Exposure to Electromagnetic Fields

1. Exposure to Electromagnetic Fields London Health & Safety Group Simon Mann 21 January 2008

2. Health Protection Agency • Independent body that protects the health and well-being of the population. • Plays a critical role in • protecting people from infectious diseases, and in • preventing harm when hazards involving chemicals, poisons or radiation occur. • Prepares for new and emerging threats, such as a bio-terrorist attack or virulent new strain of disease.

3. Simon Mann • Acting Leader of EMF Dosimetry Group in • HPA’s Radiation Protection Division • Secretary to Advisory Group on Non-ionising Radiation • UK representative to CENELEC TC106X • Member of ICNIRP’s Dosimetry Standing Committee • Project Leader for HPA’s WiFi Assessment Work Telephone: 01235 822732 E-mail: simon.mann@hpa.org.uk

4. Role of HPA Radiation Protection Division • Activities • Research • Advice • Services • Agents • Ionising rad. • Optical rad. • EMF • UVR • Ultrasound www.hpa.org.uk/radiation

5. Today’s Talk • Five sections: 1. International Exposure Guidelines 2. Basis of Guidelines 3. Implementation of Guidelines 4. Electromagnetic Modelling of the Body 5. Practical Exposure Assessment

6. 1)International Exposure Guidelines Who publishes the guidelines? What is their scope and purpose? What quantities do they restrict?

7. International Commission on Non-Ionizing Radiation Protection (ICNIRP) SC - I Epidemiology • Independent international scientific organisation • Officially recognised by WHO as its advisory body • Members are elected - none from industry • Publishes reviews, guidelines and statements Main Commission SC - IV Optical Radiation SC - II Biology SC - III Physics & Eng.

8. International Recognition of the ICNIRP Guidelines • World Health Organization - • “International guidelines developed by ICNIRP are based on a careful analysis of all scientific literature (both thermal and non-thermal effects) and offer protection against all identified hazards of RF [radiofrequency] energy with large safety margins.” • The most recent exposure guidelines from ICNIRP on exposure to radiofrequency fields were published in 1998 • International EMF Project: www.who.int/peh-emf

9. NRPB Advice on Exposure Guidelines • Updated its position in March 2004 • EMF Advice Document: Docs NRPB 15(2) • EMF Science Review: Docs NRPB 15(3) • “The review of current scientific knowledge, the adoption of a cautious approach to the interpretation of these data, and a recognition of the benefits of international harmonisation, combine in a recommendation to adopt the ICNIRP exposure guidelines for occupational and general public exposure to electromagnetic fields between 0 and 300 GHz.” • NRPB became HPA’s Radiation Protection Division • on 1 April 2005 • see: www.hpa.org/radiation

10. Protection Rationales • Stochastic effects – Ionising radiation, but not EMFs • Risk of an effect increases with increasing dose, but a risk exists for all dose levels • Limits are set based on an acceptable level of risk • Deterministic effects – EMFs and ionising radiation • Effects occur above a threshold exposure level, which may vary to some extent from person to person • Limits are set at the lower end of the expected range of thresholds in order to prevent effects

11. Scope of Guidelines • Cover exposure to EMFs from static E & H fields to lower boundary of infra-red, 300 GHz • Relate to the exposure of people, not the emissions from sources • Intended to apply to workers and members of the public • Do not apply to patients exposed for medical diagnostic and treatment purposes • Do not cover electrical interference with or heating of medical implants • Set out a framework for protection based on basic restrictions and reference levels

12. 2) Basis of Exposure Guidelines What are the effects of exposure? How can the effects be controlled? How do the effects depend on frequency?

13. Static Magnetic Fields • Adverse health effects • Nausea • Vertigo • Cardiac arrhythmia • Impaired mental function • Other sensory effects when head moved in a field gradient • Set basic restrictions on magnetic flux density • Also, when B > 3 mT • Precautions should be taken to prevent hazards from the movement of ferromagnetic objects – an indirect effect

14. Basic Restrictions on StaticMagnetic Flux Density • † Whole-body exposure averaged over the working day • ‡ Can be relaxed under certain conditions (see guidelines)

15. Time-varying Fields (f < 10 MHz) • Adverse effects on functions of the central nervous system (CNS) • Control of movement • Control of posture • Memory • Reasoning • Visual processes • Magnetophosphenes • Direct stimulation of nerves and muscles (requires higher exposures) • Set basic restrictions on root mean square induced current densityin CNS tissues

16. Basic Restrictions on Induced Current Density • Basic restrictions follow frequency dependence of biological responses • Effects are instantaneous therefore time averaging is not permitted

17. Time-varying Fields (f > 100 kHz) • Adverse effects of energy absorption • Heat stress (~38ºC) • Headaches, dizziness, thirst • Decreased sperm count (temporary) • Developmental defects • Reduced cognitive performance • Heat stroke (~41ºC) • Convulsions, unconsciousness, organ damage, death • Set basic restrictions on • SAR (frequencies below 10 GHz) • Power density (frequencies above 10 GHz)

18. Rationale for Basic Restrictions on SAR • Restrict whole-body SAR to avoid heat stress and heat stroke due to generalised heating • 1°C rise in core temperature results from a whole-body averaged SAR of 4 W kg–1 • Restrict localised SAR to avoid tissue damage • Eye damage, fetal abnormalities, etc • Restrict power density rather than SAR at frequencies above 10 GHz • Heating confined to skin and other surface tissues • Average exposures over a period of time • Increase in temperature due to energy absorption is not instantaneous

19. Basic Restrictions on Whole-body SAR • ICNIRP occupational • 0.4 W kg–1– Reduction factor of 10 • ICNIRP general public • 0.08 W kg–1– Reduction factor of 50 • The distribution of SAR in the body is to be averaged, • 1) over the entire mass of the body, and • 2) as the maximum occurring over any 6-minute period • before comparison with these values

20. Basic Restrictions on Localised SAR • Averaging masses in grams given in brackets • These apply to contiguous tissue • All SARs to be averaged over any 6-minute period • Note: a basic restriction of 10 W kg–1 averaged over any 10 g mass of tissue is equivalent to restricting the total power absorbed in any 10 g mass to 0.1 W

21. Basic Restriction Quantities (Internal Below 10 GHz)

22. 3) Implementation of Guidelines UK Safety Legislation European Directives Voluntary Measures

23. Status of Guidelines • There is presently no specific UK legislation setting exposure limits on EMFs • General UK safety legislation provides an enabling route for the guidelines • Section 3 of the Health and Safety at Work etc Act (risk assessment) • Management of Health and Safety at Work Regulations 1999 • HSE refers to HPA (NRPB) advice on EMF exposure • ICNIRP guidelines have been widely adopted on a voluntary basis to aid risk assessments • http://www.hse.gov.uk/radiation/nonionising/hse.htm

24. EU Council Recommendation (1999/519/EEC) • Published on 12 June 1999 and supported by the UK government • Bears on governments in EU Member States • Framework for restricting EMF Exposure of the general public within Europe • Incorporates the ICNIRP numbers, but with provisos,e.g. “aim to achieve respect for” • Applies, in particular, to relevant areas where members of the public spend significanttime • http://europa.eu.int/comm/health/ph_determinants/environment/EMF/emf_en.htm

25. EU Mandate M305– Product Standards • Directives with radiation (taken to include EMF) safety clauses • Radio and Telecommunications Terminal Equipment Directive • Low Voltage Directive • Machinery Directive • EU Mandate M305 - 12 October 2000 • Standards bodies to develop harmonised standards to allow a presumption of conformity • The basic restrictions and reference levels in the Council Recommendation are to be taken into account • The standards are product emission standards • http://europa.eu.int/comm/enterprise/standards_policy/mandates/database/index.cfm?fuseaction=search.detail&id=89

26. Product (Emission) Standards

27. Physical Agents Directive(2004/40/EC) • Was agreed and published in 2004 – now postponed • Would have applied to all workers within the EU • Exposure limits are similar to ICNIRP occupational values • The EU mandated CENELEC, CEN and ETSI to develop exposure assessment standards (M351) • HSE is the lead Department in the UK • http://europa.eu/scadplus/leg/en/cha/c11150.htm • http://www.europa.eu/rapid/pressReleasesAction.do?reference=IP/07/1610&format=HTML&aged=0&language=EN&guiLanguage=en

28. EU Mandate M351– Exposure of Workers • Standards are required to • Take into account the limit values and action values in Directive 2004/40/EC • Assess all relevant sources of exposure • Cover all exposure situations that can realistically be expected • Be proportionate in their practical application • Take full account of standardisation work under M305 and mandates under the medical devices Directive • Avoid introducing measurement where exposure can be calculated on the basis of compliance with product directives • Be developed in co-operation with other bodies (International standards bodies, WHO, ICNIRP, EU Commission)

29. Government Response to 2004 Advice from NRPB • Welcomed the advice and commented: • The NRPB guidelines incorporate a significant cautionary element but specifically do not take into account social or economic factors or the risks or disbenefits that may occur from action to limit exposure. • In 1999, Government agreed an EU Recommendation on public exposure (EC/519/1999) which advocated the use of ICNIRP levels but accepts the need for consideration of risks and benefits when implementing the guidelines. • Following publication of the Stewart Report on Mobile Phones and Health (2000), the mobile phone industry voluntarily adopted ICNIRP guidelines for public exposure to radio frequency fields. All cellular radio base stations comply with ICNIRP public exposure guidelines. • For all other sources, the Government expects the NRPB guidelines to be implemented in line with the terms of the EU Recommendation, that is, taking account of the risks and benefits of action. Preliminary discussions have already taken place to identify what reasonable actions might be taken. • http://www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/HealthAndSocialCareArticle/fs/en?CONTENT_ID=4089500&chk=nMzeXW

30. 4) Electromagnetic Modelling of the Human Body Calculating SAR and Induced Current Density Developing Reference Levels for Guidelines Permits Compliance Testing Through Measurements

31. Phantom Development – NORMAN • NORmalised MAN • Height: 1.76 m • Weight: 73 kg • Developed from MRI scans • 8.3 million voxels (2 mm)3 • 37 different tissue types • Frequency dependent conductivity and permittivity • Also scaled to represent children at ages 1, 5 and 10 years

32. RF Exposure at 120 MHz Anatomy SAR

33. Power Absorption from Radiofrequency Fields • Relative contributions of the body parts to whole-body SAR • Individual SAR values expressed as a rainbow spectrum: violet = lowest, red = highest • As frequency increases absorption gradually moves away from knees and ankles to the upper torso 30 MHz 100 MHz 200 MHz

34. Power Absorption from RF with Arms Up • Variation of absorption with frequency • Field absorbed below chest in a familiar way, i.e. in knees and ankles • Increase in whole-body SAR as a result of absorption in arms when held above the head 30 MHz 100 MHz 200 MHz

35. Power Absorption from RFwith Arms Out • Variation of absorption with frequency • Field horizontally polarised and so absorption almost entirely in aligned limbs, i.e. arms • Remainder of body absorbs very little of horizontally polarised field 30 MHz 100 MHz 200 MHz

36. Power Absorption from RFwhile Sitting • Variation of absorption with frequency • Similar to standing, lower frequencies absorbed in knees and ankles • At higher frequencies absorption occurs on the surface of the body R P Findlay and P J Dimbylow Phys. Med. Biol. 51(2006) 1-14

37. Effect of Grounding

38. Effect of Body Size

39. 5) Practical Exposure Assessment UK Safety Legislation European Directives Voluntary Measures

40. Basic Restriction Quantities (Internal Below 10 GHz) • First three quantities are included as Exposure Limit Values • Static B-field is omitted from Directive

41. Reference Level Quantities (Measurable) • Directive uses same quantities and values as ICNIRP • Electric field strength (1 Hz – 300 GHz) • Magnetic field strength (0 Hz – 300 GHz) • Power density (10 MHz – 300 GHz) • Limb current (10 MHz – 110 MHz) • Contact current (0 Hz – 110 MHz) • Termed Action Values in the Directive • Static magnetic field strength included • No underpinning Exposure Limit Value

42. Electric Field Reference Levelin Relation to Dosimetry

43. Magnetic Field Reference Levelin Relation to Dosimetry

44. Power Density Reference Level in Relation to Dosimetry

45. Limb Current Reference Level in Relation to Dosimetry

46. Compliance Rationale • HPA-RPD envisages a three stage compliance test • Consistent with approach in Directive • See • http://www.hpa.org.uk/radiation/understand/information_sheets/icnirp_exp_guidelines.htm

47. Draft CENELEC “Umbrella” Standard (prEN50499) • Umbrella standard provides tool for initial assessment • Table 1 – Sources/situations that can be assumed to comply with no further assessments • Table 2 – Sources/situations that may need measurement or calculations to be performed • Source or workplace specific standards will be called up, where necessary, from the umbrella standard • CE marked products where compliance with public exposure limits has been shown do not need assessment

48. Assessment Process(prEN50499 Oct 2006)

49. Voluntary Zoning Procedure(prEN50499 Oct 2006)

50. Conclusions • Exposure to electromagnetic fields can give rise to health effects of a deterministic (threshold) nature • There are few situations where exposures can reach the levels where effects can occur • International exposure guidelines provide a framework for restricting exposures • Technical standards contain practical exposure assessment procedures • Feel free to contact HPA for advice • www.hpa.org.uk/radiation