Mycotoxins as biological weapons

DEFINITION: Natural secondary metabolites produced by fungi that can produce toxic effects, most often when ingested, and in some settings, when inhaled.

SIGNIFICANCE: Forensic scientists are sometimes called upon to identify mycotoxins and toxigenic molds, which can cause severe health problems with long-term exposure. Mycotoxins are also a concern to law enforcement agencies because these agents can be readily isolated and, thus have potential for use as biological weapons.

Mycotoxin production occurs when favorable environmental conditions allow fungi to grow on plants or plant-based materials, including during pre-harvest growth and post-harvest storage. Mold and mycotoxin contamination can increase in extreme environmental conditions, such as drought, excessive precipitation, floods, sudden frost, and constant high humidity. Most of the world’s croplands, forests, and population centers are in temperate zones, prime breeding grounds for toxigenic fungi. Estimates from the 1990s suggested that at any given time approximately 25 percent of the world’s grain supply may be contaminated with mycotoxins. It has also been estimated that a significant percentage of buildings in North America are contaminated with toxigenic molds at levels that pose a risk to health.

The severity of mycotoxicosis, or mycotoxin poisoning, depends on the toxicity of the mycotoxin, the extent of exposure, and the age and health of the victim. The human health impacts of mycotoxicosis are multiple, including allergies, chronic bronchitis, skin necrosis, respiratory failure, loss of bone marrow, liver and kidney failure, skin irritation, loss of appetite, tremors, vasoconstriction, headache, chronic fatigue, cancers, vomiting, gastric and intestinal irritation, hemorrhaging, tachycardia, severe immunodeficiency, neurocognitive dysfunction, anxiety, tremors, fibromyalgia, lupus, ataxia, and reproductive problems. Because of these toxic effects, mycotoxins are part of an ongoing controversy over their use as biological weapons to produce neurological impairment.

Toxigenic fungi associated with animal and human food chains are in three main genera: Aspergillus, Fusarium, and Penicillium. Although Aspergillus and Penicillium species are important mycotoxin producers—Penicillium alone can produce twenty-seven different mycotoxins—Fusarium are most significant in their effects on crops, poultry, livestock, and farmworkers. Claviceps fungi are responsible for historical epidemics of ergotism, and Stachybotrys chartarum, considered one of the most poisonous molds on Earth, is commonly found in human dwellings.

Stachybotrys chartarum and Chaetomium are fungi often identified within domestic housing and considered the source of “sick house syndrome.” The fungi are found in dark, moist indoor environments such as wall cavities, attics, basements, and ventilation systems. The fungi produce black spores resembling soot that grow aggressively on moist drywall and are carried by circulating air. Several high-profile sick house toxic tort cases have been litigated in the United States.

Trichothecene mycotoxin (T-2 mycotoxin), a derivative of Aspergillus, Stachybotrys, and Fusarium, is considered among the most potent naturally occurring toxins. T-2 mycotoxin is the only biological active toxin effective through inhalation, ingestion, and dermal exposure. Declassified US government documents suggest that T-2 mycotoxins have been identified as agents of biological warfare since the mid-1970s in Laos, Afghanistan, Cambodia, and the Arabian Peninsula. It has been asserted that T-2 mycotoxin exposure is a causal agent of the illness known as Gulf War syndrome.

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