Estimation of the effective dose from radon ingestion and inhalation in drinking water sources of Mashhad, Iran

Background: Radon concentration was measured in 50 drinking water samples in Mashhad - Iran. Materials and Methods: The tap water used for drinking and other household usages can increase the indoor radon level. Drinking water samples were collected from various places and supplies of public water used in Mashhad. Then radon concentration has been measured by portable radon gas surveyor SILENA (PRASSI) system. Results: The results showed that about 70% of water samples had radon concentration greater than 11Bq/l the level recom- mended USA environmental protection agency (EPA). The arithmetic mean of radon concentration for all samples was 16.238 ± 9.322 Bq/l. Also the annual effective dose in stomach and lung per person were estimated in this research, with the mean value of 0.040 mSv and 0.043 mSv per year for these two organs for all samples, respectively. Conclusion: The results indicate that radon concentrations in public drinking water samples of Mashhad are mostly low enough and below the proposed concentration limits. The mean radon level was 16.238 Bq/l for all samples; which is not much greater than 11Bq/l as EPA advised level. Further, only two samples induced the total annual effective dose greater than 0.1 mSv per year.