Multipotential Toxic Metals Accumulated in Urban Soil and Street Dust from Xining City, NW China: Spatial Occurrences, Sources, and Health Risks

Bioaccumulation, biomagnification, and ecological risk of trace metals in the ecosystem around oilfield production area: A case study in Shengli Oilfield

The production for crude oil usually leads to contamination of the soil with trace metals and organic contaminants from spilled petroleum. Organic contaminants were generally paid more attention than trace metals in the oilfield pollution. Many studies have investigated the impacts of some petroleum hydrocarbon pollutants, however, the impacts and risk assessment of trace metals remain largely unexplored. Moreover, under some circumstances, the risks associated with trace metals are not necessarily lower than those associated with organic contaminants. This study aimed to investigate methods to evaluate the possible risks associated with 11 trace metals (Ti, Ba, Sr, Rb, V, Li, Mo, Co, Cs, Bi, and Tl) in soil and biota samples from the Shengli Oilfield using ICP-MS. The results showed that 11 trace metals in the surface soils exceeded the local background levels. The geo-accumulation index (Igeo) indicated that the soils had light-moderate to moderate contamination levels, with higher Igeo value of Ba, V, Li, Mo, Co, and Cs. The individual potential ecological risk indices ([Formula: see text]) demonstrated moderate Bi and Tl pollution in soils. Comparatively, the [Formula: see text] is recommended for the risk assessment of trace metals on the ecosystem around the oilfield area. Mo, Bi, and Sr easily accumulate in plants, as reflected by their bioaccumulation factor. Ti, Ba, V, Li, Co, Cs, Bi, and Tl exhibited considerable biomagnification, particularly in birds. In this study, trace metals showed considerable bioaccumulation and biomagnification, and the risks of these trace metals on the ecosystem around oilfield production area need more attention.

Apportionment and location of heavy metal(loid)s pollution sources for soil and dust using the combination of principal component analysis, Geodetector, and multiple linear regression of distance

The accurate identification of sources for soil heavy metal(loid) is difficult, especially for multi-functional parks, which include multiple pollution sources. Aiming to identify the apportionment and location of heavy metal(loid)s pollution sources, this study established a method combining principal component analysis (PCA), Geodetector, and multiple linear regression of distance (MLRD) in soil and dust, taking a multi-functional industrial park in Anhui Province, China, as an example. PCA and Geodetector were used to determine the type and possible location of the source. Source apportionment of individual elements is achieved by MLRD. The detection results quantified the spatial explanatory power (0.21 ≤ q ≤ 0.51) of the potential source targets (e.g., river and mining area) for the PCA factors. A comparative analysis of the regression equation (Model 1 and Model 3) indicated that the river (0.50 ≤ R² ≤0.78), main road (0.47 ≤ R² ≤ 0.81), and mine (0.14 ≤ R² ≤ 0.92) (p < 0.01) were the main sources. Different from the traditional source apportionment methods, the current method could obtain the exact contributing sources, not just the type of source (e.g., industrial activities), which could be useful for pollution control in areas with multiple sources.

Estimation of Ecological and Human Health Risks Posed by Heavy Metals in Street Dust of Madrid City (Spain)

In this work, sampling was carried out in the urban area of Madrid to analyze the content of total heavy metals (Zn, Pb, Cu, Cr, Ni, and Cd) in the street dust. Contamination was evaluated using various indices, such as the Contamination Factor (CF), Enrichment Factor (EF), Geo-accumulation Index (Igeo), Potential Ecological Risk Index (RI), Pollution Load Index (PLI), the Human Health Index Hazard Index (HI), and Cancer Risk (CR). Pollution indices were related to traffic density and color. Traffic density was the factor that most influenced the values of the pollution indexes, but no significant differences were found with the color of street dust. The concentration of heavy metals in the urban dust of Madrid had the following sequence: Zn (895) > Cu (411) > Pb (290) > Cr (100) > Ni (42) > Cd (1.25 mg kg−1). The pollution levels were high or very high in Pb, Zn, and Cd regarding the environmental pollution indexes. Ingestion was the main route of exposure to heavy metals contained in street dust. The CR for adults and children is less than 1 × 10−6, which means that there is no risk for the population. However, the HI was 10 times higher in children than in adults.

Source apportionment and health risk assessment for potentially toxic elements in size-fractionated road dust in Busan Metropolitan City, Korea

Potentially toxic elements' (PTEs; V, Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Pb, and Hg) pollution level was investigated in size-fractionated road dust in Busan Metropolitan City. Health risks to humans (adult and children) were also evaluated in fine particle fraction (< 63 μm) of road dust. PTE concentrations in the fine particles (< 63 μm) were ranked as follows (unit: mg/kg): Zn (2511) > Cu (559) > Cr (531) > Pb (385) > Ni (139) > V (83.8) > Sb (31.6) > Co (21.6) > As (17.2) > Cd (4.1) > Hg (0.38). The PTE concentrations in fine particles (< 63 μm) were significantly higher than those in coarse particles except for V, Co, and As. The mean PTE loadings of fine particle fraction (< 63 μm; 233 mg/m2) in road dust were up to 4.5 times higher than other particle fractions. Igeo values of Sb were higher than 5 except for > 1000-μm fraction, indicating extremely polluted status. PCA results and elemental ratios indicated that most of the PTEs in road dust were derived from non-exhaust traffic-related sources such as brake pads and tires. Cr, Pb, and Sb had higher HI values than other metals for both adults and children. Sampling sites of heavy traffic and industrial areas showed that the carcinogenic risk exceeded the maximum threshold level (10 - 4). Especially in children, the mean carcinogenic risk (ingestion pathway) of As (6.8 × 10 - 4) Cd (2.0 × 10 - 4), and Ni (4.1 × 10 - 4) exceeded the maximum threshold level, indicating that continuous exposure to road dust may pose a high cancer risk to children. Therefore, continuous monitoring and management of these metals are needed to protect human health and the urban environment.

Evaluation of pollution indices, health hazards and source identification of heavy metal in dust particles and storm trajectory simulation using HYSPLIT model (Case study: Hendijan center dust, southwest of Iran)

Atmospheric dust is one of the most recent environmental pollutions in Iran. This study examines the concentration of heavy metals and the assessment of environmental and human health risk in the dust samples of Hendijan region as one of the most important centers of wind erosion in the southwestern of Iran. ICP-MSS analysis was performed on 18 samples of fine dust to specify the concentration of heavy metals. Studies showed that the highest concentrations of metals in these fine dust samples belong to Cr, Ni, Zn, Cu, As, Pb and Cd, respectively. Examining fine dust's pollution assessment showed that the highest enrichment and geo-accumulation index belong to As, Ni and Cr metals. Environmental risk assessment shows the low environmental risk of these fine dusts. The hazard quotient in children and adults belongs to Cr, As and Ni, respectively. Human health risk assessment also showed that the highest absorption of metals in both children and adults is through ingestion. The non-carcinogenic risk of heavy metals of dust samples in children is about 9 times more than adults. The highest risk of cancer in the adult group belongs to Ni metal and in the group of children belongs to As and Ni metal. PCA analysis showed that As, Cu, Cd, Cr and Ni are of anthropogenic origin and Zn and Pb are of geogenic origin. The source of the dust phenomenon with the HYSPLIT model and the backward method indicates the tracking of this dust mass through Iraq, and its probable origin was assessed in the centers of northern Iraq and southeastern Syria.

Characteristics and Risk Assessment of 16 Metals in Street Dust Collected from a Highway in a Densely Populated Metropolitan Area of Vietnam

The present study focused on investigating the contamination and risk assessment for 16 metals in street dust from Ha Noi highway, Ho Chi Minh City. The results indicated that the concentrations of metals (mg/kg) were found, in decreasing order, to be Ti (676.3 ± 155.4) > Zn (519.2 ± 318.9) > Mn (426.6 ±113.1) > Cu (144.7 ± 61.5) > Cr (81.4 ± 22.6) > Pb (52.2 ± 22.9) > V (35.5 ± 5.6) > Ni (30.9 ± 9.5) > Co (8.3 ± 1.2) > As (8.3 ± 2.5) > Sn (7.0 ± 3.6) > B (5.7 ± 0.9) > Mo (4.1 ± 1.7) > Sb (0.8 ± 0.3) > Cd (0.6 ± 0.2) > Se (0.4 ± 0.1). The geo-accumulation index (Igeo) showed moderate contamination levels for Pb, Cd, Cu, Sn, Mo, and Zn. The enrichment factor (EF) values revealed moderate levels for Cd, Cu, Mo, and Sn but moderate–severe levels for Zn. The pollution load index of the heavy metals was moderate. The potential ecological risk (207.43) showed a high potential. Notably, 40.7% and 33.5% of the ecological risks were contributed by Zn and Mn, respectively. These findings are expected to provide useful information to decision-makers about environmental quality control strategies.

Distribution Characteristics and Risk Assessment of Heavy Metals in Soil and Street Dust with Different Land Uses, a Case in Changsha, China

Rapid urbanization and industrialization have led to the accumulation of heavy metals in urban areas. The distribution and health risk of heavy metals in soil and street dust were studied by collecting the samples in pairs from different land uses in Changsha, China. The results showed that the average contents of the heavy metals Pb, Cd, Cu, Zn, Cr and Ni in the soil were 45.3, 0.69, 46.3, 220.4, 128.7 and 32.9 mg·kg-1, and the corresponding heavy metal contents in the street dust were 130.1, 3.9, 130.8, 667.2, 223.2, 50.5 mg·kg-1, respectively. The soils in the parks and roadsides have higher heavy metal contents than those in the residential and agricultural areas. The street dust collected from parks, roadsides and residential areas contained higher heavy metal contents than agricultural areas. Significant correlations were found between heavy metals, suggesting similar sources. However, most of the heavy metals in the soil were uncorrelated with those in the street dust. The contents of heavy metals in soil are the results of long-term pollution. Street dust is easily affected by natural or human disturbances, reflecting pollution emissions in a short period. The health risks posed by heavy metals in the soil are acceptable, but the street dust may threaten children's health, especially in residential areas. Pb, Cr and Cd are the main risk contributors. Reducing the emissions from industrial plants and traffic may reduce the risk of exposure to heavy metals in the street dust.

Pollution characteristics, sources and health risk of metals in urban dust from different functional areas in Nanjing, China

Urban dust is an important medium of potential toxic metal (PTM) pollution that affects human health and the urban ecosystems. A total of 374 fugitive dust samples were collected in Nanjing, a fast-developing city in southern China, including six sub-types of dust (residential district, commercial district, industrial district, traffic district, cultural and educational district, green land). Chemical analysis of eighteen metal elements by inductively coupled plasma mass spectrometry was carried out to establish the sub-type sources profiles of fine particles for fugitive dust. The results show that these metals (Cu, Zn, Se, Sr, Mo, Cd, Sb, and Pb) are mainly from anthropogenic sources and present a high degree of pollution; Mn, As, and Ba are moderately affected by human activities and present a significant degree of pollution; Ni, Co, Cr, Tl, V, Be, and Ti mainly originate from natural sources and present significant, moderate and minimal degrees of pollution. For the dust types from different functional areas, the differences of enrichment factor (EF) values were relatively small. Metals were highly concentrated in dust from residential, cultural and educational district, which had high density population and would pose higher health risk. In all types of dust, the metals rich in crust (Ti, Mn, Ba, Sr) and the metals (Cu, Zn, Pb) closely connected with city activities were the main components. Factor analysis revealed that there were six main sources of metals in dust collected from Nanjing: industrial activity, building decoration, soil dust, metal smelting, traffic emissions, and brake abrasion. Generally, noncarcinogenic and carcinogenic health risks of metals found in dust are rarely found for children and adults based on health risk assessments. However, the noncarcinogenic risk of Pb in commercial districts for children should be noted because its hazard quotient was higher than the safety threshold level. For the accumulative health risk of eighteen metals, the noncarcinogenic risk values of dust from six functional areas for children were all over the threshold (1.0), whereas below 1.0 for adults. The difference between children and adults was relatively obvious. All accumulative risk values of carcinogenic metals did not exceed the carcinogenic risk threshold of 1 × 10^-4, which suggested that no risk prevention measures were needed.

Chemical Fractionation, Environmental, and Human Health Risk Assessment of Potentially Toxic Elements in Soil of Industrialised Urban Areas in Serbia

The primary focus of this research was the chemical fractionation of potentially toxic elements (PTEs) and their presence in several industrialised cities in Serbia. Furthermore, their origin, contamination levels, and environmental and human health risks were assessed. The results indicated that the examined soils were characterised by slightly higher Cu, Ni, Pb, and Zn levels than those set by European and national regulations. These elevated Cu, Pb, and Zn concentrations were caused by intensive traffic and proximity to industry, whereas the higher Ni levels were a result of the specific geological substrate of the soil in the study area. The environmental risk was found to be low and there was no enrichment/contamination of the soil with these elements, except in the case of Pb, for which moderate to significant enrichment was found. Lead also poses a potential non-carcinogenic risk to children through ingestion and requires special attention due to the fact that a significant proportion of this element was present in the tested soil samples in a potentially available form. Analysis of the health risks showed that children are more at risk than adults from contaminants and that ingestion is the riskiest exposure route. The carcinogenic risk was within the acceptable limits.

Assessment of Heavy Metals in Agricultural Land: A Literature Review Based on Bibliometric Analysis

A great amount of negative influence on human existence and environmental protection has been brought on by heavy metal pollution in agriculture soil. Thus, major awareness has been diverted to the evaluation of heavy metals (EHM) in agricultural land, which is used to improve the environment and ensure people’s health. Based on 3759 publications collected from the Web of Science Core CollectionTM (WoS), this paper’s aim is to illustrate a comprehensive bibliometric run-through and visualization of the subject of EHM. Contingent on influential authors, top institutions, keywords are discussed in detail. Afterwards, the ruling publications and focal assemblage of EHM and leading publications are analyzed to discover the main research topics, according to citation analysis and reference co-citation analysis. The main motive of the paper is to assist research workers interested in the area of EHM determine the ongoing potential research opportunities and hotspots.

Environmental and human health risks associated with exposure to hazardous elements present in urban dust from Barranquilla, Colombian Caribbean

Urban dust is a mixture of deposited particles from different sources usually linked to potentially toxic elements (PTEs). Despite the industrialization of many South American countries, little is known about the impact of particulate matter in large cities; these data are necessary to promote environmental policies aiming to protect human health. The main objective of this work was to evaluate the particle size distribution, composition, and environmental and human health risks of settled dust particles from Barranquilla, a Colombian Caribbean industrialized area. Trace elements were analyzed by inductively coupled plasma-mass spectrometry from 35 different sites, covering all city areas. Dust was mostly composed of 10-to-70-μm particles. The average concentrations of V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Sn, Sb, Pb, and Bi were above background. High spatial heterogeneity was observed for Cu, Zn, As, Se, Mo, Ag, Sn, Sb, and Bi. Concentration factors suggest that urban dusts are extremely contaminated by Zn and Cu. The ecological risk associated with specific elements decreased in the order Cd > Cu > As > Hg > Pb > Ni > Co ≈ Zn ≈ Cr, and the contamination load index showed that 91% of the samples are polluted by PTEs. Although the carcinogenic risks of Cr, Ni, As, Co, and Cd were low, chronic exposure to several PTEs may affect quality of life. Educational programs, as well as monitoring and greater control on traffic, industry, and construction activities are needed to protect environmental and human health.

Trace element contamination in urban topsoil in China during 2000-2009 and 2010-2019: Pollution assessment and spatiotemporal analysis

The Chinese government has launched a critical battle against soil pollution in recent years to establish an effective pollution prevention and control framework. This study sought to investigate the long-term pollution status of potentially toxic trace elements in urban topsoil nationwide, and to further investigate the effectiveness of pollution control over the past decade. The concentrations of 8 elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in urban topsoil in China between 2000-2009 and 2010-2019 were separately collected for comparative analysis. Individual and comprehensive pollution levels of the elements were evaluated at the city, provincial, regional, and national scales, and further spatially mapped using GIS. Combined with PCA, the main factors influencing these elements in soil nationwide were identified. The results revealed a severe situation in terms of potentially toxic trace element accumulation in urban topsoil, where the NNIPIs surpassed 3 in both periods. The elements As, Cd, and Hg were closely associated with industrial activity and coal burning. Hg and, in particular, Cd pollution (NPI > 3) were found to be severe in most of the cities studied. For the elements As, Cu, Pb, and Zn, pollution ranged from slight to moderate (1.0 < NPI ≤ 3.0), and Cu, Pb, and Zn were related to a significant degree with vehicle use. Soil Cr and Ni were mainly controlled by parent materials of lithogenic origin, and slight pollution was identified (1.0 < NPI ≤ 2.0). Pollution patterns showed different characteristics across the regions, and those of the same region and the nation hardly changed over time. Mercury pollution was dominant in the northern regions (NW, MYeR, NE, and NC), while Cd pollution was more severe for the south (EC, MYaR, SC, and SW). Notably, the country's comprehensive pollution level was stable across the two periods, with momentum towards improvement observed over the past decade.

Comprehensive Urumqi screening for potentially toxic metals in soil-dust-plant total environment and evaluation of children's (0-6 years) risk-based blood lead levels prediction

Environmental contaminations by potentially toxic metals (PTMs) are associated with energy exploitation and present a significant problem in urban areas due to their impacts on human health. The PTMs status in Urumqi total environment inevitably impacted by extensive development of coal and oil industries has been lack of understanding comprehensively. A series of PTMs (As, Ba, Ce, Co, Cr, Cu, Ga, La, Mn, Ni, Pb, Rb, Sr, Th, U, V, Y, Zn, Zr) in the soil-dust-plant (foliage of Ulmus pumila L.) system of Urumqi (NW China) were screened by XRF and ICPMS. Multivariate statistics, risk models, GIS-based geostatistics, Positive Matrix Factorization (PMF) receptor modelling and blood lead levels of 0-6 aged children evaluated by IEUBK model are used to determine the priority pollutants, sources and health effects of the investigated elements. The spatial distribution of PTMs in soil-dust-plant system significantly coincides with coal combustion, traffic emission, and industrial activity. Although all PTM toxicants in soil, dust and tree foliage show some effects, the priority contaminants are observed for Cu, Pb and Zn as single element. The total carcinogenic and non-carcinogenic risks from PTMs are beyond the tolerance range of 0-6 year's old children, and the dust (TCR = 1.07E-04) PTMs pose approximatively equivalent carcinogenic risk to soil PTMs (TCT = 1.09E-04). The predicted BLLs (75-83 μ g·L^-1) of 1-2 years children are most strongly influenced by Pb in soil and dust, and therefore more attention should be focused on sources of Pb to support the primary health care of the toddlers in Urumqi.

Trace elements in two particle size fractions of urban soils collected from playgrounds in Bratislava (Slovakia)

Today, it is proven that the contaminated urban soils are hazardous for the human health. Soil substrates of playgrounds call for special research as they are places where children are directly exposed to soil contaminants. Therefore, the objective of this work was to measure the pseudo-total contents and bioaccessibility of several metals and metalloids (As, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, V, Zn) in two grain sizes (< 150 μm and < 50 μm) of playground soils in Bratislava city (the capital of Slovakia). The content of metal(loid)s in the soils was controlled by a number of factors, with their increased contents (above 75% percentile or higher) at sites influenced by point sources of pollution (industry and agriculture) or at old sites located in the city centre. Cobalt, Cr, Fe, Mn, Ni and V had relatively uniform contents in soils compared to the other elements. As regression modelling with a categorical variable confirmed, the age of urban areas influenced the accumulation of As, Bi, Cd, Cu, Hg, Pb, Sb and Sn in playground soils. Exploratory statistical techniques with compositionally transformed data (principal component analysis, cluster analysis and construction of symmetric coordinates for correlation analysis) divided trace elements into the two main groupings, Co, Cr, Fe, Mn, Ni, V and Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn. Median concentrations of the elements in smaller soil grains (< 50 μm) were significantly higher than in coarser grains (< 150 μm). Cobalt, Cu, Mn, Pb, Sn and Zn had significantly higher bioaccessible proportions (% of the pseudo-total content) in < 50 μm soil size than in < 150 μm; however, the same order of bioaccessibility was achieved in both grain sizes. The highest bioaccessibility had Cd, Cu, Pb and Zn (~ 40% and more), followed by Co, As, Mn, Sb (18-27%), Hg, Ni, Sn (10-12%) and finally Cr, Fe and V (less than 4%). The hazard index and carcinogenic risk values were higher in < 50 μm than in < 150 μm and significantly decreased in the two soil sizes when the bioaccessibility results were included in the health hazard calculation.

Potentially toxic metals and the risk to children's health in a coal mining city: An investigation of soil and dust levels, bioaccessibility and blood lead levels

Coal is a primary energy source in the world. Potentially toxic metals (PTMs) emission from coal mining and combustion are posing a serious public health concern. In order to quantify and evaluate the effect of PTMs on children's health, the concentrations of 12 PTMs (As, Co, Cr, Cu, Mn, Ni, Pb, Sr, Zn, Ca, Fe, and Mg) bound in urban soil and street dust are determined and blood lead levels of these PTMs in 229 children (0-6 years old) are collected from the coal mining city of Yulin, China. In vitro pulmonary bioaccessibilities of PTMs are evaluated by artificial lysosomal fluid and Gamble's solution, and gastrointestinal bioaccessibilities by the unified BAGRE method (UBM); correlations between chemical speciation of PTMs and their bioaccessibility are examined, and children's (0-6 years old) health risks are systematically studied. Similar distribution levels of PTMs are found in soils and dusts, with the most polluted metals being Co, Sr, Ca and Pb. All PTMs (except Cr, Fe) are from the considerable artificial lysosomal fluid extraction both in soil and dust, while Ca and Co are favorably extracted in gastro and intestinal phases than others. Significant correlations are observed between the bioaccessibilities (lung and gastrointestinal) and Fe/Mn hydroxide-bound and carbonate-bound phases, which are key factors influencing and determining PTMs' bioaccessibility. Blood lead levels for children (0-6 years old) are 27.47 (21.65, 33.30) for 0-1 year olds, 32.29 (26.39, 38.19) for 1-2 year olds, 36.99 (28.16, 45.81) for 2-3 year olds, 30.79 (22.56, 39.01) for 3-4 year olds, 27.12 (17.31, 36.93) for 4-5 year olds, 34.59 (24.22, 44.97) for 5-6 year olds and 37.83 (24.15, 51.51) μg/L for 6-7 year olds, respectively, with 3.93%, 3.49%, 4.80%, 2.62%, 1.31%, 1.75% and 1.31% exceeding 50 μg/L, respectively. This indicates that the blood lead levels elevate for 1-2 year and 5-6 year old groups, which should be paid more attention. Although the non-carcinogenic and carcinogenic risks of most PTMs are under the acceptable level, the higher carcinogenic risk of Ni and non-carcinogenic risk of Pb should be monitored continuously. We suggest that further actions will be taken to reduce PTMs exposure for children through sustainable clean and ecological energy technology for coal mining, especially for those infants of 1-2 years old.

Health risk assessment of heavy metals in street dust around a zinc smelting plant in China based on bioavailability and bioaccessibility

In order to investigate pollution level, chemical speciation and health risk of exposure to heavy metals in street dust from smelting district, we carried the following studies: (a). the differences in the morphology of street dust in smelting and non-smelting districts using a scanning electron microscope; (b). the chemical speciation and bioavailability of heavy metals in <100 μm and <63 μm particles near a smelting district using a modified three-stage BCR sequential extraction procedure and in vitro digestion test, respectively; (c). the evaluation of the non-carcinogenic risk of children and adults exposure to dust based on bioaccessibility. The results showed that most of the dust particles near Huludao Zinc Plant (HZP) were relatively solid with less porosity, which might originate from incompletely burned mineral particles from the smelting process. The concentrations of Pb, Cd and Cu were much higher than the background levels: 1560, 178.5 and 917.9 mg kg^-1 in <100 μm dust samples, and 2099, 198.4, 1038 mg kg^-1 in <63 μm dust samples, respectively. Pb was mostly present in the reducible fraction and the acid exchangeable fraction, while Cd and Cu were the most common heavy metals in the acid exchangeable fraction and oxidizable fraction, respectively. The rank order of bioaccessibility for the gastric and intestinal phase was Cd (58.13%) > Pb (50.00%) > Cu (19.19%) and Cd (20.36%) > Cu (15.67%) > Pb (5.08%), respectively. Hand-to-mouth ingestion poses the greatest non-carcinogenic exposure risk compared with other exposure pathways. When bioavailability is taken into account, children experienced higher non-carcinogenic and carcinogenic risks of dust exposure compared with adults, and the <63 μm particles posed greater risks than <100 μm particles.

Pollution status and human health risk assessments of selected heavy metals in urban dust of 16 cities in Iran

Urban dust contamination is becoming progressively noticeable, and heavy metals are primary pollutants in urban environments. The contamination of heavy metals in urban dust has been affecting the urban citizens due to their adverse effects on human health, and understanding their effects is a crucial stage for its management. This study is a review of the reports of heavy metal pollution in urban dust of 16 cities in Iran, aimed at determining pollution status and health risk calculation on the nationwide scale, using geo-accumulation index (Igeo), potential ecological risk index (PER), and health risk assessment model. Six toxic elements, namely cadmium, copper, chromium, nickel, lead, and zinc were evaluated in this study. The results presented that the total heavy metal concentrations in the studied cities decreased in the sequences of Zn > Cu > Pb > Ni > Cr > Cd. The average concentrations of Cd, Cu, Ni, Pb, and Zn in the studied cities exceeded the Iran Standard Soil limits for residential areas. The mean levels of studied heavy metals for cities was in the order of Kermanshah > Tehran > Tabriz > Rafsanjan > Hamedan > Isfahan > Mashhad > Ahvaz > Abadan > Kerman > Bushehr > Kashan > Shiraz > Zahedan > Masjed-e-Soleiman > Arak. The Results of Igeo revealed that the pollution levels of Cd, Cu, Pb, Ni, Cr, and Zn in the studied cities ranged from unpolluted to moderate pollution categorizations. The mean potential ecological risk factor (Eⁱ_r) values were below (E^r_i < 40), showing a low ecological risk level. Also, Eⁱ_r values for all cities showed that Cd, Pb, and Cr had the highest ecological risks than other heavy metals. However, the total potential ecological risk index (RI) values for studied cities were 172.1, showing a moderate ecological risk level. Human health risk assessment evaluation showed that in contrast to adults, children have more possible health risks (non-carcinogenic). Among the multiple pathways of exposure, the ingestion pathway was the most important exposure for both groups of population, followed by skin exposure and then breathing exposure. Total hazard index (HI) values among three exposure routes, were less than harmless level (HI < 1), displaying that there was not a non-carcinogenic risk for both groups of population. Cancer risk (CR) study exhibited that the potential risk of cancer decreases in the order of chromium > nickel > cadmium. The CR ranks of chromium, nickel, and cadmium were less than the maximum permissible level, presented an insignificant carcinogenic risk.

Concentration, Spatial Distribution, Contamination Degree and Human Health Risk Assessment of Heavy Metals in Urban Soils across China between 2003 and 2019-A Systematic Review

This study provides an overview of the studies of heavy metal pollution regarding As, Cd, Cr, Hg, Pb, Cu, Zn and Ni in the urban soils throughout 71 cities of China, based on data from online literature, during the period 2003-2019. The concentrations, spatial distributions, contamination degrees and health risks of heavy metals in the urban soils were evaluated. The results demonstrated that the mean values of eight heavy metals all exceeded the soil background values in China, and the kriging interpolation method showed that the hot-spot cities with heavy metal contamination in urban soils were mainly concentrated in the southwest, southcentral, southeast coast, northcentral and northwest regions of China. The geoaccumulation index (Igeo) indicated that Hg and Cd were at moderate contamination levels and that the levels of the other six metals did not appear contamination. The pollution index (PI) showed that Cd and Hg reached high contamination levels, and the other metals reached moderate contamination levels. The integrated pollution index (IPI) and potential ecological risk index (PRI) indicated that the integral urban soils in the study areas ranked high contamination levels and moderate ecological risk degree, respectively, and Cd and Hg should be labeled as priority metals for control in the urban soils around China. The human health risk assessments for the heavy metals indicated that ingestion was the dominant exposure pathway for having adverse effects on human health. The mean Hazard index (HI) values of eight heavy metals all showed that adverse effects on human health were unlikely, and the mean carcinogenic (CR) values of As, Cr and Ni for children and adults all suggested an acceptable carcinogenic risk to human beings. In addition, children exposed to these heavy metals faced more serious non-carcinogenic and carcinogenic health threats compared to adults. The results could provide valuable information for demanding the better control of heavy metal pollution and mitigation of the adverse effects on residents by environmental regulators in national urban regions.

Health risk assessment and bioaccessibilities of heavy metals for children in soil and dust from urban parks and schools of Jiaozuo, China

Urban parks and schools sever as the mainly activity areas for children, but risk assessment posed by heavy metals (HMs) from soil and dust in these area has rarely been investigated. In this study, six urban parks and seven schools in Jiaozuo, China, were taken as research objects to understand the contamination level and bioaccessibility of HMs from soil and dust in urban parks and schools. The results indicated that Zn, Cu, Pb, Cd, As, Ni and Co from soil and dust were above the background values, especially Zn and Cd in dust, and As and Cd in soil. Serious Cd pollution was discovered, and respective Cd concentrations in soil and dust were 17.83 and 7.52 times the background value. Additionally, the average concentration and bioaccessibility of Zn, Mn, Pb, Cd, Cr, Ni and Co in dust were both higher than in soil. High concentration and high bioaccessibility of HMs in dust suggested that HMs contamination were serious and universal in Jiaozuo. The concentrations of most HMs were higher in the gastric phase, except for Cu and Cd which remained higher in the intestinal phase. Both in the gastric phase and intestinal phase, Mn, As and Cd in soil and dust both have high bioaccessibility which all exceed 10%. The carcinogenic and non-carcinogenic risks base on the total HMs for children (soil: 7.93, 1.96E-05; dust: 6.44, 3.58E-05) were greater than those for adults (soil: 6.35E-01, 1.32E-05; dust: 5.06E-01, 2.42E-05), and urban parks and schools posed high potential risk for children. Therefore, assessment the risk posed by HMs contamination of soil and dust in urban parks and schools is vital and urgent for children.