Read-across in substance grouping is a strategy that relies on the use of important information obtained from tests conducted on a reference substance known as the "source" substance within a group to predict the properties of another substance in the group known as the "target" Read-across is advantageous because it reduces the number of experimental tests needed during an assessment by using existing experimental data for the source substance(s) to predict the properties of the untested substance(s) . If a clear hypothesis and justification are provided, read-across can be used efficiently to predict the hazard properties of target substances and fill data gaps in the regulatory process, thereby facilitating and speeding up assessment and regulatory decisions [107]. However, read-across requires an adequate justification for use, and appropriate documentation covering all assumptions and conclusions . This can be complex and may require a certain level of expertise for interpretation . Despite its limitations, read-across can be applied to the grouping of PMT/vPvM substances.