Spatial interpretation, radiological mapping of background gamma radiation and risk evaluation for Southern regions of Tamil Nadu, India

The outdoor gamma dose rate was measured in 540 locations in southern regions (Ramanathapuram, Virudhunagar, Tirunelveli, and Thoothukudi) of Tamil Nadu, India. The measured dose rates vary from 35 to 335 nSv/h (mean 89 nSv/h). The observed mean dose rate (89 nSv/h) is 2.3 times higher than the national (India) average of 39 nSv/h (56 nGy/h) and 2.1 times higher than the world average of 41 nSv/h (59 nGy/h). Annual Effective Dose (AED) calculated varies from 0.04 to 0.41 mSv/y (mean 0.11 mSv/y). The mean AED (0.11 mSv/y) is 1.6 times higher than the world average annual effective dose of 0.07 mSv/y. 30% of the locations have higher AED values due to the higher radiation in that locations. The present study reveals that the Tirunelveli district of the southern Tamilnadu region has higher gamma radiation than the other four districts of this region and is due to the topography of coastal and mountainous areas in Tirunelveli. The higher gamma radiation dose in the study area is due to the radionuclides present in the mountainous region's rocks and the coastal regions' soils. The radiological maps were used for spatial interpretation of the outdoor gamma dose rate in the study area. The radiological cancer risk assessment reveals that the Tirunelveli district has a higher risk due to the higher background gamma radiation.