Assessment of Mixtures: Bridging Principles and Other Approaches

Abstract

In general, test data for mixtures are available only in rare cases. For a hazard assessment, a common surrogate method is to delineate their hazard potential from data of individual ingredients. Another approach exists to extrapolate from mixtures with test data to nontested mixtures. Such bridging principles have been in use in certain sector-specific applications already in the past. With the adoption of the new globally harmonized system for classification and labeling of chemicals (GHS), bridging principles gained a broad regulatory acceptance for the hazard assessment of mixtures. In order to make use of the principles, strong formal requirements must be fulfilled. This chapter describes the various applicable principles, such as the principle of “dilution,” “concentration,” “interpolation,” and “batching” of “substantially similar mixtures.”

Another way for the assessment of a mixture is the weight of evidence approach leading to an expert judgment. It is less formal, but it suffers from legal certainty and may be challenged more frequently by third parties.