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 Data from 46 peer-reviewed and unpublished investigations from 45 states and 1 US territory were included in the meta-analysis, encompassing the following coded water types: untreated (raw wastewater),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.

In this California‐wide spatial analysis, a cumulative ranking method and a trend test were used to estimate and compare concentrations of 12 contaminants and two drinking water standard violations by system size and region. The San Joaquin Valley, areas not served by water systems, and small water systems (less than 200 connections) had the highest cumulative rank with many high levels of contaminants. Large systems and the South Coast had the highest levels of disinfection byproducts and industrial contaminants. Based on a trend analysis, violations and concentrations of arsenic and cadmium decreased as system size increased, while industrial contaminant concentrations and disinfection byproducts increased as system size increased (p < .05). Although not indicative of violating drinking water standards, this study's results demonstrate where efforts to address specific contaminants can be targeted by region or system type. The results can help elucidate where contaminants may be elevated, from both an individual and multiple‐contaminant perspective.