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REGULATORY INFORMATION

252

(The following information comes from a consumer information

Website jointly sponsored by the U.S. Food and Drug Administration

(FDA) and the Federal Communications Commission (FCC), entitled

“Cell Phone Facts: Consumer Information on Wireless Phones.” The

information reproduced herein is dated July 29, 2003. For further

updates, please visit the Website:

ttp://www.fda.gov/cellphones/qa.html.)

What is radiofrequency energy (RF)? Radiofrequency energy (RF)

is another name for radio waves. It is one form of electromagnetic

energy that makes up the electromagnetic spectrum. Some of the

other forms of energy in the electromagnetic spectrum are gamma

rays, x-rays and light. Electromagnetic energy (or electromagnetic

radiation) consists of waves of electric and magnetic energy moving

together (radiating) through space. The area where these waves are

found is called an electromagnetic field.

Radio waves are created due to the movement of electrical charges in

antennas. As they are created, these waves radiate away from the

antenna. All electromagnetic waves travel at the speed of light. The

major differences between the different types of waves are the

distances covered by one cycle of the wave and the number of waves

that pass a certain point during a set time period. The wavelength is

the distance covered by one cycle of a wave. The frequency is the

number of waves passing a given point in one second. For any

electromagnetic wave, the wavelength multiplied by the frequency

equals the speed of light. The frequency of an RF signal is usually

expressed in units called hertz (Hz). One Hz equals one wave per

second. One kilohertz (kHz) equals one thousand waves per second,

one megahertz (MHz) equals one million waves per second, and one

gigahertz (GHz) equals one billion waves per second.

RF energy includes waves with frequencies ranging from about 3000

waves per second (3 kHz) to 300 billion waves per second (300 GHz).

Microwaves are a subset of radio waves that have frequencies

ranging from around 300 million waves per second (300 MHz) to

three billion waves per second (3 GHz).

How is radiofrequency energy used? Probably the most

important use of RF energy is for telecommunications. Radio and TV

broadcasting, wireless phones, pagers, cordless phones, police and

fire department radios, point-to-point links and satellite

communications all rely on RF energy.

Other uses of RF energy include microwave ovens, radar, industrial

heaters and sealers, and medical treatments. RF energy, especially at

microwave frequencies, can heat water. Since most food has a high

water content, microwaves can cook food quickly. Radar relies on RF

energy to track cars and airplanes as well as for military applications.

Industrial heaters and sealers use RF energy to mold plastic

materials, glue wood products, seal leather items such as shoes and

pocketbooks, and process food. Medical uses of RF energy include

pacemaker monitoring and programming.

How is radiofrequency radiation measured? RF waves and RF

fields have both electrical and magnetic components. It is often

convenient to express the strength of the RF field in terms of each

component. For example, the unit “volts per meter” (V/m) is used to

measure the electric field strength, and the unit “amperes per

meter” (A/m) is used to express the magnetic field strength. Another

common way to characterize an RF field is by means of the power

density. Power density is defined as power per unit area. For

example, power density can be expressed in terms of milliwatts (one

thousandth of a watt) per square centimeter (mW/cm2) or microwatts

(one millionth of a watt) per square centimeter (µW/cm2).

The quantity used to measure how much RF energy is actually

absorbed by the body is called the Specific Absorption Rate or SAR.

The SAR is a measure of the rate of absorption of RF energy. It is

usually expressed in units of watts per kilogram (W/kg) or milliwatts

per gram (mW/g).

What biological effects can be caused by RF

energy? The biological effects of radiofrequency energy should not

be confused with the effects from other types of electromagnetic

energy.

Very high levels of electromagnetic energy, such as is found in X-rays

and gamma rays, can ionize biological tissues. Ionization is a process

where electrons are stripped away from their normal locations in

atoms and molecules. It can permanently damage biological tissues

including DNA, the genetic material. Ionization only occurs with very

high levels of electromagnetic energy such as X-rays and gamma

rays. Often the term radiation is used when discussing ionizing

radiation (such as that associated with nuclear power plants).

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