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HEXAVALENT CHROMIUM  DEFINED 

What is Chromium?

 

Chromium is a steel gray, lustrous, hard metal extracted from chromite ores. In 2011, U.S. production of chromium was estimated at 160,000 metric tons, coming almost entirely from recycling stainless steel scraps. In addition, the U.S. imported 430,000 metric tons of chromium, primarily from South Africa, Kazakhstan, Russia and China.

 

Chromium is valued for its high corrosion resistance and hardness. It is most often used as an alloy (ferrochrome) in stainless steel and in chrome plating. In addition, chromium is used in the pigment and dye, tanning, and glassmaking industries, in reflective paints, for wood preservation, to anodize aluminum, to produce synthetic rubies, as a catalyst in chemical manufacturing and as an isotope in medicine. Elemental chromium is seldom found naturally in the environment.

 

The oxidized states of chromium III and chromium VI are the most important forms of the chemical. Chromium III is an essential trace element in humans but chronic exposure may be harmful. Chromium VI (hexavalent chromium) is the oxidized state of principal concern in occupational safety and health and the environment because of its extreme toxicity and designation as a human carcinogen. OSHA's hexavalent chromium safety and health topics page provides comprehensive information on health effects, exposure controls, OSHA standards, and additional resources on this toxic substance.

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Who is exposed to the common forms of chromium?

 

Occupational exposures to chromium occur primarily in the metal and chemical manufacturing industries, although exposures are also possible in other industries where chromium compounds are used.

 

Occupational exposure to chromium can occur in the following industries and operations:

  • Stainless steel welding [Cr(VI)]

  • Chromate production [Cr(VI)]

  • Chrome plating [Cr(VI)]

  • Ferrochrome industry [Cr(III) and Cr(VI)]

  • Chrome pigments [Cr(III) and Cr(VI)]

  • Leather tanning [mostly Cr(III)]

 

Occupations that may involve chromium exposures include:

  • Painters [Cr(III) and Cr(VI)]

  • Abrasive blasting workers [Cr(III) and Cr(VI)]

  • Workers involved in the maintenance and servicing of copying machines and the disposal of some toner powders from copying machines [Cr(VI)]

  • Battery makers [Cr(VI)]

  • Candle makers [Cr(III) and Cr(VI)]

  • Dye makers [Cr(III)]

  • Printers [Cr(III) and Cr(VI)]

  • Rubber makers [Cr(III) and Cr(VI)]

  • Cement workers [Cr(III) and Cr(VI)]

  • Workers involved in welding, cutting, brazing, soldering, torch and other hot work operations. [Cr(III) and Cr(VI)]

 

OSHA sets enforceable permissible exposure limits (PELs) to protect workers from the health effects of exposure to chromium metal and various chromium compounds under 1910.1000 Table Z-1 Limits for Air Contaminants. The most toxic form of chromium ishexavalent chromium. OSHA requirements for protecting workers from hexavalent chromium exposure are found in specific OSHA standards covering general industry (Chromium (VI) - 1910.1026), shipyards (Chromium (VI) - 1915.1026), and construction (Chromium (VI) - 1926.1126).

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Additional Resources for Chromium

 

Canadian Exposure
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Canadians can be exposed to chromium through its presence in food, drinking water, dust, soil and air. For Cr(VI), drinking water is the main source of exposure, followed by food, dust, air and soil.

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Effects in Humans

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Chromium toxicity in humans varies depending on the form of the compound, its valence state and the route of exposure. Little information has been reported on the trivalent form of chromium, and available data, mainly relating to mixtures with Cr(VI) and Cr(III), show little or no toxicity associated with the trivalent form. However, several studies agree on the toxicity of the hexavalent form, which is soluble in water and may represent up to 100% of the chromium present in drinking water.

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Water

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Background levels of chromium in surface water and groundwater aquifers are a direct function of regional geology, mineral weathering processes, sediment loading rates and precipitation patterns. Average concentrations of total chromium (including Cr(III) and Cr(VI) in dissolved and particulate phases) in uncontaminated surface and marine waters are generally below 1 µg/L (Erickson and Fowler, 1987; Mayer, 1988; Rossmann and Barres, 1988; Beaubien, 1993).

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Between 10% and 60% of the total chromium content in Canadian rivers may be present as dissolved Cr(VI). This range is based on measurements of filtered and unfiltered North American river water (Merritt, 1975; Gibbs, 1977; Campbell and Yeats, 1984; Allan, 1986; Kauss et al., 1988) and data obtained from studies on the speciation of dissolved chromium in aerobic lake waters (Balistrieri et al., 1992; Johnson et al., 1992; Beaubien, 1993).

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Canadian data on chromium levels in drinking water were provided by several provinces and territories. The vast majority of the samples analysed across the country were below the detection limits for chromium, which varied between 0.03 and 10 µg/L. Average detected values and maximum values are reported for each province or territory, when available.

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For Prince Edward Island, of 7622 samples from private wells tested for total chromium from June 2005 to June 2010, 3 were above the DL of 0.05 mg/L, with concentrations of 0.06, 0.08 and 0.234 mg/L (PEI Department of Environment, Energy and Forestry, 2010).

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In Newfoundland and Labrador, 3946 and 1910 drinking water samples were analysed for total chromium from surface water and groundwater sources, respectively, between 2004 and 2010. The average concentration of total chromium reported above the method detection limit (MDL) (n = 157, MDL = 0.001 mg/L) in surface water samples was 0.002 mg/L, with a maximum value of 0.013 mg/L. The average concentration of total chromium reported above the MDL (n= 417, MDL = 0.001 mg/L) in groundwater samples was also 0.002 mg/L, with a maximum value of 0.026 mg/L (Newfoundland and Labrador Department of Environment and Conservation, 2010).

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In Nova Scotia, 118 raw and 292 treated water samples were analysed for total chromium between 2004 and 2009. In raw water samples, the average concentration of total chromium reported above the MDL (n = 12, MDL = 0.6-2.0 µg/L) was2.5 µg/L, with a maximum value of 4 µg/L. The average concentration of total chromium in treated water reported above the MDL (n = 9, MDL = 1.0-2.0 µg/L) was 2.7 µg/L, with a maximum value of 5.0 µg/L (Nova Scotia Department of Environment and Labour, 2010).

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In Quebec, 17 005 results for total chromium in drinking water were reported between 2005 and 2010, of which 14 263 were below the detection limit (DL = 0.0001-0.03 mg/L). The average concentration of total chromium reported above the DL was 0.004 mg/L, with a total of 11 samples above 0.05 mg/L (Ministère du Développement durable, de l'Environnement et des Parcs du Québec, 2010).

In Ontario, 6101 results were reported for total chromium in drinking water between 2009 and 2014, of which 4038 were below the DL (DL = 0.6-5.0 µg/L). The average concentration of total chromium reported above the DL was 1.2 µg/L, with a maximum of 41.3 µg/L (OMOE, 2014).

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In Manitoba, 220 raw and 212 treated water samples were analyzed for total chromium between 2009 and 2010. In raw water samples, the average concentration of total chromium in samples above the DL (n = 26, DL = 0.001 mg/L) was 0.003 mg/L, with a maximum value of 0.014 mg/L. In treated water samples, the average concentration of total chromium in samples above the DL (n = 19, DL = 0.001 mg/L) was also 0.003 mg/L, with a maximum value of 0.013 mg/L (Manitoba Water Stewardship, 2010).

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In Saskatchewan, 2013 results were reported for total chromium in drinking water between 2002 and 2010, of which 1760 were below the DL (DL = 0.03-5.0 µg/L). The average concentration of total chromium reported above the DL was 5.4 µg/L, with a maximum of 29.0 µg/L (Saskatchewan Ministry of Environment, 2010).

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In British Columbia, 645 facilities reported results for chromium levels in drinking water between 2004 and 2010. The data for the Greater Vancouver Regional District and member municipalities and the City of Abbotsford indicate total chromium levels below 0.001 mg/L from all their source waters. Analytical results from the most populated drinking water systems indicated a maximum chromium concentration of 0.005 mg/L (B.C. Ministry of Health, 2010).

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In Yukon, 22 results were reported for total chromium in drinking water between 2007 and 2010, of which 15 were below the DL (DL = 0.2-5.0 µg/L). The average detected concentration of total chromium was 0.7 µg/L, with a maximum of 1.2 µg/L (Government of Yukon, 2010).

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In the Northwest Territories, levels of total chromium in drinking water in 2010 (n=53) were all below the reportable detection limit (RDL) of 0.001 mg/L or 0.01 mg/L, except for four sites at 0.02 mg/L and two sites at the RDL of 0.001 mg/L (Government of the Northwest Territories, 2010).

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The Ontario Drinking Water Surveillance Program for 2000-2002 reported a mean total chromium concentration of 1.4 µg/L in drinking water in Ontario (OMOE, 2004). A more recent Ontario survey of total chromium concentrations in unfiltered distributed drinking water (1997-2007) reported average concentrations ranging from ≤ 0.5 to 18.9 µg/L (n=52), from 1.08 to 1.73 µg/L (n=4), from 0.42 to 6.92 µg/L (n=49) and from 0.49 to 3.82 µg/L (n=83) in drinking water originating from groundwater, lake water, river water and surface water, respectively; the mean concentration was 2.0 µg/L(OMOE, 2008).

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These concentrations are similar to those measured, in 2005, at a Montréal drinking water treatment plant supplied from the St. Lawrence River (mean total chromium concentration: 1 µg/L; range: < 1-3 µg/L; Ville de Montréal, 2005). They are also similar to those documented in earlier monitoring programs (i.e.,< 2-5 µg/L, median 2.0 µg/L, in raw water from 71 cities across Canada in 1977, Méranger et al., 1981; and 0.51-18 µg/L, average 2.4-2.6 µg/L, for treated and distributed drinking water from over 110 sampling sites in Ontario in 1994-1995, McGrachan, 1996).

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In the United States, drinking water data indicate that 71% of the population is exposed to chromium concentrations below 10 µg/L, and 29% receive drinking water containing chromium at concentrations between 10 and 100 µg/L; only 0.001% receive drinking water containing chromium at concentrations greater than 100 µg/L (U.S. EPA, 2003a).

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Another study reported that approximately 18% of the U.S. population is exposed to chromium concentrations in drinking water between 2 and 60 µg/L, and less than 0.1% of the population is exposed to concentrations between 60 and 120 µg/L (Hirose et al., 2002). Chromium concentrations were recently measured in 10 groundwater sources from California, Nevada and Oklahoma. The total chromium concentrations ranged from 1.9 to 48 µg/L, and virtually all the chromium was present as Cr(VI)(Najm et al., 2014).

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Two Water Research Foundation projects are investigating the sources, fate, treatment and transport of chromium in both drinking water treatment plants and distribution systems (Water Research Foundation, 2014c, 2014d). Currently, the third Unregulated Contaminant Monitoring Rule (UCMR 3) requires monitoring for total chromium and Cr(VI) in the raw water, at the entry points to the distribution system and in the distribution system. Since Cr(III) can transform into Cr(VI) in the distribution system due to the presence of oxidants, monitoring for Cr(VI) in the distribution system should be done at locations with maximum residence time. This is consistent with the monitoring goals for disinfection by-products.

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Once available, the data from UCMR 3 and the Water Research Foundation projects will be used to inform the best approach for sampling(U.S. EPA, 2012a). In the interim, the U.S. EPA recommends that water systems with surface water sources collect samples quarterly and that ground water systems be sampled twice per year and that these samples (raw, entry point to the distribution system and distribution system) be collected on the same day (U.S. EPA, 2014b).

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Considering the whole data set, a concentration of 2.0 µg/L, based on the most recent survey (mean concentration in unfiltered distributed drinking water according to the Ontario Drinking Water Surveillance Program for 1997-2007; OMOE, 2008), is used to represent the total chromium concentration in Canadian drinking water.

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All of the chromium in drinking water is assumed to be in the form of Cr(VI) (Sanexen, 2009). This conservative approach is supported by the fact that different forms of chromium can interconvert in water and in the human body, depending on the conditions. It is further supported by the redox chemistry of chromium, whereby Cr(VI) is expected to predominate in the dissolved fraction of oxygenated water or in drinking water disinfected with chlorine or chloramines (Brandhuber et al., 2004).

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TO READ ENTIRE CANADA REPORT PLEASE CLICK HERE
​The Legal Limit of Hexavalent Chromium in Drinking Water?

 

For drinking water, the United States Environmental Protection Agency (EPA) does not have a Maximum Contaminant Level (MCL) for hexavalent chromium. California has finalized a Public Health Goal of 0.02 parts per billion (ppb or micrograms per liter) and established a MCL of 10 ppb.

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What Does Chromium 6 Cause?

 

Adverse health effects associated with Cr(VI) exposure include occupational asthma, eye irritation and damage, perforated eardrums, respiratory irritation, kidney damage, liver damage, pulmonary congestion and edema, upper abdominal pain, nose irritation and damage, respiratory cancer, skin irritation, and erosion and discoloration of the teeth. Some workers can also develop an allergic skin reaction, called allergic contact dermatitis.

 

This occurs from handling liquids or solids containing Cr(VI) such as portland cement. Allergic contact dermatitis is long-lasting and more severe with repeated skin exposure. Furthermore, contact with non-intact skin can lead to ulceration of the skin sometimes referred to as chrome ulcers. Chrome ulcers are crusted, painless lesions showing a pitted ulcer covered with fluid.

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General Resources

 

  • Health Effects of Hexavalent Chromium. OSHA Fact Sheet, (July 2006). Provides a concise list of industrial sources, symptoms and health effects of exposure to hexavalent chromium, and OSHA requirements for the protection of employees.

  • ToxFAQs for Chromium. Agency For Toxic Substances and Disease Registry (ATSDR), (September 2008). Answers the most frequently asked health questions about chromium.

  • Toxicological Profile for Chromium. Agency For Toxic Substances and Disease Registry (ATSDR), (September 2008). Characterizes the toxicological and adverse health effects information regarding chromium and chromium compounds.

  • Public Health Statement for Chromium. Agency For Toxic Substances and Disease Registry (ATSDR), (September 2000). Describes chromium and its effects on humans.

  • Chromium (VI) (CASRN 18540-29-9). Environmental Protection Agency (EPA), Integrated Risk Information System (IRIS), (September 1998). Lists human health effects that may result from exposure to various substances found in the environment.

  • Toxicological Review of Hexavalent Chromium. Environmental Protection Agency (EPA), Chemical Abstract Service (CAS) No. 18540-29-9, (August 1998). Provides scientific support and rationale for the hazard identification and dose-response assessment in the integrated risk information system (IRIS) pertaining to chronic exposure to hexavalent chromium.

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Cancer

 

All hexavalent chromium compounds are considered carcinogenic to workers. The risk of developing lung, nasal, and sinus cancer increases with the amount of hexavalent chromium inhaled and the length of time the worker is exposed. Studies of workers in chromate production, chromate pigment, and chrome electroplating industries employed before the 1980s show increased rates of lung cancer mortality. Certain hexavalent chromium compounds produced lung cancer in animals that had the compounds placed directly in their lungs.

 

  • Gibb, H.J., et al. "Lung cancer among workers in chromium chemical production." American Journal of Industrial Medicine (AJIM) 38.2 (July 7, 2000): 115-126. Describes a study regarding the incidence of lung cancer among workers in chromium chemical production.

  • Report on Carcinogens (RoC). U.S. Department of Health and Human Services (DHHS), National Toxicology Program (NTP). Identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a health hazard due to their carcinogenicity. The listing of substances in the RoC only indicates a potential hazard and does not establish the exposure conditions that would pose cancer risks to individuals.

  • Chromium Hexavalent Compounds. Explains the carcinogenicity, properties, use, production, exposure, and regulations regarding chromium hexavalent compounds.

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Eyes

 

Direct eye contact with chromic acid or chromate dust can cause permanent eye damage. Avoid eye contact with dust, fumes, smoke, liquids, mists, and aerosols containing hexavalent chromium.

 

Respiratory Tract

 

Hexavalent chromium can irritate the nose, throat, and lungs. Repeated or prolonged exposure can damage the mucous membranes of the nasal passages and result in ulcers. In severe cases, exposure causes perforation of the septum (the wall separating the nasal passages). Some employees become allergic to hexavalent chromium so that inhaling the chromate compounds can cause asthma symptoms such as wheezing and shortness of breath.

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Skin

 

Prolonged skin contact can result in dermatitis and skin ulcers. Some workers develop an allergic sensitization to chromium. In sensitized workers, contact with even small amounts can cause a serious skin rash.

 

  • Preventing Skin Problems From Working with Portland Cement. OSHA Guidance, (February 2008). Provides information about persistent skin rash caused by trace amounts of hexavalent chromium present in portland cement. It has been reported that skin contact from working with wet portland cement can lead to allergic and irritant forms of dermatitis.

  • A Safety and Health Practitioner's Guide to Skin Protection. Electronic Library of Construction Occupational Safety & Health (elcosh), (2000). Includes illustrations of dry skin, irritant contact dermatitis (ICD), allergic contact dermatitis (ACD), and cement burns.

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How The Health Hazards Became Known

 

 

A controversial water contaminant made famous by Erin Brockovich and a small California desert town is carcinogenic.

That conclusion by federal scientists, culminating more than a decade of debate, is likely to trigger new, more stringent standards limiting the amount of hexavalent chromium allowable in water supplies.

It’s been known for about 20 years that people can contract lung cancer when inhaling hexavalent chromium, also known as Chromium VI. But until now, toxicologists have been uncertain whether it causes cancer when swallowed.

National Toxicology Program scientists reported that their two-year animal study “clearly demonstrates” that the compound is carcinogenic in drinking water. Mice and rats contracted malignant tumors in their small intestines and mouths when they drank water containing several different doses of hexavalent chromium.

Based largely on the new cancer findings, California and U.S. Environmental Protection Agency officials are reevaluating what concentration is safe in water supplies. Within a few weeks, California is expected to announce a proposal to set a new health guideline.


The Mojave Desert town of Hinkley, population of around 1,900, has the highest levels of hexavalent chromium reported in U.S. ground water. The compound seeped into water there from a Pacific Gas and Electric facility that used it to inhibit rust in cooling towers and discharged it into holding ponds in the 1950s and 1960s.

In 1996, PG&E paid a $333 million settlement to about 600 residents of Hinkley after Brockovich, a law clerk, investigated the contamination and found high rates of cancer and other diseases. The town's plight drew national attention in 2000 from a film based on Brockovich's legal crusade. The payment was the largest tort injury settlement in U.S. history.

The animal study does not prove that people in Hinkley contracted cancer from drinking the tainted water. But it does resolve the debate over whether the contaminant is capable of causing some types of cancer.

Hinkley’s ground water contained concentrations as high as 580 parts per billion, more than 10 times California’s current drinking water standard of 50 ppb for total chromium compounds. The national standard is 100 ppb. 

Because of the cancer uncertainty, California has had a tumultuous history of setting water standards to protect people from chromium.

In 1999, after the Hinkley case, California set a water guideline, called a Public Health Goal, of 2.5 ppb. It was based on a 1968 study in Germany that found stomach tumors in animals that drank the substance. However, the U.S. EPA rejected that study as flawed and determined there was no evidence it was carcinogenic in water. California’s scientific advisors agreed, so the state rescinded its goal in 2001 and reverted to the 50 ppb standard, which was adopted in 1977 and based on the risks of skin irritation, not cancer.

The debate focused on whether hexavalent chromium is neutralized in the stomach by gastric acids that turn it into Chromium III, an essential nutrient.

California officials, seeking to resolve the controversy, asked the National Toxicology Program to conduct animal tests.

The study, published online in Environmental Health Perspectives in December, shows that although some of the substance is reduced in the stomach to Chromium III, it’s not enough to avoid toxic effects.

Cancer in the small intestine is “relatively rare” in animals, even those exposed to other chemicals, the scientists reported. In addition, chromium caused mouth cancers, and infiltrated the cells of many organs, including livers and pancreatic lymph nodes.

Mice and rats were exposed to four different doses, and they contracted cancer at lower levels than in the 1968 study, according to Michelle Hooth, a toxicologist at the National Institute of Environmental Health Sciences who was the study’s lead scientist.

That suggests California’s new goal could be as stringent as the rescinded 2.5 ppb one.
Chromium is widely used in metal plating, stainless steel production, wood preservation and textile manufacturing. It has been detected in 30 percent of drinking water sources in California, at levels mostly under the existing 50 ppb state standard, according to the state health department.

Some of the rats and mice developed malignant intestinal tumors when fed doses as low as 57,000 ppb—100 times higher than the Hinkley water levels—for up to two years, Hooth said. The higher the dose, the more cancers found among the animals.

When setting a standard, scientists use high animal doses to extrapolate to a lower dose designed to protect people from a 70-year lifetime of exposure. Water standards are usually designed to keep the cancer risk to one case in every million or 100,000 people. Gwiazda, who has served on EPA and California scientific advisory panels, said extrapolating the animal findings for humans creates uncertainty because the rodents had to be fed higher doses.

As a result, such extrapolations could lead to an overly restrictive water standard, he said. “On the other hand,” he added, “there is probably a subpopulation of sensitive individuals with diminished stomach reducing capacity due to illness.” For those people, a standard based on the animal data “may not be protective enough,” he said.

There also is human evidence that drinking hexavalent chromium-contaminated water can cause cancer. A study in China found high rates of stomach cancers in people whose water was contaminated with so much chromium from a smelter that it had turned yellow.

U.S. EPA officials also are evaluating the national 100 ppb standard and plan to release their results this fall. The agency is required by federal law to review water standards every six years. The EPA had adopted a more stringent chromium standard in 1977 but raised the allowable amount in 1991 in response to the lack of cancer evidence.  

Cleanup of Hinkley's contaminated water—an underground plume that is two miles long and one mile wide—began in the late 1980s and is continuing, according to California Water Resources Control Board documents. The contamination is still spreading, so the state issued its latest cleanup order to PG&E in August.

Brockovich, now president of a consulting firm, has since fought other legal battles related to chromium and other pollutants.

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.

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