Exposure to organophosphate esters and early menopause: A population-based cross-sectional study

Organophosphate esters (OPEs), increasingly used as new flame retardants and plasticizers in various products, have been found to have reproductive toxicity with overt endocrine disruption potential, yet the relationship between OPEs and early menopause remains unexplored. In the present study, we included 2429 women who participated in the U.S. National Health and Nutrition Examination Survey data (2011-2020) and had data of five urinary OPE metabolite levels and information of menopause characteristics, to investigate the associations of OPEs exposure with premature ovarian insufficiency (POI) and age of menopause. Multivariable adjusted linear and logistic regression were used to assess the associations of urinary OPE metabolites with age of menopause and POI, respectively. Quantile g computation (QGC) models were used to assess the relative contribution of individual metabolites to associations of OPE metabolites mixture. After adjusting for covariates, urinary bis(2-chloroethyl) phosphate (BCEP) concentration was inversely associated with menopause age (β = - 0.21; 95% confidence interval (CI): 0.41, - 0.002). Higher urinary BCEP level (>median) was associated with earlier age at menopause (β = -1.14, 95% CI: 1.83, - 0.46), and elevated odds of having POI (OR = 1.93; 95% CI: 1.02, 3.66). These associations were robust to the further adjustment of cardiometabolic diseases and related traits (e.g., body mass index). Further QGC analyses confirmed that BCEP was the dominant metabolite contributing most to the associations of OPEs mixture with age of menopause (weight = 49.5%) and POI (weight = 75.1%). No significant associations were found for the other four OPE metabolites. In this cross-sectional study, urinary BCEP level was associated with earlier menopause and increased odds of POI, highlighting the potential negative impacts of this chemical and its parent compound tris(2-chloroethyl) phosphate on ovarian function. Further studies are required to validate our findings and reveal potential underlying mechanisms.