An Epidemiologist’s Nightmare

By George Johnson | April 1, 2013 6:11 am

Chinese pollution. Photo by Robert Gagnon via Flickr

I’ll say it again: You can sympathize with the people who drank the water and abhor the polluters and still not be persuaded that there was a cancer outbreak. That sums up the message of my recent posts on Erin Brockovich and the article I wrote for Slate on the Toms River cancer cluster. It could apply just as easily to the case in Woburn, Massachusetts, which was made famous by Jonathan Harr’s book, A Civil Action.

Woburn and Toms River are the only two places in the United States where epidemiologists have found an association — a very murky one — between pollution and cancer in some of the residents. Both incidents involved childhood leukemia, and the number of excess cases finally attributed to toxic effluents was about half a dozen in each town, occurring over a period of 10 or more years. For no known reason boys were affected in Woburn and girls in Toms River. Both may have been statistical flukes.

As far as cancer clusters go, Hinkley, California, the town in Erin Brockovich, is not even considered a contender. I find all of this as surprising as anyone. As I was researching my book, The Cancer Chronicles, I was struck again and again by how many of the perceptions we share about cancer are wrong.

To find levels of  pollution high enough to cause a noticeable rise in cancer, epidemiologists have had to look to China, where lax environmental standards and the rush to industrialization surpass anything still happening in the developed world. A recent story in the New York Times describes the catastrophe. The Chinese government itself puts the economic toll for just one year at $230 billion. But money is a pale measure.

If there is any salvation to come from the harm, it is the emergence of China as a testbed for cancer epidemiology. With large numbers of people exposed for years to high levels of industrial waste, researchers might get a better sense of the link to cancer — as they did with radiation by studying the sad aftermath of Hiroshima and Nagasaki. Yet even in these extreme situations, the evidence can be frustratingly ambiguous.

It was in Liaoning Province that chromium 6 contamination was so high — 200 times the EPA limit — that the drinking water turned yellow. According to a commentary in the journal Epidemiology, there has been only one other place in the world with comparable levels: León, Mexico. Both involved people living near factories that produce chromium compounds.

In Mexico there weren’t enough residents exposed to the water to provide plausible statistics. But in villages near the Chinese plant, researchers found an elevated rate of lung and stomach cancer.

The report was published in 1987 in the Chinese Journal of Preventive Medicine (I have not been able to find a copy, in Chinese or English). But 10 years later the numbers were reanalyzed and no increased cancer was found. On the surface the revised conclusion seemed legitimate. The earlier study compared the villages near the factory with the overall population. This time the control group consisted of other nearby villages without chromium-tainted water.

That sounds like a more direct and meaningful comparison. But whatever merits the science may have had were obscured when a conflict of interest was discovered: the epidemiologist leading the study, Dennis Paustenbach, had been working at the behest of Pacific Gas and Electric, the Hinkley polluter, through his consulting firm, ChemRisk Inc.

There are other twists to the tale, which was laid out in a 2006 account in the International Journal of Occupational and Environmental Health: “Corporate Corruption of Science — The Case of Chromium (VI).”

The Paustenbach paper was later retracted but that left the question hanging: though conducted under suspicious circumstances, was the science itself right or wrong? A third and independent study did find signs of an increase in stomach cancer. But the matter is still unresolved.

In the commentary in Epidemiology, Allan H. Smith of the School of Public Health at Berkeley welcomed the new findings. But he noted that they had their own problems, suffering from “serious limitations” caused by poor demographic records.

The study involves a rather messy reanalysis of mortality. . . . [The authors] cannot even reconstruct how the place of residence at the time of death had been determined . . .

Only crude rates were available for stomach and lung cancer from any village. Data on stomach cancer were unavailable for one of the villages, and data on lung cancer were unavailable for another. To make matters worse, mortality rates were not available by individual years . . .  so any trends over time (perhaps related to latency) could not be examined. . . . There were also no sex-specific data, with mortality for men and women having been combined in the available data. This is surely an epidemiologist’s ultimate nightmare, being unable to adjust properly even for age and sex.

Dr. Smith’s criticism of the ChemRisk report elicited a testy response from Dr. Paustenbach, and then a response to the response.

As the people of China become unwitting experimental subjects, these kinds of problems are bound to recur. The highest exposures of pollution will come in places where the demographic data are crude or nonexistent. “Indeed, the future of environmental epidemiology lies in the developing world,” Dr. Smith wrote, “where studies are usually difficult to do.”

So we are left with a choice: messy studies in places with high exposures or cleaner studies in places where the levels of contaminant may be too low to have a measureable effect. That was also the problem with the Chinese meta-analysis of the effects of megadoses of fluoride, which I wrote about here in some earlier posts.

An article last week in Ars Technica gives a detailed account of what was wrong with Miles O’Brien’s PBS Frontline report on chromium: It didn’t take into account this crucial matter of dosage. In addition to Hinkley, the newscast focused on a new study by the Environmental Working Group warning that it had found 35 American cities with chromium 6 in the water. But the concentrations were all far below the E.P.A. standard. Maybe the standard needs to be drastically lowered, as it has been in California. But no science was presented that makes that case. Ars Technica’s reporter, Scott K. Johnson, asked PBS for a response and got this unsatisfactory reply:

The Newshour’s two-part report on chromium 6 in drinking water supplies examined arguments about levels of safety and about the EPA’s process for making that determination. We included different points of view in our reports: those of affected residents, environmental activists, industry spokespeople, and scientists. The EPA refused to grant an interview, and we did our best to represent the agency’s position. Any specific comment should be viewed in the context of the entire report.

It’s a sorry excuse for bad journalism, and Johnson doesn’t let the network off the hook:

[T]hat approach — letting everyone have their say, without any critical evaluation — is part of the problem. This is not a question of differing points of view, but one of carefully sifting the knowns and unknowns. Presenting opposing perspectives and leaving the viewer to decide is not the way to communicate science, and it doesn’t excuse broadcasting misleading or incomplete information.

Related posts:

Erin Brockovich

The Brockovich Story, Part 2

The Psychology of Cancer Clusters

For new readers: The inaugural post to Fire in the Mind, Lighting the Match.

CATEGORIZED UNDER: Cancer, select, top-posts
  • PittsburghDUIAttorney

    According to a comments in the publication Epidemiology, there has
    been only one other globe with similar levels: León, South america. Both
    engaged people residing near industries that generate chromium

    • Matthew Slyfield

      Unless the industry in question is utilizing nuclear reactions they are NOT generating chromium substances. Without nuclear reactions if there is chromium in the outputs there must be an equal amount of chromium in the inputs.

      • Odin Matanguihan

        So what you’re saying is, that the chromium was mined? If that’s the case, it’s perfectly plausible that chromium can be found in the water even before mining started.

        • Matthew Slyfield

          It’s difficult to say without knowing the details of specific industrial process involved. The chromium may itself be a specific input or it may be a trace element in one of the primary inputs.

  • JonFrum

    Being from Massachusetts, I’m far more familiar with the Woburn/Grace case. The controversy over this case rests on far more than the epidemiology represented in this article. That part of Woburn was full of industrial facilities, including a tannery (notorious for their waste products), a junkyard, a business that cleaned out 55 gallon drums for reuse, and many other small businesses that would have used hazardous chemicals. And it was also a known midnight dumping ground, where unscrupulous businessmen illegally dumped and ran.

    Grace was sued because Grace had the biggest pockets – not because the evidence against them was the best. The plaintiff’s lawyer claimed that the cancers had been caused by TCE, although no one had the classic symptoms of TCE exposure, and TCE was not known to cause leukimia.

    And most importantly, the town had drilled drinking water wells in this long and heavily industrialized area, in spite of the fact that they had an engineering study in hand that warned them not to. In other words, the wells weren’t polluted – the town drilled wells into polluted soil.

    This case can be looked at from the epidemiological viewpoint, but ignoring the rest only keeps the water muddied (no pun intended). The epidemiological data can only be correlational – as far as I know, there was no medical/biological explanation for how the particular substances blamed had caused the cancers. And as such, the case was closer to a witch hunt than rational, science-based analysis of the facts.

    Finally, there is a difference between feeling bad for people whose children have leukemia, and feeling bad for people whose children have leukemia and irrationally blame it on people who probably didn’t cause it. People have believed that high tension wires caused cancer in their children. Do we blame the power companies – and all the rest of us who use that power – for causing those families anguish?

    • JonFrum

      I know – too long.

  • Dwayne J. Stephenson

    Just how carcinogenic are carcinogens anyway? I feel like the first kinds of problems one expects to find associated with toxic/industrial waste should be conventional (and perhaps unconventional) kinds of poisoning. Things that screw with internal organs and the brain. Surely the cancer rates should be tiny compared to the rates of other toxicity related health problems.

  • xiaoyanzi

    Do you really want to drink water with Chromium6 and other industrial effluents in it? Would that be tasty?

    The bottom line is these companies should be controlling their effluents, not waiting for us to prove it causes cancer or kills people first.

    • Matthew Slyfield

      “Do you really want to drink water with Chromium6 and other industrial effluents in it?”

      Many of these elements and chemicals can occur naturally in water supplies and other areas of environmental exposure.

      “Would that be tasty?” That depends on the concentration. I doubt you will find anywhere in the US where the concentration is actually high enough to be detected by human senses, including taste.

  • Matthew Slyfield

    “That sounds like a more direct and meaningful comparison. But whatever
    merits the science may have had were obscured when a conflict of
    interest was discovered: the epidemiologist leading the study, Dennis
    Paustenbach, had been working at the behest of Pacific Gas and Electric,
    the Hinkley polluter, through his consulting firm, ChemRisk Inc.”

    A question: Why should a scientist working for industry be automatically assumed to have a greater conflict of interest than a scientist working for a regulatory agency seeking to expand its regulatory authority, an agency that has more money than any single corporation or industry group?

    • Tomek Brzezinski

      Taking at face value the simplified comparison there, the basic argument would be that the EPA has a lot less to gain than a single corporation. While (again taking the goals of each group at facevalue) the EPA might have a “goal” of increasing their regulatory power, that goal pales in comparison to the corporation’s interest in not getting sued to earth’s end. To bring analogy, the company might be smaller than the EPA, but their fight is a life-or-death, and as such might more vigorous. I think that would be the basic argument response to your question.

      If I was to branch past your question, I would argue that there actually is such a thing as a different ethos to the EPA than a company. But, I don’t think I know too much, and I think my argument stands while limiting it to your concept of the EPA.

      • Matthew Slyfield

        My point is that if money corrupts the process than money corrupts the process no matter what the source and more money corrupts more.

        I’d really like to see you try to make the argument that the EPA + environmental NGOs aren’t outspending the corporations on this issue.


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Fire in the Mind

Whether a subtle new pattern shows up in an experiment on the Higgs boson, an epidemiological report about a suspected cancer cluster, or a double-blind trial purporting to demonstrate ESP, it can be maddeningly difficult to distinguish between what we see and what we think we see. "Fire in the Mind" takes a look at the big questions behind today’s science news.

About George Johnson

George Johnson writes about science for the New York Times, National Geographic Magazine, Slate, and other publications. His nine books include The Cancer Chronicles: Unlocking Medicine's Deepest Mystery (August 2013), The Ten Most Beautiful Experiments, A Shortcut Through Time, and Fire in the Mind. He is a winner of the AAAS Science Journalism Award and has twice been a finalist for the Royal Society science book prize. Co-founder and director of the Santa Fe Science Writing Workshop, he can be found on the Web at Twitter @byGeorgeJohnson.


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