Page 728 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Brominated Flame Retardants and Perfluorinated Chemicals Chapter | 52 693

VetBooks.ir PHYSICOCHEMICAL PROPERTIES
Brominated Flame Retardants

TBBPA (Fig. 52.1), the highest volume flame retardant
worldwide, is primarily a reactive BFR (90%) covalently
bound to the polymer structure and less likely to be
released into the environment than are additive flame
retardants (Birnbaum and Bergman, 2010). TBBPA is
used in several types of circuit board polymers. TBBPA
is highly lipophilic (log K ow 5 4.5) and has low water sol-
ubility (0.72 mg/mL). TBBPA has been measured in the
air (Zweidinger et al., 1979), soil, and sediment
(Watanabe et al., 1983), but it is generally not found in
water samples. TBBPA is found in eggs of birds, human
milk, and umbilical cord serum. TBBPA derivatives such
as ethers are reported to be biologically active, which
may lead to health effects (Legler, 2008; Birnbaum and
Bergman, 2010). HBCD (Fig. 52.1) is a nonaromatic bro-
minated cyclic alkane with a molecular weight of 641.7,
and it is mainly used as an additive flame retardant in
thermoplastic polymers with final applications in styrene
resins (National Research Council, 2000). Like other
BFRs, HBCD is highly lipophilic, with a log K ow of 5.6,
and it has low water solubility (0.0034 mg/L) (MacGregor
and Nixon, 1997). The melting point is 185 195 C, and

vapor pressure is 4.7 3 10 27 mmHg. Studies have shown
that HBCD is highly persistent, with a half-life of 3 days
in air and 2025 days in water (Lyman, 1990), and it is
bioaccumulative, with a bioconcentration factor of
approximately 18,100 in fathead minnows (Veith and
Defoe, 1979).
FIGURE 52.3 Chemical structures of predominant perfluorinated chemi- PBDEs are composed of two phenyl rings linked by
cals, PFOS (perfluorooctane sulfonic acid) and PFOA (perfluorooctanoic an oxygen (thus the designation as “ether”; Figs. 52.1 and
acid). The metabolites perfluorooctylsulfonamide and heptadecafluoro-1-
52.2). The phenyl rings may have 1 10 bromine atoms,
decanol are shown for structural comparison.
leading to the formation of 209 possible congeners. The
exact identity and pattern of various congeners in various
As a result of widespread use of these compounds, con- commercial mixtures depend on the manufacturer and the
cern regarding PFC contamination has increased. PFOS and specific product. Among these, the commercial “penta”
perfluorooctanoic acid (PFOA) have been consistently mixture generally consists of PBDE congeners 99
detected in environmental matrices, animals, and human tis- (pentaBDE) and 47 (tetraBDE) as the major constituents
sues (Kannan et al., 2004, 2005a,b). Although PFOCs have (Fig. 52.2), which comprise approximately 70% of the
been produced since the late 1950s, these compounds were mixture (Huber and Ballschmiter, 2001). PBDE congener
first reported to occur on a global scale in 2001 (Giesy and 100 (pentaBDE) is present at less than 10%, with PBDE
Kannan, 2001). Perfluorinated contaminants, such as per- congeners 153 and 154 (hexaBDEs) at less than 5% each.
fluorobutanesulfonate, perfluorohexanesulfonate (PFHxS), The commercial “octa” mixture is 10% 12% hexaBDE,
perfluorononanoic acid (PFNA), perfluorodecanoic acid 43% 44% heptaBDE, 31% 35% octaBDE, 9% 11%
(PFDA), perfluoroundecanoic acid (PFUnDA), perfluorodo- nonaBDE, and 0% 1% decaBDE. The “deca” commer-
decanoic acid (PFDOA), and perfluorooctanesulfonamide cial mixture consists of 98% decaBDE, with a small per-
(PFOSA), are less frequently detected in biota than are centage of nonaBDEs (World Health Organization, 1994;
PFOS and PFOA. Studies suggest that PFCs accumulate in LaGuardia et al., 2006).
farm and pet animals such as chicken, cattle, goats, horses, PBDEs are structurally similar to PCBs (Fig. 52.1)
pigs, and other vertebrates (Kennedy et al., 2004; Guruge and elicit adverse effects similar to those of PCBs on ner-
et al., 2008). vous, immune, and endocrine systems. They also