RF Exposure InformationWarning

What are the health effects from exposure to EMF associated with cellular towers?

There is an increased public awareness about radiofrequency EMF exposures associated with cellular towers. Mobile (cellular) phones are a relatively new and rapidly growing technology that can cause such exposures. Several research groups are investigating the potential effects of magnetic fields associated with cell phones and cellular towers. Various research and government organizations have reviewed the available scientific evidence and concluded that while currently there are no known health risks from being around these towers, further research is needed.

A Brief Summary of Cellular Radio Systems and Emissions

Cellular radio systems use frequencies between 800 and 900 Megahertz (MHz), while PCS transmitters use frequencies in the range of 1850 – 1990 MHz. The combination of antennas and associated electronic equipment is referred to as a base station or cell site. The antennas having the appearance of rectangular panels are called sector antennas. Typically these types of antennas are arranged in groups of three, with one antenna in the group being used to transmit signals and the other two antennas receiving signals. At a cell site, the total RF power that could be emitted from each transmitting antenna depends on the number of radio channels (transmitters) that have been authorized and the power of each transmitter. Not all transmitters are expected to operate simultaneously, thus reducing typical overall emission levels.

The signal from a PCS base station antenna is essentially directed toward the horizon in a relatively narrow pattern in the vertical direction. The radiation pattern for a sector antenna is fan-shaped, like a wedge cut from a pie. As with all forms of electromagnetic energy, the power density from a PCS transmitter decreases rapidly as one moves further away from the antenna. As a result, normal ground-level exposure is much less than exposures that might be encountered if one were very close to the antenna and in its main transmitter beam. Historically, measurements made near typical cellular or PCS base station antennas have shown that ground-level power densities are well below regulatory limits.


A Case Study

The following chart is from a study done in NJ at the request of Congressman Robert Andrews' office. The study surveyed the area surrounding a water tower hosting personal communications services (PCS) antennas from AT&T and VoiceStream (formerly Omnipoint). Community members had raised concerns due to the fact that a school was located on property immediately adjacent to the water tower. The chart clearly indicates that these antenna were well below the regulatory limits.

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More Information

fcc.gif (4631 bytes)The exposure limits used by the FCC are expressed in terms of SAR (Specific Absorption Rate) , electric and magnetic field strength and power density for transmitters operating at frequencies from 300 kHz to 100 GHz. The actual values can be found in either of two informational bulletins available at the FCC web site (OET Bulletin 56 or OET Bulletin 65), http://www.fcc.gov/oet/rfsafety/