Toxicity Identification Evaluations Phase Ill Toxicity Confirmation Procedures for Samples Exhibiting Acute and Chronic Toxicity

In 1989, the guidance document for acutely toxic effluents entitled Methods for Aquatic Toxicity Identification Evaluations: Phase Ill Toxicity Confirmation Procedures was published (EPA, 19890). This new Phase Ill manual and its companion documents (EPA, 1991 A; EPA, 1992; EPA, 1993A) are intended to provide guidance to aid dischargers in confirming the cause of toxicity in industrial and municipal effluents. The toxicity identification evaluation (TIE) starts with a characterization of the effluent toxicity using aquatic organisms to track toxicity; this step is followed by identifying a suspect toxicant and then confirming the suspect toxicant as the cause of toxicity. This Phase III confirmation document provides greater detail and more insight into the procedures described in the acute Phase III confirmation document (EPA, 1989D). Procedures to confirm that all toxicants have been correctly identified are given and specific changes for methods applicable to chronic toxicity are included. Adifficult aspect of confirmation occurs when toxicants are not additive, and therefore the effects of effluent matrix affecting the toxicants are discussed. The same basic techniques (correlation, symptoms, relative species sensitivity, spiking, and mass balance) are still used to confirm toxicants and case examples are provided to illustrate some of the Phase III procedures. Procedures that describe the techniques to characterize the acute or chronic toxicity (EPA, 1988) and to identify (EPA, 1989A) toxicants have also been rewritten (EPA, 1991 A; EPA, 1992; EPA, 1993A).