Exploring the mixture assessment or allocation factor (MAF): A brief overview of the current discourse

The European Chemicals Strategy for Sustainability requests to include a mixture assessment factor (MAF) into the safety assessment of chemicals, in order to account for the elevated risks of chemical mixtures. This text first reflects on the conceptual background of the MAF, and then provides an overview of current stakeholder positions and of the studies attempting to quantify an appropriate size of the MAF. Stakeholders from industry, civil society organizations (NGOs), and regulatory authorities have already put forth statements regarding the perceived advantages and disadvantages of the MAF approach, sometimes without providing detailed arguments. A consensus seems to emerge that the so-called MAFfactor is not a suitable instrument, due to its indiscriminatory nature that penalizes even chemicals that contribute only marginally to the mixture risk. Members of the larger MAFceiling family, in particular the MAFexact, overcome this limitation and are therefore suggested as the way forward.