The combined effects of physicochemical properties of size-fractionated ambient particulate matter on in vitro toxicity in human A549 lung epithelial cells

Epithelial MAPK signaling directs endothelial NRF2 signaling and IL-8 secretion in a tri-culture model of the alveolar-microvascular interface following diesel exhaust particulate (DEP) exposure

BACKGROUND

Particulate matter 2.5 (PM2.5) deposition in the lung's alveolar capillary region (ACR) is significantly associated with respiratory disease development, yet the molecular mechanisms are not completely understood. Adverse responses that promote respiratory disease development involve orchestrated, intercellular signaling between multiple cell types within the ACR. We investigated the molecular mechanisms elicited in response to PM2.5 deposition in the ACR, in an in vitro model that enables intercellular communication between multiple resident cell types of the ACR.

METHODS

An in vitro, tri-culture model of the ACR, incorporating alveolar-like epithelial cells (NCI-H441), pulmonary fibroblasts (IMR90), and pulmonary microvascular endothelial cells (HULEC) was developed to investigate cell type-specific molecular responses to a PM2.5 exposure in an in-vivo-like model. This tri-culture in vitro model was termed the alveolar capillary region exposure (ACRE) model. Alveolar epithelial cells in the ACRE model were exposed to a suspension of diesel exhaust particulates (DEP) (20 µg/cm2) with an average diameter of 2.5 µm. Alveolar epithelial barrier formation, and transcriptional and protein expression alterations in the directly exposed alveolar epithelial and the underlying endothelial cells were investigated over a 24 h DEP exposure.

RESULTS

Alveolar epithelial barrier formation was not perturbed by the 24 h DEP exposure. Despite no alteration in barrier formation, we demonstrate that alveolar epithelial DEP exposure induces transcriptional and protein changes in both the alveolar epithelial cells and the underlying microvascular endothelial cells. Specifically, we show that the underlying microvascular endothelial cells develop redox dysfunction and increase proinflammatory cytokine secretion. Furthermore, we demonstrate that alveolar epithelial MAPK signaling modulates the activation of NRF2 and IL-8 secretion in the underlying microvascular endothelial cells.

CONCLUSIONS

Endothelial redox dysfunction and increased proinflammatory cytokine secretion are two common events in respiratory disease development. These findings highlight new, cell-type specific roles of the alveolar epithelium and microvascular endothelium in the ACR in respiratory disease development following PM2.5 exposure. Ultimately, these data expand our current understanding of respiratory disease development following particle exposures and illustrate the utility of multicellular in vitro systems for investigating respiratory tract health.

A review on potential approach for in silico toxicity analysis of respirable fraction of ambient particulate matter

Epidemiological and toxicological studies have shown the adverse effect of ambient particulate matter (PM) on respiratory and cardiovascular systems inside the human body. Various cellular and acellular assays in literature use indicators like ROS generation, cell inflammation, mutagenicity, etc., to assess PM toxicity and associated health effects. The presence of toxic compounds in respirable PM needs detailed studies for proper understanding of absorption, distribution, metabolism, and excretion mechanisms inside the body as it is difficult to accurately imitate or simulate these mechanisms in lab or animal models. The leaching kinetics of the lung fluid, PM composition, retention time, body temperature, etc., are hard to mimic in an artificial experimental setup. Moreover, the PM size fraction also plays an important role. For example, the ultrafine particles may directly enter systemic circulations while coarser PM10 may be trapped and deposited in the tracheo-bronchial region. Hence, interpretation of these results in toxicity models should be done judiciously. Computational models predicting PM toxicity are rare in the literature. The variable composition of PM and lack of proper understanding for their synergistic role inside the body are prime reasons behind it. This review explores different possibilities of in silico modeling and suggests possible approaches for the risk assessment of PM particles. The toxicity testing approach for engineered nanomaterials, drugs, food industries, etc., have also been investigated for application in computing PM toxicity.

Assessing the cytotoxicity of aerosolized carbon black and benzo[a]pyrene with controlled physical and chemical properties on human lung epithelial cells

Atmospheric particulate matter (PM) is a complex mixture of hazardous particles containing hundreds of inorganic and organic species. Organic components, such as carbon black (CB) and benzo[a]pyrene (BaP), are known to exhibit diverse genotoxic and carcinogenic effects. The toxicity of CB and polycyclic aromatic hydrocarbons has been well studied, however the combined toxicity is much less understood. A spray-drying system was used to control the size and chemical composition of PMs. PMs were prepared by loading BaP on three different sized CBs (0.1 μm, 2.5 μm, and 10 μm) to obtain BaP-unloaded CB (CB0.1, CB2.5, and CB10) and BaP-loaded CB (CB0.1-BaP, CB2.5-BaP, and CB10-BaP). We analyzed cell viability, levels of oxidative stress, and pro-inflammatory cytokines using human lung cells (A549 epithelial cells). Cell viability decreased when exposed to all PMs (PM0.1, PM2.5, and PM10), regardless of the presence of BaP. The increase in PM size due to BaP-adsorption to CB resulted in insufficient toxic effects on human lung cells compared to CB alone. Smaller CBs reduced cell viability, leading to reactive oxygen species formation, which can cause damage to cellular structures deliver more harmful substances. Additionally, small CBs were predominant in inducing the expression of pro-inflammatory cytokines in A549 epithelial cells. These results indicate that the size of CB is a key factor that immediately affects the inflammation of lung cells, compared to the presence of BaP.

Toxicological Effects of Secondary Air Pollutants

Secondary air pollutants, originating from gaseous pollutants and primary particulate matter emitted by natural sources and human activities, undergo complex atmospheric chemical reactions and multiphase processes. Secondary gaseous pollutants represented by ozone and secondary particulate matter, including sulfates, nitrates, ammonium salts, and secondary organic aerosols, are formed in the atmosphere, affecting air quality and human health. This paper summarizes the formation pathways and mechanisms of important atmospheric secondary pollutants. Meanwhile, different secondary pollutants' toxicological effects and corresponding health risks are evaluated. Studies have shown that secondary pollutants are generally more toxic than primary ones. However, due to their diverse source and complex generation mechanism, the study of the toxicological effects of secondary pollutants is still in its early stages. Therefore, this paper first introduces the formation mechanism of secondary gaseous pollutants and focuses mainly on ozone's toxicological effects. In terms of particulate matter, secondary inorganic and organic particulate matters are summarized separately, then the contribution and toxicological effects of secondary components formed from primary carbonaceous aerosols are discussed. Finally, secondary pollutants generated in the indoor environment are briefly introduced. Overall, a comprehensive review of secondary air pollutants may shed light on the future toxicological and health effects research of secondary air pollutants.

Intensive poultry farming: A review of the impact on the environment and human health

Poultry farming is one of the most efficient animal husbandry methods and it provides nutritional security to a significant number of the world population. Using modern intensive farming techniques, global production has reached 133.4 mil. t in 2020, with a steady growth each year. Such intensive growth methods however lead to a significant environmental footprint. Waste materials such as poultry litter and manure can pose a serious threat to environmental and human health, and need to be managed properly. Poultry production and waste by-products are linked to NH₃, N₂O and CH₄ emissions, and have an impact on global greenhouse gas emissions, as well as animal and human health. Litter and manure can contain pesticide residues, microorganisms, pathogens, pharmaceuticals (antibiotics), hormones, metals, macronutrients (at improper ratios) and other pollutants which can lead to air, soil and water contamination as well as formation of antimicrobial/multidrug resistant strains of pathogens. Dust emitted from intensive poultry production operations contains feather and skin fragments, faeces, feed particles, microorganisms and other pollutants, which can adversely impact poultry health as well as the health of farm workers and nearby inhabitants. Fastidious odours are another problem that can have an adverse impact on health and quality of life of workers and surrounding population. This study discusses the current knowledge on the impact of intensive poultry farming on environmental and human health, as well as taking a look at solutions for a sustainable future.

RNA-Seq Analysis of UPM-Exposed Epithelium Co-Cultivated with Macrophages and Dendritic Cells in Obstructive Lung Diseases

Background. Elevated concentrations of airborne pollutants are correlated with an enlarged rate of obstructive lung disease morbidity as well as acute disease exacerbations. This study aimed to analyze the epithelium mRNA profile in response to airborne particulate matter in the control, asthma, and COPD groups. Results. A triple co-culture of nasal epithelium, monocyte-derived macrophages, and monocyte-derived dendritic cells obtained from the controls, asthma, and COPD were exposed to urban particulate matter (UPM) for 24 h. RNA-Seq analysis found differences in seven (CYP1B1, CYP1B1-AS1, NCF1, ME1, LINC02029, BPIFA2, EEF1A2), five (CYP1B1, ARC, ENPEP, RASD1, CYP1B1-AS1), and six (CYP1B1, CYP1B1-AS1, IRF4, ATP1B2, TIPARP, CCL22) differentially expressed genes between UPM exposed and unexposed triple co-cultured epithelium in the control, asthma, and COPD groups, respectively. PCR analysis showed that mRNA expression of BPIFA2 and ENPEP was upregulated in both asthma and COPD, while the expression of CYP1B1-AS1 and TIPARP was increased in the epithelium from COPD patients only. Biological processes changed in UPM exposed triple co-cultured epithelium were associated with epidermis development and epidermal cell differentiation in asthma and with response to toxic substances in COPD. Conclusions. The biochemical processes associated with pathophysiology of asthma and COPD impairs the airway epithelial response to UPM.

Physical, chemical, and cell toxicity properties of mature/aged particulate matter (PM) trapped in a diesel particulate filter (DPF) along with the results from freshly produced PM of a diesel engine

The lifetime and efficiency of diesel particulate filters (DPFs) strongly depend on the proper and periodic cleaning and servicing. Unfortunately, in some cases, inappropriate methods are applied to clean the DPFs, e.g., using air compressors without proper disposal procedures which can have negative impacts on human health, the environment, and DPF's efficiency. However, there is no information available about the properties of this kind of PM. This research is therefore presented to explore the physicochemical and toxicity properties of aged PM trapped in a DPF (using compressed air for PM sampling) employing STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer for investigating the physicochemical properties, and assays of cell viability, cellular reactive oxygen species (ROS), interleukin-6, and tumor necrosis factor-alpha (TNF-α) for investigating the toxicity properties. Also, analyses from fresh PM samples from the diesel vehicle at two engine speeds are presented. It is found that at a certain/fixed PM number/mass for all three samples tested, the PM from DPF compared with the fresh PM can have both positive (particularly having the lowest water-soluble total carbon ratio) and negative impacts on human health (particularly having the highest cell death rate of 13.4%, ROS, and TNF-α) and the environment.

Development of a standardized in vitro approach to evaluate microphysical, chemical, and toxicological properties of combustion-derived fine and ultrafine particles

Ultrafine particles represent a growing concern in the public health community but their precise role in many illnesses is still unknown. This lack of knowledge is related to the experimental difficulty in linking their biological effects to their multiple properties, which are important determinants of toxicity. Our aim is to propose an interdisciplinary approach to study fine (FP) and ultrafine (UFP) particles, generated in a controlled manner using a miniCAST (Combustion Aerosol Standard) soot generator used with two different operating conditions (CAST1 and CAST3). The chemical characterization was performed by an untargeted analysis using ultra-high resolution mass spectrometry. In conjunction with this approach, subsequent analysis by gas chromatography-mass spectrometry (GC-MS) was performed to identify polycyclic aromatic hydrocarbons (PAH). CAST1 enabled the generation of FP with a predominance of small PAH molecules, and CAST3 enabled the generation of UFP, which presented higher numbers of carbon atoms corresponding to larger PAH molecules. Healthy normal human bronchial epithelial (NHBE) cells differentiated at the air-liquid interface (ALI) were directly exposed to these freshly emitted FP and UFP. Expression of MUC5AC, FOXJ1, OCLN and ZOI as well as microscopic observation confirmed the ciliated pseudostratified epithelial phenotype. Study of the mass deposition efficiency revealed a difference between the two operating conditions, probably due to the morphological differences between the two categories of particles. We demonstrated that only NHBE cells exposed to CAST3 particles induced upregulation in the gene expression of IL-8 and NQO1. This approach offers new perspectives to study FP and UFP with stable and controlled properties.

On the Water-Soluble Organic Matter in Inhalable Air Particles: Why Should Outdoor Experience Motivate Indoor Studies?

The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors.

Potential cytotoxicity of trace elements and polycyclic aromatic hydrocarbons bounded to particulate matter: a review on in vitro studies on human lung epithelial cells

A large number of studies have been conducted for clarifying toxicological mechanisms of particulate matter (PM) aimed to investigate the physicochemical properties of PM and providing biological endpoints such as inflammation, perturbation of cell cycle, oxidative stress, or DNA damage. However, although several studies have presented some effects, there is still no consensus on the determinants of biological responses. This review attempts to summarize all past research conducted in recent years on the physicochemical properties of environmental PM in different places and the relationship between different PM components and PM potential cytotoxicity on the human lung epithelial cells. Among 447 papers with our initial principles, a total of 50 articles were selected from 1986 to April 2020 based on the chosen criteria for review. According to the results of selected studies, it is obvious that cytotoxicity in human lung epithelial cells is created both directly or indirectly by transition metals (such as Cu, Cr, Fe, Zn), polycyclic aromatic hydrocarbons (PAH), and ions that formed on the surface of particles. In the selected studies, the findings of the correlation analysis indicate that there is a significant relationship between cell viability reduction and secretion of inflammatory mediators. As a result, it seems that the observed biological responses are related to the composition and the physicochemical properties of the PMs. Therefore, the physicochemical properties of PM should be considered when explaining PM cytotoxicity, and long-term research data will lead to improved strategies to reduce air pollution.

Biological effect of PM10 on airway epithelium-focus on obstructive lung diseases

Recently, a continuous increase in environmental pollution has been observed. Despite wide-scale efforts to reduce air pollutant emissions, the problem is still relevant. Exposure to elevated levels of airborne particles increased the incidence of respiratory diseases. PM₁₀ constitute the largest fraction of air pollutants, containing particles with a diameter of less than 10 μm, metals, pollens, mineral dust and remnant material from anthropogenic activity. The natural airway defensive mechanisms against inhaled material, such as mucus layer, ciliary clearance and macrophage phagocytic activity, may be insufficient for proper respiratory function. The epithelium layer can be disrupted by ongoing oxidative stress and inflammatory processes induced by exposure to large amounts of inhaled particles as well as promote the development and exacerbation of obstructive lung diseases. This review draws attention to the current state of knowledge about the physical features of PM₁₀ and its impact on airway epithelial cells, and obstructive pulmonary diseases.

PARP-1 overexpression does not protect HaCaT cells from DNA damage induced by SiO2 nanoparticles

Nano-SiO₂ is increasingly used in diagnostic and biomedical research because of its ease of production and relatively low cost and which is generally regarded as safe and has been approved for use as a food or animal feed ingredient. Although recent literature reveals that nano-SiO₂ may present toxicity and DNA damage, however, the underlying mechanism remains poorly understood. Since in previous studies, we found that nano-SiO₂ treatment down-regulated the expression of the poly(ADP-ribose) polymerases-1 (PARP-1), a pivotal DNA repair gene, in human HaCaT cells and PAPR-1 knockdown can aggravate DNA damage induced by nano-SiO₂. Therefore, we speculate whether PARP-1 overexpression can protect DNA from damage induced by nano-SiO₂. However, our data demonstrated that overexpression of PARP-1 in HaCaT cells slightly enhanced the cellular proliferation of undamaged cells, when compared with both empty vector control cells and parental cells, but had drastic consequences for cells treated with nano-SiO₂. The PARP-1 overtransfected cells were sensitized to the cytotoxic effects and DNA damage of nano-SiO₂ compared with control parental cells. Meanwhile, flow cytometric analysis of nano-SiO₂ stimulated poly(ADP-ribose) synthesis revealed consistently larger fractions of cells positive for this polymer in the PARP-1 overexpression cells than in control clones. Combining our previous research on PARP-1 knockdown HaCaT cells, we hypothesize that an optimal level of cellular poly(ADP-ribose) accumulation exists for the cellular recovery from DNA damage.

Insights on the biological role of ultrafine particles of size PM<0.25: A prospective study from New Delhi

When the total ambient PM_2.5 levels are several-fold higher than the recommended limit, it may be important to study the distributions of different sizes of particulate matter (PM). Here, we assess the distributions of various sizes of total PM_2.5 for 12 months (on a monthly basis) in New Delhi, India. Importantly, we found that ultrafine particles (i.e., particles <0.5 μm) contribute significantly to total PM_2.5. PM_<0.25 were the most cytotoxic particles to human lung epithelial cells in all the 12 months. In addition, PM_<0.25 were associated with significantly higher cytotoxicity per unit mass compared to other size fractions constituting PM_2.5. For any given size of PM, the amount of reactive oxygen species (ROS) generated per unit mass is higher for the month of March as compared to that for the rest of the months in the year. The higher ROS generations for all sizes of PM collected in the month of March was not explained by differences in their metal content values. Our data suggests the lack of correlation between total PM_2.5 levels and the highly cytotoxic PM_<0.25. In summary, this work establishes the need for policy changes to routinely monitor PM_<0.25 and the necessity to establish exposure limits for PM_<0.25, especially when the total PM_2.5 levels are breached.

Reactive oxygen species production and inflammatory effects of ambient PM2.5 -associated metals on human lung epithelial A549 cells "one year-long study": The Delhi chapter

The fine particulate matter (PM_2.5) was collected at academic campus of Indian Institute of Technology, Delhi, India from January-December 2017. The PM_2.5 samples were analysed for carcinogenic (Cd, Cr, As, Ni, and Pb) and non-carcinogenic (V, Cu, Zn, Fe) trace metals and their elicited effects on carcinoma epithelial cell line A549. Toxicological testing was done with ELISA kit. Same analyses were repeated for standard reference material (NIST-1648a) represents urban particulate matter. The student-t test and spearman correlation were used for data analysis. The seasonality in PM_2.5 mass concentration and chemical composition showed effect on biological outcomes. The PM_2.5 in post-monsoon and winter had higher amount of trace metals compared to mass collected in pre-monsoon and monsoon. Following the trend in PM mass concentration significantly (p < 0.5) lower cell viability was observed in post-monsoon and winter compared to other two seasons. NIST UPM 1648(a) samples always had higher cytotoxicity compared to ambient PM_2.5 Delhi sample. Strong association of Chromium, Nickel, Cadmium, and Zinc was observed with cell viability and reactive oxygen species (ROS) production. In winter IL-6, IL-8 production were 2.8 and 3 times higher than values observed in post-monsoon and 53 and 9 times higher than control. In winter season trace metals As, Cu, Fe, in pre-monsoon Cr, Ni, As, Pb, V, and Fe, in post-monsoon Cd and V strongly correlated with ROS generation. ROS production in winter and pre-monsoon seasons found to be 2.6 and 1.3 times higher than extremely polluted post-monsoon season which had 2 to 3 times higher PM_2.5 concentration compared to winter and pre-monsoon. The result clearly indicated that the presence of Fe in winter and pre-monsoon seasons catalysed the ROS production, probably OH˙ radical caused high cytokines production which influenced the cell viability reduction, while in post-monsoon PM majorly composed of Pb, As, Fe and Cu and affected by photochemical smog formation showed significant association between ROS production with cell viability. Overall, in Delhi most toxic seasons for respiratory system are winter and post-monsoon and safest season is monsoon.

Assessment of the effects of atmospheric pollutants using the animal model Caenorhabditis elegans

Air pollution is recognized as the world's largest environmental health risk. In this work we evaluated in vivo the effects of three relevant components of atmospheric dusts (brake dust, wood pellet ash and Saharan dust) employing the animal model Caenorhabditis elegans. Main endpoints of C. elegans such as life span, brood size and oxidative stress were addressed by exposing the nematodes to different dust concentrations. Brake dust and pellet ash affected the life span and increased significantly the oxidative stress of exposed nematodes, while Saharan dust showed no effects. Water soluble and insoluble fractions of these dusts were used to investigate the impact of the single fraction on C. elegans. The two fractions of brake dust and pellet ash exerted different effects on C. elegans endpoints in terms of life span and oxidative stress response. These fractions acted in different ways on the worm susceptibility to infection of two human pathogens (Staphylococcus aureus and Pseudomonas aeruginosa) affecting the sek-1 gene expression. In conclusion, our study showed that C. elegans is a valuable tool to investigate in vivo possible effects of atmospheric dusts.

Combined toxic effects of CBNPs and Pb on rat alveolar macrophage apoptosis and autophagy flux

Carbon black (CB) and heavy metals are the main components of Particulate Matter (PM). Although the individual toxicities of CB and heavy metals have been extensively studied, the combined toxicity is much less understood. In this study, we choose the nano carbon black (CBNPs) and Pb²⁺ to simulate fine particles in the atmosphere and study the combined toxic effect on rat alveolar macrophages. The data showed that CBNPs could adsorb Pb²⁺ to form CBNPs-Pb²⁺ complex and displayed an altered physical properties by particle characterization. CBNPs-Pb²⁺ synergistically induced rat alveolar macrophages apoptosis and blocked autophagy flux compared with CBNPs and Pb²⁺ individually. Consistent with this, CBNPs-Pb²⁺ could impair the mitochondrial membrane potential (MMP), activate apoptotic signaling pathways, inhibit lysosomal function.

Development of a system for the detection of the inflammatory response induced by airborne fine particulate matter in rat tracheal epithelial cells

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Atmospheric endotoxin level is related to inflammatory response induction

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Stable cell lines established to determine the expression of pro-inflammatory genes

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Our system serves monitoring of inflammatory response to airborne particulate matter

Exposure to airborne particulate matter (PM) is related to the increased risk of several diseases, including chronic and allergic rhinitis. We have previously shown that atmospheric endotoxin level was positively associated with the number of emergency department visits for asthma even after adjusting for meteorological factors, suggestive of the significant association between atmospheric endotoxin level and asthma exacerbation. Whether atmospheric endotoxin level is related to inflammatory response induction is, however, unclear. Here, we established stable cell lines to determine the promoter activity of the genes encoding pro-inflammatory cytokines such as tumor necrosis factor alpha, interleukin 6 (IL6), and IL33 by transfection of each reporter plasmid into rat tracheal epithelial EGV-4 T cells. These cells could measure the inflammatory response induced by endotoxin treatment more easily, rapidly, and sensitively than the conventional system using immunodetection assays. Furthermore, we revealed a relationship between atmospheric endotoxin level and inflammatory response induction. Thus, the system established herein may serve as a promising tool to monitor inflammatory response induced upon PM exposure.

Development of a system for the detection of the inflammatory response induced by airborne fine particulate matter in rat tracheal epithelial cells

Exposure to airborne particulate matter (PM) is related to the increased risk of several diseases, including chronic and allergic rhinitis. We have previously shown that atmospheric endotoxin level was positively associated with the number of emergency department visits for asthma even after adjusting for meteorological factors, suggestive of the significant association between atmospheric endotoxin level and asthma exacerbation. Whether atmospheric endotoxin level is related to inflammatory response induction is, however, unclear. Here, we established stable cell lines to determine the promoter activity of the genes encoding pro-inflammatory cytokines such as tumor necrosis factor alpha, interleukin 6 (IL6), and IL33 by transfection of each reporter plasmid into rat tracheal epithelial EGV-4 T cells. These cells could measure the inflammatory response induced by endotoxin treatment more easily, rapidly, and sensitively than the conventional system using immunodetection assays. Furthermore, we revealed a relationship between atmospheric endotoxin level and inflammatory response induction. Thus, the system established herein may serve as a promising tool to monitor inflammatory response induced upon PM exposure.

Copper-dependent biological effects of particulate matter produced by brake systems on lung alveolar cells

Road traffic is one of the main sources of particulate emissions into the environment and has an increasing, negative impact on the release of potentially dangerous materials. Vehicle brakes release a significant amount of wear particles, and knowledge regarding their possible adverse effects is limited. One of the most dangerous elements contained in brake pads is copper (Cu), known to be toxic for human health. Therefore, our aim was to study the cell toxicity of particulate matter (PM) produced by different combinations of braking discs and pads containing different amounts of Cu. We investigated whether brake-derived microparticles have toxic effects on lung cells proportionally to their Cu content. Analyte content was measured in friction materials by XRFS and in PM2.5 captured during braking tests using SEM/EDX. The biological impact of brake-derived PM2.5 was investigated on a human epithelial alveolar cell line (A549). Cell viability, oxidative stress, mitochondrial membrane potential, apoptosis, and the pro-inflammatory response of the cells, as well as gene expression, were assessed following exposure to increasing PM2.5 concentrations (1, 10, 100, 200, and 500 µg/ml). The brake debris with the lowest Cu content did not induce significant changes in biological effects on A549 cells compared to normal controls, except for ROS production and IL6 gene expression. PM2.5 containing higher Cu quantities induced cell toxicity that correlated with Cu concentration. Our data suggest that the toxicity of PM2.5 from the brake system is mainly related to Cu content, thus confirming that eliminating Cu from brake pads will be beneficial for human health in urbanized environments.

Toxicological screening of airborne particulate matter in atmosphere of Pune: Reactive oxygen species and cellular toxicity

Present study screened the toxicological assessment of airborne particulate matter (PM), mechanistic investigation, relationship between the physicochemical characteristics and its associated toxic response. The average concentration of both PM₁₀ and PM_2.5 exceeded the Indian National Ambient Air Quality Standards. In present study, PM bound metals; Fe, Cu, Cr, Ni, Mn, Pb, Cd, Zn, Sr and Co have been taken into account with total metal concentration of 0.83 and 0.44 μg m^-3 of PM₁₀ and PM_2.5 mass concentrations, respectively. The contribution of redox active metals (Fe, Cu, Cr, Ni and Mn) in PM was more as compared to non-redox metals (Pb, Cd and Co) indicating significant risk to the exposed population as these metals possess the ability to produce reactive oxygen species (ROS) which are responsible for various diseases. The cytotoxicity profiles of PM samples determined by MTT assay on two different cell lines (A549 and PBMC) exhibited dose-dependent effects after 24 h exposure, but the consequences differ with respect to particle size and sampling periods. A significant decrease in cell viability with varying PM concentrations (20, 40, 60, 80 and 100 μg ml^-1) with respect to control was found in both cell lines. Incubation of RBC suspension with PM samples caused pronounced disruption of RBC and thus exhibited substantial hemolytic behavior. PM samples showed a range of potency to produce reactive oxygen species (ROS). Almost all PM samples increased the level of pro-inflammatory mediator (Nitric oxide) when compared to corresponding unexposed controls suggesting the important role of reactive nitrogen species in induction of cellular toxicity.

Cytotoxicity and toxicoproteomic analyses of human lung epithelial cells exposed to extracts of atmospheric particulate matters on PTFE filters using acetone and water

Differences of cytotoxicity associated with exposure to different extracts of atmospheric particulate matters (PMs) are still not well characterized by in vitro toxicoproteomics. In this study, in vitro cytotoxicity assays and toxicoproteomic analyses were carried out to investigate toxic effects of PM collected using polytetrafluoroethylene (PTFE) filters extracted with acetone for PM_2.1 and water for PM_2.1 and PM₁₀ on A549 human lung epithelial cells. The cytotoxicity assays based on cell viability, cell apoptosis and reactive oxygen species generation indicated that PM_2.1 extracted with acetone had the highest toxicity. iTRAQ labeling and LC-MS/MS analyses indicated that the number of differentially expressed proteins in A549 cells affected by PM_2.1 extracted with acetone was noticeably higher than that of the other two groups. Hierarchical cluster analyses showed that the influences of the extracts of PM_2.1 and PM₁₀ using water on the proteome of A549 cells were similar, whereas significantly different from the effect of PM_2.1 extracted with acetone. Pathways analyses indicated that PM_2.1 extracted with acetone influenced the expression of proteins involved in 14 pathways including glycolysis/gluconeogenesis, pentose phosphate pathway, proteasome, etc. PM_2.1 extracted with water affected the expression of proteins involved in 3 pathways including non-homologous end-joining, ribosome and endocytosis. However, PM₁₀ extracted with water affected the expression of proteins involved in only spliceosome pathway. The extracts of PM using different extractants to detach PM from PTFE filters influenced the cytotoxic effects of PM and the proteome of A549 cells. Therefore, extractants should be assessed carefully before the investigations on cytotoxicity to improve the compatibility of experimental results among research teams.

Emission factors and composition of PM2.5 from laboratory combustion of five Western Australian vegetation types

This study investigated the emission of PM₁₀ and PM_2.5 (particulates with diameters of less than 10 µm and 2.5 µm, respectively) and the chemical composition of PM_2.5 from laboratory combustion of five Australian vegetation types (three grasslands, a woodland and a forest). A mix of plants representative of Banksia (woodland) and Jarrah (forest) and three types of grasses (Spinifex - Triodia basedowii; Kimberley grass - Sehima nervosum and Heteropogon contortus; and an invasive grass (Veldt) - Ehrharta calycina) were burnt in 9 combustion conditions comprised of 3 fuel moisture levels (dry, moist, wet) and 3 air flow rates (no, low and high flow). PM (particulate matter) samples were collected onto filters and measured using gravimetric analysis. PM_2.5 was then extracted and analyzed for water-soluble metals and polycyclic aromatic hydrocarbons (PAH) concentrations. The largest proportion of PM₁₀ (98%) from vegetation fires was PM_2.5. Banksia yielded the highest PM_2.5 emission factor (EF), followed by Jarrah and Spinifex. Veldt grass combustion generated significantly higher emissions of PM_2.5 compared with the other two grass types. High moisture contents and flow rates resulted in larger emissions of PM_2.5. A strong correlation (R² = 0.84) was observed between the EF for PM_2.5 and combustion efficiency, suggesting higher PM emission with lower combustion efficiencies. Potassium and sodium were the most abundant PM_2.5-bound water soluble metals, accounting for more than 97% of the total mass of metals analyzed. PAHs were found in significant concentrations, including the carcinogenic benzo(a)pyrene. Pyrene and fluoranthene were the most abundant PAHs detected, accounting for nearly 40% mass of the total PAHs. Indeno(1,2,3-cd)pyrene and benzo(g,h,i)perylene ratio (IND/IND + BghiP) appeared to be produced in a diagnostic ratio that indicated that the PAHs were derived from vegetation fires rather than other sources of emissions. The EF for PM_2.5 and its chemical composition (water-soluble metals and PAHs) were strongly influenced by the type of vegetation burned. The results presented in this study could be useful in predicting the risks of human health effects on firefighters and the public who may be exposed to regular bushfires in Australia.

Moderate-intensity physical activity reduces systemic inflammation and maintains cardiorespiratory function following chronic particulate matter2.5 exposure in rats

Aims

The purpose of the current study is to 1) examine the beneficial effects of moderate levels of physical activity (PA) on functional and biochemical markers of the cardiorespiratory system, 2) establish the detrimental effects of a single, daily particulate matter (PM) exposure event on cardiorespiratory function and 3) determine if exercising during daily PM exposure increases the deleterious effects caused by PM exposure due to increased inhalation of particulates on cardiorespiratory function.

Methods

Four groups of 16 rats were used: control (CON), PA, PM_2.5 exposed and PA combined with PM_2.5 exposure (PA + PM). Animals were purchased at 4 weeks old. However, both PA and PM exposure was initiated when the animals reached 8 weeks of age, for 8 weeks.

Results

PA alone did not alter body weight or blood pressure (BP) compared to control animals. However, there was a significant decrease in epididymal fat pad mass in the PA group. The PM exposed rats were hypertensive, showed increased systemic inflammation and oxidative stress, and had decreased spleen mass without pathological changes in the cardiac action potential or impaired vascular function. PA was able to decrease systemic inflammation in PM exposed animals, including a reduction in IL-6 serum levels, however, this did not translate to an improvement in BP or vascular reactivity. Smooth muscle relaxation in the trachea from the combination PA + PM group was not significantly different to CON and PA groups but was significantly higher than the PM group.

Conclusions

The current study showed that while there is an increased cardiovascular disease (CVD) risk associated with PM exposure, engaging in PA during exposure events imposes no increased risk with exercise providing a protective mechanism against some of the biochemical signaling changes caused by inhaled PM.

Quasi-ultrafine particles promote cell metastasis via HMGB1-mediated cancer cell adhesion

With increasingly severe air pollution, the aggravated health risks of particulate matter, especially ultrafine particles, are emerging as an urgent and sensitive topic. Considering the heterogeneity and complexity of ultrafine particles, there is insufficient evidence about their toxic effects and possible molecular mechanisms. To address this question, we analyzed the emission characteristics of quasi-ultrafine particles collected during winter in a typical coal-burning city, Taiyuan, and confirmed their contribution to lung cancer cell adhesion and metastasis. For the specific mechanism, we revealed that the endocytosis of quasi-ultrafine particles stimulated the release of HMGB1, induced NFκB-facilitated proinflammatory cytokine production through the interaction of HMGB1 with RAGE, and resulted in cancer-endothelial cell adhesion. These findings remind us of the potential effects of anthropogenic quasi-ultrafine particle pollution and provide a theoretical reference for the mitigation of tumorigenesis in a severe particulate matter contaminated environment.

Morin Protects Human Respiratory Cells from PM2.5 Induced Genotoxicity by Mitigating ROS and Reverting Altered miRNA Expression

Chronic fine particulate matter (PM2.5) exposure causes oxidative stress and leads to many diseases in human like respiratory and cardiovascular disorders, and lung cancer. It is known that toxic responses elicited by PM2.5 particles depend on its physical and chemical characteristics that are greatly influenced by the source. Dietary polyphenolic compounds that possess antioxidant and free radical scavenging properties could be used for therapeutic or preventive approaches against air pollution related health hazards. This study evaluates characteristics and toxicity of PM2.5 collected from rural, urban, industrial, and traffic regions in and around Coimbatore City, Tamilnadu, India. Traffic PM2.5 particles contained higher amounts of metals and polycyclic aromatic hydrocarbons (PAHs). It also possessed higher levels of oxidative potential, induced more intracellular reactive oxygen species (ROS), and caused more levels of cell death and DNA damage in human respiratory cells. Its exposure up regulated DNA damage response related miR222, miR210, miR101, miR34a, and miR93 and MycN and suppressed Rad52. Pre-treatment with morin significantly decreased the PM2.5 induced toxicity and conferred protection against PM2.5 induced altered miRNA expression. Results of this study showed that cytoprotective effect of morin is due to its antioxidative and free radical scavenging activity.

Different biological effects of PM2.5 from coal combustion, gasoline exhaust and urban ambient air relate to the PAH/metal compositions

Few studies have compared the biological effects of PM_2.5 from coal combustion, gasoline exhaust and urban ambient air, and the roles of polycyclic aromatic hydrocarbons (PAHs) and metals playing in the process remain unclear. In this study, PM_2.5 samples from coal combustion, gasoline exhaust and urban ambient air were analyzed for 16 PAHs and 23 metals. Cytotoxic and inflammatory effects of different PM_2.5 were evaluated on differentiated THP-1 and A549 cells, respectively. We found that the coal combustion PM_2.5 samples induced stronger cytotoxic and inflammatory effects (p < 0.05). Pearson's correlation and principal component analysis showed that the PAHs containing four or more benzenoid rings and specific metals of cadmium, thallium, zinc and lead were positively related to the biological effects. Our results suggested that coal combustion PM_2.5 might be a more serious health hazard. Specific PAHs and metals might be account for the PM_2.5 induced biological effects.

Prevalence of childhood lead poisoning and respiratory disease associated with lead smelter emissions

BACKGROUND

The city of Port Pirie in South Australia has been a world leading centre for lead and zinc smelting and processing since 1889 that continues to cause contamination of its environment and resident population. This study quantifies the effect of lead and SO₂ emissions from Nyrstar Port Pirie Pty Ltd's smelter on blood lead and respiratory health outcomes, respectively, and establishes what air quality values are required to better protect human health.

METHOD

Blood lead and emergency department presentation data collected by South Australia Health (SA Health) and lead in air and SO₂ data collected by the South Australian Environment Protection Authority (SAEPA) were obtained and analysed to quantify health outcomes due to smelter emissions in Port Pirie. Regression analysis was used to assess the relationship between the concentration of lead in air and children's blood lead levels between the years of available data: 2003 to 2017. Ambient SO₂ concentrations (SAEPA) measured continuously between 2008 and 2018 were 24-hour averaged and compared to daily local emergency department respiratory presentation rates (available from July 2012 to October 2018). Rates of emergency department respiratory presentations at Port Pirie and regional comparators were calculated as age-standardised rates.

RESULTS

The data show that increases in ambient SO₂ concentrations are associated with increased rates of emergency department respiratory presentations of Port Pirie residents, in which children are over-represented. The 30-day rolling average of respiratory presentations was significantly associated (p < 0.05) with incremental increases in SO₂. Analysis of the relationship between lead in air and blood lead shows that annual geometric mean air lead concentrations need to be <0.11 μg/m³ to ensure the geometric mean blood lead of Port Pirie children under 5 years is ≤5 μg/dL. For children aged 24 months, lead in air needs to be no greater than 0.082 μg/m³ (annual geometric mean) to ensure geometric mean blood lead does not exceed 5 μg/dL.

CONCLUSION

Current smelting emissions continue to pose a clear risk of harm to Port Pirie children. Allowable emissions must be lowered significantly to limit adverse childhood health outcomes including respiratory illness and IQ, academic achievement and socio-behavioural problems that are associated with lead exposure at levels experienced by Port Pirie children. Current SO₂ levels are likely to be responsible for increased rates of emergency department respiratory presentations in Port Pirie compared with other South Australian locations. As a minimum, Australian SO₂ air quality standards need to be enforced in Port Pirie to better protect human health. Lead in air needs to be approximately 80% lower than the current national standard (0.5 μg/m³) to ensure that the geometric blood lead of children under 5 years is less than or equal to 5 μg/dL.

Concentration, sources and human health risk of heavy metals and polycyclic aromatic hydrocarbons bound PM2.5 ambient air, Tehran, Iran

The exposure to heavy metals and polycyclic aromatic hydrocarbons (PAHs) bound to particulate matter 2.5 (PM_2.5) ambient air can result in some adverse health effect. In the current study, PM_2.5 ambient air of Tehran metropolitan, Iran, was characterized by the aid of scanning electron microscope and energy-dispersive X-ray techniques. Also, the human health risk of heavy metals and PAHs bound PM_2.5 for adults and children was assessed using the Monte Carlo simulation method. According to our findings, a size range of 0.97-2.46 μm with an average diameter of 1.56 μm for PM_2.5 was noted. The average concentration of PM_2.5 in ambient air (8.29E+04 ± 2.94E+04 ng m^-3) significantly (p < 0.05) was suppressed the national (2.50E+04 ng m^-3), World Health Organization (2.50E+04 ng m^-3) and Environmental Protection Agency (3.50E+04 ng m^-3) standard limits. The rank order of heavy metals bound PM_2.5 was determined as Al > Cu > Cd > Cr > Pb > Ni > Fe > Mn. The maximum concentration among 16 PAHs compounds investigated was correlated with Phenanthrene. Considering the principal component analysis, the main source of heavy metals (Ni, Pb and Cr) is vehicle combustion. Moreover, the rank order of exposure pathways based on their health risk was ingestion > inhalation > dermal contact. Moreover, the significant health risks for Tehran residents due to heavy metals bound PM_2.5 [target hazard quotient > 1; carcinogenic risk > 1.00E-06)] were noted based on the health risk assessment. Excessive carcinogenic risk (ECR) of PAHs bound PM_2.5 was 4.16E-07 that demonstrated that there is no considerable risk (ECR < 1.00E-06).

Seasonal variability in chemical composition and oxidative potential of ambient aerosol over a high altitude site in western India

The role of particulate matter (PM) has been well documented in causing cardiopulmonary diseases because they are redox active and generate reactive oxygen species (ROS) in situ in the human body. Capacity of PM to catalyze in situ formation of ROS is known as their oxidative potential (OP). However, studies on OP of PM over different regions are scarce. PM₁₀ samples were collected over Mount Abu (24.6°N, 72.7°E, 1680 m asl), India, from March 2014 to May 2016. These samples were analyzed for carbonaceous aerosol, major ions and dithiothreitol (DTT)-based OP. All the data were classified into four seasons (winter, spring, pre-monsoon, and post-monsoon) based on prevailing meteorological conditions. Seasonally averaged (±1σ) volume-normalized OP (OP_v) were 0.76 ± 0.52, 1.44 ± 0.48, 1.04 ± 0.57, and 1.69 ± 0.80 nmol DTT min^-1 m^-3, and mass-normalized OP (OP_m) were 14 ± 8, 14 ± 7, 10 ± 7, and 23 ± 9 pmol DTT min^-1 μg^-1 during winter, spring, pre-monsoon and post-monsoon, respectively. Observed OP_v (nmol DTT min^-1 m^-3) values (0.09-3.04) are somewhat higher than those documented over Los Angeles (0.10-0.16) and Beijing (0.10-0.49), and similar to those reported over Orinda (0.37-2.50) and Patiala (1.3-7.2). The highest OP_m and OP_v values found during post-monsoon were attributed to long-range transport of anthropogenically emitted pollutants brought by the northeasterly (NE) air-masses. It is inferred that the source(s) emitting elemental carbon also emit other species, which are more DTT-active than those species which are emitted along with anthropogenically derived inorganic species. Our results also infer that OP_v varies but OP_m do not vary drastically from region to region. This observation has broader implications in assessing the effects of aerosol on human health on regional/global scale.

Toxicity potential of particles caused by particle-bound polycyclic aromatic hydrocarbons (PPAHs) at two roadside locations and relationship with traffic

This study assessed exposure by the roadside to highly toxic particle-bound polycyclic aromatic hydrocarbons (PPAHs) that are known to adsorb preferentially on fine particles, aerodynamic diameter (d_p ≤ 1 μm). The real-time air quality measurements were conducted in March, April, and May 2015 in Kanpur at two busy roadside locations: one outside IIT Kanpur main gate, IG, and another by a residential area, M3. The locations show varying land use type and traffic density. Higher averaged daily concentrations of PM₁₀, PM_2.5, and PM₁ were observed at IG (PM₁₀ 700-800 μg/m³) owing to nature and high density of traffic, and occurrence of biomass burning nearby. Statistically significant relation (R² > 90%, p < 0.05) between PM₁ and PM_2.5 highlights the influence of mobile sources on particle load at IG. IG, the busier location, had higher daily averaged concentration of aggregate PPAHs (104 ng/m³) than M3 which is located near a residential area (38 ng/m³). In contrast, the higher average daily value of PC/DC ratio (mass per unit surface area of PPAHs on nanoparticles) at M3 (4.87 ng/mm²) than at IG (4.08 ng/mm²) suggests that PAHs of greater mass occur on particles at M3. Finer particles are known to adsorb pollutants of a larger mass that are likely to be more toxic in case of PAHs suggest that ambient air at M3 has more toxicity potential. However, this inference is not based on chemical analyses, and chemical characteristics must also be taken into account for the detailed assessment of health risk. The multiple path dosimetry model (MPPD-v3.04) reveals that the 99.02% of PM₁₀ inhaled, 77.01% of PM_2.5 and 34.54% of PM₁ are deposited in the outermost (head) region of the human respiratory tract.

Is it the time to study air pollution effects under environmental conditions? A case study to support the shift of in vitro toxicology from the bench to the field

Air pollution and particulate matter are recognised cause of increased disease incidence in exposed population. The toxicological processes underlying air pollution associated effects have been investigated by in vivo and/or in vitro experimentation. The latter is usually performed by exposing cells cultured under submerged condition to particulate matter concentration quite far from environmental exposure expected in humans. Here we report for the first time the feasibility of a direct exposure of air liquid interface cultured cells to environmental concentration of particulate matter. Inflammatory proteins release was analysed in cell medium while differential expression of selected genes was analysed in cells. Significant association of anti-oxidant genes was observed with secondary and aged aerosol, while cytochrome activation with primary and PAHs enriched ultrafine particles. The results obtained clearly show the opportunity to move from the lab bench to the field for properly understanding the toxicological effects also of ultrafine particles on selected in vitro models.

Cardiovascular and inflammatory mechanisms in healthy humans exposed to air pollution in the vicinity of a steel mill

Background

There is a paucity of mechanistic information that is central to the understanding of the adverse health effects of source emission exposures. To identify source emission-related effects, blood and saliva samples from healthy volunteers who spent five days near a steel plant (Bayview site, with and without a mask that filtered many criteria pollutants) and at a well-removed College site were tested for oxidative stress, inflammation and endothelial dysfunction markers.

Methods

Biomarker analyses were done using multiplexed protein-array, HPLC-Fluorescence, EIA and ELISA methods. Mixed effects models were used to test for associations between exposure, biological markers and physiological outcomes. Heat map with hierarchical clustering and Ingenuity Pathway Analysis (IPA) were used for mechanistic analyses.

Results

Mean CO, SO₂ and ultrafine particles (UFP) levels on the day of biological sampling were higher at the Bayview site compared to College site. Bayview site exposures “without” mask were associated with increased (p < 0.05) pro-inflammatory cytokines (e.g IL-4, IL-6) and endothelins (ETs) compared to College site. Plasma IL-1β, IL-2 were increased (p < 0.05) after Bayview site “without” compared to “with” mask exposures. Interquartile range (IQR) increases in CO, UFP and SO₂ were associated with increased (p < 0.05) plasma pro-inflammatory cytokines (e.g. IL-6, IL-8) and ET-1_(1–21) levels. Plasma/saliva BET-1 levels were positively associated (p < 0.05) with increased systolic BP. C-reactive protein (CRP) was positively associated (p < 0.05) with increased heart rate. Protein network analyses exhibited activation of distinct inflammatory mechanisms after “with” and “without” mask exposures at the Bayview site relative to College site exposures.

Conclusions

These findings suggest that air pollutants in the proximity of steel mill site can influence inflammatory and vascular mechanisms. Use of mask and multiple biomarker data can be valuable in gaining insight into source emission-related health impacts.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0270-4) contains supplementary material, which is available to authorized users.

Dust at Various Workplaces-Microbiological and Toxicological Threats

The aim of the present study was to evaluate the relation between the chemical (analysis of elements and pH) and microbiological composition (culture and metagenomics analysis) of the dust at various workplaces (cement plant, composting plant, poultry farm, and cultivated area) and the cytotoxicity effect on the human adenocarcinoma lung epithelial adherent cell line A-549 (MTT assay test). Analysis of the Particulate Matter (PM) fraction showed that the dust concentration in cultivated areas exceeded the OELs. For the remaining workplaces examined, the dust concentration was lower than OELs limits. The number of microorganisms in the dust samples was 3.8 × 10²–1.6 × 10⁸ CFU/g bacteria and 1.5 × 10²–6.5 × 10⁶ CFU/g fungi. The highest number of microorganisms was noted for dust from cultivated areas (total number of bacteria, actinomycetes, P. fluorescens) and composting plants (xerophilic fungi and staphylococci), while the least number of microorganisms was observed for dust from cement plants. Many types of potentially pathogenic microorganisms have been identified, including bacteria, such as Bacillus, Actinomyces, Corynebacterium, Prevotella, Clostridium, and Rickettsia, and fungi, such as Alternaria, Cladosporium, Penicillium, and Aspergillus. The most cytotoxic to the human lung cell line A-549 was dust from cultivated areas (IC₅₀ = 3.8 mg/mL after 72 h). The cytotoxicity of the tested dust samples depends on the PM concentration, the number of microorganisms, including potentially pathogenic genera, and the exposure time.

REDUCTION OF PM2.5 TOXICITY ON HUMAN ALVEOLAR EPITHELIAL CELLS A549 BY TEA POLYPHENOLS

Tea-derived polyphenols have anticancer and antioxidant properties, and they can regulate oxidative stress. This study was designed to quantify both the toxic effects of fine particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) and determine whether tea polyphenols could provide a protective effect against PM2.5 toxicity on human alveolar epithelial A549 cells in vitro. Cytotoxic effects of the PM2.5 on A549 cells were measured by means of cell viability, the expression of caspase-3, bax/bcl-2 and C/EBP-homologous protein (CHOP), and the generation of intracellular reactive oxygen species, malondialdehyde and superoxide dismutase. The results showed that tea polyphenols ameliorated some of the adverse effects of PM2.5 on A549 cell viability and superoxide dismutase levels. In addition, tea polyphenols decreased the production of reactive oxygen species, malondialdehyde generation, and apoptosis in response to PM2.5 exposure. Therefore, our results support a role for tea polyphenols in reducing the toxicity of PM2.5, particularly with regard to targeting oxidative stress and apoptosis.

Airborne ultrafine particles in a Pacific Island country: Characteristics, sources and implications for human exposure

The Pacific Islands carry a perception of having clean air, yet emissions from transport and burning activities are of concern in regard to air quality and health. Ultrafine particle number concentrations (PNCs), one of the best metrics to demonstrate combustion emissions, have not been measured either in Suva or elsewhere in the Islands. This work provides insight into PNC variation across Suva and its relationship with particle mass (PM) concentration and composition. Measurements over a short monitoring campaign provide a vignette of conditions in Suva. Ambient PNCs were monitored for 8 day at a fixed location, and mobile PNC sampling for two days. These were compared with PM concentration (TSP, PM₁₀, PM_2.5, PM₁) and are discussed in relation to black carbon (BC) content and PM_2.5 sources, determined from elemental concentrations; for the October 2015 period and longer-term data. Whilst Suva City PM levels remained fairly low, PM_2.5 = 10-12 μg m^-3, mean PNC (1.64 ± 0.02 × 10⁴ cm^-3) was high compared to global data. PNCs were greater during mobile sampling, with means of 10.3 ± 1.4 × 10⁴ cm^-3 and 3.51 ± 0.07 × 10⁴ cm^-3 when travelling by bus and taxi, respectively. Emissions from road vehicles, shipping, diesel and open burning were identified as PM sources for the October 2015 period. Transport related ultrafine particle emissions had a significant impact on microscale ambient concentrations, with PNCs near roads being 1.5 to 2 times higher than nearby outdoor locations and peak PNCs occurring during peak traffic times. Further data, particularly on transport and wet-season exposures, are required to confirm results. Understanding PNC in Suva will assist in formulating effective air emissions control strategies, potentially reducing population exposure across the Islands and in developing countries with similar emission characteristics. Suva's PNC was high in comparison to global data; high exposures were related to transport and combustion emissions, which were also identified as significant PM_2.5 sources.

Physicochemical characterization of ambient PM2.5 in Tehran air and its potential cytotoxicity in human lung epithelial cells (A549)

As air pollution is a major problem in Tehran, this study aimed to investigate the physicochemical characterization of the water-soluble and organic contents of ambient PM_2.5 in Tehran and determine its in vitro toxicological impact on human lung epithelial cells (A549). A total of 11 sampling stations were selected, including three categories: traffic, urban, and suburban. All sampling was carried out in the spring and summer of 2015. Ion chromatography (IC), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and GC-MS were used to analyze ionic compounds, heavy metals, and polycyclic aromatic hydrocarbons (PAHs), respectively, and an ELISA reader was used for cytotoxicity analysis. The most prevalent ionic species found for all three categories was SO₄^2-. PAH concentrations were 43.45±32.71, 50.51±37.27, and 29.13±33.29ng/m³ for traffic, urban, and suburban stations, respectively. For all sampling stations, Al and Fe had the highest values among the investigated heavy metals. Cell viability measurements, carried out using the MTT assay, showed that all three categories of samples cause cytotoxicity, although the urban station samples showed higher cytotoxicity than those from the other stations (p˂0.05). Based on the results of the present study, organic compounds and insoluble particles could be the main causes of cytotoxicity.

Selective ATP-Binding Cassette Subfamily C Gene Expression and Proinflammatory Mediators Released by BEAS-2B after PM2.5, Budesonide, and Cotreated Exposures

ATP-binding cassette subfamily C (ABCC) genes code for phase III metabolism proteins that translocate xenobiotic (e.g., particulate matter 2.5 (PM_2.5)) and drug metabolites outside the cells. IL-6 secretion is related with the activation of the ABCC transporters. This study assesses ABCC1–4 gene expression changes and proinflammatory cytokine (IL-6, IL-8) release in human bronchial epithelial cells (BEAS-2B) exposed to PM_2.5 organic extract, budesonide (BUD, used to control inflammation in asthmatic patients), and a cotreatment (Co-T: PM_2.5 and BUD). A real-time PCR assay shows that ABCC1 was upregulated in BEAS-2B exposed after 6 and 7 hr to PM_2.5 extract or BUD but downregulated after 6 hr of the Co-T. ABCC3 was downregulated after 6 hr of BUD and upregulated after 6 hr of the Co-T exposures. ABCC4 was upregulated after 5 hr of PM_2.5 extract, BUD, and the Co-T exposures. The cytokine assay revealed an increase in IL-6 release by BEAS-2B exposed after 5 hr to PM_2.5 extract, BUD, and the Co-T. At 7 hr, the Co-T decreases IL-6 release and IL-8 at 6 hr. In conclusion, the cotreatment showed an opposite effect on exposed BEAS-2B as compared with BUD. The results suggest an interference of the BUD therapeutic potential by PM_2.5.

Physicochemical properties, in vitro cytotoxic and genotoxic effects of PM1.0 and PM2.5 from Shanghai, China

Exposure to ambient particulate matter (PM) links with a variety of respiratory diseases. However, compared with coarse particles (PM₁₀) and fine particles (PM_2.5), submicrometer particles (PM_1.0) may be a more important indicator of human health risks. In this study, the cytotoxic and genotoxic effects of PM_1.0 samples from Shanghai were examined using A549 cells, and compared with the effects of PM_2.5, to better understand the health effects of PM_1.0 in this area. The PM_1.0 and PM_2.5 samples were characterized for morphology, water-soluble inorganic ions, organic and elemental carbon, and metal elements. The cytotoxicity of PMs was measured using cell viability and cell membrane damage assays. The genotoxic effects of PMs were determined using the comet assay, and DNA damage was quantified using olive tail moment (OTM) values. The physicochemical characterization indicated that PM_1.0 was enriched in carbonaceous elements and hazardous metals (Al, Zn, Pb, Mn, Cu, and V), whereas PM_2.5 was more abundant in large, irregular mineral particles. The biological results revealed that both PM_1.0 and PM_2.5 could induce significant cytotoxicity and genotoxicity in A549 cells, and that exposure to PM_1.0 caused more extensive toxic effects than exposure to PM_2.5. The greater cytotoxic effects of PM_1.0 can be attributed to the combined effects of size and chemical composition, whereas the genotoxic effects of PM_1.0 may be mainly associated with chemical species.

Evaluation of the DNA damaging potential of indigenous health hazardous quartz nanoparticles on the cultured lung cells

Quartz nanoparticles (QNPs) cause various diseases in the biological systems and are thus considered as hazardous materials; however, their properties are important in a wide range of biological and pharmaceutical entities. The present study was initiated to enhance the understanding of the genotoxic potential and focused on the mechanism involved in the indigenous quartz nanoparticles induced toxicity in A549 cells. The results show a concentration dependent decrease in the cell viability of A549 cells. Additionally, QNPs exposure results in the concentration dependent toxicity, which intensifies the generation of ROS, which in turn is confirmed by the increased lipid peroxidation and decreased GSH levels. Moreover, it also induces DNA damage in the cells exposed to QNPs as compared to the control cells. The outcome of the results confirms that QNPs have cytotoxic and genotoxic effects on the A549 cells in a concentration and time dependent manner. Western blot analysis indicates the up regulation of LC-3I/II, Beclin-1, and p62 protein levels, which confirms the occurrence of autophagy through the phosphatidylinositol 3-kinase (PI3K)/a threonine kinase (Akt)/mammalian target of rapamycin (mTOR) pathway, as well as the inhibitor of autophagy is also verified. Our study demonstrates that QNPs exposure in human lung cells causes oxidative stress and DNA damage, which leads to autophagy. Hence, from a bioremediation point of view, the remedial strategy that can be adopted from the biological DNA damage from these health hazardous materials will result in a safer environment.

Association of IL-6 with PM2.5 Components: Importance of Characterizing Filter-Based PM2.5 Following Extraction

Filter-based toxicology studies are conducted to establish the biological plausibility of the well-established health impacts associated with fine particulate matter (PM_2.5) exposure. Ambient PM_2.5 collected on filters is extracted into solution for toxicology applications, but frequently, characterization is nonexistent or only performed on filter-based PM_2.5, without consideration of compositional differences that occur during the extraction processes. To date, the impact of making associations to measured components in ambient instead of extracted PM_2.5 has not been investigated. Filter-based PM_2.5 was collected at locations (n = 5) and detailed characterization of both ambient and extracted PM_2.5 was performed. Alveolar macrophages (AMJ2-C11) were exposed (3, 24, and 48 h) to PM_2.5 and the pro-inflammatory cytokine interleukin (IL)-6 was measured. IL-6 release differed significantly between PM_2.5 collected from different locations; surprisingly, IL-6 release was highest following treatment with PM_2.5 from the lowest ambient concentration location. IL-6 was negatively correlated with the sum of ambient metals analyzed, as well as with concentrations of specific constituents which have been previously associated with respiratory health effects. However, positive correlations of IL-6 with extracted concentrations indicated that the negative associations between IL-6 and ambient concentrations do not accurately represent the relationship between inflammation and PM_2.5 exposure. Additionally, seven organic compounds had significant associations with IL-6 release when considering ambient concentrations, but they were not detected in the extracted solution. Basing inflammatory associations on ambient concentrations that are not necessarily representative of in vitro exposures creates misleading results; this study highlights the importance of characterizing extraction solutions to conduct accurate health impact research.

Effects of Particulate Matter and Its Chemical Constituents on Elderly Hospital Admissions Due to Circulatory and Respiratory Diseases

Various fractions of particulate matter have been associated with increased mortality and morbidity. The purpose of our study is to analyze the associations between concentrations of PM2.5, PM2.5-10, PM10 and their chemical constituents (soluble ions) with hospital admissions due to circulatory and respiratory diseases among the elderly in a medium-sized city in Brazil. A time series study was conducted using Poisson regression with generalized additive models adjusted for confounders. Statistically significant associations were identified between PM10 and PM2.5-10 and respiratory diseases. Risks of hospitalization increased by 23.5% (95% CI: 13.5; 34.3) and 12.8% (95% CI: 6.0; 20.0) per 10 μg/m³ of PM2.5-10 and PM10, respectively. PM2.5 exhibited a significant association with circulatory system diseases, with the risk of hospitalization increasing by 19.6% (95% CI: 6.4; 34.6) per 10 μg/m³. Regarding the chemical species; SO₄(2-), NO₃(-), NH₄⁺ and K⁺ exhibited specific patterns of risk, relative to the investigated outcomes. Overall, SO₄(2-) in PM2.5-10 and K⁺ in PM2.5 were associated with increased risk of hospital admissions due to both types of diseases. The results agree with evidence indicating that the risks for different health outcomes vary in relation to the fractions and chemical composition of PM10. Thus, PM10 speciation studies may contribute to the establishment of more selective pollution control policies.

Identification of PM10 characteristics involved in cellular responses in human bronchial epithelial cells (Beas-2B)

Notwithstanding evidence is present that physicochemical characteristics of ambient particles attribute to adverse health effects, there is still some lack of understanding in this complex relationship. At this moment it is not clear which properties (such as particle size, chemical composition) or sources of the particles are most relevant for health effects. This study investigates the in vitro toxicity of PM10 in relation to PM chemical composition, black carbon (BC), endotoxin content and oxidative potential (OP). In 2013-2014 PM10 was sampled (24h sampling, 108 sampling days) in ambient air at three sites in Flanders (Belgium) with different pollution characteristics: an urban traffic site (Borgerhout), an industrial area (Zelzate) and a rural background location (Houtem). To characterize the toxic potential of PM10, airway epithelial cells (Beas-2B cells) have been exposed to particles in vitro. Different endpoints were studied including cell damage and death (cell viability) using the Neutral red Uptake assay, the production of pro-inflammatory molecules by interleukin 8 (IL-8) induction and DNA-damaging activity using the FPG-modified Comet assay. The endotoxin levels in the collected samples were analysed and the capacity of PM10 particles to produce reactive oxygen species (OP) was evaluated by electron paramagnetic resonance (EPR) spectroscopy. Chemical characteristics of PM10 (BC, As, Cd, Cr, Cu, Mn, Ni, Pb, Zn) and meteorological conditions were recorded on the sampling days. PM10 particles exhibited dose-dependent cytotoxicity in Beas-2B cells and were found to significantly induce the release of IL-8 in samples from the three locations. Oxidatively damaged DNA was observed in exposed Beas-2B cells. Endotoxin levels above the detection limit were detected in half of the samples. OP was measurable in all samples. Associations between PM10 characteristics and biological effects of PM10 were assessed by single and multiple regression analyses. The reduction in cell viability was significantly correlated with BC, Cd and Pb. The induction of IL-8 in Beas-2B cells was significantly associated with Cu, Ni and Zn and endotoxin. Endotoxin levels explained 33% of the variance in IL-8 induction. A significant interaction between ambient temperature and endotoxin on the pro-inflammatory activity was seen. No association was found between OP and the cellular responses. This study supports the hypothesis that, on an equal mass basis, PM10 induced biological effects differ due to differences in PM10 characteristics. Metals (Cd, Cu, Ni and Zn), BC, and endotoxin were among the main determinants for the observed biological responses.

Water soluble and insoluble components of urban PM2.5 and their cytotoxic effects on epithelial cells (A549) in vitro

When PM2.5 enters human bodies, the water soluble (WS-PM2.5) and insoluble components (WIS-PM2.5) of PM2.5 would interact with cells and cause adverse effects. However, the knowledge about the individual toxicity contribution of these two components is limited. In this study, the physiochemical properties of PM2.5 were well characterized. The toxic effects of WS-PM2.5 and WIS-PM2.5, which include the cell viability, cell membrane damage, reactive oxygen species (ROS) generation and morphological changes, were examined with human lung epithelial A549 cells in vitro. The results indicated that WS-PM2.5 could induce the early response of ROS generation, multiplied mitochondria and multi-lamellar bodies in A549 cells, which might cause cell damage through oxidative stress. Meanwhile, WIS-PM2.5 was predominantly associated with the cell membrane disruption, which might lead to the cell damage through cell-particle interactions. Moreover, the synergistic cytotoxic effects of WS-PM2.5 and WIS-PM2.5 were observed at longer exposure time. These findings demonstrate the different cytotoxicity mechanisms of WS-PM2.5 and WIS-PM2.5, which suggest that not only the size and dosage of PM2.5 but also the solubility of PM2.5 should be taken into consideration when evaluating the toxicity of PM2.5.

ROS production and gene expression in alveolar macrophages exposed to PM(2.5) from Baghdad, Iraq: Seasonal trends and impact of chemical composition

The objective of this study was to assess the impact of changes in atmospheric particulate matter (PM) composition on oxidative stress markers in an in-vitro alveolar macrophage (AM) model. Fifty-three PM2.5 samples were collected during a year-long PM sampling campaign in Baghdad, Iraq, a semi-arid region of the country. Monthly composites were analyzed for chemical composition and for biological activity using in-vitro measurements of ROS production and gene expression in the AM model. Twelve genes that were differentially expressed upon PM exposure were identified and their co-associations with the composition of PM2.5 were examined. Ten of those genes were up-regulated in January and April composites; samples which also exhibited high ROS activity and relatively high PM mass concentration. ROS production was statistically correlated with total PM2.5 mass, levoglucosan (a wood burning tracer) and several trace elements of the PM (especially V and Ni, which are associated with oil combustion). The expression of several cytokine genes was found to be moderately associated with PM mass, crustal materials (indication of dusty days or dust storms) and certain metals (e.g. V, Fe and Ni) in the PM. Thus, the ROS activity association with PM2.5, may, in part, be driven by redox-active metals. The antioxidant response genes (Nqo1 and Hmox1) were moderately associated with polyaromatic hydrocarbons (PAHs) and showed a good correlation (r-Pearson of >0.7) with metals linked to vehicle-related emissions (i.e. Cu, Zn and Sb). Examining these associations in a larger sample pool (e.g. daily samples) would improve the power of the analysis and may strengthen the implication of these chemicals in the oxidative stress of biological systems, which could aid in the development of new metrics of PM toxicity.

Characterization of ambient and extracted PM2.5 collected on filters for toxicology applications

Research on the health effects of fine particulate matter (PM2.5) frequently disregards the differences in particle composition between that measured on an ambient filter versus that measured in the corresponding extraction solution used for toxicological testing. This study presents a novel method for characterizing the differences, in metallic and organic species, between the ambient samples and the corresponding extracted solutions through characterization of extracted PM2.5 suspended on filters. Removal efficiency was found to be 98.0 ± 1.4% when measured using pre- and post-removal filter weights, however, this efficiency was significantly reduced to 80.2 ± 0.8% when measured based on particle mass in the extraction solution. Furthermore, only 47.2 ± 22.3% of metals and 24.8 ± 14.5% of organics measured on the ambient filter were found in the extraction solution. Individual metallic and organic components were extracted with varying efficiency, with many organics being lost entirely during extraction. Finally, extraction efficiencies of specific PM2.5 components were inversely correlated with total mass. This study details a method to assess compositional alterations resulting from extraction of PM2.5 from filters, emphasizing the need for standardized procedures that maintain compositional integrity of ambient samples for use in toxicology studies of PM2.5.

The acidic transformed nano-VO2 causes macrophage cell death by the induction of lysosomal membrane permeabilization and Ca2+ efflux

Because of its outstanding thermochromic characteristics and metal-insulator transition (MIT) property, nano-vanadium dioxide (abbreviated as nano-VO₂ or nVO₂) has been applied widely in electrical/optical devices and design of intelligent window. However, the biological effect of nVO₂ is not well understood, especially when affected by environmental factors or living organisms. For VO₂ is an amphoteric oxide, we simulated pH's influence to nVO₂’s physicochemical properties by exposure nVO₂ in water of different pH values. We found that nVO₂ transformed to a new product after exposure in acidic water for two weeks, as revealed by physicochemical characterization such as SEM, TEM, XRD, and DLS. This transformation product formed in acidic water was referred as (acidic) transformed nVO₂). Both pristine/untransformed and transformed nVO₂ displayed no obvious toxicity to common epithelial cells; however, the acidic transformed nVO₂ rapidly induced macrophage cell death. Further investigation demonstrated that transformed nVO₂ caused macrophage apoptosis by the induction of Ca²⁺ efflux and the following mitochondrial membrane permeabilization (MMP) process. And a more detailed time course study indicated that transformed nVO₂ caused lysosomal membrane permeabilization (LMP) at the earlier stage, indicating LMP could be chosen as an earlier and sensitive end point for nanotoxicological study. We conclude that although nVO₂ displays no acute toxicity, its acidic transformation product induces macrophage apoptosis by the induction of LMP and Ca²⁺ efflux. This report suggests that the interplay with environmental factors or living organisms can results in physicochemical transformation of nanomaterials and the ensuing distinctive biological effects.

Chemical characterisation of the coarse and fine particulate matter in the environment of an underground railway system: cytotoxic effects and oxidative stress-a preliminary study

Background: Exposure to the particulate matter produced in underground railway systems is arousing increasing scientific interest because of its health effects. The aim of our study was to evaluate the airborne concentrations of PM₁₀ and three sub-fractions of PM_2.5 in an underground railway system environment in proximity to platforms and in underground commercial areas within the system, and to compare these with the outdoor airborne concentrations. We also evaluated the metal components, the cytotoxic properties of the various fractions of particulate matter (PM) and their capacity to induce oxidative stress. Method: We collected the coarse fraction (5–10 µm) and the fine fractions (1–2.5 µm; 0.5–1 µm; 0.25–0.5 µm). Chemical characterisation was determined by means of spectrometry. Cytotoxicity and oxidative stress were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Reactive Oxygen Species (ROS) assessment. Results: The concentrations of both PM₁₀ and PM_2.5 proved to be similar at the three sampling sites. Iron and other transition metals displayed a greater concentration at the subway platform than at the other two sites. The 2.5–10 µm and 1–2.5 µm fractions of PM from all three sampling sites determined a greater increase in ROS; the intensity of oxidative stress progressively declined as particle diameter diminished. Moreover, ROS concentrations were correlated with the concentrations of some transition metals, namely Mn, Cr, Ti, Fe, Cu, Zn, Ni and Mo. All particulate matter fractions displayed lower or similar ROS values between platform level and the outdoor air. Conclusions: The present study revealed that the underground railway environment at platform level, although containing higher concentrations of some particularly reactive metallic species, did not display higher cytotoxicity and oxidative stress levels than the outdoor air.