Is the Mixture Assessment Factor Still on the REACH Agenda?

Following the April 27, 2026, European Parliament Environmental Committee announcement that the European Commission (EC) would not proceed with a legislative proposal for a comprehensive revision of the European Union’s (EU) Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulation, major reforms — such as the registration of polymers — appear to be off the table. Technical amendments to the REACH Annexes through comitology remain possible, however, although it is not yet clear which of the proposed initiatives previously identified by the EC will be taken forward.

One initiative that may still be worth watching is the Mixture Assessment Factor (MAF). On August 19, 2026, the EC’s Directorate-General for Environment (DG ENV) highlighted academic research supporting the consideration of the MAF in the REACH risk assessment framework.

The MAF was identified by the EC under the Chemicals Strategy for Sustainability as a potential means of addressing a recognized limitation of the current REACH risk assessment framework. REACH focuses primarily on individual substances rather than combined exposure to multiple chemicals. Inclusion of the MAF would account for the contribution of “coincidental mixtures” to overall risk, potentially resulting in greater controls to substances that contribute disproportionately to the combined risk.

Several approaches to determining and applying the MAF have been proposed. The more recent allocation approach highlighted by the DG ENV differs from a simple generic assessment factor by seeking to allocate an acceptable overall mixture risk between substances according to their contribution to that risk. This approach adapts the “risk cup” approach originally developed by the U.S. Environmental Protection Agency in the regulation of pesticides.

The MAF is not currently required under EU law. Nevertheless, the DG ENV’s decision to highlight recent research suggests that mixture risk remains relevant to the EC’s chemical management policy agenda. Whether that interest translates into a concrete amendment to REACH remains to be seen. Companies may wish to continue to monitor the issue, particularly those involved in REACH registration and chemical risk assessment.