Airborne fungal ecological niche determination as one of the possibilitiesfor indirect mycotoxin risk assessment in indoor air

Based on the microbiological analysis of air samples from occupied spaces, some possibilities for indirect risk assessment of mycotoxin-related health problems are proposed. Airborne fungi could be classified on the basis of the relationship between the two environmental factors and their combinatio ns, i.e., temperature and water requirements (water activity a(w)). One typ e involves three different groups of molds, selected on the basis of the qu antitative and qualitative information about the ability of fungi to sporul ate under different environmental conditions: group (i), represented by Asp ergillus nidulans, A. niger, and A. ochraceus, and characterized by sporula tion which was more dependent on temperature than on water activity; (ii), represented by A. flavus and A. versicolor, in which sporulation was approx imately equal and depended on both the temperature changes and a(w), altera tions; and (iii), represented by Cladosporium sp., Penicillium cyclopium, a nd P. citrinum, in which sporulation depended more on alteration of the a(w ), conditions than on temperature changes. Another type is characterized by four sporulation rates with two levels of mycotoxin risk accumulation in t he spores (conidia) of each mold species: large (la) and moderate (Ib) spor ulation rates with a risk of mycotoxin accumulation (a(w) greater than or e qual to 86; t greater than or equal to 12 degreesC); rare sporulation (IIa) and absence of sporulation (llb), without risk of mycotoxin accumulation ( a(w) greater than or equal to 86; t greater than or equal to 12 degreesC). In conclusion, providing a useful guide for two dimensions, temperature and water activity for each of the three phases of fungal growth, i.e. germina tion, growth, and sporulation, could be important for determination of the fundamental niche of each fungus and its ability to form or accumulate myco toxin. Special emphasis should be given to the indirect mycotoxin risk asse ssment in heating, ventilation, and air conditioning systems. (C) 2001 by J ohn Wiley & Sons, Inc.