Screening for the (137)Cs body burden owing to the Chernobyl accident in Zhytomyr region, Ukraine: 2009–2018

The Chernobyl Nuclear Power Plant accident released vast amounts of various fission products, of which (131)I and (137)Cs are considered the most important because they are a major source of radiation exposure to the general public. (137)Cs, unlike (131)I, has a 30-year half-life that continues to expose people internally and externally for several decades after being deposited into the ground. (137)Cs can be easily transmitted to the body through the intake of products and wild forest foodstuffs produced in contaminated areas. In the early phase, external exposure to (137)Cs was predominant; however, it gradually diminished, mostly owing to horizontal and vertical distribution, and internal exposure started gaining dominance. Prior studies have shown that people in the affected areas have been constantly subjected to the inevitable low-grade internal exposure, which in turn has led to high anxiety and concern regarding the potential health effects. The present 10-year study assessed the latest status of the body burden among residents of the contaminated parts of the Zhytomyr region of Ukraine by measuring the internal concentration of (137)Cs using the whole-body counter installed at the Medical Center of Korosten city. Almost 110 000 examinees from eight different districts were screened between 2009 and 2018. The study area was situated to the west of Chernobyl, which experienced a significant fallout of (137)Cs and (131)I from the Chernobyl Nuclear Power Plant. We analyzed the data for internal exposure to (137)Cs by obtaining the actual magnitude, pace, and pattern of change for each year. During the study, the average (137)Cs concentration in residents fell from 21.6 Bq/kg at the beginning of the study to 3.0 Bq/kg at the end of the study. The proportion of examinees with detectable levels had also fallen rapidly, from 45% to 11%. We found a weaker seasonal effect and a significantly higher Bq/kg concentration in adolescents than in other age groups.