Some mycotoxins are carcinogenic, mutagenic, teratogenic and immunosuppressive.
Aspergillus flavus and A. parasiticus occur widely, on inadequately dried food and feed grains, in sub-tropical and tropical climates throughout the world. Pre-harvest mould growth, and aflatoxin production, is encouraged by insect damage, mechanical damage, drought stress and excessive rainfall. The aflatoxins may occur, both before and after harvest, on virtually any food or feed which supports fungal growth, including cereals, oilseeds and edible nuts. Maize, groundnuts, cottonseed, oil-palm kernels and copra are particularly associated with the occurrence of the aflatoxins. The very substantial international trade in these commodities serves to amplify the worldwide nature of the aflatoxin problem.