Titleofresearch

project:

Bioaccessibility

evaluation

ofhalogenatedandorganophosphorus flame retardants by physiologically-based extraction test with Tenax
bead: Application to settled dust from e-waste and end-of-life vehicle processing
workshops in northern Vietnam
Project members:
1. Dr. Hoang Quoc Anh, University of Science, Vietnam National University, Hanoi,Vietnam.
2. Dr. Nguyen Minh Tue, Ehime University, Japan.
3. Prof. Dr. Tatsuya Kunisue, Ehime University, Japan.
Purposes:In our previous studies, informal e-waste recycling and end-of-life vehicle (ELV)
processing activities in northern Vietnam have been characterized as potential emission
sources of HFRs and OPFRs (Tue et al., 2013; Takahashi et al., 2017; Hoang et al., 2022).
Although human exposure and risk assessment of dust-bound flame retardants wereincluded in these studies, such estimations were drawn from the hypothesis that HFRsand OPFRs in dust are 100% bioaccessible. To avoid overestimation of potential risk,
evaluating bioaccessibility of FRs from dust is critically important. In this project,
concentrations and bioaccessibility of legacy and emerging FRs will be examined insettled dust samples collected from informal waste and vehicle processing workshops innorthern Vietnam by both chemically- and physiologically-based extraction methods,
followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) quantification.
To our knowledge, this is among the first studies to characterize the bioaccessibility of
HFRs and OPFRs related to informal processing of e-waste, plastic waste, and vehicles.
Methods:
Settled dust samples were collected from Bui Dau e-waste recycling areas (HungYen Province) and Thuyen ELV processing areas (Bac Giang Province), northernVietnam. Concentrations of HFRs and OPFRs in dust samples were determined by using
methods described elsewhere (Hoang et al., 2022a). In brief, the dust samples will be
extracted with hexane/acetone (1:1, v/v) mixture using a SE-100 solvent extractor(Mitsubishi Chemical Analytech, Japan). The extracts will be separated into 2 portionsfor HFR and OPFR analysis. The HFR portions will be spiked with 13C-labeledsurrogates, and cleaned up by using gel-permeation chromatography, solid-phaseextraction (SPE), and activated silica gel chromatography. The OPFR portions werespiked with 13C-labeled surrogates and purified by using appropriate SPE cartridges.
Before instrumental analysis, labeled internal standards will be added into clean
extracts to monitor surrogate recovery. HFRs were determined using a GC-MS/MS
system (7890A series and 7000 GC/MS Triple Quad; Agilent Technologies, USA) with an
Rtx-1614 column (15 m × 0.25 mm × 0.1 µm; Restek, USA). OPFRs were determinedusing the same GC-MS/MS instrument with a DB17-HT column (30 m × 0.25 mm × 0.15µm; Agilent Technologies, USA).
3 / 6

Ingestion bioaccessibility of HFRs and OPFRs in dust samples will be investigatedby using in vitro physiologically based extraction method with Tenax bead assisted
sorption (Fang and Stapleton, 2014). Bioaccessible concentrations of HFRs and OPFRs
in dust will be determined by incubation extracting the samples with simulated digestive
fluids (e.g., gastric, intestinal, and colon fluids) and assisted sorptive Tenax beds.
Combinationofchemically-andphysiologically-basedconcentrations

andphysiochemical properties can provide relevant information about bioaccessibility and“realistic” exposure risk of HFRs and OPFRs in dust. The validity and applicability of
the Tenax bead-assisted sorptive physiologically based method and influencing factors(e.g., nature of target compounds and dust matrices) in evaluating bioaccessibility of
HFRs and OPFRs will be also discussed.
Results:
Bioaccessibility of HFRs and OPEs in the waste processing dust samples ispresented in Fig. 1. The bioaccessibility of PBDEs and other HFRs was relatively low,
ranging from 0% to 14% without a clear difference between compounds. Our results werein good agreement with those reported by previous studies, showing low bioaccessibilityof hydrophobic FRs under different in vitro conditions (He et al., 2018; Wannomai et al.,2020). These values were markedly lower than those reported by some earlier works(Abdallah et al., 2012; Fang and Stapleton, 2014), probably due to the differences inextraction methods, dust particle sizes, and dust matrix properties. Bioaccessible
fractions of BDE-209 were higher in the ELV dust (3%–13%) than in the e-waste dust
(0.5%–0.9%), while the remaining HFRs showed higher bioaccessibility in the e-waste
dust. Lower bioaccessibility of almost HFRs in the ELV dust was largely due to theirlower total concentrations, resulting in bioaccessible levels lower than the MDLs.
Information about bioaccessibility of DPs is still limited. These CFRs were generally notbioaccessible in PBET experiments without Tenax absorption sink (He et al., 2018;
Wannomai et al., 2020). Higher bioaccessibility of syn-DP over anti-DP was observed inthe e-waste dust (median 6% and 3%) and the SRM 2585 dust (25% and 18%). Meanwhile,anti-DP exhibited higher bioaccessibility in the ELV dust (median 8%) than syn-DP(bioaccessible concentrations < MDLs), largely due to lower syn-DP concentrations in thewhole dust and the digestive phases.

4 / 6Fig. 1. Bioaccessibility of HFRs and OPEs in the ELV and e-waste dust samples.
Bioaccessibility of OPEs was generally higher than that of HFRs in our dust
samples. The median bioaccessible fractions were the highest for TCEP (66%; 25%–97%),
followed by tri-n-butyl phosphate (TNBP: 52%; 19%–100%), TDCIPP (37%; 0%–60%),and TCIPP (29%; 7%–84%). The remaining non-Cl-OPEs had quite lower bioaccessibility(0%–32%). Interestingly, bioaccessibility of non-Cl-OPEs was higher in the ELV dust
than in the e-waste dust, while bioaccessibility of Cl-OPEs was not significantly different
between the two areas. For examples, median bioaccessibility values of TNBP, TPHP,and tris(methylphenyl) phosphates (m- and p-TMPP) in the ELV dust were 68%, 24%,and 11%, respectively; while these values derived for the e-waste dust were only 24%,3%, and 3%. Unlike HFRs, bioaccessibility of OPEs in the SRM 2585 sample were within
the range measured in our waste processing dust samples. TCEP, TCIPP, TDCIPP, andTNBP also exhibited high bioaccessibility from dust in other in vitro studies (Fang andStapleton, 2014; He et al., 2018; Guo et al., 2019; Wannomai et al., 2020).
Conclusion:
Gastrointestinal bioaccessibility of various legacy and alternative flame retardants
and plasticizers was assessed in workplace dust samples from Vietnamese e-waste andELV processing sites by using Tenax-assisted physiologically-based extraction test. Ourresults are in good agreement with previous studies, showing higher bioaccessibility ofCl-OPEs (e.g., TCEP, TCIPP, and TDCIPP) and short-chain alkyl OPEs (e.g., TNBP)
compared to hydrophobic BFRs (e.g., PBDEs, HBBz, BTBPE, and DBDPE) and CFRs(e.g., DPs). Specific dust matrices containing large amounts of micronized plastics or oilymaterials can affect bioaccessibility of HFRs and OPEs, especially less polar substances.
Bioaccessible fractions of PBDEs, DPs, and non-Cl-OPEs were higher in the ELV dust
than e-waste dust, while bioaccessibility of polar Cl-OPEs did not show significant
difference between the two areas. Pollutants associated with plastic debris may be
hardly eluted and absorbed in gastrointestinal tract. In contrast, oily materials

5 / 6

containing OPEs or serving as extractant of dust may enhance mobility of HFRs andOPEs. Daily uptake doses of HFRs and OPEs in dust were estimated, indicating quite
low health risks for both e-waste and ELV workers. Additional investigations on
absorption behaviors and impacts of organic pollutants in workplace dust should beperformed for multiple chemical classes and exposure pathways with relevant extraction
methods.
Future challenges:
Comparison of human levels of OPEs and HFRs is still challenging, and otherexposure pathways (i.e., dietary and inhalation) and metabolism of these substances
should be considered. In addition, the variability of dust matrices, especially those withspecific compositions, and the discrepancies between their behavior in the dynamic
digestive system as compared to the static in vitro digestion tests remain as uncertainty
factors for the application of practical bioaccessibility values for risk assessment.
Publication:Anh Quoc Hoang, Nguyen Minh Tue, Akitoshi Goto, Ryogo Karyu, Le Huu Tuyen,
Pham Hung Viet, Hidenori Matsukami, Go Suzuki, Shin Takahashi, Tatsuya Kunisue.
Bioaccessibility of halogenated flame retardants and organophosphate esters in settled
dust: Influences of specific dust matrices from Vietnamese informal e-waste and end-oflife vehicle processing areas. Submitted to Science of the Total Environment (underreview).
References:
Abdallah, M.A.E., et al., 2012. http://doi.org/10.1039/c2em30690e.
Fang, M., Stapleton, H.M., 2014. https://doi.org/10.1021/es503918m.
Guo, H., et al., 2019. https://doi.org/10.1016/j.scitotenv.2018.09.340.
He, R.W., et al., 2018. https://doi.org/10.1016/j.envres.2017.12.014.
Hoang, A.Q., et al., 2022. https://doi.org/10.1016/j.envpol.2022.119809.
Takahashi, S., et al., 2017. https://doi.org/10.1007/s10163-016-0571-3.
Tue, N.M., et al., 2013. http://dx.doi.org/10.1016/j.envint.2012.11.006.
Wannomai, T., et al., 2020. https://doi.org/10.1016/j.chemosphere.2020.126632.

6 / 6