Human health risk assessment of metal-contaminated soils in Sydney estuary catchment (Australia).

Sydney estuary catchment supports the largest city in Australia and provides essential eco-social and environmental services; however, the region has been influenced by extensive anthropogenic modification. Soil metal concentrations in the catchment had been studied previously; however, the current investigation was designed to determine the risk posed by these contaminants to human health. Soil metal concentrations were higher than observed in most global capitals and increased substantially in the south and south-east of the catchment and close to the central business district. Road-side soils and road dust contained the highest concentration of metals in the catchment. Lead in catchment soils was closely related to traffic density and sourced from the historic use of Pb in petrol. A human health assessment indicated that soil Cd, Ni and Zn posed no non-carcinogenic risk (NCR), or carcinogenic risk (CR) for children, or adults in Sydney estuary catchment and that Cu and Cr may pose minor NCR for children. Vehicle-related Pb raised the greatest human health risk in catchment soils and may pose NCR at 32% and 4.3% of sites for children and adults, respectively. Inconsistent analytical techniques used in CR and NCR evaluations produce incomparable assessments and a consistent` methodology is suggested to improve interpretation. Human health risk may well be higher than commonly calculated due to pollutants present in urban soil not being included in assessments.

Review and assessment of road-derived metals as a major contributor of metallic contaminants to urban stormwater and the estuarine environment (Sydney estuary, Australia).

Sydney Harbour (Australia). is one of the most metal-contaminated in the world and sediments are toxic over large areas. The major source of metals is stormwater, however there remains considerable debate regarding the source of metals in water entering the estuary. The current review and critical assessment of a large source of data accumulated from over three decades of research, supplemented by global studies, identified road-derived metals (RDMs) as the chief contributor of metals to stormwater and consequently to pollution of the estuary. Roads comprise almost 25% of a typical urban catchment and generate a considerable metal load from highly effective impervious surfaces and RDM is transported directly to the adjacent receiving basin with enhanced connectivity. In Sydney, industrial waste is delivered to the sewage system and is disposed of offshore, leaving RDM as a major contributor of metals to the stormwater system and estuarine environment. RDMs are modelled to be hazardous to the ecology and human health (carcinogenic and non-carcinogenic diseases) in the catchment environment driven by high metal concentrations, small size and elevated bioavailability. Remediation of RDMs is complex, requiring extensive knowledge and an experienced management team. The enormous potential for water re-use is often neglected.

Cumulative effects of multiple stressors impact an endangered seagrass population and fish communities.

Coastal ecosystems are becoming increasingly threatened by human activities and there is growing appreciation that management must consider the impacts of multiple stressors. Cumulative effects assessments (CEAs) have become a popular tool for identifying the distribution and intensity of multiple human stressors in coastal ecosystems. Few studies, however, have demonstrated strong correlations between CEAs and change in ecosystem condition, questioning its management use. Here, we apply a CEA to the endangered seagrass Posidonia australis in Pittwater, NSW, Australia, using spatial data on known stressors to seagrass related to foreshore development, water quality, vessel traffic and fishing. We tested how well cumulative effects scores explained changes in P. australis extent measured between 2005 and 2019 using high-resolution aerial imagery. A negative correlation between P. australis and estimated cumulative effects scores was observed (R2 = 22 %), and we identified a threshold of cumulative effects above which losses of P. australis became more likely. Using baited remote underwater video, we surveyed fishes over P. australis and non-vegetated sediments to infer and quantify how impacts of cumulative effects to P. australis extent would flow on to fish assemblages. P. australis contained a distinct assemblage of fish, and on non-vegetated sediments the abundance of sparids, which are of importance to fisheries, increased with closer proximity to P. australis. Our results demonstrate the negative impact of multiple stressors on P. australis and the consequences for fish biodiversity and fisheries production across much of the estuary. Management actions aimed at reducing or limiting cumulative effects to low and moderate levels will help conserve P. australis and its associated fish biodiversity and productivity.

Similarity in human health risk assessment using models of soil-blood lead levels (IEUBK) and non-carcinogenic condition (US EPA 2002).

Soil lead (Pb) concentrations in Sydney estuary (Australia) catchment are substantially elevated and strongly associated with traffic networks. This study compared the health risk predictions of blood Pb levels (BLL) in children using the soil IEUBK model and an independent, non-carcinogenic human health risk (NCR) assessment using the soil US EPA 2002 model. The predictions by the two models were significantly correlated (p < 0.001) and showed similar spatial distributions, but the NCR model may be more stringent in protection of human health when exposed to soil Pb in relation to adverse health effect, as the warning soil Pb concentration from the BLL was 4.6-fold higher than that from the NCR. The empirical IEUBK model considers gastric phase adsorption only and of the three exposure pathways (ingestion, inhalation and dermal) assessed by the theoretical NCR model, ingestion was the major exposure route. The reason for the similarity in outcomes of the two models is unknown, however the close correlation may be due to broadly similar formulations and, or that neurological and non-carcinogenic risks may be related to the adverse effects of Pb on bodily function. Parallel studies of human health risk based on BLL and NCR models have not been attempted previously and this opportunity to compare results from the two health risk assessments employing the same soil metal data is therefore unique.

Endo180 (MRC2) Antibody-Drug Conjugate for the Treatment of Sarcoma.

Although the 5-year survival rates for sarcoma patients have improved, the proportion of patients relapsing after first-line treatment remains high, and the survival of patients with metastatic disease is dismal. Moreover, the extensive molecular heterogeneity of the multiple different sarcoma subtypes poses a substantial challenge to developing more personalized treatment strategies. From the IHC staining of a large set of 625 human soft-tissue sarcomas, we demonstrate strong tumor cell staining of the Endo180 (MRC2) receptor in a high proportion of samples, findings echoed in gene-expression data sets showing a significantly increased expression in both soft-tissue and bone sarcomas compared with normal tissue. Endo180 is a constitutively recycling transmembrane receptor and therefore an ideal target for an antibody-drug conjugate (ADC). An anti-Endo180 monoclonal antibody conjugated to the antimitotic agent, MMAE via a cleavable linker, is rapidly internalized into target cells and trafficked to the lysosome for degradation, causing cell death specifically in Endo180-expressing sarcoma cell lines. In a sarcoma tumor xenograft model, the Endo180-vc-MMAE ADC, but not an isotype-vc-MMAE control or the unconjugated Endo180 antibody, drives on-target cytotoxicity resulting in tumor regression and a significant impairment of metastatic colonization of the lungs, liver and lymph nodes. These data, together with the lack of a phenotype in mice with an Mrc2 genetic deletion, provide preclinical proof-of-principle evidence for the future development of an Endo180-ADC as a therapeutic strategy in a broad range of sarcoma subtypes and, importantly, with potential impact both on the primary tumor and in metastatic disease.

Metal contamination in sediments of dam reservoirs: A multi-facetted generic risk assessment.

The quality of bottom sediments is a key factor for many functions of dam reservoirs, which include water supply, flood control and recreation. The aim of the study was to combine different pollution indices in a critical generic risk assessment of metal contamination of bottom sediments. Both geochemical and ecological indices reflected that sediment contamination was dominated by Zn, Pb and Cd. The ecological risk indices suggested a high riks for all three metals, whereas human health risks were high for Pb and Cd. An occasional local contamination of sediments with Cr and Ni was revealed, although at levels not expected to cause concerns about potential ecological or health risk. Sediments from the Rybnik reservoir for Cu only revealed a high potential ecological risk. EF turned to be as being the most useful, whereas TRI (∑TRI) was the most important ecological index. All multi-element indices suggested similar trends, indicating that Zn, Pb and Cd taken altogether had the greatest impact on the level of sediment contamination and posed the greatest potential ecological and health risks to organisms. The use of sequential BCR extraction and ecotoxicity analyses allowed for a multi-facetted generic risk assessment of metals in sediments of dam reservoirs.

Traffic emission dominates the spatial variations of metal contamination and ecological-health risks in urban park soil.

Metals in urban park soil are closely related to traffic emissions, which adversely affect soil quality and human health. However, little is known about the quantitative impacts of traffic on the spatial variations of metals in park soil after the banning of leaded gasoline. Herein, concentrations of Cu, Pb and Zn in surface soil of four recreational parks of Sydney (Ashfield, Robson, Lamberts and Leichhardt) were measured to evaluate their spatial characteristics in contamination, ecological and health risks and relationships with traffic emissions. Contamination of metals are assessed by contamination factor (CF). Normalized metal concentrations (<63 µm) in the park soil were 24-614, 23-3520 and 99-3060 mg kg-1 for Cu, Pb and Zn, respectively, and CFs ranged from 1.4 to 207, whose variations inter- and intra-parks were related to traffic volumes. Traffic emission accounted for 72-84% of metals contamination in soil of Ashfield, Robson and Lamberts by sites, whereas the values were 25-70% for Leichhardt due to the absence of a surrounding arterial road. In Ashfield and Robson Parks, metal concentrations from traffic decreased exponentially with distance from arterial roads. Metals in Lamberts Park and in areas near arterial roads in Ashfield and Robson Parks may raise ecological risk, and traffic sources contributed to 61-81% of the risk. The ranges of ecological risk zones away from arterial roads and average daily traffic volumes showed an exponential relationship. Copper and Zn in soil of the four parks have no non-carcinogenic health risk for children and adults, and Pb has negligible health risk for adults. Lead in Lamberts Park and in sites near arterial roads of Ashfield and Robson Parks may raise non-carcinogenic risk for children (HI > 1) due to traffic emissions. These results emphasize the remarkable influence of traffic emissions on urban soil metal, which can be predicated quantitatively by traffic volume.

Near-Infrared-Emitting Hemicyanines and Their Photodynamic Killing of Cancer Cells.

A series of hemicyanine dyes was synthesized starting from the vinyl chloride-based cyanine dye IR-780. The dyes absorbed and emitted in the near-infrared region, while heavy atom (bromo and iodo) substitution promoted the generation of both singlet oxygen (1O2) as well as a range of other reactive oxygen-based species (ROS) upon irradiation at wavelengths greater than 610 nm. One hemicyanine dye displayed an outstanding singlet oxygen quantum efficiency (ΦΔ = 0.8) and was successfully applied in in vitro studies to mimic photodynamic therapy application.

The use of sedimentary metal data in predictive modelling of estuarine contamination, assessment of environmental condition and pollutant source identification (Narrabeen Lagoon, Sydney, Australia).

Narrabeen Lagoon is recognized as an Intermittently Closed and Open Lake or Lagoon (ICOLL) and is the largest coastal lagoon (2.2 km2) in the Sydney metropolitan region. The catchment (53 km2) supports five major river systems, and land use comprises of 56% residential, 42% parkland and 2% light industry, commercial, hospital and education. An initial screening environmental assessment was undertaken using sedimentary metals to determine the magnitude of anthropogenic change and level of ecological risk posed by these contaminants. Results illustrated an unusual example of an estuary significantly influenced by human-induced change, but exhibiting minimal ecological risk. This anomaly was due to high anthropogenic metal concentrations in the fine fraction of surficial sediment, which was considerably diluted by abundant metal-poor coarse material resulting in reduced adverse ecological impact for total sediment. Predictive modelling to 2020 suggested that Pb concentrations will decline and Cu and Zn levels will increase slightly. Modelling of river discharge and analyses of fluvial sedimentary metals suggested stormwater derived from the most urbanized catchments and a major roadway combined with poor flushing explained surficial sediment metal distributions in the lagoon.

Pharmaceuticals, personal care products, food additive and pesticides in surface waters from three Australian east coast estuaries (Sydney, Yarra and Brisbane).

The detection rates of pharmaceuticals (Ps), personal care products (PCPs), current-use pesticides (CUPs) and a food additive (FA) in Brisbane River estuary (Queensland), Sydney estuary (New South Wales) and the Yarra River estuary (Melbourne, Victoria) were: Ps: 16/25, 7/25 and 12/25, respectively, CUPs; 28/53, 5/53 and 23/53, respectively, PCPs: 1/3, 0/3 and, 1/3, respectively and FA; 1/1, 1/1 and 1/1, respectively. Diuron was measured in all estuarine samples, simazine, MCPA and 2,4 D were also commonly measured. Pharmaceuticals: carbamazepine, iopromide paracetamol tramadol and venlafaxine were also commonly measured across the estuaries. Generally, analytes were prominent in Brisbane River estuary, followed by Yarra River/Sydney estuary. Inputs of Ps are likely from leakages or effluents of WWTPs; CUPs are potentially from agricultural and parklands via surface run-off in Brisbane River estuary, while for Sydney and Yarra estuaries, which have separate stormwater and sewer systems, sources are likely to be ingression and leakage.

Optical Molecular Imaging of Inflammatory Cells in Interventional Medicine-An Emerging Strategy.

The optical molecular imaging of inflammation is an emerging strategy for interventional medicine and diagnostics. The host's inflammatory response and adaptation to acute and chronic diseases provides unique signatures that have the potential to guide interventions. Thus, there are emerging a suite of molecular imaging and sensing approaches for a variety of targets in this area. This review will focus on two key cellular orchestrators that dominate this area, neutrophils and macrophages, with recent developments in molecular probes and approaches discussed.

Solid-phase synthesis of biocompatible N-heterocyclic carbene-Pd catalysts using a sub-monomer approach.

Taking inspiration from the assembly of so-called peptoids (N-alkylglycine oligomers) we present a new synthetic methodology whereby N-heterocyclic carbene (NHC) based Pd ligands were assembled using a sub-monomer approach and loaded with Pd via solid-phase synthesis. This allowed the rapid generation a library of NHC-palladium catalysts that were readily functionalised to allow bioconjugation. These catalysts were able to rapidly activate a caged fluorophore and 'switch-on' an anticancer prodrug in 3D cell culture.

Estimates of potential childhood lead exposure from contaminated soil using the US EPA IEUBK Model in Sydney, Australia.

Surface soils in portions of the Sydney (New South Wales, Australia) urban area are contaminated with lead (Pb) primarily from past use of Pb in gasoline, the deterioration of exterior lead-based paints, and industrial activities. Surface soil samples (n=341) were collected from a depth of 0-2.5cm at a density of approximately one sample per square kilometre within the Sydney estuary catchment and analysed for lead. The bioaccessibility of soil Pb was analysed in 18 samples. The blood lead level (BLL) of a hypothetical 24 month old child was predicted at soil sampling sites in residential and open land use using the United States Environmental Protection Agency (US EPA) Integrated Exposure Uptake and Biokinetic (IEUBK) model. Other environmental exposures used the Australian National Environmental Protection Measure (NEPM) default values. The IEUBK model predicted a geometric mean BLL of 2.0±2.1µg/dL using measured soil lead bioavailability measurements (bioavailability =34%) and 2.4±2.8µg/dL using the Australian NEPM default assumption (bioavailability =50%). Assuming children were present and residing at the sampling locations, the IEUBK model incorporating soil Pb bioavailability predicted that 5.6% of the children at the sampling locations could potentially have BLLs exceeding 5µg/dL and 2.1% potentially could have BLLs exceeding 10µg/dL. These estimations are consistent with BLLs previously measured in children in Sydney.

The mismatch of bioaccumulated trace metals (Cu, Pb and Zn) in field and transplanted oysters (Saccostrea glomerata) to ambient surficial sediments and suspended particulate matter in a highly urbanised estuary (Sydney estuary, Australia).

A significant correlation between sedimentary metals, particularly the 'bio-available' fraction, and bioaccumulated metal concentrations in the native Sydney rock oyster (Saccostrea glomerata) tissues has been successfully demonstrated previously for Cu and Zn in a number of estuaries in New South Wales, Australia. However, this relationship has been difficult to establish in a highly modified estuary (Sydney estuary, Australia) where metal contamination is of greatest concern and where a significant relationship would be most useful for environmental monitoring. The use of the Sydney rock oyster as a biomonitoring tool for metal contamination was assessed in the present study by investigating relationships between metals attached to sediments and suspended particulate matter (SPM) to bioaccumulated concentrations in oyster tissues. Surficial sediments (both total and fine-fraction), SPM and wild oysters were collected over 3 years from three embayments (Chowder Bay, Mosman Bay and Iron Cove) with each embayment representing a different physiographic region of Sydney estuary. In addition, a transplant experiment of farmed oysters was conducted in the same embayments for 3 months. No relationship was observed between sediments or SPM metals (Cu, Pb and Zn) to tissue of wild oysters; however, significant relationship was observed against transplanted oysters. The mismatch between wild and farmed, transplanted oysters is perplexing and indicates that wild oysters are unsuitable to be used as a biomonitoring tool due to the involvement of unknown complex factors while transplanted oysters hold strong potential.

Fluctuating asymmetry as a pollution monitor: The Australian estuarine smooth toadfish Tetractenos glaber (Teleostei: Tetraodontidae).

The relationship between pollution level in estuarine sediment and fluctuating asymmetry (FA) of resident smooth toadfish Tetractenos glaber was evaluated. A total of 188 fish from Sydney and Hawkesbury River estuaries (5 locations from each) were analysed for 28 bilateral skull bone characters. Sediment pollution was quantified based on analysis of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and organochlorine pesticides (DDT, DDD, DDE, chlordane, dieldrin, lindane). Sediment toxicity was characterized using the mean quotient approach (MERMQ) and ranged from low to moderate level for heavy metals and from low to severe for organochlorides. The mean shape and directional asymmetry of fish bones differed among locations, suggesting a response to local environments. FA was positively correlated with organochlorine pesticides across locations, but not with heavy metals. These results suggest that fish FA could be a useful estimator of stress caused by organic toxicity based on the MERMQ approach.

Effectiveness of remediation of metal-contaminated mangrove sediments (Sydney estuary, Australia).

Industrial activities and urbanization have had a major consequence for estuarine ecosystem health and water quality globally. Likewise, Sydney estuary has been significantly impacted by widespread, poor industrial practices in the past, and remediation of legacy contaminants have been undertaken in limited parts of this waterway. The objective of the present investigation was to determine the effectiveness of remediation of a former Pb-contaminated industrial site in Homebush Bay on Sydney estuary (Australia) through sampling of inter-tidal sediments and mangrove (Avicennia marina) tissue (fine nutritive roots, pneumatophores, and leaves). Results indicate that since remediation 6 years previously, Pb and other metals (Cu, Ni and Zn) in surficial sediment have increased to concentrations that approach pre-remediation levels and that they were considerably higher than pre-settlement levels (3-30 times), as well as at the reference site. Most metals were compartmentalized in fine nutritive roots with bio-concentration factors greater than unity, while tissues of pneumatophores and leaves contained low metal concentrations. Lead concentrations in fine nutritive root, pneumatophore, and leaf tissue of mangroves from the remediated site were similar to trees in un-remediated sites of the estuary and were substantially higher than plants at the reference site. The situation for Zn in fine nutritive root tissue was similar. The source of the metals was either surface/subsurface water from the catchment or more likely remobilized contaminated sediment from un-remediated parts of Homebush Bay. Results of this study demonstrate the problems facing management in attempting to reduce contamination in small parts of a large impacted area to concentrations below local base level.

Partitioning of trace elements in contaminated estuarine sediments: the role of environmental settings.

Estuarine sedimentary environments safeguard aquatic ecosystem health by attenuating and transforming catchment-derived contaminants. Currently these environments are under severe stress from trace element contamination due to urbanization. Sediments of Sydney estuary (Australia) are highly elevated in a range of metals due to a long period of intense urbanization and industrialization, which has had a considerable influence on coastal ecosystem health and functioning. A three-stage sequential procedure following Bureau Communautaire de Référence (Community Bureau of Reference-BCR) technique was applied to sediments collected from Sydney estuary to determine their quality, elemental partitioning and ecosystem risk in three human-impacted environmental settings (i.e., mangrove-dominated, stormwater-dominated and industrial-dominated sites) and a control site in this coastal ecosystem. In all three environmental settings, Pb and Zn concentrations exceeded Australian Interim Sediment Quality Guidelines-High (ISQG-High) values and were mostly associated with the reducible and acid soluble fractions, respectively. Copper and Cr also exceeded ISQG-High values (especially in the industrial-dominated site), however the majority of these metals were associated with the oxidizable fraction. Arsenic and Ni concentrations were mostly below ISQG-High values (except one of the stormwater-dominated sites) and were associated with the residual fraction. These results suggest that the most easily mobilized metal was Zn followed by Pb and these metals together presented a risk to estuarine ecosystems in the three selected environmental settings. However, these metals are not always the most abundant in tissue of mangroves, oysters or prawns suggesting other mechanisms are important in a complex uptake process.

Assessment of biotic response to heavy metal contamination in Avicennia marina mangrove ecosystems in Sydney Estuary, Australia.

Mangrove forests act as a natural filter of land-derived wastewaters along industrialized tropical and sub-tropical coastlines and assist in maintaining a healthy living condition for marine ecosystems. Currently, these intertidal communities are under serious threat from heavy metal contamination induced by human activity associated with rapid urbanization and industrialization. Studies on the biotic responses of these plants to heavy metal contamination are of great significance in estuary management and maintaining coastal ecosystem health. The main objective of the present investigation was to assess the biotic response in Avicennia marina ecosystems to heavy metal contamination through the determination of metal concentrations in leaves, fine nutritive roots and underlying sediments collected in fifteen locations across Sydney Estuary (Australia). Metal concentrations (especially Cu, Pb and Zn) in the underlying sediments of A. marina were enriched to a level (based on Interim Sediment Quality Guidelines) at which adverse biological effects to flora could occasionally occur. Metals accumulated in fine nutritive roots greater than underlying sediments, however, only minor translocation of these metals to A. marina leaves was observed (mean translocation factors, TFs, for all elements <0.13, except for Mn). Translocation factors of essential elements (i.e., common plant micro-nutrients, Cu, Ni, Mn and Zn) were greater than non-essential elements (As, Cd, Co, Cr and Pb), suggesting that A. marina mangroves of this estuary selectively excluded non-essential elements, while regulating essential elements and limiting toxicity to plants. This study supports the notion that A. marina mangroves act as a phytostabilizer in this highly modified estuary thereby protecting the aquatic ecosystem from point or non-point sources of heavy metal contamination.

Relationships between dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs) congener concentrations in aquatic organisms from Sydney Estuary, Australia and physiology, spatial, seasonality, trophodynamic and life history traits.

Over the past few decades, there has been considerable interest in hydrophobic persistent organic pollutants (POPs) and their accumulative properties in aquatic organisms. Several factors, such as environmental concentrations (i.e. in sediment) and physiological characteristics of organisms determine species-specific accumulation patterns of POPs in marine animal tissue. The present study investigated factors that govern species-specific accumulation patterns of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs) in a food web from Sydney Estuary (Australia). The results indicated that physiological characteristics, i.e. lipid %, spatial, i.e. distance from Homebush Bay (point source of POPs) and life history characteristics of the organisms, such as diet and home range, influence PCDD/F and dl-PCB tissue concentrations to a varying degree. For example, PCDD/F tissue concentrations increased with the presence of detritivorous diet, species with limited home range and close proximity to Homebush Bay. On the other hand, lipid %, piscivorous diet and close proximity to Homebush Bay were the main predictors causing increases in dl-PCB tissue levels. Distance from Homebush Bay was the only predictor affecting both PCDD/F and dl-PCB tissue levels at a similar rate, i.e. decreasing tissue concentrations as the distance increases from Homebush Bay.

Pollution and health risk of potentially toxic metals in urban road dust in Nanjing, a mega-city of China.

Spatial variations in concentrations of a suite of potentially toxic metals (Ba, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and Ca in road dusts (n=99) from urban trunk roads (TR) in Nanjing, a mega-city in China, were established. Metal pollution levels, sources and human health risk (non-carcinogenic) were studied. In contrast to previous studies, we labeled the indicative metals relating to non-exhaust traffic emissions by comparing metal pollution between crossroad and park road dusts, and then anthropogenic sources of metals in TR dusts were assessed combining their spatial pollution patterns, principal component analysis and Pb isotopic compositions. Results showed that the metals were enriched in TR dusts compared to background soil concentrations with mean enrichment factors (EFs) of 2.2-23, indicating considerable anthropogenic influence. The degrees of metal pollution ranged from minimal to extremely high and ranked by Ca>Cu>Pb≈Zn>Cr≈Fe>Ni≈Ba>Mn on average. Pollution of Cr, Cu, Fe, Mn, Ni, Pb and Zn in TR dusts resulted primarily from industrial emissions (e.g., coal combustion and smelting) and high pollution levels were found close to suburb industrial complexes, whereas pollution of Ba and Ca was mainly related to construction/demolition sources and was generally distributed homogeneously. The relatively minor contribution of non-exhaust traffic emissions to metal pollution in TR dusts was considered to be due to overwhelming industrial and construction/demolition contributions, as well as to the dilution effect of natural soil particles. Ingestion appears to be the major route of exposure for road dust for both adults and children, followed by dermal contact. The non-carcinogenic health risk resulting from exposure to the potentially toxic metals in TR dusts was within the safe level based on the Hazard Index (HI), except in pollution hotspots where exposure to Pb, Cr, and Cu may be hazardous to children.