Aflatoxins are naturally occurring mycotoxin

Mycotoxin

A mycotoxin is a toxic secondary metabolite produced by organisms of the fungus kingdom, commonly known as molds. The term ‘mycotoxin’ is usually reserved for the toxic chemical products produced by fungi that readily colonize crops...

s that are produced by many species of Aspergillus

Aspergillus

Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...

, a fungus

Fungus

A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, the most notable ones being Aspergillus flavus

Aspergillus flavus

Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

and Aspergillus parasiticus

Aspergillus parasiticus

Aspergillus parasiticus is a mold known to produce aflatoxin, although strains of it that do not produce this carcinogen exist. It is sometimes found on black olives....

. Aflatoxins are toxic and among the most carcinogen

Carcinogen

A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

ic substances known. After entering the body, aflatoxins may be metabolized by the liver to a reactive epoxide

Epoxide

An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in...

 intermediate or hydroxylated to become the less harmful aflatoxin M₁.
Aflatoxin-producing members of Aspergillus are common and widespread in nature.