RP/SID72-
  NATURAL RADIATION  EXPOSURE
         IN  THE  UNITED STATES
S. ENVIRONMENTAL PROTECTION AGENCY
     Office of Radiation Programs

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  The mention of commercial products or their use in connection with
material reported herein is  not  to  be construed us either an actual or
implied endorsement by t!>p Environmental Protection Agency.

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NATURAL RADIATION EXPOSURE
     IN THE UNITED STATES
            Donald T. Oakley
               June li>7-2
 U.S. ENVIRONMENTAL PROTECTION AGENCY
         Office of Radiation Program*
       Surveillance and Insertion Division
          Washington, D.C. '20460

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                                  FOREWORD
    The Office of Radiation Programs of the Environmental Protection Agency carries
out a national program designed to evaluate  population  exposure  to  ionizing and non-
ionizing radiation and to promote development of  controls necessary  to  protect  public
health and safety.
    Within the Office of Radiation Programs, the Surveillance and Inspection Division
conducts programs  relating to sources and levels of environmental radioactivity  and the
resulting population radiation dose. Reports of the findings are published in the monthly
publication Radiation Data  and  Reports, appropriate scientific journals,  and Division
technical reports.
    The technical reports of the Surveillance and Inspection Division allow comprehen-
sive publication of the results of intramural and contract projects and, as in the case of
the present report,  of studies supported by the  Division. The reports are distributed to
State and local radiological health agencies, Office of Radiation Programs technical and
advisory committees, universities, libraries and information services, industry, hospitals,
laboratories, and  other interested groups and  individuals. They are also included  in the
collections of the  Library of Congress and the National Technical Information Service.
    Readers of these reports are encouraged to inform the  Office of Radiation Programs
of any omissions or errors. Comments or requests for further information are also invited.
                                                            W. D. Rowe
                                                   Deputy Assistant Administrator
                                                       for Radiation Programs
                                                                                        in

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                           ACKNOWLEDGMENTS
    My deepest gratitude is extended to my thesis advisors: Bade W.  Moeller, principal
advisor,  Abraham  S.  Goldin, and  Robert  B.  Reed, members of the faculty of the
Harvard School of Public Health. Special thanks are due Dr. Moeller for his patient guid-
ance which  led to the thesis  topic and for his  attention to my problems and  progress
throughout the preparation of the thesis. I am especially grateful to Dr. Reed for his
numerous suggestions  for improving  the interpretation and  presentation of the  data.
and to Dr.  Goldin  for his thorough review of my work "and  for  his wise counsel that
helped me to steer clear  of contradictions and other pitfalls. Above all, I am apprecia-
tive of the many instances of kindness and wit which  accompanied  suggestions from  all
three  advisors. Although not  an advisor, Jacob Shapiro contributed substantially to my
understanding of natural radiation exposure through his teaching at the School of Public
Health, and I gratefully acknowledge  his help.

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                                       CONTENTS
Chapter                                                                              pa£,<,

          FOREWORD 	    iii
          ACKNOWLEDGMENTS 	     v
          LIST OF FIGURES 	    ix
          LIST OF  TABLES  	    xi
          ABSTRACT 	   xiii
                                                          r

    1.    INTRODUCTION 	     1
          1.1.  General 	     1
          1/2.  Estimates of natural radiation exposure 	     1
          1.3.  Sources of natural radiation exposure 	     2
          1.4.  Methology 	     3
          COSMIC  RADIATION  	
          2.1. Introduction 	
             2.1.1. Galactic- radiation
             2.1.2. Solar radiation  ...
          2.2. Cosmic ray variation  	
             2.2.1. Time  variations  	
             2.2.2. Latitude  variation	     7
             2.2.3. Altitude  variation 	     S
          2.3. Cosmic ray measurements	     9
             2.3.1. Ionizing component	     9
             2.3.2. Neutron component	    10
          2.4. Population  distribution  	'.	    11

    3.    TERRESTRIAL RADIATION EXPOSURE	    13
          3.1. Sources  	    13
          3.2. Variations in terrestrial radiation 	    17
             3.2.1. Radon daughter  products 	    17
             3.2.2. Moisture  and snow cover 	    1?
          3.3. Measurements   	    19
             3.3.1. Ground surveys  	    19
             3.3.2. Dose equivalent rate due to fallout 	    21
             3.3.3. Aerial surveys	    22
                                                                                         VII

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Chapter                                                                                 Page
     4.    NATURAL RADIATION EXPOSURE  OF THE U.S. POPULATION	    33
          4.1. External  sources  	    33
          4.2. Attenuation of external sources 	    33
              4.2.1. Housing   	    35
              4.2.2. Biological shielding	    35
          4.3. Internal sources	    36
          4.4. Dose equivalent to the gonads and bone marrow	    36
          4.5. Discussion	    37
          SUMMARY 	    41
          REFERENCES  	    4.3
          APPENDICES  	    47
              Appendix A. Calculation of average dose equivalents due to terrestrial and
                           cosmic radiation 	    49
              Appendix B. Effect of building materials on exposure 	    65
              Appendix C. Calculation of  2o- error of total dose  equivalent 	    67
vm

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                                   LIST  OF  FIGURES
Figure                                                                                       Pazp
   1    Formation of cosmic ray secondary products 	     f,
   2    Cosmic ray ground level measurements during a 3+  flare Yakutsk, F.S.S.R., 51° geo-
        magnetic  latitude 	     f>
   3    Variation of cosmic  radiation with latitude	     7
   4:    Cosmic ray dose equivalent rate variation with altitude	     *
   5    Summary of sea-level ionization cine to cosmic radiation	     9
                                                             t
   6    Cosmic ray dose equivalent vs. elevation 	    10
   7    Population distribution, 1960 	    11
   8    Dose equivalent from cosmic radiation 	    12
   9    Ionization  vs. date and local time (PST) on offshore drilling platform near Hunting-
        ton Beach, Calif 	    !•*
  10    Decrease in gamma radiation with depth of snow cover at three different densities	
  11    Dose equivalent rate due to fallout in the United States, 1958-1971	
  12    Aerial radiological measuring surveys	    -?>
  13    Dose equivalent rates in ARMS areas 	    -26
  14    Dose equivalent from terrestrial sources based on population-weighted ARMS data ....    30
  15    Dose equivalent from terrestrial sources in Coastal and non-Coastal Plain region? 	    31
  16    Population distribution vs. dose equivalent  from terrestrial and cosmic radiation  	    :U
  17    Cumulative distribution of population vs. dose equivalent from terrestrial and cosmic
        radiation   	    ;^>

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                                    LIST  OF  TABLES
Table                                                                                       Pasf.
   1    Estimates of dose equivalent due to terrestrial and cosmic radiation in several countries     2
   2    Summary of sea-level ionization due to cosmic radiation at U.S. latitudes  	     9
   3    Cosmic ray neutron dose equivalent at sea level	    10
   4    Cosmic radiation dose equivalent at sea level	    10
   5    Distribution of the U.S. population vs. elevation (1960) 	    11
   6a   Uranium-238 decay chain—uranium series {4n + 2)	    14
   6b   Thorium-232 decay chain—thorium series (4n)  	    15
   7    Gamma-ray energy released by 1 gram of rock (lithosphere) 	    15
   8    Types of bedrock in the contiguous United States	    16
   9    Radionuclide content  and dose equivalent rates from common rocks and  soil  	    16
  10    Ground surveys of background radiation in the United States	    20
  11    Dose equivalent measurements in 24 States 	    21
  12    Population in ARMS areas	    24
  13    Dose equivalent rates  in areas on or straddling the Coastal Plain	    2!>
  14    Dose equivalent rate from terrestrial sources based on population-weighted ARMS data    ?s2
  15    Dose equivalent outdoors from terrestrial and cosmic radiation	    34
  16    Ratio of indoor to outdoor dose equivalent 	    35
  17    Gonadal dose  equivalent to the U.S. population from natural radiation  	    37
  18    Estimate of errors in  determining  the gonadal equivalent	    3S
 A-l    Calculation of average dose equivalents  due to terrestrial and cosmic radiation by
        State urbanized and nonurbanized areas	    j°
 A-2    Total calculation of average dose equivalents due to terrestrial and cosmic radiation by
        States  	    60
 A-3    Program  to calculate average dose equivalents from terrestrial and cosmic radiation ....    61
 C-l    Evaluation of partial derivatives in error calculation 	    6>

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                                   ABSTRACT
    The exposure of man to natural radiation sources in the United States has been esti-
mated by  considering the distribution of the population with respect to certain factors,
principally geology and elevation, which influence  exposure to terrestrial  and  cosmic
radiation. Data obtained by aerial surveys in the United States have been used to calculate
an  average dose equivalent (DE)  estimate of 40 mrem/yr. to the population. The results
also indicate three distinct areas of terrestrial radioactivity in the United States—(1)
the Coastal Plain, which consists of all or portions  of States from  Texas to New Jersey
(23 mrem/yr.); (2) a portion of the Colorado  Front Range (90 mrem/yr.): and (3) the
rest of the United  States, i.e.,  portions of the United States not included in "1"  or "2"
(46 mrem/yr.).
    Since elevation is the primary determinant of cosmic ray DE in the United States,
the population distribution with respect to elevation was determined. The average pop-
ulation elevation of the United States was determined to be approximately 700  feet, and
the average cosmic  ray DE was estimated to be 44 mrem/yr.
    To arrive at an estimate of the gonadal DE,  the influence of housing,  biological shield-
ing, and the  DE contribution  from internal emitters was also considered. The  first two
factors serve to attenuate man's gonadal DE due to terrestrial radiation by about the same
amount that  is  contributed by internal emitters.  The  average  gonadal  DE to the U.S.
population was calculated to be 88 mrem/yr.
                                                                                       sin

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                   NATURAL RADIATION  EXPOSURE
                            IN THE UNITED STATES '

                                      D
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 Safety Laboratory, U.S. Atomic Energy Com-
 mission  (AEC)  (Beck et al., 1964ab; 1966ab).
 The second category of measurements has resulted
 from special studies, which have been conducted
 primarily for  the  purpose of estimating back-
 ground  radiation  exposure  to the  population.
 Examples of this work include studies in New
 England by  Segall  (1963)  and  Lowder  and
 Condon  (1965), and measurements in 24  States
 by Levin et al. (1968). The third category con-
 sists of aerial surveys which have been performed
 by AEC and its contractors around  nuclear in-
 stallations within the United States.
   In several other  countries, surveys have been
 performed on a countrywide basis for the pur-
 pose  of  estimating the  population exposure to
 natural  radiation   (table 1). The investigators
 have employed different techniques and  instru-
 mentation so that a direct  comparison cannot be
 made. However, even if we consider these factors
 and the  differing  emphasis on  measurements
 (open field  vs. paved areas, indoors  vs. out-
 doors), there is reasonable agreement among the
 estimates.
  Measurements obtained in  the United  States
 will be presented in the following chapters, and it
 will be soon that they are similar to measurements
 obtained in  other countries (table 1). It  should
be  noted that  the  measurements by  Hultqvist
 (1956), Herbst (1964), and Ohlsen (1969) were
made with either ion chambers or portable scin-
tillation  detectors,  and  therefore the  measure-
ments include the contribution of nuclear weapons
 fallout to the total DE. The measurements by
 Herbst, which were made during 1957 to 1959 and
 in 1961, respectively, are probably most in error
 on this account, since fallout contributed as much
 as 30 percent to the total external DE rate during
 thc.se. periods.

 1.3. Sources  of Natural Radiation
     Exposure
  Exposure to external natural radiation sources
 occurs through cosmic radiation and radioactive
 elements in the earth's crust and in building  ma-
 terials. An additional increment of external expo-
 sure, which accounts for less than 5 percent of the
 total, is due to the presence of radioactive decay
 products of radon and thoron in the atmosphere.
  The natural radiation environment  has been
 relatively constant since at  least the beginning of
 the Neolithic Age (10,000 B.C.) and probably for
 much longer. The  most recent reversal  of  the
earth's magnetic field occurred 700,000 years ago,
 and  at that  time the  cosmic  ray  intensity may
 have increased by 10 percent in equatorial regions
of  the earth  for  approximately 1,000  years
 (Black, 1967).  With the exception of short-term
variations in cosmic ray intensity, there is noth-
 ing in the literature to indicate the occurrence of
 significant changes  in natural radiation sources
since the most recent magnetic field reversal.
  Although the intensity  of natural  radiation
sources  has remained  constant in recent times,
man's living  habits have changed  in such a way
       Table 1.  Estimates of dose equivalent due to terrestrial and cosmic radiation in several countries
Reference
Hultqvist, 1956
Herbst, 1964
Yamagata and Iwashi-
ma, 1967
Ohlsen, 1969
Weng and Huang, 1970
Country
Sweden
Switzerland
Japan
E. Germany
Taiwan
Dose equivalent (mean)
(mrem/yr.)
77 wood dwellings
130 brick
197 concrete
122
87
91
112
Remarks
Measurements at centers of rooms in 086 apartments, 677
houses (all indoors); authors values of ion pairs/
cm-'-sec. converted to mrein/j'rt, assuming 1 ion pair/
cm'-si'c. = 1.
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as to  influence  liis  exposure.  Populations have
tended to migrate from coastal to inland areas,
thus increasing  their elevation and exposure to
cosmic radiation. At the same time, the outdoor
agrarian society has largely been replaced by in-
door work and life in urban centers. Man's expo-
sure has thus been  increased  in some instances
because of the natural  radioactivity of building
materials; in other instances, buildings attenuate
exposure to the outdoor terrestrial sources, result-
ing in lower exposure.
  Although this dissertation  is primarily  con-
cerned with external radiation sources, it is im-
portant to note that  additional increments of I)E
result  from ingestion and inhalation  of  natural
radionuclides. Potassium-40 is  the principal  con-
tributor of internal DE: other significant internal
emitters  are  radium-226  and -228  and  their
daughter  products,  carbon-l-t  and  radon-222
(UNSCEAR, 1962). Gonadal exposure  to  ex-
ternal  radiation is about five times greater than
that from internal sources, and the ratio  is simi-
lar for exposure to the bone marrow. With regard
to natural internal  radioactivity, Cherry et al.
(1970) have recently shown that man has rela-
tively  low concentrations  as compared to other
mammals, fish, and birds. In fact, in a comparison
of total alpha activity in the bones of 18 different
mammals, only  the  pig ranked lower  than man.
From  their  analysis of herbivore bones and ma-
rine livers, Cherry et al. predict DE in excess of
1,000 mrem/yr.  to these organs, of which 90  per-
cent or more is due to internal alpha emitters.
  The retention of inhaled radioactive daughter
products of  radon  and thoron  is the primary
source of lung DE to the general population. Al-
though the  inhalation  of  radon  daughters has
been given special attention in the case  of  ura-
nium miners (Federal Radiation Council, 1967),
exposure to  occupants  of residential dwelling
can also be significant. Hultqvist (1956) calcu-
lated a potential average lung dose of 205 mrem/
yr. to  occupants of unventilated wood dwellings
and  1,780 millirem/yr.  to  occupants of unventi-
lated concrete buildings.  More recently,  Veates
et al. (1971) have found that first-floor occupants
of frame dwellings may receive a lung  DE of 150
inrad/yr. from alpha emitters. If a quality factor
of 10 is assumed, then the  DE is 1,500 mrem/yr.
1.4. Methodology

  One of the primary objectives of this .-tudy was
to estimate the external  natural radiation  expo-
sure to the population of the United Stute-. To
do  so,  existing data on  terrestrial and cosmic
radiation  measurements were conMdt-red in Hjrht
of  population distribution  and  living habit,-..
Many measurements made for other purposes con-
tribute information on man's exposure to radia-
tion from natural  sources. For example,  much
of the existing data on cosmic radiation exposure
has resulted from interest in high-energy panicle
reactions or from studies of cosmic ray variation.
  External   exposure to  terrestrial   radiation
sources may  be estimated by direct measurement
or  calculated from chemical assays  of natural
emitters in soil. Ground analyses and soil analyses,
however,  have not  been  sufficiently extensive to
make  an  overall  estimate of exposure in  the
United States. For this  reason, the estimate of
exposure  due to terrestrial sources in this  study
relies  principally  on data from aerial surreys.
The aerial surveys, which were previously men-
tioned, have  been  made over areas  across  the
United States and  all together cover land areas
occupied by approximately 30 percent of the U.S.
population.
  A combined estimate of the total  cosmic  ray
and terrestrial DE was then made in  this  study
cm the basis of what is known concerning the di>-
tribution of the population by elevation, geology,
and living habits.
  Units of radioactivity  have perplexed practic-
ing  health physicists and those  recommending
units since the discovery of ionizing radiation. As
a result, it is common to find units of roentgens,
rads, and  rems used to describe the same thing in
radiation  protection literature. Fortunately,  the
three entities are approximately equal in the case
of ionizing radiation from external natural back-
ground sources, and  therefore the unit of DE,
the rem, is used throughout for the sake of uni-
formity. A full description of dosimetric terms
may be found in Comber (1969} and  the recom-
mendations of the  International Commission on
Radiation  Units  and  Measurements  (ICRU)
(W71).

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                         CHAPTER 2.  COSMIC RADIATION
2.1. Introduction

  Cosmic radiation is composed primarily of ga-
lactic radiation and a varying component of solar
radiation. Galactic radiation originates outside of
our own solar system, and, as the name implies,
solar radiation  results from phenomena  on the
sun.

  2.1.1. Galactic radiation
  The primary component of galactic radiation,
as it impinges on the earth's atmosphere, is esti-
mated to be 75  to 89 percent protons, 10 to 18
percent helium nuclei, and 1 to 7 percent nuclei
with Z ^=3 (UNSCEAR, 1966; Neher, 1967). The
energy range is thought to extend beyond 1019 eV,
and the average energy flux arriving at the top of
the atmosphere is 2 x 103 MeV/cmz-sec. (Korff,
1964). In addition to heavy particulate radiation,
electrons and x  rays have also been detected in
primary cosmic radiation.
  Primary cosmic ray interactions with the at-
mosphere result  in an  ionizing  component  of
cosmic radiation in the lower atmosphere, pri-
marily muons and electrons, and a minor neutron
component.  The process of formation is shown
schematically in figure 1. Of most significance to
population exposure is the formation of muons,
which are generally assumed to account for ap-
proximately 70 percent of the cosmic ray dose at
sea level (Lowder and Beck, 1966).

  2.1.2. Solar radiation
  Particulate solar radiation is comprised almost
entirely of bursts of protons and helium nuclei
with energies ranging up to several GeV. The
proton bursts, or flares, follow approximately 6
percent of the observed sunspots, and about 3 per
 cent of all flares belong to class 3  (the largest)
 (Langham, 1967). As will be discussed later, the
 relatively low energy of the solar particles pre-
 cludes their secondary radiations from  reaching
 the earth's surface in all but the largest flares.
 2.2. Cosmic Ray  Variation

   The factors which contribute to cosmic radia-
 tion variations are extensively reviewed in books
 by Rossi  (1964), Sandstrom (1965), and Haya-
 kawa  (1969). A brief summary  of the present
 knowledge of cosmic ray variations is presented
 here in order to justify the dose estimation pro-
 cedures which follow. In addition, knowledge of
 the many variations which exist is  helpful in
 understanding  rather  large differences in  the
 reported measurements.


  2.2.L Time variations

  The temporal variation of cosmic radiation has
 been observed for approximately  35 years, com-
 mencing with the work of  Forbush (1938). At
 that time, Forbush reported the effect of the "sea-
 sonal  wave" on cosmic ray magnitude and specu-
 lated upon the possibility of the influence of the
 solar cycle on cosmic ray intensity. Research thus
 far indicates that most variations in ground-level
 cosmic ray intensity are attributable to solar influ-
 ence on the interplanetary  magnetic field (For-
bush,  1954,  1958; Kuzmin  and Skrtpin, 1966a;
 Pal, 1967).  In  general, where  variations  are
 attributed to solar influence, the ionization inten-
sity on earth is inversely correlated with st»lar
activity.

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                                          PRIMARY COSMIC RAY NUCLEI
                                          INTERACTION VUTH ATOMS -N
                                            UPPER ATMOSPHERE
                         T= 2.6x10 " SECS.
                                                   7=2<10-'«SECS
                                   i 10 SECS.
                 NUCLEON CASCADES
                 SPAILATION PRODUCTS
                 NEUTRONS
                 ANTI-NUCL60NS
                                                                TJ PIONS
                                                                |/ MUONS
                                                                J) NEUTRINOS
                                                                y G.'.MMA RAYS
                                                                P ELECTRONS
                          Figure 1.  Formation of cosmic ray secondary products
  Variations in cosmic  radiation  have been ob-
served to occur in cycles of 11 years, 1  year, -11
days, and 1 day. and Xeher (It'll)  has  recently
reviewed the evidence for a cycle  which persists
for several  11-year periods. As a  result  of these
variations, the  intensity  of  sea-level ionization at
a given  location may vary by approximately 10
percent.  Based on the  consideration  of cosmic
ray-induced radionuclides  on  the earth and in
meteorites, Hayaka-wa (1969) asserts that average
cosmic ray  levels  have  remained relatively con-
stant for at least 108 years. Maximum levels prob-
ably existed during the reversals of the magnetic
field, the most  recent of which occurred 700,000
years ago, when an  increase of 10 percent may
have occurred  (Black, 1967).
  Solar  flares  occur  more frequently during the
solar maximum period of the  11-year cycle, and
therefore flares are also considered here as a tem-
poral variation. Although  the hazards  to space
travelers during this period are potentially great
(Upton, 1966; Langham,  1967; Haffner,  1967),
the magnetic field of the earth and the shielding
properties of the atmosphere result in little per-
turbation of the sea-level intensity  during a flare.
  According to  Haffner  (1967), eleven  "3 + "
solar flares  (the  largest)  occurred  during the
1958  to  1961 period  of  maximum  solar  activity.
The ground effect of a 3+ flare is shown in fig-
ure 2. Although other flares have had a more pro-
nounced temporary  effect on neutron  levels, the
lack of significant  influence on the ion  chamber
measurement is typical. Following  an  initial rise
in neutron and muon  counting rates, the levels
are observed to decrease below the preflare values.
  1.04  -
                    14   16    18
                       MAY 1959
Figure 2.  Cosmic ray ground level measurements dur-
  ing a 3+  flare, Yakutsk, U.S.S.R., 51° geomagnetic
  latitude  (Kuzmin and Skripin, 1966b)
6

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The phenomenon  is known  as  the  Forbush  de-
crease, and is due to the fact that flares are fol-
lowed by magnetic disturbances which reduce  the
low energy galactic radiation component.


  2.2.2. Latitude variation

  Of the factors which influence cosmic ray ioni-
zation  at  the earth's surface, the latitude effect
was the first to be well described. This effect re-
sults from the earth's geomagnetic field, which
approximates a dipole located 215 miles from the
earth's center with the poles at 79° X.,  69°  W.
(northwest Greenland) and 76°  S., 121° E. (Ant-
arctica) (UNSCEAR, 1966; Pal, 1967). The mag-
netic field serves to cut off incident low energy
cosmic particles, and the screening effect is larger
in the lower latitudes in both betntspherfes,
  Millikan et  al. (1936a), through a worldwide
survey, observed the cosmic ray variation at sea
level due to the latitude effect: his  results are
summarized in figure 3. As shown in  this figure.
the ionizing component of cosmic radiation varies
by  about 2 percent throughout contiguous  U.S.
latitudes, which range  from 36° to aS°  X. geo-
magnetic. Extensive reviews of later work  have
been presented  by Lowder  and Solon  (1956),
Hultqvist (1956). and UXSCEAR  (1962, 1966).
More recent work  (Raft  et al., 1970:  George.
1970) indicated a slight decrease  in  cosmic ray
ionization  commencing  around  50° geomagnetic
latitude  (a line through Washington, D.C., and
    LINES OF EQUAL COSMIC-RAY INTENSITY
    AT SEA LEVEL ( RELATIVE VALUES )
30
60
  90      120     150      180     150      120      90      60      30       0

               Figure 3.  Variation of cosmic radiation with latitude (Millikan et al.. 1936a)

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central  Oregon). However, it still appears that
the influence of latitude on cosmic radiation ex-
posure within the United States is negligible in
terms of population exposure.
  Neutron flux varies by approximately 30 per-
cent between the poles and the equator and by
15 percent within the range of latitudes covered
by United States (UNSCEAR, 1966). However,
since neutrons account for a small fraction of the
total cosmic ray exposure, the variation  of  DE
with latitude in the United States is insignificant.
Furthermore, in a comparison of cosmic ray meas-
urements in section 2.3, it will be seen that uncer-
tainties in the various measurements tend to
obscure all variations except the increase of expo-
sure with  elevation,  and,  for  purposes of dose
estimation in  the  present study, the  latitude
variation in the United States will be neglected.

  £2.3.  Altitude variation

  The atmosphere attenuates the cosmic ray flux;
the  attenuation of the secondary  particles  is
varied so the relative DE contribution from  dif-
ferent particles changes as the atmospheric depth
increases.  As a general view of cosmic ray  DE
variation  with altitude, a summary  of O'Brien
and McLaughlin's  (1970)  calculations is pre-
sented in  figure 4. In their work, O'Brien  and
McLaughlin  have  shown  that the  calculated
values agree well with measured ionization values
throughout most of the atmosphere.
  The ionizing component of cosmic radiation
in the lower atmosphere has  been measured by
workers at the California Institute of Technol-
ogy  (Bowen  et al., 1934; Millikan et al.,  1936b;
and George, 1970)  and the AEG  Health  and
Safety  Laboratory (Solon et al., 1960; Lowder
and Beck, 1966; and Raft et al., 1970). The ioniza-
tion profiles (ionization vs. elevation) up to 15,000
feet as  obtained by each investigator" have ap-
proximately the same shape, the primary  differ-
ence being in  the  absolute values.  The  profile
determined by Lowder and Beck (1966) is repre-
sentative of the existing information  and is used
to obtain the DE variation with elevation.
  The neutron contribution to  the cosmic  radia-
tion DE is approximately 15 percent  of the total
and will be discussed further in the next section.
Neutron density in the atmosphere varies expo-
   10'
 i
                                    -TOTAL
                     ,'"  	ELECTRONS
                   /..-•*'''    ^----	PROTONS
                  .*  ..*"     -*•**
•NEUTRONS
                      -'   ^	.
               //  / ^
         	
                    4      6       8
                    ALTITUDE -10* FEET
Figure 4.  Cosmic ray dose equivalent rate variation
    with altitude  (O'Brien and McLaughlin, 1970)
nentially with pressure with an e-folding thick-
ness of 165 g/cm2, or a half thickness of 114 g/
cm2  (Patterson  et  al.,  1959; Miles,  1964).  The
constant slope in the lower atmosphere indicates
that the neutron spectrum does not change over
the same range, and therefore in this report the
neutron DE  is assumed to vary as the neutron
density.
  Closely related to altitude variation is the vari-
ation of cosmic radiation with barometric pres-
sure at a  fixed  elevation; Shamos  and  Liboff
(1966), in  addition to their own work, have re-
viewed the findings in 21 investigations concerned
with this effect. The "hard component" (primar-
ily muons) varies by about 0.17%/torr, and the
"soft component" has been estimated to vary by
about 0.93%/torr. The overall variation is 0.3 to
0.4%/torr.  For purposes of long-term estimation,
8

-------
the variation  is not important. However, since
the barometric pressure may vary by about  3
percent from day to day, it represents a potential
source of  error  in correcting  and comparing
different measurements.
2.3. Cosmic Ray  Measurements

  2.3.1. Ionizing component

  The measurement of the ionizing component of
cosmic radiation is generally  expressed as ion
pairs/cm3-sec. (commonly expressed as "I"), and
corrected  to  the sea-level value at T60 torr and
0° C., although not all authors mention a temper-
ature and pressure correction. One I corresponds
to a value of 1.65 /xrem/hr. This ratio has been
used  to convert  all measurements to the  same
units.
  Summarized in figure 5 and table 2 are meas-
urements of the sea-level intensity that have been
made by  various investigators over a period of
40 years.  As can be seen, there has been a con-
siderable spread in the reported  values,  which is
remarkable even in view of the natural variations
that have been cited. Even the most recent meas-
urements  which have been reported differ by 30
                                Table 2.  Summary of sea-level ionization due to cos-
                                          mic radiation at UJS. latitudes
Reference
Hultqvist (1956) 	 	
Solon et al (I960) 	
Kastner «>t al {1963)
Sharaos and Liboff (1966) 	

Ohlsen (1!I69) 	
George (1970) 	 	
O'Brien and McLaugblln (1970) 	 	
Yeates (1970) 	 	 	


Average of post-1950 vaiuea 	 	 	

lonlzaUou
(Ion pairs/
ca?-sK.i
•2.06
252
2 78
2 IS
2 10
2 18
2.60
220
2.*9

2.22
244

                                  1 Average of 12 values from previous investigations.
                                to 40 percent. Shamos and Liboff (1966), Lowdcr
                                and Beck  (1966), and  George (1970)  have at-
                                tempted  to explain the differences through ion
                                chamber construction, calibration, alpha contami-
                                nation of  the measuring  chamber, and  radon
                                daughters in the atmosphere  (the latter two fac-
                                tors may contribute up to 15 to 20 percent of the
                                measured cosmic ray dose). However, differences
                                still remain, and, in view  of the numerous cor-
                                rections which must be made to compare measure-
                                ments at different locations,  it appears that the
s
3
                                                       *:
                                          an          !
                                           YflU OF MEASUREMENT
                    Figure 5.  Summary of sea-level ionization due to cosmic radiation

-------
differences will not be resolved soon. For the pur-
pose  of DE  estimation  in  the present work,  a
value of -2A4:  I has been assumed for the average
cosmic  ray  ionization at sea level in the United
States.  This  is  the  average  of eight reported
values since 1960 and is equi valent to 4.0 /irem/hr.,
or 35.3  mrem/yr.  The value used in this study,
35.3 mrem/yr.., compares reasonably well with the
most recent reported  UXSCEAR (1966) value of
28 mrem/yr.

  2.3.2.  Neutron  component

  Several factors have contributed to  relatively
poorer knowledge of the neutron DE rate at sea
level as compared to  the ionizing DE rate. First,
the neutron flux in the atmosphere is more sen-
sitive to the time, latitude, and altitude variations
which have been  described. Since the neutron DB
rate has been measured over a rel at i vely  shorter
time and by  fewer  investigators, the  intercom-
parison of different  work is complicated by the
greater  natural  variations.  In addition,  incon-
sistencies exist in  reporting results  so  that it is
common to  find  data reported either in dose or
DE units.
  UXSCEAR (1966) reviewed the neutron meas-
urements through 1965  and,  based upon  a re-
ported range of 0.3 to 1.1 mrad/yr., concluded that
0.7  mrad/yr.  should  be taken  as the typical sea-
level value at  middle latitudes. The International
Commission on Radiological Protection (ICRP)
(Upton,  1966),  in reviewing cosmic  radiation
hazards to supersonic jet passengers and crew, has
assumed a sea-level value of 4.3 X  10"2 prad/hr.
(0.38  mrad/yr.) and  a quality factor of 8, which
corresponds to 3.0 mrem/yr. Watt  (196T)  has
calculated a value of 6.8 mrem/yr. O'Brien and
MVLaughlin (1970),  in addition to reviewing the
discrepancies which presently exist in the neutron
data, have calculated a value of ~0.33  mrem/yr.
A quality factor of 3 may also be inferred from
their data. A summary of the preceding informa-
tion is  presented  in table 3. For the purpose of
close estimation in the present study, the recom-
mendations of UXSCEAR (1966) and Upton et
al. (1966) have been followed by using the values
of 0.7 mrad/yr. and QF = 8, respectively.
  The cosmic radiation dose rates to be used in
Table 3.  Cosmic ray neutron dose equivalent at sea level
Reference
t'NSCEAR (1966) 	 	
Upton et al (1966) 	 	 	
Watt (1967) 	 _ 	 	
O'Brien and McLaughlln (1970) 	 	
Hajnal et al. (1971) 	 	


Dose equlraleut
(mrem/yr.)
• 5.6
•30
6.8
033
3.3
5 6

  • Based on dose values presented by UNSCBAK (1966) and
QF = 8.

this study are summarized in table 4. Based upon
the adopted sea-level  values and ionization  pro-
file of Lowder and Beck (1966), the DE rates at
altitudes  up to 15,000 feet have  been plotted in
figure 6.  Estimates of  cosmic radiation DE at

Table 4.  Cosmic radiation dose equivalent at sea level
Source
Ionizing component —
Neutrons , 	 	

Total 	 	

/trem/hr.
4.0
0.64

4.6

mrem/yr.
35.3
5.6

40.9

  10'
  10'
                                NEUTRON COMPONENT
         NOTES:
         @ IONIZING COMPONENT DETERMINED BY (.EAST SQUARES FIT TO
            PROFILE OF LOVOER AND BECK HtM). AND NORUALtZED TO SEA
            LEVEL VALUE OF J It I. OR 35.3 »REMS rEAR iSEE TABLE 11.

         ® NEUTRON COMPONENT  J I -REM! TEAR . EX» I ^^^ I
                       1033 »» Mi' = 3IA LEVEL PRESSURE OF
                             U.S. STANDAttO AfMOSPKERE
                           o, = PRESSURE AI ELEVATION "a"
                      (      I     10
                  ELEVATION • THOUSANDS OF FEET
                                                      Figure 6.  Cosmic ray dose equivalent vs. elevation
10

-------
different elevations were made using data  from
this figure.


2.4. Population Distribution

  The poptilation of the United  States was dis-
tributed in  1960 as shown in figure 7, which  is
adapted from the U.S. Census  Bureau  (1963).
Through use of the population distribution map
and a U.S.  Geological  Survey topographic map
{Gannett, 1916),  the population of the  United
States was found to be distributed by elevation
as presented in table 5.  The mean populated ele-
vation of each State was computed by averaging
the population of urbanized areas, for which an
approximate elevation was available (Rand Mc-
Nally, 1971; Gannett, 1906), and the population
Table 5.  Distribution of the U.S. population vs. elevation
                     (1960)
Elevation Interval
(103 feet)
0-05
051
1 2
2—4
4 6
6-8
8-10 	 	 	
->10

Total

Population
86 629 494
63 007 720
19 746 062
5 298 236
3 938 663
618 000
71,000
14,000

179 3°3 175

Cumulative percent
48 3
83 4
94 5
97 4
99 6
99 9
100.0
100.0



of the nonurbanized  areas. The  mean elevation
of the nonurbanized  population  was  computed
by weighting the population in  each elevation
segment by the segment midpoint.  Thus, the mean
populated elevation  (feet) of the nonurbanized
area  of state =
                                                   ONE DOT EQUALS 10,000 PERSONS
                                                    OUTSIDE URBANIZED AREAS
                               Figure 7.  Population distribution, 1960
                                                                                             LI

-------
                    /No. living at\             /  No. living at  \
                    \ 0 to 500 feetj         "*"  \ 500  to 1,000 feet/
                                Nonurbanized population of State
                 X 750 ...
  Three exceptions to this  procedure were re-
quired. First, the population of Hawaii was as-
sumed to be distributed 95  percent in the  0 to
500-foot interval  and 5 percent in  the 500 to
1,000-foot interval, since the scale of the U.S.
Census Bureau map did not justify a  comparison
with  topographic data.  Secondly, several  low-
lying States on the Atlantic and Gulf Coasts have
mean elevations less than 250 feet based on geog-
raphy alone. In these States, which are Delaware,
Florida, Louisiana, and Rhode Island, Gannett's
(1894)  estimates of mean elevations were used
(60, 100, 100, 200 feet, respectively) for the non-
urbanized population.  Thirdly, it becomes neces-
sary later in this report  to divide certain  States
into Coastal Plain and non-Coastal Plain regions.
The Coastal Plain regions  (to be specified later)
are also low-lying areas  and have been assigned
mean elevations based on a comparison of popu-
lation distribution and topographic data for the
respective regions.
  The estimates of mean populated  elevations
have  been used in conjunction with  values  ob-
tained from figure  6 in order to  estimate  the
cosmic ray  DE in the United States, and this
information is summarized in figure 8. As can be
seen, the DE is relatively uniform in the eastern
half of  the country but  increases  in areas of
higher elevation in the west. The populations of
Alaska and Hawaii,  which are not  shown, were
also calculated as receiving between 40  and 50
mrem/yr.
  It is interesting  to  note that a small area
on the east  side of the Rocky  Mountains, in  the
vicinity of Leadville, Colorado, includes all of the
populated  communities in  the United  States
which are at elevations greater than 10,000 feet.
These communities are between 10,000'and 10,500
feet; this elevation corresponds to a cosmic ray
DE of 160 mrem/yr., or approximately four times
the sea-level  DE. Additional calculations  are
presented in chapter 4, where the  contribution
from  terrestrial and other sources  will  also be
discussed.
                       Figure 8.  Dose equivalent from cosmic radiation (mrem/yr.)
12

-------
             CHAPTER  3.  TERRESTRIAL  RADIATION EXPOSURE
  In the preceding chapter, the  factors which
affect exposure  to cosmic radiation  have been
discussed. In this chapter, the same approach will
be taken to discuss man's exposure  to natural ter-
restrial sources of radiation.
3.1. Sources

  Naturally  occurring  radionuclides contribute
significantly to man's external exposure. In most
of the United States, the magnitude of terrestrial
radiation exposure is relatively uniform and is
similar to that due to cosmic radiation. As far as
is known, there are no  terrestrial  areas in  the
United States which yield DE rates comparable
to the high radiation levels 10 to 100 times greater
than  "normal") which  have  been observed  in
other parts  of the world, notably  a  few popu-
lated areas  of Brazil and  India (UNSCEAR,
1962).
  The nuclides which contribute to man's natural
exposure have been  extensively  reviewed else-
where (Lowder and  Solon, 1956;  UNSCEAR,
1962). From the standpoint of man's exposure,
only  potassium-40 and  the  radioactive  decay
chains of  uranium-238  and   thorium-232   are
significant. In addition to these nuclides, Lowder
and Solon (1956)  summarized physical data  for
21 nuclides  which exist or are hypothesized to
exist; however,  long half-lives and  low abun-
dances account for their insignificant DE to man.
The presence of cosmic ray neutrons insures that
capture reactions do occur in soil at the earth's
surface and  in the atmosphere, thus resulting in
the probable occurrence of many additional radio-
active nuclides. The production of carbon-14 and
tritium are  two well-known  examples of  this
process; however, the DE  due to cosmic  ray-
induced nuclides is insignificant.
  Potassium-40 occurs as one of three potassium
isotopes. The two most abundant isotopes, potas-
sium-39 (93.1  percent)  and  potassium-41  (6.9
percent), are stable, whereas potassium-40 (0.0118
percent) decays with a half life of 1.25  X 10"
years.  A 1.46 MeV gamma ray  is  emitted in 11
percent of the  disintegrations, and this gamma
ray  is  the  source of terrestrial DE from the
nuclide.
  Thorium-232 and uranium-238  decay chains
are shown  in tables 6a and 6b. Uranium-235 is
the parent element of a third decay chain: how-
ever, as can be  seen from table 7, the energy re-
leased  from  radioactive  decay from this chain
is insignificant in comparison to  the uranium-238
and  thorium-232 chains. Although the nuclide
composition of the rock in table 7 differs slightly
from estimates  which will be  presented later, it
is clear that  uranium-238,   thorium-232,  and
potassium-40 may be assumed  to account  for
practically  all  of  man's  terrestrial radiation
exposure.
  As in the case of cosmic radiation, terrestrial
sources have been studied primarily for purposes
other than  interest  in  population exposure to
background radiation.  For example,  measure-
ments made early in this century were concerned
with geologic dating and heat seneration due to
radioactive decay. Since the 1940's, however, most
of the literature concerning uranium and thorium
has resulted from an economic interest in the  two
elements. Within the past 15 years, additional
data have been  reported which relate directly to
man's exposure to terrestrial sources.

-------
                   Table 6a.   Uranium-238  decay chain—uranium series (4n  +  2)*
                  (Courtesy  Radiological  Health  Handbook,  Revised January  1970)
Nu,.! ids
"1°
1
1
•j.'Th

234pa">
99 87" OU



--' Ll
1
1
's'STh
1
. J


2||Rn


J||Po






1
?A












99.987. 0.027.
I
^Pfa






2XeAt

i
3JjBi



99.987. 0.027.

P0
SJ<

1
210DK
ejPb

-J


Tl





-1007. .000137.
\
30
1
ag|Pb

.1


Historical
name
Uranium 1

Uranium X;

Uranium Xg


Uranium Z

Uranium II

Ionium

Radium


Emanation
Radon (Rn)

Radium A


Radium B


Astatine


Radium C

Radium C'
Radium C"


Radium D

Radium E

Radium F
Radium E"

Radium G
Half-life
•«.51xl09y

24. Id

1.17m


6.75h

2.47>lOEv

8.0 «104y

1602y


3.823d


3.05m


26.8m


-2s


19.7m

164..
1.3m


21y

5. Old

138. 4d
a. 19m

Stable
Major radiation energies (KeV)
*
4.15 (255)
4.20 (757.)
	

	


—

4.72 (28%)
4.77 (727.)
4.62 (24',)
4.68 (765.)
4.60 (6?,)
4.78 (957.)

5.49 (1007.)


6.00 (-1007.)


	


6.65 (6'-.)
6.70 (947.)

5.45 (0.0127.)
5.51 (0.0087.)
7.69 (100%)
...


J.72 (.000002%)

4.65 (.00007%)
4.69 (.00005%)
5.305 (100%)
...

...
3
	

0.103 (215.)
0.193 (795)
2.29 (98%)


0.53 (665.)
1.13 (13%)


...

	


	


0.33 (-0.019%)


0.65 (50?)
0.71 (40")
0.98 (65)
? (-0.17.)


1.0 (237.)
1.51 (40%)
3.26 (19%)
—
1.3 (25%)
1.9 (56%)
2.3 (197.)
0.016 (85%)
0.061 (157.)
1.161 (-1007.)

...
1.571 (1007.)

___
Y
	

O.Oiici (3.5"/)
0.093c (4")
0.765 (0.307.)
1.001 (0.607.)

0.100 (50%)
0.70 (24',)
0.90 (70%)
0.053 (0.27.)

0.068 (0.6%)
0.142 (0.07%)
0.186 (47.)


0.510 (0.077.)


—


0.295 (197.)
0.352 (367.)

...


0.609 (47%)
1.120 (17%)
1.764 (177.)
0.799 (0.014%)
0.296 (80%)
0.795 (1007.)
1.31 (21%)
0.047 (4%)

...

0.803(0.0011%)
1
T /

~~*
*Thls expression describes  the DUBS number of any member In this series, where «  is an Integer.
                     Example: agSPb  <4n + 2)......4(51) +2-206
tlntertsitiea refer Co percentage of disintegrations of the nuclide itself, not to original parent of series.
*Coaplex energy peak which  would be incompletely resolved by instruments of moderately low resolving power such as sciotillators.
Data taken from;  Table of  Isotopes and USNRDL-TR-802.

-------
                           Table 6b.  Thorium-232 decay  chain—thorium series  (4n)*
                        (Courtesy  Radiological Health Handbook, Revised January  1970)
Nuclide
8!?Th
«:R.
,*
)
6.29 (1007.)
6.78 (1007.)
6.05 (25%)
6.09 (107.)
8.78 (1007.)
	
•-
...
0.055 (100X)
1.18 (357.)
1.75 (12')
2.09 (12*)
---
*
0.346 (8i:>
0.586 (14')
1.55 (57.)
2.26 (557-)
1.28 (257.)
1.52 (21%)
1.80 (507.)
v
...
...
0.34ci <"155!)
0.908 C25*,)
0.96c C20"'.)
0.034 (1.6'j
0.214 (0.3'.)
0.241 (3.77,)
0.55 (0.07')
0.239 <4r,)
0.300 (3.2'-)
0.040 (2°.,)
0.727 (7^)
1.620 (l.S'.)
0.511 (23')
0.583 (86')
0.860 (12'.)
2.t>14 (100')
      *This expression describes the mass number of any member in this series, where n is an integer.
                            Example:  ""in (4n)	4(58) - 232
      tlntensities refer to percentage of disintegrations of the nucllde Itself, not to original parent of series.
      ^Complex energy peak which would be Incompletely resolved by Instruments of moderately low resolving power such as >vintillac.T

      Data tJkcn from:  Ledcrer, C. M., Hollander, J. H-, and Ferlman, I., Table of Isotopes (6th ed.; New York: John Wiley & Sons,
                    Inc.,  1967) and Hogan, 0. B., Zlgman, P. E., and Mackin, J. L., »eta Spectra (USNRDL-TR-802 [Washington, D.C.
                    U.S. Atomic Energy Commission, 1964]).
Table 7.  Gamma-ray energy released by 1 gram of rock
            (litkosphere) Kogan et al. (1971)
Isotope
TTranium-238 (In equilibrium with
Uranlum-235 (In equilibrium with
decay products) 	
Thortum-232 (in equilibrium with



Average
concentration,
percent
2.98X10-*
0.02 X1(H
11.4 X10-*
3.0
Energy
(MeV/
sec.XlOJ)
6.82
0.153
8.78
11.4
.27
  Gentry et al.  (1959)  and Grahn and Kratch-
man (1963), in investigations of fetal malforma-
tion, estimated population exposure  from  data
on  local geology  and uranium reserves,  but made
no  measurements. Segall (1963) conducted a later
study concerned with health effects of background
radiation, and, in support of the study, Billings
(1961)  prepared a  radioactivity map  (uisorad
map")  of Vermont, Xew Hampshire, and Maine,
based  upon chemical  analysis  of  bedrock.  At
                                                                                                             15

-------
about,  this time, portable multichannel gamma-
ray  spectrometers were developed,  and  these
instruments  allowed   field   determinations  of
the amounts of potassium-40, uranium-238, and
thorium-2.'5'2 present in the soil. Data reported by
Beck et al. (1964a, 1964b, 1966a) are representa-
tive of this technique.
  Extensive literature reviews exist concerning
the distribution and abundance of the naturally
occurring radioactive elements in the earth's crust
(Adams et al., 1959; Peterman, 1963; Clark et al.,
1966; Finch, 1967; Over-street, 1967; Wedepohl,
1969).  The purpose of the following text is not
to duplicate this information, but rather to pre-
sent sufficient data from  these sources  to permit
an understanding of  variations  which exist in
measurements of background  radiation.
  The  earth's crust is composed of igneous, meta-
morphic,  and sedimentary rocks;  the  first two
classifications account  for approximately 90 per-
cent of the mass of the crust. Sedimentary rocks
accumulate at the top  of  the crust, however, and
thus Jackson  (1964) estimates that sedimentary
rocks cover about 75 percent  of the earth's land
area.
  Based on an analysis of the geology map, U.S.
Geological Survey  (1971),   sedimentary rocks
cover approximately 85 percent of the contiguous
U.S. land area,  and are  distributed by geologic
age as  shown in table  8. Sedimentary rocks may
be classified  as shale, sandstone,  or limestone,
which  have a relative  abundance in the ratio of
3:1:1. Since the metamorphic and igneous rocks
of table 8 are concentrated in sparsely  inhabited
mountainous  areas, it can be assumed that the
U.S.  population lives almost entirely over rocks
of sedimentary origin.
    Table 8.  Types of bedrock in the contiguous
                  United States
Geologic period
Quaternary
Upper Tertiary
Lower Tertiary
Cretaceous
Jurassic and Triassic
Upper Paleozoic
Mid Paleozoic
Lower Paleozoic
Younger Precambri an .
Old Precambrian

Quarternary and
Tertiary
Lower Tertiary, Meso-
zole. Paleozoic
Total
Type



Sedimentary




Metamorpblc and
igneous
Volcanic — Igneous

Intrusive — Igneous

Percent of
land area
6.5
13.8
9.6
17.9
3.4
19.3
5.4
5.9
3.3



85.1





4.4
7.7

2.8
100.0
  Table 9  presents the average amounts of ura-
nium, thorium, and potassium-40 in common rocks,
soil, and the earth's upper crust. It can be seen
from the crustal average that potassium-40 and
the thorium-232 decay chain each contribute ap-
proximately 40 percent of the dose rate at three
feet above the ground, and the uranium-238 decay
chain contributes approximately 20 percent of the
total. The  uranium-238 decay chain includes the
gas radon-222, which can diffuse through the soil
and into the atmosphere. The diffusion reduces the
equilibrium concentration of radon-222 daughters
in the soil, thereby reducing the DE contribution
from the uranium-238  series  by as much as 50
percent  (Beck  and de  Planque, 1968).  The
thorium-232  decay  chain  also includes  a  gas,
            Table 9.  Radionuclide content and dose equivalent rates from common rocks and soil
Rock
Igneous *
Basic 	
Silicic (granite)
Sedimentary »
Shale 	
Sandstone 	 	 	
Limestone 	 	 	
Upper ernatjil mrorngp c
TJ.B. snrfldal average a _ 	

ppm
09
47
3.7
.45
2.2
28
1.8

Uranium
(mrem/yr.) •
62
269
21.2
2.6
12.6
16.0
10.3

ppm
27
200
12.0
1.7
1.7
10
9.0

Thorium
(mrem/yr.) •
73
53 8
323
4.6
4.6
26.9
24.2

ppm
12
50
32
11
0.32
2.4
1.8

Potansluin-40
(mrem/yr.) •
14 7
61 3
392
135
3.9
294
21.8

Total
(mrem/yr.) •
27.2
1420
927
207
21.1
72.3
56.3

   • mrem/yr./ppm.: uranium, 5.73; thorium, 2.69; potassium-4O, 12.3; Beck and de Planque (1968).
   •Clark et al. (1966).
   ' Uranium and thorium averages from Pbalr and Gottfried (1964) ; potassium from Heler and Billings (1969).
   < Lewder et al.  (1064).
16

-------
radon-220; however, the short half-life of radon-
220 (54.5 sec.) prevents a significant loss of gas
(and daughter products) to the atmosphere.
  In addition to the gamma rays from terrestrial
sources, which are the basis for the DE values
in table 9, alpha and beta particle emissions also
occur. The alpha particles may be assumed  to be
absorbed in the soil, and  it is generally  assumed
that the beta rays may also be  neglected.  Beck
et al.  (1966a) have  completed the most recent
and thorough  study  of  terrestrial  beta-ray
sources. In measurements  conducted 40 to 180 cm
above the ground  surface, they found beta rays
were  attenuated  with  a  half thickness of 150
mg/cm2. At one meter above the ground, gamma
rays and cosmic  rays produced  7  ion pair/cm3-
sec.(I) in  air and  beta rays produced 13 I. Al-
though these authors concluded that the gonads
and bone marrow received a small and negligible
DE from  beta rays, it is conceivable that this
source could present a significant exposure for
persons in special  circumstances, e.g., individuals
who live on earthen floors.  In summary, present
evidence suggests  that the  beta-ray  DE due to
terrestrial  sources  may be neglected; however,
extensive supporting evidence is lacking.
  Table 9 is intended to present a general idea of
the DE  rate  from various rocks, but practical
limitations prevent the use of these data for esti-
mating population exposure. Phair and Gottfried
(1964) have outlined some of the pitfalls in esti-
mating average elemental  contents  of various
rocks.  For  example, they  recommend that the
number of analyses of a rock type should be pro-
portional to the abundance of the rock in nature.
In practice, however, rare rocks tend to  be  over-
analyzed in relation to the common types and
thereby  contribute a  disproportionate share to
the overall mean.  In addition,  surficial events,
such as  mixing of rocks with organic matter,
glaciation, and the simultaneous occurrence of
several  rock  types, make  population exposure
from  a single  rock type  or rock derivative un-
likely. For these reasons, elemental  analyses of
rocks are not adequate for  making estimates of
population exposure, but are helpful in under-
standing  variations  which  exist  in DE  rate
measurements.
  Table  9  shows that the averages for  surficial
measurements are slightly less than for the upper
crust. This is as expected, since the surficial  data
are based  upon in situ spectromctric  inf-asure-
ments and reflect the  factors whifh have already
been discussed. Mixing  and weathering processes
at the soil/atmosphere  interface serve to reduce
the amount of variation  that one would expect
based upon bedrock analyses. Lowder and  Con-
don (1965), for example, found  that  although
bedrock  radioactivity  and  above-jrround   DE
rates could  be correlated, the L>E  rate above
ground increased only slightly  for a several-fold
increase in bedrock radioactivity.


3.2. Variations in Terrestrial  Radiation
  As one miglit expect  from section 3.1, the pri-
mary  determinant of  the terrestrial  radiation
level in a given location is the  soil concentration
of natural radionuclides.  However, the radiation
level above the ground will  vary because of the
presence of soil moisture and the amount of radon
daughters present in the atmosphere. The two fac-
tors are related but will be discussed separately.
The resulting  variations in  terrestrial radia-
tion exposure will be cyclical and can markedly
affect the observations from day to day. As  with
the variations in cosmic radiation, an understand-
ing  of the  sources  of variation in  terrestrial
sources is helpful in explaining differences in
reported measurements.

  3.2.L Radon daughter products
  Eadon-222, Ti/2 =  3.8 days, occurs in the ura-
nium-238 decay chain, and radon-220, Ti/z = 54.5
sec., in the thorium-232 decay chain. Because of
the shorter half-life  of radon-220, there is less
opportunity for diffusion from the ground, and
thus airborne concentrations of  radon-'2'J2 are
generally two orders  of magnitude greater  than
those of radon-220 (Gold et al., 1964).
  Under most conditions radon daughters in the
atmosphere contribute a few tenths of a jirem/hr.
to the DE rate (Beck et al., 1964b). Low baro-
metric pressure, atmospheric temperature inver-
sions, little wind, and low soil moisture result in
increased radon emanation from the ground and
high air concentrations of radon daughters (Ciold
et al.,  1964; Kraner  et al., 1964).  Gold et al.

-------
 (1964), in a o-year study of atmospheric radon
 levels, reported an average radon-2^-2 concentra-
 tion of 0.26 pCi /liter, with maximum concentra-
 tions (0.8 pCi/liter)  occurring  during the fall
 months. These concentrations correspond to 0.4
 and 1.3 jirem/hr., assuming the conversion factor
 of Hultqvist (1956).3 In developing this factor,
 Hultqvist assumed the radon-222 was in equilib-
 rium with its  daughters.  In fact, however, the
 daughter  concentrations are generally 50 to 100
 percent of  the values that could be estimated
 from the radon-222 concentration (Gold et al.,
 1964; Harley, 1953), so that a value of 0.3 jirem/
 hr. is probably a reasonable estimate of the aver-
 age  external DE due to radon  daughters. This
 estimate is supported by the spectrometric meas-
 urements  by Beck et  al.  (1966a),  who  reported
 gamma DE rates at several  locations to be be-
 tween 0.1 to 0.5 /trem/hr. due to radon daughters.
 There  are other  reports of outdoor radon levels
 averaging 10 percent  of the estimate cited here
 (see Lowder  and  Solon,  1956;  and  Hultqvist,
 1956), but the  estimate by Gold et al. (196-4)  is
 assumed to be more correct because of the longer
 period of observation.
  George  (1970) has provided what may be an
 example of a  relatively high DE rate due to
 radon and its daughters. In an  effort to isolate
his cosmic ray detection instruments from terres-
trial sources, he moved to an offshore drilling plat-
 form 3.6 km west of Los Angeles. By so doing,
he was able to observe increases in the ionization
 which  coincided  with the offshore winds  (fig-
 ure 9).  The difference in high and low  readings
 was  approximately 0.6 ion pairs/cm3-sec., or 1.0
 /irem/hr. Since the usual temperature inversion of
 the Los Angeles basin results in  little vertical
mixing, this value is probably close to the upper
 limit of the external DE from radon and its
 daughters.  It should be noted that radon levels
over oceans are approximately one one-hundredth
 of land values  (Hess and  Parkinson, 1953), and
thus there was probably an  insignificant  radon
 contribution from the ocean to the measurement.
  The probable  range of external DE due to
radon daughters, therefore, is 0 to 1 /irem/hr., and
 3.3
 3.2
 3.1
 3.0
 2.9
 2.8
 2.7

 2.6
 2.5
 UNION OIL DRILLING PLATFORM
 8.8 LITER IONIZATION CHAMBER
   ]LAT. 33°40'N, LONG. 118° 5' W
          ALTITUDE=.~100 FT..
          APRIL 23-27.1968
I
      6 12 18   6 1218   6 12 18   6 12 18   6 12 18
     APRIL 23 APRIL 24  APRIL 25 APRIL 26  APRIL 27
  'Ion pairs/cm'-sec. = 0.97 X radon-222 concentration
pCi/liter; 1 ion pair/cm'-sec. = 1.65 prem/hr.
Figure 9.  Ionization vs. date and local time (PST) on
  offshore drilling platform  near  Huntington Beach,
  Calif., (George, 1970)
the average  is about  0.3 /*rem/hr. Under these
circumstances, the contribution of radon daugh-
ters to the total terrestrial plus cosmic DE rate
at most locations will be less than 10 percent, and
usually less than 5 percent of the total.

  3.2.2. Moisture  and snow cover
  It has already been mentioned that  soil mois-
ture retards the  diffusion  of  radon into the
atmosphere  and  thus reduces  exposure to the
airborne daughter products;  in most  soils, the
amount of water varies  from 5 to 25 percent on
a  weight basis  (Jackson, 1964).  Beck  et  al.
(1966a)  found that  the potassium-40 DE rate
decreases by about 30 percent when the  soil water
content increases from 0 to 30 percent,  because
of the increased shielding provided by the water;
however,  soil moisture  acts  in two  conflicting
ways on the terrestrial DE rate. The first has al-
ready  been  mentioned,  e.g., the gamma-ray  at-
tenuation of the natural emitters. Conflicting with
this is the reduced radon migration to the surface
and accumulation  of radon  daughters  in the
ground. The daughters of radon account for more
than 95 percent of the gamma  ray energy from
the uranium-238 series (Kogan et al.,  1971), so
that their presence in the ground increases the
exposure from this series. The net effect is for
soil moisture to  decrease the  potassium-40 and
thorium-232  rates and to increase or  leave un-
changed the  uranium-238 series DE  rate (Beck
et al., 1966a).
18

-------
    In a  comparison of  spectrometeric measure-
  ments obtained in Denver, Beck et al. (1966a)
  observed that the measurements obtained in dry
  years (1962 and 1963) were 15 to 25 percent less
  than in  a wet year (1965). This indicates that
  the gamma ray attenuation by the soil water was
  more than offset by accompanying soil retention
  of  radon daughter products.  Therefore,  one
  would  expect  variations  of  this magnitude
  throughout the  country  where periodic drought
  and rainy periods  occur.  Once again, this empha-
  sizes the  difficulty in interpreting spot measure-
  ments and using such measurements for long-term
  exposure  estimates.
   The effect of snow  cover on  the dose rate
  from terrestrial sources was calculated by Sievert
  and Hultqvist (1952) (figure 10). The calculated
 values agree well with  measurements  reported
 in the same  reference  and with  more recent
 measurements by  Magi  et al.  (1970). Concur-
 rently  obtained  snow  cover  and  background
 radiation  measurements  are virtually nonexist-
 ent.  This fact illustrates  a bias which might
 exist in  practically  all measurements of back-
 ground  radiation. They  are obtained in  fair
            20      40     60      80
              DEPTH OF SNOW  IN cm
Figure  10.  Decrease in gamma radiation with depth
  of snow cover at three different densities (Sievert and
  Hultqvist, 1952)
  weather when personnel and equipment stress is
  at a minimum, and therefore  the  ntf-a.-urements
  may not reflect the seasonal variations of back-
  ground due to ground moisture and snow cover.
    It is possible, however, to estimate the impor-
  tance of snow cover on long-term exposure from
  the data of Magi et al. (1970). Based on summer
  measurements alone, they estimated the yearly
  DE  from natural  radiation to be 78 mrem/yr.
  at Idre,  Sweden, whereas  year-round  measure-
  ments resulted in a 10 percent  lower e-timato. 70
  mrem/yr. They attributed this difference to the
  attenuation of terrestrial sources by snow cover.
  The  average  snow cover at this location is  15
  inches and persists for approximately  ISQ days/
  yr.  (Pershagen, 1969).  Natural radiation meas-
  urements in three other Swedish cities, located in
  regions of less snowfall,  showed  no variation
  from summer to winter.
    Although the effect of snow cover on  measure-
  ments can be substantial, the overall influence on
  population exposure is assumed to be negligible
  in the United States. In most populated area?.
  there is relatively little snowfall, and it does not
  remain for long periods  of  time. In addition  to
  these factors,  the  propensity  for indoor urban
  living, and rapid removal of snow in most popu-
 lated areas in the United States, tend to  reduce
 the significance of snow buildup as an attenuator
 of terrestrial  gamma sources.
   In addition to the variation in the source term
  (terrestrial gamma-ray sources), there  are also
 other factors which affect the exposure of man to
 natural radiation. Examples of such factors are
 man's choice  of home—elevation, geology, and
 building material. In addition, shielding provided
 by the body attenuates the dose to internal or-
 gans. These factors will be discussed in chapter 4.


 3.3. Measurements

  3.3.1. Ground surveys

  A summary of ground surveys of natural ter-
restrial radiation in the  United States is pre-
sented in table 10. Lowder and Solon (1956) re-
viewed several isolated background measurements
made prior to that time, but the more extensive
measurements have been reported since 1956. The
                                                                                             19

-------
                  Table 10.  Ground surveys of background radiation in the United States
Reference
Solon, 1960

Stephens et al..
Iii61
Beck et al.. lf>64a.
l»r,4b, li>66a,
lOGOb
Somali and Reed.
1»G4

Lowder and Condon,
1965

Wollenberg et al.,
1969



Levin et al., 1963


Golden, J., 1968

Yeates et al., 1970



Llndeken et al..
1971
Location
38 U.S. towns and
cities
30 locations near
Sun Francisco
Approx. 210 loca-
tions in lio States

New Hampshire,
Vermont

New Hampshire,
Vermont

30 locations near
San Francisco
(same as Ste-
phens et al..
1961)
1102 towns In 24
States

Florida — vicinity of
phosphate beds
Boston, Mass.



Livermore. Calif..
Inside 110 lionn
-------
and an  ion  chamber reading at each  location.
The spectral data were especially important for
interpreting  measurements obtained in  the first
half of the l!)GO's, when work by Beck et al. \\ :i~.
accomplished.  In addition to  allowing for an
estimation of  the contribution of potassium-40,
thorium--2:5^, and uranium-^iS to the total terres-
trial  DE,  the  contribution of  nuclear  weapons
fallout to the total 1)E could  be estimated with
the spectrometer data. The significance <>f fallout
will be discussed later in  tins  >ection.
  Several investigators have used portable scin-
tillation detectors for measuring  natural  back-
ground. These small, hand-held instruments allow
the user to  make several  measurements in the
time  it would  take  to obtain ion chamber and
spectrum measurements at one location. Unfor-
tunately sodium iodide (Xal) detectors, the scin-
tillating medium, do not  detect cosmic radiation
as efficiently as gamma radiation. In using a 3-
by  5-inch detector with a high energy cutoff of
3.4  MeV, Beck et al.  (1964b) found that  the sea-
level  cosmic ray contribution to the energy spec-
trum was equivalent  to a  gamma-ray DK  of (>.-_!
jirem/hr. instead of the expected value of approx-
imately  3.7 /irem/hr. In  a similar  study  using
several energy bands  with  a 4- by 4-inch detector,
Beck et  al.  (1966a)  observed  a gamma-ray re-
sponse of less than 0.5 /irem/hr. up to (!.()()» feet.
This  figure is  based  on the response of several
energy bands of less than  3.4 MeV, but it is also
indicative of the lack of detector response to cos-
mic rays. Another limitation on  the  use of port-
able scintillators is the strong directional depend-
ence of the detector (see Ohlsen, 1969). However,
this limitation  can be overcome by  maintaining
the same detector orientation during calibration
and measurements.
  Notwithstanding the  limitations  which have
been  discussed, it seems  desirable  to report  in
more detail the scintillometer measurements by
Levin et al. (1968), since they greatly outnumber
all other U.S. measurements combined. Levin does
not report  the  averages for the  states in which
measurements were obtained, ostensibly  because
of the fact that measured sites were not neces-
sarily  representative  of the entire  State. How-
ever,  the averages have been computed from his
reported data and are presented in table 11. As
Table 11.  Dose equivalent measurements in 21 State1-,
          adapted from Levin et al. (1968;
State
C 1 r- 1«
Mlrhlpm
ConniK'ticut 	 	
Florida

Illinois


Maine

Massachusetts -
North <'nrolina_
N«-\v Hampshire.
New Jersey 	
New York
Oh Jo
Pennsylvania 	
Khode Island 	
South Carolina.

Virginia 	 '
Total

NumbiT of
mc;i-urt-mpnts
T'JO
2 :(."i4
1.014
41
b~'.i
31ft
4!I4
4SH
62
301
M
3-j<;
"C3
1!I2
1'Hl
4
53
.->!
1H7
34
15
1.->1
ft ci"f,

T<>*.vn«
jl
24
i

"in
07


^7
*>•»
~|S
'17
11
ti'i
4s

in
4
SO
•>o
3
43


m-'-rr./J"
117

7f,
-1

»
fc-
•"*
90
f>
79

71
44

70
( —

• Mean.
Extreme  values :  Enst of
orinm. Colo., I'-'S mrem/yr.
                       Faoil. Fla.,  ."n  mrem/.vr. . F<-
can be seen from table 11. the means vary by a-
much as a factor of two—from 6.7<"> /irem/hr.  (W
mivm'yr.)  in Florida  to  13.32  /irem/hr.  (117
mrem  yr.)  in Colorado.
  The response  to oo3) were made in the field.
it is likely that  the  reported value-  are repre-
sentative of the  terrestrial, fallout, and cosmic
radiation. Levin's observation was that "the read-
ings were  within  4  percent  of  the   ionization
chamber readings O."i percent of the time.'

  3.3.2.  Dose equivalent rate due to  fallout
  The presence of fission products on the ground
from nuclear weapons  testing complicate?  the
interpretation of terrestrial  DE  rate measure-
ments  obtained  during  the  late 19.10's and  the
early and middle  lOfiO's. Unless  spectrometric
measurements are  made, the DE  contribution
from fallout cannot be accurately assessed.  1h\~
could be a source of varying  error, since fallout
contributed a DE of a magnitude similar to that
from terrestrial sources in 1!V>2 to 19t'". whereas
more  recent measurements show the  DE rate
from fallout to be approximately 5 to  lo percent

-------
of the natural terrestrial DE rate (McLaughlin,
1970).
  An estimate  of the external DE rate  due to
fallout is presented in figure 11. The figure is
based upon estimates  and measurements  in the
United States;  the two solid lines define a range
in which most  measurements would be expected
to fall, and the dashed line represents the best
estimate  for making a fallout correction to non-
spectrometric dose measurements.
 u 1.0
 o
                                     HIGHEST
                                     ANDIOWEST
                                     ESTIMATES
                                     VALUE USED
                                     FOR CORRECTION
                      64     EC
                        YEAR
 Figure 11.  Dose equivalent rate due to fallout in the
             United States, 1958-1971
   For purposes of making corrections, it would
 be desirable to know the local and countrywide
 variations in fallout dose rate. It has been shown,
 for example, that variations in fallout deposition
 are closely related to precipitation  and, as a re-
 sult, wet areas (i.e., areas of higher precipitation)
 receive more fallout than dry areas (Straub et al.,
 1964). Unfortunately, existing data are not suffi-
ciently detailed to justify making more than one
estimate of the  DE rate contributed by  fallout
at a given time in the United States.
  Fallout measurements by  Beck  (1966a)  sug-
gest more uniformity in fallout DE rates across
tlve United States than would be expected from
rainfall patterns. For example, measurements in
relatively  "dry'  States  (Wyoming,  Nevada,
Utah) varied between 0.6 to 1.5 ^rem/hr. in 1965,
and  at  approximately  the  same time  measure-
ments in "wet"  States  (Louisiana, South Caro-
lina, North Carolina) varied between 0.7  and 1.3
/*rem/hr.  However,  too few  measurements are
reported to allow  a conclusion  as to  how the
fallout  DE rate varied across the  country.
  Three different procedures were used in de-
veloping figure 11. These are as follows:
  1958 to 1962: The range of values was obtained
froirTTNSCEAR (1964), figure 32. The correc-
tion values are 54 percent of the maximum value.
This  correction  is based on a  composite of 67
measurements in the United States between 1962
to 1965  (Beck et al., 1964a, 1966a).
  1962  to  196IK The  range of  values and the
averages are based on the same measurements by
Becket al. (1964a, 1966a).
  1966 to present: The  1965 values  of Beck et al.
 (1966a) show that 25 percent of the fallout  dose
rate was due to  ruthenium-106 and  manganese-54
and 75  percent was  due to cesium-137.  The post-
1965  values are based on the assumption that the
25 percent portion decayed with the half-life of
1 year and the To percent portion decayed with a
half-life of  28  years.  The resulting  range of
values  is  consistent with fallout  measurements
in the northern hemisphere (UNSCEAR, 1966),
in San  Francisco (Wollenberg et al., 1969), and
in the eastern United States (McLaughlin, 1970)
during  this time. Some fresh fission products have
been  added in this interval as a result  of French
and Chinese weapons tests, but their contribution
 to the total is negligible.

   3.3.3. Aerial surveys
   The U.S. Atomic Energy Commission has spon-
 sored nationwide aerial surveys of radioactivity
 in the  vicinity of nuclear facilities. During 1958
 to 1963, Aerial  Radiological Measurement  Sur-
 veys (ARMS)  were  conducted  (by  the  U.S.
 22

-------
Geological Survey and E.G.&G., Inc.)  over  ap-
proximately 25 areas which are shown  in figure
12. A  few additional areas have been  surveyed
but are not included in this analysis because of
their relatively small size and  sparse population.
  In the  course  of reviewing  available sources
of information on natural radiation sources, it
was found that none of the published ARMS data
had been used for  estimating  population  expo-
sure. As a first step in  determining if  the data
would  be useful for this purpose, the population
of each  survey area  (table 12) was estimated
from U.S. Census Bureau  Map G.E. 50, No. 1,
1963. It was found that approximately 30 percent
of the  U.S. population (1960 census) resided in
the survey areas, and thus it was concluded that
the ARMS data would be potentially useful for
making exposure .estimates.
  Details of  the  purpose and procedures of th--
ARMS surveys are presented in the reports listed
in table 12 (or see Guillou,  1964);  however, -i
brief description  is presented here in order to
introduce the measurements. The standard ARMS
survey covered an area of 10,000 square miles
encompassing a nuclear facility, although there
is some variation  in areas covered  depending on
the site  location  in  relation  to mountains  and
oceans. The surveys were intended to provide in-
formation on radiation levels in the vicinity of
nuclear installations, so that future releases of
radioactive material to the environment from the
facilities could be detected. This naturally raises
        ARMS I, U.S. GEOLOGICAL SURVEY

        ARMS H,EGiG, INC
                            Figure 12.  Aerial radiological measuring surveys

-------
                                 Table 12.  Population in ARMS areas
Reference
Bates (1962) 	 - 	 	

Bates (lOOGn) 	 - 	
Bates (l!M>6b) 	
Buok-i (1!)62) 	 	
Books (I960) 	 	
Flint nnd Pitkln 63a>
Gulllou <1903b) 	 	 — 	 - 	
Guillou (1963C) - 	
Gulllou et al (1963) 	 	
Guillou (1965) 	 	
Gulllou (1966a) 	
Guillou (1966b) - 	 - 	 - -
Gulllou (1966c) 	 	 	 	
Gulllou (1966d) 	 	
MncKallor (1962) 	 	
MarKallor (1965) 	 ~
NcUM'ht'l (1966) 	 - -

Popenoe (1964) 	 	 	 -
Popenoe (1966a) 	 	
Popenoe (IflOGb) 	 - 	
Schmidt (1962a)
Schmidt (1962b) 	 	 	
Total 	
Area (figure 10)
Oak Ridge. Tenn.
Idaho Falls, Idaho (NETS)
Pittsburgh, Pa.
Columbus, Ohio
Los Angeles, Calif.
San Francisco, Calif.
Chicago, 111.
Camden, N.J.— Philadelphia Pa
Norfolk, Va.
Galveston, Tex.
Las Vegas, Nev.
Santa Barbara, Calif. (Arguello)
Parr, S.C.
Orlando, Fla.
Cincinnati, Ohio
Albuquerque, N.Mex.
Atlanta. Ga. (GNL)
Gnome-Carlsbad, N.Mex.
Washington, D.C. (Ft. Belvolr)
Minneapolis. Minn. (Elk River)
NPW England (North)
Now England (South)
Denver, Colo. (Rocky Flats)
Augusta, Ga. (Savannah)
RlchJand, Wash. (Hanford)

Population
00 feet in the
aircraft to DE rate at 3 feet above ground was
not performed in the ARMS reports. A conver-
sion factor of 1 ftrem/hr. at 3 feet from  25 cps
at 500 feet  (for  cesium-137, 0.662 MeV gamma
ray) is reported in many of the ARMS reports
and is based on the  work of Davis and Reinhardt
(1962). It should be noted that  the monoenergetic
emission of  cesium-lH7  is probably not  repre-
sentative of  the wide spectrum  of energies ob-
served in radiation from natural  radionuclides.
A low energy component from  scattered  radia-
tion is especially prominent with these nuclides.
In  addition, the conversion  factor obtained  by
Davis and Reinhardt is based on flights over dis-
tributed point sources  on  the  surface  of the
ground rather than  over a uniform volume  source
24

-------
such as natural terrestrial radioactivity. Thus, it
does not appear valid to use this conversion (25
cps = 1 /trem/hr.) for terrestrial DE rates due
to natural background radiation. In addition, un-
published experimental work by K. Larsen (Uni-
versity  of California at Los Angeles) is quoted
in the ASMS reports  in  relation to  the contri-
bution from fallout. Larsen is quoted by Popenoe
(1966a)  as  stating that "... a  count rate  of
approximately 77,000 cps measured at 500 feet
above the ground by Geological Survey  equip-
ment over an infinite fallout source is equivalent
to 1 mR/hr. measured at three feet above the
ground . . ," or  77 cps  =  1  jirem/hr. This
value was used in conjunction with figure 11  in
order to correct the ARMS data, for fallout con-
tribution. Fourteen areas had  fallout  corrections
of less than 1 /irem/hr., whereas the fallout DE
rate in 11 areas was greater than 1 /irem/hr.
  Ground measurements  were  compared with
aerial data  from  several locations in order  to
arrive  at a conversion  for  natural  emitters.
There  are four  separate determinations of this
conversion:
1. MacKallor (1962), based on a comparison  of
  ground survey and aerial measurements, found
  a conversion of 47 cps (500 feet) =  1 jarem/hr.
  at 3 feet.  However, the ground and air meas-
  urements were taken li/fc years apart, during
  which time the dose contribution  to fallout
  changed by 1.6 /irem/hr. When this difference
  is accounted for, the conversion is 76 cps  =
  1 /trem/hr.
2. Levin et al. (1968)  reported an average DE
  rate of 8.5 /trem/hr. in Little Falls, Minn. (76
  measurements);  the  ARMS  data map  (Neu-
  schel, 1970) for this location presents an aver-
  age  of 275 cps.  To  compare the two,' 0.9
  /arem/hr.  (fallout in summer of  1965  from
  figure 11)  and 43 prem/hr.  (ionizing compo-
  nent of cosmic radiation) were subtracted from
  the ground value; the fallout value from figure
  11 in the summer of 1961  was  0.8
  or 0.3 X 77 = 23 cps. Thus,
                       et al. (1968) and Neuschel (1970) for Falcon
                       Heights, Minn. In this case, the conversion was

                                 325-23     _   90 cps
                              8.6- (0.9+4.3) ~ 1 prem/hr.

                     4. A total of 16 terrestrial measurements,  cor-
                       rected  for  fallout (Beck et al., 196ia,  1966a),
                       were obtained in Denver, Colo., in 1962, 1963,
                       and  1965.  The  average DE rate  was  11.6
                       /trem/hr. The ARMS map  for this area gives
                       a value of 850 cps in the vicinity of Denver,
                       and the fallout contribution during the ARMS
                       study was  0.37 /irem/hr., or 28 cps. The con-
                       version value is thus

                                  850-28 _   71 cps
           275-23
76 cps
        8.5-(0.9+4.3)     1 /*rem/hr.

3. A similar comparison was made from Levin
                                   11.6
Based on the comparison of aerial and ground
data, a factor of 78 cps at 500 feet = 1 /irem/hr.
at 3 feet was assumed for converting the aerial
data to dose values at the 3-foot level. In apply-
ing this factor to the  data of all ARMS areas,
it is assumed  that the  source  spectra  do not
change significantly across the  United States,
i.e.,  the relative  contributions  of potassium-40,
uranium-238, and thorium-232 do not change dras-
tically. This assumption is  supported  by the
countrywide spectrometric surveys of Beck et al.
(1964ab, 1966a). In addition,  the utility of aerial
survey data  has  been  enhanced by the  demon-
stration that the DE  rates  from potassium-40,
uranium-238, and thorium-232  show almost ex-
actly the same  variation  with height (Beck and
La Planque,  1968).
  The procedure in analyzing the aerial data may
then be summarized as follows :

counts/sec, at 500 ft. minus fallout correction
               78 cps//irem/hr.
                            = j*rem/hr. at 3 ft.

The data were then grouped in 2 /»rem/hr. inter-
vals in order to arrive at figures 13, which pre-
sent the percent of each ARMS area  vs. DE
rate. The average DE rates of the ARMS  areas
varied from  1.51 prem/hr. in the Orlando, Fla.
area to 10.23 /xrem/hr. in the Rocky Flats-Denver,
Colo., area.

-------
40
20
0
40
20
_i
1 °
g SO
ce
cvj
•<
«c 40
u.
o
a»
20
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40
20
0
*
60
40

r 20
N. NEW ENGLAND (»)
.


I I I I 1
1 '

S. N
_H , H
-
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CAMUhN / PI
..h.
- I
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*
NORFOLK, VA. (e)

L_^
40 1-
	 1 — . — V 1
20
EW ENGLAND (b) ^
£
UJ g
Z
UJ
= 40
• Ol
S
OS
fe 20
0
80
1ILADELPHIA (c)
60
i i 	 }
40
FORT BELVOiR / D.C. (d)
20


,ii.l
=3 	 1 	 1 0
,
, PARR.S.C. (f)
."""H- -^_



•

1
CAPE KENNEDY • ORLANDO, FLA. (h)
II ^ | 1 1 f i
            0    2    4    6    8    10    12   14    16
                           /JREM/HR.
02    4    6    8   10   12   14    16
               V REM HR.
                                Figure 13.  Dose equivalent rates in ARMS areas

                                           (mean denoted by arrow)
26

-------
40






20





 0



40





20





 0



60
|  40
a
20





 0



80






60






40






20
                                GEORGIA NUCLEAR LAB.

                                -ATLANTA, GA.  (i)
                                  OAK RIDGE, TENN.  0)
                                  PITTSBURGH, PA. (k)
                                   COLUMBUS, OHIO  (1)
     0    2     48    8    10   12    14    IS    18
                                                            40 r
                                                            20
                                                             60 r
                                                             40
                                                             20
                                                          Of
                                                          a.
                                                             40 r
                                                          o

                                                    -l     «' 20
                                                                                      CINCINNATI, OHIO in
                                                                                    i     I
                                                                                         CHICAGO. ILL-  in)
-
,
1


1


MINNEAPOLIS, MINN (o)
1 i i i
                                                                                       GALVESTON, TEX. (p)
                                                                                         i     i     i
                                                             02     4    6     8    10   12    14    16

                                                                                   ' HR.
                    Figure 13.  Dose equivalent rates in ARMS areas—Continued

                                      (mean denoted by arrow)

-------
        20
       40 -
       20 •
       40 r
        20 -
       40 r
                                  — ft
                                                  ROCKY FLATS -
                                                  DENVER, COLO, (q)
                                               ALBUQUERQUE, N M. ID
-
1
t



CARLSBAD (GNOME), N.M. (s)
-



1
1 1


NRTS - IDAHO FALLS, IDAHO (I)
1 1 , i , , •
                                                                       g
                                                                                            HANFORD • RtCHLAND, WASH (v)
                                                                                              SAN FRANCISCO, CALIF, (w)
                                                                                    ARGUELLO- SANTA BARBARA. CALIF. (1)
        20
                                                                          40
-JLA
                                        LAS VEGAS, NEV.  (u)
                                                                                                LOS ANGELES, CALIF,  (y)
          0    24     6    6    10   12   14    16    18   20   22   24
                                  V REM / HR.
                                                                  0    2    4    6    8    10    12    14   16
                                                                                     fJ REM / HR.
                              Figure 13.   Dose equivalent rates in ARMS areas—Continued

                                                 (mean denoted by arrow)
28

-------
  Each histogram covers between 98 to 100 per-
cent of the respective ARMS area with the excep-
tion of Las Vegas, which covers 95.2 percent of
the area. The totals do not add up to 100 percent
in each case since the count rate data for 1 to
2 percent of some areas  were presented in very
broad  contours (i.e., 1,200 to 4,000 cps)  relative
to the rest of the  map data.  In  general, the
omitted portions covered  unpopulated areas such
as mountainous terrain. The highest count rate
found in the ARMS data  occurred in the  Las
Vegas area (Guillou et al.,  1963) and the Albu-
querque area (Guillou, 1966d), where a maximum
of 4,000 cps was observed (50 /trem/hr.). In both
cases the locations were unpopulated; the Albu-
querque area maximum occurred in  the vicinity
of a uranium mine.
  The original ARMS data are grouped in count
intervals which commence at zero cps, and this is
reflected in the histograms, which in most  in-
stances commence at a zero DE  rate. Therefore,
it should be noted that the zero DE rate repre-
sents the lower limit of the ARMS reporting
method rather than an actual  estimate  of  DE
rate. The mean DE of each area was computed
by assuming that the midpoint of each DE inter-
val (1, 3, 5, etc.) was representative of the DE
for the respective  interval,  and the means are
designated by arrows on figure 13.
  By weighting the individual  distributions of
figure  13 by the population of each area, a sum-
mary  histogram  was  obtained  (figure  14), of
which  the mean is 5.0 /irem/hr.,  or 44 mrem/yr.
As shown in table 11, the overall mean of 9,026
measurements by Levin et  al.  (1968)   is  77
mrem/yr. If the ionizing component of  cosmic
radiation is assumed to  account for 36 mrem/yr.,
then the terrestrial  DE  is  41  mrem/yr., which
compares well with the mean obtained from the
ARMS data. A summary of 210 ground  survey
measurements (Beck, 1966b) also is presented in
figure  14, and, as can be seen, the  mean is ap-
proximately 40  percent higher  than the value
derived from the ARMS data. The locations of
Beck's  (1966b)  measurements  are  not  given;
however, the measurements  are  a summary  of
data reported in Beck et al. (1964ab, 1966a). The
latter references include 16 measurements  (rang-
ing from 7.1 to 15.2 ^rem/hr.) in the relatively
high  background area of Denver and  measure-
ments over  unpopulated granitic  outcrop--  in
North Carolina; this could explain the hipher
overall  mean.
  Three distinct areas of terrestrial radiation are
evident from an analysis of the ARMS data.
First, the Coastal Plain, bordering  the Atlantic
Ocean and the Gulf of Mexico, has a terrestrial
radiation level of approximately  half  the  U.S.
average. This is partially evident from the mean
exposure  of three  areas  lying entirely on the
plain: Norfolk (3.09 /irem/hr.), Orlando  (1.51
/irem/hr.)  and Galveston (2.26 prem/hr.). The
Coastal Plain includes marine deposits of Qua-
ternary, Tertiary and Late Cretaceous age (Xeu-
schel, 1966;* Schmidt, 1967a)  and  is shown in
figure 12.
  Neuschel  and Schmidt observed  in  their re-
spective reports of ARMS surveys (Washington,
D.C., and the AEC's Savannah River plant) that
the portion of the area on the Coastal Plain was
considerably less radioactive than the rest of the
area.  In order to quantitate this observation, the
radiation levels of  four areas which  straddle
the Coastal  Plain were  studied in  more detail.
Table 13  summarizes the DE rates of  the  total
and partial Coastal Plain area. It is interesting to
note that the average radiation level in the  non-
Coastal Plain portion of the mixed areas is simi-
lar to the U.S. average.
Table 13.  Dose equivalent rates in areas on or straddling
                the Coastal Plain
Area

Washington. D.C.-Fott Belvoir —
Norfolk _ 	

Savannah River 	 	

Galveston 	
Average 	
Mean dose equivalent rates
daemfla.}
Coastal
Plain
1.9
3.2
3.1
2.9
3.5
1.5
2.3
2.6
Non-
Coastal
Plain
4.9
5.0
4.0
5.S
4.9
Entire
area
2.7
4.1
3.1
3.8
3.9
1.5
2.3
3.1
  In order to compare the Coastal Plain and non-
Coastal Plain regions graphically (excluding the
Denver ARMS data),  the ARMS data for each
region  were population-weighted in  the  sam?

-------
                 40
             <  30
             oc
             LU
             UJ

              a.
             CM
                 20
                 10
                   0     2
                                 1
        SUMMARY: ARMS MEASUREMENTS

                    x = 4.98/u REM/HR.
                      = 43.7 mREM/YR.
6    8     10    12    14    16    18    20
      /I REM / HR.
                 40
                 30
              QC
                 10
        SUMMARY: 210 HASL MEASUREMENTS
                       (BECK, 1966 b)
                   x = 6.97 MREM /HR.
                    = 61  mREM'/YR.
                   0     2     4     6     8    10    12    14    16     18    20

                                           AIREM/HR.

            Figure 14.  Dose equivalent from terrestrial sources based on population-weighted
                                         ARMS data
30

-------
manner that was used to obtain figure 14, and the
resulting distributions are  presented in figure
15. As can be seen, the DE  in  approximately 80
percent of the Coastal Plain area is  less than 4
/»rem/hr. (35 mrem/yr.), whereas most of the
non-Coastal  Plain  (64 percent) lies in the range
4 to 8 f*rem/hr. (35 to 70 mrem/yr.).
                            COASTAL PLAIN
                            X =22.8 mREM / YR.
                            NON-COASTAL PLAIN
                            « = 4S.AnREII / YR.
    0    2     4     C     B    10    12
                 DOSE EQUIVALENT - IIREM / HR.

Figure 15.  Dose equivalent from terrestrial  sources
       in Coastal and non-Coastal Plain regions

  The areas  of table 13 are all on the Atlantic
Coastal Plain except Galveston, and therefore it
is assumed  with  less  certainty that  the Gulf
Coastal Plain follows the pattern of lower radio-
activity that  was observed in the Atlantic Coastal
Plain. The  natural radioactivity  of Gulf and
Atlantic beach sands has been shown to be rela-
tively uniform (Mahdavi,  1964);  yet this fact
can probably not be related to  the radioactivity
of the entire Coastal Plain since Mahdavi's sam-
ples were taken on and near the beaches. Signifi-
cant uranium ore deposits exist in the Tertiary
portion of  the Coastal  Plain  of south  Texas
(Finch, 1967), and the deposits may be reflected
 in increased radiation levels over the region  of
 the deposits. There are no reported measurements
 in the region, which  is sparsely  populated, and
 there are no other significant deposits in the en-
 tire Coastal Plain. Recognizing the limitations  on
 data from the Gulf  Coastal Pkin, it  will  be
 assumed  that the  Gulf and Atlantic  Coastal
 Plains follow the same pattern of producing low
 terrestrial radiation exposures. This assumption
 is based primarily upon the fact  that both areas
 have similar  geology, i.e., marine sediments de-
 posited since the late Cretaceous age.
  The second region of the United States, which
 stands apart from the rest, is the Denver region
 of Colorado. Based on the ARMS data analysis,
 the mean terrestrial DE rate for the Denver area
 is 10.2 /irem/hr. This is approximately 40 per<»nt
 higher than the next  highest value of 7.3 /trem/
 hr.  (Albuquerque area)  and twice the  average
 of  all the ARMS  areas. Phair  and Gottfried
 (1964)  found that  levels of uranium and tho-
 rium were twice the normal crustal concentra-
 tions over  a  7,000  square  mile area  along the
 Colorado Front  Range.  Furthermore, they ob-
 served that the Front Range was the only large
 area in the United States in which the uranium
 and  thorium concentrations in bedrock were con-
 sistently above average. Much of the Denver sur-
 vey  area is over alluvia derived from the Front
 Range,  and the  aerial data and  the previously
 mentioned  ground  data  (Beck  et  al.,  1964a,
 1966a)  corroborate  the measurements of Phair
 and Gottfried (1964), There is no evidence  to
 suggest that  other areas of  higher terrestrial
 radiation and comparable size to the Front Range
 exist in the United States.
  Levin et al. (1968)  obtained ground readings
 in 11 Colorado towns, none of which were in the
 Denver ARMS area.  They  found terrestrial  +
 cosmic  -f  fallout  DE  rates of 11.6 to  14.6
 /irem/hr.; the average of all Colorado measure-
 ments  was 13.3  /*rem/hr.  If cosmic  radiation
 and  fallout (1966) are assumed to result in 7.3
 /irem/hr., then the average terrestrial  DE  in
 Colorado  outside  the  ARMS area  is  about 6.0
/irem/hr., which  is similar  to the values ob-
tained in  many  of  the  ARMS areas. It  is
not  suggested that natural  background levels
vary according to political  units. The fact is,
                                                                                              31

-------
 however, that Xe\v Mexico, Colorado, Utah, and
 Wyoming are the principal uranium ore-bearing
 States (Finch, 1967), and it is not surprising that
 areas on alluvia derived from ore-rich  regions
 would have higher background radiation levels.
   If the Coastal Plain and Colorado may be con-
 sidered as the location of low and high values of
 terrestrial  radiation, than  the balance  of  the
 United States represents a vast Middle America,
 radiologically speaking.  A summary of ARMS-
 derived  DE  rates due to terrestrial  sources is
 presented in table 14, and these estimates will  be
used in chapter -i to compute the total  DE due
to natural radiation.
Table 14.  Dose equivalent rate from terrestrial sources
       based on population-weighted ARMS data
Area
Coastal Plain 	
Non-Coastal Plain (excluding


Average - -

Population
covered by
ARMS (1900)
6 750 772
46 781 330
1 073 624



Dose
equivalent
(mrem/yr. )
22.8
45 6
89 7

43.7

32

-------
      CHAPTER 4. NATURAL RADIATION  EXPOSURE  OF  THE  U.S.
                                      POPULATION
  In the preceding chapters, two major natural
contributors to population DE have been consid-
ered.  These are  (a)  cosmic radiation  and (b)
terrestrial  radiation.  In order  to  calculate  an
average and range of external DE in the United
States, it is necessary to consider the  influence
of population distribution on exposure from each
of these two sources.  Initial  calculations are  di-
rected to the determination of external radiation
DE from these two sources outdoors, and these
estimates will then be modified in this chapter
to consider the influence of housing construction
and  man's biological shielding on  DE to the
gonads and bone  marrow.

4.1.  External Sources

  The calculation of  DE from external sources
has been performed by considering the popula-
tion  to  be located  in either urbanized or non-
urbanized areas; an urbanized area, as described
by the U.S. Census Bureau, is a city  (including
suburbs) which has a total population  of more
than 50,000. As of the 1960 census, there were 213
urbanized areas in the  United States,  som'e of
which overlap adjoining States. The nonurban-
ized  areas of the 50 States are treated  as addi-
tional segments.  Thirteen of the  50 States  lie
partially on the Coastal  Plain as shown in figure
12. Each of these States contains two nonurban-
ized segments corresponding to the Coastal Plain
and non-Coastal Plain portions, and thus there
are 50 +  13 — 63 nonurbanized segments. The
total number of areas is 310, 247 of  which are
urbanized and 63  of which are nonurbanized.
  Urbanized  and nonurbanized areas were se-
lected as the basis for  the model because they
provide the potential for updating exposure esti-
mates in the future as new census  data  become
available.  As  a  secondary reason, manmade
sources of 'radiation  are  concentrated  around
urban areas  (hospital  use  of x rays and radio-
nuclides and nuclear power reactors), and this
model may facilitate  the  computation of total
natural and manmade radiation exposure.
  For each population segment, the cosmic ray
 (ionizing and neutron components), terrestrial,
and total external radiation DE rates have been
calculated. The cosmic  ray DE rates due to ioniz-
ing and neutron radiation were calculated based
on  the elevation of each segment and the data
presented in figure 6.  The terrestrial DE rates
for each population segment were assigned on the
basis of general estimates from table 14, except
in the case of those urbanized areas (49)  which
lie within the boundaries of ARMS areas. These
areas have been assigned a DE which was ob-
tained by converting the measured count  rate in
the same manner as discussed in Chapter  3.
  The results of the computations for each area
are shown  in appendix A, tables A-l and A-2,
and a summary of DE estimates is  presented in
table 15. The data in the table are  presented In
two different ways, urbanized vs. nonurbanized
areas and  Coastal Plain vs. non-Coastal Plain.
First, the mean and ranges of data for urbanized
areas and nonurbanized areas are given. The most
significant  difference in the two groups is  the
average and range of elevations; urbanized areas
range  in elevation  from 5  feet (New Orleans.
La.)  to  5,980 feet (Colorado  Springs,  Colo.),
vrhereas  the  nonurbanized population lives  in
areas ranging up to 10,500 feet (Leadville, Colo.,
and  vicinity). The  terrestrial  DE ranges from
                                                                                           33

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             Table 15. Dose equivalent outdoors from terrestrial and cosmic radiation (1960 census)


Nonuruanized areas 	
Coastal Plain 	


IS sinmimrv 	
Population
(>.-i,S48.4S7
83,474,688
32,140.217
147.1*2,!i.->8
1T1I.32S.715
Populated eleva-
tion (feet)
Mean
4S1
965
170
824
707
Range
5 !i 980
0-10,500
0-400
0-10,500
0-10.500
Cosmic ray DB
(mrem/yr.)
Mean
43
4o
41
44
44
Range
40-83
40-160
40-42
40-160
40-160
Terrestrial DE •
< mrem/yr. )
Mean
41
40
24
44
40
Bangc
0-120
0-120
0-90
0-120
0-120
Total external
DE •> (mrem/yr.)
Mean
83
85
65
88
84
Range
40 -200
40-300
40-130
40-300
4O-300
Inte-
grated
DE (10«
man-rem)
8.0
7.1
2.1
13.0
15.1
   • Lower and upper limits correspond to values presented In figure 15.
   'Totals are based npim the combination of cosmic ray and t«rn»*trlnl DE. The UE's for the nonurbanlzed and non-Coastal Plain
areas, and the total Vnlted States, have been rounded off to 300 mrcm/yr.
approximately  10  mrem/jT.  (12  mrem/yr. in
Orlando, Fla.) to 92 mrem/yr. (Denver, Colo.).
At present, there is no reason to  indicate that
the populations of urbanized and nonurbanized
areas  have  different  exposures  to  terrestrial
sources. A  similar  conclusion  was  reported by
Segal 1 and Eeed (1964), who found no difference
in DE to residents of urban and rural regions in
New Hampshire and Vermont. The total DE due
to external sources  is also practically  the  same
for both areas, and the difference  in integrated
exposure  (man-rem) is due to the difference in
population of each group.
  It is interesting to note from  table  A-l  that
the lowest cosmic and terrestrial DE  estimates
both occur in areas on the Coastal Plain, and the
highest values of each occur in Colorado. For this
reason the results have also been divided into the
Coastal Plain  and  non-Coastal  Plain  regions;
Denver has been placed in the latter category in
this classification. As can be seen, there is a large
difference in the ranges of cosmic and terrestrial
DE in both regions. Although the mean of cosmic
radiation DE is approximately the same in both
regions, it can be seen that the range of DE in the
non-Coastal Plain (40 to 160 mrem/yr.) is much
greater than the range in the Coastal Plain  (40
to 42 mrem/yr.). In contrast to this,  the  mean
terrestrial DE of the non-Coastal Plain region is
nearly twice that of the Coastal Plain. This is as
expected, since the  terrestrial DE  estimates are
based on the results of the ARMS surveys which
were summarized in the previous chapter. As  a
result  of  the difference in terrestrial DE, there
is considerable difference  in the total DE of the
two regions. The differences in total DE, in addi-
tion to the fact that the Coastal Plain holds only
18 percent of the population, are reflected in the
larger integrated DE  (man-rem) of  the non-
Coastal Plain population.
  Summary data for the entire United States are
presented in the last line  of table 15. As can be
seen,  the  average DE  of  the population due to
terrestrial and cosmic ray sources is 84 mrem/yr.;
this value will be used to calculate the gonadal
DE in section 4.4. The distribution of the popu-
lation vs. external  radiation levels  is presented
in figure  16.  In order to  determine the overall
distribution of population DE in figure 16, the
terrestrial DE in each population segment was
assumed to be distributed as shown in figure 15,
except for  those segments  in  ARMS areas for
which the terrestrial DE  could be directly  esti-
mated. In other words, those population segments
in table A-l for which a general estimate of ter-
restrial DE  is  given  (22.8 or 45.6 mrem/yr.)
                                         n
    0    20    10    SO   80    100   120    140   ISO   180
                   DOSE EQUIVALENT «REM TEAR


 Figure 16.  Population distribution vs. dose equivalent
         from terrestrial and cosmic radiation

-------
were  assumed to have a variation  in terrestrial
DE as shown in figure 15. A cumulative distribu-
tion of population vs. DE is presented  in  figure
17. As can be seen, virtually the entire population
receives less  than 1TO mrem/yr.
II
     0    20   «    W    JO   ICO    120   1«    160   ISO
                    DOSE EQUIVALENT mREH YEAR

Figure 17.  Cumulative distribution of population vs.
  dose equivalent from terrestrial and cosmic rediation

  The distribution in figure 16  should be  re-
garded as an approximation  of the population
distribution vs. external DE  since the distribu-
tion is based upon aerial surveys of terrestrial
DE  rather than on estimates  of population DE
within the survey areas. It should also be noted
that the distribution is based on  the two  quite
different distributions of terrestrial  DE in the
Coastal and non-Coastal Plain regions, as shown
in figure 15. The contribution of the  Coastal
Plain distribution of terrestrial  DE, which is
skewed  strongly to the right, is muted in figure
16 since only 18 percent of the population resides
in the Coastal  Plain.

4.2. Attenuation of External  Sources

  The estimate of man's DE which was presented
in section 4.1 is that due to natural external radi-
ation sources and is based on outdoor measure-
ments.  In this section, the effect on the DE of
housing construction materials, biological shield-
ing  and  the contribution  of internal emitters,
principally potassium-40, will be  discussed.

  4.2.1.  Housing
  Inasmuch as man spends most  of his time in-
doors, the nature of construction materials will
influence his exposure to natural sources. In gen-
eral, the interiors of stone houses have the highest
exposure  rates; brick and frame houses have the
next highest. The amount of time spent indoors
will, of course, determine the importance of con-
struction materials as a source. Estimates of both
factors, time and -the amount of natural radio-
activity in building materials, are based on  rela-
tively little  data, and  probably represent the
greatest uncertainty in estimating man's exposure
to natural sources.
  A summary of  indoor measurements is  pre-
sented in table 16. As can be seen, exposures in
                           Table 16. Ratio of indoor to outdoor dose equivalent
Country and reference
United States:
Solon et al. (1960) 	
United States :
Lowder and Condon (1965) —
East Germany :
Ohlsen (1969) - 	 - 	
Poland :
Pensko et al (1969) 	
United States :
Yeates et al. (1970) 	
United States :
Ilndeken et al. (1972) 	
Building material
(outer vails)
Frame, brick, and stone apart-
ments and nouses
Mostly wood frame
(half-frame
Pre-1945 ^ stone
(brick
fbrick
Post-1945 •{prefabricated
[mixed
All buildings
Concrete and brick
Frame
Brick
Steel and concrete
Mostly wood frame (96%)
Ratio of Indoor/outdoor
DB (%)
Approx. 80-100
70
78
106
81
72
68
66
82
102
82
96
87-106
78
Bemarks
17 dwellings
160 single homes
667 Indoor measurements
Single homes and apartments
732 measurements In 97 new
apartments
5 single homes. 1st floor
1 apartment. 2nd Boor
4 office buildings
110 single homes
                                                                                               35

-------
frame dwellings are 70 to 80 percent of outdoor
values.  In masonry buildings the percentage is
somewhat higher (80 to 106 percent), which indi-
cates that the DE from nuclides in the building
material partially offsets the  attenuation  of out-
door terrestrial sources. It is interesting  to  note
that, the second-floor measurements by  Yeates et
al.  (1970) in single family  frame houses  aver-
aged  84 percent of  the first-floor measurements.
In a multistory building of masonry construction,
however,  there is no apparent variation of  the
DE with height  in  the building  (Ohlsen, r.»7<>;
Pensko et al., 1969). The comprehensive measure-
ments by Ohlsen indicate that buildings of more
recent construction  (since 1945) tend to  have
lower  indoor DE  rates  than  older  buildings,
at least in the  German  Democratic  Eepublic
(DDR). Although  buildings of "mixed"  con-
struction  materials  may  include a number of
variations, the low inside DE ratio for this type
of construction possibly reflects the increased use
of glass, plastics, steel, aluminum, and other ma-
terials containing relatively little natural radio-
activity.
  In order to determine what  effect building con-
struction might  have on natural exposures,  it is
necessary to make assumptions  on how people
spend  their time in various  activities. A  basic
approach to this problem has been taken in  ap-
pendix  B, in which it  is estimated that indoor
living habits of the United States result in  the
population  receiving  80  percent of  the  out-
door DE.

  4.2.2. Biological shielding
  The estimates  of DE  in  section 4.1 are  for
tissue with  no  self-shielding. Since the gonadal
DE and bone marrow DE are often used for dose-
risk assessment, it is necessary to determine the
effect of buildup and attenuation of radiation in
the overlying tissue. The most widely quoted ref-
erence on this subject, UXSCEAR, (190-2), recom-
mends a screening factor of 0.6 for gonadal and
bone marrow dose rates  from terrestrial radiation.
This  factor  was partly based on the work of
Spiers (19.10), who found that terrestrial  gamma
radiation was reduced by factors of 0.5-2 to ().,">!)
depending on the body  orientation. In males, the
screening factor varied  from  0.67 to 0.7-2. In  both
sexes, the least  attenuation (i.e., highest screen-
ing  factor)  occurred  in the standing  position,
the greatest  attenuation was provided in a hori-
zontal position,  and intermediate attenuation oc-
curred in a sitting position.
  More recent work by Bennett (1970) indicates
that the gonadal screening factor, averaged  over
both sexes, is 0.82, and a personal communication
from Bennett indicated that he believes  the  bone
marrow screening factor also to be  closer to 0.8.
In  addition  to  discussing limitations of  earlier
work, Bennett also has inferred similar screen-
ing factors from work by Jones (1966) and Clif-
ford and Facey  (1970). Based on  these data, it
is assumed that in the  present work a screening
factor of 0.8 describes the biological shielding of
the gonads  and bone marrow by overlying tis-
sue. The shielding  factor is assumed to  apply to
the terrestrial component of  background  radia-
tion and not to cosmic  radiation,  which is more
penetrating.  This is the same approach used by
UXSCEAR  (1962, 1966).


4.3. Internal Sources

  This study is  devoted primarily to natural ex-
ternal sources of radiation, which have been dis-
cussed in the  preceding sections;  however,  in
order to arrive  at  an overall estimate of whole
body exposure, the contribution of  internal  nat-
ural emitters also  must be  considered.
  The average potassium content of the body is
about 0.2 percent. On the basis of  g K/kg body
weight, males show higher values past the age
of puberty, but this is related to the difference
in fat content of the body since fat contains  rela-
tively little potassium (Anderson  and Langham,
19,")S). Females have more fatty tissue than males
and therefore have a lower ratio of g K/kg body
weight. Ninety  percent of  the tissue DE from
potassium-40 is due to  /3 particles  (range  =  2
mm in tissue); the  remaining 10 percent is due to
gamma rays (Rundo, l!)f>0). Therefore, the tissue
DE is  largely determined  by the  potassium-40
concentrations within the tissue in  question.
  Gonadal  concentrations of  potassium  in the
I'.S. population are 0.2 percent and 0.14 percent
for males and females, respectively  (Tipton and
Cook, 1963); these concentrations correspond to
36

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DE rates of 19 and 13 mrem/yr., assuming the
conversion factor  calculated by Rundo  (1960).
For the  purpose of estimating gonadal  DE. an
average of these two values, 16 mrem/yr., will be
assumed.  Other  internally  deposited  natural
nuclides,  principally   rubidium-87,  carbon-14,
radium-226,   radium-228,   polonium-216,   and
radon-222, are assumed to  result in DE  rates to
the gonads  and bone  marrow  of 2 mrem/yr.
(UNSCEAR, 1966). These estimates will be pre-
sented in section 4.4, in which  the overall esti-
mate of population DE is  made.

4.4.  Dose  Equivalent to the Gonads
     and Bone Marrow
  Table 17 presents a summary of gonadal DE to
the U.S. population. The estimates for cosmic and
terrestrial exposure are based upon  the results
of section 4.1, and  the terrestrial DE contribution
Table 17.  Gonadal dose equivalent to the U.S. popula-
            tion from natural radiation
Source
External
Terrestrial 	 	 	 	 	
Bousing factor = 0.80 (section 4.2.1)
Screening factor = 0.80 (section 4.2.2)
Internal
Other nuclides 	 	 —
Total 	
Dose equivalent
(mrcm/yr.)
26
44
16
2
88
has  been reduced by  the housing and  gonadal
screening factors of section 4.2. As can  be seen,
the estimate of DE to the gonads from natural
radiation sources is 88 mrem/yr. Since all mem-
bers of the population are exposed to background
radiation, the gonadal  DE is also equivalent to
the genetically significant DE. It should be noted
that the reduction of terrestrial  radiation  con-
tribution to gonadal DE is 14 mrem/yr. due to
biological and housing attenuation. However, this
reduction is offset by the contribution of  internal
emitters (18 mrem/yr.).  With  this in mind, it
can be seen that figures 16 and 17 are also reason-
able approximations of the population distribu-
tion vs. gonadal DE.
  Estimates of DE to the bone marrow from in-
ternally deposited nuclides are 15 mrem/yr.  be-
cause of potassium-40 and 2 mrem/ yr. because of
the  other  nuclides  mentioned in  section 4.4.3
(UXSCEAR, 1966). As has  been di.-x-ussed,  the
same biological screening factor  is assumed  for
bone marrow as for gonads, so that the bone
marrow DE from terrestrial and cosmic sources
is the same as that  presented in table 17, or 70
mrem/yr. Thus, the  total bone marrow DE from
natural sources is 87 mrem/yr.
  The estimate of gonadal DE in table 17 is con-
siderably  lower  than  the  UXSCEAR   (1962)
worldwide estimate  of 125 mrem/yr.. which i<
often  cited in the United States as the "base-
line"  radiation  level  against  which  manmade
radiation  sources  are compared.  If the  relative
importance  of manmade sources  is evaluated by
comparing the magnitude of manmade and nat-
ural radiation DE, as is often done, then it follows
that manmade radiation sources must  be con-
sidered as a  more significant  portion of  man's
total exposure to ionizing radiation.


4.5. Discussion
  The estimates of DE in the present work are
based upon measurements and census and  housing
data from many different sources.  For this rea-
son it is not possible to calculate the variance of
the end result in the conventional manner. It is
possible, however, to discuss  the uncertainties
which affect the separate components of the over-
all totals and, based  on the uncertainties, to esti-
mate  the  accuracy   of the  several  important
factors. These contributing errors are taken to
represent in each case a sample at the 95 percent
probability  level  drawn from a normal  popula-
tion of observations.
  Cosmic radiation  accounts for approximately
40 to 70 percent of the external radiation DE to
the  U.S. population. The  ionizing and  neutron
components contribute about 85 and 15  percent,
respectively, of the cosmic ray DE. The estimate
of the sea-level ionization values, from which the
DE  estimates are derived, is probably within 10
percent of the true value; however, the sea-level
neutron value may be in error by as much as 50
percent. As  a result,  the  cosmic ray DE at a

-------
specified elevation is probably within 12 percent
of the true value.
  At this point it is appropriate to discuss the
uncertainties present in the determination of the
terrestrial DE, which is based upon the aerial data
conversion values discussed in section  3.3.3. In
this regard,  there  are  three  observations to be
made  on the  conversion determination. First,
three of the  four individiial conversion determi-
nations (1., 2., and  3.)  in section 3.3.3. required
a cosmic ray correction. The relationship is  such
that, for example,  a 10 percent decrease in the
cosmic ray DE will result in approximately a  7
percent increase in  the terrestrial DE  estimate,
so that the net effect of a change in the cosmic
ray DE on the overall DE estimate is small.
  Secondly, it should be noted that the fallout
correction  value does  not  have  a  significant
influence on the final conversion factor. For ex-
ample,  if the fallout correction  in  conversions
"1, 2, and 3'' in section 3.3.3. were  increased by
100 percent  (3.2, 1.8, 1.8, respectively)  the aver-
age terrestrial DE decreases by 20 percent (from
40 to 32 mrem/yr.), and the overall DE decreases
by  approximately  10 percent  (from  84 to 7(i
mrem/yr.). It should be noted that a 100 percent
decrease in the present fallout estimates will have
a smaller effect—approximately a 10 percent in-
crease in the terrestrial DE and 5 percent increase
in the overall DE.
  Thirdly, since the terrestrial and cosmic  ray
DE  are approximately  the same, an  arbitrary
change in the conversion  value  (with no change
in cosmic ray DE) will have a smaller impact on
the combined estimate. For example, a 10 percent
change in the conversion  value  (and terrestrial
DE) will result in a 5  percent  change in  the
overall DE.
  The average terrestrial  DE estimated for the
entire United States is probably  within 20  per-
cent of the true value.  Support  for  this belief
rests primarily on the similarity in AKMS  esti-
mates of ground DE rates and the spectrometric
data-DE estimates by Beck (1966b). The accu-
racy  of DE estimates for  individual ARMS
areas and urbanized areas within ARMS areas is
strongly influenced by the accuracy  of  the weap-
ons  fallout DE during the time of each survey.
During much of  the 1961 to 1963  period,  for
example,  the DE from weapons-testing  fallout
was 50 percent or more of the natural terrestrial
DE. As a result the DE estimates for the ARMS
areas are  probably within 30 percent of the true
value. Most of the locations in appendix A were
assigned terrestrial DE values based on location
—either   Coastal  Plain  or  non-Coastal  Plain.
These estimates may be in error by 50 percent.
  The estimate of the contribution of internal
emitters  to  gonadal  and bone  marrow  DE is
probably  within 30 percent of the true value.
The estimate in this work is slightly lower than
the  commonly quoted USSCEAR  (19<>2)  esti-
mate of 25  mrem/yr., and this is due to the use
of more recent and complete data for the potas-
sium-40 contribution to the  total.
  The biological  shielding  factor  used  in this
work is believed to be within 10 percent of the
true value,  based upon the similarity of recent
estimates  (Bennett,  1970). As has already been
mentioned,  the other major modifying influence
on the natural radiation  source term is the con-
tribution  and attenuation by  housing. Even with
the uncertainties present in the development of
the  housing factor,  it seems unlikely that this
factor is in error by  more than 20 percent. The
amount of time spent  outdoors is based on little
more than a guess;  however, if this proportion
were 0.25 instead of 0.05, the  housing factor
would only  increase to 0.84, or by 5 percent.
  A summary of the error estimates is presented
in table 18, and as can be seen the gonadal DE
is 88 ± 11 mrem/yr. The error of the bone mar-
row DE  also may be assumed to  be the same.
The error calculation  tends to impart an unin-
tended sense of precision to the overall estimate.
Therefore, one may wish  to say that the estimate
Table 18.  Estimate of errors in determining the gonadal
            dose equivalent (appendix C)
Parameter
Terrestrial DE » _ 	
Housing factor 	 _„-.

Cosmic DE
Internal emitters

Gonadal DE 	

Value
40
0.8
8
44
18

88

2
-------
of the average gonadal and bone marrow DE is
approximately 90 mrem/yr.
  In summary, the average DE from terrestrial
radiation (unattenuated by housing or biological
shielding)  and cosmic radiation to the U.S. pop-
ulation is 84  mrem/yr. There are three distinct
areas of different population DE—the Coastal
Plain, non-Coastal  Plain (excluding  Denver),
and Denver vicinity. Eighteen  percent  of the
population lives in the Coastal Plain, where the
mean DE is 65 mrem/yr., and 82 percent lives in
non-Coastal Plain regions where the mean DE is
88 mrem/yr. The Denver area, which has approx-
imately  0.5 percent of the population, receives
165  mrem/yr. Population DE  in the  United
States probably varies by a factor of 7.5, from
approximately 40 to 300 inrem/yr.
  In view of the  uncertainties which affect the
development of natural radiation exposure esti-
mates, one may question the improvement of the
results over earlier estimates  and the usefulness
of the results. The  use of the ARMS data has
provided a basis for directly estimating the nat-
ural exposure of approximately 30 percent of the
U.S. population, which is a considerably larger
sample  than can  be associated with  previous
ground surveys. In addition, the same data indi-
cate the existence  of three distinct areas of ter-
restrial radiation in the United States.  Through
the determination  of the U.S. population distri-
bution vs. elevation,  it is now possible to cite
State-to-State differences in cosmic ray  DE.
  The present data may be used as a guide to the
average U.S. background radiation exposure and
as reasonable estimates  of background  exposure
in the areas for which ARMS data exist. Caution
is advised when using the total  DE  estimates
for locations in  which  general  terrestrial DE
values have been assigned, although the  total DE
estimates for these locations are of value  in assess-
ing the relative contribution of cosmic  ray DE.
The DE estimation procedure outlined in appen-
dix A may be  refined as more specific  data be-
come  available  on natural radiation DE rates in
various sections of the country. Similarly, infor-
mation  concerning living  habits may  easily  be
factored into the computation, and the author
would be  grateful for any information which
could be  used  for updating and improving the
present DE  estimates.
                                                                                             39

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                                          SUMMARY
   Natural background  constitutes  the greatest
source of ionizing radiation to the world's popu-
lation today. This exposure is by no means uni-
form for all individuals, but  varies because of a
number  of influencing factors.  Such factors in-
clude  altitude,  geological  features, and  living
habits.  The  resulting variations  in  exposures
often exceed  those from manmade sources which
generally receive considerably  more attention. For
example, although no detailed  overall study of
the subject has  been made, published data indi-
cate that the genetically significant  dose  equiva-
lent  (DE)   from  natural background  in the
United States ranges from 80  to 200  mrem/yr.
A survey conducted  by the U.S. Public;  Health
Service  in 1964 indicated that the comparable
dose  from  medical  x radiation was only 55
mrem/yr. Other sources, such  as nuclear reactors,
fallout from  atmospheric weapons tests, etc., ac-
count for a DE less than 5 mrem/yr.
  The purposes of this study of  natural radiation
exposure in the United States  were to better esti-
mate population dose from radiation of natural
origin,  to investigate the  DE  variations  that
occur, and to examine the parameters that influ-
ence both the levels and the variations so that the
relative importance  of manmade exposures can
be better evaluated.  In undertaking these tasks,
it  was recognized  that external  exposure  to ter-
restrial radiation sources, a primary component
of natural background exposure, can  be estimated
by direct measurements or calculated on the basis
of knowledge of chemical assays of natural emit-
ters  in  the  soil. Direct measurements  and  soil
analyses,  however,  have  not  been  sufficiently
extensive  to provide  adequate data  to  make an
overall  estimate of  the population  DE  in the
United States. For these reasons, alternate meth-
 ods were sought and an answer was found in the
 series of ARMS conducted over major  areas of
 the United States under sponsorship of the AEC
   A  second  major  component of natural back-
 ground  exposure to  the  population is cosrnl-
 radiation.  The  DE from  this source was com-
 puted on the basis  of  knowledge of the distribu-
 tion of population with elevation. The third, and
 last,  major component of  population dose from
 natural background, that is, exposure from natu-
 rally occurring radionuclides deposited within the
 body, was calculated  on the  basis of published
 information. Once data were available for the DE
 from each of the three major components of nat-
 ural background, a combined estimate of the total
 cosmic and terrestrial  DE  was made taking into
 account  what is known concerning the distribu-
 tion  of  population by elevation,  geology, and
 living habits. These  data were  then combined
 with those for internal exposure to yield a final
 estimate of total population  dose  from natural
 sources.
   The primary problem in  using the information
 resulting from the  ARMS surveys  was in con-
 verting the count rate  data taken at altitude into
 DE rate data at ground level. In addition, there
 was the  necessity in certain cases of subtracting
 the contribution of  weapons testing fallout from
 the ARMS readings. Suitable corrections for this
 latter factor  were made, and a conversion factor
 for the ARMS data was determined by correlat-
 ing the measurements at a number of jioints with
 readings made at 3 feet above ground level. The
 mean terrestrial DE, obtained on the basis of -2.">
 areas surveyed under  the  ARMS program and
 weighted for the population  of  each  area, was
computed to be 44 mrem/yr. This value compared
well with results from limited ground  survt-y-
                                                                                             41

-------
within the United State?, which are summarized
in the text.
  On the basis of an analysis of the ARMS data,
it appears that the United States can be divided
into three distinct terrestrial radiation zones, or
areas. One is the Atlantic and Gulf Coastal Plain,
which includes all or portions  of all States bor-
dering the Atlantic Ocean and Gulf of  Mexico
from Texas to  Xew Jersey. For this  area, the
mean terrestrial DE was -22.8 mrem/yr. The sec-
ond area is  a portion of the Colorado  Front
Range, on the eastern slope of  the Rocky Moun-
tains, which yielded a mean  terrestrial I)E rate
of 89.7 mrem/yr. This  is somewhat as expected
since  this  area (approximately 7,000  square
miles) has crustal concentrations  of  natural
radionuclides which have been shown to  be ap-
proximately twice the U.S. average. The  DE  in
the rest of the United States, that is, excluding
the Coastal Plain and the Colorado Range, was
calculated to be 45.6 mrem/yr.  When the distri-
bution of the  population  in the three zones was
considered, the mean terrestrial  DE in the  United
States was calculated to be 40 mrem/yr.
  A detailed analysis of the distribution of pop-
ulation with elevation showed that 83 percent of
the people in the United States  live in areas with
an  elevation of less than 1,000 feet. Populated
areas, however,  occur up to  10,500  feet.  At sea
level, the ionizing  and neutron  components  of
cosmic radiation result  in  DE of 35  and  6
mrem/yr. for a total of  41  mrem/yr.  The DE
increases to 44 mrem/yr. at 1,000 feet and ranges
up to 162 mrem/yr. at 10,500 feet. On this basis,
the DE from cosmic radiation  for various popu-
lation  groups  in the United States  varies by a
factor of 4. Overall, the calculations revealed that
the average DE from this source in the  United
States was 44 mrcm/yr.
  Combining the DE from terrestrial and cosmic
radiation, the average DE to the U.S. population
from natural external radiation was computed to
be. 84 mrem/yr. per  person. Based on the 1960
census, this results in an integrated DE  of 15.1
million man-rem/yr.  The range in DE  in the
United States is 40 to 300 mrem/yr.; however,
almost the  entire population receives  less than
170  mrem/yr.
  For the purpose of determining the  DE to the
gonads and bone marrow, the influence of hous-
ing,  biological shielding,  and internal emitters
was  also considered. A  "housing  factor"  was
computed to take into account the attenuation of
terrestrial  radiation  due to building  materials.
This factor included allowances for  the major
types of building materials in use in the  United
States and for the percentage of total  time spent
indoors by the population. Also included in the
calculations was the attenuation  of  terrestrial
radiation by body tissues. On the basis of these
considerations, the ratio of indoor to outdoor DE
from terrestrial sources was calculated to  be 0.8;
coincidentally the biological  "screening  factor"
was estimated to be 0.8. Allowing for these factors
and  a DE  from  internally deposited radionu-
clides  of 18  mrem/yr.  to the gonads  and 17
mrem/yr. to the bone marrow, the  total gonadal
and  bone marrow DE  for the U.S. population
were  calculated  to  be  88  and  87  mrem/yr.,
respectively.
  It is to be noted that the gonadal DE as calcu-
lated in this study is considerably lower than the
UXSCEAR worldwide estimate of 125 mrem/yr.,
which is often cited in  the United States as the
"baseline'7 radiation level against which manmade
radiation sources are  compared. If  the results of
this  study are true, it is quite probable that cer-
tain  manmade sources, particularly medical x ra-
diation, will now be given greater importance in
terms  of their overall contribution to the popu-
lation's total dose.
42

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46

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APPENDICES

-------
                      APPENDIX  A
      Calculation of Average Dose Equivalents
      due to Terrestrial and Cosmic Radiation *
Table A-l.    Calculation of average dose equivalents due to
              terrestrial  and cosmic radiation by  State urban-
              ized and unurbanized areas
Table A-2.    Total  calculation  of average  dose  equivalents
              due to terrestrial and cosmic radiation by States
Table A-3.    Program to  calculate  average  dose equivalents
              from terrestrial and cosmic radiation
  4 Some of the values in the following tables are presented in tenths of
mrem/yr. This was done in order to avoid rounding off errors, and one
should not assume that the data are known to the accuracy indicated by
the numbers.

-------
Table A-l.  Calculation of average dose equivalents due to terrestrial and cosmic radiation by State urbanized and nonurbanized areas
1
IPCATIPN
,
I960
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,
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4
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36.?
35.7
35.7

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41.9
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39.6
36.1
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41.7
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43.0
40. 9
41 .1
41 .5
41.6
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47. 5
41.6
41.6

44.8
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41.6

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77.8
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SAN DlFT.n CA
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STA BARBARA TA
STOCKTON CA
CALIFORNIA Nil
CALIFORNIA
	 	
cniORAon SPC, rn
	 DENVER en
PUEBLO en
COLORADO Nil
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65
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391

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41
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48
48
47
48
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6. I
6.0
6.1
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5.7
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6.0
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15.1
1 7.9
17.4
36. 0
35. «
15.8
37.0
35.1
37.6
15.4
15.4
15.4
15.4
35.3
37.1
36.0

63.1
57.9
54.0
59.8
51. «
47.1
41 .8
41. 7
41. H
41.0
44.6
41 .0
41.1
41.1
41.0
40.9
44.0
42.2

82.6
74.9
69. 1
77. fl
76.2
45.6
45.6
31 .9
45.6
45.6
45.6
75.9
45.6
45.6
36.4

45.6
R9.7
45.6
45.6
65. P.
P 7. 7
P7.4
RQ.4
86.6
90.2
R6. 6
68. 7
6B.7
76.9
86.5
19.6
78.6

1 28.2
164.6
IU.7
123.4
142.0
11646
16677
i°120
14071
7?420
166905
41106
5594
12251
17 3H10

12144
132245
11854
92171
249066

-------
tnVltr BAIIATIOM Of
                                           i=7«-9
                                        TrT\L  rXT
"»%££" i"
^'flPITMM -T
So"-"""1/7
l^wn rr"""1
TNM Ml
rr«m

"FL'WAOF M'l-rP
"K««A»F

WASH nr
HASH pr.
FT LA»n rL
iuSi^i11" rL
»rNSArnL«Li=l
TAMPA FL
W PAH nci'h ei
nrPiriA

IL'ANY 01
AUANTt f,A
CMATTA fit-TS
Mgr^N CA
r.FnpiitA HII-CP
Crn«r,jA s l-Nrp
r-FORr.H
M"M1l.MU MI

HAHMI
— 3s<"»'. 	 pi 	
qo Q4/. 700

l<.fQ,QO 3"5
" \k\i-tt, ' 'mn
.'5"'34 Jft9

?7o^4 ''n
446'0? ](,<:

7«'3'3'S^ 1SQ
Tft^OSS JSQ
319051 10
3^2^69 70
3S?705 10
7OOt""% TO
179049 l^
30170(1 | *V
I14IM T>^
16<1*(<(7 70
10^0^00 'SO

3*43116 6RO
3MT-6 ,.

*7
53
53
53
51
S3
st
53
S3

51
M

50
50
„
37
39
38
3D
3ft'
38

47
44
44
45
43
43
43
47

43
21

21
S*.7
5.1
5.7
5.7
sil
4'.l
5.1

s.a
S.7
5.7

S.I
S.I
5.6
5.6
5.6
S.7
5.6
5.6
5.6
5.7
5.7

5. ft
7.1
S.«
6.5

si5
7.0
6.A


S.I
35.'
35.3
35.5
35.6
3S.3
35.4
35.3
35.7
35.9
35.6

35.4
35.4

35. S
35. S
35,'
35.3
35.3
35.4.
35.3
35.3
35.3
35.'
35.4
35.4

35.6
37.4
35. S
34.6
35.7
35.1
35.'
35.7
37, S
36.7
35.3

35.5
40.9
41.0
41.3
41.5
44.0
41.0
41.1
41.0
41.6
41.9
41.4

41.3
41.1
*I.Z

41.3
41.3
40.1
40.9
40. <)
41.1
40.9
40.9
40.9
40."
41.?
41.0

41.4 "
44.7
41 .3
43.1
41.7
41.9
40.1
41.4
44. S
43.3
40."
41.1)
41.3
"8.8
41.4
*?.?
«0.3
Tfi.O
40.0
64.4
«s!t
51.1

77.1
?o.» -

3B .4
"5.4
72.0
":5
11 .4
72. 8
"i°
27. •
72.3


47.1
45.6
77. R
72. A
45.6
'0.9

4?.6
4«,6
90, T
14.5
113.1
iu.n
•1.1
P7.S
02.5

77.5
72.0

76.7
7fr,7
63.7
43.7
6'. 7
K2, 7
•S3.T
63.7
43.7
63.7
*4, p
63.4
,
64.7
14.1
PR. 7
f4.S
63.7
-.0.1
12.2

•7.'.
P6.9
36544
31 43 «
4901
10»9S
913'
755*
17SO9
HI '49
'34503

20433
U'.°7
3M25

S3616
51414
7031S
23751
54337
I OS90
*16l
19235
11016
1'.57!3
3)3399

3741
«3'3
l in*
14?9
7315
10»31
1 36O06
3?4I30

'4597
SS003

-------
CO
Table  A-l.   Calculation of  average dose  equivalents  due to terrestrial and  cosmic radiation by  State urbanized and nonurbanized
                                                         areaa—Continued
1
LOCATION

I04HC NU
IDAHO
2
1960
POPIII ATI1N

667191
667191
5 , 4
ELEVATION MAGLAT
FFFT CFG NO

3*59 51
3650 51
COSMIC RADIATION OE
M&FMS/YR
5 &
NEUT ION
1?.3 48.1
17.3 48.1
7* 54 6
TOTAL
60.4
60.4
8
TERR DOSE EQ

45.6
45.6
9-7«fl 10-(2X9|X.001
TOTAL

106
106
EXT OE

.0
.0
MAN-REM

70751
70751
AURORA ti
CHAMPAIGN IL
CHICAGO IL
DAVENPORT Il-IA
OECATUR IL
OUBUQUE IL-IA
JOLIET IL
PEORIA IL
ROCK FORD IL
ST LOUIS IL-M1
SPRlNGFIELn IL
ILLINOIS NU
ILLINOIS
CHICAGO IN-!L
EVANSVILLF IN
FT WAYNE IN
INDIANAPOLIS IN
LOUJSV'LE IN-KY
HUNCIE IN
SO REND 11 -MI
TERRA HAUTE IN
INDIANA Ntl
INDIANA

CECAR RAPins IA
DAVENPORT IA-IL
DES HO INF S I A
OUBUQUE IA-U
1MAHA 1A-NE
SOUIX CTY IA-NE
WATERLOO IA
IOWA NU
IOWA

ST JOSEPH KS-KO
TOPEKA «S
WICHITA KS
KANSAS NU
8S522
7K014
5480767
12M58
("9516
2082
1165D5
181M'
1716BI
J76791)
111401
316?203
10081H9
478446
1 436SO
179571
639140
7?396
77S04
198514
1141 5
?79USZ
4662496

105118
101018
241115
5716S
60547
89990
102827
1999557
2757537

1191
119500
292138
1 493687
636
740
595
500
682
645
545
470
715
470
610
738
641
595
790
710
450
«50
710
495
779
729

730
590
805
645
1040
1110
850
1125
1040

850
910
1290
1570
52
50
52
51
50
52
50
51
52
48
50
52
52
52
52
50
49
51
52
50
50
50

52
51
51
52
51
52
52
52
52

48
49
48
47
48
6.5
6.6
6.4
6.4
6.5
6.5
6.3
is. 2
6.6
6.?
6.4
6.6
6.5
6.4
A.I
6.7
6.6
6.2
6.9
6.6
6.3
6.7
6.6

6.6
6.4
6.7
6.5
7.1
7.2
6.8
7.2
7.1

6.6
6.8
6.9
7.5
7.9
36.5
36.7
36.4
36.4
36.6
36.5
36.3
36.1
36.7
36.1
36.4
?6.7
36.5
36.4
35.9
36.9
36.7
36.1
37.3
36.7
36.2
36.8
36.7

36.7
36.4
36.9
36.5
37.5
37.7
37. 0
37.8
?7.6

36.8
37.0
37.2
38.3
39.2
43.0
43.4
42.8
42.8
43.1
43.0
42.6
42.3
43,3
42.3
42.9
43.3
43.0
42.8
4^.1
43. A
43.2
4?. 3
44.2
43.2
42.4
43.5
43.3

43.3
42.8
43.6
43.0
44.6
44.9
43. 8
45.0
44.6

43.4
43.8
44.1
45.6
47.1
38.6
45.6
38.6
45.6
45.6
45.6
44.3
45.6"
45.6
45.6
45.6
45.*.
41 .7
38.6
45 .6
45.6
45 .6
4S.6
45.6
45.6
45.6
44.9

45.6
45.6
45.6
45.6
45.6
45.6
45.6
45.6
45.6

45.6
45.6
45.6
45.6
45.6
81.6
89.0
81.4
88.4
B8.7
88.6
86.9
87.9
R8.9
17. 0
98.5
"8.9
84.7
81.4
P7. 7
89.2
88. P
87.9
89.8
P8.8
"8.0
89.1
88.2

88.9
86.4
")9.2
88.6
90.7
90.5
89.4
90.6
90.2

89.0
89.4
89.7
91.4
92.7
6975
6940
446088
11150
7943
184
10133
15956
15255
24299
9854
299059
853836
38986
12593
16010
56797
6362
6961
17633
7167
248721
411232

9347
8928
21511
5082
5462
8146
9193
181135
248803

24215
106
10723
26687
138512
                     KANSAS
                                      "JT78611	T395-
                                                                               46TT
                                                                                 ~4776~
91.9

-------
1
2
3
4
COSMIC RADIATION OE
LOCATION 1">60 ELEVATION MAGLAT MREMSfYB
POPULATION FEET DEC NO 5 6

CINTI KY-OH
HUNT KY-WV-OH
LEX INGTON KY
LQUISV'LE KY-IN
KENTUCKY NU-CP
KENTUCKY NU-NCP
KENTUCKY

BATON ROUGE LA
LAKE CHARLES LA
MONROE LA
NEW ORLEANS LA
SHREVEPORT LA
LOUISIANA NU-CP
LOUISIANA

179489
48091
111940
534263
1TOOOO
1994373
301815*1

1934H5
80115
80546
845237
206581
1 8". 0056
3257022

550
565
055
450
340
934
788

57
20
P2
5
204
100
77

50
49
48
49
47
48
48

40
40
42
40
42
41
41
NEUT
A. 3
6.4
6.9
6.2
A.O
6.9
A. 7

5.7
5.6
1.7
5.6
5.9
5.7
5,7
I3N
36.3
36.3
37.3
36. I
35.9
37.2
36.9

35.4
35.3
35.4
35.1
35.6
35.4
35.4
7-5*6
TOTAL
42. A
42.7
44.2
42 ,_3
41.9
44.2
43. A

41.1
40.9
41.1
40.9
41.5
41.2
41.1
8
TER» POSE 50
MREMS/YR.

30.?
4-J.6
45. h
45.6
?2 .fl
45.6
43.4

?2.8
22.8
?2.R
22.8
72.8
?2.8
22.8
9:7*8
10-12X9IX.001
TOTAL FXT OE MAN-REM
MREMS/YR

72.8
B8.3
89.8
87.9
S4. 7
89.8
87.0

43.9
63.7
63.9
63.7
64.3
«4.0
63.9

13073
4246
1005T
4*950
1 1 000
179996
264320

12354
5681
5148
53850
13407
117709
201149

LEWISTON ME
PORTLAND ME
MAINE NU
MAINE
BALTIMORE MO
WASH CCIMOI
MARYLAND NU-tP
MARYLAND NU-NCP
MARYLAND
BOSTON MA
BROCKTON MA
FALL RIV MA-RI
FITCH-LEO MA
LAW-HAVER MA-NH
LOWELL HA
NEW BEDFORD MA
PITTSFIELD MA
PRO'DENCE MA-RI
SPRNGFLD MA-CT
WORCESTER MA
MASS NU
MASS
ANN ARBOR MI
BAY CITY Ml
DETROIT MI
FLlNV MI
45751
111701
792311
969265
1418948
578«80
470000
632761
3100689
2413236
111315
1177*7
72347
165233
118547
126657
62306
43381
418313
225446
I 27*010
5148578
115282
72763
3537709
2*7>86
200
25
3«5
139
20
150
100
558
16A
27
no
40
440
65
100
15
1015
80
85
475
492
190
§18-,^
iff-
600
715
56
55
56
56
51
50
50
51
51
54
54
53
54
54
54
53
54
53
54
54
54
54
53
54
53
53
5.9
5.6
6.1
6.0
5.6
5.8
5.7
6.3
5.8
5.6
5.8
5.7
6.2
5.7
5.7
5,6
7.0
5.7
5.T
6.2
6.3
5.9
6.B
6.4
6.*
6.6
35.6
35.3
36.0
35.9
35.3
35.5
35.4
36.3
35.6
35.3
35.5
35.3
36.1
35.4
35.4
35.3
37.5
35.4
35.4
36.1
16.2
35.6
37.1
16.4
J6.4
36. T
41.5
41.0
42.1
41.9
40.9
41.3
41.2
42.7
41.4
41.0
41.3
41.0
42.2
41.1
4t.l
40.9
44.5
41.1
41.1
42.4
'4i.4
41.5
*».9
42 IS
42.8
43.3
45.6
45.6
45.6
45.6
27.4
35.4
22.8
45.6
31.9
45.6
45.6
45. A
45.6
45.6
45.6
45.6
27.9
41.9
40.0
53.1
4.5.6
45.2
45.6
45.6
43.6
45.6
87. 1
86.6
87.7
87.?
68.3
76. 7
f>4.0
88.3
73.3
86.6
06.9
86.6
87.8
86.7
86.8
86.5
72.4
83.0
81.1
95.5
88. 0
86.7
89.5
88.4
88.4
8B.9
5681
9669
69477
84827
96985
444] 6
30066
55849
227316
208910
9668
10201
6355
14321
10286
10960
4511
3601
33937
215Z2
UMU
446418
10320
H-*iz
312796
24683

-------
w        Table A-l.  Calculation  of average  dose equivalents  due to terrestrial and  cosmic radiation by  State urbanized and nnnurbani/.cd
                                                                   areas—Continued
1
2
LOCATION 1<>60
POPULATION

GRn RAPIDS MI
JACKSON M|
KALAMAZOO Ml
LANSING MI
MUSKEGCN HI
SAGINAW HI
SO REND MI-IN
MICHIGAN NU
MICHIGAN

DULL'TH MN-WI
FAPG HOOP MN-NO
MlNN-ST PAUL «N
MINNESOTA NU
MINNESOTA

294230
71*1?
115*50
169325
OS350
129215
2 04 19
29?4044
7823194

110826
25054
1377143
1910841
3413B64
3
4
COSMIC RADIATION OE
ELFVATIflN MAGLAT MREMS/YH
FEET DEC NO 5 6

610
940
Ti1*
H30
*25
•<95
710
S17
701

6i n
900
*15
1403
in*

53
53
?3
53
53
54
52
54
54

56
56
55
54
54
NEUT
6.4
>>.9
h.6
6.7
A. 4
6.4
6.6
6.7
6.6

6.4
>>.9
b.7
7.6
7,2
ION
3*. 4
37.3
36. n
31.0
36. 5
36.4
36.7
36.9
36.7

36.4
37.2
36.9
38. A
37.9
7=5+6
TQTAI
4?.o
44.2
43.4
43.7
42.9
42.8
43.7
43.7
43.2

42.0
44.0
43.7
46.3
45.1
P
9=7+9
10=1 2X91 X.001
TFPH nnsE Ft) riTAi EXT OF MAN-OEM
MREMS/YR MREHS/YR

45.6
45. *
45.6
45.6
45.6
45.6
45.6
45.6
45.6

45.6
45.6
31.2
45.6
39.8

IS.I
89. 8
89.0
R9. 3
88.5
88.4
88.8
89.3
8fl,8

88.5
89.6
'4.1
91,9
14,9

26026
4411
10205
15124
0440
11422
1814
261012
694776

9803
2245
103087
174680
289815

JACKSCN MS
•MSS'IPPI NU-CP
MISSISSIPPI

KANSAS CY MQ-KS
ST JOSEPH MP-KS
ST LOUIS in- i i
SPRINGFIELD MO
MISSOURI NU-CP
MISSOURI NU-NCP
MISSOURI
147480
20)0661
2178141

6*0026
79096
1391398
97?24
150000
1952169
4319813
294
267
269

750
850
470
1300
350
881
719
42
43
43

48
49
48
47
47
48
48
6.0
6.0
6.0

6.6
6.8
6.2
7.5
6.1
6.3
6.6
35.8
35.7
35.7

36. S
37.0
36. 1
38.3
35.9
37.1
36.7
41. 8
41.7
41,7

43.4
43.8
42. 3
45.8
41.9
43.9
43.3
22.8
2?. 8
22.8

45.6
45.6
45,6
45.6
22.8
45.6
44.8
64.6
64.5
64.5

89,0
89.4
87.9
91.4
64.7
89.5
88.1
9521
13091 8
140438

57760
7152
122369
8886
9711
174773
380651

BILLINGS MT
GRFAT FALIS MT
MONTANA NU
MONTANA
LINCCIN NF
OMAHA NE-IA
SIOUX CY NE-IA
NEBRASKA NU
NEBRASKA
LAS VEGAS NV
NEVADA NU
NEVADA
6071?
57629
556426
674^67"
136220
329334
7200
938576
1411310
89427
125662
2*5278
3120
3*30
3521
3469
1150
1040
1110
1604
1426
2030
4565
3754
54
55
54
54
50
51
52
50
50
43
45
45
1 1.0
11.5
12.0
11.8
7.2
7.1
7.2
8.0
7,7
8.8
14.8
12.8
45.5
46.5
47.4
47. 2
37.9
37. 5
37.7
39.3
38.8
40.9
53.2
49,2
56.5
58.0
59.4
59.0
45.1
44.6
44.9
47.3
46.5
49.6
68.0
62.1
45.6
45. 6
45.6
45.6
45.6
45.6
45.6
45.6
45.6
19.9
45.6
45.6
37.5
102.1
103.6
105.0
104.6
90.7
90.2
90.5
92.9
92. 1
69.5
1 13.0
113.6
99.*
6199
5970
58423
70592
12355
29709
652
87199
129915
6216
7930
14272
28*1 8

-------
   I
               1960
                      	3	4
                       ELEVATION MAGLAT
 COSMIC RADIATION Of
	MRFMS/YR	
   5	6	7^5*6
                                                                                              10=I2X9|X.OOI
LOCATION
            POPULATION   FEET
                                 PEG  NO
                                                                  TERR OOSF FO
                                                                     HREMS/YR	
TnTAl EKT OF
   MREMS/YR
                                                                                                NAN-HEM
LAM HAVER NH-HA
MANCHESTER NH
NEW HAMP NU
N HAMPSHIRE
ATLANTIC CY NJ
NEW YORK NJ-NY
PH1LAOEL NJ-PA
TRENTON >)J-1>A
WILMINRTN NJ-OF
N JEfcSFY «IIJ-CP
N JE»SFY NU-NCP
NEW JEOSFY

ALBUQUfOUE NM
NEW MEXICO NU
NEW MFXICO

ALBANY NY
B1NGHAMPTON NY
RUFFAin NY
NEW YORK NY
ROCHESTER NY
SYRACUSC NY
UTICA RQMF NY
NEW YORK NU
NEW YORK

ASHEVtLLE NC
CHARLOTTF NC
DURHAM NC
HIGH POINT NC
GREENSBORO NC
RALEIGH NC
WTNSTCN SAL NC
N CAROL NU-CP
N CAROL NU-NfP

FARC MOOR ND-MN
N DAKOTA NU

892
91698
514331
60*921
124902
3878897
531995
226561
17320
44000O
857096
6066782

241216
709807
951021

455<.*7
1581*1
1 054370
10236030
493402
11?2W
1 P7779
3863849
16782104

6859?
209551
84642
66543
123 334
93931
128176
1410000
2371386
4556155
47676
584770
632446
65
175
712
630
10
30
45
35
115
200
?««
81

4<)58
5254
1179

'0
865
5"5
50
515
400
415
544
217

2216
721
414
940
841
361
860
100
1204

900
re'B'7 	
1628
54
54
55
55
51
52
52
52
52
52
52
52

43
43
43

?4
53
54
52
54
54
54
53
53

46
46
47
47
47
47
47
47
*7
4T '
56
56
$6
5.7
5.8
6.6
6.5
5.6
5.6
5.7
5.6
5.8
5.9
6.0
5.7

16.0
16.9
16.7

^.6
6.8
6.4
5.6
6.3
6.1
6.2
6.3
5.9

«.l
6.6
h.l
6.9
6.8
6.1
6.8
5.7
7.3
6.?
6.8
8.1
8.0
35.4
35.6
36.7
36.5
35.3
35.3
35.4
35.3
15.5
35.6
35.8
35.4

55.7
57.7
57.2

35.3
37.1
36.4
35.3
36.2
36.0
36.0
36.3
35.7

'41. 6'
36.7
36.0
17.3
37. 0
35.9
37.1
35.4
18.0
	 vo 	
37.2
19.6
39.4
41. 1
41.4
4?, 2
41.0
40.9
41.0
41.0
41.0
41.3
41.5
41. P
41.1

71. h
74.6
73.8

40.9
43.9
42.8
41.0
47.5
42.1
42.2
42.6
41 .6

50.7
43.1
42.2
44.2
43. 8
42.0
43.8
41.2
45.3
43.8
44. O
47.7
4?. 5
45.6
45.6
45.6
45.6
22.8
45.6
47.5
41 .9
16.2
?2.8
45.6
43.5

69.5
45.6
51 .7

25.1
45.6
45.6
45.6
45.6
45.6
45.6
45.6
45.0

45.6
45.6
45.6
45.6
45.6
45.6
45.6
22.8
45.6
3*7? 	
45.6
45.6
45.6 	
86.7
87.0
88.8
88.6
63.7
86.6
58.5
82.9
77.5
64.1
«7.4
84.6

141.1
120.2
125.5

66.0
89.5
88. 4
86.6
8B.1
87.7
87. 8
88.2
86.6

" 46.3
88.9
87.8
89.8
89.4
87.6
89.4
64.0
90.9
82.4
89.6
93. >
9T7T 	
77
7977
45696
53750
7959
115821
46206
18780
1142
282T6
74875
513259

'4047
85315
1 19362

nos?
14147
93166
886199
41472
29231
16479
140816
1451613

6605
18625
?4?8
S974
11 02 1
8227
11464
90198
21-56T4
• • iTrju
4272
;4$Ri
5TTOTT

-------
en        Table  A-l.  Calculation of average dose equivalents  due to terrestrial and cosmic  radiation by  State urbanized and  nonurbanized
                                                                  areas—Continued
I
IOC»T

ION
f
I960
POPULATION
1
ei FVATIHN
FFFT
4
OEG NO
fnSMlC PAD1ATION DC
KOFMWYR
5 6
7»5»6
8
TFBP 0"Sf EO
9»7»1
TOTAL FXT
MRFMSS

Of
f
10>(2X9I X.
1AN-PEM
001

AXRCN OH
CANTCN 1M
CINCINNATI 1H
CLEVFUNP OH
COLU*8US OH
OAYTCN DH
HAMH TIN 1H
HUNT OH-KY-WV
LIMA CM
LO»-FLY»IA PH
SPRINGFIFin nH
STFUBENVL riH-NV
TOlfftO OH
HHFFLING OH-HV
OH 1C Nil
(IHln

FT SMITH PK-AG
LAKTC* IK
TIILSA OK
OKi/kHonMlulNrP
1KLAHCHA

FUGFKE OR
HRFGHN NIJ
ORFfiCN
AllFN-RFT* PA
E»IF PA
HARRfSRUPR °A
J1HNSTOWN PA
LANCASTER PA
PHIIAOEL PA-NJ
READING PA
5rP ANTON PA
TRFNTON PA-NJ
YORK PA
PFNN N'l
458251 1077
213574 1060
114079 5*0
1 7R4991 6RO
616741 7RO
501664 7S7
19771 605
67961 PRO
4731* 715
418211 5R7
11471 650
4014«i'l 799
9706197 717

M941 1109
29897? 744
70001 450
1466171 15J?
712R784 1M4

9S616 4??
604729 77
106R772 1063
176P697 69]
25601S 755
R1O51 URO
177411 685
96474 1185
3111213 ?45
1 P04400 760
160297 265
210676 725
15838 35
100R7? 370
47637H1 750
11
5?
"I
50
50
49
51
52
5 1
51
52
51
'2
52
52

45
43
45
44
45
45

51
5?
51
51
52
52
53
52
52
52
52
5^2
52
53
52
53
51
52
7.0
7.1
6'.5
6.*6
6.4
I'.l
7,0
6 '.5
6.7
6.6

7.2
7,1
6.6
7.8
7.5

5.7
7.1
6.6
5.9
7.1
6.5
6.1
7.3
6.1
5.7
6.6
5.9
6.6
5.6
6.5
6.1
6.6
.17.5
37.4
16. 1
16.6
36."
36. •
16.4
36.3
37, 1
16.4
37. 4
16.7
36.4
36.5
17.0
36.9
16,4

16. 1
37.7
3R. 0
16. R
36.1
39.0
38.4

J5.4
37.6
36.8
35.7
38.0
36.6
35.9
38. 0
15.9
35.4
36. A
35.7
36.7
35.3
36,5
35.9
36. A
44, 6
44.7
47.6
41.1
43.4
42. R
42.7
43.9
47.8
44, 1
43.1
47. S
41.0
41.1
43.6
41.4

42.1
44.9
45.4
41.4
42,3
46. R
45.9

41.1
44.7
43.1
41.6
45.2
41.1
42. 0
45.3
42.0
41.0
43.4
41.7
43.3
41.0
43.0
42.0
41.4
45. f
4S.6
10.?
45.6
M.*
41.9
45.6
45.6
47 .*
4«,6
45.6
60. «
45. <•
68.9
40. P
45.6
41.9

45.6
45.6
45 .6
45.6
45.6
44.9

45 .6
45,6
45.6
45.6
4e,6
4*. 6
45.6
4* ,6
45.6
45.6
42.5
52.0
45.6
45.6
41.9
45.6
45.6
27.8
90.7
72.
88.
15.
R8,4
8R.3
91,4
18.4
103.8
1R.4
111.9
14.6
19.2
87.1

87.0
90.5
9],O
19.0
65.1
12.4
90. R

17. e
86,7
90.3
88,9
«7.2
90. R
88.7
90.9
87.6
13.5
95.4
87.3
88,9
82.9
88.6
87.6
66.2
41312
19285
5929?
158366
52679
47803
7940
?198
5756
12616
8109
4909
3R731
3746
11519
358068
147149

164
5607
39040
76595
4555
115547
211508

9399
52433
96476
1 571O8
27331
7545
15745
1 8150
8766
8217
260008
172202
13988
187Z8
1313
20719
8837
315337
                                                                              4TTT
TSTT

-------
COSMIC fiAOIATlON Dt
                                          9.7*8
                                                    10-1?XS|X.001
   l**60    EiEViTtnN MAGLAT     HRFMS/Y
PQ!>UiaT10N   PEPT    DEC NO    S	6
                            HKFHS/Yft
FAIL «IV ol-MA
PRO'OENCF 91-NA
RHODE 10 Nil
OHPOE IP
AUGUST* SC-G4
CHARLESTON $<•
CdLUHBIA SC
GREENVHIF SC
S CAB 01 NII-CP
S CAROL NU-NCP
S CAHOUN*
SIOUX CV Sn-lA
MODI FALLS SO
S OAKCTA Nil
S DAKOTA

CHATTA TN-GA
KNOXVULF TN
KPMPMIS TN
NASHMILLf TN
TFNN NU-NCC
TENNESSEE

ABILFNF TX
ANARIUO T*
AUSTIN TX
8EAUNCNT TX
CORPUS CHITS TX
•3ALLAS T«
FT KORTH TX
MARLINGEN TK
HOUSTON TX
LARIOO TX
LUB60CK TX
MIDLAND TX
ODESSA TX
PORT ARTHUR TX
SAN ANJElA Tl
SAN ANTONIO TX
T»LER TX
UACO TX
6164
616161
737161
'HO^HB
12D2D
160113
162601
1Z61S7
1)10000
1110165
'.^83?5
*5
**
«5
45
52
S3
S3
53

*5
46
45
46
46
46
46

42
44
39
40
37
42
40
42
39
36
39
37
42
41
41
40
41
38
42
4l 	
5.7
5.7
5.9
5.7
5.8
5.6
5.9
6.9
5.7
6.5
fc.Z
7.2
7.6
8.7
H.6

6.5
6.8
6.0
6.2
6.0
7.0
6.6

8.2
12.1
6.3
5.6
"• 	 o
6.3
12.6
£.5
5.6
5.6
5.7
6.2
11.3
10.)
10.?
5.6
1.4
6.6
6.0
6.3
6.2
35.3
35.4
35.6
35.5
35.5
35.3
35.7
37.3
35.4
36. «,
36.1
37.7
38.6
40.7
40.5

36.6
37.1
35.7
36.1
35.5
37.5
36.8

39.8
48.2
36.3
35.3
5?.}
36.2
48.7
36.6
35.3
35.3
35.4
36.0
46.1
43.9
44.4
35.3
*6.J
36.6
35.8
36.3
U.6
41.0
41.1
41.5
41.2
41.3
40.9
41.6
44.3
41.2
43.1
42.3
44.9
46.3
49.3
49.0

43.1
44.0
41.7
42.1
41.8
44.5
43.4

48.0
60.6
42.6
41.0
41.6
42.5
61.2
43.1
40.9
41.0
*!.&
42.2
?T.l
54.2
54.9
40.9
48.6
43.2
»!.•»
42.6
4}.i
45.6
41.9
45.6
42.9
42.8
?2.8
68.3
?2.9
72. S
45.6
36.6
45.6
45. A
*5.6
45.6

45.6
60.0
??.8
45.6
72.8
45.6
39.4

45.6
4!.6
?2.8
22.8
??.»
22.8
*5.6
45.6
19.7
22.8
ICT
22.8
w.g
45.6
45.6
22.8
4J.6
22.8
zz.a
22.8
».S
06.6
R3.0
87. 1
84.2
14.1
63.7
109.9
67.1
64.0
*8.T
78.9
90.5
91.9
9*. 9
94.6

88. 7
104.0
64.5
87.9
64. A
90.1
12.8

93.6
106.2
- 65.4
63.8
6 J.I
65.3
ne.H
88. 7
60.6
63.8
60.7
65.0
101.0
99. 8
100.5
63.7
»*.?'
66. 0
64.7
69.4
45. fl
534
51150
20648
7?332
1079
10202
17877
8512
516L6
98521
1 8ROQ7
67
6116
58201
64383

1 A396
17958
35118
30470
34225
161208
295375

85~M
14649
1Z746
7599
inn
60879
ZV60Q
44579
71 56
3933
69229
3942
13M1
6314
8*73
7*18
	 «49
42371

-------
Table A-l.   Calculation of average dose equivalents due  to  terrestrial  and cosmic  radiation by  State urbanized and nonurbani/cd
                                                         areas—Continued
1
2
LOCATION I960
POPULATION

WICHMA FAll TX
TEXAS NU-C"
TEXAS NU-NCP
TEXAS
OGDEN UT
PROVO UT
SALT LAKF CY UT
UTAH NU
UTAH
VERMONT NU
VERMCNT

IYNCHBURG VA
NEWPORT NEWS VA
ROANOKE VA
RICHNQNO VA
WASH CCIVAI
VIRGINIA Nlt-CP
VIRGINIA NU-NCP
VIRGINIA

PORTLAND MA-OR
SEATTLE 'WA
SPOKANE WA
TACOHA WA
WASHINGTON NU
WASHINGTON
CHARLESTON WV
HUNT WV-KY-OH
STEUBENVL WV-OH
WHEELING WV-OM
WEST VA NU
WEST VA

102104
1040000
1336T?4
9579^77
1219?T
60795
348661
359244
190627
389811
3898<)1

59319
201874
124752
333438
465487
560000
1707254
3966949

46956
864109
2Z6938
214930
I 500281
2853214
169500
92744
34298
65430
1498399
1160421
3
4
EIFVATION MAGLAT
FEET DEC NO

946
250
73R8
863
4300
4549
4260
5028
4595
590
590

648
20
12
948
150
150
100
1214
609

77
125
1180
250
577
455
601
565
715
650
1421
1263

43
39
41
41
COSMIC RAnl&TION PF
MBF^S/YP
5 6
NF1IT ION
6.9 37.'
5.9 35.7
9.4 42.3
7.0 37.6
49 14.0 51.6
48
48
48
4.7 53.1
3.9 51.4
6.2 56. 1
48 14.9 53.5
55
55

49
48
48
48
49
50
49
49
49

52
54
55
53
54
54
49
49
51
51
50
50
6.4 36.4
6.4 36.4

*.5 36.5
5.6 35.3
5.6 35.3
6.9 37.3
5.8 35.5
5.8 35.5
S.7 35.4
7.3 38.1
6.5 36.6

5.7 35.4
5.1 35.5
7.3 36.0
5.9 35.7
6.4 36.4
6.2 36.2
6.4 36.4
6.4 36.3
6.6 36.7
6.5 36.5
7.7 38.7
7.4 38.3
R
9 = 7.1
10M2X9IX.001
TEPB DOSE FO TOTAL EXT DF MAN-RFM
7=5.6 HPEMS/YR M«CMS/YR
TOTAL
44.2
41.6
51.7
44. 6
65.6
67. R
65.3
72. 3
61.4
42.8
42.8

43.0
40.9
4O. 9
44.2
41.3
41.3
41.2
45.4
43.1

41. 1
41.2
45.7
41.6
42. 7
42*4
42.8
42.7
43.3
43.0
46.4
45.7

45.6
22. 1
45.6
29 .0
45.6
45.6
45.6
45.6
45.6
45.6

45.6
19.5
19.5
45.6
72.8
35.4
45.6
34.6

45.6
45.6
45,6
45.6
45 .6
45.6
45.6
45.6
60.5
68.9
45.6
46.7

64.4
97. 3
T3.6
111.7
113.4
110.9
1 17.9
114.0
18.4
18.4

18.6
60.4
60.4
19.1
64.1
76.7
64.0
91.0
77.7

86.7
86.1
90. P
87.2
18. ?
18.0
18.4
ft R. 3
103.8
111.9
92.0
02.4

9169
105821
130019
705323
13564
6196
42366
101494
34458
34458

5256
12626
30687
11204
21378
35710
35823
155352
308035

4071
75041
20615
18746
132523
250996
14987
8188
3559
7328
137879
171191

OULUTH WI-MN
" GRFEN SAY WI
KENOSHA WI
HAD1SON WI
MILWAUKEE wl
33937
97162
7Z852
157814
1 I 49^97
610
590
610
860
610
56
55
53
53
53
6.4 36.4
6.4 36.4
6.8 37.1
6.4 36.4
42.9
42.8
43.1
42.9
45.6
45.6
45.6
45.6
45.6
88.5
88.4
88.5
89.4
88.5
3002
1587
6444
14115
101773

-------
FIFV^TION HAGUT
  FEET    CEGNCl
                                              COSMIC KADI&TIONOE
                                             	MRFHS/rR	
                                                5     6      7-5*6
                                                                   TEPH OnSF f=0
                                                                      MBFMS/Yg
                                                                                                   10M ?X9I K.001
IHCAMUN
                                                                    flTiL EXT De
                                                                      HRfMS/YR
RALINE W!
WISCONSIN NU
                  2344153
                              968
                                      5*
                                              T.O
                                                36.5
                                                37.3
                                                                                                        8487
                                                            44.3
                                                                          45.A
WISCONSIN
                  3951T77
                              832
                                              6.4
                                                    37.0
                                                            43.7
                                         So75~
UVDPINU NU
"TJOT5S

 ^0046
                                      5T5
                                         HO

                                        T57*
                                                    5T7T

                                                    6T7T
                                                                          4S.IS
                                                                                                       41614
                                                                          4S.A
                                                                                                       41614

-------
Table  A-2.  Total calculation of average  dose equivalents due  to terrestrial and cosmic radiation by  States
                                             COSMIC RADIATION DE
                                                                                       9«7»8
                                                                                                 10=( 2X91 x. 001
    STATF
                   I960     ELEVATICN MAGLAT
                pnPIIIATinfl   FEET    DFft NO
 •4PEMS/YR
5     h
                                                                      TERR  DOSE  FO  TOTAL EXT OE   MAN-HEM
ALAPAMA
ALASKA
ARlfCNA
ARKANSAS
CALIFORNIA
CPLCPADO
crNN
DELAWARE
WASH nc
FLORIDA
GEORG
-------
 Table A-3.  Program to calculate average dose equivalents from terrestrial and cosmic radiation
ISN OOP?
                    IMPLICIT RFAL«fl (A-H.i-7)
ISN 0003
                    1! MANSION PT>n50t ,STAPnP(5l l.
                                                          I,TO<4I, A TO( '50 t , AC [M 3Sn|
                   ?»Tnnso(sn , SANP<5i i.sc
                                                            ,L&T(<; n , INTFPV(4P| ,
ISN 0004
ISN 0005
DATA  IWRITC,IHnLn,IS*ITCH,J/4*0/, INTF9V/4i «o.o, 51 *o.n,M«o.n,c
ISN 0007
ISN OOC"
on  10  1=1,0
11=1*6-5
ISN 000«
ISN 0010
                    I?=T*6
ISN 0012
ISN nnn
      c,0 17 1=9, Ih
ISN oo?* K=i*in
ISN 00?7 W=N-<»
ISN 007R
ISN 00?<»
ISN 00*0
ISN 0031
ISN 003?
ISN 0033
ISN 0035
ISN 0037
ISN 003"
ISN 0040
ISN 0041
ISN 004?
ISN 0043
ISN 0044
ISN 0045
ISN 004IS
17 CTNTINtlF
j=m
9F ADI":, 9061 (4LOC( Ii Jl ,1=1 ,4) ,ISTATc,oop(j),ELEV,GLAT,ITO,TO(4l
IF ( ISTATE.NF. IH
Ft MF(VN=ELMEAN»FLFV*'>nPU
f inNl=I.OO».030»CL».0?5*FL*El-.0038*EL**3».0304S3*EI **4-. 0000 156*
                    flCN?  -  ?.44*CI1N1
 ISN  004K
 ISN  0040
 TIHN3 = I.'.^'CIIN?
 CICN4 = H.7(,f,*r ION3
 ISN 0050
 CNIIT4= S.fr^EXPf (1033.-1033.*(.<'?146n-6*EL**4»q.30'*070- H«Et
                                                                                                61

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  Table A-3.  Program to calculate average dose equivalents from terrestrial and cosmic radiation—Continued
ISN OO^l
ISN P05*
ISN OPS?
ISN OOS4
ISN OPS';
ISN 00*7
ISN POSO
I SN 00*10
ISN P061
ISN DOS?
ISN 006?
ISN 0164
ISN 00«>S
ISN 006*
ISN 0067
ISN 006"
ISN C070
ISN 0071
ISN 007?
ISN 0071
ISN 0074
ISN 007-5
ISN 007A
ISN 0077
ISN 007ft
ISN 0070
ISN OORO
ISN 0081
ISN P01">
ISN 008?
ISN OOB4
ISN TP15
ISM pr>R>,
ISN OOP7
ISN OOP"
ISN OOOn
ISN 0001
ISN 00«2
ISN 00b
rni;HP = CI ON?*rNim
msYP « 8. 7«iC>*rnsHR
Ic( ITn.PQ. 1 K.1 Tn 120
^(ITn.PQ.?ir,n TH i?0
\t (OEO-f I60,5o!s0
*0 fTNTINUF
INTE»V(N)=INTFI>V(NI+POPII
cosYR«=&cnsYRS»rosYR*pnPl(
TonsnM= ion sow* inns n*pnpi)
ATOI JMTOPSO
Arnt JMCCSYR
SPCM( i STATE I = S"FM( 1ST AT E)*nED*DnPU
STAPOPt I ST»TFl=STAPOPlISTATei+PnPU
P?LFVUSTATFI = PFLFV(ISTATF) »POPU*ELFV
PnnNtMlTtTFE! = »CmN^'TST*TlJtpOPU*[nN4
^nFO(ISTATF) = SOEDJ ISTATF )»PEn*PnPU
PTOOSPtl STATF)-PTDOST(ISTATE)*PnPlJ*TOnsn
IANP = ANP*.001 + .">
IFIE =FLCV*.1;
\ , IE 0, IANP
r,n Tn ?n
ISMTCH=I
!HOLD=ISTATE
r,n Tn ?o
|F(STAPTP( II.OT.O. IPO^U^STAPOPII 1
1 pnp - o
IFLF-PFl EV( 1 ) ^POPU* .5
CNUT4=PCNUT4( I I/POPU
r ION4=Pf !ON4( I 1/PHPU
rnsYR=scnsYR( i I/POPU
TOOSO=PTOOSn( I ) /PHPU
OFO=SOEniI I/PTPJ
I»NR=S4NH( I»«.001».S
62

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Table A-3.  Program to calculate average dose equivalents from terrestrial and cosmic radiation—Continued
ISN 0108
ISN 0109
ISN 0110
ISN 0111
ISN 0112
ISN 0113
ISN 0114
ISN 0116
ISN 0117
ISN 0119
ISN 0120
ISN 0121
ISN 012?
ISN 0123
ISN 0124
ISN 0125
ISN 0126
ISN 0127
ISN 0128
ISN 0179
ISM 0110
ISN 0131
ISN 013?
WITE«*.900,IST.TFfI.HI.H.1.3I.IPnP.IELE.L4Tlll.fN,,T*.C!«l* f«YR
i TOOSO.OFD, I&NR ' *
IHOLO-IST4TF
on TO 30
00 tOO 1=1,51
POPU-1.050
I»OP = 0
IFtST&PTPUl.TF.O.) IPOPUI
170 CONTINUE
GO TO A5
130 DO 220 H=81,154

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Table A-3.  Program to calculate average dose equivalents from terrestrial and cosmic radiation—Continued
     ISN  0162
                         M = AHID1L t+EOSYR
     ISN  0163
     ISN  016*
                            210
     ISN  016S
     ISN  016*
                         IHNK-I I 210.200,200
                    ?00
     ISN  0167
     ISN  0168
                ?10 CONTINUE
                    INTERV(NI = I NTERV(NI»IPERCTIHI«POPU1
     ISN  016<>
     ISN  0170
     ISN  0171
                       TO
                   11X,!!<.//!		;	
                001 FORMAT UHl,inX,46HO I ST« IRIITIPN OF POPULATION VS. OOSF EQUIVALENT,
     ISN  017?
                        1//A?X.7?HTQT4L HE
                       ?  FORMAT(40X,IA.2H -
                                                  I960
                                                                               POPULATION//!
ISN 0173
ISN 017*
ISN 0175
ISN 0176
ISN 0177
ISN 0178
                    QOJ  FORMATI1H1,20X,22HTOT»1  POPULATION =
                                                                   .F12.0I
                    qn<>  FORMAT
                                       i, 121 1
                    90*  FORMAT (3FS.1,3F».? I	
                    90S  FORMAT < BA<,, A3,i2.Fs.o,F6.o,F4.o,i l,F6.K
                    qp7  FORHATI1H1, 1RX.1H1.I2X, 1H2, 10X,1H1,'»X,1H4,'IX, iqHCOSMlC RADIATION 0
                                                                          ,1'5X,RHLOCATION,7X,
                                                                                    OOSF FQ
                               EXT DE   MAN-REM,/,1H  ,? 7X, 1 OHPQPUl AT I ON , 3X ,
                                                                                     X . *HDFG
                                                                                      H  ,S6X,
     ISN 017Q
                     OQB  FORM AT (1H ,llXtlA4,A3,2X,16,2X,15,Sx,17,»X,3(F'i.l.2X),ftX,F6.1texf
     ISN OHO
                   I Tft.T^'JX,! 10)
                OQQ F"RmTX .
                                                                       . 1 3X t
                                                                                       ,OX,
                                                                                         60
                        •'TOTAL FXT OF   MAN-RFM,/,1H ,2 7X, 1 OHPOPUL AT HN 1 3X .4HFEET, AX , *HPEG
                                                                                    ,lH  ,56X,
                        S  4HNEUT.3X, 3HIPN,4X,SHTnTALi/J
                     Q10 FQRMAT(1-I , 1 2X .""A* ,4 X . T B , ?X , I % 5X ,
                                                                X , 3 I FS. 1 , ?X I , 6X , F6 . 1 , 8X , F6. 1
     ISN 01"»2
                         FORMAT(lHl,4?X,2qHSUMHARy  DATA-FXT FBNA.L DOSF  FQ, / / , 3 1 x. 27HMF AN POP
                        IUIATED  HEAN r.nsMir,^x,??HMFAN TERR oe  TOTAL  DE,3x,i3HTPTAi
                        2FHt/.?lx,?8HELEVATION-LI.S.
     ISN 0181
                                            ,10X,8HMREMS/YR)
                    FnRMATtlH0.3SX.FS.l,10X,F6.1j,jX,F6.1,7X,F8.1,2X.Il?l
     ISN f>l»4
     ISN 0185
     ISN 01«6
                         FND

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                                       APPENDIX  B
                      Effect  of  Building Materials on  Exposure
  The following assumptions are made  in esti-
mating the effect of indoor living on DE:
1. From table 16, it can be seen that the  ratio of
  the  indoor  to outdoor DE  for  wood frame
  houses ranges from 70 percent (Lowder and
  Condon, 1965) to  82  percent  (Yeates et al.,
  1970).
  Similar ratios for homes of masonry construc-
  tion range  from about 72  percent (Ohlsen,
  1969) to 106 percent (Ohlsen, 1969, and Yeates
  et al, 1970). Based on an  analysis of these
  data, it has been  assumed for purposes of this
  study that the inside to outside BE for frame
  houses is 70 percent and for masonry houses is
  100 percent.
2. Seventy-five percent of the U.S. population is
  assumed to live  in one-family  homes, based
  upon U.S. Census Bureau (1960) estimates that
  76.3 percent of all housing units are single
  homes and that the mean number of occupants
  per household does not vary significantly ac-
  cording to single or multihousing unit status.
  During 1964 to 1968, data collected by the Fed-
  eral Housing Administration (FHA) on financ-
  ing new and existing homes (U.S. Department
  of Housing  and  Urban Development, 1969)
•  showed  that the  proportion  of frame houses
  sold in the United States ranged from 75.0 per-
  cent to 92.2 percent. Although FHA-financed
  sales  account for only a  minority of home
  sales, they represent the only data available on
  housing  construction. On the basis  of these
  data, it has been estimated for purposes of this
  study that 80 percent of the single homes in
  the nation are of frame construction. Masonry
  construction is assumed to account for the bal-
  ance of single homes. It should be noted that
  the FHA designation of frame  houses refers
  to the method of roof support,  and approxi-
  mately one-third of all frame homes have some
  brick or stone facing. The other  25 percent of
  the U.S. population  is assumed to be divided
  equally between living-in-frame  and masonry
  dwellings.
3. Sixty-eight percent  of the U.S.  population
  (U.S. Census Bureau (1969) for 1966) is as-
  sumed to be engaged in away-from-home activ-
  ity (school and work) for 40  hours/week,  or
  24 percent of the time.  This time is assumed
  to be spent in buildings which are 50 percent
  frame and 50 percent masonry. The remaining
  32 percent of the population is assumed to  be
  at home.
4. Ninety-five percent of an individual's time is
  assumed to  be  spent indoors. This  value  is
  based on a survey by Robinson and Converse
  (1966), in which they summarize the ways (27
  different categories)  in which people spend
  their time. Only two  categories can be clearly
  identified as outdoor activities (gardening and
  walking) and these account for 0.1 hours/day.
  Leisure  activities  account  for 2.1 hours/day;
  50 percent of this time is  assumed to be out-
  doors, making a total of  1.2 hours/day (5 per-
  cent). Commuting time and nonwork trips aro
  assumed to be indoor activities for die purpose
                                                                                          65

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  of this study. Automobiles provide an attenua-
  tion of 0.77 (indoor/outdoor terrestrial DE)
  ^ Solon et al.. IJHiO), which is similar to  that of
  dwellings. Other modes of transportation  are
  also as>umed to similarly reduce the terrestrial
  DE. An  error may be introduced  by assuming
  that all work is done indoors. We must keep in
  mind that many  kinds of work are ''outdoor"
  occupations. On the other hand, much  of  the
  work in outdoor occupations, such as police and
  fire duty, transportation, and construction, take
  place under cover.
  Based  on these  assumptions, it is possible to
estimate a "housing factor," which is, the average
factor by which indoor living reduces man's ex-
posure to  natural  sources. The  expression  for
determining the  housing  factor  (HF)   is  as
follows:
                 Home population
    HF =  ph[(hAti) +  (hJSmt,)]
                    Scbool and labor
                   population at home
                      ftA) + (ICS.
                      School and labor
                    population at work
                Outside
                exposure
            + (Pi + Pi) to
(B-l)
where

    ph  = proportion of population at home
          (0.32),
    h{  = proportion  of population  living  in
          frame dwellings  [(0.75  X   0.8)  +
          (0.25 X 0.5) = 0.73],
    Sf  = frame attenuation (0.70),
    ti  = proportion of time spent indoors
          (0.95),
    hm  = proportion of population living in ma-
          sonry dwellings (1 -  hf = 0.27),
    Sm  = masonry attenuation  (1.0),
    PI  = proportion of population working or
          attending school (0.68),
    dh  = proportion of time spent by  workers
          and students at home  (1 — du.  = 0.76),
    Wf  = proportion of workers and students in
          frame dwellings (0.50),
    d*.  = proportion  of time  spent at  work
          (0.24),
    Wm= proportion of workers and students in
          masonry dwellings (1 — YT, = O.."»0),
          and
    t0  = proportion of time spent outdoors  (1 —
          t, = 0.05).


The housing factor is found to be 0.80, when the
above values are substituted in eq. (B-l).
66

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                                       APPENDIX C
                 Calculation of 2o-  Error  of  Total Dose Equivalent
   For the purpose of calculating an estimate of
 the errors associated with the overall  DE esti-
 mate, the method suggested by Kline and McClin-
 tock (1953)  has been used.  The overall  DE is
 calculated by                         \
DE =
                    +  X
                                   5,
                                        (C-l)
 where
     X,
     X2
     xs
     X,
     X5
terrestrial DE,
housing factor,
gonadal screening factor,
cosmic ray DE, and
internal emitter DE.
 The estimate of the ±2E = 10.7mrem/yr.
  It is interesting to note the relative contribu-
tions to the error variance of the overall estimate:
                                                    Parameter
                                            Xi — terrestrial DE
                                            X« — housing factor
                                            X3 — gonadal screening factor
                                            X« — cosmic ray DE
                                            Xs — internal emitter DE
                                   Relative
                                  contribution
                                                                            1
                                                                            5
                                                                            4
                                      For further  improvement in the total error,  it
                                      would appear most useful  to improve estimates
                                      of X,, Xi, X2, and X5, in that order. Relatively
                                      little would  be gained in  accuracy by improv-
                                      ing X».
                                      Table C-l.  Evaluation of partial derivatives  in error
                                                         calculation
                                                  Parameter
                                                                      Partial derivative
                                                                     . AXi
                                                                      = 32AXi
                                          Xi


                                          x<

                                          XB
                                                         ABB =
                                                                dDE
                                                           ADS =
                                                                        AX.
                                                                         4X»
                                                                                           6T

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                  THE ABSTRACT CARDS  accompanying this report are de-
                  signed to facilitate information retrieval. They provide suggested
                  key words, bibliographic information, and an abstract. The key
                  word concept of reference material filing is readily adaptable to a
                  variety of filing systems ranging from manual-visual to electronic
                  data processing. The cards are furnished in  triplicate to allow
                  for flexibility in their use.
                               U.S. GOVERNMENT PRINTING OFFICE: 1972 O — 465-83S
68

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NATURAL RADIATION EXPOSURE IN THE UNITED STATES, (ORP/SID
  72-1) by Donald T. Oakley; June 1072; SID, ORP, EPA

ABSTRACT: The exposure of man to natural radiation sources in the United
  States has been estimated  by considering the distribution  of the population
  with respect to certain factors, principally geology and elevation, which influ-
  ence exposure to terrestrial and cosmic radiation. Data obtained by aerial
  surreys in the United States have been used to calculate an average dose
  equivalent  (DE) estimate of 40 mrem/yr. to the population. The results also
  indicate three distinct areas of terrestrial radioactivity in the United States—
  (1) the Coastal Plain, which consists of all or portions of States from Texas
  to New Jersey  (23 mrem/yr.) ;  (2)  a portion of the Colorado Front Range
  (90 mrem/yr.); and  <3) the  rest of the United States, i.e., portions of the
  United States not included in "1" or "2" (46 mrem/yr.).
    Since elevation is the primary determinant of cosmic ray  DE in the United
  States, the population distribution with respect to elevation was determined.
  The average population elevation of the United States was determined to be
  approximately 700 feet, and the average cosmic ray DE  was estimated to
  be 44 mrem/yr.
                                                                    (over)
NATURAL RADIATION EXPOSURE IN THE UNITED  STATES, (ORP/SID
  72-1) by Donald T. Oakley; June 1972; SID, ORP, EPA

ABSTRACT: The exposure of man to natural radiation sources in the United
  States has been estimated by considering the distribution of the population
  with respect to certain factors, principally geology and elevation, which influ-
  ence exposure to terrestrial and cosmic radiation. Data  obtained by aerial
  surveys in the United States have  been used  to calculate an. average dose
  equivalent  (BE) estimate of 40  mrem/yr. to the  population. The results also
  indicate three distinct areas of terrestrial radioactivity in the United  States—
  (1) the Coastal Plain, which consists of all or portions  of States from Texas
  to New Jersey (23 mrem/yr.);  (2) a portion of the Colorado Front Range
  (90 mrem/yr.) ; and  (3)  the  rest of the United  States, te., portions of the
  United States not included in  "1" or "2" (46 mrem/yr.).
    Since elevation is the primary determinant of cosmic ray DE in the United
  States, the population distribution with respect to elevation was determined.
  The average population elevation of the United States was determined to be
  approximately 700 feet,  and the average cosmic  ray DE  was estimated to
  be 44 mrem/yr.
                                                                    (over)
NATURAL RADIATION EXPOSURE IN THE UNITED STATES, (ORP/SID
  72-1) by Donald T. Oakley; June 1972; SID, ORP, EPA

ABSTRACT: The exposure of man to natural radiation sources in the United
  States has been estimated by considering the distribution of the population
  with respect to certain factors, principally geology and elevation, which influ-
  ence exposure to terrestrial and cosmic radiation. Data obtained by aerial
  surveys in the United States have been used to calculate an  average  dose
  equivalent (DE) estimate of 40 mrem/yr. to the population. The results also
  indicate three distinct areas of terrestrial radioactivity in the United States—
  (1) the Coastal Plain, which consists of all or portions of States from Texas
  to New Jersey  (23 mrem/yr.) ;  (2)  a  portion of the Colorado  Front Range
  (90 mrem/yr.); and  (3)  the rest of the United States,  i-e.. portions of the
  United States not included in "1" or "2"  (46 mrem/yr.).
    Since elevation is the primary  determinant of cosmic ray DE is the United
  States, the population distribution with respect to  elevation was determined.
  The average population elevation of the United States was  determined to be
  approximately 700 feet, and  the average cosmic ray DE was  estimated to
  be 44 mrem/yr.
                                                                    (over)

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    To arrive at an estimate of the gonadal  DE, the influence of housing, bio-
  logical shielding, and the DE contribution from internal emitters was also
  considered. The first two factors serve to attenuate man's gonadal DE due to
  terrestrial radiation by about the same amount that is contributed by internal
  emitters. The average gonadal DE to the U.S. population was  calculated  to
  be 88 mrem/yr.

KEY WORDS: Cosmic radiation; dose equivalent; natural radiation; population
  exposure; surveillance; terrestrial radiation;  United States.
    To arrive at an estimate of the gonadal DE, the influence  of housing, bio-
  logical shielding, and the DE  contribution from  internal emitters was  also
  considered. The first two factors serve to attenuate man's gonadal  DE due to
  terrestrial radiation by about the same amount that is contributed by internal
  emitters. The  average gonadal DE to the U.S. population was calculated to
  be 88 mrem/yr.

KEY WORDS: Cosmic radiation; dose equivalent; natural radiation;  population
  exposure; surveillance;  terrestrial radiation; United States.
    To arrive at an estimate of the gonadal DE, the influence of housing, bio-
  logical shielding, and  the DE  contribution from  internal emitters was  also
  considered. The first two factors serve to attenuate man's gonadal DE due to
  terrestrial radiation by about the same amount that is contributed by internal
  emitters. The average gonadal DE to the U.S. population was calculated to
  be 88 mrem/yr.

KEY WORDS: Cosmic radiation; dose equivalent; natural radiation; population
  exposure; surveillance; terrestrial radiation; United States.

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