What are the dangers of black mold?

Updated November 21, 2016

Black mould is also called toxic mould because of the effect it can have on living things. This parasitic plant substance, which can be present in homes, schools and businesses, presents a variety of dangers. The poisons (called mycotoxins) released by mould can adversely affect the health of -- even kill -- every person and animal that comes into contact with it. Black mould also can destroy surfaces in the home; mould contamination can render a house uninhabitable.

Respiratory Risks

Toxic black mould can enter the body by touching or inhaling spores that the mould has released. As these spores lodge in the respiratory system, they can cause a variety of respiratory problems, including cold- and flu-like symptoms, sore throat, wheezing, nasal congestion, nasal drip and asthma symptoms. The most dangerous variety of mould for respiratory risks is aspergillus, which can form a "fungal ball" that lives in the lungs, releasing carcinogens (cancer-causing agents) that can be fatal.

Nervous System Risks

Toxic black mould also can cause symptoms in the central nervous system, including depression, headaches, dizziness and fatigue. Sufferers of these symptoms often do not connect them to the presence of mould until they notice the symptoms change dramatically when they are in a different environment: chronic fatigue clears up during a vacation, or dizziness occurs only in a mould-contaminated workplace and subsides when the worker is home. Stachybotrys, one mould variety, can cause serious neurological symptoms. The mycotoxin of Stachybotrys has been considered for use as a chemical warfare agent.

Physical Damage

Black mould feeds on whatever surface it attaches to, eventually eroding the surface. Mold on the surface of a leather jacket hung in a humid closet can eat away at the leather, damaging its appearance. Mold also can cause dry rot in a wooden building beam, weakening it until it no longer supports the structure. Mold often grows and spreads behind walls and under flooring, causing extensive damage before it is detected.

Building Contamination

Mold contamination in a building will increase over time as the mould colonies grow and spread. The greater the amount of mould, the higher the danger for that building's inhabitants. Mouldy building materials cannot be cleaned; mould eradication involves tearing out and replacing all contaminated materials, a service performed by special crews wearing hazardous material-protection suits. The process is often more expensive than the value of the building. Mold-contaminated homes may be deemed uninhabitable, meaning they cannot be sold on the marketplace and must be razed.


The effects of toxic mould exposure are cumulative, becoming more serious over time. Mold-related illnesses often can be treated, but are more often misdiagnosed, because mould illness can appear to be a bacterial or viral infection. If you believe you are suffering from mould exposure-related illness, alert your doctor. If you believe you are living, working or going to school in a mould-contaminated structure, request a professional mould inspection by local governmental health officials or a private inspection company. Building owners can be held legally responsible for safely removing toxic substances from their buildings. Limit your health risk by leaving any possibly contaminated building, taking care not to bring mould-contaminated furniture or other belongings with you. Wear respiratory protection if you know you'll be working in a mould-contaminated area such as a basement.

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