Liquid Crystal Monomers(LCMs)

With the rapid development of information technology,the electrical and electronic equipment(EEE)has become indispensable in modern societies.At the same time,the rapid growth of waste electrical and electronic equipment(WEEE or e-waste)has brought huge environmental concerns and challenges.The environmental fate,occurrence and adverse effects of persistent,bioaccumulative and toxic(PBT)organic contanminants in e-waste have been widely studied and reported.However,as the key materials of liquid crystal displays(LCDs),the fates and effects of liquid crystal(LCMs)in the environment are rarely studied.In order to address these knowledge gaps,an extensive investigation of LCMs and their potential P&B and long-range transport potential(LRTP)characteristics were conducted.Then,the chemical structures of LCMs in the LCDs were identified,and the occurrences and spatial distribution of these identified LCMs were investigated in several environmental matrices.Finally,the toxicity(T)of LCM mixtures collected from largely produced and used LCD devices were assessed.Conclusions were described as following:i)The present study conducted an extensive research on industries producing LCMs,published papers and patents,and generated a list containing 1173 LCMs.The OECD(Organization for Economic Cooperation and Development)Pov and LRTP Screening Tool software were used to predict the overall persistence(Pov)and long-range transport potential(LRTP)of the LCMs.And all 1173 LCMs were evaluated to identify if they were P or B or both by use of the US Environmental Protection Agency’s(US EPA)EPI Suite software.Some LCM chemicals might be likely to undergo long-range atmospheric transport,very persistent and very bioaccumulative after entering into environment.They might also contaminate regions like the Arctic and other similar remote areas.ii)LCD panels of frequently used smartphones were purchased and dismantled manually in our laboratory,and the LCM mixtures were collected.Based on the gas chromatography-mass spectrometry(GC-MS)and liquid chromatograph coupled to a hybrid quadrupole Orbitrap high-resolution mass spectrometer(LC-Orbitrap-HRMS),33 individual LCMs were identified in the LCM mixtures.All the identified LCMs were screened in 53 indoor dust samples collected from 7 indoor spaces,including laboratory building,hotel,teaching building,dormitory,electronic product maintenance center,residence,and canteen,in Nanjing city,eastern China.Twenty-five of the 33 LCMs were detectable in at least one sample of dust,the concentrations of Σ33LCM ranged from 0.01 to 5010 ng/g,dry mass(dm).The rank order(from lowest to highest)of concentrations of Σ33LCM in dust from indoor spaces was canteen < dormitory < teaching building < hotel < residence < electronic product maintenance center < laboratory building.Compared to concentrations of conventional contaminants in the same indoor dust samples,concentrations of Σ33LCM were less than those of ΣOPEs(organophosphate ester),ΣPBDEs(polybrominated diphenyl ethers),andΣNBFRs(novel brominated flame retardant).iii)An analytical method was developed for the quantitative determination of 39 LCMs in sediment samples,and n = 76 sediment samples were collected from three typical areas and analyzed to determine accurate concentrations of LCMs.Our results indicated that the developed pretreatment procedure was applicable for the determination of LCM concentrations in sediments.We observed that LCMs were detected in 75 out of the 76 sediment samples,and 23,18,and 14 out of the 39 target LCMs were quantified in at least one of the analyzed sediments from rivers around LCM or liquid crystal device(LCD)manufacturers,Taihu Lake,and rivers around e-waste recycling sites,respectively.The LCMs in the samples from rivers around LCM/ LCD manufacturers exhibited the greatest mean concentrations,followed by those from e-waste recycling site areas and Taihu Lake.The mean concentrations of LCMs were compared with other groups of organic chemical substances in sediments that were also collected from industrial areas,Taihu Lake,and e-waste recycling sites.The mean concentrations of quantifiable LCMs were relatively lower than the mean concentrations of other organic contaminants in the sediments collected from Taihu Lake and e-waste recycling sites.Compared with the traditional organic contaminants in the sediments collected from industrial areas,the mean concentrations of quantifiable LCMs were relatively higher than chlordane,polychlorinated biphenyls(PCBs),and dichloro-diphenyl-trichloroethanes(DDTs).iv)Based on the 1173 LCMs,the suspect screening of LCMs in the three typical sediment samples(n = 33)was conducted by use of gas chromatography coupled to quadrupole-time-of-flight mass spectrometry(GC-QTOF/MS).In these analyzed samples,we identified 26 LCMs(43 potential structures)in 27 samples,and 2 out of 43 candidates were confirmed by comparison of unique GC and MS characteristics with commercially pure standards.Different from the distributions of candidates in sediments from industrial areas,the number of the candidates and their peak area were relatively lower than those in samples from Taihu Lake and e-waste recycling sites.v)To investigate whether exposure to mixtures of LCM from n = 6 current-use LCD devices resulted in changes in expressions of selected mRNAs in CEHs,an avian Tox Chip,which measures the expression of mRNAs coding for 43 genes was used.The results demonstrated that five genes,CYP1A4,FGF19,LBFABP,PDK4,and THRSP were significantly dysregulated following exposure to LCM mixtures.These 5 gene targets were involved in xenobiotic metabolism,bile acids/cholesterol regulation,lipid homeostasis,glucose metabolism,and the thyroid hormone pathway,respectively.Modulation of expressions of mRNAs coding for these genes has frequently been reported for toxic(T)persistent organic pollutants(POPs).As a class of novel PBT substances,LCMs were firstly reported,and their environmental pollution status and adverse effects were studied in this thesis.Given the potential persistence,bioaccumulation,long-range transport potential of LCMs,widely detected in environmental matrices,and the potential toxic of LCM mixtures in LCDs,it is critical to understand the environmental occurrence,fate and behavior of LCMs.However,the environmetal characteristics,exposure and the ecological risks of LCMs should be addressed with future research needs and efforts.