Biological and health effects of ionising radiation

Radiobiology is based on the observation of the effects of ionizing radiation on living matter, and the ability to link observed phenomena to precise physical measurements in terms of radiation type, dose and dose rate, as well as exposure geometry for large, complex organisms. Pierre Curie's initial observations that high skin exposure led to erythema initiated an approach to the physiological effects of high-dose irradiation. The lack of precautions taken by the pioneers of radiology, radiotherapy and brachytherapy for their own radiation protection, together with animal experimentation, led to the rapid discovery of the tumorigenic and teratogenic effects of ionizing radiation. The combination of this initial, clinically-oriented radiophysiology with advances in physical measurement and, above all, cellular and then molecular biology, led to a better understanding of the phenomena involved at both cellular and genetic levels. The concepts developed in radiobiology have gone far beyond this discipline, and numerous applications, particularly in medicine, have been initiated in this science. The first bone marrow transplants were performed in the context of accidental radiation-induced aplasia, before becoming one of the flagships of hematology and oncology. In this first part, we present the physical and biological foundations on which radiobiology was built, with a particular focus on the dual issues of cellular and organism damage.