The aims of this proposal are:
1. to increase the quality and validate the doses from ionising radiation to those exposed as a consequence of the releases in the Southern Urals;
2. to increase the quality of follow?up for those exposed as a consequence of the releases;
3. to provide risk estimates for different outcomes after exposure to low levels of protracted ionising radiation thus reducing the uncertainty about health effects from low dose chronic radiation, including both environmental and occupational exposure.
In 1949, the production of plutonium for the Soviet Union nuclear weapons arsenal started in the closed city of Ozersk. The city is located 80 km. north?west of Chelyabinsk and 1200 km east of Moscow in the Southern Urals, Russia. The facility producing weapon grade plutonium is known as Mayak and comprised six uranium?graphite reactors. Metallurgical Pu?239 was produced through extraction from irradiated uranium in the radio?chemical plant. In 1950?1956 the radioactive waste from Mayak was released directly into the nearby Techa River and the period of highest exposure for those living along the river was 1951?53.
The study cohorts will be the workers at the Mayak nuclear facility and the children living along the Techa River. Data on exposure, vital status, and cause?of?death has been gathered for many years, in some instances since the 1950s, which makes it possible to use fairly unbiased information.
Nuclear energy is essential for the energy production in the European Union (EU) and will most likely be so in the future. The highest level of safety is required to protect population and environment in the normal operation process of nuclear installations or in the case of emergency situations. At present, occupational and population standards are set based on risk estimates extrapolated from high to low dose exposures, however, it remains uncertain whether biological effects in different dose ranges are comparable.
The social aim of the proposal is to estimate the impact on health on humans from ionising radiation. The major benefit from the project will be improved risk estimates for radiation?induced late health effects, which will permit safer and more efficient radiation protection practice and a better use of existing resources. The more sophisticated mathematical techniques will provide necessary tools for the radiation epidemiological risk assessment.
The results from these studies will help the scientific community to understand the effects of protracted exposure to ionising radiation on humans and give valuable information for future decisions in the field of radiation protection.
The following results have been reached;
A. In the Mayak workers, we found a strong relationship between lung cancer and -particle exposure due to incorporated plutonium. No suggestion of a departure from linearity or a threshold was given. A relative risk model with a multiplicative interaction between radiation and smoking fitted the data best. For both -particles and -rays the results of the analysis are consistent with linear dose responses.
B. For the Techa River Offspring cohort the so called late entrants have been added as a comparison group. These are the persons who first came to live in villages on the Techa River from 1953 through 1960 and they have, in most cases, received very low doses of ionizing radiation. Vital status and follow up has been extended. A total of 75 incident cancers have been found in the cohort.
C. In all, 195 and 32 cases of mental retardation have been identified in children exposed in childhood and in utero, respectively. There seems to be no influence of ionizing radiation on the risk of developing mental retardation.
D. The main achievements of the dosimetric work package have been that individual gonadel doses for the parents of the TROC members have been calculated using TRDS-2000 data. Using the concentration of 90Sr in cow milk in the period 1950-1979 fetal doses from the maternal skeleton has been calculated. Thirty-four tooth samples from the residents of the upper and middle Techa region have been selected for EPR measurements with tooth enamel. Eight samples of bricks extracted from the mill and the bell tower in the Metlino village located in the upper Techa region have been collected for the analysis of absorbed dose using luminescence method. Doses have been reconstructed.
E. Approximately 3,000 Swedish boys, treated with ionizing radiation for a skin haemangioma before the age of 18 months, were found to have a lower probability of attending the equivalent of high school and preformed worse at military intelligence tests if receiving brain doses above 80-100 mGy.
Funding SchemeCSC - Cost-sharing contracts