Pyrolysed waste materials show potential for remediation of trichloroethylene-contaminated water

Trichloroethylene (TCE) is an Environmental Protection Agency priority pollutant associated with cancer in humans. With numerous industrial applications and regular landfill disposal, TCE is a common landfill leachate pollutant. In situ treatment barriers use costly fill materials such as granular activated carbon (GAC). Here, we show that while a range of untreated waste materials had little ability to adsorb TCE, waste-derived biochar showed excellent capacity for TCE adsorption. TCE removal efficiencies by spruce and oak-derived biochars were > 99.5 %, outperforming GAC (95 %) and herbal pomace biochar (93 %). A contact time of at least 32 h was required to reach equilibrium for all of these media. Assessment of pollution swapping potential revealed release of phosphate by all biochars. Analysis of media surface characteristics by Fourier Transform Infrared Spectroscopy (FTIR) predicted that GAC should have the highest ability to adsorb TCE, followed by Oak Biochar, Herbal Pomace Biochar 1, and Spruce Biochar 2, which was not in agreement with the experimental adsorption data. These data demonstrate the potential for pyrolysed waste material to be used as an alternative fill material for in situ remediation applications, thereby also addressing the European Circular Economy Strategy.

Effects of co-existing nitrate on TCE removal by mZVI under different pollution load scenarios: Kinetics, electron efficiency and mechanisms

Microscale zero-valent iron in situ reaction zone (mZVI-IRZ) has proved to be effective and efficient for the removal of chlorinated aliphatic hydrocarbons (CAHs) from groundwater. However, nitrate (NO₃^-), which is ubiquitous in groundwater, affects the mZVI-based attenuation of CAHs in a complicated manner. Both the reaction rate constant (k) and electron efficiency (EE) of mZVI must be considered to comprehensively reflect the effects of NO₃^- on the short and long-term remediation performances of mZVI. Therefore, the influence of NO₃^- on trichloroethylene (TCE) removal under high-pollution-load (iron limited) and low-pollution-load (iron excess) conditions was investigated. Low concentrations of NO₃^- (10 and 50 mg N L^-1) were found to enhance the TCE removal rate and efficiency, whereas high concentrations of NO₃^- (100 mg N L^-1) inhibited the reaction. Although TCE removal was increased at low concentrations of NO₃^-, the EE of mZVI was dramatically decreased in the presence of NO₃^- at all concentration levels. Therefore, both the short-term TCE removal characteristics and the EE of mZVI should be considered when evaluating the long-term remediation effectiveness of mZVI-IRZ technology. The effects of NO₃^- on the TCE removal trends under high- and low-pollution-load scenarios were similar, but had different magnitudes. NO₃^- affected the TCE removal mainly by promoting mZVI corrosion, competing for electrons and affecting passivation product evolution. Our results provide guidance for the practical application of mZVI-IRZ technology.

Gas-phase trichloroethylene removal by Rhodococcus opacus using an airlift bioreactor and its modeling by artificial neural network

This study evaluated the biological removal of trichloroethylene (TCE) by Rhodococcus opacus using airlift bioreactor under continuous operation mode. The effect of inlet TCE concentration in the range 0.12-2.34 g m^-3 on TCE removal has studied for 55 days. During the continuous bioreactor operation, a maximum of 96% TCE removal was obtained for low inlet TCE concentration, whereas the highest elimination capacity was 151.2 g m^-3 h^-1 for the TCE loading rate of 175.0 g m^-3 h^-1. The carbon dioxide (CO₂) concentration profile from the airlift bioreactor revealed that the degraded TCE has primarily converted to CO₂ with a fraction of organic carbon utilized for bacterial growth. The artificial neural network (ANN) based model was able to successfully predict the performance of the bioreactor system using the Levenberg-Marquardt (LM) back propagation algorithm, and optimized biological topology is 3:12:1. The prediction accuracy of the model was high as the experimental data were in good agreement (R² = 0.9923) with the ANN predicted data. Overall, from the bioreactor experiments and its ANN modeling, the potential strength of R. opacus in TCE biodegradation is proved.

Potential for co-metabolic oxidation of TCE and evidence for its occurrence in a large-scale aquifer survey

Trichloroethylene (TCE) is a groundwater pollutant that is prevalent worldwide. In contaminated groundwater, TCE can be biodegraded following either reductive dechlorination or aerobic co-metabolic oxidation. However, since the co-metabolic process is not accompanied by indicative and easily detectable transformation products, little is known about its prominence in the environment. To estimate the environmental importance of the oxidative process, a regional groundwater survey was conducted. In this survey, polluted water from 100 wells along the Israeli Coastal Aquifer was sampled. Geochemical data indicated oxic conditions prevailing in most sites. The sampled groundwater was used for microcosm experiments, functional gene analysis, and TCE compound-specific isotope analysis (δ¹³C and δ³⁷Cl). Enrichments of methane and toluene oxidizers in microcosms indicated the high potential of the indigenous microbial community to co-metabolically oxidize TCE. This was further reinforced by the high abundance of mmoX and PHE functional genes quantified in some of the sites (yet lower abundance of TOD functional gene was found). Finally, compound-specific isotope analysis was used to assess the magnitude of TCE oxidation in practice. Applying the isotopic tool for scattered points on a regional scale demanded the consideration of a wide δ¹³C range of source TCE, hampering the ability to detect small shifts of a single permil. Thus, despite the high potential for the oxidation process, no evidence was attained for the natural occurrence of the process, and significant isotopic shifts were restricted to actively treated sites only. This limitation should be considered in future regional scale studies, in which no single source is defined.

AHR-mediated oxidative stress contributes to the cardiac developmental toxicity of trichloroethylene in zebrafish embryos

Trichloroethylene (TCE), a widely used chlorinated solvent, is a common environmental pollutant. Current evidence shows that TCE could induce heart defects during embryonic development, but the underlining mechanism(s) remain unclear. Since activation of the aryl hydrocarbon receptor (AHR) could induce oxidative stress, we hypothesized that AHR-mediated oxidative stress may play a role in the cardiac developmental toxicity of TCE. In this study, we found that the reactive oxygen species (ROS) scavenger, N-Acetyl-L-cysteine (NAC), and AHR inhibitors, CH223191 (CH) and StemRegenin 1, significantly counteracted the TCE-induced heart malformations in zebrafish embryos. Moreover, both CH and NAC suppressed TCE-induced ROS and 8-OHdG (8-hydroxy-2' -deoxyguanosine). TCE did not affect ahr2 and cyp1a expression, but increased cyp1b1 expression, which was restored by CH supplementation. CH also attenuated the TCE-induced mRNA expression changes of Nrf2 signalling genes (nrf2b, gstp2, sod2, ho1, nqo1) and cardiac differentiation genes (gata4, hand2, c-fos, sox9b). In addition, the TCE enhanced SOD activity was attenuated by CH. Morpholino knockdown confirmed that AHR mediated the TCE-induced ROS and 8-OHdG generation in the heart of zebrafish embryos. In conclusion, our results suggest that AHR mediates TCE-induced oxidative stress, leading to DNA damage and heart malformations in zebrafish embryos.

Systematic evaluation of mechanistic data in assessing in utero exposures to trichloroethylene and development of congenital heart defects

The hypothesis that in utero exposures to low levels of trichloroethylene (TCE) may increase the risk of congenital heart defects (CHDs) in offspring remains a subject of substantial controversy within the scientific community due primarily to the reliance on an inconsistent and unreproducible experimental study in rats. To build on previous assessments that have primarily focused on epidemiological and experimental animal studies in developing conclusions, the objective of the current study is to conduct a systematic evaluation of mechanistic data related to in utero exposures to TCE and the development of CHDs. The evidence base was heterogeneous; 79 mechanistic datasets were identified, characterizing endpoints which ranged from molecular to organismal responses in seven species, involving both in vivo and in vitro study designs in mammalian and non-mammalian models. Of these, 24 datasets were considered reliable following critical appraisal using a study quality tool that employs metrics specific to the study type. Subsequent synthesis and integration demonstrated that the available mechanistic data: 1) did not support the potential for CHD hazard in humans, 2) did not support the biological plausibility of a response in humans based on organization via a putative adverse outcome pathway for valvulo-septal cardiac defects, and 3) were not suitable for serving as candidate studies in risk assessment. Findings supportive of an association were generally limited to in ovo chicken studies, in which TCE was administered in high concentration solutions via direct injection. Results of these in ovo studies were difficult to interpret for human health risk assessment given the lack of generalizability of the study models (including dose relevance, species-specific biological differences, variations in the construct of the study design, etc.). When the mechanistic data are integrated with findings from previous evaluations of human and animal evidence streams, the totality of evidence does not support CHDs as a critical effect in TCE human health risk assessment.

Variable carbon and chlorine isotope fractionation in TCE co-metabolic oxidation

Identifying co-metabolic TCE oxidation in polluted groundwater is challenging due to lack of indicative by-products. This challenge may theoretically be resolved if the oxidation process can be characterized by a distinct dual isotope enrichment. In this work, we aimed to explore the carbon and chlorine isotope effects associated with TCE oxidation by a variety of oxygenases. These included pure strains and enrichment cultures of methane, toluene and ammonia oxidizers, as well as experiments with crude extracts. Isotope effects determined for TCE oxidation by toluene and ammonia oxidizers were mostly in line with expected values for epoxidation mechanism (ϵ¹³C -11.0 ± 0.7 to -24.8 ± 0.2‰ and ϵ³⁷Cl +0.9 ± 0.5 to +1.0 ± 0.4‰), whereas, the methanotrophs resulted in distinctively different isotope effects (ϵ¹³C -2.4 ± 0.4 to -3.4 ± 0.8‰ and ϵ³⁷Cl -1.8 ± 0.2 to -2.9 ± 0.9‰). It is suggested that in TCE oxidation by methanotrophs, substrate binding rather than bond cleavage is rate limiting, leading to this unexpected isotope effect. On the environmental level, our results imply that the oxidative process can be differentiated if catalyzed by toluene and ammonia oxidizers or by methanotrophs. Additionally, the oxidative process can be distinguished from the reductive one. However, using dual isotope analysis in the field may result in an under-estimation of the overall co-metabolic process if methanotrophs are to be excluded due to low isotope effects.

Characteristics of PVP-stabilised NZVI and application to dechlorination of soil-sorbed TCE with ionic surfactant

The characteristics of polyvinylpyrrolidone (PVP)-stabilised nano-zero-valent iron (PVP-NZVI) and its application, combined with surfactant, to trichloroethylene (TCE)-contaminated soil were investigated. Two surfactants (cetyltrimethylammonium bromide [CTAB] and sodium dodecyl sulphate [SDS]) were tested for their ability to enhance the remedial activity of PVP-NZVI in 3 h batch experiments. The prepared PVP-NZVI formed nanoparticles ∼70 nm in diameter. The isoelectric point of PVP-NZVI was about 8.51, similar to the initial pH. X-ray diffraction and X-ray photoelectron spectroscopy analyses revealed that ZVI was the main active component of PVP-NZVI, and carbonised products of the target were observed. The TCE dechlorination efficiency by PVP-NZVI was about 84.73%; the efficiency by PVP-NZVI was about 20% higher when combined with SDS than with CTAB. Therefore, application of PVP-NZVI with SDS represents a potential remediation approach for TCE-contaminated soil.

Effect of water leaching on biochar properties and its impact on organic contaminant sorption

When biochar (BC) is applied to soil, one process that can alter its properties and contaminant sorption is the leaching of minerals and dissolved organic carbon (DOC). This study investigated changes in properties of three BCs (cattle manure, grain husk, and wood chips), due to leaching, and the subsequent impact on sorption of trichloroethylene (TCE) and tetrachloroethylene (PCE). The manure-derived BC released 27.4 mg g^-1 DOC, which is over ten times more than that measured for the two plant-based BCs (2.5 and 1.5 mg g^-1 DOC for grain husk and wood chips, respectively). In all leachates, potassium is the dominant cation, whereas chloride, sulfate, and phosphate are the main anions. In total, the manure-derived biochar released the highest sum of total ions (73.1 mg g^-1), followed by BC produced from grain husk (15.5 mg g^-1) and wood chips (1.2 mg g^-1). Leaching increased external surface area, mesopore volume, and hydrophobicity of the manure-derived BC and decreased its polarity. This enhanced sorption via partitioning. In plant-based BCs, micropore volume and size distribution were altered, most likely through the un-blocking of pores, causing increased sorption via pore-filling for both TCE and PCE. The results indicate that, depending on feedstock material, BC leaching can alter the environmental fate of organic compounds.

Inflammatory kidney injury in trichloroethylene hypersensitivity syndrome mice: Possible role of C3a receptor in the accumulation of Th17 phenotype

Trichloroethylene (TCE) is a common organic solvent which can cause TCE hypersensitivity syndrome (THS) in exposure workers. THS is an adverse skin disorder with severe inflammatory kidney damage. Complement C3a receptor (C3aR) acts as a specific receptor for the key complement cleavage product C3a and involves multiple inflammatory responses, but the role of C3aR in TCE induced kidney inflammatory injury remains unknown. In this study, BALB/c mouse model of skin sensitization induced by TCE was set up in the presence or absence of C3aR antagonist (C3aRA). Kidney pathology and renal function, expression of inflammatory mediators and C3aR, changes in Th17 cell numbers, and activation of signal transducer and activator of transcription 3 (STAT3) in the kidney were examined. TCE sensitization produced histopathological and functional damage to the kidney, accompanied by increased levels of interleukin (IL-) 1β, IL-6, and IL-23. Local accumulation of Th17 cells and enhanced phosphorylation of STAT3 were also seen in the impaired kidney in TCE sensitization-positive mice. C3aR was mainly located in the impaired glomerulus and upregulated in TCE sensitization-positive mice. C3aRA pretreatment alleviated the structural and functional kidney damage and the inflammatory cytokine and Th17 responses by TCE sensitization, and specifically reduced the phosphorylation of STAT3. Together, our results demonstrate that C3aR signaling promotes the inflammatory responses and regulates the accumulation of Th17 phenotype via phosphorylation of STAT3 in TCE sensitization induced inflammatory kidney damage. C3aR may serve as a potential therapeutic target in TCE sensitization mediated kidney injury.

Application of γ-PGA as the primary carbon source to bioremediate a TCE-polluted aquifer: A pilot-scale study

The effectiveness of using gamma poly-glutamic acid (γ-PGA) as the primary carbon and nitrogen sources to bioremediate trichloroethene (TCE)-contaminated groundwater was studied in this pilot-scale study. γ-PGA (40 L) solution was injected into the aquifer via the injection well (IW) for substrate supplement. Groundwater samples were collected from monitor wells and IW and analyzed for TCE and its byproducts, geochemical indicators, dechlorinating bacteria, and microbial diversity periodically. Injected γ-PGA resulted in an increase in total organic carbon (TOC) (up to 9820 mg/L in IW), and the TOC biodegradation caused the formation of anaerobic conditions. Increased ammonia concentration (because of amine release from γ-PGA) resulted in the neutral condition in groundwater, which benefited the growth of Dehalococcoides. The negative zeta potential and micro-scale diameter of γ-PGA allowed its globule to distribute evenly within soil pores. Up to 93% of TCE removal was observed (TCE dropped from 0.14 to 0.01 mg/L) after 59 days of γ-PGA injection, and TCE dechlorination byproducts were also biodegraded subsequently. Next generation sequence (NGS) analyses were applied to determine the dominant bacterial communities. γ-PGA supplement developed reductive dechlorinating conditions and caused variations in microbial diversity and dominant bacterial species. The dominant four groups of bacterial communities including dechlorinating bacteria, vinyl chloride degrading bacteria, hydrogen producing bacteria, and carbon biodegrading bacteria.

Experimental studies and neural network modeling of the removal of trichloroethylene vapor in a biofilter

In this study, bamboo carrier based lab scale compost biofilter was evaluated to treat synthetic waste air containing trichloroethylene (TCE) under continuous operation mode. The effect of inlet TCE concentration and gas flow rate and its removal was investigated. Maximum TCE removal efficiency was found to be 89% under optimum conditions of inlet 0.986 g/m³ TCE concentration corresponding to a loading rate of 43 g/m³ h and 0.042 m³/h gas flow rate at empty bed residence time (EBRT) of 2 min. For the first time, Artificial Neural Network (ANN) was applied to predict the performance of the compost biofilter in terms of TCE removal. The ANN model used a three layer feed forward based Levenberg-Marquardt algorithm, and its topology consisted of 3-25-1 as the optimum number for the three layers (input, hidden and output). An excellent match between the experimental and ANN predicted the value of TCE removal was obtained with a coefficient of determination (R²) value greater than 0.99 during the model training, validation, testing and overall. Furthermore, statistical analysis of the ANN model performance mediated its prediction accuracy of the bioreactor to treat TCE contaminated systems.

Development of Lichen Planopilaris-Like Alopecia following Occupational Exposure to Trichloroethylene and Tetrachloroethylene

BACKGROUND

We report a case of acute and severe lichen planopilaris (LPP)-like alopecia in a 35-year-old male construction worker following occupational exposure to trichloroethylene (TCE) and tetrachloroethylene (PCE).

CASE REPORT

Two weeks after initiating ground-intrusive construction at a previous dry-cleaning facility site, the patient developed sudden scalp pruritus and associated patchy hair loss. As subsequent scalp biopsies revealed LPP, he was started on hydroxychloroquine at 200 mg twice daily and clobetasol solution once daily. Despite treatment, the patient's hair loss rapidly progressed to involve >95% of his scalp within 3 years. An official "work clean" policy report revealed high-concentration exposure to TCE and PCE.

CONCLUSION

Although causation cannot be proven, the close temporal relationship and rapid progression of LPP-like alopecia in an atypical patient demographic support a strong correlation between chemical exposure to TCE/PCE and scarring hair loss.

Terminal complement complex C5b-9 reduced megalin and cubilin-mediated tubule proteins uptake in a mouse model of trichloroethylene hypersensitivity syndrome

Trichloroethylene (TCE), a commonly used industrial solvent and degreasing agent, is known to cause trichloroethylene hypersensitivity syndrome (THS) with multi-system damage, including skin, liver and kidney. Clinical evidence have shown that the kidney injury occurs in THS and our previous studies suggested that the terminal complement complex C5b-9 deposited in impaired renal tubules induced by TCE with unclear mechanisms. In the present study, we questioned whether activation of the complement system with renal deposition of C5b-9 contributes to TCE-induced kidney injury in THS. We established a BALB/c mouse model of TCE sensitization with or without pretreatment of exogenous CD59, a C5b-9 inhibitory protein. H&E staining, PAS staining, and biochemical detection of urinary proteins were performed to assess renal function. Deposition of C5b-9 and expression of CD59 were evaluated by immunohistochemistry. Sub-lytic effects of C5b-9 in tubular epithelial cells were assessed by lactate dehydrogenase (LDH) cytotoxicity assay. Expression of endocytosis receptors megalin and cubilin on proximal tubules were assessed by immunofluorescence and qRT-PCR. We found that TCE sensitization induced structural and functional changes of renal tubules in mice, associated with the deposition of sub-lytic C5b-9 on proximal tubular epithelial cells. TCE sensitization decreased proximal tubule uptake of filtered proteins and renal expression of megalin and cubilin, phenotypes that were attenuated by pretreatment with exogenous CD59. Overall, our findings reveal a novel mechanism underlying sub-lytic C5b-9 acting on megalin and cubilin, contributes to the renal tubules damage by TCE exposure.

A pilot study to assess peripheral blood TCR β-chain CDR3 repertoire in occupational medicamentosa-like dermatitis due to trichloroethylene using high-throughput sequencing

We exploratively characterized T cell receptor (TCR) repertoires from occupational medicamentosa-like dermatitis due to trichloroethylene (OMDT) patients to better understand the underlying pathological mechanism. We used a combination of multiplex-PCR, Illumina sequencing and IMGT/High V-QUEST to analyze the characteristics and polymorphisms of the TCR β-chain complementarity-determining region 3 (CDR3) gene in 10 OMDT cases and 10 trichloroethylene-exposed healthy tolerant controls. Compared with the tolerant controls, OMDT cases showed no significant difference in TCR repertoire diversity including repertoire breadth, highly expanded clone, and CDR3 length distribution. However, we observed several differences in TRBV/TRBJ usage and combination between the two groups, as well as some shared and unique T cell clones in the cases. The pilot study delineated some features of TCR repertoire in OMDT patients that warrant further investigation.

Persulfate activation by natural zeolite supported nanoscale zero-valent iron for trichloroethylene degradation in groundwater

In the advanced oxidation processes, using persulfate (PS) as a radical precursor for pollutant degradation in groundwater has received increasing attention. In this study, zeolite supported nZVI composites (Z/nZVI) were synthesized through an ion exchange and borohydride reduction method to investigate their ability to activate PS for the TCE degradation. Based on preliminary screening of the PS activation by the Z/nZVI (PS-Z/nZVI) system in terms of TCE degradation, Z/nZVI composite with a zeolite to nZVI mass ratio of 1:1 (Z/nZVI (1)) was optimized as the best composition and chosen for further characterization and examination. Especially, for this PS-Z/nZVI system, PS concentration, solution matrix effects (i.e., solution pH, coexisting anions and natural organic matter) were studied. Characterization results revealed that the aggregation of nZVI particles was alleviated and they were good dispersed on the zeolite sheet with a large SSA (159.49 m²/g) compared to the unsupported nZVI (8.77 m²/g). The synthesized Z/nZVI (1) composite exhibited excellent activated ability towards PS (1.5 mM) and effectively degraded 98.8% of TCE at pH 7 within 120 min. The PS-Z/nZVI system was observed to operate effectively over a wide range of pH (i.e., 4-7) for TCE degradation. Moreover, the presence of nitrates (1 mM) and bicarbonates (10 mM) decreased the TCE degradation efficiency to 91.5% and 59.6%, respectively. Scavenger tests demonstrated that both sulfate and hydroxyl radicals participated in the TCE degradation. The ion chromatography analysis suggested the formation of oxalic acid and formic acid as the reaction intermediates during the TCE degradation process in the PS-Z/nZVI system.

Role of miR-182-5p overexpression in trichloroethylene-induced abnormal cell cycle functions in human HepG2 cells

Trichloroethylene (TCE), a widely used industrial solvent, occurs frequently in the global environment. TCE was found to induce hepatocarcinogenesis in mice and one of the underlying mechanisms was reported to involve miR-182-5p overexpression. Subsequently, miR-182-5p overexpression was shown to contribute to chemical-induced enhanced cell proliferation in mouse liver cells by targeting the gene Cited2. The aim of this study was to compare our findings in mice with those in a human hepatoma cell line HepG2. Data demonstrated that TCE at 0.1mM exerted no marked effect on human hepatoma cell line HepG2 cell migration, cell cycle, apoptosis, and DNA damage, but significantly stimulated cell proliferation rate and increased mRNA expression levels of proliferating cell nuclear antigen (PCNA), a cell proliferation biomarker. In addition, TCE enhanced miR-182-5p expression levels but lowered Cited2 mRNA expression. In summary, data showed that similar to mouse liver cells, TCE exposure also upregulated cells miR-182-5p expression and inhibited Cited2 expression in human hepatoma cell line HepG2. Our results suggest that the TCE-mediated alterations in the observed cellular functions involve interaction with miR-182-5p. It is of interest that utilization of liver cancer tissues from the Cancer Genome Atlas (TCGA) database also demonstrated that upregulated miR-182-5p expression and reduced Cited2 mRNA expression was detected suggesting that TCE-induced hepatocarcinogenesis involved processes similar to those in humans.

Photocatalytic removal of trichloroethylene from water with LaFeO3

Tricholorethylene (TCE) has been recognized as second common organic pollutant found in groundwater in Taiwan. Several advanced oxidation processes (AOPs) have been applied for TCE removal and photocatalytic is one of promising AOP techniques. In this study, LaFeO₃ is successfully synthesized via sol-gel method and investigated for its photocatalytic oxidation rate toward TCE in water. Experimental results indicate that 95% removal efficiency of TCE can be achieved in aqueous solution with LaFeO₃ (2 g/L) as photocatalyst within 1 h of Xenon lamp illumination. Additionally, the influences of initial TCE concentration, light intensity, photocatalyst loading, and pH value on the TCE removal efficiency are evaluated as well. The highest energy efficiency obtained in this study is 10.8 mg TCE/kWh and the value is higher than those reported in previous studies. Besides, removal mechanisms have been identified and the results indicate that the overall removal efficiency reaches 82%, with adsorption and photolysis accounting for 20% and 39%, respectively.

Trichloroethylene and its metabolite TaClo lead to degeneration of substantia nigra dopaminergic neurones: Effects in wild type and human A30P mutant α-synuclein mice

Parkinson's disease (PD) is characterised pathologically by degeneration of the dopaminergic (DA) neurones of the substantia nigra pars compacta (SNpc) and the presence of α-synuclein containing Lewy body inclusions. Trichloroethylene (TCE) has been suggested as a potential environmental chemical that may contribute to the development of PD, via conversion to the neurotoxin, 1-Trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo). We investigated the effect of an 8 week exposure to TCE or TaClo on wild type and, as an experimental model of PD, A30P mutant α-synuclein overexpressing mice using a combination of behaviour and pathology. TCE or TaClo exposure caused significant DA neuronal loss within the SNpc in both wild type and transgenic mice. Cell numbers were lower in A30P animals than wild type, however, no additive effect of TCE or TaClo exposure and A30P overexpression was found. TCE or TaClo did not appear to lead to acceleration of motor or cognitive deficits in either wild type or A30P mutant mice, potentially because of the modest reductions of DA neuronal number in the SNpc. Our results do however suggest that TCE exposure could be a possible factor in development of PD like changes following exposure.

The critical role for TAK1 in trichloroethylene-induced contact hypersensitivity in vivo and in CD4+ T cell function alteration by trichloroethylene and its metabolites in vitro

Occupational exposure to trichloroethylene (TCE) has been associated with severe, generalized contact hypersensitivity (CHS) skin disorder, which is considered a delayed-type hypersensitivity reaction mediated by antigen-specific T cells. Transforming growth factor-β activated kinase-1 (TAK1) is essential for regulating the development and effector function of T cells. We hypothesized that disrupting TAK1 activity might inhibit TCE-induced CHS response. In this study, a local lymph node assay was employed to build a CHS model induced by TCE combined with the inducible-TAK1 deletion system to study the effect of TAK1 on it. It was observed that TAK1 deficiency ameliorated the TCE-induced CHS response and was associated with defective T cell expansion and activation and IFN-γ production in vivo. Furthermore, we investigated the effects of TCE and its metabolites trichloroacetic acid (TCA) and dichloroacetic acid (DCA) on CD4⁺ T cell function and the effect of TAK1 on it in vitro. The results showed that TCE, TCA and DCA augmented the proliferation, activation and differentiation of CD4⁺ T cells through Jnk MAPK and NF-κB pathways. TAK1 deletion significantly attenuated these effects induced by TCE, TCA or DCA on CD4⁺ T cells. In conclusion, it is suggested that TAK1 plays a critical role both in TCE-induced CHS response in vivo and in TCE and its metabolite-induced CD4⁺ T cell activation in vitro. Local inhibition of TAK1 might offer a promising alternative feasible strategy for TCE-induced CHS.

Multiple Ion Transition Summation of Isotopologues for Improved Mass Spectrometric Detection of N-Acetyl-S-(1,2-dichlorovinyl)-L-cysteine

Multiple ion transition summation of isotopologues (MITSI) is an adaptable and easy-to-implement methodology for improving analytical sensitivity, especially for halogenated compounds and otherwise abundant isotopologues. This novel application of signal summing was applied to measure and quantitate the two most abundant ion transitions of two isotopologues of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (1DCV), a urinary metabolite of trichloroethylene (TCE). Because 1DCV is dichlorinated, only approximately half of the total potential signal is quantifiable when the monoisotopic ion transition (i.e., m/z 256 → 127 for ³⁵Cl₂) is monitored. By summing the intensity of a separate and high-abundance 1DCV isotopologue ion transition (i.e., m/z 258 → 129 to include ³⁵Cl and ³⁷Cl), overall signal intensity increased by over 70%. This summation technique improved the analytical sensitivity and limit of detection (LOD) by factors of 2.3 and 2.9, respectively, compared to monitoring the two transitions separately, without summation. Separation and detection were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in negative-ion mode with scheduled selected reaction monitoring. This approach was verified for accuracy and precision using two quality control materials. In addition, we derived a modified signal summation equation to calculate predicted signal enhancements specific to the MITSI approach. Graphical Abstract .

Association between occupational exposure to trichloroethylene and serum levels of microRNAs: a cross-sectional molecular epidemiology study in China

OBJECTIVES

The objective of our study was to evaluate the association between occupational exposure to trichloroethylene (TCE), a suspected lymphomagen, and serum levels of miRNAs in a cross-sectional molecular epidemiology study of TCE-exposed workers and comparable unexposed controls in China.

METHODS

Serum levels of 40 miRNAs were compared in 74 workers exposed to TCE (median: 12 ppm) and 90 unexposed control workers. Linear regression models were used to test for differences in serum miRNA levels between exposed and unexposed workers and to evaluate exposure-response relationships across TCE exposure categories using a three-level ordinal variable [i.e., unexposed, < 12 ppm, the median value among workers exposed to TCE) and ≥ 12 ppm)]. Models were adjusted for sex, age, current smoking, current alcohol use, and recent infection.

RESULTS

Seven miRNAs showed significant differences between exposed and unexposed workers at FDR (false discovery rate) < 0.20. miR-150-5p and let-7b-5p also showed significant inverse exposure-response associations with TCE exposure (P_trend= 0.002 and 0.03, respectively). The % differences in serum levels of miR-150-5p relative to unexposed controls were - 13% and - 20% among workers exposed to < 12 ppm and ≥ 12 ppm TCE, respectively.

CONCLUSIONS

miR-150-5p is involved in B cell receptor pathways and let-7b-5p plays a role in the innate immune response processes that are potentially important in the etiology of non-Hodgkin lymphoma (NHL). Further studies are needed to replicate these findings and to directly test the association between serum levels of these miRNAs and risk of NHL in prospective studies.

Complement regulatory protein CD59a plays a protective role in immune liver injury of trichloroethylene-sensitized BALB/c mice

Trichloroethylene (TCE) is a major occupational and environmental chemical compound which causes occupational dermatitis medicamentosa-like of TCE with severe liver damage. Our previous studies showed that complement activation was a newly recognized mechanism for TCE-induced liver damage. The objective of this study was to explore the role of the key complement regulatory protein, CD59a, in TCE-induced immune liver injury. We firstly evaluated the changes of CD59a expression in liver tissue and then investigated if the changes were associated with membrane attack complex (MAC) formation, nuclear factor kappa B (NF-κB) activation and liver damage in BALB/c mice model of TCE-induced skin sensitization in the absence or presence of soluble recombinant rat CD59-Cys. The results showed that low expression of CD59a accompanied by MAC deposition in the liver of TCE-sensitized BALB/c mice, which was consistent in time. In addition, activation of NF-κB pathway, upregulation of inflammatory cytokine and liver damage also occured. Additional experiment showed that recombinant rat sCD59-Cys alleviated inflammation and liver damage in TCE-sensitized BALB/c mice. Moreover, recombinant rat sCD59-Cys reduced MAC formation and inhibited NF-κB activation measured by P-IκBα and nuclear NF-κB p65 in the liver of TCE-sensitized BALB/c mice. In conclusion, recombinant rat sCD59-Cys plays a protective role in immune liver injury of TCE-sensitized BALB/c mice.

Differential toxicity of water versus gavage exposure to trichloroethylene in rats

Trichloroethylene (TCE) is a persistent environmental contaminant that causes male reproductive toxicity. We investigated whether transient increases in TCE exposure modulated male reproductive toxicity by exposing rats via daily oral to repeated gavage exposures (1000 mg/kg/day) and through drinking water (0.6% TCE) for 14 weeks. The gavage route resulted in reversible reduction of epididymis weight, and reduced body weight that persisted for up to 12-weeks after cessation of exposure. Physiologically-based pharmacokinetic modeling predicted that the gavage route results in higher C_max and AUC exposure of TCE compared to drinking water exposure, explaining the observed differences in toxicity between dosing regimens.

Efficient novel amphiphilic double shells layer coupled with nanoscale zero-valent composite for the degradation of trichloroethylene

An efficient novel amphiphilic material composed of core-double shells nanocomposite (CDSN) with nanoscale zero-valent iron (NZVI) as the core and PS₁₀₀-b-PAA₁₆ as inner shell and chitosan as outmost shell has been synthesized successfully. Its application to remove the trichloroethylene (TCE) in stimulated TCE solution with 7.3 ± 0.3 mg/L dissolved oxygen was investigated. The results showed that CDSN after exposure to air for a month could still remove 92.6% of TCE as compared to 61.5% removal rate of NZVI in 360 min (the gram ratio of material: TCE equals to 10:1), exhibiting the great oxidation resistance performance. Specifically, dynamic research of the total removal divided into adsorption by shell layer and degradation by reducibility of NZVI at a predetermined interval was engaged to understand the complete mass transfer process of TCE. The results revealed that CDSN adsorbed 1.5 to 2 folds time TCE as compared to NZVI in the same initial pH = 8.5 aqueous solution. Importantly, CDSN could sustain fixed reactivity to remove about 94.8% of TCE from the start to end. NZVI exhibited greater removal capacity in first 180 min, but later it lost the reducibility and finial removal rate was 89%. The selective adsorption to protonated CDSN was strengthened to increase the removal of TCE at pH 3.5 while NZVI had a worse removal in pH 3.5 performance than pH 8.5.