Central Illinois corn farmer Jerry McCulley refills his sprayer with the weedkiller glyphosate on a farm near Auburn, Ill. A new assessment of the chemical finds that the (uncertain) risks mainly affect the people who work with it or who come in direct contact with areas where it's applied. Seth Perlman/AP hide caption

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A global positioning receiver on the top of a combine harvester at a farm in Warwick, Md., in June. The equipment uses sensors and computers to help drive the combine along the route where the crops were planted, judge the composition of a crop and generate crop yield reports. Brendan Smialowski/AFP/Getty Images hide caption

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Wheat grows in a test field at Oregon State University in Corvallis. Some scientists believe that there's a chance that genetically modified wheat found in one farmer's field in May is still in the seed supply. Natalie Behring/Bloomberg via Getty Images hide caption

itoggle caption Natalie Behring/Bloomberg via Getty Images

Crop consultant Dan Steiner inspects a field of corn near Norfolk, Neb. Dan Charles/NPR hide caption

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Vernon Hugh Bowman, who took his case to the Supreme Court, lives outside the small town of Sandborn, Ind. Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR

A farmer holds Monsanto's Roundup Ready soybean seeds at his family farm in Bunceton, Mo. Dan Gill/AP hide caption

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Central Illinois corn and soybean farmer Gary Niemeyer readies his genetically modified seed corn for spring planting at his farm near Auburn, Ill. Seth Perlman/AP hide caption

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People march demanding labels for genetically modified food near the White House in Washington, D.C., on Oct. 16, 2011. Ren Haijun/Xinhua /Landov hide caption

itoggle caption Ren Haijun/Xinhua /Landov

Farmer Alan Madison fills a seed hopper with Monsanto hybrid seed corn near Arlington, Illinois, U.S. A group of organic and other growers say they're concerned they'll be sued by Monsanto if pollen from seeds like these drift onto their fields. Daniel Acker/Landov hide caption

itoggle caption Daniel Acker/Landov