What is chromium-6 in water?

Chromium-6, or hexavalent chromium, is one form of the metallic element chromium. It can occur naturally through the erosion of mineral deposits or enter the environment through certain industrial activities.

EPA currently regulates total chromium in public drinking water at 0.1 milligrams per liter, or 100 parts per billion. That standard includes both chromium-3 and chromium-6; there is not a separate federal drinking-water limit specifically for chromium-6. Testing is required to determine whether chromium is present. Learn more from the EPA.