Emerging and Legacy Traffic-Related Nitrogen-Containing Organic Compounds (TNOCs) in Pregnant Women: Exposure Levels, Seasonal Variation, and Health Risks

Abstract

As policymakers increasingly promote emission control technologies and the use of electric vehicles, urban traffic pollution patterns are shifting. Traffic-related nitrogen-containing organic compounds (TNOCs), which represent a critical yet underexplored group of chemicals, have not been comprehensively monitored in humans, particularly among sensitive populations such as pregnant women. In this study, we assessed the internal exposure of pregnant women to 20 emerging and legacy TNOCs by analyzing urine samples after deconjugation (n = 400). The results revealed a frequent detection of TNOCs (median ΣTNOCs: 34.7 ng/mL, adjusted by specific-gravity), with 2-hydroxy-benzothiazole (2-OH-BTH), N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6PPD-Q), and tolyltriazole (TTR) being the most common. Significantly negative correlations were found between PPDs and nitro-PAHs (r = −0.23 to −0.54, P < 0.01, except for 1-AP), indicating their distinct origins. Comparative analyses suggest higher BTH, 2-thiocyanomethylthio-benzothiazole (TCMTB), and xylyltriazole (XTR) in frequent commuters compared to infrequent ones (P < 0.05), implying their traffic-related origins. Seasonal variations pinpoint higher TNOC exposure burden generally during the winter, possibly due to the increased leaching from winter tires. Moreover, the median daily urinary excretion of ΣTNOCs in pregnant women was estimated to be 978 ng/kg bw/day. Such exposure burden including for 6PPD, 1,2,3-triphenylguanidine (TPG), and 2-OH-BTH had negative associations with fetal birth weight (P < 0.05), suggesting developmental adversity. Our study reiterates the recognition of TNOC contaminants and reflects a potential rise in nonexhaust emissions, further demonstrateing TNOCs’ health risks in fetal development.