Aflatoxin B2 is a naturally occurring mycotoxin produced by certain types of mold that commonly contaminate food crops. This toxic substance is a secondary metabolite generated primarily by the fungi Aspergillus flavus and Aspergillus parasiticus. It belongs to a family of four major aflatoxins, including B1, G1, and G2. Aflatoxin B2 is derived from Aflatoxin B1 but possesses a slightly different molecular structure. The presence of these toxins in the food supply poses significant concerns for human and animal health worldwide.
Primary Sources of Food Contamination
The fungi responsible for producing Aflatoxin B2 are widespread, growing in soil, decaying vegetation, and various food commodities. Favorable conditions for mold proliferation and toxin production include warm, humid climates and high moisture content in crops. Molds can infect and contaminate host plants both in the field before harvest and later during storage.
Contamination most frequently targets major global staple crops and export commodities. Highly susceptible crops include maize (corn), peanuts, cottonseed, and tree nuts, such as pistachios and almonds. Aflatoxins are also occasionally detected in spices, rice, and other cereal grains.
Pre-harvest contamination is often exacerbated by environmental stressors like drought, high temperatures, and insect damage, which create entry points for the mold. Post-harvest, the contamination risk remains high if crops are not properly dried or if they are stored in conditions with high humidity and temperature.
Biological Impact and Toxicity
Aflatoxin B2 contributes to health issues in humans and animals, characterized by either acute or chronic exposure. Acute toxicity results from ingesting a high dose over a short period, leading to severe effects mainly targeting the liver. This acute condition, known as aflatoxicosis, can cause symptoms like vomiting and abdominal pain, potentially leading to liver failure in severe cases, though this is rare in developed nations.
The more significant danger is chronic exposure, which involves consuming low doses of the toxin over a prolonged time. Chronic exposure is strongly associated with an increased risk of developing liver cancer, making aflatoxins potent environmental carcinogens. The International Agency for Research on Cancer (IARC) classifies Aflatoxin B2 as a possible human carcinogen.
Aflatoxin B2 requires metabolic activation by the liver to exert its damaging effects. During this process, the liver attempts to detoxify the compound, but this inadvertently creates reactive intermediate molecules. These intermediates can then bind to the body’s genetic material, causing DNA damage and mutations in critical genes. Although Aflatoxin B2 is less potent than Aflatoxin B1, its presence adds significantly to the overall toxic burden and the risk of chronic disease.
Strategies for Exposure Control
Controlling exposure to Aflatoxin B2 involves implementing mitigation strategies across the entire food production chain. Pre-harvest controls focus on good agricultural practices, such as effective pest management to reduce insect damage and minimize fungal entry points. Irrigation can also alleviate plant stress during drought conditions, reducing the likelihood of mold infestation.
A promising pre-harvest strategy is the application of non-aflatoxigenic strains of Aspergillus flavus to the field, which competitively displace native toxin-producing strains. Post-harvest control is equally important, focusing on rapid and proper drying of crops immediately after harvest to reduce moisture content below levels that support mold growth. Storing crops in cool, dry conditions with adequate aeration is crucial for preventing the growth of fungi during the storage phase.
Regulatory bodies, such as the U.S. Food and Drug Administration (FDA), establish specific action levels or tolerances for aflatoxins in commercial food and animal feed. Strict regulatory testing and screening of supplies before they enter the market are necessary to ensure contamination levels remain below these safety thresholds. Consumers can also reduce risk by purchasing food from reputable sources and discarding any products, especially nuts and grains, that appear moldy, discolored, or shriveled.