Toxic Molds – trichothecenes mycotoxins
Microfungi in the genera Fusarium and Staehybotrys produce the mycotoxins trichothecenes, which cause severe dermatitis (reactions such as blistering), nosebleeds, throat irritation, asthma symptoms, chest pains, and bronchial hemorrhaging. Various militaries have developed chemical warfare agents from trichothecenes, because less than 10 milligrams per kilogram of body mass is a lethal ingested dose for many animals, including human beings, and high inhaled doses can also result in shock and death.
Hallucinogenic Toxic Molds
Toxic molds like Claviceps purpurea (ergot) can produce several mycotoxins, some of which cause hallucinations (the hallucinogenic drug LSD is derived from ergot) while others cause constriction of peripheral blood vessels and lack of blood flow, thus leading to loss of fingers and toes due to gangrene. Even though ergot mycotoxins are dangerous, the vasoconstrictive ones have been used to treat migraine headaches, and the ones that cause muscle contractions have been used to assist birth.
Potentially lethal toxic molds – Aflatoxins
The microfungus Aspergillus flavus produces mycotoxins called aflatoxins, which are lethal at high doses. They are also potent carcinogens and may cause liver cancer if eaten at low levels over a long period of time. The impact of exposure to aflatoxins by ingestion can vary drastically from organism to organism. If sensitive young animals regularly eat feed with 100 parts per billion (ppb) of aflatoxins, they will develop fatal liver cancer, though the effects may be minimal in older or less sensitive animals. Nonetheless, some regulatory authorities limit the permissible levels of aflatoxins in feed to a range of about 100 ppb up to approximately 300 ppb, depending on the animal.
Researchers have found that pregnant animals can pass ingested mycotoxins to their fetuses in utero. Scientists in France exposed pregnant rats to T2-toxin (trichothecene) and found that it passed easily through the placenta. In three other human studies, doctors from hospitals in the United Arab Emirates, Thailand, and Nigeria tested the umbilical cord blood after infants were born and found aflatoxins. Even at the low levels of mycotoxins found, the results of the studies suggested that the presence of aflatoxins was associated with lower birth weights.
Whether or not a mold produces a mycotoxin depends on many variables, including temperature, water availability, and the nature of the food source. Spores could be cultured from a sample of mold producing mycotoxins in a building and yet the new colonies might not produce high levels of mycotoxins in the petri dish. If the spores were grown under conditions identical to those in the building where the mold was first found, however, toxic molds might produce mycotoxins.
Subtypes of toxic molds
The type of mycotoxins a mold produces can also vary. Within a fungal species there appear to be different “subtypes” that produce entirely different families of mycotoxins. One subtype of Stachybotrys chartarum (Black Mold) growing in a building may produce trichothecenes, while another subtype in a different building may produce a set of mycotoxins called atranones. The physiological effects of these mycotoxins are different, so toxic exposures to what is apparently the same toxic mold growing in two different buildings may yield different health consequences if mycotoxins are the cause. Finally, different genera of fungi may produce the same mycotoxins (for example, some species of Fusarium and Stachybotrys produce trichothecenes, and Aspergillus ochraceous and Penicillium viridicatum both produce ochratoxin).
It is correct to call a mold toxic only if it is producing mycotoxins, and this can only be determined by a laboratory through chemical testing of a sample of the dust containing the mold growth, or of the specific mold colony that produced the mold spores.
There is a particularly good thread on Google Groups about Symptoms of Fungal Exposure (Mycotoxicosis). It is well worth the read.