Radiation Safety Committee
Mobile telephone communication antennas: are they a health hazard?
Some Frequently Asked Questions
- Concerns of adverse health effects
- Description of the antenna and operation
- Radio-Frequency radiation
- Exposure levels and recommended limits
- Are there any adverse health effects?
- What conclusions can be drawn?
Concerns of adverse health effects
In recent times, concrete towers have been erected throughout the metropolitan areas in Australia. These towers carry the antennas that are required for the mobile (or cellular) telephone network and are located at base transceiver stations. The antennas emit radio frequency (RF) radiation. Concerns have been raised, both by people living or working adjacent to a tower and by parents of children who play or attend school near a tower, about the possibility of adverse health effects arising from exposure to this radiation.
Description of the antenna and operation
When a call is made from a mobile telephone, RF signals are transmitted between its antenna and the antenna at the nearest base station. Further RF signals are then transmitted between other base stations in the network and, finally, the destination telephone.
Mobile telephones emit signals in the frequency range 870 to 955 megahertz. These signals are picked up by rod-like antennas installed in rectangular boxes, which are supported by triangular steel frames at the top of the 30 m tower. The signals transmitted between base stations are in a higher frequency range, 15 to 23 gigahertz, and radiated as a very narrow beam by up to three dish shaped antennas, also mounted near the top of the tower.
Radio-Frequency radiation
RF radiation, as well as ultraviolet radiation, visible light, infrared radiation and power frequency fields, are types of non-ionizing radiation. These radiations, together with ionizing electromagnetic radiation (X radiation and gamma radiation) make up the electromagnetic spectrum.
When ionizing radiations collide with biological material, they create positively and negatively charged particles, which may have adverse effects. Non-ionizing radiations cannot create such particles. As far as is currently known, RF radiation, for example, can only cause the molecules in biological material to vibrate and thereby generate heat.
Exposure levels and recommended limits
The exposure levels of RF radiation are measured in microwatts per square centimeter (abbreviated as uW/cm2). One uW is a millionth of a watt. The maximum exposure levels measured adjacent to the base station towers are less than 2 uW/cm2. The exposure level decreases with increasing distance from the base of the tower.
These levels can be compared with 200 uW/cm2, which is the exposure limit for members of the public (that is, unlimited exposure duration) recommended by the current Australian Standard (AS 2772) for this radiation.
Are there any adverse health effects?
Current research indicates that, at the exposure levels indicated above, RF radiation does not have any adverse health effects.
It is considered that rises in tissue or body temperature of about 1.0 oC or more are required before any adverse effects will occur. In cases of pregnancy, rises in the temperature of the foetus of 2.5 to 5 oC are necessary before defects are seen in the newborn. These temperature rises will not occur unless the exposure level is greatly in excess of the Australian Standard mentioned above. Exposure to the low level of RF radiation emitted from base station antennas will not, in fact, cause any noticeable temperature rise.
There are many reports in the literature of research on non-thermal effects, usually of a subjective nature. This research was conducted in both Eastern and Western block countries. Studies that have investigated if RF radiation affects biological cells, other than by heating them, are inconclusive. In addition, the exposure levels used in these studies are higher than those mentioned above.
The present concern that people have about RF exposure is whether these non-thermal effects also include cancer. Human studies to assess the possibility that RF exposure increases the risk of cancer are very few in number and of poor quality. They are therefore not reliable. Review groups evaluating the state of knowledge about possible links between RF exposure and excess risk of cancer have concluded that there is no clear evidence for any links. The Australian Radiation Protection and Nuclear Safety Agency continues to closely monitor the research being conducted in this field.
What conclusions can be drawn?
No adverse health effects are expected from continuous exposure to the RF radiation emitted by the antennas on mobile telephone base station towers.