The U.S. Agriculture Department has approved the use of genetically modified corn and soybean seeds that are resistant to the weed killer 2,4-D. The herbicide made by Dow Chemical has been linked to a range of health risks including cancer and Parkinson’s disease. It was an ingredient in the toxic Vietnam War herbicide Agent Orange. Industrial farmers have been pressing for an alternative after many weeds grew resistant to Monsanto’s Roundup Ready weed killer. The EPA would still need to approve the newest version of 2,4-D; if it does, the use of the herbicide could increase by as much as 600 percent in the next several years.