137Cs daily intake with the foodstuff in the selected cohort of the village Narodychi 30 years after the Chornobyl accident

The radiation accident at the Chornobyl nuclear power plant, which occurred on April 26, 1986, led to large-scale environmental releases of radioactivity. Its consequences—radionuclide contamination of soils, agricultural products, wild mushrooms, and berries—manifest even after decades. One of the regions most affected by the Chornobyl accident was the Zhytomyr region (Polissya). The soils of Ukrainian Polissya (North of Ukraine) have high ¹³⁷Cs transfer factors, leading to corresponding food contamination, especially of milk and forest products. The current study aimed to calculate and analyze the individual daily dietary intake of ¹³⁷Cs in a cohort of rural residents based on regular sampling and radioactivity measurement of each family’s daily food rations and considering each cohort member’s quantitative food consumption indicators over 2 years. Monthly studies of ¹³⁷Cs activity concentration in foodstuff were performed to cover diet radioactivity peculiarities and estimate their impact on corresponding daily intake for the selected cohort (11 families, 2 to 6 members per family, 34 persons in total) lived in village Narodychi, Zhytomyr oblast (region) during of November 2015 to October 2017. This study included a detailed quantitative recording of the foodstuff consumed diet according to the specially developed questionnaire for each family member for one selected day of each month and laboratory gamma-spectroscopy measurement of ¹³⁷Cs activity concentration in foodstuff samples covering diet consumed by each family, the same day including three meals. Daily intake of ¹³⁷Cs was calculated by combining daily family questionnaire data and individual data on ¹³⁷Cs activity concentration in the respective family on the same day. Individual annual exposure dose estimates were made on corresponding dietary statistical ¹³⁷Cs intake estimates and age-dependent dose coefficients. Foodstuff ¹³⁷Cs radioactivity measurements showed that domestic vegetables, fruits, and berries contain one to dozens of Bq/kg. Milk and dairy dishes contain tens to several hundred when ready-made first and second courses of meat, including those adding forest mushrooms, sometimes containing up to several hundred Bq/kg. Calculations show that the daily intake of ¹³⁷Cs from the diet for different cohort members ranged from 0.1 to 704 Bq. It depends on radioactivity changes during the year in the family food basket and individual preferences in food consumption of corresponding family members, especially of milk and products prepared with milk, and to a greater extent of foodstuff of forest origin: wild berries and mushrooms, and it was higher for males. Statistical data of daily ¹³⁷Cs intake varies greatly by cohort members and families. Conservative estimates of the cohort’s irradiation dose for each year are below 0.33 mSv/year when the corresponding mean is almost twice as high in the second year. It has been shown that the individual’s annual effective irradiation dose is determined by the family’s food basket and eating habits. Educational work on avoiding certain foods should be essential in preventing high ¹³⁷Cs intake from food.