Various organizations divide electromagnetic waves into frequency
bands or ranges. Frequency is expressed in terms of a unit called the hertz
(Hz). One Hz equals one cycle per second. One kilohertz (kHz) equals one
thousand cycles per second. The names of the frequency bands can cause
confusion because different organizations may use the same band name for
different frequency ranges. This site provides information on Very Low
Frequency (VLF) and Extremely Low Frequency (ELF). For the purposes of this
web site, ELF is defined as >0 Hz to 3 kHz, and VLF as from 3 kHz to
roughly 300 kHz. Frequencies above this range are known as “radiofrequency”
(RF). For information on RF waves, see the NC Radiation Protection RF page.
By far the most common and widespread source of ELF
exposure is the electrical power grid, which operates at 60 Hz in the US
and 50 Hz in most other countries. We are all exposed to electromagnetic fields from the earth itself and
from human-made sources. Examples of human-made sources include power
lines, household wiring, and electrical appliances. The Federal
Communication Commission (FCC), in cooperation with other groups, allocates
the electromagnetic spectrum for various applications. You can see a chart
listing the types of ELF and VLF sources at each frequency here.
·
Low
Frequency. Review
of the Epidemiologic Literature on EMF and Health. International
Commission on Nonionizing Radiation Protection (ICNIRP). These sites
provide an overview of known health effects of exposure to ELF fields.
·
Electromagnetic
Fields. Extremely
Low Frequency Fields. World Health Organization (WHO). Links to studies
and publications.
·
Electric &
Magnetic Fields. National Institute of Environmental Health Sciences
(NIEHS), National Institutes of Health (NIH).
·
Electromagnetic
Fields. Wisconsin Public Services Commission.
Leukemia and Other Cancers Electric &
Magnetic Fields. National Institute of Environmental Health Sciences
(NIEHS), National Institutes of Health (NIH). 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; Monograph
Minimize Your Risk:
If you worry about your exposure to even low levels of
ELF fields, simple steps can reduce your exposure. The strength of these
fields drops quickly with increasing distance from the source. Therefore,
spending less time right next to large appliances and electric power lines
will greatly reduce your exposure.
Although extremely low frequency (ELF) exposures occur
everywhere, the potential hazard depends on the strength of the ELF fields
at the source, the distance from the source, and the duration of exposure.
Some people claim that a small percentage of the population can sense even
low-level electromagnetic fields, but most of us cannot detect the presence
of ELF fields with just our senses.
Measuring ELFs yourself with the use of a
gaussmeter is very difficult, therefore if you are concerned about ELFs
emitted by a power line or substation in your area, contact your local
power company to schedule an on-site reading.
Exposure Limits:
Based on the known thresholds for biological effects,
scientific consensus organizations have set “safe” exposure limits for ELF
and VLF. No known harmful effects occur at levels below these limits.
Organizations that have published these exposure limits include the
International Commission on Nonionizing Radiation Protection (ICNRP),
The Institute of Electrical and Electronics Engineers (IEEE), and the
American Conference of Governmental Industrial Hygienists (ACGIH). One
set of limits covers the general public. A higher
set of limits applies to workers trained in the hazards and protective
measures. Members of the general public will not
exceed the public exposure limits under normal circumstances. Workplace
exposures in some industries (for example, electric power utilities,
foundries, and other sites the handle very large electrical loads) may
exceed the public limits.
Additional information on workplace exposure to ELF
appears at:
·
Extremely
Low Frequency (ELF) Fields. American Industrial Hygiene Association
(AIHA) Position Statement.
·
NIOSH Fact Sheet: EMFs in the
Workplace NIOSH Publication No. 96-129.
·
Extremely
Low Frequency (ELF) Radiation. Occupational Safety and Health
Administration (OSHA).