What is meant by the term "National Priority List"?

The "National Priority List" is a list of the highest ranking hazardous waste sites in the U.S.It is created and maintained by EPA under the Superfund law (CERCLA).The sites,identified by EPA,are ranked on the basis of the type,quantity,and toxicity of the wastes;the number of people potentially exposed to the wastes;the different ways (e.g. ,in the air or drinking water)in which they might be exposed;the risks to contamination of aquifers;and other factors.The sites with the highest ranking are put on the National Priority List to receive priority federal and/or state attention for cleanup.At these sites,EPA makes careful scientific and engineering studies to determine the most appropriate cleanup plans.Once a site has been cleaned up,the state is responsible for managing it to prevent future environmental problems.