Seasonal variation of indoor radon in dwellings of Malwa region, Punjab

Transcription

1 Atmospheric Environment 39 (2005) Seasonal variation of indoor radon in dwellings of Malwa region, Punjab Surinder Singh a,, Rohit Mehra b, Kulwant Singh a a Department of Physics, Guru Nanak Dev University, Amritsar, India b Department of Applied Sciences, Malout Institute of Management and Information Technology, Malout, India Received 15 April 2005; accepted 7 August 2005 Abstract Indoor radon measurements in 105 dwellings belonging to 21 villages of Muktsar and Ferozepur districts of Malwa region, Punjab, have been carried out, using LR-115 type II cellulose nitrate films in the bare mode. The annual average indoor radon value in the study area varies from to Bq m 3, which is well within the recommended action level [ICRP, Protection against radon at home and work. Annals of ICRP, ICRP Publication, p. 65]. Seasonal variation of indoor radon shows high values in winter and low values in. The winter/ of radon concentn has been computed for all 105 dwellings. The winter/ of indoor radon ranges from 0.84 to 1.89 with an average of The indoor radon values obtained in the present investigation are more than the world average of 40 Bq m 3 r 2005 Elsevier Ltd. All rights reserved. Keywords: Radon; Thoron; Cancer; Dwellings; LR Introduction Radon ( 222 Rn) a decay product of radium in the naturally occurring uranium series is a radioactive inert gas and is responsible for about half of the radiation dose received by the general population (UNSCEAR, 1994). Radon isotopes can isolate themselves and migrate away from the parent mineral due to diffusion process through the soil and enter the atmosphere. The radon and its progeny attached to aerosols present in the ambient air constitute significant radioactive hazards to human lungs. During respin radon progeny Corresponding author. Tel.: ; fax: address: surinder51@yahoo.com (S. Singh). deposits in the lungs and irradiate the tissue thereby damaging the cells and may cause lung cancer. Henshaw et al. (1990) claimed that indoor radon exposure is associated with the risk of leukemia and certain other cancers, such as melanoma and cancers of the kidney and prostate.the concentn of radon and its decay products show large temporal and local fluctuations in the indoor atmosphere due to the variations of temperature, pressure, nature of building materials, ventilation s and wind speed, etc. In the study area 21 villages and five houses in each village were chosen for indoor radon studies. The houses were chosen in such a way that the dwellings constructed with different types of building materials and in different localities of the village are covered. The surveyed area (Fig. 1) is bounded on the western side by /$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi: /j.atmosenv

2 7762 S. Singh et al. / Atmospheric Environment 39 (2005) Fig. 1. Map of Punjab showing Muktsar and Ferozepur area surveyed during the present investigations. Pakistan; on the south by Rajasthan and Haryana. The latitude and longitude of Muktsar and Ferozepur districts are N, E and N, E, respectively. Most of the area is affected by the water-logging problem. For health risk assessment, radon measurements were carried out for a period of one year. The annual exposure to occupants, the annual effective dose received by them and their lifetime fatality risk estimates have been assessed in the light of guidelines given by International Commission on Radiological Protection (ICRP, 1993). 2. Experimental methods Several methods are in use for measurement of radon and its daughter elements in dwellings. Some measuring the short-term values are called active methods and others measuring the integrated values are called passive methods. LR-115 type II plastic track detector films and the bare mode technique (Mishra and Ramachandran, 1997; Ramola et al., 1998; Singh et al., 2001) have been employed to measure the concentn of radon in the indoor environment. The detectors of size 1.3 cm 1.5 cm were suspended in the rooms on quarterly basis at a height more than 2 m above the level of the ground (so that the detectors are not disturbed by the movement of the residents) and about 1 m below the ceiling of the room so that direct alpha particles from the building material of the ceiling do not reach the detectors. We have assumed that a room with a door and without window is poorly ventilated, that with one window and a door as partially ventilated and with more than two windows and a door as well ventilated. All the detectors were removed and

3 S. Singh et al. / Atmospheric Environment 39 (2005) Table 1 Indoor radon levels in the dwellings of Muktsar and Ferozepur Districts of Punjab Sr. no. Sample location (village) No. of dwellings studied (Bq m 3 ) in winter (Dec Feb) (Bq m 3 ) in spring (Mar May) (Bq m 3 ) in (June Aug) (Bq m 3 ) in autumn (Sep-Nov) Annual averageradon concentn (Bq m 3 ) Life-time fatality risk X10 4 Annual average dose (msv) Muktsar district 1 Abul Khurana Deon Khera Phoolu Khera Kabarwala Pakki Giddarbaha Badal Jandwala Jurar Malout Virk Khera Muktsar Sarawan Ferozepur district 14 Dangar Khera Abohar Khubban Radhewala Chak Himmatpura Sitoguno Balluana Ferozepur

4 7764 S. Singh et al. / Atmospheric Environment 39 (2005) Table 2 Indoor radon concentns (Bq m 3 ) during winter and for dwellings belonging to different areas of Muktsar and Ferozepur districts of Malwa region Sr. no. Sample location s dwelling 1 s dwelling 2 s dwelling 3 s dwelling 4 s dwelling 5 1 Abul Khurana Well ventilated Partially ventilated Well ventilated Well ventilated Well ventilated Deon Khera Poorly ventilated Poorly ventilated Poorly ventilated Poorly ventilated Partially ventilated Phoolu Khera Poorly ventilated Poorly ventilated Poorly ventilated Poorly ventilated Poorly ventilated Kabarwala Partially ventilated Partially ventilated Well ventilated Partially ventilated Well ventilated Pakki Partially ventilated Well Ventilated Partially ventilated Well ventilated Poorly ventilated Giddarbaha Partially ventilated Well ventilated Well ventilated Well ventilated Partially ventilated Badal Poorly ventilated Partially ventilated Partially ventilated Partially ventilated Partially ventilated Jandwala Partially ventilated Well ventilated Well ventilated Well ventilated Well ventilated Jurar Partially ventilated Partially ventilated Partially ventilated Well ventilated Poorly ventilated Malout Partially ventilated Well ventilated Partially ventilated Well ventilated Poorly ventilated Virk Khera Well ventilated Partially ventilated Well ventilated Partially ventilated Well ventilated Muktsar Poorly ventilated Well ventilated Partially ventilated Partially ventilated Well ventilated Sarawan Well ventilated Partially ventilated Partially ventilated Well ventilated Partially ventilated Dangar Khera Partially ventilated Poorly ventilated Well ventilated Poorly ventilated Partially ventilated Abohar Well ventilated Well ventilated Partially ventilated Partially ventilated Partially ventilated Khubban Poorly ventilated Well ventilated Well ventilated Well ventilated Well ventilated Radhewala Chak Poorly ventilated Poorly ventilated Partially ventilated Poorly ventilated Poorly ventilated Himmatpura Poorly ventilated Poorly ventilated Well ventilated Well ventilated Partially ventilated Sitoguno Well ventilated Well ventilated Well ventilated Well ventilated Well ventilated Balluana Partially ventilated Partially ventilated Poorly ventilated Well ventilated Partially ventilated Ferozepur Partially ventilated Partially ventilated Poorly ventilated Poorly ventilated Poorly ventilated

5 S. Singh et al. / Atmospheric Environment 39 (2005) etched using 2.5N NaOH solution at 60 1C for 90 min. The track density was counted using an optical microscope at a magnification of 400 and was converted using a calibn constant 0.02 tracks cm 2 day 1 ¼ 1Bqm 3 (Eappen et al., 2001). 3. Results and discussions The indoor radon concentn levels recorded in 21 villages of Muktsar and Ferozepur districts are given in Table 1. The annual effective dose and average lifetime fatality risk for each of the 21 villages have also been calculated. The calculations have been made using the conversion factors given elsewhere (ICRP, 1993; Raghavayya, 1994). ICRP assumes 80% occupancy (7000 h/yr) indoor and an F (equilibrium factor) value of 0.4 for dwellings. One working level month (WLM) corresponds to the exposure of an individual to radon progeny of 1 WL concentn ( mj m 3 ) for a dun of 170 h, which results 1 WLM equivalent to 3.54 mj h m 3. The conversion factors of WLM 1 and 3.88 msv WLM 1 (ICRP, 1993) are used for calculating the lifetime fatality risk and the annual effective dose, respectively. The annual average indoor radon value in the study area varies from (Sitoguno village) to Bq m 3 (Radhewala chak village). These values are two to three times more than the world average of 40 Bq m 3 (UNSCEAR, 2000). This may be due to the difference in the concentn of radioactive elements viz. uranium and radium in the soil and building materials of the study area. However, these values are less than the lower limit of the range of the action level ( Bq m 3 ), recommended by the International Commission on Radiological Protection (ICRP, 1993). The present values of indoor radon are slightly more than those in some other areas of Punjab reported by Sharma and Virk (1998) but are lower than those reported for Himachal Pradesh by Singh et al. (1998, 2001). Comparatively high values of indoor radon in some areas of Himachal Himalayas may be due to the presence of uranium mineralization reported by Kaul Annual Average Radon Concentn (Bq m -3 ) Dwellings Fig. 2. Distribution of annual average radon concentn (Bq m 3 ) in 105 dwellings of 21 villages of Muktsar and Ferozepur districts of Punjab, India.

6 7766 S. Singh et al. / Atmospheric Environment 39 (2005) et al. (1993). The annual effective dose received by the residents of the study area varies from 1.3 to 2.48 msv with an average of 1.77 msv. In all the villages surveyed, the annual effective dose is less than even the lower limit of the recommended action level (3 10 msv). The lifetime fatality risk of the residents of the study area varies from to with an average value of The average value of the lifetime fatality risk of (0.01%) is relatively a small fraction (about 4%) of the lifetime risk of lung cancer due to cigarette smoking and chewing of tobacco (Evans et al., 1981). The seasonal variations of indoor radon concentn in 105 dwellings of 21 villages are given in Table 2. It is evident from the table that the maximum value of radon concentn is observed during the winter season and minimum during the season. This is because the doors and windows of the dwellings remain closed most of the times in winter compared with and hence the ventilation is poor in winter. The winter/ of radon concentn has been computed for all 105 dwellings. The winter/ of indoor radon ranges from 0.84 to 1.89 with an average of Moreover, the results (Table 2) reveal that in general the indoor radon values are more in the poorly ventilated houses compared with the well-ventilated ones. Our results for seasonal variations show a behaviour which agrees with the findings of Mittal et al. (1998) for the dwellings of Rajasthan area and that of Singh et al. (2002) for Himachal Pradesh. Fig. 2 shows the distribution of the annual average radon concentn for all the 105 dwellings of 21 villages studied in Muktsar and Ferozepur districts. The annual radon concentn level for dwellings ranges from to Bq m 3, with an average of Bq m 3. The difference in the values of indoor radon activity may be due to the different ventilation s, the nature and type of building materials used during construction and the variation of the radioactivity level in the soil beneath the dwellings. Fig. 3 shows the frequency distribution of the annual average radon concentn levels among 105 dwellings of 21 villages of the study area. The radon concentn lies in the ranges , and Bq m 3 in about 51%, 46% and 3% of the houses, respectively. In almost all the dwellings radon concentn is well below the recommended level. 4. Conclusions 1. In general the radon concentn values in the dwellings are two to three times more than the world average of 40 Bq m 3. However, these values are lower than the recommended action level Number of dwellings Annual Average Radon Concentn (Bq m -3 ) Fig. 3. Frequency distribution of annual average radon concentn (Bq m 3 ) in 105 dwellings of 21 villages of Muktsar and Ferozepur districts of Punjab, India.

7 S. Singh et al. / Atmospheric Environment 39 (2005) Maximum value of radon concentn is observed during the winter and minimum during the season. 3. The annual effective dose in the study area is less than even the lower limit of the recommended action level (3 10 msv). Acknowledegments The authors are thankful to the residents of the study area for their co-open during the fieldwork, and to the students and staff of MIMIT, Malout, and Laboratory staff of Guru Nanak Dev University, Amritsar, India, for their support. References Eappen, K.P., Ramachandran, T.V., Shaikh, A.N., Mayya, Y.S., Calibn factor for SSNTD-based radon/thoron dosimeters. Radiation Protection and Environment 24 (1 2), Evans, R.D., Harley, J.H., Jacobi, W., MacLean, A.S., Mills, W.A., Stewart, C.G., Estimation of risk from environmental exposure to radon-222 and its decay products. Nature 290, Henshaw, D.L., Eatough, J.P., Richardson, R.B., Radon as a causative factor in induction of myeloid leukemia and other cancers. Lancet 355, ICRP, Protection against Radon at Home and Work. Ann ICRP. ICRP Pub., p. 65. Kaul, R., Umamaheshwar, K., Chandrashekaran, S., Deshmukh, R.D., Swarmukar, B.M., Uranium mineralization in the Siwaliks of Northwestern Himalayan, India. Journal 0f Geological Soceity of India 41, Mishra, U.C., Ramachandran, T.V., Indoor radon levels in India: a review. In: Proceedings Third International Conference on Rare Gas Geo-Chemistry, Amritsar. Guru Nanak Dev University Press, Amritsar, India, pp Mittal, S., Bhatti, S.S., Jodha, A.S., Kumar, S., Ramachandran, T.V., Nambi, K.S.V., A correlation study between radon in dwellings and radium concentn in soil. In: Proceedings of XIth National Symposium, SSNTD, October. Amritsar, pp Raghavayya, M., Safety standards for exposure to radon. Bulletin on Radiation Protection 17 (3 4), 1 4. Ramola, R.C., Kandari, M.S., Rawat, R.B.S., Ramachandran, T.V., Choubey, V.M., A study of seasonal variation of radon levels in different types of houses. Journal Of Environmental Radioactivity 39 (1), 1 7. Sharma, N., Virk, H.S., Indoor levels of radon/thoron daughters in some dwellings of Punjab. In: Proceedings of XIth National Symposium, SSNTD, October. Amritsar, pp Singh, S., Singh, B., Kumar, J., Uranium and radon measurement in the environs of Himachal Himalayas, an application of solid state nuclear track detectors. In: Proceedings of the XIth National Symposium, SSNTD, October. Amritsar, pp Singh, S., Malhotra, R., Kumar, J., Singh, L., Indoor radon measurements in dwellings of Kulu area, Himachal Pradesh, using solid state nuclear track detectors. Radiation Measurements 34, Singh, S., Kumar, A., Singh, B., Radon level in dwellings and its correlation with uranium and radium content in some areas of Himachal Pradesh, India. Environmental International 28, UNSCEAR, United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing Radiation: Sources and Biological Effects. United Nations, New York. UNSCEAR, United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing Radiation: Exposure due to Natural Radiation Sources. United Nations, New York.