Evaluation of triclosan in Minnesota lakes and rivers: Part II - human health risk assessment

•Triclosan enters the environment mainly from wastewater treatment plants.•Triclosan was detected, albeit infrequently, in water and sediment in Minnesota.•A human health risk assessment was conducted using measured and modeled data.•A reference dose for triclosan was derived to assess risks to human health.•Exposure doses for all age groups and exposure pathways would not pose a risk.

Triclosan, an antimicrobial compound found in consumer products, has been detected in low concentrations in Minnesota municipal wastewater treatment plant (WWTP) effluent. This assessment evaluates potential health risks for exposure of adults and children to triclosan in Minnesota surface water, sediments, and fish. Potential exposures via fish consumption are considered for recreational or subsistence-level consumers. This assessment uses two chronic oral toxicity benchmarks, which bracket other available toxicity values. The first benchmark is a lower bound on a benchmark dose associated with a 10% risk (BMDL10) of 47 mg per kilogram per day (mg/kg-day) for kidney effects in hamsters. This value was identified as the most sensitive endpoint and species in a review by Rodricks et al. (2010) and is used herein to derive an estimated reference dose (RfD(Rodricks)) of 0.47 mg/kg-day. The second benchmark is a reference dose (RfD) of 0.047 mg/kg-day derived from a no observed adverse effect level (NOAEL) of 10 mg/kg-day for hepatic and hematopoietic effects in mice (Minnesota Department of Health [MDH] 2014). Based on conservative assumptions regarding human exposures to triclosan, calculated risk estimates are far below levels of concern. These estimates are likely to overestimate risks for potential receptors, particularly because sample locations were generally biased towards known discharges (i.e., WWTP effluent).