This study aims to determine the background levels of tritium radioisotope in drinking and seawater samples of Sinop province before the
nuclear power plant was established in Sinop. In this context, a total of 174 water samples were collected, these are as follows: nine drinking
water samples from the Sinop center and districts and 165 seawater samples from the seacoast from Samsun to Kastamonu. Tritium concentrations in the collected water samples were measured by the liquid scintillation counter. The minimum detectable activity for the method
used was found to be 1.48 Bq/L. The tritium concentrations of the seawater and drinking water samples were found in the range of ,MDA
(minimum detectable activity)-6.29 Bq/L and 2.45–3.17 Bq/L, respectively. In addition, the annual effective dose rates of the people consuming these drinking waters due to the tritium radioisotope were calculated separately for infants, children and adults and found to be 12.12,
16.96 and 35.38 nSv, respectively.