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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 | Metadata Last Checked: July 31, 2025 | Last Modified: 2009-05-01
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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