Combined Radiations: Biological Effects of Mixed Exposures Across the Radiation Spectrum

The growing use of mixed radiation exposures in medicine, space exploration, and environmental contexts has emphasized the need to understand their biological effects. This review compiles and analyzes findings from over 170 studies examining combinations of ionizing and non-ionizing radiation types, including ultraviolet light, X-rays, gamma rays, alpha and beta particles, protons, neutrons, and heavy ions. Through a structured literature survey, we organized studies into three main domains: radiobiological, therapeutic, and space radiation. Results reveal frequent additive and/or synergistic interactions—especially when radiation types are applied sequentially within short intervals—that affect DNA repair kinetics, cell survival, and gene expression. The degree of synergy often depends on dose, exposure sequence, and the involvement of specific repair pathways. Therapeutic combinations, such as carbon ion–proton therapy or radiotherapy–photodynamic treatment, show enhanced efficacy and tolerability in preclinical and clinical settings. In contrast, space and environmental studies illustrate the complexity of mixed-radiation effects, including immune suppression and persistent DNA damage. This review provides a consolidated reference framework for the diverse and evolving field of combined radiations, emphasizing the need for mechanistic studies and standardized protocols to guide safe and effective implementation across applications, such as radiation protection, therapy, and space mission planning.