- Practical Guide -
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Approximations will be necessary. For instance, if the mixture consists of substances of
similar structure and molecular weight, it may be assumed that all components migrate to the
same extent and the composition of the migrated material will correspond to that of the
If it is analytically not feasible to determine the mixture as a whole, selected components of
the mixture must be measured and the totals calculate from there. This approach again
presupposes that all relevant components of the mixture migrate to the same extent.
The petitioner submits a petition for the mixture, but only presents toxicological and
migration data for one or a few components, selected as representatives of the mixture. As an
example, if the mixture consists of homologous compounds, the evaluation might be based
on the following information:
Set of toxicity data on one or on a few components of the mixture;
Scientific evidence (e.g. structure-activity correlation) showing how the toxicological
profile of the other components is related to that of the compound investigated.
This procedure combines the advantages of both previous procedures and avoids their
disadvantages. However, it remains at the SCF to decide whether the data on one or a few
components enables the evaluation of the whole mixture.
The SCF prefers Procedure A, because it facilitates the examination of the technical dossier
of the "process mixtures" and, if necessary, the definition of restrictions, but it is aware of the
possible difficulties in strictly applying Procedure A and recognises that no "a general rule"
can be established.
4.2.3 Recommended procedure for the evaluation of a mixture
In conclusion, the Commission recommends to either follow Procedure A or to proceed in
steps. In the latter case, a petition accompanied by a technical dossier is submitted,
characterising the mixture and proposing a strategy to obtain toxicological data. For instance,
if the petitioner intends to follow Procedure C, he presents evidence on how the toxicological
profile of the component(s) proposed to be tested is related to that of all others. The SCF will
respond whether the chosen strategy is acceptable or alternative routes should be followed.
The petitioner submits a technical dossier describing the mixture and proposes a
procedure (A, B or C).
2nd step: The SCF examines the dossier and decides on the most appropriate procedure.
3rd step: The petitioner carries out the toxicity and migration testing.
4th step: Final evaluation by SCF.