Predictive assessment of the aquatic toxicity of multiple chemical mixtures

Current approaches to the assessment of chemical hazards focus on toxicity studies with single, pure chemicals. In the environment, however, organisms are exposed to numerous pollutants simultaneously. We studied the toxiciti es of multiple mixtures of pesticides and antibiotics in algal and bacteria l bioassays, The test mixtures were composed of 14 to 18 components with ei ther identical or completely different specific mechanisms of action, The r esults reveal that reliable predictions of mixture toxicities can be derive d from concentration response data of single toxicants by applying two diff erent concepts: concentration addition in cases of similarly acting mixture components and independent action for substances with dissimilar mechanism s of action.