History of Radiation Biology

At the end of the nineteenth century, Wilhelm Conrad Roentgen discovered X-rays and Henri Becquerel discovered radioactivity. In the early years after that, there was a lot of misunderstanding regarding the effects of ionizing radiation and its practical applications. Medical employment of ionizing radiation began immediately after the discovery of X-rays. However, until World War Two, radioactive substances were widely used and misused. Until the early 1960s, ionizing radiation was commonly used for treatment of various diseases. Since then, however, radiation therapy has been confined nearly exclusively to cancer treatment. Two factors contributed to the phasing out of radiotherapy for non-oncological purposes: the growing awareness of radiation carcinogenesis and the development of efficient drugs (primarily, antibiotics). Radio-induced cancers have been known for above a century. The linear no-threshold (LNT) risk model considers that cancer risk is proportional to radiation dose and no radiation exposure is safe. Although LNT has never been scientifically validated, it is used for the management of radiological protection. Progress in understanding the carcinogenesis associated with ionizing radiation has resulted from a better comprehension of the DNA damage repair and other defense mechanisms.