Correspondence Comment on “Accumulation of Contaminants in Fish from Wastewater Treatment Wetlands” In their recent study on the accumulation of contaminants in fish from wastewater treatment wetlands, Barber et al. (1) reported the presence of 3,4-dichloroaniline (3,4-DCA) in filtered water obtained from the Tres Rios Wetlands near Phoenix, AZ. Interestingly, average concentrations of 3,4DCA detected at the wetlands inlet were lower than the corresponding average concentration in the outlet. These values resulted in a negative removal rate (-127%), and thus a net production of 3,4-DCA in the constructed wetlands. The authors were unable to offer an explanation for the presence of the compound since two phenyl urea herbicides, linuron and diuron, that are known to release 3,4-DCA, were not detected in either inlet or outlet water. I would like to commend the authors on this very interesting study (1) and, at the same time, offer a possible and plausible explanation for the presence of 3,4-DCA at the observed concentrations. 3,4-Dichloroaniline is not only a degradate of various monophenyl urea herbicides but also of the widely used biocide and diphenyl urea compound triclocarban (3,4,4′-trichlorocarbanilide; CAS Registry No. 101-20-2). The latter is produced at rates approaching 500 000 kg per year and its primary mode of disposal is via discharge into domestic wastewater. Triclocarban is known to occur at µg/L concentrations in raw wastewater, and at ng/L levels in effluent of wastewater treatment plants and in receiving surface waters (2). Although Barber et al. (1) did not monitor for triclocarban, this antimicrobial likely was present in inlet water and may have represented the elusive precursor whose transformation resulted in the observed in situ production of 3,4-DCA. The detection of triclosan has to be interpreted as a strong indication of the presence of triclocarban, since both chemicals have similar production rates, uses, disposal routes, and physical-chemical properties; for these reasons, they are known to co-occur in surface waters at roughly equal concentrations (3). When interpreting the levels of triclosan (and thus triclocarban) detected in wetland waters by Barber et al., it is imperative to consider the filtration step that was performed prior to further processing and analysis of the water. Due to strong particle sorption (2), the actual concentration of triclosan (triclocarban) in inlet water likely was considerably higher than what was detectable in the dissolved state following removal of suspended, filterable solids. Since triclocarban cannot be detected by gas chromatography/ mass spectrometry without prior derivatization, the compound has been overlooked consistently during environmental monitoring efforts for nearly half a century, despite its expected and predictable occurrence in U.S. wastewater and surface waters at high frequency and appreciable concentrations (3).
10.1021/es052474+ CCC: $33.50 Published on Web 04/15/2006
2006 American Chemical Society
From laboratory studies with acclimated, activated sludge enrichment cultures it is known that biotransformation of triclocarban yields 3,4-DCA as a major degradate of marked persistence (4). The detection of 3,4-DCA at concentrations in the hundreds of parts-per-trillion range is noteworthy because the limited data available today suggest that the compound causes endocrine disruption in fish and also may have genotoxic and carcinogenic properties. The European Union recently completed a risk assessment of 3,4-DCA and published an opinion paper summarizing salient findings and recommendations (5). During the risk assessment, the European commission noted a considerable lack of information on 3,4-DCA. Similarly, the U.S. Environmental Protection Agency observed a scarcity of information pertaining to triclocarban during review of the antimicrobial under the High Production Volume (HPV) Chemical Challenge program (6). Thus, the study by Barber et al. (1) yielded important information and, at the same time, identified the critical need for inclusion of both 3,4-DCA and its underappreciated precursor, triclocarban, in future environmental monitoring efforts by the U.S. Geological Survey and other Federal and State agencies.
Literature Cited (1) Barber, L. B.; Keefe, S. H.; Antweiler, R. C.; Taylor, H. E.; Wass, R. D. Accumulation of Contaminants in Fish from Wastewater Treatment Wetlands. Environ. Sci. Technol. 2006, 40 (2), 603611. (2) Halden, R. U.; Paull, D. H. Analysis of Triclocarban in Aquatic Samples by Liquid Chromatography Electrospray Ionization Mass Spectrometry. Environ. Sci. Technol. 2004, 38, 48494855. (3) Halden, R. U.; Paull, D. H. Co-occurrence of Triclocarban and Triclosan in U.S. Water Resources. Environ. Sci. Technol. 2005, 39, 1420-1426. (4) Gledhill, W. E. Biodegradation of 3,4,4′-trichlorocarbanilide, TCC, in sewage and activated sludge. Water Res. 1975, 9, 649654. (5) CSTFE. Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE) - Opinion on the Results of the Risk Assessment of: 3,4-Dichloroaniline; European Commission, Health & Consumer Protection Directorate, 2003. http:// europa.eu.int/comm/health/ph_risk/committees/sct/documents/out205_en.pdf (accessed December 9, 2005). (6) U.S. Environmental Protection Agency. Robust Summaries & Test Plans: Triclocarban; EPA Comments; USEPA: Washington, DC. http://www.epa.gov/chemrtk/tricloca/c14186ct.htm (accessed December 9, 2005).
Rolf U. Halden Johns Hopkins Bloomberg School of Public Health Center for Water and Health 615 North Wolfe Street BSPH Building, Room E6618 Baltimore, Maryland 21205 ES052474+
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