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What Molds Are

Molds are organisms that may be found indoors and outdoors. They are part of the natural environment and play an important role
in the environment by breaking down and digesting organic material, such as dead leaves. Also called fungi or mildew, molds
are neither plants nor animals; they are part of the kingdom Fungi.

Molds can multiply by producing microscopic spores (2 – 100 microns [μm] in diameter), similar to the seeds produced by plants.
Many spores are so small they easily float through the air and can be carried for great distances by even the gentlest breezes. The number of mold spores suspended in indoor and outdoor air fluctuates from season to season, day to day, and even hour to hour.

Mold spores are ubiquitous; they are found both indoors and outdoors. Mold spores cannot be eliminated from indoor
environments. Some mold spores will be found floating through the air and in settled dust; however, they will not grow if moisture
is not present.

Mold is not usually a problem indoors—unless mold spores land on a wet or damp spot and begin growing. As molds grow, they digest whatever they are growing on. Unchecked mold growth can damage buildings and furnishings; molds can rot wood, damage drywall, and
eventually cause structural damage to buildings. Mold can cause cosmetic damage, such as stains, to furnishings. The potential human health effects of mold are also a concern. It is important, therefore, to prevent mold from growing indoors.

What Mold Needs to Grow

To grow indoors, mold needs moisture and food. Moisture is the most important factor influencing mold growth indoors. Controlling
indoor moisture helps limit mold growth.

Moisture control is the key to mold control.

Mold does not need a lot of water to grow. A little condensation, in a bathroom or around a windowsill, for example, can be enough. Common sites for indoor mold growth include bathroom tile and grout, basement walls, and areas around windows, near leaky water fountains, and around sinks. Common sources of water or moisture include roof leaks, condensation due to high humidity or cold spots in a building, slow leaks in plumbing fixtures, humidification systems, sprinkler systems, and floods.*

Besides moisture, mold needs nutrients, or food, to grow. Mold can grow on virtually any organic substance. Most buildings are full of organic materials that mold can use as food, including paper, cloth, wood, plant material, and even soil. In most cases, temperature is not an issue; some molds grow in warm areas, while others prefer cool locations such as bread stored in a refrigerator. Often, more than one type of mold can be found growing in the same area, although conditions such as moisture, light, and temperature may favor one species of mold over another.

*Floods
Buildings that have been heavily damaged by floodwaters should be assessed for structural integrity and remediated by experienced
professionals. Please note that the guidelines covered in this course were developed for damage caused by clean water (not
flood water, sewage, or other contaminated water). See the EPA Resource List, which includes the EPA Fact Sheet: Flood Cleanup –
Avoiding Indoor Air Quality Problems, for more information.

Health Effects That May Be Caused by Inhaling Mold or Mold Spores

Inhalation exposure to mold indoors can cause adverse health effects in some people. Molds produce allergens (substances that
can cause allergic reactions), irritants, and, in some cases, potentially toxic substances or chemicals (mycotoxins). Inhaling or
touching mold or mold spores may cause allergic reactions in sensitive individuals. Mold does not have to be alive to cause an
allergic reaction. Dead or alive, mold can cause allergic reactions in some people.

Allergic Reactions, Asthma Attacks, Irritant Effects

Allergic reactions to mold are common and can be immediate or delayed. Repeated or single exposure to mold, mold spores, or mold fragments may cause non-sensitive individuals to become sensitive to mold, and repeated exposure has the potential to increase sensitivity.
Allergic responses include hay fever-like symptoms such as headache, sneezing, runny nose, red eyes, and skin rash (dermatitis). Molds can cause asthma attacks in people with asthma who are allergic to mold. In addition, molds can irritate the eyes, skin, nose, throat, and lungs
of individuals whether or not they are allergic to mold.

Other Health Effects

Breathing in mold may also cause Hypersensitivity Pneumonitis, an uncommon disease that resembles bacterial pneumonia. In addition, mold exposure may result in opportunistic infections in persons whose immune systems are weakened or suppressed.

When mold grows indoors, the occupants of a building may begin to report odors and a variety of symptoms including headaches, difficulty breathing, skin irritation, allergic reactions, and aggravated asthma symptoms. These and other symptoms may be associated with exposure
to mold. But all of these symptoms may be caused by other exposures or conditions unrelated to mold growth. Therefore, it is important not to assume that, whenever any of these symptoms occurs, mold is the cause.

For more detailed information on mold and its health effects, consult a health professional. You may also wish to consult your state or local health department. (Also see the Resource List for additional information.)

Homes

Areas that are always or often damp, such as bathrooms, laundry/utility rooms, and basements, are common locations for mold growth in homes. Regularly check areas that have been or are likely to get wet. If you hire a home inspector, building inspector, or other professional to locate a water or mold problem, make sure the professional has experience identifying and locating mold and water problems. Check references and look for membership in professional organizations.

Mold Sampling

Sampling may help locate the source of mold contamination, identify some of the mold species present, and differentiate between mold and soot or dirt. Surface sampling may be useful in determining if an area has been adequately cleaned or remediated. After remediation, the types and concentrations of mold in indoor air samples should be similar to those in the local outdoor air. There are no EPA or other federal standards for airborne mold or mold spores, however, so sampling cannot be used to check a building’s compliance with federal mold standards because there are none.

Sampling for mold should be conducted by professionals who have specific experience in designing mold sampling protocols, sampling methods, and interpreting the results. Several problems can occur when sampling. For example, there may be too few samples, sampling protocols may not be followed consistently, samples may become contaminated, outdoor control samples may be omitted, and since sampling can be expensive, sufficient funds may not be available to sample and to fix the water/mold problem.

Samples should be analyzed according to the analytical methods recommended by the American Industrial Hygiene Association (AIHA), the American Conference of Governmental Industrial Hygienists (ACGIH), or other professional guidelines. Types of samples include air samples, surface samples, bulk samples (chunks of carpet, insulation, wall board, etc.), and water samples from condensate drain pans or cooling towers.

Keep in mind that air sampling for mold provides information only for the moment when the sampling took place. For someone without experience, sampling results will be difficult to interpret. Experience in interpreting results is essential.

Some inexpensive and quick tests can be conducted if mold is suspected. In the case of carpets, a small portion of the suspect material can be submitted to a laboratory for identification. Most microbiology laboratories need only a little of the suspected mold on a clear strip of sticky tape to determine, using a microscope, whether it is actually mold or something that looks like mold.