Stachybotrys chartarum

Stachybotrys chartarum, also known as black mold is a species of microfungus that produces its conidia in slime heads.

S. chartarum is sometimes known as toxic black mold. While initially believed to be toxic, updated research has not shown any definitive link between S. chartarum and any health problems.

Taxonomy
The fungus was originally described scientifically in 1818 by Christian Gottfried Ehrenberg as a member of the genus Stilbospora. His diagnosis emphasized the form of the spores, which he described as minute, sub-opaque, ovate, and agglomerated into subconcentric, water-soluble irregular clusters. He noted that the fungus adheres to paper, sometimes forming circles dotted with black. Stanley Hughes transferred the taxon to Stachybotrys in 1958. This genus was circumscribed in 1832 by Czech mycologist August Carl Joseph Corda, with Stachybotrys atra assigned as its type species. The species concept of Stachybotrys chartarum has been controversial, as several studies showed that there were several closely related species and cryptic species all under this name.

There are two chemotypes in S. chartarum, one that produces trichothecene mycotoxins such as satratoxin H and one that produces atranones.

Habitat
S. chartarum is a slow-growing mold that does not compete well with other molds. It is only rarely found in nature, sometimes being found in soil and grain, but is most often detected in cellulose-rich building materials, such as gypsum-based drywall and wallpaper from damp or water-damaged buildings. It occasionally encounters human habitats with large amounts of cellulose, large temperature fluctuations, low nitrogen, no other molds, no sunlight, and ample constant humidity. The spores are released into the air when the mold is mechanically disturbed, particularly when wet. It is considered an uncommon contaminant of most indoor air.

Not all strains of S. chartarum produce mycotoxins, and under certain conditions some of these may gradually lose the ability to produce such toxins. The presence of high indoor humidity does not imply that mycotoxin-producing S. chartarum is also present.

Potential toxicity
Claims of health problems related to this mold have been documented in humans and animals since the 1930s. More recently, S. chartarum has been linked with so-called sick building syndrome. However, the link has not been firmly established in the scientific literature.

In 1994 the US Centers for Disease Control (CDC) asserted that a number of infants in Cleveland, Ohio became sick, and some died from acute idiopathic pulmonary hemosiderosis (AIPH) following exposure to unusually high levels of S. chartarum spores. A subsequent review done by the CDC found the previous investigation incorrectly analyzed data, and there was no evidence directly linking S. chartarum to AIPH. This was further supported by a lack of S. chartarum in a similar cluster of infant AIPH that occurred in Chicago, Illinois.

In one experiment, laboratory rats exposed to vapors from walls entirely covered in S. chartarum resulted in few notable biological effects (possibly because the walls were not disturbed during the experiment and the air contained few spores). In another experiment, mice showed no ill effects despite being exposed to much higher concentrations of mycotoxins from S. chartarum than a human could face in any living environment. According to one author, "These studies suggest that the concentrations of airborne spores of S. chartarum realistically obtainable in indoor air are too low to produce clinical effects." For more current information on the toxicity of S. Chartarum, review "Mold health issues" wiki: mycotoxin toxicity.