Chlorinated Diphenyl Ethers and

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Characterization of Natural and Affected Environments

Complex Mixtures of Brominated/Chlorinated Diphenyl Ethers and Dibenzofurans in Soils from the Agbogbloshie E-waste Site (Ghana): Occurrence, Formation and Exposure Implications Nguyen Minh Tue, Takafumi Matsushita, Akitoshi Goto, Takaaki Itai, Kwadwo Ansong Asante, Samuel Obiri, Saada Mohammed, Shinsuke Tanabe, and Tatsuya Kunisue Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b06929 • Publication Date (Web): 22 Feb 2019 Downloaded from http://pubs.acs.org on February 23, 2019

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Environmental Science & Technology

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Complex Mixtures of Brominated/Chlorinated

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Diphenyl Ethers and Dibenzofurans in Soils from

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the Agbogbloshie E-waste Site (Ghana): Occurrence,

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Formation and Exposure Implications

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Nguyen Minh Tue,† Takafumi Matsushita,† Akitoshi Goto,† Takaaki Itai,† Kwadwo

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Ansong Asante,†,‡ Samuel Obiri,‡ Saada Mohammed,‡ Shinsuke Tanabe,† Tatsuya

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Kunisue*,†

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†Center for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho,

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Matsuyama 790-8577, Japan

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‡CSIR Water Research Institute, P.O. Box AH 38, Achimota, Accra, Ghana

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ACS Paragon Plus Environment

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ABSTRACT: The distribution and toxic equivalents (TEQs) of brominated, chlorinated

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dibenzo-p-dioxins/dibenzofurans (PBDD/Fs and PCDD/Fs) in soils from Agbogbloshie

14

e-waste site (Ghana) were investigated. The composition of brominated/chlorinated

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dibenzofurans (PXDFs) and diphenyl ethers (PBDEs, PCDEs and PXDEs) were

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examined using two-dimensional gas chromatography–time-of-flight mass spectrometry

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to elucidate possible formation pathways of dioxins from e-waste recycling. The highest

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concentrations of PCDD/Fs and PBDD/Fs were found respectively in the open burning

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(1.3–380 ng/g dry weight) and dismantling areas (11–1000 ng/g dry weight), and were

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comparable to the highest reported for informal e-waste sites. PXDFs and PXDEs were

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detected at up to the range of hundreds of nanogram per gram. The homologue profiles

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suggest that PXDFs were formed mainly from PBDFs through successive Br-to-Cl

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exchange. However, monobromo-PCDFs were also derived from de novo-generated

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PCDFs in open burning areas. PBDFs contributed similar or higher TEQs (7.9–

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5400 pg/g dry weight) compared with PCDD/Fs (6.8–5200 pg/g dry weight), whereas

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PXDFs were also substantial TEQ contributors in open burning areas. The high TEQs of

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PBDFs in the dismantling area (120–5200 pg/g dry weight) indicate the need to consider


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brominated dioxins besides chlorinated dioxins in future studies on health implications

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for e-waste workers and local residents.

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KEYWORDS: dioxins, e-waste, Ghana, PBDD/Fs, PXDD/Fs, PXDEs

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INTRODUCTION Waste electrical and electronic equipment (e-waste) has become increasingly difficult

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to manage because of the steady growth, with an estimated annual global volume of

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44.7 million metric tons in 2016.1 E-waste contains not only valuable metals for

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reclamation but also a large number of toxic substances such as heavy metals,

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brominated flame retardants (BFRs) and various plastic additives.2 A large volume of

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these hazardous waste materials have been treated informally in developing countries,

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especially in Asia3,4 and more recently in Africa4,5 using crude thermal processes such

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as circuit board heating and open burning of wires. These processes result in serious

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environmental pollution caused by not only the emission of contaminants contained in e-

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waste2 but also the unintentional formation of complex mixtures of thermally produced

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toxic chemicals including chlorinated and/or brominated dioxin-like compounds (DLCs),

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polycyclic hydrocarbons and related compounds.6–9 There is an increasing number of

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reports on multiple adverse health effects in populations involved with informal e-waste

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recycling.10


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Although DLCs are known for their potency to cause many toxic effects,11,12 it is still

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difficult to assess the environmental and health impacts of all DLCs from e-waste due to

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their compositional complexity. Informal e-waste recycling sites (EWRSs) have been

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widely known to be contamination hotspots of polychlorinated dibenzo-p-dioxins and

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dibenzofurans (PCDD/Fs), with polyvinyl chloride (PVC)-coated wire burning as the

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major emission source.6,13 The number of studies on brominated dibenzo-p-dioxins and

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dibenzofurans (PBDD/Fs) in EWRSs is more limited, however, higher environmental

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contamination levels of PBDFs compared with PCDD/Fs have been reported.6 The

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abundance of PBDFs can be explained by their occurrence at up to hundreds of

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microgram per gram in e-waste such as circuit boards and TV cases,14,15 and by their

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possible formation through thermolytic/photolytic degradation of brominated flame

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retardants in e-waste plastics, especially polybrominated diphenyl ethers (PBDEs)14,16–

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18.

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additives can also generate mixed brominated/chlorinated dibenzo-p-

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dioxins/dibenzofurans (PXDD/Fs)16,19. However, because of the difficulties in analyzing

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PXDD/Fs with 4700 possible congeners, only a few studies have attempted to analyze

Combustion of e-waste containing both chlorinated polymers and brominated


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these mixed halogenated DLCs in a limited number of environmental samples from

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EWRSs.20,21 These studies found higher abundance of PXDFs as compared with

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PXDDs but reported different PXDF homologue profiles, suggesting that the

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composition of PXDFs varies with the waste materials and thermal conditions. In the

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light of possible inclusion of PBDD/Fs and PXDD/Fs in the World Health Organization

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Toxicity Equivalency Factor (WHO-TEF) concept,23 their formation, environmental fate

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and potential human exposure risk in informal EWRSs need to be investigated.

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Another related group of mixed halogenated compounds that can be formed during

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informal e-waste recycling is the mixed brominated/chlorinated analogues of PBDEs

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(PXDEs). Despite possible formation of PXDEs during combustion processes,24,25

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information on their occurrence in EWRSs is still severely lacking. In our knowledge,

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there is only one study22 investigating a very small subset of PXDE homologues (nona-

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brominated mono-chlorinated). Compounds tentatively identified as PXDEs were also

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detected in a soil sample from an e-waste burning area in our previous study on PXDF

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profiling using two-dimensional gas chromatography–time-of-flight mass spectrometry

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(GC×GC–ToFMS),21 but could not be quantified reliably due to extensive debromination


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on the second GC column. Considering the structural similarity with PBDEs which are

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major toxic contaminants in e-waste,2 PXDEs need to be investigated in order to assess

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their contribution to the environmental and human impacts of PBDEs. The possible role

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of PXDEs as precursors in the formation of PXDFs also needs to be explored to better

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estimate the emission of PXDFs in EWRSs.

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The Agbogbloshie scrap yard is the major hub of informal waste recycling in

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Ghana.26,27 At the time of our first survey in 2010,21 the site was primarily a burning

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ground for the recovery of copper from e-waste. Surface soils were sampled at ten

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spots, and PCDD/Fs and PBDD/Fs were detected at very high concentrations in the

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open burning areas.21 PXDFs were analyzed for one open burning soil sample using

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GC×GC–ToFMS and were found to contribute approximately 16% to the total dioxin-like

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toxic equivalents (TEQs). During our second survey in 2013, we observed at

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Agbogbloshie the stockpiling of not only e-waste but also end-of-life vehicle (ELV)-

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related waste and common solid waste, the presence of rudimentary dismantling

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workshops, and an increase in the number of open e-waste burning spots as well as the

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number of workers handling waste materials (Figure S1). The present study


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investigated a larger set of surface soil samples collected during the second survey to

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elucidate the contamination status of PCDD/Fs, PBDD/Fs and PBDEs as well as the

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composition of PXDFs and PXDEs in different areas, in order to obtain a more

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comprehensive view on the formation, toxic contribution and human exposure

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implications of various DLCs generated during informal e-waste recycling/disposal.

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MATERIALS AND METHODS Sample collection. In August 2013, surface soil samples (0–2 cm depth) were

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collected at the Agbogbloshie e-waste site using a stainless steel auger. Each sample

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consisted of five sub-samples covering a square area of approximately 1 m2. The

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samples were kept in a freezer in the Environmental Chemistry Laboratory of the Water

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Research Institute of the Council for Scientific and Industrial Research in Accra, then

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transported to Japan under frozen condition and stored at –25 °C until analysis. The soil

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samples were imported to Japan under permission (no. 25-300) from Ministry of

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Agriculture, Forestry and Fisheries, Japan based on Plant Protection Act. Forty one

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samples were selected for analysis in this study: 14 samples from open e-waste burning


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areas (areas #1 to #4), 14 from the e-waste/ELV dismantling area (consisting of sub-

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areas #6 and #7), and 13 from other areas (Figure S2).

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Sample pretreatment and extraction. Soil samples were oven-dried at 35 °C in

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separate batches according to the sampling area, and then each sample was

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homogenized and sieved through a 250-µm mesh. Extraction was carried out based on

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a previous method.28 Briefly, approximately 5 g of each sample was extracted using a

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high speed solvent extractor (SE-100, Mitsubishi Chemical Analytech) with a

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hexane/acetone mixture (1:1 v/v, 35 °C, 4 ml/min, 60 min) and then with toluene (80 °C,

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4 ml/min, 30 min). The two fractions were solvent-exchanged into hexane and

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combined.

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Quantitative analysis of PCDD/Fs, PBDD/Fs and PBDEs. A portion of the extract (up

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to 1-g equivalent) was spiked with 13C12-PCDD/Fs (2,3,7,8-, 1,2,3,7,8-, 1,2,3,4,7,8-,

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1,2,3,6,7,8-, 1,2,3,7,8,9-, 1,2,3,4,6,7,8-, octa-CDDs and 2,3,7,8-, 1,2,3,7,8-, 1,2,3,6,7,8-,

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1,2,3,7,8,9-, 1,2,3,4,6,7,8-, octa-CDFs; Wellington Laboratories), 13C12-PBDD/Fs

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(2,3,7,8-, 1,2,3,7,8-, 1,2,3,4,7,8-, 1,2,3,4,6,7,8-, octa-BDDs and 2,3,7,8-, 2,3,4,7,8-,


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1,2,3,4,7,8-, 1,2,3,4,6,7,8-, octa-BDFs; EDF-5408, Cambridge Isotope Laboratories)

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and 13C12-PBDEs (BDE-28, -47, -99, -100, -153, -154, -183, -197, -207, -209; Wellington

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Laboratories), and then cleaned-up with concentrated sulfuric acid and multi-layer silica

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gel. The cleaned-up extract was loaded onto an activated carbon-impregnated silica gel

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reversible cartridge (Kanto Chemical) for separation into a non-dioxin fraction containing

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PBDEs (eluted with 30 ml of a mixture of 25% dichloromethane (DCM) in hexane) and

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then a dioxin fraction (reverse-eluted with 80 ml of toluene). The non-dioxin fraction was

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further cleaned-up using gel-permeation chromatography (packed Bio-Bead S-X3, Bio-

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Rad Laboratories, eluted with 150 ml of a mixture of 50% DCM in hexane), and then

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spiked with 13C12-BDE126 and -BDE205 (Wellington Laboratories), whereas the dioxin

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fraction was spiked with 13C12-1,2,3,4-/-1,2,3,7,8,9-CDD (Wellington Laboratories) and

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13C

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concentrated under gentle nitrogen stream down to 50 µl.

12-1,2,3,7,8,9-BDD

(Cambridge Isotope Laboratories). Both fractions were

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PCDD/Fs and PBDD/Fs were determined using a HP-6890 gas chromatograph (GC,

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Agilent Technologies) connected to a JMS-700D magnetic sector high resolution mass

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spectrometer (HRMS, JEOL) operating in electron ionization selective ion monitoring


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(EI-SIM) mode at a resolution of >10,000 (10% valley). For tetra- to octaCDD/Fs, the

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GC column was a BPX-Dioxin-I (SGE Analytical Science, 0.15 mm internal diameter ×

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unspecified film thickness × 30 m length) and the temperature program was 160 °C

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(1 min), 20 °C/min to 200 °C, and then 3 °C/min to 300 °C. For tetra- to hexaBDD/Fs, a

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DB-17ht column (Agilent Technologies, 0.25 mm × 0.15 µm× 30 m) was used with a

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temperature program of 160 °C (1 min), 20 °C/min to 220 °C, 4 °C/min to 300 °C (hold

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10 min). For hepta- to octaBDD/Fs, a DB-5ms column (Agilent Technologies, 0.25 mm ×

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0.1 µm× 15 m) was used with a temperature program of 170 °C (1 min), 15 °C/min to

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260 °C, 10 °C/min to 310 °C (hold 8 min). Tri- to decaBDEs (BDE-17, -28, -30, -47, -49,

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-66, -71, -77, -79, -85, -99, -100, -118, -119, -126, -138 to -140, -153 to -156, -171, -180,

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-183, -184, -191, -196, -197, -201, -203 to -209) were determined using a 7890A GC

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(Agilent Technologies) connected to a 5975C quadrupole MS (qMS, Agilent

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Technologies) operating in EI-SIM mode. The GC column was a DB-5ht (Agilent

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Technologies, 0.25 mm × 0.1 µm× 15 m) and the temperature program was 110 °C

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(1 min), 40 °C/min to 135 °C, 15 °C/min to 215 °C, 5 °C/min to 250 °C, and then

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40 °C/min to 310 °C (hold 10 min).


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Every set of seven samples was accompanied by a procedural blank. The

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concentration of each homologue group was calculated from the areas of both identified

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and unidentified peaks. The recoveries of the labelled surrogate standards were from

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66% to 138%, and concentrations of the native compounds were adjusted accordingly.

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All results were expressed on a dry weight basis.

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Screening and semi-quantitative analysis of PXDFs and PXDEs. Six samples from

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two open burning areas and the dismantling area were subjected to comprehensive

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screening of PXDFs and PXDEs, two samples with the highest concentrations of

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PCDD/Fs and PBDD/Fs were selected for each of these three areas to confirm the

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representativeness of the chemical profiles. A 0.5-g equivalent portion of each selected

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soil extract was subjected to a non-destructive clean-up procedure consisting of

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activated silica gel chromatography (Wakogel® DX, Wako, 4 g, elution with 80 ml of a

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mixture of 5% dichloromethane in hexane) and gel-permeation chromatography, and

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then separated into a non-dioxin fraction and a dioxin fraction using an activated

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carbon-impregnated silica gel reversible cartridge as described above. Both fractions


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were analyzed using a GC×GC–ToFMS system consisting of a KT2006 modulator

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(Zoex, 8 s modulation time) installed on a 7890A GC (Agilent Technologies) and a JMS-

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T100GCV MS (JEOL) operating at a nominal sampling rate of 25 Hz and a resolution of

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>5000 (full width at half maximum). The first column was a DB-1ms Ultra Inert (Agilent

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Technologies, 0.18 mm × 0.18 µm × 20 m) and the second a BPX-50 (SGE Analytical

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Science, 0.1 mm × 0.1 µm × 0.75 m). The temperature program was 160 °C (1 min),

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20 °C/min to 250 °C and then 4 °C/min to 350 °C. Mass drift compensation was

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performed by adjusting with reference PBDF and PBDE congeners (listed in Table S1).

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Blobs corresponding to tetra–heptaXDFs and tetra–heptaXDEs were then identified on

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the two-dimensional chromatogram using the following criteria: presence of ions

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matching the theoretical m/z (±0.02 window) of the two most abundant ions of the

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molecular ion cluster (M+), their intensity ratio within ±15% of the theoretical value,

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presence of characteristic ions ([M−COBr]+ for PXDFs, [M−2Br]+ or [M−BrCl]+ for

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PXDEs), and retention times either close to those of the authentic standards or

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predictable from those of known homologues (for homologues without authentic

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standards). Highly brominated PXDFs and PXDEs could not be detected because of


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thermal degradation in the GC×GC modulator. However, four highly brominated PXDE

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homologues (Br7–8Cl2DEs and Br8–9ClDEs) were identified with GC–qMS by monitoring

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the theoretical m/z of their characteristic [M−2Br]+ ions using the same GC conditions as

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PBDE analysis. PXDFs were semi-quantified based on the concentrations of PBDFs

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obtained with HRMS, and PXDEs based on qMS-derived PBDE concentrations. The

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response factor of a compound was assumed as identical to that of the standard isomer

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if available, or interpolated from those of the two closest homologue groups in terms of

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molecular weight (Table S1). Identification of PXDDs was not attempted considering

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their considerably lower expected concentrations.

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RESULTS AND DISCUSSION

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Distribution of PCDD/Fs, PBDD/Fs and PBDEs. The concentrations of PCDD/Fs,

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PBDD/Fs and PBDEs in surface soil samples from the Agbogbloshie e-waste site varied

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widely, ranging over one to two orders of magnitude even within the same area

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(Table 1). The contamination levels of PCDD/Fs and PBDD/Fs were not significantly

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different between the open burning areas and the dismantling area (Wilcoxon’s rank


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sum test, p > 0.05). However, the highest concentrations of total PCDD/Fs were found

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in the open burning areas (1.3–380, median 33 ng/g as opposed to 5.6–230, median

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16 ng/g), whereas the highest concentrations of total PBDD/Fs were found in the

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dismantling area (23–1000, median 450 ng/g as opposed to 11–870, median 180 ng/g).

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The dismantling area also had significantly higher concentrations of total PBDEs (140–

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6900, median 2800 ng/g as opposed to 21–2100, median 480 ng/g; p < 0.001). In the

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other areas, the concentrations of all target compounds were lower by at least an order

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of magnitude.

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Table 1. Concentrations (ng/g dry weight) of PCDD/Fs (Cl4–8DD/Fs), PBDD/Fs (Br4–

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8DD/Fs)

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waste site (Ghana) in 2013

and PBDEs (Br3–10DEs) in soil samples collected from the Agbogbloshie e-

Open burning areas (n = Dismantling area (n = 14)

Other areas (n = 13)

14) Range

Median

Range

Median

Range

Median

Cl4DDs

0.11–19

1.2

0.76–45

1.4

0.043–0.73

0.19

Cl5DDs

0.13–32

1.5

0.70–46

1.6

0.036–1.1

0.21

Cl6DDs

0.081–23

0.79

0.37–23

0.98

0.026–1.0

0.13


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Cl7DDs

0.12–19

0.42

0.18–14

0.85

0.025–0.94

0.11

Cl8DD

0.11–12

0.32

0.16–8.5

0.85

0.054–0.51

0.10

Total PCDDs

0.75–110

4.4

2.2–140

8.0

0.18–4.2

0.69

Cl4DFs

0.22–100

8.1

1.5–43

4.2

0.082–2.0

0.70

Cl5DFs

0.20–100

6.2

0.98–31

4.6

0.066–3.0

0.77

Cl6DFs

0.064–42

2.1

0.36–14

1.5

0.027–2.6

0.28

Cl7DFs

0.039–24

1.4

0.15–6.7

0.69

0.013–2.7

0.13

Cl8DF

0.0098–5.9

0.25

0.046–1.5

0.16

0.0036–0.77 0.027

Total PCDFs

0.53–280

18

3.3–97

11

0.19–11

Br4DDs

Chlorinated Diphenyl Ethers and

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