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PM2.5 samples were collected in Suncheon during the summer (June 2–11, 2023) and winter (January 15–21, 2024). The chemical composition analysis included carbonaceous components (OC, EC), secondary ionic components (NH4+, NO3−, SO42−), dithiothreitol - oxidative potential (QDTT-OP), and volatile organic compounds. Results showed higher summer PM2.5 concentrations due to photochemical reactions and higher winter concentrations from heating and stable atmospheric conditions. The OC/EC ratio indicated greater secondary organic aerosol formation in summer. Oxidative potential (QDTT-OPv) was higher in summer (0.12 µM/m³) than winter (0.09 µM/m³), correlating strongly with OC in summer. Health risk assessment of BTEX revealed higher concentrations in winter, with benzene as the primary contributor to lifetime cancer risk (LTCR). The cumulative hazard quotient (HQ) was higher in winter, indicating increased non-carcinogenic risk. The study highlighted that oxidative potential is more influenced by chemical composition than physical characteristics, suggesting that regulating PM2.5 concentration alone may be insufficient. VOCs, as precursors of SOA, showed a positive correlation with QDTT-OPv, with benzene exhibiting the strongest correlation in winter. These findings emphasize the need for targeted management of specific PM2.5 components to mitigate health risks effectively. [ABSTRACT FROM AUTHOR]

Long-term exposure to Volatile Organic Compounds (VOCs) is a health risk for citizens. In this study, the cumulative health risk of exposure to VOCs in Tehran was assessed by investigating the concentration of these pollutants in ambient air in a five-year period. Health risk assessment was calculated by the quantitative method and the carcinogenic risk level was determined using the lifetime carcinogenic risk (LCR) method. The average concentration of benzene, toluene, ortho-xylene, and ethylbenzene was 1.4–1.8, 4.8–5.4, 5–6.5, and 3.6–4 ppb, respectively. Although HQ was not greater than 1, but it was very close in the case of benzene, ortho-xylene, meta-xylene, and para-xylene. Benzene and ethylbenzene had the largest effect in the assessed health risk. So the long-term exposure of Tehran citizens to VOCs has serious health consequences for them, which could be different according to the exposure time and spatial variations. [ABSTRACT FROM AUTHOR]

Rajasthan, experiencing rapid industrialization and urbanization, faces critical air quality challenges, particularly concerning toxic volatile organic compounds (VOCs) such as BTEX (Benzene, Toluene, Ethylbenzene, Xylene). This study presents a long-term analysis of BTEX concentrations across various cities in Rajasthan, India, using data from the Central Pollution Control Board (CPCB) from 2017 to 2022. The findings revealed that the average ∑BTEX concentrations increased from 4.15 µg/m3 in 2017 to 12.29 µg/m3 in 2022, with a temporary decline in 2020. The Hazard Quotient (HQ) values for BTEX exposure ranged from 0.052 to 0.15 for males, 0.056 to 0.17 for females, and 0.09 to 0.29 for children over the study period, indicating higher health risks for children. Similarly, the Lifetime Cancer Risk (LCR) values varied from 6.04 × 10⁻⁶ to 1.92 × 10⁻5 for males, 1.09 × 10⁻⁶ to 2.24 × 10⁻5 for females, and 1.17 × 10⁻5 to 3.73 × 10⁻5 for children. The results demonstrate that children are at a greater cancer risk from BTEX exposure compared to adults. This study emphasizes the urgent need for effective air pollution control measures and continuous monitoring to protect public health, particularly vulnerable populations like children. [ABSTRACT FROM AUTHOR]

The presence of BTEX (Benzene, Toluene, Ethylbenzene, and Xylene) compounds in beauty salons has raised concerns about potential health risks. This study aimed to measure the levels of BTEX compounds in the air of beauty salons in Lahijan, Iran and assess the associated health risks. Air samples were collected from 15 beauty salons, and the concentrations of BTEX compounds were measured according to 1501 NIOSH standard method. The results showed that the mean concentrations of benzene (20.62 µg/m3), toluene (18.3 µg/m3), ethylbenzene (38.36 µg/m3), and O and P-xylene (27.35, 23.6 µg/m3) were above the recommended levels. The indoor to outdoor ratios for benzene, toluene, ethylbenzene, O and P-xylene were 3.04, 2.36, 3.75, 4.89, and 6.54, respectively. Also, the toluene/benzene (T/B) ratio in indoor and outdoor was 20.9 and 2.68 respectively. Almost half of the technicians (49.12%) reported adverse health effects, including joint pain, itchy eyes and nose, and respiratory allergies. The IARC guideline suggests that there is a potential risk of cancer development for individuals in all salons with LCR values exceeding 10−6, but the HQ index values indicate no non-carcinogenic risk. The findings suggest that beauty salon workers and customers are at risk of developing health problems from exposure to BTEX compounds. Effective risk management strategies, such as proper ventilation, use of personal protective equipment, and substitution of harmful chemicals with safer alternatives, to minimize exposure and protect the health of salon workers and customers recommended. [ABSTRACT FROM AUTHOR]

This study put forward Melaleuca cajuputi leaves to prepare activated carbon using H3PO4 as an activating agent and examined the aqueous solution of benzene, toluene, ethylbenzene and xylene (BTEX). The surface functional group, surface morphology, and surface area were identified by employing Fourier transform infrared spectra, field emission scanning microscopy, and Brunauer-Emmett-Teller to characterize the properties of the produced activated carbon; others include pH, moisture content, and yield percentage. The activated carbon’s performance was assessed using batch adsorption experiment. 50 mg/L of BTEX disintegrates in purified water to form the standard solution and is stored at 4 °C. The study examined the effects of time spent in contact, dosage of the adsorbent and initial concentration. The results show that Melaleuca cajuputi activated carbon (MCAC2) has the optimum surface area 128 m²/g and performs very effectively as a BTEX adsorbent. According to the BTEX adsorption data, MCAC2 has 94% elimination effectiveness at 50 mg/L after 30 min of contact. To further adapt the experimental information for BTEX adsorption onto the MCAC2, Freundlich, Langmuir, and pseudo-first-order and pseudo-second-order models were used. The findings fitted pseudo-second-order with optimal values of R² = 0.979, and the isotherm model adsorption fitted Langmuir model with values of R² = 0.992 The finding reveals that Melaleuca cajuputi leaves are useful material for producing adsorbents, and successful testing outcomes demonstrate that M. cajuputi leaves products serves as a vital organic absorbent in the decomposition of BTEX. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the presence of benzene in the ground and drinking water in the eastern Niger Delta, where multiple oil and gas production facilities are present. Samples from drinking water wells were collected for measurements of benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, the dissolved organic carbon (DOC) concentration was determined for the first time to establish the groundwater's total hydrocarbon and non-hydrocarbon load. The groundwater BTEX and benzene levels were up to 3904 µg/L and 3500 µg/L, respectively. DOC concentrations were up to 49 mg/L. The highest benzene concentrations were detected in wells near an underground petroleum pipeline. However, the concentrations decreased with distance from the pipeline to levels less than 0.1 µg/L. Despite benzene contamination, the aquifer has shown promising aerobic attenuation potential, having up to a 7.5 (95%) mg/L DO level and 2.11 mg/L BTEX biodegradation capacity for DO. However, the high groundwater temperature of up to 32.5 °C may weaken attenuation. The benzene and BTEX point attenuation rates ranged from 0.128 to 0.693 day−1 and 0.086 to 0.556 day−1, respectively. Hence, by natural attenuation alone, up to 66.5 and 85 years would be required to reach Nigeria's groundwater benzene and BTEX remediation goals, respectively. [ABSTRACT FROM AUTHOR]

Abstract The presence of BTEX (Benzene, Toluene, Ethylbenzene, and Xylene) compounds in beauty salons has raised concerns about potential health risks. This study aimed to measure the levels of BTEX compounds in the air of beauty salons in Lahijan, Iran and assess the associated health risks. Air samples were collected from 15 beauty salons, and the concentrations of BTEX compounds were measured according to 1501 NIOSH standard method. The results showed that the mean concentrations of benzene (20.62 µg/m3), toluene (18.3 µg/m3), ethylbenzene (38.36 µg/m3), and O and P-xylene (27.35, 23.6 µg/m3) were above the recommended levels. The indoor to outdoor ratios for benzene, toluene, ethylbenzene, O and P-xylene were 3.04, 2.36, 3.75, 4.89, and 6.54, respectively. Also, the toluene/benzene (T/B) ratio in indoor and outdoor was 20.9 and 2.68 respectively. Almost half of the technicians (49.12%) reported adverse health effects, including joint pain, itchy eyes and nose, and respiratory allergies. The IARC guideline suggests that there is a potential risk of cancer development for individuals in all salons with LCR values exceeding 10−6, but the HQ index values indicate no non-carcinogenic risk. The findings suggest that beauty salon workers and customers are at risk of developing health problems from exposure to BTEX compounds. Effective risk management strategies, such as proper ventilation, use of personal protective equipment, and substitution of harmful chemicals with safer alternatives, to minimize exposure and protect the health of salon workers and customers recommended.

Fuel oil is widely used within Eskom, a power generation company in South Africa. Eskom's coal-fired power stations use up to 30,000 L of fuel oil per hour during a cold start-up, a consequence of which results in oil leaks to the dams. Oil contamination in water treatment plants causes irreversible membrane fouling, requiring costly replacement. This research work focused on the development of a rapid method for the identification of low concentrations of the water-soluble oil component fraction of crude fuel oil. For the developed method, known volumes of the water-soluble fraction of crude oil were spiked into various matrices of process water. FEEMs were collected using the patented HORIBA Aqualog spectrometer and data were modelled with PARAFAC. The results were well described with a four-component model, which included an oil component and three natural organic matter components, with a split-half validation match of 90%. The oil component was verified using linear regression of the PARAFAC component scores yielding an R2 value of 0.98. From the scores, a qualitative pass/fail test was developed such that process water can be analysed and subjected to the model to indicate the presence of oil contamination beyond a damaging threshold. HIGHLIGHTS Development of model using FEEM and PARAFAC for identification of low concentration (ppb) of oil contamination in process water.; PARAFAC Split-Half model for verification of the developed oil identification model was 90%.;

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters. [ABSTRACT FROM AUTHOR]

The widespread use of petroleum-based fuels poses a significant environmental problem due to the risks associated with accidental spills. Among the treatments available, phytoremediation is increasingly accepted as an effective and low-cost solution. This study aimed to evaluate the degradation of the aromatic fraction of biodiesel B10 and the soil fertility analysis in artificially contaminated soils treated with phytoremediation. The experimental design consisted of a 3x3 factorial, with three types of soil treatment: control, autoclaved, and planted with C. ensiformis L, and three levels of B10 biodiesel contamination: 0, 1, and 2%, to simulate spills of 30,000 and 60,000 L ha−1. The soil was analyzed at three depths: 0–10, 10–20, and 20–30 cm. The results indicated that aromatic compound degradation after phytoremediation was superior to 92,76% and 88,65% for 1% and 2% B10 soil contamination, respectively. The fuel contamination affected soil fertility, reducing the availability of phosphorus and zinc while increasing the Total Organic Carbon (TOC), pH, and the availability of manganese and iron for plants. NOVELTY STATEMENT: Numerous studies have been carried out on the phytoremediation of soils contaminated with diesel. However, the potential impact of biodiesel-diesel blends on soil fertility has not been fully explored, leading to a critical knowledge gap. This work investigates the novel effects of biodiesel-diesel blends on phytoremediation and soil fertility, allowing us to expand our understanding of the effectiveness of this approach to remediate contaminated sites. [ABSTRACT FROM AUTHOR]

The purpose of this review study was to assess the risk of exposure to BTEX compounds in gas station workers and operators. The main components of BTEX compounds are Benzene, Toluene, Ethyl benzene and Xylene. Petroleum, coal large quantities in crude oil and its products are the most important sources of BTEX compounds. These compounds have both high solubility (found in surface and underground waters) and evaporate quickly. Gas stations are one of the most important sources of emission of these compounds in communities. Workers who work in these places have a lot of exposure to these compounds. Exposure to these dangerous compounds can cause many problems for workers. This study was a narrative review article. According to different databases: PubMed, Web of Science, Springer, Cochran and Science Direct, 451 articles were retrieved. 55 full-text articles entered into the analysis process. Finally, 32 articles were selected in this study. The search was restricted to English-language papers published between 1 February 1995 and 13 August 2022. The results of our study showed that the carcinogenic risk (ILCR) for gas station workers in Bangkok (1.82 ∗ 10−4 − 2.50 ∗ 10−4), Shiraz (6.49∗10−7 − 1.27 ∗ 10−5), Brazil (1.82 ∗ 10−4), Ardabil (390∗10−6 ± 1884 ∗ 10−6) and Johannesburg (3.78 ∗ 10−4) was high. The non-cancer risk for oil industry workers of Dilijan (Iran) who were exposed to toluene was also reported in the range of 10−6∗176. The health of gas station workers is affected by exposure to BTEX and gasoline vapor emissions. According to the result this study, BTEX compounds cause genotoxic changes, chromosomal and genetic abnormalities. Genotoxicity at high levels in gas station workers can cause cancerous and non-cancerous risks. Improving the production process of diesel fuel and gasoline in refineries, using periodical examinations of workers and operators at gas and fuel stations, using Euro 4 and 5 fuels, and replacing worn out cars can play an important role in reducing the emission of BTEX compounds and thus reducing health risks and carcinogenic. [ABSTRACT FROM AUTHOR]

While do-it-yourself (DIY) air cleaners such as the Corsi-Rosenthal Box (CR Box) are an increasingly popular choice for low-cost, accessible air cleaning during a wildfire event, construction and performance variability remains a concern. Using the same set of instructions, materials, and location of assembly, seven CR Boxes are constructed by individuals with no prior DIY air cleaner experience and clean air delivery rates (CADRs) are experimentally determined for each of the devices. Against a challenge aerosol consisting of fresh smoke generated via pine needle combustion, average number-based, PM2.5 CR Box CADRs range from 313–396 m3/h (relative standard deviation = 7.6 %). Over this modest range of observed variability, constructed units outperform many higher-cost commercial air cleaners. A review of the literature demonstrates that across studies, substantial CADR variability is observed (285–1448 m3/h); differences in materials (including filter type) used during air cleaner construction, challenge aerosols tested, and evaluation protocol are major contributors to variability. To evaluate the potential for exposure to aromatic volatile organic compounds (VOCs) from CR Box materials, we place three devices in a large chamber for 24–72 hours immediately following construction. Toluene and C8 aromatics (ethylbenzene and xylenes) are emitted at 2289 and 89 μg/h, respectively, with emission rates decreasing by 94 % and 82 % after 12 hours. Using experimentally determined PM2.5 CADRs and VOC emission rates, a hypothetical wildfire event impacting the bedroom of a home is modeled at four outdoor air exchange rates (AERs) to assess tradeoffs between building airtightness, particle removal effectiveness, and VOC off-gassing from a newly built CR Box. PM2.5 effectiveness ranges from 0.88 to 0.95, depending on AER (0.1–1 h−1). While modeled maximum VOC concentrations remain orders of magnitude below short-term permissible exposure limits at all AERs considered, modeled and observed VOC dynamics imply that an off-gassing period of ∼6–12 hours would avoid episodic emission of VOCs at rates that may cause accumulation in excess of the lower-limit of toluene odor threshold estimates.

Benzene, toluene, ethylbenzene and xylenes, collectively known as BTEX compounds, are significant emerging contaminants in municipal wastewater. Stricter effluent quality regulations necessitate their removal, especially with concerns about organic micropollutant concentrations. Water scarcity further underscores the need for wastewater treatment to ensure safe agricultural or drinking water supplies. Although biological treatment partially reduces BTEX levels through processes like biodegradation and sorption, additional purification using physico-chemical methods is crucial for substantial reduction. This paper aims to outline plant-wide simulation methods for treating BTEX-contaminated sewage and facilitating reuse, adhering to IWA Good Modelling Practice Guidelines. The model, built upon the MiniSumo process model, incorporates equations detailing BTEX metabolism and removal kinetics, informed by an extensive literature review. Using a variant of the Benchmark Simulation Model with granular activated carbon for water reuse, the study examines strategies for improving effluent quality and minimizing operational costs. These strategies include adjusting the sludge retention time and airflow to enhance BTEX degradation and stripping, respectively, and comparing maintenance approaches for the GAC tower. [ABSTRACT FROM AUTHOR]

Bioremediation is an economically viable and sustainable clean-up strategy. Hydrodynamic, as well as transport characteristics of the porous medium, can evolve over the period as a result of biological clean-up activities. The present study proposes a 2-D numerical framework to simulate the effect of bioclogging on multiple electron acceptor–mediated petroleum hydrocarbon bioremediation in the vadose zone. For modelling, a spill of BTEX (benzene, toluene, ethylbenzene and xylene) is assumed near source zone. The developed model results are validated using three previously published datasets on flow, transport and biodegradation in the vadose zone. Simulations are performed for three types of soil, including clay, sand and loam. The analysis shows that sand has a maximum infiltration rate and clay has a minimum. Hydraulic conductivity and saturation profile peaks reach their minimal value at a shallower depth (around four times) when bioclogging is present compared to when it is absent. The migration depth and concentration of BTEX are observed to be restricted to a shallower depth in aquifers with the presence of microbial clogging. The outcome shows that electron acceptor consumption is more (around sevenfold for oxygen, fourfold for nitrate and threefold for sulphate) in the presence of bioclogging at the shallower zone. Zeroth order spatial moment and sensitivity analyses show that biological clogging, number of electron acceptors and inhibition constant substantially affect BTEX bioremediation in the vadose zone. [ABSTRACT FROM AUTHOR]

This study assessed the cleaner and sustainable environment by measuring emission levels of benzene, toluene, ethylbenzene, and xylene (BTEX) from informal food traders using charcoal as the primary source of energy at a flea market in Fordsburg, Johannesburg. Volatile organic compounds (VOCs) were measured using a real-time monitor (MiniRae 3000 photoionization detector); an indoor air quality (IAQ) monitor was used to monitor environmental parameters and passive samplers in the form of Radiello badges, which were used to determine BTEX emissions from charcoal used during food preparation. Measurements were taken at 1.5 m above ground assuming the receptor's breathing circumference using PID and Radiello. PID data were downloaded and analyzed using Microsoft Excel (Version 2019). Radiellos were sent to the laboratory to determine the BTEX levels from the total VOCs. The total volatile organic compound (TVOC) concentration over the combustion cycle was 306.7 ± 62.8 ppm. The flaming phase had the highest VOC concentration (547 ± 110.46 ppm), followed by the ignition phase (339.44 ± 40.6 ppm) and coking with the lowest concentration (24.64 ± 14.3). The average BTEX concentration was 15.7 ± 5.9 µg/m3 corresponding to the entire combustion cycle. BTEX concentrations were highest at the flaming phase (23.6 µg/m3) followed by the ignition (13.4 µg/m3) and coking phase (9.45 µg/m3). Ignition phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.09; ignition phase versus the coking phase, there was a significant difference at 95% at a p-value of 0.039; and coking phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.025. When compared to the occupational exposure limits (OELs), none of the exposure concentrations (BTEX) were above the 8 h exposure limit. The findings of this study suggest that charcoal, as a source of energy, can still be a useful and sustainable fuel for informal food traders. Shortening the ignition and flaming phase duration by using a fan to supply sufficient air can further reduce exposure to VOCs. [ABSTRACT FROM AUTHOR]

This study focuses on the impact of wildfire smoke emissions on regional, urban air quality during a wildfire event. We measured volatile organic compounds (VOCs) and fine particulate matter (PM2.5) in the San Francisco Bay Area to assess air quality during a wildfire event and compared them to those in a later non-wildfire period. VOCs were collected using thermal desorption tubes and quantified using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS). Elevated concentrations of VOCs such as 1,3,5-trimethylbenzene (0.33 ± 0.01 µg/m3), benzene (1.03 ± 0.02 µg/m3), toluene (2.15 ± 0.04 µg/m3), ethylbenzene (0.60 ± 0.02 µg/m3), and m, p-xylene (0.77 ± 0.07 µg/m3) were observed in the wildfire event. Compared with that in the non-wildfire season, the toluene concentration during the wildfire period was more than three times the non-wildfire concentration. Similarly, the benzene concentration during the wildfire was almost four times higher, and that of p, m-xylene was three times higher. The higher wildfire levels were statistically significant for sec-butylbenzene, 1,2,4-trimethylbenzene, n-propylbenzene, o-xylene, styrene, 1,3,5-trimethylbenzene, benzene, toluene, ethylbenzene, and p,m-xylene (p < 0.00001). These higher VOC levels compared with those for the non-fire period may potentially pose a public health concern. Open face passive sampler (OFPS)-collected PM was analyzed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and revealed organic carbon tar balls. The highest daily average beta-attenuation-monitored PM2.5 during the fire period was 200 µg/m3 and the highest hourly average was 270 µg/m3. Monitoring gas phase species in addition to PM concentrations is useful during wildfire season to inform public health guidance. [ABSTRACT FROM AUTHOR]

Petroleum products have contaminated groundwater with harmful organic compounds, such as benzene, toluene, ethylbenzene, and xylenes (BTEX). Collecting and analyzing polluted groundwater samples is expensive and undertaken infrequently. However, quick remedial action in case of unexpected events requires continuous monitoring. In‐situ water quality sensors (pH, EC, DO, ORP) may show correlations with the components of dissolved petroleum hydrocarbon (PHC) such as aromatics and non‐volatile mobile fractions. Correlations are prerequisite to ultimately develop real‐time prediction models. Since suitable field data sets are limited, we simulated the fate of hydrocarbons in groundwater under various realistic conditions using a reactive transport model as novel approach to explore when, where, and why correlations occur. A stationary oil source zone continuously dissolved at the top of a heterogeneous and shallow sandy aquifer over a two‐dimensional cross‐section. Our model considered transient conditions (fluctuating water table) and spatially uniform hydrogeochemical composition. We observed a strong correlation between PHCs and water quality sensors (rolling Spearman's correlation > |0.8|) at varying periods. These correlations are strongly affected by the location of observation wells, the aquifer's hydraulic conductivity, and the availability of calcite and oxide minerals, and other electron acceptors. DO and ORP are significant for the early detection of hydrocarbon contamination, whereas pH and EC are important features for the long‐term monitoring of hydrocarbons. Our findings lay the foundation for the subsequent development of a data analysis model to detect and estimate in real time PHC levels in groundwater using in‐situ water quality sensors. Plain Language Summary: Groundwater contamination by petroleum products, including benzene, toluene, ethylbenzene, and xylenes (BTEX), is a serious environmental concern. However, the collection and analysis of polluted groundwater samples are expensive and infrequently conducted. In the event of unexpected contamination, quick remedial action is crucial, which requires continuous monitoring of groundwater quality. We investigated whether in‐situ water quality sensors like pH, electrical conductivity (EC), dissolved oxygen (DO), and oxidation‐reduction potential (ORP) can predict the concentration of dissolved petroleum hydrocarbons (PHC) in groundwater. Understanding the correlations between these sensors and PHC levels is essential for developing real‐time prediction models. Since field data is scarce, we developed a reactive transport model that simulates the movement of PHC in groundwater under different conditions. Our model simulated a scenario where oil continuously dissolves at the top of a sandy aquifer. The correlation between PHC levels and water quality sensors varies depending on the location and timing of measurements. DO and ORP are particularly useful for detecting early signs of contamination, while pH and EC are important for long‐term monitoring. Our findings provide the foundation for developing data analysis models capable of real‐time detection and estimation of PHC levels in groundwater using water quality sensors. Key Points: In‐situ water quality sensors are highly correlated with petroleum hydrocarbons in groundwater when spatiotemporal variability is consideredDO and ORP are important for early detection, while pH and EC for long‐term prediction of hydrocarbon contamination in groundwaterThe aquifer's hydrogeology impacts hydrocarbon‐water quality correlations by influencing buffering capacity and flow velocity, among others [ABSTRACT FROM AUTHOR]

Permeable reactive barriers (PRBs) are passive and sustainable treatment systems for remediating the diffusion of contaminant plumes in groundwater. Several conventional reactive materials such as activated carbon (AC) have long been used as reactive media for PRBs. AC, which is known for its high adsorption capability and cost-effectiveness, is commonly used to remove multiple pollutants from groundwater. Unfortunately, among the reactive materials, AC can fill in the barrier and pose practical problems, such as a pressure drop, solid losses during handling, and safe disposal of filled sorbents, because of its low particle strength. In this study, AC balls were prepared using zeolite as the core and powdered AC, quartz, and calcite as the shell. AC ball with excellent mechanical strength and high permeability properties in the form of a core–shell layer is a good alternative to conventional reactive materials. The adsorption characteristics of benzene, toluene, ethylbenzene, and p-xylene (BTEX) from solutions using AC balls were investigated. The adsorption equilibrium is in the order of X > E > T > B. The adsorption capacity for B (4.90 mg/g), T (3.37 mg/g), E (1.16 mg/g) and X (0.46 mg/g) were observed at solution pH = 7. To validate the proposed models, batch experiments indicated that the pseudo-2nd-order (11.61 and 10.54 mg/g) and Langmuir models (8.81 and 5.27 mg/g) were the most suitable for describing the kinetics and equilibrium of benzene and toluene, respectively. Regeneration experiments were performed using chemical extraction (methanol) and microwave (MW) heating. When the AC ball was reused six times, the removal efficiency for benzene was maintained above 81 % using methanol, whereas that for benzene was increased to 91 % using MW. A series of experiments revealed that AC balls have considerable reusability. The AC ball can be effectively used as a medium for the removal of benzene in a continuous flow system such as column and sandbox. Based on these results, AC balls are a potential reactive medium for field-scale PRB practical remediation applications.

The presence of hazardous air pollutants (HAPs) entrained in end-use natural gas (NG) is an understudied source of human health risks. We performed trace gas analyses on 185 unburned NG samples collected from 159 unique residential NG stoves across seven geographic regions in California. Our analyses commonly detected 12 HAPs with significant variability across region and gas utility. Mean regional benzene, toluene, ethylbenzene, and total xylenes (BTEX) concentrations in end-use NG ranged from 1.6-25 ppmv─benzene alone was detected in 99% of samples, and mean concentrations ranged from 0.7-12 ppmv (max: 66 ppmv). By applying previously reported NG and methane emission rates throughout California's transmission, storage, and distribution systems, we estimated statewide benzene emissions of 4,200 (95% CI: 1,800-9,700) kg yr-1 that are currently not included in any statewide inventories─equal to the annual benzene emissions from nearly 60,000 light-duty gasoline vehicles. Additionally, we found that NG leakage from stoves and ovens while not in use can result in indoor benzene concentrations that can exceed the California Office of Environmental Health Hazard Assessment 8-h Reference Exposure Level of 0.94 ppbv─benzene concentrations comparable to environmental tobacco smoke. This study supports the need to further improve our understanding of leaked downstream NG as a source of health risk.

Abstract Introduction Considering the adverse carcinogenic and non-carcinogenic health effects of Volatile Organic Compounds (VOC) and specially Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) which are widely used in vehicle manufacturing industry, it is clear that monitoring and control of occupational exposure to these substances is of utmost significance. More often than not the studies on occupational exposure to VOCs in vehicle manufacturing industry—specifically BTEX—have been carried out exclusively in paint shop units. The purpose of this study was to assess occupational BTEX exposure & health risk in different units of a vehicle manufacturing industry. Material and methods Foam injection unit (FIU), gluing unit (GU), repair shop unit (RSU), molding unit (MU) as well as paint shop units (PSU) were selected for this study. Sampling and analysis were conducted based on National Institute for Occupational Safety and Health (NIOSH) 1501 guidelines by utilizing MSA personal sampling pumps set to 0.2 l/m and Gas Chromatography equipped with Flame Ionization Detector (GC-FID). Risk characterization and assessment was performed using Environmental Protection Agency Risk Assessment Information System (EPA RAIS). Results and conclusion The results revealed that the concentration of benzene in gluing and paint shop units was above occupational exposure limits. Carcinogenic risk levels in 8 out of 10 units registered in the 1E-2 to 1E-4 range, and only two units registered a risk level below EPA’s acceptable risk level (10–6). The highest risk levels were measured in gluing, paint shop and repair shop units. Furthermore, the total non-carcinogenic hazard quotient was measured higher than 1 in 8 out of 10 studied units. Considering the abundance and wide use of VOCs -most notably BTEX- and the adverse carcinogenic and non-carcinogenic health effects of these compounds, it is advised to: change the type of paint used in paint shops, improve the existing ventilation systems, develop new and more efficient ventilation systems and conduct consistent training.

Background: Crude oil related activities in the Niger Delta region has exposed the environment to various degrees of pollutants, including heavy metals (HMs) and BTEX (Benzene, Toluene, Ethylbenzene, m, p-xylene, and o-xylene). The study assessed the human health risk exposure to BTEX and HMs (Lead, (Pb), chromium (Cr), cadmium (Cd), Nickel (Ni), copper (Cu) and iron (Fe) from remediated oil spilled field. Soil and Cassava tubers were collected around the field and analysed through laboratory procedures using Atomic Absorption Spectrophotometry and Gas Chromatography Flame under ASTMD 4691 and USEPA 8260B for HMs and BTEX, respectively. Result: The mean concentration of Pb, Cd, Cr, Ni, Fe and Cu in the soil was 0.234 mg/kg, 0.004 mg/kg, 0.299 mg/kg, 0.307 mg/kg, 1.552 mg/kg and 0.527 mg/kg respectively and the concentration exceeded the allowable limit of WHO. The mean concentration of BTEX in the soil and Cassava was 0.0419 mg/kg and 0.1603 mg/kg, respectively and trended as Toluene (0.016 mg/kg) > Xylene (0.011 mg/kg) > Benzene (0.007 mg/kg) > Ethylbenzene (0.007 mg/kg) in soil and Ethylbenzene (0.057 mg/kg) > Xylene (0.051 mg/kg) > Benzene (0.034 mg/kg) > Toluene (0.02 mg/kg). The human health risk based on the target hazard quotient (THQ) for non-carcinogenic parameters in soil and Cassava ranged from “No Significant Risk of Non-Carcinogenic-NSRNc (THQ x 10-6) to Moderate Significant Risk of Non-Carcinogenic- MSRNc (THQ × 10-3)” for adults and children. The total carcinogenic risk (TCR) of the HMs and BTEX in soil and Cassava for adults and children was within the “Negligible Carcinogenic Risk for Human-ACRH (TCR × 10-6 to TCR × 10-9)”. Conclusion: Continuous consumption and bioaccumulation of Cassava means the population are not entirely free from the risk of health exposure to BTEX and heavy metals; therefore, effective environmental sustainability practices must be encouraged.

Introduction: Considering the adverse carcinogenic and non-carcinogenic health effects of Volatile Organic Compounds (VOC) and specially Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) which are widely used in vehicle manufacturing industry, it is clear that monitoring and control of occupational exposure to these substances is of utmost significance. More often than not the studies on occupational exposure to VOCs in vehicle manufacturing industry—specifically BTEX—have been carried out exclusively in paint shop units. The purpose of this study was to assess occupational BTEX exposure & health risk in different units of a vehicle manufacturing industry. Material and methods: Foam injection unit (FIU), gluing unit (GU), repair shop unit (RSU), molding unit (MU) as well as paint shop units (PSU) were selected for this study. Sampling and analysis were conducted based on National Institute for Occupational Safety and Health (NIOSH) 1501 guidelines by utilizing MSA personal sampling pumps set to 0.2 l/m and Gas Chromatography equipped with Flame Ionization Detector (GC-FID). Risk characterization and assessment was performed using Environmental Protection Agency Risk Assessment Information System (EPA RAIS). Results and conclusion: The results revealed that the concentration of benzene in gluing and paint shop units was above occupational exposure limits. Carcinogenic risk levels in 8 out of 10 units registered in the 1E-2 to 1E-4 range, and only two units registered a risk level below EPA's acceptable risk level (10–6). The highest risk levels were measured in gluing, paint shop and repair shop units. Furthermore, the total non-carcinogenic hazard quotient was measured higher than 1 in 8 out of 10 studied units. Considering the abundance and wide use of VOCs -most notably BTEX- and the adverse carcinogenic and non-carcinogenic health effects of these compounds, it is advised to: change the type of paint used in paint shops, improve the existing ventilation systems, develop new and more efficient ventilation systems and conduct consistent training. Highlights: In this paper, we report on the levels of occupational exposure workers encounter on a daily basis to a specific group of Volatile Organic Compounds (VOC): Benzene, Toluene, Ethylbenzene and Xylene(s) (BTEX) in various sections of a vehicle manufacturing industry and the resulting health risks. Reviewing previous studies revealed that as a result of low occupational exposure to BTEX in vehicle manufacturing industry, more often than not the studies on said compounds and the ensuing health effects were exclusively carried out in paint shop units, ignoring health risks in other units & creating the assumption that health risks in other units are negligible. The purpose of this study was to assess occupational BTEX exposure and its associated health risk in different units of a vehicle manufacturing industry, including foam injection unit (FIU), gluing unit (GU), repair shop unit (RSU), molding unit (MU) as well as paint shop units (PSU). Revealing the possibility of exposure to BTEX not only in paint shop units but also other previously disregarded units, the health risk calculated in some units such as gluing unit was higher than the EPA acceptable risk range (10-4). Moreover, cancer risk levels of molding (Unit No 6) and repair shop (Unit No 7) units registered in the 10-4 to 10-2 range despite meeting the TLV-TWA (0.174 PPM and 0.449 PPM respectively), suggesting the need for implementation of a health risk assessment in conjunction with exposure assessment. [ABSTRACT FROM AUTHOR]

The wellbeing of the honey bee colonies and the health of humans are connected in numerous ways. Therefore, ensuring the wellbeing of bees is a crucial component of fostering sustainability and ecological harmony. The colony collapse disorder (CCD) phenomenon was first reported in 2006 when the majority of bee colonies in Europe died out, due to an increase in infections, contamination of hives with agrochemical pesticides, and persistent organic pollutants (POPs). Only 6 years after the emergence of CCD, more than 6.5 million premature deaths were reported, as a consequence of persistent human exposure to air pollution. The insect species such as the honey bee Apis mellifera L. and the air matrix inside the beehive can be used as tools in biomonitoring, instead of traditional monitoring methods. This may have advantages in terms of cost-effective bioindicators of the environmental health status, showing the ability to record spatial and temporal pollutant variations. In this study, we present the sustainable in-field usage of the portable membrane inlet mass spectrometry (MIMS) instrument for an instant and effective determination of the level of environmental pollution by analytical identification of hive atmosphere volatile organic compound (VOC) contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), monocyclic aromatic hydrocarbons (BTEX) compounds, and pesticides. The samples were taken from hives located in urbanized and rural regions, highlighting variations in contamination. The MIMS results were benchmarked against a conventional laboratory sampling technique, such as GC-MS. [ABSTRACT FROM AUTHOR]

This research paper presents the preparation, verification and stability evaluation of a toluene calibration gas mixtures (CGMs) in nitrogen gas via gravimetric method. These toluene gas mixtures are prepared gravimetrically i. e., by wt. mixing of high‐purity gases according to the International Organization for Standardization, ISO 6142, and are validated as per ISO 6143. Toluene gas mixtures within the range of 5 to 20 μmol/mol are prepared and traceability with SI, 'International system of units', amount of substance, the ′mole′, through mass‐based measurements is achieved. The verification of prepared CGMs was carried out using a GC‐FID (gas chromatography with flame ionization detector) technique, and the outcomes demonstrated a consistent linear correlation between instrumental response and gravimetric amount fraction for all gas mixtures, which confirmed the accuracy and reliability of CGMs. The gravimetric uncertainty of the prepared gas mixtures, as projected in terms of amount fractions, is below 1 % relative, while the analytical uncertainty is in the range of 2–3 % relative at a confidence level of k=1. The stability study investigation over a period of one year demonstrated that the mole fraction of toluene remained consistent throughout the entire duration, which indicated the long‐term stability of the CGMs. [ABSTRACT FROM AUTHOR]

In the urban atmosphere of Bengaluru, various volatile organic compounds (VOCs), particularly Benzene, Toluene, Ethylbenzene, and Xylene (BTEX), have shown an increasing trend in concentration. The present research was conducted during summer and monsoon seasons, focusing on Kadubeesanahalli, a high-traffic area within the Bengaluru Metropolitan City. Hourly sample data was collected using a BTEX analyzer (Model GC955-600) and subsequently transformed into daily, monthly, and seasonal values. The study revealed distinct patterns in benzene concentrations. Benzene levels were lowest during the early morning hours, specifically from 1:00 a.m. to 7:00 a.m. Concentrations then increased from 7:00 a.m. to 9:00 a.m. and again from 4:00 p.m. to 11:00 p.m., corresponding to the morning and evening peak traffic hours. However, between 10:00 a.m. and 4:00 p.m., the concentration decreased due to reduced traffic levels. These diurnal variations in benzene concentration are influenced by meteorological parameters. Comparing the two seasons, higher concentrations of Benzene, Ethyl-Benzene, and MP-xylene were observed during the summer season. This increase is attributed to the elevated temperatures during summer, which promote the vaporization of BTEX compounds. Conversely, lower BTEX concentrations were recorded during the monsoon season due to the wet deposition process. The observed positive correlation (r > 0.5) among BTEX parameters strongly suggests a common source, most likely originating from vehicular emissions. [ABSTRACT FROM AUTHOR]

Substances like asbestos and other air pollutants, such as BTEX (benzene, toluene, ethylbenzene, and xylene), are hazardous compounds due to their adverse effects on human health. This study aims to investigate the levels, seasonal variations, spatial distribution, potential sources, and associated health risks associated with BTEX compounds and asbestos fibers in the ambient air of Tabriz. Air samples were taken at 16 different locations during the 2020–2021 period. Glass containers with charcoal were used for sample collection, and the BTEX content was determined using the GC-FID method. Phase-contrast microscopy (PCM) analysis was conducted with a low-volume peripheral pump for asbestos fiber sampling. The results showed that the average concentration of ∑BTEX was 37.94 and 27.98 μg/m3 in autumn and spring, respectively. The same parameter was 2.26 and 1.68 f/L for asbestos in the autumn and winter, respectively. The contribution of BTEX to ozone formation potential (OFP) in the research area showed that xylene and toluene were the major contributors to ozone production in different seasons. The risk of exposure to benzene compounds was 24 × 10−4 in children and 55.9 × 10−4 in adults, while the risk of exposure to ethylbenzene was 3.78 × 10−4 in children and 3.25 × 10−4 in adults. The estimated lifetime cancer risk was found to be the highest for benzene, followed by ethylbenzene. The estimated cancer risk for benzene and ethylbenzene exceeded the threshold values set by EPA, which signals a significant carcinogenic risk due to exposure to these substances in the ambient air of Tabriz. According to the EPA guidelines, the low carcinogenicity risk levels are between 10−4 and 10−6. According to the findings for the exposure to asbestos fibers, the maximum values of excess cancer risk (ECR) and estimated lifetime cancer risk (ELCR) were observed in the 16–30 age range across all locations, suggesting increased exposure to asbestos fibers compared to other age groups.

This paper represents an improved method for on-site quantitation of benzene, toluene, ethylbenzene, and xylenes (BTEX) in atmospheric air using solid-phase microextraction (SPME) and portable gas chromatography with a split/splitless inlet and photoionization detector (GC-PID). The developed method includes air pumping to four replicate 250 mL gas sampling bulbs, three of which are extracted by 85 µm Carboxen/polydimethylsiloxane (Car/PDMS) coating at 40°C, while the last one is spiked with BTEX standard in nitrogen and extracted under the same conditions. Compared to other similar SPME-based methods, the developed method does not require a standard gas generator and traceable certified permeation tubes for instrument calibration.The method was applied for on-site BTEX quantitation in air of Talgar, Almaty oblast, Kazakhstan in February and March 2024, at two different extraction times, among which 15 min was chosen as optimal because it provided sufficient detection limits of ethylbenzene, and xylenes. The on-site standard addition calibration allowed accurate BTEX quantitation. In February, only benzene (18.3 and 6.8 µg/m3) and toluene (15.7 and 8.5 µg/m3) were detected. In March samples, concentrations of benzene were 12.3 and 7.4 µg/m3, toluene - 23 and 5.4 µg/m3, ethylbenzene – 5.5 µg/m3 and not detected, m-/p-xylene - 3.6 and 2.1 µg/m3, o-xylene - 6.8 and 10.6 µg/m3. The LODs for benzene, toluene, ethylbenzene, m-/p-xylene, and o-xylene were 0.07, 0.3, 2, 0.8 and 2 µg/m3, respectively. The developed method can be recommended for quick and low-cost on-site quantification of BTEX in atmospheric air, particularly at remote locations.

Increasing of tobacco consumption around the world has led to the production of a large volume of waterpipe wastewater that enter the environment (e.g., coastal areas)and threaten aquatic creatures. However, until now, no research has been carried out on the amounts of monocyclic and polycyclic aromatic hydrocarbons (PAHs) in hookah wastewater. In the current study, the levels of PAHs and BTEX compounds in waterpipe wastewater resulting from the use of different tobacco brands were determined and their eco-toxicological effects were also evaluated. The mean levels of ƩPAHs in waterpipe wastewater of Al Tawareg, Al-Fakher, Nakhla, Tangiers and traditional tobacco brands samples were 3.48 ± 1.65, 3.33 ± 1.52, 3.08 ± 1.25, 2.41 ± 0.87 and 0.70 ± 0.13 μg/L, respectively. The mean levels of ƩBTEX in waterpipe wastewater of Al Tawareg, Al-Fakher, Nakhla, Tangiers and traditional tobacco brands samples were also 2.53 ± 0.61, 2.65 ± 0.78, 2.51 ± 0.72, 2.35 ± 0.56, and 0.78 ± 0.12 μg/L, respectively. The maximum level of PAHs and BTEX compounds in all brands/flavors samples were for naphthalene (Naph) and toluene, respectively. The concentrations of some PAHs (fluoranthene (Flrt), anthracene (Ant), benzo(b)fluoranthene (BbF), benzo(b)fluoranthene (BkF), benzo (g,h,i)perylene (BghiP) and dibenzo (a, h) anthracene (DahA)) and BTEX compounds (benzene) in the waterpipe wastewater samples were more than recommended guidelines and standards by the international reputable organizations such as World Health Organization (WHO) for water quality. Waterpipe wastewater can be introduced as an important origin for the release of these dangerous contaminants into the environmental matrixes. Therefore, more stringent regulations should be considered for the safe disposal of such hazardous wastes including waterpipe wastewater.

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters.

Background: The present research addressed the spatiotemporal variations in such pollutants as benzene, toluene, ethylbenzene, and xylene (BTEX) in the atmosphere of Arak, a city in central Iran. Also, the health risk evaluation and ozone formation potential (OFP) were assessed. Methods: The air samples were collected and evaluated through gas chromatography-mass spectrometry (GC-MS) over a one-year period. Results: The overall BTEX levels ranged between 2.7-256 µgr/m3. The seasonal levels showed considerable variations among benzene, toluene, ethylbenzene, and xylene, and the levels of total BTEX. Comparison of the air samples between morning and evening for the concentrations of BTEX components revealed that the values were higher in the evening; however, there were no significant differences observed among them. The spatial map indicated that the maximal concentration of BTEX components occurred in high-traffic zones of the city. The maximal and minimal OFP levels were recorded in the summer (254.8 µgr/m3) and autumn (64.9 µgr/m3), respectively. The average toluene/benzene (T/B) ratio found to be 4.3, indicating the fuel combustion was the major source of atmospheric BTEX from vehicles. Conclusion: The measured cancer risk value for benzene (6.68×10-5) was higher than those recommended by the WHO and U.S. Environmental Protection Agency. Therefore, exposure to atmospheric benzene had a carcinogenic risk for Arak inhabitants. This needs further investigation in future studies. The acceptable hazard quotients (

Abstract Exposure to benzene and other volatile organic compounds (VOCs) like toluene, ethylbenzene, o-, m-, and p-xylene (BTEX) at a fuel station is hazardous for the workers. This study aims to estimate the health risk for worker due to the exposure of BTEX after implementation of vapour recovery system (VRS) at fuel stations. Air samples were collected using low-flow sampling pump as per NIOSH method by using Tenax (sorbent) tubes and charcoal (sorbent) tubes. Target compounds were extracted using acetone and analysed by gas chromatography equipped with flame ionization detector (FID). The cancer risk (CR) and hazard quotient (HQ) were estimated to assess the cancer and non-cancer risk following the United States of Environmental Protection Agency (USEPA) updated methodology. The average concentration of VOCs at the fuel station is found in the order toluene > benzene > xylene > ethylbenzene which may be attributed to the composition of fuel (petrol/diesel). Benzene is the most carcinogenic among BTEX, which is found to be 217 ± 9 µg m−3 and 158 ± 9 µg m−3 in the month of November 2021 using Tenax sorbent and charcoal sorbent tubes, respectively. The high concentration observed using Tenax sorbent may be attributed to its high adsorption efficacy than charcoal due to larger surface area and porosity. The 7-month average CR value of benzene was 9 × 10−4 using Tenax sorbent and exceeds the acceptable range of 1 × 10−6. CR of benzene exposure at the fuel station under study is also compared with that of outdoor ambient air exposure. Benzene measurement data for the same duration was taken from nearby online monitoring station of Delhi Pollution Control Committee (DPCC) PUSA to estimate CR value for outdoor ambient air benzene exposure. The value of HQ for benzene was observed > 1 which exceeds the acceptable value and hence increased the non-cancer health risk also. Hazard index (HI) value for BTEX is also greater than 1 which indicates adverse health effects of benzene and other VOCs at the fuel station. The high CR and HQ values for benzene are a matter of concern for fuel station workers.

The cooking act is one of the primary sources of indoor air pollution. Frying is one of the oldest food processing methods that has received much attention in studies due to various pollutants. Oxidation of oil via the raising of temperature leads to the formation of alkadienals, known as precursors of monoaromatics hydrocarbons, such as benzene and toluene ethylbenzene, and xylene isomers (BTEX). The compounds have carcinogenic effects on human health and cause environmental effects by forming secondary organic aerosols (SOA) and ozone. Within this regard, many studies assessed the emission of the chemicals at the indoor area, stacks of commercial kitchens, and emission points, while they considered the effects of various factors like oil temperature, oil type, and additions on the formation of BTEX and another VOCs. Temperature as an accelerator factor has a direct relationship, while time has not shown specific emissions. The oils depend on their compositions, have different oxidative stability. Indeed, the oils with higher unsaturated contents are more susceptible to oxidation. Among unsaturated fatty acids, polyunsaturated than monounsaturated types have a higher oxidation rate. However, foods/additives can vary frying content compositions and influence emissions. In this paper, we attempt to review the measurement procedures, influential factors on formation and methods to assess the environmental and health impacts of BTEX. [ABSTRACT FROM AUTHOR]

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO2/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm2 and an air flow rate of 55 m3/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology. [ABSTRACT FROM AUTHOR]

This paper deals about a proposal for the remediation of soils and groundwater contaminated with hydrocarbons in a tropical aquifer, due to leaks from underground tanks in a gas station in Venezuela. The hydrocarbon measured values such as TPHs (Total Petroleum Hydrocarbons) and BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) in soils and ground water exceeded the international standards. The remediation proposal was designed using kinetic models from the modified Monod equation for two coupled bioreactors, using as design variable for the Chemical Oxygen Demand (COD). For soil treatment, the sequence was formed by Soil-Slurry Sequencing Batch Reactor (SS-SBR)and Upflow Anaerobic Filter separate in three phases (UAF-3SS) operating for 80% and 99% of COD removal, respectively. For groundwater treatment, it was set the SBR-UAF-3SS sequence performs a COD removal of 60% and 99%, respectively. [ABSTRACT FROM AUTHOR]

Featured Application: The potential application of this study's findings is to inform and guide workplace health and safety policies and practices in the retail sector. This research investigates different facets of indoor air quality and the corresponding health symptoms within a retail environment. Formaldehyde, classified as a Group B carcinogenic substance, was found within safe limits indoors, primarily originating from surface coatings, flooring products, textiles, and furniture. Monoterpenes, lactic acid, and particulate matter levels were also assessed, with varying indoor–outdoor ratios. Notably, we identified a relatively low concentration of PM2.5, possibly influenced by enhanced cleaning practices during the COVID-19 pandemic. Symptom assessment revealed that many young workers experienced work-related symptoms, notably fatigue, nose-, throat-, and skin-related issues, aligning with previous findings. Although we could not conclusively link these symptoms to sick building syndrome (SBS) or formaldehyde exposure, it underscores the importance of further investigation. Notably, we observed no gender-based differences in symptom prevalence, but this study's limited size requires caution in generalization. This study contributes to understanding indoor air quality and associated symptoms in an economically significant sector, emphasizing the need for continued research, especially considering the potential impact on workforce health in the broader context. [ABSTRACT FROM AUTHOR]

The proximity of fuel stations to the roads and the activities inside the station can contribute to PM and VOCs and impose health risks on station workers. The study presents the exposure and health risk assessment of the fuel station personnel to total volatile organic compounds (TVOCs) and particulate matter (PM) during refueling operations. TVOCs and PM monitoring were carried out at a fuel station in Chennai, India, for 1 week in March 2021, covering both weekdays and weekends. The health risks were assessed using EPA's health impact assessment methodology. Exposure to TVOCs (3177.39 ± 5450.32 μg/m3) exceeded the EPA standard of 5 μg/m3, by more than 500 times, peaking during refueling operations. The average concentrations of PM10, PM2.5, and PM1 were 76.55 ± 23.08 μg/m3, 41.81 ± 9 μg/m3, and 30.38 ± 7.56 μg/m3, respectively. The concentrations were observed to be high during morning and evening hours due to the increased traffic on the adjacent road and inside the fuel station. The synergistic health risks linked with long-term exposure to high concentrations of BTEX and PM were also estimated. At the fuel station, a significant contribution to the SOA formation potential was shown by toluene, followed by m-xylene, p-xylene, o-xylene, ethylbenzene, and benzene. Furthermore, the deposition of airborne particles in the workers' respiratory tract was calculated using the Multiple Path Particle Dosimetry model while considering the daily average exposure duration of 12 h. The results showed that 59% of PM10 particles were deposited in the head region, whereas 11% and 10% of PM2.5 and PM1 particles were deposited in the pulmonary region. Hence, the health risk assessment indicated no non-cancer risk of exposure to PM (hazard quotient = 0.13) to station personnel exposed regularly for 1 year. However, prolonged exposure to VOCs for more than 1 year can result in both carcinogenic and non-carcinogenic risk (hazard quotient = 0.045 and cancer risk > 10−6) in workers. [ABSTRACT FROM AUTHOR]

This study examined the concentration of BTEX in Tehran from 2018 to 2020 in five monitoring stations with different backgrounds, which has been accomplished using the combination of passive sampling and GC-FID method. The total concentration of BTEX was estimated to be 65.39 (µg/m3), with a higher average concentration in 2019–2020 (77.79 µg/m3) compared to 2018–2019 (53.48 µg/m3) due to the leaping concentration of Toluene in the pandemic era. Despite a Benzene concentration decline in recent years, the average annual concentration of Benzene (5.66 µg/m3) at five stations remained higher than the EU commission and India standards (5 µg/m3) as well as Japan and Iraq thresholds (3 µg/m3). Toluene dominated other species in terms of concentrations, mass distribution (~0.6%), followed by m,p–Xylene (~0.2%), Benzene (~0.05–0.1) and Ethylbenzene (< 0.05). The evidence regarding seasonal changes of BTEX in 2019 shows the maximum concentration of these compounds in autumn, which is probably due to heavier traffic compared to other seasons. In contrast, in the first half of 2020 (which encompasses the start of the pandemic period and urban lockdown), point sources seem to play a prominent role in concentration fluctuations, as confirmed by changes in interspecies relationships and lower traffic congestion. The highest mean concentrations were observed in high-traffic, residential and suburban sites, respectively. The study reveals that m,p-Xylene possess the highest Ozone formation potential (~109.46), followed by Toluene (~85.34), o-Xylene (~46.87), Ethylbenzene (~13.52) and Benzene (~2.61). Health risk assessment results indicated the high carcinogenic risk of Benzene (mean = 3.6 × 10–6) and the acceptable non-carcinogenic risk of BTEX (hazard index~0.03 < specified limit of 1). Finally, the estimated weighted exposures of BTEX emphasized that residents near the high-traffic districts are more exposed to BTEX. [ABSTRACT FROM AUTHOR]

The effect of the experimental conditions on the hydrocracking (HCK) of a hydrotreated light cycle oil (HDT LCO) was studied in this work. The catalyst tested was a 50/50 weight mixture of nickel-molybdenum-phosphorous on alumina (NiMo/Al2O3) and a commercial ZSM5 zeolite (HCK 50/50). The experimental conditions tested were 340, 350, 360, and 370 °C; 7.5 MPa; 0.9, 1.2, 1.5, and 1.8 h−1 LHSV, and H2/HC of 752 m3/m3. Two phases: gas and liquid, were obtained as HDK products. The gas phase consisted mostly of C1–C5 paraffins, iso-paraffins, and olefins. The liquid phase was characterized by GC-PIONA and was distributed in lumps as follows: NAPA by C11 to C13-naphthalenes; TET by C11 to C13-tetralins; IND by C9 to C13-indanes and indenes; AKB by C9 to C13-alkylbenzenes; BTEX by benzene, toluene, ethylbenzene, and xylenes; NAPE by C9 to C13-naphthenes; and PIP by C3 to C14 paraffin, iso-paraffin, and olefin type hydrocarbons. Using this classification, the results showed that increments in temperature and decrements in LHSV produced increments in the formation of gases, PIP, BTEX, and NAPE. At the same conditions, AKB, TET, NAPA, and IND decreased sharply. TET and NAPA derivatives were no longer present at high temperatures (360–370 °C). It seemed to be a limit of the BTEX formation directly related to the TET and IND presence, and it did not seem to depend on the transalkylation process of AKB hydrocarbons. Instead, AKB hydrocarbons were directly correlated to NAPE hydrocarbon formation by hydrogenation. A kinetic model was prepared. The model presented correlation coefficients higher than 98 %. The kinetic model that was made predicted that neither increasing the temperature nor lowering the LHSV would improve the BTEX formation when departing from this feedstock. [ABSTRACT FROM AUTHOR]

Introduction: A large part of Bulgarian people, especially in big cities, work indoors (eg in offices, schools, hospitals, banks, etc.). There, they are exposed to different types and amounts of inorganic gases and volatile organic compounds (VOCs). Due to the lack of national legislation, indoor air is essentially unregulated and uncontrolled. Pollutant levels indoors are typically significantly higher than outdoors, with typical indoor sources of VOCs including off-gassing from various office equipment, furnishings and building materials. The aim of the present study is to assess the air quality in office premises equipped with standard office equipment - computers, printers and copiers, by quantifying VOCs, CO and CO2. Material and methods: Thirty offices located in 27 big cities of the country were investigated. VOCs samples were taken on sorbent tubes with activated carbon, for 8 hours, in three consecutive years; the analyses were performed by means of gas chromatography with a mass-selective detector using the absolute calibration method. In parallel, the concentrations of CO and CO2 were measured with an automatic gas analyzer. The results of the analyses show that the concentrations of VOCs vary widely: from < LOD to tens of μg/m³. The highest concentration of BTEX (benzene, toluene, ethylbenzene and xylenes) is Σxylenes - 620.4 μg/m³, followed by ethylbenzene - 169.3 μg/m³, toluene - 126.2 μg/m³ and benzene - 14.9 μg/m³. The highest determined concentration of tetrachlorethylene was 188.3 μg/m³, and of the terpenes limonene and pinene - 197.7 μg/m³ and 198.0 μg/m³, respectively. The measured concentrations of CO in the surveyed offices ranged from 0.3 mg/m³ to 2.0 mg/m³, аnd of СО2 - from 331 mg/m³ to 1810 mg/m³. Concentrations of Σxylenes were higher than the recommended indoor air limit values of other European countries and the WHO guidelines in almost all offices studied, except one; of tetrachlorethylene - in 10 offices; of benzene - in 2 offices. Conclusion: Poor indoor air quality can significantly affect human health and the economy. This necessitates a systematic assessment of indoor air pollutants in Bulgaria. [ABSTRACT FROM AUTHOR]

The degradation of the prevalent environmental contaminants benzene, toluene, ethylbenzene, and xylenes (BTEX) along with a common co-contaminant methyl tert-butyl ether (MTBE) by Rhodococcus rhodochrous ATCC Strain 21198 was investigated. The ability of 21198 to degrade these contaminants individually and in mixtures was evaluated with resting cells grown on isobutane, 1-butanol, and 2-butanol. Growth of 21198 in the presence of BTEX and MTBE was also studied to determine the growth substrate that best supports simultaneous microbial growth and contaminants degradation. Cells grown on isobutane, 1-butanol, and 2-butanol were all capable of degrading the contaminants, with isobutane grown cells exhibiting the most rapid degradation rates and 1-butanol grown cells exhibiting the slowest. However, in conditions where BTEX and MTBE were present during microbial growth, 1-butanol was determined to be an effective substrate for supporting concurrent growth and contaminant degradation. Contaminant degradation was found to be a combination of metabolic and cometabolic processes. Evidence for growth of 21198 on benzene and toluene is presented along with a possible transformation pathway. MTBE was cometabolically transformed to tertiary butyl alcohol, which was also observed to be transformed by 21198. This work demonstrates the possible utility of primary and secondary alcohols to support biodegradation of monoaromatic hydrocarbons and MTBE. Furthermore, the utility of 21198 for bioremediation applications has been expanded to include BTEX and MTBE. [ABSTRACT FROM AUTHOR]

In this study, an integral treatment consisted of UV/Fenton/ TiO2 system in the batch systems was developed to perform degradation of synthetic Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX). Initially, the efficiency of photo Fenton catalytic degradation was compared with conventional treatment methods. Later, optimum levels of selected variables such as the initial concentration of BTEX, pH, temperature, reaction time, and initial dosage of TiO2 were analyzed using one factor at a time method. Further, screening of variables and optimization were performed using Planckett-Burman design and central composite design, respectively. Photo Fenton catalytic process showed about 1.15 fold increase in efficiency when compared with photo Fenton process. Among the selected seven variables, four variables namely, initial pH, BTEX concentration, H2O2 dosage and TiO2 dosage were identified as significant factors. Under the optimal conditions, chemical oxygen demand reduction reached about 84.54 ± 2.57% using UV/Fenton/ TiO2 system. Finally, first-order kinetic model resulted in prediction of 19.43 kJ/mol of activation energy. Thus, process optimization and kinetic study using the developed photo Fenton catalytic system could be beneficial for real time waste containing BTEX pollutants.

In this study, we test the performance of a compact gas chromatograph with photoionization detector (GC-PID) and optimize the configuration to detect ambient (sub-ppb) levels of benzene, toluene, ethylbenzene, and xylene isomers (BTEX). The GC-PID system was designed to serve as a relatively inexpensive (~10 k USD) and field-deployable air toxic screening tool alternative to conventional benchtop GCs. The instrument uses ambient air as a carrier gas and consists of a Tenax-GR sorbent-based preconcentrator, a gas sample valve, two capillary columns, and a photoionization detector (PID) with a small footprint and low power requirement. The performance of the GC-PID has been evaluated in terms of system linearity and sensitivity in field conditions. The BTEX-GC system demonstrated the capacity to detect BTEX at levels as high as 500 ppb with a linear calibration range of 0-100 ppb. A detection limit lower than 1 ppb was found for all BTEX compounds with a sampling volume of 1 L. No significant drift in the instrument was observed. A time-varying calibration technique was established that requires minimal equipment for field operations and optimizes the sampling procedure for field measurements. With an analysis time of less than 15 min, the compact GC-PID is ideal for field deployment of background and polluted atmospheres for near-real time measurements of BTEX. The results highlight the application of the compact and easily deployable GC-PID for community monitoring and screening of air toxics.

In December 2019, a novel coronavirus disease (COVID-19) outbreak occurred due to a human respiratory virus that originated in the city of Wuhan, China. During the COVID-19 lockdown, there was a significant improvement in the air quality across the world. We analyzed the data for BTEX over the three years (January to December 2019 to 2021) with pairwise comparison and trend analysis for pre-, during, and post-pandemic periods. This study demonstrates the substantial changes in the concentration of VOCs in the urban area (Punjab) due to the lockdown effects. The results indicate a substantial reduction in the mean TVOCs concentration for all the monitoring stations was found to be 8.89 ± 1.80, 5.59 ± 1.71, and 5.57 ± 1.43 μg/m3 for before, during, and post-pandemic, respectively. The level of TVOCs declined by −43% for all monitoring stations during the lockdown period compared to the previous years. A higher T/B ratio was found in Patiala (2.97 μg/m3) before the pandemic, which may indicate vehicle emission sources. The LCR values for benzene were found to be higher in children than in males and females, which indicated the possible risk. The LCR values for benzene exceeded the prescribed value by CPCB for children.

Waterpipe tobacco wastes (WTWs) may contain considerable levels of hazardous contaminants such as BTEX (benzene, toluene, ethylbenzene, o-xylene, and m/p-xylene). However, no research has been carried out on BTEX levels in WTWs and the release of these pollutants into the water environment. This research examined the levels of BTEX in WTWs of flavored/local tobacco and also the release rate of these toxins into three kinds of water, including seawater (SW), tap water (TW), and distilled water (DW) with different leaching times (15, 30 min, 1.2, 4, 8 h, and 1, 2, and 4 days). The mean contents of BTEX in WTW samples of Al-Mahmoud, Al-Fakher, Mazaya, Al-Ayan brands, and local tobacco samples were 17.0 ± 4.14, 19.1 ± 4.65, 19.6 ± 4.19, 18.8 ± 4.14, and 3.16 ± 0.63 μg/kg, respectively. The mean BTEX levels in flavored tobacco samples were considerably greater than that of local tobacco (p

The impact of hydrocarbon spills in the unsaturated zone is a significant environmental concern, particularly in locations where contamination arises from leaks in underground fuel storage tanks (USTs). This paper presents the outcomes achieved through the utilization of VLEACH, a finite-difference numerical model, to assess the concentrations of organic contaminants in the solid, liquid, and gas phases within the vadose zone. Additionally, it evaluates the mass transfer of pollutants to the aquifer as part of an environmental assessment for the placement of a forthcoming service station. The study encompasses an analysis of 18 scenarios under realistic conditions based on actual field data. These scenarios were constructed, taking into account various factors, including the nature of the leak (one-time or permanent), the depth of the phreatic level, and the soil conditions and properties. The results highlight the potential environmental consequences of a permanent leak as compared to those resulting from a specific accident. The findings further emphasize the substantial influence of soil moisture on transport phenomena within the vadose zone. Variations in soil moisture significantly alter hydraulic conductivity, impact magnitudes, transport velocities, and even the predominant transport mechanism. Consequently, precise delineation of soil moisture becomes a crucial parameter in such simulations. Additionally, it has been observed that each component of BTEX (benzene, toluene, ethylbenzene, and xylene) experiences varying transport velocities through the vadose zone. Benzene, having a greater propensity to concentrate in the liquid and gas phases, exhibits the swiftest movement through the vadose zone. The detection of benzene in aquifers can serve as an indicator of the potential future arrival of the remaining BTEX compounds. [ABSTRACT FROM AUTHOR]

This work reports the use of smectite clays (raw and modified samples) as adsorbents in the adsorption process for removing benzene, toluene, and metal ions present in wastewater generated in the petrochemical industries. Smectite clay was used in the adsorption of organic compounds and in the cation exchange process for the removal of heavy metal ions Cu(II) and Pb(II) as a post-treatment process for refinery effluents. From the chemical treatment of raw smectite clay with sodium carbonate (Na-modified smectite clay, Na-MSC) it has been achieved a good exchange of Ca(II) and Mg(II) ions for Na(I). Moreover, characterization analysis evidenced that the raw smectite and Na-MSC had mesoporous structure. The number of exchangeable ions increased from 81.34 to 89.39 meq 100 g−1 after Na-addition. The adsorption and cation exchange experiments were conducted in batch mode using the sodium clays as adsorbents in the kinetic and equilibrium study. The isotherm of Langmuir–Freundlich was the most representative, and the adsorption capacity monolayer for benzene and toluene were 7.28 and 7.39 mg g−1. The ionic exchange model was applied to represent the removal of Cu(II) and Pb(II), which indicated a capacity of 0.99 mg g−1 and 1.10 mg g−1 respectively. Kinetic constants obtained for benzene and toluene were 0.0016 L mg−1 min−1 and 0.019 L mg−1 min−1. Finally, Na-MSC obtained kinetic constants 0.049 L mg−1 min−1 and 0.063 L mg−1 min−1 for Cu(II) and Pb(II) respectively. The results acquired in batch experiments evidence the high efficiency of Na-MSC to remove BTEX and heavy metals from wastewater. [ABSTRACT FROM AUTHOR]

Hazardous organic compounds such as benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (known as BTEX) found at work and at home can cause adverse health effects of human beings throughout their lives. Biological monitoring, an exposure assessment method, considers all exposed organic and non-organic compounds. Our goal was to perform a systematic review and a statistical analysis (meta-analysis) of peer-reviewed publications to assess urinary concentrations of BTEX biomarkers in both occupationally-exposed population and the general population. Several major electronic databases, including Scopus, Embase, Medline, Web of Science, and Google scholar (grey literature), were searched for biomonitoring studies of BTEX. Overall, 33 studies met the eligible criteria for the systematic review and six met the full inclusion criteria for meta-analysis. For meta-analysis, we included studies in which unmetabolized BTEX compounds were measured in urine samples. Due to insufficient data, studies that measured BTEX metabolites in urine samples and unmetabolized BTEX compounds in blood samples were excluded from the meta-analysis but were analyzed in the qualitative synthesis. Most studies showed increased urinary concentrations of BTEX in exposed individuals (mainly workers) compared to unexposed individuals. The results showed that the highest total BTEX concentrations were recorded in painters and policemen. This study showed that the undoubted associations between lifestyle and environmental factors and urinary levels of BTEX or its metabolites have not yet been confirmed in current biomonitoring studies. This is attributed to the few studies reported in this research area, the lack of homogeneous information, and the disagreement in the published results of the studies. [ABSTRACT FROM AUTHOR]