"At the end of fiscal year 2009, the Environmental Protection Agency's (EPA) National Priorities List (NPL) included 1,111 of the most seriously contaminated nonfederal hazardous waste sites. Of these sites, EPA had identified 75 with unacceptable human exposure, 164 with unknown exposure, and 872 with controlled exposure that may need additional cleanup work. EPA may fund remedial actions-long-term cleanup-from its trust fund, and compel responsible parties to perform or reimburse costs of the cleanup. GAO was asked to determine (1) the cleanup and funding status at currently listed nonfederal NPL sites with unacceptable or unknown human exposure; (2) what is known about EPA's future cleanup costs at nonfederal NPL sites; (3) EPA's process for allocating remedial program funding; and (4) how many NPL sites some state and EPA officials expect to be added in the next 5 years, and their expected cleanup costs. GAO analyzed Superfund program data, surveyed and interviewed EPA officials, and interviewed state officials. "