Supervisors: Enn Realo University of Tartu, Institute of Physics; Rünno Lõhmus, Institute of Physics, University of Tartu
Opponents: Tõnu Viik, Senior Research Associate of Tartu Observatory; Raimo Mustonen, Deputy director in Radiation and Nuclear Safety Authority, Finland
For assessment of the dose to Estonian population there is a need to assess the doses at least from the all major components. Several dose components have been assessed; however in the current study the following additional components were assessed:
• 210Pb content was measured using aerosol airfilter samples. An arithmetic mean value was estimated to be 0.37 mBq m-3, which is slightly higher than those expected at a location of comparable latitude and longitude. The annual dose due to this component is of the order of 0.09 mSv. Dose caused by 210Pb in the air is determined mainly by the ingestion pathway.
• Radionuclides naturally occurring in building materials may significantly contribute to the annual doses. During the study 53 samples of commonly used raw materials and building products were collected and measured. Their mean values were in the ranges 7-747 Bq kg-1 for 40K, 4.4-69 Bq kg-1 for 226Ra, and 0.8-86 Bq kg-1 for 232Th. The activity index I in the 53 different building materials varied from 0.02 to 0.74 and the radium equivalent, from 6 to 239. The average annual dose for the people, caused by the building materials of dwellings was estimated to be in the range from 0.16 mSv to 0.44 mSv.
• Radiocaesium in the environment is caused from nuclear weapons testing and Chernobyl accident fallout. The deposition and vertical depth distribution of 134Cs and 137Cs in the natural undisturbed soil profiles down to 20-25 cm were studied at locations in the North Eastern Estonia, which were most strongly affected by the Chernobyl fallout in 1986. The average annual dose from radiocaesium was estimated to be 0.0009 mSv.
Taking into account the previous studies about the components of the dose to Estonian population and adding the results of the current study, we can conclude that the average annual dose to member of the public is 3.23 mSv. There is only one major component missing from this assessment and this is doses due to the medical exposures.