''Stachybotrys chartarum'' (, ), also known as black mold or toxic black mold, is a species of microfungus that produces its conidia in slime heads. It is sometimes found in soil and grain, but the mold is most often detected in

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...

-rich building materials, such as

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and dr ...

-based

drywall Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate (gypsum), with or without additives, typically extruded between thi ...

and wallpaper, from damp or water-damaged buildings.

Taxonomy

The fungus was originally described scientifically in 1818 by

Christian Gottfried Ehrenberg Christian Gottfried Ehrenberg (19 April 1795 – 27 June 1876) was a German naturalist, zoologist, comparative anatomist, geologist, and microscopist. Ehrenberg was an evangelist and was considered to be of the most famous and productive sci ...

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 Stanley Hughes (1918–2019) was a Canadian scientist who is known throughout the global field of mycology for developing and introducing a precise and meticulous system for classifying fungi that is still used today. A naturalized Canadian, he w ...

transferred the

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

to '' Stachybotrys'' in 1958. This genus was

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every po ...

in 1832 by Czech mycologist August Carl Joseph Corda, with ''Stachybotrys atra'' assigned as its

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

. 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.

Growth, reproduction, and habitat

''S. chartarum'' is a slow-growing mold that does not compete well with other molds. It is only rarely found in nature, and seldom encounters the kind of living environment occasionally produced by human habitation (i.e., large amounts of cellulose, large temperature fluctuations, low nitrogen, no other molds, no sunlight, and ample constant humidity). The spores are only released into the ambient air when the mold is mechanically disturbed, particularly when wet. It is considered an uncommon contaminant of most

indoor air Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced ...

. Not all strains of ''S. chartarum'' produce mycotoxins, and under certain conditions some of these lose the ability to produce such toxins over time; the presence of high indoor humidity does not imply that mycotoxin-producing ''S. chartarum'' is also present; even intense exposure in a laboratory setting of rats to vapors from walls entirely covered in ''S. chartarum'' resulted in few notable biological effects (possibly because the air contained almost no spores, possibly because the walls were not disturbed during the experiment). In another experiment, mice exposed to concentrations of mycotoxins from ''S. chartarum'' much greater than a human could obtain in any living environment showed no ill effects. 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."

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 Center for Disease Control verified that a number of infants in Cleveland, Ohio became sick, and some died from pulmonary hemosiderosis (bleeding in the lungs) following exposure to unusually high levels of ''S. chartarum'' spores. Subsequent investigation by the CDC did not reveal a definitive link between mold exposure and the infant deaths. There are two chemotypes in ''S. chartarum'', one that produces trichothecene mycotoxins such as satratoxin H and one that produces atranones.

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