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Ionizing and Non-ionizing Radiation
Radiation can be broadly broken into two groupings:
ionizing and non-ionizing. Ionizing
means that there is enough energy in the radiation
to alter the chemical structure of matter
upon its absorption by knocking off electrically
charged particles (ions). Non-ionizing
means that there is not enough energy in the
radiation to create ions. Instead, the energy
is usually absorbed as heat. RFR is a form
of non-ionizing radiation.
Because of their extremely high frequencies
and energies, X-rays and gamma rays are
electromagnetic types of "ionizing" radiation,
as are many types of high-energy,
high-velocity sub- atomic particles that result
from nuclear processes. When ionizing
radiation interacts with living structures,
it can cause severe damage. The chemical bonds
of molecules struck by high energy particles
can be broken, causing parts of the
molecules to be split off, often as reactive
charged particles (ions). These ions can
promote additional chemical and physical reactions.
If the absorbing molecules are DNA or
other genetic materials, cellular metabolism
can be interfered with and the cell's ability to
reproduce itself can be destroyed or caused
to malfunction (the latter sometimes leading
to cancers). (Barrett, see references.)
Electromagnetic waves of lower frequency levels
and energies, such RFR and EMFs
associated with radio systems, do not cause
ionization and consequently are referred to
as "non-ionizing" radiation. If absorbed at
all, this type of energy is absorbed as heat.
Unless generated at extremely high power densities
and at just the right resonance
frequencies so as to produce large amounts
of heat resulting in actual burns, the frequency
and resulting energy levels of non-ionizing
radiation are almost always too low to affect
biological materials. Non-ionizing radiation
is not known to damage DNA as can ionizing
radiation and generally has not been shown
to cause irreversible changes that can
accumulate over time (Yost, see references).
There is one potential problem, however. Sometimes
in a complex organic molecule short,
linear groups of atoms extend off of a main
chain or body of the complex. It has been
shown that at the right frequencies, these
extensions can be excited by strong,
non-ionizing energy so as to cause frequency
resonance to occur. The extension can then
vibrate and on occasion break off, altering
the structure of the molecule. This is the only
other known interaction between non-ionizing
radiation and biological structures. It is
considered to be a rare phenomenon, as the
frequency of the radiation must exactly match
the natural resonance of the molecule and
the power density must be very high. (Barrett,
see references.)
Why the Concern?
Most scientists maintain that RFR and lower
frequency EMFs such as those associated
with wireless communications systems generally
do not produce adverse health effects in
humans because they are non-ionizing in nature
and normal exposures are controlled so
as not to result in thermal effects. Other
researchers, however, note the possible molecular
resonance problem described above and propose
that continuous low-level exposures or
exposures in combination with other chemicals
may cause health problems that are not
immediately evident. These researchers suggest
that extra care should be taken until more
is known.
The media continue to report the work of these
researchers and the public exhibits a sharp
interest in the debate between the two sides.
Some members of the public believe that
even the remotest possibility of a health
hazard constitutes grounds for forming public
policy and regulations for facilities using
radiofrequency radiation and generating
electromagnetic fields. Consequently, there
is often keen public interest in proposals for
new wireless cell sites and facilities.
ANSI, NCRP, and IRPA Radiation Protection Guidelines
"Both private organizations and government
agencies have proposed guidelines that limit
exposure to nonionizing radiation. These standards
can be divided into broad categories:
emission standards, which set limits on the
incidental (nonpurposeful) radiation emanating
from a device; and exposure standards, which
set limits on the radiation power density to
which a person may be exposed. Emission standards
limit unwanted leakage from devices
such as microwave ovens that should contain
the radiation inside the device or that have
shielding to protect operators and others
from exposure during normal operation. Exposure
standards limit exposure of persons to radiation
present in the environment, for example
from a radio transmitter" (Yost, see references).
There is no official, mandatory federal standard
for radiation exposure protection in the
United States. The official guideline for
facilities regulated by the Federal Communications
Commission (FCC) is currently the 1982 American
National Standards Institute (ANSI)
guideline. The 1982 ANSI guidelines recommend
exposure limits covering RFR from 300
kHz (kilohertz) to 100 GHz (gigahertz). The
guidelines recognize that the human body
absorbs radiofrequency energy at some frequencies
more readily than at others. The most
restrictive limits are in the frequency range
of 30-300 MHz. However, the wireless
communications systems discussed in this paper
operate in the frequency range of 800 to
2200 MHz -- frequencies outside of the most
sensitive range.
ANSI has adopted C95.1-1992, a revision of
the 1982 standard, and the FCC has proposed
its adoption. The new standard "contains a
number
of significant differences from
guidelines and recommendations issued by ANSI
in 1982. In many respects, the 1992
guidelines are more restrictive in the amount
of environmental RF exposure permitted, and
they also extend the frequency range under
consideration to cover frequencies from 3 kHz
to 300 GHz. The new 1992 guidelines specify
two sets of exposure recommendations, one
for 'controlled environments' (usually involving
workers) and another for 'uncontrolled
environments' (usually involving the general
public). (FCC 93-142).
For controlled environments, the 1992 ANSI/IEEE
standards recommend maximum power
density levels calculated by dividing frequency
by 300 (f/300). For example, for a cellular
frequency of 888 MHz, the standard would be
calculated by dividing 888 by 300, yielding
an exposure level of 2.96 mW/cm2 (milliwatts
per square centimeter). For uncontrolled
environments, the revised standards recommend
maximum power density levels calculated
by dividing frequency by 1500 (f/1500). As
a result, for the same cellular frequency of 888
MHz, the exposure standard for the uncontrolled
environment would be 0.592 mW/cm2
(888/1500). Thus, for both controlled and
uncontrolled environments, the ANSI/IEEE
exposure standards for wireless communications
are dependent upon the technologies
frequencies.
In addition to the ANSI standard, there are
two other widely discussed public exposure
standards: that of the National Council on
Radiation Protection (NCRP) and that of the
International Radiation Protection Association
(IRPA). Because the NCRP standards cover
the 1500 MHz to 1011 MHz frequency range and
the IRPA standards cover the 2,000 MHz
to 1011 MHz frequency range, these two exposure
standards apply only to the upper
portions of the PCS frequency range. They
do not apply to the cellular or ESMR
technologies, whose frequency ranges lie between
800 and 900 MHz.
The NCRP is a non-profit corporation chartered
by the United States Congress to, among
other things, develop information and recommendations
concerning radiation protection.
The guidelines issued by the NCRP specify
a level of 1 mW/cm2 (milliwatt per square
centimeter) for the exposure of the general
public in the frequency range listed above.
The IRPA is a non-governmental international
organization representing most of the
national radiation protection societies in
the world. These recommendations form part of
the World Health Organization (WHO) United
Nations Environmental Programme (UNEP).
IRPA guidelines for public exposure also recommend
1 mW/cm2 for the frequency range
listed above. It should be noted that both
the NCRP and IRPA exposure standards are
more restrictive than the revised ANSI standards
for PCS frequencies above 1500 MHz in
uncontrolled environments and for all PCS
frequencies in controlled environments.
Some states, including Massachusetts, New Jersey,
Oregon, and Washington, as well as
some local jurisdictions have adopted their
own radiation guidelines.
Radiation Levels
The levels of RFR to which the public is routinely
exposed are far below the levels
necessary to pose a health risk. A 1989 report
by the Office of Engineering and
Technology stated that the U.S. Environmental
Protection Agency estimates that in seven
metropolitan areas studied across the United
States, 98 to 99 percent of the population is
exposed to less than 0.001 mW/cm2 of radiation.
The standards listed above are
considerably more restrictive than the exposure
levels that the majority of the public
experiences.
Additionally, the 1982 ANSI guidelines for
radiation exposure indicate that devices
operating on less than seven watts of power
at frequencies less than 1,000 MHz will not
cause immediate thermal effects. Cellular
mobile phones operate between 0.6 and three
watts of power at frequencies between 800
and 900 MHz, ESMR mobile communicators
operate between 0.5 and 1.5 watts of power
in the 800 MHz frequency band, and PCS
mobile communicators are anticipated to operate
on no more than 1 watt of power at
frequencies between 1,850 and 2,200 MHz, all
falling well below the seven watt threshold.
Typical cell sites, including monopoles, roof-mounted
antenna sites, and building-mounted
antenna sites, emit a maximum of 3,000 watts
of effective radiated power (ERP) (the power
supplied to an antenna multiplied by the relative
gain of the antenna in a given direction). In
comparison, radio broadcasting towers emit
roughly 100,000 watts ERP, and television
broadcasting towers emit approximately 5,000,000
watts ERP. The radiation emitted from
these broadcasting sources decreases according
to the inverse square principle. As a
result, exposure to radiation decreases as
distance from broadcasting sources increases.
Ongoing and Future Research
Although many studies have been conducted examining
the effects of RFR and EMFs on
animals and humans, scientists have been unable
to reach consensus on the results for
various reasons, including: difficulty in
interpreting the extrapolation of studies performed
on animals and cells to humans; difficulty
in explaining the effects of natural influences,
such as the earth's magnetic field; difficulty
in controlling crucial variables in the study,
such as the amount of energy absorbed by test
organisms; difficulty in replicating and
generalizing results obtained at specific
power levels, frequencies, and modulation
patterns, to other situations; difficulty
in distinguishing between slight normal human
changes and subject variations; and difficulty
in agreeing on the results and methodologies
of epidemiological studies.
While some studies suggest that long-term exposure
to some forms of RFR may cause
adverse health effects in humans, many other
studies do not. According to a report
published in 1994 by the United States General
Accounting Office, both the Food and Drug
Administration (FDA) and the Environmental
Protection Agency (EPA) agree that the
information from the most current studies
is insufficient to determine whether the risks are
substantive, if present at all.
In fact, some cities, such as the City of San
Diego, have addressed this issue by
distinguishing between actual and perceived
health hazards when performing CEQA
(California Environmental Quality Act) review.
The city recognizes that the public's fear of
the unknown sometimes causes "perceived health
hazards." Since studies have been
found inconclusive in relation to the thresholds
established by the ANSI standards, the city
does not identify EMF impacts on human health
as significant. Nonetheless, the policy of
the Environmental Analysis Section (EAS) of
the Development and Environmental Planning
(DEP) section of the Development Services
Department (DSD) is to disclose the presence
of EMF sources, and advise "prudent avoidance,"
where possible. An example of prudent
avoidance would be to place power lines or
other sources of radiation in places of
low-intensity human uses, such as parking
lots. Concurrently, the City of Poway has
suggested that required buffer distances would
be helpful in separating such facilities from
areas where people tend to cluster, such as
schools, residences, parks, and day care
centers.
RFR Research Related to Wireless Communications
In 1991, the California Public Utilities Commission
(CPUC) opened Investigation 91-01-012
to consider whether the CPUC should adopt
a role to mitigate potential health effects, if
any, of EMFs created by electric utility power
lines and cellular facilities. Consensus was
reached that EMF issues involving electric
utilities and cellular utilities should be
addressed separately. A cellular steering
committee composed of five individuals was
established with one individual representing
each of the following agencies: the CPUC's
Commission Advisory and Compliance Division
(CACD), the Division of Ratepayer
Advocates (DRA), the California Department
of Health Services (DHS), the Cellular Carriers
Association of California (CCAC), and the
"Citizens Concerned About Telecommunications
EMF." In July 1993, the steering committee
held an informational workshop addressing
three issues: levels of cellular utilities'
EMF and RFR impacts, issues for further
consideration, and interim safety measures.
In December 1994, the CACD released a summary
of the workshop. The report concluded
that although little is known about potential
health hazards related to EMF and RFR
exposure levels, cellular power densities
have been found to be consistently below present
exposure standards. In the absence of scientific
evidence linking cellular exposure levels to
human health risks, the steering committee
decided not to adopt a specific numeric set of
EMF and RFR exposure standards associated
with cellular facilities. However, recognizing
that future scientific research may provide
more definitive information, the CACD adopted
the responsibility to serve as a clearinghouse
of EMF and RFR research and to hold
periodic workshops informing interested parties
of new findings.
On November 8, 1995, the CPUC released Decision
95-11-017. The decision (1) adopts the
CACD's workshop report (except for a proposed
interim measure requiring cellular utilities
to consider alternative cell site locations
and restrict access to their cell sites through
warning signs or physical barriers); (2) approves
the designation of the CACD to hold
workshops as additional health information
becomes available and requires that the
workshop results be reported to the CPUC through
the resolution process; and (3) closes
Investigation 91-01-012.
In November of 1994, the United States General
Accounting Office published a report addressing
the status of scientific knowledge on the
effects of RFR caused by cellular telephones. The report
found that no long-term studies on low levels
of radiation from cellular phones have been
completed, and that the research conducted
on other sources of low-level RFR are inconclusive.
The report further determined that both epidemiological
and laboratory studies are needed to
ascertain whether portable cellular phones
produce adverse health effects. Two such studies are
under way:
1. In 1991, Motorola, Inc., contracted with
a prominent U.S. research company to study the
effects of analog and digital signals from
cellular telephones on animals and cells. Results are
expected to be released in late 1995 or early
1996.
2. In 1993, due to public anxiety that portable
cellular phones cause adverse health effects, the
Cellular Telephone Industry Association (CTIA)
allocated $15 to $25 million to study the safety of
cellular phones for three to five years, including
the effects of analog and digital radiation at
cellular and PCS frequencies. The CTIA and
other industry representatives established a Science
Advisory Group on Cellular Telephone Safety
to perform this research through epidemiological
studies, cell cultures, animal testing, and
genetic research. The research will be submitted to a
scientific peer review coordinated through
the Harvard University Center for Risk Analysis. This
research will be open for federal participation
in order to provide further objectivity.
The federal government also is undertaking
research that focuses specifically on cellular
telephone safety issues. The National Cancer
Institute has begun an epidemiological study of
people with brain cancer to ascertain whether
there is a statistical relationship between cancer
and the use of cellular telephones. It is
anticipated that this study will be completed between
1998 and 1999.
The research conducted up to the present is
considered inconclusive, but important questions
have been raised about the possible relationship
between health complications and the exposure
to radiofrequency radiation and electromagnetic
fields. The studies cited above, in combination
with other human and laboratory studies, could
provide the kind of comprehensive research
needed to determine the safety of wireless
communications devices.
RFR and EMF Information Sources
In January of 1995, the Department of Energy
released
a booklet entitled Questions and
Answers about EMFs, published by the department's
Research and Public Information
Dissemination (RAPID) program. The RAPID program
was established in 1992 as a five
year, $65,000,000 program to study if exposure
to EMFs causes adverse health effects. To
order free copies, call 1 (800) 363-2383,
or call Alicia Hillery for bulk orders at (202)
512-1708.
For additional information on EMFs, Planning
Advisory Service Report #435,
Electromagnetic Fields and Land-Use Controls,
by David Bergman, Louis Slesin, and
Matthew Connelly (Chicago: American Planning
Association, 1991) can be ordered through
the American Planning Association's Planners
Bookstore, 122 S. Michigan Ave., Suite
1600, Chicago, IL 60603; (312) 431-9100. Additionally,
the ANSI Standards, also known as
IEEE Standard for Safety Levels with Respect
to Human Exposure to Radio Frequency
Electromagnetic Fields, 3 kHz to 300 GHz,
1992 (ANSI/IEEE c.95.1-1992), and
Recommended Practice for the Measurement of
Potentially Hazardous Electromagnetic
Fields - RF and Microwave (ANSI/IEEE C95.3-1992)
are available through the American
National Standards Institute, 11 W. 42nd St.,
New York, NY 10036; (212) 642-4900.
ABBREVIATIONS OF TERMS
A/m
Amperes per meter
ANSI
American National Standards Institute
BTA
Basic Trading Area
CCAC
Cellular Carriers Association of California
CDMA
Code Division Multiple Access
CDPD
Cellular Digital Packet Data
CEQA
California Environmental Quality Act
CFR
Code of Federal Regulations
CGSA
Cellular Geographical Service Area
CPUC
California Public Utilities Commission
CTIA
Cellular Telecommunications Industry Association
DEP
Development and Environmental Planning
DHS
Department of Health Sciences
DRA
Division of Ratepayer Advocates
DSD
Development Services Department
EAS
Environmental Analysis Section
EIR
Environmental Impacts Report
ELF
Extremely Low Frequency
EMF
Electromagnetic Field
EPA
Environmental Protection Agency
ESMR
Enhanced Specialized Mobile Radio
FCC
Federal Communications Commission
FDA
Food and Drug Administration
GHz
Gigahertz
G.O.159 (A)
General Order 159 (A)
IEEE
Institute of Electrical and Electronic Engineers
kHz
Kilohertz
LCP
Local Coastal Plan
MHz
Megahertz
MSO
Main Switching Office
MTA
Metropolitan Trading Area
mW/cm2
Milliwatt per square centimeter
PCS
Personal Communications Services
RFR
Radio Frequency Radiation
RSA
Rural Statistical Area
SMR
Specialized Mobile Radio
SMSA
Standard Metropolitan Statistical Area
TDMA
Time Division Multiple Access
V/m
Volts per meter
WTB
Wireless Telecommunications Bureau
GLOSSARY
Analog Technology (see Digital Technology)
Analog technology replicates and amplifies
voice messages as they are carried from the
transmitting antenna to the receiving antenna.
Traditionally, cellular phone systems have
used analog transmission signals.
Antenna
A device used in communications which transmits
or receives radio signals.
Band
A clearly defined range of radiofrequencies
dedicated to a particular purpose.
California Public Utilities Commission (CPUC)
Governmental agency which regulates the terms
and conditions of public utilities in the
State of California. Of the three wireless
communications services discussed in the Issues
Paper, the CPUC presently regulates only cellular
service providers.
Channel
A segment of a frequency band. Also referred
to simply as “frequency.”
Co-location
Locating wireless communications equipment
from more than one provider on a single site.
Common Carrier
A public radio service in which a single licensee
provides one-way or two-way service to
multiple users.
Communications Facility
A land use facility supporting antennas and
microwave dishes that sends and/or receives
radiofrequency signals. Communications facilities
include structures or towers, and
accessory buildings.
Digital Technology
Digital technology converts voice and data
messages into digits that represent sound
intensities at specific points of time and
data content. ESMR and PCS service providers
employ digital technology, and cellular providers
are rapidly converting to digital as well.
Dish Antenna
A dish-like antenna used to link communications
sites together by wireless transmission
of voice or data. Also called microwave antenna
or microwave dish antenna.
Effective Radiated Power (ERP)
The power supplied to an antenna multiplied
by the relative gain of the antenna in a given
direction.
Electromagnetic Field (EMF)
The local electric and magnetic fields that
envelop the surrounding space. The most
ubiquitous source of EMFs is from the movement
and consumption of electric power, such
as with transmission lines, household appliances
and lighting.
Federal Communications Commission (FCC)
The federal agency responsible for licensing
and regulating wireless communications
providers. The FCC has primary regulatory
control over communications providers through
its powers to control interstate commerce
and to provide a comprehensive national system
in accordance with the Federal Communications
Act.
Frequency
The number of cycles made by electromagnetic
radiation in one second, usually
expressed in units of hertz (Hz).
Hertz
A unit for expressing frequency which is the
number of times a wave-like radio signal
changes from maximum positive to maximum negative
charge per second. 1 Hz = 1 cycle
per second. 1 kilohertz (kHz) = 1,000 Hz;
1 megahertz (MHz) = 1,000 kHz or 1,000,000
Hz; 1 gigahertz (GHz) = 1,000 MHz or 1 million
kHz or 1 billion Hz.
Interference
Disturbances to reception caused by radiofrequency
waves or other electric fields.
Microwave
Electromagnetic radiation frequencies from
3 GHz to 300 GHz; highly directional when
used for radiofrequency transmissions. Uses
relatively low transmitter power levels when
compared to other forms of transmission.
Monopole
A structure composed of a single spire used
to support communications equipment.
Non-ionizing Electromagnetic Radiation
Electromagnetic waves of low frequency, long
wavelength, and low photon energy unable to
cause ionization (i.e., to remove an electron
from an atom).
Panel Antenna
An antenna or array of antennas designed to
concentrate a radio signal in a particular area.
Panel antennae are typically flat, rectangular
devices approximately six square feet in size.
Also called directional antennae.
Power Density
The magnitude of the electromagnetic energy
flux density at a point in space, in power per
unit of area (measured in milliwatts per square
centimeter or mW/cm2).
Radio
A generic term referring to communication
of impulses, sounds, and pictures through
space by means of electromagnetic waves.
Radiofrequency Radiation (RFR)
Electromagnetic radiation in the portion of
the spectrum from 3 kHz (kilohertz) to 300 GHz
(gigahertz).
Stealth Facility
Any communications facility which is designed
to blend into the surrounding environment.
Examples of stealth facilities may include
architecturally screened roof-mounted antennas,
building-mounted antennas painted to match
the existing structure, antennas integrated
into architectural elements, and antenna structures
designed to look like light poles. Also
called concealed antennas.
Wavelength
The distance between points of corresponding
phases of a periodic wave of two constant
cycles. Wavelength = wave velocity/frequency.
Whip Antenna
An antenna that transmits signals in 360 degrees.
Whip antennae are typically cylindrical
in shape and are less than 6 inches in diameter
and measure up to 18 feet in height. Also
called omnidirectional, stick, or pipe antennas.