CONCENTRATION OF RADON IN DWELLINGS OF HEMAVATHI RIVER BASIN, KARNATAKA, INDIA

CONCENTRATION OF RADON IN DWELLINGS OF HEMAVATHI RIVER BASIN, KARNATAKA, INDIA Abstract Indoor radon, thoron and their progeny levels were measured in various types of dwellings during 2016–17 in Hemavathi river basin, Karnataka by using solid state nuclear track detector based pin-hole dosemeters; dwellings of various types were chosen for the measurement. The dosemeters containing the detector (LR-115, Type II Film) was used for this purpose. The concentration of indoor radon in the study area varied from 30.72 to 196.08 Bq m−3 with a median of 83.13 Bq m−3 and thoron concentration varied from 15.56 to 227.78 Bq m−3. Higher concentrations of radon and its progeny were observed in granite flooring and cement roofing dwellings compared to other types of dwellings. The reason for higher concentration of indoor radon and its progeny is due to activity of radium present in granite and provision of less ventilation in dwellings. The equilibrium equivalent radon, thoron concentrations and annual effective dose are discussed. Introduction Radionuclides such as uranium, radium and radon are unstable elements that pass into the human body through inhalation and ingestion and accumulate in bone marrow. They emit alpha particles with high energy that collides with living cells. The energetic alpha particles emitted from radon and its daughter elements 214Po and 218Po are highly effective in damaging the tissues and are considered as causative agent for lung cancer in human beings. Radon can also migrate from soil into groundwater, which can become another route of exposure if the groundwater is used as a water supply source(1). Nature has gifted several geological materials to mankind for building construction. Granite is one of the most important rocks used as building material. The granite rock has relatively higher content of 226Ra, 232Th and 40K(2). The indoor radon concentration varies from one dwelling to another because of the variation in radium distribution in the building material such as flooring, cement, bricks, soil, paint, soil beneath, local geology, microclimatic parameters and the life style of the occupants(3, 4). Indoor radon concentration and the annual effective dose do not have good correlation because the annual effective dose depends not only on the concentration of radon but also on the concentration of thoron and its progenies and other factor that influences the annual effective dose is activity of the soil over few hundred meters distance to a few centimeters depth from the surface(5). Inhalation dose rate in dwellings varies with types and it is reported that granite flooring and lower volume houses are having higher dose rates of radon than other types of dwellings(6). Many researchers all over the world have been actively involved in the post two decades in indoor radon measurements(7–23). Indoor radon concentrations in Bangalore city and Bangalore rural district were varied from 55 to 300 Bq m−3 with a median of 155 Bq m−3(7). Seasonal variation of radon and its decay products were reported with high concentration in winter and very less in summer(8). In recent years concern has developed about possible association of indoor radon exposure and development of cancer. In view of this, it was felt essential to have a clear image of these and an attempt was made to estimate the annual indoor levels of radon, thoron and their progeny levels and the annual effective dose due to the exposure of indoor 222Rn, 220Rn and their progeny levels in various types of dwellings like granite, cement, mud, mosaic flooring, Mangalore tile, thatched, cement roof and mud bricks with cement and mud plastering to the population of Hemavathi river basin, Karnataka. STUDY AREA The area of study selected was Hemavathi river basin located at latitude 12°32′–13°08′ N and longitude 75°24′−76°26′ E. The area of the study was part of the Malnad region and plane region of Karnataka. Study area was located in the western part of the Karnataka State. The area is covered with hilly region along with southern malnad, semi-malnad and high lands maidan, southern maidan and Valleys. The geological map of the study area is as shown in Figure 1. The river Hemavathi originates from the Western Ghats at an elevation of ~1 219 m near Ballalarayana Durga in the Chikmagalur District, Karnataka, and flows through Chikmagalur, Hassan and Mandya districts before joining the Kaveri at Krishna Raja Sagar. This is the longest tributary of Kaveri (245 km) and is the fifth largest in catchment area having ~5410 km2 and lies wholly in Karnataka. The rock formations in this area are granites, gneisses, schist and quartzite peninsular gneisses; the major type of rock found is peninsular gneiss. The soil of this river basin displays wide diversity and is quite fertile. The main soil types are red soil, red sandy soil, mixed soil and silty clay soil. The soils are derived from granites, laterites, gneisses and schists. The entire study area soil is having variable amounts of radium content. In this study more concentration is bestowed more in dharwars, granite and peninsular gneiss rock regions along with their surroundings. Figure 1. View largeDownload slide Map of the area of study (Hemavathi river basin). Figure 1. View largeDownload slide Map of the area of study (Hemavathi river basin). MATERIALS AND METHODS Concentration of indoor radon, thoron and their progeny in dwellings were measured using pin-hole dosemeter cup based on SSNTD. A schematic diagram of pin-hole dosemeter is presented in Figure 2. Pin-hole dosemeters were suspended from the mid-point of the house at a height of 2 m from ground level and were exposed for a period of 90 days in three quarters of the year. At the end of three months of exposure, the dosemeters were retrieved and SSNTDs were etched with 2.5 N NaOH solution for 1 h at a bath temperature of 60°C. After etching the thin films were separated from cellulose acetate base and track density of alphas in the film was determined using a spark counter. Figure 2. View largeDownload slide Schematic diagram of pin-hole dosemeter. Figure 2. View largeDownload slide Schematic diagram of pin-hole dosemeter. The concentration of radon (CR) and thoron (CT) were calculated using the following equations(11):   CR(Bqm−3)=T1−BtxKr (1)  CT(Bqm−3)=T2−T1txKt (2)where T1 and T2 are the track density (tracks cm−2) of the film in the radon and radon + thoron chamber, B is the background track density in unexposed LR-115 detector, measured as 6 tracks cm−2, t is the period of exposure (days) and Kr (0.017 ± 0.002 tracks cm−2 d−1 Bq−1 m−3) and Kt (0.010 ± 0.001 tracks cm−2 d−1 Bq−1 m−3) are the calibration factors of radon and radon + thoron chambers, respectively. Equilibrium equivalent thoron concentrations (EETC) were calculated using the following equation(11):   EETC(Bqm−3)=TT−BtxST (3)where TT is the track density in direct thoron progeny sensor (DTPS) as shown in Figure 3, B is the background track density in unexposed LR-115 detector, measured as 6 tracks cm−2, t is the time of exposure in days and ST is the sensitivity factor for thoron progeny (0.94 ± 0.027 tracks cm−2 d−1 Bq−1 m−3). The EETC is calculated using track density of DTPS which has absorber of 50 μm thickness and is insensitive to radon progeny species. To obtain the exact track density from radon progeny in Direct Radon Progeny Sensor (DRPS) as shown in Figure 4, the tracks obtained from DTPS were eliminated from DRPS as mentioned in the following equation(11).   TRn=TDRPS−[ηRTηTT]TDTPS (4)Where TRn are the tracks only due to radon progeny, TDRPS are the total tracks in DRPS, TDTPS are the total tracks in DTPS, ηRT is the track registration efficiency (0.01 ± 0.0004) for thoron progeny in DRPS and ηTT is the track registration efficiency (0.083 ± 0.004) for thoron progeny in DTPS. Figure 3. View largeDownload slide Direct thoron progeny sensor. Figure 3. View largeDownload slide Direct thoron progeny sensor. Figure 4. View largeDownload slide Direct radon progeny sensor. Figure 4. View largeDownload slide Direct radon progeny sensor. The equilibrium equivalent radon progeny concentrations (EERC) is calculated using the following equation(11, 22).   EERC(Bqm−3)=TRn−BtxSR (5)where SR is the sensitivity factor for radon progeny (0.09 ± 0.0036 tracks cm−2 d−1 Bq−1 m−3). The total annual effective dose received by the individuals in indoor environment is the sum of the annual effective dose from radon (AEDR) and from thoron (AEDT) due to the combined effect of gas and progeny concentrations(22).   AEDR=[(CR×0.17)+(EERC×9)]×8760h×0.8×10−6 (6)  AEDT=[(CT×0.11)+(EERC×40)]×8760h×0.8×10−6 (7)where the dose conversion factor values are 0.17 and 9 nSv Bq−1 h−1 m3 for radon gas concentration (CR) and radon equilibrium equivalent concentration (EERC), respectively, whereas the values for thoron gas concentration (CT) and thoron equilibrium equivalent concentration (EETC) are 0.11 and 40 nSv Bq−1 h−1 m3, respectively. The indoor occupancy factor was taken as 0.8, for an exposure period of one year inside the dwellings. RESULTS AND DISCUSSION The 222Rn and 220Rn gas concentrations were measured during three quarter seasons such as winter, summer and rainy in 2016–17 in different types of dwellings using pin-hole based twin cup dosemeters and the results are summarized in Table 1. It can be observed from the Table 1 that the indoor radon concentration (CR) varied from 30.72 to 196.08 Bq m−3 with a median of 83.13 Bq m−3 and with a geometrical mean of 99.35 Bq m−3. The thoron concentration (CT) varied from 15.56 to 227.78 Bq m−3 with a median of 65.08 Bqm−3 and geometrical mean of 80.56 Bq m−3. The variation in the values of CR and CT might be due to the difference in topography in different geographic location of each village, ventilation conditions and building materials used in the construction of the houses used for investigation. However the values obtained for CR and CT are within the reference level of 300 Bq m−3 prescribed by ICRP(24). The geometrical mean value of 222Rn concentration 99.35 Bq m−3 observed in the present study is almost thrice the world’s average value of 37 Bq m−3(25–27). The equilibrium equivalent concentrations of 222Rn (EERC) and 220Rn (EETC) obtained in the study area are given in Table 1. The observed values of EERC vary from 7.15 to 54.08 Bq m−3 with a median of 22.98 Bq m−3 and geometrical mean of 26.06 Bq m−3. EETC values vary from 0.86 to 5.27 Bq m−3 with a median of 2.06 Bq m−3 and geometrical mean of 2.13 Bq m−3. Variation in the concentration of progenies was observed, which might be due to the difference in temperature and humidity of different indoor environments investigated. Table 1. Average values of indoor 222Rn, 220Rn and their progeny concentrations and annual effective dose due to these in the study area. Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Note: R, Roof; F, Floor. Mud bricks with cement plastering walls in all dwellings except in huts. Table 1. Average values of indoor 222Rn, 220Rn and their progeny concentrations and annual effective dose due to these in the study area. Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Note: R, Roof; F, Floor. Mud bricks with cement plastering walls in all dwellings except in huts. The annual effective dose values of radon (AEDR) were in the range of 0.49–3.61 mSv y−1 with a median of 1.55 mSv y−1 and geometrical mean value of 1.78 mSv y−1. Annual effective dose values of thoron (AEDT) varied from 0.26 to 1.65 mSv y−1 with the median being 0.63 mSv y−1 and geometrical mean of 0.66 mSv y−1. The total annual effective dose obtained in the study area varied from 0.75 to 4.64 mSv y−1 which is within the safe range from 3 to 10 mSv y−1 recommended by ICRP (2011)(24), and also below the recommended reference level of 10 mSv y−1 (WHO 2009)(27). The concentrations of 222Rn and 220Rn and their progeny within dwellings depends mainly on building materials, geology of the local area, tightness of the floor and the activity of the radium present in soil, rocks and building materials. The building materials used are bricks and cement for walls, granite, mosaic, cement and mud for flooring and Mangalore tiles, concentrate and thatched roof for roofing. Maximum annual effective doses of radon, thoron and their progeny were observed in concrete roofing and granite floor dwellings of Nagamangala road, Sharavanabelagola of Channarayapatna taluk dwellings as compared to other dwellings of the study area. Granites have higher activity of radionuclides such as 226Ra, 232Th and 40K. Nagamangala road of Sharavanabelgola area is surrounded by dharawar type of rocks (oldest sedimentary rocks). Lower annual effective doses are observed in Mandagere village of Krishnarajapete taluk. This area is surrounded by schist, charkonite, gnesis and unclassified crystalline type of rocks(28, 29). The type of dwelling is hut with bare flooring. Huts of the area of study are made of thatched roof. Thatched roofs are made of bamboo sticks, coconut leaves and paddy or millet dry plants. Porosity is more in thatched roofs (Figure 5). Owing to this, radon gas easily diffused from the huts. Hence, less concentration of radon and its progeny were observed in huts(7, 30). The variation of total annual effective dose in different types of dwellings in Hemavathi river basin is shown in Figure 6. Granite flooring and concentrate roof dwellings have higher annual effective dose of 4.35 mSv y−1 compared to other types of dwellings. It is known that granite flooring dwellings have high concentrate of 222Rn, 220Rn and their progeny due to high content of 226Ra, 232Th and 40K in granite(19). The huts have thatched roof and bare flooring have lower annual effective dose of 0.78 mSv y−1 due to more porosity and local geology. Figure 5. View largeDownload slide A view of hut in the study area. Figure 5. View largeDownload slide A view of hut in the study area. Indoor radon concentrations are tabulated in Table 2 along with other reported values. In dwellings of Sisdol landfill site, Nepal, concentration of indoor radon varies from 71 to 2016 Bq m−3 which is higher compared to any other nation(17). Minimum indoor radon concentration 1–34.7 Bq m−3 has been reported in 16 different feed grain places of local market Samawah city, Iraq(18). In the present study indoor radon concentration varies from 30.72 to 196.08 Bq m−3 with mean value 99.35 Bq m−3 have higher indoor radon concentration than 4.6–147 Bq m−3 with a mean value 23 Bq m−3 in 1400 dwellings of India(20). Table 2. Indoor radon concentration of some countries. Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Table 2. Indoor radon concentration of some countries. Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Dwellings of Solvenia, Mexico city, Morocco, Northwest Iran, Eastern sicily (Italy), South east Italy, province of Naples (south Italy) Ramera and Asthota (Himachal Pradesh), are having higher indoor radon concentration than the values found at presented study(9–12, 14–16, 21). Alexandria city (Egypt), Shiraz city (Iran) and Malwa region, Punjab state (India) have lower indoor radon concentration(13, 19, 22). Dwellings of Bathinda district of Punjab have almost same indoor radon concentration values of present study(23) (Figure 6). Figure 6. View largeDownload slide Total annual effective dose in various types of dwellings. Figure 6. View largeDownload slide Total annual effective dose in various types of dwellings. CONCLUSIONS The equilibrium equivalent concentrations of 222Rn and 220Rn and their progenies as observed in the present study in 48 dwellings were within the prescribed limits of ICRP. Maximum annual effective dose of radon, thoron and their progeny were observed in dwellings with granite floorings in Nagamangala road, Sharavanabelagola of Channarayapatna taluk, when compared to other types of dwellings. Minimum annual effective doses were observed in huts with bare flooring and thatched roof type of dwelling of Mandagere village, Krishnarajapete taluk. The concentrations of radon, thoron and their progeny mainly depend on ventilation, building materials used and local geology. Granite floor and concrete roof dwellings have high annual effective dose, thatched roof and bare hut have low annual effective dose compared to other types of dwellings. The total annual effective doses in dwellings of the study area are within the reference level of 3–10 mSv y−1 as proposed by ICRP (2011)(24) and more than the global average value (2.4 mSv y−1)(25). ACKNOWLEDGEMENTS Authors would like to thanks Dr J. Sannappa, Professor, Department of Physics, Kuvempu University, Shivamogga, Karnataka for providing laboratory facility to carryout experimental work. Sincere thanks to Sree Ranganatha, Former CFTRI, Mysuru, for his valuable suggestions during preparation of the article. REFERENCES 1 Baysson, H., Timarche, M., Tymen, G., Gouva, S., Caillaud, D., Artus, J. C., Vergnenegre, A., Ducloy, F. and Laurier, D. Indoor radon and lung cancer in France. Epidemiology  15, 709– 716 ( 2004). Google Scholar CrossRef Search ADS PubMed  2 Lubin, J. H. and Boice, J. D. Lung cancer risk from residential radon meter—analysis of eight epidemiological studies. J. Natl. Cancer Inst.  89, 49– 54 ( 1997). Google Scholar CrossRef Search ADS PubMed  3 Minkin, L. Is diffusion, thermo diffusion, or advection a primary mechanism of indoor radon entry. Radiat. Prot. Dosim.  102, 153– 162 ( 2002). Google Scholar CrossRef Search ADS   4 Urosevic, V. and Nikezic, D. Radon transport through concrete and determination of its diffusion coefficient. Radiat. Prot. Dosim.  104, 65– 70 ( 2003). Google Scholar CrossRef Search ADS   5 Fujimoto K. Kobayashi S. 1988 Shielding effect of snow cover on indoor exposure due to terrestrial gamma radiation Proceedings of Seventh International Congress of the international Protection Association  Sydney Pergamon Press) pp. 910– 913 6 Shobha, S., Sathish, L. A., Sundareshan, S. and Ramachandran, T. V. Inhalation dose due to indoor radon. Int. J. Pure Appl. Phys.  6( 3), 257– 262 ( 2010). 7 Ningappa, C., Sannappa, J., Chandrashekara, M. S. and Paramesh, L. Concentrations of radon and its daughter products in and around Bangalore city. Radiat. Prot. Dosim.  130( 4), 459– 465 ( 2008). Google Scholar CrossRef Search ADS   8 Ramola, R. C., Kandari, M. S., Rawat, R. B. S., Ramachandran, T. V. and Choubey, V. M. A study of seasonal variations of radon levels in different types of houses. J. Environ. Radioact.  39( 1), 1– 7 ( 1998). Google Scholar CrossRef Search ADS   9 Vaupotic, J, Sikovec, M and Kobal, I Systematic indoor radon and gamma-ray measurements in Slovenian schools. Health Phys.  78( 5), 559– 562 ( 2000). Google Scholar CrossRef Search ADS PubMed  10 Franco-Marinaa, F., Segoviab, N., Ruizb, W., Godinezc, L., Taverab, L., Lopezb, A., Chavezb, A., Penab, P. and Poncianoc, G. Short and long term indoor radon survey in Mexico City. Radiat. Meas.  34( 1–6), 545– 548 ( 2001). Google Scholar CrossRef Search ADS   11 Oufnia, L., Misdaqb, M. A. and Amraneb, M. Radon level and radon effective dose rate determination in Moroccan dwellings using SSNTDs. Radiat. Meas.  40( 1), 118– 123 ( 2005). Google Scholar CrossRef Search ADS   12 Kamal Hadada, R. and Doulatdarb, S. Mehdizadehaa, Indoor radon monitoring in Northern Iran using passive and active measurements. J. Environ. Radioact.  95( 1), 39– 52 ( 2007). Google Scholar CrossRef Search ADS PubMed  13 Abd El-Zaher, M. Seasonal variation of indoor radon concentration in dwellings of Alexandria city, Egypt. Radiat. Prot. Dosim.  143( 1), 56– 62 ( 2011). Google Scholar CrossRef Search ADS   14 Catalanoa, R., Immea, G., Manganoa, G., Morellia, D. and Rosselli Tazzera, A. Indoor radon survey in Eastern Sicily. Radiat. Meas.  47( 1), 105– 110 ( 2012). Google Scholar CrossRef Search ADS   15 Trevisi, R., Leonardi, F., Simeoni, C., Tonnarini, S. and Veschetti, M. Indoor radon levels in schools of South-East Italy. J. Environ. Radioact.  112, 160– 164 ( 2012). Google Scholar CrossRef Search ADS PubMed  16 Quarto, M., Pugliese, M., Loffredo, F. and Roca, V. Indoor radon concentration and gamma dose rate in dwellings of the Province of Naples, South Italy, and estimation of the effective dose to the inhabitants. Radio Prot.  51( 1), 31– 36 ( 2016). 17 Parajuli, P., Thapa, D. and Shah, B. R. Assessment of residential radon concentration in the dwellings near Sisdol Landfill Site using solid state nuclear track detector (SSNTD). Int. J Adv. Res.  2( 7), 425– 427 ( 2016). 18 Sabbar, A. N. Radon concentration measurement in feed grains by using SSNTD Type CR-39. Int. J. Adv. Res.  4( 2), 773– 776 ( 2016). 19 Yarahmadi, M., Shahsavani, A., Mahmoudian, M. H., Shamsedini, N., Rastkari, N. and Kermani, M. Estimation of the residential radon levels and the annual effective dose in dwellings of Shiraz, Iran, in 2015. Electron Phys.  8( 6), 2497– 2505 ( 2016). Google Scholar CrossRef Search ADS   20 Ramachandran, T. V., Eappen, K. P., Nair, R. N., Mayya, Y. S. and Sadasivan, S. Radon-thoron levels and inhalation dose distribution patterns in India dwellings. Environ. Sci.  63, 115 ( 2003). 21 Virk, H. S. Indoor radon levels near the radioactive sites of Himachal Pradesh, India. Environ. Int.  25( 1), 47– 51 ( 1999). Google Scholar CrossRef Search ADS   22 Singha, S., Mehrab, R. and Singhaa, K. Seasonal variation of indoor radon in dwellings of Malwa region, Punjab. Atmos. Environ.  39( 40), 761– 7767 ( 2005). 23 Singha, S., Kumara, M. and Mahajanba, R. K. The study of indoor radon in dwellings of Bathinda district, Punjab, India and its correlation with uranium and radon exhalation rate in soil. Radiat. Meas.  39( 5), 535– 542 ( 2005). Google Scholar CrossRef Search ADS   24 ICRP (International Commission on Radiological Protection). Lung Cancer Risk From Radon and Progeny and Statement on Radon. ICRP Publication-115  ( Oxford: Pergamon Press) ( 2011). 25 UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation). Report  ( New York: United Nations) ( 1988). 26 UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation). Annex B: Exposures From Natural Radiation Sources  ( New York: United Nations) ( 2000). 27 WHO (World Health Organization). Hand Book on Indoor Radon: A Public Health Perspective  ( Geneva: WHO Press) ( 2009). 28 Ningappa, C., Sannappa, J. and Karunakara, N. Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India. Radiat. Prot. Dosim.  131( 4), 495– 502 ( 2008). Google Scholar CrossRef Search ADS   29 Sannappa, J., Ningappa, C. and Prakash Narasimha, K. N. Natural radioactivity levels in granite regions of Karnataka State. Indian J. Pure Appl. Phys.  48, 817– 819 ( 2010). 30 Ningappa, C., Hamsa, K. S., Umesha Reddy, K., Niranjan, R. S., Rangaswamy, D. R. and Sannappa, J. Study on radon concentration at the work places of Mysuru, Bengaluru and Kolar districts of Karnataka State, South India. Radiat. Prot. Dosim.  171( 2), 200– 203 ( 2016). Google Scholar CrossRef Search ADS   © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

CONCENTRATION OF RADON IN DWELLINGS OF HEMAVATHI RIVER BASIN, KARNATAKA, INDIA

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Abstract

Abstract Indoor radon, thoron and their progeny levels were measured in various types of dwellings during 2016–17 in Hemavathi river basin, Karnataka by using solid state nuclear track detector based pin-hole dosemeters; dwellings of various types were chosen for the measurement. The dosemeters containing the detector (LR-115, Type II Film) was used for this purpose. The concentration of indoor radon in the study area varied from 30.72 to 196.08 Bq m−3 with a median of 83.13 Bq m−3 and thoron concentration varied from 15.56 to 227.78 Bq m−3. Higher concentrations of radon and its progeny were observed in granite flooring and cement roofing dwellings compared to other types of dwellings. The reason for higher concentration of indoor radon and its progeny is due to activity of radium present in granite and provision of less ventilation in dwellings. The equilibrium equivalent radon, thoron concentrations and annual effective dose are discussed. Introduction Radionuclides such as uranium, radium and radon are unstable elements that pass into the human body through inhalation and ingestion and accumulate in bone marrow. They emit alpha particles with high energy that collides with living cells. The energetic alpha particles emitted from radon and its daughter elements 214Po and 218Po are highly effective in damaging the tissues and are considered as causative agent for lung cancer in human beings. Radon can also migrate from soil into groundwater, which can become another route of exposure if the groundwater is used as a water supply source(1). Nature has gifted several geological materials to mankind for building construction. Granite is one of the most important rocks used as building material. The granite rock has relatively higher content of 226Ra, 232Th and 40K(2). The indoor radon concentration varies from one dwelling to another because of the variation in radium distribution in the building material such as flooring, cement, bricks, soil, paint, soil beneath, local geology, microclimatic parameters and the life style of the occupants(3, 4). Indoor radon concentration and the annual effective dose do not have good correlation because the annual effective dose depends not only on the concentration of radon but also on the concentration of thoron and its progenies and other factor that influences the annual effective dose is activity of the soil over few hundred meters distance to a few centimeters depth from the surface(5). Inhalation dose rate in dwellings varies with types and it is reported that granite flooring and lower volume houses are having higher dose rates of radon than other types of dwellings(6). Many researchers all over the world have been actively involved in the post two decades in indoor radon measurements(7–23). Indoor radon concentrations in Bangalore city and Bangalore rural district were varied from 55 to 300 Bq m−3 with a median of 155 Bq m−3(7). Seasonal variation of radon and its decay products were reported with high concentration in winter and very less in summer(8). In recent years concern has developed about possible association of indoor radon exposure and development of cancer. In view of this, it was felt essential to have a clear image of these and an attempt was made to estimate the annual indoor levels of radon, thoron and their progeny levels and the annual effective dose due to the exposure of indoor 222Rn, 220Rn and their progeny levels in various types of dwellings like granite, cement, mud, mosaic flooring, Mangalore tile, thatched, cement roof and mud bricks with cement and mud plastering to the population of Hemavathi river basin, Karnataka. STUDY AREA The area of study selected was Hemavathi river basin located at latitude 12°32′–13°08′ N and longitude 75°24′−76°26′ E. The area of the study was part of the Malnad region and plane region of Karnataka. Study area was located in the western part of the Karnataka State. The area is covered with hilly region along with southern malnad, semi-malnad and high lands maidan, southern maidan and Valleys. The geological map of the study area is as shown in Figure 1. The river Hemavathi originates from the Western Ghats at an elevation of ~1 219 m near Ballalarayana Durga in the Chikmagalur District, Karnataka, and flows through Chikmagalur, Hassan and Mandya districts before joining the Kaveri at Krishna Raja Sagar. This is the longest tributary of Kaveri (245 km) and is the fifth largest in catchment area having ~5410 km2 and lies wholly in Karnataka. The rock formations in this area are granites, gneisses, schist and quartzite peninsular gneisses; the major type of rock found is peninsular gneiss. The soil of this river basin displays wide diversity and is quite fertile. The main soil types are red soil, red sandy soil, mixed soil and silty clay soil. The soils are derived from granites, laterites, gneisses and schists. The entire study area soil is having variable amounts of radium content. In this study more concentration is bestowed more in dharwars, granite and peninsular gneiss rock regions along with their surroundings. Figure 1. View largeDownload slide Map of the area of study (Hemavathi river basin). Figure 1. View largeDownload slide Map of the area of study (Hemavathi river basin). MATERIALS AND METHODS Concentration of indoor radon, thoron and their progeny in dwellings were measured using pin-hole dosemeter cup based on SSNTD. A schematic diagram of pin-hole dosemeter is presented in Figure 2. Pin-hole dosemeters were suspended from the mid-point of the house at a height of 2 m from ground level and were exposed for a period of 90 days in three quarters of the year. At the end of three months of exposure, the dosemeters were retrieved and SSNTDs were etched with 2.5 N NaOH solution for 1 h at a bath temperature of 60°C. After etching the thin films were separated from cellulose acetate base and track density of alphas in the film was determined using a spark counter. Figure 2. View largeDownload slide Schematic diagram of pin-hole dosemeter. Figure 2. View largeDownload slide Schematic diagram of pin-hole dosemeter. The concentration of radon (CR) and thoron (CT) were calculated using the following equations(11):   CR(Bqm−3)=T1−BtxKr (1)  CT(Bqm−3)=T2−T1txKt (2)where T1 and T2 are the track density (tracks cm−2) of the film in the radon and radon + thoron chamber, B is the background track density in unexposed LR-115 detector, measured as 6 tracks cm−2, t is the period of exposure (days) and Kr (0.017 ± 0.002 tracks cm−2 d−1 Bq−1 m−3) and Kt (0.010 ± 0.001 tracks cm−2 d−1 Bq−1 m−3) are the calibration factors of radon and radon + thoron chambers, respectively. Equilibrium equivalent thoron concentrations (EETC) were calculated using the following equation(11):   EETC(Bqm−3)=TT−BtxST (3)where TT is the track density in direct thoron progeny sensor (DTPS) as shown in Figure 3, B is the background track density in unexposed LR-115 detector, measured as 6 tracks cm−2, t is the time of exposure in days and ST is the sensitivity factor for thoron progeny (0.94 ± 0.027 tracks cm−2 d−1 Bq−1 m−3). The EETC is calculated using track density of DTPS which has absorber of 50 μm thickness and is insensitive to radon progeny species. To obtain the exact track density from radon progeny in Direct Radon Progeny Sensor (DRPS) as shown in Figure 4, the tracks obtained from DTPS were eliminated from DRPS as mentioned in the following equation(11).   TRn=TDRPS−[ηRTηTT]TDTPS (4)Where TRn are the tracks only due to radon progeny, TDRPS are the total tracks in DRPS, TDTPS are the total tracks in DTPS, ηRT is the track registration efficiency (0.01 ± 0.0004) for thoron progeny in DRPS and ηTT is the track registration efficiency (0.083 ± 0.004) for thoron progeny in DTPS. Figure 3. View largeDownload slide Direct thoron progeny sensor. Figure 3. View largeDownload slide Direct thoron progeny sensor. Figure 4. View largeDownload slide Direct radon progeny sensor. Figure 4. View largeDownload slide Direct radon progeny sensor. The equilibrium equivalent radon progeny concentrations (EERC) is calculated using the following equation(11, 22).   EERC(Bqm−3)=TRn−BtxSR (5)where SR is the sensitivity factor for radon progeny (0.09 ± 0.0036 tracks cm−2 d−1 Bq−1 m−3). The total annual effective dose received by the individuals in indoor environment is the sum of the annual effective dose from radon (AEDR) and from thoron (AEDT) due to the combined effect of gas and progeny concentrations(22).   AEDR=[(CR×0.17)+(EERC×9)]×8760h×0.8×10−6 (6)  AEDT=[(CT×0.11)+(EERC×40)]×8760h×0.8×10−6 (7)where the dose conversion factor values are 0.17 and 9 nSv Bq−1 h−1 m3 for radon gas concentration (CR) and radon equilibrium equivalent concentration (EERC), respectively, whereas the values for thoron gas concentration (CT) and thoron equilibrium equivalent concentration (EETC) are 0.11 and 40 nSv Bq−1 h−1 m3, respectively. The indoor occupancy factor was taken as 0.8, for an exposure period of one year inside the dwellings. RESULTS AND DISCUSSION The 222Rn and 220Rn gas concentrations were measured during three quarter seasons such as winter, summer and rainy in 2016–17 in different types of dwellings using pin-hole based twin cup dosemeters and the results are summarized in Table 1. It can be observed from the Table 1 that the indoor radon concentration (CR) varied from 30.72 to 196.08 Bq m−3 with a median of 83.13 Bq m−3 and with a geometrical mean of 99.35 Bq m−3. The thoron concentration (CT) varied from 15.56 to 227.78 Bq m−3 with a median of 65.08 Bqm−3 and geometrical mean of 80.56 Bq m−3. The variation in the values of CR and CT might be due to the difference in topography in different geographic location of each village, ventilation conditions and building materials used in the construction of the houses used for investigation. However the values obtained for CR and CT are within the reference level of 300 Bq m−3 prescribed by ICRP(24). The geometrical mean value of 222Rn concentration 99.35 Bq m−3 observed in the present study is almost thrice the world’s average value of 37 Bq m−3(25–27). The equilibrium equivalent concentrations of 222Rn (EERC) and 220Rn (EETC) obtained in the study area are given in Table 1. The observed values of EERC vary from 7.15 to 54.08 Bq m−3 with a median of 22.98 Bq m−3 and geometrical mean of 26.06 Bq m−3. EETC values vary from 0.86 to 5.27 Bq m−3 with a median of 2.06 Bq m−3 and geometrical mean of 2.13 Bq m−3. Variation in the concentration of progenies was observed, which might be due to the difference in temperature and humidity of different indoor environments investigated. Table 1. Average values of indoor 222Rn, 220Rn and their progeny concentrations and annual effective dose due to these in the study area. Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Note: R, Roof; F, Floor. Mud bricks with cement plastering walls in all dwellings except in huts. Table 1. Average values of indoor 222Rn, 220Rn and their progeny concentrations and annual effective dose due to these in the study area. Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Villages  Type of house  Number of houses  Concentration (Bq m−3)  Eq. Ev. Prog. Conc. (Bq m−3)  Ann. Eff. dose (mSv y−1)  Total annual effective dose (mSv y−1)  222Rn  220Rn  EERC  EETC  AEDR  AEDT  Mudigere taluk, Chikkamagalur Dist   Baggasagodu  Mangalore Tile (R) Cement (F)  2  39.87  28.89  9.96  1.36  0.68  0.40  1.08  Concrete (R) Cement (F)  1  112.42  74.44  32.74  2.01  2.20  0.62  2.82   Palguni  Mangalore Tile (R) Cement (F)  1  31.37  23.33  9.73  1.13  0.65  0.34  0.99  Concrete (R) Mosaic (F)  2  160.78  113.33  45.09  3.65  3.04  1.11  4.15   Kirgunda  Mangalore Tile (R) Cement (F)  1  43.14  40.00  7.78  1.25  0.54  0.38  0.92   Muttigepura  Mangalore Tile (R) Cement (F)  1  31.37  25.56  11.02  1.08  0.73  0.32  1.05  Sakleshpura Taluk, Hassan District   Hanbalu  Mangalore Tile (R) Cement (F)  1  38.56  23.33  11.98  0.96  0.80  0.29  1.09  Concrete (R) Cement (F)  1  60.13  62.22  17.33  1.49  1.16  0.47  1.63   Hebasale  Mangalore Tile (R) Cement (F)  3  47.06  60.00  12.43  1.36  0.84  0.43  1.27   Besooru  Concrete (R) Granite (F)  2  169.28  120.00  54.08  3.22  3.61  0.99  4.61  Concrete (R) Cement (F)  1  99.35  86.67  23.69  2.48  1.61  0.76  2.38   Ragavendra Nagara  Concrete (R) Granite (F)  2  156.21  92.22  39.92  3.77  2.70  1.13  3.83  Mangalore Tile (R) Mosaic (F)  2  130.07  98.89  40.64  3.65  2.72  1.10  3.82  Arklgud Taluk, Hassan District   Gorur  Concrete (R) Granite (F)  1  182.35  116.67  47.51  3.76  3.21  1.14  4.36  Concrete (R)Vitrified tiles (F)  2  117.65  84.44  27.22  2.84  1.86  0.86  2.72   Hebbale  Concrete (R) Mosaic (F)  1  174.51  171.11  41.28  4.11  2.81  1.28  4.10  Holenarasipura Taluk, Hassan District   Paduvalahippe  Mangalore Tile (R) Cement (F)  1  47.71  23.33  14.26  1.26  0.96  0.37  1.33  Concrete (R) Cement (F)  1  99.35  76.67  34.74  2.15  2.31  0.66  2.97   Hosakote (HN)  Concrete (R) Cement (F)  2  99.35  91.11  35.91  2.12  2.38  0.66  3.05  Channarayapatna Taluk, Hassan District   Punya Hospital  Concrete (R) Granite (F)  1  193.46  227.78  38.29  5.27  2.65  1.65  4.30   Kalyani main road, Shravanabelagola  Concrete (R) Granite (F)  3  196.08  161.11  46.77  3.76  3.18  1.18  4.36  Concrete (R) Vitrified tiles (F)  2  109.80  98.89  24.91  2.71  1.70  0.84  2.54   Nagamangala road Shravanabelagola  Concrete (R) Granite (F)  1  187.58  153.33  47.61  4.62  3.23  1.41  4.64  Concrete (R) Cement (F)  1  112.42  107.78  34.08  2.23  2.28  0.71  2.99  Krishnarajapete Taluk, Hassan District   Mandagere (KRP)  Mangalore Tile (R) Cement (F)  2  55.56  45.56  12.79  1.61  0.87  0.49  1.36  Concrete (R) Cement (F)  1  58.17  37.78  16.79  1.25  1.13  0.38  1.51  Thatched (R) Bare (F)  2  32.68  26.67  7.15  0.86  0.49  0.26  0.75   Mallinahalli (KRP)  Thatched (R) Bare (F)  1  30.72  27.78  8.25  1.11  0.56  0.33  0.89  Concrete (R) Cement (F)  2  137.91  96.67  44.80  3.44  2.99  1.04  4.03   Kattekyathanahalli (KRP)  Mangalore Tile (R) Cement (F)  1  39.87  15.56  13.80  1.09  0.92  0.32  1.23  Concrete (R) Cement (F)  2  128.76  115.56  46.41  2.48  3.08  0.78  3.87   Bookahalli (KRP)  Concrete (R) Cement (F)  1  66.67  61.11  22.25  1.37  1.48  0.43  1.91  Minimum  30.72  15.56  7.15  0.86  0.49  0.26  0.75  Maximum  196.08  227.78  54.08  5.27  3.61  1.65  4.64  Median  83.13  65.08  22.98  2.06  1.55  0.63  2.19  Geometrical mean  99.35  80.56  26.06  2.13  1.78  0.66  2.63  Note: R, Roof; F, Floor. Mud bricks with cement plastering walls in all dwellings except in huts. The annual effective dose values of radon (AEDR) were in the range of 0.49–3.61 mSv y−1 with a median of 1.55 mSv y−1 and geometrical mean value of 1.78 mSv y−1. Annual effective dose values of thoron (AEDT) varied from 0.26 to 1.65 mSv y−1 with the median being 0.63 mSv y−1 and geometrical mean of 0.66 mSv y−1. The total annual effective dose obtained in the study area varied from 0.75 to 4.64 mSv y−1 which is within the safe range from 3 to 10 mSv y−1 recommended by ICRP (2011)(24), and also below the recommended reference level of 10 mSv y−1 (WHO 2009)(27). The concentrations of 222Rn and 220Rn and their progeny within dwellings depends mainly on building materials, geology of the local area, tightness of the floor and the activity of the radium present in soil, rocks and building materials. The building materials used are bricks and cement for walls, granite, mosaic, cement and mud for flooring and Mangalore tiles, concentrate and thatched roof for roofing. Maximum annual effective doses of radon, thoron and their progeny were observed in concrete roofing and granite floor dwellings of Nagamangala road, Sharavanabelagola of Channarayapatna taluk dwellings as compared to other dwellings of the study area. Granites have higher activity of radionuclides such as 226Ra, 232Th and 40K. Nagamangala road of Sharavanabelgola area is surrounded by dharawar type of rocks (oldest sedimentary rocks). Lower annual effective doses are observed in Mandagere village of Krishnarajapete taluk. This area is surrounded by schist, charkonite, gnesis and unclassified crystalline type of rocks(28, 29). The type of dwelling is hut with bare flooring. Huts of the area of study are made of thatched roof. Thatched roofs are made of bamboo sticks, coconut leaves and paddy or millet dry plants. Porosity is more in thatched roofs (Figure 5). Owing to this, radon gas easily diffused from the huts. Hence, less concentration of radon and its progeny were observed in huts(7, 30). The variation of total annual effective dose in different types of dwellings in Hemavathi river basin is shown in Figure 6. Granite flooring and concentrate roof dwellings have higher annual effective dose of 4.35 mSv y−1 compared to other types of dwellings. It is known that granite flooring dwellings have high concentrate of 222Rn, 220Rn and their progeny due to high content of 226Ra, 232Th and 40K in granite(19). The huts have thatched roof and bare flooring have lower annual effective dose of 0.78 mSv y−1 due to more porosity and local geology. Figure 5. View largeDownload slide A view of hut in the study area. Figure 5. View largeDownload slide A view of hut in the study area. Indoor radon concentrations are tabulated in Table 2 along with other reported values. In dwellings of Sisdol landfill site, Nepal, concentration of indoor radon varies from 71 to 2016 Bq m−3 which is higher compared to any other nation(17). Minimum indoor radon concentration 1–34.7 Bq m−3 has been reported in 16 different feed grain places of local market Samawah city, Iraq(18). In the present study indoor radon concentration varies from 30.72 to 196.08 Bq m−3 with mean value 99.35 Bq m−3 have higher indoor radon concentration than 4.6–147 Bq m−3 with a mean value 23 Bq m−3 in 1400 dwellings of India(20). Table 2. Indoor radon concentration of some countries. Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Table 2. Indoor radon concentration of some countries. Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Country  Indoor radon concentration (Bq m−3)  Reference  Range  Mean  Solvenia (890 schools)    168  (9)  Mexico city (dwellings)    145  (10)  Morocco (dwellings of some cities)  40–532    (11)  Northwest Iran (Lahijan, Ardabil, Sar-Ein and Namin)    163, 240, 160 and 144  (12)  Alexandria city, Egypt (68 dwellings)  45–90    (13)  Eastern Sicily, Italy (schools and dwellings)    500  (14)  South–East, Italy (438 schools)  21–1608  209  (15)  Province of Naples, South Italy (471 dwellings)  21–722  107  (16)  Sisdol Landfill Site, Nepal (dwellings)  71–2026    (17)  Samawah city, Iraq (16 different feed grain place of local market)  1–34.7    (18)  Shiraz city, Iran (dwellings)    57.6  (19)  India (1400 dwellings)  4.6 and 147  23  (20)  Ramera and Asthota, Himachal Pradesh (dwellings)    165, 145  (21)  Malwa region, Punjab state, India (105 dwellings of 21 villages)  76.25–145.50    (22)  Bathinda district of Punjab, India (dwellings)  95–202    (23)  Present study (various types of dwellings)  30.72–196.08  99.35  –  Dwellings of Solvenia, Mexico city, Morocco, Northwest Iran, Eastern sicily (Italy), South east Italy, province of Naples (south Italy) Ramera and Asthota (Himachal Pradesh), are having higher indoor radon concentration than the values found at presented study(9–12, 14–16, 21). Alexandria city (Egypt), Shiraz city (Iran) and Malwa region, Punjab state (India) have lower indoor radon concentration(13, 19, 22). Dwellings of Bathinda district of Punjab have almost same indoor radon concentration values of present study(23) (Figure 6). Figure 6. View largeDownload slide Total annual effective dose in various types of dwellings. Figure 6. View largeDownload slide Total annual effective dose in various types of dwellings. CONCLUSIONS The equilibrium equivalent concentrations of 222Rn and 220Rn and their progenies as observed in the present study in 48 dwellings were within the prescribed limits of ICRP. Maximum annual effective dose of radon, thoron and their progeny were observed in dwellings with granite floorings in Nagamangala road, Sharavanabelagola of Channarayapatna taluk, when compared to other types of dwellings. Minimum annual effective doses were observed in huts with bare flooring and thatched roof type of dwelling of Mandagere village, Krishnarajapete taluk. The concentrations of radon, thoron and their progeny mainly depend on ventilation, building materials used and local geology. Granite floor and concrete roof dwellings have high annual effective dose, thatched roof and bare hut have low annual effective dose compared to other types of dwellings. The total annual effective doses in dwellings of the study area are within the reference level of 3–10 mSv y−1 as proposed by ICRP (2011)(24) and more than the global average value (2.4 mSv y−1)(25). ACKNOWLEDGEMENTS Authors would like to thanks Dr J. Sannappa, Professor, Department of Physics, Kuvempu University, Shivamogga, Karnataka for providing laboratory facility to carryout experimental work. Sincere thanks to Sree Ranganatha, Former CFTRI, Mysuru, for his valuable suggestions during preparation of the article. REFERENCES 1 Baysson, H., Timarche, M., Tymen, G., Gouva, S., Caillaud, D., Artus, J. C., Vergnenegre, A., Ducloy, F. and Laurier, D. Indoor radon and lung cancer in France. Epidemiology  15, 709– 716 ( 2004). Google Scholar CrossRef Search ADS PubMed  2 Lubin, J. H. and Boice, J. D. Lung cancer risk from residential radon meter—analysis of eight epidemiological studies. J. Natl. Cancer Inst.  89, 49– 54 ( 1997). Google Scholar CrossRef Search ADS PubMed  3 Minkin, L. Is diffusion, thermo diffusion, or advection a primary mechanism of indoor radon entry. Radiat. Prot. Dosim.  102, 153– 162 ( 2002). Google Scholar CrossRef Search ADS   4 Urosevic, V. and Nikezic, D. Radon transport through concrete and determination of its diffusion coefficient. Radiat. Prot. Dosim.  104, 65– 70 ( 2003). Google Scholar CrossRef Search ADS   5 Fujimoto K. Kobayashi S. 1988 Shielding effect of snow cover on indoor exposure due to terrestrial gamma radiation Proceedings of Seventh International Congress of the international Protection Association  Sydney Pergamon Press) pp. 910– 913 6 Shobha, S., Sathish, L. A., Sundareshan, S. and Ramachandran, T. V. Inhalation dose due to indoor radon. Int. J. Pure Appl. Phys.  6( 3), 257– 262 ( 2010). 7 Ningappa, C., Sannappa, J., Chandrashekara, M. S. and Paramesh, L. Concentrations of radon and its daughter products in and around Bangalore city. Radiat. Prot. Dosim.  130( 4), 459– 465 ( 2008). Google Scholar CrossRef Search ADS   8 Ramola, R. C., Kandari, M. S., Rawat, R. B. S., Ramachandran, T. V. and Choubey, V. M. A study of seasonal variations of radon levels in different types of houses. J. Environ. Radioact.  39( 1), 1– 7 ( 1998). Google Scholar CrossRef Search ADS   9 Vaupotic, J, Sikovec, M and Kobal, I Systematic indoor radon and gamma-ray measurements in Slovenian schools. Health Phys.  78( 5), 559– 562 ( 2000). Google Scholar CrossRef Search ADS PubMed  10 Franco-Marinaa, F., Segoviab, N., Ruizb, W., Godinezc, L., Taverab, L., Lopezb, A., Chavezb, A., Penab, P. and Poncianoc, G. Short and long term indoor radon survey in Mexico City. Radiat. Meas.  34( 1–6), 545– 548 ( 2001). Google Scholar CrossRef Search ADS   11 Oufnia, L., Misdaqb, M. A. and Amraneb, M. Radon level and radon effective dose rate determination in Moroccan dwellings using SSNTDs. Radiat. Meas.  40( 1), 118– 123 ( 2005). Google Scholar CrossRef Search ADS   12 Kamal Hadada, R. and Doulatdarb, S. Mehdizadehaa, Indoor radon monitoring in Northern Iran using passive and active measurements. J. Environ. Radioact.  95( 1), 39– 52 ( 2007). Google Scholar CrossRef Search ADS PubMed  13 Abd El-Zaher, M. Seasonal variation of indoor radon concentration in dwellings of Alexandria city, Egypt. Radiat. Prot. Dosim.  143( 1), 56– 62 ( 2011). Google Scholar CrossRef Search ADS   14 Catalanoa, R., Immea, G., Manganoa, G., Morellia, D. and Rosselli Tazzera, A. Indoor radon survey in Eastern Sicily. Radiat. Meas.  47( 1), 105– 110 ( 2012). Google Scholar CrossRef Search ADS   15 Trevisi, R., Leonardi, F., Simeoni, C., Tonnarini, S. and Veschetti, M. Indoor radon levels in schools of South-East Italy. J. Environ. Radioact.  112, 160– 164 ( 2012). Google Scholar CrossRef Search ADS PubMed  16 Quarto, M., Pugliese, M., Loffredo, F. and Roca, V. Indoor radon concentration and gamma dose rate in dwellings of the Province of Naples, South Italy, and estimation of the effective dose to the inhabitants. Radio Prot.  51( 1), 31– 36 ( 2016). 17 Parajuli, P., Thapa, D. and Shah, B. R. Assessment of residential radon concentration in the dwellings near Sisdol Landfill Site using solid state nuclear track detector (SSNTD). Int. J Adv. Res.  2( 7), 425– 427 ( 2016). 18 Sabbar, A. N. Radon concentration measurement in feed grains by using SSNTD Type CR-39. Int. J. Adv. Res.  4( 2), 773– 776 ( 2016). 19 Yarahmadi, M., Shahsavani, A., Mahmoudian, M. H., Shamsedini, N., Rastkari, N. and Kermani, M. Estimation of the residential radon levels and the annual effective dose in dwellings of Shiraz, Iran, in 2015. Electron Phys.  8( 6), 2497– 2505 ( 2016). Google Scholar CrossRef Search ADS   20 Ramachandran, T. V., Eappen, K. P., Nair, R. N., Mayya, Y. S. and Sadasivan, S. Radon-thoron levels and inhalation dose distribution patterns in India dwellings. Environ. Sci.  63, 115 ( 2003). 21 Virk, H. S. Indoor radon levels near the radioactive sites of Himachal Pradesh, India. Environ. Int.  25( 1), 47– 51 ( 1999). Google Scholar CrossRef Search ADS   22 Singha, S., Mehrab, R. and Singhaa, K. Seasonal variation of indoor radon in dwellings of Malwa region, Punjab. Atmos. Environ.  39( 40), 761– 7767 ( 2005). 23 Singha, S., Kumara, M. and Mahajanba, R. K. The study of indoor radon in dwellings of Bathinda district, Punjab, India and its correlation with uranium and radon exhalation rate in soil. Radiat. Meas.  39( 5), 535– 542 ( 2005). Google Scholar CrossRef Search ADS   24 ICRP (International Commission on Radiological Protection). Lung Cancer Risk From Radon and Progeny and Statement on Radon. ICRP Publication-115  ( Oxford: Pergamon Press) ( 2011). 25 UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation). Report  ( New York: United Nations) ( 1988). 26 UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation). Annex B: Exposures From Natural Radiation Sources  ( New York: United Nations) ( 2000). 27 WHO (World Health Organization). Hand Book on Indoor Radon: A Public Health Perspective  ( Geneva: WHO Press) ( 2009). 28 Ningappa, C., Sannappa, J. and Karunakara, N. Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India. Radiat. Prot. Dosim.  131( 4), 495– 502 ( 2008). Google Scholar CrossRef Search ADS   29 Sannappa, J., Ningappa, C. and Prakash Narasimha, K. N. Natural radioactivity levels in granite regions of Karnataka State. Indian J. Pure Appl. Phys.  48, 817– 819 ( 2010). 30 Ningappa, C., Hamsa, K. S., Umesha Reddy, K., Niranjan, R. S., Rangaswamy, D. R. and Sannappa, J. Study on radon concentration at the work places of Mysuru, Bengaluru and Kolar districts of Karnataka State, South India. Radiat. Prot. Dosim.  171( 2), 200– 203 ( 2016). Google Scholar CrossRef Search ADS   © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

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Radiation Protection DosimetryOxford University Press

Published: Feb 15, 2018

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