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Drinking Water Maximum Contaminant Levels (MCLs)

Published by U.S. EPA Office of Water (OW) - Office of Ground Water and Drinking Water (OGWDW) | U.S. Environmental Protection Agency | Catalog Last Checked: May 01, 2026 at 06:08 PM | Dataset Last Updated: May 01, 2009
National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water.

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