RADON EXPOSURE DURING TREATMENT IN SOME THERMAL SPA CENTERS IN GREECE

Transcription

1 RADON EXPOSURE DURING TREATMENT IN SOME THERMAL SPA CENTERS IN GREECE D.Nikolopoulos 1, A.Louizi 1, E.Vogiannis 2, C.Halvadakis 2, A.Serefoglou 1 and E.Georgiou 1 1 Medical Physics Department, Athens University, Medical School of Athens, Athens, GREECE 2 Waste Management Laboratory, Department of Environmental Studies, University of the Aegean, Mytilene, GREECE INTRODUCTION Radon is a naturally occurring radioactive gas. It disintegrates into a series of short-lived decay products ( 218 Po, 214 Bi, 214 Pb and 214 Po). Worldwide, in various studies, radon and radon decay product activity measurements have been reported, namely in the field of radiation protection, epidemiology, environment, geology, hydrogeology etc. Many of these include measurements done in dwellings, while some report measurements in spa facilities. For the case of Greece, although several groups have reported measurements on indoor radon concentrations in dwellings (1-8), limited work has been published for the natural radioisotopes of the main Greek spas including radon (9-11). Radon ( 222 Rn) present in the spa facilities has been identified as an agent of additional radiation burden for bathers (12,13). Although some researchers have been concentrated on the health impact of radon activity transient increases due to water flow of domestically used water, limited work has been reported on this effect in spa facilities. The aim of this work was to study the exposure of bathers due to water flow under working conditions in some thermal spas in Greece. In Greece there exist 147 active spa facilities built in different places. One characteristic location is the city of Loutra Edipsou, located in the northern part of the Island of Evia which is populated by about 4, inhabitants. There are more than 8 hot water springs in the city of Loutra Edipsou with temperatures varying from 28 o to 86 o C. The city of Loutra Edipsou is one of the most visited spa centers in Greece attracting as many as 25. visitors yearly, at the peak of the tourist season. Another characteristic location is the island of Lesvos which is the third largest Greek island (163 km 2 ) located in the north-eastern part of the Aegean Sea. Geologically recent great volcanic activity, which took place in Lesvos, has contributed to the formation of many hot springs in different places, some of which are used as healing baths (thermal spas) equipped with appropriate spa facilities. All thermal springs in Lesvos are situated on active faults that act as channels for the ascent of thermal fluids and probably acquire their heat content through slow percolation at relatively deep levels within the crust. Water samples from these hot springs have been analysed in the past providing a large number of geological, hydrogeological, geochemical and geophysical data (14-16). However, other properties such as the concentration of radioactive elements in these waters are not known with the exception of some measurements taken in the early thirties (17). Moreover, no measurements of 222 Rn (radon) and of subsequent decay products have been reported for the spa facilities in Lesvos. The aim of the present work was to study the variations of radon, radon daughter and ambient atmosphere during treatment in the thermal spas of the city of Loutra Edipsou and of Lesvos Island to bathers. The city of Loutra Edipsou and Lesvos Island are presented in Fig 1. The thermal spas of Lesvos Island are built in the areas of Eftalou, Thermi, and Polichnitos.

2 MATERIALS AND METHODS Measurements of indoor radon in 1 spa of the city Loutra Edipsou and in another 3 of Lesvos Island are reported in this study together with measurements of attached and unattached radon daughter concentration in these spas. Moreover, we report coarse particle (>5nm) indoor concentrations for the spas of the Island of Lesvos. Two active instruments, namely one Alpha Guard PQ2 Pro of Genitron Ltd and one EQF323 of Sarad Instruments were used for indoor radon measurements. Attached and unattached daughter concentration was measured with EQF323. Coarse particle concentration measurements were performed by a GRIMM 1.14 Portable Dust Monitor. All instruments were purchased with calibration certificates provided by the manufacturers after controlled exposures in calibration facilities. Alpha Guard PQ2 Pro is based on an ionization chamber and measures radon by application of alpha spectrometric techniques. For indoor radon measurements, radon enters the ionization chamber by diffusion through a progeny preventing glass fiber filter and measured at a 1 minute data sampling cycle. For water radon and soil gas measurements, the gas is allowed to flow into the ionization chamber via a gas tight pump (Alpha Pump) and measured at a 1-minute cycle. EQF323 is an instrument, which measures indoor radon via a measuring semiconductor sensor installed inside a chamber and radon short lived progenies, via a progeny collecting filter and two semiconductor sensors installed inside two rotating measuring heads. This instrument can make separate measurements of attached and unattached progenies by properly rotating the measuring heads over the progeny collecting filter and a 5nm-mesh grid. GRIMM 1.14 Portable Dust monitor is an instrument based on laser beam scattering which measures the total number of coarse particles per unit volume. All spa facilities under study comprise mainly a treatment room (TR) but the rest of the building structure differentiates. Two special cases exist in Lesvos Island, namely that of Polichnitos and of one of the two existing in Eftalou. These spas have been used for therapeutic purposes since Byzantine era. The TRs of these spas are continuously ventilated via a number of small roof openings permanently open. The bathtub is filled once during a day. All other spa facilities were built during the last decade. The TRs of these spas contain bathtubs of about 1 m 3. They are filled and emptied during a time period of 2-4 hours. All rooms are ventilated through window openings. In one TR of each of the 4 spa facilities studied, we have simultaneously placed for 24 hours both Alpha Guard PQ2 Pro and EQF323. The aim was to approximately assess the radon exposure of a bather during treatment. Moreover, since a bather s preferences may determine natural ventilation of the TR and mixing of thermal and drinkable water during treatment, we have applied in one TR of a spa of the city of Loutra Edipsou, five protocols, the conditions of which are shown in Table 1. From measurements of radon daughter concentration, the Potential Alpha Energy Concentration (), the equilibrium factor (F) and the unattached fraction in terms of, f p, were calculated. in MeV/L was calculated (18) according to the equation 1: a u a u a u = 3.69 (C1 + C1 ) (C2 + C 2 ) (C3 + C3 ) (1) In this equation C j indicate the concentration in Bq/m 3 of the short-lived radon decay products. The subscripts 1,2 and 3 correspond to the species 218 Po, 214 Pb and 214 Bi respectively. The

3 superscripts (a) and (u) distinguish the state of radon progeny, as attached and unattached respectively. The equilibrium factor (F), which was defined as the ratio of the total potential alpha-energy for the actual 222 Rn progeny concentrations to the potential alpha-energy concentration of the progenies if they were in full equilibrium with the 222 Rn concentration (11), was calculated according (18) to the equation (2): F = (2) 34.64* C In equation (2) C is the 222 Rn concentration in Bq/m 3. The unattached fraction f p was defined as the fraction of, which is unattached and calculated according to the equation (3): u f = p (3) In equation (3) u is the calculated from equation (1) for the unattached progeny only. RESULTS AND DISCUSSION Fig. 2 presents two characteristic cases for the variations of radon that were recorded in the indoor environment of the TRs of two of the spa facilities studied. Fig 3 presents characteristic cases of variations of radon equilibrium factor and radon daughter concentration recorded by EQF323. Peaks and decreases in radon (Figs 2,3), coarse particles (Fig 2a) and daughter nuclei concentration (Figs 3b,c,d) are recorded. A time delay up to 4 hours (Fig.4) between radon peak, and F-factor concentration has been systematically observed for each progeny nuclei (19). The measurements performed in TRs of the spas studied are presented in Table 2. The measurement results in the TR of the spa of the city of Loutra Edipsou in which the protocols of Table 1 were applied, is presented in Table 3. The errors reported are at the 95% confidence interval. Elevated indoor radon concentrations were measured in the treatment rooms of the spas of Polichnitos, Eftalou and Loutra Edipsou. Remarkable is the fact that the mean radon and attached radon concentration during protocols 1 to 3 decreases, while non-significant variations are exhibited for these parameters concerning protocols 4 and 5. As found from our measurements, the unattached fraction was below.1 % for each daughter nuclei and thus almost all progeny nuclei attach to coarse particles at their generation (2). As can be seen from Table 2 Polichnitos and Eftalou had about 1 times increase in concentration as compared to Thermi and Loutra Edipsou. This finally cannot be attributed to the different filling process protocol or to the different ventilation. It may be attributed to the increased radon potential of Polichnitos and Eftalou (2). A possible explanation for the discrepancy among radon concentrations and daughter would be seen in references (19 2). As a conclusion, bathing in spas leads to intense variations of radon, radon daughter which consequently impose an additional health impact to bathers. As expected, mixing of thermal with non-thermal water may significantly reduce this health impact (Table 3 protocols 1-3). Opening doors and windows during treatment does not seem to contribute significantly (Table 3 protocols 4,5). The study is continued so as to investigate more spa centres in Greece. References 1. Papastefanou K, Stoulos S, Manolopoulou M, Ioannidou A, Charalambus S, Indoor Radon Concentrations in Greek Apartment Dwellings, Health Phys. 66(3), (1994)

4 2. Geranios A, Kakoulidou M, Mavroidi P, Fischer S, Burian I, Holecek J, Preliminary Radon Survey in Greece, Rad. Prot. Dosim. 81(1/4), (1999) 3. Ioannides K, Stamoulis K, Papachristodoulou C, A survey of 222 Rn concentrations in dwellings of the town of Metsovo in North-Western Greece, Health Phys. 79(6), (2) 4. Geranios A, Kakoulidou M, Mavroidi P, Moschou M, Fischer S, Burian I, Holecek J, Radon Survey in Kalamata, Greece, Rad. Prot. Dosim. 93(1/4), (21) 5.Nikolopoulos D, Louizi A, Koukouliou V, Serefoglou A, Georgiou E, Ntalles K, Proukakis C, Radon Survey in Greece-risk assessment, J. Environ. Radioact. 63(2), (22) 6. Papaefthimiou H, Mavroudis A, Kritidis P, Indoor radon levels and influencing factors in houses of Patras, Greece. J. Environ. Radioact. 66, (23) 7. Clouvas A, Xanthos S, Antonopoulos-Domis M, Long term measurements of radon equilibrium factor in Greek dwellings. Rad. Prot. Dosim. 13(3), (23) 8. Clouvas A, Xanthos S, Antonopoulos-Domis M A, Combination study of indoor radon and in situ gamma srectrometry measurements in Greek dwellings, Rad. Prot. Dosim. 13(3), (23) 9. Kritidis P, Angelou P, Concentrations of 222 Rn and its short-lived decay products at a number of Greek radon spas, Nuc. Instr. Meth. Phys. Res. B17, (1986) 1. Danali-Cotsaki S, Margomenou-Leonidopoulou G, 222 Rn in Greek spa waters: correlation with rainfall and seismic activities, Health Phys. 64(6), (1993) 11. Trambidou G, Florou H, Angelopoulos A, Sakelliou L, Environmental study of the radioactivity of the spas in the island of Ikaria, Rad. Prot. Dosim. 63(1), (1996) 12. Lettner H, Hubmer A K, Rolle R, Steinhäusler F, Occupational exposure to radon in treatment facilities of the radon-spa Badgastein, Austria. Environ. Intern. 22, (1996) 13. Vaupotic J, Kobal I, Radon exposure in Slovenia spas, Rad. Prot. Dosim. 97(3), (21) 14. Papastamataki A, Katsikatsos G, Thermal springs of Polichnitos. Report Institute of Geology and Mineral Exploitation Publication, (in Greek) (1969) 15. Papastamataki A The hot springs of Polichnitos. Report 1977 Institute of Geology and Mineral Exploitation Publication, (in Greek) (1977) 16. Papastamataki A, Leonis C, Geochemical prospecting for geothermal purposes, I. Lesvos district, Report 1982 Institute of Geology and Mineral Exploitation Publication, (in Greek) (1982) 17. Pertesis M, Mineral waters in the island of Lesvos. Geological survey of Greece, Ministry of National Economy, (in Greek) (1932) 18. Nazaroff W, Nero A V Radon and its Decay Products in Indoor Air. John Wiley & Sons, USA, (ISBN: ) (1988) 19.Vogiannis S, Nikolopoulos D, Louizi A, Halvadakis C, Radon exposure in the thermal spas of Lesvos Island, Rad Prot Dosim 111(1), 1-7 (24) 2. Vogiannis E, Nikolopoulos D, Louizi A, Halvadakis C, Radon variations during treatments in the thermal spas of Lesvos Island (Greece), J.Env.Radioac. 75, (24)

5 Fig 1. The city of Loutra Edipsou and Lesvos Island.

6 Fig 2. Characteristic variations of radon concentrations in TRs recorded by Alpha Guard 2 Pro in two of the spa facilities studied. (a) Eftalou new TR fully filled with thermal water and left filled for 7 hours. (b) Polichnitos old TR fully filled with thermal water for 24 hours emptied and filled again two times. In figure (a) the coarse particle concentration (PM-1) as measured by the GRIMM 1.14 Portable Dust Monitor is also presented. (2a) Rn concentration (Bq.m Rn-222 PM particles concentration (µg.m 16: 17: 18: 19: 2: 21: 22: 23: : 1: Time (2b) Rn concentration (Bq.m :4 2:4 2:4 8:4 14:4 2:4 2:4 Time Rn concentration 8:4 14:4 2:4 2:4 8:4 14:4

7 Fig 3: Characteristic variations of measurements in a TR performed with EQF 323 in the indoor environment of the TR of Fig 2a. (a) Radon concentration and equilibrium factor (F- factor). (b) Attached and unattached 218 Po concentration (c) Attached and unattached 218 Pb concentration (d) Attached and unattached 218 Bi concentration. (3a) 25 2 Radon F-factor,8,6 222 Rn (Bq.m 15 1,4 F-factor 5,2 22:25 1:25 22:25 1:25 Time (a) (3b) 6 Po-218 att Po attached (Bq.m 4 2 Po-218 unatt Po unattached (Bq.m 22:25 1:25 22:25 1:25 Time

8 (3c) Pb attached (Bq.m 4 2 Pb-214 att. Pb-214 unatt Pb unattached (Bq.m 22:25 1:25 22:25 1:25 Time (3d) 16 8 Bi-214 att. 214 Bi attached (Bq.m Bi-214 unatt Bi unattached (Bq.m 22:25 1:25 22:25 1:25 Time (d)

9 Fig 4. Selected curves for 222 Rn, and F-factor during undisturbed usual bath use indicate the time shifting of and F-factor peaks appearance related to 222 Rn peak. (a) Eftalou (b) Polichnitos and (c) Thermi. R 2 is the correlation coefficient of fitted curves that better describe the measured data. (4a) 4 Rn-222 2,5 222 Rn (Bq.m R 2 =,8337 R 2 =,7379 2, 1,5 1,,5, (µj.m Time (h) -,5 (4b) 12 Rn-222 1, 1 F-factor 222 Rn (Bq.m R 2 =,768 R 2 =,7828,5 (µj.m Time (h),

10 (4c) 222 Rn (Bq.m R 2 =,665 Rn-222 F-factor 1,,5 (µj.m 5 R 2 =, Time(h),

11 Table 1. Conditions of the protocols followed. TW and MW represent Thermal Water and Mixed Water respectively. The later refer to a 5% mixture of thermal and drinkable water. (i/i) Conditions 1 Windows closed Doors closed (2) Baths completely filled with TW 2 Windows closed Doors closed (1) Bath completely filled with TW 3 Windows closed Doors closed (1) Bath completely filled with MW 4 Windows opened Doors closed (1) Bath completely filled with TW 5 Windows closed Doors closed (1) Bath completely filled with MW

12 Table 2. Measurements performed in the TRs of the spas studied by EQF323. ND represents non-detectable activity. This table contains data corresponding to undisturbed daily use. Location 222 Rn (Bq m 218 Po attached (Bq m 218 Po unattached (Bq m Average concentration 214 Pb attached (Bq m 214 Pb unattached (Bq m 214 Bi attached (Bq m 214 Bi unattached (Bq m F (MeV/L) Polichnitos Eftalou ND Thermi ND L.Edipsou

13 Table 3. Measurements of indoor radon, daughter concentration in the TR of the spa of the city of Loutra Edipsou were the protocols of Table 1 were applied. The 1 st column represents the protocol number according to Table 1 Radon concentration (Bqm Daughter Concentration (Bqm (MeV L -1 ) Protocol ALPHA GUARD EQF323 Attached Unattached (x1 3 ) 64±6 63±5 3±1 95±6 81±4 1 54±6 53±5 17±9 98±6 63±3 2 43±5 38±5 139±4 133±8 48± ±4 35±5 93±5 41±3 34±2 5 26±4 31±5 88±5 58±4 33±2