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

To investigate the impact of chronic and low-dose ionizing radiation (IR) exposure on the workers' hematopoietic system. 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. 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 × 10/L; = .013) with a rising trend, although not significant, at the two highest doses. Comparably, at the two lowest doses, HB (135.8 ± 11.3, < .001 and 137.4 ± 10.1 g/L, < .001) and HCT (41.8 ± 2.7, < .005 and 41.7 ± 2.7%, < .001) significantly decreased compared to controls (143.9 ± 10.6 g/L and 43.16 ± 2.95%, respectively), while not significantly increased at the >1.28 mSv highest one. 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.