Lifetime Occupational Exposure to Endocrine-disrupting Chemicals and Postmenopausal Breast Cancer Risk: A Montreal-based Case-control Study (2008-2011)

Background: Exposure to endocrine-disrupting chemicals (EDCs) suspected to increase cumulative lifetime estrogen exposure, may elevate postmenopausal breast cancer risk. Despite evidence from environmental studies, few studies on EDCs have analyzed lifetime occupational exposures and most fail to account for complex mixtures encountered in workplaces across susceptible windows of breast development. Objective: This thesis investigated the association between lifetime occupational exposure to select EDCs, grouped by biological mode of action, and postmenopausal breast cancer risk. Secondary analyses determined associations by hormone receptor subtype. Methods: Data from a Montreal-based case-control study (2008-2011) among postmenopausal women was used. Breast cancer cases (n=661) were frequency-matched to population-based controls (n=587) by age. Lifetime occupational history and risk factor data were collected by interview. Two industrial hygienists used occupational histories to assign exposure to 24 EDCs that were subsequently classified by their biological mode of action as, estrogenic, anti-estrogenic, or anti-androgenic. Exposure metrics derived included, ever/never exposed, duration of exposure (per 5-year increase), cumulative exposure (per interquartile range) and average concentration of exposure (per 1-unit increase on an ordinal scale of 1-low, 2-medium, and 3-high). Adjusted odds ratios (OR) and 95% confidence intervals [95% CI] were estimated using unconditional multivariable logistic regression to evaluate the associations between incident postmenopausal breast cancer and lifetime occupational EDC exposure, while adjusting for confounders identified using a directed acyclic graph. Results: Ever exposure antiestrogenic EDCs (OR=1.40 [0.99, 2.00]) and anti-androgenic EDCs (OR=1.49 [1.08, 2.08]) similarly increased postmenopausal breast cancer risk compared to estrogenic (OR=1.16 [0.82, 1.63]). This trend was also observed with the average concentration metric. Similar increases were observed for the duration (ORs=1.13 to 1.16) metric, whereas cumulative exposure was not associated with risk, both for all modes of action. Significant positive associations for anti-estrogenic and anti-androgenic EDC exposures were consistent across hormone receptor positive subtypes. Conclusions: Occupational exposure to EDCs, by mode of action, increases postmenopausal breast cancer risk, particularly for hormone receptor positive subtypes.

Department dc:contributor.department

Public Health Sciences

Year dc:date.issued

2026

Author dc:creator

• Reeves, Christina

Advisors dc:contributor.supervisor

• Richardson, Harriet
• Ho, Vikki

• Postmenopause
• Breast Cancer
• Endocrine Disrupting Chemicals
• Estrogenic
• Etiology
• Antiandrogenic
• Antiestrogenic
• Case-control

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/36271

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/36271