JBRBTR, 2007, 90: 65-68.

A European Directive on electro-magnetic fields was adopted in 2004and must be transposed intoNational law by April 2008 at thelatest. It followed on from recom-mendations published in 1999. Itdefines electromagnetic field expo-sure limits for all workers in the EU.If directly applied, it would seriouslycompromise certain MR examina-tions and, in the longer term, hinderthe use of higher magnetic fieldstrengths, whether for treatment orresearch purposes.

What is the field of application ofthis Directive?

The Directive concerns staff, notpatients. It deals with only short-term effects.

It includes all electromagneticfields up to 300 GHz.

The exposure limits are based onwork by ICNIRP (InternationalCommission on Non IonizingRadiation Protection) published in1993 and updated in 1998 (to berevised in 2009).

Why this Directive?

The Directive was adopted inresponse to major concerns overthe population effects of all electro-magnetic fields (from 0 Hz to300 GHz), and especially those emit-ted by mobile phones and electricalpower lines, which are regularlydebated in the media.

MRI is concerned because the fre-quencies it uses are contained with-in the spectrum of frequencies dealtwith by the Directive.

What effects do electromagneticfields have?

Electromagnetic fields can inter-act with biological systems eitherthrough the currents they induce, orthrough the energy they transfer tobiological tissues. The frequency ofelectromagnetic waves is a majordeterminant. Schematically, low fre-quencies interact mainly through

induced currents, while higher fre-quencies act mainly through theenergy they deposit in tissues.Static (zero frequency) magneticfields interact either through move-mentrelated magnetic induction, orthrough magnetic-mechanical inter-action. Contrary to ionizing radia-tion, which exerts its biochemicaleffects by breaking covalent bonds,electromagnetic fields act viainduced currents, or by creatingand/or reorienting dipoles.

Thus, MRI interacts with thehuman body in the following ways:

gradients, as they switch, inducecurrents in the target tissues

radiofrequency waves can causetissue heating

the static magnetic field has twotypes of effect: a direct effectrelated to the intensity of thefield, and effects generated aspersons move through thegradient of the field within the

EUROPEAN DIRECTIVE ON ELECTROMAGNETIC FIELDSGuy Frija, Secretary General of the European Society of RadiologyJacques Bittoun, Director of the Medical Magnetic Resonance Research Group, Universit Paris Sud/CNRS; formerPresident of ESMRMB*Gabriel P. Krestin, President of ESMRMB*David Norris, Chair of the Safety Committee of ESMRMB

*ESMRMB-European Society for Magnetic Resonance in Medicine and Biology

0 Hzstatic magnetic field

100-1000 Hzmagnetic field gradients

10-400 MHzRadiofrequencies

Spectrum of frequencies used in MRI

66 JBRBTR, 2007, 90 (1)

examination room. These per-sons are subject to time varyingmagnetic fields which can induceelectric fields.

Cut-points

Exposure limits for personnelexposed to magnetic fields havebeen established with two differentaims, namely to avoid the risk ofperipheral nerve stimulation byinduced currents, and to prevent tis-sue heating. These limits wereestablished by ICNIRP based onstudies conducted in vitro and onexperimental animals. The intensityof the induced currents must notexceed 10 mA/m2, and body heatingmust remain below one degreeCelsius.

In a general review of epidemio-logical studies on electromagneticfield effects, no causal relationshipwas found between exposure andhealth disorders.

Nausea and dizziness have beenreported by subjects exposed tohighintensity MRI fields. A burningor pins and needles sensation dueto peripheral nerve stimulation hasalso been noted and shown to bethe act of switching the gradient.

Reference values

Reference values have beenestablished by means of mathemat-ical modeling based on extrapola-tion of experimental results fromthreshold values. These referencevalues are closely dependent on thefrequency, as shown in the follow-ing table:

What are the implications for MRI?

Static magnetic fields (B0): as itstands, the Directive does notdeal with static fields. However,a person moving within a staticfield with spatial variations issubmitted to magnetic field vari-ations. With a 1.5-Tesla magnet,the 200-mT threshold recom-mended for static fields isreached about 1 meter from thecenter of the magnet; this dis-tance could double with 3-Tmagnets, depending on built-inshielding.

Gradients: MRI uses gradients(up to 66 mT/m) to locate the sig-nal in space. These gradients arecentered on the patient. Theirspatial extension outside themagnet bore is not described inthe literature, but is probablytiny. However, the recommendedreference levels (from 25 to820 Hz: 0.025 mT) would implythat this spatial extension, how-ever small, could not be neglect-ed.

Radiofrequency waves: the rec-ommended thresholds have littleimpact.

What are the practical conse-quences?

Any person working with apatient placed at the center of themagnet or in its immediate vicinityis at risk of exceeding the referencevalues. This is particularly the casefor interventional procedures, pro-cedures under anesthesia (thatrequires close patient monitoring),

simple preparation or positioning ofthe patient, or even an IV injectiongiven during the examination. Allstaff moving within the examinationroom is subject to field variationsthat, while difficult to measure,nonetheless exist. Pediatric exami-nations are especially concerned,because in most cases they requiresedation and close interaction withthe patient.

What actions?

Publication of this Directive hasgenerated a good deal of controver-sy because it is based on an extrap-olation of effects observed in exper-imental animals or in vitro to hypo-thetical effects on human health.Furthermore the limits upon which itis based are related to the possibleonset of physiological responses,which may not necessarily be harm-ful. In addition, many see the expo-sure limits as being exceptionallystringent considering the clinicalbenignity of the phenomena inquestion. Limiting exposure to thevalues contained in the Directivewould also have other conse-quences: some MRI examinationswould have to be replaced by com-puted tomography, the use ofstronger fields within the EuropeanUnion would be considerablyrestricted, whether for therapeuticor research purposes, and qualitycontrol (use of phantoms) would behindered. Finally, many questionsremain regarding the methods andimplementation of reliable dosime-try in clinical practice.

The European Society ofRadiology (ESR), in association withthe European Society for MagneticResonance in Medicine and Biology(ESMRMB) and the European Unionof Medical Specialists (EUMS),has approached the EuropeanCommissioner responsible for thisDirective. The Commission hasagreed to conduct measurements ata number of MR installations withthe purpose to establish effectiveaction values and calculate expo-sure values related to the most sen-sitive applications. However, resultsare not expected before the end of2007. Similarly, manufacturers havemobilized via COCIR (EuropeanCoordination Committee of theRadiological, Electromedical andHealthcare IT Industry). TheEuropean Federation of Academiesof Medicine has been informed ofthe difficulties likely to result fromthe application of this Directive in itscurrent form. European task forces

Frequencies Mechanism

Static magnetic field (0 Hz) Magnetic inductionMagnetic-mechanical interaction

Low frequencies (30 Hz 300 Hz) Induced currents

Radiofrequences and microwaves(0.1 MHz 10 GHz) Energy deposited in the body

Microwaves (10 GHz 300 GHz) Surface heating

Mechanisms of biological interactions with electromagnetic fields

Frequencies (f) Reference values in mT (milliteslas)

0 to 1 Hz 200

1 to 8 Hz 200 /f2 (200 to 3125)

8 to 25 Hz 25/f (3125 to 1 mT)

25 to 820 Hz 25/f (1 to 0.03 mT)

EUROPEAN DIRECTIVE ON ELECTROMAGNETIC FIELDS 67

have been created with the aim ofensuring that MRI is exempted fromthe field of application of theDirective, given the lack of scientificevidence that healthcare workersare at risk.

These actions at the Europeanlevel must be actively supported bynational radiology societies by get-ting in touch with national legisla-tive bodies in order to preventimplementation of the Directive intonational law.

Everything must be done tomodify this Directive as soon aspossible: in its present form itseverely hinders the clinical use ofMRI and also threatens research inthis field.

References

Directiveshttp://www.europa.euCouncil Recommendation. OfficialJournal of the European Communities30.7.1999 : L199/59-L199/70.Directive 2004/40/EC of the EuropeanParliament and of the Council. OfficialJournal of the European Union24.5.2004: L184/1-L184-9.

ICNIRP (International Commission onNon-Ionizing Radiation Protection)http://www.icnirp.org.Guide pour ltablissement de limitesdexposition aux champs lectriques,magntiques et lectromagntiques.

HPA (Health Protection Agency, UK)http://www.hpa.org.uk.

Review of the Scientific Evidence forLimiting Exposure to ElectromagneticFields (0-300 GHZ). 2004, Vol. 15 - N3.

EpidmiologieEpidemiology of Health Effects ofRadiofrequency Exposure. Environ-mental Health Perspectives 2004, 112(17): 1741/1754.

ESMRMB (European Society forMagnetic Resonance in Medicine andBiology)http://www.esmrmb.org.A statement with respect to safety limitsconcerning time varying magnetic fieldsas defined by: Directive 2004/40/EC ofthe European Parliament and of theCouncil.

A STATEMENT WITH RESPECT TO SAFETY MIMITS CONCERNING TIMEVARYING MAGNETIC FIELDS AS DEFINED BY THE DIRECTIVE 2004/40/ECOF THE EUROPEAN PARLIAMENT AND THE COUNCIL

Statement by Commissioner Spidlaon allegations regarding MRI

Some articles today published alle-gations that the directive on electro-magnetic fields or so-called physicalagents directive (2004/40/EC) pre-vents doctors and nurses from giv-ing proper treatment to patients. Itwas also claimed that parents willno longer be allowed to hold thehand of their child during surgery.This is completely false.

ESMRMB comment. The EU direc-tive will prevent nurses and doctors(but not parents) sitting next to MRIscanners during scanning thus mak-ing pediatric MR imaging lesspatient friendly.

1. The directive is designed to pro-tect workers against excessiveexposure to MRI (MagneticResonance Imaging) and electro-magnetic fields which scietificexperts agree is dangerous forhealth.

ESMRMB comment. MRI devicesresult only in an exposure to mag-netic fields (rather than combinedelectric and magnetic fields). Thereare no known long term effects ofexposure to magnetic fields. This isnot to argue that there should be nolimits on exposure, rather that expo-sure limits should be based on cur-rent scientific knowledge. As our

ability to generate strong staticand time-varying magnetic fieldsincreases, so does our understand-ing of the effects of these fields.Exposure limits are set according tothe degree of exposure and theassociated risk. Blanket statementssuch as that MRI is dangerous forhealth are thus not compatible withthe principles according to whichlimits are set, and certainly are notrepresentative of any body of scien-tific opinion.

2. The directive limits exposure toMRI and other radiation for workers.It was drafted by the Commissionbased on the results and recom-mendations issued by ICNIRP(International Commission for NonIonizing Radiation Protection), anindependent world wide recognizedorganisation using the expertise oftechnicians, scientists and doctorsworking in the field.

ESMRMB comment. ICNIRP isindeed the international bodyresponsible for setting limits.ICNIRP itself has recognised that itscurrent limits for occupational expo-sure to all electromagnetic fields arein need of review, a process that iscurrently taking place.

3. The European Parliament and allMember States including the UKGovernment agreed in April 2004that it is essential to have the same

standards for the health and safetyof workers regarding electromag-netic fields since the risk is the samefor nurses and doctors throughoutEurope. The directive was adoptedunanimously and has to be imple-mented by April 2008.

ESMRMB comment. This is a laud-able aim and ICNIRP should beencouraged to finalize their revisionbefore April 2008.

Commissioner for Employment,Social Affairs and Equal Opportu-nities Vladimir Spidla commented:The risk of MRI is a real one foreverybody who is exposed to itregularily, NOT to parents or theirchildren undergoing treatment. I amconcerned that those who areprotesting are underestimating theradiation of MRI at the expense ofthe health of their employees. I amglad that this directive will give asolid protection to doctors and nurs-es exposed to MRI.

ESMRMB comment. Risk assess-ment and research into safetyaspects of electro-magnetic fieldsis taken very seriously by theEuropean and international MRcommunity. Progress in the under-standing of the bioeffects of mag-netic fields is regularly discussedand reported at numerous scientificmeetings as well as at dedicatedworkshops. There are three types of

magnetic field associated with anMRI examination. The static field:this can cause transient effects suchas vertigo, but despite considerableeffort, no long term effects havebeen identified. Switched magneticfields: current safety limits for these are designed to avoid painful muscle stimulation in patients, butthere is no evidence that prolonged sub-threshold exposure is harmful.Finally the patient is exposed toradiofrequency fields: current safetylimits for patient exposure preventtissue heating, personnel are hardlyever exposed to these fields andthey are hence not relevant to thecurrent debate.

The commissioner should also bearin mind that those protesting are notunscrupulous employers intent on

exploiting their workforce comewhat may, but responsible scientistswho regularly expose themselves tothese fields and hence have a maxi-mal interest in working in a safe andwell regulated environment.

In conclusion, the ESMRMB wouldlike to point out that inflammatoryand incorrect statements such ascontained in the commissionersstatement do not contribute con-structively to the resolution of thecurrent debate about safety regula-tions for MRI. Statements such asthis can make it more difficult torecruit health workers to work withMRI and erroneously lead the publicto believe that MRI is in some waydangerous. A major factor in theextremely rapid development of MRhas been the fact, that it is (to all cur-

68 JBRBTR, 2007, 90 (1)

rent knowledge and with all due pre-caution) harmless and thus can inmany instances replace examina-tions with ionizing radiation. Thefact that despite considerable effortno long term harmful effects of MRIcould be identified, which of itselfmakes legislation difficult, shouldnot be misrepresented to create aperception of insecurity or danger.The result can be that more patientsare examined with ionising radia-tion which has definitely knownharmful side-effects.

Katharina von SchnurbeinSpokesman

Official information of the EuropeanCommission is available at any timeat http://europa.eu.int/rapid/