Toxicity of selected symmetrical hexachlorobiphenyl isomers in the mouse

Abstract

Five-week-old male mice were given: 0.3, 1, 3, 10, 30, 100, or 300 ppm of 3,4,5,3′,4′,5′-hexachlorobiphenyl (HCB); 10, 30, 100 or 300 ppm of 2,4,5,2′,4′,5′-HCB, 2,3,6,2′,3′,6′-HCB, or 2,4,6,2′,4′,6′-HCB in feed daily for 28 days. HCB residue levels were determined in adipose tissue and liver. There were marked differences in dose response and severity of pathologic effects among the isomers. 3,4,5,3′,4′,5′-HCB was the most toxic isomer causing mortality, and body and organ weight effects at all dose levels, and was the only isomer which produced excess porphyrin accumulation. It was also the most concentrated isomer in fat and liver. 3,4,5,3′,4′,5′-HCB caused subcutaneous edema, enlargement of liver with accentuated hepatic lobular markings, fatty infiltration, hepatocellular swelling and necrosis, and atrophy of the thymus. 2,4,6,2′,4′,6′-HCB and 2,4,5,2′,4′,5′-HCB caused the same lesions but to a lesser degree. Slight cardiomyopathy was observed with 2,4,6,2′,4′,6′-HCB. The decreasing order of overall toxicity was 3,4,5-HCB >> 2,4,6-HCB > 2,4,5-HCB > 2,3,6-HCB.