EMFs.info

Electric and magnetic fields and health

index/glossary | EMFs At A Glance | EMF The Facts (pdf)
  • 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
You are here: Home / Research / Mechanisms / Plausibility of biophysical mechanisms

Plausibility of biophysical mechanisms

What constitutes a "plausible" mechanisms for EMFs to interact with the body?  We give here two discussions of this issue.

  • Simple version
  • More technical version

If fields are to have any effect on people, there must be a mechanism of interaction. The field must interact with the electric charges in the body. If the field is too low, that interaction will not produce any effect on the whole body; it will get lost in the noise. So we can compare the size of the effect produced by the field with the electrical noise present in the body already.

When we do this, the conclusion is that we have not identified any mechanism where fields below about 5 µT could produce an interaction that is big enough to rise above the noise and produce an effect on the whole body. We probably have to go to 50 µT or more for the field to be big enough to produce effects.

The level of field implicated in the epidemiology is less than 1 µT. So this suggests that there are no mechanisms operating at the level implicated in the epidemiology, and this is turn casts doubt on whether the associations found in the epidemiology can be real effects of fields or not.

Of course, this is not conclusive. Maybe there is a mechanism that can operate at these low levels, and we just haven't thought of it yet. Or maybe there's a clever way one of the mechanisms we have thought of can operate at lower levels than we realise.

But most scientists see the absence of an identified mechanism that could operate at the low levels of field involved in the epidemiology as one of the arguments against EMFs being a cause of cancer.

One particular aspect of this debate concerns the energy of fields - is it enough to break bonds and damage DNA?

Examples are sometimes given of where we have accepted that something causes disease without knowing the exact mechanism.  Cholera being transmitted by water and smoking and lung cancer are two examples.  But in both these cases, there is nothing inherently implausible about the mechanism (something in water and tobacco smoke), it's just that we didn't know the exact agent.  So these aren't very good parallels with EMFs.

This page is based on an article first published in Physics World and a review paper published in Radiation Research and assumes a certain level of scientific understanding from the reader.

If fields are to have any effect on people, there must be a mechanism of interaction with a simple physical system involving electric charges or magnetic moments, and that mechanism must produce a “signal” in the biological system which is greater than whatever “noise” level exists naturally. This requirement is not unique to electric or magnetic fields, but applies to any physical stimulus which produces an effect on the whole organism. Through the evolution of specialist sensory organs, such as the eye or ear, the human body can detect signals that are comparable to the fundamental noise levels, but it cannot detect signals below that limit.

This page cannot give a comprehensive survey of every mechanism ever proposed. We will consider some of the more interesting, however, as an indication of the mechanisms proposed and the issues raised.

  • Alternating fields induce currents, and at high fields this is the basis of the known effect on the human body. But the currents induced by environmental field levels (the “signal”) seem to be less than the naturally ocurring current densities present in the body (in this context, the “noise”).
  • The induced alternating currents could modulate the unipolar voltages that exist across cell membranes. The noise is partly thermal noise, which can be calculated, and for a single cell the voltage produced by the field is much less than the noise. It might be possible for the signal to exceed the noise if a large number of cells acted cooperatively, but this would suggest a special structure optimised for the purpose, analogous to the eye or ear, for which there is no evidence in humans. In contrast, sharks do have such structures, the ampullae of Lorenzini, and use them to detect microvolt-per-metre electric fields in water.
  • The noise level could be reduced by reducing the bandwidth of the interaction mechanism, that is, by a resonance. In fact, to achieve an adequate signal-to-noise ratio, the bandwidth might have to be so narrow that the effect could be tuned to 50 Hz or 60 Hz (the power frequencies on the two sides of the Atlantic) but not both! Various resonant mechanisms involving the earth’s static field have been proposed. One of these, ion cyclotron resonance (for example of the calcium ion) cannot actually occur in a cell as the orbit would have to be over 1 m. Others, such as Larmor precession and ion parametric resonance, require unfeasibly infrequent collisions and are open to other objections.
  • 50 Hz fields do not have enough energy to break chemical bonds directly - see more detail on this.
  • Magnetic fields exert moments on ferromagnetic particles. Such particles are found in humans, but when the maximum plausible magnetic moment and the viscosity of the cell matter surrounding it are quantified, the amplitude of oscillation induced by environmental fields is less than the Brownian motion.
  • Many biochemical reactions involve free radicals, highly reactive entities produced in pairs each with unpaired electron spins. Magnetic fields can affect singlet-triplet conversion and hence affect the concentration of free radicals by altering the recombination probabilities. The appropriate “signal-to-noise ratio” for this process has never been properly addressed. However, there is another reason why it seems that it cannot underlie the epidemiological results. Free-radical reactions typically have timescales of tens of nanoseconds, compared to which 50 Hz fields are effectively static. The relevant magnetic field is therefore the instantaneous total field, which is usually dominated not by the power-frequency component but by the geomagnetic field, which is around 50 µT in the UK.
  • It has been suggested that the fields produced by transmission lines could deflect cosmic rays, concentrating them on people living nearby. The two most obvious objections to this are that with an alternating field the deflection will average to nearly zero, and the size of deflection can be estimated as a metre at most.
  • Most recently, Professor Denis Henshaw at Bristol University has pointed out that electric fields can cause movement and concentration of radon daughter products (and possibly other carcinogens as well). Daughter products attached to polarisable particles will drift towards the source of a non-uniform field, and some daughter products are attached to charged particles which oscillate in the field. Corona ions produced by high electric fields on the surface of some power-line conductors can interact with existing airborne pollutants. Whether this could lead to health consequences and in particular to an increase in leukaemia is still controversial.

Conclusion

The review paper by Swanson and Kheifets concluded:

"Some of the mechanisms are impossible, and some require specific conditions for which there is limited or no evidence as to their existence in a way that would make them relevant to human exposure. Others are predicted to become plausible above some level of field. We conclude that effects below 5 microT are implausible. At about 50 microT, no specific mechanism has been identified, but the basic problem of implausibility is removed. Above about 500 microT, there are established or likely effects from accepted mechanisms. The absence of a plausible biophysical mechanism at lower fields cannot be taken as proof that health effects of environmental electric and magnetic fields are impossible. Nevertheless, it is a relevant consideration in assessing the overall evidence on these fields."

Clearly, it would be both arrogant and rash of physicists to argue that because we have not yet been able to think of a possible physical mechanism it is impossible for there to be an effect. However, the absence of a mechanism and the absence of replicable laboratory results inevitably - and correctly - means that the epidemiological results are viewed with greater caution.

See also:

Some specific mechanisms:

  • absorption of energy
  • free radicals

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

Contact Us

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

See Contact us for more contact details including our privacy policy.

About this site

  • What this site covers and what it doesn’t
  • Industry policy
  • Sitemap

Specific questions

  • Affected by a new power line or substation?
  • Building or developing near a power line or substation?
  • EMF measurement and commercial services
  • Microshocks
  • Pacemakers and other medical devices
  • EMF policy in the UK
Site Authorship |Sitemap | Terms and Conditions | Privacy Policy | Cookies | Site Statistics
© 2021 EMFS.info
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