How do cellular telephones work?
Cellular telephones are radio transceivers which receive and 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. Some phones feature greater band widths to accommodate web-based applications, etc. Band widths are also different outside North America. For comparison, TV channel 69 used to be assigned the frequency range of 800-806 MHz. For comparison, TV channel 69 is assigned the frequency range of 800-806 MHz.
The portable telephones 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.
Can cellular telephones cause health problems?
It is not certain if electromagnetic fields from cell phones can cause health effects. Studies have not shown any clear evidence. But growing evidence tells us that we must reduce unnecessary exposures while research continues. 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 not shown any confirmed evidence of risk with relevance to 'human' cellular phone users.
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 emit electromagnetic field and 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 risk at long-term low exposure situations. There have been concerns about this aspect. However, there is no dose-response data and therefore it is not possible to set limits to prevent or minimize risk of cancer occurrence.
What are some general precautions?
We must all take precautionary measures to reduce exposure.
| Exposure Situations | Safety Measures |
| Children | |
| High use of cellar phones | - Limit use
- Hands-free headsets can help reduce exposure to head and body.
- Switch sides (ears) regularly as this limits the power and duration of the electromagnetic field emitted near your ear.
- Send text messages as they tend to be shorter, and the unit is held away from the body
- Opt for lower power units (where possible) to help reduce exposure.
|
| Proximity of unit close to the body | - As much as possible, keep or store away from the body.
- Avoid unnecessary exposures.
- Carry in the pocket with the board (back) towards the body as this means the fields move away from you rather than through you.
|
| Use while driving | - For safety, do not use while driving or doing tasks that require your attention
|
Where can I get further information?
Health Canada has published a "For Your Health - Safety and Safe Use of Cellular Phones" fact sheet.
For further information, you may wish to contact:
Consumer and Clinical Radiation Protection Bureau
(Postal locator 6301B)
775 Brookfield Road
Ottawa, ON K1A 1C1
Telephone: (613) 954-6699
Fax: (613) 952-7584
Safety Code 6 can be found at:
http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/99ehd-dhm237/limits-limites-eng.php
