Profiles, variability, and predictors of urinary benzotriazoles and benzothiazoles in pregnant women from Wuhan, China

Background: Benzotriazoles (BTRs) and benzothiazoles (BTHs) are emerging contaminants with high production volume worldwide, which exhibit potential health risk to human. To date, little is known about the exposure of BTRs and BTHs (BTs) on human, especially in the context of pregnancy. Objectives: We aimed to characterize the exposure profiles, temporal variability, and potential predictors of urinary BTs during pregnancy. Methods: Between 2014 and 2015, we recruited 856 pregnant women in Wuhan who provided urine samples at three trimesters (13.1 +/- 1.1, 23.7 +/- 3.2, and 35.7 +/- 3.4 gestational weeks). We measured the urinary concentrations of five BTRs (1-H-benzotriazole, 1-hydroxy-benzotriazole, xylyltriazole, tolyltriazole, 5-chloro-1-H-benzotriazole) and five BTHs (benzothiazole, 2-hydroxy-benzothiazole, 2-methylthio-benzothia-zole, 2-amino-benzothiazole, 2-thiocyanomethylthio-benzothiazole) to characterize the exposure profiles of BTs. We calculated the intra-class correlation coefficients (ICCs) to assess the temporal variability and investigated potential predictors of urinary BTs by using the mixed models. Results: Most of the targeted BTs were detected in over 50% of urine samples, except for 5-chloro-1-H-benzotriazole (9.3%) and 2-thiocyanomethylthio-benzothiazole (1.4%). The predominant BTRs in urine was 1-hydroxy-benzotriazole [Geometric Mean (GM): 0.77 ng/mL]. Benzothiazole was the major derivative in urine samples with a GM concentration of 1.6 ng/mL. Correlations among BTHs (r = 0.04-0.39) were higher than that among BTRs (r = 0.02-0.14). The exposure pattern was constant at low level and co-exposure to all the targeted compounds was infrequent during pregnancy. Urinary concentrations of BTRs exhibited considerable within-subject variation (ICCs: 0.12-0.56) during pregnancy. Relatively high temporal reliability was observed for urinary concentrations of BTHs with ICCs ranging from 0.42 to 0.85. It was found that parity, household income, pregnancy occupational status, sampling season and menstrual cycle were associated with urinary concentrations of BTs in pregnant women (P < 0.05). Conclusions: To the best of our knowledge, this is the first study to report the exposure profiles, variability and predictors of urinary BTs among pregnant women. Exposure assessment using multiple samples is essential in reducing measurement errors and identifying susceptible window of exposure in etiological studies. The potential predictors of urinary BTs raised concerns on tracing exposure routes and eliminating confounding variables in future studies.