GLYPHOSATE .

Glyphosate is a herbicide applied to leaves to kill grasses and weeds. It is the most-used agricultural chemical in the world, and experienced a boom in use beginning in the 1990s, according to Newsweek. Glyphosate use in agriculture was previously hampered by the product often killing not only weeds but the crops it was intended to protect. But in the 1990s, Monsanto began producing genetically modified crop strains resistant to glyphosate, to which the herbicide could be applied without damaging the crop. Oats, a very commonly used grain in breakfast foods, are not modified for glyphosate resistance. Farmers often use the product on oats to kill the crops and dry them out, to hasten harvesting. A 2013 study found that glyphosate can induce the growth of breast cancer cells in humans while another study from last year found links between applications of glyphosate and fatty liver disease in rats.