Mycotoxins are nonvolatile, relatively low-molecular weight secondary metabolic products that may affect exposed persons in a variety of ways. These compounds are considered secondary metabolites because they are not necessary for fungal growth and are simply a product of the primary metabolic processes. The functions of mycotoxins have not been clearly established, but they are believed to play a role in eliminating other microorganisms competing in the same environment. They are also believed to help parasitic fungi invade host tissues.1 The amount of toxins needed to produce adverse health effects varies widely among toxins, as well as each person’s immune system.
Fungi that produce mycotoxins are referred to as toxigenic fungi. The most frequently studied mycotoxins are produced by species of Aspergillus, Fusarium, Penicillium, Stachybotrys and Myrothecium. However, toxins have been detected from many other fungi under certain growth conditions. The kinds and amounts of toxin produced depend on the fungal strain, the growing conditions, as well as the presence or absence of other organisms. Mycotoxins accumulate on fungal spores, cell fragments, and substrates (nutrient sources).
Fungi that produce potent mycotoxins are seldom abundant in outdoor ambient air. Most toxic exposures occur from indoor growth of fungi related to excessive moisture. Some mycotoxins are carcinogenic, some are vasoactive, and some cause central nervous system damage. Often, a single mycotoxin can cause more than one type of toxic effect.
1Bioaerosols: Assessment and Control, 24.1.3. ACGIH, Cincinnati, OH 1999.
Excerpted, with permission of the author, from “Public Library Closes Down for Mold Investigation,” by Rachel L. Adams, in the January 2001 issue of Indoor Environment Connections, p. 16-19. http://www.ieconnections.com.
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