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Are All Molds Toxic?
Jason Yost • November 21, 2022
Are All Molds Toxic?
Mold comes in many unique and individual classes called species. To-date there are over 180,000 different identified species of mold. And, via something in environmental science called the biodiversity principle, many scientists believe there may be as many 1,000,000 species. All haven’t been identified, yet.
While certain species can produce toxins, generally called mycotoxins, not all can nor will just because they are in your home or office. You see, these toxins are used by producing molds for a specific purpose: the defense of the mold from other organisms and chemicals. It is their way of protecting themselves.
It’s beyond the scope of this blog to list all the toxins produced by all the mold species. Sufficient for this blog are the following examples: aflatoxins, ochratoxins, deoxynivalenol (DON, vomitoxin), T-2/HT-2 toxins, zearalenone, fumonisins, mycophenolic acid, cyclopiazonic acid (α-CPA) and ergot alkaloids.
Molds can release these toxins individually or part of an airborne fragment or spore and can be released during active times of production or during times of agitation, as during cleaning and remediation.
According to Carol Rao, Senior Researcher at the National Institute of Occupational Safety and Health (NIOSH), “We know more than 300 species [of mold] could produce mycotoxins”, but even if one could find a mold species with the ability to produce these toxins doesn’t guarantee the presence of toxins. The United States Environmental Protection Agency (U.S. EPA) puts it this way: “Some molds can produce several toxins, and some molds produce mycotoxins only under certain environmental conditions. The presence of mold in a building does not necessarily mean that mycotoxins are present or that they are present in large quantities.” (Mold Remediation in Schools and Commercial Buildings, U.S. EPA)
Whether or not a mold that can produce toxins will produce toxins depends on several factors, such as the substrate material they are feeding on, their environment’s temperature, pH, and the presence of other organisms.
“Although some mycotoxins are well known to affect humans and have been shown to be responsible for human health effects, for many mycotoxins, little information is available” says the U.S. EPA.
So, what is known about the health effects of mycotoxin exposure? According to the World Health Organization’s (WHO) guidelines on indoor air quality: moisture and mould: “Although mycotoxins can induce a wide range of adverse health effects in both animals and human beings, the evidence that they play a role in health problems related to indoor air is extremely weak.” In other words, ingesting these toxins in foods or through the skin can cause ill health effects, but there isn’t enough research right now to determine what is true about exposure to indoor airborne mycotoxin exposures and subsequent health effects. Don’t take this the wrong way, that doesn’t mean all the effects of mold exposure are hypothetical.
Mold, regardless of its ability to produce toxins, is a source of discomfort and disease for many exposed to it. Consider again that there are over 180,000 identified mold species and many others that have yet been identified. Of these molds occupants of a building may have various responses to varying concentrations; that is, one person may have an ill-response to a certain dose while another may require a larger dose before sensing a response. Where one falls on the dose—response curve depends largely on their personal sensitivity to the specific species of mold they are ingesting, inhaling, or absorbing. (I've always explained this with this analogy: My wife has a friend that she's known since high school. She gets along with her great, but I don't. Here's how that works with mold: You and your wife may go into a home or office with visible mold growth, let's say Aspergillus species, and while you have no reaction at all, your wife does has an allergic reaction; then, you both go into another home or office with less visible mold growth, let's say Cladosporium species, and while you have an allergic reaction, your wife doesn't.)
According to the Institute of Medicine (IOM, “Damp Indoor Spaces and Health” 2004) they found sufficient evidence of associations between the presence of mold in damp indoor environments and upper respiratory tract symptoms, cough, wheeze, and asthma symptoms in sensitized persons. The IOM also found limited or suggestive evidence of an association between the presence of agents in damp indoor environments and lower respiratory illness in otherwise healthy children.
Those considered sensitized were children whose immune systems had not fully developed yet, the elderly whose immune systems were weakening, those with pre-existing medical conditions like asthma or immune system disorders, and those with allergies.
The best way to control exposure is to control the thing necessary for mold growth to begin with: moisture.
In general, “moisture control in buildings includes measures for choosing building materials and measures for controlling indoor humidity through ventilation.” (WHO) In a moist climate certain building practices may be effective that would injure a similar structure in a dry climate—one method does not protect all! Knowing the effects of building design on building science and mold growth can go a long way in protecting your remodeling, restoration, remediation, or other building investments.
Keep in mind that moisture control doesn’t mean the elimination of water. “Many materials can get wet, as long as they dry quickly enough.” (WHO) With that in mind, you should always have any water damage properly and professionally mitigated to assure that your home or office is protected from microbial infestation.
To summarize:
- Some molds can produce toxins, but even those that do require the perfect environment to produce those toxins.
- Health effects of indoor airborne mycotoxins have not been extensively studied and more research is needed to determine its effects on human health.
- Mold, whether it can produce toxins or not, is considered “a public health problem” (IICRC S520 Standard for Professional Mold Remediation) because it can cause allergy and asthma responses, infections, and other health complications.
- Rather than fearing whether a mold is toxigenic or not it is better to practice good building hygiene and maintenance, controlling moisture and ventilation, and processing any water damages quickly to avoid elevated mold concentrations indoors.
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