Very Low Frequency (VLF) and Extremely Low
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
frequencies (RF) in the range of 3
from 10 to 100 kilometers. There is very little
(voice) cannot be transmitted and only low
coded signals are used. The VLF band is used for a few
navigation services, government
stations which broadcast time signals to set
clocks, and for secure military communication.
VLF waves penetrate about 40 meters into saltwater and are used for military
communication with submarines.
electromagnetic radiation (radio
from 3 to 300 Hz,
from 100,000 to 1000 kilometers. ELF radio waves are generated by
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
that can radiate such long waves, ELF frequencies have been used in
very few man-made communication systems. ELF waves can penetrate
therefore the US and Russian militaries have used ELF transmission facilities to
communicate with their deep submerged submarines.
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
current flowing in
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.
There are no health-based standards for long-term human exposure to VLF and
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
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
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.
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.
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.
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
"ELF Electromagnetic Fields and the Risk of
Cancer" by the Advisory Group on Non-ionising
Radiation of the National Radiological
(now called the Radiation
Protection Division of the Health Protection
NRPB Documents Volume 12, No. 1 (2001)
This British risk evaluation reviews the
evidence on cancer risks from residential and
occupational ELF-EMF exposures and makes
recommendations on policy and further research.
Board of the NRPB issued a Response
on its implications for
future research and EMF exposure limits.
Radiation, Part I: Static and Extremely Low
Frequency Electric and Magnetic Fields
Monograph by the
International Agency for Research on Cancer IARC
Monographs, Volume 80 (2002)
This risk assessment is part of a
highly-respected international program to
evaluate all carcinogens. The complete monograph
is available as a PDF file.
Evaluation of the Possible Risks from Electric
and Magnetic Fields (EMFs) from Power Lines,
Internal Wiring, Electrical Occupations and
(Report from the California EMF Program (2002)
This report by the California Department of
Health Services evaluates the evidence for the
risks of all diseases from exposures to
residential and occupation ELF-EMF,
concentrating on more recent studies. It uses a
new method of risk assessment, based on the
Bayesian philosophy of science. Public comments
and criticisms of this report are posted on the
same website. The California EMF Program also
Policy Options in the
Face of Possible Risk from Power Frequency
Electric and Magnetic Fields (EMF) analyzes possible government actions under
different regulatory philosophies, including a
cost-benefit analysis for power line
Extremely Low Frequency Fields – Environmental
Health Criteria 238 Monograph from the World
Health Organization (2007)
monograph reviews all aspects of ELF-EMF health
risks, research and hazard management. It also
makes recommendations for occupational health
policy, including precautionary measures to deal
with the possible cancer risks.
Minimize Your Risk:
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.
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
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
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.
NIEHS and NIH Report on the Electric and Magnetic Fields Associated with the
use of Electric Power
Institute of Health Sciences on EMF
EPA Electric and
Magnetic Field (EMF) Radiation from Power Lines
WHO on Electromagnetic Fields and Human Health
CDC on Electric and Magnetic
Electromagnetic Fields; Wisconsin Public Service Commission 2008 Report
Duke Energy Frequently Asked Questions