Lessons from past radiation accidents: Critical review of methods addressed to individual dose assessment of potentially exposed people and integration with medical assessment.

The experiences of the Chernobyl and Fukushima nuclear accidents showed that dosimetry was the essential tool in the emergency situation for decision making processes, such as evacuation and application of protective measures. However, at the consequent post-accidental phases, it was crucial also for medical health surveillance and in further adaptation to changed conditions with regards to radiation protection of the affected populations. This review provides an analysis of the experiences related to the role of dosimetry (dose measurements, assessment and reconstruction) regarding health preventive measures in the post-accidental periods on the examples of the major past nuclear accidents such as Chernobyl and Fukushima. Recommendations derived from the review are called to improve individual dose assessment in case of a radiological accident/incident and should be considered in advance as guidelines to follow for having better information. They are given as conclusions.

Realism and usefulness of multispecies experiment designs with regard to application in radioecology: A review.

Multispecies experiments like microcosms and mesocosms are widely used in many fields of research but not in radioecology. In radioecology, size limitations are important as large experimental volumes involve problems with waste (radionuclides), or shielding, absorption and available space in gamma fields (often within a climate chamber). We have therefore performed a literature review (ISI Web of Science, n = 406) of the design and properties of multispecies effect studies <100 L in size and with three or more mentioned taxa in other research fields to assess their suitability to radioecology. Studies with more mentioned taxa assess structural ecosystem parameters more often than studies with fewer mentioned taxa, while the opposite trend is seen for indirect effects/interactions. Studies of indirect effects benefit from more replicates and longer experiments. Almost all studies assess some ecosystem level parameter but only a quarter take a holistic approach assessing both structural and functional as well as indirect effects. We find that most cosms are custom-made systems, rather than standardised designs. Unmanipulated cosms consist of excised portions of the natural environment with a higher number of mentioned taxa, high ecological complexity and high realism, but have a relatively low replicability. In contrast, standardised cosms with fewer mentioned taxa have less ecological complexity but much higher replicability. This literature review shows that smaller cosm sizes have similar ecological complexity (e.g. number of taxa and trophic levels) and experimental duration as larger sized cosms, allowing for ecologically-relevant investigations, despite their small size. We encourage multispecies radioecology studies, preferably with environmental relevant doses and sufficient detail on dosimetry.

Uncertainty of fast biological radiation dose assessment for emergency response scenarios.

PURPOSE: Reliable dose estimation is an important factor in appropriate dosimetric triage categorization of exposed individuals to support radiation emergency response. MATERIALS AND METHODS: Following work done under the EU FP7 MULTIBIODOSE and RENEB projects, formal methods for defining uncertainties on biological dose estimates are compared using simulated and real data from recent exercises. RESULTS: The results demonstrate that a Bayesian method of uncertainty assessment is the most appropriate, even in the absence of detailed prior information. The relative accuracy and relevance of techniques for calculating uncertainty and combining assay results to produce single dose and uncertainty estimates is further discussed. CONCLUSIONS: Finally, it is demonstrated that whatever uncertainty estimation method is employed, ignoring the uncertainty on fast dose assessments can have an important impact on rapid biodosimetric categorization.

RENEB accident simulation exercise.

PURPOSE: The RENEB accident exercise was carried out in order to train the RENEB participants in coordinating and managing potentially large data sets that would be generated in case of a major radiological event. MATERIALS AND METHODS: Each participant was offered the possibility to activate the network by sending an alerting email about a simulated radiation emergency. The same participant had to collect, compile and report capacity, triage categorization and exposure scenario results obtained from all other participants. The exercise was performed over 27 weeks and involved the network consisting of 28 institutes: 21 RENEB members, four candidates and three non-RENEB partners. RESULTS: The duration of a single exercise never exceeded 10 days, while the response from the assisting laboratories never came later than within half a day. During each week of the exercise, around 4500 samples were reported by all service laboratories (SL) to be examined and 54 scenarios were coherently estimated by all laboratories (the standard deviation from the mean of all SL answers for a given scenario category and a set of data was not larger than 3 patient codes). CONCLUSIONS: Each participant received training in both the role of a reference laboratory (activating the network) and of a service laboratory (responding to an activation request). The procedures in the case of radiological event were successfully established and tested.

RENEB - Running the European Network of biological dosimetry and physical retrospective dosimetry.

PURPOSE: A European network was initiated in 2012 by 23 partners from 16 European countries with the aim to significantly increase individualized dose reconstruction in case of large-scale radiological emergency scenarios. RESULTS: The network was built on three complementary pillars: (1) an operational basis with seven biological and physical dosimetric assays in ready-to-use mode, (2) a basis for education, training and quality assurance, and (3) a basis for further network development regarding new techniques and members. Techniques for individual dose estimation based on biological samples and/or inert personalized devices as mobile phones or smart phones were optimized to support rapid categorization of many potential victims according to the received dose to the blood or personal devices. Communication and cross-border collaboration were also standardized. To assure long-term sustainability of the network, cooperation with national and international emergency preparedness organizations was initiated and links to radiation protection and research platforms have been developed. A legal framework, based on a Memorandum of Understanding, was established and signed by 27 organizations by the end of 2015. CONCLUSIONS: RENEB is a European Network of biological and physical-retrospective dosimetry, with the capacity and capability to perform large-scale rapid individualized dose estimation. Specialized to handle large numbers of samples, RENEB is able to contribute to radiological emergency preparedness and wider large-scale research projects.

Operational guidance for radiation emergency response organisations in Europe for using biodosimetric tools developed in EU MULTIBIODOSE project.

In the event of a large-scale radiological emergency, the triage of individuals according to their degree of exposure forms an important initial step of the accident management. Although clinical signs and symptoms of a serious exposure may be used for radiological triage, they are not necessarily radiation specific and can lead to a false diagnosis. Biodosimetry is a method based on the analysis of radiation-induced changes in cells of the human body or in portable electronic devices and enables the unequivocal identification of exposed people who should receive medical treatment. The MULTIBIODOSE (MBD) consortium developed and validated several biodosimetric assays and adapted and tested them as tools for biological dose assessment in a mass-casualty event. Different biodosimetric assays were validated against the 'gold standard' of biological dosimetry-the dicentric assay. The assays were harmonised in such a way that, in an emergency situation, they can be run in parallel in a network of European laboratories. The aim of this guidance is to give a concise overview of the developed biodosimetric tools as well as how and when they can be used in an emergency situation.

Inter- and intra-laboratory comparison of a multibiodosimetric approach to triage in a simulated, large scale radiation emergency.

PURPOSE: The European Union's Seventh Framework Programme-funded project 'Multi-disciplinary biodosimetric tools to manage high scale radiological casualties' (MULTIBIODOSE) has developed a multiparametric approach to radiation biodosimetry, with a particular emphasis on triage of large numbers of potentially exposed individuals following accidental exposures. In November 2012, an emergency exercise took place which tested the capabilities of the MULTIBIODOSE project partners. The exercise described here had a dual purpose: Intercomparison of (i) three biodosimetric assays, and (ii) the capabilities of the seven laboratories, with regards to provision of triage status for suspected radiation exposed individuals. MATERIALS AND METHODS: Three biological dosimetry tools - the dicentric, micronucleus and gamma-H2AX (the phosphorylated form of member X of histone H2A, in response to DNA double-strand breaks) foci assays - were tested, in addition to provision of the triage status results (low exposure: < 1 Gy; medium exposure: 1-2 Gy; high exposure: > 2 Gy) by the MULTIBIODOSE software. The exercise was run in two modes: An initial triage categorisation of samples (based on the first dose estimates for each assay received from each laboratory) followed by collation of the full set of estimated doses (all the results from all modes of each assay carried out by the participating laboratories) calculated using as many modes of operation as possible of the different assays developed during the project. Simulated acute whole body and partial body exposures were included. RESULTS: The results of the initial triage categorisation and the full comparison of assays and methods within and between laboratories are presented here. CONCLUSIONS: The data demonstrate that the MULTIBIODOSE approach of applying multiparametric tools to radiation emergencies is valid and effective.

Effects of different gamma exposure regimes on reproduction in the earthworm Eisenia fetida (Oligochaeta).

Ecological risk assessment of ionising radiation requires knowledge about the responses of individuals and populations to chronic exposures, including situations when exposure levels change over time. The present study investigated processes such as recovery and the adaptive response with respect to reproduction endpoints in the earthworm Eisenia fetida exposed to (60)Co γ-radiation. Furthermore, a crossed experiment was performed to investigate the influence of F0 parental and F1 embryonic irradiation history on the response of irradiated or non-irradiated F1 offspring. Recovery: The sterility induced by sub-chronic exposure at 17 m Gy/h (accumulated dose: 25 Gy) was temporary, and 8 weeks after irradiation the worms had regained their reproductive capacity (number of viable offspring produced per adult per week). Adaptive response: Adult worms were continuously exposed at a low priming dose rate of 0.14 mGy/h for 12 weeks (accumulated dose: 0.24 Gy), followed by 14 weeks exposure at a challenge dose rate of 11 mGy/h. The results suggest a lack of adaptive response, since there were no significant differences in the effects on reproduction capacity between the primed and the unprimed groups after challenge doses ranging from 7.6 to 27 Gy. Crossed experiment: The effects of exposure at 11 mGy/h for 21 weeks on growth, sexual maturation and reproduction of offspring, derived either from parent worms and cocoons both exposed at 11 mGy/h, or from non-irradiated parents and cocoons (total accumulated dose 44 and 38 Gy, respectively) were compared. There were no significant differences between the two exposed offspring groups for any of the endpoints. The reproduction capacity was very low for both groups compared to the controls, but the reproduction seemed to be maintained at the reduced level, which could indicate acclimatisation or stabilisation. Finally, parental and embryonic exposures at 11 mGy/h did not affect reproduction in the F1 offspring as adults.

Induction and repair of DNA strand breaks and oxidised bases in somatic and spermatogenic cells from the earthworm Eisenia fetida after exposure to ionising radiation.

Methods for analysing oxidised DNA lesions [formamidopyrimidine glycosylase (Fpg)-sensitive sites] in coelomocytes and spermatogenic cells from the earthworm Eisenia fetida using the Fpg-modified comet assay were established. The DNA integrity (SSBs = strand breaks plus alkali labile sites and Fpg-sensitive sites) in cells from E. fetida continuously exposed to (60)Co gamma-radiation (dose rates 0.18-43 mGy/h) during two subsequent generations (F0 and F1) were measured and related to effects on reproduction end points which have already been reported. The data suggest a slight increase of Fpg-sensitive sites in spermatogenic cells from worms exposed at 11 mGy/h in the F0 generation but not in F1, whereas reduced reproduction had been observed at dose rates at or >4 mGy/h in F0 and at 11 mGy/h in F1. Using acute X-rays (41.9 Gy/h), dose-response relationships were established for SSBs in coelomocytes and spermatogenic cells exposed in vitro. In vivo DNA repair was studied by measuring the decrease in damage (SSBs and Fpg-sensitive sites) in coelomocytes and spermatogenic cells isolated from worms at different times (0-6 h) after acute X-ray exposure (4 Gy). SSBs were repaired in coelomocytes following biphasic kinetics, i.e. with a fast and a slow half-life (t(1/2)) of 36 min (95%) and 6.7 h (5%), respectively. Fpg-sensitive sites were repaired at considerably lower rates (t(1/2) = 4-5 h). In spermatogenic cells, SSB repair during the first hour was observed but a half-life could not be estimated. Repair of Fpg-sensitive sites could not be determined. In general, a reduced repair of Fpg-sensitive sites suggests a higher potential for accumulation of oxidised lesions, compared to SSBs, in earthworms exposed to radiation and other environmental contaminants. This is the first study comparing DNA damage with reproduction in earthworms exposed to ionising radiation.

Recommendations from the International Union of Radioecology to improve guidance on radiation protection.

This brief commentary summarizes the views of a working group assembled by the International Union of Radioecology to advance the approaches used to evaluate effects of radioactive materials in the environment. The key message in both the research needs and the recommendations for management of radioactive materials centers around the need to adopt an ecocentric approach that recognizes the interconnectedness of biota, including humans, and ecological processes.

A new handbook on triage, monitoring and treatment of people following malevolent use of radiation.

Through the Euratom 6 Framework Programme, the European Commission is co-sponsoring the specific targeted research project "Triage, Monitoring and Treatment-Handbook for management of the public in the event of malevolent use of radiation" (TMT Handbook). The main aim of the project is to produce a handbook for the effective and timely triage, monitoring, and treatment of people exposed to radiation following a malevolent act. The World Health Organization contributed to this project with development of guidelines on medical and public health response. A training course based on the TMT Handbook was developed. It will help to enhance national capacity for planning and response to acts involving the malevolent use of radiation. The course will also provide a platform to identify common challenges and discuss opportunities for harmonizing response strategies throughout the European Union. Focusing on its medical and public health response aspects, this paper introduces the TMT Handbook and its potential applicability not only as practical guidance for end-users but also as a useful tool for education and training.

Premature chromosome condensation (PCC) assay for dose assessment in mass casualty accidents.

The study was undertaken to establish a dose calibration curve for a practical PCC ring assay and to apply it in a simulated mass casualty accident. The PCC assay was validated against the conventional dicentric assay. A linear relationship was established for PCC rings after (60)Co gamma irradiation with doses up to 20 Gy. In the simulated accident experiment, 62 blood samples were analyzed with both the PCC ring assay and the conventional dicentric assay, applying a triage approach. Samples received various uniform and non-uniform (10-40% partial-body) irradiations up to doses of 13 Gy. The results indicated that both assays yielded good dose estimates for the whole-body exposure scenario, although in the lower-dose range (0-6 Gy) dicentric scoring resulted in more accurate whole-body estimates, whereas PCC rings were better in the high-dose range (>6 Gy). Neither assay was successful in identifying partial-body exposures, most likely due to the low numbers of cells scored in the triage mode. In conclusion, the study confirmed that the PCC ring assay is suitable for use as a biodosimeter after whole-body exposure to high doses of radiation. However, there are limitations for its use in the triage of people exposed to high, partial-body doses.

Types of radiation mass casualties and their management.

Management of radiation mass casualty exposure that may occur as a result of nuclear or radiation accident will depend on the type of accident, and of the knowledge about the actual radiation exposure situation for those who might be involved. Management of the public after an accident in a nuclear or radiation installation will follow existing specific emergency plans, and will take advantage of existing radiation monitoring systems. In other radiation mass casualty exposures, whenever accidental or malevolent use of radiation, there will be a requirement to employ screening programs for indentifying and sorting out exposed people (radiological triage), who will need medical treatment and/or other assistance like decontamination and individual dose assessment. In the later stage after the accident the monitoring for dose assessment purposes for those who will need medical or public health assistance will be required. Demand for dose assessment for large groups of individuals may create the need for international assistance. Prompt and credible public information is vital in all radiation emergencies, and it would be even more important in situations when radiation mass casualties result from exposures to nuclear or radiological material out of regulatory control. In such situations unpredictability of the event creates increase in the risk perception and public communication activities of the authorities will be the key element to prevent unnecessary fear and panic, and the measure to reassure the populace.

Effects of chronic gamma irradiation on reproduction in the earthworm Eisenia fetida (Oligochaeta).

Eisenia fetida were exposed continuously to (60)Co gamma radiation during two generations (F(0) and F(1)). Adult F(0) reproduction capacity (i.e., number of cocoons produced, hatchability and number of F(1) hatchlings) in controls and at five dose rates (0.18, 1.7, 4, 11 and 43 mGy/h) was measured over a 13-week exposure period. Survival, growth and sexual maturation of F(1) hatchlings were observed for 11 weeks. F(1) adults were exposed for a further 13 weeks to determine their reproduction capacity. There was no radiation-induced effect on the cocoon production rate in either F(0) or F(1). For F(0), hatchability of cocoons produced during the first 4 weeks was reduced to 60% at 43 mGy/h (98% in controls), and none of the cocoons produced at 5-13 weeks hatched. At 11 mGy/h the cocoon hatchability was reduced to 25% at 9-13 weeks. In addition, the number of hatchlings per hatched cocoon was reduced at 11 and 43 mGy/h. Correspondingly, at these dose rates, the total number of F(1) hatchlings per adult F(0) was significantly lower than in the control. This number was also reduced at 4 mGy/h, but the effect was of borderline significance. For adult F(1), the hatchability of cocoons at 11 mGy/h was reduced to 45-69% during the 13-week exposure period. The number of hatchlings (F(2)) per cocoon and the total number of F(2) individuals produced was also reduced. However, and in contrast to the results observed for F(0), hatchability increased with time, suggesting a possible acclimatization or adaptation of the F(1) individuals. In conclusion, chronic irradiation reduced the reproduction capacity of E. fetida, but extensive exposure periods (13 weeks) were needed for these effects to be expressed. The lowest dose rates at which an effect was observed were 4 mGy/h in F(0) and 11 mGy/h in F(1).

[Iodine prophylaxis following nuclear accidents]. / Jodprofylakse ved strålingsulykker.

Radioactive iodine isotopes may be released to air to a varying degree during accidents with nuclear reactors. Iodine tablets, taken before or shortly after such release, protect against intake of radioactive iodine isotopes, but not against other radionuclides. Iodine prophylaxis can be a relevant countermeasure in Norway and will be implemented according to recommendations from the Crisis Committee for Nuclear and Radiological Emergencies. The Chernobyl accident confirmed that the risk for radiogenic thyroid cancer is much higher for foetuses and children and adolescents under 18 years. An epidemiological study showed that intake of iodine tablets could reduce the risk for thyroid cancer by a factor of three. For children, the WHO has therefore recommended a 10 mGy avertable dose to the thyroid. The Norwegian Radiation Protection Authority acknowledge the WHO guidelines and advise that the first priority of all emergency preparedness planning for potential releases that can cause dispersion of radioactive iodine, should be given to the protection of pregnant and breast-feeding women, newborns and children under 18 years. Iodine tablets should be taken immediately (preferably not later than a few hours) in situations where inhalation of radioactive iodine may occur. It should be underlined that iodine prophylaxis is one of several emergency countermeasures; other measures are sheltering and evacuation. The latter two countermeasures will protect not only from intake of radioactive iodine, but also against other radionuclides that may be released. Based on the present risk assessment in Norway, iodine tablets have been distributed to the counties north of Salten. In addition, there is an emergency stockpile of iodine tablets in Oslo.

Intra- and inter-laboratory variation in the scoring of micronuclei and nucleoplasmic bridges in binucleated human lymphocytes. Results of an international slide-scoring exercise by the HUMN project.

One of the objectives of the HUman MicroNucleus (HUMN) project is to identify the methodological variables that have an important impact on micronucleus (MN) or micronucleated (MNed) cell frequencies measured in human lymphocytes using the cytokinesis-block micronucleus assay. In a previous study we had shown that the scoring criteria used were likely to be an important variable. To determine the extent of residual variation when laboratories scored cells from the same cultures using the same set of standard scoring criteria, an inter-laboratory slide-scoring exercise was performed among 34 laboratories from 21 countries with a total of 51 slide scorers involved. The results of this study show that even under these optimized conditions there is a great variation in the MN frequency or MNed cell frequency obtained by individual laboratories and scorers. All laboratories ranked correctly the MNed cell frequency in cells from cultures that were unirradiated, or exposed to 1 or 2Gy of gamma rays. The study also estimated that the intra-scorer median coefficient of variation for duplicate MNed cell frequency scores is 29% for unexposed cultures and 14 and 11% for cells exposed to 1 and 2Gy, respectively. These values can be used as a standard for quality or acceptability of data in future studies. Using a Poisson regression model it was estimated that radiation dose explained 67% of the variance, while staining method, cell sample, laboratory, and covariance explained 0.6, 0.3, 6.5, and 25.6% of the variance, respectively, leaving only 3.1% of the variance unexplained. As part of this exercise, nucleoplasmic bridges were also estimated by the laboratories; however, inexperience in the use of this biomarker of chromosome rearrangement was reflected in the much greater heterogeneity in the data and the unexplained variation estimated by the Poisson model. The results of these studies indicate clearly that even after standardizing culture and scoring conditions it will be necessary to calibrate scorers and laboratories if MN, MNed cell and nucleoplasmic bridge frequencies are to be reliably compared among laboratories and among populations.