Exposure Biomarkers of Airborne Organic Pollutants in Pregnant Women and Developmental Risks: Evidence from Epidemiology to In Vitro Assessment

Air pollution control has lowered major criteria pollutants, yet airborne organic pollutants remain understudied, particularly regarding biomarkers and risks in pregnancy. We characterized 20 urinary biomarkers of airborne organic pollutants, including p-phenylenediamines, nitrated polycyclic aromatic hydrocarbons, phenylguanidines, benzothiazoles/benzotriazoles, and cotinine, in pregnant women from the prospective Towards Improved Maternal and Fetal health via Multipoint Exposure Monitoring (TIMFEM) study in China. Morning urine samples were analyzed by LC-MS/MS. Epidemiologic associations were integrated with in vitro screening in human trophoblast cells using a leave-one-out approach at human-exposure-guided doses. Among 1425 mother-infant pairs, 18 biomarkers were detected in >40% of participants. Each natural log-unit increase in N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its quinone (6PPD-Q) was associated with 27% and 23% higher risk of small-for-gestational-age (SGA), respectively. Mixture models identified 1,2,3-triphenylguanidine (TPG), cotinine, and 1-aminopyrene as additional key contributors. Although seven priority pollutants showed minimal effects on cell proliferation, they reduced pyruvate entry into the tricarboxylic acid cycle and limited isocitrate-to-α-ketoglutarate conversion, indicating impaired placental energy metabolism. Overall risk ranking highlighted cotinine, TPG, and 6PPD-Q. Maternal coexposure to airborne organic pollutants was associated with elevated SGA risk, with metabolic disruption, rather than acute cytotoxicity, suggesting a plausible mechanistic pathway.