NON-ORTHO-CHLORINE-SUBSTITUTED AND MONO-ORTHO-CHLORINE-SUBSTITUTED POLYCHLORINATED-BIPHENYLS - EMBRYOTOXICITY AND INHIBITION OF LYMPHOID DEVELOPMENT

The toxicities and 7-ethoxyresorufin O-deethylase-inducing potencies of non-ortho- and mono-ortho-chlorinated PCBs were studied in chick embryos. The non-ortho-chlorinated congeners were considerably more embryotoxic and more potent as inhibitors of lymphoid development in the embryonic bursa of Fabricius than the mono-ortho-chlorinated congeners. The EROD-inducing potencies of the PCBs correlated well with their toxicities. The mono-ortho-chlorinated congeners having a chlorine in the meta position adjacent to the ortho-chlorine were more toxic and stronger EROD-inducers than the congeners having a hydrogen in this position. Co-administration of 3,3′,4,4′,5-pentachlorobiphenyl and 2,3,3′,4,4′,5-hexachlorobiphenyl resulted in additive effects with respect to embryotoxicity and EROD activity. © 1990.