The linear no-threshold model in radiation protection—the view of the German Federal Office for radiation protection

Does ionising radiation increase the risk of cancer even at low doses? If so, what is the magnitude of risk at these low doses? This knowledge is a central component of radiation protection. In general, radiation protection relies on the linear no-threshold (LNT) model, which is based on scientific findings. According to the LNT model, the radiation-related risk of cancer decreases proportionally with radiation dose and this applies even down to very low radiation doses. The model provides a straightforward and practical description of the relationship between a radiation dose and the resulting risk of cancer. These assumptions align with the latest radiobiological and radiation epidemiological findings. Therefore, and because of its simplicity, the model is used in radiation protection (e.g. for setting dose limits). The LNT model offers a plausible basis for prudent decision- making in radiation protection. However, it does not represent a universally valid description of the relationship between ionising radiation and specific biological mechanisms of carcinogenesis. This memorandum summarises the position of the Federal Office for Radiation Protection, Germany, on the use of the LNT model in radiation protection.