thumb|right|Chemical structure of [[Aflatoxin B1|aflatoxin B<sub>1</sub>]]

Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, especially Aspergillus species such as Aspergillus flavus and Aspergillus parasiticus. According to the USDA, "They are probably the best known and most intensively researched mycotoxins in the world." The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, maize (corn), peanuts, coffee, wheat, millet, sorghum, cassava, rice, chili peppers, cottonseed, tree nuts, sesame seeds, sunflower seeds, and various cereal grains and oil seeds. They have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into milk, milk products, and meat. delayed development, and liver cancer. Some studies have reported an association between childhood stunting and aflatoxin exposure, although this link has not been consistently detected in all studies. Furthermore, a causal relationship between childhood stunting and aflatoxin exposure has yet to be conclusively shown by epidemiological studies, though such investigations are underway. Adults have a higher tolerance to exposure, but are also at risk. No animal species is known to be immune. Aflatoxins are among the most carcinogenic substances known.

  • Aflatoxin M<sub>1</sub> (AFM<sub>1</sub>), metabolite of aflatoxin B<sub>1</sub> in humans and animals (exposure in ng levels may come from a mother's milk)
  • Aflatoxin M<sub>2</sub>, metabolite of aflatoxin B<sub>2</sub> in milk of cattle fed on contaminated foods

Occurrence

[[File:Aflatossina_su_frutta_secca.jpg|thumb|At right,

fluorescence emitted under ultraviolet light from fungal growth, which indicates likely presence of aflatoxin. At left, the same fruit under natural light.]]

The staple commodities regularly contaminated with aflatoxins include cassava, chilies, corn, cottonseed, millet, peanuts, rice, sorghum, sunflower seeds, tree nuts, wheat, and a variety of spices intended for human or animal consumption. Aflatoxins have been isolated from all major cereal crops, and sources as diverse as peanut butter and cannabis. Aflatoxin transformation products are sometimes found in eggs, milk products, and meat when animals are fed contaminated grains.

Aflatoxins are produced by both Aspergillus flavus and Aspergillus parasiticus, which are common forms of "weedy" molds widespread in nature. Aflatoxins occur also in Aspergillus pseudocaelatus, Aspergillus nomius and Aspergillus pseudonomius. The presence of these molds does not always indicate that harmful levels of aflatoxin are present, but it does indicate a significant risk. The molds can colonize and contaminate food before harvest or during storage, especially following prolonged exposure to a high-humidity environment or to stressful conditions such as drought. Aflatoxin contamination is increasing in crops such as maize as a result of climate change.

The native habitat of Aspergillus is in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration, but it invades all types of organic substrates whenever conditions are favorable for its growth. Favorable conditions for production of aflatoxins include high moisture content (at least 7%) and temperatures from , where the optimum is .

A study conducted in Kenya and Mali found that the predominant practices for drying and storage of maize were inadequate in minimizing exposure to aflatoxins.

There is very limited evidence to show that agricultural and nutritional education can reduce exposure to aflatoxin in low to middle-income countries.

Pathology

thumb|Schematic summarizing the major AFB1 and AFM1 contamination/exposure routes and adverse health effects to human

No animal species is known to be immune to the acute toxic effects of aflatoxins. Adult humans have a high tolerance for aflatoxin exposure and rarely succumb to acute aflatoxicosis, as aflatoxin metabolites may intercalate into DNA and alkylate the bases through its epoxide moiety. This is thought to cause mutations in the p53 gene, an important gene in preventing cell cycle progression when there are DNA mutations, or signaling apoptosis (programmed cell death). These mutations seem to affect some base pair locations more than others; for example, the third base of codon 249 of the p53 gene appears to be more susceptible to aflatoxin-mediated mutations than nearby bases. As with other DNA-alkylating agents, Aflatoxin B<sub>1</sub> can cause immune suppression, and exposure to it is associated with an increased viral load in HIV positive individuals.

Timeline and list of outbreaks

  • 1960: Outbreak of Turkey 'X' disease in England, and aflatoxin discovery.
  • 1961: Identified Aspergillus flavus associated with toxicity of groundnuts.
  • 1962: Aflatoxin B and G identified in TLC analysis. Isolation and synthesis of aflatoxins.
  • 1963: Aflatoxin B2, G1, and G2 were identified and chemically characterized as difurocoumarin derivatives.
  • 1965: FDA approved the first regulation on aflatoxins 30 μg/kg.
  • 1966: Milk toxins were designated as AFM1 and AFM2, and AFM1 was detected in milk, urine, kidney, and liver.
  • 1973 Poland: 10 died following the opening of the tomb of Casimir IV Jagiellon, which contained aflatoxin-producing molds.
  • 2004 Kenya: acute outbreak of aflatoxicosis resulting from ingestion of contaminated maize, 125 confirmed deaths.
  • 2009–2011 International: Commercial peanut butter, cooking oils (e.g. olive, peanut and sesame oil), and cosmetics were identified as contaminated with aflatoxin.
  • 2014 (ongoing): Nepal and Bangladesh, neonatal exposures, found in umbilical cord blood.
  • 2019 Kenya: five brands of maize flour recalled due to contamination.
  • 2021 US: Contamination of pet food manufactured by Midwestern Pet Food, causing the deaths of at least 70 dogs.
  • 2021 Sri Lanka: contaminated coconut oil released for public consumption by the local government..
  • 2023 Makueni County, Kenya: In a cross-sectional study was used to determine the dietary aflatoxin exposure of 170 lactating mothers breastfeeding children aged 6 months and below. This involved the aflatoxin analysis of maize-based cooked food sample which was in their staple foods. Aflatoxins were determined using high-performance liquid chromatography and enzyme-linked immunosorbent assay. About 46% of the mothers were from low-income households, and 48.2% had not attained the basic level of education. A generally low dietary diversity was reported among 54.1% of lactating mothers. Food consumption pattern was skewed towards starchy staples. Approximately 50% never treated their maize, and at least 20% stored their maize in containers that promote aflatoxin contamination. Aflatoxin was detected in 85.4% of food samples. The mean of total aflatoxin was 97.8 μg/kg (standard deviation [SD], 57.7), while aflatoxin B1 was 9.0 μg/kg (SD, 7.7).
  • 2024 South Africa: The National Consumer Commission recalled various peanut butter brands due to contamination
  • 2012-2024 Kenya: A 13 year study conducted was the evaluation of total aflatoxins and aflatoxins B1 in peanut kernels, peanut butter, cashew nuts, and macadamia nuts. During 2021 to 2024, the Study showed that 59 to 74% of nut samples had exceeded the regulatory limits. However, some improvements were seen.

See also

  • Mycotoxins in animal feed
  • Sterigmatocystin, a related toxin
  • Other ways in which aspergillus can cause disease in mammals:
  • Aspergillosis
  • Primary cutaneous aspergillosis

References

  • Aflatoxin , ICRISAT
  • Aflatoxins – Cancer-Causing Substance
  • Aflatoxin B<sub>1</sub>