Mold is a non-scientific term for many types of unwanted fungi found both indoors and outdoors. “Mold” and “fungus” have many connotations, most of them unpleasant: musty odors, damp basements, moldy carpets, water leaks, soggy drywall, athlete’s foot, and poisonous mushrooms, among others. On the positive side, molds are also responsible for penicillin and blue cheese; yeasts are fungi (plural of fungus) used to make bread, beer, and wine; and some types of mushrooms are considered edible delicacies. And without fungi to break them down, the world would be buried in leaves, trees, grass, and garbage.
Although mold and its spores are literally everywhere, active mold growth requires moisture. Whether on visible surfaces or hiding behind drywall, in attics, or under carpets, indoor mold grows in the presence of excessive dampness or water. Also found in damp indoor environments are:
• Bacteria
• Dust mites
• Break-down products of bacteria and molds, such as proteins, cell-wall particles (glucans) and volatile organic compounds (the actual cause of the musty odor associated with mold)
• Airborne chemicals, gasses, and particulate matter caused by destruction of materials by growing molds
By definition, actively growing mold damages the material it lives on, thereby impairing structural integrity. In addition, mold is associated with some untoward health effects in humans, including allergies and infections. (Some health effects attributed to mold may in fact be caused by bacteria, dust mites, etc., found in mold-colonized environments.) The so-called “toxic mold” has been claimed as the cause of “toxic mold disease”; this syndrome remains undefined and “toxic mold” as a cause remains unproven.
Overall, mold and fungi play important roles in the environment, but can also be problematic when they grow in unwanted places or cause health issues.