Application of spatial analysis to investigate contribution of VOCs to photochemical ozone creation

This study was concerned with the temporal analysis of benzene, toluene, ethylbenzene, xylenes (BTEXs), and ozone in Rochester, New York, between 2012 and 2018. Additionally, the influence of ozone precursors (e.g., BTEXs and NO₂) and meteorological variables (e.g., relative humidity (RH), temperature along with wind speed) on ozone dispersion was investigated in the eastern half of the USA using the integrated nested Laplace approximation and stochastic partial differential equation (INLA-SPDE). The benzene variability at seasonal scale was characterized by higher values during the cold seasons. On the contrary, the long-term temporal trend of ozone depicted a repetitive cyclic behavior while an episode, with values exceeding 5 μg/m³, was detected associated with benzene in 2015. The spatial analysis by INLA-SPDE indicated that 1,3,5-trimethylbenzene and benzene were the key ozone precursors influencing ozone formation. It was demonstrated that increase of temperature had a considerable impact on ozone build-up whereas the increment of RH leads to decrease in ambient values of ozone. The amounts of root mean squared error (RMSE), mean absolute error (MAE), and bias for the validation data (e.g., 32 samples) were 0.005, 0.004, and 0.0008, exhibiting a reasonable out-of-sample forecasting by the INLA-SPDE model. The distribution map of ozone highlighted a hot spot in the state of Florida.

Personal exposure to VOCs (BTX) and women health risk assessment in rural kitchen from solid biofuel burning during cooking in West Bengal, India

In this study, personal exposure to benzene, toluene and xylene as important VOC species of incomplete combustion are assessed, considering the ventilation condition of the rural kitchens throughout the seasons. Annual mean total BTX levels were 148.51, 76.98, 34.91 and 13.34 μgm^-3 for the rural kitchens with openness of <25%, 25-50%, 50-75% and >75% respectively. Overall annual mean concentration of benzene, toluene and xylene level was found to be 52.35, 8.85 and 7.23 μgm^-3 respectively. Annual mean total BTX was found across the openness of the kitchens to be 68.43 μgm^-3. There was no significant interaction between the independent variables 'openness' and 'season' explaining pollution exposure variability. Openness of the kitchens was the only significant predictor for BTX exposure concentration variation. Average daily dose (ADD) analysis showed median value of 1.439 × 10^-3 mg/kg-day with 95% certainty range from 9.04 × 10^-4 mg/kg-day to 2.220 × 10^-3 mg/kg-day. Hazard index (HI) indicates no significant risk of non-carcinogenic effect from the exposure to benzene, toluene and xylene. In ADD and all non-cancerous risk estimates (HQ of benzene, toluene, xylene), exposure time emerges as the single most contributor whereas, annual average pollutant exposure is the second most risk contributor in all the cases. Lifetime cancer risk of benzene exceeded the acceptable level indicating probable cancer risk and inhalation unit risk alone contributes above 75%; exposure time came after with 16.3% contribution.

Diurnal variation of BTEX at road traffic intersection points in Delhi, India: source, ozone formation potential, and health risk assessment

The present study was carried out to observe the variation of volatile organic compounds (VOCs) namely benzene, toluene, ethylbenzene, and xylene isomers (BTEX) at three different sites of Delhi, during 2016-2017. Four hourly sampling was carried out day and night separately. Results showed that BTEX concentration was highest in post-monsoon and lowest in monsoon season. Again, daily variation shows that benzene (47%) and toluene (35%) were more during night than day when it was 44% and 33% respectively. Mean concentration of BTEX was observed in following order: ethylbenzene ~ o-xylene < m,p-xylene < toluene < benzene, while overall seasonal variation was observed as follows: post-monsoon > summer > winter > monsoon. Possible emission sources of BTEX were also established through corresponding ratios of individual compounds. Xylene isomers together accounted highest ozone formation potential. The risk assessments of BTEX were carried out in terms of non-cancer (the hazard quotient, HQ) and cancer (the incremental lifetime cancer risk, ILCR) regarding the inhalation exposure only. It was observed that benzene and xylene isomers possessed higher HQs than ethylbenzene and toluene at all sites throughout the study. Again, benzene was found with higher mean ILCR (3.58 × 10^-5) than ethylbenzene (1.47 × 10^-5).

BTEX and heavy metals removal using pulverized waste tires in engineered fill materials

In this study, the potential of pulverized waste tires (PWTs), either on their own or mixed with soil (well graded sand), to act as adsorptive fill materials was evaluated by conducting laboratory tests for accessing their adsorption and geotechnical properties. PWT (0, 5, 10, 15, 25, and 100 wt%) was mixed with soil to evaluate the removal of benzene, toluene, ethylbenzene, and xylene (BTEX) components and two heavy metal ions (Pb²⁺ and Cu²⁺). Adsorption batch tests were performed to determine the equilibrium sorption capacity of each mixture. Subsequently, compaction, direct shear, and consolidation tests were performed to establish their geotechnical properties. The results showed that BTEX had the strongest affinity based on the uptake capacity by the soil-PWT mixtures. The adsorption of BTEX increased for greater PWT content, with pure PWT having the highest adsorption capacity toward BTEX removal: uptake capacities for xylene, ethylbenzene, toluene, and benzene were 526, 377, 207 and 127 μg/g sorbent, respectively. Heavy metal removal was increased by increasing the amount of PWT up to 10 wt%, and then decreased beyond this ratio. Compacted soil-PWT mixtures comprising 5-25 wt% PWT have relatively low dry unit weight, low compressibility, adequate shear capacity for many load-bearing field applications, and satisfactory adsorption of organic/inorganic contaminants, such that they could also be used as adsorptive fill materials.

Distribution Characteristics of Volatile Organic Compounds and Contribution to Ozone Formation in a Coking Wastewater Treatment Plant

Ozone pollution, which can be caused by photochemical reactions, has become a serious problem. The ozone formation potential (OFP) is used to describe the photochemical reactivity. Volatile organic compounds (VOCs) are main precursors of ozone formation, and wastewater treatment plants (WWTPs) are important sources of VOCs. Therefore, it is necessary to study the concentration level and OFP of VOCs from WWTPs. In this work, a coking WWTP with anaerobic-oxic-oxic (A/O/O) processes in Shaoguan city, Guangdong province, China, was selected to investigate the characteristics of VOCs at wastewater treatment areas and office areas. The OFP of VOCs was estimated by the maximum incremental reactivity (MIR) coefficient method. Results showed that 17 VOCs were detected, and the total concentration of VOCs was the highest at the raw water tank (857.86 μg m^-3). The benzene series accounted for 69.0%-86.9% and was the main component of VOCs in the WWTP. Based on OFP data, the top six VOCs contributing most to the OFP were m-xylene, toluene, p-xylene, o-xylene, styrene, and benzene. This study provides field data and information on the environmental risk of VOCs for coking companies and environmental departments. We found that the priority control sources of VOCs were wastewater treatment units because of their larger OFP contributions.

Analytical methodology to screen UV-filters and synthetic musk compounds in market tomatoes

A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) methodology followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis was developed to extract thirteen synthetic musk compounds (SMCs: cashmeran, celestolide, phantolide, traseolide, galaxolide, tonalide, musk ambrette, musk xylene, musk ketone, musk tibetene, musk moskene, ethylene brassylate and exaltolide) and six ultraviolet-filters (UVFs: 2-ethylhexyl 4-dimethylaminobenzoate, 3-(4'-methylbenzylidene) camphor, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, benzophenone and drometrizole trisiloxane) from tomatoes. The proposed methodology was optimized: 2 g of freeze-dried tomato was extracted with 4 mL of water and 10 mL of ethyl acetate, adding 6 g of MgSO₄ and 1.5 g of NaCl, then a dispersive solid-phase extraction was performed using 3 g of MgSO₄, 300 mg of primary-secondary amino adsorbent (PSA) and 300 mg of octadecyl-silica (C18). Validation delivered recoveries between 81 (celestolide) and 119% (musk tibetene), with relative standard deviations <10%. The instrumental limit of detection varied from 0.02 (2-ethylhexyl 4-methoxycinnamate) to 3.00 pg (exaltolide and musk xylene). Regarding the method quantification limits, it ranged between 0.4 (celestolide) and 47.9 ng g^-1 dw (exaltolide). The method was applied to different varieties of tomatoes (Solanum lycopersicum), revealing UVFs and SMCs between 1 and 210 ng g^-1 dw. Higher concentrations were found for benzophenone (29-210 ng g^-1 dw) and galaxolide (9-53 ng g^-1 dw). The risk associated to the ingestion of contaminated tomatoes has also been estimated, showing that a potential health risk is unlikely.

Remediation of BTEX and Cr(VI) contamination in soil using bioelectrochemical system-an eco-friendly approach

Soil contamination with benzene, toluene, ethylbenzene and xylene isomers (BTEX) has raised increasing concern because of its high solubility in water and toxicity to biotic communities. This study aims at investigating the process and prospects of deploying bioelectrochemical system (BES) for the removal of BTEX from artificially contaminated soil using Pseudomonas putida YNS1, alongside the reduction of hexavalent chromium (Cr(VI)). The BES was setup with desired operating conditions: initial concentration of BTEX (50-400 mg/L in 100 mL of sterilized water), pH (4-10) and applied potential voltage (0.6-1.2 V) with 10 μL log-phase culture along with the addition of Cr(VI) (10 mg/L). Samples were collected at regular intervals and analysed for BTEX degradation using gas chromatography and Cr(VI) reduction using UV-Vis spectrophotometer. Under optimized conditions (initial BTEX concentration, 200 mg/L; pH 7; and applied voltage 0.8 V with Cr(VI) of 10 mg/L), 92% of BTEX was degraded and 90% Cr(VI) was reduced from the contaminated soil. The intermediates produced during degradation were analysed through gas chromatography-flame ionization detector (GC-FID), and the possible degradation pathway was elucidated. The results indicated that BES could be effective for simultaneous degradation of BTEX along with Cr(VI) reduction.

Exposure to BTEX in buses: The influence of vehicle fuel type

Diesel-fueled buses have been replaced by Compressed Natural Gas (CNG) to minimize the high level of emissions in urban areas. However, differences in indoor exposure levels to Benzene, Toluene, Ethylbenzene and Xylene (BTEX) in those vehicles have not been investigated so far. The primary aim of this study was to determine if passengers are exposed to different BTEX levels when using buses powered by CNG or by diesel, and further explore if indoor levels are influenced by external air quality. For this purpose, BTEX air concentrations were measured in bus cabins (CNG and diesel), parking stations and in a background urban area using passive air samplers. Results showed that BTEX concentrations inside vehicles were higher than outside, but no significant differences were found between buses powered by CNG or by diesel. In CNG vehicles, high and significant positive correlation was found between benzene and the number of journeys in the same route (r_s = 0.786, p < 0.05), vehicle operating time (r_s = 0.738, p < 0.05), exposure time (r_s = 0.714, p < 0.05) and exposure index (r_s = 0.738, p < 0.05), but this was not observed for diesel vehicles. Benzene in bus cabins was found to be significantly below reference value for human health protection. However, excepting p-xylene, all other aromatic pollutants have a mean concentration significantly above the lowest effect level (p ≤ 0.002 for all comparisons). Additionally, higher BTEX levels in cabin buses than in outdoor air suggest the presence of other emission sources in indoor cabins. These findings emphasize the need for further studies to fully characterize indoor emission sources in order to minimize the negative impact of BTEX exposure to human health.

Sericin-coated polyester based air-filter for removal of particulate matter and volatile organic compounds (BTEX) from indoor air

Particulate matter and volatile organic compounds have emerged as a prime environmental concern with increasing air pollution in metropolitan cities leading to lung and heart-related issues. This paper describes a facile and novel method for fabrication of polyester based air filter via surface coating with Sericin for imparting effective removal of particulate matter and volatile organic compounds. A simple dip-coating method followed by thermal fixation has been adopted to coat Sericin on the polyester fiber. The developed changes in surface functionality and morphology of the polyester fiber were confirmed by Attenuated total reflection Fourier-transform infrared spectroscopy and Field emission scanning electron microscopy analysis. The fabricated air filter was tested for removal of particulate matter (generated burning incense stick) and volatile organic compounds (generated vaporizing gasoline), in an indoor chamber. The Sericin coated filter was able to remove the PM_2.5 and PM ₁₀ (from 1000 μg/m³ level to 5 μg/m³ in a 6.28 m³ chamber) within 27 and 23 min of operation, respectively. The fabricated filter very effectively removed particulate matter for 2160 cycles with intermittent washing. The Sericin-coated air filter also proved very effective for removal of volatile organic compounds (Benzene, Toluene, Ethylbenzene and Xylene) from an indoor chamber at a varying initial concentration of 100-1000 μg/m³. The adsorption behavior was described by Langmuir-Freundlich (sips) isotherm and pseudo-first order kinetics with minimal error. The maximum adsorption capacity (mg/g) obtained with Sips Isotherm fitting followed the order Xylene (6.97)>Ethyl Benzene (5.68)> Toluene (5.35) >Benzene (4.78).

BTEX compositions and its potential health impacts in Malaysia

This study aims to determine the composition of BTEX (benzene, toluene, ethylbenzene and xylene) and assess the risk to health at different sites in Malaysia. Continuous monitoring of BTEX in Kuala Lumpur City Centre, Kuala Terengganu, Kota Kinabalu and Fraser Hill were conducted using Online Gas Chromatograph. For comparison, BTEX at selected hotspot locations were determined by active sampling method using sorbent tubes and Thermal Desorption Gas Chromatography Mass Spectrometry. The hazard quotient (HQ) for non-carcinogenic and the life-time cancer risk (LTCR) of BTEX were calculated using the United States Environmental Protection Agency (USEPA) health risk assessment (HRA) methods. The results showed that the highest total BTEX concentrations using continuous monitoring were recorded in the Kuala Lumpur City Centre (49.56 ± 23.71 μg/m³). Toluene was the most dominant among the BTEX compounds. The average concentrations of benzene ranged from 0.69 ± 0.45 μg/m³ to 6.20 ± 3.51 μg/m³. Measurements using active sampling showed that BTEX concentrations dominated at the roadside (193.11 ± 114.57 μg/m³) in comparison to petrol station (73.08 ± 30.41 μg/m³), petrochemical industry (32.10 ± 13.13 μg/m³) and airport (25.30 ± 6.17 μg/m³). Strong correlations among BTEX compounds (p<0.01, r>0.7) at Kuala Lumpur City Centre showed that BTEX compounds originated from similar sources. The values of HQ at all stations were <1 indicating the non-carcinogenic risk are negligible and do not pose threats to human health. The LTCR value based on benzene inhalation (1.59 × 10^-5) at Kuala Lumpur City Centre were between 1 × 10^-4 and 1 × 10^-5, representing a probable carcinogenic risk.

Assessment of exposure of gas station attendants in Sri Lanka to benzene, toluene and xylenes

Exposure to benzene, toluene and p-, m-, o-xylene (BTX) was studied in 29 gas station attendants and 16 office workers in Sri Lanka. The aim of this study was to assess the exposure level and identify potential exposure mitigating measures. Pre- and post-shift samples of end-exhaled air were collected and analysed for BTX on a thermal desorption gas chromatography mass spectrometry system (TD-GC-MS). Urine was collected at the same timepoints and analysed for a metabolite of benzene, S-phenyl mercapturic acid (SPMA), using liquid chromatography-mass spectrometry (LC-MS). Environmental exposure was measured by personal air sampling and analysed by gas chromatography flame ionization detection (GC-FID). Median (range) breathing zone air concentrations were 609 (65.1-1960) μg/m³ for benzene and 746 (<5.0-2770) μg/m³ for toluene. Taking into account long working hours, 28% of the measured exposures exceeded the ACGIH threshold limit value (TLV) for an 8-h time-weighted average of 1.6 mg/m³ for benzene. Xylene isomers were not detected. End-exhaled air concentrations were significantly increased for gas station attendants compared to office workers (p < 0.005). The difference was 1-3-fold in pre-shift and 2-5-fold in post-shift samples. The increase from pre-to post-shift amounted to 5-15-fold (p < 0.005). Pre-shift BTX concentrations in end-exhaled air were higher in smokers compared to non-smokers (p < 0.01). Exposure due to self-reported fuel spills was related to enhanced exhaled BTX (p < 0.05). The same was found for sleeping at the location of the gas station between two work-shifts. Benzene in end-exhaled air was moderately associated with benzene in the breathing zone (r = 0.422; p < 0.001). Median creatinine-corrected S-phenyl mercapturic acid (SPMA) was similar in pre- and post-shift (2.40 and 3.02 μg/g) in gas station attendants but increased in office workers (from 0.55 to 1.07 μg/g). In conclusion, working as a gas station attendant leads to inhalation exposure and occasional skin exposure to BTX. Smoking was identified as the most important co-exposure. Besides taking preventive measure to reduce exposure, the reduction of working hours to 40 h per week is expected to decrease benzene levels below the current TLV.

Shift of microbial diversity and function in high-efficiency performance biotrickling filter for gaseous xylene treatment

Xylene is the main component of many volatile industrial pollution sources, and the use of biotechnology to remove volatile organic compounds (VOCs) has become a growing trend. In this study, a biotrickling filter for gaseous xylene treatment was developed using activated sludge as raw material to study the biodegradation process of xylene. Reaction conditions were optimized, and long-term operation was performed. The optimal pH was 7.0, gas-liquid ratio was 15:1 (v/v), and temperature was 25 °C. High-throughput sequencing technique was carried out to analyze microbial communities in the top, middle, and bottom layers of the reactor. Characteristics of microbial diversity were elucidated, and microbial functions were predicted. The result showed that the removal efficiency (RE) was stable at 86%-91%, the maximum elimination capacity (EC) was 303.61 g·m^-3·hr^-1, residence time was 33.75 sec, and the initial inlet xylene concentration was 3000 mg·m^-3, which was the highest known degradation concentration reported. Kinetic analysis of the xylene degradation indicated that it was a very high-efficiency-activity bioprocess. The r_max was 1059.8 g·m^-3·hr^-1, and K_s value was 4.78 g·m^-3 in stationary phase. In addition, microbial community structures in the bottom and top layers were significantly different: Pseudomonas was the dominant genus in the bottom layer, whereas Sphingobium was dominant in the top layer. The results showed that intermediate metabolites of xylene could affect the distribution of community structure. Pseudomonas sp. can adapt to high concentration xylene-contaminated environments. Implications: We combined domesticated active sludge and reinforced microbial agent on biotrickling filter. This system performed continuously under a reduced residence time at 33.75 sec and high elimination capacity at 303.61 g·m^-3·hr^-1 in the biotrickling reactor for about 260 days. In this case, predomestication combined with reinforcing of microorganisms was very important to obtaining high-efficiency results. Analysis of microbial diversity and functional prediction indicated a gradient distribution along with the concentration of xylene. This implied a rational design of microbial reagent and optimizing the inoculation of different sites of reactor could reduce the preparation period of the technology.

Atmospheric fate of peroxyacetyl nitrate in suburban Hong Kong and its impact on local ozone pollution

Peroxyacetyl nitrate (PAN) is an important reservoir of atmospheric nitrogen, modulating reactive nitrogen cycle and ozone (O₃) formation. To understand the origins of PAN, a field measurement was conducted at Tung Chung site (TC) in suburban Hong Kong from October to November 2016. The average level of PAN was 0.63 ± 0.05 ppbv, with a maximum of 7.30 ppbv. Higher PAN/O₃ ratio (0.043-0.058) was captured on episodes, i.e. when hourly maximum O₃ exceeded 80 ppbv, than on non-episodes (0.01), since O₃ production was less efficient than PAN when there was an elevation of precursors (i.e. volatile organic compounds (VOCs) and nitrogen oxide (NO_x)). Model simulations revealed that oxidations of acetaldehyde (65.3 ± 2.3%), methylglyoxal (MGLY, 12.7 ± 1.2%) and other oxygenated VOCs (OVOCs) (8.0 ± 0.6%), and radical cycling (12.2 ± 0.8%) were the major production pathways of peroxyacetyl (PA) radical, while local PAN formation was controlled by both VOCs and nitrogen dioxide (NO₂). Among all VOC species, carbonyls made the highest contribution (59%) to PAN formation, followed by aromatics (26%) and biogenic VOCs (BVOCs) (10%) through direct oxidation/decomposition. Besides, active VOCs (i.e. carbonyls, aromatics, BVOCs and alkenes/alkynes) could stimulate hydroxyl (OH) production, thus indirectly facilitating the PAN formation. Apart from primary emissions, carbonyls were also generated from oxidation of first-generation precursors, i.e., hydrocarbons, of which xylenes contributed the most to PAN production. Furthermore, PAN formation suppressed local O₃ formation at a rate of 2.84 ppbv/ppbv, when NO₂, OH and hydroperoxy (HO₂) levels decreased and nitrogen monoxide (NO) value enhanced. Namely, O₃ was reduced by 2.84 ppbv per ppbv PAN formation. Net O₃ production rate was weakened (∼36%) due to PAN photochemistry, so as each individual production and loss pathway. The findings advanced our knowledge of atmospheric PAN and its impact on O₃ production.

Sorption of Tonalide, Musk Xylene, Galaxolide, and Musk Ketone by microplastics of polyethylene and polyvinyl chloride

The effects of time, temperature, and salinity on the adsorption of Tonalide (AHTN), Musk Xylene (MX), Galaxolide (HHCB), and Musk Ketone (MK) by microplastics of polyethylene (PE) and polyvinyl chloride (PVC) are studied. Results indicate that the equilibrium sorption time was about 10 h and the adsorption kinetics model conformed to the first-order adsorption kinetic model and pseudo-second order kinetic model, this indicates that the main adsorption mechanism might be chemical adsorption and physical absorption. Adsorption reached a nadir at 15 °C and 14% salinity. The adsorption capacity gradually increases, and then decreases, finally increases with an increase in NaCl concentration. Due to the specific surface area and the pore volume of PVC was larger than PE, the adsorption capacity of PVC was higher than that of PE in the equal conditions.

Study on transformation and degradation of bisphenol A by Trametes versicolor laccase and simulation of molecular docking

As a typical class of environmental endocrine disruptors, bisphenol A poses a potential threat to the sustainable survival and reproduction of living beings and human beings. In this study, the interaction between Trametes versicolor laccase and bisphenol A (BPA) was studied by molecular docking simulation, and the catalytic degradation of BPA was verified by experiments. The conditions for the laccase production of T. versicolor were optimized by orthogonal design, and the degradation of BPA was studied using its crude enzyme solution. The optimum degradation conditions were obtained by response surface methodology (RSM). Ultimately, the transformation products after 3 and 6 h of reaction were detected by gas chromatography-mass spectrometry. Docking results demonstrated that the reaction between laccase and BPA was spontaneous, and the degradation rate in 24 h reached 88.76%. RSM results showed that the highest BPA degradation rate of 97.68% was reached after 1 h reaction at 44.6 °C, 5 mg/L initial BPA concentration, and pH 5.20. The intermediate products of BPA catalyzed by laccase included ethylbenzene, p-xylene, and cyclohexanone 1-methyl-4-isopropenyl-2-cyclohexenol. This finding reveals that BPA degradation by the crude laccase from T. versicolor starts from the C atoms between two benzene rings that connect BPA. Compared with expensive pure enzyme, the crude laccase solution prepared by T. versicolor showed greater efficiency in BPA degradation. This work provides theoretical references and experimental methods for the biological processing of harmful pollutants.

Exposure and risk assessment of volatile organic compounds and airborne phthalates in Singapore's Child Care Centers

Infants and children under 6 years old spend most of daily time in Child Care Centers (CCCs), especially in the tropical regions like Singapore. Environmental exposure and associated risk during this early critical developmental stage is of great public concern. In this study, seven representative volatile organic compounds (VOCs) and five typical phthalates were analyzed in the indoor and outdoor air samples collected from 32 Singapore CCCs. The median of total VOC and phthalate concentration in indoor air was 19.03 and 5.41 μg m^-3; respectively. For both indoors and outdoors environment, benzene, toluene and xylene were the dominant VOC contributors (more than 68%). For indoor air phthalates, di(2-ethylhexyl) phthalate and di-butyl phthalate (DBP) accounts for 60-76%. The level of both VOCs and phthalates in indoor environment was significantly higher than that in outdoor, with an average indoor/outdoor ratio of 1.24 and 1.45; respectively. A strong correlation (r > 0.50, p < 0.05) was observed between indoor and outdoor air compounds. VOC and phthalate levels have no significant difference between CCCs with split-unit and centrally ventilated air conditioners. Monte Carlo simulation was used to estimate exposure uncertainty and variability for the risk assessment. Overall, the concentrations of VOC were below the healthy reference values from either EPA Integrated Risk Information System (IRIS) or Singapore guideline. However, similar to other countries' report, benzene, DBP, ethylbenzene and naphthalene were at levels that could exceed the stringent standards such as Office of Environmental Health Hazard Assessment (OEHHA) cancer and reproductive health-based benchmarks.

Occupational exposure to volatile organic compounds and health risks in Colorado nail salons

Nail salon technicians face chronic exposure to volatile organic compounds (VOCs), which can lead to adverse health outcomes including cancer. In this study, indoor levels of formaldehyde, as well as benzene, toluene, ethylbenzene and xylene, were measured in 6 Colorado nail salons. Personal exposure VOC measurements and health questionnaires (n = 20) were also performed; questionnaires included employee demographics, health symptoms experienced, and protective equipment used. Cancer slope factors from the United States Environmental Protection Agency (US EPA) and anthropometric data from the Centers for Disease Control and Prevention were then used to estimate cancer risk for workers, assuming 20-yr exposures to concentrations of benzene and formaldehyde reported here. Results show that 70% of surveyed workers experienced at least one health issue related to their employment, with many reporting multiple related symptoms. Indoor concentrations of formaldehyde ranged from 5.32 to 20.6 μg m^-3, across all 6 salons. Indoor concentrations of toluene ranged from 26.7 to 816 μg m^-3, followed by benzene (3.13-51.8 μg m^-3), xylenes (5.16-34.6 μg m^-3), and ethylbenzene (1.65-9.52 μg m^-3). Formaldehyde levels measured in one salon exceeded the Recommended Exposure Limit from the National Institute for Occupational Safety and Health. Cancer risk estimates from formaldehyde exposure exceeded the US EPA de minimis risk level (1 × 10^-6) for squamous cell carcinoma, nasopharyngeal cancer, Hodgkin's lymphoma, and leukemia; leukemia risk exceeded 1 × 10^-4 in one salon. The average leukemia risk from benzene exposure also exceeded the US EPA de minimis risk level for all demographic categories modeled. In general, concentrations of aromatic compounds measured here were comparable to those measured in studies of oil refinery and auto garage workers. Cancer risk models determined that 20-yr exposure to formaldehyde and benzene concentrations measured in this study will significantly increase worker's risk of developing cancer in their lifetime.

Exposure to BTEX in beauty salons: biomonitoring, urinary excretion, clinical symptoms, and health risk assessments

Benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations were measured in beauty salons (BS) and in the urine of the beauty practitioners and a control group. Indoor and outdoor concentrations of BTEX were measured in 36 randomly selected salons. Before- and after-shift urinary BTEX were measured from one female non-smoker employee in each salon, and repeated three times. Clinical symptoms in that beautician were assessed by a physician. Thirty-six unexposed women were included as the control group. Cancer and non-cancer risks of exposure were assessed using deterministic and stochastic methods. Average indoor concentrations of BTEX were higher than those in the ambient air. Urinary BTEX concentrations in the beauty practitioners were significantly higher than in the control group. Linear regression showed that 77% of urinary benzene and toluene variations can be explained by their airborne concentrations. A positive significant relationship was found between age and urinary BTEX concentrations. Although the BTEX cancer and non-cancer risks were not significant, BTEX led to irritation of the eyes, throat, lung, and nose. In addition, toluene caused menstrual disorders among beauty practitioners. These results suggest that it is essential to decrease the exposure of beauty practitioners to BTEX compounds.

Adsorptive removal of bisphenol A, chloroxylenol, and carbamazepine from water using a novel β-cyclodextrin polymer

The emerging organic micro-pollutants, such as bisphenol A (BPA), chloroxylenol (PCMX) and carbamazepine (CBZ), have raised concerns owing to their adverse impact on human health and ecological security. In this study, a novel cyclodextrin polymer (β-CDP) has been successfully prepared by nucleophilic substitution of β-cyclodextrin with tetrafluoroterephthalonitrile (TFP). The removal of three emerging organic micro-pollutants (BPA, CBZ and PCMX) by β-CDP under a single or mixture adsorption system was examined, and the adsorption behavior was investigated by adsorption kinetics and isotherm study. The maximum adsorption capacity of β-CDP for BPA, PCMX and CBZ according to Langmuir isotherm in single system was 164.4, 144.1 and 136.4 mg/g, respectively. Compared with single system, the competitive adsorption of each pollutant on β-CDP in mixture system was only slightly inhibited. Changing the pH, raising the presence of fulvic acid (FA) or ionic strength had no significant influence on the adsorption of BPA, PCMX and CBZ onto β-CDP. The removal of these three organic micro-pollutants was related to the value of logK_ow of the contaminants. These results demonstrated remarkable advantages of β-CDP material relevant to organic micro-pollutants removal in wastewater treatment.

Assessment of benzene, toluene, ethyl-benzene, and xylene (BTEX) toxicity in soil using sulfur-oxidizing bacterial (SOB) bioassay

The assessment of benzene, toluene, ethyl-benzene, and xylene (BTEX)-contaminated soil toxicity was performed using a sulfur-oxidizing bacteria (SOB) assay. The experiments were set up using an individual pollutant in a 25-mL bottle sealed with a rubber stopper and aluminum cap since BTEX are volatile. A large headspace volume (14 mL) was kept in the reactors to provide enough oxygen for the SOB. Soil samples were spiked with BTEX compounds in the concentration range of 1-1000 mg/kg. In reactors without BTEX compounds, approximately 85% of the theoretically required oxygen was consumed. Whereas, the reactors with benzene consumed in the range of 82-64% (5-100 mg/kg), those with toluene consumed 76-53% (1-50 mg/kg), those with ethyl-benzene consumed 44-71% (5-100 mg/kg), and those with xylene consumed 64-71% (1-10 mg/kg) of the theoretically required oxygen. The effective concentrations responsible for 50% growth inhibition (EC₅₀) for benzene, toluene, ethyl-benzene, and xylene detection were 130.2, 1.2, 15.2, and 0.7 mg/kg, respectively. These results suggest that this SOB-based bioassay can detect BTEX pollutants in soils.

A case study of BTEX characteristics and health effects by major point sources of pollution during winter in Iran

This study characterized spatio-temporal variations in the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the vicinity of gas and compressed natural gas (CNG) stations in Tehran, Iran. Health risk assessment (HRA) was computed using Monte Carlo simulations (MCS) for evaluating inhalation lifetime cancer risk (LTCR), the hazard quotient (HQ), and sensitivity analysis (SA) for BTEX exposure in different age groups (birth to <81) and as a function of distance (0-250 m) from the center of the stations. For all monitoring stations, the average values of benzene, toluene, ethylbenzene, and xylene in winter were 466.09 ± 132.25, 873.13 ± 233.51, 493.05 ± 141.22, and 910.57 ± 145.40 μg m^-3, respectively. The mean wintertime ratios of T/B for the 12 stations ranged from 1.69 to 2.04. Furthermore, there was no significant relationship between the concentration of BTEX with either the specific month or distance from the center of stations (p > 0.05). Factors promoting BTEX formation in the study region were fuel evaporation and gas/CNG station emissions. The LTCRs for the target compounds in the winter for different age groups and distances from the center of stations was limited to 2.11 × 10^-4 to 1.82 × 10^-3 and 2.30 × 10^-4 to 2.01 × 10^-3, respectively, which exceeded proposed values by U.S. EPA. Moreover, the HQs for BTEX for three age groups and distances were limited to between 2.89 × 10^-5 and 9.33 × 10^-2, which were lower than the acceptable limit (HQs < 1). The results of this work are applicable to similar areas that are heavily populated with vehicular traffic. This study motivates a closer look at mitigation strategies to limit the health effects of carcinogenic emissions such as benzene and ethylbenzene from gas/CNG stations.

A comprehensive study on spatio-temporal distribution, health risk assessment and ozone formation potential of BTEX emissions in ambient air of Delhi, India

The hazardous air pollutants like benzene, toluene, ethylbenzene and xylene (BTEX) are considered as toxic because of their role in ozone formation and adverse effects on human health. Owing to this, the present study was carried out at six spatially distributed sites in Delhi from November 2017- June 2018. Activated charcoal tubes were used to collect samples of BTEX and were further analyzed using GC-FID. The minimum BTEX concentration was found at institutional site (9.94 μg/m³) and maximum at roadside site (103.12 μg/m³) with the average of 46.66 μg/m³. Also, the levels of BTEX were 1.18-1.74 times higher during rush hours as compared to non-rush hours. The high T/B ratio (2.26-3.41) observed is the indication of the traffic-originated sources of emission. The cancer risks calculated for benzene at probability 0.50 ranged as 1.29E-06 - 1.80E-05, whereas 4.09E-06 - 3.40E-05 at probability 0.95, which were higher than the acceptable value of 1.0E-06. The non-cancer health risks in terms of hazard index were observed less than unity i.e. within acceptable limit. The total ozone formation potential (OFP) was obtained as 207.51 ± 123.40 μg/m³ with maximum potential by toluene. Such high levels of BTEX, cancer risks and OFP obtained in the study especially at roadside and connectivity hub are harmful for people residing near these areas, and also to large commuters, who are exposed to such emissions during travelling.

Urban sources of synthetic musk compounds to the environment

The occurrence and potential sources of synthetic musk compounds (SMCs) in the urban and surrounding environment were investigated. We analyzed air, soils and surface waters from a wide array of land-use types and urban densities including air from wastewater treatment plants (WWTPs), indoor, urban, rural, and remote Arctic sites; surface waters from urban and rural tributaries; and effluents of three WWTPs. In air, the median sum concentration of six selected polycyclic musks (Σ6PCMs) (i.e., galaxolide, tonalide, cashmeran, celestolide, phantolide, traseolide) were the highest from WWTP on-site > indoor > urban > WWTP off-site > rural. SMCs were not found in remote Arctic air indicating low potential for long-range atmospheric transport. SMCs were not found in soils, likely because of their high volatility and fast biodegradation rate. Galaxolide (HHCB) and tonalide (AHTN) were the two most abundant SMCs in air, tributaries and WWTP effluents. Σ6PCM concentrations in air taken along urban-rural transects and in tributary water were positively correlated with population density. In WWTP on-site air, trace levels of the toxic nitro-musks, namely musk xylene and musk ketone were detected and macrocyclic musks accounted for ∼10% of the total SMCs measured. In WWTP effluents, the concentrations of Σ6PCMs were proportional to the population served. We conclude that sources of SMCs to the outdoor urban environment and hence the surrounding region, originate from releases from indoor air, and temperature-dependent volatilization from WWTPs during treatment.

Potential for city parks to reduce exposure to BTEX in air

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are hazardous air pollutants commonly found in outdoor air. Several studies have explored the potential of vegetation to mitigate BTEX in outdoor air, but they are limited to a northern temperate climate and their results lack consensus. To investigate this subject in a subtropical climate, we deployed passive air samplers for two weeks in parks and outside nearby residences at four locations: three in an urban area and one in a rural area in Alabama, USA. All BTEX concentrations were below health-based guidelines and were comparable to those found in several other studies in populated settings. Concentrations of TEX, but not benzene, were 3-39% lower in parks than at nearby residences, and the differences were significant. Site type (park vs. residential) was a significant predictor of TEX concentrations, while distance to the nearest major road was a significant predictor of BTX concentrations. In and around two of the parks, toluene : benzene ratios fell outside the range expected for vehicular emissions (p < 0.01), suggesting that there were additional, industrial sources of benzene near these two locations. The ratio of m-,p-xylene : ethylbenzene was high at all locations except one residential area, indicating that BTEX were freshly emitted. Concentrations of individual BTEX compounds were highly correlated with each other in most cases, except for locations that may have been impacted by nearby industrial sources of benzene. Results of this study suggest that parks can help reduce exposure to TEX by a modest amount in some situations.

CuO and CeO2-doped catalytic material synthesized from red mud and rice husk ash for p-xylene deep oxidation

CuO-CeO₂ catalysts supported on material synthesized from red mud and rice husk ash (CuO-CeO₂/ZRM) were prepared by co-impregnation method. The role of CeO₂ additive in the improvement of physicochemical properties and catalytic activity of CuO-CeO₂/ZRM catalysts were emphasized. Several techniques, including Brunauer-Emmett-Teller Nitrogen physisorption measurements, X-ray powder diffraction, hydrogen temperature programed reduction, scanning electron microscopy and transmission electron microscopy (TEM) were used to investigate the properties of catalysts. Crystallite size calculated by Scherrer' equation was 17.4 - 21.8 nm. Modification of 5 wt% CuO/ZRM catalyst with CeO₂ had reduced the size of the nanoparticles leading to a significant enhancement of the catalytic activity in p-xylene deep oxidation at temperature range of 275 - 400 °C. The 5 wt% CuO/ZRM sample promoted by 3 wt% of nanoparticle CeO₂ with the average size of 17.5 nm and BET surface area of 31.3 m² g^-1 exhibited the best activity for p-xylene deep oxidation. In this sample, the conversion of p-xylene reaches to 90% at 350 °C.