RADON SURVEY IN KALAMATA (GREECE) Medicine, London SW7 2AZ U.K. Greece. Republic

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1 Radon in the Living Environment, 132 RADON SURVEY IN KALAMATA (GREECE) A. Geranios 1, M. Kakoulidou 1, Ph. Mavroidi 2, M. Moschou 3, S. Fischer 4, I. Burian 5 and J. Holecek 5 1 Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupoli , Athens Greece 2 Graduate student, Environmental Technology, Imperial College of Science, Technology and Medicine, London SW7 2AZ U.K. 3 Student at the Physics Department of the Athens University, Panepistimioupoli 15771, Athens Greece 4 Astronomical Institute of the Academy of Sciences, Bocni II 1401, 14131, Prague 4, Czech Republic 5 Institute for Testing and Disaster Medicine, Pribram-Kamenna Milin, Czech Republic A national radon survey is still lacking for Greece. Some Groups have done several more or less local or extended radon surveys and valuable experience has been gained (Anagnostakis et al. 1996, Papastefanou et al. 1997, Louizi 1997). After the first preliminary survey done by our group (Geranios et al. 1999) where 500 Kodak LR-115 etched-track detectors were placed in Greek schools and dwellings for one year, we continued indoor radon measurements by placing the same amount of detectors in a restricted area, covering the city of Kalamata, which is situated in the south of Peloponnese (a medium size city with of inhabitants). Although Kalamata was not of a special radon interest, the local authorities insisted on knowing for their citizens the level of this natural radiation. Our intention was at first, to use a different method of organisation and distribution of the etched-track detectors from the previous one (Geranios et al. 1999) attempting mainly to acquire more reliable results and to collect as much as possible detectors. Secondly, it was of great importance to test the statistics of the indoor radon concentrations for a rather small area and thirdly, to independently estimate the annual absorbed dose by children, taking into account both radon concentrations measured in their home and at school. The set of detectors readings (about 370), revealed, in general, lower values for Kalamata, compared with the ones found in the preliminary radon survey in Greece and almost all concentrations were found to be below the NRPB action level (200 ). Key words: Indoor radon measurements INTRODUCTION Due to the difficulties faced by the way the previous study was organised, in which we only got 56% only of reliable indoor radon concentrations, in the case of Kalamata we adopted another approach. A series of seminars, given to a group of 25 professors of physics, all inhabitants of Kalamata, teaching in the local schools, was held in order to prepare those people not only for the distribution and the handling of the detectors, but also to help them learn interesting issues on the radioactivity and the radon basic theory. The content of the seminars included among others, an introduction on the atomic and nucleonic structure, characteristics of corpuscular and electromagnetic radiation and their interaction with the matter, basic and multiple radioactivity, elementary dosimetry, basic theory of radon, experimental set up and organisation of radon surveys. We believed that a survey even in a such restricted area undertaken by qualified and trained people, could ensure the highest degree of success. About 80% of the detectors were collected and their readings are used for the present analysis. 1091

2 132 Radon in the Living Environment, TECHNIQUES-MEASUREMENTS In this survey we focused our attention on estimating the indoor radon concentration in schools (U.S.E.P.A. 1993). Due to the wide epoch variability of radon concentrations, it is evident that measurements be carried out over a long period of time. Therefore, we have left all the detectors measure for an entire year (Figure 1). The estimated effective dose can be strongly affected by additional uncertainties, such as the measurement technique (calibration and reproducibility, etching procedure), the location of the detector, the measurement period, and the dose-exposure conversion factor. The used parameters for the estimation of the effective doses, are shown in Table I. Arbitrarily, we have considered four categories of concentrations. Due to our intention for a better dose estimation for children, for those of whom we knew both concentrations in their school and at home, the occupancy factor was estimated separately. Taking into account the annual residence time of the children at school, we adopted an occupancy factor of 0.15 and the rest (0.5) from the total indoor residence time of 0.65, corresponds to the occupancy time at home. The occupancies were taken from the questionnaire. Tables II and III present the radon concentrations found in schools and at home, respectively and the corresponding doses as well. It should be emphasised that the dose absorbed by children in trancheobronchial region is twice as much as for adults. The Table IV, adapted from Cothern (1987). The age-dependent relative dose rate for exposure to airborne radon progeny is given and is used to calculate the mean annual distribution of effective dose taken by children (Figure 4). Since we did not receive the information to which schools all children go (but for 45 cases only), we calculated the effective doses by all children, taking the contribution of radon at home only (218 cases) and correcting doses according to their age (Table IV). This approach considers the occupancy at home only (0.5). In Figure 5 the distribution is shown. The mean effective dose received in schools (occupancy factor 0.15), increases by 0.45 msv the above distribution. CONCLUSION In our second indoor radon survey, we have tested the statistics in a rather restricted area by adopting a different practice from the one for the much larger area (Greece, Geranios et. Al., 1999), of technical organisation, distribution and collection of the radon etched-track detectors. The efficiency of this different technique was higher than the previous one getting back 80% of the initially distributed etched track. In addition, we estimated more accurately the dose absorbed by the children, by taking into account the different concentrations and occupancy factors in their school and at home. Figure 5, shows the distribution of the effective doses found in these cases. The most probable value is 200. For all children of whom we knew their age and the radon concentration at their home, we obtained a most probable mean annual effective dose of 2.4 msv/y. These estimations should be considered as the highest as the conversion factor used (5 msv per WLM) corresponds to an upper limit. 1092

3 Radon in the Living Environment, 132 Some extreme and very few cases can be faced with simple remedial actions. As a whole, Kalamata City does not exhibit large radon concentrations. The present analysis could be used as an experience for the future national radon survey in Greece, scheduled by the Greek Atomic Energy Commission. ACKNOWLEDGEMENTS We acknowledge the local authorities of the city of Kalamata supporting us with the necessary budget and the collaborating citizens, who participated to the seminars and had the responsibility of treating the detectors and keeping the corresponding data. These are alphabetically named: Angelopoulou R., Vassilopoulos D., Exarchakos G., Ilias S., Ilias M., Kliropoulos G., Kourla G., Kyriazis D., Malapanis A., Margelis S., Papadopoulos A., Papadopoulos I., Papazafeiropoulos Th., Roumeliotis G., Tsampoukos P., Dokaioulakos V. Especially, we are indepted to Koutsogiannopoulos V. for the final assistance to resume all data. REFERENCES [1] Anagnostakis M, Hinis E, Simopoulos S, Angelopoulos M. Natural Radioactivity Mapping of Greek Surface Soils. NRE VI, Environment International 1996; 22 Suppl 1: S3-S8. [2] Brill A. Radon Update. The Journal of Nuclear Med. 1994; 35: [3] Christofides S, Christodoulidis G. Airborne 222Rn Concentration in Cypriot Houses. Health Phys. 1993; 64: [4] Cothern C, Smith J. Environmental Radon. Plenum, New York, [5] Geranios A, Kakoulidou M, Mavroidi Ph, Fischer S, Burian I, Holecek J. Preliminary radon survey in Greece. Rad. Prot. Dosim. 1999; 81: [6] Geranios A, Kakoulidou M, Mavroidi Ph, Moschou, M., Fischer S, Burian I, Holecek J. [7] ICRP, Recommendations of the International Commission on Radiological Protection. Publication 65, Pergamon Press UK, [8] Jacobi W. The dose to the Human Respiratory tract by Inhalation of Shortlived 222 Rn and 220 Rn Decay Products. Health Phys. 1964; 10: [9] Louizi, A. Exposure of Greek Population from Indoor Radon Measurements. Presented at the 1 st Southeastern-European Regional Radon Workshop, Athens 3-5 April, [10] Papastefanou K, Stoulos S, Manolopoulou M, Ioannidou A, Charalambus S. Indoor Radon Concentrations in Greek Apartment Dwellings. 1 rst Southeastern-European Regional Radon Workshop 3-5 April 1997, Athens, Greece. [11] U.S.E.P.A. Radon Measurements in Schools. Office of Air Radiation Document. # E.P.A. 402-R

4 132 Radon in the Living Environment, Table I : Characteristic parameters for dose estimation Concentration, Number of measurements Mean Standard Deviation Occupancy factor Equilibrium Factor WLM Effective Dose 1, msv All factors are given annually. 1 Calculated by means of the dose conversion convention of ICRP65 Table II (Schools) : Characteristic parameters for dose estimation in schools Concentration, Number of measurements Mean Occupancy factor Equilibrium Factor WLM Effective Dose 1, msv All factors are given annually. 1 For children approximately (Jacobi 1964) Table III (Homes) : Characteristic parameters for dose estimation for children at home Concentration, Number of measurements Mean Occupancy Equilibrium Factor WLM Effective Dose 1, msv All factors are given annually. 1 For children approximately (Jacobi 1964) Table VI : The relative dose rate for different ages (218 cases) Age Years Ratio of rates to trancheob. Region * Percentage of children % Adult 1 * Those for adults. (Cothern 1987) 1094

5 Radon in the Living Environment, 132 Distribution of measuring time 30 Percentage, % Time, days Figure 1: The distribution of the measuring time of the detectors used 1095

6 132 Radon in the Living Environment, Percentage of Measurements, % Distribution of Radon Concentration (per 10 ) KALAMATA % Diff. Lognorm Concentration, Figure 2: The experimental and theoretically expected distribution (differential lognormal) 1096

7 Radon in the Living Environment, 132 Percentage of measurements, % Distribution of Radon Concentration (per 10 ) KALAMATA Acc. Lognorm % Acc Concentration, Figure 3: The experimental and theoretically expected lognormal distribution (For a better view, the accumulated theoretical curve is intentionally shifted vertically by 5%) 1097

8 132 Radon in the Living Environment, Figure 4: Distribution of the mean annual equiv. Dose absorbed by children 1098

9 Radon in the Living Environment, 132 All children at home 218 cases % Equivalent Dose, msv Figure 5: The yearly absorbed by children equivalent dose, estimated from the measured radon concentrations in their school and at home 1099

10 132 Radon in the Living Environment, 1100