Summary
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 anti-corrosion metal coating, wood preservation and textile dyeing. It can also pollute water through the erosion of soil and rock.
The Environmental Protection Agency’s national survey of chromium-6 concentrations in drinking water revealed it was found in more than three-fourths of water systems sampled, which supply water to more than two-thirds of the American population.
Click here to see EWG’s latest Tap Water Database update with the nationwide test results for chromium-6, also known as hexavalent chromium.
There is no national standard for chromium-6 in drinking water. For many years the EPA’s safety review of the chemical was stalled by pressure from the industries responsible for chromium-6 contamination.
After more than a decade, the EPA finalized the safety review for chromium-6 in 2024. The EPA is required as part of a legal settlement agreement to make a determination by 2027 for an enforceable national drinking water standard for the chemical.
In 2008 the National Toxicology Program, or NTP, found that water contaminated with chromium-6 causes cancer in laboratory animals.
Based on that study, in 2011 the California Office of Environmental Health Hazard Assessment, or OEHHA, 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 known as a maximum contaminant level, or MCL, for chromium-6 in drinking water of 10 ppb – far too high to fully protect public health. In 2017, after a legal challenge that focused on how the state calculated water treatment costs, California had to withdraw the MCL and start developing a new legal limit.
In 2020, California released a brief economic analysis of such a limit and then, in 2024, finalized a new drinking water standard at 10 ppb.
What are the toxic effects of chromium-6 in drinking water?
An NTP two-year study published in 2008 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 damage the liver and reproductive systems. It has also been found to 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.
What can be done to reduce exposure to chromium-6 in drinking water?
The EPA must set a nationwide health-protective legal limit on the chemical in drinking water, and fund efforts to clean up the most contaminated water systems.
The standard must consider the additional risks to infants, children and other people who are more vulnerable to chromium-6 exposure and toxicity. EWG concurs with the California OEHHA that that limit should be 0.02 ppb.
In the absence of such a regulation, EWG recommends using a home water filter to remove chromium-6. Specialized 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 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 2022 chromium-6 report provides a map of the EPA's findings and a more detailed analysis of this pollution.
References
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.
Environmental 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. 2022. Available at https://www.ewg.org/news-insights/news/2022/03/what-chromium-6-heres-what-you-need-know.
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.
February 2025