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Science Based Information About Toxic Mold

The term toxic mold is used to describe species of fungi capable of producing toxins, or specifically mycotoxins.  The term is not often used by the scientific community as the toxic effects from airborne exposure to mold is not well documented.  The medical community also does not typically recognize the term ‘toxic mold’, instead focusing on the well established connection between the allergenic effects of mold and the human body.

Toxic mold – facts vs. fiction

Are certain types of mold toxic?  Technically, yes, some molds can produce toxic compounds.  But like all toxins, the effect depends on the quantity of exposure.  Because humans primarily encounter molds through respiration, the amount of toxins entering our system is extremely small.  Harriet Burge, one of the leading scholars in the field, calculated that one would have to be exposed to 1,000 spores/m3 for 110 days straight before toxicity could occur.  Experiments with rats have shown that exposure to over 10 billion spores was required before any effect was observed.

Animals, on the other hand, can be exposed to dangerous levels of mold because they are more likely to ingest toxic molds.  Cattle or horses can become extremely ill and even die after ingesting moldy grains.  This is because the amount of toxins available through ingestion is dramatically higher than through inhalation.

While the evidence for the toxic affects of mold is very thin, molds can certainly cause other health problems.  A connection between asthma and allergies and mold exposure is clearly established and widely accepted in the medical community.

What about Stachybotrys?

Stachybotrys Chartarum, a type of mold, if often referred to as the toxic black mold.  This association is deceptive as many other species of mold are black in color and produce mycotoxins.  Without the assistance of microscopic investigation and viable/cultured sampling, the exact species of mold spore cannot be determined.

Toxic mold has been implicated with Sick Building Syndrome, however it is unclear the role mycotoxins play in the problem.  Even among molds that are capable of producing toxins, specific conditions are required for the production or release of mycotoxins.  For example, Stachybotrys only produces mycotoxins under specific water activity levels.  Recent research correlates the health problems associated with toxic molds with an activation of the immune system rather than the toxins themselves.  Nearly every known occurrence of human illness due to fungal toxins is due to ingestion rather than airborne exposure.  Examples of this include aflatoxins produced by Aspergillus flavus and Claviceps purpurea.

Info on toxic mold from the CDC

“I heard about “toxic molds” that grow in homes and other buildings. Should I be concerned about a serious health risk to me and my family?

The term “toxic mold” is not accurate. While certain molds are toxigenic, meaning they can produce toxins (specifically mycotoxins), the molds themselves are not toxic, or poisonous. Hazards presented by molds that may produce mycotoxins should be considered the same as other common molds which can grow in your house. There is always a little mold everywhere – in the air and on many surfaces. There are very few reports that toxigenic molds found inside homes can cause unique or rare health conditions such as pulmonary hemorrhage or memory loss. These case reports are rare, and a causal link between the presence of the toxigenic mold and these conditions has not been proven.

In 2004 the Institute of Medicine (IOM) found there was sufficient evidence to link indoor exposure to mold with upper respiratory tract symptoms, cough, and wheeze in otherwise healthy people; with asthma symptoms in people with asthma; and with hypersensitivity pneumonitis in individuals susceptible to that immune-mediated condition. The IOM also found limited or suggestive evidence linking indoor mold exposure and respiratory illness in otherwise healthy children. In 2009, the World Health Organization issued additional guidance, the WHO Guidelines for Indoor Air Quality: Dampness and Mould[PDF – 2.52 MB]. Other recent studies have suggested a potential link of early mold exposure to development of asthma in some children, particularly among children who may be genetically susceptible to asthma development, and that selected interventions that improve housing conditions can reduce morbidity from asthma and respiratory allergies, but more research is needed in this regard.”

Research & Links

  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC164220/
  • https://www.who.int/news-room/fact-sheets/detail/mycotoxins


Microscopic photo of stachybotrys

Microscopic photo of stachybotrys

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