Ambient Particulate Air Research Articles

Applications of the comet assay in particle toxicology: air pollution and engineered nanomaterials exposure.

Exposure to ambient air particles is associated with elevated levels of DNA strand breaks (SBs) and endonuclease III, formamidopyrimidine DNA glycosylase (FPG) and oxoguanine DNA glycosylase-sensitive sites in cell cultures, animals and humans. In both animals and cell cultures, increases in SB and in oxidatively damaged DNA are seen after exposure to a range of engineered nanomaterials (ENMs), including carbon black, carbon nanotubes, fullerene C60, ZnO, silver and gold. Exposure to TiO2 has generated mixed data with regard to SB and oxidatively damaged DNA in cell cultures. Nanosilica does not seem to be associated with generation of FPG-sensitive sites in cell cultures, while large differences in SB generation between studies have been noted. Single-dose airway exposure to nanosized carbon black and multi-walled carbon nanotubes in animal models seems to be associated with elevated DNA damage levels in lung tissue in comparison to similar exposure to TiO2 and fullerene C60. Oral exposure has been associated with augmented DNA damage levels in cells of internal organs, although the doses have been typically very high. Intraveneous and intraperitoneal injection of ENMs have shown contradictory results dependent on the type of ENM and dose in each set of experiments. In conclusion, the exposure to both combustion-derived particles and ENMs is associated with increased levels of DNA damage in the comet assay. Particle size, composition and crystal structure of ENM are considered important determinants of toxicity, whereas their combined contributions to genotoxicity in the comet assay are yet to be thoroughly investigated.

Analysis of gene expression changes in A549 cells induced by organic compounds from respirable air particles

A number of toxic effects of respirable ambient air particles (genotoxic effects, inflammation, oxidative damage) have been attributed to organic compounds bound onto the particle surface. In this study, we analyzed global gene expression changes caused by the extractable organic matters (EOMs) from respirable airborne particles <2.5μm (PM2.5), collected at 3 localities from heavily polluted areas of the Czech Republic and a control locality with low pollution levels, in human lung epithelial A549 cells.Although the sampled localities differed in both extent and sources of air pollution, EOMs did not induce substantially different gene expression profiles. The number of transcripts deregulated in A549 cells treated with the lowest EOM concentration (10μg/ml) ranged from 65 to 85 in 4 sampling localities compared to the number of transcripts deregulated after 30μg/ml and 60μg/ml of EOMs, which ranged from 90 to 109, and from 149 to 452, respectively. We found numerous commonly deregulated genes and pathways related to activation of the aryl hydrocarbon receptor (AhR) and metabolism of xenobiotics and endogenous compounds. We further identified deregulation of expression of the genes involved in pro-inflammatory processes, oxidative stress response and in cancer and developmental pathways, such as TGF-β and Wnt signaling pathways. No cell cycle arrest, DNA repair or pro-apoptotic responses were identified at the transcriptional level after the treatment of A549 cells with EOMs.In conclusion, numerous processes and pathways deregulated in response to EOMs suggest a significant role of activated AhR. Interestingly, we did not observe substantial gene expression changes related to DNA damage response, possibly due to the antagonistic effect of non-genotoxic EOM components. Moreover, a comparison of EOM effects with other available data on modulation of global gene expression suggests possible overlap among the effects of PM2.5, EOMs and various types of AhR agonists.

A Prospective Study of Atherosclerosis, Clinical Cardiovascular Disease, and Long-Term Exposure to Ambient Particulate Matter and Other Air Pollutants in a Multi-Ethnic Cohort (MESA Air)

Background/Aims: ‘MESA Air’ is a multi-center prospective cohort study of air pollution and cardiovascular disease (CVD) launched in 2004, combining state-of-the-art cardiovascular outcome measurem...

Ambient Air Particulates Bound Mercury Hg(p) Study Among Four Crops (Rice, White Cabbage, Arden Lettuce, and Gynura) at a Characteristic Sampling Site

The main purpose of this study was to monitor ambient air particulates and particulate-bound Hg (Hg[p]) compositions in different crops in the coastal zone in the Taichung, Taiwan, area at a sampling site during 2013 October to 2013 December. In addition, a direct mercury analyzer (DMA-80) was used to directly detect the concentration with measured results by the regression equation of Hg in the ambient air. The results indicated that: 1) the mean values of ambient air Hg(p) compositions in rice displayed no significant differences for weeks one, two, and three versus those of the other crops (white cabbage, Arden lettuce, and Gynura procumbens); 2) for white cabbage, the higher the humidity, the lower the average ambient air Hg(p) compositions that were obtained, a phenomenon that was also reflected on the crops of white cabbage and G. procumbens; 3) Arden lettuce displayed no significant differences in the leaf Hg(p) compositions during weeks one, two, and three; however, the stem portions displayed significant differences in Hg(p) compositions during weeks two and three; and 4) the Spearman statistical method showed the mean differences for ambient air Hg(p) at the Long-jing sampling site (coastal regions) with four different crops (rice, white cabbage, Arden lettuce, and Gynura) in central Taiwan. The results further revealed no significant differences in mean values.

A measurement of summertime dry deposition of ambient air particulates and associated metallic pollutants in Central Taiwan.

The purpose of this study is to characterize metallic elements associated with atmospheric particulate matter in the dry deposition plate, total suspended particulate, fine particles, and coarse particles at Taichung Harbor and Gong Ming Junior High School (airport) in central Taiwan at a sampling site from June 2013 to August 2013. The results indicated that: (1) the average concentrations of the metallic elements Cr and Cd were highest at the Gong Ming Junior High School (airport), and the average concentrations of the metallic elements Ni, Cu, and Pb were highest at the Taichung Harbor sampling site. (2) The high smelting industry density and export/import rate of heavily loaded cargos were the main reasons leading to these findings. (3) The average metallic element dry deposition and metallic element PM(2.5-10) all followed the order of Pb > Cr > Cu > Ni > Cd at the two sampling sites. However, the average metallic elements Cu and Pb were found to have the highest dry deposition velocities and concentrations in PM(2.5) for the two sampling sites in this study. (4) The correlation coefficients of ambient air particle dry deposition and concentration with wind speed at the airport were higher than those from the harbor sampling site. The wind and broad open spaces at Taichung Airport were the possible reasons for the increasing correlation coefficients for ambient air particle concentration and dry deposition with wind speed at the Taichung Airport sampling site.

Ultrafine Particles in Ambient Air of an Urban Area: Dose Implications for Elderly

Due to their detrimental effects on human health, the scientific interest in ultrafine particles (UFP) has been increasing, but available information is far from comprehensive. Compared to the remaining population, the elderly are potentially highly susceptible to the effects of outdoor air pollution. Thus, this study aimed to (1) determine the levels of outdoor pollutants in an urban area with emphasis on UFP concentrations and (2) estimate the respective dose rates of exposure for elderly populations. UFP were continuously measured over 3 weeks at 3 sites in north Portugal: 2 urban (U1 and U2) and 1 rural used as reference (R1). Meteorological parameters and outdoor pollutants including particulate matter (PM10), ozone (O3), nitric oxide (NO), and nitrogen dioxide (NO2) were also measured. The dose rates of inhalation exposure to UFP were estimated for three different elderly age categories: 64–70, 71–80, and >81 years. Over the sampling period levels of PM10, O3 and NO2 were in compliance with European legislation. Mean UFP were 1.7 × 104 and 1.2 × 104 particles/cm3 at U1 and U2, respectively, whereas at rural site levels were 20–70% lower (mean of 1 ×104 particles/cm3). Vehicular traffic and local emissions were the predominant identified sources of UFP at urban sites. In addition, results of correlation analysis showed that UFP were meteorologically dependent. Exposure dose rates were 1.2- to 1.4-fold higher at urban than reference sites with the highest levels noted for adults at 71–80 yr, attributed mainly to higher inhalation rates.

Depositional characteristics of atmospheric polybrominated diphenyl ethers on tree barks.

ObjectivesThis study was conducted to determine the depositional characteristics of several tree barks, including Ginkgo (Ginkgo biloba), Pine (Pinus densiflora), Platanus (Platanus), and Metasequoia (Metasequoia glyptostroboides). These were used as passive air sampler (PAS) of atmospheric polybrominated diphenyl ethers (PBDEs).MethodsTree barks were sampled from the same site. PBDEs were analyzed by highresolution gas chromatography/high-resolution mass spectrometer, and the lipid content was measured using the gravimetric method by n-hexane extraction.ResultsGingko contained the highest lipid content (7.82 mg/g dry), whereas pine (4.85 mg/g dry), Platanus (3.61 mg/g dry), and Metasequoia (0.97 mg/g dry) had relatively lower content. The highest total PBDEs concentration was observed in Metasequoia (83,159.0 pg/g dry), followed by Ginkgo (53,538.4 pg/g dry), Pine (20,266.4 pg/g dry), and Platanus (12,572.0 pg/g dry). There were poor correlations between lipid content and total PBDE concentrations in tree barks (R2=0.1011, p =0.682). Among the PBDE congeners, BDE 206, 207 and 209 were highly brominated PBDEs that are sorbed to particulates in ambient air, which accounted for 90.5% (84.3-95.6%) of the concentration and were therefore identified as the main PBDE congener. The concentrations of particulate PBDEs deposited on tree barks were dependent on morphological characteristics such as surface area or roughness of barks.ConclusionsTherefore, when using the tree barks as the PAS of the atmospheric PBDEs, samples belonging to same tree species should be collected to reduce errors and to obtain reliable data.

Nanoparticle uptake by airway phagocytes after fungal spore challenge in murine allergic asthma and chronic bronchitis.

BackgroundIn healthy lungs, deposited micrometer-sized particles are efficiently phagocytosed by macrophages present on airway surfaces; however, uptake of nanoparticles (NP) by macrophages appears less effective and is largely unstudied in lung disease. Using mouse models of allergic asthma and chronic obstructive pulmonary disease (COPD), we investigated NP uptake after challenge with common biogenic ambient air microparticles.MethodsBronchoalveolar lavage (BAL) cells from diseased mice (allergic asthma: ovalbumin [OVA] sensitized and COPD: Scnn1b-transgenic [Tg]) and their respective healthy controls were exposed ex vivo first to 3-μm fungal spores of Calvatia excipuliformis and then to 20-nm gold (Au) NP. Electron microscopic imaging was performed and NP uptake was assessed by quantitative morphometry.ResultsMacrophages from diseased mice were significantly larger compared to controls in OVA-allergic versus sham controls and in Scnn1b-Tg versus wild type (WT) mice. The percentage of macrophages containing AuNP tended to be lower in Scnn1b-Tg than in WT mice. In all animal groups, fungal spores were localized in macrophage phagosomes, the membrane tightly surrounding the spore, whilst AuNP were found in vesicles largely exceeding NP size, co-localized in spore phagosomes and occasionally, in the cytoplasm. AuNP in vesicles were located close to the membrane. In BAL from OVA-allergic mice, 13.9 ± 8.3% of all eosinophils contained AuNP in vesicles exceeding NP size and close to the membrane.ConclusionsOverall, AuNP uptake by BAL macrophages occurred mainly by co-uptake together with other material, including micrometer-sized ambient air particles like fungal spores. The lower percentage of NP containing macrophages in BAL from Scnn1b-Tg mice points to a change in the macrophage population from a highly to a less phagocytic phenotype. This likely contributes to inefficient macrophage clearance of NP in lung disease. Finally, the AuNP containing eosinophils in OVA-allergic mice show that other inflammatory cells present on airway surfaces may substantially contribute to NP uptake.

Total exposure to airborne particulate matter in cities: The effect of biomass combustion

The study deals with the seasonal variability of PM exposure and the effect that biomass combustion has upon it in the urban environment. The study is based on measurements, chemical analyses and modeling results performed in Thessaloniki (Greece). The measurements campaign included the assessment of outdoor and indoor air quality and the evaluation of biomass use for domestic heating. The outdoor measurements highlighted a significant increase of PM10 (from 30.1 to 73.1μg/m3) and PM2.5 (from 19.4 to 62.7μg/m3) concentrations during the transition from the warm to the cold period of the year 2012 compared to 2011. The increase in ambient air PM during the winter was attributed to the use of biomass burning for space heating. The latter was verified by the presence of levoglucosan in the PM (concentrations up to 8μg/m3), especially for samples taken from the urban background site. Outdoor PM concentrations were also modeled using an artificial neural network model taking into account major meteorological parameters; the latter explained more than 90% of PM10 and PM2.5day-to-day variability. Indoor concentrations followed a similar pattern, while in the case of fireplace use, average daily concentrations rise to 10μg/m3 and 14μg/m3 for PM2.5 and PM10 respectively. Indoor air concentrations were affected the most by the ambient air particle infiltration. Indoor air quality went down after 3h of open fire biomass combustion for space heating. Personal exposure was significantly determined by overall indoor air quality. Yet, dynamic exposure analysis revealed that peaks of intake do not correspond to peaks of ambient air PM concentrations altering thus total exposure patterns. Thus, cost-effective public health protection has to aim at reducing the exposure profile of susceptible population sub-groups combining awareness raising, emission reduction measures and financial incentives to influence the choice of space heating systems.

Tire tread wear particles in ambient air—a previously unknown source of human exposure to the biocide 2-mercaptobenzothiazole

Urban particulate matter (PM), asphalt, and tire samples were investigated for their content of benzothiazole and benzothiazole derivates. The purpose of this study was to examine whether wear particles, i.e., tire tread wear or road surface wear, could contribute to atmospheric concentrations of benzothiazole derivatives. Airborne particulate matter (PM10) sampled at a busy street in Stockholm, Sweden, contained on average 17 pg/m(3) benzothiazole and 64 pg/m(3) 2-mercaptobenzothiazole, and the total suspended particulate-associated benzothiazole and 2-mercaptobenzothiazole concentrations were 199 and 591 pg/m(3), respectively. This indicates that tire tread wear may be a major source of these benzothiazoles to urban air PM in Stockholm. Furthermore, 2-mercaptobenzothiazole was determined in urban air particulates for the first time in this study, and its presence in inhalable PM10 implies that the human exposure to this biocide is underestimated. This calls for a revision of the risk assessments of 2-mercaptobenzothiazole exposure to humans which currently is limited to occupational exposure.

Comparisons of annual ambient air pollutant concentrations and dry deposition flux variations for day and nighttime in middle Taiwan

This study monitored ambient air particles and the metallic elements Cu, Cr, Cd, Pb, and Zn in total suspended particulate (TSP) concentrations and dry deposition during the day and nighttime sampling period at a traffic sampling site in central Taiwan from 2012 March to 2013 February. The dry deposition flux ratios and seasonal concentration variations of ambient air particles and these metallic elements are also discussed. The results indicate that for all the elements, except for Zn, the highest average concentrations in TSP occurred in the spring and summer, while the lowest average was in the fall and winter for both day and nighttime sampling periods.

A simple QuEChERS-like extraction approach for molecular chemical characterization of organic aerosols: application to nitrated and oxygenated PAH derivatives (NPAH and OPAH) quantified by GC–NICIMS

An extraction procedure based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) approach has been developed and used for analysis of particle-bound nitrated and oxygenated PAH derivatives (NPAH and OPAH, respectively). Several analytical conditions, for example GC injection temperature and MS detection settings, were optimized. This analytical procedure enabled simultaneous GC-NICIMS quantification of 32 NPAH and 32 OPAH (or other oxygenated compounds), including typical components of secondary organic aerosol (SOA) formed by photooxidation of PAH (e.g. 2-formyl-trans-cinnamaldehyde and 6H-dibenzo[b,d]pyran-6-one). The QuEChERS-like approach was optimized, including the nature of the extraction solvent, the sorbent used for clean-up, and extraction time. The final extraction procedure was based on brief mechanical agitation (vortex mixing for 1.5min), with 7mL acetonitrile as solvent. Because dispersive solid-phase extraction (d-SPE) did not provide satisfactory results, SPE using SiO2 was selected for sample purification. Identical results were obtained when the QuEChERS-like and traditional pressurised solvent extraction (PLE) procedures were compared for analysis of fortified ambient air particle samples. The procedure was validated by analysis of two aerosol standard reference materials (NIST SRM 1649b (urban dust) and SRM 2787 (fine particulate matter, <10μm)). For numerous NPAH and OPAH, this is the first report of their quantification in both SRMs. Compared with other extraction methods, including PLE, the QuEChERS-like procedure resulted in increased productivity and reduced extraction cost. This paper shows that QuEChERS-like extraction procedures can be suitably adapted for molecular chemical characterization of aerosol samples and could be extended to other categories of compound.

Nonhomologous DNA end joining and chromosome aberrations in human embryonic lung fibroblasts treated with environmental pollutants

In order to evaluate the ability of a representative polycyclic aromatic hydrocarbon (PAH) and PAH-containing complex mixtures to induce double strand DNA breaks (DSBs) and repair of damaged DNA in human embryonic lung fibroblasts (HEL12469 cells), we investigated the effect of benzo[a]pyrene (B[a]P) and extractable organic matter (EOM) from ambient air particles <2.5μm (PM2.5) on nonhomologous DNA end joining (NHEJ) and induction of stable chromosome aberrations (CAs). PM2.5 was collected in winter and summer 2011 in two Czech cities differing in levels and sources of air pollutants. The cells were treated for 24h with the following concentrations of tested chemicals: B[a]P: 1μM, 10μM, 25μM; EOMs: 1μg/ml, 10μg/ml, 25μg/ml. We tested several endpoints representing key steps leading from DSBs to the formation of CAs including histone H2AX phosphorylation, levels of proteins Ku70, Ku80 and XRCC4 participating in NHEJ, in vitro ligation activity of nuclear extracts of the HEL12469 cells and the frequency of stable CAs assessed by whole chromosome painting of chromosomes 1, 2, 4, 5, 7 and 17 using fluorescence in situ hybridization. Our results show that 25μM of B[a]P and most of the tested doses of EOMs induced DSBs as indicated by H2AX phosphorylation. DNA damage was accompanied by induction of XRCC4 expression and an increased frequency of CAs. Translocations most frequently affected chromosome 7. We observed only a weak induction of Ku70/80 expression as well as ligation activity of nuclear extracts. In summary, our data suggest the induction of DSBs and NHEJ after treatment of human embryonic lung fibroblasts with B[a]P and complex mixtures containing PAHs.

Does Enhancement of Oxidative Stress Markers Mediate Health Effects of Ambient Air Particles?

Evidence indicates that oxidative stress generation may contribute to health effects associated with particulate matter (PM) exposure. We investigated oxidative stress markers in 113 workers exposed to metal-rich PM and 61 nonexposed comparable volunteers. The plasma levels of soluble NOX2-derived peptide (sNOX2-dp) and two oxidative stress markers, urinary 8-hydroxydeoxyguanosine (8-OHdG) and 8-iso-prostaglandinF2alpha (8-iso-PGF2α), were analyzed. The plasma levels of the antioxidant alpha-tocopherol were also evaluated. The workers' average exposure to PM with an aerodynamic diameter <10 μm (PM₁₀) was much higher at the workplace than in the city, where the volunteers lived. Workers had significantly higher urinary 8-iso-PGF2α and 8-OHdG and plasma sNOX2-dp levels than nonexposed subjects. Alpha-tocopherol was much lower in workers compared with nonexposed subjects. In multivariable regression models adjusted for age, body mass index, and smoking, 8-iso-PGF2α increased in workers in association with PM10 and metal exposure; 8-OHdG and sNOX2-dp were associated only with iron. Alpha-tocopherol was inversely associated with each of the oxidative stress markers. Our observation leads to the hypothesis that the enhancement of oxidative stress markers associated with exposure to high metal-rich PM levels represents a possible step in the pathways leading from particle exposure to systemic (e.g., cardiovascular) effects.

Impact of fine particles in ambient air on lung cancer

Recently, the International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter component of outdoor air pollution as class I carcinogen. Air pollution is consistently associated with lung cancer in epidemiologic and experimental studies. The IARC assessment is specifically designed as hazard identification, and it does not quantify the magnitude of the cancer risk. This article addresses the magnitude of the lung cancer risk in the population due to ambient air pollution exposure.

Diurnal concentrations variations, size distributions for ambient air particles and metallic pollutants (Cr, Mn, Ni, Cd, Pb) during summer season at a traffic area

This study characterized and discussed particulate ambient air particulate concentrations and seasonal variations for PM18, PM10, PM2.5, and PM1 during June 2013-July 2013 at this traffic sampling site. In addition, this study also characterized the ambient air particulates size distributions by using MOUDI-100S4 sampler to collect 1-day the ambient suspended particles (PM18, PM10, PM2.5, and PM1) at this sampling site. In addition, the study also showed that the main pollutants contributions were from traffic and residual areas. As for the pollutants seasonal concentrations variations, the results indicated that the average particle concentrations orders were all displayed as daytime > nighttime for PM18, PM10, PM2.5 and PM1 at this characteristic sampling site. The results further indicated that the mean highest of metal concentrations in this study indicated that the average metal concentration were all displayed as Mn > Cr > Ni > Pb > Cd for PM18, PM10, PM2.5 and PM1 on daytime and nighttime at this characteristic sampling site.

Particles Influence Allergic Responses in Mice—Role of Gender and Particle Size

Epidemiological evidence suggesting that exposure to traffic air pollution may enhance sensitization to common allergens in children is increasing, and animal studies support biological plausibility and causality. The effect of air pollution on respiratory symptoms was suggested to be gender dependent. Previous studies showed that allergy-promoting activity of polystyrene particles (PSP) increased with decreasing particle size after footpad injection of mice. The primary aim of this study was to confirm the influence of particle size on the immunoglobulin E (IgE)-promoting capacity of particles in an airway allergy model. A second aim was to examine whether the allergy-promoting capacity of particles was influenced by gender. Female and male mice were intranasally exposed to the allergen ovalbumin (OVA) with or without ultrafine, fine, or coarse PSP modeling the core of ambient air particles. After intranasal booster immunizations with OVA, serum levels of OVA-specific IgE antibodies, and also markers of airway inflammation and cellular responses in the lung-draining mediastinal lymph nodes (MLN), were determined. PSP of all sizes promoted allergic responses, measured as increased serum concentrations of OVA-specific IgE antibodies. Further, PSP produced eosinophilic airway inflammation and elevated MLN cell numbers as well as numerically reducing the percentage of regulatory T cells. Ultrafine PSP produced stronger allergic responses to OVA than fine and coarse PSP. Although PSP enhanced sensitization in both female and male mice, significantly higher IgE levels and numbers of eosinophils were observed in females than males. However, the allergy-promoting effect of PSP was apparently independent of gender. Thus, our data support the notion that ambient air particle pollution may affect development of allergy in both female and male individuals.

Nano Aerosol Chamber for In-Vitro Toxicity (NACIVT) studies

Inhalation of ambient air particles or engineered nanoparticles (NP) handled as powders, dispersions or sprays in industrial processes and contained in consumer products pose a potential and largely unknown risk for incidental exposure. For efficient, economical and ethically sound evaluation of health hazards by inhaled nanomaterials, animal-free and realistic in vitro test systems are desirable. The new Nano Aerosol Chamber for in-vitro Toxicity studies (NACIVT) has been developed and fully characterized regarding its performance. NACIVT features a computer-controlled temperature and humidity conditioning, preventing cellular stress during exposure and allowing long-term exposures. Airborne NP are deposited out of a continuous air stream simultaneously on up to 24 cell cultures on Transwell® inserts, allowing high-throughput screening. In NACIVT, polystyrene as well as silver particles were deposited uniformly and efficiently on all 24 Transwell® inserts. Particle–cell interaction studies confirmed that deposited particles reach the cell surface and can be taken up by cells. As demonstrated in control experiments, there was no evidence for any adverse effects on human bronchial epithelial cells (BEAS-2B) due to the exposure treatment in NACIVT. The new, fully integrated and transportable deposition chamber NACIVT provides a promising tool for reliable, acute and sub-acute dose-response studies of (nano)particles in air-exposed tissues cultured at the air–liquid interface.

Diurnal ambient air particles, metallic elements dry deposition, concentrations study during year of 2012–2013 at a traffic site

The main purpose of this study was to monitor ambient air particulates and metallic pollutants (Cu, Cd, Cr, Pb and Zn) concentrations, dry deposition during day and nighttime sampling periods at a traffic sampling site during 2012 March to 2013 February, In addition, four ambient air dry deposition models (Wood's, Petroff & Zhang, Baklanov and Noll & Fang) were also used to evaluate the ambient air dry deposition pollutants differences between monitored and modeling results. The result indicated that: 1) Petroff & Zhang's model exhibited better performances for the ambient air particles dry deposition predictions at the particles sizes of 10 μm, 20 μm, 23 μm than those of the other dry deposition models for both day and nighttime sampling periods: 2) Noll & Fang, Woods, and Petroff & Zhang's models exhibited best dry deposition prediction results for both day and nighttime sampling periods for metallic element Zn at the particles sizes of 10 μm, 20 μm at this traffic sampling site. However, metallic elements Cu and Cr have the least dry deposition predictions results for all the models mentioned in this study at the particles size of 23 μm for both day and nighttime sampling periods.

Traffic Particles in Ambient Air of a Major US Urban Area: Has Anything Changed over a Decade?

Few studies have addressed the potential changes in particulate matter (PM) exposure occurring in major metropolitan areas over substantial time periods, e.g., 5 or 10 years. The present study examined changes in the PM_(2.5) concentration and elemental composition between two monitoring campaigns carried out in 2002-2005 and 2010-2011 within the Greater Cincinnati area (USA). This area is recognized for high volume of diesel truck traffic (about 10 million trucks annually on regional freeways). The 24-hour filter samples were collected at four sites. General linear models were used to examine differences between the two data sets for elemental carbon (EC), organic carbon (OC), and EC/OC. The comparison was extended to the concentrations of PM_(2.5) and its relevant elemental constituents. At one site, which was previously identified as a particularly hot spot for traffic/diesel air pollution, the concentrations of most traffic related elements as well as EC and EC/OC ratio significantly decreased (p ＜ 0.05) between the two campaigns. No significant differences between carbon data generated in the two campaigns were observed at the other three monitoring stations. These findings did not depend on whether the comparison model accounted for wind speed and direction. The EC/OC determined in the recent campaign across all sites showed no significant differences between the Summer and Fall data but Winter values were significantly lower. The site with the highest traffic influence revealed no significant seasonal difference in PM_(2.5) but essentially all relevant elements showed significant seasonal variations between the Fall (higher) and Winter (lower). The findings suggest that air quality and engine exhaust control policies implemented between 2005 and 2010 have not produced significant changes in metropolitan traffic air pollution levels. However, the decreasing trends in PM_(2.5), Ti, V, Mn, Fe, Zn, Br, and Pb, EC, OC, and EC/OC may become sustainable over a longer time.