The Importance of Defining Background Water Quality

General Controls on Natural Water Chemistry Chap. 8 

TABLE 8.12 U.S. Environmental Protection Agency (1994) drinking water standards for inorganic species in community water supplies 

Note Maximum contaminant levels (MCLs) are enforceable standards for substances that may constitute a health hazard at higher concentrations. Secondaiy maximum contaminant levels (SMCLs) are not enforceable, but are set for aesthetic reasons, to avoid tastes, odors, and staining of plumbing fixtures. 

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