Liquid Crystal Monomers in Paired Indoor Dust and Urine: Compound-Specific Enrichment Patterns and External–Internal Exposure Profiles

Liquid crystal monomers (LCMs) are extensively used in liquid crystal display devices, yet the relationship between household contamination and human internal exposure remains unclear. We investigated fluorinated and nonfluorinated LCMs (FLCMs and NFLCMs) in paired indoor dust and urine samples. Widespread occurrence of LCMs was observed in 58 paired indoor dust and first-morning urine samples collected in Suizhou, with 48 of 49 LCMs detected in dust and 40 in urine. Median concentrations of ∑49LCMs were 255 ng/g in dust and 26.9 ng/mL in urine. FLCMs were predominant in dust, whereas NFLCMs contributed more to urinary burden. The dominant compounds differed markedly between dust and urine. Among these, only 2,3-difluoro-1-methoxy-4-[4-(4-propylcyclohexyl)cyclohexyl]benzene (DMPCB) showed a significant positive dust-urine correlation (r = 0.409, p < 0.01). Relative-enrichment analysis revealed compound-specific shifts, with several NFLCMs relatively enriched in urine and several FLCMs in dust. The median estimated daily intake of ∑49LCMs via dust ingestion was 0.110 ng/kg bw/day, far below levels reported for e-waste recycling areas. Although hazard quotients (HQs) for all 39 LCMs with available toxicity benchmarks were several orders of magnitude below 1, incomplete toxicity reference data remain a major source of uncertainty in risk characterization. Overall, the findings indicate widespread mixed exposure to LCMs and suggest that urinary LCM profiles may reflect contributions from multiple exposure pathways and compound-specific toxicokinetic processes in addition to household dust.