Plutonium Microdistribution in the Lungs of Mayak Workers

Modified human respiratory tract model to describe the retention of plutonium in scar tissues

The Human Respiratory Tract Model described in Publication 130 of the International Commission on Radiological Protection provides some mechanisms to account for retention of material that can be subject to little to no mechanical transport or absorption into the blood. One of these mechanisms is 'binding', which refers to a process by which a fraction ('bound fraction') of the dissolved material chemically binds to the tissue of the airway wall. The value of the bound fraction can have a significant impact on the radiation doses imparted to different parts of the respiratory tract. To properly evaluate-and quantify-bound fraction for an element, one would need information on long-term retention of the element in individual compartments of the respiratory tract. Such data on regional retention of plutonium in the respiratory tract of four workers-who had inhaled materials with solubility ranging from soluble nitrate to very insoluble high-fired oxides-were obtained at the United States Transuranium and Uranium Registries. An assumption of bound fraction alone was found to be inconsistent with this dataset and also with a review of the literature. Several studies show evidence of retention of a large amount of Pu activity in the scar tissues of humans and experimental animals, and accordingly, a model structure with scar-tissue compartments was proposed. The transfer rates to these compartments were determined using Markov Chain Monte Carlo analysis of the bioassay and post-mortem data, considering the uncertainties associated with deposition, dissolution and particle clearance parameters. The models predicted that a significant amount-between 20 and 100% for the cases analyzed-of plutonium retained in the respiratory tract was sequestered in the scar tissues. Unlike chemically-bound Pu that irradiates sensitive epithelial cells, Pu in scar tissues may not be dosimetrically significant because the scar tissues absorb most, if not all, of the energy from alpha emissions.

Localized Instantaneous Dose Rates from Inhaled Particles of 239 Pu

In this work, the authors present instantaneous local dose rates from particles of plutonium-239 oxide ( 239 PuO) embedded in various regions of the respiratory tract. For comparison, a small number of simulations were performed in a representative region of the respiratory tract with other chemical compounds including pure metallic 239 Pu, 239 PuO 2 , 239 PuO 3 , 239 Pu 2 O 3 , and 239 Pu(NO 3 ) 4 . A small number of simulations were also performed with 238 PuO, weapons grade Pu, and Pu from a typical radioisotope thermoelectric generator (RTG) source for the same reason. The self-shielding effect is minor for very small particles but gradually becomes more significant as the particle size increases. For particles that are 0.1 μm and larger (excluding Pu nitrate), the calculated dose rate within several microns of the particle may be sufficient to damage lung cells, but the implications of damage to such a small volume of tissue are unclear. However, it is reasonable to assume that clinical effects will be observed if a large enough volume of tissue is damaged, as might happen when large numbers of particles are inhaled. The instantaneous dose rate around a particle may be predictive of deterministic effects, scar tissue formation, and biokinetics.

Modelling of long-term retention of high-fired plutonium oxide in the human respiratory tract: importance of scar-tissue compartments

The U.S. Transuranium and Uranium Registries whole-body tissue donor Case 0407 had an acute intake of 'high-fired' plutonium oxide resulting from a glove-box fire in a fabrication plant at a nuclear defence facility. The respiratory tract of this individual was dissected into five regions (larynx, bronchi, bronchioles, alveolar-interstitial, and thoracic lymph nodes) and analysed for plutonium content. The activities in certain compartments of the respiratory tract were found to be higher than expected from the default models described in publications of the International Commission on Radiological Protection. Because of the extremely slow rate of dissolution of the material inhaled, the presence of bound fraction is incapable of explaining the higher-than-expected retention. A plausible hypothesis-encapsulation of plutonium in scar tissues-is supported by the review of literature. Therefore, scar-tissue compartments corresponding to the larynx, bronchi, bronchioles and alveolar-interstitial regions were added to the existing human respiratory tract model structure. The transfer rates between these compartments were determined using Markov Chain Monte Carlo analysis of data on urinary excretion, lung counts and post-mortem measurements of the liver, skeleton and regional retention in the respiratory tract. Modelling of the data showed that approximately 30% of plutonium activity in the lung was sequestered in scar tissues. The dose consequence of such sequestration is qualitatively compared against that of chemical binding.

MODELING THE LONG-TERM RETENTION OF PLUTONIUM IN THE HUMAN RESPIRATORY TRACT USING SCAR-TISSUE COMPARTMENTS

The respiratory tract tissues of four former nuclear workers with plutonium intakes were radiochemically analyzed post mortem by the United States Transuranium and Uranium Registries. Plutonium activities in the upper respiratory tract of these individuals were found to be higher than those predicted using the most recent biokinetic models described in publications of the International Commission on Radiological Protection. Modification of the model parameters, including the bound fraction, was not able to explain the data in one of the four individuals who had inhaled insoluble form of plutonium. Literature review points to the presence of-and a significant retention of-plutonium in the scar tissues of the lungs. Accordingly, an alternate model with scar-tissue compartments corresponding to larynx, bronchi, bronchioles, alveolar-interstitium and thoracic lymph nodes was proposed. The rates of transfer to the scar tissue compartments were determined using Markov Chain Monte Carlo analysis of data on urinary excretion, lung counts and post-mortem measurements of liver, skeleton and individual respiratory tract compartments, as available. The posterior models predicted that 20-100%-depending on the solubility of the material inhaled-of the activities retained in the respiratory tract were sequestered in the scar tissues.

Comparison of Local and Systemic DTPA Treatment Efficacy According to Actinide Physicochemical Properties Following Lung or Wound Contamination in the Rat

Purpose: In cases of occupational accidents in nuclear facilities or subsequent to terrorist activities, the most likely routes of internal contamination with alpha-particle emitting actinides, such as plutonium (Pu) and americium (Am), are by inhalation or following wounding. Following contamination, actinide transfer to the circulation and subsequent deposition in skeleton and liver depends primarily on the physicochemical nature of the compound. The treatment remit following internal contamination is to decrease actinide retention and in consequence potential health risks, both at the contamination site and in systemic retention organs as well as to promote elimination. The only approved drug for decorporation of Pu and Am is the metal chelator diethylenetriaminepentaacetic acid (DTPA). However, a limited efficacy of DTPA has been reported following contamination with insoluble actinides, irrespective of the contamination route. The objectives of this work are to evaluate the efficacy of prompt local and/or systemic DTPA treatment regimens following lung or wound contamination by actinides with differing solubility. The conclusions are drawn from retrospective analysis of experimental studies carried out over 10 years. Materials and Methods: Rat lungs or wounds were contaminated either with poorly soluble Mixed OXide (U, Pu O2) or more soluble forms of Pu (nitrate or citrate). DTPA treatment was administered promptly after contamination, locally to lungs by insufflation of a powder or inhalation of aerosolized solution or by injection directly into the wound site. Intravenous injections of DTPA were given either once or repeated in combination with the local treatment. Doses ranged from 1 to 30 µmol/kg. Animals were euthanized from day 7-21 and alpha activity levels were measured in urine, lungs, wound, bone and liver for determination of decorporation efficacy. Results: Different experiments confirmed that whatever the route of contamination, most of the activity is retained at the entry site after insoluble MOX contamination as compared with contamination with more soluble forms which results in very low activities reaching the systemic compartment and subsequent retention in bone and liver. Several DTPA treatment regimens were evaluated that had no significant effect on either lung or wound levels compared with untreated animals. In contrast, in all cases systemic retention (skeleton and liver) was reduced and urinary excretion were enhanced irrespective of the contamination route or DTPA treatment regimen. Conclusion: The present study demonstrates that despite limitation of retention in systemic organs, different DTPA protocols were ineffective in removing insoluble actinides deposited in lungs or wound site. For moderately soluble actinides, local or intravenous DTPA treatment reduced activity levels both at contamination and at systemic sites.

Research on the Radiotoxicology of Plutonium Using Animals: Consideration of the 3Rs-Replace, Reduce, Refine

To characterize the health effects of incorporated plutonium, many experiments have been conducted using different animal models. These range from (1) applied (tissue uptake/retention determination, decorporation therapy efficacy), (2) fundamental (gene expression, cancer induction), and (3) dosimetry models. In recent years, the use of animals for scientific purposes has become a public concern. The application of the 3Rs - Replace (use of alternative methods or animals not considered capable of experiencing pain, suffering, and distress), Reduce (reduction in animal numbers), and Refine (better animal welfare and minimization of suffering, pain and distress) - has increased to address ethical concerns and legislative requirements. The introduction of novel non-animal technologies is also an important factor as complementary options to animal experimentation. In radiotoxicology research, it seems there is a natural tendency to Replace given the possibility of data reuse obtained from contamination cases in man and animal studies. The creation of "registries" and "repositories" for nuclear industry workers (civil and military) is now a rich legacy for radiotoxicological measurements. Similarly, Reduction in animal numbers can be achieved by good experimental planning with prior statistical analyses of animal numbers required to obtain robust data. Multiple measurements in the same animal over time (external body counting, excreta collection) with appropriate detection instruments also allow Reduction. In terms of Refinement, this has become "de rigueur" and a necessity given the societal and legal concerns for animal welfare. For research in radiotoxicology, particularly long-term studies, better housing conditions within the constraints of radiation protection issues for research workers are an important concern. These are all pertinent considerations for the 3Rs remit and future research in radiotoxicology.

The Mayak Worker Dosimetry System (MWDS 2013): Soluble Plutonium Retention in the Lungs of An Occupationally Exposed USTUR Case

For the first time, plutonium retention in human upper airways was investigated based on the dosimetric structure of the human respiratory tract proposed by the International Commission on Radiological Protection (ICRP). This paper describes analytical work methodology, case selection criteria, and summarizes findings on soluble (ICRP 68 Type M material) plutonium distribution in the lungs of a former nuclear worker occupationally exposed to plutonium nitrate [239Pu(NO3)4]. Thirty-eight years post-intake, plutonium was found to be uniformly distributed between bronchial (BB), bronchiolar (bb) and alveolar-interstitial (AI) dosimetric compartments as well as between the left and right lungs. 239+240Pu and 238Pu total body activity was estimated to be 2333 ± 23 and 42.1 ± 0.7 Bq, respectively. The results of this work provide key information on the extent of plutonium binding in the upper airways of the human respiratory tract.

The Mayak Worker Dosimetry System (MWDS-2013): A Bayesian Analysis to Quantify Pulmonary Binding of Plutonium in Lungs Using Historic Beagle Dog Data

The revised human respiratory tract model, published in Part 1 of the International Commission on Radiological Protection's (ICRP) report on Occupational Intakes of Radionuclides (OIR), includes a bound fraction, fb, to represent radionuclides that have become chemically bound in the lungs following dissolution of particulates in lung fluid. Bound radionuclides are not subject to particle transport clearance but can be absorbed to blood at a rate, sb. The occurrence of long-term binding of plutonium can greatly increase lung doses, particularly if it occurs in the bronchial and bronchiolar regions. However, there has been little evidence that currently supports the existence of a long-term bound state for plutonium. The present work describes the analysis of measurements of lung data obtained from a life span study of Beagle dogs that were exposed by inhalation to different concentrations of plutonium-239 (239Pu) nitrate aerosol at Pacific Northwest Laboratories, USA. The data have been analysed to assess whether a bound state was required to explain the data. A Bayesian approach was adopted for the analysis that accounts for uncertainties in model parameter values, including uncertainties in the rates of particle transport clearance. Furthermore, it performs the analysis using two different modelling hypotheses: a model based on the current ICRP human respiratory tract model and its treatment of alveolar particle transport clearance; and a model of particle transport clearance that is based on the updated model developed by ICRP to calculate dose coefficients for the OIR. The current model better represents clearance in dogs at early times (up to 1 year following intake) and the latter better represents retention at greater times (>5 years following intake). The results indicate that a long-term bound fraction of between 0.16 and 1.1%, with a mean value of between 0.24 and 0.8% (depending on the model) is required to explain the data.

The Mayak Worker Dosimetry System (MWDS-2013): Estimate of Pu Content in Lungs and Thoracic Lymph Nodes From a Limited Set of Organ Autopsy Samples

A method to estimate plutonium content from a limited number of samples of lungs and pulmonary lymph nodes obtained at autopsies of former Mayak Production Association (MPA) workers is described. Historically from one to five samples of lung lobes and one to three respiratory lymph nodes (bronchopulmonary, tracheobronchial and paratracheal) were collected. The samples were used to estimate organ plutonium contents for cases where incomplete sets of samples were obtained, i.e. one to four lung lobes and one to two lymph nodes. This method was developed and validated using individual measurement data from 259 MPA autopsy cases with complete lung samples (five lobes) and three lymph nodes. A good correlation of plutonium content in measurements of two and four lung samples with the content estimate by five lung samples was obtained. The correlations with the individual lymph nodes were less robust than with the lung. The data are used to develop biokinetic, dosimetry and risk models for humans exposed to plutonium.

The Mayak Worker Dosimetry System (Mwds-2013): Plutonium Dissolution in The Lungs-An Analysis of Mayak Workers

Lung doses resulting from inhalation of plutonium aerosols are highly dependent on the assumed rate of particle clearance, which occurs by two competing processes: (1) particle transport clearance to the alimentary tract and to the thoracic lymph nodes and (2) clearance to systemic tissues, which occurs by dissolution of particles in lung fluid followed by uptake to blood, which is a process collectively known as absorption. Unbiased and accurate estimates of the values of lung absorption parameters are required to obtain reliable estimates of lung dose, particularly those inferred from urine bioassay. Parameter values governing the rate of absorption are best estimated from data, such as autopsy measurements of plutonium in the lungs and systemic tissues, which directly relate to the exposed workers of interest. However, because the mathematical models that determine clearance from the lungs and systemic tissues are complex and consist of many parameters, estimates of model parameter values are subject to significant uncertainties. With this in mind, this paper uses a Bayesian approach to estimate one of the most important dissolution parameters: the slow rate of dissolution. This is estimated for both plutonium nitrate and plutonium oxide bearing aerosols in the lungs of former workers of the Mayak Production Association. A value of 2.6 × 10-4 d-1 is estimated for plutonium nitrates, and 4.7 × 10-5 d-1 for plutonium oxides.

Actinide bioimaging in tissues: Comparison of emulsion and solid track autoradiography techniques with the iQID camera

This work presents a comparison of three autoradiography techniques for imaging biological samples contaminated with actinides: emulsion-based, plastic-based autoradiography and a quantitative digital technique, the iQID camera, based on the numerical analysis of light from a scintillator screen. In radiation toxicology it has been important to develop means of imaging actinide distribution in tissues as these radionuclides may be heterogeneously distributed within and between tissues after internal contamination. Actinide distribution determines which cells are exposed to alpha radiation and is thus potentially critical for assessing absorbed dose. The comparison was carried out by generating autoradiographs of the same biological samples contaminated with actinides with the three autoradiography techniques. These samples were cell preparations or tissue sections collected from animals contaminated with different physico-chemical forms of actinides. The autoradiograph characteristics and the performances of the techniques were evaluated and discussed mainly in terms of acquisition process, activity distribution patterns, spatial resolution and feasibility of activity quantification. The obtained autoradiographs presented similar actinide distribution at low magnification. Out of the three techniques, emulsion autoradiography is the only one to provide a highly-resolved image of the actinide distribution inherently superimposed on the biological sample. Emulsion autoradiography is hence best interpreted at higher magnifications. However, this technique is destructive for the biological sample. Both emulsion- and plastic-based autoradiography record alpha tracks and thus enabled the differentiation between ionized forms of actinides and oxide particles. This feature can help in the evaluation of decorporation therapy efficacy. The most recent technique, the iQID camera, presents several additional features: real-time imaging, separate imaging of alpha particles and gamma rays, and alpha activity quantification. The comparison of these three autoradiography techniques showed that they are complementary and the choice of the technique depends on the purpose of the imaging experiment.

Microdosimetric considerations of lung cancer risks from plutonium

New data from the workers at the Mayak nuclear facility near Chelyabinsk, Russia, apparently show a linear increase in the risk of lung cancer with increasing dose. Furthermore, this increase occurs without a threshold. However, these conclusions are at variance with the results reported by other investigators. A possible cause of these inconsistencies could be the lack of application of microdosimetric considerations when discussing "dose" to the lung.

Radiation risk of malignant neoplasms in organs of main deposition for plutonium in the cohort of Mayak workers with regard to histological types

This paper presents the results of analyses of the incidence of malignant neoplasms in lung, liver, and bone and associated connective tissues among Mayak nuclear workers exposed to both internally incorporated plutonium and to external gamma radiation. The study cohort included 22,373 individuals employed at the reactors and radiochemical and plutonium production facilities of the Mayak nuclear complex during 1948-1982 and followed up to the end of 2004. All analyses were carried out by Poisson regression, and the doses used were derived using a recently available update of organ doses, Mayak doses-2008. There was clear evidence for the linear association between internal plutonium dose and the risk of lung cancer. For males, there was evidence of a significant internal plutonium dose response for all histological types of lung cancer evaluated (adenocarcinoma, squamous-cell, and other epithelial); the estimated excess relative risk (ERR)/Gy for adenocarcinoma was the largest (ERR/Gy = 32.5; 95% CI: 16.3; 71.9), about 11-fold higher than that for squamous-cell lung cancer (ERR/Gy = 3.1; 95% CI: 0.3; 9.1). The relationship between liver cancer risk and plutonium exposure was best described by a linear-quadratic (LQ) function, but the LQ effect was diminished after restricting internal doses <2 Gy. Hepatocellular cancer was the most frequently observed type of liver cancer associated with internal plutonium exposure, and hemangiosarcomas were exclusively observed only at high internal plutonium doses (>4 Gy). For malignant neoplasms of bone and associated connective tissues, the trend was not statistically significant in relation to internal plutonium dose, but a statistically significantly higher risk (RR=13.7; 95% CI= 3.0; 58.5) was found among unmonitored female plutonium workers who were employed in the most hazardous plutonium production facility commissioned prior to 1950.

Microdistribution and long-term retention of 239Pu (NO3)4 in the respiratory tracts of an acutely exposed plutonium worker and experimental beagle dogs

The long-term retention of inhaled soluble forms of plutonium raises concerns as to the potential health effects in persons working in nuclear energy or the nuclear weapons program. The distributions of long-term retained inhaled plutonium-nitrate [(239)Pu (NO(3))(4)] deposited in the lungs of an accidentally exposed nuclear worker (Human Case 0269) and in the lungs of experimentally exposed beagle dogs with varying initial lung depositions were determined via autoradiographs of selected histologic lung, lymph node, trachea, and nasal turbinate tissue sections. These studies showed that both the human and dogs had a nonuniform distribution of plutonium throughout the lung tissue. Fibrotic scar tissue effectively encapsulated a portion of the plutonium and prevented its clearance from the body or translocation to other tissues and diminished dose to organ parenchyma. Alpha radiation activity from deposited plutonium in Human Case 0269 was observed primarily along the subpleural regions while no alpha activity was seen in the tracheobronchial lymph nodes of this individual. However, relatively high activity levels in the tracheobronchial lymph nodes of the beagles indicated the lymphatic system was effective in clearing deposited plutonium from the lung tissues. In both the human case and beagle dogs, the appearance of retained plutonium within the respiratory tract was inconsistent with current biokinetic models of clearance for soluble forms of plutonium. Bound plutonium can have a marked effect on the dose to the lungs and subsequent radiation exposure has the potential to increase cancer risk.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Late-occurring pulmonary pathologies following inhalation of mixed oxide (uranium + plutonium oxide) aerosol in the rat

Accidental exposure by inhalation to alpha-emitting particles from mixed oxide (MOX: uranium and plutonium oxide) fuels is a potential long-term health risk to workers in nuclear fuel fabrication plants. For MOX fuels, the risk of lung cancer development may be different from that assigned to individual components (plutonium, uranium) given different physico-chemical characteristics. The objective of this study was to investigate late effects in rat lungs following inhalation of MOX aerosols of similar particle size containing 2.5 or 7.1% plutonium. Conscious rats were exposed to MOX aerosols and kept for their entire lifespan. Different initial lung burdens (ILBs) were obtained using different amounts of MOX. Lung total alpha activity was determined by external counting and at autopsy for total lung dose calculation. Fixed lung tissue was used for anatomopathological, autoradiographical, and immunohistochemical analyses. Inhalation of MOX at ILBs ranging from 1-20 kBq resulted in lung pathologies (90% of rats) including fibrosis (70%) and malignant lung tumors (45%). High ILBs (4-20 kBq) resulted in reduced survival time (N = 102; p < 0.05) frequently associated with lung fibrosis. Malignant tumor incidence increased linearly with dose (up to 60 Gy) with a risk of 1-1.6% Gy for MOX, similar to results for industrial plutonium oxide alone (1.9% Gy). Staining with antibodies against Surfactant Protein-C, Thyroid Transcription Factor-1, or Oct-4 showed differential labeling of tumor types. In conclusion, late effects following MOX inhalation result in similar risk for development of lung tumors as compared with industrial plutonium oxide.

Radiotoxicity of inhaled (239)PuO(2) in dogs

Beagle dogs inhaled graded exposure levels of insoluble plutonium dioxide ((239)PuO(2)) aerosols in one of three monodisperse particle sizes at the Lovelace Respiratory Research Institute (LRRI) to study the life-span health effects of different degrees of alpha-particle dose non-uniformity in the lung. The primary noncarcinogenic effects seen were lymphopenia, atrophy and fibrosis of the thoracic lymph nodes, and radiation pneumonitis and pulmonary fibrosis. Radiation pneumonitis/ pulmonary fibrosis occurred from 105 days to more than 11 years after exposure, with the lowest associated alpha-particle dose being 5.9 Gy. The primary carcinogenic effects also occurred almost exclusively in the lung because of the short range of the alpha-particle emissions. The earliest lung cancer was observed at 1086 days after the inhalation exposure. The most common type seen was papillary adenocarcinoma followed by bronchioloalveolar carcinoma. These lung cancer results indicate that a more uniform distribution of alpha-particle dose within the lung has an equal or possibly greater risk of neoplasia than less uniform distributions of alpha-particle dose. The results are consistent with a linear relationship between dose and response, but these data do not directly address the response expected at low dose levels. No primary tumors were found in the tracheobronchial and mediastinal lymph nodes despite the high alpha-particle radiation doses to these lymph nodes, and no cases of leukemia were observed.

Activation of alveolar macrophages after plutonium oxide inhalation in rats: involvement in the early inflammatory response

Alveolar macrophages play an important role in the distribution, clearance and inflammatory reactions after particle inhalation, which may influence long-term events such as fibrosis and tumorigenesis. The objectives of the present study were to investigate the early inflammatory events after plutonium oxide inhalation in rats and involvement of alveolar macrophages. Lung changes were studied from 3 days to 3 months after inhalation of PuO2 of different isotopic compositions (70% or 97% 239Pu) and initial lung deposits (range 2.1 to 43.4 kBq/rat). Analyses of bronchoalveolar lavages showed early increases in the numbers of granulocytes, lymphocytes and multinucleated macrophages. The activation of macrophages was evaluated ex vivo by measurement of inflammatory mediator levels in culture supernatants. TNF-alpha and chemokine MCP-1, MIP-2 and CINC-1 production was elevated from 7 days after inhalation and remained so up to 3 months. In contrast, IL-1beta, IL-6 and IL-10 production was unchanged. At 6 weeks, pulmonary macrophage numbers and activation state were increased as observed from an immunohistochemistry study of lung sections with anti-ED1. Similarly, histological analyses of lung sections also showed evidence of inflammatory responses. In conclusion, our results indicate early inflammatory changes in the lungs of PuO2-contaminated animals and the involvement of macrophages in this process. A dose-effect relationship was observed between the amount of radionuclide inhaled or retained at the time of analysis and inflammatory mediator production by alveolar macrophages 14 days after exposure. For similar initial lung deposits, the inflammatory manifestation appears higher for 97% 239Pu than for 70% 239Pu.

Uncertainties analysis for the plutonium dosimetry model, doses-2005, using Mayak bioassay data

The Doses-2005 model is a combination of the International Commission on Radiological Protection (ICRP) models modified using data from the Mayak Production Association cohort. Surrogate doses from inhaled plutonium can be assigned to approximately 29% of the Mayak workers using their urine bioassay measurements and other history records. The purpose of this study was to quantify and qualify the uncertainties in the estimates for radiation doses calculated with the Doses-2005 model by using Monte Carlo methods and perturbation theory. The average uncertainty in the yearly dose estimates for most organs was approximately 100% regardless of the transportability classification. The relative source of the uncertainties comes from three main sources: 45% from the urine bioassay measurements, 29% from the Doses-2005 model parameters, and 26% from the reference masses for the organs. The most significant reduction in the overall dose uncertainties would result from improved methods in bioassay measurement with additional improvements generated through further model refinement. Additional uncertainties were determined for dose estimates resulting from changes in the transportability classification and the smoking toggle. A comparison was performed to determine the effect of using the model with data from either urine bioassay or autopsy data; no direct correlation could be established. Analysis of the model using autopsy data and incorporation of results from other research efforts that have utilized plutonium ICRP models could improve the Doses-2005 model and reduce the overall uncertainty in the dose estimates.

A repository of bio-specimens from Mayak workers exposed to protracted radiation

A repository of bio-specimens that includes organs from 700 deceased workers employed at the first nuclear weapons facility "Mayak" and donations of blood, buccal cells, and tissues removed at the time of surgery and/or biopsy from the members of the Mayak cohort undergoing medical treatment or diagnostic procedures has been established at the Southern Ural Biophysics Institute, in Ozyorsk, Russian Federation. The autopsied tissues include formaline-preserved organs, paraffin blocks, and histology slides. For all, occupational, dosimetry, and detailed medical information is available. For 359 individuals, information on malignant tumors, i.e., lung (171), stomach (51), liver (28), and intestine (19), as well as 32 cases of leukemia, are available. External gamma exposures are known for 95% of the 700 autopsies, of whom 560 were exposed to protracted doses exceeding 0.5 Gy, with known maximum annual doses ranging from 0.01-0.5 Gy for about 46%, and annual doses exceeding 0.5 Gy for 48%. Plutonium body burden is known for 73%, of which 40% had body burden greater than 1.5 kBq, and 15% of individuals had body burdens greater than 11.85 kBq. Newly collected specimens include frozen lymphocytes, EBV-immortalized B-cells, frozen erythrocytes, and DNA as well as frozen tumors. Donations were obtained to date from more than 1,600 individuals. For these donors external doses of exposure exceeded 0.5 Gy for 83%, and plutonium body burden exceeded 1.48 kBq for 30%. A Web site describing the Repository that also includes forms for tissue requests can be accessed at http://www.subi.ru/RHTR.