SOURCES, EFFECTS
AND RISKSOF IONIZING RADIATION
United Nations Scientific Committee on the Effectsof Atomic Radiation
1988 Report to the General Assembly, with annexes

UNITED NATIONSNew York, 1988

NOTE
The report of the Committee without its annexes appears as Official Records of theGeneral Assembly, Forty-third Session, Supplement No. 45 (A/43/45).
The designations employed and the presentation of material in this publication d o
not imply the expression of any opinion whatsoever on the part of the Secretariat of theUnited Nations concerning the legal status of any country, territory, city or area. or of its
authorities, or concerning the delimitation of its frontiers o r boundaries.

UNITED NATIONS PUBLICATION
Sales No. E.88.IX.7
ISBN 92-1- 142143-8
09000PANNEX A
Exposures from natural sources of radiation

CONTENTSParagraphs

Paragraphs

INTRODUCTION .......................
I . NATURAL SOURCES O F RADIATION .............................

. Cosmic rays ....................

7-82(c) Distribution of doses ....
(d) Elevated exposures ......
2. Internal irradiation ..........

13-25
14-24
15-17
18-19
20-21
22-24
25

B . Terrestrial sources of radiation
1. External irradiation ..........
(a) Exposure outdoors ......
(b) Exposure indoors .......
(c) Annual effective dose equivalents from gamma terrestrial radiation ........
2. Internal irradiation ..........
(a) Potassium-40 ...........
(b) Rubidium-87 ...........
(c) Uranium-238 series ......
(d) Thorium-232 series ......

....

26-80

C. Summary ......................

81-82

A

1

. External irradiation ..........
(a) Ionizing component .....
(b) Neutron component .....

I1. RADON-222 AND ITS SHORT-LIVEDDECAY PRODUCTS ...............

. Outdoor concentrations ...........
B. Indoor concentrations ...........
1. Sources of indoor radon ......
(a) Underlying soil .........
(b) Building materials .......
(c) Outdoor air ............
(d) Water .................
(e) Natural gas ............
(f) Summary ..............
2 . Indoor behaviour of radon andradon daughters .............
A(a) Radon .................

(b) Radon decay products ...

128-138

C . Exposure-dose relationships .......
I . lnhalation ..................
(a) Relationships from the
UNSCEAR 1982 Report(b) Consideration of otherinformation(c) Conclusion .............
2. Ingestion ...................
3. Summary ..................

142-162
142-159

1-6

3. Results of indoor surveys ..... 139- 14 1............ 150- 158

DA. Energy production from coal ......
................

I . Coal mining
2. Use of coal .................
(a) Coal-fired power plants(b) Domestic use(c) Coke ovens
3. Use of fuel ash
4 . Summary ..................

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

85-93

159
160-161
162. Doses ......................... 163-169

111. INDUSTRIAL ACTIVITIES .........

83-169142-149..........

B . Other energy production
I . Geothermal energy ..........
2. Oil-fired power plants
3. Natural gas .................
4 . Peat
5 . Summary........
........................
..................
C . Use of phosphate rock ............
1. Effluent discharges during phos-...

phate industrial operations
2. Use of phosphate fertilizers ...
3 . Use of by-products and wastes
4 . Summary..................

D. Non-uranium ore mining and pro-........................
.........

cessing
1 . Occupational exposures from
non-uranium mining

Paragraphs

Paragraphs(d) Copper ore mining andprocessing ............. 269-271(e) Lead ore processing ..... 272-273(f) Other metal and non-metal
274
mining ................

2. Occupational exposures fromfactory processes ............
(a) Processing of raw ilmenite(b) Industrial use of zircon
sand ..................
3. Exposures of members of the
public .................
(a) Zinc mining and processing.. .................
(b) Fireclay mine and refractory plant.. ............
(c) Aluminium ore processing

255-260256
257-260264
265-268

1. The major contribution t o the various radiation
exposures received by mankind comes from natural
sources. These include external sources, such ascosmic rays and radioactive substances in the grounda n d in building materials, and internal sources resulting from the inhalation and ingestion of naturally
occurring substances in air and diet. One characteristicof natural irradiation is that it has been experienced
by the whole population of the world at a relatively
constant rate over a long period of time.

2. Exposures from natural sources of radiation havebeen reviewed by the Committee in its 1958. 1962,
1966, 1972. 1977 and 1982 Reports. Since such
exposures d o not. to a large extent,vary with time, thechanges in the estimates of doses in successive Reports
have reflected greater knowledge in the field of naturalradiation, including wider surveys of the levels ofradioactive materials in the environment and in
human tissues, as well as changes in the dosimetricmodels and quantities used.

3. The Committee has repeatedly reviewed the exposures from natural sources of radiation for anumber of reasons including: (a) natural backgroundradiation represents a substantial fraction of the total
radiation exposure of most individuals and is generally
the most important source of radiation; (b) the
knowledge of the doses from natural background isnecessary as a basis for comparison with man-madesources of exposure: (c) some exposures vary substantially according to human practices and some of [benatural sources of radiation may be easily controllable; and (d) outing to the large variability of doses
from natural sources of radiation, some individual
doses may be high enough to warrant the introductionof remedial measures.
The purpose of this Annex is t o update information on exposures to all sources of natural radiation.
The range of activity concentrations of natural radionuclides and the range of exposures of people can bevery wide. The discussion in this Annex is focused on
the exposures associated with the higher portions of
the observed distribution, i.e.. with elevated levels ofradiation or of radioactive materials. These can

275-276Pages

262-263

Introduction

4.

IV. SUMMARY .......................

261 -274

Tobles .................................

95..............................

123

References

sometimes be identified in a comparison with theworld average value of the parameter being considered.
for example. a comparison of the external dose ratefrom cosmic radiation at a high altitude with theaverage at sea level; in some instances it may be more
appropriate to consider the average for a country o r
geographical region; for example, radon concentrations in air indoors in a part of a country comparedwith the average for that country.
5. Both occupational exposures and exposures ofmembers of the public are considered. Not consideredis any type of exposure arising from a technologicalactivity expressly designed to make use of the nuclear
or radioactive properties of a substance, such a s
exposures t o consumer products containing naturally
occurring radionuclides or exposures due to uranium
mining and milling. The latter, however. are dealt within Annex B, "Exposures from nuclear power production".

6 . The first chapter presents an overview of thenatural sources of radiation and indicates the changes
that have been made since the UNSCEAR 1982
Report. Chapter I1 presents a discussion of the doses
resulting from the inhalation of radon and its decay
products, which constitute the most important exposure
from natural sources of radiation. In chapter 111,
exposures resulting from industrial activities are considered in depth.

I.

NATURAL SOURCES OF RADIATIOK

7. Natural radiation sources are classified into two
categories: (a) External sources of extraterrestrial
origin, i.e., cosmic radiation, and radiation of terrestrial
origin, i.e.. the radioactive nuclides present in thecrust of the earth, in building materials and in air;(b) Internal sources, comprising the naturally occurring
radionuclides that are taken into the human body.

8. Table 1 summarizes the contributions of natural
sources t o the radiation exposure of human populations living in areas of normal radiation background.
The mean annual effective dose equivalent is estimatedto be 2.4 mSv. This refers to exposures of adults in the
populations.

9. Some of the contributions to the total exDosure tonatural radiation background are quite constant inspace and time and practically independent of humanpractices and activities. This is true for doses fromingestion of 'OK. which is homeostatically controlled,
and for doses from inhalation and ingestion ofcosmogenic radionuclides, as such radioactive materials are to a first approximation homogeneously
distributed over the surface of the globe. At the otherend of the spectrum are exposures that depend
strongly on human activities and practices and present
a wide variability. Doses from indoor inhalation ofradon and thoron decay products are typical: building
design and practices. as well as the choice of building
materials and of ventilation systems, influence indoor
levels, thus implying a variation with time of the doses
from radon as the techniques and practices evolve.
Variability from one dwelling to another also stems
from the wide range of radon entry rates from soil,
which are to a large extent still unpredictable. In
between those extreme types of exposures are several
other types: (a) external doses from cosmic rays
which, though affected by human practices and quite
predictable, cannot be controlled except by moving toa n area with a lower dose level; (b) doses frominhalation and ingestion of long-lived nuclides of the
23sU and ?"Th decay series, which represent a small
contribution to the total dose from natural sources
and which are relatively constant in space: (c) doses
from external irradiation by terrestrial sources, which
are also significantly altered by human activities andpractices, especially through indoor exposure. Suchdoses, however. are, as a rule, smaller than those frominhalation of radon decay products and much lessvariable.

10. In comparison to the estimates given in the
UNSCEAR 1982 Report. several changes have beenmade: ( a ) with respect to external exposures to cosmic
radiation, the new estimates of the annual effective
dose equivalents take into account the geographicaldistribution of the world population as a function ofaltitude and the shielding effect of building materials.
As a result. the new estimates of the annual effective
dose equivalents due to the ionizing and neutroncomponents are higher by 20 /IS\. and 30 pSv. respectively; (b) regarding external exposure to terrestrial
sources of radiation, the annual effective dose equivalents hat'e been re-evaluated and increased by
60pSv. as a result of better knowledge of the indoor
gamma absorbed doses in air; (c) annual effective dose
equivalents from internal exposure to primordialradionuclides have been reassessed slightly downwards
for the "'U and ?l0Pb series, as well as for the decay
products of ??ORn, whereas those for the short-lived
decay products of ?::Rn have been increased by about
300 pSv on the basis of more comprehensive results of'nation-wide indoor surveys. The net effect of these
corrections is a 20% increase in the estimate of theoverall annual effective dose equivalent from natural
sources of radiation. The various contributions to theannual effective dose equivalent are discussed in moredetail in this chapter. As in the previous reports of theCommittee, the estimates of exposures from natural
sources of radiation are essentially based on measurements in temperate latitudes, and o n dietary and living

habits also of the populations in these regions. It is
recognized that exposures to populations in tropicallatitudes may differ substantially from those in temperate latitudes, because of differences in environmental concentrations, and also in living and dietary
habits. An effort has been made to estimate theexposures to populations in tropical latitudes, but thedata base available is too small to enable a good
assessment to be made.
11. Table 1 shows clearly the magnitude of theinhalation of IZZRnand its short-lived decay products,
a topic discussed extensively in chapter 11.
12. Esposures resulting from industrial activities thatbring to the surface of the earth, or make available tothe public, materials with enhanced concentrations of
naturally occurring radionuclides do not significantly
alter the picture presented in Table 1. These exposures,
which may to a large extent be controlled, are dealt
uith in chapter 111.
A.

COSMIC RAYS

13. The high-energy radiation that enters the earth's
atmosphere from outer space is known as primarycosmic rays. Upon interaction with the nuclei ofatoms present in the air, neutrons, protons, pions a n dkaons (secondary cosmic rays) are produced, as well
as a variety of reaction products (cosmogenic nuclides)
such as 'H. 'Be, I0Be, I4C, 22Naand 24Na. The highenergy secondary cosmic rays thus formed react
further with nuclei in the air to form more secondary
particles (electrons and muons).

1. External irradiation

14. The doses from directly ionizing components ofcosmic rays and from neutrons are examined separately.

(a) Ionizing componen 1
15. In the lower atmosphere. the dose rates in air
due to the ionizing component vary little with latitude
but significantly with altitude. doubling approximately
every 1.500 metres. Figure I shows the variation ofabsorbed dose rates in air, as derived from ionizationchamber measurements aboard aircraft. for low andhigh latitudes and altitudes ranging from 0 to 12 km[HlO]. Dose rates in air are about 30 nGy h-' at sea
level for any latitude and increase to about 4 p G y h-'
at an altitude of 12 km and high latitudes [H 101.

16. The majority of the world's population lives ataltitudes close to sea level. In the UNSCEAR 1982
Report (Annex B, paragraph lo), the absorbed dose
rate in outdoor air from the ionizing component ofcosmic rays was estimated to be 32 nGy h-'; this value
is taken to be numerically equal to the effective dose
equivalent. Indoors, the doses are somewhat lower
because of the shielding effect of building structures.
Dose rates measured at the centre of various le\uels ofdecreased more slowly with depth. These measurements. however, which were made in a massivebuilding. are not representative of the average situation. A shielding factor of about 0.85 has beenreported in the case of a 0.2 m thick concrete layer[L6]. In the Netherlands, the following shielding
factors for cosmic rays were determined [J17]: 0.82 forsingle homes with wooden ceilings: 0.76 for row
houses and office buildings with wooden ceilings andfloors: 0.50 for dwellings of any kind with concrete
ceilings and floors; 0.42 for apartment buildings.
Somewhat higher values, varying according to thefloor number, were obtained in the Soviet Union[FIO]: 0.81-0.96 in wooden houses; 0.72-0.92 in oldstone buildings; 0.54-0.86 in modern buildings. A
mean shielding factor of 0.8 is assumed in this Annex.
The average indoor absorbed dose index rate at sea
level is thus estimated to be about 26 nGy h-'.

5000-

2000-

1000-

500

-

200

A - High latitudes

100

-

50

-

30

0

B - Low

I

I

I

3

6

9

latitudes

I

12

I

I

15

18

ALTITUDE (km)Figure I.

Absorbed dose rates In air as a function of altitude
and geomagnetic latitude.
[HI01

a 12-storey building showed a fairly smooth declinewith depth, i.e., from the top storey down to thebasement of the building (Table 2) [M9]. The marked
change from the roof to the twelfth floor (65%'transmission) was because of the filtering out of therelatively soft component of the cosmic-ray flux at sea
level. The value of the remaining hard component

17. Using a value of one for the quality factor of theionizing component of cosmic rays and an indoor
occupancy factor of 0.8, the annual effective dose
equivalent is estimated to be about 240pSv at sea
level. The doses received by populations living above
sea level are higher: they are discussed later in thissection.
(6)

Neutron component

18. The variation with altitude and latitude of theneutron component is similar to that of the ionizing
component (see Figure 11). At sea level. the neutron
fluence rate is about 0.008 cm-' s-I [HIO, H 1 I]. On
the basis of measurements of neutron energy spectra
carried out in New York City in 1986 during a sismonth experiment, Hajnal [H 151 calculated an averageabsorbed dose rate of 0.8 nGy h-' and a dose equivalent rate of 3 nSv h-' for neutrons incident isotropi-

1 ----

Total

Charged particles--......Neutrons

0

' 1

2

3

4

5

6

ALTITUDE (km)Figure II. Varlatlon of the annual eftective dore equivalent from the ionizing
component and the neutron component of cosmic mdlatlon as a function of altitude.
( B a d on [B38])

cally on both sides of a 30 cm thick tissue-equivalentslab. This translates into a quality factor of 3.8. In
Japan. Nakamura et al. [N20] also derived frommeasured neutron energy spectra a dose equivalent
rate of 3.3 nSv h-l. which is an overestimate of theeffective dose equivalent rate, as it was determinedusing the conversion factors from flux density tomaximum dose equivalent given in ICRP Publication
21 [I 141. Nakamura et al. [N20] also indicated that thecalculated spectra of O'Brien led to values of 2.2 nSv h-'a t the surface of a 30 cm body phantom and of
1.4 nSv h-' on average over the phantom. Thesefigures are consistent with the estimate of 2.4 nSv h-I
that was used in the UNSCEAR 1982 Report andreflect the variability associated with the choice ofgeometry used t o calculate the effective dose equivalent. Neglecting the shielding effect of building
structures, the annual effective dose equivalent for theneutron component is estimated to be about 20 pSv at
sea level.
19. On the basis of radiobiological considerations,the ICRP issued in 1985 an interim recommendationaccording to which the value of the quality factor forneutrons was to be increased by a factor of 2 [I12].
This recommendation, however, has not been followed
in most countries and has not been confirmed by the
ICRP. The value of the quality factor for neutrons has
not been modified in this report.
(c)Disrriburion of doses

20. The distribution of the effective dose equivalentfrom cosmic radiation over the globe was estimated by
Bouville and Lowder [B38] using tabulated data on
terrain heights on a 1" by l o grid [G22], combinedwith population data [UT]. On the basis of information
in [L14]. [03], [N20] and [H15], the variation of theannual effective dose equivalent from the ionizing

component H,, in pSv, as a function of altitude z (km)was expressed as
k , ( z ) = ~ ~ ([0.2050 ) exp (-1.6492) +0.795 exp (+0.45282)](1.1)
and, for the neutron component H ~as.
H,(z) = ~ ~ (exp0 (1.042))(1.2)

for z < 2 km, and as
H,(z) = ~ ~ (r1.98
0 )exp (0.698z)I(1.3)

for z > 2 km. The value used in [B38]for ~ ~ (is 0similar)
to the figure of 240 pSv a-ladopted in this Annex, whilethe value for H,(o) is the same.
21. For the purpose of this Annex. the distribution of
the effective dose equivalent from cosmic radiation overthe globe was recalculated. using the annual sea-level
effective dose equivalents of 240pSv for the ionizing
component and 20pSv for the neutron component.
~ i ~ I1~showsr e th; variation of the annual effective
dose equivalent with altitude obtained from equations(1.1), (1.2) and (1.3). It is worth noting that the dose
equivalent from the neutron component, which is small
at sea level. increases more rapidly than the dose
equivalent from the ionizing component and becomes
more important at altitudes above 6 km. The distribution of the collective effective dose equivalent as afunction of altitude. presented in Figure 111, indicatesthat although about one half of the collective dose
equivalent is received by people living at altitudes below
0.5 km, a contribution to the collective dose equivalentof about 10% is received by populations living ataltitudes above 3 km. There are large countries withmountains and sea borders, like the Soviet Union andthe United States, where the population-weighted dosefrom cosmic rays differs only slightly from the dose at
sea level because the bulk of the population in each of

ALTITUDE (km)Figure Ill.

Dlrtrlbutlon of the collective etfectlve dose equivalent from cormlc
radlatlon as a functlon of altltude.
(Based on [B38])

those countries lives at low altitudes [FIO, 0121. In
countries like Ethiopia, Islamic Republic of Iran,
Kenya or Mexico, however, large cities are situated onelevated plateaux, accounting for relatively high exposures. Figure IV presents the distribution of thecollective dose equivalent and the variation of the percaput dose equivalent as a function of latitude. The
population of the northern hemisphere accounts forabout 90% of the total collective effective dose equivalent. The per caput effective dose equivalent for theworld's population is found to be 355pSv, the ionizing
and neutron components contributing about 300 and
55 pSv, respectively.
(d) Elevaled exposures
22. Elevated exposures result from prolonged presence
at high altitudes. Populations living in high-altitudecities like Bogoti, Lhasa or Quito receive annual
effective dose equivalents from cosmic radiation inexcess of 1 mSv. Passengers and crew members aboard
commercial aircraft are exposed to much higher dose
rates. which vary according to the flight altitude and, toa smaller extent. the latitude and solar activity.
Assuming that the average altitude of commercial
subsonic flights is 8 km, the average dose equivalent ratewould be about 2pSv h -' from equations (1.1) and(1.3). the neutron component contributingabout 60% of
the total. Taking the annual number of hours spent
flying by crew members to be 600 h, the corresponding
annual effective dose equivalent is about 1 mSv. A small
fraction of commercial transport is conducted withsupersonic aircraft, which fly at an altitude of about
15 km. Dose equivalent rates received during supersonictransport have been reported to be about 1 1 pSv h-' on
average for French aeroplanes [S64] and about 9pSv h-'

on average for British aeroplanes, with a maximum ofaround 40pSv h-' [P14]. Annual dose equivalents
received by the technical and cabin crew for the period
1979-1983 were on average about 2.5 mSv. withpossible maxima of I5 mSv [P14]. For a given flight.
doses received by passengers are about the same as insubsonic flights since the higher dose rates incurred
during a supersonic flight are compensated for by theshorter travel time.
23. Using statistical data on air transportation, thecollective dose equivalents incurred by the passenger
and flight personnel of civil aviation may be estimated.
The number of passenger kilometres flown in 1984.
excluding Chinese airlines, was 1.3 lo'? [I1 51. Assuming
an average speed of 600 km h-' at an altitude of 8 km
and an effective dose equivalent rate of 2pSv h-I atthat altitude, the annual collective dose equivalent isfound to be 4.300 man Sv. Published estimates [Vl,W17] are 3.500 man Sv for the world population andno more than 1.600 man Sv for flights in the UnitedStates, while the collective dose equivalent to the flightcrews would be up to 65 man Sv. Taking the ratio of
the annual collective dose equivalent to the passengers
and to the flight crews in the United States as a guide.
the annual collective dose equivalent for the flightcrews of the world would be about 170 man Sv.
24. While travelling in space. astronauts are subjected
to primary cosmic-ray particles, radiation from solar
flares and the intense radiation present in the tworadiation belts. Radiation doses received by astronauts
represent one of the most important constraints tolong-term manned space activities [B17]. Reported
dose equivalents (assumed to be effective dose equivalents) to astronauts from recent United States

SOUTH

NORTH

LATITJDE
Figure IV.

Dlslrlbulion of the annual effective dose equivalent from cosmic radlatlon as alunction of latitude.
(Based on [B38])

B.

manned space missions range from 0.5 to 5 mSv[B18]. Similar information is available for Soviet
missions [Vl]. In a majority of cases, individual
effective dose equivalents did not exceed 5 mSv per
flight; however. for prolonged orbital flights, i.e..
those lasting longer than one month. the effective dose
equivalent exceeded 10 mSv and reached 55 mSv forexpedition IV on board Salut-6, which lasted 175 days
rv11.

2.

TERRESTRIAL SOURCES O F RADIATION

26. Terrestrial sources of radiation are the very longlived radionuclides that have existed within the earth
since its formation several billion years ago and havenot substantially decayed. The most important ofthese so-called primordial radionuclides are O' K (halflife = 1.28 lo9 a), "Rb (half-life = 4.7 1010 a). "'U(half-life = 4.47 lo9 a ) and ?':Th (half-life = 1.41 loL0a).
238Uand ?'-Th head series of 14 and 1 1 significant
radionuclides, respectively. (Figures V and VI) that
also contribute to the doses from terrestrial sources.
Other radionuclides, such as those present in the 235U
decay series, have been neglected, as they contributelittle to the total dose from natural background.

Internal irradiation

25. A large number of cosmogenic radionuciides areproduced in the stratosphere and upper troposphereby the interaction of cosmic rays with the nuclei ofatoms present in the air (e.g.. nitrogen. oxygen andargon). The production and distribution of these
nuclides in the environment was reviewed by theCommittee in the UNSCEAR 1977 Report [U?]. Only
four cosmogenic radionuclides ('H, ''C, 'Be and '2Na)
are of importance from the viewpoint of radiation
doses to man. Together they deliver annual doses
from internal irradiation ranging from 5 to 25 p G y in
the various organs and tissues of interest. The annual
effective dose equivalents are estimated to be 0.01 pSv
for 'H, 3 ~ S for
V 'Be, 12 pSv for I4C and 0.2 pSv for"&a. Because of the relative homogeneity of thecosmic-ray flus over the earth's surface, the variabilityof the annual doses from the cosmogenic radionuclides
is expected to be low.

27. The ubiquitous presence of the primordial radionuclides and of their decay products in the environment (air. water, soil, rocks, foodstuffs) and in
humans results in external and internal radiation
doses.
1.

External irradiation(a)E.~posureoutdoors

28. Activity mass concentrations of primordial radionuclides in rocks are usually higher in igneous rocks
than in sedimentary ones, while metamorphic rocks
have concentrations typical of the rocks from which
they are derived. There are. however, exceptions, a st
2 1 8 ~ ~(3.05 min)

214~0

210~o

(22.3 a )(stable)

2148i

a
214~b

206~b

(26.8 m i n )Figure V.

Uranium-238 decay series.

[I101

Figure VI.

Thorium-232 decay series.
rilal

certain sedimentary rocks, notably some shales andphosphate rocks, are highly active. The activity massconcentrations in soil, which are directly relevant tooutdoor exposure, are thought to be largely determinedby the activity mass concentrations in the source rock.
The average activity mass concentrations of 40K, 233U
and Z3ZThin soil and the corresponding absorbed dose
rates in air 1 m above the ground surface are given in
Table 3 [B32]: the calculations are for a soil density of
1.6 g cm-' and a water content of 10% and are basedon the assumption that all decay products of 238Uand
232Thare in radioactive equilibrium with their precursors. The average outdoor terrestrial absorbed dose
rate in air from gamma-radiation I m above theground surface is 44 nGy h-I. The results of a large
soil sampling programme recently carried out in the
United States are in fairly good agreement with theactivity concentrations given in Table 3 [M 101.
29. Large-scale surveys, using different methods andtypes of instrumentation, have been or are being
carried out in a number of countries in order toestimate average nation-wide exposures to outdoor
external gamma-radiation. The results for 23 countries
or areas, representing about one half of the world
population, are summarized in Table 4. Countryaveraged outdoor absorbed dose rates in air are foundto range between 24 and 85 nGy h-I, with an arithmetic mean of 55 nGy h-'.
30. It is to be noted that the two most populated
countries in the world, China and India, have recently
published the results of extensive surveys. In China,
about 40,000 outdoor measurements were carried out

by the Ministry of Public Health from 1981 to 1985,
using sodium iodide crystals and ionization chambersin 21 provinces, five autonomous regions and thecities of Beijing, Tianjin and Shanghai. Detailed
preliminary results are found in a special issue of theChinese Journal of Radiological Medicine and Protection [C19] and a summary has been prepared by
Wang Qiliang et al. [W21]. Population-weighted
means of the absorbed dose rates in air are presented
in Table 5: the value for the country as a whole isreported to be about 80 nGy h-I, which is in the upper
range of the levels observed in the world. These results
led to a large soil-sampling programme that showedthat the average concentrations of 40K, 238Uand 232Th
in soil in China are indeed higher than the estimatesby UNSCEAR of the world averages by a factor of
about 2 [W21]. Independent survey programmes ofoutdoor gamma-radiation have also been undertaken
in China by the National Environmental Protection
Agency [L18] and by the Ministry of Nuclear Industry[G29]. A comparison of the results obtained for thesame areas [P22] shows discrepancies that may havearisen from the energy dependence of the various
types of dosimeters used in the surveys and from theestimation of the cosmic-ray dose rates which weresubtracted from the readings. The average absorbed
dose rates in air in the cities, provinces and autonomous regions investigated by the Ministry of Public
Health [W21] were found to be lower than thosemeasured by the National Environmental Protection
Agency and the Ministry of Nuclear Industry. therelative differences ranging from 11% to 63% [P22].
Since the survey of the Ministry of Public Health isthe only one completed at the time of publication ofthis Annex, its results have been incorporated without
modification; however, it should be kept in mind thatthe gamma doses for China may be revised in the near
future.
31. In India, 214 locations scattered all over thecountry were monitored with thermoluminescent dosimeters. The national mean value of the outdoor
absorbed dose rate in air due to natural radiation(terrestrial sources of radiation and cosmic radiation)is estimated to be 785pGy a-I [N19]. Assuming amean dose rate from cosmic rays of 300 pGy a-I yields
an average absorbed dose rate in air from theterrestrial component of 55 nGy h-I.
32. In the UNSCEAR 1977 Report [U2]. the Committee adopted a value of 50 nGy h-I for the population-weighted average absorbed dose rate in air over
the world and estimated that 95% of the world's
population residing in areas of usual naturai radiation
live where the outdoor absorbed dose rate in air fromthe primordial radionuclides lies between 30 and
70 nGy h-I. As shown in Table 4, the available database is currently much larger than i t was in 1977. The
population-weighted average absorbed dose rate in air
for the countries in Table 4 is 63 nGy h-I. This is
likely to be an overestimate because of the probablebias in the Chinese measurements. When the Chinese
data are not taken into account. the populationweighted average absorbed dose rate in air is reduced
to 53 nGy h-I. An intermediate figure of 55 nGy h-' isadopted in this Annex as the mean absorbed dose rate
in air outdoor from terrestrial sources of radiation.
33. There are regions in the world where the usual
range of variation of outdoor terrestrial radiation
doses is substantially exceeded. The best documentedof those regions are in Brazil and India. In the coastal
areas of Kerala and Tamil Nadu in India, there arepatches of sand containing monazite with thorium
concentrations ranging between 8% and 10.5% byweight. The absorbed dose rates in air in the highradiation areas of Kerala vary between 150 and
1,000 nGy h-I; in Tamil Nadu, these may reach about
6,000 nGy h-I [S69]. I n Brazil, outdoor absorbed dose
rates of 130-1.200, 220-4,200 and 110-1,000 nGy h-'were measured in Guarapari, Meaipe and P o ~ o sde
Caldas, respectively [P24].

(6) Exposure indoors
34. Knowledge of radiation levels in buildings isimportant in the assessment of population exposures,as most individuals spend a large amount of timeindoors. Large-scale surveys of indoor exposures togamma external radiation have recently been conductedin several European countries as well as in China; theresults are summarized in Table 6. An estimation of
the world distribution of exposures may be derived
from the results presented in Table 6 or, as in previous
UNSCEAR Reports. from the indoor-to-outdoor ratios.

35. Estimates of average indoor absorbed dose rates
in air are between 23 and 120 nGy h-', most values
being in the narrow range of 60-95 nGy h-I (Table 6).
The arithmetic mean is about 70 nGy h-'. The popula-tion-weighted mean for all countries except China is
72 nGy h-' and becomes 110 nGy h-I if China is
included.
36. In previous UNSCEAR Reports, use was madeof the indoor-to-outdoor ratio, under the assumptionthat the relationship between the indoor and theoutdoor absorbed dose rates depends essentially on
the type of building materials used and their origin. If
the building materials are of local origin, it may be
expected that the value of the indoor-to-outdoor ratioof the absorbed dose rates in air lies between 1 and 7,.
because of the change in source geometn and thepresence of doors and windows. Calculations taking
into account the thickness and the dimensions of thewalls yield ratios of 1.35 for typical brick dwellingsand 1.48 for concrete buildings [Kl I].
37. Country-averaged indoor-to-outdoor ratios.
derived from the results presented in Tables 4 and 6.
range from 0.8 to 2.0. with an average of 1.3. This
figure, combined with an average outdoor absorbed
dose rate in air of 55 nGy h-I. yields an averageindoor absorbed dose rate in air of 72 nGy h-I, in
close agreement with some of the values obtained by
the first method. In this Annex, the mean indoor
absorbed dose rate in air from terrestrial sources ofradiation is taken to be 70 nGy h-l.
38. Elevated external dose rates indoors may arise
from high concentrations of natural radionuclides inbuilding materials. These building materials may beof natural origin (concrete based on alum shale,
granite, lithoid tuff) or result from industrial processes(phosphogypsum, red mud). As discussed in the
UNSCEAR 1982 Report, the resulting exposures,
calculated with pessimistic assumptions, range between
100 and 2.000 nGy h-I.
(c) Annual effective dose equivalentsfrom gamma terresrrial radiarion

39. The value of the quotient of effective dose
equivalent rate to absorbed dose rate in air is taken, as
in the UNSCEAR 1982 Report. to be 0.7 Sv per Gy forenvironmental exposures to gamma rays of moderateenergy. This value is assumed to apply equally to males
and females and to the indoor and outdoor environments. Taking the outdoor occupancy factor to be 0.2,
the annual effective dose equivalent from outdoor
terrestrial gamma-radiation is found to be
55 (nGy h-I) X 0.7 (Sv Gy-I) X 8,760 (h a-I) x 0.2 =70 pSv
For indoor exposure, using an occupancy factor of 0.8,
the annual effective dose equivalent is
70 (nGy h-') X 0.7 (Sv Gy-') X 8,760 (h a-') X 0.8 =340 pSv
40. The total (outdoor plus indoor) annual effective
dose equivalent from terrestrial radiation, averaged
over the world's population, is 410pSv. Using theinformation presented in Table 3 as a guide, thecontributions of 'OK and the radionuclides of the 238U
and 232Th
decay series to the total annual effective
dose equivalent from gamma terrestrial radiation
would be 150, 100 and 160 pSv, respectively.

2. Internal irradiation
41. Inhalation and ingestion of naturally occurring
radionuclides give rise to internal irradiation. As in
the previous reports of the Committee, the absorbed
doses a n d effective dose equivalents are derived frommeasured tissue concentrations, in so far as such data
are available.
(a)Porassium-40

42. Potassium is an essential element that is underclose homeostatic control in the body. The average
mass concentration for an adult male is about 2 g ofpotassium per kg of body weight [A4, K123. The
isotopic ratio of O
' K is 1.18 lo-' and the average
activity mass concentration of 40Kin the body is about
60 Bq kg-'. The distribution of potassium in various
tissues and organs of the body [Kl2] has been used todetermine the concentrations of 40K in those tissues
a n d organs and the corresponding absorbed dose
rates. The highest annual absorbed dose (270pGy) is
received in red bone marrow and the lowest in the
thyroid (100pGy). The annual effective dose equivalent is estimated to be 180 pSv. The variation of theconcentration of potassium in the entire body reflects
the amount of relatively potassium-free adipose tissue
that is present in lean body mass at different ages: it isfound t o vary between about 1 and 2.5 g kg-'.
(b)

Rubidium-87

43. Very little is known about the behaviour ofrubidium in the environment. Limited measurements
in foodstuffs and humans seem to indicate that thehuman body retains rubidium more s o than potassium[T12]. from the mass concentrations of rubidium
reported on by ICRP [I3]. the average activity massconcentration of 87Rbin the body is 8.5 Bq kg-!. The
assumed distribution of rubidium in various organs
a n d tissues of the body [I31 is used to calculate theresulting absorbed dose rates from R'Rb. Bone lining
cells receive the highest annual dose (14 pGy) and thethyroid the lowest (3 p G y ) The annual effective dose
equivalent is estimated to be about 6 pSv.
,

(c)

Uranium-238 series

44. Uranium-238 is the head of a series of 14
principal nuclides (Figure V). This can be divided into
subseries in which the activity of the precursor
controls to a large degree the activities of the decay
products: 2 3 8 u 234U. 230Th. 226Ra; 222Rn 214po; and'lOPb '''Po. For each subseries. the intakes byinhalation and by ingestion, as well as the concentrations in bone and in soft tissues, are estimated. The
results are presented in Tables 7 and 8. The conversions from the activitv concentrations in bone and insoft tissues to the adsorbed doses are based o n themodels described in ICRP Publication 30 [14]. Estimatesof annual absorbed doses are shown in Table 9. Presented below is a brief discussion of the exposures witha n indication of what new information has become
available since the publication of the UNSCEAR 1982
Report.

-

-

-

(i)

Uranium-238 subseries (23BU,234Th,U4mPa,UIU)

45.

In this Annex, uranium is assumed to consist of"W in radioactive equilibrium with "'Th, 34mPa and
W , SO that 1 kg of uranium contains 12 MBq of eachof the four radionuciides. The contribution of ')'U
and its decay products to the total dose from natural
background has been neglected.
46. In the atmosphere, the main natural source ofuranium, as well as of any other precursor of one of
the radon isotopes, is likely to be the resuspension ofdust particles from the earth [H24, H25. K211. Taking
a dust loading of about 50 p g m-' in surface air of
populated areas and assuming an average 235Uactivity
mass concentration in airborne dust as in soil of
25 Bq kg-' (Table 3), the activity concentration in
ground-level air is estimated to be about 1.2 pBq m-'.
The corresponding annual intake by adults throughinhalation is approximately 0.01 Bq (Table 7). This
result is applicable to all other radionuclides of the'3WUand 232Thseries that are precursors of gaseous"?Rn and 220Rn.
47. The annual dietary intake of 13" has been foundto be about 5 Bq in areas of normal natural activity(based on results from Japan. United Kingdom,
United States). Recent measurements of uranium inthe diet of New York City residents confirm thevalidity of this value [F12]. The contribution ofdrinking water to the total intake by ingestion varies
over a wide range [H26]. According to the results ofan extensive survey carried out in the United States,
involving 90.000 measurements of domestic watersupplies, average concentrations of uranium in groundwater, for a given state, are only slightly higher (up toa factor of 4) than in surface water. and the ratio of
the activity concentration of Z34Uto that of Z3sU
usually ranges between 1 and 3, with an average valueof 1.9 [DIO, H20, H211. It can be estimated from thatsurvey that the population-averaged '38U concentrations in domestic water supplies range from 0.1 Bq m-'
in several eastern states to 50 Bq m-' in a number ofwestern states, the nation-wide average in ground-watersupplies being 25 Bq m-3 [DlO, H211. Uranium-238
concentrations in European mineral water are similar
to those observed in United States ground water. withmedian values of 12 Bq m-' for France and 24 Bq m-'
for the Federal Republic of Germany. If the average
daily consumption of drinking water is taken to be 0.5
litre, the average annual intake from drinking watercontaining 25 Bq of 23mUper m3 is about 5 Bq, whichis the same value as that found for the intake fromfoodstuffs. This is an example of higher intake;however, the mean intake of uranium through ingestionof water is generally likely to be small in comparison
with the mean dietary intake.
48. Measured values of the activity mass concentration of Z38Uin bone of adults who have lived in areas
with normal dietary levels are currently more abundant[F13, F16, F18, Wig]; they lie in the range of
5-150 mBq kg-' of 23aUin dry bone. Analyses of thiswider data base indicates that a better value of theaverage activity mass concentration is 50 mBq kg-',
which is lower by a factor of 3 than the previous

estimate by the Committee. The activity mass concentrations of 2'8U in soft tissues (Table 8) are muchsmaller, with the exception of the lungs, and previously
measured high values in kidneys have not been
confirmed [ F 16. W 191. The estimated annual absorbed
doses from the 13'U subseries are up to about I jiGy inbone lining cells (Table 9): the corresponding annual
effective dose equivalent is 5 pSv.
(ii)

centrations in bottled mineral water from European
countries range up to 1,800 Bq m-' and have geometric means of 7, 44, 25 and 25 Bq m-' in Italy,
France, Austria and the Federal Republic of Germany.
respectively [F17, G27. M28, R8]. In the UnitedStates, the reported geometric mean of the "6Ra
concentration in public water supplies is 22 Bq m-'.
This leads to a n annual intake of 4 Bq. if a water
consumption rate of 0.5 litre per day is assumed.

Thorium-230

49. The activity intake of 130Th through inhalation.
estimated in the same manner as that of 23eU,is about
0.01 Bq a-'. The dietary intake of *jOTh has beenmeasured in the United States for the first time; it isabout 2 Bq a - ' [F12]. It can be derived from thesevalues and ICRP models [I41 that inhalation accounts
for about three quarters of the total uptake to theblood of " O n .
50. Thorium is a bone seeker having a long residence
time in the skeleton and is assumed to remain on thebone surfaces [I4]. The distribution of 230Thin humantissues has been investigated by Wrenn and his
collaborators [I3. S22, S55, W9]. A typical activity of"OTh in bone is 140 mBq, resulting in activity massconcentrations of approximately 20 mBq kg-' in dry
cortical bone and 70 mBq kg-' in dry trabecular bone,
assuming that the deposit of thorium is proportional tothe bone area. In soft tissues, representative values of theactivity mass concentrations could be 300 mBq kg-' inlymph nodes, 20 mBq kg-' in the lungs, 10 mBq kg-'in kidneys, 7 mBq kg-' in liver and 0.3 mBq kg ! inother soft tissues. The corresponding annual absorbed
doses (Table 9) range from 7 nGy to 7 p G y . dependingo n the organ o r tissue considered. The annual effective
dose equivalent is estimated to be about 7 pSv.
51. The doses in bone marrow and bone lining cells,
as well as the effective dose equivalent, would besignificantly lower if the activity of 230Th were
distributed uniformly over the mass of the skeleton
instead of being concentrated on the bone surfaces.
The activity mass concentration of Z30Thwould thenbe about 30 mBq kg-' in dry trabecular and corticalbone, while the calculated annual doses in bonemarrow and bone lining cells would be 0.02 and
0.4 pGy. respectively, instead of 0.56 and 7.4 pGy (seeTable 9). The annual effective dose equivalent would
be reduced from 7 t o 2 pSv.
(iii) Radium-226
52. Food is a much more important source ofradium for intake and blood uptake than is inhalation.
The Committee's previous estimate of the averageannual dietary intake of 226Ra in areas of normal
radiation background of 15 Bq has been recently
confirmed in the USSR [Dl 11 and the United Kingdom [S56] and is to be compared with 0.01 Bq for
inhalation. The contribution of drinking water t o thetotal intake is generally small when the drinking-watersupplies are drawn from surface water: however. inground-water supplies, which in many countries servea large portion of the population, 226Raconcentrations
vary widely and levels in excess of 200 Bq m-' are notuncommon (see, for example, [C18] and [H20]). Con-

53. When radium is taken into the body. its metabolic
behaviour is similar to that of calcium, and an
appreciable fraction is deposited in bone [ES]. Morethan 70% of the radium in the body is contained inbone [I5,S571. the remaining fraction being distributed
rather uniformly in soft tissues. Fisenne et al. [F4] havesummarized the available data from 26 countries o nmeasured activity mass concentrations of 226Ra in
human bone. The 26 countries sampled have 1.4 10' persons and thus represent about 30% of the world population. The population-weighted distribution was foundto have a median of 850 mBq per kg of calcium(corresponding to 170 mBq per kg of dry bone a n d t o
850 mBq in the skeleton) and a geometric standard
deviation of 1.6. If the fraction of "6Ra distributed in thesoft tissues is taken to be 17%. as given in ICRPpublication 20 [I5], the average activity mass concentration inhuman soft tissues is found to be 2.7 mBq kg-'.
54. The annual absorbed doses in tissues have been
calculated assuming that an average retention factorof 0.33 applies t o 222Rnin the skeleton (and also.
conservatively, in soft tissues) and that the concentration of radium and its decay products is uniform over
the total mass of mineral bone. The results, presented
in Table 9, show average annual absorbed doses ofless than I p G y in all organs and tissues, with the
exception of bone lining cells. The annual effective
dose equivalent resulting from Iz6Ra intake in normal
areas is found to be about 7 pSv.
55. Food samples grown in the high-radiation areasof India have been collected and analysed for several
radionuclides. including Iz6Ra. The 'I6Ra concentrations were found to be higher in leafy and root
vegetables than in fruits and fruit vegetables. T h eannual intake of 226Raby populations living in thehigh background areas was assessed to be about
200 Bq [L19]. A similar survey performed in the
Araxa-Tapira region of Brazil showed that the annual
226Ra intakes of the most exposed people ranged
between 140 and 540 Bq [P25]. The corresponding
annual effective dose equivalents are between 65 a n d
250 pSv.
(iv) Radon-222 and its short-lived decay products(218Po,214Pb,214Bi,2 1 r P ~ )56. Because of the current scientific interest in radon
exposure, a detailed treatment is provided in chapter
11.
57. Average annual intakes, activity mass concentrations in lung tissues and absorbed doses are presented
in Tables 7, 8 and 9, respectively. The resulting annual
effective dose equivalents are estimated t o be, onaverage, 70 pSv for outdoor exposure and 1,000 pSv
for indoor exposure. The variability around these
average figures is very high.
(V)~ o n ~ - l i v edecaydproducrs of radon-222 (2'0Pb,
zlog;, 210P0)

58. Radon-222 exhalation from the ground constitutes the main source of 210Pbin the atmosphere. With
respect to 210Po,the volcanic output has been estimatedto be about as important as lZZRnexhalation [LIO]. In
the mid-latitudes of the northern hemisphere, theaverage concentration of 210Pb in surface air is
0.5 mBq m-', while that of ""Po is about 0.04 mBq m-',as shown in Table 10; this is lower than the value
adopted in the UNSCEAR 1982 Report by a factor of
2.5. Assuming that the concentrations in air are thesame indoors and outdoors. the annual intakes of
non-smokers through inhalation would be 4 Bq of
210Pband 0.3 Bq of 210Po.Cigarette smoking leads toan increase in the intake of llOPb and Z1OPo[M 13, P9].
-4 cigarette contains about 20 mBq of 210Pb and
15 mBq of "OPo [P9] and both nuclides are volatile atthe burning temperature of tobacco. About 10% of the?I0Pband 20% of the "OPo contained in the cigarette
will enter the lungs with the main smoke stream [P9].
Therefore. for a person smoking 20 cigarettes a day,the values of the estimated annual intakes are 15 Bq
for 210Pband 20 Bq for llOPo. In view of the shorthalf-life of 'I0Bi (5.01 d), its activity intakes are of noimportance, as *I0Bi may be assumed to be inradioactive equilibrium with lI0Pb in the body tissues;
the absorbed doses from lI0Bi arise mainly from theintake of 'I0Pb and not from the intake of ?I0Biitself.
59. Consumption of food is usually the most important route by which ?'OPb and 'loPo enter the humanbody. Concentrations of ?I0Pb and "OPo are usually
low in meat and milk, intermediate in cereals andvegetables, and relatively high in aquatic organisms.
Annual intakes reflect the composition of the diet ofthe population in question and are approximately
20 Bq in the United States [H13. H141, 30 Bq in the
United Kingdom [S56], about 40 Bq in the Federal
Republic of Germany [G17], the USSR [L9], India[L13] and Italy [C12], and about 200 Bq in Japan [07,T53. More recent data from Japan, however, seem toindicate a much lower annual intake of 11 Bq [K18].
Concentrations of 210Pbin drinking water are generally
low [H20, (3271 and do not usually contributesignificantly to the total intake by ingestion.
60. A well-documented case of elevated intake is thatof the tens of thousands of individuals living on
reindeer or caribou meat in the Arctic and sub-Arctic
regions of the northern hemisphere. Their main foodis the meat of these animals, which contains unusuallyhigh concentrations of llOPo because in the winter the
animals graze on lichens, which accumulate ?I0Pb and2'0Po. The annual intake of lI0Pb and "OPo by the
populations living on reindeer or caribou meat areabout 140 Bq for 210Pband about 1,400 Bq for 210Po[H14, P12].
61. Lead is a bone seeker that is found incorporated
in mineral bone and has a long residence time in theskeleton. In continental areas, a typical activity massconcentration of llOPb in dry bone is about 3 Bq kg-',yielding a skeleton content of I5 Bq. The measured
ratios of 2'0Po and 210Pbactivity mass concentrations
in bone are centred around 0.8, leading to a "OPoskeleton content of 12 Bq.
62. About 30% of the body content of 2'0Pb is foundin soft tissues, with a relatively uniform distribution
throughout the body. The degree of radioactive
equilibriiim between 210Poand 'I0Pb depends on theorgan considered; i t is about 0.5 in the lungs, 0.8 in
red bone marrow, and definitely greater than 1 in theliver and kidneys. Additional intake due to smoking
leads to increased concentrations, particularly in thelungs.
63. The absorbed doses from the 210Pb subseries
depend mainly on the highly energetic alpha particlesof 2'oPo, as the contribution from the beta emissionsof 'I0Pb and Z1OBi
amounts to about 10% of the total.
The estimated annual absorbed doses of non-smokers
in areas of normal dietary intake (Table 9) are about
5 pGy in soft tissues and 36 pGy in bone lining cells.
The annual effective dose equivalents arising from thetotal intake of *lOPb, 210Bi and :loPo are about
120 pSv. The corresponding figure for the populations
living on reindeer or caribou meat would be about
10 times higher.

(d)

(i)

Thorium-232 series

Thorium-232

64. Thorium-232 is the head of a series of 11 radionuclides (Figure VI). The Z32Thseries has been divided
into three subseries: 232Thitself; 2'8Ra lZ4Ra;and
120Rn 208Pb. For each subseries, the intakes andandconcentrations are estimated as in the case of 23BU
the results are presented in Tables 7 and 8. Estimatesof annual absorbed doses are shown in Table 9.

--65. The activity mass concentration of 232Thin soil isestimated to be on average 25 Bq kg-', the same asthat of 238Uand its decay product 230Th(Table 3). The
annual intake from inhalation is estimated to be
0.01 Bq while that from ingestion, recently measured
in the United States for the first time [F12], is about
2 Bq. Wrenn and his collaborators found the activity
mass concentrations of 232Thin the body to be lower
than those of 130Th by a factor of about 2 [S22, W9].
On the basis of their measurements, the body content
of ?'?Th would be about 80 mBq, 60% of which is in
the skeleton. The activity mass concentrations adopted
in this Annex and the resulting annual absorbed doses
are presented in Tables 8 and 9. respectively. The
annual effective dose equivalent is calculated to beabout 3 pSv.
66. The dose calculations have assumed that 232Th
remains on bone surfaces. A volume distribution
would yield an annual effective dose equivalent of
about I pSv.

67. Radium is much more available to plants and toanimals than 232Th,SO that the activity concentrations

of 228Ra in humans are mostly due to the dietaryintake of 228Raitself and not to the decay of Ij2Th inthe body. Radium-228 can thus be considered to be
the head of a subseries in which 22YTh(half-life: 1.91 a)and 224Ra(half-life: 3.66 d), both alpha emitters, arethe most important contributors to the dose.
68. The annual activity intake arising from inhalation is estimated to be 0.01 Bq, while that fromingestion of foods is considerably larger, about 15 Bq
in areas of normal radiation background and about
2,000 Bq in the high background area along theKerala coast in India. Radium-228 concentrations indrinking water are comparable t o those of '26Ra but
not systematically correlated when individual watersupplies are considered. They are low in surface watera n d extremely variable in ground water [H20]. The
geometric mean of the "*Ra concentrations in publicground-water supplies in the United States is reported
to be 85 Bq m-3 [H21], corresponding to an annual
intake of 15 Bq for a daily drinking-water consumption of 0.5 litre.
69. The Committee estimated the average IZ8Ra
activity mass concentrations in bone (dry weight)
and in soft tissues (wet weight) of the human bodyto be 50 mBq kg-' and 4 mBq kg-', respectively. inareas of normal background radiation [ U l , U2].
Regarding 22'Th, Wrenn and Singh [W9] showedthat approximately 80% of the body content (about
300 mBq) is in bone.
70. The annual absorbed doses in tissues have been
calculated assuming that the 220Rn activity arisingfrom the decay of 224Rais retained in the body andthat the concentrations of 228Ra and of its decay
products are uniform over the total mass of bone. The
results presented in Table 9 show annual absorbed
doses greater than 1 pGy in the lungs, kidneys andbone lining cells. The corresponding annual effective
dose equivalent for the subseries is found to be about
13 pSv.
(iii) Radon-220 and its decay products ("6Po, :I2Pb,
212Bi, Z12p0, z08TI)

71. As is the case of 222Rn,inhalation is the major
pathway through which humans are exposed to 220Rn(thoron) and its short-lived decay products. In outd o o r air, the few available measurements of thoron
decay products [Ul, Annex D, Table 231 point to an
average 212Pb/222Rnactivity concentration ratio of
about 0.04. If the average 222Rnconcentration is taken
to be 5 Bq m-3, the average concentration of 2'2Pbin
outdoor air, representative of the equilibrium equivalent concentration of thoron decay products, would
be 0.2 Bq m-". The equilibrium equivalent concentration (EEC) of thoron, or radon, is that activity
concentration of thoron, or radon, in radioactive
equilibrium with its short-lived decay products thathas the same potential alpha energy concentration as
the actual mixture of decay products. Ground-level air
thoron concentrations in continental areas lie in therange of 2-10 Bq m-3 [Fl I].
72. The air exchange rate indoors is always muchsmaller than the radioactive decay constant of thoron(half-life = 55.6 s), so that the thoron concentration inroom air is relatively insensitive t o the value of theventilation rate. The thoron concentration in room air
is therefore mainly determined by the exhalation ratefrom the soil and building materials. As the diffusion
length of thoron in these materials is of the order of 1
cm, it is expected that the nature of the surface layer
covering the floor and the walls has a great influenceon the thoron exhalation rate; however, measurements
are needed to substantiate this assumption. The
magnitude of the equilibrium factor between thoron
and its decay products in room air has been theoreticallyestimated by Porstendorfer et al. [P4]. The difference
between the concentrations of 2''Pb and *'?Bi is always
found to be small but there is a factor of about 10-50,
depending on the ventilation rate, between the concentrations of "ORn (or Il6Po) and ?12Pb (or "'Bi), theconcentrations of "ORn being higher. The unattachedfraction of 2'2Pband "?Bi is very small (less than 1%)~41.
73. The number of indoor measurements of thoron
decay products is small in comparison to that ofradon decay products. Table 11 summarizes theavailable information on the potential alpha energy
ratio of thoron and radon decay products measured
simultaneously. The average values are around 0.5.
Using this figure and assuming a typical equilibrium
equivalent concentration of radon of 20 Bq m-' intemperate latitudes (paragraph 140). the average
equilibrium equivalent concentration of thoron (Tn) is
tentatively estimated to be

in temperate latitudes.
74. For equatorial regions measurements are unavailable. Because of the different domestic conditions, theindoor concentrations of thoron decay products are
expected t o be lower than in temperate regions. T oestimate the population-weighted world average of theindoor concentrations of thoron decay products,
account must be taken of the fact that the populationin tropical regions is about half that in temperate
latitudes. The range of possible values for that mean
concentration for the world is from 0.47 Bq m-3(assuming that the indoor concentration in tropicallatitudes is equal to zero) to 0.7 Bq m-' (assuming thatthe indoor concentration in tropical regions is thesame as that in the temperate zones). It is tentatively
assumed that the population-weighted world averageof the indoor concentration of thoron decay products
is 0.5 Bq m-).
75. Regarding exposuredose relationships, like radonand its decay products (see chapter 11). thoron gas isconsidered separately from thoron decay products.

76. Inhaled thoron, as a noble gas. is constantly
present in the air volume of the lungs at theconcentration in the inhaled air; in addition, it ispartly dissolved in the lung tissues. Due t o its shortradioactive half-life (55.6 s). however, the equilibrium
solubility in tissues other than that of the lungs will
not be reached. Thus, the decay of thoron and of its

very short-lived decay product 2'6Poleads mainly to adose in the lungs: the second decay product formed,
2'2Pb, is mainly transferred to blood cells, kidneys,
and bone surfaces [IZ].
77. Values of annual absorbed doses per unit thoron
concentrations have been derived from calculations by
Jacobi and Eisfeld [J6]. They are presented inTable 12. For concentrations of thoron gas in air in
the range of 2-20 Bq m-3, the annual doses are up to
5 pGy in the lungs, 4 pGy in bone lining cells and2 p G y in the kidneys. The corresponding annual
effective dose equivalents are less than 20 pSv.
78. With respect to thoron decay products. theabsorbed doses per unit inhaled activity have been
adapted from calculations of Jacobi and Eisfeld [J 1I]
to fit the value of 0.7 Sv J-' used in the UNSCEAR
1982 Report [UI] for the effective dose equivalent perunit inhaled potential alpha energy. The results,
presented in Table 12, show that the lungs, bone lining
cells and kidneys are by far the most exposed organs
and tissues. The absorbed doses per unit concentration, also shown in Table 12, have been estimatedusing a mean breathing rate of 0.8 m3 h-' indoors and
1 m' h-' outdoors and an average occupancy factor of
0.8 indoors and 0.2 outdoors.
79- The dosimetric coefficients of Table 12 have beenused to estimate average annual doses from inhalationof thoron decay products. Average annual doses in thelungs are 5 pGy outdoors and about 40pGy indoors.
Annual doses in other organs and tissues are lower.
The annual average effective dose equivalent resulting
from outdoor and indoor inhalation of thoron isestimated to be 160pSv.
80. Because of the few data available, the distribution of individual exposures, as well as the reliabilityof the estimated mean value, is difficult to assess atpresent.
C. SUMMARY
81. A summary of the various contributions to theannual effective dose equivalent from natural sourcesof radiation is given in Table 1. In order of importance,
inhalation of short-lived decay products of radon
comes first, with the average annual effective dose
equivalent estimated to be 1,100pSv. A detailed
discussion on the environmental behaviour of radonand of its dosimetry is provided in chapter 11. The
second most important pathway is external irradiation.
accounting for nearly 800 pSv, divided approximately
equally between cosmic radiation and terrestrial sources.
' K (180,uSv).
Less significant are the ingestion of O
inhalation of decay products of thoron (160 pSv) andinternal irradiation from 2'oPb-"0Po (120pSv). The
other natural radionuclides contribute little to the total
annual effective dose equivalent, which is estimated tobe 2,400 pSv.
82. The variability around the mean dose fromnatural sources of radiation is dominated by the radon
component, as the indoor radon concentrations spanover four orders of magnitude.

11. RADON-222 AND ITS SHORT-LIVEDDECAY PRODUCTS
83. In the UNSCEAR 1982 Report, it was estimatedthat inhalation of short-lived decay products of radon(222Rn)accounts on average for about one half of theeffective dose equivalent from all natural sources ofradiation and may sometimes lead to doses highenough to cause concern for human health. The
awareness of the potential health problems that could
be caused by radon and other pollutants in the indoor
environment has been growing steadily in the past few
years so that a large number of scientific papers,
books, reports and meetings have been devoted toquestions related to radon exposures, especially indoors(see. for example [A17], [C24], [H27], [N24] andw.51).

84. Following a brief overview of the outdoor
situation, this chapter focuses mainly on indoor
concentrations. The exposure-dose relationships forthe outdoor and indoor conditions are then established,followed by an assessment of the annual doses.

A.

OUTDOOR CONCENTRATIONS

85. Radon enters the atmosphere mainly by crossing
the soil-air interface, but there are a number of othersecondary sources. such as the ocean, ground water,
natural gas, geothermal fluids and coal combustion.
The atmospheric concentrations of radon at groundlevel are governed by the source term-the exhalation
rate-and by atmospheric dilution processes, which
are both affected by meteorological conditions. The
degree of radioactive equilibrium between radon andits decay products in the atmosphere at ground levelalso depends to a large extent upon the meteorologicalconditions.
86. When 226Radecays in soil particles, the resulting
atoms of ?'IRn must first escape from the soil particles
to air-filled pores and move through these pores inorder to enter the atmosphere. The escape from thesoil particles to the air-filled pores is thought to bemainly the result of recoil of the radon atoms
following the decay of :16Ra [MI]: if they lie close to
the surface of individual grains, they may be ejected
into the pores between the grains. In comparison, thecontribution from diffusion through the solid mineral
grains is less important, as most of the radon atoms
decay before escaping. The fraction of radon formedin the soil that escapes into the pores is known as theemanating power, coefficient, ratio or fraction; reported
values range from about 1% to 80%.
87. In order to enter the free atmosphere. the radongas must diffuse through the pores of the material,
and a fraction of it will reach the surface before
decaying. The diffusion path is tortuous and, ofcourse, some radon atoms will be ejected into closed
pores from which they cannot escape. Movement ofradon atoms may be caused by diffusion or convection. Convective movements, induced by pressure
differences created by meteorological conditions, vary89. The concentrations of radon in air vary dependingon the place, time. height above the ground andmeteorological conditions. Because the source of radonis the soil and radon has a rather short physical halflife, the radon concentration is in general constantly
decreasing with height. The geographical location isimportant: radon concentrations are as a rule lower
over locations, such as islands and Arctic areas, whichhave less soil capable of emanating radon than overcontinental temperate regions.

with time and cannot be readily quantified. The
diffusion process is described mathematically by thedefinition of an effective diffusion coefficient that
includes an allowance for the convoluted path. As in
the UNSCEAR 1982 Report (Annex D , paragraph58). the area exhalation rate. defined as the activity
transfer rate per unit area at the soil-air interface, isexpressed as= A RnFrCsoil.~a~so~l
L ~ n

(2.1)

where R is the area exhalation rate in Bq m-* s-I; i.,,is the decay constant of 222Rn(2.1 lom6s-I); F, is theemanating power: Clod.b is the activity mass concentration of Iz6Rain soil (Bq kg-I): p,, is the soil density(kg m-)); and LRnis the diffusion length of radon insoil (m), which can be expressed mathematically as thesquare root of AeM/iRnprotl.pswhere A,ff is the effective
bulk diffusion coefficient (m2 s-I) and p,,,,.,, is the soil
porosity.

90. Detailed information on the variations of radon
concentration at ground level over time was obtained
from a six-year record of hourly radon measurements
made at Chester. New Jersey, United States [F7]. T h earithmetic mean for the six years of operation was
found to be 8 Bq m-3 and the hourly data and threehour averages of radon concentrations were lognormally distributed. A seasonal pattern of a summer
maximum and a winter minimum was observed overthe period 1977-1982 with little variation from year
to year [F7]. The seasonal maximum in August wasa factor of 3 higher than the February minimum(Figure VII). The diurnal variation (Figure VIII)
shows a maximum in the night and a minimum at noon.
The diurnal maximum is a factor of 2 greater than theminimum. The three-hour average radon concentrations were tested for correlation with five meteorologicalparameters measured at the site-temperature.
dewpoint temperature, wind speed. atmospheric pressure
and precipitation-but no significant correlation was
found [F2].

Published information on experimental values ofis summarized in Table 13. Using
the representative values given in Table I3 for F,, Aenand P,,,~~,,,and assuming a 226Raactivity mass concentration In soil of 25 Bq kg-' (Table 3) and a soil
density of 1.6 lo3 kg m-3. the diffusion length of radon
LRnis approximately 1 m and the area exhalation rate
is 1.7 lo-? Bq m-' s-I. in agreement with the estimatedarea-weighted average per unit area for soil. based on
direct measurements, of 1.6 lo-? Bq m-: s-' [Wl].
Over the ocean, the area exhalation rate is about twoorders of magnitude lower than that for soil.
88.

R, F,, ACrr
and p,,,,,,II

Jan Feb

I

I

I

I

I

Mar Apr May Jun

I

Jul

I

Aug

I

I

Sep Oct Nov

I

t

Dec

MONTH
Flgure VII.

Seasonal varlatlon of outdoor radon concentratlon at Cheater,
New Jersey (1977-1982 average).

[Fll

5

0

3

6

9

12

15

18

21

24

0.77 at 1-10 m above ground. Cox et al. [CI]. at
Cincinnati. Ohio. reported an average value of 0.87.
and measurements in New Jersey and New York at
0.3-1 m above ground gave an equilibrium factor of
0.79. It seems that 0.8 may be a representative valueof the average equilibrium factor F at I m above
ground. This is higher than the value of 0.6 assumed
in the UNSCEAR 1982 Report. Combining the annual
average of the population-weighted radon concentration in outdoor air of 5 Bq m-' with an average
equilibrium factor of 0.8 yields an average equilibrium
equivalent concentration of radon of 4 Bq m-3. Annual
averages of this value vary depending on the location;a typical range, excluding extreme values, is from 1 to
10 Bq rn-j.

HOUR
Flgure VIII. Diurnal variation of outdoor radon concentration
at Chester, New Jersey (1977-1983 average of three-hour data).

[Wl

91. The compilation obtained at Chester represents
the most complete available set of data on outdoor
radon concentrations at ground level. Less extensive
series of measurements were reviewed in the UNSCEAR
1982 Report and by Gesell [GI]. With regard to theseasonal variations. other data from the United States
showed lower values in the spring than in summer andautumn [W2, Cl, G3, L2]. Data from Hungary [G9]are in agreement with those obtained at Chester.
Other seasonal patterns, however, were observed at
Livermore, California [Ll], Bombay, India [M2]. Riode Janeiro, Brazil [L2], and Japan [I8, M3, S47J; thismay be due to the fact that those locations, beingislands or coastal cities, are more affected by theannual wind rose.
92. The average value of outdoor atmospheric radon
concentration for normal areas of the United States
was estimated by Gesell [GI] to be about 9 Bq m-3
after the diurnal radon cycle was taken into account.
This is probably representative of the continental
areas in the temperate latitudes. Values lower by afactor of 2-4 are generally observed on islands and atcoastal sites [C4, F3, 18. S47, W141. In this Annex it istentatively estimated that the annual average of the
population-weighted radon concentration in outdoor
air is 5 Bq m-3. A lower value, 3 Bq m-3, was adopted
in the UNSCEAR 1982 Report.
93. The equilibrium factor F between radon and its
short-lived decay products is defined as the ratio of
the equilibrium equivalent radon concentration to theradon activity concentration:with xF = k c q . ~ n ) / ~ ~ n (2.2)+ ~0.516~ x Z + 0.379 x 3~= 0.105~.

where x,, x 2 and X , represent the activity concentrations of polonium-2 18. lead-2 14 and polonium-2 14,
respectively. A few studies were devoted to theassessment of the equilibrium factor F between radonand its short-lived decay products. At Chester, New
Jersey, George [G2] found an average value of 0.85 at
I m above ground. In the Federal Republic of
Germany, Jacobi obtained an equilibrium factor ofB.

INDOOR CONCENTRATIONS

94. There is no basic difference in the physicalbehaviour of radon and its decay products in a room
and in the open air; however, the different nature ofsome of the sources and the magnitude of the indoor
exposures warrant a separate discussion. In thissection. the various sources of indoor radon are first
discussed and quantified in order to estimate an
average and a typical range of the rate of entry ofradon into a hypothetical reference house. The principal mechanisms of transport and removal of radonand radon decay products are then considered inorder to estimate average radon and radon decay
product concentrations in the hypothetical reference
house. In the last part of this section, the results oflarge-scale indoor surveys of radon or radon decay
products are reviewed.

1. Sources of indoor radon
95. Radon enters buildings from different sources.
such as the soil or rock under or surrounding thebuildings. building materials, water supplies, natural
gas and outdoor air. Characterizing the radon entry
rate may require consideration of the rate at whichradon is generated in source materials, of the modesof radon transport through various materials and,
finally, of the manner in which radon actually enters
indoor air. Several reviews of indoor radon sources
have recently been prepared [N 1. B25, G24. N 131.
96. As in the UNSCEAR 1982 Report, reference
will be made to a hypothetical reference house; its
dimensions and relevant parameters are given in
Table 14. In the UNSCEAR 1982 Report, the radonsource in the reference house was estimated to be
74 kBq d-I, corresponding to a radon entry rate ofabout 15 Bq nl-3h-I. Figure IX presents the cumulative
frequency distributions of' radon entry rates determinedin dwellings in several countries as the product of thesimultaneously measured ventilation rate and radon
concentration [N8]. I t appears that the radon entry
rates are approximately log-normally distributed andthat there is in most countries a considerable spread
between the minimum and the maximum values. The
median radon entry rates presented in Figure IX range
from 5 Bq m-I h-I in the Federal Republic of Germany

(a) tinder/-ving soil(a) Sweden (86)(b) Canada (9)(c) US (tirneaveraged) (73)(d) US (grabsample) (101)(8) Great Britain (87)(I) FR Germany (32)

97. Radon can be transported into a building fromthe underlying soil via diffusion or via the pressuredriven flow of air through the structural elements o r
through openings in the structural elements.
98. Diffusion. For an uncracked slab of concrete ofthickness L lying on the ground, the area exhalation
rate transmitted by diffusion from the underlying soil
through the slab can be expressed as [Nl, C3]

1 ''Fsorl.pr L ~ n . r o l lLCsinh ()I(2.3)
Fslab.pr LRnshb
L~n.slab
where R is the area exhalation rate from uncoveredsoil (equation 2.1). Other formulations can be foundin the literature on the subject (see. for example,[B26]). Taking the values already given in preceding
paragraphs for the various parameters yields
0.2
RT = 1.7
Bq m-2 s-I / [cosh (-)
t
0.15
0.15 X 1
0.2= 1.2
Bq m-' s-I (2.4)
sinh (-)I
0.2 X 0.15
0.15
I

I

I

I

1

5

10

30

1

I

1

I

50 70

90 95

I

99

CUMULATIVE PROBAEI L I T Y (.'.)
Figure IX. Cumulative frequency distributions of radon entry
rate in buildings in several countries determined from theproduct of simultaneously measured ventilation rate and radon
concentration. (The number of residences In each sample isindicated in parentheses.)[N81[W6] to 102 Bq m-? h-I in Sweden [H16]: the corresponding arithmetic means, assuming log-normal
distributions, are 7 and 190 Bq m-3 h-I. respectively.
Intermediate values have been obtained in Canada[S41], the United Kingdom [C4] and the United States[N8]. Figure X shows the histogram of the radon
entry rates determined from the British survey [C4]. I tshould be pointed out that the number of houses
considered was relatively small in each of the surveys.
The various sources of indoor radon are considered
next.
RADON ENTRY RATE (Bq m - 3 h - l )
0.3

-0.2

-0.1

1

0

3

10

1.0

2.0

30

3.0

100

4.0

5.0

300

6.0

L n (RADON ENTRY R A T E )Figure X.

Distribution of radon entry rater in rooms from asurvey in the United Kingdom.

[C41

Thus, only a small percentage of the activity exhaledfrom the soil is transmitted through 0.2 m of uncracked
concrete, and this exhaled activity represents about one
half of that due to the concrete itself. The corresponding
radon entry rate in the reference house can be
estimated as
UT= RTNSF/V(2.5)
or, in numerical terms,

99. The presence of cracks in the slab may considerably increase the transmission of the diffusive
flux from the soil. Using a mathematical model of acracked slab, Landman [L3] determined that 25% of
the flux from uncovered soil would penetrate the slab
by diffusion if a gap of 1 cm existed for every metre ofslab.
100. Pressure-driven flow. The pressure-driven flowof radon-bearing air through structural elements isbelieved t o be a n important mechanism for radon
entry [Nl]; it is often the predominant source of radonin dwellings with elevated concentrations (see, forexample, [A 101. [E7], [N8]. [W 131and [W8]), especially
if the house is in direct contact with the ground [S65].
Flow through an intact concrete slab is likely t o be
negligible in comparison to flow through cracks, holes
and other penetrations. In dry soil with a density of
1.6 lo3 kg m-3, porosity of 20%. Z26Raactivity massconcentration of 25 Bq kg-I and emanating power of
20%. the calculated equilibrium radon concentration
in soil gas is 40 kBq m-3. If it is assumed that 0.25 m3
of soil gas enters a building per hour, representing
about 0.1% of the total air exchange rate, the radon
entry rate from that source is 40 Bq m-3 h-I.
101. Much attention has been given to the questionof radon entry through convective flow in countries

such as Sweden [S7, SB]. the United States [Nl].
Canada [El] and the United Kingdom [02]. where anumber of dwellings have been found to have unusuallyhigh radon concentrations. The radon entry rate
through convective flow R, is simply the product of
the radon concentration in soil gas X , and theinfiltration rate from the soil Q,. The radon concentration in soil gas depends on the activity massconcentration of radium in soil. its emanating powera n d the porosity, permeability and moisture content
of the soil. Investigations of radon concentrations insoil gas in Sweden, the results of which are presented
in Table 15, show that there is usually no longdistance transport of radon in the soil and that theradon concentrations in soil gas can be explained
assuming an emanating power of 10-30% [A 101.
102. The infiltration rate from the soil Q, depends
o n the degree to which indoor air is coupled to thesoil, which, in turn, depends o n the design andconstruction of the building structure, on meteorological parameters influencing radon movements in thesoil and on the living habits of the occupants, which
can affect the air exchange rate in the building.
Mechanisms of radon transport from soil into a househaving a vented crawl space are illustrated in Figure
XI [NlO]. The two pressure-driven flows considered
are those due to the indoor-outdoor temperature
difference, including a stack effect in winter, and
wind.

**~n
Figure XI. Schematic diagram of mechanisms related to radontransport from soll, through a vented crawl space and into ahouse.

[NlOI

103. Experimental investigations in a house with avented crawl space showed that a higher temperature
difference, including an increasing infiltration rate,
corresponded to a higher indoor radon concentration,suggesting that the increased infiltration rate is morethan compensated for by an increase in the radon
entry rate [NIO]; they also suggested that the infiltration rate from the soil into the house was, in this case,more important than the infiltration rate from thewalls. A high wind speed tended to reduce the indoor
radon concentration, presumably by increasing thecross-ventilation of the crawl space and the infiltration
rate of the living space. For this particular house, as
well a s for two other houses with vented crawl spacesthat were investigated in the study, it was found thatperhaps 50% o r more of the radon released into thecrawl space from the soil beneath the house entered
the living space [NlO]. This figure cannot, however, beapplied t o all types of construction: the floor of acrawl-space house, which is usually built of wood, islikely to have greater infiltration rates than the floor
and walls of a basement, which are usually built ofpoured concrete and concrete blocks.
104. Another extensive investigation of radon entry
through the soil was conducted in a single-family
house with a basement; real-time measurements of theindoor radon concentration, air exchange rate, sourcerelated parameters and meteorological factors were
performed for a period of five months [N4]. The
radon entry rate was calculated from the measuredradon concentration and air exchange rate. Figure XI1
shows the results obtained during a week of thatexperiment with regard t o the radon entry rate a n d theradon concentrations in the soil adjacent to the houseand in the basement sump, which collects rainwater
via a drain tile system surrounding the house at a levelnear that of the basement floor. The good correlation
between the sump activity and the radon entry ratesuggests that the sump is an important pathway forradon entry into the house, although it cannot
account for the total radon activity [N4]. The main
conclusion derived from this study is that the radon
entry rate may have two components: one may be
independent of the air exchange rate. acting in a way
similar to entry by diffusion; the other may be
proportional to the air exchange rate, behaving likepressure-driven entry [N4]. The corresponding radon
entry rates in the house were calculated to be about
2 Bq n1-3 h-' for the diffusion process and about
60 Bq m-3 h-I for the pressure-driven force [Nl].
105. Computer modelling of radon movement of soil
gas resulting from pressure differences between theunderlying soil and indoor air has been carried out in
Canada [E7, S9]. In a wind-tunnel study, variations inwind speed and direction, and not the wind speed o r
direction itself, were found to cause large variations in
the radon entry rate. The average radon entry rate wasfound to be mainly a function of the soil permeability
and only secondarily a function of the area andresistance of the house used in the computer model tosoil connections. The effect of seasonal differences onradon entry rate tvas approximately 4 to 1 from winterto summer. Stack-effect pressure differences due totemperature differences increased by a similar factor
over this period. Because the ventilation rate of thehouse depends largely on the stack effect, these results
suggest that summer and winter concentrations should
be similar unless doors and \vindows are opened insummer to increase the ventilation rate. For the same
geometry and weather, decreasing the soil permeability
from I 0-4 cm2 to lo-' cm2 (a factor of 1,000) decreased
the average radon entry rate into the house by a factor
of about 25. This suggests that the radon entry rate isroughly proportional to the square root of soil
permeability [D12]. Considerably more theoreticala n d experimental work is likely to be required todetermine entry routes and transport mechanisms
from underlying soil with some degree of confidence.

I

A.

ENTRY RATE

o t

I

I

1

rlednesdaylThursday

FridayI

Saturday1

I

SundayMondayTuesday(14-20 July 1982)

8000

i

a.

SUMPMONITOR(14-20 July 1982)

8000

1

C.

SOIL PROBE

o !

I

I

WednesdayThursdayI

I

FridaySaturdayI

1

I

SundayMondayTuesday(14-20 July 1982)
Flgure XII. Variation with tlme In a rlngle-famlly house with a basement ol (a) radon
entry rate; (b) the radon concentratlon In the basement sump; and (c) In the roll adjacentto the house.
IN41(6) Building marerials
106. A fraction of the radon activity produced bydecay of 2'6Ra in building materials enters buildings
by diffusion. The area exhalation rate can be expressedas
R = j - ~ n ~ b , : l l d C b u , l d . R a F r L ~ n t a n(LII/LRR)h(2.6)
which is an equation very similar t o that related to soil
(equation 2. I ) , the only difference being the introduction of a hyperbolic term to account for the fact that
diffusion takes place in a medium of finite thickness.
In equation (2.6). R is the area exhalarion rate
(Bq m-' s-'1; F, is the emanating power; pburldis theisdensity of the building material (kg m-9: CbulldR4
the activity mass concentration of ::6Ra in thebuilding material (Bq kg- I): L,, is the diffusion length(m); a n d Lhis the half-thickness of a slab of building
material (m).
107. The mass activity exhalation rate, expressedin Bq kg-) s-I and defined asis the quantity usually determined in laboratory
measurements [JI]. The area exhalation rate from awall o r a floor made of building material of halfthickness L,, diffusion length LRnand density p,_,,,
can then be expressed as108. Information on the mass exhalation rate. thediffusion length, the emanating power and the '26Ra
activity mass concentration in building materials ispresented in Table 16. Concrete and brick are probably
the two most tvidely used building materials, at leastin the temperate latitudes. Table 16 shotvs that eventhough the '26Ra concentrations in concrete seem tobe lower than those in brick, the 222Rnmass exhalation rates appear to be higher for concrete than for
brick. This is because of the high values of theemanating power for concrete, with o r without fly ash,in comparison to those for brick. The results presented
for gypsum (Table 16) are difficult to analyse because
the few measurements available give either high or IOU
values of the emanating pourer. Further measurements
are necessary to clarify this point.
109. s o m e data on the emanating power of theconcrete components are given in Table 16. Cementa n d fly ash have low emanating powers, probably due
to their crystalline nature. Differences in the moisture
content of the materials studied may also account inpart for the wide disparity in the results of exhalation
measurements from different countries [Nl]. I t is
worth noting that the exhalation rate from concreteshould not be derived from the emanating power of its
constituents, as chemical changes occur during manufacturing.
110. The adopted reference values for the parametersof interest in the calculation of the area exhalation
rate from concrete and brick are indicated in Table 16.
F o r building material with a thickness of 0.2 m, thereference area exhalation rates would be 2 mBq m-'
s-I and 0.3 mBq m-l s-I for concrete and for brick,respectively. The rate of entry of radon resulting fromexhalation from building materials may be expressedasU,, = N / V (2R,SF +- R,S,)(2.9)
where N is the number of seconds per hour; V is thevolume of the reference house (250 m3); S F is thesurface area of its floor or ceiling (100 m-): S, is thesurface area of its external walls ( I00 m2); and RLand
R, are the area exhalation rates from concrete andbrick. respectively.
11 1. The rate of' entry of radon from the floor andthe ceiling of the reference house would amount toabout 6 Bq ni- h - I, while the contribution from theexternal walls would be about 0.4 Bq m - ' h - ' . The
contribution from radon exhalation from the building
materials to the radon concentration in the reference
house is thus estimated t o be 6.4 Bq n1-' if the air
exchange rate is taken to be 1 h 'I.
112. Considerably greater values of the rate of entryof radon are expected to be obtained uhen building
materials with high 226Raconcentrations and normal
emanating power are extensively used. Examples ofsuchbuilding materials are granite, Italian tuff and alumshale lightweight concrete. Among these materials,
Swedish alum-shale lightweight concrete has the highest'26Ra concentrations (about 1,300 Bq kg-' on average)[S19, S20] and probably the highest ?"Rn mass
exhalation rate (440pBq k g 1s - ' i n Table 16). Assuming
a density of 2 lo3 kg m-3 and a diffusion length of
7.4 lo-' m (as measured in [J?]), a 0.2 m thick slab of
100 ni2 would lead to a rate of entry of radon of about
80 Bq m-' h-I in the reference house.
113. Techniques for reducing the radon entry rate
due to exhalation from building materials have been
investigated. In Swreden, aluminium foil has been
applied to the walls of houses built with aerated
concrete based on alum shale [S19]; the results showed
a 50% reduction in the radon entry rate. In the UnitedStates. various radon sealants have been tested underconditions representative of normal construction conditions [EZ].The radon exhalation rate was reduced
from 20% to 80%. depending on the surface coatingused. Because of the trapping of radon decay productsin the wall, there is a relatively small increase in theexternal gamma dose rate [EZ,M8]. It was also notedthat any cracks that later developed in a sealant suchas paint may lead to leaks that negate a large portionof the sealing effectiveness of the paint [Ml9].
Similarly, the radon exhalation rate from any unpainted
areas may be increased as they offer to radon a pathof least resistance in comparison with painted areas[A I I].
(c)

Outdoor air

114. Air exchange between the outdoor and theindoor environments brings some outdoor radon into
buildings. Air exchange arises from natural ventilation
through open doors a n d windows, mechanical ventilation and infiltration, the uncontrolled leakage of air
through cracks in the building envelope. Unlessotherwise stated, air exchange in this Annex isassumed to consist of infiltration only. Outdoor radoncan play a significant role in the indoor radon entry
rate if the house is poorly sealed. The radon entry rate
resulting from the infiltration of outdoor air may be
written as
U O=~zOUI"~.

(2.10)

is the radon concentration in outdoor air
where ,z,(Bq ~ n - ~E.), :is the air exchange rate (h-I); and (1 is thefraction of the air exchange rate involving outdoor air,which in all cases is close to I . Assuming an outdoor
concentration of 5 Bq m-' (see paragraph 92). an air
exchange rate of I h-I and a value of 1 for a, theradon entry rate would be 5 Bq h ! mP3. I t is worth
noting that the radon entry rate resulting from theinfiltration of outdoor air is proportional to the air
exchange rate.
(d)Cl'awr115. Radon contained in water is to some extent
transferred into room air as a result of agitation or
heating. Radon concentrations are as a rule much
lower in surface ivater than in ground water. In watersaturated soil with a density of 1.6 lo3 kg m--?,porosity of 20% and emanating power of 20% a 226Ra
activity mass concentration of 25 Bq kg-' yields atequilibrium a I"Rn concentration in ground water of
25 Bq kg-Ix 1.6 lo3 kg nl-?x 0.2/0.2 = 4 lo4 Bq m-3
In surface water, radon concentrations are expected tobe similar to those of ?26Ra,that is, about 10 Bq m-!.
116. The release of radon from water to air depends
upon the circumstances in which the water is used, as
the degassed fraction increases considerably withtemperature [G5]. Studies of radon transfer from tapwater to indoor air reported a use-weighted transfer
efficiency of 0.5-0.6 and an average water use of
0.2-0.4 m3 per day and 'per person [G5, P2]. Degassingof radon from tap-water has been found to lead toelevated indoor radon concentrations in Canada [M7],
Finland [C2] and the United States [G6]. Taking the
air-to-water concentration ratio to be typically lo-"[C6]. an indoor air concentration of 400 Bq m-j is
obtained if the radon concentration in water is
4 MBq m-3. High concentrations in water are usuallyassociated with deep wells drilled in granitic areas;
the highest reported concentrations in water are
14 MBq rn-) in Canada [M7]. 77 MBq m-' in Finland[S68] and about 20 MBq m-3 in the United States [G6,S181. The use of aeration can reduce the radon
concentration in water by a factor of about I00 [C2].
117. Measurements of radon concentrations in water
have mostly been undertaken in regions where highlevels were suspected. Measurements intended toestimate the weighted average radon concentration inwater for a country or a community are rare. Resultsof that nature are only available for Finland, Sweden
and the United States. In Finland, the populationweighted average has been estimated to be 25 kBq m-j
for drinking water distributed by water-supply plants[A2, C2], and about 60 kBq m-3 when the contribution of private wells is included [K4]. The correspond-ing value in Sweden has been found to be 38 kBq m-'[K24]. In the United States. the geometric mean radon
concentrations in municipal ground-water supplies in
the central part of the United States and in Texas were
found to be about 4 kBq m-3 [P3. W3] and 5 kBq m-I[W3]. respectively. I t was tentatively estimated in the
UNSCEAR 1982 Report (Annex D, paragraph 163)that between 1% and 10% of the world's population
consumes water containing radon concentrations of
the order of 100 kBq m-j or higher, drawn from
relatively deep wells. For the remainder, who consume
water from aquifers or surface sources. the weighted
world average concentration is probably less than
1 kBq mP3.
118. The radon entry rate due to water degassing
may be expressed as
U,=~~Q,E/V(2.11)
where x , is the radon concentration in water (Bq m I);
Q, is the amount of water used per unit time (m3h- I ) ;E is the degassing efficiency; and V is the volume of
the reference house (m'). Assuming a radon concentration of 1,000 Bq m-3 in tap-water. a degassing
efficiency of 0.5, a water use rate of 0.07 m' h i .
corresponding to 0.4 m' per day for each of the four
persons living in the reference house. the radon entry
rate is estimated to be about 0.1 Bq m-j h-I; thecorresponding mean radon concentration is 0.1 Bq m-'
in the reference house, with a very uneven distribution
within the dwelling, the highest concentrations being
expected in the rooms where radon is released(bathrooms and kitchen). In any case. average radon
concentrations in tap-water do not bring a significant
contribution to the total radon entry rate in buildings,
except. however, when the water contains high concentrations of radon. Figure XI11 shows the variationof concentrations in indoor air for a house with aradon concentration in tap-water of about 2 MBq m-'[G6]; the peaks are associated with periods of high useof water in the house. The integrated radon concentrations represented by each of the peaks in Figure XI11
are 200-400 Bq h m--'. Assuming that the characteristicsof the surveyed house are the same as those of thereference house yields a water use of 0.05-0.1 m3 per
peak.
(E)

Natural gas

119. Natural gas is sometimes mentioned as apotential significant source of indoor radon. The
radon concentration in natural gas at production wells
varies from undetectable values to levels of about
50 kBq m--' [G7, H2, 53,W4]. The industrial processing of natural gas involves the removal of impurities
and separation of hydrocarbons. Some of thesehydrocarbons are bottled under pressure for sale asliquefied petroleum gas (LPG) while others may be
used for fuel. Some of the radon activity contained in
the processed natural gas decays during the transit
time between processing and use, or while it is stored
in the bottles. When natural gas is burned in houses
for cooking or space heating the radon that is released
may enhance the radon level indoor if the appliances
are unvented. If the combustion products are vented
outside the house, this radon source is neghgible.

-4:WPU
I

I

O:WPM

!zOoJU

4:WAU

0:W Arc

l:WPL(

4:W PU

0:WPuZm

T I M E OF DAY
Figure XIII.

Variation of the radon concentration in indoor alr of a house wlth radon concenlralion in waterof about 2 MBq m-1[G61

120. The radon entry rate from the use of natural
gas may be expressed as(2.12)
U n g = x n g ~ n 1gV
where z, i+ the radon concentration in natural gas(Bq m-'); Q,, is the amount of natural gas used perunit time (m3 h-I); and V is the volume of thereference house (I). Radon concentrations in natural
gas and LPG have mainly been measured in the
United States, where the average radon concentrations
in either natural gas or LPG have been found to beabout 1,000 Bq m-' [G8, 531. For a consumption rateof 2 m3 d-I in unvented appliances, the radon entry
rate in the reference house is estimated to be about
0.3 Bq m-' h-I. The corresponding contribution to theradon concentration is 0.3 Bq m-'.

is negligible o r the ventilation system in the basement
is separate from that of the living areas of thebuilding.
2.

Indoor behaviour of radon and radon daughters

122. Radon entering indoors accumulates as a function of the air exchange rate in the bui!ding. The
activity of radon that will accumulate within abuilding is limited by its removal through ventilation.
normally expressed as the air exchange rate (measured
in air changes per hour). Radon decay productconcentrations are similarly limited; in addition, they
can also be subject t o plate-out mechanisms. notdirectly connected with room ventilation rate, which
will keep their concentration below that of radon.

Il) Summary

121. Table 17 summarizes information on the estimates of radon entry rates in the reference house.
The estimated arithmetic mean value obtained is
50 Bq m-' h-I, in agreement with arithmetic means ofexperimental surveys [NS].High values can be traced
t o a substantial flow of soil gas from the underlying
soil, the use of alum shale as a building material o relevated radon concentrations in tap-water. It should
be noted, however. that all other contributors remaining
the same, the relative importance of the flow of soil gas
is less in apartment buildings because the ratio ofvolume to ground-floor surface is much larger for themthan for the reference house. Its relative importance isalso less if dwellings are built in such a way that thecontribution of the radon entry rate from underlying
soil to the total radon entry rate in living areas is verysmall. because either the infiltration rate from the soil

(a)

Radon

123. Assuming an instantaneous and homogeneous
mixing of radon in the building, the variation of theindoor radon concentration can be described bywhere x,(t) is the radon activity concentration at time
t in Bq m-3; U(t) is the radon entry rate at time t in
Bq m-3 h-I; A,, is the decay constant of radon,
7.6 lO-'h-': and iv
is the air exchange rate a t time t
in h-I.
124. If the radon entry rate (u) and the ventilation
rate (I.,) are constant with time, the radon concentration at equilibrium is given byIf the contributions from outdoor air and pressuredriven flows through the soil are small, the indoor
radon concentration at equilibrium is, as a first
approximation, inversely proportional to the air exchange rate. This is illustrated in Figure XIV, which
presents data from an experiment in which a balanced
mechanical system-that is, one with equal intake andexhaust flows-was used to vary the air exchange ratei , without affecting the pressure-driven flow from thesoil [N5].

125. E q u ~ t i o n(2.14) can only be used as a first
approximation of the mean indoor radon concentration, as it is based on assumptions that are usually notstrictly valid. They are as follows: (a) the radon
concentration within the building is assumed to behomogeneous. There is in fact essentially universal

I

I

1

I

0.01

0.1

1

10

agreement that the radon concentrations decrease as
the storey numbers of a multi-storey building increase,especially between the basement, first and second
floor [ G I , G9, G10, SIO]. In the upper storeys ofhigh-rise buildings. the radon concentration does notalways decrease as the storey number increases. The
presence of direct routes, such as lift shafts and service
ducts between the basement, or even the sub-basementlevel, and higher storeys can distort the radon
concentration gradient; (b) the air exchange rare isassumed to be constant with time. Actually, it issubject to important variations, as it is a function ofhuman activities (opening or closing doors or windows.
turning ventilation systems on o r off) and of meteorological conditions (wind speed and direction, temperature. pressure). Figure XV shows the measured variation of the air exchange rate in an occupied houseover a few days, together with the wind speed
observed at a weather station 20 km away from thehouse [N6]. The air exchange rate is shown to varyfrom 0.5 h-' to more than 4 h-I in a matter of a feu
hours: there is in that particular case a good correlation between the wind speed and the air exchange rate,
as predicted by the model of Grimsrud et al. [G25];(c) the radon entry rate is assumed to be constant withtime. In fact, as shown in Figure XII, the entry rate
may experience significant changes in the course of
one day owing to variation with time of the different
radon sources discussed in the previous section.

A I R EXCHANGE RATE ( h ' l j
Figure XIV. Average steady-state radon concentration in a
residence as a function of ventilation rate. (The dashed line
indicates a constant radon source of 90 Bq rn-3 h-1).
[N51

0

I

I

15 March

Figure XV.

II:6 tlarch

126. According t o equation (2.14), there is a clear
relationship between the radon concentration a n d the
air exchange rate. However. simultaneous measurements of the air exchange rate and of the instantaneousradon concentration have been performed in threesurveys involving 98 houses, including both energyefficient and conventional houses. The surveys failed
to reveal such a correlation between the indoor radon
concentration and the air exchange rate, althougheach parameter varied over a wide range [N3]. Similar
results were obtained from time-averaged measurements [DZ] (Figure XVI).

1 7 :,larchf

18 March

19 March

Variation of the ventilation rate in an occupied house. The wind-speed data represent obse~ations
at a weather station 20 krn away from the house.
IN61(b) Radon decay products

Fargo
PortlandCharleston
Colorado Springs

1 .o

0.1

10

A I R EXCHANGE RATE (!I-')
Figure XVI. Scatter plot of radon-222 concentratlons versus
air exchange rate for 58 houses in four cities. Measurements
were made during a four- to five-month period between
November 1981 and May 1982.
ID21

127. Even though equation (2.14) is very simple andcan be used to derive a typical value of the mean indoor
radon concentration (for example, %,= 55 Bq mP3
with the radon entry rates given in Table 17 andi., = 1 h-I), it is clear that the prediction of the actual
radon concentration (and of its variation as a functionof time) in a given building cannot at this stage bemade with accuracy. Figure XVII shows that thevariation of the indoor radon concentration over one
week has no consistent pattern [ G I I]. Further theoretical and experimental work (as in [B26]) is required
to derive the values of x,. U and i., from themeasurements of environmental and technologicalparameters.

o L

a

I

12h

24h

24h

129. Upon alpha decay of attached Z16Po.the decay
product ?14Pbthus created may remain on the aerosolo r indoor surface o r become unattached as the resultof its recoil energy. Subsequently, the behaviour of?I4Pb is similar to that of ?I8Po. Upon the decay of
attached *I4Pb, the *I4Bi created typically remains
attached. since the recoil energy irom beta decay is
not sufficiently large to promote detachment. The
indoor behaviour of the radon decay products is
illustrated in Figure XX, where subscripts 1, 2 and 3
relate to decay products 218Po. 214Pb and :IJBi,
respectively, and superscripts fr, a and s designate theunattached state, the attached state and the presence
on indoor surfaces [B I]. Dotted lines denote theprocesses that have been neglected in this treatment.
This model of indoor behaviour of radon decay
products was first proposed by Jacobi [J4] and has
subsequently been extended and modified by a number

I

I

12h

128. When an atom of 2'8Po is formed through the
decay of radon, it is a free ion. Molecules of water
vapour or trace gases coalesce almost immediatelyaround the ion. forming a molecular cluster of 2-20 n m
in diameter (Figure XVIII). The ion and the cluster
are usually referred to as free, uncombined o r unattached decay products. Unattached 218Pois highly
mobile and, after 10-100 s, it attaches to an aerosol
particle (normal size in the range of 50-500 nm: see
Figure XIX); the other options offered to unattached'18Po are to plate out on the indoor surfaces, to betransported outdoors with the outgoing air o r to
decay into unattached *I4Pb.Attached 2'8Pois relatively
immobile and its plate-out on indoor surfaces issometimes ignored. The various processes are illustrated
in Figure XIX. The attached and the unattached decay
products are often distinguished by their environmental
behaviour and deposition pattern in the respiratory
system. In a series of air samples, the position and sizeof the peak related to the unattached fraction mayvary for reasons not yet completely elucidated [K 163.

12h

24h

I

12h

14 December 15 December 16 December 17 December
Figure XVII.

I

24h

12h

24h

18 December

12h

I
24h

19 December

Variation with time of Indoor radon concentrations.
[GHI

12h

20 December 1977

r-------'--------------- - - - - RADONI
I

EXHALATION

I

RAOON

O I C Y d -o*rra-

PLATEOUT

1

2

Flgure XVIII.

4

10
20
40
100 200
PARTICLE DIAMETER (nm)

400

1000

Histograms of size distribution of radon decay
products.

Flgure XIX.

The basic processes lnfluendng the activity
balance of radon decay products.

[PSI

[GI11

RA00r.I + RADOll DECAY PRODUCTS

I

Flgure XX.

I

RADON

I N D O O R SIIFlow chart of radon decay product behaviour under maraga
condltlons.

[Bllof researchers. notably Porstendorfer et al. [P4. PSI,
Shimo et al. [S46, S48, S49] and Bruno [Bl]. The
plate-out rate constant of unattached radon decay
products can be expressed as i. = v,S/V. where v, isthe deposition velocity (m h- ), S the total surface
area in the room and V the volume of the room. The
deposition velocity is about 2 m h-I for unattacheddaughters in still air [G12, K5, P5]. The surface tovolume quotient S/V is estimated to range from 3 to
6 m-I in rooms of dwellings if the furniture is taken
into account [PSI. The plate-out rate constant would
therefore be about 10 h-I in still air. In ventilatedrooms. the deposition velocity increases with the air
speed so that the plate-out rate constant is expected torange from 10 to 30 h-I in dwellings. Values reported
in the literature on the subject range from 2 h-I to
200 h-I [I7, I9,J4, K5, K 17, P4, S 1I, S44, L+'5].

r130. The deposition velocity for attached daughters
is approximately two orders of magnitude less thanthat for unattached decay products. leading to plareout rate constants of 0.1-0.3 h-I [K5, P5]. Consequently, plate-out of attached decay products is
negligible as a removal mechanism relative to decay
and ventilation.
131. The attachment rate X to aerosol particles has
been shown by Porstendorfer and Mercer [P6] to be a
linear function of the particle concentration
X=pZ(2.15)
where p is the attachment coefficient in cm3 h ' and Z
is the particle concentration in ~ m - Reported~.
values of
the attachment coefficient range from 1.8 lo-' cm' h-I
to 7.4 10-?cm3h'-I [P5]. For indoor air. an average
attachment coefficient of 5 10-'cm3 h-I may be assumed[P5]. The aerosol concentration indoor depends mainlyon the outdoor particle concentration, the ventilation
rate and the indoor sources of particles. Figure XXI
presents the measured variation of aerosol concentra-

Outdoors
O Indoors

-

caoo~
00

0

O0%

0

==='oaoo0
WINDOW CLOSED

lo3 1
h

6
Ba. sa--a'

4

Y11100U SLIGHTLY OPtll

4

b

I

i2 i 6 zb
412i623 June 1983
24 June 1983
TINE OF DAY (hour)

20

24

Figure XXI. Diurnal variation of aerosol concentrations outdoors and indoors of a buildlng for different ventilation rates.

[PSI

tions indoor and outdoor for different ventilation
rates [P5]. For high ventilation rates, the particle
concentration ranges between lo4 and 10' cm-3 and isabout the same indoors and outdoors. For low
ventilation rates, the indoor particle concentration
typically ranges from 2 10' to 2 lo4 cm-3 [PSI. Therefore the attachment rate X is expected to vary from
10 h-I to 500 h-I, according to the indoor particle
concentration. Average values between 20 and 50 h-'
may be expected in closed rooms with low ventilation
rates [P5].
132. The probability for recoil detachment fromaerosol particles upon alpha decay, also called recoil
factor, has been studied from the theoretical andexperimental point of view by Mercer [M4]. The recoil
energy possessed by a daughter product after alphadecay is about 100 keV, corresponding to a range ofabout 0.1 pm in solid material. For a typical aerosolof median diameter 0.2 pm, the recoil factor is about
0.8 [M4]. Upon beta decay, the recoil energy is only a
few electron volts. yielding a recoil factor of 0.01-0.02[P4]. The detachment from walls and other surfaces
has not been examined in detail in any work to date; itwould be expected that 25-50% of deposited activity
could re-enter the room air mainstream upon alphadecay [Bl, MI].
133. As already indicated. the equilibrium factor F isdefined as the ratio of the equilibrium equivalentradon activity concentration to the radon activity
concentration:
F = CYeq.Rn)/%ttn(2.16)
with
xcq,Rn = 0 . 1 0 5 +~ ~0 . 5 1 6 +~ ~0 . 3 7 9 ~ ~where 2,. x2 and x3 represent the activity concentrations of polonium-218, lead-214 and polonium-214,
respectively. The unattached fraction f, is usually
defined as the ratio of the equilibrium equivalentradon concentration in the unattached state and of thetotal:
It is also, however, sometimes defined as the ratio of
the equilibrium equivalent radon concentration that isin the unattached state and of the radon concentration:
Thc fact that two different definitions may be used forthe same quantity leads to a certain amount of
ambiguity in the interpretation of the results reported
in the literature when the definition used is not clearlyspecified. The same ambiguity exists when the unattached fraction of a given decay product of radon isreported, as the denominator of the equation call be
the radon activity concentration, the total equilibrium
equivalent radon activity concentration, or the equilibrium equivalent radon activity concentration of the
decay product under consideration. In this Annex, it isassumed in all cases that the denominator of theequation consists of the equilibrium equivalent radon
concentration, as, for example, in equation (2.17).
134. Bruno [BI] used the results of the survey
conducted by George et al. [GI I] on long-termaverage concentrations of radon and radon decay
product in 21 houses in the New York area to derive
the best fit for the attachment rate and the plate-out
constant rate. Assuming a ventilation rate of 1 h-I,
an equilibrium factor of 0.5 and a relatively highunattached fraction of 0.07, Bruno obtained i p , = 8 h-I
and X = 45 h-I, as shown in Figure XX, and indicatedthat the model would be more accuratelv validatedwith the help of simultaneous measurements ofventilation rate. radon concentrations and concentrations of attached and unattached 21BPo[B I].
135. Using another approach, Porstendorfer [P5]analysed the sensitivity of F and f, to the variations ofsome influencing parameters. H e concluded that F
and f, are only slightly influenced by the outdoor
concentrations of radon daughters (for i.,< 1 h-I),
the value of the recoil factor, the radon exhalation
rate and the plate-out rate of attached decay products;
however, F and f, are greatly influenced by the plateout rate of the unattached daughters and by theaerosol concentration in the room (Figure XXII). The
theoretical curves shown in Figure XXII conform wellto the experimental data for A, = 20-30 h-I. Since inmost cases the aerosol concentrations in dwellings
with low ventilation rates (i,,< 0.3 h-I) vary between
5 lo3 and lo4 cm-? (corresponding t o attachment ratesof 25-50 h-I [P5]), F values between 0.25 and 0.4 andf, values between 0.05 and 0.1 can be expected. This isin agreement with the experimental results of Wicke[W6] and Keller et al. [K6]. who measured median F
values of 0.37 and 0.33, respectively. in buildings in
the Federal Republic of Germany. In another study,
however, it was claimed that the model tends tounderestimate the equilibrium factor. as measured
values of the deposition rates of unattached radon
decay products in occupied buildings are found t o besmaller than those obtained in laboratory experiments[S441.
lo3,

AEROSOL CO~.ICENTRATION ( x

2
1.0

4

6

I

I

10

)

20

40

80

I

I

I

Room aerosol

0 Enhanced aerosol c o n c e n t r a t i o n
by c i g a r e t t e smoking

10loo
ATTACWIEIIT RATE

6.25

1000
(X)

(h-l)

Figure XXII. Equlllbrlum factor and unattached fraction tor
radon decay producls as a tunction of aerosol concenlratlon.

[PSI

136. The influence of the particle concentration on theequilibrium factor is further illustrated in Figure XXIII[S43], which shows the results of a study in which theequilibrium factor increased from 0.1 t o 0.8 as theparticle concentration varied from 1,000 to 25,000 cm-'.
a range typical of the indoor environment. Because of
the great influence of the aerosol concentration inbuildings on the equilibrium factor and on theunattached fraction, it is recommended that more
simultaneous measurements of the equilibrium factor
and the aerosol concentration be conducted.

PARTICLE CONCENTRATION ( p a r t i c l e s one3)
Flgure XXIII. Equilibrium factor Fversus partlcle concentratlonMeasured data and represenlatlve uncertainties are Indicated by
the solld clrcles and error ban. The solld line Is based on
calculated values for total radon decay products. while thedashed line Indicates calculated values for unattached radon
decay products.
[S431

137. In summary, the basic processes influencing theconcentrations of the radon decay products in indoor
environments are qualitatively well known. Quantitatively, it seems that the largest uncertainty lies in thedetermination of the plate-out rate of unattacheddecay products A,,. Morc simultaneous measurementsof the equilibrium factor and of the unattachedfraction, together with the aerosol concentration andthe ventilation rate, are necessary in order t o obtain aclear and consistent picture.
138. Information on the equilibrium factors measured
in several surveys is given in Table 18. In the Swedish
survey [SIZ], simultaneous measurements of the air
exchange rate and of the equilibrium factors were
perforded; the equilibrium factor was found t oincrease as the air exchange rate decreased ( F = 0.33
for i ,> 0.6 h-I: F = 0.51 for i.,.<0.3 h-I). The averagevalues obtained in the sunleys listed in Table 18 lie
between 0.3 and 0.8, most of the values being o n the
low side of this range. In this Annex, a value of 0.4 isadopted as the average equilibrium factor for radondecay products in dwellings. This is slightly lower than
the figure of 0.5 selected in the UNSCEAR 1977 and1982 Reports [U2, Ul].
3.

Results of indoor surveys

139. Large-scale surveys, usually involving morethan 100 dwellings, have recently been completed or
are in progress in several countries (Table 19). The
purposes of these large-scale surveys are to study the
distribution of population exposures, search for problem areas, or suggest remedial action to reduce
elevated natural levels or man-made enhancements.
An analysis of the results presented in Table 19 showsthat (a) in all cases, the radon and radon decay
product concentrations fit as a first approximation, alog-normal distribution. As an example, Figure XXIV
shows the histogram of indoor radon concentrations
obtained in a survey in Sweden [M30, SS], which
conforms reasonably well to a log-normal distribution
with a geometric standard deviation of 3.4. The
geometric standard deviations reported in Table 19
range from 1.6 to 5.2. The medians of the equilibrium
equivalent concentrations of radon range from lessthan 4 Bq m-3 in Poland [GI31 to about 30 Bq m-' in
Sweden [S8] and Switzerland [B4]: in the tail of the
distribution, relatively high concentrations of theorder of 100 Bq rn-j (EEC) or more were obtained;(b) the highest radon concentrations were caused by ahigh influx of radon from the soil, a high exhalation
rate from building materials, a high radon concentration in tap-water or a combination of the above
factors, depending on environmental characteristics
and the building design. In houses, a large fraction of
the highest radon concentrations could be consistently
attributed to high radon entry rates from the soil; inapartments, the influence of building materials wasmore important: (c) in most of the older surveys

radon and/or radon decay products were sampled
under conditions leading to high concentrations (basements or unventilated rooms). I n more recent surveys,
the sampling has been carried out over periods lastingfrom a few weeks to a year in order to average out thetemporal variations: the spatial variations could also
be taken into account by installing the measuring
devices in two or three locations (living-room. bedroom, basement). Thus. the intention in recent surveys
was to attempt to assess the exposures in buildings
under realistic as opposed to worst-case conditions;and (d) owing to the large influence of the radon
influx from the soil, radon concentrations tended on
average to be greater in houses than in apartments.
This was clearly shown in the Swedish survey [S8], as
well as in the survey from the Federal Republic of
Germany [W15], and may explain the relatively low
radon concentrations in Poland [GI31 and Austria[S16. S171, where a large proportion of the dwellings
are apartment buildings.
140. In the UNSCEAR 1982 Report (Annex D,paragraph 203) it was estimated that the mean indoor
equilibrium equivalent concentration of radon was
15 Bq m-3 in the temperate regions of the world. The
results presented in Table 19, although preliminary fora few surveys, make it possible to reassess this value.
The population-weighted mean of the indoor radon
concentrations obtained in the nation-wide surveys
was calculated assuming a log-normal distribution anda geometric standard deviation of 2.5 for countries
that reported only the median concentration. The
countries considered in the assessment are in thetemperate and high latitudes and represent about
750 million people. The population-weighted meanindoor concentration is found to be 5 1 Bq m-) while thearithmetic mean of the country means is 55 Bq m-j.
This is in agreement. perhaps as a coincidence, withthe mean radon concentration of 50 Bq
obtained

1 NOOOR RADON CONCENTRAT 1ON ( Bq ~ n - ~ )Flgure XXIV.

Dlrtributlon of Indoor radon concontratlons In Swedish homes.
[M30, SB]

for the reference house with a radon entry rate of
50 Bq h-I md3 and an air exchange rate of 1 h-I.
Using that round value of 50 Bq m-3 and an average
equilibrium factor between radon and its decay
products of 0.4 yields an average indoor equilibrium
equivalent concentration of radon of 20 Bq m-3 in thetemperate regions of the world: the geometric standard
deviation of the distribution is expected to be about
2.5.

will stay in the lungs. the dose rate due to alpharadiation was obtained as [IZ]:

141. There is little information on the indoor radon
concentrations in the tropical regions. At Bombay,
India, an indoor radon concentration of 19 Bq m-"
and an equilibrium factor of 0.43 are reported as
typical for normal areas [M29], while a mean radon
concentration of 34 Bq m-I may be derived fromindoor measurements at Hong Kong [T13], which is
not thought to be representative of tropical regions. It
is safe to assume that the mean indoor radon
concentrations in tropical regions are smaller than intemperate latitudes but the data base available is too
small to allow a reliable assessment to be made.
Possible values of the population-weighted world
average of the indoor conckntrations of radon gas,taking into account that the population in tropicalregions is about half that in temperate latitudes, range
from 33 Bq m-3 (assuming that the radon concentration in tropical regions is equal to zero) to 50 Bq m-I(assuming that the niean radon concentration intropical regions is the same as that in the temperatezones). I t is tentativelv assumed in this document thatthe population-weighted world average of the indoor
radon concentrations is 40 Bq m-j. The same method
can be used for the equilibrium equivalent radon
concentration: the range of possible values is from 13
to 20 Bq m-3 and the mean population-weighted
world average of the indoor equilibrium equivalentconcentrations of radon is tentatively assumed to be
15 Bq m-3.

143. For the short-lived decay products of radon.
use was made of the potential alpha-energy intake byinhalation during time period T, which is given by

C. EXPOSURE-DOSE RELATIONSHIPS
1.

(a)Inhalation

Relationships from rhe UNSCEAR 1982 Report

D,,,, (nGy h-I) = 0.04 xRn..,, (Bq m-3)

(2.20)Taking a quality factor of 20 for alpha-radiation andapplying a weighting factor of 0.12 for the lungs andof 0.88 for the other tissues. the effective dose
equivalent rate was calculated as

H ~ (, n ~ h-1)
v = 0.18 x ~ , . ~(, , ~ m-3)qI,,, = Ei.4 I," T %,.R"(2.21)(2.22)

where I,, is expressed in joules; E/A = 55.4 10-lo J Bq-'
is the potential alpha energy per unit of inhaledequilibrium equivalent activity; I,, is the mean breathing
rate, taken to be equal to 0.8 m3 h-I indoors and1 m3 h-I outdoors; T is the time period in hours; %,,.R,
is the equilibrium equivalent concentration of radon
daughters in Bq m--'.
144. The dosimetry must consider two target tissues
in the lung: the tracheo-bronchial basal cell layer(T-B) and the pulmonary epithelium (P), the latterincluding the alveolar region and the non-ciliatedterminal bronchioles. In the UNSCEAR 1982 Report(Annex D, paragraphs 140-144),the conclusions of anexpert group of the Nuclear Energy Agency (NEA) of
OECD [N 151 were adopted after taking into consideration various dosimetric models [H3, H4, J5, 56, 573.
The Committee indicated that from the dosimetricmodels, it follows that the conversion factors between
the inhaled potential alpha-energy intake I,,, of the
decay product mixture and the committed dose
equivalent H to the tracheo-bronchial basal cell layer
and to the pulmonary epithelium show nearly linear
relations with the unattached fraction fp of the total
potential alpha energy of the decay product mixture:
HFB/Iw = a,,+ bT-, fp(2.23)

and
Hp/l,,= ap(l-f,,)(2.24)

where the term a gives the conversion coefficient for
the attached decay products, which depends on theactivity median diameter (AMD) of the carrier aerosol.
It should be noted that the calculated value of I,,
applies only to the specified breathing rate.

142. Because of their different physical properties,
radon gas and radon decay products are consideredseparately. Inhaled radon, being a noble gas, isconstantly present in the air volume of the lungs at theconcentration in air and is partly dissolved in soft
tissues. Taking the solubility factor for soft tissues tobe 0.4 and assuming that the short-lived decay
products decay in the same tissue as radon gas, thefollowing relationship for soft tissues other than thelungs was derived from [I2]:145. Taking f, = 0.025 and AMD = 0.2 pm for theindoor environment. the different dosimetric models
yield
DT-B/lpol= 1.2 - 1.7 G YJ-I
and
Dp/Ip,,= 0.13 - 0.4 Gy J-'

In the case of the lungs, in addition to the dissolved
radon, the radon content of air in the lungs must be
taken into account. Assuming the air volume in thelungs to be 3.2 lo-' m1 for Reference Man andassuming further that the short-lived decay products

For the purpose of dose estimation, values of
DT-B/Ipol= 1.5 Gy J-I and Dp/I,, = 0.2 Gy J-I wereselected. Following the ICRP recommendations [I2],
the Committee decided to split the weighting factor
for the total lung and to apply a weighting factor
w = 0.06 to each of the two target tissues in the lungs.
As the doses to tissues other than the lungs can beneglected. the effective dose equivalent per unit ofinhaled potential alpha-energy intake of 222Rndecay
products was found to be in the range of
Hcrr/I,,, = 1-3 SVJ- 'A reference value of 2 Sv J-I was adopted in the
UNSCEAR 1982 Report for indoor exposures.
146. For the exposures in outdoor air. AMD was
taken to be 0.1 pm, leading to a dose equivalent perunit intake higher by a factor of 1.5 than those forindoor exposures:
DT-B/Ipot= 2.2 Gy J-I
Dp/I,, = 0.3 Gy J-I
147. Assuming steady-state conditions, the dose rates,in nGy h-I. are, for indoor exposures, approximately
equal tocorresponding to effective dose equivalent rates, innSv h-I, of148. For outdoor exposures, the dose rates, innGy h-I, are found to be
DT-B= 12Xcq.Rnand D P = 1.7 x,,.,"

while the effective dose equivalent rate. in nSv h-I, is

As indicated later (paragraph 153). this is an overestimate.
149. All the dosimetric coefficients given above referto adult members of the ~ u b l i c .correction factors
should be applied for infants and children, to accountfor the age-dependent change in lung mass andbreathing rate. The UNSCEAR 1982 Report (Annex
D, paragraph 151) estimated on the basis of the NEA
expert report [N15] that the effective dose equivalent
for the age group of up to ten years might on the
average be a factor of 1.5-2 higher than for adults.

similar. The results obtained by NCRP are given in
Table 20 as per cent changes from the nominal annual
dose for males. The standard deviation of the annual
dose to an individual is estimated to be 120%. if thevarious factors other than the radon concentration areunspecified. and less than loo%, that is. better than afactor of 2, if some of the parameters are measured orreasonably well estimated [N 141.
152. According to Table 20, the estimate of bronchialdose is very sensitive to the particle size spectrum andto the location of target cells in the tracheo-bronchialtree. The per cent variation in annual dose for a verylarge shift in the median particle size from an averageof 0.125 pm would range from + 100% for the 0.05 pm
particle to -20% for the 0.17pm particle.
153. The values of AMD adopted in the UNSCEAR
1982 Report for the calculation of doses in the
respiratory system from inhalation of radon decay
products were 0.1 pm and 0.2pm for outdoor andindoor exposures, respectively. Reported indoor AMDs
are 0.125 pm in the United States [G 1 I] and 0.17 pm(G,= 3.5) in the Federal Republic of Germany [B30,
P5]. The doses calculated by the Committee forindoor exposures may thus be slightly underestimated.
Regarding the situation outdoors, a significant shift tolarge particle sizes with a mean AMD of 0.39 pm anda mean G, of 2.3 [P5] was observed in the Federal
Republic of Germany [B30]; a similar shift had also
been measured in the United States [S45]. In anotherseries of measurements in the United States, the AMD
was found to range from 0.09 to 0.37 pm with a meanof 0.16pm [P23]. In the case of outdoor exposures,the doses calculated in the UNSCEAR 1982 Report
andshown in paragraph 148 may thus be overestimatedby a factor of about 2. If the dose coefficients related
to outdoor exposures are divided by two, the resulting
values are very similar to the dose coefficients forindoor conditions. In this Annex, the same dosimetriccoefficients, in terms of absorbed dose rates per unit
equilibrium equivalent radon concentrations, havebeen used for indoor and outdoor conditions. Thisimplies similar values of the AMD. about 0.2 pm forboth indoors and outdoors.

(6) Consideration of other information
150. NCRP [N14] estimated the variability of thebronchial dose from inhalation of radon decay products due to the uncertainties attached to the many
physical and biological parameters which are involvedin the calculation of absorbed doses per unit concentration of radon decay products. The physical characteristics include the fraction of unattached =I6Poin theatmosphere, the daughter product equilibrium, particle
deposition models, the particle size distribution in theatmosphere and the physical dose calculation. Amongthe biological characteristics are the breathing pattern(including nasal deposition), bronchial morphometry,the mucociliary clearance rate, the location of target
cells and the mucus thickness.
151. The dosimetric model used by NCRP to derive
the bronchial dose is different from that used in the
UNSCEAR 1982 Report but the parameters are thesame and the uncertainties should be qualitatively

154. The dose factor of 9 nGy h ' per Bq m-< asderived in paragraph 147, is based on a medianparticle size of 0.2 AMD for both indoor and outdoor
exposures and on breathing rates of 0.8 m3 h-I indoors
and 1.0 m3 h-' outdoors. Other investigators havedeveloped factors based on other reasonable sizes andrates. as well as other deposition models, withoutmarkedly changing the derived dose factors.
155. In the NCRP model [N14], based on the workof Harley and Pasternack [H3], the doses are calculated
for the shallow basal cells lying 12pm below theepithelial surface of the fourth generation of thebronchial tree that was found to experience themaximum deposition density. The deposition model
was based on the Weibel lung morphometry [W16] asused by several investigators. The average dose factor
for adults was 6 mGy h-I per WLM or 10 nGy h-I
per Bq m-3 (EEC). Inclusion of later information onmorphometry has tended to smooth out the maximum

dose over the entire bronchial tree. Harley and Cohen[H23] measured deposition in a bronchial cast andfound it to be very uniform. The dose factor. averaged
over all branch airways below the trachea. is 5 mGy
per WLM or 8 nGy h-I per Bq m-3 (EEC).
156. Calculations have been performed in Canada of
the bronchial dose per unit EEC radon concentrationfor various indoor aerosol conditions [D14]: the relative
range of the bronchial dose per unit EEC radon
concentration is from 1 to 5 when indoor aerosol
conditions change as a result of seasonal air circulation
practices, but is only from I to 1.6 when the bronchialdose per unit radon concentration is considered. The
bronchial dose rate per unit radon concentration was
calculated to range from 2.5-4 nGy h-' per Bq m-3 foradult males.
157. In Belgium. Vanmarcke et al. [V4] measured
indoor aerosol characteristics, as well as radon andradon decay product concentrations. under various
conditions in several different rooms and calculated
the resulting bronchial dose rates per unit radon gas
and radon EEC concentration, using the models
considered by OECD [NISI. With respect to dose
calculations, Vanmarcke et al. [V4], as in [D14].
obtained a narrower range when the bronchial dose
was related to the measured radon gas concentration
rather than to the measured equilibrium equivalentconcentration, a typical value being 5 nGy h-' per
Bq n l - b f radon gas.

158. James [J19]. in a review of all the factors
involved in the dosimetry of radon decay products.
suggested that i t would be appropriate to consider
secretory cells as well as basal cells as target cells,
implying that the bronchial dose should be calculated
for the entire depth of the bronchial epithelium rather
than for the basal cells lining the basement membranealone. This change, combined with the use of a revised
deposition model, led to an effective dose equivalent
rate per unit EEC radon concentration of 24 nSv h-I
per Bq m-3 [J19].
159. The value of bronchial dose rate per unit EEC
radon concentration adopted in this Annex for indoor
and outdoor conditions is 7 nGy h-I per Bq m (seeTable 21). If the equilibrium factor is assumed to be
0.4, the bronchial dose rate per unit radon gas
concentration is about 3 nGy h-I per Bq m '?, which isin the lower part of the range of values recently
published [D4. J19, N22, V4]. The corresponding
effective dose equivalent rate is about 10 nSv h-I per
Bq m-' (EEC) including the contribution from thepulmonary region. This is the mean dose in thespecified target tissues. I t is recognized that the dose
factors may vary within a factor of about 3 according
to the target cells considered in the dosimetry. Also,
recent studies seem to indicate that for indoor
conditions, the bronchial dose is better related to theradon gas concentration than to the equilibrium
equivalent concentration. These results. however, need
confirmation. The dose factors adopted in this Annex
are only slightly modified in comparison to those usedin the UNSCEAR 1982 Report.

-'

2.

Ingestion

160. Ingestion of water containing dissolved radon
results in doses in the body tissues from the radon gas
and the radon daughters in the water. Sluch of the
dissolved radon is released from water during cooking.
The only significant radon intake comes from thedrinking of water. The main part of the ingested radon iseliminated from the body very rapidly through thelungs. The largest dose is received by the stomach;estimates of stomach doses per unit activity of radon
ingested vary between about 2 and 10 nGy Bq-' [A3,B2. B3, C20, H7, K7, S151. In this Annex. an averagevalue of 5 nGy Bq-I has been adopted.
161. Assuming an average consumption of 0.5 litre
of water (taken from the tap, without processing) per
day and per person, the annual stomach dose equivalent per unit 2Z2Rnconcentration in water would be
0.9 nGy per Bq m-'. Using a weighting factor of 0.06
and a quality factor of 20 for alpha-radiation, theannual effective dose equivalent per unit radon concentration in water is thus about 1 nSv per Bq m-'.
3.

Summary162. Table 21 summarizes the dosimetric coefficients
adopted in this Annex for inhalation and ingestion ofradon and radon decay products. It is to be noted thatthese dosimetric coefficients apply only to adults in
the general population.

D.

DOSES

163. The annual absorbed doses resultingfrom indoor
and outdoor inhalation of radon short-lived decay
products have been derived from the estimated mean
concentrations and dose coefficients discussed previously, using occupancy factors of 0.8 and 0.2 forindoor and outdoor exposures, respectively. The population-weighted world means of the annual absorbed
doses in the lungs and in tracheo-bronchial cells add
up to about 100 pGy and 800pGy, respectively. The
corresponding annual effective dose equivalent amounts
to approximately 1,100 pSv, the contribution of outdoor exposure being 70pSv and that of indoor
exposure 1,000 pSv.
164. I t should be stressed that these values apply toadults in the general public and are averaged overlarge population groups. Very high individual doses
can be obtained, especially from indoor exposures at
the tail of the log-normal distribution. The situations
in which these elevated exposures arise have been
discussed in this section.
165. A refined methodology could distinguish theindoor concentrations in dwellings from the indoor
concentrations in working places and public buildings;
it could also take into account the daily variations of
the indoor concentrations and of the occupancy
factors.

166. Some information is available on the dependence
of indoor radon concentration upon the type ofbuilding (see, for example, Figure XXV [WlS]).
Further surveys of this type should be encouraged.
167. There is abundant information on the daily
variation of indoor radon concentrations. which could
be reviewed and used in the refined methodology.
Figure XXVI [C16] gives an example of measured
diurnal variation of indoor radon concentrations.

Detached
housesFlgure XXV.

Multifamily
houses168. A survey of diurnal variation of indoor andoutdoor occupancy factors has been published in the
United Kingdom [B23]: it is presented in Figure
XXVII. Occupancy factors reported for populationsin China [B24] are similar to those obtained in the
United Kingdom.

High r i s ebuildings

169. Information of the type presented in Figures
XXV, XXVI and XXVII can be combined to estimate
refined annual absorbed doses from inhalation ofMedian radon concentration levels In dlflerent
types of houses.

~ 1 5 1o Indoors
Indoors ( a i rcondi t i o n e d )

1
0

I

I

1

I

I

I

I

I

2

4

6

8

10

12

14

16

I

1

I

I

18 20

22

24

TIPE (hour)
Flgure XXVI.

Diurnal variation of indoor radon-222 concentrations.

[C161

-

- Indoors a t home..... Indoors elsewhere----- Out o f doors

1

-

I

I

L
I

- - - - - - - - - - - - - - - - - .............
- - - - -,...............
-I

I..

L

I1

p.r.n.-.r..tl
I

I

I

I

TIHE OF DAY (hour)
Flgure XXVII.

Average occupancy over a whole year In the Unlted Klngdorn.

P231

radon decay products. Further refinements, which
could not be implemented at present because of
insufficient information, would take into account theage distribution of the populations exposed. urban
versus rural population distribution, as well as seasonalvariations and the latitudinal distribution of the radon
concentrations.

111. INDUSTRIAL ACTIVITIES
170. The industrial processes considered are thosethat bring to the surface of the earth materials
containing above average concentrations of the naturalradionuclides, such as geothermal work or phosphatemining, and those which treat material containing
average or above average amounts of the naturalradionuclides and concentrate them in one or moreproducts or by-products, such as coal burning or the
production of fertilizer from phosphate rock. In theseindustrial processes, the hazard from radiation is
generally small compared to that from other chemical
substances; therefore, radiation is not systematicallymonitored. Assessment of such exposures is usuallybased on sketchy information derived from isolated
surveys. The only assessment at the national scale that
was available to the Committee is that of theNetherlands [P26]. In this. the naturally occurring
radioactive materials discharged to the environment
by non-nuclear industries in the Netherlands wasestimated using a crude model based on radionuclide
concentrations in raw materials, mass flow, and information on the technologies used in industrial processes. The annual effective dose equivalents received
by members of the public in the Netherlands were
estimated to be about 40pSv on average, and about
0.7 mSv for individuals of the critical group consistingof consumers of large amounts of fish [P26].

173. Although the reported activity mass concentrations range over two or three orders of magnitude. theaverages from the various countries are in fairly good
agreement. Figure XXVIII shows, for example, the23XUlevels measured in 800 samples of coal mined in
the United States [W12]; they range from 1 to
1,000 Bq kg-'. In this Annex, as in the UNSCEAR
1982 Report, it will be assumed that the average
activity mass concentrations of "OK,"SU and 23?Thin
coal are 50, 20 and 20 Bq kg-'. respectively. and thatthe decay products of ?"U and ?j2Thare in radioactive
equilibrium with their precursor.
174. The uses of coal in OECD countries are listed
in Table 23. together with the amounts involved in

171. This chapter reviews the information available
world-wide on radiation exposures from industrial
activities, classified into: (a) combustion of coal; (b)other energy production; (c) use of phosphate rock;and (d) metal mining and processing. When possible.
both occupational exposures and exposures of members of the public are considered. Collective effective
dose equivalent commitments resulting from atmospheric discharges of radioactive materials are estimatedusing the crude models described in the UNSCEAR
1982 Report ([Ul], Annex C. paragraphs 24-27).

A.

ENERGY PRODUCTION FROM COAL

172. Coal. like most materials found in nature,contains trace quantities of 40Kand of 238U,232Thand
their decay products. By burning coal, the activities ofthese naturally occurring radionuclides are redistributed from underground into the biosphere. Expressedin coal equivalent for energy purposes, the world
production of coal was 3.1 l o J 2kg in 1985 [UIS], themain producers being China, the USSR and theUnited States. Table 22 presents the amounts of coalproduced in various countries and the measured
activity mass concentrations of natural radionuclides.

ppm URANIUM
Figure XXVIII.

Dlstrlbution of uranium-238 in 800 coal samples
lrom the United States.

w121

several countries 1061. Most of the coal is used inelectric power stations and in coke ovens: even though
the use of coal for space heating is not as important as
it was years ago, i t is still significant in somecountries. It will be assumed that. on a world-widebasis. 70% of the coal produced is burned in electric
power stations, 20% in coke ovens and 10% in houses.
175. Radiation exposures occur throughout the coalfuel cycle, which consists of (a) coal mining; (b) use ofcoal: and (c) use of fly ash. Occupational exposuresand exposures of members of the public are estimated,in so far as data are available. It should be emphasized.
however, that the contribution of radiation hazards tothe overall health and environmental impact resulting
from the exploitation of coal is generally estimated tobe quite small (see, for example, [B39], [U16] and[M 1 71).
1. Coal mining

176. Coal miners are exposed to coal dust and the
decay products of radon and thoron. Coal mines areusually well ventilated to keep the methane and dustlevels low; consequently, the radon concentrations arealso relatively low. Table 24 summarizes publishedmeasurements from several countries. Radon concentrations in coal mines are comparable to thoseobserved in dwellings. From measurements in British
coal mines, a maximum individual effective dose
equivalent of 1 mSv per year, and an upper limit for
the normalized collective effective dose equivalent of
3 man Sv per GU' a have been calculated [C13, R4].
Unquantified additional exposures may result fromthe activity present in mine water [T8].
177. The global production of electrical energy bycoal burning was about 600 GW a in 1980. resulting inan upper estimate of the total collective effective dose
equivalent to coal miners of 2,000 man Sv. This figure
is taken to represent the collective effective dose
equivalent for the world for one year of mining coal.
including the mining of coal for purposes other thanelectrical energy production.
178. Members of the public are exposed to the radon
activity present in the exhaust air of coal mines. Thereare currently no measured data on emission of radonfrom coal mines. It can be assumed, as in [S32], that
20% of the radon contained in the ore is released
during the mining process and that the radon release
rate from the exposed ore surface is a factor of 7
greater than that resulting from mining. Taking themass of coal required to produce an electrical energyof I G W a to be 3 lo9 kg and a mean radon
concentration in coal of 20 Bq kg-'. the normalizedradon release from coal mines would be 36 GBq per
GW a. Another method consists in scaling the radon
releases from coal mines to the radon releases fromuranium mines, taking into account an average factorof 1,000 between the average activities of 226Raper
unit mass of uranium ore and of coal [J15]. Thismethod leads to a normalized radon release from coalmines of 600 GBq per GW a. The normalized collective
effective dose equivalent commitments corresponding

to the two values of radon releases are 6
man Sv per GW a.

and179. Using the two methods described in the previous
paragraph, the activity of radon released per year fromcoal mining all over the world is estimated to be 30 TBq
and 800 TBq, resulting in collective effective dose
equivalent commitments of about 0.5 and 10 man Sv,
respectively. Although differing by a factor of 20, thelatter values are small compared to other radiation
exposures from the coal fuel cycle and do not deserve
further investigation.
2.

Use of coal180. The uses of coal that are considered here areelectrical energy production, carbonization and spaceheating in dwellings.

(a)Coal-fired pobcer planrs

181. In the production of electric power, coal isburned in furnaces operating at temperatures of up to
1,700" C. About 3 lo9 kg of coal is required to
produce 1 G W a of electrical energy. In the combustion
process, most of the mineral matter in the coal is fused
into a vitrified ash. A portion of the heavier ash,
together with incompletely burned organic matter.
drops to the bottom of the furnace as bottom ash or
slag. The lighter fly ash, however, is carried throughthe boiler, together with the hot flue gases and any
volatilized mineral con~pounds,to the stack. where,
depending on the efficiency of emission control
devices, most is collected while the rest (escaping flyash) is released to the atmosphere. Table 25 presents
the ash content of coal burned in the United Kingdom
in power stations and for other uses, together with theamounts of ash produced; it is clear that coal
combustion in coal-fired power plants accounts forthe bulk of the total ash production. The corresponding information on the atmospheric emissions ofparticulates (Table 26), however. indicates that thepower stations are a small contributor to the total
emissions of particulates, implying that the efficiencyof the emission control devices used in power plants israther high.
182. The radionuclides included in the non-combustible mineral matter of coal are partitioned between
the bottom ash and fly ash, except for the gases andvolatilized minerals, which are incorporated directly
into the flue gases. In large power stations. there isabout 20% bottom ash and, therefore, 80% fly ash.
Owing mainly to the elimination of the organic
component of the coal, there is approximately anorder of magnitude enhancement of the activity
concentrations from coal to ash. Consequently, thenatural radionuclide concentrations in ash and slagfrom coal-fired power stations are significantly higher
than the corresponding concentrations in the earth's
crust. The arithmetic averages of the reported activity
mass concentrations in escaping fly ash are 265 Bq kg-I
for 40K, 200 Bq kg-' for 238U,240 Bq kg-I for 226Ra,
930 Bq kg-' for 2'0Pb, 1,700Bq kg-! foraOPo, 70 Bq kg-'for 232Th,110 Bq kg-' for 22aThand 130 Bq kg-' forf"Ra ([Ul], Annex C , paragraph 11). There is anenrichment by a factor of about 3 for 210Pband 5 for*"Po in relation to the rest of the "8U decay series.
This is probably because of the volatilization of "'Pb
and 210Poduring the combustion and a condensationof these radionuclides down the flue line on the finer
fly-ash particles.
183. The activities of natural radionuclides discharged
to the atmosphere from a power plant per unit
electrical energy produced depend o n a number offactors such as the activity concentration in coal, theash content of the coal, the temperature of combustion,
the partitioning between bottom ash and fly ash, andthe efficiency of the filtering system. Marked differences should therefore be expected between the measured
activities discharged per unit energy produced fromdifferent power plants. Most of the available information o n the normalized atmospheric discharges ispresented in Table 27. Apparently, there are two typesof coal-fired power plants used throughout the world:older ones, which release about lo%, of the fly ash
produced: and more modern ones. which are equippedwith sophisticated retention devices and, as a result.
release only about 0.5% of the fly ash. Table 27
presents estimates of normalized discharged activities
for such older and more modern plants. They havebeen derived on the following assumptions: the
combustion of 3 lo9 kg of coal is required to produce
a n electrical energy of I GH' a; fly ash accounts for
80% of the total ash production; the activity massconcentration in coal is 20 Bq kg-' for the radionuclides of the 13'U and of the 232Thdecay series; andthere is an enrichment factor of 3 for "OPb and "'Po.
Releases of '12Rn and of 220Rn must be estimatedseparately because radon is not collected by theparticulate control devices. The activities of ::?Rn andof :"Rn released per GU' a have been assessed at
60 GBq on the basis of the conservative assumptionthat all of the radon activity contained in the coal isdischarged to the atmosphere.
184. The main pathways through which the populations living around coal-fired power plants are exposed
to enhanced levels of natural radionuclides are inhalation during the cloud passage and external irradiationa n d ingestion follon~ingdeposition of activity on the
ground. The collective effective dose equivalent commitments due to those pathways, normalized to the generation of 1 G W a ofelectrical energy, have been estimatedusing the crude models described in the UNSCEAR
1982 Report ([UI], Annex C, paragraphs 24-27).
Tables 28 and 29 present the results obtained for thereference older and more modem coal-fired power
stations, respectively: they amount to about 6 and0.3 man Sv per G W a. Assuming that, on a worldwide scale, two thirds of the electrical energy provided
by coal-fired pouter stations is due t o old plants (andone third to modern plants), the average normalized
collective effective dose equivalent commitment isapproximately 4 man Sv per G W a, while the overall
figure for the world for one year of practice is about
2.000 man Sv.
185. The release of I4C-free carbon dioxide emitted
by the coal-fired power plants will have the effect ofdiluting the natural concentration of IJC in thebiosphere. The reduction in the natural 14C collective
effective dose equivalent commitment resulting fromthe release of activity-free carbon dioxide is estimatedto be about 60 man Sv per G W a assuming that:(a) the combustion of about 3 Tg of coal is required to
produce an electrical energy of 1 G W a; (b) the coalcontains 85% carbon by mass: (c) the natural activity
mass concentration of I4C in coal is approximately
226 Bq kg-I; and (d) the collective effective dose
equivalent commitment per unit release is 110 man Sv
per TBq. This reduction in the natural effective dose
equivalent commitment would be over thousands ofyears.
186. Annual individual effective dose equivalents
resulting from inhalation during the cloud passage
have been estimated. Assuming an effective stackheight of 100 m and a uniform wind rose, the annual
average of the ground-level air concentration per unit
release rate is estimated to be about 4 lo-& Bq m-'
per Bq s-'I at approximately I km from the stack. For
an individual of the critical group living near a coalfired power plant producing annually 1 G W a of electrical energy. the resulting annual effective dose
equivalent would be about I pSv for a modern plant
and about 2OpSv for an old plant. The annual
effective dose equivalents from ingestion and external
irradiation would be of about the same magnitudeafter 20-30 years of operation. Calculated doses fromingestion are very sensitive to the assumptions madeabout food-chain transfers. Annual individual doses
are, in any case. small; it is worth noting that recent
measurements in the environment surrounding coalfired power plants show no statistically significant
increases in the activity concentrations of naturalradionuclides in samples of air [T7], precipitation[T7]. soil [B 15. S30, T7], vegetation [S30. T7]o r cattle
organs [B16, S30. S31] that could be attributed to theoperation of power stations.
187. Only atmospheric discharges have been considered so far, as coal ash is not usually directly
discharged into the aquatic environment. It may be
stored in ash ponds. from where some activity may
leach into the aquifer. Ground water may then carrythe leachates into the nearest river. The leachability of
the ash is quite low [S27]. however, s o aquatic
discharges are not likely to pose a radiation problem.
at least in the short term.
188. Radiation exposures of workers in coal-fired
power plants are thought to be mainly caused byinhalation of airborne fly ash. Effective dose equivalents of 150 pSv per year have been estimated in the
United Kingdom for the most exposed groups ofpower station workers on the basis of exposure t o aconcentration of respirable fly ash in air a f 0.5 mg m->[C14]. In Yugoslavia, significant concentrations of
210Pbin the urine of individuals working in a coalfired power plant burning high activity coal have beenreported [B 12, B221.
189. Values of collective effective dose equivalent
received by workers in coal-fired power plants are notavailable. An upper estimate can be derived from theindividual effective dose equivalent of 150 pSv per
year calculated in the United Kingdom, assuming thata labour force of 500 persons is required to produce
an electrical energy of 1 GW a per year. The normalized
annual collective effective dose equivalent would be at
most 0.1 man Sv per GW a. The global production ofelectrical energy by coal burning was about 600 GW a
in 1980. resulting in an upper estimate of the totalcollective effective dose equivalent to workers in coalfired power plants of 60 man Sv.

/b). , Domestic use
190. Another major use of coal is domestic cooking
and heating. No information has been found in theliterature on the environmental discharges of naturalradionuclides from this source. The use of coal forcooking and heating in private homes may, however,be estimated to result in high collective dose commitments since chimneys are generally low and notequipped with ash removal systems and the population densities around sources of emission are generally
high. Figure XXIX [U16] presents trends in urban
smoke concentrations in the United Kingdom andshows that domestic sources, which have decreased inimportance since 1960, still remain substantial. I t isestimated that in a simple open fire burning coal,some 3 4 % of the coal is emitted as tarry smoke whilein smoke-reducing appliances, which have only beenmarketed since the early 1970s. only 0.3-0.6% of thecoal burned is emitted as smoke [U16]. Smoke is a
mixture of soot, tarry matter and inorganic substances,produced when bituminous coal is incompletely burned.
Measured activity mass concentrations of naturalradionuclides in smoke have not been found, bul they

can be expected to be between those in coal and ash(without enrichment) and are likely to be closer tothose in coal. Assuming that the activity massconcentrations in smoke are equal to those in coal andthat 3.5% of the coal is emitted as smoke, the annual
world-wide atmospheric releases caused by domestic
burning of coal are estimated to be 0.7 TBq of 'OK andand
0.3 TBq of each of the radionuclides of the232Thseries (radon and thoron excepted): these figures
become 20 times greater if it is assumed that theactivity mass concentrations in smoke are equal tothose in ash and that the coal burned has a 5% ash
content. Taking the average population densities
around the houses to be lo3 km-z leads to collective
effective dose equivalent commitments resulting froma yearly world-wide use of coal in the range of
2,000-40.000 man Sv. This estimate is highly uncertain,
as it is not supported by any discharge or environmental data.
(c)

Coke ovenx

191. Coal is also used in vast amounts in coke ovens:
however, relevant information on the releases ofnatural radionuclides from coke ovens has not beenfound.
3.

Use of fuel ash

192. Large quantities of coal ash (fly ash and bottom
ash combined) are produced each year throughout theworld. The global production of coal equivalent in1985 was 3.1 1012kg (Table 22); assuming that coalburned in power stations represents 70% of the total

lndustry (including r a i l w a y s )Donies t i c

Figure XXIX.

[

600
550

Smoke: trends in emissions and average urban concentrations in the United Kingdom.
tUl61

consumption and that its ash content is 13%, about
280 million tonnes of coal ash are produced annuallyin coal-fired power stations. Taking the average
activity mass concentrations of natural radionuclides
in coal to be 50 Bq kg-' for O' K and 20 Bq kg-' for?JbUand for '32Th, the average activity mass concentrations of 'OK, 238U and "?Th in coal ash are
estimated to be 400. 150 and 150 Bq kg-'. respectively.
Compared with normal soil, the average activity massconcentration of O
' K is similar, but those of ="U and
232Thare six times higher.
193. Coal ash is used in a variety of applications. thelargest of which is the manufacture of cement andconcrete. I t is also used as a road stabilizer, as roadfill. in asphalt rnix and as fertilizer. Data on thevarious uses of coal ash in several countries have beenreported [G20]. It can be estimated that about 5% of
the total ash production from coal-burning power
stations is used for constructing dwellings: this represents an annual usage of 14 million tonnes.
194. The use of coal ash in building materials may
result in changes in the indoor doses ouing to external
irradiation and to inhalation of radon decay products.
With respect to external irradiation. Siotis and Wrixon[S5], assuming that the use of concrete containing fly
ash for constructing dwellings would result in an
additional activity mass concentration of 22bRa in
concrete of 13 Bq kg-', calculated that the additional
effective dose equivalent from indoor exposure would
amount to 20 11Sv per year. Stranden [S28], on thebasis of additional activity mass concentrations of
10 Bq kg-I of lz6Raand 8 Bq kg-' of 232Th,estimatedthat the additional absorbed dose in air would be
90pGy per year in concrete houses and 40pGy per
year in wooden houses. These figures would be
reduced to 70 and 30uSv for concrete and wooden
houses, respectively. if the conversion coefficient fromabsorbed dose in air to effective dose equivalent weretaken to be 0.7.
195. There are conflicting views on the impact of theuse of fly ash on the dose from inhalation of radon
decay products. Siotis and Wrixon [S5] measured theradon exhalation rates of concrete blocks made by acement manufacturer under controlled conditions
using cement containing varying proportions of fly
ash of high 226Raactivity mass concentration (330 and
800 Bq kg-'). The concrete blocks containing fly ash
were found to present radon exhalation rates higher
than those of concrete blocks without fly ash. Siotis
and Wrixon [SS] estimated. on the basis of thesemeasurements, that the additional radon concentration in a model dwelling would be 1.5 Bq m-j.
resulting in an effective dose equivalent due to indoor
exposure to radon decay products of about 40 pSv per
year. Radon concentrations in Polish dwellings builtwith concrete blocks made almost entirely of fly ash
were found to be higher than those in dwellings builtwith concrete blocks containing no fly ash [B14].
Stranden [S28], however, observed lower radon exhalation rates from concrete blocks containing 5% fly ash
than from ordinary concrete blocks; the two types ofblocks had been especially constructed for the experiment and differed only in the inclusion of fly ash. The

resulting reductions in the radon concentrations inmodel dwellings have been calculated by Stranden[S28] to be 3 Bq rn-' in a wooden dwelling and
10 Bq m-j in a concrete dwelling. The corresponding
reduction in effective dose equivalent from indoor
exposure to radon decay products would be 90pSv
per year in a wooden building and 300 11Sv per year ina concrete dwelling. I n other controlled studies [U6.
V3], the substitution of varying amounts of ordinary
cement with fly ash cement yielded no significant
change in the radon exhalation rate from the concreteobtained, in comparison with ordinary concrete.
196. The conflicting evidence may be attributed todifferences in the properties of the components used inconcrete, their relative activity mass concentrations of226Raor the manufacturing process. I t seems that for agiven activity mass concentration of 22bRa,the radon
exhalation rate of fly-ash is usually lower than that ofconcrete, so that enhanced indoor exposures to radon
decay products may arise only when fly ash with ahigh activity mass concentration of ::('Ra is mixed
with concrete.
197. In this Annex. the use of fly ash in building
materials is assumed to result only in additional
exposures from external irradiation. Annual additional
effective dose equivalents of 30pSv i n wooden dwellings
and 70 jtSv in concrete dwellings are adopted as
representative values on a world-wide basis. Taking
the amount of fly ash concrete to be 1.3 tonnes in awooden house and 4 tonnes in a concrete building (asin [S28]), the additional effective dose equivalents
normalized per unit mass of fly ash concrete are foundto be 23 and 18 pSv a-' per tonne for wooden andconcrete dwellings, respectively. Using an intermediate
value of 20pSv a-I per tonne and assuming that an
average of four persons live in each house and that the
lifetime of the house is 50 years, the collective effective
dose equivalent commitment arising from external
irradiation attributable to the annual use of fly ash forconstructing the dwellings is estimated to be about
5 lo-'.
198. The use of fly ash as a component of cement
and concrete for constructing dwellings represents
only a small fraction of the total use of coal ash. The
Committee has not found any published information
on doses arising from other uses of fly ash (as a roadstabilizer, in asphalt mix, as fertilizer, etc.).
199. The large fraction of coal ash that does not finda commercial application is usually dumped in thevicinity of the power plant. Two disposal methods areused. Ash mixed with water in a ratio of 2 to 3 ispiped as slurry to lagoons created by adding walls toor otherwise modifying existing topographic features.
When a lagoon is filled, it is allowed to drain and, if
necessary, another lagoon is created on top. For dry
ash dumps, the ash is conditioned with water toreduce dust and transported to the dumping site. The
choice of disposal method depends on economic andenvironmental factors [U16]. When the dumping isfinished, most dry ash dumps are covered by topsoil
and converted into areas for agricultural or recreationaluse.

200. The main potential radiation hazards from ash
disposal arise from resuspension and from contamination of surface and underground water either as aresult of leaching. i.e., as certain compounds are
washed out of the ash by percolating rain water. or asa consequence of the physical erosion of the ash
surface during run-off. Dose assessments taking into
account these processes are lacking.
1. Summary

201. Radiation exposures resulting from the various
steps in the coal fuel cycle are summarized in Table 30.
The exposures are expressed in terms of collective
effective dose equivalent commitments per year ofpractice around the ~ ~ o r l dThe
. highest exposures
seem to stem from the use of coal in homes and theuse of fly ash in concrete. It should be borne in mind
that these estimates are fraught with large uncertainties
that are difficult to quantify.

B.

OTHER ENERGY PRODUCTION

202. The other types of energy production consideredin this section are geothermal energy and combustionof oil and natural gas.
1.

Geothermal energy

203. Geothermal energy is produced in Iceland,
Italy. Japan, New Zealand. the USSR and the UnitedStates. In 1980. i t amounted to only 1.5 GW a ofelectrical energy production. but its relative importance
may grow in the future. Geothermal energy makes useof hot steam or water derived from high-temperaturerocks deep inside the earth. Most of the activity foundin geothermal fluids is due to the uranium decay
chain. Isotopes of solid elements may cause problems
regarding water pollution or land disposal but only
radon. which is released into the atmosphere when thewater or steam contacts the air, is considered here.
From measurements of radon in geothermal fluids in
Italy [G18, M151, the annual releases of radon havebeen estimated to be I I0 TBq from the 400 MW
Larderello plant, 7.0 TBq from the 15 MW plant at
Piancastagnaio and 1.5 TBq from the 3 MW plantat Bagnore. The annual release of radon from the
1 1 units of the Geysers Pourer Plant in the UnitedStates, which has a net capacity of 502 MW of elcctrical energy, was assessed to be 21 TBq [A16]. Thesefigures point to an average atmospheric discharge perunit energy generated of about 150 TBq per GU' a.
The corresponding collective effective dose equivalentcommitment per unit energy generated is estimated to
be about 2 man Sv per G W year if it is assumed thatthe equilibrium factor between radon and its shortlived decay products is 0.8, the population density
around the plant is 100 km-', the effective dose
Sv Bq-I
equivalent per unit activity inhaled is 1.1
and that indoor and outdoor concentrations are thesame. The annual world-wide production of geothermal energy would yield a collective effective dose
equivalent commitment of approximately 3 man St'.

204. Annual individual effective dose equivalents
resulting from inhalation of short-lived decay products of radon is estimated to be of the order of
l0pSv at 1 km from the stack of a 100 M W geothermal
plant. The average additional radon concentration
would be about 0.1 Bq m-', compared with a background concentration of 1-10 Bq m-'. Measurements
conducted near the Larderello plant in Italy and nearother geothermal power plants in New Zealand andthe United States failed to distinguish between thecontribution of the radon activity from the plant andthat from background [A 16. G18, S59. WZO].

2.

Oil-fired power plants

205. As shown in Table 31, oil has a large number ofapplications, the most important being road transport,
generation of electric power and domestic heating.
Approximately 3 1012kg of crude petroleum wasproduced in the world in 1980. In power plants, about
2 lo9 kg of oil is needed to produce I G W a of electrical energy. As the ash content of oil is very low,
oil-fired power plants are usually not equipped withefficient ash removal systems. From measurements in
two oil-fired power plants in France. normalized
atmospheric discharges of about 200, 300, 150 and
1,000 MBq per G W a for Z'8U, 226Ra,13'Th and 40K,
respectively, have been estimated [A8]. These are very
similar to the normalized discharges of coal-fired
power plants fitted with efficient aerosol control
devices. Measurements of activity mass concentrationsof 232Th,22bRa.210Pband O' K in fuel ash from oilburning power stations of the USSR led to the sameconclusion [B13]. The collective effective dose equivalent commitment per unit electrical energy generated
has been found to be about 0.5 man Sv per GW a.
Assuming that 15% of the world-wide production of
crude petroleum is burned in electric power plants, theresulting annual collective effective dose equivalentcommitment would be about 100 man Sv. The annual
individual effective dose equivalent to a member ofthe critical group, calculated in the same way as for acoal-fired power plant. would be about 1 pSv.
206. Information on radiation exposures of workers
in the oil industry is scarce. Kolb and Wojcik [K22.
K23] measured a median ZZbRaconcentration of
4.500 Bq m-' in thermal brine, which is raised to thesurface together with oil. This brine can be used forthe extraction of oil from its deposits without any
radiation problem as long as the radium activity
remains in solution. Salt from oversaturated brine isoften precipitated after expansion, however. and scale
is formed on the inner walls of tubing, pumps andseparation and storage tanks [K23, S601. Such deposits
can be detected with common radiation protection
instruments; activity mass concentrations of up to
lob Bq kg of 226Raand l2%a have bcen detected i nsome samples. Under normal conditions of operation,
the annual effective dose equivalent for maintenancepersonnel resulting from external radiation from such
sources is estimated to be less than 5 mSv [K23].
207. Oil shale is currently being considered for the
production of synthetic oil that could be burned inpower plants. Oil shale is a sedimentary rock containing kerogen, an organic substance originating frommicro-organisms that accumulated in what were once
large shallow lakes. When the rock is heated to atemperature of at least 400' C to bring about pyrolysisof the kerogen, synthetic shale oil is produced. The
production of shale oil involves the processing of vast
amounts of material. Retorting 1 tonne of shale canyield 110 Litres of retort water, 0.8 tonne of spent shaleand 1-40 m' of retort gases [F6].
208. In the rich shale deposits of Colorado, Wyomingand Utah, known as the Green River formation, as
well as in Estonian shale. measured radionuclide
concentrations of raw oil shale (about 60 Bq kg-I of?38U,25 Bq kg-' of 232Th.500 Bq kg-' of 'OK) correspond fairly closely to those observed in typical soils[G19]: Antrim shales from the eastern United Statesand Moroccan shales show higher uranium concentrations (about 350 Bq kg-]) [G19]. After retorting,nearly all of the activity content is found in the spent
shale, with a marked increase with decreasing particle
size for most radionuclides. Average concentrations in
the respirable fraction of spent shale from the Green
River formation are about 150 Bq kg-' of 'jbU,
130 Bq kg-' of 2'6Ra. 220 Bq kg-' of 210Pb,40 Bq kg-Iof 232Thand 740 Bq kg-' of "OK [G19]. Atmosphericdischarges from an oil shale plant producing enoughoil to generate 1 GW a of electrical energy have been
estimated to be about 290 MBq of '38U, 250 MBq of'"Ra, 430 MBq of :I0Pb, 90 MBq of 23'Th and1,500 MBq of 'OK [G19]. This is again very similar to
the normalized discharges from a coal-fired power
plant equipped with an efficient ash removal system.
The collective dose equivalent commitment per unit
electrical energy generated would be about 0.5 man Sv
per GI%'a.
3.

211. The radon concentrations around a gas-fired
power plant are expected to be, in most cases,
undistinguishable from background; the individual
doses are expected to be trivial.
4.

212. Peat is burned for energy production in several
countries. notably in Finland and Sweden [E9, E10,
M311. Natural radionuclides are carried into the peatbogs by flowing surface and ground water and thenadsorbed to peat matter. In Sweden, the normal "'U
activity mass concentration in dried peat is about
40 Bq kg-', but some samples have shown concentrations up to 500 Bq kg-'; in one extreme case, the '"Uconcentration was more than 10,000 Bq kg-' [E9]. In
Finland, samples of peat used as fuel in a power plantshowed concentrations of 16 Bq kg-'
30 Bq kg-]of 210Pb,5.3 Bq kg-' of 22BRaand 28 Bq-kg-] of O'K
[M31]. Since the ash content of peat normally lies
between 3% and 8% [M31], the concentrations of
natural radionuclides in peat ash are about 20 times
those in peat.

2 13. There is little information on the environmental
discharges of natural radionuclides from peat power
plants. Assuming that 5 lo9 kg of peat is needed to
produce 1 GW a of electrical energy and using an
average 238Uconcentration in peat of 40 Bq kg-' and a
dust control efficiency of 99%. as well as the generalassumptions used for coal-fired power plants, thenormalized collective effective dose equivalent commitment is tentatively estimated to be 2 man Sv per G W a.
In the long term. storage and disposal of uranium-richpeat ash may have the greatest impact [E9].

Natural gas

209. In 1980. the world-wide production of natural
gas amounted to about 1012m3. Like oil, natural gas
has many fields of application. Its uses in OECD
countries are summarized in Table 32, the major uses
being domestic heating, generation of electric power
and as a source of heat in various industries. As discussed previously in this Annex. radon concentrationsin natural gas may vary widely around a typica! valueof 1,000 Bq m-" Since about 2 lo9 m3 of natural gas
must be burned in order to produce 1 GW a ofelectrical energy, the corresponding radon emission isapproximately 2 TBq.
210. The corresponding collective effective dose equivalent commitment per unit energy generated isestimated to be about 0.03 man Sv per GW a. The
assumptions for this estimate are that the equilibrium
factor between radon and its short-lived decay products is 0.8, the population density around the plant is
100 km-', the effective dose equivalent per unit
activity is 1.1
Sv Bq-I and indoor and outdoor
concentrations are the same. Assuming that 15% of
the world production of natural gas is burned inelectric power plants, the resulting collective effective
dose equivalent commitment per year of practicewould be about 3 man Sv.

Peat

5. Summary
214. Radiation exposures attributable to naturalradionuclide discharges from various systems of electricity production are summarized in Table 33. The
exposures are expressed i n terms of collective effective
dose equivalent commitments for one year of practicethroughout the world and are normalized to thegeneration of 1 G W a of electrical energy. The highest
radiation exposures result from the use of coal.
C.

USE O F PHOSPHATE ROCK

215. Phosphate rock is the starting material for the
production of all phosphate products; it is the main
source of phosphorus for fertilizers. The world production of phosphate rock was about 130 million
tonnes in 1982 [F9], the main producers being China.
Morocco, the USSR and the United States. There arethree types of phosphate rock: (a) phosphate rock ofsedimentary origin: this type, which covers 85% of
current needs for phosphorus, comes from deposits
spread almost throughout the world, but especially in
Morocco and Florida (United States) [Ill]; (b) phosphate rock of volcanic origin: the principal deposit ofthis type is found in the Kola peninsula (USSR);(c) phosphate rock of biological origin: the accumulated

droppings of marine birds have given rise to deposits
of guano. from which the leached phosphoric acid has
recombined with calcium from the underlying rock togive tricalcium phosphate.
216. Activity mass concentrations of natural radionuclides in phosphate rock were reviewed by UNSCEAR
in its 1977 and 1982 Reports [U2, UI]. Activity massconcentrations of lJ2Th and 40Kin phosphate rocks ofall types are similar to those observed normally in soil,
whereas concentrations of 23sUand its decay products
tend to be elevated in phosphate deposits of sedimentary origin. A typical concentration ofinsedimentary phosphate deposits is 1,500 Bq kg-'. North
American phosphate presents the highest concentrations of 238U.followed by north African phosphate.
Uranium-238 and its decay products are generally
found in close radioactive equilibrium in phosphateore.
217. Exposures of members of the public result fromthe following: (a) effluent discharges of radioactive
materials of the 238Udecay series into the environment
from phosphate rock mining and processing: (b) useof phosphate fertilizers: and (c) use of by-products
a n d wastes.
218. Occupational exposures mainly occur during
mining, processing and transportation of phosphaterock, as well as during transportation and utilizationof phosphate fertilizers.
1.

Effluent discharges during phosphate industrial
operations

2 19. Phosphate industrial operations can be divided
into mining and milling of phosphate ore, phosphateproduct manufacture by the wet process (in wetprocess phosphoric acid plants) and phosphate product manufacture by the thermal process (in elemental
phosphorus plants).
220. The technique used to mine phosphate ores
varies from area to area depending on the type ofdeposit. In Florida phosphate ore is mined using thestrip-mining technique. which involves stripping theoverburden and mining the matrix with draglines
creating mine cuts from 15 to 20 m in depth [R5].
Overburden is stored near mine cuts and used as
backfill as subsequent cuts are made. Structures later
built on reclaimed land may exhibit elevated radon
concentrations, as discussed later in this Annex.
221. After mining, beneficiation, which is a physicalseparation process using screen flotation to remove
non-phosphate components, is applied to phosphateores not rich enough in P,O,. Exposures resulting
from mining and beneficiation have not been assessed.
222. After phosphate rock has been mined andbeneficiated, it is usually dried and ground t o auniform particle size to facilitate processing. Wet
process plants produce phosphoric acid, the starting
material for ammonium phosphate and triple superphosphate fertilizers; in that process, phosphogypsum

is produced as waste or by-product. Thermal process
plants produce elemental phosphorus, which is in turnused primarily for the production of high-grade
phosphoric acid, phosphate-based detergents, a n dorganic chemicals. Waste and by-products of thethermal process are slag and ferrophosphorus.
223. The drying and grinding operations that follo\v
phosphate rock mining and beneficiation produce
significant quantities of particulate material [U9].
Very limited data are available on actual field measurements of radioactive materials from drying a n dgrinding operations. Measurements made by the UnitedStates Environmental Protection Agency (EPA) [PI61were summarized in the UNSCEAR 1982 Report [Ul].
EPA has since established the parameiers of areference phosphate rock d ~ i n gand grinding plant[U9]. which it used to calculate the emissions ofradioactive materials into the atmosphere (see Table 34);
they correspond t o a particulate emission rate ofabout 0.1 kg per tonne of phosphate rock throughput
and to radioactive equilibrium of ?'W with its solid
decay products. The atmospheric release of 222Rnhas
not been estimated by EPA: assuming an activity massconcentration of226Rain phosphate ore of 1.500 Bq kg-'
and, conservatively, a 100% release of :"Rn, would
yield 1.5 MBq per tonne of phosphate rock.
224. Some phosphate rock must be calcined before it
can be processed. The need for calcining is determinedprimarily by the amount of organic material in thebeneficiated rock, In the calcining operation, the rockis heated to about 800" C to remove unwantedhydrocarbons. Because calciners operate at a higher
temperature than driers, they have the potential forvolatilizing 2'0Pb a n d rloPo. Atmospheric releases
from elemental phosphorus plants, which are mainly
attributable to the operation of calciners, have beenmeasured in the Netherlands and the United States[B3 1, U9, U 10, U11, U12]. Estimated annual values
are presented in Table 34. Discharges of *lOPb a n d
210Poare about two orders of magnitude higher thanthose of other solid radionuclides of the 23Wdecay
series. Analyses of particles collected from the calciner
off-gas streams at two plants in the United States
showed that most of the 210Poactivity was associatedwith submicron particles and that the dissolution rateof both Z1OPband 210Poin simulated lung fluid wasvery small [U 10, U I I].
225. Results of measurements at calciners at wetprocess phosphoric acid plants are not yet available[U9]. .4tmospheric discharges of natural radionuclides
at two wet-process phosphoric acid plants not equippedwith calciners, however, have been published by EPA[PSI and summarized in the UNSCEAR 1982 Report[Ul]. EPA has since defined the parameters of areference wet-process phosphate fertilizer plant thatare used to estimate the annual discharges of naturalradionuclides into the atmosphere (Table 34). Those
discharges result from the production processes ofphosphate fertilizers a n d apparently do not include
the discharges due t o ore drying and grinding.
Releases of 226Raare estimated to be lower than thoseof 238U and 230Th because radium is chemicallyseparated from uranium and thorium in the digestion

of phosphate rock and goes predominantly to phosphogypsum.
226. Annual airborne discharges, normalized to the
production or processing of one tonne of phosphaterock, are presented in Table 35. The normalizeddischarges apply mainly to the operation of phosphateindustrial plants in the United States and may not be
representative of the world-wide situation. Estimatesof collective dose commitments corresponding to thenormalized discharges have been calculated using themethods described in the section on coal-fired power
plants and are also presented in Table 35.
227. Rough estimates of the collective dose commitments resulting from the world-wide operation ofphosphate industrial facilities. using the experience of
the United States as a guide, are presented in Table 36.
The corresponding collective effective dose equivalentcommitment is about 60 man Sv per year of practice.
228. Environmental concentrations of natural radionuclides and assessments of maximum individual
doses have been published for a few plants. At a
distance of about 2 krn from an elemental phosphorus
plant in the Netherlands, the activity concentrations of
2'0Pb and *loPo in surface air have been found to
be about 0.1 and 0.4 mBq m-' above background,respectively [D7]. For the same plant. the estimatedmaximum annual individual effective dose equivalents
due to atmospheric discharges are about 40pSv [B31,
S50]. In the United States, the atmospheric releases
from the six elemental phosphorus plants in operationin 1983 were estimated to result in annual lung dose
equivalents for nearby individuals ranging from 0.05
to 6 mSv [U9].
229. Discharges of radioactive materials into surface
water have also been. occasionally reported. In the
Netherlands, about 50 GBq of 2'0Pb and 30 GBq of
210Powere discharged from an elemental phosphorus
plant into the Scheldt estuary [B31]. In that country,
all phosphogypsum produced by fertilizer plants (2million tonnes per year) is also disposed of into theRhine 15 km from the North Sea [K19]; these annual
discharges, which contain about 0.4TBq of
2 TBq of lZ6Ra.0.7 TBq of "OPb and 2 TBq of Z'OPo.
are estimated, in a preliminary assessment, to result in
maximum individual effective dose equivalents of
150 pSv per year and annual collective effective dose
equivalents to the Dutch population of 170 man Sv
from ingestion of seafood; the main contributor to thedose is 2'0Po [K19]. In France, over 3 million tonnesof phosphogypsum was dumped into the Seine estuary[PI81 but the corresponding radiation exposures havenot been estimated.
230. In other countries, such as India and the UnitedStates, phosphogypsum is retained in sludge ponds orstockpiles near phosphate fertilizer plants; occasional
drainage or seepage of radioactive materials into
nearby surface water has been reported [A 14. P 171.
23 1. Limited information is available on occupational
exposures attributable to processing and transportof rock phosphates. In Dutch wet-process phosphoricacid plants. higher than average external radiation
doses in air, ranging from 2 to 100 pGy h-I, have been
detected in the vicinity of some piping and vessels near
gypsum filters [LIS]. Analysis of scaling samples
revealed activity mass concentrations of IZ6Raof up to
0.4 MBq kg-'; the potential radiation doses. attributable to external exposure and to inhalation of IZ6Ra
during periodic cleaning, have been estimated in eightphosphoric acid plants to be less than 2.2 mSv per
year [L15]. In the Federal Republic of Germany,
Pfister and Pauly [PI51 estimated individual andcollective external exposures for the small group of
persons who handle rock phosphates as part of theirjob; their results correspond. in terms of effective dose
equivalent, to individual exposures of 200 pSv a-' andcollective exposures of 0.5 man Sv a-I. Extrapolating
to the world's population by scaling over the phosphate
fertilizer consumption results in an annual collective
effective dose equivalent of approximately 20 man Sv.
Exposures attributable to inhalation of phosphaterock, however. have not been taken into account.

2.

Use of phosphate fertilizers

232. The world consumption of phosphate fertilizers
was about 30 million tonnes of P20, in 1982 [F9]. The
application rate of fertilizers depends on. among otherthings, the type of soil and the type of crop. The
average consumption of phosphate fertilizer per unit
area of agricultural land varied in 1982 from 3.6 kg
P 2 0 5per hectare in the developing countries to 10.9 kg
P20, per hectare in the developed countries. the world
average being 6.7 kg P20, per hectare [F9].
233. Activity mass concentrations of natural radionuclides in phosphate fertilizers have been reviewed in
the UNSCEAR 1982 Report [Ul]. For a given
radionuclide and type of fertilizer. the activity massconcentrations vary markedly from one country toanother, depending on the origin of the components.
General features are that the activity mass concentrations of O
' K and of 212Thand its decay products arealways low and that the activity mass concentrationsof the radionuclides of the "'U decay series are
5-50 times higher than in normal soil. The degree ofradioactive equilibrium between 238Uand its decay
products in a given type of fertilizer depends essentiallyon the relative contribution of phosphoric acid, since
phosphoric acid usually has a very low IZ6Raconcentration. For the purposes of this Annex, it is assumed
that "OTh and "'U are in radioactive equilibrium with"'U and that "OPb and 210Po are in radioactive
equilibrium with 226Ra. Table 37 presents average
activity mass concentrations of 238U and n6Ra in
phosphate fertilizer from four countries [D8,M21,
P15, U131: the levels range from 1,700 to 9,200 Bq
per kg P205for 238Uand from 480 to 1,700 Bq per kg
P20, for "6Ra. Typical values are 4,000 and 1,000 Bq
per kg P20, for 238Uand 226Ra,respectively.
234. Since the activity mass concentrations of 238U
and Iz6Ra in phosphate fertilizers are several times
higher than in normal soil, they constitute an additionalsource of radiation exposure for workers and membersof the public.
235. The annual application of phosphate fertilizers
can be calculated to represent less than 1% of the[M21, PIS]. Assuming an
normal soil content of 238U
accumulation of lI6Ra in the soil during the past
80 years, Pfister and Pauly [PIS] have estimated thatthe mean additional absorbed dose in air above
fertilized fields is about 0.8 nGy h-I, a small fractionof the normal natural background from terrestrial
sources of 50 nGy h-'. Small additional doses also
occur from ingestion of foodstuffs grown on fertilized
agricultural areas: Drichko et al. [D8] have shownthat although the transfer coefficient of 226Rafrom
soil to plants is practically the same whether 226Rais
included in fertilizer or soil structures, the activity
mass concentrations of ?'OPb and 2'0Po in the aerial
parts of plants seem to be independent of thecorresponding activity mass concentrations in soil;
this implies the predominance of the air-to-vegetationtransfer for such radionuclides.
236. The collective dose commitments incurred after
application of phosphate fertilizers have been roughly
evaluated by comparison with the activity massconcentrations of natural radionuclides in soil and thecorresponding dose rates. Table 38 shows the results
obtained under the following assumptions: the availability to plants of natural radionuclides is the same
whether in fertilizer or in the normal constituents ofthe soil: the ploughed layer of soil is 0.3 m deep: thedeposited activity becomes unavailable to the vegetation with a mean life of 100 years for the long-lived
natural radionuclides: the fraction of time spent by the
populations exposed on or near fertilized fields is 1%;
and one tonne of phosphate rock produces, on
average. 0.3 tonne of PIO, in phosphate fertilizer. It
can be inferred from Table 38 that the collective
effective dose equivalent commitment per unit ofphosphate rock is approximately 8 lo-' man Sv t - I .
Taking the world-wide production of phosphate rockto be 120 million tonnes, the collective effective dose
equivalent commitment resulting from the world-wide
use of phosphate fertilizers during one year is roughly
estimated to be 10,000 man Sv.
237. Occupational exposures arising from external
irradiation during transport, storage and applicationof phosphate fertilizer were assessed by Pfister andPauly [PI51 and reviewed in the UNSCEAR 1982
Report [Ul]. Mean additional absorbed dose rates in
air ranging from 20 to 200 nGy h-I were measured forvarious transport and loading operations, with peakvalues of 800 nGy h-1 [P15]. From the number ofworkers involved or the time spent in the various
operations considered, a total annual collective effective dose equivalent of 1.3 man Sv can be derived[PIS]. A rough estimate of about 50 man Sv for thecollective effective dose arising from occupational
exposure to external irradiation resulting from worldwide handling of phosphate fertilizers can be inferredfrom the results of Pfister and Pauly, using theconsumption of phosphate fertilizers as a reference
scale.

3.

Use of by-products and wastes

238. The main by-products resulting from phosphateindustrial activities are phosphogypsum in wet-process
fertilizer plants and calcium silicate slag in thermal
process plants. Significant radiation exposures may
occur if such by-products are used in the building
industry. Another source of exposure stems from thereclamation of land on which phosphate mining has
been completed and houses have been built. Since new
information on radiation exposures has not been
made available to the Committee in the past few
years, the following is, to a large extent, a summary of
the corresponding section in the UNSCEAR 1982
Report [Ul].
239. Large quantities of phosphogypsum (about
100 million tonnes per year) are produced in wetprocess phosphoric acid plants. The activity massconcentrations of 226Ra in phosphogypsum, which
depends on the origin of the phosphate ore processed.
is typically about 900 Bq kg-I [Ul, U2]. Most of thephosphogypsum is considered waste and is either
stored in ponds or stacks or discharged into theaquatic environment.
240. In the United States. a small amount ofphosphogypsum (about 0.6 million tonnes per year) isused in agriculture to improve water movement insaline-alkaline soil and as a substitute for lime o rlimestone in alkaline soil [L16, PIS].
241. Phosphogypsum is also used as a substitute fornatural gypsum in the manufacture of cement. wallboard and plaster. Japan phased out its production ofnatural gypsum in 1976 and is currently recycling
about 3 million tonnes of phosphogypsum per year
[PIS]. In Japan, approximately one half of the byproduct gypsum is used as cement set-retardant; theother half is used to make wallboard and plaster. In
Western Europe, about 10% of the phosphogypsum
production, that is 2.5 million tonnes, was used in
198 1as by-product [P 181. Phosphogypsum is commonlyused in construction blocks for floors and walls and inpartition blocks for interiors in north Africa, theMediterranean countries and the Middle East. I t will
be assumed in this Annex that 5 million tonnes ofphosphogypsum, representing 5% of the world-wide
annual production. is used annually as building
material in dwellings.
242. O'Riordan et al. [OS] estimated the additionaldoses that would be received by the occupants of aresidential building in which 4.2 tonnes of by-productgypsum would have replaced the established materials;
the additional absorbed dose rate in air was calculated
to be 0.07 pGy h-I; the additional radon concentration, using an air exchange rate of I h-I. wasestimated to be about 10 Bq m-3, resulting in anannual effective dose equivalent of 0.6 mSv. If it isassumed that 5% of the by-product gypsum is used asbuilding material in dwellings, on average four persons
live in the dwellings and the mean life of the dwellings
is 50 years, the collective effective dose equivalentcommitments resulting from one year of world-wide
use of phosphogypsum in the building industry areestimated to be 10' man Sv from external irradiationand 2 10' man Sv from internal irradiation. Theseestimates are highly uncertain and need to be confirmed by measurements in dwellings that have been
constructed using known amounts of phosphogypsum.
243. Calcium silicate slag may be used as a component for concrete. Measured activity concentrations
in slag samples range from 1.300 to 2,200 Bq kg-' ofZ2bRa [ B l l . M161. Results from a n indoor survey
indicate that the gamma absorbed dose rate in air canbe as high as 0.3pGy h-I above background in
dwellings construcred with 43% by weight slag inconcrete slabs [B I I]. In a similar survey carried out in
Canada, absorbed dose rates of up to 0.2pGy h-I
were obtained [M 161.
244. Residents in structures built on reclaimed phosphate land in Florida, United States may also be
exposed to significant radiation doses. About 600 km2
of Florida land has been mined for phosphate rock in
the past 80 years. About 200 km2 of the land has been
reclaimed to various degrees. The equilibrium equivalent radon concentrations in houses built on reclaimed
land were found t o range from 4 to 500 Bq m-3 with aweighted average of about 40 Bq m-', which is estimatedto be 26 Bq m-j above normal concentrations inhouses in that area [G21]. This average additional
concentration results in an annual effective dose
equivalent of approximately 1.6 mSv. An experimental
investigation and remedial action programme wascarried out involving 10 houses and a mobile home onland that had phosphate mineralization o r had been
affected by phosphate mining activities and for which
the annual average radon equilibrium equivalentconcentration was believed to be in excess of 100 Bq m-3[S5 I].
4.

Summary245. Table 39 summarizes the radiation exposures
attributable to the use of phosphate rock, expressed interms of collective effective dose equivalent commitment resulting from one year of practice. The totalcollective effective dose equivalent commitment isestimated to be 300,000 man Sv, essentially from theuse of by-product gypsum in dwellings.

D. NOK-URANIUM ORE MINING.4ND PROCESSING
246. Because of the presence of radon in confined
spaces, metal and non-metal mining results in occupational exposures. Ventilation of mine air, in turn,results in environmental discharges of radon andexposures of members of the public. Ore processing
gives rise to additional environmental discharges ofnatural radionuclides. Occupational exposures andexposures of members; of the public are discussed
below.
1.

Occupational exposures from non-uranium mining

247. Investigations of radon and radon decay product concentrations in non-uranium mines have been

conducted since the 1960s. This section is devoted tothe discussion of occupational exposures in nonuranium mines other than coal mines, which areconsidered in another part of this Annex.
248. Measured concentrations of radon and radon
decay products are presented in Table 40. The
potential alpha energy concentrations of radon decay
products range from 0.02 to more than 300 pJ m-',and there is no simple relationship between radon
decay product concentration and type of mine. Mines
extracting from sedimentary deposits usually have lowradon decay product concentrations but this is notalways true. Mines associated with igneous intrusions
imply high uranium content and therefore high radon
decay product concentrations. although ventilation
can obscure this relationship. Geological and hydrogeological characteristics may also be of importance.
Convective movements of air and water resulting frompressure differences between the mine and its environment explain large radon entry rates into the mine[22]. Detailed studies of the characteristics of nonuranium mines in countries of the European Economic
Community show that the primary indicator of highradiation exposures is a radon concentration in
exhaust air in excess of 400 Bq m-3 1221.
249. Occupational exposures attributable t o radiationin non-uranium mines have decreased with time [D6,S34. S351, as monitoring has led to action being taken
to relieve high exposure situations. Personal dosimetry
is now being used in Polish non-uranium mines [CIS]
and is envisaged in Italy [S37] and the United
Kingdom [M 181.
250. The degree of equilibrium between radon decay
products and radon in non-uranium mines has been
investigated in several countries. Measurements in an
Italian lead mine at a location representative of theradiological characteristics of the mine show anaverage value of 0.70 with a range of 0.50-0.85 [S37].
In 15 mines in the Federal Republic of Germany, theequilibrium factor was found to vary from 0.28 t a 0.82
with a rather flat distribution [K15]. In Norway, themean value of 210 measurements of the equilibrium
factor in different mines was 0.46. with a minimum of
0.08 and a maximum of 0.93 (S381. A typical value ofthe equilibrium factor in non-uranium mines seems tobe 0.6 with large variations around this figure.
25 1. Stranden and Berteig [BZO, S38] have establishedempirical relationships between theequilibrium factor F
and the activity concentrations~of the individual radon
decay products "'Po, IL4Pband 2MBinormalized t oradon that seem to apply to most mining conditions
when the value of F is in the range of 0.1-0.7:%(2'ePo)/ %(:lzRn) = 1.1 FO-55~ )1.0 F0.94~ ( ~ l ~ /Pxb( )= ~ R =~ ( ~ l ' B i/) %(12=Rn)= 0.77 F1.I2
252. The unattached fraction f, of the potentialalpha energy of radon decay products in non-uranium
mines was also studied by Berteig and Stranden [B20.
S381; in most working conditions, the value of f, isusually found to be smaller than 0.05. The main factor

influencing the unattached fraction seems to be theaerosol particle concentration; high values of theunattached fraction are observed with low aerosol
concentrations [G23, S381. Suggested empirical relationships between the value of f,and that of the unattachedfraction of individual radon decay products are as
follows [S38]:
f (21YPo)= 2.6 ff ('IJPb) = 0.77 f:9i
f (?14Bi) = 0.27 f

tB5

253. Radiation measurements other than those ofradon and their decay products are limited. A study ofthe complete spectrum of radiation exposures was
carried out in eight British non-uranium mines [D5].
Table 41 presents the reported concentrations and an
estimate of the resulting effective dose equivalents. In
mines associated with igneous intrusions, the calculated
doses are almost entirely due to the inhalation ofradon decay products. In sedimentary mines, thecontribution to the normal dose from the inhalationof radon decay products is always greater than 5096,
even for low concentrations of radon daughters.
Similar results have been observed for mines in theFederal Republic of Germany [K15]. The effective
dose equivalent from inhaled thoron decay products,
however, may be higher than that from inhaled radon
decay products if the ratio of the activity massconcentration of :j2Th to that of ?38Uin the minedrock is substantially greater than one, which issometimes the case [S39, S401.
254. On the basis of the results presented in Table 40,
annual effective dose equivalents received by nonuranium miners in the course of their work are
estimated to range from 0.1 mSv to about 0.2 Sv, mostof the values being between 1 and 50 mSv. If thearithmetic mean of the annual effective dose equivalentis tentatively assumed to be 10 mSv and the fractionof non-uranium miners in the world population istaken to be 5
[U14], a very rough estimate of theannual collective effective dose equivalent would be
2 lo4 man Sv.

2.

the white pigment titanium dioxide is produced fromraw ilmenite (a dark-coloured, fine-grained beachsand) containing monazite as an impurity (0.14% bymass). The activity concentrations in ilmenite feed areabout 400 Bq kg-' of 228Raand Z28Thand 75 Bq kg-'of zz6Ra. These radionuclides have been followed
throughout the pigment production process. It wasestablished that in the presence of high sulphate ion
concentrations in both the plant feed liquor and theeffluent, thorium remains in solution whereas radium,
which forms an insoluble sulphate compound, tends
to co-precipitate and is found in solid residues
throughout the process. Very high activity concentrations of 4 lo5 Bq kg-' of 226Raand 1.5 lo0 Bq kg-I of
228Thwere measured in a sample of scale scraped froma heat exchanger unit. The mass balance study of theactivity entering and leaving the plant shows, however,that essentially all of the activity entering the plant(14 MBq d-I of 226Raand 67 MBq d-I of 22SRaand of
228Th)is found in the acidic liquid effluent stream,
which is pumped to disposal lagoons and is allowed toneutralize and drain away into an estuary. Effluent
concentrations are about 6 Bq 1-1 of '28Ra and 228Th
and 1.4 Bq I-' of 22bRa,whereas in the estuary they areapproximately 0.01 Bq I-' for '?"Ra. 0.02 Bq I-' for
228Th and 0.10 Bq I-' for 22aRa. In contrast to thesituation found in the plant and the effluent stream,
radium is present in the estuary in a soluble form a n dthorium is not. leading to a possible accumulation of
232Thand of its decay products in the estuary. The
radiation doses attributable to the operation of theplant have not been assessed.

(b) Indusrrial use of zircon sand257. Zircon sand occurs in river and beach placers,
usually with monazite. About 700,000 tonnes ofzirconium minerals are produced each year, mainly inAustralia and South Africa [B37]. The activity massconcentrations of 238Uand '3'Th in zircon sand are in
general well above 500 Bq kg-[ [B36, D l 3, N 181.
Zircon sand is used in the zirconium extractionindustry, foundry sands, refractories and ceramics.
Use of the sand by foundries and the zirconium
industry has resulted in the accumulation of large
volumes of low-level radioactive waste.

Occupational exposures from factory processes

255. Industrial processes are carried out for many
purposes that use the materials extracted by nonuranium mining. In these factory processes, there areexposures to natural radioactivity but in most cases
data on measured activities o r estimates of doses havenot been reported in the literature. Examples given in
the following sections are the industrial use of zircon
sand and the processing of ilmenite; another example
not discussed separately in this Annex is the use ofthorium in coating optical lenses. Information in thisfield is extremely limited and n o reliable assessment of
the collective exposures can be made.
(a) Processing of raw ilmenite
256. The activity concentrations of natural radionuclides in samples collected at an Australian titanium
dioxide plant have been reported [C13]. In that plant.

258. Little information is available on the radiation
protection aspects of the use of zircon sand [B36,
N181. It seems clear, however, that inhalation ofradon decay products is not a problem because theexhalation rate of radon from the zircon sand is low.
Doses from external irradiation may be significant
only in storage areas. Absorbed dose rates in air of
about 700 nGy h-I have been measured at a distanceof about I m from a stack of bags of zircon sand[B36]. In an Italian factory producing electro-fusedrefractory blocks. the absorbed dose rates in air wereobserved to be near background in all representative
work places but reached about 500 nGy h-' on top of
the sand storage tanks [N18].
259. The inhalation pathway, also assessed in the
Italian factory, seems to be more important. The
airborne concentrations of natural radionuclides nearareas of high temperature processes were estimatedto be about 200 mBq m-' of 210Po (typical background: 0.04 mBq m-9 and 20 mBq m-3 for very
long-lived natural radionuclides (typical background:
0.001 mBq m-)). The particle size distribution was
bimodal with a mode at approximately 0.3pm andanother between 5 and IOpm. The resulting annual
effective dose equivalent, assuming constant occupancy
in the most highly contaminated areas, would be of
the order of 5 mSv [N 181.
260. N o information on environmental discharges
was made available to the Committee. Aquatic discharges would in most cases lead only to insignificant
doses. as zircon compounds are extremely insoluble inwater.
3.

quantities of naturally occurring radionuclides emitted
into the atmosphere during mining and manufacturing
processes [A6]. Ore samples collected from the mine
contained average 2 3 W and lJ2Th concentrations ofabout 50 and 70 Bq kg-', respectively. Equilibrium
equivalent concentrations of radon of approximately
1 kBq m-? were measured in the clay mine at theworking face; the corresponding annual emission ofradon is about I TBq. Particulate releases consist
mainly of 210Po,which is partially vaporized at thekiln's operating temperature of 1,100" C . Annual
atmospheric emissions are summarized in Table 43.
Estimated collective effective dose equivalent commitments resulting from one year of operation of thefireclay mine and refractory plant are 0.02 man Sv
from inhalation of radon decay products and less than
0.01 man Sv from inhalation and ingestion of :loPo.

Esposures of members of the public(c) Aluminium ore processing

26 1. All industrial operations involving ore mininga n d processing release natural radionuclides into theenvironment. The results of radiation surveys conducted in several industrial facilities are given below.
(a) Zinc rn ining and processing

262. Zinc is usually found in nature as a sulphide ore
called sphalerite. The ore, which usually contains
impurities of lead. cadmium and traces of otherelements. are processed at the mill to form concentrates typically containing 62% zinc and 32% sulphur.
These concentrates are processed at the smelter torecover zinc metal [U8].
263. Atmospheric emissions of naturally occurring
radionuclides were measured from an undergroundmine and mill [A71 and estimated from a reference
zinc smelter [U8]: the results are shown in Table 42.
The releases from the smelter cannot be compared tothose of the mine and mill, as they are different
facilities and the capacity of the mine a n d mill was notindicated. It is clear, however, that the only significant
emission is that of radon from the mine (8 TBq peryear). A radiation survey was conducted in thatparticular zinc mine because a relatively high radon
concentration of 2,600 Bq m-' had been measured at
the mine portal exhaust. Concentrations ofand
23ZTh.in the ore as well as in the concentrate, were
fourid to be significantly below the corresponding
average concentrations in soil; the relatively highradon concentrations observed in the mine were
attributed to the large quantity of water that flows
into the mine. The collective effective dose equivalentcommitment resulting from inhalation of radon decay
products released in one year was estimated to beabout 0.1 man Sv. The very small releases of othernatura: radionuclides due to low activity mass concentrations and to efficient particle control d o not resultin significant collective effective dose equivalent commitments.

265. Bauxite is the principal aluminium ore found innature. The ore is processed at mines to produce
alumina (A1,0,), the basic feed in the aluminium
reduction process. Aluminium metal is produced by
the reduction of alumina in a molten bath of cryolite[U81.
266. Radionuclide measurements at both an alumina
plant and an aluminium reduction plant have been
carried out in the United States [A9, U8]. The '3'Th
activities per unit mass measured in the processsamples of the alumina plant are listed in Table 44.
The levels in bauxite ore, red mud and brown mud areabout 10 times higher than the average activities perunit mass in normal soil, whereas the radioactive
content of alumina kiln feed and alumina product isless than that of normal soil.
267. Table 45 shows the estimated annual atmospheric emissions from the surveyed alumina plant
and aluminium reduction plant. Again, radon emissions are much higher than those of other naturalradionuclides. Among the particulates, :'OPb and "OPoare the most i m ~ o r t a n tcontributors to the environmental releases. as the high temperatures of the kilns
and of the reduction cells (above 950' C) cause theseradionuclides to be volatilized [A9, U8].
268. The corresponding collective effective dose
equivalent commitments are estimated to be about
0.1 man Sv; they are almost entirely due to the releasesof 210Poand "OPb.
(d)

Copper ore mining and processing(b) Firec1a.v mine and refracrory plan1

269. Copper ores are milled to produce a concentratecontaining copper. sulphur. iron and some insoluble
material (primarily silica and aluminium). This concentrate is the basic feed to the copper smelter thateventually produces the refined copper product. Prior
to smelting, part or all of the concentrates may receivea partial roast to eliminate some of the sulphur andother impurities [U8].

264. Clay mining and manufacturing is a large
industry. Clay may be used to manufacture bricks andrefractory materials. A clay mine and refractory plant
was surveyed in the United States to estimate the270. Radionuclide measurement studies at a n underground copper mine and mill. an open pit mine a n dmill and two copper smelters have been carried out inthe United States [A9, U8]. The activity mass concentrations of 238Uand 232Thin process samples from themines and mills (Table 46) were found to be at orslightly above the corresponding levels in normal soil.
Most of the ?)'Th content, however, seems to be
removed from the ore in the milling process.
271. Estimated annual atmospheric releases are presented in Table 47. Emissions from the copper smeltercannot be directly compared with those from the minea n d from the mill, the capacity of which were notindicated. Calculated collective effective dose equivalent commitments from one year of releases areabout 1 man Sv, with nearly equal contributions fromthorium isotopes and 210Pb-2L0Po.
(e)

Lead ore processing

272. Galena (PbS), frequently containing cerussite(PbCO,) and anglesite (PbSO,), is the principal leadbearing ore found in nature. Galena contains small
amounts of copper, iron, zinc and other trace elements. Lead smelting involves three distinct processes:
sintering, to convert the ore from a sulphide t o anoxide o r sulphate form and prepare the feed materials
for furnacing; furnacing. to reduce the oxide feed tolead metal; and drossing, to reduce the copper content
of the lead bullion from the furnace. Off-gases fromthe sintering machine and the blast furnace are themost significant sources of particulate emissions fromthe lead smelting process [U8].
273. As the activities of 238Uand 232Thper unit massof lead ore are similar t o the corresponding values innormal soil. the atmospheric emissions of naturalradionuclides estimated for a reference plant processing annually 0.22 million tonnes of lead [U9] are fairly
small (about 1 GBq of 2'0Pb and of 2 1 0 P ~ )The.
resulting collective effective dose equivalent commitments per year of release from the reference plant areless than 0.1 man Sv.

(0 Other meral and non-nteral mining
274. Annual radon releases into the atmosphere havebeen reported for a few other United States mines:
30 GBq for a limestone mine. 70 GBq for a fluorspar

mine and 2,600 GBq for an iron mine [S32]. The
resulting collective effective dose equivalent commitments from inhalation of radon decay products areless than 0.05 man Sv.

IV.

SUMMARY

275. Estimates of per caput annual effective dose
equivalents from external irradiation due to cosmic
rays and terrestrial sources and from internal'irradiation due t o the most important naturally occurring
radionuclides are presented in Table 48. together withthe subjectively estimated typical ranges of variation
for all the sources taken into consideration. By far themost important source of exposure is indoor ad on,which leads t o a per caput effective dose equivalent of
1,100pSv and to a wide range of variation. The
overall per caput annual effective dose equivalent isestimated to be about 2,400 pSv, corresponding toan annual collective effective dose equivalent ofapproximately lo7 man Sv. The current estimate of theoverall per caput annual effective dose equivalent is
400pSv higher than the estimate provided in the
UNSCEAR 1982 Report. This is mainly the result of are-evaluation of the mean indoor radon concentration.
The wide distribution of individual effective dose
equivalents is dominated by the variability of theindoor radon concentrations, which span several
orders of magnitude.
276. Individual exposures resulting from industrial
activities are generally small in comparison t o theoverall exposure from natural sources of radiation.
Their importance can best be characterized in termsof collective effective dose equivalent commitments.
Table 49 provides estimates of collective effective dose
equivalent commitments arising from one year ofpractice for most of the activities considered. Becauseof the scarcity, o r lack, of data for the industrial
activities listed in the table, most of the estimates arevery tentative. The total collective effective dose
equivalent commitment arising from one year ofpractice is less than 5 1 0 man Sv, representing a percaput effective dose equivalent commitment of about
I00 11Sv.

T a b l e

1

Cstlmated per caput annual effectlve dose epulvalentfrom natural sources In areas of normal background(Estimates from the UNSCEAR 1982 Report are glven \ n parentheses.)

Annual effectlve dose e ~ u l v a l e n t ( u S v )Source of lrradlatlon
External
lrradlatlon

Internal
lrradlatlon

Total

8 0 0 (650)1600 (1340)

2400 (2000)

Cosmlc rayslonlzlng component
Neutron component
Cosmogenlc radlonuclldes
Prlmordlal radlonuclldes
1;-40
Rb-87
U-238 serles:
U-238 * U-234
7h-230Ra-226
Rn-222 + Po-214
Pb-210 + Po-210
Th-232 serles:
Th-232
Ra-224Ra-228Rn-220 + Tl-208-.

Total (rounded)

Lbbsorbed dose rates ln alr derlvel from exposure rate measurements
In the centre of a 12-storey bulldlnq
I H9 I

Level

Roof
12
10
8
5
4
2
Basement

Dose rate(nGy h-1)

Transmlsslon
factorT a b l e

3

Averaqe actlvlty mass concentratlonsof potasslum-40, uranlum-238 and t h o r l u m - 2 3 2
In sol1 and absorbed d o s e rate In a l r 1 m a b o v e t h e ground surface[8321

Radlonuclldeordecay serlesa/D o s e rate per unlt
actlvlty massconcentratlon
In sol1(nGy h-l
per Bp kg-1)(wet weight)

Average
actlvlty m a s s
concentrationln roll a_/(RQ kg-l)Absorbed d o s erate ln alr a/(nGy h-1)(wet w e i g h t )The typlcal range ls glven In parentheses.

Radlonucl ldeord e c a y seriesa/Dose rate perunit speclflc
concentration
In sol1(nGy h-l
per B Q kg-))(wet uelght)

Average
speclflc

concentration

Absorbed d o s erate ln a l r a_/

In roll a_/(BQ k9-l)(nGy h-I j(wet welght)

T h e typical range Is glven in parentheses.

T a b l e

4

Estlmates of outdoor absorbed dose rate In alr from terrestrlal radlatlon sources
1 m above ground level obtalned in larue-scale surveys

Country
or
area

Year
reported

Number ofmeasurements

Absorbed dose
rate in alr(nGyh-I)Type of survey and instrumentation used
Average

Austria

1980

Canad2
Chlna

1984
1986

Chlna (Talwan
Province)
Denmark

1972

FlnlandFrance1980
1985

German Democratlc
Republic
Germany, Federal
Republic of
Hungary
lcelandlnd \ a1980

33 areas
38661

14 sltes

1969
19'18
1987

24739
123 sltes

1982
1986

Range
Ground survey In populated areas[Tg]ulth Gelger counter[Dl51
Ground survey with thermolumlnescentdoslmeters. gamna spectrometer andlonlzatlon chamber[G28]
Aerlal survey ulth a sclntlllatlon detector
Ground survey ulth lonlzatlon chambers and[WZl]sclntlllatlon detectors
Analysls of sol1 samples uslng[W181
gamna spectrometry[HI61
Ground survey wlth lonlzatlon
chamber and gamna spectrometer[L17, R7]
Ground survey wlth thermolumlnescent[ ~ s ,
dostmeters (prellmlnary results)
R6 1
Ground survey with lonlzatlon chamber[013]

Ground survey wlth sclntlllatlon detectors
Ground survey wlth thermolumlnescentdoslmeters[D9][N21 1

Ground survey ulth thermolumlnescentdoslmeters
Ground survey u \ t h lonlzatlon chamber
Ground survey wlth lonlzatlon chamber
Ground survey wtth lonlratton chamberand sclntlllatlon detectors
Ground survey wlth lonlzatlon chamber
Ground survey wlth lonlzatlon
chamber placed ln a car
Ground survey with thermolumlnescentdoslmeters
Analysls of soil samples uslng
gamna spectrometry

Irelandltaly
Japan
Netherlands
Norwdy1985
1977

Poland1980

Roman la1979

SwedenSwitzerland
UnltedKIngdom

1979
1964
1984

1400

Unlted States1972

2 5 areas

Ref.

Ground survey ulth ionlzatlon chamber
Ground survey with energy-compensatedGelger counters (prellmlnary results)
Aerlal survey wlth sclntlllatlon
detectors[E8,R71
[Nlg]
[n261
1~171
[A151
[v2 1
IS531
1~171
[TI01
[JIB, R7]
In191
[G30]
[0121

&/ Range of the means.

b/ A contrlbutlon of 1.0 VR per hour from nuclear weapons fallout was subtracted from the total exposure rate.
&/ Range of the arlthmetlc means for each province.
d/ A contrlbutlon of 3.i u R per hour from nuclear weapons fallout was subtracted from the total exposure rate.
g / Inhabited by approxlmdtely 30% of the country's populatlon.

T a b l e

5Population-uelqhted means of absorbed dose rate In alr
1 m above qround levelobtalned In a large-scale survey In Chlna(nGv h-I)

City.
provlnce or
autonomous
reglonNumber ofmeasurements

Indoors

Indoors

Outdoors

Gamna
rays

623
442
308
292
3454
1620
2073
1273
472
2149
2331
1549
1312
2093
6694
4077
1462
1677
1712
1555
89 4
992
850
230
3250
6846
698
2198
803

576
227
236
31 6
1842
1620
2650
1107
281
2149
808
1549
1312
896
1276
2236
1439
1534
1712
1555
901
230
853
257
2510
4707
682
2126
7 59

87 .O
118.7
117.1
97.0
105.9
106.5
109.1
109.9
96.0
115.7
107.0
104.1
151.4
144.3
161.6
118.1
112.7
130.4
158.2
133.6
108.3
121.6
118.6
113.9
124.1
116.5
112.5
120.0
126.4

Total f o r Chlna 53952

38611

119.5

8eiJ lng
Shangha l
Tlanjln
Hebel
ShanxtInner Mongol la
HetlongJlang
Jll lnLlaonlng
Shandong
Jlangsu
Anhul
ZheJ lang
Jlangxl
Fuj \an
Henan
Hubel
Hunan
Guangdong
Guangx\
Shaanxl
NlngxlaGansu
OlnghalXlnjlang
SlchuanGulzhou
YunnanTlbet

Cosmic rays
(lonlzlng
component)

Outdoors
Gamna
rays

Cosmlc rays
(lonlzing
component)T a b l e

6

R e s u l t s o f l a r q e - s c a l e s u r v e y s o f I n d o o r absorbed dose r a t e l n a l r
due t o qamM t e r r e s t r l a l r a d l a t l o n---

Absorbed dose r a t e
I n a l r (nGy h - 1 )CountryYearreported

Nuniber o f
dwelllngs

Type o fbulldlng

Comnents
Average

Austria

1980

1900

China

1986

53952

Denmark

1985

82

FlnlandFrance

1983
1980
1985

German Democratic
RepuDl l c
1969Germany. F e d e r a l
Republlc of
1978

1 10
81
75
110

Brlck
Concrete
wood

60 b/
50
30
BO
68b/
75

Varlous types
Varlous iypes

667

Varlous types

29996

Hungary
Iceland
Ireland
Japan

1981
1982
1965
1984

223
135

Solid
Frame
Prefabrlcated
Wood
Varlous types
Concrete
Varlous types
Varlous types

Italy

1984

600

Varlous types

Netherlands
Norway

1955
1965
1977
1984

399
2026

Sweden

1980
1983

1282

u n l r e c Klngdom

1985

2300

Varlous types
Brlck
Concrete
Coal b y - p r o d u c t
prefabrlcate
Red b r l c k
Gravel-sand
prefabrlcate
Wood
Brlck
Concrete
Aerated c o n c r e t e
Wood
Varlous types

Poland

a/
&/

123

-

1351

Populatlonw e i g h t e d p/

[ 19 1

Brlck
Concrete
Wood
Natural stone
Various types

946
5198

Ref.

71

120

Range o f t h e means:
90-160 nGy h-1
P l l o t study[ wzl 1

Estlmated

[R l1

(80)
(88)
(75)

[Mzz]

The s t u d y c o v e r e d 43%
o f t h e c o u n t r y and 50%of the populatlon

74
70
71
40
45
84
23
62 b/

-60

b/

[ 552 I

60

rRb1

10131

[ 09 1
70

(84)
(23)
(62)
50

-60

Range 10-200 nGy h - l[HZ1]Range 14- 23 nGy h - 1[E7.R71
Range 10-140 nGy h - l
In231
Calculated from outdoor[AlS,v a l u e o f 49 nGy h-1 [A151A181
and l n d o o r / o u t d o o r r a t l oo f 1.02 [A181
Range 20-110 nGy h - l[ 833 1P l l o t study[J171
Range 30-100 nGy h - 1[ 553 1
is541
The s t u d y c o v e r e d a b o u t 10% [ K 2 0 ]o f t h e c o u n t r y . Outdoor
doses f r o m t e r r e s t r l a lradlatlon are hlgher thant h e c o u n t r y average

L l v l n g areas and bedroomso f d w e l l l n g s . Standard
d e v l a t l o n 24 nGy h-1.

The numbers l n p a r e n t h e s e s a r e t h e r e p o r t e d averages. assumed h e r e t o be e q u a l
u e l g h t e d average.
The c o s m l c - r a y c o n t r l b u t l o n has been s u b t r a c t e d from t h e published v a l u e .

to

[W22]

the p o p u l a t l o n -T a b l e

7

Intakes of uranlum-238, thorlum-232,
and thelr decay products In normal areas

Annual Intake ( B Q )SourceInhalation

lngestlon

U-238 serles:
U-238
Th-230Ra-226
Rn-222
Pb-210Po-210

0.01
0.01
0.01
200000
4
0.3

5
2
15
300
40
40

Th-232 serles:
Th-232
Ra-228Rn-2200.01
0.01
1000002
15

T a b l e

8

Average actlvity mass concentratlons In organs and tissuesof uranlum-238, thorlum-232 and thelr decay products[mBg kg-1 (fresh uelght)]

SourceGonads

U-238 serles:
U-238
7
lh-2300.3
Ra-226
2.7
Rn-222
Pb-210200
PO-210200
Th-232 serles:
Th-232
0.15
Ra-2280.5(Th-228)
Rn-220BreastLungs

Corticalbone&/

Trabecularbone a/Red
bone
marrow

Thyrold

Kldney

Llver

Other
tlssues

2
0.3
2.7

15
20
2.7

50
20
170

50
70
170

2
0.3
2.7

2
0.3
2.7

5
10
2.7

3
7
2.7

2
0.3
2.i

200
100

3000
2400

3000
2400

20
15

6
50

24
50

40 c_/

-

-

200
200
0.15
0.5

look/

140
110
0.15
0.5

200
200
0.15
0.5

200
200

200
200

3
10

2
5

200
200
0.15
0.5

-

a/ Dry bone (5 kg dry bone yleldlng 2.7 kg ash per skeleton).
b/ Radon gas. The radon concentratlons in tlssues other than that of the lungs are negllglble.
c/ Thoron gas. The thoron concentratlons In tlssues other than that of the lungs are negllglble.
-

T a b l e

9Annual absorbed doses resultlng from internal lrradlatlon
by alpha emltters from the uranlum-238 and thorium-232 decay rerles( UGY

SourceGonadsBreast

Lungs

Red
bone
marrow

Bone
Ilnlngcells

Thyrold-

Kldney

Llver

Other ~ f f e c t E
tlssuesdose
equlvalent(uSv)

lh-232 rerles:
Th-232
Ra-228,Ra-224
Rn-22O+Pb-208

a/ lncludlng doses resultlng from the formation of Rn-222 and Its short-llved decay
products In the body by decay of Ra-226 (retentlon factor of one thlrd).

b/ Tracheo-bronchlal tree.
c_/Lungs.
d_/ Contrlbutlons to the annual effective dose equlvalent ( ~ S V ) .

T a b l e

10

Actlvlty concentratlon of polonlum-210 In ground-level alr
rw131Country and place

Perlod ofmeasurements

Number ofsamplesPolonlum-210
concentratlon( ~ 8 9m-3)
Ref
Mean

Range
- -

FlnlandNurmljarvl
Helslnkl
Franceloulouse
Germany. Federal Rep.
Munich-Neuherberg
Unlted Klngdom
Harwell
Chl lton
SuttonUnlted States
Boulder
USSR
Vl lnlus

32, dally
32. dally[MI) 1

37. monthly

In121207. weekly[u131

4. dally
41, monthly
5. monthly[86I

15. dally[PSI?

QuotedIn [ P 9 ]1~91

3. monthly[Mill

I P7 I[OSIPotentlal alpha energy ratto of thoron and radon decay products
in duelllngs

Potentlal alpha energy ratlo( thoron/radon)
Country

Number o f
dwelllngs

Ref.
Average(mean or medlan)

Range

AustrtaCanadaHungdry
Germany. federal
Reoubllc o f

0.2-2.7

NorwayUnlted Kingdom
Unlted States

0.1-0.7
0.1-1.5[S23][GI 5 I
[TZI
[Wb]
[U3]
[K131
[S24]
[CB]
[Sb71

0.1- 1

0.1-2.5
0 -1.9T a b l e

12Dnse factors for Indoor and outdoor lnhaldtlonof thoron and thoron decay products b y members of the publlc

Thoron gas

Thoron decay products

Dose rate
per unlt
concentratlon

Dose per unlt
lntake( u G y a-l
per 8q 171-3)(nGy Bq-l)

Indoors( v G y a-1
per Bq m-3)

(a)

(a)

(a)

Dose rate per unlt
concentratton

Organ or t l r r u ~Lungs
Red bone marrow
Bone Ilntng cells
L l ver
Kldneys
SpleenOther soft ttsrues
Iffectlve

0.25
0.02
0.18
0.02
0.10
0.004
0.002

14
0.8
9

0.96
( u S v a-1
per 8 9 m-3)

50
(nSv 80-1)

1

b
0.2
0.1

Outdoors(UGY a-'per Bq m-3)
(a)

0.6

25
1.4
16
1.8
11
0.4
0.04

280
( u S v a-1
per Bq m-3)

88
( u S v a-1
per Bq m-3)

78
4.5
50
5.6
34
1.1

T a b l e

13Ranqe and r e ~ r e s e n t a t l v evalues of parameters for estlmatlnq
the area exhalation rate of radon-222 from sollr

Parameter

SymbolUnl t

Lmanatlng powerFr

Lffcctlve bulk
dlffuslon
coef f lc lentAeff

m 2 s-IR

Bq m

Reported range

Representativeva 1ue0.01-0.8

0.2[01 ,s1 1

10-11-3 10-6

5 lo-'

Lo1 .s1 1

Ref.

Poros lty
Lxhalatlon rate

-2

s

-1

0.0002-0.07

T a b l e

0.016

[G2.M1]11

Dlmenslons and relevant parameters of the reference house------A

Parameter

SymbolValue

Vo l ume

(V)

250 m

Surtdce area ot floor
Surfdce area of external walls
dnd celllng
Total surface area, lncludlng
lntcrnal walls, furnlture, etc.

(SF)

100 m

(s*)

300m2

(5)

Alr exchange rdte
Thickness of floor and ceiling

(AV)
(LF)

4 5 0 rn2
-1
1 h
0.2 m (concrete)

lhlckness of external walls(Lw)

0.2 m (br\cks)--

T a b l e3215

Normal content o f radlum-226 and radon-222
In Swedish sotl. measured at 1 m dept_?
[A101

Sol 1 type1111, normal
1111, wlth granltlc materlal
7111, with uranlum-rlch granlte materlal
Esker gravel
Sand. sllt
Sol1 contalnlng alum shale

Radlum-226
activlty
mass
concentrat \ o n(Bq k g - \ )Radon-222
Concentratlon

15- 6 230- 175
125- 3 6 0
30- 7 5
6- 7 0175-2500

5- 3 0
10- 6 0
10- 200
10- 150
1000
50->I000(k8g m-3)

T a b l e

16

Radon-222 s o u r c e c h a r a c t e r l s t l c s f o r b u l l d l n q m a t e r i a l s

MaterlalCountry

humber o fsamples

Radlum-226
concentration(~qkg-1)

Radon-222 mass Emanatlng
exhalatlon r a t e
power(~~qkg-1s-1)

Concrete
Heavy c o n c r e t e
USSR
L i g h t w e l g h t c o n c r e t e USSR
Ord\nary concrete
SwedenAerated concrete
based on alum s h a l e
SwedenAlum-shale c o n c r e t eDenmarkf l y - a s h c o n c r e t e ( 4 % ) USA
Fly-ash concrete
GreeceHungdry
Concrete
Concrete
Oenmark
Concrete
NorwayConcrete
GreeceConcrete
USA
Concrete
USA
Concrete
USA(Adopted reference
value)Brlck
Red b r l c k
Re0 b r l c k
Red b r l c k
Red b r l c k
BrlCk
8rlck
Brlck
Slllcon brlck
Adobe b r l c k(Adopted reference
value)
GypsumGypsumGypsum board
B y - p r o d u c t gypsum(apdtl te)
B y - p r o d u c t gypsum(phosphor\ t e )L i g h t w e l g h t expanded
c l a y aggregate

USSR
Hungary
PolandUSA
Denmark
NorwayGreecePolandUSA

USA
Denmark
PolandPolandNorwayStorage rock

USA

wood

USA

f l y ash

PolandSlagPolandCementPoland
USA

Sand

USA
USA

Gravel

USA
- -

a/

C a l c u l a t e d f r o m d a t a g i v e n I n t h e r e f e r e n c e . assumlng a d l f f u s l o n l e n g t h o f 0 . 2 m.

Dlffuslon
length(m)Ref.

T a b l e

17

Sources of radon entry rates In the reference house

Radon eltry rate (8qh-I)

SourceEstlmatedarlthmettc mean
Underlvlna sol10lff;stonPressure-driven f l o w
BulldIna materials
Outdoor -at r
Water
Natural gas
Total (rounded)

Typlcal range

1.7
40
6.4
0.3

0- 1

50

2-200

a/ txcludlng alum shale: a radon entry rate of 8 0 8q rnm3 h-I

Is estimated If aerated concrete based on alum shale Is used.

T a b l e18

taulllbrlum factor F for radon daughterstqulllbrlum factor F
Country

Number ofduelllngs

Average

Range

CanadaMarch Tounshlp
13 cltles

0.19-0.67

1 Inland0.30-0.63

Ref

b/

[L)I
[Mb]
[S441

[Msl

Germany. Federal
Republlc of
Italy
Netherlands
NorwaySwedenUnlted Klngdom
Unlted States
New Jerseyg/Arlthmetlc mean of t h e ratlo of the geometric means of theequlllbrlum equlvalent concentratlon and of the radon
concentratlon ln 13 cltles.
b/ Range for the 1 3 citles.
I/ Arlthmetlc mean; Gausslan dlstrlbutlon wlth o = 0.22.
d/ Ratto of the medlans of equlllbrlum equlvalent concentratlon
and of radon concentratlon.
Calculated
g/ At mean ventllatlon rate of 2 alr changes h-1.
to be 0.40 at 1 alr change h-1.
f/ Cellars.
g/ Flrst and second floors.

T a b l e

19

Radon and equlllbrlum equivalent concentrations obtdlned In recent larqe-scale lndoor surveys

Average value (Ba n-3)
C o u n t r y o r area

Mwnber o f Type o f
d n l l l n g s duelllng

Type o f sampllng

Purpose of
the survey

Date ofcompletlon

Dlstrlbutlon
or rangeRadon

A r g e n t lna
AustrlaSalzburg

Radon EIC

Radon. pdssIve

Populat Ion
exoosure1985

3 7 (medldn)

Hones

Radon and r a d o ndaughters, g r a b
sampllng. usually
4 times a y e a r

Populatlon
exposure1980?

1 5 (sedldn)

13 houses and6 apartments

Radon, passlve.
one-year e x p o s u r eMatlo?-wlde
populatlon
exposure(prellmlndry
survey)1984

41 (medlan)

Rdd0n and radon
daughters. g r a b
samplings. preferably
In basements

Matlon-wlde
vdrldbllIty
o f exposures1900

3 3 (mean)

7 (medldn)

Remedlal oflndustrlal
contamlnatlon

1976

3 b (medlan)

11 (medlan)

Causes of
Increasedradon levels
In homes

1976

CanadaPort HopeU r a n l u m Clty

Radon and radon
daughters. g r a b
sampllng. bastments
and ilvlng a r e a s

Elllot L a k e
Bancroft

Rddon daughters, g r a b
sampllnq, bdsem4ntSand llvlng areas

Saskatchewan

RddOn daughters.
g r a b samollng

364 houses
113 apartments

Log-norm1 ?
range 4 5 - 1 9 0
BQ m - 3 (Rn)

4 8 (medlan)

1976

3 0 (medlan)
2 6 (medlan)

Index m a p o fradon p r o b l e m
drCdS

1980

11 (medlan)

Log-normal
4 7 (medlan)

2 8 (medlan)
6 5 (medlan)
1 3 (medlan)
1 6 (medtan)

Population1983

1 2 0 (mean)CXDOSUrC
Populdt \ o nexposure1987

3 0 (mean)

Range 0.6-259
8 q m - 3 (Rn)
Range 5 0 - 7 0 0
8 0 m-3

Horns

Radon. passlve
3-month exposure
In sumner dnd
In w l n t e r

Hdtlon-wide
populdt Ion
exposure(pllol survey)

1985

5 0 (medlan)

a r m d n y , FederalR e p u b l l ~o f

5970

Homes

Radon, pdsslve.
3-month erposure.
1 In bedroom.
1 In Ilvlng r o o m

Mat lon-ulde
oopulat\on
exposure1984

4 0 (medlan)
49 (mean)Ilnland

8150

Homes

Radon, passlve.
1-month e x p o s u r e
In llvlng room

Hat lor,-ulde
oopulatlon
erposLre1982

6 4 (median)
9 0 (mean)

France765

HousesRadon, p d s s l v e dnd
and RnOP. dctlve.
one-month exposure

Hdtlor-ulde
1985
44 (medlan)
populdt !on
7 6 (mean)eaposLre (vrellmlndry results)

m n g a ry

833

HOuSeS

Rddon ddughters.
grab sampllng. llvlnq
drear. d a t a reduced toI h-1 v e n t l l a t l o n rate

areland736

HousesRadon, pcsslve
6-month exposure

Ndllon-wlde
1987
3 7 (medldn)
population
exposure (prellmlnary results)

Italy

1000

HousesRadon, Dasrlve.
3-12 m o n t h exposures.

natlon-ulde
1984
4 3 (medlan)
populatlon
erposure (partldl results)

dapdn

250

HousesRadon. electrostatic
Integrdtlng. 2 m o n t h s ;total 1.5 year
exposure

Ndt\on-wlde
pop~ldtlot!
exposure1980

I0 ( m e a n )I+th~rldndS

1000

HousesRddOn. PdSSlvC.
exposure f o r 4 month5
In the Ilvlng room

Hatton-wide
populdtlon
exposure1985

24 ( m e d l d n )29 (mean)

Uorway1500

HousesRadon. passlve.

Assessment
1905
o f geographicalvarlatlon

1 week exposure

9 (medlan)

9 0 (mean)

8 0 (mean)

1 3 (medlan)

1 0 (medlan)
1 2 (mean)Ref.

T a b l e 19. continued

Average value (89 m-3)
Country or drtd

PolandSwedennu.ber of Type o f
d n l l l n g s duelllng

201

5

Detached houses
bullt before 1915

191

Apartments bullt
before 1915

96

OetdChed houses
bullt 1978-1980

38260

Sultzerland

Unltcd K l n q d o mCornwalland
other uranlferous regfons

Unlted States

Apartments

T y p e o f sampllnq

Radon and radon
daughters. grab
sanpllng In the worst
ventllatlon condltlons

Purpose of
the survey

Oate o f
cowletlon

Hatlon-wlde

1918

Radon

Radon LEC

9 (mean)

4 (mean)population

exposure
1 2 2 (mean)
6 5 (medlan)

Radon, passlve 2 - n e t
exposure. 1 In bedroom.
1 In llvlng room

Hatlon-wlde
populatlon
exnoIure1982

8 5 (mcan)
4b (medlan)

105 (mean)

59 (mean)

BOO8
123

Homes

105

HOWS

2300

nocacsRadon. passlve. 1-year
exposure In llvlnq
r o w and In
maln bedroom

Ndtlon-ulde
poculatlon
excosure1985

1 7 (medlan)
In I l v l n g - r a m s
1 2 (medlan)
In bedrooms

700

Homes

Grab sampllnq of radonand radon daughtersplus ventllatlon rateplus I-year exposure
wlth pdsslve
radon detectors

Setrch forproblem areas

1985?

1 4 0 (medlan)
In llvlng.
rooms

Var\ous

Naflon-wlde~ o p u l a t\ o nexposure

552

Slngle-famlly
homes

Ref

Log-normal 1
range 0.4-17
8 9 m - 3 (Eft)[GI31

Log-normal

[SB.
5421

Log-normdl
Log-nor~lOetached houses
bullt before 1982 Varlous
Apartment5
bullt before 1982

Search fordwelllnqs ulthhtgh radonlevelsDlstrlbutlon
or range

1986

Radon. pdsslve. detectors. 1 ln b a s m n t .
1 In llvlng r o w .
1 In bedroombO (medlan)
150 (mean)
Coapdrlson of1983
ueatherproofed
and conventlonal
houses

14 (medlan)
In llvlngrows..

Log-normalOg
3.2
o g (an)
5.2
(tEC)

1984

35 (medlan)
61 (mean)

[YE.
821.
09 1

T a b l e

20

Varlablllty of radon daughter bronchlal dose range
as a per cent chanqe from nomlnal annual dose for males[N141

FactorVarlablllty

Unattached polonium-218 from 4% t o 20%
Daughter product e ~ u l l i b r l u m(1/0.9/0.7/0.7 to 1/0.9/0.6/0.4)
Partlcle deposltlon models
Partlcle slze (change In medlan size
from 0.125 lim or 0.17 u m )Calculated physlcal dose to a glvenslte In eplthellum
Breathlng pattern (entirely actlve
pattern t o entlrely restlng)(Mouth versus nose breathing)
Bronchlal morphometry(chlld versus adult)
Mucoc l l lary clearance(normal t o complete stasls)
Mucus thickness (none to twlce
normal)locatlon of target cell (shallow- 2 2 w to average -45 w)

T a b l e

Corrments

-10
t30
- 20

4% unattached polonlum-218
20% unattached polonlum-218

A few percent
+lo0
-20

For 0.05 run partlcles)
For 0.17 u m particles)
A few percent

420
-25
(-35)
+bO

Active pattern
Restlng pattern

+lo
+20
-30
-80

No mucusTwlce normal mucus thlckness

21

Dose and effectlve dose equivalent factors per unlt concentrationof radon (or Its decay products) In alr (or water)(Appllcable only to adults ln the general populatlon.)

Dose factor(nGy h-1 per BQ m-3)

Lungs

dose
euulvalent
factor( n ~ vh-I
per 8 u m-3)

0.04

0.2

Decay of radon anddecay products in thesame tlssue; solubll\tyfactor of 0.4

10Same doslmetrlc
coefflclents for Indoor
and outdoor condltlons

Pat hua y
Stomachlnhalatlon
Radon gas

0.005

Tracheobronchlal
tree

Effective
Raln assumptlons

Radon decay
products ( L E C )1 ndoor s
Outdoors

Ingestion

Radon gas0.0001waier consumption rate
= 0.5 1 d-1

T a b l e

22

Productlon of coal and reported actlvlty mass concentrationsof natural radlonuclldes

Productlon of hard coal
1985 [U15]Actlvlty mass concentratlon(Bq kg-l)
Ref.

Coa 1
X of theequlvalentworld(109 kg) productlon
Austral laAustria
BrazllCanadaCzechoslovakia
Chlna
Germany, fed.Rep.
Blturnlnous coal
Brown coal
Greece (llgnlte)
Hungarylndla
Average
Range
Italy (llgntte)
Central Italy
Sardinla
PolandAverage
Range
South Afrlca
USSR
Average
Unlted Klngdom
Yorkshlre area
Country range
Country average
Unlted States
Average
Range
Venezuela
Yugoslavia
World

.

118

4

8
34
26
81 0

0.3
26

88

3

1

0.0

3

0.1

150

5

U-238

Th-232

K-40

30- 48
11-363
100
12
4-13
7

30
1-11
67
7

40
7-59
370
26

16

30

20
10
120-1300
1.5

c 20

24
10-70

38
20-90

192

6

173
494

[J131
15131
[PlO,Pll]
[J121

< 7

0.7-0.9

15-25
250[BlO.F5][B9][SZS][T4,T7][J121[F5,J12]83
15-440120-200

[L12]
[LIZ]
[Dl ,GI61[Dl .GI 61

6

38
2-140
30

30
7-!10
20

290
40-800
110

[T3]
[T3]
[S25]

16

28

25

120

[Lll]

3

20
2.4-19
13

240

94

20
7-94
15

[BJ]
[C~I
[S29]

741

24

18
1-540
< 20
12-530

21
2-320
< 20
21-50

52
1-710
110

[BE]
[BE)
[S25]
[891

UnltedKlngdom

Un\tedStates0.04
0.4
31 0 0

0.001
0.01

150

100

T a b l e

23

Uses of hard coal In OECD countrles. 1985
[U15]

OECO
Japan

Dornestlc
Comerclal/publlc servlce
Power statlons
Coke ovens
Iron and steel Industry
Chernlcal lndustrles
Other lndustrles
Rall transport
Other
Total

20
7
835
21 1
5
22
77
0.2
55

T a b l e

24

Radon and radon decay products In coal mlnes(Uean values wlth range In parentheses.)

Country or areaYear

Potent la1
alpha energy
concentratlonof radon a/( V J m-3)-

Radonconcentratlon(8q m-3)

European Comnunl tles

1981
1981
1981
1976

b/

Germany, federal
Republlc of
Indla

0.09
0.2
0.5

0.2
0.5
1.2

[el91
[~191
[el91
[C61

105
(up t o 400)

1981

PolandUnlted Klngdom

Annualpotentlal
Ref.
alpha energy
exposure
(mJ)

1981
1968
1976
1981

[ N9 10.02(0.01-0.04)
t 2 C/
0.4(20-500)( u p to 2)
0.5 d/

[D41
ID31
[OlO]
[Oll]

a/ 1 115 m-3 corresponds to an equtllbrlum equlvalent concentratlon of radonof 1 8 0 Bq m-3.

b/ Radon decay product concentrations and annual exposures derlved fromtwo-month measurements; log-normal dlstrlbutlons.

c/ Less than 2 pJ m-3 for 94% of the measurements.

a/ Uean annual exposure In natlonallzed mlnes, employlng 185.200 mlners; themean annual exposure In prlvate mlnes, employ\ng 1,500 mlners, was 1.0 mJ

T a b l e

25

Ash productlon In the United Klnqdom
LC11 I

SourceCoa 1
consumption

As hcontent

Ash productlon(lo9 kg)(XI(109 kg)(% o f total)

Domestic andmanufactured fuels
Pouer stations
Cdrbonlzatlon (coke. . . . )Other Industry
0ther.lncludIngexport

15.0
73.1
17.5
12.1
1.5

4.7
17.1
6.0
9.6
6.3

0.7
12.5
1.1
1.2
0.1

4.5
80.1
7.1
7.7
0.6

Total

119.2

Welghted
average
13.2

15.6

100.0

T a b l e

26

Total emiss\ons of 'esplrable particulates\ n the Urlted Kinqdom[Cll I
Total emissions
Ortgtnlo6 kgx oftotal

Domest ic
Comnerclal/publlc service
Power stations
Other Industry
Rall tranrport

3 37
12
28
68
10

74

Total

455

100

3

6
15
2

T a b l e

27

Coal-flred power plants: estimates of annual a t m o s ~ h e r i cdlscharges
per unit enerqv qenerated(MBq per GW a)

Fly-ashremovalefflclency

U-238
decay series
K-40

(X)

Canada a/Nantlcoke, 4000 HW
FranceGermany, Federal Rep. ofBrown coal
Bituminous coal
Bltumlnous dry ash
removalBltumlnous llquld ash
remova 1
lndla
Italy
Llgnlte. 250 HW
Llgnlte,
7 0 MU
Coal,
1280HW
USSR
Zaporozhje b/ 1200 MW(old)1000 nw(modern)
Unlted Ktngdom. 2000 MU

99.5?

Th-232decay serles

350
3500

Reference
U-238

Ra-226

Pb-210 Po-210

Th-232

100
7000

100
7000

300

300

70
6000

500

300
6400

2000

6000

200
10000

Th-22899

99
95

31 0 0 0200[Dl .GI61[Dl ,6161[01 .tlb][Ibl[I61[ c9 I

[C141
~4141
~ 7 1
[US1
[US1
[US1
[US I
(K141

United States

510 Mu r/
450 HW r/
M-3.
125 MW c/
M-4, 12.5 MU c/
Mllllken, 270 MW
Model plant (modern)Model plant (1970)
Model plant (modern)Model plant (1972)

M-1,
M-2.

UHSCEAR 1982 Report

[HI?]

[Us1

[US I
[BE]

[eel
97.5

4000

1500

1500

5000

5000

1500

1500

[Ul]

lhls Annex
modernolda/ Assumlng a coal consumptlon of 3 7 9 per GW a.

b/ Ash content of the coal of 30-39% (Donety. Kuznets coal field); annual coal consumptlon of 5 Tg

c/ Derlved from the ratlo of emlssion rate to actlvlty feed rate for U-238.

T a b l e

28

L s t l m t e s of collecttve effectlve dose eaulvalent c o m l t m e n t s
per unlt energy generated
resultlnq from atmospheric releases
from a typlcal .oldm coal-fired power plant a/( 1 0 - 2 man Sv per GW a)

Radlonucllde

t

-r

+

+

daughters
Po-210
daughters
daughters

Total (rounded)a_/lnhalatlon
durlng thecloud
passage

Internal
lrradlatlon
due todeposlted
activity

External
lrradlatlon
due to

135

30

Total

deposited

actlvlty

15
17
60
1.3
0.1
14

290
60

455

620

Releaslng about 10% of the fly-ash produced.

T a b l e

29

Fstimater of collectlve effectlve dose equivalent comnltment>
per unlt energy generated
resultlnq from a t m o s ~ h e r i c releases
from a t y ~ l c a lmodern coal-flred power plant a_/(10-2 man Sv per GW a )Radlonuc l lde

lnhalatlon
durlng thecloud
passage

Internal
lrradlatlon
due todeposlted
actlvlty

External
lrradlatlon
d u e todeposlted
actlvlty

Total

23

26

1.5

50

U-238
U-234
Th-230Ra-226daughters
Rn-222
Pb-210 4 Po-210
Th-232
Ra-228 * daughters
Rn-220 + daughters+

Total (rounded)a_/Uslng emlsslon control devlces
fly-ash produced to escape.

that allow only about 0.5%

of

the

T a b l e

30

Estimates of collectlve effectlue d o s e epulvalent c o m n l t m e n t s
per vear of practlce In t h e coal fuel c y c l e

Collective effectlve d o s e equlvdlent
comnltment per year of practlce( m a n Sv)
SourcePub1 lc

Workers

0.5-10Coal mlnlng
Use o f coal
Electrlcal energy production
2000
Domestic use
2000-40000
Coke ovens
Not estimated50000
Use o f f u e l a s h

T a b l e

2000
60
Not estlmdted
Not estlmdted

31

U s e of oil In the OECD coun:rIer.

1918

[Obi

ass (lo9 kg)

UseType of fuelComnerclal/publ\c servlce
Power statlons
lron and steel Industry
Chemlcals Industry
Other lndustrles
Alr transport
Road transport
Rallways

Gas/dlesel oil
Llquefled gases
Gas/dlesel oil
Residual fuel oll
Resldual f u e l oll
Resldual fuel oil
Resldual fuel oil
Jet fuel
Motor gasol lne
Gas/d\esel 011

T a b l e

32

Uses of natural g a s i n O E C D l g u n t r l e s . 1%
[U151

OECD (total)
Energy
(PJ)
-

p~

Japan

UnltedKlngdom

UnitedStater

Share
(XI

(XI

(X)

(XI

100

100

100

100

~

Domes t Ic
7980
Comnerclal/publlc servlce
4310
5850
Power statlons
Natural gas extractlon
2340
670
Petroleum reflnerles]
lron and steel Industry
Chemicals Industry] 10000
1
Other lndustrles
Other
1550
Total

32700

T a b l e

33

C o l l e c t l v e e f f e c t l v e d o s e e q u l v a l e n t c o m n l t m e n t t o m e m b e r s of the public
a t t r i b u t a b l e t o v a r i o u s s y s t e m s o f e l e c t r l c l t y production

Collective e f f e c t l v edose equlvalent
comnl tmentp e r y e a r of p r a c t l c e( m a n Sv)

T y p e ofplant

Normallzed
collectlve effectlve
dose equivalentcorm1 tment( m a n S v p e r G W a)

Coal-fired
01 I-f ired
Natural gas
GeothermalPeat

T a b l e

34

E s t l m a t e d atmospheric d l s c h a r q e s f r o m p h o s p h a t e i n d u s t r i a l p l a n t s

T y p e of plant
and locationO r e drying a n d g r l n d l n g
Unlted States.
reference p l a n t

Annuallnput ofphosphaterock(106 t)R a d l o n u c l l d e d l s c h a r g e s ( G B q a-l)
Ref.
U-238

7h-230Ra-226

2.7

Elemental p h o s p h o r u s p l a n t
Vlisslngen, N e t h e r l a n d s
0.75
Unlted S t a t e sjPocatello, I d a h o
Soda S p r i n g s , I d a h o jSllver B o w , M o n t a n a ] -4
K t . Pleasant, Tenn.
]
Columbia, T e n n .
1Coiumbta. Tenrr.
1
Wet-process f e r t l l l z e r p l a n t
Unlted States.
1
reference p l a n t

a/ Atmospherlc d l s c h a r q e s of R n - 2 2 2 e s t l m a t e d by U N S C E A R .

Rn-222a/

Pb-210Po-210T a b l e

35

Estimates of collective dose comnltments per unlt mass of ~ h o s ~ h a toreeresultlnq from atmos~heric releases from phos~hate lndustrlal ~lants

Collective dose comnitment

man Gy t-l)-

Radlonucllde

AIrborne
discharge
Lungs

Bone
surfacesRedbonemarrow

Llver

Kldneys

SpleenWet process fertlllzer plant
U-238
250
250
U-234
Th-230250
Ra-22640
Pb-210100
Po-210100
External lrradlatlon

3.2
3.8
3.6
0.04
0.1
0.1
0.9

0.5
0.4
28
0.2
1.6
1.002
0.9

0.07
0.05
2.1
0.02
0.2
0.002
0.9

0.03
0.02
0.05
0.005
0.3
0.002
0.9

0.3
0.3
0.06
0.005
0.2
0.06
0.9

0.01
0.02
0.007
0.005
0.2
0.1
0.9

0.01
0.02
0.007
0.005
0.2
0.001
0.9

0.01
0.02
0.007
0.005
0.2
0.002
0.9

Total

12

32

3.3

1.3

1.8

1.3

1.2

1.2

(Bq t-l)GastroOther
lntesttnal
soft
tract
tlssuesOre drylng and grlndlng
U-238
200
U-234
200
Th-230200
Ra-226200
Rn-222
1.5 106
Pb-210Po-210External lrradlatlon

200
200

Total
Elemental phosphorus plant
U-238
100
U-234
100
Th-230100
Ra-226100
Rn-222
1.2 106
Pb-210PO-210External lrradlatlon

5.9 lo4
2.9 105

Total

a/ Tracheo-bronchtal basal cell layer.
b/ Pulmonary eplthellum.

T a b l e

36

Estimates of collective dose comnltments
resultlnq from world-ulde annual atrnospherlc releases
from phosphate lndustrlal plants

Collectlve dose comnltment (10-3 man Gy)
Radlonucllde

Airborne
discharge
Lungs(all t-l)BonesurfacesRedbonemarrow

Llver

Kidneys

Spleen11

GastroOther
Intestinal softtract
tlssuesOre drying and grlndlng
U-238
20
U-234
20
Th-23020
Ra-226200
Rn-222130000
Pb-210Po-210External Irradlatlon

20
20

Total
Elemental phosphorus plant
U-238
1.5
U-234
1.5
Th-2301.5
Ra-226
1.5
Rn-22216000
Pb-210Po-210External lrradiatlon

800
4000

Total
Wet process fertllizer plant
U-238
10
U-234
10
Th-23010
Ra-2262
Pb-2106
PO-2106
External Irradlatlon

130
150
140
2.1
9
7
47

19
17
1100

Total

490

1300

a/ Tracheo-bronchlal basal cell layer.
b/ Pulmonary eplthellum.

1

94
0.1
47

2.7
2.1
85
1
15
0.1
41

0.7
2
0.3
16
0.1
47

1.3
10
2.2
0.3
14
3.5
47

0.01
0.7
0.3
0.3
12
6.2
47

1.3
0.7
0.3
0.3
12
0.008
47

1.3
0.7
0.3
0.3
12
0.1
47

150

67

88

68

62

62

T a b l e

37

Averaqe activlty mass concentrations of uranium-238 and radlum-226
p e r n i t mass of P2g5 in phosphate fertilizer

Bq/kg P20s
CountryRet

FlnlandGermany, Fed.Rep.of
United States
Unlon of Sovlet
Soclallst Republics

1700
2600
9200

T d b l e

480
1700
1300

[M21 ]
[PIS]
[U13]

930

[OBI

38

Estlmated collective dose c o m ~ l t m e n t per mass of phosphate rock
resultlnq from the use of phosphate fertlllzers

Organ or tlssue
U-238
Internal irradlatlon
Lungs
Bone surfaces
Red bone marrow
LI verKidneys
Other tissues

Collective dose c o m i t m e n t

man Gy t-l)

U-234

Pb-210Th-230Ra-226

Rn-222

Total

1

20
3
1
10
1

External irradldtlon
All tissues
a_/ Tracheo-bronchtal basal cell layer.

b/ Pulmonary eplthellum.

T a b l e

39

Estlmates of collectlve effectlve dose equlvalent comnltment to theworld populatlon arislnq from one year of exploltatlon of phosphate rock

Collectlve effectlve dose
equlvalent comnltment( m a n Sv)
Source of exposure
Hembersof thepub1 lc
Phosphate lndustrlal operations
Use of phosphate fertlllzers
Use of by-products and waste

Workers

6 0 a/
2 0 b/
10000
5 0 b_/
300000Not estimated&/ An addltlonal 1 7 0 man Sv t o the Dutch population Is estlmatedto result from dumplng phosphogypsum Into the Rhlne.

b/ From external Irradlatlon only.

T a b l e

40

Radon and radon decay products In non-uranium mlnes

Country

Potentlal
alpha
Radon
energyconcenconcentratlon
tratlonof radon(Bq m-3) (uJ m-3)

Year

Annualpotentialalphaenergyexposure

Germany,
FederalRep. of

1984
1984
1984

d/

280
20

1
1
0.2

l I0

4100
6600
1200 b/120

PolandSwedenUnltrdKingdom

UnitedStates

1981
19el
1981
1 gel
1981
1981
1981
1981
1981
1981
1981
1984
1966-1970
1966-1970
1966-1970
1966-1970
1972-1976
1977-1978
1970-1980
1982
1973-1975
1973-19751973
1973-1975
1973-1975
1973
1973
1973-19751973
1973-1975
1973
1973
1973-1975
1975
1981
1978
1978
1978
1978
1978
1978

Ref.

(mJ)

9000-20000 40-330a/Type of mlne

3
3
0.4

Tln, copper.
[s331
and tungsten
Lead and zlnc
[KlS]
Iron
[KlS]
Pyrlte, zlnc.
barlte[Kls]
Barl te[K151
Fluorspan, barlte [KlS]
Fluorspan[K1S 1Graphl te
[K151

0.4
1
0.4; b0.9; 14
10
25
20
60
2 &/
. 5 b/
0.2
0.4
Clay
tK151
80
200
~eldspar
[~15]
3
1
Slate
[K15l
2
0.8
[K151
011 shale
0.8
0.4
Rock salt
[KlS]
0.02
0.04
Salt sallne
iK151
0.04-0.3
Gold
*
IN9 1
1.4 -3.5
Copper[Ng]
4.8
Copper
Ln291
0.07
Gold
In291
0.7
Lead/Zlnc
~~291
0.15
Manganese
~4291
0.3
Mlca
[H291
0.04
Amlanthlnlte
[S361
1.2
Barite[ 536 1
2.5
Bauxlte[S36]
0.2
Chalcopyrlte
S3b 1
0.04; 0.2
Feldspar15361
1.5; 5.6
fluorspar[S361
0.08-11.4 p/
f luorspar
[s361
4.8
Hagnetl te(5361
0.04- 5.4 a/
Slderlte
is361
0.03- 0.7 a/
Steatlte[ 536 1
0.5: 3.4
Sulphur[S36]
0.4 - 10 c/
Not lndlcated
[S37]
1.9
1ron
[D41
3.1
Pyrlte[D41
0.6
BarlteLO41
2.2
Zlnc-lead, copper [D4]2.5 - 3.1 a/
Zlnc-lead, copper [D4]2.5
Zinc-lead. copper [CIS]
3-20 a/ 50 mlnes[s35]
5
Iron, z l n c , copper[S58]1.5-904-240g/Tln
is34 1
0.4 - 20 &/ 0.6-30 a/ Haematlte[534 12
4Iron[534 I
0.08-160 a/ 0.4-120 Fluorspar[53.11[534 1
0.2 - 14 a/ 0.7- 30 Limestone
0.2; I
0.4; 2 Calcspar
0.4: 15 Homestone[s34]
0.6; b
0.2 - 100.4- 20 Flreclay
is341
0.4
5 Ballclay[5-341
0.1: 130
1 0 ; 5 5 Lead
[534 1
6;
3
Slate
[=dl
i .s
15
40
Baritef S34 1
0.06; 0.4
0.4; 1
Salt[534 I4
2
Slllca sand[534 1
11
Other than coal
[Oil]
5 - 8
ZI nc
i 532 I
3
1ron
[S321
5
Flreclay[ 532 1
0.8
f luorspar[s321
Copper[S321
0.04-0.1
Limestone
[s321

-

p/

Range of means.

c/

Assumlng an average equlllbrlum factor of 0.7.
Average exposures decreaslng wlth time from 20 mJ ln 1970 to 3 mJ In 1980.

b/ Wlnter measurements.

a/T a b l e

41

Environmental radlatlon fields and occupational exposures
ln non-uranium mlnes of the Unlted Klngdom(Based on [05])
RADIATION CHARACTERISTICS

238~
actlvi ty
per untt mass

232Th
attlvlty
per unit mass

Potentialalpha energy
concentratlonof radondaughters

Potent la1
alpha energy
concentrdtlonof thoron
daughters(8s kg-I(0s kg-')(uJ m - 3

( v J m-3)

Ulne

1: sedlmentary
2: sedlmentary
3: sedlmentary
4: lgneous
5: redlmentary
6: lgneous
7: sedlmentary
8: lgneous

OCCUPATIONAL DOSES

Ulne

Averageannualeffectlve
dose
equlvalent( mSv )

Contrlbutlon (per cent of t h e total)
External
lrradlatlon

Inhalatlon ofradon
daughters$1

Inhalation ofthorondaughters

Inhalatlon ofore dusta/ Assumlng a 4 n geometry.
b/ Assumlng an ore dust concentratlon of 3.8 mg m-3.

T a b l e

42

Estimated atmospheric releases of natural radlonuclldesfrom zinc mlnlnq and processlns facllltles[AT, U81

Annual d t m o s ~ h e r l c releases(Mas)
Rad l onuc l lde
Ulne

Ulll

Smelterb/

T a b l e

43

Atmospheric releases of natural radlonuclldesfrom a flreclav mlne and refractory plant[A61

Annual atmospheric emissions(naq)
Rad lonuc l lde
Hlnes

Kllns

T a b l e

44

Radtonucltde actlvltles per untt mass
In surveyed alumlna plant process samples[ ~ s ,uei

Activlty per unlt mass
(8q kg-')Samp 1 e

Bauxlte ore
Alumlna klln feed
Alumlna productRed mud
Broun mudT a b l e

250
2
10
280
200

45

tstlmated atmospherlc releases of natural radlonuclldes
f r o m the surveyed alumina plant and alumlnlum reduction plant
lA9, U81

Annual atmospherlc releases (U8q)
Radlonucllde

Aluminakllns

Red mudkllns

Alumlnlum
reductionplantT a b l e

46

Radlonucllde actlvltles per unlt mass
In surveyed copper mine and mlll process samples[As, us1

Underground mlne and mlll

Open plt mlne and mlll

23811
(Bq kg-1)

238~(Bq kg-1)

SampleOre
Concentrate

232~h(Bq kg-1)

232lh(Bq kg-1)

30
24

T a b l e

47

Estimated atmospheric releases of natural rad\onuclldesfrom copper ore mlnlng dnd processins facllltles[A7, U81

Annual atmospheric releases
(naq)
.
.
Radlonucl tde
Rlne

Mill

T a b l e

Smelter48

Estimates of per c a ~ u tannual effective dose e ~ u l v a l e n t s
and of ranges, excluding extreme values,
for the most Important natural sources of radlatlon

Annual effective
dose equlvalent ( ~ S V )Source of lrradlatlon
Mean
External
Cosmlc rays
Terrestrlal sources

360
410

Internal
K-40
U-238 + Ra-226
Rn-222 + Po-214
Pb-210 + Po-210
Th-232 + Ra-224
Rn-220 + 11-208

180
20
11 0 0120
20160

Total (rounded)

2400

Typlcal range

1500-6000 a/a/ The 90th. 95th and 99th percentlles are estlmatedto be 2300, 3300 and 6 1 0 0 uSv, respectlvely,
assumlng a log-normal dlstributlon wlth a geometrlc
standard devlatlon of 2.5.

T a b l e

49

Istlmates of collective effectlve dose esulvalent comnltments
per year of practlce for varlous lndustrlal actlvitles

Collective effectlve dose
equivalent comnltment( m a n Sv)
SourcePubl lc
Coal combustlon
Power plants
Domestlc homes
Coal mlnlng
Use of coal ash ln the bulldIng lndustry
Geothermal energy production
011 combustlon In power plants
Natural gas combustlon In pouer plants
Phosphate lndustrlal operattons
Use of phosphate fertlllzers
Use of phosphogypsum in houses
Non-uranlum mining

2000
2000-40000
0.5-1050000

Workers

60
2000

3

100
3
60
10000
300000smal l

20
50
20000

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