Download: Executive Summary of the third project year

Subproject 2 is aimed at pooling the resources relevant to the dosimetric and medical follow-up of Mayak PA workers, including the tissue archive, in order to improve the risk assessment for cancer and non-cancer effects in the Mayak Worker Cohort (MWC) and current knowledge on the early pathogenesis of Pu-induced lung cancer.

Subproject 2 Internal dosimetry, dosimetry system, and health effects for the Mayak worker cohort is composed of six workpackages. Subproject 2 is aimed at pooling the resources relevant to the dosimetric and medical follow-up of Mayak PA workers, including the tissue archive, in order to improve the risk assessment for cancer and non-cancer effects in the Mayak Worker Cohort (MWC) and current knowledge on the early pathogenesis of Pu-induced lung cancer.

Results from the improvement of individual Pu dose estimates for the MWC by modelling and interpretation of measurements (workpackage 2.1 Plutonium dosimetry for Mayak PA Workers) together with input from subproject 1: cytogenetic dose estimates from workpackage 1.2 Cytogenetic Dosimetry (FISH) for Mayak PA workers and improved Mayak external dosimetry system (workpackage 1.3 External dosimetry for Mayak PA workers) will be evaluated in workpackage 2.2 Improvement of the Mayak dosimetry system and individual dose calculations in order to establish a new version of dose estimates for the MWC, Mayak Doses-2008. Mayak Doses-2008 will be used to analyse the mortality structure and death rates in the Ozyorsk population including members of the MWC (workpackage 2.3 Cause of death register Ozyorsk), to assess the risk of  cancer and non-cancer effects among Mayak PA workers (workpackages 2.4 Non-cancer effects in the Mayak worker cohort and 2.5 Cancer incidence among Mayak PA workers) and to obtain a better understanding of the early events leading to lung cancer induced by plutonium deposited in the lung.

Dosimetry work planned in this subproject will complement and integrate with the work already underway under U.S.-Russian JCCRER research program.

WP2.1 Plutonium dosimetry for Mayak PA workers

Workpackage Leaders: Alan Phipps (HPA), Victor Khokhryakov (SUBI)

 The Mayak PA workforce was exposed to photons, neutrons and internal emitters, chiefly plutonium. This workpackage will study doses from plutonium incorporated into the body.  The basis for the work will be provided by existing databases of Pu measurements and medical information for the exposed individuals.

 SUBI scientists together with American collaborators have been working extensively on improving dose assessments from internally deposited plutonium for individual Mayak PA workers under the aegis of the U.S.-Russian Joint Coordinating Committee for Radiation Effects Research (JCCRER). Between 1998 and 2001, the SUBI biokinetic model was improved and its parameters were established. The improved SUBI biokinetic model consisting of the ICRP 66 lung clearance model adapted to actual human data and the modified Langham-Durbin model for systemic Pu, served as a basis to obtain preliminary individual dose estimates for 6,900 exposed Mayak PA workers who had been exposed to plutonium (this database of dose estimates is known as Doses-2000). Doses-2000 is currently used in all studies of the Mayak PA worker population. The final individual dose estimates for Mayak PA workers (Mayak Doses 2005) will be based on the modified ICRP 66 Human Respiratory Tract Model (HRTM) model (HRTM was adapted by SUBI scientists to actual data on Pu metabolism in Mayak PA workers) and on one of Leggett's systemic models and using information on such modifying factors as the state of health and smoking status. By the autumn of 2006 newly developed uncertainty methods based on Bayesian statistical inference methods (adapted to worker dose assessment by scientists at Los Alamos national Laboratory, Los Alamos, NM, USA) will provide uncertainties in models and model parameters together with individual dose uncertainty calculations.

The enhancement of the accuracy and reliability of dose assessments for Mayak PA workers is an important task that will be carried out within the framework of this project.  To this end an integrated bioassay/dosimetry model that can accommodate multimodal exposures will be developed. This integrated model will provide a tool for more accurately assigning radiation doses from Pu intakes to workers. Another area where accuracy in assessments of doses from Pu intakes could be improved is in the verification of results and minimization of uncertainties due to radiochemical methods, sampling techniques, and interpretation of bioassay data for individual workers as a result of inter-laboratory comparison.

WP2.2 Improvement of the Mayak dosimetry system and individual dose calculations

Workpackage Leaders: Sergej Romanov (SIBI), Alan Phipps (HPA)

 Dose estimates to subcohort of Mayak PA workers obtained in a pilot study on potential of newly developed SOUL integrated bioassay/dosimetry model (WP2.1 Plutonium dosimetry for Mayak PA workers) to validate and refine existing USDOE estimates will be critically evaluated and validated in coordination with U.S. colleagues. Comparative analysis of different biokinetic models for Pu will be undertaken in order to decide which tool is most appropriate to assign accurate radiation doses to defined target organs/tissues. Special module will be developed to reconstruct typical Pu exposure patterns at specific work places and work areas and to assign doses to workers who were not monitored for internal exposure. Comparative analysis of FISH data (WP1.2 Cytogenetic Dosimetry (FISH) for Mayak PA workers) with conventional dose assessments will be accomplished, and ‘consensus’ dose estimates will be obtained on the basis of this analysis.

 Mayak Doses-2008 database will be assembled to combine external and internal organ dose estimates from this workpackage and WP1.3 External dosimetry for Mayak PA workers for all members of the MWC.

WP2.3 Cause of death register Ozyorsk

Workpackage Leaders: Fjodor Tretjakov (SUBI), Bernd Grosche (BfS)

 This work package aims to continue with the existing cause-of-death registry for the city of Ozyorsk. The existing cause of death register covers the time period 1948-1998. To this end, causes of death will be included from the city of Ozyorsk for the years by 2005. The register will give important information for the envisaged risk analysis among the Mayak Worker Cohort.

WP2.4 Non-cancer effects in the Mayak worker cohort

Workpackage Leaders: Tamara Azizova (SUBI), Colin Muirhead (HPA)

 This work package aims to establish the feasibility of analysing the risks of both mortality and morbidity from circulatory diseases among Mayak PA workers.  To this end, the study cohort of workers and control populations will be identified, information on vital status, morbidity and dosimetry will be updated, and quality control checks will be conducted.  In addition, the work conducted on the cause of death register in Ozyorsk under WP2.3 Cause of death register Ozyorsk will enable data on mortality and cause of death to be updated and validated.

WP 2.5 Cancer incidence among Mayak PA workers

Workpackage Leaders: Nina Koshurnikova (SUBI), NN

 WP2.5 aims to establish the feasibility of analysing the risks of cancer incidence among Mayak PA workers. In particular, it would be hoped subsequently to examine the influence of both radiation and non-radiation factors (smoking, alcohol consumption, occupational hazards other than radiation, e.g. prior coal mining experience or exposure to hazardous chemicals). Furthermore, radiation risks for leukaemia and solid cancers would be assessed by gender and age, taking account of the contributions from external γ-exposure and internal α-exposure from incorporated ²³⁹Pu.

WP2.6 Pathogenesis of Pu-induced lung cancer in Mayak PA workers

Workpackage Leaders: Sergej Romanov (SUBI), Falko Fend (TUM)

 Workers at the Mayak PA nuclear facility exposed to inhaled plutonium showed a significantly increased rate of lung cancer, mainly adenocarcinoma and squamous cell carcinoma. The excess relative risk (ERR) is strongly correlated to the cumulative absorbed dose from internally deposited Pu. Pulmonary fibrosis, an established effect of occupational exposure to Pu in the MWC, was also frequently observed.

 This workpackage seeks to explore relationships between deterministic (fibrosis) and stochastic (cancer) radiation effects by identifying preneoplastic lesions in archived lung tissues of Mayak PA workers from the SUBI Tissue Repository and correlate them to the distribution of fibrotic lesions as well as to plutonium deposition and possibly smoking. Precursor and cancerous lesions and morphologically normal epithelium cells from high-dose Pu-exposed workers and precancerous and cancerous lesions will also be studied on the molecular level to determine specific molecular dysfunctions associated with the early stages of radiogenic carcinogenesis.