Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts from different functional areas in Chengdu, China

STOTEN-22029; No of Pages 9 Science of the Total Environment xxx (2017) xxx–xxx

Contents lists available at ScienceDirect

Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv

Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts from different functional areas in Chengdu, China Han-Han Li a,1, Liu-Jun Chen a,1, Lin Yu a, Zhong-Bao Guo b,1, Chun-Qiao Shan c,1, Jian-Qing Lin d,1, Yang-Guang Gu e, Zhan-Biao Yang a, Yuan-Xiang Yang a, Ji-Rong Shao f, Xue-Mei Zhu a,⁎, Zhang Cheng a,⁎ a

College of Environment, Sichuan Agricultural University, Chengdu 611130, China Guangxi Academy of Fishery Sciences, Nanning 530021, China c Dalian Sanyi Bioengineering Research Institute, Dalian 116036, China d Department of Environmental Engineering, College of Food and Biological Engineering, Jimei University, Xiamen 361021, China e South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China f School of Life Sciences, Sichuan Agricultural University, Yaan 625014, China b

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• Heavy metal concentrations in street dust collected from 5 functional areas • Health risks were evaluated for the metals combined with oral bioaccessibility. • The highest total metal concentrations were found in commercial area. • Pb, Zn, Cu, Cd and Cr mainly originate from anthropogenic sources.

a r t i c l e

i n f o

Article history: Received 4 January 2017 Received in revised form 5 February 2017 Accepted 10 February 2017 Available online xxxx Editor: D. Barcelo Keywords: Urban street dust Heavy metals Functional areas Oral bioaccessibility Risk assessment

a b s t r a c t Urban street dusts were collected in commercial area (CA), traffic area (TA), educational area (EA), residential area (RA) and parks area (PA) of Chengdu, China, to investigate the concentrations of heavy metals (Pb, Zn, Cu, Ni, Cd and Cr), and analyzed to evaluated possible sources and health risk assessment. The average concentrations (mg/kg) of Pb (82.3), Zn (296), Cu (100), Cd (1.66) and Cr (84.3) in urban street dusts were all higher than the local soil background values. The concentrations of heavy metals in each functional area could be classified as follows: CA N TA N RA N EA N PA. Principal component analysis and Cluster analysis showed mainly derived from the mixed sources of nature and traffic (51.7%). The results of health risk assessment showed no non-carcinogenic and carcinogenic risks of the metals for inhabitants. However, higher concentrations and oral bioaccessibility of the heavy metals in the dusts from CA and TA, indicating there was more health risks to the inhabitants in than that in other functional areas. © 2017 Published by Elsevier B.V.

⁎ Corresponding authors at: College of Environment, Sichuan Agricultural University, Chengdu 611130, China. E-mail addresses: [email protected] (X.-M. Zhu), [email protected] (Z. Cheng). 1 These authors contributed equally to this work.

http://dx.doi.org/10.1016/j.scitotenv.2017.02.092 0048-9697/© 2017 Published by Elsevier B.V.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

2

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

1. Introduction At present, over half of the global population lives in urbanized areas (United Nations, 2012). Rapid urbanization and continuous demand of land for infrastructural development in urban areas have placed great stress on the local environment (Soltani et al., 2015). As a consequence, there is a decline in the quality of urban environment (Ball et al., 1998; Ordonez et al., 2003). Street dust, the accumulation of solid particles on outdoor ground surfaces (Ahmed and Ishiga, 2006; Li et al., 2013), is a valuable medium for characterizing urban environmental quality (Godish, 2005; Liu et al., 2014). Street dust originates from natural sources (e.g. re-suspension of soil and weathered materials) and various anthropogenic activities (e.g. vehicular traffic, power generation facilities, industrial plants, residential fossil-fuel burning, construction material and demolition activities) (Hopke et al., 1980; Li et al., 2013; Lu et al., 2010; Schwar et al., 1988). Moreover, street dust have a high surface area and are easily transported and deposited the contaminants such as polycyclic aromatic hydrocarbons and heavy metals (Irvine et al., 2009; Keshavarzi et al., 2015; Saeedi et al., 2012). Street dust contaminated by heavy metals has drawn public attention due to the properties of high toxicity, concealment, persistence and biological accumulation. In recent years, many studies about heavy metals in street dust were focused on metal contents, fraction and contamination assessment (Fujiwara et al., 2011; Li et al., 2013; Liu et al., 2014; Lu et al., 2009), spatial distribution and particle size (Fujiwara et al., 2011; Li et al., 2015; Wang et al., 2011), and source identification (Lu et al., 2010; Pathak et al., 2013; Yildirim and Tokalioglu, 2016). Heavy metals containing dust particles, particularly the fine particles can be re-suspended into atmosphere or be absorbed by humans through ingestion, inhalation and dermal adsorption (Mohmand et al., 2015; Zheng et al., 2010). Health risk assessment of exposure to total contents of metals in street dust has been attempted in lots of cities in the world, such as Luanda, Angola (Ferreira Baptista and De Miguel, 2005), Jharkhand, India (Rout et al., 2013), London, UK (Gómez et al., 2002). Beijing, China (Du et al., 2013), and Nanjing, China (Li et al., 2013). In general, these studies identified oral ingestion as the most critical exposure route to dust particles for humans, compared with inhalation and dermal contact. Oral ingestion takes place inadvertently, with food and drink or via mucociliary clearance, and with respect to children, deliberately, through their hand to mouth activities (Mohmand et al., 2015; Stapleton et al., 2008; Turner, 2011). Ultimately, ingested particles of dusts enter the digestive system where heavy metals are mobilized from the matrix to varying degrees, subsequently, may be deposited in circulatory system and may act as cofactors in other diseases (Nriagu, 1988; Zheng et al., 2010). Previous studies indicated the actual health risks of heavy metals in ingested particles depend strongly on the oral bioaccessible fraction that is soluble in the gastrointestinal tract available for absorption, so that only a fraction of the metals in dust is human accessible (Gu et al., 2016; Hu et al., 2011; Ruby et al., 1993; Ruby et al., 1996). Estimating heavy metals bioaccessibility in food and soil can be performed by in-vivo or in-vitro methods (Moreda-Piñeiro et al., 2011). And the method of in-vitro provide effective approximations to in-vivo situations and have a series of advantages of simplicity, rapidity, ease of control, low cost, high precision and good reproducibility (Li et al., 2014; Moreda-Piñeiro et al., 2011). However, there is limited information about the application of in vitro methods for street dust samples (Bi et al., 2015; Huang et al., 2014). Chengdu is the largest city in southwestern of China, and also the center of the economy, culture, transportation and education in south west China, which has a total area of approximately 1200 km2 and an urban population of about 15.7 million in 2015 (Chen et al., 2016). In recent 20 years, the central city of Chengdu has been experiencing rapid economic growth and urbanization which characterized by urban sprawl, population growth and motorization (Qiao et al., 2013). In addition, the special topography surrounding the city, Longquan Mountain to the east and Qionglai Mountain to the west of the city can hinder

the dispersion of locally produced pollutants and cause high levels of pollution under certain weather conditions (Qiao et al., 2013; Wang et al., 2013). Air pollution has become a serious problem in this city. Previous studies showed that heavy metal concentrations in the dust samples which collected from the first, second and third ring roads of Chengdu, respectively (Chen et al., 2016; Qiao et al., 2013). However, the urban area is an assembly of different land use types and the chemical composition of urban street dust at different functional areas could show a high spatial heterogeneity (Del Rio Salas et al., 2012). Accordingly, the heavy metal levels should be investigated in street dusts in different functional areas. The major objectives of this study were as follows: (1) to determine and compare the concentrations of the heavy metals (Lead, Zinc, Copper, Nickel, Cadmium and Chromium) in urban street dusts collected from different functional areas in the central city of Chengdu; (2) to identify possible sources of the heavy metals in street dust based on multivariate statistical, and (3) to evaluate the potential health risk based on the oral bioaccessibilities of the heavy metals. 2. Materials and methods 2.1. Study area and sample collection Chengdu (30°39′43″N, 104°00′56″E), the capital of Sichuan province, in the midwestern portion of the Sichuan basin. It has a subtropical humid monsoon with an average annual temperature of 16 °C and average annual rainfall 900–1300 mm (Chen et al., 2016). For response to actual difference of heavy metals content among different functional areas, a total of 75 urban street dust samples (3 sub-samples for each sampling site) were collected from five different functional areas in Chengdu city (Fig. 1). Including commercial area (CA) (N = 15), traffic area (TA) (N = 18), educational area (EA) (N = 15), residential area (RA) (N = 18) and parks area (PA) (N = 9). Samples at each sampling site (approximately 200 g each) were collected with a clean plastic brushe and a dustpan during the same dry season between October 2014 and October 2015. All dust samples were wrapped in aluminum foil, transferred to ziplock bags, labeled and then transported to the laboratory. 2.2. Chemical analysis The samples were freeze-dried and passed through a 63 μm nylon sieve for analyses in this study. The reason for analyzing the b 63 μm diameter fraction is the fact that these particles are easily transported in suspension, with the finest particles being capable of remaining airborne for considerable durations (Shilton et al., 2005; Soltani et al., 2015). Furthermore, higher environment and health risks usually associated with fine particles rather than coarser fractions (Charlesworth et al., 2011; Li and Zuo, 2013; Liu et al., 2014). To measure heavy metal concentration, about 0.25 g street dust was microwave digested with 65% HNO3 (USEPA, 1994). Then the digestion solutions were diluted with Mili-Q water to a final volume of 25 ml, and analyzed for lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd) and chromium (Cr) and manganese (Mn) by inductively coupled plasma atomic emission spectrometer (ICP-OES, Perkin Elmer Optima 8300). The in vitro digestion test was performed according to the methods described by Moreda-Piñeiro et al. (2011) and our previous study Cheng et al. (2013) with slight modifications. The entire digestion process was performed in 50 ml capped polyethylene centrifuge tubes in the dark. In brief, 0.25 g of freeze-dried samples was first added into 30 ml of synthetic gastric juice (2.0 g/l pepsin in 0.15 M NaCl, acidified with HCl to pH 1.8) and shaken at 120 rpm for 2 h at 37 °C. Afterwards, the mixture was centrifuged (10 min, 37 °C, 2000 rpm) and the supernatant was filtered through a 0.45 μm syringe filter successively. The remaining contents in the reaction tubes were added with 30 ml artificial intestinal juice (2.0 g/l pancreatin, 2.0 g/l amylase and 5 g/l bile salts, in 0.15 M

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

3

Fig. 1. Sampling sites in the study area.

NaCl, pH 6.8) and shaken at 100 rpm for 4 h at 37 °C. Finally, the tubes were centrifuged at 10000 rpm at 37 °C for 4 min to separate supernatant and solids and the supernatant was filtered through a 0.45 μm syringe filter successively. Both gastric and intestinal supernatants were filtered through 0.45 μm Millipore filters. Then, the digested solutions were stored at 4 °C before analysis with ICP-OES (Perkin Elmer Optima 8300) for Pb, Zn, Cu, Ni, Cd and Cr. 2.3. QA/QC All of the samples were tested in triplicate. Analytical blank and reference materials were included in every sequence. Two certified reference materials (CRM): NIST 1944 (New York/New Jersey Waterway sediment) was obtained from National Institute Standards and Technology (NIST, USA) and GSS-3 (GBW07403), Soil Standard Reference Material was obtained from the National Research Central (Beijing, China). The recoveries for total metals ranged from 87% to 113% (Pb, Zn, Cu, Ni, Cd and Cr). 2.4. Statistical analysis The data were statistically analyzed using the statistics software package SPSS version 19.0 for Windows. A one-way ANOVA test (p b 0.05) was used to analyze the difference in metal concentrations among different functional areas. Principal component analysis (PCA) and cluster analysis were used to elucidate the relationship among heavy metals in urban street dusts and to identify their probable sources. PCA is widely used to reduce data and to extract a small number of independent factors (principal components) for analyzing relationships among observed variables (Han et al., 2006; Lu et al., 2010; Tokalıoğlu and Kartal, 2006). To make the results more easily interpretable, PCA with varimax normalized rotation was performed, which can maximize the variances of the factor loadings across variables for each factor (Han et al., 2006; Shi et al., 2012). In this study, all principal factors extracted from the variables were retained with eigenvalues exceed 1 (Lu et al., 2010). Cluster analysis classifies a set of observations into

two or more mutually exclusive unknown groups based on a combination of internal variables (Lu et al., 2010; Yildirim and Tokalioglu, 2016). Hierarchical cluster analysis, as the most commonly applied cluster analysis method for environmental analysis, assisted in looking for groups of samples according to their similarities (Han et al., 2006; Yildirim and Tokalioglu, 2016). Cluster analysis is often coupled with PCA to check results and to group individual parameters and variables (Lu et al., 2010; Shi et al., 2012). In recent years, PCA and cluster analysis have been widely applied to various environmental media, such as sediments (González-Pérez et al., 2008; Tahri et al., 2005), soil (Facchinelli et al., 2001; Zheng et al., 2008), water (Tahri et al., 2005) and dust (Han et al., 2006; Shi et al., 2012). 2.5. Assessment of street dust quality Enrichment factor (EF) was applied to differentiate the anthropogenic sources from natural process, as well as to assess the degree of metal contamination, which was calculated as the equation formula (Eq. (1)) (Han et al., 2006; Reimann and Caritat, 2000). In this study, manganese was used as the reference element (Han et al., 2006). The background values of elements of soil in Chengdu, China (CNEMC, 1990). EF ¼ ðCx =Cref Þdust =ðBx =Bref Þbackground

ð1Þ

where Cx is the concentration of the examined metal in urban street dust samples, Cref is the concentration of Mn in urban street dust samples, Bx is the content of the examined metal in background reference, Bref is the content of Mn in background reference. The geoaccumulation index (Igeo) determines pollution levels by comparing current metal contents with preindustrial levels (Müller, 1981). The geoaccumulation index was calculated using the following equation: Igeo ¼ log2 ½Cn =ð1:5  Bn Þ

ð2Þ

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

4

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

where Cn is the measured concentration of the heavy metals in urban street dust samples, Bn is the background content soil in Chengdu, China (CNEMC, 1990). Criteria for these contamination indictors are given in Table S1. 2.6. Health risk assessment model Human exposure of heavy metals to the urban street dust can occur via diverse paths: direct ingestion, inhalation and dermal absorption (Li et al., 2013; Zheng et al., 2010). This study aimed at quantifying the noncarcinogenic and carcinogenic risks from exposure metal contaminated urban street dust by children and adults. Hence, we estimated the daily intake via ingestion (ADDing), inhalation (ADDinh) and dermal contact (ADDdermal) for each studied metal (Eqs. (3) and (5)) (USEPA, 1989, 1996).

ADDing ¼ C 

IngR  EF  ED  10−6 BW  AT

ð3Þ

ADDinh ¼ C 

IngR  EF  ED PEF  BW  AT

ð4Þ

ADDdermal ¼ C 

SL  SA  ABS  EF  ED  10−6 BW  AT

ð5Þ

For carcinogens, the lifetime average daily does (LADD) for the Ni, Cd and Cr inhalation exposure route was used in the assessment of cancer risk (Eqs. (6)) (Keshavarzi et al., 2015; USEPA, 1996, 2001c).

LADD ¼

  C  EF IngRchild  EDchild IngRadult  EDadult  þ AT  PEF BWchild BWadult

ð6Þ

where C (exposure-point content, mg/kg) is considered to yield an estimate of the ‘reasonable maximum exposure’ (USEPA, 1989), which is the 95% upper confidence limit for the mean of dust concentration (mg/kg). The details for the mathematical model, along with the values used in these equations are specified in Table S2. The potential non-carcinogenic and carcinogenic risks for individual metals were calculated using the following equations (Eqs. (7) and (9)) (USEPA, 1989):

HQ ¼

ADD RfD

ð7Þ

HI ¼ ∑HQi

ð8Þ

CR ¼ LADD  SF

ð9Þ

The values of reference dose (RfD, mg/kg d−1) (USEPA, 1993; USEPA, 2010) and slope factor (SF) (USEPA, 2001a; USEPA, 2001b) were listed in Table S3. However, USEPA has not established an RfD for Pb (USEPA, 2010), therefore RfD for Pb used in this study was 3.5 × 10−3 mg kg day calculated from provisional tolerable weekly Pb intake limit (25 μg kg bw) recommended by the FAO/WHO (JECFA, 1993; WHO, 1993). Hazard index (HI) is equal to the sum of HQ. HI values N 1 indicates there is a chance that non-carcinogenic effects may occur, while values b 1 indicated lower or no risk of non-carcinogenic effects (USEPA, 2001c). Carcinogenic risk is the probability of an individual developing any type of cancer from life time exposure to carcinogenic hazards (Ferreira Baptista and De Miguel, 2005; Zheng et al., 2010). The acceptable or tolerable risk for regulatory purposes is in the range of 1 × 10−6–1 × 10−4.

3. Results and discussion 3.1. Heavy metals concentration in urban street dust The concentrations of heavy metals (Pb, Zn, Cu, Ni, Cd and Cr) in urban street dusts (N = 75) collected from Chengdu were shown in Fig. 2. There were no significant differences (p N 0.05) in Pb, Cu and Cr concentrations in the dusts. Zinc concentration (296 ± 109 mg/kg) was higher than other metals concentration in street dusts that was similar to those reported in previous studies with dust samples from Chengdu (Chen et al., 2016; Qiao et al., 2013). The concentrations of heavy metals in street dusts were compared with that in other cities in China and other countries (Table S4) showed lower heavy metal concentrations in the street dust than that in other first tier cities in China (e.g. Beijing, Shanghai and Guangzhou) (Shi et al., 2011; Wei et al., 2015). However, the concentration of Cd (1.66 ± 1.50 mg/kg) was higher or similar to Beijing (0.72 mg/kg) (Wei et al., 2015), Shanghai (1.00 mg/kg) (Shi et al., 2011) and Guangzhou (2.14 mg/kg) (Huang et al., 2014). Cadmium is a common component of electric batteries, electroplating, pigments and coatings (Saeedi et al., 2012; Wei et al., 2010). In Chengdu, there were many residential and commercial buildings and large-scale urban construction (Tao et al., 2013). Therefore, the high concentration of Cd in street dusts in Chengdu, which could be explained by erosion and abrasion of building materials, tires and batteries and fertilizer application. The heavy metal concentrations in urban street dusts from different functional areas in Chengdu were showed in Table 1. The concentrations of all the metals (except Ni) in CA, TA, EA, RA and PA dusts, were higher than soil background values for Chengdu, indicating the metals in urban street dusts might be derived from natural and anthropogenic emission, while Ni could be a natural origin in urban street dusts (Liu et al., 2014; Wei et al., 2015). Based on the concentrations of metals in each functional area, they could be classified as follows: CA N TA N RA N EA N PA (Table 1). The highest total metal concentrations of the street dusts were observed in CA. This observation was in line with the previous studies in Villavicencio, Colombia (Trujillo-Gonzalez et al., 2016) and Zahedan, Iran (Kamani et al., 2015). The urban area is an assembly of different land use types with typical local and diffuse pollution sources (traffic, domestic and industry), the distinctive artificial activities in each functional area could release different kinds of heavy metals content, then deposited in the street surface and led to the metals concentration widely varied between functional areas (Del Rio Salas et al., 2012; Trujillo-Gonzalez et al., 2016). High concentrations of Cu, Ni and Cr in CA dust were observed in the five functional areas of the city (p b 0.05). Lead concentration in street dusts in TA (98.5 ± 30.4 mg/kg) and RA (90.2 ± 41.8 mg/kg) were higher than that

Fig. 2. The concentrations (mg/kg) of individual heavy metals in street dust from study areas.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

5

Table 1 Concentrations (mg/kg) of heavy metal in urban street dust with different functional areas. Element

CA (N = 15)

Range Mean SD Range Mean SD Range Mean SD Range Mean SD Range Mean SD

TA (N = 18)

EA (N = 15)

RA (N = 18)

PA (N = 9)

Reference valuesa

Pb

Zn

Cu

Ni

Cd

Cr

39.4–96.4 67.2 17.5 36.6–162 98.5 30.4 20.9–152 71.8 30.2 26.0–164 90.2 41.8 34.3–114 78.8 23.7 27.0

183–549 344 118 165–478 334 78.0 124–503 255 85.8 124–607 272 137 119–386 275 84.0 74.2

53–252 149 61.9 35.6–331 107 68.6 48.9–121 80.1 18.4 47.0–235 97.4 49.3 28.8–83.7 61.0 16.7 23.1

13.0–69.8 35.8 18.7 15.3–33.4 24.7 4.65 13.3–29.5 19.3 4.47 12.8–37.2 22.6 6.58 15.3–25.0 20.1 3.10 27.4

0.71–6.40 2.07 1.67 0.94–3.93 1.95 0.61 0.65–2.73 1.14 0.48 0.40–3.85 1.51 0.97 0.50–2.49 1.74 0.74 0.10

39.9–463 153 115 48.1–84.6 67.6 11.0 51.3–93.8 71.5 12.1 54.3–105 76.6 16.3 30.1–80.0 55.3 15.2 61.0

Notes: SD standard deviation; CA, commercial area; TA, traffic area; EA, educational area; RA, residential area; PA, parks area. a Local soil background values CNEMC (1990).

collected from traffic areas in Xian, China (88.6 mg/kg) (Wang et al., 2016), Zahedan, Iran (44.0 mg/kg) (Kamani et al., 2015). 3.2. Assessment of urban street dust quality Table 2 shows the EF and Igeo for each metal based on the heavy metal concentrations in urban street dusts from different functional areas in Chengdu. The mean EF values displayed the following decreasing trend: Cd N Cu N Zn N Pb N Cr N Ni. The EF values of Pb in the dust from TA and RA were higher than that from other functional areas, and principally between 2 and 5, meaning that it was moderately enriched (Table 2) by automobile exhaust in the region may be the major source of Pb in the dust resulting from atmospheric inputs (Wong et al., 2002). The EF values of Cd in CA, TA, RA and PA dust samples showed typically high values of the city, and the EF values were larger than 20 indicated that anthropogenic sources contributed a substantial fraction of Cd to urban street dusts in these functional areas (Keshavarzi et al., 2015; Saeedi et al., 2012; Wei et al., 2010). The mean values of Igeo decreased in the order of Cd N Cu N Zn N Pb N Cr N Ni (Table 2). Using the criteria of contamination indicator in urban street dust based on Igeo to assess metal contamination of urban street dust in Chengdu, Cr and Ni were unpolluted; Pb was uncontaminated to moderately contaminated; Zn and Cu were moderately contaminated; Cd was heavy contaminated. In additional, Pb was moderately contaminated in the dust from TA and RA samples; Cu was moderately to heavily contaminated and Cr was uncontaminated to moderately contaminated in the dust from CA. The Igeo and EF of heavy metals (except Pb) in the dust from CA was higher than in other functional areas. This could be associated with the socioeconomic activities that take place in the commercial sector, where a large amount

of tall buildings and a high population density (Trujillo-Gonzalez et al., 2016). In addition, factors such as high temperature and exposure to weather accelerate corrosion processes, causing wear of the wares, walls, lamps and railings which often contained the heavy metals (e.g. Zn, Cu, Cd and Cr), eventually, resulting in the release of the metals to the urban environment and accumulation in urban street dust (Kamani et al., 2015; Pathak et al., 2013; Trujillo-Gonzalez et al., 2016). 3.3. Metal source identification The PCA was performed to determine the percentage contributions of different heavy metal sources for a given dust sample (Han et al., 2006; Shi et al., 2012). For the urban street dusts, PCA of the heavy metals resulted in the first three factors (51.7%, 20.7%, and 15.0%) accounting for 87.4% of the total variability (Fig. 3). Factor 1 was heavily weighted by Ni, Cu, and Cr. Factor 2 contributed to 20.7% of the total variability and was heavily weighted by Pb and Zn; while Factor 3 loading of Cd accounted for 15.0% of the total variation. Cluster analysis of the heavy metals showed similar results with the PCA analysis, that resulted in the three clusters including: Ni, Cu and Cr (cluster 1), Cd (cluster 2), Pb and Zn (cluster 3), respectively (Fig. S1). In additional, the result of correlation coefficient analysis showed among Zn, Cu, Ni and Cr had significantly positive correlation (p b 0.05) (Table S5). Based on the results of statistical and concentration analyses and EF values probable emission origins can be identified. The heavy metals profile of factor 1 was consistent with the emission characteristic of Ni Cu and Cr composition from nature (local soil), as well as corrosion of alloys used in vehicle components, vehicle covers or other metallic surfaces and weathering materials (paints and coatings) (Chen et al., 2014; Saeedi et al., 2012). Although the leaded petrol has been banned in

Table 2 The EF values and Igeo values of heavy metal in urban street dust with different functional areas. CNEMC, 1990. (China National Environmental Monitoring Center). The background values of elements in Chinese soils. Beijing: Environ Sci Press of China. [in Chinese]. Sites

CA (N = 15) TA (N = 18) EA (N = 15) RA (N = 18) PA (N = 9) Mean (N = 75)

EF

Igeo

Pb

Zn

Cu

Ni

Cd

Cr

Pb

Zn

Cu

Ni

Cd

Cr

2.67 4.07 3.07 4.36 3.39 3.51

5.03 5.01 3.98 4.79 4.32 4.63

6.96 5.18 4.02 5.53 3.08 4.95

1.42 1.02 0.82 1.09 0.87 1.04

23.0 22.4 13.6 20.3 20.8 20.0

2.69 1.24 1.35 1.64 1.05 1.59

0.73 1.28 0.83 1.16 0.96 0.99

1.63 1.59 1.20 1.29 1.31 1.40

2.11 1.63 1.22 1.50 0.82 1.46

−0.18 −0.71 −1.07 −0.84 −1.01 −0.76

3.83 3.74 2.98 3.37 3.58 3.50

0.74 −0.44 −0.35 −0.26 −0.73 −0.21

Notes: CA, commercial area; TA, traffic area; EA, educational area; RA, residential area; PA, parks area.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

6

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

Fig. 3. PCA results in the three-dimensional space: plot of loading of the first three principal components for 6 heavy metals.

Chengdu since 2000, the content of Pb in urban soil still reflects the significant degree of historical Pb contamination and the long half-life of Pb in soil (Yang et al., 2011). Moreover, Pb could enter urban street dust from the bare soil by resuspension (Chen et al., 2014; Zhao et al., 2014). According to previous studies, the wear and tear of vulcanized vehicle tires and corrosion of galvanized automobile parts may be the main source of Zn in urban environment due to Zn alloy and galvanized components are widely used in motor vehicles (Lu et al., 2010; Shi et al., 2012; Zhao et al., 2014). Thus, the factor 2 appeared to represent originated from traffic source. Factor 3 was generally a unique-component factor in which loading of Cd was much higher than all the others. This was similar to the PCA results of street dust in Tehran, Iran (Saeedi et al., 2012) and Urumqi, China (Wei et al., 2010) which indicated that Cd generated a single important factor and accounted for nearly 11.5% and 9.92% of the total variation, respectively. Cadmium is widely used to shelter the alloy surface and building materials and also used in galvanization, batteries, plastic, and fertilizer application (Saeedi et al., 2012; Wei et al., 2010; Yildirim and Tokalioglu, 2016). Due to the fact that there are a large amount of urban constructions such as the commercial and residential construction, subway construction, road widening, and old building renovation in Chengdu during recent years (Chen et al., 2016; Qiao et al., 2013). As a consequence, Cd in the urban street dusts could mainly originated from the erosion and abrasion of tires, car batteries and building materials, but also partly from fertilizer application in the city parks.

3.4. Health risk assessment To obtain a more accurate risk assessment of human exposure to heavy metals via urban street dust ingestion, the oral bioaccessibility of each heavy metal based on the gastrointestinal model was taken into account (Table S3). The oral bioaccessibility of heavy metals in the urban street dusts from five functional areas were ranked according: Zn (43.7%) N Cd (38.6%) N Pb (26.6%) N Cu (21.3%) N Ni (18.1%) N Cr (15.0%), indicating that there were great differences in oral bioaccessibility of the heavy metals which could be explained by the different forms may occur with these metals in gastrointestinal system (Elom et al., 2014). The result was line with other related studies (Hu et al., 2011; Huang et al., 2014). The oral bioaccessibility for Pb, Ni and Cd from TA and CA are significantly (p b 0.05) higher than other areas.

The whole bioaccessible fractions of the heavy metals were used to calculate the average daily dose for metal exposure assessment. Chromium exists in the environment predominantly in two physicochemical forms: CrIII and CrVI (Keshavarzi et al., 2015). The toxicity value of CrVI, much more toxic than CrIII, was used to estimate the worst scenario of Cr (Huang et al., 2014). The HI values for the metals were all lower than the safety level of 1 indicating that there were no non-carcinogenic risks from the heavy metals for inhabitants (children and adults) (Fig. 4). The contributions of the HQing to HI were the highest (70.4% for children and 62.1% for adults), followed by dermal contact and inhalation, indicating that ingestion was the primary pathway for heavy metals in urban street dusts that were harmful to human health. This result is also consistent with other earlier studies (Ferreira Baptista and De Miguel, 2005; Wei et al., 2015). For non-carcinogenic HI risk values of Pb and Zn for inhabitants in TA were higher than the other functional areas and the highest HI risk values of Cu, Ni, Cd and Cr were all found in CA. Whether a metal caused carcinogenic risk depends on the exposure route and their specific toxicity (Huang et al., 2014). Nickel, Cd and Cr were considered as carcinogenic risk when inhaled or ingested (Fig. S2). Cancer risks of the rough concentrations of Cr contained in street dust from five functional areas especially CA (4.88 × 10−6) were slightly exceeding1 × 10−6, and were higher than Beijing (1.28 × 10−6) (Wei et al., 2015) and Guangzhou (6.2 × 10−7) (Huang et al., 2014). These results indicated that might be potential carcinogenic risks of Cr in urban street dusts in Chengdu, particularly from commercial area. When bioaccessibility was taken into consideration, the Cancer risks were all lower than 1 × 10−6, indicating that there was no carcinogenic risk of Ni, Cd and Cr due to urban street dust exposure. In fact, higher concentrations and oral bioaccessibility of the heavy metals were observed in the dusts from CA and TA, indicating that there could be more health risks to the general population in CA and TA than other functional areas, in terms of the heavy metals. The uncertainty on the risk assessment might arise from the limited number of street dust samples and the assumed values of exposure parameters in the USEPA models, which are not authentically applicable in Chengdu. In addition, there was also other probability of potential exposure to contaminated soils, indoor dust and so on, which would elevate the aggregate risk figures. However, the present study just identifies the relative risks among different metals and provides useful information on human exposure to heavy metals via street dust that should not be neglected. 4. Conclusions The concentrations of Pb, Zn, Cu, Cd and Cr in the street dust were higher than the local soil background. In comparison with the concentrations of the heavy metals in other cities, the heavy metals concentrations in Chengdu were generally at medium or low levels. Among the five functional areas, the concentrations of the heavy metals could be classified as follows: CA N TA N RA N EA N PA. The mean EF and Igeo values displayed the same following decreasing trend: Cd N Cu N Zn N Pb N Cr N Ni. Higher EF and Igeo values of heavy metals (except Pb) were found in CA than other functional areas. Principal component analysis and Cluster analysis showed heavy metals in the street dust from Chengdu were mainly derived the nature (local soil), traffic source, erosion and abrasion of tires, car batteries and building materials. There were no non-carcinogenic and carcinogenic risks from the heavy metals for inhabitants. However, higher concentrations and oral bioaccessibility of the heavy metals in the dusts from CA and TA, and there could be more health risks to the general population in CA and TA than in other functional areas. Acknowledgments Financial support from the Sichuan province project Education Fund (no. 16ZA0036), National Natural Science Foundation of China (No. 21507095), China Agricultural Research System (No. ARS-49).

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

Fig. 4. Hazard Quotient and Hazard index (∑HQ) of each heavy metal for (a) adults and (b) children population living in different functional areas.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

7

8

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx

Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.scitotenv.2017.02.092. References Ahmed, F., Ishiga, H., 2006. Trace metal concentrations in street dusts of Dhaka city, Bangladesh. Atmos. Environ. 40, 3835–3844. Ball, J., Jenks, R., Aubourg, D., 1998. An assessment of the availability of pollutant constituents on road surfaces. Sci. Total Environ. 209, 243–254. Bi, X., Li, Z., Sun, G., Liu, J., Han, Z., 2015. In vitro bioaccessibility of lead in surface dust and implications for human exposure: a comparative study between industrial area and urban district. J. Hazard. Mater. 297, 191–197. Charlesworth, S., De Miguel, E., Ordonez, A., 2011. A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk. Environ. Geochem. Health 33, 103–123. Chen, H., Lu, X., Li, L.Y., Gao, T., Chang, Y., 2014. Metal contamination in campus dust of Xi'an, China: a study based on multivariate statistics and spatial distribution. Sci. Total Environ. 484, 27–35. Chen, M., Pi, L., Luo, Y., Geng, M., Hu, W., Li, Z., et al., 2016. Grain size distribution and health risk assessment of metals in outdoor dust in Chengdu, southwestern China. Arch. Environ. Contam. Toxicol. 70, 534–543. Cheng, Z., Nie, X.P., Wang, H.S., Wong, M.H., 2013. Risk assessments of human exposure to bioaccessible phthalate esters through market fish consumption. Environ. Int. 57, 75–80. CNEMC China National Environmental Monitoring Center, 1990. The Background Values of Elements in Chinese Soils. Environ Sci Press of China, Beijing (in Chinese). Del Rio Salas, R., Ruiz, J., De la O-Villanueva, M., Valencia Moreno, M., Moreno Rodríguez, V., Gómez Alvarez, A., et al., 2012. Tracing geogenic and anthropogenic sources in urban dusts: insights from lead isotopes. Atmos. Environ. 60, 202–210. Du, Y., Gao, B., Zhou, H., Ju, X., Hao, H., Yin, S., 2013. Health risk assessment of heavy metals in road dusts in urban parks of Beijing, China. Prog. Environ. Sci. 18, 299–309. Elom, N.I., Entwistle, J.A., Dean, J.R., 2014. Oral bioaccessibility of potentially toxic elements (PTEs) in urban dusts of Abakaliki,Ebonyi State, Nigeria. J. Appl. Sci. Environ. Manag. 18, 235–240. Facchinelli, A., Sacchi, E., Mallen, L., 2001. Multivariate statistical and GIS-based approach to identify heavy metal sources in soils. Environ. Pollut. 114, 313–324. Ferreira Baptista, L., De Miguel, E., 2005. Geochemistry and risk assessment of street dust in Luanda, Angola: a tropical urban environment. Atmos. Environ. 39, 4501–4512. Fujiwara, F., Rebagliati, R.J., Dawidowski, L., Gómez, D., Polla, G., Pereyra, V., et al., 2011. Spatial and chemical patterns of size fractionated road dust collected in a megacitiy. Atmos. Environ. 45, 1497–1505. Gómez, B., Palacios, M.A., Gómez, M., Sanchez, J.L., Morrison, G., Rauch, S., et al., 2002. Levels and risk assessment for humans and ecosystems of platinum-group elements in the airborne particles and road dust of some European cities. Sci. Total Environ. 299, 1–19. Godish, T., 2005. Air quality. fourth ed. A CRC Press Company, Lewis Publishers. González-Pérez, J.A., De Andrés, J., Clemente, L., Martín, J., González-Vila, F.J., 2008. Organic carbon and environmental quality of riverine and off-shore sediments from the Gulf of Cádiz, Spain. Environ. Chem. Lett. 6, 41–46. Gu, Y., Gao, Y., Lin, Q., 2016. Contamination, bioaccessibility and human health risk of heavy metals in exposed-lawn soils from 28 urban parks in southern China's largest city, Guangzhou. Appl. Geochem. 67, 52–58. Han, Y.M., Du, P.X., Cao, J.J., Eric, S.P., 2006. Multivariate analysis of heavy metal contamination in urban dusts of Xi'an, central China. Sci. Total Environ. 355, 176–186. Hopke, P.K., Lamb, R.E., Natusch, D.F., 1980. Multielemental characterization of urban roadway dust. Environ. Sci. Technol. 14, 164–172. Hu, X., Zhang, Y., Luo, J., Wang, T., Lian, H., Ding, Z., 2011. Bioaccessibility and health risk of arsenic, mercury and other metals in urban street dusts from a mega-city, Nanjing, China. Environ. Pollut. 159, 1215–1221. Huang, M., Wang, W., Chan, C.Y., Cheung, K.C., Man, Y.B., Wang, X., et al., 2014. Contamination and risk assessment (based on bioaccessibility via ingestion and inhalation) of metal(loid)s in outdoor and indoor particles from urban centers of Guangzhou, China. Sci. Total Environ. 479-480, 117–124. Irvine, K.N., Perrelli, M.F., Ngoen-klan, R., Droppo, I.G., 2009. Metal levels in street sediment from an industrial city: spatial trends, chemical fractionation, and management implications. J. Soils Sediments 9, 328–341. JECFA, 1993. Evaluation of Certain Food Additives and Contaminants: 41st Report of the Joint FAO/WHO Expert Committee on Food Additives. World Health Organization, Geneva (Technical Reports Series No. 837). Kamani, H., Ashrafi, S.D., Isazadeh, S., Jaafari, J., Hoseini, M., Mostafapour, F.K., et al., 2015. Heavy metal contamination in street dusts with various land uses in Zahedan, Iran. Bull. Environ. Contam. Toxicol. 94, 382–386. Keshavarzi, B., Tazarvi, Z., Rajabzadeh, M., Najmeddin, A., 2015. Chemical speciation, human health risk assessment and pollution level of selected heavy metals in urban street dust of Shiraz, Iran. Atmos. Environ. 119, 1–10. Li, F., Huang, J., Zeng, G., Huang, X., Liu, W., Wu, H., et al., 2015. Spatial distribution and health risk assessment of toxic metals associated with receptor population density in street dust: a case study of Xiandao District, Changsha, middle China. Environ. Sci. Pollut. Res. Int. 22, 6732–6742. Li, H., Qian, X., Hu, W., Wang, Y., Gao, H., 2013. Chemical speciation and human health risk of trace metals in urban street dusts from a metropolitan city, Nanjing, SE China. Sci. Total Environ. 456–457, 212–221.

Li, H., Zuo, X.J., 2013. Speciation and size distribution of copper and zinc in urban road runoff. Bull. Environ. Contam. Toxicol. 90, 471–476. Li, H.B., Cui, X.Y., Li, K., Li, J., Juhasz, A.L., Ma, L.Q., 2014. Assessment of in vitro lead bioaccessibility in house dust and its relationship to in vivo lead relative bioavailability. Environ. Sci. Technol. 48, 8548–8555. Liu, E., Yan, T., Birch, G., Zhu, Y., 2014. Pollution and health risk of potentially toxic metals in urban road dust in Nanjing, a mega-city of China. Sci. Total Environ. 476–477, 522–531. Lu, X., Wang, L., Lei, K., Huang, J., Zhai, Y., 2009. Contamination assessment of copper, lead, zinc, manganese and nickel in street dust of Baoji, NW China. J. Hazard. Mater. 161, 1058–1062. Lu, X., Wang, L., Li, L.Y., Lei, K., Huang, L., Kang, D., 2010. Multivariate statistical analysis of heavy metals in street dust of Baoji, NW China. J. Hazard. Mater. 173, 744–749. Müller, G., 1981. Die Schwermetallbelastung der Sedimente des Neckars und seiner Nebenflüsse Eine Bestandsaufnahme. Chemiker-Zeitung 6, 157–164. Mohmand, J., Eqani, S.A., Fasola, M., Alamdar, A., Mustafa, I., Ali, N., et al., 2015. Human exposure to toxic metals via contaminated dust: bio-accumulation trends and their potential risk estimation. Chemosphere 132, 142–151. Moreda-Piñeiro, J., Moreda-Piñeiro, A., Romarís-Hortas, V., Moscoso-Pérez, C., LópezMahía, P., Muniategui-Lorenzo, S., et al., 2011. In-vivo and in-vitro testing to assess the bioaccessibility and the bioavailability of arsenic, selenium and mercury species in food samples. TrAC Trends Anal. Chem. 30, 324–345. Nriagu, J.O., 1988. A silent epidemic of environmental metal poisoning? Environ. Pollut. 50, 139–161. Ordonez, A., Loredo, J., De Miguel, E., Charlesworth, S., 2003. Distribution of heavy metals in the street dusts and soils of an industrial city in northern Spain. Arch. Environ. Contam. Toxicol. 44, 160–170. Pathak, A.K., Yadav, S., Kumar, P., Kumar, R., 2013. Source apportionment and spatial-temporal variations in the metal content of surface dust collected from an industrial area adjoining Delhi, India. Sci. Total Environ. 443, 662–672. Qiao, X., Schmidt, A.H., Tang, Y., Xu, Y., Zhang, C., 2013. Demonstrating urban pollution using toxic metals of road dust and roadside soil in Chengdu, southwestern China. Stoch. Env. Res. Risk A. 28, 911–919. Reimann, C., Caritat, P.d., 2000. Intrinsic flaws of element enrichment factors (EFs) in environmental geochemistry. Environ. Sci. Technol. 34, 5084–5091. Rout, T.K., Masto, R.E., Ram, L.C., George, J., Padhy, P.K., 2013. Assessment of human health risks from heavy metals in outdoor dust samples in a coal mining area. Environ. Geochem. Health 35, 347–356. Ruby, M.V., Davis, A., Link, T.E., Schoof, R., Chaney, R.L., Freeman, G.B., et al., 1993. Development of an in vitro screening test to evaluate the in vivo bioaccessibility of ingested mine-waste lead. Environ. Sci. Technol. 27, 2870–2877. Ruby, M.V., Davis, A., Schoof, R., Eberle, S., Sellstone, C.M., 1996. Estimation of lead and arsenic bioavailability using a physiologically based extraction test. Environ. Sci. Technol. 30, 422–430. Saeedi, M., Li, L.Y., Salmanzadeh, M., 2012. Heavy metals and polycyclic aromatic hydrocarbons: pollution and ecological risk assessment in street dust of Tehran. J. Hazard. Mater. 227–228, 9–17. Schwar, M., Moorcroft, J., Laxen, D., Thompson, M., Armorgie, C., 1988. Baseline metal-indust concentrations in greater London. Sci. Total Environ. 68, 25–43. Shi, G., Chen, Z., Bi, C., Wang, L., Teng, J., Li, Y., et al., 2011. A comparative study of health risk of potentially toxic metals in urban and suburban road dust in the most populated city of China. Atmos. Environ. 45, 764–771. Shi, X., Chen, L., Wang, J., 2012. Multivariate analysis of heavy metal pollution in street dusts of Xianyang city, NW China. Environ. Earth Sci. 69, 1973–1979. Shilton, V.F., Booth, C.A., Smith, J.P., Giess, P., Mitchell, D.J., Williams, C.D., 2005. Magnetic properties of urban street dust and their relationship with organic matter content in the West Midlands, UK. Atmos. Environ. 39, 3651–3659. Soltani, N., Keshavarzi, B., Moore, F., Tavakol, T., Lahijanzadeh, A.R., Jaafarzadeh, N., et al., 2015. Ecological and human health hazards of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in road dust of Isfahan metropolis, Iran. Sci. Total Environ. 505, 712–723. Stapleton, H.M., Kelly, S.M., Allen, J.G., Mcclean, M.D., Webster, T.F., 2008. Measurement of polybrominated diphenyl ethers on hand wipes: estimating exposure from hand-tomouth contact. Environ. Sci. Technol. 42, 3329–3334. Tahri, M., Benyaich, F., Bounakhla, M., Bilal, E., Gruffat, J.J., Moutte, J., et al., 2005. Multivariate analysis of heavy metal contents in soils, sediments and water in the region of Meknes (central Morocco). Environ. Monit. Assess. 102, 405–417. Tao, J., Zhang, L., Engling, G., Zhang, R., Yang, Y., Cao, J., et al., 2013. Chemical composition of PM2.5 in an urban environment in Chengdu, China: importance of springtime dust storms and biomass burning. Atmos. Res. 122, 270–283. Tokalıoğlu, Ş., Kartal, Ş., 2006. Multivariate analysis of the data and speciation of heavy metals in street dust samples from the Organized Industrial District in Kayseri (Turkey). Atmos. Environ. 40, 2797–2805. Trujillo-Gonzalez, J.M., Torres-Mora, M.A., Keesstra, S., Brevik, E.C., Jimenez-Ballesta, R., 2016. Heavy metal accumulation related to population density in road dust samples taken from urban sites under different land uses. Sci. Total Environ. 553, 636–642. Turner, A., 2011. Oral bioaccessibility of trace metals in household dust: a review. Environ. Geochem. Health 33, 331–341. United Nations, 2012. World Urbanization Prospects: The 2011 Revision (CD-ROM Edition). USEPA, 1989. Risk Assessment Guidance for Superfund Vol. I: Human Health EvaluationManual. EPA/540/1-89/002. Office of Solid Waste and Emergency Response. USEPA, 1993. Reference Dose (RfD): Description and Use in Health Risk Assessments. Background Document 1 A. Integrated risk information system (IRIS). USEPA, 1994. Method 3051 Microwave Assistant Acid Digestion of Sediment, Sludges, Soils And Oils. U.S. Environmental Protection Agency, Washington, DC.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092

H.-H. Li et al. / Science of the Total Environment xxx (2017) xxx–xxx USEPA, 1996. Soil Screening Guidance: Technical Background Document. EPA/540/R-95/ 128. Office of Solid Waste and Emergency Response. USEPA, 2001a. Child-Specific Exposure Factors Handbook. National Center for Environmental Assessment. EPA-600-P-00-002B. USEPA, 2001b. Risk Assessment Guidance for Superfund: Volume III-Part A, Process for Conducting Probabilistic Risk Assessment. Washington, D.C. EPA 540-R-02-002. USEPA, 2001c. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites. OSWER 9355.4-24. Office of Solid Waste and Emergency Response. USEPA, 2010. Estimation of Relative Bioavailablity of Lead in Soil and Soil-like Materials Using in Vivo and in Vitro Methods. OSWER 9285.7-77. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. Wang, G., Oldfield, F., Xia, D., Chen, F., Liu, X., Zhang, W., 2011. Magnetic properties and correlation with heavy metals in urban street dust: a case study from the city of Lanzhou, China. Atmos. Environ. 289–298. Wang, Q., Cao, J., Shen, Z., Tao, J., Xiao, S., Luo, L., et al., 2013. Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu, China. Particuology 11, 70–77. Wang, Q., Lu, X., Pan, H., 2016. Analysis of heavy metals in the re-suspended road dusts from different functional areas in Xi'an, China. Environ. Sci. Pollut. Res. Int. 23, 19838–19846. Wei, B., Jiang, F., Li, X., Mu, S., 2010. Heavy metal induced ecological risk in the city of Urumqi, NW China. Environ. Monit. Assess. 160, 33–45.

9

Wei, X., Gao, B., Wang, P., Zhou, H., Lu, J., 2015. Pollution characteristics and health risk assessment of heavy metals in street dusts from different functional areas in Beijing, China. Ecotoxicol. Environ. Saf. 112, 186–192. WHO, 1993. Guidelines for Drinking Water Quality. (Recommendations, seconded, vol. I). WHO, Geneva. Wong, S., Li, X., Zhang, G., Qi, S., Min, Y., 2002. Heavy metals in agricultural soils of the Pearl River Delta, south China. Environ. Pollut. 119, 33–44. Yang, Z., Lu, W., Long, Y., Bao, X., Yang, Q., 2011. Assessment of heavy metals contamination in urban topsoil from Changchun City, China. J. Geochem. Explor. 108, 27–38. Yildirim, G., Tokalioglu, S., 2016. Heavy metal speciation in various grain sizes of industrially contaminated street dust using multivariate statistical analysis. Ecotoxicol. Environ. Saf. 124, 369–376. Zhao, N., Lu, X., Chao, S., Xu, X., 2014. Multivariate statistical analysis of heavy metals in less than 100 μm particles of street dust from Xining, China. Environ. Earth Sci. 73, 2319–2327. Zheng, N., Liu, J., Wang, Q., Liang, Z., 2010. Health risk assessment of heavy metal exposure to street dust in the zinc smelting district, Northeast of China. Sci. Total Environ. 408, 726–733. Zheng, Y., Chen, T., He, J., 2008. Multivariate geostatistical analysis of heavy metals in topsoils from Beijing, China. J. Soils Sediments 8, 51–58.

Please cite this article as: Li, H.-H., et al., Pollution characteristics and risk assessment of human exposure to oral bioaccessibility of heavy metals via urban street dusts fr..., Sci Total Environ (2017), http://dx.doi.org/10.1016/j.scitotenv.2017.02.092