What is Black Mold or Toxic Mold?
There are a number of mold types/genera that are either black or gray in color
or produce black pigments on the substrate that they are growing on. These include
Cladosporium, Pithomyces, Stemphydium, Ulocladium, Aureobasidium, Alternaria,
Memmoniella, and Stachybotrys.
Stachybotrys and Memnoniella are the only black mold types that are known to produce
mycotoxins, which produce a potential exposure hazard when infested materials are disturbed.
Stachybotrys and Memnoniella infestations typically only occur on repeatedly wetted materials
that contain cellulose. These include the paper on gypsumboard, cardboard, ceiling tile,
cellulose insulation, wood, etc. If the black mold is growing on materials that do not contain
cellulose, it is unlikely that either Stachybotrys or Memnoniella are present.
As the question suggests, "black mold" growths are common in houses particularly in bathrooms
and some materials in basements. The black mold that you may see growing on shower walls, and
grouting on showers and bathtubs is unlikely to be Stachybotrys or Memnoniella. The food
source in these cases is likely to be the film of soap that gradually builds up in these
locations. Black mold can often be seen growing on painted ceilings above bathtub/showers as
well as on shower curtains. Since these materials do not contain cellulose they are unlikely
to be infested with Stachybotrys or Memnoniella.
What is the most common type of Black mold or Toxic Mold?
The most common black mold found in "black mold" growths is Cladosporium. It is not known
to pose any toxic hazard. It is the most common mold type found in air samples collected both
indoors and outdoors. As such we are likely to be exposed to it all the time. Exposures to
high levels of Cladosporium pose a risk of developing allergy or even asthma in highly
sensitive individuals.
Other mold types, which may be present in "black mold" spots, include Ulocladium, Stemphylium,
Pithomyces, Alternaria, Dresclera, and Aureobasium. None of these genera are known to produce
mycotoxins, which cause a toxic hazard on exposure.
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