Flashcard of Chromium atom

Chromium 6

October 2019


Chromium-6 is the cancer-causing chemical made notorious by the film “Erin Brockovich,” which documented the poisoning of drinking water in Hinkley, Calif. Chromium gets into drinking water as pollution from industrial uses, such as a coolant at electrical power stations, but also occurs naturally in some areas.

In 2008 the National Toxicology Program found that water contaminated with chromium-6 causes cancer in laboratory animals. Based on that study, in 2011 the California Office of Health Hazard Assessment set a public health goal for chromium-6 in drinking water of 0.02 parts per billion, or ppb – the level expected to cause no more than one case of cancer in one million people who drink it for a lifetime.

Public health goals are not legally enforceable. In 2014, California lawmakers set a legal limit for chromium-6 in drinking water of 10 ppb – still far too high to fully protect public health. In 2017, after a legal challenge that focused on how treatment costs were calculated, the state had to withdraw the maximum contaminant level for chromium-6 and start developing a new state legal limit.

There is no national standard for chromium-6 in drinking water. The safety review of the chemical by the Environmental Protection Agency has been stalled by pressure from the industries responsible for chromium-6 contamination.

Click here to see the nationwide test results for chromium-6.

How often is chromium-6 found in water?

The EPA’s national survey of chromium-6 concentrations in drinking water revealed that the contaminant was found in more than three-fourths of water systems sampled, which supply water to more than two-thirds of the American population. An EWG analysis identified Houston, Phoenix and St. Louis as the largest cities with the highest levels of chromium-6.

What concerns are there about drinking chromium-6-contaminated water?

The National Toxicology Program’s two-year study found a significant increase of stomach and intestinal tumors in rats and mice that consumed chromium-6 in drinking water. In 2015, California scientists reported an increased risk of stomach cancer in workers exposed to chromium-6.

Chronic exposure to chromium-6 in drinking water can also damage the liver and reproductive systems, and lower the body weight and delay skeletal development of the offspring of lab animals exposed to the chemical. Scientists have identified infants, children and people taking antacids, as well as people with poorly functioning livers, as being at greater risk from chromium-6 exposure.

Why is there no federal standard for chromium-6 in tap water?

The federal standard for total chromium – chromium-6 and mostly harmless chromium-3 – is 100 ppb. The standard is based on the potential for skin irritation only, because it was set before it became clear that drinking chromium-6 could cause cancer.

In 2011 the EPA completed a draft health assessment, concluding that relatively low doses of chromium-6 could increase cancer risk, but industry pressure has delayed completion of the draft. The EPA says the assessment will be published in 2017, but it could be another five years before a national drinking water standard is set.

California is the only state that has ever developed a legal limit for chromium-6 in drinking water, but at 10 ppb – 500 times the state’s public health goal – it was still not sufficiently protective. New Jersey scientists have recommended a health-based goal of 0.07 ppb, but as with California’s public health goal, that would not be an enforceable legal standard.

What can I do about chromium-6 in my water?

EWG concurs with the California Office of Environmental Health Hazard Assessment that 0.02 ppb should be the goal for the presence of chromium-6 in drinking water. The EPA must set a health-protective legal limit and fund efforts to clean up the most contaminated water systems. All standards must consider the additional risks to infants, children and other people who are more vulnerable to chromium-6 exposure and toxicity.

In the absence of regulations, we recommend using a home water filter to remove chromium-6. Ion-exchange pitcher filters and under-sink reverse osmosis filters both remove chromium-6, but reverse osmosis is more expensive. Before purchasing any filter, make sure it is certified to remove chromium-6. EWG’s Water Filter Buying Guide can help identify options.

The EPA’s national tests for chromium-6 did not include private wells. If your water comes from a well and a nearby system has tested high for the contaminant, you should install a filter or consider paying to get it tested. EWG’s September 2016 report provides a map of the EPA’s findings and a more detailed analysis of chromium-6 pollution.


California Office of Environmental Health Hazard Assessment. Final Technical Support Document on Public Health Goal for Hexavalent Chromium in Drinking Water. 2011. Available at www.oehha.ca.gov/water/phg/072911Cr6PHG.html.

Evironmental Protection Agency. Chromium Compounds Hazard Summary. 2000. Available at www.epa.gov/sites/production/files/2016-09/documents/chromium-compounds.pdf.

EPA. IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft). 2010. Available at cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=221433.

EWG. “Erin Brockovich” Carcinogen in Tap Water of More Than 200 Million Americans. 2016. Available at www.ewg.org/research/chromium-six-found-in-us-tap-water.

Hong Sun et al. Oral Chromium Exposure and Toxicity. Current Environmental Health Reports, 2015, 2(3):295–303. Available at www.ncbi.nlm.nih.gov/pmc/articles/PMC4522702/.

National Toxicology Program. Technical Report on the Toxicology and Carcinogenesis Studies of Sodium Dichromate Dihydrate (CAS No. 7789-12-0) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies). Available at ntp.niehs.nih.gov/ntp/htdocs/lt_rpts/tr546.pdf.

New Jersey Drinking Water Quality Institute. Meeting Minutes. Sept. 10, 2010. Available at www.nj.gov/dep/watersupply/pdf/minutes100910.pdf.

Roberta Welling et al. Chromium VI and Stomach Cancer: A Meta-Analysis of the Current Epidemiological Evidence. Occupational Environmental Medicine, 2015, 72(2):151–159. Available at www.ncbi.nlm.nih.gov/pubmed/25231674.

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