Ionizing and non-ionizing radiation are two types of radiation that can affect living things. Ionizing radiation has so much energy that it can remove electrons from atoms, a process known as ionization. This type of radiation can damage the tissue and DNA of genes, and can be especially harmful to cells that divide quickly. It can also be used to fight cancer, as doctors use radiation to target cancerous cells.
Non-ionizing radiation does not have enough energy to cause ionization, and is generally considered less dangerous than ionizing radiation. The mutagenic effects of radiation were first recognized in the 1920s, and since then, radiation has been used in genetic research as an important means of obtaining new mutations in experimental organisms. In 1956, the National Academy of Sciences-National Research Council (NAS-NRC) established the Committee on the Biological Effects of Atomic Radiation (BEAR Committee), which was the forerunner of the following NAS-NRC committees on the Biological Effects of Ionizing Radiation (BEIR committees). A series of reports from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has also addressed the genetic effects of radiation exposure on populations.
At the cellular level, ionizing radiation generates reactive oxygen species and ionizes DNA, leading to single-stranded and double-stranded breaks, interstrand crosslinks, and other oxidative damage. Depending on the type, quality, and dose of IR, cell repair machinery may not accurately or completely repair DNA damage that leads to cell death or transformation. Deletion of DNA segments is the predominant form of radiation damage in cells that survive irradiation.As human technology has advanced, sources of ionizing radiation exposure have multiplied, increasing the incidence of radiation-induced human diseases. These sources include nuclear attacks, civil nuclear disasters, aerospace travel, medical radiation (radiation therapy and computed tomography), and inhalation of radon gas.
It is well established that DNA damage is the primary mechanism associated with the tumorigenicity of ionizing radiation; however, ionizing radiation also causes significant aberrations in the cellular epigenome, including alterations in DNA methylation, histone modifications, and chromatin accessibility.