Virginia Cooperative Extension has three publications to help you deal with mold in your home:
• Mold Basics: What is mold? How does it grow? What are the health concerns?
• Mold Prevention: Can we prevent water problems in the home? How do we keep water problems from becoming mold problems?
• Mold Remediation: What do we do if we have mold in our homes?
We have always had mold – so why has it become such an issue today? Why do we read about mold in the media, or hear about mold litigation in the courts, or worry about mold affecting our health? There are many different reasons to consider.
Mold is a fungus. A fungus is an organism that lives by decomposing and absorbing the organic matter on which it grows. Molds, mushrooms, yeasts, smuts, rusts, and mildew are all examples of fungi. There are thousands of varieties of molds.
The term mildew is sometimes used interchangeably with mold. Mildew is often used to describe a specific mold fungus that grows on plants and is characterized by a downy, whitish or silvery appearance. Mildew is also sometimes used to describe mold growing on textiles, leather, or building exteriors.
Mold is natural and it is everywhere. Tiny particles of molds exist in both the indoor and outdoor environment. Molds are saprotropic, meaning that they gather their food from dead, moist organic matter. Molds play a major role in the ecosystem as they digest organic matter, such as dead leaves, and prevent accumulation of nature’s debris. It would be impossible to eliminate molds from our environment.
Molds grow or spread by extending hyphae, which are tiny root hairs or filament chains of cells. These hyphae extend and intertwine to form a mass, which is called the mycelium. The hyphea can grow through or into a material as well as on the surface, and often much of the mold growth is not visible on the surface of a material.
Molds reproduce by spores. The spores, which are microscopic cells, are released into the air. Acting much like seeds, the spores spread the mold colonies. Mold spores can remain dormant for long periods of time, until the right growing conditions are available. Fragments of broken hyphae can also be transplanted to start growing new mold colonies.
Some molds produce mycotoxins. A mycotoxin is a toxic substance or poison produced by a fungus. Molds that produce mycotoxins may only produce them under certain conditions, and some experts think the mycotoxins may be a defense mechanism. The mycotoxins are found in the spores.
Molds can produce volatile organic chemicals or VOCs. These VOCs are likely responsible for the musty odor associated with mold growth. Research is being conducted on the health effects of VOCs produced by molds.
Molds will grow if the environmental conditions are right. Molds need:
In buildings, molds are most commonly found on or in cellulosic building materials, such as anything with paper, wood, or natural fiber textiles. The molds eat the sugar and starch from the cellulose. Molds can also grow on non-cellulose materials, such as plastic, metal, or concrete, provided there is a food source, such as a layer of organic dirt, sometimes called a biofilm, on the surface of the material. This layer of organic dirt can be things such as residue from skin cells, grease, oils, food waste, or insect droppings. However, molds grow best on damp or wet organic material which can be used for a food source and tend to hold moisture.
Molds require a high moisture level to germinate and begin growing. Most molds require a water content of the material of 70% to 90% to begin growing. Mold spores that have been dormant for years can begin growing if adequate humidity or moisture is provided. If the air is very humid, it can provide adequate moisture for mold to start growing. After the mold has begun growing, many varieties of mold can survive at lower moisture levels, as low as 60%.
The temperature at which molds will grow is somewhat dependent on the type of mold. However, most molds will grow at a temperature range of 40 to 100 degrees Fahrenheit.
Mold can grow very quickly. The spores of some varieties can begin to germinate in as little as 4 to 12 hours, if the environmental conditions are favorable. It can be assumed that when building materials get wet, mold growth is likely to start immediately. In wet porous materials, mold can become extensive within 24 to 48 hours.
Generally, the potential health effects from molds fall into three broad categories:
There is much yet to be learned about the health effects of our exposure to mold while inside buildings. Perhaps the medical evidence is not as frightening as some of the recent media headlines and court cases have suggested. On the other hand, we do know that mold is an irritant and a sensitizer. In large amounts or over an extended time period, it can produce negative physical symptoms. Many people are susceptible to health effects from mold. The prudent action is to protect all of us from unnecessary exposure to mold in our homes.
Generally, the owner of a building is considered to be responsible for the building. However, many homeowners carry insurance to help protect their financial investment in their home and to share the liability in the event of damage to the home.
In recent years, mold has become a “hot button” in the insurance industry. If you have not recently reviewed your homeowner’s insurance, you may be surprised at how mold damage is treated. Many insurance companies now specifically exclude all claims that relate in any way to mold, mildew, or fungus. Some will pay some specified expenses for mold or fungus removal, with a pre-determined limit of liability or dollar amount, only if the claim is part of a claim for water damage.
In evaluating mold related claims, the insurance industry considers very carefully two factors:
If you live in rental housing, your landlord may ask you to sign an addendum to your lease that addresses mold concerns. This may cover issues such as reporting water leaks immediately or using exhaust fans when showering. Also, review your renter’s insurance to determine what mold coverage you do or do not have for your personal belongings.
Virginia Cooperative Extension has two additional fact sheets on mold that you can read:
You may also want to consult the following references (current as of 1/09):
For more detailed information, consult:
Photo acknowledgements: http://www.epa.gov/mold/moldcourse/imagegallery5.html
Thanks to the following professionals for their review of the Mold Fact Sheets:
Linda Jackson Cole, Extension Agent, Family and Consumer Sciences, Chesterfield, VA; Johanna Hahn, Extension Agent, Family and Consumer Sciences, Newport News, VA; Joseph Ponessa, Extension Specialist in Housing and Energy, Rutgers Cooperative Extension (retired); Cristin Sprenger, Extension Agent, Family and Consumer Sciences, Verona, VA
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
May 1, 2009