Pharmacokinetic and toxicological evaluation of dogs fed 1,2,4,5‐tetrachlorobenzene in the diet for two years

1,2,4,5‐Tetrachlorobenzene (TCB), an intermediate in several industrial processes, was administered in the diet to dogs at 5 mg/kg • d for 2 yr, followed by a 20‐mo recovery phase. The animals were examined periodically for toxicity; the concentration of TCB in the plasma and fat was measured during the 2 yr of exposure and 20 mo of recovery. After 18 mo of exposure, all clinical chemistry parameters were normal; however, after 24 mo, serum alkaline phosphatase activity and total bilirubin levels were slightly elevated in the dogs dosed with TCB. Both clinical chemistry parameters returned to normal levels within 3 mo of the cessation of exposure. After the 20‐mo recovery, gross and histopathologic examination of tissues revealed no morphological changes considered related to the ingestion of TCB. A t the end of 2 yr of exposure, TCB had reached 98 and 97% of the calculated steady‐state concentrations in fat and plasma, respectively. TCB was eliminated from the fat and plasma with half‐life values of 111 ...