Subchronic toxicity of some chlorinated dibenzofurans (PCDFs) and a mixture of PCDFs and chlorinated dibenzodioxins (PCDDs) in rats

Groups of 6 male and 6 female rats were maintained for 13 weeks on diets containing 12378-PeCDF (2, 20 and 200 μg/kg), 12348-PeCDF (600 and 6000 μg/kg), 123678-HxCDF (2, 20 and 200 μg/kg) and 2,3,7,8-TCDD (2 μg/kg). In addition, a mixture of 23478-PeCDF, 12378-PeCDD, 123678-HxCDF and 2378-TCDD was administered in the diet (20, 10, 10 and 2 μg/kg, respectively, and tenfold diluted). The parameters investigated included body weight development, food consumption, terminal organ weights, hematology and blood chemistry. Tissues were also examined microscopically. The expected toxic syndrome was observed with the toxic isomers, but dosage required to produce the same degree of lesions was quite different. The toxic potency of the isomers relative to TCDD was estimated as follows: (TCDD: 1); 12378-PeCDF: 0.01; 123678-HxCDF: 0.1; 12348-PeCDF: