The citizens in Washington state are about to make a decision that could have a big impact across the nation.

They will be voting Tuesday on Initiative 522, which would require labeling of all genetically modified (GM) foods on state supermarket shelves by 2015. If early surveys are any indication, voters there may be about to deliver the food industry a major defeat. Two-thirds of Washingtonians told pollsters last month that they will vote yes on Initiative 522, though Reuters reports that more recent surveys have the gap closing considerably.

Washington, a progressive state that has been a pioneer in legalizing marijuana and same-sex marriage, may become the first in the nation to require that controversial genetically modified foods be labeled.

If so, the food industry fears other states may soon follow suit. A coalition, which includes the Grocery Manufacturers Association and biotech giants like Monsanto, Bayer and DuPont, have poured over $21 million into a TV ad blitz to shoot down the initiative. A similar campaign in the final weeks before last year’s California “Right to Know” referendum, led to its narrow defeat (after earlier polling had shown more than 60 percent of voters there supporting labeling).

The food industry is arguing in its slickly produced spots, featuring farmers and a former state director of agriculture, that creating a new labeling system will be costly, raising grocery bills by as much as $360 per year for a family of four. Food activists counter with a study by economist Joanna Shepherd-Bailey of Emory University that predicts “food prices [are] likely to remain unchanged for consumers.”

The truth lies somewhere in between these politicized views. Changing the labels won’t cost much — manufacturers do that all the time. What Shepherd-Bailey’s analysis fails to consider (and the food industry is reluctant to say out loud) is that, if labels are mandated, skittish consumers may avoid products containing genetically modified foods altogether — as has already happened in much of Europe where labeling is required. This could indeed temporarily boost prices on some items as companies scramble to come up with conventionally grown alternatives.

At present 70 percent of the processed foods in American supermarkets contain genetically modified ingredients — mostly corn, soy, sugar (from sugar beets) and canola oil. Opponents have labeled them “Frankenfoods” (as in Frankenstein), because of biotech scientists’ seemingly scary capacity to splice together genetic materials from vastly different forms of life. There is currently no convincing scientific evidence, however, that they are dangerous to eat. On the other hand, there have also been no long-term health studies.

In addition, as I reported in Reuters in September, the FDA does not conduct tests itself, but depends on producers to evaluate and certify the safety of their own products.

The public remains deeply skeptical. Marion Nestle, professor of nutrition and public health at New York University, told me: “The corporations think a label is equivalent to putting on a skull and crossbones and that if labeled, nobody would buy them. I think the industry is excessively paranoid but if this is true, the industry brought this on itself by not labeling them in the first place.”

Nestle, who New York Times food guru Michael Pollan rates the second-most powerful foodie in America (after Michelle Obama), argues that the aggressive fight to prevent labeling makes it look like the corporations have something to hide. This has only helped fuel the public’s mistrust of genetically modified foods.

“I’m appalled at industry behavior,” Nestle said. “GMOs are about protection of patent rights, seed ownership, proprietary rights to agricultural chemicals and secrecy, and the enforcement that goes with it. They have nothing to do with providing benefits to consumers.”

Nestle, who has been tracking polls since the 1980s, says that public attitudes about genetically modified food have remained remarkably consistent. A large majority of Americans — up to 90 percent in some surveys, Democrats and Republican virtually equally — want to see them labeled.

At a time when many are focused on the importance of local production, slow foods and sustainable farming methods, genetically engineered crop varieties stand in many people’s minds for the opposite. They have also become tainted by the aggressive tactics of Monsanto, which sues farmers for saving and replanting their patented seeds.

The agrochemical giant has also developed (but not yet sold commercially) terminator crops, whose second generation seeds are sterile, which would force farmers to purchase new seed from the corporation every year. Some environmentalists worry that if terminator genes spread to wild plants, it could have disastrous consequences.

Margaret Smith, the associate director of the Agricultural Experiment Station at Cornell University, argues that the risks from genetically modified foods are not that different from new conventionally grown varieties. She cites the case of a naturally bred potato with levels of glycoalkaloids that were unsafe to eat. Fortunately, the breeders caught this problem in time and never marketed the toxic potatoes. The same kind of self-policing can work with genetically modified foods as well, she argues.

Smith believes that popular opposition to GMOs may be wide, but doesn’t run particularly deep. “There is large public support for labeling when the question is framed as a ‘right to know’ question,” she told me. “If the question is simply ‘What type of information do you think is missing from food labels,’ there are very, very few people who will come up with GE labeling.”

Yet, opposition to genetic engineering has been growing around the country. In the wake of a grass-roots movement on Hawaii, the County Council on Kaua’i, where many GMO seeds are bred, voted earlier this month to severely restrict the spraying of pesticides used in the production of the seeds. Los Angeles is currently considering a ban on the cultivation and sale of GM seeds within the city limits, which, if passed, will make it the largest GMO-free zone in the nation.

This is an especially hot issue in Washington state, where local fisherman fear that the fast-growing genetically modified “AquaAdvantage” salmon (a meld of Atlantic and Pacific salmon genes) could potentially outcompete and replace native stocks, as well as hurt the market for the more costly wild salmon.

Another local angle is that eastern Washington’s wheat growers couldn’t sell their grain to customers in Japan and South Korea this summer, after Monsanto’s unapproved GMO wheat plants showed up in fields in neighboring Oregon. These farmers are now worried that increasing U.S. dependence on genetically modified crops may destroy their export market.

If Initiative 522 passes, Washington will become the first state to mandate labeling. The Connecticut and Maine legislatures have already enacted labeling laws, but they won’t go into effect until a critical mass of neighboring states follow suit. Nearly half the U.S. state legislatures are now considering their own labeling bills.

Meanwhile, in Washington, Senator Barbara Boxer (D-Calif.) and Representative Peter DeFazio (D-Ore.) have cosponsored the Genetically Engineered Food Right-to-Know Act, a bill that would mandate that the Food and Drug Administration require labeling.

Nestle of NYU, says “people want these things labeled” and it is just a matter of time before it happens. “The industry will do everything it can to prevent states from passing labeling laws,” she predicts, but it will fail, “and at some point it may decide that the fight is too expensive and ask for federal intervention.”

If Washington State passes labeling laws, Nestle expects the food industry will challenge them in court, or attempt to cut its losses by pushing for its own preemptive law — which would call for labeling to be done inconspicuously, in small print.

With so much at stake, it is clear that the controversy over genetic engineering is not going away anytime soon.

Smith of Cornell says that’s a shame, because it diverts attention away from the critical issues now facing agriculture as climate change increasingly disrupts farming in many areas, and global population soars. We are using up our freshwater reserves, Smith says, running out of arable land and exhausting soils with unsustainable, chemical-intensive farming methods. She argues that it will be a huge challenge to grow enough of the right kinds of food in the years ahead.

“We have to provide for healthier, more nutritious diets for more people with fewer resources,” Smith says. “I do not think we can afford to rule out any tools.”

PHOTO (Top): Employees stock shelves near a sign supporting non-genetically modified organisms (GMO) at the Central Co-op in Seattle, Washington, October 29, 2013. REUTERS/Jason Redmond

PHOTO (Insert 1): A customer picks up produce near a sign supporting a ballot initiative in Washington state that would require labeling foods containing genetically modified crops at the Central Co-op in Seattle, Washington, October 29, 2013. REUTERS/Jason Redmond

PHOTO (Insert 2): A scientist shows “Golden Rice” (L), genetically modified rice grains infused with beta-carotene, a chemical substance that produces Vitamin A in the body, and ordinary rice at the laboratory of the International Rice Research Institute in Los Banos, Laguna south of Manila, August 14, 2013. REUTERS/Erik De Castro