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Measurement of Radioactivity in the Granites of Pakistan: A Review

Younis, Hannan1; Qureshi, Aziz Ahmed1; Manzoor, Shahid1; Anees, Muhammad2

doi: 10.1097/HP.0000000000000917
REVIEW PAPERS

All human beings are exposed to primordial radiation. The main source of primordial radiation has been naturally radioactive building materials. In Pakistan, among building materials, granites are most commonly used. This paper reviews the previous studies conducted for the estimation of natural radioactivity of granites from Rustam-Koga, Shewa-Shahbazgarhi, Bunair, Mansehra, and Nagarparkar. The techniques used for these studies include gamma spectrometry and field surveys. To assess the radiation hazards associated with granites of Pakistan, primordial radionuclides and corresponding radiation hazards have been estimated. Most of these granites are found to be safe except Rustam-Koga granite, which presents high excess lifetime cancer risk.

1Radiation Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Park Road, Islamabad, Pakistan;

2Pakistan Space and Upper Atmosphere Research Commission (SUPARCO), Karachi, Pakistan.

The authors declare no conflicts of interest.

For correspondence contact: Hannan Younis, COMSATS Institute of Information Technology, Park Road, Islamabad, Pakistan, or email at hannan.younis@comsats.edu.pk.

(Manuscript accepted 27 March 2018)

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INTRODUCTION

SINCE THE origin of human life, about 0.2 million years ago, human beings have been exposed to radiation from naturally occurring radionuclides mainly in building materials of terrestrial origin (Trinkaus 2005). The continuous exposure of human organs to the energetic and particulate forms of ionizing radiation released via the decay chains of 238U and 232Th in combination with 40K can cause radiation damage as well as biochemical changes (Khandaker et al. 2012).

External exposure to radiation is due to the gamma radiation emitted by 226Ra and 232Th and their decay products and by 40K. Internal radiation exposure is due to inhalation of radon (222Rn) gas, exhaled by building materials into the environment, and its short-lived decay products.

Granites, as compared to other building materials, contain higher proportions of 238U, 232Th, and 40K (Sadek et al. 2016 ; Chen and Lin 1996 ; El-Arabi 2007). According to Menager et al. (1993) and Orgun et al. (2005), the granites contain ∼5 ppm of uranium, ∼15 ppm of thorium, and ∼120 ppm of radioactive potassium. The presence of these radionuclides in granites is a potential source of radiation in the environment. Exposure to radiation can affect human health by damaging the body tissues and increasing the cancer risk (UNSCEAR 1988). Some studies have shown that the radioactivity of granites from different parts of the world is significant enough to pose a serious health risk (Sin-Eng et al. 1991).

During the last three decades, there has been an increasing interest in the study of radioactivity of building materials. Several national surveys in different countries were conducted to establish the radionuclide concentrations in building materials and their radon exhalation rates (Beretka and Mathew 1985 ; Hamilton 1971 ; Garzon et al. 1982 ; Cliff et al. 1985). Various types of granites were found to contain much higher concentrations of radionuclides as compared to other building materials. A comparison of 226Ra, 232Th, and 40K concentrations in terms of gamma activity and weight percentage (ppm) in commonly used building stones is shown in Table 1. Conversion factors for gamma-activity concentration to equivalent weight percentage (ppm) were taken from International Atomic Energy Agency (IAEA) Technical Report 309, which states that 12.5 Bq kg−1 of 226Ra is equal to 1 ppm of uranium, 20 Bq kg−1 of 232Th is equal to 5 ppm of 232Th, and 100 Bq kg−1 of 40K is equal to 4.67 ppm of 40K (IAEA 1989).

Table 1

Table 1

This paper reviews the current state of the knowledge on activity concentrations of natural radionuclides in granites of Pakistan and some dose assessment approaches. The study also provides a comparison of radioactivity and associated radiation indices of granites of Pakistan with values for the world averages of granites and building materials as well (Chen and Lin 1996 ; UNSCEAR 1993).

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Study areas

Granites in Pakistan are mostly found in the Himalaya Mountain Belt at Gilgit, Dir, Chital, Kohistan, Swat, Malakand, Bunair, Swabi, Mansehra, etc. Two main granitic bodies are found at Chagahi and Nagarparkar in the south of Pakistan (Qureshi et al. 2016). Out of these granites, five located (from south to north) at Nagarparkar, Mansehra, Shewa-Shahbazgarhi, Bunair, and Rustam-Koga (Ambela) have been studied using radiometric techniques.

It is estimated that that there are more than 1 trillion tons of granite reserves in Pakistan (Abbas 2006). Location of some of these granites is shown in Fig. 1. Locally they are used for the construction of dwellings. In urban areas, where other building materials are available, they are used as kitchen counters and vanity tops, flooring tiles, facing material for interior and exterior decoration, etc. Apart from local use, the granites from Pakistan are exported to the Middle East and other countries.

Fig. 1

Fig. 1

The granites that have been studied using radiometric techniques are discussed below.

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Rustam-Koga granite from Ambela granitic complex

Ambela granitic complex (AGC) is composed of the granitic zones of Rustam-Koga, Ambela, and Utla. The AGC covers an area of about 900 km2 and is by far the largest body of Peshawar Plain Alkaline Igneous Province located in the northwest of Khyber Pakhtun Khawa Province of Pakistan (Asghar et al. 2008). A radiometric survey was carried out using a portable scintillation detection system in the area from Rustam to Koga, and zones of higher count rate were noted. Twenty rock samples were collected randomly from the hot zones and their surroundings. The sampling depth was about 5 cm from the surface of the rock.

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Shewa-Shahbazgarhi granite

The Shewa-Shahbazgarhi granite is an isolated triangular outcrop consisting of basic and acidic metaigneous rock complex. It is located about 60 km south of the Main Mantle Thrust in the Khyber Pakhtun Khawa Province. The complex has been emplaced into a metasedimentary sequence known as the Swabi Chmala group of Martin et al. (1962) and the Jaffar Kandao Formation of Pogue et al. (1992) of Carboniferous age. The Shewa-Shahbazgarhi granite is very hard and compact and is used for house construction and road building material. Amanat et al. (2002) carried out a radiometric study to measure the concentrations of 226Ra, 232Th, and 40K and associated radiological hazards in these rocks.

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Bunair granite

Bunair granite is located in an area on the southern side of Mardan-Bunair Highway in Khyber Pakhtun Khawah. The area is covered mainly with granites and granitic boulders. Geologically, the area is a part of AGC (Qureshi et al. 2018). The Bunair granite is yellowish, subrounded granite lens. Yellowish quartz is relatively abundant as compared to other minerals. The alkali feldspars constitute up to approximately 50% of these rocks. Biotite is the dominant ferromagnesian mineral. Accessory minerals are tourmaline, muscovite, sphene, epidote, apatite, garnet, etc. Radiometric studies on this granite have been carried out by Qureshi et al. (2018).

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Mansehra granite

The Mansehra granite is a large plutonic body of approximately 200 km2 exposed in and around Mansehra City (Qureshi et al. 2014). It is a large plutonic body that crops out in the west of the western syntaxes of the Himalayas. Mansehra granite is porphyritic granite with megacrystals of potassium feldspar. The matrix is of medium grain size. The granite has quite abundant metaquartzite, mica-schist, biotite, and igneous microgranular inclusions. It is a major building stone extensively used as a basic construction and decorative material.

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Nagarparkar granite

Wynne (1867) first reported the occurrence of Nagarparkar granite from the southeastern corner of Pakistan. It is located at about 400 km southeast of Karachi (Ali et al. 2012). Kazmi and Khan (1973) assigned a Precambrian age to these rocks. Pathan and Rais (1975) proposed that these rocks are the western extension of similar rocks exposed in India connected at depth through a batholithic mass. Qureshi et al. (2016) carried out radiological studies on the Nagarparkar granite for its suitability as a building material.

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MATERIAL AND METHODS

Sample collection and preparation

In total, 107 samples were collected from the five granites of Pakistan for study using high‐purity germanium (HPGe) gamma spectrometry. The samples were crushed and sieved to attain sand-size particles. The samples were then dried in an oven at 110°C for 24 h (Yang and Wu 2005 ; Benke and Kearfott 1999) and sealed in polyethylene Marinelli beakers. The net weight of each sample was noted. The reference material (RG1) obtained from IAEA’s Analytical Quality Control Services was also packed in the Marinelli beaker. The samples and reference material RG1 were stored for a sufficient time to achieve secular equilibrium between 226Ra and 222Rn (Tufail et al. 2006).

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Activity measurements

The HPGe gamma-ray spectrometer coupled with a personal-computer-based multichannel analyzer (MCA) along with a spectroscopy amplifier were employed for the measurement of activity concentration of 226Ra, 232Th, and 40K in the samples. The detector had a vertical dipstick geometry with a liquid nitrogen cooling arrangement. The diameter of the HPGe crystal was 59 mm, and its length was 53.4 mm. The photo-peak efficiency of the detector relative to a 5 cm × 5 cm NaI (Tl) was about 52.3%, and the energy resolution was 1.85 keV (full width, half maximum [FWHM]) for the 1.33 MeV gamma transition of a cobalt (60Co) point source. The detector was kept in a cylindrical cavity shielded with lead shield of 10‐cm thickness with inner lining of 2‐mm copper followed by 2‐mm aluminum lining for protection against outer radiation (Khan et al. 1998).

The system was calibrated for energy with point sources consisting of 241Am (59.53 keV), 57Co (122.04, 136.46 keV), 137Cs (661.61 keV), 60Co (1,173, 1,332, and 508 keV), and 22Na (1,274.55 keV) as described by Knoll (2000). The calibration of the detection system was accomplished using the RG1 sample containing uranium, thorium, and potassium reference materials. The samples were analyzed by acquiring a spectrum of each sample for 20,000–30,000 s. Background collected over a weekend was averaged and subtracted from the spectra of samples. The activity concentration of 226Ra was assessed from the activities of 214Pb and 214Bi, whereas the 232Th activity was evaluated by measuring the radioactive progeny, 228Ac, 212Pb, and 208Tl. The activity mass concentration of 40K was assessed from the 1,460.8‐keV gamma transition. The gamma energies used for determination of activity concentrations of 226Ra, 232Th, and 40K are given in Table 2.

Table 2

Table 2

The activity concentration A ct of gamma rays emitted by the sample was calculated using the following equation of Quindos et al. (1987):

where A is the net area under the peak and B is the background area under the same peak, P is the probability of the emission of gamma radiation at that particular energy, t is the data collection time, W is the weight of the sample in kg, and ε is the efficiency of the detector at the photo-peak energy.

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Radiological hazard indices

Radiation hazard is broadly defined as unintentional exposure to the radiation. Exposure to radioactive material can cause damage to living tissues, which poses a direct hazard to health. Radiation hazard indices weigh the collective impact of activity concentration on a material from 226Ra, 232Th, and 40K. Formulas used for the calculation of radiological hazard indices of granites are given in Table 3.

Table 3

Table 3

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RESULTS

Rustam-Koga granite from AGC

The activity concentration of 226Ra and 232Th in Rustam-Koga granite samples range from 46–6,120 Bq kg−1 (average: 659 Bq kg−1) and 92–3,214 Bq kg−1 (average: 598 Bq kg−1). The activity concentration of 40K has a narrow range of 899–1,927 Bq kg−1 (average: 1,218 Bq kg−1). These values are considerably higher as compared to the worldwide averages of 42, 73, and 1,095 Bq kq −1 for 226Ra, 232Th, and 40K, respectively, in granites reported by Chen and Lin (1996). This is because of the presence of uranium and thorium veins in the granite (Asghar et al. 2008).

The average value of the gamma index Iγ of Rustam-Koga granite is 5.6 with a range from 1.0 to 23.4. Out of 20 samples, 9 having Iγ ≤ 2 can be used as building material. Six samples that range between ≥2 and ≤6 can be considered for restricted use. The rest of the five samples have values of >6 and cannot be recommended as a building material. The average radium equivalent (Raeq) calculated on the basis of gamma activities of 226Ra, 232Th, and 40K in Rustam-Koga granite is 1,606 Bq kg−1, which is much higher than the world average Raeq for building materials (159.89 Bq kg−1) and the permissible limit of 370 Bq kg−1. The values of the outdoor hazard index (Hout) vary from 0.7 to 18.8 with an average of 4.3. Out of the 20 samples, only 6 samples have Hout values ≤ 1. Therefore, 14 samples are not fit for use as a construction material. The outdoor gamma dose rate (Dout) varies from 125 to 3,198 nGy h−1, which is much higher than the permissible limit of 51 nGy h−1 as per the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2000). The average values of Hout (4.34), Dout (716.44 nGy h−1), outdoor annual effective dose Eout (0.88 mSv y−1), and outdoor excess lifetime cancer risk ELCRout (3.08 × 10−3) are high compared to the average of the world’s granites (0.61, 107.28 nGy h−1, 0.13 mSv y−1, and 0.46 × 10−3), average of building materials (0.43, 74.15 nGy h−1, 0.09 mSv y−1, 0.32 × 10−3), and limiting values (<1, 60 nGy h−1, 1 mSv y−1, and 1.16 × 10−3), respectively.

The indoor hazard index (Hin) varies from 0.8 to 35.3 with an average of 6.1. Except for three samples, all other samples have Hin values higher than the permissible limit of 1 and do not qualify for use as a building material. Other indoor radiation indices like indoor gamma dose rate Din, indoor annual effective dose Ein, and indoor excess lifetime cancer risk ELCRin are 1,361.52 nGy h−1, 6.68 mSv y−1, and 23.39 × 10−3, which are very high as compared to the averages of world granites (279.64 nGy h−1, 1.37 mSv y−1, and 4.8 × 10−3); world average of building materials (141 nGy h−1, 0.69 mSv y−1, and 2.24 × 10−3); and limiting values (55 nGy h−1, 2 mSv y−1, and 1.16 × 10−3, respectively). Overall the granites sampled in the Rustam-Koga area are not suitable as building materials. Table 4 compares values of hazard indices for Rustam-Koga granite with world averages of granites calculated on the basis of average gamma-activity concentration of 226Ra, 232Th, and 40K reported by Chen and Lin (1996) for world granites and with building materials as per UNSCEAR (1993).

Table 4

Table 4

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Shewa-Shahbazgarhi granite

Forty-two rock samples collected from the Shewa-Shahbazgarhi area showed somewhat higher gamma activities of 226Ra (51 Bq kg−1), 232Th (70 Bq kg−1), and 40K (1,272 Bq kg−1), as compared to the world average of 226Ra (42 Bq kg−1), 232Th (73 Bq kg−1), and 40K (1,055 Bq kg−1) for granites (Chen and Lin 1996).

The average outdoor hazard indices of Shewa-Shahbazgarhi granite (Iγ: 0.94; Raeq: 248 Bq kg−1; Hout: 0.67; Dout: 118.88 nGy h−1; Eout: 0.15 mSv y−1; and ELCRout: 0.51 × 10−3) are comparable to the average of the world’s granites but slightly higher than the world average of building materials. These values are also lower than limiting values except Dout (60 nGy h−1) and ELCRout (0.29 × 10−3).

The average indoor hazard indices of Shewa-Shahbazgarhi granite (Hin: 0.81; Din: 225.68 nGy h−1; Ein: 1.11 mSv y−1; and ELCRin: 3.88 × 10−3) are comparable to the average of world’s granites but slightly higher than the world average of building materials. The values of Din and ELCRin are higher than their respective limiting values of 55 nGy h−1 and 1.16 × 10−3 (NEA-OCED 1979 ; Belgin and Aycik 2015 ; Orgun et al. 2005), whereas the values of Hin and Ein are less than the limiting value for both of 1 (Krieger 1981 ; UNSCEAR 2000). So the Shewa-Shahbazgarhi granite can be used for any type of construction.

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Bunair granite

The gamma-activity concentration of 226Ra (42 Bq kg−1), 232Th (58 Bq kg−1), and 40K (1,130 Bq kg−1) in Bunair granite is comparable to the world average for granites of 42, 73, and 1,055 Bq kg−1, respectively (Chen and Lin 1996). Among the outdoor hazard indices, the Iγ (0.81), which determines the suitability of a material for construction purposes, is low as compared to the limiting value of 2 (Tzortzis et al. 2003). The radium equivalent (Raeq: 211 Bq kg−1), outdoor hazard index (Hout: 0.67), and outdoor annual effective dose (Eout: 0.13 mSv y−1) of Bunair granite is less than the respective permissible limits of 370 Bq kg−1, 1, and 1 mSv y−1.

The average value of the outdoor gamma dose rate (Dout: 101.56 nGy h−1) is higher than the limiting value of 51 nGy h−1. The outdoor excess lifetime cancer risk (ELCRout: 0.44 × 10−3) estimated for Bunair granite is lower than world average granite values of 0.46 × 10−3 but higher than the world average value for building materials (0.32 × 10−3) and 1.5 times higher than the limiting value of 0.29 × 10−3 (UNSCEAR 2000). On this basis, one can assume that there is negligible excess lifetime cancer risk due to outdoor gamma-radiation exposure in Bunair area.

The indoor hazard index of Bunair granite (Hin: 0.69), indoor external dose (Din: 192.84 nGy h−1), and indoor annual effective dose (Ein: 0.95 mSv y−1) is lower than the world average for granites (Hin: 0.73; Din: 202.94 nGy h−1; and Ein: 1.00 mSv y−1). Indoor excess lifetime cancer risk of Bunair granite (ELCRin: 3.31 × 10−3) is lower than that of the average of world granites (3.49 × 10−3) but slightly higher than the average of world building materials (2.24 × 10−3). However, it is 2.8 times higher than the limiting value of 1.16 × 10−3 (Orgun et al. 2005), which is also in the range of the limiting value (3.49 × 10−3) of the world average for granites (Chen and Lin 1996). On this criterion, it can be assumed that the Bunair granite does not pose any significant radiological threat as a building material.

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Mansehra granite

Outdoor and indoor radiological hazard indices for Mansehra granite were estimated on the basis of gamma-activity concentrations of 226Ra (27 Bq kg−1), 232Th (50 Bq kg−1), and 40K (953 Bq kg−1). The outdoor indices like Iγ (0.66), Raeq (171 Bq kg−1), Hout (0.46), Dout (82.41 nGy h−1), Eout (0.10 mSv y−1), and ELCRout (0.35 × 10−3) were found to be lower than the world average for granites (Iγ: 0.89; Raeq: 227 Bq kg−1; Hout: 0.61; Dout: 107.28 nGy h−1; Eout: 0.13 mSv y−1; and ELCRout: 0.46 × 10−3) and comparable to the world average for building materials (Iγ: 0.58; Raeq: 159.8 Bq kg−1; Hout: 0.43; Dout: 74.15 nGy h−1; Eout: 0.09 mSv y−1; and ELCRout: 0.32 × 10−3). The outdoor indices for Mansehra granite are close to the limiting values except Dout (82.38 nGy h−1) and ELCRout (0.35 × 10−3). The value of Dout is 1.6 times higher than its limiting value of 51 nGy h−1. The ELCRout is slightly higher than the limit of 0.29 × 10−3 based on the average annual effective dose of 0.07 mSv y−1 (UNSCEAR 2000).

The indoor hazard indices of Mansehra granite (Hin: 0.54; Din: 156.08 nGy h−1; Ein: 0.77 mSv y−1; and ELCRin: 2.68 × 10−3) are comparable to the average values for world granites and building materials. Most of these values are below or close to their permissible limits. The Mansehra granite can be used for any type of construction without posing any radiological health hazard as a building material. It is to be emphasized, however, that construction of basements or use of granite as a solo building material in the area should be avoided, and granite from such areas may be used on a limited scale only.

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Nagarparkar granite

The gamma activities of 226Ra, 232Th, and 40K measured in the Nagarparkar granite are 26, 42, and 867.00 Bq kg−1, respectively. The total activity concentration due to 226Ra, 232Th, and 40K ranges from 742.14 to 1,095.86 Bq kg−1 with an average value of 939.34 Bq kg−1 and with 40K being the main contributor (54.48%) of radioactivity.

The values of outdoor hazard indices Iγ (0.66), Raeq (152 Bq kg−1), Hout (0.41), and Eout (0.09 mSv y−1) are less than the permissible limits of 2,370 Bq kg−1, 1, and 2 mSv y−1, respectively. The average value of Dout (73.5 nGy h−1) is close to the limiting value of 51 nGy h−1. The ELCRout estimated for Nagarparkar granite (0.32 × 10−3) is equal to the world average for building materials (0.32 × 10−3) and comparable to the limit of 0.29 × 10−3 that is based on the average annual effective dose of 0.07 mSv y−1 (UNSCEAR 2000) as shown in Table 4.

The indoor hazard index Hin (0.48) and indoor annual effective dose Ein (0.68 mSv y−1) are lower than their limits of 1 and 2 mSv y−1, respectively. The indoor external dose Din (139.24 nGy h−1) is higher than the limit of 55 nGy h−1. The indoor excess lifetime cancer risk ELCRin of Nagarparkar granite is 2.4 × 10−3, which is comparable to its value for building materials (2.42 × 10−3). As per the limiting value of ELCRin, Nagarparkar granite does not possess any chance of inducing cancer when compared to the world average values for building materials. Overall, Nagarparkar granite has been evaluated as a safe and suitable building material that can be used as a basic construction material and for decoration uses.

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DISCUSSION

Before the awareness of health concerns regarding radiation, building materials containing considerable amounts of radionuclides have been used for generations the world over. Elevated levels of radionuclides causing annual doses of several mSv y−1 have been identified in some buildings in Brazil, France, India, Nigeria, Iran, etc. As individuals spend about 80% of their time indoors, the internal radiation exposure from such buildings becomes a major exposure to radiation (Beretka and Mathew 1985).

Based on the worldwide indoor average absorbed dose rate (Din) of 84 nGy h−1, the annual indoor effective dose (Ein) due to gamma rays from building materials has been estimated to be about 0.4 mSv y−1 (UNSCEAR 2000). However, Qureshi et al. (2016) reported the range of Din and Ein to be from 64 to 1,360 nGy h−1 and 0.32 to 6.68 mS y−1, respectively, from the study of 49 granites of the world.

In Pakistan a few studies regarding health effects concerning the radioactivity of building materials have been carried out. In this regard, five granites exposed at Rustam-Koga, Bunair, Shewa-Shahbazgarhi, Mansehra, and Nagarparkar have been studied for their radiological evaluation.

The gamma-activity concentrations of 226Ra, 232Th, and 40K in all granites, except Rustam-Koga granites, are comparable to the average of world granites (226Ra: 42 Bq kg−1; 232Th: 73 Bq kg−1; and 40K: 1,050 Bq kg−1) and building materials (226Ra: 50 Bq kg−1; 232Th: 50 Bq kg−1; and 40K: 500 Bq kg−1). The exceptionally high values (226Ra: 659 Bq kg−1; 232Th: 598 Bq kg−1; and 40K: 1,218 Bq kg−1) in the Rustam-Koga granites are due to the frequent existence of highly radioactive zones in the study area.

The gamma-activity concentration of 226Ra, 232Th, and 40K in the studied granites increases from south to north. The Nagarparkar granite, exposed in the southernmost part of Pakistan, has the lowest gamma-activity concentrations of 226Ra (26 Bq kg−1), 232Th (42 Bq kg−1), and 40K (867 Bq kg−1). The Mansehra granite, exposed about 1,146 km north of Nagarparkar granite, has somewhat higher gamma-activity concentrations of 226Ra (27 Bq kg−1), 232Th (50 Bq kg−1), and 40K (953 Bq kg−1). The Bunair granite, at 1,173 km north of Nagarparkar granite, has moderate gamma-activity concentrations of 226Ra (42 Bq kg−1),232Th (58 Bq kg−1), and 40K (1,130 Bq kg−1). Further to the north, the Shewa-Shahbazgarhi, exposed 1,234 km north of Nagarparkar granite, has higher gamma-activity concentrations of 226Ra (51 Bq kg−1), 232Th (70 Bq kg−1), and 40K (1,272 Bq kg−1). The Rustam-Koga granite, which is located 1,295 km north of Nagarparkar, has significantly high gamma-activity concentrations of 226Ra (659 Bq kg−1), 232Th (598 Bq kg−1), and 40K (1,218 Bq kg−1). The systematic increase in the radioactivity of the five granites is shown in Table 5 and Fig. 2.

Table 5

Table 5

Fig. 2

Fig. 2

An increased activity concentration in the northern granites is attributed to their association with the Eurasian-Indian Plate collision zone in the Himalayas of Northern Pakistan. The Nagarparkar granite is exposed in the intraplate stable zone within the Indian Plate in Southern Pakistan. Similar is the trend of outdoor and indoor radiation hazards, which increase from south to north. Levels of terrestrial radionuclides and related radiological indices in the granites of Pakistan are shown in Table 4.

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CONCLUSION

Radiological hazard indices of four out of the five granites from Bunair, Shewa-Shahbazgarhi, Mansehra, and Nagarparkar are less than or equal to the world average for granites and building materials. The indoor and outdoor excess lifetime cancer risk of these four granites is lower than the world average for granites and building materials. Radiological hazard indices of Rustam-Koga granite are very high. The outdoor excess lifetime cancer risk ELCRout in the Rustam-Koga granite environment (3.08) is sufficiently higher than the world average for granites (0.46 × 10−3) and building materials (0.32 × 10−3). The indoor excess lifetime cancer risk ELCRin is exceptionally high (23.39 × 10−3), and for this reason it is not advisable to use Rustam Koga granite for construction, such as for counter tops or decoration material. Further, the limits of outdoor annual affective dose (Eout) are 1 mSv y−1 for a common person and 20 mSv y−1 for a radiation worker as per International Commission on Radiological Protection (ICRP) 60 (ICRP 1990). The limits of 1 to 20 mSv y−1 indicate that there is no dose limit below which there is no health effect (Stadtner 2012).

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              Keywords:

              health effects; radiation dose; radiation, gamma; radioactivity, environmental

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