The National Secondary Drinking Water Standards (NSDWS) protect the public from odor and aesthetic problems in drinking water that could cause many people to stop using the affected public water system. A Suggested Maximum Contaminant Level (SMCL) for each pollutant are guidelines only. These SMCLs are referred to as the National Secondary Drinking Water Standards (NSDWS). Some of the contaminants listed above do not have established SMCLs because it is not possible to determine their levels in drinking water.The standards for these 15 contaminants are merely advisory, and EPA cannot enforce them.

Note: Individual states may enforce their own drinking water standards as long as they are no less stringent than the NPDWS regulations. Each state may regulate additional contaminants in drinking water or may establish more stringent SMCLs for the contaminants listed in the Table above. For a list of the drinking water contaminants regulated by your state, contact your state agency. EPA has a list on the
Safe Drinking Water Hotline at (800) 426-4791