ECHA’s Member State Committee (MSC) agreed to modify the approach for investigating chromosomal aberration under REACH dossier evaluation during its June meeting.

The main changes include:

• To fulfil REACH Annex VIII 8.4.2 requirements, an in vitro micronucleus study (OECD Test Guideline 487) is the default test as it allows the mode of action (clastogenicity and/or aneugenicity) to be identified.
• If a concern for chromosomal aberration is identified in vitro, a follow-up study combining an in vivo comet assay (OECD Test Guideline 489) and an in vivo micronucleus test (OECD Test Guideline 474) will be needed in most cases.

Recommendations to registrants have been modified to reflect these changes, which have applied since 1 September 2022. Exceptions to this general approach may apply. See the recommendations for more detail.