Anaerobic benzene oxidation in Geotalea daltonii involves activation by methylation and is regulated by the transition state regulator AbrB.

Benzene is a widespread groundwater contaminant that persists under anoxic conditions. The aim of this study was to more accurately investigate anaerobic microbial degradation pathways to predict benzene fate and transport. Preliminary genomic analysis of Geotalea daltonii strain FRC-32, isolated from contaminated groundwater, revealed the presence of putative aromatic-degrading genes. G. daltonii was subsequently shown to conserve energy for growth on benzene as the sole electron donor and fumarate or nitrate as the electron acceptor. The hbs gene, encoding for 3-hydroxybenzylsuccinate synthase (Hbs), a homolog of the radical-forming, toluene-activating benzylsuccinate synthase (Bss), was upregulated during benzene oxidation in G. daltonii, while the bss gene was upregulated during toluene oxidation. Addition of benzene to the G. daltonii whole-cell lysate resulted in toluene formation, indicating that methylation of benzene was occurring. Complementation of σ54- (deficient) E. coli transformed with the bss operon restored its ability to grow in the presence of toluene, revealing bss to be regulated by σ54. Binding sites for σ70 and the transition state regulator AbrB were identified in the promoter region of the σ54-encoding gene rpoN, and binding was confirmed. Induced expression of abrB during benzene and toluene degradation caused G. daltonii cultures to transition to the death phase. Our results suggested that G. daltonii can anaerobically oxidize benzene by methylation, which is regulated by σ54 and AbrB. Our findings further indicated that the benzene, toluene, and benzoate degradation pathways converge into a single metabolic pathway, representing a uniquely efficient approach to anaerobic aromatic degradation in G. daltonii. IMPORTANCE: The contamination of anaerobic subsurface environments including groundwater with toxic aromatic hydrocarbons, specifically benzene, toluene, ethylbenzene, and xylene, has become a global issue. Subsurface groundwater is largely anoxic, and further study is needed to understand the natural attenuation of these compounds. This study elucidated a metabolic pathway utilized by the bacterium Geotalea daltonii capable of anaerobically degrading the recalcitrant molecule benzene using a unique activation mechanism involving methylation. The identification of aromatic-degrading genes and AbrB as a regulator of the anaerobic benzene and toluene degradation pathways provides insights into the mechanisms employed by G. daltonii to modulate metabolic pathways as necessary to thrive in anoxic contaminated groundwater. Our findings contribute to the understanding of novel anaerobic benzene degradation pathways that could potentially be harnessed to develop improved strategies for bioremediation of groundwater contaminants.

Effect of commutation on pressure drop and microbial diversity in a horizontal biotrickling filter for toluene removal.

A horizontal biotrickling filter (HBTF) was designed to understand the toluene removal process and microbial community structures. The start-up time of the HBTF, immobilized by the dominant fungi was only about 6 days and the toluene removal efficiency was found to be more than 95% when the inlet toluene concentration remained at around 1560.0 mg/m3. In the stable operation stage of the HBTF, based on not greatly reducing the removal efficiency, a simple and convenient periodic commutation was adopted to reduce the pressure drop (△P) and regulate the distribution of microorganisms in the packing area of the HBTF. The △P decreased from about 90 Pa to 10 Pa after the commutation, which indicated its feasibility. The performance of the HBTF was improved by changing the inlet direction of waste gas flow. When the inlet concentration of toluene was about 640 mg/m3, the removal efficiency was nearly 70.0% before commutation and it remained 95.0-98.0% after commutation. Microbial abundance and diversity analysis showed that the corresponding Shannon-Weiner index was 2.73 and 1.84, respectively. The front section of the HBTF, which was exposed to toluene earlier, consistently exhibited higher microbial diversity than that in the back section. Following commutation, microbial diversity decreased in both the front and back sections, with a maximum decline of around 50%. The main fungi treating toluene were Aplanochytrium, Boletellus, and Exophiala.

An investigation of soil and groundwater metagenomes for genes encoding soluble and particulate methane monooxygenase, toluene-4-monoxygenase, propane monooxygenase and phenol hydroxylase.

Soil and groundwater were investigated for the genes encoding soluble and particulate methane monooxygenase/ammonia monooxygenase (sMMO, pMMO/AMO), toluene 4-monooxygenase (T4MO), propane monooxygenase (PMO) and phenol hydroxylase (PH). The objectives were (1) to determine which subunits were present, (2) to examine the diversity of the phylotypes associated with the biomarkers and (3) to identify which metagenome associated genomes (MAGs) contained these subunits. All T4MO and PH subunits were annotated in the groundwater metagenomes, while few were annotated in the soil metagenomes. The majority of the soil metagenomes included only four sMMO subunits. Only two groundwater metagenomes contained five sMMO subunits. Gene counts for the pMMO subunits varied between samples. The majority of the soil metagenomes were annotated for all four PMO subunits, while three out of eight groundwater metagenomes contained all four PMO subunits. A comparison of the blast alignments for the sMMO alpha chain (mmoX) indicated the phylotypes differed between the soil and groundwater metagenomes. For the pMMO/AMO alpha subunit (pmoA/amoA), Nitrosospira was important for the soil metagenomes, while Methylosinus and Methylocystis were dominant for the groundwater metagenomes. The majority of pmoA alignments from both metagenomes were from uncultured bacteria. High quality MAGs were obtained from the groundwater data. Four MAGs (Methylocella and Cypionkella) contained sMMO subunits. Another three MAGs, within the order Pseudomonadales, contained all three pMMO subunits. All PH subunits were detected in seven MAGs (Azonexus, Rhodoferax, Aquabacterium). In those seven, all contained catechol 2,3-dioxagenase, and Aquabacterium also contained catechol 1,2-dioxygenase. T4MO subunits were detected in eight MAGs (Azonexus, Rhodoferax, Siculibacillus) and all, except one, contained all six subunits. Four MAGs (Rhodoferax and Azonexus) contained all subunits for PH and T4MO, as well as catechol 2,3-dixoygenase. The detection of T4MO and PH in groundwater metagenomes and MAGs has important implications for the potential oxidation of groundwater contaminants.

Transforming Plain LaMnO3 Perovskite into a Powerful Ozonation Catalyst: Elucidating the Mechanisms of Simultaneous A and B Sites Modulation for Enhanced Toluene Degradation.

Herein, we propose preferential dissolution paired with Cu-doping as an effective method for synergistically modulating the A- and B-sites of LaMnO3 perovskite. Through Cu-doping into the B-sites of LaMnO3, specifically modifying the B-sites, the double perovskite La2CuMnO6 was created. Subsequently, partial La from the A-sites of La2CuMnO6 was etched using HNO3, forming novel La2CuMnO6/MnO2 (LCMO/MnO2) catalysts. The optimized catalyst, featuring an ideal Mn:Cu ratio of 4.5:1 (LCMO/MnO2-4.5), exhibited exceptional catalytic ozonation performance. It achieved approximately 90% toluene degradation with 56% selectivity toward CO2, even under ambient temperature (35 °C) and a relatively humid environment (45%). Modulation of A-sites induced the elongation of Mn-O bonds and decrease in the coordination number of Mn-O (from 6 to 4.3) in LCMO/MnO2-4.5, resulting in the creation of abundant multivalent Mn and oxygen vacancies. Doping Cu into B-sites led to the preferential chemisorption of toluene on multivalent Cu (Cu(I)/Cu(II)), consistent with theoretical predictions. Effective electronic supplementary interactions enabled the cycling of multiple oxidation states of Mn for ozone decomposition, facilitating the production of reactive oxygen species and the regeneration of oxygen vacancies. This study establishes high-performance perovskites for the synergistic regulation of O3 and toluene, contributing to cleaner and safer industrial activities.

Catalytic Ozonation of Low Concentration Toluene over MnFeOx-USY Catalyst: Effects of Interactions between Catalytic Components and Introduction of Gas Phase NOx.

A series of Mn and Fe metal oxide catalysts loaded onto USY, as well as single metal oxides, were prepared and characterized. The effects of interactions between the catalytic components and the introduction of gas phase NO on the catalytic ozonation of toluene were investigated. Characterization showed that there existed strong interactions between MnOx, FeOx, and USY, which enhanced the content of oxygen vacancies and acid sites of the catalysts and thus boosted the generation of reactive oxygen species and the adsorption of toluene. The MnFeOx-USY catalyst with MnOx and FeOx dimetallic oxides exhibited the most excellent performance of catalytic ozonation of toluene. On the other hand, the presence of NOx in reaction gas mixtures significantly promoted both toluene conversion and mineralization, which was attributed to the formation of nitrate species on the catalysts surface and thus the increase of both acid sites and toluene oxidation sites. Meanwhile, the reaction mechanism between O3 and C7H8 was modified in which the strong interactions between MnOx, FeOx, and USY accelerated the reaction progress based on the L-H route. In addition, the formation of the surface nitrate species not only promoted reaction progress following the L-H route but also resulted in the occurrence of the reaction via the E-R route.

In-Depth Understanding of the Oxidative Compatibility of Volatile Organic Compounds with Mn2O3 and Pt-Loaded Catalysts.

Designing suitable catalysts for efficiently degrading volatile organic compounds (VOCs) is a great challenge due to the distinct variety and nature of VOCs. Herein, the suitability of different typical VOCs (toluene and acetone) over Pt-based catalysts and Mn2O3 was investigated carefully. The activity of Mn2O3 was inferior to Pt-loaded catalysts in toluene oxidation but showed superior ability for destroying acetone, while Pt loading could boost the catalytic activity of Mn2O3 for both acetone and toluene. This suitability could be determined by the physicochemical properties of the catalysts and the structure of the VOC since toluene destruction activity is highly reliant on Pt0 in the metallic state and linearly correlated with the amount of surface reactive oxygen species (Oads), while the crucial factor that affects acetone oxidation is the mobility of lattice oxygen (Olat). The Pt/Mn2O3 catalyst shows highly active Pt-O-Mn interfacial sites, favoring the generation of Oads and promoting Mn-Olat mobility, leading to its excellent performance. Therefore, the design of abundant active sites is an effective means of developing highly adaptive catalysts for the oxidation of different VOCs.

Accelerating Toluene Oxidation over Boron-Titanium-Oxygen Interface: Steric Hindrance of the Methyl Group Induced by the Plane-Adsorption Configuration.

Elimination of dilute gaseous toluene is one of the critical concerns within the field of indoor air remediation. The typical degradation route on titanium-based catalysts, "toluene-benzaldehyde-carbon dioxide", necessitates the oxidation of the methyl group as a prerequisite for photocatalytic toluene oxidation. However, the inherent planar adsorption configuration of toluene molecules, dominated by the benzene rings, leads to significant steric hindrance for the methyl group. This steric hindrance prevents the methyl group from contacting the active species on the catalyst surface, thereby limiting the removal of toluene under indoor conditions. To date, no effective strategy to control the steric hindrance of the methyl group has been identified. Herein, we showed a B-Ti-O interface that exhibits significantly enhanced toluene removal efficiency under indoor conditions. In-depth investigations revealed that, compared to typical Ti-based photocatalysts, the steric hindrance between the methyl group and the catalyst surface decreased from 3.42 to 3.03 Å on the designed interface. This reduction originates from the matching of orbital energy levels between Ti 3dz2 and C 2pz of the benzene ring. The decreased steric hindrance improved the efficiency of toluene being attacked by surface active species, allowing for rapid conversion into benzaldehyde and benzoic acid species for subsequent reactions. Our work provides novel insights into the steric hindrance effect in the elimination of aromatic volatile organic compounds.

Modulating the Electronic Structures of Pt on Pt/TiO2 Catalyst for Boosting Toluene Oxidation.

Surface hydroxyl groups commonly exist on the catalyst and present a significant role in the catalytic reaction. Considering the lack of systematical researches on the effect of the surface hydroxyl group on reactant molecule activation, the PtOx/TiO2 and PtOx-y(OH)y/TiO2 catalysts were constructed and studied for a comprehensive understanding of the roles of the surface hydroxyl group in the oxidation of volatiles organic compounds. The PtOx/TiO2 formed by a simple treatment with nitric acid presented greatly enhanced activity for toluene oxidation in which the turnover frequency of toluene oxidation on PtOx/TiO2 was around 14 times as high as that on PtOx-y(OH)y/TiO2. Experimental and theoretical results indicated that adsorption/activation of toluene and reactivity of oxygen atom on the catalyst determined the toluene oxidation on the catalyst. The removal of surface hydroxyl groups on PtOx promoted strong electronic coupling of the Pt 5d orbital in PtOx and C 2p orbital in toluene, facilitating the electron transfers from toluene to PtOx and subsequently the adsorption/activation of toluene. Additionally, the weak Pt-O bond promoted the activation of surface lattice oxygen, accelerating the deep oxidation of activated toluene. This study clarifies the inhibiting effect of surface hydroxyl groups on PtOx in toluene oxidation, providing a further understanding of hydrocarbon oxidation.

Boosting Photothermocatalytic Oxidation of Toluene Over Pt/N-TiO2: The Gear Effect of Light and Heat.

Photothermal catalysis is extremely promising for the removal of various indoor pollutants owing to its photothermal synergistic effect, while the low light utilization efficiency and unclear catalytic synergistic mechanism hinder its practical applications. Here, nitrogen atoms are introduced, and Pt nanoparticles are loaded on TiO2 to construct Pt/N-TiO2-H2, which exhibits 3.5-fold higher toluene conversion rate than the pure TiO2. Compared to both photocatalytic and thermocatalytic processes, Pt/N-TiO2-H2 exhibited remarkable performance and stability in the photothermocatalytic oxidation of toluene, achieving 98.4% conversion and 98.3% CO2 yield under a light intensity of 260 mW cm-2. Furthermore, Pt/N-TiO2-H2 demonstrated potential practical applicability in the photothermocatalytic elimination of various indoor volatile organic compounds. The synergistic effect occurs as thermocatalysis accelerates the accumulation of carboxylate species and the degradation of aldehyde species, while photocatalysis promotes the generation of aldehyde species and the consumption of carboxylate species. This ultimately enhances the photothermocatalytic process. The photothermal synergistic effect involves the specific conversion of intermediates through the interplay of light and heat, providing novel insights for the design of photothermocatalytic materials and the understanding of photothermal mechanisms.

Enhancement Effect Induced by the Second Metal to Promote Ozone Catalytic Oxidation of VOCs.

It is a promising research direction to develop catalysts with high stability and ozone utilization for low-temperature ozone catalytic oxidation of VOCs. While bimetallic catalysts exhibit excellent catalytic activity compared with conventional single noble metal catalysts, limited success has been achieved in the influence of the bimetallic effect on the stability and ozone utilization of metal catalysts. Herein, it is necessary to systematically study the enhancement effect in the ozone catalytic reaction induced by the second metal. With a simple continuous impregnation method, a platinum-cerium bimetallic catalyst is prepared. Also highlighted are studies from several aspects of the contribution of the second metal (Ce) to the stability and ozone utilization of the catalysts, including the "electronic effect" and "geometric effect". The synergistic removal rate of toluene and ozone is nearly 100% at 30 °C, and it still shows positive stability after high humidity and a long reaction time. More importantly, the instructive significance, which is the in-depth knowledge of enhanced catalytic mechanism of bimetallic catalysts resulting from a second metal, is provided by this work.

Enhancing Oxygen Activation Ability by Composite Interface Construction over a 2D Co3O4-Based Monolithic Catalyst for Toluene Oxidation.

Developing robust metal-based monolithic catalysts with efficient oxygen activation capacity is crucial for thermal catalytic treatment of volatile organic compound (VOC) pollution. Two-dimensional (2D) metal oxides are alternative thermal catalysts, but their traditional loading strategies on carriers still face challenges in practical applications. Herein, we propose a novel in situ molten salt-loading strategy that synchronously enables the construction of 2D Co3O4 and its growth on Fe foam for the first time to yield a unique monolithic catalyst named Co3O4/Fe-S. Compared to the Co3O4 nanocube-loaded Fe foam, Co3O4/Fe-S exhibits a significantly improved catalytic performance with a temperature reduction of 44 °C at 90% toluene conversion. Aberration-corrected scanning transmission electron microscopy and theoretical calculation suggest that Co3O4/Fe-S possesses abundant 2D Co3O4/Fe3O4 composite interfaces, which promote the construction of active sites (oxygen vacancy and Co3+) to boost oxygen activation and toluene chemisorption, thereby accelerating the transformation of reaction intermediates through Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms. Moreover, the growth mechanism reveals that 2D Co3O4/Fe3O4 composite interfaces are generated in situ in molten salt, inducing the growth of 2D Co3O4 onto the surface lattice of 2D Fe3O4. This study provides new insights into enhancing oxygen activation and opens an unprecedented avenue in preparing efficient monolithic catalysts for VOC oxidation.

Climatic conditions and concentrations of BTEX compounds in atmospheric media.

Climatic and meteorological conditions are among the factors affecting the ambient concentrations of BTEX compounds. This systematic review and meta-analysis aimed to interrogate the seasonal effect of climatic conditions on the concentrations of BTEX compounds. Three electronic bibliographic databases including Scopus, PubMed, and Web of Science were systematically searched up to November 14, 2023. The search algorithm followed PRISMA guidance and consisted of three groupings of keywords and their possible combinations. For various climatic conditions, the overall mean and 95% confidence interval (CI) of effect size related to BTEX concentrations were calculated using a random-effect model. In total, 104 articles were included for evaluation in this review. BTEX ambient concentration was higher in winter (ranging from 36 out of 79 relevant studies for xylene to 52 out of 97 relevant studies for benzene) followed by summer and autumn. For humidity conditions, the highest exposure values for BTEX were detected for rainy weather (ranging from 3 out of 5 relevant studies for toluene and xylene to 4 out of 5 relevant studies for benzene and ethyl benzene) compared to dry conditions. The pooled concentration (µg/m3) of benzene, toluene, ethyl benzene, and xylene were computed as 2.61, 7.12, 2.21, and 3.61 in spring, 2.13, 7.53, 1.61, and 2.75 in summer, 3.04, 9.59, 3.14, and 5.50 in autumn, and 3.56, 8.71, 2.35, and 3.91 in winter, respectively. Moreover, the pooled concentrations (µg/m3) of BTEX were measured as 2.98, 7.22, 1.90, and 3.03 in dry weather and 3.15, 6.30, 2.14, and 3.86 in rainy or wet weather, respectively. In most seasons, the ambient concentrations of BTEX were higher in countries with low and middle incomes and in Middle Eastern countries and East/Southeast Asia compared to those in other regions (P < 0.001). The increasing concentrations of BTEX in winter and autumn followed by the summer season and during rainy/wet weather appear to be reasonably consistent despite variations in study methods, quality, or geography. Therefore, it is recommended that more serious control measures are considered for decreasing exposure to BTEX in these climatic conditions.

The selection of a nitrogen precursor for the construction of N-doped titanium dioxide with enhanced photocatalytic activity for the removal of gaseous toluene.

The preparation of nitrogen-doped TiO2 (i.e., N-TiO2) catalysts is a highly effective option to improve the photocatalytic activity of TiO2. Nonetheless, relatively little is known about the effects of dopant precursors selected for their preparation with regard to the photocatalytic efficacy. In this study, three types of dopants are selected and used as N sources (urea (U), melamine (M), and aqueous ammonia (A)) for N-TiO2 samples with the name codes of NTU, NTM, and NTA, respectively. The photocatalytic efficacy of these N-TiO2 samples is examined against toluene in a packed bed flow reactor. Under optimal conditions (e.g., relative humidity (RH) = 20% and gas hourly space velocity (GHSV) = 1698 h-1), the superiority of NTA is evident over others with a quantum efficiency (QE) of 7.03 × 10-4 molecules photon-1, a space time yield (STY) of 1.38 × 10-4 molecules photon-1 mg-1, and a specific clean air delivery rate (SCADR) of 1148.8 L g-1 h-1. The analysis based on in-situ diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography-mass spectrometry confirms the formation of several intermediates such as benzyl alcohol, benzaldehyde, benzoic acid, and alkane species through ring opening reactions. In addition, the prepared NTA photocatalyst exhibits the highest toluene photocatalytic degradation efficiency among all TiO2-based catalysts surveyed to date. Overall, this study offers as a valuable guideline for the development of advanced TiO2 catalytic systems (such as N-TiO2) for the treatment of aromatic hydrocarbons in indoor air.

Nine years of patch testing with isocyanates in a clinic of occupational dermatology.

BACKGROUND: Isocyanates are used as starting materials of polyurethane (PU) products. They are relatively important occupational skin sensitizers. OBJECTIVES: To analyse results of a large isocyanate patch test series of 19 isocyanate test substances and 4,4'-diaminodiphenylmethane (MDA), a marker of 4,4'-diphenylmethane diisocyanate (MDI) hypersensitivity. METHODS: Test files were screened for positive reactions in the isocyanate series. Patients with positive reactions were analysed for occupation, exposure and diagnosis. RESULTS: In 2010-2019, 53 patients had positive reactions in the series (16% of 338 patients tested). MDA, the well-established screening substance for MDI allergy, was positive in 30 patients, an in-house monomeric MDI test substance in 23 patients and 3 different polymeric MDI test substances in 19-21 patients. We diagnosed 16 cases of occupational allergic contact dermatitis (OACD) from MDI including 3 pipe reliners. Hexamethylene-1,6-diisocyanate (HDI) oligomers in paint hardeners caused 5 cases of OACD, more cases than 2,4-toluene diisocyanate (TDI; n = 3) and isophorone diisocyanate (IPDI; n = 1) put together. CONCLUSIONS: In contrast to previous studies, polymeric MDI test substances were not superior to a monomeric MDI. Pipe reliners may get sensitised not only by epoxy products and acrylates but also by MDI in hardeners of PU pipe coatings. HDI oligomers were the second most important causes of OACD after MDI.

Olea europaea L. leaf extract mitigates pulmonary inflammation and tissue destruction in Wistar rats induced by concurrent exposure to noise and toluene.

This study aimed to investigate the effects of combined exposure to noise (85 dB(A)) and inhaled Toluene (300 ± 10 ppm) on rat lung health. It also aimed to assess the potential therapeutic effects of Olea europaea L. leaves extract (OLE) (40 mg/kg/day) using biochemical, histopathological, and immunohistochemical (IHC) analyses, as well as determination of pro-inflammatory cytokines (TNF-α and IL-1ß), and in silico Docking studies. The experiment involved forty-two male Wistar rats divided into seven groups, each exposed to a 6-week/6-hour/day regimen of noise and Toluene. The groups included a control group, rats co-exposed to noise and Toluene, and rats co-exposed to noise and Toluene treated with OLE for different durations. The results indicated that noise and Toluene exposure led to structural damage in lung tissue, oxidative harm, and increased levels of pro-inflammatory cytokines (TNF-α and IL-1ß). However, the administration of OLE extract demonstrated positive effects in mitigating these adverse outcomes. OLE treatment reduced lipid peroxidation and enhanced the activities of catalase and superoxide dismutase, indicating its anti-oxidant properties. Furthermore, OLE significantly decreased the levels of pro-inflammatory cytokines compared to the groups exposed to noise and Toluene without OLE treatment. Moreover, the in silico investigation substantiated a robust affinity between COX-2 and OLE components, affirming the anti-inflammatory activity. Overall, our findings suggest that OLE possesses anti-inflammatory and anti-oxidative properties that mitigate the adverse effects of concurrent exposure to noise and Toluene.

Health risk assessment of exposure to benzene, toluene, ethyl benzene, and xylene in shoe industry-related workplaces.

Benzene, toluene, ethyl benzene, and xylene (BTEX) are prevalent pollutants in shoe industry-related workplaces. The aim of this study was to assess exposure to BTEX and their carcinogenic and non-carcinogenic risks in shoe-industry-related workplaces. This study was carried out at different shoe manufactures, small shoe workshop units, shoe markets, and shoe stores in Tabriz, Iran in 2021. Personal inhalation exposure to BTEX was measured using the National Institute for Occupational Safety and Health (NIOSH) 1501 method. Carcinogenic and non-carcinogenic risks due to inhalation exposure to BTEX were estimated by United States Environmental Protection Agency (U.S. EPA) method based on Mont Carlo simulation. Results showed that the concentrations of benzene and toluene were higher than the threshold limit value (TLV) in both gluing and non-gluing units of shoe manufactures. The total carcinogenic risk (TCR) due to exposure to benzene and ethyl benzene was considerable in all shoe industry-related workplaces. Also, the hazard index (HI) as a non-carcinogenic index was higher than standard levels in all shoe industry-related workplaces. Therefore, shoe industry-related workers are at cancer and non-cancer risks due to exposure to BTEX. Prevention measures need to be implemented to reduce the concentration of BTEX in shoe industry-related workplaces.

Risk assessment-based verification of the CertiPURTM limit values for toluene diamine and methylene dianiline in flexible polyurethane foam.

Flexible polyurethane foams (PUF) are used in many consumer products. PUF may contain trace levels of aromatic diamine impurities that could represent a potential health risk. The risk associated with sleeping on a PUF mattress was evaluated. Toxicity benchmarks for sensitization and non-cancer endpoints were derived from the respective points-of-departure using standard assessment factors. For the cancer endpoints, toxicity benchmarks were derived from the 25th-percentile values of animal studies. Recently published emission and migration data allowed to link exposure with the CertiPURTM voluntary quality limits of ≤5 mg.kg-1 for 2,4-toluene diamine and 4,4'-methylene dianiline in PUF. Using conservative exposure scenarios, lifetime-average daily internal doses from the combined inhalation and dermal exposures were calculated. Margins of safety for non-cancer and sensitization endpoints were >104. The theoretical excess cancer risk was ≤1.5 × 10-7. It is concluded that sleeping on a mattress that satisfies the CertiPUR limit value does not pose undue risk to consumers.

Development of a Smartwatch with Gas and Environmental Sensors for Air Quality Monitoring.

In recent years, there has been a growing interest in developing portable and personal devices for measuring air quality and surrounding pollutants, partly due to the need for ventilation in the aftermath of COVID-19 situation. Moreover, the monitoring of hazardous chemical agents is a focus for ensuring compliance with safety standards and is an indispensable component in safeguarding human welfare. Air quality measurement is conducted by public institutions with high precision but costly equipment, which requires constant calibration and maintenance by highly qualified personnel for its proper operation. Such devices, used as reference stations, have a low spatial resolution since, due to their high cost, they are usually located in a few fixed places in the city or region to be studied. However, they also have a low temporal resolution, providing few samples per hour. To overcome these drawbacks and to provide people with personalized and up-to-date air quality information, a personal device (smartwatch) based on MEMS gas sensors has been developed. The methodology followed to validate the performance of the prototype was as follows: firstly, the detection capability was tested by measuring carbon dioxide and methane at different concentrations, resulting in low detection limits; secondly, several experiments were performed to test the discrimination capability against gases such as toluene, xylene, and ethylbenzene. principal component analysis of the data showed good separation and discrimination between the gases measured.

Potential Effects of Low-Level Toluene Exposure on the Nervous System of Mothers and Infants.

In day-to-day living, individuals are exposed to various environmentally hazardous substances that have been associated with diverse diseases. Exposure to air pollutants can occur during breathing, posing a considerable risk to those with environmental health vulnerabilities. Among vulnerable individuals, maternal exposure can negatively impact the mother and child in utero. The developing fetus is particularly vulnerable to environmentally hazardous substances, with potentially greater implications. Among air pollutants, toluene is neurotoxic, and its effects have been widely explored. However, the impact of low-level toluene exposure in daily life remains unclear. Herein, we evaluated 194 mothers and infants from the Growing children's health and Evaluation of Environment (GREEN) cohort to determine the possible effects of early-life toluene exposure on the nervous system. Using Omics experiments, the effects of toluene were confirmed based on epigenetic changes and altered mRNA expression. Various epigenetic changes were identified, with upregulated expression potentially contributing to diseases such as glioblastoma and Alzheimer's, and downregulated expression being associated with structural neuronal abnormalities. These findings were detected in both maternal and infant groups, suggesting that maternal exposure to environmental hazardous substances can negatively impact the fetus. Our findings will facilitate the establishment of environmental health policies, including the management of environmentally hazardous substances for vulnerable groups.

Regulation of the co-transport of toluene and dichloromethane by adsorbed phase humic acid under different hydro-chemical conditions.

The transport behavior of combined organic pollutants in soil and groundwater has attracted significant attention in recent years. Research on the influence of humic acid (HA) on organic pollutant transport behavior mainly focuses on the study of the mobile phase HA, with less research on the adsorbed phase HA, especially regarding its interaction with combined pollutants. To enhance understanding of the regulation of co-transport and retention of combined pollutants by adsorbed phase HA, in this study, tests were conducted to investigate how toluene (TOL) and dichloromethane (DCM) are transported in the presence of adsorbed phase HA at different pH levels and ionic strengths. As the proportions of HA-coated sand increased, so did its adsorption capacity for TOL and DCM, which can be attributed to adsorbed phase HA providing more adsorption sites compared to plain sand, thereby reducing the transport potential of the pollutants. The presence of both TOL and DCM facilitated their mutual transportation due to competitive adsorption controlled by the adsorbed phase HA content in the porous medium. Furthermore, it was observed that pH levels influenced the transport behavior of TOL and DCM when adsorbed phase HA was present since adsorbed phase HA transformation into mobile phase was regulated by pH levels. The transport patterns can be effectively simulated using the chemical nonequilibrium two-site sorption model in HYDRUS-1D, accurately reflecting the retardation coefficients and transport distances based on model parameters. This work sheds new light on the regulatory role of adsorbed phase HA in TOL and DCM transport under diverse hydrochemical conditions, with implications for accurately depicting the behavior of combined pollutants, optimizing the remediation strategies and improving remediation efficiency in contaminated sites.