Toxicological assessment of hexachlorobiphenyl isomers and 2,3,7,8-tetrachlorodibenzofuran in chicks: I. Relationship of chemical parameters

Abstract

Five hexachlorobiphenyl (HCB) isomers and 2,3,7,8-tetrachlorodibenzofuran (TCDF) were fed to chicks for 21 days. Liver weights increased, with the smallest increase produced by 2,3,6,2′,3′,6′-HCB and the largest by 2,4,6,2′,4′,6′-HCB. Weight gain was decreased by 2,3,4,2′,3′,4′-, 2,3,6,2′,3′,6′-, and 2,4,5,2′,4′,5′-HCB, while 1μg/kg of TCDF did not affect body weight or liver weight. Pathological changes in the liver were greatest in the 2,4,6,2′,4′,6′-HCB group, moderate in the 2,3,4,2′,3′,4′- and 2,3,6,2′,3′,6′-HCB groups, and mildest in the 3,4,5,3′,4′,5′-, 2,4,5,2′,4′,5′-HCB, and 5μg/kg TCDF groups, with no significant effect for the 1μg/kg TCDF group. Thymic involution and edema were observed with 3,4,5,3′,4′,5′ HCB and TCDF. 3,4,5,3′,4′,5′-HCB and 5μg/kg of TCDF were lethal. HCB retention indices from gas chromatography correlated well with adipose-tissue concentration, with the exception of the 2,4,6,2′,4′,6′-isomer, which had the smallest retention index but relatively high tissue accumulation. Extraction p-values correlated poorly, but the 2,3,6,2′,3′,6′-HCB gave the smallest p-value, whereas the 2,4,6,2′,4′,6′-HCB p-value was next to the highest. The HCB retention indices generally correlated with their overall biological response and were highest in isomers with 3,4-substitution.