Ambient Polycyclic Aromatic Hydrocarbon Exposure and Breast Cancer Risk in a Population-Based Canadian Case-Control Study
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Authors
Hinton, Patrick
Date
Type
thesis
Language
eng
Keyword
Cancer , Epidemiology , Air Pollution , Breast Cancer
Alternative Title
Abstract
Background: Polycyclic aromatic hydrocarbons (PAHs) represent a class of ubiquitous pollutants which are emitted through combustion of organic materials and are recognized as established human carcinogens and endocrine-disrupting chemicals. There is a lack of epidemiological research investigating ambient PAH exposures and breast cancer risk. Additionally, PAHs have seldom been modelled at the population-level for epidemiological application, and current methods for assessment of long-term exposure are limited. This thesis evaluated associations between long-term residential exposure to ambient PAHs and breast cancer risk, both pre- and post-menopausal, in the Canadian setting.
Methods: Using the National Enhanced Cancer Surveillance System (NECSS), a population-based case-control study conducted within eight of the Canadian provinces between 1994-1997, annual fluoranthene exposures were estimated using the GEM-MACH-PAH chemical transport model on the basis of geocoded residential histories throughout a 20-year exposure window. Odds ratios (ORs) and 95% confidence intervals (CIs) controlling for potential confounders were estimated using unconditional logistic regression. Separate analyses were conducted for Ontario and national samples given a finer-resolution exposure surface available for Ontario, as well as additional risk factor information collected in Ontario.
Results: Positive associations were observed between long-term fluoranthene exposure and premenopausal breast cancer, with inconsistent findings for postmenopausal breast cancer. For premenopausal breast cancer, adjusted ORs of 2.48 (95% CI: 1.29, 4.77) and 1.59 (95% CI: 1.11, 2.29) were observed when comparing the second highest category of exposure to the lowest, amongst the Ontario and national samples, respectively. For postmenopausal breast cancer, adjusted ORs were 1.10 (95% CI: 0.67, 1.80) and 1.33 (95% CI: 1.02, 1.73). Associations for the highest level of exposure, across both samples and menopausal strata, were non-significant. Results were robust in sensitivity analysis restricted to those with more complete residence history, confounders controlled for, and simultaneous modelling of criteria air pollutant measures.
Conclusion: This study provides support for the hypothesis that ambient PAH exposures are associated with an increase in risk for breast cancer, especially for premenopausal women.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International