Expert Commentary

There's a Fungus Among Us

Learn what causes indoor air pollution and how to prevent toxic fungi from growing and infecting your air.

June 2000

In the 1990s, microbiological contamination began its climb as one of the biggest environmental problems facing building owners, contractors and architects and engineers. One of the first and most notable cases occurred in Cleveland, Ohio. From 1993 to present, 9 out of 36 infants from homes in a specified area of Cleveland died. The EPA and the Cleveland Department of Health speculate that a toxic fungus is responsible. The fungus is stachybotrys. (It should be noted that there are many variations of the fungus stachybotrys; however, this article will refer to it in general terms rather than specificity.)

Stachybotrys is a saprophytic (feeding off organic material) greenish-black fungus found worldwide that colonizes particularly well in high cellulose material, including building materials such as drywall or gypsum board, fiber board, ceiling tiles, wooden structures, and even books and papers that are continually moist or water-damaged. Stachybotrys has been documented to produce a series of potent toxins affecting the immune system resulting in adverse effects on the central nervous system and upper and lower respiratory tract, eye and skin irritation, chronic fatigue, and adverse reproduction effects.

Stachybotrys is not the only culprit causing increased awareness from health and environmental professionals, state and federal agencies, and of course, the media. In May of this year at Albert Einstein Medical Center in Philadelphia, bricklayers were removing the exterior facade to identify the source of water leaks in a building. What they found growing on the interior wallboard was what they called "a black horse-hairlike" substance. Three workers were hospitalized shortly after it was discovered that the substance contained a variety of molds and fungus including stachybotrys and another toxic fungus called aspergillus. (As in the case of stachybotrys, aspergillus has many variations, but we will refer to it in general terms.) Aspergillus is a ubiquitous fungus with similar characteristics as stachybotrys. Aspergillus can also have similar effects on human health; however, it is also documented to have a fatality rate as high as 75 percent in people with compromised immune systems such as people with low white blood cell count (bone marrow transplant, cancer treatments, AIDS, and major burns).

Incidents like the above continue to pop up throughout the country at an alarming speed. As a matter of fact, in the early 1990s, the Business Council on Indoor Air conducted a study of 695 commercial buildings. The study revealed that 35 percent of these buildings had mold/mildew and fungal growth. To compound the issue, there are no industry standards for remediating microbiological contamination, making it a very controversial topic among experts in the field. Remedial techniques being used today vary for different surfaces and structures and range from scraping, bleaching, painting, or all three with immovable woodwork. If the woodwork can be removed, it should be. When metal structures are involved such as sheet metal ductwork, they can be brushed clean. If lined ductwork is mold contaminated, the fiberglass liner may have to be removed and the sheet metal cleaned with a brush and/or a bleaching solution. Depending on the "expert," the chosen method will vary. However, one thing the industry does agree on is that the problem is not a fungal problem at all. The problem is a water problem and to stop the mold you have to stop the water.

Both fungal and bacterial microbiological contamination usually result from water entering the building envelope or high relative humidity inside the building. Typical examples include leaking exteriors, sewage backups, and improperly sized air conditioning units, which do not remove enough humidity from the air during the cooling process. Industry experts seem to agree that the owner, contractor, and architectural and engineering (A/E) firm must all share in the responsibility or liability associated with "wet buildings." Owners may be held liable as a result of poor operation and/or maintenance of the building. Liability for an A/E firm can arise from faulty design of the HVAC system, failure to consider local climates and its impact on the building envelope, and/or specifying materials that restrict the building's ability to "breathe," such as certain types of paint versus vinyl sidings.

Contractors can subject themselves to liability in a variety of ways, including incorrectly installing the heating, ventilation, air conditioning (HVAC) system. Another way for contractors to be liable is from exposing construction materials to moisture during the construction process. This happened to a contractor in Washington, D.C. On this project drywall was exposed to water during the construction of a 10,000-square-foot daycare center for children of Senate employees. Stachybotrys mold was later found growing on the sheathing inside the building. The remedial efforts only took about 2 to 3 weeks and included replacing the contaminated components; however, the project was delayed for more than a year. In addition, inadequate installation of exterior insulated finish systems (EIFS) can cause a contractor headaches as in the case of the Martin County Courthouse in Florida. Fungal growth was found inside the building in the early 1990s. The building had a leaking EIFS on the upper two of four levels. Water penetrated the building envelope and caused substantial mold growth. The building cost approximately $13 million to construct in the late 1980s. The cost to remediate and reconstruct in the mid-1990s was nearly $26 million, including rent for relocated occupants, legal fees, and a built-out fourth floor.

The risk control methods are simple yet complex: Keep the building dry. Unfortunately there probably is nothing that can be added that we are not doing today to reduce water from infiltrating a building. Some recommended measures include but are not limited to the following. First, recognize the fact that fungal growth is an issue, and train employees in this particular arena. Second, establish a peer review process of the mechanical systems throughout the building and constructibility reviews on the building's envelope. Third, ensure the building is "dried out" before systems are turned on. Fourth, consideration also must be given to how systems interact with each other in the building and the climatalogical zones in which the building is located, especially when considering placement of vapor retarders and drainage planes. For example, there could be a wide variety of permutations of a building's exterior when you consider the different hydrothermal and rain zones in the United States. Couple that with the possibility that architects may only have to comply with a single building code, and the stage is set for water problems. Fifth, when it comes to construction materials, proper storage or timely delivery is a must to prevent water damage or moisture from accumulating on those materials. In addition, assess EIFS as well as window and door seals. The most important is to ensure your company is speaking to industry professionals before you either begin construction or begin the process of remediation.


Indoor air pollution is a serious environmental loss exposure that is beginning to receive significant attention. The topic is important not only from a business perspective, but also because it "hits home," literally. Microbiological contamination not only affects commercial type structures, it also can appear in warm, damp areas of our own homes such as basements and other "moist" areas of the house. Left alone, it could have tremendous impact on our indoor air quality and may result in a variety of building-related sicknesses. Therefore, it is important for businesses and individuals to take steps to control this risk.

Opinions expressed in Expert Commentary articles are those of the author and are not necessarily held by the author's employer or IRMI. Expert Commentary articles and other IRMI Online content do not purport to provide legal, accounting, or other professional advice or opinion. If such advice is needed, consult with your attorney, accountant, or other qualified adviser.

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