Overview of the radiological accidents in the world, updated December 1989

Radiological accidents can be divided into two categories, depending on whether the accident involves large groups of the population with relatively low doses or a few individuals with high doses resulting in acute health effects. The accidents involving large groups are related to the dispersion of radioactive materials in the environment; although they may have different causes, the source is always very important. Most of the accidents which have occurred originated in civilian installations; two reactor accidents can be considered without any human consequences: the accidents in the UK (Windscale) in 1957 and in the USA (TMI) in 1979. The Chernobyl accident (USSR) in 1986 resulted in extensive contamination of the environment, with non-negligible doses to the population around the plant and large collective doses in the northern hemisphere; in addition, the Chernobyl accident caused the deaths of 31 workers and firemen who intervened to bring the installation back under control. Violations of the most elementary safety rules for the operation of medical sources were at the origin of two severe environmental contaminations with human consequences: in Mexico (1983-4) and Brazil (1987), with sources of 60Co and 137Cs, respectively. The accidents concerning only a few individuals are not always known with the same documented accuracy. Between the 1940s and 1960s six critical accidents caused eight deaths; since then only one has occurred, in Argentina in 1983. The fatal radiation accidents are due to high-energy radiation sources, such as 60Co, 137Cs, and 192Ir. The total number of deaths which has been registered is 28. The accidents related to internal exposure are not exceptional, but result very rarely in health consequences.