Environmental hazard classification of mixtures
The classification of environmental hazards of mixtures should be made on the basis of test data, where it exists. However, tests on animals are to be avoided where at all possible, and this means that vertebrate tests on aquatic toxicity, that is fish testing, should be avoided where possible.
To overcome this difficulty, CLP includes a series of options to allow people to classify the environmental hazards of mixtures and avoid testing on fish (although other forms of testing such as daphnia and algae tests are allowed):
- bridging principles, a specific form of read-across for closely-related mixtures which have already been tested
- comparison to published thresholds (this can apply to mixtures containing a single component with a particular health hazard; or to some types of hazard where the effects of several components with the same health hazard are not considered to be “additive”). A threshold can be substance-specific, and published as part of a Harmonised Classification; or it can be generic and based on the hazard classification limits.
- calculation methods (or algorithms), where there are several components with the same hazard but with varying levels of severity
- weight-of-evidence, where all of the available evidence is reviewed to arrive at a hazard classification
To help with classifying the environmental hazards of mixtures, we have produced a series of forms to guide you through the process of classifying using the first three methods (bridging principles, followed by thresholds, and algorithms, all where applicable).