Date of Award
Doctor of Philosophy
Flame retardants (FRs) represent a set of widely used industrial chemicals that are added to consumer products (e.g. electronics, plastics, and textiles), to reduce their flammability if exposed to a small flame. FRs, particularly halogenated ones, have been extensively detected in a variety of environmental compartments and biological samples worldwide, which raised significant concerns during the past decades due to their persistent, bioaccumulative and toxic potentials. Several in vivo and epidemiological studies have confirmed that FRs may interfere with neurodevelopment and endocrine systems. Therefore, the most intensively utilized group of halogenated FRs, polybrominated diphenyl ethers (PBDEs), was withdrawn from the market during 2004 – 2013. Consequently, an increase in demand for other emerging FRs was expected. Due to the phase-out of PBDEs, decreasing or plateauing trends in their concentrations have been observed in a few North American environmental matrices. However, research on emerging FRs remains limited in both terrestrial and aquatic ecosystems. In response to these knowledge gaps and research needs, my dissertation research evaluated the exposure of selected North American aquatic and terrestrial ecosystems to legacy and emerging FRs, including PBDEs, hexabromocyclododecane isomers (HBCDs), Dechlorane analogues (Dechloranes), and alternative brominated FRs (ABFRs, other non-PBDE brominated FRs). After a general introduction to contamination status of selected FRs as well as their adverse effects on test animals, ecosystems, and public health (Chapter I), the aquatic systems I investigated included the Great Lakes (Chapter II) and the San Francisco Bay (Chapter III), representing an important freshwater and estuarine ecosystem, respectively. Peregrine falcon (Falco peregrinus) eggs collected from various regions in the U.S. and Canada were analyzed to address spatial and temporal distributions of FRs in the North American terrestrial ecosystems (Chapter IV). In Chapter II, I investigated the occurrence and spatiotemporal distribution of selected FRs in the Great Lakes fish mega-composite collected from 2004 – 2016. Following the phase-out of PBDE and HBCD FRs in the North American market, the use of alternative FRs has increased. In this study the occurrence and spatiotemporal distributions of 17 Dechlorane analogues and 21 brominated FRs in Great Lakes top predator fish mega-composites was investigated. Frequently detected FRs in samples collected from 2004 to 2016 include Dechlorane (Dec) 602, 603, 604 Component B, anti-Dechlorane plus (DP), syn-DP, and Chlordene Plus, as well as several brominated benzene FRs (i.e., hexabromobenzene, pentabromotoluene, and tetrabromo-o-chlorotoluene). Concentrations of ΣDechloranes (including all Dechlorane analogues) and ΣABFRs (including all alternative brominated FRs) ranged from 0.33 – 31.9 ng/g lipid weight or lw (0.01 – 8.3 ng/g wet weight or ww) and 0.91 – 54.7 ng/g lw (0.09 – 7.1 ng/g ww), respectively. Their levels were generally one to two orders of magnitude lower than PBDEs. Flame retardant contamination exhibited chemical-specific spatial variations across the five lakes. Concentrations of ΣABFRs in Lake Erie fish were generally lower than those from other lakes. By contrast, fish concentrations and compositions of Dechloranes differed significantly between Lake Ontario and other lakes, indicating point-source influence. Temporal trend analyses revealed declining trends in ΣDechloranes and ΣABFRs in most lakes except Lake Erie, with trend slopes of -13.45% to -8.83% and -20.06% to -6.97%, respectively. Additional FR chemicals not included in the present study that are on the market and possibly subject to an increasing demand will be the subject of future studies. Continuous efforts are needed to investigate not only the myriad of alternative FRs themselves, but also their main degradation or transformation products. Chapter III presented a wide-ranging characterization of selected FRs in surface sediments and biological samples (i.e., deployed bivalves, sport fish, harbor seal blubber, and cormorant eggs) of a highly urbanized estuary, San Francisco Bay, once considered a hot spot for PBDE contamination. Among the studied FRs, PBDEs were still the most abundant contaminants in all Bay matrices as well. BDE-209 was the predominant PBDE congener in Bay sediments, while BDE-47, -99, and -100 together accounted for greater than 85% of ∑PBDEs in Bay biota. Other FR analytes detected in the Bay ecosystem (i.e., sediments and biota) included HBBZ, TBCT, 1,2-bis(2,4,6-tribromophenoxyl) ethane (BTBPE), Dec-602, Dec-603, CPlus, mono-dechlorinated DP (C11-DP), and syn- and anti-DP. Significantly higher levels of ∑PBDEs, ∑ABFRs, and ∑Dechloranes were observed in South Bay, relative to North Bay, probably due to greater urbanization in South Bay together with its geographical and hydrological features. Biomagnification (BMF > 1.0) via sport fish-harbor seal food chain were observed for BDE-47, -99, -153, TBCT, HBBZ, CPlus, Dec-602, Dec-603, syn- and anti-DP. In Chapter IV, the peregrine falcon eggs in this study were collected from the U.S. (New Jersey, Chesapeake Bay, Pennsylvania, California) and Canada (British Columbia, New Brunswick, Ontario, and Quebec). Similarly, the concentrations of ∑PBDEs (204.7 – 44224.3 ng/g lw) in the peregrine eggs were at least one order magnitude greater than those of ∑HBCDs (5.6 – 2426.4 ng/g lw), ∑Dechloranes (22.1 – 1918.2 ng/g lw), and ∑ABFRs (6.1 – 1181.8 ng/g lw). Several FRs, such as heavier PBDE congeners (octa-, nona-, and deca-BDEs), Dec-604, and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), which were not frequently detected in the Great Lakes and the San Francisco Bay organisms, were constantly quantifiable in the peregrine eggs. According to the FR burdens in recently sampled peregrine eggs, higher concentrations of ∑PBDEs and ∑ABFRs were observed in the New Jersey eggs, whereas the Ontario and Quebec eggs possessed greater levels of ∑HBCDs. The concentrations of ∑Dechloranes in peregrine eggs were comparable among the studied regions. The New Jersey, Ontario, and Quebec samples were used to elucidate the FR temporal trends in the peregrine falcon eggs. Temporal trends in concentrations of ∑PBDEs were obscure in the New Jersey and Ontario eggs, while those in Quebec eggs were significantly fitted in a quadratic curve with a breaking point at 1999. Concentrations of ∑HBCDs increased significantly in peregrine eggs from Ontario (1995 – 2015) and Quebec (1984 – 2012), while ∑Dechlorane levels declined in New Jersey and Quebec eggs collected after 1990 and 1998, respectively. No time trends were detected for concentrations of ∑ABFRs in the peregrine eggs from these three regions. In summary, although PBDEs were still the most abundant FRs, introduction of PBDE replacements have resulted in their occurrence in the North American ecosystems. Differences in FR compositional patterns were observed among the Great Lakes fish, the San Francisco Bay organisms and the peregrine falcon eggs, likely due to physiochemical properties of FRs, proximity to FR pollution sources, and human activity influences. Additionally, greater flame-retardant concentrations in organisms at higher trophic levels in the Bay ecosystem indicated their potentials to be biomagnified through the food chain.
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