STUDY ON INDOOR AND OUTDOOR RADON-222 AREA

STUDY ON INDOOR AND OUTDOOR RADON-222
CONCENTRATION IN UiTM PUNCAK ALAM CAMPUS
AREA
SITI FAZIDAH MAT YAACOB
Final Year Project Report Submitted in
Partial Fulfillment of the Requirements for the
Degree of Bachelor of Science (Hons.) Chemistry
in the Faculty of Applied Sciences
Universiti Teknologi MARA
NOVEMBER 2010
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ACKNOWLEDGEMENTS
First and foremost, all praise is be to Allah, the Almighty, the Benevolent for His
blessings and guidance for giving me the inspiration, ability and strength to
embark this project. Many people have contributed to the completion of this
project. I would like to express my gratitude to all who have helped in planning
and editing of this project.
Upon completion of this project, I would like to express my gratitude to
many parties. My heartfelt thanks goes to my supervisor, my supervisor, Assoc.
Prof. Dr. Ahmad bin Saat, and my co-supervisor Assoc. Prof. Dr. Zaini bin
Hamzah for their advices, kindness and helps me most to finish this thesis. I am
especially indebted and grateful to the members of Universiti Teknologi Mara
for their support in this project.
Besides, I would like to thank the staff of UiTM Puncak Alam for their
help and cooperation and also to the friends who involved in completing this
project.
Siti Fazidah Mat Yaacob
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATIONS
ABSTRACT
ABSTRAK
Page
iii
iv
vi
vii
vii
ix
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CHAPTER 1 INTRODUCTION
1.1
Background of Study and Problem Statement
1.2
How Radon Gas Enter Into Our House
1.3
Effect of Radon Gas
1.4
Significance of Study
1.5
Objectives of Study
1
4
7
7
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CHAPTER 2 LITERATURE REVIEW
2.1
Historical Background
2.2
Sources of radon
2.3
Radon occurrence
2.4
Radon isotopes
2.5
Factors influencing radon levels in the home
2.6
Comparison level of radon in Malaysia in different location
2.7
Comparison level of radon in Malaysia with other countries
2.8
Experimental techniques
2.8.1 Active dosimeters
2.8.2 Passive dosimeters
2.8.3 Solid state nuclear track detector (CR-39)
CHAPTER 3 METHODOLOGY
3.1
Study area
3.2
Units of measurement
3.3
Measuring procedures
3.4
Preparation of dosimeter
3.5
Laboratory work
3.6
Calculation of radon concentration
3.7
Analysis
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13
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19
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25
26
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27
30
34
34
38
38
39
40
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CHAPTER 4 RESULTS AND DISCUSSION
4.1
Result
4.2
Measurement of radon gas activity
4.2.1 Measurement of radon gas in the air (indoor)
4.2.2 Measurement of radon gas in the air (other building)
4.2.3 Measurement of the radon gas in the air (outdoor)
4.2.4 Measurement of the radon gas activity in the soil
4.3
Comparison between other locations
4.4
Discussion
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50
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CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
5.1
Conclusion
5.2
Recommendation
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56
CITED REFERENCES
APPENDICES
CURRICULUM VITAE
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62
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LIST OF TABLES
Table
Caption
Page
2.1
Indoor and outdoor mean radon concentration at 5 locations of study in
Malaysia
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2.2
Comparison of the mean indoor radon concentration in Malaysia
to the corresponding values of other countries
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4.1
Indoor radon concentration of FF2 building
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4.2
Indoor radon concentration in other building
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4.3
Outdoor radon concentration
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4.4
Radon emanation rate from soil
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4.5
Comparison of the mean indoor and outdoor concentration of radon
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4.6
Comparison of the mean indoor radon concentration of the previous
study with other countries
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LIST OF FIGURES
Figure
Caption
Page
1.1
How radon diffuse into our house
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2.1
Decay series of uranium-238
18
2.2
Radon which is not fully exposed
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2.3
Radon which is fully exposed
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3.1
Location of study area for indoor and outdoor radon concentration
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3.2
Locations for radon concentration determination in soil
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3.3
Schematic diagram of the radon dosimeter used in this study
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3.4
Picture of the dosimeter contain CR-39
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3.5
Flow chart of methodology
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4.1
Highest number of track formation
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4.2
Lowest number of track formation
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4.3
Track formation of radon in the soil
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LIST OF ABBREVIATIONS
SSNTD
:
Solid State Nuclear Track Detector
USEPA
:
United State Environment Protection Agency
U.S
:
United State
EPA
:
Environment Protection Agency
Rn
:
Radon
Po
:
Polonium
Ra
:
Radium
U
:
Uranium
NaOH
:
Sodium hydroxide
pCi/L
:
pico Curies per Liter
Bqm-3
:
Becquerel per meter cubic
Bqm-2s-1
:
Becquerel per meter squared second
Bqs-1
:
Becquerel per second
PSB
:
Plaza Satellite B
FF4
:
Fakulti Farmasi 4
FF2
:
Fakulti Farmasi 2
VC
:
Vice Chancellor
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ABSTRACT
STUDY ON INDOOR AND OUTDOOR RADON CONCENTRATION IN UITM
PUNCAK ALAM CAMPUS AREA
Radon-222 is the naturally radioactive substances that derived from Uranium-238 and
the most important natural radiation which is present in a small amount almost
everywhere in the earth crust. If radon is inhaled, it can cause harm to human cells in the
lung and our body. Radon gas cause lung cancer and it is not good for our health when it
reaches high concentration. Due to this, radon gas has been measured at UiTM Puncak
Alam Campus inside and outside of several building at this area. Objectives of this study
are to determine the indoor and outdoor radon concentration, to compare the
concentration with other locations and to determine the radon emanation rate from soil.
For this purpose radon concentration levels were measured using passive dosimeters,
SSNTD CR-39. A total of 32 dosimeters were distributed inside and outside the
academic and administrative buildings in the UiTM Puncak Alam campus area. The
exposure time started from 29 of April 2010 and lasted for 100 days which is 10 of July
2010. 32 dosimeters were located at selected area at the study area. In the laboratory,
SSNTD will chemically etch for 7 hours using 6M NaOH solution at 70˚C in the water
bath. Detectors will then wash with tap water and dried prior to microscope inspection.
Radon gas concentration levels inside the buildings were found to have an average value
of 14.396 Bqm-3. The radon gas concentrations outside the building were found to have
an average value of 11.478 Bqm-3. The radon emanation rates found from the soil have
an average value of 1.909 µBqm-2 s-1.
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ABSTRAK
KAJIAN TENTANG RADON DI DALAM DAN DI LUAR BANGUNAN DALAM
KAWASAN UITM KAMPUS PUNCAK ALAM
Radon adalah bahan radioaktif semulajadi yang terurai daripada uranium-238 dan
merupakan bahan radiasi terpenting di mana ianya hadir dalam jumlah yang kecil di
setiap tempat di dalam kerak bumi. Sekiranya gas radon ini dihidu oleh manusia, ia
boleh membahayakan sel-sel di dalam jantung dan badan kita. Gas radon boleh
menyebabkan sakit jantung dan ia memberikan kesan yang buruk apabila mencapai
tahap kepekatan yang tinggi. Merujuk kepada perkara ini, kajian tentang gas radon telah
dijalankan di dalam dan luar bangunan di kawasan sekitar UiTM Puncak Alam. Objektif
kajian ini adalah untuk menentukan kepekatan radon di dalam dan di luar,
membandingkan kepekatan dengan kawasan-kawasan lain, dan menetukan kadar radon
yang keluar dari batuan di dalam tanah. Untuk tujuan ini, kepekatan gas radon ini dikaji
dengan menggunakan pengesan pasif, CR-39 pengesan trak plastik (SSNTD). Dosimeter
tersebut dibiarkan di kawasan kajian selama lebih kurang 100 hari bermula dari 29 April
2010 dan berakhir selepas 100 hari iaitu 10 Ogos 2010. 32 dosimeter telah diletakkan di
kawasan yang telah dipilih. Di makmal, pengesan SSNTD direndam selama 7 jam
menggunakan larutan 6M NaOH pada 70 ˚C di dalam bekas air panas. pengesan
kemudiannya dicuci dengan air paip dan dikeringkan untuk diperiksa di bawah
mikroskop. Purata kepekatan gas radon di dalam bangunan adalah 14.396 Bqm-3.
Kepekatan gas radon di luar bangunan berpurata 11.478 Bqm-3. Purata gas radon yang
keluar dari batuan di dalam tanah adalah of 1.909 µBqm-2s-1.
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CHAPTER 1
INTRODUCTION
1.1 Background of study and problem statement
Radon comes from the natural breakdown of uranium in soil, rock and water and
gets into the air that we breathe. Radon is a naturally occurring radioactive gas,
which is a part of noble gas that is chemically inert and occurs in different forms
with the same atomic number but different atomic mass, called isotopes. Radon
is formed by the disintegration or breakdown of radium. It is formed in rocks and
soils and escapes into the atmosphere which is colorless, odorless, tasteless
radioactive gas. It is produced by the radioactive decay of uranium-238.
At significant concentration, when it is accumulated in buildings, drinking water
and others, it can become a health hazard. Radon is at the bottom of the noble
gas group, that is, Group 18 in the periodic table. It is the heaviest noble gas due
to it highest density and one of the heaviest gases at room temperature. Radon
gases have a half life of 3.8 days. At ordinary temperatures and pressures, radon
is colorless but when it is cooled below its freezing point it has brilliant
phosphorescence which turns yellow as the temperature is lowered and orangered at the temperature air liquefies. Radon is an odorless and colorless
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radioactive noble gas. It emanates from soil and water, and produces decay
products in the air. When radon gas and its decay products are inhaled they are
considered to have a negative effect on our health. In fact, the high concentration
of radon gas as found uranium mines is recognized to cause lung cancer
(Yamada, 2003).
Since radon is an inert gas, it does not enter into any chemical reactions within
the body, but it can be inhaled. Once it reaches the lungs, it may undergo
radioactive decay, producing other kinds of atom, called “daughters” of radon.
All of the decay products are solid materials that remain in the lung and are
chemically active. Decay product here is a radioactive substance that formed as a
result of the breakdown or decay of another radioactive element. As it undergoes
radioactive decay, radiation is released predominantly by alpha particle
emissions, which are the source of health concerns. Decay products of Radon222 are solids that can attach to the particles in the air and be transported in the
atmosphere. They can be deposited on land or water by settling or by rain. Radon
decays into radioactive metal ions by alpha radiation.
Because radon is a gas, it moves freely in the air spaces. It can move to air,
groundwater, and surface water. If a building is builds up to high concentration
in indoor air, radon and it decays product can cause lung cancer due to the
leaking from the soil. The measurement of Radon-222 and its progeny
concentration in indoor and outdoor environment are important to estimate the
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inhalation dose to the population of the region. The studies also needed to
understand the Radon-222 and its progeny concentration are dependence to what
factor of parameters such as humidity, temperature and others (Murty et al.,
2009). In recent years, substantial attention has been paid to natural radon,
particularly to the problems of exposure to radon and its progeny in buildings
and dwellings. In countries with cold climate, where energy saving has led to the
tighter sealing of windows and doors, the radon problem may be very significant
(Al-Qahtani et al., 2005).
The measurement of radon in man’s environment is of interest because of its
alpha emitting nature. Radon decays with a half-life of 3.82 days into a series of
short-lived daughter products out of which Polonium-218 and Polonium-214
emit high-energy alpha particles which are highly effective in damaging tissues.
The fact that radon, when inhaled during breathing can cause lung cancer in
human beings is known since a long time ago. The main sources of radon in
dwellings are the soil or the rock underneath, the building materials and the
public water supplies. The work on the measurement of radon concentration
levels and its short-lived decay products in different countries have been
published in the recent years. In India many research workers are engaged in the
measurement of indoor radon levels in dwellings for health risk assessments and
its control (Singh et al., 2005).
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About half of the natural radiation dose to humans is due to radon and its decay
products. It is well known that exposure to high levels of radon causes lung
cancer, but there are still little data on the effect of long term exposure to low
levels of environmental radon (Yamada, 2003). Radon-222 is the most important
source of natural radiation, so the control of the levels of its concentration in the
different geographic area is also significance. Exposure to radon and radon
progeny is the dominating source of exposure to ionizing radiation in most
countries. Radon measurement is not widely done in Malaysia. Usually, there are
two methods that can be used in this work that is active method and passive
method. But, measuring level of radon concentration is more convenience using
passive method because it can be done in many places and shorter time
consuming are needed. This study will be done at UiTM Puncak Alam Campus
because this place is a new campus area and there is no study had been done
here. Besides, there result of radon concentration measured by using SSNTD
from this study will be useful for further study.
1.2 How radon gas enter into our house
Radon is a radioactive gas. It comes from the natural decay of uranium that is
found in nearly all soils. It typically moves up through the ground to the air
above and into the house through cracks and other holes in the foundation. The
home traps radon inside, where it can build up. Any home may have a radon
problem. This means new and old homes, well-sealed and drafty homes, and
homes with or without basements. Radon from soil gas is the main cause of
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radon problems. Sometimes radon enters the home through well water. In a small
number of homes, the building materials can give off radon too. However,
building materials rarely cause radon problems by themselves. Radon gets in
through cracks in solid floors and in walls, construction joints in, gaps in
suspended floors, gaps around service pipes, cavities inside walls, and the water
supply. Nearly 1 out of every 15 homes in the U.S. is estimated to have elevated
radon levels. Elevated levels of radon gas have been found in homes in your
state. While radon problems may be more common in some areas, any home
may have a problem.
Uranium can generate radon gas by fission. The radon gas will itself undergo
further fission to produce radioactive 'daughters'. The alpha particles produced
by radon daughters are not powerful enough to penetrate the human body from
outside it. However, if radon is inhaled, the alpha particles generated by the
daughters can cause harm to cells in the lungs and elsewhere. This may result in
an increased risk of cancer. The Figure 1.1 shows how radon gas diffusing out of
the ground can be forced or sucked into houses thus resulting in much higher
concentrations indoors than outdoors. The level of radon is often highest in the
lower part of the building. Radon moves through a house by diffusion and
natural air movements and it can be distributed by mechanical equipment such as
a forced-air ventilation system. As radon moves away from the house's
foundation or other entry points, it mixes and is diluted into a greater volume of
air. In addition, more dilution often occurs in the upper levels of the house
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because there is more fresh air ventilation there. Greater dilution and less house
vacuum may also occur when the house is more open to the outdoors during the
non-heating season. The figure might give researcher some ideas as to how
exposure in houses could be reduced. For example an impermeable membrane
could be installed at floor level; fans could suck air containing radon from
underneath the ground floor and expel it directly into the atmosphere, where it
disperses (Agius R, 2009).
Figure 1.1 How radon diffuse into our house
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1.3 Effect of radon gas
Radon is present in nearly all air. Usually everyone breathes radon in every day
at very low levels. However, people who inhale high levels of radon are at an
increased risk for developing lung cancer. Radon decays quickly, giving off tiny
radioactive particles. When inhaled, these radioactive particles can damage the
cells that line the lung. Long-term exposure to radon can lead to lung cancer, the
only cancer proven to be associated with inhaling radon. According to Yamada
(2003), the radon’s half-life of 3.8 days is long enough for it to enter into indoor
and cause an increase in the indoor concentration. But, this half-life is relatively
too long to enter into the respiratory tracts and to irradiate the cells.
1.4 Significance of study
Statistics indicate that radon gas that appear from the cracked buildings affected
the health of human. Radon is cited as the second leading cause of lung cancer
after cigarette smoking. This project is important as it will be beneficial to
people in order to understand more about radon and the effect to human health.
Radon-222’s half life of 3.8 days is long enough for it to enter into indoor and
can cause the indoor concentration to increase but it is too long for it to enter into
the respiratory tracts and to irradiate the cells. The results of this research will be
useful to provide information about the risk of radiation. The result from this
study will be useful to assess and to gain an overview of the radon concentration.
This is because no study has been done in this area of study.
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1.5 Objectives of Study
The intention of this research is to know what is radon, how it is formed,
measure the presence of radioactive radon gas in outdoor and indoor buildings at
UiTM Puncak Alam Campus and why it is a human health concern. The specific
objectives of the project include:
1. To determine the indoor and outdoor radon concentration in UiTM
Puncak Alam Campus area
2. To compare the indoor and outdoor concentration of radon with other
locations
3. To determine the radon emanation rate from soil
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CHAPTER 2
LITERATURE REVIEW
2.1 Historical Background
Radon (named for radium) was discovered in 1900 by Friedrich Ernst Dorn, who
called it radium emanation. In 1908, William Ramsay and Robert WhytlawGray, who named it niton (from the Latin word nitens meaning "shining";
symbol Nt), isolated it, determined its density and that it was the heaviest known
gas. It has been called radon since 1923. The danger of radon exposure in
dwellings was discovered in 1984 by Stanley Watras, an employee at the
Limerick nuclear power plant in Pennsylvania. Mr. Watras set off the radiation
alarms on his way into work for two week straight while authorities searched for
the source of the contamination. They were shocked to find that the source was
astonishingly high levels of radon in his basement and were not related to the
nuclear plant. The risks associated in living in his house were estimated to be
equivalent to smoking 35 packs of cigarettes every day. Radon was not
considered to have a detrimental effect on human health until the late 1950s,
when uranium miners in mines with high concentrations of radon began to show
unusually high rates of lung cancer.
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Radon is an essentially inert, colorless, odorless gas at ordinary temperatures. Its
melting point is 202˚K and the boiling point is 211˚ K. When cooled below the
freezing point radon exhibits brilliant phosphorescence which becomes yellow as
the temperature is lowered and orange-red at the temperature of liquid air. The
atomic radius is 1.34 angstroms and it is the heaviest known gas, being nine
times denser than air. Because it is a single atom gas, it easily penetrates many
common materials like paper, leather, low density plastic bags, most paints, and
building materials like gypsum board, concrete block, mortar, sheathing paper,
wood paneling, and most insulation. Radon is also fairly soluble in water and
organic solvents. Although reaction with other compounds is comparatively rare,
it is not completely inert and forms stable molecules with highly electronegative
materials. Radon is considered a noble gas that occurs in several isotopic forms.
Only two are found in significant concentrations in the human environment:
Radon-222, and Radon-220. Radon-222 is a member of the radioactive decay
chain of Uranium-238, and Radon-220 is formed in the decay chain of Thorium232. Radon-222 decays in a sequence of radionuclide called radon decay
products, radon daughters, or radon progeny. Atmospheric releases of Radon222 results in the formation of decay products that are radioisotopes of heavy
metals (polonium, lead, bismuth) and rapidly attach to other airborne materials
such as dust and other materials facilitating inhalation.
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2.2 Sources of radon
Uranium is present in the earth’s crust and radon occurs in building materials,
groundwater and natural gas. The ground is the major radon sources. Building
materials made from soil or rocks always contain uranium and radium. There are
three principal sources of radon found in indoor air that is rocks and soils under
the building, building materials used in construction, and radon dissolved in the
water supply. The rocks and soils under the building are the most important.
Some kinds of rocks, and the soils that form from their breakdown, are more
prone to giving off radon than others. This is because some rocks naturally
contain more uranium and radium than others. The main natural sources of
indoor radon are soil, building materials (sand, rocks, cement, etc.), water born
transport, natural energy sources like gas, coal which contain traces of uranium238 (Mansour et al., 2005).
Radon-222 is a ubiquitous indoor air pollutant that is found worldwide. Its
sources are soil, building materials, groundwater, etc. Wood-based building
materials contain little natural radioactive substances such as radium (Yamada,
2003). Entry of radon through a home’s foundation depends on substructure
type, design, construction details and building materials. Building materials
made from stone and sand may contain uranium and radium that will produce
radon gas. Concrete and brick are examples of building materials that are porous
enough to allow the gas to escape. While the porosity or durability of building
materials used in foundation types can determine the amount of radon that can
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diffuse into home from soil, the overall contribution of building materials as a
source and pathway to indoor concentration is much less than from soil.
Radon-222 is a gas, and moves through cracks and fissures in rocks, and through
the air spaces in soil. The major factors that influence the movement of radon
into a home include the uranium and radium concentrations of the rock and soil
materials beneath the home, pathways through the rocks and soil to the base of
the home, openings from the soil directly into the inside of the home, and the
amount of suction created by air flows within the home (Figure 1.1). This
suction is caused by differences in pressure between the inside and outside of the
house. Once radon gets into a home, its concentration in the indoor air is
influenced by the amount of household ventilation. Opening windows and doors,
operating bathroom and kitchen fans, and operating clothes dryers all tend to
change the radon concentrations by increasing ventilation and/or by pulling more
radon in from the soil through the lower parts of the home. Because radon enters
the home from the underlying soil, it seldom reaches high concentrations above
the second floor of a building.
The presence of radon into buildings results from many parameters. The main
source of radon in building is generally the ground under basement. Its entry into
building is mainly due to convective forces due to pressure difference between
the soil beneath the ground floor and the inhabited volume. This pressure
difference is due to temperature difference between indoors and outdoors. It
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induces an air flow from ground porosity to the indoor environment via
basement air leakages. So that, the intensity of radon source in a building is
generally growing up with temperature difference (Collignan, 2008).
2.3 Radon Occurrence
On average, there is one atom of radon in 1 x 1021 molecules of air. Radon can
be found in some spring waters and hot springs. The towns of Misasa, Japan, and
Bad Kreuznach, Germany boast radium-rich springs which emit radon. Radon
exhausts naturally from the ground, particularly in certain regions, especially but
not only regions with granitic soils. Not all granitic regions are prone to high
emissions of radon. Depending on how houses are built and ventilated, radon
may accumulate in basements and dwellings. Radons emitted from the ground
are accumulated in the air if there is a meteorological inversion and little wind.
The United States Environmental Protection Agency recommends action for any
house with a concentration higher than 148 Bqm-3 and encourages action starting
at 74Bqm-3. Nearly one in 15 homes in the U.S. has a high level of indoor radon
according to their statistics. The U.S. Surgeon General and EPA recommend all
homes be tested for radon. Since 1985, millions of homes have been tested for
radon in the U.S. The European Union recommends that action should be taken
starting from concentrations of 400 Bqm-3 for old houses, and 200 Bqm-3 for new
ones. The average outdoor radon level varies between 5 and 15 Bqm-3. Indoor
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radon levels are higher with the highest level found in places such as mines,
caves and water treatment facilities.
Indoor radon concentration depends on the house construction and the
underlying soil. Together with climate factors and human habit, this lead to
variations in radon levels by hour, day, season and year. Furthermore, the
concentration varies between buildings and rooms, and within rooms. Radon
concentration in dwellings differs between countries because of differences in
geology and climate, in construction materials and techniques, and in domestic
customs. In an indoor environment, radon can be emitted from the building
materials containing uranium and thorium series elements or transmitted from
the surrounding soil. The alpha particles emitted from radio nuclei during the
disintegration process of these decay chains can damage body tissue. A human
body exposed to excessive amounts of radon in the atmosphere is at risk from
lung cancer. In indoor environment, building construction materials are a major
emission source of radon. The amount of radon in the building materials depends
on complex soil chemistry that would vary from different countries (Mui et al.,
2005). Radon emanates to a certain degree from all the different types of soils
and its concentration in the atmosphere depends upon the uranium and radium
concentrations present in the soils. Its presence in the biosphere is due to its
semidesintegration period of nearly 4 days, which allow it to diffuse from the
earth’s crust into the air that we breathe (Canoba et al., 2000).
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`