Science, Technology, Environment and Resources Group
The Electromagnetic Spectrum - Radiofrequency
Thermal Effects of Radiofrequency EMR -
Relation to Standards
Energy of RF Radiation from TV and Mobile
Non-Thermal Effects of RF Radiation
The acceptance of mobile phones in Australia has been
phenomenal, a total of about four and a half million being
presently in use. However, not so welcome for many people has been
the sprouting of mobile telephone towers in unexpected places close
to homes and schools. There are now about 2000 of them. It is
reported that expanding phone companies in the US are hiding the
antennae in church steeples, arena lighting, artificial trees and
flagpoles. It is the newness and the close proximity of these
towers that has made them more controversial than the established
radio and TV towers. However, all transmit electromagnetic
radiation (often referred to by officials as
'electromagnetic energy' in order to avoid the term 'radiation')
which some scientists have implicated in increased incidence of
Undoubtedly there has been an aesthetic angle to the debate on
mobile phone tower placement; some residents find them very ugly
and likely to depress house values for that reason alone. But a
Four Corners program in July 1995 alerted many Australians
for the first time to the possible health effects not only of
high-power transmitters but of mobile phone use. Anecdotal but
still compelling accounts of cancer association with exposure to
transmitters and mobile phone use featured in the program. A CSIRO
report of the previous year(1) had urged that more research on
health effects be carried out. Also in 1995, a preliminary study of
cancer incidence in Sydney appeared to show an increase of
childhood leukaemia in homes relatively close to TV
transmitters(2). Meanwhile, there has been a controversial move to
have the existing Australian radiation standard loosened by a
factor of five in order to bring it into line with overseas
This paper is intended to provide background on the two-year
Australian debate on the possible hazards of electromagnetic
radiation from transmitter towers. Of immediate importance is the
prospect of looser national electromagnetic radiation standards,
which raises questions as to the validity of the basis for such
standards in terms of what laboratory or other results have been
relied on for setting standards. The relative energy of radiation
received from transmitter towers compared with hand-held mobile
phones is relevant and is discussed. So also is the range of
reported laboratory effects on test animals and cells observed at
very low levels of radiation near the standard or less; are they
meaningful? The paper concludes with a suggested approach to
experimental work which may help us to determine whether Australian
and world standards are soundly based or not.
For an understanding of the issues involved, it is necessary to
have some knowledge of the range and nature of the
electromagnetic radiation (EMR) spectrum.
Electromagnetic radiation may be thought of in terms of waves in
air which transmit energy but can also be modulated (controlled)
through amplitude, pulsing, etc. to transmit speech, TV images and
so on. These waves have a range or spectrum of frequency expressed
in hertz, i.e. cycles per second. At the higher frequencies we have
kilohertz, megahertz and gigahertz. The greater the frequency, the
shorter the wavelength and the greater the energy transmitted.
A significant division within the EMR spectrum is the frequency
at about 10 million gigahertz above which waves become
ionising in nature, i.e. they are capable of
knocking electrons out of atoms to form ions. Thus ultraviolet
rays, X-rays and gamma radiation are ionising because they are of
greater frequency than 10 million gigahertz. When directed at the
body, such radiation is known to be capable of initiating cancer
through damage to genetic material (DNA). Too much sunlight, too
many X-rays or too much exposure to the gamma-radiating isotope
cobalt-60 can cause cancer.
That part of the EMR spectrum of concern in this paper is
non-ionising and is known as
radiofrequency/microwave radiation (RF radiation
for short). This is defined in the Australian Standard (AS
2772.-1990) as waves having frequencies from 100 kilohertz
up to 300 gigahertz. The radiofrequency spectrum includes,
in increasing order of energy, waves from AM radio, FM radio, TV
(very high and ultra high frequency), mobile phones, police radar,
microwave ovens and satellite stations.
All electromagnetic radiation involves an oscillating electric
field and a magnetic field. Whereas at the extremely low frequency
end of the spectrum (e.g. AC current at 50 or 60 hertz) the two
fields can be measured and considered separately, in the
radiofrequency spectrum they are measured together. The intensity
('power density') of the combined
fields can be readily expressed in terms of a power unit relative
to area (e.g. watts per square
centimetre) which denotes the electric and
magnetic fields as a multiple. Absorption of electromagnetic
radiation energy by living organisms can be expressed in terms of
watts per kilogram. This represents the dose, or more correctly,
the specific absorption rate (SAR). The value for SAR is not always
easy to calculate, especially in respect of individual organs or
Intense waves in the radiofrequency spectrum are readily able to
raise the temperature of, say, a culture of cells brought near the
source of radiation (the principle of the microwave oven) as wave
energy is converted to heat energy on contact with the cells. This
is known as a thermal effect. However, because the
radiation is non-ionising there is no electron stripping of
cellular DNA and therefore no direct initiation of cancer.
Radiofrequency standards to protect health are totally based on
avoiding thermal effects (see below).
The thermal or heating effects of radiofrequency radiation
(including microwaves) on living organisms are well known, they are
dose-related and they are mostly reproducible. These crucial
characteristics have been regarded by many scientists as justifying
the selection of thermal effects as a powerful and single basis for
determining health standards. The following information has been
adapted from information contained in the previously mentioned
CSIRO review report.
Heating caused by RF radiation is caused mainly by water
molecules lining up with the electric field imposed by the
radiation. Since the field is oscillating very rapidly (wave
frequency), the water molecules are rapidly swinging one way then
another in sympathy, thus generating heat. Some biological
molecules are also influenced by applied electric fields.
Exposure of people to a dose of radiofrequency radiation of less
than about 4 watts per kilogram body weight is thought to give rise
to an increase in body temperature of less than 1o Centrigrade and
can be reasonably well tolerated for short periods. Higher induced
temperatures are not tolerated, however, and have several
well-known deleterious effects, depending on the precise location
of radiation absorption. An effect observed at RF intensities
sufficient to raise the rectal temperature of an experimental
animal by 1o C or more is classified as thermal in nature. Such
effects could be induced by any method designed to raise body
- Firstly, the skin can detect RF radiation but
the sensation is much less than that from infrared radiation and is
extremely dependent on frequency which determines penetration. In
the range 0.5-100 gigahertz, skin detection is not regarded as a
reliable warning mechanism.
- Heat effects on brain tissue are thought to be
the reason why people can actually hear pulsed radiofrequencies
between 200 megahertz and 6.5 gigahertz. The sound is described as
'buzzing, clicking, hissing or popping'.
- Thirdly, the eyes are felt to be peculiarly
sensitive to RF radiation. Lens tissue has no blood supply to act
as coolant, there is little self-repair at that site and thus
damage and damage products tend to accumulate. At a threshold of
about 41o C, exposed laboratory rabbits show cataract formation.
Further work needs to be done on the susceptibility of primate
eyes, which seem to be less sensitive.
- Fourthly, rat testes exposed to RF radiation
leading to temperature increases of 1.5-3.5o C are damaged to the
extent that there is temporary infertility and an altered division
pattern of germ cells.
- Fifthly, the thermal disruption of behaviour
by RF radiation, e.g. task learning and short term memory, has been
demonstrated in the rat. Effects were observed at doses between 0.6
and 8 watts per kilogram.
- Sixthly, the circulatory and immune system in
rodents shows some alterations in response to RF radiation. For
example, blood cell counts decline in some experiments while the
immune system appears to be stimulated. Once again, these effects
appear to be thermally induced.
- One laboratory has reported symptoms similar to heat
stroke leading to death in rats following exposure at
three microwave frequencies.
- Lastly, a body temperature of 43o C in pregnant rats brought
about by a dose of 11 watts per kilogram of RF radiation caused
abnormalities and death of embryos. So long as
there is a temperature increase of at least 2.5o C, birth defects
can be expected to occur.
It has already been observed that RF standards are based on the
prevention of thermal effects since these are well accepted in the
scientific community and are generally reproducible. Two standards
will be mentioned here, namely, the American National Standards
Institute/American Institute of Electrical and Electronic Engineers
(ANSI/IEEE) Standard C95.1-1991 and the Australian Standard
2772.1-1990 (Standards Australia). Both are designed for the
RF/microwave spectrum (100 kilohertz to 300 gigahertz).
ANSI power density limits for members of the public vary within
the RF range from a low of 0.2 milliwatts per square centimetre
(mW/square cm) at 100 megahertz to a high of 10 mW/square cm from
about 10 gigahertz. The ANSI standard at the frequency used for
Australian mobile phones (800-1000 megahertz) is slightly less than
1 mW/square cm.
Australian Standard 2772.1-1990 lists a constant limit of 0.2
mW/square cm (equal to 200 microwatts/square cm for members of the
public at frequencies between 30 megahertz and 300 gigahertz. Thus,
at Australian mobile phone frequencies our national standard is
about five times stricter than the ANSI standard.
As is the case for many other US standards, the ANSI
determination is influential here and there is a strong move for
the Australian standard to be loosened by a factor of five in order
to correspond to ANSI's limit. It is therefore important to be able
to assess the basis of ANSI reckoning on RF safety.
According to the CSIRO, the US approach to its standard
has been to consider thermal effects of RF radiation only, and to
regard behavioural changes in experimental animals
as the most sensitive of those effects.
In contrast to ionising radiation, where adverse effects on people
are well documented, RF effects on humans are inadequately
described, which explains the need for animal results. Of course
this raises the immediate question: can experimental animals,
especially small animals, provide an adequate model?
Since it is always necessary to dose non-human primates with
more than 4 watts per kilogram body weight for behavioural effects
to appear, this has been taken by ANSI as the official threshold
for humans. As mentioned earlier, 4 watts per kilogram is also the
approximate threshold for human tolerance of the heat generated. A
tenfold and a fifty-fold safety factor has been applied to the
threshold for occupational and non-occupational exposure limits and
the corresponding power density figure worked out. Thus, the
five-fold stricter Australian (non-occupational) standard is 250
times (i.e. 50x5) below the experimental animal
threshold for thermally induced behavioural changes.
In this paper it has been necessary to describe RF standards and
their basis in some detail in order to assess emissions of
radiation from TV and mobile phone towers. Note that both
telecommunications carriers and broadcasting stations are required
to adhere to Australian Standard 2772.1-1990.
TV towers have a much higher power rating-and thus give out more
intense radiation- than mobile phone towers. For example, the TV
transmitter on top of Black Mountain, Canberra, is rated at 300
kilowatts. A typical mobile phone tower is emitting only about 20
watts, i.e. 15 000 times weaker. Perhaps fortunately, most large TV
towers are situated on hilltops which are relatively far from
housing. It is the occasional exception, for example, on Sydney's
North Shore, that deserves special attention.
Since radiation from both TV and mobile phone towers is not
directed vertically downwards, there is not a simple relationship
between the tower-observer distance and the strength of electric
and magnetic fields combined as EMR. Take firstly the case of
mobile phone towers. Between 0 and 10 metres from a digital mobile
phone tower, levels of exposure are approximately the same. The
level of radiation peaks at between 100 and 150 metres, intensity
values ranging from 0.1 up to 1.0 microwatt/square
cm, depending on how many telephones are in use at the time (note
that one microwatt equals one-thousandth of a milliwatt). Further
away than 10 metres, radiation intensity falls off rapidly,
approximating the 'inverse square' law. Radiation from analogue
mobile phone towers is slightly more intense, peaking at 4-6
microwatts. These figures have been supplied by the Australian
In comparison with the Australian Standard(3) (200
microwatts/square cm), a power density level of 6 microwatt/square
cm from a mobile phone tower (said to be a maximum value)
represents only 3% of the value of the maximum allowable power
density. A more typical figure of 0.1 microwatt/square cm is only
0.05% of the standard.
Turning to larger TV broadcast towers, a person standing one
kilometre away would expect to be exposed to a power density of
5-10 microwatts/square cm of radiation. At two kilometres this
reduces greatly to about 0.5 microwatt/square cm. These figures are
still far less than the prescribed limit of 200 microwatts/square
Dr Bruce Hocking, a former Telstra medical director, has
presented findings in a recent issue of The Medical Journal of
Australia(4) linking leukaemia incidence with proximity to TV
towers . Radiation levels of 8 microwatts/square cm were cited near
the towers, decreasing to 0.2 microwatts/square cm at a radius of 4
kilometres and 0.02 microwatts/square cm at a radius of 12
In summary, children under 15 years of age living in three
Sydney suburbs within 4 kilometres of TV towers (North Sydney,
Willoughby and Lane Cove) appear more likely to suffer from
leukaemia than similarly aged children from Ryde, Kuringai and
Wahroonga, localities more distant from TV towers. The data was
retrieved from the NSW Cancer Registry(5) between 1972 and 1990. A
similar type of study found increased levels of cancer in Honolulu,
Hawaii, among people living near TV towers(6).
Dr Hocking stresses that his results are preliminary but they
show that further research is warranted. The association between TV
towers and cancer is certainly not proven but can be regarded as
'hypothesis-generating'. Dr Hocking also regards the results as
unexpected because the measured radiation levels (up to 8
microwatts/square cm) are so far below the Australian Standard of
200 microwatts/square cm.
Opposition to mobile phone towers placed near houses can only
increase in response to this preliminary finding of a cancer link
in respect of TV transmitters. People tend to feel that sites near
to schools are particularly undesirable because children are
exposed throughout the day, yet have no choice in the matter and
derive no benefit. This is in spite of the fact that mobile phone
towers are of very low power. Mobile phone users have a much
greater exposure to radiation but at least they get the benefit of
the calls as well as being able to control their exposure by
What is the RF exposure from personal mobile phone use as
compared with exposure to a mobile phone tower? As described above,
such towers radiate very small power densities of not more than
about 6 microwatts but more typically 0.1 microwatt/square cm at
close range. By contrast, an analogue phone is said to generate a
power density of 0.27 milliwatts/square cm at a distance of 5
centimetres. This can be calculated as between 45 and 2700 times
greater than radiation intensity from a mobile phone tower. Much
discussion has centred on the actual dose to the head resulting
from normal use of an analogue or digital phone. In terms of power
density, however, the radiation generated is clearly of the same
order of magnitude as set out in the Australian Standard for
members of the public. This suggests that there may be some
pressure from manufacturers of mobile phones to have the Australian
Standard relaxed somewhat.
There are three levels of power densities (watts/square
centimetre readings) in relation to heating effects on tissue. They
- High power densities, generally greater than
10 milliwatts/square cm, at which distinct thermal effects
predominate (as listed earlier in this paper).
- Medium power densities, between 1 and 10
milliwatts/square cm, where weak but noticeable thermal effects
- Low power densities, below 1 milliwatt/square
cm (the Australian upper limit for occupational exposure) where
thermal effects do not appear to exist but other effects have been
This section of the paper deals with the claimed
non-thermal effects which have been reported at
low and medium power densities, and discusses the
reasons why these effects have been discounted, rightly or wrongly,
as a basis for Australian and overseas standards.
Possible behavioural changes or indirect promotion of cancer is
a principal focus of low-power radiofrequency (microwave) studies.
As stated earlier, the RF spectrum is not energetic enough to cause
mutation damage to cell genetic material (DNA) and thus directly
initiate cancer. However, among the hundreds of reports of RF
effects there are some which can be interpreted as possibly
assisting the spread of cancer.
Firstly, some experiments (e.g. Ref. 7) have indicated
radiation-caused changes in the so-called blood-brain barrier. The
healthy brain is an exclusive organ which does not admit entry of
many types of chemical and biochemical substances. The research has
measured abnormal passage across the blood-brain barrier of
protein-bound dyes, radioactively labelled sugars or peroxidase
enzyme in irradiated rats and hamsters.
Secondly, there are examples of disturbances to foetal
development (teratogenic effects) in mice, chicks and rats at low
RF power. Retarded development (low birth weight), eye
malformations, reduction in organ weight and embryonic death have
Experiments with RF radiation and cultured cells are thought by
some scientists to demonstrate low power (non-thermal) effects on
the cell membrane. The best-known work, that of Professor Ross
Adey, has shown a consistent increase of calcium loss from brain
tissue. This indicates that the membrane permeability has been
changed. Calcium is known to be a highly significant biochemical
regulator, e.g. it controls the division of certain cells. The RF
waves may be creating free radicals or changing the physical
characteristics of fats in the cell membrane.
Non-thermal treatment which increases the rate of division of
cell lines or increases cancers in whole animals is of particular
interest. Lymphocytes, a line of white blood cells, have been
reported to proliferate more rapidly under what are claimed to be
non-thermal conditions of irradiation. Spontaneous mammary cancers
and artificially induced lung and skin cancers in mice have been
said to increase under low power RF radiation applied over varying
periods up to ten months. Another study has found that the number
of spontaneous cancers in irradiated rats increases
The above examples, plus many others in the scientific
literature, are sufficient to arouse concern over possible health
consequences of non-thermal RF irradiation in the same range of
intensity or less than Australian and overseas standards. Why then
are non-thermal effects disregarded in the current standards?
The truth is that there is no scientific consensus on
non-thermal effects, and the literature overall reveals a highly
unsatisfactory state of affairs. The effects listed above represent
the most positive results; however, lack of confirmation is a
chronic problem. Many laboratories simply cannot replicate the
results of others, and negative results are difficult to have
published. One of the difficulties with this type of research is
that the experimental variables, e.g. radiation frequency,
orientation, method of modulation, etc. are numerous and very few
scientists seem to try hard enough to standardise others'
experimental conditions. Also, experiments which are claimed to be
non-thermal can be judged to involve local temperature changes or
irrelevant stress conditions. Non-thermal effects are frequently
not dose-dependent and therefore lack scientific credibility.
Lastly, there is still no universally accepted physical or chemical
mechanism to explain how RF radiation can interfere with animal
metabolism apart from heating effects. For example, the role of the
magnetic component as distinct from the electric field component,
if any, can only be guessed at.
At the Federal level there is a committee and a program dealing
with radiofrequency radiation and health.
The Committee on Electromagnetic Energy Public Health Issues is
located in the Department of Communications and the Arts. It is
made up of representatives from that Department, the Department of
Health and Family Services, The Australian Radiation Laboratory,
the Spectrum Management Agency, the Therapeutic Goods
Administration, AUSTEL and the CSIRO. The Committee's role is to
coordinate the $4.5 million Radiofrequency Electromagnetic Energy
Program announced by the Government on 15 October 1996. The Program
has three parts, namely:
- public education on radiofrequency health issues
- Australian participation in a World Health Program
- the setting up of a research program in Australia.
With regard to the research program, the Committee is preparing
a priorities paper which is intended to be released for public
discussion. When the priorities are finalised, it will be the
responsibility of the National Health and Medical Research Council
(NH&MRC) to manage the research, in the first instance by
calling for specific proposals.
Under the circumstances, the best approach for the NH&MRC
would be to encourage good quality research at low power
(non-thermal) radiation levels. Much more scientific effort has to
be invested in making the RF field respectable. While there is no
convincing evidence as yet that low power RF sources such as mobile
phone towers can increase the incidence of cancer, some caution is
warranted given that existing health standards are based on rather
narrow criteria, and that cancers often have a long lead time (as
for example, with asbestos and mesothelioma). Since the sum of less
than $4.5 million for research will not go far, a small levy on
every mobile telephone sold would help to speed up our
understanding in this area.
1. Barnett, S. B. CSIRO Report on the Status of Research on
the Biological Effects and Safety of Electromagnetic Radiation:
Telecommunications Frequencies. CSIRO Division of
Radiophysics, June 1994.
2. Hocking, B., Gordon, I. R., Grain, H. L. and Hatfield, G. E.
Cancer incidence and mortality and proximity to TV towers.
Med. J. Aust. December 1996, p. 601.
3. Australian Standard AS 2772.1 Radiofrequency Radiation Part
1: Maximum Exposure Levels-100kHz to 300 GHz. Sydney: Standards
4. Hocking et al., loc. cit.
5. HealthWiz. National health database. Commonwealth Department
of Human Services and Health. 1991-1996. Canberra: Prometheus Pty
6. Maskarinec, G., Cooper, J. and Swygert, L. Investigation
of increased incidence in childhood leukaemia near radio towers in
Hawaii: preliminary observations. J. Environ. Pathol. Toxicol.
Oncol. 1994: 13:33.
7. Salford, L.G., Brun, A., Eberhardt, J. L., Malmgren, L. and
Persson, R.R. in: Interaction Mechanism of Low-Level
Electromagnetic Fields in Living Systems. C. Ramel and B.
Norden, eds. Oxford University Press, 1992.