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Electric and magnetic fields and health

index/glossary | EMFs At A Glance | EMF The Facts (pdf)
  • What are EMFs
    • Terminology – an introduction
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      • “EMF Commercial”
    • Adding fields together
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        • 400 kV
        • 400 kV – specific cases
        • 275 kV
        • 132 kV
        • 66 kV
        • 33 kV
        • 11 kV
        • 400 V/230 V
        • Replacing a 132 kV line with a 400 kV line
      • Summaries of fields from all power lines
      • Factors affecting the field from a power line
        • Voltage
        • Current
        • Clearance
        • Height above ground
        • Conductor bundle
        • Phasing
        • Balance between circuits
        • Balance within circuit
        • Ground resistivity
        • Two parallel lines
      • Calculating and measuring fields from power lines
        • Geometries of power lines
        • Raw data
        • On-line calculator
      • Fields from power lines – more detail on the physics
        • Field lines from a power line
        • The direction of the field from a power line
        • Power law variations in the field from a power line
      • Statistics of power line fields
    • Underground power cables
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      • Fields from cables in tunnels
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      • Fields greater than 0.2 or 0.4 µT
    • Screening EMFs
      • Screening fields from underground cables
      • EMF Reduction Devices
  • Known effects
    • Induced currents and fields
    • Microshocks
      • Control of microshocks in the UK
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  • Exposure limits for people
    • Limits in the UK
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    • Limits from specific organisations
      • ICNIRP 1998
      • ICNIRP 2010
      • NRPB 1993
      • NRPB 2004
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      • EU 2013
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      • Power lines and property – UK
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You are here: Home / Exposure limits for people / Indirect effects in exposure limits

Indirect effects in exposure limits

The main effect that EMF exposure limits protect against is the direct effect on the body of induced fields and currents.  But electric fields can also have indirect effects though the way they charge conducting objects which aren't earthed.  This includes the effect of charge on the surface of the body causing hairs to vibrate, and the phenomenon of microshocks.  We summarise here what the various exposure limits say about these indirect effects.

NRPB 1993

The 1993 NRPB exposure guidelines say:

"In many exposure conditions and for most people, the annoying effects caused by electric charge on the surface of the body will not occur at power-frequency electric field strengths below 12 kV/m."

ICNIRP 1998

The 1998 ICNIRP Guidelines set a reference level for electric fields for the public of 5 kV/m and for occupational exposure of 10 kV/m, then add:

"Provided that basic restrictions are met and adverse indirect effects can be excluded, field strength values can be exceeded."

When describing how the reference levels are calculated from the basic restrictions, they also say:

"For the specific case of occupational exposures at frequencies up to 100 kHz, the derived electric fields can be increased by a factor of 2 under conditions in which adverse indirect effects from contact with electrically charged conductors can be excluded."

EU 1999

The 1999 EU Recommendation on public exposure gives basic restrictions in Annex 2 (which make no mention of indirect effects at all), and reference levels in Annex 3.  Annex 3 says:

"Provided that adverse health impacts of indirect effects of exposure (such as microshocks) can be avoided, it is recognised that the general-public reference levels can be exceeded provided that the basic restriction on the current density is not surpassed."

But the main body of the Recommendation says Member States should "aim to achieve respect of the basic restrictions given in Annex II for public exposure" without mentioning Annex 3 at all, so the status of Annex 3 is unclear.

ICES 2002

The 2002 ICES guidelines give basic restrictions on the induced electric field in various tissue types.  It is possible to derive external electric fields that correspond to these basic restrictions.  But these levels, derived from the basic restriction, would be higher than the levels ICES sets to protect against indirect effects.  So in ICES, it is the indirect effects which determine the electric-field limits.

They are termed "maximum permissible exposures" and are

  • 5 kV/m for the public in general
  • 10 kV/m (under normal load conditions) for the public on the right-of-way of a power line
  • 20 kV/m for controlled exposures
  • For a controlled environment in which an exposed individual is not within reach of a grounded object, it may be acceptable to exceed 20 kV/m

The explanation given for the higher public limit on a power-line right-of-way is:

"Power line rights-of-way fall somewhere between the definitions of “controlled” and “uncontrolled” environments for the general public in that public activity can be circumscribed by the utility, but that public access is often allowed for the public benefit. Consequently, this standard specifies a limit of 5 kV/m for the general public in regions off the right-of-way, but allows an intermediate field of 10 kV/m within the rightof-way under normal load conditions."

NRPB 2004

The 2004 NRPB advice on limiting exposures says:

“When an ungrounded person is in an electric field and comes into contact with a grounded object there is the possibility of occurrence of a spark discharge at the point of contact between the person and the object. For fields external to the body greater than about 5 kV m-1, there is the likelihood of such discharges being painful. The extent to which this is a problem in practice is unclear and further investigation is merited.

“When a person is in an electric field and comes into contact with an ungrounded object there is the possibility of occurrence of a spark discharge at the point of contact between the object and the person. For such situations, the probability and the magnitude of the effect depend on the field strength and the size of the ungrounded object.”

Current position in the UK

The most definitive statement of the position on indirect effects in the UK is contained in the Code of Practice on compliance with exposure limits:

"While indirect effects are more tangible due to effects such as microshocks, they have historically given rise to less concerns than direct effects. For indirect effects, while the Guidelines give a cautionary reference level of 5 kV m-1 for the general public as a trigger to fuller assessment of compliance with the exposure guidelines, using that as a limit is not the most appropriate way of dealing with indirect effects. Rather, there is a suite of measures that may be called upon in particular situations, including provision of information, earthing, and screening, alongside limiting the field which should be used to reduce the risk to the public of indirect effects. In some situations, there may be no reasonable way of eliminating indirect effects, for instance where erecting screening would obstruct the intended use of the land. The approach to addressing indirect effects of electric fields will be the subject of a separate document to be developed between the industry and the Health Protection Agency."

See also

Latest news

  • New publication on cancer incidence from the UK electricity industry Cohort Study August 27, 2019
  • How has the reported risk for childhood leukaemia changed over time? February 11, 2019
  • Media stories about microshocks in children’s playground September 10, 2018
  • New studies on leukaemia and distance from power lines June 1, 2018
older news

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Navigation
  • What are EMFs
    • Terminology – an introduction
    • Electric fields
    • Magnetic fields
    • Units for measuring EMFs
    • Measuring and calculating EMFs
      • “EMF Commercial”
    • Adding fields together
    • Radiofrequencies
    • Screening EMFs
  • Sources
    • Overhead power lines
      • Fields from specific power lines
        • 400 kV
        • 400 kV – specific cases
        • 275 kV
        • 132 kV
        • 66 kV
        • 33 kV
        • 11 kV
        • 400 V/230 V
        • Replacing a 132 kV line with a 400 kV line
      • Summaries of fields from all power lines
      • Factors affecting the field from a power line
        • Voltage
        • Current
        • Clearance
        • Height above ground
        • Conductor bundle
        • Phasing
        • Balance between circuits
        • Balance within circuit
        • Ground resistivity
        • Two parallel lines
      • Calculating and measuring fields from power lines
        • Geometries of power lines
        • Raw data
        • On-line calculator
      • Fields from power lines – more detail on the physics
        • Field lines from a power line
        • The direction of the field from a power line
        • Power law variations in the field from a power line
      • Statistics of power line fields
    • Underground power cables
      • Different types of underground cable
      • Fields from cables in tunnels
      • Gas Insulated Lines (GIL)
      • Underground cables with multiple conductors
      • Effect of height on fields from underground cables
      • Screening fields from underground cables
    • Low-voltage distribution
      • UK distribution wiring
      • USA distribution wiring
    • House wiring
    • Substations
      • National Grid substations
        • Static Var Compensators
      • Sealing-end compounds
      • Distribution substations
      • Final distribution substations
        • Indoor substations
    • Transport
      • EMFs from electric trains (UK)
      • EMFs from cars
    • Appliances
    • Electricity meters
      • Smart meters
      • Traditional meters
    • Occupational exposures
      • Live-line work
      • Static Var Compensators
      • Occupational exposures on pylons
    • Field levels and exposures
      • Personal exposure
      • Other factors that vary with magnetic fields
      • Fields greater than 0.2 or 0.4 µT
    • Screening EMFs
      • Screening fields from underground cables
      • EMF Reduction Devices
  • Known effects
    • Induced currents and fields
    • Microshocks
      • Control of microshocks in the UK
      • Microshocks from bicycles
      • Bees and microshocks
    • EMFs and medical devices
      • Standards relating to pacemakers and other AIMDs
    • Effects of EMFs on equipment
  • Research
    • Types of research
    • Epidemiology
    • Animal and laboratory experiments
    • Mechanisms
    • Specific studies
      • UKCCS
      • CCRG
      • French Geocap study
      • CEGB cohort
      • Imperial College study
  • Current evidence on health
    • Childhood leukaemia
      • Survival from childhood leukaemia
      • Childhood leukaemia and Downs
      • Childhood leukaemia and night-time exposure
      • The “contact current” hypothesis
    • Other health effects
    • Scientific review bodies
      • WHO
      • IARC
    • Electric fields and ions
    • Comparing EMFs to other issues
  • Exposure limits for people
    • Limits in the UK
    • Limits in the EU
    • Limits in the USA
    • Limits in the rest of the world
    • Limits from specific organisations
      • ICNIRP 1998
      • ICNIRP 2010
      • NRPB 1993
      • NRPB 2004
      • EU 2004
      • EU 2013
  • Policy
    • UK policy
      • Power lines and property – UK
    • Compliance with exposure limits
    • European EMF policy
    • Precaution
    • SAGE
      • SAGE First Interim Assessment
        • Government response to SAGE First Interim Assessment
      • SAGE Second Interim Assessment
        • Government response to SAGE Second Interim Assessment
        • SAGE Second Interim Assessment – the full list of recommendations
  • Finding out more
    • EMF measurement and commercial services
    • Links
    • Literature
    • Contact us
  • Static fields
    • Static fields – the expert view