• National Interim Drinking Water Regulations established either the maximum concentration of pollutants allowed in or the minimum treatment required for water that is delivered to customers. (These were renamed National Primary Drinking Water Standards in the 1986 SDWA amendments.)
  


• A Recommended Maximum Contaminant Level (RMCL) is the maximum level of a contaminant in drinking water at which no known or anticipated adverse health effects would occur. The 1986 amendments renamed these Maximum Contaminant Level Goals (MCLGs). MCLGs are not enforceable.
  


• A Maximum Contaminant Level (MCL) is enforceable. It is the maximum permissible level of a contaminant in water that can be delivered to any user of a public water system. An MCL is set as close to an MCLG as possible, taking into account the costs and benefits and feasible technologies.
  


• For some contaminants, there is not a reliable method that is economically and technologically feasible to measure the contaminant, particularly at low concentrations. In these cases, EPA establishes a treatment technique. A treatment technique is an enforceable procedure or level of technological performance that public water systems must follow to ensure control of a contaminant.
  


• The hazardous waste and Superfund programs also use MCLs to define acceptable cleanup levels for contaminated water.
  

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