Procedures for establishing environmentally acceptable end points for environmental cleanups include consideration of local, regional, or state background levels, waste or material-specific criteria or guidelines, risk-based generic state or federal limits, and site-specific target levels. Risk factors typically considered in developing any environmental cleanup standard or criterion have included land use and exposure to human, animal, or plant populations. However, there is evidence suggesting that a contaminant present in the subsurface or in sediments may not necessarily pose a risk to human health or the environment. Sorption is an important physical-chemical process governing the behavior of organic and inorganic contaminants and, thus, their bioavailability.