Mold Basics & Health
Allergy, toxins and infection: how mold may affect health
In plain English
R520 describes three ways mold exposure may affect people. Allergy affects only people who are already sensitized, and it explains runny nose, watery eyes and asthma flares, but not the whole range of complaints often reported in damp buildings. Hypersensitivity pneumonitis is a rarer immune lung reaction, usually linked to heavy occupational exposure, and R520 says it is uncommon in moldy buildings and often misdiagnosed there.
Some molds that grow on wet building materials, among them Stachybotrys, certain Aspergillus species, Chaetomium and Fusarium, can produce mycotoxins. R520 prefers the term toxigenic, meaning able to produce toxins, over toxic mold. It says the role of inhaled mycotoxins in building-related symptoms is still poorly understood and that a causal link has not been demonstrated. It also reports CDC's view that finding a toxin-producing species does not by itself call for more urgent remediation.
Infection from common indoor molds is mainly a risk for people with seriously weakened immune systems, such as transplant or chemotherapy patients. R520 notes that musty-smelling compounds have not been shown to cause the reported health effects, and that bird or bat droppings bring a separate hazard (histoplasmosis) that is not caused by water damage.
“a more appropriate term is 'toxigenic mold,' which indicates the capability of producing toxins”
Key points
- Allergy needs prior sensitization and affects a minority of occupants.
- "Toxigenic" means able to make toxins; it is not a diagnosis.
- The health role of inhaled mycotoxins is not settled.
- Opportunistic infection is mainly a concern for immunocompromised people.
- Bird and bat droppings carry a separate, specific hazard.
Official text
This topic is covered in our own words because the standard behind it is copyrighted; we cite it below rather than reproduce it.
Citations
- IICRC S520 Reference Guide, IICRC S520 Standard and Reference Guide for Professional Mold Remediation — Reference Guide — Ch. 3, pp. 21–25. Best practice