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Total Chromium and Hexavalent Chromium (Cr6) Frequently Asked Questions


What is chromium?

  • Chromium is the 24th element on the periodic table. It is a naturally occurring metal found in soils, plants, rocks, water, and animals.

  • There are two common forms: Chromium-3 (Cr3 or trivalent chromium) and Chromium-6 (Cr6 or hexavalent chromium).

  • Cr3 is an essential human dietary element found in vegetables, meats, fruits, grains, and yeast.

  • Chromium is used in steelmaking, metal plating, leather tanning, paints, dyes and wood preservatives. It is discharged by industrial facilities such as coal-burning power plants.


What is the difference between Total Chromium and Cr6?

  • Total chromium measurement includes Cr6 and Cr3.

  • Our data on total chromium are available on our website at http://www.fairfaxwater.org/water/imar.htm and http://www.fairfaxwater.org/water/imar_aqueduct.htm (for customers residing in the City of Falls Church).

  • The EPA currently regulates total chromium at a maximum contaminant level of 100 ppb. Fairfax Water is in compliance with this regulation.

  • Chromium converts back and forth between Cr3 and Cr6.

  • It is challenging to set a Cr6 drinking water standard because these forms of chromium can convert back and forth in water and the human body, as well as under different environmental conditions.

  • Cr3 is an essential micronutrient and has low toxicity.

  • Cr6 is more toxic and is known to cause cancer when inhaled.


Is there Cr6 in our drinking water?

  • Fairfax Water has been testing for Cr6 since 2010.

  • Since 2010, the Cr6 levels measured leaving our water treatment plants and in our distribution system have ranged from 0.04 parts per billion (ppb) up to a maximum of 0.24 ppb, with an average of 0.10 ppb.

  • These results are well below California’s maximum contaminant level (MCL) of 10 ppb.

  • There is no EPA regulation specific to Cr6 and therefore no MCL at the federal level. The California regulation set the MCL at 10 ppb.

  • We test our source water and treated drinking water for Cr6.

  • More research is needed to understand the Cr6 toxicity in drinking water and how chromium converts between Cr6 and Cr3 in the body.


How does Cr6 get into drinking water?

  • Cr6 enters water supplies from industrial contamination or occurs naturally from water interacting with rocks and soil.

  • Groundwater has higher natural levels of Cr6 than water from rivers and reservoirs.

  • Drinking water for Fairfax Water customers comes from the Potomac River and the Occoquan Reservoir.

How could I be exposed to Cr6?

  • Exposure can occur via breathing, eating contaminated food, drinking contaminated water, or through direct skin contact.

  • People working in industries that process or use chromium and chrome compounds. Industries involving spray paints, coatings, chrome plating, metal-cutting or welding, may have a higher risk of exposure.

Is there treatment to get Cr6 out of drinking water?

  • Standard drinking water treatment reduces the low levels of Cr6 in source water to minute levels in tap water.

  • Advanced treatment technology is used for systems with very high Cr6 levels.

  • Advanced treatment options include ion exchange, biological filtration, and reverse osmosis.

Is there a test for tap water in my home?

  • Most commercial laboratories don’t offer a home test for Cr6.

Is Cr6 regulated in drinking water?

  • The current EPA standard for Total Chromium was set in 1992. The level is based on risk of allergic dermatitis (skin reactions).

  • Total chromium includes all forms of chromium, Cr3 and Cr6. The MCL is 100 ppb.

  • Cr6 drinking water testing was required by EPA for the Unregulated Contaminant Monitoring Rule #3 (UCMR3). Fairfax Water’s results from the UCMR3 were posted on page 7 of our 2015 Water Quality Report. They are located at this link: http://www.fairfaxwater.org/water/ccr/2015%20CCR%20for%20web.pdf.

Will the EPA issue a Cr6 regulation?

The EPA is in the process of reviewing data in order to determine whether a Cr6 regulation is needed. This review includes: 

  • National Toxicology Program data and studies

  • Integrated Risk Information System risk characterization

  • Occurrence rates of CR6 in source water and drinking water

  • Technology, feasibility, and cost analysis

The risk characterization combined with the other data informs the decision to regulate a contaminant under the Safe Drinking Water Act.


Why are the California and EPA standards different?

  • The California Legislature passed a law requiring a state drinking water MCL for Cr6 in 2001.

  • California established a Public Health Goal (PHG) of 0.02 ppb in 2011 based on a lifetime of daily exposure.

  • California became the first state to set a MCL for Cr6 of 10 ppb in 2014.

  • EPA does not currently regulate Cr6 separately from total chromium. EPA is considering a new regulation for Cr6.

  • The drinking water standard for total chromium, which includes hexavalent and trivalent chromium, is 100 ppb.


Are Fairfax Water’s results less than the California Cr6 MCL (maximum contaminant level)?

  • Our results are well below California’s MCL of 10 ppb. Our average result is 100 times less than California’s MCL.

What Is a Public Health Goal (PHG)?

  • A PHG is the level of a chemical contaminant in drinking water that does not pose a significant health risk.

Is there a health risk if my drinking water is above the California PHG?

  • The California Office of Environmental Health Hazard Assessment (OEHHA) states that ”a PHG is not a boundary line between a ‘safe’ and ‘dangerous’ level of a chemical, and drinking water is frequently demonstrated as safe to drink even if it contains chemicals at levels exceeding their PHGs.”

  • A drinking water sample with a level above the PHG of 0.02 ppb does not necessarily represent a health concern.

  • The PHG accounts for susceptible stages in life, including infants. The levels are set so that a contaminant would not cause significant adverse health effects in people who drink that water every day for 70 years.

  • The protection factors take age into account and use higher rates of water consumption for the calculation.

  • The Cr6 PHG is set for no adverse health effects anticipated over an entire lifetime of exposure to the most sensitive population.

Why is the California MCL 500 times more than the PHG?

  • The MCL is as close to the PHG as economically and technologically feasible.

Read a Special Statement by Fairfax Water on chromium by clicking here.

Results of the monitoring program can be found by clicking here.