Ecological and Human Health Hazards of Heavy Metals and Polycyclic Aromatic Hydrocarbons (Pahs) in Road Dust of Isfahan Metropolis, Iran

Science of the Total Environment 505 (2015) 712–723

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Science of the Total Environment

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Ecological and human health hazards of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in road dust of Isfahan metropolis, Iran

Naghmeh Soltani a,⁎, Behnam Keshavarzi a, Farid Moore a, Tahereh Tavakol a, Ahmad Reza Lahijanzadeh b, Nemat Jaafarzadeh c,d,MaryamKermanie a Department of Earth Sciences, College of Science, Shiraz University, Shiraz 71454, Iran b Khuzestan Environmental Protection Ofﬁce, Khuzestan, Iran c Environmental Technology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran d School of Health, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran e Isfahan Environmental Protection Ofﬁce, Isfahan, Iran

HIGHLIGHTS

• This study assesses a comprehensive environmental risk of trace metals and PAHs pollution in road dust. • As, Cd, Cu, Pb and Zn contamination were found to be signiﬁcantly elevated in Isfahan road dust. • Trafﬁc is the major contributing source of road dust pollution. • Exposure to PAHs in road dust poses high cancer risk for Isfahan residents.

article info abstract

Article history: This study investigates trace elements and PAHs content in road dust of Isfahan metropolis, central Iran. The Received 29 June 2014 mean concentrations of As, Cd, Cu, Ni, Pb, Sb and Zn are 22.15, 2.14, 182.26, 66.63, 393.33, 6.95 and Received in revised form 27 September 2014 707.19 mg kg−1, respectively. When compared with upper continental crust, the samples generally display ele- Accepted 27 September 2014 vated trace element concentrations, except for Co and Cr. The decreasing trend of calculated enrichment factors Available online xxxx (EFs) is Cd N Pb N Sb N Zn N Cu N As N Ni N Cr N Co. Calculated potential ecological risk reveals that among the an- fi Editor: Xuexi Tie alyzed metals, Cd and Pb, have a higher potential ecological risk. Statistically, two identi ed main sources of trace elements include road traffic emissions and resuspension of soil particles. As, Cd, Cu, Pb, Sb and Zn in Isfahan road Keywords: dust are strongly influenced by anthropogenic activity, mainly traffic emissions, while Co, Cr and Ni originate Road dust from resuspension of soil natural parent particles. The sum of 13 major PAHs (∑13PAHs) mass concentration Heavy metal ranges from 184.64 to 3221.72 μgkg−1 with the mean being 1074.58 μgkg−1. PAHs sources are identified PAHs using PCA analysis. It is demonstrated that the PAHs in Isfahan road dust are mainly derived from traffic emission, Isfahan coal combustion and petroleum. Toxic equivalent concentrations (TEQs) of PAHs in the road dust ranges between 25.021 μgkg−1 and 230.893 μgkg−1. High correlation coefficients (r2 = 0.909 and 0.822, p b 0.01) between Benzo[a]pyrene, Benzo[b + k]fluoranthene and toxicity equivalent concentrations of road dust indicate that Benzo[a]pyrene and Benzo[b + k]fluoranthenes are major TEQ contributors. The total incremental life time cancer risk (ILCR) of exposure to PAHs from Isfahan metropolis urban dust is 4.85 × 10−4 for adult and 5.02 × 10−4 for children. Estimated results of ILCR indicate that Isfahan residents are potentially exposed to high cancer risk via both dust ingestion and dermal contact. © 2014 Elsevier B.V. All rights reserved.

1. Introduction urban environment (Ball et al., 1998; Ordonez et al., 2003; Brown and Peake, 2006). Road dust, an accumulation of solid particles in the form Rapid urbanization and continuous demand of land for infrastruc- of organic and inorganic pollutants on outdoor ground surfaces, is a tural development in urban areas have placed great stress on the local valuable medium for characterizing urban environmental quality environment. As a consequence, there is a decline in the quality of (Godish, 2005; Liu et al., 2014). It may act as a temporary sink of contaminants from a variety of sources and may also act as a source of ⁎ Corresponding author. Tel./fax: +98 711 2284572. materials contributing to atmospheric pollution through resuspension E-mail address: [email protected] (N. Soltani). (Amato et al., 2010; Moreno et al., 2013).

Heavy metals in road dust can remain in urban environments for a In developing countries like Iran, anthropogenic problems associated long time or be resuspended into the atmosphere and thus pose a with metal and organic pollution of surface dust is more felt due to lack potential threat to local ecosystems and public health (Li et al., 2001; of adequate pollution management, poor emission standards and Cook et al., 2005). obsolete vehicles and industrial plants. However, not many studies are Trace metals in urban road dust may originate from various mobile devoted to the sources and toxicities of trace metals and PAHs in road and stationary sources in urbanized areas, including industrial pollution, dust from metropolitans. traffic emissions (exhaust and non-exhaust), weathering of building Isfahan, metropolis in Central Iran, with a population of over and pavement, municipal activities, atmospheric deposition and natural 1.6 million inhabitants (Karimi et al., 2011), has experienced a rapid ur- geochemical processes (Manasreh, 2010; Gunawardana et al., 2012). banization and industrialization in the last decades (Esmaeili et al., Another group of contaminants in road dusts are polycyclic aromatic 2014). Industrial growth along with expanding population and increas- hydrocarbons (PAHs), which are a group of organic compounds with ing number of vehicles in Isfahan has increased heavy metals accumula- multiple aromatic rings and are ubiquitous in the environment. Sixteen tion in airborne particles (Hojati, 2010) and urban soils (Amini et al., PAHs are classified as priority pollutants by the United States Environ- 2005). According to the Isfahan meteorological office internal reports, mental Protection Agency (US EPA) and are extensively studied by the study area has desert climate with cold winters and hot summers, environmental scientists in various environmental compartments such low rainfall and a wind direction predominantly from west to east. as soil, dust, natural waters and sediments because of their mutagenic The average annual rainfall and wind speed of the region are 70 mm, and carcinogenic properties (US EPA, 1984; Ren et al., 2006). In particu- and 27 ms−1 in April and 6 ms−1 in the August, respectively. The annual lar, benzo(a) pyrene (BaP) or dibenzo (a,h) anthracene (DBA) shows mean temperature is 16.7 °C, ranging from minimum 10.6 °C in winter strong inhalation and dermal carcinogenic risk (Lee and Dong, 2011). to maximum 40.6 °C in summer (Esmaeili and Moore, 2012). It has been reported that vehicle exhausts, lubricating oils, materials The main objective of this preliminary study is to determine the con- weathered from road surfaces, tire particles, asphalt pavement, concentration and source of trace metal/metalloids (As, Cd, Co, Cr, Cu, Ni, struction materials and atmospherically deposited materials are re- Pb, Sb and Zn) and PAHs in road dust samples collected from Isfahan sponsible for PAHs concentration in the surface of road dust within city and to assess their contamination level. Also, to evaluate cancer urban areas (Aryal et al., 2006; Liu et al., 2007). Characterizing the dom- risk assessment of PAHs exposure via inhalation and dust intake. The re- inant anthropogenic sources of metals and PAHs in road dust is impor- sults of this research will provide an important insight into trace metal/ tant and helpful in implementing suitable management strategies, as metalloids and PAHs in Isfahan urban environment and is conducive to well as quantifying levels of pollution (Shi et al., 2008; Lu et al., 2010). the scientific society, the local enterprises and the policy makers of the During the past several decades, exposure to road dust, enriched municipality. with toxic metals and PAHs, has been extensively investigated for their pollution status and associated health problems (Kennedy and 2. Materials and methods Hinds, 2002; Dahle et al., 2003; Zheng et al., 2010). Moreover, metals and PAHs in road dust may be dispersed into road runoff, or mobilized 2.1. Sampling, sample preparation and analytical procedures by storm water runoff, affecting the quality of receiving water bodies (Birch and McCready, 2009; Zhao et al., 2010). Due to the strong effects Twenty-four road dust samples (each weighting approximately of trace metals and PAHs in air and water environments, road dust has 500 g) were collected from different locations in the highly urbanized become a great concern in recent years. region of Isfahan during August 2012. Samples were collected close to

Table 1 Trafﬁc loads and land use characteristics of the sampling sites over the urban area of Isfahan.

UTM zone 40N Sampling code Trafﬁc load Land use Sampling site

XY HM PAHs

567900 3617934 HM1 P4 Heavy CA-RA Chamran Expressway 581485 3622949 HM2 P19 Medium CA-RA Shahid Beheshti airport 565842 3619602 HM3 P18 Medium RA-AA Besat-Asheghe Isfahani Street 565620 3622120 HM4 P17 Medium RA Farzanegan Street 559466 3625209 HM5 P16 Medium AA Moalem Expressway 550277 3630051 HM6 P14 Heavy IA Isfahan reﬁnery 552935 3622567 HM7 P1 Heavy TA-CA Esteghlal square 559919 3616345 HM8 P15 Heavy AA-RA Imam Khomeyni Street 557666 3612971 HM9 P23 Heavy TA-AA Atashgah Street 560337 3612847 HM10 P2 Heavy RA Shahid Kharazi Expressway 557882 3609116 HM11 P11 Medium AA-RA Shahid Habibollahi Expressway 554314 3607254 HM12 P12 Medium RA Shahid Kazemi Expressway 562802 3605715 HM13 P7 Heavy CA Soffeh terminal 568072 3603278 HM14 P8 Medium AA Isfahan ringway 555243 3608217 HM15 P5 Medium AA Andisheh multi-level crossing 566220 3608345 HM16 P9 Medium RA Shahid Keshvari Expressway 562404 3610111 HM17 P10 Heavy CA Azadi square 562697 3612893 HM18 P13 Heavy CA Inghelab square 563247 3618264 HM19 P24 Heavy CA Kaveh terminal 566652 3614215 HM20 P20 Medium RA Parvin Street 569078 3615934 HM21 P21 Medium AA-RA Shahid Aghababaei Expressway 546896 3648959 HM22 P28 Heavy AA Murchekhort highway police station 535093 3594390 HM23 P26 Medium RA Foladshahr 536509 3587392 HM24 P27 Medium AA Zobahan Expressway 562953 3615088 no sample P3 Heavy CA Shohada square 564705 3601470 no sample P6 Heavy IA Intrace of Isfahan-Shiraz road 560295 3614997 no sample P22 Heavy RA Ashraﬁ esfehani junction 536108 3589946 no sample P25 Medium IA Zob-e-ahan steel mill entrance

CA = commercial area, RA = residental area, AA = agricultural area, IA = industrial area, TA = touristic area. 714 N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723

Fig. 1. The studied area and sampling locations. (For interpretation of the references to colour in this figure, the reader is referred to the web version of this article.) airport, refinery, ringway, terminal and highway police station. Table 1 reference material (multi-element soil standard OREAS45c and shows the description of the sampling sites, the traffic loads and the OREAS24p). The recovery rates for the considered metals in the land use characteristics. As shown in Fig. 1, each sample was collected OREAS were given on the standard certificate; for volatile elements by gently sweeping an area of about 2 m2 adjacent to the curb of the such as As and Sb, the recoveries were higher in Aqua Regia (AR) than road using a plastic hand broom and transferred to a clean, self-sealed those in total digestion due to the volatilization. polyethylene bag. In the laboratory, samples were first air-dried at Twenty-eight road dust samples were also simultaneously collected room temperature and then mechanically passed through a 2 mm and put into sealed amber glass Teflon-capped containers for PAHs anal- nylon sieve to remove refuse and large size particles and plant leaves. ysis. The samples were stored in an ice chest at 4 °C and conveyed to the The samples were fractionated through a 220 mesh (63 μm) for particle laboratory, where they were stored at −20 °C prior to analysis. In the size analysis and then homogenized in an agate mortar. The reason for laboratory, the samples were freed from foreign materials, air-dried to analyzing the b63 μm diameter fraction is the fact that these particles a constant weight and then sieved through a 200 μm mesh. Particles are easily transported in suspension, with the finest particles being ca- b63 μm were prepared for PAH analyses using gas chromatography/ pable of remaining airborne for considerable durations (Shilton et al., mass spectrometry system (GC/MS) in the Iranian Mineral Processing 2005). Furthermore, higher health risks is usually associated with fine Research Center (IMPRC) according to EPA SW-846 methods 3550C particles than coarser ones (Kennedy and Hinds, 2002; Charlesworth (US EPA, 2007) and EPA 8270D (US EPA, 1998). Briefly, each freeze- et al., 2011; Li and Zuo, 2013). dried samples (approximately 5 g) were spiked with surrogate stan- Heavy metals/metalloids (Al, As, Cd, Co, Cr, Cu, Ni, Pb, Sb and Zn) dards (Pyrene-D10, lot: 10510 semivolatile internal standard). Then were determined using inductively coupled plasma mass spectrometry the samples were extracted using a 30 mL mixture of organic solvents (ICP-MS) at the accredited Acme Analytical laboratory, Canada. (n-hexane and dichloromethane [DCM] in a 1:1 ratio) in an ultrasonic About 0.25 g of the prepared dust sample was heated in a concentrated bath (KUDOS, SK3210LHC model) for 30 min at room temperature.

HF-HNO3-HClO4 mixture to fuming and taken to dryness. The residue is The filtered extracts were concentrated to 2 ml by using rotary evapora- dissolved in HCL. The concentrations of trace metals of the digested tor. The concentrated extracts were then analyzed for PAHs by gas solution were determined by an inductively coupled plasma-mass chromatography coupled to a mass spectrometer (Agilent 6890 N spectrometer (ICP-MS) (model PerkinElmer EIAN 9000). QA/QC includ- 5975C, USA) equipped with a splitless injector, HP-5MS Capillary col- ed reagent blanks, analytical duplicates and analysis of the standard umn (30 m × 0.32 mm × 0.25 μm), in selected-ion monitoring (SIM) N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723 715 mode. Helium was used as the carrier gas at a flow rate of 1.5 ml/min. 2.3. Statistical analysis of apportionment sources The GC oven program consisted of an initial temperature of 60 °C (1-min hold), increased to 295 °C at a rate of 11 °C/min (5-min To identify the relationship among heavy metals and PAHs in road hold). The 13 quantified PAHs in this study include naphthalene dust and their possible sources, Spearman's correlation coefficients (Np), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Flu), and principal component analysis were performed using the commer- phenanthrene (Phe), anthracene (Ant), pyrene (Pyr), fluoranthene cial statistics software package SPSS version 19.0 for Windows. The cor- (Fl), benzo[a] anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene relation coefficient measures the strength of inter-relationship between (BbF), benzo[k]fluoranthene (BkF) and benzo[a]pyrene (BaP). Species two heavy metals. Spearman's rank correlation coefficient is defined as like dibenzo[a,h]anthracene (DahA), indeno[1,2,3-cd]pyrene (IcdP) follows: and benzo[ghi]perylene (BghiP), if present, were below the instrument X 2 detection limit. 6 di ρ ¼ 1− ð5Þ All analytical data were subjected to strict quality control to ensure nn2−1 the accuracy and precision of the analyses. These controls included employing blanks and reference material, analyzing duplicate samples where d = rank x − rank y. This coefficient is normally used when and reanalyzing samples exceeding ±20% relative percent difference Pearson's correlation coefficient is not valid due to data being clearly (RPD), and checking and calibrating the standard curves using the non-normal, or where data are provided in the form of ranks rather PAHs reference standard (PAH Mix 25). The average recoveries based than in the form of measurements. Spearman's rank correlation coeffi- on surrogate deuterated PAHs were approximately 75%–100% for the cient is also sometimes used even when Pearson's coefficient would be 13 measured PAHs. These recovery rates were used to correct the PAH valid due to simplicity of the required calculations (Moore and Cobby, concentrations in the road dust samples. 2001). PCA is an effective analytical tool to minimize a set of original variables and extract a small number of latent factors for analyzing relation- 2.2. Pollution assessment ships between observed variables and samples (Shi et al., 2008; Škrbić and Ðurišić-Mladenović, 2010). When PCA with varimax normalized ro- Enrichment factor (EF) was used to assess the degree of metal pollu- tation was performed, each principal component score contained infor- tion (Yuen et al., 2012) and probable natural or anthropogenic sources mation on all of the metals and PAHs combined into a single number, (Wei et al., 2010). EF is defined mathematically as: while the loadings indicated the relative contribution for each metal and PAHs species made to that score (Han et al., 2006; Kong et al., 2012). ¼ ðÞ= =ðÞ= ð Þ EF Cn Rre f sample Bn Bre f background 1 2.4. Cancer risk assessment where (Cn/Rref)sample and (Bn/Bref)background refer to the concentration ratios of a target metal and the reference metal in the road dust samples The identified toxicities of PAHs in the road dust samples were and in the background material, respectively (Lu et al., 2010; Yuen et al., evaluated using relative toxicity value of each PAH compound. The PAH 2012). Aluminum was used as normalizer and concentrations of ele- toxicities of road dust samples were calculated based on the set of toxicity ments in the crust were taken as background. EF can also give an insight equivalency factors (TEFs) of PAHs proposed by Nisbet and LaGoy (1992). into differentiating an anthropogenic source from a natural one. In BaP (the most toxic PAH) was taken as the reference chemical and was general, EF values much higher than 10 are mainly considered to have assigned a value of 1 in the TEF system (Nisbet and LaGoy, 1992; anthropogenic sources while values less than 10 predominantly origi- Pufulete et al., 2004). Other PAHs have their own TEF values based on nate from background soil material (Liuetal.,2003). Moreover, EF their carcinogenic level in comparison to that of BaP as reported by also assists in determining the degree of metal contamination. Five many authors (e.g. Pufulete et al., 2004; Dong and Lee, 2009). The carcino- contamination categories are recognized on the basis of the enrichment genic potency of total PAHs is obtained by summing the toxic benzo[a] factor: EF b 2statesdeficiency to minimal enrichment, EF = 2–5mod- pyrene equivalent (BaPeq) concentrations of each PAHs (Kong et al., erate enrichment, EF = 5–20 significant enrichment, EF = 20–40 very 2010; Cristale et al., 2012). The toxic equivalent concentration (TEQ) of high enrichment and EF N 40 extremely high enrichment (Yongming each road dust sample was calculated by summing the products of each et al., 2006; Birch and Olmos, 2008). individual PAH concentration and its TEF, as follows: Potential ecological risk index (RI) originally introduced by X ¼ ; ¼ ðÞ ðÞ Hakanson (1980) is also calculated to assess the degree of heavy BaPeqi PAHi TEFi and TEQ PAHi TEFi 6 metal pollution in soil, using the following equations:

where PAHi is the concentration of the PAH congener i,TEFi is the toxic Xn equivalent factor for the PAH congener i and TEQ is the toxic equivalent RI ¼ E ð2Þ i of the compound. i¼1 The incremental lifetime cancer risk (ILCR) quantitatively estimates ¼ ð Þ the exposure risk for environmental PAHs based on the US EPA standard Ei Ti f i 3 models (US EPA, 1991; Chen and Liao, 2006; Peng et al., 2011). The ILCR (unitless) in terms of direct ingestion, dermal contact and inhalation are C f ¼ i ð4Þ as follows: i B i rffiffiffiffiffiffiffiffi! 3 BW CS CSF IR EF ED where RI is the sum of the all seven risk factors for heavy metals, Ei is the ingestion 70 ingestion monomial potential ecological risk factor, T is the metal toxic factor and ILCRs ¼ ð7Þ i Ingestion BW AT 106 the values for each element are in the order of Zn = 1 b Cr = 2 b Cu =

Ni = Pb = 5 b As = 10 b Cd = 30. fi is the metal pollution factor, Ci is the rffiffiffiffiffiffiffiffi! concentration of metals in the road dust, and Bi is a reference value for 3 BW metals. Different RI classifications of metal pollution are low ecological CS CSF SA AF ABS EF ED dermal 70 risk (RI ≤ 150), moderated ecological risk (150 ≤ RI b 300), consider- ¼ ILCRsDermal able ecological risk (300 ≤ RI b 600) and high ecological risk BW AT 106 (RI ≥ 600) (Hakanson, 1980). ð8Þ 716 N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723

Table 2 Parameters used in the incremental lifetime cancer risk assessment.

Exposure variable Unit Child Adult Reference

Body weight (BW) kg 15 61.5 Shi et al. (2011) Exposure frequency (EF) day year−1 180 180 Ferreira-Baptista and De Miguel (2005) Exposure duration (ED) year 6 24 US EPA (2001) 3 −1 Inhalation rate (IRinhalation)mday 10 20 SFT (1999) −1 Dust ingestion rate (IRingestion) mg day 200 100 US EPA (2001) Dermal exposure area (SA) cm2 day–1 2800 5700 US EPA (2001) Dermal adherence factor (AF) mg cm−2 0.2 0.07 US EPA (2001) Dermal adsorption fraction (ABS) Unitless 0.13 0.13 US EPA (2001) Average life span (AT) day 70 × 365 = 25550 70 × 365 = 25550 Ferreira-Baptista and De Miguel (2005) Particle emission factor (PEF) m3 kg−1 1.36 × 109 1.36 × 109 US EPA (2001)

rffiffiffiffiffiffiffiffi! are based on the Risk Assessment Guidance of US EPA and related 3 BW CS CSF IR EF ED publications (Table 2). inhalation 70 inhalation ILCRs ¼ ð9Þ Inhalation BW AT PEF 3. Results and discussion

3.1. Trace metal concentrations where CS is the PAH concentration of dust (μgkg−1) based on toxic equivalents of BaP using the toxic equivalency factor (TEF) listed in Descriptive statistics of metal concentrations in road dusts as well as Table 7 (μgkg−1)(Nisbet and LaGoy, 1992), CSF is carcinogenic slope background values of world soils (Kabata-Pendias and Pendias, 2001) factor (mg kg−1 day−1)−1, BW is body weight (kg), AT is the average and upper crust content (Rudnick and Gao, 2003) are given in Table 3. life span (day), EF is the exposure frequency (day year–1), ED is the ex- The mean concentration of As, Cu, Ni, Pb, Sb and Zn in road dusts is 3 −1 −1 posure duration (year), IRInhalation is the inhalation rate (m day ), 22.15, 182.26, 66.63, 393.33, 6.95 and 707.19 mg kg , respectively. −1 IRIngestion is the dust intake rate (mg day ), SA is the dermal surface ex- The concentrations of As, Cd, Cu, Ni, Pb, Sb and Zn in Isfahan road posure (cm2 day−1), AF is the dermal adherence factor (mg cm−2), ABS dusts are higher than background values in world soils and upper is the dermal adsorption fraction and PEF is the particle emission factor crust. Maximum Cu concentration occurs in a sample with heavy trafﬁc (m3 kg−1). The determination of carcinogenic slope factor, based on the load (Atashgah Street, sample no. HM9), and for Zn and Pb in Isfahan cancer-causing ability of BaP; CSFIngestion, CSFDermal and CSFInhalation of ringway (sample no. HM14), and Murchehkhort Highway police station BaP, are 7.3, 25 and 3.85 (mg kg−1 day−1)−1,respectively(Knaﬂa (sample no. HM22). Minimum concentrations occur in Aghababaei et al., 2006; US EPA, 1994; Wang, 2007). Other parameters referred in (sample no. HM21) and Chamran Expressways (sample no HM1). The the model for children (1–6 years old) and adults (7– 31 years old) normality of the data was checked using one sample Kolmogorov–

Table 3 Heavy metal concentrations (mg kg−1) in road dust collected from Isfahan city.

Element Mean Median Mode SD VC Skewness Min Max World-soil averagea Upper crust contentb

Al 37533.33 37450 36600 3109.83 0.08 -0.728 30600 4200 71000 82000 As 22.15 19.85 25.20 11.40 0.51 1.31 8.80 54.10 4.7 4.8 Cd 2.14 1.47 0.48 1.80 0.84 1.72 0.48 7.90 1.1 0.09 Co 13.94 13.45 13.10 1.95 0.14 1.07 10.60 19.10 6.9 17.3 Cu 182.26 128.96 55.40 179.88 0.99 3.74 55.40 955.47 14 28 Cr 82.13 81.00 77.00 10.33 0.13 0.11 59.00 104.00 42 92 Ni 66.63 62.00 43.80 15.59 0.23 0.91 43.80 103.60 18 47 Pb 393.33 320.54 96.85 351.38 0.89 3.63 96.85 1895.80 25 17 Sb 6.95 5.86 1.85 4.61 0.66 2.44 1.85 24.17 0.48 0.4 Zn 707.19 572.20 212.40 492.82 0.70 2.14 212.40 2319.00 62 67

SD: standard deviation. Variation coefﬁcients (VC = SD/mean). aKabata-Pendias and Pendias (2001). bRudnick and Gao (2003).

Table 4 Mean concentration of trace elements (mg kg−1) in road dust in various sites of countries and cities.

City As Cd Co Cr Cu Ni Pb Sb Zn Reference

Isfahan (Iran) 22.15 2.14 13.93 82.13 182.26 70.04 393.33 6.95 707.19 This work Tehran (Iran) NA 10.7 NA 33.5 225.3 34.8 257.4 NA 873.2 Saeedi et al. (2012) Guangzhou (China) NA 2.41 13 78.8 176 23 240 NA 586 Duzgoren-Aydin et al. (2006) Baoji (China) 19.8 NA 15.9 126.7 123.2 804.2 433.2 NA 715.3 Lu et al. (2009) Ottawa (Canada) 1.3 0.37 8.31 43.3 65.84 15.2 39.05 0.89 112.5 Rasmussen et al. (2001) Calcutta (India) 23 3.12 15.6 54 44 42 536 NA 159 Chatterjee and Banerjee (1999) Luanda (Angola) 5 1.15 2.9 26 42 10 351.3 3.4 317 Ferreira-Baptista and de Miguel (2005) Oslo (Norway) NA 1.4 19 NA 123 41 180 6 412 De Miguel et al. (1997) Nanjing (China) 13.4 1.10 10.7 126 123 55.9 103 NA 394 Hu et al. (2011)

NA: not available. N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723 717

the fact that there are no universally accepted sampling and analytical procedures for geochemical studies of urban deposits. Table 4 compares the concentration of heavy metals measured in road dusts of Isfahan metropolis with other metropolitan cities in the world. Concentrations of heavy metals in road dust particles vary considerably among cities depending on the density of industrial activities in the area and technol- ogies employed, as well as local weather conditions and wind patterns. As summarized in Table 4, the mean concentration of Cu in Isfahan road dust (this work) is almost similar to those of Guangzhou, lower than Tehran, and higher than Baoji, Ottawa, Calcutta, Luanda, Oslo and Nan- jing. Lead content in Isfahan road dust, Luanda and Baoji are pretty similar but lower than Calcutta. On the other hand, the mean concentration of Zn in road dust of Isfahan is comparable with that of in Baoji (Lu et al., 2009) and higher than other metropolitan cities except Tehran. In general, each city has its own characteristic combination of elemental com- positions, and the observed similarities as well as variations may not reﬂect the actual natural and anthropogenic diversities among different urban settings. Therefore, there is a need as suggested by Duzgoren- Aydin et al. (2006), to establish a standard procedure to analyze and represent urban samples. Fig. 2. Box-plot of EF for heavy metals in Isfahan road dust.

3.2. Heavy metal contamination in road dust Smirnov test. The results show that all parameters are non-normally distributed (significant level b 0.05) except for Co, Cr and Ni (significant Heavy metals enrichment factors were calculated for each road level N 0.05). dust sample relative to the background value in the upper crust Skewness values also indicate that only Co, Cr and Ni display normal (Rudnick and Gao, 2003). In this regard, Al was taken as the refer- distribution, while other elements show a rather positively skewed pat- ence element (Fig. 2). The EF of Cd, Pb, Sb, Zn, Cu and As ranges are tern. Co, Cr and Ni contents vary over a comparatively narrow range 10.73–210.51, 11.46–267.44, 9.31–118.66, 6.33–83, 3.98–71.32 and −1 (within one order of magnitude): Co (10.60–19.10 mg kg ), Cr (59– 4.03–27.03, averaging of 52.17, 51.21, 38.18, 23.06, 14.23 and −1 −1 104 mg kg ) and Ni (43.80–103.60 mg kg ). Based on variation 10.05, respectively (Fig. 2). Heavy metals with average EF higher coefficients (VCs), the examined elements can be classified into two than 10, revealed that Cd, Pb, Zn, Cu and As in Isfahan road dust groups: Co, Cr and Ni, with VCs lower than 0.4; and the rest of the ana- mostly originate from anthropogenic sources. Ni, Cr and Co with lyzed metals with VCs higher than 0.4. Elements dominated by a natural mean EF values of 3.24, 1.94 and 1.75, respectively, are considered source are expected to have low VCs, while those affected by anthropo- to originate primarily from natural sources such as wind-blown soil genic sources should display high VCs (Yongming et al., 2006; Huang minerals. The mean EF values displayed the following decreasing et al., 2009; Wang and Lu, 2011; Yuan et al., 2014). This is especially trend: Cd N Pb N Sb N Zn N Cu N As N Ni N Cr N Co. the case for urban dusts, for they undergo erosion and aeolian transport The potential ecological risk indices (RI) are generally used to assess before ultimate deposition and therefore are fully mixed. pollution by multiple heavy metals in road dust (Hakanson, 1980). RI Comparison of mean concentrations of heavy metals in road dusts in represents sensitivity of various biological communities to toxic sub- different urban environments is a common practice (De Miguel et al., stances and illustrates the potential ecological risk caused by heavy 1997; Charlesworth et al., 2003; Duzgoren-Aydin et al., 2006), despite metals. The ecological risk index, accounting for the contamination As,

Fig. 3. Potential ecological risk indices (RI) in the road dust of Isfahan metropolis. 718 N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723

Table 5 Correlation matrix for metal concentrations.

As Cd Co Cu Cr Ni Pb Sb Zn

As 1 ⁎⁎ Cd 0.871 1 Co 0.029 0.146 1 ⁎⁎ ⁎⁎ Cu 0.576 0.604 −0.041 1 ⁎⁎ Cr −0.071 0.122 0.564 0.283 1 ⁎⁎ ⁎⁎ Ni 0.003 0.151 0.576 0.235 0.647 1 ⁎⁎ ⁎⁎ ⁎⁎ Pb 0.749 0.862 0.149 0.532 0.189 0.247 1 ⁎ ⁎⁎ ⁎⁎ Sb 0.314 0.497 0.228 0.614 0.255 0.243 0.630 1 ⁎⁎ ⁎⁎ ⁎⁎ ⁎⁎ ⁎⁎ Zn 0.684 0.862 0.15 0.623 0.228 0.363 0.851 0.612 1

⁎⁎ Correlation is signiﬁcant at the 0.01 level (2-tailed). ⁎ Correlation is signiﬁcant at the 0.05 level (2-tailed).

Cd, Cu, Cr, Ni, Pb and Zn indicate that Isfahan metropolis is suffering PCA was applied to assist in identifying the source of the pollutants. from considerable contamination. The highest RI value was seen in Table 6 displays PCA result, including factor loadings with a varimax ro- Isfahan ringway (sample no. HM 14). RI values for most sampling sites tation as well as eigenvalues. As expected, two factors were obtained, (66.67% of samples) are greater than 600, suggesting that most areas accounting for 70.051% of the total variance (Table 6). Factor 1 is dom- are at very high ecological risk from the investigated heavy metals. Fur- inated by As, Cd, Cu, Pb, Sb and Zn, accounting for 48.946% of the total thermore, RI values range from 300 to 600 for 20.83% of the road dust variance. This factor probably reflects anthropogenic sources emitted samples, indicating considerable potential ecological risk. Three sam- from road traffic, similar to results obtained in many previous studies ples (12.5% of the total samples) also display RI values between 150 (e.g. Li et al., 2001; Adachi and Tainosho, 2004; Kong et al., 2011). and 300, indicating moderate potential ecological risk posed by heavy Road traffic emissions contain not only vehicles exhaust emissions but metals. Fig. 3 shows potential ecological risk indices for the analyzed also tire and brake wear and re-suspended dust (Huang et al., 2009). road dust. As widely known, the main emission source of Pb used to be the combustion of leaded gasoline (Manno et al., 2006). Cu, Zn and Cd in atmospheric depositions are also considered to be emitted from road traffic 3.3. Source identification by Bem et al. (2003) and Sternbeck et al. (2002). Zn may have been derived from mechanical abrasion of vehicles (Jiries et al., 2001) and also In order to establish inter-element relationships in road dust from lubricating oils and tires of motor vehicles (Akhter and Madany, samples, Spearman's correlation coefficients for nine metals were calcu- 1993; Arslan, 2001). Brake dust is already recognized as a significant lated, and the results are presented in Table 5. Inter-element relation- carrier of Cu and Sb in aerosol composition (Sternbeck et al., 2002; ships provide information on trace element sources and fate (Manta Adachi and Tainosho, 2004). Cu is generally used in brakes to control et al., 2002; Huang et al., 2009; Lu et al., 2010). heat transfer (Huang et al., 2009). Industrial activities also contribute One group of elements, i.e., As, Cd, Cu, Pb, Sb and Zn, display strong significantly to the concentration of trace elements in Isfahan samples. positive correlations with each other at p b 0.01: As-Cd (0.871), Cd-Zn For example, a sample (HM9) collected from Atashgah Street, close to (0.862), Pb-Zn (0.851), Sb-Pb (0.630) and Cu-Zn (0.623). a coal-burning power plant, tire and electro-optical plants, contains The strong positive correlation indicates that the characteristics and high Cu and Zn. The concentration of As may also potentially be related origins of emission for these elements are probably similar. It is also to traffic and coal combustion sources in urban environment (Ozaki noteworthy that all mean EFs values are higher than 10 and might orig- et al., 2004; Ren et al., 2006; Lu et al., 2009). As a result, the association inate from similar sources (mainly from road traffic emissions). of trace metals in PC1 is probably related to traffic emission sources Asignificant positive correlation was also found between a second (Adachi and Tainosho, 2004; Duong and Lee, 2011). group of elements comprising Co, Cr and Ni (r = 0.564–0.576–0.647, Factor 2, characterized by Co, Cr and Ni, accounts for 21.105% of the p b 0.01), suggesting similar characteristics, fate and common origin. total variance. The emission source for this factor is probably resuspen- Mean EF values of these elements are lower than 10, reflecting crustal sion of soil-derived particles. type sources (local soil and re-suspended dust) and negligible contribution of anthropogenic sources (Park and Kim, 2005; Guo et al., 2009). 3.4. PAH concentrations

Table 6 Different levels of 13 PAHs species were detected in Isfahan road Matrix of principal component analysis loadings for metal concentrations in road dust of dust samples in all 28 investigated sites. Table 7 represents the statisti- Isfahan. cal summary of PAHs in road dust. Total PAHs concentrations in Isfahan Element Component Communities road dust display a very wide range with maximum concentration being 17 times greater than the minimum concentration. Total PAHs content 12 varies from 184.64 to 3221.72 μgkg−1. Total PAH concentrations are a As 0.933 −0.106 0.882 overwhelmingly distributed toward the lower concentration end, with Cd 0.918 −0.178 0.874 − 50% of the samples showing concentrations less than 863.44 μgkg 1 Co 0.159 0.694 0.507 μ −1 Cu 0.665 −0.03 0.710 (i.e. median) with the mean concentration being 1074.58 gkg .The Cr 0.018 0.849 0.721 highest concentration was observed at Andisheh multi-level crossing Ni −0.04 0.683 0.461 (sample no. P5), with high traffic density. The lowest value was record- − Pb 0.901 0.14 0.831 ed at Moalem Expressway (sample no. P16), with light trafficandnoin- Sb 0.574 0.525 0.605 Zn 0.960 0.145 0.943 dustrial plants. Combustion PAHs (ComPAHs, the sum of Flu, Pyr, BaA, Initial Eigenvalue 4.405 1.899 Chr, B(b + k)F and BaP, after Rogge et al., 1993; Rajput and Lakhani, Total variance % 48.946 21.105 2009) make up a significant proportion of the total concentration of Cumulative % 48.946 70.052 PAHs in measured street dust, ranging from 0.55 to 0.91. The highest av- a Factor loadings are higher in the factor shown in bold. erage concentration for PAH species in Isfahan road dust is Pyr with N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723 719

Table 7 Descriptive statistics of PAHs in road dust of Isfahan (μgkg−1).

Compounds Aromatic ring TEF Mean Min Max Median Std. Dev

Naphthalene (Np) 2 0.001 22.72 2.33 154.68 10.75 33.68 Acenaphthylene (Acy) 3 0.001 7.04 1.42 39.43 3.80 8.75 Acenaphthene (Ace) 3 0.001 4.25 0.02 39.89 1.58 7.82 Fluorene (Fl) 3 0.001 32.30 7.99 201.71 22.77 37.64 Phenanthrene (Phe) 3 0.001 167.27 26.79 544.70 120.44 131.54 Anthracene (Ant) 3 0.01 13.30 0.02 64.40 3.65 18.81 Fluoranthene (Flu) 4 0.001 162.55 15.40 907.40 93.55 201.04 Pyrene (Pyr) 4 0.001 264.18 23.06 1514.82 161.81 368.55 Benzo[a]anthracene (BaA) 4 0.1 30.17 0.02 140.50 21.76 35.88 Chrysene (Chr) 4 0.01 129.88 29.42 287.47 101.10 82.36 Benzo[b + K]ﬂuoranthene B(b + k)F 5 0.1 172.37 7.16 824.04 114.89 183.65 Benzo[a]pyrene (BaP) 5 1 68.54 18.06 189.50 57.01 39.30 ∑PAHs 1074.58 184.64 3221.72 863.44 760.31 2 ring % 2.52 0.18 18.34 1.47 3.52 3 ring % 21.83 8.17 41.24 20.90 7.40 4 ring % 49.77 33.97 79.41 47.95 12.09 5 ring % 25.88 1.63 46.45 27.98 11.65 LMW PAHs 246.89 41.65 896.96 209.61 192.40 HMW PAHs 827.69 142.99 2324.76 673.43 595.08 COMPAHs/∑13PAHs 0.76 0.55 0.91 0.77 0.08 NCANPAHs/∑13PAHs 0.58 0.48 0.94 0.54 0.87 CANPAHs/∑13PAHs 0.38 0.49 0.39 0.37 0.39 TEQ 90.88 25.02 230.893 74.67 52.18 TEQ/∑PAHs 0.11 0.02 0.21 0.11 0.05

∑PAHs: total PAH concentration, sum of individual mass concentration of 13 PAH congeners. LMW PAHs: low molecular weight 2-3 ring PAHs. HMW PAHs: high molecular weight 4–5ringPAHs. COMPAHs: combustion derived PAH concentration CANPAHS: carcinogenetic PAHs. NCANPAHs: non-carcinogenetic PAHs. TEF: PAHs toxic equivalency factor with respect to BaP (Nisbet and LaGoy, 1992). TEQ: Toxic equivalency concentration.

264.18 μgkg−1 followed by B(b + k)F, Phe, Flu and Chr with average The concentrations of total PAHs in Isfahan road dust are higher than levels of 172.37, 167.27, 162.55 and 129.88 μgkg−1, respectively. There- those measured in cities like Seoul (26.4 μgkg−1)(Lee et al., 2011), and fore, Pyr, B(b + k)F, Phe, Flu, and Chr are the major components. These Beijing (984 μgkg−1)(Wang et al., 2009). PAHs species are indicative of combustion (Hwang et al., 2003). Mean- One way of classifying PAHs is the number of aromatic rings, that is, while, the lowest measurable species in dust are Ace and Acy with aver- 2-ring including Np, 3-ring including Phe and Ant; 4-ring including Flu, age concentrations of 4.25 and 7.04 μgkg−1. The ratio of carcinogenic Pyr and Chr; 5-ring including Per, B(b + k)F and BaP; 6 rings including PAHs—BaA, BaP, Chr, BbF, BkF, (Larsen and Larsen, 1998; Rajput and DbahA, BgihP and IND. The mean concentration of lower molecular Lakhani, 2009)—to total PAHs (CanPAHs/∑PAHs) ranges between weight PAHs (LMW 2–3 rings) is 246.89 μgkg−1, making 23% of the 0.38 and 0.49. total PAH mass, while the mean concentration of higher molecular

Fig. 4. Percentage of different rings in road dust total PAHs. 720 N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723

Table 8 Correlation coefﬁcients among individual PAHs, ΣPAHs and TEQ in Isfahan road dust samples.

Np Acy Ace Fl Phe Ant Flu Pyr BaA Chr B(b + k)F BaP LMW PAH HMW PAH ∑PAHs TEQ

Np 1 Acy 0.512** 1 Ace 0.534** 0.676** 1 Fl 0.524** 0.615** 0.730** 1 Phe 0.425** 0.660** 0.826** 0.736** 1 Ant 0.054 0.381** 0.048 0.048 0.015 1 Flu 0.406** 0.858** 0.714** 0.544** 0.808** 0.335** 1 Pyr 0.235* 0.681** 0.668** 0.498** 0.835** 0.223* 0.867** 1 BaA 0.082 0.497** 0.343** 0.192 0.478** 0.24* 0.595** 0.514** 1 Chr 0.184 0.252* 0.029 0.161 0.345** −0.009 0.396** 0.409** 0.380** 1 B(b + k)F 0.033 0.07 −0.07 0.111 0.182 -0.144 0.205 0.125 0.219* 0.766** 1 BaP 0.243* 0.32** 0.255* 0.507** 0.314** 0.028 0.393** 0.325** 0.209* 0.582** 0.660** 1 LMW PAH 0.532** 0.695** 0.822** 0.804** 0.949** 0.098 0.783** 0.761** 0.416** 0.342** 0.178 0.357** 1 HMW PAH 0.252* 0.751** 0.609** 0.500** 0.798** 0.29** 0.913** 0.894** 0.637** 0.589** 0.354** 0.456** 0.679** 1 ∑PAHs 0.318** 0.770** 0.647** 0.530** 0.830** 0.266* 0.928** 0.897** 0.622** 0.566** 0.349** 0.436** 0.823** 0.992** 1 TEQ 0.144 0.412** 0.188 0.415** 0.369** 0.115 0.493** 0.398** 0.375** 0.757** 0.822** 0.909** 0.398** 0.605** 0.586** 1

**Correlation is significant at the 0.01 level (2-tailed). *Correlation is significant at the 0.05 level (2-tailed). weight PAHs (HMW 4–6 rings) is 827.69 μgkg−1, comprising 77% of the much higher toxicity factors than LMW species (Anastasopoulos et al., total PAH mass (Table 7). The percentage of total PAHs with different 2012). rings is shown in Fig. 4. Low molecular weight PAHs homologues (in- In order to improve the accuracy of the emission source identifica- cluding 2 and 3 ring PAHs) make a small fraction of total PAHs, whereas tion, the method of PCA was applied. Principal component analysis high molecular weight PAHs homologues (including 4–5ringPAHs) with varimax rotation was employed to explore and identify the main form a larger fraction, ranging from 25.88 to 49.77 percent of the total. sources of Isfahan road dust as well as to statistically select source fin- This might be due to the tendency of higher molecular weight com- gerprints (Akyüz and Çabuk, 2008; Agarwal et al., 2009). The results pounds to adhere to road dust (Wang et al., 2011). Also, the high frac- are presented in Table 9, where three principal components, probably tion of high molecular weight PAHs in total PAHs indicate that they representing three source categories, are identified. The first factor mostly come from petroleum fuels combustion (Liu et al., 2007). (44.58% of variance) displays high loading values of Acy, Ace, Fl, Phe, Ant, Flu and Pyr and represents combustion sources (Park et al., 2002; Fang et al., 2004), in which Fl, Phe, Ant, Flu and Pyr are oil combustion 3.5. PAHs source identification markers (Harrison et al., 1996; Caricchia et al., 1999; Park et al., 2002; Dong and Lee, 2009). Table 8 presents the correlation coefficients matrix among PAH com- A relatively high factor loading for Ace, Acy, Phe, Flu and Pyr derived pounds as well as ∑PAHs and TEQ based on Spearman's correlation from wood and fossil fuels such as liquefied petroleum gas, natural gas analysis. The correlation coefficient indicates that nearly all variables and coal combustion (Guo et al., 2003). are significantly correlated at the 0.05 level (Table 8). However, the The second factor, making 21.23% of the total variance, is highly higher correlations represented by r-value (r N 0.7) occur among loaded on BaA, Chr, B(b + k)F and BaP, which are identified as markers HMW compounds, which in turn is significantly (p b 0.01) correlated of gasoline emissions (Khalili et al., 1995; Park et al., 2002; Guo et al., with ΣPAHs.Inmostcases,lowmolecularweight(2–3 rings) group 2003). Hence, it can be suggested that vehicular emissions (diesel and do not show significant positive correlation with high molecular weight gasoline) form a major fraction of PAHs at Isfahan road dust. (4–5 rings) group. The poor correlation reflects different origins for the Factor 3 making 10.18% of the total variance only displays higher two groups. This could be explained by the high atmospheric mobility of loadings for Np, which could be designated as petroleum since Np is LMW compounds, which may have been transported from remote sites the signal for incomplete combustion-related sources (Jiang et al., via atmospheric transportation (Chung et al., 2007). High correlation 2009; Dong and Lee, 2009). coefficients between TEQs and HMW in Isfahan road dust (r2 =0.586, The results obtained from PCA revealed that vehicle emission, com- 0.398 and 0.605, p b 0.01) indicate that HMW species tend to have bustion and non-combusted related petroleum were probably the main sources of PAHs in road dust of Isfahan. However, the different categories of sources that have been identified in this study were based on Table 9 the PAHs source fingerprints found in international literatures. Local PCA analysis of Isfahan metropolis road dust PAHs. or regional profiles of PAHs for each type of emitting sources are needed Species Factor 1 Factor 2 Factor 3 to give more accurate identification of the characteristic PAHs for each Np 0.149 0.2 0.412 source type and thus to quantify the contribution from each emitting Acy 0.879 0.068 −0.263 sources (Kong et al., 2012). Ace 0.905 −0.204 0.217 Fl 0.819 −0.223 0.309 3.6. Carcinogenic risk assessments Phe 0.883 0.05 0.167 Ant 0.733 0.009 −0.304 Flu 0.869 −0.018 −0.145 Establishing of toxic equivalency factors (TEFs) for PAHs could aid in Pyr 0.863 −0.244 0.13 the precise characterization of carcinogenic properties of PAH mixtures − BaA 0.484 0.621 0.491 (Zhu et al., 2014). The cancer potency of each PAH is assessed on the Chr 0.075 0.877 0.163 BbF + BkF 0.045 0.875 −0.193 basis of its benzo[a]pyrene equivalent concentration (BaPeq) (Nisbet BaP 0.073 0.656 0.614 and LaGoy, 1992; IARC, 2010). Toxic equivalency concentration (TEQ) Total variance (%) 44.58 21.23 10.18 calculated for road dust of Isfahan metropolis and based on the TEF Cumulative (%) 44.58 65.81 75.99 values is shown in Table 7. The highest toxicity value of PAHs in road Sources Combustion Gasoline emission Petroleum dust is concentrated near a site with heavy traffic and high overall N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723 721

Fig. 5. Relative contribution of individual BaP TEF to the ∑BaP TEF in six different sites.

PAH concentration. However, some sites characterized by relatively low greater than that of an adult (Wang et al., 2011). Thus, the hazard health BaP-TEQ display high ambient ∑13PAH, assumed to be enriched in the risk for children exposed to urban dust PAHs is thought to be greater LMW and less toxic species. Comparisons of ∑13PAH concentrations than that of adults. Compared to children, dermal contact appeared to with BaP-TEQ suggest that ∑13PAH should not be used as a sole be the predominant exposure route with relatively higher risk for adults proxy for chronic health risk. Fig. 5 reports relative contribution in BaP (Fig. 6). This ﬁnding was similar to the human cancer risk resulted from

TEF for each individual PAH at the six sampled sites. In particular, BaP PAHs exposure in urban soils of Beijing, China (Peng et al., 2011), and and B(b + k)F are the main contributors to total TEF. On this basis, it urban surface dust of Guangzhou, China (Wang et al., 2011), and could is suggested that B(b + k)F, in addition to BaP, must be monitored in be explained by the higher values of dermal exposure area (SA) and ex- Isfahan road dust. Alternatively, a larger number of carcinogenic PAHs posure duration (ED) of adults. should be measured, and the total PAH levels must be expressed as The total cancer risk is the sum of risks incurred from exposure

∑BaP TEF. routes of ingestion, dermal contact and inhalation. In the present To assess human health risk from PAHs exposure, incremental life- study, total cancer risk for both children and adults is higher than the time cancer risk (ILCR) is used to assess human cancer risk (Wang baseline of acceptable risk (one cancer case per million people) et al., 2011; Tuyen et al., 2014). Carcinogenic potencies relative to TEQ, (Maertens et al., 2008), indicating a high potential carcinogenic risk. Ap- carcinogenic slope factor (CSF) and probabilistic risk assessment frame- parently, the risk from urban surface dust PAHs exposure is pervasive work were applied to estimate cancer risk incurred from exposure routes for the residents of Isfahan metropolis. The results suggest that children to PAHs via inhalation, ingestion and dermal contact (Table 10). Probabi- and adults in Isfahan urban area are exposed to high potential carcino- listic risk assessment for personal exposure to carcinogenic PAHs genic risk via both dust ingestion and dermal contact pathways. showed that an ILCR between 10−6 and 10−4 indicates potential risk, − whereas ILCR greater than 10 4 denotes high potential health risk 4. Conclusion (Liao and Chiang, 2006). The acceptable level is equal or lower than − 10 6 (Chiang et al., 2009). The mean cancer risk levels via dermal con- Trace elements in Isfahan road dust are distinctly enriched As, Cd, Cu, − − tact and ingestion pathway are 2.79 × 10 4 and 2.24 × 10 4 in children Ni, Pb, Sb and Zn. Calculated EF displayed a Cd N Pb N Sb N Zn N Cu N As − − and 3.10 × 10 4 and 1.75 × 10 4 in adults, while the mean cancer risk decreasing trend. The high EF for Pb, Zn and Cu in road dusts reflects con- − − via inhalation is 4.34 × 10 9 for children and 1.36 × 10 8 for adults, re- siderable pollution of these elements mostly from trafficsources.Ni,Cr spectively (Table 10). Therefore, the inhalation of resuspended particles and Co indicated no health threats arising from these metals in Isfahan through mouth and nose is almost negligible when compared with other road dust. Based on the combined descriptive, correlation and PCA anal- pathways. The risk value of direct ingestion for children is slightly higher ysis, the road dust trace elements were classified into two main groups than the corresponding risk of ingestion for adults. Young children are sources: As, Cd, Cu, Pb, Sb and Zn that originate mainly from road traffic the most sensitive subpopulation because of their hand-to-mouth activ- emission and Co, Cr and Ni that originate from resuspension of soil ity, whereby contaminated dust can be readily ingested (Meza-Figueroa particles. et al., 2007). In addition, considering the lower body weight of children, The average concentration of sum of 13 PAHs is 1074.58 μgkg−1. the PAHs intake (mg/kg-bodyweight/day) of a child is believed to be Principal component analysis revealed that vehicle emission, coal

Table 10 Risk of cancer in Isfahan metropolis due to human exposure to PAHs via urban surface dust.

Child Adult

Exposure pathways ILCRsing ILCRsder ILCRsinh Cancer risk ILCRsing ILCRsder ILCRsinh Cancer risk Mean 2.24E−04 2.79E−04 4.34E−09 5.02E−04 1.75E−04 3.10E−04 1.36E−08 4.85E−04 Min 6.16E−05 7.67E−05 1.19E−09 1.38E−04 4.81E−05 8.55E−05 3.73E−09 1.34E−04 Max 5.68E−04 7.08E−04 1.10E−08 1.27E−03 4.44E−04 7.89E−04 3.44E−08 1.23E−03 Median 1.44E−04 2.55E−04 1.11E−08 3.99E−04 1.84E−04 2.29E−04 3.56E−09 4.13E−04 722 N. Soltani et al. / Science of the Total Environment 505 (2015) 712–723

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