PROJECT SUMMARY / ABSTRACT Project 2 of the Knowledge Warding Against Toxin Levels Center will be co-led by Kari Lanphier, head of the Southeast Alaska Tribal Ocean Research Consortium, and Dr. Thomas Webster, an environmental health academic expert on chemical mixtures. The purpose of Project 2 is to evaluate different estimates of the toxicity of the saxitoxin congeners in shellfish. Specifically, Project 2 will (1) Compare predictions of shellfish saxitoxin-related toxicity using a bioassay (RBA) measuring total toxicity with estimates based on measurement of individual saxitoxin congeners (via HPLC) plus Toxic Equivalency Factors (TEF) from FAO/WHO; (2) test whether saxitoxin congeners adequately predict RBA using the TEF model; and (3) improve TEF estimates by regressing RBA against saxitoxin congener concentrations using new mixtures methods.