Environ. Sci. Technol. 2001, 35, 1078-1083
Concentrations and Spatial Variations of Polybrominated Diphenyl Ethers and Other Organohalogen Compounds in Great Lakes Air BO STRANDBERG, NATHAN G. DODDER, ILORA BASU, AND RONALD A. HITES* Environmental Science Research Center, School of Public and Environmental Affairs, and Department of Chemistry, Indiana University, Indiana 47405
Air samples were analyzed from urban, rural, and remote sites near the Great Lakes to investigate the occurrence, concentrations, and spatial and temporal differences of polybrominated diphenyl ethers (PBDE) in air. The concentrations of PBDEs were compared to those of other organohalogen compounds such as PCBs and organochlorine pesticides. The samples were collected in 1997-1999 as part of the Integrated Atmospheric Deposition Network (IADN). To minimize the variability of the data, we selected only samples taken when the atmospheric temperature was 20 ( 3 °C. PBDEs were found in all samples, indicating that these compounds are widely distributed and that they can be transported through the atmosphere to remote areas. The total concentrations of PBDEs were similar to some of the organochlorine pesticides such as ΣDDT and ranged from 5 pg/m3 near Lake Superior to about 52 pg/m3 in Chicago. In fact, the spatial trend was well correlated to those of PCBs. Our results indicate a relatively constant level from mid-1997 to mid-1999. At 20 ( 3 °C, about 80% of the tetrabromo homologues are in the gas phase and about 70% of the hexabromo homologues are associated with the particle phase. Thus, particle-to-gas partitioning in the atmosphere is an important process for these compounds.
Introduction Polybrominated diphenyl ethers (PBDEs) are flame retardants, which are added to a variety of materials. These compounds are widely used in electronic appliances, paints, and textiles to prevent the propagation of fire. Despite the chemical similarity of PBDEs to PCBs, the use of PBDE is not regulated. Toxicological data for PBDE are limited. Three investigations have shown that PBDEs may cause cytochrome P450 induction (1), decreased spawning success in sticklebacks, Gasterosteus aculeatus (2), and intragenic recombination in mammalian cells (3). The individual PBDE congeners are given numbers using the same numbering system used for PCBs (4). The annual global production of PBDEs was estimated to be 40 000 tons in 1992 (4). They are marketed as three technical mixtures, each with varying degrees of bromination; * Corresponding author:
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these products are known as “pentabromodiphenyl ether”, “octabromodiphenyl ether”, and “decabromodiphenyl ether” (5). Each of these products consists of a mixture of PBDE congeners; however, the PBDE mixtures are much simpler than commercially produced polychlorinated biphenyl (PCB) mixtures. PBDE can enter the environment during production and migrate from the treated products. Given the high rate of production, the lack of regulations, and their persistence to environmental degradation, PBDEs are now ubiquitous environmental pollutants. Even though “decabromodiphenyl ether” (primarily BDE-209) constitutes about 75% of the world’s production of PBDEs, environmental patterns often resemble those of the “pentabromodiphenyl ether” product, which consists of about 35% of the tetrabromo isomer BDE-47, 37% and 7% of the penta isomers BDE-99 and BDE-100, respectively, and some small amounts of the hexa isomers BDE-153 and BDE-154. PBDEs were first reported in the environment in soil and sludge from the United States in 1979 (6) and in fish from Sweden in 1981 (7). Since then, PBDEs have been found in a variety of environmental samples, including fish (7-11), birds (12), sediments (13-15), air (16-19), marine mammals (10), human blood (20), and human milk (21). The levels of PCB and DDT in most of these types of samples have been decreasing, but the levels of PBDEs have been increasing; for example, in Swedish human milk, PBDE concentrations have increased exponentially from 1972 to 1997 with a doubling time of about 5 years (21). Studies of guillemot eggs (22) and sediment (23) from the Baltic Sea also show an increasing trend from the early 1970s to the late 1980s. These latter studies indicate, however, a leveling off of PBDE levels in the 1990s. Although the majority of these reports are from Europe, there are a few reports on the presence of PBDE in the North American environment; for example, they have been found in fish from the Buffalo River, New York, (9) and from the Great Lakes (24). There are few studies on the concentrations and distribution of PBDEs in air. PBDEs have been found in airborne dust sampled near Osaka, Japan (17), and in air from Taiwan and Japan collected near metal recycling plants (16). Indoor dust and air collected from work environments in Sweden also contains PBDEs (18). With two exceptions (19, 25), there are no reports on the background air concentrations on these compounds. The aim of this paper is to study the concentrations and spatial distribution of PBDE in air sampled near the Great Lakes in order to investigate possible sources of contamination. These results are compared to those of PCBs and organochlorine pesticides. Temporal trends and particleto-gas partitioning processes are also discussed.
Experimental Section Sampling Sites and Sampling Techniques. Figure 1 shows the locations of the four sampling sites used in this study. These same sampling sites are also used by the Integrated Atmospheric Deposition Network (26, 27). The stations were located as follows: an urban sampling site on the south side of downtown Chicago, IL, approximately 1.6 km from the shore of Lake Michigan; two rural locations, one at Sleeping Bear Dunes, MI, on the northeast coast of Lake Michigan about 3 km from the shore and one at Sturgeon Point, NY, located about 50 m from the shore of Lake Erie and about 30 km southwest of Buffalo; and a remote site at Eagle Harbor, MI, on the Keweenaw Peninsula about 50 m from the shore of Lake Superior. The greater Chicago urban area is generally considered as a source of contaminants to the lake’s coastal atmosphere (27). Moreover, there are several plastic industries 10.1021/es001819f CCC: $20.00
2001 American Chemical Society Published on Web 02/16/2001
FIGURE 1. Sampling locations in the Great Lakes region. in this area that reportedly are using the “decabromodiphenyl ether” product (28). All other sites were assumed to be representative of the atmospheric environment close to the Great Lakes and to be distant from local sources of contamination. Details of the sampling procedures for the air samples are given elsewhere (29, 30). In short, air samples were taken every 12 days for 24 h at each site using a high-volume air sampler equipped with a quartz fiber filter and an adsorbent (XAD-2) to collect the particle- and gas-phase compounds, respectively. The air was pulled through this device at a rate giving an 820-m3 sample in 24 h. It is known that the largest source of variability in the atmospheric concentrations of semivolatile compounds, such as those discussed in this paper, is related to atmospheric temperature (27). Therefore, to minimize the variability of the data, we selected only samples taken when the average air temperature was 20 ( 3 °C. In this study, four samples from each sampling site from late May through early October in the three years, 19971999, were selected. This was a total of 48 samples. Cleanup Procedures and Chemical Analysis. A summary of the sample enrichment process and the PCB and organochlorine pesticide analysis is presented here; full details are given elsewhere (26, 29, 30). The filters and adsorbents were Soxhlet-extracted for 24 h with 50% acetone in hexane. Prior to extraction, a recovery standard (consisting of PCBs #14, 65, and 166, δ-hexachlorocyclohexane, and dibutylchlorendate) was spiked into the samples. The extract was reduced in volume by rotary evaporation, solvent exchanged into hexane, and then fractionated on a column containing 3.5% w/w water-deactivated silica gel using 25 mL of hexane (fraction 1) and 25 mL of 50% dichloromethane in hexane (fraction 2). PCBs, hexachlorobenzene (HCB), trans-nonachlor, and p,p′-DDE eluted in the first fraction, and the remaining pesticides and all of the PBDEs eluted in the second fraction. The final extracts were concentrated under a gentle stream of N2 to a volume of 1 mL and spiked with a surrogate standard containing PCB-30 and PCB-204 (fraction 1) and PCB-65 and PCB-155 (fraction 2). An aliquot was taken for the PCB and pesticide analysis. The excess solvent of the remaining fraction 2 was evaporated by N2 to a final volume of about 25 µL for the PBDE analysis. PCBs and pesticides were analyzed on a Hewlett-Packard (HP) 5890 gas chromatograph (GC) equipped with an 63Ni electron capture detector (ECD) in splitless injection mode. The GC column was a fused silica capillary coated with DB-5 (60-m × 250-µm i.d.; 0.10-µm film thickness; J&W Scientific, Folsom, CA). The temperature of the GC oven was programmed as follows: isothermal at 100 °C for 1 min, 1 °C/ min to 240 °C, 10 °C/min to 280 °C, and held at 280 °C for 20 min. PBDEs were analyzed by gas-chromatographic mass spectrometry (GC/MS) on a HP 6890 series GC connected to a HP 5973 MS. This instrument was operated in the electron impact (EI) or in the electron capture negative ionization
(ECNI) modes with selected-ion monitoring (SIM). ECNI was used to quantitate decabromodiphenyl ether (BDE-209); all other PBDEs were analyzed by EI. The GC column, which was used for the tetra- through heptabrominated PBDEs, was a fused silica capillary tube coated with DB-5-MS (30-m × 250-µm i.d.; 0.25-µm film thickness; J&W Scientific, Folsom, CA). The temperature of the GC oven was programmed as follows: isothermal at 110 °C for 1 min, 15 °C/min to 180 °C, 2 °C/min to 270 °C, 0.50 °C/min to 275 °C, and held at 275 °C for 10 min. BDE-209 was analyzed on a shorter DB-5-MS column (15-m × 250-µm i.d.; 0.25-µm film thickness; J&W Scientific, Folsom, CA) with the following temperature program: 110 °C for 1 min, 15 °C/min to 300 °C, and held at 300 °C for 17 min. The following ions (m/z) were used to monitor PBDE compounds in the EI mode; tetra-Br, 325.9 and 485.7; penta-Br, 403.8 and 405.8; hexa-Br, 481.7 and 483.7; and hepta-Br, 561.6 and 563.6. In the ECNI mode, the two bromide ions at m/z 79 and 81 were used for maximum sensitivity. The compounds analyzed are summarized in Table 1. The ΣPCB data are given as the sum of 105 di- through decachlorinated PCB congeners. The chlordane-related compound concentrations are given as the sum of the three most abundant components of technical chlordane (namely, cis- and trans-chlordane and trans-nonachlor) and of the two chlordane transformation products (namely, cis-heptachlorepoxide and oxychlordane). The ΣDDT related compound concentrations are given as the sum of the concentrations of o,p′- and p,p′-DDD, DDE, and DDT. The endosulfan concentrations are given as the sum of endosulfan I and II (which constitute the technical mixture) and their metabolite, endosulfan sulfate. The ΣHCH concentrations are given as the sum of the R- and γ-hexachlorocyclohexane isomers. The PBDE compounds investigated in this study are 2,2′,4,4′-BDE (BDE-47), 2,2′,4,4′,5-BDE (BDE-99), 2,2′,4,4′,6BDE (BDE-100), 2,2′,4,4′,5,5′-BDE (BDE-153), 2,2′,4,4′,5,6′BDE (BDE-154), 2,3,3′,4,4′,5,6-BDE (BDE-190) (from Cambridge Isotope Laboratories), and 2,2′,3,3′,4,4′,5,5′,6,6′-BDE (BDE-209). The standard for BDE-209 was made from the technical product DE-83, which is more than 98% BDE-209. Identifications of all of these compounds were confirmed, and concentrations were measured using an external quantification standard having known amounts of all the target compounds and using recovery and surrogate standard mixtures. Quality control criteria for positive identification of the target compounds for both ECD and MS were as follows: (a) The signal-to-noise ratio should be greater than 3. (b) The compounds should elute at the same GC retention time (( 0.01 min) as the standard compounds. (c) The internal standard recoveries should be between 50% and 120%. Furthermore, for the MS runs, the isotope ratios of the two ions monitored for each compound should be within (15% of the theoretical value. Our measured internal standard recoveries were 85-110% for all samples, and the concentrations of analytes were not corrected for recovery. Field and laboratory blank experiments were also performed. These blanks always contained less than 15% of the analyte masses measured in the samples; therefore, blank corrections were not needed. On two occasions, two high-volume samplers were operated simultaneously at the same sampling site to collect duplicate samples. The analytical repeatability of the method was also checked by splitting the adsorbent for nine of the samples into two individual samples, which then were processed in parallel through the analytical procedure. The BDE-209 analyses include a number of analytical difficulties (31). The results from spike experiments of our PBDE standards show that the recoveries were close to 100% for all compounds except for BDE-209, which was lower (5575%). There is some evidence to suggest that BDE-209 may VOL. 35, NO. 6, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Average Concentrations (in pg/m3) of Organohalogen Contaminants in Air Samples near the Great Lakes in 1997-1999 Eagle Harbor
BDE-47 BDE-99 BDE-100 BDE-153 BDE-154 BDE-190 BDE-209 ΣPBDEs ΣHCHs HCB ΣDDTs Σchlordanes Σendosulfans dieldrin total pest. ΣPCBs
Sturgeon Point
1997 (n ) 4)
% std error
1998 (n ) 4)
% std error
1999 (n ) 4)
% std error
avg (all years)
% std error
2.1 1.8 0.24 0.10 0.071
