The spores' health effects include suppressing the immune system because of the chemical toxins they contain. While not all molds produce such mycotoxins, all mold spores contain other substances irritating to the human respiratory tract, and can elicit allergic symptoms in sensitive individuals. Spores from numerous species of outdoor molds are typically found inside buildings at levels ranging from 10 percent to 50 percent of their levels in outdoor air. The concern for mold in buildings is not related to these species or to the outdoors as a source. Problems occur when uncommon species of molds grow indoors on building materials, especially those containing cellulose.
Mold looks nice growning in a petri dish . . .
I think of sheetrock as a sponge with food pasted to both sides. This provides an ideal environment for molds to reproduce. As they proliferate, these non-outdoor molds release spores, creating immediate and possibly future exposures for occupants. This determination requires a situation-specific evaluation, considering many factors including whether or not related health effects are being experienced by occupants. A consensus has emerged among microbiologists, certified industrial hygienists and other qualified health professionals that it is unacceptable to have ongoing mold growth in occupied buildings.