Results of long-term monitoring of cancer in different groups of ukrainian population affected by Chernobyl accident

To perform analysis of time-trends of cancer incidence rate in different group of Ukrainian population affected by Chernobyl accident there were utilized two main sources of information: - Data of local cancer register established in 1987 and covered 150000 population living in the most contaminated with radionuclides areas close to Chernobyl (retrospective since 1980 and on-going study). - Data of the State register of persons affected by Chernobyl accident (sample of 84000 clean-up workers 1986-1987 and 50000 evacuees from Pripyat city and 30 km zone). This category of affected people have received different dose of radiation. Mean dose of clean-up workers 1986-1987 evaluated in 150-170 mSv, evacuees from Pripyat city - 13 mSv, 30 km zone - 24 mSv respectively, and for residents contaminated areas expected mean dose during the life could be varied in range of 80-400 mSv. There is a very significant risk of thyroid cancer due to exposure to radioactive iodine especially in childhood. Collective absorbed thyroid dose in children of the Ukraine are 400000 man-Sv and in 8 most contaminated with radionuclides districts - 57000 man-Sv that is 14.2 % of collective dose of all children of Ukraine. 12 years after accident cancer incidence time trends in population still living on contaminated areas have slow increase. Comparative analysis of standardized incidence ratio (SIR) three groups of affected people in 1990-1993 and 1994-1997 have shown only significant increase in clean-up workers 1986-1987 in 1990-1993. A very pronounced peculiarities of times trends were found in evacuees: increase of incidence rate in young age in contrast with lack of significant increase for rest of evacuees. As to individual sites of cancer it should be noted significant increase thyroid cancer incidence in three group of population especially in evacuees. Observed number of thyroid cancer cases in this group exceeded expected one in 3-5 times. (authors)