A comparison of independently conducted dose assessments to determine compliance and resettlement options for the people of Rongelap Atoll.

Rongelap Island was the home of Marshallese people numbering less than 120 in 1954; 67 were on the island and severely exposed to radioactive fallout from an atomic weapons test in March of that year. Those resident on Rongelap were evacuated 50 h after the test, returned 3 y later, then voluntarily left their home island in 1985 due to their ongoing fear of radiation exposure from residual radioactive contamination. Following international negotiations in 1991, a Memorandum of Understanding (MOU) was signed in early 1992 between the Republic of the Marshall Islands Government, the Rongelap Atoll Local Government, the U.S. Department of Energy, and the U.S. Department of the Interior. In this MOU it was agreed that the Republic of the Marshall Islands, with the aid of the U.S. Department of Energy, would carry out independent dose assessments for the purpose of assisting and advising the Rongelap community on radiological issues related to a safe resettlement of Rongelap. The MOU enacted two action levels which were agreed to be used to establish whether mitigation should be considered as a condition for resettlement of Rongelap Island: (1) no individual should receive an annual dose in the future of 1 mSv or more, above that from natural background radiation, assuming that his/her diet consists of only locally produced foods, and (2) the total surface soil concentration of plutonium and other transuranic elements must be less than 629 Bq kg(-1) (averaged over the top 5 cm). Environmental radiological data and dietary information were collected over two years (1992-1993) for the purpose of predicting future potential doses to Rongelapese who might resettle. In 1994, four independent assessments were reported, including one from each of the following entities: Marshall Islands Nationwide Radiological Study; Lawrence Livermore National Laboratory; an independent advisor from the United Kingdom (MCT); and a committee of the National Research Council. All four assessments concluded that possibly more than 25% of the adult population could exceed the 1 mSv y(-1) dose level based on strict utilization of a local food diet. The purpose of this report is to summarize the methodology, assumptions, and findings from each of four assessments; to summarize the recommendations related to mitigation and resettlement options; to discuss unique programmatic aspects of the study; and to consider the implications of the findings to the future of the Rongelap people.

Some reflections on the role of the Scientific Advisory Panel to the Marshall Islands nationwide radiological study.

As a consequence of the U.S. Atomic Weapons Testing Program in the Trust Territory of the Pacific, now the Republic of the Marshall Islands, numerous scientists have advised the Marshallese on matters of radiation and radioactive contamination. Some of the previous advice has appeared to vary or conflict resulting in consequent uncertainty for the people. In a new initiative in 1989, the RMI Government engaged a five member multi-disciplinary Scientific Advisory Panel to oversee the assessment of, and to advise on, the radiological status of the entire nation. The formation of the Panel was accompanied by the establishment of a Resident Scientist position, and ultimately a small scientific team and laboratory on Majuro. The nationwide radiological study was conducted using ground survey methods over the period 1990-1994. Tasks undertaken by the Panel included formulating reasonable objectives for the study and attempting to establish effective communication and understanding of issues with political leaders and RMI Government agencies and people, as well as advising on and monitoring the scientific integrity of the study itself. The attempt was also made to initiate investigations to address matters of concern that emerged. The problem was faced of providing not only technical guidance on radioactivity and radiation measurements, but also explaining the significance of measured values and concepts, such as risk and probability of health effects to a diverse but nontechnical audience, generally across cultural and language barriers. The experience of the Panel in providing advice and guidance to the Republic of the Marshall Islands, while unique in many ways, parallels the difficulties experienced elsewhere in communicating information about risks from radiation exposure.

Iodine deficiency in Belarusian children as a possible factor stimulating the irradiation of the thyroid gland during the Chernobyl catastrophe.

Ten years after the Chernobyl nuclear plant catastrophe more than 500 children in Belarus are suffering from thyroid cancer. The major cause of the high incidence of thyroid cancer in children under 15 years of age appears to be contamination resulting from that catastrophe, mainly with isotopes of radioactive iodine. Another important factor may be iodine deficiency in the environment. A countrywide program for investigation of goiter prevalence and iodine deficiency has been established in the Republic of Belarus with the assistance of the European World Health Organization office. The program will oversee the examination of 11,000 children and adolescents 6 to 18 years of age from 30 schools in urban and rural areas. The results obtained in a group of 824 children and adolescents (the pilot phase) are typical for significant iodine deficiency and moderate goiter endemism. It is clear that the present situation does not completely reflect the situation that existed at the time of the Chernobyl catastrophe. However, data from epidemiologic studies conducted many years before the accident showed high goiter prevalence in the contaminated areas, indicating that the prevalence of iodine deficiency at the time of the catastrophe was similar to the present one or even greater. Such an assumption could lead to a better understanding of the thyroid pathologies that have been observed.

Perspectives in radiation and health: reflections on the International Conference in Beer Sheva.

Insofar as international conferences reflect the state of development of the subject under discussion, they provide an opportunity to question, at a rather fundamental level, the direction of and progress in the subject. With regard to the effects of radiation on health, many of the problems faced today, including uncertainties in the relationship between risk and dose and the origins of the psychosocial phenomena associated with many aspects of environmental radiation exposure, arise from a lack of adequate frameworks within which to understand the radiopathological impact of radiation exposure and the psychological and social implications of such exposures. It is concluded that in seeking an understanding of the relationship of health effects to exposure, through the underlying radiobiological processes, the perturbation of the dynamic interactions within the components of the organism should receive more emphasis. The public perception of risk from environmental radiation exposures appears to encompass factors in addition to the accrued health detriment. It is argued that the radiological protection of the public might be seen more beneficially in the context of other environmental risks.

Thyroid cancer in children in Belarus after Chernobyl.

The accident to the nuclear reactor at Chernobyl in the Ukraine in April 1986 led to the exposure of substantial populations in northern Ukraine and southern Belarus to radioactive fallout. Recently increases in the incidence of childhood thyroid cancer have been reported from these areas. The possible causal association between exposure to the isotopes of iodine in the fallout and the increased thyroid cancer is examined, with a view to predicting the public health consequences of this aspect of the accident. The reported increases are shown to be consistent with a causal association and, if this is established, then a substantial increase in thyroid cancer can be expected over the next 50 years in the exposed populations. This conclusion underlines the urgent need for research to establish beyond doubt the origin of the reported increases and to formulate an appropriate public health response, including exploration of possible mitigating measures for the future.

DNA instability, paternal irradiation and leukaemia in children around Sellafield.

The chemical instability of DNA under physiological conditions requires that cells have highly developed processes for repairing stochastic single-strand damage. It is proposed here that provided ionizing-radiation-induced single-strand damage does not occur at a rate sufficient to perturb the dynamic steady state between degradation and repair, it can be regarded as "irrelevant' to biological effect, leaving double-strand damage and DNA-protein crosslinks as "relevant' damage to biological effect. At dose rates of approximately 0.05 Gy/min low-LET radiation the rate of induced single-strand damage equals that of the spontaneous damage, and in this region a transition, with increasing dose-rate, from constant effect to increasing effect, will be expected. This is observed in studies of specific locus mutation by radiation in the male mouse. The application of this biophysical principle governing the influence of radiation dose-rate, to the association observed between paternal preconceptional dose to Sellafield workers and childhood leukaemia in their offspring, shows that the likelihood of a causal relationship is extremely remote.

Evidence for the dominance of direct excitation of DNA in the formation of strand breaks in cells following irradiation.

The yields of radiation-induced strand breaks measured in a plasmid DNA irradiated as a 'dry film' are similar to those measured in SV40 DNA irradiated in a cellular environment (Roots et al. 1985). This suggests a common mechanism, namely direct excitation of the DNA rather than indirectly inflicted damage from radiation-induced water radicals. This result is discussed in terms of a recently proposed mechanism of excitation transfer in DNA following direct excitation by ionizing radiation.

Radiological protection and the lymphatic system: the induction of leukaemia consequent upon the internal irradiation of the tracheobronchial lymph nodes and the gastrointestinal tract wall.

The excess of leukaemia among young people living in the vicinity of the nuclear fuel reprocessing plant at Sellafield has focused attention on the possibility that irradiation of the lymphatic system from particulate alpha-emitting nuclides might be responsible. We discuss below two possible routes of such exposure; namely the inhalation and ingestion of particulates. We conclude that, in spite of the real possibility of substantial doses to tissues associated with the lymphatic system, there is little reason to expect that lymphatic leukaemia will be the dominant outcome of the exposure. However, the arguments presented are not, and cannot be, wholly conclusive.

A preliminary assessment of the consequences for inhabitants of the UK of the Chernobyl accident.

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.