The Dangers of Hexavalent Chromium (Chromium 6) in California Drinking Water

photo: Dave Pot / istock

Background on Hexavalent Chromium in California

The movie Erin Brockovich alerted the public to the great suffering the little town of Hinkley, CA experienced due to the cancer-causing chemical hexavalent chromium (also known as chromium 6) in its drinking water. While the levels in most other impacted communities are much lower than Hinkley’s, hexavalent chromium was detected in 2475 California drinking water sources, spread throughout 51 out of 58 counties.

Despite the publicity from the film and the severe health effects associated with hexavalent chromium, the federal government has not regulated this toxic chemical in drinking water. Chromium occurs in the environment largely in two forms: trivalent chromium (chromium 3), which is an essential human nutrient, and hexavalent chromium (chromium 6), which is toxic.   Despite this difference, chromium is regulated in drinking water as “total chromium” at a level of 50 parts per billion.  This standard averages the toxicity of both hexavalent and the less-dangerous trivalent chromium in the water. Since state scientists have determined that the level of hexavalent chromium in drinking water that would not lead to significant health impacts is 0.2 ppb, the combined approach is clearly not adequate to protect public health.

California Takes the Lead

On April 15, 2014, the California Department of Public Health (DPH) released a final hexavalent chromium drinking water standard of 10 parts per billion (ppb) making California the only government in the U.S. to regulate the chemical in water. While this was a major step, it was not ideal given that the standard was 500 times higher than the level that State scientists determined would not result in significant public health problems and many Californians would continue to be exposed to unsafe levels of this carcinogen, DPH’s decision was primarily based on the costs of water treatment (see below for information on how drinking water standards are set in California).

Map, Detection of Chromium in CaliforniaStep Backwards

In 2017, public safety faced a major setback when the California Manufacturers and Technology Association sued in the Superior Court of Sacramento over the hexavalent chromium regulation.  Sadly, the court ruled that the standard was invalid because DPH “did not adequately document why the MCL was economically feasible” (versus being based on what would protect Californian’s health and safety). 

While Clean Water Action and its allies had opposed the original standard because it was not protective enough, we instead worked with water providers and the state legislature to establish a program that would enable full compliance with the hexavalent chromium regulation within a reasonable amount of time, despite the costs of treatment.  We also worked with the Governor’s office to move the drinking water program to the State Water Resources Control Board (State Water Board), where it will be more integrated with other water protection programs, funding sources, and public health priorities.

Next Steps

Fortunately, some water systems chose to treat the hexavalent chromium in their water even without a legally enforceable standard, protecting their consumers   Unfortunately, some communities have failed to do this, meaning that thousands or even millions of Californians continue to be at risk

The State Water Board is working to reestablish a drinking water standard for hexavalent chromium and is in the process of reevaluating the health information, as well as new technologies that could provide treatment at lower costs.

Clean Water Action is working with allied organizations and impacted communities to ensure that this time the standard is both truly health protective and stands up to legal challenges meant to delay or prevent holding polluters accountable.  We are also calling for the process to be expedited due to the threat hexavalent chromium poses to public health (see below), asking that a new enforceable standard is established by the end of 2020.

Where does hexavalent chromium come from?

In addition to natural sources, hexavalent chromium enters drinking water sources through discharges of dye and paint pigments, wood preservatives, chrome plating wastes, and leaching from hazardous waste sites. Not surprisingly, communities near chromium waste disposal sites or chromium manufacturing and processing plants are at particular risk of exposure. Probably the most impacted people are workers exposed on the job.

What are the health effects of hexavalent chromium?

Hexavalent chromium is a carcinogen and a reproductive toxicant for both males and females. As a result, it was added to California's Proposition 65 list of toxic substances (pdf) in December 2008. Exposure to hexavalent chromium occurs through breathing, ingestion, and contact with the skin. Although most of the known health impacts are related to inhalation, there is now strong data linking ingestion of hexavalent chromium, such as through drinking water, to severe health effects. In addition to cancer and reproductive harm, short and long-term exposures can lead to eye and respiratory irritation, asthma attacks, nasal ulcers, dermal burns, anemia, acute gastroenteritis, vertigo, gastrointestinal hemorrhage, convulsions, ulcers, and damage or failure of the liver and kidneys.

How are drinking water standards established?

A drinking water standard, also known as a maximum contaminant level or MCL, is an enforceable level for a contaminant in the water, which cannot be legally exceeded by a public drinking water provider. It is based on three things: health impacts, technical feasibility to detect and treat it, and the cost of the water treatment. Both the federal government and the state can establish legally enforceable drinking water standards for contaminants of concern.

In California, the establishment of drinking water standards is a two-pronged process. First Cal EPA's Office of Environmental Health Hazard Assessment (OEHHA) does a scientific analysis to establish the level in drinking water at which no significant public health effects would be expected. Based on these findings, OEHHA establishes a Public Health Goal, or PHG. Then the Department of Public Health sets a drinking water standard as close to the PHG as possible - but also based on technical and cost considerations.

Note: Drinking water standards pertain to public water systems where the water is provided by a local government agency or private company. They do not pertain to private wells. Testing private well water and any necessary treatment is the responsibility of the well owner.

What is California’s public health goal for hexavalent chromium and why is can the drinking water standard be higher?

In July 2011, OEHHA established the PHG for hexavalent chromium at .02 ppb. This is based on the potential effects on the entire population, including vulnerable populations such as children, pregnant women, and the elderly.

 State law requires that drinking water standards are set as close to the PHG as is technically and economically feasible. That means that it can be above the PHG or level at which no significant health impacts are expected, but must still prioritize public health.

Facts about Hexavlent Chromium (Chromium 6)