Activity concentration of 137Cs in soil samples from Punjab province (Pakistan) and estimation of gamma-ray dose rate for external exposure

Punjab is one of the most populated provinces of Pakistan having 34 districts. There is always a need to have baseline background level information about Cs-137 and the corresponding gamma-ray doses to the population. In this respect, soil samples were collected to a depth of 30-50 cm from all 34 district headquarters of the Punjab province of Pakistan and Cs-137 activity concentrations were measured. Cs-137 activity concentration was found to be in the range from 1.1 +/- 1.0 to 5.3 +/- 2.5 Bq kg(-1). The average value of estimated external gamma-ray dose rate from all 34 districts of Punjab province was computed to be 0.18 +/- 0.07 nSv h(-1) from Cs-137 in soil samples. The measured Cs-137 activity concentration range was compared with the reported ranges in the literature from some of the other locations in the world. Results obtained in this study show that Cs-137 concentration is of a lower level in the investigated area. The average value of estimated external effective dose rate is found far below the dose rate limit of 1.0 mSv y(-1) for members of the general public recommended by the International Commission on Radiological Protection (ICRP) as well as the external gamma radiation dose of 0.48 mSv y(-1) received per head from the natural sources of radiation assessed by UNSCEAR (2000). It is concluded that Cs-137 soil contamination does not pose radiation hazards to the population in the investigated areas.