information available for the mixture itself and for its components. Principles that have been developed for the classification of mixtures, drawing on existing systems such as the European Union (EU) system for classification of preparations laid down in Directive 1999/45/EC. The process for the classification of mixtures is based on the following steps: Where toxicological or ecotoxicological test data are available for the mixture itself, the classification of the mixture will be based on that data; Where test data are not available for the mixture itself, then the appropriate bridging principles should be applied, which uses test data for components and/or similar mixtures; If (1) test data are not available for the mixture itself, and (2) the bridging principles cannot be applied, then use the calculation or cutoff values described in the specific endpoint to classify the mixture. Testing requirements The GHS document does not include testing requirements for substances or mixtures. In fact, one of the main goals of the GHS is to reduce the need for animal testing. The GHS criteria for determining health and environmental hazards are test method neutral, allowing different approaches as long as they are scientifically sound and validated according to international procedures and criteria already referred to in existing systems. Test data already generated for the classification of chemicals under existing systems should be accepted when classifying these chemicals under the GHS, thereby avoiding duplicative testing and the unnecessary use of test animals. The GHS physical hazard criteria are linked to specific UN test methods. It is assumed that mixtures will be tested for physical hazards. Hazard communication Per GHS, hazards need to be communicated: in more than one form (for example, placards, labels or SDS's). with hazard statements and precautionary statements. in an easily comprehensible and standardized manner. consistent with other statements to reduce confusion. taking into account all existing research and any new evidence. Comprehensibility is challenging for a single culture and language, so global harmonization is complex. The GHS Purple Book includes a comprehensibility-testing instrument in Annex 6. Factors that were considered in developing the GHS communication tools include: Different philosophies in existing systems on how and what should be communicated; Language differences around the world; Ability to translate phrases meaningfully; Ability to understand and appropriately respond to pictograms. GHS label elements The standardized label elements included in the GHS are: Symbols (GHS hazard pictograms): Convey health, physical and environmental