ABSTRACT
The objective of experiment-based mixture studies is to understand organism or community responses when there is exposure to complex mixtures. This chapter reviews the results of such studies, and discusses practical implications for risk prediction. Mixture extrapolation is used to protect specific target species. Mixture extrapolation includes laboratory-to-field extrapolation, extrapolation from test species to target species, extrapolation between different matrices, and extrapolation from mixture A to mixture B. The expectation of combined effects from mixture exposure is most often founded in the basic principles of toxicology and pharmacology. The alternative concept to concentration addition is response addition, which was developed to address the issue of mixtures containing components with dissimilar actions. The protocols to aggregate compound-specific potentially affected fraction values to a single risk estimate for a mixture of compounds are derived from common toxicological theories on joint effects of compounds.
