Effects of an extract of oystercatcher (Haematopus ostralegus) eggs from the Zeehavenkanaal in The Netherlands, and of its major contaminant, hexachlorobenzene, on the chicken embryo.

Oystercatchers (Haematopus ostralegus) foraging on the canal 'Zeehavenkanaal' in the Netherlands have been shown to accumulate appreciable amounts of contaminants, especially hexachlorobenzene. The present study was performed to assess the embryotoxic effects of the present contaminants. To this end, a two step approach was followed. In step one, the toxic effects of hexachlorobenzene were studied in the chicken embryo bioassay, using concentrations realistic for the field situation. In step two, yolks of oystercatcher eggs were extracted and the embryotoxic potency of this extract was studied in the same bioassay, using doses of 1, 10 and 100% of the contaminant load in one average egg. The extract contained hexachlorobenzene and PCBs. However, presence of other compounds could not be excluded, since these were not analysed. Hexachlorobenzene induced a nonsignificant decrease in lymphocyte density in the bursa of Fabricius. The egg extract caused a 3.5 fold induction of EROD activity at the highest dose applied, and decreased lymphocyte density in the bursa of Fabricius.