Paper MEASUREMENTS OF INDOOR RADON ...

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MEASUREMENTS OF INDOOR RADON CONCENTRATION LEVELS IN DWELLINGS IN BETHLEHEM, PALESTINE Amin A. Leghrouz,* Mohammad M. Abu-Samreh,* and Ayah K. Shehadeh†

AbstractVIndoor radon level measurements were carried out in 42 dwellings in Bethlehem, Palestine, using CR-39 solid state nuclear track detectors. The measurements were performed during winter and spring seasons of the year 2010, for a period ranging from 97Y118 d using a total of 100 detectors. The detectors were installed in living rooms, bedrooms, kitchens, and storage areas of 39 houses, as well as in three schools, selected randomly in the surveyed area. The results of indoor radon levels and the annual effective dose in houses were found to vary from 26 Y 611 Bq mj3 and 0.65 Y 14.1 m Sv yj1, with average values of 117.0 Bq mj3 and 2.95 m Sv yj1, respectively. The mean values of radon concentration levels in bedrooms, kitchens, living rooms, basements, and storage areas are, respectively, 106.5, 113.1, 101.5, and 164.2 Bq mj3. The corresponding mean values of annual effective dose for the bedrooms, kitchens, living rooms, basements, and storage areas are 2.66, 2.83, 2.54, 14.1 m Sv yj1, respectively. In schools, the radon levels are found to vary from 31 Y 400 Bq mj3 with an average value of 125.1 Bq mj3. The average annual effective dose in schools is found to be 3.12 mSv yj1. This value is higher than the assigned international value. In general, the results show that radon concentration levels in 83% of the investigated dwellings are lower than the indoor radon action level of 150 Bq mj3 for the United States. Health Phys. 104(2):163Y167; 2013 Key words: detector; nuclear-track; effective dose; radon; 222 Rn; indoor

INTRODUCTION RADON IS the only naturally occurring radioactive gas resulting through the uranium decay series. It is an inert, colorless, odorless, tasteless gas that is insensible. Therefore, it can’t be detected unless a special type of detector is used. It became well known that radon enters dwell*Department of Physics, College of Science and Technology, AlQuds University, Abu-Deis, Jerusalem, P.O.BOX 20002, Palestine; †Ministry of Education, Ramallah, Palestine. The authors declare no conflicts of interest. For correspondence contact: Amin Leghrouz, Department of Physics, College of Science and Technology, Al-Quds University, AbuDeis, Jerusalem, P.O. Box 20002, Palestine, or email at aleghrouz@ science.alquds.edu. (Manuscript accepted 6 September 2012) 0017-9078/13/0 Copyright * 2013 Health Physics Society DOI: 10.1097/HP.0b013e3182733d3a

ings mainly through cracks and joints in the floor, from underground water, and from building materials (cement, rocks, granite) (Khan 2000). Radon gas can build up, depending on the geologic formation beneath the dwellings and the construction materials, to a high level in closed places (ICRP 1993; Kullab 2005). Radon level can vary even in the same dwelling and in general is higher in basements and poorly ventilated places as well as unpainted places (Virk 1999). In addition, radon concentration fluctuates daily depending on weather conditions and the habits of dwelling occupants. Radon contribution to human exposure is the highest, more than 50%, among all other natural radiation sources (ICRP 1993; UNSCEAR 2000, 2008). Exposure to radon gas and its progeny constitute a health hazard due to the interaction of the alpha particles, emitted by inhaled radon and its progeny that attach to airborne particulates, with the lining cells of the lung (Sevc et al. 1976; Lubin and Boice 1997; NRC 1999; UNSCEAR 2000; Darby and Hill 2003; Al-Zubaidy and Mohammad 2012). Therefore, indoor radon surveys were performed worldwide during the last three decades, and many of these surveys have been compiled in the literature (UNSCEAR 1993, 2000, 2008; Al-Zubaidy and Mohammad 2012). World organizations such as the International Commission on Radiological Protection (ICRP), World Health Organization (WHO), Health Canada, and U.S. Environmental Protection Agency (EPA), have recommended different guidelines listed in Table 1 for exposure to radon based on the best available scientific evidence of health risk (ICRP 1993, 2009; UNSCEAR 2000; Health Canada 2006, 2009; U.S. EPA 2009; WHO 2009). Radon contributes a large amount of absorption radiation dose in humans. The ICRP published in its report that each 1 Bq mj3 of radon level means about 0.025 mSv yj1 (ICRP 1987, 2009). So Cross found the estimate of the probability of getting lung cancer from radon concentration to be 1.65 10j2 if the radon concentration was 37 Bq mj3 (Cross 1992) In Palestine, the indoor radon survey project was initiated in 1998 by a research group at Al-Quds University. Up to now, 1,685 dwellings located in 33 locations have been 163

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Table 1. Radon concentration guidelines for residential homes. Organization

Residential radon level (Bq mj3)

Annual effective dose (mSv yj1)

References

200 100Y300 300 150 200 200

5.18 2.59Y7.78 7.78 3.89 5.18 5.18

Health Canada 2006, 2009 WHO 2009 ICRP 1993, 2009 EPA 2009 UNSCEAR 2000; ICRP 2009 UNSCEAR 2000

Health Canada World Health Organization International Commission on Radiological Protection United States Environmental Protection Agency European Union United Nations Scientific Committee on the Effects of Atomic Radiation

surveyed (Leghrouz et al. 2007, 2012). So far, detailed radon data for many locations is not available yet in Palestine. The aim of this work is to measure radon concentration levels in some parts of Bethlehem province to provide data in the hope of drawing a national radon map in Palestine. THE STUDY AREA Bethlehem district is located south of Jerusalem in a hillside mountainous terrain as shown in Fig. 1. It lies at the confluence of latitude 31.45- north and longitude 35.12- east. The surveyed region (Bayt Sahour, Al-Douha, Bayt Jala, and Bethlehem) elevation extends from about 550 Y 870 m above sea level. The rock formation in the northeastern region is dominated by dolomite and dolomite limestone, while the southwestern region is particularly chalky (Issac 1995). Such formation is characterized by low levels of radionuclides.

Modern buildings in this region are built using rocks obtained from different locations in the West Bank. The rocks used in buildings are mainly limestone, chalk, or marl types cut in specific dimensions that can be used in covering the outside of the buildings, and the space between the outside rock walls and the inside walls is filled with concrete. The inside walls are constructed using concrete blocks. The floor separations are constructed of fortified concrete of thickness usually about 0.25 m. The schools’ buildings follow the same construction trends as housing. In general, the school includes between 20Y40 classrooms, as well as the principal’s room, secretary’s room, teachers’ room, lab rooms, and other supporting rooms, which are housed in multistory buildings. The old houses are built with clay and lime, which sandwich the outside and the inside stone walls. It is worth mentioning that most dwellings are not air conditioned, and even if there is air conditioning, it is not turned on frequently and the inhabitants tend to open the windows more frequently. Thus, the buildings can be treated as an open system environment all year around. EXPERIMENTAL TECHNIQUE

Fig. 1. West Bank map and the location of the study area.

In this survey, CR-39 solid-state nuclear track detectors (SSNTDs) were used to determine indoor radon levels. The general methodology for preparing the dosimeter was explained in detail by many authors (Al-Bataina et al. 1997; Leghrouz et al. 2007, 2012). A total of 100 dosimeters were distributed in 39 houses and three schools located in the municipalities of Bayt Sahour, Al-Douha, Bayt Jala in the Bethlehem region, for a period ranging from 97Y118 d starting from November 2010 to March 2011. The dosimeters were distributed and installed at 0.5Y1.5 m height depending on the availability of a holder. Most of the surveyed dwellings are located in a mountainous area. A total of 89 dosimeters were collected. The track densities (tracks cmj2) were measured and converted to radon concentration in Bq mj3 using the calibration equation adopted by the Yarmouk University radon research group (Al-Bataina et al. 1997). The annual effective dose received has been calculated according to the equation www.health-physics.com


Indoor radon levels in Bethlehem c A. A. LEGHROUZ

agreed upon by the International Commission on Radiological Protection (Risica 1998; UNSCEAR 2000). RESULTS AND DISCUSSION Tables 2Y6 summarize the results for the indoor radon concentration levels and the annual absorbed dose in the 42 dwellings inspected. The indoor radon levels for the 39 houses surveyed were found to vary from 26Y611 Bq mj3 with a mean value of 117.6 Bq mj3. The lowest concentration value of 26 Bq mj3 was found in a living room, whereas the highest concentration of 611 Bq mj3 was found in a basement. Table 2 shows the radon levels in bedrooms, which range from 26 Y 301 Bq mj3. There are two readings above the EPA recommended safety limit of 150 Bq mj3, which might need some attention to reduce the levels to the recommended ones. One of these readings belongs to a bedroom located on the third floor, while the other one belongs to a bedroom on the ground floor. The other readings are within the acceptable level, and no action is required. Table 3 shows the measurements in kitchens; although one would expect to find some high readings there due to the presence of granite in the countertops, all the readings are below the recommended level except one reading, which was found in a kitchen under renovation. The low values in kitchens might be due to good ventilation, because the majority of kitchens have vents. Table 4 shows the radon levels in guest and living rooms; the readings are within the acceptable level, except one reading that was taken on the second floor. Table 5 shows the radon levels in basements, stairways, and storage areas; the readings are within the acceptable level except for three readings, which are expected Table 2. Radon concentration levels in bedrooms. No. Floor Radon level (Bq mj3) Annual effective dose (mSv yj1) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

1 1 1 3 1 1 1 1 3 1 0 0 0 1 1 0 0 0 1

Average

99 33 148 93 26 109 34 90 301 51 131 80 27 210 116 129 227 48 71

2.57 0.86 3.84 2.33 0.65 2.73 0.85 2.25 7.53 1.28 3.28 2.00 0.68 5.25 2.90 3.23 5.68 1.20 1.78

106.5

2.66

ET AL.

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Table 3. Radon concentration levels in kitchens. No. Floor Radon level (Bq mj3) Annual effective dose (mSv yj1) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

1 1 1 1 1 0 3 0 1 2 0 1 1 0 0 0 0 1 5 1

Average

106 56 103 63 116 78 72 73 28 127 179 320 170 111 97 99 138 154 79 93

2.65 1.40 2.58 1.58 2.90 1.95 1.80 1.83 0.70 3.18 4.48 8.00 4.25 2.78 2.43 2.48 3.45 3.85 1.98 2.33

113.1

2.83

in places that are characterized by poor ventilation, are kept closed for most of the time, and might be unpainted. Table 6 shows the radon levels in three schools; classrooms are not included in this study because from previous work, the students tend to play with and damage the dosimeters. The levels are found to vary from 31 Y400 Bq mj3 with an average value of 125 Bq mj3. The average annual Table 4. Radon concentration levels in guest and living rooms. No.

Floor

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

1 1 0 1 1 1 1 1 0 0 1 2 1 0 3 1 0 1 1 5 0 0 2 1 1 1 1 0

Average value

Radon level (Bq mj3)


93 374 72 110 109 34 34 55 41 121 74 97 33 179 39 123 97 185 185 71 73 65 102 80 43 143 125 86

2.33 9.35 1.80 2.75 2.73 0.85 0.85 1.38 1.03 3.03 1.85 2.43 0.83 4.48 0.98 3.08 2.43 4.63 4.63 1.78 1.83 1.63 2.55 2.00 1.08 3.58 3.13 2.15

101.5

2.54



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effective dose in schools is found to be 3.12 mSv y . This value is higher than the assigned international level. The mean values of radon concentration levels in bedrooms, kitchens, living rooms, basements, and storage areas are, respectively, 106.5, 113.1, 101.5, and 164.2 Bq mj3. The mean values of annual effective dose for the bedrooms, kitchens, living rooms, basements, and storage areas are 2.66, 2.83, 2.54, and 14.1 mSv yj1, respectively. The results show that 17% of measurements are higher than the assigned international radon level of 150 Bq mj3. The calculated average, excluding the basements, storage areas, and stairways, is 106.4 Bq mj3, which is 8.5% less than that of the overall average of 117.6. The annual effective dose equivalent obtained for each location is shown in Tables 2Y6. The average effective dose equivalent of 3.1 mSv yj1 for all inspected locations is about 2.4 times higher than the normal background value of 1.3 mSv yj1 given by EPA (2009) but still 0.8 times lower than the assigned guideline of 3.89 mSv yj1. The highest levels are found in places with poor ventilation. The possibility of increasing the incidence of lung cancer in the average person in Bethlehem is 1.94%. CONCLUSION The indoor radon concentrations in different locations of 42 dwellings in Bethlehem varied in the range 26Y611 Bq mj3 with an average value of 117.6 Bq mj3, which is less than the EPA-recommended safety limit of 150 Bq mj3. In general, 83% of the obtained radon level values in the surveyed dwellings are below the EPA assigned action level value. Many of the elevated values were found in uninhabited and unpainted places, usually on the ground level, which are characterized by bad Table 5. Radon concentration levels in basements, stairways, and storages. No.

Floor

Room type

Radon level (Bq mj3)


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

stairway 0 j1 0 0 j1 0 0 3 stairway 0 0 0 0 0

Stairway Basement Storage Garage Basement Basement Home library Storage Central heating Stairway Storage Basement Factory Basement Storage

81 80 140 308 611 78 114 47 124 38 102 103 35 461 141

2.03 2.00 3.50 7.70 15.3 1.95 2.85 1.18 3.10 0.95 2.55 2.58 0.88 11.53 3.53

Average

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Table 6. Radon concentration levels in schools. No. 1 2 3 4 5 6 7

Floor 3 0 0 0 0 0 0

Average value

Room Type Lab Library Secretary’s room Library Secretary’s room Teachers’ room Principle’s room

Radon level (Bq mj3) 121 62 92 120 400 31 50 79.3

Annual effective dose (mSv yj1) 3.03 1.55 2.30 3.00 10.0 0.78 1.25 1.98

ventilation. The average annual effective dose is about 2.95 mSv yj1. The increase in the probability of radonrelated cancer incidents in the surveyed region is found to be about 1.92%. To avoid unnecessary exposure to radon gas, one can draw the following conclusions: 1. Staying in unfinished and unpainted rooms will increase radon exposure (construction materials such as cement, rocks, and granite emanate a considerable amount of radon); 2. Ventilation is crucial for fresh healthy air and can reduce radon exposure; and 3. In designing new houses, it is important that the construction of the floor touching the ground be crack-free and airtight, which will reduce the buildup of radon inside houses. REFERENCES Al-Bataina B, Ismail A, Kullab M, Abumurad K, Mustafa H. Radon measurements in different types of natural waters in Jordan. Radiat Meas 28:591Y594; 1997. Al-Zubaidy NN, Mohammad AI. Health effects on public of Malka region due to radon gas, using (CR-39) detector. Advan Theor Appl Mech 5:61Y67; 2012. Cross FT. Indoor radon and lung cancer: reality or myth? In: Proceedings of the Twenty-ninth Hanford Conference on Health and Environment. Columbus: Battle Press; 1992: 27Y29. Darby S, Hill D. Health effects of residential radon: a European perspective at the end of 2002. Radiat Protect Dosim 104: 321Y329; 2003. Health Canada, Report of the Radon Working Group on a new radon guideline for Canada. 2006. Available at http://www.cbc. ca/news/background/health/pdf/WG_Report_2006-03-10_en.pdf. Accessed 24 November 2012. Health Canada, It’s your health. 2009. Available at www.hc-sc. gc.ca/hl-vs/iyh-vsv/environ/radon-eng.php. Accessed 20 September 2009. International Commission on Radiological Protection. Lung cancer risk from indoor exposure due to radon daughters. Oxford: Pergamon Press; ICRP Publication 50; Annals of the ICRP 17(1); 1987. International Commission on Radiological Protection. Protection against radon-222 at home and at work. Oxford: Pergamon Press; ICRP Publication 65; Annals of the ICRP 23(2); 1993. International Commission on Radiological Protection, International Commission on Radiological Protection statement



Indoor radon levels in Bethlehem c A. A. LEGHROUZ

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