Urinary polycyclic aromatic hydrocarbon metabolites in Chinese pregnant women: Concentrations, variability, predictors, and association with oxidative stress biomarkers

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are pervasive contaminants having adverse health effects. Urinary monohydroxylated PAHs (OH-PAHs) are commonly employed as biomarkers to estimate PAH exposure levels in humans. However, little is understood about the variability in OH-PAHs among pregnant women across trimesters and their relationship with oxidative stress biomarkers (OSBs). Based on a prospective birth cohort study conducted in Wuhan, China, we selected 644 women who donated (spot) urine samples across different trimesters and measured the concentrations of eight OH-PAHs and three OSBs (8-OHG, 8-OHdG, and HNEMA) to explore the relationship between the OH-PAHs and OSBs. Pregnant women were found to be ubiquitously exposed to the PAHs, with detection rates of the OH-PAHs ranging from 86.3 % to 100 %. 2-Hydroxynaphthalene (2-OH-Nap) had the highest urinary concentrations among the OH-PAHs during the three trimesters (specific gravity-adjusted median values for the first, second, and third trimesters: 1.86, 2.39, and 2.20 ng/mL, respectively). However, low reproducibility of the OH-PAHs was observed across the three trimesters with intraclass correlation coefficients (ICCs) ranged between 0.02 and 0.22. Most urinary OH-PAHs had the highest concentrations at the first trimester and lowest at the third trimester. Some OH-PAH concentrations were higher in pregnant women with lower educational level (2-OH-Phen and 3-OH-Phen), those who were overweight (2-OH-Nap, 2/3-OH-Fluo, 2-OH-Phen, and 4-OH-Phen), those who were unemployment during pregnancy (1-OH-Nap, 1/9-OH-Phen, and 4-OH-Phen), and the samples donated in summer (most OH-PAHs, except for 2-OH-Nap). In the multivariable linear mixed-effects model analyses, each individual OH-PAH was significantly associated with increased levels of the OSBs. For example, each interquartile range-fold increase in 2/3-OH-Fluo was associated with the largest increase in 8-OHdG (65.4 %) and 8-OHG (49.1 %), while each interquartile range-fold increase in 3-OH-Phen was associated with the largest increase in HNEMA (76.3 %). Weighted quantile sum (WQS) regression models were used to examine the joint effect of OH-PAH mixture on the OSBs, revealing positive associations between OH-PAH mixture exposure and oxidative damage to lipids and nucleic acids. Specifically, 2/3-hydroxy fluorene and 2-OH-Nap were the major contributors in the association with oxidative damage of nucleic acid (8-OHdG and 8-OHG), while hydroxyphenanthrenes and 1-hydroxypyrene were the major contributors in the association with oxidative damage of lipid (HNEMA). Further work is required to examine the potential mediating role of oxidative stress in the relationship of adverse health outcomes with elevated PAH exposure among pregnant women.