Ionizing and Non-Ionizing Radiation Ionizing radiation has so much energy that it can remove electrons from atoms, a process known as ionization. Ionizing radiation can affect atoms in living things, posing a health risk by damaging the tissue and DNA of genes. You are surrounded by ionizing radiation. It can affect cells through direct and indirect action, causing DNA damage and mutations.
This can be especially harmful to cells that divide very quickly. But sometimes this can be good, such as when doctors use radiation to fight cancer. Ionizing radiation damages the genetic material of reproductive cells and produces mutations that are transmitted from generation to generation. 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.
Although occupational exposure to high levels of radiation has always been a matter of concern, not until during and after World War II was there a concerted effort to assess the genetic effects of radiation on entire populations. These efforts were motivated by concerns about the effects of extremely large sources of radiation being developed in the nuclear industry, radioactive fallout, atmospheric testing of atomic weapons, and the rapid increase in the use of radiation in medical diagnosis and therapy. In 1956, the National Academy of Sciences-National Research Council (NAS-NRC) established the Committee on the Biological Effects of Atomic Radiation (referred to as the BEAR Committee), which was the forerunner of the following NAS-NRC committees on the Biological Effects of Ionizing Radiation (BEIR committees; of which this BEIR V report is one). 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.
Ionizing radiation (IR) is highly detrimental to life's vital processes, inducing DNA damage that underlies a variety of human diseases, including cancer. At the cellular level, IR 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. As human technology has advanced, sources of IR exposure have multiplied, increasing the incidence of radiation-induced human diseases.
This chapter reviews the main sources of human exposure to IR rays and their health consequences, including nuclear attacks, civil nuclear disasters, aerospace travel, medical radiation (radiation therapy and computed tomography), and inhalation of radon gas. Deletion of DNA segments is the predominant form of radiation damage in cells that survive irradiation. It can be caused by the (misrepair) of two separate double-stranded breaks in a DNA molecule with the joining of the two outer ends and the loss of the fragment between the breaks or (the cleaning process (enzymatic digestion of nucleotides, the component molecules of DNA) of the broken ends before rejoining to repair one double strand break. Localized DNA damage caused by dense ionizations of high-LET radiation is more difficult to repair than diffuse DNA damage caused by scattered ionizations of low-LET radiation.
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. .