Chromium-6 in U.S. Tap Water: Industry Tactics
Industry falsified key study of “Erin Brockovich chemical”
Chromium is a naturally occurring metal used in steel manufacturing, leather tanning, welding and the production of dyes, pigments and alloys. It is often used to plate metal surfaces and is a major component of pesticides used in pressure-treated lumber for outdoor decks, play sets and other structures (one form was banned in 2005). Chromium was also widely used as an anti-corrosive agent in industrial cooling towers until the federal government banned the practice in 1990 (EPA 2000). It is an essential component in making stainless steel, its most common use, and super-alloys (USGS 2010).
The toxic form of chromium is not regulated in tap water
Chromium has multiple forms, and the two most common have dramatically different consequences for human health. Trivalent chromium (chromium-3) is a nutrient essential to sugar and lipid metabolism, but hexavalent chromium (chromium-6) is a dangerous toxin. Since 1990, international health authorities have identified it as a known human carcinogen when inhaled (IARC 1990), and a growing body of evidence has linked hexavalent chromium in drinking water to stomach and gastrointestinal cancers.
In 1992, the EPA set the legal limit in tap water for total chromium — a mixture of hexavalent and trivalent chromium — at 100 ppb to protect against skin reactions known as “allergic dermatitis” (EPA 2010b). However, a safety standard that lumps levels of a toxic carcinogen with a nutrient necessary for health is like grouping arsenic and vitamin C.
Recent California Department of Public Health tests of drinking water detected hexavalent chromium in 2,208 of more than 7,000 water sources (CDPH 2009). A review of EWG’s tap water quality database indicates that more than 74 million Americans may be exposed to total chromium through tap water, and more than 13.7 million Californians may be exposed to hexavalent chromium (EWG 2009).
New evidence overturns claims that chromium-6 is harmless
Various conditions can cause trivalent chromium to change to hexavalent chromium and vice versa. The widely used tap water disinfectant chlorine, for instance, can cause trivalent to become hexavalent (Lai 2006). Highly acidic conditions can cause hexavalent to become trivalent. For years, scientists assumed that all hexavalent chromium was converted to trivalent by the stomach’s acidic environment, rendering it harmless.
It is now clear, however, that some of this toxic chemical can pass through the stomach unchanged and penetrate tissues and organs throughout the body (Costa 1997). Studies in both animals and people show that exposure to hexavalent chromium via drinking water leads to elevated chromium levels in tissues, particularly the gastrointestinal tract, blood, liver, kidneys and spleen, and in increased toxicity (Kerger 1996; Finley 1997; Anderson 2002; NTP 2008; EPA 2010a).
Industry deceit covered up cancer connection
Research on the effects of chromium-6 in drinking water has focused on increased cancer risk. More than 20 years ago, researchers found an increased risk of stomach cancer and a “significant excess of overall cancer mortality” among villagers in China’s Liaoning Province whose drinking water had been polluted by a chromium ore processing facility (Zhang 1987).
This research should have triggered a flurry of scientific and regulatory scrutiny, but the study was published in a Chinese-language medical journal, making it largely inaccessible to U.S. researchers and regulators. Ten years later, in April 1997, the Journal of Occupational and Environmental Medicine (JOEM) published a paper, purportedly by the same Chinese research team, that reversed the earlier conclusion. It said that the data from Liaoning Province “do not indicate an association of cancer mortality with exposure to [hexavalent chromium]-contaminated groundwater” (Zhang 1997).
Investigations by EWG and the Wall Street Journal (EWG 2005) revealed that ChemRisk, a consulting firm hired by Pacific Gas & Electric Co. (PG&E) to fight the Erin Brockovich lawsuit over contamination in Hinkley, Calif., had distorted data from the Chinese study and placed the falsified paper in a respected scientific journal in order to reverse the original conclusion linking hexavalent chromium to stomach cancer.
Exposé outed corrupt consultant
EWG’s review of documents and depositions from a Kettleman City, Calif. lawsuit against PG&E revealed that ChemRisk’s employees — with the knowledge of PG&E’s attorneys — had conducted their own analysis of the original Chinese data in 1995-97, deliberately excluding reports of cancer cases in the province that pointed to an association with hexavalent chromium. They then wrote and submitted their paper for publication without disclosing that they worked for ChemRisk or that PG&E had paid for the new “study.”
Kettleman City, like Hinkley, is home to a PG&E station that pumps natural gas from a Texas pipeline to California customers. Both facilities used hexavalent chromium to cool the natural gas and then dumped it into unlined ponds that allowed the contaminant to leach into groundwater.
In the Brockovich lawsuit, residents of Hinkley sued PG&E for polluting their tap water with hexavalent chromium — the basis for the Julia Roberts film released in 2000. PG&E paid $333 million to settle the Hinkley case before the falsified paper was published, but scientists and regulators — including the EPA — subsequently cited the paper in research and safety assessments. In response to EWG's request for corrective action (EWG 2006), the journal retracted the paper in 2006, citing in particular the fact that “financial and intellectual input to the paper by outside parties was not disclosed” (Brandt-Rauf 2006). Also in 2006, PG&E settled with the Kettleman City victims of chromium-6 contamination for $335 million.
As part of its toxicological review, the California Environmental Protection Agency’s (California EPA) Office of Environmental Health Hazard Assessment (OEHHA), charged with setting a public health goal for the contaminant in tap water, conducted a rigorous re-analysis of the Chinese data. That work once again demonstrated a statistically significant increase in stomach cancer among the hexavalent chromium-exposed villagers compared to Liaoning Province’s overall population (Beaumont 2008).
Laboratory studies bolster cancer link
Animal studies have provided additional evidence linking hexavalent chromium to cancer. A study by federal toxicologists on rats and mice revealed statistically significant, dose-related increases in tumors of the duodenum and small intestine in mice, and statistically significant increases in tumors of the oral cavity in rats (NTP 2008). Based on these data, the National Toxicology Program’s (NTP) Board of Scientific Counselors concluded that hexavalent chromium in drinking water shows clear evidence of carcinogenic activity (NTP 2007).
These results agree with those of an earlier study that was marred by a number of limitations, including the outbreak of a viral infection in the mice under study (Borneff 1968). Nevertheless, a thorough statistical analysis of these data that accounted for the limitations still found a significant increase in stomach tumors (OEHHA 2009).
The NTP findings led the US EPA to list hexavalent chromium as a priority for evaluation under its Integrated Risk Information System (IRIS), which last reviewed the health concerns associated with this contaminant in 1998. In September 2010, the agency released a draft toxicological review, concluding that chromium-6 in drinking water is “likely to be carcinogenic to humans” (EPA 2010a). Unfortunately, the EPA has also cited its ongoing investigation as a reason to delay adopting a more health-protective federal limit for chromium in tap water (EPA 2009).
In contrast, California has moved ahead. California EPA scientists drew a clear conclusion: “The findings of available human, animal, genotoxic, and toxicokinetic studies all indicate that hexavalent chromium is a possible human carcinogen by the oral route” (OEHHA 2009). Dr. R. Gwiazda, a reviewer of the draft public health goal for chromium-6 in tap water, summed it up best: “Overall, the document convincingly demonstrates that indeed there is a relationship between exposure to [hexavalent chromium] via the oral route and the development of cancer in the gastrointestinal tract” (Gwiazda 2008).
Some people are especially vulnerable
Some individuals may be especially susceptible to the carcinogenic effects of chromium-6. Specifically, people with less acidic stomachs appear to have limited ability to convert hexavalent chromium to trivalent chromium, exposing them to higher levels of the toxic form and putting them at greater risk.
A low-acid stomach can be caused by several widely used medications, such as antacids and proton pump inhibitors used to treat common disorders including gastroesophageal reflux disease, peptic ulcer disease and chronic gastritis. Other conditions that can inhibit stomach acid production include pernicious anemia, pancreatic tumors, infection with Helicobacter pylori (a common bacterium linked to ulcers), mucolipidosis type IV and some autoimmune diseases. People with pernicious anemia have also been found to absorb hexavalent chromium more readily (Donaldson 1966).
Fetuses, infants and children also have higher sensitivity to carcinogenic chemicals. According to the National Academy of Sciences (NAS), children’s developing organ systems are more vulnerable to damage from chemical exposures, and children are less able than adults to detoxify and excrete chemicals (NAS 1993). A recent evaluation by US EPA scientists in response to the agency’s 2005 revised Cancer Guidelines noted that hexavalent chromium causes germ cell mutations and DNA deletions in developing embryos, indicating a need for age-dependent adjustment factors for risk assessments to account for the toxin’s increased damage in developing bodies (McCarroll 2010).
Chronic exposure to hexavalent chromium in tap water is likely to raise everyone’s risk of cancer, but the young and the medically impaired may be especially vulnerable. These susceptible subpopulations deserve special protections.