Beyond Nematic and Smectic Liquid Crystal Monomers (LCMs): Identification of Cholesteric LCMs as Another Abundant Class of Liquid Crystal Display-Derived New Pollutants by Target and Suspect Screening

Liquid crystal monomers (LCMs) are new pollutants derived from emissions from liquid crystal displays (LCDs). In recent years, environmental and health concerns on LCMs have mainly focused on nematic and smectic LCMs. However, information regarding cholesteric LCMs in the environment remains lacking. Herein, we made the first comprehensive screening of cholesteric LCMs in e-waste dust. Target analysis uncovered the presence of 28 cholesteric LCMs in dust samples, including 14 fatty acid cholesteryl esters (FACEs), 9 alkyl carbonate cholesteryl esters (ACCEs), and 5 other-type cholesteryl esters. According to the analogous characteristics of FACEs, a suspect screening framework identified an additional 43 long-chain FACEs. Overall, 71 cholesteric LCMs were identified, with 30 detected in >50% of samples. The median and highest values of their sum concentrations were 94.3 and 1880 ng/g, respectively. FACEs emerged as the dominant group, with long-chain FACEs, particularly FACEs (18:0), exhibiting significantly more abundance than short-chain and medium-chain FACEs. In silico predictive modeling revealed that most of these newly identified cholesteric LCMs exhibited medium-to-high estrogenic/androgenic activities. Our findings confirm cholesteric LCMs as another abundant class of LCD-derived new pollutants in the environment and highlight the need to include these new chemicals in the future risk assessment of LCMs.