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 137Cs 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 137Cs activity concentrations were measured. 137Cs 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 137Cs in soil samples. The measured 137Cs 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 137Cs 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 137Cs soil contamination does not pose radiation hazards to the population in the investigated areas. (authors)