Primary Drinking Water Standards

• Address contaminants that are known to have an adverse effect on human health
• Are mandatory for all public water systems
• The frequency and number of contaminants monitored depend on water system size and classification

Secondary Drinking Water Standards

• Address contaminants that have an effect on the aesthetic quality of drinking water (color, odor, and taste)
• Are not known to have adverse health effects
• Are not mandatory for public water systems, although the primacy agency has the authority to require action in severe cases