QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/files/arrl/tis/bio.txt

Text File | 1994-11-27 | 22KB | 438 lines

Subject: Electromagnetic Fields and Your Health

Are the electromagnetic fields generated by power lines, TVs
ham radio gear and hundreds of other devices bathing us
in damaging radiation? The jury is still out, but you can
take steps to protect yourself from danger--real and
potential.

By Wayne Overbeck, N6NB
   14021 Howland
   Tustin, CA 92680

     There is a growing public debate about the safety of
electric power lines and the electrical equipment that we
use every day in our homes and workplaces. Not long ago, a
lawsuit was filed alleging that a Florida woman's brain
cancer was caused by electromagnetic radiation from a hand-
held cellular telephone. Although the filing of a lawsuit
proves nothing (thousands are filed every week, and this one
was promptly dismissed by a court), the lawsuit made
national headlines for weeks and caused cellular telephone
industry stock prices to decline on Wall Street.

     The news media regularly cover many facets of the
controversy over the possible health effects of
electromagnetic fields (EMFs). In addition to stories about
lawsuits, there have been numerous media accounts of medical
research concerning EMFs--some of them confusing and
seemingly contradictory. And there have been news stories
about activist groups fighting the construction of new power
lines or cellular telephone towers in their neighborhoods.

     This intense publicity has alarmed many people,
prompting them to worry about the safety of their homes,
neighborhoods, schools and workplaces. There is a growing
concern that the electromagnetic fields produced by power
lines and everyday household appliances may be hazardous.
As the tension mounts, more and more hams are faced with
this difficult question: Is your Amateur Radio station
hazardous to our health?

     Fortunately, enough research has now been done that we
know most Amateur Radio activities are quite safe. In fact,
scientists from the Federal Communications Commission and
the Environmental Protection Agency conducted a field survey
of EMFs at typical Amateur Radio stations in 1990. They
concluded that most amateur operations do not produce EMFs
strong enough to pose any health hazard. And for many years,
the American Radio Relay League's Board of Directors has
also been monitoring the ongoing research about EMFs and
health through a board-appointed Committee on the Biological
Effects of RF Energy. There is extensive coverage of the
issue of EMFs and health in both The ARRL Handbook and The
ARRL Antenna Book--with recommendations for safe Amateur
Radio operating practices.

     Amateur Radio is a hobby that can be pursued safely,
provided everyone observes a few simple precautions. This
article was written to summarize what we know about EMFs and
health, and to suggest safe operating practices.

Scientific Background

     When scientists talk about electromagnetic fields,
they're talking about several very different forms of
energy. Low frequency or "power-line frequency" fields are
produced by electric power lines and appliances, typically
operating at a frequency of 60 Hz. Much research is now
underway concerning the health effects of 60-Hz fields--the
kind of EMFs found in virtually every home and workplace.
Additional research is being done to investigate the
possible health effects of radio frequency (RF) energy,
which is much higher in frequency than the electric energy
in power lines. RF energy is produced by radio and
television transmitters, radar installations, cellular and
cordless telephones, microwave ovens and even remote
controls for garage door openers.

     Low-frequency and RF energy are forms of nonionizing
radiation: The frequency is too low to produce enough photon
energy to ionize atoms. In contrast, ionizing radiation--
which is not produced by power lines or radio transmitters--
can cause severe and well-documented health hazards. Nuclear
weapons produce enormous amounts of ionizing radiation,
while small, carefully controlled doses of ionizing
radiation are used in medical X-ray equipment, for example.

     The present controversy concerns nonionizing radiation,
including power-line frequency and RF energy. Much is now
known about the biological effects of this kind of energy,
but there is much more that we do not yet know. Before World
War II, scientists knew that non-ionizing radiation could
produce thermal (heating) effects. At sufficiently high
power levels, EMFs can cause body heating, which may result
in health hazards such as blindness or sterility. Most
ordinary household appliances and transmitted radio signals
produce EMFs far weaker than those required to produce
thermal effects. On the other hand, microwave ovens do
generate EMFs strong enough to produce thermal effects:
That's precisely why they can heat and cook food. The trick
is to keep the EMFs safely inside the oven--away from
people. For obvious reasons, microwave ovens must meet
strict safety standards.

     In recent years, a new element in the debate over EMFs
and health has been the finding that even at athermal
levels--energy levels too low to cause body heating--
electromagnetic energy appears to have various effects on
the human body. The first scientists whose work in this area
gained widespread media publicity were epidemiologists--
medical researchers who look at the health patterns of large
groups of people, using statistical methods.

     Over the last two decades, a number of epidemiological
studies have found that electrical workers have higher-than-
normal death rates from certain cancers, including leukemia,
lymphatic cancer and brain cancer. Other epidemiological
studies have shown that children living near some types of
power lines have higher-than-normal rates of leukemia. Still
other studies have concluded that persons exposed to certain
chemical agents such as solder fumes in addition to high
EMFs have up to 10 times the normal rate of certain cancers.

     All of these studies involved groups of people who were
not ordinarily exposed to EMFs strong enough to cause body
heating. Thus, their health patterns suggested that low-
level EMFs may pose health hazards.

     There have been other epidemiological studies, however,
that did not confirm some of these findings. And still other
researchers have concluded that environmental factors such
as the alignment of the earth's natural magnetic field may
interact with man-made EMFs to alter these health effects.
(The earth's magnetic field is stronger than many man-made
fields, but it is a static, direct-current field. Most man-
made EMFs are alternating-current fields operating at a
variety of frequencies and power levels.)

     There are other dimensions to this problem, too. Some
of the research that failed to confirm a correlation between
EMF exposure and health was funded by industry groups that
have a financial stake in the outcome of the research.
Critics have challenged the credibility of some of the
research for that reason. Moreover, epidemiological research
only reveals health patterns; it does not prove what caused
those health patterns. If electrical workers have an
abnormally high rate of certain cancers, that may result
from their occupation--or it could result from something
else. In short, the work of epidemiologists shows
correlations without proving causation. That raises
troubling questions without providing definitive answers.

     Responding to the questions raised by epidemiologists,
a number of medical researchers have launched laboratory
based studies of the effects of EMFs on living tissue. There
has been an explosion of knowledge about molecular biology
and the related field of genetics in recent years, and one
of the focal points of this research has been the role of
electromagnetic signals at the molecular level. Among other
things, there have been studies suggesting that certain
types of electromagnetic fields may alter the body's genetic
makeup, causing chromosome damage.

     It is also known now that some EMFs may disrupt the
flow of vital chemical and electrical signals between cells
in the human body. EMFs appear to alter the passage of
chemical and electrical signals through the cell membrane
(the thin layer of material that covers each cell). This has
caused some scientists to conclude that EMFs may sometimes
affect the work of the body's immune system in fighting
cancer.

     If the body's cancer-fighting T-cells fail to detect
that a particular cell has become cancerous because cell-to-
cell communication is disrupted by EMFs, that would increase
the risk of a tumor developing. There is also laboratory
research indicating that EMFs may inhibit the body's cancer-
fighting ability in other ways.

     Researchers have found that certain EMFs reduce the
activity of messenger enzymes called protein kinases and
also affect the way cell growth is regulated. There is also
evidence, now confirmed through research in several
countries, that EMFs sometimes work together with cancer-
promoting chemicals to increase the risk of cancer beyond
that associated with either the chemicals or EMFs alone.

     EMFs also appear to change the body's rate of
production of certain hormones that have cancer-inhibiting
effects, such as melatonin. Some studies have found that
persons sleeping under electric blankets have lower-than-
normal levels of melatonin production when the blanket is
operating, but their melatonin production returns to normal
when the blanket is switched off. Some scientists think the
effect of EMFs on melatonin production may explain many of
the apparent health effects of exposure to low-level fields.

     As with the epidemiological studies, laboratory
research has raised questions and stirred controversy. Some
laboratory studies have been difficult to replicate: Other
researchers have not always observed the same results when
they attempted to repeat some experiments. There appear to
be other variables that affect the outcome of research on
the biological effects of EMFs.

     For example, there is evidence that low-level EMFs have
significant biological effects only at certain frequencies
and intensities--and not at other frequencies or
intensities. There is a general rule about toxic and cancer-
causing chemicals: If some is bad, more is worse. That rule
may not necessarily apply to EMFs, however: Some studies
have detected biological effects of low-level EMFs--but not
when the field is stronger.

     There are also studies showing health effects at certain
frequencies but not at adjacent frequencies. And there are
studies suggesting that a radio signal modulated by certain
low frequencies, or a signal that is keyed or pulsed, has
more harmful effects than an unmodulated, steady carrier.
Scientists call these kinds of phenomena window effects, and
they greatly complicate any attempt to understand the
relationship between EMFs and health.

     There is an unfortunate footnote to this research on
window effects: Much research seems to indicate that there
is a window at 50 or 60 Hz--the exact frequency of the
electric energy traveling through millions of miles of in-
home wiring in the US and many other countries: EMFs at
higher and lower frequencies may not have the same health
effects as 60-Hz fields. And yet, the financial and
technical obstacles that would stand in the way of changing
the frequency of ordinary household ac current--should that
prove to be desirable--are staggering.


Safe Operating Practices

     After reading this far, if you are uncertain about the
possible health effects of EMFs, you're not alone: The
scientific community itself does not agree about this issue.
In fact, medical doctors, biologists, physicists and other
scientific researchers are engaged in an intense, sometimes-
emotional debate about the health effects of EMFs. There is
a computer bulletin board system for scientists concerned
about this issue; messages posted there range from esoteric
discussions of these complex issues to personal attacks on
some scientists who espouse views not shared by others!

     If the experts don't always agree, how can the rest of
us know what is safe and what isn't? The American National
Standards Institute (ANSI), a private body that sets
voluntary standards for industry, has had guidelines for
exposure to EMFs for many years. In fact, the ANSI
guidelines have been revised downward repeatedly to reduce
the recommended safe levels of EMF exposure.

     ANSI adopted its latest guidelines in 1992, but many
health scientists have questioned whether even the newest
guidelines are adequate to protect public health. Recently,
the Environmental Protection Agency publicly questioned the
adequacy of the 1992 ANSI standards in an official statement
to the Federal Communications Commission.

     Some scientists challenge the newest ANSI standard on
several grounds. For one thing, it's primarily intended to
prevent exposure to EMFs strong enough to cause thermal
effects, not exposure to weaker EMFs that may cause athermal
effects. Nor does the ANSI standard take into account the
effects of modulation. And the ANSI standard applies only to
RF energy, not to low-frequency EMFs that are so central to
public debate these days.

     There is no generally accepted standard in America for
exposure to the low-frequency fields produced by power lines
or home appliances. And in general, there is considerable
uncertainty about what level of electromagnetic energy
should be considered safe.

     Another problem is that RF fields are difficult to
measure. The price of a professional quality RF power
density meter runs well into four figures, and low-cost
meters for home use are often grossly inaccurate. Even the
best meters may not be accurate in the near field, the area
close to an antenna where the potential for hazardous RF
energy levels is greatest.

     Field strengths can be calculated using mathematical
formulas, but that, too, fails to take into account the
random hot spots that often exist in the near field.
Fortunately, the low-frequency fields from power lines and
appliances are easier to measure than RF power densities.

     If there is no consensus about safe energy levels, and
if EMFs are difficult to measure, what can we do to
minimize the potential health hazards of EMFs?

     Several years ago, Professor M. Granger Morgan of
Carnegie Mellon University offered a simple proposal:
practice prudent avoidance. Dr Morgan said we should avoid
unnecessary exposure to EMFs as a common-sense response to
potential--but not yet proven--health hazards. He didn't
suggest that we all abandon our electric appliances and go
off to live in the woods in cabins without electricity, but
he did suggest that we minimize exposure to EMFs when it's
practical to do so.

     He said, in essence, to avoid electromagnetic fields
strong enough that they may have adverse health effects. The
League has adopted Dr Morgan's approach: The RF safety
sections of major ARRL publications urge radio amateurs to
practice prudent avoidance wherever possible.

     Which amateur operating practices are clearly safe, and
which ones might be hazardous? Here are some suggestions
based on guidelines developed by the League's Bio-Effects
Committee:

     * Transmitting antennas should be mounted well away
from living areas. If medium or high transmitter power (100
watts or more) is to be used, antennas should be mounted on
a mast or tower at least 35 feet above any populated area if
possible. The FCC/EPA study indicated that with an antenna
that high, there is little RF energy where people are.

     Because feed lines can radiate in some cases, when
installing open-wire line (or even coaxial cable if the SWR
on the line is high), it's best to route it away from areas
where people will be spending a lot of time.

     * When using a ground-mounted or mobile antenna, be
careful not to transmit when anyone is near the antenna. A
good rule of thumb is to avoid transmitting when anyone is
within three feet of a car-mounted 2-meter FM whip if you're
using a typical 25-watt transceiver. With a 100-watt
amplifier, don't transmit when anyone is within five or six
feet of a whip antenna. If you're using a beam antenna and
100 watts or more, follow the 35-foot rule: Don't transmit
when anyone is within 35 feet of the front of the antenna
(the direction where the antenna is pointed). It may be safe
to transmit when people are a little closer to the antenna
if everyone is below it or behind it, not in front of it.

     * Exercise particular care when using indoor antennas,
including those mounted in attics, because in some
situations they can generate substantial RF fields. As much
as possible, try to locate indoor antennas as far from
people as possible. Use low power (10 watts output or less),
and keep your transmissions short when someone might be near
the antenna.

     * Never use a power amplifier that has its metal cover
removed. The cover provides shielding, keeping the RF energy
inside the unit--not out in the room.

     * If you're going to experiment with UHF or microwave
equipment, or do moonbounce communications, discuss your
installation with experienced operators before getting on
the air. UHF and microwave antennas and waveguides--as well
as high-gain moonbounce antennas--may produce hazardous
levels of RF energy and must be installed carefully so that
no person is in the line of fire. Never look into an
activated waveguide or stand in front of a high-gain VHF-UHF
antenna when the transmitter is on.

     * When using a hand-held transceiver, use the lowest
power possible and keep the antenna as far from your head as
possible. Within the scientific community, there is
disagreement about the safety of "handy talkies." Most hand-
helds have been exempt from the ANSI standard because their
power output is too low to produce significant whole-body
heating. However, there is growing evidence that even one-
or two-watt hand-held radios may produce significant EMFs
within the user's head, with possible health effects that
are not yet fully understood. (The potential for a health
hazard is greatly reduced when a hand-held radio is used in
its low-power position, with only a fraction of a watt of
output power.)

     * Be aware that low-frequency fields exist in your
home. If possible, avoid being within 24 inches of any
electric motor or power transformer while it is turned on.
Hair dryers, ac-operated hand drills and other electric
devices that are held close to the body when in use often
expose users to stronger EMFs than those produced by Amateur
Radio equipment. Nevertheless, it is a good idea to stay
about 24 inches away from the fans and power transformers
found in high-power amplifiers and 12-volt power supplies,
for example.


Further Information

     The issue of electromagnetic fields and health is as
complex as it is controversial. It isn't possible to cover
this topic fully in a short article such as this one. A more
detailed and technically-oriented treatment of the subject
appears in the "RF safety" sections of current editions of
The ARRL Handbook and The ARRL Antenna Book. The
bibliography there lists some of the major scientific works
in this field.

Wayne Overbeck, N6NB, holds PhD and JD degrees and is a
Professor of Communications at California State University,
Fullerton. He is a member of the ARRL Bio-Effects Committee,
and first became interested in this subject because his own
operating activities--VHF DXing and contesting with high
power portable stations on mountaintops--require special
precautions to minimize EMF exposure.


Captions for Overbeck's Bioeffects article:

[Photos A and B go together]

PHOTOS A and B: This 3-element 6-meter beam is only a few feet above
N6NB's second-story hamshack. When the antenna is pointed toward
the operating position, fields in excess of ANSI standards were
measured were measured in the shack on a laboratory-grade hazard
monitor. The transmitter power output was set to 900 watts.


PHOTO C: Dr Robert Cleveland (FCC) and Ed Mantiply (EPA) measure
RF fields generated by a hidden wire antenna at a condominium
complex. When local restrictions force hams to use indoor or
hidden antennas, extra safety measures should be taken.


[photos D and E go together]

PHOTOS D and E: Many home appliances produce strong low-frequency
electromagnetic fields. The 60-Hz field generated by this hand
drill, for example, is in excess of 1200 milliGauss. In contrast,
the field 12 inches in front of the 1-kW Amateur Radio amplifier
is about 10 mG. The main sources of 60-Hz fields in ham gear are
power transformers and cooling fans.