Frequent Questions

Regarding EPA's regulatory determinations for priority contaminants on the first drinking water contaminant candidate list (CCL), what was the final determination for regulating sulfate?

After reviewing the best available public health and occurrence information, EPA made the determination not to regulate sulfate with a NPDWR, because it would not present a meaningful opportunity for health risk reduction for persons served by public water systems (PWSs). Although sulfate occurs in many PWSs nationally, the weight of evidence suggests that the adverse health effect is generally mild, of short duration, and generally occurs at concentrations considerably greater than 500 mg/L, except in very limited circumstances when sulfate co-occurs with magnesium and high total dissolved solids, which exacerbate its laxative effects. EPA  issued a final Drinking Water Advisory to provide guidance to communities that may be exposed to drinking water with high sulfate concentrations (68 FR 42897, 42905; July 18, 2003). Information about the regulatory determinations for the first CCL is available at
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