English 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.
