Radiation Protection Dosimetry Advance Access published November 11, 2014 Radiation Protection Dosimetry (2014), pp. 1–7

doi:10.1093/rpd/ncu329

INDOOR RADON MEASUREMENTS IN TURKEY DWELLINGS N. Celebi*, B. Ataksor, H. Taskın and N. Albayrak Bingoldag Cekmece Nuclear Research and Training Centre, Yarımburgaz Mah. Nu¨kleer Aras¸tırma Merkezi Yolu No: 10, Istanbul 34303, Turkey *Corresponding author: [email protected] Received 12 June 2014; revised 30 September 2014; accepted 3 October 2014

INTRODUCTION 222

Radon ( Rn) is a naturally occurring radioactive noble gas that forms in uranium (238U) decay series, and also decay product of radium (226Ra), which is found in a wide range of rocks and soils. Radon is present in all buildings and underground locations. 222 Rn decays with a 3.8 d half-life into the short-lived particles. These short-lived isotopes are chemically active solids and attach themselves to aerosol particles. They are present in any environment where radon is found and, like radon, cannot be detected by human senses. These inhaled particles, which are deposited in the lung, continue to give doses via subsequent ionising alpha particle emission(1). Exposure to radon is the most significant element of human irradiation by natural sources. Radon is known as the second cause of lung cancer in the general population, after smoking(2). Epidemiological studies have provided convincing evidence of an association between indoor radon exposure and lung cancer, even at the relatively low radon levels commonly found in residential buildings(3). The World Health Organization first drew attention to the health effects from residential radon exposures in 1979, through a European working group on indoor air quality(3). Since then, national or regional radon surveys in many countries have been initiated to assess the doses from the inhalation of radon in dwellings. Nationwide measurements of radon activities in dwellings have been started in 1984 and completed in 2013 (Figure 1). The first radon concentration measurements were determined in Istanbul houses(4). Later, the work has spread to the entire Turkey. Several techniques have been used to measure radon and its daughters(5). Passive time-integrating method is one of the most important techniques for the measurement of radon concentration in air. Solidstate nuclear track detectors, such as LR-115, CR-39

and Makrofol, have been widely used for radon measurements. The measurements of the indoor radon activity concentrations in Turkey were carried out by using CR-39 plastic alpha-track detectors. MATERIALS AND METHODS Measurement area Turkey is situated between the continents of Asia, Africa and Europe. Turkey, which is located in the Alpine –Himalayan orogenic belt, is the mountainous country; two main orogenic belts extend on the northern and southern part of the Anatolian peninsula. Turkey is one of the volcanic areas within the Alpine orogenic belt (6). Mountains extending parallel to or perpendicular to the shores cause different climates. It is surrounded by seas; each reflects a different ecological character. The country has a varied topography that is made up of a high central plateau, narrow coastal plain and large mountain ranges. The nature of the North and East Anatolian Fault line, tectonic East Anatolian high plateau and central Anatolian plateau and plain structure makes it important to work in this area (Figure 2). Measurement technique In this work, closed etched track radon detectors with a detecting element made from poly-allyl-diglycol carbonate (CR-39) were used. The closed detector records only alpha particles originating from the radon entering the container and those from the decay products formed within the container(5). CR-39 foils of 250 mm thick (20`  20 mm) were cut and attached to the bottom of plastic cups (60 mm in diameter and 30 mm in height). Since any dust or impurity on the CR-39 detector pieces or inside the exposure pot may reduce the accuracy and reliability

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In this work, indoor radon radioactivity concentration levels have been measured in dwellings of Turkey within the frame of the National Radon Monitoring Programme. The 222Rn concentrations were measured with time-integrating passive nuclear etched track detectors in 7293 dwellings in 153 residential units of 81 provinces, and the radon map of Turkey was prepared. Indoor radon concentrations were distributed in the range of 1 –1400 Bq m23. The arithmetic mean of the radon gas concentration was found to be 81 Bq m23; the geometric mean was 57 Bq m23 with a geometric standard deviation of 2.3.

N. CELEBI ET AL.

(3.24+0.04 kBq m23) calibrated by Lucas flasks was used(7). In 2004, radon measurement system was replaced with the Radosys 2000 system (77 Elektronika, Budapest, Hungary). Measuring system has changed, but measurement technique has remained the same. The system is a complete set dedicated to the radon concentration measurement. It consists of Radometer automated microscopic image analyser with the control computer, the track analysis software, Radopot CR-39 plastic alpha-track detectors and the radobath etching unit. Calibration of the system was carried out by means of the RadoCal calibration package(8). Etching process was performed in 25 % NaOH solution at 908C for 4 h. The distribution and collection of the detectors was provided by means of the public institutions, organisations and the universities of cities. Quality assurance and quality control

Figure 1. Measurement year in the national survey of radon concentration in dwellings.

To control the quality of radon concentration measurements, the authors periodically participated in international inter-laboratory comparisons. Participations in the National Radiological Protection Board (1989, 1991, 1995, 1997, 1998 and 2000) and 2012 Health Protection Agency intercomparisons of passive radon detectors gave the authors the opportunity to check the measurement technique and the system accuracy. The measurement errors were found between ,10 and 30 %(9, 10, 11). Quality control of the radon measurement

Figure 2. The radon map of Turkey.

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of the radon test, the top of the cups were covered with a plastic cap. A pair of detectors was distributed to randomly selected houses, one of which was placed in the living room and the other in the bedroom. The period of exposure was 2– 3 months. After collection of the detectors, the CR-39 foils were chemically etched in 30 % NaOH solution at 708C for 17 h for making the tracks visible. Alpha traces of radon were counted manually under an optical microscope (`250). The background track densities varied from sheet to sheet of detector material; for this reason, unexposed detectors were evaluated under identical condition with the others for each province. For the calibration of CR-39 foils, a 225-l radon chamber

INDOOR RADON MEASUREMENTS IN TURKEY DWELLINGS

system was performed by national inter-laboratory comparisons between 2000 and 2011. Results were compatible with each other. RESULTS AND DISCUSSION Results

Statistical evaluations In order to check the frequency distribution of indoor radon measurements, one-sample Kolmogorov– Smirnov test was applied to all of the indoor radon Table 1. Seasonal correction factors based on four consecutive 3-month measurements derived from 450 homes. January– April 1.51

April– July

July– October

October– January

0.98

0.62

1.09

Figure 3. The frequency distribution of radon concentration levels in dwellings.

Figure 4. The percentage distribution of indoor radon concentration levels.

Figure

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5. Lognormal distribution of concentration values.

indoor

radon

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Results have been obtained from 153 residential areas in 81 provinces, a total of 7293 dwellings, and were corrected for the average seasonal variation. The distribution of the concentration of indoor radon is in the range from 1 to 1400 Bq m23. The arithmetic mean of the annual radon concentration is 81 Bq m23; the geometric mean is 57 Bq m23 with a geometric standard deviation of 2.3. In addition, the Turkish Republic of Northern Cyprus indoor radon concentrations were measured in 5 provinces in 42 residential areas. The arithmetic mean of the radon concentration was calculated as 35 Bq m23; the geometric mean was 34 Bq m23 with a geometric standard deviation of 1.1(12).

The frequency distribution of radon concentration levels in dwellings and the percentage distribution of radon concentration levels for Turkey are given in Figures 3 and 4, respectively. Seasonal correction factors were evaluated for the accuracy of estimates of annual mean concentrations(13). Nine provinces were chosen for representative nationwide survey. The measurements were carried out for 4 consecutive 3 months over 1 y in each case using 50 detectors in 2 locations in each home during the period January 2007–January 2008. Seasonal correction factors derived from 1800 measurements are given in Table 1. The representativeness of early measurements was also checked with this study. Findings from the individual studies were compared with the earlier measurements. The studies showed good consistency. In order to obtain results representative of population exposure, radon detectors were placed in living rooms and bedrooms in the same dwellings and a questionnaire was given to identify dwelling characteristics.

N. CELEBI ET AL. Table 2. The assessment of questionnaires obtained 731 homes. Radon level (Bq m23)

Building characteristics Low ,50 n

Middle 50– 100

High .100

%

n

%

n

%

84 52 141 66

38.4 48 54.9 31.4

110 36 84 106

50.2 33.3 32.7 50.5

25 20 32 38

11.4 18.5 12.5 18.1

0.001

21 208 93

53.8 43.3 43.9

10 192 94

25.6 40.0 44.3

8 80 25

20.5 16.7 11.8

0.148

20 276 39

38.5 42.8 46.4

24 275 33

46.2 42.6 39.3

8 94 12

15.4 14.6 14.3

0.927

254 79

41.8 45.7

265 68

43.7 39.3

88 26

14.5 15.0

0.582

71 223 5 15 21

33.2 47.0 33.3 34.9 58.3

116 183 7 20 7

54.2 38.6 46.7 46.5 19.4

27 68 3 8 8

12.6 14.3 20.0 18.6 22.2

0.001

238 83

48.5 35.2

172 121

35.0 51.3

81 32

16.5 13.6

0.001

257 83

40.7 52.9

288 46

45.6 29.3

86 28

13.6 17.8

0.001

66 150 117

38.4 37.6 60.3

90 186 43

52.3 46.6 22.2

16 63 34

9.3 15.8 17.5

0.001

n, number of houses.

concentration values. The results showed that the overall distribution of radon concentrations in Turkey dwellings was consistent with the log–normal distribution ( p , 0.05) (Figure 5). In this study, the effects of the dwelling characterisation on indoor radon concentrations were investigated. The questionnaires obtained from 731 homes were assessed with chi-square tests using SPSS software program (IBM SPSS Statistic 20), and the results are listed in Table 2. Discussion Since the source of radon is uranium and uranium is present everywhere in the earth’s crust, 226Ra and 222 Rn are also present in varying concentrations in almost all rock and all soil and water. Therefore, the radon concentration in the provinces has been

changed depending on the soil structure, building materials and water supply. Indoor radon concentrations were measured in 606 dwellings in Istanbul, and the arithmetic mean radon concentration was found to be 49 Bq m23. This value has been measured as 65 Bq m23 in Erzurum(14), 164 Bq m23 in Isparta(15), 33 Bq m23 in Antalya(16) and 40 Bq m23 in Adana(17). The arithmetic mean of the annual radon concentration is 81 Bq m23, and the geometric mean is 57 Bq m23 with a geometric standard deviation of 2.3 for 7293 dwellings in 153 residential units of 81 provinces. The results of this study were compared with the results of previous studies that surveyed 1414 homes in 27 provincials. In that work, the arithmetic mean of the indoor radon concentration was found as 35 Bq m23(18). Each new data for province have caused the different average for Turkey. Provinces

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Types Apartment with basement Apartment without basement Detached house with basement Detached house without basement Built years Before 1950 Between 1950 and 2000 After 2000 Floor material Mud Concrete Wooden Roof material Concrete Wooden Wall material Concrete Brick Wooden Stone Others Windows Single glazed Double glazed Ventilation Good ventilation Poor ventilation Heating system Central heating Stove Others

p-value

INDOOR RADON MEASUREMENTS IN TURKEY DWELLINGS Table 3. Radon concentrations in dwellings determined in indoor surveys for some countries(27). Country

1406 4690 1040 1720 20 000 15 400 .10 000 1990

Arithmetic mean (Bq m23)

Geometric mean (Bq m23)

Geometric standard deviation

81 62 75 34 46 120 86 50 107 40

57 41 57 14 25 84 42 40 82 30

2.3 2.7 2.0 3.6 3.1 2.1 3.7 1.9 2.7 2.3

with high average radon concentration such as AfyonDinar (186 Bq m23), Ardahan(19) (282 Bq m23), Aksaray (110 Bq m23), Bilecik (171 Bq m23), Denizli (96 Bq m23), I˙zmir-Dikili (20) (114 Bq m23), Konya (100 Bq m23), Nevs¸ehir-Hacıbektas¸ (220 Bq m23), Samsun(21) (106 Bq m23), Sivas(22) (120 Bq m23) and Yozgat (220 Bq m23) have led to an increase in average of Turkey. Epidemiological evidence indicates that indoor radon is responsible for a substantial number of lung cancers in the general population. The International Commission on Radiological Protection (ICRP) has taken recommendation for radiological protection against 222Rn at home and at work, and the annual exposures to radon are limited between 200 and 600 Bq m23(23, 24). The Commission has revised the upper value for the reference level for radon gas in dwellings from 600 to 300 Bq m23(25). The reference level of the annual mean of the radon concentration at home is given as 400 Bq m23 by Turkish Atomic Energy Authority(26). The annual average indoor concentration value is lower than this level but higher than the average worldwide indoor radon concentration of 40 Bq m23. For some countries, indoor average radon concentration values are given in Table 3(27). Indoor radon concentration levels of dwellings are higher than others in some cities. Çanakkale region is covered by Kestanbol granitic pluton, volcanic and metamorphic rocks, which are rich in uranium and thorium(28). Indoor radon concentrations have been measured as 190 Bq m23 in Çanakkale-Ayvacık and 167 Bq m23 in Çanakkale-Kestanbol(29). Isparta (164 Bq m23) and its environment located in active faults of western Mediterranean region has been an area with high radon concentrations. Nevs¸ehir (174 Bq m23) and its towns have soil structure composed of volcanic tuff. Mardin (208 Bq m23) is located in a volcanic area. Houses in Mardin are made with easily workable calcareous rock and surrounded by 4-mhigh walls. These walls also provide protection from harsh climatic conditions. Ardahan (282 Bq m23) is

surrounded by high mountains and has volcanic soil structure. In addition, soil samples were taken from the area, 238U radioactivity concentrations were measured and the relationship between indoor radon and the soil structure were investigated(19). 238U activity concentrations varied from 30 to 47 Bq kg21 with an average of 36 Bq kg21, which is similar to the world’s mean value of uranium in soil(1). Although the 238U concentration is within usual limits, radon concentration may be elevated, probably because of the temperature, ventilation and the lifestyle of the people living in the house. Ardahan is a province in the north-east of Turkey. Its climate is extremely cold, with temperatures below 2308 relatively frequent in winter. The highest radon concentration was found in Giresun-S¸ebinkarahisar (312 Bq m23). This region contains volcanic rocks and fault lines(30). It has been reported to have 300 tons of capacity of uranium deposits in this region by MTA (Mineral Research & Exploration General Directorate)(31). The lowest radon concentration was measured in Adıyaman. The concentration of indoor radon varied from 7 to 95 Bq m23. The arithmetic mean of the annual radon concentration found was 16 Bq m23; the geometric mean was 14 Bq m23 with a geometric standard deviation of 1.5. Adıyaman is a city in south-eastern Turkey and has a Mediterranean climate. Seventy-five per cent of that city has clay loam soil structure. At the edges of rivers and streams are also found an alluvial field. These results suggest that the nature of the soil and rocks underlying the building and ventilation rates of the dwellings are very effective on the indoor air quality. Addressing radon is important both in construction of new buildings ( prevention) and in existing buildings (mitigation or remediation)(3). In principle, radon detectors were placed in living rooms and bedrooms in the same dwellings. The radon concentration was estimated as the average of the measured radon levels in living room and bedroom for each dwelling. All values were seasonally

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Turkey France Italy Canada A.B.D Finland Spain Germany Hungary Mean of world

Maximum value (Bq m23)

N. CELEBI ET AL.

CONCLUSIONS The nationwide survey of 222Rn levels in dwellings in Turkey has been completed. In all, 7293 dwellings were sampled, using CR-39 passive detectors. Results were evaluated, and radon map of the country was

prepared. The arithmetic mean of the annual radon concentration for Turkey was 81 Bq m23, and the geometric mean was 57 Bq m23. The percentage of dwellings exceeding 400 Bq m23 was 1 %.

ACKNOWLEDGEMENTS The authors thank all the public institutions, organisations and the university members for the contribution of the indoor radon measurements in their provinces.

FUNDING This research was supported by Turkish Atomic Energy Authority. REFERENCES 1. United Nations Scientific Committee on the Effects of Atomic Radiation. Exposures from natural sources of radiation. UNSCEAR 2000 Report. Annex B. United Nations, New York (2000). 2. Biological Effects of Ionizing Radiation. Health effects of exposure to radon. BEIR VI Report. National Academy Press (1999). 3. World Health Organisation. WHO Handbook on Indoor Radon. A Public Health Perspective. WHO Press (2009). ¨ zc¸ınar, B. Indoor radon 4. Ko¨ksal, M., Celebi, N. and O concentrations in Istanbul houses. Health Phy. 65, 87– 88 (1993). 5. International Atomic Energy Agency. National and regional surveys of radon concentration in dwellings. Analytical Quality in Nuclear Applications Series. IAEA/AQ/33 (2013). 6. Atalay, I. Mountain ecosystems of Turkey. In: 7th International Symposium on High Mountain Remote Sensing Cartography, ICA. 29–38, 2002. 7. Celebi, N. and Ko¨ksal, E. M. Determination of alpha activity with CR-39 nuclear track detectors. III. National Nuclear Science Congress. 856– 860 (1989). 8. Radosys 2000 User’s Manual. Available on www. radosys.com. 9. Annual Reports of the 1989, 1991, 1995, 1997 and 1998 European Commission. Results of the European Commission Intercomparison of Passive Radon Detectors (available for download at http://europa.eu.int). 10. Howarth, C. B. and Miles, J. C. H. Result of the 2000 NRPB intercomparison of passive radon detectors. NRPB-W6 (2002) ISBN 085951 473 0. 11. Daraktchieva, Z., Howarth, C. B. and Algar, R. Results of the 2012 HPA intercomparison of passive radon detectors. Health Protection Agency Centre for Radiation, Chemical and Environmental Hazards. Chilton. ISBN 978-0-85951- XXX-X (2012). 12. Çelebi, N., Aybar, H., Tas¸delen, M., Ataksor, B., Tas¸kın, H. and Aybar, S¸. Indoor radon (222Rn) concentration measurements in North Cyprus. In: 6th International Balkan Physical Conference. 989. American Institute of Physics; 1 Edition (2007).

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corrected. The bedrooms usually had higher radon concentrations. It may depend on the ventilation rate of the rooms. In general, the bedrooms are ventilated less than the living rooms. Importance of the ventilation in decreasing the indoor radon concentration is underlined in all the ICRP and the UNSCEAR Reports. Each measurement was of 3 months of duration, and seasonal correction factors were applied for the derivation of an annual average radon concentration. The mean radon concentration was found generally higher levels in winter than in summer. Temperature and pressure differences, wind velocity and humidity also effect the indoor radon concentration. Therefore, the design of the house, the ventilation system, the heating and the cooling system play an important role in radon accumulation inside the dwellings(1). The results of the assessment of questionnaires have shown that the building type (apartment with basement, apartment without basement, detached house with basement and detached house without basement), wall construction material (concrete, brick, wooden, stone and others), windows types (single glazed and double glazed), ventilation condition (good ventilation and poor ventilation) and heating system (central heating, stove and others) are related to radon concentration ( p , 0.05). According to the results, indoor radon concentration is not related to built years of the houses, floor and roof materials. Indoor radon concentration varied with the construction of buildings and ventilation habits. The frequency distribution of radon concentration levels in dwellings and the percentage distribution of radon concentration levels are given in Figures 3 and 4. It can be seen from Figure 5 that the frequency distribution looks log–normal. In that reason, the geometric mean value of radon concentration of provinces was used for the preparation of Turkey map (Figure 2). Turkey radon map was carried out using Mapinfo. Professional 10.0 software program, which is used in the interpolation technique. The interpolation technique uses the available radon data in known locations to estimate the radon data for unmeasured locations. According to these data, the distribution of indoor radon concentrations shows a maximum between 30 and 39 Bq m23. 79.3 % of all measured dwellings are ,100 Bq m23 (reference level of WHO), 92.8 % are ,200 Bq m23 and 99 % of the dwellings are ,400 Bq m23, which is the maximum allowable annual average indoor radon concentration value set by TAEK.

INDOOR RADON MEASUREMENTS IN TURKEY DWELLINGS

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Indoor radon measurements in Turkey dwellings.

In this work, indoor radon radioactivity concentration levels have been measured in dwellings of Turkey within the frame of the National Radon Monitor...
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