Induction of liver tumors in female Sherman strain rats by polybrominated biphenyls.

Noninbred Sherman strain rats were given the polybrominated biphenyl mixture Firemaster FF-1 (PBB). Rats given a single dose of 1,000 mg PBB/kg or 12 doses of 100 mg PBB/kg body weight in corn oil by gavage had final (when less than or equal to 26 mo old) liver PBB concentrations of 17.1 and 34.8 mg/kg (wet wt), respectively. The respective incidence of hepatocellular carcinomas was 41.4 and 67.8%. No difference in PBB concentrations was found between hepatocellular carcinomas and surrounding liver tissue. In addition, most livers of PBB-dosed rats had adenofibrosis of the liver. Livers of controls were essentially normal. Rats given a single dose of 200 mg PBB/kg as above had a 31.2% incidence of neoplastic nodules, whereas none were seen in the controls. The mean PBB concentrations (when 26 mo old) were 2.68 mg/kg in liver, 244 mg/kg in adipose tissue, and 0.22 mg/kg in blood.