1 IL9806382 EXPOSURE OF GREEK POPULATION FROM RESIDENTIAL RADON - LATEST RESULTS

A.Louizi*. D.Nikolopoulos*, V.Koukouliou*, E.Lobotesi*, E.Mavroudaki*,S.Madisson **, M.Chanioti**, M.Yiakoumakis*. C.Proukakis *, * Medical Physics Department University of Athens., **School of Chemistry Physics and Radiography, Division of Physics,University of Portsmouth England

During the last decade the Medical Physics Department-University of Athens (MPD-UOA) has performed radon measurements in greek dwellings using passive methods (Louizi et al., 1994, Nikolopoulos et al.,1997). The MDP-UOA has measured about 1,500 dwellings at different locations in Greece. The duration of the measurements was 6 or 12 months. The detectors were installed in the bedroom, at ground floor or first floor if possible, although in same cases in the area of greater Athens, measurements of upper floors have also been performed. The MPD-UOA has designed a radon survey project which is in progress (Nikolopoulos et al. 1997). As part of this project the geographic region of Kriti (-5% of the total area of Greece, 5% of the Greek population) and the geographic region of Greater Athens (-0.4% of the total area of Greece, ~ 30% of the Greek population), have been fully surveyed. The minimum concentration occured from the measurements of MPD-UOA was 3 Bqm3 - at the region of greater Athens - and the maximum was 1291.3 Bqm3, at the area of Arnea . Except from the above areas/regions, other locations in Greece have been or beeing surveyed too. Table 1 gives the results of a set of 797 measurements available.

Table 1. Radon measurements in Greece Geographic Region Area Detectors Mean Min Max Makedonia 10 51.4 25.9 88.9 Domatia Dramas 36 132.9 7.4 492.1 Arnaia Chalkidikis 34 206.1 25.9 1291.3 Thesaloniki 9 90.3 22 188.7 Litochoro Pierias 18 41.8 19.7 96.5 Leptokarya Pierias 14 41.7 20.3 137.4 Ipiros 18 89 25.9 595.1 Thessalia 26 44.2 18.5 64.6 Rest of Central Tithorea 11 178 54.6 500 Greece & Evia Polidroso 11 52.2 37.5 88.2 Agean Islands 8 41.3 20.8 59.3 46 57.7 37 199.8 Limnos 9 87.6 29.6 307.1 Mitilini Lesvou 10 59.6 11.1 321.9 Peloponnisos Molaoi Lakonias 7 25.5 11.1 44.4 Megalopoli 4 26.9 25.9 37 Tripoli 13 60.9 22.2 270.1 Sparti 12 36.4 18.5 92.5 Pyrgos 17 27.4 9.4 53.8 Greater Athens Greater Athens $ Pireas 125 25.4 3 203.3 Laurio Attikis 161 38.5 2.3 260.7 Kriti Xania Department 53 60.4 9 500 Rethimno Department 27 38.7 10 126 Iraklio Department 88 37.1 8 160 Lasithi Department 30 35.2 14 106

It is observed that there is a great scatter in the average concentrations between different locations of measurements. It is also seen, that in the northern Greece (Makedonia, Ipiros), elevated concentrations seen to occur. Interesting case is that of Arnea Chalkidikis. Two sequential groups of measurements had been performed there

-289- and in both cases high concentrations were found. This fact is also seen from the high average of this area. It is possible that this is a radon prone area, but conclusion can not be drawn out due to the limited number of measurements. Similar is the case of Domatia Dranas. Many dwellings there were found with elevated cocentrations. It is mentioned that these two areas lie in a region where uranium rocks exist. In all other cases the concentrations lie far below the upper limit of 400 Bqnr3. This was also verified for the results of the fully surveyed regions, of Greater Athens and Kriti. Table 2 gives the frequency distribution from the measurements of MPD-UOA. The distribution appears to be lognormal. Assuming that in each dwelling a fixed number of persons live, it can be drawn out the only 1.1% of the Greek population is exposed to concentrations above 400 Bqm3 , which is the commonly adopted limit for existing dwellings. Considering that these data do not constitute a national survey yet, it is expected that this number will be smaller after the national survey. This is verified by the surveys of Greater Athens and Kriti. It is worth to mention, that according to the international experience, groups of dwellings are always found, in which elevated indoor radon concentrations occur. The inhabitants of the above dwellings, receive elevated lung doses. This may occur in Greece too, but the only way to locate these groups of dwellings is through a national survey.

Table 2.Frequency distribution of radon measurements in Greece Measurement results of Radon Concentrations in Greece Concentration Number of dwellings Frequency Bqm-3 0-20 200 25.1 21-40 279 35.0 41-60 150 18.8 61-80 52 6.5 81-100 29 3.6 101-150 41 5.1 151-200 24 3.0 200-400 13 1.6 >400 9 1.1

Various values of the conversion factor from indoor radon concentration to effective dose equivalent, have been proposed. A commonly used value is that proposed by CEC and NRPB, 0.05 mSv/ Bqrrr3 y of mean annual indoor radon concentration. Using this value and the data of the preccedent table, it can be drawn out about 100,000 (1%) people, according to the up to day data, are expected to receive doses above 20mSv/y. This dose is received by lung tissue. The maximum acceptable lung dose proposed by ICPR is 50 mSV/y. It is concluded from the existing data, that Greece does not seen to face a problem with radon, but a national survey should be carried out, in order that to be verified.

Louizi A., Koukouliou V., Proukakis C. (1994), A last report of Radon Concentration Studies in greek dwellings, Proceedings of the 1st Mediterrenean Congress on Radiation Protection, 5-7 April 1994, pp.398

Nikoiopoulos D., Maddison S., Louizi A., Proukakis C. (1997), Radon survey in Kriti- Greece. Design, implementation and results. Proceedings of the European Conference on Protection against Radon at Home and at work, Part II, pp 158-161

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