Abstract

Ionizing radiation and ultraviolet radiation (UV) are both physical agents with mutagenic and carcinogenic properties. However, there are some basic differences in the fundamental mechanism of their interaction with biological material that may have consequences for risk assessment. In this paper the dose-effect relationships for gamma radiation and UV at cellular level will be used to demonstrate the different radiobiological effectiveness of both agents. The results will be discussed in the framework of a biophysical model. This model is based on the assumption that DNA double-stranded lesions are crucial for the cytotoxic action. After exposure to ionizing radiation, the lesions are fixed immediately following irradiation, but after UV exposure the lethal lesions are recognized only in the next DNA systhesis phase. The combination of this concept with the mechanism of lesion induction and the possibility of repair, leads to different dose and time relationships for the radiation effects of both agents. The possi8ble consequences for risk assessment at low dose levels will be discussed.