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Indoor radon level in the dwellings of the Rajshahi and Chuadanga regions of Bangladesh
Radiation Measurements 34 (2001) 497– 499
www.elsevier.com/locate/radmeas
Indoor radon level in the dwellings of the Rajshahi and Chuadanga regions of Bangladesh A. Srivastavaa; ∗ , M.R. Zamanb , K.K. Dwivedic , T.V. Ramachandrand a Department
of Chemistry, Panjab University, Chandigarh-160014, India of Applied Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh c Arunachal University, Rono Hills, Itanagar-791111, India d Environmental Assessment Division, Bhabha Atomic Research Centre, Bombay-400085, India b Department
Received 28 August 2000; received in revised form 5 March 2001; accepted 15 March 2001
Abstract The indoor radon level in terms of equilibrium equivalent concentration (EEC) has been measured for dwellings in the Rajshahi region of Bangladesh as well as its adjoining Chuadanga region. The data were obtained using the passive time integrated method employing LR-115 (Type II) solid state nuclear track detectors. The geometric mean value for the EEC in the dwellings located in the Rajshahi region was obtained as 32:4 ± 7:1 Bq m−3 and for the dwellings in the Chuadanga region was obtained as 27:3 ± 6:2 Bq m−3 . The data obtained in the present work are compared with indoor radon levels prescribed c 2001 Elsevier Science Ltd. All rights reserved. by the International Commission on Radiation Protection. Keywords: Indoor radon; EEC; LR-115 Type (II); ICRP
1. Introduction The radiation dose, resulting due to indoor radon and its progenies, constitutes a major part of the total natural background radiation received by population all over the world. There is an increasing concern about exposure to radon and its progenies due to their detrimental e;ects on health of inhabitants (Duranni, 1993; Durrani and Ili
Corresponding author. Fax: +91-172-545074. E-mail address: [email protected] (A. Srivastava).
et al., 1993) including countries like India and Bangladesh where such a study becomes more important due to their high population density. The surveys carried so far in and around the world were from temperate countries where the living style, geological and meteorological conditions which have been found to have profound inDuence on indoor radon level are markedly di;erent from those in tropical countries. In the present work, indoor radon level in some dwellings in the Rajshahi and Chuadanga region of Bangladesh is being reported and the data generated has been discussed in the light of recommendations of the International Commission on Radiation Protection.
2. Measuring procedure Measurements were carried out using passive detector technique employing LR-115 (Type II) solid state nuclear track detectors. The detectors of size of 2:5 cm × 2:5 cm mounted on cards were exposed in the bare mode to measure
c 2001 Elsevier Science Ltd. All rights reserved. 1350-4487/01/$ - see front matter PII: S 1 3 5 0 - 4 4 8 7 ( 0 1 ) 0 0 2 1 4 - 1
498
A. Srivastava et al. / Radiation Measurements 34 (2001) 497– 499
Fig. 1. Indoor radon level in Rajshahi region.
Fig. 2. Indoor radon level in Chuadanga region.
the concentration of radon in terms of equilibrium equivalent concentration (EEC). The detectors were placed inside the most frequently used room of the dwellings of interest at a distance of about 0:1 m from any surface. They were exposed for a period ranging from 3 to 4 months during which time the alphas originating from radon and its progenies were registering tracks in it. The technical details of the exposure mode are discussed in our earlier publication (Srivastava et al., 1996). The exposed detectors were retrieved from the Geld and ◦ were chemically etched in 2:5 N NaOH at 60 C for 60 min under mild agitation. The experimental details regarding the optimization of the etching conditions are discussed in detail elsewhere (Ramachandran et al., 1995). The etched detectors were scanned by using a spark counter. The recorded track densities were converted to the actual track density arising from radon and its progenies by using a sensitivity factor which has been estimated from controlled experiments separately carried out in our laboratory facility. The standardization experiments carried out essentially consisted of an exposure chamber of 0:5 m3 capacity having inlet ports for introducing the Gltered air, aerosols and the radon gas besides an outlet tube to discharge the contents of the chamber to the open environment. The details pertaining to the calibration chamber, its function and experience gained by operating the system for more than two decades are discussed in detail in an earlier publication (Ramachandran et al., 1995). The estimated sensitivity factor for the mode of exposure made works out to be 1:02 cm−2 d −1 Bq−1 m−3 for EEC of Rn222 concentration. The experimental cumulative uncertainty in the present set of measurements worked out to be about 20%. This includes an error of 13% in detector calibration and around 3–7% uncertainty in counting statistics as the total number of tracks counted for each sample varied from 200 to 900.
in the case of dwellings in Chuadanga region the indoor radon level ranged from 19.2 to 28:3 Bq m−3 . The geometric mean value for the indoor radon level in dwellings in the Rajshahi region of Bangladesh has been calculated to be 32:4 ± 2:9 Bq m−3 and 27:3 ± 2:9 Bq m−3 for the adjoining Chuadanga region. However the Gnal geometrical mean value worked out to be 32:4 ± 7:1 and 27:3 ± 6:2 Bq m−3 for the dwellings in the Rajshahi and Chuadanga regions of Bangladesh, respectively, when the experimental uncertainties were included. The houses surveyed in the present work were generally made of cement, mud and bricks and the data was collected in the period pertaining to late summer and early autumn season when most of the ventilators, windows and doors are kept open. The indoor radon levels obtained in the present work are much below the levels recommended by International Commission for Radiation Protection. In its report ICRP-65 (ICRP, 1993) it has recommended that some remedial measures against radon in dwellings is always justiGed above a continued e;ective annual dose of 10 mSv which in terms of EEC Bq m−3 works out to be around 75 Bq m−3 . Further work is in progress in this region to get a better estimate of the radon level and to see if there is any correlation between radon level and season. It is proposed to extend this type of work in other regions of Bangladesh based on the experience gained in the present work.
3. Results and discussion The indoor radon level in terms of EEC which is expressed in Bq m−3 are shown in Figs. 1 and 2 for dwellings in the Rajshahi region and the dwellings in the adjoining Chuadanga region, respectively. The indoor radon level for dwellings in the Rajshahi region ranged from 29.6 to 37:5 Bq m−3 and
Acknowledgements The authors are thankful to Ms R. Mishra, S.P. Tripathy and Mr.A. Bayita for the assistance in carrying out the experimental work and Mr.S.K. Saini for assistance in the preparation of the manuscript. We would also like to place in record our special thanks to the Head of Environmental Assessment Division of the Bhabha Atomic Research Centre, Bombay for providing us with the calibration facility.
References Duranni, S.A., 1993. Radon as a health hazard at home: what are the facts?. Nucl. Tracks. Radiat. Meas. 22, 303–317.
A. Srivastava et al. / Radiation Measurements 34 (2001) 497– 499 Durrani, S.A., Ili
499
Ramachandran, T.V., Shaikh, A.N., Eappen, K.P., Nair, N.B., Nambi, K.S.V., 1995. Experience with a Radon calibration facility in Third International Conference on Rare Gas Geochemistry. Amritsar, pp. 50 – 68. Srivastava, A., Lalramengzami, R., Laldawngliana, C., Sinha, D., Ghosh, S., Dwivedi, K.K., Saxena, A., Ramachandran, T.V., 1996. Measurement of potential alpha energy exposure (PAEE) of radon and its progenies in dwellings of North Eastern Region of India. Radiat. Meas. 26, 291–295. Subba Ramu, M.C., Shaikh, A.N., Muraleedharan, T.S., Ramachandran, T.V., Nambi, K.S.V., 1993. Environmental radon monitoring: A plan for national e;ort. Proceedings of the Seventh National Seminar on Particle Tracks in Solids, Jodhpur, pp. 11–25.
www.elsevier.com/locate/radmeas
Indoor radon level in the dwellings of the Rajshahi and Chuadanga regions of Bangladesh A. Srivastavaa; ∗ , M.R. Zamanb , K.K. Dwivedic , T.V. Ramachandrand a Department
of Chemistry, Panjab University, Chandigarh-160014, India of Applied Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh c Arunachal University, Rono Hills, Itanagar-791111, India d Environmental Assessment Division, Bhabha Atomic Research Centre, Bombay-400085, India b Department
Received 28 August 2000; received in revised form 5 March 2001; accepted 15 March 2001
Abstract The indoor radon level in terms of equilibrium equivalent concentration (EEC) has been measured for dwellings in the Rajshahi region of Bangladesh as well as its adjoining Chuadanga region. The data were obtained using the passive time integrated method employing LR-115 (Type II) solid state nuclear track detectors. The geometric mean value for the EEC in the dwellings located in the Rajshahi region was obtained as 32:4 ± 7:1 Bq m−3 and for the dwellings in the Chuadanga region was obtained as 27:3 ± 6:2 Bq m−3 . The data obtained in the present work are compared with indoor radon levels prescribed c 2001 Elsevier Science Ltd. All rights reserved. by the International Commission on Radiation Protection. Keywords: Indoor radon; EEC; LR-115 Type (II); ICRP
1. Introduction The radiation dose, resulting due to indoor radon and its progenies, constitutes a major part of the total natural background radiation received by population all over the world. There is an increasing concern about exposure to radon and its progenies due to their detrimental e;ects on health of inhabitants (Duranni, 1993; Durrani and Ili
Corresponding author. Fax: +91-172-545074. E-mail address: [email protected] (A. Srivastava).
et al., 1993) including countries like India and Bangladesh where such a study becomes more important due to their high population density. The surveys carried so far in and around the world were from temperate countries where the living style, geological and meteorological conditions which have been found to have profound inDuence on indoor radon level are markedly di;erent from those in tropical countries. In the present work, indoor radon level in some dwellings in the Rajshahi and Chuadanga region of Bangladesh is being reported and the data generated has been discussed in the light of recommendations of the International Commission on Radiation Protection.
2. Measuring procedure Measurements were carried out using passive detector technique employing LR-115 (Type II) solid state nuclear track detectors. The detectors of size of 2:5 cm × 2:5 cm mounted on cards were exposed in the bare mode to measure
c 2001 Elsevier Science Ltd. All rights reserved. 1350-4487/01/$ - see front matter PII: S 1 3 5 0 - 4 4 8 7 ( 0 1 ) 0 0 2 1 4 - 1
498
A. Srivastava et al. / Radiation Measurements 34 (2001) 497– 499
Fig. 1. Indoor radon level in Rajshahi region.
Fig. 2. Indoor radon level in Chuadanga region.
the concentration of radon in terms of equilibrium equivalent concentration (EEC). The detectors were placed inside the most frequently used room of the dwellings of interest at a distance of about 0:1 m from any surface. They were exposed for a period ranging from 3 to 4 months during which time the alphas originating from radon and its progenies were registering tracks in it. The technical details of the exposure mode are discussed in our earlier publication (Srivastava et al., 1996). The exposed detectors were retrieved from the Geld and ◦ were chemically etched in 2:5 N NaOH at 60 C for 60 min under mild agitation. The experimental details regarding the optimization of the etching conditions are discussed in detail elsewhere (Ramachandran et al., 1995). The etched detectors were scanned by using a spark counter. The recorded track densities were converted to the actual track density arising from radon and its progenies by using a sensitivity factor which has been estimated from controlled experiments separately carried out in our laboratory facility. The standardization experiments carried out essentially consisted of an exposure chamber of 0:5 m3 capacity having inlet ports for introducing the Gltered air, aerosols and the radon gas besides an outlet tube to discharge the contents of the chamber to the open environment. The details pertaining to the calibration chamber, its function and experience gained by operating the system for more than two decades are discussed in detail in an earlier publication (Ramachandran et al., 1995). The estimated sensitivity factor for the mode of exposure made works out to be 1:02 cm−2 d −1 Bq−1 m−3 for EEC of Rn222 concentration. The experimental cumulative uncertainty in the present set of measurements worked out to be about 20%. This includes an error of 13% in detector calibration and around 3–7% uncertainty in counting statistics as the total number of tracks counted for each sample varied from 200 to 900.
in the case of dwellings in Chuadanga region the indoor radon level ranged from 19.2 to 28:3 Bq m−3 . The geometric mean value for the indoor radon level in dwellings in the Rajshahi region of Bangladesh has been calculated to be 32:4 ± 2:9 Bq m−3 and 27:3 ± 2:9 Bq m−3 for the adjoining Chuadanga region. However the Gnal geometrical mean value worked out to be 32:4 ± 7:1 and 27:3 ± 6:2 Bq m−3 for the dwellings in the Rajshahi and Chuadanga regions of Bangladesh, respectively, when the experimental uncertainties were included. The houses surveyed in the present work were generally made of cement, mud and bricks and the data was collected in the period pertaining to late summer and early autumn season when most of the ventilators, windows and doors are kept open. The indoor radon levels obtained in the present work are much below the levels recommended by International Commission for Radiation Protection. In its report ICRP-65 (ICRP, 1993) it has recommended that some remedial measures against radon in dwellings is always justiGed above a continued e;ective annual dose of 10 mSv which in terms of EEC Bq m−3 works out to be around 75 Bq m−3 . Further work is in progress in this region to get a better estimate of the radon level and to see if there is any correlation between radon level and season. It is proposed to extend this type of work in other regions of Bangladesh based on the experience gained in the present work.
3. Results and discussion The indoor radon level in terms of EEC which is expressed in Bq m−3 are shown in Figs. 1 and 2 for dwellings in the Rajshahi region and the dwellings in the adjoining Chuadanga region, respectively. The indoor radon level for dwellings in the Rajshahi region ranged from 29.6 to 37:5 Bq m−3 and
Acknowledgements The authors are thankful to Ms R. Mishra, S.P. Tripathy and Mr.A. Bayita for the assistance in carrying out the experimental work and Mr.S.K. Saini for assistance in the preparation of the manuscript. We would also like to place in record our special thanks to the Head of Environmental Assessment Division of the Bhabha Atomic Research Centre, Bombay for providing us with the calibration facility.
References Duranni, S.A., 1993. Radon as a health hazard at home: what are the facts?. Nucl. Tracks. Radiat. Meas. 22, 303–317.
A. Srivastava et al. / Radiation Measurements 34 (2001) 497– 499 Durrani, S.A., Ili
499
Ramachandran, T.V., Shaikh, A.N., Eappen, K.P., Nair, N.B., Nambi, K.S.V., 1995. Experience with a Radon calibration facility in Third International Conference on Rare Gas Geochemistry. Amritsar, pp. 50 – 68. Srivastava, A., Lalramengzami, R., Laldawngliana, C., Sinha, D., Ghosh, S., Dwivedi, K.K., Saxena, A., Ramachandran, T.V., 1996. Measurement of potential alpha energy exposure (PAEE) of radon and its progenies in dwellings of North Eastern Region of India. Radiat. Meas. 26, 291–295. Subba Ramu, M.C., Shaikh, A.N., Muraleedharan, T.S., Ramachandran, T.V., Nambi, K.S.V., 1993. Environmental radon monitoring: A plan for national e;ort. Proceedings of the Seventh National Seminar on Particle Tracks in Solids, Jodhpur, pp. 11–25.