Urinary 2,4-dichlorophenoxyacetic acid in Chinese pregnant women at three trimesters: Variability, exposure characteristics, and association with oxidative stress biomarkers.

Widespread exposure to herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) could have potential adverse health effects on pregnant women. However, related data are scarce. This study aimed to characterize 2,4-D exposure among three trimesters of pregnancy and to explore the relationship of 2,4-D with oxidative stress biomarkers [i.e., 8-hydroxy-2'-deoxyguanosine (8-OHdG), 8-hydroxy guanosine (8-OHG), and 4-hydroxy nonenal mercapturic acid (HNEMA)] in urine. The present study analyzed 3675 urine samples of 1225 women (across the three trimesters of pregnancy) in Wuhan, central China. 2,4-D was detectable in 97.4% of the urine samples. The median unadjusted concentration of 2,4-D was 0.12 ng/mL, and the corresponding concentration adjusted by urinary specific gravity (SG-adjusted) was 0.13 ng/mL. The intraclass correlation coefficient of 2,4-D (SG-adjusted concentrations) was 0.07 across the three trimesters. Significantly higher urinary levels of 2,4-D were found in samples from younger pregnant women/samples collected during winter. In addition, significantly positive association between urinary concentrations of oxidative stress biomarkers and 2,4-D were found in repeated analysis; an interquartile range increase in 2,4-D was significantly (p < 0.001) associated with a 20.8% increase in 8-OHG, a 26.7% increase in 8-OHdG, and a 30.7% increase in HNEMA, respectively. Such associations were also found in trimester-specific analyses. This is the first time to quantify the urinary 2,4-D of pregnant women in China, and this study found significantly positive associations of 2,4-D with oxidative stress biomarkers. Further studies are needed to verify such associations and explore other potential adverse effects of 2,4-D exposure.