Safety Advice for Electromagnetic Fields (PDF)
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Safety Advice(PDF)
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Powerline EMF Magnetic Fields Factsheet

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See also: Inverse Square Law | Precautions | Detection

Powerline (AC) Magnetic Fields

When an appliance is turned on, there will be a powerline magnetic field, due to current, which can be measured by an AC gaussmeter in the unit of the milligauss or microTesla.

Key scientific reports and statements on magnetic fields include the following, with 1 milligauss being the recommendation of recent scientific groups:

  1. Bioinitiative Report of 2012 -- Recommendation of 1 mG limit
  2. Seletun Scientific Panel of 2011 Recommendation of 1 mG exposure limit. See the conference proceedings.
  3. Pathophysiology Journal, August 2009 - Special Issue on EMF's
  4. Congress of the United States, Office of Technology Assessment, May 1989: Biological Effects of Power Frequency Electric and Magnetic Fields
  5. EPA Draft 1990 "Evaluation of the Potential Carcinogenicity of Electromagnetic Fields"

This stands in stark contrast to much higher official standards of 833 mG at 60 Hz, which are not sufficiently protective of public health.

Typical Sources of Powerline Magnetic Fields

Typical sources include electricity towers, appliances (point sources), and wiring errors. The most glaring issues are sometimes from reparable wiring errors.

Electricity Towers and High Voltage Lines

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Electricity towers are sources of AC magnetic fields, and homes should be sited at least ~150 meters from the larger 400 kV electricity towers. Large and small power lines both need to be considered, although the former requires more distance than the latter. PowerWatch approximates that to drop below 2mG, one should be ~150 meters away from the strongest 400 kV lines as opposed to only ~15 meters for 11 kV lines. However, it recommends measurement, since fields could vary over time.

Point Sources of Magnetic Fields

Point Sources: Anything that runs electricity, including all electrical appliances are sources of magnetic fields. However, for most point sources, the strength decreases quickly with the square of the distance (see Distance Matters). After 1 meter from typical appliances, levels are generally within limits thought to be acceptable, but conversely, levels within 1 foot of the source could be high. Coils can also generate huge magnetic fields which decrease with the cube of the distance. (Karl Riley's Tracing EMFs in Building Wiring and Grounding). For precautionary guidelines, see the Precautions table. For most household appliances, observing a 1 meter distance is usually good enough for ELF safety concerns, since the strength of the field decreases quickly with distance from the source. To give you a general feel for EMF levels of typical appliances, an alarm clock or radio measures about ~50mG (milligauss) directly at the source, ~2mG at 1 foot, and ~0.6mG at 2 feet.

Wiring Sources of Magnetic Fields

Wiring errors, such as connecting the neutrals/return wiring of 2 different branch circuits (also known as "ganged neutrals" or "paralleled neutrals"), can create large areas of high AC magnetic fields, which decrease linearly with distance, unlike point sources that decrease with the square or cube of the distance. Another common error is making neutral to ground connections outside of the main service panel. By creating multiple return paths for the return current, this causes some of the return current to travel on an unintended path, causing a deficit on the intended path and a surplus on the unintended parallel path. If there is net current on any cable (current on hot/supply and neutral/return wires do not cancel), then the strength of the magnetic field may be high, and decrease linearly with the distance rather than with the square of the distance. The resulting magnetic fields may be ranging over a wide area and may be higher than living near an electricity tower.

Wiring Correction

Wiring errors should be corrected by a licensed electrician, familiar with Karl Riley's Tracing EMF's in Building Wiring and Grounding. In some cases, due to wiring code violations, there can be larger regions with high EMF in a home or office. In this case, the recommendation is to check Karl Riley's video or book on tracing EMF's in the home, produced for the California EMF program. In a 1995 study, Karl Riley measured 150 buildings and found 65% of high fields were related to wiring violations. For more information, see California EMF Program Guidelines on Fixing Electric Wiring.

Other Sources of Magnetic Fields

Other sources of high magnetic fields include the following:

Properties of Powerline Magnetic Fields

Safety Recommendations

Recommended Limit: For long term exposures, it is recommended that the power frequency magnetic field levels be less than 1 mG, or 0.1 μT, according to the Bioinitiative Working Group and the Seletun Scientific Panel recommendations. Some standards go even further, such as SBM 2008, to recommend even lower values for sleeping areas. The World Health Organization indicates that "pooled analyses of epidemiological studies" demonstrate "a consistent pattern of a two-fold increase in childhood leukaemia associated with average exposure to residential power-frequency magnetic field above 0.3 to 0.4 μT", which corresponds to 3 to 4 mG. Samuel Milham reports over 50 residential and 100 occupational studies on the link between power frequency EMF and cancer. Sperm quality can be lowered by chronic exposures to levels as low as 1.6 mG and chick embryonic development may be affected as low as 1mG.

TCO standard (Swedish Confederation of Professional Employees)2 mG
BioInitiative recommendation (2007),
Seletun Scientific Panel recommendation (2011)
1 mG
SBM 2008 Recommendation for sleeping areas0.2 mG
Typical Ambient ExposureStrengthDuration
Average Residential, North America (Source: WHO)1.1 mGConstant
Average Residential, Europe (Source: WHO)0.7 mGConstant
Natural level (AC magnetic, not DC magnetic)<0.000002 mGConstant
Electricity TowersStrengthDuration
Childhood Leukemia Studies Near Powerlines3 mG and higherConstant
400 kV line at ~150m
or 11 kV line at ~15 meters (Source:Powerwatch)
2 mGConstant
Line SourcesStrengthDuration
Building with Wiring Error such as Ganged NeutralsCan be extremely high, up to 100+ mG in some casesWhen turned on
Point SourcesStrengthDuration
Electric shaver at 6 inches (EPA)- Keep use brief100 mG (median)Usually very brief
Color TV at 1 foot (EPA)- Children should keep at least 1 meter distance7 mG (median)When turned on

Health Risks of Power Lines

There are a number of studies, both at the cellular level, and at the epidemiological level, showing potential harm from AC magnetic field exposure.

"We know from studies done at the Cancer Therapy & Research Center in San Antonio, Texas, that our body's defenses are weaker after exposure to EMFs. Human cancer cells grow twenty-four times faster than cells that haven't been exposed to EMFs and show "greatly increased resistance to destruction by the cells of the body's defense system." (Anne Louise Gittleman, Zapped, 44)

Cellular Studies and Suggested Mechanisms

Epidemiological and Human Case Studies

Precautionary Steps

For more ideas, check out the Illustrated Table of Precautions

Further Reading


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