Electrical devices
and systems produce two different fields: an electric field like the
one produced on the surface of a wool sweater on a dry winter day,
and a magnetic field like the fields produced by a compass needle,
a small magnet or the earth itself. These fields in combination are
referred to as electromagnetic fields or EMF. EMF fields associated
with electrical devices and appliances are produced only when the
device is plugged in and operating. Devices which generate electromagnetic
fields include radio or TV station transmitters, microwave ovens,
power transmission lines, and electrical appliances.
Radiofrequency
(RF) and microwave (MW) radiation are electromagnetic radiation in
the frequency ranges 3 kilohertz (kHz) - 300 Megahertz (MHz), and
300 MHz - 300 gigahertz (GHz), respectively. RF and MW radiation are
non-ionizing in that there is insufficient energy to ionize atoms.
The primary health effect of RF/MW energy is a result of heating.
The absorption of RF/MW energy varies with frequency. Microwave radiation
is absorbed near the skin, whereas RF radiation may be absorbed in
deep body organs. Exposure standards are based on preventing thermal
problems. However, research continues on possible "non-thermal"
effects. Use of RF/M radiation includes: radios, cellular phones,
processing and cooking of foods, heat sealers, vinyl welders, high
frequency welders, induction heaters, flow solder machines, communications
transmitters, radar transmitters, ion implant equipment, microwave
drying equipment, sputtering equipment and glue curing.
Exposure to the
very high intensity electromagnetic fields found in the immediate
vicinity of certain sources such as radar installations and TV or
radio transmitters can produce electrical shock or a variety of heating
effects, which may range from a sensation of warmth to burns and eventual
cataract formation.
The National
Research Council conducted a review of the many studies which have
examined the effects and risks of exposure to low intensity EMF. The
Council's conclusion, in a report released on October 31, 1996, states
that "No clear convincing evidence exists to show that residential
exposures to electric and magnetic fields (EMFs) are a threat to human
health." The nature of most of the exposures to individuals at
Brown University are comparable to residential exposures, i.e., exposures
to common electrical devices and appliances which do not produce unusually
high intensity EMFs. However, there is one category of equipment that
needs special attention, namely Nuclear Magnetic Resonance (NMR).
For more information
please refer to the following links::
NMR Safety -
http://display.engin.brown.edu/main/safety-nmrsafety.php
Related Sites
- http://www.osha.gov/SLTC/radiofrequencyradiation/
