Toxicity of the antimicrobial compound triclosan and formation of the metabolite methyl-triclosan in estuarine systems

Triclosan, a commonly used antimicrobial compound, has been measured in aquatic systems worldwide. This study exposed marine species to triclosan to examine effects primarily on survival and to investigate the formation of the degradation product, methyl-triclosan, in the estuarine environment. Acute toxicity was assessed using the bacterium Vibrio fischeri, the phytoplankton species Dunaliella tertiolecta, and three life stages of the grass shrimp Palaemonetes pugio. P. pugio larvae were more sensitive to triclosan than adult shrimp or embryos. Acute aqueous toxicity values (96 h LC50) were 305 mu g/L for adult shrimp, 154 mu g/L for larvae, and 651 mu g/L for embryos. The presence of sediment decreased triclosan toxicity in adult shrimp (24 h LC50S were 620 mu g/L with sediment, and 482 mu g/L without sediment). The bacterium was more sensitive to triclosan than the grass shrimp, with a 15 min aqueous IC50 value of 53 mu g/L and a 15 min spiked sediment IC50 value of 616 mu g/kg. The phytoplankton species was the most sensitive species tested, with a 96 h EC50 value of 3.55 mu g/L. Adult grass shrimp were found to accumulate methyl-triclosan after a 14-day exposure to 100 mu g/L triclosan, indicating formation of this metabolite in a seawater environment and its potential to bioaccumulate in higher organisms. Triclosan was detected in limited surface water sampling of Charleston Harbor, SC at a maximum concentration of 0.001 mu g/L, substantially lower than the determined toxicity values. These findings suggest triclosan poses low acute toxicity risk to estuarine organisms; however, the potential for chronic, sublethal, and metabolite effects should be investigated. (c) 2008 Wiley Periodicals, Inc.