Natural Radioactivity in Drinking Water of Drilled Wells in Zanjan, Northwestern Iran

Background: many radioactive compounds may be released into the environmentand hence into the drinking water supplies due to the human activities. radionuclidescan also enter the food chain if the contaminated water is used for drinking or irrigationpurposes.objective: to estimate the annual effective dose of natural radioactive materialslike 226ra and 40k in drinking water of wells in zanjan, nortwestern iran.methods: 82% of drinking water in zanjan comes from drilled wells. watersamples from the main sites of drinking water from different parts of zanjan werecollected. the amount of 226ra and 40k were measured by gamma-ray spectrometryusing a nai (tl) detector. the annual effective dose of the radioactive materials wascalculated for children (2–7 years old) and adults (?17 years old) with annual waterintake of 350 and 500 l, respectively. the annual effective dose received by residentsof the city due to consumption of the contaminated drinking water was also calculated.results: the mean±sd concentrations of 226ra and 40k were 32.4±7.8 and20.5±27.4 bq/l, respectively. the mean±sd annual effective dose received byresidents of the city due to consumption of the contaminated drinking water was7.13±1.76 and 4.59±1.12 msv/y for children and adults, respectively.conclusion: the level of radioactive compounds in water of drilled wells in zanjanis significantly higher than the icrp permissible limit of 1 msv/y.