Comparison of the toxicity of reference mycotoxins and spore extracts of common indoor moulds

There is an unclear endangering potential by toxic influences of inhaled conidiospores and therefore the conidia of indoor mould species were cultured and toxicologically examined after their mechanical disintegration. For this purpose high-performance liquid chromatography (HPLC) and three colorimetric bioassays, the PTGT (pollen tube growth test), the MB (methylene blue) and the MTT (methylthiazoltetrazolium) assay were applied. The sensitivity of the biological methods was evaluated by using 12 reference mycotoxins and 3 structural cell wall components. Only in one extract of disintegrated spores (Aspergillus fumigatus) a mycotoxin (0.22 g gliotoxin/6.2×10⁸ spores) was determined. All nine spore extracts, however, turned out to be cytotoxic and in this case the MTT assay was remarkably more sensitive than the two other test methods. The IC₅₀ values of six different spore extracts determined by the MTT assay were lower than 10⁶ spores/well (well=0.2 ml) whereas the IC₅₀ values determined by the MB assay and PTGT were higher than 10⁶ spores per 0.2 ml for each spore extract. An examination of four spore extracts, which were fractionated depending on their polarity by HPLC, showed that single substances as well as synergistic effects contribute to the toxic properties of the spores. The results of this work indicate a health hazard due to toxic effects after the inhalation of extremely high spore concentrations of indoor moulds. This risk will also exist if the spores do not contain any mycotoxins.