Fate of Triclosan and Evidence for Reductive Dechlorination of Triclocarban in Estuarine Sediments

Abstract

The biocides triclosan and triclocarban are wastewater contaminants whose occurrence and fate in estuarine sediments remain unexplored. We examined contaminant profiles in 137Cs/7Be-dated sediment cores taken near wastewater treatment plants in the Chesapeake Bay watershed (CB), Maryland and Jamaica Bay(JB), New York. In JB, biocide occurrences tracked the time course of biocide usage and wastewater treatment strategies employed, first appearing in the 1950s (triclocarban) and 1960s (triclosan), and peaking in the late 1960s and 1970s (24 +/- 0.54 and 0.8 +/- 0.4 mg/kg dry weight, respectively). In CB, where the time of sediment accumulation was not as well constrained by 137Cs depth profiles, triclocarban was only measurable in 137Cs-bearing sediments, peaking at 3.6 +/- 0.6 mg/ kg midway through the core and exceeding 1 mg/kg in recent deposits. In contrast, triclosan concentrations were low or not detectable in the CB core. Analysis of CB sediment by tandem mass spectrometry produced the first evidence for complete sequential dechlorination of triclocarban to the transformation products dichloro-, monochloro-, and unsubstituted carbanilide, which were detected at maxima of 15.5 +/- 1.8, 4.1 +/- 2.4, and 0.5 +/- 0.1 mg/kg, respectively. Concentrations of all carbanilide congeners combined were correlated with heavy metals (R2 > 0.64, P < 0.01), thereby identifying wastewater as the principal pathway of contamination. Environmental persistence over the past 40 years was observed for triclosan and triclocarban in JB, and for triclocarban's diphenylurea backbone in CB sediments.