Ionizing radiations act

Haimovitz-Friedman A, Kan CC, Ehleiter D, et al. Ionizing radiation acts on cellular membranes to generate ceramide and initiate apoptosis. J Exp Med 1994 180 525-535. 

In the UK, the Ionizing Radiations Act (1985) provides details of local arrangements for the supervision of radioisotope work. 

Ionizing radiations act upon a photographic emulsion to produce a latent image much as visible light does. The radiation interacts with the emulsion to produce electrons which reduce silver halides to metallic silver. This metallic silver during development shows up as black spots. It is possible to measure the absorbed dose of radiation by densitometry of the blackened film. 

The Control of Substances Hazardous to Health (COSHH) Regulations 1989 covers virtually all substances hazardous to health. Only asbestos, lead, materials producing ionizing radiation and substances below ground in mines (which all have their own legislation) are excluded. The Regulations set out measures that employers must implement. Failure to comply with COSHH, in addition to exposing employees and others to risk, constitutes an offence and is subject to penalties under the Health and Safety at Work Act, etc. 1974. 

From a chemist s viewpoint, the most important act of ionizing radiation (usually X-rays, y-rays or high energy electrons) is electron ejection. Initially the ejected electrons have sufficient energy to eject further electrons on interaction with other molecules, but the electrons ultimately become thermalised and then are able to interact "chemically". We consider first various reaction pathways for these electrons, and then consider the fate of the "hole" centres created by electron ejection. [We refer to electron-gain and electron-loss centres rather than to radical-anions and -cations since, of course, the substrate may comprise ions rather than neutral molecules. 

Increased initial damage Agents that act to increase the initial DNA damage caused by ionizing radiation would be expected to augment the cytotoxicity caused by radiation... 

Ionizing radiation can act in two distinct ways on organic substances. In the absence of water, in condensed systems or in concentrated solution, the predominant effects occur directly on the organic molecule and produce electronic excitations or ionizations which may lead to chemical modification. In dilute solution (1% or less) the major effects are the result of reactions between the solute and reactive species produced by the radiolysis of water. These indirect effects are the subject of this article. 

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