Environmental Contamination: Mold

Health Effects and Symptoms of Mold Exposure

Based on research by the Institute of Medicine, home occupants are routinely exposed to approximately 200 species of mold, mildew, or moldlike fungi. Certain common household molds can cause a variety of health effects in occupants. Molds produce allergens and, in rare cases, mycotoxins. According to the 2009 Surgeon General's Call to Action to Promote Healthy Homes, the presence of mold in homes is associated with asthma and other common respiratory complaints. A recent estimate states that mold and higher moisture levels in homes contribute to approximately 21% of the current asthma cases in the United States.

According to the U.S. Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention (CDC), exposure to molds can cause symptoms such as nasal stuffiness, eye irritation, and wheezing. People with prior histories of asthma, chronic lung diseases, or mold allergies may experience more severe symptoms such as fever, shortness of breath, and lung infections. In addition to respiratory symptoms, mycotoxins from mold spores can cause indigestion and skin rashes. Children may have a special sensitivity to mold, and it has been found to be a common asthma trigger due to release of allergenic compounds and irritants. There are presently no common guidelines or recommendations for levels of mold spores found in the air or surfaces of a home and the resulting health effects on the occupant. Media attention has focused on the hazards of stachybotrys (black mold), but there is very little evidence to suggest that the presence of this variety of mold is increasing in homes.

The Presence and Detection of Mold

Molds thrive on interior materials such as wood, paper, fabrics, leather, and organic matter. Mold spores often enter a home through transportation on humans and animals. Spores also commonly enter a home through open windows and doors or other locations of air transfer such as cracks around doors and windows. According to many studies, mold can readily appear and spread rapidly in homes where the indoor air temperature is above 77°F (25°C), and the relative humidity is above 60%. However, some molds can thrive when the temperature and humidity are lower. Aspergillus, cladosporium, alternaria, and penicillium growth is associated with high moisture or humidity in buildings or the presence of standing water. Stachybotrys is sometimes observed in homes with continuously wet conditions, such as large roof leaks, exposed sump pumps, or flood.

Common locations of mold in homes include basement or slab leaks, unvented kitchens and baths, and areas of stagnant air flow. Because of the presence of moisture, organic material, and trapped air, hidden mold can sometimes be found in carpet padding, under wall coverings, and in building insulation. Colonies of mold often are found on walls and ceilings due to the paper facing, which is common on gypsum board materials. Mold can also thrive in attics and crawl spaces due to improper moisture control and ventilation. Mold and fungi growth in homes is common after an extreme weather event, such as flood, tornado, or hurricane, when basements and interiors are filled with large amounts of water, especially black (sewage) water.

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