Radiation Measurements 43 (2008) 1305–1314www.elsevier.com/locate/radmeas

Study of indoor radon and radon in drinking water in Greece and Cyprus:Implications to exposure and dose

Dimitrios Nikolopoulosa,∗, Anna Louizib

aDepartment of Physics, Technological Educational Institute of Piraeus, Petrou Ralli & Thivon str. 250, 12244, Aigaleo, Athens, GreecebMedical Physics Department, Medical School, University of Athens, Mikras Asias 75, 11527, Athens, Greece

Received 24 April 2007; received in revised form 13 November 2007; accepted 26 March 2008

Abstract

This paper reports passive and active radon concentrations in indoor air and drinking waters in Cyprus and Greece (Attica, Crete) togetherwith exposure–dose estimations. Passive indoor radon concentrations in Cyprus ranged between (14±3) and (74±6) Bq m−3 (arithmetic mean,A.M., 29.3 Bq m−3). Active indoor radon concentrations in Attica ranged between (5.6 ± 1.8) and (161 ± 12) Bq m−3 (A.M. 27.6 Bq m−3)and in Crete, between (1.7 ± 0.4) and (141 ± 12) Bq m−3 (A.M. 23.4 Bq m−3). The radon concentrations in drinking waters in Cyprus rangedbetween (0.3 ± 0.3) and (20 ± 2) Bq L−1 (A.M. 5.9 Bq L−1) and in Greece between (0.8 ± 0.2) and (24 ± 6) Bq L−1 (A.M. 5.4 Bq L−1).Radon is the main source of exposure and dose in both Greek and Cypriot population.© 2008 Elsevier Ltd. All rights reserved.

Keywords: Radon; Equilibrium factor; Unattached Fraction; Exposure; Dose; Indoor air; Drinking water

1. Introduction

Radon (222Rn) is a radioactive gas generated by the decayof the naturally occurring 238U series. Radon is present in soil,rocks, building materials and waters and escapes to the at-mosphere. Typical radon concentration outdoors are low (ap-proximately 10 Bq m−3) (UNSCEAR, 2000) and depend on thecomposition of the underlying soil and rock formation and onmeteorological parameters. In indoor environment radon con-centrates and may accumulate significantly. This accumulationdepends additionally on ventilation, heating and on water use(Nazaroff and Nero, 1988). Radon is the most significant natu-ral source of human radiation exposure from all natural sources(UNSCEAR, 2000) delivered mainly indoors. Therefore, themeasurement of indoor radon is important. Moreover, radon isa factor of stomach radiation burden due to water consumption(WHO, 1993). This burden is estimated by measurements ofradon concentrations in waters (US-EPA, 2000).

∗ Corresponding author. Palaion Polemiston 67, 12351, Agia Varvara,Athens, Greece. Tel./fax: +30 10 5612 071.

E-mail addresses: dniko@teipir.gr, dniko@teiath.gr,dnikolop@med.uoa.gr (D. Nikolopoulos), alouizi@gmail.com (A. Louizi).

1350-4487/$ - see front matter © 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.radmeas.2008.03.043

Due to the health impact of radon exposure, the reportingteam continuously measures radon. This paper focused on theradon exposure in Cyprus, the nearby Island of Crete and inAttica (Greece). Aims, methodology and implementation weredetermined by the published database and the movement pos-sibilities.

2. Materials and methods

2.1. Aims and measuring sites

To our knowledge, three studies reported radon mea-surements and exposure estimations for Cyprus. The first(Christofides and Christodoulides, 1993) reported 89 passivemeasurements, the second (Anastasiou et al., 2003) 84 activemeasurements and the third (Sarrou and Pashalidis, 2003)33 active measurements with 70 measurements of radon indrinking waters. Regarding Greece, the reporting team hascarried out an extensive indoor radon survey (Nikolopouloset al., 2002) with passive techniques. Other reports are alsopublished (Geranios et al., 1999; Papaefthymiou et al., 2003;Clouvas et al., 2003). To our knowledge, active indoor radonmeasurements are not reported for Attica or Crete. Morever,

1306 D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314

Fig. 1. Measurement sites of indoor radon and radon in drinking water samples in Cyprus (a) and Greece (Crete (b), Attica (c)).

the radon content of Greek potable waters is not reported andrelevant works (Vogiannis et al., 2004) focus on spa waters oron waters of certain high radon areas (Louizi et al., 2003).

The first aim was the repetition of the exposure estimationsdue to indoor radon in Cyprus through passive techniques. Pas-sive techniques were applied because these provide better an-nual estimations and because the most recent (2003) radon datain Cyprus employed active techniques only. The second aimwas the increase of sample size for Cyprus for indoor radon andradon in drinking waters through measurements at other timeperiods and, in some cases, at other locations. The third aim wasthe measurement of active indoor radon and radon in drinkingwaters in Greece. Attica was selected as the district where morethan 40% of the Greek population resides and Crete due to itsvicinity with Cyprus in the Mediterranean Sea; yet mainly be-cause it is the biggest Island of Greece, exhibiting very similarclimatic conditions and building profiles with Cyprus.

Towards the first two aims, passive indoor radon measure-ments in 50 buildings at 21 sites in Cyprus together with radonmeasurements of 40 ground, surface and tap water samplescollected from various sites (Fig. 1a) were conducted between2001 and 2003. Towards the third aim the indoor radon of129 buildings at 47 sites in Attica (90 buildings) and at 30 inCrete (39 buildings) was actively measured together with themeasurement of radon of 42 water samples collected from var-ious sites (Figs. 1b, c). Radon and progeny concentration mea-surements were also performed in 38 buildings in Attica and in2 in Crete. Measurements in Greece were conducted between2001 and 2004.

2.2. Devices and techniques

Passive measurements were conducted with a cali-brated radon dosimeter of overall uncertainty below 10%

(Nikolopoulos et al., 2002). One dosimeter was installed in thebedroom of each dwelling for 12 months similarly to protocolsfollowed in Greece (Nikolopoulos et al., 2002). Active in-door radon concentrations were measured using Alpha GuardPQ2000 Pro (AG) in 10-min measuring cycles (GenitronInstruments, 1998), whereas, indoor radon and progeny (at-tached and unattached) concentrations by EQF3020 (EQF) in2-h cycles (Sarad Instruments, 1998). In each dwelling AGand EQF were installed for one day or more. In parallel, airpressure was measured. Radon in water was measured by AGwith a special unit (Aqua Kit) as described by the manufac-turer (Genitron Instruments, 1997). Water sampling and trans-portation was performed according to published methodology(Louizi et al., 2003).

2.3. Exposure and dosimetric calculations

From the passive measurements the mean annual potentialalpha energy exposure (PAEE) rate (aPAAEr) (WLM y−1) andthe mean annual effective dose rate (aEDr) (mSv y−1) werecalculated by the equations:

aPAEEr = A0 · F · OF · ECF (1)

aEDr = A0 · F · OF · DCF · 8760 (h y−1) (2)

where, similarly to Greece (Nikolopoulos et al., 2002),A0 (Bq m−3) is the mean annual radon concentration, F = 0.4(ICRP, 1993) is the mean equilibrium factor, OF = 0.8(UNSCEAR, 2000) is the mean occupancy factor, andECF = 72 WLM y−1 per Bq m−3 and DCF = 6 nSv h−1 perBq m−3 are factors converting concentration to exposure andto dose rate, respectively.

From the active EQF measurements the potential alpha en-ergy concentration (PAEC) (MeV L−1), the equilibrium factor

D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314 1307

(F ) and the unattached fraction in terms of PAEC (fp) werecalculated within each 2-h measuring interval according to stan-dard definitions (Nazaroff and Nero, 1988):

PAEC =∑

x=a,u

(3.69 · Ax1 + 17.83 · Ax

2 + 13.12 · Ax3) (3)

F = 0.106 · (Aa1+Au

1)+0.513 · (Aa2+Au

2)+0.381 · (Aa3+Au

3)

A0(4)

fp = 3.69 · Au1 + 17.83 · Au

2 + 13.12 · Au3∑

x=a,u (3.69 · Ax1 + 17.83 · Ax

2 + 13.12 · Ax3)

(5)

Superscripts a and u distinguish the contributions of the twostates (attached, unattached) of radon progeny, subscripts 1, 2and 3 correspond to 218Po, 214Pb and 214Bi and A0, Ax

i (x=a, uand i = 1, 2, 3) (Bq m−3) are the concentrations of radon andprogeny, respectively. The numerator of (4) represents the equi-librium equivalent progeny concentration (EEPC) (Bq m−3).

From the whole active data set, average daily PAEE rate(dPAEEr) (mWLM d−1) and average daily effective dose rate(dEDr) (�Sv d−1) values were calculated considering these asadequate estimators of the corresponding daily variations dur-ing measuring intervals, according to the equations:

dPAEEr = PAEE

dt· 24 (h d−1) (6)

dEDr = EDr

dt· 24 (h d−1) (7)

(PAAE), EDr is the arithmetic mean (A.M.) of PAEE (mWLM)and effective dose rate (EDr) (nSv h−1) time series data. dt =�t, �t (h) is the measurement interval of EQF3020 (�t = 2 h)

and Alpha Guard 2000Pro (�t = 1/6 h). Time series PAEEvalues of EQF (PAEEEQF) and AG (PAEEAG) were calculatedaccording to:

PAEEEQF = PAEC · �t · OF · CF1 (8)

PAEEAG = A0(t) · �t · F · OF · CF2 · CF3 (9)

PAEC (MeV L−1) was calculated from (3) and A0(t) (Bq m−3)

is the measured AG radon concentration; both quantities con-sidered constant between t and t +dt, dt =�t, �t . As with pas-sive measurements OF = 0.8 and F = 0.4 (considered constantfor all intervals �t). CF1 = 4.446 × 10−8 (WLM/MeV L−1 h)

and CF3 = 173−1 (WLM/WLH) convert exposure units andCF2 = 3740−1 (WL/Bq m−3) converts EEPC (Bq m−3) toPAEC (WL). Time series EDr values of EQF (EDrEQF) andAG (EDrAG) were calculated according to equations:

EDrEQF(t) = PAEEEQF

�t· DCF1 (10)

EDrAG(t) = A0(t) · F · OF · DCF (11)

DCF1 = 6.1 + 42 · fp × 106 (nSv/WLM) (Porstendörfer, 2001)converts PAEE to dose. As with passive measurements OF=0.8,F = 0.4 and DCF = 6 nSv h−1 per Bq m−3.

From measurements of radon in drinking waters, the meanannual equivalent dose rate (aEDrw,s) (mSv y−1) delivered tostomach due to ingestion and the contribution to aEDr due toinhalation of radon in drinking water (Cw,i), were calculated as

aEDrw,s = Cw · Cr · DCF2 · 365 (d y−1) (12)

Cw,i = Aw

A0= Cw · f × 103

A0(13)

Cw (Bq L−1) is the radon concentration in drinking water, Cr=1(L d−1) is the average water consumption rate, DCF2 = 14.4 ×10−3 (mSv Bq−1) (EURATOM, 2001) converts concentrationto stomach dose, f = 10−4 (EML, 1990) is the mean transferfactor of radon released from water to indoor air and Aw =Cw ·f × 103 (Bq m−3) (Nazaroff and Nero, 1988) is the averageindoor radon concentration released from water use dependingon the water usage rate, the overall indoor air volume and rateof indoor air exchange.

3. Results

3.1. Radon concentrations

Passive indoor radon concentrations in Cyprus (Table 1)ranged between (14 ± 3) and (74 ± 6) Bq m−3 and distributedlognormally (P < 0.05, �2 test). The values may be consid-ered low, since the A.M. is less than the population weightedworld average of 39 Bq m−3 (UNSCEAR, 2000) and all con-centrations are well below the European Commission (1990)action level (400 Bq m−3). The low indoor radon concentra-tions in Cyprus are well justified by the geological underground(Tzortzis et al., 2003; Tzortzis and Tsertos, 2004) and the build-ing pattern of Cyprus which is combined with excellent ven-tilation (Sarrou and Pashalidis, 2003). No comparisons wereattempted between the various locations mainly due to the lim-ited number of measurements in each area.

Low concentrations have also been reported for Cyprus;however, at other ranges, e.g. 7–78 Bq m−3 (Christofides andChristodoulides, 1993), up to 35 Bq m−3 (Sarrou andPashalidis, 2003), 6.2–102.8 Bq m−3 (Anastasiou et al., 2003).The reported A.M., yet low, is significantly greater than theone published recently (7 Bq m−3, Sarrou and Pashalidis,2003, P < 0.001 (t-test), 19.3 Bq m−3, Anastasiou et al., 2003,P < 0.01 (t-test)). This could be attributed to the applied pas-sive techniques, which are advantageous due to averaging ofthe seasonal variations caused by the long measurement period.These variations introduce a source of bias that could yield tosignificant A.M. alterations (Papaefthymiou et al., 2003). In-deed in Sarrou and Pashalidis (2003) the measurement periodwas during summer and in Anastasiou et al. (2003) at scatteredtime intervals between September 2001 and May 2002. Thereported A.M. is also significantly greater (P < 0.001, t-test)than the A.M. (7 Bq m−3, Christofides and Christodoulides,1993) with passive techniques. The discrepancies could beattributed to the differences in the measurement devices in-volved, to the criteria of dwelling selection and probably to thechanges of the buildings in Cyprus during the last 15 years.

1308 D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314

Table 1Indoor radon concentrations in Cyprus with passive techniques

i/i District Area Number of Mean annual aPAEEr aEDrsamples concentration (Bq m−3) (WLM y−1) (mSv y−1)

1 Ammochostos Avgorou 2 15 ± 2 0.23 ± 0.02 0.26 ± 0.032 Derinia 4 29 ± 10 0.43 ± 0.15 0.49 ± 0.173 Liopetri 2 20 ± 2 0.29 ± 0.03 0.34 ± 0.034 Paralimni 5 74 ± 6 1.09 ± 0.08 1.24 ± 0.095 Sotira 2 38 ± 3 0.57 ± 0.05 0.65 ± 0.056 Frenaros 2 18 ± 2 0.27 ± 0.02 0.31 ± 0.037 Larnaka Axna 2 17 ± 2 0.25 ± 0.03 0.29 ± 0.038 Drosia 2 27 ± 2 0.39 ± 0.03 0.45 ± 0.049 Kato Lefkara 2 23 ± 2 0.35 ± 0.03 0.39 ± 0.04

10 Xylofagou 2 37 ± 3 0.55 ± 0.05 0.62 ± 0.0511 Pano Lefkara 2 20 ± 2 0.29 ± 0.03 0.33 ± 0.0312 Lemesos Larnaka Centre 3 24 ± 2 0.36 ± 0.03 0.41 ± 0.0413 Kato Polemidia 3 39 ± 10 0.6 ± 0.3 0.66 ± 0.3014 Lefkosia Dali 3 20 ± 2 0.29 ± 0.03 0.33 ± 0.0315 Kaimakli 2 14 ± 3 0.21 ± 0.05 0.24 ± 0.0616 Madkiatis 2 16 ± 2 0.24 ± 0.02 0.27 ± 0.0317 Palouriotissa 2 16 ± 2 0.23 ± 0.03 0.27 ± 0.0318 Patsia 2 33 ± 3 0.48 ± 0.04 0.55 ± 0.0519 Farmakas 2 53 ± 4 0.78 ± 0.06 0.89 ± 0.0720 Pafos Kato Arades 2 69 ± 5 1.02 ± 0.08 1.17 ± 0.0921 Polis Chrisochous 2 18 ± 1.8 0.27 ± 0.03 0.31 ± 0.03

Sum 50 A.M. (Bq m−3) 29.3 0.12 0.48S.D. (Bq m−3) 18.0 0.08 0.30G.M. (Bq m−3) 25.2G.S.D. 1.7

Presented errors are in the 95% confidence interval. Values of the aPAEEr and aEDr are also presented. Errors are calculated according to Eqs. (1) and (2).

Nevertheless, the number of measurements induces bias to theabove conclusions.

The passive indoor radon concentrations in Cyprus andGreece are of the same order (Geranios et al., 1999;Papaefthymiou et al., 2003). However, for comparisons un-der identical methodologies (Nikolopoulos et al., 2002, A.M.55 Bq m−3) these are significantly lower (A.M. 29.3 Bq m−3,P < 0.001, t-test). Similarly for Patra (Papaefthymiou et al.,2003), which is the third highest populated city in Greece,(A.M. 41 Bq m−3 for houses, 38 Bq m−3 for all dwellings).Moreover, passive indoor radon concentrations in Cyprus arelower than those reported for Crete (A.M. 43.4 Bq m−3, max-imum 500 Bq m−3) probably due to the higher radium con-tent of some selected areas (Apokoronas-Chania prefecture)(Nikolopoulos et al., 2002).

The results of the active indoor radon measurements inGreece are graphically presented in Fig. 2. The measurementintervals of AG ranged between (6 h, 10 min) and (196 h,10 min) and of EQF between 18 h and 382 h yet the major-ity corresponded to approximately 1–1.5 days. Concentrationresults of AG in 9 dwellings in Attica and in 6 in Crete ex-ceeded 100 Bq m−3. The 3 dwellings in Attica and 3 in Creteexceeded the level of 200 Bq m−3. The active indoor radonconcentrations in Greece are within the published range bothwith passive and active techniques and can be explained by thegeological background of Greece. All values are also withinthe international range and are significantly lower than thosefound in high radon areas in Greece (Louizi et al., 2003).

Concentration A.M. is significantly lower than the A.M. deter-mined with passive techniques (in both areas P < 0.001, t-test).This discrepancy may be attributed to the seasonal variations,as in the case of Cyprus, and the differences in the measuringmethodologies of AG, EQF and passive dosimeter. Yet this pa-per is the first attempt for the collection of such variation datain the capital of Greece (Athens–Attica) and in Crete. Further,the active indoor concentrations in Greece are higher thanthose of Sarrou and Pashalidis (2003) (A.M. 7 Bq m−3, S.D.6 Bq m−3) and comparable to those of Anastasiou et al. (2003)(A.M. 19.3 Bq m−3, S.D. 14.7 Bq m−3). Nevertheless, higherwere the maximum indoor concentration of Greece, since in9 dwellings in Attica and in 3 in Crete concentrations wereabove 100 Bq m−3 and in 3 in both areas above 200 Bq m−3

(all concentrations below 100, Sarrou and Pashalidis, 2003,1 above 100 Bq m−3, Anastasiou et al., 2003). However, thelimitations introduced by the diurnal variations of the activemeasurements and the sample sizein all previous works andthis, restrict the possibility of comparing areas in Cyprus andGreece. Moreover, since radon progeny concentrations havenot been reported for Cyprus no comparisons were attempted.

The variations of F and fp are presented graphically inFig. 3. The temporal profiles of the radon concentrations, Fand fp values did not differentiate systematically. As was ob-served from the total measurement set, the profiles presentedone or more peaks corresponding to maximum values, how-ever, of different magnitude and duration. The time of peakoccurrence was not within certain time intervals. The temporal

D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314 1309

Fig. 2. Graphical presentation of active indoor radon concentrations in Greece (129 buildings). Vertical lines represent the value range, the open circles theA.M. and the error bars the S.D. (95% confidence interval—C.I.). The uncertainties are due to instrument calibration and counting statistics.

profiles of two dwellings (i/i 35—Attica, 102—Crete, Fig. 2)are presented in Fig. 4. Both were the dwellings with the maxi-mum concentration measured with AG. The dwelling of Fig. 4bwas the one with the maximum A.M. concentration in Cretewith passive techniques (Nikolopoulos et al., 2002). As canbeen seen from Fig. 4b pressure decrease can be related to in-door radon concentration increases through pumping of radonfrom soil, yet this is not observed from Fig. 4a. Nevertheless,according to Fig. 4a the increase in the atmospheric pressureleads to radon clearance through, possibly, a reverse dwelling-to-soil pumping mechanism. Fig. 5 presents another case oftemporal variations of indoor radon, F and fp detected by EQFin the dwelling in Attica with the maximum measurement in-terval (382 h, i/i 73, Fig. 2). The peaks in F and fp may im-ply significant short-term exposures of the inhabitants at leastwhen combined in indoor radon concentration peaks. All tem-poral variations may be attributed to the differences in the ven-tilation, the overall practices followed by the inhabitants andthe geological background. Nevertheless, the detected tempo-ral variations of radon, F and fp are similar to those publishedin the literature (Mohamed, 2005).

Cw in Cyprus ranged between (0.3±0.3) and (20±2) Bq L−1

and in Greece between (0.8 ± 0.2) and (24 ± 6) Bq L−1

(Fig. 6). The highest concentrations were found in Protaras re-gion (Cyprus). No correlation with depth was found. This factmay be related to the small sample size. The concentrationsin Greece and Cyprus are of the same range and low, sinceall samples are below the EURATOM (2001) remedial actionrecommendation (100 Bq L−1). The results for Cyprus are

comparable with the range reported by Sarrou and Pashalidis(2003) yet samples presenting higher concentrations were de-tected. The discrepancies may be attributed to the differentmeasurement methodologies and may be justified by the re-stricted sample size. No comparisons between the differentregions were attempted. Following the US-EPA (2000) upperlimit for radon in water (11 Bq L−1), 5 water samples in Greeceand 2 in Cyprus presented higher radon concentrations. Nu-merous other samples presented concentrations near this limit.

3.2. Exposure and dose calculations

The aPAEEr and aEDr values due to indoor radon for Cyprusranged between (0.21 ± 0.05) and (1.09 ± 0.08) WLM y−1

and(0.24 ± 0.06) and (1.24 ± 0.09) mSv y−1, respectively(Table 1). The ranges are low and comparable to reportedranges (Anastasiou et al., 2003). The aPAEEr A.M. isabout 2.5 times lower than the value estimated for CentralEurope (1.2 mSv y−1). All values are approximately 40–60%of the values reported for Greece and about 70% of thecorresponding values for Crete (Nikolopoulos et al., 2002).Moreover, the aEDr values are high compared to the av-erage annual effective gamma dose rate range reportedfor Cyprus (0.001–0.0614 mSv y−1, Tzortzis et al., 2003,0.02–2.97 mSv y−1, Tzortzis et al., 2003). This fact indicatesthat indoor radon is an important source of radiation exposureof the Cypriot population.

EDrAG values (Fig. 7) ranged between (10.7 ± 3.5) and(310 ± 22) nSv h−1 in Attica and between (3.3 ± 0.7) and

1310 D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314

Fig. 3. Graphical presentation of (a) F and (b) fp active data measured with EQF (40 buildings). The number of measurement is identical to the one ofFig. 2. Vertical lines represent the value range, the open circles the A.M. and the error bars the S.D. (95% C.I.). The uncertainties are due to instrumentcalibration and counting statistics.

(271 ± 24) nSv h−1 in Crete. EDrEQF values ranged between(63 ± 31) and (890 ± 700) nSv h−1 in Attica. All values arecomparable to the outdoor effective gamma dose rates ofLesvos (Greece) (0.066–0.28 �Sv h−1, Petalas et al., 2005).The values are lower than the effective gamma dose ratesthat can be derived from the corresponding absorbed doserates using appropriate conversion coefficients (Clouvas et al.,2003; Petalas et al., 2005). AG dPAEEr values were in therange (0.066 ± 0.022)–(1.92 ± 0.14) mWLM d−1 in Attica

and (0.021 ± 0.013)–(1.68 ± 0.15) mWLM d−1 in Crete(Fig. 8). EQF dPAEEr values ranged between (0.101 ± 0.026)and (1.18 ± 0.05) mWLM d−1 in Attica. AG dEDr valuesranged between (0.257 ± 0.084)–(7.44 ± 0.54)�Sv d−1 inAttica and (0.080 ± 0.049)–(6.51 ± 0.57)�Sv d−1 in Crete(Fig. 8). EQF dEDr values ranged between (1.51 ± 0.74) and(21.4 ± 16.8)�Sv d−1 in Attica (Fig. 8). The temporal profilesof PAEE and EDr values differentiate according to the varia-tions of indoor radon, F and fp. As with indoor radon, PAEE,

D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314 1311

0

100

200

300

400

500

600

1014.5

1015.0

1015.5

1016.0

1016.5

1017.0

1017.5

1018.0

1018.5

1019.0Radon Concentration

Atmospheric PressureR

adon

Con

cent

ratio

n (B

q m

-3)

Rad

on C

once

ntra

tion

(Bq

m-3

)

Atm

osph

eric

Pre

ssur

e (m

bar)

Time

0

100

200

300

400

500

600

1004.0

1004.5

1005.0

1005.5

1006.0

1006.5

1007.0Radon Concentration

Atmospheric Pressure

TimeA

tmos

pher

ic P

ress

ure

(mba

r)

Fig. 4. Radon concentration and atmospheric pressure temporal variations in two dwellings in Attica (i/i 35, Fig. 2) and Crete (i/i 102, Fig. 2) withcorresponding radon error bars (95% C.I.). The uncertainties are calculated from Eqs. (4) and (5) according to the instrument calibration and counting statistics.

0.00.10.20.30.40.50.60.70.80.91.0

Time0

50

100

150

200

250Equillibrium FactorUnattached FractionRadon Concentration

F, fp

Concentration(B

q m-3)

Fig. 5. Temporal variations of indoor radon, F-factor and fp values detectedby EQF in the dwelling in Attica with the maximum number of measurementintervals (i/i 73, Fig. 2).

EDr values presented one or more peaks of different magnitudeand duration and occurrence times varied non-systematically.Two characteristic cases are presented in Fig. 9. The peaksof Fig. 9a are governed mainly by the temporal variation ofradon concentrations leading to similar curve shapes. Thefptemporal variations influence in a rather minor way. On theother hand, the peaks of Fig. 9b are influenced by the tempo-ral variation of both radon concentration and fp. The abovefindings indicate intense differences in the temporal variationsof PAEE and EDr in the studied areas of Greece. This fact isof significance since it influences the reported estimations ofthe aPAEEr and the aEDr (Nikolopoulos et al., 2002). Thisfact is reinforced by the data presented in Fig. 9. ConsideringdPAEEr and dEDr values as averages during a year aPAEEr andaEDr can be estimated through active measurements. Under

1312 D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314

Fig. 6. Graphical presentation of Cw and aEDrw,s data in Greece and Cyprus. Vertical lines represent the value range, the open circles the A.M. and the errorbars the S.D. (95% C.I.). The uncertainties in aEDrw,s are calculated from Eq. (12). All uncertainties are due to the instrument calibration and counting statistics.

Fig. 7. Graphical presentation of EDr (129 buildings—Fig. 2). Vertical lines represent the value range, the open circles the A.M. and the error bars the S.D.(95% confidence interval—C.I.). The uncertainties calculated according to Eqs. (10) and (11) according to the instrument calibration and counting statistics.

this perspective, aPEEEr range between (0.024 ± 0.008) and(0.697 ± 0.051) WLM y−1 in Attica and between (0.0076 ±0.0047) and (0.609 ± 0.051) WLM y−1 in Crete. aEDr valuesare in the range (0.093 ± 0.0031)–(2.712 ± 0.19) mSv y−1 inAttica and (0.552 ± 0.272)–(7.77 ± 6.13) mSv y−1 in Crete.The above aPAEEr values are comparable to the reportedrange for Greece ((0.024 ± 0.009)–(2.8 ± 1.0) WLM y−1,Nikolopoulos et al., 2002) through passive measurements.Similarly, aEDr values are also in the corresponding range((0.09 ± 0.04)–(11 ± 4) mSv y−1, Nikolopoulos et al., 2002).Comparing the estimated aEDr values to the reported annualaverages for Cyprus through active measurements, numerous

higher values are estimated in this paper. Indeed, accordingto Anastasiou et al. (2003) the aEDr values for Cyprus rangebetween 0.16 and 2.6 mSv y−1 and according to Sarrou andPashalidis (2003) the average aEDr for Cyprus is 0.19 mSv y−1.The aEDr values estimated for Attica and Crete through ac-tive measurements are quite higher than the average effectiveannual outdoor or indoor gamma dose rate values reported forGreece ((0.550 ± 0.064) mSv y−1, Sakellariou et al., 1995)or the corresponding effective gamma dose rate values dueto building materials or other sources (Clouvas et al., 2003;Papaefthymiou et al., 2003). Similarly higher are these valuesthan the reported average annual effective gamma dose rate

D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314 1313

Fig. 8. Graphical presentation of dPAEEr and dEDr data (129 buildings—Fig. 2). Vertical lines represent the value range, the open circles the A.M. andthe error bars the S.D. (95% confidence interval—C.I.). The uncertainties calculated according to Eqs. (6)–(11) according to the instrument calibration andcounting statistics.

values for Cyprus (Tzortzis et al., 2003; Tzortzis and Tsertos,2004). Indoor radon is the main source of radiation exposureof the Greek population.

Cw,i for Cyprus was 0.3% (Aw = 0.59 Bq m−3) and 0.1%(Aw = 0.54 Bq m−3) for Greece. Thus it is of slighter sig-nificance compared to inhalation of total radon. Yet thiscontribution is comparable or even higher than the effec-tive dose values delivered through medical uses of radiation(UNSCEAR, 2000). On the other hand, significant doses aredelivered to stomach of the Cypriot and Greek population dueto ingested radon following water consumption (Fig. 6). TheaEDrw,s for the Cypriot population was 0.085 mSv y−1 (S.D.0.080 mSv y−1) and for the Greek population 0.081 mSv y−1

(S.D. 0.081 mSv y−1) (Fig. 6).

4. Conclusions

This paper presented concentrations of indoor radon andradon in drinking waters in Greece and Cyprus derived withpassive and active techniques together with exposure and doseestimations. New passive indoor radon data are presentedfor Cyprus that together with the corresponding passive dataalready published (Christofides and Christodoulides, 1993)and the available active data (Sarrou and Pashalidis, 2003;

Anastasiou et al., 2003) could provide new information of theradon potential of dwellings in Cyprus. Significantly higherwere the indoor radon concentrations in Cyprus compared topublished data, nevertheless, of low magnitude. Similarly lowwere the radon concentrations in drinking waters in Cyprusand comparable to published values. As a first attempt, activemeasurements of indoor radon and radon in drinking waterstogether with F and fp data were presented for the capital ofGreece (Athens–Attica) and the largest Greek Island (Crete).Lower were the estimations of indoor radon exposures forGreece than those based on passive techniques yet higher thanin Cyprus. Concentrations of radon in drinking waters were ofthe same range.

This paper provided also an approximation on manipulat-ing active radon data derived by different devices for expo-sure and dose estimations. Comparisons between active databy other instruments (RADIM3, Anastasiou et al., 2003) wereattempted together with comparisons with passive data. Theabove approximation may be used in the future as a pilot forthe design of further studies in either Greece or Cyprus, onthe influences of the temporal variations of radon and radonrelated parameters (PAEC, EDr, etc.) to the average annual ex-posure and dose estimations. This is of importance, since mostof the estimations followed internationally are based on these

1314 D. Nikolopoulos, A. Louizi / Radiation Measurements 43 (2008) 1305–1314

0.0

0.5

1.0

1.5

2.0

2.5

Time

0.0

0.3

0.5

0.8

1.0

1.3

1.5

Time

EDr

Unattached fraction

Radon concentration

EDr

Unattached fraction

Radon concentration

ED

r (µS

v h-

1 )E

Dr (

µSv

h-1 )

Fig. 9. EDr values together with radon concentration and fp temporal datafor two dwellings in Attica (i/i 73 and 83 of Fig. 2). Radon concentrationand fp temporal data are presented only for comparison purposes in thesecondary axis. Value labels and units of the secondary axis are not presenteddue to the differences in the definitions of the presented parameters.

average annual estimations. It was concluded that radon is themain source of radiation human exposure both in Cyprus andGreece. The hazard is more important than other types of haz-ards (e.g. outdoor–indoor gamma irradiation, medical uses ofradiation).

Acknowledgements

We thank Mrs. Tzortzi, A., M.Sc. for her help in data collec-tion in the island of Cyprus during her M.Sc. Thesis. We alsothank Mr. Thanassas, D., M.Sc. and Mr. Lignos, L., M.Sc. fortheir help in Attica and Prof. Siannoudis, I. for providing themicroscope for the passive measurements.

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