8.2.1.4 Chiral Industrial Chemicals
Polychlorinated biphenyls (PCBs), highly persistent lipophilic industrial chemical
compounds, have been in focus as a major and ubiquitous environmental contaminant for more than five decades already. Basically, 209 structurally and chemically
related congeners are conceivable, representing a wide range of physicochemical
properties. PCBs have been used as industrial fluids, flame retardants, diluents,
hydraulic fluids and dielectric fluids for capacitors and transformers (Lang 1992;
Swanson et al. 1995; Carpenter 1998; Zabik and Zabik 1999). An extensive contamination with PCBs has occurred during the period of their industrial use, from the
early 1930s until the 1980s (Wania and Su 2004; Shi et al. 2016). Although PCBs
were banned from industrial applications since the early 1980s, they are still entering
the environment due to emissions from decommissioned installations and waste
sites. Primary sources are leakages from old so-called closed systems, such as
capacitors and transformers, and the disposal of materials contaminated with
PCBs, such as old paints, painted construction materials, lubricant oils, sealing
material and fire retardants in old fire extinguishers. Today, scientific estimations
conclude that around 40% of the totally used PCBs is still in use in old electrical
devices, paints and etc. Furthermore, a number of secondary sources of PCBs can
also be identified including resuspended river sediments, leakages from dump sites,
dumping of sewage sludges and long-range atmospheric transport (Wania and Su
2004; Shi et al. 2016).
Jensen and co-workers were the first to report PCBs extracts of Swedish whitetailed sea eagles (Haliaeetus albicilla) in the late 1960s (Jensen 1966), and subsequent analytical studies have demonstrated the presence of PCBs in almost every
compartment of the global ecosystem including the air, water, sediments, fish,
wildlife and humans. In particular, in the marine environment PCBs were not only
encountered in seawater, but also in species of different trophic levels of the marine
ecosystem (Safe 1984; Hühnerfuss and Kallenborn 1992; Lang 1992; Kamrin and
Ringer 1994; Ritter et al. 2002; Beyer and Biziuk 2009; Su et al. 2013; Gioia et al.
2014; Fang et al. 2015; Kaw and Kannan 2017; Carlsson et al. 2018).
Analytical methods for the determination of PCBs have improved in recent years,
thus permitting the determination of all 209 congeners of technical PCB mixtures in
environmental samples (Matsumoto et al. 2014; Kraft et al. 2017). In the last few
years, increasing attention has been paid to the analysis of coplanar and
atropisomeric congeners. The toxicological implications related to the structures
of these two groups will be discussed further in Chap. 10. Herein, emphasis will be
placed upon the analysis of chiral atropisomeric PCBs in environmental samples.
Basically, 78 out of 209 PCB congeners display axial chirality in their nonplanar
conformations, the so-called atropisomerism. In a pioneering account, Kaiser
predicted that 19 PCBs, nearly all of which are present in commercially available
technical PCB formulations, exist as stable atropisomers at ambient temperatures
due to restricted rotation around the C-C bond of the biphenyl system (G
*
¼
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
167
Polychlorinated biphenyls (PCBs), highly persistent lipophilic industrial chemical
compounds, have been in focus as a major and ubiquitous environmental contaminant for more than five decades already. Basically, 209 structurally and chemically
related congeners are conceivable, representing a wide range of physicochemical
properties. PCBs have been used as industrial fluids, flame retardants, diluents,
hydraulic fluids and dielectric fluids for capacitors and transformers (Lang 1992;
Swanson et al. 1995; Carpenter 1998; Zabik and Zabik 1999). An extensive contamination with PCBs has occurred during the period of their industrial use, from the
early 1930s until the 1980s (Wania and Su 2004; Shi et al. 2016). Although PCBs
were banned from industrial applications since the early 1980s, they are still entering
the environment due to emissions from decommissioned installations and waste
sites. Primary sources are leakages from old so-called closed systems, such as
capacitors and transformers, and the disposal of materials contaminated with
PCBs, such as old paints, painted construction materials, lubricant oils, sealing
material and fire retardants in old fire extinguishers. Today, scientific estimations
conclude that around 40% of the totally used PCBs is still in use in old electrical
devices, paints and etc. Furthermore, a number of secondary sources of PCBs can
also be identified including resuspended river sediments, leakages from dump sites,
dumping of sewage sludges and long-range atmospheric transport (Wania and Su
2004; Shi et al. 2016).
Jensen and co-workers were the first to report PCBs extracts of Swedish whitetailed sea eagles (Haliaeetus albicilla) in the late 1960s (Jensen 1966), and subsequent analytical studies have demonstrated the presence of PCBs in almost every
compartment of the global ecosystem including the air, water, sediments, fish,
wildlife and humans. In particular, in the marine environment PCBs were not only
encountered in seawater, but also in species of different trophic levels of the marine
ecosystem (Safe 1984; Hühnerfuss and Kallenborn 1992; Lang 1992; Kamrin and
Ringer 1994; Ritter et al. 2002; Beyer and Biziuk 2009; Su et al. 2013; Gioia et al.
2014; Fang et al. 2015; Kaw and Kannan 2017; Carlsson et al. 2018).
Analytical methods for the determination of PCBs have improved in recent years,
thus permitting the determination of all 209 congeners of technical PCB mixtures in
environmental samples (Matsumoto et al. 2014; Kraft et al. 2017). In the last few
years, increasing attention has been paid to the analysis of coplanar and
atropisomeric congeners. The toxicological implications related to the structures
of these two groups will be discussed further in Chap. 10. Herein, emphasis will be
placed upon the analysis of chiral atropisomeric PCBs in environmental samples.
Basically, 78 out of 209 PCB congeners display axial chirality in their nonplanar
conformations, the so-called atropisomerism. In a pioneering account, Kaiser
predicted that 19 PCBs, nearly all of which are present in commercially available
technical PCB formulations, exist as stable atropisomers at ambient temperatures
due to restricted rotation around the C-C bond of the biphenyl system (G
*
¼
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
167