title: Co-occurrence of triclocarban and triclosan in U.S. water resources.
abstract: Triclocarban (TCC) and triclosan (TCS) are antimicrobial additives in personal care products. Whereas TCS has been studied extensively, the environmental fate of TCC remains largely unknown. To address this data gap, we performed quantitative structure-activity relationship (QSAR) analyses that suggested a propensity of TCC to persist in various environmental compartments with predicted half-lives ranging from 0.75 days in air to 540 days in sediment. Moreover, concentrations of both antimicrobials were measured in 42 environmental samples from the Greater Baltimore region using a combination of solid-phase extraction, liquid chromatography/mass spectrometry, and isotope dilution. The co-occurrence of TCC and TCS was observed, owing to similar properties, usage, disposal, and environmental half-lives. A linear empirical correlation (R2 = 0.9882) fit the log-log-transformed data from diverse aquatic media and spanned 5 orders of magnitude in concentration. Occurrences of TCC predicted for 85 U.S. streams were statistically indistinguishable from experimental regional data (alpha < or = 0.05). Annual loading of antimicrobials to water resources probably is dominated by activated sludge treatment plants (39-67%), followed by trickling filters (31-54%) and combined and sanitary sewer overflows (2-7% and <0.2%, respectively). Study results suggest that TCC is a previously unrecognized contaminant of U.S. water resources nationwide, likely ranking in the top 10 in occurrence rate and in the top 20 in maximum concentration among 96 organic pollutants considered. The magnitude and frequency of TCC contamination (regional, 6750 ng/L, 68%; predicted nationwide for 1999--2000, 1150 ng/L, 60%) were markedly higher than non-peer-reviewed numbers (240 ng/L, 30%, U.S.) currently used by the U.S. Environmental Protection Agency for evaluating TCC's ecological and human health risks.
authors.affiliation: Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205-2103, USA. rhalden@jhsph.edu
authors.forename: Rolf U
authors.initials: RU
authors.lastname: Halden
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Paull
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000009:adverse effects / Q000032:analysis* / Q000493:pharmacokinetics; D001682:Biological Availability; D002224:Carbanilides / Q000009:adverse effects / Q000032:analysis* / Q000493:pharmacokinetics; D004784:Environmental Monitoring; D006207:Half-Life; D006801:Humans; D021281:Quantitative Structure-Activity Relationship; D018570:Risk Assessment; D014260:Triclosan / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000009:adverse effects / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D000891:Anti-Infective Agents, Local; D002224:Carbanilides; D014874:Water Pollutants, Chemical; D014260:Triclosan; C009540:triclocarban