Since the end of the Second World War, industrial and medical uses of radiation have been considerably increasing. Accidental overexposures of persons, in either the occupational or public field, have caused deaths and severe injuries and complications. The rate of severe accidents seems to increase with time, especially those involving the public; in addition, accidents are often not immediately recognised, which means that the real number of events remains unknown. Human factors, as well as the lack of elementary rules in the domains of radiological safety and protection, such as inadequate training, play a major role in the occurrence of the accidents which have been reported in the industrial, medical and military arenas.

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Bone marrow aplasia is one of the main syndromes following a high dose accidental exposure of ionizing radiation. Although both transfusion and bone marrow transplantation have been used with some success since the first treatments of patients, other therapeutic strategies are needed. The strategies involving haematopoietic growth factors for the treatment of radiation victims have been explored in vivo mainly in animal models and it is hoped that new therapeutic regimens will be elucidated from such approaches. The growth factors stimulate proliferation and/or differentiation of haematopoietic progenitor cells and possible stem cells. Furthermore, they act on the functions of mature cells. They now have specific uses in haematology, related to their role in the regulation of growth and differentiation of haematopoietic progenitor cells. The results of the clinical trials, performed with numerous patients and often randomized bring important clues about what to expect from growth factor therapy. Other factors are only entering the preclinical or clinical trials now. Although numerous in vitro or in vivo experiments suggest a benefit from their effects, their possible uses in therapy are still questionable. Some growth factors have already been used for the treatment of accidental radiation-induced aplasia and lessons have been learned from their medical management and follow-up.

Rats were administered 237Np nitrate either intravenously or intramuscularly. Similar distributions in organs were observed after intravenous injections at pH 1.5 and 7.5. Intramuscular injections were followed by a high urinary excretion-about 30 % of the total administered dose-over the 1st month, while over 60% migrated from the injection site. The ratio of "activity eliminated via urine/activity deposited in bone" was roughly equal to 1. DTPA therapy was not effective. Neptunium behavior rather followed that of alkaline earths than that of transplutonium elements.

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Whereas the pathological effects of radiation to the skin are well known, it is often difficult to assess quickly and with accuracy the level of severity, because of the delay between exposure and appearance of the lesions and because of the hidden lesions in underlying tissues. The severity depends mainly on the nature of the radiation, high-energy penetrating radiation causing much more irreversible damage than low-energy lightly penetrating radiation. Therefore, besides the clinical observation, diagnosis and prognosis should be based on many various parameters such as dosimetry, reconstruction of the accident, thermography, scintigraphy, etc. Pain is the first difficult problem to solve. It starts quickly, is constant at all stages and rapidly dominates the clinical picture. It raises the problem of the use of toxic drugs, with the risk of addiction. Medical treatment deals with inflammation, moist desquamation and ulceration. The major problem is the risk of infection. Surgical treatment deals with deep ulceration and necrosis; the requirement varies, according to the nature and energy of the radiation, the localization of the injury and its severity. The two main methods are excision and grafting; the most favourable time for intervention is difficult to specify, and should be neither too early before the establishment of the clinical picture nor too late. The combination of radiation burns with an acute radiation syndrome raises many questions, many of which are not completely solved.

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.