Triclosan and triclocarban are two ubiquitous anti-microbial compounds commonly found together in surface waters. Both compounds have been shown to undergo photodegradation in surface waters, with triclosan forming a variety of products including 2,8-dichlorodibenzodioxin, while triclocarban's degradates are unknown. Numerous studies have investigated the toxicity of the parent compounds, particularly triclosan, but little information regarding the toxicities of the photolysis products for either compound or their mixtures exist. Using the cladoceran Daphnia magna we determined 96-hour LC50s for both parent compounds in buffered water in the presence and absence of dissolved organic matter (DOM) and their photolytic products. From these LC50s we calculated toxic equivalent units (TU) for each compound and its photolysis products, and then ran 96-hour mixture toxicity tests using 0.5, 1, and 2 toxic units to determine if mixtures of these compounds/degradation products exhibit synergistic or antagonistic effects on Daphnia magna. We observed elevated levels of toxicity in certain mixtures, implying possible synergistic effects, while other mixtures exhibited no mixture effects.Degradation products exhibiting the highest toxicities were also identified.

Photolysis product toxicity and mixture toxicity of triclosan and triclocarban to <i>Daphnia magna</i>

248th National Meeting (2014)

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Photolysis product toxicity and mixture toxicity of triclosan and triclocarban to Daphnia magna