The effects of electromagnetic fields have been
studied since the 1950s. Currently, the database of the International
Electromagnetic Field Project (updated to August 2006) indicates a
total of 2,462 studies of different types, of which 2,346 pertain to
radiofrequency, including 1,137 on mobile telephony.
Type/subtype of study
Engineering & physics
Literature review, reports
Table 02. Summary of study
of radiofrequency electromagnetic fields
The above data was
taken from the following World Health Organization web page:
From the outset, it is
advisable to distinguish clearly between biological effects and health
effects. Biological effects are measurable physiological responses to
exposure to electromagnetic fields that are not necessarily dangerous
to health; whereas adverse health effects are biological effects
outside the body’s normal range of physiological compensation that are
detrimental to human health or well-being.
The energy quanta of
radiofrequencies, including mobile telephony, are extremely small,
from 4 to 7 µeV, and are not capable of altering molecular structure
or breaking molecular bonds. The maximum energy of a quantum at 300
GHz is 1.2 millielectron volts (meV). By comparison, the energy for
thermal movement at 30° C is 26 meV. To disrupt the weakest hydrogen
link requires 80 meV; and to break the weakest links of DNA molecules,
1 eV is required (Durney, C., Massoudi, H., Iskander, M., 1982; IEGMP,
rarely occur at average levels of exposure to RF well below thermal
levels, but current evidence does not enable possible biological
effects to be ruled out at levels below the international permissible
maximum limits. However, this will not necessarily imply health
effects. (ICNIRP, 98; IEGMP, 2000).
produce other effects that would only be detectable if the effects of
internal electrical fields are not masked by thermal noise resulting
from random movement and vibration of components of biological issue
as a result of the thermal energy above absolute zero possessed by all
effects investigated are those derived from movement of ions resulting
from the action of internal electrical fields, it being found that
both movement and energy are much less those caused by thermal
movement. Therefore, it can safely be concluded that movement of ions
resulting from electrical fields below thermal levels cannot produce
mechanism is that associated with the passage of current through cell
membranes, which act as rectifiers which, with the passage of
alternating current, would give rise to net potential over the
membrane. However, as the rectifiers of ions are much slower than
mobile telephony frequencies for internal field levels associated with
real exposures, the change in membrane potential would be negligible.
The results of the
scientific evidence of cell and animal studies show that neither acute
nor chronic exposure to radiofrequency, including mobile telephony,
fields – when maintained within thermoregulatory limits – can increase
the frequency of chromosomal aberration or mutation, but may cause a
slight increase in levels and activity of
Generally speaking, changes are too small to give rise to or promote
the development of cancer (ICNIRP, 1998; IEGMP, 2000).
Cell, animal, and
human studies show that pulsating signals, such as those corresponding
to mobile telephony, can cause changes in neuronal excitability,
neurotransmitter function, and innate and learned behavior if the
temperature of internal or local organs increases by about 1°C.
Otherwise, evidence is general inconsistent and unconvincing.
There is also evidence
of slight modifications in cerebral electrical activity (changes in
EEG rate) or evoked visual and auditory potentials in waking persons,
disturbance of some stages of sleep of sleeping persons, memory loss,
and changes in attention and in blood pressure. These biological
effects would occur at lower than thermal levels. However, they do
not compromise human health, disappearing when exposure ceases (IEGMP,
Effects on the
hematopoietic and immunological systems and on longevity
At low levels of
exposure to mobile telephony signals, related studies do not report
effects on blood formation and circulation-related cells (e.g.,
changes in the number of bone marrow cells, lymphocytes, or
erythrocytes, or in the number of hematocytes.
Exposure at thermal
levels implies stimulation or inhibitory immunological system
responses, but such effects are generally temporary, and return to
normal levels when exposure has ended. The results of exposure at low
levels are inconsistent.
Studies of the effect
on longevity of exposure to RF signals show no influence on human
length of life (IEGMP, 2000).
Reproductive and developmental effects
Animal studies provide
no evidence that exposure to radiofrequency signals, including from
mobile telephony, constitutes a risk to fetuses or to male fertility (ICNIRP,
Effects on the
cardiovascular system and blood pressure
Animal and human
studies show no effect whatsoever on the heart, circulation, or blood
pressure. Effects at high intensities appear to be due to thermal
effect (ICNIRP, 1998; IEGMP, 2000).
Studies of the high
incidence of headaches, anxiety, or stinging or heat sensations among
mobile telephone users are on the whole inconclusive. The symptoms
are real and there are indications that their causes may lie in pre-existing
psychiatric conditions and stress, rather than in electromagnetic
fields (IEGMP, 2000; OMS, 2005).
These are caused by
increases in body temperature produced by absorption of time variable
electromagnetic fields. Such absorption is due to the force exerted
by an electrical field on charged bodies, such as free ions within the
body, which cause their movement, resulting in electrical currents
which, on interacting with the electrical resistances of the
biological matter of the body, produce heat.
With regard to thermal
effects on the head, in a recently published study (Van Leuven et al.,
1999), the distribution of heat within the head was calculated by
adjusting a finite difference model in the time domain for SAR to a
new thermal model. The thermal model includes the convective effects
of discrete blood vessels whose anatomies were determined using the
magnetic resonance angiography of a healthy volunteer. For a bipolar
antenna at 915 MHz with time average power of 0.25 W (equivalent to a
typical mobile telephone), this study produced an SAR of nearly 1.6 W/kg
and predicts a maximum steady state increase in brain temperature of
evidence indicates that exposure to EMF by resting humans for
approximately 30 minutes producing an SAR throughout the body of
between 1 and 4W kg-1 results in an increase in body temperature of
less than 1° C. Animal data indicate an SAR threshold in the same
range. For behavioral responses, exposure to stronger fields that
produce SAR values above 4 W kg-1, the body’s thermoregulatory
capacity may break down and produce harmful levels of tissue warming.
Many non-human laboratory studies with rodents and primates have
demonstrated the broad spectrum of tissue damage resulting from
partial or total warming of the body produced by temperature increases
above 1-2° C. Sensitivity to thermal damage of the different tissue
types varies widely, but the threshold for irreversible effects on
more sensitive tissue is 4 W kg-1 and above, under normal
environmental conditions. Such data constitutes the basis for
occupational exposure limits of 0.4 W kg-1, which provides a large
margin of safety for other limiting factors, such as ambient
temperature, humidity, or levels of physical activity.
Laboratory data and
the results of a small number of human studies (Michaelson and Elson
1996) make evident that enervating thermal environments and the use of
drugs or alcohol may compromise the body’s thermoregulatory ability.
In such conditions, safety factors should be introduced to provide
adequate protection to exposed individuals.
To summarize, it may
be said that of the research conducted:
It is known that
exposure to radiofrequency fields causes health effects above 4 W/kg,
causing changes in behavior and reducing resistance as a result of
heat. That is, thermal effect is the only established effect for
The organs most
sensitive to heat are the least irrigated, i.e., the eyes and gonads.
Thermal effect is the
basis for international standards, and no effect has been established
below these limits.
Use of mobile terminals by children
documents (IEGMP, 2000; Direction Générale de la Santé de France,
2001; NRPB, 2004) recommend precaution in regard to mobile telephone
use, suggesting that mobile telephony operators not encourage the use
of mobile telephones by children under the age of 16, as they might be
more vulnerable to potential future health effects for the following
children’s nervous systems is fully under way
Absorption in the
head is greater in children than in adults as children’s skull bones
As the diameter of
the head is smaller, radiation can more easily reach the most vital
would be greater than it is for persons who begin mobile telephone
use in adolescence or adulthood.
International Electromagnetic Fields Project
National Institute for Telecommunication Research and Training (INICTEL-UNI)
Additional Information: The
National Institute for Telecommunication Research and Training
(INICTEL-UNI) will offer from June 4 to
July 13, 2007 a
distance learning course on Environmental Management of
Electromagnetic Fields in Telecommunications Course. CITEL offered
scholarships of the registration fee. This article is part of the material of the
course. Mr. Cruz is the tutor of the course. These
scholarships are subject to the availability of funds
corresponding to the 2007 regular budget.
INICTEL-UNI is CITEL’s Regional Training Center and ITU’s
Excellence Network Node.