What Is Hexavalent Chromium and How Do I Remove It from Water?

Posted by
John Woodard on January 20, 2023

Chromium is a tasteless, odorless metal that occurs naturally in rocks, soil, and animals. It manifests in two forms, one that the human body needs and one that is toxic. The healthy form of chromium, known as trivalent chromium or chromium-3, is vital in maintaining blood sugar levels. The other type of chromium, called hexavalent chromium or chromium-6, is a carcinogen that can cause long-term health problems. Both forms of chromium can reside together, and they can even switch between forms when acted upon by outside factors. Because of the toxicity of hexavalent chromium, its presence in water supplies must be limited to prevent adverse side effects. Below you can find information on what hexavalent chromium is, how it contaminates water, how to test for it, and how to remove it from your water supply.

What is hexavalent chromium?

Hexavalent chromium, also known as chromium-6, is a toxic form of chromium most commonly created in industrial and manufacturing processes. It is common in everyday items, such as stainless steel, leather, metal finishing, chrome plating, spray paints, and wood preservatives. Chromium-6 is chromium with an oxidation state of +6, meaning it contains three more valence electrons than naturally occurring trivalent chromium, commonly called chromium-3. While both chromium-6 and chromium-3 cause side effects with high exposure, chromium-6 can cause symptoms at low levels of exposure as well.

Symptoms of hexavalent chromium exposure

Both hexavalent and trivalent can cause side effects, particularly in those exposed regularly. Metals that contain chromium are a particular risk to workers, especially welders and those that work with chrome plating. Occupations that deal with spray paints, pigments, and coatings are also at risk of high chromium exposure. OSHA regulations require that workers are not exposed to more than 5 micrograms per cubic meter of air in their work environment.

Metal workers are not the only potential victims of the effects of chromium intoxication. Water sources across the country have been known to contain levels of chromium-6 that can be toxic for consumption. While the EPA regulates the levels of chromium in city-treated water, there is growing concern about the effects of chromium-6 on the human body at even minuscule levels. Well owners must be especially wary of the chromium concentrations in their drinking water.

Whether ingested through the air or water, hexavalent chromium can cause some undesirable side effects, including:

  • Increased cancer risk
  • Respiratory irritation
  • Abdominal pain
  • Skin irritation
  • Nose irritation

The more long-term the exposure, the more dangerous symptoms become. What starts as irritation to the respiratory system, nose, and skin can eventually lead to damage or cancer in these areas.

What are safe levels of chromium in drinking water?

The safe level established by the EPA for chromium in drinking water is 100 parts per billion (ppb) or fewer. Chromium can easily shift between its trivalent and hexavalent forms, so the EPA regulates the total concentration of chromium in water supplies. By treating all chromium as one, concentrations of chromium-6 do not form from elevated levels of the less harmful chromium-3. This lessens the likelihood of more severe side effects of chromium-6 exposure, such as increased cancer risk.

In 2014, California set a separate standard for chromium-6 in drinking water. This limits the total hexavalent chromium levels to 10 ppb. Some public health researchers wish for the chromium-6 allowed levels lowered to as little as .02 ppb, which would cause greater care and expense during the water treatment process. As of 2023, California is the only state to mandate separate contamination levels for chromium-6.

How does hexavalent chromium get into water?

Chromium-6 can enter water from natural chromium deposits, but a substantial increase in chromium contamination has been caused by industrial waste. The biggest contributors to chromium-6 contamination are steel mills, wastewater from cooling systems, plumbing fixtures, and improperly disposed of industrial waste. The increased chromium contamination, both in water and in the air, from manufacturing processes has become a major concern in environmental sectors.

steel mill

Is hexavalent chromium in well water?

Yes, hexavalent chromium enters well water from the erosion of rocks underground. It is most abundant in the Piedmont region of the eastern United States. This area includes Georgia, the Carolinas, Virginia, Maryland, Pennsylvania, and New Jersey. Some capacity of chromium-6 can also be found in every state outside the Piedmont region. High levels of hexavalent chromium have been found in water supplies in states like Oklahoma, Wisconsin, and even Hawaii. Regardless of location, you should test for hexavalent chromium in your well water before utilizing it for drinking or cooking.

How to test for hexavalent chromium in water

Testing for hexavalent chromium is simple and easy. Hexavalent chromium test strips can detect chromium-6 in levels from 50 ppb to 5000 ppb. These strips must be used with a photometer that uploads test results directly to your smart device. These can be used for pools, spas, wells, and other water sources for your home.

An alternative testing method for well water is laboratory analysis. If you wish to test for all possible harmful contaminants in your well water, a laboratory test will give a comprehensive breakdown of the elements in your water supply. A Watercheck Test Kit provides everything you need to send water to a laboratory for analysis. The EPA has certified laboratories in each state, making finding a local laboratory simple. Results are typically mailed and completed within 10 to 15 business days after the samples are received.

How to remove hexavalent chromium from water

Hexavalent chromium should be filtered out of water as much as possible before drinking. However, many at-home water filters, such as activated carbon filters, ceramic filters, and water pitcher filters, do not treat chromium-6, so extra care must be taken to remove it from your home’s water. The two most effective at-home water filtration and purification systems for removing hexavalent chromium are reverse osmosis systems and water distillers.

Removing hexavalent chromium with reverse osmosis

Reverse osmosis systems are possibly the most effective method of removing hexavalent chromium from a home’s water. The particle size of chromium-6 typically ranges from 1.0 to 5.6 micrometers (μm). Reverse osmosis membranes generally contain a micron rating of around .0001 microns. This gives reverse osmosis systems great efficiency in removing chromium-6, as well as almost all other water contaminants. These systems can be purchased in a whole-home configuration, or they can be installed under a sink for point-of-use treatment.

Reverse osmosis systems are advantageous over water distillers in their filtration time, the functionality of the filtered water, and the energy used during the filtration process. They do, however, require more maintenance in the form of regular filter replacement.

Learn more: What is a reverse osmosis system?

Removing hexavalent chromium with water distillation

Water distillers are an effective way to remove hexavalent chromium from water used specifically for drinking. Water distillers use a process similar to that of the hydrological cycle. Unpurified water is added to a boiling chamber, where it is heated until it evaporates. The resulting water vapor collects on the ceiling of the distiller, where it is cooled back down to a liquid. This liquid becomes too heavy to cling to the ceiling, leading the purified water to drip into a collection container. This process removes essentially all contaminants from water, and it is the only water purification or filtration method allowed in applications, such as hospitals and laboratories, that require superior water purity.

Water distillers are excellent at removing chromium-6 from water, but home water distillers are generally only used for drinking water. If you require a large amount of water to cook, a water distiller will not provide sufficient speed to meet your demand. Cooking with contaminated water is particularly harmful in pasta and rice dishes, as these foods absorb impurities from the water they are cooked in.

Learn more: What is distilled water?

Does boiling water remove hexavalent chromium?

No, boiling water does not remove chromium-6 from water. Boiling water primarily functions to make water potable by eliminating viruses, bacteria, and other living organisms. More advanced filtration systems are needed to reduce chromium levels in water. Many common kitchen water filters, like refrigerator filters and water pitcher filters, are not rated to remove it.

Does bottled water contain hexavalent chromium?

The FDA ensures that EPA standards for drinking water are followed by bottled water sold in the United States. As a result, all bottled water must contain fewer than 100 ppb of total chromium. The levels of chromium in a brand’s bottled water are dependent on the filtration method that the brand uses. Brands that utilize reverse osmosis should produce water that is lower in chromium than other brands. The chromium levels of each brand’s bottled water can be found in their water quality reports.

You can learn more about contaminants in water on our blog.



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