited areas within a framework consistent with ICRP recommendations. A new comprehensive inhabited-area dose model is also being developed for implementation in the ARGOS and RODOS decision support systems. Shortcomings of previous models are demonstrated. Decision support modelling in relation to malicious dispersion of radioactive matter in inhabited areas is also discussed. Here, the implications of, e.g., particle sizes and dispersion altitude are highlighted.

Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea)

A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units.

Performance of four clinical screening tools to select peri- and early postmenopausal women for dual X-ray absorptiometry

Several methods to select postmenopausal women for dual X-ray absorptiometry (DXA) have been proposed. We decided to compare the performance of three clinical decision rules (SCORE, ORAI, OST) with the usual case-finding strategy based on the presence of a major risk factor for future fracture (CFMRF). The study subjects were 2009 healthy, white, peri- or early postmenopausal women participating in the Danish Osteoporosis Prevention Study (DOPS). DXA results expressed as T-scores and scores on SCORE, ORAI, OST and CFMRF were extracted from the DOPS database. First, we evaluated the screening tools as originally described by the developers. The resulting sensitivities and specificities ranged from 18% to 92% and from 66% to 85%, respectively. Only OST achieved a high sensitivity (92%) with respect to femoral neck T-score < or = -2.5; however, the sensitivity with respect to lumbar spine T-score < or = -2.5 was only 51%. Next, the performance of the screening tools was evaluated against T-score < or = -2.0 (and T-score < or = -2.5) in at least one of the regions: femoral neck, total hip or lumbar spine. Using ROC curve analysis, we determined cut-offs yielding sensitivities as close as possible to 90%. The CFMRF and the ORAI tool were too coarse to yield 90% sensitivity. The performances of OST and SCORE were equal from a clinical perspective in that the sensitivities and the specificities varied from 89% to 94% and from 23% to 28%, respectively. The performance of CFMRF was no better than could be expected by chance, yielding a sensitivity of 19% and a specificity of 85%. Applying SCORE or OST 75% of the women would have to be referred for densitometry to identify 90% of the women with T-score < or = -2.0 (or T-score < or = -2.5) in at least one region. In conclusion, our results question the utility of all the evaluated tools for screening peri- and early postmenopausal women for low BMD. However, if a decision on referral has to be made, it may be based on the simple OST rule, which performed as well as or better than any of the other tools.

Environmental radioactivity in the South Urals 1990-1997. An international study supported by INTAS, EC and national funding

Radioecological studies carried out in a joint co-operation between Russian, Ukrainian and Danish Laboratories are reported. The environmental impact of routine, discharges as well as accidental events, notably the Kyshtym accident in 1957 and the Karachay wind dispersion in 1968 have been studied. From measurements and based on model assumptions it has been estimated that the Ob river system outside Mayak, i.e. first of all the Techa and Iset rivers and their floodplains contain 0.1 PBq 90Sr, 0.3 PBq 137Cs and 0.8 TBq 239, 240Pu. The uncertainty of these estimates is a factor of 3-4. The present contamination from the Kyshtym accident outside the Mayak area is calculated to 0.1-0.5 PBq 90Sr and from the Karachay incident the contamination is 0.05-0.1 Bq 137Cs. The environmental contaminations with Pu from these two events are in the order of 1 TBq. The occurrence of 99Tc, 129I and 237Np in highly contaminated Techa river sediments collected outside Mayak is for the first time reported.

Iodine-129 and caesium-137 in Chernobyl contaminated soil and their chemical fractionation

Soil samples from areas in Belarus, Russia and Sweden contaminated by the Chernobyl accident were analysed for (129)I by radiochemical neutron activation analysis, as well as for 137Cs by gamma-spectrometry. The atomic ratio of (129)I/137Cs in the upper layer of the examined soil cores ranged from 0.10 to 0.30, with an average of 0.18, and no correlation between (129)I/137Cs ratio and the distance from Chernobyl reactor to sampling location was observed. It seems feasible to use the (129)I/137Cs ratio to reconstruct the deposition pattern of 131I in these areas. The association of (129)I and 137Cs in the Chernobyl soil and Irish Sea sediment was investigated by a sequential extraction method. Similar speciation of (129)I in the Chernobyl soil and Irish Sea sediment was found. Approximately 70% of (129)I is bound to oxides and organic matter, and 10-20% is in the readily available phase, while most of the 137Cs (73%) in Chernobyl soil remains in the extraction residue.

Iodine-129 in thyroid and urine in Ukraine and Denmark

Human thyroids collected from Gomel in Belarus, sheep thyroid from Jutland and human urine from Zealand in Denmark were analysed for 129I and 127I concentrations. The ratios of 129I/127I in human thyroid in Gomel are 2.65-11.0 x 10(-9) with an average of 7.21 x 10(-9), which is one order of magnitude higher than those from Asia and South America (10(-10)), but significantly lower than those observed in west Europe (10(-8)). A weak negative correlation (P < 0.05) between 129I/127I ratio in human thyroid and the age of the subjects was observed in Gomel. The average ratio of 129I/127I in sheep thyroids from Jutland of Denmark is 1.81 x 10(-7), which is two orders of magnitude higher than those in south hemisphere, and Asia. It is also significantly higher than those observed in other west European countries before 1984 and that in human thyroid in Gomel. The high thyroid 129I level in Jutland is attributed to the release of reprocessing plants in France and UK. The 129I/127I ratios in human urine in Zealand of Denmark are 0.86-2.86 x 10(-8). The possibility of using urine 129I to evaluate the thyroid exposure to 129I is investigated.

Level and origin of iodine-129 in the Baltic Sea

Environmental samples, such as seawater, seaweed, lake water, lake sediment and grass collected from the Baltic Sea area were analyzed for 129I and 127I by radiochemical neutron activation analysis. In 2000, the concentration of 129I in the seawater from Borholm and Møen in the Baltic Sea has reached 6.0 x 10(-13) and 16 x 10(-13) g/l, respectively, these are more than two orders of magnitude higher than the global fallout level. The highest value of 270 x 10(-13) g/l being found in the seawater from the Kattegat. By comparison of the level of 129I in the lake water and precipitation in this region, it is estimated that more than 95% of 129I in the Baltic Sea originates from reprocessing emissions, especially from the French nuclear fuel reprocessing plant at La Hague. More than 30% of 129I in the south Baltic and 93% in the Kattegat directly originates from the marine discharges of the European reprocessing plants.

[Hormone replacement therapy reduces the risk of forearm fracture in postmenopausal women. Results of the Danish Osteoporosis Prevention Study]

In a prospective, controlled, comprehensive cohort trial of 2,016 healthy early postmenopausal women aged 45-58 years we studied fracture prevention through the use of oestrogen. There were two main study arms: a randomised arm (randomised to HRT [n = 502] or not [n = 504]) and a non-randomised arm (on HRT [n = 221] or not [n = 789] by own choice). After five years, an intention-to-treat analysis (n = 2,016) showed a reduction in the overall fracture risk (RR = 0.73, 95% CI: 0.50-1.05) and in the forearm fracture risk (RR = 0.45, 95% CI: 0.22-0.90) with oestrogen. Restriction of the analysis to women who had adhered to their initial allocation of either oestrogen (n = 395) or no oestrogen (n = 977) showed a significant reduction in both the overall fracture risk (RR = 0.61, 95% CI: 0.39-0.97) and the risk of forearm fractures (RR = 0.24, 95% CI: 0.09-0.69). We conclude that it is possible to reduce the number of forearm fractures in early postmenopausal women by the use of oestrogen as primary prevention.

Discordance between changes in bone mineral density measured at different skeletal sites in perimenopausal women--implications for assessment of bone loss and response to therapy: The Danish Osteoporosis Prevention Study

Assessing bone loss and gain is important in clinical decision-making, both in evaluating treatment and in following untreated patients. The aim of this study was to correlate changes in bone mineral density (BMD) at different skeletal sites during the first 5 years after menopause and determine if forearm measurements can substitute for dual-energy X-ray absorptiometry (DXA) of the spine and hip. BMD was measured at 0, 1, 2, 3, and 5 years using Hologic 1000/W and 2000 densitometers in 2,016 perimenopausal women participating in a national cohort study. This analysis comprises 1,422 women remaining in the study after 5 years without changes to their initial treatment (hormone-replacement therapy [HRT], n = 497, or none, n = 925). Despite correlated rates of change between forearm and spine (r2 = 0.11; p < 0.01), one-half of those who experienced a significant decrease in spine BMD at 5 years showed no significant fall in forearm BMD (sensitivity, 50%; specificity, 85%; kappa = 0.25). The total hip had significant better agreement with spine (sensitivity, 63%; specificity, 85%; kappa = 0.37; p < 0.01). Analysis of quartiles of change also showed significant better agreement with spine and whole body for the total hip than for the femoral neck or ultradistal (UD) forearm. In a logistic regression analysis for identification of group (HRT or control), the prediction was best for whole body (82.6%) and spine (80.9%), followed by total hip (78.5%) and forearm (74.7%). In conclusion, changes at the commonly measured sites are discordant, and DXA of the forearm is less useful than DXA of the hip or spine in determining the overall skeletal response to therapy or assessing bone loss in untreated women.

The fallacy of BMD: a critical review of the diagnostic use of dual X-ray absorptiometry

The diagnostic use of BMD should be cautious as BMD is not an ideal measure of true bone density; it is not an ideal measure of bone strength; it does not predict fractures well; and it has inherent problems of accuracy and linearity. The limitations of BMD, based on the physical deficiencies of DXA, are further obscured by the introduction of T-scores. It is suggested that BMD and BMC, when used diagnostically and for fracture risk classification, be used after correction for body size and/or bone size, age and sex, and that measured values be evaluated in the light of established mean fracture incidence data. BMD is not a parameter of sufficient validity to be the sole indicator of present and future fracture risk. A low BMD should be regarded one of several fracture risk factors. It seems that there is a need to redefine the T-score based definition of osteoporosis.

Comparison of quantitative ultrasound and dual X-ray absorptiometry in estrogen-treated early postmenopausal women

Identifying individuals at risk of developing osteoporosis is important in order to initiate early treatment. Many new techniques have been proposed as alternatives for DXA-scanning. Some of these alternatives certainly have advantages, but none have so far been demonstrated to predict fractures better, or even to identify individuals at risk of osteoporosis as well as with the standard method. In this study, comprising a group of women from the Danish Osteoporosis Prevention Study, we wished to investigate whether a technique based on quantitative ultrasound (QUS) could identify individuals with low BMC/BMD as measured by dual X-ray absorptiometry (DXA). Furthermore, we wished to test whether the method could detect differences between untreated individuals and those treated with hormone replacement therapy. We found that QUS could detect differences between the treated and untreated groups, but it was unable to identify women with low BMD, although it might be able to identify persons not at risk of osteoporosis. Low QUS values should be followed by a regular DXA measurement to confirm the presence of osteoporosis.

The metacarpal index revisited: a brief overview

Metacarpal index (MCI) is combined cortical thickness (both sides)) normalized with regard to outer bone diameter of the measuring site, the midshaft of the second metacarpal, or the three midmetacarpals of both hands. MCI is reduced with age, particularly in postmenopausal women. It correlates with axial bone mass in group studies. Measurement of the MCI in its modern version, digital X-ray radiogrammetry (DXR), requires only a plain analog radiograph, a PC, a film scanner, and reliable software. MCI can be used diagnostically and longitudinally for monitoring changes. MCI measured with DXR has few problems regarding accuracy and precision errors, and MCI is presently regaining lost territories among tests for quantification of bone mass and bone strength. It can be measured inexpensively and swiftly. MCI and other geometrical variables of bone can be measured on old radiographs, thus enabling estimation of cortical bone loss from the time of earlier recordings.

Geometric properties of distal radius and pathogenesis of Colles fracture: a peripheral quantitative computed tomography study

It is well known among clinicians that Colles fracture patients may have normal projected axial bone mineral density and that bone mass is not synonymous with bone strength. The aim of this work was to investigate whether cross-sectional properties of the distal radius in female patients with recent Colles fracture differ from those of a younger group of normal women without fracture. It was hypothesized that patients with Colles fracture had petite distal radii and that cortical thinning and reduced cortical and trabecular volumetric density are dominant features of this fracture type. We used a multilayer high-precision peripheral quantitative computed tomography (pQCT) device with a long-term precision error of 0.1% for a dedicated phantom during the measurement period (152 d). Clinical measurements were made at an ultradistal site rich in trabecular bone and a less ultradistal site rich in cortical bone. The results show that the following pQCT variables were significantly reduced in the nonfractured radius of the Colles fracture cases: mean ultradistal trabecular volumetric density, mean ultradistal and distal cortical volumetric density, mean ultradistal and distal cortical thickness (p < 0.001 for all differences). The outer cortical diameter, cross-sectional bone area, and cortical bending moment of inertia were not statistically different in the two groups. Thus, it would appear that Colles fracture cases did not have petite distal radii. The results suggest that the deforming force of Colles fracture has a transaxial direction (fall on outstretched arm), resulting in a crush fracture, and that it is not a bending force. We suggest that Colles fracture occurs as a result of the combined effect of a fall on the out-stretched arm, low trabecular and cortical volumetric bone density, and reduced cortical thickness.

Metacarpal index by digital X-ray radiogrammetry: normative reference values and comparison with dual X-ray absorptiometry

Metacarpal index (MCI), the combined cortical midmetacarpal thickness divided by the outer mid-metacarpal diameter, fell into oblivion when dual photon absorptiometry was introduced a quarter of a century ago. Modern PC-based digital X-ray diameter measurements offers a unique opportunity for precise and accurate measurements of MCI (DXR-MCI). We hypothesized that DXR-MCI in contrast to projected areal bone mineral density (BMD) (DXA-BMD) is independent of bone size and studied 384 normal women by measuring DXR-MCI and DXA-BMD of the lumbar spine, hip, and distal radius. A normative MCI database for women is presented. It has its maximum in the third decade, and a moderate biologic variation that seems to decline with age. It was found that DXR-MCI was independent of body weight and body surface area, whereas all DXA-BMD values were significantly dependent on them. Body height was significantly correlated with DXA-BMD at all sites, but less so with DXR-MCI. The latter was correlated with metacarpal bone length. It is suggested that the moderate correlation between MCI and body height would be abolished if the region of interest used for calculation of MCI be adjusted according to individual metacarpal bone length. DXR-MCI correlated significantly with DXA-BMD at the sites measured, and particularly well with that of the distal radius (r = 0.67; p < 0.0001).