Monitoring Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) Levels in Mixed-Use Residential-Commercial Buildings in Shiraz, Iran: Assessing the Carcinogenicity and Non-Carcinogenicity Risk of Their Inhabitants

The aim of this study is to investigate the concentration of Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) compounds in the indoor air of residential-commercial complexes and to compare it with other residential buildings (control) as well as to assess the carcinogenicity and non-carcinogenicity risk of these pollutants. BTEX concentration was investigated in the indoor air of 30 ground floor restaurants, 30 upper residential units of the complexes, 20 adjacent residential units (control), and their corridors. The mean BTEX concentration measured in the upper residential units was reported higher than in the control residential units, though they were not significantly different. The lifetime cancer risk (LTCR) value calculated for benzene in the upper residential units was lower than 10−4 and higher than 10−6 across all ages, indicating a carcinogenicity risk. Furthermore, the mean hazard quotient (HQ) for all compounds was obtained lower than 1, suggesting no concern about the non-carcinogenicity risk of these compounds in the studied region. Nevertheless, considering the sources of benzene production in the indoor air as well as the carcinogenicity of these pollutants and the risk they pose in human health, application towards the reduction of the sources and concentration of benzene in the indoor air are necessary.

Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites

Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O2 conc. 8 mg l−1) and micro-aerobic/oxygen-limited (O2 conc. 0.5 mg l−1) conditions using either individual (8 mg‧l−1) or a mixture of compounds (~ 1.3 mg‧l−1 of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l−1 per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Photocatalytic Degradation of Toluene and BTEX Compounds in Gas Reactor Modified by TiO2/Ti Net Nanotubes

Exposure to volatile organic compounds (VOCs), such as toluene and BTEX gas, may cause severe impacts on the environment and long-term health problems for the workers. Industry must place this issue as a priority in supporting occupational health and efforts to minimize the environmental effects. However, many industries still have not paid more attention to degrading their industrial waste containing these compounds. Several studies on VOCs degradation in liquid and aerial media were developed in line with the rapid progress of nanomaterial technology. In this work, we have successfully synthesized TiO2/Ti Net nanotubes thin film resulted from anodization of Ti plate at 25 V vs Ag pseudo-reference electrode for eight hours and physically characterized by SEM/EDX and XRD. The activity test of photocatalysis was performed to determine the TiO2/Ti Net Nanotube's performance to degrade toluene steam and BTEX standard gas. Under the optimum experimental condition, the results showed that approximately 70% of toluene and 60% of BTEX standard gas were degraded in 120 min under the optimum experimental condition. The gas reactor generated approximately 400 ppm CO2 as a byproduct.

Preliminary Investigation of Inorganic and Organic Contaminants in Soils within Wukari Metropolis, Taraba State, Nigeria

This study aimed at the preliminary investigation of inorganic and organic contaminants in soils within Wukari metropolis and to assess the contamination status and metal bioavailability. Digested soil samples for total metals and fractionation were analyzed for heavy metal concentrations in triplicates using Flame Atomic Absorption Spectrophotometer while 5 Varian Bond Elu SI SPE cartridges was used for solid phase extraction and the soil sample extracts were analyzed by GC-MS. The percentage bioavailability of metals ranged from Fe: 13.81 – 98.85 %, Ni: 65.01 - 80.93 %, Cr: 34.82 – 77.19 %, Pb: 66.93 - 86.59 % and Co: 70.35 - 99.14 % respectively. The bioavailability of Fe, Ni, Pb and Co station ST3 which is an agricultural area were above 50.00%. This indicates that food crops grown in the area may be contaminated by the metals. Irrespective of sampling points, the distribution of metals in the soil samples generally followed the order Fe: residual > carbonate > exchangeable > oxidizable; Ni: exchangeable > carbonate > oxidizable > residual; Pb: exchangeable > residual > carbonate > oxidizable; Co: exchangeable > carbonate > oxidizable > residual. Organic contaminants such as Halo alkanes; bromodichloromethane (molecular weight 162.0 g/mol) and chloroform (molecular weight 118.0 g/mol) were detected in ST1 while, 1, 1, 2 trichloroethane (molecular weight 132.0 g/mol). Another contaminant phenol d5 was recorded in sample ST2, ST3 and ST4 respectively. BTEX compounds were also contaminants present in ST5 (Fuel station near some automobile workshops).

The Seasonality Impact of the BTEX Pollution on the Atmosphere of Arad City, Romania

Benzene, toluene, and total BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations registered for one year (2016) have been determined every month for one high-density traffic area. The assessment was performed in Arad City, Romania, to evaluate these pollutants and their influence on the inhabitants’ health. The contaminants were sampled using a static sampling method and analyzed by gas chromatography coupled with mass spectrometry. Benzene was the most dominant among the BTEX compounds—the average concentrations ranged from 18.00 ± 1.32 µg m−3 in December to 2.47 ± 0.74 µg m−3 in August. The average toluene concentration over the year was 4.36 ± 2.42 µg m−3 (with a maximum of 9.60 ± 2.39 µg m−3 in November and a minimum of 1.04 ± 0.29 µg m−3 in May). The toluene/benzene ratio (T/B) was around 0.5, indicating substantial contributions from mobile sources (vehicles). The emission and accumulation of different aromatic compounds (especially benzene) could deteriorate the urban air quality. The lifetime cancer risk (LTCR) for benzene was found to be more than 10−5 in winter, including the inhabitants in the “probable cancer risk” category.

Biodegradation of binary mixtures of octane with benzene, toluene, ethylbenzene or xylene (BTEX): insights on the potential of Burkholderia, Ralstonia, Pseudomonas, and Cupriavidus isolates

The contamination of the environment by crude oil and its by-products, which mainly composed of aliphatic and aromatic hydrocarbons, is a widespread problem. Biodegradation by bacteria is one of the processes responsible for the removal of these pollutants. This study was conducted to determine the abilities of Burkholderia sp. B5, Ralstonia sp. B1, Pseudomonas sp. T1, and Cupriavidus sp. X5 to degrade binary mixtures of octane (representing aliphatic hydrocarbons) with benzene, toluene, ethylbenzene, or xylene (BTEX as aromatic hydrocarbons) at a final concentration of 100 ppm under aerobic conditions. These strains were isolated from an enriched bacterial consortium (Yabase or Y consortium) that prefer to degrade aromatic hydrocarbon over aliphatic hydrocarbons. We found that B5 degraded all BTEX compounds more rapidly than octane. In contrast, B1, T1 and X5 utilized more of octane over BTX compounds. B5 also preferred to use benzene over octane with varying concentrations of up to 200 mg/l. B5 possesses alkane hydroxylase (alkB) and catechol 2,3-dioxygenase (C23D) genes, which are responsible for the degradation of alkanes and aromatic hydrocarbons, respectively. This study strongly supports our notion that Burkholderia played a key role in the preferential degradation of aromatic hydrocarbons over aliphatic hydrocarbons in the previously characterized Y consortium. The preferential degradation of more toxic aromatic hydrocarbons over aliphatics is crucial in risk-based bioremediation.