What is STACHYBOTRYS and what are the health implications?


Stachybotrys is a greenish black mold that grows on material with high cellulose content that became water damaged.  Some examples include: hay, straw, wicker, and wood chips, as well as building materials such as ceiling tile, drywall, paper vapor barriers, wallpaper, insulation backing, cardboard boxes, paper files, fiberboard, the paper covering of gypsum wallboard, particleboard, jute, dust, and wood when these items become water damaged.  This mold requires very wet or high humid conditions for days or weeks in order to grow.  Excessive indoor humidity resulting in water vapor condensation on walls, plumbing leaks, spills from showering or bathing, water leaking through foundations or roofs may lead to growth of many types of mold, including Stachybotrys.

Individuals with chronic exposure to toxins produced by this fungus reported cold and flu symptoms, memory loss, muscle aches, sore throats, diarrhea, headaches, fatigue, dermatitis, intermittent local hair loss, cancer, and generalized malaise.  The toxins produced by this fungus will suppress and could destroy the immune system affecting the lymphoid tissue and the bone marrow.  Animals injected with the toxin from this fungus exhibited the following symptoms: necrosis and hemorrhage within the brain, thymus, spleen, intestine, lung, heart, lymph node, liver, and kidney.  Affects by absorption of the toxin in the human lung are known as Pneumomycosis.  The toxins may also suppress the immune system.  In the January 17 issue of the MMWR, Stachybotrys was implicated in a cluster of fatal pulmonary hemorrhage/hemosiderosis among infants.

In the past several years, case-control studies of occupational exposure to Stachybotrys in water-damaged building environments have generated much controversy.  In one of these investigations, significant differences in self-reported symptoms (chronic fatigue, dermatologic, constitutional, and lower respiratory tract) between cases (n=51) and controls (n=21) were attributed to exposure to Stachybotrys and other “atypical fungi.”  The study design did not include an evaluation for water damage or the presence of these fungi in the work or living environments of control subjects.

Stachybotrys chartarum was shown to have an association with acute pulmonary bleeding.

Finding Stachybotrys within a building does not necessarily mean that occupants have been exposed either to allergens (pieces of the fungus or spores that can cause allergic symptoms in people prone to allergies) or toxins produced by this fungus.  Laboratory studies indicate that molds such as Stachybotrys that have the ability to produce toxins do not always do so.  Whether a mold produces a toxin while growing in a building may depend on what the mold is growing on, conditions such as temperature, food, pH, humidity or other unknown factors.  When mycotoxins are present, they occur on spores and the small mold fragments that may be released into the air.

Stachybotrys chartarum (SC), as mentioned above, is a greenish black mold that is found throughout the world and is typically wet and slimy to the touch.  It can look also appear sooty, or even like grayish white strands depending on the amount of moisture available and the length of time it has been growing.  Stachybotrys mycelial mats are generally pigmented dark olive-gray, appear to be a slimy mass, with smooth margins, and may have either a smooth or ridged surface.  The spores are more brownish in color.  When the growth sporulates, the colony may appear to have a powdery surface.  (Note: fungi cannot be identified by their visual appearance of the mycelial mat.  Identification requires examination of the fungal spores under a microscope.)

It is important to remember that many other common indoor molds can look similar to Stachybotrys such as Cladosporium, Aspergillus, Alternaria and Dreshlera, so testing is critical to positively identifying Stachybotrys in a building.

Stachybotrys mold needs the proper conditions in order to grow, including moisture, a nutrient source, temperature, and time.  However, once the Stachybotrys begins to grow it can continue to propagate even if the surface water source dries up.  The nutrient sources that best support Stachybotrys are those with high cellulose content.  Stachybotrys survives a wide variation in temperature and grows most proficiently in temperatures that humans consider warm to moderately hot.  It tends to develop more slowly than many other molds: Growth begins in one to two weeks after moisture intrusion – as compared to one to two days for molds like Aspergillus, Penicillium, or Cladosporium.  Despite its slow start, Stachybotrys usually develops into the dominant mold if the conditions are favorable, eventually crowding out other mold types that may have colonized the material first.

Like many other molds, Stachybotrys can spread both through the generation of spores and the growth of root-like structures called mycelia.  Stachybotrys spores grow in clusters at the end of stem-like structures known as hyphae.  The spores do not easily disperse into the air if the colonized material is wet, as the spores are held together by a sticky/slimy coating.  Distribution through the air is possible when the mold dries out or is disturbed.  Because of this danger of the airborne dispersion of spores, all cleaning and removal of Stachybotrys mold should be done using appropriate controls.

Stachybotrys has a high moisture requirement, so it grows vigorously where moisture has accumulated from roof or wall leaks, or chronically wet areas from plumbing leaks.  It is often hidden within the building envelope.  When S. chartarum is found in an air sample, it should be searched out in walls or other hidden spaces, where it is likely to be growing in abundance. S. chartarum has a well-known history in Russia and the Ukraine, where it has killed thousands of horses, which seem to be especially susceptible to its toxins.

Persons handling material heavily contaminated with this mold describe symptoms of cough, rhinitis, burning sensations of the mouth and nasal passages and cutaneous irritation at the point of contact, especially in areas of heavy perspiration, such as the armpits or the scrotum.

This is a slow-growing fungus on media.  It does not compete well with other rapidly growing fungi.  The dark-colored fungi grow on building material with high cellulose content and low nitrogen content.  Areas with relative humidity above 55% and are subject to temperature fluctuations are ideal for toxin production.  Appropriate media for the growth of this organism will have high cellulose content and low nitrogen content.  With current construction materials, this could be almost anything in a new building.

It is usually difficult to see in indoor samples unless it is on the outside of a wall or physically disturbed.  The spores are in a gelatinous mass.  The spores die readily after release.  Dead spores can be quite dangerous, as they often set off mycotoxins.  As Stachybotrys produces some toxigenic spores that are potentially dangerous to humans, they can enter an air-conveyance system, damage the lungs, and create trauma to the small passage airways.  The dead spores are still allergenic and especially toxigenic.  If one tries to disturb these masses, they set off many mycotoxins, which can be even more toxic.  Percutaneous absorption has caused mild symptoms.

Neither the EPA nor the CDC has purposefully set any regulations or guidelines for determining the health risks associated with Stachybotrys atra.  Collected mold cultures of Stachybotrys atra can be tricky due to the existence of other types of fungi in the same area.  Removing cultures of Stachybotrys atra must be undertaken with great care to contain the spread of dangerous spores.