Tetrachlorocatechol is a metabolite of pentachlorophenol. Tetrachlorocatechol is one of the most toxic chlorinated catechol produced by the chlorobleaching of pulp and frequently found in the kraft pulp mill effluents[1][2].

[1]. G. Renner, et al. Acute toxicities of pentachlorophenol, pentachloroanisole, tetrachlorohydroquinone, tetrachlorocatechol, tetrachlororesorcinol, tetrachlorodimethoxybenzenes and tetrachlorobenzenediol diacetates administered to mice, Toxicological & Environmental Chemistry, 11:1, 37-50. [2]. Mukherjee, et al. Evaluation of Acute Toxicity Levels and Ethological Responses Under Tetrachlorocatechol Exposure in Common Carp, Cyprinus carpio (Linnaeus). Proc Zool Soc 67, 108-113 (2014).