<Li> Extremely Hazardous Substances: This list currently contains more than 300 chemicals . Because of their extremely toxic properties, these chemicals were chosen to provide an initial focus for chemical emergency planning . If these chemicals are released in certain amounts, they may be of immediate concern to the community . Releases must be reported immediately . </Li> <Li> Hazardous Substances: These are hazardous substances listed under previous Superfund hazardous waste cleanup regulations (Section 103 (a) of the Comprehensive Environmental Resource and Conservation Liability Act--Superfund). The current list contains about 720 substances . Releases of these chemicals above certain amounts must be reported immediately because they may represent an immediate hazard to the community . </Li> <Li> Hazardous Chemicals: These chemicals are not on a list at all, but are defined by Occupational Safety and Health Administration regulations as chemicals which represent a physical or health hazard . Under this definition many thousands of chemicals can be subject to reporting requirements if a facility manufactures, processes, or stores them in certain amounts . Inventories of these chemicals and material safety data sheets for each of them must be submitted if they are present in the facility in certain amounts . </Li> <Li> Toxic Chemicals: There are now more than 320 chemicals or chemical categories on this list, which were selected by Congress primarily because of their chronic or long - term toxicity . Estimates of releases of these chemicals into all media--air, land, and water--must be reported annually and entered into a national database . </Li>

The emergency planning and community right to know act