By C. Vipulanandan, Ph.D., P.E.
Chairman and Professor of Civil Engineering
Director, Center for Innovative Grouting Materials and Technology (CIGMAT)
Department of Civil and Environmental Engineering
University of Houston

Mold (fungi) and mildew are commonly used interchangeably, although mold is often applied to black, blue, green and red fungal growth and mildew to whitish growths. Molds produce tiny spores to reproduce. When mold spores land on a damp spot indoors, they begin growing and digesting whatever they are growing on in order to survive. Molds thrive on a great many organic substances and provided with sufficient moisture, they rapidly disintegrate wood, paper and leather.  There is no practical way to eliminate all mold and mold spores in the indoor environment; they way to control indoor mold growth is to control moisture.

The growth of mold is pervasive throughout the outdoor environment. Given the proper conditions, mold may also proliferate in an indoor setting. Because Americans spend 75% to 90% of their time indoor, they are exposed to molds that are growing indoors. Molds readily enter indoor environments by circulating through doorways, windows, heating, ventilation systems, and air conditioning systems. Spores in the air also deposit on people and animals, making clothes, shoes, bags, and pets common carriers of molds into indoor environments. The most common indoor molds are Cladosporium, Penicillium, Aspergillus and Alternaria

Experts say the increase in cases of toxic mold infestations in both public and private buildings is partially due to the use of imitation masonry materials commonly referred to as exterior insulation finish systems (EIFS) that allow building leaks and subsequent trapping of water inside the walls. This provides a perfect breeding ground for toxic mold. The problem is far more prevalent in humid areas like Houston and is compounded by flooding. 

Molds can destroy wooden studs and supports and can even make a house structurally unstable, but chronic health problems, including upper respiratory problems and skin rashes, are its most devastating effect. Many building materials are suitable nutrient sources for fungal growth. Cellulose substrates, including paper and paper products, cardboard, ceiling tiles, wood, and wood products are particularly favorable for growth of some molds. Other substrates such as dust, paints, wallpaper, insulation material, dry wall, carpet fabric and upholstery commonly support mold growth. 

Some indoor molds have the potential to produce extremely potent toxins called micotoxins. Species of mycotoxin-producing molds include Fusarium, Trichoderma and Stachybotrys. In general, the presence of these molds indicates a long-standing water problem. 

The toxic effects from mold exposure are thought to be associated with exposure to toxins on the surface of the mold spores. There are published reports on the effect of Stachybotrys on kids, adults, and animals. Little is documented about the prevalence of toxigenic molds in homes, and it is not clear how many extensive measures must be taken to achieve environments sufficiently free of molds to avoid disease. In removing molds caution must be used, because it is possible that homeowners could actually increase the levels of mold spores in the air by attempting extensive clean-up efforts without guidance from a professional (an environmental health or ventilation engineer). 

Besides being destructive, however, molds also have industrial uses, such as in the fermentation of organic acids and particular flavors of cheeses. Penicillin, a product of the green mold, revolutionized antibiotic drugs after its discovery in 1929.
Mold Clean up
The key to mold control is moisture control. It is important to dry water-damaged areas and items within 48 hours to prevent mold growth. If mold is a problem in your home, clean up the mold and get rid of the excess water or moisture. Fix leaky plumbing in other sources of water. Wash mold off hard surfaces with detergent and water, and dry completely. Absorbent material such as carpet that becomes moldy may have to be replaced. 

Mold remediation is a very serious undertaking, and could employ techniques used for asbestos and lead abatement along with others used for radon reduction. The situation is reminiscent of asbestos, because attempts to remove a substance can cause it to become airborne, creating a large hazard. 

Fixing a mold problem is a two-step process: cleaning up the contamination itself (most of it is generally hidden from view) and correcting the building defects that caused the problem to arise in the first place. Because so many mold problems are caused by infiltration of water vapor from the soil, the technique used for radon remediation is useful for preventing a recurrence once the contamination is addressed. 
What Should You Know About Mold?
1.             Potential health effects and symptoms associated with mold exposure include allergic reactions, asthma, and other respiratory complaints.
2.             There is no practical way to eliminate all mold and mold spores in the indoor environment: the way to control indoor mold growth is to control moisture.
3.             If mold is a problem in your home, school or workplace, you must clean up the mold and eliminate sources of moisture.
4.             Fix the source of water problem or leak to prevent mold growth.
5.             Reduce indoor humidity (to 30-50%) to decrease mold growth by ventilation using air conditioners, dehumidifiers and exhaust fans.
6.             Clean and dry any damp or wet building materials to prevent mold growth. Clean mold off hard surfaces with a mixture of water and detergent and dry completely.
7.             In areas where there is a continuous moisture problem, do not install carpeting.
In areas where flooding has occurred or where there has been water leaks, prompt cleaning of walls and other moisture-damaged items with water mixed with chlorine bleach, is necessary to prevent mold growth. Mold remediation is a serious undertaking and must be done with the help of professionals. Solving a mold problem is a two-step process: cleaning up the contamination itself and correcting the building defects that caused the problem. In some cases, if toxic mold is found, the only recourse may be to abandon the home and all its contents.
Standards of Threshold Limit Values (TLVs) for airborne concentrations of mold, or mold spores, have not been set and currently there are no EPA regulations or standards for airborne mold contaminants. Additional research is needed before the most appropriate recommendations for home clean up can be determined. Until then, interim guidelines must be adopted with the help of professionals.