Biomedical subjects

T G Sazykina

Publications and source records attributed to T G Sazykina.

9 recordsLinked to original sources

PubMed2006

Mathematical simulation of dose-effect relationships for fish eggs exposed chronically to ionizing radiation.

A mathematical model which simulates the observed dose-effect relationships for fish eggs exposed to chronic irradiation is presented. The model assumes that the exposed fish eggs may exist in one of the following states: normally developing, reversibly damaged, and lethally damaged. Reversible damages may be recovered by repairing mechanisms which are spent for the repairing processes. The model was applied to describe the observed differences in effects of chronic exposure for quickly (2 weeks) and slowly (up to 20 weeks) developing fish eggs. Calculations were performed for dose rates of chronic irradiation ranging from 10 to 300 mGy/day. Two types of radiation effects were considered-the effect on eggs survival (percentage of survived eggs at time t), and the depletion of the repairing pool (in percentage of its maximal value). The model predictions have been compared with the experimental data from the EPIC database. This comparison showed that the model adequately describes the radiation effects in fish eggs of different species, within a wide range of chronic radiation exposures.

Animals↗

PubMed2005

Model testing using data on 137Cs from Chernobyl fallout in the Iput River catchment area of Russia.

Data collected for 10 years following the Chernobyl accident in 1986 have provided a unique opportunity to test the reliability of computer models for contamination of terrestrial and aquatic environments. The Iput River scenario was used by the Dose Reconstruction Working Group of the BIOMASS (Biosphere Modelling and Assessment Methods) programme. The test area was one of the most highly contaminated areas in Russia following the accident, with an average contamination density of 137Cs of 800,000 Bq m-2 and localized contamination up to 1,500,000 Bq m-2, and a variety of countermeasures that were implemented in the test area had to be considered in the modelling exercise. Difficulties encountered during the exercise included averaging of data to account for uneven contamination of the test area, simulating the downward migration and changes in bioavailability of 137Cs in soil, and modelling the effectiveness of countermeasures. The accuracy of model predictions is dependent at least in part on the experience and judgment of the participant in interpretation of input information, selection of parameter values, and treatment of uncertainties.

Cesium Radioisotopes↗

PubMed2005

Model testing using data on 131I released from Hanford.

The Hanford test scenario described an accidental release of 131I to the environment from the Hanford Purex Chemical Separations Plant in September 1963. Based on monitoring data collected after the release, this scenario was used by the Dose Reconstruction Working Group of BIOMASS to test models typically used in dose reconstructions. The primary exposure pathway in terms of contribution to human doses was ingestion of contaminated milk and vegetables. Predicted mean doses to the thyroid of reference individuals from ingestion of 131I ranged from 0.0001 to 0.8 mSv. For one location, predicted doses to the thyroids of two children with high milk consumption ranged from 0.006 to 2 mSv. The predicted deposition at any given location varied among participants by a factor of 5-80. The exercise provided an opportunity for comparison of assessment methods and conceptual approaches, testing model predictions against measurements, and identifying the most important contributors to uncertainty in the assessment result. Key factors affecting predictions included the approach to handling incomplete data, interpretation of input information, selection of parameter values, adjustment of models for site-specific conditions, and treatment of uncertainties.

Iodine Radioisotopes↗

PubMed2003

EPIC database on the effects of chronic radiation in fish: Russian/FSU data.

The paper presents the extraction of data from the EPIC database, outlining the effects of chronic radiation exposure in fish. The EPIC database 'Radiation effects on aquatic biota' is compiled as part of the current EC Project EPIC (Environmental Protection from Ionizing Contaminants in the Arctic). The EPIC database is based on information from publications in Russian (Russian/former Soviet Union data). The data are focused on the effects in fish at relatively low doses of chronic radiation exposure. The effects are grouped by three key endpoints: morbidity, reproduction, and mortality/life shortening. A preliminary scale of dose-effects relationships for fish has been constructed.

Animals↗

PubMed1999

International Arctic Seas Assessment Project.

The International Atomic Energy Agency responded to the news that the former Soviet Union had dumped radioactive wastes in the shallow waters of the Arctic Seas, by launching the International Arctic Seas Assessment Project in 1993. The project had two objectives: to assess the risks to human health and to the environment associated with the radioactive wastes dumped in the Kara and Barents Seas; and to examine possible remedial actions related to the dumped wastes and to advise on whether they are necessary and justified. The current radiological situation in the Arctic waters was examined to assess whether there is any evidence for releases from the dumped waste. Potential future releases from the dumped wastes were predicted, concentrating on the high-level waste objects containing the major part of the radionuclide inventory of the wastes. Environmental transport of released radionuclides was modelled and the associated radiological impact on humans and the biota was assessed. The feasibility, costs and benefits of possible remedial measures applied to a selected high-level waste object were examined. Releases from identified dumped objects were found to be small and localised to the immediate vicinity of the dumping sites. Projected future annual doses to members of the public in typical local population groups were very small, less than 1 microSv--corresponding to a trivial risk. Projected future doses to a hypothetical group of military personnel patrolling the foreshore of the fjords in which wastes have been dumped were higher, up to 4 mSv/year, which still is of the same order as the average annual natural background dose. Moreover, since any of the proposed remedial actions were estimated to cost several million US$ to implement, remediation was not considered justified on the basis of potentially removing a collective dose of 10 man Sv. Doses calculated to marine fauna were insignificant, orders of magnitude below those at which detrimental effects on fauna populations might be expected to occur. Remediation was thus concluded not to be warranted on radiological grounds.

Animals↗

PubMed1998

Environmental contamination and assessment of doses from radiation releases in the Southern Urals.

The Southern Urals in Russia was contaminated by radioactive discharges into the Techa River (1949-1956), the Kyshtym accident (1957), and the current releases and discharges from the Mayak Nuclear Materials Production Complex. In this paper, the consequences of radioactive contamination of the Ural region are analyzed. The current content of 90Sr in the components of food chains is as follows (Bq kg(-1) wet weight): potatoes, 0.2-6.7; grain, 0.5-12.6; milk, 0.2-6.3; beef, 0.2-1.7; lake water, 0.12-1.0; river water, 0.2-8.5; fish, 7-480; mushrooms, 400-1,100; and berries, 700-16,000. The content of 137Cs is as follows: potatoes, 0.5-3.8; grain, 0.3-2.9; milk, 0.2-4.5; beef, 0.3-2.6; lake and river water, 0.002-0.019; fish, 2-32; mushrooms, 110-1,600; and berries, 150. A major fraction of the dose to humans comes from the consumption of local food products, including natural ones, which have higher contamination levels than agricultural products. The average annual dose rates in contaminated areas are (0.5-4) x 10(-4) Sv y(-1), which is lower by a factor of 10(2)-10(4) than in the periods of "acute" exposure (1950-1951 and 1957-1958). Natural organisms received very high doses up to 200-800 Gy resulting from radioactive discharges into the Techa River and the radiation accident in 1957. In all cases, including the "acute" exposure followed by the chronic irradiation, the doses to biota were by a factor of 10-10(3) higher than those to humans.

Animals↗

PubMed1997

Current and potential doses from Arctic seafood consumption.

Current collective and individual dose rates to humans are estimated from the consumption of seafood harvested in the Arctic Seas. Statistical data on catches are used for the dose assessment, as well as observed data (1991-1994) on the radioactivity of marine biota. The actual collective dose rates to the world population are estimated to be: 2.7-4.5 manSv/year due to consumption of seafood from the Barents Sea, and 0.03 manSv/year-due to seafood from the Kara Sea. The contribution of 137Cs to the collective dose rate is about 90%. Current individual dose rates to high-rate consumers are estimated to be: 2.6 x 10(-6) Sv/year due to seafood from the Barents Sea; and 4.2 x 10(-6) Sv/year-due to seafood from the Kara Sea. The future radiological impact of the radioactive waste (RW) disposals in the Kara Sea is simulated for the period over 1000 years, using the regional box model of the Arctic Seas. The model predictions are made for three hypothetical scenarios of long-term radionuclide releases, prepared within the framework of the International Arctic Seas Assessment Project. The potential collective dose to world population truncated to 3000 AD is shown to be not higher than 0.13 manSv. The maximum individual dose rates from Arctic seafood consumption are estimated to be about 1.2 x 10(-7) Sv/year. The predicted doses are much smaller than the actual doses due to the current radioactive contamination of the Arctic Seas.

Animals↗

PubMed1996

Model testing using Chernobyl data: II. Assessment of the consequences of the radioactive contamination of the Chernobyl Nuclear Power Plant cooling pond.

The "Cooling Pond" scenario is designed to test models for radioactive contamination of aquatic ecosystems, based on data for contamination of different aquatic media and biota due to fallout of radionuclides into the cooling pond of the Chernobyl Nuclear Power Plant. Input data include characteristics of the cooling pond ecosystem (hydrological, hydrochemical, and hydrobiological conditions) and estimates of the amounts of 137Cs in the cooling pond. Predictions are requested in two stages: (1) calculations for 137Cs concentrations for comparison against actual measurements, including activities of 137Cs in the cooling pond water, in sediment layers, and in fish; and (2) calculations for which actual measurements are not available, including dose and risk estimates for aquatic biota and for humans following hypothetical consumption of contaminated biota. The latter calculations are intended to provide an opportunity for intercomparison among modelers of their results for a simulated assessment problem.

Animals↗

PubMed1993

Using a bank of predatory fish samples for bioindication of radioactive contamination of aquatic food chains in the area affected by the Chernobyl accident.

From the analysis of experimental data on radioactive contamination of various fish, it is suggested that predatory fish specimens can be used as bioindicators of radionuclide accumulation in reservoir food chains of the Chernobyl emergency area. The increased content of cesium radionuclides were detected in the muscle tissue of predatory fish collected in various regions of the Chernobyl emergency area. In most of the water bodies studied, maximum contamination levels of predatory fish by radionuclides of cesium occurred in 1987-1988, whereas in 'nonpredatory' fish the concentration of cesium was maximum, as a rule, in the first year following the accident. The exposure doses of fish of various ecological groups and ages are estimated. The exposure doses of various population groups, using fish from contaminated water bodies, are also estimated. When forming the environmental data bank for the Chernobyl accident zone it is suggested that perch, pike-perch and pike be used as bioindicators of radioactive contamination of food chains.

Accidents↗