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humans is the first de-chlorination process to ira/rs-chlordane. Furthermore, it was 
confirmed that the major metabolite of heptachlor is d.s-hcptachlorcpoxidc (Tashiro and 
Matsumura, 1978). 
Oxychlordane and c/.s-hcptachlorcpoxidc are, unlike other chlordane metabolites, very 
persistent, lipophilic and accumulate even more effectively than their precursors in biota 
(Muir et al., 1988; Zhu etal., 1995). 
5.2.2A Toxicity 
Acute toxicity (LD50) of chlordane congeners and their metabolites was determined for 
rats. Pure cis- and /ran.s-chlordanc as well as a 1:1 mixture of the isomers had similar 
toxicity (LD50 = 320-400 mg/kg body weight) while the metabolite oxychlordane was 
twenty times more toxic (WHO, 1984). 
The [ 3 H]17-|3-estradiol binding to the human estrogenic receptor (hER) plays an 
important role in estrogenic action. Chlordane enhanced the competitive binding 
process for other pesticides. Synergistic effects in the order of 150-1600 fold have been 
found when testing binary mixtures of endosulfane, dieldrin, and toxaphene together 
with chlordane (Arnold et al., 1996, McLachlan et al., 1997). 
5.3 Applied methodology 
5.3.1 State of the art of PCA analysis 
The quantification of this extremely complex compound class can be considered as "the 
challenge and nightmare" in environmental analysis. The reasons are manifold: 
• PCAs consist of so many isomers and congeners, that high resolution gas chroma 
tography cannot resolve them into single compounds. 
• Electron ionisation mass spectrometry leads to a strong fragmentation of PCAs 
and, consequently, to insufficient detection limits.