Stachybotrys Chartarum, The Mold That Makes Your Building Sick!

By Martin Duggan

Toxic Black Mold

We’ve all been there. We walk into a room we haven’t entered in a long time, and a characteristic smell of dampness enters our nostrils. Apprehensively, we flip the light switch, and floating about us are tiny particles of dust. On the wall furthest the door is a green-black splotch. Looking around at the other surfaces, we see similar discolorations. Within the first few minutes of entering the room, we feel the urge to cough. “That’s strange,” we say to ourselves, “I don’t have allergies or asthma; why would this dust bother me?” Suddenly, we realize with horror: the particles in the surrounding air aren’t dust. Those particles are pieces of mold!

Those of us with allergies or asthma know all too well the dangers that result from household mold inhalation. The coughing, wheezing, and windedness that result from household mold exposure are a scourge for anyone with mold sensitivity. But for people without allergic or respiratory issues, mold seems to be more of a nuisance than a curse. In this post, we will see that not all molds are created equal. The example from the first paragraph highlights a particular type of mold that causes severe illness, not just for those with mold sensitivity but for all people. We are talking about a kind of mold called Stachybotrys, which we know better as “toxic black mold.”

Origin Story

In the early 1930s, horse handlers in Ukraine faced a troubling problem. Many of their horses were becoming sick. The illness seemed to follow a predictable pattern. First came lip swelling, rotting gums, pink eye, and a runny nose. The disease would often progress to low blood cell counts, bleeding problems, irritability, lameness, and blindness. Not long after these more severe symptoms, the horses died. The hunt for causes narrowed in on a particular fungus that appeared to have contaminated each horse’s hay. The culprit was—you guessed it—a mold called Stachybotrys. 1

Once the fodder-handlers learned about the contaminated grain, they wondered if this toxic mold could cause problems in humans. Reports of illness among people exposed to musty straw started to appear. Not just the fodder-handlers, but even people who used straw as bedding began to tell their doctors about becoming ill. Their symptoms consisted of difficulty breathing, bloody nose, and severe rashes in the armpit, groin, thigh, and elsewhere. Once again, the culprit appeared to be Stachybotrys mold. With the culprit identified, people changed hay storage practices and stopped using straw for bedding. The outbreak stopped, and the toxic black mold called Stachybotrys faded back into obscurity. 2

Flash Forward to the 1990s

Many years passed before Stachybotrys returned into the spotlight in early 1994. Toxic black mold regained fame after an outbreak of severe lung problems among infants in Cleveland. Baffled doctors named the condition Cleveland infant idiopathic pulmonary hemorrhage (IPH). In a race to save lives, investigators desperately sought clues to what caused the deadly illness. After examining each infant’s medical history for similarities, a worrying trend appeared. Researchers identified that water damage affected the homes of each child in the time before their illness. At this point, the investigators turned their attention to mold. After testing the houses in question, the mold that kept showing up in their reports was Stachybotrys. 3

n the years that followed, the CDC and the news media focused enormous attention on S. Chartarum. From local news channels to CNN, public health officials and journalists warned the public about the dangers of toxic black mold. 4,5 Fear of Stachybotrys exposure caused many to advocate for demolition of any building with significant amounts of black mold. This so-called “sick building syndrome” engendered intense debate amongst scientists and public health officials over whether destruction was preferable to deep cleaning. 6

Muddy Moldy Waters

While the debate over the appropriate way to deal with toxic black mold raged on, researchers continued to explore the relationship between Stachybotrys and severe illness. As often happens in science, the results of this intense scrutiny led to uncertainty. Infectious disease specialists had some difficulty reproducing severe respiratory disease in animals using small amounts of Stachybotrys. Many doctors and scientists felt that the inability to produce severe illness in animal models violated a vital rule called a Koch’s postulate. 7 Koch’s postulates are rules put forward very long ago to help avoid blaming the wrong thing for infections. Doctors still use these rules today. If we can’t transfer icky material into another animal and then cause that same disease in another animal, then that icky material probably doesn’t cause disease. There are exceptions.

Speaking of those exceptions, one of the most critical exceptions happens when a bacteria or fungus produces toxins. Stachybotrys cells don’t usually harm people—their toxins harm people! It sounds like a silly technicality at first. Still, the distinction between cells and the toxins produced by those cells exists for a reason. Why? Because toxins remain on surfaces even after mold cells die and inhaled toxins cause serious illness—with or without living mold cells present. In many cases, toxins don’t even show up until parts of the mold have died or broken apart. 8

Modern Problems, Modern Solutions

So, where do things stand today? Currently, the CDC website about mold lists Stachybotrys as a potential threat. The CDC acknowledges that we don’t have 100% clarity on the deadliness of toxic black mold. However, the CDC still encourages thorough cleaning of surfaces showing signs of black mold formation. Where possible, the CDC recommends the use of protective equipment during the cleaning and drying process. And the best practice is to use dehumidifiers, frequent cleaning, and good surrounding drainage to avoid water damage and moisture altogether. Finally, the CDC does not recommend routine mold testing. Instead, the best thing is to get rid of it safely, no matter what exact species of mold it is. 9

When dealing with toxic black mold, prudence is the key. Today, occurrences of sick building syndrome are rare, and demolition is seldom the answer today. With professional cleaning companies readily available, most structures can be salvaged and put back to good use. Suppose there is concern regarding water damage, and you think toxic black mold is a problem with your building. In that case, the safest thing is to call a professional inspection and testing company.


  1. Forgacs, J. 1972. Stachybotrytoxicosis, p. 95–128. In S. Kadis, A. Ciegler, and S. J. Ajl (ed.), Microbial toxins, vol. 8. Academic Press, Inc., New York, N.Y.
  2. Drobotko, V. G. 1945. Stachybotryotoxicosis, a new disease of horses and humans. Am. Rev. Soviet Med. 2:238–242.
  3. Centers for Disease Control and Prevention. 1994. Acute pulmonary hemorrhage/hemosiderosis among infants—Cleveland, January 1993–November 1994. Morb. Mortal. Wkly. Rep. 43:881–883.
  4. Centers for Disease Control and Prevention. 2000. From the Centers for Disease Control and Prevention. Update: pulmonary hemorrhage/hemosiderosis among infants—Cleveland, Ohio, 1993–1996. JAMA 283:1951–1953.
  6. Kuhn DM, Ghannoum MA. Indoor mold, toxigenic fungi, and Stachybotrys chartarum: infectious disease perspective. Clin Microbiol Rev. 2003 Jan;16(1):144-72. doi: 10.1128/cmr.16.1.144-172.2003. PMID: 12525430; PMCID: PMC145304.
  7. Jindal SK. Koch’s postulates – Pitfalls and relevance in the 21st century. Indian J Tuberc. 2018 Jan;65(1):6-7. doi: 10.1016/j.ijtb.2017.12.003. Epub 2017 Dec 15. PMID: 29332651.
  8. Mason, C. D., T. G. Rand, M. Oulton, J. M. MacDonald, and J. E. Scott. 1998. Effects of Stachybotrys chartarum (atra) conidia and isolated toxin on lung surfactant production and homeostasis. Nat. Toxins 6:27–33.

Leave a Reply

Your email address will not be published. Required fields are marked *