Temporal trends in phthalate metabolite exposure of girls in the United States across sociodemographic factors and intersectional social identities: National Health and Nutrition Examination Survey (NHANES) 2001–2018

Background: Exposure to phthalates during the pubertal window is linked to an increased risk of chronic diseases. Understanding temporal trends in exposure can inform public health initiatives. Objective: Characterize temporal trends in phthalate metabolite levels in adolescent girls overall and by sociodemographic characteristics. Methods: We used the cross-sectional data from each cycle of NHANES from years 2001–2018. We included participants aged 8–14 years who had at least one urinary measurement of the selected 12 phthalate metabolites within the study period (n = 2063). We used multivariable linear regression to assess temporal trends for selected individual phthalate metabolite concentrations (ng/ml) and source groupings of parent metabolites (sum low and high molecular weight phthalates; ∑LMW and ∑HMW), overall and by sociodemographic characteristics (race/ethnicity), nativity, socioeconomic status (SES), intersection of race/ethnicity-SES) to assess for modification. Results: Overall, levels of ∑HMW and ∑LMW declined between 2001 and 2018; however, only ∑LMW consistently differed by all sociodemographic characteristics. Trends in ∑LMW concentration were significantly higher across all racial/ethnic groups, ranging from an average of 35% (Other Hispanic) to 65% (Mexican American and non-Hispanic Black) higher than non-Hispanic White (all p-values <0.0001). Compared to non-Hispanic White, a significant decrease in MiBP concentrations was observed for non-Hispanic Black (15% decrease β_Spline = −0.16, p < 0.0001) and Other Hispanic (28% decrease, β_Spline = −0.33, p = 0.01) in 2011–2018 versus 2001–2010. Summary and individual LMW metabolite phthalate concentrations were 11%–49% higher among girls with low vs. high SES. LMW metabolites MBP and MiBP were on average 22% and 35% higher, respectively, among foreign-born vs. U.S.-born girls. Compared to non-Hispanic Whites, all racial/ethnic groups had statistically significant higher trends in ∑LMW concentrations irrespective of SES. Significance: Girls identifying with a historically disadvantaged racial/ethnic groups exhibited elevated ∑LMW concentrations irrespective of SES; suggesting the need for targeted interventions to mitigate exposure among the most historically disadvantaged strata.