Ranking of top 20 organic ground water contaminants based on number of sites at which each contaminant was detected. 2. Selected toxic organic chemicals ordered by Chemical Abstract Service Registry Number (CAS RN). Those chemicals on the U.S. EPA top 100 hazardous substances list are also noted. 3. Selected toxic organic chemicals ordered by number of carbon and hydrogen atoms. 4. Ranking of selected toxic organic chemicals by specific gravity at room temperature. 5. Solubilities of selected toxic organic chemicals. 6. Vapor pressure and boiling point of selected toxic organic chemicals and water. Ranking by vapor pressure. 7. Relative dielectric permittivities for selected toxic organic chemicals and water. 8. Ranking of selected organic chemicals by ionization potential. 9. Ranking of selected toxic organic chemicals by fire hazard. 10. Threshold limit exposure values for selected toxic chemicals.