There are two types of radiation – ionising and non-ionising.
Specific regulations in the UK require employers to protect employees from the adverse effects of ionising radiation, either from irradiation or from radioactive contamination. Non-ionising electromagnetic radiation (e.g. ultraviolet and radio waves) does not change the structure of atoms.

Ionising electromagnetic radiation has enough energy to ionise or electrically charge atoms. Ionising radiation has sufficient energy to cause changes within the DNA molecule and can therefore be a cause of cancer.

Non-ionising radiation (NIR) is the term used to describe the part of the electromagnetic spectrum covering two main regions, namely optical radiation (ultraviolet (UV), visible and infrared) and electromagnetic fields (EMFs) (power frequencies, microwaves and radio frequencies).

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 and its decay products) but can also be produced artificially. People can be exposed externally, to radiation from a radioactive material or a generator such as an X-ray set, or internally, by inhaling or ingesting radioactive substances. Wounds that become contaminated by radioactive material can also cause radioactive exposure.

Employers also have a general duty to protect employees from non-ionising radiation (e.g. over-exposure to the sun).