Article pubs.acs.org/est
Bromobenzene Flame Retardants in the Great Lakes Atmosphere Marta Venier, Yuning Ma, and Ronald A. Hites* School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405, United States S Supporting Information *
ABSTRACT: Seven bromobenzene flame retardants were measured in vaporphase samples collected at five sites, all near the shores of the North American Great Lakes during 2008−2009, inclusive. The target compounds were hexabromobenzene (HBB), pentabromobenzene (PBBz), pentabromotoluene (PBT), pentabromobenzylacrylate (PBBA), pentabromobenzyl bromide (PBBB), tetrabromo-p-xylene (pTBX), and pentabromoethyl benzene (PBEB). Detection frequencies were, on average, higher than 50% for all of the compounds, with the exception of PBBA, which was detected only in 22% of all the samples. Considering all the sampling sites together, HBB showed the highest average concentration (4.6 ± 1.0 pg/m3), followed by PBBB (3.3 ± 0.5 pg/m3) and PBEB (1.0 ± 0.1 pg/m3). The concentrations of these compounds were generally significantly correlated with one another, with the exception of PBBA, which was correlated only to PBBB. The atmospheric concentrations of PBT, pTBX, PBBB, and PBBA tracked local human population density, suggesting that these compounds are or were used in a variety of commercial products. Unexpectedly, the concentration of PBEB was highest at the remote site of Eagle Harbor in northern Michigan, whereas that of HBB was highest at Sturgeon Point, ∼25 km southwest of Buffalo, New York. The lack of dependence of these two compounds’ concentrations on human population suggests local point sources.
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concentration of about 2 pg/m3, and it is now clear that DBDPE is a worldwide contaminant.3,4 An increasing number of alternative BFRs have been identified in the environment with increasing frequency and as an increasing fraction of the total BFR load.3,5 While there have been improvements in the analytical methodologies and in the availability of standard compounds, these factors alone cannot explain the recent findings. Some of these compounds are BFR alternatives, the presence of which in the environment can be explained. However, it is much more difficult to rationalize the environmental presence of some other compounds, such as those that have been taken out of production or those that have not been discussed in the literature at all. These compounds include those that are generally described as bromobenzenes monocyclic aromatic compounds variously substituted with bromine atoms and/or with small alkyl groups. These monocyclic compounds are the subject of this paper. Seven bromobenzenes are commonly detected in the environment: Hexabromobenzene (HBB) was heavily used in Japan as an additive flame retardant; its uses have included paper, wood, textiles, electronics, and plastic goods.6 There is no information on the U.S. market, but it is currently being produced in China (by the Hangzhou Dayangchem and
INTRODUCTION
Brominated flame retardants (BFRs) have been used in a variety of commercial products around the world to minimize the spread of fires in homes and in commercial space. Until recently, the most widely used BFRs were the polybrominated diphenylethers (PBDEs), but over the last several years, the flame retardant industry has voluntarily withdrawn some of these compounds from the market. This action was a response to concerns from the scientific community about the effects of these compounds on the environment and on people. Given that regulations mandating the use of flame retardants have not changed, the BFR industry has replaced the withdrawn brominated diphenyl ethers with unregulated alternative flame retardants. For example, the penta-BDE commercial mixture was replaced predominantly by Firemaster 550, which is composed of 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), di(2-ethylhexyl) tetrabromophthalate (TBPH), and two phosphorus-based compounds.1 In fact, these alternative, unregulated flame retardants have now been detected in the environment at levels that are increasing over time.1 Another example of this industry’s cycling between banned and unregulated compounds is decabromodiphenyl ethane (DBDPE), which was introduced into the market as an alternative to decabromodiphenyl ether (deca-BDE or BDE-209). The latter compound was banned by the European Union in 2008 and will be phased out completely by the end of 2013 in the United States.2 DBDPE has now been detected in air samples from around the Great Lakes at a median © 2012 American Chemical Society
Received: Revised: Accepted: Published: 8653
April 23, 2012 July 3, 2012 July 5, 2012 July 31, 2012 dx.doi.org/10.1021/es3015919 | Environ. Sci. Technol. 2012, 46, 8653−8660
Environmental Science & Technology
Article
Table 1. Descriptive Statistics and Concentrations (in pg/m3) of the Target Compoundsa site
N
detection frequency (%)
mean
std err
minimum
maximum
median
0.13 0.017 0.11 0.08 3.0 1.0
0.099 0.021 0.073 0.023 0.34 0.021
4.5 0.37 2.8 1.5 97.2 97.2
0.33 0.037 0.22 0.18 7.79 0.39
0.15 0.004 0.09 0.015 0.06 0.06
0.052 0.012 0.025 0.012 0.013 0.012
6.8 0.05 2.3 0.22 1.6 6.8
0.34 0.025 0.12 0.061 0.086 0.12
0.08 0.4 0.15 0.011 0.06 0.1
0.13 0.26 0.049 0.012 0.013 0.012
3.5 20.8 4.6 0.12 1.9 20.8
0.73 1.2 0.51 0.045 0.086 0.60
0.03 0.014 0.07 0.017 0.09 0.03
0.033 0.012 0.018 0.025 0.012 0.012
0.92 0.26 1.6 0.34 3.0 3.0
0.22 0.025 0.11 0.073 0.14 0.12
0.9 0.17 2.3 0.2 0.6 0.5
0.071 0.036 0.18 0.047 0.053 0.036
23.8 4.3 82.4 7.1 20.8 20.8
2.8 0.18 2.2 0.45 1.2 1.0
0.17 0.02 0.09 0.04 0.3 0.07
0.13 0.023 0.039 0.023 0.021 0.021
6.3 0.72 3.8 1.4 10.5 10.5
0.57 0.057 0.31 0.11 0.47 0.23
0. 7 0.02 1.4 0.29 0.10 0.29
0.052 0.012 0.35 0.025 0.056 0.012
10.3 0.20 12.7 2.8 1.3 12.7
0.28 0.092 0.67 0.45 0.26 0.29
HBB CH EH CL SB SP all
55 60 49 47 54 265
75 45 61 45 93 64
CH EH CL SB SP all
55 60 49 47 54 265
91 22 67 38 63 56
CH EH CL SB SP all
55 60 49 47 54 265
96 98 82 21 57 72
CH EH CL SB SP All
55 60 49 47 54 265
75 37 43 43 65 52
CH EH CL SB SP all
55 60 49 47 54 265
76 65 76 72 70 72
CH EH CL SB SP all
55 60 49 47 54 265
80 75 84 77 78 78
CH EH CL SB SP all
55 60 49 47 54 265
27 13 18 21 28 22
0.65 0.084 0.46 0.33 14.5 4.6 PBT 0.68 0.027 0.30 0.078 0.23 0.36 PBEB 0.82 2.0 0.85 0.058 0.20 1.0 pTBX 0.27 0.054 0.23 0.093 0.27 0.21 PBBB 5.4 0.63 6.6 1.0 2.6 3.3 PBBz 0.88 0.12 0.44 0.18 1.0 0.53 PBBA 1.0 0.11 2.6 0.80 0.41 0.93
a
Abbreviations for the sites are Chicago (CH), Eagle Harbor (EH), Cleveland (CL), Sleeping Bear Dunes (SB), and Sturgeon Point (SP). All represents all sampling sites taken together. N is the number of samples analyzed. Detection frequency is number of samples (given as a % of N) that showed concentrations of a given compound above the minimum concentration (given in the sixth column). Mean is the arithmetic average of the detected concentrations, and std err is the standard error of that mean. Median is the median of those concentrations.
it is distributed by Ameribrom, a subsidiary of Dead Sea Bromine
Shenyang Meiyao Chemical companies) and in Japan (as Plasafety HBB by the Manac company and as FR-B by the Nippoh Chemicals Corporation). Pentabromotoluene (PBT) has been used as a flame retardant in polyester and other polymers, latex, textiles, and rubber.7 Gauthier et al. have reported that PBT is currently used in the United States and that
group (ICL Industrial Products, Israel) with the trade name of FR-105.8 Pentabromoethylbenzene (PBEB) is an additive flame retardant used in thermoset polyester resins for applications such as circuit boards, textiles, adhesives, and wire and cable coatings.6 8654
dx.doi.org/10.1021/es3015919 | Environ. Sci. Technol. 2012, 46, 8653−8660
Environmental Science & Technology
Article
carrier gas was helium (99.999%; Liquid Carbonic, Chicago) at a constant flow of 1.5 mL/min. The following GC oven temperature program was used: 100 °C for 2 min, 10 °C/min to 180 °C, 3 °C/min to 270 °C, 25 °C/min to 300 °C, and 300 °C for 6 min. The total run time was 47.2 min. This run time was necessary to separate PBBB, PBBA, and PBT. The GC/MS transfer line was maintained at 280 °C. All compounds were quantitated with the internal standard method using BDE-118 (AccuStandard, New Haven, CT) as the internal standard. Full scan mass spectra for all the compounds were obtained, both in the electron impact (EI) and in the ECNI modes. These spectra showed that ions at m/z 79 and 81 (Br−) were the most abundant ions in the ECNI mode for all of the compounds, and thus, these ions were used for selected ion monitoring. The chromatogram of the standard sample of PBBB contained two different GC peaks in a ratio of 2:1. The larger peak had a full scan mass spectrum compatible with that of PBBB, and the smaller peak had a mass spectrum and GC retention time compatible with that of PBT. Note that PBBB is a brominated homologue of PBT. In this standard sample mixture, the larger peak was used for quantitation of PBBB; we did not detect any interferences from other compounds. Because, there are very limited data on PBBB and PBBA in the environment,12,13 and because this is the first report of these compounds in atmosphere, their full scan mass spectra are reported in the Supporting Information (see Figure S1). Quality Control and Assurance. The recovery standards were BDE-77, BDE-166, and 13C12−BDE-209 (Wellington Laboratories, Guelph, ON). The recovery of at least two out of these three standards was between 70% and 130%. Either a procedural blank or a matrix spike recovery sample was run with every batch of 6−8 samples. Field blanks were collected at every site seasonally. PBT, PBEB, PBBB, and PBBA were never detected in the field blanks. For HBB, pTBX and PBBz, if concentrations were
