Environ. Sci. Technol. 2008, 42, 1452–1457
Antarctic Research Bases: Local Sources of Polybrominated Diphenyl Ether (PBDE) Flame Retardants R O B E R T C . H A L E , * ,† S T A C Y L . K I M , ‡ ELLEN HARVEY,† MARK J. LA GUARDIA,† T. MATT MAINOR,† ELIZABETH O. BUSH,† AND ELIZABETH M. JACOBS† Department of Environmental & Aquatic Animal Health, Virginia Institute of Marine Science, P.O. Box 1346, Gloucester Point, Virginia 23062, and Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California 95039
Received October 8, 2007. Revised manuscript received November 26, 2007. Accepted December 19, 2007.
Contemporary studies of chemical contamination in Antarctica commonly focus on remnants of historical local releases or longrange transport of legacy pollutants. To protect the continent’s pristine status, the Antarctic Treaty’s Protocol on Environmental Protection prohibits importation of persistent organic pollutants. However, some polybrominated diphenyl ether (PBDE) congeners exhibit similar properties. Many modern polymer-containing products, e.g., home/office furnishings and electronics, contain percent levels of flame retardant PBDEs. PBDE concentrations in indoor dust and wastewater sludge from the U.S. McMurdo and New Zealand-operated Scott Antarctic research bases were high. Levels tracked those in sludge and dust from their respective host countries. BDE-209, the major constituent in the commercial deca-PBDE product, was the dominant congener in sludge and dust, as well as aquatic sediments collected near the McMurdo wastewater outfall. The pattern and level of BDE-209 sediment concentrations, in conjunction with its limited environmental mobility, suggest inputs from local sources. PBDE concentrations in fish and invertebrates near the McMurdo outfall rivaled those in urbanized areas of North America and generally decreased with distance. The data indicate that reliance on wastewater maceration alone, as stipulated by the Protocol, may permit entry of substantial amounts of PBDEs and other chemicals to the Antarctic environment.
Introduction Antarctica remains largely pristine, sheltered from extensive human intrusion by its remote location and extreme climate. Nonetheless, past military, exploratory, and scientific activities have resulted in significant contamination of some adjacent areas (1, 2). The continent also faces escalating pressures related to increasing visitation by tourists and scientists. Antarctic research activities are international in scope, with up to 4000 individuals from 26 countries occupying 82 bases in the summer (3). To protect Antarctica, international agreements have been developed, most notably the Protocol on Environmental Protection to the Antarctic * Corresponding author fax: (804) 684-7186; e-mail:
[email protected]. † Virginia Institute of Marine Science. ‡ Moss Landing Marine Laboratories. 1452
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Treaty (4). The Protocol was written in 1991, but did not come into effect until 1998. As a result of Antarctica’s designation as a Special Conservation Area, facilities and practices have been improved and importation of specific persistent organic pollutants (POPs) has been prohibited. However, the bulk of research in Antarctica remains on longrange atmospheric transport processes and fate of legacy POPs (5). Although such pollutants are a concern, it has become apparent that additional chemicals in current usage may trigger effects by previously unappreciated mechanisms, e.g., endocrine disruption. This argues that the list of chemicals under study in Antarctica should be expanded and local sources periodically evaluated. Some of these chemicals are used conspicuously on a daily basis in homes and workplaces, including pharmaceuticals, fragrances, and cleaners. Others occupy more cryptic niches, e.g., polymer additives in furniture and electronics, including polybrominated diphenyl ether (PBDE) flame retardants. Traditionally, pollution has been associated with industrial scale activities, but many emerging contaminants are present in homes and offices. Thus, they may surface in domestic wastewater effluents (6). Their ecological consequences are uncertain. Similar to legacy POPs, some PBDE congeners exhibit substantial environmental half-lives and bioaccumulation potentials (7). PBDEs bear a striking structural similarity to thyroxine. This suggests possible interference with early neurodevelopment, an outcome supported by recent laboratory studies (8). In some locales, PBDE levels in wildlife and humans now surpass legacy POPs, such as PCBs (9). Low microgram per kilogram concentrations, consistent with long-range atmospheric transport, have recently been reported in Antarctic wildlife (10). Three commercial PBDE mixtures (penta-, octa-, and deca-), varying in their degree of bromination, are incorporated in polyurethane foams, thermoplastics, and latex back coatings (7). Therein, they may constitute several percent of the polymer’s weight. Commercial use of PBDEs began in the late 1970s. It had previously been assumed that these nonreactive additives were retained in the polymer. However, recent studies reveal that a portion of the PBDEs may escape and accumulate in indoor dust and air (11, 12). These contribute to human exposure and ultimately enter the outdoor environment (13). Escalating PBDE levels in human breast milk have been a particular concern, considering their neurodevelopmental toxicity and the propensity for young children to ingest dust (13, 14). Due in large part to environmental concerns, production of the penta- and octaPBDE formulations ceased in the European Union and North America in 2004 (12). However, deca-PBDE remains a global, high-production-volume flame retardant. Regardless of regulations, the presence of large PBDE stores in existing, long-lived polymer products and electronics ensures that emissions will continue for years. The major sources and pathways of PBDEs to the environment have been uncertain. Substantial burdens have been observed in indoor dusts, as well as wastewater sludges and aquatic biota in areas receiving discharges from plastics or textile manufacturing. No data are available on PBDE burdens in dust or wastewater sludge associated with Antarctic research bases. As no plastics or PBDE manufacturing occurs in Antarctica, any substantial indoor PBDE residues likely originate from losses from imported flameretarded plastic and electronic products. Research bases contain a high density of electronics, space is at a premium, and transport of materials to Antarctica is expensive. Fire concerns are amplified by the dry, hostile weather conditions. 10.1021/es702547a CCC: $40.75
2008 American Chemical Society
Published on Web 01/23/2008
FIGURE 1. Map of Antarctica, depicting the Ross Sea, McMurdo Sound, and sampling sites associated with the McMurdo and Scott research bases. Terra Nova, the location of a recent Italian PBDE study (10), is approximately 200 km north of McMurdo. These factors may enhance indoor PBDE levels and human exposure. To determine whether indoor dust and wastewater sludge from Antarctic research bases contain substantial burdens of PBDEs, we obtained samples from the large U.S. McMurdo and the smaller New Zealand-operated Scott station. To establish whether PBDEs have been released locally, we collected and analyzed surficial sediments and aquatic biota from sites at varying distances from McMurdo.
Materials and Methods Sampling. McMurdo is the largest research base in Antarctica, home to up to 1200 personnel in summer. Its extended aeration-based wastewater treatment plant, with a capacity of 400 000 L/day, became operational in early 2003. Scott base is 3 km away and houses up to 86. Its fixed-film aerated media treatment plant capacity is 17 000 L/day and was commissioned in late 2002. Winter populations are much lower. Both bases are located on Ross Island (Figure 1). Wastewater sludge and indoor dust were obtained from McMurdo in 2005 and from Scott in 2006. Dust was collected with household vacuums from living quarters. A variety of marine biota (rock cod (Trematomus bernacchii), clams (Laternula elliptica), sea stars (Odontaster validus), sea urchins (Sterechinus neumayeri), sponges (Haliclona sp and Homaxinella balfourensis), proboscis worms (Parborlasia corrugatus)) and surficial aquatic sediments were obtained from October to December 2003 from 11 sites at varying distances from the McMurdo wastewater outfall (Figure 1). A wastewater effluent, immediately prior to discharge, was also obtained from McMurdo in late 2003. Samples were collected in precleaned glass jars and frozen until analyzed. Sample Preparation and Analysis. Sediment and dust were sieved to BDE-100 > BDE-153 ∼ BDE-154) commercial products. Total PBDE concentrations (dry weight basis) are provided in the legend. in the case of the effluent, to monitor for potential introduction of laboratory contaminants. Target analytes were below QLs in the blanks. The analytical approach has been used successfully to determine PBDE and PCB burdens in aquatic organisms, sediment and sludges (15–17). The efficacy of the method was further assessed by analyzing a range of PBDEs in NIST Standard Reference Material household dust (SRM 2583). Results were comparable to certified concentrations.
Results and Discussion Indoor Dust. Indoor dust obtained from living quarters in the U.S.- McMurdo and New Zealand-operated Scott Antarctic bases contained substantial total PBDE concentrations, 9560 and 2240 µg /kg, respectively (Figure 2 and the Supporting Information, Table S1). It is logical to expect that burdens would track PBDE-usage within the bases’ host countries. This may be ameliorated somewhat, as countries often share facilities and exchange personnel. North America historically has consumed about half of total global PBDE production and 95% of demand for the penta-PBDE product (7, 12). This product’s constituents are more bioaccumulative than those in octa- or deca-PBDE. Accordingly, PBDE burdens in North Americans and resident wildlife are generally the highest in the world (9, 18). In contrast, New Zealand is not known to manufacture or import PBDEs, although some likely enters via imported goods (19). Harrad et al. (19) reported that indoor dust from New Zealand (Wellington) and the U.S. (Amarillo and Austin, TX) contained median/maximum tri- to hexabrominated congener totals (BDE-28, -47, -49, -66, -99, -100, -153, and -154) of 96/680 and 1600/14 000 µg/kg, respectively (19). The sum of BDE-47, -85, -99, -100, -154, and 154 (ΣPBDE6: Figure 2 and the Supporting Information, Table S1) in Scott and McMurdo indoor dust samples fell between these median and maximum values: 345 and 3550 µg/kg, respectively. ΣPBDE6 includes the major components of the Penta- commercial products, such as DE71 (20). BDE-28, -49, and -66 contribute only modestly. Harrad et al. did not determine BDE-209, the predominant constituent of the widely used deca-PBDE product, in the New Zealand dust. However, they reported median/maximum BDE-209 levels in their U.S. samples of 560/3300 µg/kg. BDE209 was the dominant congener in the McMurdo and Scott dusts, 4160 and 1650 µg/kg, respectively. Penta-PBDE commercial-mixture-related congeners made a greater contribution to total PBDEs in these Antarctic dusts than anticipated, based on U.S. and New Zealand consumption estimates. This may relate to greater release of penta-PBDE from the more fragile, high-surface-area polyurethane foam, compared to 1454
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the denser thermoplastics in which deca-PBDE is predominantly used (12). Wastewater Sludge. Laboratory and shop wastes have been sequestered at Antarctic bases and returned home for decades. However, prior to the 2002–2003 commissioning of modern treatment facilities at McMurdo and Scott, their domestic wastewaters were simply macerated and discharged directly to McMurdo Sound (2). This is consistent with the requirements of the current Protocol on Environmental Protection to the Antarctic Treaty (4). It is based on the premise that domestic wastewater constituents are biodegradable and relatively nontoxic. Hydrophobic pollutants such as PBDEs, associate predominantly with particles in aqueous waste streams (9, 21). Hence, evaluation of wastewater sludges provides insights into recent chemical usepatterns, as well as releases to receiving waters via effluentassociated suspended matter. Sludge concentrations tend to be less variable than discrete indoor dust samples, as they integrate releases from greater areas and over longer time periods. In lieu of modern wastewater treatment, which removes more than 90–95% of suspended solids, the bulk of these solids and associated contaminants will be discharged to receiving waters. To gain insight into past PBDE releases from the two bases prior to implementation of secondary treatment, as well as releases from contemporary bases still relying on maceration alone, we examined contemporary wastewater sludges from the McMurdo and Scott treatment plants. These sludges contained total PBDEs of 4690 and 637 µg/kg (dry weight), respectively. Although lower than the dust samples, the McMurdo wastewater sludge concentration was among the highest ever reported, especially for the more bioaccumulative penta-PBDE product (17, 22). Extensive use of this formulation in North American products imported into Antarctica is likely responsible. ΣPBDE6 constituted a greater percentage of total PBDEs in sludge than dust (Figure 2 and the Supporting Information, Table S1), 70% for McMurdo (3300 µg/kg) and 62% for Scott (395 µg/kg). Thus, additional sources or processes besides simple transfer of dustassociated PBDEs to wastewater sludge appear involved. Debromination of BDE-209 via photolytic and biological degradation has been previously noted (7). Production of less brominated congeners from BDE-209 poses an increased hazard as bioaccumulation potential, environmental stability and mobility, as well as toxicity increase at intermediate degrees of halogenation. However, relative to BDE-209, the sludge and dust exhibited modest contributions from expected debromination products, such as octa- and nonabrominated congeners (Figure 2). The McMurdo sludge contained a 10-fold larger ΣPBDE6 concentration than reported for European sludges, consistent with far greater U.S. penta-PBDE use (9, 18). Direct release of untreated domestic wastewaters, with their entrained burden of contemporary contaminants, continues at some Antarctic bases. Thus small research bases, which discharge directly following the maceration requirement of the Antarctic Protocol, could conceivably release as much hydrophobic contaminant as larger bases employing modern treatment. Sophisticated wastewater treatment facilities are expensive to install and maintain, disproportionately so for smaller bases. However, at a minimum, removal of wastewater particulates may be advisable. Effluent from the McMurdo wastewater plant immediately prior to discharge contained only 0.347 µg/L of ΣPBDE6. BDE-209 was below detection (
