Widespread Human Exposure to Liquid Crystal Monomers: Population-Scale Urinary Biomonitoring Reveals Spatial, Demographic, and Environmental Patterns across Several Regions in China

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Liquid crystal monomers (LCMs) are emerging contaminants released from electronic products and e-waste throughout their life cycle. However, population-level evidence of human internal exposure to fluorinated and nonfluorinated LCMs remains largely unknown. This study aimed to characterize human exposure to 49 LCMs in urine and examine the spatial, demographic, and environmental variability in exposure across several regions in China. We measured 49 LCMs in 597 first-morning urine samples collected from general populations across four urban and rural regions in eastern and western China using GC-MS/MS. Detection frequencies, concentration distributions, and estimated daily intake (EDI) were assessed. Nonparametric subgroup analyses were used to characterize demographic heterogeneity, and multivariable regression models were used to evaluate associations with environmental and policy-related factors. LCMs were detected in 99.7% of urine samples, with 31 compounds exceeding 80% detection frequency. The median total concentration (∑49LCMs) was 30.5 ng/mL, with fluorinated LCMs contributing 55.5% of the total burden. Urban populations showed higher concentrations and greater variability than rural populations. Urinary LCMs showed significant heterogeneity across age, body mass index, and occupational groups, whereas sex-related differences were limited. Higher urinary LCM levels were associated with temperature and humidity, while the novel coronavirus 2019 (COVID-19) policy indicators showed weak associations. Screening-level EDI estimates further identified several LCMs as priority compounds for future exposure assessment. This study provides multiregional biomonitoring evidence of widespread occurrence of LCMs in urine across several regions in China. Spatial and demographic variability suggests combined influences of environmental conditions, indoor source intensity, and population characteristics. The substantial contributions of both fluorinated and nonfluorinated compounds underscore the need for further investigation of exposure sources and compound-specific toxicokinetics.