September 20, 2012

Roundup scare

You’ll probably be seeing local stories about GM corn and the weedkiller Roundup coming out soon.  Here’s an overseas example. I was asked for comment on the research paper by the NZ Science Media Centre, and said

I do not think the herbicide risks look convincing, especially with respect to cancer.  There is no consistent pattern in deaths with dose of either Roundup or GM corn: this is not just showing a threshold, as the authors suggest, since in all six of their comparisons the highest-dose group has lower mortality than lower-dose groups.  The hypothesis of hormone-related cancer differences is not supported by the multivariate biochemical analysis, which found differences in salt excretion but not in testosterone or estradiol.  The strongest conclusion that could be drawn from this study is that it would be worth studying a larger group of controls than just 10 and (since there is no sign of dose-response) just a single low dose of Roundup or GM corn.

The researchers say “It is noteworthy that the first two male rats that died in both GM treated groups had to be euthanized due to kidney Wilm’s tumors”. This is noteworthy, but perhaps not in the way the researchers mean: increases in human Wilms’ tumor from GM corn or herbicide residues would already be obvious even at rates hundreds of times lower than reported in these rats.

At the time, I had only read the research paper, not any of the media stories.  There is a detail in the story I linked above that is absolutely outrageous:

Breaking with a long tradition in scientific journalism, the authors allowed a selected group of reporters to have access to the paper, provided they signed confidentiality agreements that prevented them from consulting other experts about the research before publication.

That is, we’ll let you have a scoop provided we can make sure there’s no risk of getting it right or disagreeing with us.  Embargoes on stories about scientific papers are standard, but one of the justifications is to precisely to provide journalists with time to get the facts right.   It would be interesting to know how many of the journalists who signed these agreements were willing to admit to it in their stories.

 

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Comments

  • avatar

    I’m just getting to this now. This breakdown of the stats:

    http://www.weedcontrolfreaks.com/2012/09/why-i-think-the-seralini-gm-feeding-trial-is-bogus/

    suggests that it’s quite probable that the results are due to chance – given unreported rat tumour growth baselines. I’ve had a quick scan of the paper, Suzuki isn’t referenced and I can’t immediately see anything about the fact that the ~80% of that breed of rats get tumours after 2 years anyway.
    Especially annoying as the Greens GMO chap Steffan Browning has just started promoting the study (or at least the non-critical coverage of the study).

    2 years ago Reply

    • avatar
      Thomas Lumley

      Well, they do have a small number of unexposed controls, and they claim the tumours in the exposed animals were worse. The quantitative evidence isn’t very convincing, though.

      2 years ago Reply

      • avatar
        Philippe Pognonec

        Quantitative evidence for tumors may arguably be shaky, at least for the male group. However the biochemical analyses (Figure 5 and Table 3 in the paper) are impressive. And while the testosterone and estradiol data is indeed not within the 99% confidence, the tendency is highly suspect. Let’s hope that now that this has been brought to light by a small and minimally funded lab, Monsanto will put enough money on the table to allow INDEPENDENT laboratories to clarify whatever doubt may still lurk around by running test on larger rat populations (this study already cost around 2000000€)…

        2 years ago Reply

        • avatar
          Thomas Lumley

          I don’t think the biochemical analyses are convincing or particularly impressive, even if you assume it is reasonable that glyphosate and the genetic modification should have the same effect on rats.

          If the researchers really thought the dose-independence was a priori plausible (which is necessary for the results to be even the slightest bit supportive), they should have used fewer doses and larger sample sizes per dose and done a more convincing study for the same amount of money.

          I also don’t see why Monsanto would be interested in putting up the money — it’s too late for Monsanto to have any incentive to fund a study like this, and no-one would trust the results anyway. I certainly wouldn’t trust a Monsanto-funded safety study at this point.

          Perhaps a longer study should have been done by Monsanto before approval, and perhaps longer studies should be done pre-approval in the future but that’s not the issue now. If a larger study is worth doing it should be funded by someone like the US EPA or NIH, or equivalent European groups, and be really independent. Or perhaps a joint govt/industry setup like the one the Health Effects Insitute oversees for air pollution research.

          Also, if a larger study is done, it should be in a setting that toxicologists think is relevant to human exposure — I’m not a toxicologist, but they seem to be unimpressed by full-lifetime studies in this type of rat.

          I’m not in favor of Roundup-resistant plants, especially as they are currently used, but this study shouldn’t change anyone’s mind about safety.

          2 years ago

  • avatar

    Wow. Imagine an industry-funded group had demanded similar things from the journalists as condition of access to a study showing GMOs are awesome. The story would have been entirely about suppression of journalists, not about the findings.

    2 years ago Reply

  • avatar
    James Guthrie

    More analysis over at neurologica blog…

    http://theness.com/neurologicablog/index.php/the-gm-corn-rat-study/

    2 years ago Reply

  • avatar
    Julie Middleton

    … “the authors allowed a selected group of reporters to have access to the paper, provided they signed confidentiality agreements that prevented them from consulting other experts about the research before publication”. That is truly outrageous and sounds like a cover for dodgy ‘science’ …

    2 years ago Reply

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