UNITED NATIONSREPORT OF THE
UNITED NATIONSSCIENTIFIC COI\IMITTEE
ON THE
EFFECTS OF ATOMIC RADIATIONNOTE
Throughout this report and its annexes cross-references are denoted by a letter
followed by a number: the Jetter refers to the relevant technical annex (see Tableof Contents) and the number is that of the relevant paragraph. \Vithin each technicalannex, references are made to its individual scientific bibliography by a number
without any preceding letter.
Symbols of United Nations documents are composed of capital letters combined with figures. Mention of such a symbol indicates a reference to a United
Nations document.

ANNEXES

Annex B

RADIATION FROM NATURAL SOURCES

Paragraph

I. Cosairc IUYS ....................................... 2-7
Absorption in air .................................. 3-4
Variations .......................................
Variations with altitude

5-6............................ 7111. NATURAL
RADIOACTIVE ISOTOPES IN THE E N V I R O N ~ I E N T
Uranium and thorium .............................. 10-11
Radium ......................................... 12
Radon .......................................... 13
Thoron .......................................... 14
Particle-borne radioisotopes in the atmosphere ........ 15
Potassium ....................................... 16
Carbon-14 ....................................... 17
Tritium ......................................... 18
IV. IRRADIATIONFROM EXTERNAL SOURCES
Calculated values for gamma-ray intensities. ........... 19
Measured total outdoor radiation.. ................... 20
External irradiation in buildings. .................... 21-22
Special areas ...............'...................... 23-24
Summary of irradiation by external sources ........... 25
Gonad and bone doses .............................. 26-27
V. INTERNALWIOACTIVE
SOURCESRadioactive substances in the body ................... 28
Carbon-14 ....................................... 29
Potassium-40 .....................................30-3 1
Radium ......................................... 32
Particulate air-borne activity ........................ 33

VI. IRBU)IATIONFROM INTERNAL SOURCES.. ................ 34-39
Conclusion................................................. 40

References

1. A distinguishing characteristic of irradiation by
natural sources is that the entire population of the world
is =posed to it and that it remains relatively constant in
time, while varying from place to place with local geological conditions. The various natural sources include :(a) External sources of extra-terrestrial origin(cosmic rays) and external sources of terrestrial origin,
i.e. the radioactive isotopes present in the crust of theearth and in air.
( b ) Internal sources, i.e. the radioisotopes K40 and
C14 which exist as a small percentage of these elements
and are normal constituents of the body, and other isotopes such as Razz=,ThZJ2and their decay products thatare taken up from the environment.

protons, 20 per cent of alpha particles, 0.78 per cent of
C, N, 0 nuclei and 0.22 per cent of nuclei with Z> lo.'*
The energy of the primary particles is very high andvalues up to 1019eV have been reported.

I. COS>~IC
RAYS
2. The pimalycomponent of cosmic rays is the radiation incident
theof theof theearth. I t
composed of 79 per cent (in number) of*NOTE:Throughout this report and its annexes cross-references are denoted by a letter followed by a number: the letter(s= Table of C o n t a t r )refem to the relevant technicaland the number is that of the relevant paragraph. Withip
technical annex, references are made to its individual sclenMc
bibliography by a number without any preceding letter.

Absorption in air

3. The primary particles lose energy in their passage
through matter by ionization, radiation, and nuclear interactions and thus produce new groups of rays. Thissecondary radiation, still very energetic, is composed ?felectrons, photons, neutrons and mesons. The composltion of the radiation changes with altitude.

4. The radiation a t sea level is composed of mesons(-80 per cent) which constitute the secondary hardcomponent, electrons (-20 per cent), which constitutethe secondary soft component, and some primary protons (-0.05 per cent)? T h e average mass absorption
coefficient of the soft component a t sea level has beenreported to be 8.5 s 10-scmvg (E. Regener, quoted by
Hess3).

TABLE
11.13

6. Different authors give different values for cosmic
ray intensities at sea level (table I ) even at comparable
latitudes. There are indicationsG17that the most reliable
figure for the intensity a t the middle latitudes (-SO0)
and a t sea level is 1.9 - 1.96 ion-pairs/cma.sec, which
gives a soft tissue and gonad dose of .= 28 mrad/year.
OF COSMIC IUYSTABLEI. INTENSITYAND DOSES TO
THE SOFT TISSUES AND G 0 N N ) S I N
VARIOUS REGIONS NEAR SEA LEVEL

Place ofcbservat~a

Geomagnetic
l a f i t d c in
dcgrccs

Ionization in
ion pairs per
cma -see

Dose to flusoft
tissues and gonads
i n fnrad/sear
Ref.

Great Britain.. .

55' N 1.92

28

8

United States. ..

41' N 1.96

29

6

Austria*. ......

48' N 1.928

9France .........

4g0N 1.66 !Hard 1.15
\Soft 0.51

2410........

25' N 2.35 Hard 1.76
{Soft 0.59

34

11

20
28

12

Japan.

.kgentinas..... 23' 15' S 1.4
52' 42' S

1.9
--

a

Measured by counters.

Variafio~rwith altitude

7. The ionization in ion pairs/cms.sec and corresponding dose rates in air at N T P are given in tzble I1 forcertain locations. The table shoivs that an increase inaltitude iroin 0 m to 3.000 m gives an approximately
threefold increase in intensity. while the latitude variation even at 3,000 m is only 50 per cent. Neher's data
for sea level intensity, on which table I 1 is based, are30 per cent higher tha? those of other observers. Therefore, the values glren In this table may be considered as
upper limits.

Darc raie
mrad/ycar

Intensify
ion p a i r s / m 3 .su
Alli:r&m

0 .........

.......

1500 .,
3050..
4580 .........
6100 .........

.......

5. The intensity of cosmic rays increases verystrongly .with altitude in consequence of decreased atmosphenc absorption, and increases with increasing geomagnetic latitude in consequence of the effect of theearth's magnetic field. The latitude effect is confined tolatitudes between O0 and approximately 5S0 (apparently
at all altitudes). Small, short-lived changes of intensity
in time are produced by solar flares (up to 12 percent)'e6. Temperature changes in the upper layers of theatmosphere, local increases in pressure, air fronts andother factors also produce negligible temporary variations in intensity. but they are not significant from thepoint of view of the external irradiation of the organism.

COSMIC R ~ YINTESSITIESAND DOSE RATES

A1 5Oelafiftrde

Ncor
EgiraforA1 50'
latitudeh'car
Eguabr

2.8
4.5
8.8
18
34

2.4
3.0
6.1
12
23

41

33
44
89
175
340

66
128
263
500

8. Naturally occurring radioactive isotopes such as
HS, C 4 , K40, Rbs7, ThC9' and U2Ssand the decay products of the last tcvo isotopes are widely distributed inrodcs and soils and in the air. Physical characteristics
of some isotopes are given in tables IIIa and IIIb. The
data given in these tables may be found in many textbooks, but they are included here because they illustrate
the relative importance of different radioactive elements
and are used in calculations later on. The dose rate for anelement at given concentration is determined from decay,
yield and energy of its radiation. Shielding factors areassessed in the light of the penetrating power of theradiation. The relative contribution of the decay products of radium and thorium to total doses can be calculated, and the deviation from the theoretical equilibrium
concentration of the decay products of radium in bones,
caused by partial diffusion of radon, can be taken into
account.
9. Some of the isotopes listed in the tables viz. K40,
ThZ3', U23B,
have half-lives comparable to the geologicalage of the earth, estimated at 4 x 10"ears, and for thisreason are still present in nature. Other isotopes, in spiteof their short half-lives, are also present today, because
they are decay products of long-lived isotopes like RaZ",
or because they are produced from atmospheric nuclei
by cosmic rays, like C14 and H3.
111. NATURAL
RADIOACTIVE

ISOTOPES I N
THE EXVIRONMENTUranilit~tand Thorium

10. Naturally radioactive elements are widely distributed over the earth's surface. Thorium-bearing minerals
are found in the United States (Rodry hfountains area
and the Carolinas), in India (Kerala coast), in Brazil(coastal region of Espirito Santo), on Taiwan and inother parts of the world. Uranium has been found inlarge quantities in the United States (in brown coaldeposits, petroleun~beds. and the phosphatic rocks of
Florida), the Belgian Congo. Ontario and Sasltatchewan
in Canada, Fergana in the USSR. Czechoslovakia andSouth -Africa and other areas. For fuller information on
the distribution of uranium aid thorium. see ICerr.15
11. Radioactive elements are more commonly associated with certain types of rock than with others. Acidigneous rocks are richer in them than basalts. Shales,in particular, which contain organic substances. are more
highly radioactive than other sedimentary rocks (table
IV). Potassium. thorium and radium show a tendency
to concentrate in rocks \\-ith a high silicon content(table V) . Tables IV. V and VI contain data on concentrations of radioactive elements in rocks.

TABLEIIIa. DATAOX PARTICLE RADIATION FROM CERTAIN
NATUMLLY OCCURRING RADI0.4CTIVE ISOTOPES-

IsolopeNcnu

SymbolEtiergy

B
B
4

B

0.018
0.155
1.3
4.78
5.49
6.00
0.7
3.15
7.68
0.027

..........
.........
.........

B

1.17

P

5.30
3.98
0.05
0.4-2.2
5.4
5.6
6.28
6.77
0.34
0.58
6.05
2.25
8.78
1.79

.......

....... Thorium C
Potll.. ....... Thorium C'
Bill".

a
P

a

B

B
a

P

j3

B
P

a
P

a

B
B
a

B
(I

....... Thorium C"

B

12.26
5,600
1.3 r 109
1,600
3.825
3.05
26.8
19.7
1.5-10-4
22
5.O
138
1.39.1010
6.7
6.1
1.9
3.64
54.5
0.158
10.6

K4o.. ........... Potassium-40
Pb314.. .......... Radium B
BP13.. .......... Radium C

AcB8. ...........

Pb"'.

...........

bfesothorium I1

Thorium B

Bi'J12.. .......... Thorium C

TI?ba.. ...........

Thorium C' '

years
years
years
years
days
min
min
min
sec

years
days
days
years

Yea
hours
years
days
sec
sec

hours

60.5

min

3.10J
3.1

sec

TABLEI1 Ib. DATAON GAMMA RADIATION FROM
NATURkL RADIOISOTOPES~~.

Radiooclios
half-Lijc(Ales)

Hz.. ......... TritiumC". ......... Carbon-14
K40
Potassium-40
Razz6
Radium
Ra22z
Radon
Pdla.. ....... Radium A
PPlc.. ....... Radium B
Bi214. ........ Radium C
Pdl4,. ....... Radium C'
PbZ'O.. ....... Radium D
Biz10 ......... RadiumE
Po210......... Polonium
ThB' ......... Thorium
Ram.. ....... hlesothorium I
Acza..
h,Iesothorium I1
ThzB......... Radiothorium
Rat%......... Thorium X
RnB0 ......... Thoron
Pozls.. ....... Thorium A
mu......... Thorium B

TP..

RodiafionminT - ~ B L EIV.

~ D I U V THORIUbI,
AND POTASSIU3f COXTESTSIN VARIOUS R O C K S ~ ~Ram, g/grlO"

Trpc of rockTh-, g/gxlOd

K'e. g / g x I P

Igneous rocks:
Mean value's ................
Granifes:
North America, Greenland.. ...
Finland.. ....................
Alps ........................
Basalfs:
North America, Greenland.. ...
Great Britain, Germany, Franceand Hungary ...............
Seditnenfary rocks:
approx. 0.3
Sandstone. ..................
Limestone. .................. up to 1.5 (117).Uum shales in Sweden. ........ up to 120 (6017)

TABLE
V.

drinking water is in most cases mainly due to Ra'26. The
radium content of water sources is determined by theextent to which the water is enriched by the leaching ofrocks. Water containing calcium, barium and stablestrontium is particularly likely to be enriched withradium. This is one of the reasons for the wide variations in the radium content of water. The concentration
varies between wide limits and characteristic values are
given in table VII.

~ D I U L ITHORIUbI,
AND POTASSIUbf
CONTESTS IN SILICEOUS ROCESIO

Igneous rocks:
Acid rocks>65% SiOz
Granites.. ....... 3.1
Young granites(Maxlevel) ...... 6.5(Granodiorite) 2.7
Intermediate rocks
65-55% SiOt...(Diorite) ...... 1.4
Basic roch
<55% SiOl(Gabbro) ..... 0.87
mrabusic locks:...(Peridotite) ... 0.52

...

20

3.4

59
18

5.1
2.5

6

1.i
Oceo n...

5.1

Rivers in U.S.A.
Average. .........................
Mississippi ........................

0.7

23

-

I

AND POTASSIUhf CONTENTS IN
VARIOUS R O C K S ~ ~Igneous.. ............
Sedinunhry rocks:
Sandstones.. ........
Shdes.. ............
Limestones ..........

7 x 10-17
1-3x 10-15

Public water sufiWics*
Sweden (tap water). ...............
U.S.A. (tap water)
Average for 41 towns... .........
hlaximum Uoliet, Ill.) ..........
USSR mean value (fresh water). .....
Austria, Bad Gastein (tap aater) ....
Germany, Frankfurt-am->lain (tapwater). .........................

TABLEVI. AVERAGER4DIUh1, URANIUM, THORIUM

Type d r o d.............................

Ram.

Pa, Thn:.

K.

g/grIO"c/gxlQ

1/tx1@

c/c~IO1

1.3

4.0

12

2.6

0.71
1.08
0.42

1.2
1.2
1.3

6
10
1.3

1.1

Springs in special areas
Boulder, Col., U.S.A.. ..............
Hot Springs. Japan.. ...............
Jdchymov (Joachirnstal),
Czechoslovakia. .................
Bad Gastein, Austria.. .............
France. ...........................

2.7
0.27

Radiac trt
12. The radium concentration in rocks has been ioundto vaCY between lo-" and lo-'' gram of radium pergram of rock." The average radium content in the soil
is estimated at 2 x lo-'' gram of radium per gram of
the radi~unconcentration in the soil in various
parts o i the United States has been iound by measurementZ3 to vary between 0.9 and 8.0 x 10-l9gram ofradium per gram oi soil. Tables IV to VI show radium
concentrations in various minerals. The radioactivity offresh surface water is sometimes due to radon in higher
concentration than that corresponding to the radium contration. and it should be not~cedthat many old data on
natural ra,jioactiri~ of ,vater refer to radon and not
radium concentration. The natural radioactivity ofsomemeasurements of the Ra"6 content in foodstuffs
are given in table ~ 1 1 1 .

TABLEvI I 1. R A E COXTESTS~IX FOODSTUFFS~~
Rn contort in gFoodE
of food x IOU

Wheat.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20-26
Potatoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67-123
Milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O.O375/millilitre
Meat ....................................
8.0

52

Radon13. RnZ"?,an isotope of the gaseous element radon anda decay product of Ra?26 in the uranium series, accumulates in the soil in areas where uranium-bearing minerals
are present, and diffuses into the air. The average radon
concentration in the soil is of the order of lV13 curie/gramJ1. The rate of injection into the atmosphere isapproximately 4.3 s l@1° curies per hour per square
metre of the surface (in the neighbourhood of Leningrad, USSRzB).Seasonal changes occur in the rate of
injection. The radon content of the air at ground level
depends to a considerable =tent on meteorological conditions. The average "equivalent" concentration of radon
with its decay products in the air is approximately
1-3 x 10-l3 c/l (see table XIa). In areas with higher
radioactivity (granite and other areas) the radon content may be higher than the concentrations given above
by several iactors of ten.
Thoron14. Thoron (Rn2=O) another isotope of radon is adecay product of Th23zand also diffuses from the groundinto the air. As for radon, the concentration in air
depends to a considerable extent upon meteorologicalconditions. The average concentration in air is approximately 0.5 x lV13 c/l (see table XIa) but in areas withhigher radioactivity it may be higher by several factorsof ten.

activity of ocean water is mainly due to K40 with aconcentration of 3-5 x 10-l3 c/cm3.
17. The carbon isotope C4is formed in the atmosphere as a result of nuclear reactions between cosmic
rays and atmospheric nuclei. -ill the carbonaceous substances taking part in carbon exchange with the atmosphere have a constant equilibrium concentration of C 4
equal to 7.21 x lV1' c per g of carbon,=;corresponding
to a distintegration rate of 0.27 dps per g of carbon.
Rocks in which such exchange cannot take place have adepending on their geologlower specific activity of C4,
ical age. Ancient carbonaceous rocks (marble and others)of geological age greater than the half-life of carbon1'
do not as a rule contain this isotope. Observation has
shown, however, that the concentration of C1' in nature
has been increasing recently owing to contributions froma new source, namely, the explosion of nuclear~eapons.~~~~'

Tritittm
18. Tritium (H3) has always been present in naturesince it is formed in the atmosphere by the action ofcosmic rays. The total quantity of tritium is at an equilibrium level equal to the rate of formation multiplied by
the mean radioactive lifetime. The aqueous componentof the cells of the htin~anbody probably has a tritium
concentration equal to the one observed in foodstuffs
and drinking water. The natural atomic concentration oftritium in the hydrogen of river waterJg is 5 x 1V18.
Such a tritium concentration may be calculated to result
mrad/year to soft tissues.
in a dose rate of 1.8 x

Particle-borne radioisotopes in the atmosphere
15. I n addition to radon and thoron, the atmosphere
contains their solid decay products, mainly Ra B, Ra C
and T h B, which attach themselves to small particles andthus constitute the natural particulate air-borne activity.
IV. IRRADIATIONFROM EXTERNAL SOURCES
The distribution of the aerosol-borne activity according
Calcrtlated vdrtes for ganznta-ray intensities
to particle size is shown in table IX1'. The particulate
activity can be collected by special filters or by electro19. The gamma radiation over rocks and soils constatic precipitation. Long-lived material that remains
taining known amounts of radioactive materials u-as firstafter the decay of Th B (10.6 h half-life) constitutes
calculated by Hess40 Later, Hultqvist17 calculated charonly a very minor part of the total activity. Concentraacteristic radiation values for minerals with the concentions vary widely with local and meteorological factors.
trations of radioactive materials given in table IV.
Extensive reference to data on radon equivalent content
Hultqvist developed simple numerical espressions forin both indoors and outdoors air is given by H u l t q ~ i s t , ~ ~the gamma-ray dose, corrected for the scattered raand a summary of some typical values has been given by
diation. If his formulae are used to estimate the contriLowder and(see also table XIa). The particlebution to the dose rate (D, rad/year) from various conborne radioactivity is relevant to internal irradiation
centrations of radioactive materials in the ground (s, gresulting from inhalation, since the particles, but not the
per g ) , the following expressions are obtained:
gases, accumulate in the respiratory tract.

TABLE
=.I7

DISTRIBUTIONO F RADIOACTIVITYACCORDING TO PARTICLE Dl-ULETER
Dose rates calculated from Hultqvist's equations ( 1)using the data of table VI are given in table X.

TABLE
X. DOSE RATES OF EXTERN.=

G-?iSlX-

Ra, U,IRRXDWTION FROM TBE ELEMENTS
T h A h 3 K C O N T A I 3 m I S ROC=

Potassiicnt
16. Potassium is relatively abundant in nature. Its
radioactive isotope KO' constitutes 0.0119 per cent of
the total amount of potassium and contributes 32
p-dps per g H and 3.+-dps per g K. The potassium
content of various rocks has been given in tables IV-VI.
T h e potassium concentration in the soil varies between
and 3 x 1V2g of potassium per g of soil. The radio-

Dose role in mrad/yrara frm

Type of rock

Ro-

Uxr

Th"'

K'"

Igneous rocks.. ......

24

25.8

36.8

34-6

13
20

7.7
7.7
8.4

18.4

14.6

30.6
4

36

Sedimentary rocks:

Sandstones. .......
Shales .............
Limestones. .......

7.7

3.6

Calculated from equations (1) and the data in table VI.

DOSERATES OF EXTERNAL GAMMAIRRADL4TION OUT OF DOORS I N
VrlRIOUS COUNTRIESTABLEXIV. DOSERATE OF EXTERNAL GAMMA

TABLE
XI.

IRRADIATION INSIDE BUILDINGS LV AUSTRIA%
T 9 c of building

Dose raftmrad/war.-

COUW

Great Britain.. ..
France..........

United Statess.. .
Austria
Sweden6 ........

.........

48
45-90
180-350
50-160588560-12050

Comment-.

~ e f .

41
10

Granites and shales
For 19 inhabited localities

a Values obtained by subtraction of 28 mrad/year for cosmic
raps.

OF RADOS AXD
TABLE
XIa. CONCEXTRATIONSTHORON LN EQUILIBRIU3l WITH THEIR DECAY PRODUCTSPRESENT IN THE AIR IN VARIOUS REGIONS A h D
CORRESPONDING CALCULATED DOSES
Aonopc conunlrafion
in c/l r 10"
Place of obsmvalion

Czechoslovakia. ...
Great Britain.. ....
Japan .............
FranceAustria.. .........
Sweden..

............

.........
USSR .............

Rn

8.0
3.0
1-2.5
2.0
1-3
1.0
1.0

Dare inmrad/yeor

Tn

Rn

0.6

11
4.3
1.4-3.5
2.8
1.4-4.3
1.4
1.4

0.5

Tn

F&f.

0.8

28
32
11
34
35
36
26

0.7

Arwage cnctnlrolionin -,c/Z- -r1-0-"
d i & d (oulcr walls).....................

57
112
202

48
99
158

' Using table VI of ref. 17 and excluding cosmic rays (1.9
ion-pairs/cms-sec).
TABLE
OF ExTERh.AL GILMh*
1RR.ADLkTION INSIDE BUILDINGS IN GREATB R I T - ~ I N ~ 'r w a r~~ of gBuildinrc

S%s mcmurcd

Local
gommorays Mcan(a) Aberdeen, Laboratory. ....
(b) .4berden, bell tower. .....
(c) Aberdeen, entrance hall.. ..
2. Concrete or (a) Aberdeen, rooms on various
brickfloors..................
(b) Leeds, rooms in hospitalbuilding ...............
(c) Leeds, single storey
laboratory .............
(d) Leeds.variousrcamsin house
1. All granite

107
99
101

102

73
81

Tn

Rn

Tn

0.0276
0.091

7.5
13

0.4
1.3

0.095926.4

1.35.;, ,,,

Mean dare r&. in mrad/year*

49
Brick
104
Light-weight concrete.. .... I 72
(containing alum shale)

Dose rotr. mrad/ymr*

22. ~h~ gamma radiation from radioactive Inaterial
in thebe calculated by Hultqvist's relations'yDRn= 14.2 X 1 @ 2 X C R n mrad/year. . . ...(2)DTn= 14.0 X 101'X CTnmrad/year
where C is the concentration of radon and thoron incuries per litre of air. Values corresponding to the concentrations of columns 2 and 3 of table XIa are given
in columns 4 alld 5.

C e ~ ~ ~ e o f r Highcstreadingwn:
Larrstreadinp

wood ....................

85-12875-86

a Table W,of ref. 17 was used, the calculation being madeaccording to equation (2).

DOSERATES OF EXTERNAL GAMMAIRRADIATION IN SWEDISH
B U I L D I N G S ~ ~l4
,
*d.%)

Rn

Wood ................. 0.527
Brick.. ................ 0.909
Light-weight concrete(containing alum shale) 1.86

TABLE
XII.

(-

5444

TABLE
XV. DOSERATE OF EXTERNAL G ~ I M A
IRRADIATION FROM Rn AND Tn PRESENTIN THE AIR JXSWEDISHBUILDINGS

Measttred total outdoor radiafiott
20. Total gamma ray and cosmic ray intensities havebeen measured by various authors using ionizationchambers. The experimental dose rates are given intable X I and may be compared with calculated values.
w h e r e necessary, gamma ray figures in table X I havebeen obtained by subtracting an average value of 28
mrad/year for cosmic rays.

Building maferial

All granite. .....................
Brick (brick or concrete). .........

Exfer?zal irradiatiorr in buildings
21. External irradiation by gamma rays is greater
inside buildings of brick, concrete, shales and othermaterials than out of doors because of the radioactive
elements contained in these materials. Some increase in
the dose may be produced by the accumulation of radonor thoron as a result of poor ventilation in the buildings.
On the other hand, the buildings reduce the dose of
external irradiation by absorbing .the radiation fromsources outside the buildings. Tables XII, XI11 andX I V indicate the dose rates of external gamma irradiation inside buildings, table XV the dose rate from radon
and thoron present in the air in buildings (without
ventilation).

34
35
36

Stockholm street
Igneous rocks
Clay

Dose raft. mrad/ycar

Wooden house.. .................

I

Special areas
23. Much higher values of the external radiation havebeen found in some areas where the thorium content in
the soil is particularly ligh.
24. The region of Kerala (India), which is approximately 100 k m 5 n area (about 200 krn long and several
hundred metres wide) has a population of about 100,000.
y-lle available measurements+~have been made in ten
villages of the intensity of the radiation inside buiMingsof three types constructed of various materials typical of
the region. The basic materials are brick and cement( A ) , clay ( B ) and wood (C). The results of the measurements and corresponding calculated doses are given
in tables XVII and XVIIa. The mean \-alue of the individual dose is 1,300 mrad/year, calculated from theequation
P,
A

D='

78

x,

ZP,
r

80
57

where P, is the population in village r and X, is themean value of the dose in village r.
54

TABLEXVI. EXTERXALIRRADIATION I N SPECIAL .~REXS
Geology

Location

Area.-

Monazitesand
alluvial
deposits

Brazil States ofSequence oI inter50,000
Average 500 42
Rio de Janeiro
mittent coastal
peak values
and Espirito
strips each sev1,000
Sanco (Outdoor) eral km long andseveral hundred
metres wide
htineralized Brazil States ofApproximately 6
Pasture land,
Average 1,600 42
Minas Gerais
volcanic
k m l in a dozen
scattered farms, peak values
intrusives
and Goias
scattered places
1 village with
12,000(Outdoor)
350 inhabitants

TABLE
XVII. DOSESOF EXTERNAL GAMMA IRRADIATION INSIDEBUILDINGS AT TEN INHABITED LOCALITIES IN THE I<EKUREGION INDIA)^^
Name a/ village

Area o j oillolc
in 1,000
No. ojppulation
sq. metres(in thousands)

No. ofhouses'EsLd

Mean daseralc
mrod/ycar

1. Kadiapattam.. ....
2. Manavalakuruchi .
3. IvIuttam.. .........
4. Midalarn.. ........
5. Viligem.. ........
6. Karamanal.. ......
7. ICavalen~..
8. Kullatoor.. ........
9. Vettoor. ..........
10. Varkala.. .........

.

........

TABLE
XVIIa. DOSESOF ESTERNAL G A 3 l l L - I R L T I O N INSIDE BUILDINGS OF VARIOUS TYPES IN THE K E K ~ WREGION INDIA)^^
KO. o jh c sPnccnIa;e of tala1
irumber of h c s inthr repion

Brick.. .............
Cement. ............

73

Type B. Clay.. ..............
TypeC. Wood ...............
Bamboo. ............
Palm.. ..............

62

Type of hmrse andbuilding materialType A.

TABLE
XVIII.

52

Dose. mrad/yeu
Maximum
oolrrcMinimum
value

15

2,890

66

60
25

3,150

105

3,950

145

MEAN \r.4LUES OF DOSES OF ESTER-VAL IRRADIATIONFROM VARIOUS SOURCES OF RrlDIAiTION

Sourca of rodiolion

Dosc rak. w a d / y e a r.Wear > a l u

Extreme d u e s

1. Cosmic rays.. ...................

28

20-34

Table I

Ordinary regions:
2. Gamma rays over rocks.. .........
3. Gamma rays out of doors.. .......
4. Gamma rays fro111aerial sources.. .

73
70
3

25-1 20
48-1601.4-1 1

Table X
Table XI
Table XIa

265

180-350

Table XI

131-2,814

Table XVIIActicc regions:
5. Gamma rays, granitic regions inFrance ..........................
6. Gamma rays, monazite region,
Kerala in India. .................

1,270'--a- -By subtraction of cosmic ray dose of 28 rnrad/year from total.

food and water and is present with its decay products
Suntttzary o j irradiation by externd sorircesinthe body. Radioactive material from the atmosphere
25. An approximate estimate of the level of esternal
entersthe respiratory tract by inhalation and some airirradiation from natural sources can be made from theborne
particulatematerial is retained.
above material. The measured doses out-of-doors invarious regions give a mean dose equal to 70 n~rad/year
Carbori-14(excluding highly radioactive regions). On the other
29.
The
total
carboncontent of the body is approxihand, a value for the mean dose over rocks of 73 mrad/
mately
18
per
cent
or
12.6
kg for a total body weight ofyear may be derived by calculation from the mean :oncentrations of radioactive elements in the most w~dely 70 kg. Therefore, the amount of CI4 for a total bodyweight of 70 kg is of the order o i 0.1 mc.
distributed rocks (Table X). Thus in normal regions
the mean dose can be estimated at approximately 70
Poiassiunt-40
mrad/year. Summary data on external irradiation are
30.
The
total
potassiumcontent of the body has been
given in Table XVIII, column 3 of which indicates
given as 0.185 per cent or 130 g by Sievert,* as the avermean doses, column 4 the spread of typical values, andage value of a series of observations by several authors.
column 5 of the reference to the data used in estimating
While individual values range between 0.12 and 0.35
the mean level of irradiation.
per cent, the majority of results group together rather
closely around the average value given above.
Gortad atld bone doses
31. The concentration of radioactive potassium in
26. I n calculating the doses to the gonads and bones' ~givenvarious organs, according to Forbes and L e w i ~ ,isfrom external gamma irradiation, a coefficient (shielding
in table XXI.
factor) must be introduced to allow for the partial absorption of gamma radiation by outer tissues. Spiers3'
PoT.%ssIU&~
COYTENT OF VARIOUS
TABLE=I.
gives the following estimates for the gonads :ORGANS OF M . ~ N ~ ~TABLEXIX. GONADALSHIELDING FACTOR FOR
G.%3IV%R4YS IN THREE POSITIONS:HORIZOSTAL, SITTIXG A h 9 STAhmING
Shielding falor

Fcmok

PodionAonagc

.\4&

Awagc

0.67
Horizontal. ........... 0.52
0.56
0.70
0.70
Sitting.. ............. 0.58
0.72Standing.. ............ 0.59
Mean factor for both sews: 0.63
The mean shielding factor in the case of bones will alsolbe taken
here to be 0.63

27. Estimated aggregate values can now be given for
the gonad and bone doses from natural sources of radiation--cosmic rays and radioactive elements. The populations are subdivided into three groups according tolevel of irradiation: people living in normal regions i.e. regions where the level of irradiation is not morethan 100 mrad/j-ear; population groups living in active
regions with a higher level of irradiation, up to 500
mrad/year ; and lastly, persons living in regions with ahigh level of irradiation-over 500 mrad/year. Such adivision is artificial, but is useful in considering the biological effects of irradiation.

TABLE
X X . MEAN DOSE TO GONADS AND BONESFROM NATUIUL EXTERNAL SOURCES I N NORhML
REGIONS AND blORE ACTIVE REGIONS
RegionPopulationin millions

Aggrceolr mean dose
mrcm/ycar'

1. Normal regions. .............. 2,500
2. Granitic regions in France.. ....
7
0.1
3. Lfonazite region, Kerala in India
4. Monazite region Brazil. .......
0.05

-

75
190
830
315

Using a shielding factor of 0.63 for -,-rays and a dose rare of
28 mrem/year due to cosmic rays.

V. IXTERK-AL
R~\DIOACTIVE SOURCES

Radioactive nrbsta~~ces
itt the body
28. The radioactire isotopes e4and K40 are normal
constituents of the human body. Ra2?=is taken up from

Pcrccnlogc of l o w
body w i g h t

Orgon

Skin .......................
Skeleton. ...................
Tibia. .....................
hiusdes ....................
Nervous system. ............
Liver. .....................
Heart. .....................
Lungs. .....................
Kidneys. ...................
G.I. tract. ..................
Adipose tissue. ..............
Remainder. .................
Total body weight: 73 kg
-

6.5
13.4
1.4
39.6
2.1
2.3
0.6
2.2
0.4
1.5
21.4
6.4

-~

Radiut~t
32. Radium, like calcium, is selectively incorporated
in bone. As the amount of radium daily ingested in foodhas been estimatedd6 to be around 1.6 x 1@l2 g, theuptake through drinking water is significant only if theradium concentration in the water is at least 10-l6 g
Ra2'e/cm3. Consumption of such water may result in an
increased body burden of radium, but, as the concentration is normally lower, the body content of radium isbelieved to depend in most cases on the radium content
of the food. The following figures have been reported
for the total radium content in the human body: 1.6 x
l@1°g47.3.3 x
gZ7,and 0.4--3.7 x lV1°g4=.Muth2'(table XXII) has recently published values of radium
concentrations in different tissues which seem to indicatethat a substa~ltialproportion of the radium burden islocated in soft tissues. These values have not yet been
confirmed in other laboratories.

TABLE
XXII.

&UIIUM CONTEST IY lT-4RIOUS

TISSUES~

Tirs;rc

Number ofmmpks& confcnl per E of unfrc&d lirsu8

Jfinimum toluc .Mean ualxe Maximum valuc--

Bones ...........
Lungs...........
Liver ...........
Spleen ..........
Muscles.. .......
Testicles ........

6
4
4
3
2
28

4.9
1.6
0.4
1.8

9.7
2.3
3.4
4.6
1.3
0.6

16
3.5
11
7.4

Particztlafe air-borrre activity
33. Because the disintegration products of radon andthoron are present in the air attached to the particles ofaerosols, the amount of radioactive air-borne material
retained in the respiratory tract depends upon the filtering properties of this tract for particles of ditierent sizes.
Figure 1 shows some characteristic average retention
values for particles of different sizes taken from a graphgiven by Hultqvist (ref. 17: p. 46). Virtually all theactivity is concentrated in particles of no more than
0.04 microns in diameter and up to about 70 per cent ofsuch particles will be retained in the lungs according to
the graph.

of the distribution of radium in the orgmism, but thishas not yet been confirmed by other researchers. The
local distribution of radium in bone tissue is of considerable importance in estimating osteocyte doses40*50
and it is generally studied by radioautography but at thelevel of the natural concentration of radium in the bones,
this method does not yield reliable results :the data published on radium distribution have been obtained withrelatively large concentrations of radium. The question
therefore arises whether a similar picture of radium
distribution in bone tissue would be obtained with small
concentrations. There is as yet no satisfactory answer
to this question and it is accordingly assumed here thatwhen radium is present in natural concentrations in nonactive regions, its distribution in bone tissue is uniform.
36. As the range of alpha-particles in the tissues isapprosimately of the same order as the diameter of thecavities in bone tissue. the relationship between alphaparticle range and cavity size must be taken into accountin calculating the dose. According to Spiers40 this may
be reduced to introducing into the equation for calculating the dose a geometric factor having different values
for bones of differing structure. Spiers (op. cit) expresses the equation for calculating the bone dose in thecase of alpha particles from radium in the bones in thefollowing form (in which 50 per cent of the energy isassumed to come from disintegration products) :D = 1.78 s 10" Pm mrad/year
is the mean geometric factor, m the radium
where
content in the bones in grams of radium per gram ofbone.
37. For a body burden of lVIO g RaZZa,which isaverage for normal (non-active) regions, the numericalFigure 1 Approximate "median curve" for the alveolar retenvalue of the osteocyte dose is thention The broken line refers to that magnitude range for which
D = 38 mrem/year
no experimental investigations are available. (Reproduced from
Hultqvist, ref. 17, page 46.)
= 1.48, using an RBE = 10. The mean dosewhere
to the bone marrow is largely due to the /3 activity of theradium decay products, and may be estimated to beapprosimately
0.5 mrem/year
34. The dose rates from potassium and carbon are
Dg = 0.5 mrern/year
approsimately uniform over the body and are calculated from the known concentration of these elements
38. The dose of irradiation by radon and thoron andand the specific energies of their radiations. Calculated
their distintegration products is considerably greater (asdose rates are given in table XXIII,using the following
compared with external irradiation) if these substancesparameters :are taken up into the organism with inhaled air. In thiscase the lungs are the critical organ. Assuming, in acKCO:energy of quanta E y = 1.5 Mev, 0.1 quantum
cordance with the data given above, that 60 per cent ofper disintegration, average energy of /3 particles EB =the aerosol particles carrying the radioactivity of the dis0.6 Mev, 50 per cent of the energy of the gamma quantaintegration
products of Rn and T n are retained in theis absorbed by the tissues ;tissues and that the volume of the lungs is 3,000 cmS
C4:average energy of /3 particles EB= 0.067 Mev.
and their weight 800 g, the numerical value of the lungfromdose can be calculated, according to Hultqvi~t?~*'~
35. In calculating the doses of irradiation from rathe following equations :dium taken up into the organism, only the alpha-particle
DRn= 5.0 X I@' CRn mrem/year
energy is taken into account as a rulet and all the radium.......(3)is assumed to be in the bones. Figures published reDTn= 66.5 X 101' CTn mrem/year
centlyn ,(table XXII) present a rather different picture

I

RADIOACTIVITYOF TI-IEBODY AND TISSUE DOSESFROM Kt0 .4&P C14 (standard man, 70 k g )TABLEXXIII.
Elcmcnl

Weigh1 in
pcrcenhgc

K ...........

0.20

K4o.. ........ 2.38.10-5............ 18.0.......... 2.8-10."

C
C"

a

Wright in E

140
1.66.10-2

12,6001.96-10-8

Activity inRadiolion cxricr x 10'b a d dorc. 0sk dasc
mrad/yca?
mrodiyeor

r

10.4
1.15

16.5
2.3

9.0'
2.3

4

9.0

1.6

1.6

15

Using the potassium content in the bones according to Table XXI.

TABLEXXIV.

DOSESTO LUNGS FROM R4DON AND TIIORON IN THE AIR(based on measuremeltts carried out i n Sweden)
Dose in mrcm/year:fiRn

OvlnruoU
librium

Assum- Withrn;
Mihequrlion
librium JW rec

Wood. .............. 0.527 0.537
Brick.. ............. 0.909 0.913
Light weight concrete(contain.alum shale) 1.86 1.86

Assumin;equvrr:rtt~

39. Aggregate figures for internal irradiation give thefollowing dose rates: gonads 20 ~nrem/year and osteocytes 50 mrem/year.

40. Since the data given in the text relate to individual inhabited regions and are naturally far fromcomplete, it may be asked whether they can be considered representative for the whole population of theworld. As far as the level of irradiation from sources
such as cosmic rays and radioactive elements that are
constituents of the body (potassium and carbon) is concerned, the answer is in the affirmative. In the case ofother sources of external and internal irradiation present
in the soil, water and air are capable of being taken up
into the organism, the level of irradiation depends on thegeological features of the region concerned and therefore
varies considerably from one place to another. In thiscase, only a very approximate estimate of the mean levelof irradiation is possible. The results of such an approximation are given in table XXV.

TABLEXXV. DOSESOF EXTERNAL AND INTERNALIRRADIATION FROM NATURAL SOURCES OF RADIATION
Dose mrem/yrar
o!hnsofl tissues* T o bones

irradiation:
Cosmic rays.. .............. 28
Gamma rays out-of-doors. ... 47

28
47

Commcnl

At sea level

Internal irradiulion:......................

K4Q..

19

...................... 1.6
Ra'm ......................
?
Cl4..

Total irradiadon from all sources 95

11
1.6
38

1 25

I

With
run-

1
rium

I

rqui-

I?

R'ifh

zz

lia

'&*
rium lion

263 73453 128

185 52605 173

0.0959 0.461

where C is the radon or thoron concentration in curies/
litre. The results of measurements carried out in three
types of buildings in Sweden are given in table XXIV ;the doses were calculated from equations (3) and (4).

Inadidion

IWscc

0.0278 0.136
0.0910 0.450

where C is the radon or thoron concentration in curies/
litre, and radioactive equilibrium is assumed. In anothercase-that of ventilated buildings, where the air in theofbuilding is renewed every seventeen minutes, i.e.
the air is renewed per second-Hultqvist obtained thefollowing equations :TOgonads andWill:senlibtion

At sea level--* Including bone muro\t- since the conuiburion from Ra inbone does not esceed about 0.5 rnrenl per year.

REFERENCES
1. Rossi, B., High energy particles, Prentice Hall. New
York, p. 520 (1952).
2. Rossi, B., High energy particles, Prentice Hall, New
York, p. 8 ( 1952).
3. Hess, V. F. and Vancour, R. P., J. Atm. Terrest.
Phys. 1, 13 (1950), UN document A/AC.82/G/
R102. Radiological Data, submitted by Austria.
4. Wilson, J. A. (Editor), Progress in cosmic physics,
Amsterdam, ( 1952).
5. UN document A/AC.82/G/R.15, Information submitted by Sweden, (1956).
6. Hess. V. F. and O'Donnell, C. A., Journal of gphysical research, 56, No. 4: p. 557 (1951).
7. Hess, V. F., Arch. Met. Geophys. Biol. A, 3, pp.
56-63 (1950).
8. U N document A/AC.82/G/R.2, Information submitted by the United Kingdom, (1956).
9. UN document A/AC.82/G/R.102. Information submitted by Austria, (1957).
10. UN document A/AC.82/G/R.179, Information submitted by France, (1958).
11. UN document A/AC.82/G/R.70, Information submitted by Japan, (1957).
12. U N document A/AC.82/G/R.81, Information submitted by Argentina, (1957).
13. Libby, W. F., Science, 122,57 (1955).
14. Hultqvist, B., in UN document A/AC.82/G/R.l5.
Also published in Kungl. Svenska Vetenskapsakademiens Handlingar, Vol. 6, Ser. 4, No. 3 ( 1956).
15. Kerr, P. F., International Conference on PeacefulUses of Atomic Energy, Geneva, 6,s-59 (1955).
16. Faul, H. (Editor), Nuclear geology, New York,(1954).
17. HultGist, B., Kungl. Svenska Vetenskapsakademiens Handlingar, Vol. 6, Ser. 4, No. 3 (1956).
18. Rankama, K. and Sahama, T. C., Geochemistry.
University of Chicago Press (1950).
19. Hikschfelder, J. O., Magee, J. L. and Hull, M. H.,
Phps. Rev. 73, 852 (1948) ; Holmes. A. Radioactivitat und geologie. Verhandl. Naturforsch. Ges.,
Basel. XLI, pp. 136-185 (1930).
20. Kaye. G. and Laby, T. H., Phys. and Chem. Constants, Longmans Green Co., N.Y.. (1948).
21. Leipunsky. 0. I.. Atomic Energy. 12 Val. 111, p.
530, (1957).
22. Cowan. F. P., Everyday radiation, Physics Today
5, KO. 1010 (1952).
23. UN document A/AC.82/G/R.55, Lowder, W. M.,
and Solon, L. R.. Background radiation, p. 13.

21. UN document A/AC.82/G/R.lj, Sievert, R. M.,
Measurements of low-level radioactivity, pa_rticulady the -1 radiation from living subjects, (1936).
25. U N document L4/AC.82/G/R.95, Lough, S. Allan,
Deputy Director, The radium content of soil, water,iood and hurnms. Reported values, ( 1957).
26. U N document A/AC.82/G/R.39, Information submitted by the USSR, Content of natural radioactive
su6stances in the atmosphere and in water in the
territory of the USSR, (1956).
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H. J., Brit. J. Radiobiology, Suppl. No. 7 (1957).
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Electr. et bled. Nuclhaire (in press).
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H. D., Blatz, M. and Eisenbud, M., External environmental radiation in U.S.A., U.S.A.E.C. Healthand Safety Laboratory, N.Y. (1958).
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38. Rafter, T. A. and Fergusson, G. J., N.Z.J. Scienceand Tech. B38,871 (1957).
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Leipzig, ( 1934). Cf. R. Nuhleisen :Atmospharische
Elektrizitat. Handbuck der Physik, Vol. 48 ( 1957).
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N.S. 29,175 (1956).
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43. U N document A/-AC.82/G/R 166 (1958). Bharatwal, D. S. and Vaze, G. H., Ileasurernents on theradiation fields in the monazite areas of Kerala inIndia.
44. Sievert, R. M., Intern. Conf. Peaceful Uses ofAtomic Energy, Geneva 13, 187 (1956) and UN
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Bio-assay and Anal. Chem. Meeting. National Lead
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Geneva 1 1 , 4 9 ( 1956).
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XXVI, No. 306 ( 1953).
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M.,
50. U N ddcument A / A c ; ~ ~ / G / R . ~ ~Hindmarsh,
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Appendix

LIST O F SCIENTIFIC EXPERTS
The scientific experts who have taken part in the preparation of the report while attending Committee sessions
as members of national delegations are listed below. The Committee must also express its appreciation to the many
individual scientists not directly connected with national delegations whose voluntary co-operation and good willcontributed in no small measure to the preparation of the report.
ARGENTINA:
Dr. C. Nuiiez (Representative)
Dr. D. J . Beninson
Professor E. Favret
Dr. N. Nussis
Dr. J. A. Olarte
AUSTRALIA:
Dr. C. F. Eddy (Representative-first
Mr. D. J . Stevens (Representative)
Dr. A. R W. Wilson

Dr. A. Halawani (Representative)
Dr. H. T. Daw

session)BELGIUM:
Professor Z. Bacq (Representative)
Mr. R. Boulenger
Dr. M. Errera
Professor F. Twisselman
BRAZIL:
Professor C. Chagas (Repesetrtative)
Dr. B. Gross
Professor N. Libanio
Professor C. Pavan
Father F. X. Roser, S.J.
CANADA:
Dr. E. A, Watkinson (Representative)
Dr. R. K . Appleyard
Dr. P. M. Bird
Dr. W. E. Gnunmitt
Dr. Colin Hunter
Dr. G. H. Josie
Dr. C. A. Mawson
Dr. H. B. Newcombe
Dr. F. D. Sowby
CZECHOSLOVAKIA:
Professor F. Hertik (Representative)
Professor F. BEhounek
Dr. M. HaSek
Dr. L. Novik
Professor V. Sobek
Dr. I. Ulehla
Dr. V. Zelenf

Professor L. Bugnard (Representative)
Dr. A. Allisy
Dr. J. Coursaget
Dr. H. Jammet
Dr. J. Labeyrie
Dr. J. Lejeune

INDIA:
Dr. V. R. Khanolkar (Representative)
Dr. A. R. Gopal-Ayengar
Dr. A. S. Rao
JAPAN :

Dr. M. Tsuzuki (Representative)
Dr. Y. Hiyama
Dr. D. Moriwaki
Dr. K. Murati
Dr. M. Nakaidzumi
Mr. S. Ohta
Dr. N. Saito
Dr. E. Tajima
MEXICO:
Dr. M. Martinez Baez (Representative)
Dr. F. A. Andrade
Dr. H. Zalce

Professor R. M. Sievert (Representative)
Dr. B. A. A. Aler
Dr. R. G. Bjarnerstedt
Professor G. Bonnier
Professor T. 0. Caspersson
Professor C. A. T. Gustafsson
Dr. A. G. A. Nelson* Now in the United Arab Republic.

UNIONOF SOVIETSOCIALISTREPUBLICS:
Professor A. V. Lebedinsky (Representative)
Professor K. K. Aglintsev
Professor B. M. Isaev
Professor P. M. Kireev
Professor A. N. KraevsLy
Professor A. bZ. Kuzin

UNITEDKXNGDOM
OF GREATBRITAINAND
NORTHERNIRELAND
Professor W. V. Mayneord (Represetltativefirst session)
Dr. E. E. Pochin (Represelztative)
Dr. T. C . Carter
Mr. A. C. Chamberlain
Dr. W. G. Marley
Mr. N. G. Stewart

Dr. Shields Warren (Represe~rtative)
Professor G. W. Beadle
Dr. A. M. Brues
Professor J. Crow
Professor Th. Dobzhansky
Dr. C. L. Dunham
Mr. Merril Eisenbud
Professor Sterling Emerson
Professor G. Failla
Dr. J. H. Harley
Dr. J. S. Laughlin
Professor J. V. Nee1
Dr. M. Zelle