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

itoggle caption Seth Perlman/AP

Corn farmer Jerry McCulley sprays the weedkiller glyphosate across his cornfield in Auburn, Ill., in 2010. An increasing number of weeds have now evolved resistance to the chemical. Seth Perlman/AP hide caption

itoggle caption Seth Perlman/AP

Loved ones express their grief at the burial of Ramon Romero Ramirez in Chichigalpa, Nicaragua, January 2013. The 36-year-old died of chronic kidney disease after working in the sugar cane fields for 12 years. Ramirez is part of a steady procession of deaths among cane workers. Ed Kashi/VII hide caption

itoggle caption Ed Kashi/VII