Road Dust Resuspension Research Articles

Regional and seasonal drivers of metals and PAHs concentrations in road dust and their health implications in the Czech Republic

While car exhaust emissions in the EU are clearly decreasing, the future of non-exhaust emissions looks more pessimistic. The relative importance of the latter is thus expected to increase in terms of air quality and human health. The aim of the study was to assess regional and seasonal differences in the chemical composition of road dust across the Czech Republic and the health impact of its resuspension, with special respect to polycyclic aromatic hydrocarbons and metals. The road dust samples across all regions and seasons were collected. Based on subsequent laboratory and statistical processing, the spatiotemporal distribution of elements and PAHs was evaluated. Next, the contribution of road dust resuspension to air concentrations was estimated and related health impacts were assessed. A significant regional and seasonal variations in PAHs and metals were discovered. Air quality, leading to atmospheric deposition, was the most important factor contributing to these variations. In contrast, road traffic intensity played only a minor role in influencing the concentrations of metals and PAHs in road dust. Exposure to the PM10 fraction of road dust led to an increase in premature mortality, postneonatal infant mortality, and the prevalence, occurrence, and incidence of bronchitis by several percent. It also significantly raises the annual rate of emergency respiratory hospitalizations and the number of days per year using bronchodilators. Exposure to PAHs and heavy metals in road dust causes cancer incidence on the order of a few cases per 10 million people. Air quality protection measures that lead to a decrease in atmospheric deposition rates are required for the effective reduction of health risks associated with particle resuspension by traffic.

Long-term open-pit mining activities at the world's largest light rare earth mine significantly affect light rare earth elements in road dust over long distances

The long-term effects of decades of open-pit mining at the Bayan Obo deposit, the world's largest light rare earth mine, on the concentrations of several elements in road dust over long distances are unknown. Here, bulk road dust (BRD) and resuspended road dust (RRD) were collected from different distances from the mine for subsequent analysis of mining impacts. As a result of mining activities, light rare earth elements (LREEs), especially La, Ce, Pr and Nd, show different statistical and spatial variations compared to other elements. These LREEs decrease with increasing distance from the mine, and the values found in RRD are higher than those in other particle sizes. Mining emissions and soil have the most significant influence on these LREEs compared to other factors. Spatially, these four LREEs changed significantly over a large area (up to 60 km from the mine) due to mining emissions. However, long-term mining activities affect these elements mainly through mining-contaminated soil as opposed to mining emissions. This study confirms the significant impact of mining activities on LREEs in road dust via a comprehensive data-driven framework, emphasizing the significant environmental effects of long-term open pit mining.

Emission Factors, Chemical Composition and Ecotoxicity of PM10 from Road Dust Resuspension in a Small Inland City

Road dust resuspension in urban environments can contribute to high human exposure to metal(loid)s, polycyclic aromatic hydrocarbons, and other potentially toxic organic compounds. However, for many regions, information on loadings, emission factors and chemical profiles is lacking to accurately apply emission inventories and source apportionment models. In the present study, PM10 samples were collected with an in situ road dust sampler from eleven representative streets of Bragança, an inland city of the Iberian Peninsula, and were analysed for organic and elemental carbon by a thermal-optical technique, elemental composition by ICP-MS and ICP-OES, and ecotoxicity by a luminescence inhibition bioassay with Allivibrio fischeri. A global emission factor of 5.36 ± 2.35 mg veh−1 km−1 was obtained but in suburban areas the values reached twice the average. Total carbon accounted for 14.9 ± 6.8% of the PM10 mass, while element oxides represented the largest share (28.6 ± 18.7%). Very high enrichments were found for typical traffic-related elements such as Cu, Zn, S, Pb and Ni. The geochemical index Igeo further confirmed that road dust of the study region is extremely contaminated by elements mainly originated from tyre and brake wear. Although the total non-carcinogenic and carcinogenic risks associated with metal exposure were found to be low for both children and adults, the bioluminescence inhibition assay showed (eco)toxic responses for all samples, indicating that road dust resuspension may pose a significant human health and ecological threat.

Computation of Particulate Emission Load from Vehicular Traffic on Road Network

The present study on traffic volume monitoring aims to compute total particulate emission load from urban road vehicular traffic and to find average emission factor. An industrial area Pandesara was selected as study area for its commercial and industrial activity, the contribution of public and private vehicle emissions in this area were high. Vehicle emissions include tailpipe emissions and road dust resuspensions. Tailpipe emission was the highest in off- road vehicles even their traffic volume was the least of all. Road dust resuspension due to vehicular speed was highest in 2 wheelers. Road dust resuspension concentrations due to silt fraction was found to be maximum in heavy motor vehicles. Total particulate matters concentrations emitted from vehicles and average emission factor were found to be 251616 gm/hr and 0.79 gm/Veh/Km respectively for entire Pandesara zone. Road dust resuspension plays a significant role in vehicular emission, still having less awareness among people worldwide. Keywords: Particulate Matter, Tailpipe Emission, Traffic Volume, Speed, Road Dust Resuspension, Turbulent Wake Height

Tire Wear Emissions by Highways: Impact of Season and Surface Type

With the increasing number of electric vehicles taking to the roads, the impact of tailpipe emissions on air quality will decrease, while resuspended road dust and brake/tire wear will become more significant. This study quantified PM10 emissions from tire wear under a range of real highway conditions with measurements across different seasons and roadway surface types in Phoenix, Arizona. Tire wear was quantified in the sampled PM10 using benzothiazoles (vulcanization accelerators) as tire markers. The measured emission factors had a range of 0.005–0.22 mg km−1 veh−1 and are consistent with an earlier experimental study conducted in Phoenix. However, these results are lower than values typically found in the literature and values calculated from emissions models, such as MOVES (MOtor Vehicle Emission Simulator). We found no significant difference in tire wear PM10 emission factors for different surface types (asphalt vs. diamond grind concrete) but saw a significant decrease in the winter compared to the summer.

The relationship between the inhalation bioaccessibility of potentially toxic elements in road dust from a heavily polluted industrial area and the source of their pollution

One of the sources of chronic exposure to potentially toxic elements (PTE), especially in polluted environments, is the inhalation of resuspended road dust (RD). The aim of this study is to assess the inhalation bioaccessibility of PTE in RD from highly polluted environments from mining/smelting industries and traffic, and to identify any correlations between the bioaccessibility fraction of PTE and the physicochemical characteristics of the particles. RD from the studied area contains extremely high total concentrations of Cr, V, and Mn, which are likely due to pollution from the smelting industry. Additionally, elevated total concentrations of other elements associated with traffic emissions including Zn, Cu, Pb, Sb, and Sn were also measured. The bioaccessibility of PTE was assessed using two synthetic extraction solutions - Gamble's solution (GS) and Artificial Lysosomal Fluid (ALF). The majority of elements showed negligible bioaccessibility in GS. However, quite high inhalation bioaccessibility was observed for Zn, Pb, Sb, Cd, and Mn in the ALF solution, with a mean bioaccessible fraction of 49, 51.5, 41, 50, and 40% respectively. The highest bioavailable fraction was measured for Cd (97%) in a sample collected near a steel production facility and for Pb (95%) in a sample collected near the highway. These results indicate that increased mobility of the elements in inhaled particles occurs only in the case of phagocytosis. The lowest inhalation bioavailability was measured for Cr (mean is 3%). Differential individual particle analysis revealed that about 60% of phases, mostly major (Cr,Ti,V)-bearing metallic alloys, silicates, oxides and sulphides, are stable in ALF solution, while 40% of phases, mostly (Fe,Ca,Mn)-bearing oxides, silicates, sulphides, metals and metallic alloys originating from steel production, ferrochrome, ferrosilicon and vanadium production and from traffic emissions have been heavily corroded or completely dissolved. The study provides valuable information to further assess health hazards from various emission sources.

Tree stumps as passive samplers for trace metal dust deposition

Atmospheric dust is contaminated by trace metals in many parts of the world due to human industrial activities. This study evaluates tree stumps as passive samplers of dust deposition and bioindicators of trace metal dust contamination in a mine impacted environment. Tree stumps (n = 230) and adjacent soils from Cu–Zn mining areas in northeastern China were analysed in situ for their trace metal concentrations using portable X-ray fluorescence (pXRF). Arsenic and Zn concentrations in tree stumps and roadside soils of each location all decreased with distance from the road in a power-law relationship, indicating a common pollution source (resuspension and redeposition of road dust). Micro-XRF images of vertical tree stump slices indicate that As and Zn were concentrated on the cut (uppermost) surface of tree stumps. This indicates atmospheric deposition as a primary contributor to elevated As and Zn concentrations in tree stumps. Trace metals in soils may have other sources besides atmospheric deposition (e.g., migration from buried ore-bodies or rock weathering), which may confound distinguishing sources in polluted areas. Here, we show that the analysis of tree stumps are suitable indicators of atmospheric trace metal contamination. Compared to surface soils, tree stumps can better reflect road dust resuspension and redeposition because unlike soils, atmospheric deposition is the primary contributor to their trace metal concentrations.

Research on PM2.5 road resuspension dust and its population exposure based on sliding grids

The vehicles driving causes resuspension of road dust, which deteriorates air quality and poses population health risks. Based on sliding grid technology, the distribution characteristics of resuspended PM2.5 generated from a single vehicle driving are studied, and its population exposure for drivers and pedestrians are analyzed. The results show that the concentration of PM2.5 at z = −0.03 m has a “double bracket” shape with one front and one back. The length of PM2.5 concentration distribution gradually increases from 6.825 m to 60.825 m for 1 to 10 s. The maximum height of resuspension PM2.5 increases from 3.16 m to 5.13 m from 1 to 3 s and shows a sawtooth pattern from 3 to 10 s, reaching its highest at 5.62 m at 9 s at the XZ section. The dust gradually rises from 1 to 4 s and the dust gradually spreads to both sides of the vehicle from 4 to 10 s at X = -15 m section. PM2.5 concentration for a, b, and c ranges at 0–59.0, 0–63.1and 0–39.2 μg/m3, respectively. The driver in point a poses the highest exposure concentration within 1–10 s, which is 2.1 times that of pedestrian b and 4.1 times that of pedestrian c.

Assessing Worker and Pedestrian Exposure to Pollutant Emissions from Sidewalk Cleaning: A Comparative Analysis of Blowing and Jet Washing Techniques

Sidewalk cleaning operations are essential to maintaining a clean and safe urban environment. Despite their vital role, these activities, particularly the blowing of road dust, can lead to the resuspension of road dust and associated pollutants, which poses risks to human health and the environment. While the role of blowers on particulate matter resuspension has been investigated, there is limited information on emitted bioaerosols. This study aimed to compare the occupational exposure of operators and passersby during sidewalk cleaning using two manual methods—blowing and jet washing—in two distinct urban environments. The study focused on metal road traffic tracers (copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd), and lead (Pb)) and cultivable/non-cultivable microorganisms. We showed that blowing resuspends inhalable particles containing metals (Cu, Zn, and Mn, but not Cd or Pb) and bioaerosols (fungi and Gram-negative bacteria) throughout the year. This represents an important source of exposure for the blower operators and poses a potential long-term respiratory health risk for them. Operators working in cabs are shielded from such exposure, but passersby, especially vulnerable populations, may be at risk. While jet washing reduces operator exposure to Gram-negative bacteria in comparison to blowing, it does not mitigate fungal exposure, particularly in vegetated sites. These findings underscore the necessity for the implementation of effective protective measures and the development of alternative cleaning methods to mitigate exposure risks.

Examining the effectiveness of municipal street sweeping in removing road-deposited particles and metal(loid)s of respiratory health concern

Road dust is a demonstrated source of urban air pollution. Given this, the implementation of street sweeping strategies that effectively limit road dust accumulation and resuspension should be a public health priority. Research examining the effectiveness of street sweeping for road dust removal in support of good air quality has been limited to date. To address this, the study aimed to assess the use of a regenerative-air street sweeper to efficiently remove road dust particles and metal(loid)s in size fractions relevant for respiratory exposure in Toronto, Canada. As part of this, the mass amounts, particle size distribution and elemental concentrations of bulk road dust before and after sweeping at five arterial sites were characterized.Sweeping reduced the total mass amount of thoracic-sized (<10 µm) road dust particles by 76 % on average. A shift in the size distribution of remaining particles toward finer fractions was observed in post-sweeping samples, together with an enrichment in many metal(loid)s such as Co, Ti and S. Overall, the mass amounts of metal(loid)s of respiratory health concern like Cu and Zn were greatly reduced with sweeping. Traffic volume and road surface quality were predictors of dust loadings and elemental concentrations. Road surface quality was also found to impact street sweeping efficiencies, with larger mass amounts per unit area collected post-sweeping where street surfaces were distressed.This study demonstrates that street sweeping using advanced technology can be highly effective for road dust removal, highlighting its potential to support air quality improvement efforts. The importance of tailoring sweeping service levels and technologies locally as per the quality of road surface and traffic patterns is emphasized. Continued efforts to mitigate non-exhaust emissions that pose a respiratory health risk at their source is essential.

Impact of Seasonal Heating on PM10 and PM2.5 Concentrations in Sučany, Slovakia: A Temporal and Spatial Analysis

Complying with strict PM10 and PM2.5 limit values poses challenges in many European regions, influenced by diverse factors such as natural, regional, and local anthropogenic sources. Urban air pollution, exacerbated by road transport, local industry, and dust resuspension, contrasts with rural areas affected by solid fuel-based local heating and increasing wood burning. This study focuses on village of Sučany, located in Slovakia, analysing PM concentrations during non-heating and heating seasons. The method of analysis relies on the use of the MP101M air quality analyser that utilises beta radiation absorption method. One set of measurements was conducted at five distinct locations during the heating season (18/01/2019 to 28/02/2019) and non-heating season (14/08/2018 to 1/10/2018). Significant differences emerged during the non-heating season with corresponding PM10 averages of 23.0 µg/m3 and PM2.5 at 19.3 µg/m3. In contrast, the PM10 averaged 53.9 µg/m3 and 52.8 µg/m3 during the heating season. The heating season shows PM2.5 contributing up to 98% of total PM10. The distribution of PM10 and PM2.5 pollution and the location of the potential source obtained using polar plots differed during the heating and non-heating seasons. This research underscores the impact of local heating on air quality in a typical Slovak village. The key recommendation for targeted interventions is supporting up-to-date air quality data, education, and financial incentives for citizens in order to implement cleaner and modern heating solutions.

Identification and quantification of trace metal(loid)s in water-extractable road dust nanoparticles using SP-ICP-MS

Resuspension of road dust is a major source of airborne particulate matter (PM) in urban environments. Inhalation of ultrafine particles (UFP; < 0.1 μm) represents a health concern due to their ability to reach the alveoli and be translocated into the blood stream. It is therefore important to characterize chemical properties of UFPs associated with vehicle emissions. We investigated the capability of Single-Particle ICP-MS (SP-ICP-MS) to quantify key metal(loid)s in nanoparticles (NPs; < 0.1 μm) isolated from road dust collected in Toronto, Canada. Water extraction was performed to separate the <1-μm fraction from two different road dust samples (local road vs. arterial road) and a multi-element SP-ICP-MS analysis was then conducted on the samples' supernatants. Based on the particle number concentrations obtained for both supernatants, the metal(loid)-containing NPs could be grouped in the following categories: high (Cu and Zn, > 1.3 × 1011 particles/L), medium (V, Cr, Ba, Pb, Sb, Ce, La), low (As, Co, Ni, < 4.6 × 109 particles/L). The limit of detection for particle number concentration was below 5.5 × 106 particles/L for most elements, except for Cu, Co, Ni, Cr, and V (between 0.9 and 7.7 × 107 particles/L). The results demonstrate that road dust contains a wide range of readily mobilizable metal(loid)-bearing NPs and that NP numbers may vary as a function of road type. These findings have important implications for human health risk assessments in urban areas. Further research is needed, however, to comprehensively assess the NP content of road dust as influenced by various factors, including traffic volume and speed, fleet composition, and street sweeping frequency. The described method can quickly characterize multiple isotopes per sample in complex matrices, and offers the advantage of rapid sample scanning for the identification of NPs containing potentially toxic transition metal(loid)s at a low detection limit.

Spatiotemporal prediction of particulate matter concentration based on traffic and meteorological data

Air pollution threatens worldwide human health, ecosystems, and climate change. Transportation is a major contributor to air pollution. However, the link between transportation and air pollution is intricate and influenced by multiple elements. This study employs spatiotemporal causal convolutional networks to predict air pollutants by utilizing traffic and meteorological data as inputs. Using Seoul, South Korea as a case study, a dataset of 25 regional air monitoring stations is used for prediction. The results confirm that wind speed and direction significantly impact PM2.5 dispersion, while humidity positively correlates with PM2.5 concentrations and temperature shows an inverse relationship. Additionally, vehicular traffic and subway passenger numbers exhibit positive associations, attributed to automotive emissions, road dust resuspension, and heightened human activity near subway stations, respectively. The model can potentially be utilized in a real-time air pollution tracking system to facilitate prompt interventions and reduce the harmful effects of air contamination on public health.

Correction Method for Resuspended Road Dust Emission Factors according to Vehicle Speed Using a Mobile Monitoring Vehicle

Correction Method for Resuspended Road Dust Emission Factors according to Vehicle Speed Using a Mobile Monitoring Vehicle

A mobile monitoring method for the screening of vehicle-movement-induced airborne erionite from roads in high-development residential areas

Erionite, a known carcinogenic zeolite, is prevalent in the rock strata below some parts of New Zealand. It is thought that erionite or other elongated mineral particles (EMPs) could be dispersed into the air at a concentration that is potentially harmful. Currently, there is limited understanding of the number of fibres entering the atmosphere or knowledge of the spatial variability of fibrous mineral concentrations across airsheds. It is not known if fibrous materials, when present in excavated material, are resuspended from roads and, if so, whether they remain in a ‘fibrous' form. To help answer these questions, this research describes an on-road vehicle measurement campaign involving the sampling of road dust using a portable device consisting of a pump fitted with a sampling filter. The device was fixed to a moving vehicle traveling along routes through townships currently experiencing significant levels of development and excavation activity. Erionite is known to exist close to the surface, and thus could potentially be liberated into the air during excavation. Excavated material which is transported along these routes also poses a risk. Filters were analyzed using a combination of microscopic techniques consisting of both visual morphology and elemental analysis. The methodology was successful in helping to identify EMPs, including what appears to be erionite, as well as fragments of other fibrous material within the resuspended road dust. The measurement technique could be used as a screening tool to identify areas where EMP's pose a potential risk due to excavation activity.

Size-segregated characteristics of water-soluble oxidative potential in urban Xiamen: Potential driving factors and implications for human health

Oxidative potential (OP), defined as the ability of particulate matter (PM) to generate reactive oxygen species (ROS), has been considered as a potential health-related metric for PM. Particles with different sizes have different OP and deposition efficiencies in the respiratory tract and pose different health risks. In this study, size-segregated PM samples were collected at a coastal urban site in Xiamen, a port city in southeastern China, between August 2020 and September 2021. The water-soluble constituents, including inorganic ions, elements and organic carbon, were determined. Total volume-normalized OP based on the dithiothreitol assay was highest in spring (0.241 ± 0.033 nmol min−1 m−3) and lowest in summer (0.073 ± 0.006 nmol min−1 m−3). OP had a biomodal distribution with peaks at 0.25–0.44 μm and 1.0–1.4 μm in spring, summer, and winter and a unimodal pattern with peak at 0.25–0.44 μm in fall, which were different from the patterns of redox-active species. Variations in the seasonality of fine and coarse mode OP and their correlations with water-soluble constituents showed that the size distribution patterns of OP could be attributed to the combined effects of the size distributions of transition metals and redox-active organics and the interactions between them which varied with emissions, meteorological conditions and atmospheric processes. Respiratory tract deposition model indicated that the deposited OP and the toxic elements accounted for 47.9 % and 36.8 % of their measured concentrations, respectively. The highest OP doses and the excess lifetime carcinogenic risk (ELCR) were found in the head airway (>70 %). However, the size distributions of OP deposition and ELCR in the respiratory tract were different, with 63.9 % and 49.4 % of deposited ELCR and OP, respectively, coming from PM2.5. Therefore, attention must be paid to coarse particles from non-exhaust emissions and road dust resuspension.

Seasonal variations in concentrations of PM2.5 and tire wear particle of < 2.5 μm (TWP2.5) and polymeric components of PM2.5 at a bus stop

Air pollution is a global public health concern. Bus stops have heavy traffic and local emissions. PM2.5 was collected for 2 day at a bus stop each month for one year. Polymeric components in the PM2.5 samples were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Seasonal variations of the polymeric components, PM2.5 concentration, and concentration of tire wear particles <2.5 μm (TWP2.5) were investigated. Various polymeric components were found, including natural rubber (NR) and curing agents from TWPs, bitumen originating from asphalt pavement wear particles (APWPs), plant-related components (PRCs), and poly (ethylene-terephthalate) (PET) from PET fabric lint. The PM2.5 concentrations at the bus stop were 4–124% higher than those in the regional background, and the annual average PM2.5 concentration at the bus stop was more than 1.5 times higher than that in the regional background. Non-exhanst sources such as abrasion of tires, brakes, and asphalt pavements, vehicle exhaust emissions, and road dust resuspension accounted for the high PM2.5 concentrations. The PM2.5 concentrations during winter were higher than those in the other seasons. On average, the additional generation of PM2.5 at the bus stop was approximately 10 μg/m3, while that in the winter was approximately 18 μg/m3. The annual average TWP2.5 concentration at the bus stop was 1.28 μg/m3 (0.7–1.8 μg/m3), and the seasonal order was winter > fall > spring > summer. TWP2.5 is directly generated by the abrasion of tire tread through the friction with the road surface and also is produced from primary TRWPs by pressing and breaking them upon the contact with tires while driving vehicles. The annual average contribution of TWP2.5 to the PM2.5 concentration at the bus stop was 5.5% (1.6–14.0%).

Mineral magnetic proxies for evaluation of anthropogenic pollution at children's playgrounds – a case study from Sofia city

Quality of the urban environment where children play is of great concern for protecting their health. Thus, fast and economically feasible proxy methods for assessment of urban environment are increasingly applied. In this study, settled dust from 13 playgrounds from Sofia city (Bulgaria), was investigated by mineral magnetism, portable X-ray fluorescence measurements, and scanning electron microscopy. The aim of the study was to evaluate the degree of anthropogenic pollution of playgrounds during winter and summer seasons and to identify pollution sources. Magnetic susceptibility (χ) was measured for two dust fractions - very coarse (grain sizes between 1 and 2 mm) and size fraction of d < 1 mm. In spite of this rough separation, systematic seasonal difference in χ of the two fractions is observed. Winter dust, containing larger amount of finer fraction shows lower χ. Regardless of lower relative content of d < 1 mm fraction, summer playground dusts are more strongly magnetic. Complex Pollution Load Index (PLI), calculated using contents of Cu, Zn, S, Pb (Potentially Toxic Elements (PTE)), shows higher contamination in summer dust, compared to winter. Anhysteretic and isothermal remanences of dust d < 1 mm demonstrate prevailing magnetically stable grains at playgrounds located at greater distance from major boulevards. Thermomagnetic analyses of magnetic susceptibility identified magnetite as the main magnetic mineral, although metallic iron was also evident in summer dust. Based on the meteorological models of atmospheric circulation over Sofia, the pollution sources suggested in a previous research, on one hand, and the carried out Factor Analysis, on the other hand, the results point out that in spite of higher PM10 dust load in winter, summer dust pollution causes stronger PTEs contamination. Factor analysis revealed four factors, explaining most of variability in the data. These factors were identified as: 1) re-suspension of soil and road dust; 2) fine particles magnetite of stable single domain grain size, originating probably from traffic exhaust and non-exhaust emissions; 3) emissions from installations burning waste materials; 4) coal burning.

Physicochemical characteristics of atmospheric particles in south western (Pune) region of India: Elemental size distribution, source analysis and risk assessment

Chemical characteristics of size-resolved particulate matter (PM) and bound elemental species were investigated under an intensive measurement campaign during winter of 2021 in urban dwelling of south western (Pune) region of India. During the study period, average mass concentrations of PM10, PM4, PM2.5 and PM1 were 182.4 ± 48.7 μgm−3, 76.2 ± 26.2 μgm−3, 63.5 ± 22.4 μgm−3, 17.7 ± 6.9 μgm−3 respectively. Diurnal variability indicated significant high concentration during night and early morning hours attributed to the high volume of heavy-duty vehicles. Bimodal distributions of PM mass concentrations in coarse fraction (Mass Median Aerodynamic Diameter (MMAD) ± Geometric Standard Deviation (GSD) = 4.32 ± 1.27) was noted while accumulation of elements was found higher in fine(0.43–2.1 μm) > coarse(2.1–5.8 μm) > large mode(5.8–10 μm) particles. As per size distribution characteristics, Mn, Pb, Cu, Sn, Zn, Mo were concentrated in coarse mode; As, Cr, Fe, Ni was concentrated in both large and coarse mode while Al, Si depicted multimodal distribution across coarse and fine range. High MMAD (≥1.8) and GSD (>1.2) of all elements pointed towards significance of coarse particles in this study region. Ni and Cr (VI) via inhalation exposure pathway pose highest hazard quotient (HQ) and excess lifetime cancer risk (ELCR) respectively within respirable size range(2.1–3.3 μm) while children were subject to potential health risk than adults mainly through ingestion mode of exposure. Principal Component Analysis (PCA) suggested crustal origin, resuspended road dust along with vehicular traffic and industrial emissions as major sources.

Preliminary assessment of road dust from Portuguese motorways: chemical profile, health risks, and ecotoxicological screening

Among non-exhaust emissions, road dust resuspension represents a rather important contribution to particulate matter in urban areas. This study aimed to achieve a chemical characterisation of road dust particulate matter (PM10) on two motorway sections, one rural and one urban, and to explore the related health and ecotoxicological risks. Measured PM10 dust loadings reached very low levels (0.66–1.49 mg m-2) compared to equivalent studies in other road environments in Portugal and other countries. Emission factors ranged from 33 to 62 mg veh−1 km−1. The carbonaceous content represented 14% of the total PM10 mass, whereas the highest contribution to the mass was given by mineral matter. Elements such as Si, Al, Ca, Fe and K accounted for almost three quarters of the total element mass for all samples, whilst Cu and Zn, mostly associated with brake and tyre wear, were the most enriched elements in relation to the soil composition. Nonetheless, Ti and Zr presented the highest non-carcinogenic risks for human health. Despite the low amounts of particulate matter in the aqueous solution, the ecotoxicological screening with the Aliivibrio fisheri bioluminescence inhibition bioassay allowed to classify the samples as toxic.