Comparison of observed skeleton retention of strontium in average indian adult with the value predicted by the ICRP biokinetic model

The daily dietary intake of strontium and its content in skeleton, for an Indian adult population group were estimated by experimentally measuring its concentration in total cooked diet and autopsy skeleton samples using radiochemical neutron activation analysis. The data on daily dietary intake of strontium were used to compute its contents in skeleton using ICRP Publication 67 biokinetic model for strontium. The theoretically computed value of strontium (213.8 mg) compared favourably with the measured values (GM 181.2 mg) in an urban population group living in Mumbai representing an average Indian adult (Reference Indian Man).     

Radiation dose estimates in Indian adults in normal and pathological conditions due to 99Tcm-labelled radiopharmaceuticals

ICRP Publications 53, 62 and 80 give organ dose coefficients and effective doses to ICRP Reference Man and Child from established nuclear medicine procedures. However, an average Indian adult differs significantly from the ICRP Reference Man as regards anatomical, physiological and metabolic characteristics, and is also considered to have different tissue weighting factors (called here risk factors). The masses of total body and most organs are significantly lower for the Indian adult than for his ICRP counterpart (e.g. body mass 52 and 70 kg respectively). Similarly, the risk factors are lower by 20-30% for 8 out of the 13 organs and 30-60% higher for 3 organs. In the present study, available anatomical data of Indians and their risk factors have been utilised to estimate the radiation doses from administration of commonly used 99Tcm-labelled radiopharmaceuticals under normal and certain pathological conditions. The following pathological conditions have been considered for phosphates/phosphonates--high bone uptake and severely impaired kidney function; IDA--parenchymal liver disease, occlusion of cystic duct, and occlusion of bile duct; DTPA--abnormal renal function; large colloids--early to intermediate diffuse parenchymal liver disease, intermediate to advanced parenchymal liver disease; small colloids--early to intermediate parenchymal liver disease, intermediate to advanced parenchymal liver disease; and MAG3--abnormal renal function, acute unilateral renal blockage. The estimated 'effective doses' to Indian adults are 14-21% greater than the ICRP value from administration of the same activity of radiopharmaceutical under normal physiological conditions based on anatomical considerations alone, because of the smaller organ masses for the Indian; for some pathological conditions the effective doses are 11-22% more. When tissue risk factors are considered in addition to anatomical considerations, the estimated effective doses are still found to be generally somewhat higher for the Indian, for both normal and pathological states (but lower than the values based on anatomical considerations alone). However, when the radiopharmaceutical is administered in quantities proportional to the body mass, the effective doses are 11-28% lower for the Indian under both normal and pathological conditions. It may be concluded that Indians are at a lower risk of radiation health detriment in comparison with the ICRP adult on administration of the various 99Tcm-labelled radiopharmaceuticals considered in this study.     

Monte Carlo calculations for efficiency calibration of a whole-body monitor using BOMAB phantoms of different sizes

Internal contamination due to high-energy photon (HEP) emitters is assessed using a scanning bed whole-body monitor housed in a steel room at the Bhabha Atomic Research Centre (BARC). The monitor consists of a (203 mm diameter × 102 mm thickness) NaI(Tl) detector and is calibrated using a Reference BOMAB phantom representative of an average Indian radiation worker. However, a series of different size physical phantoms are required to account for size variability in workers, which is both expensive and time consuming. Therefore, a theoretical approach based on Monte Carlo techniques has been employed to calibrate the system in scanning geometry with BOMAB phantoms of different sizes characterised by their weight (W) and height (H) for several radionuclides of interest ((131)I, (137)Cs, (60)Co and (40)K). A computer program developed for this purpose generates the detector response and the detection efficiencies (DEs) for the BARC Reference phantom (63 kg/168 cm), ICRP Reference male phantom (70 kg/170 cm) and several of its scaled versions. The results obtained for different size phantoms indicated a decreasing trend of DEs with the increase in W/H values of the phantoms. The computed DEs for uniform distribution of (137)Cs in BOMAB phantom varied from 3.52 × 10(-3) to 2.88 × 10(-3) counts per photon as the W/H values increased from 0.26 to 0.50. The theoretical results obtained for the BARC Reference phantom have been verified with experimental measurements. The Monte Carlo results from this study will be useful for in vivo assessment of HEP emitters in radiation workers of different physiques.     

Development of the Japanese reference man model for age-specific phantoms

Recent interest in improving methods for calculating radiation doses to atomic bomb survivors necessitates reinforcing the data on masses of organs of the Japanese population in 1945, including those that are not calculated by DS02, as well as increasing the number of phantoms for different ages. Reference is made to published data on the masses of organs in normal Japanese subjects of 0-90 y of age with more than 5000 samples during 1970-80, as well as the weight and size of the total body. The first Japanese Reference Man model, primarily based on these data and following the ICRP Reference Man concept, is briefly explained. It provides a set of reference values for males and females of six age groups, i.e. 3 months, 1, 5, 10, 15 and 20-50 y. To consider the organ masses of the Japanese population in 1945, the data during the period 1970-80 are compared with the literature data of normal Japanese reported in 1952. Differences between the two sets of organ data in adults are discussed in relation to changes in the national status of nutrition. Additional organ masses of current interest for the Japanese population in 1945 are preliminarily considered.     

Reference values for basic human anatomical and physiological characteristics for use in radiation protection

A new publication prepared by the ICRP Task Group on Reference Man, Basic anatomical and physiological data for use in radiological protection: reference values, is focused on those human characteristics that are important for dosimetric calculations. Moving from the past emphasis on a Reference Man, the new report presents a series of reference values for both male and female subjects of six different ages--newborn, 1, 5, 10, 15 y, and adult. In selecting reference values, the task group has used data on Western Europeans and North Americans because these populations have been well studied with respect to anatomy, body composition and physiology. When appropriate, comparisons are made between the chosen reference values and data from several Asian populations. The reference values for height and body mass are higher than those reported for various Asian populations. However, the reported masses of individual organs and tissues, particularly for China and Japan, are similar to the reference values.     

The long-term decrease of 90Sr availability in the environment and its transfer to man after a nuclear fallout

Due to its long physical half-life, and the fact that its long-term mobility in the environment as well as its radiotoxicity is higher than that of 137Cs, the long-term bio-availability of 90Sr in the environment is of importance with regard to the long-term population exposure after fallout from nuclear weapons detonations or a severe reactor accident. It will also substantially influence the time-span required until re-utilisation of highly contaminated territory is possible again. An assessment of the long-term decrease of the activity concentration in all foodstuffs relevant for internal exposure after severe 90Sr fallout was performed. The observed effective half-lives were approximately 1.8-2.1 years in the first 2-3 years after the end of fallout and 8-10 years in the following three decades. This is equivalent to a biological half-life of about 13.2 years and results in a total 50 year dose of 6.2 times the first year exposure. Due to this decline in 90Sr-availability, the average annual activity intake of 90Sr in Austria has decreased from 840 Bq at the climax of the nuclear weapons tests to about 42 Bq in 1997 for adults, and from 500 Bq to about 35 Bq for 1 year old infants. This is equivalent to a 90Sr ingestion dose of 1.2 microSv for adults and 2.5 microSv for 1 year old infants in 1997 or less than 0.4% of the ingestion dose by natural radionuclides in the diet.     

Natural and artificial radioactivity measurements in Eastern Black Sea region of Turkey

In the present work, naturally occurring radionuclides of ²²⁶Ra, ²³²Th and ⁴⁰K were measured in soil samples collected from the Eastern Black Sea region of Turkey. It was found that the activity concentrations ranged from 12 to 120 Bq kg⁻¹ for ²²⁶Ra, from 13 to 121 Bq kg⁻¹ for ²³²Th and from 204 to 1295 Bq kg⁻¹ for ⁴⁰K. Besides naturally occurring radionuclides, ¹³⁷Cs activity concentration was measured in soil, lichen and moss samples and it was found that ¹³⁷Cs activity concentration ranged from 27 to 775 Bq kg⁻¹ with for soil, from 29 to 879 Bq kg⁻¹ for lichen and from 67 to 1396 Bq kg⁻¹ for moss samples. Annual effective doses due to the naturally occurring radionuclides and ¹³⁷Cs were estimated. Ecological half-lives of ¹³⁷Cs in lichen and moss species were estimated. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1993 indicated ecological half-lives between 1.36 and 2.96 years for lichen and between 1.35 and 2.85 years for moss species.     

Using total beta-activity measurements in milk to derive thyroid doses from Chernobyl fallout

Following the Chernobyl accident, more than 200 childhood thyroid cancer cases have been observed in Brest Oblast of Belarus in territories slightly contaminated with 137Cs, but with suspected relatively high 131I fallout. The most helpful measurements available that can be used to estimate thyroid doses for the population of Brest Oblast are the total beta-activity measurements in cow's milk performed using DP-100 device within a few weeks after the accident. The 131I concentrations in milk were derived from the total beta-activity measurements on the basis of (1) a radioecological model used to estimate the variation with time of the radionuclide composition in milk and (2) the determination of the calibration factors of the DP-100 device for the most important radionuclides present in milk. As a result, 131I concentrations in milk were reconstructed for territories with different levels of 137Cs deposition. A non-linear dependence of the 131I concentration in milk on the 137Cs deposition density was obtained; it was used to estimate the thyroid doses from the consumption of 131I-contaminated cow's milk by the population of Brest Oblast. The average individual thyroid doses have been estimated to be 0.15, 0.18, 0.12, 0.06, 0.04 and 0.03 Gy for newborn, children aged 1, 5, 10 and 15 y and adults, respectively. The collective thyroid dose for the entire population of Brest Oblast is estimated to be 64,500 man Gy, the contribution from the adult population being about one half of the total. The methodology that is described could be applied in the framework of epidemiological studies of the relationship between radiation exposure to the thyroid gland and thyroid cancer in areas where numerous total beta-activity measurements in cow's milk were performed within a few weeks after the accident.     

Biological half-life of iodine in adults with intact thyroid function and in athyreotic persons

A joint project between the Human Monitoring Laboratory (HML) and the Ottawa Hospital has measured the retention of 131I in patients who have received the radioiodine diagnostically. Thirty-nine subjects with intact thyroid glands and nine athyreotic subjects were measured in the HML's whole-body/thyroid counter to determine the retention of 131I following its medical administration. The average biological half-life of 131I in 26 euthyroid subjects was found to be 66.1+/-6.3 days which may he statistically significantly lower than the ICRP recommended value of 80 days. Nine hyperthyroid patients had a mean biological half-life of 38.2+/-8.6 days and in three hypothyroid patients the corresponding value was 29.3+/-8.8 days. Thyroid 131I uptake was measured in a conventional clinical fashion at the Ottawa Hospital Civic campus 24 h after oral administration of the radioiodine using a collimated thick sodium iodide detector placed over the neck anteriorly. Measured values were 10.144+/-0.009, 0.314+/-0.035 and 0.045+/-0.010 of the administered dose in euthyroid, hyperthyroid and hypothyroid patients respectively. The euthyroid range at the hospital is 0.06 - 0.22. Uptake was significantly lower for the euthyroid group than the ICRP value of 0.3. The radioiodine retention in athyreotic subjects followed a two compartment model with biological half-lives of 1.0+/-1.2 days and 18.4+/-1.1 days.     

Analysis of trace elements in some medicinal plants by NAA and AAS techniques

The content of elements in 12 Indian medicinal plants was analyzed by instrumental neutron activation analysis (INAA) and atomic absorption spectroscopy (AAS) techniques. Specific parts of different medicinal plants like bulb, tuber, flower, gum, and rhizomes, which are often used in Indian Ayurvedic system, were used for the study. The element concentrations in different part of medicinal plants and their biological effects on humans are discussed.     

Assessments of thiyl radicals in biosystems: difficulties and new applications

The high reactivity of thiyl radicals (RS(?)), which results in half-lives on the order of microseconds, hinders their analysis in biological systems. This Feature reviews the contemporary approaches to assessment of RS(?) using EPR spin trapping, mass spectrometric, immunological, and HPLC protocols.     

Estimating individual thyroid doses for a case-control study of childhood thyroid cancer in Bryansk Oblast, Russia

Following the Chernobyl accident, radioactive fission products, including (131)I and (137)Cs, were deposited in Bryansk Oblast in Russia. Intakes of radioiodines, mainly (131)I in milk, were the principal sources of radiation doses to thyroids of residents of the contaminated areas, but those radionuclides decayed before detailed contamination surveys could be performed. As a result, (137)Cs deposition density is the primary measure of the contamination due to the accident and there are relatively few measurements of the ratio of (131)I to (137)Cs in vegetation or soil samples from this area. Although many measurements of radiation emitted from the necks of residents were performed and used to estimate thyroidal (131)I activities and thyroid doses, such data are not available for all subjects. The semi-empirical model was selected to provide a dose calculation method to be applied uniformly to cases and controls in the study. The model was developed using dose estimates from direct measurements of (131)I in adult thyroids, and relates settlement average thyroid doses to (137)Cs contamination levels and ratios of (131)I to (137)Cs. This model is useful for areas where thyroid monitoring was not performed and can be used to estimate doses to exposed individuals. For application to children in this study, adjustment factors are used to address differences in age-dependent intake rates and thyroid dosimetry. Other individual dietary factors and sources (private/public) of milk consumed are reflected in the dose estimates. Countermeasures that reduced thyroid dose, such as cessation of milk consumption and intake of stable iodine, are also considered for each subject. The necessary personal information of subjects was obtained by interview, most frequently of their mothers, using a questionnaire developed for the study. Uncertainties in thyroid dose, estimated using Monte Carlo techniques, are presented for reference conditions. Thyroid dose estimates for individual children made using the semi-empirical model and questionnaire data compare reasonably well with dose estimates made for 19 children whose thyroid burdens of (131)I were measured from May to June 1986.     

Determination of Trace Level Iodine in Biological and Botanical Reference Materials by Isotope Dilution Mass Spectrometry

A method has been developed for the determination of trace level iodine in biological and botanical materials. The method consists of spiking a sample with ¹²⁹I, equilibration of the spike with the natural iodine, wet ashing under carefully controlled conditions, and separation of the iodine by co-precipitation with silver chloride. Measurement of the ¹²⁹I/¹²⁷I ratio is accomplished by negative thermal ionization mass spectrometry using LaB₆ for ionization enhancement. The application of the method to the certification of trace iodine in two Standard Reference Materials is described.     

Chelating scintillation fibers for measurements of 137Cs

Solid scintillating fibers, coated with a dual-mechanism bifunctional polymer shown to bind Cs(I) in alkaline solutions, were developed for measurement of 137Cs. The effect of the epoxy-polymer coating thickness on attenuation of the signal from 137Cs was evaluated. After optimal coating conditions were determined, both scintillation fiber and resin functions were retained, producing stable field-ready fibers. Temporal studies were performed to examine the kinetics of 137Cs uptake into the resin. Calibration curves of the fiber response were generated by beta-emission from solutions of 137Cs dissolved in 1 M sodium hydroxide. The plots exhibited a linear response over a range of 4-3200 nCi/mL (3.4 x 10(-10)-2.7 x 10(-7) M 137Cs), with a limit of detection of 3.65 nCi/mL (approximately 42 parts per trillion 137Cs). The distribution coefficient of Cs was determined to be 490 +/- 50 mL/g from these measurements. Selectivity studies of the resin were performed in the presence of 100 fold excess of Sr(II), Al(III), and nonradioactive Cs(I). Linear calibration plots were obtained in the presence of these potential interferences, but at a reduced sensitivity. The fibers were also used to evaluate the 137Cs content of a mock tank waste sample to show the potential of the fibers in complicated matrixes.     

Recycling of Transmutation Targets in the Presence of Impurity Isotopes of Starting Nuclides

Relations were obtained for calculating the concentrations of impurity isotopes of starting nuclides ⁹⁸Tc, ¹²⁷I, ^133'134'137Cs in recycling ⁹⁹Tc, ¹²⁹I, ¹³⁵Cs targets, respectively. Conditions of removing ⁹⁸Tc from the transmutation cycle in a single irradiation run were found. The content of ¹²⁷I in the targetattains an equilibrium value, thus making unnecessary isotopic separation of iodine. For isotopic separation of cesium, a decrease of the initial content of ¹³⁷Cs in the ¹³⁵Cs target to 1% is sufficient. The ¹³³Cs and ¹³⁴Cs nuclides preserve steady-state concentrations for a long period, and for this reason the activity grows insignificantly, depending on the ¹³⁷Cs accumulation, which makes unnecessary isotopic separation of cesium from irradiated targets.     

Monte Carlo comparison of the St Petersburg phantom with a BOMAB phantom in the HML's whole-body counter

Three sizes of the St Petersburg phantom have been compared to six sizes of BOMAB phantoms measured by a virtual whole-body counter similar to the one in use in the Human Monitoring Laboratory using Monte Carlo simulations. The previously published data comparing the St Petersburg Reference Man sized phantom with a similar sized Bottle Manikin Absorber Phantoms (BOMAB) phantom at 662 keV is supported; however, the simulations also show that the smaller sized St Petersburg phantoms do not agree well with smaller BOMAB phantoms. It is concluded that the St Petersburg phantoms are system dependent meaning that all sizes of the St Petersburg phantoms should be experimentally compared over a wide photon energy range against corresponding BOMAB phantoms to validate their use for calibrating whole-body counters.     

Eliminating bias in routine bioassay when there is an unknown time of intake

Routine bioassay programmes sometimes find evidence of an unsuspected intake. If there were no workplace indicators of exposure or intake, it is necessary to assume a value for the time of intake. Under these circumstances, the International Commission on Radiological Protection (ICRP) continues to recommend using the midpoint of the interval between routine bioassay measurements (ICRP Publication 78, paragraph 106). The assumption of T/2 as the time of intake, where T is the interval between bioassay measurements, represents the expectation value of the time of intake, (t), assuming uniform probability of an intake at any given time. This assumption results in a modest bias, of the expectation value of the intake, (I), that would have been received by a population of workers who had uniform probability over time of intake. This underestimation leads to a negative or positive bias in dose estimates derived in this fashion. The bias is characterised for realistic, routine urinalysis programs for Pu, U and 3H, as well as for in vivo measurements of 125I, 131I and 137Cs. Simple numerical methods are presented for correcting the bias. The bias is greatest for radionuclides whose half-lives are short with respect to the interval between bioassay measurements. Since the primary concern is estimating intake rather than time, the assumed time of intake should be chosen as t(I) rather than T/2. The ICRP should consider revising some of the tables in its Publication 78 to reflect this.     

Environmental radioactivity measurements in Greece following the Fukushima Daichi nuclear accident

Since the double disaster of the 9.0 magnitude earthquake and tsunami that affected hundreds of thousands of people and seriously damaged the Fukushima Daichi power plant in Japan on 11 March 2011, traces of radioactive emissions from Fukushima have spread across the entire northern hemisphere. The radioactive isotope of iodine (131)I that was generated by the nuclear accident in Fukushima arrived in Greece on 24 March 2011. Radioactive iodine is present in the air either as gas or bound to particles (aerosols). The maximum (131)I concentrations were measured between 3 and 5 April 2011. In aerosols the maximum (131)I values measured in Southern Greece (Athens) and Northern Greece (Thessaloniki) were 585±70 and 408±61 μΒq m(-3), respectively. (131)I concentrations in gas were about 3.5 times higher than in aerosols. Since 29 April 2011, the (131)I concentration has been below detection limits. Traces of (137)Cs and (134)Cs were also measured in the air filters with an activity ratio of (137)Cs/(134)Cs equal to 1 and (131)I/(137)Cs activity ratio of about 3. Since 16 May 2011, the (137)Cs concentration in air has been determined to be about the same as before the Fukushima accident. Traces of (131)I were also measured in grass and milk. The maximum measured activity of (131)I in sheep milk was about 2 Bq l(-1) which is 5000 times less than that measured in Greece immediately after the Chernobyl accident. The measured activity concentrations of artificial radionuclides in Greece due to the Fukushima release, have been very low, with no impact on human health.     

The microdosimetry of low-energy photons in radiotherapy

Low energy photons are more and more in use in clinical practice, for treatment in radiotherapy as well as for imaging purposes. Their relative biological effectiveness is however still debated. In this paper, some microdosimetric parameters have been calculated for different sources: (125)I, (103)Pd, (131)Cs, an electronic brachytherapy source and various clinical mammography X-ray qualities. These parameters have been used to deduce the quality factors as defined in ICRU 40.     

Investigation of Cs(I) and Sr(II) removal using nanoporous bentonite

ABSTRACT

Bentonites are types of clays made up the dominant constituent of montmorillonite. Four types of nano-porous and nano-structured commercial bentonite clays were studied in detail for their physicochemical and mineralogical properties vs. Cs and Sr adsorption. The instrumental analyses to study samples were X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) surface area measurements, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetry (TG). The XRF and peaks of XRD patterns at 2θ?=?8, 19.9, 35, 55, and 62 clearly indicated that the main component of the bentonite samples was montmorillonite. The BET analysis showed that B1 has the highest specific surface area among the other samples which its single and multiple point BET surface area were equal to 84.85 and 85.94?m²?g^?1, respectively. These values represents the amount of montmorillonite and adsorption capacity of samples. The physicochemical, structural and morphological characteristics of different samples were investigated through instrumental analysis. The results of separation processes of Cs(I) and Sr(II) showed 59.75 and 45.5% adsorption capacities for B3 and B2 which were the highest values among the others. The results lead to the conclusion that samples B3 had a good adsorption capacity to remove Cs(I) and Sr(II).