The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish. Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48-h Daphnia magna median effective concentration (EC50) was 390 microg/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 microg/L, respectively. A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 microg/L and 71.3 microg/L, respectively, were determined with an early life-stage toxicity test with Oncorhynchus mykiss. During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 microg/L and the 96-h NOEC was 0.69 microg/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five-week test period was 4,157 at 3 microg/L and 2,532 at 30 microg/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS-containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment.

The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish. Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48-h Daphnia magna median effective concentration (EC50) was 390 microg/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 microg/L, respectively. A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 microg/L and 71.3 microg/L, respectively, were determined with an early life-stage toxicity test with Oncorhynchus mykiss. During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 microg/L and the 96-h NOEC was 0.69 microg/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five-week test period was 4,157 at 3 microg/L and 2,532 at 30 microg/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS-containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment.

Triclosan (TCS) is a broad-spectrum antimicrobial used in consumer products including toothpaste and hand soap. After being used, TCS is washed or rinsed off and residuals that are not biodegraded or otherwise removed during wastewater treatment can enter the aquatic environment in wastewater effluents and sludges. The environmental exposure and toxicity of TCS has been the subject of various scientific and regulatory discussions in recent years. There have been a number of publications in the past 5 y reporting toxicity, fate and transport, and in-stream monitoring data as well as predictions from aquatic risk assessments. State-of-the-science probabilistic exposure models, including Geography-referenced Regional Exposure Assessment Tool for European Rivers (GREAT-ER) for European surface waters and Pharmaceutical Assessment and Transport Evalutation (PhATEe) for US surface waters, have been used to predict in-stream concentrations (PECs). These models take into account spatial and temporal variability in river flows and wastewater emissions based on empirically derived estimates of chemical removal in wastewater treatment and in receiving waters. These model simulations (based on realistic use levels of TCS) have been validated with river monitoring data in areas known to be receiving high wastewater loads. The results suggest that 90th percentile (low flow) TCS concentrations are less than 200 ng/L for the Aire-Calder catchment in the United Kingdom and between 250 ng/L (with in-stream removal) and 850 ng/L (without in-stream removal) for a range of US surface waters. To better identify the aquatic risk of TCS, a species sensitivity distribution (SSD) was constructed based on chronic toxicity values, either no observed effect concentrations (NOECs) or various percentile adverse effect concentrations (EC10-25 values) for 14 aquatic species including fish, invertebrates, macrophytes, and algae. The SSD approach is believed to represent a more realistic threshold of effect than a predicted no effect concentration (PNEC) based on the data from the single most sensitive species tested. The log-logistic SSD was used to estimate a PNEC, based on an HC5,50 (the concentration estimated to affect the survival, reproduction and/or growth of 5% of species with a 50% confidence interval). The PNEC for TCS was 1,550 ng/L. Comparing the SSD-based PNEC with the PECs derived from GREAT-ER and PhATE modeling to simulate in-river conditions in Europe and the United States, the PEC to PNEC ratios are less than unity suggesting risks to pelagic species are low even under the highest likely exposures which would occur immediately downstream of wastewater treatment plant (WWTP) discharge points. In-stream sorption, biodegradation, and photodegradation will further reduce pelagic exposures of TCS. Monitoring data in Europe and the United States corroborate the modeled PEC estimates and reductions in TCS concentrations with distance downstream of WWTP discharges. Environmental metabolites, bioaccumulation, biochemical responses includ...

Triclosan, an antimicrobial compound used in personal care products, occurs in the aquatic environment due to residual concentrations in municipal wastewater treatment effluent. We evaluate triclosan-related risks to the aquatic environment, for aquatic and sediment-dwelling organisms and for aquatic-feeding wildlife, based on measured and modeled exposure concentrations. Triclosan concentrations in surface water, sediment, and biota tissue are predicted using a fugacity model parameterized to run probabilistically, to supplement the limited available measurements of triclosan in sediment and tissue. Aquatic toxicity is evaluated based on a species sensitivity distribution, which is extrapolated to sediment and tissues assuming equilibrium partitioning. A probabilistic wildlife exposure model is also used, and estimated doses are compared with wildlife toxicity benchmarks identified from a review of published and proprietary studies. The 95th percentiles of measured and modeled triclosan concentrations in surface water, sediment, and biota tissues are consistently below the 5th percentile of the respective species sensitivity distributions, indicating that, under most scenarios, adverse affects due to triclosan are unlikely.

Triclosan (TCS) is a broad-spectrum antimicrobial used in consumer products including toothpaste and hand soap. After being used, TCS is washed or rinsed off and residuals that are not biodegraded or otherwise removed during wastewater treatment can enter the aquatic environment in wastewater effluents and sludges. The environmental exposure and toxicity of TCS has been the subject of various scientific and regulatory discussions in recent years. There have been a number of publications in the past 5 y reporting toxicity, fate and transport, and in-stream monitoring data as well as predictions from aquatic risk assessments. State-of-the-science probabilistic exposure models, including Geography-referenced Regional Exposure Assessment Tool for European Rivers (GREAT-ER) for European surface waters and Pharmaceutical Assessment and Transport Evalutation (PhATE) for US surface waters, have been used to predict in-stream concentrations (PECs). These models take into account spatial and temporal variability in river flows and wastewater emissions based on empirically derived estimates of chemical removal in wastewater treatment and in receiving waters. These model simulations (based on realistic use levels of TCS) have been validated with river monitoring data in areas known to be receiving high wastewater loads. The results suggest that 90th percentile (low flow) TCS concentrations are less than 200 ng/L for the Aire-Calder catchment in the United Kingdom and between 250 ng/L (with in-stream removal) and 850 ng/L (without in-stream removal) for a range of US surface waters. To better identify the aquatic risk of TCS, a species sensitivity distribution (SSD) was constructed based on chronic toxicity values, either no observed effect concentrations (NOECs) or various percentile adverse effect concentrations (EC10-25 values) for 14 aquatic species including fish, invertebrates, macrophytes, and algae. The SSD approach is believed to represent a more realistic threshold of effect than a predicted no effect concentration (PNEC) based on the data from the single most sensitive species tested. The log-logistic SSD was used to estimate a PNEC, based on an HC5,50 (the concentration estimated to affect the survival, reproduction and/or growth of 5% of species with a 50% confidence interval). The PNEC for TCS was 1,550 ng/L. Comparing the SSD-based PNEC with the PECs derived from GREATER and PhATE modeling to simulate in-river conditions in Europe and the United States, the PEC to PNEC ratios are less than unity suggesting risks to pelagic species are low even under the highest likely exposures which would occur immediately downstream of wastewater treatment plant (WWTP) discharge points. In-stream sorption, biodegradation, and photodegradation will further reduce pelagic exposures of TCS. Monitoring data in Europe and the United States corroborate the modeled PEC estimates and reductions in TCS concentrations with distance downstream of WWTP discharges. Environmental metabolites, bioaccumulation, biochemical responses includin...