Lawmakers heard both sides of the debate Thursday in Olympia, during a public hearing for Initiative 522. The ballot measure would require food and seeds produced entirely or partly through genetic engineering and sold in Washington to be labeled as such, beginning July 1, 2015. Raw foods that are not packaged separately would have to be labeled on retail shelves.

A similar initiative failed narrowly with voters in California last year.

More than 60 countries require such foods to be labeled, but the U.S. isn't one of them. Only Alaska has enacted legislation requiring the labeling of genetically engineered fish and shellfish products.

Supporters of the Washington initiative pointed to the growing global agreement about genetic engineering and genetically modified organisms, noting that other countries have recognized concerns about new allergens and changes in nutrition levels, among other things.

Yet the U.S. government leaves it to the corporations developing the technology to determine their products' safety — self-regulation that most Americans, if they understood it, would be uncomfortable with, said Ken Cook of the nonprofit Environmental Working Group.

"If big, corporate agribusiness were so convinced there were no health risks to GMOs, they would be more than willing to label them," said Patricia Michael, who spoke in support of the measure. "Instead, they want to hide them from us."

And for good reason, she added.

"We were told that DDT was harmless, that saccharin was harmless," she said. "We have a right to know what we're eating."

Opponents argued that the requirement is likely to raise food prices and that labeling should only be required at the federal level.

Most, if not all, foods have been modified in some way with no required labels, according to Martina McLoughlin, director of the University of California's Biotechnology Research and Education Program.

In addition, genetically engineered products have been on the market for almost two decades, and billions of people worldwide have eaten the products safely, she said.

Genetic engineering also has had overwhelming positive impacts, she said, including reduction of fuel, pesticide and water use on farms. And abandoning the scientific method will slow or destroy technological advances, limiting potential for "improving nutrition, quality and sustainability in a world where we have massively increasing population, dwindling resources and a changing climate," McLoughlin said.

Some wheat growers, in particular, raised concerns that genetically modified wheat could destroy their exports to the Pacific Rim. Roughly 85 percent of all Washington state wheat is exported.

"I farmed all these years just fine without any GMOs. But I cannot farm without my markets," said Tom Stahl, 58, a wheat grower in Douglas County, who favors the initiative.

However, the Washington Association of Wheat Growers opposes the initiative.

Genetically engineered wheat is seven to 10 years away from being introduced to the market, so any fear about lost export markets is premature, said the group's Eric Maier, a Ritzville wheat grower.

"Labeling as genetically engineered would infer there is a difference in those products when none actually exists," he said.

Lawmakers have the option to vote on the initiative, take no action and send it to the November ballot, or recommend an alternative measure that will appear on the ballot with it.