Abstract The aim of the research reported in this thesis was to determine the influence of building heights on radon and thoron concentration via permeation and diffusion into the individual apartment units in a multi-storey apartment building. The hypothesis assumes that the bottom floor of the structure, similar to most any low-rise structure indoor radon experiments, has highest level of radon due to subsoil emanation. Subsequent increasing floor height, which constituted higher floor level in this fifteen floor level multi-storey building, depicts opposite relationship to indoor radon concentration. That is to say, subsoil radon gas diffusion reduces. A correlation can be determined between radon concentration and building height as a function of floor level. Being in a real-life habited residential building, control on environmental measurement is limited. Equipments used were standalone dosimeters without electricity or battery needs. Multiple on site experiments were conducted over a period of at least 30 days. Measurements of radon ranged from 11.4-42.2 Bq/m 3 (arithmetic mean values), and 11.0-42.1 Bq/m 3 (geometric mean values). Measurements of thoron ranged from 0.1-0.5 Bq/m 3 (arithmetic mean values), 0.0-0.3 Bq/m 3 (geometric mean values). The pattern of radon concentration was overall decreasing from the bottom floor level to the higher floor levels. When compared to radon concentration, there is no sharp decrease in thoron concentration as a function of floor level. They are both physically ii
different in nature. The thoron concentration would have been low due to short half-life at 55.6 second and become depleted after incurring many half-lives since. Implications of this study include the need for environmental housing policy development, and improved education and awareness to radiation risks in dwellings. iii
Abstrak Tujuan kajian yang dilaporkan dalam tesis ini adalah bagi menentukan pengaruh ketinggian bangunan terhadap kepekatan radon dan thoron dalam apartmen individu suatu bangunan perbagai tingkat, melalui proses resapan dan serapan. Hipotesis menganggapkan bahawa struktur tingkat terbawah yang sama seperti bangunan rendah mempunyai tahap radon tertinggi disebabkan resapan dari bawah tanah. Penambahan ketinggian tingkat dalam bangunan lima belas tingkat ini melihatkan perhubungan bertentangan terhadapan kepekatan radon. Ini bermakna pengaruh resapan dari bawah tanah telah berkurangan. Suatu saling hubungan boleh didapati antara kepekatan radon dan ketinggian banguanan iaitu sebagai fungsi tahap tingkat. Sebagai bangunan penginapan sebenar, kawalan terhadap persekitaran pengukuran adalah terbatas. Kajian ini mengunakan dosimeter tanpa memerlukan tenaga elektrik. Pengukuran menghasikan bacaan radon dari 11.4 42.2 Bq/m 3 (min arithmetic) dan 11.0 42.1 Bq/m 3 (min geometri), manakala bagi thoron pula bacaan adalah 0.1 0.5 Bq/m 3 (min arithmetik) dan 0.0-0.3 Bq/m 3 (min geometri). Secara keseluruhannya kepekatan radon menunjukkan pola menurun dari aras bawah kepada aras lebih tinggi. Apabila dibandingkan dengan kepekatan rdon, tiada perubahan ketara dalam kepekatan thoron sebagai fungsi aras lantai. Kedua-dua berbeza dari segi fizikal. Ketumpatan thoron rendah kerana nilai separuhnya hayat yang rendah iaitu 55.6 saat dan terhapus setelah melalui banyak separuh hayat. iv
Implikasi kajian ini termasuklah keperluan pembangunan polisi persekitaran perumahan serta penambahbaikan pendidikan terhadap bahaya radiasi dalam kediaman. v
Acknowledgement I express thanks to persons at the University and at the project site whom supported my effort in data collection, method devising, and output write up. There are also various other labourious yet meaningful exchanges that must be attributed to the success of this master s project at the University. Let me not forget that this University is a congregation of intelligence, diligence (20). Yet much amount of poor interaction and unwillingness to focus appear here also (80). I pray the 80:20 rule will be soon altered. Let me thank friends that initiated my roller coaster type journey here. That started with Yasmin Yahya (neighbour), and then there was Abdul Kariem (Professor). And in the middle there has been Teo Li Ping, Thompson Woo Haw Jiunn, Sim Cheng Kim, and all many more names I am all set for a new chapter. vi
Table of Contents Chapter One Indoor Radiation A Measurement of Environmental Radon and Thoron Concentrations in a Multi Storey Apartment Building 1.1 Introduction 1 1.2 Literature of Indoor Radon and Thoron Measurements in Dwellings around the World 2 1.3 The Radioactive Series 5 1.3.1 The Uranium Series - Radon and its Progeny 1.3.2 The Thorium Series - Thoron and its Progeny 1.4 Attachment of Radon Progeny to Aerosol Particles 8 1.5 Sources of Indoor Radon 9 1.6 Radon in Building Materials 11 1.7 Other Factors of Indoor Radon Accumulation 12 1.8 Objectives of Study 13 1.9 Organisation of the Thesis 14 Chapter Two A Review on Dosimetry and Radiological Risks 2.1 Radiological Importance of Radon 15 2.2 Health Risks of Radon 16 2.3 Smoking, Radon Inhalation, and Lung Cancer 18 2.4 The Respiratory Tract 18 2.5 Lung Dosimetry and Lung Cancer 20 2.6 Other Effects of Exposure to Low Levels of Ionising Radiation 23 vii
Chapter Three Experimental Techniques 3.1 Introduction 24 3.2 Scope of Measurements 24 3.3 Passive Sampling Method 25 3.4 Sampling Priorities 26 3.4.1 Selection Criteria of Location 28 3.5 Collection of Samples 30 3.6 Detail Description of Dosimeter 31 3.7 Processing of Samples 34 3.8 Formula Derivations of Radon, Thoron Gas Concentrations, Inhalation Doses, and PAEC 36 3.9 Survey Administration 38 Chapter Four Results and Discussion 4.1 Introduction 39 4.2 Radon Concentration Variations as a Function of Floor Level 39 4.3 Floor Level Variation of Radon Concentration 41 4.4 Thoron Concentration 44 4.5 Floor Level Variation of Thoron Concentration 45 4.6 Effective Dose Equivalent (EDE) 48 4.7 Floor Level Variation in Effective Dose Equivalent 49 4.8 Potential Alpha Energy Concentration (PAEC) 53 4.9 Floor Level Variation of PAEC 57 4.10 Results on Household Survey 61 4.10.1 Indoor Built Materials 4.10.2 Wall viii
Chapter Five Conclusions 68 APPENDIX 1: Household Survey Questionnaire 71 REFERENCES 73 ix
List of Figures Figure 1.1 Figure 1.2 Figure 1.3 Decay Chain of Uranium-238 Including Radon-222 and its Decay Products Decay Chain of Radon-220 Decay Chain of Thorium-232 Including Radon-220 and its Decay Products Schematic representation of radon production and migration in soil and its entry into building. Figure 2.1 Figure 2.2 Contribution of radiation dose from different sources Radon gas enters the lungs, which increases the health risk Figure 3.1 Figure 3.2 Figure 3.3: Figure 3.4 Figure 3.5 Apartment Abdullah Hukum, Bangsar, Kuala Lumpur (external outlook) Example of Apartment Abdullah Hukum, Bangsar, Kuala Lumpur (internal furnished spacing) SSNTDs applied inside a canister dosimeter, the twin radon-thoron cup dosimeter Internal layout plan of two neighbouring units ( BEDROOM 2 and BEDROOM 3 sharing a common apartment building wall) Twin radon-thoron dosimeter system Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5 Figure 4.6 Figure 4.7 Radon concentration variations as a function of floor level Total Charts for Radon Concentration in Bq/m 3 for individual floors in a multi-storey building Thoron Concentration Variation in between Floors Total Charts for Thoron Concentration in Bq/m 3 for individual floors in a multi-storey building Variation of EDE between Floor Levels Total charts for effective dose equivalent in msv/y for individual floors in a multi-storey building Variation of PAEC between Floor Levels x
Figure 4.8 Figure 4.9 Figure 4.10 Figure 4.11 Total Charts for PAEC in mwl for individual floors in a multi-storey building Patterns of ventilation in master bedrooms Patterns of Flooring Quality (a) for the whole building (b) by floor level. Wall finishing quality xi
List of Tables Table 2.1 Table 2.2 Ranges in Tissue of Alpha Particles Emitted by Radon and Thoron Progeny Distribution of Tumour Types in 28,000 Cases of Lung Cancer Table 4.1 Table 4.2 Table 4.3 Table 4.4 Chart for measurement values of PAEC, Tn, Rn, DE and EDE. AM- Arithmetic Means, GM- Geometric Means, STDEV-Standard Deviation. Summary of arithmetic mean and geometric mean of PAEC as a function of floor level. Tabulation Sample of Raw Data Collected: Track Intensity, PAEC Level, and Number of Exposure Days (Time) Summary of PAEC, Thoron Concentration, Radon Concentration, Wall Finishing Quality and Floor Finishing Quality xii