Aflatoxin

A forensic investigation can often involve determining whether the victim was poisoned. Many different kinds of poisons exist. While some are synthetic, others are manufactured by living organisms. One example of the latter are aflatoxins.

Aflatoxins belong to a group of toxins called mycotoxins, which are derived from fungi. In particular, aflatoxins are produced by the soil-born molds Aspergillus flavus and Aspergillus parasiticus that grow on the seeds and plants. At least 13 aflatoxins 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 of the aflatoxins.

Afatoxins are so powerful that access to them is restricted and possession or handling of them by certain individuals constitutes a crime. The USA Patriot Act enacted on October 25, 2001 and signed into law (P.L. 107-56) by President George W. Bush is in effect as of January 2005 and contains a provision prohibiting possession or access to, shipment or receipt of, a "Select Agent" by "Restricted Persons" punishable by fines or imprisonment. Aflatoxins are considered select agents.

A restricted person is defined as someone who: (1) Is under indictment for a crime punishable by imprisonment for a term exceeding 1 year; or (2) Has been convicted in any court of a crime punishable for a term exceeding 1 year; or (3) Is a fugitive from justice; or (4) Is an unlawful user of any controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802); or (5) Is an alien illegally or unlawfully in the United States; or (6) Has been adjudicated as a mental defective or has been committed to any mental institution; or (7) Is an alien (other than an alien lawfully admitted for permanent residence) who is a national of a country as to which the Secretary of State, has made a determination (that remains in effect) that such country has repeatedly provided support for acts of international terrorism (as of January 2005 these countries included Cuba, Iran, Iraq, Libya, North Korea, Sudan, and Syria); or (8) Has been discharged from the Armed Service of the United States under dishonorable conditions.

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, such as sub-Saharan Africa and southeast Asia, are at highest risk for aflatoxin poisoning.

Aflatoxins were first identified 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 shorthand 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. Aflatoxin B1 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. Aflatoxins 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 due to aflatoxin 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 of aflatoxins 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 aflatoxins extremely dangerous and suggest that in human food they should have no detectable concentration. The maximum allowable concentration of aflatoxins 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 of aflatoxins for animal consumption are up to 100 ppb. Because of the strict regulations regarding the permissible concentration of aflatoxin, 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.