print Font Size: small font medium font large font


Chromium-6 Questions and Answers

(Updated July 15, 2014)

What is chromium-6?
Chromium-6, or hexavalent chromium, is a naturally occurring metal. It is also used in several industrial processes. There are other forms of chromium such as chromium-3, which is an essential nutrient and is sold as a dietary supplement.

What are the health effects of chromium-6?
Chromium-6 has been known to cause cancer in humans when inhaled. In scientific studies in laboratory animals, chromium-6 has also been linked to cancer when ingested.

How does chromium-6 get into water supplies?
Chromium-6 can occur naturally so it may be present in some groundwater aquifers. The types of rocks and soil associated with chromium-6 are known to occur in parts of Santa Clara County. Chromium-6 can also reach water supplies from industrial uses such as stainless steel production, metal plating, and leather tanning.

Is there a drinking water standard for chromium-6?
Yes. As of July 1, 2014, California has a maximum contaminant level (MCL) of 0.010 mg/L for chromium-6. This is equal to 10 parts per billion (ppb) One part per billion is the equivalent of adding one drop of water to an Olympic size (660,000 gallon) swimming pool. This MCL is designed to protect public health and be feasible for water agencies to achieve.

This MCL is an enforceable regulatory standard that must be met by all public water systems.

California has had a drinking water standard of 50 ppb for total chromium for many years. This enforceable standard remains in effect for drinking water.

Has local water been tested for chromium-6?
The Santa Clara Valley Water District tests water from our three drinking water treatment plants for chromium-6. To date, it has not been detected in our treated water at or above 1 ppb (see “hexavalent chromium” data for treated water in our annual reports here). This is the lowest level of detection that is currently available for a state certified laboratory.

To better understand the occurrence of chromium-6 in groundwater, the water district tested wells throughout Santa Clara County between 2001 and 2004. As part of the California Dept. of Public Health’s process to establish a drinking water standard, water providers all over the state have also tested their water supplies for chromium-6.

Sampling results from 2001 to 2012 indicate that the average level of chromium-6 detected in groundwater in Santa Clara County is 1.7 ppb. The range of chromium-6 observed in groundwater varies from non-detect (below the reporting limit) up to 23 ppb.

Results from over 200 water supply wells in Santa Clara County indicate that chromium-6 levels in 98 percent of the wells tested are below the proposed MCL.

How do I know if my water meets the drinking water standard?
Water systems throughout the state have tested for chromium-6 and have reported the results to the California Dept. of Public Health. Those results can be accessed here.

You can also contact the city or water company that provides your water for more information.

If your water comes from a private domestic well, you may want to test your drinking water for chromium-6. The water district recommends that you use a laboratory that is certified to test drinking water.

What if my water has chromium-6 above the drinking water standard?
The MCL must be met by all public water systems. Public water systems with chromium-6 above the drinking water standard must work to achieve compliance, which may require treatment or blending of different water sources.

If your water comes from a domestic well, you are not subject to state water quality regulations. To protect your health, you may want to consider treating your water if it contains chromium-6 (or any other substances) at levels above drinking water standards.

Is there a filter that will remove chromium-6?
The California Dept. of Public Health website provides information that can be helpful in selecting a home treatment device. To find devices which can specifically remove chromium-6, use the NSF or WQA links in the "What does California Registration mean?" section of that webpage.

To be sure a particular treatment system will work for your situation, the water district recommends that you talk to the manufacturer or the company installing the system.

Is this the chemical that was the subject of the movie, “Erin Brockovich”?
Yes, it is. In Hinkley, California, chromium-6 has been detected in monitoring wells at levels up to 7,800 parts per billion (ppb) due to industrial contamination.

The levels of chromium-6 observed in Hinkley are many times higher than what has been observed in Santa Clara County, where the average level detected in groundwater is 1.7 ppb and the maximum is 23 ppb.

Is chromium-6 found in bottled water?
There is no chromium-6 standard for bottled water, so bottled water producers are not required to test for it. We suggest consumers contact bottled water producers directly for information about their product’s water quality.

What is the Santa Clara Valley Water District doing to address this issue?
1. We will continue to provide accurate information to the public.
2. We are coordinating with our local water retailers to respond appropriately.
3. We were actively engaged in the state and federal process to establish a science-based drinking water standard for chromium-6.
4. We continue to monitor new science regarding chromium-6 and other unregulated contaminants.