Outdoor Air Pollution and Children´s Asthma in the Census Metropolitan Area of Edmonton, Alberta: the Influence of Place of Residence and Socioeconomic Position by Laura Andrea Rodríguez Villamizar A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Epidemiology Public Health Sciences University of Alberta © Laura Andrea Rodríguez Villamizar, 2016 Abstract Background: Asthma is the most common chronic respiratory disease in children and air pollution has been implicated in its development and exacerbations worldwide. The Census Metropolitan Area of Edmonton (CMAE), Alberta, has unique air pollution sources (traffic and industrial related air pollution) compared to other Canadian cities. Previous studies conducted in the Edmonton area between 1992 and 2002 indicated that ED visits for asthma were associated with day-to-day increases in almost all the main air pollutants and that these associations were stronger among children, and older adults. Since that time, sources of air pollution and asthma management have changed. The short-term effect of multiple air pollutants on ED visits for asthma, its variation at intra-urban scale, and the effect of traffic and industrial pollution sources remain unclear in the CMAE. Similarly, the capacity of the socioeconomic position (SEP) to modify these relationships has not been explored. Objectives: To determine how place of residence and SEP influence the association between short-term variations in outdoor air pollution and ED visits for children with acute asthma in the CMAE, between April 1, 2004 and March 31, 2010 by: (1) conducting a literature review of the effect-modifier role of the SEP on the relationship between outdoor air pollution and ED visits for asthma in children; (2) analysing the relationship between the exposure to multiple air pollutants and ED visits for asthma and the effect measure modification by the SEP at individual level; (3) analysing the relationship between traffic-related air pollution, SEP and ED visits for asthma at small-area level; and (4) exploring the relationship between proximity to industrial sources of air pollution and ED visits for asthma in children. Methods: For objective 1, a systematic review of the literature was conducted. For objective 2, a case-crossover study was conducted using the Air Quality Health Index (AQHI) as a ii composite air quality measure, and NO , O , and PM as single pollutants. For objective 3, a 2 3 2.5 small-area case-crossover study was conducted at the dissemination area level using estimations of NO concentration, a proxy of traffic air pollution exposure, applying a city-specific land use 2 regression model. For objective 4, a spatial cluster analysis of disease was conducted around the two main industrial areas in the CMAE. Records of ED visits for asthma were obtained from hospital ED facilities in the Edmonton area and daily air pollution data were obtained from Environment Alberta. Health premium subsidy status was used as an individual proxy for SEP and the Chan’s Canadian socioeconomic index as an area-level SEP variable. Results: The ED visits for asthma in children, the AQHI values and the air concentrations of NO , PM all decreased during the study period compared to the previous decade. Day-to-day 2 2.5 increase in the city-wide AQHI values or in the traffic-related air pollution at dissemination area level did not increase hospital ED visits for asthma. The SEP, measured at individual or small- area level, did not modify the effect of air pollution on ED visits for asthma, in concordance with the results of the systematic review of existing literature. A cluster of ED visits for asthma was identified in close proximity to the coal-fired power plants in the Wabamum area; however, similar clustering was not identified in close proximity to Alberta’s Industrial Heartland. Conclusions: There are two key factors that potentially explain these results: the decreased ED visit rates for children with acute asthma and the decreased concentration and variability of air pollutants, compared to reports in the previous decade. The decreased ED visits may be explained, in part, by improved access to primary care and changes in asthma management over time. This dissertation results add to the available literature by suggesting that there might be children’s health benefits associated with better air quality conditions and adverse effects of industrial pollution from coal-fired power plants on hospital ED visits for asthma in children. iii Preface This thesis is an original work of Laura Andrea Rodríguez Villamizar. The research project, of which this thesis is a part, received research ethics approval from the University of Alberta Health Research Ethics Board – Health Panel, Project Name “ Outdoor air pollution and socioeconomic status: Their influence on asthma in Alberta”, No. Pro00049816, January 28, 2015 (Appendix A). Chapter 2 of this thesis has been accepted for publication in the Reviews on Environmental Health journal as Rodriguez-Villamizar LA, Berney C, Villa-Roel C, Ospina MB, Osornio-Vargas A, Rowe BH, “The role of socioeconomic position as an effect-modifier of the relationship between outdoor air pollution and children’s asthma exacerbations: An equity- focused systematic review”. iv To my loving parents José and Cecilia and the four men of my life: Gustavo, Santiago Andrés, Juan Diego, and Francisco v Acknowledgments This thesis dissertation is the result of four years of continuous work and effort to ensure this graduate degree was the best experience in my academic life. During this time I learned and grew not only academically but also personally. The completion of this work would not have been possible without the support, guidance, patience, encouragement, and friendship of many great people that I met here and people who remained with me during this challenging journey. I wish to express my deepest thanks to my supervisors Drs. Brian Rowe and Alvaro Osornio-Vargas who provided me with a wonderful experience of high research quality along with a tremendous humanity. Brian: thank you for accepting me as your student only knowing where I came from and believing in my promise of hard work and research. Alvaro: thank you for inviting me to join your wonderful team and for teaching me how to think broadly without losing the important details, in research and in life. I have had the privilege of having you as my supervisors; once I became part of your research teams, I have received valuable guidance and support from you both, and part of my success in finishing this thesis within this time frame is due to your time, effort, wisdom, and patience dedicated to challenging my results, suggesting alternatives, and reviewing my documents. I would especially like to thank the members of my supervisory committee, Drs. Rhonda Rosychuk, Paul Villeneuve, and Malcolm King, who I admire deeply for being examples of high quality researchers in their respective fields. Drs. Rhonda and Paul: thank you for your kindness, guidance, advice, detailed feedback, and fruitful discussions during this time. Dr King: thank you for your recommended readings that made me recognized the history of the Aboriginal peoples in Canada and their valuable role in Canada and elsewhere. vi I am grateful to Alberta Health Services which provided access to needed data within a reasonable period of time. I’d like to thank Dr. Susan Jelinski for her invaluable support completing the data extraction from the administrative health and population databases. I would also like to thank Drs. Ryan Allen and Perry Hystad who provided access to their land use regression models used in my analysis. Special thanks to Charlene Nielsen from the children´s environmental health research team for her enormous support in making the geographical calculations and mapping for my analysis. My appreciation goes for the faculty and staff of the School of Public Health at the University of Alberta, for their support in my learning process and for providing a global learning environment for the next generation of public health researchers and practitioners. I would also like to thank to the Universidad Industrial de Santander and the Department of Science and Technology in Colombia (COLCIENCIAS) for their financial support through a study commission and an international doctoral scholarship, respectively. My heartfelt thanks to my dearest friends Cristina and Jesus D, who are important part of this story and for whom I am deeply grateful for their joy, friendship, and unconditional support during good and hard times. Special thanks to my friend Maria Ospina who gave me practical advice for completing this dissertation document. Les agradezco infinitamente y los quiero montones, Gracias! Finally, my wholehearted thanks to my dear family members who are the most important people in my life. Papi y mami: gracias infinitas por su amor y apoyo incondicional durante todo este tiempo. March y Nana, gracias por su apoyo en la distancia. Gustavo, Santi, Juan Di y Fran, mis amores, todo mi amor y eterno agradecimiento por acompañarme en este camino, por su paciencia y por regalarme su tiempo para que yo pudiera terminarlo exitosamente. vii Table of Contents CHAPTER 1. Introduction ............................................................................................ 1 1.1. Dissertation Overview ..............................................................................................1 1.2. Children´s Asthma ....................................................................................................4 1.2.1. Definition and characteristics of pediatric asthma .................................................... 4 1.2.2. Burden of pediatric asthma ....................................................................................... 5 1.2.3. Risk factors and susceptibility for pediatric asthma .................................................. 8 1.2.4. Diagnosis of pediatric asthma .................................................................................. 13 1.2.5. Management of pediatric asthma ........................................................................... 14 1.3. Children´s Asthma and Social Determinants of Health: Socioeconomic Position ....... 18 1.4. Outdoor Air Pollution concepts and measurement .................................................. 20 1.4.1. Air Quality Surveillance Systems ................................................................................. 22 1.4.2. Intra-urban air pollution exposure models ................................................................. 24 1.4.3. The Air Quality Health Index ....................................................................................... 25 1.5. Outdoor Air Pollution and Asthma in Children ........................................................ 26 1.6. Objectives and Scope of Dissertation ...................................................................... 28 1.6.1. Study rationale and significance .............................................................................. 28 1.6.2. Research objectives ................................................................................................. 30 CHAPTER 2. The Role of Socioeconomic Position as an Effect-Modifier of the Association between Outdoor Air Pollution and Children’s Asthma Exacerbations: A Systematic Review............................................................................................................... 39 2.1. Introduction .............................................................................................................. 39 viii 2.2. Methods ................................................................................................................... 40 2.2.1. Protocol ....................................................................................................................... 40 2.2.2. Search strategy ............................................................................................................ 41 2.2.3. Study selection and data extraction ............................................................................ 41 2.2.4. Risk of bias assessment ............................................................................................... 43 2.2.5. Data synthesis ............................................................................................................. 43 2.3. Results ...................................................................................................................... 44 2.3.1. Search results .............................................................................................................. 44 2.3.2. Study characteristics ................................................................................................... 44 2.3.3. Risk of bias assessment ............................................................................................... 45 2.3.4. Effect-modification by SEP .......................................................................................... 46 2.4. Discussion ................................................................................................................. 48 2.4.1. Strengths and limitations ............................................................................................ 52 2.5. Conclusions ............................................................................................................... 53 CHAPTER 3. The Short-term Effect of Multiple Air Pollutants on Children’s Emergency Department Visits for Asthma and the Modifier Role of the Socioeconomic Position ............ 62 3.1. Introduction .............................................................................................................. 62 3.2. Methods ................................................................................................................... 65 3.2.1. Hospital emergency department visit data ................................................................. 65 3.2.2. Air pollutants and meteorological measurements ..................................................... 67 3.2.3. AQHI calculation .......................................................................................................... 68 3.2.4. Study design and statistical analysis ........................................................................... 69 3.2.5. Sensitivity analysis ....................................................................................................... 73 3.3. Results ...................................................................................................................... 74 ix 3.3.1. Descriptive Statistics ................................................................................................... 74 3.3.2. Association between Exposure to Air Pollution and ED visits for asthma .................. 76 3.3.3. Effect Measure Modification by SEP ........................................................................... 77 3.3.4. Sensitivity analyses results .......................................................................................... 78 3.4. Discussion ................................................................................................................. 79 3.4.1. Strengths and limitations ............................................................................................ 87 3.5. Conclusions ............................................................................................................... 90 CHAPTER 4. The Short-term Effect of Traffic-related Air Pollution on Children’s Emergency Department Visits for Asthma, its variation at small-area level, and the modifier role of the Socioeconomic Position .................................................................................... 106 4.1. Introduction ............................................................................................................ 106 4.2. Methods ................................................................................................................. 109 4.2.1. Hospital emergency department visit data ............................................................... 109 4.2.2. Traffic-related air pollution and meteorological data ............................................... 111 4.2.3. Socioeconomic Position data .................................................................................... 113 4.2.4. Study design and statistical analysis ......................................................................... 114 4.2.5. Sensitivity analysis ..................................................................................................... 118 4.3. Results .................................................................................................................... 119 4.3.1. Descriptive Statistics ................................................................................................. 119 4.3.2. Association between ED visits for asthma and traffic-related air pollution ............. 121 4.3.3 Effect-measure modification by SEP .......................................................................... 122 4.3.4. Sensitivity analyses results ........................................................................................ 123 4.4. Discussion ............................................................................................................... 124 4.4.1. Strengths and limitations .......................................................................................... 133 x