STEREOCHEMICAL EFFECTS OF PCBS IN THE MARINE-ENVIRONMENT - SEASONAL-VARIATION OF COPLANAR AND ATROPISOMERIC PCBS IN BLUE MUSSELS (MYTILUS-EDULIS-L) OF THE GERMAN BIGHT

The toxic potential of coplanar polychlorinated biphenyls (PCBs), expr essed by their toxic equivalent (TEQ) values according to Safe and to the recent WHO/ICPS recommendations, was determined in blue mussel (My tilus edulis L.) samples collected at six sites in the Weser, Jade, an d Elbe river estuaries during the spring and the autumn period. The ma ximum SIGMATEQ value of about 1.5 ng g-1 EOM was found in the Elbe est uary, however, at all sampling sites the SIGMATEQ values were alarming during both seasons. The non-ortho coplanar congener PCB 126 turned o ut to give a highest toxic potential in blue mussels. Based upon the p resent data set the possibilities and limitations of the TEQ concept a re critically discussed. Furthermore, the stereochemical aspect of atr opisomeric PCBs is investigated for the first time for marine biota. F ive of the nine atropisomeric congeners present in commercial PCB form ulations were found in blue mussels at all six sampling sites, i.e. PC B 88, PCB 149, PCB 183, PCB 174, and PCB 171, were their concentration s were significantly lower during the autumn than during the spring pe riod. Furthermore, the enantiomers of PCB 149 in all mussel samples co llected during the spring and autumn period were separated, which reve aled that only weak enzymatic degradation of atropisomeric PCBs occurs in blue mussels. Although sufficient evidence is available that chira lity of atropisomeric PCBs plays an important role in many recognition events associated with enzymatic processes, a risk assessment concept is lacking that might compete with the 'toxic equivalence factor' con cept applied to coplanar PCBs.