Quantitative volatile metabolite profiling of common indoor fungi: relevancy for indoor air analysis

Microorganisms such as bacteria and molds produce an enormous variety of volatile metabolites. To determine whether typical microbial volatile metabolites can be used as indicator compounds for the detection of hidden mold in indoor environments, we examined 14 typical indoor fungal strains for their growth rates and their capability to produce volatile organic compounds (VOC) on standard clinical media and on agar medium made from building materials. Air samples from Headspace Chambers (HSC) were adsorbed daily on Tenax TA tubes and analyzed by thermal desorption gas chromatography and mass spectrometry. In parallel, metabolic activity was measured by determining oxygen demand, the microbial biomass was assessed by dry weighing. Profiling of the volatile metabolites showed that VOC production depended greatly on fungal strain, culture medium, biological activity, and time. The laboratory-derived maximum emission rates were extrapolated to approximate indoor air concentrations in a hypothetical mold-infested room. The extrapolated indoor air data suggest that most of the microbial-produced VOC concentrations were below the analytical detection limit for conventional indoor air analysis. Additionally, conducted indoor air analysis in mold homes confirmed these findings for the most part. The present findings raise doubts about the utility of indicator VOC for the detection of hidden mold growth in indoor environments.