Natural radioactivity in soil, rock, building materials, and water is very important for the radiological protection point of view. Radon is one of the carcinogenic radioactive gases. Radon causes radiological risk to the public via ingestion and inhalation. The 222 Rn activity concentrations were estimated in potable water of Uttara Kannada district (Coastal region) using the Emanometry technique. Radon activity levels were found to vary from 2.37 ± 0.19 Bql −1 to 171.35 ± 1.96 Bql −1 with a mean value of 22.62 ± 0.82 Bql −1. The majority of the radon levels are within the reference level of 100 Bql −1 proposed by WHO and EU Commission. Nearly 55% of the potable water had radon activity levels exceeds the MCL of 11.1 Bql −1 proposed by USEPA. The annual average ingestion dose values are lower than the action level of 100 µSvy −1 as proposed by WHO and EU Commission. The activity concentration of 226 Ra, 232 Th, and 40 K in soil were estimated by using NaI(Tl) detector-based gamma-ray spectrometry. The average activity of 226 Ra, 232 Th, and 40 K in soil samples is 36.12, 50.45, and 315.35 Bq kg −1 , respectively, and the activity concentration of 226 Ra and 232 Th is slightly higher than the world average. The calculated radiological hazards are well within the world average value.

This paper presents the distribution of radon activity concentration in drinking water samples and their annual effective dose exposure in Shimoga district. The radon concentrations in 38 drinking water samples were measured by using Emanometry technique. The measured radon concentration in drinking water samples ranged between 3.10 ± 0.25 and 38.50 ± 1.54 Bq l -1 with an average value of 13.60 ± 1.12 Bq l -1 . This study reveals that 44.8 % drinking water samples analyzed have radon levels in excess of the EPA recommended maximum contamination level of 11.1 Bq l -1 . The total mean annual effective doses of all the samples are significantly lower than the reference level of 0.1 mSv y -1 .

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In the present study, radon concentrations were measured in 31 drinking water samples collected from different locations of the Chikmagalur city, Karnataka state, India, using emanometry technique. The measured radon concentrations ranged from 0.51 ± 0.1 Bq l-1 to 151.98 ± 3.5 Bq l-1 with an average value of 22.72 ± 1.1 Bq l-1. From this study, it is evident that 61 % of drinking water samples have radon levels higher than the maximum contaminant level of 11 Bq l-1 recommended by EPA. The estimated total annual effective dose from three locations of the studied area was found to be higher than the safe limit of 0.1 mSv y-1 recommended by WHO and EU Council.