Chemical Characterization of Seasonal PM2.5 Samples and Their Cytotoxicity in Human Lung Epithelial Cells (A549)

Toxicological effects of solvent-extracted organic matter associated with PM2.5 on human bronchial epithelial cell line NL-20

The heterogeneity and complexity of solvent-extracted organic matter associated with PM2.5 (SEOM-PM2.5) is well known; however, there is scarce information on its biological effects in human cells. This work aimed to evaluate the effect of SEOM-PM2.5 collected in northern Mexico City during the cold-dry season (November 2017) on NL-20 cells, a human bronchial epithelial cell line. The SEOM obtained accounted for 15.5% of the PM2.5 mass and contained 21 polycyclic aromatic hydrocarbons (PAHs). The cell viability decreased following exposure to SEOM-PM2.5, and there were noticeable morphological changes such as increased cell size and the presence of cytoplasmic vesicles in cells treated with 5-40 μg/mL SEOM-PM2.5. Exposure to 5 μg/mL SEOM-PM2.5 led to several alterations compared with the control cells, including the induction of double-stranded DNA breaks based (p < 0.001); nuclear fragmentation and an increased mitotic index (p < 0.05); 53BP1 staining, a marker of DNA repair by non-homologous end-joining (p < 0.001); increased BiP protein expression; and reduced ATF6, IRE1α, and PERK gene expression. Conversely, when exposed to 40 μg/mL SEOM-PM2.5, the cells showed an increase in reactive oxygen species formation (p < 0.001), BiP protein expression (p < 0.05), and PERK gene expression (p < 0.05), indicating endoplasmic reticulum stress. Our data suggest concentration-dependent toxicological effects of SEOM-PM2.5 on NL-20 cells, including genotoxicity, genomic instability, and endoplasmic reticulum stress.

Acute exposure to seasonal PM2.5 induces toxicological responses in A549 cells cultured at the air-liquid interface mediated by oxidative stress and endoplasmic reticulum stress

Atmospheric fine particulate matter (PM2.5) enters the human body through respiration and poses a threat to human health. This is not only dependent on its mass concentration in the atmosphere, but also related to seasonal variations in its chemical components, which makes it important to study the cytotoxicity of PM2.5 in different seasons. Traditional immersion exposure cannot simulate the living environment of human epithelial cells in the human body, making this method unsuitable for evaluating the inhalation toxicity of PM2.5. In this study, a novel air-liquid interface (ALI) particulate matter exposure device (VITROCELL Cloud 12 system) was used to evaluate the toxic effects and potential mechanisms of human lung epithelial cells (A549) after exposure to seasonal PM2.5. PM2.5 samples from four seasons were collected and analyzed for chemical components. After 6 h of exposure to seasonal PM2.5, winter PM2.5 exhibited the highest cytotoxicity among most toxicity indicators, especially apoptosis rate, reactive oxygen species (ROS), inflammatory responses and DNA damage (γ-H2AX). The effect of autumn PM2.5 on apoptosis rate was significantly higher than that in spring, and there was no significant difference in other toxicity indicators between spring and autumn. The cytotoxicity of summer PM2.5 was the lowest among the four seasons. It should be noted that even exposure to low doses of summer PM2.5 leads to significant DNA damage in A459 cells. Correlation analysis results showed that water-soluble ions, metallic elements, and polycyclic aromatic hydrocarbons (PAHs) were associated with most toxicological endpoints. Inhibitors of oxidative stress and endoplasmic reticulum (ER) stress significantly inhibited cellular damage, indicating that PM2.5-induced cytotoxicity may be related to the generation of ROS and ER stress. In addition, PM2.5 can induce ER stress through oxidative stress, which ultimately leads to apoptosis.

Toxicological responses of A549 and HCE-T cells exposed to fine particulate matter at the air-liquid interface

Fine particulate matter (PM2.5) can enter the human body in various ways and have adverse effects on human health. Human lungs and eyes are exposed to the air for a long time and are the first to be exposed to PM2.5. The "liquid immersion exposure method" has some limitations that prevent it from fully reflecting the toxic effects of particulate matter on the human body. In this study, the collected PM2.5 samples were chemically analyzed. An air-liquid interface (ALI) model with a high correlation to the in vivo environment was established based on human lung epithelial cells (A549) and immortalized human corneal epithelial cells (HCE-T). The VITROCELL Cloud 12 system was used to distribute PM2.5 on the cells evenly. After exposure for 6 h and 24 h, cell viability, apoptosis rate, reactive oxygen species (ROS) level, expression of inflammatory factors, and deoxyribonucleic acid (DNA) damage were measured. The results demonstrated significant dose- and time-dependent effects of PM2.5 on cell viability, cell apoptosis, ROS generation, and DNA damage at the ALI, while the inflammatory factors showed dose-dependent effects only. It should be noted that even short exposure to low doses of PM2.5 can cause cell DNA double-strand breaks and increased expression of γ-H2AX, indicating significant genotoxicity of PM2.5. Increased abundance of ROS in cells plays a crucial role in the cytotoxicity induced by PM2.5 exposure These findings emphasize the significant cellular damage and genotoxicity that may result from short-term exposure to low levels of PM2.5.

Characterization of risks and pathogenesis of respiratory diseases caused by rural atmospheric PM2.5

Forty-six percent of the world's population resides in rural areas, the majority of whom belong to vulnerable groups. They mainly use cheap solid fuels for cooking and heating, which release a large amount of PM2.5 and cause adverse effects to human health. PM2.5 exhibits urban-rural differences in its health risk to the respiratory system. However, the majority of research on this issue has focused on respiratory diseases induced by atmospheric PM2.5 in urban areas, while rural areas have been ignored for a long time, especially the pathogenesis of respiratory diseases. This is not helpful for promoting environmental equity to aid vulnerable groups under PM2.5 pollution. Thus, this study focuses on rural atmospheric PM2.5 in terms of its chemical components, toxicological effects, respiratory disease types, and pathogenesis, represented by PM2.5 from rural areas in the Sichuan Basin, China (Rural SC-PM2.5). In this study, organic carbon is the most significant component of Rural SC-PM2.5. Rural SC-PM2.5 significantly induces cytotoxicity, oxidative stress, and inflammatory response. Based on multiomics, bioinformatics, and molecular biology, Rural SC-PM2.5 inhibits ribonucleotide reductase regulatory subunit M2 (RRM2) to disrupt the cell cycle, impede DNA replication, and ultimately inhibit lung cell proliferation. Furthermore, this study supplements and supports the epidemic investigation. Through an analysis of the transcriptome and human disease database, it is found that Rural SC-PM2.5 may mainly involve pulmonary hypertension, sarcoidosis, and interstitial lung diseases; in particular, congenital diseases may be ignored by epidemiological surveys in rural areas, including tracheoesophageal fistula, submucous cleft of the hard palate, and congenital hypoplasia of the lung. This study contributes to a greater scientific understanding of the health risks posed by rural PM2.5, elucidates the pathogenesis of respiratory diseases, clarifies the types of respiratory diseases, and promotes environmental equity.

Contribution of water-soluble extracts to the oxidative and inflammatory effects of atmospheric aerosols: A critical review

Exposure to atmospheric particulate matter (PM) has been associated with heightened risks of lung cancer, cardiovascular and respiratory diseases. PM exposure also affects the immune system, leading to an increased susceptibility to infections, exacerbating pre-existent inflammatory and allergic lung diseases. Atmospheric PM can primarily impact human health through the generation of reactive oxygen species (ROS) that subsequently induce or exacerbate inflammation. These cytotoxic effects have been related with PM concentration, and its chemical constituents, including metals, solvent extractable organics (e.g., polycyclic aromatic hydrocarbons), and water-soluble ions. Although not receiving much attention, the fine aerosol water-soluble organic matter (WSOM) can account for a substantial portion of the overall fine PM mass and has been shown to present strong oxidative and immunomodulatory effects. Thus, the objective of this review is to provide a comprehensive analysis of the role of the water-soluble fraction of PM, with a specific focus on the contribution of the WSOM component to the cytotoxic properties of atmospheric PM. The chemical properties of the water-soluble PM fraction are briefly discussed, while emphasis is put on how PM size, composition, and temporal variations (e.g., seasonality) can impact the pro-oxidative activity, the modulation of inflammatory response, and the cytotoxicity of the water-soluble PM extracts.

Health benefits from substituting raw biomass fuels for charcoal and briquette fuels: In vitro toxicity analysis

PM_2.5 (particulate matters with diameter ≤ 2.5 μm) from biomass fuel combustion has been identified as a major cause of cardiopulmonary diseases. Briquette and charcoal are two representative processed fuels that exhibit different emission characteristics. This study compared three types of biomass fuels (maize straw, wheat straw, and wood branches) and their respective processed fuels in terms of their emission factors (EFs). The bioreactivity of human alveolar epithelial (A549) cells to exposure to various fuel-emitted PM_2.5 was assessed. The EFs of lactic dehydrogenase (LDH) and interleukin-6 (IL-6) were calculated to compare actual cytotoxicity. The PM_2.5 EFs of maize and wheat straw were higher than those of wood branches, and following the processes of briquetting and carbonization, the EFs of PM_2.5 and chemical components were effectively reduced. Cell membrane damage and inflammatory responses were observed after A549 cell exposure to PM_2.5 extracts. The expression of bioreactivity to briquettes and charcoals was lower than that to raw fuels. The EFs of LDH and IL-6 were also significantly reduced after briquetting and carbonization. This underscores the necessity of fuel treatment for reducing cytotoxicity. The crucial chemical components that contributed to cell oxidative and inflammatory responses were identified, including organic and elemental carbon, water-soluble ions (e.g., K⁺, Mg²⁺, and Ca²⁺), metals (e.g., Fe, Cr, and Ni), and high-molecular-weight PAHs. This study elucidated the similarities and differences of PM_2.5 emissions and cytotoxicity of three types of biomass fuel and demonstrated the positive effects of fuel treatment on reducing adverse pulmonary effects.

Pollution source and chemicals structure of the water-soluble fractions in PM2.5 that induce apoptosis in China

Identify risk drivers is the key condition in air pollution control, and biological effect-directed analysis is the most commented method for combing chemical identify and human health. The water-soluble organic matter contained in PM_2.5 plays an important role in human health, while it is also the most difficult to identify its chemical information. Exploring the structural characteristics and pollution sources of its key toxic components is the optimized strategy to meet this question. In this study, the induction of apoptosis by the water-soluble fractions (WSF) of PM_2.5 samples collected in 10 major cities in China over a period of 1 year was observed in vitro in Beas-2b cells. Organic carbon structures were examined using nuclear magnetic resonance; air potential sources were identified using δ¹³C and ¹⁴C isotopic markers. Apoptosis induction by WSF in PM_2.5 was generally stronger in northern cities than in southern cities, and in winter than in summer. Organic compounds with aromatic and double-bond carbon structures from secondary products of motor vehicle exhausts, coal-derived emissions, and emissions derived from the burning of core residues may be primarily responsible for apoptosis induction by PM_2.5. Our results will contribute to understanding the toxic substances contained in WSF and provide basic data for accurate pollution control.

Chemical Composition and Transgenerational Effects on Caenorhabditis elegans of Seasonal Fine Particulate Matter

While numerous studies have demonstrated the adverse effects of fine particulate matter (PM) on human health, little attention has been paid to its impact on offspring health. The multigenerational toxic effects on Caenorhabditis elegans (C. elegans) were investigated by acute exposure. PM_2.5 and PM₁ samples were collected and analysed for their chemical composition (inorganic ions, metals, OM, PAHs) in different seasons from April 2019 to January 2020 in Lin'an, China. A higher proportion of organic carbon components (34.3%, 35.9%) and PAHs (0.0144%, 0.0200%) occupied the PM_2.5 and PM₁ samples in winter, respectively. PM₁ in summer was enriched with some metal elements (2.7%). Exposure to fine PM caused developmental slowing and increased germ cell apoptosis, as well as inducing intestinal autofluorescence and reactive oxygen species (ROS) production. PM₁ caused stronger toxic effects than PM_2.5. The correlation between PM component and F0 generation toxicity index was analysed. Body length, germ cell apoptosis and intestinal autofluorescence were all highly correlated with Cu, As, Pb, OC and PAHs, most strongly with PAHs. The highest correlation coefficients between ROS and each component are SO₄^2- (R = 0.743), Cd (R = 0.816) and OC (R = 0.716). The results imply that OC, PAHs and some transition metals play an important role in the toxicity of fine PM to C. elegans, where the organic fraction may be the key toxicogenic component. The multigenerational studies show that PM toxicity can be passed from parent to offspring, and gradually returns to control levels in the F3-F4 generation with germ cell apoptosis being restored in the F4 generation. Therefore, the adverse effects of PM on reproductive damage are more profound.

Chemical Characteristics and Cytotoxicity to GC-2spd(ts) Cells of PM2.5 in Nanjing Jiangbei New Area from 2015 to 2019

PM_2.5 is an air pollutant with complex components. After entering the body through respiration, PM_2.5 can not only cause respiratory diseases, but also break through the blood-testis barrier and influence the reproductive system. PM_2.5 with different components may result in different toxic effects. In the first five years of Nanjing Jiangbei New Area, industrial transformation would change the concentration and chemical fraction of PM_2.5 in the local environment to a certain extent. In this study, PM_2.5 collected in Nanjing Jiangbei New Area every autumn and winter from 2015 to 2019 was analyzed. PM_2.5 concentration generally decreased year by year. The large proportion of secondary inorganic ions indicated the presence of secondary pollution at the sampling site. PM_2.5 was mainly emitted from fossil fuel combustion and vehicle exhaust. The cytotoxicity of PM_2.5 samples was evaluated by PM_2.5 exposure to mouse spermatocytes (GC-2spd(ts) cells). Cell viability was relatively low in 2016 and 2018, and relatively high in 2017 and 2019. Reactive oxygen species levels and DNA damage levels followed similar trends, with an overall annual decrease. The cytotoxicity of PM_2.5 on GC-2spd(ts) cells was significantly correlated with water-soluble ions, water-soluble organic carbon, heavy metals and polycyclic aromatic hydrocarbons (p < 0.01). According to principal component analysis and multiple linear regression, fossil fuel combustion, secondary transformation of pollutants and construction dust were identified as the major contributors to cytotoxic effects, contributing more than 50%.

Haze Air Pollution Health Impacts of Breath-Borne VOCs

Here, we investigated the use of breath-borne volatile organic compounds (VOCs) for rapid monitoring of air pollution health effects on humans. Forty-seven healthy college students were recruited, and their exhaled breath samples (n = 235) were collected and analyzed for VOCs before, on, and after two separate haze pollution episodes using gas chromatography-ion mobility spectrometry (GC-IMS). Using a paired t-test and machine learning model (Gradient Boosting Machine, GBM), six exhaled VOC species including propanol and isoprene were revealed to differ significantly among pre-, on-, and post-exposure in both haze episodes, while none was found between clean control days. The GBM model was shown capable of differentiating between pre- and on-exposure to haze pollution with a precision of 90-100% for both haze episodes. However, poor performance was detected for the same model between two different clean days. In addition to gender and particular haze occurrence influences, correlation analysis revealed that NH₄⁺, NO₃^-, acetic acid, mesylate, CO, NO₂, PM_2.5, and O₃ played important roles in the changes in breath-borne VOC fingerprints following haze air pollution exposure. This work has demonstrated direct evidence of human health impacts of haze pollution while identifying potential breath-borne VOC biomarkers such as propanol and isoprene for haze air pollution exposure.

Real-time chemical composition of ambient fine aerosols and related cytotoxic effects in human lung epithelial cells in an urban area

Particulate matter with aerodynamic diameters ≤1 μm (PM₁) in the atmosphere, especially that which is emitted from anthropogenic sources, can induce considerable negative effects on the cardiopulmonary system. To investigate the chemical emission characteristics and organic sources in Yuen Long (Hong Kong), both offline and online approaches for PM₁ samples were applied by filter-based samplers and a Quadrupole Aerosol Chemical Speciation Monitor (Q-ACSM), respectively. The toxicological effects on human A549 lung alveolar epithelial cells were investigated, and associations between cytotoxicity and organic sources and compositions were evaluated. The organics from the Q-ACSM measurement were the largest contributor to submicron aerosols in both seasons of our study, and the mass fraction was higher in winter (60%) than it was in autumn (46%). Regarding organic sources, the mass fraction of hydrocarbon-like organics (HOA) increased from 7% in autumn to 38% in winter, whereas cooking organics (COA) decreased from 30% in autumn to 18% in winter, and oxygenated organics (OOA) decreased from 63% to 45%. Organic compounds contributed more during pollution episodes, and more secondary ions were formed by means of the oxidation process. Oxidative and inflammatory responses in A549 cells were found with PM₁ exposures; the differences in chemical compositions resulted in the higher cytotoxicity in winter than autumn. The cooking organic aerosol in residential area was significantly correlated with cell inflammation. Both elemental carbon and specific inorganic ions (SO₄^2- and Mg²⁺) contributed to the intracellular cytotoxicity. This study demonstrated that specific atmospheric particulate matter chemical properties and sources can trigger distinct cell reactions; the inorganic ions from cooking emissions cannot be disregarded in terms of their pulmonary health risks in residential areas.

Toxicological effects of air settled particles from the Vitoria Metropolitan Area mediated by oxidative stress, pro-inflammatory mediators and NFΚB pathway

Atmospheric pollution is a major environmental and public health risk due to its effect on global air quality and climate. Increase in pollutants concentrations, especially particulate matter (PM), are associated with increased respiratory diseases. The pathophysiology of respiratory diseases involves molecular and cellular mechanisms as inflammatory biomarkers and reactive oxygen species production. Thus, the present study aimed to investigate the in vitro cytotoxic and pro-inflammatory effects of particulate matter (PM) of six monitoring stations (1-6) from the Vitoria Metropolitan Area (VMA), Espirito Santo, Brazil in 2018. The PM was chemically characterized by inductively coupled plasma mass spectrometry. In vitro cytotoxic effects of PM (3.12-200.0 μg/mL) were analyzed in human lung epithelial cells (A549) and macrophage cells (RAW 264.7) by MTT assay (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide). To investigate the pro-inflammatory effects of PM in RAW 264.7 cells, the levels of proinflammatory mediators such as nitric oxide (NO), superoxide anion (O₂^•-), tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and the activation of nuclear factor kappa B (NF- κB) were measured. The comet assay evaluated genotoxicity. Cell cycle, oxidative stress (DCF and DHE), and apoptosis were analyzed by flow cytometry. Chemical analysis of PM revealed aluminum (Al) and Iron (Fe) as the major chemical elements in all studied monitoring stations. In addition, worrying concentrations of mercury (Hg) were detected in the PM. The in vitro results showed that PM presents a dose-dependent cytotoxic effect in macrophage and pulmonary epithelial cell lines. The PM increased the production of NO, O₂^•-, and pro-inflammatory cytokines TNF-α and IL-6. PM also promoted alterations in the cell cycle, increased apoptosis frequency, and DNA damage. Moreover, PM increased the expression NF-κB. In addition, a positive correlation between Al and Fe and ROS production was observed. Based on the results obtained during the study period, it was concluded that the sedimented particles from the VMA might have deleterious effects on human health, which was evidenced by the increase in oxidative stress, an increase in pro-inflammatory mediators, and genotoxic effects partially mediated by the NF-κB pathway. These results add aspects to elucidate the molecular mechanisms involved in the effects of sedimented particles in vivo and in vitro.

Comparative Toxic Effects of Manufactured Nanoparticles and Atmospheric Particulate Matter in Human Lung Epithelial Cells

Although nanoparticles (NPs) have been used as simplified atmospheric particulate matter (PM) models, little experimental evidence is available to support such simulations. In this study, we comparatively assessed the toxic effects of PM and typical NPs (four carbonaceous NPs with different morphologies, metal NPs of Fe, Al, and Ti, as well as SiO₂ NPs) on human lung epithelial A549 cells. The EC50 value of PM evaluated by cell viability assay was 148.7 μg/mL, closest to that of SiO₂ NPs, between the values of carbonaceous NPs and metal NPs. All particles caused varying degrees of reactive oxygen species (ROS) generation and adenosine triphosphate (ATP) suppression. TiO₂ NPs showed similar performance with PM in inducing ROS production (p < 0.05). Small variations between two carbonaceous NPs (graphene oxides and graphenes) and PM were also observed at 50 μg/mL. Similarly, there was no significant difference in ATP inhibition between carbonaceous NPs and PM, while markedly different effects were caused by SiO₂ NP and TiO₂ NP exposure. Our results indicated that carbonaceous NPs could be served as potential surrogates for urban PM. The identification of PM model may help us further explore the specific roles and mechanisms of various components in PM.