Overview
Stachybotrys chartarum, commonly called “black mold” or “toxic black mold,” is a species that has generated significant public concern and media attention since the 1990s. However, the scientific understanding of this mold differs considerably from popular perception.
According to the Centers for Disease Control and Prevention (CDC), Stachybotrys chartarum should be handled like any other mold found in buildings. While it can produce mycotoxins, the mold itself is not considered toxic or poisonous. Its presence indicates a moisture problem that requires attention.
CDC Position: “Stachybotrys chartarum is a greenish-black mold… No test exists that proves an association between Stachybotrys chartarum and particular health symptoms.”
Common Misconceptions
❌ Myth: “Black mold is the most dangerous mold”
Fact: Many mold species appear black, and color alone cannot determine toxicity. Aspergillus niger, a generally less concerning species, is also black. The health effects of mold depend on the species, individual sensitivity, and exposure level—not color.
❌ Myth: “All Stachybotrys produces deadly toxins”
Fact: Research indicates only approximately one-third of Stachybotrys chartarum strains can produce trichothecene mycotoxins. Production depends on environmental conditions, and the presence of the mold does not guarantee mycotoxin presence.
❌ Myth: “Stachybotrys causes ‘Toxic Mold Syndrome'”
Fact: The Institute of Medicine and World Health Organization have concluded there is insufficient evidence to support a causal relationship between inhaled mycotoxins and “toxic mold syndrome” or “chronic inflammatory response syndrome” (CIRS).
What Scientific Research Shows
Mycotoxin Production
Stachybotrys chartarum can produce trichothecene mycotoxins, particularly satratoxins G and H. These are secondary metabolites—compounds the mold produces under certain conditions but not as part of normal growth. Key research findings:
- Only ~1/3 of strains are capable of producing trichothecenes
- Mycotoxin production requires specific environmental conditions
- The toxins are found in spores and mycelial fragments, not released as gases
- Indoor mycotoxin exposure levels are typically orders of magnitude below those causing health effects in laboratory animal studies
CDC Investigation History
A high-profile CDC investigation in the 1990s examined a cluster of infant pulmonary hemorrhage cases in Cleveland. A 2000 follow-up report concluded that due to data collection and analysis issues, there was insufficient evidence to establish a causal link between Stachybotrys exposure and the condition. The CDC noted other environmental factors (including tobacco smoke) may have contributed.
Current Scientific Consensus
Major health organizations, including the CDC, AAAAI, and WHO, generally agree that while mold exposure (including Stachybotrys) can cause allergic and respiratory symptoms, the evidence for severe “mycotoxicosis” from indoor exposure remains inconclusive. Research continues, but dramatic health claims from indoor Stachybotrys exposure are not well-supported by peer-reviewed studies.
Documented Health Effects
Like other molds, Stachybotrys chartarum exposure can cause symptoms in some individuals:
Symptoms Associated with Mold Exposure Generally
- Coughing and wheezing
- Nasal congestion and runny nose
- Eye, nose, and throat irritation
- Skin rash
- Aggravation of asthma
- Headaches and fatigue (in some reports)
Higher-Risk Individuals
- People with existing allergies or asthma
- Immunocompromised individuals
- Those with chronic lung conditions
- Infants and elderly persons
Important: If you experience persistent symptoms, consult a healthcare provider. Mold inspectors do not provide medical diagnoses. The CDC does not recommend testing to prove a link between specific mold exposure and symptoms.
Where Stachybotrys Is Found
Stachybotrys requires specific conditions to grow and is less common than molds like Aspergillus, Penicillium, or Cladosporium.
Growth Requirements
| Factor | Requirement |
|---|---|
| Moisture | Very high—requires wetting, not just humidity |
| Duration | Prolonged wetness (chronic water damage) |
| Substrate | High-cellulose materials (drywall paper, ceiling tiles) |
| Appearance | Greenish-black, slimy texture when wet |
Common Locations
- Areas with chronic water intrusion (roof leaks, plumbing failures)
- Flood-damaged buildings
- Behind walls with ongoing moisture problems
- Water-damaged ceiling tiles
- Chronically damp basements
Because Stachybotrys requires substantial, ongoing moisture, its presence is a strong indicator of a significant water problem that needs remediation—regardless of health concerns about the mold itself.
Testing & Appropriate Response
Should You Test for Stachybotrys?
The CDC does not recommend testing specifically to identify Stachybotrys or to prove a health connection. Their guidance: if you can see or smell mold, you should address it—regardless of the species. Testing can be useful for:
- Documenting conditions for legal or insurance purposes
- Identifying hidden contamination when musty odors persist
- Verifying remediation effectiveness
- Real estate transactions
Appropriate Response
The response to Stachybotrys should be the same as for any significant mold contamination:
- Identify and fix the moisture source — This is the priority
- Professional remediation for significant growth — EPA recommends professionals for areas larger than 10 square feet
- Follow IICRC S520 standards — Industry protocols for proper remediation
- Verification testing — Confirm successful remediation
Professional Assessment: TrueSight Environmental provides objective mold testing with no conflict of interest. We identify what’s present and document conditions—we don’t sell remediation services. Learn about our process →
Research & Citations
- Centers for Disease Control and Prevention. “Stachybotrys chartarum.” CDC.gov. https://www.cdc.gov/mold/
- American Academy of Allergy, Asthma & Immunology. “Stachybotrys Chartarum (Black Mold) and Health.” AAAAI.org.
- Institute of Medicine. “Damp Indoor Spaces and Health.” National Academies Press, 2004.
- World Health Organization. “WHO Guidelines for Indoor Air Quality: Dampness and Mould.” WHO, 2009.
- CDC. “Update: Pulmonary hemorrhage/hemosiderosis among infants — Cleveland, Ohio, 1993-1996.” MMWR, 2000.