The risk of endometriosis and exposure to dioxins and polychlorinated biphenyls: A case-control study of infertile women

Background: A case-control study was designed to determine the possible association between chronic exposure to dioxins and polychlorinated biphenyls (PCBs), and the occurrence of endometriosis. The study group consisted of 42 infertile endometriosis cases and 27 mechanical infertile controls, both groups attending one of the collaborating Centres for Reproductive Medicine, enrolled between 1996-1998. Methods: Exposure assessment to dioxin-like compounds was determined through CALUX (chemical-activated luciferase gene expression)-bioassay to measure dioxin-like total toxic equivalents (dioxins and co-planar PCBs), whereas non-co-planar PCBs were determined through chemical analysis. Results: No association was found between median dioxin-like total toxic equivalents (TEQ) and the occurrence of endometriosis in infertile women [cases (n = 34): 29; controls (n = 27): 24; NS]. When patients were subdivided based on an arbitrary cut-off value of 100 pg TEQ/g serum lipids, no statistically significant association between very high exposure to dioxin-like compounds and endometriosis was found [crude odds ratio (OR) = 4.33; confidence interval (CI) 0.49-38.19; NS]. After adjusting for body mass index, and alcohol consumption, the risk increased slightly to OR = 4.6 (CI 0.48-43.62; NS). There was no confounding by age, ovulatory dysfunction, caffeine intake, smoking or exposure to non-co-planar PCBs. Conclusions: The study results showed no statistically significant association between exposure to dioxin-like compounds and the occurrence of endometriosis in infertile women.