Trends in red blood cells and hemoglobin levels in individuals chronically exposed to ionizing radiation during occupational activities

Introduction. The hematopoietic system is sensitive to ionizing radiation. At the same time, research on hematopoietic effects in cohorts of individuals who are chronically exposed to ionizing radiation is quite limited.

Objective. To evaluate red blood cell and hemoglobin levels, and to analyze their changes over time in individuals chronically exposed to ionizing radiation.

Material and methods. The study cohort consisted of nuclear workers of the Mayak PA who were hired between 1948 and 1952, totaling 7,391 individuals. These workers were followed for a period of 15 years starting from their date of hire. The analyzed dataset included 156,490 peripheral blood counts. At the end of the follow-up period, the mean accumulated red bone absorbed dose of gamma rays from external exposure was 0.81 ± 0.79 Gy for males and 0.55 ± 0.62 Gy for females. The mean annual gamma dose was 0.10 ± 0.20 Gy for males and 0.07 ± 0.15 Gy for females, and the mean maximum annua gamma dose was 0.33 ± 0.39 for males and 0.22 ± 0.27 Gy for females.

Results. The mean red blood cell and hemoglobin levels in the study cohort of workers remained within the normal physiological range, showing only slight fluctuations throughout the entire follow-up period. Both red blood cell and hemoglobin levels in the peripheral blood decreased significantly in the first few years after the beginning of contact with ionizing radiation sources, when the highest annual absorbed gamma doses in red bone were recorded for both male and female workers. After these initial years, red blood cell and hemoglobin levels eventually returned to normal. The differences were statistically significant when the levels in first years of employment were compared to the levels reported during pre-employment health check-ups. However, no complete recovery to the pre-employment levels was observed. The hemoglobin concentration also remained within the normal physiological range throughout the entire follow-up period. However, after the recovery period, it gradually decreased until the end of the follow-up, compared to the pre-employment level. The analysis of these blood parameters in relation to gamma-ray dose from external exposure revealed a significant association of red blood cell and hemoglobin concentration with the radiation dose (p < 0,05).

Conclusion. Red blood cell levels and hemoglobin concentrations registered at the pre-employment health check-up were significantly lower in females than males. In the first 15 years of employment, the mean red blood cell and hemoglobin levels were significantly decreased compared to the pre-employment levels. The red blood cell level and hemoglobin concentration were significantly associated with the gamma-ray dose from external exposure.

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