Toxic Mold Health Risks

Learn about the health risks associated with exposure to mold.

Recently, mold and what some call "toxic mold" have been in the public eye. Health concerns about mold abound along with numerous lawsuits. Unfortunately, misconceptions about mold have led to widespread fear of toxic mold at home, in schools, in the workplace, and elsewhere, even though the health risks from exposure to mold have not yet been established with much medical certainty.

If you have discovered mold in your home or think you may be suffering from mold-related health problems, it's important to learn what we know and don't yet know about the health risks associated with exposure to mold.

What Is Mold?

Mold is a form of fungus that grows both indoors and outdoors and thrives in warm, damp, and humid environments. There are over a thousand varieties of indoor mold, and the good news is that the presence of a moderate amount of mold in your home or workplace does not generally pose much of a health risk. Most health problems related to mold exposure arise only when there is a build-up of high concentrations of mold. (To learn more about mold in general, read Nolo's article Toxic Mold Basics.)

What Are the Health Risks From Exposure to Mold?

Relatively little is known for certain about the health effects of exposure to mold. Despite a number of high-profile cases in which serious illnesses were claimed to have resulted from exposure to mold, there are still relatively few established links between mold exposure and any particular medical diagnosis.

Any discussion of the health threats caused by mold should take the following into consideration:

  • It is often challenging to figure out what may be causing certain symptoms of illness or disease in any given individual.
  • There is a lack of firm medical data connecting mold exposure to a particular set of symptoms.
  • The popular use of the term "toxic mold" has added confusion, given that all mold -- whether toxigenic or not -- may cause certain symptoms if it is present in high enough concentrations. (To learn more about toxigenic mold, read Nolo's article Toxic Mold Basics.)

It is generally accepted that certain people are more likely to be sensitive to mold exposure, including those with asthma or other lung conditions, compromised immune systems, or other pre-existing illnesses. Infants and the elderly are probably also at higher risk of developing health problems as a result of exposure to mold.

Based on current scientific knowledge, mold-related health problems generally fall into one of the following categories:

Allergic Reactions

Like allergies in general, sensitivity to mold varies from one person to the next. Symptoms typically include nasal stuffiness, irritated eyes, coughing, wheezing, or skin irritation. More severe reactions may include flu-like symptoms, fever, and shortness of breath.


Aspergillosis is actually the name for a family of diseases related to the commonly occurring mold genus Aspergillis. Allergic bronchopulmonary aspergillosis (known as "ABPA") is a non-invasive form of the disease that typically causes the allergic-type symptoms described above.

Invasive apergillosis, a far more serious form of the disease, actually invades and damages body tissue, usually in the lungs, but sometimes in other organs as well, and is capable of spreading throughout the body.

Here again, although healthy people can contract aspergillosis, the disease in its various forms is most common in people with asthma, cystic fibrosis, or other pre-existing lung conditions or health problems. Keep in mind that aspergillis is environmentally common in low levels and does not generally pose a health risk; only in unusually high concentrations is it considered potentially hazardous.

Toxin-Related Illnesses

There have been many attempts in recent years to link exposure to toxigenic mold with a number of serious diseases and injuries, including infant lung hemorrhaging, cancer, brain damage, and other cognitive deficiencies, fibromyalgia, chronic fatigue syndrome, reactive airway dysfunction syndrome ("RADS"), and various other health problems. Although these efforts to link mold exposure to such serious health risks have been the subject of much media attention, at the present time the medical or scientific evidence for such links is shaky at best.

Sick Building Syndrome

The energy crisis of the 1970s led to changes in building construction emphasizing increased insulation and more tightly-controlled airflow and ventilation in order to achieve greater energy efficiency. Some suggest that the lack of ventilation in newer buildings, combined with increased use of mold-friendly building materials, has facilitated mold infestations and resulted in "sick buildings." Sick building syndrome has been proposed as an explanation or diagnosis in situations in which a large number of people who happen to work in the same building begin to experience similar health symptoms.

It is known that mold spores travel and spread quickly and easily through air ducts and ventilation systems. But the difficulty in proving that the common health symptoms experienced by a group of fellow office workers were all caused by mold in the building -- as opposed to any number of other environmental health hazards -- has limited the effectiveness of sick building syndrome as the medical basis for a lawsuit.

If you are thinking of buying a home with noticeable mold problems, read Nolo's article Mold in the Home: What Homebuyers Need to Know. If you suspect mold in your apartment (or other rental), read Nolo's article Mold in Rentals: Landlord Liability, Responsibility, and Prevention.

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