Urban Fine Particles Research Articles

Tire Wear Chemicals in the Urban Atmosphere: Significant Contributions of Tire Wear Particles to PM2.5.

Tire wear particles (TWPs) containing tire wear chemicals (TWCs) are of global concern due to their large emissions and potential toxicity. However, TWP contributions to urban fine particles are poorly understood. Here, 72 paired gas-phase and PM2.5 samples were collected in the urban air of the Pearl River Delta, China. The concentrations of 54 compounds were determined, and 28 TWCs were detected with total concentrations of 3130-317,000 pg/m3. Most p-phenylenediamines (PPDs) were unstable in solvent, likely leading to their low detection rates. The TWCs were mainly (73 ± 26%) in the gas phase. 2-OH-benzothiazole contributed 82 ± 21% of the gas-phase TWCs and benzothiazole-2-sulfonic acid contributed 74 ± 18% of the TWCs in PM2.5. Guangzhou and Foshan were "hotspots" for atmospheric TWCs. Most TWC concentrations significantly correlated with the road length nearby. More particulate TWCs were observed than model predictions, probably due to the impacts of nonexchangeable portion and sampling artifacts. Source apportionment combined with characteristic molecular markers indicated that TWPs contributed 13 ± 7% of urban PM2.5. Our study demonstrates that TWPs are important contributors to urban air pollution that could pose risks to humans. There is an urgent need to develop strategies to decrease TWP emissions, along with broader urban air quality improvement strategies.

Impact of environmental pollution on the retrieval of hourly aerosol products from Advanced Himawari Imager (AHI) over Beijing

Advanced Himawari Imager (AHI) aboard Himawari-8 provides hourly Aerosol Optical Thickness (AOT) products, widely used to assimilation models and ground-level particulate matter (PM) concentration retrievals. However, the performance of AHI AOT products remains unclear under different air quality conditions. In this study, we evaluate the performance of the AHI hourly AOT products with ground-based AOT observations from four Aerosol Robotic NETwork (AERONET) sites for 2018 over Beijing under different pollution levels and aerosol types. Near-surface PM concentrations are used to categorize air quality as clean, moderate, and heavy pollution, and the aerosol types (biomass burning and urban/industrial (BMA_UIA), maritime (MA), dust (DA), mixed-type (MIXA)) are classified based on the threshold limits of AERONET aerosol properties. Overall, the AHI hourly AOT achieves good consistency with AERONET measurements in Beijing (correlation coefficient (R) = 0.78 and a root-mean-square-error (RMSE) = 0.29). Under clean conditions, the AOT successful retrieval rate is more than 80%, while it is deficient for moderate and heavy pollution. AOT for clean and moderate pollution performs better than that for heavy pollution. Moreover, AHI AOT retrievals for fine mode aerosol (BMA_UIA) are in good agreement with AERONET observations, and the performance is better than that under coarse mode aerosol (MA and DA) conditions. AHI AOT may capture the spatiotemporal distribution of fine particles pollution over Beijing. These findings will provide useful information for the improvement of the aerosol model of the retrieval algorithm and the monitoring of urban fine particles pollution.

Improved pollution forecasting hybrid algorithms based on the ensemble method

• The proposed model realizes the accurate multi-step forecasting for urban fine particle concentration. • The empirical wavelet transform and Stacking ensemble methods improve the accuracy of the proposed model. • The Hampel identifier and outlier robust extreme learning machine are used to realize the robustness of the forecasting. • The inverse empirical wavelet transform reconstruction solves the over-fitting problem of the forecasting. In a new fine particle concentrations forecasting model, the Hampel identifier outlier correction preprocessing detects and corrects the outliers in the original series. Empirical wavelet transform method decomposes the corrected series into a set of subseries adaptively, and each subseries are used to train the Stacking ensemble method. In the Stacking ensemble forecasting method, the outlier robust extreme learning machine meta-learner combines different Elman neural network base learners and outputs the forecasting results of different subseries. Different forecasting subseries are combined and then reconstructed by inverse empirical wavelet transform reconstruction method to get the final forecasting fine particle concentrations results. It has been proved in the study that the model proposed in the study has better accuracy and wide applicability comparing to the existing models.

THE INFLUENCE OF LEVELS OF DETAIL (LOD0-2) AND BUFFER SIZES ON PARAMETER EFFECTIVENESS FOR FINE DUST DISTRIBUTION MODELLING

Abstract. Building models represented in CityGML Level of Detail 0 to 2 were used to calculate urban morphological parameters to test their effectiveness of correlation with measured total number concentration of fine dust in Berlin. Land use regression modelling as an alternative to physical based models explains the distribution of urban fine and ultrafine particles applying a multi linear regression model. Descriptive parameters are identified by high correlations with measured fine dust values. Here, different height information and geometry representations from LoD0-LoD2 were used to calculate six parameters associated with the ventilation and advection capacity of an urban environment (‘averaged heights of buildings’, ‘height-width ratio’, ‘porosity’, ‘frontal area index’, and ‘building surfaces’ for wall surfaces and for wall and roof surfaces). Parameters were correlated with measurements of the total number concentration of fine dust in the city of Berlin. Initial results show ambivalent correlations for both, different buffer sizes and implementation of the parameters with building representations in different levels of detail.

Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation

AbstractAmmonium sulfate (AS) and ammonium nitrate (AN) are key components of urban fine particles. Both field and model studies showed that heterogeneous reactions of SO2, NO2, and NH3 on wet aerosols accelerated the haze formation in northern China. However, little is known on phase transitions of AS‐AN containing haze particles. Here hygroscopic properties of laboratory‐generated AS‐AN particles and individual particles collected during haze events in an urban site were investigated using an individual particle hygroscopicity system. AS‐AN particles showed a two‐stage deliquescence at mutual deliquescence relative humidity (MDRH) and full deliquescence relative humidity (DRH) and three physical states: solid before MDRH, solid‐aqueous between MDRH and DRH, and aqueous after DRH. During hydration, urban haze particles displayed a solid core and aqueous shell at RH = 60–80% and aqueous phase at RH > 80%. Most particles were in aqueous phase at RH > 50% during dehydration. Our results show that AS content in individual particles determines their DRH and AN content determines their MDRH. AN content increase can reduce MDRH, which indicates occurrence of aqueous shell at lower RH. The humidity‐dependent phase transitions of nitrate‐abundant urban particles are important to provide reactive surfaces of secondary aerosol formation in the polluted air.

Inhibition of inflammatory responses elicited by urban fine dust particles in keratinocytes and macrophages by diphlorethohydroxycarmalol isolated from a brown alga Ishige okamurae

Inhibition of inflammatory responses elicited by urban fine dust particles in keratinocytes and macrophages by diphlorethohydroxycarmalol isolated from a brown alga Ishige okamurae

Neurodevelopmental Deceleration by Urban Fine Particles from Different Emission Sources: A Longitudinal Observational Study.

Background:A few studies have reported associations between traffic-related air pollution exposure at schools and cognitive development. The role of PM components or sources other than traffic on cognitive development has been little explored.Objectives:We aimed to explore the role of PM sources in school air on cognitive development.Methods:A cohort of 2,618 schoolchildren (average age, 8.5 years) belonging to 39 schools in Barcelona (Spain) was followed up for a year. Children completed computerized tests assessing working memory, superior working memory, and inattentiveness during four visits. Particulate matter ≤ 2.5 μm (PM2.5) was measured during two 1-week campaigns in each school, both outdoors and in the classroom. Source apportionment resulted in nine sources: mineral, organic/textile/chalk, traffic, secondary sulfate and organics, secondary nitrate, road dust, metallurgy, sea spray, and heavy oil combustion. Differences in cognitive growth trajectories were assessed with mixed models with age-by-source interaction terms.Results:An interquartile range increase in indoor traffic-related PM2.5 was associated with reductions in cognitive growth equivalent to 22% (95% CI: 2%, 42%) of the annual change in working memory, 30% (95% CI: 6%, 54%) of the annual change in superior working memory, and 11% (95% CI: 0%, 22%) of the annual change in the inattentiveness scale. None of the other PM2.5 sources was associated with adverse effects on cognitive development.Conclusions:Traffic was the only source of fine particles associated with a reduction in cognitive development. Reducing air pollution from traffic at primary schools may result in beneficial effects on cognition.Citation:Basagaña X, Esnaola M, Rivas I, Amato F, Alvarez-Pedrerol M, Forns J, López-Vicente M, Pujol J, Nieuwenhuijsen M, Querol X, Sunyer J. 2016. Neurodevelopmental deceleration by urban fine particles from different emission sources: a longitudinal observational study. Environ Health Perspect 124:1630–1636; http://dx.doi.org/10.1289/EHP209

Increasing impact of urban fine particles (PM2.5) on areas surrounding Chinese cities.

The negative impacts of rapid urbanization in developing countries have led to a deterioration in urban air quality, which brings increasing negative impact to its surrounding areas (e.g. in China). However, to date there has been rare quantitative estimation of the urban air pollution to its surrounding areas in China.We thus evaluated the impact of air pollution on the surrounding environment under rapid urbanization in Chinese prefectures during 1999 – 2011. We found that: (1) the urban environment generated increasing negative impact on the surrounding areas, and the PM2.5 concentration difference between urban and rural areas was particularly high in large cities. (2) Nearly half of the Chinese prefectures (156 out of 350) showed increased impact of urban PM2.5 pollution on its surrounding areas. Those prefectures were mainly located along two belts: one from northeast China to Sichuan province, the other from Shanghai to Guangxi province. Our study demonstrates the deterioration in urban air quality and its potential impacts on its surrounding areas in China. We hope that the results presented here will encourage different approaches to urbanization to mitigate the negative impact caused by urban air pollution, both in China and other rapidly developing countries.

Source apportionment of urban fine particle number concentration during summertime in Beijing

Continuous particle number size distributions (15 nm–2.5 μm), particle chemical compositions, gaseous species and meteorological variables were collected at an urban site in Beijing to investigate the source apportionment of ambient fine particle number concentrations. Hourly data sets were analyzed using the positive matrix factorisation (PMF) which identified a total of eight factors: two traffic factors, two combustion factors, secondary nitrate factors, secondary sulfate + secondary organic aerosol (SOA), fugitive dust and regionally transported aerosol. Traffic (47.9%) and combustion (29.7%) aerosol were found to dominate the particle number concentrations, whereas the most important sources for particle volume concentrations were found to be regionally transported aerosol (30.9%) and combustions (30.1%). Although the diurnal pattern of each of the two traffic factors closely followed traffic rush hour for Beijing, their size modes were different suggesting that these factors might represent local and remote emissions. Biomass burning and coal-fired power plant aerosol were distinguished according to their size modes and chemical species associated with them. Secondary compounds showed similar bimodal particle number size distribution, the distinct diurnal pattern distinguished these factors as secondary nitrate and mixed source of secondary sulfate and SOA. Regionally transported material was characterized by accumulation mode particles. Overall, the introduction of combinations of particle number size distributions and chemical composition data in PMF model is successful at separating the components and quantifying relative contributions to the particle number and volume size distributions in the complex urban atmosphere.

Impact of Gobi desert dust on aerosol chemistry of Xi'an, inland China during spring 2009: differences in composition and size distribution between the urban ground surface and the mountain atmosphere

Abstract. Composition and size distribution of atmospheric aerosols from Xi'an city (~400 m, altitude) in inland China during the spring of 2009 including a massive dust event on 24 April were measured and compared with a parallel measurement at the summit (2060 m, altitude) of Mt. Hua, an alpine site nearby Xi'an. EC (elemental carbon), OC (organic carbon) and major ions in the city were 2–22 times higher than those on the mountaintop during the whole sampling period. Compared to that in the non-dust period a sharp increase in OC was observed at both sites during the dust period, which was mainly caused by an input of biogenic organics from the Gobi desert. However, adsorption/heterogeneous reaction of gaseous organics with dust was another important source of OC in the urban, contributing 22% of OC in the dust event. In contrast to the mountain atmosphere where fine particles were less acidic when dust was present, the urban fine particles became more acidic in the dust event than in the non-dust event, mainly due to enhanced heterogeneous formation of nitrate and diluted NH3. Cl− and NO3− in the urban air during the dust event significantly shifted toward coarse particles. Such redistributions were further pronounced on the mountaintop when dust was present, resulting in both ions almost entirely staying in coarse particles. On the contrary, no significant spatial difference in size distribution of SO42− was found between the urban ground surface and the mountain atmosphere, which dominated in the fine mode (<2.1 μm) during the nonevent and comparably distributed in the fine (<2.1 μm) and coarse (>2.1 μm) modes during the dust event.

Acute health effects of urban fine and ultrafine particles on children with atopic dermatitis

Although ambient particulate pollutants have been shown to exacerbate existing allergic symptoms of mucous membranes including rhinitis and asthma, the effects on skin such as atopic dermatitis in childhood deserve further study. We investigated the effects of urban particulate pollutants including ultrafine particles on atopic severity in children with atopic dermatitis. We included 41 schoolchildren, 8–12 years old, who had been diagnosed with atopic dermatitis. For 67 consecutive days, all of them measured their symptoms in a diary. To assess exposure, the daily ambient mass concentrations of particulate matter less than 10, 2.5 and 1 μm (PM 10, PM 2.5 and PM 1, respectively) and concentrations of submicron particles (0.01–1 μm) were measured at a local school. The mean mass concentrations of PM 10, PM 2.5 and PM 1 were 74.0, 57.8 and 50.8 μg/m 3, respectively. The mean concentrations were 41,335/cm 3 ultrafine particles (UFPs) and 8577/cm 3 accumulation mode (0.1–1 μm) particles. Significant associations were found between the concentrations of ultrafine particles and the itchiness symptom in children with atopic dermatitis. An interquartile range (IQR) increase in previous day ultrafine particles concentration (IQR: 28–140/m 3) was significantly associated with a 3.1% (95% confidence interval, 0.2–6.1) increase in the itch symptom score for children with atopic dermatitis. The results suggested that the concentration of ambient ultrafine particles may exacerbate skin symptoms in children with atopic dermatitis.

Oxidative stress induced by urban fine particles in cultured EA.hy926 cells

It has been reported that vascular endothelia cell damage is an important precursor to the morbidity and mortality associated with cardiovascular disease exposed to airborne particulate matter (PM). The present study investigated the hypothesis that urban fine (PM(2.5)) particles could cause cytotoxicity via oxidative stress in human umbilical vein endothelial cells, EA.hy926. The concentrations of metal elements (Cr, Fe, Ni, Cu, Zn, Mo, Cd and Pb) in PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) were determined by inductively coupled plasma - mass spectrometry (ICP-MS). Iron (Fe), Zn and Pb were highly enriched in all the samples. Exposure of the cultured EA.hy926 cells to PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) led to cell death, reactive oxygen species (ROS) increase, mitochondrial transmembrane potential (ΔΨm) disruption and NF-κB activation, respectively. The ROS increase by exposure to PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) triggered the activation of nuclear factor (NF)-κB, which means that PM(2.5) particles exert cytotoxicity by an apopotic process. However, the induction of cytotoxicity by PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) was reversed by pretreatment with superoxide dismutase (SOD). These results suggest that each fraction of PM(2.5) has a potency to cause oxidative stress in endothelial cells. ROS was generated through PM(2.5)-mediated mitochondrial apoptotic pathway, which may induce direct interaction between metal elements and endothelia cells.

Source apportionment of urban fine and ultra-fine particle number concentration in a Western Mediterranean city

Extensive measurements on particle number concentration and size distribution (13–800 nm), together with detailed chemical composition of PM 2.5 have constituted the main inputs of the database used for a source apportionment analysis. Data were collected at an urban background site in Barcelona, Western Mediterranean. The source identification analysis helped us to distinguish five emission sources (vehicle exhausts, mineral dust, sea spray, industrial source and fuel-oil combustion) and two atmospheric processes (photochemical induced nucleation and regional/urban background particles derived from coagulation and condensation processes). After that, a multilinear regression analysis was applied in order to quantify the contribution of each factor. This study reveals that vehicle exhausts contribute dominantly to the number concentration in all the particle sizes (52–86%), but especially in the range 30–200 nm. This work also points out the importance of the regional and/or urban formed aerosols (secondary inorganic particles) on the total number concentration (around 25% of the total number), with a higher impact on the accumulation mode. The photo-chemically induced nucleation of aerosols only represents a small proportion of the total number as an annual mean (3%), but is very relevant when considering only the nucleation mode (13–20 nm) fraction (23%). The other sources recognized registered sporadic contributions to the total number, coinciding with specific meteorological scenarios. This study discloses the main sources and features affecting and controlling the fine and ultra-fine aerosols in a typical city in the Western Mediterranean coast. Whereas the road traffic appears to be the most important source of sub-micrometric aerosols, other sources may not be negligible under specific meteorological conditions.

Exposition aux particules atmosphériques fines et développement des maladies allergiques de l’enfant. Résultats épidémiologiques issus de l’étude des six villes (ISAAC-2 France)

To evaluate whether fine air particles could be involved in the occurrence of atopy and allergic diseases, we performed a cross-sectional epidemiological survey involving primary schoolchildren living in six French towns with contrasted air pollution levels. Air pollution was measured during a week in the schoolyards and by standard air monitoring networks. Children get an examination in school looking for atopic dermatitis and bronchial hyperresponsiveness assessed by a standardized run test. Besides, parents or guardians provided past medical history and environmental data, especially on passive smoking. Overall, 5,338 children, aged 10.4 (±0.7) years, coming from 108 different schools and 401 different classes were included in the survey. Taking into account potential confounders, high exposure to proximity PM 2.5 was linked to a higher point prevalence of atopic dermatitis and hyperresponsiveness, to a higher cumulative prevalence of allergic asthma and a higher sensitization rate to common indoor allergens. Thus, these data suggest that chronic exposure to urban fine particles could be a risk factor for atopy, hyperresponsiveness and asthma.

Fine particle concentrations in buses and taxis in Florence, Italy

On October 2004, a sampling survey was carried out in Florence to estimate urban fine particle exposure concentrations inside commuting vehicles during workdays characterized by heavy traffic. Portable samplers were positioned inside four regularly scheduled diesel-powered buses and four taxis during eight weekdays. Each sampler consisted of a 2.5 μm size pre-separator cyclone, a direct-reading data logging photometer (pDR-1200), and a 4 L min −1 filter sampler for the determination of PM 2.5 mass concentration. Based on reflectance analysis measurements, a PM 2.5 Black Smoke Index was determined for each filter, and the elemental composition of the PM 2.5 was analyzed by Particle Induced X-ray Emission (PIXE). PM 2.5 mass concentrations inside the vehicles correlated well with the urban ambient air PM 2.5 concentrations measured at the fixed-site monitoring stations. The PM 2.5 excess above the urban ambient level was on average 32 μg m − 3 (range: 22–52 μg m − 3) and 20 μg m − 3 (range: 11–29 μg m − 3) in buses and taxis, respectively. The PM 2.5-bound sulfur concentration was also higher in the buses than in the taxis. Based on daily Time-Microenvironment-Activity-Diary (TMAD) data, the Florentines spend on average 9.7% of their day in traffic, and the corresponding average exposure is approximately 12% of their daily PM 2.5 personal exposure. The obtained data could be used to plan interventions to minimize the PM 2.5 citizen exposures in commuting.

Induction of oxidative stress and inhibition of plasminogen activator inhibitor-1 production in endothelial cells following exposure to organic extracts of diesel exhaust particles and urban fine particles

Endothelial cells play important roles in anticoagulant and fibrinolytic systems. Recent studies suggest that increases in ambient particulate matter (PM) levels have been associated with an increase in mortality rate from cardiovascular diseases. We examined the production of heme oxygenase-1 (HO-1) and factors related to the fibrinolytic function by rat heart microvessel endothelial cells exposed to organic extracts of diesel exhaust particles (OE-DEP) and urban fine particles (OE-UFP) to investigate the direct effects of these soluble organic fractions in these PM on the fibrinolytic function of endothelial cells. The cell monolayer exposed to 10 microg/ml OE-DEP produced a larger amount of HO-1 than cells exposed to 10 microg/ml OE-UFP. OE-DEP and OE-UFP exposure reduced plasminogen activator inhibitor-1 (PAI-1) production by the cells but did not affect the production of thrombomodulin, tissue-type plasminogen activator, or urokinase-type plasminogen activator. Increased PAI-1 synthesis in response to treatment with 1.0 ng/ml tumor necrosis factor-alpha or 0.5 ng/ml transforming growth factor-beta1 was reduced by OE-DEP exposure. Suppression of PAI-1 production by OE-DEP exposure was mediated through oxidative stress and was independent of HO-1 activity. These results suggest that exposure to the soluble organic fraction of PM and DEP induced oxidative stress and reduced the PAI-1 production of endothelial cells.

Respiratory Responses to Exposures With Fine Particulates and Nitrogen Dioxide in the Elderly With and Without COPD

Elderly people, with and without chronic obstructive pulmonary disease (COPD), may be susceptible to particulate matter (PM) air pollution. However, the respiratory impacts of inhaled PM combined with copollutant(s) in controlled exposure studies are unclear and warrant investigation since exposures to PM–gas mixtures constitute realistic scenarios. Thus, we exposed 6 healthy subjects and 18 volunteers with COPD (mean age 71 yr) on separate days to (a) filtered air (FA); (b) 0.4 ppm NO2; (c) concentrated ambient particles (CAP), predominantly in the fine (PM2.5) size range, at concentrations near 200 μg/m3; and (d) CAP and NO2 together. Each 2-h exposure included exercise for 15 min every half hour. Most respiratory responses, including symptoms, spirometry, and total and differential counts of induced sputum cells, showed no statistically significant responses attributable to separate or combined effects of CAP and NO2. However, maximal mid-expiratory flow and arterial O2 saturation (measured by pulse oximetry) showed small but statistically significant decrements associated with CAP, greater in healthy than COPD subjects. CAP exposure was also associated with decreased percentages of columnar epithelial cells in sputum. The results suggest that the respiratory effect of the PM–NO2 mixture may be primarily PM driven since coexposure to NO2 did not significantly enhance the responses. In conclusion, older adults exposed to urban fine particles may experience acute small-airways dysfunction with impaired gas exchange. Healthy subjects appear more susceptible, suggesting that the respiratory effect may be related to efficient penetration and deposition of inhaled toxic particles in distal small airways. More clinical investigation of the elderly population is warranted.

Sources and elemental composition of ambient PM 2.5 in three European cities

Source apportionment of urban fine particle mass (PM 2.5) was performed from data collected during 1998–1999 in Amsterdam (The Netherlands), Erfurt (Germany) and Helsinki (Finland), using principal component analysis (PCA) and multiple linear regression. Six source categories of PM 2.5 were identified in Amsterdam. They were traffic-related particles (30% of the average PM 2.5), secondary particles (34%), crustal material (7%), oil combustion (11%), industrial and incineration processes (9%), and sea salt (2%). The unidentified PM 2.5 fraction was 7% on the average. In Erfurt, four source categories were extracted with some difficulties in interpretation of source profiles. They were combustion emissions related to traffic (32%), secondary PM (32%), crustal material (21%) and industrial processes (8%). In Erfurt, 3% of PM 2.5 remained unidentified. Air pollution data and source apportionment results from the two Central European cities were compared to previously published results from Helsinki, where about 80% of average PM 2.5 was attributed to transboundary air pollution and particles from traffic and other regional combustion sources. Our results indicate that secondary particles and local combustion processes (mainly traffic) were the most important source categories in all cities; their impact on the average PM 2.5 was almost equal in Amsterdam and Erfurt whereas, in Helsinki, secondary particles made up for as much as half of the total average PM 2.5.

Urban PM2.5 Surface Chemistry and Interactions with Bronchoalveolar Lavage Fluid

This study investigated the surface chemistry of urban fine particles (PM2.5), and quantified the adsorbed and desorbed species after exposure to bronchoalveolar lavage fluid (BALF). Urban background and roadside PM2.5 samples of different mass concentration and total weight were collected in triplicate in the South Bronx region of New York City. Simultaneously, the concentrations of other atmospheric pollutants (CO, NOx, SO2, O3, elemental carbon) were measured, and weather conditions were recorded. The collected PM2.5 samples underwent one of three treatments: no treatment, treatment in vitro with BALF, or treatment in a saline solution (control). The surfaces of untreated, saline-treated, and BALF-treated PM2.5 samples were analyzed using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). These results were then compared with ambient air pollutant concentrations, weather variables, selected BALF characteristics, and results from a previous London study conducted using identical preparation methods by XPS analysis only. Both XPS and ToF-SIMS detected PM2.5 surface species and observed changes in surface concentrations after treatment. XPS analysis showed the surface of untreated urban PM2.5 consisted of 79 to 87% carbon and 10 to 16% oxygen with smaller contributions of N, S, Si, and P in the samples from both background and roadside locations. A wider variety of other inorganic and organic species (including metals, aliphatic and aromatic hydrocarbons, and nitrogen-containing molecules) was detected with ToF-SIMS. Surface characteristics of particles from the roadside and background sites were very similar, except for higher (p <. 05) nitrate concentrations at the roadside, which were attributable to higher roadside NOx concentrations. Comparable species and quantities were identified in a previous study of London PM2.5, where PM2.5 surface chemistry differed considerably depending on the source, particularly in surface concentrations of oxygen and trace species. After treatment with BALF the N-C signal detected by XPS analysis increased in the average by 372 ± 203%, indicating significant surface adsorption of protein or other N-containing biomolecules. Lower (nonsignificant) N-C signals were observed for smoker BALF, compared to nonsmoker BALF. ToF-SIMS data confirmed protein adsorption after BALF treatment—smoker BALF resulted in lower levels of adsorbed proteins compared to nonsmoker BALF. ToF-SIMS also indicated an adsorption of phospholipid on the treated PM2.5 surfaces. The primary phospholipid in BALF is dipalmitoylphospatidylcholine (DPPC), although positive identification was not possible due to low concentrations at the PM2.5 surface. Oxygen content of PM2.5 surfaces was the most significant determinant of both N-C and phospholipid adsorption. The XPS signal of the soluble species NH4+, NO32 −, Si, and S decreased in both saline- and BALF-treated samples, showing that these species may be bioavailable in the lung. Similarly, ToF-SIMS analysis suggests the bioavailability of Na+ and Al+ as well as NH4+ and Si+.

Oxidative-stress potency of organic extracts of diesel exhaust and urban fine particles in rat heart microvessel endothelial cells

Exposure to fine particulate materials is associated with an increase in mortality rate of cardiovascular diseases. Particles deposited in the lung may affect the vascular system both directly (leaching of soluble components from particles) and indirectly (via cytokines and mediators). The present study addressed cytotoxicity and oxidative stress potency of organic extracts of diesel exhaust particles (OE-DEP) and urban fine particles (OE-UFP) in rat heart microvessel endothelial (RHMVE) cells. The LC 50 values of OE-DEP and OE-UFP were calculated to be 17 and 34 μg/ml, respectively, suggesting that OE-DEP was more cytotoxic than OE-UFP. The viability of OE-DEP- and OE-UFP-exposed cells was ameliorated by N-acetyl- l-cysteine (NAC). The cell monolayer was exposed to 0 (control), 1, 3, and 10 μg/ml OE-DEP for 6 h and mRNA levels of antioxidant enzymes such as heme oxygenase-1 (HO-1), thioredoxin peroxidase 2 (TRPO), glutathione S-transferase P subunit (GST-P), and NADPH dehydrogenase (NADPHD) were quantitated by northern analysis. All those mRNA levels increased dose-dependently with OE-DEP and HO-1 mRNA showed the most marked response to OE-DEP. mRNA levels of those antioxidant enzymes and heat shock protein 72 (HSP72) in OE-DEP-exposed cells were higher than those of OE-UFP-exposed cells as compared at the same concentration. The transcription levels of HO-1 and HSP72 in OE-DEP- and OE-UFP-exposed cells were also reduced by NAC. Those results suggest that the organic fraction of particulate materials in the urban air has a potency to cause oxidative stress to endothelial cells and may be implicated in cardiovascular diseases through functional changes of endothelial cells.