Submitted to: Environmental Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/28/2008
Publication Date: 7/1/2008
Citation: Miller, T.R., Heidler, J.H., Chillrud, S.N., DeLaquil, A., Ritchie, J.C., Mihalic, J.N., Bopp, R., Halden, R.U. 2008. Fate of triclosan and evidence for reductive dechlorination of triclocarban in estuarine sediments. Environmental Science and Technology. 42(12):4570-4576. Interpretive Summary: Two biocides (triclosan (TCS) and triclocarban ) commonly used detergents and personal care products were studied to determine their fates in sediments from urban and agricultural watersheds. This study explored the 40-year history of the two biocides deposited in estuarine sediment of the Chesapeake Bay watershed in Maryland and Jamaica Bay in New York. Data show that (i) TCC, and to a lesser extent TCS, are persistent organic contaminants of estuarine sediment; (ii) TCC is more persistent and more abundant than TCS; (iii) in aged sediment, TCC can undergo slow anaerobic dechlorination but the process shows geographic variability; (iv) anaerobic transformation processes can alter the chlorine substitution pattern but do not reduce the overall quantity of carbanilide species present, and (v) TCC contamination of estuarine sediment in some locations reached concentration levels which represents potentially unhealthy levels for aquatic organisms. Further studies into the aquatic toxicity of these persistent antimicrobial additives are needed to more accurately judge their threat to aquatic ecosystems of the Chesapeake Bay and Jamaica Bay.
Technical Abstract: The biocides triclosan (TCS) and triclocarban (TCC) 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 1970s (24 ± 0.54 and 0.8 ± 0.4 mg/kg, respectively). In CB, where 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 was low or not detectable in the CB core. Interestingly, a newly observed complete sequential dechlorination process in CB sediment transformed triclocarban to dichloro-, monochloro-, and unsubstituted carbanilide (maxima: 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), identifying wastewater as the principal source of contamination and indicating persistence of the diphenylurea backbone in sediment over the past 40 years.