Releases of radioactive materials from the Mayak Production Association in 1949-1956 resulted in contamination of the Techa River; a nuclide of major interest was 90Sr, which downstream residents consumed with water from the river and with milk contaminated by cows' consumption of river water and contaminated pasture. Over the years, several reconstructions of dose have been performed for the approximately 30,000 persons who make up the Extended Techa River Cohort. The purpose of the study described here was to derive a revised reference-90Sr-intake function for the members of this cohort. The revision was necessary because recently discovered data have provided a more accurate description of the time course of the releases, and more is now known about the importance of the pasture grass-cow-milk pathway for the members of this cohort. The fundamental basis for the derivation of the reference-90Sr-intake function remains the same: thousands of measurements of 90Sr content in bone with a special whole-body counter, thousands of measurements of beta-activity of front teeth with a special tooth-beta counter, and a variety of other measurements, including post mortem measurements of 90Sr in bone, measurements of 90Sr in cow's milk, and measurements of beta activity in human excreta. Results of the new analyses are that the major intake started in September 1950 and peaked somewhat later than originally postulated. However, the total intake for adult residents has not changed significantly. For children of some birth years, the intake and incorporation of Sr in bone tissue have changed substantially.

During the years 1949-1952, the Mayak Production Association (MAYAK), which was processing weapons-grade plutonium, was discharging radioactive wastes into the Techa River. As a result, all components of the river system (water, bottom soils, and flood plains) were exposed to massive radioactive contamination. The protective measures taken in the 1950's resulted in the improvement of the radioecological conditions in the Techa River. After 1952, the radioecological conditions in the area were mostly determined by the long-lived radionuclides 9OSr and 137Cs. This article focuses on the dependencies governing the migration of radionuclides along the vertical and horizontal planes in different components of the river system over a 40-y period. Until the 1990's, a decrease in 90Sr and 137Cs contents was noted in environmental samples and foodstuffs produced in riverside villages. In the subsequent years, the radioecological situation on the Techa stabilized. The sources of the current contamination of the river are represented by the runoffs from by-pass canals and swampy upper reaches.

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The Techa River (Southern Urals, Russia) was contaminated as a result of radioactive releases by the Mayak plutonium production facility during 1949-1956. The persons born after the onset of the contamination have been identified as the "Techa River Offspring Cohort" (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general parent population to chronic radiation. The purpose of the present investigation is the estimation of (90)Sr intake from breast milk and river water in the period from birth to 6 months of life, necessary for an infant dose calculation. The investigation is based on all available data concerning radioactive contamination due to global fallouts and Mayak releases in the Southern Urals where extensive radiometric and radiochemical investigations of human tissues and environmental samples were conducted during the second half of the twentieth century. The strontium transfer factor from mother's daily diet to breast milk was estimated as 0.05 (0.01-0.13) d L(-1). Based on this transfer factor and data on (90)Sr water contamination, the average total (90)Sr intake for an infant born in the middle Techa River region was found to be equal to 60-80 kBq in 1950-1951. For the same period, calculations of (90)Sr intake using ICRP models gave values of 70-100 kBq. From 1952 onwards, the differences in intakes calculated using the two approaches increased, reaching a factor of 2-3 in 1953. The Techa River data provide the basis for improving and adapting the ICRP models for application to Techa River-specific population.

The East Urals Radioactive Trace (EURT) was formed after a chemical explosion in the radioactive waste-storage facility of the Mayak Production Association in 1957 (Southern Urals, Russia) and resulted in an activity dispersion of 7.4 × 10 Bq into the atmosphere. Internal exposure due to ingestion of radionuclides with local foodstuffs was the main factor of public exposure at the EURT. The EURT cohort, combining residents of most contaminated settlements, was formed for epidemiological study at the Urals Research Center for Radiation Medicine, Russia (URCRM). For the purpose of improvement of radionuclide intake estimates for cohort members, the following data sets collected in URCRM were used: (1) Total β-activity and radiochemical measurements of Sr in local foodstuffs over all of the period of interest (1958-2011; n = 2200), which were used for relativeSr intake estimations. (2) Sr measurements in human bones and whole body (n = 338); these data were used for averageSr intake derivations using an age- and gender-dependent Sr-biokinetic model. Non-strontium radionuclide intakes were evaluated on the basis of Sr intake data and the radionuclide composition of contaminated foodstuffs. Validation of radionuclide intakes during the first years after the accident was first carried out using measurements of the feces β-activity of EURT residents (n = 148). The comparison of experimental and reconstructed values of feces β-activity shows good agreement.Sr intakes for residents of settlements evacuated 7-14 days after the accident were also obtained from Sr measurements in human bone and whole body. The results of radionuclide intake reconstruction will be used to estimate the internal doses for the members of the EURT cohort.