Q: I live in a senior citizens' apartment complex (HUD). Many of us seniors are concerned about mold. Management/owners downplay any concern.

Many of the carpets are 10 to 12 years old and many water leaks have occurred in the past years. I sent a mold test to a lab and was advised that Cladosporium and Rhizopus/Mucor is present. Should we be concerned?

A: Carpets hold on to dust such as the human skin cells that we shed, paper dust and fibers from our clothing. If carpet becomes wet, it will support fungal growth and bacteria. Shampooing and water extraction cleaning methods don't significantly reduce microbial growth and in fact may increase growth if the water is not effectively extracted. There are a few factors that impact the amount of fungal and bacterial growth, including the locations of the carpet in the building, the heat levels and high relative humidity.

For example, a second floor carpet that gets wet during the heating season (when the humidity is low) should be expected to dry out quickly and not become contaminated with microbial growth. A slab-on-grade carpeted floor in a high-humidity climate in the summer will not dry out. The temperature of the earth is usually cooler by 20 degrees than the air temperature. Therefore, moisture will condense on the cool floor. If the floor is carpeted, the moisture will not dry quickly and microbial growth can become established.

The three mold types you listed are common fungal types. Unfortunately, I do not know of the quantities of the fungi present or the level of bacteria present. No flooring is sterile. High levels of either fungi (mold) or bacteria can be a problem, no matter what types are present. In many cases, bacteria will be the source of the musty odors and even common fungal types can cause allergies and/or sensory/pulmonary irritation. If people in the apartment complex have preexisting pulmonary problems, the carpet could be a problem, although the information you have provided is insufficient to come to that conclusion. In general, I do not recommend the use of carpets in humid environments, even without water leaks, but decisions should be made on a case by case situation. Cleaning with high temperature steam and HEPA-filtered vacuums will reduce microbial growth. In general the use of biocides in carpeting is not recommended if chemically sensitive people or children may be exposed.

Thanks to Mark Goldman, who is a senior air quality scientist for Engineering and Fire Investigations (EFI), a firm that provides mold investigation and indoor air quality services nationwide.

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