Cellular telephones are radio transceivers which receive and also transmit radiofrequency (RF) electromagnetic signals. They operate in the ultra-high-frequency (UHF) band. The incoming radio transmission from a central base station or cell-site is on a frequency between approximately 869 and 894 megahertz (MHz). The outgoing signal back to the base station is on a frequency between 824 and 850 MHz. For comparison, TV channel 69 is assigned the frequency range of 800-806 MHz. The portable units are of two types: hand-held or pocket phones with an output power of 0.6 watts, and higher power units with 3 to 6 watts of transmitter power. The higher power units may be carried in a small bag or case or installed in cars. The antennas of the hand-held or pocket type are about 10-20 cm long while those of the higher power units about 20-30 cm long.
Can cellular telephones cause health problems?
Concern about health problems linked to cellular phones began in the early 1990's when media reports alleged that there was a link between the long-term use of cellular telephones and brain cancer. Since then, there have been questions raised about the safety of exposure to the radiofrequency (RF) energy that these devices use to operate.
In laboratory studies researchers have found conflicting results - an increased tumor rate in mice - as well as decreased tumor rates in rats. All studies to date have had problems with their approach and design, and therefore the relevance of data to 'human' cellular phone users is not clear.
In an occupational setting, it is known that absorbing RF and microwave energy above safe levels can cause harmful effects because body tissues may heat-up. There is currently no evidence of such effects from exposure to RF fields from cellular telephones.
In addition, there are reports that cellular phones which use digital communications can affect the operation of some implanted cardiac pacemakers. However, this interference occurs only when the telephone is activated and only when the phones were very close to the pacemaker (within 8 cm, or about 3 inches).
What can I do to reduce the risk, just in case?
Cellular phone users who are concerned about the safety of this device may reduce the possible risk by minimizing the use of the hand-held units and switching over to car-phone units or regular telephones as much as possible.
Persons with cardiac pacemakers should consult their doctor about the possibility of interference from external electromagnetic field. As a precaution, such persons should not carry the telephone in the breast pocket of their shirt or jacket. When an incoming call is received, the phone switches automatically to an activated mode. It is in this mode that the digital cellular phone may interfere with the pacemaker signals.
Are there limits for exposure to radiofrequency energy?
Health Canada has established limits of exposure to RF energy based on a review of experimental evidence of detectable effects in animals and cell (i.e., biological) systems. The limits published by Health Canada in "Safety Code 6 - Limits of Exposure to Radiofrequency Fields at Frequencies from 10 kHz-300 GHz" (1999) have been set much lower than the levels that cause these effects. This Code also takes into account other national and international standards. In addition, testing of portable cellular telephones have shown that under normal operating conditions, the energy emitted is below the exposure limits. One of the concerns related to cellular phone is chances of cancer for which there is no dose-response data and therefore it is not possible to set limits to prevent or minimize cancer occurrence.
How do I get further information?
For further information you may wish to contact:
- Non-Ionizing Radiation Section
- Radiation Protection Bureau
- 775 Brookfield Road, Postal Locator 6301B
- Ottawa, Ontario K1A 1C1
Safety Code 6 and other Radiation Protection Bureau publications can be downloaded from their publications index list at:
http://www.hc-sc.gc.ca/cps-spc/house-domes/electron/cell/index_e.html
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