Effects of toluene and benzene air mixtures on human lung cells (A549)

Impact of indoor air pollution on DNA damage and chromosome stability: a systematic review

Indoor air pollution is becoming a rising public health problem and is largely resulting from the burning of solid fuels and heating in households. Burning these fuels produces harmful compounds, such as particulate matter regarded as a major health risk, particularly affecting the onset and exacerbation of respiratory diseases. As exposure to polluted indoor air can cause DNA damage including DNA sd breaks as well as chromosomal damage, in this paper, we aim to provide an overview of the impact of indoor air pollution on DNA damage and genome stability by reviewing the scientific papers that have used the comet, micronucleus, and γ-H2AX assays. These methods are valuable tools in human biomonitoring and for studying the mechanisms of action of various pollutants, and are readily used for the assessment of primary DNA damage and genome instability induced by air pollutants by measuring different aspects of DNA and chromosomal damage. Based on our search, in selected studies (in vitro, animal models, and human biomonitoring), we found generally higher levels of DNA strand breaks and chromosomal damage due to indoor air pollutants compared to matched control or unexposed groups. In summary, our systematic review reveals the importance of the comet, micronucleus, and γ-H2AX assays as sensitive tools for the evaluation of DNA and genome damaging potential of different indoor air pollutants. Additionally, research in this particular direction is warranted since little is still known about the level of indoor air pollution in households or public buildings and its impact on genetic material. Future studies should focus on research investigating the possible impact of indoor air pollutants in complex mixtures on the genome and relate pollutants to possible health outcomes.

Airborne Toluene Detection Using Metal-Organic Frameworks

The pollution of indoor air is a major worldwide concern in our modern society for people's comfort, health, and safety. In particular, toluene, present in many substances including paints, thinners, candles, leathers, cosmetics, inks, and glues, affects the human health even at very low concentrations throughout its action on the central nervous system. Its prevalence in many workplace environments can fluctuate considerably, which led to firm regulation with exposure limits varying between 50 and 400 ppm depending on exposure time. This therefore requires the development of technologies for an accurate detection of this contaminant. Metal-organic frameworks have been proposed as promising candidates to detect and monitor a series of molecules at even extremely low concentrations owing to the high tunability of their functionality. Herein, a high-throughput Monte Carlo screening approach was devised to identify the best MOFs from the computation-ready, experimental (CoRE) metal-organic framework (MOF) density-derived electrostatic and chemical (DDEC) database for the selective capture of toluene from air at room temperature, with the consideration of a ternary mixture composed of extremely low-level concentration of toluene (10 ppm) in oxygen and nitrogen to mimic the composition of air. An aluminum MOF, DUT-4, with channel-like micropores was identified as an excellent candidate for the selective adsorption of toluene from air with a predicted adsorption uptake of 0.5 g/g at 10 ppm concentration and room temperature. The toluene adsorption behavior of DUT-4 at low equivalent concentrations, alongside its sensing performance, was further experimentally investigated by its incorporation in a quartz crystal microbalance sensor, confirming the promises of DUT-4. Decisively, the resulting high sensitivity and fast kinetics of our developed sensor highlight the applicability of this hand-in-hand computational-experimental methodology to porous material screening for sensing applications.

In Vitro Systems for Toxicity Evaluation of Microbial Volatile Organic Compounds on Humans: Current Status and Trends

Microbial volatile organic compounds (mVOC) are metabolic products and by-products of bacteria and fungi. They play an important role in the biosphere: They are responsible for inter- and intra-species communication and can positively or negatively affect growth in plants. But they can also cause discomfort and disease symptoms in humans. Although a link between mVOCs and respiratory health symptoms in humans has been demonstrated by numerous studies, standardized test systems for evaluating the toxicity of mVOCs are currently not available. Also, mVOCs are not considered systematically at regulatory level. We therefore performed a literature survey of existing in vitro exposure systems and lung models in order to summarize the state-of-the-art and discuss their suitability for understanding the potential toxic effects of mVOCs on human health. We present a review of submerged cultivation, air-liquid-interface (ALI), spheroids and organoids as well as multi-organ approaches and compare their advantages and disadvantages. Furthermore, we discuss the limitations of mVOC fingerprinting. However, given the most recent developments in the field, we expect that there will soon be adequate models of the human respiratory tract and its response to mVOCs.

Bioremediation of lignin derivatives and phenolics in wastewater with lignin modifying enzymes: Status, opportunities and challenges

Lignin modifying enzymes from fungi and bacteria are potential biocatalysts for sustainable mitigation of different potentially toxic pollutants in wastewater. Notably, the paper and pulp industry generates enormous amounts of wastewater containing high amounts of complex lignin-derived chlorinated phenolics and sulfonated pollutants. The presence of these compounds in wastewater is a critical issue from environmental and toxicological perspectives. Some chloro-phenols are harmful to the environment and human health, as they exert carcinogenic, mutagenic, cytotoxic, and endocrine-disrupting effects. In order to address these most urgent concerns, the use of oxidative lignin modifying enzymes for bioremediation has come into focus. These enzymes catalyze modification of phenolic and non-phenolic lignin-derived substances, and include laccase and a range of peroxidases, specifically lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and dye-decolorizing peroxidase (DyP). In this review, we explore the key pollutant-generating steps in paper and pulp processing, summarize the most recently reported toxicological effects of industrial lignin-derived phenolic compounds, especially chlorinated phenolic pollutants, and outline bioremediation approaches for pollutant mitigation in wastewater from this industry, emphasizing the oxidative catalytic potential of oxidative lignin modifying enzymes in this regard. We highlight other emerging biotechnical approaches, including phytobioremediation, bioaugmentation, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based technology, protein engineering, and degradation pathways prediction, that are currently gathering momentum for the mitigation of wastewater pollutants. Finally, we address current research needs and options for maximizing sustainable biobased and biocatalytic degradation of toxic industrial wastewater pollutants.

Influence of the environmental relative humidity on the inflammatory response of skin model after exposure to various environmental pollutants

The skin is an essential barrier, protecting the body against the environment and its numerous pollutants. Several environmental pollutants are known to affect the skin, inducing premature aging through mechanisms including oxidative stress, inflammation, and impairment of skin functions. Even climate conditions can impact the skin. Therefore, using a Reconstructed Human Epidermis (RHE), we tested the effect of two samples of fine particulate matters (PM_0.3-2.5 - one metals-rich sample and the other organic compounds-rich), two Volatile Organic Compounds mixtures (VOCs - from a solvent-based paint and a water-based paint) and Tobacco Smoke (TS). All pollutants affected cellular functionality, but to a lesser extent for the water-based paint VOC. This effect was enhanced when RHE were preconditioned for 2 h by a semi-dry airflow (45% relative humidity) before pollutants application, compared to preconditioning by a humid airflow (90% relative humidity). In the absence of preconditioning, IL-1α, IL-6, IL-8, and RANTES were almost systematically induced by pollutants. When RHE were preconditioned by a semi-dry or humid airflow before being subjected to pollutants, the increase of IL-1α, IL-8, and RANTES falls into two groups. Similarly to RHE not treated with pollutants, RHE treated with VOCs after preconditioning by a semi-dry airflow showed increased IL-1α, IL-8, and RANTES release. On the contrary, RHE treated with PM or TS after preconditioning by a semi-dry airflow show a lower increase in IL-1α, IL-8, and RANTES compared to preconditioning by a humid airflow. The effect of real environmental relative humidity conditions of the air, combined with acute exposure to various environmental pollutants, seemed to relate mainly to structural changes of the skin, determining the outcome of the inflammatory response depending on the physicochemical characteristics of pollutants.

Breathing in vitro: Designs and applications of engineered lung models

The aim of this review is to provide a systematic design guideline to users, particularly engineers interested in developing and deploying lung models, and biologists seeking to identify a suitable platform for conducting in vitro experiments involving pulmonary cells or tissues. We first discuss the state of the art on lung in vitro models, describing the most simplistic and traditional ones. Then, we analyze in further detail the more complex dynamic engineered systems that either provide mechanical cues, or allow for more predictive exposure studies, or in some cases even both. This is followed by a dedicated section on microchips of the lung. Lastly, we present a critical discussion of the different characteristics of each type of system and the criteria which may help researchers select the most appropriate technology according to their specific requirements. Readers are encouraged to refer to the tables accompanying the different sections where comprehensive and quantitative information on the operating parameters and performance of the different systems reported in the literature is provided.

Toxicological responses of BEAS-2B cells to repeated exposures to benzene, toluene, m-xylene, and mesitylene using air-liquid interface method

In order to reduce exposure to toxic chemicals, the European REACH regulation (1907/2006) recommends substituting toxic molecules with compounds that are less harmful to human health and the environment. Toluene is one of the most frequently used solvents in industries despite its toxicity. The objective of this study is to better understand and compare the toxicity of toluene and its homologues in a bronchial cell model. Thus, human bronchial BEAS-2B cells were exposed to steams of toluene, m-xylene, mesitylene (1,3,5-trimethylbenzene), and benzene (20 and 100 ppm). Exposure was carried out using an air-liquid interface (ALI) system (Vitrocell) during 1 h/day for 1, 3, or 5 days. Cytotoxicity, xenobiotic metabolism enzyme gene expression, and inflammatory response were evaluated following cell exposures. BEAS-2B cell exposure to toluene and its homologues revealed the involvement of major (CYP2E1) and minor metabolic pathways (CYP1A1). A late induction of genes (EPHX1, DHDH, ALDH2, and ALDH3B1) was measured from Day 3 and can be linked to the formation of metabolites. An increase in the secretion level of inflammatory markers (TNF-α, IL-6, IL-8, MCP-1, and GM-CSF) was also observed. In parallel, regulation between inflammatory mediators and the expression of transmembrane glycoprotein mucin MUC1 was also studied. This in vitro approach with ALI system points out the relevance of conducting repeated exposures to detect potential late effects. The difference recorded after cell exposure to toluene and its homologues highlights the importance of substitution principle.

Polymer-assisted synthesis and applications of hydroxyapatite (HAp) anchored nitrogen-doped 3D graphene foam-based nanostructured ceramic framework

In the present work, a hydroxyapatite anchored nitrogen-doped three-dimensional graphene (HAp-N3DG) skeletal network (foam) based nanostructured ceramic framework (CF) was developed through a polymer-assisted solvothermal route. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) studies reveal that the nano sized 0D HAp particles are anchored on the N3DG skeletal network with an average size of less than 50 nm. EDX and X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Ca, P, O, N, and C. In addition, XPS analysis reveals the existence of N-C bonds in the prepared sample. The X-ray diffraction (XRD) patterns indicate the presence of hexagonal phase hydroxyapatite and the calculated average crystallite size was found to be 12 nm. The developed HAp-N3DG foam based nanostructured CF was found to have a mesoporous structure and the measured specific surface area (SSA) and the mean pore diameter were found to be 64.73 m2 g-1 and 23.6 nm, respectively. Electrochemical analysis shows that HAp anchored on nitrogen-doped 3D graphene foam based nanostructured CF has moderate electrochemical activity towards lithium ion charge/discharge. In addition, the prepared material showed adsorption activity values of 204.89 mg g-1 and 243.89 mg g-1 for the volatile organic compounds (VOCs) benzene and toluene, respectively. The present findings suggest that the newly developed HAp anchored nitrogen-doped 3DG (HAp-N3DG) skeletal network (foam) based nanostructured CF material can be used in energy devices and in the removal of volatile organic compounds. Moreover, the present study initiates a new kind of approach in energy device (lithium ion battery-LIB) research and in the removal of VOCs.

Assessment of pulmonary oxygen toxicity in special operations forces divers under operational circumstances using exhaled breath analysis

INTRODUCTION

The Netherlands Maritime Special Operations Forces use closed circuit oxygen rebreathers (O₂-CCR), which can cause pulmonary oxygen toxicity (POT). Recent studies demonstrated that volatile organic compounds (VOCs) can be used to detect POT in laboratory conditions. It is unclear if similar VOCs can be identified outside the laboratory. This study hypothesised that similar VOCs can be identified after O₂-CCR diving in operational settings.

METHODS

Scenario one: 4 h O₂-CCR dive to 3 metres' seawater (msw) with rested divers. Scenario two: 3 h O₂-CCR dive to 3 msw following a 5 day physically straining operational scenario. Exhaled breath samples were collected 30 min before and 30 min and 2 h after diving under field conditions and analysed using gas chromatography-mass spectrometry (GC-MS) to reconstruct VOCs, whose levels were tested longitudinally using a Kruskal-Wallis test.

RESULTS

Eleven divers were included: four in scenario one and seven in scenario two. The 2 h post-dive sample could not be obtained in scenario two; therefore, 26 samples were collected. GC-MS analysis identified three relevant VOCs: cyclohexane, 2,4-dimethylhexane and 3-methylnonane. The intensities of 2,4-dimethylhexane and 3-methylnonane were significantly (P = 0.048 and P = 0.016, respectively) increased post-dive relative to baseline (range: 212-461%) in both scenarios. Cyclohexane was increased not significantly (P = 0.178) post-dive (range: 87-433%).

CONCLUSIONS

VOCs similar to those associated with POT in laboratory conditions were identified after operational O₂-CCR dives using GC-MS. Post-dive intensities were higher than in previous studies, and it remains to be determined if this is attributable to different dive profiles, diving equipment or other environmental factors.

In vitro toxicological evaluation of emissions from catalytic oxidation removal of industrial VOCs by air/liquid interface (ALI) exposure system in repeated mode

Toxicity of toluene and by-products formed during its catalytic oxidative degradation was studied in human bronchial BEAS-2B cells repeatedly exposed. BEAS-2B cells were exposed using an Air-Liquid Interface (ALI) System (Vitrocell®) for 1 h per day during 1, 3 or 5 days to gaseous flows: toluene vapors (100 and 1000 ppm) and outflow after catalytic oxidation of toluene (10 and 100%). After exposure to gaseous flow, cytotoxicity, inflammatory response and Xenobiotic Metabolism Enzymes (XME) gene expression were investigated. No significant cytotoxicity was found after 5 days for every condition of exposure. After cells exposure to catalytic oxidation flow, IL-6 level increased no significantly in a time- and dose-dependent way, while an inverted U-shaped profile of IL-8 secretion was observed. XME genes induction, notably CYP2E1 and CYP2F1 results were in line with the presence of unconverted toluene and benzene formed as a by-product, detected by analytical methods. Exposure to pure toluene also demonstrated the activation of these XMEs involved in its metabolism. Repeated exposure permits to show CYP1A1, CYP1B1 and CY2S1 expression, probably related to the formation of other by-products, as PAHs, not detected by standard analytical methods used for the development of catalysts.

Oxidative damage and impairment of protein quality control systems in keratinocytes exposed to a volatile organic compounds cocktail

Compelling evidence suggests that volatile organic compounds (VOCs) have potentially harmful effects to the skin. However, knowledge about cellular signaling events and toxicity subsequent to VOC exposure to human skin cells is still poorly documented. The aim of this study was to focus on the interaction between 5 different VOCs (hexane, toluene, acetaldehyde, formaldehyde and acetone) at doses mimicking chronic low level environmental exposure and the effect on human keratinocytes to get better insight into VOC-cell interactions. We provide evidence that the proteasome, a major intracellular proteolytic system which is involved in a broad array of processes such as cell cycle, apoptosis, transcription, DNA repair, protein quality control and antigen presentation, is a VOC target. Proteasome inactivation after VOC exposure is accompanied by apoptosis, DNA damage and protein oxidation. Lon protease, which degrades oxidized, dysfunctional, and misfolded proteins in the mitochondria is also a VOC target. Using human skin explants we found that VOCs prevent cell proliferation and also inhibit proteasome activity in vivo. Taken together, our findings provide insight into potential mechanisms of VOC-induced proteasome inactivation and the cellular consequences of these events.

Early-onset, Severe Chronic Obstructive Pulmonary Disease with Pulmonary Hypertension that was Likely Induced by Toluene Exposure

Early-onset pulmonary emphysema is uncommon and its pathogenesis is poorly defined. A 30-year-old man was admitted to our intensive care unit with severe respiratory failure. Besides smoking heavily since the 14 years of age, he had habitually inhaled organic solvents, such as toluene, in his adolescence. High-resolution computed tomography showed evident pulmonary emphysema throughout the lung fields. Based on the findings of right heart catheterization, he was diagnosed with an acute exacerbation of chronic obstructive pulmonary disease complicated with pulmonary hypertension. Heavy smoking from a young age and exposure to toluene were the suspected causes of the patient's severe pulmonary emphysema.

Infants' indoor and outdoor residential exposure to benzene and respiratory health in a Spanish cohort

Benzene exposure represents a potential risk for children's health. Apart from being a known carcinogen for humans (group 1 according to IARC), there is scientific evidence suggesting a relationship between benzene exposure and respiratory problems in children. But results are still inconclusive and inconsistent. This study aims to assess the determinants of exposure to indoor and outdoor residential benzene levels and its relationship with respiratory health in infants. Participants were 1-year-old infants (N = 352) from the INMA cohort from Valencia (Spain). Residential benzene exposure levels were measured inside and outside dwellings by means of passive samplers in a 15-day campaign. Persistent cough, low respiratory tract infections and wheezing during the first year of life, and covariates (dwelling traits, lifestyle factors and sociodemographic data) were obtained from parental questionnaires. Multiple Tobit regression and logistic regression models were performed to assess factors associated to residential exposure levels and health associations, respectively. Indoor levels were higher than outdoor ones (1.46 and 0.77 μg/m³, respectively; p < 0.01). A considerable percentage of dwellings, 42% and 21% indoors and outdoors respectively, surpassed the WHO guideline of 1.7 μg/m³ derived from a lifetime risk of leukemia above 1/100 000. Monitoring season, maternal country of birth and parental tobacco consumption were associated with residential benzene exposure (indoor and outdoors). Additionally, indoor levels were associated with mother's age and type of heating, and outdoor levels were linked with zone of residence and distance from industrial areas. After adjustment for confounding factors, no significant associations were found between residential benzene exposure levels and respiratory health in infants. Hence, our study did not support the hypothesis for the benzene exposure effect on respiratory health in children. Even so, it highlights a public health concern related to the personal exposure levels, since a considerable number of children surpassed the abovementioned WHO guideline for benzene exposure.

Concentrations of monoaromatic hydrocarbons in the air of the underground car park and individual garages attached to residential buildings

The paper describes the characteristics of a two-level underground car park and three individual garages attached to residential buildings, differing by the resident utilization habits, located in North Poland (Tri-City agglomeration area). The strategy of collecting the analyte samples from air in mentioned enclosed areas, concerning the determination of benzene, toluene, ethylbenzene, o-xylene and p,m-xylenes (BTEX) concentrations was performed using passive sampling technique - Radiello® diffusive passive samplers with graphitised charcoal cartridge as a sorption medium. The stage of liberation and final determination of collected analytes was conducted with the use of thermal desorption-gas chromatography-flame ionisation detector (TD-GC-FID) system. As a result of the performed measurements in two-level underground car park, it was observed that the time-weighted average concentrations of BTEX in air were as follows: Level-1 - benzene - 5.2±1.1μg/m³, toluene - 12.3±2.4μg/m³, ethylbenzene 2.85±0.80μg/m³, o-xylene - 4.6±1.4μg/m³, p, m-xylenes - 8.8±2,4μg/m³; Level-2 - benzene - 5.2±1.1μg/m³, toluene - 12.9±3.6μg/m³, ethylbenzene - 2.73±0.79μg/m³, o-xylene - 4.2±1.1μg/m³, p, m-xylenes - 8.5±2.3μg/m³. As for residential garages, the time-weighted average concentrations of BTEX in air were in the following ranges: from 5.9 to 53μg/m³ (benzene), from 7.1 to 195μg/m³ (toluene), from 3.0 to 39μg/m³ (ethylbenzene), from 5.6 to 44μg/m³ (o-xylene) and from 6.3 to 99μg/m³ (p,m-xylenes). Also, BTEX concentration ratios such as: tol/benz ratio and (m, p)-xyl/et.benz coefficient, were calculated based on the obtained results to assess the "freshness" of air mass and the influence exerted by vehicle movement on the concentration of BTEX in air in studied enclosed areas.

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO₂, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO₂ is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the "zero concept" of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.

The effect of anthropogenic activity on BTEX, NO2, SO2, and CO concentrations in urban air of the spa city of Sopot and medium-industrialized city of Tczew located in North Poland

The major goal of the present study is to compare the air quality of two urban locations situated in Northern Poland - the spa City of Sopot and the medium-industrialized city of Tczew using chemometric methods. As a criterion for the assessment of atmospheric air quality, measurements of benzene, toluene, ethylbenzene and total xylenes were used (collected from atmospheric air using diffusion-type passive samplers) as well as measurements of inorganic compounds - CO, NO2 and SO2, which were subject to routine control and determined by means of automatic analysers. Studies related to determination of defined chemical compounds in the urban air in the monitored area were performed from January 2013 to December 2014. By interpreting the results obtained and using basic multivariate statistical tools (cluster analysis and principal components analysis), major sources of emissions of determined pollutants in the air in urbanized areas were defined. The study also shows the potential influence of the sea breeze on concentrations of chemical compounds in the atmospheric air in the spa city of Sopot.

BTEX in vitro exposure tool using human lung cells: trips and gains

Cytotoxicity of benzene, toluene, ethylbenzene and xylenes (BTEX) to human lung cells was explored using three different exposure methods: Method 1 - in normal 96-well plates using DMSO as a carrier vehicle, we exposed (a) human lung carcinoma A549 cells, (b) A549 cells over-expressed with cytochrome P450 2E1 cells, and (c) normal lung fibroblast LL-24 cells to benzene, toluene, ethylbenzene and xylene individually and in a mixture which models car exhaust gases for between 1-88 h. We found that the order of the BTEX potency is benzene<toluene<ethylbenzene=m-xylene with acute BTEX toxicity to A549≈LL-24>CYP2E1 over-expressed A549 cells. A significant difference was found between inter-assay responses for all 24h exposures (P<0.005) suggesting a poor assay repeatability. No sign of potency increase was found from 6 to 72 h exposures. Method 2 - Using sealed vials to expose A549 cells to benzene, toluene and ethylbenzene, we observed a twenty-fold increase in their cytotoxicity, but also with no time-course effect. Method 3 - Using air exposed hanging-drop cell culture, we were able to see both an increase of demonstration of toxicity and a time-course effect from 1 to 12h exposure. We conclude that exposing cells in sealed and unsealed media using DMSO as a carrier vehicle was not suitable for BTEX exposure studies. Hanging-drop air exposure has more potential. It should be noted that if there are any changes in their exposure matrixes, its exposure mass distribution in cells could differ.

Investigations of the Biological Effects of Airborne and Inhalable Substances by Cell-Based In Vitro Methods: Fundamental Improvements to the ALI Concept

The state of the art for cell-based in vitro investigations of airborne and inhalable material is “air-liquid interface” (ALI) technology. Cell lines, primary cells, complex 3D models, or precision-cut lung slices (PCLS) are used to represent the lung or skin by way of an in vitro barrier model. These models have been applied in toxicity or pharmacological testing. However, contrasting with a clear demand for alternative methods, there is still no widely accepted procedure for cell-based in vitro testing of inhalable substances. In the light of this, an analysis was undertaken of common drawbacks of current approaches. Hence, the pivotal improvements aimed at were the cellular exposure environment, overall performance and applicability, operability of online investigations during exposure and routine setup. It resulted in an improved device (P.R.I.T. ExpoCube) based on an “all-in-one-plate” concept including all phases of the experiment (cell culture, exposure, and read-out) and all experimental groups (two test gas groups, controls) in one single commercial multiwell plate. Verification of the concept was demonstrated in a first experimental series using reference substances (formaldehyde, ozone, and clean air). The resulting ALI procedure enables the application of inhalable substances and mixtures under highly effective exposure conditions in routine utilization.

Aircraft engine exhaust emissions and other airport-related contributions to ambient air pollution: A review

Civil aviation is fast-growing (about +5% every year), mainly driven by the developing economies and globalisation. Its impact on the environment is heavily debated, particularly in relation to climate forcing attributed to emissions at cruising altitudes and the noise and the deterioration of air quality at ground-level due to airport operations. This latter environmental issue is of particular interest to the scientific community and policymakers, especially in relation to the breach of limit and target values for many air pollutants, mainly nitrogen oxides and particulate matter, near the busiest airports and the resulting consequences for public health. Despite the increased attention given to aircraft emissions at ground-level and air pollution in the vicinity of airports, many research gaps remain. Sources relevant to air quality include not only engine exhaust and non-exhaust emissions from aircraft, but also emissions from the units providing power to the aircraft on the ground, the traffic due to the airport ground service, maintenance work, heating facilities, fugitive vapours from refuelling operations, kitchens and restaurants for passengers and operators, intermodal transportation systems, and road traffic for transporting people and goods in and out to the airport. Many of these sources have received inadequate attention, despite their high potential for impact on air quality. This review aims to summarise the state-of-the-art research on aircraft and airport emissions and attempts to synthesise the results of studies that have addressed this issue. It also aims to describe the key characteristics of pollution, the impacts upon global and local air quality and to address the future potential of research by highlighting research needs.

A model of human nasal epithelial cells adapted for direct and repeated exposure to airborne pollutants

Airway epithelium lining the nasal cavity plays a pivotal role in respiratory tract defense and protection mechanisms. Air pollution induces alterations linked to airway diseases such as asthma. Only very few in vitro studies to date have succeeded in reproducing physiological conditions relevant to cellular type and chronic atmospheric pollution exposure. We therefore, set up an in vitro model of human Airway Epithelial Cells of Nasal origin (hAECN) close to real human cell functionality, specifically adapted to study the biological effects of exposure to indoor gaseous pollution at the environmental level. hAECN were exposed under air-liquid interface, one, two, or three-times at 24 h intervals for 1 h, to air or formaldehyde (200 μg/m(3)), an indoor air gaseous pollutant. All experiments were ended at day 4, when both cellular viability and cytokine production were assessed. Optimal adherence and confluence of cells were obtained 96 h after cell seeding onto collagen IV-precoated insert. Direct and repeated exposure to formaldehyde did not produce any cellular damage or IL-6 production change, although weak lower IL-8 production was observed only after the third exposure. Our model is significantly better than previous ones due to cell type and the repeated exposure protocol.

Modulation of microRNA expression by volatile organic compounds in mouse lung

Volatile organic compounds (VOCs) are one of main pollutants indoors. Exposure to VOCs is associated with cancer, asthma disease, and multiple chemical allergies. Despite the adverse health effects of VOCs, the molecular mechanisms underlying VOCs-induced disease remain largely unknown. MicroRNAs (miRNAs), as key post-transcriptional regulators of gene expression, may influence cellular disease state. To investigate whether lung miRNA expression profiles in mice are modified by VOCs mixture exposure, 44 male Kunming mice were exposed in 4 similar static chambers, 0 (control) and 3 different doses of VOCs mixture (groups 1-3). The concentrations of VOCs mixture were as follows: formaldehyde, benzene, toluene, and xylene 3.0 + 3.3 + 6.0 + 6.0 mg/m(3) , 5.0 + 5.5 + 10.0 + 10.0 mg/m(3) , 10.0 + 11.0 + 20.0 + 20.0 mg/m(3) , respectively, which corresponded to 30, 50, and 100 times of indoor air quality standard in China, after exposure to 2 weeks (2 h/day, 5 days/week). Small RNAs in lung and protein isolated from bronchoalveolar lavage fluid (BALF) were collected and analyzed for miRNA expression using microarray analysis and for interleukin-8 (IL-8) protein levels by enzyme-linked immunosorbent assay, respectively. VOCs exposure altered the miRNA expression profiles in lung in mice. Specifically, 69 miRNAs were significantly differentially expressed in VOCs-exposed samples versus controls. Functional annotation analysis of the predicted miRNA transcript targets revealed that VOCs exposure potentially alters signaling pathways associated with cancer, chemokine signaling, Wnt signaling, neuroactive ligand-receptor interaction, and cell adhesion molecules. IL-8 isolated from BALF and nitric oxide synthase of lung increased significantly, whereas GSH of lung decreased significantly in mice exposed to VOCs. These results indicate that inhalation of VOCs alters miRNA patterns that regulate gene expression, potentially leading to the initiation of cancer and inflammatory diseases.

Hanging drop: an in vitro air toxic exposure model using human lung cells in 2D and 3D structures

Using benzene as a candidate air toxicant and A549 cells as an in vitro cell model, we have developed and validated a hanging drop (HD) air exposure system that mimics an air liquid interface exposure to the lung for periods of 1h to over 20 days. Dose response curves were highly reproducible for 2D cultures but more variable for 3D cultures. By comparing the HD exposure method with other classically used air exposure systems, we found that the HD exposure method is more sensitive, more reliable and cheaper to run than medium diffusion methods and the CULTEX(®) system. The concentration causing 50% of reduction of cell viability (EC50) for benzene, toluene, p-xylene, m-xylene and o-xylene to A549 cells for 1h exposure in the HD system were similar to previous in vitro static air exposure. Not only cell viability could be assessed but also sub lethal biological endpoints such as DNA damage and interleukin expressions. An advantage of the HD exposure system is that bioavailability and cell concentrations can be derived from published physicochemical properties using a four compartment mass balance model. The modelled cellular effect concentrations EC50cell for 1h exposure were very similar for benzene, toluene and three xylenes and ranged from 5 to 15 mmol/kgdry weight, which corresponds to the intracellular concentration of narcotic chemicals in many aquatic species, confirming the high sensitivity of this exposure method.

Detection of the cytotoxicity of water-insoluble fraction of cigarette smoke by direct exposure to cultured cells at an air-liquid interface

For the biological evaluation of cigarette smoke in vitro, the particulate phase (PP) and the gas vapor phase (GVP) of mainstream smoke have usually been collected individually and exposed to biological material such as cultured cells. Using this traditional method, the GVP is collected by bubbling in an aqueous solution such as phosphate-buffered saline (PBS). In such a way the water-insoluble GVP fraction is excluded from the GVP, meaning that the toxic potential of the water-insoluble GVP fraction has hardly been investigated so far. In our experiments we used a direct exposure method to expose cells at the air-liquid interface (ALI) to the water-insoluble GVP fraction for demonstrating its toxicological/biological activity. In order to isolate the water-insoluble GVP fraction from mainstream smoke, the GVP was passed through 6 impingers connected in series with PBS. After direct exposure of Chinese hamster ovary cells (CHO-K1) with the water-insoluble GVP fraction in the CULTEX(®) system its cytotoxicity was assayed by using the neutral red uptake assay. The water-insoluble GVP fraction was proven to be less cytotoxic than the water-soluble GVP fraction, but showed a significant effect in a dose-dependent manner. The results of this study showed that the direct exposure of cultivated cells at the air-liquid interface offers the possibility to analyze the biological and toxicological activities of all fractions of cigarette smoke including the water-insoluble GVP fraction.