Recently, concern has grown regarding the presence of triclosan (TCS) in waters because of its potential for causing ecological and human health effects. The authors present a statistical analysis of TCS concentrations reported between 1999 and 2012 in freshwater environments in the United States and provide a comparison with available health-based and aquatic guidance values. Data from 46 peer-reviewed and unpublished investigations from 45 states and 1 US territory were included in the meta-analysis, encompassing the following coded water types: untreated (raw wastewater), effluent (wastewater treatment plant effluent), effluent-impacted environmental, environmental, and finished drinking water (total n = 2305). Triclosan was most frequently detected in untreated waters (92% detection frequency; mean ± standard error, 11 270 ± 2925 ng/L; n = 237), but concentrations were significantly reduced in effluent waters (83% detection frequency 775 ± 311 ng/L; n = 192, α = 0.05). Triclosan concentration in effluent-impacted environmental waters (62% detection frequency; 130 ± 17 ng/L; n = 228) was not significantly reduced from effluent waters but was significantly greater than TCS in environmental waters not classified as effluent impacted (11% detection frequency; 13 ± 3 ng/L; n = 1195). In finished drinking water, TCS was largely undetected (1% detection frequency; 4 ± 2 ng/L n = 453), suggesting that for the United States, drinking water is not an appreciable source of TCS exposure. In posttreatment waters, average TCS concentrations were below part-per-billion levels. Although no US regulatory standard exists for TCS in aquatic systems, comparison of averages reported in the present study with a predicted-no-effect concentration (PNEC) of 500 ng/L showed that 5.3% of effluent-impacted environmental waters were above the PNEC for changes in algal biomass, while only 0.25% of environmental waters surpassed this value.
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