The toxicity of Complex Mixtures have posed problems for ecotoxicologists for years. Now KREATiS has developed a system for determination of the thermodynamic profile of an aqueous mixture coupled with a method for removing the non-bioavailable fraction and using an additivity approach for calculating lethal loadings. Unlike the CLP calculation which is extremely conservative compared to experimentation, this mixture toxicity calculation is extremely accurate. Falling within 25% of results from over a dozen laboratory WAF studies, the method can be considered to provide an accuracy equivalent to that of a laboratory study. Paul Thomas will be presenting the calculation method at SETAC in Basel. (Thursday, 15th May 2014 at 08:35 AM).