Association between Urinary Metabolite Levels of Organophosphorus Flame Retardants and Serum Sex Hormone Levels Measured in a Reference Sample of the US General Population

Use of organophosphorus flame retardants (OPFRs) in consumer materials have led to widespread human exposure.Research is needed to examine the health effects attributable to the general population's exposure to OPFRs. Using the data from the National Health and Nutrition Examination Surveys (NHANES) (2013-2014), multiple regression analyses were performed to compare the adjusted geometric means (aGMs) of serum sex hormone by quartiles of urinary metabolites of OPFRs, including diphenyl phosphate (DPhP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(2-chloroethyl) phosphate (BCEP) and dibutyl phosphate(DBuP), in children (6 - 9 years old), adolescents (10 - 19 years old) and adults(≥ 20 years old), while accounting for potential confounding factors. The aGMs of sex hormone-binding globulin increased by 36% (95% CI: 6.1 - 56.7%) in female children ( p = 0.03), 44% (95%CI: 16 - 63%) in female adolescents ( p = 0.010), and 22% (95%CI: 3.51 - 37%) in female adults ( p = 0.025), from the 1 st to 4 th quartiles of the levels of DPhP, BDCPP, DBUP, respectively. The aGMs of estradiol (EST) decreased by 64% and 77% from the 1 st to 4 th quartiles of the DBUP levels in female children ( p = 0.015) and female adolescent ( p = 0.020), respectively. The aGMs of EST increased by 31% (95%CI: 3.8 - 51%) from the 1 st to 4 th quartiles of the DBUP levels in female adults ( p = 0.031). These findings suggest that exposure to certain OPFRs is associated with the altered sex hormone levels in this sample of US population. More studies are needed to examine the mechanisms responsible for these observations.