Thomas Edward Ward

An environmental risk assessment for DTDMAC in the Netherlands

The environmental safety of the cationic surfactant, ditallow dimethyl ammonium chloride (DTDMAC), has been determined from usage rates and fate data from The Netherlands and standard, well accepted assessment techniques. An environmental concentration model was developed using DTDMAC tonnages for 1990, actual per capita waste flow, and measured removal rates in wastewater treatment plants. This model incorporated a state of the art dilution model, instream removal and background DTDMAC concentrations. Based on this model, the 90th percentile river concentration of DTDMAC below wastewater treatment plant outfalls was estimated as 0.021 mg/L (i.e., 90% of Dutch surface waters receiving wastewater effluents have environmental concentrations less than 0.021 mg/L). This estimated concentration agrees well with the maximum measured DTDMAC concentrations in Dutch surface waters. Toxicity values for the risk assessment were derived from a study which used an environmentally relevant dosing system (i.e., effluent from an activated sludge treatment system) to measure commercial DTDMAC toxicity. Based on chronic toxicity data for Ceriodaphniadubia and Selenastrumcapricornutum from this study, a no effect level of 4.53 mg/L was determined for use in the risk assessment. Thus, the DTDMAC safety factor for aquatic organisms is 215 (4.53/0.021). It is concluded that DTDMAC poses a low risk to aquatic life based on testing of sensitive species and environmental concentrations predicted by state-of-the-art assessment methods.