Traffic-generated Particulate Matter Research Articles

Diesel exhaust particle inhalation in conjunction with high-fat diet consumption alters the expression of pulmonary SARS-COV-2 infection pathways, which is mitigated by probiotic treatment in C57BL/6 male mice

BackgroundBoth exposure to air pollutants and obesity are associated with increased incidence and severity of COVID-19 infection; however, the mechanistic pathways involved are not well-characterized. After being primed by the transmembrane protease serine 2 (TMPRSS2) or furin protease, SARS-CoV-2 uses the angiotensin-converting enzyme (ACE)-2 receptor to enter respiratory epithelial cells. The androgen receptor (AR) is known to regulate both TMPRSS2 and ACE2 expression, and neuropilin-1 (NRP1) is a proposed coreceptor for SARS-CoV-2; thus, altered expression of these factors may promote susceptibility to infection. As such, this study investigated the hypothesis that inhalational exposure to traffic-generated particulate matter (diesel exhaust particulate; DEP) increases the expression of those pathways that mediate SARS-CoV-2 infection and susceptibility, which is exacerbated by the consumption of a high-fat (HF) diet.MethodsFour- to six-week-old male C57BL/6 mice fed either regular chow or a HF diet (HF, 45% kcal from fat) were randomly assigned to be exposed via oropharyngeal aspiration to 35 µg DEP suspended in 35 µl 0.9% sterile saline or sterile saline only (control) twice a week for 30 days. Furthermore, as previous studies have shown that probiotic treatment can protect against exposure-related inflammatory outcomes in the lungs, a subset of study animals fed a HF diet were concurrently treated with 0.3 g/day Winclove Ecologic® Barrier probiotics in their drinking water throughout the study.ResultsOur results revealed that the expression of ACE2 protein increased with DEP exposure and that TMPRSS2, AR, NRP1, and furin protein expression increased with DEP exposure in conjunction with a HF diet. These DEP ± HF diet-mediated increases in expression were mitigated with probiotic treatment.ConclusionThese findings suggest that inhalational exposure to air pollutants in conjunction with the consumption of a HF diet contributes to a more susceptible lung environment to SARS-CoV-2 infection and that probiotic treatment could be beneficial as a preventative measure.

Characterisation of vehicle emissions in a road tunnel in Lisbon

In urban areas, road traffic is one of the main sources of air pollutants, mainly as particulate matter (PM). Knowledge about fingerprints of vehicle emissions under real-world driving conditions is scarce for Europe, especially in Portugal. The aim of this study was to characterise and quantify vehicle emissions through road tunnel measurements. The sampling campaign was carried out during one week inside a road tunnel and simultaneously in an urban background site in Lisbon. PM2.5 and PM2.5–10 filters were analysed by PIXE for elemental composition and by a thermal-optical transmittance technique for the determination of organic carbon (OC) and elemental carbon (EC). PM2.5 and PM10 concentrations were, at least, 20 and 10 times higher than those found in the background, respectively. Inside the tunnel, particle organic matter (POM), EC and other anthropogenic compounds accounted for more than 90.0% of the PM2.5 mass. Fe, Ca, Si, S and Cu represented 88.7% of the PM2.5-bound elements, while Fe, Cl, Ca, Si, Cu, Zn, Na, S, Ba mostly contributed to the PM2.5–10 elemental mass fraction (93.8%). Total carbon represented about 58.5% of PM2.5 and 26.5% of PM2.5–10. EC presented a high tunnel/background ratio (T/B = 35.4 for PM2.5 and 48.8 for PM2.5–10). Cu, Fe, Cr, Ba, Mn, Zn and Rb, which are key tracers of tyre and brake wear, showed a T/B > 70 and very good correlations between them. The emission factors (EF) of PM2.5 and PM10 were estimated to be 139 ± 20.7 and 172 ± 23.9 mg veh−1 km−1. The average EF of OC and EC in PM2.5 were 30.9 ± 6.48 and 44.6 ± 7.33 mg veh−1 km−1. This real-world study contributes to define road traffic emission profiles in urban areas, provide data to update European emission inventories, and evaluate the impact of traffic-generated PM on human health and the environment.

Physiological and biochemical response of traffic-generated particulate matter captured by some vegetables

Physiological and biochemical response of traffic-generated particulate matter captured by some vegetables

Inhaled diesel exhaust particles result in microbiome-related systemic inflammation and altered cardiovascular disease biomarkers in C57Bl/6 male mice

BackgroundThe gut microbiota plays a vital role in host homeostasis and is associated with inflammation and cardiovascular disease (CVD) risk. Exposure to particulate matter (PM) is a known mediator of inflammation and CVD and is reported to promote dysbiosis and decreased intestinal integrity. However, the role of inhaled traffic-generated PM on the gut microbiome and its corresponding systemic effects are not well-characterized. Thus, we investigated the hypothesis that exposure to inhaled diesel exhaust particles (DEP) alters the gut microbiome and promotes microbial-related inflammation and CVD biomarkers. 4–6-week-old male C57Bl/6 mice on either a low-fat (LF, 10% fat) or high-fat (HF, 45% fat) diet were exposed via oropharyngeal aspiration to 35 μg DEP suspended in 35 μl saline or saline only (CON) 2x/week for 30 days. To determine whether probiotics could prevent diet or DEP exposure mediated alterations in the gut microbiome or systemic outcomes, a subset of animals on the HF diet were treated orally with 0.3 g/day (~ 7.5 × 108 CFU/day) of Winclove Ecologic® Barrier probiotics throughout the study.ResultsOur results show that inhaled DEP exposure alters gut microbial profiles, including reducing Actinobacteria and expanding Verrucomicrobia and Proteobacteria. We observed increased circulating LPS, altered circulating cytokines (IL-1α, IL-3, IL-13, IL-15, G-CSF, LIF, MIP-2, and TNF-α), and CVD biomarkers (siCAM, PAI-1, sP-Selectin, thrombomodulin, and PECAM) in DEP-exposed and/or HF diet mice. Furthermore, probiotics attenuated the observed reduction of Actinobacteria and expansion of Proteobacteria in DEP-exposed and HF-diet mice. Probiotics mitigated circulating cytokines (IL-3, IL-13, G-CSF, RANTES, and TNF- α) and CVD biomarkers (siCAM, PAI-1, sP-Selectin, thrombomodulin, and PECAM) in respect to DEP-exposure and/or HF diet.ConclusionKey findings of this study are that inhaled DEP exposure alters small intestinal microbial profiles that play a role in systemic inflammation and early CVD biomarkers. Probiotic treatment in this study was fundamental in understanding the role of inhaled DEP on the microbiome and related systemic inflammatory and CVD biomarkers.

Exposure to diesel exhaust particles results in altered lung microbial profiles, associated with increased reactive oxygen species/reactive nitrogen species and inflammation, in C57Bl/6 wildtype mice on a high-fat diet

BackgroundExposure to traffic-generated emissions is associated with the development and exacerbation of inflammatory lung disorders such as chronic obstructive pulmonary disorder (COPD) and idiopathic pulmonary fibrosis (IPF). Although many lung diseases show an expansion of Proteobacteria, the role of traffic-generated particulate matter pollutants on the lung microbiota has not been well-characterized. Thus, we investigated the hypothesis that exposure to diesel exhaust particles (DEP) can alter commensal lung microbiota, thereby promoting alterations in the lung’s immune and inflammatory responses. We aimed to understand whether diet might also contribute to the alteration of the commensal lung microbiome, either alone or related to exposure. To do this, we used male C57Bl/6 mice (4–6-week-old) on either regular chow (LF) or high-fat (HF) diet (45% kcal fat), randomly assigned to be exposed via oropharyngeal aspiration to 35 μg DEP, suspended in 35 μl 0.9% sterile saline or sterile saline only (control) twice a week for 30 days. A separate group of study animals on the HF diet was concurrently treated with 0.3 g/day of Winclove Ecologic® Barrier probiotics in their drinking water throughout the study.ResultsOur results show that DEP-exposure increases lung tumor necrosis factor (TNF)-α, interleukin (IL)-10, Toll-like receptor (TLR)-2, TLR-4, and the nuclear factor kappa B (NF-κB) histologically and by RT-qPCR, as well as Immunoglobulin A (IgA) and Immunoglobulin G (IgG) in the bronchoalveolar lavage fluid (BALF), as quantified by ELISA. We also observed an increase in macrophage infiltration and peroxynitrite, a marker of reactive oxygen species (ROS) + reactive nitrogen species (RNS), immunofluorescence staining in the lungs of DEP-exposed and HF-diet animals, which was further exacerbated by concurrent DEP-exposure and HF-diet consumption. Histological examinations revealed enhanced inflammation and collagen deposition in the lungs DEP-exposed mice, regardless of diet. We observed an expansion of Proteobacteria, by qPCR of bacterial 16S rRNA, in the BALF of DEP-exposed mice on the HF diet, which was diminished with probiotic-treatment.ConclusionsOur findings suggest that exposure to DEP causes persistent and sustained inflammation and bacterial alterations in a ROS-RNS mediated fashion, which is exacerbated by concurrent consumption of an HF diet.

Topographical structures in planting design of living walls affect their ability to immobilise traffic-based particulate matter

Traffic-generated particulate matter (PM) pollution is a serious threat to human health and the environment, especially in urban settings. Recent studies have revealed the effectiveness of living walls in the reduction of this pollution; these systems use variable planting designs and their topographical dynamics might have an impact on PM dry deposition. This present study, employing an experimentally manipulable living wall system using box (Buxus sempervirens L.) plants, examined whether plants arranged in a design with heterogeneous topography have a differential PM removal capacity compared to plants in a design with homogenous topography. Two planting designs using ‘short’ and ‘tall’ plants, were simultaneously used on this living wall and equally exposed to traffic-based PM for 5 consecutive days. PM accumulation on leaves was estimated using an Environmental Scanning Electron Microscope and ImageJ image analysis software. The experiment was replicated four times changing the position of each design on the wall, and any variation in PM capture levels on leaves belonging to different designs were identified using a Generalised Linear Mixed-effect Models (GLMM). The planting design with topographical heterogeneity resulted in significantly higher PM densities (PM10, PM2.5 and PM1) on leaf surfaces compared to a design with homogenous topography, indicating that topographical heterogeneity has a strong positive impact on the ability of plants to immobilise PM.

Quantification of the traffic-generated particulate matter capture by plant species in a living wall and evaluation of the important leaf characteristics

Traffic-generated particulate matter (PM) is a significant fraction of urban PM pollution and little is known about the use of living walls as a short-term strategy to reduce this pollution. The present study evaluated the potential of twenty living wall plants to reduce traffic-based PM using a living wall system located along a busy road in Stoke-on-Trent, UK. An Environmental Scanning Electron Microscope (ESEM) and ImageJ software were employed to quantify PM accumulation on leaves (PM1, PM2.5 and PM10) and their elemental composition was determined using Energy Dispersive X-ray (EDX). Inter-species variation in leaf-PM accumulation was evaluated using a Generalized Linear Mixed-effect Model (GLMM) using time as a factor; any differential PM accumulation due to specific leaf characteristics (stomatal density, hair/trichomes, ridges and grooves) was identified. The study showed a promising potential for living wall plants to remove atmospheric PM; an estimated average number of 122.08 ± 6.9 × 107 PM1, 8.24 ± 0.72 × 107 PM2.5 and 4.45 ± 0.33 × 107 PM10 were captured on 100 cm2 of the living wall used in this study. Different species captured significantly different quantities of all particle sizes; the highest amount of all particle sizes was found on the leaf-needles of Juniperus chinensis L., followed by smaller-leaved species. In the absence of an apparent pattern in correlation between PM accumulation and leaf surface characteristics, the study highlighted the importance of individual leaf size in PM capture irrespective of their variable micro-morphology. The elemental composition of the captured particles showed a strong correlation with traffic-based PM and a wide range of important heavy metals. We conclude that the use of living walls that consist largely of smaller-leaved species and conifers can potentially have a significant impact in ameliorating air quality by removing traffic-generated PM pollution to improve the wellbeing of urban dwellers.

Evaluating the impact of individual leaf traits on atmospheric particulate matter accumulation using natural and synthetic leaves

The ability of vegetation to capture and retain atmospheric Particulate Matter (PM) is directly dependent on the interactions between PM and plant surfaces. However, the impact of individual leaf traits in this respect is still under debate due to variations in published findings. This study employed standardised experimental designs with natural and synthetic leaves in three experiments to explore the impact of individual leaf traits on traffic-generated PM accumulation whilst other influential variables were controlled. The impact of leaf size on PM deposition was explored using synthetic leaves of different sizes (small, medium and large) but with the same shape and surface characteristics (n = 20 for each category). The impact of leaf shape was examined using another set of synthetic leaves of different shape (elliptical, palmately-lobed and linear) but with the same surface area and the same surface characteristics (n = 20 for each category). PM accumulation (PM1, PM2.5 and PM10) on these leaves was quantified using an Environmental Scanning Electron Microscope (ESEM) and ImageJ software. Any differences in PM capture levels due to leaf size and leaf shape were identified using one-way Anova and Tukey’s pairwise comparison. In a subsequent experiment, equal-sized, square-shaped leaf sections obtained from four plant species (n = 20 for each species) with different micromorphology were exposed to traffic-generated pollution and any PM capture differences due to leaf micromorphology identified employing the same SEM/ImageJ and statistical approach. The results of all three experiments showed significant differences in PM accumulation between different leaf sizes (p < 0.001), between different leaf shapes (p < 0.001) and between different leaf micromorphology (p < 0.001) suggesting that all these characters are influential in the capture and retention of PM on leaves. Smaller leaves and complex leaf shapes (lobed leaves) showed a greater potential to capture and retain PM. Leaf surfaces with hair/trichomes, epicuticular wax, and surface-ridges accumulated more PM compared to smooth surfaces; of these characters, leaf hairiness/presence of trichomes was found to be the most important. Species sharing most of these important leaf traits are recommended as effective PM filters.

Impact of urban land use on the bacterial phyllosphere of ivy (Hedera sp.)

The surface of the aerial parts of the plant, also termed the phyllosphere, is a selective habitat for microbes. The bacterial composition of the phyllosphere depends on host plant species, leaf characteristics, season, climate, and geographic location of the host plant. In this study, we investigated the effect of an urban environment on the bacterial composition of phyllosphere communities. We performed a passive biomonitoring experiment in which leaves were sampled from ivy (Hedera sp.), a common evergreen climber species, in urban and non-urban locations. Exposure to traffic-generated particulate matter was estimated using leaf biomagnetic analyses. The bacterial community composition was determined using 16S rRNA gene sequencing on the Illumina MiSeq. The phyllosphere microbial communities of ivy differed greatly between urban and non-urban locations, as we observed a shift in several of the dominant taxa: Beijerinckia and Methylocystaceae were most abundant in the non-urban phyllosphere, whereas Hymenobacter and Sphingomonadaceae were dominating the urban ivy phyllosphere. The richness, diversity and composition of the communities showed greater variability in the urban than in the non-urban locations, where traffic-generated PM was lower. Interestingly, the relative abundances of eight of the ten most dominant taxa correlated well with leaf magnetism, be it positive or negative. The results of this study indicate that an urban environment can greatly affect the local phyllosphere community composition. Although other urban-related factors cannot be ruled out, the relative abundance of most of the dominant taxa was significantly correlated with exposure to traffic-generated PM.

Remarkable dynamics of nanoparticles in the urban atmosphere

Abstract. Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that adverse health effects of airborne particles may scale with airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20–30 nm diameter emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m aloft. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20–30 nm diameter is much reduced with a new mode at &lt;10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and are indicative of loss of nanoparticles from air aged during less turbulent conditions. These results are suggestive of nanoparticle loss by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health.

Chronic exposure to fine particulate matter emitted by traffic affects reproductive and fetal outcomes in mice

Air pollution is an important environmental health risk factor that can result in many different gestational and reproductive negative outcomes. In this study, we have investigated the effects of two different times of exposure (before conception and during pregnancy) to urban ambient particulate matter on reproductive and pregnancy outcomes in mice. Using exposure chambers receiving filtered (F) and non-filtered (NF) air, we observed that exposed females exhibited changes in the length of estrus cycle and extended estrus and, therefore, a reduction in the number of cycles during the studied period (F 2.6±0.22 and NF 1.2±0.29, p=0.03). The mean number of antral follicles declined by 36% ( p=0.04) in NF mice (75±35.2) compared to F mice (118.6±18.4). Our results further indicate a significant increase in time necessary for mating and decreased fertility and pregnancy indices ( p=0.003) in NF couples. Mean post-implantation loss rates were increased by 70% ( p⩽0.005) in the NF2 group (exposed before and during pregnancy to NF air) compared to the F1 group (exposed before and during pregnancy to F air) and were influenced by both pre-gestational ( p<0.004) and gestational ( p<0.01) period exposure. Fetal weight was significantly higher in the F1 group when compared with the other groups ( p<0.001), at a 20% higher weight in the F1 group (0.86±0.18 g) than in the NF2 group (0.68±0.10 g). Furthermore, fetal weight was influenced by both pre-gestational and gestational period exposure, and a significant interaction between these two factors was found ( p<0.001). This study demonstrated that exposure to ambient levels of urban traffic-generated particulate matter negatively affects different functions and stages of the reproductive process. Our results also reinforce the idea that maternal exposure to air pollution is linked to negative pregnancy outcomes, even if the exposure occurs only before conception.

Oxidative damage to DNA and repair induced by Norwegian wood smoke particles in human A549 and THP-1 cell lines

Genotoxic effects of traffic-generated particulate matter (PM) are well described, whereas little data are available on PM from combustion of biomass and wood, which contributes substantially to air pollution world wide. The aim of this study was to compare the genotoxicity of wood smoke particulate matter (WSPM), authentic traffic-generated particles, mineral PM and standard reference material (SRM2975) of diesel exhaust particles in human A549 lung epithelial and THP-1 monocytic cell lines. DNA damage was measured as strand breaks (SB) and formamidopyrimidine DNA glycosylase (FPG) sites by the comet assay, whereas cell cytotoxicity was determined as lactate dehydrogenase release. The exposure to WSPM generated SB and FPG sites in both cell lines at concentrations from 2.5 or 25 μg/ml, which were not cytotoxic. Compared to all other studied particles, WSPM generated greater responses in terms of both SB and FPG sites. Organic extracts of WSPM and SRM2975 elicited higher levels of SB than native and washed PM at 25 and 100 μg/ml, whereas assay saturation precluded reliable assessment of FPG sites. During a 6 h post-exposure period, in which the medium with PM had been replaced by fresh medium, 60% of the DNA lesions generated by WSPM were removed. In conclusion, WSPM generated more DNA damage than traffic-generated PM per unit mass in human cell lines, possibly due to the high level of polycyclic aromatic hydrocarbons in WSPM. This suggests that exposure to WSPM might be more hazardous than PM collected from vehicle exhaust with respect to development of lung cancer.

Traffic-generated airborne particles in naturally ventilated multi-storey residential buildings of Singapore: Vertical distribution and potential health risks

The main objective of the study is to quantify the mass concentration exposure levels of fine traffic-generated particles (PM 2.5) at various heights of typical multi-storey public housing buildings located in close proximity, i.e. within 30 m and along a busy major expressway in Singapore. The secondary objective is to compare the potential health risks of occupants in the buildings, associated with inhalation exposure of fine traffic-generated particulate matter, based on estimated dose rates and the lowest observed adverse effect levels (loael) at the various floors of these buildings. Two typical public housing buildings, both naturally ventilated residential apartment blocks, of point block configuration (22-storey) and slab block configuration (16-storey) were selected for the study. Particulate samples were collected for both mass and chemical analysis (OC/EC ratio) at three representative floors: the lower, the mid, and upper floors of the buildings. Key meteorological parameters such as wind speed, wind direction, ambient temperature, and relative humidity were also concurrently measured at the sampling locations. For the potential health risk analysis, the occupants have been divided into four age categories namely, infants, children (1 year), children (8–10 years) and adults. The analysis takes into account age-specific breathing rates, body weights for different age categories. Experimental results explicitly showed that PM 2.5 mean particle mass concentration was highest at the midfloors of both buildings when compared to those measured at upper and lower floors during a typical day. Although the lower floors were closest to traffic emissions, the mean particle mass concentration was lower there than that at the midfloors, which could presumably be due to the interception of PM 2.5 particles by tree leaves or the inflow of clean and drier air from higher altitude with lower aerosol burden mixing with the traffic-polluted air at the lower levels thus lowering the concentration at the lower floors similar to induced chimney effect or both. The upper floors had the least fine particulate matter mass concentration due to dilution following pronounced mixing of traffic-polluted air with ambient air. The only difference between both blocks is that at corresponding floors, the mass concentration levels for slab block is much higher than that of point block. This could be attributed to the configuration of the blocks. Observational data show the slab block tends to slow down the approaching wind thus allowing the accumulation of the fine traffic-generated particulate matter in front of the building. For point block, the HR values at the mid and lower floors suggest that occupants living in these floors experience 1.81 and 1.34 times more health risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories. Similarly, for the slab block, occupants living in the mid and lower floors had 1.62 and 1.28 times more risk, respectively, in contracting respiratory diseases when compared to those living at the upper floors for all age categories.

Characterisation of traffic-generated particulate matter in Copenhagen

Fine and coarse fraction PM was simultaneously sampled with Dichotomous Stacked Filter Units at a road site and at an urban background site during both summer and winter periods. The collected mass was determined gravimetrically, and the contents of 26 elements were measured by Proton-Induced X-ray Emission (PIXE). NO x was monitored continuously at both sites. The road increments (road concentrations minus urban background concentrations) of PIXE elements, PM and NO x were analysed using the Constrained Physical Receptor Model (COPREM). Good agreement between the measured data and the model was achieved in both size fractions using four well-separated source profiles representing the emissions from exhaust, road/tyres, brakes and road salt. The analysis showed that the particles created by brake abrasion have aerodynamic diameters in the inhalable size range around 2.8 μm. This particle diameter is common mass median for a long list of heavy metals that are apportioned to the brakes source: Cr, Fe, Cu, Zn, Zr, Mo, Sn, Sb, Ba and Pb. Other significant contributions of Al, Si, K, Ca, Ti, Mn, Fe, Zn and Sr, mostly in the coarse particle fraction, are apportioned to the road/tyres source.