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Fact Sheet from the California Department of Health Services and the Office of Environmental Health Hazard Assessment
Chromium in Drinking Water
[03/27/01]

Recent testing has found detectable levels of chromium, particularly chromium 6, also known as hexavalent chromium, in drinking water in Los Angeles County and other areas of California. The California Department of Health Services (DHS) and the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) have prepared this fact sheet to answer basic questions about chromium in drinking water.

Q: What is chromium?

A: Chromium is a metallic chemical that occurs naturally in some deep aquifers, but can also enter drinking water sources through discharges of dye and paint pigments, wood preservatives, chrome plating liquid wastes and leaching from hazardous waste sites. Chromium may be present in drinking water sources in two forms: trivalent chromium (chromium 3) and hexavalent chromium (chromium 6). Chromium 3 is found naturally in foods at low levels and is an essential human dietary nutrient. Chromium 6 is the more toxic form of chromium, often found as chromate.

Q. Is chromium hazardous?

A: Yes. Chromium 6 is known to cause cancer in humans when inhaled. The hazards of airborne chromium 6 in the workplace environment have been extensively documented. A number of scientific studies have found elevated rates of lung cancer in workers with occupational exposure to chromium 6 by inhalation. A few studies of workers exposed to chromium 6 by inhalation have shown an increase in cancers of the gastrointestinal tract. There is substantial evidence from laboratory studies that chromium 6 can damage DNA and is a mutagen. There is limited evidence from a single laboratory study using mice that oral ingestion of high levels of chromium 6 may cause cancer in the gastrointestinal tract. There continues to be uncertainty in the scientific community whether or not chromium 6 can cause cancer when ingested at levels found in drinking water. Current scientific evidence indicates that chromium 6 is likely to be much more toxic when inhaled than when ingested.

In contrast, chromium 3 has relatively low toxicity and would be a concern in drinking water only at very high levels of contamination much greater than is allowed in California drinking water. Chromium 3 is an essential dietary element with a minimum daily requirement that ranges from 50 to 200 micrograms per day for an adult.

Q: How much chromium 6 is in the state's drinking water?

A: In the past, water systems were only required to test for total chromium in drinking water. So there is very little information on the amount of chromium 6 in drinking water throughout the state. In January 2001, DHS adopted a regulation requiring that all water systems test their drinking water sources for chromium 6 over the next two years.

Q: What is the current drinking water standard for chromium 6?

A: There currently are no state or federal drinking water standards specifically for chromium 6. There is a drinking water standard for "total" chromium, which assumes a mixture of chromium 3 and chromium 6. The California standard for total chromium in drinking water is 50 parts per billion (ppb), while the federal standard is 100 ppb. DHS and the U.S. Environmental Protection Agency consider the drinking water standards to be protective from the effects of chromium 6.

Q: What is a drinking water standard?

A: Drinking water standards are the maximum levels of chemicals allowed in drinking water supplied by public water systems. California law requires DHS to set drinking water standards as close to the corresponding public health goals as is technologically and economically feasible. Feasibility may reflect such things as the ability to detect the contaminant by laboratory analyses or the costs of treatment for contaminant removal. These primary drinking water standards are called maximum contaminant levels (MCLs).

Q: What are public health goals?

A: Public health goals (PHGs) are levels of contaminants in drinking water that would not be expected to pose a significant health risk to individuals consuming an average of two liters a day of that water over a 70-year lifetime. PHGs are established by OEHHA. They are based solely on health risk considerations and do not consider costs or technical feasibility. Public water systems do not have to meet public health goals. The law requires that public health goals be established at a level that, for acutely toxic substances, avoids any known or anticipated adverse effects on public health with an adequate margin of safety. For carcinogens or substances that may cause chronic disease, the law requires the PHG be established at a level that does not pose any significant risk to health. While there is no legal definition of "significant risk," OEHHA typically sets PHGs for carcinogens at levels that would not be expected to result in more than one cancer case in a population of one million people drinking the water daily for 70 years.

Q. How is the public health goal used in determining a drinking water standard?

A: The California Legislature directed DHS to adopt drinking water standards that are as close as feasible to the corresponding PHGs, placing primary emphasis on the protection of public health while taking into account technological and economic feasibility. Hence, the PHG is the starting point for DHS when it determines the most appropriate drinking water standard, balancing the cost to the public and the benefit the public receives in risk reduction. As a result, there are cases where the public health goal and the drinking water standard are at different levels.

The Legislature also intended that the public be allowed to make local decisions regarding compliance with PHGs. The law requires public water systems to report whether contaminant levels in their water exceed PHGs and to hold periodic hearings to inform their customers of the cost of complying with PHGs and respond to public comment. Customers could request a referendum on paying for the additional cost of meeting the PHGs or staying with the drinking water standard. DHS is not aware of any instances in which customers have opted to pay additional costs to meet PHGs.

Q: What is the PHG for chromium 6?

A: There is no PHG for chromium 6. In 1998, OEHHA developed a PHG for total chromium of 2.5 ppb. The PHG for total chromium was calculated based on scientific information on the potential carcinogenicity of ingested chromium 6, along with an estimate that chromium 6 comprised about 7 percent of the total chromium in water. This estimate was based on the best available data at the time. Recent studies of chromium 6 in a limited number of California water supplies indicate this percentage can be much higher; perhaps greater than 50 percent. The recently adopted regulation requiring statewide testing will help to identify the levels of chromium 6 in California drinking water supplies.

Q: Is DHS going to adopt a drinking water standard for chromium 6?

A: DHS intends at this time to develop the nation's first drinking water standard for chromium 6. DHS has initiated the first step in this process by asking OEHHA to develop a PHG for chromium 6. The California Environmental Protection Agency, on behalf of OEHHA, has requested the University of California to form a scientific panel to provide guidance to OEHHA in establishing a chromium 6 PHG. At the same time, DHS has taken steps to obtain more information on the prevalence of chromium 6 in drinking water supplies. This information will enable DHS to develop data on cost and feasibility of treatment that must be considered as part of the development of a chromium 6 drinking water standard.

In March 1999, DHS gave notice that it would be evaluating the total chromium drinking water standard to determine if the standard should be revised. After an initial review, DHS determined that there needed to be a better understanding of the distribution of chromium 3 and chromium 6 in drinking water in the state. DHS collected recent information on chromium 6 from water systems that had been sampling for the chemical. In August 1999, DHS began conducting its own chromium 6 sampling study at a limited number of water systems in various regions of the state. As a result of that work, DHS concluded that it needed additional information on the statewide occurrence of chromium 6 in drinking water before it could adequately determine a new standard. Consequently, DHS adopted regulations effective January 2001 to require statewide monitoring for chromium 6 by water systems.

Following the approval of Senate Bill (SB) 2127 by the Legislature in August 2000, DHS has been working with water systems in the San Fernando Valley to develop information on the levels of chromium 6 in drinking water provided to the Valley residents. With these data, DHS and OEHHA will be able to assess exposure and risks to the Valley residents, as required by the bill. SB 2127 requires that a report on the assessment be submitted to the Legislature by January 2002.

Q: Is drinking water with levels of chromium 6 higher than the PHG for total chromium (2.5 ppb) safe to drink?

A: Yes. There is no immediate health threat from chromium in drinking water that meets current drinking water standards. The potential health risks from chromium 6 calculated in the PHG are based on a lifetime (70 years) of exposure from drinking two liters of water per day.

For more information on chromium in California's drinking water, please visit the DHS web site at http://www.dhs.ca.gov/ps/ddwem/chemicals/
Chromium6/Cr+6index.htm

To view or download OEHHA's PHG for chromium, please visit the OEHHA web site at www.oehha.ca.gov/water/phg/pdf/chrom_f.pdf