Size-partitioning of an urban aerosol to identify particle determinants involved in the proinflammatory response induced in airway epithelial cells

CircRNA-associated ceRNA networks (circCeNETs) in chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD), a chronic airway disorder, which is mostly brought on by cigarette smoke extract (CSE), is a leading cause of death which has a high frequency. In COPD patients, smoking cigarette could also trigger the epithelial-mesenchymal transition (EMT) of airway remodeling. One of the most significant elements of environmental contaminants that is linked to pulmonary damage is fine particulate matter (PM2.5). However, the basic processes of lung injury brought on by environmental contaminants and cigarette smoke are poorly understood, particularly the molecular pathways involved in inflammation. For the clinical management of COPD, investigating the molecular process and identifying workable biomarkers will be important. According to newly available research, circular RNAs (circRNAs) are aberrantly produced and serve as important regulators in the pathological processes of COPD. This class of non-coding RNAs (ncRNAs) functions as microRNA (miRNA) sponges to control the levels of gene expression, changing cellular phenotypes and advancing disease. These findings led us to concentrate our attention in this review on new studies about the regulatory mechanism and potential roles of circRNA-associated ceRNA networks (circCeNETs) in COPD.

Temporal analysis of lung injury induced by real-ambient PM2 .5 exposure in mice

Fine particulate matter (PM2.5 ) has been shown to induce lung injury. However, the pathophysiological mechanisms of PM2.5 -induced pulmonary injury after different exposure times are poorly understood. In this study, we exposed male ICR mice to a whole-body PM2.5 inhalation system at daily mean concentration range from 92.00 to 862.00 μg/m3 for 30, 60, and 90 days. We found that following prolonged exposure to PM2.5 , pulmonary injury was increasingly evident with significant histopathological alterations. Notably, the pulmonary inflammatory response and fibrosis caused by PM2.5 after different exposure times were closely associated with histopathological changes. In addition, PM2.5 exposure caused oxidative stress, DNA damage and impairment of DNA repair in a time-dependent manner in the lung. Importantly, exposure to PM2.5 eventually caused apoptosis in the lung through upregulation of cleaved-caspase-3 and downregulation of Bcl-2. Overall, our data demonstrated that PM2.5 led to pulmonary injury in a time-dependent manner via upregulation of proinflammatory and fibrosis-related genes, and activation of the DNA damage response. Our findings provided a novel perspective on the pathophysiology of respiratory diseases caused by airborne pollution.

Role of different mechanisms in pro-inflammatory responses triggered by traffic-derived particulate matter in human bronchiolar epithelial cells

BACKGROUND

Traffic-derived particles are important contributors to the adverse health effects of ambient particulate matter (PM). In Nordic countries, mineral particles from road pavement and diesel exhaust particles (DEP) are important constituents of traffic-derived PM. In the present study we compared the pro-inflammatory responses of mineral particles and DEP to PM from two road tunnels, and examined the mechanisms involved.

METHODS

The pro-inflammatory potential of 100 µg/mL coarse (PM10-2.5), fine (PM2.5-0.18) and ultrafine PM (PM0.18) sampled in two road tunnels paved with different stone materials was assessed in human bronchial epithelial cells (HBEC3-KT), and compared to DEP and particles derived from the respective stone materials. Release of pro-inflammatory cytokines (CXCL8, IL-1α, IL-1β) was measured by ELISA, while the expression of genes related to inflammation (COX2, CXCL8, IL-1α, IL-1β, TNF-α), redox responses (HO-1) and metabolism (CYP1A1, CYP1B1, PAI-2) was determined by qPCR. The roles of the aryl hydrocarbon receptor (AhR) and reactive oxygen species (ROS) were examined by treatment with the AhR-inhibitor CH223191 and the anti-oxidant N-acetyl cysteine (NAC).

RESULTS

Road tunnel PM caused time-dependent increases in expression of CXCL8, COX2, IL-1α, IL-1β, TNF-α, COX2, PAI-2, CYP1A1, CYP1B1 and HO-1, with fine PM as more potent than coarse PM at early time-points. The stone particle samples and DEP induced lower cytokine release than all size-fractionated PM samples for one tunnel, and versus fine PM for the other tunnel. CH223191 partially reduced release and expression of IL-1α and CXCL8, and expression of COX2, for fine and coarse PM, depending on tunnel, response and time-point. Whereas expression of CYP1A1 was markedly reduced by CH223191, HO-1 expression was not affected. NAC reduced the release and expression of IL-1α and CXCL8, and COX2 expression, but augmented expression of CYP1A1 and HO-1.

CONCLUSIONS

The results indicate that the pro-inflammatory responses of road tunnel PM in HBEC3-KT cells are not attributed to the mineral particles or DEP alone. The pro-inflammatory responses seem to involve AhR-dependent mechanisms, suggesting a role for organic constituents. ROS-mediated mechanisms were also involved, probably through AhR-independent pathways. DEP may be a contributor to the AhR-dependent responses, although other sources may be of importance.

Exhaust emissions of gaseous and particle size-segregated water-soluble organic compounds from diesel-biodiesel blends

This study assessed the emissions of gaseous pollutants and particle size distributed water-soluble organics (WSO) from a diesel vehicle fuelled with ultralow sulphur diesel (B0) and 10 (B10), 20 (B20), and 30% (B30) biodiesel blends in a chassis dynamometer tested under transient mode. Particulate emission sampling was carried out in an ultraviolet (UV) test chamber using a 10-stage impactor. Samples were grouped into three size fractions and analysed by gas chromatography-mass spectrometry. Increasing the biofuel ratio up to 30% in the fuel reduced WSO emissions by 20.9% in comparison with conventional diesel. Organic acids accounted for 82-89% of WSO in all tested fuels. Dicarboxylic acids were the most abundant compound class, followed by hydroxy, aromatic, and linear alkanoic acids. Correlations between compounds demonstrated that adding biodiesel to diesel fuel reduces the emissions of nitrogen oxides (NOx), benzene, toluene, ethylbenzene and xylenes (BTEX), methane (CH4), total and nonmethane hydrocarbons (THC and NMHC), and dicarboxylic and hydroxy acids, but increases emissions of carbon dioxide (CO2) and alkanoic and aromatic acids. Emissions of dicarboxylic and hydroxy acids were strongly correlated with the biodiesel content. WSO emissions of coarse and fine (1.0-10 μm) particles decreased with the increasing biofuel content in fuel blend. The total share of ultrafine (0.18-1.0 μm) and nanoparticles (< 0.18 μm) increased in WSOs emissions from B20 and B30 blends, when compared with petrodiesel. The biodiesel content also affected the chemical profile of WSO size fractions.

Long-term effect of intermediate particulate matter (PM1-2.5) on incident asthma among middle-aged and elderly adults: A national population-based longitudinal study

BACKGROUND

There is insufficient evidence about the long-term effects of intermediate particulate matter (PM_1-2.5) on asthma development in adults aged 45 years and above. This study aimed to investigate the relationship between long-term exposure to PM_1-2.5 and the incidence of asthma in adults aged 45 years and above.

METHODS

A cohort study based on the China Health and Retirement Longitudinal Study (CHARLS) database was conducted to investigate the long-term effects of PM_1-2.5 on self-reported asthma incidence in adults aged 45 years and above in China from 2011 to 2018. The PM concentrations were estimated using a high-resolution (1 km²) satellite-based spatiotemporal model. A covariate-adjusted generalized linear mixed model was used to analyze the relationship between long-term exposure to PM_1-2.5 and the incidence of asthma. Effect modifications and sensitivity analysis were conducted.

RESULTS

After a 7-year follow-up, 103 (1.61 %) of the 6400 participants developed asthma. Each 10 μg/m³ increment in the 1-, 2-, 3-, and 4-year moving average concentrations of PM_1-2.5 corresponded to a 1.82 [95 % confidence interval (CI):1.11-2.98], 1.95 (95 % CI: 1.24-3.07), 1.95 (95 % CI: 1.26-3.03) and 1.88 (95 % CI: 1.26-2.81) fold risk for incident asthma, respectively. A significant multiplicative interaction was observed between socioeconomic level and long-term exposure to PM_1-2.5. Stratified analysis showed that smokers and those with lower socioeconomic levels were at higher risk of incident asthma related to PM_1-2.5. Restricted cubic splines showed an increasing trend in asthma incidence with increasing PM_1-2.5. Sensitivity analyses showed that our model was robust.

CONCLUSION

Long-term exposure to PM_1-2.5 was positively associated with incident asthma in middle-aged and elderly individuals. Participants with a history of smoking and lower socioeconomic levels had a higher risk. More studies are warranted warrant to establish an accurate reference value of PM_1-2.5 to mitigate the growing asthma burden.

Size fraction of hazardous particulate matter governing the respiratory deposition and inhalation risk in the highly polluted city Delhi

Delhi has been identified as one of the highly polluted cities in the world and recently associated with the highest population weighted PM_2.5 concentration. However, the unavailability of the health risk estimations using long-term data for Indian cities has been pointed out as a hurdle in performing the correct assessment. The present work estimated deposition of particles in different regions of respiratory systems (head airway = 67% deposition for 2.5 µm particles; tracheo-bronchiolar (TB) = 73% deposition for 1.0 µm particles; alveolar (AL) = 17% deposition for 0.5 µm, 0.25 µm, and < 0.25 µm particles) using PM samples collected at a breathing height of 1.5 m near the major ring road in New Delhi (India). The calculated risk index (RI) varied considerably between winter (1.21 ± 0.26 to 1.33 ± 0.50) and pre-monsoon-southwest monsoon months (0.34 ± 0.08 to 0.96 ± 0.27). Respiratory deposition dose of nanosized particles (≤ 500 nm) in the alveoli region of the lung was found to be considerable (35%) indicating the need for understanding the role of these particles in posing health risk. Although the calculated values of risk metric for exposures of PM-associated metals indicated no risk to IIT Delhi population (hazard quotient < 1 and excess risk of getting cancer < 10^-6-10^-9), continuous monitoring for particles of different sizes at inhalation height are required for protecting human health.

Road tunnel-derived coarse, fine and ultrafine particulate matter: physical and chemical characterization and pro-inflammatory responses in human bronchial epithelial cells

BACKGROUND

Traffic particulate matter (PM) comprises a mixture of particles from fuel combustion and wear of road pavement, tires and brakes. In countries with low winter temperatures the relative contribution of mineral-rich PM from road abrasion may be especially high due to use of studded tires during winter season. The aim of the present study was to sample and characterize size-fractioned PM from two road tunnels paved with different stone materials in the asphalt, and to compare the pro-inflammatory potential of these fractions in human bronchial epithelial cells (HBEC3-KT) in relation to physicochemical characteristics.

METHODS

The road tunnel PM was collected with a vacuum pump and a high-volume cascade impactor sampler. PM was sampled during winter, both during humid and dry road surface conditions, and before and after cleaning the tunnels. Samples were analysed for hydrodynamic size distribution, content of elemental carbon (EC), organic carbon (OC) and endotoxin, and the capacity for acellular generation of reactive oxygen species. Cytotoxicity and pro-inflammatory responses were assessed in HBEC3-KT cells after exposure to coarse (2.5-10 μm), fine (0.18-2.5 μm) and ultrafine PM (≤ 0.18 μm), as well as particles from the respective stone materials used in the pavement.

RESULTS

The pro-inflammatory potency of the PM samples varied between road tunnels and size fractions, but showed more marked responses than for the stone materials used in asphalt of the respective tunnels. In particular, fine samples showed significant increases as low as 25 µg/mL (2.6 µg/cm²) and were more potent than coarse samples, while ultrafine samples showed more variable responses between tunnels, sampling conditions and endpoints. The most marked responses were observed for fine PM sampled during humid road surface conditions. Linear correlation analysis showed that particle-induced cytokine responses were correlated to OC levels, while no correlations were observed for other PM characteristics.

CONCLUSIONS

The pro-inflammatory potential of fine road tunnel PM sampled during winter season was high compared to coarse PM. The differences between the PM-induced cytokine responses were not related to stone materials in the asphalt. However, the ratio of OC to total PM mass was associated with the pro-inflammatory potential.

Ambient particulate matter exposure plus a high-fat diet exacerbate renal injury by activating the NLRP3 inflammasome and TGF-β1/Smad2 signaling pathway in mice

BACKGROUND

Chronic kidney disease (CKD) is a public health problem of which the prevalence is increasing worldwide. Several studies have reported that ambient particulate matter (PM) causes kidney injury, which may be related to the risk of CKD. However, the underlying molecular mechanisms have not been fully clarified. In addition, whether a high-fat diet (HFD) could exacerbate ambient PM-induced nephrotoxicity has not been evaluated. This study aimed to investigate the combined effect of ambient PM and a HFD on renal injury.

METHODS AND RESULTS

Male C57BL/6 J mice were fed either a normal diet or a HFD and exposed to filtered air (FA) or particulate matter (PM) for 18 weeks. In the present study, we observed that renal function changed (serum blood urea nitrogen and serum creatinine), and exposure to PM and a HFD caused a synergistic effect on renal injury. Histopathological analysis showed that PM exposure induced renal fibrosis in mice, and combined exposure to PM and a HFD exacerbated these adverse effects. Moreover, ambient PM exposure activated the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome and increased the inflammatory response, as indicated by the increases in interleukin-1β, interleukin-6 and tumor necrosis factor-α in the serum and kidney, as well as the upregulation of specific renal fibrosis-related markers (transforming growth factor-β1 and p-Smad2) in the kidney tissues of mice. Furthermore, combined exposure to PM and a HFD augmented these changes in the kidney. In vitro, inhibition of the NLRP3 inflammasome by MCC950 (an inhibitor of NLRP3) reduced the levels of proinflammatory cytokines and the expression of transforming growth factor-β1 and p-Smad2 in HK-2 cells.

CONCLUSION

Taken together, our data indicated that PM exposure caused renal inflammation and induced profibrotic effects on the kidney, and combined exposure to ambient PM and a HFD exacerbated renal injury, which may involve activation of the NLRP3 inflammasome and the TGF-β1/Smad2 signaling pathway.

Statistical analysis of the temporal change of PM10 levels in the city of Sivas (Turkey)

The objective of this study is to statistically examine the variation of PM10 values measured at three stations in the center of Sivas between the years 2016 and 2020. Hourly PM10 measurement values were taken from three different stations (İstasyon Kavşağı, Meteoroloji, and Başöğretmen AQMSs) in the city center. Then the mean values of the measurements obtained between 2016 and 2020 were compared according to the years and the stations, as well as with the limit values given in the Regulation on Air Quality Assessment and Management(RAQAM). Analyses of variance were conducted to determine any differences between PM10 levels and 24-h limit values of PM10 for Turkey and between PM10 values of stations over the years. Considering the 5-year mean values, the mean value of all PM10 concentrations measured in the city center was calculated as 56.36 µg/m³. No statistical difference was found between the PM10 values measured in 2017 and 2018 at the İstasyon Kavşağı AQMS, and the comparisons of PM10 between stations over the years showed no difference between the Meteoroloji AQMS and the Başöğretmen AQMS in 2019 and 2020. The Spearman's rank-order correlation results of PM10 over the years among the stations in the city showed that the strongest relationship was a moderate one between the years 2019 and 2020 with regard to the İstasyon Kavşağı AQMS. Probable dust transports were examined for the days when PM10 was at its highest, and the conclusion was that desert dust coming from the continent of Africa (south) to the center of Sivas had been effective.

Particle composition and morphology over urban environment (New Delhi): Plausible effects on wheat leaves

Particulate matter (PM) deposition on leaves adversely affects physical, chemical and biological nature of agricultural crops resulting in their loss of productivity and yield. Wheat being a staple food in major parts of Northern India and around the World, has been selected for research purpose by designing a study to explore the probable effects of PM deposition on wheat leaves and wheat crops to ensure the food security. PM₅ (Particulate matter with aerodynamic diameter <5 μm) and Dry Deposited Particulate Matter (DDPM) on wheat leaves (Leaf_DDPM) were collected from the wheat crop field in Indian Agriculture Research Institute (IARI), New Delhi for growing and harvesting season of wheat crops (i.e. December 2014 to April 2015). The EDS (Energy Dispersive Spectroscopy) analysis was used for this study and the individual particle analysis revealed the presence of both acidic and alkaline components like C, Al, Si, Fe, Ca, K, S and Mg. The offline characterization tool i.e. SEM (Scanning Electron Microscope) was utilized for obtaining the micrographs which clearly showed the presence of some angular, sharp-edged and spherical particles consisting of both smooth and rough texture. Apart from that, prevalence of slightly non-spherical particles with aspect ratio of range (>1.20-1.40) and CIR (>0.70-0.80) for both PM₅ and leaf_DDPM were observed. The size distribution of individual particles for both PM₅(#194 particles) and Leaf_DDPM(#657 particles) revealed that Surface Equivalent Radius (SER) and Volume Equivalent Radius (VER) of particles observed to be 0.40-0.80 μm while surface area to be 0-1 μm². These particles may easily block stomatal openings (with typical diameter range: 42-51 μm) of wheat leaves and damage internal leaf tissues while particle VER determines the interaction of incoming solar radiation with leaf surfaces. Average PM₅ concentrations ± Standard deviations (μg/m³) were reported to be 231.05 ± 113.03. The XRF (X-Ray Fluorescence) spectrometer analysis of bulk PM₅ revealed the concentrations of non-carbonaceous elements (μg/m³) as N (67.34 ± 16.09), Si (27.44 ± 11.01), Al (7.79 ± 3.37), S (3.88 ± 2.24), Na (2.29 ± 0.94), Mg (1.65 ± 0.62), K (0.51 ± 0.26), Ca (0.60 ± 0.26), Fe (0.54 ± 0.26), Cr (1.10 ± 0.70), Zn (0.05 ± 0.03), P (0.10 ± 0.03), Cu (0.07 ± 0.06). The dominant elemental oxides were calculated as SiO₂, Al₂O₃, SO₄^2-, Na₂O, MgO, K₂O, CaO, Fe₂O₃, Cr₂O₃, ZnO, P₂O₅, Cu₂O with variable concentrations. In high humid conditions, with relative humidity (~85%) during the vegetative and flowering growth stages of wheat crops, presence of C and S rich acidic and hygroscopic particles may cause the corrosion of wheat leaves that ultimately affect the wheat crops.

Seasonal variation and sources of carbonaceous species and elements in PM2.5 and PM10 over the eastern Himalaya

The study represents the seasonal characteristics (carbonaceous aerosols and elements) and the contribution of prominent sources of PM2.5 and PM10 in the high altitude of the eastern Himalaya (Darjeeling) during August 2018-July 2019. Carbonaceous aerosols [organic carbon (OC), elemental carbon (EC), and water soluble organic carbon (WSOC)] and elements (Al, Fe, Ti, Cu, Zn, Mn, Cr, Ni, Mo, Cl, P, S, K, Zr, Pb, Na, Mg, Ca, and B) in PM2.5 and PM10 were analyzed to estimate their possible sources. The annual concentrations of PM2.5 and PM10 were computed as 37±12 μg m-3 and 58±18 μg m-3, respectively. In the present case, total carbonaceous species in PM2.5 and PM10 were accounted for 20.6% of PM2.5 and 18.6% of PM10, respectively, whereas trace elements in PM2.5 and PM10 were estimated to be 15% of PM2.5 and 12% of PM10, respectively. Monthly and seasonal variations in mass concentrations of carbonaceous aerosols and elements in PM2.5 and PM10 were also observed during the observational period. In PM2.5, the annual concentrations of POC and SOC were 2.35 ± 1.06 μg m-3 (66% of OC) and 1.19±0.57 μg m-3 (34% of OC), respectively, whereas annual average POC and SOC concentrations in PM10 were 3.18 ± 1.13 μg m-3 (63% of OC) and 2.05±0.98 μg m-3 (37% of OC), respectively. The seasonal contribution of POC and SOC were ranging from 55 to 77% and 33 to 45% of OC in PM2.5, respectively, whereas in PM10, the seasonal contributions of POC and SOC were ranging from 51 to 73% and 37 to 49% of OC, respectively. The positive relationship between OC & EC and OC & WSOC of PM2.5 and PM10 during all the seasons (except monsoon in case of PM10) indicates their common sources. The enrichment factors (EFs) and significant positive correlation of Al with othe crustal elements (Fe, Ca, Mg, and Ti) of fine and coarse mode aerosols indicate the influence of mineral dust at Darjeeling. Principal component analysis (PCA) resolved the four common sources (biomass burning + fossil fuel combustion (BB + FFC), crustal/soil dust, vehicular emissions (VE), and industrial emissions (IE)) of PM2.5 and PM10 in Darjeeling.

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.

Estimating seasonal variations of realistic exposure doses and risks to organs due to ambient particulate matter -bound metals of Delhi

This study aims to calculate deposition of PM_2.5 -bound hazardous metals in different organs after inhalation of particulate matter for the Delhi (India), and to estimate risks to organs following inhalation. Bio-accessible fractions of three PM-associated carcinogenic metals (As, Pb &Cd) were calculated using the metal values in simulated lung fluids. Depositions of metals in different organs were calculated using an integrated model consists of HRT and PBPK models. The calculation indicates that the major or significant deposition of metal Pb occurs in tissues, such as bone, muscle and blood. Most of the depositions of Cd happens in lung whereas most of the depositions of As happens in lung, muscle and skin. Most of the deposition of studied metals was found in lung (45% for arsenic and 70% for cadmium of their bio -dissolved contents). The following order of depositions of metals in different tissues were found (from highest deposition to smallest deposition): As: Lung > muscle = liver; Pb: bone > blood > muscle; Cd: lung > intestine. The combined exposures of PM_2.5 and its associated metals were found to give interaction-based hazard index greater than 1 for several months of the year, indicating a chance of health risk. Hazard quotient (HQ) <1 was seen for ingestion and dermal pathways, indicating no cause of concern. Findings indicate the need for doing periodic monitoring and estimating deposition doses and exposure risks of PM-associated metals to lungs and other organs for protecting human health.

Effect and underlying mechanisms of airborne particulate matter 2.5 (PM2.5) on cultured human corneal epithelial cells

Health problems caused by airborne particulate matter with a diameter less than 2.5 (PM2.5), especially in the respiratory system, have become a worldwide problem, but the influence and mechanisms of PM2.5 on the ocular surface have not been sufficiently elucidated. We investigated in vitro the onset and pathogenesis of corneal damage induced by PM2.5. Two types of PM2.5 samples originating from Beijing (designated #28) and the Gobi Desert (designated #30) were added to the culture medium of immortalized cultured human corneal epithelial cells (HCECs) to examine the effects on survival rates, autophagy, and proinflammatory cytokine production. Both types of PM2.5 significantly reduced the HCEC survival rate in a concentration-dependent manner by triggering autophagy. In particular, compared with #30, #28 induced much more severe damage in HCECs. Physical contact between PM2.5 and HCECs was not a primary contributor to PM2.5-induced HCEC damage. Among the 38 proinflammatory cytokines examined in this study, significant increases in the granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-6 levels and a significant reduction in the interleukin-8 level were detected in culture medium of PM2.5-exposed HCECs. Simultaneous addition of a GM-CSF inhibitor, suramin, alleviated the HCEC impairment induced by PM2.5. In conclusion, PM2.5 induces HCEC death by triggering autophagy. Some cytokines that are released from HCECs, including GM-CSF, may be involved in HCEC damage caused by PM2.5 exposure.

Assessment of reactive oxygen species production and genotoxicity of rare earth mining dust: Implications for public health and mining management

Mining rare earth elements (REEs) can release large amounts of metal(loid)-rich dust, which can pose significant health risks to local residents. However, compared to other types of particulates, toxicity of mining dust has been largely overlooked. To provide experimental evidence on toxicity of REE mine dust, the study assessed the oxidative stress potential and genotoxicity of inhalable particles collected in a REE mining area, and associated toxicological response with source compositions. Both source types (i.e., mine and tailing area) and distances from source (i.e., industrial and residential areas) were considered when selecting the 44 sampling sites. The particle samples contained 2.3-3.5 folds higher concentrations of tested metal(loid)s than background concentrations in soil. Specially, elevated Fe, REEs, Cd, Pb were found. In spite of low cytotoxicity in lung epithelial A549 cells, there was increased cellular ROS production by of particle exposure. Samples with higher mining-originated source contributions (Provenance Index <0.3) had higher cellular ROS production (1.72 fold, 95%CI: 1.66-1.79 fold) than samples with lower mining contributions (1.58 fold, 95%CI: 1.52-1.65 fold). The factors soil (~46%), mine (~22%), and heavy metal (~20%) sources were recognized by source apportionment analysis as the main contributors to cellular ROS production; importantly, mine and heavy metal sources counted more in industrial samples. While samples generated genotoxicity, there were no differences in DNA damage between the location groups of sampling. Collectively, the results indicate that particles in mining areas may cause ROS production and DNA damage in lung cells depending on mine dust. Coupled with the long-range transportation potential of mine dust, safety measures on open pit and dust disposal sites should be adopted.

Circular RNA circBbs9 promotes PM2.5-induced lung inflammation in mice via NLRP3 inflammasome activation

Fine particulate matter (PM_2.5) is one of the most important components of environmental pollutants, and is associated with pulmonary injury. However, the biological mechanisms of pulmonary damage caused by PM_2.5 are poorly defined, especially the molecular pathways related to inflammation. Following system exposure to PM_2.5 for 3 months in normal mice and in chronic obstructive pulmonary disease (COPD) model mice, it was found that PM_2.5 exposure increased the expression of IL-1β and IL-18 in lung tissues via NLRP3 activation, and these effects were more intense in COPD model mice. Circular RNA (circRNA) sequencing showed that the expression profiles of circRNAs were changed after PM_2.5 exposure, and the positive roles of circBbs9 in inflammation induced by PM_2.5 were verified. The circBbs9 knockdown alleviated PM_2.5-induced inflammation via NLRP3 inflammasome inactivation, as well as IL-1β and IL-18 inhibition in RAW264.7 cells, while overexpression of circBbs9 had the opposite effect. Bioinformatics and luciferase reporter assays showed that circBbs9 bound to microRNA-30e-5p (miR-30e-5p) and co-regulated the expression of Adar, a downstream target gene of miR-30e-5p. Taken together, these results revealed that PM_2.5 induced pulmonary inflammation through NLRP3 inflammasome activation regulated by the circBbs9-miR-30e-5p-Adar pathway. Our findings provide a new target, circBbs9, for the assessment of lung inflammation and COPD exacerbation induced by PM_2.5 exposure.

PM2.5 impairs macrophage functions to exacerbate pneumococcus-induced pulmonary pathogenesis

Background

Pneumococcus is one of the most common human airway pathogens that causes life-threatening infections. Ambient fine particulate matter (PM) with aerodynamic diameter ≤ 2.5 μm (PM_2.5) is known to significantly contribute to respiratory diseases. PM_2.5-induced airway inflammation may decrease innate immune defenses against bacterial infection. However, there is currently limited information available regarding the effect of PM_2.5 exposure on molecular interactions between pneumococcus and macrophages.

Results

PM_2.5 exposure hampered macrophage functions, including phagocytosis and proinflammatory cytokine production, in response to pneumococcal infection. In a PM_2.5-exposed pneumococcus-infected mouse model, PM_2.5 subverted the pulmonary immune response and caused leukocyte infiltration. Further, PM_2.5 exposure suppressed the levels of CXCL10 and its receptor, CXCR3, by inhibiting the PI3K/Akt and MAPK pathways.

Conclusions

The effect of PM_2.5 exposure on macrophage activity enhances pneumococcal infectivity and aggravates pulmonary pathogenesis.

Spatio-Temporal Variations of Satellite-Based PM2.5 Concentrations and Its Determinants in Xinjiang, Northwest of China

With the aggravation of air pollution in recent years, a great deal of research on haze episodes is mainly concentrated on the east-central China. However, fine particulate matter (PM_2.5) pollution in northwest China has rarely been discussed. To fill this gap, based on the standard deviational ellipse analysis and spatial autocorrelation statistics method, we explored the spatio-temporal variation and aggregation characteristics of PM_2.5 concentrations in Xinjiang from 2001 to 2016. The result showed that annual average PM_2.5 concentration was high both in the north slope of Tianshan Mountain and the western Tarim Basin. Furthermore, PM_2.5 concentrations on the northern slope of the Tianshan Mountain increased significantly, while showing an obviously decrease in the western Tarim Basin during the period of 2001–2016. Based on the result of the geographical detector method (GDM), population density was the most dominant factor of the spatial distribution of PM_2.5 concentrations (q = 0.550), followed by road network density (q = 0.423) and GDP density (q = 0.413). During the study period (2001–2016), the driving force of population density on the distribution of PM_2.5 concentrations showed a gradual downward trend. However, other determinants, like DEM (Digital elevation model), NSL (Nighttime stable light), LCT (Land cover type), and NDVI (Normalized Difference Vegetation Index), show significant increased trends. Therefore, further effort is required to reveal the role of landform and vegetation in the spatio-temporal variations of PM_2.5 concentrations. Moreover, the local government should take effective measures to control urban sprawl while accelerating economic development.

Screening of Cellular Stress Responses Induced by Ambient Aerosol Ultrafine Particle Fraction PM0.5 in A549 Cells

Effects of airborne particles on the expression status of markers of cellular toxic stress and on the release of eicosanoids, linked with inflammation and oxidative damage, remain poorly characterized. Therefore, we proposed a set of various methodological approaches in order to address complexity of PM0.5-induced toxicity. For this purpose, we used a well-characterized model of A549 pulmonary epithelial cells exposed to a non-cytotoxic concentration of ambient aerosol particle fraction PM0.5 for 24 h. Electron microscopy confirmed accumulation of PM0.5 within A549 cells, yet, autophagy was not induced. Expression profiles of various cellular stress response genes that have been previously shown to be involved in early stress responses, namely unfolded protein response, DNA damage response, and in aryl hydrocarbon receptor (AhR) and p53 signaling, were analyzed. This analysis revealed induction of GREM1, EGR1, CYP1A1, CDK1A, PUMA, NOXA and GDF15 and suppression of SOX9 in response to PM0.5 exposure. Analysis of eicosanoids showed no oxidative damage and only a weak anti-inflammatory response. In conclusion, this study helps to identify novel gene markers, GREM1, EGR1, GDF15 and SOX9, that may represent a valuable tool for routine testing of PM0.5-induced in vitro toxicity in lung epithelial cells.

Trace element characterization of fine particulate matter and assessment of associated health risk in mining area, transportation routes and institutional area of Dhanbad, India

Samples of PM_2.5 were collected on PTFE filters at 11 monitoring stations in Dhanbad, India, from March, 2014, to February, 2015, for the quantification of 10 PM_2.5-bound trace elements by using ICP-OES, source apportionment by using principal component analysis and health risks posed by PM_2.5-bound trace elements by using health risk assessment model developed by US EPA. The average annual PM_2.5 concentration (149 ± 66 µg/m³) exceeded the national ambient air quality standards by factor of 3.7, US EPA national ambient air quality standards by factor of 10 and WHO air quality guidelines by factor of 15. The sum total of average annual concentration of all PM_2.5-bound trace elements was found to be 3.206 µg/m³ with maximum concentrations of Fe (61%), Zn (21%) and Pb (11%). Coal mining, coal combustion, vehicular emission, tyre and brake wear and re-suspension of road dust were identified as dominant sources of PM_2.5-bound trace elements from the results of correlation and chemometric analysis. The significantly high HQ values posed by PM_2.5-bound Co and Ni and intensification of HI values (15.7, 10.8 and 8.54 in mining area, transportation routes and institutional area, respectively) for multielemental exposure indicate high potential of non-carcinogenic health risk associated with inhalation exposure. The carcinogenic health risk due to multielemental exposure in mining area (2.27 × 10^-4) and transportation routes (1.57 × 10^-4) for adults were significantly higher than threshold value indicating the vulnerability of adults toward inhalation-induced carcinogenic risk posed by PM_2.5-bound trace elements.

Resveratrol alleviates chronic "real-world" ambient particulate matter-induced lung inflammation and fibrosis by inhibiting NLRP3 inflammasome activation in mice

BACKGROUND

Inhalation of fine particulate matter (PM_2.5) induces the occurrence of lung inflammation and fibrosis, but its molecular mechanism remains unclear. Resveratrol (RES) is known to have anti-inflammatory properties in many pulmonary diseases. Here, we aimed to investigate the effect of long-term "real-world" ambient PM exposure on lung inflammation and fibrosis and further explore the protective effect and mechanism of RES.

METHODS AND RESULTS

RES (50 and 100 mg/kg.bw) was administered to C57BL/6J mice that were exposed to ambient PM for 5 months. The control group breathed filtered air without RES, and the PM group was exposed to PM without RES. The inflammatory cytokine levels in bronchoalveolar lavage fluid (BALF) and lung fibrosis were evaluated by enzyme-linked immune sorbent assay (ELISA) kits and Masson's trichrome staining. The real-time PCR and Western blot analysis were used to determine the signal pathway. In vivo, PM exposure markedly elevated the levels of inflammatory cytokines and TGF-β1 in BALF, induced lung fibrosis. Meanwhile, PM exposure triggered autophagy process and activated the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome in lung. Also, RES treatment abolished PM-induced lung inflammation and fibrosis, and inhibited autophagic process and NLRP3 inflammasome activation. In vitro, PM_2.5-induced cytotoxicity in BEAS-2B cells dose-dependently. Besides, RES alleviated PM_2.5-induced cytotoxicity, inhibited autophagic process and NLRP3 inflammasome activity and decreased IL-1β production in BEAS-2B cells.

CONCLUSION

Long-term PM exposure induced lung inflammation and fibrosis, and RES intervention alleviated these adverse effects via inhibiting autophagy-related NLRP3 inflammasome activation.

Sources and Geographical Origins of PM10 in Metz (France) Using Oxalate as a Marker of Secondary Organic Aerosols by Positive Matrix Factorization Analysis

An original source apportionment study was conducted on atmospheric particles (PM10) collected in Metz, one of the largest cities of Eastern France. A Positive matrix factorization (PMF) analysis was applied to a sampling filter-based chemical dataset obtained for the April 2015 to January 2017 period. Nine factors were clearly identified, showing mainly contributions from anthropogenic sources of primary PM (19.2% and 16.1% for traffic and biomass burning, respectively) as well as secondary aerosols (12.3%, 14.5%, 21.8% for sulfate-, nitrate-, and oxalate-rich factors, respectively). Wood-burning aerosols exhibited strong temporal variations and contributed up to 30% of the PM mass fraction during winter, while primary traffic concentrations remained relatively constant throughout the year. These two sources are also the main contributors during observed PM10 pollution episodes. Furthermore, the dominance of the oxalate-rich factor among other secondary aerosol factors underlines the role of atmospheric processing to secondary organic aerosol loadings which are still poorly characterized in this region. Finally, Concentration-Weighted Trajectory (CWT) analysis were performed to investigate the geographical origins of the apportioned sources, notably illustrating a significant transport of both nitrate-rich and sulfate-rich factors from Northeastern Europe but also from the Balkan region.

Source Apportionment of PM10 Over Three Tropical Urban Atmospheres at Indo-Gangetic Plain of India: An Approach Using Different Receptor Models

The present work is the ensuing part of the study on spatial and temporal variations in chemical characteristics of PM₁₀ (particulate matter with aerodynamic diameter ≤ 10 μm) over Indo Gangetic Plain (IGP) of India. It focuses on the apportionment of PM₁₀ sources with the application of different receptor models, i.e., principal component analysis with absolute principal component scores (PCA-APCS), UNMIX, and positive matrix factorization (PMF) on the same chemical species of PM₁₀. The main objective of this study is to perform the comparative analysis of the models, obtained mutually validated outputs and more robust results. The average PM₁₀ concentration during January 2011 to December 2011 at Delhi, Varanasi, and Kolkata were 202.3 ± 74.3, 206.2 ± 77.4, and 171.5 ± 38.5 μg m^-3, respectively. The results provided by the three models revealed quite similar source profile for all the sampling regions, with some disaccords in number of sources as well as their percent contributions. The PMF analysis resolved seven individual sources in Delhi [soil dust (SD), vehicular emissions (VE), secondary aerosols (SA), biomass burning (BB), sodium and magnesium salt (SMS), fossil fuel combustion, and industrial emissions (IE)], Varanasi [SD, VE, SA, BB, SMS, coal combustion, and IE], and Kolkata [secondary sulfate (Ssulf), secondary nitrate, SD, VE, BB, SMS, IE]. However, PCA-APCS and UNMIX models identified less number of sources (besides mixed type sources) than PMF for all the sampling sites. All models identified that VE, SA, BB, and SD were the dominant contributors of PM₁₀ mass concentration over the IGP region of India.

NLRP3 inflammasome activation and lung fibrosis caused by airborne fine particulate matter

Airborne fine particulate matter (PM_2.5) has been known capable of causing lung inflammation and fibrosis, as a result of a series of chronic respiration diseases. Although NLRP3 inflammasome activation is essential for development of many chronic diseases, the relationship between PM_2.5-induced toxicological effect and NLRP3 inflammasome activation is rarely investigated. Since PM_2.5 contains a large population of nanosized materials and many types of nanomaterials can activate NLRP3 inflammasome, the NLRP3 inflammasome activation and lung fibrosis induced by PM_2.5 were investigated in the present study. PM_2.5 was found capable of causing weak cell death but potent IL-1β secretion in THP-1 cells, which was involved in NLRP3 inflammasome activation as evidenced by Z-YVAD-FMK inhibited IL-1β secretion and overexpressed ASC and NLRP3 protein in PM_2.5 treated cells. PM_2.5 could be internalized into cells through multiple endocytosis processes, such as phagocytosis and pinocytosis (macropinocytosis, clathrin- and caveolin-mediated endocytosis), and activate NLRP3 inflammasome through cathepsin B release, ROS production, and potassium efflux. After 21 days of exposure to PM_2.5 through oropharyngeal aspiration, Balb/c mice showed increased IL-1β and TGF-β1 levels in the bronchoalveolar lavage fluid (BALF) of lung and significant collagen deposition around small airways of mice, suggesting potential lung inflammation and pulmonary fibrosis.

Insights in particulate matter-induced allergic airway inflammation: Focus on the epithelium

Outdoor air pollution is a major environmental health problem throughout the world. In particular, exposure to particulate matter (PM) has been associated with the development and exacerbation of several respiratory diseases, including asthma. Although the adverse health effects of PM have been demonstrated for many years, the underlying mechanisms have not been fully identified. In this review, we focus on the role of the lung epithelium and specifically highlight multiple cytokines in PM-induced respiratory responses. We describe the available literature on the topic including in vitro studies, findings in humans (ie observations in human cohorts, human controlled exposure and ex vivo studies) and in vivo animal studies. In brief, it has been shown that exposure to PM modulates the airway epithelium and promotes the production of several cytokines, including IL-1, IL-6, IL-8, IL-25, IL-33, TNF-α, TSLP and GM-CSF. Further, we propose that PM-induced type 2-promoting cytokines are important mediators in the acute and aggravating effects of PM on airway inflammation. Targeting these cytokines could therefore be a new approach in the treatment of asthma.

Chlorine levels and species in fine and size resolved atmospheric particles by X-ray absorption near-edge structure spectroscopy analysis in Beijing, China

An understanding of the species of chlorine is crucial in the metropolis-Beijing, which is suffering serious haze pollution with high frequency. Particulate Matters (PMs) with five different sizes were collected in Beijing from July 2009 to March 2016, and characterized non-destructively by X-ray absorption near edge structure spectroscopy. PM_<0.2, PM_0.2-0.5 and PM_>2.5 contributed for the major PMs mass in spring and summer, PM_0.5-1.0 and PM_1.0-2.5 contributed for the major PMs mass in autumn and winter. The concentrations of the three chlorine species were in the order of inorganic chlorine (Cl_inorg) > aliphatic chlorine (Cl_ali) > aromatic chlorine (Cl_aro), indicating that Cl_inorg constituted the primary chlorine fraction and less toxic Cl_ali constituted the primary total organic chlorine (Cl_ali + Cl_aro, abbreviated as Cl_org) in the PMs in Beijing. In addition, these three chlorine species exhibited identical seasonal variation in PM_2.5: winter > autumn > spring > summer. Wet precipitation is an important factor to result in the lower mass concentrations of these three chlorine species in summer. The temporal variations of both size resolved PM mass concentrations and chlorine species concentrations suggested that the air pollution prevention and control in Beijing has just won initial success.

Mechanistic insight into the impact of nanomaterials on asthma and allergic airway disease

Asthma is a chronic respiratory disease known for its high susceptibility to environmental exposure. Inadvertent inhalation of engineered or incidental nanomaterials is a concern for human health, particularly for those with underlying disease susceptibility. In this review we provide a comprehensive analysis of those studies focussed on safety assessment of different nanomaterials and their unique characteristics on asthma and allergic airway disease. These include in vivo and in vitro approaches as well as human and population studies. The weight of evidence presented supports a modifying role for nanomaterial exposure on established asthma as well as the development of the condition. Due to the variability in modelling approaches, nanomaterial characterisation and endpoints used for assessment in these studies, there is insufficient information for how one may assign relative hazard potential to individual nanoscale properties. New developments including the adoption of standardised models and focussed in vitro and in silico approaches have the potential to more reliably identify properties of concern through comparative analysis across robust and select testing systems. Importantly, key to refinement and choice of the most appropriate testing systems is a more complete understanding of how these materials may influence disease at the cellular and molecular level. Detailed mechanistic insight also brings with it opportunities to build important population and exposure susceptibilities into models. Ultimately, such approaches have the potential to more clearly extrapolate relevant toxicological information, which can be used to improve nanomaterial safety assessment for human disease susceptibility.

Air Pollution and Public Health: A PRISMA-Compliant Systematic Review

(1) Background: Particulate matter increases the risk of respiratory, allergic and oncological diseases in both exposed workers and the general population due to its toxic compounds (e.g., PAHs, gases, heavy metals, microorganisms). The aim of this review is to show the results obtained by our department regarding air pollution’s contributions to health damage in both occupationally and non-occupationally exposed people. (2) Methods: This review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching articles on PubMed, using eligibility criteria, extracting data independently from reports to reduce bias and considering the accuracy of the statistical analyses. (3) Results: Of fifteen papers, only three respected the abovementioned criteria. A total of 453 cases (174 occupationally exposed and 279 non-occupationally exposed individuals) were included in the review. Qualitative analysis showed that among workers, occupational exposure to air pollution increased the risk of allergic and pulmonary diseases, whereas environmental exposure to PM increased heavy metal intake, the last of which was characterized by well-known carcinogenic effects. 4) Conclusion: The use of personal protective equipment, a meticulous health surveillance program and specific environmental protection policies are needed to protect public health from damages due to air pollution.

Spatio-temporal variation in chemical characteristics of PM10 over Indo Gangetic Plain of India

The paper presents the spatio-temporal variation of chemical compositions (organic carbon (OC), elemental carbon (EC), and water-soluble inorganic ionic components (WSIC)) of particulate matter (PM10) over three locations (Delhi, Varanasi, and Kolkata) of Indo Gangetic Plain (IGP) of India for the year 2011. The observational sites are chosen to represent the characteristics of upper (Delhi), middle (Varanasi), and lower (Kolkata) IGP regions as converse to earlier single-station observation. Average mass concentration of PM10 was observed higher in the middle IGP (Varanasi 206.2 ± 77.4 μg m(-3)) as compared to upper IGP (Delhi 202.3 ± 74.3 μg m(-3)) and lower IGP (Kolkata 171.5 ± 38.5 μg m(-3)). Large variation in OC values from 23.57 μg m(-3) (Delhi) to 12.74 μg m(-3) (Kolkata) indicating role of formation of secondary aerosols, whereas EC have not shown much variation with maximum concentration over Delhi (10.07 μg m(-3)) and minimum over Varanasi (7.72 μg m(-3)). As expected, a strong seasonal variation was observed in the mass concentration of PM10 as well as in its chemical composition over the three locations. Principal component analysis (PCA) identifies the contribution of secondary aerosol, biomass burning, fossil fuel combustion, vehicular emission, and sea salt to PM10 mass concentration at the observational sites of IGP, India. Backward trajectory analysis indicated the influence of continental type aerosols being transported from the Bay of Bengal, Pakistan, Afghanistan, Rajasthan, Gujarat, and surrounding areas to IGP region.

Source Apportionment of PM2.5 in Delhi, India Using PMF Model

Chemical characterization of PM2.5 [organic carbon, elemental carbon, water soluble inorganic ionic components, and major and trace elements] was carried out for a source apportionment study of PM2.5 at an urban site of Delhi, India from January, 2013, to December, 2014. The annual average mass concentration of PM2.5 was 122 ± 94.1 µg m(-3). Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon. A receptor model, positive matrix factorization (PMF) was applied for source apportionment of PM2.5 mass concentration. The PMF model resolved the major sources of PM2.5 as secondary aerosols (21.3 %), followed by soil dust (20.5 %), vehicle emissions (19.7 %), biomass burning (14.3 %), fossil fuel combustion (13.7 %), industrial emissions (6.2 %) and sea salt (4.3 %).

Components of Particle Emissions from Light-Duty Spark-Ignition Vehicles with Varying Aromatic Content and Octane Rating in Gasoline

Typical gasoline consists of varying concentrations of aromatic hydrocarbons and octane ratings. However, their impacts on particulate matter (PM) such as black carbon (BC) and water-soluble and insoluble particle compositions are not well-defined. This study tests seven 2012 model year vehicles, which include one port fuel injection (PFI) configured hybrid vehicle, one PFI vehicle, and six gasoline direct injection (GDI) vehicles. Each vehicle was driven on the Unified transient testing cycle (UC) using four different fuels. Three fuels had a constant octane rating of 87 with varied aromatic concentrations at 15%, 25%, and 35%. A fourth fuel with higher octane rating, 91, contained 35% aromatics. BC, PM mass, surface tension, and water-soluble organic mass (WSOM) fractions were measured. The water-insoluble mass (WIM) fraction of the vehicle emissions was estimated. Increasing fuel aromatic content increases BC emission factors (EFs) of transient cycles. BC concentrations were higher for the GDI vehicles than the PFI and hybrid vehicles, suggesting a potential climate impact for increased GDI vehicle production. Vehicle steady-state testing showed that the hygroscopicity of PM emissions at high speeds (70 mph; κ > 1) are much larger than emissions at low speeds (30 mph; κ < 0.1). Iso-paraffin content in the fuels was correlated to the decrease in WSOM emissions. Both aromatic content and vehicle speed increase the amount of hygroscopic material found in particle emissions.

Comparison of in vitro toxicity of mainstream cigarette smoke particulate matter from nano- to micro-size

In order to investigate the interrelationship between particulate matter (PM) size and in vitro toxicological effects of mainstream cigarette smoke, PM sized between 10 nm and 10 μm in mainstream cigarette smoke was sampled and divided into six stages. The in vitro cytotoxicity, genotoxicity and cell inhibition effects of PM were assessed by the neutral red cytotoxicity assay, Salmonella mutagenicity assay, micronucleus test and flow cytometry analysis, respectively. The results showed that all test samples were cytotoxic in the neutral red cytotoxicity assay. The IC50 values in the small-sized groups were significantly lower than those in the large-sized groups. Most test samples were mutagenic in the Salmonella mutagenicity assay (TA98 with S9 and TA100 with S9) and increased the frequency of micronucleated cells. Most PM disturbed the normal progression of the cell cycle, resulting in the accumulation of cells in the G0/G1 phase and the induction of apoptosis. In these tests, PM of a large size induced less toxicity compared with PM of a small size. These findings suggest that most PM samples induced toxicity in vitro, and PM of a small size was more toxic than PM of a large size.

Particle-size-dependent cytokine responses and cell damage induced by silica particles and macrophages-derived mediators in endothelial cell

Epidemiological evidence reports silica dust exposure has been associated with increased risk of cardiovascular diseases, but the mechanisms are largely unknown. In this study, endothelial cells were exposed to increasing concentrations of two sizes silica particles and the soluble mediators released by macrophages treated with the same particles for 24 h. Expression and release of cytokines (IL-1β, TNF-α and IL-6) were measured by using ELISA. Cytotoxicity was measured by MTT assay and LDH release. We show that both ways induced increases in cell toxicity and cytokines in a dose-dependent manner. For smaller particles, the soluble mediators are more capable of increasing cytokines compared with the effect of particles directly. For larger particles, evaluating results of these two ways are similar. Either way, smaller particles make the increasing action of cell toxicity and cytokines more remarkable. Our results indicate both silica particle and macrophage-derived mediators can induce endothelial cell injury and inflammation and demonstrate the potential importance of the particle sizes in this effect.

Reduced in vitro toxicity of fine particulate matter collected during the 2008 Summer Olympic Games in Beijing: the roles of chemical and biological components

Beijing has implemented systematic air pollution control legislation to reduce particulate emissions and improve air quality during the 2008 Summer Olympics, but whether the toxicity of fine fraction of particles (PM(2.5)) would be changed remains unclear. In present study we compared in vitro biological responses of PM(2.5) collected before and during the Olympics and tried to reveal possible correlations between its chemical components and toxicological mechanism(s). We measured cytotoxicity, cytokines/chemokines, and related gene expressions in murine alveolar macrophages, MH-S, after treated with 20 PM(2.5) samples. Significant, dose-dependent effects on cell viability, cytokine/chemokine release and mRNA expressions were observed. The cytotoxicity caused at equal mass concentration of PM(2.5) was notably reduced (p<0.05) by control measures, and significant association was found for viability and elemental zinc in PM(2.5). Endotoxin content in PM(2.5) correlated with all of the eight detected cytokines/chemokines; elemental and organic carbon correlated with four; arsenic and chromium correlated with six and three, respectively; iron and barium showed associations with two; nickel, magnesium, potassium, and calcium showed associations with one. PM(2.5) toxicity in Beijing was substantially dependent on its chemical components, and lowering the levels of specific components in PM(2.5) during the 2008 Olympics resulted in reduced biological responses.

Air quality impact and physicochemical aging of biomass burning aerosols during the 2007 San Diego wildfires

Intense wildfires burning >360000 acres in San Diego during October, 2007 provided a unique opportunity to study the impact of wildfires on local air quality and biomass burning aerosol (BBA) aging. The size-resolved mixing state of individual particles was measured in real-time with an aerosol time-of-flight mass spectrometer (ATOFMS) for 10 days after the fires commenced. Particle concentrations were high county-wide due to the wildfires; 84% of 120-400 nm particles by number were identified as BBA, with particles <400 nm contributing to mass concentrations dangerous to public health, up to 148 μg/m(3). Evidence of potassium salts heterogeneously reacting with inorganic acids was observed with continuous high temporal resolution for the first time. Ten distinct chemical types shown as BBA factors were identified through positive matrix factorization coupled to single particle analysis, including particles comprised of potassium chloride and organic nitrogen during the beginning of the wildfires, ammonium nitrate and amines after an increase of relative humidity, and sulfate dominated when the air mass back trajectories passed through the Los Angeles port region. Understanding BBA aging processes and quantifying the size-resolved mass and number concentrations are important in determining the overall impact of wildfires on air quality, health, and climate.

Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation

Background

The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources.

Methods

Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines).

Results

PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel vehicles (Dakar). Desert dust events seem to produce fewer biological impacts than anthropogenic sources.

Discussion

Our study shows that combustion sources contribute to the high toxicity of F and UF PM of African urban aerosols, and underlines the importance of emission mitigation and the imperative need to evaluate and to regulate particulate pollution in Africa.

A multi-cyclone sampling array for the collection of size-segregated occupational aerosols

In this study a serial multi-cyclone sampling array capable of simultaneously sampling particles of multiple size fractions, from an occupational environment, for use in in vivo and in vitro toxicity studies and physical/chemical characterization, was developed and tested. This method is an improvement over current methods used to size-segregate occupational aerosols for characterization, due to its simplicity and its ability to collect sufficient masses of nano- and ultrafine sized particles for analysis. This method was evaluated in a chamber providing a uniform atmosphere of dust concentrations using crystalline silica particles. The multi-cyclone sampling array was used to segregate crystalline silica particles into four size fractions, from a chamber concentration of 10 mg/m(3). The size distributions of the particles collected at each stage were confirmed, in the air, before and after each cyclone stage. Once collected, the particle size distribution of each size fraction was measured using light scattering techniques to further confirm the size distributions. As a final confirmation, scanning electron microscopy was used to collect images of each size fraction. The results presented here, using multiple measurement techniques, show that this multi-cyclone system was able to successfully collect distinct size-segregated particles at sufficient masses to perform toxicological evaluations and physical/chemical characterization.

Development of a repeated exposure protocol of human bronchial epithelium in vitro to study the long-term effects of atmospheric particles

Chronic exposure to atmospheric particles is suspected of exacerbating chronic inflammatory respiratory diseases but the underlying mechanisms remain poorly understood. An experimental strategy using human bronchial epithelial cells (NHBE) known to be one of the main target cells of particles in the lung was developed to investigate the long term effects of repeated exposure to particles. Primary cultures of NHBE cells were grown at an air-liquid interface and subjected to repeated treatments to particles. Fate of particles, pro inflammatory response and epithelial differentiation were studied during the 5 weeks following the final treatment. Ultrastructural observations revealed the biopersistence of particles in the bronchial epithelium. The expression of cytochrome P450 1A1, was transiently induced, suggesting that organic compounds could have been metabolized. The release of GM-CSF and IL-6 (biomarkers of pro-inflammatory response), was induced by particle treatments and was maintained up to 5weeks after treatments. The release of amphiregulin and TGFα (Growth Factor) was induced after each treatment. The number of cells expressing the mucin MUC5AC, a differentiation marker, was increased in particle-exposed epithelium. The experimental strategy we developed is suitable for investigating in greater depth the long term effects of particles on bronchial epithelial cells repeatedly exposed to atmospheric particles in vitro.

Role of size and composition of traffic and agricultural aerosols in the molecular responses triggered in airway epithelial cells

The increased levels of fine particles in the atmosphere are suspected of aggravating cardiopulmonary diseases, but the determinants of particle toxicity are poorly understood. This work aims at studying the role of composition and size in the toxicity of size-segregated particulate matter (PM) collected at different sites on human bronchial epithelial cells. PM were sampled at a traffic urban site (Urb S) and a rural site (Rur S) during the pesticide-spreading period. Ultrafine (UF), fine (F), and coarse (C) PM were characterized by their shape and chemical composition. Whatever the site, the finest PM (UF and F) induced the mRNA expression of CYP1A1, a biomarker of polyaromatic hydrocarbons (PAH) exposure, NQO-1 and heme HO-1, two antioxidant responsive element-driven genes; and two effect biomarkers, GM-CSF, a proinflammatory cytokine and amphiregulin (AR), a growth factor. C PM have a low or no effect. Interestingly, AR is more strongly induced by rural PM at the same mass exposure. These discrepancies suggest involvement of PM chemical composition: rural PM bearing the characteristics of aged aerosols with a high content of water-soluble components, and PM at urban kerbside sites containing mainly water-insoluble components. To conclude, we provide evidence that the finest PM fractions, whatever their origin, are more prone to induce exposure and effect biomarkers. The AR differential expression suggests a source-dependent effect requiring further investigation because of the role of this growth factor in airway remodeling, a characteristic feature of chronic lung respiratory diseases exacerbated by particulate pollution.

In vitro toxicity of particulate matter (PM) collected at different sites in the Netherlands is associated with PM composition, size fraction and oxidative potential--the RAPTES project

Background

Ambient particulate matter (PM) exposure is associated with respiratory and cardiovascular morbidity and mortality. To what extent such effects are different for PM obtained from different sources or locations is still unclear. This study investigated the in vitro toxicity of ambient PM collected at different sites in the Netherlands in relation to PM composition and oxidative potential.

Method

PM was sampled at eight sites: three traffic sites, an underground train station, as well as a harbor, farm, steelworks, and urban background location. Coarse (2.5-10 μm), fine (< 2.5 μm) and quasi ultrafine PM (qUF; < 0.18 μm) were sampled at each site. Murine macrophages (RAW 264.7 cells) were exposed to increasing concentrations of PM from these sites (6.25-12.5-25-50-100 μg/ml; corresponding to 3.68-58.8 μg/cm²). Following overnight incubation, MTT-reduction activity (a measure of metabolic activity) and the release of pro-inflammatory markers (Tumor Necrosis Factor-alpha, TNF-α; Interleukin-6, IL-6; Macrophage Inflammatory Protein-2, MIP-2) were measured. The oxidative potential and the endotoxin content of each PM sample were determined in a DTT- and LAL-assay respectively. Multiple linear regression was used to assess the relationship between the cellular responses and PM characteristics: concentration, site, size fraction, oxidative potential and endotoxin content.

Results

Most PM samples induced a concentration-dependent decrease in MTT-reduction activity and an increase in pro-inflammatory markers with the exception of the urban background and stop & go traffic samples. Fine and qUF samples of traffic locations, characterized by a high concentration of elemental and organic carbon, induced the highest pro-inflammatory activity. The pro-inflammatory response to coarse samples was associated with the endotoxin level, which was found to increase dramatically during a three-day sample concentration procedure in the laboratory. The underground samples, characterized by a high content of transition metals, showed the largest decrease in MTT-reduction activity. PM size fraction was not related to MTT-reduction activity, whereas there was a statistically significant difference in pro-inflammatory activity between Fine and qUF PM. Furthermore, there was a statistically significant negative association between PM oxidative potential and MTT-reduction activity.

Conclusion

The response of RAW264.7 cells to ambient PM was markedly different using samples collected at various sites in the Netherlands that differed in their local PM emission sources. Our results are in support of other investigations showing that the chemical composition as well as oxidative potential are determinants of PM induced toxicity in vitro.