LAUSR

One hundred forty-eight water samples were collected from in and around Chennai and 222Rn concentrations were measured using radon emanometry method. The average 222Rn concentration was estimated to be 6.88, 2.01, 1.17, 0.19 and 0.10 Bq L-1 for borewell water, openwell water, tank water, metro water and lake water, respectively, which were within the U.S. Environmental Protection Agency's (USEPA) Standard limit of 11.1 Bq L-1 and World Health Organization (WHO) global average 10 Bq L-1. The total effective dose obtained has varied from 0 to 157.57 μSv y-1 with ±10% standard deviation. The mean values were 19.608, 8.092, 4.692, 0.761 and 0.423 μSv y-1 for closed borewell, open well water, tank water, metro water and for lake water, respectively. All these values were below the reference point 0.1 mSv y-1 (100 μSv y-1) set by WHO.