Watching the directives : scientific advice on the EU Physical Agents (Electromagnetic Fields) Directive : fourth report of session 2005-06 : report, together with formal minutes, oral and written evidence / House of Commons, Science and Technology Committee.

  • Great Britain. Parliament. House of Commons. Select Committee on Science and Technology.
Date:
2006
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Licence: Open Government Licence

Credit: Watching the directives : scientific advice on the EU Physical Agents (Electromagnetic Fields) Directive : fourth report of session 2005-06 : report, together with formal minutes, oral and written evidence / House of Commons, Science and Technology Committee. Source: Wellcome Collection.

    128/144 (page 66)
    MRI uses EMF in three distinct frequency ranges—a static magnetic field, time-varying magnetic fields in the frequency range 100s—1000s Hz (known as switched gradients), and radiofrequency (RF) fields (10s-100s MHz). Typical frequency values have been shown in the table in the case of time varying fields, as the limits are frequency dependent in this part of the spectrum. In the case of the static field, there is no exposure limit in the Directive but concern arises because movement through the field exposes staff to a slowly time-varying field which induces currents that almost certainly exceed the limits at 3 T and quite possibly also at 1.5 T. Where possible, references supporting the figures in the right hand column are given in Annex B in relation to question Q 810. May 2006 Annex A Comments on uncorrected transcript of oral evidence taken before the Science and Technology Select Committee, 11 May 2006 The expertise of the MR community 1. Ina number of places (Q 678, 683, 777, 788, 794, 797) Mr Biosca seeks to draw a distinction between, on the one hand, an expert scientific community that supports the ICNIRP limits and, on the other, a community of medical users of MRI who he implies are ignorant of the issues around exposure to EMF in their practice. 2. In fact the MR community is a diverse body of medical practitioners, clinical and basic scientists with a wide range of relevant expertise and experience. Those who have made representations about the Physical Agents Directive in the UK comprise physicists, medical physicists, biochemists, physiologists and other biological scientists, many of them of professorial status. They include a Nobel Prize winning physicist (Sir Peter Mansfield) and both the present Chief Executive of the MRC (Professor Colin Blakemore, a professor of physiology with directly relevant research interests) and his immediate predecessor (Sir George Radda, a professor of biochemistry).”* 3. Regarding input by manufacturers, Mr Biosca states that: In my view, manufacturers have not said anything at all, they are very happy with the Directive so far (Q 683). So far, neither from Siemens nor Philips. We do not have any complaints to the Commission so far from manufacturers of magnetic resonance equipment (Q 684). 4. Although these comments are contradicted later in the evidence (Q 742-749), it is perhaps worth reiterating that Siemens and Philips made representations about the impact of both the static and time- varying field limits on MRI to the Commission’s Social Questions Working Party as early as April 2003. I can provide the Committee with a copy of this material if required. The nature of the ICNIRP guidelines and the evidence behind the limits 5. Mr Biosca presents the ICNIRP 1998 guidelines as justification for the exposure limits contained in the Directive (eg Q 752), implying that the limits are supported by a large quantity of peer-reviewed publications (Q 712-715) and are the settled opinion of the relevant expert community. It is true that there is a large body of published research on EMF exposure, but this literature reveals a wide margin of uncertainty rather than agreement. Most published studies report negative results and many of the positive results, some of which were published over 20 years ago, lack replication. There are some established effects, such as magneto-phosphenes, but these relate to biological effects rather than adverse health effects. 6. Even in 1998, the view of ICNIRP was rather more equivocal than the Directive and Mr Biosca imply. In establishing exposure limits, the Commission recognizes the need to reconcile a number of differing expert opinions . . . [to] provide an adequate level of protection from exposure to time- varying EMF~4 7. By 2004 ICNIRP accepted that: Guidelines on occupational and general public exposure limits to all ranges of electromagnetic fields (static, time-varying gradients, radiofrequency) have been published (ICNIRP 1994, 1998). However, these guidelines were written many years ago, and they are now under review.” 8. And in the same year NRPB described adoption of the ICNIRP limits as: ...acautious approach . . . to indicate thresholds for adverse health effects that are scientifically plausible”® ee ee eee 23 See original memorandum from the MR community, Annex B. 24 ICNIRP (1998) Health Physics 74 494-522. 25 ICNIRP (2004) Health Physics 87 197-216. 26 NRPB (2004) Documents of the NRPB Vol 15 (3) p 137.