A preliminary investigation of 942 organic micro-pollutants in the atmosphere in waste processing and urban areas, northern Vietnam: Levels, potential sources, and risk assessment

A preliminary investigation of 942 organic micro-pollutants in the atmosphere in waste processing and urban areas, northern Vietnam: Levels, potential sources, and risk assessment

Contents lists available atScienceDirect Ecotoxicology and Environmental Safety journal homepage:www.elsevier.com/locate/ecoenv

A preliminary investigation of 942 organic micro-pollutants in the

atmosphere in waste processing and urban areas, northern Vietnam: Levels,

potential sources, and risk assessment

Hoang Quoc Anha,b,c, Keidai Tomiokaa, Nguyen Minh Tued,e, Le Huu Tuyene, Ngo Kim Chif,

Tu Binh Minhc, Pham Hung Viete, Shin Takahashia,⁎

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

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

cFaculty of Chemistry, VNU University of Science, Vietnam National University, 19 Le Thanh Tong, Hanoi, Vietnam

dCenter for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan

eCenter for Environmental Technology and Sustainable Development (CETASD), VNU University of Science, Vietnam National University, 334 Nguyen Trai, Hanoi,

Vietnam

fInstitute of Natural Products Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam

A R T I C L E I N F O

Keywords:

Organic micro-pollutants

PUF–PAS

AIQS–DB

Waste processing area

Urban area

Northern Vietnam

A B S T R A C T

Of 942 organic micro-pollutants screened, 167 compounds were detected at least once in the atmosphere in some primitive waste processing sites and an urban area in northern Vietnam by using a polyurethane foam-based passive air sampling (PUF–PAS) method and an Automated Identification and Quantification System with a Database (AIQS–DB) for GC–MS Total concentrations of organic pollutants were higher in samples collected from an urban area of Hanoi city (2300–2600 ng m–3) as compared with those from an end-of-life vehicle (ELV) dismantling area in Bac Giang (900–1700 ng m–3) and a waste recycling cooperative in Thai Nguyen (870–1300 ng m–3) Domestic chemicals (e.g., n-alkanes, phthalate ester plasticizers, and synthetic phenolic

antioxidants) dominated the organic pollutant patterns in all the samples, especially in the urban area Pesticides (e.g., permethrins, chlorpyrifos, and propiconazole) were found in the atmosphere around the ELV sites at more elevated concentrations than the other areas Levels of polycyclic aromatic hydrocarbons and their derivatives in the Bac Giang and Thai Nguyen facilities were significantly higher than those measured in Hanoi urban houses, probably due to the waste processing activities Daily intake doses of organic pollutants via inhalation were estimated for waste processing workers and urban residents This study shall provide preliminary data on the environmental occurrence, potential emission sources, and effects of multiple classes of organic pollutants in urban and waste processing areas in northern Vietnam

1 Introduction

Air pollution and its potential adverse effects on humans have

be-come an issue of great concern in Vietnam The major sources of air

pollutants, e.g., particulate matter (PM), inorganic gases, and organic

contaminants, in this developing country have been identified as traffic

and construction emissions, inappropriate waste disposal and recycling,

and other industrial and agricultural production activities (Huy et al.,

2017; Le et al., 2014; Luong et al., 2017; Phung et al., 2016; Tue et al.,

2013; Wang et al., 2016a) The strong associations between the daily

hospital admissions for acute respiratory diseases and the levels of

common air pollutants (e.g., PM10, NO2, SO2) have been observed in the

metropolitan areas of Hanoi and Ho Chi Minh city (Luong et al., 2017; Nhung et al., 2018; Phung et al., 2016) However, studies on the oc-currence and risk assessment of organic micro-pollutants, including highly toxic persistent organic pollutants (POPs), in Vietnam's atmo-sphere are relatively limited, mainly due to the lack of suitable sam-pling methods and cost-effective quantification tools Some legacy POPs such as dichlorodiphenyltrichloroethans (DDTs) and polychlorinated biphenyls (PCBs) were found at relatively high concentrations in the ambient air in Vietnam, as compared with some other Asian countries (Wang et al., 2016a) Elevated levels of PCBs and polybrominated di-phenyl ethers (PBDEs) were recorded in the atmosphere around some e-waste recycling households in northern Vietnam (Tue et al., 2013)

https://doi.org/10.1016/j.ecoenv.2018.10.026

Received 28 August 2018; Received in revised form 1 October 2018; Accepted 8 October 2018

⁎

Corresponding author

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

Ecotoxicology and Environmental Safety 167 (2019) 354–364

0147-6513/ © 2018 Elsevier Inc All rights reserved

T

Concentrations of phthalate esters, an emerging group of air pollutants,

in Vietnamese indoor air were comparable to those detected in some

developed countries such as US and Japan (Tri et al., 2017a) Actually,

the Vietnamese ambient air is estimated to be polluted by a great

number of organic pollutants originating from complex anthropogenic

sources (Tri et al., 2017a,b; Tue et al., 2013; Wang et al., 2016a) This

finding suggests an urgent need to conduct a comprehensive

in-vestigation into the presence and exposure risk of organic air pollutants

in Vietnam, especially for urban areas of big cities and primitive waste

processing areas

The passive air sampling method using polyurethane foam discs

(PUF–PAS) was introduced byShoeib and Harner (2002)for monitoring

of POPs such as PCBs and polychlorinated naphthalenes (PCNs) The

PUF–PAS method has been widely applied as an alternative to

con-ventional active air sampling (AAS) for organic pollutants because of its

advantages of low cost, simple handling, no power supply required, and

deployable at many sites at the same time for large scale monitoring

(Bogdal et al., 2013; Harner et al., 2006) As reviewed by

Esteve-Turrillas and Pastor (2016), several semivolatile organic compounds

(SVOCs) have been monitored in the atmosphere by using the PUF–PAS

method, for example, PCBs, PCNs, brominated flame retardants (BFRs,

e.g., PBDEs), polycyclic aromatic hydrocarbons (PAHs),

poly-chlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs),

organo-chlorine pesticides, current-use pesticides, and other emerging

pollu-tants We have found that PUF–PAS is an appropriate sampling method

for organic pollutants, especially for developing countries with limited

financial resources (Bogdal et al., 2013; Tue et al., 2013; Wang et al.,

2016a)

The gas chromatography–mass spectrometry (GC–MS) method

op-erated in selective ion monitoring (SIM) modes exhibits outstanding

separation efficiency, high selectivity, and low detection limits

However, a conventional GC–MS method usually focuses on one or a

few groups of chemicals with similar physicochemical properties and

requires much efforts to prepare and operate analytical standards,

especially for multi-residue analysis of several hundred analytes To

simultaneously determine nearly 1000 SVOCs with different

physico-chemical properties using GC–MS without using authentic physico-chemical

standards,Kadokami et al (2005)introduced a novel screening tool, an

Automated Identification and Quantification System with a Database

for GC–MS (AIQS–DB/GC–MS) The database consists of three

compo-nents including mass spectra, retention times, and calibration curves,

which are essential for both identifying and quantifying target

sub-stances, overcoming some of the limitations of traditional GC–MS

analysis (Kadokami et al., 2005) The AIQS–DB/GC–MS method has

been efficiently and inexpensively used to quantify hundreds of organic

contaminants in aquatic environments such as surface water (Kong

et al., 2015), groundwater (Kong et al., 2016), and sediments

(Kadokami et al., 2013; Pan et al., 2014) This tool has also been

ap-plied to monitor hundred organic micro-pollutants in Vietnamese sewer

systems (Ha et al., 2017; Hanh et al., 2014, 2015), and settled dusts

collected from end-of-life (ELV) vehicle processing and urban areas in

northern Vietnam (Anh et al., 2018)

To our knowledge, there have been no studies on the screening

analysis of organic pollutants in northern Vietnam In the present study,

942 organic compounds were comprehensively monitored in the air

samples collected from an informal ELV dismantling area in Bac Giang

province, a waste recycling cooperative in Thai Nguyen province, and

an urban area of Hanoi city by using the PUF–PAS coupled with

AIQS–DB/GC–MS quantification Concentrations and patterns of

mul-tiple organic air pollutants were investigated to provide an overall view

of the pollution status and their potential emission sources in some

primitive waste processing and urban areas in northern Vietnam

Human health risks associated with inhaling organic pollutants were

also estimated for waste processing workers and residents in the study

areas

2 Material and methods

2.1 Study areas

The ELV dismantling workshops were located in Thuyen village, Bac Giang province, about 60 km northeast of the capital city Hanoi ELVs and other machinery engines from all around the country are collected and then manually dismantled using rudimentary tools such as drop hammers and oxygen-fuel cutting torches The dismantled components are categorized into reusable parts for resale, recyclable materials for recycling, and low value materials for disposal (including open burning) In the survey year 2015, there were about 90 out of a total of

300 households with 200 local workers that were involved in ELV-re-lated activities in Thuyen village, while the rest of population was en-gaged in agricultural production A waste recycling cooperative located

in Tan Cuong commune, Thai Nguyen province, was also investigated

in this study Tan Cuong commune, situated 70 km north of Hanoi, is a mountainous area and well known for tea growing, without extensive industrial activities The cooperative under investigation comprised several facilities with different activities such as plastic recycling, rubber tire melting, waste oil refining, and hazardous waste com-busting For comparison, Hanoi was chosen as an urban reference site, characterized by a high degree of urbanization and high population density

2.2 Passive air sampling

The air samples were collected using the PUF–PAS method with foam discs (136 mm diameter, 13 mm thick, and 0.0140 g cm–3density; INOAC Corporation) The PUF discs were washed by acetone in Soxhlet extractors for 24 h, dried in a vacuum desiccator, covered in aluminum foil, and sealed in polyethylene bags until deployment Each sampler consisted of two stainless steel bowls (26 and 20 cm diameter for upper and lower bowls, respectively) with a 2-cm gap between the two bowls for air circulation Samplers were deployed at 2–3.5 m above the ground over a sampling period of approximately six weeks At the end

of the sampling period, the samplers were disassembled, and the PUF discs were retrieved, resealed, transported to a laboratory, and stored at

−20 °C until analysis In the ELV area, a total of ten samples were collected during September–October 2015 from nine ELV workshops (ELV-1 to ELV-9) and one control rural house (RH-1) Three samples were obtained from the waste recycling cooperative in Thai Nguyen: a

plastic recycling facility (WR-1), a waste oil refining facility (WR-2), and a rubber melting kiln (WR-3) Samples from three urban houses in

Hanoi were also collected (UH-1 to UH-3) Additional information on the sampling sites and deployment position of samplers are provided in Table S1

Air concentrations of pollutants were derived by the amounts ac-cumulated in the PUF discs and the volume of circulated air The sampled air volume is estimated by a sampling duration in days and a sampling rate (m3d–1) The sampling rates of SVOCs by the PUF–PAS method could be estimated based on calibration studies with AAS re-ferences (Bohlin et al., 2014; Shoeib and Harner, 2002), or by using depuration compounds spiked into the collecting medium before de-ployment (Birgül et al., 2017; Gouin et al., 2005; Pozo et al., 2004) According to the literature, a PUF–PAS outdoor sampler has a linear uptake duration over the first 100 days and sampling rates of 3–5 m3d–1

for chemicals with n-octanol/air partition coefficients higher than 108.5

(Harner et al., 2004; Jaward et al., 2004; Wilford et al., 2004) The sampling rates of 3.5–4 m3d–1have been widely used to derive outdoor air concentrations of typical classes of organic pollutants such as PAHs, organochlorine pesticides (OCPs), PCBs, and PBDEs (Bohlin et al., 2008; Cheng et al., 2013; Choi et al., 2012; Gevao et al., 2006; Jaward et al., 2005; Muenhor et al., 2010; Pozo et al., 2015; Tue et al., 2013; Wang

et al., 2010; Zhang et al., 2008) For indoor air, lower sampling rates of 1.66–2.5 m3 d–1 have been also used (Bohlin et al., 2008; Muenhor

et al., 2010) Unfortunately, sampling rate of PUF–PAS method for

other classes of organic pollutants, including several groups of

emer-ging contaminants, has not been fully characterized We collected air

samples mainly from primitive waste processing facilities with

semi-open workplaces reinforced by steel frames and corrugated sheets (see

illustration inTable S1), and therefore, we applied generic sampling

rates of 3.5 and 2.5 m3d–1for samplers deployed at the waste

proces-sing workshops and urban houses, respectively Further studies on the

calibration and evaluation of PUF–PAS sampling rates for organic

pol-lutants other than POPs are needed

2.3 Chemical analysis

Extraction was carried out according to the method previously

de-scribed byTue et al (2013) The PUF discs were Soxhlet extracted with

acetone for 16 h A portion of crude extract corresponding to about

30 m3of air volume was used for AIQS–DB/GC–MS analysis The

re-maining portion of extract will be used for future studies on other target

analysis and bioassays Clean-up procedure was conducted according to

Kadokami et al (2012) In brief, crude extract was solvent-exchanged

into hexane and purified using an activated silica gel column (Wakogel®

S-1, activated at 130 °C for 3 h) The eluate fractions from the silica gel

column were concentrated to 500 μL and spiked with 500 ng of each

internal standards (1,4-dichlorobenzene-d4, 4-chlorotoluene-d4,

ace-naphthene-d10, chrysene-d12, fluoranthene-d10, naphthalene-d8,

per-ylene-d12, and phenanthrene-d10; Custom Internal Standard, Restek)

before quantification All chemicals used in this study were reagent

grade for PCB analysis and obtained from Wako Pure Chemical

In-dustries, Ltd Solvents were re-distilled before use

A total of 942 semivolatile organic pollutants were quantified using

a gas chromatograph connected to a quadrupole mass spectrometer

(GCMS-QP2010 Ultra; Shimadzu) and equipped with AIQS-DB system

Target compounds were separated on a fused-silica capillary column (J

&W DB-5ms Ultra Inert, 30 m length × 0.25 mm internal diameter ×

0.25 µm film thickness; Agilent Technologies) Helium was used as

carrier gas at a linear velocity of 40 cm s–1 The temperature of the

injection port, interface, and ion source was 250, 300, and 200 °C,

re-spectively Initial column oven temperature was set at 40 °C (held for

2 min) and then increased to 310 °C (8 °C min–1, held for 5 min)

Analytes were identified and quantified based on predicted retention

times, mass spectra, and calibration curves registered in the database

Criteria for a detected compound included retention time variation

( ± 0.5 min), mass spectra similarity (> 80%), signal to noise ratio (S/

N > 3), and signal ratio of sample and blank (S/B > 3)

2.4 Quality assurance and quality control (QA/QC)

A procedural blank sample was analyzed simultaneously with each

batch of four real samples to check for interference and contamination

during chemical analysis Concentrations of target compounds were

corrected by subtracting the average blank level To reduce the blank

level, glassware was washed with detergent and tap water, dried, baked

for 2 h at 450 °C, and rinsed with solvents (i.e., acetone, toluene, and

hexane) before use Before analyzing real samples, the recovery test was

conducted using procedural blanks (n = 3) spiked with some

re-presentative groups of organic pollutants, including 10 OCPs, 62 PCBs,

and 19 PAHs and methylated PAHs Recoveries of most compounds

ranged from 60% to 120%, except for some PCB congeners (e.g.,

PCB-171, PCB-201, and PCB-202) and two pesticides (e.g., dieldrine and

methoxychlor) (Table S2) The relatively high recoveries (over 140%)

of some compounds were largely due to the co-elution peaks However,

this study focused on comprehensive analysis and semiquantitation of

multiple organic pollutants, and therefore, the relatively high

re-coveries of few individual compounds should not significantly affect

overall results For comparison, we selected some PAH congeners and

measured their concentrations in the same air samples using a similar

sample treatment protocol and quantified them using a conventional GC–MS method operated in SIM mode (GC–MS/SIM) The instrumental conditions for the target analysis of PAHs are summarized inTable S3 Instrument detection limits (IDLs) of most compounds ranged from 5 to

50 ng mL–1(Kadokami et al., 2012) Method detection limits (MDLs) were derived from the IDLs with an air sample volume of 30 m3and a final extract volume of 500 μL The MDLs ranged from 0.10 to 1.0 ng m–3for almost the target compounds, except for few omnipresent

compounds such as bis(2-ethylhexyl) phthalate (DEHP) with a MDL

value of 10 ng m–3(see details inTable S5)

2.5 Risk assessment

Inhalation daily intake doses (DIair– ng kg–1 d–1) of total organic pollutants and some representative contaminants were estimated using the following equation, assuming a 100% absorption rate:

DIair Cair F IR/BW Where Cair is concentration of target contaminant (ng m–3), F is fraction of time spent in the respective micro-environment, IR is re-spiratory rate (m3d–1), and BW is body weight (kg) F values of 8/24 and 14/24 were assigned for adults at workplaces and dwellings in the waste processing areas, respectively Children under school age are estimated to be taken care of at home with a fraction time of 24/24 The respiratory rates were estimated as 16.0 m3d–1for adults and 10.1 m3

d–1for children (US EPA, 2011) Average body weights of 60 kg and

15 kg were assigned for Vietnamese adults and children, respectively

2.6 Statistical analysis

Concentrations below MDLs were treated as zero 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 in

con-tamination levels between study locations Paired t-test at a confidence

level of 95% was applied to check the difference between the analytical results of PAHs obtained by the AIQS–DB and conventional methods Log-transformed concentrations of selected pollutants were subjected to Pearson's correlation analysis and principal component analysis (PCA)

to evaluate possible relationships

3 Results and discussion

3.1 Comparison of PAH concentrations obtained using the AIQS–DB/ GC–MS method and the conventional GC–MS/SIM method

To validate the accuracy of this screening method, we analyzed some PAHs in the same air samples using the GC–MS/SIM method with isotope dilution quantification The comparison of analytical results of PAHs in the air samples obtained by the two methods is presented in Table S4 Concentrations of the predominant PAH congeners such as fluorene, phenanthrene, fluoranthene, pyrene, and benzo[c]phenan-threne derived by using the screening method were in good agreement

with those found by the conventional method The p values from paired t-test obtained for these compounds were greater than 0.05, indicating

that the two methods do not differ significantly at a confidence level of 95%, particularly for PAH analysis In addition, ratios of the PAH concentrations generated by AIQS–DB method and SIM method ranged from 0.95 ± 0.10 (for fluoranthene) to 1.07 ± 0.13 (for fluorene), partially confirming the accuracy of this novel screening tool as com-pared with the conventional method Although confirmation using in-ternal standard method showed the negatively systematic errors for few pesticides,Kadokami et al (2009) documented that almost common semivolatile chemicals, excluding highly polar (e.g., penta-chlorophenol) and less stable compounds (e.g., benzidine), can be quantified accurately by the AIQS–DB method

356

In terms of detection limits, the MDLs obtained by screening method

(scan mode) were usually higher than those of the conventional method

(SIM mode) In this study, the MDLs of PAHs from scan mode were

about 0.10 ng m–3, which were one to two orders of magnitude higher

than the values derived by SIM mode (from 0.0010 to 0.010 ng m–3)

Therefore, some PAHs at trace levels were not detected in most samples

in this study by using the AIQS–DB method, including compounds with

high mutagenic and carcinogenic potency such as benzo[a]-, dibenzo

[a,h]-, dibenzo[a,i]-, and dibenzo[a,l]pyrene A similar situation was

expected for other pollutants such as PCBs and PBDEs, which were

previously found in Vietnamese ambient air in minor concentrations at

pg m–3levels (Tue et al., 2013; Wang et al., 2016a) This finding

sug-gests the need for further target analysis to determine highly toxic and

trace-level contaminants, such as dioxins and related compounds

However, it should be re-emphasized that this screening method can

provide a comprehensive insight into the total concentrations of major

organic pollutants from different emission sources

3.2 Overview of contamination status

A total of 167 organic pollutants, comprising 73 domestic

chemi-cals, 68 industrial chemicals and 26 pesticides, were detected at least

once in the air samples of this study Air concentrations of total organic

pollutants classified by their origins and uses, and the number of

de-tected compounds in each sampling site are presented inTable 1and

Fig 1 Air concentrations of individual pollutants are tabulated inTable

S5 As the sampling rates of PUF–PAS method have not been

char-acterized for all the detected compounds in this study, absolute mass

concentrations of organic pollutants (μg per sampler) are provided in

Table S6 However, in the main text, we use derived air concentrations

(ng m–3) to facilitate comparison with other studies

The overall concentrations of organic pollutants ranged from 870 to

2600 ng m–3 (median 1300 ng m–3) The highest contamination level

was detected in the indoor air of an urban house in Hanoi (UH-2), and

the urban indoor air samples showed a higher abundance of organic

pollutants than those collected from the waste processing sites

(p < 0.05) Domestic chemicals such as n-alkanes, phthalate ester

plasticizers, and synthetic phenolic antioxidants (SPAs) dominated the

organic pollutant patterns in all the samples, especially in the urban

indoor air (about 90%) Significant proportions of domestic chemicals

were also recorded in sediments from the sewer systems of Hanoi and

Ho Chi Minh City (Hanh et al., 2014), implying the negative

environ-mental impacts of household and business activities, especially in the

metropolitan areas Total pesticide concentrations were the highest in

samples from Bac Giang, while there was no significant difference in the

concentration of industrial pollutants between study locations

A comparison between concentrations of selected classes of organic

pollutants, including PAHs and substituted PAHs, pyrethroid

in-secticides, pharmaceutical and personal care products (PPCPs), and

phthalate and adipate ester plasticizers, in the air of our sampling sites

is presented in Fig 2 PAHs and their derivatives were observed at

higher levels at the waste processing sites than in the urban area

Al-though the contamination status of PAHs has been investigated in the

environment such as in outdoor air and road dust from some

Vietna-mese urban areas (Hien et al., 2007a,b,c; Tuyen et al., 2014a,b; Kishida

et al., 2008, 2009), information about the occurrence of these

carci-nogenic pollutants in Vietnamese working environments is limited

These preliminary data on the concentrations of PAHs and related

compounds in the air of the ELV workshops in northern Vietnam

par-tially confirmed the role of inappropriate waste processing activities as

a potential source of PAHs Concentrations of some pesticides such as

permethrins, chlorpyrifos, and propiconazole were more elevated in

samples collected from the Bac Giang ELV sites than the remaining

sites It should be noted that Thuyen village is a rural area with

in-tensive agricultural activities such as rice and crop cultivation, resulting

in widespread use of agrochemicals in this area as compared to the

remaining areas of this study Concentrations of some domestic che-micals, typically phthalate ester plasticizers and pharmaceutical and personal care products (PPCPs), showed an opposite trend with a clear urban-rural gradient Results obtained from PCA analysis suggest that the contamination of the urban air was significantly related to domestic chemicals and dyed products, whereas the air in the waste recycling areas was affected more strongly by industrial chemicals and pesticides (Fig S1) A more detailed evaluation of the contamination degree, distribution pattern, and potential sources of organic pollutants in the investigated areas will be described in the next sections

3.3 Levels and profiles of domestic chemicals

A total of 73 domestic chemicals, including 20 n-alkanes, 11

plas-ticizers (i.e., phthalate and adipate esters), 10 fatty acid methyl esters (FAMEs), 12 PPCPs, 6 synthetic antioxidants, and 14 miscellaneous compounds (e.g., disinfectants, fragrances, detergent metabolites), were detected in the air samples of this study (Table 1and S5) Con-centrations of domestic chemicals ranged from 560 to 2300 ng m–3

(median 920 ng m–3) This chemical group was the most dominant ca-tegory, accounting for 62–91% (average 75%) of total organic pollu-tants The highest domestic chemical concentration was measured in an urban house in Hanoi (UH-2), whereas the lowest level was found in the rural house in Bac Giang (RH-1) A significant difference was observed

in concentrations of domestic chemicals between the Hanoi urban area

and the ELV dismantling area (p < 0.05) The most dominant con-tributors to total levels of domestic groups were plasticizers, n-alkanes,

and SPAs The abundance of domestic chemicals in the air samples of this study suggests that household and business activities with in-creased use of new consumer products have been important sources of organic pollutants, especially in metropolitan areas

3.3.1 n-Alkanes

A total of 20 n-alkanes (C10to C32, excluding C11, C12, and C13) were detected in the air samples at a range of 17–410 ng m–3 (median

150 ng m–3) (Table 1andFig S2) The highest n-alkane concentrations

were found in the sample collected from an ELV workshop (ELV-2;

410 ng m–3) with relatively large amounts of waste engine oil released (about 50–60 L per month), followed by the sample taken near a waste rubber melting furnace (WR-3, 280 ng m–3) Levels of n-alkanes in

urban indoor air (130–250 ng m–3) were comparable to those measured

in the waste processing areas Our results were in line with levels de-tected in ambient air from urban areas of Beijing (163.0 ± 193.5 ng m–3in PM2.5;Huang et al., 2006) and Guangzhou (141–392 ng m–3in PM10; Bi et al., 2002), China; and Delhi, India (187.4 ± 4.3 ng m–3in PM10;Gupta et al., 2017) Levels of n-alkanes in

this study were much higher than those observed in Hong Kong, China (average 23.5 ng m–3 in PM2.5; Zheng et al., 2000); an urban site of Venice, Italy (15.12–38.88 ng m–3in PM1; Valotto et al., 2017); and some remote areas such as Lulang, Tibetan Plateau (0.10–21.83 ng m–3

in total suspended particulates;Chen et al., 2014) and a forest in Fin-land (7–95 ng m–3 in aerosol particles; Rissanen et al., 2006) The

emission sources of n-alkanes can be estimated by their congener

pro-files and several diagnostic parameters, for instance, carbon number of the most abundant alkanes (Cmax), carbon preference index (CPI), ratio

of low-molecular-weight to high-molecular-weight alkanes (LHR), and

contribution of plant wax n-alkanes (WNA%) (see details inFig S2and Table S7) Samples from the ELV workshops showed the major

petro-genic sources of n-alkanes with low Cmaxvalues (C17–20), most CPI and LHR values close to unity, and low WNA% (7–17%) (Guo and Fang, 2012; Gupta et al., 2017; Ladji et al., 2014; Xu et al., 2013) In contrast, samples from the rural house in Bac Giang (RH-1), two urban houses in Hanoi (UH-1 and UH-2), and a plastic recycling facility in Thai Nguyen (WR-1) presented higher values of WNA% (25–70%), suggesting the

possible emissions of n-alkanes from biogenic sources (Chen et al., 2014; Yuan et al., 2016) and/or human activities such as biomass

Table 1

Concentrations of organic micro-pollutants (ng m–3) in the atmosphere in waste processing and urban areas, northern Vietnam Numbers in parentheses indicate numbers of detected compounds

Nguyen)

Urban area (Hanoi)

n-Alkanes (20) 110 (18) 410 (19) 110 (16) 67 (15) 210 (19) 170 (16) 160 (17) 190 (16) 110 (17) 58 (16) 17 (7) 130 (17) 280 (15) 250 (15) 130 (15) 220 (18)

PPCPs and related compounds

(12)

Intermediates for organic

synthesis (21)

(101)

1300 (97) 1400 (96) 1300 (93) 1100 (96) 900 (92) 900 (78) 870 (96) 1300 (106) 2300 (80) 2600 (89) 2300 (84)

n.d – not detected

burning (Chen et al., 2017; Valotto et al., 2017).

3.3.2 Plasticizers

Phthalate and adipate esters were detected in a wide concentration

range of 51–1200 ng m–3(median 130 ng m–3) Levels of total phthalate

and adipate esters were the highest in Hanoi (median 1000 ng m–3;

range 870–1200 ng m–3), followed by the waste recycling facilities in

Thai Nguyen (350; 140–460 ng m–3) and the ELV dismantling area (93;

48–330 ng m–3) (Table 1 and Fig S3) The highest concentration of

plasticizers in waste processing areas was found in a sample collected

from the plastic recycling facility in Thai Nguyen (WR-1; 460 ng m–3)

Phthalate ester concentrations in Hanoi indoor air in this study were

within the range previously reported byTri et al (2017a)for urban

homes in the same area (low-volume air sampling, 210–2400 ng m–3)

Our values were lower than those measured in indoor air from hair

salons in Hanoi (mean 3590; range 569–16,000 ng m–3; Tri et al.,

2017a), and offices in Hangzhou, China (3070–6700 ng m–3;Song et al.,

2015), and hospitals in China (16,300–24,190 ng m–3; Wang et al.,

2015) Samples from Hanoi and some waste processing sites (e.g.,

ELV-5, WR-1, and WR-2) were dominated by DEHP and dicyclohexyl

phthalate (DCHP) with a significant contribution of di-n-butyl phthalate

(DNBP) and diisobutyl phthalate (DIBP), whereas the remaining sites were mainly polluted by DNBP and DIBP (Fig S3) Results from PCA analysis presented inFig S4 have revealed the association between phthalate esters and their potential sources The correlation between DEHP and DCHP suggests their sources as articles made of vinyl chloride resins, where they are widely used as plasticizers (Otake et al.,

2004) DNBP and DIBP were strongly related, indicating a similar en-vironmental behavior and fate, and the same applications as plasticizers and additives in cosmetics and personal care products (He et al., 2018; Zhang et al., 2018)

3.3.3 Antioxidants SPAs such as 2-tert-butyl-4-hydroxyanisole (BHA) and 2,6-di-tert-butyl-4-hydroxytoluene (BHT) and its metabolites, including 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) and

2,4-di-tert-butyl-1,4-benzoquinone (BHT-Q), were detected in air samples at elevated con-centrations (median 410; range 89–610 ng m–3,Fig S5) BHT and BHA are commonly used as antioxidants in petroleum products, polymeric materials, cosmetics and personal care products, and foodstuffs ( Nieva-Echevarría et al., 2015; Liu et al., 2017; Wang and Kannan, 2018) Although several previous studies have indicated the association Fig 1 Total concentrations (ng m–3) of organic micro-pollutants in the atmosphere in waste processing and urban areas, northern Vietnam

Fig 2 Concentrations of selected groups of organic micro-pollutants (ng m–3) in the atmosphere in waste processing and urban areas, northern Vietnam

between SPAs and their transformation products and adverse effects on

animals (Al-Akid et al., 2001; Nagai et al., 1993; Oikawa et al., 1998;

Rao et al., 2000), information about the contamination status of these

compounds in indoor environment is very scarce (Liu et al., 2017; Wang

et al., 2016b) To our knowledge, the data in this study are among the

first about SPAs in the air of Vietnam The difference between total SPA

concentrations in the atmosphere in urban and waste processing areas

was not significant, suggesting their ubiquitous occurrence in Vietnam's

environment However, their distribution patterns were quite different

between study areas (Fig S5) Most samples from the waste processing

areas (except for ELV-5) were dominated by BHT (46–80% of total

SPAs), whereas the urban samples showed a prevalence of BHT-CHO

and BHT-Q (79–95%) Concentrations of BHT-CHO and BHT-Q were

strongly correlated (Pearson's r = 0.925, p < 0.001, for all samples),

but a significant association between BHT and BHT-CHO (r = 0.618,

p < 0.05) was observed only for samples from the ELV dismantling

area The patterns of BHT and its metabolites varied among locations,

probably due to the different sources of SPAs and effects of human

activities This finding suggests the need for more extensive

investiga-tions on these common air pollutants

3.3.4 Other domestic chemicals

Thymol, acetophenone, and squalane were among the most

fre-quently detected PPCPs in our air samples, suggesting their popular use

in cosmetics and personal care products Concentrations of

acet-ophenone measured in this study (median 3.8; range n.d – 9.9 ng m–3)

were significantly lower than those found in indoor air in Leipzig,

Germany (190; 6.6–5570 ng m–3, using single charcoal sorbent wafer

passive samplers; Rösch et al., 2014) Aspirin and ibuprofen, two

common triggers of asthma, were only detected in the urban samples at

relatively high abundance as compared with other PPCPs (maximum

240 and 57 ng m–3, respectively) Triclosan, a widely used antibacterial

and antifungal agent, was found in all the Hanoi samples at

con-centrations of 2.3–6.3 ng m–3 Caffeine was detected in some ELV

workshops at a maximum concentration of 9.0 ng m–3 FAMEs were

observed in all the samples with no clear trend in the contamination

degree and profile Concentrations of 2-ethyl-1-hexanol in the Hanoi

urban houses (50–71 ng m–3) were higher than those measured in the

waste processing sites (11–30 ng m–3), but they were several orders of

magnitude lower than levels recorded in German dwellings

(0.3055–153.59 μg m–3; Rösch et al., 2014) Recent studies have

in-dicated the abundance of some other emerging organic pollutants in

indoor environment from Vietnam, for example, p-hydroxybenzoic acid

esters (parabens), bisphenol A diglycidyl ether (BADGE), and cyclic and

linear siloxanes (Tri et al., 2015, 2016, 2017a,b) However, these

groups have not been registered in the AIQS–DB system According to

Kadokami et al (2005), it is possible to add new compounds to the

database, suggesting that expanding the database size should be

con-sidered in near future

3.4 Levels and profiles of industrial chemicals

In the air samples of this study, we detected 68 industrial chemicals,

comprising 25 PAHs and their derivatives, 10 intermediates for dyes, 21

intermediates for organic synthesis, and 12 compounds of other

appli-cations such as solvents, dielectric fluids, and heat storage and transfer

agents Concentrations of total industrial chemicals ranged from 62 to

190 ng m–3(median 130 ng m–3) and accounted for an average of 10%

of total organic pollutants The highest industrial chemical

concentra-tion was found in a sample collected from an ELV workshop (ELV-2)

There was no significant difference in the air concentrations of

in-dustrial chemicals between the study areas

3.4.1 PAHs

Concentrations of total PAHs ranged from 7.3 to 69 ng m–3(median

43 ng m–3) and dominated by 3- and 4-ring compounds such as

phenanthrene, fluoranthene, fluorene and pyrene (Table S5andFig S6) The highest PAH concentration was detected in the air around the rubber melting kiln in Thai Nguyen (WR-3) Levels of atmospheric PAHs at the Bac Giang ELV sites were significantly higher than those

measured in the Hanoi urban area (p < 0.05) A worldwide

compar-ison of air concentrations of PAHs generated by using PUF–PAS method, is presented inTable S8 The air concentrations of PAHs found

in this study were in good agreement with previous studies conducted

in some other locations in China (Wang et al., 2010); Korea (Choi et al.,

2012); Chile (Pozo et al., 2012); and Mexico, Sweden, and UK (Bohlin

et al., 2008) Higher levels of PAHs were reported in the ambient air from Istanbul, Turkey (mean 85.6; range 11.7–302 ng m–3;Cetin et al.,

2017), and a petrochemical industrialized area in Lanzhou, China (mean 302; range 125–680 ng m–3; Wang et al., 2017) Information about the contamination of PAHs in Vietnamese indoor environments is limited.Kishida et al (2008)measured PAHs in both particulate matter and gas phase at some outdoor sites in Hanoi and reported relatively high concentrations of PAHs in the bulk air (average 280 ng m–3for intersection and roadside sites, and 1000 ng m–3for a site located near a terminal for buses and trucks) This observation suggests traffic emis-sion as an important source of PAHs in big cities The ratios of fluor-anthene/(fluoranthene + pyrene) in our samples ranged from 0.46 to 0.60, reflecting PAH emission sources from the combustion processes of petroleum, coal, and biomass (Yunker et al., 2002) Results of PCA analysis tabulated inFig S7indicate contributions of coal combustion and industrial/vehicle emission to the releases of PAHs in our study areas (Mao et al., 2016; Wang et al., 2017)

3.4.2 Substituted PAHs

There were 12 alkyl and phenyl substituted PAHs found in the air samples with total concentrations from 7.0 to 72 ng m–3 (median

19 ng m–3) (Table S5) Similar to the parent PAHs, concentrations of substituted PAHs were higher in the waste processing areas than urban sites A moderate correlation between total concentrations of parent

and substituted PAHs was observed (r = 0.587, p < 0.05), indicating

similar emission sources of these two groups (Chen et al., 2017; Tuyen

et al., 2014b) The most frequently detected compounds were 1-me-thylphenanthrene and 2-methyl-, 1-phenyl-, and 2-phenylnaphthalene

In almost all the samples, the ratios of total methylated naphthalenes to naphthalene were larger than one, which are commonly observed in other environmental media such as soil (Chen et al., 2017) and sedi-ment (Vondrácek et al., 2007) Ratios of methylated phenanthrenes/ phenanthrene and total methylated PAHs/parent PAHs in most samples were lower than one, confirming the pyrogenic sources of PAHs and their derivatives in these areas (Chen et al., 2017; Tuyen et al., 2014b; Vondrácek et al., 2007) However, atmospheric levels of substituted PAHs exceeded parent PAHs in some waste processing facilities, im-plying petrogenic sources of PAHs (Saha et al., 2009) Further studies should be performed to get more in-depth insights into the emission behaviors and environmental fate of PAHs and related compounds in other areas in Vietnam, for instance, industrial parks, informal waste recycling areas, and waste dumping and open burning sites

3.4.3 Other industrial chemicals

The contribution of intermediates in dyes, intermediates for organic synthesis and other industrial chemicals to total organic air pollutants ranged from 2.3% to 7.5% (average 4.8%) Concentrations of these chemicals did not show a clear trend between study areas

Benzothiazole, biphenyl, dibenzofuran, 4-tert-butylphenol, o- and

m-cresol, carbazole, and　anthraquinone were the most frequently de-tected compounds Benzothiazole has been used as a vulcanization ac-celerator in rubber production and as an additive in a variety of con-sumer products This compound has been widely detected in different environmental and biological matrices, including human bodies, be-coming an emerging contaminant of considerable interest (Wan et al.,

2016) Benzothiazole was detected in all the samples in this study in a

360

narrow range of concentrations (median 9.3; range 3.6–12 ng m–3) The

bulk air concentrations (particulate and vapor phases) of benzothiazole

in indoor air samples collected from various micro-environments in

Albany, New York, US, varied over a wide range (median 20.7;

2.94–1703 ng m–3;Wan et al., 2016) and were much higher than those

measured in our samples Some other pollutants such as

1,2,4-tri-chlorobenzene (used as dielectric fluids), heat transfer agents (e.g.,

o-and p-terphenyl), o-and industrial sovents (e.g., isophorone o-and

trans-decalin) were found only in the air from the waste processing sites

Using this screening method, we did not detect some typical industrial

contaminants such as PCBs and PBDEs, although they have been

ob-served in the atmosphere from some areas in Vietnam (Tue et al., 2013;

Wang et al., 2016a) This finding suggests the need for trace-level target

analysis of these highly toxic substances in atmospheric environments

in northern Vietnam

3.5 Levels and profiles of pesticides

There were 26 pesticides, including 13 insecticides, 7 fungicides,

and 6 herbicides, detected in the air samples in this study

Concentrations of total pesticides ranged from 43 to 370 ng m–3

(median 190 ng m–3) and decreased in the following order: Bac Giang

ELV dismantling area > Hanoi urban area > Thai Nguyen waste

re-cycling facilities (Table 1andFig S8) The average contributions of

pesticides to total organic pollutants in samples from Bac Giang, Thai

Nguyen and Hanoi were 20%, 7.4% and 3.4%, respectively The greater

abundance of pesticides in the air around the ELV sites may result from

their widespread use for both agricultural and domestic purposes in this

rural area

3.5.1 Pyrethroid insecticides

Pyrethroids with the major class of permethrins were found as the

most dominant pesticides, accounting for 48–93% of total pesticide

concentrations (except for one facility in Thai Nguyen, WR-2)

Pyrethroids have been widely applied not only outdoors in agriculture

to control insects but also indoors for public health protection

Permethrins dominated the total pesticides in river sediments from

Hanoi and Ho Chi Minh City (Hanh et al., 2014) Levels of pyrethroids

in Vietnamese sediments were generally higher than those from US, UK,

Australia and China (Li et al., 2017) Moreover, it has been suggested

that pyrethroid residues are higher indoors and their degradation rates

are much slower in indoor than outdoor environments (Tang et al.,

2018) Concentrations of total pyrethroids in the indoor air in this study

(median 120 ng m–3; maximum 230 ng m–3) were significantly higher

than levels reported in homes of the Bangkok metropolitan region,

Thailand (total pyrethroids 0.01–2.16 ng m–3;Pentamwa et al., 2011)

and dwellings in Brittany, western France (permethrin

concentra-tions < 0.6 ng m–3 and < 0.002 ng m–3 for gas phase and airborne

particles, respectively;Blanchard et al., 2014) Nevertheless, pyrethroid

concentrations in our study were several orders of magnitude lower

than those measured in some areas in China (0.01–2.69 mg m–3; as

re-viewed byTang et al., 2018)

3.5.2 Other pesticides

Propiconazole, chlorpyrifos, thiocyclam, and difenzoquat

me-tilsulfate were the important contributors to total pesticides and found

at the ELV sites at high detection frequencies Propiconazole (an azole

fungicide) and chlorpyrifos (an organophosphorus insecticide) are

re-gistered for agricultural use in Vietnam, and they have been commonly

detected in the aquatic environment in agricultural areas in the country

(Chau et al., 2015; Hanh et al., 2014; Thuy et al., 2012) However,

information about levels of these pesticides in the Vietnamese air is

scarce Concentrations of chlorpyrifos in the ambient air from the Bac

Giang ELV sites ranged from < 1.0–38 ng m–3(median 19 ng m–3) and

were within the range detected in Korean childcare facilities (median

27; range < 1–58 ng m–3;Kim et al., 2013) and Japanese houses with

termiticide application (1–350 ng m–3;Dai et al., 2003) This insecticide was found at relatively low concentrations in the indoor air of French dwellings (< 0.6–1.2 ng m–3 and < 0.002–0.007 ng m–3 for gas and particulate phase, respectively;Blanchard et al., 2014) Fenobucarb, a carbamate insecticide, was detected in all the samples from the ELV sites (median 2.2; range 1.4–3.3 ng m–3) Concentrations of chlorpyrifos and fenobucarb in our samples were still lower than guideline values of

1 and 33 μg m–3, respectively, established for indoor air by the Ministry

of Health, Labour and Welfare of Japan (MHLW, 2002).Wang et al (2016a)reported the occurrence of several organochlorine pesticides (e.g., DDTs, hexachlorocyclohexanes, hexachlorobenzene, endosulfans, chlordanes, and mirex) in the atmosphere of Vietnam with the max-imum concentration for an individual compound of about 2 ng m–3 These legacy POP pesticides were not detected in the samples of our study, probably due to their decreased usage in Vietnam and the high detection limits of these compounds by the screening method

3.6 Human exposure to organic air pollutants

Daily intake doses via inhalation (DIair) of total organic air pollu-tants and selected contaminants estimated for waste processing workers

in Bac Giang and Thai Nguyen, and residents in the Hanoi urban area, are summarized inTable S9 Residents in Hanoi were estimated to re-ceive the highest doses of total organic pollutants, mainly contributed

by chemicals released from household and business activities Phthalate esters (e.g., DNBP and DEHP) were among the most dominant con-tributors to the total uptake of organic pollutants by urban inhabitants Our DIairvalues derived for phthalate esters were consistent with those reported in a survey conducted in four northern cities in Vietnam (Tri

et al., 2017a) but were generally higher than the doses estimated for residents in the urban center of Paris, France (8.95 and 3.13 ng kg–1d–1

for DNBP and DEHP, respectively;Martine et al., 2013) It has been documented that the main routes of exposure to phthalate esters, par-ticularly high-molecular-weight compounds like DEHP, are dust in-gestion (Pelletier et al., 2017) and dietary (Martine et al., 2013), sug-gesting the need for multiple risk assessments The daily intake of PAHs such as fluoranthene and pyrene via inhalation estimated for waste processing workers was higher than those derived for urban residents in Hanoi, as well as residents in the suburbs of Tokyo, Japan (Suzuki and Yoshinaga, 2007) However, the daily intake doses received by Hanoi children were significantly lower than the levels reported for newborns and infants from Karvina city, the most air-polluted part of the Czech Republic affected by black coal mining and coke and steel production activities (Pulkrabova et al., 2016) Residents in Hanoi were exposed to higher inhalation doses of benzothiazole (median 6.1 and 1.4 ng kg–1

d–1for children and adults, respectively), compared with the doses received by waste processing workers The DIairvalues of benzothiazole

in our study were generally lower than those estimated for inhabitants

in Albany, New York, US (median 9.19 and 3.99 ng kg–1d–1for children and adults, respectively;Wan et al., 2016) A median DIairof chlor-pyrifos of 1.7 ng kg–1d–1was derived for the ELV dismantling workers

in Bac Giang, which was about two orders of magnitude greater than the value calculated for French population (2.11 × 10–2 ng kg–1d–1; Pelletier et al., 2017) Almost all the DIairvalues presented in this study were markedly lower than respective reference doses, indicating in-significant health risk associated with the inhalation of these organic pollutants Nevertheless, the more extensive assessments, considering multiple exposure pathways and trace-level but highly toxic pollutants (e.g., dioxins and related compounds, PCBs, and BFRs), should be conducted in Vietnam, especially in areas under rapid industrialization and urbanization

4 Conclusions This study is the first to report data on the levels, accumulation profiles, potential emission sources, and exposure risk related to

multiple classes of organic micro-pollutants in the air from waste

pro-cessing and urban areas in northern Vietnam A large number of 167

organic pollutants belonging to three categories such as domestic

che-micals, industrial cheche-micals, and pesticides, were detected, with their

sources revealed to be from business/household, agricultural, and

waste processing activities Total concentrations of organic air

pollu-tants were the highest in samples from the Hanoi urban area and

dominantly contributed by domestic chemicals, suggesting a possible

relationship between rapid urbanization and environmental

degrada-tion Meanwhile, the atmosphere of a rural area affected by ELV

dis-mantling activities in Bac Giang was more polluted by pesticides and

some specific industrial compounds (e.g., PAHs, dielectric fluids, and

heat transfer agents) Samples from the waste recycling cooperative in

Thai Nguyen did not show any special pattern of total concentrations,

but they revealed some interesting characteristics of the atmospheric

emission of organic pollutants from nearby sources Inhalation daily

intake doses of total organic pollutants and some representative

com-pounds were also estimated for waste recycling workers and urban

re-sidents in our study areas, implying a negligible health risk Our results

provide a comprehensive picture of the occurrence, potential sources,

and risk of organic air pollutants in some areas in northern Vietnam

Further studies using the rapid, effective, and low-cost AIQS–DB/

GC–MS method are strongly recommended for screening analysis of

multiple organic contaminants in different environmental, biological,

and human matrices from Vietnam and other developing countries

Acknowledgements

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

Research (B: 16H02963) from the Japan Society for the Promotion of

Science (JSPS) and the Environment Research and Technology

Development Fund (3K153001) from the Japanese Ministry of the

Environment We thank the staff of CETASD (VNU University of

Science) and CATE (Ehime University) for sampling activities and

sample analysis We thank Adj Prof Dennis Murphy (The United

Graduate School of Agricultural Sciences, Ehime University) for critical

reading of the manuscript

Appendix A Supporting information

Supplementary data associated with this article can be found in the

online version atdoi:10.1016/j.ecoenv.2018.10.026

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