United States
           Environmental Protection
           Agency
            Office of Air and Radiation &    402-R-95-011
            Office of Research and     March 1995
            Development
v>EPA
Summary and Results of the
April 26-27,1993
Radiofrequency Radiation
Conference
Volume 2: Papers

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                                           402-R-95-Q11
                                           March 1995
Summary and Results of the April 26-27,
      1993 Radiofrequency Radiation
                  Conference

                 Volume 2:  Papers
                      Prepared for

                  Office of Air and Radiation
              and Office of Research and Development
               U.S. Environmental Protection Agency
                     401 M Street, SW
                   Washington, DC 20460
                     Under Contract

                 Nos. 68-DO-0102 and 68-D2-0177

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ii  SUMMARY AND RESULTS OF THE RAD1OFREQUENCY RADIATION CONFERENCE: VOLUME 2
                                DISCLAIMER

      Statements,  recommendations,  and  conclusions  expressed  by  participants  of  the
Radiofrequency Radiation Conference (Bethesda, Maryland, April 26 and 27, 1993) and summarized
in this document are their own and do not necessarily represent the views of the U.S. Environmental
Protection Agency (EPA). Furthermore, mention of trade names or commercial products does not
constitute endorsement or recommendation for use by EPA.

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                                                     TABLE OF CONTTENTS  iii
                    TABLE OF CONTENTS
                                                                Page

Disclaimer	 . . ii

Abstract	,	v
A REVIEW OF RADIOFREQUENCY ELECTRIC AND MAGNETIC FIELDS IN
     THE GENERAL AND WORK ENVIRONMENT: 10 kHz to 100 GHz
     Edwin D. Mantiply et al.	1

DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS
     Arthur W. Guy	25

RF SHOCKS AND BURNS: SOME KNOWNS AND UNKNOWNS
     Om P. Gandhi	- - 47

HUMAN THERMAL RESPONSES TO RF-RADIATION INDUCED HEATING
     DURING MAGNETIC RESONANCE IMAGING
     Frank G. Shdlock	57

EPIDEMIOLOGIC STUDIES OF NON-IONIZING RADIOFREQUENCY EXPOSURES
     Genevieve MaianosM 	77

RESPONSES OF LABORATORY MAMMALS TO RADIOFREQUENCY RADIATION
     (500 kHz-100 GHz)
     Joe A. Elder	87

RADIOFREQUENCY RADIATION EFFECTS ON CELLS
     Stephen F. Cleary	101

ALTERATIONS IN ORNITHINE DECARBOXYLASE ACTIVITY: A CELLULAR
     RESPONSE TO LOW-ENERGY ELECTROMAGNETIC FIELD EXPOSURE
     Craig V. Byus	 Ill

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                                                                             ABSTRACT
                                   ABSTRACT

       On April 26 and 27, 1993, the U.S. Environmental Protection Agency (EPA) Office of Air
and Radiation and Office of Research and Development held a conference to assess the current
knowledge of biological and human health effects of radiofrequency (RF) radiation and to address
the need for and potential impact of finalization of federal guidance on human exposures to RF
radiation.  More than 200 people attended the conference.   Attendees represented the federal
government, academia,  the private sector, trade associations,  the media, and the public.   Plenary
papers presented at the meeting focused on current research findings on a variety of topics, including
exposure assessment,  dosimetry, biological effects,  epidemiology,  the basis for exposure limits, and
emerging health issues.  Panel discussions focused on identifying key scientific information needs for
and the policy implications of the development of further EPA guidance on human exposures to RF
radiation. This document, Volume 2, provides the plenary papers presented by speakers.  Volume
1, under separate cover, provides a record of much of the information presented at the conference,
outlines key recommendations provided to EPA by conference participants, and presents the EPA
strategy for addressing RF radiation.

       Two key recommendations for EPA emerged from the conference: (1) develop RF radiation
exposure guidance as soon as possible, and (2) conduct additional research in a number of areas,
particularly  with  respect to the potential  for "nonthermal" effects.  These recommendations were
considered by EPA in its decision to proceed with the development of guidelines on human exposure
to  RF radiation and  to develop a longer term strategy to address  remaining issues.   Part of this
strategy has involved  creating an inter-agency work group and requesting the National Council on
Radiation Protection (NCRP) to  assess  several remaining issues.   Information provided  at the
conference also was used as a basis for EPA comments to the Federal Communications Commission
(FCC) 1993 proposal to adopt the RF radiation  exposure guidelines developed in 1992 by the
American National Standards Institute (ANSI) and the Institute  for Electrical and Electronics
Engineers (IEEE).

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                               RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ET AL.)   1


     A REVIEW OF RADIOFREQUENCY ELECTRIC AND MAGNETIC
          FIELDS IN  THE GENERAL AND WORK ENVIRONMENT:
                                  10 kHz to 100 GHz*
                                     Edwin D. Mantiply**
                                      Samuel W. Poppell
                                        Julia A. James
ABSTRACT

       We have plotted data from a number of studies on the range of radiofrequency (RF) field levels
due to a variety of environmental and occupational sources.  This work is organized into standard
frequency bands from very-low frequency (VLF) to super-high frequency (SHF).  Electric field values
range from micro- to kilovolts per meter. Most of the reported electric fields range from 0.1 to 1000
volts/meter (V/m). The strongest fields observed are near industrial induction and dielectric heaters, close
to the radiating elements or transmitter leads of high power antenna systems and in front of onboard
aircraft radars.  Hand-held transmitters can produce near electric fields of hundreds of volts per meter.
Peak fields from air traffic radars in the general urban environment are about 10 V/m and about 300 times
greater than  the true  root-mean-square (rms)  field  strength when rotation  and pulsing are factored  in.
Loran navigational and amateur transmissions can be modulated at extremely-low frequencies.  Sources
used for heating are likely to  be  amplitude modulated at harmonics of the power frequency.  Sources
included in this  review are the following: Coast Guard navigational transmitters; a Naval VLF transmitter
at Lualualei, Hawaii; computer video displays;  induction stoves or  rangetops; industrial induction and
dielectric heaters; radio and  television broadcast transmitters;  amateur and CB transmitters; medical
diathermy and electrosurgical units; mobile and hand-held transmitters; cordless and cellular telephones;
microwave ovens; microwave terrestrial relay and  satellite uplinks;  and police, air traffic, and aircraft
onboard radars.

INTRODUCTION

       In response  to the question "Who is exposed to  what?",  this  paper graphically presents  an
overview of RF  electric and magnetic fields measured in various environmental, occupational, and product
evaluation studies.  The scope is wide in terms of the 'type of sources included.  Any  type of source
causing potential exposures can be included.  However, the scope is narrow with respect to the metrics
of exposure covered.   No discussion of dosimetry, coupling of fields to induce body currents,  or
applicability of  various exposure guidelines, is undertaken.

       In addition to field strength,  the time variation or modulation and spatial character of fields are
reviewed.  For example, data on three exposure milieu are included for broadcast stations. First, a range
of general environmental levels; second, the range of field values found on the ground or at buildings in
the immediate vicinity of the transmitting antenna; and third, possible exposure values for an individual
climbing  the antenna tower are described.

       This paper is intended to be an introduction and bibliography to RF levels. Earlier reviews contain
more descriptive information on how fields are measured, calculated, and shielded [Stuchly, 1977; Stuchly
and Mild, 1987; Mild and Lovstrand, 1990; Joyner, 1988; Hankin, 1986].
   * Key words: nonionizing radiation, exposure. This paper was updated in November 1993.

   ** Presenter. Can be contacted at the National Air and Radiation Environmental Laboratory, U.S. Environmental
Protection Agency, Montgomery, AL 36115 - 2601.

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2   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

       The review is organized into seven standard radiofrequency bands and covers the sources shown
in Table 1. Figure 1 is a summary plot showing the format of presentation without identifying the boxes
that show the field and frequency ranges for the various sources covered; Figures 2 through 8 give the
results for each band with the boxes identified.
TABLE 1. Frequency Bands and Sources Included in Review
Adjectival
Band
Designation
Very-low
frequency
Low frequency
Medium frequency
High frequency
Very-high
frequency
Ultra-high
frequency
Super-high
frequency
Abbre-
viation
VLF
LF
MF
HF
VHP
UHF
SHF
Frequency
Range
10* to 30 kHz
30 to 300 kHz
300 to 3000
kHz
3 to 30 MHz
30 to 300 MHz
300 to 3000
MHz
3 to 30 GHz**
Sources Included
omega navigational transmitters,
a Navy communication transmitter,
video displays, induction stoves
loran navigational transmitters
AM broadcast, 160 meter amateur, induction
heaters, electrosurgical units
international broadcast, amateur and CB,
dielectric heaters, shortwave diathermy
FM broadcast, VHP television, mobile and
hand-held transmitters, cordless telephones
UHF television, cellular telephones,
microwave ovens and diathermy, air traffic
radars
microwave relay, satellite uplinks, aircraft
onboard radar, police radar
* The standard start frequency for VLF is 3 kHz; 10 kHz is used here.
** No data on sources between 30 and 100 GHz was found.
VERY-LOW FREQUENCY, 10 kHZ TO 30 kHZ

       The wavelength for this frequency range varies  from 30 km at 10 kHz to 10 km at 30 kHz.
Antennas designed to transmit at these long wavelengths are large structures driven at high voltage.  The
typical antenna is similar to that for a standard AM broadcast station where the entire tower acts as the
antenna.  However,  in contrast to most AM towers, many VLF antennas use extended wire  structures
connected to the top of a tower or transmitter lead (feed line) to increase the  effective height of the
antenna.  In all cases, the radiating structure is insulated and driven at some high radiofrequency potential
referenced to a ground radial system.  Transmitting systems in the VLF frequency range that have been
studied in some detail include, omega navigational systems and the VLF submarine communication system
at Lualualei, Hawaii. Finally, near field sources such as video displays and induction heaters generate
VLF electric and magnetic  fields in their immediate vicinities.  Figure 2 displays the range of field
strengths measured for some VLF sources.

       Omega Navigational Transmitters

       There are eight omega very-long-distance navigational transmitters in the world. Two are in the
United States  one  in North Dakota and one in Hawaii [Gailey, 1987]. These VLF transmitters switch
between frequencies from  10.2 to 13.6 kHz in a repeating 10 second cycle. The transmission is a series

-------
- 51.5 A/m
- 16.3 A/m
- 5.15 A/m
- 1.6^ A/m r
- 0.51 $ A/m 5

}
- 0.163 A/m >
S
- 51.5 mA/m >

'
- 16.3 mA/m '
'
- 5.15 mA/m

- 1.63 mA/m

- 0.515 mA/m

-0.163 mA/m
- 51.5 pA/m
- 16.3 pA/m
- 5.15 pA/m
- 1,63 pA/m
- 0.515 pA/m
- 0.163 pA/m










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                                                                                                                     10GHz

                                                                            FREQUENCY
Pig.  I.  Summary chart of field levels detailed in Figures 2 through 8. Each box represents a field strength and frequency range for a particular source and region
of possible exposure.  The vertical axes for electric and magnetic fields and equivalent power density are scaled so that the three values found on a horizontal line
correspond to the fields  and power density of a plane  electromagnetic wave propagating in free space where the ratio of the electric  to the magnetic field is 377
ohms.  The vertical scales are kept constant in all figures. Electric and magnetic field measurements are plotted as  lines slanted in opposite directions so that a cross
hatched region indicates  a range of field magnitudes having a ratio similar to the value in free space.
EQUIVALENT
POWER DENSITY
_
-
-
-
-
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-

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W/cm*
W/cm2
W/cm2
mW/cm2
mW/cm2
mW/cm2
pW/cmz
pW/cm2

pW/cm2
nW/cm2

nW/cm2

nW/cm2


pW/cm2
pW/cm2
pW/cm2
fW/cm2

fW/cm2

fW/cm2




source and region
found on a horizontal line






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-------
ELECTRIC FIELD MAGNETIC FIELD
fc^s^^s^^xl Y////////////A
19.4 kV/m -
6.14 kV/m -

1.94 kV/m -

614 V/m -

194 V/m -

61.4 V/m -

19.4 V/m -

6.14 V/m -
1.94 V/m -
0.614 V/m -

0.194 V/m -
61.4 mV/m -
19.4 mV/m -
6.14 mV/m -
1.94 mV/m -
0.614 mV/m -

0.194 mV/m -
61.4 pV/m -


- 51.5 A/m
- 16.3 A/m OMEGA, ND

- 5.15 A/m

- 1.63 A/m

- 0.515 A/m

- 0.163 A/m

- 51.5 mA/m

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- 0.163 mA/m
- 51.5 pA/m
- 16.3 pA/m
- 5.15 pA/m
- 1.63 pA/m

- 0.515 pA/m
- 0.163 pA/m
EQUIVALENT
POWER DENSITY
- 100 W/cm2
- 10 W/cm2 i
^
- 1 W/cm2 *
^
- 100 mW/cm2 
jj
- 10 mW/cm2 $
c
- 1 mW/cm2 ^
o
- 100 pW/cm2 "
i
10 pW/cm2 rn
|
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- 100 nW/cm2 |
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- 10 nW/cm2 |
- 1 nW/cm2 ^
- 100 pW/cm2 S
- 10 pW/cm2 5
- 1 pW/cm2 8
- 100 fW/cm2 S
m
- 10 fW/cm2 o
- 1 fW/cm2 <
                                                  10kHz
20 kHz
                                                                                                                 30kHz
                                                                     FREQUENCY
                                                                                                                                                        m
                                                                                                                                                        ro
Fig. 2. Very-low frequency fields.  The first block shows the range of electric and magnetic fields seen near the omega transmitting antenna in North Dakota.  The
lower values was measured at 640 rn from the tower and the higher values were found at about 12 m from the tower.  The video displays box is the range of VLF
fields measured 30 cm in front of VDT's in a large number of studies.  The Lualualei box shows the range of fields seen in the community surrounding the Lualualei
Naval VLF transmitter in Hawaii.  The induction stove box shows fields measured 30 cm from induction rangetops.

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                               RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ETAL.)  5

of eight single-frequency sinusoidal carriers switched on for 0,9 to 1,2 seconds with a pause of 0.2 seconds
between each carrier. The drive voltage on omega antennas is about 250 kilo volts. For the North Dakota
station, the measured rms electric field varied smoothly along one radial from 66 volts/meter (V/m) at 640
rn to 4400 V/m at 12 rn from the tower base. The rms magnetic field varied from 20 milliamp/meter
(mA/m) at 640 m to 2,9 amp/meter (A/m) at 11 m from the tower.  The Hawaii omega station antenna
is more complex, and so are the field variations.  For example, outside the station building, reported
electric fields varied from 57 to 938 V/m and magnetic fields varied from 1.2 to 4.4 A/m. The maximum
measured  magnetic field at Hawaii  was 18 A/m near the main feed line.  Earlier investigators reported
magnetic fields of from 0.2 to 6.2 A/m in the transmitter building and near the feed line [Guy and Chou,
1982].

       VLF Transmitter at Lualualei, Hawaii

       The  U. S. Navy operates a VLF transmitter at Lualualei, Hawaii on a frequency of 23.4 kHz
[Mantiply, 1992], The signal is frequency modulated so that it appears to be a constant sinusoidal carrier
for field measurement purposes.  Outside  the station  boundary and in the surrounding community, the
measured electric Fields varied from 0.15 to 82 V/m and the magnetic field varied from 2.5 to 99 mA/m.
These  measurements were made  at distances of approximately 800 m to 7  km from the  transmitting
towers. On site measurements by the Navy in 1982 showed that the electric field varied from 972 V/m
to 700 V/m between about 80 and 150 m from the antenna. Measured magnetic fields in the transmitter
building and near the feed line  varied from 0.11 to 14 A/m [Guy and Chou, 1982].

       Video Displays

       The  common video display using  a CRT  generates a sawtooth waveform VLF magnetic  field.
This field  is used to horizontally sweep the electron beam across the screen. VLF electric fields are also
generated  by the flyback transformer. The fundamental frequency of these fields is between 15 and 35
kHz and harmonics exist up to several hundred kilohertz. Many studies and reviews have been made of
fields near video displays [Tell, 1990; Boivin, 1985; Mild and Sandstrom, 1992; Tofani and D'Amore,
1991; Stuchly  et  al, 1983; Walsh et al., 1991; Jokela et ah, 1989; Schnorr et ah, 1991; Kavet and Tell,
1991; Charron, 1988; Marha et ah, 1983; Guy, 1987].  Most studies have made this measurement 30 cm
(I foot) in front of the screen center. Reported VLF electric fields at 30 cm range from 0.22 to 52 V/m;
mean  values reported by different investigators vary from 0.83 to 12.5 V/m.  Reported VLF magnetic
fields measured at 30 cm range from 0.26 to 170 mA/rn;  mean values reported  vary from 20 to 85 mA/m.
Greater VLF fields at the same distance can be found to the sides and rear of video displays.

       Induction Heating Stoves

       Induction heating stoves are home appliances  that generate a magnetic field at tens of kilohertz
to heat food by the induction of eddy currents in cooking utensils.  Electric and magnetic fields have been
measured near two stoves heating a variety of utensils [Stuchly and Lecuyer, 1987]. At a distance  of 30
cm from the stove, electric fields averaged 4.3 to 4.9 V/m and magnetic fields varied from 0.7 to  1.6 A/m.

LOW FREQUENCY, 30 KHZ TO 300 KHZ

       Loran Navigational Transmitters

       Loran  navigational transmitters emit a pulsed signal centered  at 100 kHz.  Each  transmitter
generates  a  unique  pulse train repeating  at 10  Hz  [Gailey,  1987].   Depending on the  pulse  train,
instantaneous peak fields vary from 11 to 18 times  greater than the rms fields reported here. Electric and
magnetic fields were measured at 9 different loran stations. Electric fields varied from 28 to 350 V/m and
magnetic fields varied from 0.6 to 2.9 A/m at locations 3 to 4 m  from the tower  base or feed point. At
a distance  of 300 m the electric field varied from 3 to 9  V/m and the magnetic field varied from 6  to 41

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6   SUMMARY AND RESULTS OF THE RAD1OFREQUENCY RADIATION CONFERENCE: VOLUME 2

mA/m.  Maximum fields were generally measured near the antenna insulator or tuning coils.  At eight
stations, the maximum electric field varied from 463 to 2830 V/m and the maximum magnetic field varied
from 3,8 to greater than 10 A/m.  Magnetic fields up to 52 A/m near loran feeds have been reported [Guy
and Chou, 1982]. Figure 3 summarizes low frequency fields near loran navigational transmitters.

MEDIUM FREQUENCY, 300 kHZ TO 3 MHZ

       The medium frequency range from 300 kHz to 3 MHz has associated wavelengths of 1000 to 100
m,  AM standard broadcast operates from 535 to 1605 kHz with wavelengths of 560 to 190 m.  Amateur
radio operators also transmit  in the  MF band at 1.8 to 2.0 MHz in the 160 meter band.  Industrial and
medical sources also operate  at MF.  Figure 4 summarizes fields in the medium frequency band.

       AM Standard  Broadcast

       Studies of general population exposure in the United States by  the Environmental Protection
Agency in the late 1970's suggest that approximately 3 % of the urban population is exposed to electric
fields greater than 1 V/m due to AM broadcast.  Ninety-eight percent of the population is exposed to
greater than 70 mV/m and the median exposure is about  280 mV/m [Hankin,  1986].

       Recently, electric and magnetic fields were measured near eight AM broadcast towers [Mantiply
and Cleveland, 1991].  The fields were measured at 1 to 100 m from the center of each tower base. One
station operated at the maximum power of 50 kilowatts (kW); three  stations transmitted at approximately
5 kW; and the remaining four  stations were 1 kW transmitters. Fields were typically measured along three
radials at each station.  At distances of 1 or 2 meters, electric field values varied from 95 to 720 V/m and
magnetic fields were from 0.1 to 1.5 A/m. At 100 m from the tower, electric fields varied from 2.5 to 20
V/m; magnetic, from 7.7 to 76 mA/m.

       Fields were measured close  to five AM towers in the Honolulu, Hawaii area [U.S. EPA, 1985],
Accessible regions near the tower base or tuning network were probed for maximum electric and magnetic
fields.  Maximum electric fields at the five towers varied from 100  to 300 V/m and maximum magnetic
fields varied from 0.61 to 9.3  A/m. Magnetic fields of up to  14.4 A/m have been reported at about 2 feet
from an antenna tuning coil at the base of an AM tower [Wang and Linthicum, 1976].  Electric fields up
to 1170 V/m were measured at 2 m above ground and about 3 cm from the surface of one AM tower [Tell
et al, 1988],

       Special studies of AM field  strengths  at residences and at a school near AM radio stations have
been made in Spokane, Washington and Honolulu, Hawaii [Tell  et al., 1988; U.S. EPA, 1985].  In
Honolulu, measurements were made at highrise condominiums adjacent to  an  AM broadcast tower.
Electric  fields at  a recreational area  outside on the roof of one of these buildings were typically 100 to
200 V/m, and the AM magnetic field was 120 mA/m.  Indoors, in a thirtieth floor  apartment, the electric
field was 2 to 3 V/m and the magnetic field was 240 mA/m.  Electric and magnetic fields were measured
inside and outside a single family house in Spokane near a 50 kW AM station. At locations outside where
the  fields did not appear to be perturbed, electric fields varied from 9 to 19 V/m.  Clearly perturbed
electric fields inside the house varied from 1 to 55 V/m.  Magnetic fields outside varied from 30 to 40
mA/m and inside varied from 31 to 49 mA/m. Electric and magnetic fields were also measured inside
an elementary school in Spokane approximately  100 m from the same AM station. Electric fields in the
school varied  from 1 to 28 V/m and magnetic fields varied from 22 to 470 mA/m. Unperturbed electric
and magnetic  fields at the school were estimated to be 15 V/m and 40 mA/m. Apparently, both medium
frequency electric and  magnetic fields due to  AM broadcast can be either increased or decreased in the
indoor environment.

-------
             ELECTRIC FIELD  MAGNETIC FIELD
                              Y////////////A
                                                 EQUIVALENT
                                                POWER DENSITY
19.4
6.14
1.94
614
194
61.4
19.4
6.14
1.94
0.614
0.194
61.4
19.4
6.14
1.94
0.614
0.194
61.4
kV/m -
kV/m -
kV/m -
V/m -
V/m -
V/m -
V/m -
V/m -
V/m -
V/m -
V/m -
mV/m -
mV/m -
mV/m -
mV/m -
mV/m -
mV/m -
- 51.5 A/m
- 16.3 A/m
- 5.15 A/m LORAN
- 1.63 A/m ^
5O^X
- 0.515 A/m ^
- 0.163 A/m xV^;
- 51 5 mA/m

- 16.3 mA/m $&
/X/
- 5.15 mA/m
- 1.63 mA/m
- 0.515 mA/m
- 0.163 mA/m
- 51.5 jjA/m
- 16.3 pA/m
- 5.15 pA/m
- -(.63 jjA/m
- 0.515 j-iA/m
- 0.163 MA/m
                                                      30KHz
100kHz
                                                                   FREQUENCY
200 kHz
                                                                                                            300kHz
                                                                                                                 -  100   W/cm2
                                                                                                                    10    W/cm2
                                                                                                                    1     W/cm2
                                                                                                                    100   mW/cm2
                                                                                                                    10    mW/cm2
                                                                                                                    1     mW/cm2
                                                                                                                    100   pW/cm2
                                                                                                                    10    pW/cm2
                                                                                                                    1     jjW/cm2
                                                                                                                    100   nW/cm2
                                                                                                                    10    nW/cm2
                                                                                                                    1     nW/cm2
                                                                                                                 -  100   pW/cm2
                                                                                                                 -  10    pW/cm2
                                                                                                                 I-  1     pW/cm2
                                                                                                                 -  100   fW/cm2
                                                                                                                 h  10    fW/cm2
                                                                                                                 h-  1     fW/cm2
                                                                       Tl
                                                                       m
                                                                       D
                                                                       CO
                                                                       H
                                                                       m
                                                                       0
                                                                       m
                                                                       m
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                                                                       m
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                                                                                                                                           IS
                                                                                                                                           21
Fig. 3. Low frequency fields near loran navigational transmitters.  The upper box shows the range of rms fields measured at 9 loran stations at 3 to 4 m from the tower
base or feed line. The lower box shows the range of fields at 300 m.

-------
            ELECTRIC FIELD  MAGNETIC FIELD
PS^S^s^SS^sl
19.4
6.14
1.94
614
194
61.4
19.4
6.14
1.94
0.614
0.194
61.4
19.4
6.14
1.94
0.614
0.194
61.4
kV/m
kV/m
kV/m
V/m
V/m
V/m
V/m
V/m
V/m
V/m
V/m
mV/m
mV/m
mV/m
mV/m
mV/m
mV/m
pV/m
                             V////////7/7/R
51.5   A/m
16.3   A/m
5.15   A/m
1.63   A/m
    i
0.515  A/m
0.163  A/m
51.5   mA/m
16.3   mA/m
5.15   mA/m
1.63   mA/m
0.515  mA/m
0.163  mA/m
51.5   pA/m
16.3   pA/m
5.15   pA/m
1.63   pA/m
0.515  pA/m
0.163  pA/m
                                            INDUCTION
                                            HEATER
AM
                                                                                    AMATEUR
                                                                                     160M
                                                                 POPULATION
                                                                                      sss
                                                      _,	,
                                                       300 kHz
                                                                          1	1	1	i	T
  1 MHz
FREQUENCY
                                                             2 MHz
-r-r-r-
     3 MHz
             EQUIVALENT
            POWER DENSITY
        -   100  W/cm2
            10   W/cm2
            1     W/cm2
            100  mW/cm2
            10   mW/cm2
        -   1     mW/cm2
            100  pW/cm2
            10   pW/cm2
        -   1     pW/cm2
            100  nW/cm2
            10   nW/cm2
            1     nW/cm2
        -   100  pW/cm2
            10   pW/cm2
            1     pW/cm2
            100  fW/cm2
            10   fW/cm2
            1     fW/cm2
                                                                          >
                                                                                                                                             33
                                                                                                                                             m
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                                                                                                                                             w
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Fig. 4. Medium band fields.  The lower box shows the range of electric field exposure due to AM broadcast for about 95 percent of the U. S. urban population.  The
range of fields seen near eight AM broadcast towers at 1 meter and at 100 meters is plotted above the population exposure range. The range of fields measured directly
beneath several  amateur 160 meter band antennas is shown on the right.  The range of fields seen in several studies of exposure for induction heater operators is on
the left.

-------
                               RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ET AL.)   9

       Standard  AM  broadcast uses double-sideband amplitude  modulation  at audio frequencies.
Measurement of nine different AM signals in Las Vegas, Nevada showed ELF modulation values from
4 to 30 % in the frequency range of 3 to 100 Hz [Mantiply, 1990].

       Amateur 160 Meter Band

       Amateur radio operators can transmit up to 1.5 kW in the  160 meter wavelength band from  1.8
to 2.0 MHz. Electric and magnetic fields in this band were measured at three amateur radio installations
[Cleveland et al., 1991]. These measurements were made outdoors at 1 or 2 meters above ground beneath
active antenna wires.  The operator set the transmitter for a constant carrier at 1.95 MHz.  Beneath an
open line "modified T"  antenna feed operating at 500 watts, electric fields varied from 52 to 240 V/m and
magnetic fields varied from 37 to 310 mA/m. Beneath an "inverted V" dipole operating at 100 watts  the
electric field varied from 0.7 to 5.4 V/m, and the magnetic field varied  from 4 to 100 mA/m.  Beneath
another 160  meter dipole antenna operated at 80 watts, the electric field varied from 5 to 22 V/m and  the
magnetic field varied from 13 to 78 mA/m,

       Induction Heaters

       Induction (eddy current) heaters  are  used  in industry to heat metals  or semiconductors  by
generating a strong alternating magnetic field inside a coil. The range of frequencies can be from 50  Hz
to 27 MHz. Lower frequency units produce stronger magnetic fields that also  penetrate and  heat  the
material more  deeply.  Higher frequencies are used for surface heating.  The  strongest magnetic fields
measured have been for heaters operating at frequencies below 10.3 kHz, but these frequencies  are outside
the scope of this review [Stuchly and Lecuyer, 1985; Mild and Lovstrand, 1990]. In 5 studies [Aniolczyk,
1981; Centaur, 1982; Stuchly and Lecuyer, 1985; Conover et al., 1986; Andreuccetti et al.,  1988]
measurements  were made near medium frequency induction  heaters operating from 250 to 790 kHz.
These fields vary greatly over small distances and with  the type  of unit and process. Typically,  the
electric field may decrease from 1000 to 100 V/m and the magnetic field decreases from 20 to 0.5 A/m
as distance from the coil is increased from 20 to 100 cm.  Reported electric and magnetic field exposure
for the operator vary from 2 V/m to 8.2 kV/m and 0.1 to 21 A/m.   These field values are not corrected
for duty cycle.  It is likely that radiofrequency induction heater fields are amplitude modulated at multiples
of the power frequency.

       Electrosurgical Units

       Medical electrosurgical units operate from 0.5 to 2.4 MHz with significant harmonics and spurious
frequencies up to 100 MHz.  Electric and magnetic fields measured under typical conditions vary from
about 200 V/m and 0.1  A/m at 40 cm to about 1000 V/m and 0.35  A/m at 10 cm from the cutting probe
lead.  These values also vary depending on operating mode.  At 16 cm, fields varied from 120 to 1000
V/m and 0.06 to 0.71 A/m depending on the mode of operation.  The unit may operate with amplitude
modulation at frequencies of approximately 10 to 30 kHz [Ruggera, 1977].

HIGH  FREQUENCY,  3 MHZ TO 30 MHZ

       The HF or shortwave range of frequencies is from 3 to 30  MHz with associated wavelengths of
100 to 10 meters. One characteristic feature of the HF band is long range communication by ionospheric
reflection. Because of this propagation characteristic there is always a background of fields from distant
sources in the HF band.  For example, one set of measurements showed about 50 signals  between 0.1 and
1  mV/m  from 3  to 30 MHz [Mantiply and  Hankin,  1989].   HF  is used  for long range  radio
communications for international broadcast  by governments and  private organizations, amateur radio
operators, contract communication providers for aircraft and ships  at sea, and military communications.
Typical transmitter powers for amateurs are 100 or 1000 watts; professional communication providers use
about 10 to 30 kilowatts (kW);  and broadcasters operate at 50 to 500 kW. Over-the-horizon (OTH) radar

-------
10   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

systems can transmit up to 1200 kW. High frequency sources are also used in industry and medicine for
plastic welding and diathermy.  Figure 5 summarizes the range of fields measured for several types of HF
sources.

       Amateur Radio

       Electric and magnetic fields were measured at 9 amateur radio transmitting sites.  Fields were
determined beneath antennas at a height of 1 to 2 meters for various antenna configurations and frequency
bands [Cleveland et al, 1991], Transmitter powers varied from 100 to 1400 watts for these measurements.
The transmitters were  set to transmit a constant carrier (no duty cycle correction).  The values reported
in Table 2 are "example"  values. Fields greater than these values were measured in some bands very close
to antennas or feed points. Amateur keyed carrier and single-sideband voice transmissions  are amplitude
modulated at frequencies below 100 Hz.  For  example, one measurement of an amateur  keyed carrier
signal resulted in 90 percent modulation from 3 to 100 Hz.
              TABLE 2.  HF Amateur Fields Measured at 9 Installations
Wavelength
Band
(meters)
80
40
20
15
10
Frequency
Range (MHz)
3.5 - 4.0
7.0 - 7.3
14.00 - 14.35
21.00-21.45
28.0 - 29.7
Electric Field
Range (V/m)
1 -85
4-200
2- 14
1 -30
10-23
Magnetic Field
Range (mA/m)
4 - 1400
9-260
5-28
5 -70
2-9
       Citizen Band Radio

       Electric and magnetic fields near several CB antennas  have been investigated in some detail
[Ruggera, 1979]. Tests were performed with the antennas operating at 27.12 MHz and at 4 watts. Fields
were measured as a function of height at a horizontal distance of 5, 12, and 60 cm from the antennas.
The maximum electric and magnetic fields measured at 5 cm varied from 230 to 1400 V/m and 0.1 to 1.3
A/m; at 12 cm, from 90 to 610 V/rn and 0.05 to 0.8 A/m; at 60 cm, maximum electric fields varied from
18 to 60 V/m and maximum magnetic fields were less than the instrument sensitivity of 0.04 A/m. The
CB 40 channel band is from 26.965 to 27.405 MHz. Most transmission is AM, but single side-band can
be used.

       International Broadcast

       High power HF transmitters are used for international broadcasts by governments and private
organizations,  EPA has made measurements at two Voice of America (VOA) sites. VOA typically uses
250 kW transmitters, large rhombic or curtain type  antennas, and standard  amplitude modulation. Also,
50 kW dual  independent side-band transmitters are used for relay. On the Bethany, Ohio VOA station
property electric fields of 2.5 to  100 V/m were  measured  beneath RF transmission lines and  rhombic
antennas.  A study near the VOA transmitter site  at Delano, California emphasized measurements  of
potential exposures in the community of  McFarland,  10 km away from the  VOA  site [Mantiply and
Hankin, 1989], High frequency electric and magnetic fields in McFarland due to VOA were measured

-------
          ELECTRIC FIELD  MAGNETIC FIELD
- 51.5 A/m
- 16.3 A/m
- 5.15 A/m
AMATEUR
- 1.63 A/m 80rS
*
- 0.515 A/m ;
,
- 0.163 A/m
- 51.5 mA/m
- 16.3 mA/m

- 5.15 mA/m
^








- 1.63 mA/m
- 0.515 mA/m
- 0.163 mA/m
- 51.5 pA/m
- 16.3 pA/m
- 5.15 pA/m
- 1.63 pA/m
- 0.515 pA/m
- 0.163 pA/m










40 M


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-------
12   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

at six sites at 4 frequencies: 6.155, 9.765, 9.815, and 11.74 MHz. For any one frequency, electric field
values varied from 1.5 to 64 mV/m, and magnetic fields varied from 0.0055 to 0.16 mA/m. The maximum
HF electric and magnetic fields measured just outside the Delano VOA boundary were 8.6 V/m and 29
mA/m.

        Electric and magnetic fields were also measured on the VOA Delano site along traverses 1 meter
above ground and perpendicular to the direction of propagation in front  of a rhombic  antenna and a
conventional curtain antenna.  Fields in front a steerable curtain antenna were investigated by varying its
operating direction. All three  antennas were operated at 100 kW of input power.  At a distance of 200
m in front of the rhombic antenna operating at 9.57 MHz, the electric and magnetic fields varied from
0.45 to 5.0 V/m and 3.0 to 20  mA/m along  the traverse.  At  a distance of 100 m in  front of the
conventional curtain antenna operating at 9.57 MHz the electric and magnetic fields varied from 4.2 to
9.2 V/m and 18 to 72 mA/m along the traverse.  At a distance  of 300 m in front of the steerable curtain
antenna operating at 5.96 MHz the electric and  magnetic fields varied from 1.7 to 6.9 V/m and 14 to 29
mA/m as the antenna  was electrically  steered to angles of plus or minus 25 degrees from its boresight.

        Dielectric Heaters

        Dielectric heaters are used in industry to heat or weld non-conductors such as plastics by applying
a strong alternating electric field using  metal  plates.   The range of frequencies  can be  from  a few
megahertz to greater than 120 MHz. The most common frequency is 27,12 MHz. Fields measured at the
operators position  are non-uniform and not well correlated with system power.  In  12 studies [Conover
et al., 1975; Ruggera,  1977; Hietanen et al., 1979; Conover et al., 1980; Mild, 1980; Stuchly et al, 1980;
Aniolczyk, 1981; Cox et al., 1982; Stuchly and Lecuyer,  1985; Joyner and Bangay, 1986; Bini et al.,
1986; Conover et al., 1992] field measurements were made at various locations of the operator's anatomy
(head, chest, waist) for dielectric heaters operating from 6.5 to 65 MHz. Earlier measurements were made
with the operator present, but, more recently, measurements have been made with the operator absent.
Measured values of electric and magnetic fields varied from about 20 to 1700 V/m and 0.04 to 14 A/m.
Typical values are 250 V/m and 0.75 A/m. These field values are not corrected for duty cycle and do not
include  values reported as greater or less than the range of a measuring instrument.  Reported duty cycles
varied from 2.5 % to greater  than 50 %.  Dielectric heaters  are typically on 10 percent  of the  time.
Dielectric heater fields are probably amplitude modulated at multiples of the power frequency.

        Shortwave Diathermy

        Shortwave diathermy is a medical treatment using either continuous or pulsed 27 MHz fields to
deep heat a portion of the body. RF power is coupled into the body using either insulated plates or a loop
as an applicator.  The applicator is connected to an RF power generator using two separate insulated wires.
After the applicator is in place  the generator is tuned for efficient loading by the body.  The plates
generate relatively high electric fields to capacitively couple po%ver into the tissue, and the loop generates
relatively high magnetic fields to inductively couple power.  These fields exist along the  leads from the
generator as well as at the applicator.

        In one study  [Kalliomaki et  al.,  1982] electric and magnetic fields were measured near the
patient's body for various types of applicators or electrodes.  At the area of treatment  electric and
magnetic fields varied from 400 to 4000 V/m and 3 to 30 A/m, At areas of the body not prescribed for
treatment, fields varied from 20  to 4000  V/m and 0.2 to 14 A/m.  Another investigator  [Stuchly et al.,
1982] found that electric and magnetic fields at untreated areas  of the patient ranged from  4 to 2650 V/m
and 0.05 to  1.6 A/m.

        The dominant source of fields at the operator's position may  be the cables. Typical fields near
the cables decrease from 2000 to 200 V/m and from 3 to 0.2 A/m as the distance from the cables increases
from 5 to 35 cm.  Two major studies found similar values for fields at the operators' eyes and  waists

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTfPLY ET AL.)   13

[Ruggera, 1980; Stuchly et al., 1982]. The range of fields for the operator was 2 to 315 V/m for the
electric field and 0.05 to 0.95 A/m for the magnetic fieid,

VERY-HIGH FREQUENCY, 30 MHZ TO 300 MHZ

       The VHP frequency range, from 30 to 300 MHz, has associated wavelengths of 10 to 1  meter.
Local broadcast stations including FM and VHP television are common sources at VHP.  This frequency
range is  also popular for two-way  voice  communications.   Figure  6  gives the range of fields and
population exposure seen for some VHP sources.

       FM Radio Broadcast

       The median electric field experienced by the urban population in the United States due  to FM
broadcast at 88  to 108 MHz is about 0.1 V/m with 0,5 percent of the population above 2 V/m [Tell and
Mantiply, 1980; Hankin, 1986],  The maximum electric fields at ground level beneath FM towers in the
U. S, vary from about 2 to 200 V/m [Galley and Tell, 1985; U. S. EPA, 1987]. In one case, on a rooftop,
the field  directly beneath an active antenna at 2 m above  the roof was  800 V/m.  Measured fields on
towers near the antenna vary from 60 to 900 V/m [Tell, 1976; Mild,  1981]; higher electric fields exist
within 30 cm of an antenna element.  Magnetic fields up to 4.6 A/m have been reported near an element
radiating  about 300 watts in Sweden [Mild, 1981].  Antenna elements on U. S. towers typically radiate
5 kilowatts.

       Fields from FM broadcast are not intentionally amplitude modulated, but transmitter power supply
imperfections can cause modulation.  In one case,  significant 120 Hz AM  was  seen on an FM  signal.
Measurements on 10 FM radio stations showed modulation  of from 1 to 5 percent from 3 to 100 Hz
[Mantiply, 1990].

       VHF Television Transmitters

       The VHF television channels are separated into low VHF-TV (channels 2 through 6) at 54 to 88
MHz and high VHF-TV (channels 7 to 13) at 174 to 216 MHz. EPA calculations based on measurements
in the late 1970's [Tell and Mantiply, 1980] show that about 16 percent of the population is above 0,1
V/m and 0.1  percent is above 2 V/m due to low  VHF-TV.   For high VHF-TV, 32 percent  of the
population was calculated to be above 0.1 V/m and about  0.005 percent above 2 V/m,  The maximum
fields at ground level beneath VHF-TV towers are  estimated to  be between 1 and 30 V/m [Gailey and
Tell, 1985].  Measured electric and magnetic fields on the  tower close to a  VHF-TV antenna were 430
V/m and  2 A/m [Mild, 1981].

       The television signal consists of an amplitude  modulated video signal and an FM  audio  signal.
Amplitude modulation of 4 to 12 percent was measured for 9 TV video signals at 59.94  Hz, the vertical
retrace rate.

       Mobile Transmitters

       Electric fields near occupants of cars and trucks with an operating VHF mobile transmitter have
been documented [Lambdin, 1979; Adams  et al., 1979],  Various  vehicles  and antenna locations were
investigated.  Tests made with a 60 watt, 164 MHz FM radio resulted in electric fields ranging  from 3.4
to 30 V/m and a 100 watt 41 MHz radio resulted in electric  fields from 3.4 to 120 V/m near an occupant.
Tests using 100 watt FM radios at 25, 35, 39, 51, and 145 MHz in a midsize automobile resulted in fields
from 50 to 150 V/m [Muccioli and A wad.  1987]. The highest electric fields are normally seen near the
occupant's head or the driver's hands on the steering wheel.  The replacement of metal with plastic and
fiberglass in newer vehicles can  reduce shielding from the external antenna and increase fields.  These
fields were  measured with the transmitter keyed and no correction for duty  cycle.

-------
ELECTRIC FIELD MAGNETIC FIELD
PS^SS^^I
19.4 kV/m -

6.14 kV/m -
1.94 kV/m -

614 V/m -
194 V/m -

61.4 V/m -

19.4 V/m -
6.14 V/m -

1.94 V/m -
0.614 V/m -

0.194 V/m -
61.4 mV/m -
19.4 mV/m -
6.14 mV/m -

1.94 mV/m -
0.614 mV/m -

0.194 mV/m -

61.4 jjV/m -
Y////////////A
~ 51.5 A/m

- 16.3 A/m
- 5.15 A/m











FM HANDHELD

- 1 K\ A/m MOBILE
i.w A/m RADIO
- 0.515 A/m

- 0.163 A/m

- 51.5 mA/m
- 16.3 mA/m

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. __ A, PHONE
- 1.63 mA/m

- 0.515 mA/m
- 0.163 mA/m
- 51.5 pA/m
- 16.3 pA/m

- 5.15 pA/m
- 1.63 pA/m

- 0.515 pA/m

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- 100 W/cm2 *
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- 10 W/cm2 c
- 1 W/cm2 
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- 100 mW/cm2 1
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- 10 mW/cm2 ft
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- 1 mW/cm2 q
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- 100 pW/cm2 
- 10 pW/cm2 ^
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- 1 pW/cm2 ^
- 100 nW/cm2 3
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- 10 nW/cm2 c
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- 100 fW/CIT|2 m
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- 10 fW/cm2 |
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- 1 fW/cm2 <
                                                      30MHz
100MHz
                                                                    FREQUENCY
200MHz
300 MHz
                                                                                                                                                      m
Fig. 6. Range of fields from VHP sources.  The lower sections for TV and FM show the upper ranges of general population exposure.  The upper box for TV and
the middle section for FM show the range of maximum electric field expected on the ground beneath the transmitting antenna.  The upper box for FM gives the range
of values seen on FM towers close to antenna elements. The range of fields measured in vehicles with a VHF mobile transmitter operating is shown at about 40 MHz.
The frequency range of the mobile radios studied is actually 25 to 170 MHz.  The maximum electric and magnetic field measured 5 cm form a cordless telephone
is shown.  The maximum electric field measured 5 cm from a 2 watt hand-held radio  is shown as the small box at the  upper right.

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ET AL)   15
       Portable Transmitters

       Electric and magnetic fields near hand-held transmitters were measured at EPA by searching for
the maximum unperturbed field 5 cm from any surface of the unit.  The largest fields were typically found
near the base of the antenna. The maximum electric and magnetic fields found near a cordless telephone
handset operating at 50 MHz were 15 V/m and 18 roA/m.  Maximum fields near a 2 watt hand-held radio
operating at 164 MHz were 470 V/m and greater than 0.73 A/m - the full scale magnetic field for the
instrument.

ULTRA-HIGH FREQUENCY, 300 MHZ TO 3 GHZ

       The UHF frequency range of 300 MHz to 3 GHz (1 to O.I  m wavelength) covers UHF television,
cellular telephone, many microwave sources and air traffic control radar.  Figure 7 gives the range of
fields measured for several common UHF sources.

       UHF Television Transmitters

       The UHF-TV channels (14 to  67) are in the frequency  range of 470 to  806 MHz.   General
population exposure calculations give about 20 percent of the population above 0,1 V/m and about 0.01
percent above 1 V/m [Tell and Mantiply, 1980]. Maximum fields at ground level beneath UHF-TV towers
are estimated to be between 3 and 20 V/m [Gailey and Tell,  1985; Hankin,  1986].  The maximum
measured electric field near an antenna element is 620 V/m [Mild, 1981].  The modulation for UHF-TV
is the same as for VHF-TV.

       Cellular Telephones

       Cellular base stations transmit in the frequency band of 869 MHz to 894 MHz. Electric fields
have been measured at ground level beneath base  station towers  ranging in height from 46 to 82 m
[Petersen and Testagrossa, 1992].  For  1 to 16 channels operating, the maximum fields at ground were
0.1 to 0.8 V/m.  Cellular mobile and portable telephones transmit  in the frequency range of 824 and 849
MHz. The fields measured inside a car using an external antenna at 3 watts were between 6 and 36 V/m
[Balzano et al., 1986].  The maximum fields at 5 cm from a hand-held cellular phone operating at a
variable power of 6 to 600 mW are calculated to be from 9.4 to 94 V/m for the electric field and from
41 to 410 mA/m for the magnetic field.  The calculation is based on measurements for an 800 mW phone
[Balzano, 1984]. Cellular telephones currently use frequency modulation, although future plans call for
digital  pulse modulation.

       Microwave Ovens

       Most microwave ovens operate at 2.45 GHz. Electric fields 1 meter in front of a microwave oven
are estimated to range from 0.5 to 7 V/m,  with typical values  of 1 to 2 V/m,  Essentially all field
measurements have been made at a distance of 5 cm from the oven [Mild and Lovstrand,  1990].  The 1
meter estimates are based on  5  cm measurements  and the field  decreasing by 1/r for a point source
[Osepchuck, 1979;  Reynolds, 1989].  Microwave oven fields vary in time in several ways.  The field is
pulsed  at 60 Hz because of the power supply. Operation of the field stirrer, changes in the load (boiling),
and low power, on/off, operation also amplitude modulate microwave oven fields [Mantiply, 1990].

       Microwave Diathermy

       Electric fields measured at  the operator's location for microwave diathermy system at 2.45 GHz
were between 17 and 70 V/m [Ruggera, 1977]. Higher  operator exposure was seen for HF diathermy
because the longer  wavelength fields are more difficult to control.

-------
- 51.5 A/m
- 16.3 A/m
- 5.15 A/m

- 1.63 A/m
I
I
- 0.515 A/m
- 0.163 A/m ^
- R1 J? mA/m
%} I .O inn/Ill
-16.3 mA/m BELOW
TOWER
- 5.15 mA/m

- 1.63 mA/m POPULATION
- 0.515 mA/m

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- 0.163 mA/m
DISTANT
- 51.5 pA/m (RMS)
- 16.3 pA/m
- 5.15 pA/m
- 1.63 pA/m
- 0.515 pA/m
- 0.163 pA/m





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                                                              300MHz
                                                                            1GHz
                                                                           FREQUENCY
2 GHz
r
3 GHz
EQUIVALENT
POWER DENSITY

100

10
1
100
10
1

100
10
1
100

10

1
100
10

1
100

10
1



W/cm2

W/cm2
W/cm2
mW/cm2
mW/cm2
mW/cm2

jjW/cm2
pW/cm2
pW/cm2
nW/cm2

nW/cm2

nW/cm2
pW/cm2
pW/cm2

pW/cm2
fW/cm2

fW/cm2
fW/cm2


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Fig. 1.  Range of fields for UHF sources.  The box. labeled TV shows the range of exposure for the upper 20 % of the population and the range of fields expected
beneath UHF-TV towers. The range of fields seen for cellular hand-held and cellular vehicle antennas overlap.  Fields measured on the ground near cellular base station
towers are similar to population exposure values due to UHF-TV.  The range of fields calculated at one meter from  microwave ovens is shown below the measured
exposures for operators of medical  microwave diathermy equipment.  The range of peak and rms electric fields measured close (200 to 600 m) to several air traffic
radars at the FAA training center in Oklahoma City and the range of fields from distant radars in the San Francisco area are shown on the right.

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ET At.)   17

       Pulsed Radar

        Conventional pulsed radar emits a microwave pulse, receives a reflected pulse a short time later,
and determines the distance to the reflector or target from the time delay. For example, this delay  will
be about 540  microseconds (round trip time at the speed  of light) for  a target 50 miles  away.  The
direction to the target is determined from the direction the antenna is pointed in during this process.  For
a typical  air traffic  radar, a pulse is transmitted every  1000 microseconds and lasts for about 1
microsecond.  The antenna rotates every 5 or 12 seconds and the horizontal  width of the  beam is about
3 degrees.  This implies that the peak field during the pulse while the  narrow radar beam is directed at
a measurement point is about 400 times the rms field when pulsing and rotation averaging are taken  into
account.  The peak to rms ratio is less in the near field or below the radar where the radar  beam is not
well defined.

       Air traffic radars generally operate at about 1.3 GHz or 2.8  GHz.  Measurements at  several
locations at distances of 200 to 600 m from air traffic radars  [Tell and Nelson, 1974a] gave electric fields
from 57 mV/m rms or 4.7 V/m peak to 2.5 V/m rms or 960 V/m peak. Measurements for many distant
radars operating from 1.3 to 9.5 GHz in  the San Francisco area [Tell,  1977] gave rms  electric fields
ranging from 10 to 64 mV/m and peak electric fields for any one radar of 4 to 14 V/m.  Measurements
made close to  several onboard aircraft weather radars at  9.375 GHz typically showed rms fields ranging
from 20 V/m at 10 meters to 200 V/m at 10 cm, see Figure 8.  The calculated peak electric field in front
of any of these radars was 19 kV/m [Tell and Nelson, 1974b; Tell et al, 1976].

SUPER-HIGH FREQUENCY, 3 GHZ TO 30 GHZ

       The microwave SHF band from 3 to 30 GHz (wavelength of 10 to 1 cm) includes such sources
as terrestrial microwave relay, satellite relay uplinks, aircraft onboard  radar (see previous section), and
police radar.  Figure 8 shows  measured fields for some of these sources.

       Microwave Relay

       Terrestrial point-to-point microwave radio is typically used to relay telephone conversations and
data. The operating frequency varies from 2 to 13 GHz in several bands and electric fields at ground level
beneath microwave relay towers are in the range of 20 mV/m to 0.6 V/m [Petersen, 1980; Hankin,  1986].
Systems are being converted from FM to digital pulse modulation.

       Satcom Uplinks

       Fields  in  the community of  Vernon,  New Jersey due  to large  number of satellite  uplink
transmitters were  studied [U.S.EPA, 1986],  In the 6 GHz band fields  varied from 70 microvolts/meter
to 15 mV/m; in the 14 GHz band, from 0.2 mV/m to 33  mV/m.  On a hill in front of one  dish operating
at a low elevation angle at 6 GHz the electric field varied from  2.4 to  15 V/m.

       Police Radar

       The maximum  field in the transmitting aperture of police radar units has been evaluated for
thousands of devices [Fisher, 1993]. For hand-held 10.5 GHz units the aperture field varied from 33 to
120 V/m; for 24 GHz units the aperture field varied from 27 to 125 V/m. The field for the operator of
these units is estimated to be from 1 to 15 V/m if the unit is pointed away from the operator. Fields at
a distance of 30 to 300 m in front of these radars varied from about 1  to 0.1 V/m [Hankin, 1976].

-------
ELECTRIC FIELD MAGNETIC FIELD
P^^^^l
19.4 kV/m -
6.14 kV/m -
1.94 kV/m -
614 V/m -
194 V/m -
61.4 V/m -
19.4 V/m -
6.14 V/m -
1.94 V/m -
0.614 V/m -
0.194 V/m -
61.4 mV/m -
19.4 mV/m -
6.14 mV/m -
1.94 mV/m -
0.614 mV/m -
0.194 mV/m -
61.4 pV/m -
V////////////A
- 51.5 A/m
- 16.3 A/m
- 5.15 A/m
- 1.63 A/m
- 0.515 A/m
- 0.163 A/m
- 51 .5 mA/m
- 16.3 mA/m
- 5.15 mA/m
TERRESTRIAL
- 1.63 mA/m
- 0.515 mA/m
- 0.163 mA/m












AIRCRAFT
RADAR
VERNON
R

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RELAY



-51.5 nA/m BVEF
- 16.3 pA/m
- 5.15 pA/m
- 1.63 jjA/m
- 0.515 pA/m
- 0.163 pA/m




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POLICE RADAR
APERTURE
POLICE RADAR fl
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EQUIVALENT
POWER DENSITY
- 100 W/cm2
- 10 W/cm2
- 1 W/cm2
- 100 mW/cm2
- 10 mW/cm2
- 1 mW/cm2
- 100 pW/cm2
- 10 pW/cm2
- 100 nW/cm2
- 10 nW/cm2
- 1 nW/cm2
- 100 pW/cm2
- 10 pW/cm2
- 1 pW/cm2
- 100 fW/cm2
- 10 fW/cm2
- 1 fW/cm2
20 GHz 30 GHz
FREQUENCY
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Fig. 8. Super-high frequency fields.  Fields measured on the ground near terrestrial microwave relay towers are shown at the left. Three boxes show fields measured

in Vernon, New Jersey due to satellite uplink antennas.  The lower two  Vernon boxes show the weak fields measured in the community; the upper box is the range

of fields measured on a hill in front of one dish antenna.  The aircraft radar line shows fields at 10 cm to 10 m directly in front of the radar. The range of maximum

fields measured in the aperture of 10  and 24 GHz police radars are given.  Also, the range of fields in the police car to the  side of the radar and outside the car in

front of the radar (30 to 300 m) are estimated.

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY T AL)   19

DISCUSSION AND CONCLUSIONS

       The exercise  of assembling radiofrequency exposure data from so many diverse studies onto a
single graph seems useful as a starting point for setting priorities for further study, but may be misleading.
Some of the highest fields measured expose very few, if any, people.  There is no way to tell from such
a presentation how many people are exposed, whether the exposure is whole or partial body, or what the
modulation characteristics of the  field  are. Some attempt has been made in the text to address these
issues.

       Many sources have never been  studied but the range of fields  have probably been bracketed. It
is unlikely that any high power source  of RF exposure has not been included.  Comparing  in detail the
results of studies that have used different protocols, equipment, and judgement in measurement, especially
in highly non-uniform  near fields, is  futile.  This points out  the need for more standardization in
measurement.

       Similar studies have not always been done for similar sources; for example, FM antenna fields
have been measured close to elements; the same has not been done for TV antenna elements in  the United
States. Some measurements have been made close to sources while others attempt to determine whole
body average exposure; some are made with the exposed person present, but most have been made without
a person present.

       Intentional transmitting antennas,  being engineered to  generate  fields,  are relatively  easy to
characterize. However,  incidental sources such as video displays, microwave ovens, or industrial heaters
require significant testing and  statistical evaluation to determine  exposure.  Also, incidental and heating
sources have no requirement for  modulation control, so modulation (if of interest) must also be tested
more extensively.  The advent of new low power sources, such as personal communication devices, energy
saving lighting, or portable systems that transmit to satellites,  places the emphasis  for new work  on
dosimetry and  biological evaluation in near fields.

       The tendency to be far from high power sources and close to low power sources equivocates
setting priorities for exposure  assessment based on power or effective radiated power.  For example, a
simple point source calculation shows that a 10 watt source at 1 meter  generates the same power density
(0.08 mW/cm ) as a 100 kW source at 100 meters. In fact, devices not used for telecommunications may
generate strong near fields but radiate very little power.

REFERENCES

Adams JW, Taggart  HE,  Kanda  M, Shafer J (1979):  Electromagnetic  Interference  (EMI) Radiative
       Measurements for Automotive Applications.  Boulder, Colorado: U.S. Department of Commerce,
       National Bureau of Standards.

Andreuccetti D, Bini M, Ignesti A, Olmi R, Rubino N, Vanni R (1988):  Analysis of electric and magnetic
       fields leaking from induction heaters.  Bioelectromagnetics 9:373-379.

Aniolczyk H (1981):  Measurements and hygienic evaluation of electromagnetic fields in the environment
       of diathermy, welders, and induction heaters.  Med Pr (Medycyna Pracy) 32:119-128.

Balzano Q  (1984): Dyna TAG Exposure  Measurements.  Plantation, Florida: Motorola Inc., Portable
       Products Division.

Balzano Q,  Garay  O, Manning  T (1986): RF energy in cars from  window-mounted antennas. Conference
       Record of the 36th  Annual Conference, IEEE Vehicular  Technology Group, Dallas, TX, 32-40.

-------
20  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE:  VOLUME 2

Bini M, Checcucci A, Ignesti A, Millanta L, Olmi R, Rubino N, Vanni R (1986): Exposure of workers
       to intense RF electric fields that leak from plastic sealers.  Journal of Microwave Power 21:33-40.

Boivin WS (1985):  Laboratory measurement of radiofrequency electric fields near television  receivers.
       Bioelectromagnetics  Society,  Seventh Annual  Meeting Abstracts.   Frederick,  Maryland:
       Bioelectromagnetics Society.

Centaur Associates,  Inc. (1982):   Study of Radiofrequency  and Microwave Radiation - Phase  I.
       Washington, DC: National Technical Information Service Document No. PB83-191130.

Charron D (1988):  Health Hazards of Radiation from Video Display Terminals: Questions and Answers.
        Hamilton,  Ontario: Canadian Centre for Occupational Health and Safety.

Cleveland RF, Mantiply ED, West TL (1991): Measurements of environmental electromagnetic fields
       created by amateur  radio stations.   Bioelectromagnetic Society,  Thirteenth Annual Meeting
       Abstract Book. Frederick, Maryland:  Bioelectromagnetics Society.

Conover DL, Moss CE, Murray WE, Edwards RM, Cox C, Grajewski B, Werren DM, Smith JM (1992):
       Foot currents and ankle SARs induced by dielectric heaters. Bioelectromagnetics 12:103-110.

Conover DL, Murray WE, Foley ED, Lary JM, Parr WH (1980):  Measurement of electric- and magnetic-
       field  strengths from industrial radio-frequency (6-38 MHz) plastic sealers.  Proceedings  of the
       IEEE 68:17-20,

Conover DL, Murray WE, Lary JM, Johnson PH (1986): Magnetic field measurements near RF induction
       heaters.  Bioelectromagnetics 7:83-90.

Conover DL, Parr WH, Sensintaffar EL, Murray WE (1975):  Measurement of electric and magnetic field
       strengths from industrial radiofrequency (15-40.68 MHz) power sources. In Johnson CC, Shore
       ML(eds): Biological Effects of Electromagnetic Waves.  Rockville, Maryland:  HEW Publication
       (FDA).

Cox C, Murray WE, Foley EP (1982):  Occupational exposures to radiofrequeney radiation (18-31 MHz)
       from RF dielectric heat sealers. American Industrial Hygiene Association Journal 43:149-153.

Fisher PD  (1993);   Microwave exposure levels  encountered by police traffic radar  operators.  IEEE
       Transactions  on Electromagnetic Compatibility 35:36-45.

Gailey PC  (1987):  Modeling and Measurement of Electromagnetic Fields Near Loran-C  and Omega
       Stations. Oak Ridge, Tennessee: The EC Corporation.

Gailey PC, Tell RA (1985):  An Engineering Assessment of the Potential Impact of Federal  Radiation
       Protection Guidance on the AM, FM, and TV Broadcast Services,  Las Vegas, Nevada;  U.S.
       Environmental Protection Agency.

Guy AW (1987): Measurement and Analysis of Electromagnetic Field Emissions from 24 Video Display-
       Terminals in American Telephone and Telegraph Office Washington, D.C.,  Cincinnati, Ohio:
       National Institute of Occupational Safety and Health.

Guy AW, Chou CH (1982):  Hazard Analysis:  Low Frequency Through  Medium Frequency Range.
       Brooks Air Force Base, TX: U.S. Air Force School of Aerospace Medicine.

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT (MANTIPLY ET AL)   21

Hankin NN (1976):  Radiation Characteristics of Traffic Radar Systems.  Silver Spring, Maryland: U.S.
       Environmental Protection Agency.

Hankin NN (1986):  The Radiofrequency Radiation Environment:  Environmental Exposure Levels and
       RF Radiation Emitting Sources. Washington, DC: U.S. Environmental Protection Agency.

Hietanen M, Kalliomaki K, Kalliomaki P-L, Lindfors P (1979):  Measurements of strengths of electric and
       magnetic fields near industrial radio-frequency heaters. Radio Science 14:31S-33S.

Jokela K, Aaltonen J, Lukkarinen A (1989):  Measurements of electromagnetic  emissions from video
       display terminals at the frequency range from 30 Hz to 1 MHz. Health Physics 57:79-88.

Joyner KH (1988): Measurement of electromagnetic radiation below 100 GHz. In Repacholi MH (ed):
       Non-ionizing Radiations:   Physical  Characteristics,  Biological  Effects and  Health Hazard
       Assessment.  Proceedings of the International Non-ionizing Radiation  Workshop.   London:
       International Radiation Protection Association Publications, pp 373-393.

Joyner KH, Bangay MJ (1986):  Exposure survey of  operators of radiofrequency dielectric heaters in
       Australia. Health Physics 50:333-344.

Kalliomaki PL, Hietanen M, Kalliomaki K, Koistinen O, Valtonen E (1982):  Measurements of electric
       and magnetic stray fields produced by various electrodes of 27-MHz diathermy equipment. Radio
       Science 17:29S-34S.

Kavet R, Tell RA (1991):  VDTs:  Field levels, epidemiology, and laboratory studies.  Health Physics
       61:47-57.

Lambdin DL (1979):  An Investigation of Energy Densities  in the  Vicinity  of  Vehicles  with Mobile
       Communications Equipment and Near a Hand-held Walkie Talkie. Las  Vegas, Nevada: U.S.
       Environmental Protection Agency.

Mantiply ED, Hankin NN (1989):  Radiofrequency Radiation Survey  in the McFarland, California Area.
       Las Vegas, Nevada: U.S. Environmental Protection Agency.

Mantiply ED (1992):  Measurements of Electric and Magnetic Fields in the Waianae, Hawaii Area.
       Montgomery, Alabama:  U.S. Environmental Protection Agency.

Mantiply ED, Cleveland RF (1991):  Electric and Magnetic Fields Near AM Broadcast Towers. Las
       Vegas, Nevada: U.S. Environmental Protection Agency.

Mantiply ED (1990): Extremely-low-frequency  (ELF)  amplitude modulation measurements for selected
       environmental radiofrequency  (RF) sources.   Bioelectromagnetics Society,  Twelfth Annual
       Meeting Abstracts. Frederick, Maryland:  Bioelectromagnetics Society.

Marha K, Spinner B, Purdham J (1983): The Case for Concern About Very Low Frequency Fields from
       Visual Display Terminals:  The Need for Further Research and Shielding of VDTs. Hamilton,
       Ontario:  Canadian Centre for Occupational Health and Safety.

Mild KH, Lovstrand KG (1990): Environmental and professionally encountered electromagnetic fields.
       In Gandhi OP (ed):  Biological Effects and Medical  Applications of Electromagnetic Energy.
       Englewood Cliffs, New Jersey:  Prentice Hall,  pp 48-74.

-------
22  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

Mild KH (1981):  Radiofrequency electromagnetic fields in Swedish radio stations and tall FM/TV towers.
       Bioelectromagnetics 2:61-69.

Mild KH (1980):  Occupational exposure to radio-frequency electromagnetic fields.  Proceedings of the
       IEEE 68:12-17.

Mild KH, Sandstrom M (1992):  From VDT to radar - EM fields in our environment.  First World
       Congress for Electricity and Magnetism in Biology and Medicine.  Frederick, Maryland: W/L
       Associates.

Muccioli JP, Awad SS  (1987):   The electromagnetic environment of an automobile electronic system.
       IEEE Trans Electromagn Compat 29:245-251.

Osepchuk JM (1979):  A review of microwave oven safety. Microwave Journal 22:25-37.

Petersen RC (1980): Electromagnetic radiation from selected telecommunications systems.  Proceedings
       of the IEEE 68:21-24.

Peterson RC, Testagrossa PA (1992):  Radio-frequency electromagnetic fields associated with cellular-
       radio cell-site antennas.  Bioelectromagnetics 13:527-542.

Reynolds LR (1989):  The history of the microwave oven.  Microwave World 10:7-11.

Ruggera PS (1980): Measurements of Emission Levels During Microwave and Shortwave Diathermy
       Treatments.  Rockville, Maryland:  U.S. Department of Health and Human Services, Bureau of
       Radiological Health.

Ruggera PS (1979): Measurements of Electromagnetic Fields in the Close Proximity  of CB Antennas.
       Rockville, Maryland: U.S. Department of Health and Human Services, Bureau of Radiological
       Health.

Ruggera PS (1977):  Near-field measurements  of RF fields.  In Hazzard DG  (ed):   Symposium on
       Biological Effects and Measurements of Radio Frequency/Microwaves.  Rockville, Maryland:
       HEW publication  (FDA).

Schnorr TM, Grajewski BA, Hornung RW, Thun MJ, Egeland GM, Murray WE, Conover DL, Halperin
       WE (1991): Video display terminals and the risk of spontaneous abortion. New England Journal
       of Medicine 324:727-733.

Stuchly MA, Repacholi MH, Lecuyer DW, Mann RD (1982): Exposure to the operator and patient during
       short wave diathermy treatments. Health Physics 42:341-366.

Stuchly MA, Repacholi MH, Lecuyer DW, Mann RD (1983):  Radiofrequency emissions from video
       display terminals.  Health Physics 45:772-775.

Stuchly MA. Mild KH (1987): Environmental and occupational exposure to electromagnetic fields. IEEE
       EngMedBiol6:15-17.

Stuchly MA, Lecuyer DW (1985):  Induction heating and operator exposure to electromagnetic fields.
       Health Physics 49:693-700.

Stuchly MA, Lecuyer DW (1987):  Electromagnetic fields around induction heating stoves.  Journal of
       Microwave Power 22:63-69.

-------
                              RF FIELDS IN THE GENERAL AND WORK ENVIRONMENT {MANTIPLY ET AL)   23

Stuchly MA (1977): Potentially hazardous microwave radiation sources - a review, J Microw Power
        12:369-381.

Stuchly MA, Repacholi MH, Lecuryer D, Mann R (1980): Radiation survey of dielectric (RF) heaters in
        Canada. Journal of Microwave Power 15:113-121.

Tell RA, Nelson JC (1974b): Microwave hazard measurements near various aircraft radars. Radiation
        Data and Reports 15:161-179.

Tell RA (1977):  An Analysis of Radar Exposure in the San Francisco Area. Las Vegas, Nevada: U.S.
        Environmental Protection Agency.

Tell RA, Hankin NN, Janes DE (1976):  Aircraft radar measurements in the near field.  Proceedings of
        the Ninth Midyear Topical Symposium of the Health Physics Society, Operational Health Physics.

Tell RA (1990):  An Investigation of Electric and Magnetic Fields and Operator Exposure Produced by
        VDTs: NIOSH VDT Epidemiology Study. Cincinnati, Ohio: National Institute of Occupational
        Safety and Health.

Tell RA, Nelson JC (1974a): RF Pulse Spectral Measurements in the Vicinity of Several Air Traffic
        Control Radars.  Silver Spring, Maryland:  U.S. Environmental Protection Agency.

Tell RA, Mantiply  ED (1980);  Population exposure to VHF and UHF broadcast radiation in the United
        States. Proceedings of the IEEE 68:6-12.

Tell RA, Mantiply  ED, Wagner P (1988):  Radiofrequency Electromagnetic Fields and Induced Currents
        in the Spokane, Washington Area. Las Vegas, Nevada: U.S. Environmental Protection Agency.

Tell RA (1976):  A Measurement of RF Field Intensities in the Immediate Vicinity of an FM Broadcast
        Station Antenna.  Washington, DC:  U.S. Environmental Protection Agency.

Tofani S, D'Amore G (1991): Extremely-low-frequency and very-low-frequency magnetic fields emitted
        by video display units. Bioelectromagnetics 12:35-45.

U. S. Environmental Protection  Agency (1986):  An  Investigation of Microwave and Radiofrequency
        Radiation Levels  in Vernon Township,  New Jersey.  Las Vegas, Nevada: U.S. Environmental
        Protection Agency.

U.S. Environmental Protection Agency (1985): Radiofrequency Radiation Measurement Survey, Honolulu,
        Hawaii May 14-25, 1984.  Las Vegas. Nevada: U.S. Environmental Protection Agency.

U.S. Environmental Protection Agency (1987):  An Investigation of Radiofrequency Radiation Levels on
        Lookout  Mountain, Jefferson County,  Colorado.   Las Vegas,  Nevada:  U.S. Environmental
        Protection Agency.

Walsh ML, Harvey SM,  Facey  RA, Mallette RR  (1991):   Hazard assessment  of video display units.
        American Industrial Hygiene Association Journal 52:324-331.

Wang JC, Linthicum JM (1976):  RF Field Intensity Measurements in  Selected Broadcast Facilities.
        Washington, D.C.: Federal Communications Commission, Research and Standards Division.

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                           DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)  25


 DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS*
                                Arthur W. Guy**
      The first half of the paper provides some of the history of radio frequency (if) dosimetry, and the
latter half discusses some of the new and exciting things that are occurring in the field at the present time.
Earlier in this document, Ed Mantiply discussed electromagnetic fields in the environment, so this paper
will not discuss what is happening outside of the exposed individual (e.g., see Figure 1).

      The most important physical quantity associated with dosimetry is the specific absorption rate of
energy (SAR) expressed in units of watts per kilogram (W/kg).  Most of the effort in dosimetry is to
associate these outside environmental fields  E and H and power density with the SAR in the tissues of
the exposed body, which is where the cells are located and this is the site of any biological effects if the
SAR or the energy that is absorbed is high enough.
    SOURCE
QUANTITIES AND UNITS
                            E (Volts/meter)
                                  (V/m)
                               P (milliwatts/
                               square centimeter
                                   (mW/cm2)
                                   ^
                           H (amperes/meter)
                                  (A/m)
               SPECIFIC ABSORPTION RATE
                        (SAR) (W/KG)

              = E2/1200TT   or  P= 12rrH2
EXPOSED
SUBJECT
                     Figure 1. Relationship between vf source and dose.
The SAR can be characterized by the simple equation
                                 SAM = 0E.V1
   * This paper was updated in March 1995.

   ** Emeritus Professor, University of Washington, Seattle, Washington.

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26  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

where o is the electrical conductivity of the tissue, Et is the electric field in the tissue, and p is the density
of the tissue.

       There are several ways to obtain the parameters to solve for SAR in Equation 1.  The density and
conductivity of the tissue  may be measured by various methods.  The electric field can be measured
directly, or it can be calculated by means of a computer.  It's essentially that simple, if you obtain these
quantities for any location in the tissues of an exposed subject or laboratory preparation, you can calculate
the SAR at that location.  The important thing to realize is  that the SAR is a function of position.
Generally the impact of energy being absorbed by the body is based on what the total body absorption
is, that is the energy absorption rate AR which is simply the integration of the SAR over the entire mass,
M, of the body given by the equation

                                              M                                             -,
                                        AR  = ISAR dm                                      2
expressed in watts. This quantity may be expressed in another way as the whole-body-average SAR given
by the equation

                                        SAR =
expressed in units of W/kg.  The standards in this country are based on whole-body-average SAR, but we
must realize that since energy is absorbed non-uniforrnly, associated with a given whole-body-average
SAR, there are peak SARs that could be  20 or even  100 times  greater than the whole-body-average.
Generally the safety standards, while based on whole-body average, inherently account for peak SARs.

       A simple experimental way for measuring SAR is through temperature change  in the exposed
tissue of an irradiated subject. This method provides the most accuracy when using a high exposure rate
for a short time, thereby depositing the energy in the tissue or exposed subject so fast that the tissue can't
dissipate any significant heat during the brief time that the temperature is monitored. Then by noting the
short term temperature change, AT, in degrees Celsius,  the specific heat of the tissue, c  , in kilocalories
per kilogram, and the exposure time, t in seconds, one can calculate the SAR by  means  of the equation

                                       SAR =
There are many methods for measuring the temperature change. One approach is direct measurement with
a radio transparent probe, such as the Vitek probe invented by Bowman (1976) shown in Figure 2.  Care
must be exercised in choosing a probe that is truly radio  transparent since standard thermocouples and
temperature sensing devices have  conducting leads connecting the sensor  to  the  instrument.  These
conducting leads act as receiving antennas that perturb the Fields and introduce additional currents or
energy-absorption in the tissue where they are imbedded.

       An illustration of an example where this probe was used is the small in vivo laboratory preparation
shown in Figure 3. This was an experiment to establish the SAR related to exposures of chick brain to
amplitude modulated rf fields at levels where increased "calcium efflux" rates were reported (Bawin, 1975;
Blackman et al., 1980).  By exposing the preparations  to much higher rf fields than would normally be
used for the assessment of biological effects, one can determine the SARs in the tissue associated with
different exposure levels in the experimental exposure system.  Then based on other means of finding SAR
associated with exposures of human beings to rf radiation, information on exposure levels that would
produce the same  SAR in a human brain, for example, could be obtained.

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Figure 2.  Vitek probe invented by Bowman (1976).
to
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Figure 3, Example of a radio transparent probe in a small in vivo preparation,

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                                  DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)   29

       In order to measure the actual electric field in a tissue to determine the SAR by Equation  1, a
number of miniature sensing electric field probes have been developed.  The operation of one such probe
developed by Bassen (1975) is illustrated in Figure 4. The probe consists of a microcircuit antenna with
leads leading away from it to appropriate instrumentation calibrated to display the measured field strength.
Across that gap of the antenna is a microwave diode, which rectifies the microwave energy to produce
a DC current that is conducted through high resistance leads back  to a calibrated instrument.  The
instrument is calibrated to read the electric field strength in volts per meter, or millivolts per meter, in the
tissues where the probe is implanted. The complete probe configuration consists of three such dipoles that
are orthogonal to each other so that regardless of its orientation, the total electric field in the tissue may
be measured by summing its three orthogonal components.

       We designed a single element version of a electric field probe to measure the electric field aligned
with its dipole axis.  We were interested in the energy absorption in the head of a child that might be
peering out the back window of an automobile  while a cellular telephone was in operation.  In order to
increase the radiation intensity to a level within the  sensitivity of the probe at a distance from the antenna,
we used a 10 kilowatt transmitter with a radiation level nearly 10,000 times greater than that of a mobile
cellular phone system.  To handle this high input power, it was necessary to design a cellular telephone
antenna that could handle the power but still have the same radiation pattern as an actual cellular phone
antenna.  With high level radiation from the antenna, we  were able to measure the electric field in the
head of the  phantom child by aligning the dipole axis of the probe  with the electric field  at various
positions in  the head of the child.  We were able to characterize the  SAR in  mW/kg per 1  watt input
power to the antenna which was maximum  at  the surface of the phantom child's face.  The absorbed
energy was found to drop off very rapidly with distance into the head. The highest SAR was found to be
19 mW/kg at the bridge of the nose of the phantom child.

        Measuring electric fields and SAR with a probe in exposed tissue is rather cumbersome and slow,
so our laboratory developed more efficient methods for quantifying SAR patterns.  By employing a full-
scale tissue-equivalent phantom model of man designed to separate along the frontal plane of the body,
one can substantially increase the efficiency of quantifying the SAR through the use of thermography.
One surface of separation of the split model is first scanned with a thermograph camera to obtain its
complete temperature distribution. Then by  reassembling the model, exposing it to a radiation source of
interest  and quickly disassembling it. one  can use the thermograph to obtain  a new temperature
distribution.  By subtracting the former  temperature distribution from the latter and employing Equation
1, one can calculate the SAR distribution over the frontal plane where the model is split. As an example,
the method was employed to determine the  frontal plane SAR distribution in a phantom woman model
exposed to a 1,5 Tesla General Electric magnetic resonance imaging (MRI) machine.  The resulting SAR
distribution could be displayed on a computer monitor screen as  a map of the SAR pattern as shown in
Figure 5. The map is fairly characteristic of SAR patterns obtained both theoretically and experimentally
from homogeneous phantom human models exposed to magnetic fields. The configuration of the pattern
can be explained by the fact that the eddy currents in the model are maximum at the periphery of the body
where they encircle the greatest area that is perpendicular to the time changing magnetic field.  When the
eddy currents are diverted by sharp nonconducting wedges of air, such as where peripheral parts of the
body (arms,  legs, neck) join the trunk of the body (axilla, perineum,  shoulder) high current densities are
produced resulting in the  SAR "hot spots" seen  in Figure 5. For this case, with the rf magnetic field set
for maximum strength, the peak SAR was found to  be 7 W/kg, which is slightly less than the IEEE/ANSI
allowed peak SAR for the controlled environment  (IEEE,  1992). By using a liquid phantom tissue, one
can characterize a whole-body-average of SAR by measuring the temperature of the liquid before and after
exposure.  For such a measurement, one must be very careful to stir the liquid so that the temperature
remains uniform while taking the measurements.

       Since full-size  human models  are  fairly  large and  cumbersome  to use,  for many  exposure
conditions it is possible to use scale models, typically from one-fifth to one-tenth full scale size to quantify
the SAR patterns. Certain conditions must be met in the use of scale models. For example, for a one-fifth

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32   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

scale model,  one has to use five times the full scale exposure frequency, use five times the electrical
conductivity of the full scale tissue, and divide the measured SAR by a factor of five to obtain the full
scale SAR. The distribution pattern in the scaled  model would be the same as in  the full scale  model
except that it is scaled down to the dimensions of the former.

       Figure 6 illustrates the SAR patterns obtained thermographically for a scale model man exposed
to a magnetic field (Guy et al., 1976).  The pattern is very characteristic of the pattern of the full scale
woman model exposed to the magnetic fields of the MRI machine.

       Calorimetric  methods may be used to quantify the whole-body average SAR in animals exposed
to if fields.  One common and popular method is through the use of "twin well" calorimeters, as shown
in Figure 7.  Each device consists of two identical  brass cylinders that are insulated from each other with
the pair surrounded by,  but insulated from, an oval shaped cross-sectional brass cylinder (Guy,  1987).
The entire assembly  is placed  in an insulated box  with the oval  shaped cylinder held  at constant
temperature by thermostatically controlled electric  or liquid heaters. An array of thermocouples wired in
series are attached to the outside wells of the circular metal cylinders. The thermocouples of one cylinder
are wired so that the output voltage from the thermocouples are of opposite  polarity with that of the other
cylinder. Therefore,  if the cylinders are at the same temperature, then the output voltage from the entire
thermocouple array would be zero since the voltages from the arrays attached to each cylinder  would
cancel each other.  However, if the cylinders were of different temperatures, there would be a differential
voltage that would be proportional to the temperature difference.

       The calorimeter may be employed in two different ways to measure  the whole-body-average SAR
in laboratory  animals exposed to if fields. One method would involve drugging the animals to arrest the
action of their thermoregulatory systems prior to sham and actual exposures, and the other would involve
first sacrificing  the  animals  prior to exposure.   This  is  necessary  to allow any increases in  body
temperature of the exposed animal as compared to a control to be entirely due to the absorbed rf energy
rather than from other mechanisms. By placing the animals in the same environmental conditions, except
one is under sham exposure conditions and the other exposed to rf fields, the temperature of the latter will
rise due to the absorbed rf energy.  Each animal is then placed in individual wells of the calorimeter and
the wells are sealed  with an  insulated cap.  Since one animal will be slightly warmer than  the other,
because of the absorbed energy, there will be a voltage output from the thermocouples in the calorimeter
until the animals reach the same temperature.  The calorimeter may be calibrated by known heat or cold
sources so that by integrating the output voltage of the thermocouples over the  time  it  takes  the
temperatures of the two animals to reach the same value, one can obtain a number that is equal to the total
rf energy  absorbed by the  exposed animal.  Dividing this number by the mass of the animal and its
exposure time will provide the whole-body-average SAR related to the particular exposure. Thus the SAR
for any exposure level can be determined since there is a linear relationship between rf exposure  power
density and SAR.

       In addition to the use  of the experimental methods discussed above, there are a number of
theoretical models that have  been used to obtain induced fields and SAR distributions in animals or
humans exposed to rf Fields. The First theoretical approach in quantifying the Fields and energy absorption
in exposed subjects appears to be that of Anne et al., (1961) and his colleagues.  These researchers applied
the Mie equations, as described by Stratton (1941), to perfect spherical tissue models of various dielectric
properties to show how absorption properties changed with exposure frequency and radius of the model.
Later investigators (Shapiro, 1971; Ho and Guy,  1975) extended this work to calculate SAR patterns
within spheres with layered shells of different tissues.  The work demonstrated that  the models  would
resonate at certain frequencies and SAR "hot spots"of much greater magnitude than the surface SAR could
occur deep in the model at certain exposure frequencies. The models provided significant insight as to
how rf energy is absorbed by exposed subjects at various wavelengths and  how  at long  wavelengths
absorption  patterns from the electric  and  magnetic  components of  the exposure fields  could be
independently calculated. The studies on spherical models were followed by studies on more sophisticated

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Figure 7.  "Twin Well" calorimeters for quantifying whole-body average SAR in animals.

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                                  DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)   35

two-axis prolate spheroidal models that better represented the bodies of animals and humans (Durney et
al., 1975),  This work was followed by work on three-axis ellipsoidal models more ciosely representing
the bodies of man and many animals (Massoudi et al., 1977).

       Durney et al., (1986) have summarized much of the modelling work in various editions of a U.S.
Air Force publication called the Radiofrequency Radiation Dosimetry Handbook which contains SAR data
as a function of exposure frequency for every size and shape of subjects ranging from insects to the largest
humans.  Figure 8 is an  example of a typical chart seen in the dosimetry handbook, showing the whole-
body-average SAR versus frequency for an  average man exposed to a  1 mW/crrr radiation field. The
upper curve with the highest vertical excursion gives the SAR for E-polarization which corresponds to the
case where the electric field is parallel to the long axis of the  exposed ellipsoidal subject.  We notice that
the maximum SAR is approximately  0.25  watts per kilogram which occurs at  the so-called resonant
frequency near 70 to 80 MHz for an average size man. The SAR falls off fairly rapidly with increasing
frequency,  approaching  an asymptote of approximately 0.03 W/kg at the high frequency end of the
spectrum as shown in the figure.  The SAR falls off at a rate nearly proportional to the square of the
frequency with  decreasing  frequency  below  the resonant  peak.  The  term  "resonant frequency" is
appropriate since the elongated ellipsoidal objects representing man and animals are like radio-receiving
antennas.  The models absorb the  greatest amount of energy when exposed at the resonant  frequency.
However, if the exposure polarization is changed so that the magnetic field is parallel to the long axis of
the ellipsoid, called H-polarization, the SAR versus frequency curve does not have the sharp resonant peak
seen for E-polarization.  Finally, when the model is exposed with the direction of propagation parallel to
the long axis,  the polarization is called k-polarization.  The curves in Figure 8 indicate that dosimetry
associated with human and animal exposure is strongly dependent on the polarization of the exposure
fields. As a result of the lack of appreciation of polarization effects  on dosimetry by the authors, a
number of the older research reports on biological effects  of animal exposure leaves one in doubt as to
the value of SAR since  no polarization information is given  with the reported exposure levels.

       The simple theoretical models discussed above do not take into account the limbs of the animals
and humans nor the  realistic irregular  tissue boundaries of the subjects that they represent.  With the
availability of computers and workstations with higher speed and larger memory, there has been a surge
of interest in  the development of much more realistic models.  There have been a number of reports of
analysis of SAR distributions in realistic human models exposed to a multitude of different sources using
finite difference and finite element types of analyses.  These methods essentially divide the tissues of the
exposed human or animal subject into small cells or elements with cubicle-, triangular-,  or rectangular-
boundaries.   The proper dielectric properties  are  assigned to each cell based on the tissue type and
exposure frequency.  Maxwell's equations are  than solved numerically on the computer and the average
SAR in each cell or element is calculated. At  exposure wavelengths that are large compared to the size
of the exposed subject, an equivalent electrical circuit can be assigned to each  cell and the currents and
voltages can be calculated by applying circuit theory to the  network created by the combination of the
equivalent circuits of each cell.  This can be  done by using the admittance method based on a nodal
analysis as reported by Armitage (1983) or the impedance method using a mesh analysis as reported by
Gandhi et al.  (1984).

       Armitage (1983) applied the admittance method to study the SAR patterns produced in the tissues
of patients exposed to magnetic loops and  electric sources in  connection with  the development of if
applicators for producing hyperthermia in the treatment of cancer. Figure 9  illustrates the equivalent
circuit used to electrically characterize a cell along with the circuits of its nearest neighbors.  Each node
is shown as a black dot.  The sum of the currents arriving at the node at the center of each cell is equated
to zero. Any magnetic field present is going to introduce voltages along each one of the branches between
nodes. Any electrode source is going to introduce voltages at the nodes where applied. Trial voltages are
placed at each of the other nodes and an iterative technique called "successive over-relaxation" is applied.
By using this  technique on a  high speed computer or workstation, one  is able to calculate the current
distributions and SAR patterns.

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36  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE:  VOLUME 2
    DC
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    Figure 8. Example of typical chart shown in Radiofrequency Radiation Dosimetry (Durney et al., 1986),
       I found the admittance  method useful  in assessing  potential health  hazards  in the wireless
transmission of 60 kilohertz power from a long magnetic wire loop in the floor of passenger airliners to
a smaller receiving loops in the seats above to provide electrical power to personal entertainment systems.
This wireless transmission of power would allow ground crews to change spacing between different seats
to fit different classes of travel  without being encumbered by electrical wiring.  However, there was
concern about potential effects of the magnetic field on the passengers in the aircraft. I felt that the worst
case would be when an infant or a child happened to be laying on the floor right on top of the loop, which
was designed to be only 1/16th of an inch below the  surface of the floor. The  worst case also assumed
that the front or back of the child was pressed hard against this floor to form a flat surface against the
floor. This would never occur in a real  situation because of the roundness of the surfaces of the body.
In this case, with a 60 kilohertz magnetic exposure field of approximately 380 microtesla (uT)  at the
surface of the floor, a maximum current density of approximately 180 microamperes per square centimeter
(uA/cm2) was  calculated by the  admittance method.  A graph of the calculated current distribution is
shown in Figure 10.

       Orcutt  and  Gandhi (1988)  extended the impedance method  using a mesh analysis instead of a
nodal analysis  to calculate' the SAR in man models exposed to low frequency magnetic fields.  Gandhi
et al., (1984) had reported that the method, with an equivalent circuit of a cell and its nearest neighbors
shown in Figure 11, was  significantly faster than the admittance  method.  By summing the voltages

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                                 DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)   37
                              Figure 9.  Armitage's admittance method.
around each  one of the mesh loops and  setting the sum to zero and using the same successive
overrelaxation technique as used for the admittance method, Gandhi et al. (1984) were able to calculate
the current distribution and SAR patterns in the exposed model.

       Both  the admittance and impedance methods  allow the rapid calculation of current and SAR
distributions in complex models consisting of a million or more cells exposed to low frequency fields.
Figure 12 illustrates the current density distribution that  I calculated by the impedance  method for a
realistic homogeneous human model exposed to a 1.25 [iT, 60 Hz magnetic field.  The model is based
on measurements taken over my own body some years ago in connection with experimental measurements
of body impedance. A cell size of a 2.0 x 2.0 cm was used for the calculations.  It can clearly be seen
that the current distribution pattern is characteristic of the SAR patterns seen in the  thermographically
derived graphs of Figures 5  and 6 (high levels near the periphery of the body with  "hot spots"  at the
perineum, axilla and shoulders of approximately 1.2 nA/cm ).

       An advantage in using the admittance and impedance methods is the ease at which it may be
applied to complex models composed of different tissue types.  Orcutt and Gandhi (1988) used a realistic
man  model to calculate the induced current  distributions in man exposed to low frequency electric and
magnetic fields.  The model  was based on illustrations in an anatomy book of the cross-sectional views
of the body of man taken every inch over its entire length in a direction perpendicular to  the long axis.
Each slice, was divided up into 1,3 x 1.3 cm square cells where the tissue in each cell  was identified. A
3-dimensional impedance model with 1.3 cm cubical cells was then assembled by combining  all  of the

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38  SUMMARY AND RESULTS OF THE RADiOFREQUENCY RADIATION CONFERENCE: VOLUME 2
                     120
                                    T  !   3
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                                                          perpendicular to
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                                                          2.54x152 cm foop
                 Figure 10.  Example of application of the Armitage admittance method.
slices and identifying the dielectric properties of each cubical cell.  I used the Orcutt and Gandhi (1988)
impedance model to calculate the current distribution for the same exposure conditions  used  in the
homogeneous model, and obtained the results shown in Figure 13. The current distribution pattern  is
completely different than that shown in Figure 12 for the homogeneous model, as a result of the presence
of the tissues of the different organs.  One may note, however, that the magnitude is about the same,
reaching peak values of approximately 1.2 nA/cm".  The analysis shows that there is now a greater current
density at the top center of the body  than for the homogeneous  model.  This is probably due to the
interruption of current  flow by the air-filled lungs.

       The most powerful and popular program currently being used for field and SAR analyses is the
finite difference time domain (FDTD) method that directly solves Maxwell's equations in the time domain.
The concept was first reported by Yee (1966) at a time when computers were too  limited in speed and
memory to put it to practical use.  With the availability of improved computers, it was finally put to use
for the first time  nearly a decade later by Taflove and Brodwin (1975a)  for solving scattered fields from
a dielectric cylinder. This was followed the same year by the first  application of the FDTD to calculate
the induced fields and temperature in biological  media  the human eye exposed to microwave radiation
by Taflove and Brodwin (1975b).  With Taflove's (1980, 1988)  continuing use  of the FDTD as an
important analytical tool for solving a multitude of different electromagnetic problems, many investigators
began to use it (Lau et al., 1986; Sullivan et al., 1987, and 1988) for modelling biological systems exposed
to rf fields. The FDTD method has recently become the tool of choice for characterization of the SAR
patterns in the human head exposed to cellular telephones.

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                                 DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)   39
                              Figure 11.  Gandhi's impedance method.


       Gandhi (1995) perfected an FDTD model for calculating the SAR from exposure to RF fields from
cellular telephones.  His model is based on MRI scans on a human volunteer, obtained every 3 mm from
the top of the head to the feet, which provided a resolution of about 2 mm per pixel for each body cross
sectional slice.  He had the anatomy faculty and their students at the University of Utah identify each
tissue in the MRI scan, and code them with numbers.  Gandhi and his group identified close to 30 tissues,
and assigned each with its own unique dielectric properties.  Gandhi then analyzed the SAR patterns with
the FDTD method. Figure  14 shows the overall view of one of his scans through the head where the SAR
was the greatest, and Figure 15 shows an enlarged view where most of the absorption takes place. We see
that most of the energy is  absorbed in  the ear,  where the top of the cellular telephone is placed.  Some
energy also is absorbed in the brain, but at a much lower level than in the ear.  The FDTD technique
utilizes as input the construction details, including the RF radiating structure and excitation parameters of
the telephone as well as the characteristics and dielectric properties of the exposed body. This information
is then fed  into a computer and Maxwell's equations are solved using the FDTD  method. The result is
a detailed 3-dimensional pattern of the  electric and magnetic fields and the SAR in the tissue which may
easily be visualized by standard graphical visualization software. The highest tissue SARs found in the
analysis of eight different cellular telephones approached about  1 W/kg (specifically, 849  mW/kg in the
ear), but in the brain itself, the SAR levels were down to 0.3 W/kg or less. These value  are consistent
with those  from the analysis by Balzano (1994) based on actual measurements.  Gandhi also did some
measurements that confirmed his calculations.  On the other hand, Kuster (1994), using the same  model
as  used  by Balzano,  measured SAR  values well over 1  W/kg  in the  ear and brain  tissues when
considering the "worst case" exposure  situation. However, to obtain these higher values,  Kuster placed

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40  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
                   1001
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           Figure 12.  Example of application of the Gandhi impedance method (uniform tissue).
the cell telephone antenna at distances much closer to the model head with the microphone further from
the mouth (atypical for most cell phone users when talking into  the phone) than used by Gandhi and
Balzano. He also tested a phone with a shorter one quarter wavelength long antenna (not used in the
United States) which results in higher SAR near the base of the antenna.  This issue is one that has to be
resolved through agreement on antenna types and locations of the antenna relative to the head, typical of
cellular telephone use.

       With the advent of the higher speed workstations, it looks  like FDTD computations as described
above can become quite routine.  Various laboratories will be able to make use  of these techniques to
quickly determine the dosimetry relating to exposure from a large number of different types of rf emitters,
including MRI  scanners, hyperthermia applicators, traffic  radar, cellular telephones, handheld police

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                                DOSIMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY]   41
                  140
                            Gandhi realistic model
 GANDHf
 IMPEDANCE
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        Figure 13.  Example of application of the Gandhi impedance method (3-dimensional tissue).
telephones,  and  other wireless devices.   To give you an idea  of how rapidly computer workstation
technology is expanding, Digital Equipment Corporation has come out with a series of 64-bit workstations
employing the fastest chip in the world.   Using the  area of the Rose Bowl  as an example of the
addressable memory and performance of a 32-bit technology workstation, the memory and performance
of the new workstations will be equivalent to an area the size of the state of California. With the Cray
supercomputers adopting these chips for their new designs and other manufacturers coming out with higher
speed and capacity workstations, its not difficult to see how the power of computational methods such as
the FDTD will make it an important dosimetry too! in bioeiectromagnetics research.

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44  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE:  VOLUME 2

REFERENCES

Anne A., Saito M., Salati O.M. and Schwan H.P., 1961, Relative microwave absorption cross sections of
       biological significance. In Biological Effects of Microwave Radiation, Vo! I., New York, Plenum
       Press:153-176.

Armitage D.W., LeVeen H,H. and Pethig R.  , (1983), Radiofrequency-Induced Hyperthermia: Computer
       Simulation of Specific Absorption Rate  Distributions Using Realistic Anatomical Models. Phys.
       Med. BioL, 28(1):31.34.

Balzano Q., Garay O., Manning T., 1995, Electromagnetic energy exposure of simulated users of portable
       cellular telephones. IEEE Transactions on Vehicular Technology, In Press

Bassen H.M., Swicord M. and Abita J., 1975, A miniature broad-band electric field probe. Ann.  N.Y.
       Acad, ScL, 247:481-493.

Bawin S.M., Kaczmarek L.K., Adey W.R,, 1975, Effects of modulated VHP fields on the central nervous
       system, Ann-N-Y-Aead-Sci., 247:74-81.

Blackman C.F., Benane S.G., Elder J.A,, House D.E., Lampe J.A., Faulk J.M., 1980, Induction of calcium-
       ion efflux from brain tissue by radiofrequency radiation: effect of sample number and modulation
       frequency on the power-density window, Bioelectromagnetics. l(l):35-43.

Bowman R.R., 1976, A probe for measuring temperature in  radio-frequency heated material. IEEE Trans.
       Microwave Theory and Techniques,  MTT-24;43-45,

Durney C.H., Johnson C.C., and Massoudi H., 1975, Long-wavelength analysis of plane wave irradiation
       of prolate spheroid model of man. IEEE Tran. Microwave Theory and Tech., MTT-23:246-253.

Durney C.H., Massoudi H., Iskander M.F., 1986, "Radiofrequency Radiation Dosimetry Handbook," 4th
       Ed. Report USAFSAM-TR-85-73, October, Brooks AFB, TX:USAF SAM

Gandhi, O.P., J.F. DeFord, and H. Kanai, 1984, "Impedance Method for Calculation of Power Deposition
       Patterns in Magnetically Induced Hyperthermia," IEEE Transactions on Biomedieal Engineering,
       vol. BME-31-10:644-651, October.

Gandhi O. P., Chen J. Y., Wu D., 1995, Electromagnetic Absorption in the Human Head and Neck for
       Cellular telephones at 835 MHz. Radio Science, Special Issue, In Press

Guy A.W., Webb M. D. and Sorensen C. C., 1976, Determination of power absorption in man exposed
       to high frequency eletromagnetic fields by thermographic measurements on scale models. IEEE
       Trans. Biomed. Eng, 23(5):361-371.

Guy A.W., 1987, Dosimetry associated with exposure to nonionizing radiation: Very low frequency to
       microwaves.  Health Physics 53(6):569-584.

Ho  H.S. and Guy A.W., 1975, Development of dosimetry for  RF  and microwave radiation  -  II:
       Calculations of absorbed dose  distributions in two sizes of muscle-equivalent spheres.  Health
       Physics 29:317-324.

IEEE, 1992, "IEEE Standard for Safety Levels with  Respect to Human Exposure to Radio Frequency
       Electromagnetic Fields, 3 kHz to 300 GHz", IEEE C95.1-1991, Standards Coordinating Committee

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                                 DOSiMETRY OF RADIO FREQUENCY ELECTROMAGNETIC FIELDS (GUY)   45

       SCC28 on  Non-Ionizing Radiation Hazards,  Approved September 26,  1991, IEEE Standards
       Board.

Kuster N., Balzano Q., 1992, Energy absorption mechanism by biological bodies in the near field of
       dipole antennas above 300 MHz, IEEE Transactions on Vehicular Technology 41(1): 17-23.

Massoudi H., Durney C.H., and Johnson C.C., 1977, Long-wavelength analysis of plane wave irradiation
       of an ellipsoidal model of man. IEEE Tran. Micxrowave Theory and Tech.,  MTT-25:41-46.

Orcutt N., Gandhi .O.P, 1988, A 3-D  impedance method to calculate power deposition in biological bodies
       subjected to time varying magnetic fields. lEEE-Trans-Biomed-Eng. 1988 Aug. 35(8). P 577-83.

Shapiro A.R., Lutomirski R.F., and Yura H.T., 1971, Induced fields and heating within a cranial structure
       irradiated by an electromagnetic plane wave. IEEE Trans. Microwave Theory and Tech., (Special
       Issue on Biological Effects of Microwaves), MTT-19:187-196.

Sullivan D.M., Borup D.T. and Gandhi O.P., 1987, Use of the finite difference time  domain method in
       calculating  absorption in human tissues. IEEE Trans. Bioemed. Eng., BME-34:148-157.

Sullivan D.M., Gandhi O.P. and Taflove A., 1988,  Use of the finite difference time  domain method in
       calculating  EM absorption in man models. IEEE Trans  Microwave Theory and Tech., BME-
       35:179-185.

Taflove A. and Brodwin M.E., 1975a, Numerical solution of steady state electromagnetic  problems using
       the time dependent Maxwell's equations. IEEE Trans. Microwave Theory and Tech., MTT-23:623-
       660

Taflove A. and Brodwin M.E., 1975b, Computation of the electromagnetic fields and induced temperatures
       within a  model of the microwave irradiated human eye. IEEE  Trans. Microwave Theory and
       Tech., MTT-23:888-896.

Taflove A.,  1980, Application of the finite difference time domain method to sinusoidal steady state
       electromagnetic penetration problems. IEEE Trans. Electromagnetic Compatibility, EMC-22:191-
       202.

Taflove A., 1988, Review of the formulation and applications of the finite difference time  domain method
       for numerical modelling of  electromagnetic wave  interactions with arbitrary structures.  Wave
       Motion, 10-6:547-583.

Yee K.S., 1966, Numerical solution of initial boundary condition problems involving Maxwell's equations
       in isotropic media.  IEEE Trans. Antennas and Propagation, AP-14:302-3Q7.

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                                                              RF SHOCKS AND BURNS (GANDHI)  47


     RF SHOCKS AND BURNS: SOME KNOWNS AND UNKNOWNS*
                                       Om P, Gandhi**


INTRODUCTION

       Even though there is a great deal of data on currents induced in the human body for exposure to
radiofrequency (RF) electromagnetic fields both for plane wave, relatively uniform exposures [1-5] and
for nonuniform exposures in industrial settings [6-8] for free standing conditions as well as for conditions
of contact with energized objects, the data is much more limited on RF shocks and burns [9-11]. This
is due to the severity of the phenomenon.  From anecdotal stories it is obvious that this can be a serious
problem for people exposed to medium and high intensity electromagnetic (EM) fields.  Following up on
the pioneering work of Dalziel and colleagues  [9, 10, 12, 13], Guy and others  114-17] have  studied the
threshold currents for perception and pain ("let-go") under conditions of continuous rather than intermittent
contact with RF energized electrodes. Because of the potential for harm, currents for RF shocks and bums
for conditions of intermittent contact were not a part of these studies and thus have not been examined.
A  limited amount of data is available for transient discharge or conditions of intermittent contact with
energized conductors at 60 Hz [18,19],  From the limited data that we will present, it is likely that the
stored energy levels needed for RF shocks and burns for transient discharge may diminish with increasing
frequency up to 100 kHz, to values that are relatively independent of frequency  for frequencies in excess
of 100 kHz.  Since the absence of data on  startle reactions  by transient discharges  is  one  of  the
acknowledged weaknesses of the present day ANSI/IEEE  RF  safety guidelines [20], it is clear that
additional experimental data is needed before this important facet of RF safety is resolved.
CONTACT HAZARDS IN THE VLF TO HF BAND (10 kHz to 100 MHz)

       Ungrounded metallic objects in EM fields develop open-circuit voltages which may be written as:

                                         Voc=Eincheff                                       (1)

where Voc is the open circuit voltage, Einc is the magnitude of the incident electric field, assumed to be
relatively uniform, and heff is the effective height of the  object relative to the ground.  Effective height
of the  object is related  to, but is  not the same as, the physical height.  Effective heights of some
commonly encountered objects such as a car, van, bus, fence, metallic roof, etc. have been determined and
are given in the literature  [14,  17].  Effective height of a car, for example, is about 0.3 m.  Effective
heights are even larger for  bigger or higher objects such as a school bus, metallic roof, etc.  For incident
electric fields of a few hundred volts per meter, open circuit voltages of tens to hundreds of volts may
therefore be created  between the object and the ground.  Upon touching such an object, a current would
flow through the human body whose  magnitude will  depend  on the conditions of contact (contact area,
grounding of the body,  etc.).  Chatterjee, et  al.  [17] did a study in which  the body  impedance and
threshold currents needed to produce sensations of perception and pain were measured for 367  human
subjects (197 males and 170 females of various age groups; 18-35,  36-50  and  51-70 years) for the
frequency range 10 kHz to 3 MHz.  The study included  various types of contact such as finger contact
(contact areas 25 and  144  mm ) and grasping a rod  electrode (diameter = 1.5 cm, length =  14  cm) to
simulate the holding of the door handle of a vehicle.  The experimental data were used to develop graphs
of average threshold  incident electric fields that will cause the various sensations such as perception, let-go
     * This paper was updated in October 1994.

     ** Department of Electrical Engineering, University of Utah, Salt Lake City, UT 84112.

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48   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

(pain), or even  burns for adult males and females  [17, 21, 22].  Predictions were also made, based on
scaling, for the corresponding threshold values for ten-year old children, since the currents for perception
and pain were found to be proportional to the (contact area)I/4. Taken from reference 17, a representative
graph of the threshold incident electric fields for let-go (pain) for grounded adult males and ten-year old
children for finger contact (contact area = 25 mm2) for various vehicles is given in Figure 1.  For most
of the cases the electric fields are lower than the maximum permissible exposure (MPE) limits given in
the ANSI/IEEE C95.1-1992 [20] both for controlled and uncontrolled environments.  Given in Figure 2
are the estimated incident electric fields for a wider area grasping contact that will result in currents
needed for perception at various frequencies [17].  Average perception currents measured for 197 males
for grasping contact with a cylindrical metallic rod of diameter  1.5 cm and length 14 cm (to simulate
holding of a handle bar of an automobile) were used to estimate the incident electric fields that will result
in such currents for grounded conditions of the subjects.  Even  though the RF source available at our
disposal  did  not permit us to measure the  currents for  let-go under grasping contact conditions, we
estimate these to be 25 to 30 percent larger than those needed for perception. This would imply that the
threshold electric fields needed for let-go for grasping contact conditions would be 25 to 30 percent larger
than the values  given in Figure 2. From reference  17, perception is one of tingling/pricking sensation at
frequencies  lower  than 70-100 kHz and one of warmth at  the  higher frequencies.   Perception/let-go
currents are relatively independent of frequency for frequencies higher than 100 kHz to 50-100 MHz [17,
23].
SHOCK, FIBRILLATION, AND BURNS

       Shock and ventricular fibrillation have been discussed at length in the literature [10, 24-27] for
60 Hz currents. A review of the literature is given in [28]. The  values for painful shock and ventricular
fibrillation are presented by Dalziel for frequencies up to 10 kHz [13, 26].  It is believed that at higher
frequencies, fairly large currents can pass through a human being  without causing muscle or nerve
stimulation [29].  These currents would, however, produce heating effects in the skin as well as damage
to internal organs [25].  Becker et al. [30] and Dobbie [31] have reported values of RF currents which
produce bums. Becker  et al. [30] claim that 200 mA for 30 seconds produced reddening of the skin of
an arm or hand of each of four human subjects, 300 mA for 20 seconds produced pain and blistering, and
400 mA for 10 seconds  produced unbearable pain.  In each case, the electrode was a 3.8 cm  disposable
silver ECO electrode.  Also, 400 mA through a 1 cm2 Ferris Red Dot disposable electrode for 20 seconds
produced  a second-degree bum on the back of a subject's hand.   This  study was in reference to
electrosurgery and so the frequency, though not stated in [30], is assumed to be around 500 kHz. From
our results on perception and pain threshold currents beyond about  100 kHz [17], it  is expected that the
threshold currents for burns at other frequencies would not be any different,  Dobbie [31], studying burns
during surgical diathermy, reports that 100 mA through a needle electrode used in ECG monitoring  over
the deltoid muscle causes a unpleasantly hot sensation in  10 seconds.  Becker et al.  [30] report that 100
mA per square cm of skin for 10 seconds using ECG electrodes produced a burn.

       Our measurements of threshold pain current on 197 male subjects indicated that an average current
density of approximately 192 mA/enr for contact with the front of the index finger for frequencies greater
than or equal to 100 kHz, caused discomfort for a contact area of 25 mm.  We believe that this current
density would definitely have caused a burn had the subject been told to keep touching the copper plate.

       It has previously been mentioned that the threshold current for perception varies with the fourth
root of the contact area [17].  It is expected that the threshold current for burns will also follow the same
                                                                                    "3/4
relationship with  respect to the contact area, i.e., the current density will  vary as  (area)   .  For the
previously studied contact areas of 144 and 25 mm ,  the burn  thresholds can therefore be obtained by
scaling 100 mA/cm  needed to cause RF burns  [30], according to the relation, burn threshold current
density ~  (area)"   . This  gives a current density of 76 mA/cm  for a contact area of 144 mm  and 283
       ^ for 25 mm .

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                                                                 RF SHOCKS AND BURNS (GANDHf)  49
      103
Q
*J
uj
E

y

2

u
c
_J
o
       10
                                                     COMPACT CAR



                                                     COMPACT CAR

                                                     SCHOOL BUS
                                                       SCHOOL BUS
          10
                                     102
                                       103
104
                                            FREQUENCY (kHz)
          Fig. I.
Average threshold electric field for let-go (pain) for grounded adult males (solid

curves) and ten-year old children (dashed curves) in finger contact with various

vehicles.  Contact area = 25 mm2.

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50   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
        103
  o
 u

 2

 u
 in

 UJ

 Q
 J
 O
 X
 oo


 i
                                                                                CCWACT
                                                                              . COHPWIT CAR

                                                                                SCHOO. BUS
                                              FREQUENCY (kHz)
         Fig. 2.
Average threshold electric field for perception for grounded adult males (solid

curves) and ten-year old children (dashed curves) in grasping contact with various

vehicles.

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                                                               RF SHOCKS AND BURNS (GANDHt)   51
       The calculated results for threshold E-fields to cause RF burns are plotted in Figures 3 and 4 for
male adults and ten-year old children for contact areas of 25 mm  and 144 mm , respectively. Since the
data are not available for children, the threshold fields for children are obtained by scaling the impedance
of male adults by the ratio of the height of a standard 50th percentile ten-year old child (1.38m) to the
height of a standard 50th percentile male adult (1.75m) and by scaling the burn threshold current for male
adults by the square of the ratio  of the height of a ten-year old child to the height of a male adult.
TRANSIENT DISCHARGES

       A deficiency acknowledged in the ANSI/IEEE C95.1-1992 safety guidelines [20] is that the current
limits prescribed for induced and contact currents [Tables 1 and 2, parts B of ref. 20] "may not adequately
protect against startle reactions caused by transient discharges when contacting an energized object".  In
many situations, the hazard of transient discharge  may well be the most  important issue for safety.
Involuntary  muscular reactions to transient  spark discharges can cause many safety hazards.  In. our
evaluation of construction worker safety at a U.S. Coast Guard  Omega Transmitting Station (10.2-13.6
kHz), in collaboration with Robert Curtis (OSHA) and Gene Moss (NIOSH), we found that thresholds of
perception, annoyance, and  even  spark discharges were easily exceeded for intermittent contacts with
ungrounded  objects (such as cables, metallic  tubes, etc.) exposed to RF fields. These, of course, were a
result of the energy storage (CV    ) in these objects that could be discharged upon touching or at times
even approaching these objects.  Another interesting observation was that the perception threshold for
finger contact for the Omega site (10.2-13.6 kHz) occurred for stored energy  levels on the order of 15-20
uJ which is  considerably lower than 100-150 uJ (depending on capacitance C  of the objects) which is
estimated at 60 Hz by experimentation with  two subjects [18].  This leads us to believe that the stored
energy for perception, annoyance, and spark discharges may be frequency dependent  with values being
considerably lower at higher frequencies than at 60 Hz where most of the data are presently available.
This point of view is also shared by Dr. A. W. Guy [personal communication] who has  some unpublished
data at 23 kHz and feels that the perception  threshold for stored energy may be even lower than 15-20
uJ that we estimate for 10.2-13.6 kHz. In another paper by Delaplace and Reilly [32], data are presented
to show that threshold of spark discharge is related to energy (CV ms) for capacitance less than 575 pF
and charge (CV ms) for C > 575 pF. From these limited data, most of which are at 60 Hz,  it is obvious
that much more data need to  be obtained on the stored energy  levels for transient spark  discharge at
various frequencies.
CONCLUDING REMARKS

       Possibility of RF shocks and burns is a serious problem for personnel working close to high power
transmitting antennas in the low, medium, and high frequency bands. Even though a great deal of data
is available for threshold perception and let-go currents, the stored energy levels that will result in startle
reactions or burns for transient discharges for intermittent contacts are  not known.  Some limited data
points to the possibility that stored capacitive energies needed for transient discharge are likely to decrease
with increasing frequencies. Since startle reactions caused by transient discharges may result in accidents,
this data and instrumentation to assess which of the objects may pose such a hazard are urgently needed.

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52  SUMMARY AND RESULTS OF THE RADIQFREQUENCY RADIATION CONFERENCE: VOLUME 2
                                         J = 283 mA/cm2 for 10 s
                                                                           COMPACT CAR
 102
                         103
                  FREQUENCY (kHz)
         Fig. 3.
Threshold E-field for producing burns in adult males (solid curves) and ten-year old
children (dashed curves) in finger contact with various vehicles (contact area = 25
mm2).

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                                                        RF SHOCKS AND BURNS (.GANDHI)   53
                                  J76mA/cm2forlOi
                                       103
                                 FREQUENCY 
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54  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE; VOLUME 2

REFERENCES

1,     O. P. Gandhi, I.  Chatterjee, D. Wu and  Y.  G. Gu, "Likelihood of High Rates of Energy
       Deposition  in the Human Legs at the ANSI Recommended 3-30 MHz RF  Safety Levels,"
       Proceedings of IEEE, Vol. 37, pp. 1145-1147,  1985.

2.     D, A. Hill and J. A. Walsh, "Radio Frequency Current Through the Feet of a Grounded Human,"
       IEEE Transactions on Electromagnetic Compatibility, Vol. 27, pp.  18-23, 1985.

3.     O. P. Gandhi, J. Y. Chen and A. Riazi, "Currents Induced in a Human Being for Plane Wave
       Exposure Conditions 0-50  MHz and for RF  Sealers," IEEE Transactions  on  Biomedical
       Engineering, Vol.  33, pp. 757-767,  1986.

4.     J. Y. Chen and O. P. Gandhi, "RF Currents Induced in an Anatomically-Based Model of a Human
       for Plane Wave Exposures 20-100 MHz," Health Physics, Vol. 57,  pp. 89-98, 1989.

5.     O. P. Gandhi, Y. G. Gu, J. Y. Chen and H. I.  Bassen, "Specific Absorption Rates and Induced
       Current Distributions in an Anatomically Based Human Model for Plane Wave Exposures," Health
       Physics, Vol. 63, pp. 281-290, 1992.

6.     O. P. Gandhi and J. F. DeFord, "Calculation of EM Power Deposition for Operator Exposure to
       RF Induction Heaters," IEEE Transactions on Electromagnetic Compatibility, Vol. 30, pp, 63-68,
       1988.

7.     J. Y. Chen and O. P. Gandhi, "RF Currents Induced in an Anatomically Based Model of Man for
       Leakage Fields of a Parallel  Plate Dielectric Heater," IEEE Transactions on Microwave Theory
       and Techniques, Vol. 37, pp.  174-180, 1989.

8.     J.  Y. Chen, O. P.  Gandhi and D. L. Conover,  "SAR and Induced Current Distributions for
       Operator Exposure to  RF  Dielectric  Sealers," IEEE Transactions on  Electromagnetic
       Compatibility, Vol. 33, pp. 252-261, 1991.

9.     C. F. Dalziel, and T. H. Mansfield, "Effect of  Frequency  on Perception Currents, Trans. AIEE,
       Vol. 69(11), pp. 1162-1168, 1950.

10.     C. F. Dalziel, and W. R. Lee, "Lethal Electric Currents," IEEE Spectrum, Vol. 6, pp. 44-50, 1969.

11.     R. J. Rogers, "Radio-Frequency Burn Hazards in the MF/HF Band," in Aeromedical Review-Proc.
       Workshop on  the Protection  of Personnel Against RF Electromagnetic Radiation, Review 3-81,
       J. C. Mitchell, Ed. (USAF School of Aerospace Medicine, Brooks Air Force Base, Texas 78235),
       pp. 76-89, Sept. 1981.

12.     C. F. Dalziel, "The Threshold of Perception Currents," Trans. AIEE, Vol. 73, pp.  990-996, 1954.

13,     C. F. Dalziel,  "Electric Shock Hazard," IEEE Spectrum, Vol.  9, pp. 41-50, 1972.

14.     O. P. Gandhi and I. Chatterjee, "Radio-Frequency  Hazards in the VLF to MF Band," Proceedings
       of the IEEE, Vol. 70, pp. 1462-1464,  1982.

15.     A. W. Guy and C. K. Chou, "Hazard Analysis: Very Low Frequency  Through Medium Frequency
       Range," Final report USAF SAM Contract No. F 33615-78-D-0617, Task 0065,  1982.

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                                                             RF SHOCKS AND BURNS (GANDHI)  55

16.     A. W.  Guy and C. K, Chou, "Very Low Frequency Hazard Study,"  Final report prepared for
       USAF School of Aerospace Medicine, Brooks Air Force Base, TX, Contract No. F 33615-83-C-
       0625, 1985.

17.     I. Chatterjee, D. Wu and O. P. Gandhi,  "Human Body Impedance and Threshold Currents for
       Perception and Pain for Contact Hazard Analysis in the VLF-MF Band," IEEE Transactions on
       Biomedical Engineering, Vol. 33, pp. 486-494,  1986.

18.     D. W.  Deno and L. E. Zaffanella, "Electrostatic Effects of Overhead Transmission Lines and
       Stations," Chapter 8 in Transmission Line Reference Book: 345 kV  and Above, 2nd Edition,
       published by Electric Power Research Institute, Palo Alto, CA, 1982.

19.     J. P. Reilly, "Electrical Stimulation and Electropathology," Cambridge University Press, 1992.

20.     ANSI/IEEE C95,1-1992, "Standard for Safety Levels with Respect to Human Exposure to Radio
       Frequency Electromagnetic Fields, 3 kHz to 300 GHz," available from the Institute of Electrical
       and Electronics Engineers, Inc., 345 East 47th Street, New York, NY  10017.

21.     O. P. Gandhi,  I Chatterjee, D. Wu, J. A. D'Andrea and K. Sakamoto, "Very Low Frequency
       (VLF) Hazard Study," Final  report USAF SAM Contract No. F33615-83-R-0613,  1985.

22.     O. P. Gandhi, "ANSI Radiofrequency Safety Guide: Its Rationale, Some Problems and Suggested
       Improvements," Chapter 3 in Biological Effects and Medical Applications of Electromagnetic
       Energy, O. P. Gandhi, Ed., Prentice Hall Inc., 1990.

23.     O. P. Gandhi,  "Basis for RFR-Safety Standards in the 10 kHz-50 MHz Region," Final Report
       submitted to USAF SAM Contract No. F 33615-85-R-4522, Brooks Air Force Base, TX, 1987.

24.     L. P. Ferris, B. G.  King, P.  W. Spence, and H. B. Williams, "Effect of Electric Shock on the
       Heart," Trans. AIEE, Vol. 55, pp. 498-515, 1936.

25.     C. F. Dalziel, "Dangerous Electric Currents," Trans. AIEE, Vol. 65, pp. 579-585, 1946.

26.     C. F. Dalziel, "Effects of Electric Shock on Man," IRE Trans. Medical Electronics,  PGME-5, pp.
       44-62,  1956.

27.     W. R. Lee, "Death From Electric Shock," Proc. IEE, Vol. 113, pp.  144-148, 1966,

28.     M. S. Hammam and R. S. Baishiki, "A Range of Body Impedance Values for Low Volume, Low
       Source Impedance Systems of 60 Hz," IEEE Trans, Power Apparatus and Systems,  PAS-102, pp.
       1097-1103, 1983.

29.     L. A. Geddes, L. E. Baker, P. Cablet, and D. Brittain, "Response to Passage of Sinusoidal Current
       Through the Body," /, N. L. Wulfsohn and A. Sances (eds.), The Nervous System and Electric
       Current, Vol. 2, New York, Plenum Press, pp.  121-129, 1971.

30.     C. M. Becker, I. V. Malhotra, and J. Hedley-Whyte, "The Distribution of Radio Frequency Current
       and Burns," Anesthesiology,  Vol. 38, pp. 106-122, 1973.

31.     A. K. Dobbie, "The Electrical Aspects of Surgical Diathermy," Biomedical Engineering, Vol. 4,
       pp. 206-216, 1969.

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56  SUMMARY AND RESULTS OF THE RADJOFREQUENCY RADIATION CONFERENCE: VOLUME 2

32.     L, R, Delaplace and J, P. Reilly, "Electric and Magnetic Field Coupling from High Voltage AC
       Power Transmission Lines  Classification of Short-Term Effects on People," IEEE Transactions
       on Power Apparatus and Systems,  Vol. PAS-97, pp. 2243-2252, Nov./Dec.  1978.

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                         HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)  57


                       HUMAN THERMAL RESPONSES TO
                 RF-RADIATION INDUCED HEATING  DURING
                       MAGNETIC RESONANCE IMAGING*
                                     Frank G. Shellock**
INTRODUCTION

       During magnetic resonance imaging (MRI), patients are exposed to a static magnetic field, gradient
magnetic fields, and radio-frequency (RF) electromagnetic fields. Each of these forms of electromagnetic
radiation can cause unwanted biological effects if applied at sufficiently high exposure levels (1-12).  The
primary biological effect of exposure to RF radiation is the production of heat that occurs due to resistive
losses (1-9). Therefore, the physiologic changes associated with exposure to RF radiation  are related to
the thermogenie qualities of this electromagnetic field (1, 3-7, 10).

       Prior to 1985, there were no  published reports concerning  the thermal and  other physiologic
responses of human subjects exposed to RF radiation during MRI.   In fact, there has been a general
paucity of data obtained in human subjects with respect to their thermal responses to RF radiation.  The
previous investigations that have been performed in this field have examined thermal  sensations or
therapeutic  applications of diathermy,  usually involving only localized regions of the  body (2, 8, 9, 13,
14).

       Although   many  studies have been  performed using  laboratory  animals  to  determine
thermoregulatory reactions to tissue heating associated with exposure to RF radiation (2,  8, 9, 15, 16),
these  experiments  do not apply to MRI  because  the pattern  of RF absorption  or the coupling of
electromagnetic radiation  to biological tissues  is  highly dependent on the  organism's size, anatomical
factors, the  duration of exposure, the sensitivity of the involved tissues, and a myriad of other variables
(2, 8,  9,  15, 16).   Furthermore, there is no laboratory animal that sufficiently mimics or  simulates the
thermoregulatory system or responses of man. Therefore, experimental results obtained  in laboratory
animals cannot be simply "scaled" or extrapolated to predict thermal responses in human subjects exposed
to RF radiation (8,  15).

       Elaborate mathematic models have been devised to predict "worst case" scenarios of how human
subjects  may respond to  the RF energy that is  absorbed during MRI (17-19).  A  recognized major
limitation of modeling, though, is that it is difficult to account for the numerous critical variables (i.e., age,
drugs, cardiovascular disease, etc.) that can affect the thermoregulatory responses of human subjects. Most
individuals  that are exposed to RF radiation during  MRI have some underlying health condition or are
taking medication that can alter or impair their ability to dissipate heat. More importantly,  none of these
mathematic models of thermal responses to RF radiation have ever been validated.
   * This work was supported in part by PHS Grant No. 1 R01 CA44014-04 awarded by the National Cancer
Institute, National Institutes of Health. Portions of this paper were previously published in the monograph. Thermal
Responses in Human Subjects Exposed to  Magnetic Resonance Imaging,  New York  Academy  of  Sciences
Symposium, Biological Effects and Safety Aspects of Nuclear Magnetic Resonance Imaging and Spectroscopy,
Proceedings of the Meeting, 1992. This paper was updated in December 1994.

   ** R&D Services and Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, California.
Address correspondence to: Frank G. Shellock, Ph.D., R&D Services, 2311 Schader Drive, Suite 107, Santa Monica,
CA 90404.

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58   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

       Several investigations have been performed in the recent years that have yielded extremely useful
and important data about human thermal responses and other physiologic reactions to RF-radiation induced
heating that occurred during MRI (20-34).  This article will review and discuss these studies.

MR! AND THE SPECIFIC ABSORPTION RATE  (SAR) OF RF RADIATION

       The observed effects that human subjects have to the exposure to RF radiation during MRI are
dependent on the amount of energy mat is absorbed during the procedure.  The term that is used to
describe the absorption of RF radiation during MRI is the specific absorption rate, or SAR.  The specific
absorption rate is the mass normalized rate at which RF power is coupled to biologic tissue and is
indicated in units of watts per kilogram, W/kg (20-28, 33, 34). Both peak and whole-body averaged SARs
are used to characterize the relative amounts of RF radiation that an individual encounters during an MRI
examination.

       Measurements or estimates of SAR are not trivial, particularly in human subjects, and there are
several methods of determining this parameter for the purpose of RF energy dosimetry during MRI (20,
28, 34-38),  The SAR that is produced during MRI is a complex function of numerous variables including
the frequency (which, in turn, is determined by the static magnetic field strength), the type of RF pulse
used (i.e., 90 or 180), the repetition time, the pulse width, the  type of RF coil used (i.e., send/receive
body coil or send/receive surface coil), the volume of tissue contained within the coil, the resistivity of
the tissue, the configuration of the anatomical region exposed, the orientation of the body to the field
vectors, as well as other important factors (1, 3-7, 37, 38).

       The  efficiency and absorption pattern of RF energy are mainly determined by the physical
dimensions of the tissue in relation to the incident wavelength (2, 8, 9). Therefore,  if the tissue size is
large relative to the wavelength, energy is predominantly absorbed on the surface; if is it small relative
to the wavelength, there is  little absorption of RF power (2, 8, 9).

       During  MRI, tissue heating results primarily  from  magnetic induction  with a  negligible
contribution from the electric fields (37, 38), so ohmic heating is greatest at the surface of the body and
is minimal at the center of the body; see Figure 1.  Predictive calculations and measurements obtained in
phantoms and in human subjects exposed to MRI support this pattern of temperature distribution (2, 8,
9, 37, 38).

RECOMMENDED SAFE LEVELS OF EXPOSURE TO  RF  RADIATION  DURING MRI

       The  Food  and Drug  Administration (FDA) is  responsible  for  providing  guidelines  and
recommendations for the safe use of MRI systems in the United States. On July 28, 1988, MRI systems
were reclassified from class El, in which premarket approval is required, to class II, which is regulated
by performance standards, as long as the MRI system is within the "umbrella" of defined limits addressed
below (53). Subsequent to this reelassification, new MRI systems had only to demonstrate that they were
"substantially equivalent"  to any class  II device that  was brought to market  using  the premarket
notification process (510[k]) or, alternatively, to any of the devices described by the various MR system
manufacturers that had petitioned the FDA for such a reelassification.

       At the present time, the safe  levels for exposure to RF radiation during MR procedures
recommended by the FDA provide two options to control the risk of systemic thermal overload and local
thermal injury. Either SAR levels or temperature criteria may be adhered to, as follows (53):

       (1)     The exposure to RF  energy below the level  of concern  is  an SAR of 0.4 W/kg or less
              averaged over the body, and 8.0 W/kg or less spatial peak in any 1 gram of tissue, and
              3.2 W/kg or less averaged over the head; or

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                         HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)   59

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60   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE:  VOLUME 2

circumstances in the critical care area or operating room may be recorded during MRI, including heart
rate, oxygen saturation, end-tidal carbon dioxide, respiratory rate, blood pressure, cutaneous blood flow,
and temperature (39-42).

       For  assessment of thermal  response during MRI, volunteer subjects  or  patients  have been
continuously or  semi-continuously  monitored throughout the  experimental procedures using several
different types of devices  (20, 22-27, 31-34).  For example, sublingual  pocket or tympanic membrane
temperature (note that there is a good relationship between sublingual pocket temperature or tympanic and
esophageal temperatures (43)) were typically obtained immediately  before and after MRI using sensitive
electronic  therraometry or  infrared devices (20, 23, 26). Skin temperatures were measured immediately
before and after MRI procedures with a highly accurate infrared thermometer or thermographic equipment
(20, 22, 30, 34, 44).  Body  and skin temperatures measured at multiple sites were recorded before, during,
and after MRI with a fluoroptic thermometry system that is unperturbed by electromagnetic radiation (34,
42).  Heart rate, oxygen saturation, blood pressure, respiratory rate,  and cutaneous blood flow, which are
important physiologic variables that change in response to a thermal load, were typically monitored before,
during, and after MRI to assess the thermoregulatory system reaction of human subjects exposed to RF
radiation-induced heating  (12, 20-27, 40).  All of these parameters  were obtained with MRI-compatible
devices that have been extensively tested and demonstrated to provide sensitive and accurate data; see
Figure 2.

THERMAL AND  OTHER PHYSIOLOGIC RESPONSES TO RF RADIATION  INDUCED
HEATING DURING MRI

       The  increase in tissue  temperature caused by exposure to  RF energy during MRI depends on
multiple physiologic, physical, and environmental factors including the duration of exposure, the rate at
which energy is deposited, the ambient temperature, humidity, and airflow over and around the patient
within the MRI system, the status of the patients thermoregulatory  system, and the amount of insulating
clothing on or over the patient.

       Although the primary cause  of tissue heating during MRI  procedures is attributed solely to RF
radiation,  it  should be noted that various reports have suggested that exposure to static magnetic fields
used for MRI may also cause temperature changes (45, 46). The mechanism(s) responsible for such an
effect remains unclear, but the results of these studies have warranted investigations in human subjects
to determine if there is any contribution of the static magnetic field to the temperature changes that may
be observed during MRI.   Therefore, studies were conducted in human subjects exposed to a  1.5 Tesla
static magnetic field in order to determine if there were any changes  in body and/or skin temperatures (31,
32).   The  data revealed that there were no  statistically significant alterations observed in  any of the
recorded physiologic parameters (31, 32);  see Figure 3.  Tenforde (47)  examined this phenomenon, as
well,  in laboratory animals exposed  to static magnetic fields of as  high  as 7,55 T and also reported no
effect As far as the potential for production  of heat by gradient magnetic fields is concerned, this is not
believed to occur with the use of the conventional pulse sequences used for clinical MRI procedures (37,
38).

       The  first study of human  thermal  responses to RF radiation induced heating  during MRI was
conducted by Schaefer et al. (25).  Temperature changes and other  physiologic alterations were assessed
in volunteer subjects exposed to relatively high whole-body averaged SARs (i.e., approximately 4.0 W/kg).
The  recorded data indicated that there were no excessive temperature  elevations or  other  deleterious
physiologic consequences related to  this exposure to RF radiation (25).

       Several studies were subsequently conducted involving volunteer subjects and patients undergoing
clinical MRI procedures with the intent of obtaining information that would be applicable to the patient
population typically encountered in the MRI setting (20-28, 30, 33, 34). The whole-body averaged SARs
ranged from approximately 0.05 W/kg (i.e., for MRI procedures involving imaging with a transmit/receive

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HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING {SHELLOCK)   61
   Fig 2(a), MRI-compatible respiratory monitor.
  Fig 2(b). Heart rate and blood pressure monitor.

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62  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
                             Fig 2(c).  Cutaneous blood flow monitor.
                           Fig 2(d).  Muld-probe, fluoroptic thermometer.

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                           HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHEILOCK)   63
                                                                                V
                                  Fig 2(e). Fiber-optic pulse oximeter
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Fig 3.   Esophageal temperature measured in 11 human subjects during a 20 minute exposure to a 1.5 Tesla static
        magnetic field. There were no statistically significant changes in temperature caused by exposure to the
        static magnetic field.

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64   SUMMARY AND RESULTS OF THE RAD1OFREQUENCY RADIATION CONFERENCE: VOLUME 2

head coil) to 4.0 W/kg (i.e., for MRI procedures involving the imaging of the spine or abdomen with a
transmit/receive  body coil) (20-28, 30, 33, 34).   These  studies demonstrated that  changes in body
temperatures were relatively minor (i.e., less than 0.6C) (20-28, 30, 33, 34); see Figures 4 to 8. There
tended to be statistically significant increases in  skin temperatures that were also of no meaningful
physiologic consequence (20-28,30,33,34). Furthermore, there were no associated deleterious alterations
in any of the hemodynamic parameters that were assessed during these investigations (i.e., heart rate, Wood
pressure, and cutaneous blood flow) (20, 23, 26) (Figure 7).

       Of further note is that there was a poor correlation between body or skin temperature changes
versus  whole-body averaged SARs during clinical MRI (Figure 4). This is not unusual considering all
of the variables that may alter thermoregulation in a patient population (48-52).  Therefore, the thermal
response to  a given SAR may be  quite variable depending  on the individual's own  thermoregulatory
system and the presence of one or more underlying condition(s) that may alter or impair  the ability to
dissipate heat (4-7).    An   extensive  thermophysiology  investigation  using  multiple   fluoroptic
thermomerry probes that are unperturbed by electromagnetic fields (34) demonstrated  that human subjects
with normal thermoregulatory systems  exposed to MRI at whole body averaged  SAR levels up to 4.0
W/kg (i.e., ten times higher than the level currently recommended by the United States Food and Drug
Administration (53)) had no statistically significant increases  in body temperatures and have statistically
significant elevations in skin temperatures that were not excessive (Figure 8).  The results of this study
suggested that the  recommended  exposure to RF radiation during  MRI for patients  with normal
thermoregulatory function may be too conservative (34).

       Research has been conducted in volunteers exposed to MRI performed at a whole body averaged
SAR of 6.0 W/kg in cool (22.50C) and warm (33C) environments in order to characterize thermal and
other physiologic responses to this high exposure to RF energy since some of the newly developed pulse
sequences have  potentially  high  SARs  associated  with their  use (54-56).   Tympanic  membrane
temperature, six skin temperatures, heart rate, blood pressure, oxygen saturation, and skin blood flow were
monitored before, during, and after exposure to the RF energy; see Figure 9. In the cool  environment,
there were statistically significant increases in tympanic membrane, abdomen, upperarm, hand, and thigh
temperatures as well as heart rate and skin blood flow.  In the warm environment, there were statistically
significant increases in tympanic membrane, hand, and chest  temperatures as well  as systolic blood
pressure and heart rate. Each  of the temperature increases were within FDA guidelines (53).  These data
indicate that MRI performed  at 6.0 W/kg can be  physiologically tolerated by individuals with normal
thermoregulatory function (54).

       Of additional note is that the subjects'  perception of tissue heating was greater  when the subjects
underwent MRI at an SAR of 6.0 W/kg in the cool environment compared with their experience in the
warm environment.  This indicates that  it would not be useful to pre-cool subjects  that  will subsequently
undergo high SAR procedures in order to enable them to  better tolerate  these procedures, as has been
suggested by some researchers and manufacturers of MRI systems.

       Additional studies are presently needed in order to  assess thermal  responses of  patients  with
conditions that may impair their ability to dissipate heat (e.g., elderly patients; patients with underlying
diseases, or obesity; and patients taking medications that affect thermoregulation, such as calcium blockers,
beta blockers, diuretics, vasodilators,  sedatives, anesthetics, etc.) (48-52) before  subjecting  them to MRI
procedures that require high SARs. There is currently an on-going effort to characterize the thermal and
other physiologic responses  of  these  patient groups to  RF radiation  induced heating  during MRI
examinations that require high SARs.

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                           HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHSLLOCK)   65
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Fig 4(a).        Change in body temperature versus exposure to whole-body average SAR's during clinical MRI
                procedures. Note that there is a poor correlation, between these two variables.
                                       WHOLE BODY AVERAGE SAR (W/kg)
Fig 4(b).        Change in skin temperature versus exposure to whole-body averaged sar's during clinical MRI
                procedures. Note that there is poor correlation between these two variables.

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66   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
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Fig 5.   Sublingual pocket temperature, forehead skin temperature, ear skin temperature, and ear skin blood flow
        measured immediately before and after clinical MRI procedures involving the patients head.  There were
        statistically significant increases (p < 0.01) in sublingual pocket, forehead skin, and ear skin temperatures
        and in ear skin blood flow (see reference 23).
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                                              IR1   MRI  MRI    MR!  MRI    MRI  MRI
                                       FOREHEAD   OUTER      UPPER      HAND
                                                   CANTHUS      ARM
Fig 6.   Average body (sublingual pocket) and skin temperatures measured immediately before and after MRI of
        the brain at 1.5 T/64 MHz using a head coil (N=35).  There were statistically significant increases in
        forehead and skin and outer canthus skin temperatures (see reference 26).

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                           HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)   67
                      100 i-
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                    PRE POST
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                    DIASTOLIC
Fig 7.   Average heart rate and systolic and diastolic blood pressures immediately before and after MRI of the brain
        at 1.5 T/64 MHz using a head coil (N-35). There were statistically significant decreases in each of these
        measured parameters (see reference 26),
                      BASELINE
                                              MR IMAGING
                                                                     POST UK WAGING
                                            30   35   40

                                             TIMi (MINUTES)
Fig 8.   Sublingual and multiple skin temperatures measured at 1-min intervals with a fluoroptic thermometry system
        (Luxtron) before (baseline), during (MR imaging), and after (post-MR imaging) MRI performed at whole-
        body averaged SAR of 2.8 W/kg. Note that there was little or no change in sublingual or body temperature,
        whereas  there were  slight to moderate changes in skin temperatures (depending on the site of the
        measurement) during MW. After MRI, some skin  temperatures returned to the baseline level, whereas
        others remained elevated during the 20-min post-MRI evaluation period (see reference 34).

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68   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
                                              TBfPESATUiE CRAHGES
                      TYMPANIC  ABDOMEN
                                          CC0122.5-C  K WARM 33.8" C  i
Fig 9(a).        Changes in tympanic membrane, abdomen, forehead, upper arm, hand, chest, thigh, and calf skin
               temperatures associated with MRI performed (N = 6 volunteers) at a whole body averaged SAR
               of 6.0 W/kg in cool and warm environments (see reference 54).
                                                                        02 SAT      BLOOD FLOW
SYSBP
                                      ICOOL22JC  & WARM 33.8 C
Fig 9(b).       Changes in  systolic blood pressure, diastolic blood pressure, mean blood pressure, heart rate,
               oxygen saturation and cutaneous blood flow associated with MRI performed (N = 6 volunteers)
               at a whole body averaged SAR of 6,0 W/kg in cool and warm environments (see reference 54),

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                         HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)   69

MRI AND TEMPERATURE-SENSITIVE ORGANS:  THE TESTIS AND EYE

       Certain human organs that have reduced capabilities for heat dissipation, such as the testis and eye,
are particularly sensitive to elevated temperatures. Therefore, these are primary sites of potentially harmful
effects if RF radiation exposures during MRI are excessive.

       For example, laboratory investigations have demonstrated detrimental effects of testicular function
(i.e., a reduction or cessation of sperraatogenesis, impaired sperm motility, degeneration of seminiferous
tubules, etc.) caused by RF radiation-induced heating from exposures sufficient enough to raise scrotal
and/or testicular tissue temperatures between 38 to 42C (57).

       Scrotal skin temperatures (which are  an index of intratesticular temperatures because  a high
correlation has been demonstrated between intratesticular and scrotal skin temperatures)  (58) were
measured in volunteer subjects undergoing MRI at a whole-body averaged SAR of  1.1 W/kg (27). The
largest change in scrotal skin temperature was 2.1C and the highest scrotal skin temperature recorded was
34,2C (27). These temperature changes  were  below the threshold known to impair testicular function
(57).   However, inordinately heating the scrotum during MRI could exacerbate  certain pre-existing
disorders associated with increased scrotal/testicular temperatures (e.g., acute febrile illnesses, varicocele,
etc.) in patients  who  are already oligospermic and could lead to temporary  or  permanent sterility.
Therefore, additional studies designed to  investigate these  issues are needed,particularly if patients are
scanned at whole-body averaged SARs higher than those previously evaluated (which is entirely possible;
since there is a trend to use newly developed pulse sequences that  have associated high SARs to image
the scrotum).

       Dissipation  of heat from the eye is a  slow  and inefficient process  due to its relative lack of
vascularization. Acute near-field exposures of  RF radiation to the  eyes or heads of  laboratory animals
have been demonstrated to be eataractogenic as a result  of the thermal disruption of ocular tissues if the
exposure is of a sufficient intensity and duration (59). An investigation conducted  by Sacks et al. (60)
revealed that there were no discernible effects on the eyes of rats produced by MRI at exposures that far
exceeded typical clinical imaging levels.  However, as previously indicated, it may not be acceptable to
extrapolate these data to human subjects considering the  coupling of RF radiation to  the anatomy and the
tissue volume of laboratory rat eyes compared to those of humans.

       Cornea! temperatures (corneal temperature is a representative site of the average temperature of
the human eye) (61) have been  measured in patients undergoing MRI of the brain using a send/receive
head coil at local SARs up to 3.1 W/kg (24). The largest comeal temperature change was 1.8C and the
highest temperature measured was 34.4C.  A more recent study (33) examined  corneal temperatures in
patients with suspected ocular pathology who underwent MRI using a special eye coil;  again,  there were
no excessive corneal temperature elevations. Because the temperature threshold for RF radiation-induced
cataractogenisis in animal models has been  demonstrated to be between 41 to 55C for acute near-field
exposures, it does not appear that clinical MRI using a head coil or an eye coil has the potential to cause
thermal damage in ocular tissue.  The effect of MRI performed using higher SARs and the long-term
effects of MRI on ocular tissue remains to be determined.

MRI AND "HOT SPOTS"

       Theoretically, RF radiation "hot spots" caused by an uneven distribution of RF power may arise
whenever current concentrations are produced in association with restrictive conductive patterns.  There
has been the suggestion that RF radiation "hot  spots" may occur during MRI and generate thermal "hot
spots"  under  certain conditions.   Because RF radiation  is  mainly absorbed  by peripheral tissues,
thermography has been used to study the  heating pattern  associated with MRI  at high whole-body
averaged SARs (22, 30). This research demonstrated that there was no evidence of surface thermal "hot
spots" related to performing MRI in human subjects.  The thermoregulatory system  apparently responds

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70  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

to the heat challenge induced by RF radiation by distributing the thermal load, producing a "smearing"
effect of the surface temperatures; see Figure 10, However, there is a possibility that internal thermal "hot
spots" may develop during MRI,  This issue is currently undergoing investigation in human subjects.

        A report by Shuman et al. (35) indicated that significant temperature rises occur in internal organs
produced during MRI performed in laboratory dogs.  This study was conducted on anesthetized animals
and is unlikely  to be pertinent to conscious adult human subjects  because of the previously discussed
factors relating to the physical dimensions as well as to the dissimilar thermoregulatory systems of these
two species. However, these data may have important implications for the use of MRI in pediatric patients
because this patient population is typically sedated or anesthetized for MRI examinations and the physical
dimensions of the dog are comparable to those of the pediatric population that frequently is examined by
MRI.  Obviously, research is required to examine this issue more closely.

FUTURE STUDIES OF THERMAL RESPONSES TO RF-RADIATION INDUCED HEATING
DURING MRI

        Recent advances in MRI have produced special pulse sequences (i.e. RARE, fast spin echo, etc.)
that allow imaging to be performed five to ten  times faster than previously possible (56).  This requires
a substantial increase in RF power that is predicted, in some cases, to exceed a whole-body averaged SAR
of 10 W/kg (D.J. Schaefer, General Electric Company, personal communication, 1991). Both the clinical
importance and  the cost-effective use of MRI accomplished with these new pulse sequences are obvious.
However, the safety of subjecting patients to RF energy at these potentially excessive levels is unknown.
Therefore, studies are currently examining the human thermoregulatory responses to SARs that are even
higher than those that have been studied in recent years (54). As previously indicated, preliminary results
of these  investigations are encouraging  with  respect to the  ability  of individuals  with  normal
thermoregulatory function to tolerate MRI examinations with high SARs.

        In addition, there are now whole-body MRI systems with a static magnetic field strength of 4.0-T
that are being used for a combination of imaging and spectroscopy on human subjects (62, 63). Imaging
at 4.0-T uses approximately seven times as much RF energy as a 1.5-T MRI scanner (62).  Investigations
evaluating thermal responses in human subjects will also be needed to assess the safety of these powerful
MRI devices.
REFERENCES

l.PerssonBRR, Stahlberg F. Health and Safety of Clinical NMR Examinations 1989.  CRC Press, Boca
       Raton, Florida.

2. Michaelson SM, Lin JC. Biological Effects and Health Implications of Radiofrequency Radiation 1987.
       Plenum, New York.

3. Shellock FG, Crues JV. MRI:  Safety considerations in magnetic resonance imaging.  MRI Decisions
       1988; 2: 25-30.

4. Shellock FG.  Biological  effects and safety aspects  of magnetic resonance imaging. Magn Reson Q
       1989; 5: 243-261.

5. Kanal E, Shellock FG,  Talagala L. Safety considerations in MR imaging.  Radiology 1990; 176: 593-
       606.

6. Shellock FG, Crues JV. Biological effects and safety considerations of magnetic resonance imaging.
       In: Magnetic Resonance Imaging Syllabus. American College of Radiology 1991.

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                          HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)  71
Fig 10.  Thermographs obtained from the back of a human subject before (top) and after (bottom) a 45-min
        procedure performed on the abdomen with a 1,5-T/64-MHz MRI scanner at a whole-body average SAR of
        3.2 W/kg. There was no evidence of any surface "hot spots" or of excessive temperature elevations. The
        thermoregulatory system produced a "smearing" effect such that the increased surface temperatures after
        MRI were evenly distributed (see references 22 and 30).

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72  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

7, Shellock FG.  MRI bioeffects and safety.  In: Magnetic Resonance Imaging of the Brain and Spine
       1990. S. Atlas, Ed.  Raven Press, New York.

8. NCRP.  Biological effects and exposure criteria for radiofrequency electromagnetic fields. Report No.
       86. National Council on Radiation Protection and Measurements 1986. Bethesda, MD.

9. Gordon CJ.  Thermal physiology.  In: Biological Effects of Radiofrequency Radiation  1984; pp. 4-1
       to 4-28. EPA-600/8-83-026A.

10. Edelman RR, Shellock FG, Ahladis J. Practical MRI for the technologist and imaging specialist.  In:
       Clinical Magnetic Resonance 1990. R.R. Edelman & J. Hesselink, Eds.  Saunders, Philadelphia.

11. Beers J. Biological effects of weak electromagnetic fields from 0 Hz to 200 MHz:  A survey of the
       literature with special emphasis on possible magnetic resonance effects.  Magn Reson Imag 1989;
       7: 309-331.

12. Adey WR.  Tissue interactions with nonionizing electromagnetic fields. Physiol Rev 1981; 61: 435-
       514.

13. Shellock FG.  Thermal Responses in Human Subjects Exposed to Magnetic Resonance Imaging. New
       York Academy of Sciences Symposium,  Biological Effects  and Safety Aspects of Nuclear
       Magnetic Resonance Imaging and Spectroscopy, Proceedings of the Meeting, 1992,

14. Coulter S, Osbourne SL. Short wave diathermy in heating of human tissues. Arch Phys Ther 1936;
       17: 679-687.

15. Gordon CJ. Normalizing the thermal effects of radiofrequency radiation: Body mass versus total body
       surface area.  Bioelectromagneties 1987; 8: 111-118.

16. Gordon CJ.  Effect of radiofrequency radiation exposure on thermoregulation, ISI Atlas Sci Plants
       Anim 1988; 1: 245-250.

17. Athey TW,  A model of the temperature rise  in the head due  to  magnetic resonance imaging
       procedures. Magn Reson Med 1989; 9: 177-184,

18. Adair ERR, Berglund LG, On the thermoregulatory consequences of NMR imaging.  Magn Reson
       Imag 1986; 4:  321-333.

19. Adair ER, Berglund LG. Thermoregulatory consequences of cardiovascular impairment during NMR
       imaging in warm/humid environments.  Magn Reson Imag 1989; 7: 25-37.

20. Shellock FG, Crues JV. Temperature, heart rate, and blood pressure changes associated with clinical
       MR imaging at 1.5-T.  Radiology 1987; 163: 259-262.

21. Kido DK,  Morris TW, Erickson JL, et al.  Physiologic changes during high-field strength MR
       imaging.  Am J Neuroradiol 1987; 8: 263-266.

22, Shellock FG, Schaefer DJ, Grundfest W, et al.  Thermal effects of Mghfield (1.5 Tesla) magnetic
       resonance imaging of the spine: Clinical experience above a specific absorption rate of 0.4 W/kg.
       Acta Radiol Suppl 1986; 369: 514-516.

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                        HUMAN THERMAL RESPONSES TO MAGNETIC RESONANCE IMAGING (SHELLOCK)  73

23, Shellock FG, Gordon CJ, Schaefer DJ.  Thermoregulatory response to clinical magnetic resonance
       imaging of the head at 1.5 Tesla: Lack of evidence for direct effects on the hypothalamus. Acta
       Radiol Suppl  1986; 369; 512-513,

24. Shellock FG, Crues JV. Corneal temperature changes associated with high-field MR imaging using
       a head coil. Radiology 1988;  167: 809-811.

25. Schaefer DJ, Barber BJ, Gordon CJ, et al. Thermal effects of magnetic resonance imaging. In: Book
       of Abstracts, Soc Magn Reson Med 1985; 2: 925.

26. Shellock FG, Crues JV.  Temperature changes caused by clinical MR imaging of the brain at 1.5 Tesla
       using a head coil.  Am J Neuroradiol 1988; 9: 287-291.

27. Shellock FG, Rothman B, Sarti D.  Heating of the scrotum by highfield-strength MR imaging.  Am
       J Roentgenol  1990; 154: 1229-1232.

28. Vogl T, Krimmel  K, Fuchs A, et al. Influence of magnetic resonance imaging of human body core
       and intravascular temperature.  Med Phys 1988; 15: 562-566.

29. Crues JV, Shellock FG, Levy T.  Prevalence  of high-field MRI  procedures requiring specific
       absorption rates below and above 0,4 W/kg: Experience in 639 patients. In: Book of Abstracts,
       Soc Magn Reson Med 1986; 1030-1031.

30. Schaefer  DJ, Shellock FG, Crues JV  et al.  Infrared thermographic studies of human  surface
       temperature in magnetic resonance imaging. In: Proceedings of the Bioelectromagnetics Society,
       Eighth Annual Meeting, 1986; p. 68.

31. Shellock FG, Schaefer DJ, Gordon CJ.  Effect of a 1.5 Tesla static magnetic field on body temperature
       of man, Magn Reson Med 1986; 3: 644-647.

32. Shellock FG, Schaefer DJ, Crues JV.  Effect of a 1.5 Tesla static magnetic field on  body and skin
       temperatures of man.  Magn Reson Med 1989;  10: 371-375.

33. Shellock FG, Schatz CJ. Increases in corneal temperature caused by MR imaging of the eye with a
       dedicated local coil. Radiology 1992; 185: 697-699.

34. Shellock FG, Schaefer DJ, Crues  JV.   Alterations  in body and skin temperatures caused by MR
       imaging:   Is the recommended exposure for radiofrequency radiation too conservative? Br J
       Radiol 1989; 62: 904-909.

35, Shuman WP,  Haynor DR, Guy AW, et al.  Superficial and deep-tissue increases in anesthetized dogs
       during exposure to high specific absorption rates in a 1.5-T MR imager.  Radiology 1988; 167:
       551-554.

36, Barber BJ, Schaefer DJ, Gordon CJ, et al.  Thermal effects of MR imaging:  worst-case studies in
       sheep. Am J  Roentgenol 1990; 155: 1105-1110.

37. Bottomley PA, Redington RW, Edelstein WA, et  al. Estimating radiofrequency power deposition in
       body NMR imaging.  Magn Reson Med 1985; 2: 336-349.

38. Bottomley PA, Edelstein WA. Power deposition  in whole body NMR imaging. Med Phys 1981; 8:
       510-512.

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74   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

39. Shellock FG.  Monitoring during MRI: An evaluation of the effect of high-field MRI on various
       patient monitors, Med Electron 1986; Sept: 93-97,

40. Holshouser B, Hinshaw DB, Shellock FG. Sedation, anesthesia, and physiologic monitoring during
       MRI.  In: ARRS Categorical Course Syllabus: Spine and Body Magnetic Resonance Imaging
       1991. AN Hasso & DD Stark, Eds. pp. 9-15.

41. Kanal E, Shellock FG.  Patient monitoring during clinical MR imaging.  Radiology,  1992; 85: 623-
       629.

42. Wickersheim KA, Sun MH. Fluoroptic thermometry. Med Electron 1987; February: 84-91.

43. Houdas Y, Ring EFJ.  Temperature distribution. In: Human Body Temperature:  Its Measurements
       and Distribution 1982; pp. 81-103. Plenum, New York.

44. Shellock FG, Rubin SA, Everest CE. Surface temperature measurement by IR.  Med Electron 1986;
       86:  81-83.

45. Sperber D, Oldenbourg R, Dransfeld K.  Magnetic field  induced temperature change in mice.
       Naturwissenschaften 1984; 71: 100-101.

46. Gremmel H, Wendhausen H, Wunsch F. 1983.  Biologische Effeckte Statischer Magnetfelder bei
       NMR-Tomographic Am Menshen.  Wiss. Mitt.  Univ.  Kiel Radiol.  Klinik.

47. Tenforde TS. Thermoregulation in rodents exposed to high intensity  stationary magnetic fields.
       Bioelectromagnetics 1986; 7: 341-346.

48. Burch GE, DePasquale NP. Hot climates, man and his heart. Thomas.  1964 Springfield, IL.

49. Jauchem JR.  Effects of drugs on thermal responses to microwaves. Gen Pharmacol  1985; 16: 307-
       310.

50. Rowell LB.  Cardiovascular aspects of human thermoregulation. Circ Res 1983; 52: 367-379,

51. Shellock FG, Drury JK, Meerbaum S, et al. Possible hypothalamic thermostat increase produced by
       a calcium blocker.  Clin Res 1983; 31: 64A.

52. Kenny WL. Physiological correlates of heat intolerance. Sports Med 1985; 2: 279-286.

53. Food and Drug Administration,  Magnetic resonance diagnostic device; panel recommendation and
       report on petitions for MR reelassification. Fed Regist 1988; 53: 7575-7579.

54. Shellock FG, Schaefer DJ, Kanal E.  Physiologic responses to MRI performed at an SAR of 6.0 W/kg
       in cool and warm environments. Radiology 1994; 192:865-868.

55. Shellock FG, Litwer C, Kanal E.  MRI bioeffects, safety, and patient management: a review. Reviews
       in Magnetic Resonance Imaging, 1992; 4: 21-63.

56. Hennig J, Nauerth A, Friedburg H.  RARE imaging: A fast imaging method for clinical MR. Magn
       Reson Med 1986; 3: 823-833.

57. Berman E. Reproductive effects. In:  Biological Effects of Radiofrequency Radiation, 1984; pp. 5-29
       to 5-42. EPA-600/8-83-026A.

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                        HUMAN THERMAL RESPONSES TO MAGNETO RESONANCE IMAGING (SHELLOCK)   75

58. Kurz KR, Goldstein M.  Scrotal temperature reflects intratestieular temperature and is lowered by
       shaving.  J Urol 1986;  135: 290-292.

59. Elder JA,  Special senses. In: Biological Effects of Radiofrequency Radiation, 1984; pp. 5-64 to 5-
       78. EPA-600/8-83-026A.

60. Sacks E, Worgul BV, Merriam GR, et al.  The effects of nuclear magnetic resonance imaging on
       ocular tissues.  Arch Ophthalmol 1986; 104: 890-893.

61. Mapstone R. Measurement of cornea! temperature. Exp Eye Res 1968; 7: 233-243.

62. Redington RW, Dumoulin  CL, Schenck F, et al. MR  imaging and bioeffects in a whole body 4.0
       Tesla imaging system.  In: Book of Abstracts,  Soc  Magn Reson Imag 1988; 1: 20.

63. Ortendahl DA.  Whole-body MR imaging and spectroscopy at 4 Tesla: Where do we go from here?
       Radiology 1988; 169: 864-865.

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                              EPIDEMIOLOGIC STUDIES OF NON-IONIZING RF EXPOSURES (MATANOSKI)   77


                EP1DEMIOLOGIC STUDIES  OF NON-IONIZING
                        RADIOFREQUENCY EXPOSURES*
                                    Genevieve Matanoski**
       This paper discusses several epidemiology studies on the potential risks of radiofrequency (RF)
exposures.   The studies in the literature have little information  on the details  of exposures to  the
population.  Few studies include large populations from which  we could gain information on human
responses to RF.  In fact, the RF exposed workers are often a subset of a larger population exposed to
non-ionizing radiation.  Despite these limitations, we will review the few studies in the recent literature
in an attempt to determine whether there are any chronic effects from RF exposures.

       For ease of discussion, the studies have been divided into groups. The first group will be cohort
studies that looked at electromagnetic (EM) fields in general. Within these studies (see Table 1), specific
jobs which may have resulted in RF exposures, such as electronics, can be selected for review.  However,
these job titles are nonspecific in regard to actual exposures to RF.  The studies by Vagero (1983, 1985)
and by DeGuire (1988) demonstrate a positive risk for melanoma of the skin in individuals who are in
the telecommunications and electronics industries.  However, the studies do not indicate which jobs may
have been related to the risks.  However, in each of the studies, tihe relative risks were significant and the
values ranged from levels of 1.5 to about 2.5. These studies did not report excess risks of brain cancers
or leukemia, which are often reported in studies of electrical workers. These are the only studies reporting
excesses of melanomas. However, this does not mean that the other studies are necessarily negative; many
studies never looked for melanoma as an outcome.

       McLaughlin (1987) looked at only leukemia risks in association with electrical jobs and found no
excess risk in electricians, powerline workers, or telecommunications employees. Lin (1989) investigated
the risks of brain tumors in the telecommunications  industry and found no association between leukemia
and work in the industry; however, he did find an association with  brain cancers based on a very small
number of  cases.  Again, both studies use a non-specific characterization of the telecommunications
industry and do not designate jobs or exposures.

       A study of Navy personnel by Garland (1990) only reported on leukemia risks. Although no other
risks were reported, authors usually examine other  diseases in any  cohort study to see if anything else
appears to be occurring in excess.  The personnel jobs were broken down into three groupings: radio men,
electronics technicians, and electricians' mates.  The only group at risk was the electricians, not the radio
men or the electronics technicians.

       Tornqvist (1991) studied the jobs of Swedish  workers  with leukemia and brain cancers and
compared the risk of electrical and electronics workers to all other workers. The group of tele-radio and
TV repair technicians who might be suspected of having RF exposures showed no significantly  elevated
standard  mortality ratios (SMRs).  He reports a very small excess risk of leukemia when he puts all
electric work into one  group which includes engineers and technicians. In general, he has found no risk
for either leukemia or brain tumors in the group who might be  exposed to RF non-ionizing radiation.
However, both SMRs just exceeded 1.0.
     * This paper was updated in October 1994.

     **  School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205.

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78   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

Table 1. General Studies:  Electrical Workers Exposed to RF Radiation
Author
Vagero 1985
Vagero 1983
McLaughlin 1987
DeGuire 1988
Lin 1989
Garland 1990
Hutchinson 1991
Tornqvist 1991
Subjects/Exposure
Telecommunications Industry
Electronics Industry
Electricians
Powerline workers
Telecommunications
Telecommunications
Telecommunications
Navy Personnel
Electricians' mates
Electronics technicians
Radiomen
All electric
Telegraph, radio, radar operators
Electronics technicians
Television, radio repairmen
Radio, radar mechanics
All Swedish workers
All elec./electronic
engineers and technicians
Tele-radio TV repair
Risks
Melanoma 2.5*Sig, No/xs brain,
leukemia
Melanoma l,35*Sig. No/xs brain,
leukemia
Only leukemia reported
0.8 (42 cases)
1.0 (13)
1.1 (13)
Melanoma 2.7*Sig. (10)
[No other cancer reported]
All cancers 1,01 (129)
Brain cancer 2.4 (5)
[No other cancer reported]
Only leukemia reported
2.4*Sig. (7)
1.1 (5)
1.1 (4)
Summary of all data on leukemia
Cl, 95%
1.19 (1.12, 1.26)
1.59 (1.29, 1.96)
1.18 (0.75, 1.88)
2.24 (1.37, 3.66)
0.47 (0.18, 1.26)
Leukemia Brain
SMR 95%, Cl SMR 95%, CI
1.3 (1.0, 1.7) 0.9 (0.7, 1.3)
1.1 (0.6, 1.8) 1.2 (0.7, 2.0)
       Hutchinson (1991) reported a summary or meta-analysis of all the studies on leukemia  and
possible exposures to EM fields.  The summary focused on leukemia as reported in al studies done to that
date.  He examined the risks in the various subsets of occupations within the studies.  The overall group
showed about a  1.2-fold  excess risk of leukemia for all  individuals  who worked anywhere in the
electrical/electronics industry.  For the total group, there was a significant difference in risk.  He has
examined telegraph radio/radar operators as a subgroup in these combined studies. There is a significant
excess of risk of 1.6 in this group of workers.   In addition, television  and radio repairmen have a
significant excess risk of 2.24.   The telecommunications industry and electronics industry  as a whole
showed no excess risk of leukemia.  Essentially, compiling all of the studies on  leukemia, there  is a
significant excess risk for the radar and radio operators, and for television repairmen. The jobs of radio
repairmen and radio mechanics show conflicting results in two subgroups which  include these workers.

       These general studies of cohorts of workers who are assumed to have RF exposures have shown
some excesses  of leukemia; however, there are  inconsistencies across the studies and there  is no
information on the actual exposures in these jobs.  From Hutchinson's meta-analysis, the excess risk of
leukemia may be  associated with work as a radio or radar operator. Only one cohort study examined the

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                                EPIDEMIOLOGIC STUDIES OF NON-IONIZING RF EXPOSURES (MATANOSKf)   79

association between brain tumors and radiofrequeney exposures and three cohort studies examined the
association with melanoma.  Brain tumor and work in jobs with possible RF exposures was not significant
in the one study,  while  melanoma were  significantly associated with work  in the telecommunications
industry in three studies. No studies actually associated the cancers with exposures to RF radiation in
these jobs,

       Table 2 presents ease-control studies of brain cancers.  These studies compare the occupations of
individuals with brain cancer to those of people with no brain cancer. The cases are often identified from
a cancer registry, hospital records, or deaths.  In these studies, occupations are often identified from death
certificates or hospital records. The best studies seek information on occupations from the patient or the
next of kin. The investigators try to determine the type of work performed by the cases and controls and
try to characterize that work in detail.  The problem the investigators have is that cases of brain cancer
are usually deceased, but the controls are living.  Thus, the quality of the data  between cases and controls
differs.

Table 2.  General Studies:  Brain Cancer
        Author
        Subjects/Exposure
                 Risks
  Lin 1985
Glioma/astrocytoma deaths 519
Controls: non-cancer deaths 519

 Occupation on death certificate
 Panel rating exposures:  by job
Definite EM    2.15    (1.10,4.06)
Probable EM    1.95    (0.94, 3.91)
Max. risk: electric and electronics engineers
18 cases/6 controls among gliomas
  Thomas 1987
435 brain cancer
386 other deaths as controls

 Occupation:  next-of-kin
 Panel rating exposures
 No control other occ. materials
MW/RF Expos.          1.6      (1.0,2.4)
MW/RF Expos, in elec.
 or electronics          2.3      (1.3,4.2)
Exposed but never in
 elec. or electronics     1.0      (0.5,1.9)
Dose response by duration worked in
MW/RF exposure
Astrocytomas higher 4.6    (1.9,12.2)
  Savitz 1989
1,095 brain cancer in 16 U.S. states

 Occupation on death cert.
Electric workers  1.5
Elec. and electronic
 tech           3.1
Elec. power repair 2.4
(1.02, 2.J
  Brownson 1990
Cancer registry
312 WM brain
1,248 other cancers

 Occupation on hospital record
Communication workers  1.4      (0.5, 4.1)
Utilities and
 sanitation services  0.5          (0.1, 1.7)
        Several case-controls studies are presented. One is a study by Lin (1985) which examined deaths
from brain cancers and non-cancer deaths in Maryland and compared each individual's occupation as listed
on a death certificate,  A panel then examined those jobs and judged whether the jobs on the list exposed
individuals to various types of EM fields.  The first group consisted  of electricians, electrical engineers,
and other electrical poweer workers.  The second group consisted of electronics engineers and others
primarily exposed  to  RF waves.  The number of cases was large, 579.   Lin reported a significant
difference in  risk for  those who were likely to be highly exposed to  electric  fields.   He showed a
somewhat lesser risk for those who has "probable" EM exposures and for a group of electronics engineers

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80   SUMMARY AND RESULTS OF THE RAD1QFREQUENCY RADIATION CONFERENCE: VOLUME 2

who may have had RF exposures. The maximum risk was for electronics engineer: almost three-fold for
gliomas. This particular study offers  little information in regard to pure RF or microwave exposures.

        Thomas (1987) used a similar case-control study of brain cancer deaths and other death controls
in three states.  The author examined  the occupations  of cases and controls through interviews with the
next of kin.  This  allowed comparison of total occupational histories.  Although this  information is
somewhat limited since next of kin may not know exactly  what work an individual performed, this, in
general, is a better study than the one  previously described.  A panel rated the exposures relating to each
job to determine which jobs were likely to have had microwave or RF exposures.  Thomas was specific
about the exposures of interest.  Individuals whose jobs exposed them to microwaves and RF radiation
had a significant excess risk of brain tumors with an odds ratio of 1.6.  The odds ratio was higher (2.3)
and still significantly  increased in those who worked in electronics or electrical jobs and were exposed
to RF or microwave radiation.  Those who were exposed but never worked in the electronics and electrical
industry had no excess risk. Thus, it  would appear that exposure to microwaves and RF  waves, which
was associated with brain cancer in this study, was strictly in individuals exposed and working in the
electronics industry. There was a positive dose-response relationship with increasing risk of brain cancer,
associated with increasing duration of work with microwave and RF radiation exposures. The odds ratio
was increased to 4.6 when the exposure was associated with a specific brain tumor, astrocytomas.  The
study by Thomas is one of the stronger studies in terms of design and exposure estimation.  The study
still does not identify  exactly what exposure, and at what level, RF or microwave radiation is associated
with brain cancer. This study does correct for smoking, but does not correct for other materials that might
have been present in the occupational setting.

        There are two  other case-control studies of brain tumors. Loomis and Savitz (1989) examined the
risk of brain cancer using the  occupations as listed on death certificates. The occupation on the death
certificate supposedly represents  the  "usually  occupation", but the  information  often is given  by  a
respondent at time of  death or is taken from a hospital  record. If someone has had two or three jobs, the
most recent occupation is usually listed on the death  certificate.  This death certificate occupation has
limited value in identifying exposures compared to taking a complete work history as done by Thomas.
Exposures to non-ionizing radiation were based on job title.  The Loomis and Savitz study showed an
apparent increased risk of brain cancers  for electrical workers in general  and for electric and electronics
technicians (odds ratio, OR = 1.5).  Again, the odds ratio was increased (OR=3.1)  in the group classified
as electric and electronics technicians.

        Brownson (1990) conducted a case-control study which selected other cancers from a registry as
controls and used the  occupation as listed on the hospital record  as an exposure measure.  This study
found absolutely no association between brain cancer an exposure to work in the communications industry.
The odds ratio is slightly above 1.0 for the communications workers (OR=1.4), but is not significant.  It
would be hard to put any weight on this study. Three of these case-control studies have shown significant
excess risks of brain cancer in people  exposed to the electronics industry and, in one study, specifically
to exposures to microwaves and RF radiation in that industry.

       The third group of studies (Table 3) are those which specifically  focus on cohorts of individuals
known to be exposed  to either microwaves or radio waves.  In the first cohort, Lilienfeld (1978) studied
individuals who were exposed to  microwaves  as  a jamming device when stationed in the American
embassy in Moscow.  The study compared individuals from that embassy and those from other embassies
in various parts of the world.  This study collected specific questionnaire data on disease and cancer and
tried to estimate the actual SAR of these individuals, which was very low. Personnel in the embassy had
changed quickly.  They represented both diplomatic service people as well as military personnel, making
the follow-up of these individuals very difficult. Researchers took medical records from the individual
directly  through a questionnaire, and also examined the medical treatment records for these  individuals
when they were part of the government service. Information on the causes of death were obtained  from
the records  of deceased individuals.  The medical  records  indicated  a few differences  such  as  a

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                               EPIDEMIOLCX3IC STUDIES OF NON-IONIZING RF EXPOSURES (MATANOSK!)   81

Table 3,  Cohort Studies With Specific Exposures
Author
Lilienteld 1978
Robinette 1977,
1980
Milham 1988
Hill 1988
Samigielski 1988
Subjects/Exposure
4,300 employees
Moscow 1,800
8,200 dependents
Moscow 3,000
Questionnaire
SAR est. MilxlO'4
F:7xlO-4
40,000 veterans
General division
Radar operator and others
Radar operators-low
Gunfire control and electronics
tech.-high
SAR < 0.05
Amateur radio
67,829 licenses (1979-84)
Est. expos.  license expertise to
determine exposure
Developed radar at MIT
1,492 males
Est. expos.  old radar systems
0.1 to 0.4 W/KgSAR
Expos related job class
Polish military
Expos. MW and RF
Risks
Medical: Increased protozoal infections.
Others not clear
Deaths: All cancer 0.84 (0.5, 1.4)
Brain 0
Leukemia 2.5 (0.3, 9.0)
Breast 4.0 (0.5, 14.4)
Cancer
digestive 1.14
respiratory 1.14
lymphomhemo 1.19
Highest exposed
Circulatory dis. 1.17
Cancers: resp. 2.20
lymphohemo 1 .64
AML= I.76*Sig.
Other lymphatic and mult, myeloma t.62*Sig.
No difference by license level
All cancers 1.09 (0.08, 1.45)
lymphomas 2.12 (0.59, 5.42)
leukemias 0.64 (0.08, 2.30)
Hodgkins 10.34 (2.13, 30.23)
Brain 1.07 (0.22,3.13)
Gall bladder/bileducts 14.29 (1.69, 50.29)
Use of physician controls decreased Hodgkins
(4.0) but gall bladder high (11.3) and found risk
for melanoma (3.8 NS)
Increased incidence
hemotolympho ea. 50.8/7.4 RR=6.8
significantly increased risk of protozoal infections, which probably occurred by chance. The investigators
commented that the employees of the Moscow Embassy more frequently reported the occurrence of ill-
defined symptoms such as headache and fatigue but they discounted these  findings.

       The  study  demonstrated no  significant excess risks associated with work at the Embassy.
However, the risks of death from leukemia and breast cancer deserve comment because of observations
in other studies.  There was  a 2.5-fold excess risk of leukemia and a 4.0-fold risk of breast cancer which
were non-significant and based on small numbers.  The finding on breast cancer was noted only because
there has been some suspicion that, at least in very low frequency EM fields, there  may be an effect on
melatonin  production and cycling.   This population  was followed shortly after initial exposure, and
therefore, the latency for development of cancer was limited.

       In two studies, Robinette (1977, 1980)  determined the deaths of veterans who worked in areas
where microwave or radar or RF exposures would have occurred. Robinette combined them into one
group and initially analyzed the total population and found several non-significant excesses of 1.1 or so.

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82   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

In a subsequent nested case-control study, the investigators looked at specific exposures related to the jobs
of subjects.  The highest exposures were in the gun control and electronics areas.  For this group, there
were no significant differences in the risks of any disease although the odds ratio for respiratory cancers
(OR=2.2) and for lymphomas (OR=1,6), were above 1. Both of these studies do not provide evidence of
any risks from RF exposures but the follow-up of the exposed individuals is short.

       Milham (1988) followed a cohort of 67,829 amateur radio operators from 1979-1984. Exposure
level was estimated by the type of license issued.  This study reported significant increased risks of acute
myelogenous leukemia (SMR=1.76) and lymphomas and multiple myeloma (SMR=1,62).  There were no
changes in risk according to the type of license.

       Hill (1988) has reported in a thesis on a follow-up of 1,492 men who helped develop radar.  The
exposures were estimated to be higher than those in the other studies and were related to jobs.  Despite
the small size of the population, the investigator reported non-significant excesses of lymphomas and
melanoma and significant and high risks of 10.3 and 14.3 for Hodgkins disease and gall bladder and bile
duct cancers, respectively.

       Samigielski (1988) reported on Polish military who had exposure to microwaves  and RF. Very
few details of the study population were provided, but the authors report an increased relative risk of 6.8
for hematolyrnphopoietic cancers.

       In summary, the data on the  possible  risks associated  with RF  exposures differ somewhat
depending on the type of study design and the focus of the study.  Those studies which have examined
cohorts who might have had exposure to any non-ionizing radiation have found  few cancer risks except
possibly  leukemia, when all studies are combined, and melanoma.  In some of these studies, the risks
appear to be in telecommunication workers but no exposures  are documented.  The case-control studies
emphasize brain cancer and RF exposures.  The best of these studies suggests that there may be an excess
risk of brain cancer  in  electronics workers who have RF exposures.  The cohort studies of workers
exposed to  microwaves, radar, or radiowaves were generally  negative and had short follow-up. Those
studies which did report risks usually found cancers of the lymphohematopoietic system.  In general, the
evidence of a carcinogenic effect from RF is weak.

       An examination  of the literature to determine whether there is  any evidence of non-cancer effects
from RF reveals even less information and much of it is old (Table 4).  Studies of reproductive effects
report very few significant findings, and results differ from study to study. Decreased sperm counts have
been reported  in exposed males (Lancranjan, 1975; Buiatti, 1984). Brain tumors have been reported in
the offspring of exposed males (Spitz 1985; Johnson 1989).  Fetal malformations or death have also been
reported (Sigler 1965; Cohen 1977; Kallen 1982).  Several studies on the effect of exposures of the lens
of workers in military installations show no changes.  A single proportional mortality ratio (PMR) study
suggested that suicide was higher in radio operators (Baris  1990).  A study of neurologic effects on
exposed  workers showed no changes in either psychometric or neurologic tests in exposed  workers
although  there was an abnormal increase in a single protein band in the  cerebrospinal fluid. The latter
finding could not be  tied to any physical changes.  Because of the small number of studies examining
other possible effects from exposure to RF non-ionizing radiation, it is difficult to draw any conclusions.

       In conclusion, studies of the effects of RF and microwave radiation are not adequate to determine
whether there are any effects on humans from these exposures.

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                             EPIDEMIOLOGIC STUDIES OF NON-IONIZING RF EXPOSURES (MATANOSKI)   83
Table 4.  Other Effects
Author
SubJeetsflSxposure
Risks
Reproductive Effects
Sigler 1965 and
Cohen 1977
Kallen 1982
Lancranjan 1975
Buiatti 1984
Spitz 1985
Johnson 1989
Paternal exposure as radar operator
2,018 Swedish physio therapists
31 exposed males
30 non-expos.
Case/control
History of radio elec-work
Occup. birth cert,
(157 neuroblastoma)
Electronics
Occup, birth cert.
(449 CBNS cases)
Electronics manufacture
Radio operators
Downs Syndrome +_
No difference with national comparison
Internal comparison:
Iner. in dead and malform. infants with
 short wave exposure
Examination spermatic fluids and hormones
No hormone change
Stat. sig. decrease in sperm
Azoospermia/oligo spermia
OR = 5.89 (0.86, 40.8)
NS
CNS cancers in offspring and fathers occupation
11.75 (1.40,98.5)
CNS cancers in offspring and fathers occupation
3.56 (1.04, 12.2)
2.01 NS
Ocular Effects
N/A
N/A
One study cataracts: medical
records
military populations or
installations
Five studies
military populations or
installations
Ophthalmology exam: slit lamp.
Neg.
1 changes in lens
4 no changes in lens
Neurological Effects
Baris 1990
Nilsson 1989
Mech, radar/radio
TV/radio operators
17 expos.
12 non-expos.
Suicide mortality: PMR
153 ( 92, 239)
256 (123, 471)
No psychometric or neurologic changes in tests.
Increase in protein band, CSF

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84  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

REFERENCES

Baris  1990.

Brownson 1989.

Buiatti 1984.

Cohen, B.H., A.M. Lilienfeld, S. Kramer, and L.C. Hyman. 1977. Parental factors in Down's Syndrome:
Results of the Second Baltimore Case-Control Study. In: Population cytogeneties-Studies in Humans,
E.B. Hook and I.H. Porter, eds.  Academic Press, New York, New York.  pp. 301-352.

DeGuire, L. G.  Theriault, H. Iturra, S. Provencher, D. Cyr, B.W. Case.  1986,   Increased Incidence of
Malignant Melanoma of the Skin in Workers in a Telecommunications Industry.  Br. J. Ind. Med 42:824-
8.

DeGuire  1988.

Garland, F.C., et al.  1990. Incidence of Leukemia in Occupations with Potential Electromagnetic Field
Exposure in United States Navy Personnel. Amer. L of Epidem. 134(4):340-347.

Hill, D.  1988.  A Longitudinal Study of a Cohort With Past Exposure to Radar:  The MIT Radiation
Laboratory Follow-up Study.   [Dissertation].  Ann Arbor, MI:  University of Michigan Dissertation
Service.

Hutchinson, G., et al.  1991.  EMF-Related Cancers; a  Meta-Analysis of Epidemiologic Studies.  In:
Electric Power Research Institute (EPRI) Proceedings: Future Epidemiologic Studies of Health Effects
of Electric and Magnetic Fields (TR-101175).

Johnson,  S.C.,  M.R. Spitz.   1989.   Childhood  Nervous System Tumors:  An Assessment of Risk
Associated With Paternal Occupations Involving Use, Repair or Manufacture of Electrical and Electronic
Equipment. Int. J. Epiderniol  18:756-762.

Kallen, B., G. Malmquist, and U. Moritz.  1982.  Delivery Outcome Among Physiotherapists in Sweden:
Is Non-Ionizing Radiation a Fetal Hazard? Arch. Environ. Health. 37:81-85.

Lancranjan, L, M. Majcanescu, E. Rafaila, L Klepsch, and H.I. Popescu.  1975. Gonadic Function in
Workmen With Long-Term Exposure to Microwaves. Health Phys.  29:381-383.

Lilienfeld A.M., et al. 1978.  Foreign Service Health Status Study:  Evaluation of Health  Status of
Foreign Service and Other Employees From Selected Eastern European Posts. Final Report, Contract No.
6025-619073.  Washington, DC, U.S. Department  of State,

Lin 1989.

Lin, R.S., et al.  1985. Occupational Exposure to Electromagnetic Fields and the Occurrence of Brain
Tumors.  J. Occup. Med. 27:413-19.

Loomis, D. and D. Savitz. 1990. Mortality From Brain Cancer and Leukemia Among Electrical Workers.
Brit. J. of Ind. Med.  47:663-638.

Loomis, D.P. and D.A. Savitz.  1989.  Brain Cancer and Leukemia Mortality Among Electrical Workers.
Am. J. Epidemiol.  130:814 (abstract).

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                              EP1DEM1OLOGIO STUDIES OF NON-IONIZING RF EXPOSURES (MATANOSKI)   85

McLaughlin, J.K., et al.  1987. Occupational Risks for Intracranial Gliomas in Sweden, J. Natl. Cancer
Inst. 78:253-257.

Milham, S.  1985.  Mortality in Workers Exposed to Electromagnetic Fields.  Environ. Health Persp.
62:297-300.

Milham, S. 1988. Mortality by License Class in Amateur Radio Operators. Am. J. Epidem. 128(5): 1175-
1176.

Nilsson 1989.

Robinette  C.D., et al.  1980.  Effects Upon Health of Occupational Exposure to Microwave Radiation
(RADAR). Amer. J. of Epidem.  112:39-53.

Robinette, C.D., C, Silverman.  1977.  Causes of Death Following Occupational Exposure to Microwave
Radiation   (Radar)  1950-74.   In:   Symposium  on  Biological  Effects  and  Measurements,  of
Radiofrequency/Microwaves, Hazzard, D.G., ed. Food and Drug Administration, Rockville, MD.  HEW
Publication (FDA) 77-8026, pp. 338-344.

Szmigielski, S., et al.   1988.  Immunological  and  Cancer-Related Aspects of Exposure to Low-Level
Microwave and Radiofrequency Fields.  In:  Marino, A., ed. Modern Electricity. Marcel-Dekker, Inc.

Savitz  1989.

Sigler, A.T., A.M. Lilienfeld, B.H. Cohen, and I.E. Westlake.  1965.  Radiation Exposure in Parent of
Children with Mongolism (Down's Syndrome). Bull. J. Hopkins Hosp.  177:374-399.

Spitz, M.R., C.C. Johnson. 1985. Neural Blastema and  Paternal Occupation. A Case-Control Analysis.
Am. J. EpidemioL  121:924-9.

Thomas, T.L., et al.  1987. Brain Tumor Mortality Risk Among Men with Electrical and Electronic Jobs:
A Case-Control Study.  JNCI 79:233-238.

Tornqvist, S., et al.  1991.  Incidence of Leukemia and Brain Tumors in Some Electrical Occupations.
Brit. J. Ind. Med 48:597-603.

Vagero, D. A. Ahlbom, R, Olin, and S. Sahlsten.   1985.  Cancer Morbidity Among Workers in the
Telecommunications Industry. Brit. J. Ind. Med. 42:191-5

Vagero, D. and R. Olin. 1983. Incidence of Cancer in the Electronics Industry: Using the New Swedish
Cancer Environment Registry as a Screening Instrument. Brit. J. Ind. Med. 40:188-92.

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                                  RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)  87
               RESPONSES OF LABORATORY MAMMALS TO
            RADIOFREQUENCY RADIATION (500  kHz-100 GHz)*
                                       Joe A. Elder**
INTRODUCTION

       This report is a review of selected papers describing responses of laboratory mammals exposed
to radiofrequency (RF) radiation that, in keeping with the goals of this conference,  1) focuses on the
frequency range from 500 kHz-100 GHz; 2) discusses important studies published since the completion
of the EPA review entitled "Biological Effects of Radiofrequency Radiation" (Elder and Cahill 1984) as
well as pre-1984 reports that support conclusions and generalizations regarding biological effects of RF
radiation in the following subject areaslethality, thermoregulatory responses, development, immunology,
nervous system, ocular effects, life span, and cancer; 3) addresses some issues remaining unresolved since
publication of the EPA review;  and 4) comments on the experimental animal data used to establish the
adverse effect level from which voluntary public and occupational exposure guidelines for RF radiation
were developed by the National Council on Radiation Protection and Measurements (NCRP 1986) and the
Institute of Electrical and Electronics Engineers (IEEE 1992); the latter guidelines were adopted by the
American National Standards Institute (ANSI 1992).

LETHALITY

       A few studies describe exposure conditions that cause lethality in laboratory mammals and provide
information  that  helps explain  the  cause of death  from  exposure  to high-intensity RF  radiation.
Michaelson et al. (1961) conducted an experiment with a dog that showed how rectal temperature changed
during an 85-min exposure at 2790 MHz (pulsed) at a dose rate (specific absorption rate, SAR) of 6.1
W/kg.  Three phases of the animal's response were described.  During the first phase  (0-25 min), called
the initial heating phase, the temperature increased about 2C, The animal exhibited panting and an
increased respiratory rate.  During the second phase (25-65 min) called the thermal equilibrium period,
the temperature remained at the elevated level.  After 65 min of exposure,  the temperature began to
increase, rapidly and within the next 20 min the temperature  exceeded 42C (107.6F).  Phase 3 (65-85
min) was characterized as breakdown in thermal equilibrium and  collapse.  In the authors* words, the
temperature "continues increasing rapidly until a critical temperature of 107F, or greater, is reached.  If
exposure is not stopped, death will occur" (Michaelson et al. 1961, p. 352). Other results showed that an
SAR equal to about 60% of the lethal level could be tolerated for several hours, i.e., 3.7 W/kg for up to
6 h did not cause a critical rectal temperature in dogs.  The work of Michaelson et al. (1961) and other
investigators not cited here shows that lethality in laboratory mammals exposed to  high-intensity RF
radiation is caused by heat stress resulting from absorbed RF energy.

       Berman et al. (1985) determined exposure conditions causing lethality in rats and displayed the
data in plots of probability of lethality with time of exposure  and different ambient  temperature.  The
threshold SAR for lethality for a 4-h exposure (2450 MHz) at an ambient temperature of 30C  was about
4 W/kg.  If the animals were exposed for the same duration (4 h) but at a lower ambient temperature
   * This paper has been reviewed in accordance with U.S. Environmental Protection Agency policy and has been
approved for publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use. This paper was updated in February 1995.

   ** Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC
27711.

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88   SUMMARY AND RESULTS OF THE RAD1OFREQUENCY RADIATION CONFERENCE; VOLUME 2

(20C), the lethality threshold increased to about 7 W/kg. These data provide support for the following
general conclusion:   effective SARs for thermal effects in  laboratory mammals are reduced when RF
exposure occurs at higher ambient temperature (Elder 1984a).  A similar point is made in F.G. Shellock's
paper in these proceedings that described responses of human beings exposed to RF radiation in magnetic
resonance imaging (MRJ) devices. At 6 W/kg, the increase in body temperature measured at the tympanic
membrane was greater in a warm (33,8C) than in a cool environment (22C) (Shellock  1995).

       The Rhesus monkey is  more similar in its anatomical  structure and also  its  thermoregulatory
ability to the human  being than many laboratory mammals  such as the dog, rat, and mouse. For these
reasons, thermoregulatory experiments have been done with Rhesus monkeys exposed to RF radiation.
The results show that the rectal temperature  of a Rhesus monkey exposed at 5 W/kg (225 MHz) rose to
41.5C in about 90 min (Lotz 1985).  Exposure was terminated when the temperature reached 41.5C
because the experimenters knew that possible irreversible damage (i.e., death) may occur if the exposure
continued and the rectal temperature increased above 41.5C (106.7F). Exposure to a higher SAR greatly
reduced the time to reach the critical temperature. At 10 W/kg, for example, the rectal temperature of the
monkey reached 41.5C in just a few minutes.  In human beings, a core temperature of this magnitude
is at the limit of tolerance at which a healthy person is likely to develop heat stroke (Athey 1992; Hardy
and Bard 1974).

       The papers cited here help define the dose rates and other exposure conditions that  cause death
and significant thermal stress in a variety of laboratory animals. With regard to frequency, the worst case
scenario would be exposure of the animal to  its resonant frequency, the frequency at which RF energy is
maximally coupled into  the animal and maximal heating  occurs (D'Andrea et al. 1977). Resonant
conditions occur  when  the wavelength of  the  incident RF  radiation is comparable to the  physical
dimension of the body (Weil and Rabinowitz 1984).  The resonant frequency for the adult rat is about 600
MHz.  Behavioral and thermal effects in rats exposed below,  at, and above resonance  were reported by
D'Andrea et al. (1977).  The study by Lotz (1985) was designed to investigate responses in Rhesus
monkeys exposed to a frequency (225 MHz) near their resonant frequency. In summary, the experimental
results indicate that exposure to RF radiation at SARs  ranging from 5-7 W/kg  for  1.5-4.0 h at normal
laboratory temperatures of 20-24C, will cause lethality and severe thermal stress in the Rhesus monkey,
rat, and dog (Elder et al.  1989).

THERMOREGULATORY RESPONSES

       RF intensities at lethal  and sublethal levels can activate  thermoregulatory effectors  such as
evaporation, vasodilation and behavior.  Some of these effectors  were activated in the  dog in the
Michaelson et al. (1961) experiment, e.g., the animal panted to increase evaporative water loss to cool its
body. In  heat-stressed animals including those exposed to RF radiation, cutaneous vasodilation raises skin
temperature  leading to increased heat dissipation.  Animals  may also take some  form  of behavioral
adjustment to avoid hot environments if at  liberty to do so.  Animals in relatively cool environments
exposed to RF radiation lower their metabolic heat production and thereby lower the  overall heat load
from RF  energy absorption (Adair and Adams 1982, Gordon and Long 1987).

       Sufficient information is available to draw a general conclusion regarding the SARs that affect
metabolism and thermoregulatory effectors such as evaporation, vasodilation and behavior. The conclusion
is based on a comparative analysis of the SARs that activate  these four  physiological responses in the
mouse and squirrel monkey (Elder et al. 1989),  For the smaller animal, the effective SAR to activate
these responses varied from 5.3  to 29 W/kg (Ho  and Edwards 1977; Gordon  1982,  1983, 1984); the
effective SAR for the larger animal, the squirrel monkey, varied from 0.6 to 1.5 W/kg (Adair  1981; Adair
and Adams I980ab, 1982). These data illustrate the general principle that the larger the  animal, the lower
the dose rate (SAR) to activate physiological responses (Gordon 1982, Elder et al. 1989).

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                                   RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)   89

       In related work, Gordon determined the SAR that caused a rectal temperature increase of 1 C in
four different species (mouse, hamster, rat and rabbit) (Gordon et al.  1986, Gordon 1992).  The results
showed that the SAR to cause a 1C rise in body temperature decreased with the mass of the animal, i.e.,
the mouse, the smallest animal, required the highest SAR to elevate its body temperature by  1C,  This
observation is explained by the more efficient heat loss by small animals due in part to their large surface-
area-to-body-mass ratio (Gordon and Ferguson 1984).  It has been suggested that dose rate  expressed in
terms of body surface area (i.e., W/m2) rather than body mass (i.e., W/kg)  would allow more reliable
prediction  of thermal  effects  across species  (Gordon  1987,  1992).   These observations  should  be
considered carefully when interpretating and comparing RF radiation effects in the laboratory species used
in Gordon's study.

       An important issue is how well Gordon's data predicts temperature responses in other species
including non-human primates and human beings exposed to RF radiation.  Extrapolation to animals
similar in mass (4.2-6.5 kg) to the Rhesus monkeys used in studies by Krupp (1983)  and Lotz (1985)
indicates that an SAR of less than 1 W/kg would increase body temperature  by 1C in  1 h.  The
experimental results show that a higher SAR is required.  In monkeys exposed near resonance, Krupp
(1983, see  Fig.  3) found that about 3.5 W/kg and Lotz (1985, see Fig. 2) showed that about 2.5 W/kg
would cause a 1C rise  in rectal temperature in 1 h.  The relationship described by Gordon between body
mass and SAR  causing a 1DC  rise in body temperature in 1 h may apply best to small, heavily-furred
laboratory animals on which the supporting data were derived.

       Extrapolation of Gordon's data to a larger mass, 70 kg, the mass of the typical adult male human
being, indicates that a relatively low SAR of 0.1 W/kg would raise human body  temperature by 1C in
1 h. The accuracy of this prediction cannot be determined  because of the lack of human data showing
a relationship between  RF exposure conditions and body temperature comparable to the animal data
collected by Gordon et al.  (1986).  The animals were exposed whole-body to a frequency at or near
resonance that would cause deep-body heating whereas reports of human thermal responses to RF radiation
have usually involved localized exposure  of body areas. MRI studies, for example, provide SAR and
human body temperature data but these results are not comparable to the data in Gordon  et al, (1986)
because  1) MRI exposure is generally partial-body exposure and 2) the exposure results in maximal
heating at  the surface  of the exposed body area and minimal heating at the center of the body area
(Shellock 1994).  These two reasons help to explain why MRI data are in poor agreement with Gordon's
prediction,  i.e.,  MRI exposure for 20-30 min at SARs  much greater than 0.1 W/kg do  not elevate body
temperature by  1C. The results presented in Shellock's paper in these proceedings show that a relatively
high SAR (6 W/kg) caused a 0.4C increase in human body temperature.

       The thermoregulatory ability of laboratory mammals is known to be limited in comparison to that
of human beings (Adair 1983, Gordon 1993). This limitation contributes to the difficulty in extrapolation
of thermal  regulatory effects in furred laboratory animals, such as mice, rats, and dogs, to the human
being. Regardless of the comparative abilities for thermal regulation of laboratory animals versus human
beings, the absolute value of temperature increase appears to cause similar responses in these mammals
at the molecular and cellular level.  As temperature increases, enzymatic rates increase and metabolic
pathway  dynamics are altered.  High temperature may cause denaturation of enzymes and other proteins
resulting in irreversible molecular and cellular damage that  may affect the animal adversely.

       If the body core temperature  approaches 42C, an increase of about 5C above the normal
temperature of human beings and many laboratory mammals, severe thermoregulatory distress develops
and  death may  occur if the thermal insult continues over many minutes at normal or elevated ambient
temperatures.   The reader is  probably  well aware of the concern for possible irreversible  health
consequences resulting  from prolonged elevated body temperature in children and adults during episodes
of fever.  Concern for work environments that may cause a significant increase in body temperature is
documented in the recommendation from the American Congress of Governmental Industrial  Hygienists
(ACGIH) that workers cease activity in environments that cause a 1 C rise in body temperature (ACGIH

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90   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

1990).  Recognition of the potential adverse effects of increased body temperature resulting from any
exposure condition or agent, including RF radiation, influenced the exposure limit recommended by the
panel advising the Food and Drug Administration (FDA) on MRI devices.  The panel recommendation
states that  "the patient  is exposed to radiofrequency magnetic fields insufficient to  produce a core
temperature increase in excess of 1C" (FDA 1988, p. 7577).

        Thermoregulatory  behavior was one of the effectors mentioned above that may be used by an
animal to adjust to hot and  cold environments.  There are other  types of behavior such as learned
behavior, i.e., the performance of a learned task, that have been shown to be affected by conditions that
elevate body temperature.   The literature describing the effect of RF radiation on learned behavior in
laboratory animals is very important because 1) the results show that dose rate (W/kg), not incident power
density (mW/cm ), is the better predictor of biological effects and 2) the results have been used to define
the hazardous effect level that is the basis for the voluntary RF safety guidelines published by the NCRP
(1986),  IEEE (1992), and ANSI (1992).  No public exposure guidelines for RF radiation have been
promulgated by the Federal government.

       A brief description of the experimental protocol will aid an understanding of the significance of
any disruption in an  animal's performance of a learned task.  In a typical protocol, animals are fed a
restrictive diet to maintain  the animal's weight below normal because a hungry animal can be trained to
perform for a food reward. An animal, for example, can be trained to press a bar or button a specific
number of times in a specific period of time. When the task is done correctly, the animal earns a food
reward. When trained animals are exposed to noxious agents such as toxic chemicals or high-intensity
RF radiation, the performance of the learned response may be detrimentally affected,  i.e., the hungry
animal reduces or ceases its effort to work for food. Disruption in an animal's performance of a learned
task is used as a sensitive indicator of exposure to noxious chemicals and stressful environmental agents.
Work disruption is a descriptive term for this effect on learned behavior.

       A number of reports describe the effect of RF radiation on work disruption in several laboratory
animal species (rats, squirrel monkeys, and Rhesus monkeys) exposed to different frequencies and various
intensities (de Lorge  1976, 1979, 1983,  1984).  Review of the data shows that the range of threshold
values expressed in incident power density of RF radiation varied over a much greater range than threshold
values expressed in dose rate (SAR). The threshold power densities that caused work disruption in the
Rhesus monkey, for example, varied  with frequency from 8 to 140 mW/cm", a factor greater  than 17.
Threshold SARs, on the other hand, ranged from 3,2 to 8.4 W/kg, a factor less than three (NCRP 1986,
Table 12.1). These data support the conclusion that SAR is a better predictor of biological response than
power density. For this reason, the effective SAR is given for each of the biological responses discussed
in this report.

       As mentioned above, the data on learned behavior were used to derive the hazardous effect level
in exposure guidelines developed by NCRP (1986), IEEE (1992) and ANSI (1992).  The relatively narrow
range of dose-rate threshold values (3.2-8.4 W/kg) for work disruption despite a considerable difference
in radiofrequency  (400 to 5800 MHz), species (rodents  and monkeys), and  exposure parameters
(continuous  wave and pulsed-modulation exposures, near- and far-field exposures, etc.) led to the choice
of 4 W/kg for the hazardous effect level (IEEE 1992).

       There has been considerable debate on whether or not the voluntary RF exposure limits developed
in the United States are "thermal guidelines."  In my judgement, the crux of the debate rests  with the
question: is the hazardous  effect level based on thermal effects  of RF radiation? The answer is yes.  The
dose-rate threshold for work disruption, the basis for the guidelines, is associated with an increase in body
temperature. Since the hazardous effect level defined in the NCRP, IEEE, and ANSI guidelines is an SAR
associated with an effect resulting from a known mechanism of interaction (RF heating), the guidelines
are protective of effects arising from a thermal mechanism, but not from all possible mechanisms (EPA
1993).

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                                   RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)   91

       The association between dose-rate threshold and body  temperature increase is acknowledged
explicitly in the guidelines recently published by IEEE and ANSI by the statement reading "...potentially
harmful biological effects were based on the disruption of ongoing behavior associated with an increase
of body temperature in the presence of electromagnetic fields" (IEEE 1992, p. 27). Review of the data
for the Rhesus monkey, for example, showed that the body temperature increase varied from 0.8 to 1.4C
at the SAR threshold for work disruption at four different frequencies (Elder 1994). Recently published
British NRPB  (National Radiological  Protection Board)  exposure guidelines  for  RF radiation  are
principally based on acute thermal effects.  These guidelines state that "Heating is a major consequence
of exposure to RF (including microwave) radiation.  Restrictions on exposure are intended to prevent
adverse responses to increased heat load and elevated body temperature" (NRPB 1993, p. 2). The interim
nature of RF guidelines is evident because human safety limits are based principally on effects of acute
exposure of laboratory animals that cause a significant increase in body temperature.  Acute exposure data
have  been  used  because  few studies have  employed  long-term,  low-level  exposures typical  of
environmental exposure to RF radiation.

DEVELOPMENTAL EFFECTS

       Effective dose rates for developmental effects in laboratory animals have progressively decreased
during the past decade.  The  1984 EPA review states that developmental effects in laboratory animals
occur at SARs greater than 15 W/kg  and that these effects are definitely associated with thermal stress as
indicated by increases  in body temperature.  The update (Elder 1987) of the conclusions in the 1984
review states that effective dose rates for developmental effects range from 9-11 W/kg based on results
by Berman et al. (1982) and Lary et al. (1982,1986). These values were derived from  acute exposure
studies. As discussed below,  a lower threshold for developmental effects was observed  in rats exposed
chronically to RF radiation.

       Why, one might ask, should there be concern for developmental effects at 9-11 W/kg when earlier
text reported death in the same species (rat) at a lower dose rate (7 W/kg)?  The 7 W/kg threshold for rat
lethality was based on a 240 min  exposure;  the developmental  studies, on the  other hand, usually
employed a shorter exposure of 100 min.  In addition to duration of exposure, effects in laboratory animals
are known to be related to dose rate, radiofrequency, body mass,  ambient temperature, and other factors.

       In one of the few chronic exposure studies of developmental effects, Berman et al.  (1992) exposed
pregnant rats for 22 h/day for 19 days of the rat's gestational period of 20-21 days; ambient temperature
was 22C. Developmental effects were observed at 4.8 W/kg, a value about half of the threshold observed
in acute exposure studies summarized  above;  the lower effective dose rate  was attributed to chronic
exposure.  Lower SARs (0.07 and  2.4 W/kg) did not cause developmental effects in chronically exposed
rats.  In the published paper, Berman et  al. attributed the effect at 4.8 W/kg to thermal stress that caused
the death of two of 12 animals in the highest exposure group. In summary, the developmental studies
show that RF radiation is a teratogen, but effective dose rates  during acute and chronic exposure approach
lethal levels for pregnant animals due to thermal stress.

       The above conclusion is based on a synthesis of results from a significant number of reports that
together demonstrate  that developmental effects are associated with  a significant  body temperature
increase. This set of literature does not  include a paper reporting developmental effects in rats at 0.0001
W/kg, an SAR thousands of times less than the effective SARs cited above.  This very low SAR  would
not cause a significant body temperature increase in the rat and is characterized as a nonthermal exposure.
Further work is needed to confirm  or  refute the finding of developmental effects in  rats exposed to
nonthermal levels of RF radiation  as reported by Tofani et al. (1986).

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92   SUMMARY AND RESULTS OF THE RADiOFREQUENCY RADIATION CONFERENCE: VOLUME 2

IMMUNOLOGY

       The Chou et al. (1992)  study, commonly known as the University of Washington study, was a
chronic exposure study in which rats were exposed to 0.15-0.40 W/kg for 21.5 h/day for up to 25 months.
These relatively low dose rates and an ambient temperature of 21C would have combined to minimize
any  significant effect on body temperature which was not measured.  Based on other measures of
thermoregulation (oxygen consumption, carbon dioxide production, food consumption, etc.), the authors
concluded that the rate of RF energy deposition  was not sufficient to produce robust changes  in the
metabolism of mature rats. The study evaluated 155 biological parameters including immune responses.

       After 13 months of exposure, a significant effect on the immune system was found but the effect
was  not observed after 25 months of exposure.   In a follow-up study done by these researchers, the
stimulatory effect observed in the original study was not confirmed (Chou et al. 1992). The absence of
a reproducible immune response in the two University of Washington  studies is consistent with the
following  conclusions  in a review of in vivo  immune effects:  1) many if not all of the RF-induced
alterations in the immune system can be attributed to a nonspecific thermal stress response, and 2) studies
investigating the reversibility of immune responses have shown the effects to be transient (Smialowicz
1987).   Future research should address the physiological significance, if any,  of transient  immune
responses  in laboratory animals exposed to RF radiation.

NERVOUS SYSTEM

       The nervous system is considered to be one of the more sensitive systems to RF radiation.  Recent
studies on the effects of low dose rates on the efficacy of nervous system drugs and on the blood-brain
barrier have been selected to describe the sensitivity of the nervous system to RF radiation.

       Work in Lai's laboratory showed that the efficacy of some nervous system drags was affected by
dose rates as low as 0.1 to 0.6 W/kg; some effects of drags were enhanced while other effects were
attenuated (Lai  1992).  Based on the similarity of the effects of RF radiation and those of established
sources of stress, Lai (1992) speculated that RF radiation is a stressor.  Reports showing that RF radiation
affects neural mechanisms known to be involved in stress responses provide additional support for this
hypothesis (see Lai 1992).  Another important conclusion was the lack of convincing  evidence  that
repeated, acute RF radiation  exposure (45 min at 0.1-0.6 W/kg) caused irreversible neurological effects
(Lai  1992).

       There were reports in the 1970's describing effects of RF radiation on the blood-brain barrier, the
unique physiological system in the brain that prevents entry of unwanted molecules.  These studies were
especially  interesting because the results indicated an important effect on the central  nervous system at
nonthermalizing levels of RF radiation.  A number of studies in the 1980's, however, failed to confirm
and extend the earlier results on the blood-brain barrier.  While there is the criticism that no effects were
observed at low exposure levels because the studies were not true replicates of the earlier experiments,
these and other studies did validate that thermal insults caused at high SARs will disrupt the integrity of
the blood-brain barrier (Ward et al. 1982, Lin and Lin 1982, Williams et al. 1984, Ward and Ali 1985).

       A  recent paper by Salford et al. (1993) has refocused attention on the blood-brain barrier as a
system that should be investigated further. These investigators reported effects on the blood-brain barrier
in mice exposed at 900 MHz at a low SAR (0.33 W/kg).  An independent validation of this  result is
needed and, if successful, effective exposure conditions  and threshold SAR need to be determined.

OCULAR EFFECTS

       It  is well documented that acute exposure to the rabbit eye can  cause cataracts, but the effective
SAR that  causes cataracts is very high (150 W/kg).  The animal survived the cataractogenic exposure

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                                    RESPONSES OF LABORATORY MAMMALS TO RF RADIATION {ELDER)  93

because the exposure to the eye that developed a cataract was so localized that the other eye served as the
control.  A substantial temperature increase in the lens  of the eye is associated with cataract formation,
thus demonstrating that cataracts are caused by a thermal  mechanism, i.e., the proteins in the lens are
denatured by heat resulting from the absorbed RF energy (Elder 1984b).

       In recent studies with monkeys concerning ocular effects other than cataracts, effects on cells in
the cornea and effects on permeability in the iris were observed at 2.6 W/kg. Pretreatment of the eye with
an ocular drug (timolol) reduced the effective dose rate by a factor of 10 to  0.26 W/kg (Kues et al. 1992).
In a preliminary report, D'Andrea et  al.  (1993)  reported no effect on visual performance in monkeys
exposed to RF radiation conditions similar to those reported by Kues et al. to cause ocular effects. At this
time, the level of concern for the low SAR-induced ocular effects reported by Kues et al. (1985, 1992)
is attenuated by lack of independent replication of these results.

LIFE-SPAN AND CANCER

       There is convincing data in the chemical toxicity literature that show a positive correlation between
decreased life-span and increased cancer development, especially for leukemia and mammary tumors. The
data were reported by Haseman and Rao (1992) who compiled and analyzed data from 88 two-year cancer
bioassay studies sponsored by the National Toxicology Program.  Both human leukemia, animal mammary
tumors, and other cancers are mentioned in the RF literature (Milham 1988, Szmigielski et al. 1982). The
latter paper reported that survival time of mice exposed to  RF radiation was significantly shorter due to
the earlier appearance of mammary tumors  and benzopyrene-induced skin cancer.  The discussion here
addresses the strength of the association between decreased life-span and increased cancer development
in RF-exposed animals (Elder  1994).

       Seven animal studies reporting data on life-span utilized a variety of experimental conditions
including different species, frequencies, modulation, and  dose rate (Prausnitz and Susskind 1962, Spalding
et al. 1971, Preskorn et al. 1978, Szmigielski et al. 1982, Santini et al. 1988, Chou et al. 1992, Liddle et
al. 1994). Six of the seven studies used mice; rats were used in the University of Washington study (Chou
et al. 1992).  It is interesting that two of  these studies reported a significant increase in life-span in the
RF-exposed animals (Prausnitz and Susskind 1962; Preskorn et al. 1978) and two papers (Spalding et al.
1971; Chou et al.  1992) reported  that the average life-span was  increased but the increase was not
statistically significant.  The results of these four studies support a finding of no adverse effect on life-span
because the data indicate a trend toward  an increase in life-span of laboratory animals exposed to RF
radiation rather than a decrease in life-span. No effect on survival was observed by Santini et al. (1988)
who exposed mice to  both continuous wave and  pulsed  microwave fields.  Details  of the exposure
conditions of the studies mentioned here are given below in the discussion of the cancer results.

       Two studies reported RF exposure  conditions that decreased life-span.  In a chronic exposure
study, Liddle et al. (1994) showed  no life-span effect in mice exposed 1 h/day, 5 days/wk for life, at 2
W/kg, a dose rate that would cause minimal or no thermal stress in this experiment; however, there was
a decrease in life-span  at 6.8 W/kg that was attributed  to thermal stress.  In earlier work, Liddle  et al.
(1987) reported that exposure of mice at 6.8 W/kg caused a maximal body temperature increase of 0.8C
within  30 min after initiation of exposure.

       Szmigielski et al. (1982) exposed female mice with a high  incidence of spontaneous mammary
cancer to 2450 MHz for 2 h/day from the sixth week of life up to age 12  months.  RF exposure at 2-3
and 6-8 W/kg reduced survival time. These  authors also reported reduced survival time due to the earlier
appearance of cancer in RF-exposed mice  that developed benzopyrene-induced skin cancer.  The animals
were exposed simultaneously to benzopyrene (every second day for 5 months) and RF radiation (2 h/day
for 5 months). The mean survival  time of 50% of the mice was 331 days for controls and 165 days at
6-8 W/kg (see Szmigielski et  al. 1982, Figure 10). No detectable increase in rectal temperature was
reported  in mice exposed at 6-8 W/kg but there is no description of how or when temperature was

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94   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

measured.  The maximal temperature increase due to RF exposure may not have been observed because
Liddle et al. (1987) has presented data demonstrating that timing of the temperature measurement is
critical.  As mentioned above, Liddle et al. (1987) reported that mice exposed to 2450 MHz at 6.8 W/kg
had a maximal body temperature increase of 0.8C.  Based on these data, mice exposed at the SAR range
(6-8 W/kg) in the Szmigielski et al. study did receive a significant thermal load from absorbed RF energy,
In summary, the results  of these seven studies indicate that life-span is  not adversely affected by RF
radiation unless  exposure causes a significant increase in body temperature.

       Five of the RF radiation studies on life-span have cancer data and three of these studies reported
no  increase in cancer incidence.   The  results  of Preskorn  et al. (1978)  showed a delay in tumor
development, but no change in total number of tumors in the RF-exposed groups. Prausnitz and Susskind
(1962) concluded that the incidence of cancer of the white cells was not significant.  In both studies, mice
were exposed to very high SARs [40 W/kg, 4.5 min/day, 5 days/wk, 59 wks in Prausnitz and Susskind5 s
study and 35 W/kg, 20 min/day, 4 days (prenatal) in Preskorn et al.'s study].  Microwaves did not affect
tumor development in mice exposed 2.5 h/day, 6 days/wk to either continuous wave or pulsed fields at
1.2 W/kg (Santini  et  al. 1988).   In  this experiment,  female mice  at age  35 days  were exposed to
microwaves 15 days prior to implantation of melanoma cells until death (up  to 690 h of irradiation).

       Two chronic exposure studies reported statistically significant effects.  Chou et al. (1992) exposed
rats at 0.15-0.40 W/kg for 21.5 h/day for up to 25 months and found a statistically  significant increase in
malignancies when all types of malignancies were summed.  In their interpretation  of the biological
significance of the increase in malignancies, the authors were influenced by their data on life-span.  Rather
than a decrease in life-span, they found an increase although the increase was not statistically significant.
The  authors concluded therefore that the biological significance of the cancer incidence is questionable.
There has been much discussion about the validity of the summing procedure resulting in the statistically
significant increase in cancer.  Most importantly, further work is  needed to confirm or refute the finding
of increased cancer incidence in rats exposed chronically to low dose rates  as reported by Chou et al.
(1992).  The life-span data, the controversial summing procedure, and the  lack of replication support the
conclusion  that  the Chou et  al.  (1992) study does not prove a cause-and-effect relation between RF
radiation and cancer.

       In experiments involving exposure durations of several months, Szmigielski et al. (1982) observed
that  SARs  of 2-3 and 6-8 W/kg  increased  cancer incidence in three different  models: spontaneous
mammary tumors, benzopyrene-induced skin cancer, and lung tumors.  These researchers also found that
mice subjected to chronic confinement stress and mice exposed at 2-3 W/kg had a similar increase in
tumor development; these results were significantly different  from control  values.  Szmigielski et al.
discussed speculations to explain their  findings of increased cancer incidence from chronic confinement
stress and RF radiation.  While  the results are suggestive of an association between RF radiation and
cancer development in mice, the scientific process required to prove a cause-and-effect relationship is not
complete. In the 13 years since publication of the Szmigielski et al. paper, no independent replication of
the experiments  has been reported  in the  literature.  Information  on the replicability of these findings is
an important void in our knowledge of the carcinogenic potential of RF radiation.

       In my opinion, the conclusion that no causal relationship has been established between cancer and
RF radiation seems consistent with the life-span data showing no detrimental effect in the absence of
thermal stress from RF exposure. The author notes that this conclusion is based on a few studies that used
very different exposure  conditions and biological  models to  collect data on life-span and  cancer in
laboratory mammals.  In the  author's opinion, the data on cancer and life-span  effects in laboratory
mammals are not useful in revision of  voluntary RF exposure guidelines developed in the U.S. because
1) there are relatively few reports that describe effects due to long-term, low-level exposure, 2) effects that
have been reported have not been independently replicated,  and 3) dose-rate/response relationships have
not been established.

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                                    RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)   95

SUMMARY

       The literature describing responses of laboratory mammals exposed to RF radiation is sufficiently
developed to draw the following conclusions.

1)     Lethality in laboratory animals exposed to high-intensity RF radiation appears to be due to thermal
       stress, i.e., absorbed RF energy results in an increase in body temperature beyond life-sustaining
       limits.

2)     Dose rates ranging from 5-7 W/kg for 1.5-4.0 h at normal laboratory temperatures of 20-24C will
       cause lethality and severe thermal stress in the Rhesus monkey, rat, and dog.

3)     A variety  of effects occur in mammals exposed at sublethal RF intensities  associated with
       significantly increased  body temperature.  Such exposure can cause birth defects and affect the
       thermoregulatory system, immune system,  blood-brain barrier and  behavior.   Developmental
       effects, for example, result from acute and chronic RF exposures  that approach lethal levels for
       pregnant animals due to thermal stress. Cataracts have been caused in some laboratory animal
       species by sublethal, localized exposure that significantly increased the temperature in the lens of
       the eye.

4)     Although there are major thermoregulatory differences between laboratory animals and human
       beings, the absolute magnitude of body temperature increase appears to correlate well with many
       similar molecular, cellular, and physiological effects in these mammalian species,

5)     Dose rate  (specific absorption rate, SAR, expressed in units of W/kg)  is a better predictor of
       biological response than power density (e.g., mW/em ).

6)     Effective  SARs for thermal  effects are reduced  when RF  exposure  occurs at higher ambient
       temperatures.  Humidity, air flow, and other ambient factors that affect thermoregulation would
       also influence effective SARs for biological responses in mammals.

7)     Effective SARs for thermal effects in small laboratory animals are higher than for larger animals
       because, in part, of more efficient heat loss by small animals due to their larger surface-to-mass
       ratio.

8)     In the absence of thermal stress, no adverse effect on life-span of RF-exposed laboratory animals
       has been substantiated.

9)     No effect on life-span in the absence of thermal stress is consistent with the conclusion that no
       causal relationship  has  been proven between  RF radiation  and cancer incidence in laboratory
       mammals. The author notes that the conclusions on life-span and cancer  are based on a small
       number of studies that used very different exposure conditions and biological models,

       The data on cancer and life-span effects in laboratory mammals, in the author's opinion, are not
useful  in revision of  voluntary RF  exposure guidelines developed in the U.S.  because  1)  there are
relatively few reports that describe effects due to long-term, low-level exposure, 2)  effects that have been
reported have not been independently replicated, and 3) dose-rate/response relationships have not been
established.

       Specific biological effects described in this paper that have been reported to occur in laboratory
mammals exposed to low dose  rates of RF radiation include the following; 1) the statistical significant
cancer incidence in rats exposed at 0.14-0.4 W/kg in the University of Washington study (Chou et al.
1992); 2) effects on the primate eye at 0.26 W/kg (Kues et al. 1985,1992); 3) blood-brain barrier changes

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96   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

at 0.33 W/kg (Salford et al. 1993); 4) drag potentiation effects in the central nervous system at 0.1-0.6
W/kg (Lai  1992); and 5) developmental effects in rats exposed to 0.0001 W/kg (Tofani et al. 1986).
These effects can be characterized as having been reported in a singular paper or in a series of papers from
one research team.  The independent replicability of these observations, therefore, is very important to an
assessment  of the potential health effects of RF radiation. Further research is needed to confirm or refute
potentially  significant biological effects, including cancer, blood-brain barrier and other central nervous
system alterations, developmental effects, and  ocular  effects,  that have been reported in  laboratory
mammals exposed at low levels of RF radiation. Also, comparative studies of thermoregulatory responses
in mammals exposed to RF radiation would aid extrapolation of data across  species, including human
beings.

REFERENCES

ACGIH (1990). 1990-1991 Threshold Limit  Values for Chemical Substances and Physical Agents and
       Biological Exposure Indices. American Conference of Governmental Industrial Hygienists, 6500
       Glenway Avenue, Building D-7, Cincinnati, OH 45211-4438.

Adair, E.R. (1981), Microwaves and Thermoregulation.  In: USAF Radiofrequency Radiation Bioeffects
       Research Program - A Review (J.C. Mitchell, editor), Review 4-81, USAF School of Aerospace
       Medicine, San Antonio, TX, pp. 145-158.

Adair, E.R.  (1983). Microwaves and Thermoregulation (E.R, Adair, editor), Academic Press, New York,
       NY.

Adair, E.R. and B.W. Adams (1980a). Microwaves Induce Peripheral Vasodiiation in Squirrel Monkey.
       Science 207:1381-1383.

Adair, E.R. and B.W. Adams (1980b).  Microwaves Modify Thermoregulatory Behavior  in  Squirrel
       Monkey. Bioelectromagnetics 1:1-20.

Adair, E.R. and B.W. Adams (1982).  Adjustments in Metabolic Heat Production by Squirrel Monkeys
       Exposed to Microwaves.  J. Appl. Physiol, 52:1049-1058.

ANSI (1992). IEEE Standard for  Safety Levels  with Respect to Human Exposure to Radio Frequency
       Electromagnetic Fields, 3  kHz to 300 GHz. ANSI/IEEE C95.1-1992. Revision of ANSI C95.1-
       1982. American National Standards Institute, 11 W. 42nd Street, New York, NY 10036.

Athey, T.W. (1992). Current FDA Guidance for MR Patient Exposure and Considerations for the Future.
       In:  Biological Effects and  Safety  Aspects  of Nuclear Magnetic  Resonance  Imaging and
       Spectroscopy (R.L. Magin, R.P. Liburdy, and B. Persson, editors), Annals of the NY Academy
       of Sciences 649: 242-257.

Herman, E., H.B. Carter and D. House (1982). Observations of Syrian Hamster Fetuses after Exposure
       to 2450-MHz Microwaves. J. Microwave Power 17(2):107-112.

Berman, E., J.B. Kinn, J. Ali, H.B. Carter and B, Rehnberg (1985). Lethality in Mice and Rats Exposed
       to 2450 MHz Circularly Polarized  Microwaves As a Function of Exposure Duration and
       Environmental Factors. J.  Appl. Toxicol. 5, 23-31.

Berman, E., H.B. Carter, C. Weil, P.A. Phillips and D.E. House (1992). Fetal and Maternal Effects of
       Continual Exposure of Rats to 970-MHz Circularly-Polarized Microwaves.  J. Bioelectricity 11:35-
       46.

-------
                                   RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)   97

Chou, C.K., A.W. Guy, L.L. Kunz, R.B. Johnson, JJ, Crowley, and J.H. Krupp (1992). Long-Term, Low-
       Level Microwave Irradiation of Rats, Bioelectromagnetics 13: 469-496.

D'Andrea, J.A., A. Thomas, DJ. Hatcher and T.L. DeVietti (1993). Rhesus Monkey Contrast Sensitivity
       During Extended Exposure to High Peak Power 1.3-GHz Microwave Pulses. Abstract Book, The
       Bioelectromagnetics Society, 15th Annual Meeting, Los Angeles, CA, June 13-17, 1993, p. 61.

D'Andrea, J.A., O.P. Gandhi  and J.L. Lords (1977).  Behavioral and  Thermal Effects of Microwave
       Radiation at Resonant and Nonresonant Wavelengths.  Radio Science 12(6S): 251-256.

de Lorge, J.O, (1976). The Effects of Microwave Radiation on Behavior and Temperature in Rhesus
       Monkeys, In:  Biological Effects of Electromagnetic Waves (C.C. Johnson and M.L. Shore,
       editors), Vol. 1, pp. 158-174, U.S.  Department of Health, Education, and Welfare Publication
       (FDA) 77-8010, Rockville, MD 20857.

de Lorge, J.O; (1979). Operant Behavior and Rectal Temperature of Squirrel Monkeys During 2.45-GHz
       Microwave Irradiation. Radio Science 14(6S), 217-225.

de Lorge, J.O. (1983). The Thermal Basis for Disruption of Operant Behavior by Microwaves in Three
       Animal Species. In: Microwaves and Thermoregulation (E.R. Adair, editor), Academic Press, New
       York, NY, pp. 379-399.

de Lorge, J.O. (1984).  Operant Behavior and Colonic Temperature of Macaca Mulatta Exposed to Radio
       Frequency Fields At and Above Resonant Frequencies.  Bioelectromagnetics 5:233-246.

Elder, J,A. (1984a). Summary  and Conclusions. In: Biological Effects of Radiofrequency Radiation (J.A.
       Elder and D.F. Cahill, editors). U.S. Environmental Protection Agency publication EPA-600/8-83-
       026F, pp. 6-1 - 6-9. Available from National Technical Information Services, Report No. NTIS
       PB-85120848, Springfield, VA.

Elder, J.A. (1984b). Cataractogenic Effects. In: Biological Effects of Radiofrequency Radiation (J.A. Elder
       and D.F. Cahill, editors).  U.S. Environmental Protection Agency publication EPA-600/8-83-026F,
       pp. 5-64 - 5-70. Available from National Technical Information Services, Report No. NTIS PB-
       85120848, Springfield, VA.

Elder, J.A. (1987). A Reassessment of the Biological Effects of Radiofrequency Radiation:  Non-cancer
       Effects. A report to the Office of Radiation Programs, U.S. Environmental Protection Agency, July
       21, 1987. 19 pages.  Unpublished report available from J.A. Elder, U.S. EPA (MD-51), Research
       Triangle Park, NC 27711,

Elder, J.A. (1994). Thermal, Cumulative, and Life Span Effects and Cancer in Mammals  Exposed to
       Radiofrequency Radiation. In: Biological Effects of Electric and Magnetic Fields (D.O. Carpenter
       and S. Ayrapetyan, editors), Academic Press, San Diego, Vol. 2, pp. 279-295.

Elder, J.A. and Cahill D.F. (1984), Biological Effects of Radiofrequency Radiation, U.S. Environmental
       Protection  Agency, Report  No. EPA-600/8-83-026F.   Available  from National Technical
       Information Services, Report No. NTIS PB-85120848, Springfield, VA.

Elder, J.A., P.A. Czerski, M.A. Stuchly, K.H. Mild and A.R. Sheppard (1989). Radiofrequency Radiation.
       In: Nonionizing Radiation Protection,  second edition (MJ. Suess and D.A.  Benwell-Morison,
       editors), WHO Regional Publications, European Series, No. 25, Copenhagen, pp. 117-173.

-------
98  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE:  VOLUME 2

EPA (1993). Letter dated November 9,1993 from Margo T. Oge, Director, Office of Radiation and Indoor
       Air, U.S.  Environmental Protection Agency to  Thomas  P. Stanley,  Federal Communications
       Commission.

FDA (1988). Magnetic Resonance Diagnostic Devices; Panel Recommendations and Report on Petitions
       for MR Reclassification. Federal Register 53(46), March 9. 1988, pp. 7575-7579.

Gordon, CJ. (1982). Effects of Ambient Temperature and Exposure to 2450-MHz Microwave Radiation
       on Evaporative Heat Loss in the Mouse. J. Microwave Power 17:145-150.

Gordon, C.J. (1983). Influence of Heating Rate on Control of Heat Loss from the Tail in Mice.  Am. J.
       Physiol. 244:R778-R784.

Gordon, CJ. (1984). Thermal Physiology. In: Biological Effects of Radiofrequency Radiation (J.A. Elder
       and D.F. Cahill, editors). U.S. Environmental Protection Agency publication EPA-6QQ/8-83-Q26F,
       pp. 4-1 - 4-28. Available from National Technical Information Services, Report No. NTIS PB-
       85120848, Springfield, VA.

Gordon, C.J. (1987). Normalizing the Thermal Effects of Radiofrequency Radiation: Body Mass Versus
       Total Body Surface Area. Bioelectromagneties 8, 111-118.

Gordon, CJ. 1992. Local and Global Thermoregulatory Responses to MRI Fields. In: Biological Effects
       and Safety Aspects of Nuclear Magnetic Resonance Imaging and Spectroscopy (R.L. Magin, R.P.
       Liburdy, and B. Persson, editors), Annals of the NY Acad. Sci. 649, 273-284.

Gordon, CJ. (1993). Temperature Regulation in Laboratory Rodents. Cambridge University Press, New
       York, NY.

Gordon, CJ. and J.H. Ferguson (1984).  Scaling the Physiological Effects of Exposure to Radiofrequency
       Electromagnetic Radiation: Consequences of Body Size.  Int.  J. Radiat. Biol. 46:387-397.

Gordon, CJ. and M.D. Long (1987). Reduction in Metabolic Heat Production During Exposure to Radio-
       Frequency Radiation in the Rat. J. Appl. Physiol. 62: 1814-1818.

Gordon, CJ.,  M.D. Long  and  K.S. Fehlner (1986). Temperature Regulation in the Unrestrained Rabbit
       During Exposure to 600 MHz Radiofrequency Radiation.  Int. J. Radiat. Biol. 49; 987-997.

Haseman, J.K, and G.N. Rao (1992). Effects of Com Oil, Time-Related Changes, and Inter-Laboratory
       Variability on Tumor Occurrence in Control Fischer 344 (F344/N) Rats. Toxicologic Pathology
       20, 52-60.

Hardy, Y.O, and P. Bard (1974). Body Temperature Regulation. In: Medical Physiology (13th edition)
       (V.B.  Mountcastle, editor), Mosby, St. Louis, MO, 1305-1342.

Ho, H.S. and WP. Edwards  (1977).  Oxygen-Consumption Rate of Mice under Differing Dose Rates of
       Microwave Radiation. Radio Sci. 12(6S): 131-138,

IEEE  (1992).  IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency
       Electromagnetic Fields, 3 kHz to 300 GHz.  IEEE C95.1-1991  (Revision of ANSI C95.1-1982).
       Institute of Electrical and Electronics Engineers, Inc., 345 East 47th Street, New York, NY 10017.

-------
                                  RESPONSES OF LABORATORY MAMMALS TO RF RADIATION (ELDER)   99

Krupp, J.H. (1983), In Vivo Temperature Measurements During Whole-Body Exposure of Macaca Mulatta
       to Resonant and Nonresonant Frequencies. In: Microwaves and Thermoregulation (E.R. Adair,
       editor), Academic Press, New York, pp. 95-107.

Kues, H.A., L.W. Hirst, G.A, Lutty, S.A. D'Anna, and G.R, Dunkelberger (1985).  Effects of 2.45-GHz
       Microwaves on Primate Corneal Endothelium.  Bioelectromagnetics 6:177-188.

Kues, H.A., J.C. Monahan, S.A. D'Anna, D.S. McLeod, G.A. Lutty, and S. Koslov (1992). Increased
       Sensitivity of the Non-Human Primate Eye to Microwave Radiation Following Opthalmic Drag
       Pretreatment. Bioelectromagnetics 13:379-393.

Lai, H. (1992). Research on the Neurological Effects of Nonionizing  Radiation at the Univerity of
       Washington.  Bioelectromagnetics 13:513-526.

Lary,  J.M., D.L. Conover, E.D. Foley and P.L. Manser (1982).  Teratogemc Effects of 27.12 MHz
       Radiofrequency Radiation in Rats.  Teratology 26:299-309.

Lary, J.M., D.L. Conover, P.H. Johnson and R.W. Hornung (1986). Dose-Response Relationship Between
       Body Temperature and Birth Defects in Radiofrequency-Irradiated Rats.  Bioelectromagnetics
       7:141-149.

Liddle, C.G., J.P. Putnam and O.H. Lewter (1987). Effects of Microwave Exposure and Temperature on
       Survival of Mice Infected with Streptococcus Pneumonia. Bioelectromagnetics 8: 295-302.

Liddle, C.G., J.P. Putnam and O.P. Huey (1994). Alteration of Life Span of Mice Chronically Exposed
       to 2.45 GHz Microwaves. Bioelectromagnetics 15: 177-181.

Lin, J.C.  and M.F. Lin (1982). Microwave Hypertherrnia-Induced Blood-Brain Barrier Alterations. Rad.
       Res. 89, 77-87.

Lotz,  W.G. (1985).   Hyperthermia in Radiofrequency-Exposed Rhesus  Monkeys:  A  Comparison of
       Frequency and Orientation Effects. Rad. Res. 102:59-70.

Michaelson, S.M.,  R.A.E. Thomson and J.W. Howland  (1961). Physiologic  Aspects of Microwave
       Irradiation of Mammals. Am. J. Physiol. 201,  351-356.

Milham, S. Jr. (1988). Increased Mortality Due to Lymphatic and Hematopoietic Malignancies in Amateur
       Radio Operators. Am. J. Epidemic!, 127:50-54.

NCRP (1986).  Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields.
       National Council  on Radiation  Protection  and  Measurements (NCRP Report No. 86), 7910
       Woodmont Avenue, Bethesda, MD 20814.

NRPB (1993). Board Statement on Restrictions  on Human Exposure to Static and Time  Varying
       Electromagnetic Fields and Radiation. Documents of the NRPB (National Radiological Protection
       Board), Vol. 4, No. 5. Chilton, Didcot, Oxon OX11 ORQ.

Prausnitz, S. and C, Susskind (1962), Effects of Chronic Microwave Irradiation on Mice. IRE Transactions
       in Bio-medical Electronics 9, 104-108.

Preskorn, S.H., WJD, Edwards and D.R. Justesen (1978). Retarded Tumor Growth and Greater Longevity
       in Mice After Fetal Irradiation by 2450-MHz Microwaves. J. Surgical Oncology 10, 483-492.

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100  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

Salford, L.G., A. Bran, J.L. Eberhardt and B.R.R. Persson (1993). Permeability of the Blood-Brain Barrier
       Induced by 915 MHz Electromagnetic Radiation, Continuous Wave and Modulated at 8,  16, 50
       and 200 Hz, Bioelecricity and Bioenergetics 30, 293-301.

Santini, R,, M. Hosni, P. Deschaux and H. Pacheco (1988). B16 Melanoma Developement in Black Mice
       Exposed to Low-Level Microwave Radiation. Bioelectromagnetics 9: 105-107.

Shellock, F.G. (1995), Human Thermal Responses to RF-Radiation Induced Heating During Magnetic
       Resonance Imaging. These Proceedings.

Smialowicz,   RJ.  (1987).  Immunologic  Effects of Nonionizing  Electromagnetic Radiation.  IEEE
       Engineering in Medicine and Biology Magazine, March 1987, pp. 47-51.

Spalding, J.F., R.W. Freyraan and L.M. Holland (1971). Effects of 800-MHz Electromagnetic Radiation
       on Body Weight, Activity, Hematopoiesis and Life Span in Mice. Health Physics 20, 421-424.

Szmigielski, S., A. Szudzinski, A. Pietraszek, M. Bielec, M. Janiak, and J.K. Wrembel (1982). Accelerated
       Development of Spontaneous and Benzopyrene-Induced Skin Cancer in Mice Exposed to 2450-
       MHz  Microwave Radiation.  Bioelectromagnetics 3: 179-191.

Tofani, S., G.  Agnesod  and P. Ossola (1986).  Effects  of Continuous Low-Level  Exposure to
       Radiofrequency Radiation on Intrauterine Development  in Rats.  Health Physics 51:489-499.

Ward, T.R., J.A. Elder, M.D. Long, and D. Svendsgaard (1982).  Measurement of Blood-Brain Barrier
       Permeation  in Rats During Exposure to 2450-MHz Microwaves. Bioelectromagnetics 3:371-383.

Ward, T.R., and J.S. Ali (1985). Blood-Brain Barrier Permeation in the Rat During  Exposure to Low-
       Power 1.7-GHz Microwave Radiation.  Bioelectro-magnetics 6:131-143.

Weil, C.M. and J.R. Rabinowitz (1984). RF-Field Interactions with Biological Systems. In: Biological
       Effects of Radiofrequency Radiation (J.A. Elder and D,F. Cahill, editors).  U.S. Environmental
       Protection Agency publication EPA-600/8-83-026F, pp. 3-6 - 3-24.   Available from National
       Technical Information Services, Report No. NTIS PB-85120848, Springfield, VA.

Williams, W.M., W. Hoss, M. Formaniak and S.M. Michaelson (1984). Effect of 2450 MHz Microwave
       Energy on the Blood-Brain Barrier to Hydrophilic Molecules.  A. Effect on the Permeability to
       Sodium Fluorescein.  Brain Research Reviews 7:165-170.

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                                                    RF RADIATION EFFECTS ON CELLS (CLEARY)   101


          RADIOFREQUENCY RADIATION  EFFECTS ON  CELLS*
                                     Stephen F. Cleary**
INTRODUCTION

       Mammalian  cells or biomolecules exposed in vitro afford a unique opportunity to investigate
biological effects of radiofrequeney electromagnetic radiation (REER) under  conditions of precise
experimental control of variables including: (a) induced electric (E) or magnetic (B) field strength; (b)
modulation; (c) dose rate or specific absorption rate (SAR); (d) temperature; and (e) composition of cell
exposure medium. The interaction of RFER with mammalian cells and biomolecules is also amenable to
theoretical determination of the magnitude and spatial distribution of induced E and B fields and hence
cell or molecular level SAR distributions.  Consequently, mammalian cells and biomolecules provide the
most direct approach to determining basic interaction mechanisms of RFER biological effects.  In  vivo
systems do not afford this opportunity due to inherent dosimetric and densitometric complexities that place
practical  limitations on the  accuracy of E-, B-field or SAR determinations in tissue.

       In vitro studies of the  effects of RFER on various  cell physiological endpoints include:   (a)
membrane  cation transport  and  binding; (b)  neuroelectrical  activity; (c) proliferation;  and  (d)
transformation.  The results of these studies have been the subject of review articles (1-4). The primary
purpose of this communication will be to review recent in vitro studies that: (a) provide additional insight
regarding possible RFER cellular interaction mechanisms; (b) provide evidence of direct or athermal RFER
cellular effects; and (c) are of potential relevance to human health effects such as reported associations
of RFER exposure and cancer incidence.  It is not the purpose of this communication to  provide a
comprehensive review of in vitro cellular effects of RFER (for more comprehensive reviews refer to
references 1-4).

       Based upon the results of the studies reviewed here it may be concluded that under some exposure
conditions RFER directly alters mammalian cell physiology in the absence of indirect thermal  effects.
Although specific interaction  mechanisms are uncertain the data suggest that the most likely interaction
site for many of the cellular effects of RFER is the cell plasma membrane. Further insight  regarding in
vivo effects of REER, such as cancer induction or promotion  can be provided by appropriately designed
in vitro cell studies.

MEMBRANE CATION PERMEABILITY AND CALCIUM BINDING

       Studies of cell membrane cation permeability provided the first indication of direct nonthermal
effects of RFER, Exposure  of human, rabbit, and canine  erythrocytes to 2.45-, 3.0  and 3.95 GHz
continuous wave (CW) microwave radiation at SARs of up to 200 W/kg resulted in intracellular K+
leakage and osmotic lysis.  Temperature control studies conducted over the same  temperature range (26
to 44C)  suggested, however, that the effects were due to REER-induced heating (5),  In a subsequent
study  of passive cation (Na+,  Rb+) efflux from rabbit erythrocytes exposed to 2.45 GHz RFER at SARs
of 100,-190- and 390 W/kg statistically significant increases were detected, but only at a temperature of
22.5C (6).  In agreement with the results of Liu et al. (5), RFER had no direct effect at temperatures
greater than 22.5 C.  Additional evidence of direct RFER-induced membrane permeability changes in the
range  of  17.7  to 19.5C was reported (7,8,9). The effect of RFER (2.45 GHz) was enhanced when
   * This paper was updated in March 1994.

   ** Physiology Department, Medical College of Virginia, Virginia Commonwealth University, Richmond,
Virginia.

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102  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

erythrocytes were exposed under hypoxic conditions or when exposed in the presence of plasma (8).
Increasing the cell membrane cholesterol content or treatment with antioxidants, on  the other hand,
inhibited the effect of RFER exposure (8).

       An indication that REER-induced changes in cell membrane cation permeability were not highly
frequency  specific was provided by the results of a study of the effect of 8.42 GHz REER on  K+ release
from rabbit erythrocytes. Cleary et al. (10) exposed erythrocytes to SARs of 21 to 90 W/kg.  Compared
to temperature controls, RFER had no effect on K+ release, except under conditions when the steady state
temperature was maintained at 24.6C during exposure.  RFER exposure at lower or higher temperatures
was ineffective. The results of these experiments (5-10) suggested an interaction between RFER exposure,
cation transport, and a  gel-to-liquid crystal membrane phase transition (10). Since temperature-specific
effects on erythrocyte cation transport could not be induced in the absence of RFER exposure they were
interpreted as a direct effect on the red cell membrane (3).

       A  molecular interaction mechanism for the effect of RFER on membrane cation transport was
suggested by Allis and Sinha-Robinson (11). Human erythrocyte membranes were exposed to 6W/kg 2.45
GHz RFER at 1C temperature increments between 23 and 27C.  When membrane Na^/JC1" ATPase
activitity was monitored spectrophotometrically,  it was found that enzyme activity was inhibited only at
25C (11).  This led to the hypothesis that inhibition resulted from a direct interaction of RFER with the
ATPase enzyme.  This  interaction mechanism is consistent with reported effects of RFER on erythrocyte
cation (K+, Na*, Rb+) transport at the membrane phase transition (5-10).

       Evidence of direct RFER effects on cells was also revealed by a series of studies of effects on
calcium (Ca+ ) binding to nerve cell membranes.  In contrast to  effects on membrane cation transport,
which occurred following CW or pulse modulated RFER exposure, effects on Ca+2 binding were strongly
dependent upon RFER modulation at extremely  low frequencies (ELF), most prominently 15-  or 16Hz
(12). The Ca+ efflux response went through a series of maxima as the modulation rate or RFER intensity
was increased. (13,14).  These responses, referred to as  frequency or power "windows" occurred under
conditions not associated with RFER-induced heating.  The generality of the effect was indicated by
similar responses of synaptosomes (15) and neuroblastoma cells (16).

MOLECULAR/BIOCHEMICAL EFFECTS

       Detailed  mechanisms explaining molecular level biochemical effects of RFER are not yet
available.  Insight is provided, however, by studies of specific biomolecular interactions conducted under
conditions involving different molecular microenvironments. Fisher et al. (9) detected a 40% reduction
in ouabain sensitive Na+ efflux from erythrocytes exposed at 23-24C to 2.45 GHz RFER at a SAR of
3W/kg.  This response was attributed to a field-induced effect on membrane Na+/K+ ATPase.  Using this
same frequency of RFER, Allis  and Sinha-Robinson (11) induced a  35% decrease in Na+/K+ ATPase
activity in erythrocyte membrane fragments at a SAR of 6 W/kg. Brown and Chattopadhyay (17), on the
other hand, reported a 23% decrease in Na+/K+ ATPase activity at 24.9C when the enzyme was exposed
in solution to 9.14 GHz CW RFER at a SAR of 20W/kg. In view of previous evidence that the effect of
RFER on Na+/K+ membrane transport was not highly frequency dependent (10), the results of these studies
suggest that the RFER intensity needed to alter enzyme activity may depend upon the microenvironment
of the Na+/K* ATPase. The  fact that the minimum RFER intensity required to  affect Na+/K+ ATPase
activity occurred in intact membranes suggests an interaction between RFER energy and metabolic energy.
Maximum RFER intensity was required for Na+/K+ ATPase inactivation in solution in the absence of cell
metabolic energy sources.  This hypothesis is supported  by the results of previous studies of the effects
of low-intensity RFER  on biomolecules in solution which have, in general, yielded negative results (18).

       Additional evidence of direct biochemical interactions of RFER was reported by Phelan et al. (19)
who investigated  effects on the structure of cell or liposome  membranes. RFER (2.45 GHz) exposure at
intensities  as  low as 0.2 W/kg caused a shift from a fluid to gel state in membranes that contained

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                                                     RF RADIATION EFFECTS ON CELLS (CLEARY)   103

melanin. In the absence of melanin, RFER exposure had no effect on membrane structure. The fact that 
the RFER effect was inhibited in the presence of superoxide dismutase (SOD), indicated the involvement
of free radical generation (19). The results and conditions for the molecular/biochemical studies of RFER
reviewed here are summarized in Table 1.

MEMBRANE ION CHANNELS

       Evidence of direct athermal interactions  of RFER with biomolecules  other than enzymes is
provided by studies of effects on membrane ion channels and  excitable membranes.  Sandblom and
Theander (20) investigated effects of 10 GHz pulsed RFER on the kinetics of gramicidin-A-channels in
artificial lipid bilayer membranes. A 1 min. exposure to short (1 usec)  high instantaneous power (350
W/kg), RFER pulses had no effect on the lifetime or conductance of gramicidin-A-channels.  However,
RFER exposure decreased significantly the rate of channel formation (20).  Since it is well known that
the rate of single channel formation increases with increasing temperature, the RFER effect was concluded
to be a direct effect on the gramacidin-A-channel molecular complex. The effect was attributed to either
field-induced dipole reorientation, changes in  lipid conformation, or altered structure of water inside
channel  peptide helices (20).
       A similar effect on ion channels was reported by D'Inzeo et al. (21) who briefly (30-120 s)
                                                                           n
exposed chick myotubes to CW 9.75 GHz RFER at low intensities (-1-2 uW/cm ).  RFER exposure
decreased the frequency of single-channel openings of acetylcholine-induced channels. (21).
       Direct effects of RFER on excitable membranes have also been reported. The rate of rapid, burst-
like changes in the firing rate of molluscan neurons was increased by exposure to pulse modulated (PM)
900 MHz RFER at SARs of 0.5 W/kg or higher (22).  In this range of SARs, CW RFER did not affect
the neuronal firing rates.   The specificity of  the effect on the neuronal membrane firing rate was
demonstrated by the finding that mediator-induced activation of acetylcholine, dopamine, serotonin, or
gamma-aminobutyric acid membrane receptors was not affected by either PM or CW RFER (22). These
studies are summarized in Table 2.

FUNCTIONAL AND GENOMIC ALTERATIONS

       A variety  of in vitro functional and genomic cellular alterations have  been attributed to direct
effects of RFER exposure.  Cleary et.al (23,24,25) reported altered proliferation of normal resting human
peripheral lymphocytes and human or rat glioma following a 2h exposure, to 27- or 2450 MHz CW or PM
RFER at SARs in the range of 0.5 to 200 W/kg.  Altered cell proliferation persisted for up to 5 days after
RFER exposure. The effect was biphasic; maximum increased proliferation occurred at 25 W/kg whereas
exposure at 50 W/kg or higher  generally suppressed proliferation (25).  Since cells  were exposed under
isothermal conditions (370.2C) altered proliferation was attributed occurred  at 25 W/kg whereas
exposure at 50 W/kg or higher  generally suppressed proliferation (25).  Since cells  were exposed under
isothermal conditions (370.2C) altered proliferation was attributed to a direct effect of RFER.  Similar
direct effects of pulsed RFER on lymphoblastoid transformation were reported following a 5 day exposure
to 2.45 GHz RFER at a maximum SAR of 12.3 W/kg(26).

       Neoplastic cell transformation has also  been reported as a direct  effect of  low intensity RFER
exposure.  Mammalian embryonic fibroblasts were exposed for 24h to 0.1, 1, or 4.4 W/kg 2.45 GHz
RFER pulse modulated at 120 Hz(27). In the absence of the tumor promoter 12-0-tetradecanoyl-phorbol-
13-acetate (TPA) RFER did not affect cell  survival or the rate of neoplastic transformation. Cells treated
with TPA and RFER experienced a statistically significant  dose-dependent increase  in neoplastic
transformation  rate. Exposure to 4.4 W/kg  RFER with TPA had  a neoplastic transformation effect
equivalent to exposure to 1.5  Gy  of X-radiation.  It was determined that  RFER and  X-rays  acted
independently in inducing neoplastic transformation (27). Evidence of direct genomic effects of RFER
on human somatic  cells have also been reported including chromosmal aberrations (acentric fragments and

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                                  Table 1.  MOLECULAR/BIOCHEMICAL EFFECTS OF RFER
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   SOURCE DESCRIPTORS
                                 TYPICAL EFFECT
                                   FIELD
                                PARAMETERS/
                                THRESHOLDS
                              COMMENTS
 9.14 GHz CW microwaves
                               altered Na+/K+ ATPase
                               enzyme activity
                               20W/kg
                     enzyme activity increased at temp.
                      between 7 and 43.8C; 23% decrease
                      at 24.9C; inhibitory effect of
                      ouabain significantly reduced by
                      microwave exposures at T>24.9C
                     attributed to direct molecular
                      level interaction of microwaves
                      (Ref.17)
 2.45 GHz CW microwaves
                              altered Na+/K+ ATPase
                               activity in erythrocyte
                               membrane fragments
                               6W/kg
                     enzyme activity decreased 35% at
                      25C only, not at other temp, in
                      range 23-27C
                     ouabain-insensitive Ca+2 ATPase
                      activity also altered (Ref.ll)
2.45 GHz pulsed
microwaves
altered Na+/K+ ATPase
activity in erythrocytes
3 W/kg
 40% decrease in ouabain sensitive
 Na+ efflux at 23 and 24C (Ref.9)
2.45 GHz pulsed
microwaves
altered membrane
structure in melanoma
cells or melanin
containing liposomes
0.2 W/kg
 microwaves induced shift from
  fluid to gel state in membrane in
  presence of melanin
 effect inhibited by SOD
 microwave effect may be mediated by
  temp, dependent generation of O2
  radicals (Ref.19)

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                                   Table 2. MEMBRANE ION CHANNEL EFFECTS OF RFER
   SOURCE DESCRIPTORS
    TYPICAL EFFECT
      FIELD
   PARAMETERS/
   THRESHOLDS
          COMMENTS
 10 GHz pulsed microwaves
 single channel kinetics of
 gramicidin-A-channels in
 lipid bilayers
 1 jas pulse
  350 W/kg
  instantaneous
 105 V/m
  instantaneous
 103 p.p.s
 1 min exposure
 no effect on channel conductance or
  lifetime
 significant decrease in rate of channel
  formation
 opposite from heating effect
 due to direct interaction with channel-
  forming molecules (Ref.20)
 9.75 GHz CW microwaves
 single channel kinetics of
 acetlycholine-induced
 channels in chick myotubes
  -1-2
  30-120s
  decreased frequency of single-
  channel openings (Ref.21)
 900 MHz pulsed
 microwaves
' firing rate of molluscan
 neurons
 0.5 W/kg
 threshold
0.5-110pps
 2 min exposure
  increased rates of rapid, burst-like
  firing
  lesser effect of CW microwaves at
  same SARs
  direct effect on neuronal membrane
  (Ref.22)
30
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106   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

dicentric chromosomes) micronuclei formation and mutagenic characteristics typical of chemical mutagens
(28,29). Studies of the functional and genomic effects of RFER are summarized in Table 3.

SUMMARY AND CONCLUSIONS

       In vitro cellular and molecular level studies provide evidence of direct athermal effects of RFER
on cellular processes including:  (1) membrane ion transport  and binding; (2) membrane structure; (3)
membrane single ion channel kinetics; (4) neuronal activity; (5) proliferation/activation; and (6) neoplastic
transformation. Cellular alterations were reported under a variety of exposure conditions:  (1) SARs from
0.2 to greater than 100 W/kg; (2) frequencies of from 2 GHz to 50 GHz; (3) CW and PM RFER exposure.
The majority of in vitro REER in vitro studies involved acute exposures (periods of a few hours or less).
There is insufficient data to define time or intensity thresholds or RFER frequency-dependence for the
majority of the reported in vitro effects.

       In spite of the limitations of the available  data some general conclusions may be arrived at:  (1)
RFER can  directly induce cell physiological alterations in vitro under conditions that  do not involve
temperature elevations; (2) although detailed mechanisms are unknown, the cell plasma membrane is the
most  likely RFER interaction site; (3) RFER  affects  a  variety of biomolecular systems with no clear
indication  of specific molecular sensitivities; and  (4) effects of RFER on mammalian cells in vitro are
generally consistent with reported in vivo exposure effects including increased cancer incidence as related
to effects  on promotion and/or the  rate of neoplastic transformation. There is an obvious need for
additional data to more adequately relate in vitro and in  vivo effects of RFER exposure.

REFERENCES

1. Cleary, S. F.: Cellular effects of radiofrequency electromagnetic fields. In Gandhi, O.P. ed. Biological
       Effects and Medical Applications of Electromagnetic  Energy,  Englewood Cliffs, N.J. Prentice
       Hall, 1990, pp. 339-356.

2. Cleary, S. F.:  Biological effects of radiofrequency radiation:   an  overview.  In Franeeschetti, G.,
       Gandhi, O. P., Grandolfo, M., eds Electromagnetic Biointeraction, New York, Plenum Press, 1989,
       pp. 59-79.

3. Cleary, S. F.:  Cellular effects of electromagnetic radiation.  IEEE Eng. Med. Biol. Magazine 6:26-30,
       1987.

4. U.S. Environmental Protection Agency, in J. A. Elder and D. F.  Cahill (Eds.), Biological Effects of
       Radiofrequency Radiation, No. EPA-600/8-83-026F, Research Triangle Park, NC: USEPA, 1984.

5. Liu, L. M., Nickless,  F. G.,  and  Cleary, S. F.:  Effects of microwave  radiation  on erythrocyte
       membranes.  Radio ScL, 14:109-155, 1979.

6. Olcerst,  R.  B., Belman, S.3 Eisenbud, M., Mumford, W. W., and Rabinowitz, J. R.: The increased
       passive efflux of sodium and rubidium from rabbit erythrocytes by microwave radiation. Radiat
       Res., 82:2444-256, 1980.

7. Liburdy, R. P. and Penn, A.:  Microwave bioeffects  in the erythrocyte are temperature and pO2
       dependent: Cation permeability and protein shedding occur at the membrane phase transition.
       Bioelectromagnetics, 5:283-291, 1984,

8. Liburdy, R.  P. and Vanek, P. F.:  Microwaves  and  the cell membrane II. Temperature, plasma, and
       oxygen mediate microwave-induced membrane  permeability in the  erythrocyte. Radiat. Res.,
       102:190-205, 1985.

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                                  Table 3. FUNCTIONAL AND GENOMIC EFFECTS OF RFER
   SOURCE DESCRIPTORS
                                   TYPICAL EFFECT
                                   FIELD
                                PARAMETERS/
                                THRESHOLDS
                               COMMENTS
 27 MHz CW or pulsed
 2.45 GHz CW or pulsed
                                altered proliferation of
                                human or rat glioma and
                                human lymphocytes
                               0.5 to 200 W/kg
                               2 h isothermal
                               (37C) exposure
                       proliferation altered for 1-5 d
                       postexposure
                       evidence of cumulative effect
                       similar effects of CW or pulsed
                       fields
                       biphasic dose rate effect
                      (Ref.  23,24,25)
 2.45 GHz pulsed
 microwaves
                                transformation of
                                C3H/10T 1/2 mouse
                                embryo fibroblasts
                              . 4.4 w/kg
                               37.2  0.1 C
                               24 h exposure
                       latent transformation revealed by
                       TPA treatment of cells exposed to
                       X-radiation and microwaves (Ref.27)
 7.7 GHz CW microwaves
                                chromosomal aberrations
                                micronuclei formation in
                                human lymphocytes
                               O.S-,10-,
                               30 mW/cm2
                               10-,30-,60 min
                       higher frequency of chromosomal
                       aberrations in all exposed samples
                       increased frequency of micronuclei
                       in exposed samples correlated with
                       specific chromosomal aberrations
                       (Ref.28)
                                                                                                                                    33
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                                                                                                                                    P
                                                                                                                                    2
                                                                                                                                    3)
 2.45 GHz CW or pulsed
 microwaves
lymphoblastoid
transformation of human
lymphocytes
 5 d exposure
 1 us pulse
 100-103 PPS
 max SAR
 12.3 W/kg
 temperature dependent increase in
 control and CW microwave exposed
 samples
 pulsed microwaves increased
 lymphoblastoid transformation
 without heating (Ref.26)

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108  SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
9, Fisher, P. D.,  Poznarsky, M. J., and Voss, W. A. G.: Effect of microwave radiation (2450 MHz) on
       the active and passive components of 24 Na+ efflux from human erythroeytes. Radiat., Res.,
       92:411-422, 1982.

10.  Cleary,  S, F., Garber, F., and Liu, L, M.:  Effects  of  X-band microwave exposure on rabbit
       erythroeytes. Bioelectromagnetics,  3:453-466, 1982.

11. Allis, J, W.,  and Sinha-Robinson, B. L.: Temperature specific inhibition of human red cell Na+/K+
       ATPase by 2450 MHz microwave radiation.  Bioelectromagnetics 8:203-212, 1987.

12.  Adey, W. R.:  Frequency  and  power windowing in tissue interactions with weak electromagnetic
       fields.  Proc. IEEE, 68:119-125, 1980.

13. Joines, W. T. and Blackman, C. F.: Power density, field intensity, and carrier frequency determinants
       of RF-energy-induced calcium-ion efflux from brain tissue. Bioelectromagnetics, 1:271-275,1980.

14. Blackman, C. F., Benane, S.  G.,  House, D. E., and Joines, W. T.:  Effects of ELF (1-120 Hz) and
       modulated  (50  MHz)  RF  fields on the efflux of calcium  ions from brain tissue in vitro.
       Bioelectromagnetics, 6:1-11, 1985.

15. Lin-Liu, S. and Adey, W. R.;  Low frequency amplitude modulated microwave fields change calcium
       efflux rates from synaptosomes. Bioelectromagnetics, 3:309-322, 1982.

16. Dutta, S. K., Subramonian, A.,  Ghosh, B.,  and Parshad, R.:  Microwave radiation-induced calcium
       ion efflux from human neuroblastoma cells in culture.  Bioelectromagnetics, 5:71-78, 1984.

17.  Brown, H. D. and Chattopadhyay:  Ouabain inhibition of kidney ATPase  is altered by 9.14 GHz
       radiation. Bioelectromagnetics 12:137-143, 1991.

18. Cleary, S. F.: Uncertainties in the evaluation of the biological effects of microwave and
       radiofrequency radiation.  Health Physics 25:387-395, 1973.

19. Phelan, A. M., Lange, D. G., Kues, H.  A. and Lutty, G. A.:  Modification of membrane fluidity in
       melanin-containing cells by low-level microwave radiation.  Bioelectromagnetics  13:131-146,
       1992.

20. Sandblom, J. and Theander, S.:  The effect of microwave radiation on the stability and formation of
       gramicidin-A channels in Mpid bilayer membranes.  Bioelectromagnetics 12:9-20, 1991.

21. D'Inzeo, G.,  Bemardi, P, Eusebi, F., Grassi, F., Temburello and Zani, B. M.: Microwave effects on
       acetylcholine-induced channels in cultured chick myotubes. Bioelectromagnetics 9:363-372,1988.

22. Bolshakov, M. A, and Alekseev, S.I.: Bursting responses of Lymnea neurons to microwave radiation.
       Bioelectromagnetics 13:119-129, 1992.

23. Cleary, S. F., Liu, L. M. and Merchant, R. E.: Lymphocyte proliferation induced by radiofrequency
       radiation under  isothermal conditions.  Bioelectromagnetics 11:47-56, 1990.

24. Cleary, S. F., Liu, L. M. and  Merchant, R. E.:  Glioma proliferation modulated in vitro by
       isothermal radiofrequency radiation exposure. Radiation  Res. 121:38-45, 1990.

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                                                    RF RADIATION EFFECTS ON CELLS (CLEARY)   109

25. Cleary, S. F., Liu, L. M. and Cao, G.:  Effects of RF power absorption in mammalian cells.  Annals
       of the N. Y. Acad. Sci. 649:166-175, 1992.

26. Czerska, E., Elson, E. C. Davis, C. C., Swicord, M. L. and Czerski, P.:  Effects of continuous and
       pulsed 2450-MHz radiation on spontaneous lymphoblastoid transformation of human lymphocytes
       in_vitrp_.  Bioelectromagnetics 13:247-259, 1992.

27. Balcer-Kubiczek, E, K. and Harrison, G. H.: Neoplastic transformation of C3H/10T1/2 cells following
       exposure to 120-Hz modulated  2.45-GHz microwaves  and phorbol ester  tumor promoter.
       Radiation Res. 126:65-72, 1991.

28. Garaj-Vrhovac, V., Fucic, A. and Horvat, D.: The correlation between the frequency of micronuclei
       and specific chromosome aberrations in human lymphocytes exposed to microwave radiation in
       vitro. Mutation Res.  281:181-186, 1992.

29. Fucic, A., Garaj-Vrhovac, V., Skara, M. and Dimitrovic, B.: X-rays, microwaves and vinyl choride
       monomer:  their clastogenic and aneugenic activity, using  the rnicronucleus assay  on human
       lymphocytes.  Mutation Res. 282:265-271, 1992.

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                               ODC ACTIVITY: A CELLULAR RESPONSE TO LOW-ENERGY EMF (BYUS)   111


      ALTERATIONS  IN ORNITHINE  DECARBOXYLASE ACTIVITY:
                 A CELLULAR RESPONSE TO LOW-ENERGY
                   ELECTROMAGNETIC FIELD  EXPOSURE*
                                      Craig V. Byus**
INTRODUCTION

       The enzyme ornithine decarboxylase (ODC) is, under most situations, the controlling enzyme in
polyamine biosynthetic pathway (1,2). This enzyme decarboxylates, or removes, the carboxyl group from
ornithine to yield  putrescine or diaminobutane.  Through  another  series  of  enzymatic  reactions,
propylamine moieties  can  be added sequentially  to putrescine to yield spermidine and  spermine,
respectively. The polyamines are found ubiquitously in nature and have been most closely linked to the
processes of cellular proliferation, hypertrophy and differentiation in  eukaryotic cells (1,2).  Use of
selective inhibitors of polyamine biosynthesis and preparation of mutants lacking polyamines have
presented convincing  evidence that the polyamines are essential for  many functions inside the cell
involving macromolecules with negative charges.  The polyamines possess the highest positive charge to
mass ratio of any biosynthesized molecule and, in general, are believed to be highly bound inside of cells
to a number of macromolecules with negative charges.

       Given the enormous importance of polyamine biosynthesis for the continued proliferation and
differentiation of mammalian cells, study of the regulation of this enzyme has received a considerable
amount of attention. In general, in quiescent or non-growing cells, the level of ODC activity is extremely
low.  However, following stimulation of the cell to grow or divide by any of a number of hormones or
growth factors, ODC activity can increase markedly (i.e., up to 500-fold)  and rapidly from these low basal
values (3).  Increases in ODC have been shown to involve a number of specific molecular mechanisms
including: increases in ODC-specific mRNA brought about by increases in the transcription of the ODC
gene, increases in the half-life of ODC mRNA, altered translation of ODC mRNA, and increases in the
half-life of the ODC protein posttranslationally  (3).  While all of these mechanisms have been shown to
be important in specific instances, it is currently believed that to a great extent ODC activity is controlled
by posttranslational mechanisms  involving degradation of the  enzyme in response  to increases in
polyamine levels (4).

       Due to the high sensitivity of this enzyme to a large variety of stimuli and the involvement of
changes in ODC activity and polyamines in a variety of pathologies including cancer, ODC appeared to
be a logical choice to  investigate as a potential  marker of exposure of cells or tissues to low-energy
electromagnetic fields.  For these reasons we began a series of investigations to study whether ornithine
decarboxylase activity was altered following exposure  of a variety of animal and human cells in culture
following  exposure to  three low-energy  electromagnetic  fields  including low-frequency amplitude
modulated microwave fields, pulsed magnetic fields, and electric fields (5-7). The discussion of data in
this manuscript will be confined to experiments involving a field of 450 MHz, amplitude-modulated at
low frequencies.
   * This paper was updated in September 1994.

   ** Division of Biomedical Sciences and Department of Biochemistry, University of California, Riverside, CA
92521-0121.

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112  SUMMARY AND RESULTS OF THE RADiOFREQUENCY RADIATION CONFERENCE: VOLUME 2

MATERIALS AND METHODS

       Field exposure, which employed a Crawford cell exposure system, was operated in the same
general configuration  as  described in detail (5,6).  The cell was designed  to operate as a coaxial
transmission line with a characteristic impedance of 50 ohms a spectrum of frequencies.  With biological
test specimens or cell culture dishes in place, a 50-ohms non-inductive termination standing wave ratio
(SWR) did not exceed 1.17:1 at the operating frequency of 450 MHz,  Cell viability was not altered by
exposure to any of the fields used in the studies presented here. A field-generating system comprised of
low-frequency waveform generator served as a modulating signal source. This signal was applied through
a PIN diode modulator with an output of a 450 MHz phase-lock  loop controlled signal generator. The
generator drove  a broad  band linear power  amplifier with  a maximum power of 20 W.   Depth of
sinusoidal amplitude modulation  was monitored with an oscilloscope and with an in-line modulation
meter/forward reflected power meter.  Modulation depth was maintained at 75 to 85%.  An input of 1.7-
watts peak envelope power (PEP) to the cell produced a peak field intensity of 1.0 mW/cm .  PEP levels
were adjusted to this level with a carrier wave modulated to a depth of 75 to 85% in all experiments. The
SAR under these exposure conditions was 0.08 W/kg.  The Crawford cell was housed in a large incubator
maintained at 37C. Temperature changes after equilibration and during  field exposures were typically
around  0.1 C.  Exposed culture dishes were maintained in  a similar humidified plexiglass box in the
same incubator placed outside the Crawford cell. Cultures of Reuber H35 hepatoma cells and the other
cells described were maintained under standard culture conditions as described in detail (6-9).

       Measurement of ODC activity occurred in  supernatant preparations made from cells following
exposure at the indicated  times to the field.  ODC activity is represented as the amount of I4CO2 from
0.25 uCi[  C]L-ornithine  during a 60-minute incubation of the supernatant under control conditions at
37C at a total ornithine concentration of 0.2 mM (see reference 8 for details).

       Total   RNA   was   isolated  using  the   method   of    Chomczynski   and   Sacchi
(acid/guanidinium/phenoychloroform) (10) and resuspended in 10  mM tris buffer, pH 7.5. Twenty ug of
the total RNA was added to a microfuge tube containing formaldehyde and then denatured by boiling for
1 minute before being loaded  onto a 1.1% agarose  gel. After electrophoretic separation, the RNA was
transferred to a nylon membrane using a vaccublot (IBN) vacuum transfer apparatus. The membrane was
then vacuum baked and placed in a bag along with 20 ml of rapid hybridization buffer (Amersham) and
incubated at 65C for  one hour.  After prehybridization was complete, 10 million CPM of a random-
primer  P-labelled ornithine decarboxylase probe (specific activity > 2 x 109 CPM/ug) was added to the
bag to hybridize for 3 hours at 42C.  When hybridization was complete,  the filter was washed in 0.2 X
SSC to remove the nonspecifically bound probe. The washed filter was then subjected to autoradiography
at  70C for 48 hours.  After processing the film, only the bands corresponding to ODC mRNA were
clearly visible.  The autoradiograph was scanned  with a densitometer  and the density  of  the bands
compared as  an  indication of the relative  amounts of ODC mRNA present in the various samples.
Polyamine concentrations in the culture media of cultured cells were determined as described in detail in
reference 11.

       For all the experiments illustrated in Figures 1, 2 and 3, the cultured cells were exposed to the
field for a 1-hour period after which they were removed and assayed at the times indicated.  In Figure 4,
the effects of field exposure upon  the amount of putrescine exported in the culture media is analyzed.  In
this case, the cells were exposed continuously to the amplitude-modulated microwave field.
RESULTS

       The effects of a 1 -hour exposure of Reuber H35 hepatoma cell culture and 294T human melanoma
cell culture to the 450 MHz field amplitude-modulated at 16 Hz for a period of 1 hour is illustrated in
Figures la and b.  During the 1 hour of field exposure the activity of ODC can be observed to increase

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                                ODC ACTIVITY: A CELLULAR RESPONSE TO LOW-ENERGY EMF (BYUS)   113
                      40
                      30
                   S  20
                   N
                   O
                   a
                   "o
                   
                   a
10
                          O FIELD (16Hz)
                          * NO FIELD
                                             REUBER H35 MEPATOMA CELLS
                                                JU
                               -10123
                                       HR POST EXPOSURE

                                          Figure la

                                294T HUMAN MELANOMA CELLS
                         PLUS AND MINUS 16 Hz FIELD (1 HR EXPOSURE)
                     15
                    10
                                         _L
                                                   JL
                                0123
                                            HOURS

                                          Figure Ib

from a value of 20 pinoles CO2/mg protein per hour x 10"2 to a value of 30, an increase of approximately
50%.   At time 0 the cells were removed from the field and assayed for an additional 3-hour period as
illustrated.  The activity of ODC in the field exposed cells can be observed to remain elevated during the
3-hour period subsequent to field exposure. A similar early effect of field exposure was observed in the
294T human melanoma cells.  Following 1-hour exposure to the field the activity of ODC was observed
to increase by approximately 50% as shown by the 0 hour value.  The activity of ODC in these cells
remained elevated for only a 1 hour period after being removed from the field whereupon they return to
the control or sham field values illustrated by the solid circles and solid lines.

       The effects of the frequency of the amplitude modulation  upon the ability of RF field to induce
increases in omithine decarboxylase activity is shown in Figure 2.  In these experiments the Reuber H35
hepatoma cells were placed in the field for a 1-hour period and assayed immediately upon removal from
the field, i.e., comparable to the time 0 points  shown in Figure  1.  The data is shown relative to  the

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114   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2
                   200-
                                                                     5%
                                     40            80            120

                              MODULATION  FREQUENCY (Hz)
                                          Figure 2

control value of ornithine decarboxylase observed in the unmodulated 450 MHz field shown as the cross-
hatched bar. It is apparent that only low-frequency amplitude modulated 450 MHz fields were capable
of altering the activity of ornithine decarboxylase in these cells. Amplitude modulation frequencies of 12,
16 and 20 Hz produced increases in ornithine decarboxylase activity in this system. The unmodulated and
higher modulation frequencies were without effect.

                     ALTERATIONS IN ODC mRNA IN  REUBER H35  CELLS  FOLLOWING
                         EXPOSURE TO  AMPLITUDE-MODULATED 450 MHz  FIELD
                c
                o
             cc
              E
                OJ
                u
                t-
                QJ
                Q_
                    150
100
 50-
                             - SHAM FIELD
                            O - FIELD
                             450 MHz,  16 Hz Modulation.
                             1.0 HtW/cin2 P. E.P.
                          -101234
                                      HOURS POST EXPOSURE

                                          Figure 3

       A number of investigators have reported that 60 Hz magnetic fields as well as pulsed magnetic
fields of a variety of nature were capable of inducing alterations in eukaryotic gene expression (12-14).
In addition, it has been known for many years that many of the stimuli which lead to an increase in
ornithine  decarboxylase activity inside of cells increased the level of messenger RNA specific for ODC
under these conditions (15). For these reasons, we investigated the ability of 16 Hz modulated microwave
field to lead to alterations in the mRNA for ODC.  The Reuber H35 hepatoma cells were exposed for a

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                                 ODC ACTIVITY: A CELLULAR RESPONSE TO LOW-ENERGY EMF (BYUS)   115

1 -hour period to the field and assayed for the presence of ODC mRNA at the times indicated as described
in the materials and methods.  For these experiments, triplicate samples were analyzed by Northern  gel
analysis and the autoradiograms scanned with a densitometer.  The data is represented relative to  the
amount of ODC mRNA observed in control or sham exposed cells. As can be  seen in Figure 3, the same
field exposure which resulted in an increase in ODC activity did not cause any change in the relative
amount of mRNA specific for ODC in these cells throughout a 4-hour post-exposure period.  We have
additionally analyzed for the amount of ODC mRNA produced during the exposure to the field, i.e., -1
hour to 0 hours and also have observed no increase in ODC mRNA relative to control values (data  not
shown).  Under these  identical culture conditions the phorbol ester derivative TPA  led to an  8-fold
increase in  ODC mRNA within a 4-hour period, and insulin causes an 11-fold increase within an 8-hour
period (data not shown).

       Recently our laboratory has begun to explore the phenomenon of putrescine export or efflux from
the inside of the H35 cells to the outside (16).  We have recently characterized a transport system present
in most eukaryotic cells which is capable of transporting putrescine from the inside of the cell to  the
outside of the cell in a highly regulated manner. We wished to determine whether exposure to low-energy
electromagetic fields would effect this important parameter in the regulation of polyamine metabolism and
ODC activity.  We continuously exposed  the H35  cell cultures to the 16 Hz  amplitude-modulated
microwave field  TPA as described in Figure  4.   After 5 hours the ceils receiving TPA showed
significantly more putrescine exported into the culture medium than did the cells not receiving TPA.
Exposure to the field had an inhibitory effect on the constituitive level of putrescine export in control cells
and upon the TPA-stimulated export process.

                              EFFECT OF MODULATED RF FIELD ON PUTRESCIIC  EXTORT
                                      IN REUBER H35 RAT HEPATOMA CELLS
                lu .?
                ^r ^"
                fj IB
                -> J2
10

 8

 6
                             A CONTROL
                              FIELD (CONTJWJOUS)
                             *TPA
                              TPA * FIELD (CONT)
                                0       1
                        2       3      4
                          HOURS
                                            Figure 4
DISCUSSION

       Exposure of cultured cells to athermal levels of amplitude-modulated 450 MHz fields led to a
significant and long-lasting (relative to the exposure time) increase in the mtracellular enzyme omithine
decarboxylase.  Even a transient 1-hour exposure to the field resulted in a longer than 4-hour elevation
in ornithine decarboxylase activity  (Figure 1).  The ability of the 450 MHz microwave field to induce
ornithine decarboxylase activity in this cell system furthermore depended upon the frequency of the
amplitude modulation (Fig. 2).  The microwave carrier wave alone was ineffective in leading to a change

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116   SUMMARY AND RESULTS OF THE RADIOFREQUENCY RADIATION CONFERENCE: VOLUME 2

in activity, with the maximum degree of enhancement of enzyme activity occurring with an amplitude
modulation of 16  Hz,

       Many laboratories have now observed increases in the enzyme omithine decarboxylase in cultured
cells following exposure to a variety of electromagnetic fields (Table 1) (18-22). At least six separate
laboratories have observed changes in ODC activity comparable to what is reported here when monolayer
cultured cells were exposed to a number of ELF exposure paradigms including pulsed electromagnetic
fields, amplitude modulated 450 MHz fields, 60 Hz electric fields, and 50-65 Hz electromagnetic fields,
The general observations made by all  these investigators was that: only relatively "low-energy athermal
fields" were required to cause these changes in this enzyme, only a reasonably  short (in the hour range)
time of field exposure was required to change the activity of the enzyme and there was a variety of cell
types that were sensitive to field-mediated changes in ODC activity. For these reasons, changes of ODC
activity  following field exposure could be used  as  a convenient "marker" for assaying the "field
responsiveness" of a given cell or tissue. By using changes  in ODC activity as an endpoint, various
combinations of frequency, dose, time, magnetic vs. electric parameters, could be interrelated in terms of
defining which aspects of ELF exposure are the most critical and important in terms of causing cellular
responses.  Taken in total, the results described in Table 1 alone argue persuasively that mammalian cells
are capable of sensing and responding to "low-energy" ELF.
                                           Table I
                   Studies Reporting Alterations in Ornithine Decarboxylase
                      Activity Following ELF Exposure in Cultured Cells
Authors
Somjen et al, 1983 (18)


Cain et al., 1985 (19)


Byus et al., 1985 (5)



Byus et al., 1987 (6)


Litovitz et al., 1991 (20)


Mattson et al., 1992 (21)

Cain et al., 1993 (22)
Field

pulsed electric field


pulsed magnetic field


AM, 450 MHz



60 Hz electric field


55 and 65-Hz EMF


50 Hz EMF

60 Hz EMF
Cell Type

primary bone
cells

primary bone
cells

H35 hepatoma,
294T
melanoma

H35 hepatoma,
CCM, P3

L929
fibroblasts

HL-60

C3H/10T 1/2
fibroblasts
       The molecular mechanism responsible for the ELF induced alterations in ODC activity appear not
to involve any transcriptional events.  In the data presented here,  Figure 3 and in reference 21, ELF
exposure which caused consistent reproducible changes in intracellular ODC activity failed to alter the
level of ODC-specific mRNA in  these cells.  Current data indicate  that a highly significant mechanism
for the rapid and marked changes in intracellular ODC activity involve polyamine-mediated stimulation

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                                ODC ACTIVITY: A CELLULAR RESPONSE TO LOW-ENERGY EMF (BVUS)   117

or modulation of ODC degradation potentially involving another protein and termed the "ODC antizyme"
(23).  It is believed that changes in product polyamine levels feedback through at least one other protein
to lead to the inhibition/degradation of ODC protein controlling the amount of polyamine produced at any
given time (4).

       For this reason we believe that our recent observations concerning the ability of the low-frequency
amplitude-modulated RF field to significantly alter the export or efflux of putrescine from the cell (Figure
4) may offer an attractive hypothesis for further investigation concerning the mechanisms involved in field
mediated stimulation of ODC activity.  By effecting the amount of putrescine which is present inside the
cell, field exposure could profoundly influence the activity of ornithine decarboxylase by regulating the
rate of degradation  of this  enzyme.  We are  concentrating our efforts  on understanding the role that
putrescine export plays in the regulation of ODC activity, and characterizing the molecular nature of this
export system more  fully  so that we  can investigate the specific manner in which ELF interacts with the
export system.

       Does the observation that ELF causes changes in ODC activity in many different cell types allow
a better understanding of any potential deletory health effects of ELF exposure in the human population?
This is a very difficult and very important question.  In terms of the cancer process as studied in a variety
of animal models, changes in ornithine decarboxylase activity have been linked to the "promotion"  phase
of tumorigenesis by a number of investigators (24-26). Increases in ODC activity in animal tumor models
have been shown to be essential but not sufficient  for the tumorigenic process (25).  A point of interest
is that normally  during the  process  of tumor promotion  induced by various chemicals, the changes or
increases in ODC activity which are observed are of a considerably greater magnitude than what has been
observed for ELF-induced ODC changes.  However, it is difficult to establish meaningful dose-response
relationships between ODC activity changes and tumor incidence using promotional chemicals in animal
models, particularly  at the extremely low end of chemical treatment and  ODC induction.

       Does the fact that low-energy ELF exposure leads to changes in ODC activity  mean that field
exposure is serving as a tumor promoting stimuli in the cell or tissue being observed? This question can
not be answered with the current information  at hand..   There are many examples of chemical stimuli
which will  change ornithine decarboxylase activity yet do not serve as a tumor promoting stimulus (25).
Detailed experiments must be performed to assess the appearance of tumors or a transformation phenotype
using promotion and co-promotion  protocols  in order to determine  the promotional activity of field
exposure  in  relation to  ODC activity.    Recent experiments  in  the mouse model of  epidermal
carcinogenesis, a model where polyamines have been shown to be essential for tumorigenesis, have shown
a potential copromotional effect of 60-Hz magnetic fields (27-28).  Statements suggesting that there can
be no deleterious health effects from low-energy ELF exposure because there can  be no "effects" of ELF
exposure are  arguably incorrect.

       Further research into the molecular biophysical mechanisms of field, cell, and tissue interactions,
a better understanding of the basic science involved in the process of transformation, studies using tumor
endpoints involving  promotion and co-promotional effects of ELF field exposure in animal models, and
further studies of an epidemiological nature,  will all be necessary to provide an  accurate health  risk
assessment for environmental effects of electric and magnetic field exposure.  Unfortunately, given the
complex nature  of these phenomenon, such answers will not be forthcoming in a short  period of time.
However, these questions will ultimately be answered if not ignored.

       This work was supported by the Department of Energy, Office of Energy Storage and Distribution,
Contract DE-AI01-85CE76260 and by the NIH RO1 ESO6128.

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118  SUMMARY AND RESULTS OF THE RAD1OFREQUENCY RADIATION CONFERENCE: VOLUME 2

REFERENCES

1. Pegg, A.E. (1986)  Biochem. J. 234: 249-262.

2. Tabor, C.W. and Tabor, H. (1984) Ann. Rev. Biochem. 53: 749-790.

3. Wu, V.S., Donato,  NJ. and Byus, C.V. (1981) Cancer Res. 42: 3384-3391.

4. Van Daalen Wetters, T., Macrae, M, Brabant, M. Sittler, A. and Coffino, P.  (1989) Mol. Cell. Biol.
       9: 5484-5490.

5. Byus, C.V., Kartun, K., Peiper, S. and Adey, W.R. (1988)  Cancer Res. 48: 4222-4226.

6. Byus, C.V., Pieper, S.E. and Adey, W.R. (1987) Carcinogenesis 8: 1385-1389.

7. Byus, C.V. (1990)  Acute Myelogenous Leukemia: Progress and Controversies, pp. 51-60 (Wiley-Liss,
       Inc.).

8. Wu, V.S.  and Byus, C.V. (1984) Biochim. Biophys. Acta 804: 89-99.

9. Byus, C.V. and Wu, V.S. (1991) J. Cell. Physiol. 149: 9.

10. Chomzcynski, P. and Sacchi, N. (1987) Analytical Biochem. 162: 156-159.

11. Gilbert, R.S., Gonzalez, G.G., Hawell III, L. and Byus, C.V. (1991)  Anal. Biochem.  199: 86-92.

12. Goodman, R., Bassett, C.A.L. and Henderson, A.S. (1983) Science 220: 1283-1285.

13. Goodman, R., Wei, L.-X., Xu, J.-C. and Henderson, A. (1989) Biochim. Biophys. Acta 1009: 216-220.

14. Phillips, J.L., Haggren, W., Thomas, W.J., Ishida-Jones, T,  and Adey, W.R, (1992) Biochim. Biophys.
       Acta 1132: 140-144.

15. Heby, I.  and Persson, L. (1990) TIBS 15: 153-158.

16. Wallace, H.M. and Keir, H.M. (1981) Biochim. Biophys.  Acta 676: 25-29.

17. McCormick, F. (1978) Biochem. J. 174:  427-432.

18. Somjen,  D., Yariv, M., Kaye, A.M., Korenstein, R.. Fischler, H. and Binderman, I.  (1983) Adv.
       Polyamine Res. 4: 713-718.

19. Cain, C.D., Donato, N.J., Byus, C.V., Adey, W.R, and Luben, R.A.  (1986)  International Conference
       on Electric and Magnetic Fields in Medicine and Biology, pp. 9-13.

20. Litovitz, T.A., Krause, D. and Mullins, J.M. (1991) Biochem. Biophys. Res. Commun. 178: 862-865.

21. Mattsson, M.-O., Mild, K.H. and Rehnholm, U. (1992)  Proceedings of the First World Congress for
       Electricity and Magnetism in Biology and Medicine, p. 44.

22. Cain, C., Thomas, D.L. and Adey, W.R. (1993) Carcinogenesis  14: 955-960.

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                               ODC ACTIVITY: A CELLULAR RESPONSE TO LOW-ENERGY EMF (BYUS)  119

23, Porter, C.W., Pegg, A.E, Granis, B.M., Adhabala, R. and Bergeron, RJ. (1990) Biochem. J. 268:207-
       212.

24. Gonzalez, G.G. and Byus, C.V. (1991) Cancer Res. 51: 29-35.

25. Reiners, JJ. Pavone, A., Rupp, T. and Canto, A.R. (1990) Carcinogenesis 11: 128-137.

26. Takigawa, M., Verma, A.K., Simsiman, R.C. and Boutwell, R.K. (1983) Cancer Res. 43: 3732-3738.

27. Stuchly, M.A., Lecuyer, D.W, and McLean, J. (1991) Bioelectromagnetics 12: 261-271.

28. McLean, J.R.,  Stuchly, M.A., Mitchel, R.E., Wilkinson, D., Yang, H., Goddard, M., Lecuyer, D.W.,
       Schunk, M., Callary, E. and Morrison D. (1991) Bioelectromagnetics 12: 273-287.

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                                           TECHNICAL REPORT DATA
                                  (Please read Instructions on the reverse before completing)
 1. RfPORTNO.

  402-R-95-0-11
                                                                         3, RECIPIENT'S ACCESSION NO,
4. TITLE AND SUBTITLE
  Summary  and  Results  of  the  April  26-27,  1993
  Radiofrequency Radiation  Conference
  Volume  2:   Papers
                                                        5. REPORT DATE

                                                          4(95	
                                                        6. PERFORMING ORGANIZATION CODE
7. AUTHOFMS)
 USEPA
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                                                        14, SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
 ,. ABSTRACT ,
      On ApriHz6and 27., 1993, the U.S. Environmental Protection Agency (EPA) Office of Air
and Radiation and Office of Research and Development held a conference to assess the current
knowledge of biological and human health effects of radtefreijuency (RF) radiation and to; address;
the need for and potential impact of finalization of federal guidance on. human exposure ,to -RF,
radiation.  More than 200%people attended the conference. Attendees represented the federal
government, academia, the private sector, trade associations, .the media, and the public.  plenary
papers presented at the meeting focused on current research findings on a variety of topics,' including
exposure assessment,, dosimetry, biological effects, epidemiology, (the basis; for exposure limits, and
emerging health issues. Panel discussions focused on identifying key scientific information needsfor
and the policy implications Of the development of further EPA guidance on human exposure to RF
radiation. <9HHHBPIi Volume 1, provides a record of much of the information presented at the
conference, outlines key recommendations provided to EPA by conference participants, and presents
the EPA strategy for addressing RF radiation.  Volume 2*pHiBp(^BW*HBSprovides the plenary
papers presented by invited speakers.

      Two jcey  conclusions emerged from the conference:  (1) there is sufficient information on
thermal exposure/effects on which to base an RF radiation exposure standard; and (2) EPA should
develop some type of RF radiation exposure guidelines.' These conclusions were considered by EPA
in its decision to proceed with the development of guidelines on buman exposure to RF radiation and
to  develop a longer term strategy to address  remaining issues. Part of this strategy ha? involved
creating an inter-agency work group and requesting the National Council on Radiation Protection
(NCRP) to  assess several remaining issues. Information  provided at the conference also was used
as  a basis for EPA comments to the Federal Communications Commission (FCC) 1993 proposal to
adop| the RF radiation exposure guidelines developed in  1992 by the American National Standards
Institute'fANSI) and the Institute for Electrical and Electronics Engineers (IEEE).  :	
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