Liquid crystal monomers (LCMs) are emerging organic pollutants due to their potential persistence, toxicity, and bioaccumulation. This study first characterized the levels and compositions of 19 LCMs in organisms in the Pearl River Estuary (PRE), estimated their bioaccumulation and trophic transfer potential, and identified priority contaminants. LCMs were generally accumulated in organisms from sediment, and the LCM concentrations in all organisms ranged from 32.35 to 1367 ng/g lipid weight. The main LCMs in organisms were biphenyls and analogues (BAs) (76.6%), followed by cyanobiphenyls and analogues (CBAs) (15.1%), and the least were fluorinated biphenyls and analogues (FBAs) (11.2%). The most abundant LCM monomers of BAs, FBAs, and CBAs in LCMs in organisms were 1-(4-propylcyclohexyl)-4-vinylcyclohexane (15.1%), 1-ethoxy-2,3-difluoro-4-(4-(4-propylcyclohexyl) cyclohexyl) benzene (EDPBB, 10.1%), and 4\'-propoxy-4-biphenylcarbonitrile (5.1%), respectively. The niche studies indicated that the PRE food web was composed of terrestrial-based diet and marine food chains. Most LCMs exhibited biodilution in the terrestrial-based diet and marine food chains, except for EDPBB and 4,4\'-bis(4-propylcyclohexyl) biphenyl (BPCHB). The hydrophobicity, position of fluorine substitution of LCMs, and biological habits may be important factors affecting the bioaccumulation and trophic transfer of LCMs. BPCHB, 1-(prop-1-enyl)-4-(4-propylcyclohexyl) cyclohexane, and EDPBB were characterized as priority contaminants. This study first reports the trophic transfer processes and mechanisms of LCMs and the biomonitoring in PRE.

BACKGROUND: Liquid crystal monomers (LCMs) have been classified as emerging organic pollutants. Efficient isolation and extraction is a critical step in the determination, and then knowing the occurrence and distribution of LCMs in environmental waters. However, the reported sample preparation techniques still suffer some dilemmas such as using large amount of organic solvent, low extraction capacity, tedious operation procedure and employment of expensive extraction column. To circumvent the disadvantages, new extraction format and adsorbent with quickness, less consumption of organic solvent, superior extraction performance and low cost should be developed for the analysis of LCMs.
RESULTS: Using 1H,1H,2H,2H-heptadecafluorodecyl acrylate and 9-vinylanthracene as mixed functional monomers, a task specific magnetic adsorbent (TSMA) was prepared by one-pot hydrothermal technique for the highly efficient capture of LCMs under magnetic solid phase extraction (MSPE) format. Due to the abundant functional groups, the developed TSMA/MSPE presented satisfactory capture performance towards LCMs. Satisfactory enrichment factors (132-212) and high adsorption capacity (18 mg/g) were obtained. Additionally, the relevant adsorption mechanism was studied by the combination of density functional theory calculation and experiments about adsorption kinetics and adsorption isotherm. Under the beneficial conditions, a sensitive and reliable method for the monitoring of studied LCMs in environmental waters was established by the combination of TSMA/MSPE with HPLC equipped with diode array detector (DAD). The achieved limits of detection and spiked recoveries were 0.0025-0.0061 μg/L and 81.0-112 %, respectively. Finally, the developed method was employed to monitor LCMs levels in the North Creek watershed of Jiulong River.
UNASSIGNED: The current study provided a new adsorbent for quick and efficient capture of LCMs at trace levels. In addition, a sensitive, reliable and anti-intereference method for the monitoring of trace LCMs in actual waters was established. Moreover, for the first, the contents, occurrence and distribution of LCMs in North Creek watershed was investigated based on the developed method.

Tree bark has been proven as an effective passive air sampler, particularly where access to active sampling methods is limited. In this study, 60 target liquid crystal monomers (LCMs; comprising 10 cyanobiphenyl and analogs (CBAs), 13 biphenyl and analogs (BAs), and 37 fluorinated biphenyl and analogs (FBAs)) were analyzed in 34 tree barks collected from the vicinity of a liquid crystal display (LCD) manufacturer situated in the Pearl River Delta, South China. The concentrations of LCMs in tree barks ranged from 1400 to 16000 ng/g lipid weight, with an average of 5900 ng/g lipid weight. Generally, bark levels of BAs exponentially decreased within 5 km of the LCD manufacturer. The profiles of LCMs in tree barks are similar to previously reported patterns in gaseous phase, suggesting bark\'s efficacy as a sampler for gaseous LCMs. The inclusion of different congeners in existing studies on the environmental occurrence of LCMs has hindered the horizontal comparisons. Therefore, this study established a list of priority LCMs based on environmental monitoring data and the publicly accessible production data. This list comprised 146 LCMs, including 63 REACH registered LCMs that haven\'t been analyzed in any study and 56 belonging to 4 types of mainstream LCMs.

Liquid crystal monomers (LCMs) are biphenyl- or cyclohexane-based organic chemicals used in electronic digital displays, and several of them possess bioaccumulative and toxic properties. Little is known about their occurrence in indoor dust from the United States. We analyzed 60 LCMs in 104 residential indoor dust samples collected from 16 states across the United States. Forty-seven of 60 LCMs were detected in dust samples at a median ∑LCM concentration of 402 ng/g (range: not detected to 4300 ng/g). Trans-4-propylcyclohexyl trans,trans-4\'-propylbicyclohexyl-4-carboxylate (MPVBC) and (trans,trans)-4-fluorophenyl 4\'-pentyl-[1,1\'-bi(cyclohexane)]-4-carboxylate (FPeBC) were frequently detected in dust samples. We investigated potential sources of LCMs in dust by determining concentrations and profiles of these chemicals in smartphone screens, desktop and laptop computer monitors, and displays of other electronic devices and found that profiles in smartphones matched closely with those found in dust. The calculated median daily intake of ∑LCM through dust ingestion was 1.19 ng/kg bw/d for children, whereas that through dermal absorption was 0.18 ng/kg bw/d for adults in the United States.

Liquid crystal monomers (LCMs) are a class of emerging contaminants of concern predicted to be persistent, bioaccumulative and toxic (PBT). Being one of the key components in liquid crystal displays (LCDs), the disposal of LCD containing devices is closely related to the emission of LCMs into the environment. LCMs have been detected in a wide range of environmental matrices including dust, sediment, soil, sewage leachate, and air, with concentration ranges between 17 and 2121 ng/g found in indoor residential dust. Furthermore, they have been detected on human skin at concentrations up to 2,071,000 ng/m2 and in the serum of e-waste dismantling workers, at concentrations ranging from 3.9 to 276 ng/mL. Despite the far-reaching contamination of these compounds, there is limited knowledge of their environmental behaviour, fate, and toxicity. Model predictions show that 297 of 330 LCMs are persistent and bioaccumulative compounds, with many more indicated as being toxic. However, current knowledge of their physicochemical and PBT properties is largely restricted to theoretical predictions and limited to a small number of experimental toxicity studies. As an emerging class of contaminants of concern, a lack of standardisation between studies was identified as a key challenge to advancing the state of knowledge of these compounds. Not only are harmonised analytical methods for their determination and quantification in environmental media yet to be established, but there is also a need for a universal abbreviation system. To further harmonise the reporting of data on LCMs we propose reporting the sum concentration of ten priority LCMs, selected on the basis detection frequency, toxicity and potential for human exposure. Of the ten priority LCMs five are fluorinated biphenyls and analogues, four are biphenyls/bicyclohexyls and analogues and one is a cyanobiphenyl.

Liquid crystal monomers (LCMs), which are commonly used in electronic device screens, have attracted attention as a potential class of emerging organic pollutants with persistent, bioaccumulative, and toxic (PBT) properties. This study involved the collection of 54 surface soil samples around one LC industrial park at increasing spatial distances within 1 km, 1-3 km, and 3-5 km from the center of the LC industrial park. Our observations revealed the presence of LCMs in 46 of 54 surface soil samples examined. Of the 39 target LCMs, 36 were identified, comprising 14 non-fluorinated and 22 fluorinated LCMs. Nine LCMs were detected at frequencies exceeding 20%, with 3bcHdFB exhibiting the highest detection frequency of 59% in the soil samples. The total LCM concentrations across the 46 sampling locations varied from 0.0072 to 17.24 ng/g dw, with the highest total concentrations at sampling sites within 1 km of the liquid crystal plant, suggesting that manufacturing processes may be a potential source for LCM release into the environment. Differences were observed in the LCM contamination patterns among the three sampling areas. Additionally, we observed a decrease in the median LCM concentration with increasing distance from the center of the LC industrial park. However, no statistically significant differences (p > 0.05) in LCM concentrations were observed across the three distances assessed in this study. This may be owing to the limited variety of target compounds analyzed and the limited number of soil samples. Our results emphasize that further studies on the emissions and pollution characteristics of LCMs during production are warranted.

The Pearl River Estuary (PRE), one of the primary e-waste recycling centers in the world, has been suffering from the pollution of Liquid Crystal Monomers (LCMs), critical materials with persistent, bio-accumulative, and toxic substances used in electronic devices. It has been detected in seabed sediment with both high frequency and concentration near PRE - Hong Kong (HK) waters. In the same area, dredging operations with in-situ sediment have been frequently used in the last decades for coastal land reclamation projects. Dredging is known to cause a huge amount of sediment re-suspension into water columns, with potential damage to marine ecosystems and biodiversity. In this study, we proposed a new risk assessment strategy to estimate the secondary pollution due to the re-suspension sediment highly contaminated by LCMs. We formulate a robust and reliable probabilistic approach based on unsupervised machine learning and hydrodynamic and sediment transport numerical simulation. New risk indexes were also proposed to better quantify the impact of contaminated sediments. We applied the methodology to assess the potential impact of dredging operations in the PRE and Hong Kong waters on the local marine ecosystem. The results of the analysis showed how the potentially contaminated areas depended on the dredging locations.

Liquid crystal monomers (LCMs) are emerging contaminants characterized by their persistence, bioaccumulation potential, and toxicity. They have been observed in several environmental matrices associated with electronic waste (e-waste) dismantling activities, particularly in China. However, there is currently no information on the pollution caused by LCMs in other developing countries, such as Pakistan. In this study, we collected soil samples (n = 59) from e-waste dismantling areas with different functions in Pakistan for quantification analysis of 52 target LCMs. Thirty out of 52 LCMs were detected in the soil samples, with the concentrations ranging from 2.14 to 191 ng/g (median: 16.3 ng/g), suggesting widespread contamination by these emerging contaminants. Fluorinated LCMs (median: 10.4 ng/g, range: 1.27-116 ng/g) were frequently detected and their levels were significantly (P < 0.05) higher than those of non-fluorinated LCMs (median: 6.11 ng/g, range: not detected (ND)-76.7 ng/g). The concentrations and profiles of the observed LCMs in the soil samples from the four functional areas varied. The informal dismantling of e-waste poses a potential exposure risk to adults and infants, with median estimated daily intake (EDI, ng/kg bw/day) values of 0.0420 and 0.1013, respectively. Calculation of the hazard quotient (HQ) suggested that some LCMs (e.g., ETFMBC (1.374) and EDFPB (1.257)) may pose potential health risks to occupational workers and their families. Considering the widespread contamination and risks associated with LCMs, we strongly recommend enhancing e-waste management and regulation in Pakistan.

Liquid crystal monomers (LCMs) are widely used in electronic devices and emerging as an environmental pollutant, while their occurrence in indoor environments is still less studied. In this study, 32 out of 37 target LCMs were detected in indoor residential dust samples (n = 112) from Beijing, China. Concentrations of Σ32LCMs ranged from 17.8 to 197 ng/g, with a median value of 54.7 ng/g. Fluorinated biphenyls and analogs (FBAs) and cyanobiphenyls and analogs (CBAs), with median concentrations of 22.8 and 15.9 ng/g, respectively, were the main kinds of LCMs. Although 32 LCMs can be detected, four monomers with the highest contamination levels contributed to almost 70% of the total LCMs. Spearman correlation analysis found significant correlations among some monomers, which indicated that they might share similar sources in the residential environment. Estimated daily intakes (EDIs) of LCMs via indoor dust for Beijing residents were calculated, and the results showed that dust ingestion and dermal contact were both main intake pathways to LCMs, and younger people may face higher exposure to LCMs. A comparison to the results of China\'s total diet study showed that EDIs of LCMs via food consumption might be higher than that via dust intake, while health risks caused by exposure of LCMs for the general population, both through food and dust, were insignificant at present.

The widespread existence of liquid crystal monomers (LCMs) in various environmental matrices has been demonstrated, yet studies on the toxicological effects of LCMs are considerably scarce and are urgently needed to be conducted to assess the adverse impacts on ecology and human health. Here, we conducted a bacteriological study on two representative human commensal bacteria, Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), to investigate the effect of LCMs at human-relevant dosage and maximum environmental concentration on growth, metabolome, enzymatic activity, and mRNA expression. Microbial growth results exhibited that the highest inhibition ratio of LCMs on S. epidermidis reached 33.6% in our set concentration range, while the corresponding data on E. coli was only 14.3%. Additionally, LCMs showed more dose-dependent toxicity to S. epidermidis rather than E. coli. A novel in vivo solid-phase microextraction (SPME) fiber was applied to capture the in vivo metabolites of microorganisms. In vivo metabolomic analyses revealed that dysregulated fatty acid metabolism-related products of both bacteria accounted for >50% of the total number of differential substances, and the results also showed the species-specific and concentration-dependent metabolic dysregulation in LCM-exposed bacteria. The determination of enzymatic activity and mRNA relative expression levels related to oxidative stress confirmed our speculation that the adverse effects were related to the oxidative metabolism of fatty acids. This study complements the gaps in toxicity data for LCMs against bacteria and provides a new and important insight regarding metabolic dysregulation induced by environmental LCMs in human commensal bacteria.