Fumonisins are mycotoxins produced by the fungus Fusarium moniliforme. F. moniliforme is a frequent, almost universal, inhabitant of corn. Fumonisin B1, B2 and B3 are present in most corn samples tested, often totaling greater than 1 ppm. Fumonisin is thought to cause equine leukoencephalomalacia in horses, swine pulmonary edema, and human esophageal cancer. The FDA/USDA Working Group on Fumonisin advises less than 4 ppm for products for human consumption, less than 5 mg/kg in horse feed, less than 10 mg/kg for swine feed, and less than 50 mg/kg for cattle feed.