American growers sprayed 280 million pounds of glyphosate on their crops in 2012, according to U.S. Geological Survey data. That amounts to nearly a pound of glyphosate for every person in the country. The use of glyphosate on farmland has skyrocketed since the mid-1990s, when biotech companies introduced genetically engineered crop varieties (often called GMOs) that can withstand being blasted with …