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We Don’t Need to Freak Out About ‘Toxic Mold' After a Hurricane

The final word on the mythical monster.
Ted Soqui / Getty Images

The word "mold" typically stirs up feelings of disgust. Google image search results don't help. Cheese and bread left out too long yield a tolerable level of discomfort, though. The notion of black mold conquering family homes and commercial buildings post-storm is slightly more alarming. Where does this terror come from? The ever-present myth of "toxic mold" has become well-established on the internet, ironically similar to the the way stubborn mold clings to indoor surfaces in damp environments. And just as moist environments help mold survive indoors, constant misinformation helps the myth of toxic mold survive online. Of course, in the wake of hurricanes Harvey and Irma, the mold fears have started to flood the internet yet again.


As a physician, I have encountered many instances of unfounded fears regarding mold exposure, as have many of my colleagues. We cautiously explain what the current scientific evidence tells us, even using previously published statements by experts in the field of asthma, allergy, and immunology. Still, very few people are willing to accept the fact that otherwise healthy individuals have nothing to worry about from mold itself. But all the sensational articles in the world cannot change the bottom line: A healthy person with no pre-existing conditions who is exposed to mold will not suddenly become an unhealthy person. According to the CDC, molds themselves are not "toxic." Barring very rare clinical situations, at most mold exposure can potentially exacerbate underlying health conditions, not directly cause overt, new health issues.

David Stukus, a Columbus, Ohio-based allergist/immunologist tells me that while the visibility of the mold stirs up fears, the main culprit for health effects from water-damaged buildings is usually the dampness and subsequent poor air quality. Stukus says that poor air quality—regardless of whether the poor quality is due to dampness or ozone action days—can exacerbate chronic health conditions ranging from allergies and asthma to migraines. Perhaps the most important point Stukus makes is that it is "virtually impossible to separate the effects of direct mold exposure from the associated poor air quality in research studies."


So what does mold actually do?
Stukus confirms what has already been previously stated, that "mold can cause health problems within vulnerable individuals." Most commonly, mold exposure can trigger allergic and inflammatory responses. Thus, anybody who is sensitive to mold allergens could experience upper and/or lower respiratory symptoms with mold exposure, much like the sneezing, watery eyes, and nasal congestion that greet me whenever I am around cats or like the asthmatic response a friend of mine has around dogs. Similarly, anybody who is prone to atopy (e.g. asthma, eczema, and allergic rhinitis) could notice worsening of their symptoms in the presence of mold.

Others who would be considered vulnerable in this context are "people diagnosed by a physician as having a compromised immune system." Stukus says these immunocompromised individuals could become infected by mold and end up with mold-related sinusitis, pneumonia, or skin infections. So while these individuals can have systemic infections due to mold, these infections have little to do with the myth of "toxic mold." Immunocompromised individuals are prone to systemic infections from a multitude of organisms, including bacteria, viruses, and yes, mold. Last, but certainly not least, there are exceedingly rare health conditions associated with very high occupational exposures to mold, but these levels would likely not be found in water-damaged buildings.


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What's the bottom line for flooded homes?
With most everything in evidence-based medicine, what doctors say is rooted in the available science. What we know about molds are that they are ubiquitous in our environment, both indoors and outdoors, and that they thrive in damp conditions. Flooded homes and buildings filled with standing water can become breeding grounds for all sorts of microorganisms, mold included. And echoing what Stukus says, this standing water and moisture is what compromises indoor air quality more than anything else.

Getting rid of flood waters and controlling dampness should be the priority in post flood homes, with both the EPA and the CDC warning against any attempts to measure mold in flood devastated homes because there are no known "safe" standards to measure something that naturally occurs everywhere.

The WHO has issued guidelines for dealing with poor indoor air quality due to dampness, and while these same guidelines discuss mold mycotoxins at length, they also clearly state that "the evidence that they play a role in health problems related to indoor air is extremely weak." To suggest otherwise is irresponsible and does nothing beyond contributing to mold hysteria and the internet lore of "toxic mold syndrome."

Farah Naz Khan is a physician, board certified in internal medicine and endocrinology fellow at Emory University in Atlanta.

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