Radon makes up approximately half of the total dose of radiation were received naturally. The majority of it comes from the inhalation of progeny of 222Rn and is prominent in a closed atmosphere. The continuous measurement of the levels of 222Rn concentration in different geographical areas is of great importance, particularly in living places. In this study, the concentration of radium and radon in 120 samples of drinking, springs and rivers water sources of northwest regions of Mashhad city have been measured. Solid state nuclear track detectors were used for measuring the concentration. The average value of radon and radium concentrations in the studied area is found to be 30.2±5.1 and 18.4±2.2 Bq m- 3, respectively. The dose rate due to radon, radium and their progenies received by the population in the studied location between 0.1-0.5 mSv y-1. The arithmetic and geometric mean concentrations are 0.2±0.05 and 0.2 mSv y-1, respectively. The results show no significant radiological risk for the inhabitants of the studied regions.

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