Bridging principles and read-across for mixture classification

Where you do not have published test data on a mixture for health or environmental hazards, it is sometimes possible to compare the substance with similar mixtures which have been tested.

CLP includes “bridging principles” in section 1.1.3, which lay out the exact circumstances when you can use test data from a similar mixture, which cover:

• dilution or concentration of a tested mixture
• batch variation between mixtures
• interpolation between two tested mixtures
• read-across to two or more substantially similar mixtures
• changes in concentration of components in a mixture

The bridging principles are easy to understand and don’t require specialist knowledge.

It is also possible to use other types of read-across or expert judgement when classifying a mixture for CLP, and anyone carrying out this work should be a trained chemist or toxicologist.

To help you use the bridging principles, these are included in our mixture classification forms (where applicable).