 Electric fields are created by differences in voltage: the
higher the voltage, the stronger will be the resultant
field. Magnetic fields are created when electric current
flows: the greater the current, the stronger the magnetic
field. An electric field will exist even when there is no
current flowing. If current does flow, the strength of the
magnetic field will vary with power consumption but the
electric field strength will be constant.
Natural sources of electromagnetic
fields
Electromagnetic fields are
present everywhere in our environment but are invisible to
the human eye. Electric fields are produced by the local
build-up of electric charges in the atmosphere associated
with thunderstorms. The earth's magnetic field causes a
compass needle to orient in a North-South direction and is
used by birds and fish for navigation.
Human-made sources of electromagnetic
fields
Besides natural sources the
electromagnetic spectrum also includes fields generated by
human-made sources: X-rays are employed to diagnose a broken
limb after a sport accident. The electricity that comes out
of every power socket has associated low frequency
electromagnetic fields. And various kinds of higher
frequency radio waves are used to transmit information –
whether via TV antennas, radio stations or mobile phone base
stations.
Summary of health effects
What happens when you are exposed to
electromagnetic fields?
Exposure to electromagnetic
fields is not a new phenomenon. However, during the 20th
century, environmental exposure to man-made electromagnetic
fields has been steadily increasing as growing electricity
demand, ever-advancing technologies and changes in social
behavior have created more and more artificial sources.
Everyone is exposed to a complex mix of weak electric and
magnetic fields, both at home and at work, from the
generation and transmission of electricity, domestic
appliances and industrial equipment, to telecommunications
and broadcasting.
Tiny electrical currents exist
in the human body due to the chemical reactions that occur
as part of the normal bodily functions, even in the absence
of external electric fields. For example, nerves relay
signals by transmitting electric impulses. Most biochemical
reactions from digestion to brain activities go along with
the rearrangement of charged particles. Even the heart is
electrically active - an activity that your doctor can trace
with the help of an electrocardiogram.
Low-frequency electric fields
influence the human body just as they influence any other
material made up of charged particles. When electric fields
act on conductive materials, they influence the distribution
of electric charges at their surface. They cause current to
flow through the body to the ground.
Low-frequency magnetic fields
induce circulating currents within the human body. The
strength of these currents depends on the intensity of the
outside magnetic field. If sufficiently large, these
currents could cause stimulation of nerves and muscles or
affect other biological processes.
Both electric and magnetic
fields induce voltages and currents in the body but even
directly beneath a high voltage transmission line, the
induced currents are very small compared to thresholds for
producing shock and other electrical effects.
Heating is the main biological
effect of the electromagnetic fields of radiofrequency
fields. In microwave ovens this fact is employed to warm up
food. The levels of radiofrequency fields to which people
are normally exposed are very much lower than those needed
to produce significant heating. The heating effect of
radiowaves forms the underlying basis for current
guidelines. Scientists are also investigating the
possibility that effects below the threshold level for body
heating occur as a result of long-term exposure. To date, no
adverse health effects from low level, long-term exposure to
radiofrequency or power frequency fields have been
confirmed, but scientists are actively continuing to
research this area.
Biological effects or health effects?
What is a health hazard?
Biological effects are
measurable responses to a stimulus or to a change in the
environment. These changes are not necessarily harmful to
your health. For example, listening to music, reading a
book, eating an apple or playing tennis will produce a range
of biological effects. Nevertheless, none of these
activities is expected to cause health effects. The body has
sophisticated mechanisms to adjust to the many and varied
influences we encounter in our environment. Ongoing change
forms a normal part of our lives. But, of course, the body
does not possess adequate compensation mechanisms for all
biological effects. Changes that are irreversible and stress
the system for long periods of time may constitute a health
hazard.
An adverse health effect
causes detectable impairment of the health of the exposed
individual or of his or her offspring; a biological effect,
on the other hand, may or may not result in an adverse
health effect.
It is not disputed that
electromagnetic fields above certain levels can trigger
biological effects. Experiments with healthy volunteers
indicate that short-term exposure at the levels present in
the environment or in the home do not cause any apparent
detrimental effects. Exposures to higher levels that might
be harmful are restricted by national and international
guidelines. The current debate is centered on whether
long-term low level exposure can evoke biological responses
and influence people's well being.
Widespread concerns for health
A look at the news headlines
of recent years allows some insight into the various areas
of public concern. Over the course of the past decade,
numerous electromagnetic field sources have become the focus
of health concerns, including power lines, microwave ovens,
computer and TV screens, security devices, radars and most
recently mobile phones and their base stations.
Effects on general health
Some members of the public have attributed a diffuse
collection of symptoms to low levels of exposure to
electromagnetic fields at home. Reported symptoms include
headaches, anxiety, suicide and depression, nausea, fatigue
and loss of libido. To date, scientific evidence does not
support a link between these symptoms and exposure to
electromagnetic fields. At least some of these health
problems may be caused by noise or other factors in the
environment, or by anxiety related to the presence of new
technologies.
Effects on pregnancy
outcome
Many different sources and exposures to electromagnetic
fields in the living and working environment, including
computer screens, water beds and electric blankets,
radiofrequency welding machines, diathermy equipment and
radar, have been evaluated by the WHO and other
organizations. The overall weight of evidence shows that
exposure to fields at typical environmental levels does not
increase the risk of any adverse outcome such as spontaneous
abortions, malformations, low birth weight, and congenital
diseases. There have been occasional reports of associations
between health problems and presumed exposure to
electromagnetic fields, such as reports of prematurity and
low birth weight in children of workers in the electronics
industry, but these have not been regarded by the scientific
community as being necessarily caused by the field exposures
(as opposed to factors such as exposure to solvents).
Cataracts
General eye irritation and cataracts have sometimes been
reported in workers exposed to high levels of radiofrequency
and microwave radiation, but animal studies do not support
the idea that such forms of eye damage can be produced at
levels that are not thermally hazardous. There is no
evidence that these effects occur at levels experienced by
the general public.
Electromagnetic fields and
cancer
Despite many studies, the evidence for any effect remains
highly controversial. However, it is clear that if
electromagnetic fields do have an effect on cancer, then any
increase in risk will be extremely small. The results to
date contain many inconsistencies, but no large increases in
risk have been found for any cancer in children or adults.
A number of epidemiological
studies suggest small increases in risk of childhood
leukemia with exposure to low frequency magnetic fields in
the home. However, scientists have not generally concluded
that these results indicate a cause-effect relation between
exposure to the fields and disease (as opposed to artifacts
in the study or effects unrelated to field exposure). In
part, this conclusion has been reached because animal and
laboratory studies fail to demonstrate any reproducible
effects that are consistent with the hypothesis that fields
cause or promote cancer. Large-scale studies are currently
underway in several countries and may help resolve these
issues.
Electromagnetic
hypersensitivity and depression
Some individuals report "hypersensitivity" to electric or
magnetic fields. They ask whether aches and pains,
headaches, depression, lethargy, sleeping disorders, and
even convulsions and epileptic seizures could be associated
with electromagnetic field exposure.
There is little scientific
evidence to support the idea of electromagnetic
hypersensitivity. Recent Scandinavian studies found that
individuals do not show consistent reactions under properly
controlled conditions of electromagnetic field exposure. Nor
is there any accepted biological mechanism to explain
hypersensitivity. Research on this subject is difficult
because many other subjective responses may be involved,
apart from direct effects of fields themselves. More studies
are continuing on the subject.
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Services:
Electromagnetic Field Investigation
North Bay Office
1990 N. California Blvd., 8th Floor
Walnut Creek, California 94596
(800) 660-1808 Toll Free
(925) 937-0700 Phone
South Bay Office
6472 Camden Ave., Ste. 102B
San Jose, California 95120
(800) 660-1808 Toll Free
(408) 866-4141 Phone
"In May of 2002, I moved into a 20-storey government
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I
immediately began experiencing symptoms of a dizzy-off
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ERT, Inc. to perform an investigation of my unit, and they
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that were affecting my health and wellbeing. I was able to
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ERT, Inc.!"
Melissa
Newkirk
Oakland, CA |
