The data summarized in this section are taken mainly from the 2000 Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and generally refer to occupational exposures assessed to have been experienced during the earlyand mid-1990s [1]. Occupational exposures in the United Kingdom from 1998 to 2003 have been reviewed recently by the Radiation Protection Division of the Health Protection Agency [2]. Soon after its discovery by Roentgen in 1895, ionizing radiation was exploited in medicine as a diagnostic and therapeutic tool, leading to the inadvertent exposure of medical staff. In the early years of the 20th century, exposures to medical personnel tended to be large, sometimes leading to deterministic effects such as epilation and skin burns. The first substantial epidemiological evidence for the carcinogenic effects of radiation was obtained from observations on radiologists. The use of radiation in medicine grew throughout the last century and currently includes a variety of diagnostic techniques (e.g. fluoroscopy and cardiac catheterization), dental radiography, radionuclides used for organ imaging in nuclear medicine, radiotherapy and other uses such as biomedical research. Initially, it was X-rays that were employed, but techniques became more sophisticated such that other radiations [e.g. densely ionizing alpha particles (He) and neutrons] were introduced. Medical workers now constitute the largest group occupationally exposed to man-made sources of radiation: throughout the world, 2.5 million medical workers are monitored for exposure to radiation (the majority of these being employed in the countries of the Organization for Economic Cooperation and Development), leading to an average annual collective effective dose of 1000 person.Sv. In contrast to the high-level exposures experienced by early medical workers, the reported annual occupational doses in excess of 15 mSv are now rare. The industrial use of radiation is multifarious and includes radiography, irradiation (e.g. the sterilization of medical products), luminizing, radionuclide production and distribution, well logging and accelerator operation. Some 0.75 million workers are monitored for exposure, leading to an average annual collective effective dose of 400 person.Sv. Although individual doses are generally small, a few workers (such as those involved in site radiography) receive annual doses in excess of 15 mSv, and occasionally serious over-exposures are reported. The luminizing of dials with radium-based paint in the first half of the last century led to accidental ingestion of the paint and, particularly in the United States, high intakes of radium. Occupational exposure also occurs in educational establishments ( 0.33 million monitored workers worldwide) and in veterinary medicine ( 50 000 radiation workers), leading to average annual collective effective doses of 30 person.Sv and 10 person.Sv, respectively. The discovery of neutron-induced nuclear fission in the 1930s led to the development of the nuclear weapons and power industries in the second half of the 20th century and consequent occupational exposure to natural and man-made sources of radiation. Workers in these industries are involved in mining and processing of uranium, nuclear fuel production, reactor operation, irradiated fuel reprocessing and product and waste management. Additional occupational exposures occur in research and development activities and in production and testing of nuclear weapons. The exposure of workers at the Mayak facility in the Southern Urals to external sources of gamma and neutron radiation and to alphaemitting plutonium before 1959 were very high, occasionally sufficiently so to produce deterministic effects. The total number of monitored workers in the commercial nuclear fuel cycle is 0.8 million and the average annual collective effective dose is 1500 person.Sv. Accurate figures for the defence industry are difficult to come by, but the annual collective effective dose worldwide is likely to be in the range of 100–300 person.Sv. By far, the largest source of occupational exposure is naturally occurring radiation. The excess risk of lung Correspondence to: Richard Wakeford, 6 Bourne Street, Wilmslow, Cheshire SK9 5HD, UK. Formerly: British Nuclear Fuels plc, 1100 Daresbury Park, Warrington WA4 4GQ, UK. e-mail: richard.wakeford@Gmail.com
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Jun 1, 2008
Eli Dolev + 5
Open Access