Residential Radon Levels Around the World

DB Chambers, SENES Consultants Limited, ON, Canada

JM Zielinski, Health Canada, Ottawa, ON, Canada, and University of Ottawa, Ottawa, ON, Canada
& 2011 Elsevier B.V. All rights reserved.

Introduction
Abbreviations
222
Rn Radon with an atomic mass of 222.0
The most common isotope of radon is 222Rn (hereafter
amu
226
‘radon’). Radon, an inert noble gas, is a member of the
Ra Radium with an atomic mass of 226.0
uranium (238U) radioactive decay series. Uranium occurs
amu
238
naturally in all rocks and soils and produces radon, some
U Uranium with an atomic mass of 238.1
fraction of which escapes in the air.
amu
Radon occurs naturally in varying levels in all rocks
AM Arithmetic Mean
and soils. Some fraction of radon produced in rocks
APRL Average Population Radon
and soils escape to the atmosphere and therefore radon is
Level
present everywhere in the atmosphere. Owing to dilution
DQO Data Quality Objectives
from atmospheric processes, the concentrations of radon
EPA Environmental Protection Agency
in the open air are usually quite low; however, in en-
EU European Union
closed spaces, mines, caves, and homes, for example, the
GBD Global Burden of Disease
levels of radon can be quite high.
GM Geometric Means
Sources of radon in homes include radon from the
ICRP International Commission on
soil on which the home is built, radon from building
Radiological Protection
materials, and radon from groundwater used in homes. In
IRP International Radon Project
buildings with high radon levels, the main mechanism
UNSCEAR United Nations Scientific Committee
for entry of radon is pressure-driven flow of soil gas
on the Effects of Atomic
through cracks in the floor. However, in addition to
Radiation
pressure differences, other factors including relative
WHO World Health Organization
humidity and soil moisture, can also influence radon
levels in buildings. Radon gas enters homes from the
Glossary ground through cracks between concrete floors and walls,
Potential alpha energy concentration The through gaps in the floor, and through small pores in
concentration of short-lived radon decay products in air hollow-block walls. Consequently, radon levels are usu-
in terms of the alpha energy released during complete ally higher in basements, cellars, and ground floors.
decay through polonium-214. J m3; Although most building materials contain small
1 J m3 ¼ 1.80  108 Bq m3 amounts of radium (226Ra) (a member of the 238U
Radon levels Radon concentration in air. pCi L1; radioactive decay chain and the actual source of the
1 pCi L1 ¼ 0.037 Bq L1; 1 pCi L1 ¼ 37 Bq m3 radon) and hence produce some radon, certain home
Relative risk coefficient The ratio of the risk in an construction materials may contain elevated levels of
exposed population to that in a similar unexposed radium and hence act as significant sources of indoor
population per unit exposure. radon. Such materials have a combination of elevated
Working level Any combination of the short-lived levels of radium and a porosity that allows radon gas to
decay products of radon in 1 l of air that will result in the escape. Examples are lightweight concrete with alum
emission of 1.3  105 MeV of potential alpha energy. shale, phosphogypsum, and Italian tuff.
WL; 1 WL ¼ 100 pCi L1 (assuming 100% equilibrium, Radon is soluble in water and is therefore present
i.e., F ¼ 1); 1 WL ¼ 250 pCi L1 (assuming 40% in the groundwater that passes through uranium-bearing
equilibrium, i.e., F ¼ 0.4) soils and rocks. When radon-rich groundwater is brought
Working level month The cumulative exposure from into a home and depressurized, for example, during a
breathing an atmosphere at a concentration of 1 WL for shower, or used as drinking water, people are exposed
a working month of 170 h. WLM; both through water consumption and by radon being
1 WLM ¼ 3.54  103 J h m3; released from water to the air and being inhaled.
1 WLM ¼ 6.38  105 Bq h m3; 1 WLM ¼ WL  exposure Depending on a number of factors, the concentration
time; (h a1)/(170 h per WLM) of radon indoors varies from year to year, with the time of
year, from day to day, and from hour to hour. Moreover, it

828
 Residential Radon Levels Around the World 829

is possible for one home to have elevated levels of radon The WHO IRP used national APRLs to estimate the
whereas a neighboring home does not. Measurement is global burden of disease (GBD) associated with exposure
the only reliable way to determine levels of radon in a to radon. Although the current database provides some
home. Measurements are normally carried out using estimates of APRL for most of the world’s population, it
special detectors left in the home for periods from days to is important to understand that radon data for most
months. Because radon levels vary from day to day and countries of the world are sparse and where available,
from season to season, measurements over several months quite variable both within a country and between coun-
or even years are better than short-term measurements tries. In addition, many of the currently available radon
for estimating annual average radon levels. The sources data are focused on radon-prone areas and thus biased.
of indoor radon are well described in the 2000 United
Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR) report. UNSCEAR Radon Surveys

In the international community, a prominent role is

World Health Organization International played by UNSCEAR that was established by the
Radon Project General Assembly of the United Nations in 1955. Its
mandate in the United Nations system is to assess and
Recent analyses of pooled residential radon case–control report levels and effects of exposure to ionizing radiation.
studies in Europe and North America support a small Governments and organizations throughout the world
but detectable lung cancer risk from residential radon rely on the committee’s estimates as the scientific basis
exposure, with the risk increasing as the radon concen- for evaluating radiation risk and establishing radiation
trations increase. In view of these observations, the World protection guidance. UNSCEAR reports are regarded by
Health Organization (WHO) initiated an international the scientific community as authoritative and balanced
radon initiative, referred to as the ‘World Health reviews of the exposures to and potential health con-
Organization’s International Radon Project’ and formed a sequence of ionizing radiation. The work of UNSCEAR
network of key partner agencies from some 40 member receives considerable leverage from contributions in kind
states. The first meeting of the International Radon provided by 58 national organizations and by four
Project (IRP) was held in Geneva in January 2005. The international organizations, including the International
following key objectives of the IRP were formulated at Commission on Radiological Protection (ICRP) and the
this meeting: WHO, which participate in its deliberations. UNSCEAR
has recently completed a thorough review of radon in a
• impact
Identify effective strategies for reducing the health
of radon; new annex.
A table from the UNSCEAR 2006 report provides a
• gation programs
Promote sound policy options, prevention, and miti-
to national authorities; summary of concentrations of radon in indoor air de-
termined from surveys carried out by UNSCEAR and
• sequences of exposure
Raise public and political awareness about the con-
to radon; from literature cited in the table. As indicated in the
table, in many cases new data, that is, subsequent to that
• home mortgages to the potentialinstitutions
Raise the awareness of financial supplying
impact of elevated provided in the UNSCEAR 2000 report, was not avail-
radon levels on property values; able and the old data were simply carried forward. Since
the publication of UNSCEAR 2000 report, UNSCEAR
• Monitor and periodically review mitigation measures
to ensure their effectiveness; has conducted three surveys of the natural radiation
environment in 2001, 2004, and 2006 and the data are
• Estimate the global health impact of exposure to
residential radon and so allow resources to be allo- reflected in Table 1. According to UNSCEAR, typical
cated effectively to mitigate the health impact of outdoor levels of radon and thoron gas are each in the
radon; and oreder of 10 Bqm3. In addition to UNSCEAR survey,
the data in Table 1 considers numerous primary refer-
• Create a global database (including maps) of resi-
dential radon exposure. ences cited in the UNSCEAR 2006 report.
Outdoor, ambient radon levels vary from location
The work reported in this article contributed to the to location depending on factors such as local geology
last stated objective of the WHO’s IRP. In brief, a data- (especially the amount of uranium in near-surface
base was developed from generally available information soils and rocks) and with meteorological conditions. For
on national residential levels around the world. By re- example, at night and in the early morning hours,
viewing the information, a number of countries with atmospheric (temperature) inversion conditions tend to
reliable estimates of average population radon level trap the radon closer to the ground. This means that
(APRL) were identified. outdoor radon concentrations can vary diurnally by a
830 Residential Radon Levels Around the World

Table 1 Concentrations of radon in indoor air

Region/country Population (106) Indoor radon (222Rn) (Bq mBq/m3) Notes

Arithmetic Geometric Maximum Geometric

meana meana value standard
deviation

Africa
Algeria 28.78 30 140 –
Egypt 63.27 9 24 –
Ghana 17.83 340 –

North America
Canada 29.68 34 14 1 720 3.6
Canada 32.27 28.35 11.2 1 720 3.9
Mexico 107.03 140 90 1 193
United States 269.4 46 25 3.1 National survey

South America
Argentina 38.75 35 25 211 2 Countrywide average
Brazil 186.40 81.95 310.0
Chile 14.42 25 86 –
Paraguay 4.96 28 51 –
Cuba 11.20 7.7 5.2 15.3 3.3 Countrywide average
Brazil 186.40 81.95 310.0
Ecuador 200
Paraguay 4.96 28 51 –
Peru 27.97 32.29 50.20
Venezuela 26.75 52.50 346

East Asia
China 1315.84 43.8 34.4 596 National average based on
sampling 3098 dwellings
China 1232 24 20 380 2.2 –
–Hong Kong SAR 6.19 41 140 –
–Taiwan 22.89 10.0 8.5 63.5 0.6 Countrywide average
India 944.6 57 42 210 2.2 –
Indonesia 213.67 35.1 35.1 165 1.2 Countrywide average
Japan 125.4 16 13 310 1.8 –
Kazakhstan 14.83 5 000 Countrywide average
Republic of Korea 48.85 53.4 43.3 1 350 1.8 Countrywide average
Malaysia 20.58 14 20 –
Pakistan 140.0 30 83 –
Philippines 75.90 23 22 62 1.13 Countrywide average
Philippines 76.57 23 23 62 76 Countrywide average
Russian Federation 50–60
Thailand 58.7 23 16 480 1.2 –

West Asia
Armenia 3.64 104 216 1.3
Islamic Republic of Iran 63.76 82 3 070 Countrywide average
Islamic Republic of Iran 795 2745 31 000 High background area
Islamic Republic of Iran 600 1 000 High background area
Kuwait 1.69 14 10.6 119.2 0.74 Countrywide average
Palestine 0.95 34 105 –
Saudi Arabia 16 36 –
Syrian Arab Republic 14.57 44 520

North Europe
Denmark 5.2 59a 39a 1 200 2.2 Countrywide average
Estonia 1.47 120 92 1 390
Finland 5.2 120 84 20 000 2.1 Countrywide average
Iceland 0.3 10 26 Countrywide average
Lithuania 3.73 49 38 1 900 Countrywide average
Lithuania 3.49 55 36.5 636 Countrywide average
Norway 4.35 73 40 50 000 –
Sweden 8.88 108 56 84 000 Countrywide average

West Europe
Austria 8.11 15 190 –
Belgium 10.22 48 38 12 000 2 Countrywide average

(Continued )
 Residential Radon Levels Around the World 831

Table 1 Continued
Region/country Population (106) Indoor radon (222Rn) (Bq mBq/m3) Notes

Arithmetic Geometric Maximum Geometric

meana meana value standard
deviation

France 58.33 62 41 4 690 2.7 –

89.3 53.5 4 964 Population-weighted mean of
63 Bq mBq/m3 based on
12 261 measurements in
dwellings
Germany 81.92 50 40 410 000 1.9
Ireland 3.84 89 57 7 000 2.4 Countrywide average
Liechtenstein 0.03 80 1 098
Luxembourg 0.22 110 70 2 500 2.0 Countrywide average
The Netherlands 15.58 23 18 380 1.6 –
Switzerland 6.71 75 41 10 000 Countrywide average
Switzerland 142b 81b 15 000b 2.6b Countrywide average
73c 59c 15 000c 1.8c
United Kingdom 58.14 20 14 17 000 3.2
England 90 50 Population-weighted average
(20 Bq mBq/m3)
Wales 84 48

East Europe
Belarus 31.8 221 Countrywide average
Bulgaria 8.10 22 250 2.1 Countrywide average
Czech Republic 118 94.4 70 000 1.84 Countrywide average
442 20 000 High background area
214 20 000 High background area
124 70 000 High background area
112 20 000 High background area
136 6 000 High background area
214 6 500 High background area
Hungary 10.05 107 82 1 990 2.7 –
Poland 38.12 49.1 1 300 Countrywide average
Poland 38.17 49 31 3 260 2.3 Countrywide average
Romania 22.55 25.0 564 Countrywide average
Slovakia 5.35 87 3 750 –

South Europe
Albania 3.40 120 105 270 2.0 –
Croatia 4.50 35 32 92 –
Cyprus 0.76 7 7 78 2.6 –
Greece 10.49 73 52 490 –
Greece 55 44 1 700 2.4 Countrywide average
Italy 57.23 75 57 1 040 2.0 –
Italy 57.3 70 52 1 036 2.1 Countrywide average
Montenegro (Yugoslavia) 0.60 184 110 1 128 2.74 Countrywide average
Portugal 9.81 62 45 2 700 2.2 –
Slovenia 1.92 87 60 1 330 2.2 –
Spain 36.72 90.38 45.69 15 400 Countrywide average
Spain 0.001 748.5 242.64 15 400 High background area
Spain 40.84 90.4 45.7 15 400 2.9 Countrywide average
Spain 0.02 610.0 1 400.0 High background area

Oceania
Australia 18.06 11 8 420 2.1 –
New Zealand 3.81 21.5 19.5 80 Countrywide average
a
Population-weighted average.
b
Upper value, unweighted data.
c
Lower value, data weighted for floor dependence, population distribution, error of exposition, and mobility.
d
Annual mean.
832 Residential Radon Levels Around the World

factor of as much as 10. Seasonal variations, related to the States, Japan, and China. However, data for many coun-
effects of precipitation or to changes in prevailing winds, tries are extremely limited or nonexistent.
also exist. In this article, the term ‘radon’ primarily refers The first large national residential radon survey was
to radon (222Rn) from the 238 U decay chain. However, carried out in Canada in 1977, 1978, and 1980, respect-
there is also a radon (220Rn) from the radioactive thorium ively. Single grab sample for both radon and radon
(222Th) decay chain that is also present in the atmos- daughters were taken in 14 000 home in 19 Canadian
phere. Since thorium is present everywhere in rocks cities. The distribution of radon concentrations in homes
and soils, so is 220Rn (commonly referred to as thoron); as approximately followed a lognormal distribution with a
discussed in the 2006 UNSCEAR report, there is an GM of 11.2 Bq m3, geometric standard deviation of 3.9,
increasing interest in the levels of thoron in homes and and corresponding AM of 28.4 Bq m3. A major survey of
the influence of thoron on the measurement of radon. radon concentrations in US homes measured radon levels
This subject is beyond the scope of this article. Readers in 5694 homes from 125 counties in 50 states. Approxi-
interested in this subject are referred to the ‘Further mately 6.1% of the homes surveyed exceeded the US
reading’ section and the materials cited therein. There is, EPA’s action level of 148 Bq m3 (4 pCi L 1). This study
however, a wide range of long-term average concen- indicated that the distribution of radon concentrations
trations of radon, from approximately 1 to more than in homes could be reasonably described by a lognormal
100 Bq m3, with lower levels typical of isolated small distribution. The overall GM (median) of the radon
islands or coastal regions and higher levels typical of sites concentration data was 25 Bq m3 with a geometric
with high radon exhalation over large surrounding areas. standard deviation of approximately 3.1.
Indoor radon levels can never be lower than those out-
doors and in some instances, outdoor levels of radon can
be significant.
Substantial compilations of available radon measure- Table 2 Summary of information on indoor radon data
availability by continent
ments appeared in the UNSCEAR 2000, 1993, and 1988
Continent No. of countries No. of countries Countries with
reports. On the basis of data available at the time, (Total) with radon data radon data
UNSCEAR deduced values of 40 and 30 Bq m3 for the available available (%)
arithmetic and geometric means (AM and GM) of indoor
Africa 53 3 6
radon gas concentrations worldwide, with a geometric Asia 45 17 38
standard deviation of (approximately) 2.3. The infor- Europe 46 34 74
mation collected for the annex on radon suggests that North America 23 4 17
these values are still appropriate. Australia and 14 2 14
Oceania
Although considerable information is available from South America 12 7 58
data provided to UNSCEAR through its surveys, there is Total 193 67 35
great variation by country with respect to the coverage and
Continent Total Population of Population with
quality of available radon data. In general terms, countries population countries with radon data
in Western Europe where the European Union (EU) is radon data available (%)
developing a radon map have the most comprehensive available
coverage, such as the United Kingdom and France. For Africa 904 305 412 128 999 490 14
illustration, consider the United Kingdom for which a Asia 3 893 470 170 3 314 703 215 85
great deal of information is available from radon meas- Europe 742 491 636 663 052 098 89
North America 511 362 031 448 779 940 88
urements in homes. A national survey carried out in the
Australia and 33 105 457 25 078 384 76
early 1980s selected more than 2000 dwellings according Oceania
to postal codes. The mean radon level from the survey, South America 374 997 087 315 551 179 84
after adjustment for dwelling types, was 20.5 Bq m3. The Total 6 459 731 793 4 896 164 306 76
same study also reported data from studies carried out Continent Total surface Surface of Surface with
in regions of the United Kingdom with elevated uranium square countries with radon data
mineralization, which indicate average radon levels of up kilometer radon data available (%)
available
to 300 Bq m3 in areas of southwest England, approxi-
mately 15 times the national average. Subsequently, more Africa 30 042 810 3 621 723 12
than 400 000 measurements were made throughout the Asia 31 713 399 24 408 412 77
Europe 23 215 582 22 255 613 96
United Kingdom aimed at identifying dwellings with North America 22 300 343 21 668 763 97
elevated radon levels; this information is available for Australia and 8 480 726 7 952 834 94
England, Wales, Scotland, and Northern Ireland. Oceania
South America 17 730 252 14 938 952 84
Various non-European countries have also carried out
Total 133 483 112 94 846 297 71
national surveys. Among them are Canada, the United
 Residential Radon Levels Around the World 833

Arithmetic Mean Radon Level by Country

(Based on Data up to 2007)

Rn Level (Bq/m3)
7−25
25−50
50−100
100−184
No data

W E 0 2 500 5 000 10 000 km

S
Scale 1:115 000 000 Robinson Projection

Figure 1 Availability of indoor radon data in the world: whole world.

Arithmetic Mean Radon Level in Africa by Country

(Based on Data up to 2007)

Algeria
Egypt

Ghana

Rn Level (Bq/m3)
9
30
No data
N
W E
S
0 950 1 900 3 800 km

Scale 1:49 000 000

Azimuthal Equal-Area Projection

Figure 2 Availability of indoor radon data in the world: Africa.

834 Residential Radon Levels Around the World

Several studies have been carried out in Japan, in- the report, in some instances the national authorities
cluding nationwide indoor radon surveys. One survey provided this judgment, whereas in some instances
included more than 7000 dwellings and using passive judgments were made by the authors of the UNSCEAR
radon detection reported a mean radon concentration of 2006 report. In all instances, precedence was given to data
20.8 Bq m3. In the 1980s and 1990s, two nationwide provided to UNSCEAR as opposed to literature values.
surveys of indoor radon decay products were completed The data in the table from UNSCEAR 2006 report
in China, and found an AM of the indoor radon show considerable variability both within countries and
concentration of 24 Bq m3, and a GM of 21 Bq m3 from country to country, for example, reported nominal
according to the summarized results. Since 1996, China’s GM indoor levels ranging from o10 Bq m3 in Egypt
housing situation has undergone great change, and a and Cuba, upward to more than 100 Bq m3 in a number
new survey of indoor radon in 26 cities and regions of European countries, and above 600 Bq m3 in parts
was carried out during 2001 and 2005 using alpha-track of Iran.
detectors. The AM of indoor radon concentration was In 2000, UNSCEAR reported (national) worldwide AM
43.8737.7 Bq m3 and the GM was 34.471.95 Bq m3 values of 46 Bq m3 (unweighted) and 39 Bq m3 (popu-
with the median of at 32.9 Bq m3. lation weighted). Worldwide, GM values of 37 Bq m3
Many of the indoor radon data were collected for (unweighted) and 30 Bq m3 (population weighted) with
areas or regions where indoor radon levels were thought corresponding geometric standard deviation of 2.2 (un-
to be elevated and thus, in terms of a ‘national average’ weighted) and 2.3 (population weighted), respectively.
are likely to be biased toward higher levels. The last Given the wide variety and disparity of data currently
column of Table 1 from UNSCEAR 2006 report pro- available to UNSCEAR, it considered that the national
vides a qualitative (subjective) evaluation of the data and average values reported in the UNSCEAR 2000 report
whether the data provided in the table may be considered remained reasonable. In the research reported in this
as some form of ‘national average’ or are more indicative article, it has been attempted to update and validate the
of radon levels in a region or local area. As described in national and global average radon levels using currently

Arithmetic Mean Radon Level

in Asia by Country
(Based on Data up to 2007)

Russia

Cyprus Kazakhstan
Armenia
Syria
Israel
Sau

Kuwait Iran
di A

Japan
South Korea
rab

n China
ista
ia

k
Pa

Rn Level (Bq/m3) India China Taiwan

7−25 China, HK
25−50 N
50−100 Philippines
W E
100−104 Thailand
No data S

0 1 000 2 000 4 000 km

Malaysia

Scale 1:53 000 000 Indonesia

Albers Equal-Area Conic Projection

Figure 3 Availability of indoor radon data in the world: Asia.

 Residential Radon Levels Around the World 835

available data. This, in turn, will facilitate more reliable survey closely followed a stratified random sampling
estimation of the GBD due to radon. design (with cities being strata). It is widely accepted that
the distribution of indoor radon concentration follows
a lognormal distribution. This allows for the calculation
Average Population Radon Level of parameters of the distribution of radon concentration
in the housing stock. For radon gas measurements, the
As indicated earlier, one of principal goals of the WHO’s estimated GM and geometric standard deviation are
IRP was the estimation of the GBD associated with 11.2 Bq m3 and 3.9, respectively. The corresponding
residential radon exposure. To help conducting the GBD AM is 28.4 Bq m3. Alternatively, the APRL for Spain
calculations, it was assumed that the risk was directly was derived from the national radon population distri-
proportional to the exposure and that the risk per unit bution. This distribution was defined as a mixture of
exposure from recent pooled residential case–control regional radon distributions weighted by the proportions
radon studies applied to all populations of the various of Spanish population living in a given region. The
countries of the world. resulting estimated GM and geometric standard devi-
To support these calculations, a database of national ation are 25.2 Bq m3 and 3.4, respectively. In general,
radon levels around the world was created building the latter approach does not require any assumptions
on initial information from the surveys conducted by on the shape of the radon distributions regionally or
UNSCEAR from 2001 through 2006 for its annex on nationally.
radon. Rather than attempting to calculate the APRL for
each country, the validity of reported values based on
publicly available information has been assessed. For Database of National Residential Radon
example, in Canada, the APRL was derived from the Levels
Canadian 19 cities survey. The sample included 14 000
homes in the largest Canadian cities, and represented In developing the world radon database, a systematic
over 50% of the housing stock. Within the 19 cities, the review of all original documents contributing information

Arithmetic Mean Radon Level in Europe by Country

(Based on Data up to 2007)

Icela
nd
Finland

Russia
n
Swede
ay
rw
No

Estonia

Latvia

Denmark Lithuania
us
Ireland United Kingdom lar
Be
Poland
Rn Level (Bq/m3)
y

Netherlands
German

10−25 Belgium
25−50 Luxembourg Czech Republic
Slovakia
50−100
Austria ary
100−184 ng
France Switzerland Hu Romania
No data
Slovenia Croatia N

Montenegro W E
Ita ia
gar
ly Bul S

Portugal Albania 0 250 500 1 000 km

Spain
Greece
Scale 1:20 000 000
Lambert Conformal Conic Projection

Figure 4 Availability of indoor radon data in the world: Europe.

836 Residential Radon Levels Around the World

to the database has been conducted, and all other rele- conference proceedings, internal reports, UNSCEAR
vant and reasonably available documents have been surveys, WHO 2006 survey, and personal communi-
collected to enhance the database. Among the sources of cation. However, it was realized that for the purpose of
data, considered in addition to data from the recent assessing reliability of the national indoor radon levels
UNSCEAR surveys and the UNSCEAR 2000 report, are the above-mentioned classification does not work well
‘An Overview of Radon Surveys in Europe’ and infor- given that most of the information has been published in
mation from searches of MEDLINE for the keywords ‘gray literature’ and some of this literature is of very
indoor and radon (searched on 20 September 2007). The high quality. Therefore, for the purpose of developing
MEDLINE search returned 992 references, from which the global radon database, journal publications, confer-
87 were retained as contributing information about ence proceedings, and internal reports were treated
national/regional indoor radon levels. equally as long as they are publicly and relatively easily
In addition, on 29 September 2007, from a search available (on the web, for example). For each reference,
of tables of content of Radiation Protection Dosimetry it was discussed (among ourselves) whether there was
(keywords: indoor, environmental, radon, and survey), sufficient evidence (limited evidence or inadequate
some 300 items were identified and 103 were retained evidence) for using the value reported in this reference
as contributing relevant information about national/ as national average radon level for a given country.
regional indoor radon levels. A similar search of tables Currently, the database contains information on
of content of Radiation Measurements (on 3 December national indoor levels from 67 countries (out of 193
2007) returned 11 relevant references out of 102 initially recognized by WHO). These 67 countries represent 76%
identified. of the world’s population and 71% of its landmass. The
For the purpose of data quality objectives (DQO), radon information varies by continent with only 3 African
first the following evaluation order was used to classify countries (out of 53) and 34 European countries (out of
the reliability of the references: journal publication, 46) with data (Table 2).

Arithmetic Mean Radon Level in

North America by Country
(Based on Data up to 2007)

Canada
Rn Level (Bq/m3)
7−25
25−50
50−100
100−140
No data

United States

W E

S Mexico
0 750 1 500 3 000 km

Scale 1:46 000 000

Lambert Conformal Conic Projection

Figure 5 Availability of indoor radon data in the world: North America.

 Residential Radon Levels Around the World 837

Mapping National Residential Radon web-based Earth browsers. It is a file format for managing
Levels around the World the display of geographic data in Google Earth and
Google Maps. There are a few different software packages
Using data from the database, a map of national levels of to convert geographic data to KML format, such as Export
residential radon around the world has been created. to KML 2.4.5 (http://arcscripts.esri.com/details.asp?dbid ¼
Three different types of mapping practices have been 14273); KMLer (http://www.mi-perm.ru/gis/programs/
considered and used to develop maps. First, traditional kmler/); Arc2earth Pro (http://www.arc2earth.com/
static maps are created using ArcMap and exported as products/default.htm); Tiles2kml Pro 2.31 (http://www.
image files in GIF or JPG format. This approach does not supershareware.com/info/tiles2kml-pro.html). It was acco-
require JavaScript or any dynamic page loading and can mplished by converting the map of radon level on the
be easily downloaded or printed. Second, interactive maps World to KML format using XTools (www.xtoolspro.com).
in web format – using dynamic HTML script and In addition to the static maps (see Figures 1–7), a pre-
JavaScript technologies – and conventional static map liminary web version (http://www.mclaughlincentre.
images were combined to present radon information ca/research/map.shtml) and Google Earth version
interactively. When moving the mouse on the map, a small of the map (http://www.mclaughlincentre.ca/research/
box pops up to display more information as shown on map_radon/World_Rn.km1) have been implemented. It
the website http://www.mclaughlincentre.ca/research/ is necessary to have Google Earth installed on a com-
map.shtml. Softwares used to develop the webpage puter to view this map; see http://earth.google.com/).
include MapEdit (http://www.boutell.com/mapedit) and Currently available radon levels for countries, provinces
DHT ML tip messages (http://simplythebest.net/scripts/ or cities, and towns are presented in boundary maps of
DHTML_scripts/dhtml_script_120.html). And the third, the whole world, continent, and countries using ArcMap.
interactive map in KML format – KML (Keyhole Markup The boundary files were taken from CDs of ESRI Arc-
Language) is an XML-based language schema for ex- View software and websites (http://biogeo.berkeley.edu/
pressing geographic annotation and visualization on gadm/, http://research.cip.cgiar.org/gis/index.php). The

Arithmetic Mean Radon Level in Australia/Oceania by Country

(Based on Data up to 2007)

Australia

Rn Level (Bq/m3)

11−21.5
No data
N

W E
0 375 750 1 500 km
S
Scale 1:23 000 000
Azimuthal Equal-Area Projection New Zealand

Figure 6 Availability of indoor radon data in the world: Australia and Oceania.
838 Residential Radon Levels Around the World

Arithmetic Mean Radon Level in South America by Country

(Based on Data up to 2007)

Ven
e zue
la

Ecuador

Brazil
Rn Level (Bq/m3) Peru
25
25−50
50−100
No data Paraguay

W E
Chile
S Argentina

0 500 1 000 2 000 km

Scale 1:41 500 000

Azimuthal Equal-Area Projection

Figure 7 Availability of indoor radon data in the world: South America.

projected coordinate systems used for most maps were in minimizing potential excessive radon exposures and
those shown on maps collected by the University of corresponding risks. Such information also helps national
Texas Libraries from the original publishers (http:// and local government radon programs to focus on the
www.lib.utexas.edu/maps/). Radon levels on the map areas at most risk of having high radon levels. It outlines
were expressed by red, yellow, and green colors to rep- areas where radon preventive measures are likely to be
resent different levels of risk based on widely used color required in new buildings. It allows house buyers to find
codes in risk assessment and management systems, that is, out whether there is a likelihood of high radon levels in a
on a relative basis, red means high risk; yellow represents house they may wish to buy.
moderate risk, and green signifies a low risk. It should be acknowledged that the current map
has many deficiencies; however, even in its present form,
such data are useful. The present work also suggests that
Conclusions international agencies such as UNSCEAR (UNEP) and
WHO as well as national agencies develop such a web-
Radon maps are a clear and easily understood way of based product, after improvements and extensions. Such
presenting the radon issue to the public and policy a tool would provide a useful means for UNSCEAR
makers, and essential for persuading people to take it or other agencies to facilitate collection, review, and
seriously. Although radon levels vary widely from house evaluation of radon data from around the world as well as
to house, radon maps are valuable in identifying areas facilitating the broad dissemination of such data. Com-
where it is important to measure, or to prevent high municating information about the radon data in such a
radon levels in new buildings. Such maps facilitate edu- database, facilitating electronic updates of the database,
cating the public and government agencies about the and subsequently mapping of the data are potentially a
potential risks associated with natural background levels very important tool for communicating the risks arising
of indoor radon. Such information helps to ensure that from exposure to radon. Such a web-based tool could be
both public and private monies are used most effectively extended over time to other sources of exposure.
 Residential Radon Levels Around the World 839

See also: Exposure Guidelines and Radon Policy, Radon Wrixon, et al. (1988) Natural Radiation Exposure in UK Dwellings.
Measurement. Chilton, United Kingdom: National Radiological Protection Board.

Further Reading Epidemiology

Darby S, et al. (2005) Radon in homes and risk of lung cancer:
Billon S, et al. (2005) French population exposure to radon, terrestrial
Collaborative analysis of individual data from 13 European case-
gamma and cosmic rays. Radiation Protection Dosimetry 113: 314.
control studies. British Medical Journal 330: 223.
Dubois G (2005) An Overview of Radon Surveys in Europe, EUR 21892
Krewski D, et al. (2005) Residential radon and risk of lung cancer:
EN. Luxembourg: Office for Official Publications of the European
A combined analysis of 7 North American case-control studies.
Communities.
Epidemiology 16: 137.
Fujimoto K (2004) Mapping of nationwide indoor radon survey in Japan,
NIRS-M. National Institute of Radiological Sciences. 171: 107.
Garcia-Talavera M, Matarranz JL, Martinez M, Salas R, and Ramos L
(2007) Natural ionizing radiation exposure of the Spanish population.
Radiation Protection Dosimetry 124(4): 353--359.
United Nations Organizations
Green BMR, Miles JCH, Bradley EJ, and Rees DM (2002) Radon Atlas United Nations Scientific Committee on the Effects of Atomic Radiation
in England and Wales. Chilton, United Kingdom: National (2000). Sources and Effects of Ionizing Radiation, UNSCEAR 2000
Radiological Protection Board. Report to the General Assembly, with Scientific Annexes, vol.1,
Green BMR, Lomas PR, Miles JCH, Ledgerwood FK, and Bell DM, Sources, United Nations, New York.
(1999) Radon in dwellings in Northern Ireland: Atlas and 1999 United Nations Scientific Committee on the Effects of Atomic Radiation
review. NRPB-R308, National Radiological Protection Board. (2006) Effects of Ionizing Radiation, UNSCEAR 2006 Report to the
Letourneau EG, McGregor RG, and Walker WB (1984) Design and General Assembly, with Scientific Annexes, Volume II, Annex E,
interpretation of large surveys for indoor exposure to radon Sources-to-Effects Assessment for Radon in Workplaces and
daughters. Radiation Protection Dosimetry 7: 303. Homes, United Nations, New York.
Marcinowski F, Lucas RM, and Yeager WM (1994) National and regional Zielinski JM, Carr Z, Krewski D, and Repacholi M (2006) World Health
distributions of airborne radon concentrations in U.S. homes. Health Organization’s International Radon Project. Journal of Toxicology
Physics 66: 699. and Environmental Health 69: 759.
McGregor RG, Vasudev P, Letourneau EG, McCullough RS, Prantl FA,
and Taniguchi H (1980) Background concentrations of radon and
radon daughters in Canadian homes. Health Physics 39: 285.
Sanada T, Fujimoto K, Miyano K, et al. (1999) Measurements of Relevant Websites
nationwide indoor Rn concentration in Japan. Journal of
Environmental Radioactivity 45: 129. http://www.lib.utexas.edu/
Shang B, et al. (2006) Radon Levels Survey in Residences in China. The University of Texas Libraries.
China: National Institute for Radiological Protection. http://www.epa.gov/radon
United States Environmental Protection Agency, EPA (2003) U.S. Environmental Protection Agency.
Assessment of Risks from Radon in Homes, EPA 402-R-03-003, http://www.who.int/ionizing_radiation/env/radon/en/
Washington, DC. World Health Organization.