Radiological conditions and risk quantifications in CIS. EU-CIS joint study project 2

The radiological conditions after the Chernobyl accident in the CIS republics Ukraine, Belarus and Russia have been evaluated for the period following 1991. Differential population distributions on dose rate or surface contamination density and differential mass distributions for milk on activity concentration of ¹³⁷Cs in milk have been used to calculate individual avertable and residual doses. The residual lifetime doses in the three republics with reference to the year 1991 have been calculated to be of the order of 30 mSv on average. The potential avertable individual lifetime doses are therefore less than the lifetime doses from the natural background radiation and less than 10% of the variation of the lifetime doses from natural background radiation in Europe. The corresponding residual individual lifetime risks have been calculated from the European ASQRAD model to be of the order of 0.06-0.14%, depending on age at start of exposure, and assuming an effective half-life of the annual exposure of 10 years and a dose and dose rate effectiveness factor (DDREF) of 2. A risk model is being developed in Russia for the assessment of risks to the exposed populations from atmospheric nuclear weapons tests in the Semipalatinsk region (Altai region) in the forties and fifties. Calculated age-dependent risks from an acute exposure of the Altai population have been compared with results from similar calculations with the ASQRAD model and reasonable agreement has been found between the two models.