Symptoms and cognitive effects of exposure to magnetic stray fields

1. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Symptoms and cognitive effects of exposure to magnetic stray fields • Frank de Vocht Occupational and Environmental Health Research Group. The University of Manchester. Email: frank.devocht@manchester.ac.uk

2. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Setting the scene • General public ceiling value • ICNIRP 1994 Guidelines 40 mT • ICNIRP 2009 Guidelines 400 mT • Static Magnetic Field TWA exposure • EU Directive 2004/40/EC 200 mT/8hrs • ICNIRP 1994 Guidelines 200 mT/8hrs - • Static Magnetic Field Peak exposure • EU Directive 2004/40/EC 2 T (torso) / 5 T (limbs) • EU Directive 2008/46/EC • ICNIRP 1994 Guidelines 2 T (torso) / 5 T (limbs • ICNIRP 2009 Guidelines 2 T (torso) / 8 T (limbs) 8 T (controlled) • Time-varying MF exposure (0-7Hz) • EU Directive 2004/40/EC 200mT/f2 (f~1/(2tp)) ~ • IEEE 2002 Standards 767.9 mT/sec

3. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative “older” data • Soon after the introduction of MRI as a medical imaging modality studies were conducted to ensure patient safety1,2. - Neuropsychological and EEG effects absent in patients scanned at 0.5 and 1.5 Tesla. • Subsequent work3 at higher exposure levels (≤4 T) did not report adverse effects, although volunteers reported sensory complaints • Consensus: no chronic effects and no adverse acute neurobehavioral effects <2T 1Bartels et al. Forschr Rontgenstr 1986; 145: 383-385. 2Besson et al. J Neurol Neurosurg Psychiatry 1984; 47(3): 314-6. 3Schenck et al. Med Phys 1992; 19(4): 1089-98.

4. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Semi-acute effects • One study assessed health complaints and neuropsychological effects among MR technicians5. • no neuropsychological effects at the end of the working day compared to pre-work shift measurements. • self-reported vertigo, metallic taste, and concentration problems higher than in reference department. • prevalence of health complaints associated with duration and intensity of exposure (0.5-3 Tesla). 5de Vocht et al. J Magn Reson Imaging 2006; 23(3): 197-204.

5. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Acute effects – controlled trails • Assessment of neurobehavioral acute effects • 0.5-9.4 Tesla MRI systems • >600mT and >150mT/s exposure • no effects found immediately after exposure ended1 • no effects found during exposure in the magnet bore2 • working memory was not affected3,4 • switched gradients typically used in MRI have no effect on primary retinal or visual processing5. • No effects from time-varying MF-peaks only, but only during co-exposure to SMF5,6. 1Atkinson et al. 2007; 2Chakeres and de Vocht. 2005; 3de Vocht et al. 2007; 4de Vocht et al. 2006; 5Glover et al. 2007;6de Vocht et al. 2007;

6. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Acute effects – controlled trails • Vertigo-like symptoms can be induced by MF changes1,2,3. • Movement in the heterogeneous stray field associated with adverse effects on4-7 visuo-ocular reflex -0.7%/100mT visual contrast sensitivity -1%/100mT visuo-motor effects -0.2/0.7% per 100mT • Effects associated with intensity of exposure • Effects could already be measured below the previously reported 2 Tesla17 1ICNIRP, 1994; 2Glover et al. jMRI 2007; 3Glover et al. Bioelectromagnetics 2007; 4Chakeres and de Vocht. Prog Biophys Mol Biol 2005; 5de Vocht et al., 2007; 6de Vocht et al., 2006; 7de Vocht et al. jMRI 2007.

7. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Why do we find effects in the stray field only?

8. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Why do we find effects in the stray field only?

9. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Why do we find effects in the stray field only?

10. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure data • De Vocht, Muller, Engels, Kromhout. Personal exposure to….MRI system test procedures. jMRI 2009; in press. • Personal exposure measured using dosimeter • MrDoseTM (Wave Instruments Ltd) • worn around waist • Measures MF (B) and MF temporal change (dB/dt) • 22 measurements among 10 system engineers • Tasks Routinely conducted by system engineers • Required engineers to enter stray field and bore regularly • Whole body MRI systems • 1.0T open • 1.5T and 3.0T cylindrical

11. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure & effect values

12. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure & effect values

13. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure & effect values

14. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure & effect values

15. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Personal exposure & effect values

16. Exposure variability Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative

17. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Conclusions (I) • Affected domains • visuo-ocular reflex • visual contrast sensitivity • visuo-motor effects • Affecting diffuse cellular networks rather than single neuron threshold • Symptoms and cognitive effects • Associated to movement in stray fields • Acute • Transient • Exposure-dependent • Measurable from 600mT and 150mT/s exposure

18. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative Conclusions (II) • TWA exposure levels are not useful as exposure limits • Data suggests effects associated to peaks • Exposure patterns show large differences in time • Peak exposure levels regularly exceed both: • Proposed limit values. • Current minimum measured effect levels. • Variance components suggest • Only ~50% explained by system and task Can be addressed by engineering factors • Other 50% caused by inter/intra individual factors Can be addressed by addressing management and individual factors

19. Occupational Exposure to Electromagnetic Fields: paving the way for a future EU initiative ACKNOWLEDGMENTS • IRAS – Utrecht University, the Netherlands • Prof. Hans Kromhout, • Dr. Berna van Wendel-de Joode, • Tobias Stevens, • Floris Muller • SPMMRC – University of Nottingham • Prof. Penny Gowland, • Dr. Paul Glover • Philips Medical Systems • Dr. Hans Engels