Aflatoxins belong to a group of toxins called mycotoxins, which are derived from fungi. In particular, they are produced by the soil-born molds Aspergillus flavus and Aspergillus parasiticus that grow on the seeds and plants. At least 13 types have been identified including B1, B2, G1, G2, M1 and M2. The B aflatoxins fluoresce blue and the G aflatoxins fluoresce green in the presence of ultraviolet light. The M aflatoxins are present in milk products. Aflatoxin B1 is the most ubiquitous, most toxic and most well studied. Aspergillus spp. contamination occurs as a result of environmental stresses on plants such as heat, dryness, humidity or insect infestation. It can also occur if plants are harvested and stored in hot, humid environments. As a result, people who live in the regions of the world most prone to these conditions, sub-Saharan Africa and southeast Asia are at highest risk for aflatoxin poisoning.
They were first discovered in England in 1960 when more than 10,000 turkeys and ducks died within a few months. The disease contracted by these animals was called Turkey X disease and its cause was traced to Aspergillus flavus contamination of peanut meal that had originated in Brazil. The toxin was named for the short hand of its causative agent: A. fla . Aflatoxins are the most toxic, naturally occurring carcinogens known. Aflatoxin B1 is an extremely hepatocarcinogenic compound, causing cancer of the liver in humans. Its exposure results in both steatosis (an accumulation of fat) and necrosis (cell death) of liver cells. Symptoms of aflatoxicosis are gastrointestinal including vomiting and abdominal pain. Other symptoms can include convulsions, pulmonary edema, coma and eventually death. They also pose a threat to developing fetuses and they are transferred from mother to infant in breast milk. Aflatoxins B1, G1 and M1 are carcinogenic in animals.
Poisoning occurs from ingestion of crops that have been infested with Aspergillus spp. or from eating animal products from animals that have ingested these crops. High concentrations are most often found in plants with very nutritive seeds such as maize, nuts and cereal grains in Africa and rice in China and Southeast Asia. In the United States, peanuts are routinely tested for aflatoxin concentrations, and contamination has also occurred in corn, rice, and cereal grains. Most consider them extremely dangerous and suggest that in human food is only acceptable with no detectable concentration. The maximum allowable concentration set by the United States FDA is 20 parts per billion (ppb). Foreign markets usually reject grains with concentrations of 4 to 15 ppb. Acceptable levels for animal consumption are up to 100 ppb. Because of the strict regulations regarding the permissible concentrations, exporting countries often reserve contaminated grains for consumption within their own country. Because Aspergillus spp. is usually colorless and does not break down during cooking, it is difficult to know whether or not people are consuming contaminated food.