Cancer Mortality Among Techa Riverside Residents (Southern Urals). Chronically Exposed to Radiation During the Prenatal Period and in Childhood

Imperfect technology and lack of management and utilization facilities for reprocessing liquid waste released by the Mayak PA resulted in a protracted combined (external and internal) environmental radiation exposure of the population resident on the banks of the Techa River. The followup of 8.640 subjects exposed during the prenatal period and in childhood covered the period of 49 years (1.1.1950-31.12.1998), the total person-years under observation amounted to 222,686. From 1950 through 1998 1,231 death cases were registered in the catchment area (5 raions in Chelyabinsk OBlast through which the Techa flows). In 70 cases death was caused by solid cancers, and in 12 cases by leukemia. Analyses of solid cancer mortality yielded higher rates for men as compared to women (p<0.001). No significant differences in death rates were observed between different ethnic groups (Slavs vs Tartars and Bashkirs). A statistically significant increase in solid cancer mortality with attained age was shown (p<0.001). The age at first exposure was demonstrated to be a factor modifying the solid cancer mortality rate (p=0.049). The highest risk of death from solid cancers was manifested by persons whose exposure started in the prenatal period or at the age under 5 years. There were 4.6 excess cases in this group of 30 observed solid cancer cases, whereas in the group including subjects aged 5 years or older at first exposure only 1 excess case was registered among the 40 observed cancer cases. The obtained leukemia mortality ERR value (CLL excluded) was 7.76, p=0.09. The excess leukemia death was found to be 7.6 out of of 10 observed cases. The analysis performed should be regarded as a preliminary one, taking into account the need to further extend the followup of the cohort and a potential verification of dose estimates in the future. (Author) 11 refs