aflatoxins (ăf`lətäk'sĭnz), a group of secondary metabolites that are cancer-causing byproducts of a mold that grows on nuts and grains, particularly peanuts. Although aflatoxin is most commonly produced when the potentially affected foods are improperly stored, recent studies have documented its production in the field, particularly if severe climatic changes occur or if the plants are attacked by insects. Most industrialized nations strictly regulate the aflatoxin level in human food. However, many of these products are used in animal feed, and if an animal consumes infected food, the aflatoxin passes to people in contaminated milk and meat products. Aflatoxin is a carcinogenic for certain animals, particularly cattle. Among humans, it is associated with liver cancer, particularly in Third World nations where malnutrition and other health problems are also prevalent.