The U.S. Environmental Protection Agency (U.S. EPA) proposes to use a leaching test as one of the criteria for estimating the environmental hazard of on-land disposal of hazardous wastes. There are many significant technical problems with the specific protocols proposed for use, such as not specifying a defined redox condition under which the tests are to be conducted. The most significant deficiency is in the proposed method for interpretation of leaching test results. The use of these tests as currently formulated could readily result in chemicals that present minimal risk to the environment and human health, being classified as hazardous. More importantly, their use could cause truly hazardous wastes to be classified as acceptable for on-land disposal with minimum restrictions. Adopting the U.S. EPA's proposed approach will result in unnecessarily large amounts of money being spent for control of “hazardous” chemicals and, in some cases, without providing adequate environmental or human health protection.

This paper reviews some of the problems associated with the use of the U.S. EPA Resource Conservation and Recovery Act (RCRA) leaching test for classifying the hazardous nature of chemicals destined for land disposal. Recommendations are made for modification of the RCRA leaching test, to provide for a site-specific evaluation procedure to more properly evaluate the potential hazard associated with on-land disposal of hazardous wastes. An approach is discussed which combines environmental physics (transport and mixing), chemistry-fate, and biology (toxicology, bioconcentration) information. This approach is presented as a basis for interpretation of the results of the leaching tests in terms of the hazard associated with the disposal of a particular waste at a particular site. This “hazard assessment approach,” which has been adapted for application to solid wastes by the authors, is a sequential, selective testing-interpretation scheme for combining information on environmental physics (transport and mixing), chemistry-fate, and biology (toxicology and bioconcentration) of a waste and disposal site to determine potential environmental hazard.