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Occupational & Environmental Epidemiology

Mold

Mold is a term used to describe a type of fungus that is an often fuzzy-looking growth that appears on the surface of organic materials in damp conditions, both outdoors and indoors. Molds may be gray, black, green, yellow, orange or various other colors, and may have a velvety or wooly texture.

Like other fungi, molds produce tiny spores in order to reproduce. Mold spores continually waft through the air, both indoors and out-of-doors. When mold spores land on a damp spot, they may begin growing and digesting whatever they are growing on in order to survive. Indoors, molds can grow on wood, paper, fabrics, carpet, foods and other organic materials.

Molds are a natural part of the environment, but human health problems may result when people are exposed to large amounts of mold, particularly indoors. Inhaling excessive quantities of airborne mold particles or spores may lead to allergic illness, trigger asthma, cause respiratory infections, or bring about toxic effects from certain chemicals in the mold cells.

When excessive moisture or water accumulates indoors, mold growth will often occur, particularly if the moisture problem remains undiscovered or unaddressed. There is no practical way to eliminate all mold and mold spores indoors. However, indoor mold growth can be controlled by controlling moisture.

Health Effects of Indoor Mold

Exposure to mold can occur when airborne mold cells, mostly spores, are inhaled. We breathe in these cells every day, indoors and out. Usually these exposures do not present a health risk. But when exposure is great, some individuals, particularly those with allergies and asthma, can experience illness that could be mild to serious or anywhere in between. The following is a description of the health problems that can be caused by exposure to mold.

Allergic Illness

When mold cells are inhaled and land in the respiratory tract, the body's immune system's response to those invading cells can cause allergic illness. The immune system tries to destroy the mold as it would an agent, like a flu virus, that might cause infection. In a relatively small portion of the population (about 10 percent of people in the U.S.), the immune system overreacts and causes the allergic response that results in symptoms such as runny nose, scratchy throat and sneezing. Most of us know this allergic illness as "hay fever" or "allergic rhinitis."

Asthma

Asthma is a lung disease in which the airways that carry oxygen to the lungs can partially close, causing breathing difficulties ranging from mild (such as a dry cough) to life-threatening (inability to breathe). According to the Centers for Disease Control and Prevention (CDC), one in 12 adults and one in 11 children in the United States has asthma. More than half of asthmatics have respiratory allergies, often to mold. Molds can trigger asthma episodes in sensitive asthmatics. Learn more about asthma in North Carolina.

Respiratory Infection

Some mold species can cause respiratory infection when the live mold invades the tissues of the lungs or respiratory tract. This is not a significant risk for healthy people, but can be dangerous for individuals with severely weakened immune systems.

Toxic Effects

Very large doses of certain molds, whether inhaled or ingested, can result in poisoning caused by toxins, called mycotoxins, in the mold cells. It is not clear whether an individual can receive a high enough exposure to mold growing indoors to experience these toxic effects.

One particular type of mold that has been highlighted in the media is Stachybotrys chartarum (also known as Stachybotrys atra), commonly referred to as "black mold". Stachybotrys is a greenish-black mold that grows on materials with high cellulose content (drywall, wood, paper, ceiling tiles) that are chronically wet or moist. It is one of several molds that can produce mycotoxins under certain environmental conditions. The health effects of breathing mycotoxins are not well understood, but we do know that most molds can present some health risks, such as allergic reactions. Therefore, any mold growth in a building should be cleaned up, regardless of the type of mold.

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