With the growing popularity of hand-held cellular phones (or cell phones), questions have been raised about the safety of being exposed to the radiofrequency (RF) energy they emit.

Cell phones are portable radio devices that transmit and receive signals from a network of fixed low-power base stations. The transmitting power of a cell phone varies, depending on the type of network and distance from the base station. The power generally increases as you move farther away from the nearest base station.

All analog cell phones operate in a lower cellular frequency band than that of the digital system,. which was introduced later. The electromagnetic energy given off by cell phones is a type of non-ionizing radiation, similar to the radiation that occurs naturally in thunderstorms.

RF electromagnetic energy is used in radio communications and broadcasting, as well as in medical treatments and industrial heating. Unlike the ionizing radiation given off by X-ray machines, RF electromagnetic energy from cell phones and other devices cannot break chemical bonds. In other words, it is unlikely to damage your body's genetic material.

The RF electromagnetic energy generated by cell phones can penetrate your body. The depth of penetration and the amount of energy you absorb depends on many factors, such as how close you hold the cell phone to your body and how strong the signal is. The important indication of RF exposure is the rate of energy absorbed in your body. This is called the "specific absorption rate" or SAR and it is measured in watts (unit of power) per kilogram.

So far, there is no convincing evidence from animal or human studies that the energy from cell phones is enough to cause serious health effects, such as cancer, epileptic seizures or sleep disorders. Some scientists have reported that cell phone use may cause changes in brain activity, reaction times, or the time it takes to fall asleep. But these findings have not yet been confirmed.

Cell phone use is, however, not entirely risk-free. Studies have shown that:

• Using cell phones while driving may increase the chance of traffic accidents.
   
• Cell phones may interfere with medical devices such as pacemakers, defibrillators and hearing aids. They can also interfere with aircraft electronics.

There is no firm evidence to date that RF emissions from cell phones cause ill health. Only you can decide if you can live with the possibility of an unknown risk from cell phone use. If you are concerned, you can reduce your risk by limiting the length of your cell phone calls and using "hands-free" devices that keep cell phones away from your head and body. Also, because of the risk of traffic accidents, don't use your cell phone while driving.