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Non-Ionizing Home                   Very Low Frequency and Extremely Low Frequency


Very Low Frequency (VLF) and Extremely Low Frequency (ELF) are usually expressed in terms of a unit called the hertz (Hz). One Hz equals one cycle per second. One megahertz (MHz) equals one million cycles per second. 

VLF refers to radio frequencies (RF) in the range of 3 kHz to 30 kHz and wavelengths from 10 to 100 kilometers. There is very little bandwidth in this band of the radio spectrum; therefore, audio (voice) cannot be transmitted and only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations which broadcast time signals to set radio clocks, and for secure military communication. VLF waves penetrate about 40 meters into saltwater and are used for military communication with submarines.


ELF waves are electromagnetic radiation (radio waves) with frequencies from 3 to 300 Hz, and corresponding wavelengths from 100,000 to 1000 kilometers.  ELF radio waves are generated by lightning and natural disturbances in the Earth's magnetic field, thus they are a subject of research by atmospheric scientists. Because of the difficulty of building antennas that can radiate such long waves, ELF frequencies have been used in very few man-made communication systems. ELF waves can penetrate seawater, therefore the US and Russian militaries have used ELF transmission facilities to communicate with their deep submerged submarines.

ELF is important from a public health standpoint because of the widespread use of electrical current at the 50 or 60 Hz frequency. Electric currents create extremely low-frequency electromagnetic fields (EMF), which are at the low-energy end of the electromagnetic spectrum. The frequency of alternating current flowing in electric power grids falls within this frequency band, making power grids are an unintentional source of ELF radiation.  We are all exposed to electromagnetic fields from the earth itself and from man-made sources.   Examples of man-made sources include power lines, household wiring, and electrical appliances (when they are on).  Modern television and computer screens give off several kinds of radiation, most of which is in the extremely low frequency (ELF) range.


US Regulations:  

There are no health-based standards for long-term human exposure to VLF and ELF in the United States
Public and employee concerns about EMF exposure have grown as a result of increased media coverage over the last few years. The issue of ELF radiation is very controversial.  The 50 to 60 Hz range is of particular interest because it is associated with electrical power distribution, and equipment utilizing alternating current.  

Exposure levels for the general population are typically 5–50 V/m for electric fields and 0.01–0.2 mT for magnetic fields. Considerably higher exposure occurs for shorter durations and in some occupational settings.


International Perspectives:


The World Health Organization (WHO) has weighed in on the subject of ELF, particularly electromagnetic fields (EMF): "a number of national and international organizations have formulated guidelines establishing limits for occupational and residential EMF exposure. The exposure limits for EMF fields developed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) - a non-governmental organization formally recognized by WHO, were developed following reviews of all the peer-reviewed scientific literature, including thermal and non-thermal effects. The standards are based on evaluations of biological effects that have been established to have health consequences. The main conclusion from the WHO reviews is that EMF exposures below the limits recommended in the ICNIRP international guidelines do not appear to have any known consequence on health."

The International EMF Project has compiled a worldwide standards database limiting exposure to EMF.

Comparison of International Policies on Electromagnetic Fields Netherlands National Institute for Public Health and Environment




Concerns have been raised about possible health problems associated with ELF
.  Research has focused on possible carcinogenic, reproductive, and neurological effects. Other suggested health effects include cardiovascular, behavioral, hormonal and immune system changes.
Studies suggest that ELF and VLF may cause accumulation of charge on body surfaces and disturbance of nerve & muscle responses.  However, the major focus of research has been on childhood leukemia

The International Agency for Research on Cancer states there is limited evidence in humans for the carcinogenicity of extremely low frequency magnetic fields in relation to childhood leukemia. Extremely low-frequency magnetic fields are possibly carcinogenic to humans (Group 2B) IARC Press Release

While a number of studies are available, reliable data on adult cancer and residential exposure to ELF electric and magnetic fields, including the use of appliances, are sparse and methodologically limited. None of the studies reported so far has included long-term or personal measurements. Although there have been a considerable number of reports, a consistent association between residential exposure and adult leukemia and brain cancer has not been established.  Research in this area continues.


Five major evaluations of the evidence for health risks from exposures to occupational and residential ELF-EMF have been published since 1999. Four of them were accompanied by statements on managing EMF exposures and directions for future research.


Minimize Your Risk:

Although extremely low frequency (ELF) exposures occur everywhere, potentially hazardous exposure depends on the strength of the ELF fields at the source, the distance from the source, and possibly the duration of exposure.  If exposures to electromagnetic fields in the VLF and ELF frequency ranges are of concern, a conservative way to deal with this concern is to reduce the amount of exposure time.  It is also important to remember that the strength of a magnetic field decreases dramatically with increasing distance from the source.   It is also possible that only a small percentage of the population is actually sensitive to the electromagnetic fields and that is why it is taking so long to come to conclusions.  In this latter case, most people would not be at risk. 

People concerned about possible health risks from power lines can reduce their exposure by:

  • Increasing the distance between you and the source – The greater the distance between you and the power lines the more you reduce your exposure.   It is important to remember that the strength of a magnetic field decreases dramatically with increasing distance from the source.

  • Limiting the time spent around the source – Limit the time you spend near power lines to reduce your exposure.

  • Shielding – Consider shielding as a last resort.  It is very costly and when fields result from sources outside of the building such as power lines and engulf the entire structure, shielding will not be a viable field-reduction strategy. 
    If you are concerned about EMFs emitted by a power line or substation in your area, you can contact your local power company to schedule an on-site reading. You can also measure EMFs yourself with the use of a gaussmeter, which is available for purchase online through a number of retailers and local home stores.


Professional Resources:


NIEHS and NIH Report on the Electric and Magnetic Fields Associated with the use of Electric Power

National Institute of Health Sciences on EMF

EPA Electric and Magnetic Field (EMF) Radiation from Power Lines

WHO on Electromagnetic Fields and Human Health / ELF


CDC on Electric and Magnetic Fields


Electromagnetic Fields; Wisconsin Public Service Commission 2008 Report


Duke Energy Frequently Asked Questions




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