The Superfund Chemical Data Matrix (SCDM) Appendix B Tables are a source for factor values and benchmark values applied when evaluating potential National Priority List (NPL) sites using the Hazard Ranking System (HRS). The HRS assigns factor values for toxicity, gas migration potential, gas and ground water mobility, surface water persistence, and bioaccumulation potential based on the physical, chemical, and radiological properties of hazardous substances (defined for HRS purposes as CERCLA hazardous substances plus CERCLA pollutants and contaminants) present at a site for a particular migration pathway. The HRS also assigns extra weight to targets with exposure levels to hazardous substances that are at or above benchmarks. These benchmarks include both screening concentrations and concentrations specified in regulatory limits for the hazardous substances present at a site for a particular migration pathway. Appendix B-1 contains an HRS factor value and benchmark tables (organized by pathway) for nonradioactive hazardous substances, Appendix B-2 contains similar tables for radionuclides.