Toxic molds are fungi that can produce substances that are harmful to humans. Not all fungi are toxic. In fact, some may not be harmful or may even beneficial to humans.
Mycotoxins are the harmful substances produced by toxic molds. They may be harmful if inhaled or ingested. Less commonly, skin exposure can be the source of mycotoxin poisoning. More than 300 different compounds are recognized as mycotoxins.
The single-celled spores of molds can be resistant to cold, heat, drying, and pressure. The lightweight spores become airborne and will germinate and begin cell division if they land in an appropriately moist environment with a food source, such as dead organic matter. Eventually, they produce a visible colony of simple, multi-celled filaments that appear fuzzy, like a common bread mold. This filamentous structure is more complex than yeast, which grows as single cells that are not associated with each other, but not as organized as a mushroom, which has large organized structures with a substantial stem and definite cap.
Since mold spores are easily dispersed in the air, they are extremely common, both indoors and outdoors, and will grow into colonies of filaments in almost any humid area, if provided with nutrients. This ability to use many different types of nutrients and grow in wet areas is why so many different types of fungi, both molds and mushrooms, can be found in swampy and wetland areas. This also makes molds a particular problem after floods or leaks if clean up is not done immediately and thoroughly.
Nutrient sources may include nearly any type of organic matter, including food and household materials, such as fiberboard, drywall, wood, carpets, or dust. In general, fungi secrete unique digestive enzymes that allow them to break down and use carbohydrates in substances that animals cannot digest, such as lint or the cellulose in wood and paper. Because of this property, fungi are often used in bioremediation, which uses plants or microorganisms to degrade wastes or toxic products that would otherwise persist in the environment.
Many fungi produce small molecules that can be toxic to other organisms. For example, the antibiotic penicillin is produced by a mold and is toxic to some bacteria. Yeast produces ethanol, which, although a component of beer, wine, and other alcoholic beverages, can be poisonous to humans, especially in large quantities. Several types of mushrooms produce substances that can cause illness or death in humans.
The mycotoxins in toxic molds can cause illness in humans called mycotoxosis. Mycotoxosis is not an infection, but rather mold poisoning. It is similar to the way mushroom poisoning is caused by a poisonous compound in the mushroom.
Yeasts and molds can also cause infections in humans, especially those who have weakened immune systems. This type of illness, called a mycosis, occurs when fungal cells grow within the body and cause harm. Although the fungal cells may produce harmful substances, the main illness is caused by the growth of the invading fungal cells.
The most common mycotoxosis is aflatoxin poisoning, discovered in 1962 when 100,000 turkeys in England died from eating peanut meal in which aflatoxin-producing mold had grown.
Some substances that are classified as mycotoxins are not toxic, but beneficial to humans. For example, substances that are toxic to bacteria may be used as antibiotics to fight against bacterial infections in humans. Examples include penicillin, produced by the Penicillium mold, and cephalosporin, produced by the Cephalosporium mold.
General: An illness caused by mycotoxins, which are small molecules produced by molds that can be harmful to humans and animals, is called mycotoxosis. Mycotoxosis is not contagious.
Mycotoxins may enter the body after being inhaled or ingested. Most cases of mycotoxosis are from toxins that are eaten as part of mold-contaminated food. Any food can be contaminated with a toxic mold, but the most well-known examples come from eating contaminated grains, fruits, nuts, or products derived from them.
Less commonly, skin exposure can be the source of mycotoxin poisoning. In these rare cases, handling a substance contaminated with a toxic mold allows the toxin to enter the body through a wound or skin abrasion.
Inhaled toxins: Inhaling mold toxins is generally thought to cause health problems such as respiratory distress, although making a precise diagnosis is often difficult. Many factors, including individual responses to toxins, may contribute to the symptoms and complicate linking a particular mold to a particular illness.
Studies from the 1990s speculated that an outbreak in infants of the lung disease acute idiopathic pulmonary hemorrhage (AIPH) was caused by high levels of mold spores in the home, possibly from damage caused by leaks or flooding. This disease is also known as idiopathic pulmonary hemosiderosis (IPH). The assumption was that the disease was caused by inhalation of either mold spores or a mold toxin. The adults in the home did not appear to have the disease. The mold Stachybotrys chartarum, also known as Stachybotrys atra, was suspected as the cause of the disease in the infants, but a U.S. Centers for Disease Control (CDC) review of studies up to 2004 found flaws in mold sample collection, data analysis, and statistical methods of the studies. Therefore, no link was found between Stachybotrys and AIPH. The topic is controversial, however, and investigations are continuing, with the CDC establishing criteria for future monitoring of AIPH.
Ingested toxins, aflatoxin: The most common ingested mycotoxin is aflatoxin, from the Aspergillus molds. This group of molds includes ordinary bread mold and others that often cause household food spoilage when they grow using the food as a nutrient source. The species A. flavus and A. parasiticus are agricultural pests that produce aflatoxins, but not all members of these species produce aflatoxins and the amount produced varies. However, since spores from these and other molds are common in the air, both the toxin-producing mold species and non-toxic mold species may come in contact with agricultural products.
More than a dozen related chemicals make up the aflatoxins, but aflatoxin B1 is most commonly responsible for illnesses. It can be found in the products of any crop in which A. flavus or A. parasiticus grows, including cereals and grains like corn; nuts like peanuts, Brazil nuts, pecans, pistachio nuts, and walnuts; oils like cottonseed oil; and tobacco. Cows that eat aflatoxin-contaminated grain may produce aflatoxin-contaminated milk.
Ingested toxins, ergot alkaloids: Ergot alkaloids are small organic compounds produced by species of Claviceps molds that infect rye, sorghum, triticale, wheat, barley, and other grasses.
Ingestion of the ergot alkaloid toxins is usually through bread made from contaminated flour. It causes the illness known as ergotism, or St. Anthony's fire, because it is associated with a burning pain in the legs. If untreated, ergotism may lead to gangrene. Modern agricultural practices, including more careful monitoring of agricultural products, have made this rare in humans, although cattle, sheep, pigs, and chickens may be affected if their feed becomes contaminated.
Since some ergot alkaloids induce smooth muscle contraction, the infected grasses have been used as a folk medicine to induce abortions or accelerate labor. Ergot alkaloids provided the basic chemical structure for the synthetic hallucinogen d-lysergic acid (LSD), which affects receptors in neurons that normally bind signaling molecules.
Ingested toxins, trichothecenes: Trichothecenes are mycotoxins produced by several different mold types that infect barley, oats, rye, and wheat.
All trichothecenes prevent cells from making proteins, but small chemical differences in T-2 and diacetoxyscirpenol make them especially toxic to animals and humans, causing vomiting and suppressing the immune system. Some researchers have suggested that T-2 might be the cause of a disease called alimentary toxic aleukia, which begins with inflammation of the gastrointestinal system and proceeds to a low white blood cell count and rash.
Stachybotrys molds (Stachybortys atra, S. chartarum) produce trichothecenes called satratoxins. Illness from the toxins of this mold were first described in horses exposed to wet, moldy hay. The connection between Stachybotrys mold and human disease is still under investigation.
Sick-building syndrome, or building-related illness, has been suggested to result from mold exposure, particularly Stachybortrys. In this phenomenon, workers in climate-controlled buildings, where the air supply goes through air-conditioning and ventilation ducts that may be dusty or moldy, experience symptoms such as eye and throat irritation and headaches. Symptoms are relieved when they leave the building. Analysis of studies on Stachybortrys and sick-building syndrome concluded that the cause of this syndrome remains unknown.
Ingested toxins, other: Citrinin is produce by some Aspergillus and some Penicillium molds. It is a kidney toxin in animals and although its effect on humans is unknown, it can be found in foods like wheat, oats, rye, corn, barley, and rice.
Fumonisins are produced by some Fusarium molds that infect corn. Fumonisins interfere with the production of cell surface components and may be harmful to the liver and kidneys. Chronic exposure is linked to esophageal cancer in humans.
Ochratoxins are produced by certain species of Aspergillus and Penicillium molds and are toxic to kidneys. Among the agricultural sources that can transmit ochratoxins to humans are pigs, poultry, and wine grapes. Since ochratoxins are stored in fat, humans can ingest these toxins from the fat of exposed animals, or ochratoxins can occasionally be detected in wine. Their effect on humans is still under investigation.
Patulin was originally isolated in the 1940s as an antibiotic from a species of Penicillium mold, which is also the group of molds that produces penicillin. Patulin-producing mold is found in rotting apples. Patulin was subsequently found to be possibly cancer-causing in animal study. It was possibly toxic to the immune and nervous systems in studies using model animals, and it is no longer used as an antibiotic.
Zearalenone is produced by a type of Fusarium mold. It is not a toxin; it is a compound that resembles a human hormone and is produced by a fungus. It resembles estrogen in its chemical form and it can affect the reproductive system of animals, causing infertility. Substances that resemble estrogen can promote types of cancer, such as breast cancer, but the impact of zearalenone on the human population is still under investigation. It is currently thought to be very low.
Because of the prevalence of molds, the complete elimination of molds and the naturally occurring toxins they produce from foods is thought to be an unattainable objective. Naturally occurring toxins such as mycotoxins are not regulated as food additives.
Inhaled toxins: A study in 1994 suggested that an outbreak in babies of acute idiopathic pulmonary hemorrhage (AIPH), a type of bleeding in the lungs, was because of exposure to Stachybotrys molds. Levels of mold spores were particularly high in the houses of affected babies. Leaks, flooding, and cigarette smoke were also associated with the outbreak. The cause of this AIPH outbreak was originally thought to be Stachybortrys molds, but the U.S. Centers for Disease Control (CDC) have shown this conclusion to be unfounded and the actual cause remains controversial.
In 2004, the CDC reviewed the available studies on AIPH among infants and Stachybotrys chartarum (Stachybotrys atra) mold. They found no link between the disease and Stachybotrys molds.
A 1984 study suggested that Dutch workers in a peanut-processing plant who were chronically exposed to peanut dust contaminated with aflatoxin B1 had a higher incidence of lung cancer compared to unexposed workers.
Ingested toxins: The liver neutralizes toxins, including mycotoxins, so it is especially susceptible to damage from any intoxication, or poisoning, because it must work to rid the body of the toxin. Since the liver also functions in maintaining blood components, this can have broad physiological effects.
In 1974, 100 people in India died from liver failure from what is suspected to have been an unusually heavy aflatoxin contamination of corn. From estimates of the amount of aflatoxin consumed in this outbreak, a lethal dose for humans was calculated to be 10-20 milligrams. A woman who deliberately ingested more than 40 milligrams of aflatoxin in a suicide attempt survived, and when she was examined by qualified physicians 14 years after the event, the doctors found no detectable effects on her health.
Cases of acute human aflatoxin poisoning, like the 1974 outbreak in India, are rare and test animals vary in their susceptibility to aflatoxin; research on the effects of aflatoxin exposure is limited.
Several studies have linked chronic aflatoxin exposure to liver cancer, especially in people who have had hepatitis B, but investigations are complicated by the difficulty of measuring an individual's long-term exposure to aflatoxin. Nonetheless, aflatoxin is considered a co-carcinogen with hepatitis B for liver cancer.
Impact and treatment: The impact of mycotoxins may be acute in which symptoms occur rapidly or chronic from low-dose, long-term exposure.
Since the liver processes and neutralizes mycotoxins, it is especially susceptible to them.
People react differently to exposure to different chemicals, so individual reactions to mycotoxins may depend on factors such as age, sex, general health, or genetics of the exposed individual. For these reasons, maximum tolerable doses depend on both the particular mycotoxin and the exposed individual.
Specific medications for mycotoxin exposure do not yet exist, so when symptoms occur, treatment is usually supportive, preventing dehydration and ensuring proper nutrition while the body recovers from the exposure.
Molds that can be seen or smelled represent a potential, but by no means certain, health risk.
Mold exposure may cause breathing difficulty in individuals who have a chronic respiratory disease, such as asthma.
Exposure to some mycotoxins has been linked to cancers. For example, chronic exposure to fumonisin has been linked to esophageal cancer in humans. A single study found patulin to be carcinogenic in model animals.
Animals may also be affected by mycotoxins. For example if ergot alkaloids, patulin, ochratoxins, or trichothecenes contaminate their feed.
Cleaning and food: The U.S. Centers for Disease Control (CDC) says that for most people, mold that is not disturbed in a way that causes the release of spores is not a health hazard. They recommend routine cleaning measures, using common household cleaning products, to control mold growth in the home or workplace. Mold grows slowly in colder, drier areas, so store food accordingly. Avoid areas with visible mold contamination.
To clean visible mold, wear gloves and a face mask, if possible. Use soap and water, or a bleach solution of no more than one cup of bleach in a gallon of water, following directions on the bottle. Extensive amounts of mold may require throwing items away or the help of a professional if the extent of mold growth is too pervasive to be removed with soap and water or bleach solution.
Mycotoxin exposure may be limited by preventing molds from growing on food. At the agricultural level, this means drying crops after harvest or using plants bred by traditional plant-breeding selection methods to be mold-resistant. At the regulatory level, moldy foods must be removed from the food supply. Unfortunately, people in countries where food is limited or regulations are not consistently enforced are at greater risk for eating mycotoxins like aflatoxin.
Note that Aspergillus species like A. orzyzae and A. sojae are used to produce soy sauce, miso, and
sake, but these species do not appear to make aflatoxins.
FUTURE RESEARCH OR APPLICATIONS
Although the U.S. Centers for Disease Control and Prevention (CDC) found no link between the mold Stachybotrys and the disease called acute idiopathic pulmonary hemorrhage (AIPH), they recommended further research. They developed a precise definition of the disease to give physicians a standard for diagnosis and further investigation.
Some mycotoxins, such as aflatoxin and the trichothecene T-2, have been discussed as bioterrorism agents. However, mycotoxins must be used at a very high dose to be lethal, and they tend to cause chronic symptoms rather than immediate death. These factors make them unlikely bioweapons.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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