Metabolism of Tetrachlorophenols in the Rat

The three isomers of tetrachlorophenol were administrated intraperitoneally to rats and the urinary excretion products studied. Tetrachloro-p-hydroquinone was identified as a major metabolite of 2,3,5,6-tetrachlorophenol, constituting about 35% of the dose given. Trichloro-p-hydroquinone was identified as a minor metabolite of both 2,3,4,5- and 2,3,4,6-tetrachlorophenol. 2,3,5,6-tetrachlorophenol was eliminated within 24 h, 2,3,4,6-tetrachlorophenol within 48 h while only 60% of the given dose of 2,3,4,5-tetrachlorophenol could be recovered within 72 h. The acute toxicity of the tetrachlorophenols and tetrachloro-p-hydroquinone was studied in mice upon oral and intraperitoneal administration. 2,3,5,6-tetrachlorophenol (LD50p.o. 109 mg . kg-1) was the most toxic compound followed by 2,3,4,6- and 2,3.4,5-tetrachlorophenol (LD50p.o. 131 and 400 mg . kg-1, respectively). Tetrachloro-p-hydroquinone proved to have low oral toxicity (LD50p.o. 500 mg . kg-1) but was more toxic than the tetrachlorophenols when administered intraperitoneally. The oral LD50 for pentachlorophenol, under identical experimental conditions was found to be 74 mg . kg-1.