This is a rapidly evolving area and more research is ongoing. The growth of molds is pervasive throughout the outdoor environment. Given the proper conditions, molds may also proliferate in the indoor setting. Molds readily enter indoor environments by circulating through doorways, windows, heating, ventilation systems, and air conditioning systems. Spores in the air also deposit on people and animals, making clothing, shoes, bags, and pets common carriers of mold into indoor environments.
Many building materials are suitable nutrient sources for fungal growth.
Cellulose substrates, including paper and paper products, cardboard, ceiling tiles, wood, and wood products, are particularly favorable for the growth of some molds. Species of mycotoxin-producing molds include Fusarium, Trichoderma, and Stachybotrys. In general, the presence of these molds indicates a long-standing water problem. The toxic effects from mold exposure are thought to be associated with exposure to toxins on the surface of the mold spores, not with the growth of the mold in the body. The investigators documented that this mold was producing trichothecene mycotoxins.