TAM-A1 - Dose Reconstruction Centennial Ballroom 300A 09:30 - 10:30
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| Chair(s): Mauritius Hiller
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TAM-A1.1
09:30 Revision of the post-Chernobyl Thyroid Dosimetry System in Ukraine S Masiuk, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine
; M Chepurny, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; V Buderatska, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; O Ivanova, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; Z Boiko, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; N Zhadan, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; G Fedosenko, State Institution “National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine; A Kukush, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine; M Talerko, Institute for Safety Problems of Nuclear Power Plants, National Academy of Sciences of Ukraine, Kyiv, Ukraine; V Drozdovitch*, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA
Abstract: The increase risk of thyroid cancer among individuals exposed in utero, during childhood and adolescence to Iodine-131 (131I) is the main statistically significant long-term effect of the Chornobyl accident. Several radiation epidemiological studies are currently in progress in Ukraine, to assess the risk of radiation-related health effects in exposed populations. The measurements of 131I thyroid activity, so-called ‘direct thyroid measurements’, performed in May–June 1986 in 146,425 individuals served as the basis to estimate thyroid doses to the subjects of these studies. However, limitations in the direct thyroid measurements have been recently recognized including improper measurement geometry and unknown true values of calibration coefficients for unchecked thyroid detectors and, therefore, the values of measured 131I thyroid activity were revised. The revised estimates of 131I thyroid activity along with the thyroid-mass values specific to the Ukrainian population and the revised 131I ground deposition densities in Ukrainian settlement were used to develop an updated Thyroid Dosimetry System (TD20). The TD20 estimates the thyroid doses for the residents of the settlements divided into three levels depending on availability of measurements of 131I thyroid activity among their residents. The arithmetic mean of the thyroid doses due to 131I intake among 146,425 measured individuals was 0.23 Gy (median of 0.094 Gy); about 99.8% of them received doses less than 5 Gy. The highest average population-weighted thyroid doses from 131I were estimated for residents of the most contaminated raions located closed to the Chornobyl Nuclear Power Plant: Narodychi (0.83 Gy for arithmetic mean), Poliske (0.68 Gy) and Luhyny (0.43 Gy). TD20 has been also used to revise the thyroid doses for the 13,204 Ukrainian-American cohort members exposed during childhood and adolescence and 2,582 members of the Ukrainian in utero cohort. The revised thyroid doses and associated uncertainties are being used to assess the radiation-related risk of thyroid cancer and other thyroid diseases in individuals exposed to Chornobyl fallout.
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TAM-A1.2
09:45 Estimation of radiation gonadal doses for the American-Ukrainian trio study of parental irradiation to Chornobyl fallout and germline mutations in offspring V Drozdovitch*, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA
; E Bakhanova, National Research Centre for Radiation Medicine, Kyiv, Ukraine; V Kryuchkov, Burnasyan Federal Medical and Biophysical Centre, Moscow, Russia; I Golovanov, Burnasyan Federal Medical and Biophysical Centre, Moscow, Russia; K Chizhov, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA, Burnasyan Federal Medical and Biophysical Centre, Moscow, Russia; D Bazyka, N Gudzenko, N Trotsuk, National Research Centre for Radiation Medicine, Kyiv, Ukraine; K Mabuchi, M Hatch, EK Cahoon, MP Little, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA; T Kukhta, United Institute of Informatics Problems, Minsk, Belarus; A Berrington de Gonzalez, SJ Chanock, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA; V Chumak, National Research Centre for Radiation Medicine, Kyiv, Ukraine
Abstract: Radiation doses of parents exposed from the Chornobyl accident as cleanup workers or evacuees were estimated in the NCI-NRCRM trio (i.e. father, mother, offspring) study aimed at investigating the radiation effects on germline de novo mutations in children as well as other outcomes. This study requires assessing the gonadal doses of the parents of offspring accumulated during the preconception period. The unique features of this study included an independent estimation of doses to both parents (even presumably non-exposed), consideration of doses to the gonads (ovaries and testes) accumulated over a specific, individually defined period, and consideration of both external and internal components of Chornobyl-related exposure. Gonadal doses were reconstructed for 298 trios for the periods from the time of the accident on 26 April 1986 to two time points before the child’s date of birth (DOB): 51 (DOB-51) and 38 (DOB-38) weeks. The two doses, DOB-51 and DOB-38 were found to be equal (within 1 mGy) on most instances, except for 35 fathers where the conception of the child occurred within three-months of exposure or during exposure. The arithmetic mean of gonadal DOB-38 doses was 227 mGy (median=11 mGy, range 0–4,080 mGy) and 8.5 mGy (median=1.0 mGy, range 0–550 mGy) for fathers and for mothers, respectively. Gonadal doses varied considerably depending on the exposure pathway, the highest gonadal doses being received during the cleanup mission (mean doses of 376 mGy and 34 mGy for fathers and mothers, respectively), followed by exposure during residence in Pripyat (7.7 mGy and 13 mGy), and during residence in other settlements (2.0 mGy and 2.1 mGy). Stochastic simulations were used to estimate the parental gonadal doses and associated uncertainties. The geometric standard deviations (GSDs) in the individual parental stochastic doses due to external irradiation during cleanup mission varied from 1.2 to 4.7 (mean of 1.8), during residence in Pripyat varied from 1.4 to 2.8 (mean of 1.8) while the mean GSD in doses received during residence in settlements other than Pripyat were 1.3 and 1.4 for external irradiation and ingestion of 134Cs and 137Cs, respectively.
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TAM-A1.3
10:00 Dose reconstruction in the village of Metlino, Techa River region, Southern Urals, Russia M Hiller*, Independent Researcher
; C Woda, Helmholtz Zentrum München; M Degteva, Urals Research Center for Radiation Medicine; N Bugrov, Urals Research Center for Radiation Medicine; B Napier, Pacific Northwest National Laboratory
Abstract: The village of Metlino, located 7 km downstream from the nuclear facilities of Mayak, Southern Urals, Russia, was only evacuated years after the contamination of the Techa River had started. Thus, the inhabitants received considerable doses from the contaminated water and banks of both the Metlinsky Pond and the Techa River. A dosimetry system, the Techa River Dosimetry System (TRDS) 2016, describes the dose attributed to inhabitants living in settlements alongside the Techa River. Dose reconstruction in the village of Metlino is a crucial step in the validation of the TRDS 2016 and has so far been accomplished for the external exposure due to the Techa River banks and floodplains using the church tower as a dose archive (Hiller et al. 2017). A similar validation study for the exposure due to the Metlinksy Pond was carried out (Hiller et al. 2021).
To perform the latter study, dose and dose rate measurements in bricks from the granary and in the area in front of the granary have recently been published (Woda et al. 2020). For the validation of the TRDS, these experimental data are combined with Monte Carlo simulations of the present day and historic exposure geometries, in order to reconstruct the integral air kerma at the shoreline of the Metlinsky Pond.
This presentation will show results of the dose reconstruction study and give an update on the current state of the dose reconstruction process for the location of the granary in Metlino and discuss current challenges.
References:
Hiller et al. (2017) External dose reconstruction for the former village of Metlino (Techa River, Russia) based on environmental surveys, luminescence measurements, and radiation transport modelling. Radiat. Environ. Biophys. 56, 139-159.
Woda et al. (2020) Luminescence dosimetry for evaluation of the external exposure in Metlino, upper Techa River valley, due to the shore of the Metlinsky Pond: a feasibility study. J. Env. Rad 214-215.
Hiller et al. (2021) External dose reconstruction at the shore of the Metlinsky Pond in the former village of Metlino (Techa River, Russia) based on environmental surveys, luminescence measurements and radiation transport modelling. Radiat. Environ. Biophys, online.
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TAM-A1.4
10:15 Reconstruction of Organ Dose from Emergency Work Dose at Fukushima: J-EPISODE H Furuta*, Radiation Effects Association
; S Kudo, Radiation Effects Association; S Saigusa, Radiation Effects Association
Abstract: J-EPISODE, a Japanese nuclear worker cohort study, has developed organ dose conversion coefficients from dosimeter readings for normal work dose, following the established methods adopted by International Agency for Research on Cancer 15-Country Collaborative Study. Emergency work doses derived from the Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 were provided as the sum of external and internal emergency doses by fiscal year (FY; April to March) and worker. Challenges for reconstructing organ dose for risk analysis were as follows; 1) partitioning into external and internal doses, 2) disaggregation of internal doses evaluated in committed doses into doses derived from intake of I-131 and Cs-137, and 3) conversion from committed doses to annual internal doses. Partitioning was conducted using a sample of ad-hoc lifting designation records, which included detailed dose history, but was not available for those keeping to work. ICRP CD1, Database of dose coefficient, was used for conversion from committed doses to annual internal doses. To compliment lack of information, several assumptions were employed; 1) for external exposure, the photon energy and geometry distribution was the same as those of normal work, 2) intake of I-131 and Cs-137 was conducted at the first day of emergency work based on the conservative acute exposure scenario by the Ministry of Health, Labour and Welfare; on 12 Mach 2011 for committed doses in FY 2010 and on the first April 2011 for those in FY2011, and 3) the amount of intake of I-131 and Cs-137 were proportional to those concentrations in the air. As a result, the emergency work external dose was halved from 19 mSv in FY2010 to 11 mSv in FY2011, and the internal dose was reduced by about one-tenth, from 10 mSv to 0.7 mSv. The internal dose in March 2011 was mostly derived from I-131, and since most of it was accumulated in the thyroid gland after inhalation, the effect on other tissues/organs doses was smaller than the effective dose coefficient by two orders of magnitude. Except for the thyroid gland, the contribution of emergency work doses on the specific cumulative organ-absorbed doses was limited. J-EPISODE will use organ-absorbed doses including both normal and emergency work doses for the coming risk analysis. This study was funded by Nuclear Regulation Authority, Japan.
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