is the responsibility of independent drinking water quality regulator (dwqr). in northern ireland the drinking water inspectorate (dwi) regulates drinking water quality of public and private supplies. the current standards of water quality are defined in the water supply (water quality) regulations (northern ireland) 2017. united states the safe drinking water act requires the u.s. environmental protection agency (epa) to set standards for drinking water quality in public water systems (entities that provide water for human consumption to at least 25 people for at least 60 days a year). enforcement of the standards is mostly carried out by state health agencies. states may set standards that are more stringent than the federal standards. epa has set standards for over 90 contaminants organized into six groups: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides. epa also identifies and lists unregulated contaminants which may require regulation. the contaminant candidate list is published every five years, and epa is required to decide whether to regulate at least five or more listed contaminants. local drinking water utilities may apply for low interest loans, to make facility improvements, through the drinking water state revolving fund.