Iron can produce rusty brown stains on plumbing fixtures, fabrics, dishes, and utensils when it combines with oxygen in the water (Manual of Small Public Water Supply Systems; EPA570-9-91-003; May 1991). Iron also produces a noticeable bitter or metallic taste in water, food, and beverages such as coffee and tea. The daily nutritional requirement for iron is 1-2 mg, yet the average diet contains 16 mg (National Secondary Drinking Water Regulations; EPA570-9-76-000; June 1984). The amount of iron causing staining or objectionable taste is a small fraction of the normal daily intake and does not have toxicological significance (42 FR 17143, 17144; March 31, 1977). EPA set a non-enforceable secondary maximum contaminant level of 0.3 mg/L in order to prevent aesthetic effects (e.g., staining, taste).
To help determine the cause(s) of aesthetic or cosmetic effects from your drinking water, contact your local drinking water system. Additional guidance for household well owners is available at http://water.epa.gov/drink/info/well/index.cfm. General information on nuisance chemicals is available at http://water.epa.gov/drink/contaminants/secondarystandards.cfm .
What can cause red, brown, or orange stains on items in contact with tap water?
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