2012; Yang et al. 2014; Lorente et al. 2015; Kania-Korwel and Lehmler 2016a, b;
Wu and Lehmler 2016; Uwimana et al. 2017; Guo et al. 2018).
10.2.2 Hexachlorocyclohexane
Hexachlorocyclohexane (HCH) was and still is in some countries an important
pesticide used to regulate pest. α-HCH is chiral while the corresponding γ-isomer
(alias Lindane
® ) is achiral, but its transformation product γ-pentachlorocyclohexene
(PCCB) is chiral. Several papers have been published on the enantioselective
accumulation characteristics of α-HCH (as outlined earlier). So, it is clear that the
biochemistry of the α-HCH enantiomers is dissimilar. Möller et al. (1996) reported
different toxicity of the α-HCH enantiomers as well as different growing stimulation
in rat hepatocytes. The cytotoxic effect was determined as a limit to the severe
toxicity of α-HCH, while the development motivation may be linked to the enduring
toxicity, for example, tumour promotion. The authors cultured hepatocytes in the
presence of (+)- and (–)-α-HCH discretely and described 100% death in the presence
of 3 Â 10
–4 M (+)-α-HCH, while the same amount of (–)-α-HCH 75% mortality was
tolled. Further, the authors described no lethal effect of (–)-α-HCH at a low amount
(1 Â 10
–4 M), while the mortality rate was 62% at this amount of the (+)-α-HCH
enantiomer (Fig. 10.1).
The authors also considered the mimetic rates of α-HCH enantiomers in rats.
5 Â 10
–5 M of both enantiomers were inserted distinctly in rats, and it was observed
that the noteworthy mitosis arisen in the presence of the (+)-α-HCH enantiomer
(factor 2.4) as compared with the induction by the (–)-α-HCH enantiomer (factor
1.7). So it may be concluded that the (+)-enantiomer of α-HCH is more toxic than the
(–)-enantiomer. The mortality in primary cultures of rat hepatocytes as a function of
(+)- and (–)-α-HCH concentrations and stimulation of mitosis in primary rat hepatocytes by (+)- and (–)-α-HCH are given in Fig. 10.1a and b, respectively.
After these pioneering studies, several reports on enantioselective toxicity of
α-HCH were extending the scientific information on the environmental behaviour
of these priority pollutants. Already during the early 2000s, Hegeman and Laane
attempted to develop a system for prediction of enantiomer-selective enrichment and
degradation in biological systems for α-HCH and other chiral organochlorine pesticide residues (Hegeman and Laane 2002). They conceptualised the predicted
mechanisms of enantiomer-selective accumulation and up-concentration into a
hypothetical model aiming at applying this concept for better regulatory purposes
(Hegeman and Laane 2002).
Yang et al. (2010) investigated the enantioselective toxicity of α-HCH enantiomers in mouse and quail tissues under laboratory conditions after single-dose
exposure. The authors reported a significant decrease of the (+)-a-HCH enantiomeric
fractions (EFs) in non-brain tissues and concluded that this enantiomer is continuously degraded in mice. Also, in quail, tissue-specific EF depletion was observed.
However, here the (–) enantiomer was degraded substantially. This species
282
10 Chirality in Environmental Toxicity and Fate Assessments
Wu and Lehmler 2016; Uwimana et al. 2017; Guo et al. 2018).
10.2.2 Hexachlorocyclohexane
Hexachlorocyclohexane (HCH) was and still is in some countries an important
pesticide used to regulate pest. α-HCH is chiral while the corresponding γ-isomer
(alias Lindane
® ) is achiral, but its transformation product γ-pentachlorocyclohexene
(PCCB) is chiral. Several papers have been published on the enantioselective
accumulation characteristics of α-HCH (as outlined earlier). So, it is clear that the
biochemistry of the α-HCH enantiomers is dissimilar. Möller et al. (1996) reported
different toxicity of the α-HCH enantiomers as well as different growing stimulation
in rat hepatocytes. The cytotoxic effect was determined as a limit to the severe
toxicity of α-HCH, while the development motivation may be linked to the enduring
toxicity, for example, tumour promotion. The authors cultured hepatocytes in the
presence of (+)- and (–)-α-HCH discretely and described 100% death in the presence
of 3 Â 10
–4 M (+)-α-HCH, while the same amount of (–)-α-HCH 75% mortality was
tolled. Further, the authors described no lethal effect of (–)-α-HCH at a low amount
(1 Â 10
–4 M), while the mortality rate was 62% at this amount of the (+)-α-HCH
enantiomer (Fig. 10.1).
The authors also considered the mimetic rates of α-HCH enantiomers in rats.
5 Â 10
–5 M of both enantiomers were inserted distinctly in rats, and it was observed
that the noteworthy mitosis arisen in the presence of the (+)-α-HCH enantiomer
(factor 2.4) as compared with the induction by the (–)-α-HCH enantiomer (factor
1.7). So it may be concluded that the (+)-enantiomer of α-HCH is more toxic than the
(–)-enantiomer. The mortality in primary cultures of rat hepatocytes as a function of
(+)- and (–)-α-HCH concentrations and stimulation of mitosis in primary rat hepatocytes by (+)- and (–)-α-HCH are given in Fig. 10.1a and b, respectively.
After these pioneering studies, several reports on enantioselective toxicity of
α-HCH were extending the scientific information on the environmental behaviour
of these priority pollutants. Already during the early 2000s, Hegeman and Laane
attempted to develop a system for prediction of enantiomer-selective enrichment and
degradation in biological systems for α-HCH and other chiral organochlorine pesticide residues (Hegeman and Laane 2002). They conceptualised the predicted
mechanisms of enantiomer-selective accumulation and up-concentration into a
hypothetical model aiming at applying this concept for better regulatory purposes
(Hegeman and Laane 2002).
Yang et al. (2010) investigated the enantioselective toxicity of α-HCH enantiomers in mouse and quail tissues under laboratory conditions after single-dose
exposure. The authors reported a significant decrease of the (+)-a-HCH enantiomeric
fractions (EFs) in non-brain tissues and concluded that this enantiomer is continuously degraded in mice. Also, in quail, tissue-specific EF depletion was observed.
However, here the (–) enantiomer was degraded substantially. This species
282
10 Chirality in Environmental Toxicity and Fate Assessments