Keywords: efficient defences, reactive oxygen species, ROS, metabolic processes, thermal instability, DNA damage, low radiation, ionising radiation, linear no threshold model, LNT modelling, hormetic models, societal penalties, Chernobyl aftermath, precautionary principle
The paradigm that failed
About 2.3 billion years ago, the advent of an oxidative atmosphere, which was lethal for anaerobic biota, stimulated the surviving organisms to develop efficient defences against the enormous flux of Reactive Oxygen Species (ROS) produced by metabolic processes. Even earlier, similar defences were developed against the thermal instability of molecules and other events that damaged DNA. These powerful ancient defence mechanisms also protect the extant oxygen-loving organisms against the DNA damage caused by low levels of ionising radiation, which is one of the smallest risks in the environment, and contributes just a tiny fraction to the spontaneous rate of the DNA-damaging events. In this perspective, the Linear No Threshold (LNT) model of the radiation effects appears inappropriate for the current needs. Because of statistical reasons, it cannot be falsified. On the other hand, the hormetic model has the capacity to be tested in the observable zone. The precautionary principle, an offspring of LNT, leads to unacceptable societal penalties, as demonstrated in the aftermath of the Chernobyl catastrophe.