SACRAMENTO (CBS / AP) — A closely-eyed ballot measure to label food containing genetically modified ingredients was trailing by a double-digit margin Tuesday night.

“No matter what happens, we’ve raised awareness of a very important issue,” said Grant Lundberg, chief executive of Lundberg Family Farms, who co-chairs the California Right to Know campaign.

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The initiative sparked a backlash from agribusiness and chemical conglomerates, which spent $46 million to swamp airwaves and mailboxes with advertisements in a bid to crush Proposition 37.

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Consumer activists and the organic food industry said shoppers crave information about what they’re eating and should be given all the information they need to decide for themselves whether to buy products containing genetically altered ingredients.

Opponents feared labeling would amount to placing a skull-and-crossbones symbol on their products even though studies showed bio-engineered food to be safe. They also warned of higher grocery bills if the initiative passes.

A win would put California at odds with the federal government, which does not require such labels because bio-engineered foods are not significantly different in taste, texture and nutrition.

It also could rattle American agriculture, which has long harvested corn, cotton, soybean and other plants in which the DNA has been tinkered with in the laboratory to resist pesticides and ward off disease. GMO crops are used for animal feed or processed into food ingredients found in many cereals, baked goods and sodas.

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Despite scientific consensus that genetically modified foods on the market are as safe as conventional foods, some consumers remain leery and efforts have been mounted to force special labels. Mandatory labeling exists elsewhere, including the European Union.

More than a U.S. dozen states this year introduced GMO labeling bills, but all failed. A citizen’s petition to mark genetically engineered foods nationwide is pending before the U.S. Food and Drug Administration.

Under Proposition 37, most processed foods would have to bear the label “partially produced with genetic engineering” or “may be partially produced with genetic engineering” on boxes, cans and bottles by 2014. The words “genetically engineered” would be required to appear on the front package of a small variety of produce or on store shelves.

Such products also would be prohibited from using the terms “natural” or “naturally made” in their advertising.

Excluded are organic products, restaurant meals and alcoholic beverages. Meat and dairy also are exempt, even if the animals were fed with genetically modified grains.

Grocers and other retailers would be responsible for ensuring their shelves are stocked with correctly marked items.

The state and private attorneys could sue for violations and obtain a court injunction to halt the sale of a product. The nonpartisan California Legislative Analyst’s Office estimated that the initiative could cost more than $1 million a year to enforce.

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