Developmental Toxicity of Triclosan in the Presence of Dissolved Organic Carbon: Moving Beyond Standard Acute Toxicity Assays to Understand Ecotoxicological Risk.

Triclosan (TCS) is an ionizable synthetic antimicrobial that has been found to be a persistent environmental contaminant with potential for bioaccumulation. Standard laboratory assays have shown that TCS is toxic to aquatic organisms; however, varied environmental conditions could impact this risk. For example, we would predict that sorption to dissolved organic carbon (DOC) in natural surface waters would reduce the bioavailability and, therefore, toxicity of TCS. To better understand the potential risk that TCS poses to wild fish, we evaluated the toxicity of TCS to zebrafish in the presence of DOC. Zebrafish were exposed to TCS (0-900 μg TCS/L), DOC (0-25 mg/L), or TCS (0-900 μg TCS/L) together with either 10 or 25 mg DOC/L from 8 to 120 h postfertilization through static waterborne exposure. We compared impacts of TCS alone or in conjunction with DOC on mortality, development, and hatching success. Exposure to TCS in the presence of DOC improves survival and hatching success, and reduces the incidence of developmental toxicity. However, since the presence of DOC did not completely prevent sublethal toxicity, our data suggest that given its bioaccumulation potential, developmental toxicity of TCS under environmental conditions still warrants concern.