Molds are a type of fungi that may be found throughout the natural environment. Fungi are a large and diverse class of microorganisms that live on organic nutrients. In nature they play an important role in the natural breakdown of dead organic matter.
Like most fungi, the majority of molds reproduce by producing spores, which are microscopic cells, usually between 2-20_m and oblong shaped, and can become airborne very easily. These spores then can attach to surfaces that are wet and new growths called colonies may then form if the right conditions are present. These ideal conditions include high humidity (usually over 65% relative humidity) or moisture content. Ideal temperature range for mold growth is between 50 and 90 degrees Fahrenheit (10-32 Celsius). No mold is able to grow in the absence of moisture. When the spores settle on a surface and begin to germinate they produce a branching network called hyphae. The mold then begins digesting the surface that they are growing on in order to survive.
The problem with molds start when they are found in excessive amounts in the indoor environment. Because they are so small, mold spores can easily be brought indoors on clothing, pets, shoes etc. The spores may also enter a building through open doors, windows, or ventilation systems. It is impossible and impractical to attempt to eliminate all indoor molds, but it is necessary to prevent significant accumulation.
Mold growths may be detected visibly by discovering growths that appear cottony, velvety, granular, or leathery that may first appear as stains or discolorations. These growths may differ in color, varying between white, gray, brown, black, yellow, green, or fluorescent. The other common indicator that there is a mold problem may be the detection of a musty or moldy odor, caused by volatile organic compounds. This method may help when there is a case of hidden mold, which may occur behind wallpaper or ceiling tiles, and is not noticeably visible.
It is estimated that there are around one hundred common indoor mold types that have the potential to be hazardous to one’s health in a wide variety of ways. The most common molds encountered include: Alternaria, Aspergillus, Cladosporium, Memnoniella Mucor, Penicillium, and Stachybotrys (also known as “toxic black mold”).
Stachybotrys is a greenish-black mold that may have whitish edges. When wet it appears slimy. Stachybotrys can be found worldwide, is widespread in North America and is commonly found indoors. This particular mold is found only on cellulose products, such as can be found in wood, wallpaper, sheet-rock, ceiling tiles, insulation, etc. Stachybotrys will not grow on tiles or concrete. Constant moisture is required for growth of Stachybotrys. Mycotoxins, toxic chemicals released by toxigenic fungi, can be found in the spores of Stachybotrys, or on mold fragments. When wet the spores are not easily aerosolized, but when released into the air, they can easily be inhaled and cause health effects. The ideal conditions for toxin production include about 55% relative humidity and fluctuating temperatures. Because it thrives on cellulose materials, leaks behind walls, under floors, or above ceilings may serve as ideal environments for significant growth.
Certain species of Penicillium are pathogenic, causing severe sickness in humans.
There are over 150 species in the Aspergillus genus, only a few of which may be found indoors or may be potentially pathogenic, or harmful to the health of humans and animals. This genus is found world-wide, and is especially common in the Northern Hemisphere in autumn and winter. Most people are naturally immune to the effects of Aspergillis, but when disease occurs, it may take on several forms. Aspergillus produces many well known toxins such as aflatoxins, ochratoxins, and sterigmatocystin. Aflatoxin from Aspergillus flavus and A. parasiticus are associated with stored peanuts and grains.
Cladosporium is the most common of the “black molds.” It produces a black pigment that is useful in protection from Ultraviolet light, which may explain why it is so common in nature. Certain species in this genus are pathogenic, but no major mycotoxins are associated with Cladosporium.
Mold related problems have been on the rise. One potential cause for this may be that there have been changes in the construction industry since the 1970’s. The methods and materials have changed, resulting in the homes not “breathing” and the trapping of moisture vapors.
II. EXPOSURE PATHWAY
The two most common pathways for exposure are inhalation and dermal contact. Another possible pathway would include accidental ingestion.
Exposure by inhalation may occur when people become exposed to allergens produced by the mold. This type of exposure usually occurs when spores, fragments, or mold products (such as mycotoxins) become airborne, such as if the mold becomes damaged or disturbed. This is the most common type of exposure.
Dermal exposure may occur if people accidental come into contact with the mold, or if they are attempting to clean the infested area without proper safety equipment.
Reactions by any pathway may be immediate or delayed, depending on the sensitivity of the individual.
People at greater risk for experiencing hazardous health effects include infants and children, the elderly, and anyone who is immune deficient, such as caused by chemotherapy or disease.
REFERENCES
* Ammann, Harriet M. Is Indoor Mold Contamination a Threat to Health? Washington State Department of Health. Available at: http://www.doh.wa.gov/ehp/oehas/mold.html.
Viewed on 09/22/02.
* Aspergillus for Patients. Apsergillus and Common Diseases. Available at: http://www.aspergillus.man.ac.uk/patients/articles/whatisaspergillus.html. Viewed on: 09/09/02.
* Black Mold Facts: Stachybotrys A.K.A. Black Mold. Available at http://www.eliminatemold.com/black_mold.html. Viewed on: 09/23/02.
* Haz-Mold, Inc. Certified Microbial Remediation. Home Safety-Toxic Household Mold FAQ. Available at: http://www.haz-moldinc.com/faq.html. Viewed on: 09/09/02.
* Health and Energy Testing and Consulting Company.
http://www.healthandenergy.com/stachybotrys.htm
http://www.healthandenergy.com/toxic_effects_of_fungi.htm
http://www.healthandenergy.com/penicillium.htm
http://www.healthandenergy.com/penicillium.htm
http://www.healthandenergy.com/aspergillis.htm
http://www.healthandenergy.com/cladosporium.htm
* Illinois Department of Public Health: Division of Environmental Health. Stachybotrys Fact Sheet. Available at: http://www.idph.state.il.us/envhealth/factsheets/stachybotrys.htm. Viewed on: 09/23/02.
* Sealey, Geraldine. The Fungus Among Us. ABC News Report. Available at: http://www.abcnews.go.com/sections/us/DailyNews/tonicmold020509.html.
Viewed on 05/09/02.
* U.S. Environmental Protection Agency. A Brief Guide to Mold, Moisture, and Your Home. Available at: www.epa.gov/iaq/molds.
* U.S. Environmental Protection Agency. Indoor Air-Mold/Moisture: Mold Resources. Available at: http://www.epa.gov/cgi-bin/epaprintonly.cgi. Updated 07/31/02.
