independent agency in the executive branch charged with controlling and abating environmental pollution. The EPA maintains separate programs dealing with air and radiation, water, solid waste, and pesticides and toxic substances. Among the agency's principal tasks are establishing pollution control standards, regulating the discharge of certain materials, issuing permits for the treatment or disposal of hazardous waste, monitoring air and water quality, administering the so-called "Superfund" for the cleanup of toxic waste sites, tracking the transport of hazardous compounds, registering insecticides and similar chemical treatments, and generally providing regulatory guidance to industry and other federal agencies. Although the EPA encourages voluntary compliance with federal environmental laws, it has authority to enforce regulations where violations occur. It maintains regional offices in 10 major U.S. cities in an effort to cooperate with state and local authorities in carrying out its mission.