Moreover, the researchers identified no dose-related response: The rats fed higher doses of pesticide or GM corn didn't consistently get sicker than those fed lower doses. In fact, some rats fed higher doses did better than the others.
Seralini offered no explanation why rats fed a pesticide should show the same pathology as rats fed genetically modified corn but not the pesticide, although Roundup and genetically modified corn are totally different things with, one would presume, different effects on the organism. That points to another shortcoming of the paper, which is that there's no explanation or even hypothesis of why either impurity should produce the tumors Seralini found.
"They don't show a plausible biochemical or molecular mechanism for the effect," observes Kevin Folta, a plant biologist at the University of Florida who has written critically about the Seralini paper. "It happens with two completely independent treatments, the herbicide and the [genetically modified] product, and to get the same unusual response from both is beyond suspicious."
The ultimate complicating factor is that the strain of lab rat Seralini used is predisposed to tumors, especially mammary tumors. By about 2 years of age, 80% of these rats will have them, on average. Therefore, the longer the experiment proceeds, the cloudier the data become, because most of the rats would eventually be tumor-ridden anyway. In other words, the length of the study isn't a virtue, as Seralini contends, but may be a flaw.
Seralini responds that his paper does propose a mechanism for toxicity — that sex hormones are disrupted by Roundup. But the paper is a lot more vague about why genetically modified corn would have the same effect, and other researchers don't find his supposition persuasive.
He agrees that it would have been better to have tested 600 rats rather than 200, but then the study would have cost $26 million, not $4 million. "I agree it has limits," Seralini says. "I don't say my study is absolutely perfect. Any study can be improved. But that doesn't mean it's wrong."
Still, it's the political exploitation of a manifestly imperfect study that's disturbing. The use of poor information to promote an initiative aimed at creating an informed consumer is a defining flaw of the Proposition 37 campaign.
That flaw is compounded by the failure of the initiative itself to achieve its own ends, rife as it is with ambiguities and exemptions — for example, dairy products, fresh meat and restaurant food all fall outside its labeling mandate. Furthermore, lumping together all the myriad forms of genetic engineering into one catchall category, as though they're all equally worthy of concern, will leave the average consumer with no usable guidepost to what to buy and what to avoid.
The critics of Seralini's paper suggest that it was designed to frighten, not inform. Even if that's not so, it's been used that way by its promoters. As Eisen says, "Public policy shouldn't be designed to cater to that level of ignorance."
Michael Hiltzik's column appears Sundays and Wednesdays. Reach him at email@example.com, read past columns at latimes.com/hiltzik, check out facebook.com/hiltzik and follow @latimeshiltzik on Twitter.