A cellular phone or ‘cell’ phone is a wireless device. Cell phones use high-frequency radio signals, which they receive from cellular towers. These towers are located all around the calling area for the phone. There is an exclusive range of frequencies that were allocated for cell phone use. The range is from 806-890 megahertz (MHz) and 1850-1990 MHz. These energies are considered non-ionizing because they are not strong enough to remove electrons from an atom in living tissue.
A customer dials a number to make a call. The cell phone sends a message to the tower with the connection information. The tower sends the call to the public switched telephone network (PSTN) using a switch. The area around a tower is called a cell. Control of signal strength, phones roaming from cell to cell, and prevention of calls being picked up by others are some of the issues that cellular phone companies deal with daily.
Cellular phones use Radiofrequency (RF) energy. All RF energy has electrical and magnetic parts and both are measurable. A unit called the Specific Absorption Rate (SAR) measures the RF energy that is absorbed by the body. This number has recently become the focus of scientists and cellular phone companies due to reports of tumors from the radiation.
Several departments of the government are working together to monitor the development of this issue. In 1996, the FCC ruled that wireless phones in the United States had to comply with human exposure limits of 1.6 watts per kilogram. There are many websites, as well as the company’s web site, that lists this number.
Digital cellular phones use microwave pulses of electromagnetic radiation to send information. The United States limits to 50 per second these pulses. An international standard called Global System for Mobile Communications (GSM) allows up to 217 pulses per second. Each pulse spreads low-level microwave radiation all over the brain. This spread happens because the antenna, being built into the phone, is very close to the head.
Over the last decade, a number of research studies have been performed in the United States and Europe. Results tend to be inconclusive due to many variables. Varying designs in the handsets place the antenna in different locations. The shape of the person’s head will make for differences as well as which side of the head the phone is held.
The latest study from Sweden shows that a single two-hour exposure to some cellular phone microwaves killed brain cells in rats. Although the study does not show any evidence of this for people, recommendations are being made. The use of a hands-free device is one of the recommendations. This is because RF energy decreases with distance from the source. A limit on the length of phone calls is the other major suggestion being made.
Studies are continuing in this area as more people acquire cell phones. Long-term risks are difficult to determine since the technology is still new. Other considerations will come from the increasing amount of microwaves in other wireless technologies.