Excretion, distribution and metabolism of 1,2,4-trichlorobenzene in rats.

1,2,4-Trichlorobenzene (TCB) labeled with C-14 was given perorally to rats at a dosage of 50 mg/kg for excretion and distribution studies. About 66% and 17% of the oral dose was excreted in the urine and feces, respectively, within 7 days. Trapped radioactivity in the expired air amounted to 2.1% of the dose, but production of labeled carbon dioxide was negligible. Tissue residues were evenly distributed throughout the organs and tissues examined, except for the adipose tissue which consistently had a little higher concentration. The urinary, fecal and expiratory metabolites were identified. Free 2,4,5- and 2,3,5-trichlorophenol (TCP) and their conjugates were mainly detected in the urine. 5- or 6-Sulfhydryl, methylthio, methylsulfoxide and methylsulfone derivatives of TCB were also detected as minor metabolites. Dichlorobenzenes and unchanged TCB were confirmed in the expired air. Reductive dechlroination seems to be catalysed by intestinal microflora enzymes.