Organochlorine Pesticides and Risk of Endometriosis: Findings from a Population-Based Case-Control Study

BACKGROUND: Endometriosis is considered an estrogen-dependent disease. Persistent-environmental chemicals that exhibit hormonal properties, such as organochlorine pesticides (OCPs), may affect endometriosis risk. OBJECTIVE: We investigated endometriosis risk in relation to environmental exposure to OCPs. METHODS: We conducted the present analyses using data from the Women's Risk of Endometriosis (WREN) study, a population-based case-control study of endometriosis conducted among 18-to 49-year-old female enrollees of a large health care system in western Washington State. OCP concentrations were measured in sera from surgically confirmed endometriosis cases (n = 248) first diagnosed between 1996 and 2001 and from population-based controls (n = 538). We estimated odds ratios (OR) and 95% CIs using unconditional logistic regression, adjusting for age, reference date year, serum lipids, education, race/ethnicity, smoking, and alcohol intake. RESULTS: Our data suggested increased endometriosis risk associated with serum concentrations of beta-hexachlorocyclohexane (HCH) (third vs. lowest quartile: OR = 1.7; 95% CI: 1.0, 2.8; highest vs. lowest quartile OR = 1.3; 95% CI: 0.8, 2.4) and mirex (highest vs. lowest category: OR = 1.5; 95% CI: 1.0, 2.2). The association between serum beta-HCH concentrations and endometriosis was stronger in analyses restricting cases to those with ovarian endometriosis (third vs. lowest quartile: OR = 2.5; 95% CI: 1.5, 5.2; highest vs. lowest quartile: OR = 2.5; 95% CI: 1.1, 5.3). CONCLUSIONS: In our case-control study of women enrolled in a large health care system in the U. S. Pacific Northwest, serum concentrations of beta-HCH and mirex were positively associated with endometriosis. Extensive past use of environmentally persistent OCPs in the United States or present use in other countries may affect the health of reproductive-age women.