The results of dosimetric evaluations carried out after Chernobyl accident in the Health Physics Department of Niguarda Ca' Granda Hospital (Milan) on air, rain and ground contamination are presented. The results obtained show that the incidence of stochastic late effects, both somatic and genetic, will be so low that practically will not be distinguishable from "natural" incidence.
Erratum In: Radiol Med (Torino) 1986 Dec;72(12):986
I had originally thought that by this time, nearly 1 year after the Chernobyl reactor accident, I would be in a position to describe fully its impact on the UK in terms of radiation doses, economics and future emergency planning. However, only one of these is reasonably clear-the radiological impact. We shall continue our measurements, particularly those of activity in persons, and doubtless we shall refine our estimates of collective dose, but they are unlikely to change significantly. We can therefore be certain that the radiological impact on the UK was small and that the health effects will not be detectable. Predictions of the consequences of accidental releases of radionuclides have in the past, perforce, relied upon models of environmental transfer. Data on which the models are based were obtained from investigations of weapons fallout and of routine releases from nuclear facilities. The Chernobyl accident provided a situation of activity deposition that was well characterised in time and in geographical distribution, and measurements along environmental pathways will allow us to validate or refine our models. This accidental deposition reinforced the importance of some effects that we knew about-such as the importance of wet deposition-and will cause us to consider the need to take account of specific situations that we had not considered previously in adequate detail-in particular, the behaviour of radionuclides in upland ecosystems. The overall economic impact is not yet clear and, unfortunately, is unlikely to become so until all restrictions on the movement and slaughter of sheep are removed and the farmers have received compensation. The effect on international trade may never be quantified. Some international agencies are evaluating the consequences of Chernobyl and their reports will become available during 1987. International agreements on intervention levels are also still under discussion and it would be premature to speculate about the need for any fundamental revisions to Emergency Reference Levels and derived quantities. Similarly, we are aware of the need for revision of the national emergency plan, but we are awaiting the government decision on this. One effect of the Chernobyl accident, however, is clear: the public's awareness of radiation issues has reached a new height. Members of the public demand information and advice, and better means of communicating these must be provided. Advice to take some action may provoke unnecessary alarm, but advice that no action is required may be distrusted. We cautiously assume that any dose, no matter how small, has some deleterious effect and yet, in situations of accidental releases, we may tell the public that no actions are required to reduced doses that they may consider appreciable and avoidable. We clearly need to promote a better understanding of the nature and acceptability of the risk of radiation doses in such circumstances and we intend to do so.
Radiocaesium contamination of dusts from external (road and school yards) and internal (house) environments within Barrow-in-Furness was found to be derived from the primary input event of Chernobyl fallout. The specific activity of radiocaesium in the dust reservoirs studied, decreased exponentially, enabling environmental half-lives to be calculated (190-370 day). The broad similarity of these half-lives indicated that secondary contamination processes, such as atmospheric deposition of resuspended dust, cause all the internal and external reservoirs to be linked into a system encompassing much of Barrow-in-Furness. Mean residence times of external dust were derived from the calculated environmental half-lives and measurements of atmospheric deposition (150-250 day). These mean residence times are dependent on local processes and are thus site specific, whilst the environmental half-lives represent an integration of all the processes operating in Barrow-in-Furness.
The degree of nonuniform distribution of plutonium in the human lung has not been determined; thus current dosimetric models do not account for nonuniform irradiation. A better scientific basis is needed for assessing the risk of developing radiation-induced disease from inhaled alpha-particle-emitting radionuclides. We measured the distribution of plutonium activity in the lung by autoradiography and related the activity to specific compartments of the lung. The study materials were lung specimens from deceased workers employed by the Mayak Production Association. The approach to analyzing these lung samples used contemporary stereological sampling and analysis techniques together with quantitative alpha-particle autoradiography. For the first time, plutonium distribution has been quantified in the human lung. The distribution of long-term retained plutonium is nonuniform, and a significant portion of plutonium was retained in pulmonary scars. In addition, a large fraction of plutonium was present in the parenchyma, where it was retained much longer than was estimated previously. The sequestration of plutonium particles in scars would greatly reduce the radiation exposure of the critical target cells and tissues for lung cancer. Thus the prolonged retention of plutonium in lung scars may not increase the dose or risk for lung cancer.
The accident with the nuclear power reactor at Chernobyl in the USSR resulted in the release of substantial quantities of radioactive material and subsequent increases in radioactivity in the environment in many countries. In this paper the situation in the UK is considered and, from the preliminary monitoring measurements, the major routes of exposure of the population are identified and quantified. For the most part exposures in the UK are within variations in levels of natural background radiation to be found in Europe. An exception is the dose likely to have been received by the thyroids of young people in the north of the UK. From reported measurements of I-131 in milk it is predicted that thyroid doses up to 10-20 times the annual doses received from 'normal' natural background radiation might have affected young children drinking fresh cows' milk. The ways in which this component of exposure could have been reduced and the criteria that govern decisions as to whether or not to implement counter-measures are discussed. The importance of I-131 in milk as a route of exposure of the population to radioactivity is a feature that the Chernobyl accident has in common with the Windscale accident in the UK in 1957, and underlines the importance of milk-producing regions in relation to reactor-sitting policy.
The radiation incident at Chernobyl, USSR, on April 26, 1986 was first detected in Sweden on April 29, when increased radioactivity was observed at a nuclear facility in that country. Subsequently, higher levels of radioactivity were observed in most of Eastern Europe and then in Western Europe. Increased radioactivity was eventually noted in the United States beginning about May 5. The three-day interval between the incident and its discovery outside the USSR caused great apprehension. This chain of events indicates the very important role for the nuclear medicine physician, the medical physicist and their colleagues. It is likely that this medical specialty area is staffed by personnel who are best qualified to interpret these findings and to determine the necessary course of action both for patients and the general public. The nuclear medicine specialist can provide valuable input in estimating the radiation dose impact resulting from such an incident. This estimate may be accomplished either by combining measured activity levels with the physiological and physical factors involved; or by actual in vivo counting and quantitation of radioactivity in individuals exposed to radionuclides. From the measured activities in air, water and food, and assumed intakes for various age groups, doses can be estimated both for inhalation and ingestion of radionuclides. In vivo measurements of radionuclides can be performed with conventional instrumentation used routinely in nuclear medicine laboratories.
Due to lack of measurements of activity concentrations in air, the assessment of the inhalation dose of the population evacuated from the 30-km zone after the Chernobyl accident is not possible from continuous filter measurements. Since the evaluation of the inhalation dose in each settlement of the zone is of great interest for epidemiological purposes, an approach was chosen that utilizes the available data on ground deposition of 137Cs, a recently performed best estimate of the radionuclide vector and its spatial distribution as well as the radionuclide dependent deposition velocity. The derived inhalation dose values in the 30-km zone range between 3 mSv to 150 mSv effective dose for adults depending on the distance to the reactor site and the day of evacuation. For 1-y-old infants the values range between 10 to 700 mSv. In Chernobyl town, an effective inhalation dose of 25 mSv until evacuation day was assessed. Thyroid doses due to inhalation ranged from 0.02 to 1 Sv for adults, for 1-y-old infants from 0.02 to 6 Sv. The inhalation dose in each settlement of the 30-km zone is approximately 8-13 times higher than the external exposure in each settlement if evacuation of the settlement occurred at an early stage. For settlements with evacuation at a later stage (day 10 or later) the inhalation dose was about 50-70% higher than the external dose. The dominant contribution to the effective inhalation dose comes from 131I (about 40%) and tellurium and rubidium isotopes (about 20-30%). Despite high zirconium and cerium ground depositions, zirconium and cerium isotopes contribute rather little to the inhalation dose which is mainly due to the great particle sizes to which they are attached. The relative contribution of short-lived radionuclides is, despite higher activities than at greater distances, less than 5%.
Comment In: Health Phys. 2003 Jul;85(1):110-1; author reply 111-212852478