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Toxic Molds

Not all molds are toxic — in fact, very few of the more than 100,000 species are. Finding fungi growing in a bathroom, basement, attic, crawl space, on any other indoor locations, on outdoor areas or on various materials is not cause for panic.

How Can You Tell If You're Dealing with A Toxic Variety?

The short answer is that the only way to be certain is to conduct a mold test.


Some of the common forms of dangerous household fungi include Aspergillus, Penicillium and Stachybotrys — the “toxic black kind”. Not all toxic varieties are black, though black molds have gotten the most media exposure and may be among the most dangerous kinds. But, for example, Aspergillus can cause a variety of very severe health effects, and it's greener in appearance, though sometimes it has a greenish-blackish hue.

For sensitive or immune-compromised individuals, for the very young and very old and/or those with existing conditions, allergies or asthma, molds can cause a variety of reactions and health challenges, but that doesn't make them necessarily toxic.


Interestingly, it's not really the molds themselves that are toxic, rather it is a metabolic byproduct — called mycotoxins — that are given off as certain fungi eat their way through whatever material they're growing on.

Exposure and danger to humans can come via breathing in the mycotoxins, getting them on the skin, or ingesting. Species known to potentially produce mycotoxins include Acremonium, Alternaria, Aspergillus, Chaetomium, Cladosporium, Fusarium, Penicillium, Pithomyces and Stachybotrys. Reactions vary greatly from individual to individual, the type of mold, and the extent of exposure, but often include cold/flu-like symptoms, fever, sore throats, headaches, nosebleeds, fatigue, diarrhea, dermatitis, and immune suppression. Some mycotoxins may also be carcinogenic (cancer causing) and/or teratogenic (causing birth defects).

Types of Mycotoxins

Tricothecene: Probably the most serious of all the mycotoxins. It is given off by stachybotrys and fusarium. It can cause a host of serious conditions and even death.

Aflatoxin: from the aspergillus mold is known to be carcinogenic.

Ochratoxin: also produced by aspergillus and also by penicillium, is suspected as a carcinogen and is known to impair the immune system, kidneys and liver.

Toxic molds can grow on cloth, carpets, leather, wood, drywall, insulation and just about anywhere that moist, damp, wet or humid conditions exist.

Note: Different mold species can have varying health effects, but it is important to remember that any excessive mold growth needs to be taken care of, regardless of the species because it can lead to increased allergies, toxicity, and house/building structural problems.

If you're not a trained, experienced remediator, it is strongly recommended that you contact one for cleaning toxic mold.

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