are in accordance with those reported by Hühnerfuss et al., for the Iceland seal
blubber tissues and for the two brain tissues; also high ratios of 28 and 32 were
determined. The ratio found in the milk sample reflects enantioselective processes in
the mother animal. The slightly enhanced ratios in the tissues of the normal and
stillborn fur seals are assumed to be indicative of additional metabolic discrimination
of the later eluting enantiomer. However, the neonatal fur seal, which died of the
white muscle syndrome, shows the smallest ratios. It cannot be excluded that the
disease may have influenced the enzyme induction potential and thus reduced the
potential to metabolise xenobiotics like α-HCH.
Müller et al. (1996a, b) extended the data sets thus far available for the enantiomeric composition of α-HCH in seal tissues by a systematic investigation including
two different seal species, eight harbour seals (Phoca vitulina L.) and eight grey
seals (Halichoerus grypus (FABR.)), which were shot on western Iceland. For both
seal species, ER values of ER +/À > 1 were determined in blubber extracts, which is
fully in accordance with the results of other authors (Table 8.10). With mean values
of ER ¼ 1.4 (harbour seals) and ER ¼ 1.3 (grey seals), no species-dependent effects
were observed for these two seal species. Up to now, hooded seals are the only
marine mammals for which ER < 1 for α-HCH were reported (Hummert et al. 1995).
Müller et al. did not verify any correlation between α-HCH levels or enantiomeric
ratios with age or sex for the two seal species.
Wiberg et al. (1998a, b, c) investigated enantioselective processes of organochlorines including α-HCH in the Arctic marine food chain, placing special emphasis on
the polar bear (Ursus maritimus PH.) food chain, which is simply due to the limited
biodiversity in the Arctic marine environment. The main food for polar bears is the
blubber of ringed seals (Phoca hispida, ERX.), which in turn largely consume fish
and pelagic crustaceans, in particular Arctic cod (Boregadus saida LEP.) and
amphipods.
The Arctic cod tissue extracts showed near-racemic ERs, indicating that
bioaccumulation takes place without or with minor selective metabolism. This
conclusion is fully in accordance with results of other authors who reported enantiomeric ratios of α-HCH in Atlantic cod liver (Gadus morhua) or fish oil extracts
from other species between 0.98 and 1.23 (Mössner et al. 1992; Koske et al. 1999;
Wong et al. 2002; Wiberg et al. 2006). The tissue extracts of ringed seal and polar
bear exhibited large ER changes. Obviously, (+)-α-HCH becomes more abundant
relative to (À)-α-HCH in top predators (Fig. 8.13). Therefore, Wiberg et al. calculated separate biomagnification factors (BMFs) for the (+)- and the (À)-enantiomers.
For the first step, from cod to seal, the BMFs are comparable ((+)-α-HCH: BMF ¼
2.0; (À)-α-HCH: BMF ¼ 1.7); however, during the next step, from seal to polar
bear, only the (+)-enantiomer biomagnifies (BMF ¼ 1.4), in contrast to the (À)enantiomer (BMF ¼ 0.7). For the complete chain, from cod to polar bear, the values
are for the (+)-enantiomer BMF ¼ 2.8 and for the (À)-enantiomer BMF ¼ 1.2,
respectively. The data set used for the calculations by Wiberg et al. comprised
40 samples. At least qualitatively, the results are fully in line with the observation
that the (+)-enantiomer is increasingly dominant up the polar bear food chain.
The above selection of research studies illustrates the importance of α-HCH as the
first and most comprehensively investigated chiral persistent environmental
144
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
blubber tissues and for the two brain tissues; also high ratios of 28 and 32 were
determined. The ratio found in the milk sample reflects enantioselective processes in
the mother animal. The slightly enhanced ratios in the tissues of the normal and
stillborn fur seals are assumed to be indicative of additional metabolic discrimination
of the later eluting enantiomer. However, the neonatal fur seal, which died of the
white muscle syndrome, shows the smallest ratios. It cannot be excluded that the
disease may have influenced the enzyme induction potential and thus reduced the
potential to metabolise xenobiotics like α-HCH.
Müller et al. (1996a, b) extended the data sets thus far available for the enantiomeric composition of α-HCH in seal tissues by a systematic investigation including
two different seal species, eight harbour seals (Phoca vitulina L.) and eight grey
seals (Halichoerus grypus (FABR.)), which were shot on western Iceland. For both
seal species, ER values of ER +/À > 1 were determined in blubber extracts, which is
fully in accordance with the results of other authors (Table 8.10). With mean values
of ER ¼ 1.4 (harbour seals) and ER ¼ 1.3 (grey seals), no species-dependent effects
were observed for these two seal species. Up to now, hooded seals are the only
marine mammals for which ER < 1 for α-HCH were reported (Hummert et al. 1995).
Müller et al. did not verify any correlation between α-HCH levels or enantiomeric
ratios with age or sex for the two seal species.
Wiberg et al. (1998a, b, c) investigated enantioselective processes of organochlorines including α-HCH in the Arctic marine food chain, placing special emphasis on
the polar bear (Ursus maritimus PH.) food chain, which is simply due to the limited
biodiversity in the Arctic marine environment. The main food for polar bears is the
blubber of ringed seals (Phoca hispida, ERX.), which in turn largely consume fish
and pelagic crustaceans, in particular Arctic cod (Boregadus saida LEP.) and
amphipods.
The Arctic cod tissue extracts showed near-racemic ERs, indicating that
bioaccumulation takes place without or with minor selective metabolism. This
conclusion is fully in accordance with results of other authors who reported enantiomeric ratios of α-HCH in Atlantic cod liver (Gadus morhua) or fish oil extracts
from other species between 0.98 and 1.23 (Mössner et al. 1992; Koske et al. 1999;
Wong et al. 2002; Wiberg et al. 2006). The tissue extracts of ringed seal and polar
bear exhibited large ER changes. Obviously, (+)-α-HCH becomes more abundant
relative to (À)-α-HCH in top predators (Fig. 8.13). Therefore, Wiberg et al. calculated separate biomagnification factors (BMFs) for the (+)- and the (À)-enantiomers.
For the first step, from cod to seal, the BMFs are comparable ((+)-α-HCH: BMF ¼
2.0; (À)-α-HCH: BMF ¼ 1.7); however, during the next step, from seal to polar
bear, only the (+)-enantiomer biomagnifies (BMF ¼ 1.4), in contrast to the (À)enantiomer (BMF ¼ 0.7). For the complete chain, from cod to polar bear, the values
are for the (+)-enantiomer BMF ¼ 2.8 and for the (À)-enantiomer BMF ¼ 1.2,
respectively. The data set used for the calculations by Wiberg et al. comprised
40 samples. At least qualitatively, the results are fully in line with the observation
that the (+)-enantiomer is increasingly dominant up the polar bear food chain.
The above selection of research studies illustrates the importance of α-HCH as the
first and most comprehensively investigated chiral persistent environmental
144
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants