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Molds are organisms that can occur both 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. Molds are neither plants nor animals. They belong to the kingdom of fungi (fungi).

Fungi are not plants. Fungi are not animals. Fungi belong to their own kingdom. Plants convert carbon dioxide directly into carbohydrates for food. Animals and fungi must find complex carbon in the environment for food. While animals ingest the food and break it down internally, fungi secrete chemicals (enzymes) into the environment that convert the complex carbon into soluble form. Fungi do not make their own food as green plants do. Fungi feed on other living things. The main role of fungi in the ecosystem is to break down dead material such as dead leaves, trees, insects and animals. The same enzymes that help fungi break down dead materials can also damage woodwork in a building. Mold can damage food, stored goods, and building materials of homes. Yeast, mold, mildew, and fungus are terms commonly used to describe fungi. Mold is essentially a description of fungi that grow on surfaces (like the black substance on a moldy shower wall). Mold and mildew often refer to the same fungus. All molds are fungi, but not all fungi are molds.

Molds come in many colors, including white. "Black mold" is not a specific type of mold, nor is "toxic mold" In the media, the terms "toxic mold" and "black mold"are sometimes used to refer to molds that can produce mycotoxins or to a specific mold, Stachybotrys chartarum. Molds that produce mycotoxins are often referred to as toxigenic fungi. Molds can reproduce by producing microscopic spores (2 to 100 micrometers [μm] in diameter), much like the seeds of plants. Many spores are so small that they float easily through the air and can be carried long distances by even the lightest breeze. The number of mold spores suspended in indoor and outdoor air varies from season to season, from day to day, and even from hour to hour. No one knows how many species of fungi there are, but estimates range from tens of thousands to perhaps three hundred thousand or more. Some of the most common indoor molds are Penicillium, Aspergillus, Cladosporium, and Alternaria.

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 on settled dust;   however, they will not grow if moisture is not present.

Why be Concerned?

Mold is not usually a problem indoors - unless the mold spores land on a wet or damp spot and begin to grow. When molds grow, they digest whatever they grow on. Uncontrolled mold growth can damage buildings and furnishings; mold can rot wood, damage drywall, and eventually cause structural damage to buildings. Mold can cause cosmetic damage such as stains on furnishings. The potential effects of mold on human health are also a concern. Therefore, it is important to prevent the growth of mold indoors. There are three reasons to be concerned about indoor mold:

1) the potential health effects of exposure to fungi and their byproducts;

2) the impact of fungal contamination on the structural integrity of a building; and

3) the negative esthetic effects that fungi can have both visually and on the human olfactory system.

Although the issue of whether exposure to indoor   fungi causes adverse health effects is controversial, there is no doubt that a   seriously mold-contaminated building can suffer structural damage and that a   foul-smelling, fungus-filled building is aesthetically unpleasing. Controversies   about health effects aside, the latter two reasons are sufficient to merit a   complete mold inspection and remediation when an environment is found to have   fungal contamination. 

People who have concerns about structural damage   or the aesthetic effects of indoor fungi should seek the services from a   certified mold inspector. People who have concerns about health effects of mold   exposure should seek the counsel of a health care professional.

Health Effects and Mold

Indoor mold inhalation can cause 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 can cause allergic reactions in sensitive individuals. Mold does not have to be alive to cause an allergic reaction. Whether dead or alive, mold can cause allergic reactions in some people.

There are different types of people who may be affected by mold more severely and earlier than others. These include infants, children, the elderly, people with respiratory illnesses and sensitivities such as allergies and asthma, and people with weakened immune systems (e.g., people with HIV infection, chemotherapy patients, organ transplant recipients).

Sensitive individuals should avoid mold-prone areas such as compost piles, mowed grass, and wooded areas.

Allergic reactions to indoor mold occur in many sensitive people. However, there is no conclusive evidence that mold in a building directly causes illness. More research is needed. Mold research continues. Exposure to mold and human health is a complex and fledgling science.

Symptoms of Mold Exposure

There are many symptoms of mold exposure. Current evidence suggests that allergy is the type of illness most commonly associated with mold. An allergic reaction is the most common symptom, which may include wheezing and difficulty breathing.

Inhalation of fungal spores, fragments (parts), or metabolites (mycotoxins and volatile organic compounds) from a variety of fungi can trigger or exacerbate immunological (allergic) reactions, cause toxic effects, or cause infections.

Repeated or single exposure to molds, mold spores, or mold fragments may cause nonsensitive individuals to be sensitive to mold, and repeated exposure may increase sensitivity. Allergic reactions include "hay fever"-like symptoms such as headache, sneezing, runny nose, red eyes, and skin rash (dermatitis). Mold can trigger asthma attacks in asthmatics who are allergic to mold. Indoor fungi can cause or exacerbate allergy symptoms, especially in people who have a history of allergic conditions (such as asthma and rhinitis).3 In addition, molds can irritate the eyes, skin, nose, throat, and lungs of people whether or not they are allergic to mold. Other symptoms include stuffy noses and sinuses; burning, watery, and red eyes; sore throat; dry cough; and general skin irritation.

These and other symptoms may be associated with exposure to mold. However, all of these symptoms can also be caused by other exposures or illnesses unrelated to mold growth. Therefore, when any of these symptoms occur, it is important not to assume that mold is the cause. The effects of mold exposure can be acute or chronic. An acute effect is an immediate, severe reaction to a large exposure. A chronic effect may take days, months or years to show up and is usually due to small, repeated exposures.

If a person experiences these symptoms only when they are in a particular building, they may be experiencing symptoms of mold exposure.

There are four major allergenic molds found indoors. They are Penicillium, Aspergillus, Cladosporium and Alternaria. Alternaria and Cladosporium are molds that are found outdoors, but can also be found indoors if the doors or windows of a building are open and the spores are carried by air currents.

You can get more detailed information about molds and their effects on health from a health care professional. You may also want to contact your state or local health department.

Infections

Only a small group of fungi are associated with infectious diseases. Aspergillosis is an infectious disease that can occur in immunosuppressed individuals.

3 The health effects can be severe in this population. People with chronic lung disease, such as obstructive pulmonary disease, may develop mold infections in the lungs. 4 Several species of Aspergillus are known to cause aspergillosis. The most common is Aspergillus fumigatus. Exposure to this common mold, even in high concentrations, is unlikely to cause infection in a healthy person.

Inhalation of mold can also cause hypersensitivity pneumonitis, a rare disease that resembles bacterial pneumonia. In addition, mold exposure can lead to opportunistic infections in individuals whose immune systems are weakened or suppressed.

There are fungal infections that can also affect healthy people. These are pathogenic fungi that are sometimes found in buildings: Blastomyces (in rotting wood), Coccidioides (in the southwestern United States), Cryptococcus (in bird droppings), and Histoplasma (in bat droppings). People who come into contact with bird or bat droppings, such as those found in attics, without proper personal protective equipment (PPE) may be at very high risk. People with weakened immune systems can be severely affected by fungal infections.

Exposure to fungi associated with bird and bat droppings (Histoplasma capsulatum and Cryptococcus neoformans) can cause health effects, usually transient flu-like illnesses, in healthy individuals. Severe health effects are seen primarily in immunocompromised individuals.

Mycotoxins

As molds grow, some (but not all) of them may   produce potentially toxic byproducts called mycotoxins   under some conditions. 1  Some of these molds are commonly found in moisture damaged   buildings. Exposure to mycotoxins can occur from inhalation, ingestion, and skin   contact. More than 200 mycotoxins from common molds have been identified, and   many more remain to be identified. The amount and types of mycotoxins produced   by a particular mold depends on many environmental and genetic factors.  

No one can tell whether a mold is producing   mycotoxins just by looking at it.

Many fungi, including species of Aspergillus,   Penicillium, Fusarium, Trichoderma, Memnoniella, and   Stachybotrys Chartarum, can produce potent mycotoxins, some of which are   identical to the compounds produced by Stachybotrys Chartarum.3  Mycotoxins are fungal metabolites that have been   identified as toxic agents.

There are studies that suggest an association   between Stachybotrys Chartarum and pulmonary hemorrhage/hemosiderosis in   infants, generally those less than six months old. Toxic substances (mycotoxins)   can enter a human body through inhalation, ingestion, or skin absorption. The   effects of the toxic substance depend upon the chemical or material, the   concentration, the route of entry, and the duration of exposure.

Smoking, alcohol, medication, gender, existing   health problems are factors that can influence the effects of a toxic substance   entering a body.

Some mycotoxins are known to affect people, but   for many mycotoxins little health information is available. Research on   mycotoxins is ongoing.

What Mold Needs to Grow

Most of the mold found indoors comes from   outdoors, because mold spores can easily float on gentle air currents. If the   spores land on suitable organic material inside a building, mold can begin to   grow. But mold needs certain things in order to grow and survive. Mold needs (1)   moisture and (2) food.

Moisture

Mold does not need much moisture to grow. A little condensation, such as in a bathroom or on a windowsill, can be enough. Common places for mold growth indoors are bathroom tiles and grout, basement walls, and areas around windows and sinks. Common sources of water or moisture include leaking roofs, condensation from high humidity or cold spots in a building, slow leaks from plumbing fixtures, humidification systems, sprinkler systems, and flooding.

Mold has been shown to germinate, grow, and produce spores within 24 hours of water intrusion.

Indoor relative humidity (RH) should be between 20% and 40% in the winter and below 60% the rest of the year. Some experts recommend that indoor humidity should generally be between 40% and 60%.

Humidity is the most important factor affecting mold growth indoors. Controlling indoor humidity helps limit mold growth. Humidity control is the key to mold control.

Food

In addition to moisture, mold needs nutrients or food to grow. Mold can grow on virtually any organic matter. Most buildings are full of organic materials that molds can use as food, including paper, fabric, wood, plant material, and even soil. Molds secrete digestive fluids that break down the substrate, making nutrients available. Molds can digest some synthetic materials such as adhesives, pastes, and paints.

Molds can grow on inorganic materials such as concrete, glass, and metal because they can settle on the dirt or dust on the surface of these materials.

In most cases, temperature is not a factor; some molds grow in warm spaces, while others prefer cool places, such as bread stored in the refrigerator. Molds thrive well in an environment with a temperature of 40° to 100° Celsius. (Does this sound like your home?)