Human health hazard of polycyclic aromatic hydrocarbon in road dust in Ha Noi metropolis

Journal of Science and Technology 54 (2A) (2016) 27-34 HUMAN HEALTH HAZARD OF POLYCYCLIC AROMATIC HYDROCARBON IN ROAD DUST IN HA NOI METROPOLIS Vo Thi Le Ha 1, * , Nguyen Thi Thu Hien 1 , Minoru Yoneda 2 1 School for environmental Science and Technology, Hanoi Univesity of Sience and Technology, 01 Dai Co Viet Road, Hanoi, Vietnam 2 Kyoto University, KyotoDaigakuKatsura, Nishikyo-ku, Kyoto 615-8540, Japan * Email: ha.vothile@hust.edu.vn Received: 6 May 2016; Accepted for publication: 20 June 2016 ABSTRACT This study investigates PAHs content in road dust of Hanoi metropolis, Vietnam. The samples were colected from the roads around city and analyzed by gas chromatography mass spectrometry (GC/MS). The total PAHs mass concentration ranges from 33.88 µg/kg to 5588,16 µg/kg, with the mean of 356,24 µg/kg in which HMW accounted up 70 % and LMW made up 30 %. The toxic equivalence factors (TEFs), mutagenic potency equivalent factors (MEFs) and the incremental lifetime cancer risk (ILCR) methodologies were applied to evaluate human exposure to carcinogenic PAHs sources. Carcinogenic equivalents (BaP-TEQ) and mutagenic equivalents (BaP-MEQ) were calculated from the potency relative to BaP (TEF) and BaP (MEF). The value of BaP-TEQ for 8 PAHs varied from 1.13 µg/kg to 195.23 µg/kg with mean of 24.34 µg/kg, while the value of BaP-MEQ ranged 1.45 µg/kg to 123.15 µg/kg with mean of 19.96 µg/kg. Basing on ILCRs model, the total cancer risk for children and adults was up to 1.6×10 -5 and 3.9×10 -5 , posing a moderate potential cancer risk, respectively. Key words: Heath risk, road dust, PAHs, ILCR, Hanoi metropolis 1. INTRODUCTION Polycyclic aromatic hydrocarbons (PAHs) are known as a group of organic compounds containing two or more fused aromatic rings. They can enter into the environment via pyrogenic and petrogenic sources [1, 2]. Pyrogenic sources are those where PAHs are generated by high temperature combustion of fossil (coal and petroleum) such as vehicle exhaust particles and biomass (burning of grass, and wood, bush fires), whereas petrogenic sources are derived from crude oil and its refined products (oil, petro, and diesel leaks, tyre particles, asphalts sealant) [2- 4]. Ratios between low and high molecular weight PAHs as well as specific PAH isomers have been used to identify the sources of PAHs [2, 5]. Principle component analysis has been employed to quantify the source contribution of PAHs [6]. Due to their potential to bioaccumulation, persistence, and carcinogenic and mutagenic potencies, the United States Vo Thi Le Ha et al. 28 environmental protection agency (EPA) has identified several PAHs as significant pollutant due to deleterious effects on the environment and biological bodies and considered as priority pollutants to be controlled and routinely analyzed. Road dust which is deposited in two sides of road has a high potential source of PAHs generated from vehicles’ activities as well as asphalt pavement and tire rubber constitute [7]. PAHs from car exhausts, coal emissions and tobacco smoke make up nearly all the carcinogenic PAHs [7]. In some recent years, road dust has been a significant source of PAHs in the environment media which has adverse effects on ecological function and human health via ingestion, dermal contact and inhalation [1]. The elevated concentration of PAHs in water, air and soil can be toxic to the aquatic organism, human [1, 7]. In Vietnam, anthropogenic problems associated with organic pollution of road dust such as PAH are more felt gloomy due to lack of database, inadequate pollution management. Especially in Hanoi, the rapid urbanization, population blooming as well as poor infrastructure system has been in great challenge due to ever-increasing motor-traffic density. A fast growing fleet of motor vehicles at the rate of 12 % - 15 % annually results in a most serious environmental burden and elevates road dust loadings [8]. However, very few studies are devoted to the occurrence, source and toxicity of PAHs in road dust from metropolis. Therefore, to evaluate the health risk of PAHs exposure via inhalation, dust intake and dermal contact is utmost necessary. The main objective of this study is to identify the PAHs concentration and possible source in Hanoi road dust. Also, to evaluate human hazard to carcinogenic PAHs exposure through multiply pathway. These results will provide an important insight to PAHs in Hanoi urban environment and is conductive to the scientific society, the local enterprises and policy makers of municipality. 2. MATERIAL AND METHOD 2.1. Sampling collection × 2.2. PAH Analysis The samples were sieved through a metal sieves with mesh of 60 µm. Then, a 5.00 g sample was extracted ultrasonically 3 times with 150ml dichloromethane. The extract was then concentrated under a rotary evaporator, the aliphatic (non-aromatic) hydrocarbons and PAH fractions were isolated by the standard silica-alumina column [9 - 16]. The extraction was removed into the Figure 1. Sampling locations at Hanoi city. Human health hazards of polycyclic aromatic hydrocarbons in road dust of Hanoi metropolis 29 standard silica-alumina column filled with 10 g silicagel (60–100 mesh) on which it is covered by amorphous sodium sulfate. Then the aliphatic fraction was washed by hexane (50 ml) and was abandoned, while PAH fraction was washed by dichloromethane-hexane (1:1) (50 ml) and was kept and then re-concentrated with ultra-pure nitrogen to exactly 1 ml. The concentrated extracts were then analyzed for PAHs by a gas chromatography coupled to mass spectrometry (Agilent 6980N, U.S.A) equipped with a fused-silica DB-5MS capillary column (30 m × 0.32 mm i.d. 0.25 μm film thickness) [16 - 9]. The identification of individual PAHs was based on the comparison of retention times (chromatographic column) and mass spectra of PAHs in samples with those of PAH standards. Quantification of PAHs was performed in selected ion monitoring (SIM) mode. 2.3. Quality control The GC/MS was calibrated with a diluted mixture of 16 standard PAHs: Nap, Ace, Acy, Flu, Phe, Ant, Fl, Pyr, BaA, Chry, BbF, BkF, BaP, IdP, DbA and BgP. Analysis of serial dilutions of the PAH standards showed that the detection limit for individual PAHs ranged from 50 ng/g to 7500 ng/g. 2.4. Health risk assessment from PAHs exposure To quantify the toxicity or carcinogenic potency of PAHs relative to BaP, the toxic equivalent factors (BaPTEF) and mutagenic equivalent factors (BaPMEF) relating the carcinogenic mutagenic potency of individual PAH to BaP have been used [9-10, 12-11]. The BaP carcinogenic equivalent (BaPTEF) and BaP mutagenic equivalent (BaPMEQ) for the individual PAHs was calculated in Eq (1.2): (1) (2) wwhere BaPTEF, BaPMEF is the cancer, mutagenic potency relative to BaP, respectively and Ci is the individual PAH concentration. Residents are exposed to urban road dust through three main pathways: ingestion, inhalation and dermal contact with dust particles [1]. Evaluation of Incremental Lifetime Cancer Risk (ILCR) was carried basing the equations as follow: (3) (4) (5) where: ILCRing, ILCRderm, ILCRinh are the incremental lifetime cancer risk for ingestion, dermal and inhalation routes respectively. CSFingestion, CSFiinhalation, SFdermal is carcinogenic slope factors (7.3, 3.85, 25 mg.kg -1 d -1 , respectively [10-12, 12-11, 13]); BW is body weight (15 kg and 60 kg for child and adult, respectively [10-12, 11-14]); AT is the average life span (25550 days [11- 14]); L is lifetime (70 years [10-12, 16-9]); EF is the exposure frequency (180 d.year -1 [10-12, 11-14]); ED is the exposure duration (6 and 24 years for child and adult, respectively [10-12, Vo Thi Le Ha et al. 30 11-14]), IRair is the inhalation rate (5 and 20 m 3 /day for child and adult, respectively [11-14]), IRsoil is the soil intake rate (200 and mg.d -1 for child and adult, respectively [10-12, 11-14]); SA is the dermal surface exposure (2800 and 5700 cm 2 for child and adult, respectively [11-14]); AF is the dermal adherence factor (0.2 and 0.07 mg.cm -2 for child and adult, respectively [10- 12]); ABS is the dermal adsorption fraction (0.13 [11]) and PEF is the soil dust produce factor (1.36×10 9 mg kg -1 [11-14]). The total risks were the sum of risks associated with all exposure routes. 2.6. Statistical analyses Principle component analysis (PCA) can be used to reduce data and extract a smaller number of independent factors to find the relationship among observed variables. Classic statistical analyses were processed using IBM SPSS software version 20. A probability level of P < 0.05 was considered statistical significant. 3. RESULTS AND DISCUSSION 3.1. Total PAHs concentration Different levels of 16 PAH congeners were detected in all Hanoi metropolis road dust samples. Table 1 represented the levels of PAHs in road dust. Total PAHs concentrations in road dust samples displayed a very wide range from 33.88 µg/kg to 5588,16 µg/kg, with the mean of 356,24 µg/kg. Maliszewska KordyBach (1996) divided contamination levels in to four categories according to the total PAHs: non-contaminated (< 200 µg/kg), slightly contaminated (200 - 600 µg/kg), contaminated (600-1000 µg/kg), and heavily contaminated (>1000 µg/kg) [13]. Using these criteria, all road dust samples were fallen in slightly contaminated. However, the categories of contamination levels varied largely among the sites consisting of roundabout, highway, bus station and residential road and shown in Table 2. The total PAHs concentrations in road dust at roundabout, highway, bus station and residential road ranged from 30.88 to 5588 µg/kg, 87.38 to 378.32 µg/kg, 55.89 to 288.88 µg/kg and 45.09 to 314.78 µg/kg, with the mean of 876.13 µg/kg, 215.38 µg/kg, 141.62 µg/kg and 121.69 µg/kg, respectively. Consequently, the roundabout was classified into contaminated level, following to highway with slightly contaminated, while residential and bus station revealed non-contaminated. The total PAHs concentrations in roundabouts were much higher than those of other traffic areas and decreased in order: roundabouts > highway > bus station > residential area. This may be due to the increased traffic density, multiple traffic sources, including a high fraction of diesel vehicles such as trucks and buses in highways. The low vehicle speeds around roundabouts may make the longer traveling time in the circulations due to traffic congestion increase traffic volumes, energy consumption and surface abrasion that can release higher loadings of PAHs [15]. The contribution in LMW (Low molecular weight) and HMW (high molecular weight) portion comparing to total PAH mass differentiated among sites. The order of distribution was followed by roundabout (78.85 %) > Residential areas (69.43 %) > Station (66.58 %) > highway (62.49 %). The HMW were prevail in PAH congeners in all sites that agreed the previous studies [3,15]. This may be due to the tendency of higher molecular weight compounds to adhere to road dust [15]. Also, the high fraction of HMW PAHs in total PAHs mass indicated that they mostly came from source of vehicle emission [3]. This result was similar with the speciation of PAHs in gasoline vehicle soots enriched with HMW PAHs, revealing a dominant influence of gasoline vehicle release [2]. The elevated concentration of HMW PAHs in solid surface can be understood that the HMW PAHs are likely associated with airborne particulate that undergo Human health hazards of polycyclic aromatic hydrocarbons in road dust of Hanoi metropolis 31 “single hop” transport behavior committing more of the HMW PAHs to settle and accumulate in road surface close to emission sources [5]. Table 1. Occurrence of PAHs in road dust in Hanoi metropolis (n = 32) (µg/kg). Table 2. PAH contamination levels in sites basing on Maliszewska-Kordybach (1996). Position PAHs (µg/kg) Contamination degree Highway 215,38 Slight contaminated Residential 121,69 No contaminated Bus station 141,62 No contaminated Roundabout 876,13 Contaminated 3.2. Identification of the sources PAHs Principal component analysis (PCA) is powerful tool for distinguishing pollution sources. According to the initial Eigen values, two principle components had Eigen values greater than 1 and cumulatively represented 86.25 % of data variance. The 16 PAH congeners were separated into two distinct components on the factor loading plot (Figure 2). The first component included BaA, Flu, Pyr, Fl, Phe, Ant, Acy, Chry, Ace and Nap describing 61,27 % of total variance of data while the second component included BbF, BkF, BaP, DbA, BgP and IdP accounting up 24.97 %. The first component consisted of both light molecular weight (2-4 rings) and high molecular weight PAHs (4-6 rings) suggesting mixed sources, in which Nap, Ace, Acy, Fl, Phe, Flu, Pyr and Ant could be considered as combined component of petroleum and cooking source [2.7], while Chry, BaA were derived from coal combustion and vehicle emission [5]. The Compounds Aromatic ring TEF[3,13,16] MEF[3,13,16] Mean Min Max Std.De v Naphthalene (Nap) 2 0.001 52.9 0.11 529.89 99.59 Acenaphthylene (Acy) 3 0.001 4.02 0.11 28.82 5.28 Acenaphthene (Ace) 3 0.001 4.01 0.11 27.79 6.66 Flourene (Fl) 3 0.001 6.05 0.06 34.76 6.78 Phenanthrene (Phe) 3 0.001 7.3 0.11 73.51 12.83 Anthracene (Ant) 3 0.01 5.76 0.12 63.63 11.05 Flouranthene (Flu) 4 0.001 33.09 9.41 181.05 32.20 Pyrene (Pyr) 4 0.001 44.88 0.14 259.15 48.33 Benzo(a) anthracene (BaA) 4 0.1 0.082 13.62 0.21 64.42 12.64 Chrysene (Chry) 4 0.01 0.017 141.36 0.11 4252.1 750.25 Benzo(b)flouranthene (BbF) 5 0.1 0.250 9.53 1.52 35.34 8.11 Benzo(k)flourathene (BkF) 5 0.1 0.11 8.0 0.11 52.36 11.83 Benzo(a) pyrene (BaP) 5 1 1 7.7 0.11 53.04 11.67 Dibezo(ah) anthracene (DbA) 5 1 0.29 12.02 0.11 127.93 26.36 Benzo(ghi) perylene (BgP) 6 0.01 0.190 6.68 0.11 66.19 13.51 Indeno (1,2,3-cd) pyrene (IdP) 6 0.01 0,310 2.31 0.11 7.23 2.27 PAHs 356.24 30.8 5588.1 964.62 BaP-TEQ 24.34 1.13 195.23 40.58 BaP - MEQ 19.96 1.45 123.15 30.40 Vo Thi Le Ha et al. 32 second component was heavily weighted by BbF, BkF, BaP, DbA, BgP and IdP which were consistent with emission characteristics of PAHs from coal combustion and vehicle [4] while BbF was consistent with emission of diesel [5]. It could be included that primary sources of PAHs in Hanoi Metropolis road dust are vehicle exhausts, coal combustion and petroleum components and secondary source is the deposits coming from long-range atmospheric transport. 3.3. Mutagenic and carcinogenic equivalent of PAhs and their contribution The theoretical mutagenic and carcinogenic equivalents of PAH were calculated by multiphying the concentrations in road dust by appropriate mutagenic and carcinogenic potencies relative to BaP and the total values were expressed as BaP-MEQ and BaP-TEQ, respectively which gave the best information of PAH toxicity and were calculated by equation 1, 2 [10, 11]. The results showed that total BaP-equivalent concentration ranged from 1.23 µg/kg to 195.63 µg/kg, averaging 24.55 µg/kg. While BaP carcinogenic equivalent (BaPTEQ) varied from 1.13 µg/kg to 195.23 µg/kg with mean of 24.34 µg/kg, BaP mutagenic equivalent (BaPMEQ) were from 1.45 µg/kg to 123.15 µg/kg with mean of 19.96 µg/kg. The contribution of mutagenic and carcinogenic potencies was shown in Figure 3. Figure 3: contribution of individual PAH to mutagenic and carcinogenic potencies. While contributions of individual PAHs to mutagenic potencies was in the order of BaP (31.08 %) > BbF (26.09 %) > BaA (13.15 %) > DbA (10,83 %) > BgP (5.95 %) > IdP (5.34 %) > BkF (3.66 %) > Chry (3.9 %), Those to carcinogenic potencies was in the order of BaP (32.24 %) > DbA (27.6 %) > BaA (20.34 %) > BbF (12.68 %) > BkF (3.48 %) > Chry (3.13 %) > BgP (0.33 %) > IdP (0.2 %). The findings revealed that the contributions of PAH congeners in mutagenic and carcinogenic potencies were similar. While BaP, BbF, BaA and DbA are the major mutagenic and carcinogenic contributors in Vietnamese road dust while BaP and B(b+k)F; IdP + BgP and BaP are predominant in mutagenic and carcinogenic potencies in Korea [15]. Figure 2. PCA of road dust. Human health hazards of polycyclic aromatic hydrocarbons in road dust of Hanoi metropolis 33 3.4. Health risk assessment This study has identified the potential carcinogenic risk due to the exposure of human (child and adult) to PAHs in road dust samples. The Incremental lifetime cancer risk model (ILCR) has been applied to assess the potential risk of cancer induction in exposed human to environmental toxicants [1, 14, 16]. Carcinogenic potencies relative to BaP, carcinogenic slope factor (CSF) and probabilistic risk assessment framework were applied to estimate the cancer risk to human who exposed road dust though three pathways. The carcinogenic total risk was calculated from the summation of individual risks through each route of exposure. Exposure carcinogenic risk is calculated using equation 3-5. The cancer risk levels for children via ingestion, inhalation and dermal contacts were 7×10 -6 , 1×10 -9 , and 9×10 -6 , respectively, while these for adults were 1.4×10 -5 , 1×10 -8 , and 2.5×10 -5 . Cancer risks of inhalation of children and adults were low, almost 10 3 times lower than from ingestion and dermal contact. Therefore, the inhalation of resuspended particles through mouth and nose were almost negligible when compared with other pathway. Ingestion and dermal contact appeared to be predominant exposure route for both children and adult. These findings were consistent with previous studies in China and Nigeria [3, 16]. Cancer risk between 10 -6 and 10 -4 indicate moderate health risk, while greater than 10 -4 suggests high potential health risk [14]. The total cancer risk is the sum of risks incurred from exposure routes of ingestion, dermal contact and inhalation. In this study, the total cancer risk for adult and children were up 3.9 ×10 -5 and 1.6×10 -5 , respectively, which indicates a moderate potential cancer risk. Cancer risk via derma contact and digestion for adults was relatively higher than children due to larger exposure area and longer exposure duration, respectively. However, the children can be vulnerable due to high physical contacts (hand to mouth) with road dust from out-door activities. In addition, considering the smaller body weight, the PAH intake of a child were believed to be greater than that of an adult. Thus, the hazard health risk for children exposed to PAHs in road dust is thought to be greater than that of adult. The findings obtained in this study also raised the concern over the potential effect of ambient air contaminated with PAHs on the occurrence of common respiratory and skin diseases related to urban air pollution in Hanoi urban areas [8] and such effects need immediate attention. 4. CONCLUSION Polycyclic aromatic hydrocarbons are pervasive in the road dust of Hanoi metropolis. The road dust samples were classified into slightly contaminated by PAHs for overall sampling sites according to Maliszewska-KordyBach (1996). However, there was stringent different contamination level among sites including roundabout, highway, bus station and residential areas in which the roundabout and highway were classified into contaminated level and slightly contaminated, respectively, residential and bus station presented non-contaminated. The vehicle exhausts, coal combustion and petroleum components were primary sources of PAH accumulated in road dust in Hanoi metropolis. Basing on TEQ and MEQ calculation, BaP, BbF, BaA and DbA are good makers in assessing PAHs related with health risks. The adopted approach in this study is very useful in determining the overall toxicity of road dust as well as evaluating specific chemical components in the environment samples. 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