Both biotic and abiotic transformations generally result in transformation products (TPs) with significantly higher mobility (lower log KOW) than their parent compounds or precursors, making them more mobile in the environment. This seems intuitive as one of the "goals'' of metabolism and wastewater treatment processes is to increase the polarity of the compounds. For metabolic processes, this allows the compounds to be expelled from the body with the urine. However, some persistent substructures may be retained during the transformation resulting in similar toxic properties between the parent compound and TPs. For example, decabromodiphenyl ethane forms 6 metabolites that were found to be carcinogenic like the parent compound . In other cases, even small structural changes can result in large differences in toxicity such as for bis(pentabromophenyl) ether, which has low thyroid binding affinity itself but can form the TP 2,3,5,6-tetrabromo-4-(2,3,4,5,6-pentabromophenoxy)phenol with a strong thyroid binding affinity . Therefore, it is of interest not only to identify parent compounds that may be PMT/vPvM, but also compounds that can form PMT/vPvM TPs, along with identifying the common persistent and mobile moieties that were retained and not readily metabolized. Such an approach would be consistent with the approach to substance grouping in REACH of identifying "common breakdown products via physical and biological processes, which result in structurally similar chemicals" (REACH Annex XI, Section 1.5).