You’d think that if 93 percent of Americans could agree on something, their government might just pay attention. In the case of labels for GMO foods, you’d be wrong: Polls show overwhelming consumer support [PDF] for labels. But for some not particularly convincing reasons, neither Congress, the FDA, nor the USDA have been willing to respond.

As this excellent new report from Food and Water Watch documents, it’s now virtually impossible to avoid eating GMOs. As much as 94 percent of the soy and 88 percent of the corn in the U.S. is grown from genetically modified seed. Supermarket meat comes from livestock given GMO feed, and any processed food that’s not certified organic will invariably contain corn or soy-derived genetically modified ingredients, such as lecithin or high fructose corn syrup. And without a label, there’s no way to know for sure, so consumers are left in the dark.

But a new groundswell of activism might just force the government to act. For the first two weeks of October, a group calling itself Right2Know has been marching from New York through Philadelphia to Washington, D.C. to demand GMO labeling. You can follow along here and sign up to march here (on Thursday, Oct. 6, the march will be holding a major event in Philadelphia mere blocks from my house at the Weavers Way Coop). I’ve often made the point that nothing much will happen in food reform until people take to the streets — and now that a group is doing just that, it will be interesting to see how Washington and the media react.

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Not coincidentally, another campaign called JustLabelIt launched today; it’s backed by a coalition of 400 businesses and organizations “dedicated to food safety and consumer rights.” And they’ve released this clever video:

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JustLabelIt’s initial move was to petition the FDA to force companies to label food with genetically modified ingredients. However, as USA Today indicated in their coverage, the FDA is unlikely to cooperate. While refusing to comment on the petition, FDA spokeswoman Tamara Ward said the agency “has not found that foods from genetically engineered organisms, as a class, present different or greater safety concerns than their conventional counterparts.”

Of course, the FDA can say that, because — as Tom Philpott reports — the science behind the safety of GMOs is limited to nonexistent. And not by accident. As he details, there is almost no research on the health impacts of genetically engineered food; the food industry convinced the FDA it wasn’t necessary and companies who control the patents on GMO seeds refuse to allow scientists access unless they agree not to look into safety.

As long as GMO foods are considered identical to their conventional counterparts, forcing the FDA to act is a longshot. It is true that, unlike E. coli-contaminated meat or listeria-contaminated cantaloupe, genetically modified foods do not appear to cause acute symptoms. But what about chronic conditions like allergies, or what Philpott calls “slow-moving, unspectacular conditions that could take years to detect”?

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Many advocates are as concerned by this lack of information — and the scientific precedent they set — as they are by the possible long-term effects of GMOs. Labeling would cause an inevitable tide of curiosity among less-informed, well-meaning eaters. Not only would labels infuse shopper’s everyday environments with language about genetic engineering (think about the labeling of high-fructose corn syrup, for instance), but it might also make more people aware that they’re eating the product of an industrialized food chain.

The question about whether GMOs are different from conventional foods is a longstanding one. Interestingly, the federal courts are starting to conclude that what science exists might in fact counter the FDA (and USDA) position on GMOs, which suggests labeling may end up in court. Even the business-friendly Supreme Court, which ruled to approve Roundup-ready alfalfa, admitted that the crop had been prematurely approved.

In the end, a simple law requiring labels would be far easier than a court battle. And while there is an active bill that would force the FDA to label GMO salmon, should they approve it, there are no other high-profile GMO labeling bills on the public radar. But it is possible that the action will shift to the states. In California, there is an effort to get a GMO labeling referendum on the ballot. If advocates succeed there, other states may follow suit — and consumers will at least get the transparency they deserve.