HazDat, the Agency for Toxic Substances and Disease Registry's Hazardous Substance Release/Health Effects Database, is the scientific and administrative database developed to provide access to information on the release of hazardous substances from Superfund sites or from emergency events and on the effects of hazardous substances on the health of human populations. To search, go to Site Activity Query.
 

This map lets you click on the desired state to receive a list of HazDat sites for that state. 
To find out more, go to Site Activity Query Map.
 

This lets you search for a specific chemical to see if it's at a site in your community. 
To search, go to Internet HazDat - Site Contaminant Query.