Environmental behavior, toxic potencies, and risks of liquid crystal monomers: A critical review

Abstract

Liquid crystal monomers (LCMs), prized for their unique optical properties, are ubiquitous in a range of electronic products. However, their growing use and disposal have led to a continuous influx of LCMs into the environment as contaminants. This review synthesizes information on the sources, environmental distribution, migration, transformation, toxicity, and risks associated with LCMs. It also introduces predictions of adverse outcomes related to protein binding potential, grounded in the Adverse Outcome Pathway framework. It was pointed out for the first time that the fundamental causes of LCM contamination were informal recycling and dismantling patterns, coupled with obsolete liquid crystal processing technologies. The significant variability among different types of LCMs in distribution patterns, environmental persistence, bioaccumulation, mobility, and toxicity were emphasized. Notably, fluorinated LCMs, especially fluorobiphenyls, which posed the greatest comprehensive risk, were prone to accumulate in atmospheric dust. Our molecular docking results showed that monomers containing cyano groups, which had greater direct toxicity, carcinogenic, and mutagenic risk, also exhibited strong binding affinity, underscoring the need for priority control strategies. Additionally, this review delved into LCM exposure pathways and the heightened toxicity during degradation and metabolism. It emphasizes the importance of risk assessments for LCMs and identifies key scientific questions that require further investigation. The insights provided a scientific foundation for preventing environmental risks and promoting green chemical alternatives related to LCMs.

Graphical Abstract

Keywords:

• emerging contaminants
• LCMs-F and LCMs-CN
• liquid crystal monomers
• metabolites
• riskstoxicity

HANDLING EDITOR:

• Hyunjung “Nick” Kim

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the National Natural Science Foundation of China (42277235) and supported by the Interdisciplinary Platform for Ecological Civilization, Major Innovation & Planning Interdisciplinary Platform for the “Double-First Class” Initiative, Renmin University of China. The research published in this paper is part of the project titled “Next generation solutions to ensure healthy water resources for future generations” funded by the Global Water Futures program, Canada First Research Excellence Fund. Additional information is available at www.globalwaterfutures.ca. Prof. Giesy was supported by the Canada Research Chair program, the 2012 "High Level Foreign Experts" (#GDT20143200016) program, funded by the State Administration of Foreign Experts Affairs, the P.R. China to Nanjing University and the Einstein Professor Program of the Chinese Academy of Sciences and a Distinguished Visiting Professorship in the Department of Environmental Sciences, Baylor University in Waco, TX, USA.