For mobility, the chemical substructures that are associated with low KOC values are those that are highly polar or ionic, as this favours their water solubility over sorption to soil organic carbon . A 2022 review found that most ionic compounds with measured log KOC values have log KOC values <4.0 . Thus, the presence of many hydrophilic substituents may be a predictor of mobility, and conversely, chemicals with largely hydrophobic substructures are unlikely to be mobile in the environment. However, an important limitation of mobility is size. Extremely large molecules that are highly polar and ionic may not be mobile if they have sufficient hydrophobic substructures to decrease their solubility, or (as in the case of water-soluble polymers) can aggregate for charge neutrality and therefore lose/reduce their mobility as an aggregate .