Introduction
What kind of radiation do base stations produce?
Where is this radiation directed?
Known effects
Other effects (non-thermal)
What about cancer?
Conclusion
Further web reading
Introduction
Mobile communication networks have operated in various forms
for more than 50 years. However, with the introduction of cellular
mobile telephone networks in Australia in 1987 and the ready availability
of mobile phones, the use of mobile telephone services has expanded
rapidly. Consequently, mobile phone base stations have become
a common sight around cities and along highways. Concerns have
been raised about whether exposure to radiation from the base
stations may have an adverse effect on human health.
What kind of radiation do base stations produce?
 Base
stations produce radiofrequency (RF) radiation that is part of
the electromagnetic radiation spectrum. Most of the aerials on
base stations transmit and receive RF radiation at frequencies
of between 870 and 960 megahertz (MHz). RF radiation in the environment
is also produced in varying amounts by radio and television towers,
CB and UHF aerials, pager services, as well as cordless phones
and some remote controlled devices. A ‘background’ of RF radiation
from these devices and also a small component from natural sources
such as the human body and the sun was in the environment even
before mobile telephone networks began.
Where is this radiation directed?
The design and installation of the antenna determines the distribution
pattern of the RF radiation transmitted from the base station.
The RF radiation is normally directed at or just below the horizon.
Although in general the exposure level decreases with increasing
distance, this is not necessarily the case in areas close to the
base station. For example, the exposure level immediately below
a base station can be much lower than the level a few hundred
metres away in the direction of the aerials. The presence of trees,
hills, buildings and other structures can distort the RF radiation
causing variations in its strength.
Known effects
Scientists have known for a long time about the ability of RF
radiation to cause heating, which can lead to severe health effects
on the body such as fatigue, reduced mental concentration and
cataracts, if exposed to very high levels. These effects are known
as thermal effects, some of which can be created by subjecting
a person to a warm environment. The Radiation Protection Standard
for Maximum Exposure Levels to Radiofrequency Fields - 3 kHz to
300 GHz (2002) specifies limits on public exposure to RF radiation
from various sources, including mobile phone base stations. The
level at which these limits are set is much lower than the levels
at which any thermal (heating) effects can occur. All base stations
must comply with this Standard. Only at a distance closer than
a few metres directly in front of an antenna would the limit be
exceeded. Of course, these antennae are located high up on towers
and buildings, which have restricted access. At ground level,
RF radiation levels are very much lower than the limit specified
in the Standard (typically less than one ten thousandth of this
limit).
Other effects (non-thermal)
Other effects, such as changes to cell membrane permeability
that cannot be explained by induced heating are the subject of
further studies. There has been no conclusive evidence to date
that these non-thermal effects result in injury to tissue. Furthermore,
these effects take place at exposure levels at or near the limits
set in the Standard and not at the much lower exposure levels
surrounding base stations.
What about cancer?
 In
recent years attention has been focussed on the possibility that
long term exposure to low levels of RF radiation may be responsible
for serious health effects, such as cancer. Of the many studies
into possible health effects that have been completed, only a
small number have looked at exposure to low levels of RF radiation
over a long period of time. These studies found no conclusive
evidence of ill-effects, even though the exposed populations were
subjected to higher RF radiation levels than would be received
near a base station.
It may be significant that incidence rates of those cancers on
which attention has been focussed have not changed much in the
last 50 years (some have actually decreased), even though the
use of RF radiation has increased in our society.
Conclusion
Although more research into the effects of RF radiation is being
undertaken to answer unresolved questions, there is no convincing
evidence that prolonged exposure to very low levels of RF radiation
causes any adverse health effects. Note that it is a requirement
of the ACMA (see 'Further web reading' below) that mobile phone
towers be designed and operated such that RF radiation exposure
is minimised.
For further information please contact the Radiation Protection
division.
Further web reading
The Australian Radiation Protection Standard
www.arpansa.gov.au/rps_pubs.htm
The report of the UK's Independent Expert Group on Mobile Phones
www.iegmp.org.uk/report/index.htm
The Australian Communications and Media Authority news release
regarding siting of mobile phone towers
www.acma.gov.au/ACMAINTER.2097270:STANDARD::pc=PC_1751
This page was last modified 11-03-2008
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