Source: WQA Glossary of Terms-Copyright 1991, 1995 by the Water Quality Association.
All other users refer to original source
Standards that define allowable water quality limits for potable and domestic water supplies.
The U.S. Environmental Protection Agency (EPA) is responsible for the National Primary Drinking Water Regulations, which are health-related standards that establish the Maximum Contaminant Levels (MCL's) for regulated substances in drinking water. An MCL is the highest permissible level of a contaminant allowed in water delivered to the consumer's tap. MCL's are enforceable at public water systems under the Safe Drinking Water Act. The EPA has also set Maximum Contaminant Level Goals (MCLG's) at levels at which no known or anticipated adverse effects on the health of persons occur and which allow an adequate margin of safety. The enforceable MCL is set as close to the MCLG as reasonable, taking into consideration the costs and treatment techniques available to public water systems.
National Secondary Drinking Water Regulations, also issued by the EPA, pertain to aesthetic characteristics of water, and are advised but not enforceable by the Federal Government.