The Environmental Protection Agency's (EPA's) list of the most serious uncontrolled or abandoned hazardous waste sites identified for possible long-term remedial action under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The list is based primarily on the score a site receives from the Hazard Ranking System described in 40 CFR Part 300, Appendix A. EPA must update the NPL at least once a year. See: Comprehensive Environmental Response, Compensation, and Liability Act