Evaluation of background radiation level and excess lifetime cancer risk in Doon valley, Garhwal Himalaya

Radionuclides such as Ra-226, Th-232 & K-40 occurs naturally in the earth crust from its creation and are main contributor to the dose received by human beings. The present study was carried-out in the Doon valley which is outlined in the Main Boundary Thrust (MBT) region of Garhwal Himalaya in Uttarakhand, India. The collected soil/rock samples were analyzed by NaI(Tl) Gamma ray spectrometry for the analysis of radionuclides and hence measuring the various health hazard indices and Excess lifetime cancer risk. Radionuclide ( 226 Ra, 232 Th & 40 K) content were found to vary from 47 ± 9 to 442 ± 50 Bq Kg −1 , 45 ± 17 to 101 ± 16 Bq Kg −1 & 320 ± 281 to 947 ± 197 Bq Kg −1 respectively and were higher than the world average values which are 35 Bq Kg −1 , 30 Bq Kg −1 and 400 Bq Kg −1 respectively. Higher radionuclide content contributes to higher amount of absorbed doses which was found to vary from 93 to 259.6 ηGyh −1 with a mean value of 112.5 ηGyh −1 and Gamma index which found to vary from 0.73 to 1.92 with a mean value of 0.96. Lastly, on the basis of annual effective doses received to humanoid, Excess lifetime cancer risk was measured which varies from 0.48 × 10 –3 to 1.34 × 10 –3 with an average value of 0.65 × 10 –3 and was much below the world’s average value of 1.45 × 10 –3 .