From 1952 to 1966, the Pacific Gas and Electric Company (PG&E) released approximately 370 million U.S. gallons (1.4 × 10 liters) of wastewater containing chromium into open ponds without lining near the town of Hinkley, California. This town is located in the Mojave Desert, about 120 miles (190 kilometers) north-northeast of Los Angeles.

PG&E used chromium 6, also known as hexavalent chromium, in its natural-gas pipeline compressor stations. This substance was chosen because it was inexpensive and effective at preventing rust. However, chromium 6 is a type of cancer-causing substance.

In 1993, a legal clerk named Erin Brockovich began looking into the health effects of the pollution. A group of residents filed a lawsuit against PG&E over the contamination. The case was resolved on July 2, 1996, with a payment of $333 million (equivalent to about $651 million in 2024). By 2008, PG&E had settled all remaining legal claims related to Hinkley. Since then, the town’s population has decreased significantly. In 2016, The New York Times reported that Hinkley had become a nearly empty town, often described as a ghost town.

History

In the early 1950s, Pacific Gas & Electric built two compressor stations in Topock, Arizona, and Hinkley. These stations were part of a large natural-gas transmission system that connected eight compressor stations with 40,000 miles (about 64,000 kilometers) of distribution pipelines and 6,000 miles (about 9,700 kilometers) of transport pipelines. This system served 4.2 million customers from Bakersfield to the Oregon border. At the Topock and Hinkley stations, a substance called hexavalent chromium was used to prevent rust in cooling towers. Water containing this substance was then disposed of near the stations. Although this disposal happened between 1952 and 1966, PG&E did not inform local water officials about the contamination until December 7, 1987.

Residents of Hinkley filed a class-action lawsuit against PG&E and others. The case was handled by Judge LeRoy A. Simmons in a California court. In 1993, Erin Brockovich, a legal clerk for a lawyer named Edward L. Masry, found evidence linking health problems in Hinkley to hexavalent chromium. The case was sent to arbitration, where a maximum of $400 million could be awarded to more than 600 people. After initial arbitration for 40 people resulted in about $120 million, PG&E decided to stop arbitration and settle the case. In 1996, the case was settled for $333 million, the largest class-action settlement in U.S. history at the time.

During negotiations, judges told PG&E’s lawyers that a 1987 study by a Chinese scientist, Jian Dong Zhang, linking chromium 6 to cancer in humans would influence their decision. In 1997, Zhang retracted his 1987 study. A firm called ChemRisk, which had worked with PG&E since 1995, updated Zhang’s analysis and published it in a medical journal. This updated version was published under Zhang’s name and another scientist’s name, despite Zhang’s objections. A reporter for The Wall Street Journal noted that Zhang’s son was upset about the retraction. A report by the Center for Public Integrity stated that the revised study suggested chromium was not likely the cause of cancer, which influenced California health officials to delay new drinking water standards for chromium.

In March 2001, the California Environmental Protection Agency (CalEPA) asked the University of California, Berkeley, to form a panel of experts called the Chromate Toxicity Review Committee. The committee met in July 2001 to discuss scientific questions about whether chromium 6 could cause cancer when ingested. The panel was led by Jerold A. Last, with Dennis Paustenbach as vice-president, and included other scientists. Paustenbach, Silvio De Flora, and John Froines later resigned from the committee.

On August 31, 2001, the Chromate Toxicity Review Committee, which included scientists like Russell Flegal and Marc Schenker, submitted a report titled Scientific Review of Toxicological and Human Health Issues Related to the Development of a Public Health Goal for Chromium(VI). The report claimed that reports about high chromium levels in southern California were exaggerated and suggested that further research should be done in laboratories, not by regulators. The report cited the 1987 Zhang study and its 1997 retraction. Based on this report, the Office of Environmental Health Hazard Assessment withdrew its 1999 public-health goal for chromium in drinking water.

In 2001, a law firm called Engstron, Lipscomb and Lack filed a follow-up lawsuit on behalf of 900 people in Hinkley and Kettleman, California, over chromium contamination. In 2003, Senator Deborah Ortiz held a Senate hearing about concerns about interference in scientific reviews of chromium 6 toxicity. At the hearing, a lawyer from Engstron, Lipscomb and Lack testified that the 2001 report by the Chromate Toxicity Review Committee had negatively affected their case against PG&E.

Since the Hinkley lawsuit, scientists from groups like the Desert Sierra Cancer Surveillance Program and ChemRisk have argued that chromium 6 is not strongly linked to cancer and have downplayed the number of cancer cases in the area.

According to the lawsuit, PG&E was required to stop using chromium 6 and clean up contaminated groundwater. By 2008, the contamination had spread, and by 2011, it received media attention. In November 2010, PG&E began offering to buy homes and provide bottled water in Hinkley. By 2013, the contamination area was over six miles long and two miles wide.

In 2006, PG&E agreed to pay $295 million to settle claims from 1,100 people across California related to chromium 6. In 2008, PG&E settled the last Hinkley claims for $20 million. That same year, the U.S. Environmental Protection Agency (EPA) responded to research showing that heavy doses of chromium 6 caused cancer in mice and rats.

In July 2014, California became the first U.S. state to officially link ingested hexavalent chromium to cancer. The state set a maximum contaminant level (MCL) for hexavalent chromium at 10 parts per billion (ppb). Hexavalent chromium is measured in micrograms per liter (μg/L). The EPA does not have an MCL for hexavalent chromium in drinking water but has an MCL of 100 parts per billion for all forms of chromium.

Groundwater pollution

PG&E operates a compressor station in Hinkley for its natural-gas transmission pipelines. Natural gas must be re-compressed about every 350 miles (560 kilometers), and the station uses cooling towers to cool the gas after compression.

From 1952 to 1966, the water in the cooling towers contained hexavalent chromium, now recognized as a carcinogen, to prevent rust in the machinery. The water was stored between uses in unlined ponds, which allowed the water to soak into the ground. This caused groundwater pollution, affecting soil and contaminating water wells near the compressor station. The polluted area, called a plume, was originally about two miles (three kilometers) long and nearly one mile (1.6 kilometers) wide. By 2013, the plume had grown to six miles (ten kilometers) long and nearly two miles (three kilometers) wide.

Average hexavalent chromium levels in Hinkley were recorded as 1.19 parts-per-billion (ppb), with an estimated peak of 20 ppb. According to the PG&E Background Study, the PG&E Topock Compressor Station averaged 7.8 ppb and peaked at 31.8 ppb. The proposed California health goal for hexavalent chromium was 0.02 ppb in 2011. In 1991, when the EPA raised the federal MCL for total chromium to 100 ppb, California kept its standard at 50 ppb. According to CalEPA in 2015, "At the time Total Chromium MCLs were established, ingested Hexavalent Chromium associated with drinking water was not considered to pose a cancer risk, as is now the case."

Plume

In August 2010, samples showed that the contaminated water plume had started to move into the lower aquifer. In September 2013, CalEPA reported that the plume had grown to 6 miles (9.7 km) long and 4 miles (6.4 km) wide. In 2015, the California Regional Water Quality Control Board, Lahontan Region, issued an order to PG&E to clean up the effects of the chromium discharge. At the time of the report, the plume was 8 miles (13 km) long and about 2 miles (3.2 km) wide, covering the Hinkley Valley and extending into Harper Dry Lake Valley.

Cleanup

By 2013, PG&E had spent more than $750 million on cleanup efforts. Sheryl Bilbrey, who leads PG&E's cleanup work, explained that the process was slow because the project was very complex. PG&E must follow many rules, and many groups are involved. She also said it was important to do the work correctly.

For their 2013 series Science for Sale, PBS NewsHour journalist Miles O'Brien interviewed Kevin Sullivan, PG&E's director of chromium cleanup. Sullivan said PG&E had cleaned up 54 acres (22 hectares) but would need 40 more years to complete the work. PG&E built a long concrete wall to stop the spread of contaminated water, pumped ethanol into the ground to change harmful chromium 6 into less dangerous chromium 3, and planted large areas of alfalfa. O'Brien also spoke with Erin Brockovich, who was surprised that PG&E had not finished the cleanup it promised more than a decade earlier.

In a letter to Sullivan, the Water Board noted that by 2014, chromium from PG&E's past releases at the Hinkley Compressor Station had moved from the upper aquifer to the lower aquifer, causing harmful levels of hexavalent chromium in the lower aquifer. Information about the cleanup at Hinkley is available on the CalEPA website.

Debates

In 2007, a report by the National Toxicology Program showed that high amounts of chromium 6 caused stomach and intestinal cancers in rats and mice when they drank water with more than 5 mg/L (5 ppm or 5,000 ppb).

In Hinkley, average levels of hexavalent chromium in water were 1.19 ppb, with the highest recorded level at 20 ppb. At the PG&E Topock Compressor Station, average levels were 7.8 ppb, with the highest at 31.8 ppb, according to a PG&E study. In 2013, PG&E’s Sheryl Bilbery told a PBS reporter that scientists are still discussing the health risks of hexavalent chromium. She said this is why it has taken time for governments to decide on safe limits. In July 2014, California’s Environmental Protection Agency (CalEPA) set a maximum safe level of 10 ppb for chromium 6 in drinking water after new research linked it to cancer.

California became the first state to set a drinking water limit for hexavalent chromium in July 2014, setting the level at 10 ppb. A 2015 report by the United States Geological Survey (USGS) reviewed the U.S. Environmental Protection Agency’s (EPA) 2010 findings about chromium 6 in water. After California’s 2014 limit, Illinois worked with the USGS to study the topic further. The USGS report said the EPA proposed in 2010 that chromium 6 is likely to cause cancer in humans when ingested over a long time. Water pollution levels are measured in micrograms and milligrams per liter (μg/L and mg/L), with 50 μg/L equal to 50 ppb and 50 mg/L equal to 50 ppm.

Since January 1, 1988, all cancer cases in California have been reported to the California Cancer Registry (CCR). Hinkley, in San Bernardino County, is covered by the Desert Sierra Cancer Surveillance Program (DSCSP), part of the California Department of Public Health. John Morgan, an epidemiologist, began working with the DSCSP in 1995.

Morgan has written over 100 reports and presentations, some of which were reviewed by other scientists. Some of his work tries to explain that chromium pollution did not cause a cancer cluster in Hinkley or that cancer rates there are normal. In a 2010 study, Morgan said cancer rates in Hinkley stayed the same from 1988 to 2008. In a later study with M. E. Reeves, he wrote that 196 cancer cases reported between 1996 and 2008 were fewer than expected based on local population data.

In a 2012 presentation, Morgan used cartoon characters to explain that inhaled chromium 6 is a known cancer cause, but water-based chromium 6’s role in cancer is still debated. He also wrote a letter to promote a poster of his work. In 2013, the Center for Public Integrity found problems with Morgan’s 2010 study, saying it ignored evidence of a real cancer cluster in Hinkley and excluded people most affected by pollution.

Dennis Paustenbach has worked as a consultant for companies facing lawsuits about environmental issues. He founded ChemRisk, a scientific consulting firm, and worked with Brent Kerger, a senior scientist. Their clients included PG&E and BP.

Paustenbach was involved in a controversy over a 1987 study by Chinese scientist Jian Dong Zhang, who found higher rates of stomach cancer in villages near a chromium-ore smelter in China. CalEPA’s 2008 review agreed with Zhang’s findings. PG&E hired ChemRisk to help with its chromium-related legal cases.

The Center for Public Integrity reported that Zhang’s 1997 study, which did not mention PG&E’s involvement, influenced California to delay new water safety rules for chromium. The EPA used this study to allow chromium in wood preservatives, and the Agency for Toxic Substances and Disease Registry downplayed chromium 6’s cancer risk.

In 2006, the Journal of Occupational and Environmental Medicine reviewed Zhang’s 1997 study. Zhang had died by then, but his co-author agreed the study should be retracted. The retraction, written by editor Paul Brandt-Rauf, said the study’s findings were not reliable.

In 2005, The Wall Street Journal reported that ChemRisk helped write the 1997 study for PG&E, which was being sued over chromium pollution. Paustenbach later worked with Exponent, and both ChemRisk and Paustenbach faced scrutiny from journalists.

In September 2010, EPA scientists said even small amounts of chromium 6 in tap water might cause cancer. Steven Patierno, an expert witness in seven chromium 6 lawsuits, was named to a panel reviewing EPA findings. The Center for Public Integrity reported this as a conflict of interest.

Patierno, who worked for PG&E, was a deputy director at the Duke Cancer Institute and a professor at George Washington University. He studied chromium and said low doses of chromium 6 do not cause cancer. He co-authored papers with Paustenbach, another expert for PG&E. In 1996, Paustenbach and Patierno wrote a paper saying chromium 6 is not harmful to DNA.

Film

The contamination and lawsuit were the focus of Erin Brockovich, a 2000 movie based on real life, in which Julia Roberts played the role of Erin Brockovich. The film was very well received, and Roberts won a Golden Globe Award for Best Actress in a Motion Picture – Drama and an Academy Award for Best Actress. Brockovich stated that the movie was about 98 percent accurate and appeared briefly in the film.