Association of Urinary Phthalate Concentrations With Endometriosis and Uterine Leiomyomata: Preliminary Findings From NHANES 1999–2002

ISEE-734 Objective: Phthalates are ubiquitous environmental contaminants that have been linked to reproductive disorders in animals. Although human data are limited, emerging evidence suggests that some phthalates are related to hormone-dependent pathologies of the female reproductive tract. In previous studies, plasma concentrations of di-(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), and di-n-octyl phthalate (DnOP) were positively associated with risk of endometriosis, whereas plasma concentrations of DEHP and its main metabolite, mono-ethylhexyl phthalate (MEHP), were inversely associated with risk of uterine leiomyomata. We investigated the relation of urinary phthalates concentrations with self-reported endometriosis and uterine leiomyomata. Materials and Methods: We conducted analyses among 947 women aged 20 to 54 from 2 waves of the National Health and Nutrition Examination Survey (1999–2000: n = 461; and 2001–2002, n = 486). The survey was designed to represent the noninstitutionalized US civilian population. We calculated creatinine-corrected urinary concentrations of 4 common phthalate metabolites: MEHP, mono-n-butyl phthalate (MnBP), mono-ethyl phthalate (MEP), and mono-benzyl phthalate (MBzP). Sixty-six women (7%) reported a history of endometriosis and 111 (12%) reported a history of uterine leiomyomata. Age- and race-adjusted logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CI). Results: Higher levels of MnBP, but not MEP, MEHP, MBzP, were associated with history of endometriosis and uterine leiomyomata. The ORs for endometriosis increased with increasing quartile of urinary MnBP concentration (Ptrend = 0.14), and the OR comparing women in the highest quartile with the lower 3 quartiles was 1.43 (95% CI = 0.89–2.32). The ORs for uterine leiomyomata were similar (Ptrend = 0.14; OR = 1.48, 95% CI = 0.88–2.48). Overall, women in the highest quartile of MnBP had a 60% increase in the odds of having either condition (n = 151) as compared with women in the lowest 3 quartiles (95% CI = 1.10–2.23). Conclusions: The observed positive associations between MnBP and both endometriosis and uterine leiomyomata warrant further investigation.