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Chromium in Drinking Water

Water Contaminants: Chromium

Chromium contamination of drinking water was highlighted in the year 2000 movie “Erin Brockovich”. The movie was based on a true story, where a town in California was discovered to be suffering from drinking water contaminated with a toxic form of chromium.

Chromium occurs naturally in rocks, soil, plants and animals. Chromium also has a wide range of industrial uses, including pigments, paints, photography, leather tanning, catalysts, chrome plating, chrome alloys, ceramic and glass, and pesticides.

“Although chromium-3 itself is not harmful, chromium can convert back and forth between chromium-3 and chromium-6 in water and the human body, depending on the chemical conditions.”

There are two forms of chromium that commonly occur in water: trivalent chromium (chromium-3) and hexavalent chromium (chromium-6). Chromium-3 is actually an essential nutrient for humans, and it is found in many fruits, vegetables, grains and meats. Chromium-6 is harmful to humans, and it occurs in association with natural chromium deposits and industrial activities. Chromium-6 from industrial sources can enter the environment from leakage of waste or poor waste disposal practices. Although chromium-3 itself is not harmful, chromium can convert back and forth between chromium-3 and chromium-6 in water and the human body, depending on the chemical conditions.

Typical concentrations of chromium in groundwater and river water are very low, but elevated concentrations can occur due to industrial contamination.

Chromium and Human Health

Chromium-3 is an essential mineral nutrient that humans need in very small quantities. The necessary amount of chromium is usually acquired through food. However, large doses of chromium can result in severe health problems.

Chromium-6 is well known as a carcinogenic (cancer-causing) substance, and it can cause DNA damage in human cells. Long-term exposure to chromium-6 can lead to lung cancer, stomach and gastrointestinal cancer, and dermatitis.

For drinking water, the U.S. Environmental Protection Agency (USEPA) has set a maximum contaminant level (MCL) for total chromium (chromium-3 plus chromium-6) of 0.1 milligrams per liter (mg/L or parts per million) in municipal water supplies. This is the maximum concentration of chromium that is legally allowed in public drinking water systems under the Safe Drinking Water Act. The long-term health risks from consuming water with concentrations above the MCL are considered to be unacceptable.

The USEPA does not require water supplies to monitor chromium-6 concentrations, but California requires municipal water supplies to monitor this chemical and sets a limit of 0.010 milligrams per liter.

Detection of chromium in water requires chemical testing.

Interesting fact: Stainless steel contains up to 20% chromium by weight.

How to Remove Chromium 6 from Drinking Water

Chromium can be removed from drinking water by reverse osmosis. Reverse osmosis works by forcing the water through a membrane that allows water molecules to pass through but blocks larger ions, such as ones associated with iron, lead and chromium. In homes, small reverse osmosis systems (called point-of-use systems) can be located near the kitchen sink.