Determination of 226Ra, 232Th, 40K, and 137Cs activity concentrations in tea leaf samples from Rize, Türkiye, 30 years after the Chernobyl accident, and associated radiological risk parameters

Abstract

137Cs, released into the atmosphere in large quantities following the Chernobyl accident, is one of the most hazardous radionuclides, as it can persist in the environment for a long time due to its physical half-life of 30 years. Along with 137Cs, 226Ra, 232Th, and 40K which are naturally occurring radioactive elements, can enter the human body through ingestion, acting as internal sources of radiation and potentially causing adverse health effects in the long term. Rize is one of the most important tea-growing regions in the world and was affected by the Chernobyl accident in 1986. This study aimed to determine the activity concentrations of 226Ra, 232Th, 40K, and 137Cs in tea leaf samples collected from Rize, Türkiye, 30 years after the Chernobyl accident, and to estimate the associated radiological risk parameters, such as annual effective ingestion dose and excess lifetime cancer risk for consumers. Radioactivity analyses of tea leaf samples collected from 36 different stations were carried out with a high purity gamma spectroscopy system. The mean activity concentrations of both 226Ra and 232Th were calculated as 3.3 Bq/kg. The mean 137Cs and 40K activity concentrations were determined to be 10.5 Bq/kg, and 373.7 Bq/kg, respectively. These values were compared to the results obtained from similar studies conducted in Türkiye and other countries. Additionally, the mean 137Cs activity concentration was found to be significantly lower than the permitted limit of 1000 Bq/kg for foods set by the ICRP (2005), EU (2016), and FAO (2011). Based on the detected 226Ra, 232Th, and 137Cs activity concentrations, the highest total annual effective ingestion dose for the samples was estimated as 14.9 µSv/y. This value did not exceed the global annual average ingestion dose from the ingestion of terrestrial radionuclides to be 290 µSv/y reported by the UNSCEAR (2008). The total excess lifetime cancer risk values for the samples ranged from 0.08 × 10−5 to 2.88 × 10−5, and were found to be considerably lower than the limit of 2.5 × 10−3, as reported by the ICRP (1991). Based on these findings, it can be stated that the analyzed tea leaf samples in this study were radiologically safe and did not pose any carcinogenic risk to public health.