Survey on national practices regarding iodine thyroid blocking in 2016-2017.

Severe nuclear accidents may lead to a release of radioactivity, including radioactive iodine, into the environment. The thyroid gland in the human body needs natural or stable iodine to function properly and this iodine is normally absorbed in small quantities from food. Following a release of radioactive iodine from a nuclear or radiological accident, the body will absorb and accumulate the radioactive iodine in the thyroid gland. This increases the risk of thyroid cancer, especially in children. Since the thyroid gland cannot distinguish between radioactive and stable iodine, stable iodine can be taken to prevent the absorption of radioiodine by the thyroid in the event of a nuclear emergency. This is referred to as Iodine Thyroid Blocking (ITB). In 2017, the World Health Organization published revised guidelines entitled 'Iodine Thyroid Blocking: guidelines for use in planning for and responding to radiological and nuclear emergencies'. The purpose of these guidelines is to support Member States in planning for and implementation of ITB before and during a radiation emergency. To enable the monitoring and measurement of the impact of a specific recommended intervention, a baseline should be established against which the impact will be measured over a certain period of time. With that in mind, a global WHO survey of national policies on ITB was carried out in 2016-2017. Here, an overview of some core findings of this survey is provided.

Childhood leukemia near nuclear sites in Belgium: An ecological study at small geographical level.

BACKGROUND: A previous investigation of the occurrence of childhood acute leukemia around the Belgian nuclear sites has shown positive associations around one nuclear site (Mol-Dessel). In the following years, the Belgian Cancer Registry has made data available at the smallest administrative unit for which demographic information exists in Belgium, i.e. the statistical sector. This offers the advantage to reduce the potential misclassification due to large geographical scales. METHODS: The current study performed for the period 2006-2016 uses Poisson models to investigate (i) the incidence of childhood acute leukemia within 20 km around the four Belgian nuclear sites, (ii) exposure-response relationships between cancer incidence and surrogate exposures from the nuclear sites (distance, wind direction frequency and exposure by hypothetical radioactive discharges taking into account historical meteorological conditions). All analyses are carried out at statistical sector level. RESULTS: Higher incidence rate ratios were found for children <15 years (7 cases, RR = 3.01, 95% CI: 1.43;6.35) and children <5 years (< 5 cases, RR = 3.62, 95% CI: 1.35;9.74) living less than 5 km from the site of Mol-Dessel. In addition, there was an indication for positive exposure-response relationships with the different types of surrogate exposures. CONCLUSION: Results confirm an increased incidence of acute childhood leukemia around Mol-Dessel, but the number of cases remains very small. Random variation cannot be excluded and the ecological design does not allow concluding on causality. These findings emphasize the need for more in-depth research into the risk factors of childhood leukemia, for a better understanding of the etiology of this disease.

Thyroid cancer incidence near nuclear sites in Belgium: An ecological study at small geographical level.

In Belgium, variations in thyroid cancer incidence were observed around the major nuclear sites. The present ecological study investigates whether there is an excess incidence of thyroid cancer among people living in the vicinity of the four nuclear sites at the smallest Belgian geographical level. Rate ratios were obtained from a Bayesian hierarchical model for areas of varying sizes around the nuclear sites. Focused hypothesis tests and generalized additive models were performed to test the hypothesis of a gradient in thyroid cancer incidence with increasing levels of surrogate exposures. No evidence was found for more incident cases of thyroid cancer near the two nuclear power plants. Regarding the two industrial and research nuclear sites, no evidence for a higher incidence in the vicinity of Mol-Dessel was observed, whereas a slightly nonsignificant higher incidence was found in the close vicinity of Fleurus. In addition, significant gradients for thyroid cancer incidence were observed with the different types of surrogate exposure considered in the 20 km area around the site of Fleurus (decreasing distance, increasing wind direction frequency and increasing exposure to estimated hypothetical radioactive discharges of iodine-131). In the investigation at the smallest Belgian geographical level, variations in thyroid cancer incidence were found around the Belgian nuclear sites. Significant exposure-response relationships were also observed for the site of Fleurus. Further investigations into these findings could be useful to allow inferring causal relationships on the origin of variations in incidence and to provide information at the individual level.

Childhood leukaemia near nuclear sites in Belgium, 2002-2008.

This paper describes an ecological study investigating whether there is an excess incidence of acute leukaemia among children aged 0-14 years living in the vicinity of the nuclear sites in Belgium. Poisson regression modelling was carried out for proximity areas of varying sizes. In addition, the hypothesis of a gradient in leukaemia incidence with increasing levels of surrogate exposures was explored by means of focused hypothesis tests and generalized additive models. For the surrogate exposures, three proxies were used, that is, residential proximity to the nuclear site, prevailing winds and simulated radioactive discharges, on the basis of mathematical dispersion modelling. No excess incidence of acute leukaemia was observed around the nuclear power plants of Doel or Tihange nor around the nuclear site of Fleurus, which is a major manufacturer of radioactive isotopes in Europe. Around the site of Mol-Dessel, however, two- to three-fold increased leukaemia incidence rates were found in children aged 0-14 years living in the 0-5, 0-10 and the 0-15 km proximity areas. For this site, there was evidence for a gradient in leukaemia incidence with increased proximity, prevailing winds and simulated radioactive discharges, suggesting a potential link with the site that needs further investigation. An increased incidence of acute leukaemia in children aged 0-14 years was observed around one nuclear site that hosted reprocessing activities in the past and where nuclear research activities and radioactive waste treatment are ongoing.

Thyroid Cancer Incidence around the Belgian Nuclear Sites, 2000-2014.

The present study investigates whether there is an excess incidence of thyroid cancer among people living in the vicinity of the nuclear sites in Belgium. Adjusted Rate Ratios were obtained from Poisson regressions for proximity areas of varying sizes. In addition, focused hypothesis tests and generalized additive models were performed to test the hypothesis of a gradient in thyroid cancer incidence with increasing levels of surrogate exposures. Residential proximity to the nuclear site, prevailing dominant winds frequency from the site, and simulated radioactive discharges were used as surrogate exposures. No excess incidence of thyroid cancer was observed around the nuclear power plants of Doel or Tihange. In contrast, increases in thyroid cancer incidence were found around the nuclear sites of Mol-Dessel and Fleurus; risk ratios were borderline not significant. For Mol-Dessel, there was evidence for a gradient in thyroid cancer incidence with increased proximity, prevailing winds, and simulated radioactive discharges. For Fleurus, a gradient was observed with increasing prevailing winds and, to a lesser extent, with increasing simulated radioactive discharges. This study strengthens earlier findings and suggests increased incidences in thyroid cancer around two of the four Belgian nuclear sites. Further analyses will be performed at a more detailed geographical level.

The First Meeting of the WHO Guideline Development Group for the Revision of the WHO 1999 Guidelines for Iodine Thyroid Blocking.

The meeting held in May 2014 in Würzburg, Germany, discussed the scope of the revision of the 1999 WHO guidelines for iodine thyroid blocking (ITB) by following the WHO handbook for guideline development. This article describes the process and methods of developing the revised, evidence-based WHO guidelines for ITB following nuclear and radiological accidents, the results of the kick-off meeting as well as further steps taken to complete the revision.

Basic radiation protection training for nurses and paramedical personnel: Belgian experience and future perspectives.

When using ionising radiation for medical diagnosis or treatment of patients, understanding of relevant radiation protection principles and issues is indispensable. In Belgium, nurses and paramedical staff are required to acquire knowledge for protecting the patient against the detrimental effects of ionising radiation by means of a vocational training course. The experience with and challenges for this training course are presented here from a lecturer's point of view, together with a proposal for a future approach that harmonises the training content, its level and quality, according to European recommended standards.

Clinical imaging guidelines part 2: Risks, benefits, barriers, and solutions.

A recent international meeting was convened by two United Nations bodies to focus on international collaboration on clinical appropriateness/referral guidelines for use in medical imaging. This paper, the second of 4 from this technical meeting, addresses barriers to the successful development/deployment of clinical imaging guidelines and means of overcoming them. It reflects the discussions of the attendees, and the issues identified are treated under 7 headings: ■ Practical Strategy for Development and Deployment of Guidelines; ■ Governance Arrangements and Concerns with Deployment of Guidelines; ■ Finance, Sustainability, Reimbursement, and Related Issues; ■ Identifying Benefits and Radiation Risks from Radiological Examinations; ■ Information Given to Patients and the Public, and Consent Issues; ■ Special Concerns Related to Pregnancy; and ■ The Research Agenda. Examples of topics identified include the observation that guideline development is a global task and there is no case for continuing it as the project of the few professional organizations that have been brave enough to make the long-term commitment required. Advocacy for guidelines should include the expectations that they will facilitate: (1) better health care delivery; (2) lower cost of that delivery; with (3) reduced radiation dose and associated health risks. Radiation protection issues should not be isolated; rather, they should be integrated with the overall health care picture. The type of dose/radiation risk information to be provided with guidelines should include the uncertainty involved and advice on application of the precautionary principle with patients. This principle may be taken as an extension of the well-established medical principle of "first do no harm."

Thyroid cancer incidence around the Belgian nuclear sites: surrogate exposure modelling.

BACKGROUND: In a recent ecological study among residents living around Belgian nuclear sites (the NUCABEL study), significant increased incidences of thyroid cancer were observed around the two nuclear facilities with industrial and research activities (Mol-Dessel and Fleurus), prompting further research. METHODS: The data from the NUCABEL study were reanalysed to test the hypothesis of a gradient in cancer incidence with increasing levels of exposure from these sites using three measures of surrogate exposure, being (i) residential proximity, (ii) prevailing wind directions and (iii) simulated dispersion of radioactive discharges. Single-site focussed hypothesis tests were complemented with Generalized Additive Models to estimate the exposure-response relationships. RESULTS: For Mol-Dessel, the results of the focussed hypothesis tests were far from significant. For Fleurus, the p-values were much closer to significance with p=0.05 for Bithell's Linear Risk Score using radioactive discharge estimates as surrogate. CONCLUSIONS: The re-analyses refute an association with the nuclear facilities for the site of Mol-Dessel. For the site of Fleurus, one of Europe's major production sites of radio-iodines, the results were less conclusive and further research suggests itself.

Thyroid cancer incidence in the vicinity of nuclear sites in Belgium, 2000-2008.

BACKGROUND: Public health concern about nuclear activities have existed since the 1980s. Most studies on this subject investigated childhood leukemia. Thyroid cancer may be another health outcome of interest, because some nuclear installations are a potential source of radioactive iodine isotopes in the environment and because thyroid cancer is known to occur after exposure to these isotopes. METHODS: This study describes an ecological study investigating whether there is excessive thyroid cancer incidence among residents living in the vicinity of nuclear sites. Single-site analyses using indirect standardization (standardized incidence ratios [SIRs]) and Poisson regression modeling (rate ratios [RRs]) were conducted. The proximity area is typically defined as a circular zone with a radius of 20 km centered on the site. However, the choice of the size of this area is somewhat arbitrary. Therefore, a sensitivity analysis was carried out to investigate whether the results vary with radii of increasing proximity. RESULTS: No increased thyroid cancer incidence was found within the 20 km proximity area around the nuclear power plants of Doel (SIR=0.74 [95% confidence interval (CI)=0.64; 0.84] and RR=0.72 [95% CI=0.63; 0.83]) and Tihange (SIR=0.86 [95% CI=0.70; 1.01] and RR=0.85 [95% CI=0.70; 1.02]). For the sites of Mol-Dessel and Fleurus, where a combination of nuclear research and industrial activities are located, the incidences of thyroid cancer within the 20 km proximity area were higher than expected (Mol-Dessel: SIR=1.19 [95% CI=1.01; 1.36] and RR=1.19 [95% CI=1.02; 1.38]; Fleurus: SIR=1.15 [95% CI=1.02; 1.28] and RR=1.17 [95% CI=1.04; 1.33]). For Chooz, a French nuclear power plant close to the Belgian border, the results were unstable as a result of the small population denominator. For all Belgian nuclear sites, the results were generally insensitive to the choice of the proximity area. CONCLUSIONS: No evidence for excessive thyroid cancer incidence around the Belgian nuclear power plants was found. On the other hand, an increased incidence of thyroid cancer was observed around the sites with other nuclear activities. Further research is recommended to verify whether the observed increases could be related to the site-specific nuclear activities.