Association between urinary heavy metals, phthalates, phytoestrogens, and polycyclic aromatic hydrocarbons and endometriosis: A cross-sectional study from NHANES 1999 to 2016

Research on the association between urinary heavy metals, phthalates, phytoestrogens (PEs), polycyclic aromatic hydrocarbons (PAHs), and endometriosis (EM) is limited. Data were from the National Health and Nutrition Examination Survey 1999 to 2016. Logistic regression models were used for analysis. In addition, qgcomp and Bayesian kernel machine regression models were employed to evaluate the effects of mixed exposures. After adjusting for covariates, compared with the first quartile (Q1), the fourth quartile (Q4) of urinary cobalt (95% confidence interval [CI] = 1.3-3.9) and urinary lead (95% CI = 1.0-3.1) were significantly associated with an increased risk of EM. Conversely, 1-naphthol (95% CI = 0.3-0.9), 2-fluorene (2-Flu; 95% CI = 0.3-0.9), 3-phenanthrene (95% CI = 0.3-1.0), and 2-phenanthrene (95% CI = 0.3-0.9) were negatively correlated with EM risk. When concentrations exceeded the 50th percentile, elevated levels of urinary heavy metal mixtures and PAH mixtures were positively associated with EM. In the Bayesian kernel machine regression mixture analysis, 2-Flu showed a positive association with EM, while 1-pyrene was negatively correlated, although the direction for 2-Flu differed from single-pollutant logistic regression. Analyses of chemical mixtures suggested possible associations for specific substances, including the PAH 2-Flu, the phthalate monobutyl phthalate, and the PEs enterodiol and enterolactone; however, the overall phthalate and PE mixtures were not significantly associated with EM, and these findings require further confirmation. Heavy metals (cobalt and lead) were consistently associated with increased EM risk.