Ionising radiation is so called because it is very energetic and can ionise the atoms in the matter it interacts with. "Ionisation" is the process by which electrons are stripped from atoms. This process produces molecular changes that can lead to damage in biological tissue, including effects on the genetic material DNA. Ionising radiation occurs as either electromagnetic rays (such as X-rays and gamma rays) or particles (such as alpha and beta particles). It occurs naturally (e.g. from the radioactive decay of natural radioactive substances such as radon gas) but can also be produced artifically. People can be exposed externally to radiation from a radioactive material or generator such as an X-ray set, or internally by inhaling or ingesting radioactive substances, or through wounds that may become contaminated by radioactive material. Everyone is exposed to natural background radiation and many people also have the medical or dental X-ray examinations.
Non-ionising radiation is so called because it is not energetic enough to ionise atoms in the matter it interacts with. Non-ionising electromagnetic radiation (NIEMR) is the term used to describe the part of the electromagnetic spectrum covering two main regions, optical radiation (ultraviolet (UV), visible and infrared) and electromagnetic fields (EMFs) (electrical power frequencies, microwaves and radiofrequencies). Many industrial processes generate NIEMR, but more commonly known sources include the sun and sunbeds, lasers, electrical equipment, telecommunications and electricity supply. Over exposure to NIEMR can cause a variety of ill-health effects.