ABSTRACT
Radon and its short-lived decay products in dwellings are recognized as the main sources of public exposure from the natural radioactivity. The tap water used for drinking and other household uses can make variable contributions to the indoor radon level. This study has provided data on radon concentrations in domestic water supplies in Tehran. Water samples were collected from various sources supplying domestic water in Tehran. Sample preparation for measuring waterborne radon by liquid scintillation counting was carried out in place. A modified sample preparation method providing higher measurement sensitivity was applied in this work. According to measurements, the mean 222Rn concentrations in groundwater and surface water supplies were 46.40 +/- 11.50 and 2.50 +/- 1.20 Bq.L-1, respectively. The mean radon concentration in tap water was 3.70 +/- 0.94 Bq.L-1. The annual total effective dose to adults due to waterborne radon in Tehran was estimated to be about 10 microSv. The radon concentrations in tap water actually used by people in Tehran are low enough and below the proposed limits in other countries