Int. J. Environ. Res. Public Health 2009, 6 188 water and that external exposures were the same in 1950 and 1951 because approximately the same amounts of radioactivity were assumed to have been released. Analysis of historical monitoring data and modeling radionuclide transport in river water has shown both these assumptions to be wrong, causing overestimates of external doses. The decrease in exposure rate downstream was actually much greater than the decrease in radionuclide concentrations in river water and amounts of radioactivity accumulated in bottom sediments were significantly greater in 1951 compared to 1950 [30]. Further development of external dose reconstruction also included the decrease in doses that occurred with distance from the river banks and a reassessment of behavioral data. The indoor and outdoor dose rates in other areas of the villages were then estimated according to factors like distance from the shoreline and type of area (e.g. building, forest, garden or the street). The new estimates of external dose showed that approximately 80 % of the population received total doses of less than 0.1 Gy, as opposed to “old” calculations where only 25 % received doses less than 0.1 Gy [39]. Table 5. Percentage of about 30,000 ETRC members within different total dose ranges to different organs from 1950 to 1990. (from [39]). Organ RBM BS LLI ULI SI ST Testes Ovaries Uterus ≤ 1 mGy 7.9 9.0 11 12 14 14 13 16 15 1-10 mGy 12 9.5 12 16 56 58 59 58 58 10-100 mGy 23 13 44 54 22 20 20 20 20 100 mGy-1 Gy 55 57 34 18 7.7 7.6 8.2 7.1 7.1 > 1 Gy 1.7 11 - - - - - - - The distributions of total dose accumulated through 1990 for about 30,000 members of ETRC are presented in Table 5 (RBM - red bone marrow; BS - bone surface; LLI and ULI - walls of the lower and upper parts of the large intestine; SI - the wall of the small intestine; ST - stomach wall). 2.4. Current Doses Early assessments of average intake of 90Sr and 137Cs in Muslyumovo and Brodokalmak in 1999 are presented in Table 6. Corresponding estimated internal doses for different ages are presented in Table 7 [25].