Bioassay Measurements Research Articles

Modeling Plutonium Decorporation in a Female Nuclear Worker Treated with Ca-DTPA after Inhalation Intake.

The present work models plutonium (Pu) biokinetics in a female former nuclear worker. Her bioassay measurements are available at the US Transuranium and Uranium Registries. The worker was internally exposed to a plutonium-americium mixture via acute inhalation at a nuclear weapons facility. She was medically treated with injections of 1 g Ca-DTPA on days 0, 5, and 14 after the intake. Between days 0 and 20, fecal and urine samples were collected and analyzed for 239Pu and 241Am. Subsequently, she was followed up for bioassay monitoring over 14 y, with additional post-treatment urine samples collected and analyzed for 239Pu. The uniqueness of this dataset is due to the availability of: (1) both early and long-term bioassay data from a female with plutonium intake; (2) data on chelation therapy for a female; and (3) fecal measurement results. Chelation therapy with Ca- and/or Zn-salts of DTPA is known to aid in reducing the internal radiation dose by enhancing the excretion of plutonium and americium from the body. Such enhancement affects plutonium biokinetics in the human body, posing a challenge to the internal dose assessment. The current radiation dose assessment practice is to exclude the data affected by Ca-DTPA from the analysis. The present analysis is the first to explicitly model the chelation-affected bioassay data in a female by using a newly developed chelation model. Thus, the bioassay data collected during and after the Ca-DTPA administrations were used for biokinetic modeling and dose assessment. The Markov Chain Monte Carlo method was used to investigate model parameter uncertainty, based on the bioassay data and assumed prior probability distributions. A χ2/nData (number of data points) ≈ 1 was observed in this study, which indicates self-consistency of the data with the model. Results of this study show that the worker's 239Pu intake was 12 Bq, with a committed effective dose to the whole-body of 1.2 mSv and a committed equivalent dose to the bone surfaces, liver, and lungs of 37.8, 9.1, and 0.8 mSv, respectively. This study also discusses the worker's dose reduction due to chelation treatment.

A high-affinity, cis-on photoswitchable beta blocker to optically control β2-adrenergic receptors in vitro and in vivo

This study introduces (S)-Opto-prop-2, a second-generation photoswitchable ligand designed for precise modulation of β2-adrenoceptor (β2AR). Synthesised by incorporating an azobenzene moiety with propranolol, (S)-Opto-prop-2 exhibited a high PSScis (photostationary state for cis isomer) percentage (∼90 %) and a favourable half-life (>10 days), facilitating diverse bioassay measurements. In vitro, the cis-isomer displayed substantially higher β2AR binding affinity than the trans-isomer (1000-fold), making (S)-Opto-prop-2 one of the best photoswitchable GPCR (G protein-coupled receptor) ligands reported so far. Molecular docking of (S)-Opto-prop-2 in the X-ray structure of propranolol-bound β2AR followed by site-directed mutagenesis studies, identified D1133.32, N3127.39 and F2896.51 as crucial residues that contribute to ligand-receptor interactions at the molecular level. In vivo efficacy was assessed using a rabbit ocular hypertension model, revealing that the cis isomer mimicked propranolol’s effects in reducing intraocular pressure, while the trans isomer was inactive. Dynamic optical modulation of β2AR by (S)-Opto-prop-2 was demonstrated in two different cAMP bioassays and using live-cell confocal imaging, indicating reversible and dynamic control of β2AR activity using the new photopharmacology tool.In conclusion, (S)-Opto-prop-2 emerges as a promising photoswitchable ligand for precise and reversible β2AR modulation with light. The new tool shows superior cis-on binding affinity, one of the largest reported differences in affinity (1000-fold) between its two configurations, in vivo efficacy, and dynamic modulation. This study contributes valuable insights into the evolving field of photopharmacology, offering a potential avenue for targeted therapy in β2AR-associated pathologies.

New penta-Coordinated Cadmium(II) Complexes: Synthesis, Characterization, Thermal, Antimicrobial, Antioxidant and Cytotoxicity Properties.

In this paper, a new tridentate Schiff base ligand (L) with nitrogen donor atoms and its cadmium(II) complexes with the general formula of CdLX2 (X=Cl-, Br-, I-, SCN-, N3 -, NO3 -) have been synthesized and characterized by physical and spectral (FT/IR, UV-Vis, Mass, and 1H, 13C NMR spectroscopies) methods. Also nano-structured cadmium chloride and bromide complexes were synthesized by sonochemical method and then used to prepare nanostructured cadmium oxide confirmed by XRD and SEM techniques. Thermal behavior of the compounds was studied in the temperature range of 25 to 900 °C under N2 atmosphere at a heating rate of 20 °C/ min. Moreover, thermo-kinetic activation parameters of thermal decomposition steps were calculated according to the Coats-Redfern relationship. Antimicrobial activities of the synthesized compounds against two gram-positive and two gram-negative bacteria such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and two fungi of Candida albicans and Aspergillus niger were investigated by well diffusion method. SEM technique was used to monitor the morphological changes of the bacteria treated with the compounds. The 2,2-Diphenyl-1-picrylhydrazyl(DPPH) and the ferric reducing antioxidant power (FRAP) methods were used to evaluate the antioxidant ability of the ligand and its cadmium(II) complexes. In final, the cytotoxicity properties of the ligand and some cadmium(II) complexes against PC3 cancer cells were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) bioassay and nitric oxide (NO) level measurement. The morphological changes of prostate cancer (PC3) cells due to treatment with the ligand and its complexes confirmed their anticancer effectiveness.

Biodegradable and Biocompatible Thermoplastic Poly(Ester-Urethane)s Based on Poly(ε-Caprolactone) and Novel 1,3-Propanediol Bis(4-Isocyanatobenzoate) Diisocyanate: Synthesis and Characterization.

A series of non-toxic biodegradable and biocompatible polyurethanes bearing p-aminobenzoate moieties are presented. The introduction of this attractive motif was carried out by the synthesis of a novel isocyanate. These biodegradable polymers were chemically and physically characterized by several techniques and methods including bioassay and water uptake measurements. The molecular weight of the soft segment (poly-ε-caprolactone, PCL) and hard segment crystallinity dictated the mechanical behavior and water uptake. The behavior of short PCL-based polyurethanes was elastomeric, whilst increasing the molecular weight of the soft segment led to plastic polyurethanes. Water uptake was hindered for long PCL due to the crystallization of the soft segment within the polyurethane matrix. Furthermore, two different types of chain extender, hydrolyzable and non-hydrolyzable, were also evaluated: polyurethanes based on hydrolyzable chain extenders reached higher molecular weights, thus leading to a better performance than their unhydrolyzable counterparts. The good cell adhesion and cytotoxicity results demonstrated the cell viability of human osteoblasts on the surfaces of these non-toxic biodegradable polyurethanes.

Differences in Medium-Induced Conformational Plasticity Presumably Underlie Different Cytotoxic Activity of Ricin and Viscumin.

Structurally similar catalytic subunits A of ricin (RTA) and viscumin (MLA) exhibit cytotoxic activity through ribosome inactivation. Ricin is more cytotoxic than viscumin, although the molecular mechanisms behind this difference are still poorly understood. To shed more light on this problem, we used a combined biochemical/molecular modeling approach to assess possible relationships between the activity of toxins and their structural/dynamic properties. Based on bioassay measurements, it was suggested that the differences in activity are associated with the ability of RTA and MLA to undergo structural/hydrophobic rearrangements during trafficking through the endoplasmic reticulum (ER) membrane. Molecular dynamics simulations and surface hydrophobicity mapping of both proteins in different media showed that RTA rearranges its structure in a membrane-like environment much more efficiently than MLA. Their refolded states also drastically differ in terms of hydrophobic organization. We assume that the higher conformational plasticity of RTA is favorable for the ER-mediated translocation pathway, which leads to a higher rate of toxin penetration into the cytoplasm.

131I Intake and Regulatory Compliance Following Administration of Capsular 131I Sodium Iodide for Treatment of Thyroid Disorders.

Intake of 131I by nuclear medicine technologists and physician Authorized Users was evaluated using bioassay data from administration of 131I sodium iodide in capsular form during a 5-year period. Maximum estimated annual intake of 131I sodium iodide, based on bioassay measurements performed at 24 hours post administration, ranged from 10.9 to 35.6 kBq for all staff. Intake by Authorized Users was higher than that by nuclear medicine technologists due to state requirement for Authorized Users to physically administer therapeutic dosages of radiopharmaceuticals. All intake values were less than 10% of the 131I thyroid ALI of 50 microcurie3 (1,850 kBq), indicating that monitoring may be discontinued for staff participating in routine administration of 131I capsules in which volatilization is not suspected. Elimination of bioassay performance has permitted more flexibility in patient scheduling and improved workflow and efficiency.

URINARY EXCRETION OF PLUTONIUM IN MAYAK WORKERS DURING AND AFTER CA-DTPA ADMINISTRATION.

Chelation therapy is sometimes used after potential exposures to plutonium to increase urinary excretion of the radionuclide to improve the accuracy of bioassay measurements. The purpose of this report is to describe the enhancement of urinary excretion of plutonium during and after the administration of the trisodium salt of calcium diethylenetriaminepentaacetate (Ca-DTPA) daily for 3d to a group of male and female plutonium workers from the Mayak Production Association in Ozyorsk, Russia. One-hundred and two cases (18 females and 84 males) were selected where urinary contents of plutonium, prior to chelation, exceeded the detection threshold. Daily urine collections were obtained during the 3d of Ca-DTPA treatments. In addition, 58 of these cases had urine bioassays at 1-45d after chelation. The daily enhancement over baseline values excretion of plutonium was found to be 50.4×/1.4 (geometric mean and geometric standard deviation); 58.9×/1.2; 72.9×/1.4 in the first, second and third days of Ca-DTPA administration. The mean enhancement for the 3-d period was 60.1×/1.7. The rate of plutonium excretion from 1 to 45d after chelation decreased with a half-period of 3.9d and the chelation enhancement factor (Кenh-i) is described by the function Кenh-i=(0.79±0.24)+(42.9±1.2)×e-(0.18±0.01)×day.

Effects of temperature shocks on the formation and characteristics of soluble microbial products in an aerobic activated sludge system

The present study investigated the impacts of temperature shocks on the generation of soluble microbial products (SMPs) in an aerobic activated sludge system, focusing on biopolymers and low molecular weight (LMW) substances that significantly impact the effluent quality. The results indicated that raising the temperature increased SMP production. At 25 and 35 °C, all size fractions of SMPs increased linearly with the aeration time, and biopolymers comprised a large proportion of SMPs. At 5 and 15 °C, in contrast, only biopolymers increased linearly with the aeration time, and LMW substances were the predominant fraction of SMPs. The reduced bio-utilization of SMPs with an increase in temperature was associated with the decreased relative abundance of LMW substances, which is supported by the assimilable organic carbon bioassay measurements. The mass of the biopolymers for the SMPs and extracellular polymeric substances (EPS) was balanced at all temperatures, wherein a negative correlation was observed, indicating that increased SMPs in the water phase led to a decrease in EPS. The results of the reactive oxygen species (ROS) and toxicity assays confirmed that the immune defense reaction of the bacteria (induced by ROS) was the key factor for variations in LMW substances in the SMPs and EPS under temperature stresses.

Plutonium in Manhattan Project workers: Using autopsy data to evaluate organ content and dose estimates based on urine bioassay with implications for radiation epidemiology.

PurposeRadiation dose estimates in epidemiology typically rely on intake predictions based on urine bioassay measurements. The purpose of this article is to compare the conventional dosimetric estimates for radiation epidemiology with the estimates based on additional post-mortem tissue radiochemical analysis results.MethodsThe comparison was performed on a unique group of 11 former Manhattan Project nuclear workers, who worked with plutonium in the 1940s, and voluntarily donated their bodies to the United States Transuranium and Uranium Registries.ResultsPost-mortem organ activities were predicted using different sets of urine data and compared to measured activities. Use of urinalysis data collected during the exposure periods overestimated the systemic (liver+skeleton) deposition of 239Pu by 155±134%, while the average bias from using post-exposure urinalyses was –4±50%. Committed effective doses estimated using early urine data differed from the best estimate by, on average, 196±193%; inclusion of follow-up urine measurements in analyses decreased the mean bias to 0.6±36.3%. Cumulative absorbed doses for the liver, red marrow, bone surface, and brain were calculated for the actual commitment period.ConclusionOn average, post-exposure urine bioassay results were in good agreement with post-mortem tissue analyses and were more reliable than results of urine bioassays collected during the exposure.

Maximum Possible Doses for a Cohort of Individuals with Intakes Possibly Containing a Component of a Ceramic-type Material.

Recently, a glovebox breach led to the potential exposure of 15 Los Alamos National Laboratory employees to 238Pu. Given what is known about the material involved in the incident, the possibility of an intake with a ceramic-type component must be considered. Incidents in which intakes of ceramic solubility-type material is suspected represent a challenge for internal dose assessment via urine bioassay because even relatively large doses cannot be detected in urine until many months after the intake. Ideally, in these situations fecal samples should be collected to assess the intake, but in this case fecal sampling was delayed. This paper presents a method to calculate the maximum possible doses for all individuals involved in an incident using only early time-decreasing urine bioassay measurements.

Inhalation of Soluble Plutonium: 53-year Follow-up of Manhattan Project Worker.

This whole-body tissue donor to the United States Transuranium and Uranium Registries was occupationally exposed to plutonium nitrate-dioxide mixture via chronic inhalation. This individual was involved in the Manhattan Project operations and later participated in medical follow-up studies. Soft tissues and bones collected at autopsy were analyzed for 238Pu, 239+240Pu, and 241Am. Fifty-three years post-intake, 700±2 Bq of 239+240Pu were still retained in the skeleton, 661±11 Bq in the liver, and 282±3 Bq in the respiratory tract. Bioassay measurements and organ activities at the time of death were used to estimate the intake and radiation doses using the TAURUS internal dosimetry software. For this individual, an ICRP Publication 130 Human Respiratory Tract Model with case-specific particle size of 0.3 μm, ICRP Publication 100 Human Alimentary Tract Model, and ICRP Publication 141 Plutonium Systemic Model adequately described long-term plutonium retention and excretion. The total cumulative 239+240Pu intake of 31,716 Bq was estimated, of which 24,853 Bq (78.4%) were contributed by inhalation of plutonium nitrate and 6,863 Bq (21.6%) of plutonium dioxide. The committed equivalent doses to the red bone marrow, bone surface, liver, lungs, and brain were 0.71 Sv, 6.5 Sv, 8.3 Sv, 3.8 Sv, and 0.068 Sv, respectively. The committed effective dose was 1.22 Sv.

Comparison of the Chemiluminescence Immunoassay LIAISON® with the Radioimmunoassay for Aldosterone and Renin Measurement.

Determination of renin plasma levels is useful in the diagnosis of hypertension and in the therapeutic follow-up of hypertensive patients. Plasmatic concentration of renin decreases in patients with hypertension due to a primary hyperaldosteronism, contrary to renovascular hypertension where concentrations of renin and aldosterone are both elevated. Blood samples (serum, EDTA plasma) were analysed using two different chemiluminiscent methods CLIA LIAISON® and radioimmunoassay for aldosterone (IMMUNOTECH Beckman Coulter) and renin (Cisbio Bioassay) measurements were compared. We used both methods to ascertain the correlation between serum vs. EDTA plasma levels of aldosterone (RIA, CLIA) and renin (IRMA, CLIA) and to compare aldosterone to renin ratios for CLIA and for radioimmunoassay: serum aldosterone to plasma renin and plasma aldosterone to plasma renin. We compared serum aldosterone CLIA vs. RIA (rP=0.933, P<0.001) and plasma renin determined using CLIA vs. IRMA (rP=0.965, P=0.062). Furthermore, we used both methods to establish the correlation between the serum vs. plasma levels of aldosterone: RIA (rP=0.980, P<0.001); CLIA (rP=0.994, P=0.353) and serum vs. plasma levels of renin: IRMA (rP=0.948, P<0.001); CLIA (rP=0.921, P=0.011). Aldosterone (serum, plasma) to plasmatic renin ratios for CLIA (rP=0.999, P=0.286) and for radioimmunoassay (rP=0.992, P=0.025). Our data demonstrate that renin and aldosterone concentrations obtained using CLIA correlate with renin and aldosterone concentrations using radioimmunoassay methods. Correlation coefficients of pair results ranged from 0.921 to 0.994. Aldosterone (serum, EDTA plasma) to plasmatic renin ratios are comparable and any of them can be used with no significant differences found.

Experience and performance of In Vivo Monitoring Laboratory of NIRP in 2017 thyroid measurement intercomparison

Determination of the 131I activity in the thyroid of exposed people or workers is one of the major concerns that needs to be addressed following a nuclear or radiological emergency. International intercomparison exercises on bioassay measurements are one of the effective methods to improve the capability and quality of internal dose assessment. In 2017, Working Group 1 (Internal Dosimetry) of the Asian Radiation Dosimetry Group (ARADOS) organized an intercomparison exercise on the thyroid measurement, aiming at enhancing and coordinating the radiation dosimetry capabilities of Asian countries. This paper describes the measurement experience and results of In Vivo Monitoring Laboratory of NIRP in the 2017 intercomparison exercise, which can provide technical reference for laboratories that have not yet participated in such thyroid measurement intercomparsion. It covers technical aspects such as calibration, measurement and data processing. The results presented in this intercomparison are within an acceptable range of performance criteria on the bioassay measurements. In addition, further research work considered in the field of thyroid measurement is described in the discussion section.

INTERNAL DOSIMETRY TOOL FOR THE IMPLEMENTATION AND USE OF NEW ICRP/OIR MODELS: A CAESIUM STUDY.

In case of accidental intake of radioactive material, the dose assessment requires information on the radionuclide distribution in the body. Measurements of retention or excretion are compared with model's predictions to estimate the intake. The reference models for internal dosimetry purposes are those proposed by ICRP and have been recently updated in the 'Occupational Intakes of Radionuclides (OIR)' series. This work focusses on the implementation of the new caesium model in a computer package, ICRP130Models (integrated in the toolbox BIOKMOD), together with new features aimed at estimating the intake and the dose from bioassay measurements. The software gives the best fitted intake and the committed effective dose, as well as the chi-squared test and the p-value as an indication of the goodness of the fit in the assessment process. The possibility to build the model as a function of a parameter allows the user to look for different options when fitting the bioassay measurements.

Internal dosimetry of uranium workers exposed during the nuclear fuel fabrication process in Spain

Workers in the Juzbado plant of ENUSA in Spain are exposed to intakes of low enriched uranium during the fabrication of nuclear fuel elements for Nuclear Power Plants. CIEMAT started in 2014 an individual monitoring program for ENUSA workers consisting in routine bioassay measurements of uranium in urine by alpha spectrometry and a methodology of dose assessment based on ICRP Publications 78/68, ISO 27048 standard and IDEAS Guidelines V2. The individual monitoring program is complemented with workplace monitoring using Static Air Samplers (SAS) at the Juzbado facility. Results of routine monitoring data of 24 h-urine samples of Juzbado workforce confirmed low level of chronic intakes of uranium oxides in the plant, combined with acute intakes associated to incidents. IMBA software allows the dose assessments in complex intake regimes of occupational inhalation of Type S uranium compounds. Uncertainties of monitoring data were evaluated using the Scattering Factor approach (ISO 27048) for the intake calculation in the defined internal exposure scenario. A total of 200 workers at risk of internal exposures in the Juzbado facility were included in routine, special, confirmatory or task-related monitoring programs established by CIEMAT in agreement with ENUSA. Annual chronic intakes were assessed for 106 workers with monitoring results above the Minimum Detectable Activity (MDA = 0.50 mBq.sample−1 of 234U, 238U and 235U). Committed Effective Doses E(50) > 1 mSv/year were initially detected in 50% of these cases. Maximum annual intakes correspond to few cases of long term exposed workers with E(50) around 5 mSv/year. The preliminary study of the impact on the dose assessment using the new uranium model according to ICRP Publication 137 is presented here, showing a reduction of E(50) around a factor of 4 for workers exposed to uranium oxides re-defined as Type M/S materials (more soluble compounds, higher urinary excretion, lower dose coefficients than Type S uranium materials defined by ICRP Publications 78/68).

The first World Health Organization International Standard for in vitro biological activity of darbepoetin

The expiry of patents protecting the manufacture and sale of therapeutic darbepoetin products is expected to lead to the emergence of biosimilar products. In response to this, the first World Health Organization (WHO) International Standard (IS) for darbepoetin has been developed. A lyophilized preparation of darbepoetin, coded 17/204, was evaluated in an international collaborative study, the results of which suggest that the candidate preparation is suitable to serve as an IS. This material defines the International Unit (IU) of in vitro biological activity of darbepoetin and should be used to calibrate of in vitro potency assays of darbepoetin preparations. It is envisaged that widespread use of the IS will promote the consistency and harmonization of darbepoetin in vitro bioassay measurements in laboratories worldwide. Each ampoule contains 100,000 IU of darbepoetin activity. The IU is not intended to revise product labelling or dosing requirements, decisions regarding which lie solely with the regulatory authority. Additionally, the IS is not intended to define the specific activity of darbepoetin, as this may differ between products in the future. Finally, the IS is not intended to serve any regulatory role in defining biosimilarity (i.e. as a reference medicinal product).

Nuclear medicine: workplace monitoring and internal occupational exposure during a ventilation/perfusion single-photon emission tomography.

The administration of 99mTc-HDP to diagnose pulmonary thromboembolisms leads to the presence of 99mTc in the environment of a nuclear medicine department, which could pose a potential risk of internal contamination to medical staff. Therefore, air samples from the administration room, gamma camera room and corridor of such a department were taken for the purpose of performing a workplace monitoring program of the medical centre under study, with maximum activity values of 640 ± 30kBq/m3, 1.5 ± 0.1kBq/m3 and 54 ± 3kBq/m3, respectively, being obtained. These results correspond to committed effective doses received by exposed employees, via inhalation, when one ventilation/perfusion single-photon emission tomography study was performed, of 0.7μSv, 0.004μSv and 0.2μSv, respectively. As inhalation is the employees' main exposure pathway to radio-aerosols, the internal dose of the nuclear medicine department's medical staff was also evaluated via urine bioassay measurements. Nuclear medicine nurses showed the highest 99mTc activity in 24-h urine samples (2100 ± 130Bq/day), resulting in a committed effective dose of 21μSv for each diagnostic study performed. Even so, the performance of ventilation/perfusion diagnostic studies did not constitute a substantial radiological risk since the annual dose limit for exposed employees was not exceeded.

MPS dose reconstruction for internal emitters: some site-specific issues and approaches

Background As part of the Million Person Study (MPS), dose reconstructions for internal emitters have been performed for several U.S. facilities where large quantities of radionuclides were handled. The main challenges and dominant sources of potential error in retrospective dose estimates for internally exposed workers have been found to vary from site to site. This article discusses some important issues encountered in dose reconstructions performed for selected MPS sites and the approaches used to address those issues. The focus is on some foundational components of retrospective dose assessments that have received little attention in the literature. Methods The discussion is built around illustrative exposure data and dose reconstructions for workers at selected facilities addressed in the MPS. Related findings at some non-MPS sites are also discussed. Results Each of the following items has been found to be a major source of potential error in reconstructed tissue doses for some MPS sites: identification of all dosimetrically important internal emitters; the time pattern of intake; the mode(s) of intake; reliability of bioassay measurements; application of surrogate (coworker) information in lieu of, or in conjunction with, worker-specific monitoring data; the chemical and physical forms of inhaled radionuclides; and the relation of air monitoring data to actual intake. Conclusions (1) Much of the dose reconstruction effort for internal emitters should be devoted to development of best feasible exposure scenarios. (2) Coworker data should be used to assign exposure scenarios or dose estimates to workers with missing exposure data only if there is compelling evidence of similar coworker exposure. (3) Bioassay data for some radionuclides and periods of operation at MPS sites are of questionable reliability due to sizable uncertainties associated with contamination, recovery, or background issues. (4) Dose estimates derived solely from air monitoring data should be treated as highly uncertain values in the absence of site-specific information demonstrating that the data are reasonably predictive of intake. (5) For intakes known or assumed to be via inhalation, the uncertainty in lung dose typically is much greater than the uncertainty in dose to systemic tissues, when dose estimates are based on urinary excretion data. (6) The lung dose estimate often can be improved through development of site-specific respiratory absorption parameter values. (7) There is generally insufficient site-specific information to justify development of site-specific systemic models.

Bayesian Analysis of Plutonium Bioassay Data at Los Alamos National Laboratory.

The main concern of operational internal dosimetry is to detect intakes and estimate doses to the worker from a series of bioassay measurements. Although several methods are available, the inverse problem of internal dosimetry-i.e., determination of time, amount, and types of intake given a set of bioassay data-is well suited to a Bayesian approach. This paper summarizes the Bayesian methodology used at Los Alamos National Laboratory to detect intakes and estimate doses from plutonium bioassay measurements. Some advantages and disadvantages of the method are also discussed. The successful application of Bayesian methods for several years at Los Alamos National Laboratory, which monitors thousands of workers annually for plutonium, indicates that the methods can be extended to other facilities.

GHSI EMERGENCY RADIONUCLIDE BIOASSAY LABORATORY NETWORK: SUMMARY OF A RECENT EXERCISE.

The Global Health Security Initiative (GHSI) established a laboratory network within the GHSI community to develop their collective surge capacity for radionuclide bioassay in response to a radiological or nuclear emergency. A recent exercise was conducted to test the participating laboratories for their capabilities in screening and in vitro assay of biological samples, performing internal dose assessment and providing advice on medical intervention, if necessary, using a urine sample spiked with a single radionuclide, 241Am. The laboratories were required to submit their reports according to the exercise schedule and using pre-formatted templates. Generally, the participating laboratories were found to be capable with respect to rapidly screening samples for radionuclide contamination, measuring the radionuclide in the samples, assessing the intake and radiation dose, and providing advice on medical intervention. However, gaps in bioassay measurement and dose assessment have been identified. The network may take steps to ensure that procedures and practices within this network be harmonised and a follow-up exercise be organised on a larger scale, with potential participation of laboratories from the networks coordinated by the International Atomic Energy Agency and the World Health Organization.