|
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.
Scientific/Medical:
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.
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:
Comparison of International Policies
on Electromagnetic Fields
Netherlands National Institute for Public Health and Environment
Professional Resources:
Resources:
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.
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
|
