The Truth about Black Mould

Photo by Danielle Dolson on Unsplash

Black mould is one of the most misunderstood species on the planet. Although much has been advertised about its danger to human health and building material, few people can describe why and how black mould is dangerous. Few can even describe what black mould is. Thankfully, getting to the truth about black mould doesn’t take long. Being more aware about the effects of black mould and where it occurs will certainly come in handy in every homeowner's life.  

What is Black Mould?

Black mould can refer to any number of fungi that present with slimy, greenish-black splotches. Stachybotrys chartarum is the closest thing to a stereotypical black mould. This species is the “dangerous” one. But it’s not the colour that makes Stachybotrys dangerous (there are plenty of harmless black moulds), it’s the production of mycotoxins. Stachybotrys is capable of producing these toxic chemicals, but only from select strains. Also, many other species of fungi produce mycotoxins, most of which aren’t black or slimy. Black mould is therefore far from the only fungus to worry about, and it’s often not worth the worry.      

How Dangerous Is it, Really?

Although there is evidence linking black mould to serious health issues, it is sporadic and incomplete. Stachybotrys is never the only species of mould occupying a building, so there are other culprits to blame when residents fall ill. In fact, the symptoms of black mould exposure, like dry eyes, sore throat, and fatigue, are consistent with allergic reactions caused by living in a dwelling with excessive moisture and poor air quality. In such a building, black mould may be the least of one’s problems.

Black Mould Prevalence in Buildings

Stachybotrys only grows on damp materials that are high in cellulose, such as wood, drywall, and sheetrock. It is thus commonly encountered by contractors, but it is not as common as people may think. According to certain studies, a mould called Penicillium is present in 96 percent of samples taken from damp buildings. Cladosporium was found in 89 percent of samples; Ulocladium in 62 percent; and Geomyces pannorum in 57 percent. By contrast, Stachybotrys was found in just 4.5 percent of samples and 12.8 percent of dwellings, while other studies declared its prevalence at below 3 percent. Clearly, much of the black mould discovered in buildings is not the black mould.

Black mould may not be as prevalent or dangerous as originally thought. However, this doesn’t mean that an infestation shouldn’t be treated seriously and removed with 100 percent precision. But all mould infestations are serious; black mould is just a drop in the bucket.

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