Mushrooms are a type of fungi that have been consumed by humans for thousands of years as both food and medicine. However, among the vast diversity of mushroom species on Earth, some varieties are highly toxic and can cause severe poisoning or even death if ingested. Determining exactly how many poisonous mushroom species exist globally is a complex question, as new varieties continue to be discovered even as toxicity levels can vary greatly within certain species.
Defining Poisonous Mushrooms
Mushrooms contain a wide array of chemical compounds, some of which are toxic to humans and other animals. Toxicity levels can range from mild to extremely deadly depending on the mushroom type, the amount consumed, and the susceptibility of the individual. Poisonous mushrooms contain toxins such as:
- Amatoxins – interfere with RNA synthesis, causing organ failure
- Orellanine – causes kidney failure
- Muscarine – mimics acetylcholine neurotransmitter, causing respiratory failure
- Psilocybin – causes hallucinations and psychotropic effects
- Coprine – metabolizes into a chemical that causes illness when combined with alcohol
However, the same mushroom species can be harmless to some people and toxic to others depending on factors like age, health conditions, and regional variation in toxin concentration. For example, the commonly consumed button mushroom (Agaricus bisporus) is generally safe, but contains agaritine which can cause reactions in sensitive individuals.
Documented Cases of Mushroom Poisoning
According to a study published in the journal Toxins, approximately one death per million population occurs annually due to accidental mushroom poisoning globally. However, the precise number of mushroom poisonings is difficult to determine:
- Many cases go unreported or undiagnosed
- Wild mushroom foraging is popular in many regions
- Toxins may only cause mild, flu-like symptoms
- Poisoning can easily be misdiagnosed as another condition
Certain regions do report higher rates of mushroom poisoning. For example, in 2016 the New Jersey Poison Control Center reported 42 cases of poisoning from eating wild mushrooms. Between 2009-2018, over 1000 food mushroom poisoning incidents were recorded in Poland. These statistics demonstrate that while uncommon overall, mushroom toxicities are an important public health concern in areas with significant wild mushroom foraging.
Major Types of Poisonous Mushrooms
Among the thousands of mushroom species worldwide, some of the most notorious in causing fatal poisonings include:
Death Cap (Amanita phalloides)
The death cap mushroom contains two powerful toxins, amatoxins and phallotoxins. Found across North America, Europe and Asia, it has been responsible for the majority of human deaths from mushroom poisoning. Just one mushroom can be lethal to an adult human.
Webcaps (Cortinarius species)
There are over 1000 known webcap species globally. They can cause kidney toxicity via orellanine, with symptoms setting in suddenly one or more days after consumption. A few caps can cause toxicity. Cases have been reported in Europe, North America and Japan.
Autumn Skullcap (Galerina marginata)
Common across the Northern Hemisphere, Autumn skullcaps contain the same amatoxins found in the death cap mushroom. They have been responsible for poisonings when mistaken for edible lookalikes. 2-3 caps can be deadly.
Podostroma cornu-damae (Hongo de la “Dama de la Muerte”)
Responsible for poisonings in Mexico, this mushroom causes digestive issues, hallucinations, kidney and liver failure. Contains muscarine, bufotenine, and orellanine. Can be lethal in small doses.
Fly Agaric (Amanita muscaria)
This iconic red-and-white mushroom causes hallucinations and impaired coordination. Found across the Northern Hemisphere, poisonings have occurred when assumed edible, though fatalities are rare. Contains ibotenic acid and muscimol.
| Mushroom | Toxins | Region |
|---|---|---|
| Death Cap (Amanita phalloides) | amatoxins, phallotoxins | North America, Europe, Asia |
| Webcaps (Cortinarius sp.) | orellanine | North America, Europe, Japan |
| Autumn Skullcap (Galerina marginata) | amatoxins | Northern Hemisphere |
| Podostroma cornu-damae | muscarine, bufotenine, orellanine | Mexico |
| Fly Agaric (Amanita muscaria) | ibotenic acid, muscimol | Northern Hemisphere |
Estimating the Number of Poisonous Mushrooms Worldwide
Determining a precise global number of poisonous mushroom species is challenging. However, we can estimate a range based on a few considerations:
- Approximately 140,000 mushroom species are thought to exist globally
- Roughly 10-20% of known mushroom species are considered poisonous, according to fungi databases and field guides
- Of the 10,000 documented mushroom species, around 100 are known to be potentially lethal
- New species continue to be catalogued, including new poisonous varieties
- Toxicity varies greatly within the same mushroom species depending on location and environmental conditions
Based on these points, a reasonable estimate for the number of poisonous mushroom worldwide is between 14,000 – 28,000 species globally.
By Region
We can further estimate the number of poisonous mushrooms within certain regions:
- North America – Around 3,000 mushroom species, with ~300-600 poisonous varieties
- Europe – Around 12,000 species, with 1,200-2,400 poisonous varieties
- Asia – Up to 27,000 species, with ~2,700-5,400 toxic species
- Africa – Over 1,000 species, with ~100-200 poisonous types
- Australia – Around 2,000 species, with ~200-400 poisonous varieties
Again, these numbers are rough estimates, but help convey the diversity and abundance of toxic mushroom species across various continents and ecosystems.
Most Common Mushroom Toxins
While dozens of toxic compounds have been identified in poisonous mushrooms, some of the main toxins to be aware of include:
Amatoxins
Amatoxins like α-amanitin are found in several lethal genera including Amanita, Galerina, and Lepiota. They inhibit RNA polymerase and cause liver failure.
Orellanine
Orellanine causes delayed kidney failure and is found in mushrooms like Cortinarius orellanus. It can persist in the body for up to 72 hours before symptoms appear.
Muscarine
Muscarine is found in Inocybe and Clitocybe species. It stimulates the nervous system, causing sweating, salivation, tears, and breathing issues.
Gyromitrin
Gyromitrin is converted to toxic monomethylhydrazine (MMH) in the body. It causes nausea, vomiting, delirium and liver damage and is found in Gyromitra esculenta.
Psilocybin
Hallucinogenic psilocybin is found in “magic mushrooms” of the Psilocybe genus. Though not usually lethal, psilocybin causes psychological effects that can be distressing.
| Toxin | Effects | Found In |
|---|---|---|
| Amatoxins | Liver failure | Amanita, Galerina, Lepiota species |
| Orellanine | Kidney failure | Cortinarius species |
| Muscarine | Nervous system stimulation | Inocybe, Clitocybe |
| Gyromitrin | Nausea, vomiting, liver damage | Gyromitra esculenta |
| Psilocybin | Hallucinations | Psilocybe species |
Staying Safe When Foraging for Mushrooms
If gathering wild mushrooms, some tips to avoid poisoning include:
- Positively identify the mushroom – get guidance from a trained mycologist or mushroom reference book for your region.
- Avoid lookalikes – many toxic species resemble edible varieties. When in doubt, throw it out.
- Only pick young, fresh mushrooms – avoid old or worm-eaten ones.
- Consume a small amount first – wait 24 hours before eating more to check for reactions.
- Cook thoroughly – some toxins can be destroyed through heating.
Consuming store-bought or professionally cultivated mushrooms can also reduce the risk of poisoning. Seek medical help immediately if experiencing symptoms of mushroom poisoning.
Conclusion
Estimates suggest there are between 14,000 – 28,000 poisonous mushroom species globally. While human fatalities are relatively rare, dozens of toxic compounds have been identified in mushrooms capable of causing severe liver, kidney and neurological damage. By educating oneself on the main toxic mushroom types for a given region, and taking proper precautions when foraging, the risk of accidental poisoning can be minimized. Increased awareness and caution are the best defenses against the diverse array of poisonous mushrooms in the wild.
