May 17, 2007 The Pump Handle 6Comment

By David Michaels

Many people first heard about hexavalent chromium, or chromium 6, from the movie Erin Brockovich, which is based on the true story of a lawsuit over chromium-contaminated groundwater in the town of Hinkley, California.

Less well-known is the campaign waged by companies that manufacture or use chromium 6 to convince regulatory agencies that the chemical, which has recognized as a lung carcinogen for more than 50 years, just isn’t so dangerous. There’s a lot of chromium-contaminated water out there, and if chromium 6 in drinking water were acknowledged to be a cause of cancer, it would cost industry a lot of money in clean-up costs.

It won’t surprise regular readers of this blog – or anyone who’s seen our case study on industry efforts to delay OSHA’s chromium 6 standard – to hear that these companies have turned to product defense firms, and that the firms have produced studies that differ markedly from those completed by non-industry-funded scientists.

To independent scientists, most of the evidence has suggested that that chromium in drinking water increases cancer risk. A study just released by the National Toxicology Program adds to that evidence:

Researchers announced today that there is strong evidence a chemical referred to as hexavalent chromium, or chromium 6, causes cancer in laboratory animals when it is consumed in drinking water. The two-year study conducted by the National Toxicology Program (NTP) shows that animals given hexavalent chromium developed malignant tumors.

“Previous studies have shown that hexavalent chromium causes lung cancer in humans in certain occupational settings as a result of inhalation exposure,” said Michelle Hooth, Ph.D., NTP study scientist for the technical report. “We now know that it can also cause cancer in animals when administered orally.”

As this kind of evidence has mounted, chromium manufacturers and PG&E (defendant in the Hinkley suit and source of much ground water pollution) have hired the product defense firms ChemRisk and Exponent to do what they do best: manufacture uncertainty. Recently, Environmental Working Group uncovered one of the tactics:

A consulting firm hired by Pacific Gas & Electric Co. (PG&E) to fight the “Erin Brockovich” lawsuit distorted data from a Chinese study to plant an article in a scientific journal reversing the study’s original conclusion that linked an industrial chemical to stomach cancer, according to documents obtained by Environmental Working Group (EWG).


The Wall Street Journal reported today that the San Francisco-based consultants, ChemRisk, “conceived, drafted, edited and submitted to medical journals” a “clarification” of the Chinese study, according to documents filed in another chromium lawsuit against PG&E. They did so despite a letter of objection from the Chinese scientist who led the original study, calling their reversal of his findings an “inappropriate inference.”

When this all came to light, the Journal of Occupational and Environmental Medicine, which had published the problematic study, issued a retraction. (The saga didn’t end there, however; see this post for more.)

Most of what product defense firms produced doesn’t get retracted, though. They run their own studies, whose conclusions are promised to their clients ahead of time, or they re-analyze the studies of other scientists until statistical significance disappears, and they publish the results. When enough of this adds up, the product defense firms are able to claim that the science is too uncertain to regulate their clients’ products or find their client’s products guilty in court.

The new NTP study is another important piece of evidence showing the carcinogenicity of ingested chromium 6, and it could have important repercussions. California’s Congressional delegation and the California Environmental Protection Agency requested NTP to study the toxicity and carcinogenicity of orally ingested chromium 6 because the substance had been found in human drinking water supplies; hopefully they will use the results of NTP studies to set a lower allowable limit for chromium 6 in drinking water.

Environmental Working Group senior analyst Renee Sharp summed it up nicely when she told Reuters that “NTP’s findings will finally allow state and federal regulators to set drinking water standards based on up-to-date sound science, rather than having to rely on old, inadequate, and/or biased studies often funded by chromium polluters.”

We’ll probably see more studies funded by chromium polluters – perhaps even one designed specifically to counter the NTP study. But this study and others like it should help regulators to set an appropriate drinking water standard.

David Michaels heads the Project on Scientific Knowledge and Public Policy (SKAPP) and is Professor and Associate Chairman in the Department of Environmental and Occupational Health, the George Washington University School of Public Health and Health Services.

6 thoughts on “New Study Strengthens Chromium-Cancer Link

  1. Please correct me if this is wrong, because it’s an important point with numbers attached which can be checked.

    The old standard was a ceiling standard. Ceiling means a limit not to be exceeded for any time, but generally considered to be 15 minutes or the shortest sampling period in which the exposure is above the limit of quantitation. The new standard is an 8 hour time weighted average.

    Thus, under the old rule, a job with an intermittant exposure above 52 ug/m3 violated the PEL, requiring the employer to install improved controls. It’s plausible, given the types of applications of chromates, that exposure could be a single period of 15 minutes. Under the new standard, an exposure as high as 320 ug/m3 limited to 15 minutes would be in compliance. Or, 80 ug/m3 for an hour…you can do the math.

    In short, the new rule allows higher short term exposures than the old rule. Even at the former proposal of 1 ug/m3, somewhat increased short term exposures would have been permitted.

  2. Frank,
    I recall that Peter Lurie and Sid Wolf did an analysis of OSHA enforcement data and specifically examined Cr(VI) sample results taken between 1990-2000. My quick glance of the article suggests that OSHA was enforcing the 52 ug/m3 as an 8-hour PEL (or TWA equivalent.)

    A link to the Lurie & Wolf paper is here:

    If I’ve interpreted this incorrectly, please let me know.

  3. China clearly is not concerned about carcinogens in their products and we keep on buying them. l wish I knew how to start a grass-roots program to ban all products made in China. First lead in our children’s toys, then carcinogens in dry wall, now cadmium in kid’s trinkets. Their goal is money and we keep spending. When is America going to wake up??????

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