Seasonal indoor radon concentration in the North West Frontier Province and federally administered tribal areas - Pakistan

Indoor radon levels have been measured in several districts, namely Swabi, Mardan and Charsadda of the North West Frontier Province as well as in the Mohmand and Bajuar Agencies of the federally administered tribal areas, using CR-39-based radon dosimeters. In order to carry out this study, 200 houses were carefully selected and season wise indoor radon levels were measured throughout the year in four cycles. Seasonal correction factor was determined. Yearly arithmetic mean of 76 +/- 37 and 68 +/- 25 Bq m(-3) was found in bedrooms and drawing rooms, respectively. Weighted arithmetic mean of the area was found to be 72 +/- 32 Bq m(-3). Yearly minimum values of 38 +/- 7 and 39 +/- 5 Bq m(-3) were found in bedrooms and drawing rooms, respectively. A maximum value of 189 +/- 5 Bq m(-3) was observed in the Charsadda district. Yearly weighted average minimum value of 47 +/- 5 Bq m(-3) was found in the Mohmand agency and a maximum value of 150 +/- 5 Bq m(-3) was found in the Charsadda district. Minimum indoor radon concentrations were found in the summer season whereas maximum levels were observed in the winter season. Seasonal correction factors for spring, winter, autumn and summer seasons were found to be 1.14 +/- 0.43, 0.89 +/- 0.47, 0.91 +/- 0.35 and 1.15 +/- 0.49, respectively. Weighted yearly average minimum indoor radon of 66 +/- 27 and 66 +/- 29 Bq m(-3) were observed in the Swabi and Mardan districts and maximum level of 83 +/- 39 Bq m(-3) was observed in the Bajuar agency. Using ICRP 65 conversion factor, minimum and maximum mean effective doses were found to be 0.46 +/- 0.20 and 0.85 +/- 0.40 mSv, respectively. (C) 2007 Elsevier Ltd. All rights reserved.