Airborne mold spores are present throughout indoor and outdoor environments. They are very common in soil and plant material. Mold spores are a common allergenic agent. It is estimated that 10% of the population is allergic to mold. Other health effects that have been attributed to mold include upper respiratory conditions and in rare cases respiratory fungal infection, though this is limited almost exclusively to those with severely depressed immune function. The National Academy of Sciences, Institute of Medicine has evaluated the weight of evidence for relationships between mold exposure and other non-respiratory health effects and concluded there is insufficient evidence of an association.

There is no standard for an acceptable level of airborne mold exposure. Current professional guidance suggests that in a building with filtered mechanical ventilation, indoor airborne mold levels should be less than outdoor levels. Indoor levels may be closer to outdoor levels when a building is more open to the outdoors such as with open windows. Dominant (most prevalent) mold species in the outdoor sample should be the same as the indoor dominant species.

There are some species of mold that are well adapted to damp, moist environments and are referred to as “indicators” of water damage. Examples of indicator mold species include Fusarium, Stachybotrys, Chaetomium, Aspergillus and Rhodotorula. In addition to mold levels and species dominance, the presence of such species can suggest an indoor moisture condition or mold growth even when total counts are less than outdoor levels.

While occasional exposure to molds in some form is unavoidable in everyday life, it is nonetheless important to minimize potential for constant exposure in our living and workspaces. The best way of doing so is by quick response to water infiltration when identified. If you have questions about mold, please contact the EHS Department at 608-265-5000.

[1] Adverse Human Health Effects Associated with Molds in the Indoor Environment. An Evidence-Based Statement. American College of Occupational and Environmental Medicine. 2002.

[2] Damp Indoor Spaces and Health, Board on Health Promotion and Disease Prevention, Institute of Medicine, 2004.


Brian Higby
Environmental Health Specialist; Abatement
Cell phone: 608-622-9765