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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 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 from 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 antennas 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 1/10,000 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 focused 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 focused 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 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 Branch.
Further reading
- The Stewart Report of the UK's Independent Expert Group on Mobile Phones
- The Australian Communications and Media Authority news release regarding siting of mobile phone towers
Last modified: 04/03/2011 03:28 pm
