Fluorinated Liquid-Crystal Monomers Distribution in Paired Urine from Mothers and Infants.

Liquid-crystal monomers (LCMs) serve as the primary functional components in liquid-crystal displays (LCDs), with each display utilizing 15 to 30 different types of LCMs (Zhang et al., 2023; Cheng et al., 2024). Among these, fluorinated liquid-crystal monomers (FLCMs) are particularly significant due to their advantageous properties (Gang et al., 2021). As of 2023, China dominates global LCD production, accounting for 69% of total capacity (Laricchia et al., 2022). However, the increasing use of electronic devices and the decreasing lifecycle of these products have led to the gradual disposal of old LCDs, transforming them into electronic waste (e-waste) (Zhang et al., 2017; Su et al., 2019). This trend raises the risk of LCMs-integral components of LCDs being released into the environment after disposal. Recent reports of pollutant detection indicate that LCMs, especially FLCMs, have quietly penetrated our living environment, including air (Li et al., 2021), dust (Su et al., 2019; Dubocq et al., 2021), river bottom sediments (Su et al., 2022; Tao et al., 2022), soil (Li et al., 2023) and even waste leachate (Jin et al., 2022). A study conducted in Nanjing, China, detected LCMs in indoor dust from environments unrelated to LCD production or dismantling, such as schools, hotels, and residences, with concentrations ranging from 0.130 to 2,213 ng/g (Su et al., 2019). LCMs are also present in the soil as a result of atmospheric deposition or the use of sewage sludge as a soil amendment, with particularly significant residual concentrations in agricultural areas (not detected, ND-250 ng/g) of the Guangdong province’s Great Bay region (Li et al., 2023). In addition, traces of LCMs have been discovered in river sediments in Lake Taihu (0.076 ng/g dry weight, dw) (Su et al., 2021) and the Pearl River Estuary (0.90-31 ng/g dw) (Tao et al., 2022). More worryingly, increased pollution of the water environment has led researchers to find LCMs in aquatic organisms (0.13 ng/g wet weight, ww) (Wang et al., 2022). This cumulation in the food web has resulted in LCMs in freshwater fish, legumes, vegetables, and a wide range of plant and animal foods (5.30 ng/g ww, 3.40 ng/g ww), suggesting a growing risk to dietary health (Yang et al., 2023).

Humans are exposed to LCMs through multiple pathways, including air, dust, soil, drinking water, and food, with dietary intake being the predominant route. Studies have shown that the Estimated Daily Intakes (EDIs) of certain LCMs exceed the Threshold of Toxicological Concern (TTC), indicating that they may be potentially genotoxic (Yang et al., 2023). Such exposure routes have led to the detection of LCMs in human body fluids. A study in Beijing showed that FLCMs contamination in breast milk poses a significant risk for infants who consume it (Yang et al., 2023). Another cohort study of pollutant monitoring in serum found higher concentrations of FLCMs in serum than conventional persistent organic pollutants (POPs), and exposure to FLCMs was associated with elevated blood glucose and lipid levels in humans, which may increase the risk of atherosclerosis (Yang et al., 2024). The current scientific research on the toxic effects of LCMs is still limited and has focused on in vitro studies based on cellular experiments. These experiments suggest that LCMs may be potential PPAR? antagonists (Zhao et al., 2023) and can cause significant disturbances in cellular gene expression (Su et al., 2019). In addition, an in vivo test on Daphnia magna showed that LCMs are potential endocrine disruptors, leading to reduced reproductive rates by interfering with the molting process in aquatic organisms (He et al., 2024). Although four different predictive models (ISS, IRFMN/Antares, CAESAR, IRFMN/ISSCAN-CGX) suggest a possible carcinogenic risk associated with LCMs, the carcinogenic potential of LCMs remains inconclusive (Feng et al., 2022).

Infants possess immature metabolic systems and are at a sensitive developmental stage, making them more susceptible to harmful chemicals than adults (Darnerud et al., 2001). Studies have demonstrated that FLCMs are detected in breast milk and infant formula frequently. Despite being in non-occupationally exposed environments, specific EDIs for infants exposed to FLCMs via breast milk and formula were 700 ng/kg bw/day (Yang et al., 2023) and 267 ng/kg bw/day (Liu et al., 2024), respectively. However, there is still a lack of knowledge about the internal exposure levels in infants. In light of this, the present study concentrated on FLCMs, a dominant group of LCMs in the environment that exhibit persistence, bioaccumulation, and toxicity (PBT) characteristics (Li et al., 2018). The primary objectives of this study included (1) measuring the concentrations of 39 FLCMs in paired maternal and infant urine samples, (2) exploring the relevant factors affecting the residual levels of these compounds, and (3) evaluating the level of internal exposure of infants to FLCMs along with the associated health risks.