REPORT OF THE
UNITED NATIONSSCIENTIFIC COMMITTEE
ON THE
EFFECTS OF ATO~IIC RADIATIONGENERAL ASSEMBLY

OFFICIAL RECORDS : TWENTY-FIRST SESSIONSUPPLEMENT No. 14 (A/ 6314)

UNITED NATIONSGENERAL ASSIEMBLY

OFFICIAL RECORDS : TWENTY-FIRST SESSIONSUPPLEMENT No. 14 (A/6314)....,...,, ..,,..
'II:;>• ..
t·•'<I/ 7 7
UNITED NATIONSNew York, 1966

Annex A

RADIATION FROM NATURAL SOURCESCONTENTSParagraphs

Paragraphs
INTRODUCTION

1-5

II. Cos:mc RAYS

6-49

l.

III.

23-28
26-28
29-38
32-38
39-47
41-47
48-49

TERRESTRL-U. RADIO-ACTIVITY

50-90

Soil ...................................... .
External radiation ........................ .
Neutrons ............................... .
Natural activity in waters ................. .
Oceans ................................. .
Fresh waters ........................... .
The natural radio-activity of ah- ........... .
Horizontal distribution and variability ... .
Measured concentrations of natural radioactivity ............................... .
Long-lived decay products of radon-222 ..

THE

TRANSFEROF

ENVIRONMENTAL

RADIO-

ACTIVITY TO MAN •.•••••••..••••••.••.••.•.

Introduction .............................. .
Intake by man ........................... .
\.Yater .................................. .
Typical levels of natural radio-nuclides
in \11ater ........................ · · .. .
Areas with high concentrations of radium
and radon in drinking water ........ .
Foodstuffs .............................. .
Areas of typical "normal" levels of intake
Special food chain mechanisms and areasof high natural radio-activity ....... .
Air .................................... .
Levels in man ............................. .
Metabolic data on Ra226 and the Pb210_
Bi210.po210 chain ..................... .
Normal levels of natural radio-activity in
man .................................. .
Aireas of high natural radio-activity andspecial food chain mechanisms ....... .
Doses from internal irradiation by naturalradio-active nuclides ..................... .

6-13
14-21
22

Introduction
Geomagnetic effects ....................... .
Energy spectrum of ·primary radiation ..... .
Cosmic rays in the atmosphere ............ .
Radio-nuclides produced by cosmic rays ..
Cosmic-ray neutrons ...................... .
Flux densities and energy spectra ....... .
Cosmic-ray dose rates ..................... .
Neutron dose rates ..................... .
Conclusions ............................... .
••.••.••.•..••..

IV.

50-51
52-65
61-65

66-72
66

67-72
73-90
81-84

V. RECAPITULATION OF DOSE RATES ••••••••••••••

91-148
91-95
96-116

97-10399-101

102-103104-113104-109110-113114-116

117-133

118-125
126-133
130-133
134-148
149
Page

85-90

TABLES •.••.•••••••.•••••••••••••••••••..••

28

89-90

REFERENCES ••.•••••.•••••••••••••••••••••••

36

I. Introduction

or, in the case of shorter-lived radio-isotopes, they arecontinually being produced by radio-active decay or
nuclear reactions. Some radio-isotopes are produced by
the interactions of secondary cosmic rays, mainly neutrons, with atmospheric gases and, to a small extent,
by the ·interactions of the cosmic rays that reach theearth's surface.
4. Owing to the varying content of natural radioactive elements in the soil and the underlying rock, theintensity of external radiation and the levels of radioactive intake by man vary from place to place. Becauseof limited geographical representation and of the obvious limitation of sampling. the arithmetic means
calculated from the most frequent values were accepted,
but they may not be strictly representative for thewhole world population.
5. It is obvious that arbitrary criteria are used toseparate typical situations from those where backgroundradiation is considered elevated either because of local
abundance of radio-active material or because of special
food chain mechanisms. In the present review, only
those situations will be described as non-typical inwhich at least one of the factors contributing to thenatural irradiation of man is higher than typical by
one order of magnitude or more.

1. Radiation from natural sources was examinedboth in the 19581 and in .the 1962 2 reports of the Committee. Its importance lies ·in the fact that the humanspecies has always been e..xposed to natural radiation
at relatively stable average levels and that doses fromnatural radiation are being used by the Committee asa standard of comparison with those received fromother, man-made, sources.
2. The present review is essentially an updating of
the earlier ones and should be read in conjunction withthem. The relative emphasis here given to individual
topics-as, for instance, neutron doses and radio-activity
in air-thus reflects the amount of new information
which has become available since 1962 rather than theiractual importance in the over-all study of naturalradio-activity. Much of the new information has been
the result of improvements in instrumentation whichhave been stimulated by ,the study of environmental
contamination.
3. Natural radiation arises from two sources: cosmic
rays, entering the atmosphere from outer space, andradio-active materials in the earth's crust. These materials were already present when the earth was formed,

13

II. Cosmic rays

About 20 per cent of the energy from the incident
primary radiation is transferred to nucleonic cascades.
Most of it, however, is absorbed before reaching theearth's surface. Slow protons are stopped by ionizations,and slow neutrons are captured mainly in nitrogen,forming C14•
12. The electron-photon component. The electronphoton component includes electrons, positrons andphotons. They originate mainly from the electronpositron-photon cascade resulting from the decay ofthe extremely short-lived neutral -;r 0 meson produced
when high energy primary radiation interacts withatmospheric nuclei. The spontaneous decay of muonsalso contributes some high energy electrons to thiscomponent.
13. Vlhen cosmic rays are measured, the neutrons
are usually dealt with separately from the other components. The latter, including gamma rays, are further
subdivided according to their penetration power. The"soft" component consists of the radiations that arecompletely absorbed in about 15 cm of lead. At low
altitudes. this component includes the bulk of theelectrons, gammas, and protons, as well as a few slow
muons. The "hard" component, some of which is only
slightly attenuated by 15 cm of lead. may be able topenetrate much thicker layers. The "hard" component
at sea level consists mainly of muons and of high energy
protons.

INTRODUCTION

6. Cosmic radiation consists of primary radiationentering the atmosphere from outer space and of
secondary cosmic radiation produced by interactionsof the primary radiation with nuclei in the atmosphere.
1fost measurements of the primary component havebeen carried out at atmospheric depths of 15 g/cm 2 ormore (up to about 30 km), but extrapolations to outerspace as well as direct measurements indicate that the
primary component consists of highly energetic, positively charged nuclei, with protons constituting 83-89
per cent of the primary radiation, alpha particles 10-15
per cent, leaving 1-2 per cent for nuclei having Z ;;::: 3
and for some energetic electrons. About one positively
charged particle/cm2 X second with an average energyof 2 X 103 MeV arrives at the top of the atmosphere.3·12
7. This primary radiation is incident from all directions. The major portion of the primary cosmic radiation is of galactic origin. Lmv energy particles of solar
origin in the 10 MeV range may reach the earth during
large sunflares. The contribution of solar particles tothe total cosmic-ray intensity in the lower atmosphereis negligible, however, if averaged over long periods.
Slight annual modulations of cosmic-ray flux densities,
as well as variations during magnetic solar storms,
have been observed.13"17
8. The secondary cosmic-ray component comprises
many types of radiation produced by nuclear collisionsof the primary particles with nitrogen, oxygen or argon
nuclei mainly in the upper atmosphere. At about sea
level. this secondary radiation is usually divided into
three separate groups: the muon, the nucleon, and theelectron component. Some properties of the main
secondary particles in cosmic radiation are summarizedin table I.
9. The nmon component. Muons (previously calledf'-mesons) are the daughters of short-lived pions. The
pious result from the interaction of high energy protons
with atmospheric nuclei. The maximum muon flux
density occurs at an atmospheric depth of about 1SO
g/cm2 (usually at a height of about 12 km). Ionization
due to cosmic rays detected at low altitudes is mainly
due to the penetrating muons (about 70 per cent).18• 19
The muon component still contributes about 50 per centto the ionization from cosmic .rays at an altitude of
3 km, and its relative share continues to decrease
with altitude.
10. The nucleon component. The nucleon component
consists of nuclear fragments, mainly neutrons andprotons.7• 12• 20 • 21 It multiplies by cascade processes involving nuclear spallation in the atmosphere, whereby
the secondary fragments knocked out of atomic nuclei
possess high enough energy to produce still further
fragments in subsequent nuclear interactions. As nitrogen and oxygen consist of an equal number of protor.sand neutrons, the initial nucleonic cascade in air consistsof approximately equal numbers of protons andneutrons with high energies. Below about 500 MeV,
however. ionization losses of protons in the air startcompeting with nuclear absorption : protons are therefore progressively removed from the cascade which,below a few hundred Me V. consists mainly of neutrons.
11. As neutron emission is the most probable deexcitation reaction when nitrogen and oxygen are
excited to energies of about 8 MeV, neutrons in therange of a few 1feV will be evaporated isotropicallyduring the terminal process in nucleonic cascades. 21 • 22

GEOMAGNETIC EFFECTS

14. An approximation to the external geomagnetic
field is obtained by assuming a magnetic dipole located
340 km off the centre of the earth. with poles pointing
towards 80.1°N, 82.7°W, and 76.3°S, 121.2°E. Thisterrestrial magnetic field acts as a momentum selector
for the primary charged particles. Consequently, thecosmic ray flux entering the upper atmosphere is latitudedependent as well as directional. 7·9
15. The net result of these effects is that particles
with the lowest energies reach the earth only in thevicinity of the geomagnetic poles, whereas those withenergies in excess of about 6 X 104 MeV can reachthe earth anywhere.23.2s
16. The minimum momentum that an incident
charged particle must possess in order to reach theearth's atmosphere despite the deflecting influence ofits magnetic field is called the threshold rigidity. It
varies with geomagnetic latitude as Cos 4<f> and depends
on the angle of incidence of the charged particle.
17. The threshold rigidity for vertically incident
charged primaries at the geomagnetic equator is about
5.7 X 107 gauss X cm corresponding to a proton energyof 1.7 X 104 MeV. 7• 27 However, the intensity of theionization due to cosmic rays measured at sea level is
only about 10 per cent higher near the geomagnetic
poles than the ionization recorded at the equator. Thus.
about 90 per cent of the ionization detected at sea level
results from primaries which had enough momentum
to arrive at the earth's geomagnetic equator. The
primaries of lower momentum are relatively ineffective
in producing penetrating muons.
18. The latitude variations are more pronounced
in the case of the nucleonic component, as shown infigure 1. This latitude effect of neutrons (and of
secondary protons) demonstrates that the nucleoniccomponent is mainly produced by low energy primaries
that ~re prevented by the earth's magnetic field fromreachmg the earth between 50°N and 50°S but that
14

100

-------------it-2.0,L,,,f1,,,,,,\

0..

'11Ill111111111111 rn JI.,: l 11IJI1111 J Ill"-0

lcniz1ng component

1.8

;.

.,,..
~

...
(\

1.6

3(..)

.,,
...
0

."'

i
(\

1.4

1.2

50..,_~~-.-~~--.-~~--.-----~-,-~~---.~~---,.--~~...-~~...-~~+l.0
1()0

2CJO

30"

4CJO
50°
Geomagnetic latitude

700

90°

Figure 1. Geomagnetic latitude dependence of the ionizing component and neutrons at sea
JeveJO, 27, 28

therefore, most of the secondary rays will be produced.
The term, "very low energy radiation", is reserved forprimaries below 1.7 X 103 MeV, whose abundance undergoes seasonal changes correlated with solar events.

do reach the polar regions. Pion production, on theother hand, predominates at higher energies (above
a few 104 MeV) and therefore is much less affectedby the geomagnetic field.
19. The apparent plateau region for the secondary
components at high geomagnetic latitudes has beene.'Ctensively studied. 4 • 11 • 13-17 Atmospheric attenuation
due to ionization losses, and insufficient sensitivity ofsome experimental equipment, might partially accountfor it. However. there seems to be a real decline in
the flux density of primary particles of galactic origin
for energies less than 2 X 104 MeV per nucleon. Low
energy primaries reaching the upper atmosphere aremostly of solar origin.
20. As the geomagnetic poles do not coincide withthe earth poles and as the magnetic dipole representation of the geomagnetic field itself is a rather crude
approximation which needs correction terms (higher
magnetic moments) to account for the actual energy
cut-off of primary cosmic rays, it is easy to explain
the slight longitudinal effect observed in the relative
intensities (up to 15 per cent) of cosmic radiation.
Temporal distortions of the geomagnetic field due tosolar activity are also observed.
21. It should be emphasized that the geomagnetic
latitude effect revealed by the secondary cosmic radiations should be wholly attributed to the primary component. Owing to their comparatively short trajectoryfrom the point of production in the atmosphere to
ground level, no appreciable geomagnetic deviation is
expected for the secondary charged particles.

COSMIC RAYS IN THE AT~OSPHERE

23. Figure 3 shows the altitude variations of themain components of cosmic radiation in the atmosphere.7·9· 20 • 29 Production of the secondary particles

c

0
iJ
0

~
II)

10

2

IQ)

p...
-0

c

0
0

Q)

II)

IQ)

a..
N

E
IQ)

10-2

a..
II)

Q)

-g_

.~

!...

E:l\ERGY SPECTRUM OF PRIMARY RADIATION

10-4

c

22. Figure 2 represents the integral energy spectrumof primary protons. 6 -12 • 20 • 2 9, 30 The integral energy
spectrum per nucleon of the total primary radiation issimilar within the e.xperimental accuracy. The latitudesensitive portion of cosmic radiation up to about
6 X 104 MeV-the threshold rigidity for positively
charged protons from the east at the magnetic
equator-is often referred to as ';low energy radiation".
As low energy particles are much more abundant. mostof the cosmic-ray energy ·will reach polar regions where,

x

::>

Li..

Energy (eV)Fig11r11 2. Integral energy spectrum of the primary cosmic-ray
protons9. 10

15

Altitude (km)I'-N

l'--00-0l.'1"'<1"~

O:t-.:..0...tcv)NI

pheric absorption of secondary radiation and muon
decay are minimal for vertical incidence. The east-west
effect being small compared to the absorption effectat various angles, the lower threshold rigidity ofparticles coming from the west does not compensate
for the additional attenuation of the secondary radiationin the atmosphere. For radiation from the east, thehigher rigidity threshold and atmospheric attenuation
both operate to diminish the secondary flux arriving
at sea level.

It)

M

·o

5,000
c

0
-0
0

2,000

Radio-nuc/ides produced by cosmic rays

!...

2Ill

1,000

26. Some of the nuclear fragments resulting fromspallation of atmospheric nuclei during the nucleoniccascade process are radio-active. 31-3 8 About 1.7 spallations/cm2 X second is the global average induced bycosmic rays. They occur in atmospheric gases in proportion to their relative abundance (nitrogen : o:>...7gen :argon ,..._, 76.5 : 22.5 : 1). The distribution of nuclide
production rates within the atmosphere, taking into
account the energy spectrum of the nucleon componentof cosmic radiation, was calculated by Lal. 32• 39 Most
radio-nuclides are produced in the stratosphere by low
energy neutrons, their rate of production being approximately proportional to the neutron flU-x density
and subject to its pronounced latitude dependence.
27. The main radio-nuclides produced by cosmic rays
are listed in table II with some of their nuclear properties, calculated production rates and activity concentrations in the lower troposphere. C14 is mainly
formed by the N 14 (n, p)C14 capture reaction withatmospheric nitrogen. About two-thirds of the neutrons
produced by cosmic rays are removed through thisprocess from the atmosphere.
28. The production rates of radio-active spallation
fragments from oxygen and nitrogen (H 3 , Be7 and Be1°)
exceed by far the production rate of fragments due toargon spallation. Cosmic rays which reach the earth's
surface can interact and produce radio-active nuclides,
but these have extremely low activity and are unimportant in comparison with other nuclides of natural
origin.

!...

Cl>

a..
-0

c

500

0

u
0

Ill
!...

Cl

a..
N

E
!...

200
100

a>

a..
){
:J

;:;:::

50

Cl>

.~

.....

!...

0

CL

20

0
0

.....!...

10

Cl)

>

5

2

0

200

400

600

800

1,000

2
Atmospheric depth (g/cm )Cos:!.UC-RAY l\'EUTRONS

Fig1we 3. The vertical flux densities for the main componentsof cosmic radiation as a function of atmospheric depth (atgeomagnetic latitude of 45°N)7

29. As neutrons usually elude detection when ionization chambers are used, this nuclear component ofcosmic radiation should be assessed separately. Cosmicray neutrons are produced by two kinds of reactions. 5• 23 · 28· 41 ·49 First, neutrons are knocked out of
nuclei as a result of nuclear collision of high energy
cosmic rays. These neutrons have energies from a few
MeV up to more than 1,000 MeV. A larger source ofneutrons in the atmosphere, however. is represented
by evaporation neutrons which have an energy distribution peaked at about 1 MeV. 12 • 21 • 23 • 43 · 50 • 52 The
evaporation process may account for about 80 per centof the atmospheric neutron flux density according toestimates derived by Hess et al. 44
30. Neutrons produced in the atmosphere will
eventually either leak out of the uppe~ atmosphere in~ospace or disappear through absorption. Atmosphericabsorption occurs largely through N 14 ( n, p) C 14 capture
reactions after the neutrons have been slowed down byelastic and inelastic collisions in some 150 g/cm 2 ofair. A stationary condition in time is thus maintained
where the neutron flux density in the atmosphere is
proportional to the neutron production rate at a somewhat higher altitude.

increases with atmospheric depth up to about 150 g/cm2(down to about 12 km) where the maximum flux
density of cosmic rays is found. Below this altitude,
particle loss through capture, ionization and muon
decay predominates over production, and the various
secondary cosmic-ray components decrease exponentially with decreasing altitude. The primary radiation
carries almost all the energy above 25 km, while themuon component predominates below 3 km.
24. Atmospheric effects depending on barometricpressure and temperature are known to affect somewhat
the cosmic-ray intensity at sea level, especially the muoncomponent. The muon flux density reaching sea level
depends on the thickness of the atmosphere below thepoint of production, and, because some muons decay
in flight. will also depend on their path length in theatmosphere. These local changes are of the order ofa few per cent and will not be discussed any further.
25. The vertical component of cosmic radiation isof relatively large significance at sea level, as atmos-

16

..

'

31. Owing to the low flux density of neutrons
produced by cosmic rays at sea level, most measurements
concerning tf:e neutron component were carried out atvarious heights in the atmosphere within the equilibrium
recrion, below 150 g/cm2 (up to 12 km) where theen~r!!Y spectrum of neutrons is essentially constan;.~s. H-5s From these measurements. estimates ofneutron fluxes at sea level were obtained through extrapolations. It is, however, difficult in making such
ext:-apolations to allow for the actual situation thatobtains at sea level because of the presence of an interphase and of backscatter 'vith a consequent breakdown of the atmospheric equilibrium conditions.

Flux densities and energy spectra
32. A major limitation in comparing the results ofdifferent experimenters is the interdependence between
the energy spectrum, which is assumed, and the absolute
neutron flux density that is derived from the measurements. Each detector is sensitive in a limited energy
range only, and its sensitivity is often energy dependent.41 Thus. the interpretation of counting rates
obtained through detectors of different kinds presupposes a detailed knowledge of the energy spectrum of
cosmic-ray neutrons.
33. Figure 4 shows the cosmic-ray neutron energy
spectrum in the equilibrium region as derived by Hesset al. 44• 52 They used a set of detectors sensitive todifferent energy ranges from thermal energies up to
about 104 MeV. Their extrapolation to sea level
yielded a flux density of 4 X 10-2 n/cm2 X second, of
which 15 per cent were between 1 and 10 MeV, 75
per cent had lower energies, and about 10 per centwere above 10 MeV.
34. l\1iyake et al. 43 obtained an energy spectrumof cosmic-ray neutrons from 1 to 15 MeV by observing
recoil protons by means of a high pressure cloud
chamber filled with hydrogen. Their derived energy
spectrum for 1 eV to 104 MeV neutrons is in good
agreement with figure 4, especially above 10 MeV andin the eV region.
35. Another calculation of the equilibrium spectrumof neutrons in the atmosphere up to energies of 20 MeV
was performed by Newldrk. 51 This spectrum also differsfrom Hess' spectrum mainly in the energy range of
0.1 to 4 MeV, and thus agrees better with othermeasurements. 03 • 55
><>
~

.
...

a.
u

COSMIC-RAY DOSE R..\.TES8

39. In the 1962 report, 2 the dose rate to soft tissue
due to the ionizing component of cosmic rays at sea
level at middle latitude \Vas estimated as 28 mrad/year.
Recent reported values generally agree with thisfigure. 18• 19 • 62 •00 Table III lists the reported values
in ion pairs/cm3 X second as well as in mrad/year.
40. Recent surveys 18 confirmed the altitude dependence of the ionizing component as discussed in the
1962 report. Muons are the main contributors to absorbed dose at low altitudes (some 80 per cent of thea The "dose" concept. The interaction between radiation andmatter results in a variety of processes that include absorption,
scattering and the production of secondary radiations. Hence,
when the human body is exposed to radiation, the distributionof absorbed energy is usually not uniform. Although such
quantities as the surface dose, the maximum dose and theaverage dose can therefore differ appreciably depending on thenature, energy and direction of the incident radiation, it isfrequently desirable to utilize a single numerical index to specify
the degree of irradiation. This is usually termed the "dose"and e.."pressed in the unit "rad" or its submultiples (mrad, etc..).
The usual meaning is the one that will be adopted here when
the term "dose" is employed without further specification. It
corresponds to(a) The kinetic energy of the secondary charged particles
produced per unit mass of soft tissue of approximate composition (H 40 C5 0 8 iN)n, in the case of indirectly ionizing
radiations (neutrons, photons and other uncharged particles) :(b) The energy deposited per unit mass in matter of the same
composition as given in (a), in the case of directly ionizing
radiations (all charged particles) .
These quantities are obtained when the absorbed energy iscomputed from the appropriate interaction cross sections for thebcident radiation spectrum. They v.dll also be obtained withina few per cent, if the absorbed dose is determined in a small
tissue-equivalent detector having a wall of sufficient thickness
to establish secondary charged particle equilibrium. In most
instances, the "dose" thus determined will differ by lesS' thana factor of two from the ma..--cimum dose in a human phantom.
It is recognized that the above definitions do not conformwith recently recommended usage.69 In particular, (a) defines
tissue kerma rather than the absorbed dose.OS This departurefrom rigorous terminology is necessitated by the fact that mostof the literature sources use this approach and by the absenceof an acceptable term for (b)_The relative biological effectiveness (RBE) of any radiation
depends not only on its type and quality but also on the effectunder study and on other factors, such as dose, dose rate andthe value of physiological parameters. This is because. evenwhen equal amounts of different radiations are absorbed in any
tissue, their effect is usually different as a result of differencesin the microscopic distribution of the absorbed energy.67

1o5
1o4
1o3

..."'
oil

102

0..

"

10

"' uE
...

l
10-l

"'a. 10-2

-~c:

10-4

c:

10-5

~

10-6

z

10-7

~

,_

0

·········~

10-3

.,,"
x

Evaporation source •••••••

spectru-"'!.·/\\·····..

Knock-on source spectrum f\

i !

CJ

I

0.1 eV1

10 eV .

'

1 keV

100 keV36. Subsequent workers arrived at 1ov·;er estimates
for the total neutron flux density.49 • 55 -:rn The lower
values might partly be due to the special care taken tominimize neutron production in the instruments themselves and in the surrounding materials. In particular,
lightweight detection equipment flown with balloons
was used instead of heavier aircraft-borne detectors.
37. Kastner et al. oo using a liquid scintillator.
reported a fitLX density of 4.5 X 10-a n/cm:? X second
for neutrons with energies from 1 to 10 :MeV as
measured directly at an altitude of 180 metres. They
mggested a total neutron flux density at sea level( 41°N) of about 10-2 n/cm 2 X second, 15-25 per centof which are in the energy range 1 to 10 MeV. andi:.bout 70 per cent have lower energies.
38. It seems reasonable to follow the suggestionof Kastner et al. 60 and to assume the value of
10-2 n/cm 2 X second as the total neutron flux density
at sea level. A lower value of 0.54 X 10-2 n/cm2 X
second at sea level as given by Haynes, 58 was recently
used as a basis for dose estimates. 61

"·...

'\.

10 MeV

EnergyFigure 4. The equilibrium neutron flu."'< density versus energy
at sea level ( 44?N)H (the assumed spectra oi the two neutron
sources are also shown)17

ionizing component according to Lillicrap, 19 70 per
cent according to Lowder and Beck18 ).

detailed knowledge on the composition of the building
materials is available.

N cutron dose rates
41. On the basis of Hess' energy spectrum 44 • G!? andthe usual factor to convert· flux densities to dose
rates, 61 • 70• n 10-2 n/cm 2 X second is assumed to correspond to a dose rate of 0.7 mrad/year. Hov;ever, thisvalue is considered to be an over-estimate, since thespectrum derived by Newkirk 51 gives a lower dose rate
for the same total flux density of neutrons. As most of
the other experimental values for flux densities range
from 0.4 to 1.5 X I0- 2 n/cm X second,53 • 5 5 , s7, 5 s. 60 one
obtains a range from 0.3 mrad/year to 1.1 mrad/year
for the neutron dose rate at sea level.
42. Neutron flux densities. and to a lesser extent
the energy spectrum. are latitude dependent. Thus,
assuming 0.7 mrad/year at 41 °N, slightly higher dose
rates will be encountered near polar regions, 57 • 61
whereas at the equator the neutron dose rate might beabout 30 per cent lower or approximately 0.5 mrad/year.
43. Correction factors. A number of factors need
to be considered when estimating radiation dose rates
to human tissue (outdoors or in buildings) from anestablished neutron flux density in air with a known
energy distribution. Owing to the abundance ofhydrogen atoms in the human body, neutrons producedin the atmosphere lose their energy faster in traversing
I g/cm 2 of tissue than in traversing 1 g/cm 2 of air. 72 •76
44. Practically all neutrons entering the human bodywith energies below 5 Me V lose their energies byelastic collisions with hydrogen and are finally absorbedby H(n, y)D or },.Tl 4 (n. p)CH reactions. The neutron
dose decreases rapidly with increasing depth 71 • 75 and at
10 cm beneath the surface the dose is about one-third
to one-tenth of that at the skin, depending on theenergy and isotropy of the neutrons.
45. As neutrons lose on the average about half of
their energy in the first collision with a hydrogen
nucleus. neutrons of higher energy (above 5 MeV)
lose significantly more of their energy in the humanbody than in the same mass of air (or other nonhydrogenous materials). However, neutrons above 5
MeV are relatively rare in the equilibrium spectrumof air, thus limiting this additional contribution tohuman tissue dose to 20 per cent at most of the neutron
dose.
46. Neutron production in the human body must also
be considered. One may assume that the cross sections
per atom for the production of evaporation neutrons
in the body (oxygen, carbon) are comparable withthose in air ( o:;.,.-ygen, nitrogen). The neutron component which is responsible for most of this terminal
stage in the nuclear cascade leading to evaporation
neutrons has a significantly shorter mean free path in
the body than in air. More neutrons will therefore
reach this final stage of evaporation interactions in the
body than in an equivalent mass of air. thus tending
to raise the average tissue dose received from neutrons.
47. As to the shielding by buildings and the computation of neutron dose indoors. tissue equivalentmaterial might be as likely to add somewhat to thedose as to shield part of it, because of the scattering
effects and the possibility of higher production rates inthese materials as mentioned above. Heavy construction
materials. such as lead and iron. tend to add to theneutron background.~ 2 • • 7• 79 Thus, it seems unjustified
to a11ow for the shielding effect on neutron doses unless(ONCLUSIO::-.l"S

48. The contribution of the ionizing component ofcosmic rays at sea level was estimated in the 1962
report as 28 mrad/year at middle latitudes, which isalso the best value agreed upon lately .18• 63 • 65 Thisdose rate of ionizing radiation is mainly delivered bymuons 19 and is subject to the slight variations due tolatitude effects which may lower the dose rate by about
10 per cent near the equator. The total dose rate approximately doubles for every 1,500-metre increase
in altitude for the first few kilometres. 2 • 18• 64 The
relative importance of the nucleonic component as compared to the muon component increases with altitude.
These facts will be of importance in assessing doses
received at high altitudes, including space flights andother high altitude flights. 61
49. Revised data on cosmic-ray neutron flux densities
indicate that. without allowing for shielding by building
structures and for screening by body tissues, the corresponding absorbed dose is 0.7 mrad/year (range
0.3-1.1 mrad/year) in temperate and polar regions,while in equatorial regions it is likely to be around
0.5 mrad/year. This value may be compared with thedose rate of 2 mrad/year which can be inferred fromthe estimate given in the 1962 report.
III. Terrestrial radio-activity
SOIL

50. Practically all the natural enviromental radiationof terrestrial origin is due to radio-nuclides of theuranium and thorium series and to K 40 • Typical abundance figures for the accessible lithosphere are 2.8
parts per million of uranium and about eleven parts
per million of thorium. The nuclides belonging to these
two radio-active series and their more important properties are listed in tables IV and V. The U 235 series
is of lesser importance but is listed for completenessin table VI. A schematic representation of these three
decay series is given in figure 5.
51. There are other primordial radio-nuclides inthe earth's crust. Of these, the greatest contributor toterrestrial radiation is K 40 , which makes up about
0.01 per cent of natural potassium. Certain propertiesof this nuclide are listed in table VII, along with theproperties of selected primordial radio-nuclides which
are of lesser importance because of low abundance, long
half-life or weak radiations.
EXTERNAL RADIATION

52. External natural radiation is prod11ced mainlyby the gamma emitters of the natural radio-active
series and by K 40 in soils, rocks and construction
materials, by cosmic radiation as discussed in part II.
and to a small extent by atmospheric radio-activity.
Outdoor and indoor terrestrial gamma dose rates
measured before 1961 were summarized in tables IV. V
and VI of annex E oi the 1962 report.
53. 11feasurements of the total gamma dose obtainedby means of high pressure argon or tissue equivalent'
ionization chambers, so- 53 were recently supplemented by
gamma spectroscopy in order to assess separately
the various contributions to the e::-..--ternal radiation
dose. 64 • si- 59 • 91 • 92 Figure 6 shows a typical gamma
spectrum on which the K 40 photo-peak of 1.46 MeV
and the main peaks of the uranium and thorium series
are indicated.
18

0
0
0

......

\0UI
9
4.5 >: 10 y00

8
7.1.10 y

ux 2

234

231

uxl

UY

232

226

Ro

1.2 per cent

AcX

~

5.8 y

r:---1---.~

j223
I

HX

228 Mc Thi

II1,620y

I

AcK;/

1

L-~~~~·:.._J

222

Rn'

219

218

220

An

3.9 sec '

3.8d

215

RoA

AcA

216

2.to- 3 sec_3 minTn

54 secTliC'

ThA

0,16 sec

RaE

5d
214

RcB

27 min

Pb

211

AcB

36 mlnPb

Stobl,.

212

Tl.B

Pb

10.6 h

3.1 min .

Figure 5. Decay schemes of the natural seriesn (boxes show atomic weight, historical name an<l half-Ii f e)
0

Th

25.6h

24 d •

0
0
0
El

0
0
0

235

238

)'araJlcl decay branches of less than l per cent are not included.

•

••
• •

Gamma expo·sure rates inµ. R per hour

•

2

•

•

K40

•
•

•
•

•

1.3

Th

3.5

0.58-0.61•.

(Th) (U)

. i
....

0.77
(U)

·.19·..

2

1.46
0.91-0.97

(K)

(Th)

..l

l l

...

••

1.12
(U)

l •• •·......•• l
•

•

1.24
(U)

• 1.61

I..

::>
0
.<:::

....

•

I..

8..
0

u

Fall-out 0.5••c"'::>

2.3

•

2

u

(Th)

•
•
•

2.62

1.76

(Th)

(U)

..!

. ...i.
••• 1

.

••
• •

-.., .....·.,, ....
•

•

•

•
•

•

••••
•

•

•

•
2

•

..
•.

.•
......

•
•

5

0

400

.800

1,600

1,200

2,000

2,400

2,800

•

•

3,200

P~.oton energy - keV

Figure 6. Environmental gamma radiation spectrum, 4 X 4" NaI (Tl)-scintillation detector, Denver, Colorado, 12 August 1965241

to the external dose at ground level. Dose rates can becorrelated with the gamma-emitting daughters of theradon retained in soil. The concentrations of thedaughters is only a fraction of the actual Ra226 concentration in upper soils.93 • 94 Moreover, U 238 is not
likely to be in equilibrium with Ra226 because of thegreater tendency of uranium to leach from upper soil
layers during soil formation and weathering processes.
56. An increase in water content of soil will increase the density and consequently the attenuation of
gamma rays from K 40 and the radio-active series andwill thus cause temporal variations in the dose rate
correlated to soil moisture. The dose rates from theuranium series may, however, be affected also in the
opposite direction. since clogging of the pores in thesoil impedes the escape of radon from soil air into theatmosphere, thus resulting in an increased dose rate

54. The contribution of each component to the air
dose, as derived from the evaluation of gamma spectra,using the 2.62 MeV photo-peak of Tl2° 8 to represent
the thorium series, the 1.46 MeV photo-peak for K 40
and the 1.76 MeV photo-peak of B 214 for the uranium
series, were often compared with doses estimated on thebasis of the measured abundance of Th232 , K 40 and U 238
in underlying soils or rocks. 80-88 In general, the two
methods gave results consistent within 5-10 per cent for
K 40 and Th232 • when soil densitv and moisture content'
were taken into account.
55. No such close correlation between the dose
determined from Bi 214 and the U 238 concentrations inunderlying soils was found, however. 84 • 89 • 113 Nor could
it be e--x:pected. since the movement of free radon outof the upper layers of the soil into the atmospheregenerally reduces the contribution of the uranium series
20energies. These upper limits are twelve and fourteen
for the uranium and thorium series, respectively.
65. Thus, taking three parts per million of uraniumand eleven parts per million of thorium as representativeof the upper earth's crust, 111 an average production
rate of 13-24 n/year X g soil and of 20-50 n/year X g
granite is obtained. Assuming sixty parts per million of
uranium and 110 p~rts per million of thorium as possible
upper limits of concentrations in granite, one would
obtain a production rate of 450-800 n/year X g granitefrom (a.. n) reactions which might add a few per cent tothe cosmic-ray neutrons observed at elevated altitudes.
The 28 n/year X g granite from spontaneous fission forthis case would still remain insignificant.

from radon daughters. Furthermore, during rainfall,
the wash-out of short-lived gamma-emitting daughtersof radon from the atmosphere will temporarily increase
the e.xiernal dose rate attributed to the uranium
series.s-1, so, 90, 94-9<
57. The measured average external radiation dose
rates one metre above soil in populated areas fall mostly
in the range 30-65 mrad/year with a representative
yaJue oi about 50 mrad/year. 8 -1, 9 ~• 9 ;-ioo Potassium andthorium each generally contribute more than one-third,
while the contribution from the uranium series is usuallysomewhat less.
58. From the point of view of many human populations, exposure levels out of doors are more relevant
than indoors. Indoor doses depend primarily on theradio-active content of construction materials and on
the attenuation of outside radiation by roofs and walls.
There seems to be no reason for changing the value ofSO mrad/year adopted in the 1962 report, as the few
additional experimental results 101 • 102 fall within theranges quoted earlier.
59. Unusually high natural radiation areas werediscussed in the 1962 report and the five major inhabitedareas with increased terrestrial radiation were tabulated
in table XX of anne.x E of that report. Further studies
concerning e.xternal dose rates to the populations inthese areas supplement and confirm previous data. 103 •107
60. The comments made in the 1962 report concerning the insignificance of external beta radiation to
gonad or bone marrow doses must still be accepted. The
external radiation dose rate from natural airborne radioactivity is usually of the order of 2 mrad/year. Since
it is small compared to the dose variations discussed inparagraph 56, atmospheric radio-activity as an externalradiation source will not be dealt with separately.

NATURAL ACTIVITY IN WATERS

Oceans
66. The natural radio-activity of sea water 112 • 113 ismainly due to K-1° (300 pCijlitre). Rb 87 and theuranium series contribute about 3 pCijlitre each to
the total activity of oceans. Natural H 3 in the upper
oceanic layers might range from 0.6 to 3 pCijlitre,while all other radio-isotopes, including those of thethorium series, contribute less than 0.2 pCijlitre tosea water activity.
Fresh waters
67. Natural radio-activity in fresh waters is due tosome activity transfer from soils and the atmosphere.
Thus the activity concentrations found in waters dependon the concentrations encountered in the rocks withwhich the waters are in contact. 36 • 114 Members of aradio-active series in water are rarely in radio-active
equilibrium with each other because of differences inchemical and physical properties such as solubility,
sorbability, etc. K 40 is often the main contributor to
the beta activity in water.
68. As drinking water is one of the media by which
natural radio-isotopes are transferred to man . the concentrations of specific nuclides, mainly belonging to
the Ra2 !! 6 chain, have been e.xtensively measured formany years. 104 • 106 • 115•128 Typical concentrations in continental waters, as well as usual concentrations of Pb 210
and Po210 found in rain, are given in table VIII. Tables
VII and VIII in annex E of the 1962 report list someearlier values of natural radio-activity in natural waters,
springs and public water supplies for various countries.
Recent information accumulated since 1962 is summarized in table IX.
69. Ra226 concentrations in drinking water vary byorders of magnitude, though most waters show values
between less than 0.1 to about 1 pCi/litre. Surface
waters (lakes, rivers) usually show less activity thanthose derived from deep wells, especially in areas where
the concentration of natural radio-active minerals in
the earth's crust is higher than usual.
70. Rn222 concentrations in fresh water may varyfrom less than 1 pCi/litre up to the order of 106 pCi/
litre. 2 • 120·130 Levels less than 10 pCijlitre are foundin lakes and rivers, and the highest concentrations observed have been reported for some spas and springwaters.123• 128 Concentrations of 102-104 pCi/litre havebeen found in ground waters and even higher concentrations in deep wells (table VIII).
71. Pb 210 in water is mainly derived from the decayof radon in the air and the resulting deposition of thisnuclide with rain. for Pb 210 concentrations in surface
water seem to exceed those in water from deep wells. 117

Neutrons
61. Neutrons in the earth's crust may be produced
by interactions of soil elements with cosmic rays, byspontaneous fission of U 238 , by (a., n) and possibly by( y, n) reactions. ·while of no significance as far as doses
are concerned, these neutrons, some of which escapefrom soils and rocks, are of interest to geologists, andmay sometimes be confused with cosmic-ray neutrons.
62. An indirect estimate for the production rate ofneutrons due to the interactions of cosmic rays in upper
soils may be obtained by dividing the average neutron
flax density at sea level by the neutrons' mean free pathin air, thus neglecting the differences in atomic composition of soil relative to air. A production rate of
7 X IQ-iln/second X g soil at mid-latitudes (corresponding to about 2,000 n/year X g soil) is consistent withthe extrapolated cosmic ray neutron flux density of
10-2 n/cm 2 X second at sea level and a mean free pathof 150 g/cm 2 as discussed in paragraphs 29-38.
63. Spontaneous fission of U 238 (half-life 8 X 10115
years, and 2.2 n/fission) 108 gives rise to a production
rate of the order of only 1.4 n/year X g soil (assuming
three parts per million U/g soil).
64. Gorshkov et al. report the ~perimental yieldof 0.107-0.014 n/106 alphas for the (a., n) reaction of
Po 210 alphas on Si0 2 . and a value of 0.238 n/10 6 alphas
for granite. 109 The conversion factor from the Po 210
alpha yield to the alpha yield from the uranium series
in equilibrium should be at least eight and for thethorium series at least six. Upper limits were derived
from Gurfinkel's110 values for the (a., n) reaction on
0 18 , taking into account the increase in yield with alpha21

Pb210 concentrations in water do not fluctuate asstrongly as Ra2:rn, and there is no correlation between
the two elements nor between Pb210 and the sulfate,calcium or fluoride content of water. Typical concentrations are between 0.05 and 0.2 pCijlitre.
72. Information on Ra228 or Th228 concentrations inwater is extremely limited.36 • 104· 119 Turner et al, 123
observed the presence of short-lived Th-series nuclides(Ra224) in water sampled in the United Kingdom.
Long-lived elements, such as Th228 and Ra228 , were
present only in trace.s. Th 228 cons?t~1tin_g a very small
fraction of the long-lived alpha activity m water.

100

Rn222
2lf
Pb "'

., ~--..
Bi_J,. ••••

..·-.
..

10
.?:-

· \.. Rn220

pf?12

.::

u

.................,.12'?""'" ............ ~..... 111.0 •• ,,,,,,,
Bi-

0

Cl,)

c..

Vl

73. The natural radio-activity of the atmosphere iscaused mainly by Rn222 , Rn220 and their radio-active
decay products. The contribution of Rn219 or it~ radioactive daughters is negligible.s 4 • 36 • 37 Radio-active nuclides produced by cosmic rays (table II) are of minor
importance as sources of atmospheric radio-activity_; theradio-activity in dust particles blown from the s01I bywind, or from K 40 brought into the atmosphere by theevaporation of sea-water spray is also extremely low.
These sources will therefore not be discussed any
further.
74. A simple mathematical model to account forradon exhalation rates from soils. and to estimate concentration profiles of the radon isotopes in the troposphere was developed by Israel. 131 His model, withsome minor changes at times, has been widely followedby many authors.37 • 132-134
75. The spreading out of Rn222 and Rn220 in theatmosphere after their exhalation from the ground iscaused by turbulent diffusion and convection. The decay
products of the radon gases, being isotopes of heavy
metals, become readily attached to aerosol particles.
At ground level, more than 99 per cent of the Pb214,
Bi2 14 and Pb 212 atoms, and about 75 per cent of theshorter-lived Po218 atoms are carried by aerosols. 34• 36 •37, 131-13 7 The fraction of natural radio-activity not attached to aerosol particles increases with altitude. As
concentrations of aerosols in the atmosphere are about
106 times higher than the concentrations of radon
daughters, radio-active aerosol particles will usuallycontain a single radio-active atom each.
76. The effective radius of aerosols which containthe main portion of natural atmospheric radio-activity is
bet\veen 50 mµ. and 80 mµ.. 37• 135 As aerosols are unstable
and tend to increase in size as a consequence of condensation and coagulation processes,. reported size .distributions of activity are only vahd for short-lived
radio-active decay products. Long-lived isotopes likePb 210 and daughters are therefore expected to be attached to larger aerosols.
77. The distribution of the radio-active decay products of radon in the atmosphere is consequently controlled not only by radio-active decay and diffusion,
but also by sedimentation and wash-out related to theremoval of aerosols.
78. Figure 7 gives a vertical distribution of concentrations for the radon isotopes and their radioactive decay products for "normal" conditions, assuminu a half removal time of twenty days for all theradon °daughters. 134- 136 Full radio-active equilibrium atground level air for Rn 222 and its short-lived radioactive daughters is not reached because of the continuous elimination of radio-active aerosols by downward
diffusion and settling. However, equilibrium between

' 11

\

~

u

c

'·.............,...

~

·~

\

0

THE XATURAL RADIO-ACTIVITY OF AIR\..,,,,,, .. ,,,,,, ... ,,,u,,.,,,,,,,,,,,;;:.~,,.,.,,

0.1

"\

~

pf?lO

\

10

100

'\
\

0.01
0.001
1,000

10,000

Altitude in metres
Figure 7. V crtical distribution of concentration of the radon
isotopes and their radio-active decay productsl34

Rn 222 and its short-lived daughters is approached quite
closely a few metres above ground.
79. Rn220 is virtually never in equilibrium with its
radio-active decay products. The 10.6-hour half-life of
Pb 212 greatly exceeds that of Rn 220 so that Pb212 atoms
after their formation can diffuse to higher altitudes than
Rn220 (or Po 216 ). A very low Pb212/Rn220 ratio, as
expected, was measured by Fontan et al. 139 in groundlevel air. An excess of Pb 212 over Rn220 is expected at
somewhat higher altitudes. Owing to their short halflives, the concentrations of Rn220 and of any of its
decay products become insignificant, when comparedto Rn2:: 2 concentrations. at some ten metres above
ground.
·80. The concentrations of Pb 210 , the long-lived decay
product of Rn 222 , and its radio-active products Bi210 andPo 210 must be extremely low in the troposphere owing to
removal by precipitation. Their concentrations. however,increase gradually in the upper troposphere, and actually
exceed those of their short-lived parents in the stratosphere. Concentration ratios of Po210 to Pb210 depend
critically on the mean removal rate and increase rapidly
above 1 km. Observed Bi210/Pb210 and Po 210/Pb210
ratios in air and precipitation have therefore been used
to determine the mean residence time of natural aerosolsin the troposphere.s1, 140-145

Horizontal distribution and variability
81. Local concentrations of the radon isotopes andtheir radio-active daughter products depend not only
on the emanation rate of radon gases from the soil but
also on a nriety of local meteorological conditions.
\Vind direction is of special importance in coastal sites.
on the sea and in the polar regions, as radon is mainly
carried by continental air masses.
82. \Vinds reduce Rn 222 concentration in the upper
soil layers. thus enhancing the exhalation rate. All air
motions near the earth-atmosphere interphase are turbulent; they assist to some extent in the extraction ofradon gases from the upper soil air. These air motions,22•

on the other hand, may enhance the removal rate ofradio-active daughters formed in the lower atmospherebv increasing their in1pact on the ground. They areaiso mnoved by precipitation and dry settling ofaerosols. a•, l34-1s1, 145
83. Diurnal, seasonal or more irregular variations
oi the radio-activity at a given site have been reported.135· Ha-m During night hours. a temperature
inversion usually develops near the ground. which
reduces the vertical mixing of the radon gases after
their exhalation from the ground. thus producing abuild-up of radio-activity which reaches its ma.'<imumconcentrations in the early morning hours. The risingtemperature during day-time will break this temperature inversion and facilitate turbulent mixing, thus
reducing radio-activity concentrations near the ground.
~Iinimum concentration values are usually found during
the afternoon. Diurnal variations may cause concentrations to change by a factor of two to three on the:iverage. but variations e..xceeding a factor of ten havebeen reported.
84. In some locations. the average radon conc~ntra­
tions in the air during winter and early spring arelower than those prevailing during summer.3G, n1, 151, 15:?
This may be due to the known seasonal variations inescape of radon from the ground, the relatively low
winter and spring values being attributable to thehigher moisture content of the soil. Frozen ground
reduces escape considerably. and thick layers of snowor ice stop it completely. In other locations. the maximum radon concentrations are observed during autumn
and \vinter and minimum ones in spring and summer,in accordance with variations of atmospheric conditions,e.g. the rate of vertical turbulent exchange. 139, 153, 154
Measured concentrations of natural radio-activity
85. The release of Rn22 :i and Rn220 is considerably
greater from land than over water. Typical measured
levels in ground level air over continents range from30 to 300 pCi Rn 222/m3 and 0.5 to 10 pCi Pb 212 /m3 ;14 6160• 1 1i 2·157 over the oceans. the concentrations are between one and two orders of magnitude lower.37, 131 •158• 1!19 Concentrations of the order of 2 pCijm3 forRn 222 and less than 0.3 pCijm3 for Pb212 were measured
in Antarctica. 160· 161
86. Concentrations of Rn222 and Rn220 in groundlevel air in various regions were summarized in table IXof annex E of the 1962 report, and in some recent
publications.36· 37· 135 Only a few determinations forRn 2 :w have been reported, based on the beta decayof Pb212 • The erroneous assumption of radio-active
equilibrium of the Pb2 12 with the short-lived Rn 220 in
the air sampled is partly responsible for the low Rn 220 /Rn222 ratios reported.37, 131, 16!?, 163
87. Radon concentrations indoors are generally
higher than outdoor concentrations, depending on theconstruction materials. the degree of ventilation and theescape from indoor water sources. Average values ofRn 222 concentrations indoors at various locations werereviewed in annex E of the 1962 report and summarized there in table XI.
88. On theoretical grounds, it can be expected thatthe concentration of radon in air in deep layers ofundisturbed soils can be of the order of 105 pCijm3
air ;37, 131 therefore. such radon concentrations are to
be expected in the air of caves and unventilated underground mines. Measurements made in mines, particularly uranium or thorium mines. give results consistent
with this e..'<pectation.110-1 73
23

Long-lived decay products of radot:-222
89. The general features of the circulations of Pb 210
and Po 210 resemble the patterns of stratospheric fall-out<:of artificial nuclear debris. The concentrations of Pb210
in ground level air are dependent on iatitude and on the
distribution of land masses and oceans. Lower values
were found in tropical and polar regions than in temperate areas. 10·1 Concentrations in the southern hemisphere are lower than those in the northern hemisphere,
because the land surfaces from which radon is exhaleda:-e smaller in the southern hemisphere. The observed
range of the average coniinental Pb 210 concentrations
vary from 0.002 to 0.016 pCi/m3 air (excluding Antarctica). Data reported by other authors for selected
locations were of the same order of magnitude. 140· H 2·
114· HG, 10:.-1c9 Only a small fraction of the Po 210 in equilibrium with Pb 210 is present in the lower troposphere.
90. Yearly deposition rates of 1.7 mCi Pb21o/km2
were measured for the United Kingdom. 140 and 2.4 mCi
Pb 210 /km 2 were reported f:-om Fr:ince. 160 Under equilibrium conditions, Pb 210 and Po 210 activity in upper soil
layers could thus amount to some 60 mCi/km 2 each.
IV. The transfer of environmental radio-activity
to manINTRODUCTION

91. N aturally-<>ecurring radio-active nuclides enter
the body mainly through food and water, inhalation
being of secondary importance. The information on K 40 ,C14 and tritium transport through the food chain has
remained unaltered since the 1962 report was issued ;this subject, therefore, will not be discussed again here.
Rb 87 accompanies potassium in metabolic processes. anddoses to man due to this element. which is commonly
distributed in the biosphere, will be dealt with in paragraph 136.
92. As was pointed out earlier, the radio-active
elements of the uranium series in soil are seldom inequilibrium because of their different chemical properties which detem1ine the varying behaviour of theseelements in the processes of weathering, soil formation,
redistribution of minerals in the lithosphere, etc.
Uranium is taken up by plants; however, because of its
low .specific activity and the low concentrations found in
the biosphere. its radio-activity may be disregarded.
Thorium is absorbed very poorly by the root systems.174·li7 Therefore, only radium isotopes (Ra226,
Ra228 ), and possibly lead (Pb 210 ) and polonium( Po 210 ), among the Jong-lived nuclides of both theuranium and thorium ·series are taken up by plants toa degree that may be important when further transferof radio-activity to animals and to man is considered.
On the other hand. significant amounts of Pa2 10 and
Pb210 are deposited on plants from the atmosphere.
93. Ra226 and Ra 228 decay, directly or indirectly, toRn222 and Rn 220 , respectively. The latter are chemicallyinactive gases. They leave the soil and, together with
their short- and long-Jived daughter products, form themost significant part of the natural radio-activity thatis inhaled by man.
94. Areas of "nornwl'' activity. As reported in the
1962 report. the content of Ra226 in soil varies considerably with geological and geochemical conditions.
The levels reported from the United States, which arepossibly typical, 178 are of the order of 0.09 to 0.8 pCijg
soil. No extensive measurements of Ra228 , or Th228
have recently been reported. Because of the short half-life oi Ra 228 , it may be assumed that its concentration
in soils is closely related to that of its parent, T'11232 •From the data on the escape of radon from soil and on
deposition of Pb 210 from the atmosphere it has been
postulated that equilibrfom levels of this nuclide in the
few upper inches of soil should be about 60 mCijkm2(paragraph 90).
95. Areas of high natural radio-activity. Those areasin the State of Kerala in India, and the States of Riode Janeiro and Espirito Santo in Brazil, where levelsof radio-activity in soil are high because of the presenceof monazite sands of high thorium content, were discussed in the 1962 report. Since then, additional data
have been reported on the availability of radio-active
elements from these soils to plants177 • I79 • 180 and will
be discussed in paragraphs 110 and 111. together withthe data on accessibility to plants of Ra226 and Ra228 in
the high background area of volcanic intmsives in theState of Minas Gerais, Brazil.
INTAKE BY MAN%. In addition to K 40 , Rb 87 and C14, which are
not considered in this section. radium (Ra226 andRa228 ), radon (Rn222 ), radio-lead (Pb 210 ) and polonium (Po210 ) contribute appreciable doses to man
through food. Vlhen inhaled, radon (Rn222 and Rn220 )with their short-lived decay products, and possibly
radio-lead (Pb 210 ), contribute to lung doses and mustalso be considered.

Water
97. The relative importance of drinking water as asource of natural radio-activity in human diet wasstudied by numerous investigators.117, 120, 123, 120, 16~.
I80-I8298. Sanitary (usually chemical and physico-chemical)
treatment of \Yater, as commonly applied in a majorityof urban centres in a number of countries, may remove
large proportions-up to 90 per cent--of Ra226 andPb:; 10 .11 7 • 122 Water-softening procedures seem to be especially effective in this respect. Chemical treatment( e.g chlorination and subsequent aeration) and storage
may reduce the radon level in tap water, and boiling
may further remove radon from the water which isactually consumed.
Typical levels of natural mdio-nttclides in water
99. \\Tater consumption contributes only a small percentage to the total intake of the nuclide (of the orderof a few to 10 per cent-table X). As indicated in the
1962 report, the waters consumed by the majority of
the world population usually contain less than 0.1 pCi/
litre Ra226 •
100. Typical concentrations of Rn222 in waters derived from lakes. rivers and shallow wells, which areconsumed by the majority of the world's population,
are indicated in table VIII.
101. The contribution of drinking water to the total
intake of Pb210 and Po 210 has been estimated to be of
the order of 1-10 per cent for the typical diet in the
United States.165
Areas with high concentrations of radium and radonin dr·inking water
102. In some areas. where Ra 226 concentrations inwater of several pCi/litre or even more are not uncommon. water may be a significant or even a dominant
contributor to the total intake of Ra226 • Thus, in rather
24

exceptional situations, involving populations relatively
limited in size (less than 1 per cent of the populationof the country as a ·whole in the cases investigated sofar), the total intake of Ra226 may be twice as high as
the average for the country (Cornwall in the United
Kingdom), 123 or even higher by an order of magnitude(some regions of the midwestern States of the UnitedStates). 122 • 182· 183 However, in the monazite area in
the State of Kerala, India, where elevated intakes ofradium were noted, the relative role of water as a contributor of radium was limited to about 10 per cent,because of higher concentrations of Ra 226 both in waterand foodstuffs of plant origin from local sources. Iso103. Consumption of water with high concentrationsof dissolved radon (deep wells in some areas. and spa
waters which show concentrations of about 20 to 200
nCiflitre, with the highest known value of 5.000 nCij
litre)1 20 is rather exceptional. In some areas. such as
those found in the States of Maine and New Hamphirein the United States,Is.i well waters supplying a population of the order of 100,000130 contain radon at average
concentrations of about 16 and 30 nCiflitre. Average
concentrations of 1 to a few nCi/litre were foundin central Sweden129 (population of about 300,000),
Cornwall123 (population of about 300.000), the Federal
Republic of Germany and elsewhere (see also 1962
report). Many factors discussed in paragraph 98 reducethe intake considerably. The possible significance ofdoses from radon taken in with water will be discussed
in paragraph 148.
Foodstuffs
Areas of typical "normal" levels of intake
104. The total intake of Ra226 and the contributionof different food categories was studied in the United
Kingdom, 181• 185 the United States, 186·189 and India.ISO
The average estimates reported for areas with apparently normal concentrations of Ra226 in drinking
water and foodstuffs vary between 0.7 and 5 pCi/day(table X), while smaller variations in the values of
the Ra/Ca ratio have been reported.
105. In both the United States187 and the United
Kingdom 181 • 185 the main sources of radium in the dietare not the same as those from which the main proportion of calcium is derived (table X). In all thecircumstances investigated so far, foodstuffs of plantorigin (cereals and grain products, fruits and vegetables) form a major source of dietary Ra226 • The relative availability for absorption in the gastro-intestinal
tract of radium from water and different foodstuffs is
unknown.
106. The daily intake in very low-income groups
in Puerto Rico 190 is slightly less than 1 pCi/day. However, the calcium intake is also low. and thus the resulting Ra226/Ca ratio in the diet is. similar to that inother regions of the United States. It could be inferredfrom the data of Chhabra180 that a similar picture may
obtain in India-at least for the area investigatedwhere the intakes of both radium and calcium seem tobe low. 2
107. The intake of Ra228 has not been studied on ascale comparable to that of Ra226 , but the data derived
from alpha-spectrometric measurements in different materials, including \Yater, foodstuffs and human tissues.191• 192 indicate that the intake of Ra228 is. on theayerage, about two to four times less than that of Ra226 .
108. The Pb 210 intake has not been specifically determined, and only some indirect estimates are avail-

r
I

I

able111~ which show that, on the average, the total intake

The usual levels to which human populations are exposed, however, are heavily influenced by indoor concentrations. Indoor concentrations are normally higher
than those found outside because of the accumulationof radon and thoron from building materials in closed
or poorly ventilated premises. The problem was reviewed in the 1962 report, and no recent data are available which would warrant a change in the position
adopted therein. It will be maintained, therefore, thatthe typical average effective concentration of Rn222 towhich the world population is e..xposed is about 500
pCi/ m3 • Daughter products, from Po 218 through B i214 ,are assumed to be present in concentrations between
100 and 500 pCi/m3. Corresponding average concentrations of thoron daughter products (Po 216 , Pb212 andPo212 ) are based on an estimate by Jacobi200 and havebeen assumed to equal about 600, 10 and 10 pCi/m3 ,respectively.
115. High concentrations. It needs to be mentioned
here that. because of their occupation in undergroundmines, some groups of workers are exposed to air concentrations of Rn222 and daughter products higher thanusual (paragraph 88). The fraction of the population
subjected to this type of e..xposure. even in industrializedcountries, does not exceed a fraction of I per cent. The
importance of the problem and the health hazards involved were discussed in the 1964 report (anne..x B,
paragraphs 152-174) and elsewhere.201
116. The downward flow of cold air gives rise toincreased concentrations of radon at the bottom ofvalleys. Rn222 values ten times higher than the night
concentrations over flat country have been observed invalleys by Servant.202

r day should be of the order of 1-10 pCi. This seems
be typical for most regions. wit!: th~ exceptio_ns discussed in paragraph 113. The contributions of different
foodstuffs are not known, but those of plant origin
probably play the dominant role.
109. The estimated usual intake of Po 210 is of theorder of several pCi per day, 193• 194 in agreement withthe results of total dietary analyses. 189 The data areconsistent with a faecal excretion of 1.8 pCifday as
determined by Holtzman16;; or of 1.7-6.4 pCi/day as
found by Hill. 193 The data indicate that the main sources
are fresh leafy vegetables and, in some circumstances, a
few animal tissues (kidney, liver).

f;Special food chaiti mechanisms and areas of high naturalradio-activity
110. Information on the intake of natural radioelements in areas of high radio-activity in the soil isvery limited. In Brazil, locally grown foodstuffs withhigher than normal radio-activity are found in somelocalities near the towns of Araxa and Tapira, in theState of Minas Gerais. H 9 In these areas, the concentrations of Ra226 and Ra228 in edible plants are about
one to two orders of magnitude ,higher than normal.
However. estimates of intake in this area are not yet
available. Food from the monazite areas of Brazil contains only the normal amount of Tadio-activity fromboth the uranium and the thorium series. This seems
to be due to the very low solubility of the minerals of
which the monazite sands are composed.
Ill. In India, in the high activity area of Kerala
State, recent studies180 have revealed that the radium
intake due to locally grown plant foodstuffs may behigher by a factor of four to five than in the Bombay
area, and is still considered within the range of values
typical of other countries.
112. Brazil nuts are known to accumulate theheavier alkaline earth elements. radium and barium, toan unusual e..xtent. This effect has been observed insamples from Brazil, l\falaya and Guyana ;1s1. l96, 196
concentrations in kernals usually range from one to fivepCi Ra22il/gramme. Thus the quantity of Ra 226 in one
gramme of Brazil nuts is comparable to the estimatedaverage daily intake of the population shown in table X.
It is not known whether the radium from Brazil nuts
is absorbed in the gastro-intestinal tract of man to thesame extent as radium in other foods.
113. In the 1964 report (annex A, paragraphs 118,128), a special food chain mechanism, transferring unusually high activities of Cs 137 from lichens throughreindeer or caribou meat to man, was discussed. The
same applies to Pb 210 and Po210 of natural origin. andfragmentary data are available (table XV). showing
high concentrations of both Pb 210 and Po 210 in lichensand in the meat of reindeer and caribou. which grazein arctic regions. 193· 197 It was postulated that the
dietary Pb 210 and Pa210 intakes of people subsisting onlarge amounts of caribou or reindeer meat may beelevated by an order of magnitude above the typicalvalues observed elsewhere. 197 This is supported by still
fragmentary evidence of Pb 210 and Po 21 0 in humantissues from northern Canada 108 and Finnish Lapland 199(paragraph 133).

LEVELS IN MAN

117. Our knowledge of concentrations of naturallyoccurring radio-active potassium (K40 ). carbon (C14 ),tritium (H 3 ) and beryllium (Be7 ) in human tissues
and of their distribution in different organs has remained essentially unchanged since the 1962 report wasissued, but substantial new information has become
available on radium isotopes and nuclides of the Pb210-Bi21o_po210 chain.

Metabolic data on Ra116 and the Pb 110 -Bi110 -Po'10 chain
118. Several investigators have shown recently2° 3•
204that about 80-85 per cent of radium in the body iscontained in the skeleton, the remaining fraction being
distributed approximately uniformly in soft tissue asshown in table XIII. The concentration of radium pergramme of ash from soft tissues is similar to that inthe ·skeleton, but is lower by a factor of about twenty
when calculated on a fresh weight basis.203
119. The concentration of Ra226 per gramme ofbody ash of man is constant throughout the entire life
span, starting from the earliest period of foetal life
(four months) in which the determinations were possible.205 The rise of body calcium and radium in theprocess of growth is apparently parallel. and no significant discrimination between the two elements seems
to take place at the placental barrier. The total bodyburden becomes constant in adult age and displays theorgan distribution described in the foregoing paragraph.
120. Under steady-state conditions the ratio of radium to calcium in the body contrasts markedly withthat in diet. The observed ratio (OR), defined as

Air
114. Normal concentrations. The normal concentrations of radon and thoron in ground level atmospheric
air have been discussed in paragraphs 79, 85 and 86.

Ra/Ca in bone,
Ra/Ca in diet25

for adults is about 0.016. 186 • 190 This compares withratios of about 0.25 for strontium and 0.08 forbarium. 207 The consistency of the OR for radium under
difierent conditions of dietary composition suggests ~hatthe content in bone is determined by the dietary ratiooi the two elements.190
121. The content of Pb210 in the human body has
been the subject of several studies in recent years; theresults of measurements are collected in tables XII
and XIII. There is apparently little correlation of Pb 210
with the content of Ra226 in bone from the same places.
122. :Most of the total Pb 210 present in the body isin the skeleton. 165 • 199 The distribution of Pb210 in theskeleton appears to be uniform within a factor of two.
with slightly but significantly higher concentrations intrabecular than in compact bone. Concentrations in thebone tissue of males are somewhat (about one-third)
higher than in that of females. 165
123. The contributions of different sources of Pb210
to the total body burden are not known in detail. However. inhaled air and dietary intake seem to be themain contributors. The decay of radon in the body
(both the atmospheric radon and that formed fo situ
from the disintegration of Ra226 ) and the intake of
Pb 210 \Vith water seem to account for only a few percent of the activity present in the human body. 165
124. The distribution of Pb 210 in human soft tissues
is not known in detail. The ratio of Po210 to Pb 210 isJess than unity in most of .them with values close toequilibrium in the liver. and with some excess Pa2 10 in
the kidneys and ovaries. 193 The origin of this e.xcess
Pa210 is still open to question. However, as pointed out
by Holtzman. 208 there are kinetical reasons for supposing that by far the largest fraction of Po210 in
the body, including this so-called "unsupported
Po2101 ', comes mainly from the redistribution of that
Po210 that is formed by radio-active decay of Pb210 in
the body rather than from direct dietary intake.
125. Hunt et al.209 showed that, despite marked differences between individual teeth and observable variations between trabecular and compact bone in the sa:neperson, the average levels of Ra226 and Pb 210 in bone
were closely correlated with those in teeth. The average
concentrations of radium in bone and teeth were equal.
whereas those for Pb210 were twice as high in bone. It
may be concluded. therefore, that teeth analyses forRa226 may be used to study average population levelsin the ·skeleton when bone material is not available
and when no significant and prolonged changes in therate of intake are expected. On the other hand, as thelength of the physical half-life of Pb 210 (T % = 19.4
years) is comparable with the human life span, and themineral turnover of the skeleton may significantly differ
from that of the teeth, the Pb 210 concentration in teeth
as a measure of skeletal levels demands further study.
N annal levels of natttral radio-activity in man
126. Ra226 has repeatedly been determined in humantissues by several investigators. The results publishedsince 1962 are collected in tables XI and XIII.
127. The Ra 2!! 6 values as reported in table XI indicate that bone levels in most areas of normal dietaryintake of this nuclide are similar. the most freque:it
values clustering around 1-1.5 X 10-2 pCi/g ash, corresponding to an average of about 30 to 40 pCi Ra226
in the skeleton of a standard man (assuming an averageof 2.800 grammes of ash in the skeleton). This value
is substantially lower than the value of 60 pCi acceptedin the 1962 report. It seems appropriate therefore tosuggest, for the purpose of dose-rate calculation, a valueof 30 pCi Ra226 as typical of the whole skeleton burden
in areas of normal rates of intake.
128. Ra228 is the only important long-lived elementof the thorium series that is absorbed to a significant
degree from the gastro-intestinal tract. Ra228 decays
through Ac228 to Th228 (T% = 1.9 years), which inturn decays through a series of short-lived nuclides tothe stable isotope Pb2° 8• Very small fractions of theamounts of radio-active decay products of Th228 foundin bone leave the skeletal deposition site of Ra228 andTh 228•210 The latter nuclide has recentlv been determined in bone, together with Ra226 • In ~'O studies, theaverage ratio between activities of Th 228 and Ra 226 inbone ash varied between 0.25 183 and 0.4.203 These values
are consistent with results reported earlier.211 and it
seems appropriate to accept that the value of 0.3 to 0.4
is closer to the real situation than the figure of 0.7,
which was assumed in the 1962 report. Thus. a naturalskeletal burden of 10 pCi Th228 in a standard man
seems typical.
129. From table XII it follows that the typical Pb 210
burden in the skeleton of an adult is about 270 pCi.
As only a small fraction of Po210 formed by the radioactive decay of Pb2 10 and Bi210 in bone is removed fromits site of formation. the activities of all three nuclides
in the skeleton are close to radio-active equilibrium. 165•203 212 214••
It seems that. in contrast to the 1962 report
where a ratio of Po 210/Pb 210 of 0.5 was assumed, avalue of about 0.9 is closer to reality.
Areas of high 11aftlral radio-activity and special foodchain mechanisms
130. In some areas of the midwestern States of theUnited States. where concentrations of Ra226 in drinking water of about 1 to 10 pCi/litre are not uncommon,
Ra226 levels in bone are three to four times higher thanthose typical elsewhere (table XI). The population of
the area concerned is about 1.000,000.122
131. Preliminary data215 from those areas of highnatural radio-activity in Brazil where high activities ofradium in plants of local origin were found (towns of
Araxa and Tapira, State of Minas Gerais) show thatthe concentrations of Ra226 in teeth collected from theinhabitants are higher than in "normal" areas but only
by a factor of two to three (table XIV). In view ofthe fact that a significant correlation exists between
concentrations of Ra226 in bones and teeth209 (paragraph 125), these observations suggest that the skeletal
levels of Ra226 in this area of Brazil might be elevatedby a similar factor. The population living in the areasof Araxa and Tapira is about 15.000.
132. The data from the monazite area in Kerala
State in India are even more scanty. As shown in table
XI, in five samples of human bone analyzed so far, 180 •216 the concentrations of radium were on the average
higher than those typical for "normal" areas by one
order of magnitude. The population residing in themonazite area of Kerala State amounts to about 80,000
people.
133. As discussed in paragraph 113. high concentrations of Pb 210 and Po210 in lichens and in caribou
and reindeer meat were found in arctic regions. Fragmentary data available on Pb210 and Pa2 10 show thathuman beings subsisting to a significant degree on
caribou meat display levels of both nuclides that differ
widely from those usually found in the northern temperate zone. Thus, Hill 198 was able to demonstrate that

26
I

.
.
the average concentrat10n
ot. p o210 m
p1acentae of
Eskin10 women f:;_·om ~orthern. Canada who consumed
larO'e amounts or caribou, reindeer or moose meatm~umed to 59 pCijkg fresh \veight, whereas in women~ubsisting on a. diet normal for England and Can~da" 3 and 5.0 pC1/kg were found. Kauranen and M1etti~en•99 reported levels of Po210 in the blood of reindeerbreeding Lapps which were eigl~t times ~i&'her thanthose in the blood of southern Fmns. A smular trend
w~s observed for Pb 210 in Eskimo bones, as can beerred from tab.le XI.L The size ~f .the popul.ations
living in the arctlc reg10ns an~ sub~1stl~g on ~emde~ror caribou meat as one of their mam dietary items isdifficult to evaluate but may be as high as 1,000,000.

mf

DOSES FROM IKTERNAL IRRADIATION BY NATURAL
RADIO-ACTIVE NUCLIDES

134. Dose rates in millirads per year from internalsources of natural radiation to the gonads, to cells
lininO' Haversian canals, to osteocytes and to the bonemar;'ow contained in trabecular bone have been assembled in table XVI. The per cent contributions ofalpha radiation to the total dose rates are also indicated.
135. It is realized that for the purpose of comparing
risks, doses in rads ought to be weighted by appropriate
RBE values. In the case of alpha emitters, however,
the information on RBE is so uncertain and the values
proposed by various aut~1ors so widely ~ifferent that
it is reasonable to consider them as still unknown.
although it is possible that they may be higher than
one.67 If this were so, and if unweighted dose rates
from natural sources as given in table XVI were used
as a standard for obtaining comparative risks fromother, man-made, sources, the comparative risks would
thus be m·er-estimated depending on the RBE values
applying to any given effect.
136. The estimates of doses from KW, C14 and Rn222
and short-lived daughter products in soft tissues otherthan the respiratory tract are the same as those given in
the 1962 report. Other values have been recalculated on
the basis of different estimates of tissue concentrations
and/or by introducing some changes in the methodof dose calculation. Doses to gonads from Rb 87 amountto about 0.3 mrad/year : they are certainly less inosteocytes and in bone marrow.
137. The doses of alpha radiation to osteocytes
and Haversian canals from Ra226 and daughter products, Ra228 and daughter products, and Po 210 have been
calculated by the method of Spiers. 217 The assumed
diameters of the cavities were 5 p. for the osteocytic
lacunae and 50 p. for the Haversian canals. The valuesof the geometrical factors for Ra226 were those calculated by 01arlton and Cormack, 218 assuming one-third
retention of Rn222 and its short-lived daughter products(through Po 214 ), while those for Ra228 and daughtersin equilibrium and for Po 210 were those given by
Stahlhofen. 203 Doses to bone from beta emission of all
nuclides of these series were ignored because the percentage of energy delivered from beta decay in bone
constitutes. under the conditions of equilibrium assumed, only about 2. 4 and 7 per cent of the totalenergy of the Ra 226 , Ra228 and Pb 210 chains, respectively.b The dose of beta radiation to bone marrow fromb Recent evidence indicates that it is the irradiation of theendosteal cells lining the inner surface of bone, rather thanthat of osteocytes or the cells of Haversian canals, which
is of relevance to the induction of bone tumours. The doses
delh·ered to endosteal cells will normally be less than thosequoted in this report for osteocytes and will often also be lessthan those given for cells of the Haversian canals.

these series was also ignored as it amounted to approximately 0.1 millirad per year.
138. The alpha dose rates in fresh bone from individual nuclides that result from these calculations are
significantly higher than those obtained in 1962. The
doses from Ra 2 ~ 6 and Ra 228 differ only slightly fromprevious estimates, whereas those from Po 210 are
definitely higher, both because higher concentrations
have now been assumed and because a different methodof dose computation has been used.
139. In the present review, the dose rate to themarrow contained in trabecular bone from Po 210 has
been assessed on the basis of the presumed concentration of the nuclide in soft tissues ( ,_.3 pCijkg fresh
weight) rather than in the mineralized bone itself as
was done in the 1962 report.
140. If the total annual dose estimates from internalsources presented in table XVI are compared with thedose estimates given in the 1962 report e-xpressed inmillirads, very little difference is seen.
141. At the time when the 1962 report was adopted,
it was realized that the irradiation of the respiratory
tract from natural sources exceeded that of any otherorgan of the human body. On the other hand, only
approximate calculations of average doses to different
volumes of tissues in the respiratory tract were possible.
Since then, however, significant progress has been madein better understanding the mechanisms by whichdaughter products of Rn222 and Rn 220 are depositedand transported in the respiratory tract of man.
142. Thus, Altshuler et al. 110 have calculated thedoses of alpha radiation from Po 218 and Po2 14 • These
doses account for almost the whole of the dose toalveolar, bronchiolar, bronchial and tracheal epithelia,
and, in estimating them, allowance was made for the
distribution of radio-activity (Po 218, Pb 21 4, Po214 ) between free ions and natural aerosols of varying particle
size, for the deposition of ions and particles in different
parts of the respiratory tract, for the upward transportof radio-activity in the bronchial tree with the flowof mucus, and for the physical and anatomical factors
involved in the penetration of alpha particles throughthe mucus and the bronchial epithelium.
143. A similar study has been made by Jacobi 200
for both Rn 222 and daughter products, and Rn 2 w anddaughter products by applying somewhat different
physical and anatomical criteria. In both studies, it was
assumed that the critical irradiated tissue was the basal
layer of ceI!s of the bronchial epithelium.
144. Both studies yielded similar results, pointing
to the fact that the dose rates from Po 218 and Po2 H
alpha particles are highest in the epithelium of segmental
and lobar bronchi. \rVith average concentrations ofPo~ 1 s. Po 214 and Bi 214 • each between 100 and 500
pCijm3 . the results of both studies indicate that thedose rate in these parts of the respiratory system isof the order of several hundreds of millirads per year,
the doses to alveolar tissues and to bronchioli being
lower by two and to the trachea by one order ofmagnitude. At average concentrations of Po 216 , Pb 212
and Bi212 of 600. 10 and 10 pCijm3 , respectively. as
are assumed for the purpose of the present annex, theirradiation from these nuclides adds onlv another few
per cent to the value:; given above for doses fromp 0 ~1s and p 0 214.200

145. The quantitative agreement between the resultsof the two studies may be somewhat fortuitous, andfurther studies are necessary to provide sounder infor27

unknown, but it appears most unlikely to be appreciablein view of the low doses involved.
148. The metabolism of radon ingested with waterand the doses attributable to this source of radio-activity
were studied by von Dobeln and Lindell129 and by
Hursh et al. 180 The dose per unit of activity ingested
seems highest in the stomach (-20 mrad/14Ci Rn222 ),those to other organs being lower by two orders ofmagnitude. At normal or typical concentrations of radonin drinking water of surface origin, which are of theorder of a few picocuries per litre, 123 the doses are
negligible. In those areas where concentration of Rn222
in drinking water is of the order of nanocuries per litre,
the doses to the stomach could be correspondingly
higher-of the order of a few millirads per year.

mation on several of the critical parameters, especiallythose of a physiological and anatomical nature.219 • 220
It must be mentioned that higher doses may be received
if some uptake and retention of radio-activity by :hetissues of the respiratory tract is assumed, but sucha possibility is neglected at present for lack of relevant
information. 170
146. On the other hand, rapid dissociation of Poz 18,
Pb214 and Bi214 atoms (or ions) from aerosol particles
deposited in the respiratory tract with subsequent directtransfer to the blood stream and other organs could reduce the dose significantly. That such a possibility exists
was demonstrated by Pohl.2 21 Even so, however, it isstill uncertain whether the demonstrated resorption ofradon decay products takes place predominantly fromthe alveolar regions or from the bronchial tree, which
would be more significant from the dosimetric pointof view. In any case, the doses to the critical cells insome areas of bronchial epithelium thus obtained seem
higher by at least one order of magnitude than thoseto the whole respiratory organ that were accepted in
the 1962 report.
147. An additional exposure to natural polonium
may result from cigarette smoking. 193 • 222•228 Averagealpha-radiation doses to the respiratory tract of smokers
from excess Po 210 deposition is not expected to exceed about 1 mrad/year. In some areas of bronchial
epithelium where concentrations up to 0.3 pCi/gramme
have been detected,228 the alpha dose due to Po210
might reach the level of some tens of millirads per
year. The biological significance of this irradiation is

TABLE I.

V. Recapitulation of dose rates

149. Estimates of dose rates to man from natural
sources are summarized in table XVI!. For comparison,
the estimates given in the 1962 report but expressedin millirads per year are also included. The differences
between the two sets of estimates are slight. The dose
rates to cells lining Haversian canals, however, include
a larger contribution from alpha particles, whereas thoseto the gonads and bone marrow include a smaller contribution than the dose rates obtained in 1962. Dose
rates to the lung tissues are not given in the tablesince no exact estimate is available, but those to theepithelium of segmental and lobar bronchi are believed
to be of the order of several hundreds of millirads
per year (paragraph 144).

PROPERTIES OF THE MAIK SECONDARY PARTICLES IN COSMIC RADIATION

Rest n:us
Electric
chargeParticle

J.frV

940

0
+1
±1
0
±1
±1

11

p
11':
11' 0

µ=
e=

938
140
135

106
0.511

Electr<m
masstsMeanlifetime
seconds

1,839
1.836
273
264
20/
1

103
Stable1(}-8
2.51(}-162
2.2
IQ-6
Stable*Decay #odi1cts

e-+,,+v

x
x
x

µ=+v
2 'Y

e=+2v

*A ,positron (e +) is annihilated by combining with an electron, and two photons are
emitted.

T ABU: II.

So:ME IL\DIO-NUCLIDEs PRODUCED BY cos"l>nc RA vs31-40

Half-life

J.fa.rimum energyof beta radiati~n
ill keV

H-3

12.3y

18

Spallation of):14 or Ql6

Be-7

53d

Be-10 ....

2.7

Electroncapture550

C-14 .....

5,760y165

Spallation of
NH or QlG
Spallation of:NH or QlC
1\14 (n, p) 04

540

Spallation ofRadio-nuclide

Na-22 ...

x 106 y2.6yMain mode offormation

A40

Si-32 ...

700y

Spallation of

100

A40

28

Calculattd
Calcs1lated
concetitration
atmo.rPhcricin the lower/>roduction ratetrot>os1>here( atonu I cm• X year)(t>Cilm')sx 106
2.5 x 106
1.4-2.6 X JOG

x 106
1.8 x 103
5-6 x 103

50-65

5

x 10-2
0.5

5 X 10-8
1.3-1.6

x 10-:1
8 x 10-7
5TABLE II.

So!llE RADIO-NUCLIDES PRODUCED BY COSMIC RAYs31~0 (co11ti111ud)

J'1 aximum en.erg::;of beta radiationin keV

Half.fifeRadio-11 uclidt

jfcin mode offormation

Spallation of

1,720

14.3d

P-32 .....

Calculated
Calculated
conctntra::"onatmosf>}U!ric
in :he lowtr
prod11cti(}11 rate
troposf,}1tr1(atoms I cm• X ;;tar) (pCi m')

x 10-2

2.5 x 104

1.1

2.1 X104

6 x 10-3

4.4 x 104

6Xlo-3

3.5 x 104

1.2 x 10-S

A40

P-33

25d

Spallation of

250

A40

S-35

87d

Spallation of

165

A40

Cl-36

....

3.1x10Sy

Spallation of

710

A4o

TABLE III. THE IONIZING COMPO~C:XT OF COSMIC RAYS AT SEA LEVEL

Ytar

AuthorUNSCEAR2
Shamos and Liboff65 ................... .
Herbst64 ............................... .
Kastner66 .............................. .
Lowder and Beck18 .................... .
LillicraplO ............................. .

1962

1965
1963
1965
1965
1965

Ion Pairs/cm' X second(STP)

mrad/3tar

1.90 - 1.96
2.2 ± 0.06

28.5 ±0.8282829 ± 1.3
27.6± 1.3
26 ± 1.5

2.2 ± 0.1
2.1 ± 0.1*v

*Energy absorbed in a water Cerenkov detector.

TABLE IV. URA)<'IUM SERIEsn

I sotoPt

AtomicnumberHistoricalname

Alpha and/or beta.ray
energ•es(MeV)bHalf-life

U-238 .....
Th-23492
90

4.5 x 109y
Uranium I
UraniumX1 24.1 da4.18(n), 4.13(23),130.19(65), 0.10(35)Pa-23491

UraniumX 2 1.18min

U-234 .....
Th-230Ra-226
Rn-222
Po-218
Pir214

92
90
88
86
84
82

Uranium II 2.50 x 105 y
Ionium8.0 x 104yl,622yRadium
3.82d
Radon
Radium Ac 3.05 min
Radium Be 26.8min

Bi-214 .....

83

Radium,132.31(93),1.45(6),0.55(1)114.77(72), 4.72(28)a4.68(76), 4.62(24)a4.i8(94), 4.59(6)aS.48(100)a6.00(100),131.03 ( 6). 0.66 ( 40)0.46(50), 0.40(4)p3.18(15), 2.56(4),1.79(8)' 1.33 ( 33).
1.03(22), 0.74(20)Po-214 ....
Pb-210 ....
Bi-210 .....
Po-210Pb-206 ....

84

Radium C'c 160 X l~sec
Radium De 19.4y
Radium Ee 5.0d
Radium F
138.4 dRadium G
Stable

82
83
84
82

cc

19.7 mina7.68(100),130.06(17), 0.02(83)/:11.16(100)aS.30(100)a Based on ,reference 230.
b Figures in parentheses indicate per cent yield per disintegration.
c Parallel decay branches of less than 1 per cent are not listed.

29

Gamma ray energies(MeV)•

0.09(15)' 0.06(7),0.03(7)1.01(2),0.77(1),0.04(3)0.05(28)0.19( 4)0.35(44)' 0.29(24),0.24 ( 11)' 0.05 (2)2.43(2), 2.20(6),2.12(1), 1.85(3),1.76(19), l.73(2),1.51(3),1.42(4),1.38(7), 1.28(2),1.24(7). 1.16(2)'l.12(20). 0.94(5).
0.81 (2). 0.77 (7)'0.61 ( 45)0.05( 4)TABLE

Atomicnumb~rIsotope

,!

:,1

t1I

I I

Half·lif•

Ga.m1na ray enc1·ai~J(J.feV)b89

1.41x1010 y
5.Syc
6.13 ha4.01(76), 3.95(24),B0.05(100),82.18(10), 1.85(9).
1.72(7). 1.13(53),0.64(8), 0.45(13)Th-228
Ra-224 ...
Rn-220 ...
Po-216 ...
Pb-212 ...

90
88
86
84
82

Radio-thorium
Thorium X
ThoranThorium Ad
Thorium B

1.91 y3.64d54.5 sec
0.158 sec
10.64h...

83

Thorium C

60.5 minPo-212 ...
Tl-208 ...

84
81

Thorium C
Thorium C"

0.30 X 10-11 sec
3.lmina.5.42(72)' 5.34(28)a.5.68(95), 5.45(5)a.6.28(99 +)a.6.78(100),B0.58(14), 0.34(80),0.16(6)a.(35%) 6.09(10),6.04(25),8(65%) 2.25(56),1.52(4), 0.74(1),0.63(2)a.8.78(100),82.37(2). 1.79(47),
1.52, 1.25

Pb-208 ...

82

Thorium D

Stable..

Bi-212·i1

Alplra at1d/
or beta ray
e-ucrves(Me )bThorium
Mesothorium I
Mesothorium II

Th-232 ...
Ra-228 ...
Ac-228 ...

1:Historical
namev. THORIUM SERIES&

90880.06(24)
1.64(13), 1.59(12),1.10, 1.04, 0.97 (18)'0.91(25), 0.46(3),0.41(2),0.34(11),0.23, 0.18(3),0.13(6), 0.11, 0.10,
0.08
0.08(2)0.24(5)0.30(5), 0.24(82),0.18(1), 0.12(2)(35%) 0.04(1),(65%) 220(2),1.81(1), 1.61(3),1.34(2). 1.04(2),0.83(8), 0.73(10)2.62(100), 0.86(14),0.76(2). 0.58(83),0.51(25), 0.28(9),0.25(2)a Based on reference 230, except where otherwise indicated.
b Figures in parentheses indicate per cent yield

per disintegration.

e From reference 231.

d Parallel decay branches of less than 1 per cent are not listed.

TABLE VI. ACTINIUM SERIES•:1

Alpha and/or beta rayenergies(MeV)bAtomicnumberHistoricalname

Half-Hfe

U-235 ....

92

Actinouranium

7.13 X lQBy

a4.59(5), 4.55(4),4.50(1), 4.41(4),4.39(57), 4.36(18).
4.32(3), 4.21(6)0.204(6), 0.185(54),0.164(5), 0.143(11),0.110(3)Th-231 ...

90

Uranium Y

25.64hr,B0.30(45), 0.22(20),0.13(20), 0.09(15)0.095(2), 0.084(7),0.026(12)Pa-231 ...

91

Protoactinium

3.47x104ya5.05(11), 5.02(23),5.00(25), 4.97(2),4.94(23), 4.84(1),4.72(10), 4.68(3)0.33(1), 0.30(2),0.10(2), 0.06(13),0.04(15), 0.029(90),0.025 ( 11). 0.02( 4),0.0165(20)Ac-m ...

89

Actinium21.6ya(l.2%) 4.94(1),others (weak),8(98.8%) 0.046(100)IsotopeGamma ray energies(MeV)•

Fr-223 ...

87

ActiniumK

21 min,Bl.15 (100)0.08(24), 0.05(40)Th-227 ...

90

Radio-actinium

18.17 da6.04{23), 6.01(3),5.98(24), 5.96(4),5.87(3), 5.76(21),5.i0(19), 5.67(2)0.33(7), 0.31(4),0.30(5), 0.29(2),0.28(2). 0.26(7)'024(13), 0.17(1),0.11(4), 0.10(1),0.08(5), 0.06(9),0.05(16), 0.03(39)Ra-223 ...

88

ActiniumX

11.68 da5.87(1), 5.75(10),5.71(52), 5.61 (25),
5.54(9), 5.50(1),5.43(2)0.45(1), 0.34(7),0.27(13), 0.15(11)Rn-219 ...

86

Act in one

3.92 sec

a6.81(80). 6.54(13).
6.42(7)0.40(5), 0.27(9)30TABLE VI. ACTINIUM SERJEsa ( co11tin11ed)
Alpha end/or b1:a_ra:;lsot~eA!cmicr.umbn-Historical

Po-21584

Actinium A

1.83 X 1Q-3 sec

ct7.37(100)Pb-211

82

ActiniumB

36.1 minpl.36(92), 0.95(1),na~tnergus(MeV)bHalf·life

Gamma. ray er.ergits(MeV)•

0.53(6), 0.25(1)0.83(4), 0.70(1),0.43(1), 0.40(4)Bi-211

83

Actinium Cc

2.16 minct6.62(83), 627(17)0.35(14)

Tl-207

81

Actinium C"

4.76min/jl.47 (100)0.87(1)

Pb-20782

ActiniumD

Stable11

Compiled by vV. M. L;>wder from "Nuclear Data Sheets".

b Figures in parentheses indicate per cent yield per disintegration.

c Parallel decay branches of less than 1 per cent are not listed.

TABLE VII.

lsoloP1

Alnlndance ;,. thelitos(l}.ere(parts ptr million I

K-40 .........
V-50 .........
Rb--87 ········
In-115 ........
La-138
Sm-147
Lu-17611

SoYE NON-SERIES PRIMORDIAL RADIO-ISOTOPES2, 111, 2:?11

3
0.2
75
0.1
0.01
1
0.01

HaJf.lif1(:1ears)

x
x
x
x
x
x

1.3 1()9
5
1014
4.7
1()10
6
1014
1.1
1()11
1.2 1011
2.1 X I()lO

Alflha or blta ray energies(MeVJ•

Gamma ra~en.t'f"11ies(Me JaJ!l.32(89)Electron capture
p0.27(100)p0.6(100)

1.46(11)
0.71, 1.59~.20(30)

0.81 (30), 1.43(70)a224
fi0.42(100)0.088(100), 0.202(100),0.309(100)Figures in parentheses indicate per cent yield per disintegration.

TABLE VIII. TYPICAL CONCENTRATIONS OF Ra226 AND DAUGHTERS IN CONTINENTAL WATERS(pCi/litre) 36

Spa waters anddeep wells ·····
Ground water ....
Surface water ...
Rain-water ......

R,....

Rn""

Pb"'"

Po=

1-10
O.lLl
<l

104-105
102-10310
103-1()5 b<OJn<0.1 11
<0.5
0.5-3

-0.02
-0.01

a Below detection limits.
through presence of short-lived Rn222 daughters.

b As determined

31

-0.5

TABLE IX. RECENT DATA (RE.PORTED SINCE 1962) ON CONCENTRATION OF NATtJRAL lUUJIO-ACTIVE NUCLIDES IN WATER(Co11ce11lratio11 in pCi/litre)
Sauret of waterc.,..,,,t~· or area

Surface reservoirs
AUSTRALIA ..........••.•••
BRAzn., high backgroundarea of Morro di Ferro { Different sources(volcanic intrusives) ....
Tap, wells and springs
BRAZIL,Tap and wells

monazite area

Ra=s

Ra""'

Tap water (Bombay)l.?>.llIA, normal areas ...... ·{ Surface waters
Springs and wells
INDIA, monazite areaof Kerala State ........ . Shallow wells

I~aSurface waters
Springs, wells and..... ·[
boreholes
Dead Sea (lake)
Surface waters (rivers)
JAPAN
Artesian wells
NEW ZEALAND ......•.•.••
Surface waters
SWEDEN .•.......••....•..
Tap water of varying
origin (deep boredwells, inclusive)

Refere,.cu

Rr.!!20.1-0.2

232

11.9(0.12-107)
0.3-1.6

233

0.3
0.02
O.OS-0.6A
0.16-0.5•

0.2-32104

0.2-1.6

104
180
106
106

0.14

180

<2

18-180128< 2-21, 300
620.04-1.4

128
128
119
234
234
129

20
-0-1,0000.3- 1,000(100-33,000)

Ul\"UED STATES

30-300Ground waters

Raw surface waters
Illi""'' ................ ·{ Treatedsurface waters
Florida ................ .
South Carolina . . . . . . . . . .
Utah, nearGreat Salt Lake . . . . . .
0

0.127
0.019
0.05

Raw wt:ll water
Thermal and mineralsprings
Wells

0.3-3.3
1.4-2.8

Artesian wells

0.1-2.0

117, 165
15, 81, 117, 165
15, 81, 117, 165
15, 81, 117, 165
121235

400-1.800

Including Ra223 and Ra224.

TABLE

X. ESTIMATES OF TOTAL INTAKE OF Ra226 AND OF CONTRIBUTIONS FROM DIFFERENT FOODSTUFF CATEGORIESUNITED STATESUNITED
KINGDOM"'

IND/Al/JO

Cour.try-'Utidt
study

Bombay 3! ona..-ite crco

Cousir11iers" Union

Ca11oory of foods

Fivt·;I:lTeenagerfwnily·t-..CO•city st,.d:v'8'

Nr.r York,
Ns.m

Cliicooo,
1/1."1San Francisco,Cal. 1111

0.56
0.38

O.i6
0.37

0.51
0.2S

0.17
0.38

0.41

1.48

San '1rnn,
P.R.u1J

stud

Kera/a State

Cereals and grain
products ... ····Meat, fish, eggs
Milk and dairy products
vegetable;,Green
fruits a.'1d pulses
Root vegetables
Water
Total pCi/day ..

0.14

0.12

0.13

0.14

0.04

0.19

0.81
0.40
- 0.02
-2..3

0.56
0.22
-0.03
-2.1

0.48
0.26
- 0.01
- l.i

-0.7

0.32
0.10
0.07
- 1.2

O.li
0.02n
0.06
-0.7

0.81
O.Oia.
0.29- 2.8

pCi Ra~~6/g Ca ...

2.2

2.0

1.6

1.3

' 1v!iscellaneous.

32-3(2.2-1.3)
1.9-5(2.S-6.5)
? -

--~

1.1

TABLE Xl.

Ra226 IN HU:!JAN BONE AS REPORTED AFI"ER 1962

Location of aria

PCi/o asli

pCi/o Ca

Total' in theskeleto11 ( pCi)

R,fer..,.ce.r

NORMAL AREAS
U~'"TRAL A:l!ERICA

United States
Puerto Rico ........
EUROPE
Federal Republic of Germany
United Kingdom ...........

0.006

0.017

17

190

0.013

0.040

36

203

0.00~.02

NORTH A:llERICA
United States
Illinois ····· .............
:\ew England ............
New York, N.Y. ....
Rochester, N.Y. .....
San Francisco, Cal.

0.012b0.014
0.012
0.010; 0.017
0.0096
HIGH

ASIA
India
State of Kerala(monazite area)
NORTH AMERICA
United States
Illinois ······· .......
Illinois ··········· .......

32

183

39

209

0.032

32

0.026

28,48
27

186
204
186

LEVEL AREAS

0.096(0.03-0.14)-270

180,216

0.0J7C

-100
78

165
183

o.ozsca Skeleton of 7,000 g fresh weight yielding 2,800 g ash was assumed.
b In people consuming water with "normal" levels of Ra226.
c In people consuming water with elevated Ra228 concentration.

TABLE

XII. Pb210 AND Po210 IN HUMA.>; BONE
(Number of samples in brackets)
Pb=

pCi/g fruh

A rt 1 C'r locatio11

p"ao

pCi/11 a.sisb""epCi/g fresh
bcne

Po"•

pCi/g ash

Pb=

TotaJPon•in tlieskeleton•(pCi)

Rritrences

290

213

210

203

250

23i

160

238

120

239

120

214

410

165

200

183

360

209

95

212

300

240

960

193

NORMAL AREAS
FEDERAL REPUBLIC OF{GERMANY .........

0.032
(20)

0.11
(20)

0.037
POLA!'D ·············U><=

K<NOOO~

0.040
(20)
0.026

0.13
(20)
0.8

(5)
•

0.017
(6)
0.017
(9)

•{

U::.tITED STATES
Illinois (mostly)
Illinois

0.031
(20)
O.C30

0.150
(128)
0.080
(32)
0.140
(25)

...........

New England .....
Rochester, N.Y....

0.015
(18)

0.120
(28)
Hren LEVEL AREAS

San Juan, P.R.....

CANADA (Eskimos) ..

0.140[0.0~.71](10)"Calculated qirectly from Po~?lO or from dzta on Pb210. In the latter case, if no data
for Po2IO/Pb~IO ratio were reported the value of 0.9 wa!; a:osumed. Skeleton of 7,000 g fresh
weight yielding 2,800 g ash was further assumed. If the data were reported both for fresh tis;ueand tissue ash, the values in pCi/g ash were useci to estimate the total skeletal bu;den.

33

T ..\BLE XIII. NATURAL ALPHA EMITTING R..AlllO-NUCUDES IN HUMAN SOFT TISSUES IN ARE-.. S
OF NORMAL BACKGROUND RADIO-ACTIVITYVALUES ARE GIVEN IN pCifkg FRESH WEIGHTFor Po210 the ranges include the average values reported by vari011.r authors
Pon•

Ra~

Ti.rme,...., 0.1203, 206

Soft tissues in general
Liver .......•.......
Kidney ............ .
Gonads ........... ..
Spleen ............ .
Lung .............. .
Skeletal muscle .... .

- 0.04203- 0.2204
0,12040.1204

O.Q62lH,..., 32os
11-17116, 193, 198, 208, 214, 230
5-17103, 198,203,214, 239
J-4198, 198,214,239
J203, 239, 240
2-5198, 198,214, 228,239
1-6165, 193,203,239

TABLE XIV. Ra228 IN HUMAN TEETH FROM DIFFERENT AREAS
Vali~s in pCi/g ash; 1mmber of samples fo parentheses

Locality

Ranae

Mea11

RrltrtllCCS

Remarks

NORMAL AJU:AS
BRAZIL
Vitoria··············

0.030

Rio de Janeiro .......

0.037

Por;os de Caldas

0.015

UNITED STATESNew England

0.008-0.079(14)
0.006--0.123(13)
0.006-0.031(13)
0.01-0.062
(25)

0.016
Arur.As

OF

215
215
215

209

HIGH TE!\RESTRIAL RADIO-ACTMTY

BR...-1.ZIL

Guarapari ············

0.036..............

0.023

Araxa and Tapira ....

0.077

MeaipeTABLE xv.

Materiols

Nmnlur ofsamples

Grass (dried) United
Kingdom
Dry lichen (Caloplaca
elegans) United Kingdom
Dry lichen (Cladonia
alpestris) Lapland .. ....
Dry lichen (Cladonia
alPestris) Canada ·······
Edible green vegetables(United Kingdom)
Carrots and potatoes(United Kingdom)
Breads and cereals(United Kingdom)
Dried milk powder(United Kingdom)
Beef and lamb muscle(United Kingdom)
Beef and Jamb liver(United Kingdom)............... 24

0.006-0.104(23)
0.(}06-0.077(15)
0.008-0.204(52)

Monazite sand areas

215

Monazite sand areas

215

Areas of high radioactivity due to volcanic intrusives

Po210 CONTENT OF VEGETABLES AND ANIMAL TISSUES193

Po'l:l.0 specificactivity(PCi/ka)

Pf>'10/Pt>"'0
activityratio

400-16,0llO

1-5

2

7,800; 10,000

36,600-8, 100

Materials

Beef and Jamb kidney(United Kingdom) . ....
Lamb kidney (north Wales)
Reindeer (Lapland) summer killed:Muscle ...........
Liver ......
Kidney ········ ·········
Reindeer (Canada, Northwest Territory) winterkilledMu;cle .................
Liver .............. ...
Kidney .................
Spleen .................
Cockles (United Kingdom,
east and west coasts) ...
(United
Kingdom,Crabsouth coast)
Plank-ton (south Pacific) ..

3,500

5

215

6-90

1-3

2

4

1-7

3

2-6

2

3;3

3

4-100

0.7

34

Number ofsamples

3
6

6

5
4

Pon•spui/ic

Pb'l• IP o"O

4~270

0.05-190-1,80002

activity(pCi!ka)

activity
ratio

15-50
350-750
110-490222200; 210
2,400 ; 5,600
4,200; 2,300980

3400-900

2

1.300; 1,400
2,000

0.1-0.2

TABLE XVI.

INTERNAL DOSES FRO!>! NATURAL RADIO-ACTIVITY ;n VALUES IN MILLIRADS PER YEAR

(bi parentheses, fractit:m fo per ce11t of total yearly dose derived from alpha radiatio1i)
BoneHa:.·ersian.V'"lidc

GonadsK40 .........................
Rb Si ........................
CH .... ·········· .. ········
Ra22s .......................
Ra22S ······ ········ .........
p 0 210 ...... ·············· ...

20
0.3
0.7

········-········-· ....

Rn222

TOTAL

cat:als(50" dia~tcr)

Osteoc:;tcs( 50 JJ. diameter)

15
<0.3
1.6
0.6f· d0.7f, b2.1r. c
0.3f
20.3
(18)

15
<0.3
1.6
i.4t, d1.J!, b

_e
_e

0.3t
0.3f
21.6
(3)

4.zr, c
0.3f
23.6
(30)

Bone
tnarrow(trabecular

bcme)

15
<0.3
1.6
0.03!
0.03!
0.3!
0.3!
17.3
(4)

a Doses of alpha radiation to tissues of respiratory tract are discussed in paragraphs 141-148. The highest doses are µiost probably those delivered to basal layers of bronchial epitheliumin segmental and lobar bronchi. They may reach the level of some hundreds of millirads per
year at assul'l1ed average cmicentrations of Po218, Pb214 and Po2H.
b Accepted concentration of Ra228 (in equilibrium with daughter products) of 1.4 X lQ-ll
pCi/g fresh bone.
c Accepted concentration of Po210 of 3.3 X 10-2 pCi/g fresh bone.
d Accepted concentration of Ra226 (plus one~third of short-lived daughter products throughPo2H) of 4.3 X 10-s pCi/g fresh bone.
e Doses to gonads from Ra226 and daughter products and Ra228 and daughter products
could not be estimated with reasonable accuracy. The upper limits seem to be 0.02 and 0.03
mrad/year, respectively.
f Doses of alpha radiation.

TABLE XVI!. DOSE RATES DUE TO E."tTER)fAL AND INTERNAL IRRADIATIOX FRO!ll NATURAL
SOURCES IN "NORMAL" AREAS(111 italics, estimates given in the 1962 report)
Dos1 raJ's (mrad/:v)
Source of irradiation

E.rterual irradiatio11
Cosmic rays
Ionizing component

Neutrons················

Terrestrial radiation(including air) ··········
Internal irradiation
K40·······················

RbM .......................
CH ..... ····· ·····-·· ...

..

Ra22a

Haversian

Gonads·················-···.....................
p 0 210·················· ..

Ct111alTOTAL8Percentage from alphaparticles and neutrons

Paraarat>hs

28
28
0.7
2.5

28

28

48

28
0.7
2.5

28
0.7
2.5

49

50
50

50
50

so
so

58

20
20
0.3
0.7
0.7

15
15
<0.3
1.6

136

0..08
0.3
0.03
0.3
0.3
100
102

15
15
<0.3
1.6
1.6
0.6
0.54
0.7
0.86
2.1
0.36
0.3
0.03
99
99

1.3
3

4.4
2.8

1.4
3

0.05

Ra22a

Rn2!?2 (dissolved in tissues) ..

Bo11emarrotoa Totals were rounded off to two significant figures.

35

136
136

1.6

O.Q3
0.06
0.03

135-139
135-139

0.1

0.3
0.04
0.3
0.3
96
98

135--139
135-139

REFERENCES
15. McDonald, F. B., Review of galactic and solar
cosmic rays. NASA, Goddard Space Flight
Center report X-611-65-94 (1965).
16. McDonald, F. B., C. H. Ludwig, V. K.
Balasubrahmanyan, Low energy galactic cosmic
ray results from IMP-1, p. 966 iti Space Research
V. King-Hele, D. G., P. Muller, G. Righini, eds.,
North-Holland Publishing Co., Amsterdam, 1965.
17. Webber, W. R., Time variations of low rigidity
cosmic rays during the recent sunspot cycle, pp.
75-244 in Progress in Elementary Particle andCosmic Ray Physics, vol. VI. Wilson. J. G., S. A.
Wouthuysen, eds., North-Holland Publishing Co.,
Amsterdam, 1962.
18. Lowder, W. M .. H. L. Beck, Cosmic ray ionization in the lower atmosphere. J. Geophysical Res.
In press.
19. Lillicrap, S. C., Determination of the energy
absorbed in water from relativistic cosmic ray
particles using the Cerenkov effect. Phys. Med.
Biol. 10: 17-24 (1965).
20. Puppi, G., N. Dallaporta, The equilibrium of thecosmic ray beam in the atmosphere, pp. 315-391
in Progress in Elementary Particle and Cosmic
Ray Physics, vol. I. Wilson. J. G.. S. A.
Wouthuysen, eds .. North-Holland Publishing Co.,
Amsterdam, 1952.
21. Harvey. B. G.. Spallation. pp. 89-121 in Progressin Nuclear Physics. vol. 7. Frisch, 0. R., ed.,Pergamon Press, N. Y.. 1959.
22. Geiger, K. \V., Evaporation neutrons from cosmic
ray nuclear interactions in various elements.
Canadian J. Phys. 34: 288-303 (1956).
23. Korff. S. A .. Production of neutrons by cosmic
radiation, chap. 26. pp. 427-440 in The Natural
Radiation Environment. Adams, J. A. S., \V. M.
Lowder, eds .. The University o{ Chicago Press,
Chicago, Ill., 1964.
24. Lord, J. J .. The altitude and latitude variation in
the rate of occurrence of nuclear disintegrations
produced in the stratosphere by cosmic rays. Phys.
Rev. 81: 901-909 (1951).
25. Neher. H. V .. Recent data on geomagnetic effects,
pp. 243-314 in Progress in Elementary Particle
and Cosmic Ray Physics. vol. I. Wilson, J. G.,
S. A. Wouthuysen. eds .. North-Holland Publishing Co., Amsterdam, 1952.
26. Pomerantz. l\I. A .. S. P. Aganval. Spatial distribution of cosmic ray intensity and geomagnetic
theory. Philosophical !\fag. 7: 1503-1511 (1962).
27. Quenby. J. J .. G. J. \Venk, Cosmic ray threshold
rigidities and the earth's magnetic field. Philosophical Mag. 7: 1457-1485 (1962).
28. Simpson, J. A., Neutrons produced in theatmosphere by cosm!c radiations. Phys. ReY. 83:
1175-1188 (1951).
29. Puppi, G.. The energy balance of cosmic radiation,
pp. 339-388 in Progress in Elementary Particle
and Cosmic Ray Physics. vol. III. Wilson. J. G..

1. United Nations Scientific Committee on the Effects of Atomic Radiation, Report of the United
Nations Scientific Committee on the Effects ofAtomic Radiation. General Assembly document,
13th session, Suppl. No. 17 (A/3838). United
Nations, N. Y., 1958.
2. United Nations Scientific Committee on the Effects of Atomic Radiation, Report of the United
Nations Scientific Committee on the Effects ofAtomic Radiation. General Assembly document,
17th session. Suppl. No. 16 (A/5216). United
Nations. N. Y., 1962.
3. Donnan. L. I., Geophysical and astrophysicalaspects of cosmic radiation, pp. 1-~35 in Progr.es5
in Elementary Particle and Cosmic Ray Physics,
vol. VII. Wilson, J. G., S. A. Wouthuysen, eds.,
North-Holland Publishing Co., Amsterdam, 1963.
4. Elliot, H., Time variations of cosmic ray intensity, pp. 453-514 in Progress in Elementary
Particle and Cosmic Ray Physics, vol. I. Wilson,
J. G.. S. A. Wouthuysen, eds.. North-Hollan:iPublishing Co., Amsterdam. 1952.
5. Mav. H., L. D. Marinelli, Cosmic-ray contribution
to ·the background of low-level scintillation
spectrometers, chap. 29. pp. 463-480 in The
Natural Radiation Environment. Adams, J. A. S.,
W. M. Lowder, eds., The University of Chicago
Press, Chicago, Ill., 1964.
6. Peters, B .. The nature of primary cosmic radiation, pp. 191-242 in Progress in Elementary
Particle and Cosmic Ray Physics, vol. I. Wilson.
J. G., S. A. \Vouthuysen, eds., North-Holland
Publishing Co., Amsterdam, 1952.
7. Peters, B., Cosmic rays. chap. 12, part 9, pp.
9-201 - 9-244 in Handbook of Physics. Condon,
E. U .. H. Odishaw. eds., McGraw-Hill Book
Co.. N. Y., 1958.
8. Rossi, B., Cosmic Rays. ~kGraw-Hill, N. Y.,
1964.
9. Sandstrom. A. E .. Cosmic Ray Physics. John
\Viley & Sons. N. Y., 1965.
10. Singer, S. F., The primary cosmic radiation andits time variations, pp. 205-335 in Progress in
Elementary Particle and Cosmic Ray Physics, vol.
IV. Wilson, J. G .. S. A. \Vouthuysen, eds .. NorthHo!land Publishing Co .. Amsterdam. 1958.
11. Waddington, C. J., The composition of the
primary cosmic radiation. pp. 3-45 in Progressin Nuclear Physics, vol. 8. Frisch. 0. R.. ed.,Pergamon Press. N. Y., 1960.
12. Hopper, V. D., Cosmic Radiation and HighEnergy Interactions. Prentice-Hall. Inc., Englewood Cliffs, N. J .. 196-l.
13. Forbush. S. E., Solar influences on cosmic rays.
Proc. Nat'l. A.cad. Sci. (US) 43: 28-41 ( 1957).
14. Simpson, }. A .. Solar origin of changes in tl1e
primary cosmic radiation. Proc. Nat'l. Acad. Sci.
(US) 43: 42-56 (1957).
36

eds., The University of Chicago Press, Chicago,
Ill., 1964.
47. Boella, G., G. Degli Antoni, C. Dilworth, et aJ..,
Measurement of the cosmic ray neutron flux inthe atmosphere. Nuovo Cimento 29: 103-117(1963).
48. Boella, G., G. Degli Antoni, C. Dilworth. et al.,Measurement oi cosmic rav neutron flux at 4.6
BeV geomagnetic cutoff rigidity. J. GeophysicalRes. 70: 1019-1030 ( 1965).
49. Boella. G., G. Degli Antoni. C. Dilworth, et al.,Albedo neutron flux at 4.6 BeV geomagnetic
cut-off rigidity, p. 617 in Space Research V. KingHele, D. G .. P. Muller, G. Righini, eds .. NorthHolland Publishing Co., Amsterdam, 1965.
50. Bernardini. G., G. Cortini, A. ~Ianfredini, On
the nuclear evaporation in cosmic rays and theabsorption of the nucleonic component. Phys.
Rev. 76: 1792-1797 (1949).
51. Newkirk, L. L., Calculation of lo,v-energy neutron
flux in the atmosphere by the Sn method. J.
Geophys. Res. 68: 1825-1833 ( 1963).
52. Hess, W. N., H. W. Patterson, R. Wallace, et a/,,,Cosmic ray neutron energy spectrum. Phys. Rev.
116: 445-457 (1959).
53. Tajima, E., M. Adachi, T. Doke, et al., Spectrumof cosmic ray produced neutrons. To be published.
54. Haymes, R. C., S. A. Korff, Slow neutron intensity at high balloon altitudes. Phys. Rev. 120:
1460-1462 (1960).
55. Mendell, R. B., S. A. Korff. Fast neutron flmc
in the atmosphere. J. Geophysical Res. 68 :5487-5495 ( 1963).
56. Bame, S. J., J. P. Conner, F. B. Brumley, et al.,Neutron flux and energy spectrum above theatmosphere. J. Geophysical Res. 68: 1221-1228(1963).
57. Miles, R. F., Density of cosmic-ray neutrons in
the atmosphere. J. Geophysical Res. 69: 1277-1284(1964).
58. Haymes, R. C., Fast neutrons in the earth's
atmosphere. 1. Variation with depth. J. Geophysical Res. 69 : 841-852 ( 1964).
59. Hill. C. R., D. S. Woodhead, Tissue dose due
to neutrons of cosmic-ray origin, chap. 28, pp.
449-461 in The Natural Radiation Environment.
Adams, J. A. S., W. M. Lowder. eds., The
University of Chicago Press, Chicago, Ill .. 1964.
60. Kastner, J .. B. G. Oltman. L. D. Marinelli, et a/,,,Measurement of the cosmic-ray fast neutron
background, pp. 71-76 in Argonne National
Laboratory Radiological Physics Division Annual
Report, July 1963 through June 1964, ANL-6938.
61. International Commission on Radiological Protection. Task Group on the Biological Effects ofHigh-Energy Radiations, Radiobiological aspectsof the supersonic transport. Health Physics 12:
209-226 (1966).
62. Shamas. M. H., A. Liboff. J. Siderowitz, Thinwall ion chambers for low-level radiation environment, chap. 37, pp. 627-641 in The Natural
Radiation Environment. Adams, J. A. S .. W. M.
Lowder. eds .. The University of Chicago Press,
Chicago. Ill.. 1964.
63. Appendix 3, Intercalibration e.."<periment, ibid.,
pp. 1029-1032.

S. A. Wouthuysen, eds., North-Holland Publishing Co .. Amsterdam, 1956.
30. Malhotra, P. K., P. G. Shukla, S. A. St~phens,
et al.. Energy spectrum of primary cosmic-rays.
Nature 209: 567-569 ( 1966).
31. Lingenfelter, R. E., Production of carbon-14 bycosmic-ray neutrons. Review of Geophysics 1 :35-55 ( 1963).
32. LaL D .. B. Peters, Cosmic ray produced isotopes
and their application to problems in geophysics,
chap. I. pp. 3-74 in Progress in Elementary
Particle and Cosmic Ray Physics, vol. VI. 'Wilson,
J. G., S. A. Wouthuysen, eds., North-Holland
Publishing Co .. Amsterdam. 1962.
33. Ha.xel, 0., G. Schumann, Erzeugung radioaktiver
Kernarten <lurch die kosmische Strahlung, pp.
97-135 in Nuclear Radiation in Geophysics. Israel,
H., A. Krebs, eds., Academic Press, N. Y., 1962.
34. Kapo.1JD n. .JI.. l\la.11aXOB c. r., Ilpmrnnenrre ecTe-

CTBeHHDIX paµ;noaKTIIBHhlX Il30TOIIOB B aTMocqrnpe,il;JIH MeTeOpOJIOI'IftleCKilX IICCJie)l;OBaHnli, CTp.

5-42

n RJIIITe: BonpocDI $I)l;epnoii MeTeopoJiorrrn. Kapo.111> H . .JI., MaliaXOBr., pep;., rocaTOMIIB,il;aT,MocKBa, 1962; v.e. USAEC report AEC-tr-6128,

c.

pp. 1-51 (1%2).
35. Perkins, J., M. Nielsen. Cosmic-ray produced
radionuclides in the environment. Health Physic;s
11: 1297-1304 ( 1965).
36. Adams, J. A. S., Geochemical studies of the levelof natural radiation exposure to the population.
Houston. Texas. To be published.
37. Junge, E., Air Chemistry and Radioactivity. Academic Press, N. Y., 1963.
38. Radel, W., Cosmic-ray-produced and artificial
sodium 22 in the atmosphere. J. Geophysical Res.
70: 4447-4452 ( 1965).
39. Lal, D., Study of long and short-term geophysicalprocesses using natural radioactivity, pp. 149-157
in Radioactive Dating. IAEA, Vienna, 1963.
40. Hagemann, F. T., J. Gray, Jr., L. Machta,
Carbon-14 measurements in the atmosphere-1953
to 1964. Health and Safety Laboratory report
HASL-159, 1 April 1965; v.e. United Nations
document A/AC.82/GjL.1003.
41. Korff. S. A., R. B. Mendell, S. S. Holt, Measurements of the neutrons produced by the cosmic
radiation. To be published.
42. Soberman, R. K., High altitude cosmic-ray
neutron intensity variations. Phys. Rev. 102:1399-1409 ( 1956).
43. l\fiyake, S .. K. Hinotani, K. Nunogaki. Intensitj
and energy spectrum of fast neutrons in cosmic
radiation. J. Phys. Soc. (Japan) 12: 113-121(1957).
44. Hess, W. N ., E. H. Canfield. R. E. Lingenfelter,
Cosmic-ray neutron demography. J. GeophysicalRes. 66: 665-677 (1961).
45. Reidy, W. P., R. C. Haymes. S. A. Korff, A
measurement of slow cosmic-ray neutrons up to
200 kilometres. J. Geophysical Res. 67: 459-465(1962).
46. Kastner, J., B. G. Oltman, L. D. Marinelli,
Progress report on flu.x and spectrum measurements of the cosmic-ray neutron background,chap. 27, pp. 441-448 in The Natural Radiation
Environment. Adams, J. A. S., vV. M. Lowder,37

64. Herbst, Vv., Investigations of environmental radiation and its variability, ibid., chap. 48, pp.
781-796.
65. Shames, M. H., A. R. Liboff, A new measurementof the sea level cosmic ray ionization intensity.
To be published.
66. Kastner, J., Private communication.
67. International Commission on Radiological Protection. Report of the RBE Committee to the International Commissions on Radiological Protection and on Radiological Units and Measurements.
Health Physics 9: 357-386 (1963).
68. Rossi, H. H .. Absorbed dose versus kerma. Health
Physics 11: 779-780 (1965).
69. National Bureau of Standards, Radiation quantities and units, International Commission on
Radiological Units and Measurements (ICRU),
Report lOa. United States Department of Commerce, NBS Handbook 84 (1962).
70. Patterson, H. W., W. N. Hess, B. J. Moyer, et al.,The flux and spectrum of cosmic-ray produced
neutrons as a function of altitude. Health Physics
2: 69-72 (1959).
71. National Bureau of Standards, Protection against
neutron radiation up to 30 million electron volts.
United States Department of Commerce. NBS
Handbook 63 (1957).
72. Rossi, H. H .. Neutron and heavy-particle dosimetry, pp. 98-107 in Radiation Dosimetry. Reed,
G. W., ed., Academic Press, N. Y., 1964.
73. Baarli, J., A. H. Sullivan, Radiation dosimetry
for protection purposes near high energy particle
accelerators. Health Physics 11 : 353-361 ( 1965).
74. Turner. J. E., C. D. Zeroy, R. L. Woodyard,
et al., Calculation of radiation dose from protons
to 400 MeV. Health Physics 10: 783-808 (1964).
75. Snyder, W. S., J. Neufeld . Calculated depth dose
curves in tissue for broad beams of fast neutrons.
British J. Radiology 28: 342-350 (1955).
76. Neufeld, J., W. S. Snyder, J. E. Turner, et al..
Calculation of radiation dose from protons andneutrons to 400 MeV. Health Physics 12:
227-237 (1966).
77. Bercovitch, M., H. Carmichael, G. C. Hanna,
et al., Yield of neutrons per interaction in U, Pb,
W, and Sn by protons of si..x energies between
250 and 900 MeV selected from cosmic radiation.
Phys. Rev. 119: 412-431 (1960).
78. Citron, A., L. Hoffman, C. Passow, Investigationof the nuclear cascade in shielding materials.
Nuclear Instruments and ).fethods 14: 97-100(1961).
79. May. H. A., Neutron production in massive
shields and effect upon the low-energy gamma-ray
background. pp. 50-65 in Argonne National
Laboratory Radiological Physics Division Semiannual Report. January through June 1962,
ANL-6646.
80. Spiers. F. W .. :M. J. McHugh. D. B. Appleby.
Environmental y-ray dose to populations : Surveys
made with a portable meter, pp. 885-905 in The
Natural Radiation Environment. Adams. J. A. S.,
W. M. Lowder, eds., The University of Chicago
Press. Chicago. Ill. 1964.
81. Gustafson. P. F., J. Kastner, J. Luetzelschwab,
Environmental radiation measurements of dose
rates. Science 145: 44-47 (1964).

82. Lowder, W. M., A. Segall, W. J. Condon,
Environmental radiation survey in northern New
England, chap. 56, pp. 907-917 in The Natural
Radiation Environment. Adams, J. A. S., W. M.
Lowder, eds., The University of Chicago Press,
Chicago, III., 1964.
83. Beck, H. L., W. M. Lowder, B. G. Bennett, et al.,Further studies of external environmental radiation. USAEC report HASL-170 (1966).
84. Lowder, W. M., W. J. Condon, H. L. Beck,
Field spectrometric investigations of environmental radiation in the U.S.A., chap. 35, pp.
597-616 in The Natural Radiation Environment.
Adams, J. A. S., W. M. Lowder, eds., The
University of Chicago Press. Chicago, Ill., 1964.
85. Foote, R. S., Time variation of terrestrial
y-radiation, ibid., chap. 46, pp. 757-766.
86. Gustafson, P. F., S. S. Brar, Measurement of
y-emitting radionuclides in soil and calculationof the dose arising therefrom, ibid., chap. 31, pp.
499-512.
87. Adams, J. A. S., Laboratory y-ray spectrometerfor geochemical studies, ibid., chap. 30, pp.
485-497.
88. Adams, J. A. S., G. E. Fryer, Portable y-ray
spectrometer for field determination of thorium
uranium, and potassium, ibid., chap. 34 pp'.
577-596.
89. Beck, H. L., W. J. Condon, ~..v. M. Lowder,
Spectrometric techniques for measuring environmental gamma radiation. USAEC report HASL150 (1964 ).
90. Appendix 2, Editor's postscript, pp. 1025-1027 in
The Natural Radiation Environment. Adams,
J. A. S., W. M. Lowder, eds., The University of
Chicago Press, Chicago, III., 1964.
91. Lowder, W. M., H. L. Beck, W. J. Condon,
spectrometric determination of dose rates fromnatural and fall-out gamma-radiation in the UnitedStates. 1962-63. Nature 202: 745-749 (1964).
92. Beck. H. L., W. J. Condon, W. M. Lowder Environmental measurements in the South-ea~ternCentral and Western United States, 1962-1963'.
USAEC report HASL-145: v.e. United Nations
document A/AC.82/GfL.939.
93. Tru;iner, A. B., Radon migration in the ground: areview, chap. 9. pp. 161-190 in The Natural
Radiation Environment. Adams, J. A. S., W. M.
Lowder, eds., The University of Chicago Press
Chicago, III., 1964.
'
94. Osburn, Vv. S., Primordial radionuclides : theirdistribu~ion, movement, and possible effect withinterrestnal ecosystems. Health Physics 11: 12751295 ( 1965).
95. Sievert, R. M .. Note on the increase of aamma
radiation from the ground during September
lst-November 30th. 1961. Tellus 15: 309-312(1963).
96. Thompson, T .. P. A. Vviberg. Some obsen•ationsof variations of the natural background radiation.
Tellus 15: 313-318 (1963).
97. Swedji;mark. G. A .. Gamma radiation at ground
leYel m Sweden during 1960-1965. ~ational
Institute of Radiation Protection, Stockholm,
Sweden. 1966.
98. ~piers, F. ·w., Gamma-ray dose-rates to humantissues from eA'ternal sources in Great Britain,pp. 66-70, appendi.x D in The Hazards to Man 1114. Eriksson. E., Radioactivity in hydrology, pp.
47-60 in Nuclear Radiation in Geophysics. Israel,of Nuclear and Allied Radiations. Second Report
H., A. Krebs, eds., Academic Press, N. Y., 1962.
of the Medical Research Council, HMSO, Cmnd.
1225 (1960); v.e. United Nations document
Wortley,G., Survey of radionuclides of natural
115.
A/AC.82/G/L.555.
origin in the soil-vegetation-human food chain.
The Joint FAO/IAEA Division of Atomic
99. Sievert, R. M., B. Hultqvist, Variations m
Energy in Agriculture, Vienna, 1965; v.e. United
natural gamma radiation in Sweden. Acta Radial.
Nations document A/AC.82/G/L.1037.
37: 388-398 ( 1952) ; v.e. United Nations document A/ AC.82/G/R.15, part 2.
116. Geslin, N., P. Urbain, A study of the radioactivityof thermal waters and rocks in the area of100. Doke. T., H. Takahashi, T. Higashimura. et al.,
Lamalou and Bedarieu.x (Herault). Bull. Soc.
External gamma dose rates from natural radioFranc;. Miner. Crist. LXXXIV: 194-198 (1961).
nuclides in Japan. Scientific Papers of the Instituteof Physical and Chemical Research 56 : 40-46
117. Holtzman, R. B., Lead-210 (RaD) and polonium(1962).
(RaF) in potable waters in Illinois, chap. 12, pp.
227 -237 in The Natural Radiation Environment.
101. Pinkerton, C., W. Y. Chen, R. G. Hutchins, et al.,Adams, J. A. S., W. M. Lowder, eds., The UniBackground radioactivity monitoring of a pilot
versity of Chicago Press, Chicago, Ill., 1964.
study community in Washington County, Maryland, chap. 57, pp. 919-956 in The Natural Radia118. Lucas, H. F., Jr., F. H. Ilcewicz, The naturaltion Environment. Adams, J. A. S., W. M.
Ra-226 content of Illinois municipal waters, pp.
Lowder, eds., The University of Chicago Press,
125-135 in Radiological Physics Division SerniChicago, Ill.. 1964.
annual Report, July through December 1957.
Argonne National Laboratory report ANL-5829
102. Lowder, W. M., W. J. Condon, Measurement of(1958).
the exposure of human populations to environmental radiation. Na tu re 206: 658-662 (1965).
119. Miyake, Y., Y. Sugimura, H. Tsubota, Content
of uranium, radium, and thorium in river waters
103. Roser. F. X., T. L. Cullen, External radiationlevels in high-background regions of Brazil, chap.
in Japan, chap. 11, pp. 219-225 in The Natural
Radiation Environment. Adams, J. A. S., W. M.
51, pp. 825-836 in The Natural Radiation Environment. Adams, J. A. S., W. M. Lowder, eds.,
Lowder, eds., The University of Chicago Press,
The University of Chicago Press, Chicago, Ill.,
Chicago, Ill., 1964.
1964.
120. Muth, H., B. Rajewski, H. J. Hantke. et al., The
104. Eisenbud, M., H. Fetrow, R. T. Drew, et al.,normal radium content and the Ra226/Ca ratio
Naturally occurring radionuclides in foods andof various foods, drinking water and different
waters from the Brazilian areas of high radioorgans and tissues of the human body. Healthactivity, ibid.. chap. 52, pp. 837-854.
Physics 2: 239-245 (1960).
105. Roser, F. X.. T. L. Cullen, Radiogeology of121. Osmond, J. K., The distribution of the heavysome high-background areas of Brazil, ibid., chap.
radioelements in the rocks and waters of Florida,
53, pp. 855-872.
chap. 8, pp. 153-159 in The Natural Radiation
Environment. Adams, J. A. S., W. M. Lowder,106. Karnath, P. R., A. A. Khan, S. R. Rao, et al.,eds., The University of Chicago Press, Chicago,
Environmental natural radioactivity measurements
Ill., 1964.
at Trombay Establishment, ibid., chap. 58, pp.
122. Samuels, L. D., A study of environmental ex957-978.
posure to radium in drinking water, ibid, chap.
107. Roser, F. X., H. Gomes, N. Leal da Costa, et al.,13, pp. 239-251.
A study of natural and artificial radioactive contamination in Brazil, 1965. USAEC report NY0123. Turner, R. C., J. M. Radley, W. V. Mayneord,
2577, report No. 2 (1965).
Naturally occurring alpha-activity of drinking
waters. Nature 189 : 348-352 ( 1961 ) .
108. Hyde, E. K., p. 74 and p. 211 in The Nuclear
Properties of the Heavy Elements, vol. III. Hyde,124. Weaver, L., A. W. Hoadley, S. Baker, RadioE. K., I. Perlman. G. T. Seaborg, eds .. Prenticeactivity in surface waters of the United States
Hall, Englewood Cliffs, N. J., 1964.
1957-1962, pp. 306-316 in Radiological Health
Data, vol. 4 (1963); v.e. United Nations docu109. ropmKOB r. B .. 3JI61mn B. A., TI;neTEOB 0. C., BhIment A/AC.82/G/L.851.
XO)l; nefiTJlOHOB no peali.l:urn (a. n) II3 Be, B, C,
125. BeJ10ycoBa H. M.. illTJKKen6epr IO. }I.. EcTe0, F, Mg. Al. Si n rpanIITa no.n; .n;eitcTBneM a-tJaCTIIII IIOiIOHIIJI. A'IOlmaJI eneprnJI 13: 65-67 (1962).
CTBenna.a pa,J,IIOal\TIIBHOCTI>. 1Ie.n;rn3, .MocKBa,
1961.
110. Gurfinkel, Y., (a, n) reactions on heavy isotopesof oxygen. M.Sc. thesis, Hebrew University,
126. Muth, H., A. Schraub, K. Aurand, et al.,Jerusalem, 1963.
Measurements of normal radium burdens. British
111. Adams, J. A. S .. Radioactivity of the lithosphere,
J. Radiology, Suppl. No. 7: 54-66 (1957).
pp. 1-17 in Nuclear Radiation in Geophysics.
127. Lucas. H. F .. Jr .. Illinois municipal water supplies
Israel, H., A. Krebs. eds., Academic Press, N. Y ..
having unusually high concentration of Ra22 6 ,1962.
pp. 58-60 in Argonne National Laboratory
112. Koczy, F. F., J. N. Rosholt, Radioactivity inRadiological Physics Division Semiannual Report,
oceanography, ibid., pp. 18-46.
January through June 1958, ANL-5919.
128. Mazor, E., Radon and radium content of some113. Suschny, 0., Radioactive contamination of theoceans, chap. III, pp. 123-146 in MeteorologicalIsraeli water sources and a hypothesis on underAspects of Atmospheric Radioactivity. Bleeker,
ground reservoirs of brines, oils and gases in theW. ed .. WMO Technical Note No. 68, Geneva,
Rift Valley. Geochim. Cosmochim. Acta 26:
765-786 (1962).
Switzerland, 1965.
39

washout by rain. J. Geophysical Res. 71: 15251535 (1966).
146. Gold. S., H. Barkhan, B. Shleien. et al., Measurement of naturally occurring radionuclides in air,chap. 22. pp. 369-382 in The Natural Radiation
Environment. Adams, J. A. S., W. 11. Lowder,eds., The University of Chicago Press, Chicago,
Ill., 1964.
147. Kawano, M., S. Nakatani, Some properties ofnatural radioactivity in the atmosphere, ibid.,chap. 16. pp. 291-312.
148. Lockhart. L. B.. Jr.. Atmospheric radioactivity
level at Yokosuka, Japan, 1954-1958. J. Geophysical Res. 64: 1445-1449 (1959).
149. Lockhart, L. B., Jr., Radioactivity of the radon222 and radon-220 series in the air at groundlevel, chap. 18, pp. 331-344 in The Natural Radiation Environment. Adams, J. A. S., W. M.
Lowder, eds., The University of Chicago Press,
Chicago, Ill., 1964.
150. MaJiaXOBr., ltOB}l;a A. B., Coornomerurn MBIB,ll;Y
KOHil.eHTpan;nIDrn pa.n;oHa n rrpo.u;yKTOB ero pacrra,ll;a
B aTMOCqlBpHOM noa.u;yxe, Ilaµ;-no .AH COCP, OepnJI
reoqma. :N2 5, CTp. 789-792 (1961).
151. Moses, H .. A. F. Stehney, H. F. Lucas, Jr., Themeteorological variables upon the vertical andtemporal distributions of atmospheric radon. J.
Geophysical Res. 65: 1223-1238 (1960).
152. El-Nadi, A. F .. H. M. Omar, Radon and thoron
content in atmospheric air at Giza, Egypt. Geofisica Pura e Applicata 45: 261-266 (1960).
153. Murayama, N., Mean level of natural radioactivity
in the surface air in Japan. To be published in
J. Rad. Res. (Japan).
154-. ~fa!Iaxonr., 1IepHhIIlleBa II. r., 0 ceaomrnx H3MeHeHIIJIX KOHIJ;eHTpaD;IIlI pa.n;ona n Topona B rrpnaeMHOM C!IOe aTMoccpepI:.I, CTp. 81-92 B KH.: Pa,n;noaKTIIBIThie II30TOJThI B aTMOccpepe II IIX llCIIO.iTh30BaHIIe n MeTeopo21ornn. Kapo!ID I:I. .[., KIIpII1IeHXo.JI. B., RpacHorre:BI:i;eB ID. B. rr ,n;p., pe)l;., ATOMll3,ll;aT,
1'1Ioc1ma. 1965.
155. Anderson. W., W. V. Mayneord. R. C. Turner,
The radon content of the atmosphere. Nature 174:424-426 ( 1954).
156. Behounek, F .. M. l\fajerova, Radon content of
the air. Nature 178: 1457 (1956).
157. Hosler, C. R.. L. B. Lockhart, Simultaneous
measurements of Rn222 , Pb 214 and Bi 214 in air
near ground. J. Geophysical Res. 70: 4537-4546(1965).
158. Fontan, J., D. Blanc, A. Bouville, et. al .. Concentration of radon and thoron in the air above
the Atlantic Ocean. J. Phys. 24: 165-166 (1963).
159. Lambert. G., G. Polian, Sur la diffusion a basse
altitude des masses d"air continentales et oceaniques clans chaque hemisphere. C. R. Acad. Sc.
256: 4265-4267 (1963).
160. Lockhart, L. B., Jr., R. L. Patterson, Jr .. A. W.
Saunders, Jr., Atmospheric radioactivity in Antarctica 1956-1963. U.S. Naval Research Laboratory report NRL-6341 (1965); v.e. United
Nations document A/AC.82/G/L.1068.
161. Lambert, G., G. Polian, Etude de la radioactivite
naturelle de !'atmosphere aux Iles Kerguelen et
en Terre Adelie. Comite national frarn;ais desrecherches antarctiques, No. 12 ( 1965).

129. Dobeln, W. von, B. Lindell, Some aspects ofradon contamination following ingestion. Arkiv
for Fysik 27: 531-572 (1964).
130. Hursh, J. B., D. A. Morken. T. P. Davis, et al.,The fate of radon daughters ingested by man.
Health Physics 11 : 465-476 ( 1965).
131. Israel. H .. Die Natiirliche und Kiinstliche Radioaktivitiit der Atmosphare, pp. 76-96 in Nuclear
Radiation in Geophysics. Israel, H., A. Krebs,
eds., Academic Press, N. Y., 1962.
132. Kraner, H. W., G. L. Schroeder, R. D. Evans,
Yleasurernents of the effects of atmospheric variables on radon-222 flux and soil-gas concentrations, chap. 10, pp. 191-215 in The Natural
Radiation Environment. Adams. J. A. S .. W. M.
Lowder, eds., The University of Chicago Press,
Chicago, Ill., 1964.
133. Itnp1rnemw .il. B., BepTIIRaJIDHOe pacnpe,n;eJieHIIe
npo,n;JRTOB pacrra,n;a pa.u;ona n cno6o,n;Hofi aTMoccpepe, cTp. 75-103 B :&HI1re: Bonpom sr.u;epnofi MeTeopoJIOTIIII. I~apOJib II..!I., :Ma!IaXOB
r .. pe)l;., rocaTOllii3,ll;aT. l\Ioc:&Ba. 1962; v.e. USAEC report
AEC-tr-6128, pp. 92-124 ( 1962).
134. Jacobi, W., The natural radioactivity of theatmosphere. Biophysik 1: 175-188 (1963).
135. Jacobi, V·l., The natural radioactivity of theatmosphere and its significance for the radiation
protection of man. Hahn-Meitner-Institut fiir
Kernforschung. Berlin, report HMI-B 21 ( 1962).
136. Tacobi. Vil.. K. Andre. The vertical distribution
radon-222, radon-220 and their decay productsin the atmosphere. J. Geophys. Res. 68: 3799-3814(1963).
137. Junge, C. E., Radioaktive Aerosole, pp. 169-201
in Nuclear Radiation in Geophysics. Israel, H.,
A. Krebs. eds., Academic Press. N. Y .. 1962.
138. Havlovic, U., Natural radioactive aerosols in the
ground-level air of a Czechoslovak locality withrespect to the radiological exposure of its population. Health Physics 11 : 553-566 ( 1965).
139. Fontan, J .. A. Birot. D. Blanc, Variation de laconcentration des gaz radioactifs naturels et del'equilibre entre ces gaz et leurs descendants, dansl'air, au niveau du sol. Geofisica e meteorologia
XIII: 80-87 (1964).
140. Burton, vV. M., N. G. Stewart, Use of long-lived
natural radioactivity as an atmospheric tracer.
Nature 186: 584-589 (1960).
141. Lambert, G., M. Nezami, Determination of themean residence time in the troposphere by measurement of the ratio between the concentrationsof lead-210 and polonium-210. Nature 206:
1343-1344 (1965).
142. Lehmann, L., A. Sittkus, Bestimmung vonAerosolverweilzeiten aus dem RaD und RaF
Gehalt der atmosphiirischen Luft und des Niederschlages. Naturwissenschaften 46: 9-10 (1959).
143. K.aro!. I. L.. An estimate of the rate at which
natural radioactive aerosols are remand fromthe atmosphere by clouds and rain. Izv. Akademii
Nauk. Geophys. Ser. No. 11: 1718-1729 (1963).
144. Frv. L. !vl.. K. K. Menon. Determination of the
trO'pospheric residence time of lead-210. Science
137: 994-995 ( 1962).
145. Gat, J. R.. G. Assaf. A. Miko, Disequilibrium
between the short-lived radon daughter productsin the lower atmosphere resulting from their

c.

c.

of

c.

40

176. Mayneord, W. V., R. C. Turner, J. ivI. Radley,
Alpha activity of certain botanical materials.
Nature 187: 208-211 (1960).
177. Mistry, K. B., A. R. Gopal-Ayengar, K. G.
Bharathan, On the radioactivity of plants fromthe high radiation areas of the Kerala coast andadjoining regions. II. Studies on the uptake ofalpha and gamma emitters. Health Physics 11 :1459-1470 (1965).
178. Lowder, vV. M., L. R. Solon, Background radiation-A literature search. USA.EC report KY04712 (1956); v.e. United Nations document A/
AC.82/G/R.55.
179. Penna Franca, E., C. Costa Ribeiro, M. Teitakowski, et al., Survey of radioactive content offood grown on Brazilian areas of high naturalradioactivity. Health Physics 11: 1471-1484( 1965).
180. Chhabra, A. S., Radium-226 in food and man in
Bombay and Kerala State (India). British J.
Radial. 39: 141-146 (1966).
181. Turner, R. C., The ingestion of radium-226 infood and water in Great Britain. British J. Cancer
16: 200-208 (1962).
182. Lucas, H. F., Correlation of the natural radioactivity of the human body to that of its environment: Uptake and retention of Ra226 from foodand water, pp. 55-66 in Argonne National Laboratory Radiological Physics Division Semiannual
Report, July through December 1960, ANL-6297(1961).
183. Lucas, H. F., Jr., RB. Holtzman. D. C. Dahlin,
Radium-226, radium-228, lead-210 and fluorine
in persons with osteogenic sarcoma. Science 144 :
1573-1575 (1964).
184. Smith, B. M., W. N. Grune, F. B. Higgins, Jr., etal., Natural radioactivity in ground water suppliesin Maine and New Hampshire. J. Amer. Water
Works Assoc. 53: 75-88 (1961).
185. Smith, K. A., P. G. Watson, Radium-226 in dietin the United Kingdom in 1963. pp. 79-80 inAgricultural Research Council Radiobiological
Laboratory Annual Report 1963-64, ARCRL 12( 1964) ; v.e. United Nations document A/AC.82/
GjL.964.
186. Hallden. N. A., I. M. Fisenne, J. H. Harley,
Radium-226 in diet and in human bone. Science
140: 1327-1329 (1963).
187. United States Atomic Energy Commission, Healthand Safety Laboratory, Table 20-Annual radium226 intake in tri-city diets. p. 42 in HASL Contributions to the Study of Fallout in Food Chains,
HASL-147 (1964); v.e. United Nations document A/ AC.82/GjL.959.
188. Michelson, I., Radium-226 in the total diet. Health
Physics 5 : 229-230 ( 1961).
189. Michelson. I.. Radioisotopes in the 1963 diet.
Health Physics 11: 56-60 (1965).
190. Hallden, N. A., J. H. Harley, Radium-226 in dietand human bone from San Juan. Puerto Rico.
Nature 204: 240-241 (1964).
191. Turner, R. C., Discussion. p. 90 in Diagnosis
and Treatment of Radioactive Poisoning. IAEA,
Vienna, 1963.
192. Overton, T. R.. P. R. J. Burch. A coincident
gamma-ray spectrometer and its application to162. Israel, H., The radon-220 content of the atmosphere, comment on chapter 16, pp. 313-314 in
The K atural Radiation Environment. Adams, J.
A. S .. W. M. Lowder, eds., The University of
Chicago Press, Chicago, Ill., 1964.
163. Israel, G. W .. Thoran (Rn-220) measurementsin the atmosphere and their application in meteorology. Tell us 17: 383-388 ( 1965).
164. Patterson. R. L., Jr., L. B. Lockhart, Jr., Geographical distribution of lead-210 (RaD) in the
ground-level air, pp. 383-392 in The Natural
Radiation Environment. Adams, J. A. S., W. M.
Lowder, eds .. The University of Chicago Press,
Chicago. Ill., 1964.
165. Holtzman, R. B., Measurement of the naturalcontents of RaD (Pb 210 ) and RaF (Po 210 ) in
human bone-estimates of whole-body burdens.
Health Physics 9 : 385-400 ( 1963).
166. Lambert, G., 11. Nezami. Importance des retombees seches clans le bilan du plomb 210. Annales
de Geophysique 21: 245-251 (1965).
167. BmieHciilllt B. ,n;., ,ll;aBhI,iJ;OB E. H., l\la,mxoB c. r.,
K norrpocy o ce3omrrilX n reorpaqmlleCKHX Il3MeHeHllRX co)J.ep;Kamrn: CB~a-210 n a'rnocc}Jepe, CTJl.
120-131 n 1mnre: Pa,iJ;IIOaR.TllDHLie n30TOIThl B aT~ocq;epe n nx ncrro.1030Banne B MeTeopo:ronm.
Kapo.1Th H. JI.. l{11pul!emw .JI. B., Kpacnorrenn;eB IO. B. n ,iJ;p., pe,i!;., Aro:r.nI3].l;aT, MocKna, 1965.
168. Peirson, D. H., R. S. Cambray, G. S. Spicer,
Lead-210 and polonium-210 in the atmosphere.
Paper presented at the Symposium on Atmospheric Chemistry, Circulation and Aerosols, August 18-25, 1965, Visby, Sweden.
169. Nezami. M .. G. Lambert, C. Lorius. et al .. Mesure
du taux d'accumulation de la neige au bord ducontinent antarctique par la methode du plomb
210. C. R. Acad. Sc. (Paris) 259: 3319-3322( 1964 ).
170. Altshuler, B .. N. Nelson, M. Kuschner, Estimation of lung tissue dose from the inhalation ofradon and daughters. Health Physics 10: 11371161 (1964).
171. Oosthuizen, S. F., W. G. Pyne-Mercier, T.
Fichardt, et al.. Experience in radiological protection in South Africa, pp. 25-31 ·in Proc. 2nd
Int'l. Conf. Peaceful Uses Atomic Energy, vol. 21.
United Nations, Geneva, 1958.
172. Schroeder, G. L., R. D. Evans, Effect of appliedpressures on the radon characteristics of an underground mine environment, pp. 122-159 in Radium
and Mesothorium Poisoning and Dosimetry andInstrumentation Techniques in Applied Radioactivity. Massachusetts Institute of Technology
report l\IIT-952-2 ( 1965).
173. United States Department of Health, Educationand \Velfare, Public Health Service, Control ofRadon and Daughters in Uranium Mines andCalclulations on Biological Effects. Public HealthService Puhl. No. 494 (1957).
174. Mistry, K. B., Absorption by plants of naturally
occurring radioactive materials, pp. 86-89 in Agricultural Research Council Radiobiological Laboratory Annual Report 1962-63, ARCRL 10 (1963);
v.e. United Nations document A/AC.82/GjL.858.
175. Squire, H. M .. Tracer studies on the absorptionof thorium, ibid... p. 90.

41

measurements of low level radioactivity. Phys.
Med. Biol. 11: 47-61 (1966).
193. Hill, C. R., Po 210 in man. Nature 208: 423-425(1965).
194. Hill, C. R., Po 210 : a naturally occurring component of fall-out. Paper presented at the Symposium on Radioactivity in Scandinavia, Denmark,Riso, October, 1964.
195. Mercer, E. R., W. A. Mitchell, K. A. Smith,Absorption of radium by Brazil nuts, pp. 82-83 inAgricultural Research O:iuncil Radiobiological
Laboratory, Annual report 1961-62, .1\RCRL 8;
v.e. United Nations document A/AC.82/G/L.806.
196. Smith, K. A., Private communication.
197. Holtzman, R. B., The Pb 210 (RaD) concentrations of some biological materials from Arctic
regions, pp. 59-69 in Argonne National Laboratory Annual Report, July 1962-June 1963, ANL6769 (1963).
198. Hill, R. C., Po210 content of human tissues inrelation to dietary habit. Science 152: 1261-1262(1966).
199. Kauranen, P., J. K. Miettinen, 210 Po and 210 Pb
in environmental samples in Finland in University of Helsinh.-1, Department of Radiochemistry
Annual Report 1965. Helsinki. 1966.
200. Jacobi, W., The dose to the human respiratory
tract by inhalation of short-lived 222 Rn- and220Rn-decay products. Health Physics 10: 11631174 (1964).
201. International Atomic Energy Agency, Radiological Health and Safety in Mining and Milling of
Nuclear Materials, Proceedings of a Symposium
in two volumes. IAEA, Vienna, 1964.
202. Servant, J., Temporal and spatial variations of theconcentration of the short-lived decay productsof Rn in the lower atmosphere. Symposium on
Atmospheric Chemistry, Circulation and Aerosols,
August 18-25 ( 1965), Visby, Sweden.
203. Stahlhofen, \V., Measurement of the natural content of Th228, Ra226 , and their daughters in the
hunlan body, p.p. 505-519 in -~sessment of Radioactivity in Man, vol. II. IAEA, Vienna, 1964.
204. Hursh, J. B., A. Lovaas, Radium-226 in boneand soft tissues of man. Nature 198: 265-268(1963).
205. Mayneord, M. V., The natural radioactivity of
the human body, pp. 2-24 in Progress in Biophysics and Biophysical Chemistry, vol. 11.
Butler, J. A. V., B. Katz. R. E. Zirkle, eds.,
Pergamon Press. N.Y., 1961.
206. Rajewsky, B., L. E. Belloch-Zimmermann, W.
Stahlhofen, Ra 226 in human embryonic tissue,
relationship of activity to the state of pregnancy.
The measurement of natural Ra226 occurrence inthe human placenta. Health Physics 11: 161-169(1965).
207. Grummitt, \V. E .. Strontium and barium in boneand diet, pp. 376-380 in Radioactive Fallout from
Nuclear Weapon Tests, Proceedings of a Conference held in Germantown. Maryland. Nov.
15-17. 1961. Book 2. TID-7632 (1962); v.e.
United Nations document A/AC.82/G/L.776.
208. Holtzman. R. B., The source of unsupported Po21 0(RaF) in tissue. Letter to the editor. Health
Physics 10: 763-764 ( 1964).

209. Hunt, V. R., E. P. Redford, Jr., A. I. Segall,
Comparison of concentrations of alpha-emitting
elements in teeth and bones. Int'l. J. Rad. Biol.
7: 277-287 (1963).
210. Stover, B. J., D. R. Atherton, C. W. Mays,
Studies of the retention and distribution of Ra2 26 ,Pu239, Ra22 s, (MsTh1 ), Th228 , (RdTh), and Sr9-0
in adult beagles, pp. 7-25 in Some Aspects ofInternal Irradiation. Dougherty, T. F., W. S. S.
Jee, C. \V. Mays, et al., eds., Pergamon Press,
N.Y.. 1962.
211. Stehney, A. F., Radioisotopes in the skeleton:
naturally occurring radioisotopes in man, pp. 366381 in Radioisotopes in the Biosphere. Caldecott,
R. S., L. A. Snyder, eds., University of Minnesota, Minneapolis, Minn., 1960.
212. Hursh, J. -B., Natural lead-210 content of man.
Science 132: 1666-1667 (1960).
213. Groos, E., E. L. Sattler, W. Stahlhofen, Der
Natiirliche RaD und RaF Gehalt in Knochen
des Menschen. Atomkernenergie 8: 32-33 (1963).
214. Osborne, R. V., Lead-210 and polonium-210 inhuman tissues. Nature 199: 295 only ( 1963).
215. Penna-Franca, E., Radiochemical and radioecological studies on Brazilian areas of highnatural radiation (table IV). Progress report,
April 30, 1965, vol. II. Universidade do Brasil.
216. Wallace, D. E., Th22 S and Ra226 analyses of bones
from Kerala, India, pp. 67-70 in Argonne National Laboratory Radiological Physics Division
Semiannual Report, January through June 1961,
ANL-6398 ( 1961).
217. ~piers, F. "'vV., Dosimetry of radioisotopes in soft
tissues and in bone, pp. 269-279 in Radiation
Dosimetry. Reed, G. W., ed., Academic Press,
N.Y., 1964.
218. Charlton, D. E., D. V. Cormack, Energy dissipation in finite cavities. Rad. Res. 17: 34-49 (1962).
219. Thomas, J., A method for calculation of the absorbed dose to the epithelium of the respiratory
tract after inhalation of daughter products ofradon. Amer. Occup. Hyg. 7: 271-284 (1964).
220. International Commission on Radiological Protection, Task Group on Lung Dynamics, Deposition and retention models for internal dosimetryof the human respiratory tract. Health Physics
12: 173-207 (1966).
221. Pohl, E., Dose distribution received on inhalationof Rn222 and its decay products, pp. 231-236 inRadiological Health and Safety in Mining andMilling of Nuclear Materials, vol. I. IA.EA,
Vienna, 1964.
222. Kelley, T. F., Polonium-210 content of mainstream cigarette smoke. Science 149: 537-538(1965).
223. Gregory, L. P., Polonium-210 in leaf tobacco
from four countries. Science 150: 74-76 (1965).
224. Yavin. A. J., G. De PasqualL P. Baron. Polonium
in cigarettes-spectroscopic analysis. K ature 205 :899-900 ( 1965).
225. Tso. T. C.. N. A. Hallden. L. T. Alexander,
Radium-226 and polonium-210 in leaf tobacco andtobacco soil. Science 146: 1043-1045 ( 1964).
226. Turner, R. C., J. M. Radley, Naturally occurringalpha activity of cigarette tobaccos. Lancet i:
1197-1198 (1960).

42..

227. Radford, E. P ., V. R. Hunt, Polonium-210: avolatile radioelement in cigarettes. Science 143:247-249 ( 1964).
228. Little, J. B., E. P. Radford, H. L. McCombs,
et al., Polonium-210 in lungs and soft tissues ofcigarette smokers. Rad. Res. 22 : 209 ( 1964).
Abstract.

229. Strorninger, D. , J. M. Hollander, G. T. Seaborg,
Table of isotopes. Revs. Modern Phys. 30: 585904 (1958) .
230. Appendix 4, Properties of the uranium andthorium series, pp. 1033-1036 in The Natural
Radiation Environment. Adams, J. A. S., W. M.
Lowder, eds., The University of Chicago Press,
Chicago, Ill., 1964.
231. Mays, C. W ., D. R. Atherton, R. D. Lloyd, et al. ,The half-period of Ra228 ( mesothorium) , pp. 92105 in Research in Radiobiology, Annual Reportof Work in Progress on the Chronic Toxicity
Program. Utah University, College of Medicine,
report C00-225 ( 1962).

232. Pallister, E.T., J. H. Green, Radium-226 content
of natural waters and coal in New South \.Vales.
Nature 201: 813-814 (1964).
233. Roser, F. X., G. H. Kegel, L. Hainberger, et al.,A study of artificial and natural radioactive contamination in Brazil. Instituto de Fisica, Pontificia
Universidade Catolica, Rio de Janeiro, August 1,
1964.

43

234. Marsden, E ., Radioactivity of some rocks, soils,
plants, and bones, chap. 50, pp. 807-824 in The
Natural Radiation Environment. Adams, J . A. S.,
W. M. Lowder, eds., The University of Chicago
Press, Chicago, Ill., 1964.
235. Edgar, W. F., Radium content of drinking waterin the Central Savannah River area. E. I. Du Pont
de Nemours & Co., report DPSPU 63-30-10(1963).
236. Tanner, A. B., Physical and chemical controls on
distribution of radium-226 and radon-222 inground water near Great Salt Lake, Utah, chap.
14, pp. 253-276 in The Natural Radiation Environment. Adams, J. A. S., \\'. M . Lowder, eds.,
The University of Chicago Press, Chicago, Ill.
1964.
'
237. Jaworowski, Z. S., Content of radium D in humanbones and hair. Nukleonika 10: 297-301 (1965).
238. Hill, C.R., Z. S. Jaworowski, Lead-210 in somehuman and animal tissues. Nature 190: 353-354(1961).
239. Hill, C. R., R. V. Osborne, W. V. Mayneord,
Studies of alpha radioactivity in relation to man,pp. 395-405 in The Natural Radiation Environment. Adams, J. A. S., W. M. Lowder, eds.,
The University of Chicago Press, Chicago, Ill.,
1964.
240. Holtzman, R. B., 210 Pb (RaD) in inhabitantsof a Caribbean island. Health Physics 11 : 477-480(1965).
241. Lowder, W. M., Private communication.