University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2018-12-17 An Analysis of Human Exposure to Alpha Particle Radiation Stanley, Fintan Stanley, F. (2018). An Analysis of Human Exposure to Alpha Particle Radiation (Unpublished doctoral thesis). University of Calgary, Calgary, AB. http://hdl.handle.net/1880/109368 doctoral thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY An Analysis of Human Exposure to Alpha Particle Radiation by Fintan Stanley A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY GRADUATE PROGRAM IN BIOCHEMISTRY AND MOLECULAR BIOLOGY CALGARY, ALBERTA DECEMBER, 2018 © Fintan Stanley 2018 Abstract High linear energy transfer (LET) ionizing radiation (IR) is the predominant source of IR humans are exposed to. Radon gas, which emits a high energy alpha-particle, represents the greatest single lifetime source, but also remains comparatively understudied versus low LET IR sources such as x-rays. The inhalation radon (222Rn) gas from indoor air exposes lung tissue to alpha particle radiation, damaging DNA and increasing the lifetime risk of lung cancer. Buildings can concentrate radioactive radon (222Rn) gas to harmful levels. To enable cancer prevention, I examined how Canadian Prairie radon exposure is modified by environmental design and human behavior and evaluated different radon test modalities. I also developed a high-throughput, benchtop alpha-particle irradiation system to facilitate future research into the biological consequences of high LET radiation exposure. Initially, I examined 90+ day radon test results from 2,382 residential homes from an area encompassing 82.5% of the Southern Alberta population. Remediated homes were retested to determine efficacy of radon reduction techniques in this region. Subsequently, 11,726 Alberta and Saskatchewan homes were radon tested, coupled to geographic, design and behavior metrics. Canadian Prairie homes contained 140 Bq/m3 average radon (min <15 Bq/m3; max 7,199 Bq/m3) and 17.8% were ≥ 200 Bq/m3. Geostatistical analysis indicates significant variation between regions. More recently constructed homes contain higher radon versus older. Finally, I also designed and validated a benchtop, 96 well plate-based 241Am irradiation system to expose cultured eukaryotic cells to alpha particles in a controlled environment. My validation of this novel setup includes quantification of nuclear alpha particle-induced DNA damage signalling (γH2AX) using a purpose-designed 3D analysis method, physical readouts of alpha particle-induced DNA damage by alkaline comet assay, and an investigation of cellular viability after alpha particle exposure. This method brings significant advances over existing techniques in its ease of setup and use, affordability, accessibility and flexibility and should enable future alpha particle radiation biology. Collectively, my work demonstrates that radon is a genuine public health concern in the Canadian Prairies, legitimatizes efforts to understand the consequences of radon exposure to the public, and suggest that radon testing and mitigation is likely to be an impactful cancer prevention strategy. ii Preface Certain introductory material in this thesis has also been peer-reviewed and published as: Berger ND, Stanley FKT, Moore S, Goodarzi AA. ATM-dependent pathways of chromatin remodelling and oxidative DNA damage responses. Philosophical Transactions B. 2017 Oct 5;372(1731). Invited Review. Stanley FKT, Moore S, Goodarzi AA. CHD chromatin remodelling enzymes and the DNA damage response. Mutat Res. 2013 Oct;750(1-2):31-44. Invited Review. Moore S, Stanley FKT, Goodarzi AA. The repair of environmentally relevant DNA double strand breaks caused by high linear energy transfer irradiation - no simple task. DNA Repair. 2014. 17:64-73. Invited Review. The work detailed in Chapter two of this thesis has been peer-reviewed and published as: F.K.T. Stanley, S. Zarezadeh, C.D. Dumais, K. Dumais, R. MacQueen, F. Clement, & A.A. Goodarzi, “Comprehensive survey of household radon gas levels and risk factors in southern Alberta.”. CMAJ open, 2017, vol. 5, issue 1, E255-E264 The remainder of the thesis is original, unpublished, independent work by the author, Fintan K.T. Stanley The experiments reported in Chapters 2-3 were covered by Ethics Certificate number REB17-2239, issued by the University of Calgary Conjoint Health Ethics Board for the project “The Albertan ‘Evict Radon’ Radon Awareness and Testing Campaign” on December 15, 2016. iii Acknowledgements My thanks to Dr. Aaron Goodarzi for his mentorship and guidance throughout my studies. Thank you for fostering such a broad and rewarding experience during this time. Thanks also to Dr. Susan Lees-Miller & Dr. Jen Cobb for years of generous advice and support. I warmly thank the members of the lab past and present for their support. My thanks to the many students I had the honor to attempt to share some knowledge with, teaching always reconnected me to the wonder of science. For keeping me close to that thank you, and I hope you all take a little of that wonder with you in your many successful journeys. I greatly appreciate all the hours of help and support from those at the Arnie Charbonneau Cancer Institute, particular thanks to Carmen, Carin, Anne, and most especially Shilpa. Thank you to the Department of Biochemistry and Molecular Biology whose dedication to the students’ experience is a testament to the quality of its leadership, thank you Sarah and Jonathan, and special thanks to Leslie. I thank all my collaborators, no matter what came of the work, I most expressly thank you for engaging in co-operative science and promoting a more altruistic approach in research. Most distinct thanks here to Dan Berger who has been inspiring advocate for this philosophy. For the many ideas that bore fruit at the bench and the multiples more that did not, thank you for helping me test and refine them. And with the deepest deference I thank my friends, I feel too lucky to have half of you in my life. Your belief in me got me through this, and I shall endeavour second to live up to your ideal of me, and first to remind you each, as often as I can, what wonderful generous people you are. Thank you UREKA. Thank you Heather. Thank you Dan. Thank you all so very much & also thank you Canada! iv Dedication For my family, With special thanks to my parents, Audrey and Bob, for always supporting my wandering, And to my brothers and sisters, for always welcoming me home again. v Table of Contents Abstract................................................................................................................................ ii Preface ................................................................................................................................ iii Acknowledgements ............................................................................................................ iv Dedication............................................................................................................................ v Table of Contents ............................................................................................................... vi List of Tables ...................................................................................................................... xi List of Figures and Illustrations ......................................................................................... xii List of Symbols, Abbreviations and Nomenclature ......................................................... xiv Epigraph .......................................................................................................................... xvii Chapter One: Introduction ................................................................................................. 18 1.1 A Short History of the Discovery of Ionizing Radiation ......................................... 18 1.2 Radiobiology meets DNA in the 20th century ......................................................... 21 1.3 Radiation and Cancer – DNA damage is the missing link ...................................... 25 1.3.2 In Brief: DNA Damage Signalling and Repair Pathways ............................... 27 1.3.3. In Detail: IR-induced DNA Double Strand Break Signalling ........................ 30 1.3.4. In Detail: IR-induced DNA Double Strand Break Repair Pathway Choice .. 32 1.4.5. Factors Influencing DSB Repair Kinetics ...................................................... 33 1.4 Radiation Quality, Linear Energy Transfer and Relative Biological Effects .......... 35 1.5 ICRP models in the context of DNA damage ......................................................... 37 1.6 Defining Clustered DNA damage and implications for DSB repair ....................... 39 1.7 Radon Inhalation – The Most Common Form of Human IR Exposure .................. 43 1.8 Other Sources of High LET IR Exposure ............................................................... 46 1.10 Hypothesis and Specific Aims .............................................................................