Accumulation of polychlorinated biphenyls and brominated flame retardants in breast milk from women living in Vietnamese e-waste recycling sites Nguyen Minh Tuea, Agus Sudaryantob, Tu Bin
Trang 1Accumulation of polychlorinated biphenyls and brominated flame retardants in breast milk from women living in Vietnamese e-waste recycling sites
Nguyen Minh Tuea, Agus Sudaryantob, Tu Binh Minhc, Tomohiko Isobeb, Shin Takahashia,⁎ ,
a
Center for Marine Environmental Studies (CMES), Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan
b
Senior Research Fellow Center, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan
c
Centre for Environmental Technology and Sustainable Development, Hanoi University of Science, 334 Nguyen Trai, Hanoi, Vietnam
a b s t r a c t
a r t i c l e i n f o
Article history:
Received 28 October 2009
Received in revised form 6 January 2010
Accepted 8 January 2010
Available online 8 February 2010
Keywords:
Breast milk
E-waste
Exposure pathway
HBCD
PBDE
PCB
This study investigated the contamination status of PCBs, PBDEs and HBCDs in human and possible exposure pathways in three Vietnamese e-waste recycling sites: Trang Minh (suburb of Hai Phong city), Dong Mai and Bui Dau (Hung Yen province), and one reference site (capital city Hanoi) by analysing human breast milk samples and examining the relationships between contaminant levels and lifestyle factors Levels of PBDEs, but not PCBs and HBCDs, were significantly higher in Trang Minh and Bui Dau than in the reference site The recyclers from Bui Dau had the highest levels of PBDEs (20–250 ng g− 1 lipid wt.), higher than in the reference group by two orders of magnitude and more abundant than PCBs (28–59 ng g− 1lipid wt.), and were also the only group with significant exposure to HBCDs (1.4–7.6 ng g− 1lipid wt.) A specific accu-mulation, unrelated to diet, of low-chlorinated PCBs and high-brominated PBDEs was observed in e-waste recyclers, suggesting extensive exposure to these compounds during e-waste recycling activities, possibly through inhalation and ingestion of dust The estimated infant intake dose of PBDEs from breast milk of some mothers occupationally involved in e-waste recycling were close to or higher than the reference doses issued
by the U.S EPA
© 2010 Elsevier B.V All rights reserved
1 Introduction
Waste electrical and electronic equipment, also known as e-waste,
refers to end-of-life products encompassing
information-communi-cation devices, consumer electronics and household appliances Owing
to the short life span of devices such as computers, television sets,
stereo systems, printers and cell phones, e-waste is generated in large
amounts, with an annual volume of 20–50 million tonnes world-wide
and increases rapidly at a rate of 3–5% per year (UNEP, 2005) The
hazard of e-waste lies in the high content of many toxic substances
(BAN and SVCT, 2002) including heavy metals (lead, mercury,
cadmium, etc.) and persistent organohalogen compounds such as
polychlorinated biphenyls (PCBs) and brominatedflame retardants
(BFRs) PCBs are present in older electrical capacitors and transformers
as coolants and dielectrics whereas BFRs are additives found in most
polymeric parts (printed circuit boards, cable coatings, plastic casings,
etc.) There are increasing evidences that BFRs, such as
polybromi-nated diphenyl ethers (PBDEs) and hexabromocyclododecanes
(HBCDs), exhibit a range of toxic effects similar to PCBs, including
endocrine disruption as well as reproductive and neurodevelopmental toxicity (Legler and Brouwer, 2003; Birnbaum and Staskal, 2004) Uncontrolled e-waste recycling has become a topic of serious concern in recent years It is estimated that up to 80% of e-waste from industrialised countries is exported to Asian developing countries for recycling, exploiting the inexpensive cost of labour and weak enforcement of environmental laws (BAN and SVCT, 2002) Large scale waste processing operations employing primitive practices such
as uncontrolled dismantling, acid stripping and open burning in Chinese e-waste recycling sites (EWRSs) have resulted in severe environmental contamination (Wong et al., 2007) The human exposure levels to PCBs in Taizhou region (Zhao et al., 2007) and to PBDEs in Guiyu town (Bi et al., 2007) are two of the highest ever reported In other Asian developing countries such as Cambodia, India, Philippines and Viet Nam, although open waste disposal sites have been identified as potential sources of PCBs and dioxin-like com-pounds (Minh et al., 2003), information on EWRS are lacking Avail-able data, albeit limited, indicate that the levels of PCBs and BFRs in the general populations from these countries are lower than those from developed countries (Schecter et al., 2004; Sudaryanto et al.,
2005, 2008a; Malarvannan et al., 2009); nevertheless EWRSs are suspected as potential hotspots of these contaminants In this context, the present study was carried out to assess the human exposure to persistent organohalogen compounds related to e-waste recycling in
⁎ Corresponding author Tel./fax: +81 89 927 8196.
E-mail address: shint@agr.ehime-u.ac.jp (S Takahashi).
0048-9697/$ – see front matter © 2010 Elsevier B.V All rights reserved.
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Trang 2Viet Nam Breast milk was selected as bioindicator on account of the
simple and non-invasive sampling, relatively high content of lipid and
lipophilic contaminants, and relevance to infants' health PCBs, PBDEs
and HBCDs were determined in human breast milk collected from
three EWRSs and a reference site in view of contamination levels,
congener patterns, influence of lifestyle factors and potential health
risk for breastfeeding infants
2 Materials and methods
2.1 Study locations
End-of-life electrical and electronic equipment in Viet Nam are
often picked up by scrap collectors, through purchase from their
former owners or by scavenging domestic waste disposal sites The
wastes are then transported to trade villages specialised in recycling
The present study investigated three e-waste recycling sites located in
the Red River delta region, in the northern part of the country; Dong
Mai (DM, Hung Yen province, battery recycling), Trang Minh (TM,
suburb of Hai Phong City, e-waste dismantling) and Bui Dau (BD,
Hung Yen province, e-waste dismantling) All study locations were
small villages with approximately 80 households or less E-waste
recycling as a trade started in these villages very recently at the
beginning of the decade, except in the case of DM where the recycling
of lead from batteries has been occurring for almost four decades
Most businesses are family-based and e-waste is recycled in the
backyard of the house The waste processing often consists of only
dismantling, retrieval of easily accessible metals and grinding plastic
casings intro reusable pellets Circuit boards are not processed and
instead sold to foreign buyers Alongside these recent recycling
activities, the villages still maintain traditional crop production A
minority of the families also raise livestock or aqua-culturefish in
limited quantities in-house, but the main supplies of livestock
neighbouring communes
2.2 Sample collection
The sampling survey was conducted in August 2007 In each of the
three recycling sites, the number of nursing mothers was limited to
around 20 or less Four breast milk samples from DM, eleven from TM
and nine from BD were collected from the mothers who agreed to
donate As reference, another nine samples were collected from the
capital Hanoi (HN), a typical urban area Informed consents were
obtained from all donors Questionnaire survey was also conducted to
acquire personal information on age, height and weight
measure-ments, number of deliveries and duration of nursing periods,
occupation (recyclers or non-recyclers), period of involvement in
recycling activities and dietary habit (Table 1) All donors were
non-smokers and appeared healthy Breast milk was expressed by the
donor or with the help of a midwife into a solvent-precleaned glass
container with Teflon-lined screw caps The samples were kept in
gel ice immediately after collection and then sent within 8 h to our
laboratory in Viet Nam and frozen at−20 °C Later the frozen samples were air-transported with gel ice to the Environmental Specimen Bank (es-BANK, Ehime University, Japan) and stored at−25 °C in until analysis
2.3 Chemical analyses Approximately 40 g of sample was freeze-dried and then Soxhlet-extracted with 300 ml diethyl ether and 100 ml hexane for 7 h About 10% of the extract was used for determination of the lipid content using the gravimetric method The remaining extract was spiked with
13C12–PCBs,13C12–PBDEs (5 ng each) and13C12–HBCDs (10 ng each)
as standard surrogates, subjected to gel permeation chromatography (packed Bio-Bead S-X 3, Bio-Rad Laboratories, USA) for lipid removal using a hexane/dichloromethane (DCM) mixture (1:1 v/v) as eluant The cleaned-up extract was then concentrated and passed through 4 g
of activated silica gel (Wakogel® DX, Wako, USA) packed in a glass
fraction containing PCBs and PBDEs, eluted with a mixture of hexane/ DCM (95:5 v/v, 80 ml), was spiked with 5 ng 13C12–BDE-139 as internal standard and solvent-exchanged into iso-octane The HBCD fraction, eluted with another mixture of hexane/DCM (75:25 v/v,
100 ml), was concentrated until dryness and then redissolved in a methanol solution containing deuterium-labelled HBCDs-d18(10 ng each) as internal standards
PCBs (62 congeners) and PBDEs (14 congeners commonly found in abundance in the technical PBDE mixtures (La Guardia et al., 2006), namely BDE-3, -15, -28, -47, -99, -100, -153, -154, -183, -196, -197, -206, -207, and -209) were quantified using a gas chromatograph (Agilent 7890 series) equipped with a mass-selective detector (Agilent 5975 series) and a DB-1 fused silica column (J&W Scientific) having 0.25 mm i.d × 30 m × 0.25 µm film thickness for PCBs and mono- to hepta-BDEs or 0.25 mm i.d × 15 m × 0.1 µmfilm thickness for octa- to deca-BDEs The GC oven temperature program for PCBs was: from 120 °C to 180 °C at 20 °C min− 1, 2 °C min− 1to 260 °C,
5 °C min−1 to 300 °C and held for 4 min PCBs were monitored in selective ion monitoring mode (EI-SIM) at masses of [M]+and [M+ 2]+
for mono- to tetra-CBs, [M+ 2]+and [M+ 4]+for penta- to nona-CBs and [M+ 4]+and [M+ 6]+for deca-CB The instrumental set-up for PBDE analysis has been described previously (Sudaryanto et al.,
according to the methods described elsewhere (Isobe et al., 2007) Procedural blanks were analysed simultaneously with samples to check for interferences and contamination Detection limits were calculated as three times the procedural blank, and were in the range
of 0.01–0.05 ng g− 1lipid wt for all target compounds Recoveries of
13C-labelled surrogates were in the range of 57%–107% for PCBs, 63%–
breast milk described above followed our common procedure employed for animal tissues For quality assurance and control, our laboratory participated in an intercalibration exercise on BFRs using the blubber of a marine animal as the reference material and our data were in good agreement with those reported by other laboratories
Table 1
General characteristics of the donors of breast milk.
Parameters Hanoi (n = 9) Dong Mai (n = 4) Trang Minh (n = 11) Bui Dau (n = 9) Age (year) 23–35 (28.2) 25–31 (28.3) 18–26 (23.6) 24–35 (29.3) Weight (kg) 46–62 (54.3) 42–52 (46.0) 41–50 (45.5) 40–46 (44.0) Height (cm) 155–167 (160.9) 153–155 (154.5) 150–160 (154.6) 150–155 (154.0) Body mass index (kg m− 2) 16.5–25.4 (21.1) 17.9–21.6 (19.3) 16.4–21.3 (19.1) 16.7–21.6 (19.1) Number of children 1–2 (1.67) 1–4 (2.3) 1–2 (1.55) 1–4 (2.2) Total nursing time (month) 4.5–25 (12) 4–57 (26) 1.5–24 (12) 9.5–79 (34) Occupation 89% office worker 25% recycler 55% recycler 55% recycler
11% housewife 75% farmer 45% housewife 45% others
Trang 3(Isobe et al., 2007) Concentrations were expressed on a lipid weight
basis unless otherwise specified
2.4 Statistical analyses
The Wilcoxon rank sum test was used for assessing whether the
contaminant levels between groups were significantly different In
this analysis, non-detectable levels were set to zero Principal
component analysis (PCA) was employed to categorise PCB and
PBDE congeners according to their variation patterns This analysis
included only the congeners detected in at least 70% of the samples
The influence of socio-demographic parameters on the total
concen-tration of each category was then analysed qualitatively using
multiple linear regressions The parameters used as independent
variables included: age, body mass index (BMI), total duration of
nursing, period of involvement in recycling activities and
consump-tion rate of food from animal origin (total rate of meat,fish and dairy
products, servings per week) Other location-specific factors were
assumed to be negligible and not considered Parameters with a
relationship with contamination level In these later two statistical
analyses, non-detectable concentrations were set to half of the
detection limit and then all concentrations were log-transformed to
bring the data distribution closer to normality All calculations were
performed using the statistical software package R version 2.9.0
2.5 Risk assessment
The risk for infants exposed to contaminants in mother milk was
assessed using hazard quotients (HQs) An HQ is defined as the ratio of
the estimated daily intake dose (DI) of the compound via
breastfeed-ing to the correspondbreastfeed-ing maximum acceptable oral dose for human, or
reference dose (RfD) A value of HQ higher than 1 indicates potential
risk The DIs were calculated based on the assumption that an infant in
average weighs 5 kg and consumes 700 g mother milk daily (Oostdam
et al., 1999) HQs of total PCBs, BDE-47, BDE-99, BDE-153 and total
HBCDs were calculated using RfD values of 1 (Oostdam et al., 1999), 0.1, 0.1, 0.2 (EPA, 2008) and 0.2 µg kg− 1day− 1(European Chemicals Bureau, 2007), respectively
3 Results PCBs, PBDEs and HBCDs were detected in all the samples analysed (Table 2) In terms of total concentrations, PCBs were more abundant than PBDEs and HBCDs by one order of magnitude or higher in majority
of the samples However, PBDEs were more abundant than PCBs in three donors who were involved in the recycling of e-waste in BD
Total PCB levels were statistically comparable among locations but significant differences were observed with individual PCB congeners The residents of the three recycling sites had statistically lower (p < 0.05) levels of high-chlorinated congeners such as CB-138, -153 and -180 but somewhat higher levels of tri- and tetra-chlorinated congeners (tri- and tetra-CBs) than those of the urban reference site CB-28 was detected at significantly higher (p<0.05) levels in TM and
BD (recyclers only) than in HN, and the highest levels of CB-28 and CB-74 were found in battery recyclers from DM In each recycling site, the total levels of tri- and tetra-CBs were higher in the recycler group than in the non-recycler group, with the median being 30 vs 10, 6.7 vs 4.9 and 5.0 vs 2.8 ng g− 1lipid wt in DM, TM and BD, respectively However, these differences were not statically significant (p>0.05), probably due to the limited number of samples The preferential accumulation of these low-chlorinated biphenyls in the recycling sites resulted in distinctive PCB congener profiles As seen inFig 1, the profile in the reference site followed the order of
CB-138>CB-153 > CB-118 > CB-180 > CB-99 > CB-74 > CB-28 whereas in TM and
BD, 28 and 74 were as abundant as 99 and more than
CB-180 In DM, the battery recycling site, CB-28 and CB-74 were the dominant congeners Based on the PCA results PCB congeners were divided into three categories (Fig 2): (a) high-chlorinated PCBs (HighCB), including hepta to deca congeners and two hexa congeners
(PC1) which accounted for 57% of the total variance; (b)
low-Table 2
Concentrations (ng g− 1lipid wt.) of major PCB congeners, PBDE congeners and HBCD isomers in human breast milk collected from Hanoi and Vietnamese e-waste recycling sites Compound Hanoi Dong Mai Trang Minh Bui Dau non-recyclers Bui Dau recyclers
Median Range Median Range Median Range Median Range Median Range CB-28 1.1 0.42–7.6 5.6 1.0–34 2.0 0.72–10 0.85 0.42–14 1.9 1.5–14 CB-74 2.8 1.3–6.0 5.9 1.2–15 2.7 0.42–7.6 1.6 0.56–3.7 2.7 1.6–8.6 CB-99 2.9 1.2–7.3 2.5 0.88–4.6 2.1 0.60–4.3 1.7 0.60–2.0 2.8 1.9–3.6 CB-118 4.8 2.0–13 3.5 1.2–8.3 3.3 1.0–6.9 2.8 1.0–3.3 4 3.6–5.6 CB-138 9.7 3.8–17 4.0 2.1–11 5.8 1.9–11 4.8 1.7–6.0 5.5 4.6–6.7 CB-153 8.2 3.8–16 3.5 1.7–9.0 5.7 1.8–11 3.6 1.5–5.2 4.6 3.6–5.6 CB-180 3.7 1.9–5.5 1.0 0.51–3.5 1.8 0.71–4.3 1.4 0.50–2.1 1.6 1.3–1.7
8.4–28 34 28–59 BDE-15 0.040 0.014–0.073 0.011 0.010–0.032 0.030 0.010–0.34 0.057 0.022–0.075 0.35 0.16–1.5 BDE-28 0.029 0.017–0.067 0.010 n.d.–0.044 0.074 0.024–1.0 0.21 0.13–0.27 0.96 0.82–8.2 BDE-47 0.13 0.070–0.25 0.097 0.041–0.20 0.40 0.11–1.8 0.81 0.63–1.0 4.8 3.5–32 BDE-99 0.057 n.d.–0.12 n.d n.d.–0.028 0.11 0.032–0.51 0.38 0.22–0.56 3.2 2.2–15 BDE-100 0.040 n.d.–0.10 n.d n.d 0.082 0.022–0.21 0.13 0.083–1.6 0.80 0.54–3.1 BDE-153 0.098 0.062–0.14 0.10 0.061–0.25 0.40 0.021–1.5 0.65 0.27–1.0 4.4 2.1–23 BDE-154 n.d n.d.–0.037 n.d n.d 0.021 n.d.–0.069 n.d n.d.–0.035 0.39 0.27–2.1 BDE-183 0.029 n.d.–0.038 0.050 0.029–0.11 0.13 0.022–1.2 0.14 0.053–0.22 1.2 0.49–2.7 BDE-196 0.010 n.d.–0.015 0.010 n.d.–0.018 0.036 n.d.–0.14 0.037 0.027–0.056 0.59 0.25–5.1 BDE-197 0.045 0.016–0.11 0.046 0.026–0.14 0.26 0.032–0.78 0.47 0.17–0.61 7.5 3.1–29 BDE-206 n.d n.d.–0.027 0.024 n.d.–0.10 0.05 0.012–0.23 0.014 n.d.–0.03 0.26 0.16–4.5 BDE-207 0.025 n.d.–0.057 0.030 0.011–0.11 0.10 0.041–0.41 0.15 0.10–0.18 3.5 1.3–51 BDE-209 n.d n.d 0.17 0.069–0.50 0.42 0.12–7.3 0.11 n.d.–0.16 4.1 0.87–96 ΣPBDEs 0.57 0.24–0.8 0.73 0.26–1.1 2.3 a
0.55–13 3.2 a
2.0–4.0 84 a
20–250 α-HBCD 0.33 0.066–1.4 0.43 0.11–0.97 0.38 0.12–3.3 0.36 0.29–1.2 1.9 1.4–7.5 β-HBCD n.d n.d n.d n.d n.d n.d.–0.051 n.d n.d n.d n.d γ-HBCD n.d n.d.–0.13 n.d n.d n.d n.d.–0.27 n.d n.d 0.045 n.d.–0.099 ΣHBCDs 0.33 0.070–1.4 0.42 0.11–0.97 0.38 0.11–3.3 0.36 0.29–1.2 2.0 a 1.4–7.6 n.d.: not detected.
a Significantly different from reference site (p<0.05).
Trang 4chlorinated PCBs (LowCB), consisting of mainly tri and tetra
congeners, aligned with PC2 (17% of variance); and (c) others
(MediumCB), mostly penta and a few hexa congeners including
CB-99, -101, -118, -128, etc., contributing to both PCs
PBDE levels in the battery recycling site DM were comparable with
those in the reference site HN whereas the levels in the two e-waste
dismantling sites, TM and BD, were statistically higher (Table 2) In TM,
the recycler and non-recycler groups had similar levels of total PBDEs,
with an overall median higher than in the reference group by a factor of 4
In BD, although the levels in the non-recycler group were only
comparable to those in TM, the recycler group had the highest PBDE
levels of all donors, approximately two orders of magnitude higher than
those in the residents of HN In the reference site, BDE-47 and BDE-153
were the dominant PBDE congeners whereas BDE-209 was at non-detectable levels (Fig 1) BDE-209 was detected in most of the samples collected from the recycling sites with varying proportions up to 50% Octa to nona congeners were also observed at higher percentages
BDE-197 and -207 were prominent in samples from recyclers living in BD, with levels comparable to BDE-47 PCA of PBDE congeners indicated that these compounds could be considered as a single category because 86% of the variance could be represented by PC1 (Fig 2), suggesting a high degree of correlation among congeners with the exception of BDE-209, main contributor to PC2 (only 7.4% of the variance)
HBCDs levels were not statistically different among residents of HN,
DM and TM (both recyclers and non-recyclers) and BD (non-recyclers) Recyclers from BD had significantly higher levels than the other groups,
Trang 5with a 6-fold difference compared with the reference group (Table 2).
α-HBCD was the dominant isomer in all the samples, accounting for
more than 90% of the total HBCD levels.γ-HBCD was detected in eight
samples with a proportion of less than 10% andβ-HBCD was detected in
only one sample
Results from the fitting of chemical concentrations to multiple
linear regression models of socio-demographic parameters (Table 3)
showed that LowCB and PBDEs were associated only with
involve-ment period in recycling activities, HighCB correlated positively with
consumption of food from animal origin but negatively with nursing
time whereas MediumCB had positive associations with both food
consumption and recycling activities Age and BMI did not show any
significant influence on contaminant concentrations
4 Discussion
4.1 Contamination levels
The similarity in PCB levels in the three Vietnamese e-waste
recycling sites as also seen in the reference site indicates that the
former were not major sources of PCBs Total PCB levels in Vietnamese human breast milk were in comparable ranges with those reported in other Asian developing countries and lower than in developed nations (Table 4) The levels observed in this study were similar to the serum PCB levels in the residents of Guiyu (median 52 ng g− 1lipid wt.), the largest recycling site of electronic waste in China, reported byBi et al (2007) These authors also did notfind any significant difference between the exposed and the reference populations Thus e-waste related PCB contamination is believed to involve old electric materials, especially transformers, rather than electronic waste The case of Luqiao, the largest Chinese disassembly site of electrical waste, is an example where very high PCB levels in human breast milk associated with e-waste recycling were reported (median 359 ng g− 1lipid wt., Zhao et al., 2007) The absence of substantial PCB contamination suggests that in the Vietnamese recycling sites, the occurrence of waste materials containing PCBs may be uncommon and the recycling
of these materials is of limited scale
Significant exposure to PBDEs was observed in the two e-waste dismantling sites, TM and BD, especially in BD recyclers Compared with the levels reported by other studies, the PBDE levels in the
Table 3
Coefficients (β) and p-values of socio-demographic parameters in linear models of contaminant concentrations.
Nursing time 0.008 0.11 −0.002 0.49 −0.0074 0.007 0.013 0.12 0.009 0.13 Recycling a
0.145 0.009 0.076 0.022 0.061 0.34 0.180 0.029 0.101 0.13 Diet b
0.008 0.85 0.070 0.013 0.080 0.002 −0.037 0.64 0.003 0.96
R 2
p
a
Period of involvement in recycling activities (years).
b
Consumption rate of food from animal origin (total rate for meat, fish and dairy products, servings per week).
Table 4
Comparison of PCBs and BFRs in human breast milk from Viet Nam with other countries.
Asian developing countries
Subramanian et al (2007), Sudaryanto et al (2005)
Vietnam (BD non-recylers) 2007 28 3.2 0.36 This study
Other countries
Gómara et al (2007), Eljarrat et al (2009)
2006–2007
0.35 Lignell et al (2003)
United Kingdom 2001–2003 180 6.3 b
Kalantzi et al (2004)
United States 2002–2003 126 50.4 0.5 Ryan et al (2006), She et al (2007)
Concentrations are given as median if available (or arithmetic mean otherwise) and expressed in nanogram per gram lipid wt.
a
Mono- to hepta-BDEs only.
b
Mono- to hexa-BDEs only.
c
Trang 6reference group in this study (HN) were among the lowest in the
world (Table 4), consistent with thefindings ofSchecter et al (2004)
Levels in TM and BD non-recyclers were higher in Indonesia and Japan
and close to those in European countries whereas levels in BD
recyclers were in the same range with American levels which are the
highest reported among non-occupationally exposed populations
The differences in waste materials, workload and processing methods
may contribute to the variation of PBDE contamination levels in the
Vietnamese recycling sites For instance, PBDEs may be minor
con-taminants in waste batteries as suggested by the low levels
accu-mulated in the battery recyclers in DM On the other hand, the
elevated levels in recyclers from BD may be the result of processing
large amounts of waste materials with high PBDE contents using
methods which facilitate the release of these contaminants from the
waste matrices, such as burning and other thermal processes It is also
remarkable that in BD recyclers, the PBDEs levels exceeded those of
PCBs, despite the long legacy of the latter compounds This unusual
feature (comparison inTable 4) has so far been observed only in case
of uncontrolled e-waste recycling (Bi et al., 2007) It clearly indicates
an extensive exposure to PBDEs with different sources from those of
legacy persistent organic pollutants (POPs); nevertheless the highest
PBDE levels in breast milk in this study were still lower than those in
serum of Chinese e-waste dismantling workers from Guiyu (median
600 ng g−1lipid wt.,Bi et al., 2007) by an order of magnitude This large
difference in lipid weight-normalised concentrations, albeit in two
separate human matrices, again infers that Vietnamese recycling sites
are still less contaminated in terms of PBDEs than their Chinese
counter-parts, probably on account of a smaller scale of e-waste processing
Although information on HBCDs in human matrices is still limited,
available data indicate that the accumulation levels of HBCDs in
human breast milk from Asia, USA and several European countries are
very low (<1 ng g− 1lipid wt.,Table 4) The HBCD levels in HN, DM
and TM observed in this study also fell within this range, suggesting
that products containing HBCDs may be scarce in Viet Nam and also
uncommon in the e-waste In contrast, the contamination levels were
reported to be somewhat higher in Japan and very high in Spain
(Table 4), reflecting an extensive usage of HBCDs in Japan and some
European countries (Watanabe and Sakai, 2003) In Vietnamese e-waste
recycling sites, exposure to waste materials containing HBCDs appeared
to be limited to recyclers from BD, coincidentally the group most
exposed to PBDEs The HBCD levels in this group were comparable with
those in Japanese women; nevertheless these exposure levels associated
with e-waste recycling were still much lower than the non-occupational
exposure levels reported in Spain
4.2 Accumulation patterns
Higher levels of tri- and tetra-CBs in the recycling sites indicate a
specific exposure in e-waste recycling processes This is further
supported by a significant positive relationship between LowCB level
and period of involvement time in recycling activities (Table 3) The
source of these congeners may be old electric devices such as
capacitors and small transformers which contain PCBs as heat transfer
and dielectricfluids Several PCB technical mixtures such as Aroclor
1016, 1242 or Kaneclor 300 contain principally congeners with low
degrees of chlorination (Takasuga et al., 2006) Moreover,
low-chlorinated biphenyls from e-waste can be more accessible to human
due to their relatively higher volatility (Bamford et al., 2000) This
exposure source may explain the highest levels of tri- and tetra-CBs
found in DM, a site recycling exclusively electrical waste
The elevated relative concentrations of octa- to deca-BDEs in the
recycling sites were the distinctive feature compared with the PBDE
profile in HN which was dominated by lower-brominated congeners
such as BDE-47 and BDE-153 The latter pattern seems to be common
in human breast milk from many countries in Asia (Inoue et al., 2006;
Sudaryanto et al., 2008a), Europe (Polder et al., 2008a) and North
America (She et al., 2007) There are several plausible explanations for the preferential accumulation of BDE-47 and BDE-153 in human: they are major constituents of the PentaBDE technical mixtures (La Guardia et al., 2006), have relatively good bioavailability (Hakk and Letcher, 2003) and strong bioaccumulation features (Burreau et al., 2006) and can be metabolites of higher-brominated congeners (Stapleton et al., 2004) Therefore secondary exposure via diet may
be the major pathway of BDE-47 and BDE-153 On the other hand,
through food webs (Burreau et al., 2006) BDE-209 also has a very low assimilation rate (<1%) and a fast clearance rate in mammals (Hakk and Letcher, 2003) Thus accumulation of high-brominated BDEs is often attributed to a sustained exposure to Octa and DecaBDE technical mixtures at elevated levels, especially in an occupational context such as the case of rubber and cable manufacturing workers in Sweden (Thuresson et al., 2005) or e-waste recycling workers in China (Bi et al., 2007) Therefore the presence of octa- to deca-BDEs in breast milk of the mothers in Vietnamese e-waste recycling sites could be an indication of primary exposure to Octa and DecaBDE technical mixtures from e-waste The large variation in relative con-centrations of these congeners even within the same group suggests that either human exposure to higher-brominated BDEs may vary with different microenvironments depending probably on the composition of theflame retardants contained in waste materials, or the toxicokinetics of these compounds may be different in individual donors
4.3 Exposure pathways
As PBDE levels did not correlate with HighCB levels (Pearson's r =
−0.012, p=0.95), the two groups of compounds may have different exposure sources/pathways In case of HighCB, the main pathway is likely to be dietary intake, evidenced by a positive association with consumption of food from animal origin (Diet parameter,Table 3) This
is often the case with legacy POPs such as high-chlorinated PCBs that have been accumulated in biota, especially fatty tissues of animals, during their extensive release in the past A dietary exposure also explains the higher accumulation in the urban population that had richer diets than the residents of the recycling sites On the other hand, exposure to PBDEs and LowCB seems to be mainly non-dietary and related to the recycling of e-waste, as indicated by a single significant positive association with involvement time in recycling activities (Recycling parameter,Table 3) This occupational exposure may occur through accidental ingestion/inhalation of particulate matters gener-ated during activities such as dismantling, shredding or thermal treat-ment of e-waste In another case of uncontrolled e-waste recycling, elevated concentrations of air particles and extremely high concen-trations of air particle-bound PBDEs have indeed been reported (Wong
et al., 2007) In this study, dietary intake did not appear to be an important factor contributing to PBDE levels, partly because the main supplies of food from animal origin were not produced on site and thus not directly contaminated by the recycling activities
The exposure to HBCDs may occur in a similar fashion to PBDEs as their levels correlated with each other (Pearson's r = 0.72, p < 0.0001) HBCD levels also have a positive association with recycling acti-vities, though not statistically significant (p =0.13,Table 3) In case
of PCB congeners in the MediumCB category, the exposure path-ways may be both dietary and non-dietary through occupational contact with e-waste, as suggested by the positive associations with Diet and Recycling parameters (p = 0.013 and 0.022, respec-tively,Table 3)
4.4 Depuration by lactation Another noteworthy detail is the difference in depuration feature
of the target compounds In the literature, legacy POPs such as PCBs
Trang 7tend to have lower levels in multiparae (mothers having given birth
twice or more) than in primiparae (first-time mothers) because a
significant portion of the mother's body burden is transferred to the
child during nursing, as remarked byTanabe and Kunisue (2007)in a
review on POPs in human milk However, in the case of emerging POPs
such as BFRs, the decrease in the mother's burden by lactation was
reported to be not appreciable (Hooper et al., 2007; Schecter et al.,
2003; Sudaryanto et al., 2008a) because recent intake may
compen-sate the loss via breastfeeding In this study, BFR levels also did not
show any negative correlation with nursing time, unlike HighCB,
indicating that human exposure to BFRs is continuous and that the
intake rate may be comparable to the rate of depuration via lactation
4.5 Infant health risk
As shown inFig 3, the health risk for infants exposed to the target
contaminants via breastfeeding in general may not be serious since
the majority of HQ values are below 1, albeit the HQs of PCBs are
relatively high (>0.1) in most cases Thus PCB accumulation in
Vietnamese human milk, as a consequence of a long usage history
(Minh et al., 2008) rather than e-waste recycling, should still be
considered with respect to safe consumption by infants HQ values of
BFRs are generally lower than 0.1, with the exception of recyclers in
BD This group has high HQs related to PBDEs, with several values
close to or exceeding 1, indicating potential health risk for their
children The health effects for the infant in the event of daily intake
dose of PBDEs exceeding the RfDs, which were derived from studies
on neurobehavioural developmental toxicities (EPA, 2008), may
include altered motor behaviour, decreased habituation capability,
decreased learning/memory ability or more serious effects More in
depth epidemiological studies are necessary to assess the effects of
PBDE exposure on the development of children in these recycling
sites
5 Conclusions
The present study found a significant accumulation of PBDEs in
breast milk of women living in two Vietnamese e-waste dismantling
sites, possibly through non-dietary intake by accidental ingestion/
inhalation of dust The highest PBDE levels were found in recyclers
from the village Bui Dau, higher than the reference levels by two orders of magnitude and comparable to the highest levels reported in industrialised countries PBDEs levels in these recyclers also exceeded those of legacy POPs such as PCBs These Vietnamese e-waste re-cycling sites may be less contaminated than their Chinese counter-parts in terms of PCBs and PBDEs; nevertheless the levels of BDE-47 and BDE-99 in breast milk of some mothers occupationally involved in recycling were sufficiently high to be considered unsafe for breast-feeding infants Thus it is clear that the contamination caused by the recycling of e-waste should be mitigated to reduce human exposure
to PBDEs and also to a multitude of other toxic substances released during e-waste recycling activities such as heavy metals, dioxin-like compounds, polyaromatic hydrocarbons, etc In order to have a more complete understanding of the impact of e-waste recycling in the study locations, these contaminants should be considered in future works and dust may provide a good sample matrix for assessment of human exposure
Acknowledgements The authors thank Mr Bui Hong Nhat for coordinating the sampling survey This study was partly supported by the grants-in-aid for scientific research (S) (no 20221003) from Japan Society for the Promotion of Science (JSPS), the global environment research fund (RF-064) and the waste management research grants (K2062, K2129 and K2121) from the Ministry of the Environment, Japan, and grants from global COE program from the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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