Characterization of 209 polychlorinated biphenyls in street dust from northern Vietnam: Contamination status, potential sources, and risk assessment

Characterization of 209 polychlorinated biphenyls in street dust from northern Vietnam: Contamination status, potential sources, and risk assessment

Characterization of 209 polychlorinated biphenyls in street dust from

northern Vietnam: Contamination status, potential sources, and

risk assessment

Hoang Quoc Anha,b,c, Isao Watanabea, Keidai Tomiokaa, Tu Binh Minhc, Shin Takahashia,⁎

aCenter of Advanced Technology for the Environment (CATE), Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama 790-8566, Japan

b

The United Graduate School of Agricultural Sciences (UGAS-EU), Ehime University, 3-5-7 Tarumi, Matsuyama 790-8566, Japan

c

Faculty of Chemistry, VNU University of Science, Vietnam National University, 19 Le Thanh Tong, Hanoi, Viet Nam

H I G H L I G H T S

• Concentrations of 209 PCBs were

deter-mined in street dusts from northern

Vietnam

• PCB levels in industrial and urban

sam-ples were significantly higher than

rural ones

• Street dusts exhibited different patterns

of PCBs between study areas

• PCB-11 was among the most abundant

congeners in all the street dust samples

• Street dusts contributed about 2% to

total DI of PCBs by occupationally

ex-posed groups

G R A P H I C A L A B S T R A C T

a b s t r a c t

a r t i c l e i n f o

Article history:

Received 12 September 2018

Received in revised form 11 October 2018

Accepted 17 October 2018

Available online 18 October 2018

Editor: Adrian Covaci

A full congener-specific determination of polychlorinated biphenyls (PCBs) was conducted for street dusts in some areas in northern Vietnam Total 209 PCB concentrations (median and range) of 14 (2.2–120), 11 (6.6–32), and 0.25 (0.10–0.97) ng g−1were measured in the street dusts from an industrial park, an urban area, and a rural commune, respectively, suggesting environmental loads of PCBs related to industrialization and urbanization in northern Vietnam PCB patterns of street dusts from the industrial park were dominated by lightly chlorinated homologs (tri- and tetra-CBs), while more highly chlorinated homologs (penta- and hexa-CBs) were the major contributors

to total PCBs in the urban samples, indicating different emission sources Linear correlations of log-transformed sum of 7 indicator congeners with total PCBs and sum of dioxin-like PCBs were observed PCB-11, an inadvertently produced congener of pigment manufacturing processes, was detected in all the samples with more elevated pro-portions in the urban and rural areas than industrial park Our results have revealed complex emission sources of PCBs in the study areas, including both historical (e.g., the past usage of imported PCB-containing oils and old electric equipment) and current sources such as releases from industrial activities and increasing use of new consumer products Occupationally exposed persons (e.g., street sweepers, street vendors, and traffic policemen) and children

in the urban and industrial areas were estimated to receive much higher doses of dust-bound PCBs than general population, suggesting the need for appropriate protection conditions

© 2018 Elsevier B.V All rights reserved

Keywords:

PCBs

PCB-11

Street dust

Human exposure

Northern Vietnam

Science of the Total Environment 652 (2019) 345–355

⁎ Corresponding author.

E-mail address:takahashi.shin.mu@ehime-u.ac.jp (S Takahashi).

https://doi.org/10.1016/j.scitotenv.2018.10.240

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1 Introduction

The term polychlorinated biphenyls (PCBs) refers to a class of 209

chlorinated biphenyl isomers that were commercially synthesized and

widely used in numerous industrial applications from 1929 to the late

1970s Because of outstanding features such as chemical stability, fire

resistance, high thermal conductivity, and electrical insulation

proper-ties, the most common uses of PCBs were additives in dielectric fluids

in transformers and capacitors, and heat transfer fluids and hydraulic

fluids in partially closed-industrial systems (UNEP, 1999;WHO, 2000)

PCBs have been also used as additives in lubricants, casting waxes,

sur-face coatings, adhesives, plasticizers, inks, and other open applications

(Erickson and Kaley II, 2011;UNEP, 1999) Moreover, PCBs can be

unin-tentionally produced during combustion, chlorination of water, and

dif-ferent industrial production processes (Erickson, 1997) PCBs are

extremely persistent in the environment and they have been detected

in various environmental media in virtually all parts of the world

(Stringer and Johnston, 2001;UNEP, 1999;WHO, 2000) Unfortunately,

PCBs can enter the ecosystem, then bioaccumulate and cause a variety

of adverse effects on humans, including both carcinogenic risk and

non-carcinogenic effects such as acute toxicity, endocrine disruption,

developmental toxicity, and neurotoxicity (ATSDR, 2000;Stringer and

Johnston, 2001;WHO, 2000) In 2001, PCBs were identified as one of

the ‘dirty dozen’ persistent organic pollutants (POPs) and listed under

Annex A (elimination) and Annex C (unintentional production) of the

Stockholm Convention (UNEP, 2001)

In Vietnam, PCBs have been detected in different environmental

media such as ambient air (Tue et al., 2013;Wang et al., 2016), indoor

dust (Takahashi et al., 2017;Tue et al., 2013), soil and freshwater

sedi-ment (Carvalho et al., 2009;Hoai et al., 2010;Romano et al., 2013;

Toan and Quy, 2015;Toan et al., 2007), and marine sediment (Hong

et al., 2008;Tri et al., 2016) Several studies focusing on the residue

levels of PCBs in biological samples and foodstuffs from Vietnam have

been also published since the 1990s (Carvalho et al., 2008, 2009;

Kannan et al., 1992, 1995;Minh et al., 2006;Nhan et al., 1999, 2001;

Ramu et al., 2007;Schecter et al., 1990) Furthermore, PCBs have been

found in Vietnamese human tissues such as breast milk (Minh et al.,

2004;Schecter et al., 1989;Tue et al., 2010a) and blood (Eguchi et al.,

2015;Hansen et al., 2009,Schecter et al., 1992, 1993) The relatively

high concentrations of PCBs in soils and foodstuffs from southern

Vietnam in the 1990s probably resulted from the operation of the US

chemical weapons during the Second Indochina War (Kannan et al.,

1992, 1995;Thao et al., 1993a, 1993b) In a more recent study,Wang

et al (2016)reported that atmospheric PCB levels in Vietnam were

higher than those observed in some other countries in Asia (Jaward

et al., 2005) and Europe (Jaward et al., 2004), even though Vietnam

has never produced PCBs Several studies have revealed the

contribu-tion of current emission sources of PCBs in Vietnam such as the leakages

of PCBs from old electrical equipment (Hoai et al., 2010), traffic-related

activities (Toan et al., 2007), industrial activities (Hue et al., 2016), and

primitive waste processing and recycling activities (Anh et al., 2018b;

Eguchi et al., 2015;Takahashi et al., 2017;Tue et al., 2013)

Street dust is a complex mixture of particulate materials such as soil,

construction matter, vehicular emission, and atmospheric deposition

(Cao et al., 2017;Klees et al., 2015;Shi et al., 2014) Street dust has

been considered as a sink of heavy metals (Phi et al., 2017;Xu et al.,

2015;Zhao et al., 2016); and organic contaminants such as

organochlo-rine pesticides (OCPs) (Shi et al., 2013;Sohail et al., 2018), polycyclic

ar-omatic hydrocarbons (PAHs) and their derivatives (Shi et al., 2013;

Tuyen et al., 2014a, 2014b), brominated flame retardants (BFRs) (Anh

et al., 2018a;Cao et al., 2017), organophosphorus esters (He et al.,

2017;Khan et al., 2016), polychlorinated dibenzo-p-dioxins and

diben-zofurans (PCDD/Fs) (Klees et al., 2015), and PCBs (Chakraborty et al.,

2016;Klees et al., 2015, 2017;Sohail et al., 2018;Wang et al., 2013)

Pol-lutants associated with street dust can also pose a risk to human health,

especially for occupationally exposed persons (e.g., professional street

sweepers, street vendors, and traffic policemen) and children (Anh

et al., 2018a;Cao et al., 2017) Street dust samples have been collected from some areas in northern Vietnam to examine the occurrence of heavy metals and organic pollutants.Phi et al (2017)reported that con-centrations of lead and zinc in street dusts in Hanoi varied between dif-ferent functional zones, with the highest levels detected in downtown areas Levels of PAHs and their methylated derivatives and aryl hydro-carbon receptor agonists in street dusts collected from an urban area

of Hanoi were higher than those found in a rural village in northern Vietnam, as well as two metropolitan cities in India (Tuyen et al., 2014b).Anh et al (2018a)suggested that street dust can act as an indi-cator of outdoor contamination by polybrominated diphenyl ethers (PBDEs) and novel BFRs in northern Vietnam

To our knowledge, so far there is no study that investigates the oc-currence of PCBs, a typical class of persistent toxic substances, in Vietnamese street dusts In the present study, we collected street dust samples from some representative areas in northern Vietnam, charac-terized by the land use types, population densities, and traffic densities,

to determine concentrations of 209 PCB congeners Results of this study may provide basic information on the current pollution status and spa-tial distribution of PCBs in Vietnamese street dusts, revealing environ-mental loads of PCBs related to industrialization and urbanization in some areas in northern parts of this developing country Full congener and homolog profiles of PCBs in the street dusts were characterized, providing a comprehensive evaluation of their emission sources Chronical daily intake doses and potential health risks caused by inges-tion of dust-bound PCBs were also estimated for individuals in the study areas

2 Material and methods

2.1 Study areas and sample collection

A total of 32 street dust samples were collected during August and September 2016 in three areas in northern Vietnam, including an

inner urban zone of Hanoi (n = 16), an industrial park in Thai Nguyen province (n = 10), and a rural commune in Bac Giang province (n =

6) Hanoi capital city is the country's second biggest city with an area

of 3358.9 km2and a population of approximately 7.7 million inhabitants

in the year 2017 The urban area of Hanoi consists of twelve districts, which covers only 9% of total municipal area of this city but supports N50% of total population This area is characterized by high population density and mixed land use combining residential, institutional, com-mercial, and light industrial uses Sixteen samples were obtained from the main streets with high traffic density in seven inner districts of Hanoi, including Ba Dinh, Cau Giay, Dong Da, Hai Ba Trung, Hoan Kiem, Long Bien, and Thanh Xuan Song Cong I industrial park is situated

in Song Cong city, Thai Nguyen province Established in 1999, Song Cong

I is the first industrial park of Thai Nguyen province, comprising a pro-duction area of 2.2 km2 The major industrial sectors are metallurgy, ore refining, automotive and machinery part manufacturing, construc-tion materials, plastics, garments, and electronics Ten samples were taken along October Revolution street and its branch roads in Song Cong city Mai Dinh, a rural commune in Hiep Hoa district, Bac Giang province, was chosen as the control site of this study This commune covers an area of nearly 9.1 km2with mixed agricultural/residential land uses Six samples were collected from narrow paths of low traffic density, next to rice fields Sample names and further description about the sampling sites are provided in Table S1 of Supporting Information

At each sampling location, a composite sample of five sub-samples was collected by sweeping street surface using non-plastic brush and pan Each sub-sample of 40–50 g street dust was obtained on an area

of about 1 m2along the road, within 0.5 m adjacent to the curb The composite samples were thoroughly mixed, transferred into paper bags, and sealed in PE zip-lock bags At laboratory, the samples were

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

dried at room temperature and sieved through a 100-μm stainless steel

sieve The homogenized samples were wrapped in solvent-washed

alu-minum foil, sealed in PE zip-lock bags, and stored at −20 °C until

chem-ical analysis

2.2 Chemical analysis

The street dust samples were treated according to our method for

POP analysis previously described byAnh et al (2018a) In brief, about

2 g homogenized dust sample was weighted into a 50-mL glass tube

and subsequently extracted with 10 mL of acetone and 10 mL of

ace-tone/hexane mixture (1:1, v/v) using a focused ultrasonic processor

(VCX 130, 130 W, 20 kHz; Sonic & Materials, Inc.) After extraction,

the sample tube was centrifuged at 3000 rpm for 10 min The

superna-tants were combined, evaporated, and solvent-exchanged into hexane

A portion of the crude extract corresponding to 1 g dust was used for

PCB analyses and the remaining portion will be used for other target

analyses and bioassays The crude extract was spiked with surrogate

standards (1 ng of each congener,13C12-PCB-1, -3, -4, -8, -15, -19, -28,

-52, -54, -70, -77, -81, -95, -101, -104, -105, -114, -118, -123, -126,

-138, -153, -155, -157, -167, -169, -170, -180, -188, -189, -202, -205,

-208, and -209; Wellington Laboratories) and successively purified by

treating with concentrated sulfuric acid and passing through an

acti-vated silica gel column (Wakogel® S-1, actiacti-vated at 130 °C for 3 h)

The target compounds were eluted from the silica gel column by using

80 mL of dichloromethane/hexane mixture (5:95, v/v) The eluate was

concentrated, solvent-exchanged into decane, and spiked with internal

standards (1 ng of each congener,13C12-PCB-9, -37, -79, -111, -162,

-194, and -206; Wellington Laboratories) before GC/MS quantification

Chemicals and solvents used in this study were reagent grade for the

de-termination of PCBs and purchased from Wako Pure Chemical

Indus-tries, Ltd

PCBs (209 mono- to decachlorinated congeners) were quantified

using a 6890 N gas chromatograph (Agilent Technologies) connected to

a JMS-800D high resolution mass spectrometer (JEOL) The separation

was performed on a HT8-PCB capillary column (60 m length × 0.25 mm

internal diameter × 0.25μm film thickness, Kanto Chemical) Helium

was used as carrier gas at a constant flow of 1 mL min−1 Inlet

tempera-ture was 280 °C A sample volume of 1μL was injected in splitless injection

mode Column oven temperature was programmed from 120 °C,

in-creased to 180 °C (20 °C min−1), to 260 °C (2 °C min−1), and ramped to

300 °C (5 °C min−1, hold 4 min) Mass spectrometer was operated in

pos-itive electron ionization (EI) mode at a resolution of ≥10,000 at 10% valley

Ionization energy was 38 eV and acceleration voltage was 10 kV

Temper-ature of interface and ion source was 280 °C Data were acquired in

se-lected ion monitoring (SIM) mode using two molecular ions for each

native and13C12-PCB congener Further descriptions about our

quantifica-tion method are provided in Table S2

2.3 Quality assurance and quality control (QA/QC)

The analytical method validation was performed by triplicate

analy-ses of solid matrix (i.e., sodium sulfate) spiked with native standards of

PCBs (1 ng of each congener, 62 mono- to deca-CBs) and Standard

Ref-erence Material® 2585 (NIST, Gaithersburg, MD, US) Analytical results

of the spiked samples and SRM samples are tabulated in Tables S3 and

S4, respectively, indicating acceptable levels of precision and accuracy

of our procedure Concentrations of the analytes were reported to two

significant figures because relative standard deviations (RSD) of

tripli-cate analyses of above validation samples were up to 15% for some

con-geners Instrument detection limits (IDLs) were estimated as 3 times of

standard deviations (SD) from replicate analyses (n = 5) of the lowest

concentration standard (0.5 ng mL−1of each native congener) Method

detection limits (MDLs) were estimated from the IDLs with a sample

weight of 1 g and a final volume of 200 μL The MDLs of PCBs ranged

from 0.0030 to 0.030 ng g−1 (Table S5) To reduce blank levels,

glassware was washed with detergent and tap water, baked at 450 °C for at least 2 h, rinsed with solvents (i.e., acetone, toluene, and hexane),

and covered by aluminum foil before using Procedural blanks (n = 6)

were analyzed with real samples of each batch to control any contami-nation during chemical analysis Levels of almost all PCB congeners in the blanks were lower than the MDLs Peak areas of the target com-pounds were subtracted by identical peaks in the blanks when these were found to be significant Average recoveries (±SD) of13C12-PCBs ranged from 68 ± 5% to 93 ± 7% (Table S6)

2.4 Risk assessment of PCBs associated with street dust

Chronical daily intake doses (ID – ng kg−1d−1) of PCBs via street dust ingestion were estimated using Eq.(1)

CID ¼ C  IR  FT  EF  EDð Þ= BW  ATð Þ ð1Þ where C is the concentration of total PCBs in street dust (ng g−1) At the urban and industrial areas, high-end dust ingestion rates (IR) of 0.2 g d−1and 0.05 g d−1were assigned for children and adults, respec-tively; whereas medium IRs of 0.05 g d−1and 0.02 g d−1were assigned for children and adults at the rural site, respectively (Anh et al., 2018a;

Jones-Otazo et al., 2005) An IR of 0.16 g per working day was applied for occupationally exposed persons, including street sweepers, street salesmen, and traffic policemen (Anh et al., 2018a;Cao et al., 2017)

An absorption efficiency of 100% was assumed Fraction of time (FT) for traveling on the streets was 3/24 for all individuals An additional

FT of working time of 8/24 was accounted for occupational group Expo-sure frequency (EF) was 365 d year− 1for traveling and 240 d year− 1for working Exposure duration (ED) of children and adults were 5 years and 30 years, implying average time (AT) of 1825 days and 10,950 days, respectively Average body weights (BW) were 60 and

15 kg for adults and children, respectively

Non-carcinogenic hazard quotient (HQ) and lifetime cancer risk (CR) due to the ingestion of PCBs associated with street dust were esti-mated by Eqs.(2) and (3), respectively

CR ¼ C  IR  FT  EF  ED  10 −6 CSF= BWð  LTÞ ð3Þ

A reference dose (RfD) of 20 ng kg− 1d− 1of total PCBs was used (ATSDR, 2000) The cancer slope factor (CSF) of 2 (mg kg−1d−1)−1

was proposed byUS EPA (2017) Mass unit conversion factor was

10−6 Lifetime (LT) was estimated as 25,550 days, corresponding to

70 years

2.5 Statistical analysis

Statistical analysis was performed using Microsoft Excel (Microsoft Office 2010) and Minitab 16® Statistical Software (Minitab Inc.)

Mann-Whitney U test at a confidence level of 95% was used to assess

the differences of contamination levels between study locations After logarithmic transformation, the dataset was subjected to Pearson's cor-relation analysis, regression analysis, and principal component analysis (PCA) to evaluate possible relations among PCB congeners For the PCA analysis, the component matrix was rotated using a varimax rotation Homolog compositions of PCBs in the street dusts and selected technical mixtures were analyzed by hierarchical cluster analysis using Ward linkage method and Euclidean distance measure to identify original

for-mulations of PCBs Level of statistical significance was set at p b 0.05 A

summary of results of correlation and regression analysis is presented

in Table S7, while those of cluster and PCA analysis are shown in Figs S1 and S2, respectively

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

3 Results and discussion

3.1 Concentrations of total PCBs

PCBs were found in all the street dust samples of our study The

con-centrations of total 209 PCBs (Σ209PCBs), 10 homologs, and selected

congeners are presented in Table 1 Concentrations (median and

range) ofΣ209PCBs in street dusts from industrial, urban and rural

areas were 14 (2.2–120), 11 (6.6–32) and 0.25 (0.10–0.97) ng g−1,

re-spectively The total PCB levels in samples from industrial and urban

areas were significantly higher than those from rural sites (p b 0.01).

However, there was no statistical difference between industrial and

urban areas (p N 0.05), probably due to the large variation in PCB

con-centrations in the Thai Nguyen samples (RSD = 137%), as compared

with those from Hanoi (RSD = 52%) In the industrial area, the highest

PCB levels were found in samples collected near a diesel engine

manufacturing company and in samples from the central area of the

in-dustrial park, comprising numerous factories in different sectors

(e.g., TN-01, -02, -08, and -10) In Hanoi, the most contaminated sample

was obtained along a main gateway to the city center with several

auto-motive repair shops (HN-01), followed by a sample collected from a key

road of the southeastern part of the city, crossing a busy and chaotic bus

station (HN-26) Street dusts from the rural area showed the lowest

contamination levels with little variation The decreasing order of PCB levels in street dusts from industrial, urban, and rural areas of our study was consistent with those reported for outdoor dusts in Guang-zhou and Hong Kong, China (Wang et al., 2013), and the Indus river basin, Pakistan (Sohail et al., 2018)

A comparison of PCB concentrations in outdoor dusts between dif-ferent study locations are shown inTable 2 Levels of total PCBs in street dusts from the industrial and urban areas in northern Vietnam were within the ranges reported for outdoor dusts from an urban area of Hong Kong (Wang et al., 2013) and several sites along the Indus (Sohail et al., 2018) Total PCB concentrations in the Thai Nguyen and Hanoi samples were generally higher than those detected in dusts from nearby highways in the urban center and suburban industrial roadsides of Chennai, India (Chakraborty et al., 2016), but still lower than urban outdoor dusts in Guangzhou, China (Wang et al., 2013) Ex-tremely high PCB concentrations were recorded in street dusts in the surroundings of an e-waste recycling facility (760–16,000 ng g−1;

Klees et al., 2017) and some industrial sites (3600–63,000 ng g− 1;

Klees et al., 2015) in North Rhine-Westphalia, Germany, that were sev-eral orders of magnitude higher than our detected levels Concentra-tions of PCBs in the rural street dusts from Bac Giang were also significantly smaller than those found in some rural sites in western Germany (Klees et al., 2015) As information about the contamination

Table 1

Concentrations of PCBs (ng g −1 ) in street dust from northern Vietnam.

Σ7in-PCBs b

Σdl-PCBs c

a

Not detected.

b

Total of 7 indicator PCBs (PCB-28, -52, -101, -118, -138, -153, and -180).

c

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

of street dusts by PCBs in Vietnam is limited, we included data of surface

soils to facilitate the comparison The literature shows that the PCB

levels in agricultural soils in northern Vietnam do not exhibit a large

variation over time (Thao et al., 1993a;Toan et al., 2007,Toan and

Quy, 2015) and are generally lower than levels in urban and industrial

soils (Hue et al., 2016;Toan et al., 2007) Besides the similar spatial

dis-tribution affected by land use types, PCB levels in the street dusts of

urban and industrial areas of this study were in line with levels detected

in urban soils from Hanoi (15–190 ng g−1;Toan et al., 2007) and

indus-trial soils from Thai Nguyen (18–104 ng g−1;Hue et al., 2016) A similar

contamination level of PCBs was reported for house dusts from urban

(median 10, range 5.6–85 ng g−1

) and suburban (5.6, 3.6–20 ng g−1) areas of Hanoi (Tue et al., 2013) The degree of PCB contamination in

street dusts of our study were much lower than the hazardous waste

threshold of 5000 ng g−1proposed by the Vietnam Ministry of Natural

Resources and Environment (MONRE, 2009) Also, our detected levels

of PCBs in Vietnamese road dust were still lower than soil quality

guide-lines issued by the Canadian Council of Ministers of the Environment

(500; 1300; and 33,000 ng g−1for agricultural, residential, and

indus-trial land use;CCME, 1999)

The composition of PCB homologs in street dusts from northern

Vietnam are presented inFig 1 Interestingly, samples from the

indus-trial, urban, and rural areas exhibited quite different PCB accumulation

profiles Concentrations of tri- and tetra-CBs in the industrial samples

were significantly higher than those detected in the urban and rural

sites, whereas the urban samples were more heavily contaminated by

higher chlorinated homologs (e.g., penta- to octa-CBs) In the industrial

park, tetra-CBs (33.6 ± 8.4%) and tri-CBs (28.3 ± 8.6%) were the most

predominant homologs, followed by penta-CBs (16.1 ± 5.9%),

hexa-CBs (11.2 ± 5.7%), di-hexa-CBs (6.2 ± 2.9%), and hepta-hexa-CBs (3.7 ± 2.2%)

The PCB patterns in street dusts from the industrial area of this study

were similar to those detected in surface soils and sediments from Thi

Nai lagoon, central Vietnam, that has been affected by rapid

industrialization (Romano et al., 2013) The prevalence of tetra-CBs was also found in street dusts of Mambakkam, an already established in-dustrial zone in Chennai, India (Chakraborty et al., 2016) The homolog patterns of PCBs in street dusts from Thai Nguyen were quite similar to those detected in street dusts from the surrounding of an e-waste recycling enterprise in Essen-Kray, Germany, implying a near-source emission of low-molecular-weight PCBs (Klees et al., 2017) The urban samples showed a decreasing order as follows: penta-CBs (37.0 ± 6.5%) N hexa-CBs (28.8 ± 2.6%) N tetra-CBs (13.4 ± 2.2%) N hepta-CBs (7.4 ± 3.9%) ≈ di-CBs (7.4 ± 3.1%) N tri-CBs (4.5 ± 2.4%) The domi-nance of penta- and hexa-CBs was detected in indoor dusts from Hanoi urban and suburban areas and some informal waste recycling sites in northern Vietnam (Takahashi et al., 2017;Tue et al., 2013)

Table 2

Comparison of PCB concentrations (ng g −1 ) and TEQs of dl-PCBs (pg WHO-TEQ g −1 ) in outdoor dusts from different study locations.

nb ΣPCBs c

TEQs c

Reference

(2.2–120)

0.82 (0.0079–2.3)

This study

(6.6–32)

1.2 (0.036–3.6)

This study

(0.10–0.97)

0.00030 (n.d d –0.0036)

This study

(0.2–7)

30 (0.0007–100)

Chakraborty et al., 2016

(0.1–9)

2 (n.d.–30)

(0.95–125)

1.87 (0.9–34.5) e 0.12 (0.07–0.25) f

Sohail et al., 2018

Germany, North-Rhine Westphalia E-waste recycling area 2014 Total g

(760–16,000)

82 (16–560)

Klees et al., 2017

(3600–63,000)

210 (n.d.–830)

Klees et al., 2015

(85–950)

6.7 (1.4–59)

(140–800)

6.8 (3.7–17)

(100–190)

6.5 (4.7–8.3)

(4.02–228)

2.61 (0.22–131)

Wang et al., 2013

(7.75–114)

9.78 (1.98–50.6) a

Number of PCB congeners.

b Number of samples.

c Mean and range for data from Chakraborty et al (2016) , median and range for other studies.

d

Not detected.

e

TEQs for non-ortho dl-PCBs (PCB-77, -126, and -169).

f

TEQs for mono-ortho dl-PCBs (PCB-105, -114, -118, and -156).

g

Total PCBs estimated as five times of Σ6PCBs (PCB-28, -52, -101, -138, -153, and -180).

Characterization of 209 polychlorinated biphenyls in street dust from northern Vietnam:

Contamination status, potential sources, and risk assessment

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

Penta- and hexa-CBs were found as the major homologs in street dusts

from traffic area of Guangzhou, China (Wang et al., 2013) Di-CBs were

the largest contributors to total PCBs in the rural street dusts (45.4 ±

25.4%), followed by penta-CBs (22.9 ± 11.6%), hexa-CBs (15.8 ±

12.6%), tetra-CBs (8.6 ± 9.4%), tri-CBs (3.6 ± 4.2%), and hepta-CBs

(3.5 ± 4.9%) This unusual profile was largely due to the presence of

congener 3,3′-dichlorobiphenyl (PCB-11), which will be discussed in

detail inSection 3.2 Minor proportions of the remaining homologs

(i.e., mono- and octa- to deca-CBs) were observed in all the samples

3.2 Concentrations of 3,3′-dichlorobiphenyl (PCB-11)

The congener PCB-11 has been considered as an inadvertent

by-product of pigment manufacturing processes and detected in a variety

of commercial paint pigments and consumer products (Anezaki and

Nakano, 2014;Guo et al., 2014;Hu and Hornbuckle, 2010; Shang

et al., 2014) As reviewed byVorkamp (2016), PCB-11 has been found

in ambient air, wastewater, storm water, receiving waters, snow, ice,

sediment, soil, plants, animals, and humans The high abundance of

this congener has been demonstrated in the atmosphere of different

parts of the world such as the US (Du et al., 2009;Hu et al., 2008),

Japan (Anezaki and Nakano, 2014), Korea (Kim et al., 2003), and even

in polar regions (Li et al., 2012;Wang et al., 2017) Information about

the presence of PCB-11 in Vietnam's environment is still limited

Romano et al (2013)reported that PCB-11 was among the most

domi-nant congeners detected in surficial sediments and soils collected from

Thi Nai lagoon, central Vietnam, accounting at least 7% of total PCBs

To our knowledge, this is the first dataset reporting the occurrence of

PCB-11 in outdoor dusts PCB-11 was detected in all the samples of our

study, suggesting the widespread distribution of this compound in

these areas Levels of PCB-11 were the highest in street dusts from the

Hanoi urban area (median 0.71, range 0.35–1.5 ng g−1), followed by

the industrial (0.22, 0.15–0.51 ng g−1) and rural samples (0.10,

0.059–0.12 ng g−1) PCB-11 accounted for 3.8 to 13.9%, with an average

of 7.0% of total PCB concentrations in the urban samples that is

signifi-cantly higher than those recorded in the industrial sites (average 3.1%,

range 0.3–8.7%) Although levels of PCB-11 were the lowest in Bac

Giang, this congener exhibited the largest contributions to total PCBs

in the rural samples (44.5%, 11.1–84.6%), probably due to the low

abun-dance of other congeners, which mainly derived from technical PCB

mixtures Levels of PCB-11 correlated highly with total PCBs (Pearson's

r = 0.657, p b 0.001), indicating the prevalence of this congener in the

urban and rural road dusts However, there is no significant association

between PCB-11 and other individual congeners, suggesting the unique

sources of PCB-11 Concentrations of PCB-11 in street dusts of this study

were comparable with those detected in sediments (median 0.25,

max-imum 0.61 ng g− 1) and soils (median 0.30, maximum 1.31 ng g− 1)

col-lected from Thi Nai lagoon and its mainland (Romano et al., 2013)

3.3 Concentrations of seven indicator PCBs (in-PCBs)

The term indicator PCBs refers to a group of two mono-ortho

(i.e., PCB-28 and -118) and five di-ortho (i.e., PCB-52, -101, -138, -153,

and -180) substituted congeners, that dominated the PCB patterns in

technical mixtures as well as environmental samples and foodstuffs

(Babut et al., 2009;Capel et al., 1985;Kim et al., 2004) Concentrations

ofΣ7in-PCBs (median and range) in the street dusts from Thai Nguyen,

Hanoi, and Bac Giang were 3.0 (0.54–22), 3.4 (2.1–9.7), and 0.055

(0.0070–0.33) ng g−1, respectively Similar to the trend observed for

Σ209PCBs, levels of Σ7in-PCBs in the rural samples were the lowest,

and the difference between the industrial and urban samples was

insig-nificant The contamination degree of seven in-PCBs in our samples was

much lower than those of six in-PCBs (excluding PCB-118) detected in

street dusts from different functional areas (e.g., rural, urban,

industri-ally influenced urban, and industrial sites) in North Rhine-Westphalia,

Germany (median 59, range 17–12,600 ng g−1;Klees et al., 2015)

Concentrations of in-PCBs in the street dusts from Hanoi and Thai Nguyen were comparable to levels reported for surface soils from agri-cultural areas, but slightly lower than those from industrial and urban areas of Hanoi (Toan et al., 2007;Toan and Quy, 2015) Levels of Σ7in-PCBs detected in this study were generally lower than a threshold of

277 ng g−1

specified for freshwater sediment (MONRE, 2012)

A linear regression relationship (R = 0.97, p b 0.0001) between

log-transformedΣ7in-PCBs and Σ209PCBs established for the whole dataset

is presented by Eq.(4): logΣ209PCBs ¼ 0:623 0:023ð Þ þ 0:880 0:028ð Þ  logΣ7in−PCBs ð4Þ The full congener-specific measurements of PCBs are time-consuming and costly, so multiplying the sum of certain indicator con-geners by a multiplication factor is a simplified way to estimate the total PCB concentrations.Klees et al (2017)have derived total PCB levels in plants and dusts by multiplyingΣ6in-PCBs (Σ7in-PCBs exclud-ing PCB-118) by a factor of five Four times of Σ7in-PCBs have been used

to calculate total PCB levels in sediment (Hoai et al., 2010) and fish (Froescheis et al., 2000) Based on our measured data, a general multi-plication factors of 4 can also be applied to extrapolate total PCB concen-trations fromΣ7in-PCBs in the street dusts from northern Vietnam However, the conversion factors derived for the samples in Thai Nguyen industrial park (4.7 ± 0.9) were higher than those estimated for the Hanoi urban samples (3.2 ± 0.2) This difference probably reflects orig-inal formulations of PCBs dominating in the Thai Nguyen and Hanoi road dusts For a simple comparison, the proportions ofΣ7in-PCBs in total PCBs are about 16 and 31% in Aroclor 1248 and 1254, respectively, that correspond to the conversion factors of 5 and 3 as described above (Frame et al., 1996) A more detailed estimation of origins of PCBs in our road dust samples will be discussed inSection 3.5

Proportions of seven indicator congeners in total PCB concentrations were the highest in Hanoi samples (31.4 ± 2.2%), followed by industrial (22.0 ± 3.9%), and rural ones (20.2 ± 10.4%) A high prevalence of penta- and hexachlorinated congeners (i.e., PCB-101, -118, -138, and -153) was detected in samples from the Hanoi urban area, which was consistent with congener patterns in other environmental media such

as indoor dust, soil, and sediment collected from the same areas (Hoai

et al., 2010;Toan and Quy, 2015;Tue et al., 2013) Whereas, tri- and tetrachlorinated congeners such as PCB-28 and PCB-52 were signifi-cantly more abundant in the industrial street dusts from Thai Nguyen PCB-28 was also identified as the most predominant indicator congener

in outdoor dusts from Guangzhou and Hong Kong, China (Wang et al.,

2013) It is noteworthy that lightly chlorinated congeners are less per-sistent and more volatile than heavily chlorinated congeners, and thus, these compounds were not detected or found at low levels in soils and sediments from some areas in northern Vietnam (Hoai et al.,

2010;Toan and Quy, 2015) The abundance of PCB-28 and PCB-52 in the samples from Thai Nguyen reveals a near-source and ongoing emis-sion of PCBs in this industrial area, and emphasizes the feature of street dusts as an indicator of current pollution status of PCBs and other or-ganic pollutants as well (Klees et al., 2015, 2017;Sohail et al., 2018) The samples from Bac Giang showed a variegated pattern of seven in-PCBs, possibly due to relatively low detection rates and concentrations

of these congeners in this rural area

3.4 Concentrations of dioxin-like PCBs (dl-PCBs)

Concentrations of dl-PCBs and toxic equivalent quantity (WHO-TEQ) derived for dl-PCBs in the street dusts from northern Vietnam are shown inTables 1 and 3, respectively The dl-PCB concentrations and WHO-TEQ levels in the urban samples were a little higher than those from the industrial park, but the difference was not statistically significant Levels of dl-PCBs and WHO-TEQ in our street dust samples were lower than those detected in outdoor dusts from other countries such as China (Wang et al., 2013), Germany (Klees et al., 2015, 2017),

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

India (Chakraborty et al., 2016), and Pakistan (Sohail et al., 2018)

Con-centrations of dl-PCBs in the Hanoi street dusts (median 1.5, range

1.1–5.2 ng g−1) were comparable to levels found in soil (3.8,

3.0–5.0 ng g−1

) but lower than levels in sediment (11, 9.1–16 ng g−1)

collected from surrounding areas of this city such as Kieu Ky agricultural

area and Cau Bay river (Toan and Quy, 2015)

The proportion (average ± SD) of dl-PCBs in total PCBs in the

sam-ples from Hanoi was 16.1 ± 2.7%, that much higher than those from

Thai Nguyen (7.9 ± 2.9%) and Bac Giang (7.3 ± 7.2%) The most

domi-nant dl-PCBs were PCB-118, -105, -77, and -156 (Fig 2) The pattern

of dl-PCBs in the Hanoi street dusts (PCB-118 N −105 N −156 N −77

N −167) was quite similar to those detected in soil samples from Kieu

Ky area (Toan and Quy, 2015) The samples from Thai Nguyen industrial park showed a markedly higher proportion of PCB-77 than those from Hanoi and Bac Giang PCB-77 was clarified as the most important copla-nar congener in road dusts from SIPCOT industrial region in Chennai, India with possible emission sources related to the combustion of coal and industrial waste (Chakraborty et al., 2016) Furthermore, the prev-alence of PCB-77 in the atmospheric environment around steel and iron industrial complexes in China (Li et al., 2011) and Korea (Choi et al.,

2008), suggests the emission of PCB-77 from metallurgical plants in Thai Nguyen Although PCB-126 was detected at minor levels, this con-gener exhibited the largest contribution to WHO-TEQs in most samples from Hanoi and Thai Nguyen that accounted up to 98.2% of TEQ values

Table 3

TEQ concentrations of dl-PCBs (pg WHO-TEQ g −1 ) in street dust from northern Vietnam.

Non-ortho substituted congeners

Mono-ortho substituted congeners

a Toxic equivalency factors WHO 2005 TEF ( Van den Berg et al., 2006 ).

b Not detected.

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

The contributions of other congeners such as PCB-81, -114, -123, -157,

-169, and -189 were insignificant

After removing two values of non-detected dl-PCBs in the rural area,

log-transformedΣdl-PCBs and Σ7in-PCBs were linearly correlated (R =

0.95, p b 0.0001) (Eq.(5)), suggesting their similar emission sources

logΣdl−PCBs ¼ −0:374 0:031ð Þ þ 1:005 0:046ð Þ

As previously discerned, a detailed and accurate determination of

dl-PCBs is relatively complicated and expensive, and therefore, various

in-PCB schemes have been evaluated to generate interconversion factors

between in-PCBs and dl-PCBs (Gandhi et al., 2015) Linear regression

analysis also indicates a moderate relationship between logΣ7in-PCBs

and log(dl-PCB-TEQs) in our road dust samples (R = 0.63, p b 0.0001).

However, in order to obtain more reliable conversion factors, an

inten-sive investigation with larger sample size under different schemes is

needed Similar to those observed for the ratios ofΣ7in-PCBs to total

PCBs, ratios ofΣ7in-PCBs to Σdl-PCBs in the Hanoi and Thai Nguyen

road dusts (average 2.3 and 3.2, respectively) were in line with the

values reported for mixtures Aroclor 1254 (2.6) and Aroclor 1248

(3.5) (Frame et al., 1996)

3.5 Potential sources of PCBs

In order to track the origins of PCBs in the outdoor environment of

the investigated areas, we analyzed PCB homolog compositions in street

dust samples and in selected technical formulations by hierarchical

cluster analysis (Fig S1) Almost all the samples from the industrial

park in Thai Nguyen were clustered with lightly chlorinated mixtures

such as Aroclor 1016, 1242, and 1248, or Kanechlor 300 and 400

These formulations have been applied as additives in dielectric fluids

in capacitors and transformers, heat transfer fluids and hydraulic fluids

in industrial systems, and other open applications such as plasticizers,

adhesives, and wax extenders (IARC, 2016) The homolog patterns of

PCBs in urban street dusts were similar to those existed in more highly

chlorinated mixtures such as Aroclor 1254 or Kanechlor 500, which

have been extensively used for both closed and partially-closed systems

(e.g., dielectric fluids, hydraulic fluids, and lubricants) and open

applica-tions (e.g., plasticizers, adhesives, wax extenders, dedusting agents,

inks, cutting oils, sealants, and caulking compounds) (IARC, 2016) The

patterns of urban samples were also in accordance with the homolog

profiles of PCB mixtures from Russia (Sovol) or China (PCB5), that

were imported into Vietnam in the 1960–1990 period (Kawano and

Thao, 2012;Minh et al., 2008;Toan et al., 2007) Samples from the

rural area showed a non-uniform pattern that requires more extensive

investigations with larger sample sizes According to the Vietnam

Na-tional Implementation Plan for the Stockholm Convention on POPs, it

has been estimated that there were 7000 tons of potentially

PCB-containing oils in Vietnam as of 2006 Of these, approximately

1400 tons were transformer and capacitor oils belonging to the

Vietnam Electricity and other independent power plants through the

country However, information about PCB usage in other industrial

sec-tors is still obscure (The World Bank, 2015)

Principal component analysis of congener-specific profiles has been

considered as a useful way to estimate the potential emission sources of

PCBs (Chakraborty et al., 2016;Wang et al., 2016) This multivariate tool

was applied for log-transformed concentrations of selected PCB

conge-ners with detection rates over 70% in the whole sample set Four

major principal components (PC-1, -2, -3, and -4) were extracted,

con-stituting 48.9, 30.8, 8.5, and 5.6% of total variance, respectively

(Fig S2) PC-1 highly correlated with penta- and hexachlorinated

con-geners, including major components in PCB mixtures such as PCB-95,

-99, -101, -110, -138, and -153, and most dl-PCBs (e.g., PCB-105, -114,

-118, -123, -156, -157, and -167) The correlation in this PC can be

pos-sibly explained by the leakages of PCBs from insulating oils in old

electric equipment and lubricating oils in motor vehicles (Hoai et al.,

2010;Toan et al., 2007); the outgassing of PCBs from PCB-containing construction materials in buildings, roads, or transport infrastructure (Klees et al., 2015;Shanahan et al., 2015); and the emission due to inap-propriate disposal of PCB-containing wastes (Romano et al., 2013) A co-planar congener (i.e., PCB-77) and six lightly chlorinated congeners such as PCB-28, -52, -44, -49, -70, and -74 were loaded with PC-2, sug-gesting the emissions from metallurgical plants in industrial area (Cetin,

2016;Chakraborty et al., 2016) and the use of PCBs in paints, surface coatings, and plastic additives (Wang et al., 2016) PC-3 is associated with two heptachloro congeners as PCB-170 and PCB-180, that domi-nated highly chloridomi-nated mixtures (e.g., Aroclor 1260 and Kanechlor 600) and exist in transformer oils, hydraulic fluids, plasticizers, and dedusting agents (IARC, 2016) The last PC showed a high loading with only PCB-126, a typical dioxin-like congener that is unintentionally released during combustion and high temperature processes (Chakraborty et al., 2016) Nevertheless, the ratios of (PCB-126 + PCB-169) / (PCB-77 + PCB-126 + PCB-169) in the samples from Hanoi and Thai Nguyen were 9.5 ± 8.3 and 6.3 ± 7.4%, respectively, and were more similar to those of commercial PCB mixtures than those from pyrogenic sources (Kannan et al., 1987;Sakai et al., 1994)

In addition, the strongly correlation between logΣdl-PCBs and logΣ7in-PCBs (Eq.(5)) partially confirmed the emission of dl-PCBs from PCB mixtures Our results were consistent with values reported for sediment samples from Hanoi urban area and rural area in Hue city, Vietnam, and urban and suburban areas in Osaka, Japan (Kishida

et al., 2010)

PCB-11 did not show any significant relationship with other conge-ners, suggesting its unique emission source PCB-11 can be inadver-tently formed during the production of pigments and it has been found as a dominant impurity in different types of commercial pigments and paints such as monoazo yellow, diarylide yellow, bisacetoacetic arylides, and quinophthalone (Anezaki and Nakano, 2014;Hu and Hornbuckle, 2010;Shang et al., 2014) Because of the wide applications

of these pigments, PCB-11 has been detected in various consumer prod-ucts, e.g., cardboard, newspaper, magazine, plastic bag, and printed tex-tiles (Guo et al., 2014;Rodenburg et al., 2010) The associations between environmental levels of PCB-11 and human population densities have been demonstrated elsewhere (Basu et al., 2009).Baek et al (2010) sug-gested that the source of PCB-11 is located in the residential areas rather than in industrial and semirural areas The omnipresence of PCB-11 in the street dusts from northern Vietnam, especially in the Hanoi urban area, has been likely associated with human activities utilizing pig-ments, for example, the increasing use of color-printed and dyed con-sumer products (Hu and Hornbuckle, 2010;Romano et al., 2013) Besides, the emission of PCB-11 from construction materials and deco-ration and furnishing items of the buildings should be also considered (Baek et al., 2010) It should be noted that PCB-11 is a non-ortho substituted congener, and therefore, it may represent dioxin-like toxic-ity (Rodenburg et al., 2010) Our findings on the ubiquitous presence of PCB-11 in street dusts suggest an urgent need for further investigations

on this unique congener in Vietnam, such as emission source tracking, air pollution monitoring, spatial distribution, and seasonal variation studies

3.6 Human exposure to PCBs via road dust ingestion

Daily intake doses of total PCBs and dl-PCB-TEQs, and HQ and CR values of total PCBs in the street dusts from northern Vietnam are sum-marized in Table S8 The occupationally exposed persons in the indus-trial and urban areas were estimated to receive the highest PCB doses (4.2 × 10−3to 2.3 × 10−1ng kg−1d−1), that were about one order of magnitude higher than those received by general population (2.3

× 10−4to 1.3 × 10−2ng kg−1d−1) This observation suggests that more consideration should be given to labor protection for some occu-pational groups, for instance, providing them with dust-proof clothing

H.Q Anh et al / Science of the Total Environment 652 (2019) 345–355

such as masks with effective dust filtration and dust-proof glasses and

gloves The median daily intake doses of total PCBs of 2.3 × 10−2and

1.8 × 10−2ng kg−1d−1were estimated for children in industrial and

urban areas, respectively, that were comparable to those derived for

oc-cupational groups In Vietnam, due to the lack of playgrounds, children

have played for hours per day on the pavement and some toddlers have

been ‘strolling’ fed, resulting in a higher body burden of contaminated

outdoor dusts Residents in the Bac Giang rural area were exposed to

markedly lower doses of PCBs in street dusts of 2.6 × 10−5and 4.2

× 10−4ng kg−1d−1for adults and children, respectively Nevertheless,

all the HQ and CR values were several orders of magnitude

lower than critical values (HQ b 1 and CR b 10−6), indicating

negligible non-cancer and cancer risks of PCBs associated with street

dusts in these study areas Furthermore, the daily intakes of

dl-PCB-TEQs in our study were also smaller than tolerable daily intake range

of 1–4 pg TEQ kg−1d−1(Van Leeuwen et al., 2010) As compared

with the overall daily intake of PCBs (comprising diet, indoor dust

inges-tion, and inhalation pathways) of 50 ng d− 1previously reported byTue

et al (2013)for Hanoi residents, the contribution of street dust

inges-tion was insignificant for normal adults but it can contribute about 2%

in total PCB intake by occupationally exposed individuals

The above results on risk assessment need further confirmation and

reconsideration because of some limitations Firstly, we assumed a 100%

absorption for dust-bound PCBs because of the absence of

bioaccessibi-lity estimation Secondly, we report the ID values estimated only for

road dust ingestion, while indoor dust ingestion, air inhalation, and

food consumption are major sources of PCBs (Harrad et al., 2009;Tue

et al., 2013) Thirdly, dioxin-like activities in dusts should be evaluated

by in vitro bioassays combined with chemical analysis of

dioxin-related compounds other than dl-PCBs (Tue et al., 2010b) Therefore, a

more comprehensive/detailed risk assessment, comprising multiple

ex-posure pathways, bioaccessibility determination, and questionnaire

survey, should be conducted to generate more accurate and meaningful

information about human health effects of PCBs in Vietnam, especially

for occupationally exposed individuals

4 Conclusions

This is the first data set reporting levels and accumulation profiles of

209 PCB congeners in street dust samples collected from northern

Vietnam Concentrations of total PCBs in street dusts from the industrial

park and urban area were significantly higher than those detected in the

rural ones, suggesting their emissions related to rapid industrialization

and urbanization The specific patterns of PCBs characterized for street

dusts from each study area have revealed the relative contributions of

different emission sources and original PCB technical mixtures Beside

the historical release from imported PCB-containing oils and old

electri-cal equipment, PCBs have been emitted from other emerging sources

such as consumer products, building materials, and vehicle lubricants,

especially in urban areas Industrial activities have been also a

consider-able contributor to total PCB emission in northern Vietnam with a

par-ticular pattern dominated by lightly chlorinated homologs PCB-11 has

been found as an abundant congener in street dusts from all the study

areas, indicating the widely application of consumer products

contain-ing it in northern Vietnam Although human health risks associated

with PCBs in street dusts of this study were generally low, a more

com-prehensive evaluation comprising different exposure pathways should

be conducted for this typical class of POPs in Vietnam

Acknowledgements

This study was supported in part by Grants-in-Aid for Scientific

Re-search (B: 16H02963) of the Japan Society for the Promotion of Science

(JSPS) and the Environment Research and Technology Development

Fund (SII-3-2) of the Environmental Restoration and Conservation

Agency of Japan (ERCA); and the Vietnam's National Foundation for

Science and Technology Development (NAFOSTED) under grant num-ber 104.04-2017.310 We thank the staff of VNU University of Science, TNU University of Science (Thai Nguyen University, Vietnam), and CATE in sampling activities and sample analysis We wish to thank Prof Alexander Scheeline (University of Illinois at Urbana-Champaign, US) for critical reading of the manuscript

Appendix A Supplementary data Supplementary data to this article can be found online athttps://doi org/10.1016/j.scitotenv.2018.10.240

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