Estimation of radiation risk in presence of classical additive and Berkson multiplicative errors in exposure doses.

In this paper, the influence of measurement errors in exposure doses in a regression model with binary response is studied. Recently, it has been recognized that uncertainty in exposure dose is characterized by errors of two types: classical additive errors and Berkson multiplicative errors. The combination of classical additive and Berkson multiplicative errors has not been considered in the literature previously. In a simulation study based on data from radio-epidemiological research of thyroid cancer in Ukraine caused by the Chornobyl accident, it is shown that ignoring measurement errors in doses leads to overestimation of background prevalence and underestimation of excess relative risk. In the work, several methods to reduce these biases are proposed. They are new regression calibration, an additive version of efficient SIMEX, and novel corrected score methods.

Individualized internal exposure doses reconstruction for the persons of Ukraine State Register: Report 2. Locally-specific models and doses of persons living in Kozelets and Ripky raions of Chernihiv oblast. / Rekonstrukciya individualizirovannyx doz vnutrennego oblucheniya sub""ektov Gosudarstvennogo Registra Ukrainy: Soobshhenie 2. Lokal''no-specificheskie modeli i dozy oblucheniya zhitelej Kozeleckogo i Repkinskogo rajonov Chernigovskoj oblasti.

Study objective. Development a system of models and procedures for the individualized internal exposure doses reconstruction for the subjects of Ukrainian State Register of persons, affected due to the Chornobyl accident (SRU) and residing in radioactive contaminated territories of Kozelets and Ripky raions of Chernihiv oblast. Materials and methods. A description the schematic diagram and mathematical equations of ecological-dosimetric models are given that allow to reconstruct the individualized exposure doses from consumption of food contaminated with radiocesium of Chornobyl origin for inhabitants of two raions of Chernihiv oblast. Parameterization of the reconstruction models is based on the mathematical analysis of results for radioecological (radiocesium milk contamination) and dosimetric (radiocesium human body burden) monitorings, that were calculated in the period of 1986-2012 in the settlements of raions under consideration. Due to quite low level of radioactive cesium depositions on the ground in 1986, the territory of these raions was divided into two "territorial zones": TZ-1, an area where the 137Cs ground depositions density in 1986 exceeds 37 kBq/m2, and TZ-2, an area where this rate does not exceeds 37 kBq/m2. For each territorial zone in each raion, the initial time moment (year) was introduced in the reconstruction model. Since this year the concept of the so-called "reference dose" has been using. Its value was assigned to all persons, regardless of the results and availability of monitoring. The results of radioecological and dosimetric monitorings were used for setting in raion specific functions: the annual average concentration of 137Cs in milk per unit of 137Cs ground depositions for Kozelets raion, function of the temporary dynamic of 137Cs concentration in milk for Ripky raion, absolute raion milk equivalent of the diet (ARMEr), and relative age dependent intake of radiocesium with the diet. Results and conclusions. Models for individualized internal exposure doses reconstruction were applied to 27811 SRU subjects from Kozelets raion and 14553 SRU subjects from Ripky raion. Results of doses individualization are given as annual average values of internal and summarized (internal and external) exposure doses for the period of 1987-2012, as well as the distribution of SRU subjects of different raions according to the intervals of accumulat-ed doses over the entire period of observation.

Individualized internal exposure doses reconstruction for the persons of Ukraine State Register: Report 1. Locally-specific models and doses of persons living in Rokytne raion of Rivne oblast, Ovruch raion of Zhytomyr oblast and Ivankiv raion of Kyiv oblast. / Rekonstrukcija individualizirovannyh doz vnutrennego obluchenija subektov Gosudarstvennogo Registra Ukrainy: Soobshhenie 1. Lokal''no-specificheskie modeli i dozy obluchenija zhitelej Rokitnovskogo rajona Rovenskoj oblasti, Ovruchskogo rajona Zhitomirskoj oblasti i Ivankovskogo rajona Kievskoj oblasti.

Study objective. Dosimetric support of the Ukrainian State Register of persons, affected due to the Chornobyl accident (SRU). Development the system of models and procedures for the individualized internal doses reconstruction for the subjects of SRU residing in radioactive contaminated territories of Rokytne raion of Rivne oblast, Ovruch raion of Zhytomyr oblast and Ivankiv raion of Kyiv oblast. Materials and methods. A detailed description for the schematic diagram of the methodology and mathematical relations of ecological-dosimetric models are given. It allows to reconstruct the individualized doses from the ingestion of food contaminated by radiocesium after the Chornobyl accident for the subjects of SRU from three raions of Rivne, Zhytomyr and Kyiv oblasts. Phenomenologically, the developed models are close to the previously developed complex of ecological and dosimetric models intended to estimate the reference doses for the entire population of Ukraine. Calibration of model parameters is based on mathematical treatment for results of extensive radioecological (radiocesium milk contamination) and dosimetric (radiocesium burden in human body) monitorings, that were provided in the period of 1986-2012 in the settlements of raions under consideration. Completeness and periodicity of radioecological and dosimetric monitorings allowed to realize the settlement-specific approach for dose reconstruction, wherein for each settlement either the function of radiocesium intake with diet or the function of time-variation of radiocesium concentration in the local cow's milk were established. Absolute raion milk equivalent of the diet (ARMEr) and relative age dependent intake of radiocesium with diet are specified as a raion-specific functions for each raion. ARMEr is used to calculate the doses of adults in the settlement for which the function was specified. RRI is used to calculate the doses for the subjects of four children age groups (< 2 years old, 3-7 years old, 8-12 years old, 13-17 years old). Results and conclusions. Models for individualized internal exposure doses reconstruction of SRU subjects are developed. The individualized doses are estimated for 28711 SRU subjects from Rokytne raion, 18790 SRU subjects from Ivankiv raion and 41585 SRU subjects from Ovruch raion. Results of doses individualization are given as annual average doses for the period of 1987-2012. The distribution of SRU subjects of different raions over the intervals of doses accumulated over the entire observation period is also given. Values of total (from internal and external exposure) doses for SRU subjects of the raions under consideration are given, as well.

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident--report 2. Ingestion doses of the rural population of Ukraine up to 12 y after the accident (1986-1997).

Doses from the ingestion of 134Cs and 137Cs during 12 y following the Chernobyl accident have been estimated for approximately 3 million persons living in rural areas of the Zhitomir, Rivne, and Kyiv Oblasts of northern Ukraine. This assessment is based upon an extensive monitoring campaign that provided measurements of 137Cs in more than 120,000 samples of milk and in more than 100,000 persons; such measurements were made in approximately 4,500 locations. Two approaches were used for the dose assessment. In the first approach a so-called reference dose is estimated for each settlement on the basis of measured 137Cs concentration in milk, determination of the milk equivalent of diet, and consumption rates; a further assumption is that a high fraction of the food consumed is produced locally. The reference dose is used as the official dose estimate, which is the basis for any decision on possible financial compensation and economic privileges. In a second step, the so-called real age-dependent dose is estimated from the results of whole body counter measurements and the kinetics of radiocesium in the human body. Real doses above 0.5, 5, and 50 mSv were received by about 40%, 10%, and 0.2%, respectively, of the considered population. With the exception of 1986, for which the monitoring results were limited, the real individual doses derived from whole-body counting are consistently lower than the reference doses. However, this difference declined from a factor of 3-4 in 1987-1989 to a factor of approximately 1.5 in the mid 1990's. The difference between reference and real doses is attributed to the effectiveness of countermeasures implemented after the accident. The effectiveness of these countermeasures decreased with time due to increasing economic problems in Ukraine. The collective reference and real doses of the rural population due to the intake of 134Cs and 137Cs are estimated to be 13,300 and 5,300 person-Sv, respectively. Thus, about 8,000 person-Sv is estimated to have been averted by countermeasures.

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident. Report 1. General model: ingestion doses and countermeasure effectiveness for the adults of Rovno Oblast of Ukraine.

The Chernobyl accident, which occurred in April 1986, resulted in the atmospheric release of about 70--100 PBq of 137Cs. This paper examines the doses to the adult population of the northern part of Rovno Oblast, Ukraine, from ingestion of 137Cs. Fallout of 137Cs in these regions was lower than in other regions of Ukraine. However, the transfer of 137Cs from soil to milk in the region considered is high (up to 20 Bq L-1 per kBq m-2) and results in the predominance of internal doses compared to those from external exposure. Numerous measurements of 137Cs soil deposition, 137Cs milk contamination, and 137Cs body burden have been made in the area and form the basis of a general model of internal exposure from the ingestion of foods contaminated by 137Cs. This paper has two main purposes. The first is to develop the general phenomenological description of the process leading to internal exposure from the ingestion of 137Cs contaminated foods in the situation where different countermeasures are realized. The second is to apply the model for the adult population of the northern part of the Rovno Oblast (first report) for the limited time period of up to six years after the accident. The doses actually received by the adults are estimated to be four to eight times smaller than the doses calculated for the situation without countermeasures.

Dosimetric support of the International Programme on the Health Effects of the Chernobyl Accident (IPHECA) pilot project: main results and problems.

The problem of post-Chernobyl dosimetry is unique in its complexity in the history of radiation medicine and radiation protection. This is because the early experience of mass exposure of people (bombing of Hiroshima and Nagasaki, Windscale and South-Ural accidents, exposure of inhabitants of Nevada in the United States of America, the Semipalatinsk area in the former USSR, the Marshall Islands, and the Goiånia accident in Brazil, and others) differed both in the much simpler structure of the irradiation source and in the number and characteristics of exposed persons. It is obvious that post-Chernobyl dosimetry, both as an independent problem, and as a tool for epidemiological studies, requires significant expertise and economic and technical expenditures. Extensive and deep research has been carried out in Ukraine for the past 10 years. This article reviews the main results of these studies.

[Transit of radiocesium and radiostrontium from the fallout to the soil of the Ukrainian S.S.R. due to the Chernobyl AES accident into plants and milk]. / Perekhod radiotseziia i radiostrontsiia, vypavshikh na pochvy USSR v rezul'tate avarii na Chernobyl'skoi AES, v rasteniia i moloko.

Dietary components making a great contribution to the formation of human internal irradiation dose were defined. The values of soil-milk transition ratios that are ranging 0.3 to 41 E-9 MBq.kg-1.Bq-1.m2 have been obtained from the examination of 1300 milk specimens by radiochemical assay for 90Sr. The relationship of soil-milk and soil-plant transition ratios was examined to the type of soils and the distance from the NPP.