Aflatoxin - Late Assignment 7 by A. Reeve

In unfavorable conditions, of temperature and humidity, certain strains of Aspergillus flavus and A. parasiticus fungi, which grow on foods and feeds, will produce a toxic compound known as aflatoxins. Tree nuts, peanuts, and other oil seeds, such as corn and cottonseeds, seem to be more commonly associated with aflatoxins.

In 1965, George Buchi, Gerald Wogan, a group of toxicologist, and a group of organic chemists, identified aflatoxins as part of a collaborative effort at the Massachusetts Institute of Technology. They grew Aspergillus flavus mold on peanuts, then they isolated tiny amounts of the substances responsible for the poisonous properties of the groundnut meal. They named these substances in such a way to indicate their source, thus the origins of alfatoxins.

This team of scientists discovered that aflatoxin is a mixture of four different but closely related chemicals which contain the same molecular foundation of carbon, hydrogen, and oxygen atoms, yet differ slightly. These chemicals are designated as Aflatoxin B₁ (C₁₇H₁₂O₆) and B₂ (C₁₇H₁₄O₆), because they emit a blue florescence when irradiated with ultraviolet light; and Aflatoxin G₁ (C₁₇H₁₂O₇) and G₂ (C₁₇H₁₂O₇), because they emit a green florescence when irradiated with ultraviolet light. Aflatatoxin B₁ is the most toxic, and usually the more predominant, of these aflatoxins.

Scientists were having difficulty finding definitive proof of the harm aflatoxins posed to humans. They determined that the amount of aflatoxins reaching humans via foods were not as potent as those found in the contamined animal feeds, because they were processed, whereas the animal feed is not. However, studies conducted with a variety of animals have revealed that aflatoxins cause acute necrosis, cirrhosis, and carcinoma of the liver. Furthermore, it has been determined that there are no animal species which are resistant to the acute toxic effects of aflatoxins, thus it is a logical assumption that humans will be similarly affected.

In light of this evidence, the Food and Drug Administration (FDA) decided that products were unfit for human consumption if they contained in excess of 30 parts aflatoxin per billion parts of food (ppb). This standard was later dropped to 20 ppb. The decrease in the acceptable limits of human exposure to aflatoxin was due to improvements in analytical technology. In other words, when the FDA believes that there is no way to establish a completely safe level of human consumption for a cancer-causing agent, then any presence of the agent is unacceptable. Since the smallest amount of aflatoxin that could be detected was 30 ppb, that amount or an excess thereof was deemed to be unsafe. As technology improved, and smaller amounts of toxins could be detected, the limit changed to 20 ppb.

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REFERENCES

Rodricks, J.V., Calculated Risks: The Toxicity and Human Health Risks of Chemical in our Environment, Cambridge University Press, 2007, pp 3-6.

Reddy, S.V. & Farid Waliyar, Properties of Aflatoxin and its Producing Fungi, Retrieved from http://www.aflatoxin.ingo/aflatoxin.asp. 2000.

Walderhaug, M., Aflatoxins, U.S. Food & Drug Administration, Retrieved from http://www.cfsan.fda.gov/~mow/chap41.html. January 1992.