Early dose assessment in criticality accidents.

Early estimation of dose is useful in the medical evaluation of severe radiation accidents. In a prior publication, lymphocyte depletion kinetics were shown to follow an exponential decline for gamma accidents in which the average whole-body dose was in the range 50 cGy < D < 8-10 Gy. In that study, the depletion rate constant was linearly related to dose, within the statistical variation of the historical hematological data. This simple technique has now been extended to include analysis of various types of criticality accidents (liquid process; water moderated systems; metallic systems). Lymphocyte depletion in high-level mixed gamma/neutron accidents is found to be approximately equal, at a given effective dose, to that for gamma accidents. This universality would indicate a neutron RBE for human lymphocytes close to unity. Furthermore, the technique appears to be insensitive to the shape of gamma and neutron spectra, therefore making it especially robust for initial, approximate dose estimation.

An Internet-based exercise as a component of an overall training program addressing medical aspects of radiation emergency management.

The use of ionizing radiation and radioactive materials continues to increase worldwide in industry, medicine, agriculture, research, electrical power generation, and nuclear weaponry. The risk of terrorism using weapons of mass destruction or simple radiological devices also has increased, leading to heightened concerns. Radiation accidents occur as a consequence of errors in transportation of radionuclides, use of radiation in medical diagnosis and therapy, industrial monitoring and sterilization procedures, and rarely, nuclear power generation. Compared to other industries, a small number of serious radiation accidents have occurred over the last six decades with recent cases in the Republic of Georgia, Peru, Japan, and Thailand. The medical, psychological, and political consequences of such accidents can be considerable. A number of programs designed to train medical responders in the techniques of radiation accident management have been developed and delivered in many countries. The low frequency of serious radiation accidents requires constant re-training, as skills are lost and medical staff turnover occurs. Not all of the training involves drills or exercises in which responders demonstrate learning or communication over the broad spectrum of medical response capabilities. Medical preparedness within the context of a total emergency response program is lacking in many parts of the world, particularly in Central and Eastern Europe and the Newly Independent States. This paper describes an effort to enhance medical preparedness in the context of a total program of international cooperation and conventions facilitated by the International Atomic Energy Agency. The paper concludes that novel application of telecommunications technology as part of a training activity in radiation accident preparedness can help address gaps in training in this field in which preparedness is essential but experience and practical field exercises are lacking.

Early dose assessment following severe radiation accidents.

Early treatment of victims of high level acute whole-body x-ray or gamma exposure has been shown to improve their likelihood of survival. However, in such cases, both the magnitude of the exposure and the dosimetry profile(s) of the victim(s) are often not known in detail for days to weeks. A simple dose-prediction algorithm based on lymphocyte kinetics as documented in prior radiation accidents is presented here. This algorithm provides an estimate of dose within the first 8 h following an acute whole-body exposure. Early lymphocyte depletion kinetics after a severe radiation accident follow a single exponential, L(t) = L(o)e(-k(D¿t), where k(D) is a rate constant, dependent primarily on the average dose, D. Within the first 8 h post-accident, K(D) may be calculated utilizing serial lymphocyte counts. Data from the REAC/TS Radiation Accident Registry were used to develop a dose-prediction algorithm from 43 gamma exposure cases where both lymphocyte kinetics and dose reconstruction were felt to be reasonably reliable. The inverse relationship D(K) may be modeled by a simple two parameter curve of the form D = a/(1 + b/K) in the range 0 < or = D < or = 15 Gy, with fitting parameters (mean +/- SD): a = 13.6 +/- 1.7 Gy, and b = 1.0 +/- 0.20 d(-1). Dose estimated in this manner is intended to serve only as a first approximation to guide initial medical management.

Accidental radiation injury to the hand: anatomical and physiological considerations.

A case study describing an accident in Mexico caused by failure to de-energize an x-ray spectrometer prior to repair is presented. The evolution, medical management, and outcome of the radiation injury to the hand are briefly reviewed. A discussion follows, with radiation injury and thermal burns compared and contrasted. The anatomy and physiology of thick skin and the vascular system of the hand are reviewed so that the reader will have a better understanding of the role of vascular injury in the pathological process that leads to tissue atrophy and radiation necrosis. Hyperbaric oxygen therapy, sympathectomy, and other techniques for improving circulation in involved areas are reviewed.

The 1986 and 1988 UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) reports: findings and implications.

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has published a substantive series of reports concerning sources, effects, and risks of ionizing radiation. This article summarizes the highlights and conclusions from the most recent 1986 and 1988 reports. The present annual per person effective dose equivalent for the world's population is about 3 mSv. The majority of this (2.4 mSv) comes from natural background, and 0.4 to 1 mSv is from medical exposures. Other sources contribute less than 0.02 mSv annually. The worldwide collective effective dose equivalent annually is between 13 and 16 million person-Sv. The Committee assessed the collective effective dose equivalent to the population of the northern hemisphere from the reactor accident at Chernobyl and concluded that this is about 600,000 person-Sv. The Committee also reviewed risk estimates for radiation carcinogenesis which included the new Japanese dosimetry at Hiroshima and Nagasaki. These data indicate that risk coefficient estimates for high doses and high dose rate low-LET radiation in the Japanese population are approximately 3-10% Sv-1, depending on the projection model utilized. The Committee also indicated that, in calculation of such risks at low doses and low dose rates, a risk-reduction factor in the range of 2-10 may be considered.

The medical technologist and the radiation-accident victim.

Radiation accidents may produce external or internal contamination with radionuclides, local or whole-body exposure to penetrating radiation, or a combination of these. Trauma and medical problems which require rapid diagnosis and treatment may accompany a radiation injury. The role of the medical technologist in the early post-injury period may include the use of precautions in handling of contaminated specimens, prompt and repeated determinations of the absolute lymphocyte count, establishment of baseline values of the cellular and chemical components of the blood, and urinalysis. Following significant whole-body exposure to penetrating radiation, laboratory tests are required to monitor the development of granulocytopenia and thrombocytopenia and to provide information necessary for the prevention, control, and treatment of infection and/or bleeding. Chromosome analysis may aid in dosimetry, and a procedure for collecting and shipping blood for analysis by experts in radiation cytogenetics is described.

Emergency department radiation accident protocol.

Every emergency department faces the potential problem of handling one or more victims of a radiation accident. While emergency departments near nuclear power plants or isotope production laboratories probably have a detailed protocol for such emergencies, a similar protocol is needed for the emergency department that may have to handle an isolated event, such as a vehicular accident that spills radioactive material and contaminates passengers or bystanders. This communication attempts to answer that need, presenting a step-by-step protocol for decontamination of a radiation victim, the rationale on which each step is based, a list of needed supplies, and a short summary of decorporation procedures that should be started in the emergency department.