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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  chromatography ­
  cannot  resolve  them  into  single  compounds.
•  Electron  ionisation  mass  spectrometry  leads  to  a  strong  fragmentation  of  PCAs
and,  consequently,  to  insufficient  detection  limits.