ABSTRACT
Assessing the risk of a mixture of chemicals occurring in the environment is one of the main challenge. Thousands of chemical compounds find their use in different sectors of human activities like cosmetics, pharmaceuticals, cleaning products, pesticides and many others. This chapter describes the current mixture risk assessment procedure and discusses their limits. It presents the risk assessment for a mixture using Lake Geneva and the Rhone River as case studies. The chapter provides a discussion on the mixture risk predictions of herbicides with in-situ temporal phytoplankton fluctuations in a mid-sized lake. A robust methodology to assess the risk of mixture would be the assessment of mixture effects for different species, that allow building SSD curve for this mixture. The methodologies are based on the principle of concentration addition (CA) and are recommended as a first step on a tiered process because the simplifications in the mixture effects theory tends to give an overestimation of the toxicity.
