National Primary Drinking Water Regulations (NPDWRs, or primary standards)
Legally enforceable federal standards that apply to public water systems. Primary standards limit the levels of contaminants in drinking water. A 1996 amendment to the Safe Water Drinking Act (SDWA) requires that the United States Environmental Protection Agency establish a list of contaminants every five years that are known or anticipated to occur in public water systems and may require future regulations under the SDWA.