Journal articles: 'Exposure to benzene, toluene and xylene (BTX)' – Grafiati (2024)

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Benzene, toluene, and xylenes (BTX) commonly co-exist. Exposure to individual components and BTX-rich mixtures can induce hematological effects. However, the hematological effects of long-term exposure to BTX are still unclear, and respective reference levels based on empirical evidence should be developed. We conducted a follow-up study in BTX-exposed petrochemical workers. Long-term exposure levels were quantified by measuring cumulative exposure (CE). Generalized weighted quantile sum (WQS) regression models and Benchmark Dose (BMD) Software were used to evaluate their combined effects and calculate their BMDs, respectively. Many hematologic parameters were significantly decreased at the four-year follow-up (p < 0.05). We found positive associations of CE levels of benzene, toluene, and xylene with the decline in monocyte counts, lymphocyte counts, and hematocrit, respectively (β > 0.010, Ptrend < 0.05). These associations were stronger in subjects with higher baseline parameters, males, drinkers, or overweight subjects (Pinteraction < 0.05). BTX had positive combined effects on the decline in monocyte counts, red-blood-cell counts, and hemoglobin concentrations (Ptrend for WQS indices < 0.05). The estimated BMDs for CE levels of benzene, toluene, and xylene were 2.138, 1.449, and 2.937 mg/m3 × year, respectively. Our study demonstrated the hematological effects of long-term BTX co-exposure and developed 8h-RELs of about 0.01 ppm based on their hematological effects.

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BackgroundBenzene, toluene and xylene (BTX) are aromatic hydrocarbons with inconclusive evidence of lung carcinogenicity. The aim of this research was to assess the associations between occupational exposures to BTX agents and lung cancer.MethodsIn a population-based case-control study of lung cancer, occupational histories were obtained and exposures were assessed by experts. Unconditional multivariate logistic regression was used to estimate ORs and 95% CIs, among men, between various metrics of occupational exposure to BTX and lung cancer, while adjusting for established and possible risk factors.ResultsConsiderable overlap was found between occupational exposure to BTX, where the majority of exposed participants were exposed to all three chemicals. Lung cancer was associated with exposure to benzene (OR=1.35; 95% CI 0.99 to 1.84), toluene (OR=1.31; 95% CI 0.99 to 1.74) and xylene (OR=1.44; 95% CI 1.03 to 2.01). While these results were adjusted for smoking and other recognised and possible lung cancer risk factors, they were not mutually adjusted among the three BTX agents.ConclusionsOur study provides suggestive evidence that occupational exposure to one or more of the BTX agents may be associated with lung cancer.

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Laboratorium merupakan tempat kerja untuk melakukan percobaan atau eksperimen uji dimana bekerja di tempat tersebut membutuhkan perilaku kehati-hatian dalam menggunakan peralatan dan bahan. Salah satu jenis bahan kimia yang terdapat di laboratorium adalah pelarut organik yang memiliki fungsi sebagai pelarut bahan kimia lainnya. Potensi risiko kanker payudara pada pekerja wanita di laboratorium pada studi kohort ini adalah paparan pelarut organik. Pelarut organik yang sering digunakan di laboratorium adalah benzene, toluene dan xylene (BTX). Dengan adanya pajanan bahan kimia BTX di tempat kerja dan risiko kesehatan yang ditimbulkan, maka perlu dilakukan penilaian tingkat risiko pajanan bahan kimia terhadap kesehatan pekerja di laboratorium melalui inhalasi secara kuantitatif dengan menggunakan metode CHRA DOSH Malaysia tahun 2018. Penelitian dimulai dengan pengambilan sampel inhalasi dan udara di lingkungan kerja. Data hasil sampling diolah untuk mengetahui Tingkat Bahaya (Hazard Rating), Tingkat Pajanan (Exposure Rating), dan Tingkat Risiko (Risk Rating) secara kualitatif dan kuantitatif. Tingkat risiko pajanan melalui inhalasi secara kualitatif diperoleh nilai tingkat risiko pajanan (RR) benzene, toluene dan xylene secara bertutut-turut RR= 20, 12, dan 8. Tingkat risiko pajanan melalui inhalasi untuk benzene memiliki risiko tinggi sedangkan toluene dan xylene memiliki risiko moderat. Tingkat risiko pajanan melalui inhalasi secara kuantitatif dengan metode CHRA. nilai tingkat risiko pajanan (RR) benzene, toluene dan xylene secara kuantitatif secara berturut-turut adalah RR= 5, 3, dan 2. Berdasarkan metode kuantitatif, nilai tingkat risiko pajanan melalui inhalasi untuk benzene memiliki risiko moderat sedangkan toluene dan xylene memiliki risiko rendah terhadap pekerja di laboratorium pengujian migas PT SCI

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Benzene, toluene, and xylene, commonly known as BTX, are hazardous aromatic organic vapors with high toxicity towards living organisms. Many techniques are being developed to provide the community with portable, cost effective, and high performance BTX sensing devices in order to effectively monitor the quality of air. In this paper, we study the effect of decorating graphene with tin oxide (SnO2) or tungsten oxide (WO3) nanoparticles on its performance as a chemoresistive material for detecting BTX vapors. Transmission electron microscopy and environmental scanning electron microscopy are used as morphological characterization techniques. SnO2-decorated graphene displayed high sensitivity towards benzene, toluene, and xylene with the lowest tested concentrations of 2 ppm, 1.5 ppm, and 0.2 ppm, respectively. In addition, we found that, by employing these nanomaterials, the observed response could provide a unique double signal confirmation to identify the presence of benzene vapors for monitoring occupational exposure in the textiles, painting, and adhesives industries or in fuel stations.

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ObjectivesWhile several monocyclic aromatic hydrocarbons are classified as definite or possible carcinogens to humans, little data exist on their role in prostate cancer (PCa). We examined occupational exposure to benzene, toluene, xylene (BTX) and styrene and PCa risk in a population-based case–control study in Montreal, Canada.MethodsCases aged ≤75 years diagnosed with PCa in 2005–2009 (n=1920) and population controls frequency-matched on age (n=1989) provided detailed work histories. Experts evaluated the certainty, frequency and concentration of exposure to monocyclic aromatic hydrocarbons in each job lasting ≥2 years. Logistic regression estimated OR and 95% CIs for PCa risk, adjusting for potential confounders.ResultsExposures to BTX were highly intercorrelated, except for durations of exposure at substantial levels. Ever exposure to any BTX was associated with overall PCa (OR 1.27, 95% CI 1.05 to 1.53), while the OR for styrene was 1.19. However, increases in risk were largely confined to low-grade tumours, with ORs of 1.33 (95%CI 1.08 to 1.64) and 1.41 (95% CI 0.85 to 2.31) for ever exposure to any BTX and styrene, respectively, and a duration response pattern for any BTX. Risks for low-grade tumours were elevated among men exposed ≥25 years at substantial levels of benzene (OR 2.32) and styrene (OR 2.44). Some cumulative exposure categories showed increased risks but without clear trends.ConclusionExposure to any BTX was associated with higher risks of overall PCa. Prolonged exposures at the substantial level to benzene and styrene increased risks of low-grade tumours. These novel findings were independent from PCa screening.

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Background: Benzene, toluene, and xylene (BTX) are ubiquitous in the community environment. However, workers who handle them are concerned about adverse effects such as neurotoxicity and carcinogenicity. On the other hand, recently, in a general indoor environment, low-concentration BTX exposure due to release from a house has attracted attention as a cause of sick building syndrome and multiple chemical sensitivity. In order to understand the exposure status of BTX, it is effective to measure the unchanged BTX in biological samples such as blood and urine. However, the burden on the subject when collecting samples cannot be ignored. Method: To generalize BTX measurement of biological samples in the field, the author has developed a syringe equilibrium / headspace gas chromatography using a small amount of biological sample and Portable GC and analytical accuracy was tested. Also, considering the case of bringing small samples back to the laboratory for analysis, ways to store biological samples containing BTX for extended periods of time was determined. And BTX contamination survey of newly built condominiums was conducted to verify the practicality. Result: The reproducibility of syringe equilibrium / headspace gas chromatography with standard -added blood. In all BTX, the relative standard deviation was found to be within 10%, and according to the internal standard method, the relative standard deviation was found to be within 5%. BTX contamination survey of newly built condominiums completed successfully. Benzene and toluene were detected in the urine of the resident, but only toluene was detected indoors. Conclusion: This method and the use of a portable GC with a photoionization detector enable assessment from microexposure in the living environment to occupational exposure levels with 50 μl microblood, reducing the burden on the subject. In addition, a long-term storage method of biological samples containing BTX, was developed to consider the case of bringing small samples back to the laboratory for analysis.

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Background. The nonracial leukopenia may be a result of exposure to polycyclic derivatives (benzene-toluene-xylene (BTX)) and may arise from a possible change in the bone marrow microenvironment. The present study sought to evaluate the association of genetic polymorphisms in xenobiotic-metabolizing enzymes with hematological and biochemical profiles.Methods. We evaluated 89 African descendant children, exposed indirectly to benzene derivatives. Laboratory parameters were investigated by automated methods and genetic polymorphisms by PCR-RFLP and PCR multiplex.Results. Children with leukopenia had significantly decreased white blood cells (WBCs) and platelet counts, which is not consistent with benign leukopenia. In the same group, we have found that carriers of theCYP2E1variant allele had decreased WBC and lymphocytes. Those withNQO1variant allele had decreased WBC, neutrophil, eosinophil, monocyte, and lymphocyte counts. Carriers of theMPOvariant allele had decreased WBC, neutrophil, eosinophil, basophil, monocyte, lymphocyte, and platelet counts and an elevated free iron level. Children withGSTTandGSTMnull exhibited decreased WBC, neutrophil, basophil, and lymphocyte counts. Our multivariate analysis model reveals that females were independently associated with leukopenia.Conclusion. Our results suggest that the polymorphisms investigated were associated with hematological changes in the studied population. These alterations could be heightened by exposure to benzene derivatives.

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Hydrocarbons, especially aromatic volatile organic compounds (AVOCs) and polyaromatic hydrocarbons (PAHs), emitted by IC engines, indisputably have a negative impact on the environment and public health. Even though current legislation strongly impacts on their low concentration in the exhausts, not quantity but the quality of those substances determines fumes toxicity. The paper presents results of the researches on a photocatalytic device dedicated to BTX (benzene-toluene-xylene) removal from IC engine exhausts, which can be applied in a vehicle cabin ventilation system. According to the results, the system is able to decrease toxic compounds concentration (caused by mobile emission sources) in inlet-air delivered to the vehicle interior. In effect, the system application reduces the users of a vehicle to exposure on contaminants.

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In this study, hollow fibers of commercial polyimide were arranged into membrane modules to test their capacity and performance towards natural gas processing. Particularly, the membranes were characterized for CO2/CH4 separation with and without exposure to some naturally occurring contaminants of natural gases, namely hydrogen sulfide, dodecane, and the mixture of aromatic hydrocarbons (benzene, toluene, xylene), referred to as BTX. Gas permeation experiments were conducted to assess the changes in the permeability of CO2 and CH4 and related separation selectivity. Compared to the properties determined for the pristine polyimide membranes, all the above pollutants (depending on their concentrations and the ensured contact time with the membrane) affected the permeability of gases, while the impact of various exposures on CO2/CH4 selectivity seemed to be complex and case-specific. Overall, it was found that the minor impurities in the natural gas could have a notable influence and should therefore be considered from an operational stability viewpoint of the membrane separation process.

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With an objective to fabricate Carbon nanotubes (CNTs) based sensors, the solution route is investigated. The dispersion routes are chosen here to avoid the CNTs to form bundles which can reduce their surface area. The results show that SWNTs-based gas sensors made by the surfactant method is possible if the annealing temperature is correctly chosen. The use of a surfactant allows preparing sensing layers which present responses to NO2 exposure in the 50-200 ppb Range. In a second procedure the CNTs are noncovalently functionalized and used as sensing material for BTX (Benzene, Toluene and Xylenes) detection. The noncovalent functionalisation occurs through p-p stacking between the SWNTs framework and the highly delocalized π-system of the macrocycle which are phthalocyanines and porphyrines derivatives. The SWNTs materials are characterized by standard techniques (UV-Vis spectroscopy, TGA, TEM, Raman analysis). For BTX detection, we used a double transduction mode: IDEs (Interdigitated electrodes) and QCM (Quartz Crystal Microbalance) in order to get insight into the sensing mechanism.

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Benzene, toluene, ethyl benzene and xylene (BTEX) are important toxic volatile organic compounds in the air. In a closed working environment, they have various emission sources such as paints, solvents, adhesives and cleaning agents. When they are released into the environment, they quickly mix into the air and can easily enter the body through respiration. It causes acute and chronic health problems in employees. The measurement and analysis results of occupational hygiene laboratories are very important in terms of being a source for the measures to be taken in the workplaces and guiding the necessary improvements. In this study, personal BTEX exposure results entered into the İSG-Katip system between 21 January 2016 and 21 October 2020 by the occupational hygiene laboratories were evaluated according to the sectoral field of activity, geographical region and city where the measurement was made, hazard classes, exceeding the limit value or being close to the limit value. Out of a total of 162331 data, 8435 were found to relate to results for BTEX concentration in air. BTEX data were obtained from 1089 workplaces located in 63 different cities, 11% of which were in the less hazardous, 64.9% of them dangerous and 24.1% of them in the very dangerous classes. It was determined that 5.3% of 6361 personal exposure data were close to or above the limit value. When the data were scanned by sector, the measurements made in 242 fields of activity were gathered under 31 sectors. The three sectors with the most measurement and analysis were determined as machinery and equipment manufacturing, textile products and clothing manufacturing, and rubber and plastic products manufacturing. As a result of the study, it was aimed to evaluate the BTEX exposures on a sectoral basis, to reveal the current situation in our country and to create a resource for those working in the field of occupational health and safety.

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ABSTRACT Enrichment cultures obtained from soil exposed to benzene, toluene, and xylene (BTX) mineralized benzene and toluene but cometabolized only xylene isomers, forming polymeric residues. This observation prompted us to investigate the metabolism of 14C-labeled BTX hydrocarbons in soil, either individually or as mixtures. BTX-supplemented soil was incubated aerobically for up to 4 weeks in a sealed system that automatically replenished any O2consumed. The decrease in solvent vapors and the production of14CO2 were monitored. At the conclusion of each experiment, 14C distribution in solvent-extractable polymers, biomass, and humic material was determined, obtaining14C mass balances of 85 to 98%. BTX compounds were extensively mineralized in soil, regardless of whether they were presented singly or in combinations. No evidence was obtained for the formation of solvent-extractable polymers from xylenes in soil, but14C distribution in biomass (5 to 10%) and humus (12 to 32%) was unusual for all BTX compounds and especially for toluene and the xylenes. The results suggest that catechol intermediates of BTX degradation are preferentially polymerized into the soil humus and that the methyl substituents of the catechols derived from toluene and especially from xylenes enhance this incorporation. In contrast to inhibitory residues formed from xylene cometabolism in culture, the humus-incorporated xylene residues showed no significant toxicity in the Microtox assay.

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The removal of benzene, toluene and p-xylene (BTX) from water is necessary to avoid various health and environmental concerns. Among various techniques, adsorption is suitable and widely used for the removal of BTX from water. In this study, the adsorption of BTX from water was performed using carbon nanotubes that were impregnated with zinc oxide nanoparticles. The impregnation was performed using the wet impregnation technique. The synthesized materials were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) spectroscopy, thermogravimetric analysis (TGA) and nitrogen adsorption–desorption analysis. In batch adsorption experiments, the effect of adsorbent dosage, initial concentration, and contact time were investigated. The percentage removal for a given time and dosage was in the order of p-xylene > toluene > benzene. The kinetics models’ fitting revealed that the pseudo-second-order model fits well the adsorption of benzene, toluene and p-xylene with R2 > 99.4%. The results of adsorption isotherm fitting revealed the best fit with Sips isotherm model (R2 > 99.7%) and the adsorption capacity was p-xylene: 125 mg/g > toluene: 105 mg/g > benzene: 70 mg/g. This behavior is observed probably due to a decrease in solubility and an increase in the molecular weight of BTX.

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Benzene, toluene and xylene (BTX) are an important part of the volatile organic compounds (VOCs) to be detected and monitored in the air, due to their toxicity towards human health. One of the most reliable technique used in BTX detection is gas chromatography (GC), which presents a high sensitivity. On the other hand, it has important drawbacks, such as high costs, the need for qualified personnel and frequent maintenance. To overcome these drawbacks, this work reports the development of a low cost and portable BTX gas detection system based on a mini chromatographic cartridge, a photo ionization detector (PID), a simple control unit (based on Arduino architecture) and a mini pump. In order to separate the BTX components, we propose the use of a cartridge 80 mm in length, composed of several commercial chromatographic column sections. To test the system performances, we have injected different amounts (from about 0.3 to 5.3 µg) of benzene, toluene and xylene and two of the most frequent possible interferents (ethanol, acetone). Experimental results have shown different retention time values (i.e., 25 ± 0.5 s, 51 ± 1.2 s and 117 ± 4 s, respectively) for benzene, toluene and xylene.

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A splitless thermal desorber unit that interfaces a differential mobility spectrometry (DMS) sensor has been devised. This device was characterized by the detection of benzene, toluene, and xylene (BTX) in water. The detection of BTX in water is important for environmental monitoring, and ion mobility measurements are traditionally difficult for hydrocarbons in water because water competes for charge and quenches the hydrocarbon signals. This paper reports the use of a DMS with a photoionization source that is directly coupled to a solid-phase microextraction (SPME) desorber. The separation and detection capabilities of the DMS were demonstrated using BTX components. Detection limits for benzene, toluene, and m-xylene were 75, 50, and 5 μg mL−1, respectively.

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In the present study, the concentrations of three volatile organic compounds (VOCs), namely, acronym for benzene, toluene, and xylenes (BTX) were assessed because of their role in the tropospheric chemistry. Two representative sites, a roadside and a petrol pump, were chosen for sample collection. VOCs were collected using SKC-activated charcoal tubes and SKC personal sampler and characterized by gas chromatograph using flame ionization detector. Among BTX, benzene had the highest concentration. At the roadside, mean concentration of benzene, toluene, o-,m-xylene, and p-xylene were 14.7 ± 2.4 μgm−3, 8.1 ± 1.2 μgm−3, 2.1 ± 0.8 μgm−3, and 5.1 ± 1.2 μgm−3, respectively. At the petrol pump, the mean concentrations of benzene, toluene, o-,m-xylene and p-xylene were 19.5 ± 3.7 μgm−3, 12.9 ± 1.1 μgm−3, 3.6 ± 0.5 μgm−3and 11.1 ± 1.5 μgm−3, respectively, and were numerically higher by a fraction of 2. Monthly variation of BTX showed maximum concentration in winter. Inter-species ratios and inter-species correlation indicated traffic as the major source of BTX. Extracts of samples were positive in both Salmonella typhimurium tester strains TA98 and TA100 without metabolic activation suggesting the presence of direct mutagens in ambient air that can cause both frame-shift and base-pair mutation. The mutagenic response was greater for TA100 than TA98 suggesting greater activity for base-pair mutagenicity than frame-shift mutagenicity and was found to be statistically significant.

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Các hydrocarbon thơm như benzene, toluene và xylene (BTX) là thành phần chính của xăng và là dung môi được sử dụng rộng rãi trong công nghiệp. BTX cũng được xem là những hợp chất ô nhiễm phổ biến đối với nước mặt và nước ngầm. Dòng vi khuẩn Rhodococcus sp. XL6.2 được phân lập từ hệ thống xử lý nước thải có khả năng phân hủy xylene hiệu quả. Kết quả nghiên cứu cho thấy dòng vi khuẩn Rhodococcus sp. XL6.2 cũng có khả năng phân hủy benzene, toluene và hỗn hợp BTX ở các nồng độ khác nhau, trong đó 0,1% (v/v) BTX là nồng độ tối ưu cho sự tăng trưởng của vi khuẩn sau 24 giờ nuôi cấy. Dòng vi khuẩn Rhodococcus sp. XL6.2 có khả năng tăng trưởng và phân hủy hỗn hợp BTX hiệu quả trong môi trường khoáng tối thiểu có bổ sung BTX như là nguồn cung cấp carbon duy nhất ở nồng độ 0,1% (v/v) trong điều kiện pH = 7 - 8 và được thông khí.

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An experimental strategy is introduced for studying the biodegradation of wastewaters containing volatile contaminants using an alternating anoxic/microaerobic sequencing batch reactor (SBR). Benzene, toluene, and the xylene isomers (BTX) served as model volatile contaminants for this study. The reactor was configured to overcome stripping the volatile BTX compounds into the atmosphere to provide opportunities for BTX biodegradation. Oxygen-free anoxic and microaerobic (&lt; 0.2 mg/L dissolved oxygen) conditions were established using a novel laboratory reactor configuration. ORP was successfully used to monitor different electron acceptor conditions in the SBR. Toluene and m-xylene were amenable to anoxic (denitrifying) metabolism while benzene, o-, and p-xylene were biodegradable under microaerobic conditions. The results demonstrate that establishing microaerobic conditions in full-scale bioreactors may be an appropriate way to encourage the biodegradation of aerobically biodegradable volatile contaminants. Additionally, the laboratory reactor configuration introduced in this paper may be useful in subsequent studies involving microaerobic metabolism.

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This study aimed to present the chemical composition of samples of type C gasoline sold in gas stations in the Metropolitan Region of Rio de Janeiro, Brazil. The composition of benzene, toluene and xylene (BTX) were determined by infrared absorption. The results were compared with the specification limits given by the Petroleum, natural gas and biofuel Natioonal Agency, (ANP, No. 309), which specifies a maximum of 1% by volume for benzene, the levels of toluene and xylene are not specified by this agent regulator. The results showed that gasoline sold in some gas stations had benzene levels above the specified limit. In the total levels of toluene, xylene and benzene for samples of gasoline station without a flag were respectively: 2.1 Vol%, 3.4% Vol and 1.0 Vol%. As for the samples of petrol stations with the flag, the average was 2.4% Vol for toluene, 4.0% Vol for xylene and 1.1 Vol% for benzene, indicating a level of action by ANP mainly by the toxic action of benzene.

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Environmental monitoring of a particular locality is very important because it has become a serious threat to human beings.The levels of benzene, toluene and xylene of Rohtak (one of the districts of Haryana) were monitored by Passive sampling method. The air samples collected from six different sites using thermal desorption tube were analyzed by Gas Chromatography (GC) with flame ionization detector (FID). Among all the selected sites, levels of benzene were found maximum at petrol pump as compared to the residential site, traffic intersection and industrial area. During winter season the BTX level was higher (Benzene: 4.3, 16.5, 12.2, 7.6, 22.3 and 15.6 µg/m3, Toluene: 16.3, 56.2, 30.9, 40.8, 55.5 and 50.2 µg/m3, Xylene: 6.3, 9.6, 8.5, 8.9, 9.2 and 8.4 µg/m3) as compared to summer (Benzene: 4.0, 12.6, 8.5, 8.8, 12.3 and 10.8 µg/m3, Toluene: 38.2, 53.1, 39.8, 42.6, 49.6 and 47.2 µg/m3 xylene: 2.3, 8.4, 6.8, 8.0, 7.5 and 5.4 µg/m3) and monsoon (Benzene: 2.3, 7.2, 5.6, 6.0, 7.0 and 7.4 µg/m3, Toluene: 5.0, 24.0, 14.5, 16.3, 24.8 and 24.6 µg/m3, Xylene: 1.8, 6.6, 4.2, 6.3, 6.6 and 6.4 µg/m3) seasons among all the sites. The levels of toluene were observed three times higher (50.2 µg/m3) than the benzene (15.6 µg/m3). The benzene level at petrol pump, industrial area and traffic intersection were observed higher than the standard values.

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Vapors of volatile organic compounds such as benzene, toluene, and xylene (BTX) may cause health concerns. The sensitive detection of these compounds in air remains challenging. In this study, we reported on modification of the Quartz Crystal Microbalance (QCM) sensing chip using polyvinyl acetate (PVAc) film as active coating for the analysis of BTX vapors. The PVAc film was deposited on the QCM sensing chip surface by a spin coating technique. The morphology of the PVAc films was confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensitivities of PVAc based QCM system for benzene, toluene, and xylene analyses were 0.018, 0.041, and 0.081 Hz/ppm, respectively. The high sensitivity of the proposed QCM system for analysis of BTX vapors is believed to be due to the effective interaction between the PVAc film and BTX molecules. The analyte vapor pressure appears to also affect the sensitivity. These data show that the prepared QCM sensor has a low time constant, good reproducibility, and excellent stability. It offers an alternative to the developed methods for detection of BTX and possibly other aromatic hydrocarbons in the air.

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Catalytic pyrolysis of crude glycerol over a shaped H-ZSM-5 zeolite catalyst with (partial) recycling of the product oil was studied with the incentive to improve benzene, toluene, and xylene (BTX) yields.

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To fabricate mass and resistive sensors based on reduced graphene oxide (RGO), we investigated the functionalization of RGO by tetra tert-butyl phthalocyanine (PcH2tBu), which possesses a macroring and tert-butyl peripheral groups. Herein, we present the gas sensor responses of the functionalized RGO toward benzene, toluene, and xylene (BTX) vapors. The RGO was obtained by the reduction of graphene oxide (GO) using citrate as a reducing agent, while the functionalization was achieved non-covalently by simply using ultrasonic and heating treatment. The sensor devices based on both QCM (quartz crystal microbalance) and resistive transducers were used simultaneously to understand the reactivity. Both the GO and the RGO showed less sensitivity to BTX vapors, while the RGO/PcH2tBu presented enhanced sensor responses. These results show that the p-network plays a very important role in targeting BTX vapors. The resistive response analysis allowed us to state that the RGO is a p-type semiconductor and that the interaction is governed by charge transfer, while the QCM response profiles allowed use to determine the differences between the BTX vapors. Among BTX, benzene shows the weakest sensitivity and a reactivity in the higher concentration range (>600 ppm). The toluene and xylene showed linear responses in the range of 100–600 ppm.

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We study the interaction between benzene, toluene, ethylbenzene and xylene (BTEX) molecules with ZnO(100) surface by means of density functional theory-based calculations. We find that these interactions result in the physical adsorptions of BTEX gases with adsorption distances larger than 2 Å. These adsorptions are governed by the van der Waals interaction instead of the covalent interaction. We also find that the trend of the strength of BTX adsorptions on ZnO(100) surface is in line with the experimental trend of sensitivity of ZnO material towards BTX gases (benzene < tolune < xylene). We explain this relation by using one of the sensing mechanism within the ionosorption model. By using this relation, we also predict that the response of ZnO towards ethylbenzene will be similar to the response towards toluene since these two molecules have similar adsorption energies on ZnO(100) surface.

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AbstractA less common cyclic process of decontamination of benzene, toluene and o-xylene (BTX) using a dual function adsorbent-catalyst, referred to as the temperature swing oxidation, is introduced and discussed in this research. Preparation technique and characterization of the dual function adsorbent-catalyst CuO-CeO2/NaX are presented. The temperature swing oxidation of BTX consists of two stages: adsorption of the VOC from the stream saturating the adsorbent-catalyst at different levels and catalytic oxidation of concentrated VOC induced by raising bed temperature at different flow rates of regenerative air. The results indicate that at lower saturation levels and lower flow rates of regenerative air a complete oxidation performance is better. The highest obtained values of the overall conversion of toluene, o-xylene and benzene into CO2 and H2O were 99.3, 99.8 and 77.5%, respectively, proving that the temperature swing oxidation using a dual function adsorbent-catalyst is a promising VOC decontamination technique under properly selected operating conditions.

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Abstract A novel strategy for the degradation of high gaseous hourly space velocity benzene, toluene, and xylene (BTX) by double dielectric barrier discharge (DDBD) coupled with Mn3O4/ activated carbon fiber (ACF) catalysts was proposed in this work. A series of Mn3O4/ACF catalysts were synthesized using the hydrothermal method and characterized. The results showed that all the prepared catalysts could improve the degradation of BTX in the DDBD system and inhibit the production of ozone. Among the catalysts with different Mn loading, the 5.6%Mn3O4/ACF, with the highest Mn(+3) content (43.2%) and the highest absorbed oxygen content (38.5%), presented the best catalytic performance. In the 5.6% Mn3O4/ACF + DDBD system, the degradation efficiency of benzene, toluene and xylene could reach 49.9%, 79.7% and 97.1%, respectively, with a specific input energy of 400 J l−1. The carbon balance and CO2 selectivity, meanwhile, were 83.3% and 51.1%, respectively. It seemed that Mn(+3) and absorbed oxygen content could be a reference for the catalytic performance of Mn3O4/ACF catalysts. The higher the Mn (III) and absorbed oxygen, the better the catalytic performance of the Mn3O4/ACF catalysts. The organic by-products were identified by chromatography-mass spectrometry, and a possible reaction mechanism of BTX in the DDBD reactor and catalyst surface was proposed based on the composition of organic by-products.

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Health effects of benzene, toluene and xylene emissions from a Nigerian Petroleum Products depot make stringent adherence to maximum allowable concentration very important. The storage facilities and distribution network and other installations of petroleum products depot are significant sources of benzene, toluene and xylene therefore ambient air of the depot requires observation and assessment. The ambient air concentrations of BTX were been measured within Pipelines and Product Marketing Company, Mosimi Depot and its immediate environment. Air samples were collected on granular activated charcoal through low volume air sampler and extracted with carbon disulphide (CS2) by desorption process.The extracted solutions were subjected to Flame Ionization Detection analysis in a gas chromatograph (Model: HP 6890) using a capillary column HP 5MS with length, inner diameter and particle size set at 30 m × 0.25 mm × 0.25 μm. The gas chromatograph was powered with chemstation RevA09.01 [1206] software to determine the concentrations of each of the identified VOCs species. The concentrations of benzene, toluene, p xylene, m xylene and o xylene ranged between 0.0104 - 0.0711, 0.0019 - 0.0998, 0.0010 - 0.0022, 0.0014 - 0.0026 and 0.0006 0.0019 mg/m3 respectively. The mean values were 0.0277, 0.0389, 0.0013, 0.0019 and 0.00010 mg/m3, respectively. On the average, the observed concentrations did not exceed the tolerance (air concentrations) limits set for Nigeria environment by the National Environmental Standards and Regulations Enforcement Agency (NESREA).

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In this study, UiO-66 was selected as sorbent media packed in the tube to selectively enrich trace levels of benzene hom*ologues such as benzene, toluene, and xylene (BTX) in ambient air prior to thermal desorption (TD)-GC-MS determination. A series of experiments were conducted to obtain the optimal TD conditions. The results indicated that the optimal TD parameters were as follows: desorption temperature of 180°C, desorption flow rate of 50 mL min−1, and desorption time of 30 min. Furthermore, the method based on UiO-66 enrichment integrated with TD-GC-MS for trace levels of BTX was successfully developed. It exhibited a good linearity (R2 > 0.99) in the range of 50–1000 ng, except for p, m-xylene in the range of 100–2000 ng, and achieved the recovery of 69.4–101.3%, and the relative standard deviation of 3.8–6.4%. The detection limits of BTX were 1.6–4.0 ng; according to 10 L of sampling volume, the method detection limits would be in the range of 0.16–0.40 µg m−3. Additionally, the method was successfully applied to determine BTX in indoor air and showed good selectivity and sensitivity. In summary, the findings in this work revealed that UiO-66 was an attractive adsorbent for selective enrichment trace levels of BTX compounds in ambient air, which was favorable for the subsequent detection by TD-GC-MS.

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The study was conducted to assess the health risks of workers due to exposure to toxic gases including benzene, toluene, ethylbenzene, m, p-xylene, o-xylene, formaldehyde and acetaldehyde at gasoline retail stations. In this study, data on the concentrations of the toxic gases were collected from the previously published studies in the qualified scientific journals. The health risk assessment was followed by the process of the United States Environment Protection Agency (U.S. EPA). The results show that the concentrations of benzene, toluene, ethylbenzene, m, p-xylene, o-xylene, formaldehyde, and acetaldehyde were in the range of 12.40 - 357.5, 12.47 - 574.17, 2.05 - 156.5, 4.57 - 218, 2.36 - 77.04, 3.64 - 153.93 and 1.27- 27.83 µg/m3 , respectively. Life time cancer risk for gasoline station workers due to exposure to benzene, ethylbenzene, formaldehyde, and acetaldehyde was calculated in the ranges of 2.13x10-5 - 6.14x10-4 , 4.96x10-7 - 3.79x10-5 , 4.81x10-6 - 2.03x10-4 , and 7.99x10-7 - 1.75x10-5 , respectively. For non-carcinogenic compounds, the hazard index due to benzene, toluene, m, p-xylene, o-xylene were respectively in the range of 0.13 - 3.81, 7.97x10-4 - 0.04, 0.01 - 0.70 and 0.01 - 0.25. The findings revealed that there is high risk of cancer and non-cancer for the workers working at the gasolines stations if they are not taking good preventive measures. The calculation showed that the limit levels of benzene, toluene, ethylbenzene, xylene, formaldehyde and acetaldehyde should be reduced to 5.82x10-4 , 15.64, 4.13x10- 3 , 0.31, 7.57x10-4 and 1.59x10-3 mg/m3 , respectively to meet the safety levels for the workers at the gasoline stations. Keywords: benzene, toluene, ethylbenzene, xylene, formaldehyde, acetaldehyde, life-time cancer risk, health

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The presence of benzene and similar aromatic compounds in civil environments is due to anthropic actions but also to natural sources. Natural gas consists of a gas mixture where benzene and related compounds are usually presents. Thus, the detection of these compounds in natural gas pipelines is of the utmost importance as well as the control of the concentration level, which must remain below the limits consented by law. In this regard, it is of striking interest to engineer devices able to detect these compounds by automatic and continuous remote control. Here, we discuss the application of an optical device designed for the measurement of sulfured odorizing agents in natural gas pipelines aiming at the detection and the measurement of benzene, toluene, and xylenes (BTX) in the same contexts. The instrument consists of a customized UV spectrophotometer connected to an automatic control system able to provide in-field detections of BTX through a continuous and remote check of the gaseous mixture. Relatively to benzene, the instrument is characterized by values of LOD (level of detection) and LOQ (level of quantification) equal to 0.55 and 1.84 mg/Sm3, respectively. Similar limits are found for toluene and xylenes (LOD of 0.81, 1.05, 1.41, and 1.00 mg/Sm3 for toluene, meta-, ortho-, and para-xylene, respectively).

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Acid-activated montmorillonite (smectite) clay was used to eliminate olefins and transform thiophenes and mercaptans present in aromatic BTX (benzene-toluene-xylene) streams from the aromatic extraction unit of COPESUL - Companhia Petroqufmica do Sul. The working temperature of the mineral clay was raised above normally specified values since difficulties were encountered to meet the specification for hydrogen sulfide in xylene and trimethylbenzene. The experimental results showed that montmorillonite (smectite) clay was suitable for olefin elimination and sulfur compounds transformation at higher reaction temperatures (200 °C) and that the useful life for catalytic operations could be prolonged by raising the temperature.

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<p>Efek negatif dari polusi udara terhadap kesehatan manusia banyak diteliti termasuk polusi akibat sistem transportasi. Emisi kendaraan bermotor menghasilkan Benzena, Toluena dan Xylena (BTX) yang merupakan bahan kimia yang bersifat karsinogenik dan petugas pintu tol merupakan kelompok berisiko terpajan BTX. Penelitian bertujuan mengetahui risiko kesehatan akibat pajanan BTX pada petugas pintu tol. Desain penelitian adalah <em>cross-sectional</em> dengan pendekatan Analisis Risiko Kesehatan Lingkungan (ARKL) dan faktor-faktor antropometri. Hasil penelitian menunjukkan pada pintu tol rata-rata konsentrasi (mean<span style="text-decoration: underline;">+</span>SD) benzena sebesar 0,00167<span style="text-decoration: underline;">+</span>0,000056 mg/m³, toluena sebesar 0,00124<span style="text-decoration: underline;">+</span>0.000049 mg/m³ dan xylena sebesar 0,00147<span style="text-decoration: underline;">+</span>0,000063 mg/m³ sedangkan pada kantor administrasi konsentrasi tidak terdeteksi oleh alat (<em>Method Detection Limit</em>). Rata-rata risiko non karsinogenik (RQ) BTX pada petugas pintu tol lebih tinggi secara signifikan dibandingkan dengan rata-rata RQ BTX petugas administrasi. Risiko kesehatan non karsinogenik dan karsinogenik belum menunjukkan adanya risiko kesehatan yang signifikan. Upaya pencegahan berupa pengelolaan manajemen risiko untuk pengendalian risiko bahan berbahaya di lingkungan perlu ditingkatkan.</p><p> </p><p><strong>Kata Kunci:</strong> Pintu Tol, Benzena, Toulena, Xylena</p><p> </p><p>The researches of BTX (Benzene, Toluene and Xylene) related to the health impacts have been done and published in any publications. One of the risk groups is toll gate’s workers who have been exposed every day with BTX. The design of this study is cross-sectional with Environmental Health Risk Analysis to determine the magnitude of health risks of BTX on the toll gate. The results showed at the toll workers’s respondents have benzene concentration 0.00167+0.000056 mg/m³, toluene 0.00124+0.000049 mg/m³ and xylene 0.00147+0,000063 mg/m³ respectively, while in the administrative office’s respondents, BTX was undetectable (Minimum Detection Limit). The average RQ of toll gate respondents was significantly higher than administrative office’s respondents. In conclusion, the risk of all workers have the RQ ≤ 1. Non carcinogenic and carcinogenic health risks to all toll gate’s workers recently have not shown any risk yet. Nevertheless, risk management system should be developed and improved.</p><p> </p><p><strong>Keywords</strong>: Toll Gate, Benzene, Toulene, Xylene</p>

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Benzene, toluene và xylene (BTX) là thành phần chính của xăng và là dung môi được sử dụng rộng rãi trong công nghiệp. Do có khả năng hòa tan trong nước nên BTX cũng được xem là một trong những hợp chất gây ô nhiễm nước phổ biến. Dòng vi khuẩn Rhodococcus sp. XL6.2 được phân lập từ hệ thống xử lý nước thải phòng thí nghiệm có khả năng phân hủy hiệu quả BTX. Nghiên cứu này được thực hiện nhằm tìm chất mang phù hợp để tồn trữ vi khuẩn Rhodococcus sp. XL6.2 làm cơ sở cho việc sản xuất chế phẩm sinh học xử lý BTX trong nước thải. Sáu loại vật liệu làm chất mang gồm bã mía, mạt cưa, cám, rơm, bột talc và bã cà phê được sử dụng riêng lẻ hoặc phối trộn để tạo 11 chất mang. Kết quả đếm sống và phân tích sắc ký khí GC-FID cho thấy bột talc duy trì mật số (>106 CFU/g) và khả năng phân hủy BTX của vi khuẩn Rhodococcus sp. XL6.2 (>92%) trong 6 tháng tồn trữ. Vitamin B12 được bổ sung giúp vi khuẩn đạt mật số cao hơn so với nghiệm thức đối chứng.

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Abstract In this work, a natural zeolite, modified and loaded with iron (NZ-A-Fe) as a heterogeneous catalyst, was characterized for its suitability as a permeable reactive barrier (PRB) material for treatment of aromatic hydrocarbons in groundwater. Adsorption and oxidation processes were analyzed. Batch adsorption tests for benzene, toluene and xylene (BTX) aqueous concentrated solutions were performed at neutral pH. Kinetic adsorption was described with the pseudo-second-order model. Experiments were performed using a stirred batch reactor with near 11 mM initial BTX concentration applying NZ-A-Fe as solid catalyst and H2O2 as an oxidant. BTX removal reached 80% in 600 min in these experimental conditions. Catalytic oxidation was described with a pseudo-first-order kinetic model. No significant iron leaching was detected during all the experiences. These investigations show that coupling adsorption with catalytic oxidation with this novel system is a promising procedure to simultaneously remove BTX from moderately concentrated aqueous solution at neutral pH in groundwater.

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Benzene, toluene and xylene (BTX) are relatively soluble aromatic compounds of gasoline. Gasoline storage tank leakages generally lead to an extensive contamination of groundwater. In the natural environment for instance, these compounds might be biodegraded under a variety of reducing potentials. The objective of this work was to examine the influence of the addition of sulphate and Fe(OH)3 in a methanogenic horizontal-flow anaerobic immobilized-biomass reactor treating gasoline-contaminated water. Three different conditions were evaluated: methanogenic, sulphidogenic and sulphidogenic with the addition of ferric ions. Methanogenic condition showed the higher BTX degradation rates and the addition of sulphate negatively affected BTX removal rates with the production of H2S. However, the addition of ferric ions resulted in the precipitation of sulphur, improving BTX degradation by the consortium. Metanosphaera sp., Methanosarcina barkeri and Methanosaeta concilii were identified in the consortium by means of 16S and directly related to the addition of ferric ions.

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Anthropogenic activities are largely responsible for the vast amounts of pollutants such as polycyclic aromatic hydrocarbons, cyanides, phenols, metal derivatives, sulphides, and other chemicals in wastewater. The excess benzene, toluene and xylene (BTX) can cause severe toxicity to living organisms in wastewater. A novel approach to mitigate this problem is the benthic microbial fuel cell (BMFC) setup to produce renewable energy and bio-remediate wastewater aromatic hydrocarbons. Several mechanisms of electrogens have been utilized for the bioremediation of BTX through BMFCs. In the future, BMFCs may be significant for chemical and petrochemical industry wastewater treatment. The distinct factors are considered to evaluate the performance of BMFCs, such as pollutant removal efficiency, power density, and current density, which are discussed by using operating parameters such as, pH, temperature and internal resistance. To further upgrade the BMFC technology, this review summarizes prototype electrode materials, the bioremediation of BTX, and their applications.

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A D-grade type coal was burned under simulated domestic practices in a controlled laboratory set-up, in order to characterize the emissions of volatile organic compounds (VOCs); namely, benzene, toluene, ethylbenzene, and xylenes (BTEX). Near-field concentrations were collected in a shack-like structure constructed using corrugated iron, simulating a traditional house found in informal settlements in South Africa (SA). Measurements were carried out using the Synspec Spectras GC955 real-time monitor over a three-hour burn cycle. The 3-h average concentrations (in µg/m3) of benzene, toluene, ethylbenzene, p-xylene, and o-xylene were 919 ± 44, 2051 ± 91, 3838 ±19, 4245 ± 41 and 3576 ± 49, respectively. The cancer risk for adult males and females in a typical SA household exposure scenario was found to be 1.1 and 1.2 respectively, which are 110- and 120-fold higher than the U.S. Environmental Protection Agency (EPA) designated risk severity indicator (1 × 10−6). All four TEX (toluene, ethylbenzene, p-xylene and o-xylene) compounds recorded a Hazard Quotient (HQ) of less than 1, indicating a low risk of developing related non-carcinogenic health effects. The HQ for TEX ranged from 0.001 to 0.05, with toluene concentrations being the lowest, and ethylbenzene the highest. This study has demonstrated that domestic coal burning may be a significant source of BTEX emission exposure.

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The adsorption of benzene, toluene and xylene (BTX) was investigated covering different types of commercially available activated carbons with varied surface area and surface functional groups. The physico-chemical properties were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy and the Boehm titration method. Experiments to assess the adsorption isotherms and kinetics of adsorption were performed and the results are presented. An increase in the surface acid functional groups was found to decrease the adsorption capacity, with the highest adsorption capacity corresponding to carbon with lowest acid functionality.

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The hydrocracking reaction of a pyrolysis fuel oil fraction using in situ generated nano-sized NiWS-sulfide catalysts is studied. The obtained catalysts were defined using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The features of catalytically active phase generation, as well as its structure and morphology were considered. The catalytic reactivity of in situ generated catalysts was evaluated using the hydrocracking reaction of pyrolysis fuel oil to obtain a light fraction to be used as a feedstock for benzene, toluene, and xylene (BTX) production. It was demonstrated that the temperature of 380 °C, pressure of 5 MPa, and catalyst-to-feedstock ratio of 4% provide for a target fraction (IPB −180 °C) yield of 44 wt %, and the BTX yield of reaching 15 wt %.

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