Water Quality Regulations

Maximum Contaminant Level Goal (MCLG)

Non-enforceable safe concentration limits; allow for a margin of safety & are public health goals

Maximum Contaminant Level (MCL)

Legally enforceable concentration limits; set as close to MCLGs as possible with the available technology

National Primary Drinking Water Regulations (NPDWRs or primary standards)

legally enforceable standards that apply to public water systems; protects public health by limiting the levels of contaminants in drinking water.

National Secondary Drinking Water Regulations (NSDWRs)

non-enforceable guidelines regulating contaminants that may cause cosmetic effects (skin or tooth discoloration) or aesthetic effects (taste, odor, or color) in drinking water

Unregulated Contaminants

contaminants that are known or anticipated to occur in public water systems but are not subject to any proposed or promulgated national primary drinking water regulation (NSDWRs)

Contaminant Candidate List

primary source of priority contaminants for which we conduct research to make decisions about whether regulations are needed.

known or anticipated to occur in public water systems; currently unregulated by existing national primary drinking water regulations

6 EPA drinking water contaminant categories

OC – organic chemical; IOC – inorganic chemical; M – microorganisms; D – disinfectant; DBP – disinfection byproduct; R – radionuclides