Humans are constantly exposed to environmental pollutants and hazardous chemicals, yet we lack effective tools for monitoring the concentrations of these substances within the body. Traditional biomonitoring programs rely on blood and urine samples, but the invasiveness of these collection methods can discourage participation and impose financial limitations. To address this, alternative human matrices are being explored to provide more convenient means of biomonitoring. One promising yet underutilized matrix is tear fluid, which is easily accessible, interfaces with ambient air, and communicates dynamically with blood, offering insights into both environmental exposures and internal physiological processes. This thesis aims to characterize and develop a method for tear-based biomonitoring by introducing a novel means of passive sampling. To this end, a sample preparation and analysis protocol was optimized for extracting, identifying, and quantifying polar and nonpolar chemicals from tear fluid passive samplers (silicone hydrogel contact lenses). To validate the passive sampling material could retain chemicals of interest, targeted approaches were developed with hydrophilic interaction liquid chromatography coupled with triple quadrupole mass spectrometry (HILIC-MS/MS) for polar metabolites and Orbitrap gas chromatography-mass spectrometry (GC-MS) for semi-volatile organic compounds. Additionally, to comprehensively characterize the chemical profile captured by the passive samplers, an optimized nontargeted workflow using high-resolution mass spectrometry was developed. Further, multiple platforms were utilized for broad coverage of chemicals, including HILIC and reverse-phase liquid chromatography (RP-LC) with quadrupole time-of-flight mass spectrometry (QTOF-MS), as well as Orbitrap GC-MS. This work lays the groundwork for a user-friendly biomonitoring approach that enables personalized chemical exposure assessment with convenient sampling. It also has the potential to facilitate larger-scale studies involving vulnerable or hard-to-reach populations. A comprehensive biomonitoring survey using tear fluid could uncover valuable insights into sources and persistence of chemical exposures and their correlations with health trends across time and regions. / Thesis / Master of Science (MSc)

Exposomics aims to characterize the totality of exposures over the lifespan, and their impact on human health. Currently, chronic exposure to harmful chemicals from air pollution and/or tobacco smoke, along with a suboptimal diet, remain leading causes for preventable mortality and morbidity worldwide. As a result, new analytical methods are needed to measure robust biomarkers of smoke exposure and food intake for improved risk assessment of clinical events. This thesis aims to develop high throughput methods to rapidly quantify urinary biomarkers of environmental smoke in high-risk occupations, and diverse global populations using multisegment injection-capillary electrophoresis-mass spectrometry (MSI-CE-MS) technology. Chapter II outlines an inter-laboratory method comparison for the targeted analysis of urinary 1-hydroxypyrene (HP) when using gas chromatography-high resolution mass spectrometry (GC-HRMS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) on urine samples collected from firefighters. This work revealed the critical role of incomplete enzymatic deconjugation on method bias and underreporting of true smoke exposures. Chapter III introduces a high throughput MSI-CE-MS/MS method (< 3 min/sample) to directly analyze the intact glucuronide conjugate of HP (HP-G) in urine without complex pre-column enzyme deconjugation and derivatization procedures. Importantly, firefighters deployed under emergency conditions at the 2016 Fort McMurray wildfire had creatinine normalized HP-G concentrations below the biological exposure index, likely caused by delays in urine collection under emergency conditions, at early stages of firefighting. Chapter IV extends from targeted biomonitoring of occupational smoke exposure, towards elucidating the relative risk of tobacco smoking in an international cohort of participants (n=1000) from the Prospective Urban and Rural Epidemiological (PURE) study. Comprehensive analysis of nicotine metabolites in urine by MSI-CE-MS allowed for reliable determination of the total nicotine equivalent and nicotine metabolic ratio as robust indicators of recent tobacco smoke exposure and nicotine dependence, respectively. This method also offers a more accurate approach for biochemical verification of smoking status in large-scale epidemiological studies that are prone to social desirability and gender bias when relying on standardized questionnaires. Lastly, Chapter V employs a nontargeted metabolomics workflow using MSI-CE-MS to identify urinary metabolites that may serve as objective dietary biomarkers of food intake in participants across 14 countries from the PURE cohort. A panel of robust and generalizable metabolites were validated for biomonitoring of complex dietary exposures, that may further exacerbate the hazards of tobacco smoking. In summary, this thesis contributes high throughput analytical tools for characterizing the human urine exposome to better decipher the roles of smoke exposure, and suboptimal diet on chronic disease burden among diverse populations and regions worldwide. / Thesis / Doctor of Philosophy (PhD)

Exposomics applies metabolomics methods and technologies to the comprehensive analysis of all low molecular weight molecules (< 1.5 kDa) in complex biological samples to characterize the interaction between cellular metabolism and exogenous lifestyle exposures that determine health and quality of life. To fully access the diverse classes of biological molecules related to an individual’s metabolic profile, metabolomics frequently requires the use of complementary analytical platforms, and employs targeted and untargeted molecular profiling strategies to identify biomarkers that are clinically relevant to an individual’s health status. Chapter 2 describes a quinoline-based boronic acid biosensor for N-acetylneuraminic acid that undergoes a striking binding enhancement under strongly acidic conditions. For the first time, this work allows for direct analysis of acidic sugars with high selectivity when using UV absorbance or fluorescence detection based on formation of a highly stable boronate ester complex with metabolites containing an α-hydroxycarboxylate moiety. Chapter 3 describes a targeted analysis of 24 different organic contaminants using GC-MS that can serve as biomarkers of recent smoke exposure following search-and-rescue training exercises by firefighters located at three different sites across the province of Ontario. Importantly, skin and possible respiratory uptake of various polycyclic aromatic hydrocarbons, methoxyphenols, and resin acids was confirmed by peak excretion of several wood smoke biomarkers in urine within 6 h following acute exposure. Chapter 4 applied a cross-platform metabolomics strategy based on CE-MS and GC-MS in order to identify and validate dietary biomarkers in matching plasma and urine samples collected from healthy participants in the pilot Diet and Gene Interaction Study (DIGEST). For the first time, we demonstrate that a panel of metabolites can serve as reliable biomarkers following contrasting Prudent and Western diets over 2 weeks of food provisions, which correlated well with self-reported diet records. This work paves the way for the development of objective biomarkers for accurate assessment of wood smoke exposures, as well as complex dietary patterns as required for new advances in occupational health and nutritional epidemiology. / Dissertation / Doctor of Philosophy (PhD) / Exposomics is an emerging multidisciplinary science aimed at deciphering the complex interactions that impact human health and gene expression, such as lifestyle choices (i.e., habitual diet) and lifelong environmental exposures. There is growing interest in identifying biomarkers that can be readily measured for chronic disease prevention given an alarming global prevalence of obesity and cardiometabolic disorders, including heart disease, type 2 diabetes and cancer. The research in this thesis focuses on developing new analytical methods for identifying and quantifying metabolites that may allow for better assessments of human health, and has contributed to the development of novel biosensors for the targeted analysis of N-acetylneuraminic (sialic) acid and related acidic sugars, as well as high resolution methods for broad spectrum analysis of biotransformed organic contaminants from smoke exposure by GC-MS, and plasma and urinary metabolites that differentiate contrasting Prudent and Western diets and correlate well with self-reported diet records.