Synergistic Genotoxic Effects of Gamma Rays and UVB Radiation on Human Blood

Exposure to ionizing and non-ionizing radiation from environmental and clinical settings can significantly threaten genomic stability, especially when combined. This ex vivo study investigates the potential combined effects of gamma radiation and ultraviolet B (UVB) light on human peripheral blood mononuclear cells (PBMCs) from healthy donors by exposing whole blood and isolated PBMCs to 1 Gy of gamma rays, 100 J/m² of UVB, or to their combination. DNA damage and repair were assessed using the γH2AX immunofluorescence assay at 1 hour and 24 hours post-irradiation. Combined exposure resulted in significantly elevated γH2AX foci formation and chromosomal aberrations relative to individual stressors, with the most pronounced effects observed in isolated PBMCs. Notably, lymphocytes from some donors failed to proliferate after UVB or co-exposure. Based on our results, a predictive biophysical model derived from dicentric yield was developed to estimate the gamma-ray equivalent dose from co-exposure, indicating a potential ~9% increase in lifetime cancer risk. These findings highlight the need to account for mixed radiation exposures in genotoxic risk assessment and radiation protection, while also supporting a protective role of the whole-blood environment.