A review of the genotoxicity of ethylbenzene

Volatile organic compounds and ionic substances contamination in cell processing facilities during rest period; a preliminary assessment of exposure to cell processing operators

Introduction

Cell processing operators (CPOs) use a variety of disinfectants that vaporize in the workspace environment. These disinfectants can induce allergic reactions in CPOs, due to their long working hours at cell processing facilities (CPFs). Ionic substances such as CH₃COO^- generated from peracetic acid, nitrogen oxides (NOx) and sulfur oxides (SOx) from outdoor environment are also known to pollute air. Therefore, our objective was to assess the air quality in CPFs and detect volatile organic compounds (VOCs) from disinfectants and building materials, and airborne ionic substances from outdoor air.

Methods

Sampling was conducted at three CPFs: two located in medical institutions and one located at a different institution. Air samples were collected using a flow pump. Ion chromatographic analysis of the anionic and cationic compounds was performed. For VOC analysis, a thermal desorption analyzer coupled with capillary gas chromatograph and flame ionization detector was used.

Results

Analysis of the ionic substances showed that Cl^-, NOx, and SOx, which were detected in large amounts in the outdoor air, were relatively less in the CPFs. Ethanol was detected as the main component in the VOC analysis. Toluene was detected at all sampling points. As compared to the other environments, air in the incubator contained larger amounts of VOCs, that included siloxane, tetradecane, and aromatics.

Conclusions

No VOCs or ionic substances of immediate concern to the health of the CPOs were detected during the non-operating period. However, new clinical trials of cell products are currently underway in Japan, and a variety of new cell products are expected to be approved. With an increase in cell processing, health risks to CPOs that have not been considered previously, may become apparent. We should continue to prepare for the future expansion of the industry using a scientific approach to collect various pieces of information and make it publicly available to build a database.

Ethylbenzene induces hearing loss by triggering mitochondrial impairments and excess apoptosis in cochlear progenitor cells via suppressing the Wnt/β-catenin signaling

Ethylbenzene (EB) is widely distributed at low levels in the environment from vehicle emissions, industrial discharge, cigarette smoke, and in some food and consumer products. Evidence shows that EB exposure is associated with hearing loss, yet the mechanisms are unclear. This study aimed to explore the role of the Wnt/β-catenin signaling pathway, which plays a key role during cochlear development, in EB-induced hearing loss. In vitro, we found that EB treatment decreased the viability of cochlear progenitor cells (CPCs), isolated from the cochleae of neonatal rats and crucial for cochlear hair cells generation and hearing construction, via inducing mitochondrial impairments and excessive apoptosis. These were accompanied by the inactivation of the Wnt/β-catenin signaling cascade, as manifested by the decreased levels of related molecules β-catenin, LEF-1 and Lgr5. These findings were further confirmed by knocking down β-catenin and immunofluorescence analysis. Interestingly, adenovirus-mediated β-catenin overexpression activated the Wnt/β-catenin signaling network, alleviated mitochondrial impairments, reduced cell apoptosis, therefore promoting CPCs survival under EB treatment conditions. Finally, using adult Sprague-Dawley rats as an in vivo model with EB inhalation for 13 weeks, we found that exposure to EB decreased body weight gain, increased the hearing thresholds at different exposure stages, along with Wnt/β-catenin signaling pathway suppression in cochlear tissue. More importantly, cochlear microinjection of recombinant lentivirus expressing β-catenin significantly reversed EB-elicited these deleterious effects. Collectively, our results indicate that EB induces hearing loss by triggering mitochondrial impairments and excess apoptosis in CPCs via suppressing the Wnt/β-catenin signaling, and provide clues for the possible therapy.

Two novel zinc-based MOFs as luminescence sensors to detect phenylglyoxylic acid

Automobile exhaust gases, plastic pollutants, smoking, and other harmful substances can cause serious harm to human beings and the environment. Styrene, as a common airborne toxin, enters the human body through breathing or the skin and is discharged in the form of phenylglyoxylic acid (PGA). Therefore, specific, sensitive and trace detection of PGA is particularly important. Here, two zinc-based metal-organic frameworks {[Zn₂L₁(DMF)₂H₂O](DMF)₂H₂O}_n, {[Zn₄(L₂)₂(DMF)₂(H₂O)₃](DMF)₈}_n (L₁ = 2,5-bis((3-carboxylphenyl)amino)terephthalic acid, L₂ = 2,5-bis((4-carboxyphenyl)amino)terephthalic acid) have been reported as 1 and 2, respectively. Both 1 and 2 present 3D structures, which can both be simplified as 4,4,4-c net topology. It is worth mentioning that 2 has two different kinds of Zn SBUs as connecting nodes in the structure. Besides, compared with the other materials for the detection of PGA, 1 and 2 exhibit relatively low detection limits (LODs), both in water and in urine (where the LODs for 1 in water and urine were 0.33 μM and 0.43 μM in the range of 0-0.39 mM, and those for 2 were 0.28 μM and 0.49 μM in the range of 0-0.59 mM, respectively). In addition, the sensors have excellent anti-interference ability, high stability, rapid response, and can easily distinguish between different concentrations of PGA with the naked eye. The developed paper probes were suitable for practical sensing applications for portable detection of PGA in urine.

The Effect of Metro Construction on the Air Quality in the Railway Transport System of Sydney, Australia

Sydney Metro is the biggest project of Australia’s public transport, which was designed to provide passengers with more trains and faster services. This project was first implemented in 2017 and is planned to be completed in 2024. As presented, the project is currently in the construction stage located on the ground stations of the Sydney Trains Bankstown line (T3). Based on this stage, several construction activities will generate air pollutants, which will affect the air quality around construction areas. Moreover, it might cause health problems to people around there and also the passengers who usually take the train on the T3 line. However, there is no specific data for air quality inside the train that may be affected by the construction from each area. Therefore, the aim of this study is to investigate the air quality inside the train carriage of all related stations from the T3 line. A sampling campaign was conducted over 3 months to analyze particulate matter (PM) concentration, the main indoor pollutants including formaldehyde (HCHO) and total volatile organic compounds (TVOC). The results of the T3 line were analyzed and compared to Airport & South line (T8) that were not affected by the project’s construction. The results of this study indicate that Sydney Metro construction activities insignificantly affected the air quality inside the train. Average PM2.5 and PM10 inside the train of T3 line in the daytime were slightly higher than in the nighttime. The differences in PM2.5 and PM10 concentrations from these periods were around 6.8 μg/m3 and 12.1 μg/m3, respectively. The PM concentrations inside the train from the T3 line were slightly higher than the T8 line. However, these concentrations were still lower than those recommended by the national air quality standards. For HCHO and TVOC, the average HCHO and TVOC concentrations were less than the recommendation criteria.

Targeted and Nontargeted Detection and Characterization of Trace Organic Chemicals in Human Serum and Plasma Using QuEChERS Extraction

Humans are exposed to a broad range of organic chemicals. Although targeted gas chromatography mass spectrometry techniques are used to quantify a limited number of persistent organic pollutants and trace organic contaminants in biological samples, nontargeted, high-resolution mass spectrometry (HRMS) methods assess the human exposome more extensively. We present a QuEChERS extraction for targeted and nontargeted analysis of trace organic contaminants using HRMS and compare this method to a traditional, cartridge-based solid-phase extraction (SPE). Following validation using reference and spiked serum samples, the method was applied to plasma samples (n = 75) from the Prospective investigation of Obesity, Energy, and Metabolism (POEM) study. We quantified 44 analytes using targeted analysis and 6247 peaks were detected using the nontargeted approach. Over 90% of targeted analytes were at least 90% recovered using the QuEChERS method in spiked serum samples. In nontargeted analysis, 84% of the peaks were above the method detection limit with area counts up to 3.0 × 105 times greater using the QuEChERS method. Of the targeted compounds, 88% were also identified in the nontargeted analysis. We categorized the 4212 chemicals assigned an identity in using EPA's CompTox Dashboard and 1076 chemicals were found in at least one list. The category with the highest number of chemicals was "androgen or estrogen receptor activity." The findings demonstrate that a QuEChERS technique is suitable for both targeted and nontargeted analysis of trace organic contaminants in biological samples.

Nano-magnetite supported by biochar pyrolyzed at different temperatures as hydrogen peroxide activator: Synthesis mechanism and the effects on ethylbenzene removal

Nano-magnetite supported by biochar (nFe₃O₄/BC) pyrolyzed at temperatures of 300 °C-600 °C was developed to activate hydrogen peroxide (H₂O₂) for the efficient degradation of ethylbenzene in aqueous solution. It was revealed that the degradation efficiency of ethylbenzene and TOC removal were 96.9% and 36.2% respectively after the reaction for 40 min in the presence of initial concentration of 0.1 mmol L^-1 ethylbenzene, 2.76 g L^-1 nFe₃O₄/BC₅₀₀ with the mass ratio of nFe₃O₄ to BC₅₀₀ of 4:1 and 2.0 mmol L^-1 H₂O₂ at pH 7.0. Based on electron paramagnetic resonance (EPR), quenching experiment and X-ray photoelectron spectroscopy (XPS) data, both OH and O₂^- radicals were generated in the nFe₃O₄/BC₅₀₀ activated H₂O₂ system, and the OH radicals were the predominant species for the degradation of ethylbenzene. Through electron transfer process, mechanisms of Fe(II), phenolic hydroxyl group and persistent free radicals (PFRs) on BC surfaces accounted for the generation of OH radicals, and Fe(III) in nFe₃O₄ and formed from Fe(II) oxidation responsible for the generation of O₂^- radicals in the nFe₃O₄/BC activated H₂O₂ system were proposed.

Inoculated Clitoria ternatea with Bacillus cereus ERBP for enhancing gaseous ethylbenzene phytoremediation: Plant metabolites and expression of ethylbenzene degradation genes

Air pollutants especially polyaromatic hydrocarbons pose countless threats to the environment. This issue demands for an effective phytoremediation technology. In this study we report the beneficial interactions of Clitoria ternatea and its plant growth promoting endophytic bacteria Bacillus cereus ERBP by inoculating it for the remediation of 5 ppm airborne ethylbenzene (EB). The percentage efficiency for ethylbenzene removal among B. cereus ERBP inoculated and non-inoculated sterile and natural C. ternatea has also been determined. The inoculation of B. cereus ERBP has significantly increased EB removal efficiency of both sterile and natural C. ternatea. The inoculated natural C. ternatea seedlings showed 100% removal efficiency within 84 h for the aforementioned pollutant compared with the sterile inoculated C. ternatea seedlings (108 h). The degradation of EB by C. ternatea seedlings with and without B. cereus ERBP was assessed by measuring the intermediates of EB including 1-phenylethanol, acetophenon, benzaldehyde and benzoic acid. In addition, cytochrome P450s monooxygenase (CYP83D1) and dehydrogenases (LOC100783159) involved in the oxidation of hydrocarbons are well reported for their bio catalytic activities under xenobiotic stress conditions. Hence, the co-effect of the native endophyte B. cereus ERBP inoculation and EB exposure on the expression level of CYP83D1 and dehydrogenase were also determined. The targeted genes CYP83D1and dehydrogenases have shown an increased expression level under the 5 ppm of EB exposure enabling C. ternatea to withstand and remediate the pollutant.

Risk assessments for chronic exposure of children and prospective parents to ethylbenzene (CAS No. 100-41-4)

Potential chronic health risks for children and prospective parents exposed to ethylbenzene were evaluated in response to the Voluntary Children's Chemical Evaluation Program. Ethylbenzene exposure was found to be predominately via inhalation with recent data demonstrating continuing decreases in releases and both outdoor and indoor concentrations over the past several decades. The proportion of ethylbenzene in ambient air that is attributable to the ethylbenzene/styrene chain of commerce appears to be relatively very small, less than 0.1% based on recent relative emission estimates. Toxicity reference values were derived from the available data, with physiologically based pharmacokinetic models and benchmark dose methods used to assess dose-response relationships. An inhalation non-cancer reference concentration or RfC of 0.3 parts per million (ppm) was derived based on ototoxicity. Similarly, an oral non-cancer reference dose or RfD of 0.5 mg/kg body weight/day was derived based on liver effects. For the cancer assessment, emphasis was placed upon mode of action information. Three of four rodent tumor types were determined not to be relevant to human health. A cancer reference value of 0.48 ppm was derived based on mouse lung tumors. The risk characterization for ethylbenzene indicated that even the most highly exposed children and prospective parents are not at risk for non-cancer or cancer effects of ethylbenzene.

BTEX air concentrations and self-reported common health problems in gasoline sellers from Cotonou, Benin

To examine the relation between BTEX exposure levels and common self-reported health problems in 140 gasoline sellers in Cotonou, Benin, a questionnaire documenting their socioeconomic status and their health problems was used, whereas 18 of them went through semi-directed qualitative individual interviews and 17 had air samples taken on their workplace for BTEX analysis. Median concentrations for BTEX were significantly lower on official (range of medians: 54-207 μg/m³, n = 9) vs unofficial (148-1449 μg/m³, n = 8) gasoline-selling sites (p < 0.05). Self-reported health problems were less frequently reported in sellers from unofficial vs official selling sites (p < 0.05), because, as suggested by the semi-directed interviews, of their fear of losing their important, but illegal, source of income. Concluding, this study has combined quantitative and qualitative methodological approaches to account for the complex socioeconomic and environmental conditions of the investigated sellers, leading to their, in some cases, preoccupying BTEX exposure.

Application of micronucleus test and comet assay to evaluate BTEX biodegradation

The BTEX (benzene, toluene, ethylbenzene and xylene) mixture is an environmental pollutant that has a high potential to contaminate water resources, especially groundwater. The bioremediation process by microorganisms has often been used as a tool for removing BTEX from contaminated sites. The application of biological assays is useful in evaluating the efficiency of bioremediation processes, besides identifying the toxicity of the original contaminants. It also allows identifying the effects of possible metabolites formed during the biodegradation process on test organisms. In this study, we evaluated the genotoxic and mutagenic potential of five different BTEX concentrations in rat hepatoma tissue culture (HTC) cells, using comet and micronucleus assays, before and after biodegradation. A mutagenic effect was observed for the highest concentration tested and for its respective non-biodegraded concentration. Genotoxicity was significant for all non-biodegraded concentrations and not significant for the biodegraded ones. According to our results, we can state that BTEX is mutagenic at concentrations close to its water solubility, and genotoxic even at lower concentrations, differing from some described results reported for the mixture components, when tested individually. Our results suggest a synergistic effect for the mixture and that the biodegradation process is a safe and efficient methodology to be applied at BTEX-contaminated sites.

Behavioral alteration and DNA damage of freshwater snail Bellamya aeruginosa stressed by ethylbenzene and its tissue residue

To study the sublethal effects induced by ethylbenzene and the capability of a freshwater gastropod Bellamya aeruginosa to take up and depurate ethylbenzene, the snail was subjected to two treatments, a 23-day exposure period followed by a 17-day depuration period. Behavioral alteration, namely retraction response, was observed during the exposure period, and the proportion of retracted snails increased under each treatment as the exposure time prolonged but there was no linear relationship between the retracted proportion and the exposure dose. Such behavioral alteration was probably due to the disturbance of membrane permeability stressed by ethylbenzene. Ethylbenzene uptake in unretracted snails was greater than in retracted snails, while the depuration abilities in the two different responses of snails had no significant difference from each other. Because of the limited capability of snails to detoxify ethylbenzene, the depuration was mainly through a slow excretion process and therefore ethylbenzene was still present in the tissue of snail after 17-day depuration. DNA damage was induced significantly in snails exposed to ethylbenzene, and the levels of DNA damage showed positive time-response and dose-response relationships, and moreover the levels of DNA damage had no difference between the two different responses of snails. There was no linear relationship between the level of DNA damage and the amount of residual ethylbenzene in tissue, which may be related to the adaptation mechanism in snail. Overall, the results suggest that the snail has high capability to take up ethylbenzene and low ability to depurate it, and ethylbenzene has potential genotoxicity to snail.

Cellular damages in the Allium cepa test system, caused by BTEX mixture prior and after biodegradation process

Petroleum and derivatives have been considered one of the main environmental contaminants. Among petroleum derivatives, the volatile organic compounds benzene, toluene, ethylbenzene and xylene (BTEX) represent a major concern due to their toxicity and easy accumulation in groundwater. Biodegradation methods seem to be suitable tools for the clean-up of BTEX contaminants from groundwater. Genotoxic and mutagenic potential of BTEX prior and after biodegradation process was evaluated through analyses of chromosomal aberrations and MN test in meristematic and F(1) root cells using the Allium cepa test system. Seeds of A. cepa were germinated into five concentrations of BTEX, non-biodegraded and biodegraded, in ultra-pure water (negative control), in MMS 4×10(-4)M (positive control) and in culture medium used in the biodegradation (blank biodegradation control). Results showed a significant frequency of both chromosomal and nuclear aberrations. The micronucleus (MN) frequency in meristematic cells was significant for most of tested samples. However, MN was not present in significant levels in the F(1) cells, suggesting that there was no permanent damage for the meristematic cell. The BTEX effects were significantly reduced in the biodegraded samples when compared to the respective non-biodegraded concentrations. Therefore, in this study, the biodegradation process showed to be a reliable and effective alternative to treat BTEX-contaminated waters. Based on our results and available data, the BTEX toxicity could also be related to a synergistic effect of its compounds.

Thinner inhalation effects on oxidative stress and DNA repair in a rat model of abuse

Humans can come into contact with thinner by occupational exposure or by intentional inhalation abuse. Numerous studies of workers for genotoxic effects of thinner exposure have yielded conflicting results, perhaps because co-exposure to variable other compounds cannot be avoided in workplace exposure studies. In contrast, there is no data concerning the genotoxic effects of intentional inhalation abuse. The aim of this project was to examine the genotoxic effects of thinner inhalation in an animal model of thinner abuse (rats exposed to 3000 ppm toluene, a high solvent concentration over a very short, 15 min time period, twice a day for 6 weeks). The data presented here provides evidence that thinner inhalation in our experimental conditions is able to induce weight loss, lung abnormalities and oxidative stress. This oxidative stress induces oxidative DNA damage that is not a characteristic feature of genotoxic damage. No significant difference in DNA damage and DNA repair (biomarkers of genotoxicity) in lymphocytes from thinner-treated and control rats was found. Lead treatment was used as a positive control in these assays. Finally, bone marrow was evaluated as a biomarker of cellular alteration associated with thinner inhalation. The observed absence of hemopoietic and genetic toxicity could be explained in part by the absence of benzene, the only carcinogenic component of thinner; however, benzene is no longer a common component of thinner. In conclusion, thinner did not cause genotoxic effects in an experimental model of intentional abuse despite the fact that thinner inhalation induces oxidative stress.

Involvement of mitochondria-mediated apoptosis in ethylbenzene-induced renal toxicity in rat

Ethylbenzene is an important industrial chemical that has recently been classified as a possible human carcinogen (International Agency of Research on Cancer class 2B), but the available data do not support the genotoxic mechanism of ethylbenzene-induced tumors in kidney. We investigated the effects of ethylbenzene on renal ultrastructure and explored the nongenotoxic mechanism of mitochondria-mediated apoptosis pathway. Forty male Sprague-Dawley rats were used as a vivo model with ethylbenzene inhalation for 13 weeks, and the metabolites of ethylbenzene, mandelic acid (MA), and phenylglyoxylic acid (PGA) in urine were examined by high-performance liquid chromatography. Meanwhile, the ultrastructure of renal tubular epithelial cells was observed, and cell apoptosis was detected via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. Furthermore, we investigated the expression levels of messenger RNA (mRNA) and protein of bax, bcl-2, cytochrome c, caspase-9, and caspase-3 in rat kidney. With respect to levels of MA, PGA, and MA + PGA, a significant dose-dependent increase was observed in 4335 and 6500 mg/m(3) ethylbenzene-treated groups against the control group. The mitochondria of renal tubular epithelial cells became a compact and vacuolar structure in 6500 mg/m(3) ethylbenzene-treated group, and ethylbenzene induced a significant increase in the number of apoptotic cells as compared to the control group. In addition, enhanced mRNA and protein expression levels of all measured genes were observed in various ethylbenzene-treated groups except the decreased bcl-2 expression levels. Our results indicated that ethylbenzene may induce apoptosis of renal tubular epithelial cells via mitochondria-mediated apoptotic pathways. MA and PGA in urine might be a parameter of biological dose in vivo after ethylbenzene inhalation.