Spatial Variability of Flame Retardants in Indoor Dust
Simona Jilková
1, Lisa Melymuk
1, Šimon Vojta
1, Pernilla Bohlin Nizzetto
2, Martina Krátká
1, Jana Klánová
11Research Centre for Toxic Compounds in the Environment (RECETOX), Masaryk University, Kamenice 753/5, pavilon A29, 625 00 Brno, Czech Republic
2Norwegian Institute for Air Research, Instituttvein 18, PO Box 100, NO-2027, Kjeller, Norway E-mail contact: [email protected]
1. Introduction
Indoor dust is commonly used to evaluate levels of semivolatile organic compounds (SVOCs) indoors [1], and particularly for compounds with indoor sources, such as flame retardants (FRs). Yet there are many questions about the type of information that can be obtained from indoor dusts. Indoor dusts have been used to compare SVOC levels indoor environments [2], estimate human exposure to SVOCs via dust [3], infer SVOC air concentrations [4] and identify SVOC sources [5]. However, the utility of dust for any of these outcomes relies on assumptions about the dust, for example, that dust concentrations are relatively homogeneous within the indoor environment, or that dust is related to SVOC sources in close proximity.
However, there is conflicting evidence for all these assumptions. To address these questions, we use an indoor dust sampling campaign to assess within room variability in dust concentrations of FRs. We conducted floor and surface dust sampling to assess spatial variability in indoor dust concentrations and surface loadings, the relationship between FR sources and dust, and the influence of dust collection surface on concentrations and surface loadings. From this, we assess the utility of dust for source identification, for representing overall room concentrations, and for evaluating exposure, and describe what assumptions or practices in dust collection must be used to achieve these outcomes.
2. Materials and methods
In one residential living/dining room/kitchen 18 individual samples were collected, representing a range of surfaces in the room, including carpet, hardwood floor, furniture and electronic surfaces, and windows. For elevated surfaces (tables, windows, electronics, hard furniture) samples were collected by wiping the surface with a kimwipe moistened with reagent grade 2-propanol. For the floor surfaces and couch, dust samples were collected by a nylon sock inserted in the intake tube of a household vacuum cleaner.
Samples were analyzed for 10 PBDEs and 18 novel halogenated flame retardants (NFRs). The specific compounds were BDE-28, 47, 66, 85, 99, 100, 153, 154, 183, 209, 2,4,6-tribromophenyl allyl ether (TBP- AE), 2-bromoallyl-2,4,6-tribromophenylether (TBP-BAE), 2,3-dibromopropyl-2,4,6-tribromophenylether (TBP- DBPE), 2,3,5,6-tetrabromo-p-xylene (TBX), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), hexabromobenzene (HBB), hexachlorocyclopentenyldibromocyclooctane (DBHCTD), 2-ethylhexyl-2,3,4,5- tetrabromobenzoate (EH-TBB), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), Dechlorane Plus (DDC-CO), bis(2-ethylhexyl)tetrabromophthalate (BEH-TEBP), decabromodiphenylethane (DBDPE), tetrabromoethyl- cyclohexane (DBE-DBCH), 1,2,5,6-tetrabromocyclooctane (TBCO), 1,2,3,4,5-pentabromobenzene (PBBZ), 3,4,5,6-tetrabromo-2-chlorotoluene (TBCT), and pentabromobenzyl acrylate (PBBA). Sampling, sample processing are analysis procedures are published elsewhere [6].
3. Results and discussion
3.1. Concentrations and surface loadings
Concentrations of Σ10PBDEs ranged from 53.8 to 620 ng/g, and all individual congeners were detected in all samples. Surface loadings ranged from 0.575 to 278 ng/m2. BDE-209 was by far the dominant compound in the dust, comprising 43 to 97% of Σ10PBDEs. However this distribution also had a distinct spatial profile. The contribution of BDE-209 in floor dust was consistently higher than on elevated surfaces (furniture, tables, cupboards, windows), with BDE-209 making up 83-97% of Σ10PBDEs, while on surfaces only 26-87%.
Of the 18 targeted NFRs, eight were below detection in all samples (TBP-BAE, TBX, DDC-CO-MA, TBP- DBPE, TBCO, TBCT and PBBA). Concentrations were dominated by BEH-TEBP, syn- and anti-DDC-CO, and α- and β-DBE-DBCH. Σ15NFR concentrations were 75.9-884 ng/g, and surface loadings were 0.807-685 ng/m2.
3.2. Spatial distribution of PBDEs and NFRs
We examined the hypothesis that the electronics (TV, DVD player, satellite box) may be the primary source of BDE-209 in the room by examining the contribution of BDE-209 to Σ10PBDEs as a function of distance from the possible source. In the furniture surface samples, no relationship was apparent (Figure 1a), but an examination of the relative contribution to floor dust suggested a strong correlation between fraction of BDE- 209 in the floor dust and distance from the TV unit (Figure 1b).
For NFRs we tested the hypothesis that the polyurethane foam (PUF) furniture, in this case the couch, was the source of BEH-TEBP, one of the components of Firemaster 550, known to be used in PUF furniture. In this case the spatial correlations were weaker, but there was a significant relationship between distance from couch and furniture surface fraction of BEH-TEBP (R2=0.46, p<0.02). No correlation was found for floor dust.
The difference in the relationship with floor dust for BDE-209 and surface dust for BEH-TEBP may be due to the primary release mechanism of each compound, e.g., direct abrasion of material for BDE-209 and volatilization for BEH-TEBP.
(a) (b)
Figure 1: Distance from TV unit vs. fraction of BDE-209 in dust for (a) furniture surfaces and (b) floor dust.
4. Conclusions
The spatial distribution of PBDEs and NFRs in a residential environment had strong spatial variability related to proximity to sources, surface properties, and dust surface loadings. This case study suggested that spatial distributions of FRs in indoor dust can be used as a source identification technique, but that the appropriate matrix (e.g., floor dust vs. furniture surface dust) may depend on the expected release pathway of the compound in question. More information on the relationship between sources and the spatial distribution of FRs in indoor dust is needed.
5. References
[1] Lioy PJ, Freeman NCG, Millette JR. 2002. Dust: A Metric for Use in Residential and Building Exposure Assessment and Source Characterization. Environ. Health Perspect. 110:969–983.
[2] Harrad SJ, Ibarra C, Diamond ML, Melymuk L, Robson M, Douwes J, Roosens L, Dirtu AC, Covaci A.
2008. Polybrominated diphenyl ethers in domestic indoor dust from Canada, New Zealand, United Kingdom and United States. Environ. Int. 34:232–8.
[3] Abdallah MA-E, Harrad SJ, Covaci A. 2008. Hexabromocyclododecanes and tetrabromobisphenol-A in indoor air and dust in Birmingham: implications for human exposure. Environ. Sci. Technol. 42:6855–61.
[4] Weschler CJ, Nazaroff WW. 2010. SVOC partitioning between the gas phase and settled dust indoors.
Atmos. Environ. 44:3609–3620.
[5] Wang J, Tian M, Chen S-J, Zheng J, Luo X-J, An T-C, Mai B-X. 2011. Dechlorane Plus in house dust from e-waste recycling and urban areas in South China: sources, degradation, and human exposure.
Environ. Toxicol. Chem. 30:1965–72.
[6] Melymuk L, Bohlin P, Vojta Š, Krátká M, Klánová J. 2014. Distribution of legacy and emerging semi- volatile organic contaminants in a residential environment. Indoor Air. International Society of Indoor Air Quality and Climate, Hong Kong, July 7-14, ID 567 [Platform Presentation].
Acknowledgements - The authors thank Roman Prokeš for sampling assistance. This work was supported by the European Social Fund and the Czech state budget ("Employment of Best Young Scientists for
International Cooperation Empowerment" CZ.1.07/2.3.00/30.0037 and "Employment of Newly Graduated Doctors of Science for Scientific Excellence" CZ.1.07/2.3.00/30.009). RECETOX infrastructure was supported by the Czech Ministry of Education (LM2011028 and LO1214).
0 0.2 0.4 0.6 0.8 1
0 1 2 3 4 5 6
Fraction BDE-209
Distance from electronics (m)
y = -0.042x + 1.0 R² = 0.92
p<0.001
0.8 0.85 0.9 0.95 1
0 1 2 3 4 5
Fraction BDE-209
Distance from electronics (m)
