Triphasic Dose-Response of Hematological Parameters in Healthcare Workers Exposed to Ionizing Radiations

Objectives: To investigate the impact of chronic and low-dose ionizing radiation (IR) exposure on the workers’ hematopoietic system. Methods: Hematological parameters in IR exposed healthcare workers (n. 180) were compared to those determined in unexposed controls (n. 180). The relationship with the 5-year cumulative doses: <0.45; 0.45-1.28 and >1.28 mSv, was assessed. Results: Red blood cells (RBCs), hemoglobin (HB) and hematocrit (HCT) showed significant differences compared to controls. A non-linear relationship was determined with respect to the cumulative doses. RBCs showed a significant decrease at the first <0.45 mSv IR-dose compared to controls(4.72 ± 0.31 vs 4.90 ±0.38 ×1012/L; P= .013) with a rising trend, although not significant, at the two highest doses. Comparably, at the two lowest doses, HB (135.8 ± 11.3, P < .001 and 137.4 ± 10.1 g/L, P < .001) and HCT(41.8±2.7,P<.005and41.7±2.7%,P<.001)significantlydecreasedcomparedtocontrols(143.9±10.6g/Land 43.16 ± 2.95%, respectively), while not significantly increased at the >1.28 mSv highest one. Conclusions: IR exposure affected the hematopoietic system according to an hormetic phenomenon, intended as a biphasic dose-response with a low-dose stimulation and a high-dose inhibition, and, potentially, through a triphasic dose-response. These results deserve attention to define/implement suitable IR occupational risk assessment and management strategies.