ABSTRACT
Biological damage depends also on the nature or type of ionizing radiation; for example, alpha particles can be eighty times more harmful than gamma rays or beta particles. Different types of unit are used to measure radiation and its effects: some types of unit measure the quantity of radioactivity emitted by a substance and others the biological effect produced on exposure to radiation, and units have changed with the introduction of Systeme International (SI) units. The evidence of damaging biological effects from exposure to radiation has resulted in the setting up of national and international protection organizations. The first of these was an unofficial British X-ray and Radium Protection Committee, formed in 1921 to formulate standards for protection of those occupied in medical application of X-rays and radium. The International Commission on Radiological Protection (ICRP) has been firm in its caution when issuing guidance on dose limits for occupational and public exposure to man-made radiation sources other than medical exposures.
