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You are here: Home / Sources / Field levels and exposures / Fields in different countries

Fields in different countries

Average field levels in different countries

This graph shows the range of fields found in a number of different countries

 comparison of fields in different countries

 

The UK has lower fields than many countries - roughly half the level in the USA - see below for the explanation. Differences between countries are largely caused by different wiring practices and different usages of electricity.

Reminder: 1000 nanotesla (nT) = 1 microtesla (µT)

Prevalence of high fields in different countries

The UK also has a lower percentage of homes with high fields.  more on these "high fields".

 

Country
% exposed to long-term average fields greater than:
 0.2 µT0.4 µT
USA9.20.9
Canada11.83.3
UK1.50.4
Germany1.40.2

Why are fields in the UK lower than the USA?

Average magnetic fields in homes in the USA appear to be about 2-3 times bigger than in the UK (see above).

There are several features of wiring practices that help explain this:

  • Magnetic fields come from "net currents" which are produced when the neutral is multiply earthed or grounded.  In both countries the final distribution circuits ("secondaries" in the USA) are multiply earthed, allowing net currents.  But in addition, in the USA, the next voltage up - "primaries" - are multiply grounded too.  The equivalent voltage in the UK, 11 kV, is not.
  • Further, transformers in the USA are smaller and serve fewer homes each, but there are a lot more of them.  So the USA primaries - which supply each transformer - tend to get closer to more homes than 11 kV circuits in the UK.
  • Because the transformers are smaller (and usually single-phase as well), there is a greater tendency for loads to be unbalanced, so resulting in a bigger neutral current and in turn bigger net currents.
  • The USA voltage for final distribution is 120 V, half (roughly) the UK's 230 V, so for the same power, currents (and magnetic fields) are doubled.
  • Finally, electricity consumption is higher in the USA anyway - perhaps 2.5 times higher.

Against these factors:

  • USA homes usually have two "hot legs", each at 120 V, sharing a neutral.  Smaller appliances are connected to one or other hot leg, larger appliances are connected at 240 V across the two.  So there is some cancellation of the neutral currents from loads on the two hot legs, which should reduce the neutral current and hence the magnetic field.

These factors were first listed in a paper published in 1994.

See also:

  • Sources of fields
  • Low-voltage distribution - the commonest source of field
  • fields above 0.2 or 0.4 µT

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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To contact the electricity industry’s EMF Unit Public Information Line (UK only):
telephone 0845 7023270 or email [email protected].

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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