Characterization of prenatal polycyclic aromatic hydrocarbon (PAH) metabolites in 5 U.S. metropolitan areas

Abstract

Background/Aim: Prenatal exposure to polycyclic aromatic hydrocarbons (PAH) has been associated with adverse birth and developmental outcomes in children. We characterized patterns of prenatal PAH exposure in a large and geographically diverse cohort study.Methods: We included 1,669 women who were enrolled in two ECHO PATHWAYS cohorts: TIDES (n=674; Minneapolis, Rochester, San Francisco, and Seattle) and CANDLE (n=995; Memphis). We measured seven individual metabolites of four PAH parent compounds (naphthalene, fluorene, phenanthrene, pyrene) in second trimester urine and adjusted for specific gravity. We analyzed PAH concentrations by region, season, and maternal sociodemographic characteristics. We calculated geometric means (GM) and standard deviations (GSD) and used analysis of variance to compare across subgroups.Results: Hydroxylated metabolites of naphthalene [GM=5.33 (GSD=2.81) ng/mL) and fluorene [0.89(2.49) ng/mL] were found at the highest concentrations, accounting for approximately 74% and 15% of total PAH exposure, respectively. GM (GSD) concentrations of hydroxylated naphthalene (1-NAP, 2-NAP), fluorene (2/3/9-FLUO) and pyrene (1-PYR) varied by site [range across sites: 2.33(3.14)-7.31(2.38), 0.54(2.05)-1.08(2.33), 0.01(3.82)-0.15(2.22) ng/mL, respectively). The highest mean concentrations of all metabolites were in Memphis and Rochester samples. Overall, hydroxy-naphthalene concentration (1-NAP, 2-NAP) was higher among women who were younger [<24y: 7.77(2.40) v. >34y: 3.65(2.87) ng/mL], had a lower income [<$15k/y: 8.18(2.74) v. >$75k/y: 3.34(2.43) ng/mL], were less educated [less than high school: 9.19(2.54) v. some graduate level: 2.93(2.65) ng/mL] and were black [8.26(2.42) v. white: 3.73(2.67) ng/mL]. Hydroxy-fluorene (2/3/9-FLUO) concentration was higher among non-Hispanics [0.90(2.46) ng/mL] than Hispanics [0.82(3.06) ng/mL]. By study region, PAHs’ relationships with sociodemographic characteristics and seasonality varied, though concentrations tended to be highest in summer and/or autumn.Conclusions: In this multi-site US sample, we observed evidence that women of color and lower socioeconomic status are disproportionately impacted by prenatal PAH exposure. Future studies will examine associations of these biomarkers with environmental exposures and child health outcomes.