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New advice for using read-across

ECHA’s advice helps companies create robust and complete read-across adaptations for their substances, including those of unknown or variable composition, complex reaction products or biological materials (UVCBs). It covers changes to the REACH annexes that started to apply in January 2022.

Helsinki, 6 May 2022 – Companies are required to adequately justify and document the use of grouping and read-across in their registrations. They need to include robust study summaries for each study performed on a source substance which is used to provide information for the target substance. Their registrations also need to contain justifications and evidence for the read-across hypothesis.

The changes to the REACH annexes clarify the need for companies to give information on their substance compositions to demonstrate structural similarity. Establishing structural similarity is a prerequisite for performing grouping and read-across. For UVCBs, this is done based on the information that companies provide on the composition of their substances.

Companies also need to explain if the possible differences between the structures of the source and target substances have an impact on the prediction of hazardous properties. If the identification of all constituents is not technically possible or it is impractical, companies need to demonstrate structural similarity by other means and justify it.

Our Guidance on Information Requirements and Chemical Safety Assessment – Chapter R.6 is also being revised to reflect the changes. It is expected to be published later in 2022.


Grouping and read-across are commonly used alternative approaches for filling data gaps in REACH registrations. These approaches use relevant information from a source substance to predict the properties of a similar target substance. If grouping and read-across are applied correctly, testing can be reduced as there is no need to test every target substance.