Photolysis- and Dissolved Organic Matter-Induced Toxicity of Triclocarban to Daphnia magna

Triclocarban (TCC) is a common antimicrobial compound used in soaps and other household products and is found globally in many surface waters. This study investigated the acute toxicity of TCC and its photolyzed products to Daphnia magna using 50% 96-h lethal concentration (LC 50 ) tests. The effects of dissolved organic matter (DOM) on the toxicity of TCC photoproducts to D. magna were also studied. Direct photolysis of TCC formed photoproducts that were significantly less toxic (LC 50 value of 2.67 ± 0.6 μM) than the parent TCC compound (LC 50 value of 0.087 ± 0.3 μM). In contrast, the indirect photolysis of TCC in the presence of DOM produced photoproducts that were significantly more toxic (LC 50 value of 0.032 ± 0.015 μM). Chlorinated anilines and isocyanates, identified by mass spectrometry, were formed in the presence of DOM as indirect photolysis products of TCC and were shown to be partially responsible for the observed toxicity.