Occurrence and Health Risk of Emerging Liquid Crystal Monomers (LCMs) in Human Milk from Hunan, China

Liquid crystal monomers (LCMs) have attracted increasing attention due to their bioaccumulation potential and dioxin-like toxicity. However, human exposure to LCMs remains unclear. Fifty-eight of the 78 targeted LCMs were detected in human milk collected from Hunan Province, China. For the first time, 20 nonfluorinated LCMs were quantified in human milk, with concentrations ranging from ND to 60.0 ng/g lipid weight (lw). The ∑LCMs concentrations (median: 27.1 ng/g lw) were higher than those of other persistent organic pollutants. Fluorinated biphenyls and analogues (69%) were the predominant group of LCMs, followed by biphenyls and analogues (17%) and cyanobiphenyls and analogues (14%). Trans-1-Ethoxy-2,3-difluoro-4-(4-pentylcyclohexyl) benzene (EDPeB) was the most abundant compound, contributing 22.5% to the ∑LCMs concentration. The levels of certain LCMs significantly correlate with maternal body mass index, parity, and dietary preference on meats and aquatic food (p < 0.05). Breastfeeding was identified as the primary exposure pathway for infants, with median estimated daily intakes (EDIs) of LCMs (0.133-101 ng/kg bw/day) surpassing those from dust ingestion, dermal contact, and complementary food intake. Despite an acceptable hazard index (HI < 1), the EDIs of EDPeB and trans,trans-4-(4-fluorophenyl)-4'-propylbicyclohexyl exceeded their threshold of toxicological concern values, indicating potential health concerns.