PARENT SESSION

2A - Mixture Toxicity
Hall 6
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Hermens, J.¹, ¹
Co-chair: Toy, R.², Backhaus, T.³, ^{2 3}

(MO6/10) Useful Methods to Understand Complex Surfactant Mixture Toxicity of Effluents from Wastewater Treatment Plants.

Belanger, Scott¹, Nuck, Barb¹, Gausman, Maria¹, Federle, Thomas¹, Price, Bradford¹, ¹ The Procter & Gamble Company, Cincinnati, OH, USA

ABSTRACT- Many surfactants used in consumer product applications are themselves complex mixtures. Because of varying compositions of commercial anionic and non-ionic surfactants used across industry the environmental distributions may comprise as many as 200 homologues. Physical-chemical properties differ for each homologue that is present. This represents a particular problem for risk assessments constructed for he surfactantwhen fate and effects of each homologue contribute differentially. Toxicity tests will usually be conducted on commercial forms of the surfactant and the ultimate environmental distribution leaving sewage treatment may be substantially different. In this paper we present the rationale and some supporting evidence for use of coupled laboratory model wastewater treatment systems (porous pots, continuous activated sludge units, etc.) used to simulate environmentally realistic homologue distributions for use in laboratory toxicity studies. The work can be applied to assess complex mixtures defined as entire down-the-drain use of a cleaning product application. Results can be used to compare environmental compatibility of alternative formulations as well as predict the totality of environmental fate and single species aquatic toxicity in a single test environment. Further, this work can be extended to assess uptake, elimination, and biotransformation of complex surfactant mixtures in whole organisms via the critical body burden concept. This takes the effluent exposure to a logical next step in understanding the environmental risk of surfactant mixtures at the single species level. Limitations and advantages to these approaches will also be presented related to complex surfactant mixture risk assessments.

Key words: surfactant, mixture toxicity, wastewater treatment, environmental fate