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Radon concentrations in air and water in the thermal spas of ischia island M. Pugliese, M. Quarto and V. Roca Indoor and Built Environment published online 22 April 2013 DOI: 10.1177/1420326X13480053 The online version of this article can be found at: http://ibe.sagepub.com/content/early/2013/04/16/1420326X13480053

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Indoor and Built Environment

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Radon concentrations in air and water in the thermal spas of ischia island

Indoor and Built Environment 0(0) 1–5 ! The Author(s) 2013 Reprints and permissions: sagepub.co.uk/ journalsPermissions.nav DOI: 10.1177/1420326X13480053 ibe.sagepub.com

M. Pugliese1,2, M. Quarto1 and V. Roca1,2

Abstract The aim of the paper is to give information about radon concentration in air and in water of 16 thermal spas of the Isle Ischia to assess the corresponding mean effective dose for workers. Measurements of air radon concentration were carried out by means of Electret Passive Environmental Radon Monitor (E-PERM) devices in long-term configuration, while radon activity concentration in water was measured using the same detectors in short-term configuration. In each plant, several kinds of rooms of different uses (office, muddy room, massage room, relax room, aerosol, mud pit and medical treatment room) were selected. Results show a great variability among the measurements relative to the different kinds of rooms of the spas. In some cases, the dose received by workers was higher than 3 mSv/y, which is the effective dose limit for occupational exposure imposed by Italian legislation.

Keywords Radon, E-PERM, Thermal spas, Effective dose, Water, Ischia Island Accepted: 2 February 2013

Introduction Radon and its short-living decay products are the most important contributors to natural radiation exposure for general population. UNSCEAR 20001 estimates that the contribution from radon family exposure represents 50% of the indoor total effective dose. Because people spend most of their time in indoor spaces such as homes or workplaces, the measurement and limitation of radon concentration in these places are necessary.2 In Italy, the current law,3 by transposing the Euratom Directive 96/29,4 imposes the control and monitoring of radon concentration in various kinds of workplaces such as basements, mines and thermal environments. In particular, in spas environment, radon and its decay products have been considered as the main ionizing radiation exposure for both users and workers,5 therefore the radon in spas should be monitored. The main pathway through which the radon enters the spas atmosphere, where it can reach very high concentrations, is the radon water-borne transport. Radon concentrations in water vary on a wide range, from 0.1 Bq L–1 to 1,000 Bq L–1, and because radon is poorly soluble in water, about 70% of the gas is released in the air6 when thermal waters reach the surface inside a thermal spa. The aim of our study

was to measure the radon concentrations inside some thermal spas of the Isle Ischia and to assess the annual effective doses received by the workers. The Isle Ischia is situated to 35 km from Naples and it belongs to Phlegreo Archipelago and presents a surface area of 46.5 km2 and a maximum elevation of 787 m of Mt. Epomeo. From the geologic point of view, the island of Ischia has a volcanic character and it originated from various eruptions in approximately 150,000 years. Its territories is made up of both effusive (lava flow) and explosive volcanic products (green tuff, Citara tuff) whose composition is constituted mainly by trachybasalt to latite, trachyte, alkali-trachyte and phonolite.7 In Ischia, there are about seventy thermal spas that offer medical therapy services and they are the main tourism resources as well and for this reason, up today, 1

Dipartimento di Fisica, Universita` degli Studi di Napoli Federico II, Italy 2 Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Napoli, Italy Corresponding author: M. Quarto, Dipartimento di Fisica, Universita` degli Studi di Napoli Federico II, Complesso Universitario Monte Sant’Angelo, via Cinthia I-80126 Naples, Italy. Email: [email protected]




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we do not have any data regarding the exposure of workers to radon and its daughters. For reducing this lack of information, we carried out surveys in 16 of them. The results, consisting of radon concentrations in air and in water, are reported in this paper. Moreover the annual effective dose for workers has been evaluated.

Materials and methods Measurements of radon activity concentration in air Measurements were carried out in 16 thermal spas of Ischia whose location in the 6 municipalities (Lacco Ameno, Casamicciola, Ischia, Serrara Fontana, Forio and Barano) of the island is shown in Figure 1. The measurements of radon concentrations were not performed simultaneously in all 16 spas. Overall, the measurement campaign was carried out between October 2005 and March 2009. In any spa, the detectors were exposed for two consecutive periods whose total duration coincided with the opening period of each spa. All monitored rooms were located at underground level. Radon concentrations in air were measured using commercial E-PERM devices in long-term configuration (LLT) (Rad. Elec. Inc, Frederck, Maryland, USA).8,9 The E-PERM device consists of an ion chamber made with electrically conductive plastic. Inside, there is an electret which is a Teflon disk that has been electrically charged by a special process so that it may retain the charge permanently. Within the E-PERM chamber, the electret produces an electrostatic field

1

capable of attracting ions generated by the decay of radon gas and its decay products within the chamber. So the surface voltage of the electret decreases proportionally when the ions are collected on the electret. The change in voltage is determined by measuring the change in the superficial voltage of the electrets. The change in the surface voltage of an electret during an exposure period gives a measure of the time-integrated radon concentration in the E-PERM chamber during that period. Since the radon concentrations measured by E-PERM are sensitive to gamma radiation, it is necessary to evaluate and subtract the radon concentration equivalent background gamma in order to avoid any overestimation. The gamma dose rate Ggamma was measured at each site using a proportional counter (Berthold Technologies, Germany), the equivalent radon concentration was calculated using an adequate factor furnished by the manufacturer of the electrets devices (C3 in the following formula) and this value was subtracted from the measured total radon concentration to obtain the corrected value. In the monitored environments, the gamma dose rate ranged between 15 mR h–1 and 45 mR h–1. In order to know the radon concentration, the change of surface voltage of the electrets was measured by a dedicated electrometer (Rad. Elec. Inc., Frederck, Maryland, USA). Using appropriate calibration factors and considering the exposure time, the radon concentration was calculated using equations (1) and (2) as follows: CRn

ðVi Vf Þ ðGgamma C1 Þ 37 ¼ CF T

2

LACCO AMENO CASAMICCIOLA TERME 3

16 FORIO 14

4

5

15

6

7

SERRARA FONTANA 12

13

10

ISCHIA 8

9

BARANO 11

Figure 1. Map of Isle Ischia with the position of sites of measurement.


ð1Þ


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CF ¼ C2 þ C3 ðVi þ Vf Þ=2

ð2Þ

where Vi and Vf are the electret voltages before and after the exposure, respectively, T is the exposure time in days, Ggamma is the gamma dose rate in mR h–1 and C1 ¼ 0.137, C2 ¼ 0.02383 and C3 ¼ 0.0000112 are constants that are given by the manufacturer and they depend on the configuration and on the volume of the E-PERM chamber. The experimental uncertainty on radon concentration measured by E-PERM in LLT configuration is a function of the gamma dose rate, of the V value, of the calibration factor and its range was between 5% and 9% of the concentration value.

Measurement of radon activity concentration in water

ð3Þ

where B1 takes into account the delay period between the collection of the water sample and at the beginning of the measurement, B2 is the constant based on the analysis period and B3 is the ratio between the volume of the jar and the water sample.10 In particular, the constants B1 and B2 are given from equations (4) and (5): B1 ¼ eTD B2 ¼

TA 1 eðTAÞ

Annual effective dose calculation The annual effective dose for workers of thermal spas of Isle Ischia due to the exposure to radon indoor was calculated using equation (6) as imposed by Italian law: H¼CTD

Also for the measurement of the radon concentration in water samples, the method based on E-PERMs was used. A 130 mL water sampling bottle was used for this purpose. The sample was collected directly with the bottle, avoiding water bobbling and the consecutive radon lack. The bottle was placed without cap at the bottom of a glass jar of 3.72 L volume, and an E-PERM chamber with a short-term configuration (SST) was suspended over the water spread on the bottom. The jar was sealed and remained closed for 48 h. The radon was then left to reach equilibrium with its daughters. In this case, the measurement was based on the voltage difference produced by ionization in the jar’s air, on the gamma dose rate measured in the laboratory and on the radon concentration measured in the air inside the jar, normalized to the volume of the water sampled taking into account the values of the two volumes. Therefore, after measuring the radon concentration in the air using equation (1), the radon concentration in the water was calculated by multiplying CRn by the constants B1, B2 and B3 of equation (3) as follows: CRn ðwaterÞ ¼ CRn B1 B2 B3

where TD is the delay period between the time of collection of the water sample and the measurement starting time of the sample, TA is the measurement period from the time of inserting the sampling bottle into the jar until the E-PERM is removed and ¼ 0.1814 is the decay constant of radon in unit per day. The constant B3, which is the ratio between the volume of the jar and that one of the sampling bottle, in our case was equal to 29.

ð4Þ ð5Þ

ð6Þ

where C is radon concentration (Bq m–3), T is occupancy factor and D (3 109 Sv per Bq m–3) is dose conversion factor and it takes into account an average equilibrium factor between radon and its daughters of 0.4.11

Results and discussion The ranges of radon concentrations in air measured in the 16 spas of Isle Ischia are reported in Table 1. Approximately 46% of the total air 222Rn concentrations were found higher than recommended action level (500 Bq m–3) for radon concentration in underground workplaces given by Italian legislation.3 The results show a great variability among the measurements of radon concentrations measured in the spas. In particular, the highest concentration values were found in sites of Ischia and Casamicciola municipalities. With the exception of the site 9, the lower limits of the measured concentration ranges, although widely different, were very close to the action level given by the Italian law for the radon concentration in houses. On the contrary, the upper limits of these ranges were very high and, in some cases, were higher than the action level imposed by the Italian law for the radon concentration in workplaces. In Figure 2, the data grouped by the type of rooms are reported. Looking at the figure, there is a large gap between lower and higher limits of the concentration ranges measured for each kind of rooms. This suggests that the values of measured radon concentrations do not depend on the kind of rooms but on the way they are constructed and used. In particular, radon concentrations could be affected by different mode of ventilation of the rooms, different construction materials used, etc.: all these factors may have an influence on all kinds of environments in a transversal way.




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Overall, the results of the present work show higher values for radon activity concentrations than the ones of other reported surveys carried out in other countries. In the thermal baths of Riccione (Italy), Desideri et al.12 found that all radon concentrations in air

Table 1. Range of radon concentrations in air (Cair) and radon concentrations in water (Cwater) in thermal spas of Ischia Island. Measurement point

Cair (Bq m–3)

Cwater (Bq L–1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

53–532 122–259 264–2045 171–936 175–3417 68–1475 223–771 161–534 1404–3983 170–2522 109–468 120–599 44–908 52–697 30–456 667–998

19 3 31 3 21 3 21 3 13 2 71 54 4 71

17 1 11 1 98 13

varied in the range 6 – 70 Bq m–3 and in the same range were the values reported by Vaccari in some thermal spas of Emila-Romagna (Italy).12 Also results reported for 10 thermal spas in Croatia ranged between 10.9 – 109 Bq m–3 with an average value of 40.3 Bq m–3 13. Moreover, in the Slovenian spas, many radon concentrations were found to be lower than the ones reported here.14 On the contrary, two surveys carried out in Spain show concentrations of 222Rn in the range 3560 – 6650 Bq m–3 15 and 800 – 5200 Bq m–3 16 which were both higher than our results. In Table 1 are also the concentrations of radon in water measured in 11 spas. They varied among plants in the range 7 – 98 Bq L–1. All concentrations were below 100 Bq L–1 limit as imposed by Italian Law.17 Their range was comparable with the one of several studies in other countries.13 Voggianis et al. show similar radon concentration in thermal waters in Greece except that for 2 sites.18 Also Horvat et al. found radon concentration in water of northern Venezuela within the range of our results.19 Higher values were reported by many other authors of several countries.15,16,18,20 On the basis of the measurements in air, the average annual effective dose to workers due to radon exposure was estimated. Because effective dose depends on exposure period, it has been estimated on the basis of the times by which the workers stayed in the single environment. The annual effective dose ranges for the workers in different type of the rooms and their respective mean occupancy time for that room type are

4500 4000

Lowest value Highest value

Radom Concentration (Bq/m3)

3500 3000 2500 2000 1500 1000 500 0 Muddy room

Mud pit

Aerosol

Relax room

Message room

Figure 2. Lowest and highest concentration measurements for different kind of room.


Office

Medical treatment room


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Table 2. Effective doses to workers of the 16 spas of Isle Ischia.

Type of room

Range of effective dose (mSv/y)

Range of occupancy time (h)

Muddy room Mud pit Aerosol Relax room Massage room Office Medical treatment room

0.12–3.56 0.30–1.24 0.22–2.40 0.46–4.20 0.01–1.53 0.10–7.03 0.08–1.38

50–600 40–1404 99–600 50–819 50–1404 50–1040 50–1040

reported in Table 2. The effective doses due to radon inhalation varied from 0.01 to 7.03 mSv/y, and those of workers of muddy room, relax room and office are higher than the limit, 3 mSv, imposed by the Italian legislation.3

Conclusion Measurements of radon activity concentration in air and water of thermal spas of Isle Ischia were reported. The measurements in air were conducted using E-PERM detectors in long-term configuration (LLT) while measurements in water were conducted by the same detectors in short-term configuration (SST). The results show that in the majority of measurement points, the indoor radon air levels were lower than the Italian action level of 500 Bq m–3. Among the selected sites, the concentrations of radon in water present a large variability but all concentrations were below the limit of 100 Bq L–1 imposed by Italian law. Finally, the estimation of annual effective dose for workers was evaluated taking into account the working time and the measured radon concentration in air. References 1. UNSCEAR-2000. United Nations Scientific Committee on the Effects of Atomic Radiation Report to the General Assembly: Sources, effects and risks of ionizing radiation. United Nations, New York, 2000.

2. Risica S. Legislation on radon concentration at home and at work. Radiat Prot Dosim 1988; 78(1): 15–21. 3. Decreto Legislativo n. 241/2000: Attuazione della Direttiva 96/ 29/EURATOM in materia di protezione sanitaria della popolazione e dei lavoratori contro rischi derivanti dalle radiazioni ionizzanti. Italian Parliament, Rome, 2000. In Italian. 4. Euratom Directive, 26/96: G.U.C.E. 159, 26/6/1996. 5. Steinhausler F. Radon spas. sources term, doses and risk assessment. Radiat Prot Dosim 1988; 24(1): 257–259. 6. Nero AV and Nazaroff WW. Characterising the source of radon indoors. Radiat Prot Dosim 1984; 7(1–4): 23–29. 7. Frattini P, De Vivo B, Lima A, et al. Elemental and gamma-ray survey in the volcanic soil of Ischia Island, Italy. Geochem Exploration Environ Anal 2006; 6: 325–339. 8. Kotrappa P, Dempsey JC, Hickey JR, et al. An electret passive environmental 222Rn monitor based on ionization measurement. Health Phys 1988; 54(1): 47–56. 9. Kotrappa P, Dempsey JC, Ramsey RW, et al. A practical EPERM (Electret Passive Environmental Radon Monitor) system for indoor 222Rn measurement. Health Phys 1988; 58(4): 461–467. 10. Kotrappa P and Jester WA. Electret ion chamber radon monitors measure dissolved 222Rn in water. Health Phys 1993; 64: 397–405. 11. ICRP-65. Protection against Rn 222 at Home and at Work. ICRP Publication 65: Ann ICRP Vol. 23, No. 2, Oxford, Pergamon Press, 1993. 12. Desideri D, Bruno MR and Roselli C. 222Rn determination in some thermal baths of a central eastern Italian area. J Radianalyt Nucl Chem 2004; 261(1): 37–41. 13. Vaccari S. Indagine sull’esposizione al radon in alcuni stabilimenti termali dell’Emilia-Romagna: Proc of National Congress of Radioprotection; La Maddalena, 26-28-09-2001, 12–14. 14. Radolic V, Vukovic B, Smit G, et al. Radon in the spas of Croatia. J Environ Radioactivity 2005; 83(2): 191–198. 15. Vaupotic J and Kobal I. Radon exposure in Slovevian spas. Rad Prot Dosim 2001; 97(3): 265–270. 16. Soto J, Fernandez LP, Quindos LS, et al. Radioactivity in Spanish spas. Sci Total Environ 1995; 162: 187–192. 17. Decreto legislativo 31/01: Attuazione Direttiva 98/83/CE relative alla qualita` delle acque destinate al consumo umano. Italian Parliament, Rome, 2001. In Italian. 18. Voggianis E, Nikolopoulos D, Louzi A, et al. Radon variations during treatment in thermal spas of Lesvos Island (Greece). J Environ Radioactivity 2004; 75: 59–170. 19. Horvat A, Bohus LO, Urbani F, et al. Radon concentrations in hot spring waters in northern Venezuela. J Environ Radiactivity 2000; 47: 127–133. 20. Przylibski TA. 222Rn concentration changes in medicinal groundwaters of Laked Zdroj (Sudety Mountain, SW Poland). J Environ Radiactivity 2000; 48: 327–347.
