fast facts 

 Indoor Air Quality - Mold

 Questions and Answers on Mold 

December 2008 

Office of Compliance 

advancing safety, health, and workplace rights in the legislative branch 

www.compliance.gov 

WHAT ARE MOLDS? 

“Mold” is the common term for multicellular fungi that 

grow as a mat of intertwined microscopic filaments 

(hyphae). Fungi are plant-like organisms that, because they 

lack chlorophyll, are dependent upon external food sources. 

Familiar fungi include yeasts, smuts, rusts, mushrooms, 

puffballs, and bracket fungi. Molds live in the soil, on 

plants, and on dead or decaying matter. Outdoors, molds 

play a key role in the breakdown of leaves, wood, and other 

plant debris. Without molds, our environment would be 

overwhelmed with large amounts of dead plant matter. 

WHAT CAUSES MOLDS TO GROW INDOORS? 

Molds reproduce by means of spores. Mold spores are microscopic and are naturally present in both indoor and outdoor air. Some molds 

have spores that are easily disturbed and waft 

into the air and settle repeatedly with each disturbance. Other molds 

have sticky spores that 

cling to surfaces. When 

mold spores land on a 

damp spot indoors, they 

may begin growing and 

digesting whatever they 

are growing on in order to 

survive. Mold can grow on wood, paper, carpet, and 

food. When excessive moisture or water accumulates indoors, mold growth often occurs, particularly if the moisture problem continues unabated (Figure 1). Spores may 

remain able to grow for years after they are produced. In 

addition, whether or not spores are alive, the allergens in 

and on them may remain potent for years. There is no 

practical way to eliminate all molds and mold spores in 

the indoor environment; the only way to control indoor 

mold growth is through moisture control. 

WHAT DO WE CURRENTLY KNOW ABOUT THE 

HEALTH EFFECTS OF EXPOSURE TO MOLDS? 

Most fungi generally are not harmful to healthy people. 

A number of fungi commonly cause superficial infections involving the feet, groin, dry body skin, or nails, 

e.g., “athlete’s foot.” A very limited number of pathogenic fungi infect non-immunocompromised individuals. 

Immunocompromised individuals are people with severely impaired immune function, e.g., cancer patients 

receiving chemotherapy, organ transplant patients receiving immunosuppressant drugs, AIDS patients, and patients with uncontrolled diabetes are at 

significant risk for 

more severe opportunistic fungal infections. 

About 10% of the 

population is allergic 

to fungal spores and 

hyphae (Figure 2). 

Only half of these would 

be expected to show 

clinical illness. Allergic responses include allergic 

asthma or allergic rhinitis (“hay fever”). Rarely, hypersensitivity pneumonitis (an inflammation of the deep 

lung tissue caused by high sensitivity to inhaled organic 

dusts) may follow exposure to very high concentrations 

of fungal (and other microbial) proteins. 

Some species of fungi, including some molds are known 

to produce secondary metabolites, often referred to as 

mycotoxins. Mycotoxins are always produced in exceedingly small quantities. Some mycotoxins, when concentrated and purified, find a valuable clinical use, e.g., 

penicillin, cyclosporine. Current scientific evidence does 

not support the proposition that human health has been 

adversely affected by the minute levels mycotoxins that 

might be inhaled in mold contaminated homes, schools, 

or office environments. 

Figure 1: Dark Mold Growing on Water 

Damaged Wall behind Wall Paper 

Figure 2: Mold Spores (Left) and Plant 

Bodies - Hyphae (Right)
 

This information does not constitute advice or an official ruling of the Office of Compliance or the Board of 

Directors and is intended for educational purposes only. For further information or comments concerning this 

Fast Facts, please refer to the Congressional Accountability Act (2 U.S.C. 1301 et seq.) and the regulations 

issued by the Board, or you may contact the Office of Compliance, 202-724-9249.

The Office of Compliance advances safety, 

health, and workplace rights in the U.S. 

Congress and the Legislative Branch. Established as an independent agency by the 

Congressional Accountability Act of 1995, 

the Office educates employees and employing offices about their rights and responsibilities under the Act, provides an impartial 

dispute resolution process, and investigates 

and remedies violations of the Act. 

If you have any questions, please do not 

hesitate to contact the Office of Compliance: 

Room LA 200, John Adams Building 

110 Second Street, SE 

Washington, D.C. 20540 

t/ 202-724-9250 

tdd/ 202-426-1912 

f/ 202-426-1913 

Peter Ames Eveleth 

General Counsel 

Mary-Margaret Smith 

Editor Download the entire Fast Facts suite at http://www.compliance.gov 

HOW CAN WE CONTROL INDOOR MOLD GROWTH? 

Since mold spores can be found on all surfaces in all buildings, the key to controlling mold growth is to control the 

excess moisture it needs to live. In your office, if you see a water leak, moisture visible on walls or window sills, 

or if you think you see mold growing on surfaces, report your observations to your building representative. It is 

important to dry water-damaged areas and items within 24-48 hours to prevent mold growth. Fix leaky plumbing, 

roofs, basement walls or other sources of water. Wash mold off hard surfaces with detergent and water, and dry 

completely. Absorbent materials (such as ceiling tiles & carpet) that become moldy usually have to be replaced. 

For further information on mold, please visit these websites: 

http://www.epa.gov/mold/

http://www.osha.gov/dts/shib/shib101003.html

http://www.osha.gov/SLTC/mold/

http://www.niesh.nih.gov/health/topics/agents/mold/index.cfm

Fast Stats 

• There are 100,000 species of mold. 

• 1% of these mold species have known health affects. 

• 10% of the population is allergic to molds. 

• 100% of mold problems result from loss of moisture control.