Pub. date: 2008 | Online Pub. Date: November 27, 2007 | DOI: 10.4135/9781412953948 | Print ISBN: 9781412928168 | Online ISBN: 9781412953948| Publisher:SAGE Publications, Inc.About this encyclopedia
In the context of epidemiology, it is useful to divide radiation into two types: ionizing and nonionizing. Ionizing radiation contains sufficient energy to remove electrons from atoms or molecules, leaving positively charged particles known as ions. X rays, neutrons, alpha particles, beta particles, and gamma rays are forms of ionizing radiation. Nonionizing radiation does not contain sufficient energy to remove electrons from their atoms: types of nonionizing radiation include radiowaves and microwaves. Ionizing radiation is known to be harmful to human tissue in some dosages and can cause damage to DNA. Although some people believe that human health can be harmed by nonionizing radiation emitted by electronic products, such as the radiofrequency radiation used by cell phones, this has not been established scientifically. Everyone is exposed to small amounts of ionizing radiation, often referred to as ‘background radiation,’ from the sun, rocks, water, soil, and so on. For this reason, ...