Radiation Protection Division of the UK Health Protection Agency
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WHO International EMF Project International Advisory Committee Meeting 19-20 June 2008 National Collaborating Institute Report Radiation Protection Division of the UK Health Protection Agency The Health Protection Agency (HPA) was formed in 2003 and brought together several organisations in order to provide an integrated approach to protecting UK public health. The HPA has a large network of approximately 3000 staff based at three major centres, and regionally and locally throughout England. There is a small central office based in London. The Agency works closely with locally based colleagues employed within the devolved administrations of Wales, Scotland and Northern Ireland. The Centre for Infections at Colindale is the base for communicable disease surveillance and specialist microbiology. The Centre for Radiation, Chemical and Environmental Hazards (CRCE), is based at Chilton and the Centre for Emergency Preparedness and Response, focusing on applied microbiological research and emergency response, is based at Porton Down. On 1 April 2005 the National Radiological Protection Board merged with the Health Protection Agency (HPA) forming its Radiation Protection Division (RPD). Together with the Chemical Hazards and Poisons Division of HPA it forms the Agency’s Centre for Radiation, Chemical and Environmental Hazards (CRCE). RPD carries out the Health Protection Agency’s work on ionising and non-ionising radiations. It undertakes research to advance knowledge about protection from the risks of these radiations; provides laboratory and technical services; runs training courses; provides expert information and has a significant advisory role in the UK. Patient and Volunteer Exposures in MRI Revised advice on limiting the exposure of patients and volunteers to the static magnetic fields, time varying electromagnetic fields and acoustic noise from magnetic resonance imaging (MRI) will be published shortly by HPA. Previous advice was published in 1991 by the predecessor of RPD, the National Radiological Protection Board. More recently the International Commission on Non-Ionizing Radiation Protection (ICNIRP, 2004) has reviewed the science relevant to possible adverse health effects from such exposures and published its advice. Recognising the importance of global harmonisation, the HPA review takes account of the ICNIRP review and focuses on the ICNIRP recommendations, and particularly as to their possible application in the UK. The new advice is being developed by a working group comprising RPD staff and external experts in the field of MRI and its applications. The group has reviewed published scientific data in the life and physical sciences about the possible adverse effects on people of exposure to MRI. The reviewers took into account the clear benefits to individual patients undergoing MRI examinations and the potential benefits from research involving volunteer exposures which can increase medical knowledge. A draft document was made available for expert comment from June 2007 and for general consultation from October 2007. Input was sought input from all interested parties, including corporate and professional bodies and MRI equipment developers and users, particularly in respect of any potential problems in the development and use of MRI equipment were the ICNIRP 2004 guidelines on patient and volunteer exposure to be implemented in the UK. The advice is expected to be published in Documents of the HPA within the next few months and the consultation document (now closed) remains available on the HPA website: http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoListName/Page/1204542909765?p=1 204542909765 UK ELF stakeholder group SAGE is the Stakeholder Advisory Group on ELF EMFs which has been set up by the Department of Health to explore the implications and make practical recommendations for a precautionary approach to power frequency electric and magnetic fields. SAGE has representation from public concern groups who advocate greater precaution as well as from the power supply industry, government departments and the Health Protection Agency. The SAGE website can be found at www.rkpartnership.co.uk. SAGE published its first interim report on 27 April 2007. The report considered a wide range of possible health effects, and mitigation options such as the 'corridor option', in which no development would not occur within a certain distance of power lines, optimal phasing of lines to reduce electric and magnetic fields, the design and promotion of low magnetic field appliances and changes in wiring practice, and provision of information in the public domain. HPA has given Health Ministers advice on the first interim assessment. The advice highlighted the recommendation issued in 2004, by the National Radiological Protection Board (NRPB - now the Radiation Protection Division of the HPA), to adopt in the UK the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for limiting exposures to ELF EMFs and confirmed that this advice remains extant. In addition, the uncertainties in the underlying evidence base led NRPB to recommend in its 2004 document that the Government should consider the need for further precautionary measures in respect of exposure of people to ELF EMFs. In doing so, it should note that the overall evidence for adverse effects of ELF EMFs on health at levels of exposure normally experienced by the general public is weak. The least weak evidence is for the exposure of children to power frequency magnetic fields and childhood leukaemia. SAGE was not set up to review the scientific evidence relating to the health effects of ELF EMFs. Rather, it took as its starting point the NRPB advice to “consider the possible need for further precautionary measures….” However, SAGE identified two broad viewpoints on the science. In one, exposure to ELF EMFs is assumed to be a risk factor (possibly causal) for childhood leukaemia. This is termed by SAGE the “WHO/HPA” position, short-handed as CL. The other viewpoint allows for the possibility of a larger number of illnesses attributable to exposure to ELF EMF (e.g. adult leukaemia and brain tumours, miscarriage and amyotrophic lateral sclerosis). This viewpoint is short-handed as CL+, or the “ California” position in the SAGE report. The scientific evidence, as reviewed by HPA, supports the view that precautionary measures should address solely the possible association with childhood leukaemia and not other more speculative health effects. HPA advises that it would be wise to err on the side of caution, but with a proportionate response. HPA supports precautionary measures that have a convincing evidence base to show that they will be successful in reducing exposure, are effective in providing reassurance to the public, and where the overall benefits outweigh the fiscal and social costs. The full advice from HPA, including responses to the range of measures identified by SAGE can be found on the HPA website: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1204276682532?p=12078 97920036 Summary of EMF-related research ongoing at HPA-RPD Theoretical dosimetry studies Finite-Difference Time-Domain (FDTD) calculations of SAR from 50 MHz to 6 GHz in a series of child phantoms have been performed. The University of Florida (UF) Series B paediatric phantoms were developed for medical and radiation protection photon dosimetry. The series includes a 9-month male, a 4-year female, an 8-year female, an 11-year male and a 14-year male. They have been adapted to calculate electromagnetic fields in the body for plane wave exposure. A comparison has been made with the previous linearly scaled versions of NORMAN and NAOMI for calculations at 2 mm resolution. Further FDTD calculations were performed at resolutions of 1 and 0.7 mm above 900 MHz to elucidate the effects of grid resolution on SAR. The external electric fields required to produce the basic restriction for public exposure on whole-body averaged SAR have been calculated. A study has been performed to identify uncertainties and problems in the practical application of the ICNIRP low frequency basic restriction on current density. This quantity should be averaged over a cross-section of 1 cm2 perpendicular to the current direction. There are difficulties in finding a square cm of spinal cord over which to average. The consequences of including neighbouring tissues in the averages has been investigated in the male and female voxel models NORMAN and NAOMI for applied uniform electric and magnetic fields at 50 Hz. A contract for the Electrical Power Research Institute (EPRI) has been completed on calculations relating external fields to basic restrictions in the body between 65 MHz and 2 GHz. Exposure conditions included plane-wave irradiation in a variety of orientations and near-field exposure from half-wave dipole antennas. Whole-body SAR, localised SAR, ankle current values and spatially averaged fields were calculated for these exposure conditions. A paper has been published on calculated SAR distributions in the NORMAN voxel phantom due to the reflection of electromagnetic fields from a ground plane. The SAR calculations were performed for standing waves set up in the computational domain to investigate any problems this may cause regarding compliance with electromagnetic guidelines. An intercomparison of head/eye thermal models with the Japanese institutes at NIT (Nagoya) and NICT (Tokyo) is underway. Anatomical models and parameter sets have been exchanged and differences discussed.