What is the National Secondary Drinking Water Regulation for aluminum?

• A. 0.01-0.05 mg/L
• B. 0.05-0.2 mg/L
• C. 0.1-0.3 mg/L
• D. 0.1-0.5 mg/L

Answer: (B)

Secondary drinking water standards set guidelines for cosmetic and aesthetic qualities of drinking water, not health-based limits. For aluminum, the EPA’s recommended range is 0.05 to 0.2 mg/L. This range balances how aluminum behaves in different waters—depending on factors like pH, alkalinity, and overall water chemistry—to minimize taste, color, and staining issues while avoiding noticeable deposition or turbidity. Utilities monitor and adjust treatment to stay within this range so most customers don’t notice any adverse aesthetic effects. If levels rise above 0.2 mg/L, consumers are more likely to perceive taste changes, discoloration, or staining, which is why keeping within this upper limit is important. The lower end helps ensure that even low concentrations don’t introduce perceptible cosmetic effects in typical waters.