Individual dose estimation—our experience with the Karunagappally study in Kerala, India

A radiation cohort consisting of four panchayats and a control area consisting of two panchayats was identified in the high background radiation area of Karunagappally after measuring air kerma values of indoor and outdoor radiation levels in 75,052 houses in the area. Radioactivity in the soil was estimated from 181 samples collected from seven panchayats. Thoron-in-breath analysis was done in 87 subjects living in low, medium and high radiation level areas. Occupancy factor of 7711 subjects in different age groups was also estimated. Annual effective dose of individuals was calculated assuming the cosmic ray component of 0.227 and 0.252 mGy/year indoor and outdoor, respectively. Risk analysis will be attempted after measuring the individual dose of a sample population in the area.