United States
       Environmental Protection
       Agency
            Region 10
            Radiation Program M/S 533
            1200 Sixth Avenue
            Seattle WA 98101
       Air & Hazardous Materials   February 1979
&EFK
Population Exposure to
VHP
Broadcast Radiation
In the Seattle and Portland
Metropolitan Areas

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               POPULATION EXPOSURE TO VHP BROADCAST RADIATION
                                   IN THE
                  SEATTLE AND PORTLAND METROPOLITAN AREAS
                               Edward Cowan*

                                    and

                             Richard A. Tell**

                                 July 1979
              U.S. Environmental Protection Agency - Region 10
                     Air & Hazardous Materials Division
                          Waste Management Branch
                             1200 Sixth Avenue
                         Seattle, Washington  98101
 *Radiation Representative, EPA - Region 10

**Physicist, Electromagnetic Radiation Analysis Branch
  Office of Radiation Program, P.O. Box 18416,
  Las Vegas, Nevada  89114

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             Population Exposure to VHP Broadcast Radiation
                                 in the
                Seattle and Portland Metropolitan Areas
Introduction
The U.S. Environmental Protection Agency (EPA) conducts a nationwide
program of monitoring and assessment of radiofrequency (RF) and
microwave (MW) levels as they relate to the potential for hazards in
the environment.  EPA began measuring RF and MW radiation in urban
areas in 1975 as part of a program to determine the need for standards
to control environmental radiofrequency exposure.  Current population
exposure levels will be a major factor in determining if guidance is
needed to limit population exposure.  Seattle, Washington and Portland,
Oregon were among 15 metropolitan areas surveyed for environmental
levels (Table 1).  This report provides the results of environmental
measurements for the Seattle and Portland metropolitan areas and
presents estimates of population exposure based upon the
measurements.  Measurements were made in urban areas because sources
are concentrated in and around regions of high population density.
Broadcast bands are the principal bands of interest with other bands
contributing insignificantly to general environmental levels of
radiofrequency radiation.

The measurement system is installed in a 27 foot van.  The system
consists of seven antennas, and a scanning spectrum analyzer
interfaced to a minicomputer data acquisition system.  Antennas are
mounted on a telescoping mast which is elevated about six meters above
ground level.  Signals from the antennas are detected by the spectrum
analyzer then digitized and processed by the minicomputer with data
correction and analysis routines.  A computer algorithm uses these
measurements to estimate the broadcast exposure for census enumeration
districts within the metropolitan boundaries.

Nonionizing Radiation Sources

Virtually everyone is exposed to radiofrequency waves.  Nonionizing
sources of interest include the following:

   - radio and television broadcast stations

   - radars

   - satellite communications system earth terminals

   - point to point microwave communications

   - mobile communications systems

   - microwave ovens

   - industrial heating equipment
                               -1-

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This paper is concerned only with nonionizing radiation from radio and
television broadcast radiation.  Ionizing radiation is a different
kind of radiation which is produced by medical, dental, and industrial
x-ray equipment and by radioactive materials which emit particles such
as protons, betas, neutrons and alphas.

Previous studies have determined that FM radio and VHP and UHF
television transmissions are responsible for almost all of the RF and
MW exposure in the general environment.  Table 2 summarizes the
broadcast bands for which data is presented in this report.  Though
field intensity measurements were also performed in the AM standard
broadcast band (0.54-1.6 MHz), these data are not considered here
because of significantly decreased absorption of these lower
radiofrequencies by the human body.  No UHF television stations
operate in Seattle or Portland.  The frequency range of the surveyed
sources was from 54 to 216 megahertz.

Effects of Nonionizing Radiation

Radiofrequency radiation can be absorbed by tissue and can interact
with biological systems.  Absorption depends on the radiation
wavelength and its relationship to the physical shape, size and
orientation of the body to the incident electromagnetic field,
electrical characteristics of the body tissues at specific frequencies
and the intensity of the radiation.  Localized heating or nonuniform
absorption can occur in humans because the complex tissue structure
absorbs energy differently in different parts of the body.

Two kinds of effects on humans due to exposure to radiofrequency
radiation are usually discussed: thermal effects from high-level
exposures, and possible low-level or "nonthermal" effects.

Thermal effects, normally thought to result from irradiation with
power densities above 10,000 microwatts/square centimeter (uW/cm2)
involve tissue heating with the possibility of thermal damage.  They
may include increased body temperature and resulting heat stress,
cataract formation, and testicular effects. (Table 3)

Low-level effects are a subject of controversy.  Effects of exposure
to 1,000 (uW/cm2) or less have not been well documented.  In fact, all
U.S. scientists do not agree that they exist.  Some Russian scientists
believe that they occur, but as a result of nonthermal effects or
effects which occur without an increase in tissue temperature.  Their
views are based on animal research and statistical studies of workers'
exposure histories and medical records.  Considered to be mainly
central nervous system effects, symptoms attributed to low-level
nonthermal exposure include headache, weariness, dizziness,
irritability, emotional instability, partial loss of memory, loss of
appetite, cardiovascular effects, blood chemistry changes, changes in
respiration, and possible genetic effects.
                               -2-

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While U.S. scientists are skeptical of the conclusions of the Eastern
European experts, there has been little research conducted in the U.S.
involving long term exposures to low-level microwave and
radiofrequency radiation.  Some U.S. scientists believe that the
effects observed, could result from non-uniform energy distributions
and very small localized temperature changes in the body.

Exposure Standards

At present, there are no Federal standards or guides for controlling
environmental levels of radiofrequency waves in the U.S.   There is an
advisory standard for occupational exposure issued by the Occupational
Safety and Health Administration.  This advisory standard specifies an
upper limit of 10,000 uW/cm2 for exposure durations greater than 6
minutes and allows higher values for shorter durations.  (Table 4)

The U.S.S.R has the most conservative standards with an occupational
limit of 10 uW/cm2 and a general environmental exposure limit of one
uW/cm2. Canada, Great Britian and West Germany have occupational
exposure standards similar to those of the U.S.  Canada is considering
a general population standard of 1,000 uW/cm2.  The U.S.S.R.'s more
restrictive occupational and general population standards are
presumably based upon the occurrence of nonthermal effects while the
U.S. and most Western European standards are based upon thermal
effects without consideration of possible nonthermal effects.

Population Exposure in Seattle and Portland

Population exposure to nonionizing radiation means the number of
people exposed to various levels of power density.  To obtain
population exposure, two kinds of information are required; the
distribution of the population and the distribution of power densities
in the area of interest.  The population is obtained through the use
of the Census Bureau's Census Enumeration Districts (CED) and power
densities are measured using EPA's electromagnetic radiation analysis
van.  Measurements were taken at 35 sites in metropolitan Seattle and
at 38 sites in Portland.  The measurement data was subsequently used
in a computer modeling program to estimate the exposure which would
exist at each CED in Seattle and Portland.  Resulting exposure at each
CED is assumed to apply to all the population within each CED.  Final
results are presented in terms of the accumulative fraction of the
population which are exposed to certain power density levels.  Summary
field study information is presented in Table 5.

Table 6 lists each measurement location in Portland with the determined
power density.  Table 7 does the same for the Seattle area.  The
geographic location of all measurement locations are shown for
Portland and Seattle on Maps 1 and 2.  The location numbers in Tables
6 and 7 correspond to location numbers used on Maps 1 and 2.

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Table 8 shows the fraction of Portland population exposed as a
function of power density for FM radio, high VHP, low VHP television
transmissions and the total exposure from all of these.  Table 9 does
the same for the population of Seattle.  It can be seen that FM radio
broadcast transmissions create the highest ground levels of field
intensity and is clearly most responsible for overall exposure.
Conversely, the high VHP and low VHP television transmissions make
relatively small contributions to the total power density.

The results of the Seattle and Portland survey are presented in Table
10.   Three different indices can be used to discuss the results.  The
first is the median exposure, that level to which 50 percent of the
population are exposed less than and 50 percent are exposed to more
than.  The other indices are the percent of the population exposed to
less than 1 uW/cm2 and the percent of the population exposed to more
than 10 uW/cm2.   In Seattle the median exposure level is 0.007 uW/cm2
which is exactly the median level for 10 other cities previously
surveyed.  The median exposure level for Portland is higher but is
still only 0.020 uW/cm2.  In both Seattle and Portland over 99 percent
of the population is exposed to less than 1 uW/cm2.  Only a small
fraction of the population is exposed to more than 10 uW/cm2, 0.001
percent in Seattle and 0.016 percent in Portland.

The highest power density level in Portland was measured at site
number 13.  This level, 153 uW/cm2, was determined directly under a
transmitter so the exposure levels in nearby houses would be somewhat
lower.  Site number 36 taken on Cougar Mountain had the highest power
density level in the Seattle survey.  The power density level of 87
uW/cm2 was not included in the Seattle results because the site was
outside the area used for calculating population exposure.  Cougar
Mountain was a specific source type of measurement because of its
location and the few people affected.

Summary

Environmental power densities have been measured and the population
exposure estimated for the Seattle and Portland metropolitan areas.

FM radio transmitters are the most significant environmental sources
of nonionizing radiation.

In Seattle, 99.81 percent of the population is exposed to less than 1
uW/cm2 and only 0.001 percent of the population is exposed to over 10
uW/cm2.

In Portland, 99.70 percent of the population is exposed to less than 1
uW/cm2 and only 0.016 percent of the population is exposed to over 10
uW/cm2.

There are no Federal standards or guides for controlling envirnomental
levels of radiofrequency waves in the U.S.  However, the environmental
exposure levels for over 99 percent of the population in Seattle and
Portland would meet the very restrictive U.S.S.R. standard of one
uW/cm2.
                                -4-

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                      Table 1.  Environmental Surveys
                             Survey Period             Sites Surveyed
Portland                     7/25-8/5 1977                     38
Seattle                      7/10-7/21 1978                    35
                   Table 2.  Frequency Range of Measured
                              Broadcast Bands
Frequency*                             Use
  54-88                                Low VHF Television Broadcast
  88-108                               FM Broadcast
 174-216                               High VHF Television Broadcast

* Megahertz (millions of cycles per second)
                               -5-

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Table 3
                         EFFECTS OF NONIONIZING RADIATION

               Pain Threshold in Humans
          830
          150
           100
           60
      oc
      UJ

      tL

      5
      P
      z
      UJ
      O
      LU
      GC
      <
      D
      O
      CO
      oc
      i
 25
13.0
10.0
               Cataractogenic Threshold in Rabbits
               Warmth Sensation Threshold in Humans
           Aversive Reaction in Rats
     Warmth Sensation Threshold in Humans
                                                   Thermal Effects
                                                   Dominate
           5.0
                                                   Area of Uncertainty

                                                   For Transient

                                                   Behavioral Changes
           1.0
      OC   0.3
      D
      0)
      O
      Q.   0.2
      X
      111

           0.1
          0.02
          0.01
         0.001
                                                   Possible
                                                   Nonthermal Effects
     Avoidance Behavior in Rats
    .Evoked Auditory Response Threshold in Humans
               Evoked Auditory Response Threshold in Cats

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Table 4
              NONIONIZING RADIATION STANDARDS
          10.0'
                                          .U.S. Standard for
                                          Occupational Exposure
      OC
      UJ
       UJ
       O
       UJ
       OC
       <
       D
       O
       (/>

       OC
       UJ
       Q.

5.0
           1.0
                                                     FDA Standard for
                                                     Microwave Oven
                                                     Leakage
           0.1
       UJ
       OC
       D
       (/)
       O
       Q.
       X
       UJ
0.01
USSR Standard for
Occupational Exposure
          0.001
                                          USSR Standard for
                                          ' General Population Exposure

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            Table 5.  Summary of Field Study Information
                              No. Field
                                                   No.  of Stations
          CED's     Population    Strength Values  FM

Seattle   1315      872,442           820          16    2
Portland  1194
                818,040
816
12
                                                            VH   Total
                                                                 20
18
No. of
Sites

35


38
Radio-frequency detection van on display at University of Washington.
                                     -8-

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Table 6        Power Density Measurements  for  Portland Area
                     (microwatts per square  centimeter)
Site Location Number                                 Total Power Density

        1                                                     .0109
        2                                                     .0101
        3                                                     .0258
        4                                                     .0651
        5                                                     .0334
        6                                                     .1090
        7                                                     .0549
        8                                                     .0149
        9                                                     .0775
       10                                                     .0991
       11                                                     .0726
       12                                                     .1090
       13                                                  153.7900
       14                                                     .5000
       15                                                    1.0600
       16                                                     .1660
       17                                                     .1140
       18                                                     .5330
       19                                                  16.4600
       20                                                     .5620
       21                                                     .1190
       22                                                     .2850
       23                                                     .1200
       24                                                     .1300
       25                                                     .1070
       26                                                     .0270
       27                                                     .0272
       28                                                     .0440
       29                                                     .0757
       30                                                     .0158
       31                                                     .0426
       32                                                     .0236
       33                                                  14.2600
       34                                                     .0172
       35                                                     .0826
                                                              .0295
                                                              .0686
                                                              .0239
                                       -9-

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          Table 7    Power Density Measurements  for Seattle Area


Site Location Number                                   Total Power Density

          1                                                      .0872
          2                                                      .1450
          3                                                      .3200
          4                                                      .1650
          5                                                      .1730
          6                                                      .1650
          7                                                      .1910
          8                                                      .4330
          9                                                    1.4000
         10                                                    6.5300
         11                                                   22.7400
         12                                                    1.1900
         13                                                      .4340
         14                                                      .0175
         15                                                      .0315
         16                                                      .0685
         17                                                      .1170
         18                                                      .0576
         19                                                      .0555
         20                                                      .0264
         21                                                      .0224
         22                                                      .5010
         23                                                   26.6000
         24                                                      .8660
         25                                                    6.0400
         26                                                      .0195
         27                                                      .0280
         28                                                      .0949
         29                                                      .0093
         30                                                      .1180
         31                                                      .1930
         32                                                      .0207
         33                                                      .0270
         34                                                      .1130
         35                                                      .0337
         36                                                   87.9000
                                        -10-

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MAP 1:  MEASUREMENT LOCATIONS IN THE PORTLAND AREA
                                                                Scale in Miles
                                                              12345
O
                                                             Less than one microwatt
                                                             per square centimeter

                                                             Greater than one microwatt
                                                             per square centimeter

                                                             Greater than five microwatts
                                                             per square centimeter
     O

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MAP 2: MEASUREMENT LOCATIONS IN THE SEATTLE AREA
                                                    Greater than one microwatt
                                                    Greater than five microwatts
                                                    per square centimeter

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                       FRACTION OF POPULATION EXPOSED
                       AS A FUNCTION OF POWER DENSITY
                                                                    Q>
                                                                    cr
                                                                                          00
.99




.95


.90


.80

.70
3  .60

&>
-  .40
U.
O  .30
z
O  .20
   .10
   .05
   .01
      PORTLAND
                                        0
                                    o
              1
                    n

                    A
                                             D
                                    n
                                    A
                                                    B
                                                 S
                                                                      A  Total Exposure
                                               D  FM Radio

                                               O  High VHF TV

                                                 Low VHF TV
             .00001
.0001        .001        .01        .1
             POWER DENSITY
     (Microwatts per square centimeter)
                                                                      10
                                                                               100

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                 FRACTION OF POPULATION EXPOSED
                 AS A FUNCTION OF POWER DENSITY
                                                                          0)
                                                                          z
                                                                          
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                 Table 10.  Population Exposure Results for
                  Seattle, Portland, and Ten other Cities
Location
Median Exposure
Percent of Pop
Exposed to Less
Than 1 microwatt
Percent of Pop.
Exposed to More
than 10 microwatt
Seattle
Portland
Ten Cities
.007
.020
.007
99.81
99.70
99.33
.001
.016
__ _
Radiofrequency detection equipment and minicomputer inside equipment van
                              -15-

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                                    REFERENCE
1. Tell, R.A. and E.D. Mantiply, "Population Exposure to VHP and  UHF  Broadcast
   Radiation in the United States," Technical  Note,  ORP/EAD 78-5,  U.S.
   Environmental Protection Agency, Las Vegas, NV
   June 1978

2. Athey, T.W., R.A. Tell, N.N. Hankin, D.L. Lambdin, E.D.  Manitiply, and
   D.E. Janes, "Radiofrequency Radiation Levels and  Population Exposure
   in Urban Areas of the Eastern United States,"  Technical Report,
   EPA-520/2-77-008, U.S. Environmental Protection Agency,  Silver Spring,
   MD, May 1978

3. Tell, R.A., "A Measurement of RF Field Intensities in the Immediate
   Vicinity of an FM Broadcast Station Antenna,"  Technical Note,  ORP/
   EAD-76-2, U.S. Environmental Protection Agency, Silver Spring,  MD,
   January 1976.

4. Tell R.A.  and P.J. O'Brien,  "An Investigation of Broadcast Radiation
   Intensities at Mt. Wilson, CA."  (ORP/EAD-77-2),  U.S. Environmental
   Protection Agency, Las Vegas, NV, April 1977.

5. Tell, R.A., "An Analysis of  Radiofrequency and Microwave Absorption
   Data With Consideration of Thermal  Safety Standards," Technical  Note,
   ORP/EAP-78-2,  U.S. Environmental Protection Agency,  Las Vegas,  NV.
   April 1978.

6. Radiological Quality of the Environment in the United States,  1977.
   U.S. Environmental Protection Agency, Office of Radiation Programs,
   Washington, D.C.  20460.

7. Radiation Protection Activities 1977.  U.S. Environmental Protection
   Agency, Office of Radiation Programs,  Washington D,C. 20460
                                        -16-

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